Fuzzy based Gains Tuning of PD controller for joint position control of AIT Leg Exoskeleton-I (ALEX-I)

This paper is focused on designing of fuzzy based gains tuning of proportional-derivative (FTPD) controller for joints positions control of the Asian Institute of Technology´s leg exoskeleton-I (ALEX-I). The main objective of this research is to obtain the desired gait motion of the whole system. The gait data from simulation is used as the input (set point) of ALEX-I, this data is simulated based on body CM balancing criteria. Fuzzy logic controller applies five membership functions of error and rate of error, four KP and three KD singletons output gains are adjusted according with the defined fuzzy rules. The COGS defuzzification output is sent to ARM7 controllers which control all the system joints. The performance of FTPD controller is then compared with the conventional PD controller. The results show superior performance of FTPD in smaller position error, less percentage of power consumption and less oscillation of gait motion on ALEX-I.