2DOF compact seat mover

Hi all,

I d like to share my 2dof seat mover project. Many of you may notice details that are inspired by your designs.

It is designed as a detachable module that can be installed under my (static) gaming seat to convert it to a motion sim.

It is designed to be as compact as possible.

Its a "box" measuring 40x40cm width and 15cm height.

The same design can probably be installed under any static seat to convert it in a 2DOF motion seat.

parts list:
• 12v 47A 575Watt server Psu
• Arduino Uno R3
• 9v ( 2.1mm centre positive plug) psu for arduino UNO
• Pololu Dual VNH5019 motor driver shield for Arduino
• 2x single turn Cermet 10k linear pots
• 2x SWF VALEO 24v wiper motors
• two 40cmx40cm steel plates + 15cmx15cm steel plate for Ujoint + 40cmx10cm bended steel sheet for motor chassis
• USB isolator
• AWD Suzuki vitara Ujoint
• 12v 7Ah UPS battery
Cost:
300-350 euros

So starting from this:



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A Suzuki Vitara u-joint is probably an overkill but it was for free and its future proof.

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First thing to do was calibrate and drill holes to the steel plate.


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Welding the U-joint's base.
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Quick preview.

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Closeup on the motor chassis.



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Connecting rods (for motor)
Dimensions:
5mm thick
2cm x 6 cm
Drilling:
10mm hole for motor
8mm hole for rod-end bolt.

center to center "C-C" distance is 2,5cm and 3,5cm (for motion adjustment purposes).

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The holes require some more "refining" because their inner surface has to obtain a conical profile.
When fitting the rod, make sure it sits very tightly on the "dents" of the axle.


The easiest way to achieve this is to choose a "softer" metal alloy for the rod (not steel). So when you install it on the motor axle and as you progressively tighten the securing nut, the grooves of the axle will be "registered" on the softer alloys surface. Just don't go for a very weak alloy for this rod because it is a very crucial part of the motion transmission assembly.
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Powerplant assembled.





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For the potentiometer,i tried to find the best solution amongst many presented on every possible project online.

After trial and error i ended up with a custom solution from the r/c racing world(cogs with 45t/17t~2,7:1 ratio).
I intend to use 90* to 100* (+/- 45* to +/- 50* from resting/center point) of rotation of the wiper motor axle, so this equals to 243* to 270* of rotation on the potentiometer axle.
This way i can take advantage of full 270* potentiometer range -and arduino ADC range- for better resolution).

The motors are designed to work From -45 degrees to +45 degrees from rest (horizontal rod) position, for more linear motion.

A combined use of both motors can output a maximum of about :
10 degrees LEFT or RIGHT(-10 to +10),
OR
5 degrees Front or BACK(-5 to +5),
tilt on the seat.

The cogs have a fine pitch of 48p (small dents) to increase "sensitivity" for finer motion tuning.
I have heared pinions make noise when they turn on some projects ... this is not the case here .. no sound is heard at all.
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Round head nuts ...Some drilling and some treatment with the lathe and.


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This s how it looks.



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The potentiometer mounts are pieces cut from a fairly soft pvc drain pipe:
1)They protect the pots in the rare case something goes wrong and the pots go out of travel.
2)They electrically isolate the pots from the chassis.


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Some measurements.

HP model DPS-600PB
When the psu is plugged in the fan starts to spin but there is no power output.

A “Y” cable to short pins 6-9-10, and...


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Shorting pins 4-8 reduce the fan rpm to minimum. The fan still spins up when needed but stays quiet when the psu doesn't require cooling.

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Pololu Dual VNH5019 Motor Driver Shield for Arduino.

Features:
1. Low price … 49.95USD
2. Compact … 2 Motor channels on a single pcb
3. Arduino uno compatible and stackable(allowing for a more compact design)
4. Works with up to 24volt VIN
5. 12Amp continuous output current per channel (30Amps peak per channel)

"short durations (on the order of milliseconds) of 30 A and several seconds of 20 A without overheating"

6. 24Amp continuous output current for single motor connected to both channels(60Amps total peak)
7. Ultrasonic PWM frequency 20kHz (works stacked on arduino uno)for quiet motor operation
8. Reverse voltage protection
9. overvoltage shutdown
10. thermal shutdown
11. Short protection


Taking a look at the arduino board ... six ICSP pins seem to stand very close to the power input/output of the Hbridge (which sits on top of the arduino board).



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Phobya Thermal Pads.(high thermal conductivity of about 5W/mk, while also being flexible enough).
Brushless fan .
Aluminium heatsink.






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Twisted power cables.

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a standby UPS battery in parallel with the psu.
It is cheaper and more compact than a big 12v capacitor.
Its puspose is just to assist momentarily the psu.


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Testing.

cool man, looking forward to seeing it all done!

Very neat setup there, @pipis2015 . Everything looks solid enough while keeping the construction simple. Top work!
Can I ask what you used to mount the Arduino board to the base? Is that directly mounted to what looks like a steel plate?\

I have placed both the psu and the stacked boards on a 10x40cm plywood board. For stability and electric isolation.
pics will follow when things are settled to a descent configuration.

Good idea. Yet again, simple and effective.

Nice job. been there, done that

Nice sim, nice documentation. Thank you for taking the time to put it together!

Very nice building and detailed post!

Eager to see a video and to hear how ultrasonic arduino PWM is more silent

Thx Mat.

All i can say is that thanks to your code and some provisional thinking from pololu (H-bridge PWM pins match arduino's TCCR1B) i managed to keep things simple, compact and quiet.

The camera is placed 20cm from the motors.

Good job​

Testing the simulator with max pwm(255) values and low tolerance(10-20) values (for maximum speed and maximum sensitivity/response) i ended up with some -expected- psu shutdowns.
So...
Latest addition(10 euro)...



... a standby UPS battery in parallel with the psu.
It is cheaper and more compact than a big 12v capacitor.
Its puspose is just to assist momentarily the psu.
To be honest it is something that i expected so there was more than enough room to fit.

But, boy what a difference in performance!!!

Good job!
Yeah, at full max speed and short dead zone, the code pushes the smolka to a high level!

Are your teeths okay?

rumble-strip test

Appears to be lacking a little travel/movement. what % are you running for the heave axis ?

This was just an artificial test to show the finest oscillation that can be achieved.

This is a test run @ nordschleife endurance with formula abarth(AC).
Axis used are only sway and surge.

With your suggestion in mind, i would like to ask this...
What is the -lets say- suggested mechanical tilt/seat angle that is sufficient for a 2dof seat mover to provide "proper" experience.

I am at: - 3,5 to +3,5 degrees at the moment for both front/back and left/right.

That Abrath run looks like its supposed to, Minus a few of the forces of coarse. Why aren't you running Heave and Pitch or Roll ? FYI the heave is where the kerb osculation comes from.

the degrees of movement all depend on YOUR particular setup, some want more movement some want less.