Energy efficiency path planning for a quadrotor aerial vehicle

Unmanned aerial vehicles are used today in many real-world applications. In all these applications, the vehicle endurance (flight time) is an important constraint that affects mission success. This study investigates the limitations of embedded energy for a quadrotor aerial vehicle. We consider a quadrotor simple tasked to travel from an initial hover configuration to a final hover configuration. In order to have a precise approximation of the consumed energy, we propose a power consumption model with battery dynamic, motor dynamic, and rotor efficiency function. We then introduce an optimization algorithm to minimize the energy consumption during quadrotor aerial vehicle mission. The proposed algorithm is based on an optimal control problem formulated for the quadrotor model and solved using nonlinear programming. In the optimal control problem, we seek to find control inputs (rotor velocity) and vehicle trajectory between initial and final configurations that minimize the consumed energy during a point-to-point mission. We extensively test in simulation experiments the proposed algorithm under normal and windy weather conditions. We compare the proposed optimization method with a nonlinear adaptive control approach to highlight the saved amount of energy.

On-Orbit Implementation of Discrete Isolation Schemes for Improved Reliability of Serial Communication Buses

Serial communication buses are used in electronic systems to interconnect sensors and other devices, but two of the most widely used protocols, I²C and SPI, are vulnerable to bus-wide failures if even one device on the bus malfunctions. For aerospace applications demanding increasingly more distributed processing and sensing capability, the compounding risk to system reliability as device count scales becomes a limiting factor in mission scope, performance, and lifetime. We propose a simple external circuit to be added to each node on a communication bus that automatically isolates the node in the event of device failure. By automatically isolating failed devices, the integrity of the bus is preserved without requiring additional signals or processing overhead from the host controller. In this article, I²C and SPI isolation circuits are simulated, fabricated, and experimentally verified to be effective at preserving bus integrity in the event of peripheral device failure. Generalized reusable circuit blocks were designed and integrated into three spacecraft systems for the successful NASA V-R3x mission deployed in January 2021. The addition of serial bus isolation significantly improved system reliability for the V-R3x mission by eliminating single-point failure modes of the I²C and SPI buses interconnecting sensors and radios necessary for mission success. The developed protection schemes are a new tool for decoupling system reliability from serial bus device count and can readily be integrated into existing aerospace systems.

On-Orbit Implementation of Discrete Isolation Schemes for Improved Reliability of Serial Communication Buses

Serial communication buses are used in electronic systems to interconnect sensors and other devices, but two of the most widely used protocols, I²C and SPI, are vulnerable to bus-wide failures if even one device on the bus malfunctions. For aerospace applications demanding increasingly more distributed processing and sensing capability, the compounding risk to system reliability as device count scales becomes a limiting factor in mission scope, performance, and lifetime. We propose a simple external circuit to be added to each node on a communication bus that automatically isolates the node in the event of device failure. By automatically isolating failed devices, the integrity of the bus is preserved without requiring additional signals or processing overhead from the host controller. In this article, I²C and SPI isolation circuits are simulated, fabricated, and experimentally verified to be effective at preserving bus integrity in the event of peripheral device failure. Generalized reusable circuit blocks were designed and integrated into three spacecraft systems for the successful NASA V-R3x mission deployed in January 2021. The addition of serial bus isolation significantly improved system reliability for the V-R3x mission by eliminating single-point failure modes of the I²C and SPI buses interconnecting sensors and radios necessary for mission success. The developed protection schemes are a new tool for decoupling system reliability from serial bus device count and can readily be integrated into existing aerospace systems.

