AU2019283905A1

AU2019283905A1 - Improved Articulated Vehicle

Info

Publication number: AU2019283905A1
Application number: AU2019283905A
Authority: AU
Inventors: Ian James Spark
Original assignee: Spark Ian James Dr
Current assignee: Spark Ian James Dr
Priority date: 2018-12-29
Filing date: 2019-12-18
Publication date: 2020-07-16

Abstract

The invention relates to articulated road trains consisting of one prime mover, one semi trailer and at least three improved dog trailers. In order to avoid overloading bridges, the train is separated into two sub trains while on the move. One physical drawbar is supplemented with a virtual drawbar of controllable length. Before arriving at the bridge, the front of the train is disconnected from the rear of the train. The drawbar that has been disconnected from the preceding semi-trailer is supplemented with a virtual drawbar. The length of the virtual drawbar is increased to increase the separation of the forward and rear sub trains until the desired separation is achieved. The length of the virtual drawbar is then kept constant until both sub trains have crossed the bridge. The length of the virtual drawbar is then reduced to zero. The physical drawbar is then reconnected to the hitch located at the rear of the preceding trailer. For forward motion a slave reference point on each improved dolly is made to follow a master reference point on the prime mover by controlling the angle between the longitudinal axes of each dolly and the drawbar attaching it to the preceding trailer. The correct angle is deduced by numerical means which gives the correct value even for non-steady state turns. Alternatively, the angle between the longitudinal axes of the dolly and the drawbar attaching it to the preceding trailer can be fixed at zero degrees, and the path of the dolly controlled by turning the dolly wheels which are now rotatably attached to the ends of the fixed axles of the dolly. If the articulation angle between the drawbar and the longitudinal axis of the preceding semi trailer, and the articulation angle between the longitudinal axes of the dolly and the following semi-trailer are also controlled to achieve cooperative redundancy, jack-knifing of the train should no longer be possible. 332 / rW /N ~~C1O 17I

Description

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IMPROVED ARTICULATED VEHICLE Technical Field The invention relates to articulated trains consisting of one prime mover, one semi-trailer and at least three improved dog trailers. Each improved dog trailer consists of a semi-trailer, the front of which is supported by an improved dolly. The invention overcomes the problem of long trains overloading bridge spans by separating the train while on the move into two sub trains by supplementing the physical drawbar with a virtual drawbar whose length can be varied in a controlled manner. Prior Art Spark (Australian Patent 2010201258) describes and claims an improved B double semi trailer, where slave reference points located towards the rear of each trailer are made to follow the path of a master reference point located towards the rear of the prime mover. This is achieved by steering all the wheels of each trailer where the wheel angles required are determined in real time by a numerical approximation. Note that this method works for any path, and not just for steady state paths where all the rigid bodies (prime mover, first semi trailer and second semi-trailer) have the same instant centre. Spark (Australian Patent Application 2016201024) describes and claims an improved dog trailer, where two slave reference points located on each dog trailer are made to follow the path of a master reference point located on the truck. This is achieved by steering all the wheels of each trailer where the wheel angles required are determined in real time by a numerical approximation. Note that this method works for any path, and not just for steady state paths where all the rigid bodies (truck, first dolly, semi-trailer, second dolly and second semi-trailer) have the same instant centre. In this previous work, all trailer wheels are steered so that all the wheels on one trailer have a single instant centre. This eliminates scuffing and makes the path of the trailers kinematically determinate. However, the disadvantage of this approach is that having to steer all trailer wheels involves significant complication and expense. Spark (Australian patent Application 2017276355) describes and claims a train of improved dog trailers where the scuffing associated with unsteered six-wheel groups (or four-wheel groups) is accepted. In this prior invention, complication and cost is reduced by only steering the dollies to reduce off-tracking (corner cutting). Scuffing associated with four or six-wheel axle groups is accepted, as it is for traditional semi-trailers and dog trailers. In the prior invention, the presence of scuffing makes the path of the dollies and the trailers kinematically indeterminate. To overcome this uncertainty, in the first instance, it is assumed that the path of each dolly or trailer is approximated by the path of a notional unsteered master wheel located at the centre of each set of parallel wheels. The actual path of each dolly or trailer can be determined by locating angle-measuring instrumented non-load-bearing castors (hereafter referred to as "castors") at opposite ends of each semi-trailer. These instrumented castors are pressed against the ground so that they record the movement of the ground relative to their position on the semi-trailer. Note that a vertically-aligned video camera or modified laser mouse could be used as a virtual instrumented castor. In this case no contact with the ground is required. There is no delay associated with the rotation of the castor to a new equilibrium position, and no problems with shimmy. Also, the error caused by the offset of the wheeled castor is eliminated. Such virtual castors are effectively virtual velocity vector monitors (or meters) The prior invention uses the principle of cooperative redundancy to solve some of the safety problems inherent to trailers consisting of a prime mover and associated semi-trailer and at least one dog trailer. The problems that were eliminated where as follows: 1. Off tracking of the dollies of the dog trailers. 2. Difficulty of reversing trains of semi-trailers and dog trailers. 3. Jack-knifing of the prime mover, semi-trailer, dog trailer train. The essential feature of the prior invention is that a slave reference point on each dolly is made to follow the path of a master reference point at or close to the axis of the fifth wheel of the prime mover. This is achieved in the first instance by controlling the angle between the drawbar and the longitudinal axis of the associated dolly. If the angle between the drawbar and the longitudinal axis of the preceding semi-trailer to which it is attached, is also positively controlled, we have one level of redundancy. If the angle between the longitudinal axis of the dolly and the longitudinal axis of the associated semi-trailer is also positively controlled, a second level of redundancy results. If these three angles are controlled so that they produce identical steering effects, we now have two levels of cooperative redundancy for each dog trailer dolly. Note that the prime mover can be regarded as a powered dolly whose drawbar is replaced by the axis of the prime mover. In this case the "draw bar" is steered by turning the front wheels of the prime mover. If we also positively control the angle of the fifth wheel to produce the same steering effect, we have a further level of cooperative redundancy. We have now replaced a linkage of 2N rigid bodies, where N is the number of semi-trailers, with a single rigid body whose shape is controlled to match the path selected by the driver. Note that the improved dollies must be positively rotated to be tangential to the master path. The current problem to be solved Although in principle, any number of improved dog trailers could be added to a train of improved dog trailers without increasing off-tracking, problems can arise when crossing bridges. If the total weight of the train is supported by a single bridge span and this weight exceeds the load carrying capacity of this span, the bridge may fail. The solution proposed Before arriving at the bridge, the front of the train is disconnected from the rear of the train. The drawbar that has been disconnected from the preceding semi-trailer is supplemented with a virtual drawbar. The length of the virtual drawbar can be increased to increase the separation of the forward and rear sub trains until the desired separation is achieved. The length of the virtual drawbar is then kept constant until both sub trains have crossed the bridge. The length of the virtual drawbar is then reduced until it has a length of zero. The physical drawbar is then reconnected to the hitch located at the rear of the preceding trailer. The invention may be better understood by reference to the following figures. Figure 1 shows a train comprising a prime mover, semi-trailer and two traditional dog trailers executing a steady state turn.

