Specifications and applications of force feedback interfaces: virtual reality and gesture and movement assistance

Force-feedback interfaces were invented in the nuclear industry to safely handle radioactive materials at close range within secure, radiation-shielded enclosures. Initially, they were integrated into mechanical telehandlers in which the control interface (called the “master arm”) and the robot (called the “slave arm”) are connected by a system of rods, linkages, and cables. These transmission mechanisms allow the robot to faithfully replicate the operator’s movements, while the operator, in turn, feels the forces applied to the robot. Such devices, which are still used in the nuclear industry, are highly effective but not always ergonomic, since the operator must perform movements similar to those of the slave arm—movements that are sometimes of large amplitude and/or require significant effort. To overcome this difficulty, the master and slave arms were separated and motorized as soon as technical advances made it possible, and each of these subsystems was optimized separately: the master arms to enable natural and ergonomic manipulation, and the slave arms to perform the target tasks. These developments have enabled these systems to find a wide range of applications in teleoperation [S 7 742]. Today, they are used wherever humans cannot intervene directly because the environment is hostile or inaccessible, and where autonomous robots cannot replace them because the tasks and missions to be carried out are too complex and/or require a level of reliability and safety that these robots, given the current state of the art, are still unable to achieve.

The master interfaces for these devices are also very useful in virtual reality, where, to interact with computer-generated synthetic environments from which they are physically excluded, humans must rely on “remotely” controlled avatars. In this context, force-feedback interfaces—referred to here as haptic interfaces—are particularly valuable. They allow users to control the movements of certain objects in the virtual scene in a highly intuitive manner while feeling, just as in the real world, the forces acting on these objects when they come into contact with their environment. The sense of immersion is thereby enhanced, and interactions are more natural and effective than with motion capture systems, for example.

The primary function of force feedback is to allow the operator to feel the forces exerted on a remote robot or an avatar, but it can also be used to generate synthetic forces intended, for example, to prevent the operator from reaching sensitive areas that need to be protected, or to assist the operator’s movements by guiding them along a reference path or helping them carry a heavy load. Naturally, these assistive functions have sparked keen interest that extends far beyond teleoperation and virtual reality, and force-feedback interfaces are also...