A Procedure for Optimization of Truck Suspensions

The purpose of this paper is to develop a procedure based on covariance analysis and nonlinear programming techniques which can be used for the parameter selection of optimum truck suspensions. The procedure is applied to explore the differences in parameter selection caused by the changes in the frequency content of the road input or by changes in the criteria for optimization. The equations of motion for a tractor-semitrailer truck are cast in state space form. The road excitations are represented by the output of a white noise excited shaping filter taking into consideration the time delays between the different vehicle axles. Shape filters to represent human perception of vibration in both the vertical and longitudinal directions in the time domain are presented and realized in terms of state variables. The suspension parameters of the road-vehicle-human body system are optimized using a direct search algorithm.     

Extended Ground-Hook - New Concept of Semi-Active Control of Truck's Suspension

SUMMARY

This paper deals with the novel control concept, so called ground-hook for active and mainly semi-active suspension of vehicles with the ultimate objective to minimize the tyre-road forces and thus the road damage. The basic ground-hook concept is extended to the several variants which enable to decrease criteria of road damage as well as to increase driver's comfort for a broad range of road unevennesses. Parameters of control law are determined by the parameter optimization for generally nonlinear model. The influence and interaction of the damping rate limits and time constants of variable shock absorbers are also taken into account. The influence of implementation of more complicated truck models is also discussed.     

道路清障车的制动过程分析

建立了道路清障车拖带车辆制动工况力学模型，绘制了道路清障车拖带车辆行驶时的制动器制动力分配曲线Ｉ，分析了被牵引车结构参数的改变对制动过程的影响，并建议对这种轴荷变化的道路清障车应安装感载阀，以提高制动稳定性。     

AUTHOR INDEX VOLUME 39 AND 40

SUMMARY

This paper presents a state observer design for an adaptive vehicle suspension. Based on simulations, two main issues are investigated, (a) the selection of measurement signals in relation to estimation accuracy and sensing needs and (b) the effects of variations in both road inputs and vehicle parameters on estimation accuracy. Meanwhile, the system stabilities are also examined concerning the effects of using different combination of measurement states and the system parameter variations in practical, possible ranges.     

Roadway Elevation Profile Generation for Vehicle Simulation

SUMMARY

With a simplified approach for creating road surface elevation information for simulation of vehicle vertical response to roadway unevenness, roadways for single and parallel track simulations and averaged roads for variable velocity simulation are developed. Sets of correctly chosen random roadway slopes are averaged appropriately for the variable velocity simulation. The procedure generates approximately “white” slope spectral density roadways in the frequency ranges of interest, and the elevation profiles are representative of average road profiles. The method is simple in practice yet suffices for many parameter studies of suspensions and vehicle dynamics.     

Effect of obstacles on roads with different waviness values on the vehicle response

Abstract

The effect of the increasing number of cosine-form obstacles, which are superposed on a standard homogeneous longitudinal road profile, is studied when the waviness of the basic road profile changes in the range from 1.5 to 3.5. First, the effect of the composed profile on the power spectral density (PSD) is analysed. It appears that the primary PSD in the form of a straight-line in the log–log plot breaks into two straight-line partial segments with quite different waviness values in the long and short wavelength bands. This seems to be a suitable model of a highly deteriorated road. Next, the effect on the response of two typical vehicles, viz. a personal car and a three-axle truck, is studied, and rather different results were obtained. In a summary valuation, it appears that the presence of additional obstacles causes independence of some of the vehicle response quantities of the primary waviness.     

Advanced vehicle dynamics of heavy trucks with the perspective of road safety

ABSTRACT

This paper presents state-of-the art within advanced vehicle dynamics of heavy trucks with the perspective of road safety. The most common accidents with heavy trucks involved are truck against passenger cars. Safety critical situations are for example loss of control (such as rollover and lateral stability) and a majority of these occur during speed when cornering. Other critical situations are avoidance manoeuvre and road edge recovery. The dynamic behaviour of heavy trucks have significant differences compared to passenger cars and as a consequence, successful application of vehicle dynamic functions for enhanced safety of trucks might differ from the functions in passenger cars. Here, the differences between vehicle dynamics of heavy trucks and passenger cars are clarified. Advanced vehicle dynamics solutions with the perspective of road safety of trucks are presented, beginning with the topic vehicle stability, followed by the steering system, the braking system and driver assistance systems that differ in some way from that of passenger cars as well.     