Figure 2 shows a train comprising a prime mover, semi-trailer and two improved dog trailers being driven forward around a steady state turn. Figure 3 shows a train comprising a prime mover, semi-trailer and three improved dog trailers being driven forward around a non-steady state turn. Figure 4 shows the train shown in Figure 3 where the last two improved dog trailers have been separated from the prime mover semi-trailer and first improved dog trailer. Figure 5 shows the location of the notional master wheels used to derive the path of the rigid bodies and the location of the angle-measuring castors used to determine the instant centres of the semi-trailers. Figure 6 shows the location of the instrumented castors used to deduce the instant centres and thereby the actual path of the rigid bodies. Figure 7 shows the structure of an instrumented castor? Figure 8(a) shows a vertical section AA which is close to the longitudinal axis of an improved dog trailer, showing three rotary actuators used to positively control the three articulation angles of an improved dog trailer. Figure 8(b) shows a stepped horizontal section BB which is just above the improved dolly, showing three rotary actuators used to positively control the three articulation angles of an improved dog trailer. Figure 9 shows three pairs of linear actuators that could be used to positively control the three articulation angles of an improved dog trailer. Figure 10 shows an alternative means of steering the dolly wheels independently of the drawbar. Here a traditional dolly/draw bar is fitted with axles with steerable wheels. Figure 10(a) shows a vertical section CC through the longitudinal axis of the dolly with steerable wheels and the semi-trailer it supports. Figure 10(b) shows a horizontal section DD that lies between the dolly with steerable wheels and the semi-trailer it supports. Figure 10(c) shows a section through the longitudinal axis of a centring actuator. If we have N semi-trailers, we will 2N rigid bodies or links, N-1 dollies and one prime mover, which can be regarded as a (drawbar-less) dolly which is steered by turning two or more front wheels where the rear wheels are powered (see above). 1. Reducing off tracking of a train consisting of one prime mover, one semi trailer and N-1 dog trailers. If a train of one prime mover 1, an associated semi-trailer 2 and N-1 dog trailers is moving in a straight line, the rigid bodies will all have instant centres perpendicular to their motion located at infinity. If the radius of curvature of prime mover is reduced to a finite value, the radius of curvature of the dog trailers will progressively reduce until the prime mover and trailers eventually asymptotically achieve the same instant centre. When the whole train has a single instant centre the shape of the train becomes stable and the turn is now a steady state turn. See Figure 1. It can be seen from Figure 1 that the outermost front wheel 3 of the prime mover has a steady state path with the maximum radius. The radius of the steady state path of the inner drive wheels 4 of the prime mover will be less, and the radius of the steady state path of inner second last wheel 5 of the first semi-trailer will be less again. The radius of the steady state path of inner second last wheel 6 of the second semi-trailer will be less again and the radius of the steady state path of inner second last wheel 7 of the third semi-trailer will be less again. The swept path width SPW of the wheels of the train is the difference between the steady state radii of the outer front wheel of the prime mover and the inner second last wheel of the third semi-trailer. As the SPW is almost equal to the steady state radius of the outer front wheel of the prime mover, it is not possible to add a fourth trailer and still attain a steady state for a turn of the curvature kappa depicted in Figure 1 (where curvature equals the reciprocal of the radius of curvature). This is because it is no longer possible for the axis of the second last wheel of the fourth trailer to pass through the common instant centre. Figure 2 shows a train similar to that shown in Figure 1 except that the longitudinal axis of the last two dollies 8 and 9 no longer coincide with the longitudinal axis of the associated draw bar. In this improved train the angle between the drawbar 10 and the longitudinal axis of the dolly 11 is controlled to ensure that the second and third semi-trailers follow the same track as the first semi-trailer. In this case slave reference points coincide with the articulation (or fifth wheel) axis of the first and second dollies 8 and 9, and these follow a master path generated by the master reference point which is (or close to) the articulation (or fifth wheel) axis of the prime mover 12. In this case the sweep path of all the semi-trailers will be the same. At least two more improved dog trailers could be added to this train. The number of trailers is only limited by the maximum curvature of the steady state turn that avoids interference between the first and last rigid bodies in the train. The curvature Kof the path of the notional master wheel 13 located at the midpoint of the drive wheels of the prime mover is approximately proportional to the rotation of the steering wheel. From the variation of K and the speed of the prime mover with respect to time, the trajectory of the master reference point can be calculated by an on-board computer by numerical integration of the Serret-Frenet equations using the trapezoidal approximation. From this trajectory, the required instant centre for each semi-trailer can be deduced. From these instant centres the angle required between each dolly 8, 9 and its draw bar 10 can be calculated and implemented by a control system. The on-board computer can also calculate the correct angle between the longitudinal axis of the dolly 11 and the longitudinal axis of the preceding semi-trailer 14, 15. If this angle is enforced by a control system we have one level of cooperative redundancy between two steering systems. The on-board computer can also deduce the correct angle between the draw bars 10 and the longitudinal axes of the semi trailers following them 15 and 16. If these angles are also enforced by a control system, we have a second level of cooperative redundancy between three steering systems. This cooperative redundancy can be applied to all dog trailers. Note that the on-board computer can also deduce the correct angle between the longitudinal axis of the prime mover 17 and the following semi-trailer 14. If this angle is also enforced by a control system, we have cooperative redundancy between the steering effect of the angle of the front wheels of the prime mover and the angle of the steering effect of the active articulation axis (or fifth wheel). If the maximum possible cooperative redundancy is imposed on an improved train consisting of 2N rigid bodies is transformed into a single rigid body of variable shape where this shape matches the master path selected by the driver with the steering wheel. Note that the longitudinal axis of all N-1 improved dollies will be positively controlled to be tangential to the master path.

