A METHOD FOR OPERATING A VEHICLE

Abstract

The invention relates to a method for operating a vehicle (1), wherein the vehicle (1) comprises: a driveline (2, 4) configured to provide a driving power to at least one wheel (3) of the vehicle (1) for propulsion of the vehicle (1); and a wheel brake system (5) configured to brake the vehicle (1), wherein the method comprises the steps of: receiving (S1) a control signal indicative of a request for acceleration or deceleration of the vehicle (1), wherein the acceleration or deceleration control signal is generated by an accelerator device, such as an accelerator pedal, configured to be acted upon by a driver of the vehicle (1); and controlling (S2) the driveline (2, 4) in response to the acceleration or deceleration control signal. The method comprises the steps of: providing (S3) an acceleration or deceleration threshold limit representing i) the highest vehicle acceleration that can be allowed for the received acceleration control signal in the current circumstances, or ii) the lowest vehicle deceleration that can be allowed for the received deceleration control signal in the current circumstances; determining (S4) a resulting vehicle acceleration or deceleration that is or will be the result from the step of controlling the electric driveline in response to the acceleration or deceleration control signal; comparing (S5) the resulting vehicle acceleration or deceleration with the corresponding acceleration or deceleration threshold limit and determining whether the resulting vehicle acceleration is or will be higher than the acceleration threshold limit or whether the resulting vehicle deceleration is or will be lower than the deceleration threshold limit; and when the resulting vehicle acceleration is or will be higher than the acceleration threshold limit or when the resulting vehicle deceleration is or will be lower than the deceleration threshold limit; applying (S6) the wheel brake system (5) so as to reduce an actual vehicle acceleration or increase an actual vehicle deceleration towards the corresponding acceleration or deceleration threshold limit.

Claims

1. A method for operating a vehicle, wherein the vehicle comprises: a driveline configured to provide a driving power to at least one wheel of the vehicle for propulsion of the vehicle; and a wheel brake system configured to brake the vehicle, wherein the method comprises the steps of: receiving a control signal indicative of a request for acceleration of the vehicle, wherein the acceleration control signal is generated by an accelerator device, such as an accelerator pedal, configured to be acted upon by a driver of the vehicle; and controlling the driveline in response to the acceleration control signal, characterized in that the method comprises the steps of: providing an acceleration threshold limit representing the highest vehicle acceleration that can be allowed for the received acceleration control signal in the current circumstances; determining a resulting vehicle acceleration that is or will be the result from the step of controlling the driveline in response to the acceleration control signal; comparing the resulting vehicle acceleration with the corresponding acceleration threshold limit and determining whether the resulting vehicle acceleration is or will be higher than the acceleration threshold limit; and when the resulting vehicle acceleration is or will be higher than the acceleration threshold limit; applying the wheel brake system so as to reduce an actual vehicle acceleration towards the corresponding acceleration threshold limit.

2. The method according to claim 1, wherein the resulting vehicle acceleration is the actual vehicle acceleration and wherein the method comprises the step of: determining the actual vehicle acceleration based on measurements of the vehicle's actual acceleration and/or actual speed.

3. The method according to claim 1, wherein the method comprises the step of: determining a magnitude or rate of change of the acceleration control signal.

4. The method according to claim 1, wherein the method comprises the step of: determining a current weight and/or a current speed of the vehicle.

5. The method according to claim 1, wherein the method comprises the step of: determining an inclination of the vehicle in a longitudinal direction thereof.

6. The method according to claim 1, wherein the method comprises the step of: determining whether a reverse gear of the vehicle is selected.

7. The method according to claim 1, wherein the driveline is an electric driveline comprising: an electric motor configured to provide a driving power to the at least one wheel of the vehicle for propulsion of the vehicle; a rechargeable energy storage system configured to provide the electric motor with electric energy; and a regenerative braking system configured to supply energy to the energy storage system while braking the vehicle, wherein the wheel brake system is configured to brake the vehicle as a complement or alternative to the regenerative braking system.

8. The method according to claim 7, wherein the method comprises the step of: determining a capacity of the regenerative braking system to supply energy to the energy storage system.

9. The method according to claim 8, wherein the wheel brake system is applied only when the capability of the regenerative braking system to supply energy to the energy storage system is below a capacity threshold limit.

10. The method according to claim 5, wherein the wheel brake system is applied only when the inclination of the vehicle in the longitudinal direction thereof is above an inclination threshold limit.

11. The method according to claim 6, wherein the wheel brake system is applied only when the reverse gear of the vehicle is selected.

12. Vehicle comprising: a driveline configured to provide a driving power to at least one wheel of the vehicle for propulsion of the vehicle; a wheel brake system configured to brake the vehicle; and a control circuit configured to perform the steps of claim 1.

13. The vehicle according to claim 12, wherein the driveline is an electric driveline provided with: an electric motor configured to provide a driving power to the at least one wheel of the vehicle for propulsion of the vehicle; a rechargeable energy storage system configured to provide the electric motor with electric energy; and a regenerative braking system configured to supply energy to the energy storage system while braking the vehicle, wherein the wheel brake system is configured to brake the vehicle as a complement or alternative to the regenerative braking system.

14. A computer program product comprising program code for performing the steps of claim 1 when said program code is run on a computer.

15. A computer readable medium carrying a computer program comprising program code for performing the steps of claim 1 when said program product is run on a computer.

