In the last blog post, we covered why and how to create UI Messages. Now that we have a way to use TestStand to run a VI In the LabVIEW operator interface and even set a variable back in TestStand, we can start thinking about ways to use that technology to get our test data back from TestStand.
National Instruments TestStand is software for running test sequences that automates many of the functions that are common to a piece of test software, like user permission management, UUT data input, report generation, and database logging. However, in some cases the built-in TestStand functionality is either not specific enough or not required.
Suppose you find yourself needing to rotate a point in three-dimensional space about an arbitrary axis. This problem comes up frequently in robotic kinematics, for example. You can use Euler angles and rotation matrices. However, this approach, while computationally efficient, has a few drawbacks. One is that it is not particularly easy to invert. Another is gimbal lock. Quaternion rotations do not suffer from either of these drawbacks. While quaternions are not quite as computationally efficient as rotation matrices, modern computer hardware makes this drawback less important for most applications.
The Hough Circle Transform has been known for some time. The Hough Circle Transform takes in data and a known radius, and outputs the center of the circle with that radius, that best fits the data. It does this by setting up an accumulator grid, all initialized to zero, in which each data point votes on where it thinks the circle center is. A more formal description follows.