An Immersion and Invariance Controller for Aerial Manipulation

With the development of rotor aerial robot, it has been widely used as a stabilized flying platform to achieve observation, communication relay and so on by equipping corresponding equipment, which are always called passive tasks. However, many applications need rotor aerial robots to possess more active capability, such as grasp, carry and assemblage. Thus, the demand for an aerial manipulation system gradually appears, and becomes a hot research issue in recent years. Aerial manipulator system, usually composed of rotor aerial robot and the manipulator, is a new type of robot system with active operating capability. Compared with the mobile manipulator based on the ground and underwater mobile robot which is now widely applied, the aerial manipulation has lager working range and better flexibility obviously. Unfortunately, the new aerial manipulation system also brings new challenges, such as strong dynamics coupling, the modeling and stabilization problem, etc. which may affect its further application. Thus, in our work, an actual physical aerial manipulator system is designed and implemented for its system and application research. Based on the system, the preliminary modeling and control was researched and also an experiment for grasping and carry application is conducted. The conclusions of these researches will help us to realize and improve the system in the future.

A key challenge in the use of drones for an aerial manipulation task such as cutting tree branches is the control problem, especially in the presence of an unpredictable and nonlinear environment. While prior work focused on simplifying the problem by modeling a simple interaction with branches and controlling the system with nonlinear and non-robust control schemes, the current work deals with the problem by designing novel robust nonlinear controllers for aerial manipulation systems that are appropriate for vegetation sampling. In this regard, two different potential control schemes are proposed: nonlinear disturbance observer-based control (NDOBC) and adaptive sliding mode control (ASMC). Each considers the external disturbances and unknown parameters in controller design. The proposed control scheme in both methods employs a decoupled architecture that treats the unmanned aerial vehicle and the manipulator arm of the sampler payload as separate units. In the proposed control structures, controllers are designed after comprehensively investigating the dynamics of both the aerial vehicle and the robotic arm. Each system is then controlled independently in the presence of external disturbances, unknown parameter changes, and the nonlinear coupling between the aerial vehicle and robotic arm. In addition, fully actuated and underactuated aerial platforms are examined, and their stability and controllability are compared so as to choose the most practical framework. Finally, the simulation findings verify and compare the performance and effectiveness of the proposed control strategies for a custom aerial manipulation system that has been designed and developed for field trials.

Torch relay is an important tradition of the Olympics and heralds the start of the games. Robots applied in the torch-relay activity can not only demonstrate the technological capability of humans to the world but also provide a sight of human lives with robots in the future. This article presents an aerial manipulator designed for the robot-to-robot torch-relay task of the Beijing 2022 Winter Olympics. This aerial manipulator system is composed of a quadrotor, a 3 degree of freedom (DoF) manipulator, and a monocular camera. This article primarily describes the system design and system control scheme of the aerial manipulator. The experimental results demonstrate that it can complete a robot-to-robot torch-relay task under the guidance of vision in the ice and snow field.

Expanding an unmanned aerial vehicle (UAV) with an equipped robotic arm increases the ability of the UAV to actively interact with the environment. During the process of active tasks, precise motion control under model uncertainties and external disturbances is a challenging issue. To solve this issue, an active modeling based control scheme is proposed in this paper. In this scheme, the aerial manipulator system (AMS) is modeled with consideration of various uncertainties represented by the model error and the process noise. The model error caused by the gravity and movement of the manipulator is estimated by the unscented kalman filter (UKF). The estimation is further integrated into a nominal controller to achieve high-precision motion control. Detailed experimental results on the self-bulit testbed illustrate the effectiveness and good performance of the proposed method.

