Platoon Control Under a Novel Leader and Predecessor Following Scheme With the Use of an Advanced Aerodynamic Model

Author(s):  
Hakan Köroğlu ◽  
Maryam Mirzaei ◽  
Paolo Falcone ◽  
Siniša Krajnović

The longitudinal platoon control problem is considered under a leader and predecessor following scheme with a novel velocity-dependent spacing policy. With this spacing policy, the steady-state intervehicle distances increase with increasing cruise velocity and more so for vehicles that are closer to the leader. Since significant changes might be encountered in intervehicle distances during the travel due to the variations in the velocity of the leader, the problem is studied together with a more accurate modeling of aerodynamic effects within a platoon formation. Based on a standard feedback linearization approach, a dynamic output feedback synthesis problem is formulated with two H∞ performance objectives. One of the performance objectives is linked to the string stability of the platoon formation, while the other can be shaped in a way to maintain small spacing errors without aggressive vehicle maneuvers. A synthesis procedure is then outlined based on linear matrix inequality optimization (LMI). The new control scheme is investigated for a three-vehicle platoon by using an advanced aerodynamic model developed based on extensive fluid dynamic simulations. It is observed in this investigation that a desirable platoon operation can be achieved even with a simple aerodynamic model, provided that the controller is designed in a way to ensure good disturbance attenuation. Nevertheless, an accurate modeling of aerodynamic disturbances might be needed especially for the first vehicle after the leader when the cruising velocity varies over a wide range.

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Alfred von Loebbecke ◽  
Rajat Mittal ◽  
Frank Fish ◽  
Russell Mark

Three-dimensional fully unsteady computational fluid dynamic simulations of five Olympic-level swimmers performing the underwater dolphin kick are used to estimate the swimmer’s propulsive efficiencies. These estimates are compared with those of a cetacean performing the dolphin kick. The geometries of the swimmers and the cetacean are based on laser and CT scans, respectively, and the stroke kinematics is based on underwater video footage. The simulations indicate that the propulsive efficiency for human swimmers varies over a relatively wide range from about 11% to 29%. The efficiency of the cetacean is found to be about 56%, which is significantly higher than the human swimmers. The computed efficiency is found not to correlate with either the slender body theory or with the Strouhal number.


Author(s):  
So-Ryeok Oh ◽  
Sunil K. Agrawal

Robotic applications require coordination of multiple manipulators. This paper discusses an approach for control of manipulators with given end-effector stiffness properties. The approach is designed for concurrent regulation of position of a work piece and grasping force applied by the manipulators on the work piece. The approach is based on input-output feedback linearization. Simulations demonstrate feasibility of the proposed control scheme.


2020 ◽  
Vol 13 (12) ◽  
pp. 6547-6565
Author(s):  
Zhikui Guo ◽  
Lars Rüpke ◽  
Chunhui Tao

Abstract. Herein, we introduce HydrothermalFoam, a three-dimensional hydro-thermo-transport model designed to resolve fluid flow within submarine hydrothermal circulation systems. HydrothermalFoam has been developed on the OpenFOAM platform, which is a finite-volume-based C++ toolbox for fluid-dynamic simulations and for developing customized numerical models that provides access to state-of-the-art parallelized solvers and to a wide range of pre- and post-processing tools. We have implemented a porous media Darcy flow model with associated boundary conditions designed to facilitate numerical simulations of submarine hydrothermal systems. The current implementation is valid for single-phase fluid states and uses a pure-water equation of state (IAPWS-97). We here present the model formulation; OpenFOAM implementation details; and a sequence of 1-D, 2-D, and 3-D benchmark tests. The source code repository further includes a number of tutorials that can be used as starting points for building specialized hydrothermal flow models. The model is published under the GNU General Public License v3.0.


2008 ◽  
Vol 2008 ◽  
pp. 1-9 ◽  
Author(s):  
Elkhatib Kamal ◽  
Magdy Koutb ◽  
Abdul Azim Sobaih ◽  
Sahar Kaddah

Extraction of maximum wind power of variable speed wind turbines in hybrid wind-diesel-storage system (HWDSS) is considered due to economical purposes. The proposed control algorithm utilizes extended fuzzy-linear matrix equalities (FLMEs) systems design of stabilizing fuzzy controllers for nonlinear systems described by Takagi-Sugeno (TS) fuzzy models. The algorithm maximizes the power coefficient for a fixed pitch. Moreover, it reduces the voltage ripple and stabilizes the system over a wide range of wind speed variations. The control scheme is tested for different profiles of wind speed pattern and provides satisfactory results.


