Investigation of Semi-Active Hydro-Pneumatic Suspension for a Heavy Vehicle Based on Electro-Hydraulic Proportional Valve

Hydro-pneumatic suspension is widely used in heavy vehicles due to its nonlinear characteristics of stiffness and damping. However, the conventional passive hydro-pneumatic suspension can’t adjust parameters according to the complicated road environment of heavy vehicles to fulfill the requirements of the vehicle ride comfort. In this paper, a semi-active hydro-pneumatic suspension system based on the electro-hydraulic proportional valve control is proposed, and fuzzy control is used as the control strategy to adjust the?damping force of the semi-active hydro-pneumatic suspension. A 1/4?semi-active hydro-pneumatic suspension model is established, which is co-simulated with AMESim and MATLAB/Simulink. The co-simulation results show that the semi-active hydro-pneumatic suspension system can significantly reduce vibration of the vehicle body, and improve the suspension performance comparing with passive hydro-pneumatic suspension.

Advances in Active Suspension Systems for Road Vehicles

Active suspension systems(ASSs)have been proposed and developed for a few decades,and have now once again become a thriving topic in both academia and industry,due to the high demand for driving comfort and safety and the compatibility of ASSs with vehicle electrification and autonomy.Existing review papers on ASSs mainly cover dynamics modeling and robust control;however,the gap between academic research outcomes and industrial application requirements has not yet been bridged,hindering most ASS research knowledge from being transferred to vehicle companies.This paper comprehensively reviews advances in ASSs for road vehicles,with a focus on hardware structures and control strategies.In particular,state-of-the-art ASSs that have been recently adopted in production cars are discussed in detail,including the representative solutions of Mercedes active body control(ABC)and Audi predictive active suspension;novel concepts that could become alternative candidates are also introduced,including series active variable geometry suspension,and the active wheel-alignment system.ASSs with compact structure,small mass increment,low power consumption,high-frequency response,acceptable economic costs,and high reliability are more likely to be adopted by car manufacturers.In terms of control strategies,the development of future ASSs aims not only to stabilize the chassis attitude and attenuate the chassis vibration,but also to enable ASSs to cooperate with other modules(e.g.,steering and braking)and sensors(e.g.,cameras)within a car,and even with high-level decision-making(e.g.,reference driving speed)in the overall transportation system-strategies that will be compatible with the rapidly developing electric and autonomous vehicles.

Integrated Active Suspension and Anti-Lock Braking Control for Four-Wheel-Independent-Drive Electric Vehicles

This paper presents an integrated control scheme for enhancing the ride comfort and handling performance of a four-wheel-independent-drive electric vehicle through the coordination of active suspension system(ASS)and anti-lock braking system(ABS).First,a longitudinal-vertical coupled vehicle dynamics model is established by integrating a road input model.Then the coupling mechanisms between longitudinal and vertical vehicle dynamics are analyzed.An ASS-ABS integrated control system is proposed,utilizing an H∞controller for ASS to optimize load transfer effect and a neural network sliding mode control for ABS implementation.Finally,the effectiveness of the proposed control scheme is evaluated through comprehensive tests conducted on a hardware-in-loop(HIL)test platform.The HIL test results demonstrate that the proposed control scheme can significantly improve the braking performance and ride comfort compared to conventional ABS control methods.

Stochastic sampled-data multi-objective control of active suspension systems for in-wheel motor driven electric vehicles

This paper addresses the sampled-data multi-objective active suspension control problem for an in-wheel motor driven electric vehicle subject to stochastic sampling periods and asynchronous premise variables.The focus is placed on the scenario that the dynamical state of the half-vehicle active suspension system is transmitted over an in-vehicle controller area network that only permits the transmission of sampled data packets.For this purpose,a stochastic sampling mechanism is developed such that the sampling periods can randomly switch among different values with certain mathematical probabilities.Then,an asynchronous fuzzy sampled-data controller,featuring distinct premise variables from the active suspension system,is constructed to eliminate the stringent requirement that the sampled-data controller has to share the same grades of membership.Furthermore,novel criteria for both stability analysis and controller design are derived in order to guarantee that the resultant closed-loop active suspension system is stochastically stable with simultaneous𝐻2 and𝐻∞performance requirements.Finally,the effectiveness of the proposed stochastic sampled-data multi-objective control method is verified via several numerical cases studies in both time domain and frequency domain under various road disturbance profiles.

