A damper valve with an adjustable effective stiffness of a shim. The damper valve includes a piston. The piston has a fluid path formed therethrough. A shim is disposed proximate the fluid path formed through the piston. A stiffness adjustment feature is coupled to the shim, and the shim is disposed between the piston and the stiffness adjustment feature. The stiffness adjustment feature is configured to adjust the effective stiffness of the shim without affecting a preload applied to the shim.

A method to control, while driving along a curve, a road vehicle with a variable stiffness and with rear steering wheels. The method comprises the steps of: determining an actual attitude angle of the road vehicle; establishing a desired attitude angle; determining an actual yaw rate of the road vehicle; establishing a desired yaw rate; and changing, in a simultaneous and coordinated manner, the steering angle of the rear wheels and the distribution of the stiffness of the connection of the four wheels to the frame depending on a difference between the actual attitude angle and the desired attitude angle and depending on a difference between the actual yaw rate and the desired yaw rate.

A control system includes: a target volume module configured to determine a target volume of hydraulic fluid within a suspension system of a vehicle based on a target pressure of the hydraulic fluid within the suspension system; a volume command module configured to generate a volume command based on the target volume and a present volume of the hydraulic fluid within first and second circuits; a command module configured to, based on the volume command, generate: a pump command for an electric hydraulic fluid pump; and first and second valve commands for first and second seat valves that regulate hydraulic fluid flow to and from the first and second circuits, respectively; a valve control module that actuates the first and second seat valves based on the first and second valve commands, respectively; and a pump control module that controls operation of the pump based on the pump command.

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 suspension system and associated control methods that reduce temperature related fluctuations in the internal pressures and stiffness of the suspension system. A manifold assembly is connected in fluid communication with a plurality of dampers via hydraulic circuits and a pump assembly via a pump hydraulic line. Onboard sensors generate real-time data regarding the vehicle. A suspension control unit, arranged in electronic communication with the aforementioned components, monitors the real-time data, sets a target stiffness and a target pressure, calculates an effective stiffness based on the real-time data, determines if the effective stiffness is above or below the target stiffness and sets a new target pressure accordingly by making stepwise decreases or increases until the new target pressure is reached.

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 system for grading filling of a suspension system includes: a pump control module configured to, during first and second periods, operate an electric pump of the suspension system in first and second directions and decreasing and increasing hydraulic fluid pressure within the suspension system, respectively; a monitoring module configured to: store a first pressure of hydraulic fluid within the suspension system measured using a pressure sensor when the first pressure is less than or equal a first predetermined pressure while the pump is operated in the first direction; and store a second pressure measured using the pressure sensor when the second pressure is greater than or equal a second predetermined pressure while the pump is operated in the second direction; and a grade module configured to determine a grade value for the filling of the suspension system based on the first and second pressures.

A suspension system and associated control methods for improving the effectiveness of driver assistance systems is disclosed where the driver assistance systems can generate and send requests to a suspension control unit (SCU) of the suspension system to actuate (e.g., close) one or more comfort valves in the suspension system to increase the roll stiffness and/or pitch stiffness of the suspension system when the driver assistance systems are taking corrective action. As part of a two-way communication between the suspension control unit (SCU) and the driver assistance systems, the suspension control unit (SCU) communicates target stiffnesses and/or calculated effective stiffnesses to the driver assistance systems, which is used to update the vehicle stability models used by the driver assistance systems.

A suspension system for a land vehicle is provided with at least one actuator connected to a chassis and an axle of a land vehicle spaced apart from a pivotal connection of the axle. A suspension circuit is in cooperation with the at least one actuator. A controller is in operable communication with the suspension circuit and is programmed to receive input indicative of a travel speed of the land vehicle. The suspension circuit is closed at a low speed travel range to permit the axle to pivot in response to variations in an underlying support surface. The suspension circuit is opened to permit selective actuation of the at least one actuator at a higher speed travel range in response to variations in the underlying support surface.