Search

This work addresses the predefined-time convergence problem for a class of second order nonlinear systems subjected to matched disturbances. A novel family of sigmoid function based terminal sliding surfaces is proposed for which robust fixed time convergence is guaranteed. The stability properties are established through the Lyapunov framework. In the proposed technique, bound on the settling time is user-defined for arbitrary initial conditions. Furthermore, switching control law is designed to avoid singularity, thus sufficient condition for singularity free controller is determined. The utility of proposed control scheme is validated by simulating two numerical examples from recent relevant literature.

This paper presents output feedback control for longitudinal dynamics of fixed-wing aircraft using singular perturbation techniques. The longitudinal dynamic model is separated into two timescales. A composite feedback control law based on sliding mode control (SMC) is designed for slow and fast subsystems to track the aerodynamic velocity and flight path angle references. Additionally, two separate high-gain observers (HGO) are designed for the slow and fast subsystems to estimate system states. The proposed technique not only simplifies the design but also is computationally efficient. Simulations are performed in MATLAB/Simulink environment with results demonstrating that the proposed output feedback control method robustly achieves trajectory tracking.

Purpose The purpose of this study is to provide the full-state mathematical model and devise a nonlinear controller for a balloon-supported unmanned aerial vehicle (BUAV). Design/methodology/approach Newtonian mechanics is used to establish the nonlinear mathematical model of the proposed vehicle assembly which incorporates the dynamics of both balloon and quadrotor UAV. A controllable form of the nine degrees of freedom model is derived. Backstepping control is designed for the proposed model and simulations are performed to assess the tracking performance of the proposed control. Findings The results show that the proposed methodology works well for smooth trajectories in presence of wind gusts. Moreover, the final mathematical model is affine and various nonlinear control techniques can be used in the future for improved system performance. Originality/value Multi-rotor unmanned aerial vehicles (MUAVs) are equipped with controllers but are constrained by smaller flight endurance and payload carrying capability. On the contrary, lighter than air (LTA) aerial vehicles have longer flight times but have poor control performance for outdoor operations. One of the solutions to achieve better flight endurance and payload carrying capability is to augment the LTA balloon to MUAV. The novelty of this research lies in full-order mathematical modeling along with transformation to controllable form for the BUAV assembly.

Purpose The purpose of this paper is to provide a comprehensive and unified presentation of recent developments in skid-steer wheeled mobile robots (SSWMR) with regard to its control, guidance and navigation for the researchers who wish to study in this field. Design/methodology/approach Most of the contemporary unmanned ground robot’s locomotion is based upon the wheels. For wheeled mobile robots (WMRs), one of the prominent and widely used driving schemes is skid steering. Because of mechanical simplicity and high maneuverability particularly in outdoor applications, SSWMR has an advantage over its counterparts. Different prospects of SSWMR have been discussed including its design, application, locomotion, control, navigation and guidance. The challenges pertaining to SSWMR have been pointed out in detail, which will seek the attention of the readers, who are interested to explore this area. Findings Relying on the recent literature on SSWMR, research gaps are identified that should be analyzed for the development of autonomous skid-steer wheeled robots. Originality/value An attempt to present a comprehensive review of recent advancements in the field of WMRs and providing references to the most intriguing studies.

Purpose This paper aims to devise a robust controller for the non-linear aircraft model using output feedback control topology in the presence of uncertain aerodynamic parameters. Design/methodology/approach Feedback linearization-based state feedback (SFB) controller is considered along with a robust outer loop control which is designed using Lyapunov’s second method. A high-gain observer (HGO) in accordance with the separation principle is used to implement the output feedback (OFB) control scheme. The robustness of the controller and observer is assessed by introducing uncertain aerodynamics coefficients in the dynamic model. The proposed scheme is validated using MATLAB/SIMULINK. Findings The efficacy of the proposed scheme is authenticated with the simulation results which show that HGO-based OFB control achieves the SFB control performance for a small value of the high-gain parameter in the presence of uncertain aerodynamic parameters. Originality/value A HGO for the non-linear model of aircraft with uncertain parameters is a novel contribution which could be further used for the unmanned aerial vehicles autopilot, flight trajectory tracking and path following.

