Distributed velocity controllers of the individuals of emerging swarm clusters

This paper presents the distributed velocity-based control laws of n ∈ N individuals considered rigid bodies, which gives rise to swarm clusters in a partially known environment. The motion of the individuals is based on Reynold's rules of separation, alignment, and cohesion. If two individuals are in the detection range of each other, there is an attraction between the two for alignment. There is a short-range repulsion to avoid the inter-individual collision. A total potential function is developed using attractive and repulsive potential functions, representing general anisotropic swarms. The decentralized velocity-based controllers of the individuals, which gives rise to a gradient system, are derived from the total potential function. The effectiveness of the decentralized velocity-based controllers is validated through computer simulations carried out using the Mathematica software

Assistive technology: autonomous wheelchair in obstacle - ridden environment

The benefits for the advancement and enhancement of assistive technology are manifold. However, improving accessibility for persons with disabilities (PWD) to ensure their social and economic inclusion makes up one of the major ones in recent times. This paper presents a set of new nonlinear time-invariant stabilizing controllers for safe navigation of an autonomous nonholonomic rear-wheel drive wheelchair. Autonomous wheelchairs belong to the category of assistive technology, which is most sought in current times due to its usefulness, especially to the less abled (physically and/or cognitively), hence helping create an inclusive society. The wheelchair navigates in an obstacle-ridden environment from its start to final configuration, maintaining a robust obstacle avoidance scheme and observing system restrictions and dynamics. The velocity-based controllers are extracted from a Lyapunov function, the total potentials designed using the Lyapunov based Control Scheme (LbCS) falling under the classical approach of the artificial potential field method. The interplay of the three central pillars of LbCS, which are safety, shortness, and smoothest course for motion planning, results in cost and time effectiveness and the velocity controllers’ efficiency. Using the Direct Method of Lyapunov, the stability of the wheelchair system has been proved. Finally, computer simulations illustrate the effectiveness of the set of new controllers

Landmarks as navigation - aids for multiple robots

The paper presents selected landmarks as navigation-aids or waypoints for multiple car-like robots in a contained workspace cluttered with randomly fixed obstacles and landmarks. A new metrics is designed to select specific landmarks (which are treated as waypoints) falling in the robots’ field of view and with a minimum distance away from each other and their targets. A new metric is also defined to obtain the robot’s field of view at every iteration. Using the Lyapunov-based control scheme (LbCS) nonlinear acceleration-based stabilizing control laws are derived for navigation amongst obstacles and landmarks en route the final destination via selected landmarks or waypoints. The proposed technique and the new control laws are verified via interesting computer simulations

Strategic creation and placement of landmarks for Robot navigation in a partially - known environment

Navigation of autonomous robots in uncharted or uncertain, and constrained or hazardous environment is a common problem but integrated with multiple challenges. This paper considers a subsection of such an environment and essays a feasible yet innovative solution for accurate parking and obstacle avoidance of a car-like mobile robot. The new method is based on strategic creation and positioning of landmarks in a bounded workspace that will aid or guide the robot to safely navigate the workspace and finally park correctly inside of the designated parking bay. By autonomously controlling its translational velocity and the steering angle, the car-like robot navigates from one (newly fixed) landmark to another (newly fixed) and finally converges to a target with a pre-defined posture. Attaining accurate posture is very important in real-life situations which involve tasks such as loading or off-loading and deliveries in constrained spaces. The paper establishes practical posture stability of the system. The computer simulations verify the effectiveness of the proposed method and the proposed control inputs

Motion control of an articulated mobile manipulator in 3D using the Lyapunov - based control scheme

Finding feasible solutions to motion planning and control problem of robotic systems in different environments with various applications is an active area of research. This article presents a new solution to the motion planning and control problem of a three-dimensional articulated mobile manipulator comprising a car-like mobile platform and a three-dimensional n-link articulated arm using the Lyapunov-based control scheme. The motion of the system is described as twofold: first, the car-like mobile platform moves from an initial position to its pseudo-target, and second, when the mobile platform is within some predefined distance from the pseudo-target, the end-effector of the robot arm is attracted to its designated target. Therefore, presenting a new 2-Step Algorithm in this paper for dual movement of the articulated mobile manipulator in 3D. In addition, a workspace cluttered with fixed spherical and rod obstacles of random sizes and positions is considered in this research. For the mobile manipulator to avoid an obstacle, the Minimum Distance Technique is adapted where a point on the robot that is closest to an obstacle will avoid the obstacle. The convergence of the two bodies and the stability of the mechanical system are guaranteed by the Lyapunov's direct method. The continuous nonlinear control laws proposed from the control scheme also take into account all mechanical singularities and velocity limitations associated with the system. Theoretical proofs and computer simulations validate the new continuous, acceleration-based, nonlinear, time-invariant control laws

Stable switched controllers for a swarm of UGVs for hierarchal landmark navigation

This paper presents the development of a new set of switched velocity controllers of a swarm of unmanned ground vehicles (UGVs) from multiple Lyapunov functions, which are invoked according to a switching rule. The Lyapunov-based Control Scheme (LbCS) has derived the multiple Lyapunov functions that fall under the artificial potential field method of the classical approach. Interaction of the three main pillars of LbCS, which are safety, shortness, and smoothest path for motion planning, bring about cost and time effectiveness and efficiency of the velocity controllers. The switched controllers enable the UGVs to navigate autonomously via hierarchal landmarks in a cluttered workspace to their equilibrium state. The switched controllers give rise to a switched system whose stability is proven using Branicky’s stability criteria for switched systems based on multiple Lyapunov functions. Simulations results are presented to show the effectiveness of the nonlinear time-invariant controllers. Later, effects of noise are included in the velocity controllers to show system robustness

