Acceleration-level control of the CyberCarpet

The CyberCarpet is an actuated platform that allows unconstrained locomotion of a walking user for VR exploration. The platform has two actuating devices (linear and angular) and the motion control problem is dual to that of nonholonomic wheeled mobile robots. The main control objective is to keep the walker close to the platform center. We first recall global kinematic control schemes developed at the velocity level, i.e., with the linear and angular velocities of the platform as input commands. Then, we use backstepping techniques and the theory of cascaded systems to move the design to control laws at the acceleration level. Acceleration control is more suitable to take into account the limitations imposed to the platform motion by the actuation system and/or the physiological bounds on the human walker. In particular, the availability of platform accelerations allows the analytical computation of the apparent accelerations felt by the user.