Modeling of an ER fluid's time delay for servo systems

A particle type ER (Electro-Rheological) fluid damper in which viscosity was controlled for fast and precise positioning control have been developed in a previous study. However, for improvement of control performance or new control demands of mechatronics devices using particle type ER fluids, it will be needed to further investigate a response time of the fluids. It is commonly said around 5-milliseconds, but, the formula structure of that delay has not been clear. This study aims to develop a functional damper (attenuators), that can control its viscous characteristics in real time using ER fluids as its working fluid. ER dampers in this case are useful to accomplish high precision positioning not to prevent high speed movement of the motor. To realize the functional damper that can be manipulated according to situations or tasks, the modeling and control of ER fluids are necessary. This paper investigates time delay affects of ER fluids and makes an in-depth dynamic model of the fluid by utilizing simulation and experiment. The mathematical model has a dead-time and first ordered delays of the fluid and the high voltage amplifier for the fluid.