Output feedback control and parameters influence analysis of active suspension electro-hydraulic servo actuator

The hydraulic servo actuator of heavy vehicle active suspension is investigated to clarify the correlation between system parameters and the control characteristics of active suspension hydraulic servo system.Accordingly, a nonlinear physical model of electro-hydraulic servo active suspension system is built.Compared with the conventional nonlinear modeling, the model in this study considers the asymmetry of working areas caused by single rod hydraulic cylinder in the suspension system.In accordance with the model, a nonlinear output feedback controller based on backstepping is designed, and the effectiveness of the controller is proved based on the experimental platform.The dynamic response curve of the electro-hydraulic servo control system under the change of parameters is generated based on the simulation model.The sensitivity of electro-hydraulic servo control performance to the change of system physical parameters is investigated, and two evaluation indexes are proposed to quantify and compare the effect of all physical parameter changes on position control system.As revealed by the results, the position control characteristics of suspension actuator are more sensitive to the changes of flow gain of the servo valve, system supply oil pressure and effective working areas of cylinder, and the two evaluation indexes are over 10 times higher than other physical parameters.

Improving rail vehicle dynamic performance with active suspension

Today,it is difficult to further improve the dynamic performance of rail vehicles with conventional passive suspension.Also,simplified vehicle respectively running gear layouts that significantly could reduce vehicle weights are difficult to realize with modern requirements on passenger vibration comfort and wheel and rail wear.Active suspension is a powerful technology that can improve the vehicle dynamic performance and make simplified vehicle concepts possible.The KTH Railway group has,together with external partners,investigated active suspensions both numerically and experimentally for 15 years.The paper provides a summary of the activities and the most important findings.One major project carried out in close collaboration with the vehicle manufacturer Bombardier and the Swedish Transport Administration was the Green Train project,where a 2-car EMU test bench was used to demonstrate different active technologies.In ongoing projects,a concept of single axle-single suspension running gear is developed with active suspension both for comfort improvement and reduced wheel wear in curves.The results from on-track tests in the Green Train project were so good that the technology is now implemented in commercial trains and the simulation results for the single-axle running gear are very promising.

OPTIMAL CONTROL OF AN ACTIVE SUSPENSION SYSTEMEMPLOYING HIGH SPEED ON/OFF SOLENOID VALVE

Previous studies have confirmed that an active suspension system with high speed ON/OFF solenoid valves could provide the same vibration isolation efficiency as that of system with pressure proportional valve. In this study, by using Linear-quadratic optimization technique and Kalman filter method, an optimal regulator controller with a state observer was designed for the proposed system. Simulation and experimental research was conducted on a quarter car model. The simulation analysis of the system frequency characteristic suggested that the peak value of magnitude response curve in the case of system with an optimal controller would be lowered significantly, and the experiment results also showed that an improvement in the vibration isolation effect was obtained in using the designed optimal controller over the sky hook damper controller.

