Electric power steering apparatus

Patent metadata

Field	Value
Publication number	US-2016347357-A1
Application number	US-201414651949-A
Country	US
Kind code	A1
Filing date	Sep 25, 2014
Priority date	Feb 12, 2014
Publication date	Dec 1, 2016
Grant date	—

Abstract

[Problem]
An object of the present invention is to provide an electric power steering apparatus that is capable of positively returning a steering wheel to a neutral point in such a running state as to return to a going straight state by calculating a return control current corresponding to a steering angle and a steering speed and compensating a current command value.
[Means for solving the problem]
An electric power steering apparatus comprising: a steering wheel return control section that calculates a return control current with a steering angle, a vehicle speed and a steering speed, and drives a motor with a compensated current command value left by the subtraction of the return control current from a current command value, wherein the steering wheel return section comprises a base-return control current calculating section that calculates a base-return control current, a target steering speed calculating section that calculates a target steering speed, a return control gain calculating section that calculates a deviation between the target steering speed and the steering speed, performs coding, and at a same time calculates a return control gain by using at least two control calculations among a P-control calculation, an I-control calculation and a D-control calculation, a limiter that limits a maximum value of the return control gain, and a correcting section that corrects the base-return control current with an output gain of the limiter and outputs the return control current.

First claim

1 - 11 . (canceled)

12 . An electric power steering apparatus that calculates a current command value based on a steering torque and a vehicle speed, drives a motor based on said current command value, and performs assist control of a steering system by drive-control of said motor, comprising:
a steering wheel return control section that calculates a return control current with a steering angle, said vehicle speed and a steering speed, and drives said motor with a compensated current command value left by the subtraction of said return control current from said current command value, wherein said steering wheel return section comprises a base-return control current calculating section that calculates a base-return control current based on said steering angle and said vehicle speed, a target steering speed calculating section that calculates a target steering speed based on said steering angle and said vehicle speed, a return control gain calculating section that calculates a deviation between said target steering speed and said steering speed, performs coding, and calculates a return control gain using by at least two control calculations among a P-control calculation, an I-control calculation and a D-control calculation, a limiter that limits a maximum value of said return control gain, and a correcting section that corrects said base-return control current with an output gain of said limiter and outputs said return control current.

13 . The electric power steering apparatus according to claim 12 , wherein
said return control gain calculating section comprises a subtracting section that calculates a deviation between said target steering speed and said steering speed, an inverting section that inverts said deviation, a coding section that obtains a positive or negative sign of said steering angle, a multiplying section that multiplies an inverted deviation from said inverting section with said sign, and a control calculating section that outputs said return control gain by performing the P-control calculation and the I-control calculation of an output from said multiplying section and adding an output of the P-control calculation and an output of the I-control calculation.

14 . The electric power steering apparatus according to claim 12 , wherein
said return control gain calculating section comprises a subtracting section that calculates a deviation between said target steering speed and said steering speed, an inverting section that inverts said deviation, a coding section that obtains a positive or negative sign of said steering angle, a control calculating section that outputs said return control gain by performing the P-control calculation and the I-control calculation of an output from said inverting section and adding an output of the P-control calculation and an output of the I-control calculation, and a multiplying section that multiplies said return control gain with said sign.

15 . The electric power steering apparatus according to claim 12 , wherein
said return control gain calculating section comprises a subtracting section that calculates a deviation between said target steering speed and said steering speed, an inverting section that inverts said deviation, a coding section that obtains a positive or negative sign of said steering angle, a control calculating section that outputs said return control gain by performing the P-control calculation, the I-control calculation and a D-control calculation of an output from said inverting section and adding an output of the P-control calculation, an output of the I-control and an output of the D-control calculation, and a multiplying section that multiplies said return control gain with said sign.

16 . The electric power steering apparatus according to claim 12 , wherein
said return control gain calculating section comprises a subtracting section that calculates a deviation between said target steering speed and said steering speed, a first inverting section that inverts said deviation, a coding section that obtains a positive or negative sign of said steering angle, a second inverting section that inverts said steering speed, a control calculating section that outputs said return control gain by performing the P-control calculation and the I-control calculation of an output from said first inverting section, performing the D-control calculation of an output from said second inverting section, subtracting an output of said D-control calculation from an output of said I-control calculation and adding an output of said P-control to a result of a subtraction, and a multiplying section that multiplies said return control gain with said sign.

17 . The electric power steering apparatus according to claim 12 , wherein
said return control gain calculating section comprises a subtracting section that calculates a deviation between said target steering speed and said steering speed, a first inverting section that inverts said deviation, a coding section that obtains a positive or negative sign of said steering angle, a second inverting section that inverts said steering speed, a control calculating section that outputs said return control gain by performing the I-control calculation of an output from said first inverting section, performing the P-control calculation and the D-control calculation of an output from said second inverting section and subtracting an addition result of an output of said P-control calculation and an output of said D-control calculation from an output of said I-control, and a multiplying section that multiplies said return control gain with said sign.

18 . The electric power steering apparatus according to claim 12 , wherein
said return control gain calculating section comprises a subtracting section that calculates a deviation between said target steering speed and said steering speed, a first inverting section that inverts said deviation, a coding section that obtains a positive or negative sign of said steering angle, a first multiplying section that multiplies an inverted deviation from said first inverting section with said sign, a second inverting section that inverts said steering speed, a second multiplying section that multiplies an inverted steering speed from said second inverting section with said positive or negative sign, and a control calculating section that outputs said return control gain by performing the I-control calculation of an output from said first multiplying section, performing the P-control calculation of an output from said second multiplying section and subtracting an output of said P-control calculation from an output of said I-control calculation.

19 . The electric power steering apparatus according to claim 12 , wherein
said return control gain calculating section comprises a subtracting section that calculates a deviation between said target steering speed and said steering speed, a first inverting section that inverts said deviation, a coding section that obtains a positive or negative sign of said steering angle, a second inverting section that inverts said steering speed, a control calculating section that outputs said return control gain by performing the I-control calculation of an output from said first inverting section, performing the P-control calculation of an output from said second inverting section, subtracting an output of said P-control calculation from an output of said I-control calculation, and a multiplying section that multiplies said return control gain with said sign.

20 . The electric power steering apparatus according to claim 12 , wherein
said maximum value is “1.0”, and said correcting section is a multiplying section.

21 . The electric power steering apparatus acc

Assignees

• Nsk Ltd

Inventors

• Kitazume Tetsuya

Classifications

• B62D15/0235

  by measuring or deriving directly at the electric power steering motor · CPC title

• B62D6/10

  characterised by means for sensing {or determining} torque · CPC title

• B62D6/04

  responsive only to forces disturbing the intended course of the vehicle, e.g. forces acting transversely to the direction of vehicle travel · CPC title

• B62D6/008

  Control of feed-back to the steering input member, e.g. simulating road feel in steer-by-wire applications · CPC title

• B62D5/0472

  for damping vibrations · CPC title