2020 ◽  
Author(s):  
Zhikui Guo ◽  
Lars Rüpke ◽  
Chunhui Tao

Abstract. Herein, we introduce HydrothermalFoam, a three dimensional hydro-thermo-transport model designed to resolve fluid flow within submarine hydrothermal circulation systems. HydrothermalFoam has been developed on the OpenFOAM platform, which is a Finite Volume based C++ toolbox for fluid-dynamic simulations and for developing customized numerical models that provides access to state-of-the-art parallelized solvers and to a wide range of pre- and post-processing tools. We have implemented a porous media Darcy-flow model with associated boundary conditions designed to facilitate numerical simulations of submarine hydrothermal systems. The current implementation is valid for single-phase fluid states and uses a pure water equation-of-state (IAPWS-97). We here present the model formulation, OpenFOAM implementation details, and a sequence of 1-D, 2-D and 3-D benchmark tests. The source code repository further includes a number of tutorials that can be used as starting points for building specialized hydrothermal flow models. The model is published under the GNU General Public License v3.0.


Author(s):  
S-S You ◽  
S-K Jeong

This paper is concerned with the active robust autopilot design of a four-wheel steering vehicle against external disturbances. Firstly, the effect of four-wheel steering and independent wheel torques for lateral/directional and roll motions is modelled by a set of linear models under proper manoeuvring conditions. To enhance the dynamic performance of an automobile system, a mixed H2/H∞ synthesis with pole constraint is designed on the basis of full state feedback applying linear matrix inequality (LMI) theory. For lateral/directional and roll motions, the steering angles are actively controlled by steering wheel angles through the actuator dynamics. The wheel power and braking are also controlled by independent wheel torques. Simulation results indicate that the proposed control approach can achieve predetermined performance (or acceptable level of disturbance attenuation) and stability as well as robustness even when external disturbances are severe. The active 4WS car along with steering and wheel torque control algorithms allows greater manoeuvrability and improved stability in a wide range of uncertainty.


2018 ◽  
Vol 35 (4) ◽  
pp. 62-64
Author(s):  
Nazar Ul Islam Wani

Pilgrimage in Islam is a religious act wherein Muslims leave their homes and spaces and travel to another place, the nature, geography, and dispositions of which they are unfamiliar. They carry their luggage and belongings and leave their own spaces to receive the blessings of the dead, commemorate past events and places, and venerate the elect. In Pilgrimage in Islam, Sophia Rose Arjana writes that “intimacy with Allah is achievable in certain spaces, which is an important story of Islamic pilgrimage”. The devotional life unfolds in a spatial idiom. The introductory part of the book reflects on how pilgrimage in Islam is far more complex than the annual pilgrimage (ḥajj), which is one of the basic rites and obligations of Islam beside the formal profession of faith (kalima); prayers (ṣalāt); fasting (ṣawm); and almsgiving (zakāt). More pilgrims throng to Karbala, Iraq, on the Arbaeen pilgrimage than to Mecca on the Hajj, for example, but the former has received far less academic attention. The author expands her analytic scope to consider sites like Konya, Samarkand, Fez, and Bosnia, where Muslims travel to visit countless holy sites (mazarāt), graves, tombs, complexes, mosques, shrines, mountaintops, springs, and gardens to receive the blessings (baraka) of saints buried there. She reflects on broader methodological and theoretical questions—how do we define religion?—through the diversity of Islamic traditions about pilgrimage. Arjana writes that in pilgrimage—something which creates spaces and dispositions—Muslim journeys cross sectarian boundaries, incorporate non-Muslim rituals, and involve numerous communities, languages, and traditions (the merging of Shia, Sunni, and Sufi categories) even to “engende[r] a syncretic tradition”. This approach stands against the simplistic scholarship on “pilgrimage in Islam”, which recourses back to the story of the Hajj. Instead, Arjana borrows a notion of ‘replacement hajjs’ from the German orientalist Annemarie Schimmel, to argue that ziyārat is neither a sectarian practice nor antithetical to Hajj. In the first chapter, Arjana presents “pilgrimage in Islam” as an open, demonstrative and communicative category. The extensive nature of the ‘pilgrimage’ genre is presented through documenting spaces and sites, geographies, and imaginations, and is visualized through architectural designs and structures related to ziyārat, like those named qubba, mazār (shrine), qabr (tomb), darih (cenotaph), mashhad (site of martyrdom), and maqām (place of a holy person). In the second chapter, the author continues the theme of visiting sacred pilgrimage sites like “nascent Jerusalem”, Mecca, and Medina. Jerusalem offers dozens of cases of the ‘veneration of the dead’ (historically and archaeologically) which, according to Arjana, characterizes much of Islamic pilgrimage. The third chapter explains rituals, beliefs, and miracles associated with the venerated bodies of the dead, including Karbala (commemorating the death of Hussein in 680 CE), ‘Alawi pilgrimage, and pilgrimage to Hadrat Khidr, which blur sectarian lines of affiliation. Such Islamic pilgrimage is marked by inclusiveness and cohabitation. The fourth chapter engages dreams, miracles, magical occurrences, folk stories, and experiences of clairvoyance (firāsat) and the blessings attached to a particular saint or walī (“friend of God”). This makes the theme of pilgrimage “fluid, dynamic and multi-dimensional,” as shown in Javanese (Indonesian) pilgrimage where tradition is associated with Islam but involves Hindu, Buddhist and animistic elements. This chapter cites numerous sites that offer fluid spaces for the expression of different identities, the practice of distinct rituals, and cohabitation of different religious communities through the idea of “shared pilgrimage”. The fifth and final chapter shows how technologies and economies inflect pilgrimage. Arjana discusses the commodification of “religious personalities, traditions and places” and the mass production of transnational pilgrimage souvenirs, in order to focus on the changing nature of Islamic pilgrimage in the modern world through “capitalism, mobility and tech nology”. The massive changes wrought by technological developments are evident even from the profusion of representations of Hajj, as through pilgrims’ photos, blogs, and other efforts at self documentation. The symbolic representation of the dead through souvenirs makes the theme of pilgrimage more complex. Interestingly, she then notes how “virtual pilgrimage” or “cyber-pilgrimage” forms a part of Islamic pilgrimage in our times, amplifying how pilgrimage itself is a wide range of “active, ongoing, dynamic rituals, traditions and performances that involve material religions and imaginative formations and spaces.” Analyzing religious texts alone will not yield an adequate picture of pilgrimage in Islam, Arjana concludes. Rather one must consider texts alongside beliefs, rituals, bodies, objects, relationships, maps, personalities, and emotions. The book takes no normative position on whether the ziyāratvisitation is in fact a bid‘ah (heretical innovation), as certain Muslim orthodoxies have argued. The author invokes Shahab Ahmad’s account of how aspects of Muslim culture and history are seen as lying outside Islam, even though “not everything Muslims do is Islam, but every Muslim expression of meaning must be constituting in Islam in some way”. The book is a solid contribution to the field of pilgrimage and Islamic studies, and the author’s own travels and visits to the pilgrimage sites make it a practicalcontribution to religious studies. Nazar Ul Islam Wani, PhDAssistant Professor, Department of Higher EducationJammu and Kashmir, India


