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 follow paths specified in a MATLAB gui.

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

GUI

The GUI used to control the arm was programmed in MATLAB using the "guide" function. The GUI code calls the other MATLAB functions and is rather small as far as the amount of new code in contains.

[insert screenshot of gui on the right]

Usage

There are a few main sections to the GUI that allow user inputs. The first section is the "Path" section, which allows users to specify the type of path the arm will follow. There are currently three path choices: "go to," "circle," and "trace." The "go to" path allows the user to specify a point that the arm will go to from its current position in five seconds. The "circle" path is determined through five values. The first two are the (x, y) of the center of the circle. The next two are coefficients on sin and cosine terms that are effectively the radii [CHECK THIS WITH SAM}. The last value is the time in seconds for the arm to complete the circle.

Results

It was awesome.