The exoskeletons

The current context for exoskeletons remains unique for several reasons.

First of all, exoskeletons are highly visible, high-profile technological objects. Yet, although there are a multitude of research platforms, few of these devices are actually commercially available and used in practice. The media hype surrounding certain specific products tends to obscure the real complexity of current systems, their limited performance, their total lack of versatility (each type of device responding to a specific, highly constrained set of specifications) and therefore the many underlying technological and scientific challenges still to be overcome.

As will be shown in the remainder of this article, the current trend in exoskeleton development is towards simplification of devices, with a reduction in the number of joints and actuators (in favor of passive mechanical elements) and a lightening of structures, and thus an evolution towards more environmentally-friendly coated devices.

This article therefore proposes a taxonomy (built around an analysis of the various mechanical and control characteristics of these systems) that allows us to organize and distinguish this field of exoskeletons more finely.

Based on this technological analysis, a detailed state-of-the-art of existing devices is presented for the four different types of exoskeleton, presenting their respective specifications as well as their current applications and possibilities.

Finally, the challenges and prospects of the field are discussed, addressing the many aspects that still need to be considered to improve these devices: adaptation to the body and control of interaction and physical interfacing, system transparency, sharing of control with the operator and respect for motor intentions (in conjunction with their detection and with a better understanding of the human sensorimotor system), safety management and ease of use. Indeed, although a number of technological hurdles have been overcome in recent years, the revolution in the development and mass adoption of exoskeletons will necessarily involve resolving these complex, multidisciplinary scientific challenges.