Adaptive entry guidance for the Tianwen-1 mission

To meet the requirements of the Tianwen-1 mission, adaptive entry guidance for entry vehicles, with low lift-to-drag ratios, limited control authority, and large initial state bias, was presented. Typically, the entry guidance law is divided into four distinct phases: trim angle-of-attack phase, range control phase, heading alignment phase, and trim-wing deployment phase. In the range control phase, the predictor—corrector guidance algorithm is improved by planning an on-board trajectory based on the Mars Science Laboratory (MSL) entry guidance algorithm. The nominal trajectory was designed and described using a combination of the downrange value and other states, such as drag acceleration and altitude rate. For a large initial state bias, the nominal downrange value was modified onboard by weighing the landing accuracy, control authority, and parachute deployment altitude. The biggest advantage of this approach is that it allows the successful correction of altitude errors and the avoidance of control saturation. An overview of the optimal trajectory design process, including a discussion of the design of the initial flight path angle, relevant event trigger, and transition conditions between the four phases, was also presented. Finally, telemetry data analysis and post-flight assessment results were used to illustrate the adaptive guidance law, create good conditions for subsequent parachute reduction and power reduction processes, and gauge the success of the mission.

Distributed Autonomous Economic Control Strategy for Microgrid Considering Event Triggering Mechanism

To fully adapt to the distributed access of renewable energy, microgrid technology has been developed rapidly. Aiming at the coordination and efficient regulation of distributed resources in microgrid, this paper proposes a distributed autonomous economic control strategy for microgrid considering event triggering mechanism. First, a distributed autonomous economic control architecture is built to provide a distributed operation architecture for optimal regulation of the microgrid. Secondly, a distributed secondary control strategy based on the consensus control theory is established to realize the economic allocation of active power as well as safe and stable operation of the microgrid. On this basis, an event trigger protocol based on the consensus error of the control variables is constructed, which is conductive to reduce redundant communication. The stability of the event trigger protocol is deduced by means of Lyapunov function analysis. The simulation analysis based on the equivalent microgrid verifies that the proposed control strategy can reduce redundant communication and acquire fair distribution of reactive power and active power among DGs, realizing distributed, economical and safe operation of microgrid.

Adapting the influences of publishers to perform news event detection

Online news outlets have the power to influence public policy issues. To understand the opinions of the people, many government departments check online news outlets to manually detect events that interest people. This process is time-consuming. To promptly respond to public expectations, this research proposes a framework for detecting news events that may interest government departments. This article proposes a method for finding event trigger words used to represent an event. The news media can be a critical participant in ‘agenda-setting’, which means that more widely discussed news is more attractive and critical than news that is less discussed. However, few studies have considered the influence of news media publishers from the ‘agenda setting’ perspective. Therefore, this study proposes an ‘agenda setting’-based filter to establish a high-impact news event detection model. The proposed framework identifies trigger words and utilises word embedding to find news event–related words. After that, an event detection model is designed to determine the events that are attractive to government departments. The experimental results show that purity increases from 0.666 when no extraction method is used to 0.809 when the extraction method in this study is used. The overall improvement trend shows significant improvement in event detection performance.

A STRATOSPHERIC BALLOON FLIGHT PLATFORM AND ITS EMPLOYMENT IN GRAVITATIONAL WAVE COUNTERPART OBSERVATION EXPERIMENTS

The Cubesats Applied for MEasuring and LOcalising Transients (CAMELOT) initiative proposes to deploy a fleet of 3U nanosatellites in order to localise GRBs with all-sky coverage. The operation is based on measuring the time delay of the event trigger between satellites that are otherwise uniformly distributed around the Earth in low-Earth orbit (between 500 - 600 km of altitude). In this design, caesium-iodide crystals interact with soft gamma radiation by emitting optical photons. Utilization of this effect, each member of the fleet is equipped with four of such scintillators and the emitted photons are detected by multi-pixel photon counters (MPPCs). Precise timing is crucial for this concept, the timestamping of the events and the synchronisation is provided by GPS. In order to demonstrate the feasibility of the CAMELOT concept, a single-unit CubeSat, named "GRBAlpha" is currently being developed. GRBAlpha is equipped with a single block of scintillator but the other subsystems are all the same as it will be on the CAMELOT units. We describe this single-unit platform system, focusing on the model versions suitable for high-altitude stratospheric balloon flights. This model has a standardized layout (including pin-out configuration, signalling and bus communication) and compatible with significant proportion of CubeSat system vendors. This system of ours is also capable of hosting multiple payloads at the same time, optimizing the utilization of balloon experiments.