Robust Model Predictive Control of Biped Robots with Adaptive On-line Gait Generation

Reza Heydari,Reza Heydari 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.1

In this paper, an on-line gait control scheme is proposed for the biped robots for walking up and down thestairs. In the proposed strategy, the nonlinear model predictive control approach is used for the trajectory planningand as well as for the control of the robot. The motion of the robot is expressed in the form of a cost functionand some constraints that are related to the stable walking of the robot. The main feature of this method is that itdoes not need any off-line trajectory planning and the walking gait is formulated such that the environmental andstability constraints of the robot are satisfied. This on-line trajectory planning gives the important ability to therobot to adjust its gait lengths. In this way, the robot is able to ascend and descend the stairs without knowing theheight and depth of the stairs in advance. In the control algorithm, the Radial-Basis Function (RBF) neural networkwith on-line training method is used to model the behavior of the robot over the prediction horizon. The stabilityanalysis of the closed-loop system is performed using the Lyapunov method as well as the Poincaré map. Theproposed method is applied to a 5-DOF biped robot in the sagittal plane. The simulation results show effectivenessof the proposed method.

Exact solution for transverse bending analysis of embedded laminated Mindlin plate

Heydari, Mohammad Mehdi,Kolahchi, Reza,Heydari, Morteza,Abbasi, Ali Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.5

Laminated Rectangular plates embedded in elastic foundations are used in many mechanical structures. This study presents an analytical approach for transverse bending analysis of an embedded symmetric laminated rectangular plate using Mindlin plate theory. The surrounding elastic medium is simulated using Pasternak foundation. Adopting the Mindlin plate theory, the governing equations are derived based on strain-displacement relation, energy method and Hamilton's principle. The exact analysis is performed for this case when all four ends are simply supported. The effects of the plate length, elastic medium and applied force on the plate transverse bending are shown. Results indicate that the maximum deflection of the laminated plate decreases when considering an elastic medium. In addition, the deflection of the laminated plate increases with increasing the plate width and length.

Exact solution for transverse bending analysis of embedded laminated Mindlin plate

Mohammad Mehdi Heydari,Reza Kolahchi,Morteza Heydari,Ali Abbasi 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.5

Laminated Rectangular plates embedded in elastic foundations are used in many mechanical structures. This study presents an analytical approach for transverse bending analysis of an embedded symmetric laminated rectangular plate using Mindlin plate theory. The surrounding elastic medium is simulated using Pasternak foundation. Adopting the Mindlin plate theory, the governing equations are derived based on strain-displacement relation, energy method and Hamilton’s principle. The exact analysis is performed for this case when all four ends are simply supported. The effects of the plate length, elastic medium and applied force on the plate transverse bending are shown. Results indicate that the maximum deflection of the laminated plate decreases when considering an elastic medium. In addition, the deflectionof the laminated plate increases with increasing the plate width and length.

Size-dependent bending analysis of FGM nano-sinusoidal plates resting on orthotropic elastic medium

Reza Kolahchi,Ali Mohammad Moniri Bidgoli,Mohammad Mehdi Heydari 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.5

Bending analysis of functionally graded (FG) nano-plates is investigated in the present work based on a new sinusoidal shear deformation theory. The theory accounts for sinusoidal distribution of transverse shear stress, and satisfies the free transverse shear stress conditions on the top and bottom surfaces of the plate without using shear correction factor. The material properties of nano-plate are assumed to vary according to power law distribution of the volume fraction of the constituents. The size effects are considered based on Eringen's nonlocal theory. Governing equations are derived using energy method and Hamilton’s principle. The closed-form solutions of simply supported nano-plates are obtained and the results are compared with those of first-order shear deformation theory and higher-order shear deformation theory. The effects of different parameters such as nano-plate length and thickness, elastic foundation, orientation of foundation orthtotropy direction and nonlocal parameters are shown in dimensionless displacement of system. It can be found that with increasing nonlocal parameter, the dimensionless displacement of nanoplate increases.

