Clinical potential and design of programmable mechanical impedances for orthotic applications

Abstract

A person with a moderate or severe motor disability will often use specialised or adapted tools to assist their interaction with a general environment. Such tools can assist with the movement of a person's arms so as to facilitate manipulation, can provide postural supports, or interface to computers, wheelchairs or similar assistive technologies. Designing such devices with programmable stiffness and damping may offer a better means for the person to have effective control of their surroundings.This paper addresses the possibility of designing some assistive technologies using impedance elements that can adapt to the user and the circumstances. Two impedance elements are proposed. The first, based on magnetic particle brakes, allows control of the damping coefficient in a passive element. The second, based on detuning the P-D controller in a servo-motor mechanism, allows control of both stiffness and damping. Such a mechanical impedance can be modulated to the conditions imposed by the task in hand. The limits of linear theory are explored and possible uses of programmable impedance elements are proposed.

Biomechanical Modelling of the Upper Limb for Robotics-Based Orthotic Tremor Suppression

“…One of the specific and important common aspects to the field of orthotic rehabilitation is the intrinsic interaction between human and robot. This issue, in its simplest manifestation, implies a mechanical interaction between the robot and the human, most often solved through impedance control approaches (Harwin et al 1998). The basic principles and considerations regarding impedance control were addressed by Hogan (1985) in an excellent work.…”

Modelling the Air-Gap Field Strength of Electric Machines to Improve Performance of Haptic Mechanisms

“…Several authors have tried to divert this energy into programmable or auxiliary damping. For example Weir et al used both passive damping and controlled damping implemented in analogue electronics [12], Harwin et al used magnetic particle brakes [4] whereas Gosline and Hayward [3] and Mohand-Ousaid et al [6] used eddy current braking. Although the haptic fidelity and stability are improved, this is at the expense of complexity.…”

Analysis of the Human Interaction with a Wearable Lower‐Limb Exoskeleton

“…From a robotics perspective, exoskeletons are mechatronic devices in which their segments and joints have a correspondence and are coupled with those of the human body (Rocon 2005). Robotic exoskeletons are used in different rehabilitation applications that can be classified under several categories (Harwin et al 2002). For instance, they can serve as posture-support mechanisms.…”