Electric Propulsion Research Articles

Nonlinear dynamic morphing of conical bistable dielectric elastomer actuator

The bistable dielectric elastomer actuator (BDEA) possesses two stable positions which offers notable advantages of stable-state self-maintenance, fast response, and threshold snap-through characteristic in comparison with conventional dielectric elastomers. However, the strong nonlinearity induced by the coupling among materials, structure, and electrostatic fields greatly affect the dynamic response and gives rise to stability issues. Hence, a novel BDEA is proposed by introducing DEA film centrally connected with one mass block and linear spring, and the bistability can be adjusted by applying external voltage. A nonlinear dynamical model considering the electro-mechanical coupling effects is established using the Euler-Lagrange method, with which the snap-through procedure is theoretically analyzed and validated through the analytic method and finite element method. The influences of the electric actuation and structural parameters on the number of stable states and natural frequency are analyzed. Additionally, the supercritical pitchfork bifurcation and saddle-node bifurcation are investigated through dynamic analysis under forced vibration. Furthermore, the ranges of electrical actuation parameters can be determined for preventing the bifurcation phenomena under parametric excitations. Moreover, an active morphing strategy for achieving nonlinear dynamic morphing between steady states of BDEA using drive voltage is obtained, thereby enhancing the versatility of conical BDEA.

Analysis for Levitation of EHD and Electrostatic Propulsion Device in Direction of Gravity using Optical Flow Method

Electro hydro dynamic (EHD) and electrostatic propulsion devices have no moving parts and, in the air, operate on electrical energy. Thus, electric propulsion systems without moving parts such as propellers are expected to be developed in the future. EHD devices levitate in the direction opposite the direction of gravity when a high voltage is applied. In this study, detailed properties of the accurate propulsion direction, speed, and acceleration were clarified by imaging analysis. The analysis clarified that even if the orientation of the device was initially tilted from a horizontal line, the device was made to levitate vertically upward in the same direction as the direction of gravity, and a restoring force acts to return the orientation to a horizontal line during the levitation. These phenomena are very strange and different from those of drones with propellers. When the device levitates, the acceleration does not become constant immediately after the voltage is applied, but after passing through 0, it increases linearly in temporal duration of sub 0.1 s and saturates. The saturation of the acceleration changed with the input voltage. In this study, we used optical flow analysis, which is a well-known and proven imaging analysis, to analyze the trajectory of an object using image analysis. Detailed levitation properties have not been analyzed until now. First, as a result of analyzing the free flight characteristics of a single plate electrode, a single unit that has been very well researched in many papers, it was revealed that the direction of propulsion changes from the lateral direction to the direction of gravity midway through. Analysis on the levitation property of a EHD device, which has a special structure with a large area on the ground at a triangular center, and a propulsion device revealed that the EHD device can only levitate in almost the same direction as gravity. The maximum acceleration of the EHD device in these experiments was estimated to be 7 m/s2 .

Development and flight test of a manned electric propulsion lightweight airplane

Electrically powered airplanes can cope with global warming by reducing the use of fossil fuels and reduce airplane costs in the long run through the efficient use of energy. For this reason, advanced aviation countries such as the United States and several countries in the European Union are leading the development of innovative technologies to realize a fully electric airplane in the future. Currently, research and development efforts are underway domestically to convert existing two-seater airplanes into electric-powered airplanes. In this study, the KLA-100X, which was developed by converting the existing two-seat lightweight sport airplane KLA-100 into an electric propulsion airplane, was introduced. In this text, the main specifications, design characteristics, and performance of KLA-100X are examined. In addition, the performance of the major components of the propulsion system, in this case the propulsion motor, inverter, and battery developed for application to KLA-100X are assessed, and the control system, additionally altered according to electric propulsion modification, is explained. Finally, the applicability of the developed major components to an electric propulsion airplane is confirmed by conducting ground and flight tests on the KLA-100X and presenting the results. In the future, the expansion of research aimed at improving the performance of current electric propulsion airplanes can be reviewed through the development of a dedicated platform for an electric propulsion airplane.

