Dynamic Performance Requirements Research Articles

A framework for dynamic modelling of railway track switches considering the switch blades, actuators and control systems

The main contribution of this paper is the development and demonstration of a novel methodology that can be followed to develop a simulation twin of a railway track switch system to test the functionality in a digital environment. This is important because, globally, railway track switches are used to allow trains to change routes; they are a key part of all railway networks. However, because track switches are single points of failure and safety-critical, their inability to operate correctly can cause significant delays and concomitant costs. In order to better understand the dynamic behaviour of switches during operation, this paper has developed a full simulation twin of a complete track switch system. The approach fuses finite element for the rail bending and motion, with physics-based models of the electromechanical actuator system and the control system. Hence, it provides researchers and engineers the opportunity to explore and understand the design space around the dynamic operation of new switches and switch machines before they are built. This is useful for looking at the modification or monitoring of existing switches, and it becomes even more important when new switch concepts are being considered and evaluated. The simulation is capable of running in real time or faster meaning designs can be iterated and checked interactively. The paper describes the modelling approach, demonstrates the methodology by developing the system model for a novel “REPOINT” switch system, and evaluates the system level performance against the dynamic performance requirements for the switch. In the context of that case study, it is found that the proposed new actuation system as designed can meet (and exceed) the system performance requirements, and that the fault tolerance built into the actuation ensures continued operation after a single actuator failure.

Response Analysis and Stator Optimization of Ultrahigh-Speed PMSM for Fuel Cell Electric Air Compressor

For the requirement of the complex dynamic performance for the fuel cell vehicle (FCV), the wide operation range and rapid dynamic response ability are essential to the fuel cell electric air compressor, which are limited by the output torque of the permanent magnet synchronous motor (PMSM) commonly used in FCV. The purpose of this study is to improve the output torque of the stators and its rapid dynamic response capacity of PMSM using the mathematical model, multi-objective optimization and experimental validation. Firstly, a mathematical model of speed regulation response of ultra-high speed PMSM is established, which provides a basis for taguchi legal sub-optimization in this study. Secondly, stator parameters were selected as optimization variables based on Taguchi method, and the optimal combination of optimization variables was selected with the maximum electromagnetic torque, minimum cogging torque, minimum stator copper loss and minimum stator iron loss as optimization objectives. Finally, the effectiveness of the optimization method is verified by simulation analysis and bench test. At the target speed of 110652rpm, 124364rpm and 146876rpm, the overall response times before optimization are 1.9386s, 2.3902s, and 2.7844s. Respectively, the overall response times after optimization are 1.8604s, 2.2856s, and 2.6132s. The speed response time after optimization is 0.0782s, 0.1046s and 0.1712s less than before optimization, respectively.

Co-design of a multirotor UAV with robust control considering handling qualities and motor failure

Over the last few decades, multirotor UAVs have become significantly popular because of their various applications. However, multirotors suffer from poor endurance performance as compared to other aircraft configurations with lifting surfaces. This limitation can be addressed by improving the technology of components or by developing design optimization approaches at the vehicle level. This paper presents a co-design approach for the multirotor structure and propulsive system to improve the vehicle's energetic efficiency while respecting dynamic performance requirements. For this purpose, the approach uses a bi-level formulation to optimize the design and control concurrently. The methodology offers the possibility to activate or not a passive fault tolerant strategy in the controller synthesis to be tolerant to single rotor failure. In contrast to conventional design approaches that sequentially design each part, the co-design approach leads to a better optimal solution by considering the interactions and couplings between design and control. With the proposed co-design approach, the results show the soundness of the proposed design methodology and a significant reduction in the consumed energy compared to a reference non-optimal design while maintaining the same requirements in terms of dynamic performance.

Kinematics and Dynamics Simulation of Lower Limb Exoskeleton Walking Assist Mechanism

To solve the problem of rehabilitation training for patients with limited mobility of lower limbs, a scheme of lower limb exoskeleton walking assistance mechanism was proposed. The D-H model of the walking assist mechanism is established, and the forward kinematics is solved. The exoskeleton workspace is analyzed by the Monte Carlo method. The kinematics and dynamics simulation analysis of the walking assist mechanism is completed by using ADAMS software, and the rationality of the kinematics and dynamics performance is verified. The results show that the lower limb exoskeleton walking assist mechanism can meet the requirements of movement space, movement performance, and dynamic performance of patients with lower limb movement limitation and meet the basic needs of normal human wearing. The research results lay a foundation for the structural optimization of the following lower limb exoskeleton walking assist mechanism.

