48 research outputs found
Link!: Potential Field Guidance Algorithm for In-Flight Linking of Multi-Rotor Aircraft
Link! is a multi-center NASA e ort to study the feasibility of multi-aircraft aerial docking systems. In these systems, a group of vehicles physically link to each other during flight to form a larger ensemble vehicle with increased aerodynamic performance and mission utility. This paper presents a potential field guidance algorithm for a group of multi-rotor vehicles to link to each other during flight. The linking is done in pairs. Each vehicle first selects a mate. Then the potential field is constructed with three rules: move towards the mate, avoid collisions with non-mates, and stay close to the rest of the group. Once a pair links, they are then considered to be a single vehicle. After each pair is linked, the process repeats until there is only one vehicle left. The paper contains simulation results for a system of 16 vehicles
Project Link!: Dynamics and Control of In-Flight Wing Tip Docking
Project Link! is a NASA-led effort to study the feasibility of multi-aircraft aerial docking systems. In these systems, a group of vehicles physically link to each other during flight to form a larger ensemble vehicle with increased aerodynamic performance and mission utility. This paper presents a dynamic model and control architecture for a system of fixed-wing vehicles with this capability. The dynamic model consists of the 6 degree-of-freedom fixed-wing aircraft equations of motion, a spring-damper-magnet system to represent the linkage force between constituent vehicles, and the NASA-Burnham-Hallock wingtip vortex model to represent the close-proximity aerodynamic interactions between constituents before the linking occurs. The control architecture consists of a guidance algorithm to autonomously drive the constituents towards their linking partners and an inner-loop angular rate controller. A simulation was constructed from the model, and the flight dynamic modes of the linked system were compared to the individual vehicles. Simulation results for both before and after linking are presented
Modular Hydraulic Propulsion: A Robot that Moves by Routing Fluid Through Itself
This paper introduces the concept of Modular
Hydraulic Propulsion, in which a modular robot that operates
in a fluid environment moves by routing the fluid through
itself. The robot’s modules represent sections of a hydraulics
network. Each module can move fluid between any of its
faces. The modules (network sections) can be rearranged
into arbitrary topologies. We propose a decentralized motion
controller, which does not require modules to communicate,
compute, nor store information during run-time. We use 3-D
simulations to compare the performance of this controller to
that of a centralized controller with full knowledge of the task.
We also detail the design and fabrication of six 2-D prototype
modules, which float in a water tank. Results of systematic
experiments show that the decentralized controller, despite its
simplicity, reliably steers modular robots towards a light source.
Modular Hydraulic Propulsion could offer new solutions to
problems requiring reconfigurable systems to move precisely
in 3-D, such as inspection of pipes, vascular systems or other
confined spaces
Finding Optimal Modular Robots for Aerial Tasks
Traditional aerial vehicles have limitations in their capabilities due to
actuator constraints, such as motor saturation. The hardware components and
their arrangement are designed to satisfy specific requirements and are
difficult to modify during operation. To address this problem, we introduce a
versatile modular multi-rotor vehicle that can change its capabilities by
reconfiguration. Our modular robot consists of homogeneous cuboid modules,
propelled by quadrotors with tilted rotors. Depending on the number of modules
and their configuration, the robot can expand its actuation capabilities. In
this paper, we build a mathematical model for the actuation capability of a
modular multi-rotor vehicle and develop methods to determine if a vehicle is
capable of satisfying a task requirement. Based on this result, we find the
optimal configurations for a given task. Our approach is validated in realistic
3D simulations, showing that our modular system can adapt to tasks with varying
requirements