Lecture 1 - Introduction to Control Flashcards
vestibulo-ocular reflex (VOR)
eye movement reflex that stabilizes imagines on the retina during head movement
control theory + genetics =
systems biology
control theory has been applied to which fields?
- motor physiology - gene regulatory networks
define: plant
thing we want to control/influence
___ receives input and sense commands to the plant
controller
types of control
- open loop 2. feedback 3. internal feedback
open loop
input -> controller -> plant -> outcome
- controller receives no feedback
Another name for open-loop
ballistic control
Limitation of open-loop control
cannot recover from malfunctions or disturbances happening at the plant
Feedback control
Control system which monitors its own progress and adjusts its commands accordingly
Examples of feedback control:
- Mechanical
- Biological
- Heat seeking missile
- balance
What body parts do we use for balance/posture?
- Inner ears
- Vision
Limitation of feedback control
- disturbance is too great
- Delay around the loop
In feedback control, ____ send information about outcomes back to controller.
Sensors
Solution to feedback delay
Use plant models and internal feedback
define: plant model
- Mimic the actions of the plant (what the plant is doing or what it is about to do)
- Send info to controller with little delay (located close to controller)
Disadvantage of plant model
If the model is inaccurate or ignores some disturbances in the real plant, the system malfunctions
Information about how to move your eyes come from _____ when head is moving.
Inner ear
____ measures head rotation and is responsible for VOR
inner ears
VOR’s plant is…
the eyeballs
VOR’s input comes from…
semicircular canals of the inner ear (there are 3 canals – x, y and z axis plane)
- each canal is responsible for firing afferent nerve fibres at a rate proportinal to the rotary head velocity in the plane of that canal
The semicircular canals sense… (VOR)
rotary head velocity
The semicircular canals are called _____ organs because they lin within a chamber called the _____ in the inner ear
- vestibular organs
- vestibulum
Why is the VOR called VOR?
it uses information from vestibular sensors to control the eyes
Pathway for VOR control
- Semicircular canals
- Primary vestibular neurons (in vestibular gangion)
- Secondary vestibular neuronsneurons (in vestibular nucleus)
- Motoneurons (in cranial nerve nuclei 3, 4, 6)
- Eye muscles
How many cranial nerves do we have on each side of the brain?
12
Which cranial nerves do the VOR involve?
3, 4, 6
Streptomycin is a…
antibiotic
VOR is ____ control. Why?
open-loop
head velocity→controller→eyes→eye position
Since the inner ear regulates VOR, it can’t “see” if the images are actually stable on the retina
VOR: eye velocity should =
- head velocity
Plant equation (gives eye velocity)
dx/dt = (u - kx) / p
- v = head velocity
- u = controller / command
- x = eye position
- k, p = constant (mechanical properties of the eye muscles)
What part of the plant equation does the controller alter? What does it want it to equal?
- Alters u
- dx/dt = -v
The controller’s law is called…
control law
Control Law
u = kx - pv
- Brain sends this command to the eye muscles to keep retinal images stable
control law keeps head velocity = -eye velocity provided that…
k and p (constants) used by the controller and the plant are the same
What happens if the controller’s p’ value is 80% of the plant’s p value? (p’ = 0.8p)
eye velocity is 80% as large as head velocity (dx/dt = 0.8v)
- On the graph, amplitude changes
What happens if the controller’s k’ value is 50% of the plant’s k value? (k’ = 0.5k)
eye velocity is out of phase with head velocity
- On the graph, displacement in the x direction changes
In general, a control system only funtions properly if…
Its controller is tuned to its plant
- k’ = k
- p’ = p
VOR’s controller involves several brain structures, but its core is _______
brainstem neurons
