Ch 13: Control Systems

Question 1

when is a control system linear?

Answer 1

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

Question 2

T/F: most biological systems are non-linear

Answer 2

true

Question 3

how does a negative feedback system work?

Answer 3

the output of the system is subtracted from the signal in an earlier part of the path

Question 4

component of the negative feedback control system

Answer 4

• stimulus as input
• response as controlled variable
• forward loop
• feedback loop
• summing junction
• error signal
• controller
• plant

Question 5

in negative feedback control, the controller represents

Answer 5

neural processing

Question 6

in negative feedback control, the plant represents

Answer 6

the effector organs (in this case, extra ocular muscles)

Question 7

T/F: negative feedback systems normally operate in closed-loop mode

Answer 7

True

Question 8

what happens to the negative feedback system in open-loop mode?

Answer 8

the switch is opened which prevents normal feedback

Question 9

what is unique about the feed-forward system?

Answer 9

has no negative feedback

-response is driven quickly by the input using the feed-forward gain (G)

Question 10

how do feed-forward systems still have “feedback”

Answer 10

over time, they monitor their post-task performance and adapt the controller properties to obtain better responses

Question 11

example of feed forward system

Answer 11

adaptation to new spectacles- the vestibulo-ocular response must alter its gain due to changes in the prismatic effect in off-axis viewing

Question 12

what does system bias represent?

Answer 12

the steady response of the system in the absence of stimulation, and after all transient behavior in the system has died down

Question 13

what is an example of system bias?

Answer 13

dark vergence after three minutes in total darkness

Question 14

what are tonic adaptive components?

Answer 14

they change the system bias and or controller characteristics based on the history of the response

Question 15

tonic adaptive components are important to understanding what 2 things

Answer 15

vergence and accommodation

Question 16

how do tonic adaptive elements help with vergence and accommodation?

Answer 16

-the elements lead to slow improvements in accuracy in mergence and accommodation for a steady object
(provide a more stable, comfortable response)

Question 17

what are the two parts of the controller?

Answer 17

• phasic controller

- tonic adaptive controller

Question 18

what are cross links?

Answer 18

connections between two otherwise independent systems

Question 19

what are two important cross links in oculomotor systems?

Answer 19

• accommodative convergence (convergence driven by accommodation)
• convergence accommodation (accommodation driven by vergence)

Question 20

what is a steady state response?

Answer 20

the response to a steady stimulus after the initial dynamic part of the response is complete (not truly steady though)

Question 21

what is a bode plot?

Answer 21

-is one of gain and phase as a function of stimulus temporal frequency (Hz)
(basis is linear systems theory)

Question 22

what is the response of a linear system to sinusoidal input

Answer 22

sinusoidal response

Question 23

what is gain

Answer 23

it equals the amplitude of the response divided by the amplitude of the stimulus G=R/S

Question 24

for ‘closed loop gain’ what does a gain of zero indicate? what does a gain of 1 equal

Answer 24

G=0, no response

G=1, perfect response amplitude

Question 25

what is phase?

Answer 25

phase is the time difference (sec) between waveform peaks in stimulus and response, divided by the stimulus period (sec), and then multiplied by 360 degrees

Question 26

what does a phase lag indicate?

Answer 26

phase lag= response does not keep up with stimulus

Question 27

what does a phase lead indicate?

Answer 27

phase lead= response runs ahead of the stimulus

Question 28

phase of 0=

Answer 28

perfect phase

Question 29

what does a bode plot show?

Answer 29

it plots gain as a function of temporal frequency

Question 30

when pass-band of a system is a low pass system,

Answer 30

it responds well to low frequencies

Question 31

when pass-band of a system is a high pass system,

Answer 31

it responds well to high frequencies but poorly to lower frequencies

Question 32

what is a main sequence diagram used for?

Answer 32

is a form of analysis not reliant on control systems theory, but useful for analyzing eye movements

Question 33

what does a main sequence diagram plot for?

Answer 33

peak velocity of motion as a function of amplitude of motion