Hanso
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Thanks PKW. I've worked today on the grabber. I tried pincers first, but I wanted to stick to the triangle form. With three pincers, grabbing a rectangular container wasn't working. That's why I came up with a mechanism that opens and closes with diaphragm blades, enclosing the container. The result is the following: A video of the grabber can be viewed on Youtube: Hope you like it. /Hans -
When I was building the Robot Arm (see my mail thread here), I stumbled upon the ABB robot flex picker (also known as a delta robot). I was amazed about the simple construction and how fast it can work. Although I am definitely not making the first one of Lego, I wanted to build my own version of it. In this thread you can follow the work in progress. I have now build the base and the three arms that will support the grabber. The grabber will be able to pick up the candy containers and move them to a different location. Don't know yet what its place will be on the layout, but I am confident that it will have its use. Photos can be found at Flickr, click on the picture below to see some more pics and an animated gif. Please let me know that you think of it. Enjoy, Hans
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RohanBeckett was right. Doubling the number of driven wheels, also increased the number of gears and therefore the friction. With four wagons attached, the train did run but you cannot say it was a smooth ride. So, I decided to use the regular train motor 88002. Persistence may be good, but having an open mind is even better ;-) As a team we decided to use existing Lego parts only (with the only exception for Mindstorms sensors from other suppliers). Meaning: how to control this 88002 PF motor by an EV3 without altering anything? The solution is simple: the rechargeable battery box 8878 has a power control dial (see photo below). If you connect this dial to an EV3 motor, you can simply control the speed. The first prototype looks like this: This concept works really fine. As you can see at the right of the previous photo, two PF motors 88002 are connected to the battery box. Both the front and the rear bogie are now powered, giving the locomotive enough momentum to pull the four wagons and run smoothly through the curves. A video of the working train can be viewed on Youtube: As you can see in the photos as well, it wouldn't be possible to recharge the battery. There is simply no room for the power plug. Since this functionality is also mandatory, I made a second concept. The principle is the same, but now with a little room to insert the power plug. Enjoy, Hans
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Thanks, Aventador2004. And a thanks to your kind reply as well. Happy Easter, Hans
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In one of the previous updates, you can read about the pneumatic compressor with a automatic start/stop. This was a mechanical system: between the battery power and the motor driving the pump, a switch was installed. The switch was connected to lever. The lever was connected to a shock absorber and a piston. The principle worked fine, but it was very difficult to get it fined tuned. The last version turned the motor off at a pressure of 34 - 38 Psi (which was good), but the motor was turned on again when the pressure dropped below 10 Psi. This pressure is too low for the grabber, there was not enough grip causing the container to fell off. So, I bought a digital air pressure sensor (Mindsensors, PPS58-Nx): This sensor reads the actual air pressure with a maximum of 58 Psi. I connected it a Mindstorms NXT: The minimum air pressure is set to 20 Psi and the maximum is set to 35 Psi. By this means, there is always enough pressure to operate the grabber of the robot arm. You can see a video of the pneumatic compressor with digital auto start/stop at our Youtube channel: Enjoy, Hans
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Thanks, KikoTube.
