US 2015/0307128 A1Published application

A control method of a power steering system for a vehicle having two steered axles

AssigneeVolvo Truck Corporation

InventorsJean-Marc BLOND, Jean-Baptiste DORAY

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Abstract

A power steering system includes a first steering device which controls the steering of the first wheels of the vehicle according to a first steering angle α1 and includes a first actuator capable of providing a steering assistance effort, a second steering device including a second actuator controlled by a controller as a function of a parameter related to the steering wheel movement, and controlling the steering of the second wheels, according to a second steering angle α2. In normal operation of the power steering system, α2 is set according to a first rule depending on the first steering angle α1. In case the steering wheel torque is greater than a predetermined threshold, the second steering device is operated in a forced mode by setting the second steering angle according to a rule depending on the first steering angle and taking into account at least one different or additional data, in order to cause an offset-oversteering of the second wheel. The first and second steering devices, which are mechanically independent, and furthermore preferably hydraulically independent, thereby increasing the system security. The invention is of course not limited to the embodiments described above as examples, but encompasses all technical equivalents and alternatives of the means described as well as combinations thereof.

Claims24

Dependent claims

A control method of a power steering system for a vehicle having two steered axles, the two steered axles comprising a first steered axle joining two first wheels, and a second steered axle joining two second wheels, the power steering system comprising:

a first steering device designed to control the steering of at least one of the first wheels, according to a first steering angle (α1), the first steering device comprising:
a mechanical transmission of the movement from a steering wheel of the vehicle to at least one of the first wheels;
a steering assistance device including a first actuator controlled as a function of a parameter related to the steering wheel movement and capable of providing a steering assistance effort to at least one of the first wheels;
a second steering device comprising a second actuator controlled by a controller as a function of a parameter related to the steering wheel movement, and designed to control the steering of at least one of the second wheels, according to a second steering angle (α2) which is set according to a first rule (F1(α1)) depending on the first steering angle (α1), in normal operation of the power steering system;
wherein the control method comprises:
detecting or estimating whether a steering wheel torque (SWT) is greater than a predetermined threshold (SWTth);
in case the steering wheel torque (SWT) is greater than the threshold (SWTth), operating the second steering device in a forced mode by setting the second steering angle (α2) according to a rule (F2, F1) which depends on the first steeling angle (α1) and which takes into account at least one different or additional data, in order to cause an offset-steering of the second wheel.

4 more elements

A power steering system for a vehicle having two steered axles, the two steered axles comprising a first steered axle joining two first wheels, and a second steered axle joining two second wheels, the power steering system comprising:

a first steering device designed to control the steering of at least one of the first wheels according to a first steering angle (α1), the first steering device comprising:
a mechanical transmission of the movement from a steering wheel of the vehicle to at least one of the first wheels;
a first actuator controlled as a function of a parameter related to the steering wheel movement and capable of providing a steering assistance effort to at least one of the first wheels;
a second steering device comprising a second actuator controlled by a controller as a function of a parameter related to the steering wheel movement, and designed to control the steering of at least one of the second wheels (10), according to a second steering angle (α2) which is set according to a first rule (F1) depending on the first steering angle (α1), in normal operation of the power steering system;
wherein the power steering system further comprises detecting means (50) which are capable of detecting or estimating a steering wheel torque (SWT) greater than a predetermined threshold (SWTth), and which are coupled to the controller, the controller being designed to set the second steering angle (α2) according to a rule (F2, F1) which depends on the first steering angle (α1) and which takes into account at least one different or additional data, in a forced mode in which the steering wheel torque (SWT) is greater than the threshold (SWTth), in order to cause an offset-steering of the second wheel.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 14/647,518Filed 27 Dec 2012
Published: 29 Oct 2015
Term ends: Not estimatedThe source records don’t support an estimate.

Classification4 codes

B62D 7/159
Characterised by means varying the ratio between the steering angles of the steered wheels: characterised by computing methods or stabilisation…
B62D 5/20
Fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle: specially adapted for particular type of steering…
B62D 7/144
Specially adapted for particular vehicles, e.g. tractors, carts, earth-moving vehicles, trucks: for vehicles with more than two axles
B62D
Motor vehicles