Abstract: The hitch on a vehicle is moved by a hydraulic actuator. A method for controlling the hydraulic actuator defines a draft force setpoint in response to separately averaging two forces acting on lateral sides of the hitch, while operating in a configuration mode. During regular operation, a draft load is calculated from sensing those two forces and deriving a draft force error from difference between the draft load and the draft force setpoint. The draft force error is used to control fluid flow to and from the hydraulic actuator. One aspect of the control method derates the draft force error as the hitch moves beyond a predefined threshold position.

Abstract: The hitch on a vehicle is moved by a hydraulic actuator. A method for controlling the hydraulic actuator defines a draft force setpoint in response to separately averaging two forces acting on lateral sides of the hitch, while operating in a configuration mode. During regular operation, a draft load is calculated from sensing those two forces and deriving a draft force error from difference between the draft load and the draft force setpoint. The draft force error is used to control fluid flow to and from the hydraulic actuator. One aspect of the control method derates the draft force error as the hitch moves beyond a predefined threshold position.

Abstract: A hydraulic suspension system for a vehicle includes a pair of cylinders on opposite sides of the vehicle. Each cylinder is divided by a piston into two chambers. When the vehicle is not making a significant turn, a switching valve connects the chambers in the same cylinder together and when a significant turn occurs, the switching valve cross connects the chambers of the two cylinders. That cross connection increases resistance of the suspension system to roll of the vehicle, as compared to when the cylinder chambers are not cross connected. A load leveling function also is included in the hydraulic suspension system.

Abstract: A hydraulic suspension system for a vehicle includes a pair of cylinders on opposite sides of the vehicle. Each cylinder is divided by a piston into two chambers. When the vehicle is not making a significant turn, a switching valve connects the chambers in the same cylinder together and when a significant turn occurs, the switching valve cross connects the chambers of the two cylinders. That cross connection increases resistance of the suspension system to roll of the vehicle, as compared to when the cylinder chambers are not cross connected. A load leveling function also is included in the hydraulic suspension system.

Abstract: A suspension system dampens motion between two components of a vehicle, such as the wheels and the chassis. An assembly of a cylinder and a piston is connected to both components. The piston defines first and second chambers in the cylinder and has a shaft with an end surface exposed to pressure within a third chamber of the cylinder. A first accumulator is connected to the first chamber by a first accumulator valve and a second accumulator valve connects a second accumulator to the second chamber. A damping valve alternately connects the third chamber to either the second chamber or a fluid tank wherein that connection defines the stiffness of the suspension system and is made in response to force acting on the suspension system. A load leveling circuit also is described.

Abstract: A vehicle has an axle connected to a frame by at least one hydraulic cylinder with two chambers separated by a piston. A hydraulic circuit controls flow of fluid between two cylinder chambers and between the chambers and an accumulator to dampen motion of the frame relative to the axle. The hydraulic circuit includes a control valve and a pair of check valves arranged so that the single control valve is able to lock-out the cylinder to emulate a rigid connection of the frame to the axle, as needed.

Abstract: A suspension system dampens motion between two components of a vehicle, such as the wheels and the chassis. An assembly of a cylinder and a piston is connected to both components. The piston defines first and second chambers in the cylinder and has a shaft with an end surface exposed to pressure within a third chamber of the cylinder. A first accumulator is connected to the first chamber by a first accumulator valve and a second accumulator valve connects a second accumulator to the second chamber. A damping valve alternately connects the third chamber to either the second chamber or a fluid tank wherein that connection defines the stiffness of the suspension system and is made in response to force acting on the suspension system. A load leveling circuit also is described.

Abstract: A hydraulic actuator for an active of semi-active vehicle suspension system has a cylinder with a piston therein. A piston rod is attached to the piston and extends out of the cylinder. First and second chambers are formed on opposites sides of the piston enabling the piston to be driven in a manner that counteracts vibrations in the vehicle, A third chamber is provided in the cylinder for connection to a load leveling apparatus. A novel structure reduces the overall length of the hydraulic actuator. A displacement sensor is incorporated into the hydraulic actuator to provide an electrical signal that indicated how far the piston rod extends from the cylinder.