Stuttering motor problem

Hey guys,

While building my 2dof sim I have reached the point where I'm connecting my pots to my motors, but I'm having some issues while doing this. When trying to output test my motors from the simtools game-engine, my motors stutter everytime and then stop moving. In a previous attempt of connecting my pots with a rubber tube I had slightly more success and my motors were stuttering a bit less. I managed to do this by loosening the grip of the tube on the pot. Right now I'm using a coupling and I tried having it not screwed at all to tighter and everything in between. Please see my video as well. Who will become the hero of the day and help me fix this?

I'm following the tutorial by RacingMat, so I'm using the wiring from his tutorial.

Increase "tol" from 20 to 30.
Increase "braking distance" from 30 to 40.

Thanks a lot!! That already helped quite a bit. I will play around a bit more with those values and with the tightness of the coupling tomorrow and hopefully I will get a good result.

For better result...change also this:

if (gap>50) pwm=215;
if (gap>75) pwm=235;
if (gap>100) pwm=255;

to this:

if (gap>50) pwm=225;
if (gap>100) pwm=230;
if (gap>150) pwm=235;
if (gap>200) pwm=240;
if (gap>250) pwm=245;
if (gap>300) pwm=250;

It seems to have reversed the polarity of the motor or potentiometer.

@Colicab Nothing to do with your present problem, but just a suggestion, in your final assembly attach the pot mounting bracket to the motor and not the base just in case the motor mounting plate flexes even microscopically putting strain on the pot shaft. I had that problem with an earlier design a few years back. Good luck

Thanks for your feedback so far guys! Changing the code helped a bit, but the problem still persists. I do have an idea now what might cause the problem. The motor has a hollow tube of 12mm and I put a threaded rod through it of 8mm since I didn't have anything else laying around. This threaded rod is bolted onto the motor, but because of the difference in diameter, it's not entirely straight. This results in the end of the rod bouncing a bit as soon as the motor is running, which in the end puts too much resistance on the coupling/potmeter. I plan on swapping the threaded rod with a 12mm rod and this should align the rod with the potmeter perfectly. Do you guys agree?

I say that this can happen.
You've checked ?.

@Colicab :
the problem is not the code because it's used by dozens of people... and a perfectly rigid coupling has to be fine
but let's start some troubleshooting: it can be ground issues, H-bridge default, potentiometer default...

0/ are your motor and pot ungrounded?

1/

what is happening without simtools? only arduino + Hbridge
please follow the steps (in my signature) and don't bypass one

2/ what is your Hbridge? can you film it as well?

3/ have you tried with another potentiometer? another motor?

@RacingMat :

Thank you for your response!

0: I'm using motion dynamics worm drive motors: https://www.motiondynamics.com.au/worm-drive-motor-12v-24v-200w-180-rpm-20nm-torque.html When I open them up I see the following:

The back cover of the motor:


The container with the motor brush:


So as far as I can see, there is no wire going anywhere to the body of the motor. I have taken the motor even further apart, and there is no wire connected to the body. So as far as I know this should be ok right?

1: I will try to do this as soon as possible.

2: I am using the sparkfun monster moto which is wired the same as written in your tutorial. I will make a video as soon as I can.

3: I only used parts that were confirmed to be working by other people in this community. So for the motors I am using the motion dynamics motor, and for the potmeters I am using the ones you suggested in your tutorial.

My pots: http://www.gotronic.fr/art-potentiometre-lineaire-cermet-10k-8486-11293.htm

I do have some other motors on the way which i could try once everything else fails, but this will still take at least a week.

That looks like a WHOLE lot of metal shaving's in that Can.....where the heck did those come from ?

Hehe yes one of the bolts unfortunately went haywire, so I had no option but to cut it.. but that bolt's all sorted out now

Please explain, It might help a fellow enthusiast... Not.... do what you did. Thanks.

@RacingMat :

Probably a very stupid question, but how exactly do I send commands directly from the serial monitor. In your tutorial you wrote for instance to input R7FL7F for horizontal position.. but do i just copy paste this and hit enter or does it need extra stuff? Because with me nothing happens when I enter something. Last week I have made quite a few changes but my motors still respond the same. I will make a lot of videos tomorrow and post them here.

I know this problem.i have it too. reversed the polarity of the potentiometer ,and everythink works fine.

Did you solve this problem, I have same issue, I been trying to fix for 3 years off n on

Make sure your potentiometer wiring is correct. I had the same problem and checked everything 10 times over and it took me 2 weeks to realize that I had my potentiometer wiring incorrect.

I have not, I Looked it over, I will try this out, Do I just leave the 3rd motor setting to OFF?

I dropped off my motor Shafts off today to get rebuild to correct size and pot holes center drilled, mine were off a bit and shaft loose in motor.