Small-amplitude bogie hunting identification method for high-speed trains based on machine learning

Hunting stability is a critical aspect of the dynamic performance of high-speed trains. However, the current evaluation criteria only address heavy hunting motion, and they require supplementation and improvement to meet the increasing requirements of dynamic performance. Therefore, a study was conducted to develop an identification method for small-amplitude bogie hunting (SABH) motion. A total of 39,816 samples were obtained from field-measured bogie lateral acceleration and manually labelled as normal and SABH. The distribution comparison, Pierce coefficient, and importance ranking showed that harmonic character-related features (the autocorrelation coefficient, approximate entropy and etc.) should be considered more for SABH identification than amplitude-related features (maximum and RMS). The most critical features for SABH identification were the autocorrelation coefficient and spectral frequency spread. The classifier performance comparison showed that the decision tree was the best-performing classifier, followed by the support vector machine, while the linear discriminant, K-nearest neighbour, and naive Bayes classifiers were less effective. Sensitivity analysis indicated that the proposed method worked well with a sampling frequency of 50–200 Hz and a window length of 5–10 s. This research provides theoretical support for hunting instability monitoring and real-time active control studies for high-speed trains.

Design and analysis of high dynamic actuator and implementation on quadruped robot

Legged robot research is increasingly pursuing higher speed and higher dynamic manoeuvrability under higher load conditions, however, it poses more stringent challenges to the design of actuator. Under the constraints of actual size and weight restrictions, designing actuators that meet the requirements of high dynamic performance has become the pursuit of many robot designers, and has even become a key factor to limit and constrain the robot’s capability boundary. This paper takes the quadruped robot as the research object, and focuses on analysing the technical requirements of actuators under various gaits and working conditions, A 3-DOF pseudo-direct-drive actuator configuration scheme based on axial magnetic field is proposed. Under the control of the designed force-position hybrid control strategy, the test results of actuator and robot prove that the designed scheme can meet the high mobility with dynamic locomotion capability of the robot.

Investigation of Nonlinear PI Multi-loop Control Strategy for Aircraft HVDC Generator System with Wound Rotor Synchronous Machine

In order to enhance the transient performance of aircraft high voltage DC (HVDC) generation system with wound rotor synchronous machine (WRSM) under a wide speed range, the nonlinear PI multi-loop control strategy is proposed in this paper. Traditional voltage control method is hard to achieve the dynamic performance requirements of the HVDC generation system under a wide speed range, so the nonlinear PI parameter adjustment, load current feedback and speed feedback are added to the voltage and excitation current double loop control. The transfer function of the HVDC generation system is derived, and the relationship between speed, load current and PI parameters is obtained. The PI parameters corresponding to the load at certain speed are used to shorten the adjusting time when the load suddenly changes. The dynamic responses in transient processes are analyzed by experiment. The results illustrate that the WRSM HVDC generator system with this method has better dynamic performance.

Modular-based test system for proportional valves

Based on the dynamic and static test performance requirements of a company for proportional valves, a hydraulic schematic and electrical control system for a proportional valve test bench was designed, on the basis of which a LabVIEW-based proportional valve test system was developed. The test and control software is based on a modular design, which allows the required functions to be handled in a modular way, greatly reducing the development cycle of the test software and facilitating later improvements and maintenance. The test results show that the test bench has high accuracy and stable performance, and can provide a reliable test basis and test means for the development and online inspection of proportional valves.

The lightweight design for the frame structure of FSEC

Vehicle light-weighting is aimed at reducing the curb weight of the vehicle to ensure its strength, safety, and performance, as well as to reduce fuel consumption and exhaust emissions. The use of modern simulation technology in structural optimization design is one of the most important methods to achieve structural lightweight. In this paper, we study the size optimization of the frame structure based on the rules and requirements specified in Formula Student Eclectic China (FSEC), following the race’s rules and requirements, while satisfying the vehicle’s dynamic and static performance requirements. First, a three-dimensional geometric model of the frame structure is developed, and the static and dynamic performance of the frame is simulated using the finite element method. Next, structural size optimization is carried out under the premise of ensuring structural performance. Finally, the feasibility of the optimized structure is evaluated by comparing its performance before and after optimization. The research results show that the final frame structure has been reduced by 7.6 kg and the weight reduction has reached 22.4%. All performance indices meet the requirements of the competition, and a good lightweight effect has been achieved.

