Custom optoelectronic force sensor based ground reaction force (GRF) measurement system for providing absolute force

We propose an optoelectronic force sensor based insole type ground reaction force (GRF) measurement system, which can be used to measure the absolute GRFs produced by the user. Although force sensitivity resistors (FSR) has been widely used to measure the GRFs, they provide only the relative weight of the user. Accurate measurement of GRFs is essential to control robotic devices, such as lower-limb exoskeleton and prosthesis and to make a diagnosis for gait abnormality. To validate the performance of the developed insole type GRF measurement system, we measured GRFs during level ground walking and compared the results with FSRs. For measured GRFs, the GRF data from our system was identical compared with that from a force plate, but the GRF data from FSRs was saturated due to capacity of FSR (~450N). Our insole type measurement system provided the absolute GRFs in walking.