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I tested the extended loco in a durability test. Started with a fully charged battery, the train ran for 3 hours and 45 minutes. Better than I expected. A full round took at the start 22,3 seconds and at the end 27,1 seconds (including a 4 second break at the yellow marker). So, the train speed is quite constant. A video of the test can be viewed on Youtube: Please note that the color sensor has been placed under an angle. If not, it would read the colors correctly. I used two bars (4L, id 30374) to achieve this angle. Enjoy, Hans
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For our Sioux.NET on Track project (see https://siouxnetontrack.wordpress.com), we not only write a PC application in Microsoft.NET (C#). But we also write quite some code that runs on the EV3 bricks. In this article, you'll find programming tips & tricks for the Lego Mindstorms EV3 programming environment. Is it possible to have two or more EV3’s in Daisy Chain mode and use WiFi to connect to the PC application? Yes, you can. Read the full article how you can achieve this at the blog: https://siouxnetontrack.wordpress.com/2017/04/08/how-to-ev3s-in-daisy-chain-mode-plus-wifi You can use two or more threads in parallel to run on an EV3. But how do you synchonize them? Read the article how to do this at the blog: https://siouxnetontrack.wordpress.com/2017/04/02/how-to-synchronizing-two-threads/ More to come later. Enjoy, Hans (moderator of our Wordpress blog Sioux.NET on Track)
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Thanks for the compliment. I would love to share the LDD, but I don't have one. And I don't think that I will make one (too much work). You'll have to do it with the pictures, sorry for that. Kind regards, Hans
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Have been busy with 'real work' the last couple of weeks. Finally got some time to work on the project again. I have written a test program to I have made a small test program for the robot arm to load the train with two containers. Loading the two wagons was done in one minute, so much faster than the candy crane. Have a look at the video and please share with me what you think of it. Kind regards, Hans
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Thanks for the compliment. I assume that you mean "with the EV3 motor", it is not a NXT motor. And yes, one of the goals of our project is that we forbid ourselves to modify any Lego parts. The thinking behind this, is that in our "real projects", you also have to face these kind of challenges and that we are restricted to specific hardware because of the costs. Apart from silicon spray, we definitely need an extra pair of rechargeable batteries ;-) Hans
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Instead of adding weight to the train, I decided to add traction by means of an extra powered axle. The train has therefore been extended to an articulated version. The first three axles of the locomotive are powered: And this is how the real versions look like: And by the way, I now use the elements as advised by RohanBeckett to make the bogies much stronger. Thanks again for the tip. /Hans
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In the Netherlands, in the last class of the secondary school, you have to write a study project (for the Dutch: "een profielwerkstuk"). My son (17) choose to build the soccer robot from the Eindhoven University. More information about the real robot can be found here: http://www.techunited.nl/en. For the study project, my son wanted to know if it would be possible to build a single robot with the same functionality as the real one, meaning: The robot should drive in any direction using omni wheels The robot can see the ball The robot can drive towards the ball The robot can grab the ball The robot can shoot the ball The robot 'knows' its location on the playing field The robot has been build by Lego Mindstorms, with a total of 4 EV3 bricks, 9 large motors for the movement of the robot, a Pixycam camera for the vision, 2 large motors for grabbing the ball and 2 medium motors for the shooting. A gyro sensor is used to make sure that the robot only makes one full turn (360 degrees) when it is searching for the ball. Apart from the Pixycam, everything is regular Lego. The result of his study project is shown on the picture below. The robot is able to drive, locate the ball (it should be in a range of 2,5 meters otherwise the camera won't see it), drive to the ball using a simple PID control algorithm, grabs the ball and shoot the ball (if you click on the picture below you will be teleported to my Flickr page containing more images of the robot): Last Saterday, during the open house of his school, my son was invited to demonstrate the result of his study project to the visitors. A small video of the robot during the demonstration can be viewed on my Youtube channel. Please let me know what you think of his study project. And if there is more interest, I can post some more details. Kind regards, Hans
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Until 2016, the train was a PF powered train and a NXT + HiTechnic IRLink to control it. The NXT was connected using Bluetooth with the PC application. Everything works fine, but the BT connection was quite unreliable. Therefore, we decided to switch to a EV3 powered train for Lego World 2017. Although I really appreciate the suggestions for the PF + NXT, this is not the direction that we want to go to. /Hans
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Dear RohanBeckett, Thank you for your suggestion. I have now used the 87082 element to keep the middle section in place: That works fine. But your element is even better, I will order a couple of them. Do you have any suggestions for me for the traction problem? Regards, Hans
