EvanF's basic 2DOF motion simulator using recycled parts

UPDATE 17/01/08

Made a cockpit

A few more tweaks still to be done to the T-Bar, mount a monitor and shell the cage, but now can concentrate on the positional feedback part. With the help of a buddy I'm going for a home-made optical sensor system and count the number of strobes per revolution of the lead-screw.

http://www.youtube.com/watch?v=tvjZ9zQ4w8Q


UPDATE 07/01/08

Today I made connecting rods for cam/crank motor. I have put it together and it is very very fast. ..Like a mousetrap. If the linear actuator is 300mm/sec then this version is over 1000mm/sec! I was worried I might take my fingers off when I first powered them up.

It is too hard to test without a motor controller as too fast and powerful trying to manually switch it with full power. I think it will simulate collisions very well. Definitely need a racing harness if I used it like this.

Tomorrow I will replace the short conrods with longer ones and attach them to the original mounting points of the linear actuators in the intention of slowing the system down a bit and giving the travel some more finesse.

Nice to be able to work on slowing them down than trying to speed them up!

If all goes well I'll video the motions and compare with the linear actuator motors

http://www.youtube.com/watch?v=mz9JaF04edk

UPDATE 03/01/08

Today I bolted the T-Bar cradle to the chair and attached the Linear Actuators. Ran some subjective load tests manually using the original transformer that comes with the actuator. You can hear the motors straining as they demand more juice from the low power supply. So I tried with a couple of SLA batteries and the motors definitely sound a lot happier. I still want to compare the linear actuator with a reduction gearbox and crank setup.

Please comment on what you think about the power/speed. Do you think it needs more or do you think combined with visuals, sound and gaming immersion that the movement is enough to give a good thrilling experience.

http://www.youtube.com/watch?v=vO8p9JX7jBc





Here's what I did on the 28/12/07 EST ..

Video posted up on YouTube documenting it
http://www.youtube.com/watch?v=8QAhLHSW2IE



EvanF

Cool! I love this stuff Thanks for the vid!

By using the cardan joint you dont need to place control rods under the seat to prevent rotation. Good.

Keep up the great modding work and keep us updated!

And be aware of these actuators mate. They could kill you if they're out of control ;D

regards
ego

Cheers mate!

Yep them beasties are scary, I'm reliant on Thanos' expertise to control 'em! :top:

(haven't figgered out a way to mount the pots yet)

Evan

You should use encoders :-X
Pots dont have enough resolution.

ego

great videos, good job!

Thanks,
Tobi

Awesome video! Very describing! Thanks for that!

Can't wait to see it in motion!

Regards, Thanos

Thanks for the primo feedback all,
Today I managed to cut and shape a T-Frame for the back of the chair, but ran out of time to finish it off for the video when my kids demanded my time to play T-Ball (like softball).
I wont be able to do anything for a few more days but once I finish off the T-Frame I'll post up episode 2.
EvanF

Woah! Those actuators look awesome!

Surely you don't need that much power ;-). At least crashes will be realistic!

I read from the specs of the SCN5 that Frex use that it takes MAXIMUM of 2 amps. That's pretty low current draw for something so fast. I noticed you have used act's and crank/motors. Have you noticed that actuators are that much more efficent (no off axis torque)?

My own setup will use DC motors, but I want to keep the current and motor size as low as possible to create a decent result.

Hi matt_tighe,

I've just added a T-frame to the chair and cranked it up. With the transformer that came with the original actuator it went reasonably well but you could hear the motors struggling as they demanded more juice on the upward motion. So I tried again with 2 SLA cells (12V 4.5A/H x2) The motors sounded a lot smoother and didn't struggle on the upward motion.

But I'm not convinced I'll be entirely happy. Time will tell if the nylon nut inside the actuator will cope. There seems to be a lot of mechanical effort for such a simple task. I want more speed and power.

