A VEHICLE AND A METHOD OF CONTROLLING THE PROPULSION OF A VEHICLE

Abstract

A vehicle includes a first axle provided with at least a pair of first wheels, and a second axle provided with at least a pair of second wheels. The second axle is a steered axle allowing said second wheels to be turned. At least one first electric machine provides propulsion torque to the first axle. At least one second electric machine provides propulsion torque to the second axle. A control unit is configured to control the first and second electric machines, wherein the control unit is configured to limit the propulsion torque provided by said at least one second electric machine in dependence of a current state of the second axle.

Claims

1. A vehicle, comprising: a first axle provided with at least a pair of first wheels, a second axle provided with at least a pair of second wheels, wherein the second axle is a steered axle allowing said second wheels to be turned, at least one first electric machine for providing propulsion torque to the first axle, at least one second electric machine for providing propulsion torque to the second axle, and a control unit configured to control the first and second electric machines, wherein the control unit is configured to limit the propulsion torque provided by said at least one second electric machine in dependence of a current state of the second axle, wherein the vehicle further comprises a chassis, wherein the second axle is provided with a height-adjustable connector, such as a damper, operatively connecting the chassis to the second axle for enabling adjustment of the distance between the chassis and the ground, wherein said current state of the second axle is a current set height of the height-adjustable connector of the second axle, wherein the control unit is configured to limit the propulsion torque provided by said at least one second electric machine: to a lower value when said set current height is decreased, and to a higher value when said current height is increased.

2. The vehicle according to claim 1, wherein said current state is a current steering angle of at least one of said second wheels of the second axle.

3. The vehicle according to claim 2, wherein the control unit is configured to limit the propulsion torque provided by said at least one second electric machine: to a lower value when said current steering angle increases, and to a higher value when said current steering angle decreases.

4. The vehicle according to claim 2, wherein the control unit is configured to increase the torque split ratio between said at least one first electric machine and said at least one second electric machine when said current steering angle increases.

5. The vehicle according to claim 2, wherein said at least one second electric machine comprises two second electric machines, one at a left end of the second axle and one at a right end of the second axle, wherein the control unit is configured to limit the propulsion torque provided by the second electric machines at the left end in dependence of the current steering angle of the second wheel at the left end of the second axle, and to limit the propulsion torque provided by the second electric machine at the right end in dependence of the current steering angle of the second wheel at the right end of the second axle.

6. (canceled)

7. (canceled)

8. The vehicle according to claim 1, wherein said current state of the second axle is a measure of how much lateral force that is generated by tyres of said second wheels of the second axle, or wherein said current state of the second axle is a measure of how much lateral slip is generated by the tyres of said second wheels of the second axle.

9. The vehicle according to claim 8, wherein the control unit is configured to limit the propulsion torque provided by said at least one second electric machine: to a lower value when said generated lateral force or lateral slip is increased, and to a higher value when said generated lateral force or lateral slip is decreased.

10. The vehicle according to claim 1, wherein the first axle is located rearwardly of the second axle as seen in the normal driving direction of the vehicle.

11. The vehicle according to claim 1, wherein the first axle is configured as a low speed range axle, and wherein the second axle is configured as a high speed range axle.

12. The vehicle according to claim 1, wherein the first axle is configured as a startability axle to be powered when initially accelerating the vehicle, and the second axle is configured as a cruise axle to be powered when the vehicle is cruising.

13. The vehicle according to claim 1, wherein the first axle has a higher gear ratio than the second axle.

14. The vehicle according to claim 1, wherein the first axle is declutchable, and the second axle is not declutchable.

15. A method of controlling the propulsion of a vehicle, wherein the vehicle comprises: a first axle provided with at least a pair of first wheels, a second axle provided with at least a pair of second wheels, wherein the second axle is a steered axle allowing said second wheels to be turned, at least one first electric machine for providing propulsion torque to the first axle, at least one second electric machine for providing propulsion torque to the second axle, the method comprising: limiting the propulsion torque provided by said at least one second electric machine in dependence of a current state of the second axle wherein the vehicle further comprises a chassis, wherein the second axle is provided with a height adjustable connector, such as a damper, operatively connecting the chassis to the second axle for enabling adjustment of the distance between the chassis and the ground, wherein said current state of the second axle is a current set height of the height-adjustable connector of the second axle, the method further comprising limiting the propulsion torque provided by said at least one second electric machine: to a lower value when said set current height is decreased, and to a higher value when said current height is increased.

