US3656037A - Car propulsion scheme utilizing married pairs of propulsion units - Google Patents

Abstract

This invention relates to a single or multivehicle propulsion control system having at least one married pair of propulsion units. The system is comprised of at least one married pair of propulsion units each having a plurality of selectable operating modes, one being a primary propulsion unit, while the other is a secondary propulsion unit. A propelling effort control device having a first and second state is operatively coupled to the secondary unit. A propulsion control logic unit is operatively coupled directly to the primary unit and indirectly to the secondary unit through the propelling effort control means. The propulsion units are controlled by the propulsion control logic unit and propelling effort control means to select a predetermined number of married pair operating modes, the selection of these modes closely approximating the propelling effort required to maintain a preselected vehicle speed relatively free from accelerating and decelerating effects.

Description

United States Patent Donaldson [54] AR PROPULSION SCHEME [is] 3,656,037 [4 1 Apr.11,l972

3,305,712 2/1967 Hoffman ..318/63 UTILIZING MARRIED PAIRS OF PROPULSION UNITS Primary Examiner-Bemard A. Gilheany Assistant Examiner-Thomas Langer [72] Inventor: George W. Donaldson, McKeesport, Pa. Att0rney-H. Williamson, A. G. Williamson, Jr. and .l. B. [73] Assignee: Westinghouse Air Brake Company, Swiss- Sotak Vale} 57 ABSTRACT [22] filed: 1970 This invention relates to a single or multivehicle propulsion [2]] A N 21,594 control system having at least one married pair of propulsion units.

52 us. Cl ..3l8/59 T y t is p of at least, one married p of P PP 51 int. Cl. ..H02p 7/68 .umts each having 'p y of Selectable Operating [58] Field ofSearch ..3 1 8/5 1, 53, 60-64, modes, one e g a P i eropulsion t while w r is 318/95 96, 5.9, 301404, 318 a secondarypropulsion unit. A propelling effort control device having a first and second state is operatively coupled to {56] kefernces Cited the secondary unit. A propulsion control logic unit is operatively coupled directly to the primary unit and ndirectly to the UNITED STATES PATENTS secondary lunit through the propelling Effort coiitrol means. The propu sion units are control ed y t e propu sion control 805,188 11/1905 Dey ..318/303 logic i and propelling effort control means to select a 3 312318 4/1967 slaples 18/318 predetermined number of married pair operating modes, the 2523J43 9/1950 f "318/53 selection of these modes closely approximating the propelling 2566 898 9/1951 Li ht fi 318 64 c en 6 effort required to maintain a preselected vehicle speed rela- E tively free from accelerating and decelerating effects. ewis 2,933,667 4/1960 Purifdy ..318/60 9 Claims, 8 Drawing Figures c -170 175a- "170a 17Za-- Kapuka'm 81 07256 0126*.

Q? 197 50 I Wau'z Speed t:- 3 filfgorw'ed I w Tue/201226 691. 1199 pepformmcp (la/we Train gamed .S'eecc'oa I Command Cozzr'o. 0366- I 95% 1231222555035 l m I 99\ I01 I 191a II? I veocir g 1/217 Hcua .5 a J Pflcpabc'arz VI pee f 1120 I Cbzzro PM Command 995465200 I 15 0990, IVQZLUOP/i Qmzparafiol? IIZe I 4 112/ 1i i J Patented April 11, 1972 5 Sheets-Sheet 5 l lllllll CAR PROPULSION SCHEME UTILIZING MARRIED PAIRS OF PROPULSION UNITS My invention relates to a vehicular propulsion control system.

More specifically, my invention relates to a single or multivehicle propulsion control system having at least one married pair of propulsion units. Where a single vehicle is involved the one or more married pairs of propulsion units would be on the single vehicle, while in the case of a multi-vehicle operation, pairs of vehicles could have one of the married pairs of propulsion units per vehicle. The propulsion control system will cause the vehicle or vehicles to move along a predetermined path at a preselected speed relatively free from accelerating and decelerating effects. The system is comprised of at least one married pair of propulsion units each having a plurality of selectable operating modes, one being a primary propulsion unit, while the other is a secondary propulsion unit. A propelling effort control device having a first and a second state is operatively coupled to the secondary propulsion unit. A propulsion control logic unit is operatively coupled directly to the primary propulsion unit and indirectly to the secondary, propulsion unit through the propelling efiort control device. The propulsion control logic unit selects a particular one of the operating modes for the primary and secondary propulsion units and directly actuates that particular mode in the primary propulsion unit. The secondary propulsion unit is actuated into the particular operating mode only when the propelling effort control device is in its second state. When the propelling effort control device is in its first state, the secondary propulsion unit operates at a preselected reference mode. The state of the propelling effort control device is controlled by the propulsion control logic unit in accordance with the propelling effort required to maintain the above-noted preselected vehicular speed relatively free from accelerating and decelerating effects.

Mass transit in the years just past has been and will continue to be like a struggling giant shackled by the enormous capital investment that gave the birthright to rapid transit nearly a half century ago. Something must be done to revitalize the quality of the ride experienced by the passengers. Recent years have seen an exodus of passengers from rapid transit forms of transportation to the now ubiquitous automobile. The poor quality of the ride from the passengers viewpoint has been a factor. The mass transit giant has been in urgent need of a transfusion to keep it alive. This transfusion is under way as new ideas and innovations are pumped into the existing systems. The most common approach has been to propose entirely new schemes to enhance rapid transit passenger comfort and thereby lure the masses back .to the train. These approaches invariably require that entire existing systems be abandoned. There is no question but the creation of sophisticated solid state speed control systems available today is to be lauded.

A major problem lies in passenger comfort while moving in transit from one spot to another. Almost all recent development work in the field of automatic operation of rapid transit systems has generally required fairly precise (:tl to 2 mph.) speed regulation to permit short headway operation in combination with various safety assurance methods such as overspeed protection. The majority of existing transit systems as well as foreseeable transit systems use or will use contacts to switch resistance in series with the propulsion motor armature, shunts in parallel with the motor field, and various motor configurations to provide propulsion control. This type of speed control which is commonly a cam control type has only a few, usually three or four, permanent operating states. Precise speed regulation with these types of propulsion controls has severe limitations. There are only a few speeds at which the available tractive effort exactly balances the forces tending to retard the train and these speeds vary widely with grade.

Anyone who has traveled on the subways and intracity transit trains is familiar with the annoying acceleration and jerky ride that continually vexes the passengers aboard such trains. The invention to be described hereafter solves many of the above-noted types of problems related to passenger comfort without the need to go to new transit propulsion systems, all at a cost simplicity that elevates the invention to be described into the realm of invention of the highest order.

Not only does the invention to be described cope with the problems of existing systems but also it provides a teaching that will greatly enhance the operation of future systems which will call for discrete velocity operating speeds. These latter noted advantages will become evident as the description that follows progresses.

It is therefore an object of this invention to provide an improved propulsion system for existing transit systems without the need for replacing the existing propulsion units.

Another object of this invention is to provide a smoother ride while maintaining a preselected speed by the use of various combinations of propulsion effort modes when one or more married pairs of propulsion units are involved.

Yet another object of this invention is to provide an inexpensive, highly effective propulsion control system suitable for incorporation in existing rapid transit systems which, because of its simplicity, is much lower in cost than currently available propulsion control systems of comparable control capabilities.

Still another object of this invention is to provide a propulsion control system which, because of its automated nature and basic simplicity, greatly reduces the training time required of motormen currently employed.

Another object ofthis invention is to provide a married pair propulsion unit control which will enhance all future propulsion unit control whenever each propulsion unit has preselected operating states or modes.

Another object of this invention is to provide married pair propulsion unit control, which married pair of propulsion units consists of a primary and a secondary propulsion unit, the primary unit being actuated into a preselected operating mode and the secondary propulsion unit being turned on into the same preselected operating mode or being turned off in accordance with the propelling effort required for operation of the married pair of units in a preselected manner, the tuming on or off of the secondary propulsion unit accomplished through a propulsion effort control means known as the X r-elay.

Another object of this invention is to provide married pair propulsion unit control, which is economical in cost, simple in structure, reliable in operation, durable in use, and efficient in service.

In the attainment of the foregoing objects, a vehicular propulsion control system is provided which includes at least one married pair of propulsion units, one a primary propulsion unit, the other a secondary propulsion unit, for causing vehicular movement along a predetermined way at a preselected speed at a relatively constant velocity.

Basically, the system operates with a married pair of propulsion units, each having a plurality of selectable operating" modes. The propulsion units in the preferred embodiment are" series-connected DC electric motors. A propelling effort control relay having a plurality of contacts and a first and second state to control corresponding first and second states for each of the contacts is operatively coupled to the secondary propulsion unit. A propulsion control logic unit is operatively coupled directly to the primary propulsion unit and indirectly to the secondary propulsion unit through the propelling effort control relay and its plurality of contacts.

The propulsion control logic unit selects a particular one of the plurality of operating modes for the primary and secondary motor and directly actuates that particular mode in the primary motor. The secondary motor is also actuated into that particular operating mode only when the propelling effort control relay and its plurality of contacts are in their second state. The secondary motor operates at a predetermined reference operating mode which is the coast mode in the preferred embodiment, when the propelling effort control relay, or X relay, and its contacts are in their first states.

The states of the propelling effort control relay and, in turn, its plurality of contacts are controlled by the propulsion control logic unit in accordance with the propelling effort required to maintain the preselected vehicle relatively speed free from accelerating and decelerating effects.

The selection of the above-noted particular operating mode, and the control of the states of the propelling effort control relay and its plurality of contacts is a function of the combined effects of acceleration and change in velocity.

The propulsion control logic unit could include acceleration and deceleration responsive devices, but for purposes of setting forth the most basic approach there need only be a mechanism that is responsive to change in velocity. Therefore, while velocity is the only parameter being measured, acceleration and deceleration inherently play a part in the selection of any particular operating mode.

