Ride Vibration Measurements of Agricultural Tractor and Trailer Combinations

Tractor ride vibration levels have been measured when operating with and without a two wheel (2W) unbalanced and a four wheel (4W) balanced trailer. Measurements were made in the vertical, pitch, longitudinal and roll directions with the trailers unladen and laden over four typical farm surfaces

The results showed that tractor ride vibration levels were usually increased in all directions-particularly the longitudinal direction- when operating with the laden trailers. But for the unladen trailers, they were increased only in the longitudinal direction. Predominant tractor frequencies tended to be lower with the trailers attached, and coupling between the tractor longitudinal, vertical, roll and pitch co-ordinates was generally increased

Comparisons of the results with the trends predicted by a simplified theoretical model of a tractor and 2W trailer, suggested that the model should be extended to include, (a) the roll direction, (b) more realistic ground inputs, and (c) a 4W trailer     

A Theoretical Analysis of the Ride Vibration of Agricultural Tractor and Trailer Combinations

SUMMARY

A six degree of freedom model of an agricultural tractor and trailer combination has been developed. Results from eigenvalue and frequency response calculations indicated that tractor operator vibration levels will be higher when operating with a trailer than for the tractor alone, due mainly to increased tractor pitch motion.

Although minor improvements could be made to present tractor and trailer combinations by moving the hitch forward of the tractor rear axle or providing some damping at a sprung hitch, the scope for a significant improvement in ride lies in changing the configuration. If higher speed specialised transport vehicles prove economical for agriculture, there are some advantages in ride vibration to be gained by changing the layout of the tractor and trailer combination to resemble an off-road version of a commercial articulated lorry.     

A Theoretical Analysis of the Ride Vibration of Agricultural Tractor and Trailer Combinations

A six degree of freedom model of an agricultural tractor and trailer combination has been developed. Results from eigenvalue and frequency response calculations indicated that tractor operator vibration levels will be higher when operating with a trailer than for the tractor alone, due mainly to increased tractor pitch motion.

Although minor improvements could be made to present tractor and trailer combinations by moving the hitch forward of the tractor rear axle or providing some damping at a sprung hitch, the scope for a significant improvement in ride lies in changing the configuration. If higher speed specialised transport vehicles prove economical for agriculture, there are some advantages in ride vibration to be gained by changing the layout of the tractor and trailer combination to resemble an off-road version of a commercial articulated lorry.     

A Dynamical Analysis of a Towed Two-Wheel Trailer1

SUMMARY

The towed trailer method for skid resistance measurements is a practical one for characterizing the friction characteristics of highway pavements, and has been standardized by the ASTM 11). Numerous papers have been published about the improvement of equipment and field-testing techniques but little has been done toward a theoretical explanation.

This paper presents a mathematical model of the trailer which includes roll, pitch, and vertical motion. The skid resistance calculated by using this model gives an excellent check on the standard ASTM skid number formula. The response time and damping effect after locking one test wheel can be clearly seen in this model. Possible effects of the dimensions of trailer, stiffness of suspension system, tire pressure, etc. to skid resistance can also be examined.     

Frequency Response Analysis of Canadian Logging Trucks

SUMMARY

This paper examines the frequency responses often logging truck configurations currently operating in the interior of British Columbia in Canada. The work is an extension of a previous study conducted at the National Research Council (NRC) in 1990. The previous study presented an extensive analysts of the directional responses and frequency responses of four Canadian log-hauling truck configurations; a tractor/pole trailer, a tractor/triaxle trailer, a tractor/quadaxle trailer (with a single load), and a tractor/single-axle-jeep/pole trailer. In the current study, the frequency responses of these four configurations are compared with those of six more log-hauling truck configurations; a tractor/ tandem-axle-jeep/pole trailer, a doglogger, a double doglogger, a tractor/quadaxle trailer (with a dual load), a tractor/jeep/triaxle trailer, and a tractor/jeep/quadaxle trailer. The current study makes use of three models developed by NRC in the previous study, and a new model developed at NRC in cooperation with the University of Victoria.

