AU592089B2 - Electric motor vehicle control system - Google Patents

Description

592009 FIRM 10 SPRUSQN FERGUSON COMMON4WEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION FOR OFFICE USE: !5 7s Class Int. Class I -kibN dkwucLjz2 contains Emeninents made uindgr Section~ 49, Complete Specification Lodged: Acc'eptLed: Published: *0

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CC C CCC C C Name of Applicant: Address of Applicant: Actual Inventor(s): Address for Service: MVITSUBISHI DENKIt KAPiJSHIKI KAISHA No. 2-3, Marunouchi 2-chome, Chiyoda-ku, Tokyo, 100 Japan SHT.NZO H-IRAO, H-IDEO TERASAWA and HIDEKI SOGIH-ARA Spruson Ferguson, Patent Attorneys, Level 33 St Martins Tower, 31 Market Street, Sydney, New South Wqales, 2000, Australia Coitplete Specification for the invention entitled: "ELECTRIC MOTOR VEHICLE, ZONTROL SYSTEM" The following including the statement is a full description this invention, best method of performing it knownL SB R /JS /0100 U This invention relates to an electric motor vehicle Scontrol system and more particularly to the construction of such a control system capable of demonstrating maximum adhesive performance.

Electric motor vehicles can be driven by making use of frictional force between wheels and rails. It is therefore essential in vehicle technology to make the most of the frictional force. Fig. 8 is a characteristic diagram showing the relation of the frictional coefficient between the wheel and the rail to slip speed and the frictional coefficient itself cdrastically fluctuates according to rail surface conditions, weather, travel speed, etc. If tractive force of o 0 the wheel relative to the wheel load exceeds the frictional a S coefficient at the point P of Fig. 8, a big slip will occur and cuase not only mechanical damage to rotary means a traction motor and a gear, the rail surface and the wheel S tread but also reduction in tractive force. The pending problem is accordingly zo implement operation in such a state as close to the point P as possible. Generally, an area where the slip speed is lower than the point P is called a small slip, a creep area, whereas an area where it is higher than the point P is called a slip area. Control

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systems conventionally adopted are intented to cope with the so-called slip produced, to reduce the tractive force after the slip has occured. .igs. 9 through 11 show conventional slip detection methods in electric motor vehicle control systems, illustrating a voltage comparison method, a current comparison method and a speed/generator method, respectively, Detectin sensitivity, operating principles S3 and problems inherent in those methods are shown in the pk/213d -2- ,i L a I following table.

Slip detection Detection Operating Problems: method: sensitivity: principles: Voltage comparison Difference in Slip detection by Detection method: speed: by voltage sensitivity is low; 6-7 km/h comparison in No detection is traction motor possible if at each axle: comparative axles Vmamotor, rpm simultaneously slip; Detection after slip occurrence.

Current comparison Current Slip detection Detection speed is method: relatively by current low; slowly changes comparison in No detection is and slip traction motor at possible if detection Is each axle; comparative axles delayed. Reduction in simultaneously slip; current in Detection after slip slipping motor is occurrence.

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O0o o0 0 o a• 9009 0 0* 00* 0 0 400" a a t C S009 0 0( 0 0 0 0** Speed/generator method: Difference in speed: 3ke/h Detection of difference in speed of traction motor at each axle.

Mailunction if slip detection sensitivity is raised; No detection is possible if comparative axles simultaneously slip.

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The detection sensitivity by means of the above-described slip detection methods slight differs in the conventional electric motor vehicle control system and, since the slip detection is carried out after a slip has occurred, ie, in the slip area in any one of such methods, the slip is detected in the neighbourhood of the point R of Figure 8 and to the point S. Consequenitly, the control system is employed in an area where the practical adhesion coefficient is relatively low and disadvantageous in that, in the case of an electric locomotive, production costs become high because the number of driving axles must be increased on one hand and the pull load becomes small provided that the number of driving axles is constant on the other. In the case of an electric car, the percentage of S motive power units (motive power units/trailers) of a train increases, thus causing high production and maintenance costs.

rr*The present invention is intended to solve the above problems and it is therefore an object of the invention to provide an electric motor vehicle control system which will ameliorate disadvantages of the prior art.

