devyte/AccelLimiter.h

## AccelLimiter.h
class AccelLimiter
{
public:
  int accel; // unit is Hz/s, i.e.: pulses/s2, always positive
  int maxAccel; //this is the physical limitation. A frequency change above this value between consecutive updates is not allowed. Always positive.

  AccelLimiter(int accel, int maxAccel)
   : accel(accel), maxAccel(maxAccel)
   {
   }

private:
  unsigned long prevFreq = 0;
  unsigned long prevTime = 0;
  bool firstTime = false;

  unsigned long targetFreq = 0;


public:
  unsigned long calculateNewFreq()
  {
    if(firstTime)
    {
      prevTime = millis();
      firstTime = false;
      return 0;
    }

    unsigned long now = millis();

    unsigned long deltaTime = now - prevTime; //should be about the same as the periodic update time
    long deltaFreq = accel * deltaTime / 1000;  //accel is Hz/s, deltaTime is in ms
    deltaFreq = std::min(deltaFreq, maxAccel); //cap rate at maxAccel between updates, this ensures sticking to the limit if there is stretching of time between accel updates

    long errorFreq = targetFreq - prevFreq; //This says how far away we are from the target speed (may be negative)

    //cap the freq error: if target is closer than deltaFreq, then just change by the missing amount, because the entire delta would overshoot
    if(errorFreq >= 0)
      deltaFreq = std::min(errorFreq, deltaFreq);
    else
      deltaFreq = std::max(errorFreq, -deltaFreq);

    long newFreq = prevFreq + deltaFreq;

    newFreq = std::max(newFreq, 0L); //because paranoid

    prevFreq = newFreq;
    prevTime = now;
    return newFreq;
  }

  void setTargetFreq(int newTarget) {targetFreq = newTarget;}
  void reset() {prevFreq = 0; firstTime = true;}
  bool isStopped() {return prevFreq == 0;}
};

## accellimitertest.ino
#include "AccelLimiter.h"
...

void setup()
{
...
}

/*
Use should be along the lines of the below.
Need to check that setting the same speed again in the waveform gen has no negative impact. If it does, then StepperManager::setSpeed() should only set a new speed if different than current speed.
*/

periodic timeToUpdate(100);

StepperManager s1(...);
StepperManager s2(...);

AccelLimiter a1(...); //args are: desired accel, maxAccel
AccelLimiter a2(...);

void stepperOverseer(StepperManager s, AccelLimiter a)
{
  //Beware: there is a min on the settable frequency for a stepper. The AccelLimiter is not aware of that. Going to freq == 0 means trying to set a speed below that min, which the waveform gen should ignore.
  //To be explicit: AccelLimiter::isStopped() can be true, returned freq will be 0, but the steppers will continue to move when setting speed below the waveform gen min.
  //The following check is meant to address that: if the accel shows freq dropped to 0, just stop the stepper. In between the min waveform gen freq and 0, the stepper should continue to move at min freq.
  if(a.isStopped())
  {
    s.stop();
  }
  else
  {
    auto newFreq1 = a1.calculateNewFreq();
    s1.updateSpeed(newFreq1);
  }
}

void loop()
{
...

  auto newTargetFreq1 = GetNewTargetFreq1FromSomewhere();
  auto newTargetFreq2 = GetNewTargetFreq2FromSomewhere();

  a1.setTargetFreq(newTargetFreq1);
  a2.setTargetFreq(newTargetFreq2);

  if(timeToUpdate)
  {
    stepperOverseer(s1, a1);
    stepperOverseer(s2, a2);
  }

...
}
	class AccelLimiter
	{
	public:
	int accel; // unit is Hz/s, i.e.: pulses/s2, always positive
	int maxAccel; //this is the physical limitation. A frequency change above this value between consecutive updates is not allowed. Always positive.

	AccelLimiter(int accel, int maxAccel)
	: accel(accel), maxAccel(maxAccel)
	{
	}

	private:
	unsigned long prevFreq = 0;
	unsigned long prevTime = 0;
	bool firstTime = false;

	unsigned long targetFreq = 0;


	public:
	unsigned long calculateNewFreq()
	{
	if(firstTime)
	{
	prevTime = millis();
	firstTime = false;
	return 0;
	}

	unsigned long now = millis();

	unsigned long deltaTime = now - prevTime; //should be about the same as the periodic update time
	long deltaFreq = accel * deltaTime / 1000; //accel is Hz/s, deltaTime is in ms
	deltaFreq = std::min(deltaFreq, maxAccel); //cap rate at maxAccel between updates, this ensures sticking to the limit if there is stretching of time between accel updates

	long errorFreq = targetFreq - prevFreq; //This says how far away we are from the target speed (may be negative)

	//cap the freq error: if target is closer than deltaFreq, then just change by the missing amount, because the entire delta would overshoot
	if(errorFreq >= 0)
	deltaFreq = std::min(errorFreq, deltaFreq);
	else
	deltaFreq = std::max(errorFreq, -deltaFreq);

	long newFreq = prevFreq + deltaFreq;

	newFreq = std::max(newFreq, 0L); //because paranoid

	prevFreq = newFreq;
	prevTime = now;
	return newFreq;
	}

	void setTargetFreq(int newTarget) {targetFreq = newTarget;}
	void reset() {prevFreq = 0; firstTime = true;}
	bool isStopped() {return prevFreq == 0;}
	};
	#include "AccelLimiter.h"
	...

	void setup()
	{
	...
	}

	/*
	Use should be along the lines of the below.
	Need to check that setting the same speed again in the waveform gen has no negative impact. If it does, then StepperManager::setSpeed() should only set a new speed if different than current speed.
	*/

	periodic timeToUpdate(100);

	StepperManager s1(...);
	StepperManager s2(...);

	AccelLimiter a1(...); //args are: desired accel, maxAccel
	AccelLimiter a2(...);

	void stepperOverseer(StepperManager s, AccelLimiter a)
	{
	//Beware: there is a min on the settable frequency for a stepper. The AccelLimiter is not aware of that. Going to freq == 0 means trying to set a speed below that min, which the waveform gen should ignore.
	//To be explicit: AccelLimiter::isStopped() can be true, returned freq will be 0, but the steppers will continue to move when setting speed below the waveform gen min.
	//The following check is meant to address that: if the accel shows freq dropped to 0, just stop the stepper. In between the min waveform gen freq and 0, the stepper should continue to move at min freq.
	if(a.isStopped())
	{
	s.stop();
	}
	else
	{
	auto newFreq1 = a1.calculateNewFreq();
	s1.updateSpeed(newFreq1);
	}
	}

	void loop()
	{
	...

	auto newTargetFreq1 = GetNewTargetFreq1FromSomewhere();
	auto newTargetFreq2 = GetNewTargetFreq2FromSomewhere();

	a1.setTargetFreq(newTargetFreq1);
	a2.setTargetFreq(newTargetFreq2);

	if(timeToUpdate)
	{
	stepperOverseer(s1, a1);
	stepperOverseer(s2, a2);
	}

	...
	}