Effect of added inertia on the pelvis on gait

Moog Robotics, Nieuw-Vennep, The Netherlands.
IEEE International Conference on Rehabilitation Robotics : [proceedings] 06/2011; 2011:5975493. DOI: 10.1109/ICORR.2011.5975493
Source: PubMed


Gait-training robots must display a low inertia in order to allow normal-looking walking. We studied the effect of inertia added to the pelvis during walking. We attached subjects to a mechanism that displays inertia to the pelvis in the anterior/posterior (AP) direction and the lateral direction independently. During walking we measured EMG, metabolic rate and kinematics of nine subjects. We found that inertias up to 5.3 kg added in lateral direction had no significant effect on gait. We found that 4.3 kg added in the AP direction had a significant but not relevant effect on the range of motion (RoM) of pelvis AP displacement and acceleration, and on hip flexion. 10.3 kg caused a significant and relevant difference in pelvis acceleration RoM. 6 kg is estimated as the maximum inertia that gait-training robots can add to the pelvis, without affecting the gait.

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    • "However, the presence of a robot could change these motions even if the user can still apply these strategies to their motion, even if only partially. The effect of the change in physical characteristics was tested by Arellano et al. [4] and Meuleman et al. [5]. The results of these studies can help us consider the effect of the mass and inertia of the robot. "
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    IEEE International Conference on Robotics and Biomimetics; 12/2014
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    • "However, some of these devices affect human dynamics in an undesirable manner because of their intrinsic dynamics due to large moving inertia. In [16], it was reported that a robot could affect subjects' gait significantly if it adds more than 6 kg mass on the human pelvis. Similar inertia effects on stability of leg kinematics were reported in [17]. "
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    ABSTRACT: An active Tethered Pelvic Assist Device (A-TPAD) has been presented in this paper. TPAD is a cable robot for studying force adaptation in human walking by applying external forces and moments on the human pelvis. A two stage control strategy was implemented to apply the desired force-moment profile. The controller includes (i) a quadratic programming based optimization scheme, (ii) a real-time human motion monitoring system and (iii) a PID feedback loop to plan and implement the required cable tensions. The control strategy was validated first by testing it on a dummy pelvis setup. A pilot experiment was then conducted with a human walking on a treadmill with A-TPAD. The goal was to apply a vertical downward force vector equivalent to 10% of subject's body weight (BW) at the pelvis. Results showed that the applied vertical force was acting downwards over the full gait cycle and was between 8-13% of the BW. Other force-moment components were maintained within a specified range during the experiment. Increased foot pressure was reported in the presence of vertical force. In summary, A-TPAD provides the capability of applying and controlling a desired force-moment profile on the human pelvis over a gait cycle.
    Proceedings - IEEE International Conference on Robotics and Automation 05/2014; DOI:10.1109/ICRA.2014.6906933
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    ABSTRACT: This paper introduces GaitEnable, a robotic gait trainer composed of an actuated omnidirectional mobile base, a passive body weight support (BWS) system, and a reactive control system that can initiate, sustain, stabilize or perturb a user's gait. The device is designed to provide minimal constraints to the user's natural motion, and its actuated mobile base can move cooperatively with the user in any direction. Data from preliminary experiments performed by a healthy male subject confirm that the reactive control system can compensate for the device's inertial effects and that the device's omnidirectional mobile base reduces pelvis and torso motion constraints. The results also demonstrate that GaitEnable can easily be programmed to simulate different types of behaviours or motion constraints.
    Mechatronics and Automation (ICMA), 2012 International Conference on; 01/2012
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