A German company has developed a range of electrically adjustable dampers with reaction times measured in milliseconds. Bansbach’s dampers are based on electrorheological fluids (ERFs) whose viscosity changes when they are exposed to electrical fields. The reversible effect occurs within a few milliseconds and, in a strong enough field, the fluid can become solid.

Bansbach’s EasyERF dampers (above) combine smart PID control with cylinders containing ERFs to provide instantaneous, continuously adjustable control of dynamic damping. The damping can be varied by applying signals including 0–4V analogue, PWM or 24V DC supplies. The dampers can deliver forces from 100–2,500N through strokes from 25–125mm, with positioning accurate to within 0.1mm.

Bansbach originally developed the technology for automotive suspension systems but it is now offering the technology for industrial applications such as machine suspensions, precision actuators and self-adaptive, end-of-stroke damping elements.

The easyERF system (above) consists of a piston with an annular gap between the housing and piston. Two chambers are filled with a silicon-based electrorheological fluid. With no electrical field applied, the fluid flows through an annular valve, as in a standard damper. But when an electrical field is applied, the viscosity of the fluid increases, choking the valve and increasing the damper resistance. Raising the electrical field to its maximum, solidifies the ERF, stopping any movement.

The “smart” PID system adds an amplifier and controller to the damper. In its basic, open-loop form, the controller is adjusted manually to modify the damping properties. For autonomous closed-loop systems, sensors can be added to measure variables such as acceleration, displacement and weight.

The technology is said to be energy efficient, with a power consumption of 2–20W. It is silent and has no moving parts to maintain. There is a wide span between soft and hard damping characteristics, and the PID controller needs only a few milliseconds to increase the damping force, allowing processes to be controlled at high frequencies.

The easyERF dampers are available in the UK from Albert Jagger.