Electric Propulsion Research Articles

Optimizing a Hall thruster with aft-loaded magnetic field by aft-loading design of gas flow

Electric propulsion systems with high-specific impulses have replaced chemical propulsion systems in many space missions. The aft-loaded magnetic field technology of Hall thrusters moves the ionization and acceleration processes downstream of the channel by varying the magnetic field distribution. Consequently, ion bombardment of the channel walls is inhibited, and the service life of the Hall thrusters is substantially increased. However, neutral gas leaks because of the rapid diffusion near the channel outlet, where strong ionization occurs. Thus, the propellant atoms are ionized insufficiently, resulting in a decline in the performance. Therefore, an aft-loading design for the neutral gas flow field was developed to optimization distribution of the neutral gas in this study. A 1.5 kW Hall thruster was verified experimentally. The experimental results show that the aft-loaded neutral gas flow field significantly improved the ionization and acceleration processes. The propellant utilization efficiency increased by 4–8% within the discharge voltage range of 300–900 V. The ion energy distribution moved toward the high-energy direction significantly, promoting an overall improvement in the performance, with a thrust increase of 7.3–11.5 %. The anode efficiency increased from 49–57 % to 58–61 %. The results of this study are significant for the design of high-performance, long-life Hall thrusters.

A demand forecasting model for urban air mobility in Chengdu, China

The successful application of new technologies such as remotely piloted aircraft systems, distributed electric propulsion systems, and automatic control systems on electric vertical take-off and landing(eVTOL) aircraft has prompted Urban Air Mobility (UAM) to be mentioned frequently. UAM is a newly raised transport mode of using eVTOL aircraft to transport people and cargo in urban areas, which is thought to share some of the traffic on the ground. One of the prerequisites for UAM to operate on a regular basis is that its demand can support the operating costs, so forecasting UAM demand is necessary. We conduct UAM demand forecasting based on the four-step method, focusing on improving the third-step modal split, and propose a demand forecasting model based on the logit model. The model combines a nested logit (NL) model with a multinomial logit (MNL) model to solve the problem of non-existent UAM sharing rates. We use Chengdu, China as an example, and focus on forecasting the UAM traffic demand in 2030 with the help of the four-step method. The results show that UAM is suitable for shared operation during the early stages. With a fully shared operation, the UAM share rate increases by 0.73% for every kilometer increase in distance. Moreover, UAM is more competitive than other modes for delivery distances exceeding 15 ​km. Finally, using the distributions of the share rate and traffic flow pattern from the simulation, we propose the routes that can be prioritized for UAM operations in Chengdu.

Recent Patents on Artificial Muscle Actuators

Background: With the development of automation technology, various actuators are widely used in fields such as robotics and biomedical equipment. However, traditional mechanical actuators have some problems, such as poor movement flexibility and insufficient movement flexibility, because of the characteristics of the mechanical structure. As a new driving mode, artificial muscle actuators can provide enough power and speed while remaining light and flexible, making them highly adaptable in various applications. As a result, artificial muscle actuators are gaining increasing attention. Objective: The purpose of this study is to give an overview of the patents related to artificial muscle actuators and introduce their principles, classifications, latest progress, and future development. Methods: This paper reviews the current representative patents related to artificial muscle actuators, such as fluid pressure artificial muscle actuators, thermal deformation artificial muscle actuators, and electrical deformation artificial muscle actuators. Conclusion: The optimization of artificial muscle actuators is beneficial to make the output of artificial mechanical devices more stable and more convenient for human-machine combinations. More related patents will be invented in the future.

