Spiral trajectories induced by radial thrust with applications to generalized sails

In this study, new analytical solutions to the equations of motion of a propelled spacecraft are investigated using a shape-based approach. There is an assumption that the spacecraft travels a two-dimensional spiral trajectory in which the orbital radius is proportional to an assigned power of the spacecraft angular coordinate. The exact solution to the equations of motion is obtained as a function of time in the case of a purely radial thrust, and the propulsive acceleration magnitude necessary for the spacecraft to track the prescribed spiral trajectory is found in a closed form. The analytical results are then specialized to the case of a generalized sail, that is, a propulsion system capable of providing an outward radial propulsive acceleration, the magnitude of which depends on a given power of the Sun-spacecraft distance. In particular, the conditions for an outward radial thrust and the required sail performance are quantified and thoroughly discussed. It is worth noting that these propulsion systems provide a purely radial thrust when their orientation is Sun-facing. This is an important advantage from an engineering point of view because, depending on the particular propulsion system, a Sun-facing attitude can be stable or obtainable in a passive way. A case study is finally presented, where the generalized sail is assumed to start the spiral trajectory from the Earth’s heliocentric orbit. The main outcome is that the required sail performance is in principle achievable on the basis of many results available in the literature.

A Plug and Play Transparent Communication Layer for Cloud Robotics Architectures

The cloud robotics paradigm aims at enhancing the abilities of robots by using cloud services, but it still poses several challenges in the research community. Most of the current literature focuses on how to enrich specific robotic capabilities, overlooking how to effectively establish communication between the two fields. Our work proposes a “plug-and-play” solution to bridge the communication gap between cloud and robotic applications. The proposed solution is designed based on the mature WebSocket technology and it can be extended to any ROS-based robotic platform. The main contributions of this work are the definition of a reliable autoconnection/autoconfiguration mechanism as well as to outline a scalable communication layer that allows the effective control of multiple robots from multiple users. The “plug-and-play” solution was evaluated in both simulated and real scenarios. In the first case, the presence of users and robots was simulated with Robot Operating System (ROS) nodes running on five machines. In the real scenario, three non-expert users teleoperated, simultaneously, three remote robots by using the proposed communication layer with different networking protocols. Results confirmed the reliability at different levels: at startup (success_rate = 100%); during high-rate communications (message_lost = 0%); in performing open-loop spiral trajectories with enhancement, with respect to similar works; and in the quality of simultaneous teleoperations.

The Relativistic Cyclotron Radiation in the Circular Rotating Frame of the Moving Heavy Particle

In the current paper we tackle the task of determining the formula for the cyclotron radiation as measured from a frame co-moving with the particle being accelerated. In the case of cyclotrons, as opposed to synchrotrons, the magnetic field is constant, resulting into spiral trajectories for light particle, like electrons and into circular trajectories for heavier particles, like protons, as we will demonstrate in the current paper. This due to the fact that the braking force is a very small percentage of the accelerating (Lorentz) force, as will be shown later in our paper. These proofs have never been attempted before owing to the difficulty of dealing with rotating frames. Our paper is divided into two main sections, the first section deals with cyclotron radiation measured in the inertial frame of the lab, the second section deals with cyclotron radiation as measured in a frame co-rotating with the particle along a circular path, at a uniform speed.

Gliding Robotic Fish: An Underwater Sensing Platform and Its Spiral-Based Tracking in 3D Space

Gliding robotic fish are a new type of underwater robot that combines the advantages of energy efficiency of underwater gliders and high maneuverability of robotic fish. Tail-enabled spiraling, as a novel locomotion pattern of gliding robotic fish, uses a buoyancy-driven mechanism and features a small turning radius. This paper investigates the spiral trajectory characteristics from the viewpoint of differential geometry and exploits them for curve tracking in the 3D space. The influences of control inputs on spiral trajectories are investigated through both simulation and experiments. A simulation example using a combined feedforward and feedback controller illustrates the proposed curve-tracking approach.