16. A control circuit for controlling a vehicle, the control circuit being configured to perform the steps of the method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

[0046] In the drawings:

[0047] FIG. 1 shows a schematic view of a vehicle arranged to be operated by the method of this disclosure, and

[0048] FIG. 2 shows an example of a flow diagram for the method of operating the vehicle of FIG. 1.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0049] FIG. 1 shows a schematic view of a vehicle in the form of a bus 1 having a longitudinal direction extending between a front 1a and a rear 1b and being provided with an electric driveline. The electric driveline comprises an electric motor 2 configured to provide a driving power to at least one wheel 3 of the vehicle for propulsion of the vehicle, a rechargeable energy storage system 4 configured to provide the electric motor 2 with electric energy, and a regenerative braking system configured to supply energy to the energy storage system 4 while braking the vehicle 1. The driveline also includes a gearbox (not shown) allowing at least a selection between a forward gear and a reverse gear. In this example, the energy storage system 4 may be a Li-ion battery pack and the electric motor 2 works also as an electric generator and thus forms part of the regenerative braking system.

[0050] The vehicle 1 further comprises a wheel brake system 5 (indicated in FIG. 1 to be located where the wheel 3 is located) configured to brake the vehicle 1 as a complement or alternative to the regenerative braking system. The wheel brake system may include conventional friction brakes arranged at each wheel 3.

[0051] Further, the vehicle 1 is provided with a control circuit 6 configured to control the electric driveline, the wheel brake system 5 and other components. The control circuit 6 is arranged to receive signals from e.g. a driver of the vehicle 1 and from various components and sensors. Control circuits of this type and controlling operation of vehicles like the one in FIG. 1 are well known as such.

[0052] The vehicle 1 is arranged for being driven by a driver and it is further provided with a set of (not shown) devices allowing the driver to send control/command signals to the control circuit 6. These devices include an accelerator pedal that when pressed down or released or is kept in a certain position or at a certain angle sends a signal indicative of an acceleration or deceleration request to the control circuit 6 that controls the driveline in response to this signal. These devices also include a braking pedal that when pressed, or at least when pressed hard, leads to activation of the wheel (friction) brake system.

[0053] An angle ? indicates that the vehicle 1 in FIG. 1 is inclined in the longitudinal direction thereof, i.e. the vehicle 1 is positioned on a hillside with its front 1a directed upwards and its rear 1b directed downwards. An arrow 7 indicates that the vehicle 1 is moving or is about to move backwards down the slope.

[0054] The vehicle 1 is further provided with a variety of sensors including sensors for measuring the vehicle's speed, acceleration/deceleration, inclination and weight, and for determining the temperature of e.g. the energy storage system/battery 4. Further, means are provided for determining a capacity of the regenerative braking system to supply energy to the energy storage system 4. Such means may include a battery management system (BMS) arranged to control charging and functioning of the energy storage system/battery 4.

[0055] FIG. 2 shows an example of a flow diagram for a method of operating the vehicle 1 of FIG. 1. In this example the driver has selected the reverse gear so as to start accelerating backwards/downwards as indicated by arrow 7 in FIG. 1.

[0056] In FIG. 2, the step S1 is receiving, by the control circuit 6, a control signal indicative of a request for acceleration of the vehicle 1, wherein the acceleration control signal is generated by the accelerator pedal acted upon by the driver of the vehicle 1.

[0057] During the next step S2, the control circuit 6 controls the electric driveline in response to the acceleration or deceleration control signal.

[0058] Step S3 is providing an acceleration threshold limit representing the highest vehicle acceleration that can be allowed for the received acceleration control signal.

[0059] The subsequent step S4 is determining a resulting vehicle acceleration that is or will be the result from the step of controlling the electric driveline in response to the acceleration or deceleration control signal.

[0060] The step S5 represents comparing the resulting vehicle acceleration with the corresponding acceleration threshold limit and determining whether the resulting vehicle acceleration is or will be higher than the acceleration threshold. When the resulting vehicle acceleration is or will be higher than the acceleration threshold limit, step S6 is performed, applying the wheel brake system 5 so as to reduce an actual vehicle acceleration towards the corresponding acceleration threshold limit.

[0061] In a variant of the example above the resulting vehicle acceleration in step S4 is the actual vehicle acceleration and in that case step S4 may take the form of step S41, comprising determining the actual vehicle acceleration based on measurements of the vehicle's actual acceleration and/or speed.

[0062] In variants of the example above, the method may comprise one or more of the following steps: [0063] determining a magnitude or rate of change of the acceleration control signal; [0064] determining whether a capacity of the regenerative braking system to supply energy to the energy storage system 4 is below a capacity threshold limit; [0065] determining a current weight and/or a current speed of the vehicle 1; [0066] determining whether an inclination of the vehicle 1 in a longitudinal direction thereof is above an inclination threshold limit; and/or [0067] determining whether a reverse gear of the vehicle 1 is selected.

[0068] Various triggers can be used for activating the step S6, where the wheel brake system 5 is applied by automatic means (and not by the driver). When the method uses triggers it may comprise one or more of the following: [0069] the wheel brake system 5 is applied only when the capability of the regenerative braking system to supply energy to the energy storage system 4 is below the capacity threshold limit; [0070] the wheel brake system 5 is applied only when the inclination a of the vehicle 1 in the longitudinal direction thereof is above the inclination threshold limit; and/or [0071] the wheel brake system 5 is applied only when the reverse gear of the vehicle 1 is selected.

[0072] It is to be understood that the present invention is not limited to the embodiments described above 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. For instance, it is not necessary that the vehicle is provided with an electric driveline.