Abstract: The current control strategies of constant air flow rate without external sensors have limited performance. To settle this problem, a control strategy of dynamic constant air flow rate based on load torque observer is proposed. A reduced order Luenberger load torque observer is constructed, which realizes the real time observation of fan’s load torque and air duct’s parameters, further calculating the wind pressure and air flow rate. The air flow rate calculated in real time is closed-loop controlled by PI, constructing the air flow rate-speed-current three-loop control structure. The experimental results indicate that the proposed method has high control precision for air flow rate without external sensors, which gives consideration to low cost and high performance effectively.

Key words: Load torque observer, Constant air flow rate, Three-loop control