Novel Electric Propulsion System Analysis Method for Electric Vertical Takeoff and Landing Aircraft Conceptual Design

This paper proposes novel enhancements to the electric propulsion system analysis method for electric vertical takeoff and landing (eVTOL) aircraft conceptual design by considering the electrical characteristics of each electrical device in a more accurate manner. To this end, three modules for motor, inverter, and battery analysis are constructed using equivalent circuits and semi-empirical models. First, the motor analysis module is developed using equivalent circuit analysis with the operation control strategy for a permanent-magnet synchronous motor. Second, the inverter analysis module is built using average loss models for the switching and conduction losses. Third, the battery analysis module is improved using the near-linear discharge model to consider the voltage drop during operation. Moreover, additional modules, such as those for calculating the battery stack in series and parallel, as well as regression models for the motor and inverter performance parameters and consideration of the drive system type (direct or indirect, including a reduction gear), are implemented. A comparative study is presented from an analysis and design perspective while changing the drive system type (direct or indirect) and gear ratio, which highlights the importance of modeling electrical characteristics during eVTOL aircraft conceptual design.

About the Wing and Whirl Flutter of a Slender Wing–Propeller System

Next-generation aircraft designs often incorporate multiple large propellers attached along the wingspan (distributed electric propulsion), leading to highly flexible dynamic systems that can exhibit aeroelastic instabilities. This paper introduces a validated methodology to investigate the aeroelastic instabilities of wing–propeller systems and to understand the dynamic mechanism leading to wing and whirl flutter and transition from one to the other. Factors such as nacelle positions along the wing span and chord and its propulsion system mounting stiffness are considered. Additionally, preliminary design guidelines are proposed for flutter-free wing–propeller systems applicable to novel aircraft designs. The study demonstrates how the critical speed of the wing–propeller systems is influenced by the mounting stiffness and propeller position. Weak mounting stiffnesses result in whirl flutter, while hard mounting stiffnesses lead to wing flutter. For the latter, the position of the propeller along the wing span may change the wing mode shapes and thus the flutter mechanism. Propeller positions closer to the wing tip enhance stability, but pusher configurations are more critical due to the mass distribution behind the elastic axis.

Overall eVTOL aircraft design for urban air mobility

Electric vertical takeoff and landing (eVTOL) aircraft have emerged as a potential alternative to the existing transportation system, offering a transition from two-dimensional commuting and logistics to three-dimensional mobility. As a groundbreaking innovation in both the automotive and aviation sectors, eVTOL holds significant promise but also presents notable challenges. This paper aims to address the overall aircraft design (OAD) approach specifically tailored for eVTOL in the context of Urban Air Mobility (UAM). In contrast to traditional OAD methods, this study introduces and integrates disciplinary methodologies specifically catered to eVTOL aircraft design. A case study is conducted on a tilt-duct eVTOL aircraft with a typical UAM mission, and the disciplinary performance, including initial sizing, aerodynamics, electric propulsion systems, stability and control, weight, mission analysis and noise, is examined using the OAD methodologies. The findings demonstrate that the current approach effectively evaluates the fundamental aircraft-level performance of eVTOL, albeit further high-fidelity disciplinary analysis and optimization methods are required for future MDO-based eVTOL overall aircraft design.

DSP based space vector PWM control for solar electric vehicle

Solar Electric Vehicles (SEV) are considered the future vehicles to solve the issues of air pollution, global warming, and the rapid decreases of the petroleum resources facing the current transportation technology. However, SEV are still facing important technical obstacles to overcome. They include batteries energy storage capacity, charging times, efficiency of the solar panels and electrical propulsion systems. Solving any of those problems and electric vehicles will compete-complement the internal combustion engines vehicles. In the present work, we propose an electrical propulsion system based on three phase induction motor in order to obtain the desired speed and torque with less power loss. Because of the need to lightweight nature, small volume, low cost, less maintenance and high efficiency system, a three phase squirrel cage induction motor (IM) is selected in the electrical propulsion system. The IM is fed from three phase inverter operated by a constant V/F control method and Space Vector Pulse Width Modulation (SVPWM) algorithm. The proposed control strategy has been implemented on the texas instruments TM320F2812 Digital Signal Processor (DSP) to generate SVPWM signal needed to trigger the gates of IGBT based inverter. The inverter used in this work is a three phase inverter IRAMY20UP60B type. The experimental results show the ability of the proposed control strategy to generate a three-phase sine wave signal with desired frequency. The proposed control strategy is experimented on a locally manufactured EV prototype. The results show that the EV prototype can be propelled to speed up to 60km/h under different road conditions.