A Stable Nonlinear Switched System for Landmark-aided Motion Planning

To guarantee navigation accuracy, the robotic applications utilize landmarks. This paper proposes a novel nonlinear switched system for the fundamental motion planning problem in autonomous mobile robot navigation: the generation of continuous collision free paths to a goal configuration via numerous land marks (waypoints) in a cluttered environment. The proposed system leverages the Lyapunov based control scheme (LbCS) and constructs Lyapunov like functions for the system’s subsystems. These functions guide a planar point mass object, representing an autonomous robotic agent, towards its goal by utilizing artificial landmarks. Extracting a set of nonlinear, time invariant, continuous, and stabilizing switched velocity controllers from these Lyapunov like functions, the system invokes the controllers based on a switching rule, enabling hierarchical landmark navigation in complex environments. Using the well known stability criteria by Branicky for switched systems based on multiple Lyapunov functions, the stability of the proposed system is provided. A new method to extract action landmarks from multiple landmarks is also introduced. The control laws are then used to control the motion of a nonholonomic car like vehicle governed by its kinematic equations. Numerical examples with simulations illustrate the effectiveness of the Lyapunov based control laws. The proposed control laws can automate various processes where the transportation of goods or workers between different sections is required

Oral Contraceptive Pills Are Not a Risk Factor for Deep Vein Thrombosis or Pulmonary Embolism After Arthroscopic Shoulder Surgery

Background: Worldwide, more than 100 million women between the ages of 15 and 49 years take oral contraceptive pills (OCPs). OCP use increases the risk of venous thromboembolism (VTE) through its primary drug, ethinylestradiol, which slows liver metabolism, promotes tissue retention, and ultimately favors fibrinolysis inhibition and thrombosis. Purpose: To evaluate the effects of OCP use on VTE after arthroscopic shoulder surgery. Study Design: Cohort study; Level of evidence, 3. Methods: A large national payer database (PearlDiver) was queried for patients undergoing arthroscopic shoulder surgery. The incidence of VTE was evaluated in female patients taking OCPs and those not taking OCPs. A matched group was subsequently created to evaluate the incidence of VTE in similar patients with and without OCP use. Results: A total of 57,727 patients underwent arthroscopic shoulder surgery from 2007 to 2016, and 26,365 patients (45.7%) were female. At the time of surgery, 924 female patients (3.5%) were taking OCPs. The incidence of vascular thrombosis was 0.57% (n = 328) after arthroscopic shoulder surgery, and there was no significant difference in the rate of vascular thrombosis in male or female patients (0.57% vs 0.57%, respectively; P \u3e .99). The incidence of VTE in female patients taking and not taking OCPs was 0.22% and 0.57%, respectively (P = .2). In a matched-group analysis, no significant difference existed in VTE incidence between patients with versus without OCP use (0.22% vs 0.56%, respectively; P = .2). On multivariate analysis, hypertension (odds ratio [OR], 2.00; P \u3c .001) and obesity (OR, 1.43; P = .002) were risk factors for VTE. Conclusion: OCP use at the time of arthroscopic shoulder surgery is not associated with an increased risk of VTE. Obesity and hypertension are associated with a greater risk for thrombolic events, although the risk remains very low. Our findings suggest that patients taking OCPs should be managed according to the surgeon’s standard prophylaxis protocol for arthroscopic shoulder surgery

New players in intelligent transportation: Autonomous Segway in a dynamic environment

This paper heralds a mathematical treatment of Segways as autonomous robots for personal transportation and deliveries and courier services in constrained dynamic environments from a bird’s-eye view. New velocity-based stabilizing controllers of an autonomous nonholonomic two-wheeled self-balancing personalized Segway robot are extracted from a total potential developed by employing the Lyapunov-based Control Scheme (LbCS) for navigation in a partially known environment. Velocity controllers’ cost and time effectiveness and efficiency result from the interaction of the three prominent pillars of LbCS: smoothest, shortest, and safest path for motion planning. Furthermore, the autonomous personal transporter has an obstacle avoidance sensor with a limited detection range ideal for fast navigation in dynamic environments with narrow corridors, tracks, and pathways. This also successfully facilitates navigation in a partially known environment where the sensors only receive and avoid static and dynamic obstacles in a limited range. The results are numerically validated, and the efficacy of the new controllers is exemplified via computer simulations, which illustrate the forward, backward, and zero-turn radius maneuvers of the Segway robot. Introducing the particular autonomous personal transporter would contribute to transportation systems of smart cities

Mathematics and ICT bring new intelligent traffic light control system

As road networks in urban areas become increasingly complex and complicated when accommodating for the fast-growing numbers and diversity of vehicles and infrastructure, researchers have a tremendous interest in designing intelligent and robust traffic light control systems to manage traffic. Traditional traffic light control (TLC) systems operate on a fixed time basis, whereby each stream of traffic is allocated a fixed amount of time for vehicles to move through the intersection. This system's main drawback is that it does not account for actual traffic densities, leading to longer waiting times and higher fuel consumption. With the emergence and proliferation of digital technologies in the 21st century, humans have begun to use technology in every facet of their daily lives, including getting help in performing dull, dirty, and dangerous tasks that can be automated and repetitive. This paper combines ICT and mathematics to design a new robust system for traffic light control. A novel Intelligent Traffic Light Control System (ITLCS) model is proposed to accommodate the immediate number of vehicles and pedestrians' presence at the intersections. The system has been implemented in selected software for testing and validation, and the analytics are highlighted. The arterial aim is to show the importance of mathematics, which can produce a robust and intelligent system that can achieve a better traffic flow at varying traffic densities when combined with ICT