Optimizations of Patch Antenna Arrays Using Genetic Algorithms Supported by the Multilevel Fast Multipole Algorithm

We present optimizations of patch antenna arrays using genetic algorithms and highly accurate full-wave solutions of the corresponding radiation problems with the multilevel fast multipole algorithm (MLFMA). Arrays of finite extent are analyzed by using MLFMA, which accounts for all mutual couplings between array elements efficiently and accurately. Using the superposition principle, the number of solutions required for the optimization of an array is reduced to the number of array elements, without resorting to any periodicity and similarity assumptions. Based on numerical experiments, genetic optimizations are improved by considering alternative mutation, crossover, and elitism mechanisms. We show that the developed optimization environment based on genetic algorithms and MLFMA provides efficient and effective optimizations of antenna excitations, which cannot be obtained with array-factor approaches, even for relatively simple arrays with identical elements

Contact-Implicit Trajectory Optimization Based on a Variable Smooth Contact Model and Successive Convexification

In this paper, we propose a contact-implicit trajectory optimization (CITO) method based on a variable smooth contact model (VSCM) and successive convexification (SCvx). The VSCM facilitates the convergence of gradient-based optimization without compromising physical fidelity. On the other hand, the proposed SCvx-based approach combines the advantages of direct and shooting methods for CITO. For evaluations, we consider non-prehensile manipulation tasks. The proposed method is compared to a version based on iterative linear quadratic regulator (iLQR) on a planar example. The results demonstrate that both methods can find physically-consistent motions that complete the tasks without a meaningful initial guess owing to the VSCM. The proposed SCvx-based method outperforms the iLQR-based method in terms of convergence, computation time, and the quality of motions found. Finally, the proposed SCvx-based method is tested on a standard robot platform and shown to perform efficiently for a real-world application.Comment: Accepted for publication in ICRA 201

Hardware-in-the-loop simulations and control design for a small vertical axis wind turbine

Control design plays an important role in wind energy conversion systems in achieving high efficiency and performance. In this study, hardware-in-the-loop (HIL) simulations are carried out to design a maximum power point tracking (MPPT) algorithm for small vertical axis wind turbines (VAWTs). Wind torque is calculated and applied to an electrical motor that drives the generator in the HIL simulator, which mimics the dynamics of the rotor. To deal with disturbance torques in the HIL system, a virtual plant is introduced to obtain an error between the speeds in the HIL system and virtual plant. This error is used by a proportional-integral (PI) controller to generate a disturbance torque compensation signal. The MPPT algorithm is tested in the HIL simulator under various wind conditions, and the results are compared with numerical simulations. The HIL simulator successfully mimics the dynamics of the VAWT under various wind conditions and provides a realistic framework for control designs

The evolution of Tsarist policy on the Armenian question in the South Caucasus (1903-1914)

From the Tsarist confiscation of the properties of the Armenian Church in 1903 to the outbreak of the First World War, relations between Russia and its Armenian subjects gradually changed. This thesis scrutinizes how and why this gradual change took place between 1903 and 1914 by looking at the interaction between the Russian administration and the three political pillars of the Russian Armenians (the Dashnaktsutiun, the Armenian Church, and the Armenian bourgeoisie) as well as Russian foreign policy considerations. The confiscation decree of 1903 triggered an immense reaction by the Russian Armenians against the Russian government, which became part of the revolutionary unrest in the South Caucasus in 1905. The relations began to improve with the arrival of the viceroy of the Caucasus, Illarion I. Vorontsov-Dashkov as a general Tsarist recovery was underway. From 1907 to 1912, the Russian authorities reformulated their relations with the political pillars of the Russian Armenians. In this period, by eliminating the Dashnaktsutiun as a political threat in the South Caucasus and sorting out its differences with the Armenian Church and the Armenian bourgeoisie, the Russian regime had improved its relations with the Russian Armenians. By 1912, there were no serious disagreements between the Russian Armenians and the Tsarist authorities, for whom other threats, such as the pan-Islamist movement in the South Caucasus took precedence. This study also adds the foreign policy dimension to the picture as it became the dominant aspect of the relations between the Russian administration and the Russian Armenians between 1912 and 1914. The changes in the international dynamics, particularly regarding the future of the Ottoman Empire, further solidified the improved relations as Russia decided to become the patron and the defender of Armenians in late 1912