Optimal control for quadrotors during inspection of power utility assets

Renewable energy and power utilities inspection by autonomous aircraft enables rapid and effective risk-free assessment of the state of systems, and provides a qualitative and accurate assessment of defects and damages. To realize maximum operational benefits of aerial inspections, effective controls for autonomous aircraft must be ensured and the system should be operated in an optimal policy. Hence, the objective of this paper is to consider optimal control strategies for a quadrotor helicopter type UAV. Based on some structural properties of the considered system, in particular the flatness property, we suggest a control strategy that ensures tracking a time parameterized path that connects two given points in the state space while minimizing the energy consumption. The proposed controller enables longer-endurance missions for the quadrotor and effective supervision and inspection of large energy systems and power plants. In this paper the analysis of the control law takes into consideration the highly nonlinear dynamic model of the quadrotor and the electrical actuator model. The current approach in solving the optimal control problem under consideration allows one to eliminate the differential equation and to reformulate the optimal control problem to a nonlinear dynamic programming problem. The approach can make monitoring operations of renewable energy plants by aerial vehicles, more efficient.

Feasibility study of a Solar Electric Propulsion mission to Mars

Traditionally, space missions to outer planets have relied on large amounts of chemical propellant or flybys to achieve their objectives. This large mass consumption may be significantly reduced using electric propulsion (EP), since it allows for larger specific impulses. However, this improvement is counteracted by the lower thrust per power levels achievable with EP engines compared to chemical thrusters. Here we discuss how to find a balance for a purely solar EP (SEP) uncrewed mission to Mars. We present system engineering and mission analyses focused on the orbital mechanics. The result is the conceptual design of a realistic mission to Mars, in which any target orbit around Mars can be reached using solely present SEP technology. In particular, for a 2000 kg spacecraft propelled with a Hall effect thruster (HET), the interplanetary transfer can be performed in 363 days with less than 400 kg of fuel consumption, provided that the vehicle leaves the Earth orbit with a suitable specific energy that is attainable using current launchers. Subsequently, 300 kg of propellant are sufficient to allow for the planetary capture, plane change, and circularisation manoeuvres, finally inserting the spacecraft into a polar orbit of height between 300 km and 1000 km above the surface of Mars.

Concerning the ignition of a C12A7 electride plasma-based cathode

Hollow cathodes are crucial components for many electric propulsion systems used for space applications. However, they also represent a challenging and sometimes even limiting element for the propulsion systems. Particularly in recent times when alternative propellants are under evaluation for the thruster, and the design and the limits of the cathodes are being pushed. Consequently, significant improvement in the technology is desired. This publication tests a heaterless cathode using the emitter material C12A7 electride, particularly reviewing its ignition behavior and performance during an ignition cycling campaign. Stable heaterless ignition has been reliantly achieved in only a few milliseconds at an ignition potential of less than 400 V and 20 sccm Kr flow rate. Furthermore, two ignition cycling campaigns at different flow rates are presented, one reaching 3300 ignitions, the other igniting at only 6 sccm Kr flow rate. The degradation of the emitter materials and the influence on the ignition performance is discussed.

Distributed satellite system autonomous orbital control with recursive filtering

In this article, we propose a recursive orbital elements filter for autonomous control of Distributed Satellite Systems (DSS) that significantly reduces the variance of relative orbital elements between the observed and the desired satellite orbits. Leveraging satellite kinematics and control inputs data, combined with a model of relative dynamics, the filter provides smooth and continuous orbital control, while minimizing propellant consumption. In conjunction with Precise Point Positioning (PPP) navigation, the proposed filter enables onboard continuous low-thrust control compatible with high-performance electric propulsion. We also propose a restricted transverse/normal control law that simplifies the thruster's configurations and/or attitude manoeuvres required for propulsion pointing. The applicability and validity of our proposed techniques are verified by numerical simulations with two case studies: a constellation for Differential Interferometric Synthetic Aperture Radar (DInSAR) for global infrastructure monitoring; and a maritime domain awareness mission based on along-track interferometric synthetic aperture radar which requires single-pass interferometry for responsive ship traffic surveillance, and the coverage of a very large maritime zone with high revisit rates.

