Electric power steering control apparatus and electric power steering control method

Patent metadata

Field	Value
Publication number	US-10536102-B2
Application number	US-201515569150-A
Country	US
Kind code	B2
Filing date	May 1, 2015
Priority date	May 1, 2015
Publication date	Jan 14, 2020
Grant date	Jan 14, 2020

Abstract

A main controller includes: a d-axis current limiter configured to calculate a d-axis current limiting value with priority, based on a dq-converted current limiting value, and calculate a limited d-axis current command value by clipping the d-axis current command value to be the d-axis current limiting value or less; a q-axis current limiter configured to calculate a q-axis current limiting value, based on the dq-converted current limiting value and the limited d-axis current command value, and calculate a limited q-axis current command value by clipping the q-axis current command value to be the q-axis current limiting value or less; and an inverter controller configured to control motor current, based on the limited d-axis current command value and the limited q-axis current command value.

First claim

The invention claimed is:

1. An electric power steering control apparatus comprising a main controller configured to control motor current for driving an AC motor assisting steering of a steering wheel, based on a d-axis current command value and a q-axis current command value, wherein
the main controller includes, when a dq-converted current command value, which is a root-sum-square of the d-axis current command value and the q-axis current command value, is limited:
a d-axis current limiter configured to calculate a d-axis current limiting value with priority, based on a dq-converted current limiting value, which is a limiting value of the dq-converted current command value, and calculate a limited d-axis current command value by clipping the d-axis current command value to be the d-axis current limiting value or less;
a q-axis current limiter configured to calculate a q-axis current limiting value based on the dq-converted current limiting value and the limited d-axis current command value calculated by the d-axis current limiter, and calculate a limited q-axis current command value by clipping the q-axis current command value to be the q-axis current limiting value or less; and
an inverter controller configured to control the motor current, based on the limited d-axis current command value and the limited q-axis current command value.

2. The electric power steering control apparatus according to claim 1 , wherein
the d-axis current limiter calculates the d-axis current limiting value using the following expression,
Id _ LIM=Id _MAX×( Idq _ LIM/Idq _MAX)

where
Id_MAX denotes a d-axis current rated value,
Idq_MAX denotes a dq-converted current rated value,

Idq_LIM denotes the dq-converted current limiting value, and
Id_LIM denotes the d-axis current limiting value.

3. The electric power steering control apparatus according to claim 2 , wherein
the q-axis current limiter calculates the q-axis current limiting value using the following expression,
Iq _ LIM =√{( Idq _ LIM ) 2 −( Id ′) 2 }

where
Id′ denotes the limited d-axis current command value calculated by the d-axis current limiter,

Idq_LIM denotes the dq-converted current limiting value, and
Iq_LIM denotes the q-axis current limiting value.

4. The electric power steering control apparatus according to claim 3 , wherein
the main controller includes:
a temperature sensor configured to measure an ambient temperature of the main controller; and
a limiting value computing unit configured to determine the dq-converted current limiting value for overheating protection, based on the ambient temperature measured by the temperature sensor.

5. The electric power steering control apparatus according to claim 2 , wherein
the main controller includes:
a temperature sensor configured to measure an ambient temperature of the main controller; and
a limiting value computing unit configured to determine the dq-converted current limiting value for overheating protection, based on the ambient temperature measured by the temperature sensor.

6. The electric power steering control apparatus according to claim 1 , wherein
the q-axis current limiter calculates the q-axis current limiting value using the following expression,
Iq _ LIM =√{( Idq _ LIM ) 2 −( Id ′) 2 }

where
Id′ denotes the limited d-axis current command value calculated by the d-axis current limiter,

Idq_LIM denotes the dq-converted current limiting value, and
Iq_LIM denotes the q-axis current limiting value.

7. The electric power steering control apparatus according to claim 6 , wherein
the main controller includes:
a temperature sensor configured to measure an ambient temperature of the main controller; and
a limiting value computing unit configured to determine the dq-converted current limiting value for overheating protection, based on the ambient temperature measured by the temperature sensor.

8. An electric power steering control apparatus comprising a main controller configured to control motor current for driving an AC motor assisting steering of a steering wheel, based on a d-axis current command value and a q-axis current command value, wherein
the main controller includes:
a temperature sensor configured to measure an ambient temperature of the main controller;
a limiting value computing unit configured to determine a dq-converted current limiting value for overheating protection, based on the ambient temperature measured by the temperature sensor;
a d-axis current limiter configured to calculate a d-axis current limiting value with priority, based on a dq-converted current limiting value, which is a limiting value of the dq-converted current command value, and calculate a limited d-axis current command value by clipping the d-axis current command value to be the d-axis current limiting value or less,
a q-axis current limiter configured to calculate a q-axis current limiting value based on the dq-converted current limiting value and the limited d-axis current command value calculated by the d-axis current limiter, and calculate a limited q-axis current command value by clipping the q-axis current command value to be the q-axis current limiting value or less; and
an inverter controller configured to control the motor current, based on the limited d-axis current command value and the limited q-axis current command value.

9. An electric power steering control method executed by a main controller controlling motor current for driving an AC motor assisting steering of a steering wheel, based on a d-axis current command value and a q-axis current command value, the method comprising: by the main controller, when a dq-converted current command value, which is a root-sum-square of the d-axis current command value and the q-axis current command value, is limited;
a first step of acquiring a dq-converted current limiting value, which is a limiting value of the dq-converted current command value;
a second step of calculating a d-axis current limiting value with priority, based on the dq-converted current limiting value acquired in the first step;
a third step of calculating a limited d-axis current command value by clipping the d-axis current command value to be not more than the d-axis current limiting value, which has been calculated in the second step;
a fourth step of calculating a q-axis current limiting value based on the dq-converted current limiting value acquired in the first step and the limited d-axis current command value calculated in the third step;
a fifth step of calculating a limited q-axis current command value by clipping the q-axis current command value to be not more than the q-axis current limiting value, which has been calculated in the fourth step; and
a sixth step of controlling the motor current, based on the limited d-axis current command value, which has been calculated in the third step, and the limited q-axis current command value, which has been calculated in the fifth step.

Assignees

• Mitsubishi Electric Corp

Inventors

• Kishioka Hiroyuki
• Zeniya Susumu
• Goto Takashi
• Tanaka Daisuke
• Takashima Akiyoshi
• Iwami Eiji

Classifications

• H02P21/0089

  using field weakening · CPC title

• H02P29/032

  Preventing damage to the motor, e.g. setting individual current limits for different drive conditions · CPC title

• H02P27/12

  pulsing by guiding the flux vector, current vector or voltage vector on a circle or a closed curve, e.g. for direct torque control · CPC title

• H02P21/22 Primary

  Current control, e.g. using a current control loop · CPC title

• H02P29/68

  based on the temperature of a drive component or a semiconductor component · CPC title