GB2563561B

GB2563561B - Suspension control system

Info

Publication number: GB2563561B
Application number: GB1704845.5A
Authority: GB
Inventors: Burdock William; Ficca Riccardo
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2017-03-27
Filing date: 2017-03-27
Publication date: 2019-11-06
Anticipated expiration: 2037-03-27
Also published as: GB2563561A; DE102018204606A1; GB201704845D0; DE102018204606B4

Description

Suspension Control System

TECHNICAL FIELD

The present disclosure relates to a suspension control system for a vehicle. In particular, the disclosure relates to a controller configured to control an active suspension system of a vehicle. Aspects of the invention relate to a controller, an active suspension system, to a vehicle and to a method.

BACKGROUND

It is well known that vehicles benefit from having a means of controlling vehicle roll during cornering, as this has a direct effect on the way in which the vehicle handles. Typically the vehicle roll is controlled by antiroll bars or sway bars mounted to each axle as part of a suspension system. These are often passive mechanical devices that provide a fixed roll torque distribution to the vehicle and resist vehicle roll during cornering. Typically these devices are not optimised to driving conditions.

For example, vehicle handling characteristics vary significantly depending on the direction a vehicle is travelling in. When a vehicle is travelling in reverse the vehicle is subject to inversed yaw motion when cornering since the steering wheels are to the rear of the direction of travel. As a result of the inversed yaw motion, the vehicle handles in a different manner and many passive antiroll bars are not optimised to deal with such conditions. Drivers may experience unpleasant driving conditions resulting from increased vehicle roll whilst driving in reverse in vehicles fitted with passive antiroll bars.

The present invention has been devised to mitigate or overcome at least some of the above-mentioned problems.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a suspension control system, a method, a controller and a vehicle.

According to an aspect of the present invention there is provided a controller for an active suspension system, the controller configured to: receive an input signal indicative of a direction of travel of a vehicle, determine a target roll characteristic for the vehicle in dependence on the direction of travel, and output the target roll characteristic to the active suspension system, wherein the controller comprises at least a forward and a reverse roll characteristic model, and wherein the controller is configured to select one of the forward or reverse roll characteristic models in dependence on the direction of travel.

The controller provides the advantage of actively controlling an active suspension system within a vehicle in dependence on parameters of the vehicle, including the direction in which the vehicle is travelling. This improves the vehicle handling in both the forward and reverse directions. The roll characteristic model accurately models vehicle handling characteristics and may determine at least one of a target vehicle roll angle, a target total roll torque or a roll torque distribution for the active suspension system. The roll characteristic model may use look-up tables to determine the target roll characteristic based on the input parameters or the roll characteristic model may model the vehicle dynamics to determine a target roll characteristic.

The target roll characteristic may include at least one of a target vehicle roll angle, a total roll torque or a roll torque distribution. The total roll torque controls the body roll angle of the vehicle. Thus, by determining a target total roll torque the controller is also determining the target body roll of the vehicle in dependence on the direction of travel of the vehicle.

The controller may comprise a vehicle data processor module configured to determine the at least one vehicle parameter based on an input from at least one vehicle sensor.

The reverse roll characteristic model may be configured to determine at least one of a target vehicle roll angle, a total roll torque and a roll torque distribution in dependence on at least one other vehicle parameter in addition to the direction of travel. In one embodiment of the invention the controller is configured to output the target roll characteristic in real-time (i.e. instantaneously in response to the vehicle conditions at the time). Real-time may be considered to relate to outputting the calculated target roll characteristic to the suspension control module within milliseconds so that it is available at the active suspension system virtually immediately. This provides the advantage of determining and outputting a target roll characteristic to the suspension system quickly in dependence with vehicle parameters. This ensures that the output target roll characteristic is appropriate for the current driving conditions experienced by the vehicle.

The vehicle parameters may include at least one of: selected gear, lateral acceleration, yaw rate, roll rate, pitch rate, steering wheel angle, steering wheel rotation rate, vehicle speed, surface friction, selected driver mode, surface roughness, terrain type, longitudinal incline of the vehicle, vehicle’s weight distribution, vehicle’s centre of gravity, suspension height, an individual wheel torque request, and tyre pressure.