The Attitude and Orbit Control System of the 3 axis stabilised spacecraft (S/C) XMMNewton was designed to use three reaction wheels (RW) with a fourth wheel in cold redundancy. The 3 wheel configuration has been used for more than 13 years for the momentum management, to re-orientate the S/C with slews in order to achieve the required scientific pointing. With 3 wheels, frequent reaction wheel unloading is used both to compensate the external torque and to re-orientate the angular momentum to allow the slew execution, which results in fuel consumption of around 6 Kg per year. A fourth wheel in control gives the advantage of a higher momentum envelope and introduces the null space in the wheels matrix, allowing a wheel speed variation without changing the total angular momentum. With four wheels the reaction wheel bias will compensate only for the accumulation of angular momentum due to the external torques, resulting in saving a significant amount of fuel and extending the mission lifetime. The use of four reaction wheels implied the development of new attitude control algorithms and a software change on board. A design phase of this change was successfully completed and the project went through the implementation

This thesis focuses on a novel aerial robot system composed of an unmanned aerial vehicle (UAV) and one or more robotic arms, which is employed for aerial manipulation tasks. In particular, this research tries to transform UAVs from a predominantly data gathering platform into a flying robot, frequently called as unmanned aerial manipulators (UAMs), that can physically interact with the object or surrounding environment. This is challenging due to the existing design limitations imposed by the attachment of robotic arms to floating platforms. Furthermore, adding on to the cross-coupled dynamics of the UAV platform and arms, the presence of strong nonlinearities, external disturbances (e.g., wind), and parameter variations further complicates the deployment of UAMs in day-to-day life. Moreover, having such redundant aerial robots, especially when employing two manipulators, imposes additional challenges to successfully perform UAM missions. Motivated by these challenges, the main contributions of this thesis are threefold. Firstly, we propose a novel design of the dual-arm manipulator specifically developed for UAM missions. The dual-arm system is designed such that it can be attached to different multirotors with minimum design modifications. In addition, the proposed dual-arm design employs prismatic joints to introduce three distinctive features: 1) ability of each arm to dynamically adjust its COG for better flight performance; 2) extended workspace and reach of the arms for enhancing operational capability and improving safety during UAM missions; 3) fully independent control of each arm for performing different tasks simultaneously. Secondly, we present a learning-based intelligent control approach, the fusion of artificial neural networks and type-2 fuzzy logic controllers, namely type-2 fuzzy neural networks, for the control of UAMs under time-varying working conditions. The proposed control strategy eliminates the need for precise tuning of conventional controllers, and it can compensate for the internal and external disturbances caused by the motion of the arms and unforeseen environmental changes, opening the door for the widespread use of UAMs in daily life. Thirdly, we propose two different trajectory generation with redundancy resolution strategies for UAMs. The first strategy is based on a weighted damped least-squares method, while the second approach employs a nonlinear model predictive control-based technique. The proposed approaches are capable to exploit the system redundancy by modifying the UAM configuration and simultaneously generate the feasible trajectories during the execution of the assigned tasks while enforcing the system constraints. The contributions mentioned above are evaluated throughout extensive simulation studies and experimental flight tests with real UAM platforms. Overall, these contributions aim for extending the autonomous functionalities and operational capabilities of UAMs in the transportation and assembly type of scenarios, with the ambition to assist lessening the current gaps that hinder the widespread deployment of aerial robotic workers in real-world applications.

<p>Traditional aerial manipulation systems were usually composed of rigid-link manipulators attached to an aerial platform, arising several rigidity-related issues such as difficulties of reach, compliant motion, adaptability to object’s shape and pose uncertainties, and safety of human-manipulator interactions, especially in unstructured and confined environments. To address these issues, partially compliant manipulators, composed of rigid links and compliant/flexible joints, were proposed; however, they still suffer from insufficient dexterity and maneuverability. In this article, a new set of compliant aerial manipulators is suggested. For this purpose, the concept of aerial continuum manipulation system (ACMS) is introduced, several conceptual configurations are proposed, and the functionalities of ACMSs for different applications are discussed. Then, the performances of proposed aerial manipulators are compared with conventional aerial manipulators by implementing available benchmarks in the literature. To enhance the comparison, new features with related benchmarks are presented and used for evaluation purposes. In this study, the advantages of ACMSs over their rigid-link counterparts are illustrated and the potential applications of ACMSs are suggested. The open problems such as those related to dynamic coupling and control of ACMSs are also highlighted.</p>

