AU2018203105B2 - Improved Articulated Vehicles - Google Patents

Abstract

A road train consisting of a truck (1) and one or more trailers (2, 3) where the path of the truck (1) is determined by the driver with a steering wheel which controls the angles of the front wheels of the truck relative to the longitudinal axis of the truck, where each trailer has at least two wheels located near its front and at least two wheels located near its rear, where the front of the trailer is connected to the truck or forward trailer by means of a drawbar, where all trailer wheels are positively steered so that a slave reference point located on the longitudinal axis of the trailer is made to be tangential to a master path which is the locus of a master reference point located on the longitudinal axis of the truck. r~k

Description

A road train consisting of a truck (1) and one or more trailers (2, 3) where the path of the truck (1) is determined by the driver with a steering wheel which controls the angles of the front wheels of the truck relative to the longitudinal axis of the truck, where each trailer has at least two wheels located near its front and at least two wheels located near its rear, where the front of the trailer is connected to the truck or forward trailer by means of a drawbar, where all trailer wheels are positively steered so that a slave reference point located on the longitudinal axis of the trailer is made to be tangential to a master path which is the locus of a master reference point located on the longitudinal axis of the truck.

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Amended specification (including amended claims)5-9-2023

IMPROVED ARTICULATED VEHICLE (2018203105) Definitions:

Semi-trailer: Trailer where usually un-steered wheels are concentrated at the rear. The front of the semi-trailer is supported by the rear of a prime mover or a dolly. The under-side of the front of the semi-trailer is fitted with a kingpin, which engages with a fifth wheel located on the top of the rear of the prime mover or dolly. The kingpin is generally located slightly ahead of the CRAG.

Tag Trailer: A semi-trailer (with wheels concentrated at its rear) where a rigid drawbar is used to connect it to the rear of the preceding vehicle by means of a pintle hitch or similar A type coupling. Note that this coupling is subjected to a large vertical load.

Pig Trailer: This is a trailer where the wheels are located close to the centre of the load carrying surface. It is connected to the rear of the preceding vehicle by means of a pintle hitch or similar A type coupling, which is subjected to a relatively small vertical load. Caravans and boat trailers are forms of pig trailers.

Box trailer: A small pig trailer meant to be towed by a car, utility or 4WD vehicle using a tow ball.

Prime mover: A vehicle with steerable front wheels which cannot directly carry a useful load. It is used to support the front end of a semi-trailer which carries the useful load.

Truck: A vehicle with steerable front wheels which can directly carry a useful load. A tray can be used to carry palleted loads. A tub (often tippable) is used for loose solids such as sand or rocks. A tank is used to carry liquids or gasses.

Fifth wheel: A fifth wheel coupling is located at the rear of a prime mover or semi-trailer. It can also be located at or close to the centre of the axle group of a dolly. It has two degrees of rotational freedom. These are pitch and yaw. A semi-trailer is connected to the prime mover, dolly (or a lead semi-trailer) by reversing the prime mover so that the king pin of the semi-trailer automatically engages the fifth wheel. The fifth wheel can carry a substantial vertical load. The fifth wheel is often referred to as a B type coupling.

Dolly: (sometimes called a converter dolly, (as it converts a semi-trailer into a dog trailer), is a short trailer which can be connected to the rear of the preceding trailer by means of an A type coupling located at the front of a drawbar. There are three main types of A couplings. These are:

Pintle hitch: Here a hook with an opening latch is attached to the rear of the preceding vehicle, and an eye is attached to the front end of the drawbar of the dolly. The drawbar is connected to pintle hitch by opening the latch, engaging the eye, and closing the latch.

Tow Ball: Here a spherical tow ball is attached to the rear of the preceding vehicle, and a coupling with a hemispherical cavity is attached to the front end of the drawbar. The drawbar is connected to the tow ball by placing the coupling over the tow ball and then preventing it fromde-coupling.

Automatic Pin: (sometimes called a Ringfeder coupling). Here a mouth with a vertical pin is attached to the rear of the preceding vehicle, and an eye is attached to the front end of the drawbar. The drawbar is connected to the coupling by raising the automatic pin, placing the eye inside the mouth and lowering the pin through the eye automatically.

All three A couplings have three degrees of rotational freedom. However, the range of allowable pitch angles is limited. Some back lash is inevitable in the pintle hitch and the automatic pin to allow the three degrees of rotational freedom. However no back lash is required with the tow ball. These A couplings can carry very little vertical load.

Dolly with B hitch at both front and rear: Here the A coupling at the front of a conventional dolly is replaced by a fifth wheel which engages a kingpin attached to the underside of the preceding vehicle. This means the dolly is roll-coupled to the preceding vehicle. This is a relatively new innovation which is said to improve the handling of dog trailers.

Dog Trailer: This is an Australian term. In other countries dog trailers are sometimes referred to as an A trailer. A dog trailer is a trailer with wheels at both the front and the rear. It generally comprises a dolly and a semi-trailer where the front of the semi-trailer is connected to the dolly by means of a fifth wheel. Since the dolly and semi-trailer cannot roll independently, they are said to be roll coupled.