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Yesterday, I wrote a new test program to see how the speed will drop when the battery gets empty. The test program keeps the train running, getting a 4 second break at the yellow mark and measures the time for a full round (including the break): The locomotive doesn't have enough traction, so I added some weight (approx 200 gram) on the front of the locomotive so the wheels have more traction. Of course, I will need to solve this problem. I started the test with a full battery. After 90 minutes of continuously driving, the battery was almost completely dry: I downloaded the file to my PC and calculated the time for each round. At the start, the train needed about 24 seconds for a full round (including the break of 4 seconds). At the end, the same full round took the train 8 seconds more. In the picture below you can see all the data plotted in a graph: Everything together can be viewed in a small Youtube video: So, what have I learned: I need to add weight to the front of the train to get more traction or redesign the train that it will be more balanced. Since the train won't be driving continuously, I expect that a full battery can be used in a train for 2 hours, maybe 2,5 hours. At Lego World, we need to have a spare battery since the train should run from 10:00 am until 5:00 pm (= 7 hours in total) If you have any suggestions to make, please drop me a note. /Hans
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You can watch a short video with a test run of the Lego trains driven by a Mindstorms EV3. During the test, I found out two things: The gear ratio is wrong The bogies are not strong enough Gear ratio When I designed and build the locomotives, the gears looked like this: But even on a motor speed of 90, the train was moving forward slower than a disabled turtle. Apart from the train speed, a high motor speed means also a high power consumption. Switching the gears did the trick: Sometimes, a solution can be so simple ... Bogies The bogies are designed like this: In principle, they work fine. However, if the train speed should increase, the torque on the gears is sometimes too much. Resulting in a middle part coming loose from the bogie: I have looked for a piece that would fit in between, but cannot find another brick than the new element 27940 (so, if you have a better suggestion please let me know): If I put this element in between, I hope that it will hold the middle section in place (marked red): I have ordered them at the Lego site, it normally takes 2 - 3 weeks (!) to arrive. I will let you know later if it works. A video of the train test, can be watched on Youtube: In the video, the train speed is set to 40 (out of 100) with the new gear ratio. I will add some more bricks (= weight) inside the front part of the train to get more traction on the wheels. The train has run for more than an hour without any problems. I didn't have the idea that the train speed dropped too much, the battery indicator was still on 'fully charged'. In a second test I will measure the time for each round to see how the train speed drops (when and how fast). I'll keep you posted. Enjoy, Hans
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The pneumatic pressure for opening and closing of the grabber, is generated by a motorized pump. To prevent the air pressure to be too high, I made an automatic start/stop system for the motorized pump based on the air pressure. The principle is simple: connect a pneumatic piston to a shock absorber. When the air pressure is high enough, a PF switch turns into the 'stop' modus. If the air pressure is beyond a threshold, the shock absorber turns the PF switch back into 'start' modus. In the pictures below you see the elements needed for this auto start/stop system: In total, three shock absorbers (with soft spring) are needed to generate enough backforce for the piston. The result with the air pump and the motor looks as follows: If you connect this to the robot arm, you see how the automatic start/stop works: Enjoy, Hans
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And here is a first video of the robot arm picking up a candy container: It is just a small test to see if the robot arm can pick up a container from a predefined place. Enjoy, Hans
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Thanks, Capparezza, for your kind words. The pneumatic has been added to the robot arm. The pneumatic switch is controlled by a Mindstorms M motor. Photos can be found on Flickr: Video can be found on Youtube: Enjoy, Hans
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Thanks "Nerds for President". Will definitely vote for you when you will be candidate. Regards, Hans
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I have updated the driving of the turntable for the 5th axis, see pictures below. Now this movement is also working fine. Next on the To Do list: adding the pneumatics to control the grabber. Hope to have this finished by the weekend. Best, Hans
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Click on the picture to watch a small video with the pneumatic pump and that we reached almost 3 bar with this simple pump system. Enjoy, Hans
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Hi Busterhaus, I needed to remove the black gears because they were to tight. The two tan driving gears leave a little bit more space, but now the 5th rotation is indeed jerky. I need to look into that. Putting back the black gears is however also not a good option. What you can't see (I think) on the video, is that movement 4 (wrist roll) often fails. I use the technique you mentioned to determine the end stops. That is, if the rotation power is zero, then it has reached an end stop. But too often the rotation is a bit too heavy, which also result in an (early) motor stop. I will have to look into that as well. Summarized: it all works, the base is there. But is does not work good enough. But that is the fun part: making it work perfectly. Thanks again and keep you all posted. Enjoy, Hans
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New photos posted on Flickr (all movements implemented now, the opening/closing of the grabber is on the todo list): All six movements can be viewed on Youtube: As you can see on the photos, I have add a manometer (Lego 64065) as well. Just for fun ;-) Enjoy, Hans