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A comprehensive comparison between an air-inflated seat cushion designed for truck seats and a commonly used foam cushion is provided, using a single-axis test rig designed for seat dynamic testing. Different types of tests were conducted in order to evaluate various aspects of each type of cushion; in terms of their response to narrowband (single frequency) dynamics, broadband input of the type that is commonly used in the trucking industry for testing seats, and a step input for assessing the damping characteristics of each cushion. The tests were conducted over a twelve-hour period—in four-hour intervals—measuring the changes that occur at the seat cushion over time and assessing how these changes can affect the metrics that are used for evaluating the cushions. The tests indicated a greater stiffening of the foam cushion over time, as compared with the air-inflated cushion that showed almost no change in stiffness when exposed to a static weight for twelve hours.

This study pertains to motion control algorithms using statistical calculations based on relative displacement measurements, in particular where the rattle space is strictly limited by fixed end-stops and a load leveling system that allows for roll to go undetected by the sensors. One such application is the cab suspension of semi trucks that use widely-spaced springs and dampers and a load leveling system that is placed between the suspensions, near the center line of the cab. In such systems it is possible for the suspension on the two sides of the vehicle to settle at different ride heights due to uneven loading or the crown of the road. This paper will compare the use of two moving average signals (one positive and one negative) to the use of one root mean square (RMS) signal, all calculated based on the relative displacement measurement.

This study provides a numerical evaluation of the dynamic coupling that exists between the powertrain, suspensions, and tire dynamics in class 8 trucks. The spatial dynamics of the driveline, including the offset angels that commonly exist in practice, are modeled along with a lumped-parameter representation of the suspension and tire dynamics in vertical, longitudinal, and torsional directions. The model is used to show how the suspension dynamics and the angle change that it causes in driveline geometry can affect the vibrations resulting from the powertrain. The numerical model is also used for a parametric study in which the effect of various suspension and powertrain parameters on the dynamic coupling that exists between the two is evaluated.

This paper studies the effect of different longitudinal load conditions, roundabout cross-sectional geometry, and different semi-truck pneumatic suspension systems on roll stability in roundabouts, which have become more and more popular in urban settings. Roundabouts are commonly designed in their size and form to accommodate articulated heavy vehicles (AHVs) by evaluating such affects as off-tracking. However, the effect of the roadway geometry in roundabouts on the roll dynamics of semi-tractors and trailers are equally important, along with their entry and exit configuration. , Because the effect of the roundabout on the dynamics of trucks is further removed from the immediate issues considered by roadway planner, at times they are not given as much consideration as other roadway design factors.

Two alternative methods are presented for studying the comfort, and possibly fatigue, effects of vehicle seats, in particular truck seats that include a seat suspension. The methods, named “aPcrms” and “SPD%” for the purpose of this study, are based on analyzing the pressure profile at the seat cushion/human body interface in a manner that accounts for the contact area, pressure distribution, and change in contact pressure. The alternative methods are compared with methods suggested in the past for vehicle seats, using a laboratory test rig and a truck seat with a conventional foam cushion and an air-inflated seat cushion. The results show that the proposed methods better highlight the human comfort differences between the two cushion types, and provide objective measures that better correlate with subjective measures from a separate field study on the same types of seats.

One popular complement to track testing that successful race teams use to better understand their vehicle’s behavior is dynamic shaker rig testing, such as 7-post and 8-post testing. Compared to track testing, rig testing is more repeatable, costs less, and can be conducted around the clock. While rig testing certainly is an attractive option, an extensive number of tests may be required to find the best setup. To make better use of rig test time, more efficient testing methods are needed. One method to expedite rig testing is to use rig test data to perform system identification and generate a model of the experiment, which may then be applied to identify potential gains for further rig study. This study develops a system identification method for use in rig testing, using data generated from a known physical model. The results show that this method can be used to accurately predict sensor response during an 8-post test for different shock selections.

The primary purpose of this paper is to evaluate how various time-domain system identification techniques, which have been successfully used for different dynamic systems, can be applied for identifying heavy truck dynamics. System identification is the process by which a model is constructed from prior knowledge of a system and a series of experimental data. The parameters obtained from the identification process can be used for developing or improving the mathematical representation of a physical system. In contrast to lighter vehicles, heavy trucks have considerably more flexible frames. The frame can exhibit beaming dynamics in a frequency range that is within the range of interest for evaluating the ride and handling aspects of the truck. Understanding the dynamic contributions of the truck frame is essential for improving the ride characteristics of a vehicle. This understanding is also needed for designing new frame configurations for the existing or new production trucks.

