Engine Mounting System Research Articles

Multidisciplinary design optimization of engine mounts with consideration of the driveline

This paper discusses the multidisciplinary design optimization of an engine system to improve the idle refinement of the vehicle and to remove the possibility of interaction between the powertrain system and vehicle systems. The driveline model attempts to provide practical support to engine mount development by providing sufficient detail for design modification assessment in a stable and efficient modelling environment. By applying forced vibration analysis for vehicle systems and mode decouple analysis for the engine mount system to the design of the engine mount, it is shown that an improved optimization result is obtained.

Dynamic analysis and control of an active engine mount system

Dynamic characteristics of a prototype active engine mount (AEM), designed on the basis of a hydraulic engine mount, have been investigated and an adaptive controller for the AEM has been designed. An equivalent mass-spring-damper AEM model is proposed, and the transfer function that describes the dynamic characteristics of the AEM is deduced from mathematical analysis of the model. The damping coefficient of the model is derived by considering the non-linear flow effect in the inertia track. Experiments confirmed that the model precisely describes the dynamic characteristics of the AEM. An adaptive controller using the filtered-X LMS algorithm is designed to cancel the force transmitted through the AEM. The stability of the LMS algorithm is guaranteed by using the secondary path transfer function derived on the basis of the dynamic model of the AEM. The performance test in the laboratory shows that the AEM system is capable of significantly reducing the force transmitted through the AEM.

DESIGN SENSITIVITY ANALYSIS AND OPTIMIZATION OF AN ENGINE MOUNT SYSTEM USING AN FRF-BASED SUBSTRUCTURING METHOD

The FRF-based substructuring method is one of the most powerful methods in analyzing the responses of complex built-up structures with high modal density. In this paper, a general procedure for the design sensitivity analysis of a vibro-acoustic system has been presented using the FRF-based substructuring formulation. For an acoustic response function, the proposed method gives a parametric design sensitivity expression in terms of the partial derivatives of the connection element properties and the transfer functions of the substructures. The derived noise sensitivity formula is combined with a non-linear programming module to obtain the optimal design for the engine mount system of a passenger car. The objective function is defined as the area of the interior noise graph integrated over a concerned r.p.m. range. The interior noise variations with respect to the dynamic characteristics of the engine mounts and bushings have been calculated using the proposed sensitivity formulation and transferred to a non-linear optimization software. To obtain the FRFs, a finite element analysis was used for the engine mount structures and experimental techniques were used for the trimmed body including the cabin cavity. The optimization based on the sensitivity analysis gives the ideal stiffness of the engine mount and bushings. The resultant interior noise in the passenger car shows that the proposed method is efficient and accurate.

Sensitivity Analysis of Engine Mount System using FRF-based Substructuring Method

A general procedure for the design sensitivity analysis of structural dynamic problems has been presented in frame of the FRF-based substructuring formulation. For a system response function, the proposed method gives a parametric design sensitivity formula in terms of the partial derivatives of the connection element properties and the transfer matrix of the subsystems. The derived design sensitivity formula is applied to an engine mount system. An interior noise problem in the passenger car is analyzed using the FRF-based substructuring method and the proposed formulation is adopted to study the response variations with respect to the dynamic characteristics of the engine mounts and the bushes. To obtain the FRFs, a finite element model is built for the engine mount structures, and test data is used for the trimmed body including cabin cavity. The comparison of sensitivities derived by the proposed method and the finite difference method shows that the proposed method is efficient and accurate. The proposed sensitivity analysis method indicates effectively the most sensitive location to the interior noise among the engine mounts and the bushes.

A literature review of automotive vehicle engine mounting systems

The ideal engine mount system should isolate engine vibration caused by engine disturbance force in engine speed range and prevent engine bounce from shock excitation. This implies that the dynamic stiffness and damping of the engine mount should be frequency- and amplitude-dependent. The development of engine mounting systems has mostly concentrated on improvement of frequency- and amplitude-dependent properties. The conventional elastomeric mounts do not meet all the requirements and can only offer a trade-off between static deflection and vibration isolation. Passive hydraulic mounts can provide a better performance than elastomeric mounts especially in the low frequency range. Semi-active techniques are usually used to further improve performance of hydraulic mounts by making them more tunable. The active engine mounting system can be very stiff at low frequency and be tuned to be very soft at the higher frequency range to isolate the vibration. The active engine mounts have been considered as the next generation of engine mounts. The optimization of engine mounting systems is quite desirable. The current work on the optimization of the engine mount systems shows some limitations.

