Charge Management System Research Articles

Advanced Charge Control Dynamics Simulation for the LISA Gravitational Reference Sensor

Abstract A gravitational wave detector in space, the Laser Interferometer Space Antenna (LISA) will be able to detect gravitational waves in the frequency range of 0.1 mHz to 1 Hz, adding to humanity’s knowledge of the dark cosmos. The LISA gravitational reference sensor contains a test mass (TM) and is used to determine the local inertial reference frame and as endpoints for the interferometry. The TM is surrounded by an electrode housing to detect changes in TM position and orientation, which is fed back to the spacecraft thrusters for
drag-free control. As seen on LISA Pathfinder, the TM builds up charge over time from the space environment and needs to be discharged in order to keep the resulting force noise as low as possible. The operation of intelligently discharging
the TM is known as charge control, and is one area of improvement to be explored for LISA.

To explore new methods of TM discharge, UV LEDs will be pulsed synchronized with an existing 100 kHz high frequency electric field to facilitate photoelectron current direction and to achieve lower UV light powers by duty cycling. This paper addresses new pulsed methods for the LISA Charge Management System, which require in-depth modeling, analysis, and testing because space environment validation will not be possible prior to LISA launch. Therefore, it is necessary to model the dynamics of charge movement to determine
the force noise contribution of pulsed continuous charge control. The charge dynamics model is described, and simulation results featured for charge control efficacy in a deep space radiation environment. Experimental testing of the simulation results could be done in the University of Florida Torsion Pendulum, a key technology to testing GRS performance in a space-like environment.

Dual-Loop Charge Management for Space-Based Gravitational Wave Detection

In space-based gravitational wave detection missions, inertial sensors act as the inertial reference, requiring the test mass (TM) to maintain exceptionally low residual acceleration noise. High-energy particles, cosmic rays, and ion pumps during ground tests can quickly lead to charge accumulation on the TM surface, necessitating a charge management system to regulate surface charges. To manage the TM surface potential, this paper develops a mathematical model of the charge management system using established ultraviolet (UV) discharge simulation methods. The model describes how photoelectron emission or absorption on the TM surface varies with UV light-emitting diodes (LEDs) power and bias voltage. For the first time, a dual-loop control method is implemented for charge control, highlighting its practical significance. The controller precisely regulates the TM surface potential and residual charges to specified values, achieving a control accuracy of 1.1×106e, meeting the stringent requirements of space-based gravitational wave detection missions. This approach offers a closed-loop charge management solution and provides valuable insights for designing future charge management systems.

Charging and Discharging Modeling of Inertial Sensors Based on Ultraviolet Charge Management

Inertial sensors act as inertial references in space gravitational wave detection missions, necessitating that their internal test mass (TM) maintains minimal residual acceleration noise. High-energy particles and cosmic rays in space, along with ion pumps in ground-based torsion pendulum experiments, can cause charge accumulation on the TM surface, leading to increased residual acceleration noise. Consequently, a charge management system was introduced to control the TM’s charge. The complex light path propagation within the electrode housing (EH) makes the TM’s charging and discharging process difficult to theoretically calculate and fully simulate. To address this issue, we propose a simulation method for charging and discharging inertial sensors within ultraviolet (UV) charge management systems. This method innovatively considers the impact of photoelectron emission angle and the TM’s position offset from symmetry on performance. The method also simulates charging and discharging rates over time under conditions of symmetry and preliminarily examines factors affecting the TM’s equilibrium potential. Simulation results indicate that this method effectively models the charge management system’s operation, providing a valuable reference for system design.

Design of High-Precision Driving Control System for Charge Management

Due to the interaction of accumulated charges on the surface of a test mass with the surrounding electric and magnetic fields, the performance of inertial sensors is affected, necessitating charge management for the test mass. Discharge technology based on Ultraviolet LEDs is internationally recognized as the optimal solution for charge management. Precision driving of Ultraviolet LEDs is considered a key technology in charge management. This paper presents the driving control system used for Ultraviolet LEDs, achieving precision pulse-width-modulation-type current output with controllable pulse width and amplitude. The system generates the pulse-width-controllable pulse voltage signal via analog pulse-width modulation, and subsequently regulates the amplitude of the PWM signal through range switching. To convert the voltage into the pulse-width-modulation-type driving current, the improved Howland current source is employed. The test results demonstrate that the driving control system can output controllable current in the range of 0.01 mA to 10 mA, with a minimum step of 0.01 mA. The accuracy of the current reaches 1%, the stability within 1 h is better than 1%, and the load regulation is better than 2%. The driving control system provides an important reference for the integration of charge management system and the precision drive control method for LEDs.

