Real-time Simulation Method Research Articles

A Discrete Small-Step Synthesis Real-Time Simulation Method for Power Converters

The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> -based fixed-admittance model ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> model) is usually used in the real-time simulation for power electronic converters. However, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> switch model suffers from the problems of virtual power loss and complicated optimal parameter settings. This article proposes a small-step synthesis real-time simulation method suitable for power electronic converters. By modeling the power electronic converter with a small (nanosecond) time-step and simulating with a normal (microsecond) time-step, the issue of virtual power loss of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> model caused by the transient process after the switching action is solved. The real-time simulation experiments with different type converters based on one set of simulation parameters are carried out on field-programmable gate array separately to verify the insensitivity to converter topologies. Furthermore, the real-time simulation results of the small-step synthesis method using the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> model are compared with those of the traditional electromagnetic transient program (EMTP) method using the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> model and the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</sub> model. The simulation results provide verification of the effectiveness of the small-step synthesis method as well as the insensitivity to carrier frequencies, and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> model parameters.

Suppression of Chattering in the Real-Time Simulation of the Power Converter

The achievement of the time-step below 500-ns in the field-programmable-gate-arrays (FPGAs)-based real-time simulation is of importance for the power converters having high switching frequencies. However, most of the existing focus on addressing the power converter modeling under the continuous conduction mode (CCM). Nevertheless, toward practical applications, the modeling of discontinuous conduction mode (DCM) with a light-load is of a greater challenge due to the “chattering” around zero point. In order to solve the chattering problem under the light-load, this article proposes a zero-regulation (ZR) method for FPGA-based real-time simulation. The proposed ZR method can not only represent CCM and DCM with a unified formula but also solve the chattering problem and improve accuracy and stability. In addition, results using different switch models are also given to demonstrate the feasibility and the generality of the proposed method. Finally, a case study of the series load resonant converter is presented. Simulation results are validated against a reference model at a 100-ns time step and a 10-kHz switching frequency.

To Improve the Real-Time Performance of Airborne Data Link Communication System

Ground-to-air data link communication has the advantages of fast transmission rate, strong anti-interference ability, and large data communication volume and has been widely used in the field of civil aviation. This article mainly studies the measures to improve the real-time performance of the airborne data link communication system. The design of the hardware platform of the jamming environment simulator needs to comprehensively consider the implementation complexity of the jamming environment model and the real-time simulation method adopted by the UAV data link system. This paper uses the multicore and multithread in the Linux operating system to simulate the functions of the original data link communication system and uses the TFT screen to display the data communication process in the multicore and multithread design scheme. When evaluating and scoring the evaluation indicators, it must be carried out in accordance with certain standards. However, most of the indicators cannot be directly assessed quantitatively only through certain specific values. This article mainly uses the AHP method to analyze the weight of indicators. In the simulation, user information is generated by a random code generator and then distributed to each branch through serial-to-parallel conversion (S/P), and the spreading process is completed by long-code spreading on each branch, respectively, by BPSK. It is modulated on different carriers to form a transmission signal; the signal passes through a Gaussian white noise channel, and a certain frequency offset noise is added at the same time to reach the receiving end; the receiving end uses correlated demodulation, and after despreading, the error rate is counted. The data shows that under different distances, the frame loss rate of the data link is different. The frame loss rate in the 500 m range is about 1%, and the frame loss rate in the 2 km range is about 2.3%. The results show that the real-time performance of the data link communication system in this paper has been greatly improved.

Real-time simulation method of MVDC integrated power system based on heuristic partitioning method and terminal resistance decoupling interface

In the process of real-time simulation of MVDC integrated power system, the traditional system partitioning method is low in efficiency, poor in the stability of decoupling interface, and unsatisfactory in use. In order to solve these problems, a complete set of real-time simulation method is proposed in this paper. The method involves a heuristic system partitioning scheme for the average distribution of switches and the smallest number of subsystems which is obtained by balancing the computational amount and combining the adjacent subsystems, a real-time simulation decoupling interface design method based on the terminal resistance for the purpose of dealing with the poor stability of the traditional ideal transformer interface, and a way to get values of the terminal resistance under the constraints of decoupling stability and accurate calculation. Then, a real-time model of MVDC integrated power system is established. And the proposed real-time simulation method is shown to be of high efficiency and stability on the Rt-lab real-time simulation platform. Compared with the traditional methods, it can greatly improve the accuracy of simulation.

