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24    ANATOMY OF A ROBOT





















                                                          Figure 2-12  Legs allow a robot to navigate
                                                          where wheels or tracks can’t. Plus they look cool.
                                                          This design uses four motors and six legs. It
                                                          walks by moving its legs in specific patterns.



                   Power Systems


                   We humans eat food that is then processed by our bodies to power muscles. While you could
                   probably design a digestive system for a robot and feed it hamburgers, french fries, and other
                     semi- radioactive foods, an easier way to generate the power to make your robot go is to take
                   a trip to the store and buy a set of batteries. Connect the batteries to the robot’s motors, cir-
                   cuits, and other parts, and you’re all set.

                   TYPES OF BATTERIES
                   There are many kinds of batteries, and Chapter 18, “All About Batteries,” goes into more
                   detail about which ones are best for robots. Here are a few quick details to start you off.
                     Batteries generate voltage and come in two distinct categories: rechargeable and nonre-
                   chargeable. Nonrechargeable batteries include the standard zinc and alkaline cells you buy at
                   the supermarket, but only the alkaline kind is truly useful in robotics.
                     Rechargeable batteries include  nickel- cadmium (NiCd), nickel metal hydride (NiMH), sealed
                     lead- acid cells, and special rechargeable alkaline. NiCd and NiMH batteries are popular
                   choices because they are relatively easy to find, come in common sizes, and can be recharged
                   many times using an inexpensive charger.

                   OTHER POWER SOURCES
                   Small robots can be powered by solar energy when they are equipped with suitable solar cells.
                     Solar- powered robots can tap their motive energy directly from the cells, or the cells can
                   charge up a battery over time.  Solar- powered bots are a favorite of those in the BEAM  camp— a
                   type of robot design that stresses simplicity, including the power supply of the machine.
                     Hydraulic power uses oil or fluid pressure to move linkages. You’ve seen hydraulic power
                   at work if you’ve ever watched a bulldozer move dirt from pile to pile. And while you drive,









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