Figure 3 shows a train comprising a prime mover 1, a semi-trailer 14 and three dog trailers , 16 and 17 executing a path of variable curvature. The master path commences with a straight line followed by a sharp 180 degrees left hand turn followed by a less sharp right hand turn. Note that the sharp left-hand turn is too short to allow a steady state turn to be attained so that the second last 16 and third last semi-trailers 15 executing the sharp left hand turn have different instant centres, as do their respective drawbars 10. The last dog trailer 17 is still travelling in a straight line so its instant centre will be at infinity off the top of the page. However, the prime mover 1 and first semi-trailer 14 executing the less sharp right-hand turn are now executing a steady state turn, as indicated by their single instant centre. COC is the centre of curvature of the master path for a steady state (constant radius) turn. Note that the technique for determining the correct articulation angles outlined above works for both steady state and non-steady state turns. For steady state turns all rigid bodies have a single instant centre whereas for non-steady state turns each rigid body will generally have a unique instant centre. However, the line joining the instant centres of two linked rigid bodies must pass through their articulation point in accord with Kennedy's three centre theorem. 2 Means of separating the train into two sub trains and then re-joining them Figure 4 shows a train where the physical drawbar 18 of the second last dog trailer has been disconnected from the hitch point 19 located at the rear of the first dog trailer 15. The physical drawbar 18 has been supplemented with a virtual drawbar 20 whose length has been increased in a controlled way by controlling the speed of the dolly of the second last trailer 16. All or some of the wheels of this dolly, hereafter referred to as the powered dolly 21 are driven at the desired speed by electric motors. Power to the electric motors is provided by one or more batteries where these batteries are charged by regenerative braking of the dolly. Note that the slave reference point located at the centre of the powered dolly 21 of the second last dog trailer 16 is kept on the master path by controlling the articulation angle of the improved dolly and the longitudinal axis of the semi-trailer of the second last dog trailer 16. When the two sub trains are separated, the physical drawbar 18 could be raised in the interests of safety. When both sub trains have crossed the bridge, the length of the virtual drawbar 20 can be reduced in a controlled way to zero. The physical drawbar 18 can now be rotated (and lowered) until it coincides with the virtual drawbar 20. The forward end of the physical drawbar 18 can now be reconnected to the hitch 19 located at the rear of the third last dog trailer 15. When the two halves of the train are connected, the electric motors of the powered dolly could be used to assist the engine of the prime mover when the train is climbing hills.

