João Valente

An Air-Ground Wireless Sensor Network for Crop Monitoring

This paper presents a collaborative system made up of a Wireless Sensor Network (WSN) and an aerial robot, which is applied to real-time frost monitoring in vineyards. The core feature of our system is a dynamic mobile node carried by an aerial robot, which ensures communication between sparse clusters located at fragmented parcels and a base station. This system overcomes some limitations of the wireless networks in areas with such characteristics. The use of a dedicated communication channel enables data routing to/from unlimited distances.

Aerial remote sensing in agriculture: A practical approach to area coverage and path planning for fleets of mini aerial robots

In this paper, a system that allows applying precision agriculture techniques is described. The application is based on the deployment of a team of unmanned aerial vehicles that are able to take georeferenced pictures in order to create a full map by applying mosaicking procedures for postprocessing. The main contribution of this work is practical experimentation with an integrated tool. Contributions in different fields are also reported. Among them is a new one-phase automatic task partitioning manager, which is based on negotiation among the aerial vehicles, considering their state and capabilities. Once the individual tasks are assigned, an optimal path planning algorithm is in charge of determining the best path for each vehicle to follow. Also, a robust flight control based on the use of a control law that improves the maneuverability of the quadrotors has been designed. A set of field tests was performed in order to analyze all the capabilities of the system, from task negotiations to final performance. These experiments also allowed testing control robustness under different weather conditions.

Mini-quadrotor attitude control based on Hybrid Backstepping & Frenet-Serret theory

This paper is about modeling and control of miniature quadrotors, with a special emphasis on attitude control. Mathematical models for simulation and nonlinear control approaches are introduced and subsequently applied to commercial aircraft: the DraganFlyer quadrotor, which has been hardware-modified in order to perform experimental autonomous flying. Hybrid Backstepping control and the Frenet-Serret theory is used for attitude stabilization, introducing a desired attitude angle acceleration function dependent on aircraft velocity. Finally, improvements on disturbance rejection and attitude tracking at moderate aircraft speeds are validated through various simulation scenarios (indoor navigation based on camera tracking), and flight experiments conducted on the DraganFlyer quadrotor.

An Aerial–Ground Robotic System for Navigation and Obstacle Mapping in Large Outdoor Areas

There are many outdoor robotic applications where a robot must reach a goal position or explore an area without previous knowledge of the environment around it. Additionally, other applications (like path planning) require the use of known maps or previous information of the environment. This work presents a system composed by a terrestrial and an aerial robot that cooperate and share sensor information in order to address those requirements. The ground robot is able to navigate in an unknown large environment aided by visual feedback from a camera on board the aerial robot. At the same time, the obstacles are mapped in real-time by putting together the information from the camera and the positioning system of the ground robot. A set of experiments were carried out with the purpose of verifying the system applicability. The experiments were performed in a simulation environment and outdoor with a medium-sized ground robot and a mini quad-rotor. The proposed robotic system shows outstanding results in simultaneous navigation and mapping applications in large outdoor environments.

Near-optimal coverage trajectories for image mosaicing using a mini quad-rotor over irregular-shaped fields

Aerial images are useful tools for farmers who practise precision agriculture. The difficulty in taking geo-referenced high-resolution aerial images in a narrow time window considering weather restrictions and the high cost of commercial services are the main drawbacks of these techniques. In this paper, a useful tool to obtain aerial images by using low cost unmanned aerial vehicles (UAV) is presented. The proposed system allows farmers to easily define and execute an aerial image coverage mission by using geographic information system tools in order to obtain mosaics made of high-resolution images. The system computes a complete path for the UAV by taking into account the on-board camera features once the image requirements and area to be covered are defined. This work introduces a full four-step procedure: mission definition, automatic path planning, mission execution and mosaic generation.

Multi-robot visual coverage path planning: geometrical metamorphosis of the workspace through raster graphics based approaches

Aerial multi-robot systems are a robust remote sensing choice to collect environmental data from the Earths surface. To accomplish this mission in a collaborative way, unmanned aerial vehicles must perform a full coverage trajectory over a target area while acquiring imagery of it. In this paper we address the multi coverage path planning problem with an aerial vehicles team. The approach proposed is hybrid, since is it is composed by an on-line and an off-line steps. This work is based on an optimal solution which is discretized to compute the coverage paths. This work proposes a multi coverage path planning solution making use of computer graphics tools in the world transformation from continuous to discrete, focusing on the aerial images acquisition. The workspace transformation from continuous to discrete is discussed and raster graphics based algorithms are employed.

Aerial Fleet in RHEA Project: A High Vantage Point Contributions to ROBOT 2013

The RHEA project is based on the cooperation among aerial and ground vehicles aiming at performing several precision agriculture tasks. This work is focused on the description of the aerial mission in the mentioned project. The work includes a description of the units, the goals and mission types, the requirements involved in the mission planning as well as their supervision and monitoring. The missions are performed by using a fleet of last-generation hex-rotors that rely on high payload and extraordinary stability. These features allow taking steady pictures with high quality cameras in large extension fields. As result, high-resolution images of the field to cover are obtained in order to provide with weeds pots positions to ground units for their removal.

QuadLab: A Project-Based Learning Toolkit for Automation and Robotics Engineering Education

It is frequently claimed that the students must have an active role in building and transforming their own knowledge, and the teachers labor is to provide the students the necessary tools in order to reach specific learning objectives, included in a course program. This paper presents an aerial robotic system as a toolkit, and proposes a series of activities focused on the learning in automation and robotics. These proposed activities have been designed based upon the project-based learning methodology, and they facilitate the achievement of the learning objectives presented by Spanish automation committee(CEA) in conjunction with The International Society of Automation (ISA) to satisfy the Accreditation Board for Engineering and Technology (ABET) standard. The toolkit and the activities are oriented to impulse the practical teaching, giving the student additional motivation and, in consequence, improving his or her active role. Besides, the toolkit and the activities give the teacher a tool in which it is possible to assess the students learning process.

Integrating Autonomous Aerial Scouting with Autonomous Ground Actuation to Reduce Chemical Pollution on Crop Soil

Many environmental problems cover large areas, often in rough terrain constrained by natural obstacles, which makes intervention difficult. New technologies, such as unmanned aerial units, may help to address this issue. Due to their suitability to access and easily cover large areas, unmanned aerial units may be used to inspect the terrain and make a first assessment of the affected areas; however, these platforms do not currently have the capability to implement intervention.

Using ROS in Multi-robot Systems: Experiences and Lessons Learned from Real-World Field Tests

This chapter presents a series of experiences and lessons learned during several implementations and real-world tests of ROS-based Multi-Robot Systems. It also describes, analyses and compares several ROS components relevant for these applications, taking into account the scenarios where they can be used. Also, some general issues of importance of Multi-Robot Systems on real-world, such as software and communications architectures, types of information shared are described in detail. Finally, the difficulties and specific challenges that arose when using a Multi-Robot Systems for any application will be discussed.