Christopher B. Winkler

Measurement and Representation of the Mechanical Properties of Truck Leaf Springs

The force-vs.-deflection characteristics of truck leaf springs were investigated with respect to the influences of stroking frequency and amplitude and nominal static load on hysteretic damping and effective spring rate. Measurements were made on five currently employed leaf springs at five stroking frequencies (0.5 to 15.0 Hz) for three stroking amplitudes at two static loads. Test results indicate that the stroking frequency over the studied range has no influence on the spring rate and energy dissipation properties of truck leaf springs. Truck leaf springs are highly nonlinear devices for which the average damping force in a stroking cycle increases directly with either the stroking amplitude or nominal static load, and the effective spring rate decreases inversely with the stroking amplitude or directly with the static load. A mathematical method is presented which represents the force-vs.-deflection characteristics of truck leaf springs in a form suitable for use in the simulation (digital calculations) of vehicle dynamics.

Simplified Analysis of the Steady-State Turning of Complex Vehicles

SUMMARY The classic analysis of the steady-state turning of the motor vehicle is based on a simple vehicle model in which lateral acceleration is the only motion variable that affects tire slip angles. This paper examines a more complex vehicle whose slip angles depend on lateral acceleration plus another motion variable. Trucks with multiple, nonsteering rear axles are one example of the complex vehicle. A general analysis of the complex vehicle together with analyses of linear and nonlinear trucks provide new insights into the understeer/oversteer quality of all vehicles. It is shown that a complex vehicle can be represented as a simple vehicle with an equivalent wheelbase. A physical interpretation of equivalent wheelbase for trucks and a method for its measurement are presented.

Directional performance issues in evaluation and design of articulated heavy vehicles

This review of the dynamics of heavy road–vehicle systems emphasizes directional performance. The review presents information on the following topics: why are articulated vehicles used; units, hitches, and combination vehicles; multiple axle suspensions and steering systems; important performance issues; models and simulation tools; and controlling directional performance. The concluding section summarizes the material presented and provides ideas regarding the application of vehicle system dynamics concepts in developing controllers for road trains.

USING BRAKING TO CONTROL THE LATERAL MOTIONS OF FULL TRAILERS

Abstract This paper provides analytical and simulation results showing the performance benefits available from using an electronic braking system to apply yawing torques (through differential side-to-side braking) so as to aid in controlling the lateral snaking motions of multiply articulated heavy vehicles employing full trailers.

An electrorheologically controlled semi-active landing gear

This study is to explore the application of electrorheology (ER) to the real-time control of damping forces that are transmitted through the nose landing gear for an F-106B aircraft. The main part of the landing gear is a strut that consists of a pneumatic spring and an ER controlled damper that is situatted on the strut centerline and applies a force directly opposing the vertical displacement of the nose wheel. The damping element rotates in response to strut displacement, employing a co-axial arrangement of stator and rotor plates connected to the opposing electrodes in the control circuit. The vertical displacement is conveted into rotation of the damper through a screw-nut mechanism. The ER fluid between the electrodes is thus engaged in shear along circumferential lines of action. This design results in a fast time response and a high ratio of strut forces achieved under Er-vs. zero-field control. Compact size and simplicity in fabrication are also attained. The analysis shows that when using an ER fluid of a yield stress of 7kPa, the energy absorption efficiency of the landing gear can reach almost 100% at various sink rates.

A TEST FACILITY FOR THE MEASUREMENT OF HEAVY VEHICLE SUSPENSION PARAMETERS

The Highway Safety Research Institute (University of Michigan) Heavy Vehicle Suspension Testing Facility is described, a new installation for the measurement of compliance, kinematic, and coulomb friction properties of heavy-vehicle suspension and steering systems as they react to vertical force, roll moment, lateral force, brake force, and aligning moment. The facility was designed and constructed under the sponsorship of the Motor Vehicle Manufacturers Association, Ad Hoc Committee on Heavy Truck Braking and Handling. Single and tandem-axle suspensions (maximum tandem spread 180 cm. or 70 in.) of all common on-highway truck widths can be tested in their normal configuration or as mounted on an abbreviated frame section. All measurements are performed at steady-state or quasi-steady-state. The facility has three major mechanical systems: a static structure, a movable table, and four wheel pad assemblies. Various test procedures are described, and qualitative findings to date are reviewed. Detailed descriptions of machine elements and specific suspension data are appended.

Intelligent Systems for Aiding the Truck Driver in Vehicle Control

This paper describes two prototype systems designed to aid truck drivers in controlling an articulated heavy-duty vehicle. The systems involve a roll stability advisor (RSA) and a rearward amplification suppression system (RAMS). Both systems are described in terms of their concept, design, and application.

Benefits and Costs of Four Approaches to Improving Rollover Stability of Cargo Tank Motor Vehicles

Four broad approaches to decreasing the number of cargo tank rollovers were evaluated: driver training, electronic stability aids, improvements in design of the vehicle itself, and highway design. A study of rollover crash statistics confirmed many expectations, but a few of the factors were not as strong as might have been expected. The portion of rollovers that occur on freeways is 15% to 20%. A driver error of one kind or another (e.g., decision or performance error) figures in about three-fourths of cargo tank rollovers. Inattention and distraction account for about 15%. Evasive maneuvers were a factor in 5% to 10% of rollovers. Drivers must be trained to appreciate the diverse causes for rollovers and to anticipate the situations that lead to them. Adherence to viable work and rest schedules is crucial. Electronic stability aids automatically slow the truck when it rounds a curve too fast. They can be remarkably effective in preventing this scenario. However, crash statistics and anecdotal accounts consistently show many other factors that can lead to rollovers. Significant reductions in rollover rates can be achieved with modest changes in vehicle stability. Cargo tank trailers of improved stability are currently available for some cargoes. When mountainous terrain or other factors dictate highway designs that can contribute to rollovers, drivers need to be made aware through signage or dispatch instructions. A comprehensive benefit–cost analysis, conducted from a societal point of view during a 20-year window, projected that the improvements will be cost beneficial.

A New Facility for Testing Motorcycle Tires

Analysis of the dynamic modes of the single-track vehicle has been hampered by the general lack of facilities for gathering force and moment data on motorcycle tires under dynamic test conditions. The facility described was designed and constructed by UMTRI under the sponsorship of the HONDA Research and Development Company in order to alleviate this problem. Unlike conventional tire dynamometers, this new facility allows for testing under dynamic conditions and provides for non-zero path curvature. These particular capabilities hold promise for advancement in the state-of-the-art understanding of the dynamic operating modes of the single-track, pneumatic-tired vehicle. The facility is unique in its physical design in that it employs a small, light tire-mounting head which is controlled by a mechanically simple system of servo-controlled hydraulic cylinders. This mechanical simplicity is achieved, however, at the cost of a complex electronic control system involving substantial on-line digital calculation.

Lateral-acceleration experience of six commercial vehicles

Abstract This communication provides a detailed review of the lateral‐acceleration experience of six tractor‐semitrailer combinations in real commercial service for approximately one year. Lateral‐acceleration experience is described in histograms of travel time. Influences of speed, load, road geometry, driving style, and longitudinal position on the vehicle are examined. Distributions of both path curvature and lateral acceleration are presented. The six vehicles studied were all five‐axle, tractor‐semitrailer combinations. The semitrailers were cryogenic tankers for transporting liquid nitrogen. The fleet operated from La Porte, Indiana and serviced much of Illinois, Indiana, Michigan, and Wisconsin. Data from nearly 10,000 hours and more than 770,000 km of travel were collected and analyzed.