WE CLAIM:
[Claim 1]
A method for controlling a torque of an electric power steering (EPS) system (1110) of a vehicle, comprising:
determining (1120), using a state (1117) of a lateral movement of the vehicle, current torques acting on the vehicle and a torque applied on the steering wheel by a driver, constraints defining a range of values (1125) of the torque of the EPS system satisfying the constraints (1122), wherein the constraints (1122) include at least one constraint (1124) on an effect of the torque of the EPS system on the steering wheel, wherein the constraint (1124) on the effect includes a constraint on a minimal value and a constraint on a maximal value of the torque of the EPS system in relation to the torque applied on the steering wheel by a driver, wherein the minimal and maximal values of the constraint (1124) on the effect are determined from the current torques acting on the vehicle;
selecting (1130) a value (1135) of the torque within the range of values (1125) based on an objective (1153) of the movement of the vehicle;
commanding (1140) a motor of the EPS system (1110) to generate the torque according to the value (1135) of the torque; and
repeating the determining (1120), the selecting (1130) and the commanding (1140) steps in response to a change of at least one of the state of the steering wheel (1111), the state of the EPS system (1113) and the state of the vehicle (1115), such that the constraints defining the range of values of the torque of the EPS system are different for at least two different time periods.
[Claim 2]
The method of claim 1, further comprising:
determining (1150) the objective (1153) of the movement of the vehicle;
selecting the constraints (1122) and a cost function (1133) according to the objective (1153); and
optimizing the cost function (1133) subject to the constraints (1122) to determine the value (1135).
[Claim 3]
The method of claim 1, wherein the constraint (1124) on the effect is a function of at least some of the torque of the EPS system (1110), an alignment torque exerted by a road
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through wheels of the vehicle on a steering column of the vehicle and a torque applied to the steering wheel of the vehicle.
[Claim 4]
The method of claim 1, wherein the constraint (1124) on the effect includes a constraint on a minimum and a maximum amount of feedback torque on the steering wheel.
[Claim 5]
The method of claim 1, wherein the constraint (1124) on the effect includes a constraint on a maximum intervention torque on the steering wheel.
[Claim 6]
The method of claim 1, wherein the constraint (1124) on effect includes a constraint on a percentage of the alignment torque propagated to the steering wheel.
[Claim 7]
The method of claim 1, wherein the constraint (1124) on the effect includes a difference between an intervention torque on the steering wheel and a current torque applied to the steering wheel by a driver.
[Claim 8]
The method of claim 1, wherein the constraint (1124) on the effect includes a constraint on an intervention over an alignment torque.
[Claim 9]
The method of claim 1, wherein the objective (1153) is a cornering performance of the vehicle.
[Claim 10]
The method of claim 1, wherein the objective (1153) is stability of the vehicle.
[Claim 11]
The method of claim 1, wherein the objective (1153) is maintaining a position of the vehicle with respect to a road.
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[Claim 12]
The method of claim 1, further comprising:
repeating the determining (1120), the selecting (1130) and the commanding (1140) step periodically every period of time θ.
[Claim 13]
A method for controlling a torque of an electric power steering (EPS) system (1110) of a vehicle, comprising steps of:
determining (1150) an objective (1153) of a lateral movement of the vehicle;
determining a cost function (1133) of the movement of the vehicle based on the objective (1153) of the movement;
determining constraints (1122) defining a range of values (1125) of the torque of the EPS system, wherein the constraints (1122) are determined using a state of the lateral movement and a torque applied on the steering wheel by a driver and include at least one effect constraint (1124) on effect of the torque of the EPS system on a steering wheel of the vehicle, and at least one objective constraint (1126) selected based on the objective (1153) of the lateral movement of the vehicle, wherein the constraint on the effect includes a constraint on a minimum and a maximum amount of feedback torque on the steering wheel;
optimizing the cost function (1133) subject to the constraints (1122);
generating a control signal for controlling the torque of the EPS system according to the optimizing step; and
wherein the steps are performed by a processor.
[Claim 14]
The method of claim 13, wherein the constraints (1122) include a switching constraint, further comprising:
determining switching conditions of the switching constraint;
selecting an entry of the switching constraint according to the switching conditions;
enforcing the entry during the optimization for a time period θ.
[Claim 15]
An electric power steering (EPS) system (1110) of a vehicle, comprising: a processor (1101) for determining (1120), based on a state (1117) of a lateral movement of the vehicle and a current torque applied on the steering wheel by a driver, constraints defining, a range of values (1125) of the torque of the EPS system satisfying the
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constraints (1122) and for selecting (1130) a value (1135) of the torque within the range (1125) based on an objective (1153) of the movement of the vehicle, wherein the constraints include at least one constraint (1124) on an effect of the torque of the EPS system on a steering wheel determined using the state of the lateral movement and the current torque, wherein the constraint on the effect includes a difference between an intervention torque on the steering wheel and the current torque applied to the steering wheel by a driver; and
a motor generating the torque according to the selected value (1135).
[Claim 16]
The EPS of claim 15, wherein the processor (1101) receives the objective (1153) of the movement of the vehicle from an external system (1160), selects the constraints (1122) and a cost function (1133) according to the objective (1153) and optimizes the cost function (1133) subject to the constraints (1122) to determine the value (1135).
[Claim 17]
The EPS of claim 15, wherein the constraint (1124) on the effect is a function of at least some of the torque of the EPS system (1110), an alignment torque exerted by a road through wheels of the vehicle on a steering column of the vehicle and a torque applied to the steering wheel of the vehicle.
[Claim 18]
The EPS of claim 17, wherein the processor (1101) determines the value (1135) of the torques in response to a change of the alignment torque.