Showroom Ken Sim Rig - 6DOF Stewart with open design actuators.

I will now start my thread of the 6DOF sim rig I'm building.
The build started about two years ago so my first posts will show info and pictures as a catch up.
Because of the fact that life holds more than building a sim rig this project is on a sporadic time plan.

After seeing all the impressive builds in this forum I started to plan for a build of my own.
My plan is to build a 6DOF stewart platform with actuators in a open design.
By "open" I mean that the ball screw rod itself is the supporting construction.
I will manufacture the cylinder mechanics my self with standard plastic components.
I have not found any similar constructions already made so that makes me wonder if I'm on the way of doom.

The motors, the motor drivers and the ball rods will be the expensive part for me because I will buy them from external supplier.
When it comes to the controller and sensor system I will also use expensive parts but this I have access to because of my profession. I work with mobile control systems at a electronic manufacturing company.


In this first post I will show the first tests I performed in Jan 2022.

To try out the idea of this open design actuator I created a prototype by a steel pipe cylinder and mounted the ball screw rod in a simple way with welded threaded rods along the pipe.
Because of the supporting function of the ball screw rod itself I choose the more robust one, SFU2005.

I mounted two inductive sensors for end and home position sensing.
I mounted also two inductive sensors and a simple metal cam plate for counting the position of the actuator.

The upper end of the actuator was attached to a platform loaded with some heavy stuff like an old car battery etc.

The ball screw rod is driven by a 24V / 800W DC motor mounted on a wood fixture serving as a joint.


To control the motor I use a controller from ifm electronic, the ecomatController CR711S. It reads the end position sensors and the position sensors on fast counter inputs to calculate the level position of the actuator. The controller outputs a 24V PWM and a directional signal. The controller programming software is CoDeSys 3.5.
The controller output current is not enough to power the motor so the PWM- and directional-signal is fed to a DC motor driver, the Cytron MD30C. The driver only handles 5V signal so the 24V signals needs to be devided which is done on the Bread board.

Everything is powered by a 20A power supply from ifm electronic.


The test turned out well enough to continue the project.
If I figure out how, I will add a movie of the test later on.

If this open design is a disadvantage I will probably soon find out. Perhaps it's to mechanically week.
Perhaps it's to noisy or vulnerable to dust.
If anyone now why this design is not used, please advice.


I hope to show the next step soon.
Br Kenneth

In this second post I will show the making of the frame.

First a look at the sketch of the construction. (It was drawn in the end of 2020)
The design of the lower part has not yet been determined


As you can see it's a pretty week construction. I want to keep the weight down. I will only run this in VR so no need for monitors.
If the project reaches the final stage with acceptable simulation feeling I will probably strengthen the construction with diagonal braces.

In the summer of 2020 I put together the frame holding the seat, the steering and the pedals.




I figured it could be good to know the center of gravity, of the seat and the driver, before continuing with the main frame. In that way I can make sure that it is placed in the middle of the actuator mounts. (I probably read it in the forum somewhere.) For this I used a plumb line and my camera. The photos turned out to be quite funny so I post them as well.




After that the welding took a break until summer 2022 when I put together the outer frame.




Next post will show the construction of the actuators.
I will collect the photos and show them soon, I hope.
Br Kenneth

Now the actuators.
My idea is to build a actuator with only the ball screw rod as the supporting construction.
I haven't found any similar design in the forum (yet..) so perhaps there are some obvious and known issues with this construction that keeps everyone away from doing it this way but my tests so far has not been catastrophic so I continue.
If someone know of such issues, please advice.

The complete actuator looks like this.


I've used a thick walled plastic tube which I lathed in the ends to fit the end parts.

The upper end part of the actuator consists of a simple standard plastic tube end attached to a joint, welded together out of parts from a socket wrench set etc.


The lower end part is a standard plastic sleeve glued on to get a wider diameter to fit the ball screw nut.


The ball screw rod is equipped with a ball bearing in the upper end to slide inside the plastic tube. The bearing also serves as a target for the inductive end sensors.
The lower end of the ball screw rod is mounted into the motor fixture.

The motor fixture holds the ball screw rod end bearings, the shaft coupling and the inductive positioning sensors. The shaft couplings also serves as the target for the inductive positioning sensors.


The complete picture...

The motor fixture will be mounted to the floor frame in a kind of pivot joint construction.
This part is still in development and will be presented later on.

See you later.
Br Kenneth

are you using brushess motors ? what s the power of them ?

what is your ballscrew pitch ?

what of speeds have you been able to get in mm / sec ?

Choice of position sensor is very interesting.

Hi @Gadget999
Now I'm using a MAHLE AME1117. It's a brushed DC motor of 24V, 800W.
The ballscrew is a SFU2005, so pitch is 5mm.
I'm not sure if it exist any standardised method of measuring the speed but when running a single actuator, with the other 5 actuators in mid position, I get a maximum speed of 300..400mm/s, depending on the angle and direction.

So far I have only motors for two of the actuators. The other 4 actuators are equipped with fixed legs. This is for cutting expences until concept proven.
Before I invest in more motors I will evaluate these motors and consider the BLDC option.

Kenneth

Hi @superwhitewish
The inductive sensor used so far is the IGS6125 and the IES200 from ifm electronic.
Kenneth

hi,
very interesting I am the subject too.

I have 750w brushed motors in diy actuator, that's nice because I thought that these motors were no longer used much because a lot of them are on the st80-90!!
strength to us…lol câlin :