3 Means of accounting for scuffing of multiple wheels In previous inventions (Spark 258 and 024) relating to trains involving semi-trailers and dog trailers, off-tracking was minimised and scuffing was eliminated at the same time. However, the elimination of scuffing requires the independent steering of all trailer wheels - which makes the exercise costly. However, the scuffing associated with four-wheel and six-wheel axle groups is generally accepted by the road transport industry. In the present invention no attempt is made to reduce the scuffing associated with turning four-wheel and six-wheel axle groups, so that the environmental benefits of the previous inventions cited cannot be expected. In the present invention off-tracking is minimised by focusing improvements on the dollies of the dog trailers. However, this approach leads to problems, which must be addressed. Scuffing occurs if all the wheels of a rigid body do not have a single instant centre. In this case the kinematics of the rigid body, and therefore its path become indeterminate. In order to estimate the path, we assume the path is predicted by a notional master wheel (with a slip angle of zero) located at the mid-point of the axle group. Half the actual wheels are expected to experience positive slip angles and the other half negative slip angles. It is assumed that the dynamic effect of these slip angles cancel out. In the first instance these notional master wheels will be used to deduce the theoretical instant centres and thereby the theoretical path of the rigid bodies (prime mover, dollies and semitrailers). Note that the notional master wheels are shown as black. See Figure 5. 4 Method of determining actual instant centres In view of the assumptions associated with the deduction of the theoretical instant centres of the rigid bodies in the train, it is desirable to check these against the actual instant centres. This could be done by locating instrumented angle-measuring castors (hereafter referred to as castors) at the opposite ends of each rigid body. These castors will align to show the direction of the movement of the ground relative to the position of the castor on the rigid body. If we draw a line at right angles to motion of the ground at the position of each castor, the instant centre of the rigid body will be given by the intersection of these lines. Accuracy can be maximised by locating the castors as far apart as possible. If the castors are located at the articulation points they will be shared by the two linked rigid bodies. The most convenient location for the castors on the axis of the semi-trailers is just behind the rear of the dolly (or prime mover) and just forward of the pintle hitch. These locations are shown in Figures 5 and 6. The means by which two instrumented castors are used to determine the instant centre of a rigid body and its angular velocity about this instant centre are described and claimed by Spark in US patent 7,464,785 and Australian patent 2003201206. The coordinates of the instant centre of a rigid body Rx and Ry are calculated from the equation; Ry = (e + d)/(tan PF - tan (R) and Rx = (d tan R+e tan F)/(tanPF - tan (R) where Ry is the distance of the instant centre of the rigid body to the left of the longitudinal axis of the rigid body, Rx is the distance of the instant centre forward of the centre of the rear axle group (CRAG) of the rigid body, e is the distance of the rear instrumented castor behind the CRAG, and d is the distance of the front instrumented castor ahead of the CRAG, where (R and F are the angles of the instrumented castor wheels relative to the longitudinal axis of the rigid body, where PF and (R are positive if measured in an anti-clockwise direction. Note that PF and RWill generally have different signs. Figure 7 shows the structure of an instrumented angle-measuring castor. A vertical inverted mast 22 is attached to the longitudinal axis of each semi-trailer 14, 15 and 16 at the two chosen positions. The mast is encompassed by a cylinder 23 that is free to rotate and slide relative to the mast. For simplicity any necessary bearings are not shown. An offset castor

24 is attached to the bottom of the cylinder 23. Each castor 24 is pressed against the ground with a spring 25 positioned between a flange 26 on the mast 22 and a flange 27 on the cylinder 23. A transducer 28 is attached to the mast by means of a bracket 29. This transducer 29 records the rotation of the offset of the castor relative to the axis of the semi trailer. Note that a vertically-aligned video camera or modified laser mouse could be used as a virtual instrumented castor. In this case no contact with the ground is required. There is no delay associated with the rotation of the castor to a new equilibrium position, and no problems with shimmy. Furthermore, the error caused by the offset of the wheeled castor is eliminated. Figure 5 shows how the instant centre of the semi-trailer can be determined by the intersection of the intersection of the rotational axes of two castor wheels. Note that if the instant centres of adjacent semi-trailers are deduced, then the instant centres of the drawbar that links them can also be deduced. Note that if the notional master wheel of the dolly is to lie on the master path, it must also have the same instant centre as the semi-trailer it supports. Figure 5 shows the ideal case where the notional master wheels 30, 31 and the castors 32 deduce the same instant centres. The articulation (or hitch) points connect two rigid bodies, such as a drawbar and a semi trailer. For non-steady state turns, the instant centres of the two rigid bodies will be different. However, in accord with Kennedy's three centre theorem, the hitch point and the two instant centres must lie on a straight line. If the actual instant centre is different to that of the theoretical notional master wheel, the position of the actual notional master wheel can be determined. It is the position on the longitudinal axis of the semi-trailer whose perpendicular passes through the actual instant centre. The driver selects the curvature of the path of the prime mover with the steering wheel. This is a process of trial and error. The theoretical path can be deduced from the angle of the steering wheel by assuming the slip angles for the front wheels and the notional master wheel are zero. If some slip angles are not zero, the actual path will differ from the theoretical path. However, the driver will compensate for small slip angles without thinking about it. Note that the actual master path can be determined with the aid of two castors located on the first semi-trailer. From the two castor angles the instant centre of the semi-trailer can be deduced for any time (or distance travelled). The master reference point is the articulation axis of the dolly. Movement of the master reference point will be perpendicular to the line joining the master reference point to the instant centre. The curvature of the master path will be the reciprocal of the distance between the master reference point and the instant centre. This distance is sometimes referred to as the radius of curvature. The object of the present invention is to make the first and second slave reference points on the second and third semi-trailers follow the master path. To do this we need to know the position of the pintle hitch of the preceding semi-trailer. We can then deduce the heading of the drawbar required to locate the slave reference points on the master path. Since the heading of the dolly must be tangential to the master path, we can deduce the required angle between the drawbar and the dolly. We can also deduce the required angle between the drawbar and the longitudinal axis of the preceding semi-trailer. Two methods can be used to deduce the position of the pintle hitch of the semi-trailers.

