Damping of voltage-controlled brushless motors for electric power steering systems

• US 6,647,329 B2
• Filed: 04/09/2001
• Issued: 11/11/2003
• Est. Priority Date: 04/07/2000
• Status: Expired due to Term

• Current Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust), Steering Solutions IP Holding Corporation (Nexteer Automotive Group Ltd.)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Chandy, Ashok, Kleinau, Julie A.
• Primary Examiner(s): Beaulieu, Yonel
• Application Number:
  US09/829,311
• Publication Number:
  US 20010047233A1
• Time in Patent Office: 946 Days
• Field of Search: 701/41, 701/42, 180/442, 180/443, 180/446, 180/412, 318/254, 318/448, 318/461, 318/718, 318/802, 318/632, 318/432, 318/434, 318/138, 318/139
• US Class Current: 701/41
• CPC Class Codes: B62D 5/046 Controlling the motor
• CPC Class Codes: B62D 5/0463 calculating assisting torque from the motor based on driver input
• CPC Class Codes: B62D 5/0466 for returning the steering wheel to neutral position

Abstract

An electric power steering system includes a steering wheel, a voltage-controlled electric assist motor connected to the steering wheel or column, and an electronic controller electrically connected to the assist motor that receives a first signal representing a torque command to the assist motor and a second signal representing an angular velocity of the assist motor, and produces a voltage signal according to an assist-dependent damping function of the first and second signals, and uses the voltage signal to control the voltage-controlled electric assist motor in response to the assist-dependent damping function.

Claims

1. An electric power steering system comprising a steering input member, a voltage-controlled electric assist motor coupled to the input member, and an electronic controller in signal communication with the assist motor;

the electronic controller comprising;

a first signal input for receiving a first signal indicative of a torque command to the assist motor;

a second signal input for receiving a second signal indicative of an angular velocity of the assist motor;

an assist-dependent damping function responsive to the first and second signal; and

a signal output for providing a voltage signal in communication with the voltage-controlled electric assist motor;

wherein the voltage signal is responsive to the assist-dependent damping function.

2. An electric power steering system as defined in claim 1;

the electronic controller further comprising;

a third signal input for receiving a third signal indicative of a road speed of a vehicle; and

an input-dependent damping function responsive to the third signal;

wherein the voltage signal is responsive to the input-dependent damping function.

3. An electric power steering system as defined in claim 2, further comprising:

a steered member coupled to the steering input member; and

a torque sensor coupled to the steered member for sensing a driver torque input;

wherein;

the input-dependent damping function is responsive to the driver torque input; and

the voltage signal of the electronic controller is responsive to the input-dependent damping function.

4. An electric power steering system as defined in claim 2 wherein the input-dependent damping function is responsive to at least one of the first and second signals.

5. An electric power steering system as defined in claim 2 wherein at least one of the input-dependent damping function and the assist-dependent damping function comprises a look-up table.

6. An electric power steering system as defined in claim 2 wherein at least one of the assist-dependent damping function and the input-dependent damping function comprises a direct computation.

7. An electric power steering system as defined in claim 2 wherein at least one of the assist-dependent damping function and the input-dependent damping function comprises a constant.

9. An electric power steering system as defined in claim 2;

the controller further comprising a vehicle speed signal wherein at least one of the input-dependent damping function and the assist-dependent damping function is responsive to the vehicle speed signal.

10. An electric power steering system as defined in claim 1 wherein the voltage-controlled electric assist motor is brushless.

8. An electric power steering system comprising a steering input member, a voltage-controlled electric assist motor coupled to the input member, and an electronic controller in signal communication with the assist motor;

the electronic controller comprising;

a first signal input or receiving a first signal indicative of a torque command to the assist motor;

a second signal input for receiving a second signal indicative of an angular velocity of the assist motor;

an assist-dependent damping function responsive to the first and second signal; and

a signal output for providing a voltage signal in communication with the voltage-controlled electric assist motor;

a phase advance function in signal communication with the assist motor, wherein the phase advance function in responsive to at least one of the first and second signal; and

wherein the voltage signal is responsive to the assist-dependent damping function.

