# US 10,099,720 B2 · Steering system detecting vehicle motion states

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- Number: US 10,099,720 B2
- Document ID: US10099720B2
- Status: Granted
- Kind: B2
- Application number: 15/434,482
- Filed: 2017-02-16
- Published: 2017-08-17
- Granted: 2018-10-16
- Earliest claimed: 2016-02-16
- Assignees: Steering Solutions IP Holding Corporation
- Applicants: Steering Solutions IP Holding Corporation
- Inventors: Rangarajan Ramanujam; Scott T. Sanford; Tejas M. Varunjikar; Tao Yang
- Web page: https://patentgrep.com/patent/US10099720B2

## CPC

- B62D 5/0463: {calculating assisting torque from the motor based on driver input}
- B62D 6/003: {in order to control vehicle yaw movement, i.e. around a vertical axis (B62D6/007 takes precedence)}
- B62D 6/008: {Control of feed-back to the steering input member, e.g. simulating road feel in steer-by-wire applications}
- B62D 6/02: responsive only to vehicle speed
- B62D 6/10: characterised by means for sensing {or determining} torque
- B62D 15/025: {Active steering aids, e.g. helping the driver by actively influencing the steering system after environment evaluation (B62D1/28 takes precedence)}
- B60Y 2300/0223: related to over-steering
- B60Y 2300/0227: related to under-steering
- 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: 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)
- B60Y: INDEXING SCHEME RELATING TO ASPECTS CROSS-CUTTING VEHICLE TECHNOLOGY

## Abstract

Technical features are described for a steering system to compute a state flag value that is indicative of a vehicle motion state, such as an understeer or an oversteer condition. The steering system further generates a reference torque signal based on the state flag value, and generates a motor-assist torque signal based on the reference torque signal. The state flag value indicates the vehicle motion state in both a dynamic-state or a steady-state. Further, the steering system generates the reference torque signal based on the state flag value by blending a first rack force generated based on a vehicle-speed signal and motor angle, and a second rack force generated based on a motor torque and an input torque provided to a handwheel of the steering system.

## Claims

### Claim 1

A steering system comprising:
a motor; and
a control module that:
computes a first yaw-rate and a yaw-acceleration based on a road-wheel angle signal, a vehicle-speed signal, and a measured yaw-rate signal;
computes a state flag value that is indicative of a vehicle motion state using the first yaw-rate and the yaw-acceleration;
generates a reference torque signal based on the state flag value;
generates a motor-assist torque signal based on the reference torque signal; and
applies the motor-assist torque signal to the motor for generating corresponding amount of torque.

### Claim 2 (depends on 1)

The steering system of claim 1, wherein the state flag is computed based on a vehicle-speed signal, a yaw-rate signal, and an angle signal indicative of a position of a motor of the steering system.

### Claim 3 (depends on 1)

The steering system of claim 1, wherein the vehicle motion state detected is a dynamic state.

### Claim 4 (depends on 1)

The steering system of claim 1, wherein the vehicle motion state detected is a steady state.

### Claim 5 (depends on 1)

The steering system of claim 1, wherein the reference torque signal is generated based on the state flag value by blending a first rack force generated based on a vehicle-speed signal and motor angle, and a second rack force generated based on a motor torque and an input torque provided to a handwheel of the steering system.

### Claim 6 (depends on 1)

The steering system of claim 1, further comprising a reference yaw module configured to compute a reference yaw-rate and a reference yaw-acceleration based on the road-wheel angle signal, and the vehicle-speed signal, wherein the reference yaw-rate and the reference yaw-acceleration are used to compute the state flag.

### Claim 7 (depends on 6)

The steering system of claim 6, further comprising an error calculation module configured to compute a yaw-rate error and a yaw-acceleration error by computing differences between the first yaw-rate and the reference yaw-rate, and between the yaw-acceleration and the reference yaw-acceleration, respectively, wherein the first yaw-rate and the yaw-acceleration are used to compute the state flag.

### Claim 8 (depends on 1)

The steering system of claim 1, further comprising a condition threshold calculation module configured to compute a plurality of thresholds corresponding to each condition from a plurality of oversteer and understeer conditions.

### Claim 9 (depends on 8)

The steering system of claim 8, wherein the thresholds are computed based on a vehicle-speed signal.

### Claim 10 (depends on 8)

The steering system of claim 8, wherein the thresholds are computed based on a surface-friction signal.

### Claim 11

A method for computing an assist torque by a steering system, the method comprising:
detecting, by the steering system, a non-neutral vehicle motion state the detection comprising:
computing a yaw-rate error and a yaw-acceleration error; and
comparing the yaw-rate error and the yaw-acceleration error with a plurality of thresholds corresponding respectively to a plurality of types of the vehicle motion state;
in response, determining a blending-factor based on a type of the vehicle motion state;
generating a rack force signal by blending a first rack force from a vehicle model and a second rack force from a steering system observer model based on the blending-factor; and
generating the assist torque based on the rack force signal.

### Claim 12 (depends on 11)

The method of claim 11, wherein the vehicle motion state is a dynamic-state condition.

### Claim 13 (depends on 11)

The method of claim 11, wherein the vehicle motion state is a steady-state condition.

### Claim 14 (depends on 11)

The method of claim 11, wherein the plurality of types of the vehicle motion state comprise a dynamic-state understeer condition, a dynamic-state oversteer condition, a steady-state understeer condition, and a steady-state oversteer condition.

### Claim 15 (depends on 11)

The method of claim 11, wherein computing the yaw-rate error and the yaw-acceleration error further comprises:
generating a yaw-rate and a yaw-acceleration based on a road-wheel angle signal, a vehicle-speed signal, and a measured-yaw signal;
generating a reference yaw-rate and a reference yaw-acceleration based on the road-wheel angle signal and the vehicle-speed signal; and
computing differences between the yaw-rate and the reference yaw-rate, and the yaw-acceleration and the reference yaw-acceleration as the yaw-rate error and the yaw-acceleration error respectively.

### Claim 16 (depends on 11)

The method of claim 11, further comprising computing the plurality of thresholds based on a vehicle-speed signal.

### Claim 17 (depends on 11)

The method of claim 11, further comprising computing the plurality of thresholds based on a surface-friction signal.

### Claim 18 (depends on 11)

The method of claim 11, wherein the vehicle motion state is detected based on a vehicle-speed signal, a yaw-rate signal, and a motor-angle signal indicative of a position of a motor of the steering system.