Other objects and advantages of the present invention will become apparent from the ensuing description of illustrative embodiments thereof, in the course of which reference is had to the accompanying drawings in which:

FIG. 1 illustrates train propulsion curves typical of prior art single or multi-train car operation.

FIG. 2 illustrates train or vehicularv performance curves which result from the incorporation of the invention.

FIG. 2a illustrates a two-car arrangement, each car having five modes of operation, including coast.

FIG. 3 depicts a low speed portion of the train or vehicular performance curves shown in FIG. 2, as well as velocity error which arises during normal operation.

FIG. 4 sets forth in block diagram form a preferred embodiment of the invention.

FIGS. 5 and 50 represents a circuit diagram of the embodiment set forth in block diagram form in FIG. 4.

FIG. 6 portrays the required alignment for the viewing of FIGS. 5 and 5a.

A description of the above embodiments will follow and then the novel features of the invention will be presented in the appended claims.

Reference is now made to FIG. 1 which illustrates train propulsion curves typical of prior art single or multi-train operation. These propulsion curves are shown and described in the following publications: General Electric Instruction Manual GET2866, pages 1 to 43; The Electric Railway" by Morris Buck, 1915, pages 84 to 126, specifically pages 111 to 120; or Applications and Industry, July 1955, pages 147 to 152, specifically page 148. This graph shown in FIG. 1 is of importance to the contribution to be described hereafter because it sets forth in graphic detail the mode and manner in which prior art train propulsion systems operated. As has been noted in the past, trains that operated in our rapid transit-environments were limited to a group of train propulsion curves which were generally defined as being an inching mode of operation or switching mode, a low speed operation, a medium speed operation, and a high speed mode of operation.

Reference is now made specifically to FIG. 1 in which the curve 11 is a switching or inching curve. This curve is a train motor propulsion curve and, as one can see, as the velocity increases, the tractive effort, which is measured on the ordinate axis, decreases. Velocity is shown on the abscissa. Accordingly, the vehicle may operate on this switching or inching curve for a few seconds of its initial operation when the train is starting to move from a zero velocity. It should be recognized that whenever trains of this type are employed, the operator of the train may only select a single discrete mode of operation. In other words, he may move a master controller lever, not depicted, to a point which is indicative of low speed operation. When this occurs the inching or switching mode of operation is automatically entered. In the alternative he may select a medium, or two higher speed modes of operation. Whenever this is done, the entire train and all the propulsion units in each of the cars on the train operate in exactly the same mode. In other words, all train cars connected one after the other are placed in the switching or inching mode as the vehicle starts its initial movement.

The second curve of significance here is the curve designated by the reference numeral 12 which is the low speed propulsion curve. To the right of it appears medium speed propulsion curve 13, as well as high speed propulsion curve 14. As the legends indicate, when the inching mode of operation, or switching mode as it may be termed, is being accomplished, the motors on the respective cars are connected in series, and as is well known in the art, all external resistance is placed in series with the motors creating the speed tractive ef fortcurves shown in the figure. The curves that are depicted in FIG. 1 are typical of all train propulsion curves wherever there is a series motor employed and portions of the series resistance is shorted out in steps as the vehicle increases in speed. Therefore, it will be appreciated that if a train is commanded to enter into a low speed mode of operation, which is defined by the train propulsion curve 12, there will of necessity be certain mechanisms on the train which will be activated to control the deletion of resistances in series with the motors. As these resistances are deleted, a family of train propulsion curves will be generated and these curves are shown as dotted lines in this figure on curves 18, 19 and 21. They may be termed incremental resistance curves and when the train throttle is positioned in a low speed mode of operation, the train will automatically follow the path shown by the arrows which originate on curve 111, the switching curve, and which arrows meet the incremental resistance curve 18, and after a brief moment of performance along this incremental resistance curve, determined by timing and/or a current limit relay, the next incremental resistance curve is approached as is indicated by the arrow which originates on the curve 18 and stops on curve 19.

The deletion of resistances as a vehicle comes up to a speed of approximately six miles per hour is automatic, and when this speed reached the vehicles operate on the low speed propulsion curve 12. This automatic deletion of resistance forms no part of the invention which will be described hereafter.

Once the vehicle has reached a speed, for example, of approximately six miles per hour, the train propulsion curve 12 is the curve which the vehicles propulsion units will then follow. This assumes that the master controller, which is conventional, is in its proper position. This is true whenever two or more vehicles are employed and in actuality will also occur when a single vehicle is employed. This figure, however, is intended to convey the situation where at least two vehicles are employed, having two individual propulsion units.

Returning now to the description of the performance of these vehicles, once the low speed propulsion curve 12 is reached, the arrow 15 designates the direction which the train propulsion effort will follow. Accordingly, as speed increases, the vehicles tractive effort will decrease until we reach, for example, a preselected speed of 15 miles per hour, shown as point 20 on the curve 12. At this point the operator of the vehicle, not desiring to exceed 15 miles per hour, would move the throttle handle to its off or coast position and the tractive effort would drop to small negative tractive effort 'as indicated by point 24 at the tip of the arrow 25. This small negative tractive effort is present because both trains are in a coasting mode of operation and are experiencing slight dynamic brak: ing. The negative tractive effort of dynamic braking is illustratedby the plurality of dynamic braking curves 16 shown interconnected by solid vertical lines.

If, as has been proposed in this suggested illustration, the operator of the train desires not to exceed 15 miles per hour, he would wait a period of time, and the train, because of train resistance and small dynamic braking effort, would begin to decelerate. The operator would then have to make a decision as to when to return to his low speed propulsion effort, and this might be determined by a velocity error which he could note in a speedometer located in the cab of the train. Accordingly, should, as this figure illustrates, the speed drop to 1 1 miles per hour, the operator of the train would then put the throttle into its low speed mode of operation, and as the arrow 23 indicates, the tractive effort would return to a point on he curve 12.

With all the motors connected in series with all external resistance removed, the train would follow the train propulsion curve 12 back down again to the point 20, and at that point the operator would again turn the controller to its off position and the tractive effort would drop to the coast mode of opera tion, that is, point 24 on one of the dynamic braking curves 16. It can therefore be seen that the vehicle, in order to maintain a constant speed of 15 miles per hour,would have to hunt over a velocity error which may well be as much as 3 or 4 miles per hour, and in so doing there must be a repeated application of low speed propulsion effort to bring the vehicle back to the desired 15 miles per hour velocity. It is this hunting action coupled with large changes in tractive effort that provides the present discomfort experienced by passengers when the vehicle is suddenly accelerated in order to bring it back up to the desired speed.

Not mentioned up to this point is the presence of the curve 17 which is termed a train resistance curve, and which train resistance curve has been reduced to a formula referred to as the Davis formula. This formula appears below:

where:

R Train resistance in lbs/ton n Number of axles V= Velocity in miles per hour A Front area in square feet W= Wt./axle in tons It can now be appreciated from a review of this formula that the train resistance curve will be one in which the train resistance increases asthe velocity increases. Of special importance to us here is that this train resistance curve 17 passes through the area enclosed by the arrows 25 and 23, propulsion curve 12, and dynamic braking curve 16. It should be noted that there is no train propulsion curve which passes through the point 26 which is the point where the train propulsion effort, if it could match the train resistance, would exactly balance the load and therefore allow the train to remain at a constant velocity. It is to this problem that the invention to be described hereafter provides a solution in that by the incorporation of the invention there may be accomplished an almost perfect balance of tractive etfort versus train resistance, and thereby provide an extremely smooth ride at a relatively constant velocity.

Before leaving FIG. 1, mention should be made of the incremental resistance curves 22 at the top of this figure, which incremental resistance curves are automatically utilized as the train is brought up to its maximum speed, or its medium speed, in a manner which forms no part of this invention, but is conventional in train propulsion systems now in use. To reiterate further, the curve 13, which is the medium speed curve, employs two motors in parallel with full field and two motors in series, hereafter referred to as the series parallel mode. The high speed propulsion curve 14employs two motors in series, two motors in parallel, with series fields shunted, hereafter referred to as the series parallel with shunted field mode. These propulsion curves, of course, are typical of all series motors used in rapid transit today.

As noted earlier, FIG. 1 depicts a set of dynamic braking curves 16, which curves reflect the variable nature of dynamic braking. The dynamic braking curve 16 enter the picture whenever the vehicles are in their coast mode of operation. The fact that this curve is shown as a stepped curve is due to the fact that the curves 16 are brought about by the automatic addition or deletion of resistance to the motor windings. The availability of this stepped curve plays a significant role in the invention to be described. Curve 16 has been shown as a stepped curve, but in reality is made up of a plurality of curves which have been shown connected by vertical lines.

Reference is now made to FIG. 2. This figure illustrates train or vehicular performance curves which result from the incorporation of the invention which is to be described more fully hereafter. FIG. 2a, which is positioned to the right of FIG. 2, illustrates a two-car married pair arrangement, and while not shown it is to be understood that each car has four propulsion modes of operation plus coast. The first of the five modes of operation which were illustrated in FIG. I is the coasting mode with both vehicles having their propulsion motors turned off, and this of course produces the dynamic braking mentioned with reference to FIG. 1. The second mode is that of the switching or inching mode represented in FIG. I, as well as FIG. 2 by the curve 1 1. The third mode is the low speed mode of operation represented by the curve 12 in both FIG. 1 and FIG. 2. The fourth mode of operation is that of medium speed operation depicted by the curve 13 in FIG. 1 and FIG. 2, and, the fifth mode of operation, of course, speed which is represented by the curve M in both FIG. 1 and FIG. 2.