Extended Ground-Hook - New Concept of Semi-Active Control of Truck's Suspension

This paper deals with the novel control concept, so called ground-hook for active and mainly semi-active suspension of vehicles with the ultimate objective to minimize the tyre-road forces and thus the road damage. The basic ground-hook concept is extended to the several variants which enable to decrease criteria of road damage as well as to increase driver's comfort for a broad range of road unevennesses. Parameters of control law are determined by the parameter optimization for generally nonlinear model. The influence and interaction of the damping rate limits and time constants of variable shock absorbers are also taken into account. The influence of implementation of more complicated truck models is also discussed.     

Application of Sensitivity Methods to Analysis and Synthesis of Vehicle Dynamic Systems

SUMMARY

The development and application of sensitivity methods for determining the effects of parameter changes on the response of vehicle dynamic systems is presented. The procedures shown can be used to enhance the analysis and synthesis processes of virtually any road or rail vehicle system regardless of its complexity. The parametric sensitivity of vehicle models in time domain, steady state models and vehicle models in frequency domain can be investigated using different types of sensitivity functions, both dimensional and dimensionless including first order standard, percentage, logarithmic, second order standard, and logarithmic and percentage sensitivity measures. These sensitivity functions and measures are determined as functions of partial derivatives of system variables taken with respect to system parameters. In the case of sensitivity functions in the frequency domain the variable values are computed as either the magnitude or phase angle of a complex element of the transfer function matrix. The methods presented enable to determine the influence of all system primary (constant) and secondary (non-constant) parameters on system primary and secondary variables. The primary variables are state variables or elements of the transfer function matrix and the secondary variables may be any functions of primary variables and system parameters. Typical secondary system parameters which can be examined include initial conditions, time variant coefficients, natural frequencies, loads, and typical secondary variables are forces, weight transfers, stability factors and energy components. The analysis of sensitivity results obtained for three vehicle handling models in both linear and nonlinear regimes of vehicle performance and utilizing various types of sensitivity functions is also presented.     

Optimal Control of the Tractor-Semitrailer Truck

SUMMARY

This paper is concerned with the braking performance and the handling behavior of the tractor-semitrailer truck under optimal braking. Optimal control theory is used in order to deal with the problem and a combination of the steepest descent method and the Davidon Fletcher Powell method is used to solve it numerically. Results for some chosen braking maneuvers are obtained for a nonlinear truck model which has 14 degrees of freedom. These results show that, for the chosen maneuvers an idealized anti-skid braking is close to being optimal in the sense defined in this paper. Implementation of an idealized anti-skid braking on the tractor-semitrailer truck, however, may be not desirable.     

Tractor-Semitrailer Dynamics: Design of the Fifth Wheel∗

SUMMARY

The nonlinear equations of motion are derived for a tractor-semitrailer truck where both the itractor and the semitrailer yaw, pitch, roll, and translate. Special emphasis is placed on the constraints imposed by the fifth wheel on the vehicle motion. In particular, the effects of two proposed fifth wheel design changes on the jackknifing behavior of a vehicle in a turning, braking maneuver are studied. The results demonstrate that the tendency of the vehicle to jackknife can be reduced with a geometric modification of the fifth wheel.     

关于25t汽车起重机转向系统的选型设计

介绍了起重机转向系统的选型设计,利用MSC Adams软件对转向梯形机构进行了运动仿真,对其转向性能进行了优化,该起重机的道路试验结果表明所设计的转向机构性能符合设计要求。     

Steady-State Curving Performance of Railway Freight Truck with Damper-Coupled Wheelsets

SUMMARY

The focus of this paper is on the steady-state curving behaviour of a freight car system with Damper Coupled Wheelset (DCW), where the wheels of conventional shape within an axle are coupled through a damper element. A freight truck model with two DCW and pseudo-car body on curved track is developed to study the influence of wheelset coupler parameter on the curving response and performance. The response is primarily evaluated in terms of wheelset tracking error and yaw misalignment in response to track curvature and cant deficiency. The curving performance is evaluated in terms of slip and flange boundaries. The results in general, indicate that when the value of coupler parameter is reduced, the wheelset response to track curvature increases, and results in flanging and wheel slip on a less tighter curve than those corresponding to conventional rigid axled wheelsets.     