Kinetic simulations of low-pressure inductively coupled plasma: an implicit electromagnetic PIC/MCC model with the ADI-FDTD method

Low-pressure inductively coupled plasma (ICP) is promising for space electric propulsion. For the first time, an implicit electromagnetic particle-in-cell Monte Carlo collision model based on the alternating-direction-implicit finite-difference time-domain (ADI-FDTD) method is developed to investigate low-pressure xenon plasma characteristics of a miniature ICP source. The induced simulated electric field is well consistent with that calculated by the finite element method, indicating that this method can provide an accurate estimation of the electromagnetic field. The simulation time step used in the ADI-FDTD method is no longer restricted by the Courant–Friedrichs–Lewy constraints. Compared with the FDTD method, the ADI-FDTD method increases the size of the time step and significantly improves computational efficiency. The method is validated by comparing the simulated and measured electron density and plasma potential profile and reasonable agreement is reached. Therefore, the model is used to investigate the temporal and spatial distribution of plasma properties and the influence of the current amplitude of radio frequency (RF) coil, applied frequency of RF coil and neutral gas pressure on the plasma dynamics in the ionization chamber of a miniature gridded RF ion thruster. To explain the influence of the operating parameters, a concept called ‘the energy relaxation characteristics of electrons in response to the change of electric field’ is proposed and verified. The simulations also find that the oscillation frequency of plasma properties is twice the applied frequency of RF coil. The oscillation characteristics reveal the dynamic energy balance in the ICP. The experiment on the gridded RF ion thruster BHRIT-4 confirms the oscillation by measuring the plasma sheath potential.

Deflagration thruster for air-breathing electric propulsion in very low Earth orbit

This study establishes the performance requirements for an air-breathing electric propulsion device to operate in very low Earth orbit (<450 km). We demonstrate that existing electric propulsion architectures, including electrostatic thrusters, fail to generate enough thrust while operating on flow rates of air that can be harvested in orbit. Instead, we develop and characterize a type of electromagnetic pulsed thruster that operates in a magneto-deflagration mode (i.e., forms an expansion wave during the acceleration process) that becomes more efficient as less propellant is used. We show this mode of operation can generate specific impulses up to 104 s, thrust per power >2 mN/kW, thrust densities >100 mN/m2, and thrust efficiencies up to 10% while consuming <100μg of air per discharge. We map these performance metrics on a candidate spacecraft to show the deflagration thruster can enable fully air-breathing drag compensation at altitudes ranging from ∼200 km to 350 km depending on its geometry and is extendable to other altitudes if stored propellant is utilized.

Design and testing of a Mini-RF plasma thruster with permanent magnets

Compared with traditional electric propulsion, RF plasma thruster have attracted much attention due to their characteristics of no electrodes, long life, and high ionization rate. In recent years, the development of micro-nano satellites has put forward requirements for the miniaturization, modularization, and integration of satellite thrusters, and the miniaturization of RF plasma thrusters has a broad prospect. In this paper, a mini-RF plasma thruster with a discharge chamber inner diameter of 10 mm is designed, and a magnetic field is generated around it by two annular samarium cobalt permanent magnets. The discharge state and plasma parameters of the mini-RF thruster are tested using optical emission spectrometry (OES) and target thrust stand. In the experiment, we changed the flow rate of argon gas, the presence or absence of a magnetic field, the power of the RF source and analyzed the effects of these factors on the mode transition, plasma density, electron temperature, and thrust. According to the experimental results, it is found that the magnetic field (maximum strength 0.14T) helps to increase the plasma density at low power but delay the jump power threshold of the CCP-ICP.

