Sample Distance

In the example of Overview, the plots show the acceleration along the path as 1000, even though 2000 was specified for compositeAcc. This occurs because of the profile calculation method of path interpolation with look ahead.

To obtain a velocity profile that more closely matches the specified parameters, the sampleDistance parameter can be set. Setting this parameter to a value above 0 will sample the profile at every specified distance along the path, improving the granularity of the generated profile. However, each additional sample will occupy a point in the buffer, meaning that a larger buffer must be created with CreatePathIntplLookaheadBuffer.

Sample Distance Example

The following sample code modifies the previous example by setting the sampleDistance to 100. This will collect approximately 10 samples along each segment of the square shaped path.

//Create the path interpolation with look ahead buffer
wmxlib_AdvancedMotion->advMotion->CreatePathIntplLookaheadBuffer(0, 1000);

//Configure the path interpolation with look ahead channel
AdvMotion::PathIntplLookaheadConfiguration conf;
        
conf.axisCount = 2;
conf.axis[0] = 0;
conf.axis[1] = 1;
conf.compositeVel = 1000;
conf.compositeAcc = 2000;
conf.sampleDistance = 100;

wmxlib_AdvancedMotion->advMotion->SetPathIntplLookaheadConfiguration(0, &conf);

//Add the path interpolation with look ahead commands
AdvMotion::PathIntplLookaheadCommand path;

path.numPoints = 4;
        
path.point[0].type = AdvMotion::PathIntplLookaheadSegmentType::Linear;
path.point[0].data.linear.axisCount = 2;
path.point[0].data.linear.axis[0] = 0;
path.point[0].data.linear.axis[1] = 1;
path.point[0].data.linear.target[0] = 1000;
path.point[0].data.linear.target[1] = 0;

path.point[1].type = AdvMotion::PathIntplLookaheadSegmentType::Linear;
path.point[1].data.linear.axisCount = 2;
path.point[1].data.linear.axis[0] = 0;
path.point[1].data.linear.axis[1] = 1;
path.point[1].data.linear.target[0] = 1000;
path.point[1].data.linear.target[1] = 1000;

path.point[2].type = AdvMotion::PathIntplLookaheadSegmentType::Linear;
path.point[2].data.linear.axisCount = 2;
path.point[2].data.linear.axis[0] = 0;
path.point[2].data.linear.axis[1] = 1;
path.point[2].data.linear.target[0] = 0;
path.point[2].data.linear.target[1] = 1000;

path.point[3].type = AdvMotion::PathIntplLookaheadSegmentType::Linear;
path.point[3].data.linear.axisCount = 2;
path.point[3].data.linear.axis[0] = 0;
path.point[3].data.linear.axis[1] = 1;
path.point[3].data.linear.target[0] = 0;
path.point[3].data.linear.target[1] = 0;

wmxlib_AdvancedMotion->advMotion->AddPathIntplLookaheadCommand(0, &path);

//Execute path interpolation with look ahead
wmxlib_AdvancedMotion->advMotion->StartPathIntplLookahead(0);

//Wait for the path interpolation with look ahead to complete
AdvMotion::PathIntplLookaheadStatus pathStatus;
wmxlib_AdvancedMotion->advMotion->GetPathIntplLookaheadStatus(0, &pathStatus);
while(pathStatus.remainCommandCount > 0) {
    Sleep(10);
    wmxlib_AdvancedMotion->advMotion->GetPathIntplLookaheadStatus(0, &pathStatus);
}

//Move the axes to Idle state
wmxlib_AdvancedMotion->advMotion->StopPathIntplLookahead(0);

//Wait until the path interpolation with look ahead is in Stopped state
wmxlib_AdvancedMotion->advMotion->GetPathIntplLookaheadStatus(0, &pathStatus);
while(pathStatus.state != AdvMotion::PathIntplLookaheadState::Stopped) {
    Sleep(10);
    wmxlib_AdvancedMotion->advMotion->GetPathIntplLookaheadStatus(0, &pathStatus);
}

//Free the path interpolation with look ahead buffer (normally, the buffer should only be freed at the end of the application)
wmxlib_AdvancedMotion->advMotion->FreePathIntplLookaheadBuffer(0);

The following plots show the two-dimensional trajectory and the velocity of each axis when the above sequence is executed from position (0, 0).