Classification of Standing and Walking States Using Ground Reaction Forces

Abstract

The operation of wearable robots, such as gait rehabilitation robots, requires real-time classification of the standing or walking state of the wearer. This report explains a technique that measures the ground reaction force (GRF) using an insole device equipped with force sensing resistors, and detects whether the insole wearer is standing or walking based on the measured results. The technique developed in the present study uses the waveform length that represents the sum of the changes in the center of pressure within an arbitrary time window as the determining factor, and applies this factor to a conventional threshold method and an artificial neural network (ANN) model for classification of the standing and walking states. The results showed that applying the newly developed technique could significantly reduce classification errors due to shuffling movements of the patient, typically noticed in the conventional threshold method using GRF, i.e., real-time classification of the standing and walking states is possible in the ANN model. The insole device used in the present study can be applied not only to gait analysis systems used in wearable robot operations, but also as a device for remotely monitoring the activities of daily living of the wearer.

Ground-Reaction-Force-Based Gait Analysis and Its Application to Gait Disorder Assessment: New Indices for Quantifying Walking Behavior

“…The sensor locations were selected according to our previous study [ 31 ]. Details regarding the insole device are presented in Appendix A of [ 34 ].…”

“…The GRF data were used to calculate COPx, in accordance with Equation (7). In this equation, represents the position of the i th pressure sensor, which is defined by the wearer’s height [ 34 ]. Moreover, to assess the COPx value as a ratio relative to the outermost sensor of the foot, it was calculated by dividing the relative position of COPx, i.e., , by the position of the pressure sensor on the fifth metatarsal bone.…”

Capacitive-Type Pressure Sensor for Classification of the Activities of Daily Living

“…Figure 2 shows the insole system used in the present study, which consisted of (1) pressure sensors; (2) an insole where the pressure sensors were attached; (3) PCB for GRF data processing. This insole system was the same system that the authors used in their previous studies on fall detection and gait analysis [24,27]. Figure 2a,b show the insole connected to the data processing PCB and capacitive-type pressure sensors; placement of the insoles inside the shoes; and an illustration of the GRF data processing.…”

“…Center of pressure (COP), x-axis These five motions were simultaneously measured using a motion capture system (Osprey Motion Analysis Corporation, Santa Rosa, CA, USA). To compare the GRF data acquired with the insole system and the motion data measured using the motion capture system, a third device was used to generate synchronization signals to synchronize the two sets of data [24]. The synchronized GRF data were used to classify the motions of the participants, and the results were compared with the motion detection results obtained with the motion capture system to evaluate whether the five motions from the TUG test could be classified with the insole system.…”

“…In a previous study by the authors [24], FSRs were used to measure the ground reaction force, and ADLs were classified into standing and walking. However, for reliable gait rehabilitation, it is necessary to classify the ADLs states in more detail.…”