At this point it should be kept in mind that today, transit systems are generally limited to one of these five modes of operation unless some solid state motor speed control has been added to give them an infinite variation of tractive effort over a given velocity change. But, as has been noted, this is very expensive. Therefore, it is in this environment that applicants invention emerges because it has been recognized that there are in fact more performance curves to operate on then previously recognized. This invention recognizes the fact that there are actually more train performance curves than there are train propulsion curves. In the past, because all propulsion motors were operated simultaneously in the same modes on all most rapid vehicles of a train, the propulsion curves which were shown in FIG. 1 also became the train performance curves. But this invention recognizes the fact that aside from the train propulsion curves there are other train performance curves for married pairs of propulsion units which may and will appear when one of the married pair of units is placed in one mode of operation and the other turned on into the same modeof operation or turned off to coast in accordance with the propelling effort required to maintain a constant velocity. For example, a married-pair propulsion curve 31, not present before, will appear when the car A of FIG. 2a is in its switching mode of operation and the car B is in its coasting mode of operation and therefore applying a dynamic braking. We can see that the curve 31 intersects the ordinate at approximately half the tractive effort shown by the switching curve 1]. Accordingly, we now have a train not available.

Similarly, the married-pair propulsion curve 32, not present before, will appear when the car A in FIG. 2a is in its series mode of operation and the car B is in its coasting mode of operation. We can see that married-pair performance curve 32 initially represents a little less than half the tractive effort that would appear were both cars A and B in series operation. The effect of dynamic braking in the train car B causes this curve 32 to be less than half the tractive effort than when both cars A and B are in the series mode of operation shown by performance curve 12.

Similarly, the married-pair propulsion curve 34, not present before, will appear when the car A in FIG. 2a is in its seriesparallel mode of operation and car B is in its coasting mode of operation. Married-pair performance curve 34 initially represents a little less than half the tractive effort (due to dynamic braking) that would appear were both cars A and B in series-parallel operation.

Finally, the married-pair propulsion curve 38, not present before, will appear when the car A in FIG. 2a is in its seriesparallel with shunted field mode of operation and car B is in its coasting modeof operation. Married-pair performance curve 38 initially represents a little less than half the tractive effort that would appear were both cars A and B in series-parallel with shunted field operation.

In view of the above discussion, it should now be readily apparent that there are actually available a greater number of performance curves than heretofore recognized. In fact, we see in this particular embodiment a total of eight performance curves plus a ninth coasting curve, not shown, which may be contrasted to five performance curves which were available in the prior art arrangements. This means that if there is prois that of the high performance curve heretofore vided a means to jump from curve to curve, as shown in FIG. 2, the operator of such a train would then be able to select a train performance curve which most nearly approximated the tractive effort necessary to balance the train resistance as shown by train resistance curve 17. This ability, of course, will allow the maintenance of a relatively constant velocity free from the inherent necessity to apply large amounts of tractive effort to bring the train back up to speed once the train has slowed to some preselected velocity error. In fact, while this description has been directed to the situation where there is one married pair of cars A and B employed, it must be recognized that any number of married pairs may be employed. At this point it should also be understood that, while the description up to this point has been of typical train cars having four propulsion motors, it is intended that the four propulsion motors of each can be recognized basically as a propulsion unit, having different modes of operation.

The invention, of course,is not to be limited to the situation where there are only four propulsion motors employed, but is to be extended to wherever there is a married pair of propulsion units or motors each having more than one mode of operation. Therefore, all descriptive material hereafter will refer to propulsion motors as propulsion units and reference will be made to the different modes of operation of propulsion units rather than going into the detail of noting that these propulsion units have in this preferred embodiment a number of separate propulsion motors within the propulsion motor units.

As may well be appreciated from the recent study of FIG. 2 and FIG. 2a, there is the presence of a multiple of married-pair train performance curves that may be utilized in the operation of the train. For purposes of illustrating the invention, only the curves 31, ll, 32, and 12, shown in FIG. 2, will be treated as it is quite apparent that the invention when explained in this environment will make obvious the added structures and circuits that would be necessary to cover the full range of available performance curves that are established by the incorporation of this invention. Accordingly, all discussion hereafter will be directed to a system which is functioning between the curve 31 and the curve 12 shown in FIG. 2.

With specific reference to FIG. 3, only the four above-noted curves have been illustrated along with dynamic braking curve 16. It is the environment of FIG. 3 where the married-pair train performance curve selection will take place and to which the descriptions of FIGS. 4, 5 and 5a are tied for purposes of function operation.

Reference is now made specifically to FIG. 3 which illustrates the married-pair train propulsion performance curves of a train having at least one married-pair of propulsion units where each propulsion unit is considered to have only three modes of operation. The first is the coasting mode which is represented by the stepped curve 16. The second is depicted by the curve 11, which has been termed the switching curve, and the third mode of operation is the series operation married-pair train propulsion curve 12. Curves 31 and 32 are generated whenever car A of FIG. 2a is in its switching mode and car B is in its coasting mode, and whenever car A of FIG. 2a is in its series mode and car B is in its coasting mode, respectively. Superimposed on FIG. 3 are two additional curves not shown in FIG. 2. These curves are train resistance curves 17a and 17b. It will be noted that these curves appear in a relatively parallel relationship to train resistance curve 17, and it is intended that these curves 17a and 17b represent different grades upon which the vehicles are operating. Accordingly, the train resistance curve moves upward towards 17a when an increasing grade is being approached, and this train resistance curve would fall below curve 17 should the train be moving on a decreasing grade. Curve 1712 reflects the change in position of the train resistance curve should the train approach a decreasing grade.

Before entering the discussion of the meaning of the curves of FIG. 3, it would be well to point out in advance the desired pattern of train operation that is to be explained by this series of curves. Here, for example, if a selectable speed of 15 miles per hour were preselected, then it would be desirable for the train to start from zero or the standing position and move at the maximum rate of acceleration possible up until approximately 15 miles per hour. In order to prevent overshooting the 15 mile per hour mark and reaching an overspeed condition which would require the application of brakes, it has been arbitrarily selected to reduce the tractive effort applied when the train is approximately 1 mile per hour below the set or desired speed of 15 miles per hour. This hopefully would, in some situations, depending upon grade, allow the train to come up to the set speed and the propulsion effort would just balance the train resistance force and the desired speed of 15 miles per hour would be maintained. But thisis a rare situation and more than likely will be only infrequently encountered. Once the speed of 15 miles per hour is reached it is, of course, important to automatically reduce the tractive effort to zero and then start what will be described as a search of the existing married-pair train propulsion and performance curves for a curve which nearly matches the train resistance at the given velocity. Once this matching is accomplished, the train will then stay on the trainperformance curve which most closely approximates the tractive effort necessary to maintain the speed of the vehicle close to the set speed desired, in this case 15 miles per hour.

With this thought in mind, attention is directed to FIG. 3. When the train starts from zero, the tractive effort presented to the wheels is-represented by the married-pair train. performance curve 11. The vehicle would then, in its operation, move down along the curve 11, which is called the inching curve, to a point where arrow 27 interrupts this curve. At this point, due to the inherent characteristics of a current limiting relay, typically in the system, there would be an automatic subtraction of resistance from the propulsion units causing the motors to move to a new incremental resistance curve 18, and then after a suitable change invelocity there would be another shift, as indicated by the arrow 28 to the incremental resistance curve 19, and again on change in velocity, another shift to a higher curve 21, as indicated by the arrow 29.

Finally, in the last step, with the train operating along the curve indicated by the reference numeral 21, the train would then shift onto the married-pair train performance curve 12 via the previously mentioned curve 22.

v The train would then proceed down along the married-pair train performance curve 12 to a point 61, which point 61 can be seen to be directly above the 14 mile per hour indication shown on the abscissa. At that point the train would reduce its tractive effort by one half. This would be accomplished by maintaining the first car of the married-pair in series operation and permitting the second car of the married-pair to be in its .coast operation. This would cause the tractive effort at this point to drop, as shown by the arrow that starts at point 61, and go down to the curve 32 at point 61a. If the train resistance is represented by curve 17, the train operating point would move to the left along curve 32 to point 60 where a balance point is reached. If the train resistance is less the train will continue to accelerate to the point 62 along the curve 32 at which point 62 the set speed having been reached the tractive effort would drop to coast, i.e., minimum dynamic brake, which is at point 64 on curve 16. It is apparent that with the tractive effort negative and the train resistance curve 17 positioned where it is, the load on the train and its inherent resistance will result in the train decelerating.

As the train decelerates the curve selection process will take place. It will be seen that when the vehicle has reached its set speed of 15 miles per hour or zero velocity error, deceleration will begin occurring from point 64 until the train reaches a velocity error of minus one (1) mile per hour, or 1 mile per hour below set speed. This error is shown at point 65 on curve 16, at this velocity error the train will continue to decelerate due to the fact that the train resistance curve 17 is greater than the tractive effort provided by the propulsion effort afiorded by the train operating on married-pair train performance curve 31. The train propulsion control logic and propelling effort control means to be described hereafter would then select married-pair train performance curve 31 and point 66 thereon, whereupon the curve 31 would be followed back to point 67 which is representative of a minus two (-2) miles per hour velocity error. Here again, since the tractive effort is insufficient to balance the train resistance as represented by curve 17, a continued deceleration would be experienced, and to cope with this, the propelling effort control means would actuate the propulsion unit of car B of FIG. 2a into its switch mode, while car A of FIG. 2a would be actuated into its switch mode by the propulsion control logic, married-pair train performance curve 11 being selected thereby, and as the arrow indicates there would be a move from point 67 on curve 31 to point 68 on curve 11. Again, since the tractive effort is insufficient to balance the train resistance as represented by curve 17, continued deceleration would be experienced, and the propelling effort control means would actuate the propulsion unit of car B of FIG. 2a into its coast mode, while car A would be actuated into its series mode by the propulsion control logic, married-pair performance curve 32 being selected thereby, and as the arrow indicates there would be a move from point 69 on curve 11 to point 70 on curve 32 at a speed error of minus three (-3) miles per hour. Here it will be noted that for the first time at point 69 on curve 32 the tractive effort available is greater than the train resistance shown by curve 17. Accordingly, follow married-pair train performance curve 32 from point 70, as indicated by the arrow down to point 60 where the tractive effort will just balance the train resistance. If the grade remains constant, the train will proceed at a constant speed with just slightly more than 1 mile per hour velocity error. It should be understood that while the set speed of 15 miles per hour is desirable, it is permissible to have errors on the order of /z to 4 miles per hour. These errors are quite acceptable as long as the train maintains the given error without significant variation in velocity.

