Biomedical Engineering Reference
In-Depth Information
of a motion, and the remained motion are pre-programmed by FES or robot in a
passive pattern.
Currently, FES and rehabilitation robot are still separate systems. In compar-
ison with FES, robot system uses the motor to provide external assistive force;
it does not have the effect as in FES, which directly activates a person's own
motor power from the paretic muscles to generate the assistive force. However,
difficulties also could be encountered when using FES to activate groups of mus-
cles with dynamic limb movements, since electrode size and the number of FES
channels would be challenges of whether the paretic muscle groups could achieve
movements with desired kinematic qualities, such as speeds and trajectories. FES
can cause muscle contractions, and this contraction could activate feedback from
natural sensors in the body through the afferent nerves back to the central nervous
system, which may help in motor relearning during training (Chae and Yu 1999;
Bhakta 2000). It is possible that a combined rehabilitation system with both FES
and robotic supports may enhance the training effects by either pure robot or FES
training.
Upper limb functions are highly related to the daily activities of a person.
However, in rehabilitation training, many stroke survivors experienced reasonable
motor recovery of their proximal upper limb (shoulder and elbow) but limited
wrist recovery at the distal (Chae and Yu 1999; Bhakta 2000). Improvement of
the wrist functions can directly increase the usage of the affected hand of persons
after stroke (Broeks et al . 1999). In this chapter we introduced a combined FES-
robot system, which may assist wrist rehabilitation training for persons after stroke
interactively to their voluntary residual motor intentions.
8.2 THE COMBINED FES-ROBOT SYSTEM
The FES-robot system could assist wrist training for persons after stroke contin-
uously and interactively according to their voluntary residual motor intentions
detected by electromyography (EMG) during training. The system was developed
based on the robotic prototype of the continuous interactive rehabilitation robot
as introduced in Chapter 5 . Figure 8.1(a) shows the experimental setup of the
FES-robot system when doing the wrist training, with EMG and FES electrodes
attached on the antagonist muscle pairs of flexor carpi radialis (FCR) and extensor
carpi radialis (ECR). The EMG and FES electrode configuration on a muscle is
shown in Figure 8.1(b) . A subject would be asked to conduct the wrist flexion and
extension in a horizontal plane from -45 (the negative sign represented extended
positions) to 60 (the positive sign represented flexed positions) with a selected
velocity by tracking with a target cursor. During a wrist tracking task, both the
robot and the FES parts would provide assistance to the subject, and the detailed
structure of the FES-robot system is illustrated in Figure 8.2(a) .
The system mainly consisted of an FES part, a robot part, and a personal
computer (PC) based control platform. The interface between the PC and the
 
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