Search results

The shock absorber is an important component of vehicle suspension that attenuates the vehicle vibration. Its running state directly affects the performance of the vehicle suspension. The purpose of this paper is to quantitatively study the relationship between damping characteristics and air chamber and oil properties in single-tube pneumatic shock absorber.

Combined with the principle of fluid dynamics and hydraulic transmission technology, the rebound stroke and compression stroke mathematical models, and damping characteristics simulation model are established to investigate the effect of the air chamber and oil property on damping characteristics.

Research results show that the initial pressure of the air chamber is the key parameter which influences the damping characteristics of the shock absorber. The change of the initial pressure has more impact on damping force, and less impact on the speed characteristic; the initial volume of the air chamber almost has no effect on the damping characteristics. The density and viscosity of the oil have certain influence on the damping characteristics. Therefore, selecting suitable damping oil is very important.

Using Matlab/Simulink software to build simulation models, its results are very accurate. The conclusions can provide a theoretical reference for the structure design of a single-tube pneumatic shock absorber.

This paper aims to design an active shock absorber scheme for use in conjunction with a passive shock absorber to suppress the horizontal vibration of elevator cars in a smaller range and shorter time. The developed active shock absorber will also improve the safety and comfort of passengers driving in ultra-high-speed elevators.

A six-degree of freedom dynamic model is established according to the position and condition of the car. Then the active shock absorber and disturbance compensation-based adaptive control scheme are designed and simulated in MATLAB/Simulink. The results are analysed and compared with the traditional shock absorber.

The results show that, compared with traditional spring-based passive damping systems, the designed active shock absorber can reduce vibration displacement by 60%, peak acceleration by 50% and oscillation time by 2/3 and is more robust to different spring stiffness, damping coefficient and load.

The developed active shock absorber and its control algorithm can significantly reduce vibration amplitude and converged time. It can also adjust the damping strength according to the actual load of the elevator car, which is more suitable for high-speed elevators.

In order to improve the ride comfort of vehicle suspension, this paper first proposed a shock absorber with four-stage adjustable damping forces. The purpose of this paper is to validate its modeling and characteristics, indicator diagrams and velocity diagrams, which are the main research points.

In order to validate the fluid flow modeling, a series of mathematical modeling is established and solved by using Matlab/Simulink. An experiment rig based on electro-hydraulic loading servo system is designed to test the prototype. Finally, indicator diagram and velocity diagram are obtained and compared both in simulation and experiments.

Results indicate that at the same damping position, damping force will increase with the rise of rod’s velocity: if the rod’s velocity is fixed, the damping force changes apparently by altering the damping position. The shock absorber is softest at damping position 1, and it is hardest at damping position 4; although there is no any badly empty stroke and skewness in indicator diagram by simulation, a temporary empty stroke happens at maximum displacement of piston rob, both in rebound and compression strokes.

Compared with results of the simulation and experiments, the design of a four-stage damping adjustable shock absorber (FDASA) is validated correctly in application, and may improve the overall dynamic performance of vehicle.

This paper is mainly focused on the design and testing of an FDASA, which may obtain four-stages damping characteristics, that totally has a vital importance to improve the performance of vehicle suspension.

Suspension 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.

First, 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.

The 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.

The 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.

A local equivalent linearization methodology is proposed to simulate non‐linear shock absorbers and dual‐phase dampers in the convenient frequency domain. The methodology based on principle of energy similarity, characterizes the non‐linear dual‐phase dampers via an array of local damping constants as function of local excitation frequency and amplitude, response, and type of non‐linearity. The non‐linear behaviour of the dual‐phase dampers can thus be predicted quite accurately in the entire frequency range. The frequency response characteristics of a vehicle model employing non‐linear dual‐phase dampers, evaluated using local linearization algorithm, are compared to those of the non‐linear system, established via numerical integration, to demonstrate the effectiveness of the algorithm. An error analysis is performed to quantify the maximum error between the damping forces generated by non‐linear and locally linear simulations. The influence of damper parameters on the ride improvement potentials of dual‐phase dampers is further evaluated using the proposed methodology and discussed.

THE object of the trip was to ascertain German experience of aeroplane under‐carriages and their methods of design, testing and manufacturing them. Inquiries were also made about their methods of testing wheels for strength.

The purpose of this paper is to demonstrate the application of Six Sigma/design of experiments (DOE) hybrid framework for improving damping force (DF) generation process in a shock absorber assembly unit.

The study adopted a case study research method with single case (holistic) design. This research design was found to be appropriate for testing the projected framework for integrating DOE approaches within Six Sigma define-measure-analyze-improve-control (DMAIC) cycle. In the proposed framework, Shainin’s component search technique (CST) was deployed at the “analysis” phase of DMAIC for the first stage filtering of process parameters, followed by the use of Taguchi orthogonal arrays (OA) at the “improve” phase for identifying the optimal setting of the parameters.

The application of Shanin CST facilitated in ascertaining that assembly component (piston with rebound stopper) was causing the variation and not the assembly process. Further, the use of Taguchi OA at the improve phase allowed the collection of necessary data to determine the significant piston parameters with minimum experimentation (eight experimental runs in this case as opposed to the expected 64) and analysis of variance on the collected data facilitated the selection of parameter settings to optimize the “critical to quality”, i.e. rebound DF.

This study provided a stimulus for wider application of integrated DOE approaches by the engineering community in the problem solving and the identification of parameters responsible for poor performance of the process.

For Marx, workers would be the prime motivators for a fundamental change toward a new economic system. They produce the output of the economy but have little control over their working environment, the product or the direction that economic change would take. They are alienated although often without a consciousness of the systemic source of their alienation. The social system results in workers having to work longer than necessary to reproduce their socially defined needs as workers. The surplus product, taking the form of surplus value, generates property income in the form of rents, interest and profit. Those holding ownership of the means of production claim the results of the workers' labour. The existence of wage labour creates a necessary condition for means of production becoming capital. This concept of capital is different from both chattels and personal property. Stander notes such a difference between these two and capital, but he does not note the difference between means of production and capital which seem to be identical for him.

The purpose of this paper is to investigate payout smoothing in two emerging markets – China and Taiwan. The authors conduct a comparative study of two emerging market economies that have common cultural and historical characteristics but have experienced different government systems and different approach to the market-based system.

The authors collect firm-level data from Standard and Poor's Compustat Global database, which covers 5,298 public firms in China and Taiwan during the period 1996–2015, and use a variance decomposition methodology to estimate the smoothness of corporate payout in a common empirical framework that includes net income, and debt and investment policies.

Overall, the empirical findings support recently proposed theories of joint determination of corporate payout behavior with debt and investment policies. The authors find that debt and investment policies absorb the majority of shocks to net income, and that debt policy is the main shock absorber. Furthermore, the authors show that firms in China follow a similar strategy with their counterparts in United States and smooth their payout. In contrast to firms in China and US, the payout of the Taiwanese firms is relatively highly sensitive to net income shocks.

To the best of authors’ knowledge, this study is the first to use a joint model to empirically investigate the extent to which debt and investment policies are used to keep corporate payout smooth in emerging markets.