Designing Multiple PID Controllers Based on an FPGA for Controlling the Temperature of TEM-cell Surfaces

A field programmable gate array (FPGA) has been configured to control the temperature average value and spatial uniformity of a TEM-cell. The system is composed of 24 Peltier elements (PE) and 52 temperature sensors (TS) distributed all around the TEM-cell. The FPGA controls each PE independently computing a proportional-integral-derivative (PID) controller with 24 different sets of parameters. The 52 TS are read using 18 Inter-Integrated-Circuit buses wired to a single master controller. This allows running the PID controller for the 24 sub-systems at a maximum frequency of 2 kHz. To compute this, a custom programmable architecture has been designed to carry out calculations with 36-bit signed values with a fixed point. The final design uses around 1600 logic elements (one logic element = one register and one 4-input lookup table), some multipliers, and some memory bits. The temperature precision obtained is around 0.1°C. The component used is an EP2C5T144C8 configured in a hardware description language Verilog with the Quartus software.