Biomedical Engineering Reference
In-Depth Information
The assistance from the FES part was defined as
Assistance
FES
=
K
·
W
max,FCR
·
M
Flexion
, During the flexion tracking phase
,
(8.2)
·
W
max,ECR
·
K
M
Extension
, During the extension tracking phase
where,
K
was a constant gain factor set before experiment, ranging from 0 to 1,
W
max,FCR/ECR
was the maximum stimulation impulse width applied on the FCR
or ECR muscles, which were the threshold values to evoke maximal wrist flexion
and extension when the forearm was put horizontally on a table with the wrist
EMG
m,Flexion/Extension
−
EMG
mREST
M
Flexion/Extension
¯
=
,
(8.3)
EMG
mIMV
−
EMG
mREST
where EMG
m,Flexion/Extension
was the EMG of the agonist muscle,
m
,initscon-
traction phase during the tracking (e.g. the EMG of FCR during the wrist flexion
phase, or the EMG of ECR during the wrist extension phase);
EMG
mREST
was the
averaged EMG of the muscle,
m
, during its resting state; and
EMG
mIMV
was the
maximal EMG value of the muscle,
m
, during its isometric voluntary contractions
(IMVC). All EMG signals were first processed by the full wave rectification and
that during the electrical stimulation, stimulation artifacts would contaminate
EMG signals. Sample-and-hold software (S/H, by LABVIEW) was applied for
reducing the stimulation artifacts after the EMG signals were digitized. The S/H
program had the functions first to detect the onset of a stimulation artifact (usually
3
0
-3
8
10
12
14
16
18
20
22
24
3
Stimulation
Artifact
2
M Wa ve
Volun tar y EMG
1
0
-1
9.83
9.84
9.85
9.86
9.87
9.88
9.89
9.9
9.91
9.92
9.93
t s
Figure 8.3
The captured EMG signals after the process of sample-and-hold. The upper
panel shows the EMG signal before (dotted line) and after (solid line) the process of sample-
and-hold. The lower panel shows the enlarged signals in the upper panel. For color
reference, see page 218.
