Center of Gravity Compensation for Dynamically-Balanced Two-Wheeled Wheelchair System

概要

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Two-wheeled systems have many advantages compared to statically stable systems. This paper describes a control strategy of dynamically-balanced two-wheeled wheelchair system that does not have any front casters. In this system, rider can sit the seat and control the motion of the system by adjusting CoG of his/her body. Unlike other commercial two-wheeled systems, CoG position of the upper body is mainly determined by the position of the user. Thus, there is a possibility that CoG position may not overlap with the wheel axis. In that case, sensor information cannot be used to measure the exact position of the CoG. This paper shows an estimation of method of the unknown CoG position for Two-Wheeled Dynamically-Balanced Wheelchair (TWDBW) is considered. Gravity torque observer with a compliance control is utilized to realize stable compensation according to the variable CoG position. Backstepping based nonlinear control design is applied to regulate and track the CoG motion of the upper body in the TWDBW. The validity of proposed method is verified by simulation and experimental results.