Survey of advanced suspension developments and related optimal control applications

SUMMARY Based mainly on English language literature, information relating to the design of automobile suspension systems for ride comfort and control of wheel load variations for frequencies below body structure resonances is reviewed. The information is interpreted in the context of vehicles which travel through a wide speed range on roads of markedly differing quality, which do so carrying different loads and which are required to possess good handling qualities. Sections are devoted to describing road surfaces, modelling vehicles and setting up performance criteria, and to passive, active, semi-active and slow-active system types. Methods for deriving active system control laws are outlined. Strengths and weaknesses of the various systems are identified and their relative performance capabilities and equipment requirements are discussed. Attention is given to adaptation of the suspension or control system parameters to changing conditions. Remaining research needs are considered.

Road Vehicle Suspension System Design - a review

In the five decades since the founding of the ASME Design Engineering Division, the important problem of vibration isolation has been attacked first through the design of passive spring-damper suspensions and later by the use of active and semi-active elements. This paper reviews the historical development of theoretical concepts necessary for the design of isolation systems and indicates how control theory began to influence vibration isolation in the last half of this period. Practical active and semi-active suspensions have only recently become possible with the advent of powerful but relatively inexpensive signal processors. To illustrate these developments for engineers who have not been intimately involved with active systems, only simple vibrational system models will be discussed, although some modem hardware will be shown which is now being applied to complex systems. Instead of attempting to review the many theoretical concepts which have been proposed for active systems, this article will focus on a relatively simple idea with which the author has been associated over the past thirty years ; namely the skyhook damper. This idea came through purely theoretical studies but is now used in combination with other concepts in production suspension systems. Two quite different application areas will be discussed. The first involves stable platforms to provide extreme isolation for delicate manufacturing operations against seismic inputs and the second involves automotive suspensions. Although similar concepts are found in these two application areas, the widely varying requirements result in very different suspension hardware. The special case of the semi-active damper, which requires very little control power and is presently reaching production, will also be discussed.

Active and semi-active vibration isolation

A steering column assembly for a vehicle, comprises a shroud comprising an axially movable upper portion and an axially fixed lower portion, which move telescopically to provide adjustment for reach of the steering column assembly, a steering shaft supported by the shroud, a pivot which connects a part of the lower portion to a fixed part of the vehicle, a clamp mechanism which releasably fixes the upper and lower portions and the shroud in position relative to a further fixed part of the vehicle. A sprung support assembly is secured to a fixed part of the vehicle and includes an axle that passes underneath the upper portion of the shroud and a cylindrical roller that surrounds a part of the axle and has an outer surface that engages the underside of the shroud and an inner surface that bears on the axle, the sprung support at least partially supports the weight of the shroud when the clamp mechanism is released, and the cylindrical roller rotating around the axle as the shroud is adjusted for reach.

Steering column assembly

A method of on-demand energy delivery to an active suspension system comprising an actuator body, hydraulic pump, electric motor, plurality of sensors, energy storage facility, and controller is provided. The method comprises disposing an active suspension system in a vehicle between a wheel mount and a vehicle body, detecting a wheel event requiring control of the active suspension; and sourcing energy from the energy storage facility and delivering it to the electric motor in response to the wheel event.

Active vehicle suspension system

In a suspension control system, accelerations detected by acceleration sensors are differentiated by a differentiator to calculate acceleration derivative values. Based on these values, a target electrical current calculating section calculates a target electrical current that is supplied to an actuator which controls a damping force of a damper. Before a rolling or pitch angle occurs in the vehicle, the change of the rolling or pitch angle is predicted to control the damping force of the damper, thereby improving the response of rolling angle and pitch angle control to achieve, simultaneously, an accurate posture control and a satisfactory riding comfort. Because the target electrical current calculating section corrects the target electrical current of the actuator based on a damper speed obtained by differentiating a damper displacement, even when a large input is applied to the damper due to an unevenness of the road surface, a proper posture control is performed.

Suspension control system

Integrated control system between active control suspension and four wheel steering for the 1989 CELICA

Toyota Electronic Modulated Suspension (TEMS) System for the 1983 Soarer

An electromagnetic directional control valve for changing over flow paths of fluid comprises a plunger disposed in a case and being capable of moving from a neutral position in one axial direction by a first solenoid and in the other axial direction by a second solenoid to participate in the changeover of the flow paths. First and second stoppers bearing against the plunger are moved together with the plunger respectively in one axial direction and the other axial direction. First and second springs bias the first and second stopper respectively in the direction of abutting against the plunger. The plunger is stopped at the first neutral position held by the first and second springs, at a second position to which the plunger is moved in one axial direction by the first solenoid against the first spring and a third position to which the plunger is moved in the other axial direction by the second solenoid against the second spring.

Electromagnetic directional control valve

An air suspension comprises a shock absorber having a piston rod in which is disposed a control rod for adjusting a damping force, an air spring having a main air chamber and an auxiliary air chamber, a valve body for affording and shutting off communication between both air chambers to adjust the spring constant of the air spring, a support having a rigid member to which the piston rod is fixed and in which the valve body is disposed and connected to a car body and an actuator provided above the support to adjust at the same time the damping force of the shock absorber and the spring constant of the air spring. The actuator is provided with an electric motor, a gear fixed to the motor and a pair of rods arranged parallel to each other and extended toward the rigid member of the support, one rod being coupled with the control rod and the other being coupled with the valve body. The pair of rods are coupled respectively with a pair of tubes supported rotatably by a bracket through pins. A gear is fixed to each tube and at least one of two gears meshes with the gear of the motor.

Yuji Yokoya

Papers

Suspension control system

Integrated control system between active control suspension and four wheel steering for the 1989 CELICA

Toyota Electronic Modulated Suspension (TEMS) System for the 1983 Soarer

Electromagnetic directional control valve

Damping capacity adjusting mechanism for an air suspension