Dynamic braille display based on surface-structured PVC gel

Braille displays are a class of human–computer interaction electromechanical devices that display dynamic braille through an array of actuators. However, existing actuators for braille displays suffer from issues such as bulky size, heavy weight, and small tactile displacement, leading to difficulties in improving their resolution and readability. To address the above issues, we developed a novel electroactive artificial muscle actuator and applied it to braille displays. The novel actuator consists of a surface-structured PVC gel and planar electrodes. To investigate the effect of surface structure on the performance of novel PVC gel actuators, four types of surface-structured PVC gels were fabricated by a casting process, and their actuation performance was tested. The results show that the conical and frustum conical array structures are more favorable for improving the displacement of novel PVC gel actuators, while the cylindrical and quadrangular array structures are more favorable for improving their recovery forces. We observed both surface structure and dynamic electrical actuation, suggesting that the actuation of the novel actuator is mainly caused by the deformation of the surface structure of the array. We also analyzed electrowetting effects in PVC gels using the Lippmann–Young equation, to explain the differences in the performance of surface-structured PVC gels with different contact angles. Moreover, six multilayer actuators composed of PVC gels with a conical surface array structure are applied to the braille display unit to display the braille digits from 0 to 9. It has been shown that the novel PVC gel actuator has excellent mechanical properties, which makes it an ideal solution for braille displays.

Actuators for Improving Robotic Arm Safety While Maintaining Performance: A Comparison Study

Since robotic arms operating close to people are becoming increasingly common, there is a need to better understand how they can be made safe when unintended contact occurs, while still providing the required performance. Several actuators and methods for improving robot safety are studied and compared in this paper. A robotic arm moving its end effector horizontally and colliding with a person’s head is simulated. The use of a conventional electric actuator (CEA), series elastic actuator (SEA), pneumatic actuator (PA) and hybrid pneumatic electric actuator (HPEA) with model-based controllers are studied. The addition of a compliant covering to the arm and the use of collision detection and reaction strategies are also studied. The simulations include sensor noise and modeling error to improve their realism. A systematic method for tuning the controllers fairly is proposed. The motion control performance and safety of the robot are quantified using root mean square error (RMSE) between the desired and actual joint angle trajectories and maximum impact force (MIF), respectively. The results show that the RMSE values are similar when the CEA, SEA, and HPEA drive the robot’s first joint. Regarding safety, using the PA or HPEA with a compliant covering can reduce the MIF below the safety limit established by the International Organization for Standardization (ISO). To satisfy this ISO safety limit with the CEA and SEA, a collision detection and reaction strategy must be used in addition to the compliant covering. The influences of the compliant covering’s stiffness and the detection delay are also studied.

PMBLDC motor (PMBLDCM) with non-linear controller usage in electric propulsion of electric vehicles to control rotor speed (RS) and torque (EMT)

In present days existing vehicles are replaced with electric vehicles (EVs) with usage of PMBLDCM motors because of simplicity in design, rough usage, responding speed, and high efficiency. Due to the usage of dynamic loads in electric vehicles with PMBLDCM motor controlling speed and electromagnetic torque were major problems. These problems along with other problems faced in electric propulsion system (EPS) of electric vehicles (EVs) can be solved with the usage of the proposed non-linear controller (ANF-SMC) along with the usage of PMBLDCM motor for speed regulation and fuzzy parameter tuning based on motor performance under variable speed conditions. The proposed controller is designed by the usage of simulation software along fuzzy logic. To validate the proposed non-linear control system performance results compared with others exhibiting one linear and three non-linear controllers. Simulation results proved that with various loaded conditions proposed system performs well in all aspects when compared to four existing controllers.

