Extended temperature range piezo actuator system with very large movement

The Servocell planar bimorph actuator employs a very simple novel construction which provides a very large movement (up to 3mm) in a compact profile. It provides solid state actuation for high volume, cost sensitive applications e.g. valves, locks and circuit breakers. Thermal variations in the piezoelectric properties usually result in a compromise in performance, particularly at low temperature. This paper presents new data on the effects of thermal variations in piezoelectric properties on actuator performance. These data are used to devise a control regime which takes advantage of thermal variations in piezo activity to provide a wide operating window across the temperature range -40 to +125°C. It is shown how the stroke of the actuator can actually be increased at lower temperatures. The system is very simple and can thus be implemented using a very low cost microcontroller. The use of the system is illustrated by real life applications in optical switching, valves, locks, and trip mechanisms.