Hydraulically Interconnected Suspension Research Articles

Backstepping sliding mode control for an active hydraulically interconnected suspension

This paper presents a backstepping sliding mode control (BSMC) method for an active anti-roll hydraulically interconnected suspension (HIS) system. The proposed control strategy enables the active HIS system tracking desired anti-roll moment within the working area. Based on the tracking error, the BSMC controller calculates the flowrate of the control cylinder. This flowrate successively changes the pressure in the accumulators and cylinder chambers, and finally determines the output anti-roll moment of the HIS. The HIS system parameters uncertainty and the system’s nonlinear characteristic are both considered in the proposed BSMC controller. To comprehensively design and validate the proposed control method, a 4-DOF half car model and a corresponding nonlinear active anti-roll HIS model are firstly established. Next, a linear quadratic regulator (LQR) upper layer controller is designed to optimize the vehicle’s roll motion, and the result of the LQR controller is set as a tracking target. Thereafter, the proposed BSMC bottom layer controller is designed to track the target moment. Finally, numerical simulation and experiments on the test bench are conducted to validate the proposed control method. The simulation and bench test results indicate that the proposed active HIS performs well in tracking target and tolerating disturbance. The proposed active HIS expands about additional ±1000 N/m dynamic anti-roll moment compared to a passive HIS at each roll angle, and the response time is less than 70 ms. The field test results show that the active HIS with proposed control method improves anti-roll property compared with a passive HIS by 23.3% in the double lane change test.

A multi-objective optimization method for hydraulically interconnected suspension system

To enhance the ride comfort and roll stability of the special vehicle, this study concentrates on the inherent parameters optimization of the hydraulically interconnected suspension (HIS) system. A road-tire-HIS-body model of a special vehicle is established based on the AMESim/Simulink co-simulation platform. Then the sensitivity of the HIS system is analyzed to determine the design variables to be optimized through the AMESim/Simulink/Isight co-simulation. Two objectives including improving the ride comfort and roll stability of the vehicle are proposed. In order to enhance the population diversity and accelerate the convergence velocity, the improved non-dominated sorting genetic algorithm II (NSGA-II) based on orthogonal experimental design method is used for multi-objective optimization problem of the HIS system. The numerical simulations indicate that the improved NSGA-II (INSGA-II) can generate better distributed Pareto solutions than traditional NSGA-II. Furthermore, simulation results indicate that both of the ride comfort and roll stability of the vehicle are improved based on the HIS system optimized by INSGA-II than NSGA-II. Compared with the NSGA-II method, the vehicle ride comfort and roll stability of HIS system optimized by INSGA-II are increased by 17.62% and 8.56% in sinusoidal conditions, respectively.

Nonlinear modeling and experimental characterization of hydraulically interconnected suspension with shim pack and gas-oil emulsion

Although hydraulically interconnected suspension (HIS) have been regarded as one of the promising suspension architectures in recent years, it’s application is still limited due to the many simplifying assumptions in the modeling and analyzing. There has been no published detailed analysis of the effects of shim pack deflection and entrapped gas within oil in HIS system to date. In this study, a nonlinear physical model of HIS is presented with an emphasis on the shim pack deflection and gas-oil emulsion properties and their effects on the stiffness and damping performances. The deflection of the shim pack is formulated based on shim pack deflection theory, and a nonlinear correction function (NCF) is proposed to compensate the errors of the analytical model. The finite element analysis (FEA) method is adopted for parameter identification. Also, the formulation of gas-oil emulsion is derived, in which the variations in the mass density and bulk modulus of the emulsion are formulated as a function of the gas volume fraction. The bench tests for the stiffness and damping characteristics are carried out to validate the developed physical model using the measured strut forces. The measured data and the model are analyzed to highlight the effects of gas-oil emulsion on the stiffness and damping characteristics. Furthermore, the effects of the initial gas volume fraction within oil is discussed under different motion-mode excitation. The results show that the entrapped gas volume changes the compressibility of the emulsion and thus cause significantly reduction to damping forces in a highly nonlinear manner but approximately linear increase to spring forces. It also suggests that the gas volume fraction should be controlled within 4%, so as to reduce the unexpected elastic force caused by gas compression.

