Aerial Grasping Research Articles

High-Speed Detector for Low-Powered Devices in Aerial Grasping

High-Speed Detector for Low-Powered Devices in Aerial Grasping

Design, Localization, Perception, and Control for GPS-Denied Autonomous Aerial Grasping and Harvesting

Design, Localization, Perception, and Control for GPS-Denied Autonomous Aerial Grasping and Harvesting

Thrust Microstepping via Acceleration Feedback in Quadrotor Control for Aerial Grasping of Dynamic Payload

Thrust Microstepping via Acceleration Feedback in Quadrotor Control for Aerial Grasping of Dynamic Payload

Ring-Rotor: A Novel Retractable Ring-Shaped Quadrotor With Aerial Grasping and Transportation Capability

This letter presents a novel and retractable ring-shaped quadrotor called Ring-Rotor that can adjust the vehicle's length and width simultaneously. Unlike other morphing quadrotors with high platform complexity and poor controllability, Ring-Rotor uses only one servo motor for morphing but reduces the largest dimension of the vehicle by approximately 31.4%. It can guarantee passibility while flying through small spaces in its compact form and energy saving in its standard form. Meanwhile, the vehicle breaks the cross configuration of general quadrotors with four arms connected to the central body and innovates a ring-shaped mechanical structure with spare central space. Based on this, an ingenious whole-body aerial grasping and transportation scheme is designed to carry various shapes of objects without the external manipulator mechanism. Moreover, we exploit a nonlinear model predictive control (NMPC) strategy that uses a time-variant physical parameter model to adapt to the quadrotor morphology. Above mentioned applications are performed in real-world experiments to demonstrate the system's high versatility.

TRIGGER: A Lightweight Universal Jamming Gripper for Aerial Grasping

This work introduces TRIGGER, the first lighTweight univeRsal jammInG Gripper for aErial gRasping. TRIGGER is an omnidirectional, landing-capable aerial grasping system with resilience and robustness to collisions and inherent passive compliance. In particular, this work presents the design, fabrication, and experimental validation of a novel, intelligent, modular, universal jamming gripper specifically designed for aerial applications. Leveraging recent developments in particle jamming and soft granular materials, TRIGGER produces 15N of holding force with only a relatively small activation force of 2.5N. Experiments show the relationship between fill ratio and activation force and reveal that adding an additive to the membrane's silicone mixture improves the holding force by up to 52%. The concept is validated by mounting TRIGGER onto a multicopter performing a pick-and-release task under laboratory conditions. Based on the experimental data, a model for robotic simulators is introduced to facilitate future controller developments.

Aerial Grasping and the Velocity Sufficiency Region

A largely untapped potential for aerial robots is to capture airborne targets in flight. We present an approach in which a simple dynamic model of a quadrotor/target interaction leads to the design of a gripper and associated velocity sufficiency region with a high probability of capture. A model of the interaction dynamics maps the gripper force sufficiency region to an envelope of relative velocities for which capture should be possible without exceeding the capabilities of the quadrotor controller. The approach motivates a gripper design that emphasizes compliance and is passively triggered for a fast response. The resulting gripper is lightweight (23 g) and closes within 12 ms. With this gripper, we demonstrate in-flight experiments that a 550 g drone can capture an 85 g target at various relative velocities between 1 m/s and 2.7 m/s.

Closed-Structure Compliant Gripper With Morphologically Optimized Multi-Material Fingertips for Aerial Grasping

Aerial grasping empowers unmanned aerial vehicles to find applications beyond structured logistics. However, it brings a number of challenges including inaccurate positioning of the end effector and limited energy sources. Moreover, solutions so far have difficulty in handling a variety of objects. A novel closed structure compliant gripper was developed to address the challenges above. The gripper has a large self-centering work envelope and is normally-closed for passive grasping. Introduction of compliance as a form of morphological computation was also considered to enhance grasping capabilities, where multi-material 3D printing would facilitate rapid design changes based on target application. To grasp different objects, the gripper has hot-swappable 3D printed fingertips which are optimized with a multi-objective Bayesian Optimization process using physical bench experiments mimicking drone grasping and ascent on a common object set. The morphology of the fingertip including tip width, curvature and distribution of soft and hard material on contact surface, are optimized with a bench test that mimics quadcopter takeoff and landing. The best design from optimization shows an improvement of more than 10% from the initial design in successful grasp operations, demonstrated by field tests with a quadcopter.

Adaptive Aerial Grasping and Perching With Dual Elasticity Combined Suction Cup

To perch on or grasp the objective surface using the suction cup-based manipulator, the precise contact control is commonly required. Improper contact angle or insufficient contact force may cause failure. To enhance the tolerance to flight control insufficiency, a suction cup that comprises an inner soft cup and an outer firm cup to facilitate its engagement without reducing the adhesion stiffness is investigated. The soft cup is adaptable to the angular error induced by the multicopter and the resulting adhesion force can draw the firm cup and correct the angular error between the firm cup and the surface. These effects increase the engagement rate and reduce the dependence on precise control. The outer firm cup is devoted to providing a large adhesion force and a stiff base for subsequent tasks. To reduce the air evacuation time in the firm cup, a novel self-sealing structure is designed. Based on the combined cup, we build a multifunctional aerial manipulation system which can execute perching or lateral aerial grasping tasks. With the proposed prototype, the comparative flight experiments involving perching on a wall under disturbance and grasping an object are conducted. The results demonstrate that our proposed suction cup outperforms the conventional cup.

Aerial Grasping with a Lightweight Manipulator Based on Multi-Objective Optimization and Visual Compensation.

