One of our great readers Ivan just sent this through to me.
He has created a video explaining how a PID (proportional / integral / derivative ) controller works and shows an example of it running on a simple NXT robot towards the end.
Now the video is in Portugese (who says we don't cater for the international audience! :D) and although I've only done a semester of learning Spanish at university, I was able to keep track of what was going on.
Even if I didn't understand any of the writing (he goes through a *lot* of post-it notes!), it was still great fun to watch, the style, pace and music of it just perfect. I loved the little things that happen throughout, such as running out of room to write and having to add another post-it, and trying (unsuccessfully) to attach the NXT with masking tape :)
Ivan's offering to put in English subtitles, so if you're interested, please make a comment!
**EDIT: Ivan has added English subtitles! :) **
Showing posts with label PID control. Show all posts
Showing posts with label PID control. Show all posts
Monday, November 28, 2011
Saturday, May 14, 2011
Useful NXT-G Motor Block: Absolute position control
HiTechnic has released a new motor block that you can use in NXT-G. Here's an excerpt from the description found on the HiTechnic website.
Why the HiTechnic Motor PID Block?
This block is an alternative to the standard LEGO Motor Block. Unlike the Motor block, which when used with a duration of degrees or rotations, gives you relative control over the position of the motor, the PID Block is designed to give you absolute position control. With the standard Motor block, you might use it to go forward 45 degrees, go another 45 degrees, then go backward 90 degrees. Each time the motor turns an amount that is relative to the position that the block starts in. With the PID Block you specify an absolute position. For example, if you want the motor to go to position 45, you can pass in that value to the Set Point input of the PID Block and it will drive the motor to that position. If the motor starts at position 100, then it will go backward to 45; if it starts at 0 then it will go forward.
This type of control makes sense when your motor has a limited range of motion. For example, if you are using the motor to control the position of a robotic arm, you will likely want to make the arm go to a certain position and then have it do something. Since you may not want to keep track of the current position, it is often easier if you can just specify the position to go to. That is what this block lets you do. If you use the standard Motor block, then the direction and duration needed to get to a certain position will depend on the current position.
Here are some possible uses for the Motor PID Block:
- Steering mechanism on a car
- Linkage control system to follow the input from a sensor
- A selector mechanism for a sorter.
- A gripper mechanism that has multiple positions that you want to select between. Perhaps: Open, Closed, Crunch.
- A panning control mechanism where you want to accurately control the direction something is pointing.
Gus Jansson from HiTechnic demonstrates the block in the video below. Find more information and a download link here.
Why the HiTechnic Motor PID Block?
This block is an alternative to the standard LEGO Motor Block. Unlike the Motor block, which when used with a duration of degrees or rotations, gives you relative control over the position of the motor, the PID Block is designed to give you absolute position control. With the standard Motor block, you might use it to go forward 45 degrees, go another 45 degrees, then go backward 90 degrees. Each time the motor turns an amount that is relative to the position that the block starts in. With the PID Block you specify an absolute position. For example, if you want the motor to go to position 45, you can pass in that value to the Set Point input of the PID Block and it will drive the motor to that position. If the motor starts at position 100, then it will go backward to 45; if it starts at 0 then it will go forward.
This type of control makes sense when your motor has a limited range of motion. For example, if you are using the motor to control the position of a robotic arm, you will likely want to make the arm go to a certain position and then have it do something. Since you may not want to keep track of the current position, it is often easier if you can just specify the position to go to. That is what this block lets you do. If you use the standard Motor block, then the direction and duration needed to get to a certain position will depend on the current position.
Here are some possible uses for the Motor PID Block:
- Steering mechanism on a car
- Linkage control system to follow the input from a sensor
- A selector mechanism for a sorter.
- A gripper mechanism that has multiple positions that you want to select between. Perhaps: Open, Closed, Crunch.
- A panning control mechanism where you want to accurately control the direction something is pointing.
Gus Jansson from HiTechnic demonstrates the block in the video below. Find more information and a download link here.
Thursday, July 29, 2010
Hispabrick Magazine 008 with MINDSTORMS articles and interviews
Jetro informed me that Hispabrick Magazine has just released their eighth issue. You can view the magazine online using this link, or download the complete PDF by going to this link, and clicking "HM008 - English". Each of these options are free of charge.
Hispabrick Magazine is about LEGO in general, but this issue is especially an interesting read for MINDSTORMS owners, as several articles focus explicitly on MINDSTORMS NXT.
You will find an article about the MINDSTORMS Community Partners, as well as interviews with three of them, including Xander Soldaat, Fay Rhodes and me.
Furthermore, you'll find a tutorial: "A PID Controller for LEGO MINDSTORMS Robots". Finally, the article "Actuators for the NXT" talks about several actuators, including the new FIRGELLI Linear Actuators.
The issue also covers non MINDSTORMS topics, like Technic, Space, as well as reviews of new LEGO sets. You may also want to read the interview with Kjeld Kirk Kristiansen, the owner of The LEGO Group.
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