CAG = Centre of Axle Group. This applies to dollies and semi-trailers as they generally only have one axle group.

CRAG = Centre of Rear Axle Group: This applies to a prime mover or a truck. Note that a dolly and a semi-trailer generally only have one axle group. If all the wheels are un-steered, then the direction of movement of all wheels is approximated by the movement of a notional wheel located at the centre of the axle group. Also note that for non-steady state turns, the prime mover, truck, dolly or semi trailer will seesaw (in horizontal plane) about the CAG or CRAG.

Improved Semi-trailer: A semi-trailer where all or some of the wheels are actively steered.

Improved Dog Trailer: A dog trailer where all or some of the wheels are actively steered.

IDTDD: (Improved dog trailer, double dolly). An improved dog trailer where the front of the dog trailer is supported by a dolly where the dolly wheels can be positively steered relative to the drawbar. The rear of the dog trailer is supported by a dolly that that can be actively steered relative to its longitudinal axis.

IDTDH (Improved dog trailer double hinge). An improved dog trailer where both ends of the dog trailer are supported by fixed axles with steerable wheels. In this case the drawbar must have a hinge with a vertical axis at both its front and rear ends.

Longitudinal axis of wheeled rigid bodies: The longitudinal axis of a rigid body is the longitudinal centre line in the plan view of the rigid body. In other words, it is the intersection of the plane of longitudinal symmetry and a horizontal plane. Therefore, the longitudinal axis will generally pass through the midpoint between the front wheels and the midpoint between the rear wheels of the rigid body. If the rigid body only has one group of wheels, the longitudinal axis will pass through the centre of the axle group and an articulation point that connects the rigid body to a linked rigid body. If the rigid body has front and rear articulation points, these will generally lie on the longitudinal axis of the rigid body.

MRP = Master Reference Point. A point generally on the longitudinal axis of the prime mover, truck or semi-trailer that traces out a master path. If the MRP is located at the CRAG of the prime mover, truck or first semi-trailer, it will be at the fulcrum of the seesaw, and therefore not subject to the see-saw effect during non-steady state turns. This will eliminate non-steady state perturbations in the master path.

SRP = Slave Reference Point. Points on longitudinal axis of dollies or semi-trailers that are made to follow the master path by steering all or some of the wheels of the dolly or semi-trailer. If the SRPs are located at the CAGs of the dollies or semi-trailers, they will be located at the fulcrum of the seesaw and therefore not subject to the seesaw effect during non-steady state turns. This will mean that the trailer wheel steering systems will not have to counter-act perturbations in the path of the slave reference points caused by the seesaw effect.

Off-tracking: This is where points located on the linked rigid bodies (i.e. the prime mover, truck, dolly or semi-trailer follow different paths. Note that different points on each rigid body will generally have different but generally parallel paths. Paths will not be parallel when the instant centre of the rigid body is changing, so that the rigid body is in an unsteady state. If the rigid body goes from a left hand to a right hand turn the paths must cross so that the inside paths become the outside paths and vice versa. All points on a rigid body must always rotate about a single instant centre of the rigid body. At any instant, the normals to these paths must intersect at the instant centre (i.e. IC). Although all points on a rigid body must have a single instant centre, their paths will generally have different radii of curvature.

Off-tracking is easier to define if we only consider points on the longitudinal axes of the linked rigid bodies. These longitudinal axes run between the articulation points. When the train is travelling in a straight line, all points on the longitudinal axes of the rigid bodies will also lie on a straight line. However, if the path of the first rigid body in the train becomes curved, the paths of all points on the longitudinal axes of the rigid bodies will now be different. We can deduce the paths of semi-trailers or dollies relative to the path of the CRAG of the prime mover or truck. We can change the instant centre of the prime mover or truck instantly by changing the steering wheel angle and thereby the angle of the front wheels of the prime mover or truck. However, if the prime mover or truck is towing a semi-trailer with un-steered wheels, the semi-trailer can only change its instant centre gradually. If the prime mover is executing a steady state turn, its instant centre will be stationary relative to both the prime mover frame of reference and the global frame of reference. The instant centre of the semi-trailer will eventually become identical to the instant centre of the prime mover. This generally takes approximately a quarter of a turn (i.e. a 90 degree turn). If all the rigid bodies in the train have the same instant centre, the whole train is in a steady state turn, and behaves as if it were a single rigid body. In such a steady state turn all the articulation angles will remain constant. They can easily be calculated if the single instant centre is known.

Note that all linked rigid bodies in a train must obey Kennedy's Three Centres Theorem. If two rigid bodies are linked at an articulation point, then the articulation point and the instant centres of the two rigid bodies must lie in a straight line. Therefore, the instant centre of the semi-trailer must move along this line until it eventually coincides with the steady state instant centre of the prime mover.