This experimental study determines the effect of truck frame stiffness on truck ride, as measured by B-post vertical and fore-aft accelerations. After describing the test setup, the paper will describe the details of two truck frames that are used in a series of tests conducted on a class-8 truck in the laboratory. The frames that are used for the tests include what commonly is used in production trucks in North American markets (called “baseline” frame), and a frame that is 15% thinner (called “thin” frame). The test results, which are analyzed in frequency domain, are compared for the two frames. They indicate that the thin frame performs similar to the baseline frame when the truck is subjected to heave inputs. For roll inputs, the thin frame causes an increase in B-post accelerations, mostly at frequencies associated with the frame beaming and the primary (axle) suspension resonance.

This study provides an experimental account of the effect of panhard rod suspensions on heavy truck ride, as evaluated by the B-post vertical and fore-aft accelerations. After describing the test setup, the paper will describe the details of two rear cab suspensions that are commonly used in North American trucks. Cab suspensions with dampers or similar elements that are used to provide lateral forces at the rear of the cab (called “baseline” cab suspension for the purpose of this study) and those that use a lateral link with a torsion spring at one end-commonly called “panhard rod”-are the two classes of rear cab suspensions that are considered in this study. The tests are performed on a class 8 truck that is setup in the laboratory for the purpose of providing good test repeatability and conducting an accurate design of experiment. The test results, which are analyzed in frequency domain, are compared for the two cab suspensions.

This paper presents the results of a study on the effect of truck configurations on the roll stability of commercial trucks in roundabouts that are commonly used in urban settings with increasing frequency. The special geometric layout of roundabouts can increase the risk of rollover in high-CG vehicles, even at low speeds. Relatively few in-depth studies have been conducted on rollover stability of commercial trucks in roundabouts. This study uses a commercially available software, TruckSim®, to perform simulations on four truck configurations, including a single-unit truck, a WB-67 semi-truck, the combination of a tractor with double 28-ft trailers, and the combination of a tractor with double 40-ft trailers. A single-lane and multilane roundabout are modeled, both with a truck apron. Three travel movements through the roundabouts are considered, including right turn, through-movement, and left turn.

The effect of primary suspensions (shock absorbers) on the body and axle motion of heavy trucks is investigated. A simulation program is used to show how damper tuning of conventional passive dampers and “skyhook” semiactive dampers effect ride, as measured by body acceleration, and axle motion, as measured by tire acceleration and tire deflection. Special attention is made to the coupling and interaction between the body and the axle motion. It is shown that passive and semiactive dampers have a different effect on the axle and body dynamics.

Race teams frequently use tools like shock dynamometers (dynos) to characterize the complex behavior of shock absorbers after they are built and before they are put on the race car for testing to make sure they perform as expected. One way to make use of this shock dyno data is to use it to create a model to predict shock absorber performance over a wide range of inputs. These shock models can then be integrated into vehicle simulations to predict how the vehicle will respond to different shock selections, and aid the race engineer to narrow down possible shock setups before track testing. This paper develops an intuitive nonlinear dynamic shock absorber model that can be quickly fit to experimental data and implemented in simulation studies. Unlike other existing dynamic race shock models, it does not suffer from the complexity of modeling complex physical behavior, or the inefficiencies of unstructured black-box modeling.

This study reports the objective results from a project investigating the effectiveness of several newly proposed metrics to compare fatigue performance between two distinct truck seat cushions, specifically standard foam versus air-inflated cushions. The subjective results from this project have shown the drivers in our study prefer the air-inflated seat cushion over their normal foam cushion, and that air-inflated seat cushions provide advantages in terms of comfort, support, and fatigue [1]. This study aims to further explore the differences between these two different seat cushions by highlighting the differences in objective pressure distribution measurements. Road tests were performed using existing commercial trucks in the daily operations of Averitt Express. A retrofit air-inflated seat cushion was installed in the fleet's trucks, and the drivers were allowed to adjust to the seats over approximately one week.

