Fire Fighting Robot

Posted on Feb 5, 2014

When deciding how to move the robot through the house, the designers realized that precision movement would be necessary in order to avoid touching the walls and receiving penalties. In order to achieve the required precision in movement, it was decided that the robot would utilize stepper motors. The main benefit of stepper motors is that they are able to

Fire Fighting Robot
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turn a specific number of degrees for every step. A four phase stepper motor has four coils that, when energized in a specific sequence, rotate a driving magnetic field which, consequently, rotates a set of permanent magnets. These permanent magnets are attached to a rotor which drives an output shaft. Thus, by pulsing the coils in a certain sequence, a clockwise or counterclockwise movement can be attained. A change in the coil states (ie. changing from state 2 to state 3 as shown above) results in a single step of the motor shaft. Direction is easily controlled by running through the above sequence either forward or backward. It should also be noted that the coils A and A` are always oppositely charged, as are coils B and B`. By inverting the signals going to coils A and B, the corresponding signals A` and B` can be attained. Thus, only two control lines are required to place the motor into any one of the 4 possible states. Even though this is an important consideration for certain applications, the controller used in this implementation has a sufficient number of lines to control each coil. Furthermore, because two of the coils are always energized at any given time, the rotor is held into place by the two magnetic fields and hence will not easily slip - even when the motor is not turning. This is another benefit of stepper motors. Figure 2 provides an internal diagram of a typical four phase stepper motor. The stepper...

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