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Engineers from Budapest University of Technology and brake supplier Knorr-Bremse have developed a magnetic shock absorber.

The damping force is created electromagnetically, not hydraulically. Coupled to electronic control, it provides an active or semi-active suspension damper. The unit can also act as a generator, feeding current back into the vehicle’s electrical system.

Electronically controlled suspension systems are all fundamentally the same: a piston moving through a fluid-filled cylinder.

The new design replaces the piston with a permanent magnet. Stator windings surround the casing. Switching the voltage in the windings achieves different levels of damping for any given “piston” velocity.

The damper was modelled in Matlab and Maple. Magnetic fields were calculated with FEA tools. Key performance variables are casing length and diameter and the magnetic properties of the piston, stator and casing.

Researchers have rig-tested a prototype, validating the simulation model. They have also completed the control logic model.

The design has similar performance to conventional dampers of a similar size, developing several kilonewtons of force at a piston speed of 0.5m/s – typical of the operation of a passenger car suspension.

Active suspension control benefits ABS and ESC strategies because all systems can be networked, providing optimised responses. Suppliers are also developing electrically actuated brake systems, which link well with electronic dampers as part of a corner module.

Hybrids and better energy management makes such systems attractive to OEMs.