This list is not exhaustive and other vehicle parameters relevant to determining a target roll characteristic for a vehicle may be used.

According to an aspect of the invention there is provided an active suspension system comprising the aforementioned controller.

According to an aspect of the invention, there is provided a method of controlling an active suspension system within a vehicle, the method comprising receiving an input signal indicative of a direction of travel of a vehicle, determining a target roll characteristic for the vehicle in dependence on the direction of travel, outputting the target roll characteristic to the active suspension system, the method may comprise selecting one of a forward or reverse characteristic model in dependence on the direction of travel of the vehicle. The method may comprise inputting parameters of the vehicle into the reverse roll characteristic model in dependence on receiving an input indicating the vehicle is travelling in reverse.

The target roll characteristic may include at least one of a target vehicle roll angle, a total roll torque or a roll torque distribution.

The method may comprise inputting parameters of the vehicle into a reverse roll characteristic model in dependence on receiving an input indicating the vehicle is travelling in reverse. In another embodiment the input signal is indicative of vehicle sensor data and the target roll characteristic may be determined in dependence on the vehicle sensor data.

The method may comprise outputting a signal to a suspension control module and controlling an active suspension system in dependence with the output signal. The output signal may be output to the active suspension system in real-time. The output signal may be indicative of at least one of a target vehicle roll angle, a total roll torque or a roll torque distribution.

According to an aspect of the invention, there is provided a controller configured to perform the previously described method.

According to another aspect of the invention, there is provided a vehicle comprising a suspension control system. The vehicle may comprise an electronically controlled suspension system. The vehicle may comprise an actively controlled suspension system. The vehicle may comprise an electromechanically controlled suspension system. The vehicle may be an autonomous vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a vehicle comprising a suspension control module of the present invention;

Figure 2 is a fully active suspension system comprising anti-roll bars and the suspension control module of Figure 1;

Figure 3 is an alternative fully active suspension system and the suspension control module of Figure 1;

Figure 4 is a block diagram of the suspension control module of Figure 1; and

Figure 5 is a flow chart of the method steps followed by the suspension control module of Figure 1.

DETAILED DESCRIPTION

In general terms, embodiments of the invention provide a suspension control system including a suspension control module for determining a target vehicle roll angle, in dependence on vehicle parameters including the direction in which the vehicle is travelling. A suspension control module receives inputs indicative of various vehicle parameters and determines, based on the vehicle parameters, a target vehicle roll angle. The suspension control module outputs the target vehicle roll angle or a signal indicative of the target vehicle roll angle to the active suspension system to configure or control the active suspension system in dependence on the determined target vehicle roll angle by controlling the total roll torque and roll torque distribution of the active suspension system.

The “total roll torque” within the active suspension system provides a means of controlling and limiting the roll angle of the vehicle. The “roll torque distribution” is the ratio between front and rear axle roll stiffness and contributes to the vehicle cornering characteristics.

Controlling the active suspension system in dependence with the direction of travel provides greater control of the vehicle roll angle when travelling both forwards and backwards, improved comfort for passengers within the vehicle, improved vehicle composure, increased off-road capabilities and greater ability to configure the vehicle handling characteristics. A specific embodiment of the invention will now be described, with numerous specific features discussed, to provide a thorough understanding of how the inventive concept as defined in the claims may be implemented in practice. However, it will be apparent to the skilled person that the invention may be put into effect in other ways and that in some instances well known methods, techniques and structures have been summarised to avoid obscuring the invention unnecessarily.

To place embodiments of the invention in a suitable context, Figure 1 illustrates schematically a vehicle 10 that is suitable for use with embodiments of the invention. The vehicle 10 includes a suspension control module 12, an active suspension system 14 and vehicle sensors 16.

The vehicle sensors 16 output vehicle data including data indicative of the direction of travel and lateral acceleration to the suspension control module 12. The suspension control module 12 is a controller configured to control the active suspension system 14 in response to data from the vehicle sensors 16. The active suspension system 14 is a suspension system with a variable total roll torque and variable roll torque distribution that is controlled by a signal indicative of a target vehicle roll angle received from the suspension control module 12.

