4DOF hybrid motion platform (electro-hydraulic)

[DoctorD]

Hi everyone,

Here's my best attempt at a home driving/flying simulator...
I guess I've held back from posting my project because a part of me was worried that I wouldn't finish it if I did

Over the last 2 years I have designed and built (well, 99% built) this thing:

CAD Render.jpg (98.58 KiB) Viewed 34434 times

Preliminary CAD concept

Sim at workshop.jpg (236.27 KiB) Viewed 34432 times

4DOF Sim - Mechanical work near completion (Pitch up)

Sim at workshop 2.jpg (221.85 KiB) Viewed 34429 times

4DOF Sim - Mechanical work near completion (Pitch down + yaw)

I'll start with some stats I guess:
4DOF - Roll, Pitch, Yaw and Heave
(30 degrees Roll & Pitch, 45 degrees Yaw, 280mm Heave)
Alloy construction
4 No. Power steering racks (Dodge Ram) - servo & hydraulic power input
Central column - 4 linear rails, internal pulley system for counterbalance (as required)
Servo specs: 90V 40A DC servo motors (w 500 line encoders)
Gearing: Belt reducers at steering input (variable, 1:4 to 1:8)
Servo drivers: Dugong 160V 35A
Central processor: Arduino Mega + custom breakout board (mostly safety stuff)
Power supplies: 2 No. 1.5kW toroidal (to drive servos only)
Hydraulic system (separate, only for 2+ occupants): 3.5kW AC single phase feeding hydraulic pump and piping manifold
Safety: Double redundant micro switch array (16 total), 3x Safety stop buttons, current limiting, encoder/position validation, frangible belt at servo connection (torque limiting), accelerometer position validation on platform

I'm aiming at simulating racing cars and fighter planes for the single person experience, with a 2 person setup (change gear belts and add hydraulics) on the horizon. I hope to make multiple interchangeable cockpits for the platform.

I'm still working through the software side of things, with a view to have it up and running in mid 2014. At the moment it starts up (servo only, hydraulics later) and calibrates the encoders. I have performed a few in-situ servo load tests on a single actuator and it achieved 0.7Hz (sinusoidal) at full travel with 60kg directly over the connection point. I haven't tried anything heavier or faster because the bolts I was using for the upper universals weren't anywhere near as big as I would have liked.

Using fibreglass and extruded polystyrene beams, I've managed to create some pretty interesting structural elements for my first platform (not shown). The first pair I constructed weighed less than 2kg each, were 3 meters long and could withstand my 90kg standing in the centre.
I've done some rough calculations and believe I can make a full fighter cockpit for roughly 10-15kg (projectors and controls excluded) and a barebones 'Oculus' cockpit at around 10kg.

Hopefully I can post some tests and/or software info in the next few weeks.
I hope you like. Any questions or comments are always appreciated.

Sincerely,
DoctorD

[DoctorD]

A more recent picture of the simulator.
Electronics further implemented and more safety features installed.

image.jpg (168.16 KiB) Viewed 34643 times

4DOF Sim - Electronics 90% installed - Shown in full down position

Further CAD work (with a view to possibly implimenting a Matlab/Simulink application for testing).

0001.jpg (1.25 MiB) Viewed 34373 times

Inventor model of simulator - Mechanical properties added to assemblies

[RacingMat]

Cheers! Great simulator! It looks like Appollo landing module

What speed can reach your actuators?
Mat

[tronicgr]

Wow! That looks like transformers...

How much is the cost for these steering wheel racks?


Thanos

[mazak515]

Wow great !

[DoctorD]

Hey guys,

Thanks for the responses and questions.

@Mat
The most I've set them to at the moment is 0.7Hz sinusoidal motion (full travel just under 300mm), but with the servo specs stating max constant speed at 3200 RPM, I'd hazard that I could move them at least twice that speed (at usable torque). Although I really wouldn't like to be on the ride for that kind of motion

BTW - The gearing is set at the moment to approx. 1:12 reduction (1:4 reduction belts/pulleys and 1:3 reduction inherent in the steering rack unit)

...possibly for small movements, yes - the higher frequency could be used for vibration reproduction (engine vibration, touchdown, ripple strips, stones, etc.) but I'm not that far into the software side just yet.
Also, I really need to make sure that the frame is up to the task. I used to work on helicopters and I know just how much havoc that constant vibration can cause on structures and fasteners. ...lots of testing needed

@Thanos
(Firstly: Wow, a reply from the man himself - I just want to say great job for all that you've done )
The power steering racks were around $150 US each (delivered to Australia from the US) - bought reconditioned from eBay. It was cheaper to buy all four from the USA than it was for me to buy a single unit from my country

Best regards,
DoctorD

[sirnoname]

Top!

[Racerr87]

Wow different approach than all the other sims nice .

So you use a servo to replace the original steering input to the steeringrack?

Got a movie of it i action?

[DoctorD]

@Racerr87
Yes, the servo is attached to the steering wheel input shaft via a reduction timing belt. You can make out the belt/timing pulley rotation at the base of the actuator.

I've just uploaded an early video on YouTube for you to look at:
Note: It starts off a little slow, but it moves faster towards the end (more comments on the YouTube page)


It's an early video, showing a single actuator under manual control. I was a little reluctant to do much more at that stage due to fear of damaging the racks (if I hit the end stops at full speed). It gives a good impression of the speed and response though. Very crisp.

I will endeavour to upload something more current after I have installed Ver. 2 of the control board (work in progress).

As always, thanks for the response,
Doc

[vicpopo]

Hi,
Very impressive , seems to be fast and powerfull !! But dangerous if speed not good controlled ...

It's like a Star wars machine ! lol

Is itt possible to watch D2R2 and 6PO ... I'm joking

Good job and good luck for your project, Thanks to share it.