Fuzzy Chaos Control for Vehicle Lateral Dynamics Based on Active Suspension System

The existing research of the active suspension system（ASS） mainly focuses on the different evaluation indexes and control strategies. Among the different components, the nonlinear characteristics of practical systems and control are usually not considered for vehicle lateral dynamics. But the vehicle model has some shortages on tyre model with side-slip angle, road adhesion coefficient, vertical load and velocity. In this paper, the nonlinear dynamic model of lateral system is considered and also the adaptive neural network of tire is introduced. By nonlinear analysis methods, such as the bifurcation diagram and Lyapunov exponent, it has shown that the lateral dynamics exhibits complicated motions with the forward speed. Then, a fuzzy control method is applied to the lateral system aiming to convert chaos into periodic motion using the linear-state feedback of an available lateral force with changing tire load. Finally, the rapid control prototyping is built to conduct the real vehicle test. By comparison of time response diagram, phase portraits and Lyapunov exponents at different work conditions, the results on step input and S-shaped road indicate that the slip angle and yaw velocity of lateral dynamics enter into stable domain and the results of test are consistent to the simulation and verified the correctness of simulation. And the Lyapunov exponents of the closed-loop system are becoming from positive to negative. This research proposes a fuzzy control method which has sufficient suppress chaotic motions as an effective active suspension system.

Finite Frequency Fuzzy H∞Control for Uncertain Active Suspension Systems With Sensor Failure

This paper investigates the problem of finite frequency fuzzy H_∞ control for uncertain active vehicle suspension systems, in which sensor failure is taken into account. TakagiSugeno(T-S) fuzzy model is established for considered suspension systems. In order to describe the sensor fault effectively, a corresponding model is introduced. A vital performance index,H_∞ performance, is utilized to measure the drive comfort. In the framework of Kalman-Yakubovich-Popov theory, the H_∞ norm from external perturbation to controlled output is optimized effectively in the frequency domain of 4 Hz-8 Hz to enhance ride comfort level. Meanwhile, three suspension constrained requirements, i.e., ride comfort level, manipulation stability,suspension deflection are also guaranteed. Furthermore, sufficient conditions are developed to design a fuzzy controller to guarantee the desired performance of active suspension systems. Finally, the proposed control scheme is applied to a quarter-vehicle active suspension, and simulation results are given to illustrate the effectiveness of the proposed approach.

Decentralized Dynamic Event-Triggered Communication and Active Suspension Control of In-Wheel Motor Driven Electric Vehicles with Dynamic Damping

This paper addresses the co-design problem of decentralized dynamic event-triggered communication and active suspension control for an in-wheel motor driven electric vehicle equipped with a dynamic damper. The main objective is to simultaneously improve the desired suspension performance caused by various road disturbances and alleviate the network resource utilization for the concerned in-vehicle networked suspension system. First, a T-S fuzzy active suspension model of an electric vehicle under dynamic damping is established. Second,a novel decentralized dynamic event-triggered communication mechanism is developed to regulate each sensor's data transmissions such that sampled data packets on each sensor are scheduled in an independent manner. In contrast to the traditional static triggering mechanisms, a key feature of the proposed mechanism is that the threshold parameter in the event trigger is adjusted adaptively over time to reduce the network resources occupancy. Third, co-design criteria for the desired event-triggered fuzzy controller and dynamic triggering mechanisms are derived. Finally, comprehensive comparative simulation studies of a 3-degrees-of-freedom quarter suspension model are provided under both bump road disturbance and ISO-2631 classified random road disturbance to validate the effectiveness of the proposed co-design approach. It is shown that ride comfort can be greatly improved in either road disturbance case and the suspension deflection, dynamic tyre load and actuator control input are all kept below the prescribed maximum allowable limits, while simultaneously maintaining desirable communication efficiency.

Active suspension in railway vehicles:a literature survey

Since the concept of active suspensions appeared,its large possible benefits has attracted continuous exploration in the field of railway engineering.With new demands of higher speed,better ride comfort and lower maintenance cost for railway vehicles,active suspensions are very promising technologies.Being the starting point of commercial application of active suspensions in rail vehicles,tilting trains have become a great success in some countries.With increased technical maturity of sensors and actuators,active suspension has unprecedented development opportunities.In this work,the basic concepts are summarized with new theories and solutions that have appeared over the last decade.Experimental studies and the implementation status of different active suspension technologies are described as well.Firstly,tilting trains are briefly described.Thereafter,an indepth study for active secondary and primary suspensions is performed.For both topics,after an introductory section an explanation of possible solutions existing in the literature is given.The implementation status is reported.Active secondary suspensions are categorized into active and semi-active suspensions.Primary suspensions are instead divided between acting on solid-axle wheelsets and independently rotating wheels.Lastly,a brief summary and outlook is presented in terms of benefits,research status and challenges.The potential for active suspensions in railway applications is outlined.

