[EV3] Fully Automated Candy Warehouse

[Hanso]

8 hours ago, ColletArrow said:

Looking good! I really can't wait to see this in action.

Thanks, ColletArrow. Have now ordered some bricks, will take some time to get them delivered (Lego shop takes normally 2 - 3 weeks when you order spare elements).  Meanwhile, I will be working on motorizing the stuff.

Hans

[Hanso]

New photos of the work in progress have been added to the Flickr Page.

Enjoy, Hans

[Hanso]

Most of the bricks were finally delivered to finish building of the shelves. I wrote a first test program to test the stacker robot. Although the robot cannot move horizontally, the other movements work as expected.

Photos can be found on Flickr (click here or on the picture below).

 

And a video on Youtube:

 

[Hanso]

Some additional background information about the first test run.

 

Up/down movement

The motor on top of the stacker robot is taking care of the up/down movement of the platform with rollers. The height of the 32M axle is exactly enough to reach the four levels of shelves. The bottom and top position are determined by touch sensors, the two positions in between are determined by the number of rotations.

I do prefer a solution that uses a (touch) sensor to 'find' the correct position for all levels, but have not find a suitable and workable way to do this.

 

Horizontal movement of the platform

The horizontal movement of the platform is controlled by the motor that is connected to one of the up/down sliders, see left photo below. A color sensor is used to 'find' the middle position (the motor next to it is for the rollers of the platform).

When the platform moves to an outer position (remember that it can reach to both sides), the end position is determined by the rotation sensor. If the motor power goes to zero, it is interpreted as 'end position' reached and the motor stops. Don't forget to put a small waiting time between 'motor on' and the sensor read; because of the program execution speed, the motor speed is still zero when the sensor value is read which results in the platform not being moved at all and more important, it is then considered that the end position is already reached. There is no way (yet) to determine if the platform is correctly connected to the shelf.

 

Platform rollers

The rollers are driven by the motor on top of the platform. It is just switched on/off for a certain time, there is no guarantee that the container was successfully picked up from or delivered to the shelf. I am thinking of adding a (ultrasonic) sensor to determine if the container has successfully left the platform / reached the platform. What holds me  back, is the reliability of the ultrasonic sensor in  detecting the container. But I guess I''ll just have to try to find out. Another hesitation comes from the number of available ports. I will need (at least) another port for the sensor that will be responsible for the horizontal movement of the stacker robot. If you add the two touch sensors for the top/bottom position of the platform and the color sensor for the horizontal positioning of the platform, all four sensor ports are already taken. If I can find a way to determine the four levels with one sensor, I will have a free position for the container detection sensor.

 

So, although the first test run is already quite nice, there is still some work to do ;-)

 

Ideas are of course always welcome.

/Hans

 

Edited August 22, 2017 by Hanso

[Hanso]

New photos have been added to the Sioux.NET on Track Flickr page (click the photo below):

 

On the photo, it seems that both sides of the stacker crane has shelves now. But it's not. The left half has been build just a little (not enough bricks ;-).

 

The horizontal movement has now been added, a video of a test run where a container is delivered to the warehouse and then is stored on an upper shelf, can be viewed on Youtube:

 

What needs to be changed, is how the stacker crane can determine the exact stopping position in front of a shelf (= horizontal movement). In the video, the stopping position was hard coded, i.e. the number of rotations from the end position at the right. But I noticed that the stacker crane stopped not always at the right position. So that's something that needs improvement.

Another improvement that needs to be done, is how the cables 'hang around'. So, enough things to do ;-)

 

Please let me know what you think of it.

Enjoy, Hans

[GroundskeeperWillie]

Looks great!

Regarding horizontal positioning, the motion appears a bit jerky. Maybe that's why it is sometimes off. I'd say that given the gearing, using number of rotations should provide adequate positioning. An improvement might be to always overshoot and move a little back when moving in one direction. That should eliminate gear slack.

[thekitchenscientist]

Have you considered mounting a roller on one touch sensor in the tower? You could have a corresponding vertical track which kept the sensor depressed between levels but allowed it to spring out to signal a stop. This could have the added benefit of being able to count the 'clicks' so you know which position you are in.

Speak of clicking, could you use an NXT sound sensor to sense/count clicks. Could the protective gear from the power functions provide the noise?

[Hanso]

10 hours ago, GroundskeeperWillie said:

Looks great!

Regarding horizontal positioning, the motion appears a bit jerky. Maybe that's why it is sometimes off. I'd say that given the gearing, using number of rotations should provide adequate positioning. An improvement might be to always overshoot and move a little back when moving in one direction. That should eliminate gear slack.

I noticed the jerky motion too, but didn't think of a solution yet. I think that it is caused by (the combination of) 1) the weight of the stacker crane and 2) the fact that the motor is on top of the tower and the rotation is needed at  the bottom. Or the reason  is the cabling hanging around. Well, as you see I don't know yet but it needs to be solved.

