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ENERGY CONTROL AND SOFTWARE 189
Writing a software program to simulate coordination is a complex task. A good, first-
order approximation would be to write separate control algorithms for each component.
For example, we can write one control loop for the arm and one control loop for the
waist. While the control loop for the waist is rotating toward the wall, the control loop
for the arm will recognize the optimum time to start moving the arm.
It is possible to run into some trouble with many control algorithms running in par-
allel, but these difficulties can be overcome. Detecting and avoiding hazards, for
instance, can become a problem. Moving one component at a time is more predictable
because only one control loop is active at a time. If the waist and arm control loops are
both operating at the same time, they must be coordinated if obstacles must be avoided.
Coordination involves communication and falls prey to all the difficulties we discussed
previously in parallel processing. If we watch the pitfalls, we can reap the rewards in
energy savings.
Another example of coordination involves the rotation of mass. Ice skaters pull in
their arms when they go into fast spins. A robot that must rotate should pull in its arms
before the rotation. Not only does it help avoid punching the operator, but also less rota-
tional energy is needed.
A good article on designing a low-power system is at www.iapplianceweb.com/
story/OEG20020623S0006, and a review of some of the electrical engineering tech-
niques we’ve discussed can be found at http://academic.csuohio.edu/yuc/talks/
low-energy2k1021.pdf.
Another interesting article can be downloaded from wwwhome.cs.utwente.nl/
havinga/thesis/ch2.pdf. The author clearly views the world in terms of energy. Table
3 in this article seems to indicate the average human expends daily the energy equiva-
lent of a kilogram of coal, or roughly the energy in 10 beers. Check the chart out; it
might explain some of the neighbors!
Bottom line, the conservation and control of the robot’s energy reserves requires great
care. Software algorithms, property written, can minimize the robot’s consumption of
energy.