Distributed Feedback Controllers for Stable Cooperative Locomotion of Quadrupedal Robots: A Virtual Constraint Approach

This paper aims to develop distributed feedback control algorithms that allow cooperative locomotion of quadrupedal robots which are coupled to each other by holonomic constraints. These constraints can arise from collaborative manipulation of objects during locomotion. In addressing this problem, the complex hybrid dynamical models that describe collaborative legged locomotion are studied. The complex periodic orbits (i.e., gaits) of these sophisticated and high-dimensional hybrid systems are investigated. We consider a set of virtual constraints that stabilizes locomotion of a single agent. The paper then generates modified and local virtual constraints for each agent that allow stable collaborative locomotion. Optimal distributed feedback controllers, based on nonlinear control and quadratic programming, are developed to impose the local virtual constraints. To demonstrate the power of the analytical foundation, an extensive numerical simulation for cooperative locomotion of two quadrupedal robots with robotic manipulators is presented. The numerical complex hybrid model has 64 continuous-time domains, 192 discrete-time transitions, 96 state variables, and 36 control inputs

Non-Hermitian Floquet-free analytically solvable time-dependent systems [Invited]

The non-Hermitian models, which are symmetric under parity (P) and time-reversal (T) operators, are the cornerstone for the fabrication of new ultra-sensitive optoelectronic devices. However, providing the gain in such systems usually demands precise control of nonlinear processes, limiting their application. In this paper, to bypass this obstacle, we introduce a class of time-dependent non-Hermitian Hamiltonians (not necessarily Floquet) that can describe a two-level system with temporally modulated on-site potential and couplings. We show that implementing an appropriate non-Unitary gauge transformation converts the original system to an effective one with a balanced gain and loss. This will allow us to derive the evolution of states analytically. Our proposed class of Hamiltonians can be employed in different platforms such as electronic circuits, acoustics, and photonics to design structures with hidden PT-symmetry potentially without imaginary onsite amplification and absorption mechanism to obtain an exceptional point

Distributed Feedback Controllers for Stable Cooperative Locomotion of Quadrupedal Robots: A Virtual Constraint Approach

This paper aims to develop distributed feedback control algorithms that allow cooperative locomotion of quadrupedal robots which are coupled to each other by holonomic constraints. These constraints can arise from collaborative manipulation of objects during locomotion. In addressing this problem, the complex hybrid dynamical models that describe collaborative legged locomotion are studied. The complex periodic orbits (i.e., gaits) of these sophisticated and high-dimensional hybrid systems are investigated. We consider a set of virtual constraints that stabilizes locomotion of a single agent. The paper then generates modified and local virtual constraints for each agent that allow stable collaborative locomotion. Optimal distributed feedback controllers, based on nonlinear control and quadratic programming, are developed to impose the local virtual constraints. To demonstrate the power of the analytical foundation, an extensive numerical simulation for cooperative locomotion of two quadrupedal robots with robotic manipulators is presented. The numerical complex hybrid model has 64 continuous-time domains, 192 discrete-time transitions, 96 state variables, and 36 control inputs

Formulation and Optimization of Oral Mucoadhesive Patches of Myrtus Communis by Box Behnken Design

Purpose: Recurrent aphthous stomatitis (RAS) is the most common painful ulcerative disease of oral mucosa happening in ~20% of people. Aimed to develop Myrtus communis L. (Myrtle) containing oral patches, we applied box-behnken design to evaluate the effect of polymers such as Polyvinyl pyrrolidone (PVP), Gelatin, Methylcellulose (MC) and Pectin. Methods: The patches properties such as tensile strength, folding endurance, swelling index, thickness, mucoadhesive strength and the pattern of myrtle release were evaluated as dependent variables. Then, the model was adjusted according to the best fitted equation with box behnken design. Results: The results indicated that preparation of myrtle patch with hydrophilic polymers showed the disintegration time up to 24h and more. Using of polyvinyl pyrrolidone as a water soluble polymer and a pore-former polymer led to faster release of soluble materials from the patch to 29 (min-1). Also it decreases swelling index by increasing the patch disintegration. Gelatin and Pectin, with rigid matrix and water interaction properties, decreased the swelling ratio. Pectin increased the tensile strength, but gelatin produced an opposite effect. Thinner Myrtle patch (about 28μm) was obtained by formulation of methyl cellulose with equal ratio with polyvinyl pyrrolidone or gelatin. Conclusion: Altogether, the analysis showed that the optimal formulation was achieved with of 35.04 mg of Gelatin, 7.22 mg of Pectin, 7.20 mg of polyvinyl pyrrolidone, 50.52 mg of methyl cellulose and 20 mg of Myrtle extract

Position Control of the Single Spherical Wheel Mobile Robot by Using the Fuzzy Sliding Mode Controller

A spherical wheel robot or Ballbot—a robot that balances on an actuated spherical ball—is a new and recent type of robot in the popular area of mobile robotics. This paper focuses on the modeling and control of such a robot. We apply the Lagrangian method to derive the governing dynamic equations of the system. We also describe a novel Fuzzy Sliding Mode Controller (FSMC) implemented to control a spherical wheel mobile robot. The nonlinear nature of the equations makes the controller nontrivial. We compare the performance of four different fuzzy controllers: (a) regulation with one signal, (b) regulation and position control with one signal, (c) regulation and position control with two signals, and (d) FSMC for regulation and position control with two signals. The system is evaluated in a realistic simulation and the robot parameters are chosen based on a LEGO platform, so the designed controllers have the ability to be implemented on real hardware

