High-Performance Tracking for Piezoelectric Actuators Using Super-Twisting Algorithm Based on Artificial Neural Networks

Piezoelectric actuators (PEA) are frequently employed in applications where nano-Micr-odisplacement is required because of their high-precision performance. However, the positioning is affected substantially by the hysteresis which resembles in an nonlinear effect. In addition, hysteresis mathematical models own deficiencies that can influence on the reference following performance. The objective of this study was to enhance the tracking accuracy of a commercial PEA stack actuator with the implementation of a novel approach which consists in the use of a Super-Twisting Algorithm (STA) combined with artificial neural networks (ANN). A Lyapunov stability proof is bestowed to explain the theoretical solution. Experimental results of the proposed method were compared with a proportional-integral-derivative (PID) controller. The outcomes in a real PEA reported that the novel structure is stable as it was proved theoretically, and the experiments provided a significant error reduction in contrast with the PID.This research was funded by Basque Government and UPV/EHU projects

The impact of wave slamming indused vibration on human factors and equipment on board the SA Agulhas II

Thesis (MEng)--Stellenbosch University, 2016.ENGLISH ABSTRACT: An investigation of wave slamming phenomenon was performed in the context of human factors on-board the S.A. Agulhas II, a South African Polar Supply and Research Vessel. Full scale vibration measurements were conducted during the vessel’s voyage to Marion Island in 2014 and Antarctica in 2014/15. The measurements captured vibrations in the vertical direction as per the directives of ISO 2631-1 (1997). A questionnaire survey was conducted on both voyages to acquire the human response to wave slamming. The study for the Marion Island voyage focused on measurement and analysis of vibration due to slamming using the metrics recommended by ISO 2631-1 (1997). The analysis revealed that slamming events produce impulsive accelerations of high magnitude resulting in broad band excitation of the vessel. The weighted r.m.s acceleration levels resulting from slamming exceeded the comfort threshold provided by the standard. The qualitative analysis of human response indicated that slamming not only caused discomfort on-board but also affected work and equipment. The study performed during the Antarctic voyage was designed to identify and correlate measured slamming vibration data with human response and to investigate their association. Statistical analysis, performed using Kendall’s coefficient, indicated that slamming vibration was correlated to human complaints on-board the S.A. Agulhas II. The highest correlation found was the cumulative Vibration Dose Values (VDV) which proved to be the best metric amongst all others to represent slamming vibration for human factors. In addition to that, the study evaluated the effects of some environmental factors such as swell height and wind speed on wave slamming. It was concluded that even moderate sea states can lead to heavy incidences of slamming. Finally, operational deflection shapes were calculated for the visualization of the structural response of the vessel during bow and a stern slamming event. Time domain response and frequency response was calculated to observe the motion of the ship as it undergoes a slamming event. The analysis indicated that the area of impact (bow or stern) comes under severe loading immediately. Both slamming events produce bending and twisting of the entire structure. It was also noted that the long duration of heavy oscillations produced by slamming may affect human comfort and performance on-board the vessel.AFRIKAANSE OPSOMMING: Ondersoek is ingestel oor die menslike impak van ‘n branderklap-verskynsel aan boord die S.A. Agulhas II, ’n Suid-Afrikaanse Voorraad-en-navorsingskip. Volskaal vibrasie-metings is op die skip uitgevoer tydens vaarte na Marioneiland in 2014 en Antarktika in 2014/15. Die metings het vibrasies opgeneem in die vertikale rigting soos per die aanwysings van ISO 2631-1 (1997). ’n Opname was ook uitgevoer op beide vaarte om die menslike reaksie tot branderklap te verkry. Die studie vir die Marioneiland-vaart het gefokus op die meting en analise van vibrasie as gevolg van branderklap deur gebruik te maak van die maatstawwe soos aanbeveel deur ISO 2631-1 (1997). Die analise het getoon dat branderklap impulsiewe versnellings van beduidende grootte produseer wat lei to breë-band opwekking van die skip. Die geweegde w.g.k. vlakke versnellings veroorsaak deur branderklap het die standaard se ongemak drumpelwaarde oorskry. Die kwalitatiewe analise van menslike reaksie het aangedui dat branderklap nie net ongemak aan boord veroorsaak het nie, maar ook werk en toerusting geaffekteer het. Die studie uitgevoer tydens die Antarktiese vaart is ontwerp om die gemete branderklap vibrasiedata te identifiseer en te korreleer met menslike reaksie en die verband daartussen te ondersoek. Statistiese analise, uitgevoer met behulp van Kendall se koeffisiënt, het aangedui dat branderklap vibrasie gekorreleer is met menslike klagtes aan boord die S.A. Agulhas II. Die hoogste korrelasie wat gevind is, was die kumulatiewe Vibrasie Dosis Waarde (VDW) wat die beste maatstaf van almal was om die branderklap vibrasies vir menslike faktore te verteenwoordig. Daarby het die studie die effek van omgewingsfaktore soos deining-hoogte en windspoed op branderklap evalueer. Die gevolgtrekking dat selfs matige seetoestande kan lei to beduidende insidensies van branderklap is gemaak. Operasionele defleksie vorms is uitgewerk vir die visualisering van die strukturele reaksie van die skip tydens ’n boeg en agterboeg branderklap gebeurtenis. Tyddomein respons en frekwensie respons is apart uitgewerk om die beweging van die skip waar te neem wanneer dit ’n branderklap beurtenis ondergaan het. Die analise het aangedui dat die area van impak (boeg of agterboeg) onmiddelik onder belasting verkeer. Beide branderklapgebeure lei tot buiging en verwringing van die golbale struktuur. Daar word ook waargeneem dat die lang duur van ossilasies geproduseer deur branderklap menslike gemak en uitvoering prestasie op die skip kan affekteer