A comfort performance improved anti-pitch hydraulically interconnected suspension system with switchable dual accumulators

This paper introduces a novel switchable dual accumulators hydraulically interconnected suspension (SDAHIS) system. The proposed SDAHIS system can improve the ride comfort and anti-pitch performances simultaneously compared with the existing anti-pitch hydraulically interconnected suspension (HIS) system. The SDAHIS system uses a two-way valve for accumulators switching. The developed SDAHIS system achieve the function by controlling the connection of the two switchable accumulators. To comprehensively study the proposed system, the SDAHIS system model and the seven-DOF vehicle model are established. The model of the SDAHIS system is validated by the bench test. The simulation results of the full vehicle with the proposed SDAHIS system show that the anti-pitch and ride comfort performances are simultaneously improved. This research further exploits the potential of the HIS system which can help to better design the suspension system.

Modeling, bench test and ride analysis of a novel energy-harvesting hydraulically interconnected suspension system

A novel energy-harvesting hydraulically interconnected suspension (EH-HIS) is proposed, modeled, built and tested in this paper to enhance riding comfort and road handling performances for vehicles while converting the vibration energy traditionally wasted into usable electricity. A sub-module prototype has been developed to validate the analytical model and tested to study the damping characteristics and energy harvesting capability of the EH-HIS. The studies are performed to compare the dynamic responses and energy harvesting performance of the full-vehicle equipped with the traditional suspension, hydraulically interconnected suspension (HIS), hydro-electromagnetic energy-harvesting shock absorber (HESA) and the proposed EH-HIS, respectively. Bench test results show that the damping coefficient of the EH-HIS ranges from 3608 to 9913 Ns/m. The average harvested power of the sub-module reaches 82 W at the excitation of 2 Hz frequency and 20 mm amplitude, while the full-size SUV equipped with the EH-HIS can obtain 215 W and 525 W average power on D-class road with a driving velocity of 60 km/h and 80 km/h, respectively. Moreover, the vehicle equipped with EH-HIS has better riding comfort on rough terrains and satisfying handling stability compared with other suspension systems. The analysis also indicates that EH-HIS exhibit 60% and 11% improvements in the anti-rolling and anti-pitching performances over the traditional suspension during emergency steering and braking maneuvers.

An LQG Controller Based on Real System Identification for an Active Hydraulically Interconnected Suspension

Rollover prevention is always one of the research hotspots in vehicle design. Active hydraulically interconnected suspension (HIS) is a promising technology to reduce vehicle body roll angle caused by different driving inputs and road conditions. This paper proposes a novel actuator of the active HIS system. The actuator consists of two cylinders, a ball screw, and only one motor. The actuator proposed can reduce the number of motors needed in the system. Meanwhile, forced vibration identification (FVI) is used to identify the transfer function of a half-car physical model and a Kalman state observer is applied to eliminate the influence of sensor noise. The FVI method can eliminate most model uncertainties and hidden variables. Aggressive and moderate optimal linear quadratic Gaussian (LQG) methods are implemented to control the motion of the vehicle body based on the identified transfer function of the physical model. The performance of an active HIS system with an aggressive and moderate LQG controller is compared with that of a passive HIS system. The effectiveness of the LQG controller is validated by simulation and experimental results. Also, the obtained results show that the stabilization speed of the active HIS system is 20% faster than that of the passive HIS system and the roll angle can be reduced up to 55% than that of the passive HIS system.

A Study of a New Bidirectional Pressure-Regulating Valve for Hydraulically Interconnected Suspension Systems

Abstract Due to inevitable inner leakage in hydraulic circuits and structural limits of a hydraulically interconnected suspension (HIS) system, pressure difference between HIS's two independent hydraulic circuits leads to vehicular unbalance under noncornering driving conditions and deteriorates HIS's performance under steering driving conditions. In order to address this problem, a new bidirectional pressure-regulating valve was designed to balance hydraulic pressures in the two HIS's hydraulic circuits under noncornering driving conditions. Moreover, it separates the two hydraulic circuits and enables HIS's antirollover function under cornering driving conditions. Detailed structure and functions of this valve were introduced first. Systematic and computational fluid dynamics (CFD) simulation results show that the gap between the spool and cylinder is of importance to valve's performance. Experimental results validate that the developed valve satisfies all requirements of the HIS. Furthermore, the valve can distinguish steering and nonsteering conditions and enables HIS's function accurately without any pressure shock.