16. The method according to claim 15, wherein said current state is a current steering angle of at least one of said second wheels of the second axle.

17. The method according to claim 16, comprising limiting the propulsion torque provided by said at least one second electric machine: to a lower value when said current steering angle increases, and to a higher value when said current steering angle decreases.

18. The method according to claim 16, comprising controlling the torque split ratio between said at least one first electric machine and said at least one second electric machine to increase when said current steering angle increases.

19. The method according to claim 16, wherein said at least one second electric machine comprises two second electric machines, one at a left end of the second axle and one at a right end of the second axle, the method comprising: limiting the propulsion torque provided by the second electric machines at the left end in dependence of the current steering angle of the second wheel at the left end of the second axle, and limiting the propulsion torque provided by the second electric machine at the right end in dependence of the current steering angle of the second wheel at the right end of the second axle.

20. (canceled)

21. (canceled)

22. The method according to claim 15, wherein said current state of the second axle is a measure of how much lateral force that is generated by tyres of said second wheels of the second axle, or wherein said current state of the second axle is a measure of how much lateral slip that is generated by tyres of said second wheels of the second axle.

23. The method according to claim 22, comprising limiting the propulsion torque provided by said at least one second electric machine: to a lower value when said generated lateral force or lateral slip is increased, and to a higher value when said generated lateral force or lateral slip is decreased.

24. (canceled)

25. A computer program comprising program code for performing the steps of claim 15 when said program is run on a computer.

26. A non-transitory computer readable medium carrying a computer program comprising program code for performing the steps of claim 15 when said program code is run on a computer.

27. A control unit for controlling the propulsion of a vehicle, the control unit being configured to perform the steps of the method according to claim 15.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0078] With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

[0079] In the drawings:

[0080] FIG. 1 illustrates a vehicle according to at least one exemplary embodiment of the invention.

[0081] FIG. 2 illustrates very schematically parts of a vehicle according to at least one exemplary embodiment of the invention.

[0082] FIG. 3 illustrates very schematically parts of a vehicle according to at least one other exemplary embodiment of the invention.

[0083] FIG. 4 schematically illustrates a method according to an exemplary embodiment of the invention.

[0084] FIG. 5 schematically illustrates a control unit according to at least one exemplary embodiment of the invention.

[0085] FIG. 6 schematically illustrates a computer program product according to at least one exemplary embodiment of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0086] The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain aspects of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments and aspects set forth herein; rather, the embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Accordingly, it is to be understood that the present invention is not limited to the embodiments described herein and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims. Like reference numerals refer to like elements throughout the description.

[0087] FIG. 1 illustrates a vehicle 1 according to at least one exemplary embodiment of the invention. The exemplary illustration in FIG. 1 shows a tractor unit for towing a trailer unit (not shown), which together make up a semitrailer vehicle. However, the invention is applicable to other types of vehicles as well. For instance, the vehicle may be a different type of vehicle for cargo transport, such as a truck, or a truck with a dolly unit arranged to tow a trailer unit, etc. It should furthermore be understood that the inventive concept is not limited to heavy duty vehicles, but may also be implemented in other vehicles, such as cars.

[0088] The vehicle 1 may be driver-operated, wherein the driver operates the vehicle 1 from within a cabin 2. However, in some exemplary embodiments, the vehicle 1 may be autonomous.

[0089] The illustrated vehicle 1 is supported on wheels 4. Although the vehicle 1 in FIG. 1 only has two axles carrying wheels, the inventive concept is applicable to vehicles having more axles carrying wheels, such as in the above-mentioned different types of vehicles.