Primary off-tracking of trailers with un-steered wheels. Here corner cutting is defined as positive off-tracking and outswing is defined as negative off-tracking. In a steady state turn, the greatest off tracking of a semi-trailer relative to the CRAG of the prime mover occurs at the trailer CAG. If a second semi-trailer is added, its greatest off-tracking also occurs at its CAG. Primary off-tracking increases with each semi-trailer added to the train. As the curvature of the steady state turn(=1/ ROC) the number of semi-trailers that can be added to the train decreases.

Secondary off-tracking of improved trailers. We can reduce primary off-tracking to zero by steering the wheels of the semi-trailer so that the path of the slave reference point (SRP) is identical to the path of the master reference point (SRP). However, every other point on the axis of the semi-trailer is subject to off-tracking. This is defined as secondary off-tracking. It will tend to be maximum half way between the SRP and the forward articulation point.

Swept Path Width (SPW). Every point on every linked rigid body will generate a path. The SPW is the distance between a tangent to the outermost path and a parallel tangent to the innermost path. We can vary the gradient of the parallel tangents until we find the maximum SPW.

The principle of cooperative redundancy between multiple steering systems. Semi-trailers can have 4, 6 or 8 parallel wheels. Each two wheels produces a steering effect characterized by a theoretical instant centre (TIC). The total number of wheel angle steering effects is N(N-1)/2 where N is the number of wheels. Dual wheels attached to a single hub are counted as a single wheel. For N =6 the number of steering effects is 15. For N=8 the number of steering effects is 28. In order to make a SRP located near the rear of the semi-trailer follow the master path, we must steer the wheels at the rear of the semi-trailer. However, if we steer them in such a way they have a single instant centre, we have a Cooperative Redundant Multiple Steering System (CRMSS). In this case all the steering effects reinforce each other, and the semi-trailer is kinematically determinate. This will minimize scuffing leading to minimization of road damage, tyre wear and fuel consumption on turning. Note that the energy required to damage the road and wear the tyres comes from burning more fuel. Ideally each wheel should be steered by a dedicated actuator.

The easiest way to steer the wheels on a semi-trailer is to take one or more self-aligning axles and convert them to actively steerable axles by replacing the (anti-shimmy) damper with a computer controlled hydraulic actuator. Self-aligning axles are often erroneously referred to as self-steering axles. Ideally, they have zero steering effect, whereas fixed wheels have a definite steering effect. These actively steered axles use one actuator/axle and a four-bar linkage to approximate Ackermann steering. This will produce a small amount of scuffing.

The principle of equivalence of positions of master and slave reference points. The best location for the MRP is the CRAG of the prime mover, since this is immune to the seesaw effect. Here the longitudinal axis of the prime mover is tangential to the master path. If the SRP is to be equivalent, the axis of the trailer must also be tangential to the master path at the SRP. Note that this condition uses up two DOF since position and direction are both defined. As we cannot have more reference points than rigid bodies, we can only have a tangential SRP on every second rigid body. Note we can approximate a tangential SRP by locating two SRPs on either side of the midpoint between the CAG of the dolly and the CRAG of the semi-trailer and moving them together. If all reference points are located at equivalent positions the swept path width (SPW) of the train will be minimized.

Prior Art:

Spark (Australian Patent 2010201258) describes and claims an improved B-Double train where the swept path of the train is reduced by making slave reference points on the semi-trailers follow a master path which is the locus of a master reference point on the prime mover. In this prior patent the master reference point is the hitch point, which is also the centre of the rear axle group (CRAG) of the prime mover, and the slave reference points are the centres of the rear axle groups of the semi-trailers, which are also the hitch points. To achieve this effect all wheels on the semi-trailers are steered so that all wheels on a particular semi-trailer always have a single instant centre. The articulation (or hitch) angles can also be positively controlled to produce the same instant centre. Such positive control of the articulation angles should make jack knifing impossible. Note that this system works for both steady state (where all the linked rigid bodies have the same instant centre) and non-steady state turns where the linked rigid bodies can have different instant centres.

Spark (Australian Patent Application 2015900713) describes and claims a train of improved dog trailers where two slave reference points on opposite ends of each improved dog trailer are made to follow a master path which is the locus of a master reference point located on the longitudinal axis of the truck. In this application, the slave reference points are the articulation points at the front and rear of each trailer. In order to make the swept path of the trailers lie within the swept path of the truck the master reference point has been moved forward or back from the centre of the rear axle group (CRAG)ofthe truck.

The problem to be solved:

Although the system outlined in Spark 2015900713 works well in steady state turns, unfortunate side effects arise in non-steady state turns. Although the slave reference points can still be made to follow the master path, the wheel angles and articulation angles required show transient humps (blunt spikes) with respect to time. These humps cause two problems for the angle control systems. Firstly, the range on angles required is significantly increased. Large ranges of trailer wheel angles are difficult to accommodate in the design of the improved dog trailers. Secondly, the humps mean that a rapid change in angles is required (i.e. a high angular acceleration about a vertical axis). This will increase the inertial load on the actuators and make it difficult for the control system to deliver the required angular acceleration.

