1792 réponses à ce sujet

[firened]

2) it's too fast in my opinion. I don't see how this robot could drive around on a table between glasses and plates. It also makes the direction control very sensitive, while driving forward, a slight turning nudge and the Robot points in any other direction. Could a motor with 33-50% speed be used?

1769080250860_garfield2144_CakeOnIce.mp4   1,13 Mo

[Mike118]

We can select motors with higher gear ratio to reduce speed, but we can also just reduce the max pwm sent to the motors.

[Mike118]

The robot is fast because the motors run with 2S voltage and the mecanum wheels ( 48mm) are bigger than the standard 40mm wheels

[Mike118]

There is an IMU in the ups board, this can be used for more advanced users to solve this. You can add weight in the back of the base to adjust the center of gravity, and the default "standard" robot will be with standard wheels not mecanum ones.

[Mike118]

We can also cheat by adjusting the control to reduce the front wheels speed when moving side to side ... But adjusting the center of gravity should be the first thing to work on.

[firened]

Great.
- slower rpm
- standard wheels
- i already set the GAIN for rotation to 0.25 on robot UPS, it helps.

[Mike118]

Yes. Settings for 2s should be adjusted... right now with 1S config :
100:1 gear ratio was the standard gear ratio and 50:1 gear ratio was the " racer config " ...

I gues that we can use 150:1 as standard config and 75:1 as racer config and 100:1 as in between.

[firened]

Doubling the voltage gets ~double the rpm.
I'd suggest 200:1 or 300:1.

I just really dislike if the handling is sensitive, it's so annoying.

Those are still the Pololu High Power versions, right? What happens if rotation is blocked and controls are set to full speed. Do they burn out or break gears?

[Mike118]

Increase voltage provide a larger range of control.
8.4v allow to go faster with same available torque.
Use 8.4v pwm allow to give better acceleration too...

I would recommend to use 150:1 gear ratio and decrease a little the max pwm value if you want to reduce speed.
Increase too much the gear ratio can be a problem. You don't need more torque. And if the gear ratio is too big you can break the gearbox by trying to manually move the wheel...

[firened]

0) Note: if you're only using a keyboard, you might not notice what I'm talking about, because you press the key for a specific duration to get a specific ° degree rotation. but using the joystick, I can't rotate for 0.2s and stop multiple times a second. joystick requires proportional speed that goes considerably slower and still has torque.

1) you say i can lower maximum output pwm % to achieve slower speed. I set OUTS to -50 to 50. mathematically it checks out, that should work, but why does it not really help in practice?

[firened]

Here are some experiment, do them using the joystick, not keyboard:
A) Come and try to slowly drive a straight line right next to the 2m ruler. this is my attempt with the robots UPS and ibiouda:

1769259071824_firened_PepitoBots.mp4   969,12 Ko

1769258523360_firened_PepitoBots.mp4   1,16 Mo

[firened]

Come and press the yellow and green buttons in succession. Tell me how often you accidentally overshoot a rotation.

[firened]

2) regarding torque: it's true we don't need more torque at full speed, but we do need torque at a slow speed. slowest possible constant rotation speed:
on ibiouda it's 20°/s (that is only 6.3 rpm!)
on UPS it appears considerably higher.

1769252396317_firened_Ibiouda.mp4   790,84 Ko

1769252507032_firened_Ibiouda.mp4   1 Mo

[firened]

3) just made some full speed measurements for reference:
ibiouda, 40mm wheels: 5.2s for 2m = 38.5 cm/s = 184 rpm
ups, 48mm wheels: 2.2s for 2m = 91 cm/s = 362 rpm

[Mike118]

Just to be sure we need to verify if we are comparing the same motors. I am not 100% sure about what kind on motors you have in your robot.

[firened]

Given that UPS's rpm is so close to double of ibiouda's, they're almost surely the same model.

And Pololu lists 330 rpm @ 6V for that model, that checks out.

[Mike118]

The modele we usually use is the HP version not hpcb. But yes I should have send you the 100:1 gear ratio.

[Mike118]

Do you think you would prefer drive the motors at 5v instead of the 2S voltage ?

[firened]

2S is fine in my opinion. Perhaps limit max PWM like you said to reduce the worst possible stress

[firened]

Center of Gravity data.
@Mike118 thank you for measuring the new board.
@blacksmith