11. A method for controlling an electric power steering system comprising a steering input member, a voltage-controlled electric assist motor coupled to the input member, and an electronic controller in signal communication with the assist motor;

the method comprising;

receiving a first signal indicative of a torque command to the assist motor;

receiving a second signal indicative of an angular velocity of the assist motor;

computing an assist-dependent damping function responsive to the first and second signals; and

adapting an output voltage in signal communication with the voltage-controlled electric assist motor in response to the assist-dependent damping function.

14. A method for controlling an electric power steering system as defined in claim 11, further comprising:

receiving a third signal indicative of a vehicular road speed;

computing a first input-dependent damping function responsive to the third signal; and

adapting the output voltage in response to the first input-dependent damping function.

12. A method for controlling an electric power steering system comprising a steering input member, a voltage-controlled electric assist motor coupled to the input member, and an electronic controller in signal communication with the assist motor;

the method comprising;

receiving a first signal indicative of a torque command to the assist motor;

receiving a second signal indicative of an angular velocity of the assist motor;

computing an assist-dependent damping function responsive to the first and second signals;

adapting an output voltage in signal communication with the voltage-controlled electric assist motor in response to the assist-dependent damping function;

adding the first signal to the computed assist-dependent damping function; and

limiting the added assist-dependent damping function.

13. A method for controlling an electric power steering system comprising a steering input member, a voltage-controlled electric assist motor coupled to the input member, and an electronic controller in signal communication with the assist motor;

the method comprising;

receiving a first signal indicative of a torque command to the assist motor;

receiving a second signal indicative of an angular velocity of the assist motor;

computing an assist-dependent damping function responsive to the first and second signal;

adapting an output voltage in signal communication with the voltage-controlled electric assist motor in response to the assist-dependent damping function;

limiting the computed assist-dependent damping function; and

adding the first signal to limited assist-dependent damping function.

15. A method for controlling an electric power steering system comprising a steering input member, a voltage-controlled electric assist motor coupled to the input member, a torque sensor coupled to the steering input member, and an electronic controller in signal communication with the assist motor;

the method comprising;

receiving a first signal indicative of a torque command to the assist motor;

receiving a second signal indicative of an angular velocity of the assist motor;

computing an assist-dependent damping function responsive to the first and second signals;

adapting an output voltage in signal communication with the voltage-controlled electric assist motor in response to the assist-dependent damping function;

receiving a third signal indicative of a vehicular road speed;

computing a first input-dependent damping function responsive to the third signal;

adapting the output voltage in response to the fist input-dependent damping function;

receiving a fourth signal indicative of a driver torque input upon the steering input member;

computing a second input-dependent damping function responsive to the driver torque input; and

adapting the output voltage in response to the second input-dependent damping function.

16. A method as defined in claim 15 wherein adapting the output voltage in response to the second input-dependent damping function comprises multiplying the computed first input-dependent damping function by the computed second input-dependent damping function and adapting the output voltage in response to the product of the multiplication.

17. A method for controlling an electric power steering system as defined in claim 15 wherein at least one of computing an assist-dependent damping function and computing a first input-dependent damping function and computing a second input-dependent damping function comprises:

using at least one of the first, second, third and fourth signals as an index to a look-up table;

looking-up an intermediate result responsive to the at least one signal;

interpolating the intermediate result in response to the difference between the at least one signal and the corresponding table index to compute the at least one damping function.

18. A method for controlling an electric power steering system as defined in claim 15 wherein at least one of computing an assist-dependent damping function and computing a first input-dependent damping function and computing a second input-dependent damping function comprises directly computing the function result.

19. A method for controlling an electric power steering system as defined in claim 15 wherein at least one of computing an assist-dependent damping function and computing a first input-dependent damping function and computing a second input-dependent damping function comprises multiplying by a constant.

20. An electric power steering, system for a vehicle comprising a steering input member, a voltage-controlled electric assist motor coupled to the input member, and an electronic controller in signal communication with the assist motor;

the electronic controller comprising;

means for receiving a first signal indicative of a torque command to the assist motor;

means for receiving a second signal indicative of an angular velocity of the assist motor;

means for computing an assist-dependent damping function responsive to the first and second signals;

means for receiving a third signal indicative of a road speed of the vehicle;

means for receiving a fourth signal indicative of a driver torque on the input member;

means for computing an input-dependent damping function responsive to the third and fourth signals; and

means for producing an output voltage in signal communication with the assist motor that is responsive to at least one of the assist-dependent damping function and the input-dependent damping function.