An apparatus and a method for controlling steering

Abstract

An apparatus (104) and a method (800) for controlling steering of rear wheels (103) of a vehicle (100) are disclosed. The apparatus (104) comprises a control means (105) configured to receive a first signal indicative of a front wheel steering angle and a second signal indicative of a selected mode selected from at least a first mode and a second mode. The control means is also configured to determine a proposed rear wheel steering angle in dependence on the first signal and the second signal and to provide an output signal configured to cause steering of rear wheels (103) at the proposed rear wheel steering angle.

1 . An apparatus for controlling steering of rear wheels of a vehicle, the apparatus comprising at least one control device configured to:
 receive a first signal indicative of a requested steering angle;   receive a second signal indicative of a selected mode selected from at least a first mode and a second mode;   determine a proposed rear wheel steering angle in dependence on the first signal and the second signal; and   provide an output signal configured to cause steering of rear wheels at the proposed rear wheel steering angle.   
     
     
         2 . The apparatus according to  claim 1 , wherein the at least one control device is configured to receive a third signal indicative of the current speed of the vehicle and determine the proposed rear wheel steering angle in dependence on the third signal. 
     
     
         3 . The apparatus according to  claim 1 , wherein: the proposed rear wheel steering angle is the product of a front wheel steering angle and a gain value; and the at least one control device is configured to determine the proposed rear wheel steering angle with a gain value that depends on the selected mode indicated by the second signal. 
     
     
         4 . The apparatus according to  claim 3 , wherein, the at least one control device is configured to: cause steering of the rear wheels at the proposed rear wheel steering angle out of phase with the front wheel steering angle in dependence on the current speed being below the threshold speed; and cause steering of the rear wheels at the proposed rear wheel steering angle in phase with the front wheel steering angle in dependence on the current speed being above the threshold speed. 
     
     
         5 . The apparatus according to  claim 3 , wherein the at least one control device is configured to select the threshold speed in dependence on the selected mode. 
     
     
         6 . The apparatus according to  claim 1 , wherein the at least one control device is configured to receive the second signal from a terrain estimation system configured to produce the second signal in dependence on detected characteristics of the ground on which the vehicle is travelling. 
     
     
         7 . The apparatus according to  claim 1 , wherein the at least one control device is configured to: select the first mode in dependence on a determination that friction between wheels of the vehicle and the ground in contact with the wheels is below a first friction threshold; and select the second mode in dependence on a determination that said friction is above the first friction threshold. 
     
     
         8 . The apparatus according to  claim 1 , wherein the at least one control device is configured to: select the first mode in dependence on a determination that the ground in contact with wheels of the vehicle is deformable by the wheels of the vehicle. 
     
     
         9 . The apparatus according to  claim 1 , wherein the second signal is produced in response to an input at a user input device. 
     
     
         10 . The apparatus according to  claim 1 , wherein at least one performance characteristic of the vehicle is determined in dependence on the selected mode, the at least one performance characteristic comprising at least one of the group: throttle pedal map; transmission map; stability control settings. 
     
     
         11 . The apparatus according to  claim 1 , wherein: the at least one control device is configured to determine a current condition of the vehicle as one of a plurality of predefined conditions and determine a proposed rear wheel steering angle that depends on the current condition; and the predefined conditions comprise at least one of: a low traction condition; oriented with a roll angle above a threshold roll angle; moving backwards down an incline. 
     
     
         12 . The apparatus according to  claim 1 , wherein the at least one control device comprises an electronic memory device having instructions stored therein; and an electronic processor electrically coupled to the electronic memory device and configured to access the electronic memory device and execute the instructions. 
     
     
         13 . A system comprising the apparatus of  claim 1  and at least one actuator for controlling a steering angle of the rear wheels of the vehicle in response to the output signal. 
     
     
         14 . The system according to  claim 13  comprising a terrain estimation system configured to determine characteristics of a terrain on which the vehicle is travelling, wherein the at least one control device is configured to select the selected mode in dependence on signals received by the at least one control device from the terrain estimation system. 
     
     
         15 . A vehicle comprising the apparatus of  claim 1 . 
     
     
         16 . A method of controlling steering of rear wheels of a vehicle, the method comprising:
 receiving a first signal indicative of a requested steering angle;   receiving a second signal indicative of a selected mode selected from at least a first mode and a second mode;   determining a proposed rear wheel steering angle in dependence on the first signal and the second signal; and   causing steering of rear wheels at the proposed rear wheel steering angle.   
     
     
         17 . A computer program which when executed by a processor causes the processor to perform the method according to  claim 16 . 
     
     
         18 . The apparatus according to  claim 3 , wherein the at least one control device is configured to select the gain value in dependence on whether the current speed is below or above a threshold speed.