Firstly, we can assume that the theoretical instant centre of the semi-trailer lies on the rotational axis of a notional master wheel located on the longitudinal axis of the semi-trailer. If this notional master wheel 30 is located at the centre of the six-wheel axle group it will be assumed to have a slip angle of zero. The instant centre will also be expected to lie on the rotational axis of a notional master wheel 31 located at the centre of the four-wheel axle group of the dolly. The theoretical instant centre is the point of intersection of the two axes. From this the theoretical position of the pintle hitch can be deduced. Alternatively, the actual instant centre of the semi-trailer can be determined with the aid of two castors 32 and 33 (as outlined above). From this instant centre the actual position of the pintle hitch can be deduced. 5 Means of positively articulating the rigid bodies of the train to achieve cooperative redundancy. The key requirement of the invention is the need to rotate the dolly relative to its drawbar in a controlled way. Figure 8 shows a means of doing this using a rotary actuator 34. Figure 8(a) shows a vertical section AA close to the longitudinal axis of an improved dog trailer. Figure 8(b) shows horizontal section BB just above the fifth wheel of the dog trailer. The semi-trailer 15 or 16 is rotatably connected to the drawbar 35 and improved dolly 36 by means of a vertical kingpin 37. The drawbar contains a hinge 38 with a transverse horizontal axis which limits the transfer of vertical force to the preceding semi-trailer 14 or 15. The front of the drawbar is connected to preceding semi-trailer by means of a pintle hitch 20 or 21 with limited three degrees of rotational freedom. A gear segment 39 is attached to the bottom of the drawbar between the hinge 38 and the kingpin 37. This large gear 39 engages a small gear 40 attached to and thereby driven by a rotary actuator 41 which is attached to the front of the dolly by means of bracket 42. Rotation of actuator 42 will cause the angle between the longitudinal axes of the dolly and the drawbar to change. Consequently, the latter angle can be controlled by actuator 41. The angle between the axes of the drawbar 35 and the preceding semi-trailer 15 or 14 can also be controlled by actuator 43 attached to the top of the drawbar 35 between the pintle hitch 20 or 21 and the hinge 38. This actuator coaxially drives a long vertical gear 44 which engages a much larger gear segment 45 which is attached to the rear of the preceding semi trailer 15 or 14 above the pintle hitch. This gear segment 45 is attached to a horizontal rod 46 which can slide and rotate inside a cylinder 47 attached to the rear of the preceding semi trailer 15 or 14. A compressed coil spring 48 is used to press the large gear segment 45 against the long gear 44. This arrangement accommodates relative rotation of the drawbar and the preceding trailer about longitudinal and transverse axes passing through the pintle hitch. The angle between the longitudinal axes of the drawbar and the preceding trailer can now be positively controlled by actuator 43. The angle between the longitudinal axes of the dolly 36 and the following semi-trailer 15 or 16 can also be controlled by actuator 49, which is attached to the rear of the dolly 36. This actuator 49 coaxially drives a small gear 50 which engages with a large gear segment 51 which is attached to the underside of the supported semi-trailer 15 or 16. Figure 9 shows an alternative means of controlling the three articulation angles. In this case linear actuators are used that are connected to the linked rigid bodies by means of ball joints. The actuators could be hydraulic cylinders or electric screw actuators. These actuators are deployed in symmetrical pairs. Strictly only three actuators are required. Actuators 52 and 53 are used to control the angle between the longitudinal axes of the dolly 8 or 9 and the drawbar 10. Actuators 54 and 55 are used to control the angle between the longitudinal axes of the preceding semi-trailer 15 or 14 and the drawbar 10. Actuators 56 and 57 are used to control the angle between the longitudinal axes of the dolly 8 or 9 and the following semi-trailer 15 or 16. Note that the angle between the axes of the drawbar and the following semi-trailer is equal to the sum of the angles between the dolly and the following semi-trailer and between the dolly and the drawbar. Note that if the three articulation angles are controlled to achieve cooperative redundancy (where they are all trying to enforce a single instant centre on each semi-trailer), then jack knifing of the train of dog trailers should no longer be possible. Figure 10(a) shows a third method of positively controlling the angles of the dolly wheels relative to the longitudinal axis of the draw bar, the longitudinal axis of the supported semi trailer and the longitudinal axis of prime mover or preceding trailer. In this case, the angle between the longitudinal axes of the drawbar and the associated dolly is fixed at zero and the angles of each steerable dolly wheel relative to the longitudinal axis of the dolly and drawbar is controlled by means of a hydraulic steering actuator 58 connecting the steering arm 59 to the axle 60 supporting the steerable wheel 61. There is also a double ended hydraulic centring actuator 62 which when activated, over-rides the steering actuator 58 and brings the wheel angle to the straight ahead (zero angle) position. The centring actuator 62 is activated at higher speeds and when a fault is detected in the dolly wheel steering system. Ideally there should be one steering actuator and one centring actuator per wheel. For the front axle of the dolly, the right-hand wheel has been centred by the front right centring actuator, whereas the angle of the left-hand front wheel is controlled by the front left hand steering actuator. However, the dolly wheel steering system could be simplified by connecting the left hand and right-hand wheels with a four-bar linkage. However, four-bar linkages only achieve pure Ackermann steering (where the rotational axis of all wheels on a rigid body intersect at a single point) for three wheel angles. The error associated with four bar linkages increases greatly for non-steady state turns where the required instant centre 63 of the dolly (although well away from the longitudinal axis of the dolly) moves forward or backwards relative to the centre of the dolly four axle group. The rear wheels of the dolly with steerable wheels are steered by means of a four-bar linkage. In this case only one steering actuator 64 is used to turn the right-hand wheel and the left-hand wheel is turned by means of a tie bar 65. In this case a single centring actuator 66 acts on the tie bar. Here, the dolly front wheels 66 and rear dolly wheels are steered to produce an instant centre 63 that ensures that a slave reference point on the dolly follows the master path generated by a master reference point on the prime mover. The master and slave reference points could be the articulation axes (or hitch points) of the prime mover and dolly respectively. However other reference points could be chosen. Figure 10(c) shows a section through the longitudinal axis of a centring actuator. When this actuator is activated, hydraulic fluid forces the opposing pistons to the ends of their stroke. In this condition the outer ends of the opposing piston rods contact two prongs attached to the piston rod of the now de-activated steering actuator or tie rod, thus forcing the either to the zero wheel-angle position. It is possible to combine the steering actuator and the centring actuator within a single cylinder. This has not been done here in the interests of clarity. One level of cooperative redundancy could be achieved by also positively controlling the angle between the longitudinal axes of the prime mover or preceding trailer 67 and the drawbar 68/dolly 69 with linear 54 and 55 or rotary 43 actuators as described above, so as to produce the same instant centre as the angles of the dolly wheels. A second level of cooperative redundancy could be achieved by also positively controlling the angle between the longitudinal axis of the drawbar 68/dolly 69 and the semi-trailer 70 supported by the dolly 69 with linear 56 and 57 or rotary 49 actuators as described above, so as to produce the same instant centre as the angle of the dolly wheels.

