Adaptive High Precision Temperature Control of a Thermo-Mechanical Test Bench

Material testing is an essential element in the technological development of airplane turbines. The blades are subject to very high stresses, both thermal and mechanical. To assess material suitability, thermo-mechanical test benches are used where a typical thermo-mechanical load is applied to the test rigs. The sensitivity of the fatigue assessment is very high which requires a very high control precision over a large temperature range and a fast adaptation to different setups. This paper discusses two approaches where the first is a self tuning inverse control loop. The second approach is a data based control method where identification routines are used to dynamically compute the approximated system inverse and use this information to automatically tune the control system for saw-tooth profiles. It is shown that a simple two-zone thermal model describes the behavior of the probe and is then used to derive the inverse model and a control strategy. Finally experimental results of a typical test cycle are presented.