A suspension characteristic is changed depending on a travel state by a simple structure. An ECU uses a vehicle speed-spring constant setting part to calculate a target spring constant depending on a vehicle speed, and uses a spring constant-frequency setting part to calculate a set frequency corresponding to the target spring constant. An oscillation input calculation part generates a signal representing an oscillation input oscillating at the set frequency. A superimposition part sets a value acquired by superimposing the oscillation input on a target driving force to a new target driving force. As a result, the wheel exhibits a minute oscillation in a longitudinal direction, resulting in an input of the minute oscillation to a suspension bush. The suspension bush changes in a spring constant and a damping coefficient depending on the frequency of the input minute oscillation. As a result, the suspension characteristic can be changed.

A damping force control device for controlling damping forces of shock absorbers by a control device, which is configured to to estimate first vertical speeds at the positions of wheels based on the vertical accelerations of a vehicle body at the positions of the wheels, to estimate second vertical speeds of the vehicle body caused by driver's driving operation based on driving operation amount of the driver, to calculate target damping forces by subtracting products of damping coefficients of the ride comfort control and second vertical speeds from the sums of products of the damping coefficients of the ride comfort control and first vertical speeds and products of damping coefficients for controlling posture change of the vehicle body and the second vertical speeds, and to control damping coefficients of the shock absorbers based on the target damping forces.

An active chassis control for a motor vehicle with an adaptive control circuit for reducing body vibrations (A.sub.actual) of the motor vehicle, in which a control unit is integrated, which, depending on a current body vibration (A.sub.actual) or a parameter correlating therewith (a), controls a chassis actuator. The control unit is followed by an adaptive unit which adapts an actuating signal (S) generated by the control unit with a driving speed-dependent scaling factor (f(v)), in particular by generating an adapted actuating signal (S′) with which the chassis actuator can be controlled. Depending on the situation, a factor allowance (Δf) can be added to the driving speed-dependent scaling factor (f(v)) in the event of a significantly greater body vibration (A.sub.o) in order to effectively dampen the significantly greater body vibration (A.sub.o).

In a suspension controlling apparatus for a vehicle including a suspension whose damping force is variably settable and a control unit capable of controlling the damping force of the suspension, for appropriately obtaining a pitch behavior. When a vibration state of a vehicle in a vertical direction exceeds a given vibration state, a control unit controls damping force of suspensions on the basis of a target damping force in order to execute a skyhook control. However, when acceleration in a forward and rearward direction of the vehicle is outside a given range, a decision condition for the given vibration state is changed to a condition on the side on which the skyhook controlling damping force control of the suspensions is less likely to be started.

An electronic control suspension apparatus for controlling a damping force of a damper installed at each of a front wheel and a rear wheel includes: a reception unit configured to receive a vehicle manipulation signal; a driver tendency analysis unit configured to calculate a driver tendency analysis value by analyzing a driver's driving tendency based on the vehicle manipulation signal received by the reception unit; a driver mode determination unit configured to determine a driver mode to which the driver tendency analysis value calculated by the driver tendency analysis unit belongs; and a damping force control unit configured to control the damping force of the damper by changing a current value to be applied to a solenoid valve according to the determined driver mode.

To improve off-road travel performance, ECU is configured to: set one of front left and right wheels and rear left and right wheels as roll stiffness decrease subject wheels and set another as non-roll stiffness decrease subject wheels; bring a spring switching valve and a leveling valve into an open state for each of the roll stiffness decrease subject wheels, causing left and right hydraulic cylinders to communicate to each other for the roll stiffness decrease subject wheels; and bring the spring switching valve and the leveling valve into a closed state and bring a bypass valve into the open state for one of the left and right wheels of the non-roll stiffness decrease subject wheels, to cause a second gas spring for one of the left and right wheels of the non-roll stiffness decrease subject wheels to communicate to the hydraulic cylinders of the roll stiffness decrease subject wheels.

A vehicle height control apparatus considering a strong wind traveling situation may include: a strong wind zone determining unit for obtaining wind speed information of a current position by using map information to which the wind speed information is corresponded and current position information of a vehicle, and generating strong wind zone information by comparing the obtained wind speed information with a predetermined reference wind speed to determine a strong wind zone; a strong wind traveling situation determining unit for generating strong wind traveling situation information by determining the strong wind traveling situation based on the strong wind zone information and the vehicle speed information of the current position; and a control signal generating unit for generating a control signal of a vehicle height adjusting device according to the strong wind traveling situation information.

A method and system for estimating surface roughness of a ground for an off-road vehicle to control steering of a vehicle, an implement, or both, comprises detecting motion data of an off-road vehicle traversing a field or work site during a sampling interval. A first sensor is adapted to detect pitch data of the off-road vehicle for the sampling interval to obtain a pitch acceleration. A second sensor is adapted to detect roll data of the off-road vehicle for the sampling interval to obtain a roll acceleration. An electronic data processor or surface roughness index module determines or estimates a surface roughness index based on the detected motion data, pitch data and roll data for the sampling interval. The surface roughness index can be displayed on the graphical display to a user or operator of the vehicle.

In a suspension controlling apparatus for a vehicle which includes a suspension whose damping force is variably settable and a control unit capable of executing skyhook control on the basis of target damping force for skyhook control to control the damping force of the suspension, the vehicle stability is raised upon skyhook control during turning of the vehicle. Target damping force limit value determination device provided in a control unit determines target damping force limit values for skyhook control such that a value obtained by subtracting, from the target damping force limit value on the decompression side when the suspension is in a decompressed state, the target damping force limit value on the compression side when the suspension is in a compressed state increases as a roll angle detected by a roll angle sensor increases. The control unit limits the target damping forces with the target damping force limit value.

A vehicle height adjustment apparatus includes a control device. The control device controls the opening degree of the solenoid valve to allow a movement amount of the support member to reach a movement amount target value that corresponds to the vehicle height set in advance, in accordance with the weight applied to the vehicle. The control device controls the opening degree of the solenoid valve to change the movement amount of the support member based on a difference between a value based on the information related to the vehicle height and a vehicle height-related target value, on condition that the movement amount of the support member reaches the movement amount target value and the value based on the information related to the vehicle height obtained by the information obtaining device does not reach the vehicle height-related target value that corresponds to the vehicle height set in advance.