Electric power steering apparatus

Patent metadata

Field	Value
Publication number	US-9346487-B2
Application number	US-201214353542-A
Country	US
Kind code	B2
Filing date	Jan 11, 2012
Priority date	Jan 11, 2012
Publication date	May 24, 2016
Grant date	May 24, 2016

Abstract

The apparatus herein provided includes a plurality of systems including driving circuits ( 20 a, 20 b ) for driving motor coils ( 3 a, 3 b ) corresponding thereto, and a control unit ( 10 ) for controlling control values of the driving circuits ( 20 a, 20 b ), wherein, when a fault occurs in at least one of the plurality of systems including the motor coils ( 3 a, 3 b ), the control unit ( 10 ) decreases a control value of a system(s) in which the fault occurs from an ordinary time control value or stops the drive by the system(s) in which the fault occurs, and also increases a control value of another system(s) in which the fault does not occur to more than an ordinary time control value.

First claim

What is claimed is:

1. An electric power steering apparatus configured to assist in steering force of a driver by driving force of a motor having a plurality of independent motor coils, the electric power steering apparatus comprising:
a plurality of systems including driving circuits which are provided for every one of the plurality of motor coils, and configured to drive the motor coils corresponding to the driving circuits; and
a control unit configured to control values of the driving circuits,
wherein, when a fault occurs in at least one of the plurality of systems including the motor coils, the control unit decreases a control value of a system in which the fault occurs from an ordinary time control value thereof or stops the drive by a system in which the fault occurs, and increases a control value of a system in which the fault does not occur to more than an ordinary time control value thereof,
wherein the control unit comprises:
a fault detection unit configured to detect a fault of the plurality of systems including the motor coils corresponding thereto;
an ordinary control-value calculation unit configured to calculate an ordinary time control value of the plurality of systems in ordinary times when the fault detection unit does not detect the fault, and output the ordinary time control value being calculated to the plurality of systems; and
a fault control-value calculation unit configured to calculate a first fault-time control value, when the fault detection unit detects the fault, so that the control value is decreased or the drive is stopped in accordance with a state of the fault and output the first fault-time control value being calculated to the system in which the fault occurs, and to calculate a second fault-time control value that is increased more than an ordinary time control value and output the second fault-time control value being calculated to the system in which the fault does not occur; and
the plurality of motor coils are driven by the driving circuits of the systems corresponding thereto based on an output from the ordinary control-value calculation unit, when the fault detection unit does not detect the fault, and are controlled by the driving circuits of the systems corresponding thereto based on an output from the fault control-value calculation unit, when the fault detection unit detects the fault,
wherein the fault control-value calculation unit decreases stepwise, in accordance with a state of the fault, the first fault-time control value outputted to the system in which the fault occurs.

2. The electric power steering apparatus as set forth in claim 1 , wherein, when a fault occurs in at least one of the plurality of systems, the control unit increases, corresponding to the decrease of the control value of the system in which the fault occurs, the control value of the system in which the fault does not occur.

3. The electric power steering apparatus as set forth in claim 1 , wherein the fault control-value calculation unit is capable of increasing, in accordance with a state of the fault, the second fault-time control value outputted to the system in which the fault does not occur, up to a value given by multiplying the ordinary time control value by the number of the systems.

4. The electric power steering apparatus as set forth in claim 1 , wherein the fault control-value calculation unit changes, in accordance with a state of the fault being detected, a sharing ratio of output quantities between the first fault-time control value for the system in which the fault occurs and the second fault-time control value for the system in which the fault does not occur.

5. The electric power steering apparatus as set forth in claim 1 , wherein the fault control-value calculation unit increases the second fault-time control value so that it becomes substantially larger than an ordinary time control value when a wheeled-vehicle speed is lower, and outputs the increased second fault-time control value to the system in which the fault does not occur.

6. The electric power steering apparatus as set forth in claim 1 , wherein the number of steps being decreased stepwise comprises the number depending on the number of the systems.

7. The electric power steering apparatus as set forth in claim 1 , wherein the plurality of motor coils is constituted of two sets of three-phase motor coils;
the plurality of systems is constituted of two sets of systems corresponding to the two respective sets of motor coils;
the two sets of systems including the motor coils are periodically monitored for a presence or absence of the fault; and
objects for the monitoring include at least a terminal voltage of the motor and an electric current thereof.

8. The electric power steering apparatus as set forth in claim 1 , further comprising a notification device configured to notify the driver of an occurrence of the fault at a time when the fault occurs.

9. The electric power steering apparatus as set forth in claim 1 , wherein an alternating-current value in an audible frequency range is superimposed on the second fault-time control value outputted from the fault control-value calculation unit to the system in which the fault does not occur.

Assignees

• Kimpara Yoshihiko
• Mori Akihiko
• Matsushita Masaki
• Okada Jiro
• Mitsubishi Electric Corp

Inventors

• Kimpara Yoshihiko
• Mori Akihiko
• Matsushita Masaki
• Okada Jiro

Classifications

• G08B3/10

  using electric transmission; using electromagnetic transmission · CPC title

• B62D5/0463

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

• B62D5/0487

  detecting motor faults (B62D5/0496 takes precedence) · CPC title

• B62D5/0484 Primary

  for reaction to failures, e.g. limp home · CPC title