Cost-Effective Design of Port Approaches Using Simulation Methods Based on the Example of a Modernized Port in the Ustka

Port design and approaches are usually carried out using real-time computer simulation methods for ship manoeuvring. So-called ship real-time simulation methods are relatively expensive, especially in terms of survey time. Several real-time simulation scenarios carried out by masters and pilots are usually performed, with several simulation attempts in each scenario. Each such attempt can last up to one hour, which, with a large number of scenarios, prolongs the research and increases its cost. Particularly time-consuming is the repetition of many scenarios with alternative solutions for infrastructure development and in various hydrometeorological conditions. To reduce the time-consuming of the tests, a new two-stage method was used to design the target approach on the modernized Port of Ustka. In the first stage, the simulations were carried out with significantly reduced floating navigation marking, and in the second stage with the target marking. Moreover, the so-called “Soft-Bank” method was introduced, i.e., the effects of a collision with the seabed and infrastructure were excluded. Such a solution leads to significant time benefits in conducting research and at the same time does not reduce confidence in the results obtained.

Real-time Simulation Methods for Robots with a Flexible Arm Based on Computer Graphics Technology

A robot with a flexible arm that is controlled with a remotely operated water-pressure mechanism has been developed for dismantling objects that are heavily contaminated by radioactive materials during decommissioning of nuclear power plants. The objective of this research is to develop a process planning support system and method that can improve the accuracy of estimating the time required by the robot to complete its dismantling activity, support recovery from delays, and determine the feasibility of conducting a dismantling process in the reactor building. Since the flexible arm has a more complex mechanism and shapes those that of multi-axis robots, unique movable arm structures were modeled with a tool for three-dimensional (3D) computer graphics (CG) technology. The 3D CG model was used to make valid operation sequences for planning the motion of the robot. With the help of a prototype system, motion planning can perform to calculate the duration needed for the robot to complete its operation. The calculated duration is then used for updating the planned duration of a specific activity in a dismantling schedule. To plan the robot behaviors for complex dismantling processes, a simplified planning method with few virtual controllers based on a spline inverse kinematics (IK) with a non-uniform rational B-spline (NURBS) curve for an arm comprised of pistons and cylinders pressurized by water was studied. A prototype system for planning the behaviors of the robot was evaluated, and it was confirmed that the movement trajectory of the robot and the three-dimensional isometric display could be visualized using the mesh model generated from point-cloud data used to make the environment model of the robot. It was also confirmed that the operations involved in a specific activity of the robot could be completed within the duration determined in the simulation.

Application of Gauss principle of least constraint in multibody systems with redundant constraints

Redundancy in the constrained mechanical systems often occurs in complex multibody mechanic systems in the existence of excessive constraints and singular positions due to system motion. In this work, Gauss principle of least constraint (GPLC) is applied to solve the dynamic motion of system with redundant constraints without changing the physics of system. Furthermore, the particle swarm optimization method is used to handle the minimization optimization problem. Eventually, the effectiveness of GPLC is validated through the dynamic modelling and simulation of two numerical examples (a planar four-bar mechanism and a spatial parallelogram mechanism). The simulation results are analyzed and compared with those obtained from Udwaia-Phohomsiri formulation and augmented Lagrangian formulation, in terms of constraint violation, computational efficiency and variation of the mechanical energy. From the viewpoint of computational efficiency and accuracy, GPLC can be regarded as a practical real-time simulation method for multibody systems with redundant constraints.

Real-time hybrid simulation of high-speed train-track-bridge interactions using the moving load convolution integral method

Train-track-bridge interactions (TTBIs) in high-speed railways affect the response of the train on the bridge and involve complicated dynamics. This study introduced an improved real-time hybrid simulation (RTHS) method, wherein a physical train model was tested on a shake table, while the dynamics of the track-bridge structure were determined numerically. The moving load convolution integral method (MLCIM) was proposed for the real-time calculation of the track-bridge structure dynamics independent of the complexity of the numerical model. The results obtained using the MLCIM were compared to those obtained using the traditional finite element method to verify its accuracy and efficiency. Next, the TTBI characteristics of a train moving across a seven-span simply supported bridge with the track structure were analyzed for cases of different girder stiffnesses and train speeds. The results demonstrated that the improved RTHS method using the MLCIM effectively represented the TTBI dynamics. The girder stiffness and train speed were shown to substantially influence the responses of the moving train. Further, a ride comfort evaluation confirmed the operational performance of a train on the studied track-bridge structure.

