Many of you out there sure heard of the PID controller or the three terms controller (Ibrahim, 2006). With the application in more than 90% of industrial process and control, surely it attracts mostly everyone to use it in robotics application. I know this because I am one of them who tried to use it on my robots.
After searching for algorithm to program the PID, I found out that it is quite simple per se. You just need to have an integrator, a derivation and a proportional value of the error in the desired and actual value.
By the time I saw this, I kept wondering how should I have integrator and derivative in my programming. Only after sometimes that I realize that numerical methods are needed. Numerical methods is actually converts known mathematics to discrete form. Anything can be transformed, integrator, derivative, ordinary differential equation, partial differential equation, matrixs, anything you can name.
Moving on, with the discrete form PID, I put it to test. I was doing a DC motor position control using a simple DC motor and a potentiometer. Turns out, it did not worked out as miraculous as the great PID claimed. The motor was shaky like some earthquake is happening.
The ideal version of PID does not seems to convert well to practical usage. In fact, anything that is ideal or theoretical never can convert well to practical or real world usage. There are more stuff to consider before implementing the PID in a real system. Two of the most common problems are saturation windup and derivative kick.
Stay tuned for the next part.
Inspiring Creative and Innovative Minds
Ng Khin Hooi
Faculty of Electrical Engineering
Universiti Teknologi Malaysia
This blog is officially closed. Do check out the new blog at http://www.utmrobocon.com
Friday, November 5, 2010
What a Solid Works Wonder, to draw and render a motor from scratch. Kudos to Fazzlil for the picture. Some notes on DC motor here.
Some say that DC motor is very good and robust but the performance does not last long. That is why it is necessary to purchase new motor each year (provided there is money). The speed and torque can be very high. On the other hand, DC Brushless Motor performs less than DC Brushed Motor but it can last much longer. Give and take, I guess the DC brushless motor is better in terms of price.
Some times, DC Brushed Motor can be a dangerous object to play with. That is why a good motor driver is needed to run a motor. Companies have tried for years researching the best motor driver. That is why a good motor driver is very expensive, ranging from hundreds to thousands.