Comparing the Quality of Iodine in Edible Salt in Iranian Households Living in the Southern Province of Khorasan-e-Razavi Using WHO Standards (Years 2010–2015)

Iodine deficiency disorder among Iranians is a major health-related issue. The aim of this study was to determine iodine concentration in household salt. To sample the iodized salt products, the authors visited all wholesale warehouses of two cities of Bajestan and Gonabad in Khorasan-Razavi, Iran, and randomly purchased three packages of each brand of factory salt distributed through those centers. The sampling procedure was continued over the course of five years (2010–2015). In the 5-year study period, 82 samples of 23 different brands of factory salt were sampled. The most frequent samples were classified into three groups based on their iodine content (ppm = mg iodine per kg of salt): under standard limit (<20 ppm); allowable standard limit (20–50 ppm); over standard limit (>50 ppm). The tests showed that 67% of samples maintained a good level, 26.8% possessed an acceptable level, and 6% had unacceptable levels of iodine. Mean and standard deviation of the salt iodine content were 24.7 and 13.7, respectively. According to the results, the iodine content of samples showed significant differences with international standards (40 ppm), and this highlights the necessity of stricter monitoring of the salt production

Does resveratrol affect prepared sperm parameters and chromatin quality in normozoospermic and asthenozoospermic patients before and after freezing? A lab trial study

Background: Previous studies have examined the effect of resveratrol as a potent antioxidant for free radicals in semen. While, the prepared spermatozoa are more affected by ROS factors due to centrifugation and incubation. Objective: To evaluate the RSV’s effects on the prepared sperm parameters and chromatin quality in both normozoospermic and asthenozoospermic cases before and after freezing. Materials and Methods: The sample of 10 normozoospermic and asthenozoospermic men was prepared through the swim-up method. The groups were then divided into two samples of control and experimental (exposure to 30 μmol/l of RSV) to evaluate and compare the sperm parameters and chromatin quality before and after freezing. Results: The motility and viability of spermatozoa were seen to be significantly different before and after freezing separately in the control and treatment samples of the groups (p ≤ 0.001 and p = 0.001, respectively). However, the stated difference between the control and treatment samples of normozoospermic and asthenozoospermic patients were not significant (p &gt; 0.05). In addition, the sperm morphology and chromatin quality were not significantly different between the two samples of each group; nonetheless, chromatin quality of the treated sample was better than that of the control before and after freezing. Conclusion: Despite the protective effects of RSV on the semen samples, RSV cannot affect significantly the prepared sperms parameters and chromatin quality in normozoospermic and asthenozoospermic patients. Key words: Resveratrol, Chromatin, Motility, Spermatozoa, Freeze

Determinants of the Total Quality Management Implementation in SMEs in Iran (Case of Metal Industry)

Abstract Total Quality Management (TQM) is able to recognize the necessary techniques and tools in production proces

Virtual Constraints and Hybrid Zero Dynamics for Realizing Underactuated Bipedal Locomotion

Underactuation is ubiquitous in human locomotion and should be ubiquitous in bipedal robotic locomotion as well. This chapter presents a coherent theory for the design of feedback controllers that achieve stable walking gaits in underactuated bipedal robots. Two fundamental tools are introduced, virtual constraints and hybrid zero dynamics. Virtual constraints are relations on the state variables of a mechanical model that are imposed through a time-invariant feedback controller. One of their roles is to synchronize the robot's joints to an internal gait phasing variable. A second role is to induce a low dimensional system, the zero dynamics, that captures the underactuated aspects of a robot's model, without any approximations. To enhance intuition, the relation between physical constraints and virtual constraints is first established. From here, the hybrid zero dynamics of an underactuated bipedal model is developed, and its fundamental role in the design of asymptotically stable walking motions is established. The chapter includes numerous references to robots on which the highlighted techniques have been implemented.Comment: 17 pages, 4 figures, bookchapte

Studying the effect of fatigue and sleepiness of long-haul truck drivers on road accidents by adopting structural equation models analysis

The significant increase in transportation and heavy vehicle traffic has caused freeway routes with heavy traffic to face a decrease in safety levels. Furthermore, fatigue and sleepiness are proven to be two of the main reasons of road accidents, and therefore focus on these issues is crucial. Factors such as “use of engineering (safety) technology for road transport”, “informing the drivers on various educational methods”, “controlling the drivers’ work hours”, “use of different routes (alignment inconsistency)” and “observing the drivers’ mental health” should be approached to reduce the accidents caused by fatigue and sleepiness. Given the complex interrelationships between these variables and the number of road accidents, structural equation modelling has been used in this study to estimate the effect and relationships between multiple variables. Data were collected during a 5-month period by interviewing heavy vehicle drivers (2765 filled-out questionnaires). The Confirmatory Factor Analysis (CFA) has also been used to ascertain the validity of the questionnaires. The mentioned factors affecting the drivers’ fatigue were analyzed using SPSS 24.0 package, which allowed ascertaining that the drivers’ mental health is the factor of greater influence on road accidents caused by fatigue and drowsiness. Therefore, actions to improve the drivers’ mental and emotional health (by improving the currently used engineering (safety) technology and alignment inconsistency) should be enhanced rather than excessive controls on the drivers’ work hours by using GPS, work papers and inspections