The solution proposed:

The transient humps can be greatly reduced by making the master reference point the centre of the rear axle group (CRAG) of the truck. The swept path of the trailers can be moved within the swept path of the truck by making the location of the slave reference points on the trailers equivalent to the location of the master reference point on the truck. If the master reference point is the CRAG, the longitudinal axis of the truck is tangential to the master path. If the two slave reference points on the axis of each trailer are replaced with a single slave reference point, where the longitudinal axis of the trailer is tangential to the master path, the master reference point and the slave reference point will be equivalent. If the single tangential slave reference point is at the midpoint between the articulation points at the front and back of the trailer the swept path of the trailer will be moved outwards. This midpoint, corresponds to the location on the longitudinal axis of the trailer associated with the minimum path radius for steady state turns.

In order to better explain the invention, the following figures are attached:

Figure 1 depicts the off-tracking associated with a train comprising a truck and two conventional dog trailers in a steady state turn.

Figure 2 depicts the reduced off-tracking associated with a train comprising a truck and three improved dog trailers where the trailer dollies can be positively steered with respect to their drawbars (after Spark, 2015900713).

Figure 3 shows how the dollies can be steered relative to the trailer and the drawbar can be steered relative to both the trailer and the truck or forward trailer.

Figure 4 depicts the reduced off-tracking associated with a train comprising a truck and three improved dog trailers where the trailer axles are fixed but the steerable wheels are attached to their ends by means of kingpins, where the wheel angles and the angles between the drawbar and the longitudinal axes of the trailer and the truck (or forward trailer) are positively controlled (after Spark 2015900713).

Figure 5 shows how the wheels can be steered relative to the trailer, and the drawbar can be steered relative to both the trailer and the truck or forward trailer.

Figure 6 depicts a path that includes both steady state and non-steady state turns.

Figure 7 shows how the trailer wheel angles must change if the slave reference points are to follow the master path, where the master reference point is the centre of the rear axle group (CRAG) of the truck.

Figure 8 shows how the trailer wheel angles must change if the slave reference points are to follow the master path where the master reference point is on the longitudinal axis of the truck 4.03 metres ahead of the centre of the rear axle group (CRAG) of the truck. Note the transient angle humps that precede the steady state.

Figure 9 shows how the hitch angles must change if the master reference point is located at the CRAG of the truck.

Figure 10 shows how the hitch angles must change if the slave reference points are to follow the master path where the master reference point is located on the longitudinal axis of the truck 4.03 metres ahead of the centre of the rear axle group (CRAG) of the truck.

Figure 11 shows the preferred form of the invention where the master reference point is the centre of the rear axle group of the truck and the longitudinal axis of each trailer is tangential to the master path at the midpoint between the forward and rear hitches. These midpoints are tangential slave reference points.

Figure 12 shows a train of double hinge improved dog trailers (DHIDTs) manoeuvring within a double doughnut.

Figure 13 shows a train of linked semi-trailers manoeuvring within a double doughnut.

Figure 14 shows a train of linked semi-trailers where each semi-trailer is capable of carrying a 12m shipping container.

Figure 1 shows a truck 1 towing two standard dog trailers (SDTs) 2 and 3. Each dog trailer comprises a dolly 4 which rotatably supports the front of a semi-trailer. Each dolly 4 is connected to the preceding truck or semi-trailer by a drawbar 5. The front end of the drawbar is connected to the preceding vehicle by means of a pintle (or other) hitch 6 with three degrees of rotational freedom, with a limited range of angular movement. The rear end of the drawbar is attached to the dolly with a hinge with a horizontal axis 7.

The truck has been driven along a circular path until steady state has been attained where all three rigid bodies have the same instant centre (IC) 8. The two standard dog trailers have attained the same instant centre as the truck. The inner and outer radii of the truck wheels are 8m and 12m respectively. The inner and outer radii of the swept path of the first dog trailer are 6.2m and 10m respectively. The inner and outer radii of the swept path of the second dog trailer are 3.6m and 8.2m respectively. Note that it is not possible to attain a steady state condition if a third standard dog trailer is added.

The corner cutting of the inner rear wheels of the first and second standard dog trailers are defined here as positive off-tracking. Therefore, the off-tracking of the first and second standard dog trailers are 8 - 6.2 = 1.8m and 8 - 3.6 = 4.4m respectively. The steady state condition is characterised by the rotational axes of the rear wheels of the truck and first and second dog trailers all passing through a single point, so that they have the same instant centre 8.

Figure 2 shows a train comprising a truck towing three improved dog trailers (IDTs) 9, 10 and 11 around a circular steady state right hand turn. The fixed wheels at the rear of the standard dog trailers have been replaced with wheels mounted on a rotatable dolly 12. Also, the draw bar 13 of the front dolly 14 can be rotated relative to the dolly 14. The angles of rotation of the front and rear dollies are controlled so that slave reference points (SRPs) on the improved dog trailers are made to follow the path traced out by a master reference point (MRP) on the truck. This configuration will be referred to as a Double Dolly Improved Dog Trailer (DDIDT).

