Re: traject planner

["Lawrence Glaister" <lg-at-jfm.bc.ca>]

Greetings Luc

its interesting you are seeing the speed spikes. I am running a CVS version from around Nov 4. I see these spikes as well using stepper drive. As you mention, the spike seems to come at the end of a move... its almost like the motion blending has a problem. I have been trying to track it down as it can be a real problem for steppers. It only happens at the end of some of the moves and where an x move blends into a radius. I have been using the cds.ngc demo program to test with and there are at least 10 places in the code where the x axis drive seems to take off with no regard to the programmed max speed or accel. I'm not sure if anyone else sees this problem. It may be happening on other axis, but my test setup only has 1 stepper on the

x drive. I see the problem with both the old and the g code interpreter, so I dont think it is a g code related problem. In my test setup, I have the feed speed at 45ipm. I thought for a while that one of the real-time tasks was getting behind and playing catch-up, but I rearranged some of the task intervals to make sure there was some available CPU time with no effect. The resulting accel is way beyond the programmed max, which I have at 1.0. Does anyone see this problem in the aug11 release? or in older releases?

=======================================================
Lawrence Glaister VE7IT             email: lg-at-jfm.bc.ca
1462 Madrona Drive                  http://jfm.bc.ca
Nanoose Bay BC Canada  
V9P 9C9                        
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----- Original Message -----

From: Luc Vercruysse

To: Multiple recipients of list

Sent: Tuesday, November 14, 2000 2:32 PM

Subject: traject planner

Hi ,

 

I am developping an "intelligent servo driver"...(I try it). It is a driver  with a microcontroller on board (89S8252 from atmel) and a ispLSI 1016 (LATTICE) that contains a quadrature decoder + counter, a pulse width modulator that feeds a H-bridge to let turn the motor.

I want to acces the board with my parallel port in EPP or ECP mode (to speed up data transfert and to acces more than one device).

The microcontroller receives the goal positions  from the EMC-interpolator, reads its actual position of the encoder, and generates a PWM signal (that feeds the H-bridge => motor) using the PID stuf from EMC (using fixed point math).

Right now I am making a prototype.

To test the microcontroller software, I separated the trajectory planner and interpolator.

Following program is suposed to move the X and Y axes to make 2 lines.

I capture positions and speed in a file and plot it out using GNUplot.

The postions seems to be OK, but when I plot the speed, there is a "spike" (speed increments up to 150% of its programmed speed) on the point where the Y-axis starts turning.

Is this normal , or is there a bug in my test program ??

 

 

PS. As soon the prototype is finished, I'll drop it in the drop box.

 

Luc Vercruysse.

 

 

void main(void)
{

 

 FILE *data;
 CUBIC_STRUCT xCubic;
 CUBIC_STRUCT yCubic;
 CUBIC_STRUCT zCubic;
 PID_STRUCT xPid;
 PID_STRUCT yPid;
 PID_STRUCT zPid;
 PID_STRUCT Pid;

 

 double OutPut[3];

 

 TP_STRUCT queue;
 TC_STRUCT tcSpace[100];

 

 PmPose pos;

 

 PmCartesian center;
 PmCartesian normal;
 PmPose end;

 

 double vMax = 0.1;
 double aMax = 1.0;
 double CycleTime = 0.01;
 double vMaxAxes = 5.0;
 double SpeedX, SpeedY, SpeedZ;

 

 data = fopen("Data.dat","wt");

 

 

 

 tpCreate(&queue, 100, tcSpace);

 

// set traj parameters

 

 tpSetCycleTime(&queue, CycleTime);
 tpSetVmax(&queue, vMax);
 tpSetAmax(&queue, aMax);
 tpSetVlimit(&queue, vMaxAxes);

 

 cubicInit(&xCubic);
 cubicSetSegmentTime(&xCubic,CycleTime / 10);
 cubicSetInterpolationRate(&xCubic,10);
 cubicInit(&yCubic);
 cubicSetSegmentTime(&yCubic,CycleTime / 10);
 cubicSetInterpolationRate(&yCubic,10);
 cubicInit(&zCubic);
 cubicSetSegmentTime(&zCubic,CycleTime / 10);
 cubicSetInterpolationRate(&zCubic,10);

 

 

 

 pos.rot.x =  0.0;
 pos.rot.y =  0.0;
 pos.rot.z =  0.0;

 

 pos.tran.x = 1.0;
 pos.tran.y = 0.0;
 pos.tran.z = 0.0;
 tpAddLine(&queue,pos);

 

 pos.tran.x = 2.0;
 pos.tran.y = 1.0;
 pos.tran.z = 0.0;
 tpAddLine(&queue,pos);

 

 while(!tpIsDone(&queue)) {

 

   while(cubicNeedNextPoint(&xCubic)) {
     tpRunCycle(&queue);
     pos = tpGetPos(&queue);
     cubicAddPoint(&xCubic,pos.tran.x);
     cubicAddPoint(&yCubic,pos.tran.y);
     cubicAddPoint(&zCubic,pos.tran.z);
   }

 

   pos.tran.x = cubicInterpolate(&xCubic,0,&SpeedX,0,0);
   pos.tran.y = cubicInterpolate(&yCubic,0,&SpeedY,0,0);
   pos.tran.z = cubicInterpolate(&zCubic,0,&SpeedZ,0,0);
   fprintf(data,"\n%f %f %f %f",pos.tran.x,
    pos.tran.y,
    pos.tran.z,
    sqrt(SpeedX*SpeedX + SpeedY*SpeedY + SpeedZ*SpeedZ));
 } 
 fclose(data);
}