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Technical Paper

145 - 210 Horsepower Agricultural Tractor Noise Reduction Program

This paper summarizes the techniques and guidelines which were used to reduce the driver perceived noise level of a 145-210 HP series of agricultural tractors. Graphs of case study test results and comments on subjective noise quality are provided to guide the acoustic novice through the complexities of the vehicle sound environment in a methodical problem solving format.
Technical Paper

3D Aeroacoustics Simulation of a Complete Bus Exhaust System

Health related problems in over populated areas are a major concern and as such, there are specific legislations for noise generated by transport vehicles. In diesel powered commercial vehicles, the source for noise are mainly related to rolling, transmission, aerodynamics and engine. Considering internal combustion engine, three factors can be highlighted as major noise source: combustion, mechanical and tailpipe. The tailpipe noise is considered as the noise radiated from the open terminations of intake and exhaust systems, caused by both pressure pulses propagating to the open ends of the duct systems, and by vortex shedding as the burst leaves the tailpipe (flow generated noise). In order to reduce noise generated by vehicles, it is important to investigate the gas interactions and what can be improved in exhaust line design during the product development phase.
Technical Paper

5480 Reach Truck-A New Concept in Reach Track Design

The new 5480 Reach Truck, designed at Dynamic Industries, introduces a movable frame between the main frame and the telescopic boom. The use of this movable frame allows the usually fixed boom pivot to be elevated for greater lifting heights with smaller boom sections. By combining the motions of the boom and the movable frame, horizontal motion at the boom tip is possible without moving the truck. With the movable frame, the total machine height and length can be reduced for a given lifting goal. Another advantage of the movable frame is the ability to reach further below grade than is now possible in the industry. The 5480 Reach Truck has a maximum lift of 54 feet (16.5 meters) and can reach 24 feet (7.3 meters) below-grade.
Technical Paper

A 900 Ton Crawler Crane with 12’ × 12’ Main Boom Cross Section Disassembles for Truck Transport on the Interstate

The LTL-900 Transi-Lift crane features front and rear crawler-mounted load platforms connected with a hoist-supporting five foot diameter pipe section. The pin-together main boom is available in lengths up to 400 feet and completely disassembles for ease of transport to and from the jobsite. The crane requires three operators and can hoist, boom, swing and travel simultaneously with maximum loads. Upending, moving and setting large refinery vessels is facilitated by the mobility of the crawler-supported crane on unprepared surfaces. Up to 1000 tons of 36 ton concrete beams or equivalent are required as counterweight to develop the ANSI B30.5 approved capacities.
Technical Paper

A Bus for Denver’s Mall

A unique shuttle bus is being constructed by Minicars, Inc., and Walter Vetter Karosserie-werk for Denver’s Transitway/Mall. The bus is designed for frequent stop, low speed service in a downtown pedestrian environment. It features a very low floor and multiple wide doors for rapid passenger boarding and deboarding. Two versions will be supplied for comparative evalation, a low noise diesel configuration and a battery-electric configuration. Either version can subsequently be converted to the alternative propulsion system.
Technical Paper

A Commercial Excavator: Analysis, Modelling and Simulation of the Hydraulic Circuit

The paper addresses some aspects of an ongoing research on a commercial compact excavator. The interest is focused on the analysis and modelling of the whole hydraulic circuit that, beside a load sensing variable displacement pump, features a stack of nine proportional directional control valves modules of which seven are of the load sensing type. Loads being sensed are the boom swing, boom, stick and bucket, right and left track motors and work tools; instead, the blade and the turret swing users do not contribute to the load sensing signal. Of specific interest are the peculiarities that were observed in the stack. In fact, to develop an accurate AMESim modelling, the stack was dismantled and all modules analysed and represented in a CAD environment as 3D parts. The load sensing flow generation unit was replaced on the vehicle by another one whose analysis and modelling have been developed using available design and experimental data.
Technical Paper

A Distributed Sensor for Sensing Dynamic Deflections

A distributed sensor is created to sense the rate of change in deflection of beam-like structures such as crane booms. This sensor will be useful in electrohydraulic compensation of boom deflections. The sensor is made of an array of strain-sensitive segments such as strain gages or piezoelectric film. In this example, segments of piezoelectric film convert strains on the surface of a vibrating beam into electrical outputs. These outputs are connected to low impedance signal conditioners. The output of the signal conditioners are then interpolated with a weighting vector that incorporates Lagrange polynomials, specified boundary conditions, and the desired location(s) of measurement. A simple linear combiner circuit combines the electrical outputs into the deflection velocity at the desired points.
Technical Paper

