NV Countermeasure Technology for a Cylinder-On-Demand Engine – Development of Active Control Engine Mount

Engine vibrations and noise are demanding issues in automotive industry from long times ago up until nowadays. These vibrations could be derived from rotating components, structural resonances, or combustion forces, which could potentially lead to discomfort, efficiency loss, and structural fatigue. For those reasons, vibration isolation devices have been developed to minimize these effects, such as Rubber Engine Mounts (REM), Hydraulic Engine Mounts (HEM), Active Engine Mounts (AEM), or Blance Shafts and Harmonic Dampers. This paper selects Hydraulic Engine Mounts (HEM) as the objective of study due to their remarkable damping characteristics and broad frequency effectiveness. To be more specific, traditional rubber mounts are useful for high-frequency vibration isolation but struggle with low-frequency engine operation. With the fluid damping mechanism, the HEM provides effective isolation over a broader spectrum of vibrations in both low-frequency and high-frequency conditions. On the other side, the Active Engine Mounts (AEM) bring out superior real-time vibration control, but they require sensors and electronic control units, raising up the cost and complexity of the system. According to these given drawbacks, the HEMs come out as the most advantageous solution due to their cost-effectiveness, complexity, and performance. Hydraulic Engine Mounts (HEM) are extensively used in automotive powertrains for effective vibration isolation and noise reduction, playing an important role as an energy-absorbing element, thus increasing the customers’ assuagement. The Hydraulic Engine Mount is composed of a double-chambers, an inertia track, a decoupler, and a plunger. As an energy-absorbing element, the HEM is anticipated to provide applicable frequency response characteristics under different operating conditions. Traditionally, a lumped parameter mechanical model is utilized for modeling the dynamic characteristics of HEM based on an analogy between electrical systems and mechanicalhydraulic systems, in which the system parameters are usually obtained by experiments. In this paper, a fluid-structure interaction 1(FSI) finite element analysis (FEA) and transient structural modules of ANSYS would be used to model and simulate the Hydraulic Engine Mount. The model is used to study the mechanism of Hydraulic Engine Mount and analyze key parameters of the mount for the effectiveness of vibration reduction. A CAD model of the HEM is built in Autodesk Inventor with a proper volume of the fluid in the mount with appropriate boundary conditions. Further, the model will be imported into ANSYS with fluid-solid interaction and transient structural modules to study fluid flow and understand dynamic mechanisms. The challenges in this study are to properly modify the volume of the fluid in the model to import to ANSYS Fluent Module and to set up the dynamic input boundary conditions in ANSYS Transient Structural Module before pairing these two modules in the System Coupling Module.

In automotive industry, engine vibration isolation has been a challenging task, and given the emergence of new vehicles with more stringent performance characteristics, engine vibration isolation has become an even more demanding issue. Most engine mounts are passive — that is, their parameter values and characteristics are fixed — and as a result, they may not properly attenuate the complicated vibration transmitted from the engine. In this paper, the development of a new active mount is described. This paper describes modeling, development, and experimental analysis of an active engine mount, which is specifically designed to address the Variable Displacement Engine (VDE) isolation problem. An electromechanical actuator is fabricated and retrofitted inside the inertia track plate of a hydraulic engine mount. The plunger of the electromechanical actuator moves upon receiving the signal from the controller, and it changes the dynamic performance of the mount accordingly based on frequency, amplitude, and phase of the activation signal. Experimental results are presented for different control signals. Simulated and experimental results are compared to validate the mathematical model. The experimental results demonstrate the performance of the designed active engine mount to deal with complicated vibration patterns, specifically those created by VDEs.

<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>

This paper is focused on design of a new active control engine mount (ACM), which is both compact in size and cost effective. The ACM, consisting of an electrodynamic actuator as the active element, flat springs and a sliding ball joint, is different in structure from the previous ACM designs based on the conventional hydraulic engine mount. Dynamic characteristics of the proposed ACM are extensively investigated before a prototype ACM, which meets the design specifications, is built in the laboratory. For cost effectiveness, a feed-forward control algorithm without a feedback sensor is used for reduction of the transmitted force through the ACM by the engine. The prototype ACM is then harmonic-tested with a rubber testing machine for verification of its control performance as well as adequacy of modeling. Experimental results show that the proposed ACM is capable of reducing the transmitted force by 20 dB up to the frequency range of 60 Hz.

<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>

The authors have developed a new type of active engine mount. The active engine mount is consisted of an electromagnetic actuator and an inertia-modulator hydraulic mount. The decoupler's motion is controlled by the dynamic force generated by the electromagnetic actuator .The pressure in the upper chamber is variational, as a result the total output force from the mount to the chassis is controlled. Fuzzy control method was chosen as the control method. Based on force analyses of system parts, a mathematical model of the active engine mount was established. An experimental device was designed and made. The experimental results indicated that the active engine mount can achieve better vibration isolation performance than passive engine mount.

