Connecting a Human Limb to an Exoskeleton

Abstract

When developing robotic exoskeletons, the design of physical connections between the device and the human limb it is connected to is a crucial problem. Indeed, using an embedment at each connection point leads to uncontrollable forces at the interaction port, induced by hyperstaticity. In practice, these forces may be large because in general the human limb kinematics and the exoskeleton kinematics differ. To cope with hyperstaticity, literature suggests the addition of passive mechanisms inside the mechanism loops. However, empirical solutions proposed so far lack proper analysis and generality. In this paper, we study the general problem of connecting two similar kinematic chains through multiple passive mechanisms. We derive a constructive method that allows the determination of all the possible distributions of freed Degrees of Freedom (DoFs) across the different fixation mechanisms. It also provides formal proofs of global isostaticity. Practical usefulness is illustrated through two examples with conclusive experimental results: a preliminary study made on a manikin with an arm exoskeleton controlling the movement (passive mode) and a larger campaign on ten healthy subjects performing pointing tasks with a transparent robot (active mode).

Proof of Concept for Robot-Aided Upper Limb Rehabilitation Using Disturbance Observers

“…This problem is addressed in several studies. For instance, Jarrasse and Morel provided formal proofs for minimizing hyperstaticity while connecting two mechanisms with different kinematic chains [23]. Ergin and Patoglu proposed and implemented a novel joint design with self-aligning capabilities [24].…”

Bounded Control of an Actuated Lower-Limb Exoskeleton

“…In the second scenario, two simulations that show the wearer, providing a percentage of the human torque used in resisting the orthosis control ability to track the desired angular position and velocity trajectories are presented (see Figures 6,7,8 and 9) for the first simulation and (see Figures 10, 11, 12, and 13) for the second simulation. In both cases, the human torque ℎ ̸ = 0, and it is a percentage of the estimated torque given by ℎ =̂, where = 0.1 and 0.2.…”

“…However, the conceptual design with regard to performance-augmenting applications is always based on maintaining the human-exoskeleton kinematic compatibility [6]. This was addressed in [7]; nevertheless, for the purpose of simplicity, in this work, human-exoskeleton misalignment is not considered, and the human-exoskeleton joint axes are assumed to align. In addition, the development of active exoskeletons determines its future and some eventual activities associated with the rehabilitation systems in conjunction with expanding its working capabilities with humans [8].…”

Self-adjustment mechanisms and their application for orthosis design

“…This paper extends the results of previous research [19] by presenting a more complete model of the horizontal self-adjustment movement together with the analysis of the vertical self-adjustment movement. In contrast to other designs, employed more particularly in active orthoses, where additional DOFs remain free all throughout the joint movements [20][21][22][23][24][25], we focus in this work on passive orthoses. The extra DOFs are blocked after a short period of self-adjustment, after which the orthosis can work normally to protect the anatomical joint.…”