Open-Loop Versus Closed-loop Control for Hydraulic Engine Mounts

<div class="section abstract"><div class="htmlview paragraph">Engine mount is one of the temperature sensitive components in the vehicle under-hood. Due to increasing requirements for improved fuel economy, the under-hood thermal management has become very challenging in recent years. In order to study the effects of material thermal degradation on engine mount performance and durability; it is required to estimate the temperature of engine mount rubber during various driving conditions. The effect of temperature on physical properties of natural rubber can then be evaluated and the life of engine mount can be estimated.</div><div class="htmlview paragraph">In this paper, a bench test is conducted where the engine mount is exposed to a step change in the environment around it, and the temperature of the rubber section is recorded at several points till a steady state temperature is reached. A time response curve is generated, from which a time constant is determined. Based on the time constant, an engine mount thermal model is built using a series of first order system response curves. The developed model is compared against measured temperatures from actual vehicle test data. Modeling approach and results discussed in this paper provide guidance for predicting temperature distribution inside the engine mount rubber material under various driving conditions for future vehicle programs to improve the component robustness and durability.</div></div>

<div class="section abstract"><div class="htmlview paragraph">During the last decade, fuel economy mandates (CAFE regulations) have driven engine downsizing and down-speeding trends. More recently, downsized turbos are percolating down to heavier SUVs and trucks. Larger/heavier vehicles require high torque engines to provide attractive dynamic performance. While higher torque requirements can be satisfied with new innovations like the variable compression engine, larger and more upscale vehicles also need to deliver higher quietness requirements. For this, the vibration control system for combustion induced forces with high torque engines become very important. To address both dynamic performance and quietness requirements, active engine mounts have been previously adopted, however challenges for light-weighting, downsizing, and costs have still persisted.</div><div class="htmlview paragraph">A new vibration isolation technology using passive and active vibration isolation system named Active Torque Rod(ATR) was studied for application to a new vehicle to realize quietness targets with a smaller, lighter, and less expensive engine mount system. The basic concept of the active torque rod is to set it’s resonance below 200 Hz so as not to degrade the acceleration noise due to down-sizing by utilizing the passive vibration-isolation region. However, the engine primary order (2<sup>nd</sup> order) booming noise degrades due the torque rod resonance below 200 Hz. Therefore, the resonance amplitude is suppressed by utilizing an inertia mass actuator in the torque rod and inputting an out-of-phase control force corresponding to the engine 2nd order input.</div><div class="htmlview paragraph">Technical details of ATR has been previously presented by R. Yamauchi, et al. [<span class="xref">4</span>]. Therefore this paper focuses on the benefits of applying an ATR to a premium C-segment SUV under development with a new inline 4-cylinder turbocharged engine. In order to achieve the acceleration noise targets, an active upper torque rod was applied to counter the large roll reaction force input. Acceleration noise levels were reduced by about 4 dB in the 250-800 Hz range when compared to conventional (passive) torque rod system. Both acceleration noise and booming noise achieved class leading levels. The proposed mounting system is approximately 8 kg lighter than the existing active control engine mount system.</div></div>

<div class="htmlview paragraph">The feasibility of frame vibration control in automotive vehicles using active hydraulic engine mounts is investigated. The focus of the study is on engine idle conditions. A 38<sup>th</sup> dynamic model of a simplified vehicle system is used. The simplified system consists of a powertrain and a bare chassis supported by air pillow mounts at four corners. A modified LQG (linear-quadratic-Gaussian) control design method was used to synthesize a reduced order controller with improved robustness to harmonic disturbances. This modified LQG controller design is compared to a standard LQG controller.</div> <div class="htmlview paragraph">First, the conceptual implementation of active hydraulic mounts is proposed. The proposed mounts use a close-coupled servo-valve for high-speed fluid injection. The active mounts are capable of producing either attractive or repulsive forces between the powertrain and chassis.</div> <div class="htmlview paragraph">Predictions are made for levels of frame vibration reduction and actuator power consumption from simulation of closed-loop system responses. These results provide an estimate of hardware requirements for the implementation of an active mount system.</div> <div class="htmlview paragraph">Various issues in control design for flexible structures are addressed. Chief among these are the issues of model order reduction and controller order reduction. Other issues addressed are disturbance robustness and parameter robustness.</div>

