Leader Robot Research Articles

Stability Data Xbee S2b Zigbee Communication on Arduino Based Sumo Robot

Wireless technology is a solution to reach hard-to-reach places using cable technology. The use of wireless technology can reach these areas without using copper or cables in the data transmission process. Communication technology using wireless is one solution to connect the control system to support the creation and achievement of the goals of the 4.0 revolution so that control and monitoring become easier. With the convenience provided by wireless technology such as connecting various types of system devices between other systems. One type of wireless technology is WPAN, especially on the ZigBee system from Digi International with the IEEE 802.15.4 protocol standard with low power consumption and working at a frequency of 2.4 GHz. Utilization of the communication system from the ZigBee protocol can control according to the range capabilities of the ZigBee system. ZigBee's ability and use of communication can perform communication control robot sumobot (slave robot) and remote control (robot leader) as an introduction to command data to carry out movements on the slave robot in accordance with the orders from the robot leader After trying XBEE to send data at a certain distance without experiencing data loss, the best distance is obtained, namely 1 - 100 meters with the firmware coordinator and router settings. Data delays can be minimized with a transfer rate of 3 kbps in the data transfer rate.

Improved Q‐Learning Method for Multirobot Formation and Path Planning with Concave Obstacles

Aiming at the formation and path planning of multirobot systems in an unknown environment, a path planning method for multirobot formation based on improved Q‐learning is proposed. Based on the leader‐following approach, the leader robot uses an improved Q‐learning algorithm to plan the path and the follower robot achieves a tracking strategy of gravitational potential field (GPF) by designing a cost function to select actions. Specifically, to improve the Q‐learning, Q‐value is initialized by environmental guidance of the target’s GPF. Then, the virtual obstacle‐filling avoidance strategy is presented to fill non‐obstacles which is judged to tend to concave obstacles with virtual obstacles. Besides, the simulated annealing (SA) algorithm whose controlling temperature is adjusted in real time according to the learning situation of the Q‐learning is applied to improve the action selection strategy. The experimental results show that the improved Q‐learning algorithm reduces the convergence time by 89.9% and the number of convergence rounds by 63.4% compared with the traditional algorithm. With the help of the method, multiple robots have a clear division of labor and quickly plan a globally optimized formation path in a completely unknown environment.

Interface Design of Semi-autonomous Leader-Follower System for Excavation based on Bifurcation, Stagnation, and Deformation of Trajectory in Nonlinear Dynamical System using Low DOF Leader Robot

Interface Design of Semi-autonomous Leader-Follower System for Excavation based on Bifurcation, Stagnation, and Deformation of Trajectory in Nonlinear Dynamical System using Low DOF Leader Robot

Breaking Symmetries on Tessellation Graphs via Asynchronous Robots: The Line Formation Problem as a Case Study

Concerning the coordination of autonomous mobile robots, the main focus has been on the important class of Pattern Formation problems, where the robots are required to arrange themselves to form a given geometric shape. This class of problems has been extensively studied in the continuous environment (e.g., the Euclidean plane), whereas few results exist when robots move in a discretization of the plane, like infinite grids. In this environment, to form any pattern, the problem of breaking symmetries emerges. Breaking the symmetry by moving some leader robot is not a straightforward task due to the movement restrictions as all the adjacent nodes of the leader may be occupied. It may even happen that before obtaining the requested asymmetric configuration, most of the robots must be moved. Due to the asynchrony of robots, this fact greatly increases the difficulty of the problem. We assume very weak robots moving on any regular tessellation graph as a discretization of the Euclidean plane, and we devise an algorithm Abreak able to solve the Symmetry Breaking problem on both the square and triangular grids. It is important to note that Abreak is proposed so that it can be used as a module for solving more general problems. As a case study, we use Abreak to deal with the Line Formation problem, where n≥3 robots must arrange themselves to occupy n contiguous vertices along a grid line. In this respect, we first provide an algorithm ALF- able to partially solve this problem (it works with configurations in which it is not necessary to break symmetries), and then we show how Abreak and ALF- can be combined to form ALF. We provide a complete characterization of the solvability of the Line Formation problem on the considered topologies by showing that ALF solves the problem in each configuration where this is possible.

