Development and evaluation of a versatile semi-active suspension system for high-speed railway vehicles

With the increase in speed of high-speed trains, their vibration will become fiercer and fiercer, especially when the lateral resonance of the car body occurs. This paper develops a versatile semi-active suspension system with variable stiffness (VS) magnetorheological elastomer (MRE) isolators and variable damping (VD) magnetorheological (MR) dampers for high-speed trains, aiming to improve ride comfort by avoiding car body resonance and dissipating vibration energy. As the first step, a multifunction VSVD semi-active suspension system for high-speed railway vehicles was designed and prototyped, including four VS-MRE isolators and two VD-MR dampers. After that, a scaled train model, composing of a car body and a secondary lateral suspension system was designed and built to evaluate the performance of the new VSVD suspension system; a control strategy based on short-time Fourier transform (STFT) and sky-hook was proposed to control the new suspension system. Two different excitations, harmonic excitation and random excitation, were applied to evaluate the train\u27s VSVD suspension. As a comparison, four alternative suspension systems, including passive-off suspension, passive-on suspension, pure VS suspension, and pure VD suspension were also evaluated. The evaluation results verified that the VSVD suspension of the train can avoid lateral resonance of car body and dissipate the vibration energy efficiently. The comparison verified that the VSVD suspension system outperforms the passive-off suspension, passive-on suspension, pure VS suspension, and pure VD suspension

Impact analysis of lateral damper on the ride quality of metro vehicle

In view of the lateral and vertical vibration problem of car body in actual operation, dynamic simulation and relevant line tests are carried out to study the impact of lateral damper on the ride quality. To facilitate comparative analysis, dynamic models of metro vehicle are set up and simulation results indicate that ride quality when using a single lateral damper is better than when using double dampers. On this basis, line comparison tests are conducted, with ride index in time domain as an indicator. Acceleration sensors are utilized to conduct lateral and vertical acceleration tests when using a single lateral damper and double dampers, respectively. Ride index of every 5 seconds at normal operating velocity is obtained after post-processing of data collected from the tests. Comparison of ride index of two adjacent stations obtained by statistics has found that, in actual operation, metro vehicle with a single lateral damper mounted on the bogie has a better ride quality both laterally and vertically than that with double dampers. Single lateral damper model can also effectively solve abnormal vibration problem of the metro vehicle

Advanced suspension system using magnetorheological technology for vehicle vibration control

In the past forty years, the concept of controllable vehicle suspension has attracted extensive attention. Since high price of an active suspension system and deficiencies on a passive suspension, researchers pay a lot attention to semi-active suspension. Magneto-rheological fluid (MRF) is always an ideal material of semi-active structure. Thanks to its outstanding features like large yield stress, fast response time, low energy consumption and significant rheological effect. MR damper gradually becomes a preferred component of semi-active suspension for improving the riding performance of vehicle. However, because of the inherent nonlinear nature of MR damper, one of the challenging aspects of utilizing MR dampers to achieve high levels of performance is the development of an appropriate control strategy that can take advantage of the unique characteristics of MR dampers. This is why this project has studied semi-active MR control technology of vehicle suspensions to improve their performance. Focusing on MR semi-active suspension, the aim of this thesis sought to develop system structure and semi-active control strategy to give a vehicle opportunity to have a better performance on riding comfort. The issues of vibration control of the vehicle suspension were systematically analysed in this project. As a part of this research, a quarter-car test rig was built; the models of suspension and MR damper were established; the optimization work of mechanical structure and controller parameters was conducted to further improve the system performance; an optimized MR damper (OMRD) for a vehicle suspension was designed, fabricated, and tested. To utilize OMRD to achieve higher level of performance, an appropriate semi-active control algorithm, state observer-based Takagi-Sugeno fuzzy controller (SOTSFC), was designed for the semi-active suspension system, and its feasibility was verified through an experiment. Several tests were conducted on the quarter-car suspension to investigate the real effect of this semiactive control by changing suspension damping. In order to further enhance the vibration reduction performance of the vehicle, a fullsize variable stiffness and variable damping (VSVD) suspension was further designed, fabricated, and tested in this project. The suspension can be easily installed into a vehicle suspension system without any change to the original configuration. A new 3- degree of freedom (DOF) phenomenological model to further accurately describe the dynamic characteristic of the VSVD suspension was also presented. Based on a simple on-off controller, the performance of the variable stiffness and damping suspension was verified numerically. In addition, an innovative TS fuzzy modelling based VSVD controller was designed. The TS fuzzy modelling controller includes a skyhook damping control module and a state observer based stiffness control module which considering road dominant frequency in real-time. The performance evaluation of the VSVD control algorithm was based on the quarter-car test rig which equipping the VSVD suspension. The experiment results showed that this strategy increases riding comfort effectively, especially under off-road working condition. The semi-active control system developed in this thesis can be adapted and used on a vehicle suspension in order to better control vibration

