Biomedical Engineering Reference
In-Depth Information
achieves the position control, force control, or novel controls of pneumatic and
cable-wired actuators on each degree of freedom. Usually one form of impedance
controllers is utilized. Impedance control and admittance control are duality
but may not be mutually convertible in non-linear systems (Marchal-Crespo and
Reinkensmeyer, 2009). The high-level controller schedules the trajectories or paths
that potentially achieve the purpose of rehabilitation. Simple linear movement
with simple velocity profile is relatively easy to design. Yet, manual treatments
usually involve complex maneuvers with resistive or assistive force imposed at
specific times of the movement. Circular or more complex movements with
predefined imposing force are more difficult to design. In the following, the
existing robotic systems for the rehabilitation of the upper limbs with an emphasis
on controller implementation are reviewed.
Hogan
et al
(Krebs
et al.
, (1998). designed a planar robot (MIT-Manus) with
impedance control for guiding patients to do movements along the specified
planar trajectories. A five-bar-link drive mechanism with decoupled joint dynam-
ics (Asada and Youcef-Toumi, 1984), which facilitated the controller design, was
adopted for constructing the robot. Noritsugu
et al.,
(1997). for treating patients
with trauma, designed an arm-like robot with 2 degree-of-freedom (DoF) and
developed four modes of planar linear motion. Each actuator comprises two
rubber artificial muscles (Rubbertuator RUB-835S (link 1), RUB-825S (link 2) from
Bridgestone Company, Japan) to strengthen the generated torque. Impedance
control for position was implemented. Hybrid position/force controllers (Raibert,
Craig and Hybrid, 1981; Suh
et al.
, 1991), controlling position in one direction and
force in the orthogonal direction, have the advantage of simultaneously maintain-
ing the desired movement trajectory and force for the planar movements. Lum
and co-workers (Burgar
et al.
, 2000) developed the mirror-image motion enabler
(MIME) robot that enabled 3 dimensional (3D) rehabilitation movements of the
affected side guided by the intact side according to the master-slave principle. The
robot and its controller were based on a commercially available model (Staubli
PUMA-560). The robot provided a viscous resistance in the direction of desired
movement and spring-like forces in all other directions. Thus, the system had
position control in one direction and velocity-dependent force control in the other
direction. Cozens (1999), using a single-axis robot and torque control mode,
applied resistive or assistive torque to the elbow for rehabilitation of patients with
spasticity and weakness. Colombo
et al.
, (2005). designed a planar robot based on
three linear motion guides and implemented admittance control. Reinkensmeyer
et al.
, (1999) developed ARM-guide that had a passive linear constraint to limit
the movement of the upper limb to a linear path and a single motor to assist arm
movement. The robot, in a general sense, also implemented position control in
one direction and force control in the other direction. Yet, the position control
was provided by the hardware constraint. Similar to an admittance controller, a
counterpoise assistive controller that compensated for gravity and elbow passive
properties was implemented for force control. Bi-Manu-Track (Hense
et al.
, 2003)
was developed for rehabilitation of the distal parts of the upper limb and allowed
