ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

the previous mechanisms and supply de unloading force, is a linear guiding system
consisting of a carriage plate supported by four linear bearings rolling over 30mm
shafts. L3 is powered by a linear motor with rated delivering capabilities of 6000 N
peak force and 2000 N of holding force.
Fig. 4. The developed IBWSS and a detail of the load transference interface
6. EXPERIMENTAL RESULTS
We designed a preliminary control setup in order to validate the functionality of the
IBWS system, and performed initial experiments on normal subjects to assess the effect
on gait parameters during weight-bearing walking. The experimental subject was of an
84Kg adult male. Treadmill speed was set at 0.8m/s for all experiments. Vertical ground
reaction forces and ischiatic seats reaction forces were estimated from in-shoe pressure
and mats pressure measurements, respectively (Novel dynamic pressure measuring
systems: X-Pedar and X-pliance). The results for walking at different levels of support
are shown in Fig. 5, where data for two strides are plotted; colour lines indicate the
corresponding support level. Top panel shows consistent reductions of ground reaction
forces. Stance phase reduction is appreciated as support level is increased. Shortening of
inter stride period were induced in the subject for higher rates of body support [9]. The
reaction forces at the ischiatic support are shown in bottom panel, the data correspond to
the sum of reaction forces on the individual ischiatic seats. High frequency components
correspond to the response of the force control trying to maintain the reference, which
also correlates with the drive current. The mean value of the ischiatic reaction force
corresponds to the support provided by the system. Dynamics of pelvic motion
represented by the phase plane response of acceleration versus speed along V, AP, and
ML axis is shown in Fig. 8.. Trajectories on the M axis are more convoluted than on
other axes. Regularity on trajectories of V and AP axes is increased as level of support
increases. Trajectories along the AP axis presented higher regularity among different
support levels and all axes, in a lesser way the V axis does. For all cases peak
acceleration values presented low variability. These findings indicate that IBWS system
preserves pelvic kinetics while provides significant load relief.
7. DISCUSSION
A body weight support system with ischiatic support is described. The pelvic socket
design allowed full range of motion of torso, arms and legs. Load transfer was stable
with minimal discomfort. The actuation mechanisms of the load transference interface