There is a further feature that should be recognized at this point and that is, as shown in the figure, there are superimposed on this graph two additional curves 55 and 56 which are in reality portions of curves. These curves 55 and 56 are meant to reflect the fact that when a train is operating on the married-pair train performance curve 32, the second car of the married-pair combination will be coasting. With a car coasting, the propulsion motors are operating in a dynamic braking manner as these motors are driven in generator fashion. At this point it should be understood that when a car is in a coast operation, the dynamic braking that takes place varies depending upon the velocity and the amount of resistance being switched automatically into the motor winding arrangement to prevent overloading due to the generator action. Accordingly, the coasting car presents a varying dynamic force which varies as a function of train speed or as a result of the resistance being added or subtracted. It is this varying load effect of the coasting car which is intended to be conveyed by the curves 55 and 56, which in effect are added to the train resistance at that given velocity. In other words, since the second car of the married-pair is dynamically braking at increasing or decreasing amounts, depending upon the resistance being provided by the dynamic braking, the curve 17 will actually experience a fluctuation which will move in a range defined by the curves 55 and 56, and by so doing it will cause the overall train operation to float back and forth across the train resistance curve 17 and provide a dynamically fluctuating situation in which the tractive effort will continuously balance the train resistance load required to maintain the train at any given speed with a minimum of acceleration and deceleration.

Returning now to the system operation and a further study of the curves of FIG. 3, while the discussion up to this point has been directed to that situation where the train resistance curve 17 has been principally considered, it should be recalled that curves 17a and 17b also show train resistance curves that reflect respectively the tractive effort necessary when a train is on an increasing grade and a decreasing grade relative to curve 17.

In the functional description of a train coming up to a set speed of 15 miles per hour with train resistance curve 17 in mind no mention was made of train resistance curve 17b. Should train resistance curve 17b have been the curve under consideration, then the train would have proceeded, functionally speaking that is, to hunt over the performance loop defined by the points 62, 64, 65, 66, 67, 68, 69 and 70. It should be noted that this is a smaller loop in area in comparison to the prior art loop shown in FIG. 1 and defined therein by point 20, line 25, point 24, line 23, and curve 12. We return now to an expanded discussion of FIG. 3, and particularly the occurrence of events should the train continue to decelerate from point 70. In the event that the train resistance curve was even higher than curve 17a, namely, above the point 70 on curve 32 and below the point 76 on curve 12, then when the train would be experiencing a continued deceleration from point 70 on curve 32, the train would continue on married-pair train performance curve 32 until it reached point 71. At point 71 there would be a velocity error of minus four the train will begin to accelerate and the train will (-4) miles per hour and the propelling effort control means would actuate the propulsion unit of car B of FIG. 2a into its series mode, while propulsion unit of car A in FIG. 2a would be maintained in its series mode by the propulsion control logic and, once again, married-pair train performance curve 12 would be selected at point 76. There would then be sufficient tractive effort to overcome the trains resistance and there would be a halt to deceleration. The train would then accelerate up to the point 61 on curve 12, at which point the velocity error would be minus one (-1) mile per hour and, as noted earlier, the propulsion control logic and propelling effort control means would select married-pair train performance curve 32 and move from point 61 to point 610. The train would then hunt over the loop defined by points 61, 61a, 70, 71, and 76. The selection of the married-pair train performance of FIG. 3 has been tailored to the circuits and apparatus described in FIGS. 4, 5 and 5a.

Reference is now made to FIG. 4 which illustrates a preferred embodiment of the invention in blockdiagram form. In this embodiment and the one depicted in FIGS. 5 and 5a, only three modes of operation are considered to be present in each of the married-pair of propulsion motors depicted in order that the curves set forth in FIG. 3, which show the capability of moving from married-pair performance curved to married-pair performance curve, be employed to point out how the invention may be readily involved in any multi-married-pair propulsion unit system. Specifically, FIG. 4 shows a car A and a car B having respectively married propulsion units 81 and 82. The cars A and B travel along rails 83 and 84 and receive power for the married-pair of propulsion units from third rail 86 via contact 87 and lead 88, which enters the married-pair performance curve selection logic, and which in conjunction with propelling effort control means 91 provides performance curve selection to be described more fully hereafter.

There is shown leaving the married-pair performance curve selection logic four lines, three of which are train lines to which the propulsion units 81 and 82 are either directly or indirectly electrically coupled. These three lines are the leads 170, 172, and 173. Propulsion unit 81 of car A is directly coupled to leads 170, 172, and 173 respectively via leads a, 172a, and 173a and propulsion unit 82 of car 13 is indirectly controllably coupled to leads 170, 172 and 173 through propelling effort control means 91 which is electrically coupled to propulsion unit 82 via leads 170e, 1720 and 1730, respectively. A fourth line leaving married-pair performance selection logic 80, or lead 167, electrically controllingly coupled married-pair performance curve selection logic 80 to propelling effort control means 91, which controls actuation of particular modes in propulsion unit 82 of car B.

There has been designated by the legend to the left of the dotted outline portion the title Propulsion Control Logic",

also referred to by numeral 95. This propulsion control logic 95 includes, immediately beneath the'propulsion unit 81 and shown in schematic form, a train speed tachometer 98 which has a driving connecting link, shown by dotted line 97, connected to a wheel 96 of car A. This rotating input 97, or driving link, will provide the train speed tachometer 98 with a rotary input that will be converted into a DC output which isa conventional output for this type of tachometer. The DC output will appear on lead 99, and have a direct relationship to the velocity at which the train cars are traveling. Immediately beneath the train speed tachometer 98, and also a portion of the' propulsion control logic 95, is a .train speed command control 100. It will be seen in this block 100 that there are a number of circular shaped buttons designated by their markings l0, 15, 2O, 25, 30 and 35 miles per hour. In operation, this train speed command control unit 100 would be normally located in the lead vehicle, in this case car A, and the selected speed would be made by pushing one of the buttons just noted which would produce an output on lead 101, which in turn would be delivered to the actual speed versus command speed comparator 102, which has, as has been noted, the lead 99 from the train speed tachometer 98, also entering it. It will be noted that selection of a set speed may also be accomplished via wayside cab signaling, but for purposes of illustration the present type of selection is incorporated.

The output signal which would appear from this conventional voltage comparator would be a DC signal indicative of the velocity error as a measure of the different in voltage that exists between the train speed command and actual speed at which the train is moving as has been measured by the train speed tachometer 98. This DC signal will be delivered over the electrical lead 111 to a velocity error detection network 110. This velocity error detection network 110 also receives as an input the output from train speed command control unit 100 over leads 101 and 101a. The reception of the command speed on these leads will control the number of propulsion unit operating modes to be employed in the married-pair performance curve selection logic. It has been assumed for purposes of illustration'of the invention that the command speed on leads 101 and 101a will be such that only the three previously stated modes of propulsion unit operation will be employed. Accordingly, the velocity error detection network 110 will, depending upon the velocity error and required tractive or propelling effort to overcome that error, provide one or more outputs which are preferably electromagnetic outputs designated by arrows 112a through 112f which will in turn be delivered to the married-pair performance curve selection logic 80, which, as was noted with reference to FIG. 3, in conjunction with propelling effort control means 91, will cause, depending upon the velocity error present, a selection of a train performance curve that ultimately will balance the train resistance with a tractive effort sufficient to maintain a con stant velocity, or cycle between modes to maintain average speed.

Reference is now made to FIGS. 5 and 5a which will be studied in conjunction with FIG. 3, previously discussed. The alignment of these FIGS. 5 and 5a is shown in FIG. 6. FIGS. 5 and 5a contain a circuit illustration of one embodiment of the invention which sets forth the manner in which the marriedpair train performance curves, noted earlier, may be selected as the train moves in a dynamic fashion up to a preselected speed. Shown in FIG. 5 is the train consisting of married cars A and B having married propulsion units 81 and 82 respectively. The train is traveling on rails 83 and 84 and receiving power from a third rail 86, over contact 87 via lead 88 to the married-pair performance curve selection logic 811 in FIG. 5a which has three output leads 170, 172, and 173 directly coupled to propulsion unit 81 of car A over leads 170a, 172a, and 173a, and indirectly coupled to propulsion unit 82 of car B through contacts a, b, and c of relay X and respectively, leads 1700, 172s, and 1730. The contacts a, b, and c and relay X comprise the propelling effort control means 91. Relay X is labeled the X relay. Output lead 167 of married-pair performance curve selection logic controls the energization and deenergization of the X relay which, in turn, controls the opening and closing of contacts a, b, and c all of which are hereafter. Further in the case of propulsion unit 81, or the primary propulsion unit of the married-pair of propulsion units 81 and 82, whenever lines 172 and 173 are energized propulsion unit 81 will be in its series mode of operation. Whenever line 173 only is energized propulsion unit 81 will be in its switch mode of operation. Finally, if neither line 170, 172, or 173 is energized then propulsion unit 81 will be in its coast mode of operation.

