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Topic: From linear to exponential PWM output (Read 22420 times) previous topic - next topic

backbone

Hi Mitch and others,

OK after a long radio silence I report back again.
Worked on the code to get the menu navigation by analog port and 10 switches.
Finally I got it to work.
Happy with it I checked the working of the controller then found out some other code was not working.
Had to sort that out too. To much time taken sofar but learned a lot again.
Have to check this week if the look up table and the connection (by bluetooth) is working with the PC.
Then the guys have to do some more testing t the track.

Keep you informed about the progress.

Paco
Never to old to learn and I learn every day

Techylah


backbone

Hum,

Still debugging code (nemu navigation still working fine :-) )
While moving the speed trigger I suddenly see the deaband led coming ON and OFF even if we are not in the deadband range.
Never seen this behavior before.
It looks like the constrain function is not working.
MIN = 48 MAX = 212 are calibrated for the full throw of the trigger.
As soon as sensorRawValue passes the 212 the sensorValue jumps to "0" I can see on the display.

Hum again.

Do I overlook something basic?

Code: [Select]

void loop()
{
sensorRawValue = analogRead(sensorspeedPin); // read the raw value from the linear hall sensor / potentio meter:
sensorValue = map(sensorRawValue, sensorMin, sensorMax, 0, 255);// map the calibration to the sensor reading from the hall sensor / potentiometer
}

Never to old to learn and I learn every day

Techylah

#108
Oct 03, 2012, 04:35 pm Last Edit: Oct 03, 2012, 09:47 pm by Techylah Reason: 1
Hi!
I think you did.
Add the constrain line in between, to make it:
Code: [Select]
sensorRawValue = analogRead(sensorspeedPin); // read the raw value from the linear hall sensor / potentiometer
sensorRawValue = constrain(sensorRawValue, sensorMin, sensorMax);
sensorValue = map(sensorRawValue, sensorMin, sensorMax, 0, 255);// map the calibration to the sensor reading from the hall sensor / potentiometer

The problem is that analogRead is returning values outside the range MIN to MAX
Mitch

backbone

Mitch,

Your on the spot. Thanks
Moving the constrain upwards did the trick.
Due to the fact the speed trigger potentiometer is giving eratic values I am converting to neodyne magnet and linear hall sensor.
Hope to have it ready at the end of the week.
From now on I use an original slot race controller body (with the magnet) instead of the custom made white controller handle.
To be continued.

paco
Never to old to learn and I learn every day

backbone

#110
Oct 17, 2012, 09:27 pm Last Edit: Oct 18, 2012, 07:26 pm by backbone Reason: 1
One step forward 2 steps back.  :)

The magnet and hallsensor are working like a charm now.

Stuck in the lookuptable again.
I cant figure out why.
Nothing in this part of the code has changed (as far as I can see).
SpeedfinalValue never passes the switchpointYValue.With endcurvepower set to 1.0 the speedfinale value should follow sensormapped value as in previous codes.
As usual it must be so simple I over look it.

Code: [Select]
 //  +++++++++++++++  regular speed - brake mode  +++++++++++++++

 // in regular mode control the outputs with output cross block function to prevent speed and brake to be ON together
 sensorRawValue = analogRead(sensorspeedPin); // read the raw value from the linear hall sensor / potentiometer
 sensorRawValue = constrain(sensorRawValue, sensorMin, sensorMax);
 sensorValue = map(sensorRawValue, sensorMin, sensorMax, 0, 255);// map the calibration to the sensor reading from the hall sensor / potentiometer
 sensormappedValue = map(sensorValue, 0, 255, speedstartValue, 255); // full linear control mapped with startspeed
 
 //  ++++  curve section  +++++++
 speedfinalValue = lookupTable[sensormappedValue];
 //  ++++  curve section  +++++++
 
 if (sensorValue > deadbandXvalue)
 {
   analogWrite(pwmoutspeedPin, speedfinalValue);
   analogWrite(pwmoutbrakePin, 0);
   digitalWrite(led8Pin, LOW);
   digitalWrite(led7Pin, HIGH);
 }
 else
 {
   //speedValue = 0;
   analogWrite(pwmoutspeedPin, 0);
   analogWrite(pwmoutbrakePin, brakeNValue);
   digitalWrite(led8Pin,HIGH);
   digitalWrite(led7Pin, LOW);
 }


endcurvepower is currently set to 10 so diveded by 10 will give 1 and so a linear powerline.

Code: [Select]
void fillLookupTable()
{
 speedstartValueold = speedstartValue;
 switchpointXValueold = switchpointXValue;
 switchpointYValueold = switchpointYValue;

 Serial.print("B,");
 Serial.println(speedstartValue);
 Serial.print("C,");
 Serial.println(switchpointXValue);
 Serial.print("D,");
 Serial.println(switchpointYValue);

 switchpointXValue = constrain (switchpointXValue,deadbandXvalue, 255);
 switchpointYValue = constrain(switchpointYValue,speedstartValue, 255);
 
 for (int i=0; i<256; i++)
   if (i < deadbandXvalue)
   {
     lookupTable[i] = 0;
   }
   else
     if (i < switchpointXValue)
     {
       lookupTable[i] = map(i, deadbandXvalue, switchpointXValue, speedstartValue, switchpointYValue);
     }
     else
     {
       lookupTable[i] = (int)(0.5 + switchpointYValue + (255-switchpointYValue) * ( 1.0 - pow( (255-x)/(255-switchpointXValue), endCurvePower/10) ));
     }
     
     
  for (int i=0; i<256; i++)
  {
  Serial.print(lookupTable[i]);
  if (i<255)
  {
  Serial.print("|");
  }
  }      
  Serial.println();


Paco
Never to old to learn and I learn every day

backbone

Found the trouble maker not the solution yet.
Reverted back to old code and replaced it line by line.
Line with the arrow with the POW function is causing the stop at switchpointYValue.
If I replace the line with the line above speedfinalValue nicely runs till 255.