I don't understand your suggestion for improvement how this would help the gear slack?

8 hours ago, thekitchenscientist said:

Have you considered mounting a roller on one touch sensor in the tower? You could have a corresponding vertical track which kept the sensor depressed between levels but allowed it to spring out to signal a stop. This could have the added benefit of being able to count the 'clicks' so you know which position you are in.

Yes, I considered that. Even better, that would be the ideal solution since it would be far more accurate (although the worm gears are quite accurate so far, much more than the gear rack). But there is not enough place for a touch sensor without changing  the current structure too much.

8 hours ago, thekitchenscientist said:

Speak of clicking, could you use an NXT sound sensor to sense/count clicks. Could the protective gear from the power functions provide the noise?

Nice idea, but would that be accurate enough. But if I'm right, the NXT sound sensor responds to decibels, so someone clapping his hands or a dog barking could give false measurements.

 

[GroundskeeperWillie]

Hi Hans. My suggestion would not remove gear slack, but by always approaching a stop in the same direction, the revolution count would accurately determine the position regardless of gear slack. When moving "left" you would stop normally, after maybe 100 revolutions. When moving "right" you would move too far (maybe 110 revolutions) and then a little left (10 revolutions) and stop. Then any slack will not affect the position (as long as no gear skipping occur). Of course, a sensor based solution is more fancy.

The jerky motion looks like the motor is being stressed. If that is the case, it could be fixed by lower gearing or a more powerful motor.

[Hanso]

5 hours ago, GroundskeeperWillie said:

Hi Hans. My suggestion would not remove gear slack, but by always approaching a stop in the same direction, the revolution count would accurately determine the position regardless of gear slack. When moving "left" you would stop normally, after maybe 100 revolutions. When moving "right" you would move too far (maybe 110 revolutions) and then a little left (10 revolutions) and stop. Then any slack will not affect the position (as long as no gear skipping occur). Of course, a sensor based solution is more fancy.

The jerky motion looks like the motor is being stressed. If that is the case, it could be fixed by lower gearing or a more powerful motor.

Hi GroundskeeperWillie,

First of all, thank you for thinking with me. But I still don't understand the suggestion. Why would "100 rotations left" result in more accuracy than "110 rotations left followed by 10 rotations right"? Hope you can explain it to me.

Best,
Hans

[GroundskeeperWillie]

19 minutes ago, Hanso said:

First of all, thank you for thinking with me. But I still don't understand the suggestion. Why would "100 rotations left" result in more accuracy than "110 rotations left followed by 10 rotations right"? Hope you can explain it to me.

It will if there are, say, 5 motor rotations of slack in the gearing. Then, whenever the direction is turned, the first 5 rotations would not change the position. So whenever the direction is changed, 100 rotations would only move 95 rotations' worth. By moving first 110 you get to "position 105", then moving another 10 in the other direction you would end up at "position 100". Does it make sense?

Of course, if you could measure the slack precisely, you could account for it directly when changing direction. The approach above should work without an exact measurement as long as the extra motion is larger than the slack.

[Hanso]

Aha, I understand now. Smart thinking ;-)

Will give it a try in the next weekend, but still, I don't want to 'rely' on this. My direction of thinking is still using a touch sensor with a 'click' per column of shelves.

 

[karmajay]

Thanks for this thread! I have a project I'd like to build in Lego and need to just get started but I don't have any "deep" technic experience besides building sets. This thread both seems to make it possible AND unreachable at the same time!

 

[Hanso]

12 hours ago, karmajay said:

Thanks for this thread! I have a project I'd like to build in Lego and need to just get started but I don't have any "deep" technic experience besides building sets. This thread both seems to make it possible AND unreachable at the same time!

Haha, that is a very nice compliment. When I look at my own buildings from the period I started to create my own stuff and compare it with today, I dare to say that my skills increased (and my wallet becomes more empty ;-). But that took time, so don't let it keep you from starting your project and you will see that it is also possible for you.

Enjoy, Hans

Edited September 7, 2017 by Hanso

[Hanso]

I've added a cable carrier to make sure that the cable doesn't get stuck when the platform is moving up and down.

As you can see on the picture, I use the Mindsensor flexicables and the connectors to extend the length of the cable. I really can recommend these cables, they are much easier to use than the original Mindstorms cables.

 

In the video you can see how the cable carrier works:

Enjoy, Hans

Edited September 24, 2017 by Hanso

[OneMoreRobot]

The Energy Chain looks excellent & thanks for sharing the info about Mindsensor flexicables - I shall start using them myself.  

Need to route the cable for the other Medium motor through it as well.

Cheers OMR

[Hanso]

19 hours ago, OneMoreRobot said:

The Energy Chain looks excellent & thanks for sharing the info about Mindsensor flexicables - I shall start using them myself.  