An embodiment of the active suspension system 14 is shown in further detail in Figure 2. The vehicle 10 comprises two steerable wheels 26, 29 mounted on suspension arms 22, 25 toward the front of the vehicle 10 and two non-steerable wheels 27, 28 mounted on suspension arms 23, 24 toward the rear of the vehicle 10 (i.e. a front wheel steer vehicle). The suspension arms 22, 23, 24, 25 are mounted to a chassis (not shown) via their inner ends and are pivotable around their mounting. A first anti-roll torsion bar 20 couples the front suspension arms 22, 25 and a second anti-roll torsion bar 21 couples the rear suspension arms 23, 24. The anti-roll torsion bars 20, 21 oppose vertical movement of the suspension arms 22, 23, 24, 25 and provide a variable torque counteracting the roll of the vehicle 10 when cornering. The anti-roll torsion bars 20, 21 are connected to and controllable by the suspension control module 12. The suspension control module 12 may vary the torque of the front and rear anti-roll bars 20, 21 independently, in dependence on parameters of the vehicle 10, thus enabling a fully customisable roll torque distribution and total roll torque. The front and rear anti-roll torsion bars 20, 21 are typically operable by means of hydraulic or electro-mechanical actuators in a manner which would be familiar to a person skilled in the art.

The roll torque distribution is defined as the ratio of front axle roll stiffness to rear axle roll stiffness. The roll torque distribution defines a vehicle’s cornering characteristic and thus handling. Controlling the active suspension system 14 to vary the total roll torque and roll torque distribution in dependence on various vehicle parameters provides the advantage of being able to configure a vehicle’s handling in dependence with road conditions and direction of travel.

Figure 3 shows an alternative embodiment of the active suspension system 14 that is suitable for use with the invention. In this embodiment the vehicle 10 has a fully active air suspension system. The fully active air suspension system does not include anti-roll torsion bars but instead includes actuators such as pneumatic cylinders or electromechanical actuators provide a variable stiffness to the suspension arms.

The alternative embodiment of the active suspension system 14 of Figure 3 comprises two steerable wheels 26, 29 mounted on suspension arms 22, 25 toward the front of the vehicle 10 and two non-steerable wheels 27, 28 mounted on suspension arms 23, 24 toward the rear of the vehicle 10 i.e. a front wheel steer vehicle. Each suspension arm 22, 23, 24, 25 is controlled by a pneumatic actuator comprising a gas strut 30, 32, 34, 36 that is controllable by the suspension control module 12. The suspension control module 12 adjusts the pneumatic pressure supplied to each gas strut to control the roll torque distribution and thus handling of the vehicle 10. The suspension control module 12 has the ability to control each suspension arm 22, 23, 24, 25 independently to deliver a fully customisable active suspension system 14.

The suspension control module 12 is shown in more detail in Figure 4. The suspension control module 12 comprises a vehicle data processor module 42 and a plurality of directionally-dependent roll characteristic models 40, 44. In the embodiment shown there is a forward roll characteristic model 40 and a reverse roll characteristic model 44. The suspension control module 12 also has an input for receiving vehicle data from the vehicle sensors 16 and an output for outputting a determined target vehicle roll angle to the active suspension system 14.

The roll characteristic models 40, 44 are configured to receive inputs indicative of vehicle parameters from the processor module 42, to determine a target vehicle roll angle, based on input vehicle data including the direction of travel, and to output the target vehicle roll angle to the vehicle processor module 42. In an embodiment of the invention there may be independent models for calculating the target vehicle roll angle or this may be calculated by a single model.

The roll characteristic models 40, 44 use look-up tables to determine the target roll angle of the vehicle 10 based on the input vehicle conditions. The target vehicle roll angle is output by the roll characteristic models 40, 44 to the vehicle processor module 42. In another embodiment of the invention the roll characteristic models 40, 44 may dynamically model the vehicle in real time to determine the desired vehicle roll angle based on the input vehicle parameters which can then be output to the vehicle data processor module 42.

