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Technical Paper

Novel, Compact Devices for Reducing Fluid-Borne Noise

2011-05-17
2011-01-1533
Hydraulic systems pose a particular problem for noise control. Due to the high speed of sound in hydraulic fluids, components typically designed to reduce fluid-borne noise can easily exceed practical size constraints. This paper presents novel solutions to creating compact and effective noise control devices for fluid power systems. A hydraulic silencer is presented that utilizes a voided polymer lining in lieu of a pressurized bladder. Theoretical modeling is developed which predicts device performance and can assist in future design work. Experimental results are presented to demonstrate the performance of the device. Both voided and non-voided liners are tested to show the effect of the voiding on the performance. In addition, theoretical modeling and experimental results are presented for a prototype Helmholtz resonator that is two orders of magnitude smaller than previously developed devices.
Journal Article

Gerotor Pumps for Automotive Drivetrain Applications: A Multi Domain Simulation Approach

2011-09-13
2011-01-2272
This paper presents a simulation model for the analysis of internal gear ring pumps. The model follows a multi domain simulation approach comprising sub-models for parametric geometry generation, fluid dynamic simulation, numerical calculation of characteristic geometry data and CAD/FEM integration. The sub-models are interacting in different domains and relevant design and simulation parameters are accessible in a central, easy to handle graphical user interface. The potentials of the described tool are represented by simulation results for both steady state and transient pump operating conditions and by their correlation with measured data. Although the presented approach is suitable to all applications of gear ring pumps, a particular focus is given to hydraulic actuation systems used in automotive drivetrain applications.
Technical Paper

Engine Oil Air Entrainment and Release - Preliminary Studies

2009-06-15
2009-01-1874
Modern engines rely more and more on the engine oil to serve increasingly complex hydraulic functions such as, for example, controlling cylinder deactivation - a means of significantly increasing fuel efficiency. However, the success of hydraulic methods of activating mechanical responses in engines (or other devices) is dependent on the degree of incompressibility of the hydraulic fluid. As a consequence, those engine oil properties that impart susceptibility to foam formation in areas of hydraulic operations of the engine are detrimental to the engine's performance and durability. This paper is an initial study of aeration, air entrainment, and air release under pressure decrease using a simple bench test. The preliminary information reported suggests the potential application of the instrumental approach developed to measure the rate of foam formation from the air entrained in engine oils and the resistance of such foam to collapse.
Journal Article

Experimental Procedure for Measuring the Energy Consumption of IC Engine Lubricating Pumps during a NEDC Driving Cycle

2009-06-15
2009-01-1919
The paper presents an experimental procedure for comparing different families of IC Engine lubricating pumps in terms of total consumed energy in a NEDC driving cycle. Measures are performed on a test rig able to reproduce the oil temperature profile, the lubrication circuit permeability and its variation during the engine warm-up. The pump under test is driven by a variable speed electric motor supplying the engine velocity profile of the driving cycle. The load on the pump is generated by means of a variable restrictor controlled in a closed loop by a proper combination of speed, temperature, flow rate and pressure signals in order to replicate the typical permeability of the lubricating circuit.
Technical Paper

Vibro-Acoustic Simulation of Diesel Injection Ducts

2009-05-19
2009-01-2057
High pressure pipes of the diesel injection system seem to represent a weak point in terms of vibration and acoustic radiation of the whole injection system. Investigations have highlighted this phenomenon. The injectors induce acoustic waves which propagate in the viscous diesel contained in the injection pipes. A strong coupling can occur sometimes between these acoustic waves and the duct structural modes leading to intensive mechanical vibration and acoustic radiation; and sometimes to a possible failure of the pipe. Numerical simulations offer a good platform to predict such vibration and can be used in order to prevent any structural component failure and to decrease the resulting acoustic radiation. This paper presents a vibro-acoustic study performed with the finite element code ACTRAN to estimate which parameters play a role in this process and to provide some guidelines for avoiding problems.
Technical Paper

