Starting speed before acceleration

[HeldeReis]

Hello,

I came across your library when my application (rotating a mass 45°) started missing steps. During the project development the mass increased and I was not able to change the motors.
Your library behaved wonderfully helping me to keep the rotation of the mass as fast as I needed without missing steps, but I believe it could benefit from having a fixed starting/stopping speed. The idea is to start rotating the motor at a fixed speed (user configurable) and then generate the ramp as is done right now. This would allow (in applications like mine) to achieve the maximum rotating speed in the minimum time.

[gin66]

Could you please give it a try in your project ?

At start of a ramp (so from standstill), the speed is regulated by the performed steps aka s on the ramp:

FastAccelStepper/src/RampConstAcceleration.h

Line 162 in 86556d8

performed_ramp_up_steps = 0;

Please change the value of 0 to any value greater than 0. I expect, the ramp generator then jumps to the related speed and then continues to accelerate. Perhaps this works.

That value s is linked to speed via s = v²/2a. So your start speed should then be v = sqrt(2 * a * s) with the chosen value s being greater than 0. That value is independent of the direction, so only positive values make sense.

[gin66]

Increase of stop speed is a way more complicated, so please try with start firstly. Besides, if the app knows, that stop is upcoming, the app can increase the acceleration value (which is then for deceleration ), which provides a faster stop.

[gin66]

btw: if shortest time to max. speed is required, then a linear speed ramp does not fit.

[gin66]

The upcoming 0.29.2 implements a jump start feature, which allows to jump on any point on the ramp from standstill. As every point in the ramp relates to a speed, the start speed can be controlled in this way.

[HeldeReis]

The upcoming 0.29.2 implements a jump start feature, which allows to jump on any point on the ramp from standstill. As every point in the ramp relates to a speed, the start speed can be controlled in this way.

Thank you gin66

Right now i don't have the hardware to test it anymore, but when i have i will report it here.