DESIGN OPTIMIZATION OF MARINE ENGINE-MOUNT SYSTEM

Design optimization of marine engine–mount system for vibration control is presented in this paper. The engine is modelled as a rigid body with supports connected to a rigid floor. The mounts are modelled as three-dimensional isolators with hysteresis damping. The objective is to select the stiffness coefficient and orientations of individual mount in order to minimize the vertical force transmitted from the engine to the floor to control the structure-borne noise. Constraints are imposed to keep the isolator static and dynamic deflection within the desired limits and a minimum gap between system natural frequency and engine excitation frequency for avoiding possible system resonance. The sequential quadratic programming (SQP) technique has been applied as the optimization algorithm. The typical force and moment of a 4-stroke engine with one cylinder is analyzed and input in the optimization system. The results of optimization are compared with that of a conventional engineering design with the isolators working under their maximum allowable deflection. This comparison shows that, as compared with force transmission of the conventional isolation system, the value of optimized system is only half for multi-frequencies excitation and one-fourth for single frequency excitation. The mechanism of vibration isolation involved in the optimization is investigated with the frequency response of the system. Sensitivity study of the system with the variation of the design parameters is also carried out and proves that the minimum obtained is the global value in the range of design parameters.

ANALYTICAL METHODS OF DECOUPLING THE AUTOMOTIVE ENGINE TORQUE ROLL AXIS

This paper analytically examines the multi-dimensional mounting schemes of an automotive engine–gearbox system when excited by oscillating torques. In particular, the issue of torque roll axis decoupling is analyzed in significant detail since it is poorly understood. New dynamic decoupling axioms are presented an d compared with the conventional elastic axis mounting and focalization methods. A linear time-invariant system assumption is made in addition to a proportionally damped system. Only rigid-body modes of the powertrain are considered and the chassis elements are assumed to be rigid. Several simplified physical systems are considered and new closed-form solutions for symmetric and asymmetric engine-mounting systems are developed. These clearly explain the design concepts for the 4-point mounting scheme. Our analytical solutions match with the existing design formulations that are only applicable to symmetric geometries. Spectra for all six rigid-body motions are predicted using the alternate decoupling methods and the closed-form solutions are verified. Also, our method is validated by comparing modal solutions with prior experimental and analytical studies. Parametric design studies are carried out to illustrate the methodology. Chief contributions of this research include the development of new or refined analytical models and closed-form solutions along with improved design strategies for the torque roll axis decoupling.

Review of automotive vehicle engine mounting systems

The ideal engine mount system should isolate engine vibration caused by engine disturbance force in engine speed range and prevent engine bounce from shock excitation. This implies that the dynamic stiffness and damping of the engine mount should be frequency and amplitude dependent. The development of engine mounting systems has mostly concentrated on improvement of frequency and amplitude dependent properties. The conventional elastomeric mounts do not meet all the requirements and can only offer a trade-off between static deflection and vibration isolation, but there is still some room for improving the properties of elastomeric mounts. Passive hydraulic mounts can provide a better performance than elastomeric mounts especially in the low frequency range. Semi-active techniques are usually used to further improve performance of hydraulic mounts by making them more tunable. The active engine mounting system can be very stiff at low frequency and be tuned to be very soft at the higher frequency range to isolate the vibration. The active engine mounts have been considered as the next generation of engine mounts. The optimisation of the engine mounting system is quite useful both in terms of speed and more effective design. The current work on optimisation of the engine mount systems shows some limitation. Further work is needed to consider the nonlinear variations in properties of different types of mounting systems.

Elastic foundation effects on the dynamic response of engine mount systems

This paper discusses flexible foundation effects on the dynamic response of engine mount systems using computer simulation techniques. The dynamic flexibility of the foundation is represented by a finite element modal model, and the equations of motions are derived for the engine mount system and foundation, which are coupled together. The developed computational method is applied to a Jeep-type passenger car, and the natural frequencies and forced vibration responses of an engine mount system can be simulated accurately. It is shown that the flexibility of the vehicle frame structure may have significant effects on the dynamic response of the engine mount systems, especially near the natural frequencies of the vehicle frame structure, and by applying the proposed method to the optimization routine it is also shown that improved optimization results can be obtained by considering the foundation flexibility.

