Showroom My 3 DOF seat mover + GS-4 + Simvibe

Going to be hard to hit that E-stop from the driving position!


Did you fab those pot mounts from scratch. Whole setup looks very good!

a couple of days later and the seat frame is starting to take shape.

The universal is from a Datsun drive shaft



We built the frame to go around the GS-4 Servos.



We slotted the universal mounting bracket so we could make fine adjustments to the pivot point. We also mounted my big buttkicker to the base.

I have 2 kill switches. One is on the controller box and the other is up the front on my dashboard, right next to my steering wheel.

This means I can reach a kill switch no matter where I am. So if I am racing then I can hit the one next to my wheel but if I am around the back playing with the motors etc then I can hit the rear kill switch from back there. This came in really handy while I was configuring it because most the time I was around the back checking motor travel etc and there was a few times that I needed to hit the back kill switch, i.e setting the PID I had to hit the rear killswitch to stop an oscillation.

The rear kill switch is just wired directly in to circuit and the front kill switch triggers a relay in the controller box so I don't have to have high current going to the front of my rig. You will see more on this when I get up to the controller section.

Yes, the pots mounts are made from scratch. I used the same guys who build my race cars and classic cars so they did an awesome job on the fabrication.

I figured you had another kill switch. Was just poking fun. I can tell from your build and previous setup that it is well planned out.

Pot mounts are top notch. The shop has some nice tools obviously!

Also, sorry to keep butting in during your write-up. I'll shutup until you are done now.

Next we created the top section of the seat frame and the shoulder mounts.



At this stage we started working out the maths and drawing the frame layout. We went for 30 degrees back and 15 degrees out which we hit perfectly.

Thanks. Yeah I spent a lot of time in the planning phase. I was really worried about out of control motors etc so I went for extra kill switches. We also have fuses for Africa, one in the battery charger, one between the charger and the batteries, one between the batteries and the controller box and another one in the controller box it's self.

The shop has some awesome tools. Way better than I could ever do. They also have a water jet cutter next door so we can design parts in CAD and cut them out. We did this for the belt tensioners and the lever arms etc.

Next up we tacked up the lower part of the frame so we could check all our maths and it was spot on.



From the top you can see the layout a bit better.

Next up on the project list was the lever arms. The whole theme of this build was heavy duty so we came up with this design which we created in CAD and then cut out on the water jet cutter.



At the same time I decided to strip the rest of my rig down so I would make a new dashboard. I had to take off my handbrake and sequential shifter because they connected to the back half of the frame and wouldn't work with the new frame. At this point my rig looked very sad and I was wondering if I would ever get it back together again. It very much reminds me of the classic cars I have restored. There comes a point in the project when you look at how much you have stripped it down and you get this sinking feeling like, "what have I done? have I ruined something that was good before? will I be able to finish it?". It is sort of the tipping point of the project, the point of no return.

Now with the lever arms done and the upper and lower frame finished it was time to make the connecting rods and connect everything up to make sure we got everything right.



We also finished welding up the lever arms.



And we did a test fit of the POTS with the flex coupler that @Nick Moxley recommended.



We finished the top shoulder mounts.

Now the project really started to come together and I could see the light at the end of the tunnel.



We added some plywood to the base to mount all the electronic to.



We spaced out the seat belt tensioner so we had enough room for the charger and batteries.



We made some mounts for the POTS



And left enough room for the controller box

Next up I added some vibration isolation. This helps with Sim Vibe.



I used rubber vibration isolation feet with a low friction slider pad on the bottom. I have these on the rest of my rig so I can slide it out of the way when I am not using it.

Finally I had my rig back home again!!!

Now that the mechanical side was done it was down to the scary part. The electronics!!!

Luckily one of my friends is an amazing electrical engineer so do made me this awesome controller box.

Here you can see the 2 fans at the back which are blowing air over the 2 JRK's. We used some big heatsinks that we cut down to size on the water jet cutter then attached with thermal adhesive paste.

Next to the JRK's you can see the relay for the front kill switch and the rear kill switch attached to the top on the box. We also added an LED to the back so I can tell if the controller box is switched on.

Next up he worked on the external connectors and spacing of all the electronics

That controller box is amazing! Great work!

Again @Avenga76 - stunning! I can only hope that my build is half as professional as yours.

Thanks. My friend did an amazing job on this. I was totally blown away.

Thanks. I had a lot of help from some very talented people.

So after we had the controller box it was time to mount everything to the plywood and do all the final connections.







We used Anderson power connectors to connect the motors to the controller box. This are really heavy duty connectors and are soldered in to the lugs with a ton of solder.

The batteries are just held down by cable ties and the battery box has it's own mounting brackets that came with it. The controller box in sitting on rubber feet which are screwed down through the bottom of the case and in to the plywood.

The USB hub I went for is magnetic so it sticks to the top of the controller box and runs the 2 JRK's and my GS-4.

We spent the whole day connecting and mounting everything up. We had @Nick Moxley helping us out on Steam chat, and with his help by the end of the day we had it moving.

