Evaluation of a force platform free gait analysis

Abstract

Using multiple cameras such as motion capture systems with force platforms is a classical and popular method for gait analysis. Calculating a driving force of each joint by solving equation of motion on each body segment is common sense. The ground reaction force acting on the force platform is the requirement for this calculation. However, it is difficult to measure natural walking, because the subjects have to adjust the step length to place on the force platform. In addition, for the measuring of multiple steps, it requires large space. This study proposes two rigid body linked segment models to calculate the driving force of each joint and ground reaction force without force platform. For this solution, the authors solved the equation of the motion from the terminal segment toward the stance side of the foot. In order to validate the accuracy of the two different models, the authors compared their kinematic parameters, such as the joint reaction forces with those of classic model’s on the lower limbs. The results showed that two proposed models could be estimated the ground reaction force and the joint force with high accuracy. In addition, using the center of pressure from force platform could also estimate the joint torque with high accuracy. These results suggest that we can estimate the joint force, ground reaction force and joint torque with high accuracy, if provided by the center of pressure.