A New Method Development to Predict Brake Squeal Occurrence

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.
Technical Paper

A New Milestone is Set for Light and Medium Truck Transmission Profiles

The paper covers a new generation of manual transmissions for light and medium-duty trucks, vans and buses, initially introduced in a 5-speed version. The product reflects levels of driving comforts which are new to this class of vehicle worldwide with respect to shiftability, shift feel, noise emission, efficiency and durability.
Technical Paper

A New Narrowband Active Noise Control System in the Presence of Frequency Mismatch and its Application for Steady-State Blower Noise

In order to reduce high-frequency harmonic noise produced by the blower in the auxiliary system of a fuel cell vehicle (FCV), a narrowband active noise control (ANC) method instead of conventional passive mufflers is adopted since the blower demands clean air condition and expects good acoustic performance. However, in ANC practical applications, the frequency difference between reference signal and actual primary signal, i.e., frequency mismatch (FM), can significantly degrade the high-frequency performance of narrowband ANC system. In this paper, a new narrowband ANC system is proposed to compensate for the performance degeneration due to the existence of FM and improve noise reduction at high frequencies. The proposed system consists of two parts: the Filtered Error Least Mean Square (FELMS) algorithm filtering the primary signals at wide frequency range other than those at the targeted frequencies, and the FM removal algorithm proposed by Yegui Xiao.
Technical Paper

A North European Tractor Cab

A farm tractor protection cab made of thin steel sheet pressings is described. The cab is designed and produced using entirely automotive-type procedures. Curved glasses and a dampening suspension of the glasses are found to be an important means of achieving a low noise level in the cab. Using the pressing technique when producing a steel cab makes it possible to give the various cab details rigidity with a minimum of material. When welded together, these details form a very stiff cab body, which gives the necessary mechanical strength. The curved surfaces, the radii, and the round forms, which from a tooling point of view are natural for pressed steel parts, also have a vibration-dampening effect on the entire cab construction, thus making it easier to design a quiet tractor cab. Mounted on a farm tractor of conventional design, the cab meets the noise rating number ISO N85.
Technical Paper

A Study of Sound Source Characteristics for Vehicle Airborne Transfer Function Measurement

Transfer function measurements are the basis for construction of conventional test based source-path-receiver model of a vehicle. Interior noise of a vehicle can be synthesized using source excitation (both acceleration at source and near source sound pressure level) and its corresponding transfer function (Vibro-Acoustic Transfer Function (VATF) and Acoustic Transfer Function (ATF) respectively) to the interior of vehicle. Ideally ATF should be linear and independent of sound source, dependent only on size of air cavities, body structure and its material characteristics in between receiver and source location. But practically because of the type of excitation signal used to excite the sound source and characteristics of sound source itself, there is a possibility of variations in amplitude of acoustic transfer function.
Technical Paper

A Study of the Vehicle Acoustic Control for Booming Noise Utilizing the Vibration Characteristics of Trunk Lid

An acoustic control technique for reducing booming noise caused by road surface roughness is described. This noise, mainly in the frequency range between 25 and 40Hz and accompanied by a pressure sensation, is closely related to suspension vibration characteristics and the acoustic response of the vehicle compartment. A reduction method which separates the highest acoustic response from suspension resonance in this frequency region is proposed. An acoustic simulation model is used to estimate the effects of the luggage compartment on this noise and of trunk lid vibration characteristics in optimizing acoustic properties of the compartment. As a result, a frequency region for trunk lid resonance which lowers booming noise is obtained. Estimated booming noise reduction is experimentally confirmed in road tests. A study of human auditory characteristics is also conducted to ascertain the frequency range and booming noise level which produce uncomfortable sensations.
Technical Paper

A Study on Drum-Brake Noise of Heavy Duty Vehicle

This paper presents an experimental study on the brake noise having a main frequency of about 500 Hz. From the vibration modes of the brake components during the brake noise occurrence, some resonance systems which might be the cause of the noise were considered. As a result of investigating these resonance systems experimentally, the resonance system which concerns to the noise was found out. From the resulting evaluation of the noise by changing the vibration characteristics of the resonance system through modification of the brake components, it was found that the spring constant and the damping coefficient of the wheel brake component correlate well to the brake noise level. Using these correlations have made it easier to improve the brake noise.
Technical Paper


