Showroom WKOM 6DOF AC Servo Motion Platform

Hello,

This is my first post to describe the project I have just completed. 6DOF motion platform based on the AC Servo drives, Arduino based controller and my own software both for the controller and the PC. The result looks like on the pictures attached. In the following posts I will send the link to the short movies on how it works and the design and build steps.

Wojtek

The control unit with the AC servo drivers is housed in the PC type case (see picture attached). The software on the PC links to the SimTools via "memory file".

And these are the short movies on how it works:

Congratulation on a nice compact design , and more and more it seems AC systems is moving towards the the average joes sim budget .. very nice .. of course wrre a nosey lot here but in a nice way .. so gonna ask for some specs regarding Servo drivers and Motors ...are those Planetary gearboxes , and also the magic figures of speed and weight Thanks for posting and adding another well built DIY 6dof project to the Xsimulator.net stables

Great!!! so compact and powerful. I want to see more development information.

Well done! Very neat and looks like a lot of range whilst being very compact.

Just thought of a question.
I see in the video description that you used 1KW motors.
Do you think you have plenty of power headroom with these?
What Im getting at is, do you think 500W could have been sufficient?
Im only asking as the time will come when Im looking to go AC servo and just trying to get a feeling for what is feasible.

I think my configuration could be considered as a bit overpowered. I would give a chance 500W servos. Here is why:
- I am a bit heavy (95kg) and the rig does not seem to notice I am sitting on it.
- I have reduced the angular speed of the servos by the factor of 2 (via the controller software), because the full speed seemed to me too scary
- You could stick with the full angular speed and slightly reduce the servos' arms length to deal with the lower torque.

Anyway, the servo motors and the controllers after 2 hours of play are as cold as at the beginning.

In the beginning, the project of the 6DOF motion platform was a kind of excuse to fulfill my dream of having a mechanical workshop. As I was a great fan of the flying simulators and an engineer with the programming skills I wanted to extend my technical adventure into the realm of the heavy hardware. Therefore I needed to learn how to: weld, CNC machine, precisely cut the steel profiles, polish and paint them. I started with the welding equipment and skills. I was really surprised how "computerized" it is these days.

The welding machine is digitally controlled piece of hardware. You just set all the parameters on the screen and off you go!

This is my first welding:

Not so pretty however, the fun was great.
The first project was the solid table for my CNC machine:

Speaking of the CNC machine, I needed it to mill the precise parts of the motion platform (servo arms, servo holders, encoder holders, etc.). I decide to buy a cheap Chinese CNC 3D machine. I have changed some parts (this might be a topic for a separate thread) and I am happy with the results. The machine helped me a lot with the motion platform build.


Then I needed the precise loop-saw which was necessary to cut the steel profiles at the specific angle. It is a heavy thing, more than 12o kg, fluid cooled and works perfectly.



And at the end, the precise drill:


The workshop looks like that:


In the next posts, I will present the 6DOF motion platform build process.

I like your thinking.
You want a motion platform which means you need a well equiped workshop. Double win!
Every project is an excuse to buy some equipment.
Over the years, Ive spent more time setting up the workshop than I have actually building anything in it.

When the workshop started to be fully operational, I welded the main parts of the frame. As my welding skills were on a beginner level, there was a lot to be polished on the steel profiles (the joining points).

Anyway, the final effect is OK.


I painted the frame parts with the black matt spray and did some preliminary assembly:

CNC machine milling the servo arm from aluminum.

As a result of the milling process, I got the servo arms and the servo gearbox mounting plates. They needed some polishing however, the CNC machine did a good job.

About the equipment I decided to use (all of them from Xlichuan company):
1. AC Servo motor: LCMT-10L02NB-90M04025B
2. Driver for the AC servo motor: LCDB2-102002-LB822
3. Planetary gearbox: PLF90 with the reduction ratio 20:1

The development rig to figure it out, how to control the servo and how to integrate the additional encoder on the gearbox output axis.

After seeing your work, I just developed a need for a CNC mill

Yeah, that CNC...

Why didn't you use the encoder on the motor and got another one?
Couldn't you control positioning directly on the controllers?

Like the compactness. That would probably be tolerated by my wife inside the house...

In fact, I use both encoders. The one in the motor is very precise and fast, but as it is the incremental encoder, the readout is relative. The additional encoder, on the gearbox output axis, gives the real angular position of the servo arm vs. the frame. I use the latter just to align (zero) the incremental encoder and additionally, it is used to control the servo arm just in case it moves outside the allowed angle range. I found the resolution and sampling rate of the A/D converter in Arduino much below what could provide the smooth operation of the motion platform. On the other hand, the incremental encoder is accurate and fast.
I could get rid of the angular encoders, but then I will need to manually zero the rig before each session. And there will be no safety guard provided by the angular encoders. It makes the Arduino controller code a bit more complicated, but in fact, this where the majority of the fun comes from for me (I am more towards developing software than designing and building hardware).

Like me...
Did you saw my rig?

I use internal hall sensors on the bldc motors to determine position, not an encoder, but works like one with low resolution.
All with an ESP32 that is able to control 3 motors (I use two for the 6 actuators). They are really fast.

I use switches to detect limits. You could use magnetic switches or something similar.

The idea is:
When we connect the rig, she searches for the minimum switch.
When we reach minimum I set position to zero.
Then look for maximum switch counting turns or steps. In your case the incremental of the encoder.
Wen we reach maximum I store that position as maximum.

In operation, to be safe if we lost position, what happens is if we enable one of the switches, then the code resets the counter to zero if minimum or to the maximum steps if maximum switch.
This allows the rig to keep working on limits. She auto corrects.

Yes, I saw your rig. It is impressive work you've done!

Your idea to use the micro-switch for the endpoint detection could make my rig a bit cheaper and less complicated. What is important, this would not compromise the quality. In fact, I could just detect only one endpoint while starting the session. The long term accuracy of the AC servo combo makest this idea doable. I do not need to determine each time the movement range, as it is already determined by the step size and the step count of the AC drive. The second micro-switch would play the role of the safety guard.

Hello Woyteck.
Nice to see another great sim! Really impressive and outstanding work. For sure you've put a lot of effort into building it.
It would be interesting to read about how you drive the servo amplifier from the microcontroller. Do you use analog speed mode or maybe you use step dir position mode on the servo drive as input? I'm currently playing around with one Chinese AC servo drive and exploring different controll methods, thus it would be interesting to know how you are doing it.
Also if I understand it correctly you've squezzed servo aplifiers into a PC case? Can you post a picture how did you layed them out inside the case? What's the size of this case - a typical midi tower?

Cheers from Wrocław!