In the case of propulsion unit 82 of car B, or the secondary propulsion unit of the married-pair of propulsion units 81 and 82, whenever line 167-is energized, thereby energizing the X relay of propelling effort control means 91 and closing contact a, b and c of the X relay, and simultaneously lines 170, 172, and 173 are energized, propulsion unit 82 will be in its series-parallel mode of operation. Once again, it will be noted that for purposes of illustration energization of line 170 will be locked out and the series-parallel mode will not be employed in the description of the preferred embodiment. Further in the case of propulsion unit 82, whenever line 167 is energized, thereby energizing the X relay and closing its contact a, b, and c and lines 172 and 173 are energized, propulsion unit 82 will be in its series mode of operation. Whenever lines 167 and 173 only are energized propulsion unit 82 will be in its switch mode of operation. If neither line 170, 172, or 173 has power, then propulsion unit 82 will be in its coast mode of operation. Finally, if line 167 is.not energized, the X relay will not be energized and contacts a, b, and c of the X relay will be opened allowing no power to propulsion unit 82 and causing propulsion unit 82 to be in its coast mode of operation.

Each of lines 167,170, 172, and 173 is energized in accordance with the circuit operation of the married-pair performance curve selection logic 80. It will be seen from FIGS. 5 and 5a that power is delivered to the married-pair performance curve selection logic 80 from third rail 86 over contact 87 and lead 88. Line 167 to the X" relay of propelling effort control means 91 may be energized in one of two ways, i.e., there are two paths of energization provided for the energization of line 167. The first is from the third rail 86 over contact 87 and lead 88, lead 151, front contact Z2 of the relay Z included in the velocity error detection network 110, to be described more fully hereafter, front contact B2 of relay B included in the velocity error detection network 110, lead 156, front contact SP2 of the relay SP included in the velocity error detection network 110, lead 169, front contact P2 of the relay P included in the velocity error detection network 110, lead 188, lead diode 202 to lead 167. The second path of energization for the line 167 to the X relay of propelling effort control means 91 is from the third rail 86 over contact 87 and lead 88, front contact Z2 of relay Z, front contact B2 of relay B, lead 154, back contact SP1 of relay SP, included in the velocity error detection network 110, lead 158, lead 165, front contact S2 of relay S, included in the velocity error detection network 110, lead 181, lead 184, to line 167.

Line 170, as previously noted, will never be energized in this description due to the fact that back contact L02 of the lockout relay LO, included in the velocity error detection network, will remain open through the selection operation, i.e., relay will remain deenergized for reasons to be explained hereafter.

There are also two possible paths of energization for the line 172, keeping in mind that back contact L01 of the relay LO from contact Z2 of relay Z, front contact B2 of relay B, lead 156, front contact SP2 of relay SP, lead 169, front contact P2 of relay P, lead 188, diode 201, diode 204 to lead 172.

There are three possible paths of energization for the line 173. The first is from third rail 86 over contact 87, lead 88, lead 151, front contact Z2 of relay 2, front contact B2 of relay B, lead 154, back contact SP1 of relay SP, lead 158, lead 163, back contact S1 of relay S, lead 180, to line 173. The second path of energization for line 173 is from third rail 86 over contact 87, lead 88, lead 151, front contact Z2 of relay Z, front contact B2 of relay B, lead 154, back contact SP1 of relay SP, lead 158, lead 165, front contact S2 of relay S, lead 181, diode 200, lead 182, to line 173. Finally, the third possible path of energization for the line 173 is from third rail 86 over contact 87, lead 88, lead 151, front contact Z2 of relay Z, front contact B2 of relay B, lead 156, front contact SP2 of relay SP, lead 160, lead 166, back contact P1 of relay P, lead 187, diode 204, diode 207, to line 173.

The coast mode for both cars A and B is achieved whenever relay Z of velocity error detection network 110 is energized thereby causing back contact Z1 to close and-front contact Z2 to open, producing an open circuit condition such that no power will reach either of the lines 167, 170, 172 and 173.

Also shown protruding from the velocity error detection network 110 is a lead 145 to a brake control circuit which brake control circuit will be actuated whenever the train, consisting of cars A and B, reaches an overspeed condition, ar-

bitrarily selected to be /2 mile per hour velocity error. The energization path for lead 145 to the brake circuit extends from third rail 86 over contact 87, lead 88, lead 150, back contact Z1 of relay Z, back contact B1 of relay B, lead 145 to the brake control circuit. It will be noted that due to orientation of contacts B1 and B2 of relay B and contacts Z1 and Z2 of relay Z, brake and propulsion will never occur simultaneously.

A description of the velocity error detection network 110 and the energization and/or deenergization of the relays LO, X, SP, P, S and B will now ensue-Shown also in FIG. 5 is the actual versus command speed comparator 102 which receives as inputs the actual train speed on lead 99 from train speed tachometer 98 and the preselected command speed on lead 101 from train speed command control 100. These speed indications on the leads 99 and 101 enter conventional speed error amplifier A1 through current limiting resistors R1 and R2 respectively. In the feedback path of amplifier A1 there is shown a large capacitor C in parallel with a resistor R to prevent rapid changes in value and compensate for noise effects on amplifier Al. Zener diodes D1 and D2 limit amplifier voltage within a permissible range. A parallel output from the train speed command control 100 on lead 101a conveys the set speed to one input of a conventional amplifier A2 which along with feedback resistor R8 and a second input from potentiometer PR7 comprises a lock out comparator incor* porated to prevent the use of series-parallel operation modes for propulsion units 81 and 82 at very low speeds. The output of comparator A2 is delivered to the base electrode of conventional N-P-N transistor Q1 through base current limiting resistor R9. The potentiometer PR7 is set at such a value so as not to allow the comparator A2 to produce an output whenever the input on lead 101a is representative of a set speed below a predetermined lock out speed, i.e., if the set speed is below the predetermined lock out speed the output of amplifier A2 will be negative and the transistor 01 will be in a nonconducting state thereby rendering transistorQ7, in the lock out relay circuit nonconducting and deenergizing lock out relay L0. The deenergization of lock out relay LO will cause tion of relay P. Upon energization back contacts L01 and L02 located in the married-pair performance curve selection logic to be opened. As was previously noted, the description of the preferred embodiment of the invention in FIGS. 5 and 5a will be limited to a situation in which the set speed, 15 miles per hour being chosen, appearing on input lead 101a to amplifier A2 will be one below a predetermined lock outspeed, arbitrarily chosen at 17 miles per hour, and lock out relay LO will remain deenergized throughout the married-pair performance curve selection operation, i.e., the series-parallel mode of operations for propulsion units 81 and 82 will not be incorporated into the present description. 7

The output of the comparator amplifier A1 of the actual speed versus command-speed comparator 102 appears across the resistor R6. A portion of the voltage across resistor R6 is tapped by the velocity error detection network as shown in FIG. 5 and appears on lead 111. Shown within the velocity error detection network 110 is a series of comparator circuits for receiving the output of comparator amplifier A2 on lead 111 and respectively controlling the energization and deenergization of relays Z, SP, P, S, and B. The amplifier comparator circuit for the energization and deenergization of relay S, including amplifier A6 is substantially the same configuration as was the case with respect to the amplifier comparator circuit for the lock out relay L0. The amplifier comparator circuits for the energization of relay Z, SP, P, and B and respectively including amplifier comparators A3, A4, A5 and A7 only differ from the amplifier circuits for energization and deenergization of relays L0 and S in that an additional potentiometer is included in each of them, namely, potentiometer POTl, POT2, POT3, and POT4 respectively through back relay contacts Z3, SP3, P3, and B3 respectively. Otherwise resistors R12, R13, R15, R16 and R17, transistors 02 and O8 in the circuit for the energization and deenergization of relay Z, resistors R19, R20, R22, R23, and R24, transistors 03 and O9 in the circuit for the energization and deenergization of relay SP, resistors R26, R27, R29, R30, and R31, transistor Q4 and Q10 in the circuit for the energization and deenergization of relay P, andresistors R40, R41, R43, R44, and R45, transistors 06 and Q12 of the circuit for the energization and deenergization of relay B all perform the same type functions as resistors R3, R8, R9, R10, and R11, transistors Q1 and Q7 in the circuit for the energization and deenergization of relay L0, and resistors R33, R34, R36, R37, and R38 and transistors 05 and Q11 in the circuit for the energization and deenergization of relay S do. Further, diodes 500,501, 502, 503,504 and 505 are incorporated in their respective circuits to provide field shunting to prevent inductive transient voltage spikes and protected respective transistors associated therewith. Resistors R1 1c, R18, R25, R32, R39 and R46 are incorporated in their respective circuits to match relay voltages with required polarity.

The potentiometers POTl, POT2, POT3 and POT4 add hysteresis to their respective circuits in a predetermined fashion such that the corresponding relays 2, SP, P, and B will be energized at given preselected speed errors (referred to earlier as lower states) whenever the vehicle carrying propulsion units 81 and 82 are accelerating, and de'energized at different preselected speed errors whenever the vehicle is decelerating. For example, with reference to energization and deenergization of relay P, should the train be accelerating towards the set speed, or zero speed error, at a speed error of minus one (-1) mile per hour, or one (1) mile per hour below set speed, the potentiometer PR28 is set such that the output of amplifier A5 will go positive thereby causing the energizaof relay P, back contact P3 of relay Pwill close thereby adding the value at which potentiometer POT3 is set in combination with that of potentiometer PR28. The combined effect of potentiometers PR28 and POT3 will be such that relay P amplifier A5 will produce no output until a speed error of minus four (-4) miles per hour or four (4) miles per hour below set speed when the train is decelerating is attained. Similarly, with reference to the energization and deenergizawill not be deenergized, i.e.,

tion of relay Z, should the train be accelerating towards set speed, at the set speed, or zero speed error, potentiometer P1114 is set such that the output of amplifier A3 will go positive thereby causing the energization of relay Z. Upon energization of relay Z, back contact Z3 of relay Z will close thereby adding the value at which the potentiometer POTl is set in combination with that of potentiometer PR14. The combined effect of potentiometers -PR14 and POTl will be such that relay Z will be deenergized at a speed error of minus one (I) mile per hour or one (l)mile per hour below set speed when the train is decelerating.

