Showroom 3 DOF racing sim

I appreciate your reply and would like to say I haven't been random choosing values and saying "this is what will work". I have read those those posts in the links you provided many times and have a good understanding of PID loops (even before starting this project). I got to those values after trail and error over that past 6 months or so and have admittedly changed things on the fly so as to see how a specific parameter may affect how things perform. If you see something that is totally out of whack, I definitely appreciate you or anyone questioning why that was chosen or even making recommendations.

As for the Fpwm, it was my understanding that the lower the frequency, the higher the effective torque delivery and subsequently the cooler the drivers are by reducing switching transitions. I hadn't seen in those initial guides that 25 kHz was the recommended "set it and forget" figure.

In any case, I took your advice and started from scratch again. Below is the bare bones start having added just enough PWMmax to get the motor to move:


As you can see I am back to the question I've asked before; why isn't the the target received (dark blue) not reaching the target sent (light blue)? Since I am at square one basically, is this something to do with the SMC3 code in the arduino? The reason I am hung up on this, is because I don't get much movement at all from motors 1 and 2 whereas motor 3 (the one that the received value reaches the sent) moves a noticeable amount.

If you are using 3 motors on one arduino, the 3rd pwm has less resolution so it may be making bigger steps compared to tbe other two

We're all good. Like I said before, I appreciate you trying to help and understand the difficulty of doing so remotely and not in real time. Every setup is different whether it be the geometry or equipment or configuration.

They are hall effect sensors and they are being driven at a ratio of 1:2.5. I feel like this is something to do with the code though because the moment I click and command for movement, the sent and received signals don't match/diverge like seen in the screenshot. I have ordered another arduino though and will load SMC3 on it and swap out to see if maybe it's something to do with the .ino file or the arduino itself.

I have tried lowering and raising the pwm of motors 1 & 2 but that doesn't affect any change in this issue.

Well I figured out what was causing the problem and I admit it was totally my fault. When I started this a few years ago and was bench testing the motor driver and the motor, I enabled the "pot_scaling" in the SMC3 code:

I don't remember why I enabled that but I do vaguely remember back then doing so. Commenting that back out gives me the full received target that is sent (matching light and dark blue lines) for both motors 1 and 2 now. It is laid out what it does here AND in full caps says don't do it unless a POT is attached:

Since nothing was terminated to A5, my guess is it must default to 50% which is what I was experiencing. Turns out this setting doesn't get applied to motor 3. I am so embarrassed and feel quite stupid. I am sorry for asking for help on what turned out to be a problem I caused.

Glad you found the issue NickD, been watching your thread.

I'm in the process of building my first 2DoF and still learning what is feasible.

Wish I would have seen your thread before starting my build as I like your IBT-2 set up. I did not know this configuration was possible. When reading the Arduino can run three motors, makes sense. Didn't realize you can run six IBT-2's for the three motors.

One question I have, could the IBT-2's at any time handle full 24DVC motor builds without flyback protection and not get burned out? When running 12 volt motors, does the flyback not burn the IBT-2's due to the extra voltage overhead?

I didn't plan on 4 IBT's for my build so would have to create another control box to house the additional IBT-2's. May have to do that if issues arise on mine.

The one thing for your set up I would suggest are Zener diodes for the power lines to your motors to prevent flyback. Really cool layout to take the stress off a single IBT-2.

Really like your build and glad you stuck with the project. You're in the home stretch now!

Just got mine up and running and tuned with SCM2, I'm the wheelchair build in this section.

How funny it is you ask and mention the flyback because tonight I got to actually run WRC 10, (my favorite rally game) and play around with some settings, and I am getting some shutdowns after a few minutes of gameplay. I believe you are 100% right I need that protection as it seems to be cutting out my power supplies.

As for the IBT-2's, I know they can handle 24 V but apparently if you are running at 24V, the IBT-2s are much more sensitive to "spikes" during heavy transitions. If your PSUs have a voltage adjustment screw, you can back them down slightly to 21V or 22V. This was mentioned by noorbeast in earlier posts.

I have been able to start playing around in Simtools and doing so in WRC 10 (YAY ) but ran into shutdown problems after only a few minutes of gameplay (BOO ). Below is my current axis assignment:

Here is the filtering I added to the sway:

And these are my current Min/Max tuning:

I have been changing this little by little to tune it in but it is hard when I can't run the motion rig for more than a couple of minutes before shutdown. I will add a flyback diode or capacitors across the motor terminals as Garrett suggested and hope this keeps the shutdowns from happening. I also tuned a bit more in SMC3 and reduced my pwmmax in hopes that there wasn't clipping happening in the background.

