Dear all,

I have a question regarding the cubic spline interpolation.

When I reading the source of src/emc/motion/motion.c, I found the
cubic spline interpolation segment time is set to be servoCycleTime
(usually servoCycleTime=1 millisecond, TrajCycleTime=10 millisecond).

static int setServoCycleTime(double secs)
{
//////////////////////////////////////
  /* set the cubic interpolation rate and PID cycle time */
   for (t = 0; t < EMCMOT_MAX_AXIS; t++) {
       cubicSetInterpolationRate(&(joints[t].cubic),
           emcmotConfig->interpolationRate);
       cubicSetSegmentTime(&(joints[t].cubic), secs);
   }
/////////////////////////////////////
 }

Also in the src/emc/kinematics/cubic.c, The cubic spline interpolation
time step (ci->interpolationIncrement) is defined as

int cubicSetInterpolationRate(CUBIC_STRUCT * ci, int rate)
{
//////////////////////////////////////////////////////////
 if (ci->configured == ALL_SET) {
       ci->interpolationIncrement =
           ci->segmentTime / ci->interpolationRate;
   }
//////////////////////////////////////////////////////////////
 }

MY QUESTION IS:
Suppose that
trajCycleTime =10 milliseconds,
servoCycleTime =1 millisecond,
interpolationRate=trajCycleTime / servoCycleTime=10,
Is it true that cubic spline interpolation time step is 0.1
millisecond? Can the time step equal to servoCycleTime?

Can anyone kindly help me to understand?

Xuecheng

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