The frequency response method has been applied in this study to predict the lateral acceleration at the centre of gravity of each articulated vehicle unit, and the rearward amplification ratio. The logging truck simulation results have been compared with corresponding results, obtained using UMTRI's simplified models, for three conventional highway vehicles; a tractor/semitrailer, a B-train, and an A-train. The comparison provides a useful indication of the differences between the behaviours of logging trucks and conventional highway trucks in their shared environment.     

Ride quality evaluation of a vehicle with a planar suspension system

The longitudinal connection between a chassis and a wheel in a conventional vehicle suspension system is commonly very stiff than the vertical connection. Such a mechanism can efficiently isolate vibrations and absorb shocks in the vertical direction but cannot sufficiently attenuate the impact in the longitudinal direction. In order to overcome such a limitation, a planar suspension system (PSS) with spring–damper struts in both the longitudinal and vertical directions is proposed so that the vibration along any direction in the wheel rotation plane can be isolated. In this paper, the dynamic responses of a vehicle with PSS due to a single bump and random road unevenness are investigated. The ride quality of the vehicle with PSS is evaluated in accordance with ISO 2631. A comparison with that of a similar conventional vehicle is conducted to demonstrate the promising potentials of the PSS in improving the vehicle ride quality.     

Ride dynamic evaluations and design optimisation of a torsio-elastic off-road vehicle suspension

The ride dynamic characteristics of a novel torsio-elastic suspension for off-road vehicle applications are investigated through field measurements and simulations. A prototype suspension was realised and integrated within the rear axle of a forestry skidder for field evaluations. Field measurements were performed on forestry terrains at a constant forward speed of 5 km/h under the loaded and unloaded conditions, and the ride responses were acquired in terms of accelerations along the vertical, lateral, roll, longitudinal and pitch axes. The measurements were also performed on a conventional skidder to investigate the relative ride performance potentials of the proposed suspension. The results revealed that the proposed suspension could yield significant reductions in magnitudes of transmitted vibration to the operator seat. Compared with the unsuspended vehicle, the prototype suspended vehicle resulted in nearly 35%, 43% and 57% reductions in the frequency-weighted rms accelerations along the x-, y- and z-axis, respectively. A 13-degree-of-freedom ride dynamic model of the vehicle with rear-axle torsio-elastic suspension was subsequently derived and validated in order to study the sensitivity of the ride responses to suspension parameters. Optimal suspension parameters were identified using the Pareto technique based on the genetic algorithm to obtain minimal un-weighted and frequency-weighted rms acceleration responses. The optimal solutions resulted in further reduction in the pitch acceleration in the order of 20%, while the reductions in roll and vertical accelerations ranged from 3.5 to 6%.     

Lateral Dynamics of Commercial Vehicle Combinations A Literature Survey

SUMMARY

This paper presents a review of theoretical and experimental works relative to the handling performance of commercial vehicle combinations. A commercial vehicle combination (road train) is defined as a tractor unit and an arbitrary number of trailers. The review contains literature corresponding the most widely used types of trains: tractor-semitrailer, truck-trailer and tractor-semitrailer-semitrailer (doubles). The vehicle dynamic performance has been investigated taking into consideration the following features: directional performance, roll dynamics, braking performance and combined braking and directional performance. With the aim of evaluating the present state of research activities in the field of lateral dynamics of articulated commercial vehicles, the author has compiled some 250 references.     

A Dynamical Analysis of a Towed Two-Wheel Trailer1

The towed trailer method for skid resistance measurements is a practical one for characterizing the friction characteristics of highway pavements, and has been standardized by the ASTM 11). Numerous papers have been published about the improvement of equipment and field-testing techniques but little has been done toward a theoretical explanation.

This paper presents a mathematical model of the trailer which includes roll, pitch, and vertical motion. The skid resistance calculated by using this model gives an excellent check on the standard ASTM skid number formula. The response time and damping effect after locking one test wheel can be clearly seen in this model. Possible effects of the dimensions of trailer, stiffness of suspension system, tire pressure, etc. to skid resistance can also be examined.     