<div class="htmlview paragraph">It was desired to optimize an existing design concept of an active engine mount technology intended for engines with controlled cylinder deactivation. Specifically, this case study addresses how this active Noise & Vibration countermeasure was optimized using techniques derived from Taguchi Robust Engineering and DFSS strategies.</div> <div class="htmlview paragraph">This paper will focus primarily on how the appropriate robust design strategy was applied including the selection of the response function, a properly sized orthogonal array for the design control factors, and a sufficient noise strategy.</div> <div class="htmlview paragraph">A discussion of the design control factors, noise factors, Design of Experiment (DOE), and post-experiment standardized signal-to-noise ratio optimization analysis of the non-linear response function will be presented.</div> <div class="htmlview paragraph">Design control parameters included passive attributes of hydraulic engine mounts, as well as active/electronic components. Noise strategy was defined using three variables; heat and load cycling aging, ambient temperature, and static preload.</div> <div class="htmlview paragraph">In addition, passive performance of the active mount was analyzed using non-dynamic response functions and checked against best practice performance requirements.</div> <div class="htmlview paragraph">Results obtained from the study have documented the process to optimize a design for variation using dynamic response function for the active behavior of the mount, and nominal-the-best Type I from Taguchi Methods for passive behavior. The optimized design is planned to be prototyped and verified by experiment.</div> <div class="htmlview paragraph">The paper documents the application of the latest thinking in the field of Robust Engineering and DFSS strategies. The methods, techniques, and process are equally applicable to other elastomer based anti-vibration devices.</div>

<div class="htmlview paragraph"><b>VIBRATION formerly was classed as such without much thought as to the determination of its sources, Mr. Taub states, and then came isolation of the various causes. The first two vibrations to be segregated and vigorously attacked were the secondary inertias of reciprocating units and torsional vibration. The development of the six-cylinder engine was among the earliest attempts to eliminate secondaries, and it was also the earliest producer of torsional vibration.</b></div> <div class="htmlview paragraph"><b>Dynamics, combustion roughness, torsional roughness and structural weakness, are a few of the contributing causes of engine roughness. Consideration must be given to all these factors if an engine is to be considered inherently smooth, and each is analyzed.</b></div> <div class="htmlview paragraph"><b>Engine mountings should have low resistance to rotation about the longitudinal principal axis and to rotation about the vertical axis through the center of gravity, together with minimum shift of affective principal axis and vertical axis. The kind of material used in engine mountings should be determined after considering the overall characteristics of the mounting and the durability of those characteristics.</b></div>

<div class="htmlview paragraph">The ride and noise behavior of a vehicle is significantly affected by vibration transferred from the engine to the chassis through the engine mounts. In this paper conception and design strategies for engine mount systems based upon calculation and experimental methods are discussed. Analyses for static and dynamic engine loads and for idle shake vibrations are presented. The finite element analysis is applied to optimize a mount's rubber spring geometry. Furthermore, the role of the transfer path analysis in the optimization of an engine mount system is illustrated. Passive and semi-active engine mounts that significantly improve the isolation of the idle shake vibration will be discussed. Finally, fully active vibration absorbers which can be applied to solve noise problems, even at a late stage of a new car development program will be presented.</div>