A novel method for measuring the width and angle of corrosion in Hall thrusters using three-dimensional point cloud

Hall thrusters are electric propulsion devices that are widely used in modern spaceflight. To obtain the critical corrosion data effectively and accurately during long-life tests of Hall thrusters, this paper proposes an automated corrosion measurement method based on three-dimensional point cloud technology. This method uses binocular structured light scanning method to obtain surface point cloud data. The point cloud topology relationship of these disordered data is also established by KD-tree and radius filtering. The base plane is determined according to the average of the outer circle plane in the discharge chamber, and the original point cloud data is sliced transversely and longitudinally. The point cloud of section data is extracted and the corrosion width data is obtained according to the round hole feature extraction and center of circle calculation. The corrosion angle is calculated according to the angle between the straight line and the normal of the section. The proposed method has been verified and the results show that the overall error accuracy is within 60 μm, which meets the requirements for automatic measurement of Hall thruster corrosion. It is a real and effective method to obtain the critical corrosion data during long-life tests of Hall thrusters.

Rapid Design Method of Heavy-Loaded Propeller for Distributed Electric Propulsion Aircraft

On Distributed Electric Propulsion (DEP) aircraft, the deployment of numerous high-lift propellers with small diameters on the wing’s leading edge significantly enhances lift during low-speed flight. The increase in the number of propellers leads to a decrease in diameter, which increases the disc loading. In this paper, a rapid design method applicable to heavy-loaded propellers is developed and does not require iterative calculations compared to traditional heavy-loaded propeller design methods, enabling rapid completion of the propeller design. The results of CFD computation show that the relative thrust error of the method proposed in this paper is within 5% for disc loading ranging from 600 Pa to 1400 Pa, features a high-accuracy design of propellers with required thrust, and high thrust coefficients are achieved within large advance ratio range.

Optimal Hybrid Pulse Width Modulation for Three-Phase Inverters in Electric Propulsion Ships

Global interest in environmentally friendly ships has surged as a result of greenhouse gas reduction policies and the demand for carbon neutrality. Despite growing demand for electric propulsion systems, there is a lack of research and development on crucial components. Efficiency and stability are primarily influenced by the performance of inverters, which are essential for driving propulsion motors. Existing inverter control techniques can be of two types: continuous-PWM (pulse width modulation) methods for harmonic performance enhancement and discontinuous-PWM methods for efficiency improvement by reducing losses. However, there are limitations in that each PWM method exhibits substantial variations in inverter performance based on its operating conditions. To address these challenges, this study proposes the hybrid pulse-width-modulation (HPWM) method for optimal inverter operation. By analyzing the inverter’s operating conditions, the proposed HPWM method adopts various pulse-width-modulation (PWM) strategies based on a modulation index to achieve harmonic improvement and loss reduction. Our focus is on comparing and analyzing diverse PWM techniques under varying modulation indices and frequency conditions to attain the optimal operating conditions. Experimental validation of the proposed method was conducted using a 2.2 kW dynamometer. In comparison with existing PWM methods, the proposed method demonstrated superior performance.

Highly thermal conductive graphene-based heatsink tailored for electric propulsion SiC-based inverter

This study introduces an innovative multidisciplinary design approach for highly conductive and lightweight pin-fin-based heatsinks leveraging the advantages of graphene technology. The primary objective is to optimize the thermal management of silicon carbide (SiC) based inverters within electric vehicles (EVs). To closely emulate the real SiC power module, comprehensive analyses, including scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), are performed on the module. A detailed fluid dynamics model utilizing a 3D-conjugate heat transfer (CHT) methodology is employed to evaluate the thermal behavior of SiC power switches in contact with the coolant. The multidisciplinary analysis is initially implemented on an aluminum-based heatsink, validated experimentally, and subsequently compared to graphene. The integration of graphene in the heatsink design demonstrates notable improvements, including a 24.4 % increase in the heat transfer coefficient (HTC) and a 19.6 % reduction in thermal resistance (sink to fluid) at a 6 l/min fluid flow rate compared to its aluminum counterpart. Consequently, the SiC chips within the graphene-based heatsink exhibit an 11.5 % lower temperature rise compared to the aluminum version. The improvements in the cooling solution for SiC inverters in EVs, achieved through the adoption of graphene instead of traditional metals, serve as a proof of concept. This signifies a step forward in prioritizing the crucial balance between performance and power density.

