POWER ASSIST WHEELCHAIR, POWER ASSIST UNIT FOR WHEELCHAIR, CONTROL DEVICE FOR POWER ASSIST WHEELCHAIR, CONTROL METHOD FOR POWER ASSIST WHEELCHAIR, AND PROGRAM

A power assist wheelchair includes a wheel, an electric motor that drives the wheel, an encoder that detects rotation of the electric motor, and a control device that controls the electric motor. The control device includes a total torque value calculator that calculates a total torque value based upon only a detection signal of the encoder, an assist torque value calculator that calculates an assist torque value based upon an output current of the electric motor, a manual torque value calculator that calculates a manual torque value based upon a difference obtained by subtracting the assist torque value from the total torque value, and a target current determiner that determines a target current of the electric motor based upon the manual torque value.