According to one aspect of the present invention there is disclosed an electric motor vehicle control system comprising a vibration detector for detecting the natural vibration frequency component of ,O torsional self-excited vibration of a wheel set driven by an electric motor to produce a detection signal; and a motor control for unitizing levels of said vibration detection signal, using total signal level, comparing said unitized vibration detection signal with a preset urtized allowable maximum amplitude standard of said natural vibration frequency component and controlling the rotational force of said motor supplied to the motor set so as to make constant the unitized natural vibration frequency component.

By way of example cnly, preferred embodiments of the invention will now be described with reference to the accompanying drawings in which: 1LA4v- -4- E BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram showing an electric motor vehicle control system embodying the present invention.

Figure 2 is a chart showing the amplitudes of the primary and secondary natural vibration frequency components of torsional vibration.

Figure 3 is a characteristic diagram showing the relation between vehicle speed and the amplitude of the natural vibration frequency component.

Figures 4 through 7 are block diagrams showing other electric motor vehicle control systems embodying the present invention.

Figure 8 is a characteristic diagram showing the relation between the slip speed (factor) between the wheel and the rail and an adhesive coefficient.

Figures 9 through 12 show voltage comparison, current comparison and speed/generator methods as conventional slip detecting methods for an electric motor vehicle control system.

Figure 12 shows an arrangement of a bogie, a wheel set and a gear.

Figure 13 shows a block diagram showing a ci!rcuit construction for unitizing.

Figure 14 shows a graphical diagram of filter having its output unitized.

SFigures 15 and 16 show graphical representations showing examples of the unitized outputs.

In the drawings, the following coded references are used: t TM...traction motor as a motor, VS...vibration detector, RA...unitizing circuit, AS...unitized allowable maximum amplitude standard, TMC...motor control, BG...bQgle, AX...wheel set, G...gear.

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i:l Figure 1 is a block diagram showing the construction of an electric motor vehicle control system embodying the present invention. In 7igure 1, the motor control comprises a pantograph Pan, a chopper circuit CH for controlling a d.c. input from the pantograph Pan and supplying the d.c. current to a traction motor TM, an axle torque sensor TS for detecting the torisional vibration of a sheet set of a bogie BG, a digital filter circuit DF for obtaining a natural vibration frequency component as a preslip driving phenomenon out of the torsional vibration detected by the axle torque sensor TS and a circuit RA for unitizing the signal levels of the frequency component which forms the preslip driving phenomenon as an output from the digital filter circuit DF by using the total signal level.

Since the intensity of the signal detected by the axle torque sensor varies with the frictional state (fluctuating according to the axle load, the vehicle speed and the like) between the wheel and the rail surface, the T5 influences of the axle load and the vehicle speed can be prevented. The digital filter circuit DF is equipped with an amplifier (not shown) at its input means and designed to allow frequency bands within a given range to -6ii II 1 i 3 RI II pass therethrough and extract the frequency component resulting from the preslip driving phenomenon using a microprocessor, which converts the frequency component into a digital value and processes the signal as extremely fast as several ms. The axle torque sensor TS and the digital filter circuit DF constitute a vibration detecting circuit VS. The i motor controller further comprises a comparator CPR for comparing the unitized allowable maximum amplitude standard AS of the natural vibration frequency component with the output of the unitizing circuit RA, a creep control SC for generating a control signal for controlling the creepage on receiving the output from the comparator CPR and an amplifier AMP for receiving the control signal and an acceleration current command IP from the creep control SC, the main traction motor current IM detected by a d.c. transformer DCCT and sending a gate signal to the chopper circuit CH. Tha chopper circuit CH, the unitizing circuit RA, the comparator CPR, the creep control SC and the amplifier AMP constitute a chopper control TMC as the motor control.