Robust Tracking Model Predictive Control With Quadratic Robustness Constraint for Mobile Robots With Incremental Input Constraints

This article proposes a robust model predictive control (MPC) algorithm for the tracking problem of wheeled mobile robots. The robots are subject to bounded disturbances and various practical constraints. Particularly, the incremental input constraint is introduced in the consideration of the safety and comfortability needs in real life. Conditions on the acceleration of the leader robot are derived to guarantee the satisfaction of the incremental input constraint of follower robot. To compensate for the effect of disturbances, a disturbance observer is designed to obtain the estimation of the disturbances, which together with the optimal control input of MPC optimization is contained in the actual control input. Also, a novel quadratic robustness constraint is developed to handle the disturbance estimation error, which allows the designer to balance the initial feasible region and control performance. The proposed algorithm can ensure recursive feasibility, robust constraint satisfaction, and closed-loop stability. Finally, both simulation and experiment results are provided to verify the theoretical properties.

Navigation of Three Cooperative Object-Transportation Robots Using a Multistage Evolutionary Fuzzy Control Approach.

This article proposes a new multistage evolutionary fuzzy control configuration and navigation of three-wheeled robots cooperatively carrying an overhead object in unknown environments. Based on the divide-and-conquer technique, this article proposes a stage-by-stage evolutionary obstacle boundary following (OBF) fuzzy control of each of the three robots through multiobjective continuous ant colony optimization. In the first stage, a set of evolutionary nondominated fuzzy controllers (FCs) for a single robot (a leader robot) in the execution of the OBF behavior is learned. In the second stage, a follower robot is controlled by two evolutionary FCs in combination with a switched compensation FC so that the leader and follower robots can cooperatively transport an object while executing the OBF behavior along obstacles containing corners with right angles. In the third stage, the third robot functions as an accompanying robot and is learned to enter into a predicted triangular formation with the leader-follower robots to transport a larger object while executing the OBF behavior. In the navigation of the three object-transportation robots, a new cooperative behavior supervisor is proposed to coordinate the learned OBF behavior and a target seeking behavior. Successful navigations in simulations and experiments verify the effectiveness of the multistage evolutionary fuzzy control approach and navigation scheme.

Multi-robot control for a static polygon formation using Neighbor-Leader algorithm

One of the biggest open challenges to the robotic system is controlling robots formation. Its importance has been noted in a wide variety of applications, from truck platoons to robot-based standalone parcel delivery. In this paper, a new central approach to controlling a polygon-shaped formation called the Neighbor-Leader Algorithm is proposed for a group of neighbor robots randomly distributed in an unknown environment. Firstly, a localization procedure for multi-robots is used to estimate the real-time positions and orientations of a leader robot and its neighbor robots. This information is collected using an equipped RP LIDAR sensor on each robot then the collected information is sent to the leader one. Secondly, neighbor robots are rearranged into a regular distribution by moving them around the leader one in circular paths to produce a new distribution with equal angles between each two neighbor robots. In the last step, the direction of each neighbor robot is changed toward the leader robot. After that, all neighbor robots move towards the leader until they reach a virtual circle that passes through the required polygon vertices. The simulation results illustrate the integrity of this algorithm.

RoVaLL: Design and Development of a Multi-Terrain Towed Robot With Variable Lug-Length Wheels

Robotic systems play a very important role in exploration, allowing us to reach places that would otherwise be unsafe or unreachable to humans, such as volcanic areas, disaster sites or unknown areas in other planets. As the area to be explored increases, so does the time it takes for robots to explore it. One approach to reduce the required time is using multiple autonomous robots to perform distributed exploration. However, this significantly increases the associated cost and the complexity of the exploration process. To address these issues, in the past we proposed a leader-follower architecture where multiple two-wheeled passive robots capable of steering only using brakes are pulled by a leader robot. By controlling their relative angle with respect to the leader, the followers could move in arbitrary formations. The proposed follower robots used rubber tires, which allowed it to perform well in rigid ground, but poorly in soft soil. One alternative is to use lugged wheels, which increase the traction in soft soils. In this letter we propose a robot with shape-shifting wheels that allow it to steer in both rigid and soft soils. The wheels use a cam mechanism to push out and retract lugs stored on its inside. The shape of the wheel can be manipulated by controlling the driving torque exerted on the cam mechanism. Through experiments we verified that the developed mechanism allowed the follower robots to control their relative angle with respect to the leader in both rigid and soft soils.