Similarly, with reference to the energization and deenergization of relay SP, should the train be accelerating towards set speed, at the set speed, or zero speed error, potentiometer PR21 is set such that the output of amplifier A4 will go positive thereby causing the energizationof relay SP. Upon energization of relay SP, back contact SP3 of relay SP will close thereby adding the value at which the potentiometer POT2 is set in combination with that of potentiometer PR21. The combined effect of potentiometers PR21 and POT2 will be such that relay SP will be deenergized at a speed error of minus three (3) miles per hour or three (3) miles per hour below set speed when the train is decelerating.

Similarly, with reference to the energization and deenergization of relay B, should the train be accelerating and overshoot set speed at a speed error of 7% mile per hour or /2 mile per hour above set speed, potentiometer P42 is set such that the output of amplifier A7 will go positive thereby causing the energization of relay B. Upon energization of relay B, back contact B3 of relay B will close thereby adding the value at which potentiometer POT4 is set in combination with that of potentiometer PR42. The combined effect of potentiometers PR42 and POT4 will be such that relay B will be deenergized at a speed error of miles per hour, or the set speed when the train is decelerating.

With reference to the energization and deenergization of relay S, potentiometer PR3S is set such that the output of amplifier A6 will go positive at a speed error of minus two (2) miles per hour when the train is accelerating, and when the train is decelerating will go negative at a velocity error infinitesimally numerically greater than minus two (2) miles per hour.

SYSTEM OPERATION Considering FIGS. and 5a and the systems functional operation set forth in FIG. 3, let us assume that a desired velocity for the train including married vehicles A and B is miles per hour, in order to better understand the circuitry set forth within the propulsion control logic 95. At this point in the description it is reiterated that selection ofa 15 mile per hour speed limit is intended only to be illustrative of the function of one embodiment of the invention. Accordingly, the 15 mile per hour button 103 of the train speed command control unit 100 is pushed, or activated and a circuit is completed to deliver a signal representative of a 15 mile per hour desired speed to the actual speed versus command speed comparator 102 over lead 101. It should be noted at this time that each of the commands for the set speeds of l0, 15, 20, 25, 30 and 35 miles per hour has respectively electrical connections, not shown, to lead 101 and the actual speed versus command speed comparator 102. Hence, assuming a speed of 15 miles per hour is desired, a signal indicative of the desired speed of 15 miles per hour is present on lead 101 and is delivered to actual speed versus command speed comparator 102 along with the signal on lead 99 from the train speed tachometer 98 indicative of train velocity which we will consider to be initially 0 miles per hour. Since the speed of 15 miles per hour has been selected and is below arbitrarily selected lock out speed of 17 miles per hour, the signal indicative of the desired 15 miles per hour speed on lead 1010 to amplifier A2, the comparator circuit for the energization and deenergization of lock out relay LO, will not be enough to overcome the effect of potentiometer PR7 at the other input of amplifier A2, and hence, the output of amplifier A2 will not go positive and relay LO remains deenergized. The effect, of course, is that back contacts L01 and L02 of relay LO will remain open and the series-parallel mode of operation for either of married cars A or B will not be employed due to the fact that no energization path is provided for the line 170, the energization of which is required for series-parallel operation. Since, initially the actual train speed is zero, i.e., a speed error of -15 miles per hour or 15 miles per hour below set speed is encountered, the output of amplifier A1 of the actual speed versus command speed comparator 102 will go positive, a signal appearing-on output 111 of amplifier Al indicative of a 15 mile per hour speed error and a portion of this signal will be tapped from resistor R6 to lead 111 and to the velocity error detection network 110. All of the potentiometers PR14, PR21, PR28, PR35, and PR42 input respectively to amplifiers A3, A4, A5, A6 and A7 are set such that their respective amplifiers produce no outputs and relays Z, SP, P, S, and B will not be energized. Accordingly, back contacts Z1 and Z3 of relay Z,

B1 and B3 of relay B, SP1 and SP3 of relay SP, S1 of relay S and P1 and P3 of relay P will remain open, while front contacts Z2 of relay 2, B2 of relay B, SP2 of relay SP, P2 of relay P, and S2 of relay S will remain closed. With these contacts in their respective positions at the speed error of -15 miles per hour, referring to married-pair performance curve selection logic 80, a circuit will be completed from third rail 86 over contact 87, lead 88, lead 151, front contact 22 of relay Z, front contact B2 of relay B, lead 156, front contact SP2 of relaySP, lead 160, lead 169, front contact P2 of relay P, lead 188, diode 201, diode 204, to line 172 thereby energizing line 172. A circuit will also be completed from third rail 86 over contact 87, lead 88, lead 151, front contact Z2 of relay Z, front contact B2 of relay B, lead 156, front contact SP2 of relay SP, lead 160, lead 169, front contact P2 of relay P, lead 188, diode 201, diode 204, diode 207, to line 173 thereby energizing line 173. Hence, with lines 172 and 173 energized propulsion unit 81 of car A is placed into its series mode of operation. A circuit is also completed from third rail 86 over contact 87, lead 88, lead 151, front contact Z2 of relay Z,

front contact B2 of relay B, lead 156, front contact SP2 of relay SP, lead 160, lead 169, front contact P2 of relay P, lead 188, lead 190, diode 202, to line 167 thereby energizing line 167 and accordingly energizing the X relay of propelling effort control means 91 causing contacts a, b, and c of the X" relay to close and allow lines 172 and 173 to place propulsion unit 82 of car B in its series mode of operation, line not being energized. Since both propulsion units 81 and 82, cars A and B respectively are in their series modes of operation they provide a combined tractive effort which is reflected by the train propulsion and performance curve 12 of FIG. 3.

A study of FIG. 3 will reveal that once the cars A and B of the married pair are commanded into their series modes of operation, the automatic nature of the existing married pair of propulsion units or motors comes into effect and the train initially will attempt to follow the performance curve 11, which is the switching curve. A CHANGE IN VELOCITY WILL AUTOMATICALLY CAUSE THE INCREMENTAL ADDI- TION OR SUBTRACT ION OF RESISTANCES TO THE WINDINGS OF THE PROPULSION UNITS 81 and 82 to allow, as has been described earlier, the married-pair to move along at a maximum acceleration rate up to the curve 12.

Therefore, the train will continue to accelerate as the tractive effort presented by the married-pair performance curve 12 is greater than the train resistance as illustrated by the train resistance curve 17. The trains velocity accordingly, will increase toward the set speed of 15 miles per hour and follow the curve 12 downwardly to the point 760 on the curve 12, which is at a speed error of minus two (2) miles per hour and decreasing numerically. The potentiometer PR35, input to amplifier A6 in the circuit for the energization and deenergization of relay S in velocity error detection network 110, is set such that the output of amplifier A6 will go positive at a velocity error of minus two (-2) miles per hour when the train is accelerating and relay S will be energized thereby closing back contact S1 of relay S and opening front contact S2 of relay S. Due to potentiometer PR35 relay S will remain energized until a speed error infinitesimally numerically greater than minus two (-2) miles per hour is encountered when the train is decelerating. However, since back contact SP1 of relay SP remains open, there will be no effective change in train performance and the train will continue along curve 12 until it reaches point 61 on curve 12. When the point 61 on curve 12 is reached at the arbitrarily selected velocity error of minus one (1) mile per hour, the potentiometer PR28 input to amplifier A in the circuit for the energization and deenergization of relay P, is set such that the output of amplifier A5 will go positive thereby causing the energization of relay P and accordingly, the closing of back contacts P1 and P3 of relay P and the opening of front contact P2 of relay P. The closing of back contact P3 now allows the combining of potentiometers POT3 and PRZS to add-hysteresis to the circuit for energization and deenergization of relay P, the effect being that relay P will not deenergize until a velocity error of minus four (-4) miles per hour is reached when the train decelerates. The closing of back contact P1 of relay P and opening of front contact P2 of relay P causes a change in energization paths in the married pair performance curve selection logic 80. A path for the energization of line 172 is still maintained from third rail 86 over contact 87, lead 88, lead 151, front contact Z2 of relay Z, front contact B2 of relay B, lead 156, front contact SP2 of relay SP, lead 160, lead 166, back contact P1 of relay P, lead 187, diode 204, to line 172. A path for the energization of line 173 is also still maintained from third rail 86 over contact 87, lead 88, lead 151, front contact Z2 of relay Z, front contact B2 of relay B, lead 156, back contact SP2 of relay SP, lead 160, lead 166, back contact P1 of relay P, lead 187, diode 204,

- diode 207, to lead 173. Hence, since lines 172 and 173 remain energized, propulsion unit 81 of car A remains in its series mode of operation via leads 172a and 173a. However, because of the opening of from contact P2 of relay P, and the direction of diode 201, power to line 167 will now be cut off thereby causing the deenergization of the X relay of the propelling effort control means 91 and the opening of contacts a, b, and c of the X relay. Hence, with the opening of contacts a, b, and c of the X relay, no power whatsoever reaches propulsion unit 82 of car B and car B is now in its coast mode of operation. With car A in its series mode of operation and car B in its coast mode of operation, the tractive effort of the married pair of cars is decreased by approximately one-half so that the train will begin to follow married pair performance curve 32 at point 61a which indicates a minus one (-1) mile per hour velocity error.

The train now continues to accelerate to the zero velocity error, or set speed, corresponding to a point 62 on married pair performance curve 32. This, of course, presumes that the tractive effort afforded by the curve 32 exceeds the train resistance'which is'represented by the family of curves 17, 17a, and 17b. It should be kept in mind that the curves 17, 17a and 17b are dynamically fluctuating in their movement as grade and wind force act upon the train.