The vehicle data processor module 42 is configured to receive vehicle data from the vehicle sensors 16 and to determine vehicle parameters based on the received input data. The vehicle data processor module 42 determines the direction that the vehicle 10 is travelling in and, depending on the direction of travel, the vehicle data processor module 42 inputs the determined vehicle parameters into the relevant directionally dependent roll characteristic model, for example either the forward roll characteristic model 40 or the reverse roll characteristic model 44.

The directionally dependent roll characteristic models receive inputs indicative of the various vehicle parameters from the vehicle data processor 42 and, based on the inputs, determines a target total roll torque and roll torque distribution for the vehicle 10. The target total roll torque and roll torque distribution is calculated by the relevant roll characteristic model in dependence on the direction of travel of the vehicle 10 and the vehicle parameters. The vehicle data processor module 42 outputs the target total roll torque and roll torque distribution to the active suspension system 14.

The active suspension system 14 provides feedback indicative of the vehicle roll angle to the suspension control module 12 thus providing closed loop feedback to the suspension control module 12. This improves the accuracy of the actual vehicle roll to the target vehicle roll as determined by the suspension control module 12.

In one example, the vehicle data processor module 42 receives an input from the vehicle sensors 16 indicating that the vehicle 10 is travelling in a forward direction. In this case, the vehicle data processor 42 inputs the determined vehicle parameters into the forward roll characteristic model 40. The forward roll characteristic model 40 uses the input vehicle parameters to determine a target total roll torque and roll torque distribution for the vehicle 10. The target optimal total roll torque and roll torque distribution is input to the vehicle data processor module 42 which provides an output signal indicative of the target total roll torque and roll torque distribution to the active suspension system 14. The process occurs in real-time thus enabling the active suspension system 14 to adapt substantially instantaneously according to the current driving conditions, and direction, at that time.

In another example, the vehicle data processor module 42 receives an input from the vehicle sensors 16 indicating that the vehicle 10 is travelling in reverse. The vehicle 10 handles differently in reverse so it is not appropriate to calculate a target vehicle roll angle using the forward roll characteristic model 40. In this scenario, the vehicle data processor 42 inputs the vehicle parameters into the reverse roll characteristic model 44 to determine a target vehicle roll angle for when the vehicle is travelling in the reverse direction.

The reverse roll characteristic model 44 outputs the target vehicle roll angle to the vehicle data processor 42 which provides an output signal indicative of the target vehicle roll angle to the active suspension system 14. The active suspension system 14 varies the total roll torque and roll torque distribution to best achieve the target vehicle roll angle input from the vehicle data processor 42. The process occurs in realtime thus enabling the active suspension system 14 to adapt substantially instantaneously according to the current driving conditions at that time.

The reverse roll characteristic model 44 predicts or estimates vehicle yaw and rotational motion whilst travelling in reverse, or is based on modelled and/or empirically derived vehicle yaw and rotational motion whilst travelling in reverse. This enables the suspension control module 12 to output a target vehicle roll angle to the active suspension system 14 to provide improved vehicle 10 handling whilst travelling in reverse. The reverse roll characteristic model 44 analyses the input vehicle parameters in real time and outputs the target vehicle roll angle to the active suspension system 14.

Prior to use, the directionally dependent roll characteristic models 40, 44 are calibrated to determine a target vehicle roll angle, for forward and reverse driving directions, based on modelling or measuring vehicle behaviours in different scenarios and determining the desired vehicle response. During use, the various vehicle parameters are then input to the appropriate model to extract a target vehicle roll angle in dependence on vehicle parameters including driving direction.

Typically, the suspension control module 12 contains either a model of the vehicle 10 that can be used to predict the dynamic response in both the forward and reverse driving directions or two roll characteristic models 40, 44, one for the forward direction of travel and one for the reverse direction. This is because the vehicle handling characteristics are variable between the forward and reverse directions of travel. However, the skilled person will appreciate that in an embodiment of the invention there may only be one model which accounts internally for the direction of travel before processing is initiated, or there may be greater than two models that may receive an input indicative of the direction of travel, and one or more other variable vehicle parameters which give rise to a different target vehicle roll angle (e.g. the terrain response mode when driving in a forward direction). In practice an embodiment incorporating one or two models only may be desirable.

