Page 69 - Modern Control Systems

Problems 43

[61] is becoming an important issue, especially for
commercial satellite companies that plan to "fly" their
satellites through orbit altitudes where other satellites
are operating, and through areas where high concen-
trations of space debris may exist. Sketch a block dia-
gram of a space traffic control system that commercial
companies might use to keep their satellites safe from
collisions while operating in space.
PI.26 NASA is developing a compact rover designed to
transmit data from the surface of an asteroid back to
Earth, as illustrated in Figure PI.26.The rover will use
a camera to take panoramic shots of the asteroid sur-
face. The rover can position itself so that the camera
can be pointed straight down at the surface or straight
up at the sky. Sketch a block diagram illustrating how
the microrover can be positioned to point the camera
FIGURE P1.21 Two helicopters used to lift and move a in the desired direction. Assume that the pointing
large load.
commands are relayed from the Earth to the micro-
rover and that the position of the camera is measured
and relayed back to Earth.

shows a typical "two-point pendant" twin lift config-
uration in the lateral/vertical plane.
Develop the block diagram describing the pilots'
action, the position of each helicopter, and the posi-
tion of the load.
P1.22. Engineers want to design a control system that will
allow a building or other structure to react to the force
of an earthquake much as a human would. The struc-
ture would yield to the force, but only so much, before
developing strength to push back [47]. Develop a
block diagram of a control system to reduce the effect
of an earthquake force.
P1.23 Engineers at the Science University of Tokyo are
developing a robot with a humanlike face [52]. The
robot can display facial expressions, so that it can
work cooperatively with human workers. Sketch a
block diagram for a facial expression control system FIGURE P1.26 Microrover designed to explore an
of your own design.
asteroid. (Photo courtesy of NASA.)
P1.24 An innovation for an intermittent automobile
windshield wiper is the concept of adjusting its wiping
cycle according to the intensity of the rain [54]. Sketch P1.27 A direct methanol fuel cell is an electrochemical
a block diagram of the wiper control system. device that converts a methanol water solution to
electricity [75]. Like rechargeable batteries, fuel cells
P1.25 In the past 40 years, over 20,000 metric tons of directly convert chemicals to energy; they are very
hardware have been placed in Earth's orbit. During often compared to batteries, specifically rechargeable
the same time span, over 15,000 metric tons of hard- batteries. However, one significant difference between
ware returned to Earth. The objects remaining in rechargeable batteries and direct methanol fuel cells
Earth's orbit range in size from large operational is that, by adding more methanol water solution, the
spacecraft to tiny flecks of paint. There are about fuel cells recharge instantly. Sketch a block diagram of
150,000 objects in Earth's orbit 1 cm or larger in size. the direct methanol fuel cell recharging system that
About 10,000 of the space objects are currently tracked uses feedback (refer to Figure 1.3) to continuously
from groundstations on the Earth. Space traffic control monitor and recharge the fuel cell.