Design of Robust Control System of Magnetic Suspension and Balance System through Harmonic Excitation Simulation

Dong-Kyu Lee

doi:10.3390/aerospace8100304

Abstract

The magnetic suspension and balance system (MSBS) uses magnetic force and moment to precisely control the movement of the test object located at the center of the test section without mechanical contact, and at the same time measure the external force acting on the test object. If such an MSBS is installed around the test section of the wind tunnel so that the position and attitude angle of the test object follow the harmonic function, various vibration tests can be performed on structures subjected to aerodynamic loads without the influence of the mechanical support. Because the control force and moment in the MSBS is generated by a number of electromagnets located around the test section, it is necessary to apply the adaptive control algorithm to the position and attitude control system so that the experiment can be carried out stably despite the sudden performance change of each electromagnet and electric power supply. In this study, a fault-tolerant position and attitude angle control system was designed through an adaptive control algorithm, and the effectiveness was verified through simulation under the condition that the electric power supply of MSBS failed.

Highlights

The wind tunnel test is an experiment in which an air flow is artificially generated around a test object having various shapes and changes around the test object are observed
The test object can be fixed in the center of the test section using a support device such as a post, and the forces and moments acting in each axial direction can be measured
In order to perform the wind tunnel test using the magnetic suspension and balance system (MSBS) stably and to increase the accuracy of the results, it is necessary to increase the command-following performance of the MSBS position and attitude control system, and to design a control system that is robust to environmental changes such as equipment failure

Summary

Introduction

The wind tunnel test is an experiment in which an air flow is artificially generated around a test object having various shapes and changes around the test object are observed . Dress of NASA Langley Research Center conducted an experiment to measure the drag coefficient acting on a spheroid in the low Reynolds number region using the MSBS, which can fix five degrees of freedom of the test object, of which the size was 27.2 × 31.9 cm. When the control command is restored at a desired instant, the corresponding degree of freedom of the test object is constrained by the restored magnetic force or moment Lee showed that it is possible, utilizing these features, to conduct intensive flight tests while the safety of the UAV is guaranteed through wind tunnel tests using the MSBS [23]. The resistance and the inductance of the electromagnets were 0.8 Ω and 6 mH, respectively, according to the manufacturer specifications Those electromagnets can generate variable magnetic forces and moments to control six degrees of freedom (DOF) of the test object inside the test section. Two small neodymium permanent magnets with an outer diameter of 35 mm and a thickness of 40 mm were inserted inside so that the position and attitude can be controlled by the magnetic force and moment generated by MSBS

Equation of Motion

Harmonic Excitation Simulation with Power Supply Failure

Effect of Natural Frequency of Low Pass Filter

Findings

Conclusions