In one embodiment, therefore, independent software modules are provided for each of the forward and reverse roll characteristic models 40, 44. In another embodiment the roll characteristic models form part of a common software module. In still further embodiments, there may be separate models for different vehicle settings (e.g. a selected driver mode dependent on terrain type), as described above.

As described previously, the suspension control system 12 receives vehicle parameters gathered from vehicle sensors 16 which are input to the vehicle data processor 42. The vehicle data processor 42 determines the vehicle parameters based on the input vehicle data. In one embodiment of the invention the suspension control module 12 receives inputs from a steering wheel rotation sensor, at least two lateral accelerometers or an integrated sensor module that can provide lateral acceleration, roll rate and yaw rate and a signal indicative of the direction of travel to determine the cornering forces experienced by the vehicle 10. The suspension control module 12 determines various vehicle parameters based on the aforementioned input vehicle data. The vehicle parameters are input into the appropriate roll characteristic model 40, 44 (forward or reverse) in dependence on the determined direction of travel. The target vehicle roll angle is calculated by the model based on at least the steering angle, lateral acceleration and the direction of travel, this is then output to the active suspension system 14 and the total roll torque and roll torque distribution of the system is then varied to best achieve the vehicle roll angle.

The amount of vehicle roll is controlled continuously by the suspension control module 12 based on the calculated target vehicle roll angle. At low lateral accelerations the roll torque provided by the active suspension system 14 minimises vehicle roll to provide the driver with a comfortable ride. At a higher lateral acceleration the target vehicle roll angle allows a degree of roll of the vehicle 10 so that the driver can feel the effects of the high lateral acceleration.

It may also be desirable to input into the roll characteristic models 40, 44 vehicle parameters indicative of: the selected gear, vehicle speed, direction of wheel rotation, steering wheel angle, steering wheel rotational rate, vehicle’s weight distribution, vehicle’s centre of gravity, suspension ride height or brake system individual wheel torque requests. These vehicle parameters may be used by the roll characteristic models 40, 44 to calculate a target vehicle roll angle for the relevant direction of travel.

The directionally dependent roll characteristic 40, 44 receive the input vehicle parameters and provide an output to the vehicle data processor module 42 indicative of a target vehicle roll angle. The output from the models is indicative of the manner in which the vehicle 10 will handle under those specific driving conditions. The output is transmitted to the active suspension system 14 to control the total roll torque and roll torque distribution of the active suspension system 14 for the vehicle conditions to best achieve the target vehicle roll angle.

Figure 5 shows schematically an example flow chart that may be used in the suspension control module 12. As the first step 50 in the process, the suspension control module 12 determines if the vehicle 10 is travelling. If the vehicle 10 is not travelling this process repeats until such a time that the vehicle 10 is travelling. If the vehicle 10 is travelling, the second step 52 completed by the suspension control module 12 is to determine if the vehicle 10 is travelling forward. If the vehicle 10 is travelling forward, the suspension control module 12 inputs vehicle parameters into the forward roll characteristic model 40 as shown in step 54 and a target vehicle roll angle is determined based on the vehicle parameters and the fact that the vehicle 10 is travelling forward, as described previously. The target vehicle roll angle is output to the active suspension system 14 as shown in step 58 and the total roll torque and roll torque distribution of the active suspension system 14 is controlled in dependence on the determined vehicle roll angle.

If the vehicle 10 is travelling backwards, the suspension control module 12 inputs vehicle parameters into the reverse roll characteristic model 44 as shown in step 56 and a target vehicle roll angle is determined based on the vehicle parameters and the fact that the vehicle 10 is travelling backwards, as described previously. The target vehicle roll angle is output to the active suspension system 14 as shown in step 59 of Figure 5.

The manner of handling the vehicle 10 varies significantly depending on the direction the vehicle 10 is travelling. The forward roll characteristic model 40 therefore provides a suitable output to control the total roll torque and roll torque distribution when the vehicle 10 is travelling forward and being steered by the front wheels. The reverse directional roll characteristic model 44 is configured to provide a suitable target vehicle roll angle output to control total roll torque and roll torque distribution when the vehicle is travelling in reverse and is thus being steered by the rearward wheels in dependence on the input target vehicle roll angle. In this latter scenario the vehicle 10 is subject to inversed yaw forces when cornering so it may be desirable to adapt total roll torque and roll torque distribution in the active suspension system 14.