Need to route the cable for the other Medium motor through it as well.

Cheers OMR

Thanks. Yes, and the cable for the color sensor need to go through it. So that means three cables, don't know if that is possible. Maybe I just need three cable carriers...

[Aventador2004]

Interesting, it looks wobbly though.

[Hanso]

On 26/09/2017 at 5:35 AM, Aventador2004 said:

Interesting, it looks wobbly though.

I started redesigning the Candy Container Warehouse. First step: improve the horizontal movement.

Will upload pictures of the work in progress. Below you find the motor that is controlling the horizontal movement, now being built in into one of the towers.

As you can see, there is no gear reduction yet. Need to figure that out in the small space ...

Enjoy,
Hans

[ColletArrow]

It looks good, and I'm glad to see this neat topic getting revived. I'm sure you'll figure out a way round the problem, you always do!

[Hanso]

On 28/03/2018 at 3:40 PM, ColletArrow said:

It looks good, and I'm glad to see this neat topic getting revived. I'm sure you'll figure out a way round the problem, you always do!

Thanks, ColletArrow. And you were right, I found a way for the gear reduction. I also had to make a bit more room where the EV3 cable was connected.

Enjoy,
Hans

Edited March 31, 2018 by Hanso

[Hanso]

Another thing: the final version of the Warehouse will have two stacker cranes. One crane will be storing the candy containers arriving from the Automatic Candy Sorter, the other crane will retrieve container to send it to the delta crane.

That means that every storage compartment needs to be accessed from two sides. I made a proof of concept to check if the container can be stored from one side and retrieved from the other side:

And hooray, it works!

In the next period, I will need to work on one stacker crane. When it is working, I will clone the crane and extend the warehouse.

Enjoy,
Hans

 

[Hanso]

I uploaded a new video of the redesigned stacker crane that is part of the Candy Warehouse:

Some parts are still missing (in backorder), so some bricks are not in the right color (like the yellow liftarm in the base of the crane).

Updated:

• Horizontal movement of the crane has been improved (much smoother now). Major change: motor is now inside the left tower.
• 'Stops' added to determine the horizontal location of the crane.
• Motor responsible for horizontal platform movement is now fixed to the top (you can see it at the top of the right tower)

I will add some more detailed information about the improvements later this week.

Enjoy, Hans

Enjoy

Edited April 14, 2018 by Hanso

[Hanso]

As promised more detail of the improvements.

Horizontal movement of the stacker crane
In the previous version of the stacker crane, the motor that was responsible for the movement, was build on top of the crane. Resulting in a very long axle going through the left tower to the bottom of the crane. In the current version, the motor is build-in into the left tower. This results in a almost direct coupling to the corresponding gears, and that results in a smooth movement. See the photo below.

 

Horizontal stop locations for the stacker crane
The stacker crane needs to stop exactly in front of a container storage. If not, the gears will not connect which results in the container not stored or retrieved correctly. Because of the distance, counting the number of rotations will probably not be accurate enough. In the previous version, the gear racks for the horizontal movement were placed in the middle. In the current version, I moved them to the two sides. I didn't have to move the gears in the stacker crane, so this was a relatively easy change. Having now room 'in the middle', just like the motor that was build-in into the tower, I now build-in a touch sensor into the tower. An axle with a Technic Ball Joint (32474) at the end, makes sure that the axle glides smoothly along the flat tiles. A stop is made by two slopes (85984), the axle with ball joint lowers and the touch sensor goes to 'released' state.

 

Horizontal platform movement
In the previous version, the motor responsible for the horizontal movement of the platform, was attached to the slider of the right tower. In principle, this worked fine. However, it has two disavantages: 1) The weight of the sliders and 2) The motor needed a cable carrier.

Because the platform also has a motor build-in for the platform rollers and a color sensor for the positioning, the platform would need three cable carriers in total. It might be possible to use one cable carrier for two cables, but definitely not for three.

I moved the motor that is responsible for the horizontal movement of the platform, to the top of the stacker crane. A long axle in combination with a worm gear, is used to transfer the rotation to the platform. The worm gear can slide smoothly along the long axle, in the picture below you see how the motor rotation is transferred to the platform, keeping the vertical movement in tact.

Edited April 22, 2018 by Hanso

[Hanso]

Uploaded a new video to demonstrate the work in progress.

 

In the video, two containers are stored in the warehouse. Not only to see if it works, but also to measure the time needed. The loading platform is at the right of the warehouse. The first container is stored at the nearest position to the loading platform (= bottom, right). The second container is stored at the most far position from the loading platform (= top, left).

Storing the two containers is less than 75 seconds which is perfectly acceptable.

 

 

Still waiting for more bricks to arrive to continue building ...

Edited May 1, 2018 by Hanso