Thesis
Optimal placement of a hall sensor inside an MR-brake for hysteresis elimination
Washington State University
Master of Science (MS), Washington State University
2017
Handle:
https://hdl.handle.net/2376/100302
Abstract
The braking torque of magnetorheological brakes (MR-brakes) is controlled by the amount of induction generated by its electromagnet. Being partially constructed of steel, which experiences ferromagnetic hysteresis, it remains partially magnetized after the electromagnet is turned off. This residual magnetization leaves the brake partially activated which creates hysteresis in the braking torque. Previous research discovered that a Hall-effect sensor could eliminate this hysteresis when used in conjunction with a proportional-integral-derivative (PID) controller. In this work, through many simulations and experiments, a set of guidelines for optimizing the placement of this Hall-effect sensor were developed. An experimental setup was designed and constructed with the typical features of an MR-brake to measure the induction at various locations. Computer simulations of the device were validated using hardware to show that the simulated values were within 15% of the measured values. From these tests, a few features were discovered that were considered promising candidate sites for placing Hall-effect sensors. Next, an actual MR-brake, with the same features as the experimental setup, was simulated and four locations, that corresponded to the ones found previously, were identified for further testing. Two were located outside the brake, one was in an aluminum ring just inside the brake, and one was in steel. All these sensors canceled the hysteresis except for the one located in the steel. The remaining sensors also passed a variety of benchmarking tests. From these results the following guidelines were derived: 1. The Hall-effect sensor should be placed near discontinuities in the path of a strong magnetic flux. The best place is one that is above a discontinuity and outside the brake. The sensor should never be located inside steel as this prevents it from controlling the hysteresis. If possible, the brake should be simulated as visualizing the flux path helps in identifying locations meeting these criteria. 2. The induction at the sensing location should be strong enough for a Hall-effect sensor to measure accurately over the whole range of coil currents without being swamped with noise.
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Details
- Title
- Optimal placement of a hall sensor inside an MR-brake for hysteresis elimination
- Creators
- Christian James Sturtevant
- Contributors
- Hakan Gürocak (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Electrical Engineering and Computer Science, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525035701842
- Language
- English
- Resource Type
- Thesis