Process Optimization Based on Analysis of Dynamic and Static Performance Requirements of Ion Beam Figuring Machine Tools for Sub-Nanometer Figuring

Extreme ultraviolet lithography objective lenses require surface figure accuracy of approximately sub-nanometer root mean square (RMS). As the key equipment for sub-nanometer accuracy figuring, the dynamic and static performance of ion beam figuring (IBF) machine tools are critical. However, the related research is not sufficient and comprehensive. To this end, a general model of dynamic and static performance requirements on three-axis IBF machine tools was established. The requirements on dynamic and static performance under different figuring process for different surface shape were comprehensively analyzed. Analysis results revealed that the three-axis IBF machine tools require typical motion accuracy better than 100 μm and certain dynamic performance for achieving sub-nanometer accuracy. According to the theoretical and simulation results, a process optimization based on analysis of dynamic and static performance requirements of IBF machine tools for sub-nanometer figuring is proposed. To verify the proposed method, a Φ90 mm mirror with 2.594 nm RMS was figured to 0.251 nm RMS by optimizing the processing parameters to ensure that the IBF machine tool with measured performance (positioning error of 52.74 μm, 53.04 μm, 37.71 μm, and maximum acceleration of 1.0 m/s2, 1.3 m/s2, and 1.5 m/s2 for axes x, y, and z, respectively) meets the performance requirements. The proposed method can promote the application of three-axis IBF machine tools in sub-nanometer accuracy figuring.

Transient Response Characteristics Analysis of High-Power Piezoelectric Transducers.

Highlights What are the main findings? Derive the characteristics of transient equations under different excitations, and conclude the time constant is the key to the stability of the transducers.Applying a vector reduction method to analyze a series RLC transient matching scheme, which can change the electromechanical damping and improve the transient response time of the system. What is the implication of the main finding? A matching scheme combined with full-bridge inverter, transformer and series LC, is adopted to improve the transient response characteristic, which can provide suitable electrical damping without causing energy losses. To improve suitability in applications with high dynamic performance requirements, the transient response characteristics of high-power piezoelectric transducers should be studied quantitatively. This paper proposes the vector reduction method to solve the complex transient equations and obtains a transient matching scheme clarifying the mechanism of electrical matching resistance on electromechanical damping. A matching scheme with a combination of full-bridge inverter, transformer and series LC circuit is designed and validated, which can provide suitable electrical damping without causing energy losses. Consequently, the experiment verifies the transient properties of the proposed scheme. For a typical piezoelectric cutting transducer with 100.8 ms response time, our scheme is verified to have high dynamic performance within frequency response time of 5.5 ms and vibration response time of 15.0 ms.

Linear parameter-varying gain-scheduled preview-based robust attitude control design for a staring-mode satellite

It is challenging to precisely control the attitude of a satellite when performing a fast and large-angle maneuver, for instance, in the staring mode. To solve this issue, this paper investigates a gain-scheduled preview-based robust attitude control method in the framework of linear parameter-varying control theory. Firstly, the linear parameter-varying model of an observation satellite with large-angle rotations is developed by choosing the attitude angles as scheduling parameters to take the dynamics variation into consideration. In order to ease the implementation in practical engineering applications, the structure of the linear parameter-varying controller is in the form of modified proportional-integral-derivative control. To simultaneously satisfy the requirements of fast rotational speed and high dynamic tracking performance, a gain-scheduled proportional-integral-derivative controller is designed with the future information of desired attitude signals included in the feedforward path. The proposed controller is synthesized within the framework of H∞ robust control to enhance the robustness against inaccurate previewed information and external disturbances. The corresponding control synthesis condition is derived as an optimization problem with linear matrix inequality constraints. Monte Carlo simulation results demonstrate that the dynamic tracking accuracy of the proposed control algorithm can be guaranteed to be less than 0.01 deg in the face of fast large-angle commands, inaccurate previewed information and external disturbances.