Development of an Active Control Engine Mount System

In an attempt to reduce idling vibration and booming noise in automobile engines, the authors have developed an engine mounting system we call the ACM(Active Control engine Mount) system. Comprising a pair of electromagnetic actuators and hydraulic mounts, the system incorporates an adaptive control strategy based on the synchronized filtered-X LMS (SFX) algorithm. The crank angle pulse signal is detected as the synchronization signal and the force transmitted to the car body through the engine mounts is detected as a residual signal. Application of the ACM system to a vehicle with a transversally mounted four-cylinder engine resulted in significantly reduced idling vibration and booming noise.

Automotive Vehicle Engine Mounting Systems: A Survey

This study divided into three portions to provide performance requirements; overview and development of various engine mounts; and the optimization of engine mount systems. The first part provides an insight about the ideal engine mount system that should isolate vibration caused by engine disturbance force in various speed range and prevent engine bounce from shock excitation. This implies that the dynamic stiffness and damping of the engine mount should be frequency and amplitude dependent. Therefore, the development of engine mounting systems has mostly concentrated on improvement of frequency and amplitude dependent properties. The second part starts discussion on the conventional elastomeric mounts that offer a trade-off between static deflection and vibration isolation. The next level, passive hydraulic mounts can provide a better performance than elastomeric mounts especially in the low frequency range. Subsequently, semi-active and active techniques are used to improve performance of hydraulic mounts by making them more tunable. The active engine mounting system can be very stiff at low frequency and be tuned to be very soft at the higher frequency range to isolate the vibration. The final part is about the optimization of engine mounting systems. An overview of the current work on this optimization shows some limitations. Further study is needed to consider the nonlinearities and variations in properties of different types of mounting systems.

ANALYSIS OF AN ENGINE-MOUNT SYSTEM WITH TIME-DEPENDENT MASS AND VELOCITY MATRICES

In this paper a formulation of a dynamic model of a flexibly supported engine is presented, in which the contribution of rotating and reciprocating parts are taken into account with accuracy. This dynamic model contains a mass matrix and a velocity matrix as periodic functions of time. The derivation of these equations of motion on the basis of Lagrange's equations is presented.Using the formulated dynamic model, an analysis of parametric resonance phenomena for engine–mount systems is conducted. Numerical examples demonstrate the possibility of dynamic instability in some cases.As a particular case, flexibly supported rotor systems can be treated as well using the developed dynamic model.

制振ストッパを伴うエンジンマウント系の定常不規則衝突振動

In this paper we present some results of a theoretical study of stationary random oscillations of an engine mounting system with motion-limiting stops. The dynamic model of the vehicle is reduced to a two degree-of-freedom system with stops which limits the relative motion of the engine body to the vehicle. The nonlinear impact force model is statistically reduced to a spring-damper model with equivalent linear coefficient of stiffness and damping between two masses. The response of the system to a roughness input of a roadway with Gaussian probability distribution is determined from the Fokker-Planck equation. Results are given for mean-squared level of the response. The accuracy of the theoretical approach is investigated by means of numerical simulations.

PERIODIC RESPONSE OF MECHANICAL SYSTEMS WITH LOCAL NON-LINEARITIES USING AN ENHANCED GALERKIN TECHNIQUE

A new semi-analytical framework for the study of mechanical systems with local non-linearities is presented. It recognizes that many practical built-up structures consist of non-linearities, typically at joints or junctions, with a few degrees-of-freedom, coupled with many linear degrees-of-freedom of the adjoining components. Unlike linear systems, sinusoidal excitation produces a periodic response, including super and subharmonics. A Galerkin based computational method for the solution of the steady state periodic response of mechanical systems with local non-linearities, defined in the time and/or frequency domains is proposed. The method incorporates a form of order reduction and numerical continuation with distinct benefits. Order reduction enables inclusion of the extensive and necessary, but often linear, assembled component dynamics with minimal computational cost. Additionally, the proposed form of reduction allows non-linearities explicitly defined in the frequency and the time domain to be handled simultaneously. The continuation scheme, based on the QR decomposition, facilities parametric studies for design by using the system solution for one set of parameters to optimally predict the steady state periodic solution for a similar set of parameters. Two specific examples have been chosen to illustrate the key concepts and methodology of the dual domain method. In the first example, a rigid body connected to a simply supported elastic beam via a non-linear spring is considered. The hydraulic engine mounting system is presented as the second example; a practical representative of the issues discussed in this article. Results of digital and analog computational studies verify the accuracy of the proposed method and highlight its unique capabilities.