Claims

The claims defining the invention are:

1. A road train consisting of a prime mover, a semi-trailer and at least one dog trailer, where each dog trailer consists of a semi-trailer, the front of which is supported by a dolly, where each dolly is connected to the rear of the preceding semi-trailer by means of a drawbar the front end of which engages with three degrees of rotational freedom, a pintle or other hitch fixed to the rear of the preceding semi-trailer, where the rear end of the drawbar is rotatably connected to both the dolly and the supported semi-trailer by means of a vertical kingpin, where the angle between the longitudinal axis of the supported semi-trailer and the longitudinal axis of the dolly is positively controlled so that a slave reference point on each dolly is made to follow the path of a master reference point on the prime mover, where the drawbar of one dog trailer can be disconnected and reconnected from the forward semi trailer on the move, so that the physical drawbar is supplemented with a virtual drawbar whose length can be varied in a controlled way, where the prime mover has a minimum of two rear drive wheels, each dolly has a minimum of two wheels and each semi-trailer has a minimum of two wheels.

2. A road train according to claim 1 where the master reference point is the axis of the fifth wheel of the prime mover, and the slave reference points are the axes of the fifth wheel of the dolly associated with each following dog trailer.

3. A road train according to claims 1 or 2 where the correct angle between the longitudinal axes of each semi-trailer and its associated dolly is calculated by numerical means and then implemented.

4. A road train according to claims 1, 2 or 3 where the correct angle between the longitudinal axes of the semi-trailers and their associated dollies is calculated when the train is transitioning from one steady state (with a single instant centre) to another steady state (with a different instant centre), where such transitions are characterised by the prime mover, the dollies and the semi trailers having different instant centres at any instant of time.