Optimal design of space assembly microsatellite structure based on sequential quadratic programming

PurposeOn-orbit assembly technology is a promising research topic in spaceflight field. For purposes of studying the dynamic performance and reducing weight of an on-orbit assembly satellite structure frame, this paper aims to propose a structural optimization design method based on natural frequency.Design/methodology/approachThe dynamic stability of the satellite under working condition depends on the mechanical properties of the structure matrix. A global structural optimization model is established, with the objective of mass minimization and the constraints of given natural frequencies and given structure requirements. The structural optimization and improvement design method is proposed using sequential quadratic programming calculation.FindingsThe optimal result of objective function is effectively obtained, and the best combination of structural geometric parameters is configurated. By analyzing the relationship between the structural variables and optimization parameters, the primary and secondary factors to the mass optimization process of the microsatellite satisfying the dynamic performance requirements are obtained, which improves the effectiveness and accuracy of the system optimization design.Originality/valueThis method can coordinate the relation between satellite vibration stability and weight reduction, which provides an effective way for the optimization design of on-orbit assembly microsatellite. It has reference significance for the similar spacecraft framework structure design.

Ion beam figuring strategy for aluminum optics with minimal extra material removal.

With the application spectrum moving from infrared to visible light, aluminum optics with complex forms are difficult to fabricate by the majority of existing processing methods. Possessing the highest machining precision and low processing contamination, ion beam figuring (IBF) is a better method for fabrication of aluminum optics. However, the surface roughness deteriorates with the removal depth during IBF. In this study, the extra material removal during the IBF process is studied systematically. Extra material removal consists of two parts, determined by the convolution process and the limitation of the dynamic performance of machining tools. Extra material removal can be reduced by filtering out the surface residual error with a spatial frequency higher than the cut-off frequency and reducing the iterations of the machining process. Then, the executability of the dwell time matrix and the figuring ability of the removal function are analyzed. Adjusting the working parameters (volume removal rate) reduces the requirements for dynamic performance of machining tools. Finally, a minimal material removal processing strategy for aluminum optics based on power spectral density analysis and a spatial frequency filtering method is proposed. A simulation is conducted to verify the feasibility of the proposed strategy. With the same final precision (59.8 nm PV and 4.4 nm RMS), the maximum material removal decreases nearly 36 nm by applying the strategy, which reduces roughness nearly 10 nm. This study promotes the application of IBF in the field of aluminum optics fabrication as well as improves the machining precision of aluminum optics.

Control reconfiguration strategies for Remaining Useful Life extension

Extending the Remaining Useful Life (RUL) of dynamic systems functioning in closed loop in accordance with damage progression dynamics is a challenging task. Such target combines the challenges emanating from the domain of Prognostic Health Management (PHM) and engineering of the control theory. The main contribution of the paper consists in the synthesis and the analysis of two control reconfiguration strategies in order to achieve such objective.This paper presents two control strategies, one reconfigures the controls input and the other reconfigures the setpoint. The first structure modifies the controls input sent to the system using a modulation parameter. The second structure proposes a modification to the operational setpoint of the system's control loop. These modulations are obtained from an optimization algorithm making it possible to achieve a trade-off between the dynamic performance requirement and the RUL criteria.The optimization algorithm is based on the prediction of the RUL and on the estimation of the deterioration. A numerical example illustrates the use of each of these two strategies, through the results of estimating the deterioration, predicting RUL, and obtaining the modulation parameter from the optimization. The RUL extension and its impact on performance trade-off are illustrated to evaluate the performances of both strategies.

Electric vehicles body frame structure design method: An approach to design electric vehicle body structure based on battery arrangement

Although the electric vehicles (EVs) have become the main development of the automotive industry, there is still very limited knowledge about the design method of EVs’ body structure. This paper substantially increases this limited knowledge by developing an EV’s aluminum alloy body frame structure design (EVFD) method based on battery arrangements. The main concept of the EVFD approach is the development of the parametric knowledge base to facilitate performance driven design of body structure in concept design stage, including the battery sub-libraries designed by vehicle power performances and the modular body frame structure sub-libraries and cross section of profile sub-libraries designed by structure performances. The layout of vehicle is firstly determined based on battery volume which calculated on the basis of power performance of EVs. And then, the body frame structures are designed by multi-load topology optimization and multi-objective parametric optimization based on the body structure performance, considering the battery layout and its mass distribution. The developed body structure knowledge base is screened through comparing their structural mechanical properties. The feasibility and accuracy of selected EV’s aluminum alloy body frame structure is verified by experiment. In this paper, the case study demonstrates that the proposed EVFD method based on battery arrangement can be effectively used to design aluminum alloy body frame structure of EVs, which provides a reference to other EV’s body structure design. Due to the performance driven design concept employed, the designed body structure for EV meets the requirements of lightweight, dynamic performance, and structural mechanical properties.

