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This paper reviews the history of heavy truck noise legislation in the U.S. Both legislative activity and the response of vehicle and engine manufacturers are described. The cost cycle experienced by manufacturers is also described. Over a period of time, the costs involved in meeting noise regulations are reduced without increasing truck noise levels. Data is presented which shows that public complaints about truck noise are often related to modified vehicle exhaust systems. The data shows that modified exhaust systems have an especially severe effect on compression brake noise. Additional results suggest that some trucks with extensively modified exhaust systems may be able to pass the in-use noise standard.

Structural attenuation of a running diesel engine measured by a new technique showed a constant value regardless of engine speeds. It was verified by this result that structural attenuation is a physical quantity unique to the structure of each engine and, therefore, a good indicator for evaluation of low noise engine structure. In addition, a hydraulic excitation test rig was devised to measure structural attenuation directly and to make effective use of it for noise reduction. Based on the accurate measurements by the excitation test rig, modal analysis and system simulation were conducted for implementation of countermeasures against noise.

Filtering the road unevenness, i.e. comfortable ride for passengers, and vibration and shock isolation for freight, is one of the main thrusts behind the development of active and semi-active suspensions. For control of these systems, a variety of different schemes, mainly from the linear stochastic control area, have been proposed by researchers: and 1/4-car active and semi-active suspension models are used to simulate these schemes. Besides the main input an exogenous input is also considered, namely a velocity disturbance originating from the road unevenness. In most of the literature in this area, this disturbance is considered as white noise, which it hardly is. This a-priori statistical description of the disturbances, is necessary for using stochastic control techniques. In this paper, a comparison of some of these control schemes is performed.

When truck tires have a deformation such as radial runout, flat spot, and abnormal wear as a result of panic braking, they affect vehicle vibration in the form of displacement input whose spectrum involves higher order terms of tire revolution. While a truck has vibration modes of frame bending as well as pitching and unsprung-mass viberation in the input frequency range, the tire displacement input induces vehicle vibration as a combination of these modes. Results of calculations and experiments of a 4x2 medium-duty truck are analyzed and an example of means for improving ride comfort is described in this paper.

The sounds traditionally used as auditory displays and warnings in truck cabs have no meaning outside the context of the particular environment in which they are used. If an operator changes equipment, often an entirely new set of warnings and the associations between the various sounds and the situations to which they refer must be learned, while at the same time long-standing associations learned from previous experience must be overcome. Furthermore, research has shown that people operating complex systems can effectively differentiate only five or six different alarm or warning sounds. In an attempt to overcome these shortcomings, a new class of auditory display, referred to as auditory icons, is being investigated. Whereas conventional auditory displays are defined by their particular acoustic parameters, auditory icons are caricatures of naturally occurring sounds. Such sounds are representational in that they have stereotypical meanings across large portions of the population.

In July 1989, Hino Motors, Ltd. launched a new medium-duty truck series called the Cruising Ranger (Fig. 1), replacing its nine-year-old conventional model. The Cruising Ranger series has been developed under the concept of a “Stylish, Driver-Friendly, Profitable Truck” with an emphasis on harmonization with the social environment. It features major changes in exterior style and interior design, and improvements in basic performance such as comfort, drivability, safety, and fuel efficiency with careful consideration given to market requirements. The series also meets the 1989 Japanese exhaust emission standards. To accomplish these design enhancements, a number of new technologies have been introduced in the Cruising Ranger.

“Beaming” in trucks is due to a bending vibration of the frame resulting in a fore-aft motion at the driver location. It has been found that beaming motions are relatively unaffected by the suspension type or components, and, in particular, by the shock absorbers. Since beaming is due to a distributed dynamic effect, it is believed that modal nodes exist near the suspension attachments to the frame thus rendering the suspension ineffectual at controlling beaming. Another explanation of beaming is that an overall system dynamic mode exists such that at a specific frequency the relative velocity across the suspension is near zero thus producing little damping for that mode. This concept is developed here through the use of some simple models. The sensitivity of beaming to system configuration is then demonstrated through use of a rather complete overall tractor/trailer model.