On-Orbit Implementation of Discrete Isolation Schemes for Improved Reliability of Serial Communication Buses

Serial communication buses are used in electronic systems to interconnect sensors and other devices, but two of the most widely used protocols, I²C and SPI, are vulnerable to bus-wide failures if even one device on the bus malfunctions. For aerospace applications demanding increasingly more distributed processing and sensing capability, the compounding risk to system reliability as device count scales becomes a limiting factor in mission scope, performance, and lifetime. We propose a simple external circuit to be added to each node on a communication bus that automatically isolates the node in the event of device failure. By automatically isolating failed devices, the integrity of the bus is preserved without requiring additional signals or processing overhead from the host controller. In this article, I²C and SPI isolation circuits are simulated, fabricated, and experimentally verified to be effective at preserving bus integrity in the event of peripheral device failure. Generalized reusable circuit blocks were designed and integrated into three spacecraft systems for the successful NASA V-R3x mission deployed in January 2021. The addition of serial bus isolation significantly improved system reliability for the V-R3x mission by eliminating single-point failure modes of the I²C and SPI buses interconnecting sensors and radios necessary for mission success. The developed protection schemes are a new tool for decoupling system reliability from serial bus device count and can readily be integrated into existing aerospace systems.

Production of PHB From CO2-Derived Acetate With Minimal Processing Assessed for Space Biomanufacturing

Providing life-support materials to crewed space exploration missions is pivotal for mission success. However, as missions become more distant and extensive, obtaining these materials from in situ resource utilization is paramount. The combination of microorganisms with electrochemical technologies offers a platform for the production of critical chemicals and materials from CO2 and H2O, two compounds accessible on a target destination like Mars. One such potential commodity is poly(3-hydroxybutyrate) (PHB), a common biopolyester targeted for additive manufacturing of durable goods. Here, we present an integrated two-module process for the production of PHB from CO2. An autotrophic Sporomusa ovata (S. ovata) process converts CO2 to acetate which is then directly used as the primary carbon source for aerobic PHB production by Cupriavidus basilensis (C. basilensis). The S. ovata uses H2 as a reducing equivalent to be generated through electrocatalytic solar-driven H2O reduction. Conserving and recycling media components is critical, therefore we have designed and optimized our process to require no purification or filtering of the cell culture media between microbial production steps which could result in up to 98% weight savings. By inspecting cell population dynamics during culturing we determined that C. basilensis suitably proliferates in the presence of inactive S. ovata. During the bioprocess 10.4 mmol acetate L –1 day–1 were generated from CO2 by S. ovata in the optimized media. Subsequently, 12.54 mg PHB L–1 hour–1 were produced by C. basilensis in the unprocessed media with an overall carbon yield of 11.06% from acetate. In order to illustrate a pathway to increase overall productivity and enable scaling of our bench-top process, we developed a model indicating key process parameters to optimize.

A Review of Operational Ensemble Forecasting Efforts in the United States Air Force

United States Air Force (USAF) operations are greatly influenced and impacted by environmental conditions. Since 2004, USAF has researched, developed, operationalized, and refined numerical weather prediction ensembles to provide improved environmental information for mission success and safety. This article reviews how and why USAF capabilities evolved in the context of USAF requirements and limitations. The convergence of time-lagged convection-allowing ensembles with inline diagnostics, algorithms to estimate the sub-grid scale uncertainty of critical forecasting variables, and the distillation of large quantities of ensemble information into decision-relevant products has led to the acceptance of probabilistic environmental forecast information and widespread reliance on ensembles in USAF operations worldwide.

Robotic Exploration of an Unknown Nuclear Environment Using Radiation Informed Autonomous Navigation

This paper describes a novel autonomous ground vehicle that is designed for exploring unknown environments which contain sources of ionising radiation, such as might be found in a nuclear disaster site or a legacy nuclear facility. While exploring the environment, it is important that the robot avoids radiation hot spots to minimise breakdowns. Broken down robots present a real problem: they not only cause the mission to fail but they can block access routes for future missions. Until now, such robots have had no autonomous gamma radiation avoidance capabilities. New software algorithms are presented that allow radiation measurements to be converted into a format in which they can be integrated into the robot’s navigation system so that it can actively avoid receiving a high radiation dose during a mission. An unmanned ground vehicle was fitted with a gamma radiation detector and an autonomous navigation package that included the new radiation avoidance software. The full system was evaluated experimentally in a complex semi-structured environment that contained two radiation sources. In the experiment, the robot successfully identified both sources and avoided areas that were found to have high levels of radiation while navigating between user defined waypoints. This advancement in the stateoftheart has the potential to deliver real benefit to the nuclear industry, in terms of both increased chance of mission success and reduction of the reliance on human operatives to perform tasks in dangerous radiation environments.