Author(s):  
Jatin K Pradhan ◽  
Arun Ghosh

It is well known that linear time-invariant controllers fail to provide desired robustness margins (e.g. gain margin, phase margin) for plants with non-minimum phase zeros. Attempts have been made in literature to alleviate this problem using high-frequency periodic controllers. But because of high frequency in nature, real-time implementation of these controllers is very challenging. In fact, no practical applications of such controllers for multivariable plants have been reported in literature till date. This article considers a laboratory-based, two-input–two-output, quadruple-tank process with a non-minimum phase zero for real-time implementation of the above periodic controller. To design the controller, first, a minimal pre-compensator is used to decouple the plant in open loop. Then the resulting single-input–single-output units are compensated using periodic controllers. It is shown through simulations and real-time experiments that owing to arbitrary loop-zero placement capability of periodic controllers, the above decoupled periodic control scheme provides much improved robustness against multi-channel output gain variations as compared to its linear time-invariant counterpart. It is also shown that in spite of this improved robustness, the nominal performances such as tracking and disturbance attenuation remain almost the same. A comparison with [Formula: see text]-linear time-invariant controllers is also carried out to show superiority of the proposed scheme.


2021 ◽  
pp. 073490412199344
Author(s):  
Wolfram Jahn ◽  
Frane Sazunic ◽  
Carlos Sing-Long

Synthesising data from fire scenarios using fire simulations requires iterative running of these simulations. For real-time synthesising, faster-than-real-time simulations are thus necessary. In this article, different model types are assessed according to their complexity to determine the trade-off between the accuracy of the output and the required computing time. A threshold grid size for real-time computational fluid dynamic simulations is identified, and the implications of simplifying existing field fire models by turning off sub-models are assessed. In addition, a temperature correction for two zone models based on the conservation of energy of the hot layer is introduced, to account for spatial variations of temperature in the near field of the fire. The main conclusions are that real-time fire simulations with spatial resolution are possible and that it is not necessary to solve all fine-scale physics to reproduce temperature measurements accurately. There remains, however, a gap in performance between computational fluid dynamic models and zone models that must be explored to achieve faster-than-real-time fire simulations.


Author(s):  
Hua-Nv Feng ◽  
Bao-Lin Zhang ◽  
Yan-Dong Zhao ◽  
Hui Ma ◽  
Hao Su ◽  
...  

Marine structures are inevitably influenced by parametric perturbations as well as multiple external loadings. Among these loadings, earthquake is generally more destructive and unpredictable than others. It is significant to develop effective active control schemes to guarantee the safety, stability, and integrity of marine structures subject to earthquakes and parametric perturbations. In this paper, the problem of networked [Formula: see text] robust damping control is addressed to stabilize a marine structure subject to earthquakes. First, in consideration of perturbations of the structure parameters, an uncertain model of the networked marine structure under earthquakes is presented. Second, a robust networked [Formula: see text] control scheme is presented to suppress seismic responses of the structure. By using stability theory of time-delay systems, several sufficient conditions on robust stability of the networked marine structure system are obtained, and the linear matrix inequality methods are utilized to solve the gain matrix of the controller. Finally, simulation indicates that compared with the traditional robust [Formula: see text] control and the proposed networked [Formula: see text] control, the seismic responses amplitudes of the marine structure under the two controllers are almost the same, while the latter is more economic than the former.


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