Advancing Electric Flight through Innovative Materials in Aerospace Propulsion Systems

The advent of electric aircraft heralds a transformative era in aviation, offering a sustainable alternative to conventional aircraft that significantly contribute to carbon emissions. This paper discusses the application of advanced materials in overcoming the technical hurdles associated with electric propulsion systems, focusing on their application in airframe construction, electrical conductors, thermal management, and battery technology to enhance the performance and sustainability of electric aircraft. Advanced composites like carbon fiber reinforced polymer (CFRP) are explored for their potential to reduce aircraft weight and improve mechanical properties. The paper also addresses the challenges of thermal management in electric propulsion systems, highlighting the use of phase change materials (PCMs) and advanced ceramics for efficient heat dissipation. Furthermore, the exploration of high-energy-density cathode materials, innovative anode materials, and solid-state electrolytes is discussed in the context of developing lightweight, high-capacity batteries for electric aircraft. Despite the promising advancements in material science and the potential benefits of electric aviation, the paper acknowledges the existing challenges, including the high cost of advanced materials, the need for improved energy storage solutions, and the environmental impact of material production.

Analytical review of driving axles with integrated traction electric motors for commercial vehicles

Trucks with electric propulsion are one direction in the development of transport vehicles. Electric propulsion trucks have different transmission schemes: a classic one including a traction motor, gearbox, driveshaft, driving axle, and a scheme where the traction motor, gearbox, motor cooling system, and axle lubrication system are directly integrated into the driving axle. The layouts of driving axles with integrated traction motors can be divided into three groups: axles with a longitudinal arrangement of the traction motor, axles with a coaxial arrangement of the traction motor and vehicle wheels, and axles with a parallel arrangement of the traction motor axis and vehicle wheels. The layout largely determines technical solutions and requirements for transmission components. The layout is determined by the level of production and set tasks, such as high standardization with the produced products, or using components from the manufacturer’s standard product range.

The IAI Robot Control System in Researching Phone Speaker Production Lines

This article presents research on the IAI Robot control system in a phone speaker production line being operated in Vietnam. In assembly and handling technology, electric actuators are used for linear, rotary, or clamping movements. Single-axis IAI robots become flexible when paired together. IAI robots (Intelligent Actuators) meet significantly high requirements in terms of payload, speed, and travel length. The IAI Robot's control program is programmed on Keyence PLC and uses expansion modules to ensure the IAI Robot's stable operation, high accuracy, and fast processing speed. The results of research, construction, and direct experiments at the factory show that the system operates stably with high accuracy.

Harness EMI Problems for the Hybrid and Electric Aeronautical Propulsion Systems of Tomorrow

Harness EMI Problems for the Hybrid and Electric Aeronautical Propulsion Systems of Tomorrow

Comparative Analysis of Conventional and Electric Motor Propulsion Systems for “Sandek” Fishing Boats in West Sulawesi from a Sustainable Economical Aspect

Indonesia as a tropical country has abundant potential of solar energy. The Indonesian government is very serious about implementing efforts towards net zero emissions which are continuously encouraged. Using solar energy is one of the solutions to reduce greenhouse gas emissions use of fossil fuels. One of the efforts made is to apply technology to replace the propulsion system of ships powered by fossil fuel engines to electricity from solar energy. This research takes the case of a conventional engine-powered “Sandek” fishing boat converted to a solar-powered electric motor in West Sulawesi. The aim is to compare the level of profit and return on investment before and after conventional motor ships are replaced with electric powered ships. The research method used is a descriptive method with investment parameters including NPV, IRR, and Payback Period. The results hopefully can be used as a reference for investment who will develop the transition from conventional motor boats to electric boats. The conclusions of this research can be used as a model for the sustainable use of electric fishing boats in Indonesia.

Multiphysics Modeling and Co-Simulation of Ship Electric Power and Propulsion Systems for Virtual Testing and Verification

Multiphysics Modeling and Co-Simulation of Ship Electric Power and Propulsion Systems for Virtual Testing and Verification