An aerial manipulator system consisting of a quadrotor UAV and a one-DOF manipulator is introduced for contacting operations in the air. As the system is interacting with external environment to do some operations, there will exist contact force. According to the practical aerial contact manipulation features, it is known that an aerial manipulator usually performs operations as the UAV platform is in hover flight or nearby. To realize controlling the force, the hovering UAV acting as a spring-mass-damper system is firstly proved. Then, based on the derived model and the impedance control algorithm, a contact force control method is presented. That is, the position error is controlled in order to control the contact force ultimately. The actual flight experiments show that the developed system is enable to realize the contact force control without a force sensor.

The proximity between the multirotor blades and the environmental obstacles restricts the application of aerial manipulators in inspection tasks due to the risk of impacts, the limitation in the reach of the arm, and the physical interactions. This paper presents a long reach aerial manipulator consisting of a hexarotor platform equipped with a 2-DOF compliant joint arm attached at the tip of a one-meter-length link in passive pendulum configuration. The arm integrates magnetic encoders for force/torque estimation-control based on joint deflection, a range sensor in the forearm link for measuring the distance to the contact point, and a camera for visual inspection. A 2-DOF wearable exoskeleton interface has been developed, allowing the teleoperation of the arm with visual feedback in a more intuitive way. The paper also covers the kinematics and dynamics of the aerial manipulator, including the dynamics of the flexible long reach link. The developed system has been evaluated in test-bench and in outdoor flight tests.

This paper describes the architecture and performance of a PC-based configuration controller for dexterous 7-DOF manipulators. The computing platform is a 486-based personal computer equipped with a bus extender to access the robot Multibus controller, together with a single-board computer as the graphical engine, and a parallel I/O board to interface with a force-torque sensor mounted on the manipulator wrist. The Windows environment is enhanced by the iRMX real-time operating system that runs the configuration control algorithms for redundancy resolution. The position control algorithm is executed every 2.5 ms; motions can be simulated and displayed in real-time by the graphical engine on a separate monitor. The results of several experiments carried out with a Robotics Research manipulator have shown motion control capabilities comparable to those obtained with more extensive computing systems, thus validating the use of PCs for dexterous manipulator control. PC-based motion controllers for RRC arms, incorporating the configuration control software, are currently produced by the Robotics Research Corporation.

Small, man portable Uninhabited Aerial Vehicle (UAV) autopilot syst ems in use today are severely restricted in their operational capability for a variety of reasons. The size of the UAV introduces unique problems in the development of Guidance, Navigation, and Control (GNC) algorithms since aerodynamic models of this clas s of UAVs are difficult to define and are specific to each airframe. These low Reynolds number vehicles are affected by adverse environmental flight conditions, such as wind gusts, and require a GNC system that can adapt to these flight conditions in real -time. Limitations associated with hosting complex flight control systems are due to the limited availability of small footprint computing systems with sufficient computational power, memory, and interfaces as well as accurate attitude and heading sensors. This paper presents the Adaptive Autopilot Micro -controller, AAM, which addresses these issues. The AAM system architecture is a modular approach that decouples the flight processing functions from the sensor processing and actuator control by utilizing tw o dedicated micro -processing units, the Flight Processing Unit (FPU) and the Sensor Data AcQuisition unit (SDAQ), which balances the load required of each processor to maintain aircraft stability and navigation, yet leaves ample computational power to expa nd the systems flight control algorithms . Since the autopilot must accommodate adverse flight conditions and a variety of airframes may be used and the airframe parameters are normally time varying, the autopilot must adjust accordingly. Consequently, a di rect adaptive Proportional Integral Derivative (PID) control architecture was implemented. The adaptive control portion is based on Widrow’s update laws as: e