Despite the size and importance of the fleet market, refiners have little information on the antiknock requirements of commercial vehicles. Considerable interest has been displayed in obtaining reliable data in this area. Some road survey data have been obtained in the past; however, truck engines are more prone to high-speed knock due to today’s more sensitive fuels and higher governed speeds. Knock under these conditions is more damaging and cannot be heard due to the masking effect of the high level of vehicle noise on the road. A chassis dynamometer technique has been developed to overcome this noise barrier and thereby provide realistic octane requirement data. Data obtained with this technique on commercial-type fuels were used to construct what is described as an “octane requirement map”. This map extends the usefulness of the data and is a unique and effective means of expressing octane requirements, particularly how requirements are related to the sensitivity of the fuel.
Technical Paper

A Transfer Path Approach for Experimentally Determining the Noise Impact of Hydraulic Components

This work contributes to the overall goal of identifying and reducing noise sources and propagation in hydraulic systems. This is a general problem and a primary design concern for all fluid power applications. The need for new methods for identification of noise sources and transmission is evident in order to direct future modeling and experimental efforts aimed at reducing noise emissions of current fluid power machines. In this paper, this goal is accomplished through the formulation of noise functions used to identify contributions and transfer paths from different components of the system. An experimental method for noise transfer path analysis was developed and tested on a simple hydraulic system composed of a reference external gear pump, attached lines, and loading valve. Pressure oscillations in the working fluid are measured at the outlet of the pump. Surface vibrations are measured at multiple locations on the pump and connected system.
Technical Paper

Acoustic Analysis of Truck Cab

This paper presents the results of acoustic analyses of light duty truck cabs by actual vehicle testing and by numerical analysis utilizing the boundary element method (BEM). In the resonance mode analysis using BEM, by taking into account the vibration characteristics of cab panels, the presence of the modes other than the purely acoustic cavity resonance modes were confirmed. The contribution of the panel vibrations to booming noise that occurs in actual light duty trucks was analyzed. BEM analysis showed that some of the panel vibration had a negative contribution to booming noise. In other words, decreasing vibration in such a section was shown to increase sound pressure. The results of the BEM analysis match well with actual test results. It has thus been demonstrated that BEM is an effective method for analyzing truck interior noise reduction.
Technical Paper

Acoustic Design of an Innovative Sound Package for Heavy-duty Cabin for Future Generation European Trucks

An innovative methodological approach for the virtual design of heavy-duty truck cabin acoustic packages is described together with its application to a truck model forecasted in 2008. A properly tailored version of Statistical Energy Analysis numerical approach to truck cabin peculiarities has been defined, with a special focus on aerodynamic noise investigation, being one of the most relevant noise sources in a truck cabin running on highways at constant speed. Moreover, an innovative concept for acoustic packages has been defined and applied, achieving a significant improvement in the mid-frequency range and speech intelligibility in the experimental verifications on the road.
Technical Paper

Active Vibration Damping for Construction Machines Based on Frequency Identification

Typically, earthmoving machines do not have wheel suspensions. This lack of components often causes uncomfortable driving, and in some cases reduces machine productivity and safety. Several solutions to this problem have been proposed in the last decades, and particularly successful is the passive solution based on the introduction of accumulators in the hydraulic circuit connecting the machine boom. The extra capacitance effect created by the accumulator causes a magnification of the boom oscillations, in such a way that these oscillations counter-react the machine oscillation caused by the driving on uneven ground. This principle of counter-reacting machine oscillations through the boom motion can be achieved also with electro-hydraulic solutions, properly actuating the flow supply to the boom actuators on the basis of a feedback sensors and a proper control strategy.
Technical Paper

Advanced Hydraulic Systems for Active Vibration Damping and Forklift Function to Improve Operator Comfort and Machine Productivity of Next Generation of Skid Steer Loaders

Mobile Earth Moving Machinery like Skid-steer loaders have tight turning radius in limited spaces due to a short wheelbase which prevents the use of suspensions in these vehicles. The absence of a suspension system exposes the vehicle to ground vibrations of high magnitude and low frequency. Vibrations reduce operator comfort, productivity and life of components. Along with vibrations, the machine productivity is also hampered by material spillage which is caused by the tilting of the bucket due to the extension of the boom. The first part of the paper focuses on vibration damping. The chassis’ vibrations are reduced by the use of an active suspension element which is the hydraulic boom cylinder which is equivalent to a spring-damper. With this objective, a linear model for the skid steer loader is developed and a state feedback control law is implemented.