For purposes of illustration only the description that will ensue will assume for a brief moment that at this point in the description the inertia of the train will approach set speed at a lower rate, but that set speed will be reached. Accordingly, when zero velocity error is attained, the potentiometer PR14 input to amplifier A3 of the comparator circuit for the energization and deenergization of relay Z, is set such that at zero velocity error the output amplifier A3 will go positive thereby causing the energization of the relay Z and the closing of back contacts Z1 and Z3 of relay Z and the opening of front contact Z2 of relay Z. Also at zero velocity error, potentiometer PR21 input to amplifier A4 of the comparator circuit for the energization and deenergization of relay SP, is set such that the output of amplifier A4 will go positive thereby causing the energization of relay SP and the closing of back contacts SP1 and SP3 of relay SP and the opening of front contact SP2 of relay SP. The closing of back contact Z3 of relay Z combines potentiometer POT1 with potentiometer PRM as an input to amplifier A3 thereby adding hysteresis to the circuit for the energization and deenergization of relay Z. The effect of this added hysteresis will be such that relay Z will not be deenergized until a speed error of minus one (-1) mile per hour is reached when the train is decelerating. Similarly, the closing of back contact SP3 of relay SP combines potentiometer POT2 with potentiometer PR21 as an input to amplifier A4 thereby adding hysteresis to the circuit for the energization and deenergization of relay SP. The effect of this added hysteresis will be such that relay SP willnot be deenergized until a speed error of minus three (-3) miles per hour is attained when the train is decelerating. The closing of back contact Z1 of relay Z and opening of front contact Z2 of relay Z at zero speed error when the train is accelerating now causes an open circuit with respect to power entering married-pair performance curve selection logic since back contact B1 of relay B remains open and now front contact Z2 of relay Z is open. Hence, none of the lines 167, 170, 172, or 173 will be energized and both propulsion units 81 and 82 of cars A and B, respectively, will be in their coast modes of operation. With both cars A and B in their coast modes of operation, a dynamic braking effect will occur as well as decelerating effects due to train inertia. The train will now begin to follow the dynamic braking curve 16 at point 64. This dynamic braking curve 16 has been described in detail with reference to FIG. 3 and no further explanation will be entertained at this point in the description. Should the train continue to accelerate, for example, due to a sudden down grade, an overspeed braking will occur at a velocity error of mile per our, or 1% mile per hour above set speed. If this /2 mile per hour velocity error is attained, the potentiometer PR42, input to amplifier A7 of the circuit for the energization and deenergization of relay B, is set such that at /2 mile per hour velocity error the output of amplifier A7 will go positive thereby causing the energization of relay B and the closing of back contacts B1 and B3 of relay B and the opening of front contact B2 of relay B. The closing of back contact B3 of relay B combines potentiometer POT4 with potentiometer PR42 as an input to amplifier A7 thereby adding hysteresis to the circuit for the energization and deenergization of relay B. The effect of this added hysteresis will be such that relay B will not be deenergized until a zero speed error, or set speed, is attained when the train is decelerating. The opening of front contact B2 maintains the open circuit condition with respect to energization paths within the married pair performance curve selection logic 80 such that neither car A or B receives signals from the marriedpair performance curve selection logic 80. Keeping in mind that back contact Z1 of relay Z is still closed, the closing of back contact B1 of relay B completes a circuit from third rail 86 over contact 87, lead 88, lead 150, back contact Z1 of relay Z, back contact B1 of relay B, lead to a braking relay located on car A, thereby energizing the brake control circuit and causing a mechanical braking to prevent further overspeed of the train.

By the application of actual train brakes coupled with the ever present inherent dynamic braking when both cars A and B are in coast, the train begins deceleration along the curve 16 until it reaches, once again, the zero velocity error, or set speed indicated at point 65 on curve 16. Since, upon deceleration the train has once again reached zero velocity error, or set speed, relay B, as previously described, will now become deenergized thereby causing the opening of back contacts B1 and B3 of relay B and the closing of front contact B2 of relay B. The opening of back contact B1 of relay B will cause relay B to be deenergized thereby releasing the mechanical train brakes. Because contact Z2 of relay Z remains open, no paths of energization for lines 167, 170, 172, or 173 out of marriedpair performance curve selection logic 80 are present. Hence cars A and B are both in their coast modes of operation, the train now following dynamic braking curve 16 at point 64 which represents zero velocity error.

higher total tractive effort. Accordingly, at a velocity error of minus one (1) mile per hour, represented by point 65 on curve 16, relay Z will be deenergized due to the previously described added hysteresis to the circuit for the energization and deenergization of relay Z. Hence, back contacts Z1 and Z3 of relay Z will be opened and front contact Z2 of relay Z will be closed. Recalling that relays SP and S are still energized, an energization path will be completed from third rail 86 over contact 87, lead 88, lead 151, front contact Z2 of relay Z, front contact B2 of relay B, lead 154, back contact SP1 of relay SP, lead 158, lead 163, back contact S1 of relay S, lead 180, to line 173 thereby energizing line 173. Line 172 will not be energized because front contact SP2 of relay SP is open, back contact L01 of relay L is open, and also because of the direction of the diodes 200 and 207. Nor will line 167 be energized because front contact SP2 of relay S is open and because of the direction of diode 200. Hence, with line 173 being the only line to be energized, propulsion unit 81 of car A will be placed in its switch mode of operation via lead 1730. Since line 167 is not energized, the X relay of propelling effort control means 91 remains deenergized, and contacts a, b, and c of the X relay remain open. Accordingly, propulsion unit 82 of car B will remain in its coast mode of operation. Hence, with car A in its switch mode of operation and car B in its coast mode of operation, the train will now follow marriedpair performance curve 31, beginning at the point 66, which is located above the 14 mile per hour velocity shown in FIG. 3.

Should the train continue to decelerate, it will follow married-pair performance curve 31 until it reaches a point 67, directly above the 13 mile per hour velocity indication, or at a velocity error of minus two (2) miles per hour. Accordingly, at a velocity error infinitesimally to the left of minus two (-2) miles per hour, relay S will be deenergized due to the effect of potentiometer PR35 on the circuit for the energization and deenergization of relay S, as previously described. Hence, back contact S1 of relay S will be opened, and front contact S2 of relay S will be closed. Recalling that relay SP is still energized, an energization path will be completed from third rail 86 over contact 87, lead 88, lead 151, front contact Z2 of relay Z, front contact B2 of relay B, lead 154, back contact SP1 of relay SP, lead 158, lead 165, front contact S2 of relay S, lead 181, diode 200, lead 182, to line 173, thereby maintaining line 173 in an energized state. Line 172 will not be energized because back contact L01 of relay L0 is open and because of the direction of diode 207. However, an energization path for line 167 is provided from third rail 86 over contact 87, lead 88, lead 151, front contact Z2 of relay Z, front contact B2 of relay B, lead 154, back contact SP1 of relay SP, lead 158, lead 165, front contact S2 of relay S, lead 181, lead 184, to line 167. Since line 173 and not line 172 is energized, propulsion unit 81 of car A will continue to operate in its switch mode of operation via lead 173a. Further, because line 167 is once again energized, the X relay of propelling effort control means 91 will be energized thereby causing contacts a, b, and c of the X" relay to close, and with line 173 being the only other line to be energized, propulsion unit 82 of car B will be placed in its switch mode of operation via lead 1730. Both cars A and B being in their switch modes of operation, the train follows the next higher married-pair tractive effort curve, namely, married-pair performance curve 11, beginning at point 68 thereon in FIG. 3.

Should the train decelerate further, it will follow marriedpair performance curve 11 until a velocity error of minus three (3) miles per hour is reached as indicated by point 69 i on curve 11. Accordingly, at an error infinitesimally numerically greater than minus three (3) miles per hour, the previously described added hysteresis of potentiometer POT2 to the circuit for the energization and deenergization of relay SF will cause the deenergization of relay SP as previously noted. Hence, back contacts SP1 and SP3 of relay SP will be opened, while front contact SP2 of relay SP will be closed. With the closing of front contact SP2 of relay SP, recalling that relay P third rail 86 over contact 87, lead 88, lead 151, front contact Z2 of relay Z, front contact B2 of relay B, lead 156, front contact SP2 of relay SP, lead 160, lead 166, back contact P1 of relay P, lead 187, diode 204, to line 172 thereby energizing line 172. A circuit is also completed from third'rail 86 over contact 87, lead 88, lead 151, front contact Z2 of relay Z, front contact B2 of relay 13, lead 156, front contact SP2 of relay SP, lead 160, lead 166, back contact P1 of relay P, lead 187, diode 204, diode 207, to line 173 thereby energizing line 173. No path of energization is provided for line 167 because of open front contact P2 of relay P and also because of the direction of diode 201 and, therefore, line 167 will be deenergized. With the deenergization of line 167, the X relay of the propelling effort control means 91 will be deenergized causing contacts a, b, and c of the X relay to be opened. Hence, with energization of both lines 172 and 173, propulsion unit 81 of car A will be placed in its series mode of operation via leads 172a and 173a respectively. However, since contacts a, b, and c of the X" relay are opened, no power will reach propulsion unit 82 of car B and that unit will be placed in its coast mode of operation. Due to a higher tractive effort afforded by car A being in its series mode of operation and car B in its coast mode of operation, the train will now begin to follow married-pair performance curve 32 at the point 70 in FIG. 3.