The dynamic and economic performance study of a new Simpson planetary gearset based dual motor powertrain for electric vehicles

The dual motor powertrain is superior to the single motor powertrain in terms of economic performance for electric vehicles. To further improve the dynamic and economic performance of dual motor powertrain, a new Simpson planetary gearset based dual motor powertrain (SPGDMP) is proposed. The SPGDMP can realize six driving modes, including four single motor driving modes and two dual-motor driving modes. A simplified dynamic model which considers the gear meshing efficiency is built to implement the parameters design and formulate the energy management strategy (EMS). The genetic algorithm is used to optimize the parameters of SPGDMP to minimize the total power of the drive motor and meet the predetermined dynamic performance requirements at the same time. The EMS is formulated by minimizing the instantaneous consumed power of two motors. To demonstrate the performance of SPGDMP, the parallel axle based dual motor powertrain (PADMP) that meets the same dynamic performance requirement is used as the reference. The simulation results show that the proposed SPGDMP requires lower total power of driving motors to achieve the same dynamic performance and has much better economic performance.

Low voltage ride-through control strategy based on cascaded H-bridge that can avoid overmodulation and power backflow

Because of its multi-level output voltage and modular structure, the cascaded H-bridge(CHB) multi-level inverter can expand the system to higher voltage and power levels. It has good development and application prospects in the photovoltaic grid-connected market. Under the power grid fault voltage sag, the system should generate reactive power according to national codes and meet the dynamic performance requirements to maintain the connection with the grid, and achieve the minimum target requirements of low voltage ride through(LVRT). Aiming at the over-modulation and the unique power backflow problem of cascaded H-bridges, a LVRT control algorithm that can avoid over-modulation and power backflow is studied, and MATLAB simulation verification is carried out under common grid faults, which proves the correctness of the theory.

A new reaching law for sliding mode observer of controllable excitation linear synchronous motor

This paper presents a sliding mode observer (SMO) with new reaching law (NRL) for observing the real-time linear speed of a controllable excitation linear synchronous motor (CELSM). For the purpose of balancing the dilemma between the rapidity requirement of dynamic performance and the chattering reduction on sliding mode surface, the proposed SMO with NRL optimizes the reaching way of the conventional constant rate reaching law (CRRL) to the sliding mode surface by connecting the reaching process with system states and the sliding mode surface. The NRL is based on sigmoid function and power function, with proper options of exponential term and power term, the NRL is capable of eliminating the effect of chattering on accuracy of the angular position estimation and speed estimation. Compared with conventional CRRL, the SMO with NRL achieves suppressing the chattering phenomenon and tracking the transient process rapidly and accurately. The stability analysis is given to prove the convergence of the SMO through the Lyapunov stability theory. Simulation and experimental results show the effectiveness of the proposed NRL method.

Using an inerter to enhance an active-passive-combined vehicle suspension system

Performance of a passive vehicle suspension can be improved with the help of an active actuator, however, with potentially problematic control requirements, such as high energy consumption and large actuator forces. To maximize performance benefits without requiring significant control efforts, the passive and active parts need to be designed and work synergistically. In this paper, a novel combined passive and active vibration suppression approach of which the passive part is enhanced by an inerter is proposed for improving the trade-off between dynamic performance and control requirements. Via this approach, the optimal passive configuration consisting of inerter(s), spring(s) and damper(s) with pre-determined numbers and the optimal active control parameter can be identified. The approach is demonstrated using a case study where the combined suspension is designed considering a quarter-car model and a typical active controller (i.e., the skyhook control). It will be shown that, compared with a conventional passive part of a spring-damper, adding an inerter in parallel can significantly improve the pareto optimality between the ride comfort and power (or force) requirements. The improvement is further enhanced by systematically exploring all passive network possibilities with a pre-determined complexity via the structure-immittance technique. This approach is also applicable to the vibration suppression of other engineering structures.