In this article, a finite-time robust tracking control of output constrained multirotor unmanned aerial vehicle (UAV) is proposed. A finite-time sliding mode control (SMC) technique with barrier Lyapunov function (BLF) is used to assure robustness of the derived control laws while maintaining the output in specified constraints. A comparison of the proposed controller is carried out with conventional SMC to manifest the effectiveness of the output-constrained tracking control. Numerical simulations of quadrotor UAV with exogenous disturbances and time-invariant output constraints demonstrate the efficacy of the proposed controller regarding robustness, finite-time convergence, and chattering reduction.

A nonlinear control technique for autonomous control of a tri-rotor unmanned aerial vehicle is presented in this paper. First, a comprehensive mathematical model is developed using the Newton–Euler approach for a tri-rotor, which is found to be highly nonlinear and coupled. Then, the equivalent input affine model is extracted by applying a suitable transformation. Finally, the sliding mode control for trajectory tracking is chosen which is immune to matched external disturbances, parametric uncertainties, and modeling errors. The proposed controller performance has been verified for appropriate inputs under wind disturbances using MATLAB, and the simulation results are presented.

This paper presents the output feedback control (OFC) of flexible joint single link robotic manipulator via extended high gain observer (EHGO). Conventional high gain observer (HGO) is sensitive to noise and external disturbances. Therefore, EHGO is used to reject the effect of noise and external disturbances on the output of the system. A feedback linearizing control (FLC) is used to track the desired output of the manipulator and EHGO is used for state estimation. A detailed comparative analysis of HGO and EHGO is presented. The controller and observer designed are validated using simulations and the results show that the EHGO along with globally bounded FLC perfectly tracks the system's output in the presence of noise and external disturbances.

Single link flexible joint robotic manipulators are highly nonlinear systems is being widely used in many industries which are most of the time suffer from external disturbances and dynamical parametric uncertainties. In this paper, robust nonlinear output feedback tracking control is designed for single-link flexible joint robotic manipulator system. The designed controller is based on the feedback linearization control technique which is opted owing to its simplicity. A conventional high gain observer is used to estimate the states, but it is sensitive to external disturbances and parametric uncertainties. To handle the aforementioned drawbacks, an extended order high gain observer is used which has the capability to eliminate the effects of external disturbances and parametric uncertainties. A feedback linearizing control technique is used to track the desired output of the robotic manipulator and extended order high gain observer is used for state estimations. The proposed controller and observers are validated using MATLAB simulations. The results show that the extended order high gain observer along with globally bounded feedback linearizing control perfectly tracks the trajectory of the system's output in the presence of external disturbances and parametric uncertainties. This robustness of the extended order high gain observer against external disturbances and parametric uncertainties makes it appropriate for practical implementation to the flexible joint n-link manipulators.

The robust decentralized formation control for the multiagent quadrotor is investigated in this article. The leaderless formation protocol is proposed for a class of square multi-input multi-output nonlinear multiagent systems with an undirected communication graph. The six degree of freedom underactuated nonlinear model of multiagent quadrotor is considered and altered to a four-input four-output model by stabilizing two states internally using sliding mode control (SMC). Later, the sliding mode-based finite-time position, altitude and heading formation is established based on Lyapunov stability theory. The numerical simulations are performed using MATLAB/ Simulink which validate the proposed formation protocol.

Robust output tracking of uncertain systems requires nonlinear controllers due to approximate parameters and exogenous disturbances. However, the design of nonlinear control is often more complex for practical implementation. This article presents a simple nonlinear robust control for the ball and beam system based on integral sliding mode control. In addition to this a low pass filter is designed to estimate the disturbance and alleviate the chattering effect. A comparison of the proposed technique with the conventional sliding mode control is carried out using MATLAB/ SIMULINK. The simulation results validate the efficacy and improved performance of the proposed technique in the presence of exogenous disturbances and parametric uncertainties.

