Electric power steering control device

• US 8,626,394 B2
• Filed: 10/21/2010
• Issued: 01/07/2014
• Est. Priority Date: 10/30/2009
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Kezobo, Isao, Kurishige, Masahiko, Endo, Masaya, Kifuku, Takayuki
• Primary Examiner(s): To, Tuan C.
• Assistant Examiner(s): Kan, Yuri
• Application Number:
  US13/497,103
• Publication Number:
  US 20120185132A1
• Time in Patent Office: 1,174 Days
• Field of Search: 701/31.4, 701/36, 701/41, 701/42, 701/1, 701/22, 180/443, 180/444, 180/446, 318/400.22, 318/609
• US Class Current: 701/41
• CPC Class Codes: B62D 5/0472 for damping vibrations

Abstract

An electric power steering control device includes: a vibration extracting filter for performing filter processing on a rotation speed of a motor to reduce a gain on a low frequency side so as to output a vibration-component signal; a current variable gain map for detecting a current flowing through the motor as a first state quantity so as to calculate a current variable gain based on the current; a rotation-speed variable gain map for detecting the rotation speed of the motor as a second state quantity so as to calculate a rotation-speed variable gain based on the rotation speed; a correction mechanism calculating a vibration suppression current; and current controller calculating a target current so as to control the current flowing through the motor.

Claims

1. An electric power steering control device, comprising:

an assist map for outputting an assist torque current based on a steering torque applied to a steering wheel by a driver;

a vibration extracting filter for performing filter processing on the steering torque or a rotation speed of a motor of the electric power steering control device for generating an assist torque to reduce a gain on a low frequency side so as to output a vibration-component signal;

a current variable gain map for detecting a current flowing through the motor as a first state quantity so as to calculate a current variable gain based on the current;

a rotation-speed variable gain map for detecting the rotation speed of the motor or a rotation speed of the steering wheel as a second state quantity so as to calculate a rotation-speed variable gain based on the rotation speed;

correction means for calculating a vibration suppression current based on the vibration-component signal, the current variable gain, and the rotation-speed variable gain; and

current control means for calculating a signal obtained by correcting the assist torque current with the vibration suppression current as a target current so as to control the current flowing through the motor,

wherein;

the current variable gain map receives an input of the detected current flowing through the motor and outputs the current variable gain to be a constant positive value when the detected current is at or below a first predetermined value, outputs the current variable gain according to a gradually decreasing function when the detected current is above the first predetermined value but below a second predetermined value, and outputs the current variable gain to be zero when the detected current is at or above the second predetermined value, wherein the value of the detected current above the first predetermined value corresponds to a predetermined range of the current where a disturbance transmission characteristic indicating an amplification factor of transmission from a disturbance to the steering wheel has a small value; and

the rotation-speed variable gain map receives an input of the rotation speed of the motor or a rotation speed of the steering wheel and outputs the rotation speed variable gain to be a constant positive value when the detected rotation speed is at or below a third predetermined value, outputs the rotation speed variable gain according to a gradually decreasing function when the detected rotation speed is above the third predetermined value but below a fourth predetermined value, and outputs the rotation speed variable gain to be zero when the detected rotation speed is at or above the fourth predetermined value, wherein the value of the detected rotation speed above the third predetermined value corresponds to a predetermined range of the rotation speed where the disturbance transmission characteristic has a small value.

2. An electric power steering control device according to claim 1, wherein the variable gain map further includes a vehicle-speed variable gain map for detecting a vehicle speed corresponding to a running speed of a vehicle as a fourth state quantity so as to increase and output a vehicle-speed variable gain when the vehicle speed is high and the electric power steering control device outputs a value obtained by further multiplying the already calculated variable gain by the vehicle-speed variable gain as a variable gain.

3. An electric power steering control device according to claim 1, further comprising a variable filter frequency map for calculating a variable filter frequency in accordance with the rotation speed,

wherein the vibration extracting filter varies a filter frequency in accordance with the variable filter frequency calculated by the variable filter frequency map.

4. An electric power steering control device according to claim 1, further comprising a variable filter frequency map for calculating a variable filter frequency in accordance with the rotation speed,

wherein the vibration extracting filter varies a filter frequency in accordance with the variable filter frequency calculated by the variable filter frequency map.

5. An electric power steering control device according to claim 2, further comprising a variable filter frequency map for calculating a variable filter frequency in accordance with the rotation speed,

wherein the vibration extracting filter varies a filter frequency in accordance with the variable filter frequency calculated by the variable filter frequency map.

6. An electric power steering control device, comprising:

an assist map for outputting an assist torque current based on a steering torque applied to a steering wheel by a driver;

a vibration extracting filter for performing filter processing on the steering torque or a rotation speed of a motor of the electric power steering control device for generating an assist torque to reduce a gain on a low frequency side so as to output a vibration-component signal;

a gradient variable gain map for detecting a gradient of the assist torque current with respect to the steering torque on the assist map as a third state quantity so as to output a gradient variable gain based on the gradient;

a rotation-speed variable gain map for detecting the rotation speed of the motor or a rotation speed of the steering wheel as a second state quantity so as to output a rotation-speed variable gain based on the rotation speed;

correction means for calculating a vibration suppression current based on the vibration-component signal, the gradient variable gain, and the rotation-speed variable gain; and

current control means for calculating a signal obtained by correcting the assist torque current with the vibration suppression current as a target current so as to control a current flowing through the motor,

wherein;

the gradient variable gain map receives an input of the detected gradient of the assist torque current with respect to the steering torque on the assist map and outputs the gradient variable gain to be a constant positive value when the detected gradient is at or below a first predetermined value, outputs the gradient variable gain according to a gradually decreasing function when the detected gradient is above the first predetermined value but below a second predetermined value, and outputs the gradient t variable gain to be zero when the detected gradient is at or above the second predetermined value, wherein the value of the detected gradient above the first predetermined value corresponds to a predetermined range of the gradient where a disturbance transmission characteristic indicating an amplification factor of transmission from a disturbance to the steering wheel has a small value; and

the rotation-speed variable gain map receives an input of the rotation speed of the motor or a rotation speed of the steering wheel and outputs the rotation speed variable gain to be a constant positive value when the detected rotation speed is at or below a third predetermined value, outputs the rotation speed variable gain according to a gradually decreasing function when the detected rotation speed is above the third predetermined value but below a fourth predetermined value, and outputs the rotation speed variable gain to be zero when the detected rotation speed is at or above the fourth predetermined value, wherein the value of the detected rotation speed above the third predetermined value corresponds to a predetermined range of the rotation speed where the disturbance transmission characteristic has a small value.

7. An electric power steering control device according claim 6, wherein the variable gain map further includes a vehicle-speed variable gain map for detecting a vehicle speed corresponding to a running speed of a vehicle as a fourth state quantity so as to increase and output a vehicle-speed variable gain when the vehicle speed is high and the electric power steering control device outputs a value obtained by further multiplying the already calculated variable gain by the vehicle-speed variable gain as a variable gain.

8. An electric power steering control device according to claim 6, further comprising a variable filter frequency map for calculating a variable filter frequency in accordance with the rotation speed,

wherein the vibration extracting filter varies a filter frequency in accordance with the variable filter frequency calculated by the variable filter frequency map.

9. An electric power steering control device according to claim 7, further comprising a variable filter frequency map for calculating a variable filter frequency in accordance with the rotation speed,

wherein the vibration extracting filter varies a filter frequency in accordance with the variable filter frequency calculated by the variable filter frequency map.