A comparative study of intranasal desmopressin and intranasal ketamine for pain management in renal colic patients: A randomized double-blind clinical trial

Heydari Farhad,Azizkhani Reza,Majidinejad Saeed,Zamani Majid,Norouzian Aref 대한응급의학회 2024 Clinical and Experimental Emergency Medicine Vol.11 No.1

Objective Urolithiasis is one of the most common urological diseases worldwide, usually presenting as renal colic that leads to severe pain that requires analgesic treatment. This study aimed to compare the efficacy of ketamine and desmopressin in the pain management of renal colic patients. Methods This double-blind, randomized clinical trial was conducted on renal colic patients referred to the emergency department from June 2021 to July 2022. Patients were randomly assigned to three groups. In the desmopressin group, patients were treated with intranasal desmopressin and intravenous ketorolac. The ketamine group was treated with intranasal ketamine and ketorolac. The control group received ketorolac and an intranasal placebo. Vital signs were evaluated at baseline and 60 minutes; and pain scores were assessed at baseline, 10, 30, and 60 minutes after treatment. Results Enrollment included 135 patients, the mean (standard deviation) age was 44.1±11.4 years, and 82 (60.7%) were men. The mean visual analog scale scores were significantly lower at 10, 30, and 60 minutes in the ketamine group (5.6±1.2, 3.0±1.1, and 0.9±0.9, respectively) compared to the control (8.2±1.1, 5.1±2.0, and 2.3±2.6, respectively) and desmopressin (6.7±1.8, 4.2±2.2, and 1.3±1.4, respectively) groups (P<0.05). Although patients in the desmopressin group had lower mean pain scores than the control group at 10, 30, and 60 minutes, this difference was only significant at 10 minutes after the intervention (P<0.05). No significant differences in vital signs were found at 60 minutes after treatment. Conclusion Ketamine showed more favorable analgesic effects in renal colic patients than desmopressin, although desmopressin showed efficacy in the first minutes posttreatment.

Strategies for sustaining and enhancing nursing students’ engagement in academic and clinical settings: a narrative review

Mohammad Reza Ghasemi,Hossein Karimi Moonaghi,Abbas Heydari 한국의학교육학회 2020 Korean journal of medical education Vol.32 No.2

Students’ engagement in academic-related learning activities is one of the important determinants of students’ success. Identifying the best teaching strategies to sustain and promote nursing students’ engagement in academic and clinical settings has always been a challenge for nurse educators. Hence, it is essential to provide a set of strategies for maintaining and enhancing the academic engagement of nursing students. The purpose of this review was to explore and summarize the strategies that nurse educators use to sustain and promote nursing students’ engagement in academic and clinical settings. A narrative literature review was conducted. CINAHL (nursing content), ProQuest, Medline, the Cochrane, Google Scholar, and Scopus were searched. Of 1,185 retrieved articles, 32 teaching strategies were identified and extracted from the nursing literature. We used thematic analysis approach to organize these strategies into five main categories as follows: technology-based strategies (15 articles), collaborative strategies (10 articles), simulation-based strategies (two articles), research-based strategies (two articles), and miscellanea learning strategies (three articles). As a general comment, these strategies have the potential to promote nursing students’ engagement. Among the strategies discussed in this review, the use of technology, particularly the response system and online learning, was more common among nursing educators, which is in line with today’s advances in smart technologies. The collection presented in this review can be used as a starting point for future research to evaluate the effectiveness of an educational intervention on the academic engagement of nursing students. Nevertheless, due to the lack of experimental studies, the optimal strategies remain to be elucidated through future high-quality experimental study.

Experimental and mathematical analysis of electroformed rotating cone electrode

Hamid Heydari,Salman Ahmadipouya,Amirhossein Shoaee Maddah,Mohammad-Reza Rokhforouz 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.4

In this study, we present results of a mathematical model in which the governing equations of electroforming process were solved using a robust finite element solver (COMSOL Multiphysics). The effects of different parameters including applied current density, solution electrical conductivity, electrode spacing, and anode height on the copper electroforming process have been investigated. An electroforming experiment using copper electroforming cell was conducted to verify the developed model. The obtained results show that by increasing the applied current density, the electroforming process takes place faster, thereby resulting in a higher thickness of the electroformed layer. In addition, higher applied current density led to non-uniformity of the coated layer. It was revealed that by increasing electrolytic conductivity from 5 to 20 S/m, the electroformed layer became thicker. By considering three different anode heights, it was found that if the cathode and anode are the same height, the process will be more effective. Finally, it was concluded that there is an optimum value of anode-cathode spacing: above it, energy consumption and plating time are high; while below it, the resultant layer is non-uniform. The present study demonstrates that the developed model can accurately capture the physics of electroforming with a reasonable computational time.