In Figure 2 the MRP is the hitch point at the rear of the truck, and the SRPs are the articulation points of the three DDIDTs. In this case the inner and outer radii of the swept path of the truck are 8m and 12.4m respectively. The inner and outer radii of the swept path of all the DDIDTs are 7.7m and 10.7m respectively. Note that the position on the trailer with the minimum radius of curvature (ROC) is midway along the right-hand side of the DDIDTs. This off-tracking will be referred to as secondary off-tracking. It includes the maximum separation of an arc and a chord. Thus, the off tracking of the DDIDT relative to the truck is 8 - 7.7 = 0.3m.

Figure 3 shows how the angles between the longitudinal axes of the DDIDT and the front and rear dollies can be controlled by hydraulic cylinders. Cylinders 21 and 22 control the angle of the rear dolly relative to the axis of the DDIDT. Cylinders 23 and 24 control the angle of the front dolly relative to the axis of the axis of the DDIDT. Cylinders 25 and 26 are redundant, but if they positively control the angle between the drawbar 13 and the axis of the DDIDT they introduce one level of cooperative redundancy, which should increase resistance to jack-knifing. Cylinders 27 and 28 are also redundant, but if they positively control the angle between the drawbar 13 and the axis of the truck (or preceding dog trailer), they introduce a second level of cooperative redundancy. Note that if the angle between the rear of the drawbar and the DDIDT, and the angle between the front of the drawbar and the preceding truck or trailer are both positively controlled, then jack-knifing should be impossible.

Strictly only one cylinder is required to control each oh the four angles. However, a second cylinder has been added to improve reliability. All cylinders are controlled to make the slave reference points on the trailers follow the master reference point on (or relative to) the truck.

Figure 4 shows a train comprising a truck 1 towing three dolly-less improved dog trailers around a steady state circular path. Here the front and rear dollies shown in Figure 3 are replaced with axles 29 fixed to the improved dog trailers (via a suspension system). These axles have left 31 and right 32 steerable wheels 30 attached to said axles 29 with substantially vertical kingpins. Each improved dog trailer is attached to the preceding truck (or trailer) by means of a double hinge drawbar 31. This drawbar is attached to the preceding truck or trailer by means of a pintle (or other) hitch 6 with three degrees of rotational freedom (with limited angle range). The drawbar 31 is attached to the following dog trailer by means of a hinge 32 with a vertical axis. The drawbar will also contain a hinge 33 with a transverse horizontal axis close to its rear end. The purpose of the horizontal hinge 33 is to limit the transmission of vertical forces between the leading and following vehicles.

These improved dog trailers will be referred to as double hinge Improved dog trailers (DHIDTs). Once again, the angles of the trailer wheels relative to the axis of the DHIDT will be controlled in order to make slave reference points on the trailers follow in the path of the master reference point located on (or related to) the truck 1.

The advantage of the DHIDT over the DDIDT is that the load-carrying capacity can be readily increased simply by adding more steerable axles, where the wheel angles are controlled so that all wheels on the trailer have a single theoretical instant centre. This eliminates the scuffing that results when parallel axles are forced to turn. Figure 4 implies DHIDTs with five axles apiece.

In Figure 4 the master reference point is the hitch point at the rear of the truck, and the slave reference points are all six other hitch points (including where the hitch point would be on the rear of in last trailer).

In Figure 4 the inner and outer radii of the swept path of the truck are 8m and 11.8m respectively. The inner and outer radii of the swept path of each of the three DHIDTs are 7.5m and 9.8m respectively. Hence the positive secondary off-tracking of the DHIDTs is 8 - 7.5 = 0.5m. This is more than for the DDIDT, but this is mainly due to the increased distance between the front and rear slave reference points on the DHIDTs.

Ideally the inner radii of the swept path of the truck and the improved dog trailers should be identical. This can be achieved by shifting the master reference point from the first hitch point

1.86m behind the CRAG of the truck to 4.03m ahead of the CRAG. Shifting the master reference point 4.03m behind the CRAG would produce the same effect for steady state turns.

Figure 5 shows how the wheel angles and hitch angles of a DHIDT can be controlled with hydraulic cylinders. In this case the angles of the left and right rear wheels of the DHIDT are controlled with hydraulic cylinders 34 and 35 respectively. Similarly, the left and right front wheels of the DHIDT are controlled with hydraulic cylinders 36 and 37 respectively. If three more axles were added to the DHIDT six more hydraulic cylinders would be required. The number of hydraulic cylinders required can be halved if the left and right wheels were connected by means of a four-bar linkage. However, such a linkage would introduce wheel angle errors. Especially at large wheel angles.

