Ch 13: Control Systems Flashcards
when is a control system linear?
if the response to the sum of two stimuli is equal to the sum of the responses to those individual stimuli, for all pairs of stimuli
T/F: most biological systems are non-linear
true
how does a negative feedback system work?
the output of the system is subtracted from the signal in an earlier part of the path
component of the negative feedback control system
- stimulus as input
- response as controlled variable
- forward loop
- feedback loop
- summing junction
- error signal
- controller
- plant
in negative feedback control, the controller represents
neural processing
in negative feedback control, the plant represents
the effector organs (in this case, extra ocular muscles)
T/F: negative feedback systems normally operate in closed-loop mode
True
what happens to the negative feedback system in open-loop mode?
the switch is opened which prevents normal feedback
what is unique about the feed-forward system?
has no negative feedback
-response is driven quickly by the input using the feed-forward gain (G)
how do feed-forward systems still have “feedback”
over time, they monitor their post-task performance and adapt the controller properties to obtain better responses
example of feed forward system
adaptation to new spectacles- the vestibulo-ocular response must alter its gain due to changes in the prismatic effect in off-axis viewing
what does system bias represent?
the steady response of the system in the absence of stimulation, and after all transient behavior in the system has died down
what is an example of system bias?
dark vergence after three minutes in total darkness
what are tonic adaptive components?
they change the system bias and or controller characteristics based on the history of the response
tonic adaptive components are important to understanding what 2 things
vergence and accommodation
how do tonic adaptive elements help with vergence and accommodation?
-the elements lead to slow improvements in accuracy in mergence and accommodation for a steady object
(provide a more stable, comfortable response)
what are the two parts of the controller?
- phasic controller
- tonic adaptive controller
what are cross links?
connections between two otherwise independent systems
what are two important cross links in oculomotor systems?
- accommodative convergence (convergence driven by accommodation)
- convergence accommodation (accommodation driven by vergence)
what is a steady state response?
the response to a steady stimulus after the initial dynamic part of the response is complete (not truly steady though)
what is a bode plot?
-is one of gain and phase as a function of stimulus temporal frequency (Hz)
(basis is linear systems theory)
what is the response of a linear system to sinusoidal input
sinusoidal response
what is gain
it equals the amplitude of the response divided by the amplitude of the stimulus G=R/S
for ‘closed loop gain’ what does a gain of zero indicate? what does a gain of 1 equal
G=0, no response
G=1, perfect response amplitude
