Sensorless temperature estimation and control of Peltier devices

Abstract

Peltier devices, also known as thermoelectric devices (TEDs), are solid state junctions of two dissimilar materials in which heat transfer and electrical conduction are coupled. A current running through a TED causes heat to flow; likewise, the presence of an external temperature gradient will induce an electrical potential across the TED. The former effect is known as the Peltier effect; the latter is known as the Seebeck effect. While TEDs are used primarily as heat pumps, they can also serve as temperature sensors. This thesis presents the design for a controller which uses a TED to simultaneously sense and control the temperature of a shape memory alloy (SMA) wire. The pulse width-modulating driving circuitry in the controller is capable of measuring the undriven voltage across the TED at a rate of 200 Hz between pulses. A low order ARX model is then used to estimate the SMA temperature. The SMA temperature can be controlled using this estimate. This method will enable the production of large arrays of TED-driven SMA tendon actuators, particularly for large DOF robotic systems.