Intelligent electric vehicle charging optimization and horse herd-inspired power generation for enhanced energy management

This article focuses on optimizing electric vehicle charging in distribution networks, emphasizing technical and economic considerations. Unlike traditional methods, the proposed intelligent approach tailors each EV's charging based on specific daily trip energy requirements. Vehicle owners provide trip data to the charge management system, enabling precise charging calculations considering factors such as energy tariffs, distribution network limits, and charging levels. The paper introduces the horse herd optimization algorithm, inspired by horse herd behavior, offering advantages like reduced computational time and improved convergence in maximizing power generation, especially under shading conditions. The comparative analysis of smart EV charging under normal and fast conditions, considering various constraints and load response programs, demonstrates the proposed method's effectiveness. Numerical results reveal a 46.02 % average load reduction and a 20.53 % peak load decrease with a Load Response Program. Charging costs are optimized, with Case 2 exhibiting a 2.61 % cost reduction compared to Case 3. The study delves into charging frequencies, discharge frequencies, total unsupplied energy, and unloaded energy for each case, providing crucial insights into algorithmic performance. The horse herd optimization algorithm-based approach proves superior, offering a promising solution for efficient and cost-effective electric vehicle charging in distribution networks. Furthermore, graphical representations illustrate the algorithm's impact on charging power, energy allocation, power passing through distribution posts, and megavolt-ampere flow through network lines. These numerical and graphical analyses provide a comprehensive understanding of the horse herd optimization algorithm capabilities, emphasizing its potential to optimize power distribution, reduce costs, and enhance the resilience of residential distribution networks.

Simulation for the test mass charging rate in the Tianqin orbit

For the purpose of detecting gravitational waves from space, high-energy particles will infiltrate the satellite’s structure and accumulate charges on the test mass, consequently diminishing detection performance. Present investigations into the charging rate of the test mass typically rely on the particle distribution of Earth orbit. However, the influence of the Earth’s magnetosphere needs to be considered for the Tianqin detector because of its geocentric orbit. In this paper, artificial neural network is used to fuse satellite data and the galactic cosmic rays model to give the distribution of high-energy particles in the Tianqin orbit. And then, the charging rate is estimated by Monte Carlo simulation. The simulation results show that the flux of hundreds of MeV particles is a little higher than that in Earth orbit, which lead to 3−4 e s−1 higher than LISA, i.e. the charging rate of approximately 43 e s−1 during periods of solar minimum and 19 e s−1 during periods of solar maximum. These findings hold substantial implications for guiding the design of the charge management system.

A Plating-Free Charging Scheme for Battery Module Based on Anode Potential Estimation to Prevent Lithium Plating

Since fast charging schemes for lithium-ion batteries are known to lead to a reduction in battery capacity, there is a need to avoid lithium plating during the charging process. This paper designed an anode potential observer and a plating-free charging scheme for a battery module to avoid the risk of lithium plating for all cells in the module. The observer was designed using an electrochemical cell model and an electrical busbar model to estimate the anode potential of all cells within a parallel connected battery module. Due to its simplicity and low computational loads, the observer was easy to implement in a charge management system. The results demonstrated that the designed observer and charging scheme can accurately estimate the anode potential of all cells in the module. The estimation results of the observer were used in the plating-free charging scheme. Compared to conventional charging methods, the proposed scheme added an additional stage to estimate and control the anode potential, therefore reducing the risk of lithium plating during charging. It also reduced the peak temperature of the battery by approximately 9.8% and reduced the overall charging time by 18%.

Design and performance characterization of a new LISA-like (laser interferometer space antenna-like) gravitational reference sensor and torsion pendulum testbed.

