Steerable wheel axle arrangement and method of controlling a steerable wheel axle arrangement

1 . A steerable wheel axle arrangement for a vehicle, the steerable wheel axle arrangement being connectable to a pair of wheels and comprising:

a steering linkage connectable to the pair of wheels;

a cylinder comprising a fluidly controlled piston movable within the cylinder, the fluidly controlled piston connected to the steering linkage and movable between:

a first end portion of the cylinder adapted to be in fluid communication with a first wheel brake of the vehicle for controlling braking of a first wheel of the pair of wheels;

a second end portion of the cylinder adapted to be in fluid communication with a second wheel brake of the vehicle for controlling braking of a second wheel of the pair of wheels; and

a fluidly controlled brake actuator, comprising:

a first fluidly controlled brake actuator adapted to be in fluid communication with the first wheel brake of the vehicle and the first end portion of the cylinder; and

a second fluidly controlled brake actuator adapted to be in fluid communication with the second wheel brake of the vehicle and the second end portion of the cylinder;

wherein, upon actuation of the first fluidly controlled brake actuator, fluid flows to the first wheel brake and the first end of the cylinder to move the fluidly controlled piston away from the first wheel to increase a first yaw moment caused by the first wheel brake;

wherein, upon actuation of the second fluidly controlled brake actuator, fluid flows to the second wheel brake and the second end of the cylinder to move the fluidly controlled piston away from the second wheel to increase a second yaw moment caused by the second wheel brake.

2 . The steerable wheel axle arrangement of claim 1 , further comprising a steer control valve arrangement arranged in fluid communication between the fluidly controlled brake actuator and the cylinder for controllably directing a flow of fluid from the fluidly controlled brake actuator to the first end portion and the second end portion of the cylinder.

3 . The steerable wheel axle arrangement of claim 1 :

wherein the fluidly controlled piston is arranged to exert a steering force on the steering linkage when a pressure level of an actuation fluid from the fluidly controlled brake actuator exceeds a first predetermined threshold limit; and

wherein at least one of the first wheel brake and the second wheel brake is arranged to be actuated when the pressure level of the actuation fluid exceeds a second predetermined threshold limit;

the second predetermined threshold limit being higher than the first predetermined threshold limit.

4 . The steerable wheel axle arrangement of claim 1 , wherein the cylinder comprises a motion damper connected to the fluidly controlled piston.

5 . The steerable wheel axle arrangement of claim 1 , further comprising:

a valve arranged in fluid communication between the fluidly controlled brake actuator and the wheel brake, the valve being controllable between:

a first state, in which the fluidly controlled brake actuator is in fluid communication with the wheel brake; and

a second state, in which a flow of fluid from the fluidly controlled brake actuator is prevented from reaching the wheel brake.

6 . The steerable wheel axle arrangement of claim 1 , wherein the steering linkage comprises:

a steering knuckle connectable to the wheel;

a steering rod to which the fluidly controlled piston is connected; and

a pivot joint connected between the steering knuckle and the steering rod;

wherein the pivot joints pivot and rotate the steering knuckle when the fluidly controlled piston exerts a steering force on the steering rod.

7 . The steerable wheel axle arrangement of claim 1 , wherein the fluidly controlled brake actuator is one of a pneumatic brake actuator or a hydraulic brake actuator.

8 . A vehicle comprising the steerable wheel axle arrangement of claim 1 , a pair of wheels connected to the steering linkage, and a wheel brake in fluid communication with the fluidly controlled brake actuator.

9 . A method of controlling a steering system connectable to a pair of wheels of a vehicle, the steering system comprising the steerable wheel axle arrangement of claim 1 , the method comprising:

receiving a signal indicative of a steering operation for the vehicle; and

controlling the fluidly controlled brake actuator to supply a flow of fluid to the cylinder for the piston to exert a steering force on the steering linkage to steer the pair of wheels.

10 . The steerable wheel axle arrangement of claim 2 , wherein the steer control valve arrangement comprises:

a first steer control valve arranged to controllably deliver a flow of fluid from the first brake actuator to the first end portion or the second end portion of the cylinder; and

a second steer control valve arranged to controllably deliver a flow of fluid from the second brake actuator to the first end portion or the second end portion of the cylinder.

11 . The steerable wheel axle arrangement of claim 2 , wherein the steer control valve arrangement is configured to controllably prevent a flow of fluid from being supplied from the fluidly controlled brake actuator to the cylinder.

12 . The vehicle of claim 8 , further comprising:

a primary steering system for steering the steerable wheel axle;

wherein the cylinder and fluidly controlled piston form part of a secondary steering system.