Hydraulic Damper Research Articles

Design and Preliminary Testing of a Novel Variable-Damping Prosthetic Knee

This article proposes a variable-damping prosthetic knee (ReKnee) with a novel hydraulic damper, and the intelligent control system is proposed. The LSTM network is proposed to identify the locomotion pattern under five road conditions. Predictive control is first applied to the hydraulic damping control for prosthetic knee. Prototype experiments are carried out to verify the performance of the control system. The experiment results show that LSTM possesses better accuracy and robustness than the traditional RNN network and other shallow machine learning algorithms, and NNPC damping control improves the gait symmetry compared to fuzzy logic control with decreasing in the range of 5.75–19.27% of the SI values when walking speed varies. It is demonstrated that the ReKnee can make a good performance on enhancing the accuracy of angle tracking and the approximation of normal gait characteristics.

Effect of mounting and fluid parameters on dynamic damping characteristics of a hydraulic damper

A mathematical model describing the dynamic damping characteristics (DDC) of a high-speed rail hydraulic damper is built and experimentally validated, followed parameter effect simulation on DDC of the damper is conducted by using the model. Simulation results show that the change of rubber attachment stiffness and entrapped air ratio would have apparent influence on Force-displacement characteristics of the damper, i.e., increasing of rubber attachment stiffness k0 would increase the main damping indices, but increasing of entrapped air ratio ε would decrease all of the dynamic damping characteristic indices apparently, so this implies that air entrapment of the fluid would apparently decrease the elasticity modulus of the fluid and weaken the dynamic characteristics of the damper. The established damper model and obtained result would be useful in the context of high-speed train research and design.

Numerical study on a rotational hydraulic damper with variable damping coefficient

The rotational hydraulic damper has advantages in the design and control of rotational machines. This paper presents a novel hydraulic rotational damper with the characteristic of adjusting the damping coefficient. It is composed of a shell, a gap, a rotor shaft, sliding vanes, a valve, and a motor, just like a combination of a sliding pump system and a valve driven by a motor. A new cam ring slot designed to guide the radial motion of sliding vanes could reduce friction resistance force, which will also benefit the design of the sliding pump. The damping coefficient model of this damper is established based on dynamic analysis. Series of numerical simulations validate the impact of factors on the damping coefficient. Frictional resistances have little influence on the damping coefficient during most conditions. The total coefficient is positively correlative with the angular velocity and the valve angle. Therefore, changing the valve angle according to the rotor shaft’s angular speed could adjust the damping coefficient.

Experimental investigation into the role of nonlinear suspension behaviour in limiting feedforward road noise cancellation

Feedforward control of road noise in cars is limited by the difficulty of finding reference signals that have adequate coherence with the sound at the passenger head positions. The dynamics of car suspensions are known to be nonlinear and could therefore restrict the coherence between reference and error sensors and limit the performance of linear feedforward road noise control systems. This paper presents two sets of experiments that investigate nonlinear vibration transmission through a car suspension and its implications for road noise control. The first experiment was conducted on an electric car; an analysis of the maximum theoretical cancellation that can be achieved with different sets of reference signals is presented and the influence of ‘smooth’ and ‘rough’ road surfaces is investigated. In the second set of experiments, components from the car’s suspension systems are tested in a laboratory. The experiments show that the car’s hydraulic dampers are strongly nonlinear at low audio frequencies, and suggest that they limit the cancellation that can be achieved with a linear controller.

Modelling, validation and parameter sensitivity of regenerative hydraulic-electric shock absorber

PurposeSuspension is a significantly important component for automotive and railway vehicles. Regenerative hydraulic-electric shock absorbers (RHSA) have been proposed for the purpose of attenuating vibration of vehicle suspension, and also recover kinetic energy originated from vehicle vibration that is conventionally dissipated by hydraulic dampers. To advance the technology, the paper aims to present an RHSA system for heavy-duty and railway vehicles and create a dynamic modelling to discuss on the development process of RHSA model.Design/methodology/approachFirst, the development of RHSA dynamic model can be resolved into three stage models (an ideal one, a second one with an added accumulator and a third one that considers both accumulator and system losses) to comprehensively evaluate the RHSA's characterisation. Second, a prototype is fabricated for testing and the results meet desired agreements between simulation and measurement. Finally, the study of key parameters is carried out to investigate the influences of hydraulic-cylinder size, hydraulic-motor displacement and accumulator pre-charged pressure on the RHSA system.FindingsThe findings of sensitivity analysis indicate that the component design can satisfy the damping characteristics and power performance required for heavy-duty vehicle, freight wagon and typical passenger train. The results also show that reducing the losses is highly beneficial for saving suspension energy, improving system reliability and increasing power-conversion efficiency.Originality/valueThe paper presents a more detailed method for the development and analysis of a RHSA. Compared with the typical shock absorbers, RHSA can also recover the vibration energy dissipated by suspension.