Ride evaluations of prototype semi-active suspensions have demonstrated that acceleration alone is not sufficient in determining acceptable ride quality. The problem involves transient force behavior that is inherent to a semi-active suspension. This transient behavior can be present in both on-off and continuously variable semi-active suspensions. Force discontinuities created by semi-active suspensions can create jerk (the derivative of acceleration) and unwanted audible noise. This paper proposes simple solutions for eliminating unwanted jerk and noise. These solutions involve modifications to the basic control algorithms or system hardware.

This paper reports on the analysis of mechanisms concerning the engine exciting force and the rotational couple of forces. Because the new V10 engine has the biggest power and displacement which is 441kw and 30 litters respectively, its exciting force of 2.5th and 5th orders are very large. On the other hand, as the V-bank angular is 80 degrees, the additional 1st order yawing vibration is also occurred by the generation of the rotational couple of forces. So, the optimum design is needed to reduce these vibrations by the frequency response analysis when these forces are added to the engine crank shaft. Finally, the vibration level could be reduced much lower than the lower-powered engine by the optimum design of engine mounting by using the FEM and the adoption of the new mechanism for the cancellation of a rotational couple of force.

The 4M5 series of four-cylinder, in-line, direct-injection diesel engines has been released by Mitsubishi Motors Corporation for light and medium-duty trucks and buses. Featuring an updated structure and reflecting the employment of state-of-the-art technology in the design of every component, the new engine series offers high reliability and compact dimensions. Moreover, the new series well meets contemporary demands for high performance, low noise, and clean combustion.

During the starting of the vehicle, the friction clutch engagement sometimes generates judder. Judder prevents vehicles from starting smoothly, harms the ride comfort, and may produce damage to the drivetrain components. This unpleasant phenomenon, which often manifests in the form of noisy torsional vibrations of the drivetrain or a violent surging of starting vehicles, is an example of the many annoying problems that automotive engineers have been experiencing since the car was invented. Engineers and scientists have identified some causes of transient torsional oscillations connected to judder. Vibrations generated by the clutch facings when a special type of relationship between the friction coefficient and sliding speed occurs account for the most important source of judder.

Due to the rapid development in advanced complex machinery, the analysis of torsional vibrations for multi-junction, multi-branch systems is becoming a subject of increasing interest. Torsional vibration may occur within an operation range in a rotating system and cause a serious failure in the machine. This is the case when an excitating frequency gets close to the natural frequency of the system. In this paper, an efficient and accurate method has been developed to calculate torsional natural frequencies of complex rotating systems. The method is used in designing a drive-train of a chassis dynamometer simulating a multi-junction, multi-branch rotating system. Natural frequencies and mode shapes of the drive-train have been determined and used for further development in the components of the system.

Torsional rubber heavy vehicle suspensions have been used for over 60 years. The historical background makes an interesting engineering case study. A new simplified updated redesign of the system has been accomplished. It retains the long-life, relatively soft spring rate and roll stability advantages of the original design. Reduced adhesion stresses and a simplified vehicle leveling system are new advantages. Vehicle comparison testing with other suspension systems indicates significant improvement in ride comfort, stability and vibration reduction. Future designs will likely use new more sophisticated compression springs operating in combination with the torsional springs to further improve the ride.

Torsional vibration of a truck's powertrain system is due to the exciting force generated by the angular velocity fluctuation originating from the setting angle of the universal joint of the propeller shaft, which can cause such problems as rattling noise, booming noise, etc.. This paper will clarify the difference between a 6x4 truck and a 6x2 truck in the torsional vibration characteristics from the experimental results. This is accomplished by computation with a simple torsional vibration model of the powertrain system and investigating the contribution of torsional rigidities of the powertrain system's various components by a parameter study. As a result it has been clarified that the torsional rigidity of the through shaft for transmitting power to the two rear axles has a great influence on Noise, Vibration and Harshness of 6x4 trucks.

