I have a question concerning the tri-track at low speed. When I power the tri-track and send a low speed command it seems to me the the movement is not vary smooth and is jumpy. The motors look like they are not getting enough power for them to turn correctly. Even the sound that the motors produce is not uniform at low speeds. If I increase the speed then the movement fixes and the motors come to life. Is it supposed to be like that or is it only my setup.
Mind you that the chassis of my tri-track was made by me (with PCB CNC router) using templates provided by Jim. Every thing fit to place according to the tutorial and the slack of the track is OK and not very tight.
All my tests are done with the tri-track perched on a base in order to permit free movement of the tracks.
Electronics used:
2x5 RC sabertooth for motor control
1 arduino compatible board for the logic (my botboard is used in my HEX).
Most likely it’s working properly. The PWM does reduce the power available to the motor. Servo motors are specifically wound to have smooth power at low speeds. They often have skewed armatures as well. Hobby and lower-cost motors have generalized construction and are less efficient.
And then there is the limited resolution of the R/C commands if they are used to command the motor driver.
The info you left out was, what motors and battery are you using, and what type of floor surface it’s being operated on. Our TriTrack kits do not act like this. I’m not sure what the problem is.
The motors that are installed are GHM-02 Spur Gear Head Motors 12V/120rpm/50:1 and the battery is a 10cell (12V) 2Ah Ni-Mh pack.
As I mentioned earlier, the tri-track is perched on a base so the tracks move freely.
Does anyone have any video of the tri-track tracks turning at different speeds so I can compare the movement ?
If the hardware set-up is the same, then it’s time to look into the software. Perhaps the PWM commands are being sent erratically. I believe you said arduino was your processor, so we have no good way to judge the software. Although your description sounded to me more like coarse PWM or cogging at low speeds.
This is a quick video of the track in slow rotation.
I’m not sending any pwm signals to the motors, that sabertooth is doing that for me. I’m controlling the saber tooth with normal servo pulses with the arduino clone.
The video shows how the tracks rotate when the sabertooth gets a 1,3ms continuous pulse
Dude, sit the thing on the ground and run a few batteries through it. It looks to me like the track axles aren’t broken in. It will get smoother as you use it.
I’ll try what you suggested and report back.