Electric power steering apparatus

Patent metadata

Field	Value
Publication number	US-9446789-B2
Application number	US-201414419085-A
Country	US
Kind code	B2
Filing date	Feb 3, 2014
Priority date	Mar 8, 2013
Publication date	Sep 20, 2016
Grant date	Sep 20, 2016

Abstract

An electric power steering apparatus that realizes vibration suppression of response characteristics and has a control performance having resistance properties against disturbances such as a road surface change by using a velocity I-P control (a proportional-lead type PI control) in a vehicle having functions of an automatic steering control and a manual steering control.

First claim

The invention claimed is:

1. An electric power steering apparatus that calculates a first motor current command value on a basis of a steering torque and a vehicle velocity, performs an assist control of a steering system by driving a motor on the basis of said first motor current command value, and has a function for switching between an automatic steering control and a manual steering control, comprising:
a steering angle control section that calculates a second motor current command value in said automatic steering control so as to bring an actual steering angle close to a target steering angle; and
a switching section that inputs said first motor current command value and said second motor current command value and switches between said first motor current command value and said second motor current command value depending on a switching signal,
wherein said steering angle control section comprises:
a rate limiter that performs smoothing with respect to said target steering angle;
a position control section that inputs a first deviation between an output of said rate limiter and said actual steering angle; and
a velocity control section that inputs a first motor velocity command value from said position control section, obtains a second deviation between said first motor velocity command value and said motor angular velocity, comprises an integral section for inputting said second deviation and a proportional section for inputting said motor angular velocity, subtracts an output of said proportional section from an output of said integral section, and outputs said second motor current command value.

2. The electric power steering apparatus according to claim 1 , wherein a first low pass filter is provided at a post-stage of said rate limiter.

3. The electric power steering apparatus according to claim 1 , wherein a feedforward control section that velocity-componentizes said output of said rate limiter and adds said velocity-componentized output to said first motor velocity command value is provided.

4. The electric power steering apparatus according to claim 2 , wherein a feedforward control section that velocity-componentizes said output of said rate limiter and adds said velocity-componentized output to said first motor velocity command value is provided.

5. The electric power steering apparatus according to claim 3 , wherein said feedforward control section comprises a differential section and a gain section.

6. The electric power steering apparatus according to claim 4 , wherein said feedforward control section comprises a differential section and a gain section.

7. The electric power steering apparatus according to claim 5 , wherein a second low pass filter is provided at an output section of said feedforward control section.

8. The electric power steering apparatus according to claim 6 , wherein a second low pass filter is provided at an output section of said feedforward control section.

9. An electric power steering apparatus that calculates a first motor current command value on a basis of a steering torque and a vehicle velocity, performs an assist control of a steering system by driving a motor on the basis of said first motor current command value, and has a function for switching between an automatic steering control and a manual steering control, comprising:
a steering angle control section that calculates a second motor current command value on the basis of said steering torque, a target steering angle, an actual steering angle and a motor angular velocity of said motor; and
a switching section that inputs said first motor current command value and said second motor current command value to switch,
wherein said steering angle control section comprises:
a position control section that outputs a motor velocity command depending on a deviation angle between said target steering angle and said actual steering angle;
a velocity control section that inputs said motor velocity command and said motor angular velocity to perform a velocity control;
a steering wheel damping control section that inputs said steering torque to perform a steering wheel damping control; and

an output section that processes a third motor current command value from said velocity control section and a fourth motor current command value from said steering wheel damping control section to output said second motor current command value,
wherein said velocity control section comprises:
an integral section that integrates a deviation between said motor velocity command and said motor angular velocity;
a second gain section that multiplies said motor angular velocity by a gain; and
a subtraction section that obtains a deviation between an output of said integral section and an output of said second gain section,

wherein said switching section is switched depending on a switching command of said automatic steering control and said manual steering control, said motor is drive-controlled on the basis of said second motor current command value in said automatic steering control.

10. The electric power steering apparatus according to claim 9 , wherein said position control section is a first gain section.

11. The electric power steering apparatus according to claim 9 , wherein said steering wheel damping control section comprises
a third gain section that multiplies said steering torque by a gain; and
a differential gain section that differentiates said steering torque and multiplies said differentiated steering torque by a gain.

12. The electric power steering apparatus according to claim 10 , wherein said steering wheel damping control section comprises
a third gain section that multiplies said steering torque by a gain; and
a differential gain section that differentiates said steering torque and multiplies said differentiated steering torque by a gain.

13. The electric power steering apparatus according to claim 9 , wherein said steering wheel damping control section comprises a phase compensating section that performs a phase compensation with respect to said steering torque and a fourth gain section.

14. The electric power steering apparatus according to claim 10 , wherein said steering wheel damping control section comprises a phase compensating section that performs a phase compensation with respect to said steering torque and a fourth gain section.

15. The electric power steering apparatus according to claim 11 , wherein said steering wheel damping control section comprises a phase compensating section that performs a phase compensation with respect to said steering torque and a fourth gain section.

16. The electric power steering apparatus according to claim 12 , wherein said steering wheel damping control section comprises a phase compensating section that performs a phase compensation with respect to said steering torque and a fourth gain section.

17. The electric power steering apparatus according to claim 9 , wherein said output comprises an addition section and a limiter that limits upper and lower limit values.

18. The electric power steering apparatus according to claim 10 , wherein said output comprises an addition section and a limiter that limits upper and lower limit values.

19. The electric power steering apparatus according to claim 11 , wherein said output comprises an addition section and a limiter that limits upper and lower limit values.

20. The electric power steering apparatus according to claim 12 , wherein said output comprises an addition section and a limiter that limits upper and lower

Assignees

• Nsk Ltd

Inventors

• Tsubaki Takahiro
• Kitazume Tetsuya
• Yoshida Keita

Classifications

• B62D6/002

  computing target steering angles for front or rear wheels (B62D7/159 takes precedence) · CPC title

• B62D5/046

  Controlling the motor · CPC title

• B62D5/0463

  calculating assisting torque from the motor based on driver input · CPC title

• B62D5/0472 Primary

  for damping vibrations · CPC title

• B62D15/0285

  Parking performed automatically · CPC title