# US 8,541,965 B2 · Motor controller and electronic power steering apparatus

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- Number: US 8,541,965 B2
- Document ID: US8541965B2
- Status: Granted
- Kind: B2
- Application number: 12/935,774
- Filed: 2009-03-30
- Published: 2011-02-03
- Granted: 2013-09-24
- Earliest claimed: 2008-03-31
- Assignees: Jtekt Corporation
- Applicants: Takeshi Ueda; Yuji Kariatsumari; Shigeki Nagase; Noboru Niguchi; Hiroshi Sumasu
- Inventors: Takeshi Ueda; Yuji Kariatsumari; Shigeki Nagase; Noboru Niguchi; Hiroshi Sumasu
- Web page: https://patentgrep.com/patent/US8541965B2

## CPC

- B62D 5/046: {Controlling the motor}
- H02P 21/0089: {using field weakening}
- H02P 21/06: Rotor flux based control involving the use of rotor position or rotor speed sensors
- H02P 29/032: Preventing damage to the motor, e.g. setting individual current limits for different drive conditions
- B62D: MOTOR VEHICLES; TRAILERS (steering, or guiding on a desired track, of agricultural machines or implements A01B69/00; wheels, castors, axles, increasing wheel adhesion B60B; vehicle tyres, tyre inflation or tyre changing B60C; connections between vehicles of a train or the like B60D; vehicles for use on rail and road, amphibious or convertible vehicles B60F; suspension arrangements B60G; heating, cooling, ventilating or other air treating devices B60H; windows, windscreens, non-fixed roofs, doors or similar devices, protective coverings for vehicles not in use B60J; propulsion plant arrangements, auxiliary drives, transmissions, controls, instrumentation or dashboards B60K; electric equipment or propulsion of electrically-propelled vehicles B60L; power supply for electrically-propelled vehicles B60M; passenger accommodation not otherwise provided for B60N; adaptations for load transportation or to carry special loads or objects B60P; arrangement of signalling or lighting devices, the mounting or supporting thereof or circuits therefor, for vehicles in general B60Q; vehicles, vehicle fittings or vehicle parts not otherwise provided for B60R; servicing, cleaning, repairing, supporting, lifting, or manoeuvring, not otherwise provided for, B60S; brake arrangements, brake control systems or parts thereof B60T; air-cushion vehicles B60V; motor-cycles, accessories therefor B62J, B62K; testing of vehicles G01M)
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

A command current setting portion has a target value corrector that calculates d-axis and q-axis current command values idc, iqc that are to be supplied to an open-loop controller, based on d-axis and q-axis current target values id*, iq*. When d-axis and q-axis voltage target value vd*, vq* calculated from the d-axis and q-axis current target values id*, iq* by the motor circuit equations exceed a voltage limit, this target value corrector 26 corrects the d-axis and q-axis current target values id*, iq* by the field weakening control such that d-axis and q-axis voltages vd, vq and d-axis and q-axis currents id, iq satisfy √(vd2+vq2)≦Vlim and √(id2+iq2)≦Ilim respectively. The d-axis and q-axis current command values idc, iqc are obtained by this correction.

## Claims

### Claim 1

A motor controller capable of applying a field-weakening control to drive a brushless motor, comprising:
a command current setting section that decides d-axis and q-axis current command values indicating a current that is to be supplied to the brushless motor;
a control operating section that calculates d-axis and q-axis voltage command values indicating a voltage that is to be applied to the brushless motor, based on the d-axis and q-axis current command values decided by the command current setting section; and
a driving section that drives the brushless motor based on the d-axis and q-axis voltage command values calculated by the control operating section,
wherein the command current setting section decides the d-axis and q-axis current command values within a predetermined voltage limit value and a predetermined current limit value so that the d-axis and q-axis voltage command values and the d-axis and q-axis current command values satisfy both inequalities given as follows,
√{square root over ( )}(vd2+vq2)≦Vlim,
√{square root over ( )}(id2+iq2)≦Ilim,
where vd is the d-axis voltage command value, vq is the q-axis voltage command value, Vlim is the voltage limit value, id is the d-axis current command value, iq is the q-axis current command value, and Ilim is the current limit value.

### Claim 2 (depends on 1)

The motor controller according to claim 1, wherein the command current setting section includes:
a target current setting section that sets a target current of the current to be supplied to the brushless motor; and
a target value correcting section that calculates the d-axis and q-axis current command values by correcting d-axis and q-axis components of the target value so that the d-axis and q-axis voltage command values vd, vq satisfy a following equation with regard to the voltage limit value Vlim, when the voltage that is to be applied to the brushless motor to supply the current of the target value to the brushless motor exceeds the voltage limit value Vlim,
√{square root over ( )}(vd2+vq2)=Vlim.

### Claim 3 (depends on 1)

The motor controller according to claim 1, wherein the command current setting section includes a reduction-in-torque compensating section that compensates the q-axis current command value so that a reduction in an output torque of the brushless motor caused by the d-axis current command value is compensated and both inequalities are satisfied,
wherein the control operating section calculates the d-axis and q-axis voltage command values by using the d-axis current command value and the corrected q-axis current command value subjected to a correction by the reduction-in-torque compensating section.

### Claim 4 (depends on 3)

The motor controller according to claim 3, wherein the reduction-in-torque compensating section includes:
a first maximum value deciding section that calculates a maximum value, that is allowed for the q-axis current command value iq when the q-axis current command value iq is changed to satisfy an inequality indicating a limit given by the voltage limit value Vlim out of both inequalities, as a first maximum value;
a second maximum value deciding section that calculates another maximum value, that is allowed for the q-axis current command value iq when the q-axis current command value iq is changed to satisfy an inequality indicating a limit given by the current limit value Ilim out of both inequalities, as a second maximum value;
a correcting section that corrects the q-axis current command value so that a reduction in output torque of the brushless motor caused by the d-axis current command value is compensated; and
a selecting section that selects a smallest value out of the q-axis current command value subjected to the correction by the correcting section, the first maximum value, and the second maximum value as the q-axis current command value subjected to the correction.

### Claim 5 (depends on 1)

An electronic power steering apparatus for applying a steering assist force to a steering mechanism of a vehicle by a brushless motor, the electronic power steering apparatus comprising:
the motor controller set forth in claim 1,
wherein the motor controller drives the brushless motor that applies the steering assist force to the steering mechanism.