A Portable Knee Ankle Foot Robot for Gait Rehabilitation
Yu Haoyong, Huang Sunan, and Chen Gong
A Novel Compact Compliant Actuator
Introduction
This project aims to develop and evaluate an
intelligent compact and modular powered kneeankle-foot orthosis for gait rehabilitation at
outpatient and home settings. Stroke is among the
top 10 causes of hospitalization in Singapore and a
major cause of adult gait disability. Due to the
brain plasticity, physical therapy is the main
treatment for patients to regain motor function.
However, physical therapy is labor intensive,
limiting the availability and compliance, especially
for patients at outpatient centers. Robots can help
relieve the therapies from the strenuous work and
improve the functional outcome. However, current
rehabilitation robots are bulky, expensive and only
available at large institutions. We aim to develop
inexpensive, light weight and wearable devices for
this group of patients.
System Concept of the Robot
A novel compliant force control actuator has been
developed for the robot as shown in figure 2. Using
one soft spring at low speed output end and one
stiff spring at high speed end, the actuator has high
fidelity force control, low output impedance, and
high bandwidth. Figure 3 shows the force tracking
performance of the actuator.
Encoder
Torsional spring
DC Motor
Connection joint
Motor encoder
Compressive spring
Force output pin
Ball screw shaft
Figure 2. The novel series elastic actuator
Figure 1 shows the mechanical system design. The
modular system consists of an ankle foot module and
a knee module. The knee module can be removed
from the system through the quick release joint when
the system is used an ankle foot robot. When the user
only needs knee assistance, the actuator for the ankle
module can be easily removed from the system. Each
module is driven with the same compact compliant
force controllable actuator as shown in Figure 2.
Figure 3. Force tracking Performance
At 10 Hz
Knee module
strap
Knee joint
sensor
Knee module
actuator
Release
joint
Ankle module
strap
Ankle module
actuator
Ankle joint
sensor
Foot plate and
pressure sensor
Rotary arm
output
Figure 1. System Concept
Conclusion and Future Plan
Experimental results for
the actuator has proved
its
excellent
force
control performance. A
functional prototype has
been fabricated. We
are currently doing
sensor integration and
controller design. We
will conduct healthy
subject test and move
on the patient trial at
the hospitals.
Figure4. The Prototype