Küçük dikey eksenli rüzgâr türbini için basit kontrol tasarımı (Simple control design for a small vertical axis wind turbine)

Bu makalede, küçük dikey eksenli rüzgâr türbinin elde ettiği enerjiyi maksimize edecek basit bir kontrolör tasarlanmıştır. Bu önerilen kontrol algoritmasının amacı mevcut sistemlere kıyasla daha basit bir yapıda olmasıdır. Algoritma kontrol işlemini sisteme uygulanan yük katsayısını önceden belirlenen değer aralıklarında müdahalede bulunarak yapabilmektedir. Bunu yapmak için önceden enerjiyi maksimize eden bir optimizasyon yöntemiyle belirlenmiş olan sınır değerlerinden faydalanmaktadır. Bu makalede, değişik simülasyonlar sonucu elde edilen enerjiyi maksimize ederken, basitleştirilmiş bir dikey eksenli rüzgâr türbini modeli kullanılmıştır

Plan-Guided Reinforcement Learning for Whole-Body Manipulation

Synthesizing complex whole-body manipulation behaviors has fundamental challenges due to the rapidly growing combinatorics inherent to contact interaction planning. While model-based methods have shown promising results in solving long-horizon manipulation tasks, they often work under strict assumptions, such as known model parameters, oracular observation of the environment state, and simplified dynamics, resulting in plans that cannot easily transfer to hardware. Learning-based approaches, such as imitation learning (IL) and reinforcement learning (RL), have been shown to be robust when operating over in-distribution states; however, they need heavy human supervision. Specifically, model-free RL requires a tedious reward-shaping process. IL methods, on the other hand, rely on human demonstrations that involve advanced teleoperation methods. In this work, we propose a plan-guided reinforcement learning (PGRL) framework to combine the advantages of model-based planning and reinforcement learning. Our method requires minimal human supervision because it relies on plans generated by model-based planners to guide the exploration in RL. In exchange, RL derives a more robust policy thanks to domain randomization. We test this approach on a whole-body manipulation task on Punyo, an upper-body humanoid robot with compliant, air-filled arm coverings, to pivot and lift a large box. Our preliminary results indicate that the proposed methodology is promising to address challenges that remain difficult for either model- or learning-based strategies alone.Comment: 4 pages, 4 figure

A Comparative Analysis of Contact Models in Trajectory Optimization for Manipulation

In this paper, we analyze the effects of contact models on contact-implicit trajectory optimization for manipulation. We consider three different approaches: (1) a contact model that is based on complementarity constraints, (2) a smooth contact model, and our proposed method (3) a variable smooth contact model. We compare these models in simulation in terms of physical accuracy, quality of motions, and computation time. In each case, the optimization process is initialized by setting all torque variables to zero, namely, without a meaningful initial guess. For simulations, we consider a pushing task with varying complexity for a 7 degrees-of-freedom robot arm. Our results demonstrate that the optimization based on the proposed variable smooth contact model provides a good trade-off between the physical fidelity and quality of motions at the cost of increased computation time.Comment: 6 pages, 7 figures, 4 tables, IROS 2018 camera-ready versio

REFLECTIONS ON KANT’S VIEW OF THE IMAGINATION

  Abstract The paper elaborates the theory of imagination in Immanuel Kant’s Critique of Pure Reason and Critique of Judgment. From the first Critique to the third Critique, the imagination emerges under different titles such as reproductive, productive or transcendental imagination. The paper shall try to decide whether its functions suggested in the first Critique and its performance in the third Critique are contradictory or developmental with respect to Kant’s critical philosophy.Thus, it will examine of the power and the scope of the imagination in the first Critique and of its status and performance in the third Critique.