MODELING AND CONTROL OF HUMAN AND WHEELED ROBOTIC WALKER COUPLED DYNAMICS

Abstract

The control of assistive robotic walkers are usually designed without considering the coupled dynamics of the user and the walker. This paper proposes a coupled dynamic modeling for human walking with a wheeled robotic walker and then control of this model. The 2D linear inverted pendulum mode (LIPM) is used to model human walking. The wheeled robotic walker is modeled as a simple wheeled subsystem moving on an even ground. To simulate the human arm, a parallel linear spring and damper set is then used to indicate the interaction forces. An optimal fixed final-state controller is used to control the walking model and to keep it balanced. To check whether the LIPM model walking is balanced, the zero-moment point position is calculated and checked to be in the support polygon. The results are validated with the experimental data of human walking along with a wheeled walker for three healthy subjects. The relative positions of center of mass, the absolute positions of the human and the walker, and the velocities are considered for comparison and discussion. The results for each subject is compared with the experiments through L2 norm of the error between human and walker positions in simulation and experiments. The proposed model can be utilized in developing controllers for robotic walkers that consider the user's dynamics.