Abstract: [Objective] In this paper a feed forward PID high precision control method is proposed to solve the problem of temperature and humidity oscillation caused by dew point water tank replenishment in the process,which is used to detect formaldehyde and volatile organic compounds(VOCs) released from the furniture in 30 m³ climate chamber.[Method] The feed-forward PID control system and actuator are designed based on the analysis of dew point tank temperature. When dew point tank needs water supply, the system will automatically refill water to the dew point tank, until the dew point tank temperature is reached, minimizing the temperature disturbance of the dew point tank. In this way, the structure of limited open loop and global double closed loop control system is formed, and dynamic and high-precision control can be realized.[Result] The result of this study show that:1) The temperature and dew point temperature control accuracy of 30 m³ climate chamber are within ±0.1℃ and ±1.5% respectively; 2) When the temperature is set at 23.0℃ and the relative humidity is 45.0%, under continuous operating conditions for 3 to 28 days, the deviation under non-large inertia disturbance does not exceed ±0.1℃ and ±2%, and the temperature and humidity oscillation time after each replenishment is less than 1 h; 3) Under winter conditions with a constant temperature of 23.0℃ and a relative humidity of 45.0%, the transition period does not exceed 4 h.[Conclusion] The control method of intelligent feedforward PID can effectively solve the problems of instability and the poor steady state response of the 30 m³ chamber control system. The accuracy and quality of the control system have reached the advanced level in world.

Key words: formaldehyde and VOC detection, chamber, feedforward control