The Nonlinear Behaviour of a MacPherson Strut Wheel Suspension

Three nonlinear models of a MacPherson strut wheel suspension have been studied. The nonlinearities considered are due to the nonlinear geometrical effects in the mechanism, the amplitude limitation due to the bumpstop, the progressive stiffness of the bumpstop and the different damping coefficients for the shock absorber in bump and rebound. The models have been derived according to physical parameter values of. the MacPherson strut wheel suspension of the car SAAB 9.000. The most suitable model was further studied with special attention to nonlinear phenomena. For harmonic forcing the system had phenomena such as multiple solutions and subharmonics. For some parameter values the solution was very sensitive to changes in the integration tolerances in the numerical integration routine. No chaotic steady state solutions were found for the parameter values studied.     

Contributors to this issue

Contributors to this issue     

重新审视砂再生

过去10年,美国环境保护机构已经对铸造工厂施加了更大的压力,以迫使他们减少废弃物的排出. 在金属铸造业,废砂占到整个铸造业废弃物总量的近70%.每生产1 t铸件,大约平均要用363kg砂,这就意味美国铸造工业每年大概要产出700～800万t废砂.     

Intraunion conflict: the changing marine engineer

In this paper we describe the shift in membership of the Marine Engineers' Beneficial Association (MEBA), the major us marine engneer labour union, and the problems asssociated with this change. The problematic nature of this change is examined by describing the changing membership of MEBA: demonstrating a relationship between the occupational socialzation of members prior to entering the union and their behaviour as members; and by explaining how the actions of MEBA led to the creation of the problem and the policy it implemented to alleviate the sitution. Data are gathared from participant observation, interviews with union officials and marine engineers. Implications for the formation of sentient groups are discussed.     

Experimental validation of a mathematical model of a reed-valve reciprocating air compressor from an automotive-braking system

Mathematical simulation is the process of designing a model of a real system and then conducting experiments with the simulation to understand the system’s behavior. Mathematical simulation is widely used for investigating and designing compressors, and with a minimal number of simplifying assumptions, mathematical models can be used in conjunction with modern computing tools to solve complicated problems. A considerable amount of previous research has focused on the mathematical modeling of reciprocating air compressors used in automotive braking. The aim of the present work was to experimentally validate the mathematical model for such compressors. We present a simplified and effective mathematical model for estimating compressor performance, and this model can easily be executed using personal computers. Parameters such as compressor speed, discharge pressure and clearance volume were evaluated in terms of their effect on the thermodynamic behavior of compressors. The model can predict cylinder pressure, cylinder volume, cylinder temperature, valve lift and resultant torque at different crank angles; it can also predict the free air delivered and the indicated power of the compressor. Therefore, the model has been validated using experimental results.     

Method for analyzing epicyclic gearboxes

This paper presents a method for analyzing epicyclic gearboxes by evaluating the speeds, torques and power of the external elements in epicyclic gear mechanisms, as well as the total ratios of the gear box. The method is based on the equations that describe each epicyclic gear mechanism and rules that assign appropriate codes to the external elements. The method emphasizes how power flows are transmitted through the epicyclic gears, as well as power losses. Analysis of an epicyclic gear box is performed to illustrate the proposed method.     

Four-wheel vehicle kinematic and geometric constraints for definition of tire slip angle

When considering vehicle safety, tires and all that they represent are a fundamental topic. Tire studies have received a considerable amount of attention from the research community because their improvement has a direct and strong impact on vehicle handling and braking. Within this eld of analysis lies an important behavioral feature: the tire slip angle, which is a consequence of lateral forces acting on the tire. This characteristic is predicted in some cases and evaluated experimentally in others. This paper addresses another way to assess the slip angle. We propose a mathematical model that describes a constraint linking the slip angle and steering angle that make a vehicle turn. We present a simplied kinematic model (based on the classic bicycle model) and a four-wheel model, which makes all of the angles involved compatible with each other. In our case, the match will be given by the determination of the turning radius. Two different scenarios, understeering and oversteering vehicles, were simulated, and the results and conclusions reached are presented herein.     

美国铁路发展政策中的政府作用

在美国铁路的发展过程中,政府通过独特的参与手段确保铁路的发展。在全国性货运线路政策上,政府放松了对铁路的经济管制,充分发挥政府监管作用。在地方和地区性货运线路政策上,政府制定政策以确保路网的连续性。在通勤铁路政策方面,政府利用标准铁路线路建立通勤铁路系统。在城际客运铁路政策方面,通过立法成立全国铁路客运公司(Amtrak),并获得非常有限的政府资助,政府支持城际客运铁路业务的作用仍需加强。     

Walking infrastructure design assessment by continuous space dynamic assignment modeling

For the planning and design of walking infrastructure, characterized by the fact that the pedestrians can choose their paths freely in two‐dimensional space, applicability of traditional discrete network models is limited. This contribution puts forward an approach for user‐optimal dynamic assignment in continuous time and space for analyzing for instance walking infrastructure in a two‐dimensional space. Contrary to network‐based approaches, the theory allows the traffic units to choose from an infinite non‐countable set of paths through the considered space. The approach first determines the continuous paths using a path choice model. Then, origin‐destination flows are assigned and traffic conditions are calculated. The approach to determine a user‐optimal assignment is heuristic and consists of a sequence of all‐or‐nothing assignments. An application example is presented, showing dynamic user equilibrium traffic flows through a realistic transfer station. The example is aimed at illustrating the dynamic aspects of the modeling approach, such as anticipation on expected flow conditions, and predicted behavior upon catching or missing a connection.