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.     

High-speed optimal steering of a tractor–semitrailer

A high-speed optimal trailer steering controller for a tractor–semitrailer is discussed. A linear model of a tractor–semitrailer with steered trailer axles is described, and an optimal trailer steering controller is introduced. A path-following controller is derived to minimise the path-tracking error in steady-state manoeuvres using active trailer steering. A roll stability controller is introduced by adding the lateral acceleration of trailer centre of gravity as another objective in the steering controller, so as to improve roll stability in transient manoeuvres. A strategy to switch between these two control modes is demonstrated. Simulation results show that the steering controller can ensure good path tracking of articulated vehicles in steady-state manoeuvres and improve roll stability significantly in transient manoeuvres, while maintaining the path-tracking deviation within an acceptable range. Tests with an experimental tractor–semitrailer equipped with a high-bandwidth active steering system validate the controller design and simulation results. The roll stability controller reduces the measured rearward amplification by 27%.     

A Full-Car Roll Model of a Vehicle with Controlled Suspension

SUMMARY

The full-car roll model of a vehicle suspension with static and dynamic control (using wheel, body and seat) is described by means of vertical and lateral input for both static and dynamic states. It is shown that the control deteriorates the static performance of the vertical response and improves the performance of the lateral response.     

Automotive Stability and Handling Dynamics in Cornering and Braking Maneuvers

SUMMARY

Automotive steering behaviour is classified for steady-state cornering and the definitions of over-/understeer and stability/instability are well known. In this paper it is intended to apply these definitions to combined cornering and braking maneuvers i.e. to extend the criteria to quasi-steady-state conditions. This way of investigation was chosen because it gives a clear idea of the typical handling behaviour. Furthermore, the vehicle behaviour is analyzed using the cornering stiffness of the axles and front/rear cornering stiffness ratio because this is always of primary significance. The following contribution is based on a theoretical analysis considering the most important non-linear vehicle properties.

The paper deals with two groups of vehicles: single vehicles (passenger cars) and combinations (passenger car/caravan and tractor/semitrailer). In the case of combinations the effect of trailers on the towing vehicles is examined. So, careful attention is paid to the coupling forces, which alter the wheel loads and influence steerability and stability.     

Semi-Active Attitude and Vibration Control

SUMMARY

The paper discusses the attitude and vibration control of a passenger car on the basis of a full vehicle model. The analysis presented consists of two parts: (I) The introduction of a newly developed semi-active anti-roll/pitch system, (ii) An example of an actively suspended full vehicle model using a simple control strategy to improve ride comfort. The attitude control using semi-actively generated compensation forces prevents the car from rolling in curves and pitching during braking or accelerating. The strength of the system is the small energy consumption. The performance of the combination of both attitude and vibration control can compete with a fully active suspension system.     

Validation of an Articulated Vehicle Simulation

SUMMARY

Tests were performed on a typical UK articulated vehicle to measure dynamic tyre forces and sprung mass accelerations. The measured road profile data and vehicle response data are used to determine some of the important characteristics of articulated vehicle vibration behaviour. In particular, roll motions and their effect on dynamic tyre forces are examined. The measured data are used to validate two and three-dimensional computer models of the vehicle. Attention is given to modelling the tandem leaf-spring trailer suspension. The conditions under which a two-dimensional model can accurately simulate vehicle behaviour are examined.     

