# US 10,118,638 B2 · Motor driven power steering system and control method thereof

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- Number: US 10,118,638 B2
- Document ID: US10118638B2
- Status: Granted
- Kind: B2
- Application number: 15/371,067
- Filed: 2016-12-06
- Published: 2017-06-08
- Granted: 2018-11-06
- Earliest claimed: 2015-12-07
- Assignees: Hyundai Mobis Co., Ltd.
- Applicants: Hyundai Mobis Co., Ltd.
- Inventors: Kevin McLaughlin; Hyung Ju Kwon; Jonah Shapiro
- Web page: https://patentgrep.com/patent/US10118638B2

## CPC

- 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)
- B62D 5/0463: {calculating assisting torque from the motor based on driver input}
- B62D 15/021: {Determination of steering angle}
- 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)

## Abstract

A motor driven power steering (MDPS) system may include: a torque sensor configured to measure a steering torque caused by a steering operation of a driver; a steering angle sensor configured to measure a steering angle of the steering operation; and a controller configured to determine a control torque according to the steering angle measured through the steering angle sensor, calculate an input torque based on the control torque and the steering torque measured through the torque sensor, and determine an assist torque based on the calculated input torque.

## Claims

### Claim 1

A motor driven power steering (MDPS) system comprising:
a torque sensor configured to measure a steering torque (τ) caused by a steering operation of a driver;
a steering angle sensor configured to measure a steering angle (θ) of the steering operation; and
a controller configured to:
determine a control torque according to the steering angle measured through the steering angle sensor,
calculate an input torque by subtracting the control torque from the steering torque measured through the torque sensor,
determine an assist torque by applying a first boost gain (KB) to the calculated input torque, wherein the first boost gain is determined using the steering torque (τ) as an input to a predetermined function defining boost gain with respect to steering torque;
cause a motor of the MDPS system to generate the assist torque such that the assist torque changes in consideration of the steering angle via the control torque;
wherein the control torque is computed using the steering angle (θ) and a stiffness function (fs) satisfying the following Equation 1:
∂
f
s
∂
θ
=
(
K
B
-
K
b
K
B
)
×
g
v
×
S
g
,
where Sg is a steering gain representing a desirable partial derivative of the steering torque with respect to a lateral acceleration of the vehicle, gv is a constant, KB is the first boost gain, and Kb is a second boost gain to achieve the steering gain (Sg) assuming the assist torque from the motor is generated based on the steering torque (τ) without considering the steering angle (θ),
wherein the second boost gain satisfies the following Equation 2:
K
b
=
M
g
S
g
-
1
,
where Mg represents a constant based on a vehicle characteristic, and Sg represents the steering gain.

### Claim 2 (depends on 1)

The MDPS system of claim 1, wherein the first boost gain (KB) has a larger value than the second boost gain (Kb).

### Claim 3

A control method of an MDPS system, comprising:
measuring, by a controller, a steering torque caused by a steering operation of a driver;
measuring a steering angle of the steering operation;
determining a control torque according to the measured steering angle;
calculating an input torque by subtracting the control torque from the steering torque;
determining an assist torque by applying a first boost gain (KB) to the calculated input torque, wherein the first boost gain is determined using the steering torque (τ) as an input to a predetermined function defining boost gain with respect to steering torque;
controlling a motor of the MDPS system to generate the assist torque such that the assist torque changes in consideration of the steering angle via the control torque;
wherein the control torque is computed using the steering angle (θ) and a stiffness function (fs) satisfying the following Equation 1:
∂
f
s
∂
θ
=
(
K
B
-
K
b
K
B
)
×
g
v
×
S
g
,
where Sg is a steering gain representing a desirable partial derivative of the steering torque with respect to a lateral acceleration of the vehicle, gv is a constant, KB is the first boost gain, and Kb is a second boost gain to achieve the steering gain (Sg) assuming the assist torque from the motor is generated based on the steering torque (τ) without considering the steering angle (θ),
wherein the second boost gain satisfies the following Equation 2:
K
b
=
M
g
S
g
-
1
,
where Mg represents a constant based on a vehicle characteristic, and Sg represents the steering gain.

### Claim 4 (depends on 3)

The control method of claim 3, wherein the first boost gain (KB) has a larger value than the second boost gain (Kb).