Frequency-Based Modeling of a Vehicle Fitted With Roll-Plane Hydraulically Interconnected Suspension for Ride Comfort and Experimental Validation

A frequency-based modeling approach has been developed for the vehicle fitted with Hydraulically Interconnected Suspension (HIS) system. This frequency-based model has fewer degrees of freedom (DOF) than the reference time-based model. Several physical parameters of HIS system are selected to analytically investigate their effects on several indicators of vehicle roll, pitch and bounce modes, such as roll and pitch angular acceleration, vertical acceleration, and tire ground force. The HIS system parameters are also coordinately tuned and optimized to meet the ride comfort requirement. The full vehicle drop test is conducted for the experimental validation. The analytical results of the proposed model have a good agreement with the measurements.

Vibration Performance Analysis of a Mining Vehicle with Bounce and Pitch Tuned Hydraulically Interconnected Suspension

The current investigations primarily focus on using advanced suspensions to overcome the tradeoff design of ride comfort and handling performance for mining vehicles. It is generally realized by adjusting spring stiffness or damping parameters through active control methods. However, some drawbacks regarding control complexity and uncertain reliability are inevitable for these advanced suspensions. Herein, a novel passive hydraulically interconnected suspension (HIS) system is proposed to achieve an improved ride-handling compromise of mining vehicles. A lumped-mass vehicle model involved with a mechanical–hydraulic coupled system is developed by applying the free-body diagram method. The transfer matrix method is used to derive the impedance of the hydraulic system, and the impedance is integrated to form the equation of motions for a mechanical–hydraulic coupled system. The modal analysis method is employed to obtain the free vibration transmissibilities and force vibration responses under different road excitations. A series of frequency characteristic analyses are presented to evaluate the isolation vibration performance between the mining vehicles with the proposed HIS and the conventional suspension. The analysis results prove that the proposed HIS system can effectively suppress the pitch motion of sprung mass to guarantee the handling performance, and favorably provide soft bounce stiffness to improve the ride comfort. The distribution of dynamic forces between the front and rear wheels is more reasonable, and the vibration decay rate of sprung mass is increased effectively. This research proposes a new suspension design method that can achieve the enhanced cooperative control of bounce and pitch motion modes to improve the ride comfort and handling performance of mining vehicles as an effective passive suspension system.

HIS‐Based Semiactive Suspension Dual‐Frequency‐Range Switching Control to Improve Ride Comfort and Antiroll Performance

The parameter sensitivity analysis of a hydraulically interconnected suspension (HIS) system shows that the sensitivity of the vibration responses in the bounce and roll modes to the hydraulic parameters are complementary. A novel HIS‐based semiactive control method was thereby proposed to improve ride comfort and antiroll performance. In addition, the classic sky‐hook max‐min damping switched strategy provides significant benefits around the body resonance, but otherwise performs similarly to, or sometimes even worse than, passive suspension. Therefore, a dual‐frequency‐range switching strategy, which has optimal max‐min damping in both frequency ranges, was developed for improving the ride comfort in a wider frequency bandwidth. In this study, a 9‐DOF HIS system dynamics model was established, and the hydraulically interconnected subsystem model was validated experimentally. Subsequently, the elastic and damping characteristics of the hydraulically interconnected subsystem, as well as the parameter sensitivity in bounce mode and roll mode, were analyzed. Next, the sensitive parameters were optimized under sinusoidal excitation at various frequencies, and a frequency‐range selector used to determine the excitation frequency range and adjust the shock absorber damping was designed. Finally, simulations in the frequency domain and time domain show that the proposed HIS‐based semiactive dual‐frequency‐range switching control suspension improves the ride comfort in a wider frequency bandwidth and enhances the antiroll performance in the transient and steady steering process.

Switched anti-roll control design for hydraulically interconnected suspension system with time delay

To improve a vehicle's anti-roll performance while consuming less energy, an active/passive dual-mode switched control method based on a hydraulically interconnected suspension (HIS) is proposed. This method has two key components as follows: modelling the “mechanical-liquid-gas” coupled dynamic system consisting of hydraulic cylinders, a hydraulic pump and accumulators; and robustly controlling a time-delayed system with uncertain model and lag time. In this study, the nonlinear characteristics of the underlying actuators were considered, and a four degrees-of-freedom (4DOF) roll-plane half-car model was employed. The backstepping algorithm was adopted to maintain the body in the desired posture. Subsequently, a modified Smith predictor and a Taylor expansion of lateral acceleration were applied simultaneously to compensate for the time delay. Finally, simulations with uncertain parameters and lag time were performed. The results indicate that the proposed method is robust in the case of an uncertain control system and can effectively improve the vehicle's anti-roll performance.