Aeronautical engineering: A continuing bibliography, supplement 122

This bibliography lists 303 reports, articles, and other documents introduced into the NASA scientific and technical information system in April 1980

Feasibility of elastomeric composites as alternative materials for marine applications: A compendious review on their properties and opportunities

© IMechE 2022. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1177/14750902221095321The term elastomer is a curtailment of two words, which are elastic and polymers. Accordingly, elastomers are polymer materials with elasticity. The significant challenges hindering the development of materials for naval applications, similar to other engineering sectors, include achieving a competitive light elastomeric structure. Marine structures are susceptible to various damage responses due to various loads throughout their service life. Being flexible, elastomer has a low modulus of elasticity, exhibits higher values of failure strain and yield strength. In these regards, elastomers are attractive materials for applications that require elasticity because they offer substantial advantages compared to traditional materials. However, the low fire resistance of these elastomeric materials jeopardizes their use in some critical applications. As a result, elastomeric blends and composites containing flame retardant (FR) additives are commonly used. On the other hand, elastomers possess (i) high strength-to-weight ratio, (ii) excellent impact properties, (iii) low infrared, magnetic, and radar signatures, (iv) excellent durability, and (v) high resilience to extreme loads. Hence, the scope of this study focuses on review and awareness regarding the feasibility of marine applications of elastomers/ elastomeric composites, their current scientific and technological drawbacks, and future outlooks or prospects to support several applications in the marine industry.Peer reviewe

Aeronautical engineering: A special bibliography with indexes, supplement 80

This bibliography lists 277 reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1977

Virtual Audio - Three-Dimensional Audio in Virtual Environments

Three-dimensional interactive audio has a variety ofpotential uses in human-machine interfaces. After lagging seriously behind the visual components, the importance of sound is now becoming increas-ingly accepted. This paper mainly discusses background and techniques to implement three-dimensional audio in computer interfaces. A case study of a system for three-dimensional audio, implemented by the author, is described in great detail. The audio system was moreover integrated with a virtual reality system and conclusions on user tests and use of the audio system is presented along with proposals for future work at the end of the paper. The thesis begins with a definition of three-dimensional audio and a survey on the human auditory system to give the reader the needed knowledge of what three-dimensional audio is and how human auditory perception works

Research and technology highlights of the Lewis Research Center

Highlights of research accomplishments of the Lewis Research Center for fiscal year 1984 are presented. The report is divided into four major sections covering aeronautics, space communications, space technology, and materials and structures. Six articles on energy are included in the space technology section

Robust adaptive terminal sliding mode control for dynamic positioning of a semi-submersible offshore platform

In this paper, a robust adaptive terminal sliding mode controller is proposed for dynamic positioning of a semi-submersible offshore platform. First, a state feedback controller is designed to stabilize the nominal system. Then a robust adaptive terminal sliding mode compensator is developed to eliminate the effects of uncertain dynamics and disturbances. It is shown, using Lyapunov methods, that the tracking error is driven to zero in finite time using the proposed control. The efficacy of the control algorithm is validated using simulation studies; it is shown that recent developments in the domain of robust exact differentiation are very helpful for controller implementation