Application of Hydraulic Body Mounts to Reduce the Freeway Hop Shake of Pickup Trucks

2009-05-19
2009-01-2126
When pickup trucks are driven on concrete paved freeways, freeway hop shake is a major complaint. Freeway hop shake occurs when the vehicle passes over the concrete joints of the freeway which impose in-phase harmonic road inputs. These road inputs excite vehicle modes that degrade ride comfort. The worst shake level occurs when the vehicle speed is such that the road input excites the vehicle 1st bending mode and/or the rear wheel hop mode. The hop and bending mode are very close in frequency. This phenomenon is called freeway hop shake. Automotive manufacturers are searching for ways to mitigate freeway hop shake. There are several ways to reduce the shake amplitude. This paper documents a new approach using hydraulic body mounts to reduce the shake. A full vehicle analytical model was used to determine the root cause of the freeway hop shake.
Technical Paper

A Model for the Mechanical Subsystem of an Air Brake System

2009-12-13
2009-28-0058
Ensuring the safety of passengers is one of the prime challenges for vehicle design engineers. The braking system is the most important safety feature incorporated in a vehicle. Most of the commercial vehicles such as trucks, buses, etc., are equipped with an air brake system. The air brake system is sensitive to maintenance and needs to be monitored regularly to ensure its proper functioning. Current monitoring methods of air brake systems are predominantly manual in nature and can be performed only when the vehicle is stationary. One of the most important parameters that are critical for the proper functioning of an air brake system is the push rod stroke. The push rod stroke is related to the clearance between the brake pad/shoe and the brake drum and hence is indicative of brake wear. The objective of this research work is to study the mechanical subsystem of the air brake system and develop a mathematical model for the same.
Technical Paper

Characterization and Reduction of Power Steering Hiss noise for Passenger Car

2009-12-13
2009-28-0049
Passenger comfort has become one of the key areas to achieve success in the passenger car market segment. New upcoming products are rejected by customers not because of durability, but more by irritants like noise and vibrations. Hiss noise is one of the major irritants in passenger cars employing hydraulic power steering. This paper describes an attempt to evolve a structured methodology to identify and characterize power steering hiss noise from a rack and pinion type hydraulic power steering system. Extensive testing and detailed analysis of noise data was performed for characterization of power steering hiss noise, from which frequencies responsible for hiss noise were identified at vehicle level and component level. Subsequently several solutions were tried to reduce the hiss noise to an acceptable level considering the limitations of manufacturing and cost. Test results show the effectiveness of approach and methodology towards arriving at a solution for hiss noise.
Technical Paper

Closed Loop Pressure Control System Requirements and Implementation

2011-04-12
2011-01-0391
Electro-hydraulic actuation has been used widely in automatic transmission designs. With greater demand for premium shift quality of automatic transmissions, higher pressure control accuracy of the transmission electro-hydraulic control system has become one of the main factors for meeting this growing demand. This demand has been the driving force for the development of closed loop pressure controls technology. This paper presents the further research done based upon a previously developed closed loop system. The focus for this research is on the system requirements, such as solenoid driver selection and system latency handling. Both spin-stand and test vehicle setups are discussed in detail. Test results for various configurations are given.
Technical Paper

Theoretical and Experimental Investigation of Flow Rate of Leveling Valve with Filters for Different Operating Angles

2013-01-09
2013-26-0042
Leveling valves are typical pneumatic flow control valves which are fitted in the vehicle chassis to supply or deplete air pressure in the bellows so as to maintain the chassis always in a horizontal position, under the loaded or unloaded condition of vehicle or trailer. Therefore it is necessary to study the flow rate of air for different operating angles of leveling valve corresponding to the vehicle load. Filters are provided, one at the upstream and two at the downstream in order to prevent dust from entering into the valve and bellows. All flow control valves have an inherent flow characteristic that defines the relationship between ‘valve opening’ and flow rate under constant pressure conditions. Hence Computational Fluid Dynamics (CFD) can be utilized as a useful design tool to optimize the flow area of leveling valve and also to study the difference in pressure between upstream and downstream of a filter in order to push the fluid through the filters.
Technical Paper