Powertrain torsional vibration has become a subject of increasing concern for the heavy duty truck industry in recent years. This is due in part to truck and diesel engine developments, and to drivetrain system trends. A computer simulation is an effective tool in analyzing this problem. A powertrain vibration analysis program has been developed by the authors. It has been used extensively in the evaluation and optimization of powertrain system performance. In this paper, first the heavy duty powertrain is characterized as a vibrating system. Its natural frequencies, mode shapes and frequency response characteristics are reviewed. Second, the theory of torsional vibration and its application in the simulation are described. The drivetrain is described as a discreet model. An undamped modal analysis is given as an eigenvalue problem.

This report presents a linear model for friction-induced vibration. The solutions to this model might be unstable in spite of a constant coefficient of friction. This is in agreement with the fact that squeal occurs not only just before stops. The method has been used to analyze squeal in both drum and disc brakes. The drum brake model consists of a drum and a shoe, the shoe being flexible while the drum is stiff. The analysis shows that instability may occur in the shoe-drum contact even with a stiff drum. Thus the shoe might be the “motor” of the vibration that propagates to the other parts of the brake system. The mode shapes for these unstable solutions occur as non-synchronous wave motions rather than as simple harmonic motions. These wave motions correspond well to measured motions of squealing brake shoes. The disc brake analysis shows similar instability, i.e. unstable non-synchronous wave motions with a flexible pad and a stiff disc.

The effect of adjusting the kick-off speed to attain a “worst case vehicle configuration” on drive-by noise measurements using test procedure SAE J986OCT88 was investigated. It was determined that similar noise results were obtained for both the “forced worst-case” vehicle and the actual worst-case vehicle. This information is a useful development tool due to the fact that a wide variety of axle ratios, tires, and transmissions are available as options on light duty trucks, making it difficult to determine or obtain the actual worst-case vehicle. Forcing the worst-case configuration allows for the testing of vehicles when the exact worst case vehicle is not available.

The ride dynamics of articulated heavy trucks were studied to assess the benefits of applying electronically controlled suspension elements. Computer simulations were used to compare passive, two-state and continuous semi-active, and fully active suspensions. These results prompted further work to develop a prototype active suspension, operating according to a limited bandwidth strategy, which was tested on a full size, single-wheel-station vibration rig. With the active prototype, root mean square body vertical acceleration was 30% lower than with a production air suspension, during a test simulating travel over a very good road profile. RMS dynamic tyre forces, generated by the active prototype were similarly 20% lower. Mean power consumption during this test was 1.2kW. Further consideration of the limited bandwidth active suspension led to the invention of a substantially passive equivalent.

Numerical and experimental methods are applied effectively to reduce the interior noise of a mini-bus. In the frequency range where the booming noise occurs, acoustic forced response analysis is carried out, where experimentally measured vibrations of the floor by excitation test are used as boundary conditions. Through this analysis, the panels having positive effects to the interior noise are identified and confirmed through vehicle test. Then the coupling between the floor panels and the interior acoustic field is considered and the coupled acoustic field is analyzed by Boundary Element Method(BEM). As the result, the interior noise level of the bus is reduced effectively by structural modifications of the panels.

A new method to predict brake squeal occurrence was developed by MSC under contract to Ford Motor Company. The results indicate that the stability characteristics of this disc brake assembly are governed mainly by the frictional properties between the pads and rotor. The stability is achieved when the friction coefficient of the pads is decreasing as the contact force increases. Based on the results, a stable brake system can be obtained without changing the brake structure by incorporating the appropriate frictional coefficient in the brake system. The method developed here can be also used as a tool to test the quality of any brake design in the early design stage.