In this paper, we present the design and performance of the upgraded University of Florida torsion pendulum facility for testing inertial sensor technology related to space-based gravitational wave observatories and geodesy missions. In particular, much work has been conducted on inertial sensor technology related to the Laser Interferometer Space Antenna (LISA) space gravitational wave observatory mission. A significant upgrade to the facility was the incorporation of a newly designed and fabricated LISA-like gravitational reference sensor (GRS) based on the LISA Pathfinder GRS. Its LISA-like geometry has allowed us to make noise measurements that are more representative of those in LISA and has allowed for the characterization of the mechanisms of noise induced on a LISA GRS and their underlying physics. Noise performance results and experiments exploring the effect of temperature gradients across the sensor will also be discussed. The LISA-like sensor also includes unique UV light injection geometries for UV LED based charge management. Pulsed and DC charge management experiments have been conducted using the University of Florida charge management group's technology readiness level 4 charge management device. These experiments have allowed for the testing of charge management system hardware and techniques as well as characterizations of the dynamics of GRS test mass charging. The work presented here demonstrates the upgraded torsion pendulum's ability to act as an effective testbed for GRS technology.

Adaptive charge control for the space inertial sensor

Inertial sensors are key components of gravitational wave observations and Earth geodesy missions. An inertial sensor includes an isolated free-floating test mass (TM) surrounded by capacitive electrodes and a housing frame (EH) to perform the relative-position measurement and control the TM in six degrees of freedom. Owing to galactic cosmic rays and solar energetic particles, many additional accelerations are introduced through the Coulomb interaction between charged TMs and their surrounding conducting surfaces. Thus, the TM charge control is critical in space-based missions. A contact-free and ultraviolet light-based charge management system (CMS) was developed to reduce charge-induced noises acting on the TMs and minimize force disturbances that can perturb measurements or interrupt science tasks. However, the operating environment for space charge control is full of uncertainties and disturbances. Physical parameters in the discharging process are rarely measured and will vary owing to changes in solar activity, temperature, and so on. The unpredictability and variability of these parameters affects the CMS performance in long-term space missions and must be evaluated or eliminated. This paper presents a simplified physical model for the discharge process based on electron exchange between the TM and the opposing EH. Subsequently, a model reference adaptive control (MRAC) is proposed for the CMS with parametric uncertainties to maintain the TM charge below a certain level and improve its robustness. The simulation results show that the MRAC can automatically adjust control parameters to eliminate the effect of the variability of the aforementioned physical parameters, and the control precision can reach 0.1 mV under uncertainties, which is superior to that of a classic proportional–integral–derivative controller. This study demonstrated the effects of adaptive charge control and its potential for actual applications.

Electric Vehicle Charging System in the Smart Grid Using Different Machine Learning Methods

Smart cities require the development of information and communication technology to become a reality (ICT). A “smart city” is built on top of a “smart grid”. The implementation of numerous smart systems that are advantageous to the environment and improve the quality of life for the residents is one of the main goals of the new smart cities. In order to improve the reliability and sustainability of the transportation system, changes are being made to the way electric vehicles (EVs) are used. As EV use has increased, several problems have arisen, including the requirement to build a charging infrastructure, and forecast peak loads. Management must consider how challenging the situation is. There have been many original solutions to these problems. These heavily rely on automata models, machine learning, and the Internet of Things. Over time, there have been more EV drivers. Electric vehicle charging at a large scale negatively impacts the power grid. Transformers may face additional voltage fluctuations, power loss, and heat if already operating at full capacity. Without EV management, these challenges cannot be solved. A machine-learning (ML)-based charge management system considers conventional charging, rapid charging, and vehicle-to-grid (V2G) technologies while guiding electric cars (EVs) to charging stations. This operation reduces the expenses associated with charging, high voltages, load fluctuation, and power loss. The effectiveness of various machine learning (ML) approaches is evaluated and compared. These techniques include Deep Neural Networks (DNN), K-Nearest Neighbors (KNN), Long Short-Term Memory (LSTM), Random Forest (RF), Support Vector Machine (SVM), and Decision Tree (DT) (DNN). According to the results, LSTM might be used to give EV control in certain circumstances. The LSTM model’s peak voltage, power losses, and voltage stability may all be improved by compressing the load curve. In addition, we keep our billing costs to a minimum, as well.

