Tuning PID Constants Over a Range

[Ether]

Originally Posted by wesleyac

The RoboRIO has the power required to calculate motion profiles on-the-fly. In fact, despite not having any changing setpoints last year, we still did trapezoidal motion profiling largely on-the-fly.

Let's say at some time t_i your setpoint changes to x_s, and your present position, velocity, and acceleration are x_i, v_i, and a_i.

What formulas are you using to compute the new motion profile given these non-zero initial conditions?

[wesleyac]

Originally Posted by Ether

Let's say at some time t_i your setpoint changes to x_s, and your present position, velocity, and acceleration are x_i, v_i, and a_i.

What formulas are you using to compute the new motion profile given these non-zero initial conditions?

As I mentioned, we didn't have changing setpoints last year, so this wasn't a problem that we ran into - we basically solved it by ignoring it

When I said calculating motion profiles, I was simply referring to generating a trapezoidal acceleration profile based on a given distance, acceleration, and velocity. We found that it was unnecessary to precalculate the profiles, as they were fairly simple to calculate.

[thatprogrammer]

Originally Posted by wesleyac

As I mentioned, we didn't have changing setpoints last year, so this wasn't a problem that we ran into - we basically solved it by ignoring it

Where in your code are you calculating the profiles on the fly? I had come up with a method of calculating them by looping for each time stamp (using the formulas to calculate needed P and V for each iteration of the time), but that wouldn't be fast enough to calculate profiles on the fly (at least, I think).

[Ether]

Jared Russell's online adaptation of Paul Copioli's motion profile generator


Sinusoidal acceleration motion profile equations

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[Ether]

Originally Posted by wesleyac

When I said calculating motion profiles, I was simply referring to generating a trapezoidal acceleration profile based on a given distance, acceleration, and velocity.

I think you mean generating a trapezoidal acceleration profile based on a given distance, max acceleration, and max velocity, starting with zero velocity and acceleration.

We found that it was unnecessary to precalculate the profiles, as they were fairly simple to calculate.

Yes, but that didn't seem to be the question being asked in post50:

Is there an advantage to using a motion profile with a constantly changing set-point? Obviously, the advantage of a motion profile is that you can travel over a pre-calculated path in a fairly efficient manner. How does this translate if you are dynamically adjusting your set point

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