Connectivity-Maintenance Teleoperation of a UAV Fleet With Wearable Haptic Feedback

This article presents the design of a decentralized connectivity-maintenance algorithm for the teleoperation of a team of multiple UAVs, together with an extensive human subject evaluation in virtual and real environments. The proposed connectivity-maintenance algorithm enhances earlier works by improving their applicability, safety, effectiveness, and ease of use, by including: 1) an airflow-avoidance behavior that avoids stack downwash phenomena in rotor-based aerial robots; 2) a consensus-based action for enabling fast displacements with minimal topology changes by having all follower robots moving at the leader’s velocity; 3) an automatic decrease of the minimum degree of connectivity, enabling an intuitive and dynamic expansion/compression of the formation; and 4) an automatic detection and resolution of deadlock configurations, i.e., when the robot leader cannot move due to counterbalancing connectivity- and external-related inputs. We also devised and evaluated different interfaces for teleoperating the team as well as different ways of receiving information about the connectivity force acting on the leader. The results of two human subject experiments show that the proposed algorithm is effective in various situations. Moreover, using haptic feedback to provide information about the team connectivity outperforms providing both no feedback at all and sensory substitution via visual feedback. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —The control of one drone is usually performed with a remote controller (similar to a joypad) that uses radio-wave signals. When controlling more than one drone, even a simple task, such as moving the whole team around, becomes very challenging. Developing an easy, yet efficient way to impart commands to a formation of drones is necessary to achieve any complex task. This article proposes a framework to control a fleet of drones (quadrotors) in an intuitive way while receiving meaningful and effective information on the state of the formation. The proposed technique does not rely on any absolute positioning system (e.g., GPS) or centralized command center. Instead, it only uses the relative position of the drones with respect to each other, and all computations are designed in a decentralized fashion. These features make the proposed framework ready for deployment in different high-impact applications, such as in surveillance, search-and-rescue, and disaster response scenarios.

An Adversarial Approach to Private Flocking in Mobile Robot Teams

Privacy is an important facet of defence against adversaries. In this letter, we introduce the problem of private flocking. We consider a team of mobile robots flocking in the presence of an adversary, who is able to observe all robots' trajectories, and who is interested in identifying the leader. We present a method that generates private flocking controllers that hide the identity of the leader robot. Our approach towards privacy leverages a data-driven adversarial co-optimization scheme. We design a mechanism that optimizes flocking control parameters, such that leader inference is hindered. As the flocking performance improves, we successively train an adversarial discriminator that tries to infer the identity of the leader robot. To evaluate the performance of our co-optimization scheme, we investigate different classes of reference trajectories. Although it is reasonable to assume that there is an inherent trade-off between flocking performance and privacy, our results demonstrate that we are able to achieve high flocking performance and simultaneously reduce the risk of revealing the leader.

Non-line-of-sight error mitigating algorithms for transmitter localization based on hybrid TOA/RSSI measurements

Rendezvous control of multiple robots without losing network connectivity has important implications in multi-robot system including formation control, coordinated task assignments, and cooperative robotic missions. This paper introduces a new coordinate-free, bearing-based algorithm to enable rendezvous of distributed mobile robots at any designated leader robot node using hierarchical tracking of wireless network topology. An assumption is made that the robot can only sense and communicate with their neighbors (i.e., local sensing). The proposed approach preserves connectivity during the rendezvous task, adapts to dynamic changes in the network topology (e.g., losing or re-gaining a communication link), and is tolerant of mobility faults in the robots. We theoretically analyze the proposed algorithm and experimentally demonstrate the approach through simulations and extensive field experiments. The results indicate that the method is effective in a variety of realistic scenarios in which the robots are distributed in a cluttered environment.

Collaboration and Task Planning of Turtle-Inspired Multiple Amphibious Spherical Robots.

