A Study of a Handrim Sensor for a Power-Assisted Wheelchair

The power-assisted wheelchair (PAW) is a hybrid of the conventional manual wheelchair and the electric wheelchair. The PAW is designed to mitigate the physical work of a wheelchair user by detecting human power and using a driving motor to create a supplemental force that corresponds to the detected power. Currently, various types of sensors for PAWs have been commercialized. This includes the use of circular connectors and force sensors, rotation of the driving part and battery together but without a circular connector, and the detection of torsion between a rigid body and a gear. This study proposes a method that uses a noncontact inductive sensor to transmit rotating handrim signals to a fixed controller without rotating. The rotating part uses metal of a specific geometric shape. An inductive sensor (LDC1000, Texas Instruments), which is an inductance-to-digital converter, is positioned in the fixed part to identify the user’s driving intention by detecting handrim movements. We designed the sensor part and manufactured a prototype to test its performance. The test results showed that the proposed method can be used in PAWs because it can output reliable signals according to handrim movements. The proposed sensor method can sense the movements of a handrim accurately without using circular connectors.