<div class="htmlview paragraph">The production unit number of small diesel engine cars tends to decline except recreational vehicles in Japanese market in recent years, while the production unit number in Europe market keeps on increasing owing to the merits of the durability and the fuel consumption. The small diesel engines will have to be improved in the near future by solving major problems such as noise and vibration pollution, environmental pollution, improvement in performance of diesel engines, in order to expand the production of the engines.</div> <div class="htmlview paragraph">This paper refers to a basic study on the experimental and analytical methods for the reduction of resonant vibration in each vibration mode on some cylinder blocks of small high-speed diesel engines in rated engine speed range. Hammering test method, which is easy and useful for measuring frequency response functions, is carried out in the experiments. In this test, the cylinder blocks are directly excited with the impulse hammer, and more the main journals are excited via the newly-made force transmission parts in the next experiment. Two kinds of the engines which have been recently recognized as low noise and vibration engines are chosen in this study. The cylinder blocks of the engines are called of long skirt type and ladder frame type, respectively. The vibration characteristics of these cylinder blocks are obtained in the frequency range from 500 <i>Hz</i> to 2 <i>kHz</i> using the experimental modal analysis. This frequency range is chosen in consideration of the reliability of the vibration experiments. And the force transmission routes from the piston heads to the crank journals of each cylinder block are considered as mentioned in the latter experimental method. The experimental results are used to calculate the natural frequencies by the modal analysis and the calculated results are compared with the ones obtained from FEM analysis. Furthermore, the cylinder blocks are remodeled in order to reduce the vibrations of all modes using FEM analysis.</div> <div class="htmlview paragraph">Consequently, it has been shown that the vibration stress of the cylinder block can be reduced by higher rigidities and more lightening weights of the crankcase and the crank journals in the measured frequency range.</div> <div class="htmlview paragraph">The conclusions are described as follows;</div> <div class="htmlview paragraph"> <ol class="list nostyle"> <li class="list-item"> <span class="li-label">1</span> <div class="htmlview paragraph">The hammering test method using the force transmission parts is useful to measure the natural frequencies of a cylinder block. This method can be easy to get the equal results with the measured ones on running conditions without engine operation.</div> </li> <li class="list-item"> <span class="li-label">2</span> <div class="htmlview paragraph">The hammering test method using the force transmission parts can easily analyze the natural frequencies at all the vibration modes on equal conditions with running ones. Then the method is a useful tool for improving the vibration characteristics.</div> </li> <li class="list-item"> <span class="li-label">3</span> <div class="htmlview paragraph">It has been proved from the analytical viewpoints that the cylinder block of the ladder frame type can be adopted as low-noise, small diesel engines with little increase of the engine weight while maintaining higher rigidity.</div> </li> </ol> </div>

A rubber engine mount (EM) is a mechanical coupling between the engine and the chassis, and its main function is to diminish, in the chassis, the amplitude of vibrations caused for the engine operation. Such vibrations cause discomfort for vehicle passengers and reduce the EM lifetime. To increase the comfort of vehicle passengers and the lifetime of the EM, this paper presents an EM optimization by means of reducing three main criteria: the EM mass, the displacements transmitted to the chassis, and the mechanical stress in the EM rubber core. For carrying out the EM optimization, the optimum global determination by linking and interchanging kindred evaluators (GODLIKE), assisted by artificial neural networks (ANN) and finite element method (FEM), was used. Because of the optimization process, a reduction greater than 10 % was achieved in the three criteria in comparison with a baseline design. The frequency responses were compared and showed that although the optimization was carried out for the range of 5 Hz to 30 Hz the trend of reduced responses continues beyond this range. These results increased the comfort of vehicle passengers and the lifetime of the EM; in addition, the reduction of mass diminishes its production costs.

<div class="htmlview paragraph">In recent years, high performance engines and the reduction in engine room due to aerodynamic styling has caused increases in engine room temperature. Because of this increasing temperature, the conventional natural rubber engine mount is now at the marginal point on its performance and durability. Several heat resistant materials have been considered for engine mount applications because of this reason. Polychloroprene rubber could be a strong candidate for engine mount application due to its balance of heat resistance, dynamic properties, and fatigue life. This paper will discuss the development of the technology, property characteristics and part performance simulations on the HYUNDAI BUSH TYPE COMPLEX ENGINE MOUNT (for 2.0L DOHC ENGINE). This type of mount requires higher creep resistance and fatigue life than those of other designs, such as block or simple shear type mounts. Early evaluations of polychloroprene mounts have shown some deficiencies in creep resistance. Therefore to adress this concern, the design and formulation development to overcome the initial lack of creep resistance of polychloroprene are shown. Also, the effect of heat aging on dynamic characteristics and performance are investigated. All the test results are compared with those of natural rubber mounts. The results will show the possibility of the first application of polychloroprene rubber on this type engine mount giving improved fatigue life even after heat aging with balanced dynamic properties.</div>

