Thermal Response Simulation for Tuning PID Controllers in a 1016 mm Guarded Hot Plate Apparatus
Robert R. Zarr, William C. Thomas
A mathematical model has been developed and used to simulate the controlled thermal performance of a large guarded hot-plate apparatus. The control system consists primarily of three PID controllers that regulate the output voltage of three programmable power supplies. Three feedback parameters are required for each controller: proportional, integral, and derivative gain. The objectives are to determine an improved set of gains and reduce the time and expense required with traditional tuning methods that entail operating the actual apparatus. The analytical model is based on aggregated thermal capacity representations of the primary components and includes the same control algorithm as used in the hot-plate apparatus. The model, accounting for both thermal characteristic and temperature control, was validated by comparisons with test data. The simulation model was used to derive a set of gain parameters that met the temperature control criteria for testing insulation materials of interest, including certifying NIST thermal insulation Standard Reference Materials. The tuning methodology used with the simulation model is described and results are presented. The ensuing set of performance parameters have been used in the actual apparatus without modification for several years of testing materials over wide ranges of thermal conductivity, thickness, and insulation resistance values.
building technology, guarded hot plate, mathematical simulation, PID, temperature control, thermal response, thermal conductivity