Steady-state and transient models for the electrical response of an electrorheological catch system

The outstanding advantage of an electrorheological (ER) fluid as a mechatronic power transmission medium is the speed of its shear-stress response to the application of an electric field. The costs of this speed of response are the highly capacitive nature of the interface and a high voltage requirement, which together impose a severe demand on the pulsed power supply. An electrical model of the fluid accurate enough for the elucidation of its control and supply is thus a primary requirement if the full potential of the flexible motion concept is to be realised; the switch on/off time constants of the controller limit the precision of digital motion generation capability, and fluid heating from resistive as well as viscous loading requires simulation. Electrical models for the steady-state and transient response of a typical ER fluid to large on and off voltage steps are identified using realistic engineering-scale experimental data from tests on an ER cylindrical/Couette flow system. The results include a study of the variation of interelectrode spacing, shear rate, electrode length and the all-important fluid temperature as well as magnitude of the step field excitation