[0090] Each wheel 4, or each group of wheels, may be associated with a torque actuator in the form of an electric machine. In some exemplary embodiments, one or more of the electric machines may be a regenerative torque actuator which is able to slow down wheel rotational velocity upon request.

[0091] The electric machines are controlled by a control unit, which may control the torque applied to the wheels 4 by means of the electric machines. The electric machines and the control unit are not illustrated in FIG. 1, but will be discussed in more detail in connection with other figures. The electric machines may be provided on an axle level, i.e. one electric machine is used for providing torque to both left and right wheels of an axle, e.g. via an open differential. In other embodiments, the electric machines may be provided on a wheel level, i.e. one electric machine provides torque to an associated wheel 4. In some exemplary embodiments, the vehicle may have electric machines on both the axle and the wheel level. Furthermore, in some exemplary embodiments, an individual wheel 4 may be powered by more than one electric machines, such as two or three electric machines.

[0092] From the above it should be understood that there are a number of different conceivable configurations of electric machines, for which the general inventive concept may be implemented. In summary, there may be provided one or more electric machines for providing a propulsion force to an axle of the vehicle 1.

[0093] The control unit may be communicatively coupled to local control modules, such as axle modules or wheel end modules, which can activate/deactivate the electric machines. Such local control modules may also be operatively connected to other torque actuators such as friction brakes, for activating/deactivating such other torque actuators. Thus, the control unit may communicate with the local control modules and thereby provide instructions on controlling of the electric machines, and possibly other torque actuators. It should, however, be understood, that in some exemplary embodiments, the control unit may be in direct communication with the electric machines. Furthermore, it should be understood that the control unit may comprise a number of sub-units distributed across the vehicle 1, or it may be a single physical unit.

[0094] FIG. 2 illustrates very schematically parts of a vehicle according to at least one exemplary embodiment of the invention. The vehicle comprises a first axle 10, here illustrated as a non-steered rear axle, and a second axle 12, here illustrated as a steered front axle. It should, however, be understood that in other exemplary embodiments the first axle may be a front axle and the second axle may be a steered rear axle.

[0095] Each one of the first axle 10 and the second axle 12 is provided with a pair of wheels 4. Thus, the first axle 10 is provided with a pair of first wheels 4 and the second axle 12 is provided with a pair of second wheels 4. Since the second axle 12 is a steered axle, said pair of second wheels 4 on the second axle 12 may be turned. Although only one left wheel 4 and one right wheel 4 are illustrated for each axle 10, 12, in other exemplary embodiments, it is conceivable to have more wheels, such as two rear left wheels and two rear right wheels on the first axle 10.

[0096] The vehicle also comprises at least one first electric machine 14 for providing propulsion torque to the first axle 10. In the illustrated example, there are provided two first electric machines 14, one for each wheel 4. Similarly, the vehicle comprises at least one second electric machine 16 for providing propulsion torque to the second axle 12. In the illustrated example, there are provided two second electric machines 16, one for each wheel 4.

[0097] The vehicle also comprises a control unit 50 which is configured to control the electric machines 14, 16.

[0098] Furthermore, the control unit 50 is configured to limit the propulsion torque provided by said at least one second electric machine 16 in dependence of a current state of the second axle 12, including the components it is provided with.

[0099] The current state may, for instance, be a current steering angle of at least one of said second wheels 4 of the second axle 12, a current set height of a height-adjustable connector of the second axle 1, and/or a measure of how much lateral force or lateral slip that is generated by tyres of said second wheels 4 of the s second axle 12. In the following disclosure, focus will be on the first example, i.e. the steering angle.

[0100] Thus, the control unit 50 may be configured to limit the propulsion torque provided by said at least one second electric machine 16 in dependence of a current steering angle of at least one of said second wheels 4, i.e. one of the wheels 4 at the second axle 12. The control unit may suitably receive input signals representative of the current steering angles, such as input signals from angle sensors 17 (only one illustrated in FIG. 2, however, it should be understood that the right wheel may of course also have an angle sensor). As previously explained in this disclosure, other means for directly or indirectly measuring the steering angles may additionally or alternatively be provided, such as measuring parameters related to a power steering assist arrangement.