Amphibious Spherical Robots (ASRs) use an electric field to communicate and collaborate effectively in a turbid water of confined spaces where other mode communication modalities failed. This paper proposes an embedded architecture formation strategy for a group of turtle-inspired amphibious robots to maintain a long distance-parameterized path based on dynamic visual servoing. Inspired by this biological phenomenon, we design an artificial multi-robot cooperative mode and explore an electronic communication and collaborate devices, the control method is based in particular on underwater environment and also conduct a detailed analysis of control motion module. The objectives of control strategies are divided into four categories: The first strategy is that the leader robot controls the action of the overall robots to maintain collaborate together during motion along a desired geometric path and to follow a timing law that the communication efficiency and the arrival times to assigned sites. Furthermore, we design an adaptive visual servoing controller for trajectory tracking task, taking into account system dynamics with environment interactions. After that, the third strategy is a centralized optimization algorithm for the redistribution of target mission changes. Finally, this paper also proposes a new method of control strategies in order to guarantee that each robot in the team moves together according to the preset target toward its location in the group formation based on communication and stability modules.

Leader-Follower Formation Suboptimal Control for Quadrotors

In this work, a leader-follower formation control problem of quadrotors is investigated. The quadrotor dynamic model is represented by unit quaternion with the consideration of external disturbance. Nonlinear H∞ design approach is introduced and robust controllers for both leader and follower robots are derived by solving a Hamilton-Jacobi inequality following from a result for general nonlinear affine systems. Then some robustness conditions of the proposed controllers are obtained by selecting appropriate parametrised Lyapunov functions. The resultant state feedback controllers establish the asymptotically stability of the closed-loop nonlinear system. In addition, integral backstepping (IB) controllers are also derived for the leader-follower formation control problem. The purpose of designing IB controllers is to evaluate the robustness of H∞ controllers by comparison. The simulation results from both types of controllers are compared and robustness performance of the H∞ controllers over the IB controllers are demonstrated.

Performansi Navigasi Robot Leader-Follower menggunakan Algoritma Logika Fuzzy Interval Tipe 2

A leader-follower robot is used to perform different tasks without continuous human assistance. The movement of robot leader-follower to environment who do not structure, avoid persecution and achieving goals is very difficult. Related to the problem, the robot leader-follower requires navigating robots independently using Interval Fuzzy Logic Type-2 (IFLT) 2 Algorithm. The IFLT 2 algorithm performance is successfully applied to this leader-follower robot, with 8 base rules less than the Fuzzy Logic Type 1 Algorithm. This simulation, the robot successfully moves to avoid obstacles and go hand in hand with the position of the follower robot always following the position of the robot leader.

Leader-Follower Mobile Robots Control Based on Light Source Detection

This paper deals with the leader-following control of multiple autonomous mobile robots based on a new sensing method. In this method, we have mounted a light source on the leader robot and installed a photovoltaic sensor at the front end of the follower robot. The photovoltaic sensor consisting of seven micro solar modules acts as a light sensor for the follower robot which helps it to move in accordance with the leader robot by detecting the light source of the leader robot. From the relative angle measurement and ultrasonic measurement of the relative distance, angle offset and distance information between leader robot and follower robot can be estimated. Then, based on an intuitive control method for angle steering proposed in this paper, the follower robot can be controlled smoothly to achieve leader following purpose. The new leader-following control method could overcome the disadvantages of other existing formation control methods. The experimental results show that the leader following based on light source tracking is a comparatively efficient, accurate, and cost-effective method.

Lyapunov-Based Formation Control of Underwater Robots

SUMMARYToday, automatic diving robots are used for research, inspection, and maintenance, extensively. Control of autonomous underwater robots (AUVs) is challenging due to their nonlinear dynamics, uncertain models, and the system underactuation. Data collection using underwater robots is increasing within the oceanographic research community. Also, the ability to navigate and cooperate in a group of robots has many advantages compared with individual navigations. Among them, the effectiveness of using resources, the possibility of robots’ collaboration, increasing reliability, and robustness to defects can be pointed out. In this paper, the formation control of underwater robots has been studied. First, the kinematic model of the AUV is presented. Next, a novel Lyapunov-based tracking control algorithm is investigated for the leader robot. Subsequently, a control law is designed using Lyapunov theory and feedback linearization techniques to navigate a group of follower robots in a desired formation associated with the leader and follow it simultaneously. In the obtained results for different reference paths and various formations, the effectiveness of the proposed algorithm is represented.

