by Timmo » Tue Oct 24, 2006 6:46 pm
found this....I need a diagram to get my head around it though:
START
Vibration damping can be achieved by mechanical impedance coupling or the superposition of out-of-phase antivibrations. A passively damped system's response is fixed and, therefore, represents a compromise at all but one, or at most a few, rates of energy input. Adaptive systems slowly adjust, or require manually set damping (impedance) characteristics, to accommodate a broader range of input situations.
Semiactive systems make such damping adjustments automatically, in several tens of a millisecond response times. Passive and semiactive systems are energy absorbing, whereas active systems input energy to a system. Active approaches are complex and energy-demanding processes that restore a system to its desired state or position. In automobiles, the feel of active systems can be closely approximated by semiactive means at much lower cost.
The basic elements of any automotive suspension system (viscoelastic engine mounts, springs, shock absorbers, and tires) are part of a complex vibration and acoustics system. Traditional passive suspension systems are evolving to adaptive, semiactive, and active control systems. Suspension dynamics, for comfort, performance and safety, can be controlled in real time. Active and semiactive control systems are based on inputs of accelerations, steering angle, road conditions, tire deflection, relative positions of wheels and body, traction, etc. Ceramic sensor demand will exceed that for actuators.
High-speed piezoceramic valve actuators were introduced by Toyota (Aichi, Japan) (1983 TEMS, Toyota Electronically Modulated Suspension) to achieve a broad range of damping forces via the semiactive control of shock absorbers. A PZT sensor stack, colinear with a larger actuator stack, provided the system with a control signal that indicated vertical motion. Atsugi Unisia (Japan) introduced a completely active hydraulically pumped system at about the same time. Each suffered from high cost, but the latter in particular suffered from high weight and power consumption with adverse affects on fuel economy.
More recent active approaches involve composite springs, PZT or magnetostrictive motor and suspension mounts, and engine performance controls, such as PZT knock sensors. System simplicity and integration cost will be the prime factors in determining which ceramics-based approaches are accepted. Ceramics will face stiff competition from magnetostrictive actuators and electromechanical, pneumatic or hydraulic systems in actuator applications.
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It also mentions Toyotas 'Active' Suspension....such an amazing system but just too expensive: I would love to go for a blast in a Uzz32 'Active' Soarer one day
Lightweight baby
1991 MX5 Supercharged