[0101] When the current steering angle is increased the control unit 50 may suitably lower the maximum propulsion torque that the second electric machine(s) 16 are allowed to provide to the second axle 12. When the current steering angle is decreased, the control unit 50 may instead increase the maximum allowable propulsion torque for the second electric machine(s) 16. By limiting the maximum allowable propulsion torque in dependence of the current steering angle, vehicle components such as universal joints may be spared from adverse effects, and their lifetime can be extended. The control unit 50 may suitably be configured to increase the torque split ratio between the first electric machines 14 on the one hand and the second electric machines 16 on the other hand when said current steering angle increases. Thus, the control unit 50 may allocate a larger proportion of the total torque request to the first electric machines 14 when said current steering angle is increased. Conversely, when the steering angle is decreased the control unit 50 may decide to provide a somewhat smaller proportion of the total torque request to the first electric machines 14, as long as the second electric machines 16 can be kept within the torque limitation determined by the control unit 50.

[0102] The first axle 10 may have different properties compared to the second axle 12. Furthermore, the first electric machines 14 may have different properties compared to the second electric machines 16. The control unit 50 may take into account the different properties in its control strategy.

[0103] The control unit 50 may be configured to identify which one of the first electric machines 14 and the second electric machines 16 that have the highest electric efficiency for operating the vehicle at a current or a desired vehicle operating condition. The control unit 50 may, based on the identification, control the identified electric machines to provide a propulsion torque to its associated axle. For instance, the efficiency map for the first electric machines 14 may be such that they have relatively high efficiency at low speeds and high torques, while the efficiency map for the second electric machines 16 may be such that they have relatively high efficiency at high speeds and low torques. In such case, the control unit 50 may, for instance, identify the first electric machines 14 at an uphill start situation, but identify the second electric machines 16 when the vehicle is at cruising speed on a flat road.

[0104] When the total torque or the total power that is needed for needed for maintaining a current vehicle operating condition, or for reaching a desired vehicle operating condition, is not achieved by solely controlling the identified electric machines, then the control unit 50 may also control the other one of the first and second electric machines 14, 16 to provide torque to its associated axle 10, 12 so that said total torque or total power is obtained. Thus, the non-identified electric machines may be used to fill up the torque or power need. For instance, if the start is in a very steep uphill slope, and the control unit 50 notes that operating the first electric machines 14 is not enough for attaining the desired torque/power, then the control unit 50 may also control the second electric machines 16 to provide additional torque/power. However, if the uphill start also involves turning the vehicle, the control unit will depending on the steering angle limit the maximum allowable torque(s) that the second electric machine(s) 16 may provide to the second axle 12.

[0105] Although not illustrated in the schematic view, each electric machine 14, 16 may suitably be operatively connected to a respective wheel end module. In such case, the control unit 50 may send requests to each wheel end module which in turn operates its associated electric machines 14, 16. The wheel end modules may also operate the activation and deactivation of other torque actuators, such as friction brakes. Instead of wheel end modules, there may be provided axle module which may be operatively connected to all torque actuators on an axle. In such case, the control unit 50 may send requests to the axle module.

[0106] As mentioned above, the first axle 10 may have different properties compared to the second axle 12. For instance, the first axle 10 may have a higher gear ratio than the second axle 12. As an example, the first axle 10 may have a gear ratio of 22:1 and the second axle 12 may have a gear ratio of 10:1. As understood from previous discussions, the first axle 10 may suitably be configured as a startability axle to be powered when initially accelerating the vehicle, and the second axle 12 may be configured as a cruise axle to be powered when the vehicle is cruising. As already mentioned, one of said different properties of the first axle 10 compared to the second axle 12 may be that the second axle 12 is a steered axle and the first axle 10 is a non-steered axle. Another possible difference in property is that the first axle 10 may be declutchable, while the second axle 12 is not declutchable. Depending on the type of electric machines 14 propelling the first axle 10, it may be desirable to declutch the first axle 10 to reduce the risk of energy losses (due to unused electric machine resistance) when the vehicle is driving in a cruise mode.

