Model-Free Adaptive Temperature Control for a Dual-Channel Water Circulation Bioreactor

The single-heat-exchanger dual-channel water circulation structure is a critical process configuration in laboratory-scale bioreactors. However, frequent switching between heating and cooling modes and the difficulty of establishing an accurate mechanistic model make precise temperature regulation challenging. To address this issue, a model-free adaptive temperature control scheme based on a second-order universal model is proposed, together with a real-time implementation algorithm. Separate controllers are designed for the heating and cooling processes to ensure accurate regulation under different operating conditions. Pulse-width modulation is employed to achieve equivalent continuous actuation of switching-type actuators, and a temperature dead-zone mechanism is introduced to suppress excessive actuator switching. For practical implementation, controller parameters are initialized offline using particle swarm optimization based on experimental data. Experimental results demonstrate that the proposed method satisfies the ±0.1 °C process requirement while achieving small steady-state fluctuations, low overshoot, and short settling time, thereby verifying its effectiveness for bioreactor temperature regulation under mode-switching conditions.