MotorEncoder

[peehrlich2]

In my experiments with a large Motor I found some interesting things:

1. You can receive an update from the Motorencoders every 2 ms. Unfortunately I can´t found a specification, were I can see the official upate-rate of the Encoders. Perhaps it is possible to increase it?
2. When you use get_Power, the calculated values are not correct.
   Example: I drive a Motor for 500 MotorDegree with a constant Power. It takes 0,552998s.
   So it is 500 Degree/ 0,552998s=904 Degree/s --> get_Power has to provide a value of 90 but it shows 78-79 at every time!
3. If you do a set_Power with a value more then 100 you get some strange effects: Than the Robot had delays up to 60 ms between the cycles.
4. In https://avr.icube.unistra.fr/en/index.php/EV3.14 I found a discription, how to double the EncoderResolution from 1 degree to 0.5 degree. This would be also a cool feature in EV3RT.

[JakubVanek]

1. You can receive an update from the Motorencoders every 2 ms. Unfortunately I can´t found a specification, were I can see the official upate-rate of the Encoders. Perhaps it is possible to increase it?

The code that controls this is in d_pwm: https://github.com/ev3rt-git/ev3rt-hrp2/blob/master/target/ev3_gcc/drivers/motor/d_pwm/Linuxmod_AM1808/d_pwm.c (the 2 ms period is here)

I don't think there is any hardware limit apart from the CPU processing power & the optical resolution of the encoder. It seems that the people behind EV3.14 have done optimizations on the tacho tracking algorithm though.

2. When you use get_Power, the calculated values are not correct.
   Example: I drive a Motor for 500 MotorDegree with a constant Power. It takes 0,552998s.
   So it is 500 Degree/ 0,552998s=904 Degree/s --> get_Power has to provide a value of 90 but it shows 78-79 at every time!

Yes, this irritates me as well; however this is likely inherited from the LEGO-provided drivers. AFAIK LEGO did not do speed calculation in degrees per second, rather they used some percent speed units (calculation here).

3. If you do a set_Power with a value more then 100 you get some strange effects: Than the Robot had delays up to 60 ms between the cycles.

This is strange - power is explicitly checked to be in the specified bounds (here). The syslog call might be slow, but that sounds strange to me.

4. In https://avr.icube.unistra.fr/en/index.php/EV3.14 I found a discription, how to double the EncoderResolution from 1 degree to 0.5 degree. This would be also a cool feature in EV3RT.

The authors have provided the source code (GPL FTW), so the changes could be ported to EV3RT.