A simplified gravitational reference sensor for satellite geodesy

We describe a Simplified Gravitational Reference Sensor (S-GRS), an ultra-precise inertial sensor for future Earth geodesy missions. These sensors are used to measure or compensate for all non-gravitational accelerations of the host spacecraft so that they can be removed in the data analysis to recover spacecraft motion due to Earth's gravity field, which is the main science observable. Low-low satellite-to-satellite tracking missions like GRACE-FO that utilize laser ranging interferometers are technologically limited by the acceleration noise performance of their electrostatic accelerometers, in addition to temporal aliasing associated with Earth's dynamic gravity field. The S-GRS is estimated to be at least 40 times more sensitive than the GRACE accelerometers and more than 500 times more sensitive if operated on a drag-compensated platform. The improved performance is enabled by increasing the mass of the sensor's test mass, increasing the gap between the test mass and its electrode housing, removing the small grounding wire used in the GRACE accelerometers and replacing them with a UV LED-based charge management system. This level of improvement allows future missions to fully take advantage of the sensitivity of the GRACE-FO laser Ranging Interferometer in the gravity recovery analysis. The S-GRS concept is a simplified version of the flight-proven LISA Pathfinder GRS. Our performance estimates are based on models vetted during the LISA Pathfinder flight and the expected Earth orbiting spacecraft environment based on flight data from GRACE-FO. The relatively low volume, mass, and a power consumption enables use of the S-GRS on ESPA-class microsatellites, reducing launch costs or enabling larger numbers of satellite pairs to be utilized to improve the temporal resolution of Earth gravity field maps.

Coupling efficiency improvement of light source with a convex lens for space charge managements

Since Charge Management in space is mainly based on ultraviolet discharge technology, the ultraviolet light source system is one of the key devices of the charge management system, which significantly affects the performance of Charge Management. As reported recently, the coupling efficiency of the UV LED light source system is only about 13%. This paper analyzes the coupling types of UV LED light source system and establishes the LED-lens–fiber coupling model, next numerical simulations and experiments are carried out, finally the coupling efficiency of the UV light system is improved to 30%. Since improving the coupling efficiency can effectively reduce the power consumption and increase the useful life, the LED-lens–fiber coupling method has a strong prospect in space missions.

A charge control method for space-mission inertial sensor using differential UV LED emission.

Various space missions and applications require the charge on isolated test masses to be strictly controlled because any unwanted disturbances will introduce acceleration through the Coulomb interaction between the test masses and their surrounding conducting surfaces. In many space missions, charge control has been realized using ultraviolet (UV) photoemission to generate photoelectrons from metal surfaces. The efficiency of photoelectron emission strongly depends on multiple physical parameters of gold-coated surfaces, such as the work function, reflectivity, and quantum yield. Therefore, to achieve satisfactory charge control performance, these parameters need to be measured accurately. This paper describes a charge control method that achieves self-adaptive charge neutralization while removing the need to measure the above-mentioned physical parameters. First, to explain the principle, a differential illumination model is constructed based on the typical structure of an inertial sensor. A charge management system based on a torsion pendulum system is then introduced along with an UV light emitting diode coupling system. Finally, experimental results are obtained in a vacuum chamber system with a pressure of 10-7 mbar, showing that precise calibration allows the test mass potential to be automatically controlled below 10 mV without considering the physical parameters or measuring the potential of the test mass before or after the control process.

Investigation of charge management using UV LED device with a torsion pendulum for TianQin

TianQin is a Chinese space-based observatory concept with three drag-free spacecraft orbiting the earth to observe gravitational-waves in the millihertz range. Electrical charge is inevitably accumulating on its isolated test masses which are used as the mirrors for interferometers to measure gravity variation. Charge management system based on ultraviolet (UV) light is developed to reduce the charge-induced noises acting on the test mass in space gravitational experiments such as GP-B, LISA, LISA Pathfinder and TianQin mission. The UV LED is a new UV light source with some advantages relative to mercury lamps, such as smaller size, lighter weight, lower power consumption and higher efficiency. For these reasons, ground-based tests for the combination of UV LED and inertial sensor are essential. This paper presents the development of a charge management system based on a UV LED, its application to a torsion pendulum system with a TianQin-like test mass, and assesses the charge-management performance of the system. The experimental results indicate that the isolated test mass can be charged positively or negatively through UV illumination. It demonstrates that the charging and discharging rates can both reach higher than 105 e s−1, as well as spectral measurement of the pendulum charge resulting in a white noise level equivalent to ∼5 × 105 e Hz−1/2, satisfying the TianQin requirement.

Architecture of pile charge management system for electric vehicle

To improve the pile charge efficiency of EVs, this paper develops and primarily designs a pile charge management system architecture for Electric Vehicles (EVs) based on the Internet of Things (IoT), data information storage, and the like. After the test, the system proposed in this paper beats the target as preset thanks to its high availability. This technology can facilitate the management process for the operators and improve the human-computer interaction experience for the consumers, hence to benefit the advancement and development of the EV industry.

