Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


48269.pdf (6.69 MB)

ETD Abstract Container

Abstract Header

Air Bearing Balance Platform with Z-Zeroing

Hoffmann, Jacob
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1721230882493873

Abstract Details

2024, MS, University of Cincinnati, Engineering and Applied Science: Mechanical Engineering.
Testing the free rotation of a satellite in a ground-based laboratory setting presents significant challenges but is essential for the development and validation of a satellite’s attitude determination and control system (ADCS). This thesis describes a novel design of a spherical air-bearing based testbed and its control system, specifically engineered for rapid balancing of the floating platform in all three axes for any tested CubeSat, even when the satellite's mass center is unknown. Unlike many other spherical air-bearing testbeds, this design utilizes only three actuators, which is the minimal number of actuators required to achieve quick balancing of the floating top platform across all three rotational axes without prior knowledge of the tested satellite's mass center location. To achieve complete passive rotational balance of a tested satellite, the combined mass center of the floating platform and the satellite must align with the geometric center of the spherical air-bearing. This alignment is challenging due to the unknown mass center of the satellite. A two-step balance control strategy has been developed to achieve the desired balance. The first step involves using Inertial Measurement Unit (IMU) data to move three weights in a coordinated manner, to align the unknown mass center of the floating platform (including the tested CubeSat) to the vertical axis (the Z axis) passing through the rotational center of the spherical air-bearing. A Kalman filter was implemented to process the IMU data, and an acceleration feedback loop provides a quick response to any disturbances causing imbalance. The second step is the vertical, Z-axis alignment. By rapidly moving the actuators in a horizontal direction a disturbance is introduced. This is referred to as a ‘twitch stage.’ With the platform moving, the acceleration of the system is then measured during the ‘drift stage.’ The results of the drift stage are processed by a proportional–integral–derivative (PID) error calculation. Output of the PID loop is then used to move the three actuators simultaneously in the Z direction. Actuators move the mass center along the vertical axis to align it with the spherical air-bearing's center until the acceleration response nears zero. This step is particularly challenging because the final location of the mass center must be at a marginally unstable equilibrium point, precisely at the boundary between static stability and instability. The three linear actuators are symmetrically positioned about the center of the platform, forming a set of three legs angled toward the ground. The hemispherical air-bearing is centrally placed on the platform, with the angle and length of the legs designed to accommodate the full range of motion of the air-bearing (+/-) 45 degrees about the planar axes) as it sits atop the pedestal. Weighted plates are attached to each leg, with adjustable mass and number of plates to support various payload sizes. Stepper motors enable rapid and precise adjustments of the weights on each leg. Once the equilibrium position is established, the actuators are locked in place, and the system is ready for testing the CubeSat’s ADCS.
Janet Jiaxiang Dong, Ph.D. (Committee Chair)
Xiaodong Jia, Ph.D. (Committee Member)
Ou Ma, Ph.D. (Committee Member)
146 p.
Robotics
Robotics; Airbearing; CubeSat; PID loop

Recommended Citations

Citations

  • Hoffmann, J. (2024). Air Bearing Balance Platform with Z-Zeroing [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1721230882493873

    APA Style (7th edition)

  • Hoffmann, Jacob. Air Bearing Balance Platform with Z-Zeroing. 2024. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1721230882493873.

    MLA Style (8th edition)

  • Hoffmann, Jacob. "Air Bearing Balance Platform with Z-Zeroing." Master's thesis, University of Cincinnati, 2024. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1721230882493873

    Chicago Manual of Style (17th edition)

ucin1721230882493873
21
© 2024, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.