The Necessity of Resetting Memory in Adams–Bashforth Method for Real-Time Simulation of Switching Converters

The field-programmable gate array implementation of real-time hardware-in-the-loop techniques is constantly growing due to its high speed. However, hardware implementation of switched-mode power supplies introduces some challenges because their equations are changed depending on the state of the switches. This becomes more important in multistep numerical methods, which use several previous values. This letter presents the implementation scheme of the Adams-Bashforth method, which allows the designer to correctly apply it to switching power converters. The global accuracy and utilization results of the approach are analyzed in this letter. The results show that the proposed modification makes sense due to the high-accuracy improvement at the expense of a reasonable increase in resources.

Real-Time Hybrid Test Using Two-Individual Actuators to Evaluate Seismic Performance of RC Frame Model Controlled by AMD

Seismic responses of a single-story RC frame building model under control using an active mass damper (AMD) are demonstrated through a real-time hybrid simulation (RTHS) method. In this study, the RTHS test is carried out by using a hydraulic actuator and a shaking table under a synchronization. Most parts of the target RC frame model are provided as an analytical model for an online computer simulation, and the only single column of the first story is prepared as an experimental substructure. A hydraulic actuator deforms the actual RC column, and uncertainty or nonlinearity of the RC column’s behavior is focused on this RTHS test. At the same time, a control device of AMD is actually tested under a situation of installing it on the target building's floor. The floor response of the target building model is generated using a shaking table. A control motion of the AMD is manipulated based on an online simulation of the entire RC building model. Firstly, a time delay compensation of the hydraulic actuator is considered. Time delay parameters are identified using a combination model of a time lag and a first-order delay. A PID controller and a time series compensator (TSC) are applied to improve actuator performances. Next, the reproducibility of the RTHS test using two-individual actuators is evaluated. The tracking of a restoring force and deformation of the actual RC column specimen generated by the hydraulic actuator and floor motion responses reproduced on the shaking table are investigated. To improve the online numerical simulation based on the measured force responses of the RC column specimen, a high-pass filter (HPF) is applied for a force correction to utilize its phase-lead property. The effect of this HPF force correction is evaluated in both a linear region and a strong nonlinear region of the actual RC column specimen. Finally, the RTHS test results are compared to fully-numerical simulations, and the control effect of the AMD to increase the damping effect for the target RC building model is also investigated.

A framework for hybrid simulation with online model updating suitable for hard real‐time computing

The hybrid simulation method is used to test one or some components of a prototype structure subjected to a plausible loading history, accounting for their interaction with the untested ones, which are simulated numerically. If tested components have similar numerical counterparts, a possible approach to reduce simulation errors is to update the parameters of numerical substructures based on tested physical substructures. For this reason, online parameter estimation has gained the attention of the hybrid simulation community in the last decade. The term online indicates that the parameters of the identification model of the physical substructure are updated during the experiment. Main state-of-the-art middleware tools (e.g., OpenFresco and UI-SIMCOR) have been extended to support online model updating for the pseudodynamic hybrid simulation method. In this case, both numerical substructures and dynamic identification models are implemented on existing finite-element analysis software, which communicates with the middleware using a data exchange protocol with non-deterministic time schedule (e.g., TCP/IP). On the other hand, fast- and real-time hybrid simulation methods require a deterministic data exchange schedule between substructures, which imposes the adoption of hard real-time implementations. In this context, partitioned time integration is proposed to coordinate the parallel execution of simulation and model updating processes with heterogeneous sampling rates. As a result, the allocation of computational resources can leverage parallelization capabilities of multi-core CPUs.

Adaptive Feedforward and Feedback Compensation Method for Real-time Hybrid Simulation Based on a Discrete Physical Testing System Model

ABSTRACT This study proposed a general framework for adaptive delay compensation in real-time hybrid simulation(RTHS). This framework is composed of two main parts: an adaptive feedforward controller to handle variable time delay and amplitude discrepancies, and a feedback controller to enhance the robustness of compensation. In particular, the adaptive feedforward controller is determined using a discrete physical testing system (PTS) model, whose parameters are estimated using the least-squares method. Moreover, the feedback controller is introduced to reduce dependency on the PTS model of the feedforward controller. Results of virtual and actual RTHS alongside five other compensation strategies revealed the superiority of the proposed compensation method.