Cylinders 38 and 39 are redundant, but if they positively control the angle between the drawbar and the axis of the DHIDT they introduce one level of cooperative redundancy, which should increase resistance to jack-knifing. Cylinders 40 and 41 are also redundant, but if they positively control the angle between the drawbar and the axis of the truck (or preceding dog trailer), they introduce a second level of cooperative redundancy. Note that if the angle between the rear of the drawbar and the DDIDT, and the angle between the front of the drawbar and the preceding truck or trailer are both positively controlled, then jack-knifing should be impossible.

So far only steady state turns have been considered. However, in the real world every steady state (constant radius) turn is generally preceded and succeeded by a non-steady (variable radius) turn. Consequently, any path following system must be able to handle non-steady state turns.

Figure 6 shows a modelled path containing both steady state and non-steady state turns. Here the driver increases the speed from 0 to 5 m/s in the first 2 seconds, after which this speed is maintained. Curvature of the path of the CRAG is 0 for first 5s, then decreased linearly to -1/20 (giving a right hand turn of radius 20 m) over a period of Is. The turn is maintained for 5s before increasing back to 0 over a period of Is. This is followed by a further increase of curvature to 1/10 over Is. This left turn with a radius of 10m is held for 5s before being linearly decreased back to 0 and held for a further 6s. Note this path includes a point of inflection.

Figure 7 shows the trailer wheel angles as a function of time to make the slave reference points follow the master path, if the master reference point is located at the CRAG of the truck.

Figure 8 shows the trailer wheel angles required if the master reference point is located 4.03 m ahead of the CRAG.

Figure 9 shows the hitch angles required to make the slave reference points follow the master path if the master reference point is located at the CRAG.

Figure 10 shows the hitch angles required if the master reference point located 4.403 m ahead of the CRAG.

Although shifting the master reference point 4.03m ahead of the CRAG can eliminate secondary off tracking, it has an unfortunate side effect for non-steady state turns. Transient humps in the required trailer wheel angles precede each steady state. Corresponding transient humps also appear in the required hitch angles. These transient angle humps have two undesirable effects. Firstly, the range of trailer wheel angles required is increased significantly, and large trailer wheel angles are hard to accommodate without the wheels touching the trailer chassis or suspension system. Secondly the transient angle humps require high angular acceleration of the trailer wheels about their kingpins. This means a more powerful angle control system will be required.

Figure 11 shows a solution to both the transient humps problem and the secondary off-tracking problem. Here a truck tows three DHIDTs around a circular path. In this case the master reference point (MRP) is the CRAG. However, the slave reference points at each end of each DHIDT are moved along the axis of the trailer until they meet at the midpoint to form a single slave reference point at which the longitudinal axis of the DHIDT must be tangential to the master path. As the master reference point (MRP) is also tangential to the master path, the master and slave reference points are located at equivalent positions on their rigid bodies.

In Figure 11 the inner and outer radii of the swept path of the truck are 8m and 12m respectively. The inner and outer radii of the swept path of all the DHIDTs are 8.1m and 10.7m respectively. In this case there is no secondary off-tracking of the DHIDTs relative to the truck as the swept path of the former now fits within the swept path of the latter.

Note that other points on the axis of the DHIDT could be chosen for the tangential slave reference point. Also, if we select two non-tangential slave reference points that straddle the desired tangential slave reference point the behaviour of the latter will approximate to the behaviour of the former.

Ideally, a path following method should be able to handle non-steady state turns in general and path inflexions in particular. However, drivers do not generally manoeuvre their lead vehicle by consciously selecting a sequence of path curvatures. Rather they attempt to make a reference point on the lead vehicle follow a path on the ground. The Europeans have a rule that a vehicle or train of vehicles must be able to manoeuvre within a doughnut with inner and outer radii of 5.3m and 12.5m respectively. One test involves entering the doughnut from a straight-line path, executing 1.25 revolutions (450 degrees) and exiting the doughnut along a straight line. In this case there will be non-steady state turns associated with entering and exiting the doughnut, but no path inflections.

A new test is proposed where the vehicle train is required to manoeuvre within a double doughnut. Where the vehicle train enters the left doughnut from a straight line and executes a 450 degree right hand turn followed by a 450 degree left hand turn within the right hand doughnut before exiting along a straight line. In order to allow a seamless inflection, the two doughnuts must overlap by 2(r +

rm ) where r and rm are the outer radii of the doughnut and the radius of the path of the master reference point which allows the outer front corner of the truck to stay within the doughnut. In this case the master reference point is the CRAG of the truck, where rm = (r 2 - 2)O.5 - t/2 where r, I and t are the outer radius of the doughnut, distance to the front of the truck from the CRAG, and the width of the truck respectively. See Figure 13.

Note that the train shown in Figure 13, comprising a truck towing four DHIDTs easily stays within the double doughnut. In this case the master reference point (MRP) is the CRAG of the truck and the slave reference points (SRPs) are the midpoints of the DHIDTs at which the longitudinal axis of the DHIDT must be tangential to the master path.