It should be kept in mind that at any pointalong any particular married-pair performance curve, which the train is following, should the train be above the train resistance curve 17, as is point 70 on married-pair performance curve 32, the train will once again begin accelerating in accordance with the particular married-pair performance curve until it reaches a point where it may follow a lower married-pair performance curve due to a lower tractive effort requirement. But for purposes of illustration, let us assume that such an occurrence does not happen. In order to trace the remaining circuits, it will be presumed that the train resistance is greater than the tractive effort being supplied.

Accordingly, should the train further decelerate, it will follow along married pair performance curve 32, beginning from point 70, to a point 71, directly above the minus four (4) miles per hour. velocity error indication in FIG. 3. Accordingly, at an error infinitesimally numerically greater than minus four (4) miles per hour, the previously described added hysteresis of potentiometer POT3 to the circuit for the energization and deenergization of relay P will cause the deenergization of relay P as previously noted. Hence, back contacts P1 and P3 of relay P will be opened, while front contact P2 of relay P will be closed. With the closing of front contact P2 of relay P, and keeping in mind that at this point none of the relays LO, Z, SP, P, S, or B is energized, an energization path will be completed from third rail 86 over contact 87, lead 88, lead 151, front contact Z2 of relay Z, front contact B2 of relay B, lead 156, front contact SP2 of relay SP, lead 160, lead 169, front contact P2 of relay P, lead 188, diode 201, diode 204, to line 172 thereby energizing line 172. Ah energization path will also be completed from third rail 86 over contact 87, lead 88, lead 151, front contact Z2 of relay Z, front contact B2 of relay B, lead 156, from contact SP2 of relay SP, lead 160, lead 169, front contact P2 of relay P, lead 188, diode 201, diode 204, diode 207 to line 173 thereby energizing line 173. An energization path is also provided from third rail 86 over contact 87, lead 88, lead 151, front contact Z2 of relay Z, front contact B2 of relay B, lead 156, front contact SP2 of relay SP, lead 160, lead 169, front contact P2 of relay P, lead 188, lead 190, diode 202, to line 167 thereby energizing line 167. With lines 172 and 173 energized, propulsion unit 81 of car A will be maintained in its series mode of operation via leads'172a and 173a. Further, with line 167 energized the X" relay of propelling effort control means 91 will be energized thereby causing contacts a, b, and c of the X relay to be closed and allowing power from the lines 172 and 173 to reach propulsion unit 82 of car B via leads 1720 and 1730, respecis still energized, an energization path will be completed from tively. Accordingly, propulsion unit 82 of car B will be placed in its series mode of operation. With car A in its seriesmode of operation and car B being placed in its series mode of operation from its coast mode of operation, a higher overall married pair tractive effort will be produced. Accordingly, the train will now follow the married-pair performance curve 12 beginning at point 76. It will be seen that the entire speed control process just recited will now recycle.

It will be appreciated that while the specific married-pair vehicular operation shown and disclosed is directed to only a portion of the family of married-pair performance curves, shown in the aforementioned preferred embodiment of the invention in FIG. 2, that portion illustrated in FIG. 3, the underlying inventive concept extends itself to the entire family of curves associated with the preferred embodiment, although not shown herein.

From the foregoing teachings it is apparent that, while the invention is described in a preferred embodiment of a mar ried-pair train propulsion system, there are other areas where the, teachings are equally applicable. For example, where there is a pair or pairs of motors available to drive a given variable load and each of the motors has more than one mode or operating state, then married pair motor control logic may be employed in conjunction with a load driving control X relay to provide smoother control over the variable load.

In addition, the teachings of the invention will find equally applicable use in married-pair propulsion systems of the future where the technology is advancing with reference to the use of solid state devices. It is becoming increasingly apparent that propulsion systems will not experience a sudden metamorphosis to produce total changeover to solid state control of propulsion motors. The change will be one of evolution wherein more solid state devices will be employed in the system control, but this will not obviate the basic economics which call for the continued use of many of the proven control techniques. It is to this evolution that the current teachings provide the economic salve to ease the change.

While the invention has been shown and depicted with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that other embodiments may be made therein without departing from the spirit and scope of the invention.

Having thus described my invention, what i claim is:

l. A multiple vehicle propulsion control system for causing vehicular movement along a predetermined path at a preselected speed relatively free from accelerating and decelerating effects, said system comprising:

a. a separate propulsion unit on each vehicle, each vehicle propulsion unit having a plurality of distinct selectable operating modes in addition to a braking mode, one of said propulsion units being a primary propulsion unit, another of said propulsion units on another vehicle being a secondary propulsion unit,

b. propelling effort control means having a first and a second state determined in accordance with the propelling effort required to maintain said preselected vehicular speed relatively free from accelerating and decelerating effects and operatively coupled to said secondary propulsion unit,

c. vehicle-carried propulsion control logic means controllingly coupled directly to said primary propulsion unit and indirectly to said secondary propulsion unit through said propelling effort control means, said vehicle-carried propulsion control logic means including,

1. vehicular speed command control means,

2. vehicular speed measuring means,

3. speed comparator means, said speed comparator means coupled respectively to said vehicular speed command control means and said vehicular speed measuring means to thereby provide an output indicative of vehicular velocity change,

'4. velocity error detecting means coupled to said speed comparator means and controlled by said speed comparator means output to provide an error si na l output,

5. propulsion unit operating mode selection logic means which is mutually coupled to a power supply and said velocity error detecting means and is controlled by said velocity error detecting means error signal output,

a. said propulsion unit operating mode selection logic means having an output to select a particular set of one of said plurality of operating modes in addition to said braking mode for said primary and secondary propulsion unit and directly actuating said particular operating mode in said primary propulsion unit, said secondary propulsion unit being actuated into said particular operating mode only when said propelling effort control means is in said second state,

b. said secondary propulsion unit operating at a predetermined reference operating mode when said propelling effort control means is in said first state.

2. The vehicular control system of claim 1 wherein said propulsion units are electric motors.

3. The vehicular control system of claim 2 wherein said electric motors are do. series-connected motors.

4. The vehicular control system of claim 3 wherein said plurality of operating modes are equivalent to series-connected electric motor performance curves.

5. The vehicular control system of claim 4 wherein said preselected reference operating mode corresponds to a coasting electric motor performance curve.

6. The vehicular control system of claim 1 wherein each of said propulsion units has an equal number of propulsion modes of similar propulsion effort.

7. The vehicular control system of claim 1 wherein each of said propulsion units is positioned on a separate vehicle.

8. The vehicular control system of claim 1 wherein said propelling effort control means is an electromagnetic device.

9. The. vehicular control system of claim 8 wherein said electromagnetic device is a relay with multiple contacts.

Claims (13)

1. A multiple vehicle propulsion control system for causing vehicular movement along a predetermined path at a preselected speed relatively free from accelerating and decelerating effects, said system comprising: a. a separate propulsion unit on each vehicle, each vehicle propulsion unit having a plurality of distinct selectable operating modes in addition to a braking mode, one of said propulsion units being a primary propulsion unit, another of said propulsion units on another vehicle being a secondary propulsion unit, b. propelling effort control means having a first and a second state determined in accordance with the propelling effort required to maintain said preselected vehicular speed relatively free from accelerating and decelerating effects and operatively coupled to said secondary propulsion unit, c. vehicle-carried propulsion control logic means controllingly coupled directly to said primary propulsion unit and indirectly to said secondary propulsion unit through said propelling effort control means, said vehicle-carried propulsion control logic means including, 1. vehicular speed command control means, 2. vehicular speed measuring means, 3. speed comparator means, said speed comparator means coupled respectively to said vehicular speed command control means and said vehicular speed measuring means to thereby provide an output indicative of vehicular velocity change, 4. velocity error detecting means coupled to said speed comparator means and controlled by said speed comparator means output to provide an error signal output, 5. propulsion unit operating mode selection logic means which is mutually coupled to a power supply and said velocity error detecting means and is controlled by said velocity error detecting means error signal output, a. said propulsion unit operating mode selection logic means having an output to select a particular set of one of said plurality of operating modes in addition tO said braking mode for said primary and secondary propulsion unit and directly actuating said particular operating mode in said primary propulsion unit, said secondary propulsion unit being actuated into said particular operating mode only when said propelling effort control means is in said second state, b. said secondary propulsion unit operating at a predetermined reference operating mode when said propelling effort control means is in said first state.

2. vehicular speed measuring means,

2. The vehicular control system of claim 1 wherein said propulsion units are electric motors.

3. The vehicular control system of claim 2 wherein said electric motors are d.c. series-connected motors.

3. speed comparator means, said speed comparator means coupled respectively to said vehicular speed command control means and said vehicular speed measuring means to thereby provide an output indicative of vehicular velocity change,

4. velocity error detecting means coupled to said speed comparator means and controlled by said speed comparator means output to provide an error signal output,

4. The vehicular control system of claim 3 wherein said plurality of operating modes are equivalent to series-connected electric motor performance curves.

5. The vehicular control system of claim 4 wherein said preselected reference operating mode corresponds to a coasting electric motor performance curve.

5. propulsion unit operating mode selection logic means which is mutually coupled to a power supply and said velocity error detecting means and is controlled by said velocity error detecting means error signal output, a. said propulsion unit operating mode selection logic means having an output to select a particular set of one of said plurality of operating modes in addition tO said braking mode for said primary and secondary propulsion unit and directly actuating said particular operating mode in said primary propulsion unit, said secondary propulsion unit being actuated into said particular operating mode only when said propelling effort control means is in said second state, b. said secondary propulsion unit operating at a predetermined reference operating mode when said propelling effort control means is in said first state.

6. The vehicular control system of claim 1 wherein each of said propulsion units has an equal number of propulsion modes of similar propulsion effort.

7. The vehicular control system of claim 1 wherein each of said propulsion units is positioned on a separate vehicle.

8. The vehicular control system of claim 1 wherein said propelling effort control means is an electromagnetic device.

9. The vehicular control system of claim 8 wherein said electromagnetic device is a relay with multiple contacts.

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