Wristy

Wristy is an autonomous and user controlled Vex Robotics arm bot that I fully designed, constructed, and coded throughout my junior and senior year at Auburn High School. Wristy (named after a floating variable in the code) has three individual programs including a user controlled mode, autonomous drive function, and the ability to both fold itself for storage and unfold for use. This project began at the request of my engineering teacher, Mr. Gilmore, who wanted a physical representation of the engineering department at the high school in order to attract the interest of incoming students. Starting work with one other student, I took over the project early in 2017 and designed everything that currently comprises the final robot. I proudly completed this project at the end of my senior year at Auburn High School and am happy to say that Wristy is still in the engineering department, inspiring future students to take on extra curricular activities similar to my own.

The claw and wrist of the robot is able to both twist and tilt along two axes in order to give the user more precise control of the arm. Each axis of movement is limited through the use of potentiometers to prevent the wires from twisting and the arm breaking. The potentiometers are also used to tell the robot where its arm is in real time, allowing for motor speeds to be varied to account for changing momentum depending on the position of the arm and direction of movement.

The waist of the robot is powered by an upward facing drive motor that is directly connected to the turntable, as seen in the top right image of this section. It was important for the bracket on top of the turntable to sit flush on its surface in order to eliminate the wobbling of the arm as the robot swings through various positions. Furthermore, the waist's movement is limited by the two limit switches in the rear of the robot as seen in the image above to the left. Two limit switches were used so that the robot knows which direction it's able to safely rotate towards in order to prevent it from twisting the wires that run through its middle.

The robot's drive system operates with only two motors, freeing up space on the cortex for motors to be used elsewhere. In order to make this possible, the wheels on corresponding sides are powered by the same motor, using a chain and sprocket system to connect the different wheels. This two motor drive system allows the robot to make a swing turn by varying the speeds on each side, or complete a point turn by setting one side to move in the opposite direction as the other. The image above on the right shows that the cortex is housed under the waist in order to effectively manage the wiring and allow for easy access to the wires and battery.

In the rear of the robot, a bumper switch and potentiometer are used to toggle between functions. By using the limits of the potentiometer, the user is able to turn the axle which in turn changes the function that commands the robot. First, the robot will undergo a set of autonomous commands when turned on that unfolds the arm and prepares the robot to be used. After this action is complete, the robot then reads the potentiometer in the rear and waits for further action. If the potentiometer is turned to the left, the robot will automatically begin its user controlled function, giving full control of the system to the remote controller. If the potentiometer is rotated in the middle of its limits, then the controller no longer operates the system and the robot will stop moving. Once the bumper switch is pressed, the robot will undergo a series of commands to fold the arm for storage. Lastly, if the potentiometer is rotated to the right after the robot is turned on, the robot will again cease to move until the bumper switch is pressed, and then it will run an autonomous function, moving the robot through a driving pattern as well as a set of arm movements until returning to a resting position. While the robot is turned on, it will continuously check the position of the potentiometer in order to update which function is desired by the user.