If some extra hardware is added to the train of DHIDTs they can easily be reversed by effectively transposing the master reference point and the last slave reference point. For no-skill reversing, the master reference point is located on the rearmost trailer and the last slave reference point is now the CRAG of the truck. A reversing camera is attached to the rear of the last DHIDT. A joystick or auxiliary steering wheel or knob enables the driver to control the reversing path of the last trailer. An automatic steering system for the truck is also required to keep its longitudinal axes tangential to the master path at the CRAG.

The driver steers the last trailer by making a convenient driver reference point follow the desired path on the ground. This driver reference point could be the left or right rear corner of the last trailer. The rear centre of the last trailer could also be used. In this case the master reference point is midway between the front hitch point of the last trailer and where the rear hitch point would be located if fitted. Note that the on-board computer has remembered the prior path of the reversing train. This master path is continually updated as the train moves in reverse. The master path the truck has already past can be deleted from the memory.

In this case the first slave reference point is the midpoint of the second last trailer. This must be kept tangential to the master path, which enables its instant centre to be determined. The process is repeated for the third and fourth last trailer. The CRAG of the truck must also be kept tangential to the master path. Note that the instant centres of the draw bars can easily be determined using Kennedy's three centres theorem that states that instant centres of two linked rigid bodies and their hitch point must lie on a straight line. If three rigid bodies are linked, if the instant centres of the first and third rigid bodies are known, then the instant centre of the second rigid body lies at the intersection of two lines. The first line passes through the instant centre of the first rigid body and its hitch point to the second rigid body. The second line passes through the instant centre of the third rigid body and its hitch point to the second rigid body. Once all the current instant centres are determined, the correct wheel angles and hitch angles can easily be calculated. Appropriate control systems can then implement these angles.

The principle of equivalence of location of the master reference point and the slave reference points can be extended to a train comprising a prime mover towing a number of connected semi-trailers. In this case the odd numbered semi-trailers replace the drawbars of the train of linked DHIDTs shown in Figure 13. In this case the master reference point is the CRAG of the prime mover and the slave reference points are the midpoint between the hitch points of every second semi-trailer (i.e. the even-numbered semitrailers). The axes of the even semi-trailers must be tangential to the master path at their slave reference points.

Figure 14 shows a train comprising a prime mover towing a train of six semi-trailers 43 to 48, where the train is being driven around a double doughnut. The tangential slave reference points 49 to 51 allow the instant centres of the even-numbered semi-trailers to be determined. Note that the instant centres of the odd-numbered semi-trailers 43, 45 and 47 can also be determined from instant centres of the even-numbered semi-trailers (see above). Once the instant centres of the semi-trailers are known, the correct angle for any wheel on the semi-trailers can be easily determined. The correct hitch angles can also be determined. These angles can then be implemented with control systems. Note that the train shown in Figure 14 easily fits within the double doughnut.

A significant difference between a train of dog trailers and a train of semi-trailers is the significant amount of overlap required for the latter. Semi-trailers are generally connected to the preceding vehicle by means of a turntable (also referred to as a fifth wheel) which makes overlap inevitable. Dog trailers on the other hand are connected by drawbars engaging hitches located at the rear of the preceding vehicle.

Figure 15 shows a train comprising a prime mover 42 towing four semi-trailers 52 to 55 around the double doughnut. In this case each semi-trailer is capable of carrying a 12m shipping container. Once again, the master reference point is the CRAG of the prime mover, and the slave reference points are the midpoint between the hitch points of the even-numbered semi-trailers 53 and 55, where the axis of the semi-trailer is tangential to the master path at the slave reference point. In this case the train of much longer semi-trailers almost fits within the double doughnut.

No skill reversing of trains of semi-trailers can also be achieved using the same technique described above for a train of DHIDTs. Note that the odd-numbered semi-trailers act as the drawbars for the even-numbered semi-trailers. Once the current instant centres of all the rigid bodies are determined, the correct wheel angles and hitch angles can be easily calculated.

Claims (2)

The amended (5-9-2023) claims defining the invention are: Amended claims (5-9-2023) The claims defining the invention are:

1. A train consisting of a truck and one or more trailers where the path of the truck is determined by a driver with a steering wheel which controls the angles of two front wheels of the truck relative to the longitudinal axis of the truck, where each trailer has at least two wheels located near its front and at least two wheels located near its rear, where the front of the trailer is connected to the truck or forward trailer by means of a drawbar, where all trailer wheels are positively steered so that the longitudinal axis of each trailer is tangential to a master path at a nominated slave reference point, where the master path is a locus of a master reference point located on the longitudinal axis of the truck, and the longitudinal axes of the truck and trailer are their respective centrelines in a plan view.