Anti-Skid Braking of a Tractor-Semitrailer Truck

ABSTRACT

This paper describes a study of anti-skid braking and the effects of such braking on the handling behavior and braking performance of a tractor-semitrailer truck. The truck, represented by a digital computer model having fourteen degrees of freedom, is taken to be in a cornering maneuver that involves braking and driver steering. Conventional braking or one of three types of anti-skid braking is used in the maneuver. The results show that the effects of anti-skid braking on the handling behavior and braking performance of the truck are beneficial. The results also show that the behavior of the wheels and the handling behavior and braking performance of the truck depend on the type of anti-skid braking used.     

Optimization for Vehicle Suspension I: Time Domain

SUMMARY

A numerical procedure for finding the optimum values of a number of parameters describing a model vehicle suspension has been studied. The vehicle has been modelled by dynamic systems of linear springs and dampers, and the goal is to obtain lower acceleration peaks at an elected design point in the vehicle.

The problem is stated as a mathematical programming problem which can be solved by means of the sequential linear programming technique. The procedure has been implemented for a four wheel independent suspension model capable of being subjected to road irregularities and to centrifugal and braking accelerations.     

Optimal Linear Active Suspensions with Vibration Absorbers and Integral Output Feedback Control

SUMMARY

The bandwidth of the body response to a road input in an active suspension may be considerably reduced if the axle motions are independently controlled and if, at the same time, the effects of static and dynamic loads are counteracted by integral action in the body force control system. The paper presents a further application of the Ferguson-Rekasius method, leading to optimal output control with incomplete state feedback. To achieve narrow bandwidth body response the support springs are replaced by hydraulic actuators, and vibration absorbers or active wheel dampers are employed for the control of the axle motions. Active wheel damping is the more effective and gives good results. Proportional-plus-integral control action is shown to reduce the transient body displacements due to external forces.     

山区高速公路移动瓶颈效应对车流状态影响研究

我国高速公路大型货车混入率较高,山区高速公路交通流受移动瓶颈效应影响尤为突出。鉴于此,利用运动学波理论对因低速货车超车形成的移动瓶颈效应进行分析,应用vissim软件进行模拟仿真,通过对不同交通流状态下不同低速货车混入率的仿真结果分析,发现随着交通量以及货车混入率的增加,移动瓶颈效应对车流状态的影响呈加剧趋势,导致小客车行驶速度明显下降,并逐渐接近货车行驶速度。各慢行车队之间出现的较大空隙导致道路资源浪费,道路通行能力下降。该研究结论对深入研究山区道路通行能力具有重要指导意义。     

Optimal Suspension Parameter Distributions and Roadway Profiles for Isolation of Heavy Trucks

Heavy trucks are known to have ride problems and are difficult to isolate from roadway unevenness. Heavy trucks are rich in modal density and are stiffly sprung, a combination that makes isolation difficult. Due to their inherent mass, trucks create roadway unevenness as they move along a roadway. Each following truck is excited by the unevenness created by the preceding one, and the road condition worsens over time. It is shown that trucks create roadway profiles from which perfect isolation is possible by having the proper parameter distribution in the suspension units. One distribution is best for rigid body isolation and one is best for 'beaming' isolation.     

Stationar- und Ubergangsverhalten von Sattel- und Lasttugen bei der Kreisfahrt: Lineare Berechnungen

ABSTRACT

Steady and Transient Turning of Tractor-Semitrailer and Truck-Trailer Combinations: A Linear Analysis

A simplified analysis is made of the yaw stability and control of the two types of the commercial vehicle combinations (tractor-semitrailer, truck-trailer) at a constant forward velocity during steady and transient turning. The combined vehicle is treated as a linear dynamic system (Fig. 2). The steer angle at the front wheels of the tractor (or truck) and the steady-state responses if the road verhicle train (yaw rate, articulation angles and sideslip angle) are calculated (Equations 18 to 25). Exploratory calculations are performed to determine the influence of the cornering stiffness of the tires for the two types of the vehicle combinations upon the steady-state responses (Figs. 7 to 10). For a linear simplified model of articulated vehicle the steady-state turning behaviour is stable also under conditions of rather high driving speed (70 km/h). A simplified analysis of the transient turning behaviour of the two types of road trains has shown the tractor-semitrailer to preserve stability even under driving speeds exceeding 70 km/h (Fig. 13), whereas the truck-trailer combinations appear to become oscillatory unstable if the driving speed rises above the 60 km/h margin (Fig. 14).