Specifications and applications of force feedback interfaces: general introduction and teleoperation

There are environments in which humans cannot intervene directly because the environment is hostile, remote, or inaccessible on a human scale. To work under these conditions, robots must be used. However, despite continuous advances in mechatronics, control systems, and artificial intelligence, their capabilities are still insufficient to autonomously carry out complex missions—where the unexpected plays a major role—with a satisfactory level of reliability and safety. This is particularly true in environments where errors can have dramatic consequences (e.g., nuclear power, surgery) or a major financial impact, given the costs and strategic importance of the structures where the robots operate (e.g., space, deep offshore). Under these conditions, it is preferable to keep humans in the loop so that, by remotely controlling these robots, they retain control and the power to make decisions as a last resort. This is referred to as teleoperation. In practice, relatively simple control interfaces (such as joysticks, motion capture systems, or even voice interfaces) can be used to maneuver such robots into position—for example, to move a camera—but they are no longer sufficient when it comes to regulating the forces involved in interacting with the environment. In this case, force-feedback interfaces called “master arms” must be used; the robots they control are referred to as “slaves.”

The same challenge arises in virtual reality. Thus, to interact with computer-generated virtual environments from which they are physically excluded, humans must rely on “remotely” controlled avatars, which requires the use of specialized peripherals. 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 while feeling—just as in the real world—the forces acting on these objects when they come into contact with their environment. This enhances the sense of immersion, and interactions are more natural and effective than with motion capture systems, for example.

In both cases, the primary role of force feedback is to allow the operator to feel, as realistically as possible, the forces applied to the slave robot or 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 applications, and force-feedback interfaces are also finding applications in the field of gesture or motion assistance, whether at work or at home....