Page 57 - Mechatronics with Experiments

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JWST499-Cetinkunt
JWST499-c01
INTRODUCTION 43
1.4 PROBLEMS
1. Consider the mechanical closed loop control system for the liquid level shown in Figure 1.4. a)
draw the block diagram of the whole system showing how it works to maintain a desired liquid level,
b) modify this system with an electromechanical control system involving a digital controller. Show
the components in the modified system and explain how they would function. c) Draw the block
diagram of the digital control system version.
2. Consider the mechanical governor used in regulating the engine speed in Figure 1.5. a) Draw
the block diagram of the system and explain how it works. b) Assume you have a speed sensor on
the crank shaft, an electrically actuated valve in place of the valve which is actuated by the fly-ball
mechanism, and a microcontroller. Modify the system components for digital control version and
draw the new block diagram.
3. Consider the web tension control system shown in Figure 1.7. a) Draw the block diagram of the
system and explain how it works. b) Assume the analog electronic circuit of the op-amp and command
signal source is replaced by a microcontroller. Draw the new components and block diagram of the
system. Explain how the new digital control system would work. c) Discuss what would be different
in the real-time control algorithm if the microcontroller was to control the speed of the wind-off roll’s
motor instead of the wind-up roll’s motor. Assume wind-up motor speed is constant.
4. Consider the room temperature control system show in Figure 1.8. The electric heater and fan
motor is turned ON or OFF depending on the actual room temperature and desired room temperature.
a) Draw the block diagram of the control system and explain how it works. b) Replace the op-amp,
command signal source, and timer components with a microcontroller. Explain using pseudo-code
the main logic of the real-time software that must run on the microcontroller.

3. Hoist pulley
with drum brakes
(Primary and emergency),
flywheel

1. Control box:
drives
2. Electric motor

4. Car

5. Sliding guide rails

6. Counter weights

FIGURE 1.33: Elevator control system and its components (Source: http://www.
smartelevatorsco.com/ropedelevators.html).