That was the coolest feeling and I had the biggest of grins when it moved under it's own power for the first time.

Later that night I installed Simtools and got all the axis setup.

The next day I had a Skype call with @Nick Moxley and he walked me though how to get Simtools up and running and how to set up all the different DOF's

Big thanks to @Nick Moxley I couldn't have got it all going without your help and sorry for nagging you so much with all my silly questions and ideas.

I did some testing in Simtools and started creating motion profiles.

I am getting really good results and I am really happy with the speed, power and movement of the rig.

Because if the design of my rig and the size of my motors I did run it to some trouble with extremely bumpy parts like when I go off track.

If I checked the JRK utility it would say that there was "Motor Driver Errors" and it would stop and start the motors quickly.

My friend came over and we installed a shunt in to the circuit.



We connected it up to an oscilloscope and found the problem.

These motors are beasts, we were seeing peaks of over 70amps per motor, over 140amps through the entire system. The JRK's can handle this for a short time but if it is too bumpy then they throw their hands up and give the motor controller error.

My solution was to limit the max duty cycles down to 400. I did some driving with the JRK graph open, watching the duty cycle graph. And most of the cornering effects are around 200 duty cycles, things like gear changes are up to about 300 and rumble strips are up around the 350 mark. The only time it went over 400 duty cycle was off track or on a very bumpy corner like the carousel at Nords. Anything over 400 duty cycles it will just clip to 400 to save my JRK's which is fine because 400 is pretty damn violent, any more and I would be hurting myself

These motors are very torquey. I went for the 50:1 ratio motors because I am quite big so I wanted to make sure that they had no problems moving me around, and they do a great job at that. The motor speed is 5500rpm Vs the 3600rpm of the 25:1 ration boxes. The output speed is a bit slows than the 25:1 motors with 100rpm Vs 160rpm so I went for longer lever arms. The motors don't spin back at all when they are powered off. We tried turning one by hand and it is impossible. Even when we were doing up the bolts on the shaft. Which is awesome because it means I can sit in the rig when it is powered off and it won't move at all.

I am really happy that I went for the design I did with the batteries. Those 70amp spikes would have tripped out anything but the most powerful power supply. But because the batteries can handle such a massive spike it does cause the problem with the JRK's tapping out. With the batteries the max current is massive so if I do have too much of a problem with the JRK's then I will have to find a way of limiting the current. But at the moment everything seems to run fine with the duty cycles limited to 400.

Next up I did some PID tweaking.

I ended up going for P=0.5 I=0 D=0.8

I found I got oscillation at P=1.3 and I halved that down to P=0.75 at first but I found that I couldn't add enough D to get it from overshooting.

I ended up dropping the P back to 0.5 and then I could set a D of 0.8 to get it to stop nicely.

It also seems to help my over all speed having the lower P and D.

Here are some test I did.

First up the PID tests.

This was at the higher PID P=0.75 I=0 D=1.2. I could stop it on the way up but on the way down it would over shoot. This is stepping the motor from a target of 1000 to 2000 and back again





This is what I settled on at P=0.5 I=0 D=0.8





I am not an expert in PID but I think that looks pretty good. It is stopping on target pretty good. Should I run less D and not worry so much about overshoot?

Now next up are some speed tests.

To put this in scale I have a total of 96mm of travel (48mm up/48mm down)

This test involves moving the arms to the lowest position then instructing the JRK's to move the arms to the top most position. I then used photoshop to measure the amount of pixels from when I issued the command until when the arm reached the top of it's movement. I then compared that to the scale in the JRK graph and did some maths to convert it in to mm/s. I did measure from when I issued the command and not when the motors started moving so there is a few ms delay. This would mean that the actual speed of my rig would be slightly faster than listed here.

I will start with the fastest results.

This first test was done with no load in the seat. i.e it didn't have to push my fat ass around. The is at P=0.5 I=0 D=0.8 with a max duty cycle of 500 and it works out to 350mm/s



When I limit that to 400 duty cycles I get 299mm/s



When I am sitting in the seat then the speed does drop down a bit.

At 500 duty cycles I get 260mm/s



and at 400 duty cycles I get 236mm/s



This last one is how I run it now. 236mm/s seems fast enough for me. Early on @bsft said his was getting around 250mm/s so that is what I aim for and it pretty much gets that under load. I am around 125kg and pretty tall so there is a lot of me to move around. I built my system to handle that rather than outright speed and it seems like I made the right choice. I don't think you would 24mm/s between 400 duty cycles and 500 duty cycles so I will leave it on a cap of 400. I don't think the little 25:1 motors would have worked well with the amount it has to push with me and the GS-4

Feel free to poo poo my math or testing methods. I tried to be as scientific as I can with my testing but I may have something horribly flawed in my understanding of all this. There is a lot to get your head around.

That pretty much brings me up to today. So feel free to tell me what your think.

Things left to do.

Seat belts
New custom dashboard for all my gauges and displays
powder coat the frame and all the parts
paint the plywood
insulate the battery terminals
get back to doing some racing