Page 73 - Modern Control Systems

Design Problems 47

FIGURE DP1.7 An artist illustration of a
nanorobot interacting with human blood
cells.

to deliver a cancer drug to a specific location within
the human body. The target site might be the location
of a tumor, for example. Using the control design
process illustrated in Figure 1.15, suggest one or more
control goals that might guide the design process. Rec-
ommend the variables that should be controlled and
FIGURE DP1.4 Robot welder.
provide a list of reasonable specifications for those
variables.
maximum at a low slip. Develop a block diagram DP1.8 Consider the human transportation vehicle (HTV)
model of one wheel of a traction control system. depicted in Figure DP1.8. The self-balancing HTV is
actively controlled to allow safe and easy transporta-
DP1.6 The Hubble space telescope was repaired and tion of a single person [97]. Using Figure 1.3 as a
modified in space on several occasions [44, 46, 49]. model for the block diagram, describe a closed-loop
One challenging problem with controlling the Hub- feedback control system to assist the rider of the HTV
ble is damping the jitter that vibrates the spacecraft in balancing and maneuvering the vehicle.
each time it passes into or out of the Earth's shadow.
The worst vibration has a period of about 20 seconds,
or a frequency of 0.05 hertz. Design a feedback sys-
tem that will reduce the vibrations of the Hubble
space telescope.
DP1.7 A challenging application of control design is the
use of nanorobots in medicine. Nanorobots will re-
quire onboard computing capability, and very tiny
sensors and actuators. Fortunately, advances in bio-
molecular computing, bio-sensors, and actuators are
promising to enable medical nanorobots to emerge
within the next decade [98]. Many interesting medical
applications will benefit from nanorobotics. For exam-
ple, one use might be to use the robotic devices to pre-
cisely deliver anti-HlV drugs or to combat cancer by
targeted delivering of chemotherapy.
At the present time, we cannot construct practical
nanorobots, but we can consider the control design
process that would enable the eventual development
and installation of these tiny devices in the medical FIGURE DP1.8 Personal transportation vehicle.
field. Consider the problem of designing a nanorobot (Photo courtesy of newscom.com.)