System Modeling and Controls Design of a Two - Stage Spool Valve System of an Off - Road Vehicle

2013-01-09
2013-26-0111
A two-stage spool valve system is common in the hydraulic system of an off-road vehicle and used as hydraulics control element for controlling the hydraulic cylinder. Off-road vehicle industries mostly use a fixed-gain PID based controller for the flow control of the two-stage spool valve system. A hydraulic spool valve system exhibits highly nonlinear behavior, which makes it challenging to design a PID based controller to control its dynamics. This paper presents a method for the dynamic system model development of the two-stage spool valve system. This model will be useful to study the impact on the valve dynamics due to lubricating oil properties variation to avoid the potential system hazards and machine failure scenarios. An alternative control system design approach is also proposed based on the gain-scheduled control technique, wherein the non-linear dynamics of the valve system is linearized at different equilibrium points and PID gains are scheduled at these points.
Journal Article

Research on Vibration Isolation of Semi-Active Controlled Hydraulic Engine Mount with Air Spring

2014-04-01
2014-01-0008
Aiming at the abnormal vibration of driver seat of a passenger car in idle condition, vibration acceleration of engine, frame and seat rail was tested to identify vibration sources. Order tracking and spectrogram analysis indicated that the second order self-excitation of engine was the main cause. To solve the problem, semi-active controlled hydraulic engine mount with air spring of which characteristics could shift between a high dynamic stiffness and a low one was applied. Then the structure and principle of the mount with variable characteristics was introduced and control mode was analyzed. Dynamic characteristics were obtained by bench test. With sample mount applied, vibration of seat rail was tested again in multiple vehicle and engine working conditions. Dates showed that abnormal vibration in idle condition was extremely reduced and the mount could also meet the requirement of engine to dynamic stiffness in driving conditions.
Technical Paper

Dynamic Characteristics of a Full Car Fitted with Torsion-Eliminating Hydraulically Interconnected Suspension

2014-04-01
2014-01-0115
Abstract In this paper, a torsion-eliminating Hydraulically Interconnected Suspension (THIS) is proposed for the first time to reduce the undesired articulation (warp) stiffness of a two-axis vehicle. The dynamic characteristics of a typical sport utility vehicle (SUV) fitted with the THIS is investigated in the frequency domain. The equations of motion of the coupled mechanical and hydraulic sub-systems are presented. The vehicle basic mechanical sub-system is modeled as a 7 degrees of freedom (DOF) mass-spring-damper system. The hydraulic impedance method is employed to model the fluid sub-system. The relationships between the dynamic fluid states, i.e. pressures and flows, are determined by transfer matrices. Then the mechanical and hydraulic sub-systems are coupled through the mechanical-fluid boundary conditions.
Journal Article

Handling Analysis of a Vehicle Fitted with Roll-Plane Hydraulically Interconnected Suspension Using Motion-Mode Energy Method

2014-04-01
2014-01-0110
This paper employs the motion-mode energy method (MEM) to investigate the effects of a roll-plane hydraulically interconnected suspension (HIS) system on vehicle body-wheel motion-mode energy distribution. A roll-plane HIS system can directly provide stiffness and damping to vehicle roll motion-mode, in addition to spring and shock absorbers in each wheel station. A four degree-of-freedom (DOF) roll-plane half-car model is employed for this study, which contains four body-wheel motion-modes, including body bounce mode, body roll mode, wheel bounce mode and wheel roll mode. For a half-car model, its dynamic energy contained in the relative motions between its body and wheels is a sum of the energy of these four motion-modes. Numerical examples and full-car experiments are used to illustrate the concept of the effects of HIS on motion-mode energy distribution.
Journal Article