<div class="htmlview paragraph">In recent years, the fraction of air conditioning systems installed in American automobiles has increased to approximately 85%. Concurrently, efforts to improve fuel economy have resulted in smaller engines. The point has been reached in which load from a cycling fixed-displacement compressor can significantly affect vehicle drivability and performance. To remedy this problem, variable-capacity A/C systems have been developed with mechanically controlled compressor displacements.</div> <div class="htmlview paragraph">An alternative electronic approach to cooling capacity modulation is presented in this paper. The system utilizes a variable-speed brushless dc motor to drive a fixed-displacement compressor, thus achieving continuous control of cooling output independent of the engine drive belt. Compared to variable-displacement compressors, electrically driven A/C systems provide the following additional benefits: <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">Hermetic motor/compressor assembly (no shaft seal leakage)</div></li> <li class="list-item"><div class="htmlview paragraph">Smaller, less complex compressor</div></li> <li class="list-item"><div class="htmlview paragraph">Flexible packaging (no drive belt)</div></li> <li class="list-item"><div class="htmlview paragraph">Full cooling capacity at any engine speed</div></li> <li class="list-item"><div class="htmlview paragraph">Control of conditioned air temperature without reheat</div></li> </ul></div> <div class="htmlview paragraph">This paper deals with the development of a brushless dc drive system suitable for powering an automotive air conditioner. Two 5 hp motors were designed and built with maximum operating speeds of 6000 and 7000 rpm. These motors were then tested in a typical automotive air conditioning system over a range of operating conditions in order to determine their performance envelopes. The results are discussed, and conclusions are drawn as to the type of compressor and control strategy best suited for electric automotive A/C. Issues that are critical to the further development of electrically driven A/C systems are identified. An example simulation of annualized A/C system performance is also provided to quantify some of the benefits of cooling capacity modulation.</div>

<div class="htmlview paragraph">A vehicle drifts due to several reasons from its intended straight path even in the case of no steering input. The multibody dynamic analysis of vehicle drift during accelerating and braking are performed. This paper focuses on modeling and evaluating effects of suspension parameters, differential friction, engine mounting and C.G. location of the vehicle under multibody dynamic simulation environment.</div> <div class="htmlview paragraph">Asymmetry of geometry and compliance between left and right side is considered cause of drift. The sensitivities of the suspension parameters are presented for each driving condition. In case of acceleration, the interaction of differential friction and driveshaft stiffness and their influence on drift are also studied. For braking condition, suspension parameters such as initial toe variation of rear coupled torsion beam axle type suspension and kingpin inclination deviation of front suspension are studied including the braking force difference.</div> <div class="htmlview paragraph">The significant factors of drift are ordered and compared for straight line accelerating, driving and braking condition. Using a co-simulation model, it is shown that significant parameters for accelerating condition are driveshaft angle and its stiffness difference between left and right side. It is shown that the location of center of gravity altered by passenger seating position has a great influence on drifting under braking condition.</div>

<div class="section abstract"><div class="htmlview paragraph">In recent years the 2-wheelers engines companies have been focused on increasing the overall engine efficiency, that can be achieved amongst other by engine down-speeding, engine down-sizing and by reducing the frictions; however, to maintain or improve vehicle performance, it is necessary to provide a corresponding increase in specific power.</div><div class="htmlview paragraph">In accordance with these trends, the studied approaches and methodologies have been exploited, during the development of the new Piaggio small scooter engine.</div><div class="htmlview paragraph">In this work a multi-objective analysis has been applied to the valve train system design, in order to optimize the engine performance in terms of friction reduction, power curve and timing system response. Along with this optimization methodology, a robust design has been studied to make the peak cranking compression pressure insensitive to the engine starting device working. These calculation methodologies have been followed using commercial software as GT-SUITE® code and the modeFRONTIER® platform for the multi-objective optimization analysis.</div><div class="htmlview paragraph">The several configurations investigated have allowed to reach the desired trade-off between the appropriate and efficient valve train behavior and the engine performances.</div><div class="htmlview paragraph">The global engine friction reduction has been obtained thanks to low resisting cam torque profiles, a specific valve springs set and a new compression releaser device (during engine starting phase).</div><div class="htmlview paragraph">The results have been further validated by an experimental campaign carried out on the test bench for engine performance and on the specific cold test bench to evaluate friction losses.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Quieter cabins are indispensable in today’s evolving automobile industry. The effective isolation of vehicle noise and vibrations are essential to achieve the above. Since, low frequency powertrain induced NVH has been one of the major contributors affecting noise and vibration levels inside the passenger cabin. Thus, use of hydraulic mounts is a natural choice for all major OEMs. The objective of this study is to optimize the design of the hydraulic mount de-coupler unit, to reduce the abnormal noise felt inside the cabin. This condition was observed when the vehicle was driven at 20~30 km/h over undulated road surface, found very often in Indian drive conditions.</div><div class="htmlview paragraph">Due to lack of accuracy and repeatability errors during NVH data acquisition in actual driving condition, the above road profile was captured and subsequently simulated in an acoustically treated BSR (Buzz, Squeak and Rattle) four poster simulator. Problem investigation and countermeasure validation were also performed in this facility.</div><div class="htmlview paragraph">A significant improvement in cabin noise level by ~6 dB(A) in the problematic frequency zone, with the countermeasure, without negatively affecting any other NVH performance parameters, was achieved.</div><div class="htmlview paragraph">A novel test methodology has been established for expedited root cause investigation & counter-measure validation of the problem statement. Design modification of the de-coupler membrane for eliminating such noise is a new approach.</div></div>

