Biomedical Engineering Reference
In-Depth Information
The agonist and antagonist active-state tensions are given by the following low-pass
filtered pulse-step waveforms and are illustrated along with their corresponding neuro-
logical control signals in Figure 13.11.
0
1
t
t ac
@
e
A u ðÞ ut t 1
F ag ¼ F g 0 u ð t Þþ F p þ F g 0 F p
ð
ð
Þ
Þ
ð
13
:
36
Þ
0
1
t
t t
ð
Þ
1
t ac
1
@
e
A e
t de
þ F gs þ F p þ F g 0 F p
F gs
ut t 1
ð
Þ
t
t de
F ant ¼ F t 0
u ð t Þþ F t 0
e
ð
u ðÞ ut t
ð
Þ
Þ
1
0
0
1
1
t 1
t de
t t 1
ð
Þ
@
@
A e
t ac
A ut t 1
þ F ts þ F t 0 e
F ts
ð
Þ
where
F g 0
¼
initial magnitude of the agonist active-state tension
F p ¼
pulse magnitude of the agonist active-state tension
F gs ¼
step magnitude of the agonist active-state tension
F t 0 ¼
initial magnitude of the antagonist active-state tension
F ts ¼
step magnitude of the antagonist active-state tension
t ac ¼
activation time constant
t de ¼
deactivation time constant
t 1 ¼
duration of the agonist pulse active-state tension
Final parameter estimates for the saccadic eye movement model are found using the
system identification technique, a frequency response method. The oculomotor system
operates in an open-loop mode while executing a saccade. After completing the saccade,
the central nervous system operates in a closed-loop mode and compares eye and target
position [5]. Figure 13.32 presents a block diagram illustrating the open-loop, closed-loop
operation of the oculomotor system, with the feedback element H operating only during
discrete time intervals when a saccade is not being executed. The system identification is
used to estimate the parameters and the input during the open-loop mode of the saccade.
The steady-state active-state tensions are given by
23
0
:
14
þ
0
:
0185y N for y
<
14
:
F ag ¼
23
0
:
0283y
N for y
14
:
23
0
:
14
0
:
0098y N for y
<
14
:
F ant ¼
ð
13
:
37
Þ
23
0
N for y
14
:
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