Hybrid Control with Multi-Contact Interactions for 6DOF Haptic Foot Platform on a Cable-Driven Locomotion Interface

The control of haptic devices is a challenging task due to some inherent limitations and disadvantages that must first be taken into account. The difficulties are heightened when considering a locomotion interface where a walker produces large wrenches and where one must simulates the tactile sensation of any virtual object, be it rigid or soft. A Cable-Driven Locomotion Interface (CDLI), embedded as a peripheral in a virtual environment, is thus designed to address some of the aforementioned issues, since the use of cables as a mechanical transmission is known to provide many advantages such as low inertia, high speed, high acceleration and large workspace, among others. A CDLI walker would then navigate in a virtual environment with the aid of two haptic platforms (one for each foot) that can be regarded as two independent parallel robots sharing a common workspace as well as constraints in six degrees of freedom (DOF). The architecture of the CDLI framework has two components: the virtual environment manager and the controller manager. The former contains the definition of the environment in which the user navigates, as expressed by a graphic rendering engine and a communication interface. The second component computes and controls the wrenches from two physical models to accurately simulate soft and rigid virtual objects, thereby allowing haptic simulation of virtual objects using hybrid admittance/impedance with multi-contact interactions.