Anibal Ollero

Universidad de Sevilla | US · Systems Engineering and Automatics

In this work, we present an experimental setup and guide to enable the perching of large flapping-wing robots. The combination of forward flight, limited payload, and flight oscillations imposes challenging conditions for localized perching. The described method details the different operations that are concurrently performed within the 4 second pe...

The increasing usage of multi-rotor aerial platforms and the reliability of flights enabled researchers to add equipment and devices to them for application. The addition of lightweight manipulators, grippers, and mechanisms to fulfill specific tasks has been reported frequently recently. This work pushes the idea one step ahead and uses an Artific...

The flapping-wing technology has emerged recently in the application of unmanned aerial robotics for autonomous flight, control, inspection, monitoring, and manipulation. Despite the advances in applications and outdoor manual flights (open-loop control), closed-loop control is yet to be investigated. This work presents a nonlinear optimal closed-l...

This letter is focused on the benchmark evaluation and comparison of the flapping and fixed wing flight modes on an hybrid platform developed for the realization of autonomous inspection operations outdoors. The platform combines the high range and endurance of fixed-wing UAVs (unmanned aerial vehicles), with the higher maneuverability and intrinsi...

The sampling and monitoring of nature have become an important subject due to the rapid loss of green areas. This work proposes a possible solution for a sampling method of the leaves using an ornithopter robot equipped with an onboard 94.1 g dual-arm cooperative manipulator. One hand of the robot is a scissors-type arm and the other one is a gripp...

The cruising velocity of animals, or robotic vehicles, that use flapping wings or fins to propel themselves is not constant but oscillates around a mean value with an amplitude usually much smaller than the mean, and a frequency that typically doubles the flapping frequency. Quantifying the effect that these velocity fluctuations may have on the pr...

This letter presents a novel deformable propeller concept, 3D-printed in flexible thermoplastic polyurethane, which stores impact energy in the form of elastic energy for smooth collisions, reducing risk in human-UAV interactions. However, such a design experiences elastic deformations when exposed to aerodynamic and centrifugal loads. The most rel...

One of the motivations for exploring flapping-wing aerial robotic systems is to seek energy reduction, by maintaining manoeuvrability, compared to conventional unmanned aerial systems. A Flapping Wing Flying Robot (FWFR) can glide in favourable wind conditions, decreasing energy consumption significantly. In addition, it is also necessary to invest...

This letter describes a method for autonomous aerial cinematography with distributed lighting by a team of unmanned aerial vehicles (UAVs). Although camera-carrying multi-rotor helicopters have become commonplace in cinematography, their usage is limited to scenarios with sufficient natural light or of lighting provided by static artificial lights....

This paper presents a multi-layer software architecture to perform cooperative missions with a fleet of quadrotors providing support in electrical power line inspection operations. The proposed software framework guarantees the compliance with safety requirements between drones and human workers while ensuring that the mission is carried out succes...

Flapping wings produce lift and thrust in bio-inspired aerial robots, leading to quiet, safe and efficient flight. However, to extend their application scope, these robots must perch and land, a feat widely demonstrated by birds. Despite recent progress, flapping-wing vehicles, or ornithopters, are to this day unable to stop their flight. In this p...

A novel terminal sliding mode control is introduced to control a class of nonlinear uncertain systems in finite time. Having command on the definition of the final time as an input control parameter is the goal of this work. Terminal sliding mode control is naturally a finite-time controller though the time cannot be set as input, and the convergen...

This work studies a stabilization problem of flapping-wing flying robots (FWFRs) before a take-off phase while a robot is on a branch. The claw of the FWFR grasps the branch with enough friction to hold the system steady in a stationary condition. Before the take-off, the claw opens itself and the friction between the claw and branch vanishes. At t...

Control and stabilization of aerial manipulators is a challenging problem due to the effects of the relative movements of the arm and aerial platform on the dynamics. In many cases, conventional multirotor controllers and autopilots are based on the cascaded structure of underactuated mechanical systems, and consider these effects as perturbations....

In the last years, aerial manipulators, UAVs (Unmanned Aerial Vehicles) with robotic manipulators, have been used for several applications such as inspection tasks, systems monitoring or transportation of loads. In order to supervise the missions, a GCS (Ground Control Station) is used. However, the GCS of the commercial autopilots are just designe...

This paper presents a comparative study of three operation modes for an aerial manipulation robot, considering as illustrative application example the realization of maintenance operations on power lines while flying, holding, or perching. Relying in our previous works, and taking into account practical considerations and limitations of the aerial...

The use of multirotors has grown significantly in recent years. Understanding their operation and control is essential to continue developing the field of multirotors. Because of this, it is essential to introduce multirotor control in engineering classes in a simple and effective way. However, most multirotor simulators are designed for high-level...

The growing market in Remotely Piloted Aircraft Systems (RPAS) and the need for cost-effective “Detect and Avoid (DAA)” systems are critical issues up to date towards enabling safe beyond visual line of sight (BVLOS) operations. In hopes of promoting earlier threat detection on DAA systems, we benchmark several object detection algorithms on multip...

