Lecture 5 'Control' Flashcards
The Mercury space capsule control panel controls three types of movements, what are they?
roll = {cartwheel}
pitch = {fall forward}
yaw = {turn on feet}Under pressure, what kinds of mappings or motions do people revert to in terms of control?
Those which are more naturally compatible
What kind of control violations underlie many accidents and incidents with equipment?
violations of stimulus response (SR) compatibility
> a) Out of the following control knobs, which did Bradley (1954) find to be the rated as the most natural (SR compatible) and linked to the least amount of starting/setting errors?
b) Which was rated last?
A - direct drive, left-right increase, clockwise=decrease
B - direct drive, right-left increase, clockwise=increase
C - reversed drive, left-right increase, clockwise=increase
D - reversed drive, right-left increase, clockwise=decrease
A - direct drive; left>right, clockwise=decreases
D. = last
According to McCormick and Sanders, Location/Spatial compatibility is the relationship between what two things?
Physical arrangement in a space of controls + associated displays
The target zone for the depth of anesthesia is between __ -__
60-40
Awareness under anesthesia affects ___% of patients
0.1-0.2%
According to Myles et al (2004), the Bispectral Index (BIS) monitoring system _______ the risk of patients at high-risk of awareness under anesthesia.
Was this supported by Avidan (2008)?
reduced
No - did not replicate findings
Describe the Utah drug display as outlined in Cooke & Durso?
> Utah drug display shows =
a) current/past drug dosing
b) predicted pharmacokinetics
c) combined effects on levels of sedation, analgesia and neuromuscular blockade
(Q. 29) A drug takes several minutes to reach its full effect even after it starts to hit receptor sites in the
brain. This is an example of which phenomenon in closed-loop control?
Lag
Answer the following related to closed-loop control;
Delay = _______
Lag = _______
Gain = _______
Order of control = _______
Delay = time before response starts
Lag = time for response to get to full strength
Gain = multiplier of input (big/small reaction)
Order of control = position / velocity / acceleration
What is the main difference between closed-loop and open-loop controls?
open-loop controls do not have feedback on which to base corrections; you have to “know” how it will respond in advance (“ballistic”)
(Q. 30) I move a joystick to 2 cm to the left. The speed of a dot on my screen start moving to the left,
building up speed until it reaches a relatively low constant speed. This is an example of what kind
of control dynamics?
A 1st order system with a lag and low gain
Describe a 0-order control?
identical movements as control (e.g. like a mouse moving on the screen the same way/speed you move it in your hand)
Describe a 1st -order control?
builds up velocity/speed GRADUALLY then stays at a constant speed
Describe a 2nd -order control?
accelerates quickly, builds speed and keeps getting faster
(Q. 28) When controlling a process such as depth of anesthesia, what is the input signal that the
controller (human or machine) responds to?
a. The desired output.
b. The error between actual and desired output.
c. The actual output.
d. The brain’s response.
b. The (+/-) error between actual and desired output
Liu et al (2006) showed that a proportional differential controller (PD) does a _________ job than an manual human controller (the anesthetist). What does it do?
better
Try to nullify the BIS error without making response unstable or making it sluggish
> BIS stays between 40-60
Patients wake up faster
Less overall control error
Drug “effect-site delay” means what?
the DELAY and LAG in how long it takes a drug (e.g. propofol) to have its full pharmacological effect
(Q. 34) What does the drug display for anesthesia (Syroid et al. 2002; Drews et al. 2006) actually show?
A graphical model of a patient’s physiological response to the anesthesia drugs over time.
When tested, the drug display resulted in what three positive effects?
- patients woke up earlier
- anesthetists = lower mental workload
- anesthetists = feel better performance
According to an ICU clinical information systems (CIS) evaluation of displays, answer the following.
Nurses detected change faster with which displays? Which of these was better?
Doctors agreed more closely about which systems had failed with which display?
Doctors agreed more closely about diagnoses with which display?
Nurses detected change faster with = PAPER and ELECTRONIC prototypes (compared to traditional chart)
> ELECTRONIC = better
Doctors agreed about failed system = ELECTRONIC (vs. paper vs. traditional)
Doctors agreed about diagnoses = PAPER (vs. electronic vs. traditional)
(Q. 35) Consider the connection between human trust and automated control of anesthesia with a PID
controller. What must the anesthetist trust?
> Measures of depth of anaesthesia
> PID control dynamics