The goal of this research is a development of a new haptic interface realizing Physical Human-Machine Interaction. The new haptic interface termed Active Polyhedron is devised. Active Polyhedron can display force on multi-point, making this device realize operation to complex continuum. In this report, the active icosahedron, which is one of Active Polyhedron and pneumatically-driven, is developed. The active icosahedron consists of 30 pneumatic cylinders which have position sensor. In previous research, position-control algorithm and force-control algorithm were reported. Position-control algorithm computes positions of active icosahedron's apex based on displacements of link-length. Force-control algorithm computes output-forces on cylinder based on output-forces on apexes. Applying these algorithms, active icosahedron can realize input-position and output-force. We develop a new type of an application, which is 3D-CAD/CAM operation. In this application, an operator can perform advanced-design to generate commonly used CAD/CAM data, using the active icosahedron. At the same time, the operator feels stiffness of the model as if he touches to it. As a result, finer and more complex design is able to be performed.

_ Flanders Hydraulics and the Maritime Technology Division of Ghent University have proposed a hybrid testing platform for the development and validation of motion control algorithms for autonomous navigation in shallow and confined water, which consists of towing tank facilities and simulators. Within this framework, the towing tank at Flanders Maritime Laboratory, Ostend, Belgium, featured in large size, tuneable water depth, and a state-of-the-art free-running system, a series of autonomous manoeuvering tests with increasing complexity are designed and carried out. These manoeuvres, including acceleration with heading keeping, path following, speed control, and their combinations, are enabled by implementing guidance and control algorithms on a physical ship model, namely the benchmark ship KVLCC2 at a scale of 1/75. The controllable environment and large space of the tank basin facilitate the upgrade of the existing algorithms and the development of new algorithms. The definition of the autonomous manoeuvres, experimental setup, and parameter settings are elaborated and the effect of implementing different guidance strategies is discussed. Recorded results demonstrate good agreement between the measurements and the expectations, and control accuracy is quantified with evaluation indices. In summary, the feasibility and flexibility of the testing platform and the effectiveness of the algorithms are proved through extensive experiments. Keywords guidance and control; free-running test; physical testing platform; path following; speed control

The analysis and development of ATM network traffic control algorithms is often performed using theoretical traffic models. Algorithms for traffic shaping, policing, flow control, and switch architectures have been proposed based on these models. While the models help to obtain preliminary solutions, the success and validity of the proposed algorithm will be a function of how close the assumed models resemble real traffic patterns. The paper presents ATMTraP, an experimental prototype asynchronous transfer mode traffic and performance measurement tool which could be used in the characterization of sources and elements that form the ATM network. ATMTraP has been used in the Nectar Gigabit Testbed to collect preliminary traffic statistics from sources, such as, a Cray C-90 supercomputer, Sun workstations, and an iWARP systolic array.

Aerial manipulators can manipulate objects while flying, allowing them to perform tasks in dangerous or inaccessible areas. Advanced aerial manipulation systems are often based on rigid-link mechanisms, but the balance between dexterity and payload capacity limits their broader application. Combining unmanned aerial vehicles with continuum manipulators emerges as a solution to this trade-off, but these systems face challenges with large actuation systems and unstable control. To address these challenges, we propose Aerial Elephant Trunk, an aerial continuum manipulator inspired by the elephant trunk, featuring a small-scale quadrotor and a dexterous, compliant tendon-driven continuum arm for versatile operation in both indoor and outdoor settings. We develop state estimation for the quadrotor using an Extended Kalman Filter, shape estimation for the continuum arm based on piecewise constant curvature, and whole-body motion planning using minimum jerk principles. Through comprehensive fundamental verifications, we demonstrate that our system can adapt to various constrained environments, such as navigating through narrow holes, tubes, or crevices, and can handle a range of objects, including slender, deformable, irregular, or heavy items. Our system can potentially be deployed in challenging conditions, such as pipeline maintenance or electricity line inspection at high altitudes.