Page 172 - Anatomy of a Robot
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ENERGY AND POWER SYSTEMS 157
Energy Sources
Energy can be acquired and stored in many ways, but we won’t go into the different
types of battery technologies here and now. Articles about batteries and alternate power
sources can be found at the following web sites:
www.powerstream.com/BatteryFAQ.html
www.powerstream.com/tech.html
www.motionnet.com/cgi-bin/search.exe?a=cat&no=1308
www.batterystuff.com/battery/battery_tutorial.htm
Instead of talking about power sources directly, let’s list the characteristics we should
pay attention to in the search for power:
Weight versus energy The weight of the power source is a prime concern in
satellites, mobile systems, and portable systems like laptops. Some battery and
fuel cell systems will be lighter per watt-hour than others. Certainly, any mobile
robot should be as light as possible to avoid expending unnecessary energy.
Capacity How many watt-hours can the battery store? How is the end of its use-
ful life measured?
Peak currents Some batteries are better than others at delivering large peak cur-
rents. Besides checking the magnitude of the peak current, determine how long
the battery can sustain such a current. It may not be able to do so for very long.
Lifetime What mechanisms may cause the battery to fail as it ages?
Temperature Will the battery function at sufficient levels over the required
temperature range?
Recharging How is it recharged? Are there any special requirements?
Cost How expensive is the battery and can it be readily replaced?
Safety We discussed before the many hazards that batteries can present. Have
the proper safeguards been taken?
Warm-up Will the battery require any warm-up time to function properly?
Metering Is the battery smart enough to communicate with the computer?
Failing that, is the battery relatively predictable in its charge/discharge character-
istics? We may have to simulate the state of the battery in the robot’s software.
Availability How special is the battery? Will it be supported by the industry for
some years to come? Will replacements be available on the open market?
Like humans, robots will only work well when fed enough and exercised within their
capabilities. Understanding energy, power and motion are key to building a successful
robot.