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Range of Motion

Robots are often comprised of several mechanical subsystems, such as arms, claws, and drivetrains. These mechanical subsystems create different types of movement, which allow the robot to complete different tasks. Each subsystem has its own range of motion, which is the term used to describe how far it can rotate or slide before hitting some sort of limit.

Subsystems such as the drivetrain usually have a full range of motion, since the motors, gears, and wheels can freely spin continuously without hitting any limit. This is important, since the robot may need to traverse substantial distances in order to complete a task.

Subsystems such as claws or arms usually have a limited range of motion, which prevent them from spinning continuously. Claws can only open or close so much before reaching a mechanical limit. Likewise, the range of motion of an arm is often limited by the ground or the body of the robot itself. When working with subsystems with a limited range of motion, it is very important to stay within that range, regardless of whether you are remote controlling the robot or programming it to move autonomously. Continuing to provide power to the motors once a subsystem has reached a limit will cause unnecessary stress on the motor and any connected components.

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When first programming arms and claws, students will often reach the mechanical limit of their device and not understand why the project seems to stop at that point and not progress. This happens because the project is unable to rotate the motor to the specific number. If a rotation number is past the limit of what is physically available from a motor, the project will continue to wait for the motor to reach that number.