The suspension control module 12 may be used in autonomous vehicles to improve the comfort of the ride through the use of an active suspension system 14, not only when the vehicle 10 is travelling forward but also in reverse. It may also be desirable to reduce the roll rate of autonomous vehicles whilst travelling in reverse to give passengers a greater feeling of control.

Many modifications may be made to the above examples without departing from the scope of the present invention as defined in the accompanying claims.

Claims

1. A controller for an active suspension system, the controller configured to: receive an input signal indicative of a direction of travel of a vehicle, determine a target roll characteristic for the vehicle in dependence on the direction of travel, and output the target roll characteristic to the active suspension system, wherein the controller comprises at least a forward and a reverse roll characteristic model, and wherein the controller is configured to select one of the forward or reverse roll characteristic models in dependence on the direction of travel.

2. The controller of any preceding claim, comprising a vehicle data processor module configured to determine at least one vehicle parameter based on an input from at least one vehicle sensor.

3. The controller of claim 2, wherein the reverse roll characteristic model is configured to determine at least one of a target vehicle roll angle, a total roll torque or a roll torque distribution in dependence on at least one other vehicle parameter in addition to the direction of travel.

4. The controller of claim 2 or claim 3 wherein the at least one vehicle parameter includes at least one of: selected gear, lateral acceleration, yaw rate, roll rate, pitch rate, steering wheel angle, steering wheel rotation rate, vehicle speed, surface friction, selected driver mode, surface roughness, terrain type, longitudinal incline of the vehicle, vehicle’s weight distribution, vehicle’s centre of gravity, suspension height, an individual wheel torque request, and tyre pressure.

5. The controller of any preceding claim, configured to output the target roll characteristic in real-time.

6. An active suspension system comprising the controller of any of claims 1 to 5.

7. A method of controlling an active suspension system within a vehicle, the method comprising; receiving an input signal indicative of a direction of travel of a vehicle; determining a target roll characteristic for the vehicle in dependence on the direction of travel; and outputting the target roll characteristic to the active suspension system, wherein the method comprises selecting one of a forward or reverse characteristic model in dependence on the direction of travel of the vehicle.

8. The method of claim 7, comprising inputting parameters of the vehicle into the reverse roll characteristic model in dependence on receiving an input indicating the vehicle is travelling in reverse.

9. The method of claim 7 or claim 8, wherein the roll characteristic includes at least one of a target vehicle roll angle, a total roll torque or a roll torque distribution.

10. The method of any of claims 7 to 9, wherein the input signal is indicative of vehicle sensor data and wherein the target roll characteristic is determined in dependence on the vehicle sensor data.

11. The method of any of claims 7 to 10, comprising outputting a signal to a suspension control module and controlling an active suspension system in dependence with the output signal.

12. The method of claim 11, wherein the output signal is indicative of at least one of a target vehicle roll angle, a total roll torque or a roll torque distribution.

13. The method of claim 11 or claim 12, comprising outputting the signal to the active suspension system in real-time.

14. The method of any of claims 7 to 13, wherein the vehicle parameters are at least one of: direction of travel, selected gear, lateral acceleration, yaw rate, roll rate, pitch rate, steering wheel angle, steering wheel rotation rate, vehicle speed, surface friction, selected driver mode, surface roughness, longitudinal incline, vehicle’s weight distribution, vehicle’s centre of gravity height, suspension height, individual wheel torque requests or tyre pressures.

15. A controller configured to perform the method of any of claims 7 to 14.

16. A vehicle comprising a controller according to any one of any of claims 1 to 5 or

17. The vehicle as claimed in claim 16, comprising an electronically controlled suspension system.

18. The vehicle as claimed in claim 16, comprising an actively controlled suspension system.

19. The vehicle as claimed in claim 16, comprising an electromechanically controlled suspension system.

20. The vehicle as claimed in any of claims 16 to 19, being an autonomous vehicle.