Multiple UAV Systems for Agricultural Applications: Control, Implementation, and Evaluation

The introduction of multiple unmanned aerial vehicle (UAV) systems into agriculture causes an increase in work efficiency and a decrease in operator fatigue. However, systems that are commonly used in agriculture perform tasks using a single UAV with a centralized controller. In this study, we develop a multi-UAV system for agriculture using the distributed swarm control algorithm and evaluate the performance of the system. The performance of the proposed agricultural multi-UAV system is quantitatively evaluated and analyzed through four experimental cases: single UAV with autonomous control, multiple UAVs with autonomous control, single UAV with remote control, and multiple UAVs with remote control. Moreover, the performance of each system was analyzed through seven performance metrics: total time, setup time, flight time, battery consumption, inaccuracy of land, haptic control effort, and coverage ratio. Experimental results indicate that the performance of the multi-UAV system is significantly superior to the single-UAV system

A Multiplicatively Weighted Voronoi-Based Workspace Partition for Heterogeneous Seeding Robots

Multi-robot systems (MRSs) are currently being used to perform agricultural tasks. In this regard, the deployment of heterogeneous MRSs will be essential for achieving more efficient and innovative farming in the future. In this paper, we propose a multiplicatively weighted (MW) Voronoi-based task-allocation scheme for heterogeneous agricultural robots. The seed points for area partitioning using a Voronoi diagram are obtained by performing node clustering using a k-means clustering algorithm. Heterogeneous robots have different specifications for performing various tasks. Thus, the proposed MW Voronoi-based area partitioning for heterogeneous robots is applied by considering various weighting factors. The path for each robot is computed such that the robot follows the nodes, and the computed paths serve as inputs for the workload distribution strategy that assigns paths to the robots. Simulations and field experiments were conducted to verify the effectiveness of the proposed approach

Maintenance Robot for 5-MW Offshore Wind Turbines and its Control

This paper presents a novel gigantic robotic system for the operation and maintenance (O&M) of 5-MW offshore wind turbines. The robotic system consists of a mobile platform and two manipulators. The mobile platform performs vertical climbing on the turbines' towers and blades using a wire-driven parallel mechanism, while the manipulators perform cleaning and inspection using phased array ultrasonic testing (PAUT) devices, which require normal directional contact with the blade. For achieving the vertical climbing motion, height, and attitude control schemes are proposed, which overcome limitations such as varying nonholonomic constraints and unknown initial positions. For the manipulators' tasks, hybrid position/force control schemes using the linear least-squares method are proposed for achieving the conditions of the PAUT devices that allow inspection images to be captured under wind disturbance. To validate the robustness of our robotic system and control schemes in the environment of the 5-MW offshore wind turbines, we conducted a highly realistic experiment that involved part of a full-size tower and blade, and a wind velocity of 6.51 m/s. The results of this experiment show that the proposed robotic system and control schemes have sufficient robustness against wind disturbance to allow the O&M of 5-MW offshore wind turbines. © 2016 IEEE.FALS

Enhancement of Human Operator's Perceptual Sensitivity for Telesurgical Systems via Polytopic System Approach

A suturing including knot tying is one of the more difficult operations to learn in telesurgical systems. Apprentice surgeons commonly suffer from suture breakage or knot failure. The difficulty, generally, comes from the absence of feedback of interaction force cues in a medical device (e.g., a needle and a thread) . Even if there is haptic feedback to the operator, the operator may have a difficulty to detect a specific force such as suture breakage force. To deal with this problem, we propose a control method which can detect a suture breakage force more sensitively by considering human perception characteristics. A performance objective of the control method is designed according to the human perceptual factor, just noticeable difference. By convex optimization of the performance indices, a stabilizing H_inf controller is proposed for the telesurgical system. Finally, the proposed control scheme is validated via a simulation study

Enhancement of Human Operator's Perceptual Sensitivity for Telesurgical Systems via Polytopic System Approach

Abstract-A suturing including knot tying is one of the more difficult operations to learn in telesurgical systems. Apprentice surgeons commonly suffer from suture breakage or knot failure. The difficulty, generally, comes from the absence of feedback of interaction force cues in a medical device (e.g., a needle and a thread) . Even if there is haptic feedback to the operator, the operator may have a difficulty to detect a specific force such as suture breakage force. To deal with this problem, we propose a control method which can detect a suture breakage force more sensitively by considering human perception characteristics. A performance objective of the control method is designed according to the human perceptual factor, just noticeable difference. By convex optimization of the performance indices, a stabilizing H∞ controller is proposed for the telesurgical system. Finally, the proposed control scheme is validated via a simulation study

Haptic teleoperation of multiple unmanned aerial vehicles over the internet

Abstract — We propose a novel haptic teleoperation control framework for multiple unmanned aerial vehicles (UAVs) over the Internet, consisting of the three control layers: 1) UAV control layer, where each UAV is abstracted by, and is controlled to follow the trajectory of, its own kinematic virtual point (VP); 2) VP control layer, which modulates each VP’s motion according to the teleoperation commands and local artificial potentials (for inter-VP/VP-obstacle collision avoidance and inter-VP connectivity preservation); and 3) teleoperation layer, through which a remote human user can command all (or some) of the VPs ’ velocity while haptically perceiving the state of all (or some) of the UAVs over the Internet. Masterpassivity/slave-stability and some asymptotic performance measures are proved. Semi-experiment results are presented to validate the theory. I

Gain-Scheduling Control of Teleoperation Systems Interacting With Soft Tissues

Surgical teleoperation systems are being increasingly deployed recently. There are, however, some unsolved issues such as nonlinear characteristics of the interaction between the slave robot and soft tissues and difficulty in employing force sensors in the surgical end-effectors of the slave. These issues make it difficult to generalize any approach to develop a control for the system. This paper addresses these issues by proposing a H-infinity suboptimal controller preserving robust stability and performance. The environment, i.e., soft tissues, is characterized with the nonlinear Hunt-Crossley model. This nonlinear characteristics of soft tissues are expressed with an affine combination of linear models within a predefined parameter polytope. For this linear parameter-varying system, a gain-scheduling control scheme is employed to design a suboptimal controller while guaranteeing its stability. To avoid using any force measurement in slave, we used position-position (PP) control architecture. The developed gain-scheduling control is validated with quantitative experimental results. The developed gain-scheduling PP control scheme shows good tracking capacity and high transparency for varied experimental conditions. Error of the transmitted impedance is significantly lower compared with other conventional control schemes for frequencies less than 2 Hz, which is frequently recommended for surgical teleoperation