The natural vibration crequency in the self-vibration as the preslip driving phenomenon of the wheel set is determined by the torsional rigidity of the torsion spring i system of the wheel set and the inertial moment of the wheel J gear and the rotor of the traction motor, whereas primary and secondary torsional natural vibration frequencies exist.

Fig. 2 shows that the amplitudes of the torsional natural vibration frequQncies have a good relationship to the slip factor. As shown Fig. 2, the greater the slip factor, the greater the amplitude of the torsional natural vibration frequency becomes proportionally.

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lu The operation of an electric motor vehicle thus constructed according to the present invention will subsequently be described. An axle is driven by the traction motor TM incorporated with the wheel set of a bogie BG and, it slip speed is generated between the wheel and the rail, I torsional vibration is also generated in the axle. As shown in Fig. 2 the natural vibration frequency component of the Storsional vibration increases as the slip factor increases.

1 The natural vibration frequency component of the torsional .vibration increases roughly in proportion to the vehicle speed as shwon in Fig. 3 and accordingly the unitizing circuit RA is installed so as to prevent the frequency component from being affected by the vehicle speed.

Accordingly, the axle torque sensor TS is used to de:9ct the torsional vibration and the digital filter circuit DF is I employed to extract only the natural vibration component therefrom and then the output is unitized by the unitizing circuit RA. The comparator CPR compares the vibration component corresponding to the point Q of Fig. 8 with the unitized allowable maximum amplitude standard AS and the result of comparison is supplied to the amlifier AMP through the creep control SC. On receiving the accelerating current command IP, the amplifier AMP controls the gate control circuit in the chopper circuit CH so as to control the tractive force of the traction motor TM by controlling the tractive motor current command IP in such a manner that the torsional vibration component maintains a value within a ta'nge close to the point Q of Fig. 8.

The electric motor vehicle thus controlled according to the above embodiment is operated at a slip speed Vs pk/213d -8-

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corresponding to the point Q of Fig. 8 and, because a value roughly close to the maximum adhesive coefficient between the wheel and the rail can be utilized, irrespective of the rail surface and weather conditions, the number of driving axles can be reduced 6 to 4 axles) in the case of an electric locomotive. In consequence, a resource and energy-saving electric locomotive may be manufactured by far less costly because of improved efficiency resulting from an increase in the capacity of a single machine such as a traction motor. Moreover, the improved adhesive coefficient makes it possible to reduce the percentage of electric motor cars of a train run by electricity, initial investment to a larqe extent, resources and the weight of the train resulting in energy-saving, and maintenance cost.

Fig. 4 is a block diagram showing the construction of another electric motor vehicle control system embodying the present invention, the control system comprising a thyristor phase control as a motor control icluding a main transformer MTR in place of the chopper circuit CH of Fig. I, a thyristor bridge circuit THB connected to the secondary side of the main transfo),mer MTR, a unitizing circuit RA, a unitized allowable maximum amplitude standard AS, a comprator CPR, a creep control SC and an amplifier AMP. The effects similar to those according to the previous embodimePt van be attained in this a.c. electric motor vehicle.

Fig. 5 shows still another embodiment of the pLesent invention, wherein the digital filter circuit DV of Fig. I is replaced with an analog filter circuit AF and a detector circui DET, the natural vibration frequency component being detected by the axle torque sensor TS out of the torsional pk/213d -9vibration of a wheel set.

Fig. 6 shows still znother embodiment of the present invention, wherein the digital filter circuit DF of Fig. 4 is replaced with an analog filter circuit AF and a detector circuit DET, the natural vibration frequency component being detected by the axle torque sensor TS out of the torsionai vibration of a wheel set.

According to the embodiments of Figs. 5 and 6, the amplitude of the unitized natural vibration frequency component is compared with the unitized allowable maximum amplitude standard AS and the tractive force of the traction Q 0, motor TM is so controlled as to make constant the unitized to t natural vibration frequency component, whereby the electr4c motor vehicle thus provided is capable of demonstrating C maximized adhesive performance while allowing the slip factor.

