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Explain to students that JASON's maneuverability depends upon feedback or the transmission of signals between the ROV and its surface vessel. An array of sensors determines the ROV's exact location and relays this information to a
navigational computer system. The computer processes these data and
determines if the ROV is on course. Adjustments to the ROV's position are
made automatically through the transmission of commands to the vehicle's
thrusters.
Explain that in order to supervise JASON's programmed navigation, this
shipboard operator closely monitors the information displayed by JASON's sensors. This feedback information supplies the operator with precise details about the position and movement of the ROV.
The human operator can use a joystick to modify the programmed ROV path.
But all human input, or supervisory control, must first be processed and
integrated by the computer system. If the system "approves" of the course input, the new commands are transmitted to the thrusters.
JASON's navigational system is so precise it can track JASON plus or minus
two centimeters of actual location. Computers on the ship established a
detailed "no-go" envelope around the vent site. The computers prevent JASON from entering the "no-go" envelope by overriding an operator's controls.
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JASON's navigational system depends upon feedback
loops. In a feedback loop, information about an ongoing task is continually
relayed to the task controller. The controller uses this feedback to
determine how to complete the task.
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Students will be able to do the following:
- Remotely operate a vehicle.
- Use a feedback loop to modify the vehicle's movements.
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- Radio-controlled vehicle
- Meter stick
- Ten dominoes
- Stopwatch
- Tape
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Activity
- Assign students to cooperative groups. In each group of four, have
Student A use a meter stick and tape to mark off a square area of the floor
about 2 meters on each side. Explain that the taped area represents the
ROV's field, or "envelope of operation."
- Have Student B place 10 dominoes in a random pattern within the
marked-off square.
- Tell Student C that his or her role will be to knock over as many
dominoes as possible with the radio-controlled vehicle. Give students time
to examine the placement of dominoes. Then have Student B place the vehicle
anywhere within the square.
- Have Student C stand about a meter from the square facing away from the
dominoes and the car. Students A and B should take positions on opposite
sides of the square.
- Student D will use a watch to keep time. On Student D's signal, Student
C will use the controls to drive the car without watching its movement.
(NOTE: if the car travels out of the square, Student A or Student B is to
return it to its starting location.)
- At the end of 2 minutes, Student D will stop the activity and students
will count and record the number of fallen dominoes.
- Now repeat steps 2 through 6. On this second run, however, permit
operators to watch the movements of their radio-controlled vehicles.
- Exchange roles so every student gets a chance to control the car
with and without a feedback loop mechanism (with and without watching and
responding to its movements).
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Request that students "brainstorm" extensions for this activity.
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Discuss the difference between the motion of the
unwatched car and its purposeful movement when the operator can
observe its course and make corrections. Explain that the second kind of
operation illustrates a feedback loop-the operator provides data to the
machine, the machine provides data (or feedback) to the observing operator,
and the operator supplies more data (further feedback) in response. Without feedback it would be unlikely for the car to strike all ten dominoes in a short time.
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Last modified: 11-June-99
Copyright Notice
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Deep Sea Technology - Feedback Loops