Research into the problem of wheel tread spalling caused by wheelset longitudinal vibration

This study mainly focuses on the mechanism of wheel tread spalling through wheelset longitudinal vibration that has been often neglected. Analysis of two actual cases of the wheel tread spalling problem leads to the conclusion that the wheel tread spalling is closely related to the wheelset longitudinal vibration in some locomotives, and many of these problems can be reasonably explained if the wheelset longitudinal vibration is considered. For better understanding of some abnormal wheel spalling problems, the formations of the wheelset longitudinal vibration and the wheel/rail contact parameters were analysed in the initial wheel tread spalling. With the preliminary analytical results, the wheelset longitudinal dynamic behaviour, the characteristics of wheel/rail contact and the mechanics in the condition of the wheelset longitudinal vibration were further studied quantitatively. The results showed that the wheelset longitudinal vibration changed not only the limit of these parameters and the position of principal stress, but also the direction of the principal stress on the surface of wheel/rail contact patch. It is likely that the significant stress changes provoke too much stress on the surface of wheel/rail contact patch, cause fatigue in wheel/rail contact patch and eventually lead to wheel tread spalling. The results of these studies suggest that the suppression of the wheelset longitudinal vibration extends wheel/rail life and the addition of a vertical damper with an ahead angle provides a possible solution to the wheel spalling problem.     

High Speed Stability for Rail Vehicles Considering Varying Conicity and Creep Coefficients

SUMMARY

The critical or hunting speed of solid axle rail vehicles is known to be a strong function of primary suspension stiffness, wheel/rail profile geometry (conicity and gravitational stiffness), wheel/rail friction forces (creep coefficients), bogie/carbody inertia properties, and secondary suspension design. This paper deals with the problem of maximizing the critical speed through design of the primary and secondary suspension but with control only over the range of wheel/rail geometry and friction characteristics. For example, the conicity may varie from .05 to .3 and the linear creep coefficients from 25% to 100% of the predicted Kalker values.

It is shown that the maximum critical speed is greatly limited by the wheel/rail geometry and friction variations. It is also shown that, when lateral curving and ride quality are considered, the best design approach is to select an intermediate primary longitudinal stiffness, to limit the lowest value of conicity (e.g. to .1 or .2) by wheel profile redesign, increasing the secondary yaw damping value (yaw relaxation) and optimizing the primary and secondary lateral stiffness.     

Chaotic Motion of Wheels

Abstract

Trolleys have wheels which can choose the direction of their rolling. Studying the motion of a wheel like this, we can often find periodic motions (“shimmy”) or even chaotic ones. It has also been experienced that the chaotic motions sometimes disappear quite unexpectedly. A strongly simplified model of these systems is analysed in the paper by means of the methods of bifurcation theory. Analytical and numerical results are shown to characterize the system, including simulation results. Similar behaviour can be found in more complicated systems as well, like the trailers or the nose-gears of aeroplanes. The development of the so-called transient chaotic motion is explained in these systems.     

Roll and pitch independently tuned interconnected suspension: modelling and dynamic analysis

In this paper, a roll and pitch independently tuned hydraulically interconnected passive suspension is presented. Due to decoupling of vibration modes and the improved lateral and longitudinal stability, the stiffness of individual suspension spring can be reduced for improving ride comfort and road grip. A generalised 14 degree-of-freedom nonlinear vehicle model with anti-roll bars is established to investigate the vehicle ride and handling dynamic responses. The nonlinear fluidic model of the hydraulically interconnected suspension is developed and integrated with the full vehicle model to investigate the anti-roll and anti-pitch characteristics. Time domain analysis of the vehicle model with the proposed suspension is conducted under different road excitations and steering/braking manoeuvres. The dynamic responses are compared with conventional suspensions to demonstrate the potential of enhanced ride and handling performance. The results illustrate the model-decoupling property of the hydraulically interconnected system. The anti-roll and anti-pitch performance could be tuned independently by the interconnected systems. With the improved anti-roll and anti-pitch characteristics, the bounce stiffness and ride damping can be optimised for better ride comfort and tyre grip.     

超重型可拼装式全挂车设计

超重型可拼装式全挂车可满足超重、超长、超高货物的运输要求，采用拼装式结构可根据所运货 需要随时拼装成满足运输要求的全挂车，文中所述的可拼装式全挂车车架结构简单，可拼装成８种挂车方式，采用液压悬架系统、可升降式平台、机械式全轮转向系统，承载范围为８０ｔ～４００ｔ。