Concept and Feasibility Evaluation of Distributed Sensor-Based Measurement Systems Using Formation Flying Multicopters

Unmanned aerial vehicles (UAVs) have been used for increasing research applications in atmospheric measurements. However, most current solutions for these applications are based on a single UAV with limited payload capacity. In order to address the limitations of the single UAV-based approach, this paper proposes a new concept of measurements using tandem flying multicopters as a distributed sensor platform. Key challenges of the proposed concept are identified including the relative position estimation and control in wind-perturbed outdoor environment and the precise alignment of payloads. In the proposed concept, sliding mode control is chosen as the relative position controller and a gimbal stabilization system is introduced to achieve fine payload alignment. The characterization of the position estimation sensors (including global navigation satellite system and real-time kinematics) and flight controller is carried out using different UAVs (a DJI Matrice M600 Pro Hexacopter and Tarot X4 frame based Quadcopter) under different wind levels. Based on the experimental data, the performance of the sliding mode controller and the performance of the gimbal stabilization system are evaluated in a hardware-in-the-loop simulation environment (called ELISSA). Preliminary achievable control accuracies of the relative position and attitude of subsystems in the proposed concept are estimated based on experimental result

Reinforcement Learning to Control Lift Coefficient Using Distributed Sensors on a Wind Tunnel Model

Arrays of sensors distributed on the wing of fixed-wing vehicles can provide information not directly available to conventional sensor suites. These arrays of sensors have the potential to improve flight control and overall flight performance of small fixed-wing uninhabited aerial vehicles (UAVs). This work investigated the feasibility of estimating and controlling aerodynamic coefficients using the experimental readings of distributed pressure and strain sensors across a wing. The study was performed on a one degree-of-freedom model about pitch of a fixed-wing platform instrumented with the distributed sensing system. A series of reinforcement learning (RL) agents were trained in simulation for lift coefficient control, then validated in wind tunnel experiments. The performance of RL-based controllers with different sets of inputs in the observation space were compared with each other and with that of a manually tuned PID controller. Results showed that hybrid RL agents that used both distributed sensing data and conventional sensors performed best across the different tests.</p

Orbital operations study. Volume 2: Interfacing activities analyses. Part 3: Data management activity group

A summary of the findings of the data management group of the orbital operations study is presented. Element interfaces, alternate approaches, design concepts, operational procedures, functional requirements, design influences, and approach selection are described. The following interfacing activities are considered: (1) communications, (2) rendezvous, (3) stationkeeping, and (4) detached element operations

Saving Special Places: Community Funding for Land Conservation

In New Hampshire communities, there is a groundswell of interest and activity in conserving land. New Hampshire currently has more than forty-five land trusts. There are conservation commissions in all but a handful of towns. Many of them are engaged in conserving their special natural lands. Over half of the towns in the state have conservation funds fueled by the Land Use Change Tax. There have been 62 applications for land conservation projects to the Land and Community Heritage Investment Program since its inception in 2000. New Hampshire voters are appropriating significant taxpayer funds to conserve undeveloped land. Twelve communities, mostly in the south central and southeastern tier of the state, including Amherst, Brookline, Newfields, and Stratham, approved bonds and appropriations totaling nearly $20.2 million in 2002 alone. New Hampshire is losing 12,000 to 15,000 acres of open space a year to development. That is equivalent to building houses, roads and shopping areas in an area half the size of an average New Hampshire town. It is open space that gives our towns their traditional character and appearance. Unless towns protect open space strategically and intentionally, it will be consumed by development. The goal of this guidebook is to help you, as a concerned citizen, elected official, or conservation commission member, achieve your town’s land conservation goals by securing local funding for land conservation in your community