5. A road train according to any one of claims 1 to 4 where the angle of the front wheels of the prime mover and the speed of the drive wheels of the prime mover are sampled at regular intervals and used to deduce discrete points on the path of the master reference point, where this master path must be followed by the slave reference points, where it is assumed that the instant centres of the prime mover and the semi-trailers lie on the rotational axis of notional master wheels located at the midpoint of the prime mover drive wheel group and the midpoint of the semi-trailer rear wheel group, where the angle required between the longitudinal axes of the drawbar and the associated dolly can be deduced.

6. A road train according to any one of claims 1 to 4 where two or more angle measuring castors located on the longitudinal axis of the first semi-trailer are used to determine the instant centre of the first semi-trailer and thereby the path of the master reference point, and two or more angle-measuring castors located on the longitudinal axes of the following semi-trailers are used to determine their instant centres, from which the angle required between the longitudinal axes of the semi-trailers and their associated dolly can be deduced; where the coordinates of the instant centre of a rigid body Rx and Ry are calculated from the equation;

Ry = (e + d)/(tan PF - tan (R) and Rx = (d tan R +e tanI F)/(tanPF - tan (R)

where Ry is the distance of the instant centre of the rigid body to the left of the longitudinal axis of the rigid body, Rx is the distance of the instant centre forward of the centre of the rear axle group (CRAG) of the rigid body, e is the distance of the rear instrumented castor behind the CRAG, and d is the distance of the front instrumented castor ahead of the CRAG, where (R and F are the angles of the instrumented castor wheels relative to the longitudinal axis of the rigid body, where PF and (R are positive if measured in an anti-clockwise direction.

7. A road train according to any one of claims 1 to 6 where the correct angle between the longitudinal axes of the drawbar and the preceding semi-trailer is also calculated by numerical means and then implemented to produce one level of cooperative redundancy for each semi-trailer, excluding the first.

8. A road train according to claim 1 where the angle between the longitudinal axes of the drawbar and dolly is fixed at zero degrees, but where the wheels of the dolly are rotationally attached to their axles by means of kingpins (or ball joints) so that the angle between the rotational axes of the dolly wheels and their axles can be controlled by means of actuators that ensure that the rotational axes of the dolly wheels intersect at a single instant centre where this instant centre is controlled to ensure that slave reference points on the dolly follow the master path generated by a master reference point located on the prime mover.

9. A road train according to claim 8 where the master reference point is the axis of the fifth wheel of the prime mover, and the slave reference points are the axes of the fifth wheel of the dolly associated with each following dog trailer.

10. A road train according to claims 8 or 9 where the correct instant centre of the dolly is calculated by numerical means and then implemented.

11. A road train according to claims 8, 9 or 10 where the correct instant centre of the dolly is calculated when the train is transitioning from one steady state (with a single instant centre) to another steady state (with a different instant centre), where such transitions are characterised by the prime mover, the dollies and the semi-trailers having different instant centres at any instant of time.

12. A road train according to any one of claims 8 to 11 where the angle of the front wheels of the prime mover and the speed of the drive wheels of the prime mover are sampled at regular intervals and used to deduce discrete points on the path of the master reference point, where this master path must be followed by the slave reference points, where it is assumed that the instant centres of the prime mover and the semi-trailers lie on the rotational axis of notional master wheels located at the midpoint of the prime mover drive wheel group and the midpoint of the semi-trailer rear wheel group, where the correct instant centre of the dolly can and thereby the correct angle of the dolly wheels be deduced.

13. A road train according to any one of claims 8 to 11 where two or more angle measuring castors located on the longitudinal axis of the first semi-trailer are used to determine the instant centre of the first semi-trailer and thereby the path of the master reference point, and two or more angle-measuring castors located on the longitudinal axes of the following semi-trailers are used to determine their instant centres, from which the angle of the dolly wheels can be deduced.

14. A road train according to any one of claims 8 to 13 where the correct angle between the longitudinal axes of the drawbar and the preceding semi-trailer is also calculated by numerical means and then implemented to produce one level of cooperative redundancy for each semi-trailer, excluding the first.

15. A road train according to any one of claims 8 to 13 where the correct angle between the longitudinal axes of the dolly and the following semi-trailer is also calculated by numerical means and then implemented to produce a second level of cooperative redundancy for each semi-trailer, excluding the first.

16. A road train according to any one of claims 1 to 15 where the correct angle between the longitudinal axes of the dolly and the supported semi-trailer is controlled with a rotary actuator attached to the rear of the dolly where the vertical shaft of the actuator is keyed to a gear which engages a gear segment attached to the bottom of the supported semi-trailer, so that rotation of the actuator causes the said angle to change.

17. A road train according to any one of claims 1 to 15 where the correct angle between the longitudinal axes of the dolly and the supported semi-trailer is controlled by means of two cooperative redundant linear actuators that connect the rear left and right hand sides of the dolly to the centre of the supported semi-trailer, so that changing the length of these actuators causes the said angle to change.

