91.548 Meeting 9: Motion Control

This week and next, we will looking at feedback systems and motion control.

I will be procuring a number of Gamatronix “Gamoto” PID motor control boards, along with motors that have built-in shaft encoders. (Note: for reasons that are not yet understood, the gamatronix.com web site does not work from the computer in the Engaging Computing Lab.)

Your task: design a mechanical system that uses the Gamoto board and a motor with quadrature encoder feedback. Look at the “Art of Motion Control” site (link below) for inspiration.

Use the Handy Cricket or a serial connection from a PC to talk to the Gamoto board. Play with PID control parameters, and get your system to demonstrate control problems like overshoot, damped oscillation, and (if it’s not dangerout) un-damped oscillation. Figure out a way to capture this data, and make graphs showing position-vs-time that demonstrate these modes (Gamatronix’ “Moto-View” software may be helpful).

Then get your system to reach a target without these problems.

Report on your work in a printed write-up. Include graphs. Describe what you have learned about motion control.

Motion Control projects are due Thursday, April 22.

Motion Control links:

• Motion control tutorial (pdf file), by Newport Corp. A good introduction to the main technical issues in motion control, typical mechanical systems, sensing, and feedback control. Original web link is here. This document was handed out in class.

• The Art of Motion Control, by Bruce Shapiro. From the home page: “The purpose of this site is to suggest that motion control is also an emerging medium for artistic expression.” A wonderful collection of science museum exhibits involving controlled movement that creates patterns and 3-dimensional structures.

• Feedback and Temperature Control introduction with interactive simulator, by Charles D.H. Williams. Solid introduction to control theory in textbook style but with web links and live simulator. Focuses on temperature control, but theory is directly applicable to motion control.

• Control, Dynamics, and Systems intro slide presentation, by R. M. Murray of Caltech. An excellent introduction to the field, showing the progression of control theory since the 1940s, and including contemporary engineering applications (e.g., anti-lock brakes, aircraft turbine engine control).

• Quick PID introduction, from a 1991 trade magazine article.

• FAQ on tuning a PID Controller. Practical recipes for getting a PID system to operate.

• Motion control for two robots, by Larry Barello. A nice narrative about developing a complete motion control solution for two Trinity Fire-Fighting contest robots.

• PID Control Information from John Shaw. Practical guides to PID controllers. eBooks for sale.