Improving model-based compensation method for real-time hybrid simulation considering error of identified model

Time delay is a critical and unavoidable problem in real-time hybrid simulation. An accurate and effective compensation method for time delay is necessary for the safety of real-time hybrid simulation and the reliability of test results. Generally, a model-based compensation method can be adopted, which is derived from the identified transfer function by assuming the latter can accurately represent the real plant. However, there must be some differences between the transfer function and the real plant. To facilitate the development of real-time hybrid simulation, we proposed a two-stage feedforward compensation method considering the error between the transfer function identified and the real plant. The compensation strategy proposed in this study was not only based on the transfer function but also introduced an error model as a second-stage compensation into a compensator to realize the synchronization of command and measurement. To verify the efficiency of the proposed method, comparisons in time domain and frequency domain with the feedforward compensator in a model-based feedforward–feedback control method were carried out. Compared with the feedforward compensator, the two-stage method achieved better tracking performance, especially in the high-frequency bandwidth. The test results verified that for a band-limited white noise of 0–30 Hz, the phase lag of the actuation system can be limited to ±5°. Finally, the two-stage method was applied to a real-time hybrid simulation of a two-story frame to illustrate its compensation effect on time delay.

Real-Time Aeroelastic Hybrid Simulation of a Base-Pivoting Building Model in a Wind Tunnel

The wind tunnel test is one of the most reliable methods for evaluating the dynamic response of high-rise buildings in regards to wind-structure interaction. In conventional aeroelastic wind tunnel tests the calibration of stiffnesses, masses and the damping properties of a scaled specimen is required. This takes extensive time and effort, especially when the tests need to be repeated with various geometric designs during design iterations. This study introduces a new testing method that combines a numerical simulation and the conventional aeroelastic wind tunnel test through the real-time hybrid simulation method. The stiffness, damping and partial mass of a scaled building model are represented numerically, while the rest of the mass, the wind-induced pressure around the model and the wind-structure interaction are represented physically in a wind tunnel. The building model in the wind tunnel rests on a base-pivoting system, which is controlled with a linear motor. The base moment induced by wind pressure and the inertial force from the mass of the physical specimen are measured; those measurements are then fed back into a numerical integration scheme. A delay-compensation scheme is implemented to minimize the effects of actuator delay on the dynamic response of the system. Several tests are carried out to validate and calibrate the developed test apparatus and control scheme including 1) tests for the identification of actuator delay, 2) free vibration tests for characterization of the dynamic properties of the hardware and the control system and 3) wind tunnel tests for system validation through aeroelastic real-time hybrid simulation. This paper presents the overall design of the experimental apparatus, the adopted delay compensation and numerical integration schemes, and a summary of the test results. Test results confirmed that the developed experimental technique can replace the conventional aeroelastic wind tunnel tests of a building model, thus improving the efficiency of the aeroelastic wind tunnel testing.

Test Verification of Two-Stage Adaptive Delay Compensation Method for Real-Time Hybrid Simulation

Real-time hybrid simulation (RTHS) is a versatile testing technique for performance evaluation of structures subjected to dynamic excitations. Research revealed that compensation for the delay induced by the dynamics of the loading system and other factors is a critical issue for obtaining reliable test results. Lately, a two-stage adaptive delay compensation (TADC) method was conceived and performed on the benchmark problem of RTHS. For this method, the main part of the system delay is coarsely compensated by the classic polynomial extrapolation (PE) method; the second stage represents a fine remedy for the remaining delay with adaptive compensation based on a discrete model of the loading system. As an extension of this study, this paper aims to further verify and reveal the performance of this method through real tests on a viscous damper specimen. In particular, loading tests with a swept signal and RTHS with sinusoidal and seismic excitations were carried out. Investigations show that the TADC method is endowed with smaller parameter variation ranges, simple yet effective initialization or a soft-start process, less dependence on initial parameter estimation accuracy, and best compensation performance.

Multi-Rate Real-Time Simulation Method Based on the Norton Equivalent

For the problem of poor accuracy of the existing multi-rate simulation methods, this paper proposes a multi-rate real-time simulation method based on the Norton equivalent, compared with multi-rate simulation method based on the ideal source equivalent. After the Norton equivalence of the fast subsystem and the slow subsystem are established, they are solved simultaneously at the junction nodes. In order to reduce the amount of the simulation calculation, the Norton equivalent circuit is obtained by incremental calculation. The data interaction between the fast subsystem and the slow subsystem is realized by extrapolation method. For ensuring the real-time performance of the simulation, the method of the slow subsystem calculates ahead of the fast subsystem is given for the slow subsystem with a large amount of calculation. Finally, the AC/DC hybrid power system was simulated on the real-time simulation platform (FPGA-based Real-Time Digital Solver, FRTDS), and the simulation results were compared with the single-rate simulation, which verified the correctness and accuracy of the proposed method.

