<title>Human performance evaluation of isometric and elastic rate controllers in a six-degree-of-freedom tracking task</title>

In this article, a six-degree-of-freedom (6-DOF) micro-vibration platform (6-MVP) based on the Gough–Stewart configuration is designed to reproduce the 6-DOF micro-vibration that occurs at the installation surfaces of sensitive space-based instruments such as large space optical loads and laser communications equipment. The platform’s dynamic model is simplified because of the small displacement characteristics of micro-vibrations. By considering the multifrequency line spectrum characteristics of micro-vibrations and the parameter uncertainties, an iterative feedback control strategy based on a frequency response model is designed, and the effectiveness of the proposed control strategy is verified by performing integrated simulations. Finally, micro-vibration experiments are performed with a 10 kg load on the platform. The results of these micro-vibration experiments show that after several iterations, the amplitude control errors are less than 3% and the phase control errors are less than 1°. The control strategy presented in this article offers the advantages of a simple algorithm and high precision and it can also be used to control other similar micro-vibration platforms.

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Six degree of freedom quasi-zero stiffness magnetic spring with active control: theoretical analysis of passive versus active stability for vibration isolation

Journal of Sound and Vibration ◽

10.1016/j.jsv.2021.116086 ◽

2021 ◽

pp. 116086

Author(s):

Nur Afifah Kamaruzaman ◽

William S.P. Robertson ◽

Mergen H. Ghayesh ◽

Benjamin S. Cazzolato ◽

Anthony C. Zander

Keyword(s):

Theoretical Analysis ◽

Active Control ◽

Vibration Isolation ◽

Degree Of Freedom ◽

Magnetic Spring ◽

Six Degree Of Freedom

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Design and Calibration of a Hall Effect System for Measurement of Six-Degree-of-Freedom Motion within a Stacked Column

Sensors ◽

10.3390/s21113740 ◽

2021 ◽

Vol 21 (11) ◽

pp. 3740

Author(s):

Olafur Oddbjornsson ◽

Panos Kloukinas ◽

Tansu Gokce ◽

Kate Bourne ◽

Tony Horseman ◽

...

Keyword(s):

Hall Effect ◽

Degrees Of Freedom ◽

Reactor Core ◽

Degree Of Freedom ◽

Life Extension ◽

Scale Model ◽

Design Development ◽

Seismic Safety ◽

Six Degrees Of Freedom ◽

Six Degree Of Freedom

This paper presents the design, development and evaluation of a unique non-contact instrumentation system that can accurately measure the interface displacement between two rigid components in six degrees of freedom. The system was developed to allow measurement of the relative displacements between interfaces within a stacked column of brick-like components, with an accuracy of 0.05 mm and 0.1 degrees. The columns comprised up to 14 components, with each component being a scale model of a graphite brick within an Advanced Gas-cooled Reactor core. A set of 585 of these columns makes up the Multi Layer Array, which was designed to investigate the response of the reactor core to seismic inputs, with excitation levels up to 1 g from 0 to 100 Hz. The nature of the application required a compact and robust design capable of accurately recording fully coupled motion in all six degrees of freedom during dynamic testing. The novel design implemented 12 Hall effect sensors with a calibration procedure based on system identification techniques. The measurement uncertainty was ±0.050 mm for displacement and ±0.052 degrees for rotation, and the system can tolerate loss of data from two sensors with the uncertainly increasing to only 0.061 mm in translation and 0.088 degrees in rotation. The system has been deployed in a research programme that has enabled EDF to present seismic safety cases to the Office for Nuclear Regulation, resulting in life extension approvals for several reactors. The measurement system developed could be readily applied to other situations where the imposed level of stress at the interface causes negligible material strain, and accurate non-contact six-degree-of-freedom interface measurement is required.

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Stability and Manoeuvrability Simulation of a Semi-Autonomous Submarine Free-Running Model SUBOFF with an Autopilot System

Applied Sciences ◽

10.3390/app11010410 ◽

2021 ◽

Vol 11 (1) ◽

pp. 410

Author(s):

Yu-Hsien Lin ◽

Yu-Ting Lin ◽

Yen-Jun Chiu

Keyword(s):

Optimal Control ◽

Experimental Tests ◽

Degree Of Freedom ◽

Line Of Sight ◽

Pd Controller ◽

Free Running ◽

Simulation Results ◽

Guidance Algorithm ◽

Logic Operations ◽

Six Degree Of Freedom

On the basis of a full-appendage DARPA SUBOFF model (DTRC model 5470), a scale (λ = 0.535) semi-autonomous submarine free-running model (SFRM) was designed for testing its manoeuvrability and stability in the constrained water. Prior to the experimental tests of the SFRM, a six-degree-of-freedom (6-DOF) manoeuvre model with an autopilot system was developed by using logic operations in MATLAB. The SFRM’s attitude and its trim polygon were presented by coping with the changes in mass and trimming moment. By adopting a series of manoeuvring tests in empty tanks, the performances of the SFRM were introduced in cases of three sailing speeds. In addition, the PD controller was established by considering the simulation results of these manoeuvring tests. The optimal control gains with respect to each manoeuvring test can be calculated by using the PID tuner in MATLAB. Two sets of control gains derived from the optimal characteristics parameters were compared in order to decide on the most appropriate PD controller with the line-of-sight (LOS) guidance algorithm for the SFRM in the autopilot simulation. Eventually, the simulated trajectories and course angles of the SFRM would be illustrated in the post-processor based on the Cinema 4D modelling.

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