Vibration Control of Engine Roll and Bounce Using Hydraulic Engine Mounts

This paper shows the optimum design method for hydraulic engine mounts. Engine mounts have been developed recently to significantly reduce the vibration in car bodies caused by engines. The resonance peaks of conventional engine-mounting systems can not be suppressed sufficiently. Hydraulic engine mounts are able to suppress the resonance peaks by using the fluid reaction effect of the fluid enclosed in the mounts. The design was recently modified by trial and error experiments. Due to lack of information on a suitable design, the ability of this design has not been effectively demonstrated. In this paper, after the mount is analyzed, its optimum design formula is obtained in a simple and useful manner, similar to the design equation for dynamic absorbers. This design formula is applied for designing two hydraulic engine mounts to control engine vibrations in the roll and bounce modes. The effectiveness of the formula is confirmed theoretically and experimentally.

The development of a new type of engine mounting system using electronically controlled hydromounts

The development of a new type of engine mounting system using electronically controlled hydromounts

Control of Engine Roll and Bounce Vibrations Using Hydraulic Mounts

A method for designing an engine mounting system using hydraulic insulators has been developed with the aim of controlling low-frequency engine vibrations in the roll and bounce modes. This method includes a design optimization theory for each hydraulic insulator and a procedure for determining the equivalent mass for various modes at the mount locations, and is applicable to integrated system optimization. Computer simulation results show that resonance peaks can be effectively reduced with a hydraulic engine mount system designed on the basis of this method.

A study of passive and adaptive hydraulic engine mount systems with emphasis on non-linear characteristics

Passive hydraulic mounts exhibit excitation frequency variant and deflection amplitude sensitive stiffness and damping properties. Such non-linear dynamic characteristics are examined by using analytical and experimental methods, both at the device level and within the context of a simplified vehicle model. A new lumped parameter non-linear mathematical model of the hydraulic mount is developed by simulating its decoupler switching mechanism and inertia track dynamics. The low frequency performance features and limitations of several passive mounts are made clear through the non-linear vehicle model simulation and comparable laboratory vibration tests. The high frequency performance problems of the passive hydraulic mount are identified by applying the quasi-linear analysis method. Based on these results, a new adaptive mount system is developed which exhibits broad bandwidth performance features up to 250 Hz. It implements an on-off damping control mode by using engine intake manifold vacuum and a microprocessor based solenoid valve controller. A laboratory bench set-up has already demonstrated its operational feasibility. Through analytical methods, it is observed that our adaptive mount provides superior dynamic performance to passive engine mounts and comparable performance to a small scale active mount over a wide frequency range, given the engine mounting resonance control, shock absorption and vibration isolation performance requirements. Although technical prospects of the proposed adaptive system appear promising, the in situperformance needs to be evaluated.

Optimization of aircraft engine suspension systems

An interactive computer program has been developed to design aircraft engine mounting systems used for vibration isolation. Mount design is largely driven by two competing criteria. Mounts must be soft enough to provide vibration isolation, yet stiff enough to support the engine without excessive motions. The constrained variable metric optimization technique is used to determine the mount design parameters which minimize the transmitted forces in the mounts, subject to constraints on the maximum allowable deflection of the engine to static forces. The design parameters are the stiffness and orientation of each individual engine mount. The aircraft engine is modeled as a rigid body that is mounted to a rigid base representing the nacelle. An example is used to show that the optimization technique is effective in designing engine mounting system.

Design Optimization of Aircraft Engine-Mount Systems

Design optimization of aircraft engine-mount systems for vibration isolation is presented. The engine is modeled as a rigid body connected to a flexible base representing the nacelle. The base (nacelle) is modeled with mass and stiffness matrices and structural damping using finite element modeling. The mounts are modeled as three-dimensional springs with hysteresis damping. The objective is to select the stiffness coefficients and orientation angles of the individual mounts in order to minimize the transmitted forces from the engine to the nacelle. Meanwhile, the mounts have to be stiff enough not to allow the engine deflection to exceed its limits under static and low frequency loadings. It is shown that with an optimal system the transmitted forces may be reduced significantly particularly when orientation angles are also treated as design variables. The optimization problems are solved using a constraint variable metric approach. The closed form derivatives of the engine vibrational amplitudes with respect to design variables are derived in order to determine the objective function gradients and consequently a more effective optimization search technique.