Active suspension control of electric vehicle with in-wheel motors

In-wheel motor (IWM) technology has attracted increasing research interests in recent years due to the numerous advantages it offers. However, the direct attachment of IWMs to the wheels can result in an increase in the vehicle unsprung mass and a significant drop in the suspension ride comfort performance and road holding stability. Other issues such as motor bearing wear motor vibration, air-gap eccentricity and residual unbalanced radial force can adversely influence the motor vibration, passenger comfort and vehicle rollover stability. Active suspension and optimized passive suspension are possible methods deployed to improve the ride comfort and safety of electric vehicles equipped with inwheel motor. The trade-off between ride comfort and handling stability is a major challenge in active suspension design. This thesis investigates the development of novel active suspension systems for successful implementation of IWM technology in electric cars. Towards such aim, several active suspension methods based on robust H∞ control methods are developed to achieve enhanced suspension performance by overcoming the conflicting requirement between ride comfort, suspension deflection and road holding. A novel fault-tolerant H∞ controller based on friction compensation is in the presence of system parameter uncertainties, actuator faults, as well as actuator time delay and system friction is proposed. A friction observer-based Takagi-Sugeno (T-S) fuzzy H∞ controller is developed for active suspension with sprung mass variation and system friction. This method is validated experimentally on a quarter car test rig. The experimental results demonstrate the effectiveness of proposed control methods in improving vehicle ride performance and road holding capability under different road profiles. Quarter car suspension model with suspended shaft-less direct-drive motors has the potential to improve the road holding capability and ride performance. Based on the quarter car suspension with dynamic vibration absorber (DVA) model, a multi-objective parameter optimization for active suspension of IWM mounted electric vehicle based on genetic algorithm (GA) is proposed to suppress the sprung mass vibration, motor vibration, motor bearing wear as well as improving ride comfort, suspension deflection and road holding stability. Then a fault-tolerant fuzzy H∞ control design approach for active suspension of IWM driven electric vehicles in the presence of sprung mass variation, actuator faults and control input constraints is proposed. The T-S fuzzy suspension model is used to cope with the possible sprung mass variation. The output feedback control problem for active suspension system of IWM driven electric vehicles with actuator faults and time delay is further investigated. The suspended motor parameters and vehicle suspension parameters are optimized based on the particle swarm optimization. A robust output feedback H∞ controller is designed to guarantee the system’s asymptotic stability and simultaneously satisfying the performance constraints. The proposed output feedback controller reveals much better performance than previous work when different actuator thrust losses and time delay occurs. The road surface roughness is coupled with in-wheel switched reluctance motor air-gap eccentricity and the unbalanced residual vertical force. Coupling effects between road excitation and in wheel switched reluctance motor (SRM) on electric vehicle ride comfort are also analysed in this thesis. A hybrid control method including output feedback controller and SRM controller are designed to suppress SRM vibration and to prolong the SRM lifespan, while at the same time improving vehicle ride comfort. Then a state feedback H∞ controller combined with SRM controller is designed for in-wheel SRM driven electric vehicle with DVA structure to enhance vehicle and SRM performance. Simulation results demonstrate the effectiveness of DVA structure based active suspension system with proposed control method its ability to significantly improve the road holding capability and ride performance, as well as motor performance

Vibration suppression in high-speed trains with negative stiffness dampers

Copyright © 2018 Techno-Press, Ltd. This work proposes and investigates re-centering negative stiffness dampers (NSDs) for vibration suppression in high-speed trains. The merit of the negative stiffness feature is demonstrated by active controllers on a high-speed train. This merit inspires the replacement of active controllers with re-centering NSDs, which are more reliable and robust than active controllers. The proposed damper design consists of a passive magnetic negative stiffness spring and a semi-active positioning shaft for re-centering function. The former produces negative stiffness control forces, and the latter prevents the amplification of quasi-static spring deflection. Numerical investigations verify that the proposed re-centering NSD can improve ride comfort significantly without amplifying spring deflection

