Analysis of a Radial-Flux Eddy Current Brake Incorporating a Halbach Array

Overview

Eddy current braking (ECB) technology has many advantages over conventional friction brakes, including less wear, faster activation time, and intrinsic properties similar to anti-lock braking mechanisms. To improve ECB performance, the possible torque output should be increased to decrease braking time and enable heavier loads. To accomplish this goal, the magnetic field of the ECB should be altered and strengthened. A design for an ECB incorporating a Halbach array with 3 pole pairs was proposed with 24 discrete magnets, and compared to a design using alternating magnetization directions on the same 24 magnets. Their output torques were measured across the speed range from 250-1500 RPM using Finite Element Analysis. The deceleration of each design was also measured over 0.02s starting at 1000 RPM. The ECB using the Halbach array was found to produce greater torques than the alternating design at 750 RPM and below, and the alternating array produced higher torques for angular speeds 1000 RPM and above. This, however, contradicts the deceleration data, which showed the Halbach ECB dissipating more kinetic energy at 1000 RPM than the alternating design. This contradiction made conclusions on these datasets impossible to any practical specificity. However, the eddy current density, and magnetic flux density created in the brake disk was also recorded, showing that the Halbach ECB created fewer eddy currents with stronger electrical current, while the alternating ECB created more numerous eddy currents with weaker electrical currents. How Does Depth Perception Play a Role in Serve Percentage? Teven McCarthy Sigonella MHS In this research project, the researcher sought to find out how big of a role depth perception played in volleyball; more specifically the “serving” aspect. They wanted to test if the control results of the standard, unassisted serves are near or equal to the results of the serves with depth assistance. If that was true, then the added bulletin board would help with depth perception, as well as serve percentage. To test this, they gathered a group of seven volunteers from their high school volleyball team and asked them to serve ten times each how they would do it in a real game setting. The researcher then added a bulletin board on the far boundary line and asked them to serve the same amount of times once more. The results showed a significant increase in serve percentage, proving that this assisted their depth perception during the serve. They then removed the bulletin board and had each volunteer serve ten more times. Despite the results being lower than the serves with the bulletin board, they were much higher than the original serves. This proved that practicing with the depth perception assistance had long lasting effects on the volunteers’ serve percentage. This experiment proved how large of a role depth perception plays in serve percentage.