[0107] As mentioned above, the first electric machines 14 may have different properties compared to the second electric machines 16. For instance, the first electric machines 14 may have a different efficiency map than the second electric machines 16. The efficiency maps may suitably be adapted to different vehicle operating conditions, such as start mode, acceleration mode and cruise mode. Suitably, the maximum electric efficiency (i.e. the maximum efficiency in the efficiency map) of the second electric machines 16 is higher than the maximum electric efficiency of the first electric machines 14, such as 95-96% compared to 92%-93%. One of said different properties of the first electric machines 14 compared to the second electric machines 16 may be that the first electric machines 14 are configured for handling larger transient torques than the second electric machines 16. The second electric machines 16 may suitably be dimensioned and configured for powering the second axle 12 when the vehicle is cruising, such as at a predefined cruising speed range and a predefined slope. The second electric machines 16 may be configured for powering the second axle 12 at continuous torque, substantially without any transients. The first electric machines 14 may be configured for powering the first axle 10 at hill start, such as providing a transient maximum torque for a relatively short time length, for instance 30 seconds at a slope of 15%. The first electric machines 14 may suitably be induction motors, in which case declutching capability may be omitted. However, the first electric machines 14 may instead be permanent magnet motors, in which case they may suitably be declutchable from the first axle 10 to reduce the risk of energy losses due to unused electric machine resistance. The second electric machines 16 may suitably be permanent magnet motors.

[0108] As already explained previously in this disclosure, under some vehicle operating conditions, it may be more efficient to only control one of the two first electric machines 14. For instance, when the total torque or the total power needed for maintaining a current operating condition, or for reaching a desired vehicle operating condition, is below a predefined threshold value, then the control unit 50 may control only one of said two first electric machines 14 to provide a torque to the first axle 10, while the other one of said two first electric machines 14 is controlled not to provide any torque to the first axle 10.

[0109] Similarly, the control unit 50 may determine to control only one of said two second electric machines 16 to provide a torque to the second axle 12, while the other one of said two second electric machines 16 is controlled not to provide any torque to the second axle 12.

[0110] As already mentioned, instead of having two first electric machines 14 and two second electric machines 16, which act on a wheel level, as illustrated in the FIG. 2, in some exemplary embodiments there may be an electric machine (or more electric machines) which act on an axial level. In such axial level embodiments, the control unit may limit the torque of the second electric machine(s) based on the current steering angle of one or both wheels of the second axle. In FIG. 2, however, the control unit 50 is suitably configured to limit the propulsion torque provided by the second electric machine 16 at the left end of the second axle 12 in dependence of the current steering angle of the second wheel 4 at the left end of the second axle 12. Similarly, the limiting of the second electric machine 16 on the right hand side may be based on the current steering angle of the wheel 4 at the right end of the second axle 12.

[0111] FIG. 3 illustrates very schematically parts of a vehicle according to at least one other exemplary embodiment of the invention. In addition to the first axle 10 and the second axle 12, the vehicle is provided with two additional wheel axles 20, 22. In this exemplary embodiment the first axle 10 may be a lift axle which is liftable from the ground. The lift axle (first axle 10) is here illustrated as a pusher axle, although a tag axle would also be conceivable. The first axle 10 is suitably a startability axle which is used when starting and accelerating the vehicle, but which may be lifted from the ground when the vehicle reaches the cruise mode. In the cruise mode it may be enough to provide propulsion force to the second axle 12. Similarly, to FIG. 2, the exemplary embodiment of FIG. 3 includes first electric machines 14 operatively connected to the first axle 10, and second electric machines 16 operatively connected to the second axle 12, and a control unit 50 which controls the electric machines 14, 16 (either directly or via wheel end modules/axle modules).