Modeling and Robust Control of Integrated Ride and Handling of Passenger Cars

Vehicle industries in the last decade have focused on improving ride quality and safety of passenger cars. To achieve this goal, modeling and simulation of dynamic behaviour of vehicles have been widely studied to design model based and robust control strategies. This PhD work presents a new integrated vehicle model and a nonlinear robust controller. The thesis is divided into two main sections: dynamic modeling and controller design. A new fourteen Degrees of Freedom integrated ride and handling vehicle model is proposed using Lagrangian method in terms of quasi-coordinates. The governing equations are derived considering the interaction between the ride and handling systems, Euler motion of the frames attached to the wheels and body, the load transfer among the wheels, acceleration and braking. A non-dimensional factor called coupling factor is introduced to study the coupling among different DOFs of the dynamic system for a defined vehicle maneuver. The coupling factor is considered as an indicator parameter to demonstrate the advantages of the developed model over the existing dynamic models. The improved model is validated using ADAMS/Car for different manoeuvres. The simulation results confirm the accuracy of the improved dynamic model in comparison with the ADAMS/Car simulations and the models available in the literature. Considering the proposed nonlinear integrated ride and handling vehicle model, a nonlinear robust controller is designed for an intermediate passenger car. The H∞ robust control strategy is designed based on the Hamiltonian-Jacobi-Isaacs (HJI) function, Linear Matrix Inequality and State Feedback techniques. In order to improve the ride and handling quality of the vehicle, a Magneto-rheological (MR) damper and a differential braking system are used as control devices. A frequency dependent MR damper model is proposed based on the Spencer MR damper model. The parameters of the model are identified using a combination of Genetic algorithms and Sequential Quadratic Programming approaches based on the experimental data. A mathematical model is validated using the experimental results which confirm the improvement in the accuracy of the model and consistency in the variation of damping with frequency. Based on the proposed MR damper model, an inverse model for the MR damper is designed. A differential braking system is designed to assign desired braking action. The dynamic behavior of the controlled vehicle is simulated for single lane change and bump input, considering three different road conditions: dry, rainy and snowy. The robustness of the designed controller is investigated when the vehicle is under these road conditions. The simulation results confirm the interactive nature of the ride and handling systems and the robustness of the designed control strategy

Improvement of semi-active control suspensions based on gain-scheduling control

This study presents the development of a non-linear control strategy for a semi-active suspension controller using a gain-scheduling structure controller. The aim of the study is to overcome the constraints of conventional control strategies and improve semi-active suspension to achieve performance close to that of full active control. Various control strategies have been investigated to improve the performance of semi-active vibration control systems. A wide range of semi-active control strategies have also been experimentally tested by researchers in the attempt to enhance the performance of semi-active suspension systems. However, the findings published in the literature indicate that there appears to be a ceiling to performance improvements with the control strategies that have been proposed to date, which is about the half of what could be achieved with full active control. The main constraint for semi-active devices such as Magnetorheological (MR) dampers is that they are only capable of providing active control forces by dissipating energy, in their active mode, and they switch to work as simple passive dampers, the passive mode, when energy injection is demanded by the associated control laws. The split in durations of time between the active and passive modes for the conventional semi-active control strategies is around 50:50. This study will focus on the development of a novel semi-active control strategy that aims to extend the duration of the active mode and hence reduce the duration of the passive mode for semi-active suspensions by using a gain-scheduling control structure that dynamically changes the control force demanded by the operating conditions. The proposed control method is applied to both vertical and lateral suspensions of a railway vehicle in this study and the improvements in ride quality are evaluated with several different track data. For the purpose of performance comparison, a semi-active controller based on skyhook damping control integrated with MR dampers and also a vehicle with passive suspensions are used as the benchmark, and are used as a reference case for assessment of the proposed design. Numerical simulations are carried out to assess the performance of the proposed gain-scheduling controller. The simulation results obtained illustrate the performance improvement of the proposed control strategy over conventional semi-active control approaches, where the ride quality of the new controller is shown to be significantly improved and comparable with that of full active control. Potentially, this kind of adaptive capability with variable control approaches can be used to deliver the level of the performance that is currently only possible with fully active suspension without incurring the associated high costs and power consumption

