A hydraulic suspension system for a motor vehicle having at least a pair of road engaging wheels. The suspension system includes, a hydraulic cylinder coupled with the each of the pair of road engaging wheels, the hydraulic cylinder defining a cap end volume and a rod end volume separated by a piston. A hydraulic supply circuit for the hydraulic cylinder includes, a high pressure hydraulic source, a low pressure hydraulic drain, a pair of hydraulic sub circuits each coupled to one of the hydraulic cylinder cap and rod end volumes. Each hydraulic sub circuit includes, a proportional supply flow valve coupled with the high pressure hydraulic source and one of the cylinder volumes, a return flow control proportional valve coupled with the low pressure hydraulic drain and the one cylinder volume, and an accumulator coupled to the associated hydraulic cylinder volume through an accumulator fill control proportional valve.

A suspension system and associated control methods for improving comfort by disabling passive pitch stiffness in the suspension system by holding open electromechanical comfort valves positioned in a manifold assembly of the suspension system. The manifold comfort valves are held open to disable the passive pitch stiffness of the suspension system if the vehicle is traveling down a rough road or if the vehicle is approaching a discrete road event like a pot-hole or speed bump. Deactivation of the passive pitch stiffness of the suspension system is determined based on road classification information, saved road events, and/or real-time vehicle data from on-board sensors. The suspension system therefore reduces pitch angles during pitch events induced by inertial forces caused by driver inputs and disables the pitch stiffness when the pitch event is caused by road inputs.

A system includes: a state module configured to selectively set a present state to a first state; a valve control module configured to determine first target open and closed states for valves of a suspension system based on the present state and to open and close the valves according to the first target open and closed states, respectively; a pump control module configured to, when the valves are in the first target open and closed states, respectively, selectively operate an electric pump in a first direction to increase hydraulic fluid pressure in a first portion of the suspension system; and a leak module configured to selectively diagnose a leak in a first one of the valves associated with the first state based on a first pressure in the first portion of the suspension system while the valves are open and closed according to the first target open and closed states.

A state module selectively sets a present state to a first state in a predetermined order of states; a valve control module determines first target open and closed states for valves of a suspension system based on the present state and opens and closes the valves according to the first target open and closed states, respectively; a pump control module configured to, when the valves are in the first target open and closed states, respectively, selectively operate an electric pump of the suspension system in a first direction and pump hydraulic fluid toward the suspension system; and a diagnosis module configured to: record first and second values of pressures within the suspension system measured using pressure sensors, respectively, before and after the operation of the electric pump in the first direction, respectively; and selectively diagnose faults in a first subset of the valves based on whether pressure increases occurred.

A bed truck having multiple axles has a hydraulic suspension including multiple hydraulic cylinders for each axle, a ride height sensor associated with each hydraulic cylinder, a high pressure hydraulic circuit connecting each of the cylinders and accumulators to a hydraulic pressure source, a low pressure hydraulic circuit connecting each of the cylinders to a fluid tank, and a plurality of valves operable to isolate operation of any one hydraulic cylinder from some or all of the other hydraulic cylinders. A control system is operable to control each of the hydraulic cylinders, either independently of all the other hydraulic cylinders, or in concert with one or more other hydraulic cylinders, such control including locking any one or more of the hydraulic cylinders at a minimum ride height position.

A suspension device includes an actuator capable of generating a thrust force and a controller. The controller includes a first vibration suppression force computation unit configured to obtain a first vibration suppression force from a vertical velocity of a sprung member, a second vibration suppression force computation unit configured to obtain a second vibration suppression force from a vertical velocity of the unsprung member or a relative velocity between the sprung member and the unsprung member, a low-pass filter having a breakpoint frequency between a sprung resonance frequency and an unsprung resonance frequency and processing a signal in the course of obtaining the second vibration suppression force using the second vibration suppression force computation unit, and a target thrust force computation unit configured to obtain a target thrust force of the actuator on the basis of the first vibration suppression force and the second vibration suppression force.

A suspension device includes: a damper that has an extension-side chamber and a contraction-side chamber; an extension-side passage connected to the extension-side chamber; a contraction-side passage connected to the contraction-side chamber; a switching device that connects one of the extension-side passage and the contraction-side passage to the supply passage and connecting the other of the extension-side passage and the contraction-side passage to the discharge passage selectively; an extension-side damping element provided in the extension-side passage; a contraction-side damping element provided in the contraction-side passage; a control valve capable of adjusting a pressure in the supply passage; an intake check valve provided midway in the intake passage; and a supply-side check valve provided in the supply passage between the control valve and the pump.

A vehicle height adjustment device includes a changer, a detector, and a controller. The changer is configured to change a relative position of a body of a vehicle to an axle of a wheel of the vehicle. The detector is configured to detect the relative position. The controller is configured to control the changer to change the relative position based on a detection value detected by the detector so as to control a height of the body as a vehicle height. The controller is configured to control the changer to maintain the vehicle height when there is a possibility of a malfunction in the detector.

A vehicle height adjustment device includes a changer and a controller. The changer is configured to change a relative position of a body of a vehicle relative to an axle of a wheel of the vehicle. The controller is configured to control the changer to make the relative position a target value so as to control a vehicle height of the body. The controller is configured to control the changer to maintain the relative position when there is a possibility of a malfunction in a detector configured to detect a parameter for control.

A suspension device includes an actuator device provided with an extensible/contractible actuator body interposed between a sprung member and an unsprung member of a vehicle, a pump that supplies fluid to the actuator body to extend or contract the actuator body, and a controller that controls a rotation number of the pump. The controller has a road surface state index obtainment unit that obtains a road surface state index and a target rotation number determination unit that determines a target rotation number of the pump on the basis of the road surface state index.