Programming an Arm to a Position

In the Encoder Navigation section the concept of moving the motor to a specific position based on encoder ticks was introduced. The process highlighted in Encoder Navigation focused on how to convert from encoder ticks to rotations to a linear distance. A similar procedure can be utilized to move the arm to a particular position. However, unlike the drivetrain, the arm does not follow a linear path. Rather than convert to a linear distance it makes more sense to convert the encoder ticks into an angle measured in degrees.

In the image below two potential positions are showcased for the ClassBot arm. One of the positions - highlighted in blue below - is the position where the arm meets the limit of the touch sensor. Due to the limit, this position will be our default or starting position. From the Class Bot build guide, it is known that the Extrusion supporting the battery sits a 45 degree angle. Since the arm is roughly parallel to these extrusion when it is in the starting position, we can estimate that the default angle of the arm is roughly 45 degrees.

The goal of this section is to determine the amount of encoder ticks it will take to move the arm from its starting position to a position around 90 degrees. There are a few different ways this can be accomplished. An estimation can be done by moving the arm to the desired position and recording the telemetry feedback from the Driver Station. Another option is to do to the math calculations to find the amount of encoder ticks occur per degree moved. Follow through this section to walk through both options and determine which is the best for your team.