Facile one-pot three-component route to an assembly of 2-amino-4H-chromenes and spirochromenes promoted via ceria nanoparticles in a benign manner

Khorshidi Naimeh,Heydari Reza,Maghsoodlou Malek Taher,Fatahpour Maryam 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.6

In this study, a series of 2-amino-4H-chromenes and spirochromenes were elaborated and synthesized via a new sustainable one-pot three-component strategy from easily available materials including phloroglucinol, malononitrile, and aldehydes/isatins. Ceria nanoparticles (CeO2 NPs) were successfully applied as an effective catalyst that recycled and reused with a marginal decrement in its catalytic performance. The Lewis acid–base nature of the described nanocatalyst afforded the high yields of target products. The reaction is run in ethanol as a green solvent to create an environment-friendly process. The other salient merits of this methodology are a broad substrate scope, a simple operation, shorter reaction times, and no need for column chromatographic purification.

Investigation of Surface Nanostructuring, Mechanical Performance and Deformation Mechanisms of AISI 316L Stainless Steel Treated by Surface Mechanical Impact Treatment

Milad Rostami,Reza Miresmaeili,Asghar Heydari Astaraee 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.4

Nanostructured materials exhibit superior properties with respect to their bulk counterpart. Recently, a new processingmethod for surface nanostructuring of metallic materials called surface mechanical impact treatment (SMIT) was developed. In this study, the surface microstructural features due to the refinement process of AISI 316L stainless steel by means ofSMIT and subsequent mechanical performance were investigated. The effects of SMIT processing parameters, i.e. ball sizeand treatment duration, were studied in terms of microstructural evolutions using X-ray diffraction, transmission electronmicroscopy, optical microscopy, and field emission scanning electron microscopy analyses, and mechanical propertiesthrough hardness and tensile tests. A gradient nanostructured surface layer was successfully formed on the surface of thetreated samples. The mean grain size was measured to be ~ 20 nm in the topmost surface layer and increased with increasingdepth. Microstructural examinations showed that the twins and their intersections (rhombic blocks) formed in the surfacelayers. It was found that the mechanical performance of the treated samples is effectively enhanced. The surface hardnessof the treated samples increased about 3 times while the yield strength of the samples increased with increasing SMIT timeand size of the ball up to 2.5 times. The grain refinement mechanisms, mechanical properties, and fracture behavior weresubsequently analyzed and discussed.

Adaptive plasticity of morphological and anatomical traits of Brant’s oak (Quercus brantii Lindl.) leaves under different climates and elevation gradients

Soheili Forough,Heydari Mehdi,Woodward Stephen,Abdul-Hamid Hazandy,Naji Hamid Reza 한국산림과학회 2023 Forest Science And Technology Vol.19 No.2

The morphological and anatomical characteristics of leaves are sensitive and adaptable to environmental changes. Determining eco-physiological patterns of leaf characteristics along elevational gradients allows for a better understanding and prediction of how plants might respond to climate change. In this work, the ecological adaptation mechanisms related to morphological and anatomical characteristics of Brant’s oak (Quercus brantii Lindl.) leaves were studied at three elevation classes (low, middle, and high) in two different Mediterranean and subhumid climates in Zagros forests in western Iran. There were no sig- nificant changes in leaf length, although the leaf-specific area was higher at low and middle elevations in subhumid climates. In addition, stomata length, width, density, and stomatal pore index were higher in the upper elevations of subhumid climate than in the Mediterranean climate. At low and middle elevations, dry matter content was higher at sites from the Mediterranean climate. The results of plasticity indices showed that individuals of Q. brantii from middle-elevation sites exhibited greater plasticity than those from low and high-elevation sites. Overall, Q. brantii, the dominant oak species in Zagros forests, appears to respond to elevational and environmental changes, suggesting that leaves can adapt to these changes through morphological and anatomical traits. These results provide new insights into the environmental adaptation strategies of plants at the morphological and anatomical levels against climate change.