Electric power assisted steering systems

Patent metadata

Field	Value
Publication number	US-9815493-B2
Application number	US-201214354586-A
Country	US
Kind code	B2
Filing date	Oct 29, 2012
Priority date	Oct 27, 2011
Publication date	Nov 14, 2017
Grant date	Nov 14, 2017

Abstract

A vehicle comprising an electric power assist steering (EPAS) system, wherein the EPAS system is configured to receive a detected value of steering wheel angle and/or steering wheel angular velocity and wherein the EPAS system is configured to improve the accuracy of the detected value of steering wheel angle and/or steering wheel angular velocity by compensating for any one or more of an angular phasing of the joint between any two linked components of the steering mechanism and the effect on steering wheel angle of the deflection across a torque sensor at least substantially due to the stiffness of that torque sensor.

First claim

The invention claimed is:

1. A vehicle comprising an electric power assist steering (EPAS) system having a controller unit, a steering wheel, an electric motor, and a rack coupled to and disposed between both the steering wheel and the electric motor, wherein the controller unit of the EPAS system is configured to receive a detected value of steering wheel angle and/or steering wheel angular velocity at a position between the steering wheel and the rack, and wherein the controller unit of the EPAS system is configured to improve the accuracy of the detected value of steering wheel angle and/or steering wheel angular velocity by compensating for an angular phasing of the joint between any two linked components of the steering mechanism by carrying out a computation to derive an improved value of steering wheel angle and/or steering wheel angular velocity from the detected value of steering wheel angle and/or steering wheel angular velocity, which computation accounts for an angle at a joint (δ 5 ) between the two linked components that is located between the steering wheel and the position corresponding to the detected steering wheel angle value and/or the steering wheel angular velocity value, and wherein said compensation is carried out using any one or more of the following relationships:

β
.

5

α
.

5

=

ω
b

ω
a

=

cos
⁢

⁢

δ
5

1
-

sin
2

⁢

δ
5

⁢

cos
2

⁢

α
5

;

β
5

=

arctan
⁢

⁢
2
⁢

(

sin
⁢

⁢

α
5

,

cos
⁢

⁢

α
5

·
cos

⁢

⁢

δ
5

)

;
and

α
5

=

arctan
⁢

⁢
2
⁢

(

sin
⁢

⁢

β
5

,

cos
⁢

⁢

β
5

cos
⁢

⁢

δ
5

)

wherein the two linked components are disposed at the angle δ 5 relative to one another, wherein the angle of rotation at the input is α 5 and the angle of rotation at the output is β 5 and wherein ω a and ω b are the angular velocities (in rad/s) of the two linked components having angles of rotation of α 5 and β 5 respectively.

2. A vehicle according to claim 1 wherein the EPAS system is configured to use the improved value of steering wheel angle and/or steering wheel angular velocity to compute the amount of assistive torque supplied by a motor of the EPAS system.

3. A vehicle according to claim 1 wherein a sensor for detecting the angle of rotation of the steering wheel is disposed within the steering mechanism and is not directly connected to the steering wheel.

4. A vehicle according to claim 1 , wherein the EPAS system is configured to compensate for the effect of angle phasing of the joint between two linked components of the steering mechanism using a computation that includes an approximation and/or equivalent function or value for any one or more of:
the cosine and/or sine of the angle between the two linked components (cos δ 5 and/or sin δ 5 );
(ii) the square of the cosine of the angle input to the joint (cos 2 α 5 );
(iii) the square of the sine of the angle between the two linked components (sin 2 δ 5 );
(iv) the cosine and/or sine of the angle input to the joint (cos α 5 and/or sin α 5 );
(v) the arctangent in the range of −π/2 and π/2 of the sine of the angle input to the joint and of the cosine of the angle between the two linked components multiplied by the c

Assignees

• Jaguar Land Rover Ltd

Inventors

• Bean Alex
• Pucci Paolo

Classifications

• B62D6/10 Primary

  characterised by means for sensing {or determining} torque · CPC title

• B62D15/02

  Steering position indicators {; Steering position determination; Steering aids} · CPC title

• B62D15/0235

  by measuring or deriving directly at the electric power steering motor · CPC title

• B62D5/0463

  calculating assisting torque from the motor based on driver input · CPC title

• B62D15/0215

  by measuring on the steering column · CPC title