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A simple ADAMS model was developed for simulating one possible mechanism that causes low-frequency (less than 1 kHz) noise in disc brake assemblies for heavy-duty and medium-duty trucks. The model consists of: truck tire, axle housing, torque plate, caliper, push rods, inner pad, outer pad, and rotor. Only one component (the torque plate) was modeled as a flexible body (using a finite element model), while all other parts are considered as infinitely rigid. A lumped parameter representing the suspension wrap-up stiffness resists the axle pitch motion. When the brakes are not engaged, the system has two distinct modes of vibration, namely, the axle pitch mode which is governed by the suspension wrap-up stiffness, and the caliper transverse (side-to-side) mode, which is governed by the stiffness of the torque plate (out-of-plane deflection of the torque plate) and by the suspension lateral stiffness.

In this paper, we describe the development of multi-axis, accelerated durability tests for commercial vehicle suspension systems. The objective of the exercise is to design accelerated durability tests that have well-defined correlation with customer usage. The procedure starts with a definition of the vehicle's duty cycle based on the expected operational parameters, namely: road profile, vehicle speed, and warranty life. The second step is determining the durability proving ground test schedule such that the accumulated pseudo-damage (based on spindle loads) is representative of the vehicle's duty cycle. The third step in the process is developing a multi-axis laboratory rig test for the suspension system, such that the accumulated damage in the proving ground is replicated in a compressed time frame.

A target-setting procedure for the design of the suspension system of a tractor-semi-trailer combination is described in this paper. This procedure is based on computer modeling and simulation of the complete vehicle system, as well as the modeling and simulation of suspension subsystems. The procedure relies heavily on computer-aided engineering software which provides the capability for automating the modeling and simulation of various suspension configurations, designing the screening test matrix, generating the response surface associated with each vehicle performance metric, and performing the multi-objective optimization with deterministic and stochastic constraints. The key to the success of this procedure is having a vehicle model wherein the inputs to the model are the attributes of the suspension subsystem, which in turn, become the design targets during the design of the suspension subsystem.

The ride performance metrics of three different designs of trailer suspension systems are compared by means of computational methods. The three types of trailer suspension systems that are considered in this study are the following: 1) 4-spring suspension with multiple-leaf steel springs; 2) 4-spring suspension with single-leaf composite springs; and 3) parallelogram suspension with air springs. The ride performance metrics of the different suspension systems are determined numerically through ADAMS modeling and simulation of these suspension systems. The ride performance metrics that are considered in this study are the vertical acceleration of the sprung mass and the vertical forces at the spindles. Two scenarios are considered in this study: a rough road scenario and a discrete bump scenario.

The effect of kingpin inclination angle and wheel offset on various vehicle performance metrics such as steering effort, vehicle handling, and steering system vibration is described in this paper. A simple ADAMS model of a medium-duty truck has been developed for this study. The front axle consists of an idealized solid axle suspension with suspension system components represented by rigid bodies. The tire model used in this study is a linear tire model, and estimates of tire force coefficients were obtained as an average of several published estimates of medium-duty truck tires. Experimental design procedures (DOE) have been conducted to determine the effects of kingpin inclination angle and wheel offset on various steering system performance measures. For each performance metric, a 2-variable (KPIA and wheel offset), 5-level DOE was performed using the full factorial matrix for a total of 25 tests for each performance metric.

This paper presents the results of a sensitivity study on the effect of tire stiffness parameters on selected handling performance metrics of a medium-duty truck. The tire stiffness parameters considered in the study are radial stiffness, longitudinal or braking stiffness, and cornering stiffness. An ADAMS model of a medium-duty truck was developed to simulate vehicle handling maneuvers. Two handling scenarios were considered: a combined braking and cornering scenario and a split-μ, straight-line braking scenario. The results of the study indicate that all three tire stiffness parameters are important in accurately predicting vehicle handling performance. Furthermore, when conducting design studies on suspension and steering system design variables other than tire stiffness parameters, the choice of specific values used for the tire stiffness parameters can significantly influence the results of the design studies.

The uniqueness and challenge of heavy and medium duty vehicle manufacturing is that the vehicle&s subsystems and major components are procured from different suppliers. As a consequence, engineering task coordination for total vehicle performance optimization is required even if the intended design modification is only on one component. In the case of suspension design, related subsystems such as the drive axle, driveline, brake system, steering system, and engine mounts should all be included for review. The related potential problems for study fall into three categories, namely: function, durability, and NVH. The effective approach in addressing all these issues early in the design stage is through computer modeling and dynamic system simulation of the suspension system and related subsystems.

The uniqueness of heavy and medium duty vehicle powertrain design, compared to that of passenger cars, is two fold: vast variations exist from vehicle to vehicle because of mission requirements, and powertrain components are sourced from a diverse group of suppliers. Vehicle powertrain design involves selection of the appropriate major components, such as the engine, clutch, transmission, driveline, and axle. At this design stage the main focus is on power matching, to ensure that the vehicle's performance meets specifications of gradability, maximum speed, acceleration, fuel economy, and emissions[1, 2, 3, 4 and 5]. The general practice also demands that the durability of the drivetrain components for the intended vocation or application be verified. Equally important but often neglected in the design phase is the system's NVH (Noise Vibration and Harshness) performance, such as torsional vibration, U-joint excitation, and gear rattle.