Real-Time Construction Simulation Coupling a Concrete Temperature Field Interval Prediction Model with Optimized Hybrid-Kernel RVM for Arch Dams

Joint grouting simulation is an important aspect of arch dam construction simulation. However, the current construction simulation model simplifies the temperature factors in joint grouting simulation, which leads to the difference between the simulation results and the actual construction schedule. Furthermore, the majority of existing temperature prediction research is based on deterministic point predictions, which cannot quantify the uncertainties of the prediction values. Thus, this study presents a real-time construction simulation method coupling a concrete temperature field interval prediction model to address these problems. First, a real-time construction simulation model is established. Secondly, this paper proposes a concrete temperature interval prediction method based on the hybrid-kernel relevance vector machine (HK-RVM) with the improved grasshopper optimization algorithm (IGOA). The hybrid-kernel method is adopted to ensure the prediction accuracy and generalization ability of the model. Additionally, the improved grasshopper optimization algorithm (IGOA), which utilizes the tent chaotic map and cosine adaptive method to improve the algorithm performance, is developed for the parameter optimization of HK-RVM. Thirdly, concept drift detection based on variable window technology is proposed to update the prediction model. Finally, an arch dam project in China is used as a case study, by which the superiority and applicability of the proposed method are proven.

Applications of the RST Algorithm to Nonlinear Systems in Real-Time Hybrid Simulation

Real-time substructure testing (RST) algorithm is a newly developed integration method for real-time hybrid simulation (RTHS) which has structure-dependent and explicit formulations for both displacement and velocity. The most favourable characteristics of the RST algorithm is unconditionally stable for linear and no iterations are needed. In order to fully evaluate the performance of the RST method in solving dynamic problems for nonlinear systems, stability, numerical dispersion, energy dissipation, and overshooting properties are discussed. Stability analysis shows that the RST method is only conditionally stable when applied to nonlinear systems. The upper stability limit increases for stiffness-softening systems with an increasing value of the instantaneous degree of nonlinearity while decreases for stiffness-hardening systems when the instantaneous degree of nonlinearity becomes larger. Meanwhile, the initial damping ratio of the system has a negative impact on the upper stability limit especially for instantaneous stiffness softening systems, and a larger value of the damping ratio will significantly decrease the upper stability limit of the RST method. It is shown in the accuracy analysis that the RST method has relatively smaller period errors and numerical damping ratios for nonlinear systems when compared with other two well-developed algorithms. Three simplified engineering cases are presented to investigate the dynamic performance of the RST method, and the numerical results indicate that this method has a more desirable accuracy than other methods in solving dynamic problems for both linear and nonliner systems.

The enhancement of the prescribed track for unmanned air vehicles

Purpose Unmanned aerial vehicles (UAVs) are more affected by adverse wind conditions in especially landing. Therefore, they need to change the runway in use. In case of this change, to eliminate the uncertain maneuvers, there is a need for a special prescribed track. The purpose of this study is the construction of a prescribed track at a single runway to provide a facility to change the runway in use. Design/methodology/approach Two forms of prescribed tracks, as standard and alternate, were constructed for UAVs by taking into consideration the key parameters to design flight procedures. Both tracks were assessed in a real-time simulation method. Moreover, unmanned vehicle simulation was used for a validation process. Findings According to the real-time simulation results, 8.14 NM and 6.64 NM of flight distance and 5.43 min and 4.43 min of flight time for the standard and alternate prescribed tracks were found, respectively. The obtained results were in favor of the alternate prescribed track. Furthermore, the prescribed track was assessed and validated in both air traffic control and UAV simulations. The feedback of pilots and controllers was very positive for a prescribed track, as it provided them with foresight and time to take care in any situations. Practical implications The prescribed track in this paper may be applied by airspace designers and UAV users to perform safe and efficient landing in adverse wind conditions. Originality/value In this study, a prescribed track was constructed for UAVs. Quantitative results were achieved using a real-time simulation method in terms of flight distance and flight time. Additionally, validation of the prescribed track was achieved by unmanned air vehicle simulation.

A Real-Time Hybrid Fire Simulation Method Based on Dynamic Relaxation and Partitioned Time Integration

AbstractThe use of simplified numerical substructures in hybrid fire simulation is clearly advantageous as long as the resulting simulation accuracy is sufficient. However, excluding geometrical an...