Autonomous grasping with an aerial manipulator in the applications of aerial transportation and manipulation is still a challenging problem because of the complex kinematics/dynamics and motion constraints of the coupled rotors-manipulator system. The paper develops a novel aerial manipulation system with a lightweight manipulator, an X8 coaxial octocopter and onboard visual tracking system. To implement autonomous grasping control, we develop a novel and efficient approach that includes trajectory planning, visual trajectory tracking and kinematic compensation. Trajectory planning for aerial grasping control is formulated as a multi-objective optimization problem, while motion constraints and collision avoidance are considered in the optimization. A genetic method is applied to obtain the optimal solution. A kinematic compensation-based visual trajectory tracking is introduced to address the coupled affection between the manipulator and octocopter, with the advantage of discarding the complex dynamic parameter calibration. Finally, several experiments are performed to verify the effectiveness of the proposed approach.

Autonomous Vision-Based Aerial Grasping for Rotorcraft Unmanned Aerial Vehicles.

Autonomous vision-based aerial grasping is an essential and challenging task for aerial manipulation missions. In this paper, we propose a vision-based aerial grasping system for a Rotorcraft Unmanned Aerial Vehicle (UAV) to grasp a target object. The UAV system is equipped with a monocular camera, a 3-DOF robotic arm with a gripper and a Jetson TK1 computer. Efficient and reliable visual detectors and control laws are crucial for autonomous aerial grasping using limited onboard sensing and computational capabilities. To detect and track the target object in real time, an efficient proposal algorithm is presented to reliably estimate the region of interest (ROI), then a correlation filter-based classifier is developed to track the detected object. Moreover, a support vector regression (SVR)-based grasping position detector is proposed to improve the grasp success rate with high computational efficiency. Using the estimated grasping position and the UAV?Äôs states, novel control laws of the UAV and the robotic arm are proposed to perform aerial grasping. Extensive simulations and outdoor flight experiments have been implemented. The experimental results illustrate that the proposed vision-based aerial grasping system can autonomously and reliably grasp the target object while working entirely onboard.

Hierarchy-Based Adaptive Generalized Predictive Control for Aerial Grasping of a Quadrotor Manipulator

In this paper, an adaptive generalized predictive control (GPC) based on hierarchical control strategy is designed for a quadrotor with a robotic arm. For this nonlinear and coupled system, a two-layer control structure is adopted to achieve more precise trajectory tracking and keep the tracking performance after aerial grasping. The inner-layer controller is a proportional-derivative (PD) controller. The outer-layer subsystem is linearized by input-output linearization first and an adaptive generalized predictive controller is applied. The effectiveness of this approach is verified through the simulation using MATLAB/Simulink. A PD controller with feedforward control input is applied on such a system for a comparative study. Simulation results show that a better tracking performance can be achieved by the proposed strategy.

Aerial Grasping of an Object in the Strong Wind: Robust Control of an Aerial Manipulator

An aerial manipulator is a new kind of flying robot system composed of a rotorcraft unmanned aerial vehicle (UAV) and a multi-link robotic arm. It gives the flying robot the capacity to complete manipulation tasks. Steady flight is essential for an aerial manipulator to complete manipulation tasks. This paper focuses on the steady flight control performance of the aerial manipulator. A separate control strategy is used in the aerial manipulator system, in which the UAV and the manipulator are controlled separately. In order to complete tasks in environments with strong wind disturbance, an acceleration feedback enhanced robust H∞ controller was designed for the UAV in the aerial manipulator. The controller is based on the hierarchical inner-outer loop control structure of the UAV and composed of a robust H∞ controller and acceleration feedback enhanced term, which is used to compensate for the wind disturbance. Experimental results of aerial grasping of a target object show that the controller can suppress the wind disturbance effectively, and make the aerial manipulator hover steadily with sufficient accuracy to complete aerial manipulation tasks in strong wind.

Passive Aerial Grasping of Ferrous Objects

Aerial transportation is probably the most efficient way to supply quick and effective aid especially in cases of emergency like search and rescue operations. Thus the ability to grasp and deliver objects is of vital importance in all sorts of unmanned and autonomous aerial operations. We detail a simple yet novel approach for aerial grasping of ferrous objects using a passive magnetic pickup and an impulse based drop mechanism. The design enables our gripper to grasp ferrous objects using single as well as multiple gripping pads, with visual as well as pickup and drop feedback. We describe the various components of the gripper with emphasis on its low mass and high lift capability since weight is a matter of high consideration in all aerial applications. In addition, we investigate and address the issues that may cause our design to fail. We demonstrate by experiments that the proposed design is robust and effective, based on its high payload capability, its sturdiness against possible slide during aggressive aerial maneuvers, and optimum performance of the drop mechanism for the designed range of payloads. We also show that the gripper is able to pick up and drop a single as well as multiple ferrous objects of different shapes, curvature, and inclination, which also involves picking up an object and then grasping the next, while keeping hold of the previous one.

Toward Aerial Grasping and Manipulation with Multiple UAVs

In this paper, a multiple UAVs control scheme is developed considering the full nonlinear position/orientation model of a j-Quadrotor system. A novel second order sliding mode controller is presented which guarantees exponential and robust tracking of admissible time-varying pose. The harmful chattering is not involved and no dynamic model is required to implement the controller to yield fast and precise tracking. Additionally, well-posed terminal and controlled time convergence allows an enforced contact at given pre-defined stable contact points at the same time. A stiffness control is proposed for grasping objects considering virtual linkages approach. Our approach yields high performance from the control system, in contrast to other simple controllers proposed for load carrying. In this sense, our advanced nonlinear control solves the apparent limitations imposed by the available technology from the viewpoint of the precise tracking control, and control of the inherent unstable underactuated dynamics, for frictionless contact points (neither rolling nor sliding are considered). A numerical simulation study, under various conditions, shows the numerical feasibility of the proposed approach.