Control of a reversible electric machine included in the vehicle suspension

The relevance of the work is due to the constantly growing requirements for the ride comfort of automobiles. The purpose of the study is a rational choice and combination of principles for constructing an algorithm for controlling an electric machine, replacing a hydraulic damper in the design of a vehicle’s suspension system. The study of the behavior of suspension, depending on the applied control algorithms, was carried out by the method of mathematical modeling. In this work, the control of the suspension of one wheel was considered. The angular and longitudinal oscillations of the body were not the subject of this study. In this regard, the applied design scheme is two-mass. The positive and negative aspects of various principles for calculating the target force generated by an electric machine are considered, and an algorithm for calculating the magnetic flux and armature current of an electric machine necessary for the implementation of the target force under various conditions is developed. It is shown that the calculation of the target force should be based on a combination of several principles, since this allows significant expanding of the suspension operating conditions range.

A Study on the Capacity Spectrum Seismic Design Method for Building with Self-centering Hydraulic Damper

In order to determine the reasonable mechanic parameters of the damper on the passive energy dissipation structure, which combined with the basic principle of Chinese seismic design code and capability spectrum. It is important for the self-centering hydraulic damper to fully consider their additional stiffness and the additional damping ratio. Then determining the parameters and quantities of the damper through the performance limit of the story drift. In this paper, taking a six-story steel frame structure as an example. The damper parameters of passive energy structure are designed and the nonlinear response history analysis is used in the OpenSees. The calculation and example analysis shows that the performance-based seismic method is feasible.

A Magnetoelectric Hybrid Hydraulic Damper for the Mining Robot Suspension System

In order to improve the damping and controllability of the mining robot suspension system, a new magnetoelectric hybrid suspension hydraulic damper, which is a semiactive suspension damper, is proposed based on the traditional hydraulic damper by introducing the magnetic-electric hybrid suspension structure. The structure and working principle of the damper are introduced, respectively, and the mathematical models of the equivalent stiffness and equivalent damping of the system are calculated by the magnetic circuit method and the oil circuit method, while AMESim/Simulink cosimulation is carried out. In order to test the damping performance, a prototype of the magnetoelectric hybrid suspension hydraulic damper was fabricated. The results show that the vibration displacement amplitude can be reduced by 20% and the vibration acceleration amplitude can be reduced by 10% by adjusting the stiffness and damping of the system due to the magnetoelectric hybrid suspension structure. Moreover, the experimental results are consistent with the simulation results, which verify the effectiveness and superiority of this type of damper.

Numerical calculation and model experiment of a novel external buoy type wave energy converter for navigation lighted buoys numerical study of a novel wave energy converter

A novel external buoy type wave energy device with hydraulic conversion system used for navigation lighted buoys, named floating external double buoys wave energy device, is put forward and investigated by numerical calculations and model experiments. The hydrodynamic performance of the device under regular waves is numerically calculated based on linear potential flow theory and boundary element method. The generalized modal method is used to solve the hydrodynamic problems of multi-buoy with hinged constraints. The model experiments are carried out in a 2D wave tank with a depth of 0.9 m. The wave height is set to 1/40 of the wavelength. The influence of wave period and damping loads on the hydrodynamic performance of the device is tested. The results of numerical calculations and model experiments have shown that the appropriate selection of hydraulic damping coefficient is of great significance to improve the capture width ratio of the device, and this device has good capture performance in a certain wave range, and it is expected to effectively solve the problem of continuous power supply for middle and small types of navigation lighted buoys.

Realising embedded stiffness in hydraulic implementations of stiffness-damping-inertance configurations

The performance benefits of passive vibration suppression with network configurations consisting of stiffness, damping and inertance elements have been demonstrated for a wide range of mechanical systems. Considering physical implementations of these beneficial network configurations, hydraulic realisations have the advantages of durability and simplicity for integration with existing hydraulic dampers. Such designs are exemplified by fluid inerters and fluid-inerter-damper devices. However, in contrast to the convenience of realising inertance and damping elements, realising ‘embedded’ stiffness is very challenging. We use ‘embedded’ to refer to a network element, which is not purely in series or in parallel with the remainder of the network but instead lies within the network layout. In this work, a setup using a rubber membrane to realise such embedded stiffness is proposed, together with a procedure for hydraulic implementations of any stiffness-damping-inertance configurations. The nonlinear properties of the embedded stiffness due to rubber membrane properties are then investigated both theoretically and experimentally. In addition, the effectiveness of both the membrane setup and the design procedure are demonstrated via a case study of suspension design for passenger vehicle ride comfort enhancement.