Switched anti-roll control design for hydraulically interconnected suspension system with time delay

To improve a vehicle's anti-roll performance while consuming less energy, an active/passive dual-mode switched control method based on a hydraulically interconnected suspension (HIS) is proposed. This method has two key components as follows: modelling the “mechanical-liquid-gas” coupled dynamic system consisting of hydraulic cylinders, a hydraulic pump and accumulators; and robustly controlling a time-delayed system with uncertain model and lag time. In this study, the nonlinear characteristics of the underlying actuators were considered, and a four degrees-of-freedom (4DOF) roll-plane half-car model was employed. The backstepping algorithm was adopted to maintain the body in the desired posture. Subsequently, a modified Smith predictor and a Taylor expansion of lateral acceleration were applied simultaneously to compensate for the time delay. Finally, simulations with uncertain parameters and lag time were performed. The results indicate that the proposed method is robust in the case of an uncertain control system and can effectively improve the vehicle's anti-roll performance.

Enhanced Lateral and Roll Stability Study for a Two-Axle Bus via Hydraulically Interconnected Suspension Tuning

Enhanced Lateral and Roll Stability Study for a Two-Axle Bus via Hydraulically Interconnected Suspension Tuning

Dynamic Characteristics Analysis of Vehicle Incorporating Hydraulically Interconnected Suspension System with Dual Accumulators

A novel roll‐resistant hydraulically interconnected suspension with dual accumulators on each fluid circuit (DHIS) is proposed and dynamic characteristics of vehicle incorporating DHIS subsystem are studied in this paper. A 10‐degrees‐of‐freedom (DOFs) vehicle model coupled with DHIS subsystem is established and validated. Four physical parameters of DHIS subsystems which are crucial to vehicle responses are selected with prescribed variation ranges to explore their relationships with the vehicle performance. Simulations of vehicle conducting sine‐wave steering maneuvers are carried out to evaluate handling performance with roll angle and vertical tyre force for DHIS subsystem with the parameters varying, compared with the results for vehicle with the original spring‐damper suspension and conventional hydraulically interconnected suspension (HIS). On the other hand, ride comfort performance indicated by total weighted root mean square accelerations at the center of gravity is studied when vehicle is excited by three different types of road pavements when the four parameters vary in the prescribed ranges. Simulation results are compared to investigate the special merits of DHIS subsystem, and the parameters that influence the handling performance and ride comfort most are identified. Overall, the DHIS subsystem can effectively enhance the vehicle handling performance compared with the original spring‐damper suspension, and it can also benefit much to the ride comfort in contrast to the HIS subsystem.

A study of the hydraulically interconnected inerter-spring-damper suspension system

ABSTRACTA new hydraulically interconnected inerter-spring-damper suspension (HIISDS) is developed to compensate for traditional passive suspension limitations, such as the imbalance of ride performance and handling stability. In this article, the structure and mechanism of the HIISDS system is briefly introduced at first, and compiled with hydraulically interconnected suspension (HIS) mode and hydraulic inerter-spring-damper (ISD) suspension mode. A vehicle dynamic model of HIISDS system is then derived through these two suspension modes by using Matlab/Simulink. Two different road excitations are used to validate the adaption of the two suspension modes. The effectiveness of HIISDS has been verified by simulation results, in which vehicle ride comfort and handling stability are effectively coordinated through the HIISDS model switch. Finally, an HIISDS suspension prototype is designed based on Simulink results, and test results reconfirm the partial performances of HIISDS modes effectively.

Dynamics analysis and design methodology of roll-resistant hydraulically interconnected suspensions for tri-axle straight trucks

A new hydraulically interconnected suspension (HIS) system is proposed to enhance the roll dynamics of the tri-axle straight trucks. The impedance of the hydraulic system is derived with impedance transfer matrix method, and integrated to establish the equations of motion of the mechanical and hydraulic coupling system. Based on the obtained equations, the additional mode stiffness/damping of the vehicle body and wheel state forces are explicitly described with the physical parameters of the hydraulic system. The obtained results indicate that the proposed HIS system can be able to independently enhance the mode stiffness/damping, in which the additional bounce/pitch and roll/warp mode stiffness are determined by the difference and summation of the top and the corresponding bottom piston surface area, respectively. The mode damping is caused by the direction and roll damper valves, simultaneously. The later valves alter the mode damping like the accumulators change the mode stiffness. The comparison of dynamic responses between the trucks with the conventional suspension and the HIS system shows that the HIS system can effectively suppress the roll motion of the truck body and favorably reduce the warp mode force for the wheel stations. Finally, the loss coefficients of the damper valves are tuned in terms of dimensionless factors to handle the compromising indices based on the dynamic responses.