Fig. 7 shows still another embodiment of the present invention, wherein a thyristor variable voltage variable frequency control TMC using a variable voltage variai le frequency control circit VVF is applied. This electric motor vehicle control sys:tem employs a three-phase cage type induction motor as a traction motor TM, Fig. 12 is a diagram showing an arrangement of the bogie BG, the axle AX, the gear G and the traction motor TM.

The axle torque sensor TS is mounted on the axle AX shown by TS according to the above embodiiment. As shown in Fig. 12, however, the torque is transmitted from the traction motor TM to the axle AX through the gear G and, because the axle AX is incorporated therewith as a rotkmry body, selIf-excited v ibration as the preslip driving phenomenon can be detected even if the axle torque sensor TS is mounted on the traction pk/21,id -i0- I L motor shaft.

As set forth above, the natural vibration frequency component of the torsional vibration of a wheel set as a driving phenc,inon prior to the occurrence of a big zlip is detected and the signal level of the natural vibration frequency component is unitized according to the total level in order to nullify the dependence of the detected signal on speed. Then the signal is compared with the unitized allowable maximum amplitude standard and the tractive force of a motor is controlled so as to make constant the natural vibration frequency component and allow the slip factor between the wheel and the ail, Consequently, an adhesive coefficient close to the maximum adhesive performance of an electric motor vehicle is effectively exhibited.

Figure 13 is a block diagram showing an example of a circuit construction for unitizing, In figure 13, the unitizing is carried out by 15 the fifth block "ratio* in order to Increase the accuracy in detection.

An example of the "unitizing" is to divide a signal level at a center frequency of a filtered, 25(Hz) for instance In this example by the power of total signal levels. Figure 14 is a graphic diagram showing an example of the output characteristic of the filter, Figures 15 and 16 are graphical representations showing examples t t I of the output of a filter (A 2

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2 and the unitized output thereof, respectively.

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Claims (6)

1. 2. An electric motor vehicle control system as claimed in claim 1, wherein said vibration detector comprises an axle torque sensor mounted on the wheel set, said vibration detector being used to detect the self-excited vibration of said wheel set and produces a detection signal, said control system further comprising a filter circuit for receiving said detection signal, taking out the natural vibration frequency component of said self-excited vibration and generating a vibration detection signal,
2. 3. An electric motor vehicle control system as claimed in claim 2, wherein said filter circuit is a digital filter circuit, 4 An electric motor vehicle control system as claimed in claim 2, wherein said filter circuit comprises an analog filter circuit and a detector circuit, An electric motor vehicle control -ystem as claimed in any one i 25 of the claims 1 through 4, wherein siod motor control is a chopper control for controlling the tractive force of said motor by controlling the motor current using a chopper circuit,
3. 6. An electric motor vehicle control system as claimed In any one of the claims 1 through 4, wherein said motor control is a thyristor phase control for controlling the tractive force of said motor by controlling the motor current using a thyristor bridge circuit.
4. 7. An electric motor vehicle control system as claimd in any one of the claims 1 through 4, wherein said motor control is a thyrstor variable voltage variable frequency control for controlling the tracti force of a three-phase cage type induction motor, 12,- I i i -(1~~1~111- I I i
5. 8. ,n electric motor vehicle rol system as claimed in claim 1, wherein said vibration detector is mounted on the electric motor shaft through the wheel set and gears and wherein said vibration detector comprises the axle torque sensor for detecting the self-excited vibration of said wheel set on the traction motor shaft and producing a detection signal, said control system further comprising a filter circuit for receiving said detection signal, taking out the natural vibration frequency component of said sief-excited vibration and generating a vibration detection signal.
6. 9. An electrical motor vehicle control system substantially as described herein with reference to the drawings. II *i I I iI I Ia DATED this SEVENTH day of AUGUST 1989 Mitsubishi Denki Kabushiki Kaisha Patent Attorneys for the Applicant SPRUSON FERGUSON i I g i I t -13- HRF/1 38y fW**