2. A train according to claim 1, where a master reference point is located at the centre of the rear axle group of the truck and slave reference points are located at the equivalent position on each trailer which is midway between the front and rear of each trailer. -3- A train according to any one of claims 1 and 2 where the trailer wheels are steered by locating them at the ends of a coaxial axle where these axles are mounted on dollies which can be positively rotated about vertical axes located on the longitudinal axes of each trailer, where this rotation ensures that the longitudinal axis of each trailer is tangential to a master path at a nominated slave reference point, where the master path is a locus of a master reference point located on the longitudinal axis of the truck. 4. A train according to any one of claims 1 and 2 where the trailer wheels are steered by locating them at the ends of axles that are fixed at right angles to the longitudinal axes of the trailers and where the wheels are connected to these fixed axles by means of kingpins where the axis of each kingpin is approximately vertical, where the wheels can be positively rotated about the kingpin axis, where this rotation ensures that the longitudinal axis of each trailer is tangential to a master path at a nominated slave reference point, where the master path is a locus of a master reference point located on the longitudinal axis of the truck 5. A train according to claim 3 where the front of each drawbar is connected to the truck or forward trailer with a coupling that allows three degrees of rotational freedom, where the rear of the drawbar is connected to the trailer by a coupling which has one degree of rotational freedom about the vertical axis of the dolly, where the drawbar has a hinge with a horizontal axis located towards its rear end. 6. A train according to claim 4 where the front of each drawbar is connected to the truck or forward trailer with a coupling that allows three degrees of rotational freedom, where the rear of each drawbar is connected to the trailer by a coupling which has one degree of rotational freedom about a vertical axis on the longitudinal axis of the trailer, where the drawbar has a hinge with a horizontal axis located towards its rear end. 7. A train according to claim 5 where the angle between the longitudinal axes of the drawbar and the trailer is positively controlled by one or more hydraulic rams, where one end of each ram is connected to the draw bar and the other is connected to the front of the trailer, where these rams also ensure that the longitudinal axis of each trailer is tangential to a master path at a nominated slave reference point, where the master path is a locus of a master reference point located on the longitudinal axis of the truck to produce one level of cooperative redundancy. 8. A train according to claim 6 where the angle between the longitudinal axes of the drawbar and the trailer is positively controlled by one or more hydraulic rams where one end of the rams is connected to the drawbar and the other is connected to the front of the trailer, where these rams also ensure that the longitudinal axis of the trailer is tangential to the master path at the slave reference point to produce one level of cooperative redundancy. 9. A train according to claim 7 where the angle between the longitudinal axes of the drawbar and the truck or forward trailer is positively controlled by one or more hydraulic rams, where one end of these rams is connected to the drawbar and the other is connected to the rear of the truck or forward trailer, where these rams also ensure that the longitudinal axis of the trailer is tangential to the master path at the slave reference point to produce a second level of cooperative redundancy. 10. A train according to claim 8 where the angle between the longitudinal axes of the drawbar of the truck or forward trailer is positively controlled by one or more hydraulic rams, where one end of the rams is connected to the drawbar and the other is connected to the rear of the truck or forward trailer, where these rams also ensure that that the longitudinal axis of the trailer is tangential to the master path at the slave reference point to produce a second level of cooperative redundancy. 11. A train according to claims 3, 5, 7 or 9 where additional wheels are added to the trailers where these wheels are positively steered to ensure that the rotational axes of all wheels on each trailer intersect at a single point and therefor have the same theoretical instant centre. 12. A train according to claims 4,6, 8 or 10 where additional wheels are added to the trailers where these are positively steered to ensure that the rotational axes of all wheels on each trailer intersect at a single point and therefor have the same instant centre. 13. A train according to claims 1, 2, 4, 6, 8, 10 and 12 where the train is driven in reverse, where the driver steers the wheels of the rearmost trailer with reversing camera and auxiliary joystick, where the master reference point (MRP) is relocated to the midpoint of rearmost trailer, and the slave reference points (SRPs) are the midpoints of the remaining trailers and the centre of the rear axle group (CRAG) of the truck, where an extra control system is deployed to steer the front wheels of the truck. 14. A train according to claims 1 to 13 where the truck is eliminated and the front wheels of the first trailer are replaced with a self-propelled steerable dolly, which is steered by a driver located on the said dolly. 15. A train according to claim 14 where the self-propelled steerable dolly is a traditional prime mover with driven wheels at the rear and steerable wheels at the front which are turned by the driver by means of a steering wheel. 16. A train according to claims 2, 4, 6, 8 and 12 where the drawbars are replaced with semi trailers, where the master reference point is the centre of the rear axle group of the truck or prime mover, and the slave reference points are the midpoints of every second semi-trailer, where the longitudinal axes of every second semi-trailer is tangential to the master path at the said slave reference point. 17. A train according to claim 16 with an even number of trailers, where the train is driven in reverse, where the driver steers the wheels of the rearmost trailer with a reversing camera and auxiliary joystick, where the master reference point (MRP) is relocated to the midpoint of rearmost trailer, and the slave reference points (SRPs) are the midpoints of the even-numbered trailers and the centre of the rear axle group (CRAG) of the truck, where control systems are deployed to control the trailer wheel angles, the hitch angles and the front wheels angles of the truck.