Control Research of Dual Chamber Hydro-Pneumatic Suspension

Vehicle riding comfort and handling stability are directly affected by suspension performance.A novel dual chamber hydro-pneumatic(DCHP)suspension system is developed in this paper.Based on the structural analysis of the DCHP suspension,an equivalent suspension model is proposed for the control purpose.A cuckoo search(CS)based fuzzy PID controller is proposed for the control of the DCHP suspension system.The proposed controller combines the advantage of fuzzy logic and PID controller,and CS algorithm is used to regulate the membership functions and PID parameters.Compared with tradition LQR controller and passive suspension system,the CSFPID controller can reduce the sprung mass acceleration,and at the same time with no deterioration of tire deflection.

Design and optimization of a semi-active suspension system for railway applications

The present work focused on the application of innovative damping technologies in order to improve railway vehicle performances in terms of dynamic stability and comfort. As a benchmark case-study, the secondary sus- pension stage was selected and different control techniques were investigated, such as skyhook, dynamic compensation, and sliding mode control. The final aim was to investigate which control schemes are suitable for optimal exploitation of the non-linear behavior of the actuators. The performance improvement achieved by adoption of the semi-active dampers on a standard high-speed train was evaluated in terms of passenger comfort. Different control strategies have been investigated by comparing a simple SISO （single input single output） regulator based on the skyhook damper ap- proach with a centralized regulator. The centralized regulator allows for the estimation of a near optimal set of control forces that minimize car-body accelerations with respect to constraints imposed by limited performance of semi-active actuators. Simulation results show that best results is obtained using a mixed approach that considers the simultaneous applications of model based and feedback compensation control terms.

Development of a Composite Suspension with a Coil and Hydro-Pneumatic Spring

A new composite suspension is developed, where a coil spring and a hydro-pneumatic spring are used in order to improve the poor reliability of off-road vehicle with pure hydro-pneumatic suspension. According to road conditions, the two springs play different roles. The method for matching the composite suspension stiffness and distributing the load is proposed. The working pressure of hydro-pneumatic spring as well as the load and stiffness characteristics of composite suspension is compared with a pure hydro-pneumatic suspension. In addition, the ISO weighted vehicle body acceleration, suspension travel and relative dynamic load of the wheels between two kinds of suspension are analyzed with a quarter vehicle mode. The simulation result shows that the developed composite suspension is more suitable for off-road vehicle than the one hydro-pneumatic suspension, because the composite suspension can reduce the working pressure, improve the reliability and keep a similar ride comfort with hydro-pneumatic suspension.

Linear Quadratic Integral Control for the Active Suspension of Vehicle

The quarter model of an active suspension is established in the form of controllable autoregressive moving average （CARMA） model. An accelerometer can be mounted on the wheel hub for measuring road disturbance; this signal is used to identify the CARMA model parameters by recursive forgetting factors least square method. The linear quadratic integral （LQI） control method for the active suspension is presented. The LQI control algorithm is fit for vehicle suspension control, for the control performance index can comprise multi controlled variables. The simulation results show that the vertical acceleration and suspension travel both are decreased with the LQI control in the low frequency band, and the suspension travel is increased with the LQI control in the middle or high frequency band. The suspension travel is very small in the middle or high frequency band, the suspension bottoming stop will not happen, so the vehicle ride quality can be improved apparently by the LQI control.

