V1.46 questions

[Lizard]

Hi,

after upgrading my HPI Blur to Firmware 1.46 I have some questions.

Torque Control:
What is the maximum value for Torque Control? In the Castle Link software, there are values from 0 to 10 in the dropdown box, but manually I could type in let's say "20". Will that have an effect, i.e. when I type in 20, will I have less torque limiting than with 10? The reason why I'm asking is follows: I like to have all the torque possible but would basically like to filter out "current spikes" that sometimes happen when landing on throttle or when tires get stuck, little rocks lock up the drivetrain etc.

So my thinking was: Use a high value (so that I won't notice the torque limiting while bashing around) but low enough so that the current spikes are filtered out.


The cogging issues with FW 1.2x onwards to 1.45:
I have read alot on forums on cogging issues with newer Beta firmwares, now with 1.46 the issue is supposed to be better. However, I still have light cogging that wasn't there with the original Firmware. Is there something I can do about this? I was thinking about playing with the "start power" values, will that help?


It has been more than three years without a final version now, will there be a final version with cogging issues fixed sometime in the future?

I'm thinking about getting a Mamba XL2, does it run the same firmware?

cheers,
Lizard

[Pdelcast]

Originally Posted by Lizard

Hi,

after upgrading my HPI Blur to Firmware 1.46 I have some questions.

Torque Control:
What is the maximum value for Torque Control? In the Castle Link software, there are values from 0 to 10 in the dropdown box, but manually I could type in let's say "20". Will that have an effect, i.e. when I type in 20, will I have less torque limiting than with 10? The reason why I'm asking is follows: I like to have all the torque possible but would basically like to filter out "current spikes" that sometimes happen when landing on throttle or when tires get stuck, little rocks lock up the drivetrain etc.

So my thinking was: Use a high value (so that I won't notice the torque limiting while bashing around) but low enough so that the current spikes are filtered out.


The cogging issues with FW 1.2x onwards to 1.45:
I have read alot on forums on cogging issues with newer Beta firmwares, now with 1.46 the issue is supposed to be better. However, I still have light cogging that wasn't there with the original Firmware. Is there something I can do about this? I was thinking about playing with the "start power" values, will that help?


It has been more than three years without a final version now, will there be a final version with cogging issues fixed sometime in the future?

I'm thinking about getting a Mamba XL2, does it run the same firmware?

cheers,
Lizard

Hi Lizard,

The actual number in torque control specifies the maximum voltage drop across the motor...

So to calculate maximum current at a specific torque control level, divide the torque control number by the resistance of the motor.

So, for a torque number of, say, 2, the maximum current would be 2.0 / motor resistance. If the motor resistance was 12 milliohms, that would be 2.0 / .012 = 166 amps.

Note that this is maximum instantaneous current -- average current will be MUCH lower.

Thanks!

Patrick

[Lizard]

Hello Patrick,

thanks for your reply, now I get the idea, it's basically a current limiter.

Did some more testing on the weekend, I have to say I really like the feature, however as far as I see it, I have to change the Torque control settings based on the surface I run, i.e. if I have set the TC to a high value for high traction surface it will have too much torque/tirespin on a low traction surface.

Would it be possible to implement Traction control based on the speed the motor RPM changes? Basically that would mean to make a full acceleration run on highest traction surface (with little tirespin), then determine the maximum engine RPM change per time unit. Now let's assume on a high traction surface the motor takes 3 seconds to spool from 0 zo 30.000rpm, that would be a max. increase of 1000rpm per 0.1 seconds.

Now when driving on a low traction surface, the ESC could monitor motor RPM every 0.1 seconds and decrease throttle as soon as it detects a change in RPM greater than 1000.

[Pdelcast]

Originally Posted by Lizard

Hello Patrick,

thanks for your reply, now I get the idea, it's basically a current limiter.

Did some more testing on the weekend, I have to say I really like the feature, however as far as I see it, I have to change the Torque control settings based on the surface I run, i.e. if I have set the TC to a high value for high traction surface it will have too much torque/tirespin on a low traction surface.

Would it be possible to implement Traction control based on the speed the motor RPM changes? Basically that would mean to make a full acceleration run on highest traction surface (with little tirespin), then determine the maximum engine RPM change per time unit. Now let's assume on a high traction surface the motor takes 3 seconds to spool from 0 zo 30.000rpm, that would be a max. increase of 1000rpm per 0.1 seconds.

Now when driving on a low traction surface, the ESC could monitor motor RPM every 0.1 seconds and decrease throttle as soon as it detects a change in RPM greater than 1000.

What you are talking about is traction control...

And yes, we've experimented with it. It's just much tougher to implement on an RC car because the inertia of the driveline is so low...

I'll ask my engineers about it - -I know they have been doing some testing recently with similar algorithms. But I don't know the status.

Thanx!

[Dr_T]

Hi Patrick,

I'm thinking of getting an XL2 ESC, or its successor. Could you please explain how the Torque control and Current limit functions for the XL2 are related? Given your explanation above, they both do the same thing, no?

Thanks!

[Pdelcast]

Originally Posted by Dr_T

Hi Patrick,

I'm thinking of getting an XL2 ESC, or its successor. Could you please explain how the Torque control and Current limit functions for the XL2 are related? Given your explanation above, they both do the same thing, no?

Thanks!

They are not related. Current limit is a maximum allowed average current (to protect the controller) and interrupts PWM. Torque limit varies PWM to limit maximum torque from the motor. Torque limit does not use the same hardware as current limit.

Thanks!

[Dr_T]

Originally Posted by Pdelcast

They are not related. Current limit is a maximum allowed average current (to protect the controller) and interrupts PWM. Torque limit varies PWM to limit maximum torque from the motor. Torque limit does not use the same hardware as current limit.

Thanks!

Thanks for your quick reply Patrick!

So, for limiting the magnitude of Current spikes, I should use the Torque limiter then, right? And what does "interrupting" PWM mean, setting throttle / motor input Voltage to zero?

[Pdelcast]

Originally Posted by Dr_T

Thanks for your quick reply Patrick!

So, for limiting the magnitude of Current spikes, I should use the Torque limiter then, right? And what does "interrupting" PWM mean, setting throttle / motor input Voltage to zero?

Torque limit would be good for limiting current spikes during hard acceleration. The current limiter has just a couple settings, can't really be used as a general purpose current limit - -it's not designed that way. The PWM is shut down for several commutation cycles when it trips.

Thanx!

[Dr_T]

Sorry for the late reply Patrick - thanks for your answer, much appreciated!