Variable formation control of multiple robots via VRc and formation switching to accommodate large heading changes by leader robot

This article describes a novel multi-robot formation control based on a switching technique that allows follower robots to maintain formation when the leader robot’s direction changes rapidly or unexpectedly. The formation pattern is determined using Virtual Robot’s Center of the multi-robot formation. To avoid collision, the formation of robots reformed in optimal size by estimating the distance between the robot and an obstacle in real time. When the leader robot suddenly changes its direction, waypoints of follower robots are switched and the formation is quickly reconstructed. This prevents follower robots from colliding with each other and reduces their radius of movement and allows them to follow the leader robot at higher speed. The proposed method which is inherently a flexible control of multi-robot formation guarantees collision avoidance and prevents sudden changes in waypoints of the system by gradually changing its size. The validity of the proposed method is demonstrated via simulation and experimental results.

Lyapunov and Sliding Mode Based Leader-follower Formation Control for Multiple Mobile Robots with an Augmented Distance-angle Strategy

In this paper, a new two-layer control strategy which combines Kinematic Controller based on Lyapunov Theory (KCLT) with Dynamic Controller based on Sliding Mode (DCSM) is proposed to solve the problem of leader-follower formation control for multiple wheeled mobile robots (M-WMR). An augmented distance-angle leader-follower formation kinematic is constructed to describe the formation states, and a 2D LiDAR sensor is utilized to measure the states instead of using camera and image processing on each follower. Instead of transferring the measured formation states into reference position command for each follower, KCLT is designed to generate follower’s velocity command. By taking the velocity command of followers as reference signals, DCSM is implemented to realize formation control. Lyapunov stability theory verifies that with the designed controller all the error signals can converge to 0 theoretically, which implies formation control of M-WMR under the proposed method can be realized. Real experiments with one leader and two followers are carried out to demonstrate the effectiveness of the proposed control schema. In order to verify the robustness of the proposed method, the reference rotational velocity of the leader robot is designed to change between +0:2 rad/s and -0:2 rad/s at some specified position. And the experimental results are compared with that of traditional proportional-integral-derivative (PID) method.

Quantum Network of Cooperative Unmanned Autonomous Systems

A quantum network may be realized by the entanglement of particles communicated by qubits between quantum computers, where the entangled photons of light are transferred for communication purposes. This technology has been proven to be feasible experimentally through free-space distribution of entangled photon pairs. Sending photons of light through nonlinear crystals produces correlated photon pairs, by splitting each photon into two half particles with each particle having the same level of energy, which results in entangled pairs. This entanglement is represented by photons, having both either horizontal or vertical polarization. This paper investigates collaborative robotic tasks of unmanned systems in a network where the agents are entangled. For instance, a leader robot sends two identical photons (e.g. with vertical polarization) to two follower robots/autonomous vehicles to communicate information about various tasks such as swarm, formation, trajectory tracking, path following and collaborative tasks. The potential advantages of quantum cooperation of robotic agents is the speed of the process, the ability to achieve security with immunity against cyberattacks, and fault tolerance, through entanglement. If a Quantum Network is implemented in a robotic application, it would present an effective solution; for example, for a group of unmanned systems working securely together. An analytical basis of such systems is investigated in this paper, and the formulation of quantum cooperation of unmanned systems is presented and discussed. The concept of experimental quantum entanglement, as well as quantum cryptography (QC), for robotics applications is presented.

Observer-Based Leader-Following Formation Control for Multi-Robot With Obstacle Avoidance

This paper focuses on the observer-based leader-following formation tracking control for multi-robot with obstacle avoidance. First, based on the leader-follower formation control method, setting the trajectory of the leader robot, then the follower robots track the leader robot. Second, an observer for the followers is designed to estimate the state of the leader robot, which can limit the estimation errors to a small value at short time-frame. Moreover, the gain controller and corrective controller are presented to complete the formation task and implement the trajectory transformation, respectively. In addition, an improved obstacle avoidance algorithm is devised to avoid the obstacles by adjusting the angle between the leader robot and the followers. Finally, the simulation results are presented to verify the effectiveness of the proposed control scheme. The main advantages of this paper are both an observer-based controller includes gain control and corrective control is developed for the nonlinear multi-robot system, and the obstacle avoidance problem during movement is solved with the optimal method.