Sticky Notes

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Thursday, February 17, 2011

Practical PID Controller Part III

Before starting this part of the article, I would like to share some knowledge about realization of PID controller. What I have discussed in the first and second part of the article are about digital realized PID. In other words, the PID controller is written in form of coding and implemented in a microcontroller or microprocessor.

On the other hand, there is also the analog PID which can be realized using operational amplifiers (op-amp). I will not discuss much about this analog PID but basically, if you have attended Electronic Devices classes, there are some circuit where op-amps are used as summing junction, amplifiers, integrator and differentiator. This is where the circuit can be combined to perform as a PID controller.

Back to the Practical Digital PID Controller, I will discuss about the integrator part of the controller. The problem with integrator in a PID controller is the saturation wind up.

For example, let's us look at a motor driver, driving a DC motor. Let's put that the driver's supply voltage is only 24 Volts and the PID controller output is 26 V, it will be saturated to 24 V. The error will be held constant at 2 V until infinity time.

If the controller output contains the integral element, the error will cause the integral term to be integrated to a large amount. If the desired set point is about to reach, the error will cause a large overshooting and undershooting about the reference point.

Therefore to prevent the integral term to integrate, a flag is used. If the controller output is saturated, the flag will be set. And for the next sampling time, the integral term will not integrate. If the controller output is not saturated, then the integral term will be allowed to integrate.

This method is actually not a proven method to prevent from saturation wind up. For a complete analysis and proofs of PID controller this site can be referred to.

The source code for the implementation of Practical PID Controller can be downloaded here. Note that the code is released under the GNU General Public License.

The code too could be checked out from using Subversion at this server

Practical PID Controller Part II
Practical PID Controller Part I

Monday, February 14, 2011

ROBOCON Thailand 2011 Contest Video

Wow, the Thailand ROBOCON teams were fast. They even have participated in the local contest.

Monday, February 7, 2011

Think Big - Donald Trump

Here are some quotation from Trump:

“What separates the winners from the losers is how a person reacts to each new twist of fate,” says Trump. 

"My style of deal-making is quite simple and straightforward. I aim very high, and then I just keep pushing and pushing and pushing to get what I’m after. Sometimes I settle for less than I sought, but in most cases I still end up with what I want. You can’t be scared. You do your thing, you hold your ground, you stand up tall, and whatever happens, happens."

"My experience is that if you’re fighting for something you believe in – even if it means alienating some people along the way – things usually work out for the best in the end. The most important thing in life is to love what you’re dong, because that’s the only way you’ll ever be really good at it."

"Experience taught me a few things. One is to listen to your gut, no matter how good something sounds on paper. I’m a great believer in asking everyone for an opinion before I make a decision."

Although he is an entrepreneur, his concept in life more or less can be used to win in ROBOCON.

Extracted from the UTM Library Blog post

Tuesday, February 1, 2011

Singapore Robotic Games 2011

Singapore Robotic Games 2011 (SRG) which is also known as the Robot Olympics of Singapore since 1993. Recently, it was held  on 25 January 2011 - 27 January 2011 at Science Centre Singapore.

This event was organized to inculcate the automation culture to general public. It acts as a platform for the young engineers to expose more knowledge and experience in robotics sector.

There are 17 competitions were carried out by the organizer as listed below:
  • Open Category
  • Legged Robot Obstacle Race 
  • Legged Robot Marathon Race 
  • Wall Climbing Robot Competition 
  • Pole-Balancing Robot Competition
  • International Robot Contest - Challenge Course
  • RC Sumo Robot Competition
  • Autonomous Sumo Robot Competition
  • Micromouse Competition (Open, JC/ITE and Sec.Sch.)
  • Robot Colony Competition
  • Schools Robotic Competitions (for secondary schools)
  • RC & Autonomous Underwater Robot Competition
  • Robot Soccer Competition, and
  • Humanoid Robot Competition 

Cute puppies dance in open categories competition.

One of the wall-climbing robot was training...

Pole balancing robot competition is one of the most intriguing competition that attracted me the most.
During the competition, the robot have to carry the free fall pole with two axes of freedom and move along the specific path to perform the task.

High resolution rotary encoder was mounted at the moving axes in order to get the feedback so that it can maintain the pole in a stable vertical position.

Obviously, SRG required a higher technology level compare with Robocon. Robot like underwater robot, humanoid robot, intelligent robot needed advance of technology in term of mechanical, electronics and as well as programming. 


On the other hand, ABU Robocon with the different theme of  games every year make it even more challenging and interesting for the participated team. Robocon is an output of a team, thus it  required technology as well as the value of team work that bring the team for the victory. 

G-Robot from RT Corporation

All the young generation are encouraged to join this kind of event because it creates valuable friendship among young enthusiasts with similar interest and enable them to realize their dreams and improve their technical skills through the self-invented robots.

by kkx
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