Electric power steering apparatus

Patent metadata

Field	Value
Publication number	US-10214232-B2
Application number	US-201515031883-A
Country	US
Kind code	B2
Filing date	Jun 4, 2015
Priority date	Jun 25, 2014
Publication date	Feb 26, 2019
Grant date	Feb 26, 2019

Abstract

A safe electric power steering apparatus with a good steering feeling is provided that includes a function for getting out from restraint of a lateral flow or a one-sided flow, and enables acquisition of a better effect that a driver's load is reduced in the lateral flow or the one-sided flow. The safe electric power steering apparatus corrects a current command value by a motor current correction value based on a motor correction signal.

First claim

The invention claimed is:

1. A control unit that calculates a current command value of a motor which provides a steering mechanism with a steering assist torque based on a steering torque and a vehicle speed of a vehicle, and drives and controls said motor by feedback control, comprising:
a processor that is configured to perform functions that require said control unit to judge a running state of said vehicle based on an action force added to said steering mechanism, a steering angle of said steering mechanism and said vehicle speed, and correct said current command value by calculating a motor current correction value based on a judgment result of said running state and said action force,
wherein said processor is configured to execute a plurality of software sections comprising:
a straight running state judging section that judges a straight running state of said vehicle to obtain a straight running judgment result (SR),
an adaptive calculating section that calculates a motor correction signal based on at least said straight running judgment result (SR), said steering angle, and said action force,
a vehicle speed sensitive gain section that obtains a vehicle speed gain corresponding to said vehicle speed, and
an output calculating section that multiplies said motor correction signal by said vehicle speed gain to obtain said motor current correction value,

wherein said adaptive calculating section resets said motor correction signal to zero based on said steering angle and said action force when said vehicle departs from said straight running state, sets at least one first threshold smaller than a maximum correction value for said motor correction signal, sets a second upper threshold for a steering information of said steering mechanism and a third lower threshold for said steering information, and in said straight running state of said vehicle, gradually reduces said motor correction signal by using said motor correction signal, said at least one first threshold, said steering information, said second upper threshold and said third lower threshold when judging that a driver steers in said straight running state of said vehicle, and
wherein said control unit corrects said current command value by said motor current correction value.

2. A control unit (ECU) that calculates a current command value of a motor which provides a steering mechanism with a steering assist torque based on a steering torque and a vehicle speed of a vehicle, and drives and controls said motor by feedback control, comprising:
a processor that is configured to perform functions that require said control unit to judge a running state of said vehicle based on an action force added to said steering mechanism, a steering angle of said steering mechanism and said vehicle speed, and correct said current command value by calculating a motor current correction value based on a judgment result of said running state and said action force,
wherein said processor is configured to execute a plurality of software sections comprising:
a straight running state judging section that judges a straight running state of said vehicle to obtain a straight running judgment result (SR),
an adaptive calculating section that calculates a motor correction signal based on at least said straight running judgment result (SR), said steering angle, and said action force,
a vehicle speed sensitive gain section that obtains a vehicle speed gain corresponding to said vehicle speed, and
an output calculating section that multiplies said motor correction signal by said vehicle speed gain to obtain said motor current correction value,

wherein said adaptive calculating section resets said motor correction signal to zero in accordance with said steering angle and said action force when said vehicle departs from said straight running state, sets an upper first threshold (TA 1 ) and a lower second threshold (TA 2 ) that are smaller than a maximum correction value for said motor correction signal, controls a memory to store said steering angle at a time when an absolute value of said motor correction signal exceeds said upper first threshold (TA 1 ) as a first steering angle, sets a third threshold (TA 3 ) larger than said first steering angle and a fourth threshold (TA 4 ) smaller than said first steering angle, and gradually reduces said motor correction signal when said steering angle is out of a range between said third threshold (TA 3 ) and said fourth threshold (TA 4 ), and
wherein said control unit corrects said current command value of said motor by said motor current correction value.

3. The ECU according to claim 2 , wherein gradually reducing said motor correction signal is gradually reducing said motor correction signal towards zero.

4. The ECU according to claim 2 , wherein said upper first threshold (TA 1 ) and said lower second threshold (TA 2 ) are larger than zero, and wherein said third threshold (TA 3 ) minus said first steering angle equals a predetermined value (SA) and said first steering angle minus said fourth threshold (TA 4 ) equals said predetermined value (SA).

5. The ECU according to claim 2 , which releases storing of said first steering angle and setting of said third threshold (TA 3 ) and said fourth threshold (TA 4 ) when said motor correction signal becomes smaller than said lower second threshold (TA 2 ) after gradually reducing said motor correction signal.

6. The ECU according to claim 2 , wherein said processor obtains a first judgment output (CA 1 ) based on a present value and a previous value of said motor correction signal, obtains a fourth judgment output (CA 4 ) and a fifth judgment output (CA 5 ) based on said straight running judgment result (SR), said steering angle, said first judgment output (CA 1 ), said motor correction signal and a second judgment output (CA 2 ), obtains a third judgment output (CA 3 ) based on said steering angle, said fourth judgment output (CA 4 ) and said fifth judgment output (CA 5 ), and obtains a steering state signal by a logical product of said straight running judgment result (SR) and said third judgment output (CA 3 ), inputs said fifth judgment output (CA 5 ) into said memory, stores said fifth judgment output (CA 5 ) as said second judgment output (CA 2 ), and
wherein said ECU switches generation of said motor correction signal to be provided to said motor by said third judgment output (CA 3 ).

7. The ECU according to claim 6 , wherein said ECU outputs said first judgment output (CA 1 ) by comparing said present value and said previous value of said motor correction signal with said upper first threshold (TA 1 ).

8. The ECU according to claim 6 , wherein said processor obtains said fourth judgment output (CA 4 ) equal to 0, said steering angle or said previous value and obtains said fifth judgment output (CA 5 ) equal to 0, 1 or said previous value based on comparison with said lower second threshold (TA 2 ), a state of said second judgment output (CA 2 ), a state of said straight running judgment result (SR) and said first judgment output (CA 1 ).

9. The ECU according to claim 7 , wherein said processor obtains said fourth judgment output (CA 4 ) equal to 0, said steering angle or said previous value and outputs said fifth judgment output (CA 5 ) equal to 0, 1 or said previous value based on comparison with said lower second threshold (TA 2 ), a state of said second judgment output (CA 2 ), a state of said straight running judgment result (SR) and said first judgment output (CA 1 ).

10. The ECU according to claim 6 , wherein said processor obtains said third judgment output (CA 3 ) based on a state of said fifth judgment output (CA 5 ) and a result caused by comparing said steering angle with said th

Assignees

• Nsk Ltd

Inventors

• Sakaguchi Toru
• MARUYAMA Shoya

Classifications

• B62D15/0215

  by measuring on the steering column · CPC title

• B62D6/02

  responsive only to vehicle speed · CPC title

• B62D5/0463 Primary

  calculating assisting torque from the motor based on driver input · 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

• B62D6/10

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