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

PHASE PLANE PORTRAITS OF PELVIC MOVEMENT AS A TOOL
FOR DESIGNING ROBOTIC SYSTEMS WITH PELVIC SUPPORT FOR
GAIT REHABILITATION
A. Salguero 1 , G. Yamhure 2 , M. Manrique 3 , C. Cotrino 4 , L. Jimenez 5 , and A.
Camacho. 6
1. ABSTRACT The current development of robot assisted gait rehabilitation provides multiplicity of
configurations and actuation methods, with a prevailing use of pelvis and torso harnesses for body weight
support. This type of support only allows partial unloading of limb joints and additionally restricts the
movement to the pelvis and upper body. We explored a more anatomical and physiological approach to
body support for assisting gait training by transferring body loads to an external support directly from the
pelvis. We used the phase portraits of linear velocities and accelerations of the pelvis and applied the
inverted pendulum model of locomotion to estimate, at the body center of mass, power profiles of gait
which were used to define the required response of the actuators along vertical, anterior-posterior and
medial-lateral axes. We developed an ischiatic body weight support system (IBWSS) that in preliminary
studies showed very stable pelvic support and natural gait training patterns during walking and jogging on
a treadmill.
2. INTRODUCTION
The evolution of the field of robot assisted gait rehabilitation gives rise to a diversity
design configurations and actuation methods [1]. However, there is a pervading use of
pelvis and torso harnesses for body weight support [2]. This type of support has
important drawbacks: while knee and ankle joints are unloaded, the hip joint is not,
because of the traction exerted by the harness on the proximal thigh. A second
drawback relates to the movement restrictions this support imposes to the pelvis and
upper body [2]. To take a more anatomical and physiological approach to assist gait
training; we explored the biomechanics of transferring body loads to an external support
directly from the pelvis. As a global description of gait dynamics we used the phase
portraits of linear velocities and accelerations of the pelvis [3], [4]. Based on this
description, we applied the inverted pendulum model of locomotion to estimate, at the
body center of mass, normalized curves of mechanical power, which were used to
define the power limits of the actuators and the controller required response at vertical,
anterior-posterior and medial-lateral axes. As result, we developed a load transfer
interface conformed by a socket that provides tight grip and support of the pelvis, a
Cartesian robot, and passive yaw and roll joints linking the socket to the robot.
Preliminary studies show that the developed system provides a very stable pelvic
support during walking and jogging on a treadmill. The design configuration and
actuation method generate natural gait training patterns.
3. PHASE PLANE PORTRAITS OF PELVIC MOVEMENT
In this section we introduce the dynamic representation of pelvic movement based on
phase plane portraits of acceleration versus velocity of linear translations along the
vertical (V), antero-posterior (AP) and medial-lateral (ML) axes. Linear accelerations,
1 Professor, Department of Electronics, Pontificia Universidad Javeriana. Calle 40 No. 5.50, Bogotá, Colombia.
2 Professor, Department of Electronics, Pontificia Universidad Javeriana. Calle 40 No. 5.50, Bogotá, Colombia.
3 Professor, Department of Industrial Eng, Pontificia Universidad Javeriana. Calle 40 No. 5.50, Bogotá, Colombia.
4 Professor, Department of Electronics, Pontificia Universidad Javeriana. Calle 40 No. 5.50, Bogotá, Colombia.
5 Graduate Student, Department of Electronics, Pontificia Universidad Javeriana., Bogotá, Colombia.
6 Graduate Student, Department of Electronics, Pontificia Universidad Javeriana., Bogotá, Colombia.