Force sensorless control of power-assisted wheelchair based on motion coordinate transformation

• A force sensorless power-assisted control of wheelchair is presents in this paper.
• The motion coordinate transformation method is applied to inherent dynamic-coupling.
• The force/torque observer realizes the force sensorless power-assisted control.
• The power-assisted control is validated by an assistant performance index (API).

Wheelchairs used by disabled people or caregivers are typical human-in-the-loop systems, of which the power-assisted control in accordance to a human’s perception is essential. This paper presents a force sensorless control based on a force/torque observer with a motion coordinate transformation for power-assisted wheelchairs. The output linear movement and angular velocity motions of a power wheelchair can be controlled independently by inherent coupling dual-driving-wheels with this transformation. A force observer design without numerical differentiation, which is utilized to indirectly measure the human’s pushing force, is proposed for realizing the force sensorless power-assisted control. An assistant performance index is adopted to evaluate the validity of the power-assisted control according to a specified power-assisted gain. Experimental results show that the proposed method can effectively estimate the human force exerted on the wheelchair for achieving power-assisted control.