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Lack of throttle control / too fast

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mgisch
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Lack of throttle control / too fast

Hi all,

Just got my first vesc running for a custom rover application. It's working ok except for 1 issue so far - It appears to be extremely keen to get to top speed asap whenever I so much as look at the throttle and I'd like a broader range of control over the speed.

Input is a Taranis X7 r/c transmitter and corresponding receiver going into an arduino which in turn sends signals to the vesc using the servo library; so effectively it pretends to be a standard r/c transmitter. The symptom I'm getting is that moving the throttle even a tiny amount makes the motor run at top speed. There is no distinction in speed between throttle at 5% vs 100%. I seem to either get stopped or full speed.

ESC is a Flipsky fsesc v4.12 running FW 3.53. The motor detection wizard seemed to run well. Motor is the common 6.5in balance board motor, 350W, it has hall sensors.
Battery is a 10S2P ~36V that these type of boards normally come with.

The input detection wizard seemed to see a full & smooth range of ppm signal from 1.2ms up to 2.2ms with a 1.7ms center and default 15% deadband.

VESC is setup in FOC mode with hall sensors, motors currently limited to 20A (It detected max ~26A).

Can anyone suggest what needs tuning to achieve better slow speed control and variable throttle from 0 to 100%? Finding the amount of settings a little overwhelming.

I've tried playing with the throttle curve settings which indeed makes it accelerate slower but still to the maximum speed; I cannot hold it at anything in-between. I don't understand what PID is or how it relates and how ERPM limit translates to real world rpm...I assume they're not 1:1? Since this is a direct drive motor at 170mm wheel diameter the default limit of 10K ERPM would be roughly 320Km/h. I've measured the actual physical RPM of the motor at current full speed is around 600rpm which is more than enough for my application. Tried setting erpm limit to 600 and it just stutters and does little stops & starts so that seemed wrong.

Appreciate any advice on what to look at next.

Thanks,
-Martin.

mgisch
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May have figured something out here. Changing the PPM control type from Current to PID Speed Control behaves much closer to what I'm looking for. It now runs at a speed that appears relative to the throttle position. It does however suffer from quite noticeable 'bumpyness' as it changes speeds. Not sure exactly how to describe it; I have the chassis propped up on a wooden desk and it sounds like physical jolts when it happens. Once at a speed it will run smoothly but changing speeds feels a bit rough. Any ideas what causes that?

Thanks.

moto_guy
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oh, It's better to ask Flipsky for help .  

Flipsky sell it to customer, they should support customer first,because they take money from this open project,not benjamin, so they have to do the support by themselves.

 

mgisch
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And in the last mapping mode with Duty cycle I still get decent speed control and the bumpyness is gone. The only oddness in this one is how it behaves at near maximum throttle. It feels like it jumps from ~75% speed to 100% and back very suddenly near max throttle. So far though this seems the smoothest for this application.

frank
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You can't determine the throttle response on the bench. It is current control and you need resistance (e.g. stand /sit on the board). Current control is what you need BTW.

Do the mapping again and press Apply. check if you get nice 100% on brake and acceleration. For further issues you need to get back to the vendor.

This topic will be moved to third party hardware.

 

thewho
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As frank said, you want current control. It's the same as your car, it reaches rev limit even with partial throttle with low load.

'E'rpm is divided by the number of poles of the motor. For example, 10k erpm on a 10pole motor would be 1000rpm

mgisch
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Thanks guys for the responses. I currently only have a single esc for testing but once I get the others and get it on the ground I'll re-test the current control mode under load.
This motor was detected as having 46 poles so now some of the erpm numbers make more sense too.
Cheers.