Multi Objective Optimization in Charge Management of Micro Grid Based Multistory Carpark

Distributed power supply with the use of renewable energy sources and intelligent energy flow management has undoubtedly become one of the pressing trends in modern power engineering, which also inspired researchers from other fields to contribute to the topic. There are several kinds of micro grid platforms, each facing its own challenges and thus making the problem purely multi objective. In this paper, an evolutionary driven algorithm is applied and evaluated on a real platform represented by a private multistory carpark equipped with photovoltaic solar panels and several battery packs. The algorithm works as a core of an adaptive charge management system based on predicted conditions represented by estimated electric load and production in the future hours. The outcome of the paper is a comparison of the optimized and unoptimized charge management on three different battery setups proving that optimization may often outperform a battery setup with larger capacity in several criteria.

Lifetime testing UV LEDs for use in the LISA charge management system

As a future charge management light source, UV light-emitting diodes (UV LEDs) offer far superior performance in a range of metrics compared to the mercury lamps used in the past. As part of a qualification program a number of short wavelength UV LEDs have been subjected to a series of lifetime tests for potential use on the laser interferometer space antenna (LISA) mission. These tests were performed at realistic output levels for both fast and continuous discharging in either a DC or pulsed mode of operation and included a DC fast discharge test spanning 50 days, a temperature dependent pulsed fast discharge test spanning 21 days and a pulsed continuous discharge test spanning 507 days. Two types of UV LED have demonstrated lifetimes equivalent to over 25 years of realistic mission usage with one type providing a baseline for LISA and the other offering a backup solution.

Ground testing and flight demonstration of charge management of insulated test masses using UV-LED electron photoemission

The UV-LED mission demonstrates the precise control of the potential of electrically isolated test masses. Test mass charge control is essential for the operation of space accelerometers and drag-free sensors which are at the core of geodesy, aeronomy and precision navigation missions as well as gravitational wave experiments and observatories. Charge management using photoelectrons generated by the 254 nm UV line of Hg was first demonstrated on Gravity Probe B and is presently part of the LISA Pathfinder technology demonstration. The UV-LED mission and prior ground testing demonstrates that AlGaN UVLEDs operating at 255 nm are superior to Hg lamps because of their smaller size, lower power draw, higher dynamic range, and higher control authority. We show laboratory data demonstrating the effectiveness and survivability of the UV-LED devices and performance of the charge management system. We also show flight data from a small satellite experiment that was one of the payloads on KACST’s SaudiSat-4 mission that demonstrates ‘AC charge control’ (UV-LEDs and bias are AC modulated with adjustable relative phase) between a spherical test mass and its housing. The result of the mission brings the UV-LED device Technology Readiness Level (TRL) to TRL-9 and the charge management system to TRL-7. We demonstrate the ability to control the test mass potential on an 89 mm diameter spherical test mass over a 20 mm gap in a drag-free system configuration, with potential measured using an ultra-high impedance contact probe. Finally, the key electrical and optical characteristics of the UV-LEDs showed less than 7.5% change in performance after 12 months in orbit.

Characterising and testing deep UV LEDs for use in space applications

Deep ultraviolet (DUV) light sources are used to neutralise isolated test masses in highly sensitive space-based gravitational experiments. An example is the LISA Pathfinder charge management system, which uses low-pressure mercury lamps. A future gravitational-wave observatory such as eLISA will use UV light-emitting diodes (UV LEDs), which offer numerous advantages over traditional discharge lamps. Such devices have limited space heritage but are now available from a number of commercial suppliers. Here we report on a test campaign that was carried out to quantify the general properties of three types of commercially available UV LEDs and demonstrate their suitability for use in space. Testing included general electrical and UV output power measurements, spectral stability, pulsed performance and temperature dependence, as well as thermal vacuum, radiation and vibration survivability.

The Stereoscopic Parking System Equipment of Electric Vehicles and its Application Mode Research

In view of the current situation of the stereoscopic parking system for the electric vehicles and its overall development trend, we first research on its key module technology. Then, we research on its internal dynamic management pattern, the application mode of radio frequency identification (RFID), the application mode of charge management system and the application mode of control system. Thus, the popularity of electric vehicles is promoted by the stereoscopic parking system with intelligence, efficiency and saving of storage space.