I’ve been playing around with some of the vescs other settings to get more “oomph” in my torque and acceleration and I’ve found an often overlooked setting that will virtually double your acceleration AND deceleration response (keyword response).
With all the vescs I’ve used, I’ve noticed my full-throttle-from-stand-still (let’s call this dragster performance) was lacking compared to my previous Evolve GT. The GT’s dragster performance nearly knocked me off my feet. I wanted the flexibility to do that on my vesc driven board as well, and after researching and toying around with it enough, I’ve found a great solution, which brings us to…
Max Current Ramp Step (at 1khz):
For Vesc veterans, this should be a very familiar term. Last year (and still some today), nearly all vescs were plagued with a buggy version of the 2.18 fw which caused this value to multiply itself by 10 every time you wrote to the vesc noted here. This has led to a bunch of burnt DRV chips and tears. Though there issue has been solved for newer 2.18 firmwares, Ive always been curious about the setting since it sounds like exactly what i want to mess with to get the performance i wanted. And i was right.
What does it do?
Credit to @Ackmaniac for explaining this one to me in another thread. The value indeed does affect acceleration response performance by controlling how fast the vesc ramps up from a given current to another. The math is as follows…
Given current / <“value”> / 1khz == time in seconds of how long it’ll take to get from 0A current to given current in the motor.
For example, assume the following:
- Motor Max = 50A
- Max Current Ramp Step (at 1khz) = .04 (default)
In this case it would take 1.25 seconds to go from 0 to 50 amps of current in the motor, which is what I’ve noticed when doing dragster throttling at street lights. If you simply double the value (.08) you’ll effectively cut that amount of time in half. Let’s try this again.
50A / .08 / 1000 = .625 seconds!
Before going crazy with increasing Motor Max current to insane levels, try playing around with this setting to see if it’ll suit your needs for better accelerating/braking performance. Just be careful not to set the value too high as it may cause the vesc to ramp up way too quickly and burn out the DRV or other components
I had to make substantial adjustments to these as well to get my 4wd board to ride smoothly with the high battery and motor amp settings I am running. I cut the ramp up in half and doubled the ramp down and it tamed the beast! Ramp down was an was especially big improvement. Prior to the adjustment if you let off the accelerator abruptly it would almost buck me off. Now its much more manageable but will still try to rip you a new one if you try and bury the throtttle.
Awesome thread @Jinra
This kind info is gold.
So what would you call a safe ramp up limit and does it depend on motor max current?
And what about the Duty Ramp Step? What’s the story with that setting?
@evoheyax You might want to try this out sometime. You can probably get similar throttle performance without the crazy current settings.
Be aware that this is only the case for BLDC Mode. FOC doesn’t use the parameter.
True, is there an equivalent calculation on the vesc for FOC?
Is your accelaration as good as the GT now?
Wonder what the setting on the Vesx X is on the Raptor2 ?, which from tests i’ve seen on youtube accelarates faster that the GT ?
isn’t the Raptor 2 running on FOC?
@Jinra thanks for unpacking this setting! I had been ignoring it but now I’ll explore!
Shiiiit. I unknowingly ran a current ramp step maxed out at 50, instead of the default 0.04, for months
At what point would it become dangerous? I’m gonna decrease the current value by half as you suggested and will report back.
@ackmaniac any possibility to include this parameter on Vesc Monitor?
I actually doubled mine, not cut off half
Thanks for the advice. Will look into it. I do miss the few mph top speed I lose from FOC. Would really like to get to at least 30 mph. I’m going to rewind all of my motors this week to hopefully about 100 kv. Will give me a slight boost in top speed. If all goes as planned, I’ll be ready with rewound hummie motors by Sunday.
We need DUTY CYCLE to get good acceleration and speed based control. It doesn’t have neutral though in vesc
afraid to try this on BLDC w/ FOCBOX will wait for other vesc to arrive to try… did anybody run bldc on BOX yet?
i thought they were specifically designed to run in FOC mode best
people run bldc all the time, it’s safer than foc
@jinra where did you ever end up with your ramping? did you keep it doubled at .08? Any issues or concerns since you have been running it?
I use .1 now. No issues so far
What about the ramp down? Did you mess with that any? Are these settings in the advanced tab as I haven’t seen these anywhere I don’t think…
max current ramp step also controls ramp down