A robotic platform for lower limb optical motion tracking in open space

Characterization of gait is largely used for research on locomotion or for clinical improvement and follow up. There exists two main technologies for measurement of the kinematics of walking: IMU systems and optical tracking. Inertial measurement units are getting more and more popular because of their integrability, cost and lack of spatial limitations. Despite these advantages, optical motion tracking solutions offer a higher precision which is for various applications such as kinetics analysis. In that sense, the present study proposes a solution for the extension of one lower limbs’ optical measurement system toward open space applications. The tracking solution has the specificity of using only one “camera” placed behind the subject. Thus, by fastening the “camera” to a robotic vehicle, the markers on the subject’s body can be kept in the measuring range while the subjects is free from space limitations. The wheeled robotic platform can manage smooth motions while sustaining a precise pursuit of the measured subject. Investigations will be made to compare the mobile with the static measurement on treadmill

Evaluation of an active optical system for lower limb motion tracking

Observation of lower limb kinematics is essential for the characterization of gait and related activities disorders. Robust, flexible and easy to use measurement systems are precious for patients’ follow-up in different medical domains. This study aims to characterize a lower limb optical tracking system based on one detector and seven active markers. Post-processing, which includes skeleton reconstruction and joints’ angular position calculation, is integrated as part of the data acquisition approach. Evaluation of the repeatability of measurements is done through intrasubject gait analysis under repeated runs in identical conditions. The system RMS error is assessed by looking at the dispersion of the calculated distances between the estimated articulations and the markers attached to the body segments. Positional and angular precisions obtained are smaller than 6mm and 2° respectively. Experimental data acquisition is recorded at the average rate of 80Hz. This tool perfectly fits specifications for medical applications. Moreover it presents diverse practical advantages such as its ease of use and its compactness

Mechanisms for actuated assistive hip orthoses

Mobility is often a central problem for people having muscle weaknesses. The need for new devices to assist walking and walk related activities is therefore growing. Lower limb actuated orthoses have already proven their positive impact with paraplegic patients and are potentially promising for assisting people with weak muscles. However, the transfer from the existing systems of mobilization towards assistance implies several technical challenges as the seamless integration and the reduction of power consumption. In this paper two assistive orthoses which use different types of actuation mechanisms are presented and discussed. The first one is based on a ball screw and an excavator-like mechanism while the second one is based on a double differential actuation. Their technical capabilities are compared and contextualized for diverse activities. Objective characteristics such as the range of motion of the devices, the transparency, the maximal torque that they can provide or the RMS torque during cyclic trajectories are compared to point out which device is better adapted for specific situations