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Asked — Edited
Resolved Resolved by Nomad 6R!

Roli Rolling To The Left

I got my new Roli up and running Sunday, but after a bit, when driving forward it began pulling left and seemed somewhat slower. In reverse, it goes straight and is noticeably faster. Has anyone else had this happen? I was driving it and had done a 180 degree turn just before the veer started.


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You can adjust the speed of each motor as no motors are the exact same speed. The speed is adjusted on init by either editing the initialization script - or - by manual adjusting the speed sliders in the movement panel.

Thanks DJ. So far I haven't had any luck as the laptop I have with me is having trouble connecting to the Rover and the mobile app won 't let me access the sliders (I'm away from home for now). The odd part is for the better part of an hour everything was fine. It also seems odd that everything is fine when I drive in reverse; no veering, it runs straight as an arrow. I'll keep trying to get in via the laptop until I get back home and can try on my desktop machine.

I figured out my connection issue; anti-virus was blocking it. JUst as I starting working with the sliders, got a low battery warning, so I'll play around more tomorrow.

Thanks again
I've adjusted the sliders for speed control and got it tracking, but to do so, I've had to drop the right speed to almost 25% which drops overall speed to slightly slower than track speed in a turn. Reverse speed doesn't seem to be affected; it positively RIPS in reverse LOL.
I have been able to do some testing on my home set up and there is definitely an issue in the left continuous rotation servo. going forward it is running approximately 75% slower than the right; so much so that when I bring the slider down on the right drive servo to get a straight path, the robot barely moves. Doing a continuous left turn (spinning in a circle), both servos are running the same speed and it does the turn rather quickly; by watching the wheels you can see they are turning the same speed. Doing a spin to the right, the left servo moves forward at a quarter of the speed of the right, which is going in reverse. This tends to suggest there is an issue with the signal being sent from the controller to the left servo for forward movement. I could verify this by swapping the connections, but don't want to do so without getting verification that this would not introduce any other control issues.

Does anyone have any suggestions?
Your not going to cause any lasting damage by swapping the connections. It's a good trouble shooting test. When done you can just swap the connections back and all will be as it was. ;)
i had this fenomen to.see on the bottem in the middle is a cap,you can unscrew that.take the one that runs the slowest.take the rubber off and adjust the motor,
by pulling it chently out and move it with one teeth fort or back.
that how i did it.
here a pic

the left side goes slower,so mean to adjust the motor 1 teeth backwarts.

if not possible take right side 1 teeth forwarts.

User-inserted image
Roli is not continuous rotation servos, it is motors and an H-bridge controller. If one of your motors is 75% off and only in one direction, it could be a bad motor or H-bridge, or possibly binding on something. How comfortable are you with taking things apart? I would swap the left and right motor connections on the H-bridge to see if the problem follows the H-bridge ports (could also swap the forward and reverse connections on the H-bridge, similar reasoning. See if the motor or the H-bridge is the issue). Could also remove the motors and bench test them with direct battery connections to eliminate any binding in the body and verify if there is a motor problem.

Might want to reach out through the Contact Us page, or during the week day see if James (customer service) is online to chat to see how much troubleshooting you should do before determining it is a warranty issue, but that much difference in speed is certainly a problem. If it was only 5-10% it would just be normal variation, but 75% and only in one direction is certainly not acceptable variation.

What Nomad is suggesting is that perhaps one of the treads is too loose or too tight. He is showing how to adjust the tension. Taking the treads off and seeing if the wheels spin at different rates would tell you if this is the issue.

Also, make sure the treads are not just slipping on the slow side. This can be fixed by tightening the tread, as Nomad shows, or wrapping the wheel in friction tape (available in the electrical section of any hardware store).

that is correct alan,you can see the two screws,if they in line as in pic.
you can look further.you can also clean the wheels with little alcohol,
also the rubber inside.
Found the issue thanks to the both of you; when I took the treads off, the left front wheel is binding badly. When it goes into reverse, since the drive wheels are at the rear, they were able to overcome the drag. I'll have to get my mini Allen wrenches from work to take off the wheel. Thanks for the help Nomad an Techguru!

can you post if this solution has worked for you.would be a good topic to ,
ad in the tutorial lessons.