Semi-active control for independently rotating wheelset in railway vehicles with MR dampers

This thesis presents details of an investigation of a controller for MR damper in the implementation of semi-active control, for primary suspensions of the independently rotating railway vehicles. This research focuses on using MR damper and it addresses on three main aspects when designing semi-active control systems for this application.One aspect is magnetorheological dampers categorised as a controllable fluid damper which can reversibly change from a flowing viscose fluid to semi-solid viscose fluid. The second aspect is the controllable yield strength can change in a millisecond by inducing an electric or magnetic field. Third aspect is MR damper is cheaper than actuators which are usually use in full active controllerThis research is a combination of a lookup table based on the inverse MR damper model to control the current input (to the MR damper) from required force and relative velocity of the device. The MR damper produces the desired force as precisely as possible. However, it is not possible to have precise knowledge of MR parameters and it is also difficult to account for the hysteresis present in MR dampers in the lookup table. Therefore, an additional local PI feedback controller is also used to improve the robustness for the MR control.As the main result, this study provides a comparison between semi-active controller with the use of MR damper and a full active controller system. The results show semi-active controller with the use of MR damper performed as good as full active controller. However semi-active control systems with MR dampers offer an overall efficiency and robustness when compared to the full active control system. Also, this system delivers comparable performance with the benefit of increased reliability and lower cost.In order to assess the developed system comprehensively, a two–axle vehicle model and a full bogie vehicle model are both evaluated individually in the study.The performance and robustness assessments of the developed semi-active controller with the full active control system are evaluated with the use of both two–axle vehicle model and the full bogie vehicle model with different operational track features such as curved track and straight track with lateral irregularities with various travel speeds.This study designed and developed a semi-active control systems with use of MR damper in primary suspension for independent rotation wheelsets in railway vehicles. Computer simulation results verified the suggested semi-active control is able to provide required stability and guidance control for independently- rotating wheelsets. Also, the result performed as well as full active control with the advantage of utilizing a lower cost device for semi-active control rather than an expensive actuator for full active control

Active suspension co-design for lateral stability of rail vehicles

Railroad transportation is one of the most cost-effective and energy-efficient modes of land transportation. With an eye toward improving these efficiencies, many efforts have focused on developing high speed railways. Traditionally railways have utilized passive suspension systems, but maintaining dynamic stability at higher speeds demands enhancements to existing rail vehicle suspensions. One strategy to improve dynamic performance is to incorporate active or semi-active elements, such as force actuators or variable dampers, within the suspension system. Modern day road and rail vehicles often utilize such actively-controlled suspensions to improve stability, ride comfort and ride quality at high speeds. The dynamic performance of such mechatronically-controlled suspension systems is related closely to the congruence of the design of passive elements in conjunction with the chosen control system strategy. Historically, design of controlled dynamic systems has followed a sequential process (mechanical design followed by control design). In the field of mechatronics, engineers typically use design rules or heuristics that help account for design coupling, but cannot produce system optimal designs. Passive elements are optimally designed first, followed by the addition of controllers for system performance improvements. New integrated design strategies are required to realize the full potential of such advanced complex dynamic systems and to capitalize on design coupling. This thesis aims to explore and apply a recently developed synergistic approach to design of controlled dynamic systems, called co-design. Theoretical models of existing partitioned, optimization-based design methods are compared to this combined active and passive system design strategy. Parameters for a reduced and a full-scale rail vehicle model are then designed using the developed optimal design formulations. Different control techniques within the co-design framework are tested and compared. Typically feedback controllers are required for actual implementation of control strategies. Early-stage co-design strategies are normally based on open-loop control, therefore, are limited for functional implementation. However, co-design methods provide designers with better knowledge about the true performance limits of dynamic systems, help them make more informed design decisions, and provide a foundation for development of implementable feedback control systems. The results obtained in this thesis show significant improvements achieved by co-design strategies over passive system design and sequential design approaches. The results also demonstrate the potential of this framework in helping systematic selection of optimal plant design variables, controller architecture, and implementable control techniques. Future work includes designing practical feedback controllers built upon results from co-design strategies for rail vehicles using non-linear vehicle models to provide a complete active rail suspension solution