In the highly competitive global automotive market and with the taste of customer becoming more refined, the need to develop high quality products and achieve product excellence in all areas to obtain market leadership is critical. Buzz, squeak and rattle (BSR) is the automotive industry term for the audible engineering challenges faced by all vehicle and component engineers. Minimizing BSR is of paramount importance when designing vehicle components and whole vehicle assemblies. Focus on BSR issues for an automobile interior component design have rapidly increased due to customer's expectation for high quality vehicles. Also, due to advances in the reduction of vehicle interior and exterior noise, engine mounts have recently been brought to the forefront to meet the vehicle interior sound level targets. Engine mounts serve two principal functions in a vehicle, vibration isolation and engine support. The objective of this paper to experimentally analyze the impact of conventional engine mount design on the rattle and whistling noise audible from the engine mounts when the vehicle is subjected to rough road conditions and pot holes at slow speeds. The test methodology demonstrates how to simulate and co-relate the actual vehicle level noise on a BSR 4 poster test rig. A design change is proposed to abate the rattle noise from engine mounts considering the numerous variables involved and without affecting the critical NVH (Noise, Vibration and Harshness) and durability performance parameters. The level of noise reduction achieved is quantified through the substantial reduction in BSR demerit score which in turn reflects the improvement in perceived quality of the vehicle, increased customer satisfaction index and improved JD power (JDP) ratings.

<div class="section abstract"><div class="htmlview paragraph">With an objective of improving the range as well as other safety and comfort aspects, thermal management becomes increasingly important in the development of electrified vehicles both at the component as well as system level. The considerable increase in complexity of the thermal management system and its tighter interactions with the complete vehicle is driving an increasing trend towards system simulation compared to expensive testing.</div><div class="htmlview paragraph">At the system level, different sub-systems interact with each other at varying extents. An example of one such strong interaction is between the coolant and AC circuits using battery chillers. Thermal management system simulation models must be capable of simulating such interactive systems.</div><div class="htmlview paragraph">At the component level, ensuring the efficacy of the several components used in these intricately linked systems becomes increasingly important. An accurate prediction of temperature distribution inside the battery pack is essential to avoid damaging situations such as thermal runaway. An integrated approach of 1D-flow inside the cooling plates combined with 3D-thermal analysis of battery cells and cooling plates in GT-SUITE is described in this study.</div><div class="htmlview paragraph">Also, a new predictive electrochemical and thermal battery models to analyze and optimize both component and system level behavior is described. This allows selection of cell chemistry and design in addition to providing heat rejection values for design of the cooling system. Aging predictions at both the cycle and calendar time scales are described that consider effects of varying environmental and operating conditions.</div><div class="htmlview paragraph">After the e-powertrain, the HVAC compressor is the largest consumer of electrical energy. For optimizing compressor power consumption without compromising on human thermal comfort attention is focused on localized cooling inside the cabin. This paper outlines an integrated co-simulation approach, that allows an investigation of the trade-off between passenger comfort and driving range, or to develop smart controls of the HVAC system.</div></div>