Closed-Loop Temperature Control of Cobalt Ferrite Ferrofluids Using Continuous Modes Controllers

摘要

Precise temperature control of a cobalt ferrite ferrofluid (2.5% w/w in heptane) was achieved using continuous mode controllers and a custom-made, variable frequency, magnetic field generator. Proportional-Integral (PI) and Proportional-Integral-Derivative (PID) controllers were implemented using LabVIEW and used to control the amplitude of the magnetic field applied to the ferrofluid. A fluoro-optic thermometer (Luxtron) was used to record temperature. The applied magnetic field had a maximum value of 7 kA/m (100% controller output), and a frequency of 507 kHz. The temperature (process variable) range was 0-100°C (0-100%). When properly tuned, the proportional-integral (PI) controller yielded excellent results, achieving 1.1 percent overshoot (%OS), a settling time (T_s) of 50 s, and a steady-state error of 0.10°C, for a setpoint of 40°C. The implementation of accurate and fast temperature controllers allows for the consideration of transient responses in fields of study in which magnetic nanoparticles are employed as heat sources.