A sensor-less control method for locally heating and cooling Shape Memory Alloy (SMA) actuators using an array of thermoelectric devices (TED) for both temperature measurement and actuation is presented in this paper. Each SMA wire is divided into many segments whose thermal state is controlled independently and selectively for generating a desired displacement of the SMA wire. In lieu of dedicated temperature sensors, each TED used to heat and cool the SMA wires can also be used to monitor the local temperature difference across each device via the Seebeck effect. A pulse width-modulated control system is implemented to drive the thermoelectric device and sample the Seebeck voltage of each TED between pulses. Least-squares system identification is employed to fit an auto-regressive/exogenous input model to the measured temperature of the SMA wires using the Seebeck voltage and the ambient temperature as inputs. A feedback controller is presented which, using this model, is able to control the temperature of the shape memory alloy wires to within 3 °C over a target temperature range between 30 °C and 80 °C.

Volume Subject Area:
Dynamic Systems and Technology
Topics:
Actuators, Shape memory alloys, Thermoelectric devices, Temperature, Wire, Control equipment, Control systems, Displacement, Feedback, Heat, Heating and cooling, Sensors, Temperature measurement, Temperature sensors, Thermoelectricity
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