This paper describes a compensation system for soft aerial vehicle stabilization. Balancing the arms is one of the main challenges of soft UAVs since the propeller is freely tilting together with the flexible arm. In comparison with previous designs, in which the autopilot was adjusted to deal with these imbalances with no extra actuation, this wor...

A new forward-flight model for bird-like ornithopters is presented. The flight dynamics model uses results from potential, unsteady aerodynamics to characterize the forces generated by the flapping wings, including the effects of the dynamic variables on the aerodynamic formulation. Numerical results of the model, which are validated with flapping...

This letter presents the first design of a soft and lightweight UAV, entirely 3D-printed in flexible filament. The drone's flexible arms are equipped with a tendon-actuated bending system, which is used for applications that require physical interaction with the environment. The flexibility of the UAV can be controlled during the additive manufactu...

Online event-based perception techniques on board robots navigating in complex, unstructured, and dynamic environments can suffer unpredictable changes in the incoming event rates and their processing times, which can cause computational overflow or loss of responsiveness. This paper presents ASAP: a novel event handling framework that dynamically...

Event cameras can capture pixel-level illumination changes with very high temporal resolution and dynamic range. They have received increasing research interest due to their robustness to lighting conditions and motion blur. Two main approaches exist in the literature to feed the event-based processing algorithms: packaging the triggered events in...

This work proposes a novel proportional-derivative (PD)-type state-dependent Riccati equation (SDRE) approach with iterative learning control (ILC) augmentation. On the one hand, the PD-type control gains could adopt many useful available criteria and tools of conventional PD controllers. On the other hand, the SDRE adds nonlinear and optimality ch...

Most current insect research techniques are ground-based and provide scarce information about flying insects in the planetary boundary layer (PBL), which remains a poorly studied ecological niche. To address this gap, we developed a new insect-sampling method consisting of a fixed-wing drone platform with net traps attached to the fuselage, a mobil...

Flapping wings are a bio-inspired method to produce lift and thrust in aerial robots, leading to quiet and efficient motion. The advantages of this technology are safety and maneuverability, and physical interaction with the environment, humans, and animals. However, to enable substantial applications, these robots must perch and land. Despite rece...

Flapping wings are a bio-inspired method to produce lift and thrust in aerial robots, leading to quiet and efficient motion. The advantages of this technology are safety and maneuverability, and physical interaction with the environment, humans, and animals. However, to enable substantial applications, these robots must perch and land. Despite rece...

This letter proposes a novel bio-inspired wing design to improve some characteristics of Flapping Wing Unmanned Vehicles (FWUV) related to their potential applications such as payload capability, maneuverability, low injury risk, and energy improvement. The suggested solution takes advantage of a broadly based avian research, focusing on the integr...

In this work, the application of an optimization algorithm is investigated to optimize static and dynamic engineering problems. The methodology of the approach is to generate random solutions and find a zone for the initial answer and keep reducing the zones. The generated solution in each loop is independent of the previous answer that creates a p...

This paper presents the first design of a soft, 3D-printed in flexible filament, lightweight UAV, capable of adapting to the industrial environment using soft tendons, specifically landing and stabilizing on pipelines without the need for an auxiliary system. The flexibility of the UAV can be controlled during the additive manufacturing process by...

In recent years, aerial manipulators with fully-actuated capabilities are gaining popularity for being used in aerial manipulation operations such as critical infrastructure inspection or aerial manipulation tasks. Those scenarios usually demand the aerial platform to operate in constrained and narrow scenarios. It is well known that in these situa...

Many sensor systems in robotics are bio-inspired by similar mechanisms in living creatures. Birds frequently use their beaks to grasp and manipulate objects. This work proposes a very lightweight sensor system that emulates a birds beak, thus allowing flapping aerial robots to interact with the environment, as e.g. to perform grasping or manipulati...

Multirotor aerial robots are becoming widely used for the inspection of powerlines. To enable continuous, robust inspection without human intervention, the robots must be able to perch on the powerlines to recharge their batteries. Highly versatile perching capabilities are necessary to adapt to the variety of configurations and constraints that ar...

The quaternion is a powerful and common tool to avoid singularity in rotational dynamics in three-dimensional (3D) space. Here it has been particularly used as an alternative to Euler angles and rotation matrix. The application of the quaternion is exercised in quadrotor modeling and control. It changes the dynamics and represents a singularity-fre...

In recent years, several countries have developed the use of sterile insect techniques (SIT) to fight against mosquitoes that transmit diseases. From a technical and economic point of view, the use of drones in the aerial release of sterile mosquitoes leads to important improvements in aerial coverage and savings in operational costs due to the req...

The unsteady aerodynamics of flapping low-aspect-ratio ellipsoidal-wings in ornithopters is analyzed and modeled by the use of three dimensional Computational Fluid Dynamics (CFD) simulations. The range of interest is high amplitude, moderate frequency flapping, and low to moderate angles of attack at Reynolds around 10⁵, where autonomous ornithopt...

