# US 2019/0168801 A1 · Electric power steering apparatus

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- Number: US 2019/0168801 A1
- Document ID: US20190168801A1
- Status: Published application
- Kind: A1
- Application number: 16/320,664
- Filed: 2017-08-16
- Published: 2019-06-06
- Earliest claimed: 2016-08-24
- Assignees: Nsk Ltd.
- Applicants: NSK Ltd.
- Inventors: Hiroaki TAKASE; Ryo MINAKI; Hideki SAWADA; Takayoshi SUGAWARA
- Web page: https://patentgrep.com/patent/US20190168801A1

## CPC

- B62D 5/0463: {calculating assisting torque from the motor based on driver input}
- B62D 5/046: {Controlling the motor}
- B62D 6/00: Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits (means for initiating a change in direction B62D1/00; steering valves B62D5/06; combined with means for inclining the vehicle body or wheels on bends B62D9/00)
- H02M 1/38: Means for preventing simultaneous conduction of switches
- H02M 7/5395: by pulse-width modulation
- H02P 21/06: Rotor flux based control involving the use of rotor position or rotor speed sensors
- H02P 27/08: with pulse width modulation
- H02M 1/385: {with means for correcting output voltage deviations introduced by the dead time}
- 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)
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

An electric power steering apparatus of vector control system that calculates steering assist command values of dq axes based on at least a steering torque, calculates dq-axes current command values from the steering assist command values, converts the dq-axes current command values into 3-phase duty command values, driving-controls a 3-phase brushless motor by an inverter of a PWM control, and applies an assist torque to a steering system of a vehicle, wherein the electric power steering apparatus has plural dead time compensating functions of which efficiencies to respectively perform a dead time compensation of the inverter are different each other, and performs the dead time compensation by gradually shifting from one of the plural dead time compensating functions to an another dead time compensating function while mixing the plural dead time compensating functions.

## Claims

### Claim at position 1

1-10. (canceled)

### Claim 11

An electric power steering apparatus of a vector control system that calculates steering assist command values of dq-axes based on at least a steering torque, calculates dq-axes current command values from said steering assist command values, converts said dq-axes current command values into 3-phase duty command values, driving-controls a 3-phase brushless motor by an inverter of a pulse width modulation (PWM) control, and applies an assist torque to a steering system of a vehicle,
wherein said electric power steering apparatus has two dead time compensating functions A and B of which efficiencies to perform a dead time compensation of said inverter are different,
wherein said dead time compensating function A is a compensation function based on motor terminal voltages and has an effect in a low speed steering maneuver, and said dead time compensating function B is a compensation function based on a motor rotational angle and has an effect in a low speed steering maneuver and a middle speed steering maneuver, and
wherein said dead time compensation is performed by gradually switching from one of said dead time compensating functions A and B to other dead time compensating function while mixing said dead time compensating functions A and B.

### Claim 12 (depends on 11)

The electric power steering apparatus according to claim 11, wherein a ratio of mixing operation is linearly or nonlinearly changing based on a steering assist command value of a d-axis.

### Claim 13

An electric power steering apparatus of a vector control system that calculates steering assist command values of dq-axes based on at least a steering torque, calculates dq-axes current command values from said steering assist command values, converts said dq-axes current command values into 3-phase duty command values, driving-controls a 3-phase brushless motor by an inverter of a pulse width modulation (PWM) control, and applies an assist torque to a steering system of a vehicle, comprising:
a dead time compensating section A that calculates first dq-axes compensation values relating to said dq-axes of said inverter based on 3-phase terminal voltages of said 3-phase brushless motor;
a dead time compensating section B that calculates second dq-axes compensation values relating to said dq-axes of said inverter based on a motor rotational angle; and
a compensation-value switching section that gradually and mutually switches while mixing said first dq-axes compensation values and said second dq-axes compensation values based on said steering assist command value of said q-axis, and outputs dq-axes dead time compensation values,
wherein a dead time compensation of said inverter is performed by a correction of said dq-axes current command values with said dq-axes dead time compensation values.

### Claim 14 (depends on 13)

The electric power steering apparatus according to claim 13, wherein said compensation-value switching section comprising:
a switch judging section to judge a compensation-value switch based on said steering assist command value of said q-axis;
a mixing-ratio calculating section to calculate a mixing-ratio RtA (%) of said first dq-axes compensation values and a mixing-ratio RtB (%) of said second dq-axes compensation values due to a compensation-value switch judgment flag from said switch judging section; and
a mixing section to input said first dq-axes compensation values and said second dq-axes compensation values, and to calculate said dq-axes dead time compensation values based on said mixing-ratio RtA (%) and said mixing-ratio RtB (%).

### Claim 15 (depends on 14)

The electric power steering apparatus according to claim 14, wherein said mixing section comprising:
a switch which inputs a count-up value and a count-down value and is switched due to said compensation-value switch judgment flag;
a count-value limiting section to limit, via an adding section, said count-up value or said count-down value from said switch and output said mixing-ratio RtB (%);
a holding unit which holds said mixing-ratio RtB (%) and adds to said adding section; and
a subtracting section to output said mixing-ratio RtA (%) by subtracting said mixing-ratio RtB (%) from a value of 100%.

### Claim 16 (depends on 15)

The electric power steering apparatus according to claim 15, wherein said count-up value and said count-down value are changeable.

### Claim 17 (depends on 14)

The electric power steering apparatus according to claim 14, wherein said mixing section comprising:
a first multiplying section which multiplies said first dq-axes compensation values with said mixing-ratio RtA (%);
a second multiplying section which multiplies said second dq-axes compensation values with said mixing-ratio RtB (%); and
an adding section to output said dq-axes dead time compensation values by adding a multiplied result of said first multiplying section and a multiplied result of said second multiplying section.

### Claim 18 (depends on 15)

The electric power steering apparatus according to claim 15, wherein said mixing section comprising:
a first multiplying section which multiplies said first dq-axes compensation values with said mixing-ratio RtA (%);
a second multiplying section which multiplies said second dq-axes compensation values with said mixing-ratio RtB (%); and
an adding section to output said dq-axes dead time compensation values by adding a multiplied result of said first multiplying section and a multiplied result of said second multiplying section.

### Claim 19 (depends on 14)

The electric power steering apparatus according to claim 14, wherein said mixing-ratio RtA(%) and said mixing-ratio RtB (%) non-linearly vary and have a relation being RtA(%)+RtB(%)=100%.

### Claim 20 (depends on 15)

The electric power steering apparatus according to claim 15, wherein said mixing-ratio RtA(%) and said mixing-ratio RtB (%) non-linearly vary and have a relation being RtA(%)+RtB(%)=100%.

### Claim 21 (depends on 14)

The electric power steering apparatus according to claim 14, wherein said correction is performed by an adding calculation of said dq-axes dead time compensation values and said dq-axes current command values.

### Claim 22 (depends on 15)

The electric power steering apparatus according to claim 15, wherein said correction is performed by an adding calculation of said dq-axes dead time compensation values and said dq-axes current command values.