Sampled-Data Asynchronous Fuzzy Output Feedback Control for Active Suspension Systems in Restricted Frequency Domain

This paper proposes a novel sampled-data asynchronous fuzzy output feedback control approach for active suspension systems in restricted frequency domain.In order to better investigate uncertain suspension dynamics,the sampleddata Takagi-Sugeno(T-S)fuzzy half-car active suspension(HCAS)system is considered,which is further modelled as a continuous system with an input delay.Firstly,considering that the fuzzy system and the fuzzy controller cannot share the identical premises due to the existence of input delay,a reconstructed method is employed to synchronize the time scales of membership functions between the fuzzy controller and the fuzzy system.Secondly,since external disturbances often belong to a restricted frequency range,a finite frequency control criterion is presented for control synthesis to reduce conservatism.Thirdly,given a full information of state variables is hardly available in practical suspension systems,a two-stage method is proposed to calculate the static output feedback control gains.Moreover,an iterative algorithm is proposed to compute the optimum solution.Finally,numerical simulations verify the effectiveness of the proposed controllers.

Control algorithm for vehicle height adjustable system of hydro-pneumatic suspension based on LuGre model

In order to control the vehicle body position precisely,1/4 nonlinear mathematical model of hydro-pneumatic suspension is established,and the influence of the frictional force in a hydraulic cylinder is analyzed.The friction characteristics are described based on the LuGre model when the piston of a hydraulic actuator is operated at a low speed.Due to the fact parameters of the friction model are effected by the system condition,an adaptive friction compensation（AFC）controller is designed through the Backstepping method,and a dual-observer has been implemented to estimate the friction state.The global asymptotic convergence of a closed-loop system is proven by the Lyapunov theorem.The simulation results show that the positional accuracy of the adaptive friction compensation yiedls a significant improvement in the vehicle height adjustment as compared to the PID control,demonstrating the effectiveness of the adaptive fiction compensation method in the vehicle height adjustable system of the hydro-pneumatic suspension.

Performance of a novel energy-regenerative active suspension system

A novel energy-regenerative active suspension(NEAS) system was designed to solve the problem of low energy recovery efficiency caused by frequent alternation of energy-recovery mode and active-control mode in a traditional energyregenerative active suspension(TEAS) system. The energy recovery and active control could be implemented simultaneously in the NEAS. The transforming processes and the corresponding computational formulas of power conversion in the NEAS were provided. The simulation results show that the performances of energy recovery of the NEAS are improved, and the selfsustaining of power supply for the NEAS can be realized.

Static-Output-Feedback Based Robust Fuzzy Wheelbase Preview Control for Uncertain Active Suspensions With Time Delay and Finite Frequency Constraint

This paper proposes a static-output-feedback based robust fuzzy wheelbase preview control algorithm for uncertain active suspensions with time delay and finite frequency constraint.Firstly,a Takagi-Sugeno(T-S)fuzzy augmented model is established to formulate the half-car active suspension system with consideration of time delay,sprung mass variation and wheelbase preview information.Secondly,in view of the resonation between human’s organs and vertical vibrations in the frequency range of 4–8 Hz,a finite frequency control criterion in terms of H∞norm is developed to improve ride comfort.Meanwhile,other mechanical constraints are also considered and satisfied via generalized H2 norm.Thirdly,in order to maintain the feasibility of the controller despite of some state variables are not online-measured,a two stage approach is adopted to derive a static output feedback controller.Finally,numerical simulation results illustrate the excellent performance of the proposed controller.

A Novel Energy-regenerative Active Suspension for Vehicles

In order to regenerate electric power from the vibration excited by road unevenness,a novel energy- regenerative active suspension for vehicles was proposed with the description of its structure and its working principle with two modes switched in different operating conditions.Then,the novel active system was modeled and simulated to show the performance improvement in ride comfort in its electrical motor mode.Finally,the performance tests of the actuator prototype were carried out,which proves its capability for damping in its regenerative braking mode.The research results can provide useful guidance for the similar electrical active suspension design and development.