Page 172 - Anatomy of a Robot
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06_200256_CH06/Bergren  4/10/03  12:00 PM  Page 157
                                                                         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.
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