Structural dynamic response of a locomotive hydraulic damper with welding imperfections

Railway vehicle hydraulic dampers are usually subject to premature structural failures, so it is meaningful to investigate the dynamic response of its welded main structure. FEA modelling of the welded rod-and-attachment assembly with imperfections of a Chinese electric locomotive axle-box hydraulic damper is performed, and load spectra of the axle-box hydraulic damper both under nominal and actual in-service conditions are obtained. Structural dynamics response analysis of the welded rod-and-attachment assembly of the damper is then conducted by using the FEA model and load spectra, and demonstrates that all of the maximum dynamic stresses have increased by 40% or so when using the actual in-service load spectra regardless of the weld joint condition, if the weld joint is with imperfection of misalignment of rod and attachment, the maximum dynamic stress has increased by 41.46%. Therefore, railway hydraulic dampers are usually subject to actual in-service load spectra instead of the nominal load spectra used in the design process, if the damper also has got welding imperfections, the damper would be readily subject to premature failures, this is why many current railway vehicle hydraulic dampers are still subject to premature failures despite with ‘perfect’ designs. The FEA model, the structural dynamic response analysis approach and results obtained in this work would be instructive in improving damper structure design, welding quality control and inspection.

Performance enhancement of pumped storage units for system frequency support based on a novel small signal model

The fast and stable regulation of pumped storage is a basic guarantee for supporting various scenarios of renewable energy system. The operator pursues sensitive tracking performance, while underestimates the dynamic characteristics of hydraulic system and damping characteristics of pumped storage unit (PSU). These may aggravate the wear-tear of PSU operation, and decrease the frequency stability of power system. Therefore, a systematical study of improving overall regulation performance is conducted by applying PSU modeling, co-optimization and operation evaluation. First, the novel small signal model is proposed and the high-order hydraulic damping model is further derived. Apart from the ultra-low frequency oscillation mode, a new frequency oscillation mode caused by surge tanks is captured. Second, the co-optimization strategy is presented to coordinate the stability-tracking conflict. And then a comprehensive evaluation model, integrating 14 indicators is conducted to quantify the PSU performance and its contribution to power system, driving the favorable decision making of operators. Compared with the original scheme, the overall performance of PSU is improved by 20.76%, at the cost of 10.88% tracking capacity. The comparison of three measures including 12 scenarios verifies the competitive advantage of co-optimization strategy in multi-machine system. This paper supplies a novel tool for performance enhancement of PSU. It may have potential value in the stability of renewable energy systems with multiple hydropower units.

Design of a Semi-Active Prosthetic Knee for Transfemoral Amputees: Gait Symmetry Research by Simulation

The key technology of the prosthetic knee is to simulate the torque and angle of the biological knee. In this work, we proposed a novel prosthetic knee operated in semi-active mode. The structure with ball-screw driven by the motor and the passive hydraulic damping cylinder was presented. A four-bar linkage was adapted to track the instantaneous center motion of human knee. The mathematical models of hydraulic cylinder damping and active torque were established to simulate the knee torque and angle. The results show that the knee torque symmetry index is smaller than 10% in the whole gait. The knee angle symmetry index value is 34.7% in stance phase and 11.5% in swing phase. The angle in swing phase is closer to the intact knee. The semi-active prosthetic knee could provide similar torque and angle of the biological knee in the simulation. It has shown good potential in improving the gait symmetry of the transfemoral amputee.

Математичне моделювання роботи гідравлічного демпфера у складі шарнірного механізму протеза колінного суглоба людини

В даній роботі досліджено роботу гідравлічного демпфера у складі протеза колінного суглоба людини в продовж тривалої роботи, вплив на неї конструктив параметрів, різних умов експлуатації та властивостей робочого середовища. Проведено перевірку правильності математичного моделювання робочих процесів у MATLAB Simscape.
 In the article the work of the hydraulic damper in the prosthesis of the human knee joint was researched. The research includes the impact on work processes of the design parameters, different operating conditions and properties of the working environment. The correctness of mathematical modeling of work processes in MATLAB Simscape was checked.

A study on the wear allowance of a railway vehicle hydraulic damper

Railway vehicle hydraulic dampers are usually subject to wear-induced premature failures, so it is meaningful to evaluate the wear allowance of the hydraulic damper. Mathematical modelling of damping characteristics of a railway vehicle hydraulic damper under wear conditions is carried out, the model describes the functions of main damping characteristics indices vs. inner tube wear M1 and rod wear M2 . Simulation is then performed using the model, and indicates that increase of M1 would lead to significant drop of the maximum extension damping force, fading of the damping coefficient and significant rising of the damping force asymmetry rate, but the maximum compression damping force keeps to be constant, while increase of M2 would lead to significant drop of almost all of the indices except for the asymmetry rate. A wear allowance line for the damper is finally obtained when both of M1 and M2 work in real situations, the area enclosed by the wear allowance line and two axles is a safe area, any dot with a combination of M1 and M2 outside the safe area means the damper has exceeded its wear allowance and should be maintained or replaced. The mathematical model and the wear allowance line obtained in this work can be used for health status evaluation and design optimization of railway hydraulic dampers.