A Primer on Building a Hardware in the Loop Simulation and Validation for a 6X4 Tractor Trailer Model

2014-04-01
2014-01-0118
This research was to model a 6×4 tractor-trailer rig using TruckSim and simulate severe braking maneuvers with hardware in the loop and software in the loop simulations. For the hardware in the loop simulation (HIL), the tractor model was integrated with a 4s4m anti-lock braking system (ABS) and straight line braking tests were conducted. In developing the model, over 100 vehicle parameters were acquired from a real production tractor and entered into TruckSim. For the HIL simulation, the hardware consisted of a 4s4m ABS braking system with six brake chambers, four modulators, a treadle and an electronic control unit (ECU). A dSPACE simulator was used as the “interface” between the TruckSim computer model and the hardware.
Technical Paper

Development of Composite Brake Pedal Stroke Simulator for Electro-Hydraulic Braking System

2014-04-01
2014-01-0117
Abstract A brake pedal stroke simulator for Electro-hydraulic Braking System (EHBS) was developed to ensure the comfort braking pedal feel for the brake-by-wire system. An EHBS with an integrated master cylinder was proposed, and a composite brake pedal stroke simulator was designed for the EHBS, which was comprised of two inline springs and a third parallel one. A normally closed solenoid valve was used to connect the master cylinder booster chamber and the stroke simulator. The suitable brake pedal stroke was achieved by three stages of these springs' compression, whereas the solenoid valve was shutdown to enable mechanical control of the service brakes when electrical faults appeared.
Technical Paper

Noise Identification and Reduction in Multiple-Piston Hydraulic Pump

2005-05-16
2005-01-2460
The noise problem in a multiple-piston hydraulic pump was investigated through computer simulation combining lumped and distributed parameter models (CFD). Analysis results have shown that the source of noise is the turbulence flow and pressure perturbation in the pump gallery caused by check valve flow interference. It was identified that this flow induced noise can be reduced by modifying the check valve characteristic and its flow profile without compromising pump performance.
Technical Paper

Sideband and Sound Field Spatial Considerations in the Measurement of Gear Noise

2005-05-16
2005-01-2517
Measurement of gear noise requires accurate measurement of gear mesh harmonic sound levels. The sound signal may include sidebands, such that the frequency bandwidth and computation method of respective “order tracking” analysis will have a profound effect on measured sound levels. A further consideration is the spatial distribution of the sound field inside typical passenger cars and light duty trucks, in which sound levels can change dramatically within small distances. This paper provides a discussion of the data processing and measurement location effects at hand. It explains their influence and provides guidelines for their selection.
Technical Paper

Multivariate Statistical Methods for the Analysis of NVH Data

2005-05-16
2005-01-2518
The present work discusses the application of multivariate statistical methods for the analysis of NVH data. Unlike conventional statistical methods which generally consider single-value, or univariate data, multivariate methods enable the user to examine multiple response variables and their interactions simultaneously. This characteristic is particularly useful in the examination of NVH data, where multiple measurements are typically used to assess NVH performance. In this work, Principal Components Analysis (PCA) was used to examine the NVH data from a benchmarking study of hydraulic steering pumps. A total of twelve NVH measurements for each of 99 pump samples were taken. These measurements included steering pump orders and overall levels for vibration and sound pressure level at two microphone locations. Application of the PCA method made it possible to examine the entire set of data at once.
Technical Paper

Experimental And Numerical Study On Vibro-Acoustic Performance Of Axial Piston Pump

2005-05-16
2005-01-2320
An extensive experimental and numerical investigation was completed to improve the vibration and acoustic performance of a piston pump. A parametric study was carried out using an FEM model of the pump. The BEM model of the corresponding model was built to predict the noise levels and document the improvements during the dynamic optimization process of the system. Experimental modal and acoustic tests were done in order to verify the numerical results. Good correlation was observed between experimental and numerical results in both dynamic and acoustic parameters. Based on the modeling results, which were validated experimentally, design improvements were made.
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