The isolation of the body from engine vibration is the most challenging and disruptive vibrational problem. Active engine mounts (AEMs), especially electromagnetic AEMs, achieve a significant performance improvement in decreasing the wide frequency band vibration. Increasing research interest is necessary to provide the academic community with a guideline for electromagnetic AEMs. Therefore, the current review aims to comprehensively supplement the review of AEMs. The key reviews of electromagnetic AEMs focus on (1) general considerations of electromagnetic AEMs, (2) models, and (3) control strategies. This paper presents a review of the current status and developmental progress of AEMs. A theoretical model, a finite-element model, and the identification (or experimental modelling) of electromagnetic AEMs during the last 2 decades are then studied. Finally, control strategies, such as classical control, adaptive control, and two degree of freedom (2DOF) control, are discussed and compared. The main purpose of this paper is to meet the needs of researchers and engineers engaged in electromagnetic AEM analysis and control.

Experimental and analytical study of secondary path variations in active engine mounts

<div class="htmlview paragraph">This paper presents an analytical modeling and performance analysis of the hydraulic engine mount by using bond graph method, which is becoming more common in the industry for engine vibration and noise control. It is well known that the hydraulic engine mount can provide excellent frequency and amplitude response characteristics compared to the conventional elastic rubber type one. Numerous study has been attempted up to now to explain the complex dynamic performance characteristics of this mount through a variety of analytical methods but it is not yet fully understood. In the present study, the bond graph design model, having an analytical simplicity and clarity, have been developed to analyze and predict the design performance of a “sandwich type” hydraulic engine mount with a spiral inertia track and free decoupler specifically designed for an in-line gasoline engine in order to control and reduce the high amplitude low frequency engine vibration and noise in the frequency range 1 - 50 Hz in particular. To investigate the reliability of the present developed methodology the dynamic response spectra results from the bond model such as the dynamic stiffness and the loss angle are validated with the experimental data over 1-50 Hz and 1-100 Hz frequency range. The bond graph method developed in the study had shown excellent agreements with the experimentals over the cases investigated. The present study results has shown that the bond method has an excellent applicability for the analysis and prediction of hydro engine mount performance if the dynamic system can be properly modeled.</div>

Active engine mounts significantly contribute to ensure the comfort in vehicles with emission-reducing engine technologies, e.g., cylinder-on-demand (COD), downsizing or turbochargers. To control active engine mounts, either adaptive or non-adaptive feedforward control is commonly employed. Since both approaches have previously been treated separately, this study proposes methods to connect them in terms of multiple-input-multiple-output Newton/FxLMS adaptive filters with self-trained, grid-based look-up tables. The look-up tables are incorporated as parameter-maps or parallel-maps, respectively. By combining the two feedforward control strategies, their inherent advantages, i.e., the adaptivity of adaptive filtering and the direct impact as well as the tracking behavior of map-based feedforward control, are utilized. The proposed control structures are illustrated by simulation and experimentally demonstrated in a vehicle with a V8-COD engine. While both methods significantly reduce the convergence time of the adaptive filter, the parallel implementation additionally improves the tracking behavior during fast engine run-ups.

A comparison of two adaptive algorithms for the control of active engine mounts

The hydraulic engine mount (HEM) has been designed to provide a vibration isolation characteristic to control road and engine induced vibrations in vehicles by using two fluid passages known as decoupler and inertia track. These types of engine mounts are known for their best noise, vibration, and harshness (NVH) suppression performance among other different types of engine mounts. However, a low cost technique to recycle the dissipated energy of the system in the process of vibration suppression is significantly advantageous. A novel design structure in which the decoupler is replaced with a water turbine to capture and restore the vibration energy of the system is presented in this paper. The turbine design and selection has been done based on the upper and lower chamber pressures and the fluid flow rates in the system’s resonant frequency. The mount vibration isolation and energy generation performance is studied in both frequency and time domains. The simulation results demonstrate that a considerable amount of energy can be harvested from the engine vibration sources. This recent study demonstrates a novel energy harvesting technique in vehicles that require minimum design modifications of conventional hydraulic mounts.

Model based feed-forward control of electromagnetic type active control engine-mount system

Hydraulic engine mounts (HEMs) are important vibration isolation components in vehicle powertrain mounting systems. The vibration isolation characteristics of HEMs may greatly affect the noise, vibration and harshness (NVH) properties of vehicles. Therefore, it has great significance to acquire the vibration isolation characteristics of HEMs. A simplified lumped model of a HEM and a new method to identify the parameters in this model are proposed in this study. The vibration isolation characteristics of the HEM can be easily obtained by this model and parameter identification method. Dynamic characteristic experiments and road simulation tests of the HEM are also done in this study. The results imply the simulation vibration isolation characteristics of the HEM by modelling agree well with the experimental results and the test fatigue life of the HEM satisfies with the design requirement. This parameter identification method is instructive for the design and tuning of the vibration isolation characteristics of HEMs.

<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>