Time-resolved ion energy measurements using a retarding potential analyzer for electric propulsion applications.

To completely characterize the evolving state of a plasma, diagnostic tools that enable measurements of the time-resolved behavior are required. In this study, a gridded ion source with superimposed oscillations was utilized to verify the functionality of a high-speed retarding potential analyzer (HSRPA), at frequencies equivalent to the low frequency oscillations occurring in Hall effect thrusters (HETs). The verification of this device provides an effective alternative to existing diagnostics for measuring time-resolved ion energies. Retarding potential analyzers (RPAs) have established themselves as a fundamental diagnostic in the field of electric propulsion (EP), enabling the measurement of ion energy distributions within the plumes of EP thrusters. The work presented here has demonstrated the capability of a standard RPA in conjunction with high-speed circuitry and data fusion techniques to produce time-resolved ion energy distribution functions (IEDFs) at higher frequencies and beam potentials than have previously been investigated. Tested frequencies ranged between 20 and 80kHz with 10V peak-to peak oscillations at a mean beam potential of 570V. In addition, measurements were conducted with several waveforms, functioning as the superimposed oscillation, including a sine wave, triangle wave, and noisy sine wave. Data from the HSRPA were successfully reconstructed into time series utilizing two data fusion techniques: the empirical transfer function method and shadow manifold interpolation. Time-resolved IEDFs were produced at all frequency set points and waveforms. This investigation has demonstrated the HSRPA effectiveness at producing time-resolved measurements under conditions similar to those occurring in HETs.

Design and Analysis of a Novel Electromagnetic-Propulsion Rotary Machine With External Blending-Shaped Tessellation Magnet Pattern

One major challenge for the design of rotary machine of electric propulsion aircraft is how to improve its torque output and power density. The objective of this paper is to propose a novel external blending-shaped tessellation (EBT) magnet pattern for electromagnetic rotary machine. It can offer several advantages. First, it helps to increase the magnetic flux density in the airgap, and thus the torque output of the rotary machine is increased. Second, it enhances the self-shielding effect greatly, and thus the back iron can be removed completely and replaced with low-density materials. As a result, the rotor mass can be reduced and the system dynamics could be improved. Third, the improved torque and the reduced mass may contribute to the high power density as well. The design concept and operating principle of the proposed external blending-shaped tessellation magnet pattern are presented. Following that, the magnetic field distribution is formulated analytically through Laplace's and Poisson's equations. Then the torque generation of the rotary machine is modeled mathematically. Subsequently, the numerical simulation is conducted to validate the analytical models of the magnetic field distribution and torque output. The magnetic flux density and torque output of the proposed magnet pattern are compared with those of conventional magnet arrays. A research prototype of the electric rotary machine with the EBT magnet pattern is developed, and an experimental test platform is constructed. Experiments are conducted on the magnetic flux density and torque output to verify the proposed design and analytical models. The experimental results validate the derived analytical model of magnetic field and the output torque, and the effectiveness of the magnet array in improving the output characteristic. It shows that the output torque generated by the proposed design is larger than that of conventional Halbach array by 27 percent.

Payload Optimization for EnVision Mission Using an Electric Propulsion Module for Interplanetary Transfers

This paper presents a study on the feasibility of using electric propulsion (EP) for interplanetary transfer in the context of an Earth–Venus mission. Extensive research has been conducted on EP modules for Mars missions, demonstrating their potential for faster mission times and greater flexibility compared to all-chemical propulsion (CP) systems. However, there is a notable gap in our understanding regarding EP systems for Venus missions, despite the unique and challenging environment that Venus presents. This study aims to bridge that gap by evaluating the performance of an EP module compared to a conventional all-CP spacecraft, which serves as the backup mission for the EnVision mission by the European Space Agency. The objectives of the study include identifying key drivers for the EP module’s preliminary design, analyzing tradeoffs and challenges associated with EP systems, and evaluating the feasibility of achieving payload mass delivery. The results reveal that the all-EP spacecraft delivers a higher payload mass compared to the all-CP EnVision mission, highlighting the superiority of EP over CP for interplanetary missions. This research provides valuable insights into the potential advantages of EP systems for future interplanetary missions and emphasizes the necessary design considerations when utilizing EP technology.