So to compare I'm going to make up another T-frame but shorter this time (around the lumbar support area of the seat) and bolt 2 gearhead motors onto the MDF board. The gearheads are 30:1 and they are quick when the crank is short. The conrods will be nice and short too.

I think there may be some rumble doing it this way as the reduction gearbox does freewheel where as the linear actuator stays where it stops. The rumble will probably be most pronounced at 0 degrees at rest and the chair is not balanced due to obvious reasons so the system will work harder to keep the chair in the one position.

Personally I think I will run with the crank setup as they will be faster but it will be a trade off for smoothness at low speed I think.

Anyway I've recorded what I've done so far and hopefully if I am not disturbed will edit and caption it sometime today and post up to youtube tonight (EST time)

EvanF

Updated original post

Nice

Hmm, how bout connecting stronger motors

The farer the seat gets off center, the more force is needed to center it again. But as you'll need just a fraction of the max movement range of the actuators, it could be enough.

Keep in mind that you have to reach the wheel with your hands.
I think 150mm should be the maximum movement range of the actuators.

regards
Christian

@ego

I think the motors will perform faster and stronger when I use the 24V 14A/hr batteries that are being used on the 3DOF.

And because the motors are rated at 24V I can probably put (up to) 36V into them without too much exta heat if I need to. But yes as a last measure I could simply replace the motors with 200w scooter motors.

Then theres the possibility of moving the pivot back a bit or even situate the t-bar above my head to balance everything a bit better like a pendulum. But I believe the motors should be made powerful enough to over-rule that kind of over design.

So you are saying I should only need 150mm movement. How many degrees does that equate to? I think the motors are working in that range without crying for more amps. But I just want them to move to opposite extremes faster.

EvanF

Updated 1st post

your project is just great!!! I love it

We want juice

Tobi

Hi EvanF

Always a pleasure to see how you build things! Cool!

I guess you only need to get the AVR motion controller done to move it from the computer too! ;-)

Regards, Thanos

Updated 1st post with youtube link to new vid.

@Rene'
The speed is awesome and scary. I think neck braces will be the order of the day! My son loves it ..after the rush, but is nervous before it. I think it comes close to a thrill seeking platform for computer gaming.

@Thanos.
Yes I believe the important electronic components will arrive here tomorrow and I will order the PCB etching locally tomorrow too. This only takes a day from email to my door. I am not quite convinced the new connectors for the 'removable' mosfets will endure constant changes in heat over time. I think I will try and make a daughter board for the mosfets and have them slot onto the main board instead.
(And then I will be pestering you for a 3DOF coupled firmware update so I can compare my very soon to have 2 systems!)

Cool Video ;-)

The speed of the motors is incredible... although they *are* pretty big!

The actuators look distinctly average when compared. Are they actually realising the 300mm/sec speed in the video?

I have just got some medium sized DC motors for my own platform. I was wondering how you built the crank arm that you use?

My motors have a solid output shaft with a flat machined into it. The only way I can think to connect to it is to have a crank arm machined from steel on a water jet machine or something that can cut out the keyed hole for the motor shaft?!? This is reasonably expensive :-(

Thats awesome!!

I guess this is the new definition of a torture chair :lol:

With little more force you can convert it to eject seat! Or accuratelly simulate crashes on the wall by shooting the driver over the simulator!!!!

I didn't expect them to be so strong! Cool!

Frex looks like a toy next to it! ;-)

Can't wait to see it in driving...

Regards, Thanos

@matt_tighe

The output shaft although keyed already had circular plates welded to it so wheels could be bolted on. It was a simple matter of welding some old angle iron from an old wire fence to it.

I still like the linear actuators because they are tamer to control. Bear in mind I was only using a low current power supply. They can go faster but then will have more friction to overcome. ie: wear. The challenge will be mounting the positional feedback device. It is easier to mount on the crank version. Rotary encoder/pot, output 1:1 or motor 30:1 shaft.

@tronicgr

me too can't wait