[0112] FIG. 4 schematically illustrates a method 100 according to an exemplary embodiment of the invention. More specifically, there is illustrated a method 100 of controlling the propulsion of a vehicle, wherein the vehicle comprises: [0113] a first axle provided with at least a pair of first wheels, [0114] a second axle provided with at least a pair of second wheels, wherein the second axle is a steered axle allowing said second wheels to be turned, [0115] at least one first electric machine for providing propulsion torque to the first axle, [0116] at least one second electric machine for providing propulsion torque to the second axle, the method 100 comprising:

[0117] in a step S1, limiting the propulsion torque provided by said at least one second electric machine in dependence of a current state of the second axle.

[0118] In some exemplary embodiments, in step 1, the propulsion torque provided by said at least one second electric machine is limited in dependence of a current steering angle of at least one wheel of the second axle. In some exemplary embodiments, said step S1, may comprise limiting the propulsion torque provided by said at least one second electric machine: [0119] to a lower value when said current steering angle increases, and [0120] to a higher value when said current steering angle decreases.

[0121] The method 100 may in some exemplary embodiments comprise, in an optional step S2, controlling the torque split ratio between said at least one first electric machine and said at least one second electric machine to increase when said current steering angle increases.

[0122] When said at least one second electric machine comprises two second electric machines, one at a left end of the second axle and one at a right end of the second axle, the method may comprise, in an optional step S3, [0123] limiting the propulsion torque provided by the second electric machines at the left end in dependence of the current steering angle of the second wheel at the left end of the second axle, and [0124] limiting the propulsion torque provided by the second electric machine at the right end in dependence of the current steering angle of the second wheel at the right end of the second axle.

[0125] FIG. 5 schematically illustrates a control unit 50 according to at least one exemplary embodiment of the invention. In particular, FIG. 5 illustrates, in terms of a number of functional units, the components of a control unit 50 according to exemplary embodiments of the discussions herein. The control unit 50 may be comprised in a vehicle, such as illustrated schematically in FIGS. 2 and 3. Processing circuitry 510 may be provided using any combination of one or more of a suitable central processing unit CPU, multiprocessor, microcontroller, digital signal processor DSP, etc., capable of executing software instructions stored in a computer program product, e.g. in the form of a storage medium 530. The processing circuitry 510 may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA.

[0126] Particularly, the processing circuitry 510 is configured to cause the control unit 50 to perform a set of operations, or steps, such as the method discussed in connection to FIG. 4. For example, the storage medium 530 may store the set of operations, and the processing circuitry 510 may be configured to retrieve the set of operations from the storage medium 530 to cause the control unit 50 to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus, the processing circuitry 510 is thereby arranged to execute exemplary methods as herein disclosed.

[0127] The storage medium 530 may also comprise persistent storage, which, for example may be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[0128] The control unit 50 may further comprise an interface 520 for communications with at least one external device such as the electric machines, a battery module, sensors (e.g. angle sensor 17 in FIGS. 2 and 3), etc. . . . As such, the interface 520 may comprise one or more transmitters and receivers, comprising analogue and digital components and a suitable number of ports for wireline or wireless communication.

[0129] The processing circuitry 510 controls the general operation of the control unit 50, e.g. by sending data and control signals to the interface 520 and the storage medium 530, by receiving data and reports from the interface 520, and by retrieving data and instructions form the storage medium 530. Other components, as well as the related functionality, of the control unit 50 are omitted in order not to obscure the concepts presented herein.

[0130] Thus, with reference also to the previously discussed figures, FIG. 5 shows an exemplary control unit 50 for controlling the propulsion of a vehicle, the control unit 50 being configured to perform the steps of the method of FIG. 4, including any embodiments thereof.

[0131] FIG. 6 schematically illustrates a computer program product 600 according to at least one exemplary embodiment of the invention. More specifically, FIG. 6 illustrates a computer readable medium 610 carrying a computer program comprising program code means 620 for performing the methods exemplified in FIG. 4, when said program product is run on a computer. The computer readable medium 610 and the program code means 620 may together form the computer program product 600.