Semi-automated Laser Measuring Device
The main goal of this project was to create a device that could record precise measurements quickly and reliably. The object to be measured was a stack of laminated steel pieces, often found in electrical motors and magnetic gearboxes. The measurements were recorded in the axial direction so that a deflection profile could be obtained. These measurements can then be compared to theoretical calculations and simulated values.
The first step was to acquire and calibrate the necessary equipment. A laser measuring device was chosen because a non-contact device was preferred (a CMM was used later for additional validation). The minimum and maximum range was set to 76 mm and 82 mm respectively. The minimum range needed to be far enough away to clear the other fixtures, but not too far where the accuracy would be affected. The closer the maximum range was to the minimum range determined the overall measurement range and therefore the precision (a smaller range gives better precision). However, the total measurement range needs to be greater than the maximum expected deflections to be measured. This configuration allowed for deflection measurements of less than 0.001". The sensor was then calibrated by taking a series of measurements with known distances using the linear actuator. These points were then plotted and curve fit was used to obtain the formula to be used in the Arduino code to convert the input data to distances.
Next, the stepper motor and other electrical components were connected to a data acquisition device (Arduino Mega). The stepper motor would rotate the inner rotor to various positions and hold it there while measurements were recorded. A rotary encoder was used to control the stepper motor manually when needed. A gearbox and larger motor controller with a fan was added later to increase the torque from the stepper motor. Three separate power supplies were used for the Arduino, laser, and stepper motor to ensure that the measurements would not be affected. All of the components were connected with a small test bed made of acrylic, extruded aluminum, and 3D printed parts. This test bed was designed to be adjustable to allow for alignment and use for various configurations.
The assembly was then moved down to the machine shop and fixed in a milling machine which provided a sturdy surface that could be aligned accurately. A 3D printed adapter (better seen in the first picture) was used to fix the laser in the collet. The mill's auto feed feature was used to provide a consistent axial movement while taking measurements.
The data was analyzed by a PhD student who was also part of the magnetic gear research team. The results were valuable because there is scarce experimental knowledge of radial lamination deflections in electrical motors and magnetic gearboxes. These deflections are crucial because of the extremely small air gaps in between the rotors of such devices (often less than 1 mm) and the effects they have on performance and longevity.