Improved fuzzy control method for temperature in water tank of intelligent viscometer

The accuracy and stability of temperature in water tank of viscometer is one of the key factors of fluid viscosity measurement. An improved fuzzy control (IFC) method with PWM control for water tank temperature is proposed, which combines basic fuzzy control, improved Bang-Bang control with human-simulated intelligent control (HSIC), and is implemented by DSP, When the temperature error e between the desired temperature and actual temperature in the water tank is large, the improved Bang-Bang controller is employed in rapidly reducing the error; to decrease the system overshoot, the basic fuzzy controller is used; to reduce the steady-state error of basic fuzzy controller, the human-simulated intelligent controller is applied. A tuning method for parameters of the improved fuzzy controller is also discussed. The intelligent viscometer with IFC is practically built and tested, and all experimental results show that the improved fuzzy controller has satisfied performances such as slight overshoot, small steady-state error and good robustness etc., and the temperature control in the water tank is stable and accurate. The steady-state error of improved fuzzy controller for water temperature is less than 0.05degC, which is better than the Chinese National Standards for viscosity measurement.