In this paper, the mathematical modeling and model-based control of the planar rigid-flexible manipulator has been presented. Small deflection has been assumed in flexible link. Modeling is based on frame transformation matrices which describe the rotation of the frames. The Lagrangian approach has been used to derive the ideal dynamic model of the rigid-flexible manipulator, for which kinetic and potential energies of the system have been calculated. For simulation and control purposes, a finite-dimensional model was required, for which the assumed mode method (AMM) has been used. The model-based controller has been designed and simulations are successfully carried out in MATLAB/Simulink.

Naval applications need refined regulation, to meet modern era standards, which eventually leads to the requirement of more accurate mathematical modeling of all subsystems. All naval autonomous systems are equipped with electromechanical actuators, which are often controlled for linear operating range and nonlinearities which may lead to chaotic behavior, are ignored. Additionally, the necessary use of observers for the linear model limits the level of autonomy. In this paper, a typical solenoid actuator is studied with the inclusion of third-order nonlinear dynamic properties. A nonlinear output feedback control is designed for tracking the position of the plunger in solenoid actuator. High gain observer (HGO) is realized to estimate the unknown states. The proposed topology for solenoid actuator uses feedback linearization along with the HGO to achieve the performance of state feedback control which solidifies the effectiveness of HGO. The results are obtained using MATLAB/ SIMULINK.

Anterior cruciate ligament injuries are very commonly encountered during routine MRI reporting and various signs have been described for their identification. However, the diagnosis of isolated bundle tears is difficult using MRI, thus can be easily overlooked, especially isolated tear of posterolateral bundle. We present a case of a young male with "Gap" and "Footprint" signs on MRI knee joint, which are considered highly specific of posterolateral ACL bundle tear.

In this modern era research in mechanical ventilator model designing has increased a lot. Mathematical model of lungs is used to distinguish the pulmonary diseases. In this work bond graph model of breathing mechanism i.e. inspiration and expiration of lungs is developed. Hydraulic analogies are allocated to lungs using cylinders and accumulators. From nostrils to trachea single cylinder is considered having resistance and compliance effect associated with it. Trachea to lower lung section comprised of 23 generations of airways. In this study, 2 generations are considered with resistance, compliance and inertial effect, whereas resistance and compliance effect, of 3rd to 17th generations are lumped. These generations are modelled with cylinders with decreasing sizes. 17 to 23 are modelled as accumulators with resistance and compliance. Model parameters were estimated using grey box estimation.20 sim is used to make the bond graph model and determine the relationship of pressure and volume curves. Model can be used for screening of lungs diseases. Model can be used for clinical trials with any existing mechanical ventilator.

Micro gyroscopes are among the rapidly aggrandizing field of the micro electro mechanical systems (MEMS), which is procured with its extensive range of applications around the globe. This paper depicts an innovated approach of designing and modeling of a novel brawny multi-mass gyroscope to acquire dynamic motion amplification and spacious bandwidth. The proposed resonator block is accompanied by a series of proof masses coupled to each other where the primary mass defines the driving unit, secondary mass passes on the dynamic energy, tertiary mass is oscillating mass. The main crux of this design is that increasing the number of masses ameliorates the model with respect to amplification by manifolds and enhances the bandwidth. To analyze this structural model, assistance of finite element method (FEM) based analysis is pursued and simulations are carried out for the examination of distinct frequency modes and frequency response of this robust system. The wide bandwidth of over 3 kHz is achieved by this proposed dynamic model.

In modern technological era research in Mechanical Ventilators (MV) has drastically increased in designing model based MV treatment. In model based MV treatment mathematical model of lung is used to detect lungs diseases. In proposed work, inspiration and expiration mechanism of lungs has been modelled using Bond Graphs. Lung segments are assigned Hydraulic analogies using cylinders and accumulators. Upper airway from nostrils to trachea is modelled as single cylinder having resistance and associated compliance effect. Trachea to lower lung segment consists of 23 generations of airways. In this study, 4 generations are considered with their respective resistance and compliance, whereas resistance and compliance effect, of 5th to 17th generations are lumped. These are modelled with cylinders of decreasing size. Generation 17 to 23 are considered as respiratory zone that are modelled as accumulator having compliance and resistance associated. Grey-Box model estimation is used to estimate model parameters of 4 generations and controller is designed. 20 sim software is used to determine the relationship between Pressure (P) and Volume (V) and evaluate the model performance. Model is capable of predicting the true PV curves and thus leading to screening of lungs diseases. Model can be used for clinical trials with any existing MV.