Code: [Select]
lookupTable[i] = map(i, switchpointXValue, 255, switchpointYValue, 255 );       // this could get replaced by a curve after all is working
//>>>>>>>>>>>lookupTable[i] = (int)(0.5 + switchpointYValue + (255-switchpointYValue) * ( 1.0 - pow( (255-x)/(255-switchpointXValue), (endCurvePower/10)) ));


Paco
Never to old to learn and I learn every day

Techylah

Hi Paco,
Sorry, I think I made a typo. That "255-x" should be"255-i" in the problem line.
The line should be:
Code: [Select]
lookupTable[i] = (int)(0.5 + switchpointYValue + (255-switchpointYValue) * ( 1.0 - pow( (255-i)/(255-switchpointXValue), (endCurvePower/10)) ));

There is no "x" at this time. The lookuptable is being calculated for all 256 values, via the loop index "i".
That should work well.
Good Luck!
Mitch

backbone

#113
Nov 11, 2012, 02:05 pm Last Edit: Nov 11, 2012, 02:07 pm by backbone Reason: 1
Hi Mitch,

Your correct the X was wrong and it should be i but the result is was not as expected.
If i correct the X for i then after the switch point the line goes straigth roof high. See screenshot.
In the case I use the other line without the curve it is nice and straigth.

However in both cases when I use the lookuptable we never start at the startspeed value but always higher as soon as the trigger leaves the deadband zone.
If I do not use the lookptable we nicely start at the startspeed point.

Any thoughts about this all?

As you can see the graphing at the PC is working now as intended.
As soon as on the controller we change either startspeed or X or Y point up or down this is shown in the graph so we know what we are doing.

Cheers, Paco
Never to old to learn and I learn every day

dhenry

Quote
Now I like to make this output not linear but exponential


Calculate the mapping offline and load the value in a table into your code. Much faster than any calculation you can find any mcu.

PeterH


If i correct the X for i then after the switch point the line goes straigth roof high. See screenshot.


If you're trying to store a curve in the array, why don't you just calculate the values you want and put them in a static initialiser?

If you're trying to approximate the curve with three straight lines then I don't see the benefit of the lookup table - you might just as well do a range check, scale and offset. If execution time is critical then you could implement that logic during setup and cache the result, but I'd still calculate it doing three linear transforms rather than trying to write it as a single expression. But the circumstances where it's sensible to pre-calculate a linear transform are pretty unusual imo.
I only provide help via the forum - please do not contact me for private consultancy.

backbone

Dhenry

Do not fully understand what you mean with Offline calculation of the mapping.

PeterH

This whole slotrace controller project is not standard so we try the things step by step.
Currently all controllers that have an exponential curve just run from the startspeed point to full speed.

For those just stepping in and try to help.
With the selectable XY switchpoint we try to be different and this has not been tried or tested before.
Now for this step in the project we like only to curve the last straight line by changing a curve value.
1 is a straight line and 3 a full curve.
We have to test if good slot race drivers can benefit from this last line to be linear or to be curved.
Also even if the lines are linear we not yet tested with drivers if this would be enough and the curving is not needed at all.
But I like to have it already and then test drive all possible options at one day to have comprehensive comparising with same drives and track conditions.

All settings to XY and curve value need to be changeable while the controller is plugged in and in use.

This is where the project currently stands and we are not ready yet.
I am eager to learn but my level of programming and mathematics in not at the same level you guys are. :-(

Your given options are acabadabra to me so I cant say if this or that would be better or give an other result that is desired.

Cheers, Paco

Never to old to learn and I learn every day

backbone

Mitch,

Can you chime in?.
SpeedfinaleValue never starts at speedstartValue when the lookuptable is used.
VB nicely shows the lookuptable is filled with correct values.
If startspeed is 100 and Y value is 175 as soon as the trigger leaves deadband zone it jumps to 183 instead of 101.
Looks like it does not use the first part of the line from startspeed to XY point.

Code: [Select]
void fillLookupTable()
{
  speedstartValueold = speedstartValue;
  switchpointXValueold = switchpointXValue;
  switchpointYValueold = switchpointYValue;

  Serial.print("B,");
  Serial.println(speedstartValue);
  Serial.print("C,");
  Serial.println(switchpointXValue);
  Serial.print("D,");
  Serial.println(switchpointYValue);

  switchpointXValue = constrain (switchpointXValue,deadbandXvalue, 255);
  switchpointYValue = constrain(switchpointYValue,speedstartValue, 255);
 
  for (int i=0; i<256; i++)
    if (i < deadbandXvalue)
    {
      lookupTable[i] = 0;
    }
    else
    //++ knicked powerline at X and Y value ++ SETTING
    if (i < switchpointXValue)
    lookupTable[i] = map(i, 0, switchpointXValue, speedstartValue, switchpointYValue);
    else
    lookupTable[i] = map(i, switchpointXValue, 255, switchpointYValue, 255 );       // this could get replaced by a curve after all is working
    streamUp();
}   


It looks as it does not use the
Code: [Select]
lookupTable[i] = map(i, 0, switchpointXValue, speedstartValue, switchpointYValue);

and always starts from the XY Value point set.

Paco

Never to old to learn and I learn every day

robtillaart

Can you post the output of the function?
What are the values used in the function??
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

backbone

Rob the output of the function I read too into the VB application for displaying where the immidiate screen nicely show the lookuptable values to be correct and start at 104 and go upto 255.
See the screenshot.

Paco
Never to old to learn and I learn every day

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