Ultimately, I think my rig is too heavy for my motors and I could probably get away with swapping out my gearboxes with 60:1 instead of my current 50:1. Don't really want to spend that but I found some that total to $100 (but doubles on checkout due to tariff fees): https://www.alibaba.com/product-detail/Flange-Ratio-5-7-5-10_1601038313125.html?spm=a2706.products_search.normal_offer.8.53c367afpy1H3r&selectedCarrierCode=SEMI_MANAGED_ECONOMIC@@ECONOMY&priceId=0acaa57a6b4d442da7f29e0907ffb370. I also could do with a MUCH lighter seat too, but again don't want to spend the money when I already bought one...

Flyback voltage is more likely to cause failures with the IBT-2's and is not an issue with the motors losing power.

Are the motor housings getting hot to the touch? They will lose power as they heat up.

What are your current settings in SCM Utilities for motors 1-3?

Be it 12VDC or 24VDC the voltage is constant, it's the current draw that creates the heat and stress during normal operation.

When looking at other 3DoF threads, some people use gas struts to alleviate the lifting action required of the motors reducing the excessive current draw that leads to heating issues.

PWMin setting should be a little higher than what is needed to keep the rig in place with your weight on it. If the rig droops then add a little more. The motors may get louder with higher settings as well. You should be able to get in and out without it drooping.

Kp you can think of as the overall force or energy applied when commanded to move. You want this to be just high enough to power the rig without it feeling "sluggish". Higher settings increase the current draw thus heat.

PWMax might be a little trial and error. You want it high enough to respond but the green line should not over shoot the intended motor blue line position. Too much tends to show as an overshoot especially when moving upward against gravity.

PWRev is how hard it will reverse position, the higher the value the more current draw and jarring the ride may be.

If the SCM tracking looks good I'd then run the Live for Speed demo repeatedly without weight in the seat and monitor the motor housings, are they warming up? Then with weight in the seat.

If the SCM motor tuning is good and the motor housing are still getting hot, you may need to use gas struts for lifting assist to alleviate the issue.

Right now it seems to be my PSU's shutting down on safety. Once things stop working, I don't see my 12VDC when metering the input power to the IBT-2's and it comes back after I power cycle them. I've order some 10,000 microfarad 35 V capacitors to put across the input power terminal block.

The motors get a little warm but I'm not concerned about them. The IBT-2's got fairly hot a few times but I just didn't have my fan positioned just right for cooling. I'm going to try to place some computer fans in front of them to help out. I have a bunch of old ones someone was going to throw away years ago.

Not near my computer to give a screenshot of my current SMC3 settings but will do so next time I work on this when I get my capacitors.

As for the gas struts, I got a couple of them to put on the front two motors and so far they seem to work great and don't restrict the motors.

Sounds good.

Just trying to help out as I'm learning too and the membership activity is low on this site right now.

What are you using for your E-Stop interrupt? I was thinking about just dropping the 5VDC line to the IBT-2's in order to stop the motors and it's a low voltage signal as opposed to the 120 VAC.

Absolutely, I'll take any help I can get!

I thought about perhaps doing that too but the mini contactor I got was only $13 opened new in the box off Ebay so I figured there couldn't be much of an edge case failure if I cut power to everything insread of just the control voltage. But you're right in that doing just the control voltage, you could use just a single cheap E-stop like I have and be good off just one N.C. contact.

If you look at my post on 3/21 you can see the latching wiring schematic I used for my momentary start and E-stop tied to the contactor. I guess a benefit to my start/stop setup is that it can power cycle my PSU's all at once too but it's only mildly helpful as the power strip I have also has individual power switches.

Ok, so initial testing with the capacitors show promise as I was able to drive 3 shakedowns in WRC 10 without any of the power supplies shutting down on safety. Very happy about that! I didn't want to push my luck so I stopped and decided to install those old 12 VDC computer fans next to the IBT-2's. Before I started working on that, I took the front frame off and painted it. This way while I work on the fans the paint could dry.

I will say that I didn't notice or rather pay much attention to how much the Thrustmaster pedals and FFB wheel weighed. Between the two of them, they're 20-22 pounds. Add the handbrake and shifter and that's another 5-6 pounds. I definitely am pushing the limits of the weight these motors will move around.

I used some old aluminum gutter bracing to use as brackets for the fans to mount and went with a quick and simple approach of using 3M VHB tape to attach it to the base. It's holding up quiet well. I'll have to see though how effective these will be but I imagine they'll be better than the floor fan I had angled up against one side of the rig while in use before.

I'll hopefully get it put back together tomorrow and actually get to tune and properly use it!

That's good news Nick.

Are you using Simtools V3 or 2.6? Windows 10 or 11?

I'm having some issues.