18. A road train according to claims 1 to 16 where the correct angle between the longitudinal axes of the dolly and the drawbar is calculated by numerical means and then implemented by a rotary actuator fixed to the front of the dolly, where a gear keyed to the vertical shaft of the actuator meshes with a gear segment fixed to the underside of the rear of the drawbar, so that rotation of the actuator causes the said angle to change.

19. A road train according to claims 1 to 15 and 17 where the correct angle between the longitudinal axes of the dolly and the drawbar is calculated by numerical means and then implemented by means of two cooperative redundant linear actuators that connect the front left and right hand side of the dolly to the left and right hand side of the rear of the drawbar, so that changing the length of these actuators causes the said angle to change.

20. A road train according to any one of claims 1 to 16 and 18 where the correct angle between the longitudinal axes of the drawbar and the preceding semi trailer is also calculated by numerical means and then implemented with a rotary actuator attached to the front of the drawbar, where the vertical shaft of the actuator is keyed to a gear which engages a gear segment attached to the rear of the preceding semi-trailer, so that rotation of the actuator causes the said angle to change.

21. A road train according to any one of claims 1 to 15, 17 and 19 where the correct angle between the longitudinal axes of the drawbar and the preceding semi-trailer is also calculated by numerical means and then implemented with two cooperative redundant linear actuators that connect the left and right hand sides of the drawbar to the left and right hand corners of the preceding semi-trailer respectively, so that changing the length of these actuators causes the said angle to change.

22. A road train according to any one of claims 6 to 21 where the angle measuring castors are replaced with angle-measuring video cameras trained on the ground.

23. A road train according to any one of claims 6 to 21 where the angle measuring castors are replaced with a modified laser mouse.

24. A road train according to anyone of claims 1 to 23 where the two sub trains created by disconnecting the physical drawbar from the preceding semi-trailer are separated by increasing the length of the virtual drawbar, so that these sub trains can traverse bridges without subjecting a single span of the bridge to the total weight of the train.

25. A road train according to claims 1 to 24 where some or all, of the wheels of the dolly associated with the virtual draw bar are positively driven so as, to control the length of the virtual draw bar to any desired value.

26. A road train according to claims 1 to 25 where one or more of the wheels of the dolly associated with the virtual drawbar, hereafter referred to as the powered dolly, are driven by electric motors, where the energy required to drive the electric motors is provided by one or more batteries, where the batteries can be charged by regenerative braking.

27. A road train according to claims 1 to 26 where the disconnection/reconnection of the physical drawbar is accompanied be the disconnection/reconnection of pneumatic, hydraulic or electric circuits running between the two sub trains.

28. A road train according to claims 1 to 27 where the energy stored in the battery or batteries can be used to supplement the engine of the prime mover when the train is climbing hills.

29. A road train according to claims 1 to 28 where angle and speed measuring castors are attached to each rigid body in order to determine the true instant centre (as opposed to the theoretical instant centre) and the true angular velocity of each rigid body about its true instant centre, thus increasing the accuracy of the determination of the master and actual paths.

30. A road train according to claims 1 to 29 where further sensors are added to the last trailer of the leading sub train, and the physical drawbar, in order to increase the accuracy of the process of reconnecting the physical drawbar to the forward truck or trailer.

31. A road train according to claims 1 to 30 where during the reconnecting process, the powered dolly is kept on the correct path by controlling the angle between the longitudinal axes of the powered dolly and the supported semi trailer, while the physical draw bar is aligned with its hitch point on the forward trailer or truck by positively rotating the physical drawbar about a vertical axis relative to the powered dolly.

32. A road train according to claims 1 to 31 where, when the physical drawbar is disconnected, all the energy required to drive the driven wheels of the smart dolly, turn the smart dolly and the physical drawbar and power the control systems comes from the one or more batteries.

33. A road train according to claims 1 to 32 where, when the physical drawbar is disconnected, information relating to the master path is relayed from the prime mover to a computer on the powered dolly by wireless means, so that said computer can calculate the required angles of the smart dolly and physical drawbar, and the required speed and the required angles of the powered dolly and physical drawbar, and the required speeds of the driven wheels of the powered dolly.

34. A road train according to claims 1 to 32 where, when the physical drawbar is disconnected, a master computer located on the prime mover, calculates from the trajectory of the master reference point, the required angles of the powered dolly and physical drawbar, and the required speeds of the driven wheels on the powered dolly, and relays this information to control systems on the smart dolly by wireless means.

35. A road train according to claims 1 to 33 where slave reference points located on each semi-trailer are made to follow a master path traced out by a master reference point located on the prime mover, where a numerical method is used to calculate the required instant centre of each semi-trailer and thereby the required angles of both the dolly and the drawbar relative to the longitudinal axis of each semi-trailer, where both these angles are positively enforced by control systems.

36. A road train according to claim 34 where the angle between the longitudinal axis of the physical drawbar and the longitudinal axis of the forward trailer is also positively controlled to produce the same steering effect as the angle between the longitudinal axes of the smart dolly and the supported semi-trailer, thus making jack-knifing impossible.

37. A road train according to claims 1 to 36 where, when the physical drawbar is disconnected, the forward end of the latter is raised to a height less than the height of the tallest trailer in the train.