High Speed Motor Control

Overview

The project suggested was to design a system for high speed motor control using the PIC 32. To demonstrate the motor control, a two degree of freedom (2DOF) robot arm was designed to throw and catch one ball with itself.

Team Members

• Sam Bobb (Electrical Engineering senior)
• Daniel Cornew (Mechanical Engineering junior)
• Ryan Deeter (Mechanical Engineering junior)

Mechanical Design

Theory of Parallelogram Design

Equations of Motion

Commanding the arm is much easier for a user to do in x- and y- coordinates than in motor angles or encoder counts. Therefore, equations were required that would translate x- and y- coordinates into angles from horizontal and then into encoder counts. Equations to express the reverse (encoder counts to angles to x- and y- coordinates) were also needed to evaluate the accuracy of the execution with respect to the command path.

$x=L\cos(\theta _{1})\ +\cos(\theta _{1}+\alpha )$

$y=L\sin(\theta _{1})\ +\sin(\theta _{1}+\alpha )$

$\alpha =cos^{-1}\left({\frac {x^{2}+y^{2}-L^{2}-(2L)^{2}}{2L^{2}}}\right)$

$\theta _{1}={\frac {-(2L\sin(\alpha ))x+(L+2L\cos(\alpha ))y}{(2L\sin(\alpha ))y+(L+2L\cos(\alpha ))x}}$

$\theta _{2}=\theta _{1}+\alpha \,$

Note: $\alpha \,$ is used to calculate $\theta _{1,2}\,$ in the MATLAB code and is not ever sent to the PIC.

Materials and Construction

The arm is constructed from aluminum and carbon fiber. These materials were chosen due to their light weight and their availability. The extended link of the arm is made of carbon fiber, as are two of the other supporting links. The final link is made from bent aluminum sheet because that link houses two bearings and removing

Results

It was awesome.