Rat movement

If the stupid pet trick was a success, the following assignment was… less so. I was initially undecided about which movement to imitate, so I did not think twice when I saw a rat toy lying on my roommate’s bed. I wanted to use two regular DC motors to create circular motion of the rats’ legs and thus give the appearance that the toy is running. The first pair of legs would be connected to one motor and the second pair of legs to the other motor. However, the plan did not turn out the way I had hoped. DC motors are just too fast. Even when I PWM-ed the motors to make them operate at slower speed, I could not imagine the toy successfully handling such rapid movements. Scott suggested I use a stepper motor instead, because it can rotate at slower speed. However, I did not have enough time to learn how to properly wire and control stepper motors, so I ended up using servo motors to mimic rat motion. The only servos I could find in the lab were micro servos from our Sparkfun kits. Those servos were unable to handle the weight of the rat and thus produced jerky motion. Above and beyond, the whole structure was quite shabby (as can be seen in the last part of the video). So the lesson I have learned is to use stepper motors the next time I want to imitate rat movement.

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