This study reports the subjective results from a project investigating the effectiveness of several newly proposed metrics to compare fatigue performance between two distinct truck seat cushions, specifically standard foam versus air-inflated cushions. We also highlight some of the fundamental differences between air-inflated and foam seat cushion based on driver's perceptions. Road tests were performed using existing commercial trucks in the daily operations of Averitt Express. A retrofit air-inflated seat cushion was installed in the fleet's trucks, and the drivers were allowed to adjust to the seats over approximately one week. After this adjustment period, twelve drivers rode on both the air-inflated seat cushion and their original foam seat cushion during their regularly scheduled routes. Surveys were collected throughout the test sessions and the truck seats were fitted with instrumentation to capture physical measurements of seat pressure distribution.

The 2014 SAE Buckendale Lecture will address the past developments and challenges of electromechanical “smart” systems for improving commercial vehicles' functionality. Electromechanical systems combine traditional mechanical devices with electrical components to provide far higher degree of functionality and adaptability for improved vehicle performance. The significant advances in microprocessors and their widespread use in consumer products have promoted their implementation in various classes of vehicles, resulting in “smart” devices that can sense their operating environment and command an appropriate action for improved handling, stability, and comfort. The chassis and suspension application of electromechanical devices mostly relate to controllable suspensions and vehicle dynamic management systems, such as Electronic Stability Control.

This paper provides an insight into some of the benefits of evaluating heavy truck dynamics in the laboratory. Recognizing that the vast majority of ride and engineering tests that are commonly conducted on heavy trucks occur in the field or on test tracks, the paper shows that there is much to be gained from dynamic testing of a truck in the laboratory under proper conditions. Of course, the main reasons for considering laboratory testing are that the tests can be conducted a) at much lower costs than field testing, and b) in a much more repeatable manner. The argument against laboratory tests has always been that they may not represent the true dynamic environment that a truck would experience in revenue service. Some of the issues related to properly setting up a truck in the laboratory such that the experiments can relatively accurately emulate what occurs in the field are presented.

This paper presents the setup and test results for evaluating kinematics characteristics of heavy truck suspensions in their actual environment, while installed on the truck. The paper will provide the truck suspension kinematics that are important to the truck dynamics, namely vertical stiffness, roll stiffness, and roll steer. It also presents the nature of the hysteresis that commonly exists in heavy truck suspensions. Next, we present a detailed account of the issues that must be taken into consideration in practice, when measuring various kinematics aspects of a truck suspension. Using a successful laboratory setup for measuring kinematics of heavy truck suspensions, the paper provides an evaluation of a class 8 truck with a trailing arm suspension. The description of the setup provides the details of the instrumentation and means of actuation that are necessary for collecting good kinematics data.

Dynamic game theory brings together different features that are keys to many situations in control design: optimization behavior, the presence of multiple agents/players, enduring consequences of decisions and robustness with respect to variability in the environment, etc. In the presented methodology, vehicle stability is represented by a cooperative dynamic/difference game such that its two agents (players), namely, the driver and the direct yaw controller (DYC), are working together to provide more stability to the vehicle system. While the driver provides the steering wheel control, the DYC control algorithm is obtained by the Nash game theory to ensure optimal performance as well as robustness to disturbances. The common two-degree of freedom (DOF) vehicle handling performance model is put into discrete form to develop the game equations of motion.

A detailed study of the effects of shim stack assemblies on performance of hydraulic mono-tube vehicle shock absorbers is presented. Currently, shim stacks are modeled as blow-off valves in hydraulic models of shock absorbers. Using this simplification, important material and geometrical properties of shim stacks cannot be studied and their effects cannot be understood on overall damper performance. In this paper, shim stack deflection is investigated and a mathematical model is presented for shim stack deflection. This model is then incorporated into the mathematical model of a hydraulic damper and various properties of shim stack and their effects on damper characteristics are studied. Energy and variational methods were used to develop the mathematical model of the shim stack. The mathematical model also takes into account the sliding effects of the shims on each other when the shim stack is deflected.

This study provides a simulation evaluation of the effect of maintaining balanced airflow, both statically and dynamically, in heavy truck air suspensions on vehicle roll stability. The model includes a multi-domain evaluation of the truck multi-body dynamics combined with detailed pneumatic dynamics of drive-axle air suspensions. The analysis is performed based on a detailed model of the suspension's pneumatics, from the main reservoir to the airsprings, of a new generation of air suspensions with two leveling valves and air hoses and fittings that are intended to increase the dynamic bandwidth of the pneumatic suspensions. The suspension pneumatics are designed such that they are able to better respond to body motion in real time. Specifically, this study aims to better understand the airflow dynamics and how they couple with the vehicle dynamics.