Sustainability in all aspects of our life is certainly an emerging trend. All industries including Construction Industry are taking active initiatives to support sustainability practices. Construction always has been a major player in Canada's economy. In the global economy, construction occupies a still larger position. Around the world this industry accounts for $8 trillion a year of economic activity or about 15% of the world's GDP. Moreover, this amount is projected to grow to $12 trillion by 2020. During this time period, Canada is expected to move from seventh to fifth place in terms of the world's largest construction market. This emphasizes the need for aptly trained professional in all domains of sustainability. There is a growing need for design and construction professionals with sustainability skillsets, which are crucial for enhancing sustainability practices, especially given the growing complexity of construction projects and construction-related environmental law. Academic institutions have a responsibility to address this emerging need of the industry to support national economy. Construction projects are complex because they involve many human and non-human factors and variables. Design and construction students learn more effectively where they get involved in life-cycle of a building project i.e., from conceptual design to completion stage dealing with major issues like resources, cost, quality and time. Project-based learning is an appropriate paradigm for addressing design and construction project management problems. Due to the technical expertise required for sustainable building projects, it is integral for learners to go through a practicum environment to understand the sustainability aspects of a construction project in the industry environment. Work Integrated Learning (WIL) is becoming increasingly popular as an essential pedagogy for undergraduate construction education. Active participation through WIL provides the students with an experiential learning experience in a professional environment in the industry. Sustainable design is the backbone of sustainable built environment. Training professionals with the core skillsets and competencies in the sustainable construction domain requires an interdisciplinary design and construction project platform. Interdisciplinary projects lie at the heart of training architects and construction professionals with sustainable design practices. This paper sets the foundation for an interdisciplinary sustainable construction lab providing an invaluable platform for students from Architecture, Construction, Civil Engineering, Alternative Energy, Project Management and Construction Trades programs to work on a sustainable building project collaboratively. The research paper recommends that WIL in an interdisciplinary project environment is an effective pedagogy for transferring technical knowledge and soft skills related to sustainable design and construction to young professionals that eventually enhance their employability in the construction industry. The research findings will be valuable for all professionals, academicians and researchers involved in sustainable design and construction practices in the construction industry.

Alexander disease, less commoniy known as fibrinoid leukodystrophy is an extremely rare, non- familial, progressive, lethal leukodystrophy which is characterized predominantly by abnormalities of white matter in bilateral frontal regions. It usually presents early within first 2 years of life with clinical features of macrocephaly, recurrent seizures and psychomotor retardation. Diagnosis of this white matter disorder is possible with certain features seen on magnetic resonance imaging (MRI), even without the need for histological confirmation. Our case is a one year old male infant who presented with repeated episodes of focal seizures to the paediatrician. He was referred for an MRI and subsequently based on typical MRI findings the diagnosis of Alexander disease was made.

Congenital diaphragmatic hernia is a very common intrathoracic fetal anomaly with Morgagni hernia typically seen on right side anteriorly and Bochdalek hernia on left side posteriorly, because of the protective effects of liver and heart on either side respectively. Hiatal hernias range from herniation of a small portion of stomach into thoracic cavity to herniation of entire stomach into the left thoracic cavity. Very rarely the herniated stomach has been reported in the right thoracic cavity. Early diagnosis and treatment of all diaphragmatic hernias is essential to reduce the associated morbidity and mortality. We present a very rare and interesting case of an 18 months old baby girl with reverse scenarios. She had a large hiatal hernia with right intrathoracic stomach along with a left sided Morgagni hernia in combination.