The manipulation capabilities of flapping-wing flying robots (FWFRs) is a problem barely studied. This is a direct consequence of the load-carrying capacity limitation of the flapping-wing robots. Ornithopters will improve the existent multirotor unmanned aerial vehicles (UAVs) since they could perform longer missions and offer a safe interaction i...

This paper presents a threat management methodology for Unmanned Aircraft Systems (UAS) operating in the civil airspace. The work is framed within an Unmanned Traffic Management (UTM) system based on the U-space initiative. We propose a new method that focuses on providing the required automated decision-making during real-time threat managemen...

Drone autonomous operations near power lines are growing steadily and require innovative techniques to keep them on air. This paper presents a novel electromechanical recharging station that can be mounted on energized AC power line to charge the drone battery wirelessly without a need to modify the electrical infrastructure. The work shows a thoro...

Flapping wing robots show promise as platforms for safe and efficient flight in near-human operations, thanks to their ability to agile maneuver or perch at a low Reynolds number. The growing trend in the automatization of these robots has to go hand in hand with an increase in the payload capacity. This work provides a new passive morphing wing pr...

The inspection and maintenance tasks of electrical installations are very demanding. Nowadays, insulator cleaning is carried out manually by operators using scaffolds, ropes, or even helicopters. However, these operations involve potential risks for humans and the electrical structure. The use of Unmanned Aerial Vehicles (UAV) to reduce the risk of...

This paper investigates the inspection-of-pipe topic in a new framework, by rotation around a pipe, peculiar to industrial sites and refineries. The evolution of the ultimate system requires prototype design and preliminary tests. A new benchmark has been designed and built to mimic the rotation around a pipe, with the main purpose of assessing the...

This paper presents a novel algorithm to plan energy-efficient trajectories for autonomous ornithopters. In general, trajectory optimization is quite a relevant problem for practical applications with Unmanned Aerial Vehicles (UAVs). Even though the problem has been well studied for fixed and rotatory-wing vehicles, there are far fewer works explor...

This work investigates the gravity compensation topic, from a control perspective. The gravity could be levelled by a compensating mechanical system or in the control law, such as proportional derivative (PD) plus gravity, sliding mode control, or computed torque method. The gravity compensation term is missing in linear and nonlinear optimal contr...

This paper addresses autonomous fire-fighting missions with a heterogeneous team of Unmanned Aerial Vehicles (UAVs). We use UAVs with different capabilities to extinguish cooper- atively fires on the ground and on facades of high-rise buildings. The former is done by deploying fireproof blankets, whereas a water-jet system is used to extinguish fir...

The development of perception and control methods that allow bird-scale flapping-wing robots (a.k.a. ornithopters) to perform autonomously is an under-researched area. This paper presents a fully onboard event-based method for ornithopter robot visual guidance. The method uses event cameras to exploit their fast response and robustness against moti...

The inspection of public infrastructure, such as viaducts and bridges, is crucial for their proper maintenance given the heavy use of many of them. Current inspection techniques are very costly and manual, requiring highly qualified personnel and involving many risks. This article presents a novel solution for the detailed inspection of viaducts us...

This paper presents a localization system for Unmanned Aerial Vehicles (UAVs) especially designed to be used in infrastructure inspection, where the UAVs have to fly in challenging conditions, such as relatively high altitude (e.g., 15 m), eventually with poor or absent GNSS (Global Navigation Satellite System) signal reception, or the need for a B...

This work presents the application of an aerial manipulation robot for the semi-autonomous installation of clip-type bird flight diverters on overhead power line cables. A custom-made prototype is designed, developed, and experimentally validated. The proposed solution aims to reduce the cost and risk of current procedures carried out by human oper...

This paper describes a method for autonomous aerial cinematography with distributed lighting by a team of unmanned aerial vehicles (UAVs). Although camera-carrying multi-rotor helicopters have become commonplace in cinematography, their usage is limited to scenarios with sufficient natural light or of lighting provided by static artificial lights....

The power grid is an essential infrastructure in any country, comprising thousands of kilometers of power lines that require periodic inspection and maintenance, carried out nowadays by human operators in risky conditions. To increase safety and reduce time and cost with respect to conventional solutions involving manned helicopters and heavy vehic...

A safe integration of UAVs into the airspace is fundamental to unblock all the potential of drone applications. U-space is the drone traffic management solution for Europe, intended to handle a large number of drones into the airspace, especially at Very Low Level (VLL). This paper is focused on conflict management for multiple unmanned aerial vehi...

Although ground robots have been successfully used for many years in manufacturing, the capability of aerial robots to agilely navigate in the often sparse and static upper part of factories makes them suitable for performing tasks of interest in many industrial sectors. This paper presents the design, development, and validation of a fully autonom...

The use of aerial manipulators for the inspection and maintenance of the power grid requires the safe interaction of the robot with high voltage power lines. In order to identify possible faults or malfunctions during the approaching or interaction phases, this paper presents experimental results in a real 15 kV power line, considering four differe...