Currents drawn under high fields often present practical limitations to electrorheological (ER) fluids usefulness. For heavy-duty applications where large torques have to be transmitted, the power consumption of a ER fluid can be considerable, and for such uses a current density of ~100μ A cm -2 is often taken as a practical upper limit. This investigation was conducted into designing a fluid which has little extraneous conductance and therefore would demand less current. Selected semi-conducting polymers provide effective substrates for ER fluids. Such polymers are soft insoluble powdery materials with densities similar to dispersing agents used in ER formulations. Polyaniline is a semi-conducting polymer and can be used as an effective ER substrate in its emeraldine base form. In order to provide an effective ER fluid which requires less current polyaniline was coated with an insulating polymer. The conditions for coating was established for lauryl and methyl methacrylate. Results from static yield measurements indicate that ER fluids containing coated polyaniline required less current than uncoated polyaniline i.e. 0.5μ A cm -2. The generic type of coating was also found to be important.
Abstract
Active material actuators present a significant challenge to researchers interested in applying them to aerospace structures. Materials such as shape memory alloys, piezo-ceramcs and electrorheological fluids exhibit hysteresis to varying degrees. Not only do they exhibit hysteresis, but in some cases the hysteresis is non-stationary. We present a methodology that allows for design of controllers for the structural system from linear system theory. This is accomplished by compensating, or linearizing, the hysteresis nonlinearity using an adaptive model of hysteresis. Experimental results for adaptive control of shape memory alloy actuators with non-stationary hysteresis are provided.
Induced permittivity increment of electrorheological fluids in an applied electric field in association with chain formation: A Brownian dynamics simulation study