Slow-speed motor for electric actuators

Slow-speed motor for electric actuators

Evaluating the Reliability and Safety of Lithium-Ion Batteries in Electric Vehicles: Advancements, Challenges, and Environmental Considerations

Background: The global transportation sector is facing increasing challenges related to air pollution, greenhouse gas emissions, and climate change. As a result, there is a growing need to shift towards cleaner and more sustainable modes of transportation. Electric vehicles (EVs) have gained significant attention as a promising solution to reduce emissions and dependence on fossil fuels. Central to the operation of EVs are lithium-ion batteries, which provide the necessary energy storage capacity for electric propulsion. Lithium-ion batteries have emerged as a leading technology in the field of energy storage due to their high energy density, low self-discharge rate, and versatile design options. However, ensuring the reliability and safety of these batteries remains a critical aspect for the widespread adoption of EVs. Figure 1 explain the Electric Vehicle architecture in details.

Monte Carlo Simulation of Inlet Flows in Atmosphere-Breathing Electric Propulsion

A comprehensive numerical study is performed to investigate gas flows inside the inlet of the atmosphere-breathing electric propulsion system using the direct simulation Monte Carlo method. The effects of inlet geometries and gas–surface interaction (GSI) accommodation coefficients on gas pressure and flow rate are analyzed in depth, and a comprehensive assessment of the compression and collection performances of inlets is conducted. Inlet geometries have noticeable effects on gas pressures inside inlets, and the gas pressures of the two concave inlets are the highest. Among the four inlets considered here, the rounded concave inlet performs the best in terms of compression and collection performances. Relative to the simple slope inlet, the rounded concave inlet achieves a rate of increase of over 120% in gas pressure and more than 110% in gas flow rate. GSI accommodation coefficients play a crucial role in both the pressure and mass flux inside the inlet, and the drop of the GSI accommodation coefficient from 1 to 0.2 brings about a considerable increase in the pressure and mass flux, achieving an increase of a factor of 8 and 5, respectively. Therefore, smoothing the inlet surface is an effective means of improving the compression and collection performances of inlets.

Aerodynamics and Flowfield of Distributed Electric Propulsion Tiltwing During Transition With Deflected Trailing-Edge Flap

Abstract The aerodynamics and flowfield of a rectangular semiwing equipped with four four-bladed propellers and a 40%-chord full-span plain trailing-edge flap were investigated by using force balance and particle image velocimetry (PIV). The distributed electric propulsion (DEP) wing was tilted from zero to 90-deg angle of attack. The maximum lift coefficient, lift-curve slope, and stall angle of the DEP wing were found to increase significantly with increasing propeller rotation. The DEP wing also exhibited a gradual stall in contrast to the sudden stall of the baseline wing. The lift coefficient of the DEP wing positioned vertically at 90 deg was also found to be greatly increased with increasing propeller rotation. Regardless of the magnitude of propeller rotation, the general pattern and behavior of the lift curve were consistent. The deployment of the flap led to a further increase in the maximum lift coefficient and lift-curve slope but an earlier stall and an increased drag of the DEP wing as compared to the unflapped wing. The flap deflection also led to a lowered lift coefficient in the poststall angle-of-attack regime as compared to the unflapped DEP wing. Gurney flap was also employed to further increase the lift generation of the DEP wing. The lift augmentation produced by the propeller slipstream was supplemented by the PIV flowfield measurements.

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.