Implementation of fuzzy controller for measuring instantaneous arterial blood pressures via tissue control method

A fuzzy controller to implement tissue control method (TCM) proposed by Lin et al. (in physiol Meas, 2006) to measure the instantaneous arterial blood pressure is presented. The TCM adopts a piezo-actuator to move the pressure transducer up and down to maintain the mean blood pressure measured on the skin by tracking the variation in the blood pressure. Since the operation of the piezo-actuator exhibits hysteresis behaviour in the actuator movement, the controller should have the ability to track the blood pressure variation as well as compensate for the hysteretic movement. A Takagi-Sugeno fuzzy model is adopted to represent the Bouc-Wen model in describing the hysteresis with parameters identified from the dynamic responses of the actuator. On the basis of the model, a stable fuzzy observer is developed to linearise the movement of the piezo-actuator, and a PI controller is designed to track the variation in blood pressure. The designed fuzzy controller has successfully tracked various command signals during software and hardware tests. The fuzzy controller is located in an instrument that measures the instantaneous blood pressure. The experimental results show that the proposed fuzzy controller is feasible and satisfactory for controlling the piezo-actuator.