Structural parameter effect of a railway hydraulic damper on its dynamic damping characteristics

A parametric dynamic damping characteristics model, which includes the dynamic force equilibrium equation, the flow continuity equation, the flow losses model, the comprehensive stiffness model and the valve dynamics, is established and validated by experiments. Numerical simulation of structural parameter effect on dynamic damping characteristics of the hydraulic damper is performed. The analyses show that increase of inner tube height would cause drop of dynamic stiffness of the damper, however, increase of piston diameter would lead to obvious increase of dynamic stiffness and dynamic damping coefficient, therefore, the biggest piston diameter under constraint is usually used in engineering; in addition, fluid leakage would apparently decrease damping capability of the damper, increase of leakage coefficient would lead to significant drop of dynamic stiffness and dynamic damping coefficient, and also remarkable damping force lag. The obtained full parametric model and analysis result in this work would be instructive and meaningful in further railway vehicle dynamics research and design procedures.

Modeling and dynamic analysis of hydraulic damping rubber mount for cab under larger amplitude excitation

In order to improve the ride comfort of the cab of construction machinery and reduce the harm of vibration to the driver, the lumped parameter model of passive hydraulic damping rubber mount (PHDRM) considering the nonlinearity of multi-inertial tracks is first established. Then the overall FE (finite element) fluid-solid coupling model of the vibration isolator is proposed by using ABAQUS combined simulation mode in this paper. Meanwhile, Combined with bidirectional strong coupling algorithm, the parameters of the rubber main spring and inertial track are identified respectively. Also, the dynamic characteristic experiments of the PHDRM samples are carried out. The experiment results show that the analytical solution and FE modeling method of the HDRM system are reliable and accurate under larger amplitude excitation. On the basis of this, the effects of the rubber main spring and inertial track of PHDRM on low frequency dynamic characteristics under larger amplitude excitation are respectively analyzed and discussed. It provides practical reference value for nonlinear modeling method research and dynaimc performance analysis of PHDRM with complex structure further.

Application of semi-active yaw dampers for the improvement of the stability of high-speed rail vehicles: mathematical models and numerical simulation

The aim of this work is to introduce a new concept for a hydraulic semi-active yaw damper (SAYD) for the improvement of the stability of a high-speed rail vehicle. This concept represents a further elaboration of Secondary Yaw Control but envisages the use of semi-active hydraulic dampers instead of full-active electromechanical dampers, simplifying the design of the system and facilitating the design of a safe and fault tolerant device. Two control algorithms are proposed for the semi-active damper: maximum power point tracking and skyhook with Karnopp approximation. A multi-physics model of the SAYD is introduced and used in co-simulation with a multi-body model of a high-speed vehicle. Using these models, numerical simulations are performed to assess the behaviour of the semi-active damper in terms of improving the running stability of the rail vehicle at very high speed, showing that the use of the SAYD in combination with any of the two control strategies considered allows to improve substantially the stability of the vehicle. The results of experimental investigations performed in the project will be reported in a companion paper.

Wear Mechanism and Failure Analysis of A High-speed Train Hydraulic Damper Using CFD Approach

To evaluate wear-induced hydraulic damper failures, wear mechanism of a Chinese CRH train hydraulic damper by invaded dust and sand particles under vibration conditions is firstly analysed, CFD modelling of the working chamber of the damper is then carried out and fluid dynamics analysis of the damper under different vibration speed input conditions is performed. The CFD results demonstrate that under wear conditions both the fluid discharge speed and produced pressure would drop significantly, the maximum fluid discharge speed and pressure are far smaller than that under non-wear conditions, the damping force would have a maximum decrease of 62.3%. The wear mechanism, CFD model established and analysis results obtained in this study can be used for further railway hydraulic damper evaluation and optimal designs.

Modelling and Experimental Validation of the Dynamic Damping Characteristics of A High-speed Train Hydraulic Damper

Aiming to understand the effects of damper parameter on vehicle system dynamics in the context of railway vehicle system design, a full parametric damper model, which includes the complete valve system dynamics, the dynamic force equilibrium equation, the flow continuity equation, the flow losses model and the comprehensive stiffness model, is established in this work. Both numerical simulation using the established damper model and bench test of dynamic performance of the damper are carried out, the comparison shows that the maximum relative error between simulation and bench test is only 2.6%, in addition, the rates of asymmetry are near and both small. Therefore, the simulation result agrees well with the test result, the established full parameter damper model is validated, the model would be accurate in predicting damper parameter effects in further high-speed train dynamics research and vehicle design.