No abstract

Fluid power transmission based on the electro-rheological clutch is taken beyond the concept-proving stage. A typical electro-rheological fluid is characterized over a range of engineering conditions and is found to usefully approximate to a continuum of Bingham plastic form. The clutch is optimized from this standpoint, and the limits of its performance are estimated. The state of the art is discussed alongside an outline of the infrastructure required to achieve maximum potential.

Electro-stress and electron-hydraulic time delay are investigated in shear mode tests on ERF (electro-rheological fluid). These parameters are examined using a concentric, Couette clutch operating over a range of shear rates, volume fraction of solid in the ERF, and temperature. Pointers to system design, associated control strategy, fluid selection and optimal operating conditions are derived from these results.

Experimental measurements of the time response of an electrorheological fluid in a high natural frequency Couette type of rheometer system are reported for both step and variable frequency, DC biased small amplitude sine wave voltage excitation. The effects of both the speed of the rotating element of the rheometer and the magnitude of its voltage relative to the stationary element as well as the fluid temperature level are presented for time, frequency and steady domains. For a given DC voltage level and over the range of tests carried out, the fluid response time improves considerably with both increase in the temperature and speed, whereas the effect on the magnitude of the steady state ER torque value is marginal. Very encouraging results are obtained when the performance of the fluid with regard to the step tests are compared with results of transformed data taken from a larger and more practical clutch system and those acquired from the same fluid but in the flow mode valve arrangement.

A tactile array system, when incorporated in an information system, provides a means of conveying tactile data to the user. Such arrays have many applications including simulators for training purposes and Braille systems for the blind. The use of ER fluids in these systems would provide an inexpensive alternative to the existing technologies because of the simple and flexible designs. An experimental study has been conducted which involves a simple 5×5 array of tactels, each tactel being independently energised in order to configure a variety of shapes. A series of tests are carried out on two different types of ER fluids under a range of electric fields and sensor speeds. The results show that for the given tactel spacing, the programmed shapes are easily detected for all conditions and are directly comparable to similar tests undertaken on a solid shape.