That’s what I was thinking. Gearing ratios and wheel size at high speeds can cause the board to feel like it’s braking when you release the throttle. With single gears, we’re using our motors at high rpms to attain more speed, but once we let off the trigger, compression brakes take over. Just like running your car at higher rpms in lower gears.
Like Maxid, I solved this by switching to hubs. Since there’s no gears, you just coast when you let off the throttle regardless of how fast you’re going. Acceleration and braking are more responsive and at the same time, smoother. With a geared setup, I imagine the closer you get to a 1:1, the less compression you will feel when you let off the throttle. When I was riding a belt drive, I would let off the throttle slowly when at high speeds to avoid jerking.
I get what you are saying. The board coasts pretty good. Its no pusher but you get the picture.
Think about it this way. When you are accelerating the rider experiences, lets say, .5G of acceleration. When the throttle is released the rider suddenly feels 0G. Its not a negative G in the other direction, but the sudden decrease to zero G, or near zero after taking in the inevitable drag that some you have alluded to.
By ramping the acceleration down to zero in this scenario over a second or so, it would make for a smoother ride.
As I mentioned in near the top, braking could have a little or no time delay for obvious performance/emergency reasons mentioned by @trampa. I totally get that.
I appreciate everyone’s feedback. Its really helpful to gather everyone’s experience.
Increasing the ppm median timing in Vesc will smoothen it out. The median timer in vesc by default if im not mistaken is 5 seconds. So it will average the last 5 seconds throttle position. If you increase it by 10 seconds it will really smoothen it out nicely.
This is probably the easiest effective solution to implement without needing custom code.
As a Mechanical Engineer I would limit the ‘jerky feel’ by limiting the jerk which is actually the time derivative of acceleration or ‘change of acceleration’. Jerk on a E-board sucks because you need to lean forward or backward to counterbalance acceleration or braking, meaning that if you apply throttle (acceleration) very quickly, you have to adjust your leaning angle very quickly too, so it feels unstable and hard to balance. Averaging the throttle works as a low pass filter so it limits the jerk.
Credit of the idea goes to laurnts, i just second it with some physics
Im building a short wheelbase 2x 6355 board so will probably also use this method to tame it a little bit.
@mainstreet, If we had access to the PID controller, we would be able to control the throttle response way better. Once the summer rolls around my gf will give the VESC a go to produce a better controller.
She’s a CS/ME major with controls background so it should be a fun project.
This parameter controls how fast the motor current can raise and therefore how fast the force that accelerates you can increase. If you lower this value, from default of 0,04 to 0,001 or even less you can pull the trigger completely and the power of the board builds up slowly until maximum is reached.
Wow. Yeah. That could be part of it. The challenge is that you may want more variables to make it more ridable. But that description reads like a solution to item 1. I outlined below.
To be clear and beat the dead horse
Accelleration - Acceleration is defined as the rate at which an object (skater) changes its velocity (speed). An object is accelerating if it is changing its velocity (speed).
As I see it there are four states where you may want the acceleration to be ramped.
1. Forward - The rate at which acceleration is increased in the forward direction.
ie when you pin the throttle
2. Forward Decrease - The rate at which acceleration is reduced in the forward direction.
ie when you release the throttle and it snapps to middle
3. Braking - The rate at which acceleration is increased in the negative direction while braking.
ie you may wan this to be a very steep ramp to the brakes are responsive but not so much that you get thrown off yet still have full braking power after the ramp time.
4. Braking Decrease - The rate at which acceleration is decreased in the negative direction while braking.
_ie when you release your brakes, it can be done over a short period of time to make it less jerk_y.
I know we have all learned to feather our throttle thumbs for a smooth ride but when the boards get more powerful they begin to act like less like a refined product and become much less approachable to less experienced riders. Now I know there are lots of little arguments like why is a less experienced ride on such a powerful board, but I think the main driver for me is to create a technically refined and approachable boards.
Again, guys, appreciate all the great conversation here.
The proportional gain controls how fast you reach your command. Think of it as a spring, the stiffer it is the faster it will pull to it’s commanded position.
The derivative gain dampens the command. So think about that spring without a damper, you’ll reach your command, most likely overshoot and then oscillate about the commanded position. With a damper, it’ll decrease the oscillations over time and reach a steady state faster
Your integral gain looks at the error between your command and where you are, if there is a difference between where you ended up and where you commanded then it’ll shrink that over time.
By adjusting gains you can fine tune how fast your board responds, not overshoot the commanded position and remove any oscillations that might be happening.
@PXSS Yeah I’m quite familiar with PID from the automation work I do. Is the VESC capable of the functions required to calculate it with without bogging down the processor?
I cant help but think a simple linear relationship between acceleration and time may work well given the calculation is so much more light-weight in the VESC processing.
One consideration when using PID is that you will be constantly changing your target value as the throttle is adjusted. It may prove to processor intensive in respect to all the other routines the VESC is running.
Give my firmware mod a try and then we can talk about something that might can be changed. And please also post your VESC settings to have some real numbers.
Pretty sure it’s more than capable. Have you seen the tiny quadcopter flight controllers??? They’re like .5"x.5" and run PIDs on throttle, roll, yaw, and pitch at 8kHz on a 16bit processor
@PXSS Can u give a more explanatory answer as what PID is?
Im starting to witness a delay in my remote’s signal vs what the car esc does (yes, not owning a vesc unfortunately)…
Im not sure but i think at the beginning of using the board / riding it, there was no delay!
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Do you have any ‘‘explanations’’ on why else the delay might be caused?
I can only set the trim on the remote itself, im using mini remote, which is 2.4ghz… Do you think it can be modded with the help of some other componenets to adjust the signal or delay?
I’ve heard that for ‘‘trimming’’ a simple resistor can be placed in chain with the potentiometer, thus ‘creating beginner mode’’ for the remote… not sure is it possible to modulate the signal or make other adjustments in such a simple way…
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What Im refering to ‘delay’ is that power starts to be delivered (esc - motor responds) only 1-2 seconds after I have sqeezed the trigger,
I’ve been planning on re-setting the 0 and high / low point of the remote once again but Im a little bit afraid, since last time it took some time before I managed to set it right and get it working…
My 2nd guess as why Im experiencing delay is that maybe there is a problem with antenna wire? Im sort of having it outside of power cables, so it is not in direct contact…
The only problem is, Im not having it in straight line up in the air but it is layed sideways along the enclosure… though this did not cause problems before so Im not 100% sure it is just the antenna which is delaying / messing with the signal
Im building a short wheelbase 2x 6355 board so will probably also use this method to tame it a little bit.