A Piecewise Hysteresis Model for a Damper of HIS System

A damper of the hydraulically interconnected suspension (HIS) system, as a quarter HIS, is prototyped and its damping characteristic is tested to characterize the damping property. The force-velocity characteristic of the prototype is analyzed based on a set of testing results and accordingly a piecewise hysteresis model for the damper is proposed. The proposed equivalent parametric model consists of two parts: hysteresis model in low speed region and saturation model in high speed region which are used to describe the hysteresis phenomenon in low speed and nonhysteresis phenomenon in high speed, respectively. The parameters of the model are identified based on genetic algorithm by setting the constraints of parameters according to their physical significances and the corresponding testing results. The advantages of the model are highlighted by comparing to the nonhysteresis model and the permanent hysteresis model. The numerical simulation results are compared with the testing results to validate the accuracy and effectiveness of the proposed model. Finally, to further verify the proposed model’s wide applicability under different excitation conditions, its results are compared to the testing results in three-dimensional space. The research in this paper is significant for the dynamic analysis of the HIS vehicle.

Steady-state response of fluid-structure interactions in hydraulic piping system of passive interconnected suspensions

Pressure changes in the liquid-filled fluid circuit of a hydraulically interconnected suspension (HIS) system can induce vibrations of the whole pipeline and the associated structure, and hence become a source of structural noise which degrades ride comfort. This paper presents a numerical and experimental investigation into the vibration of the hydraulic piping system of a passive interconnected suspension. The transfer matrix method (TMM) is used to develop a mathematical model, which consists of various pipe sections, hose sections, concentrated masses, spring supports, elbows, damper valves, and accumulators. Laboratory experiments are performed on two liquid-filled piping systems. The measured steady-state responses of the hydraulic circuits are compared with those obtained from numerical simulations of the developed model. It is found that the developed model of the hydraulic system has a reasonable accuracy in the frequency range of interest, and thus can be employed to optimise the design of the hydraulic system.

Steady-state response of fluid-structure interactions in hydraulic piping system of passive interconnected suspensions

Pressure changes in the liquid-filled fluid circuit of a hydraulically interconnected suspension (HIS) system can induce vibrations of the whole pipeline and the associated structure, and hence become a source of structural noise which degrades ride comfort. This paper presents a numerical and experimental investigation into the vibration of the hydraulic piping system of a passive interconnected suspension. The transfer matrix method (TMM) is used to develop a mathematical model, which consists of various pipe sections, hose sections, concentrated masses, spring supports, elbows, damper valves, and accumulators. Laboratory experiments are performed on two liquid-filled piping systems. The measured steady-state responses of the hydraulic circuits are compared with those obtained from numerical simulations of the developed model. It is found that the developed model of the hydraulic system has a reasonable accuracy in the frequency range of interest, and thus can be employed to optimise the design of the hydraulic system.

Characteristic Analysis of Roll and Pitch Independently Controlled Hydraulically Interconnected Suspension

ABSTRACT This paper presents the modeling and characteristic analysis of roll-plane and pitch-plane combined Hydraulically Interconnected Suspension (HIS) system. Vehicle dynamic analysis is carried out with four different configurations for comparison. They are: 1) vehicle with spring-damper only, 2) vehicle with roll-plane HIS, 3) vehicle with pitch-plane HIS and 4) vehicle with roll and pitch combined HIS. The modal analysis shows the unique modes-decoupling property of HIS system. The roll-plane HIS increases roll stiffness only without affecting other modes, and similarly pitch-plane HIS increases the pitch stiffness only with minimum influence on other modes. When roll and pitch plane HIS are integrated, the vehicle ride comfort and handling stability can be improved simultaneously without compromise. A detailed analysis and discussion of the results are provided to conclude the paper. CITATION: Xu, G. and Zhang, N., Characteristic Analysis of Roll and Pitch Independently Controlled Hydraulically Interconnected Suspension,