Kinematic Design to Improve Ergonomics in Human Machine Interaction

Automation and Robotics Section, Mechanical Engineering Department, European Space Research and Technology Centre, European Space Agency, 2201 AZ Noordwijk ZH, The Netherlands.
IEEE Transactions on Neural Systems and Rehabilitation Engineering (Impact Factor: 3.19). 01/2007; 14(4):456-69. DOI: 10.1109/TNSRE.2006.881565
Source: PubMed


This paper introduces a novel kinematic design paradigm for ergonomic human machine interaction. Goals for optimal design are formulated generically and applied to the mechanical design of an upper-arm exoskeleton. A nine degree-of-freedom (DOF) model of the human arm kinematics is presented and used to develop, test, and optimize the kinematic structure of an human arm interfacing exoskeleton. The resulting device can interact with an unprecedented portion of the natural limb workspace, including motions in the shoulder-girdle, shoulder, elbow, and the wrist. The exoskeleton does not require alignment to the human joint axes, yet is able to actuate each DOF of our redundant limb unambiguously and without reaching into singularities. The device is comfortable to wear and does not create residual forces if misalignments exist. Implemented in a rehabilitation robot, the design features of the exoskeleton could enable longer lasting training sessions, training of fully natural tasks such as activities of daily living and shorter dress-on and dress-off times. Results from inter-subject experiments with a prototype are presented, that verify usability over the entire workspace of the human arm, including shoulder and shoulder girdle.

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    • "This decoupling can reduce the constraints resulting from the misalignment. The idea has been successfully demonstrated for upper limb exoskeletons [11], [12], and one goal of the new exoskeleton is to investigate if those results can be successfully transferred to lower limb exoskeletons with a different limb anatomy, movement patterns and load cases. 3) Position of the Interfaces: The interfaces between the robotic exoskeleton and the human body (usually cuffs) are of special importance because they transfer the loads between the exoskeleton and the human. "
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    ABSTRACT: Designing the underlying mechanical structure of lower limb exoskeletons for assistance and rehabilitation is a demanding task that requires a good understanding of the interaction that takes place between the exoskeleton and the human user wearing it. Often the effects of a given mechanical design on the user are not straightforward or intuitive. One obstacle for research is that existing rehabilitation systems do not offer the flexibility that is necessary to investigate different designs and ideas. In this paper we present a passive experimental lower limb exoskeleton that is specifically built to evaluate exoskeleton design-elements and different characteristics. These are namely a joint misalignment compensation mechanism, a three DOF hip joint design, the lack of mechanical transparency as well as the placement of the interfacing cuffs. The motivation and mechanical design of the system is presented along with the results of pilot trials to validate the system as a suitable experimental platform for our investigations.
    IEEE/RAS-EMBS International Conference on Rehabilitation Robotics (ICORR 2015); 08/2015
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    • "According to [1], the instantaneous screw axis of the elbow joint (which is generally seen as a hinge joint) varies from 2.6 • to 5.7 • in direction and from 1.4 mm to 2 mm in translation during flexion/extension. For this reason, passive joints have to be added between the driving axis of the active mechanical system and the anatomical axis to cancel the residual stresses produced by the misalignment of these two axes [4][11]. B. Design rules The table I show the rules that designers can use to determine the total general mobility of the mechanism (type synthesis) and the number of passive joints they must include into the mechanism to make the whole system become isostatic. "
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    ABSTRACT: This paper addresses the design of instrumented single joint and multi-joints active orthoses for musculoskeletal and neuromuscular disorder exploration and functional reha-bilitation. The use of these multi-contact exoskeletons, operating a selective limb joint mobilization, allows the measurement and the control of physiological parameters (instantaneous helical axis (IHA) motion, joint motion and torque) of each individual anatomical joint. Passive joints have to be added into the kinematic chain of the exoskeleton in order to eliminate residual stresses in limb/orthose interaction due to misalignment between the device principal axis of rotation and the IHA of the anatomical joint. The kinematic design and the control of spatial orthotic mechanisms to obtain an adaptation and a best-fit to the joints kinematics are discussed afterward. Examples of active orthosis design for knee, elbow joint and lower limbs are also given.
    Proceedings of the 2014 IEEE International Conference on Robotics and Biomimetics, Bali, Indonesia; 12/2014
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    • "Moreover, shoulder joint is even more difficult due to its complex anatomy and translation of Glenohumeral joint center (GH-c) during arm motion. Poorly aligned joint axes may induce large reaction forces and moments at the joints [12] and may further cause skin sores and soft tissue damage. Second, the mechanical links must be adjusted to match the lengths of the arm segments. "
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    ABSTRACT: In recent years, the authors have proposed lightweight exoskeleton designs for upper arm rehabilitation using multi-stage cable-driven parallel mechanism. Previously, the authors have demonstrated via experiments that it is possible to apply “assist-as-needed” forces in all directions at the end-effector with such an exoskeleton acting on an anthropomorphic machine arm. A human-exoskeleton interface was also presented to show the feasibility of CAREX on human subjects. The goals of this paper are to 1) further address issues when CAREX is mounted on human subjects, e.g., generation of continuous cable tension trajectories 2) demonstrate the feasibility and effectiveness of CAREX on movement training of healthy human subjects and a stroke patient. In this research, CAREX is rigidly attached to an arm orthosis worn by human subjects. The cable routing points are optimized to achieve a relatively large “tensioned” static workspace. A new cable tension planner based on quadratic programming is used to generate continuous cable tension trajectory for smooth motion. Experiments were carried out on eight healthy subjects. The experimental results show that CAREX can help the subjects move closer to a prescribed circular path using the force fields generated by the exoskeleton. The subjects also adapt to the path shortly after training. CAREX was also evaluated on a stroke patient to test the feasibility of its use on patients with neural impairment. The results show that the patient was able to move closer to a prescribed straight line path with the “assist-as-needed” force field.
    IEEE Transactions on Neural Systems and Rehabilitation Engineering 06/2014; 23(1). DOI:10.1109/TNSRE.2014.2329018 · 3.19 Impact Factor
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