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Modelling and Optimization of Electromagnetic Type Active Control Engine Mount System

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Modelling and Optimization of Electromagnetic Type Active Control Engine Mount System
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  International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 60-72 © IAEME   60   MODELLING AND OPTIMIZATION OF ELECTROMAGNETIC TYPE ACTIVE CONTROL ENGINE-MOUNT SYSTEM Prabhat Kumar Sinha, Dan Bahadur Patel * , Mohd Tariq, SaurabhaKumar Mechanical Engineering Department, Shepherd School of Engineering and Technology, Sam Higginbottom Institute of Agriculture, Technology and Sciences Allahabad U.P. 211007 India ABSTRACT This paper presents a low-cost prototype active control engine mount (ACM) designed for commercial passenger vehicles, requiring a good engine vibration isolation performance. To construct such an ACM system, all feedback sensors normally required for full ACM systems are replaced by the model based feed forward algorithm, consisting of a vibration estimation algorithm, a current shaping controller and an enhanced ACM model. The current shaping control compensates for degradation of control performance due to elimination of feedback control sensors. The proposed current shaping control improves the actuator control performance, and the vibration estimation algorithm provides the anti-vibration signals for vibration isolation The dynamic loads that are generated due to the shaking forces within the engine and the road loads that are transmitted to the engine through the tire patch are discussed. The geometrical shape of the engine mount is also considered in this work. All models discussed herein deal with solving the optimization problem for the engine mount system such that the transmitted forces to and from the engine are minimized in which the mount parameters are used as design variables. While work has been done in the past in the area of engine mount design, this dissertation tries to fill in the gap when it comes to designing a comprehensive mounting system that takes into account modeling of the mount characteristics, the excitation load present in the system, and a determination of the final geometrical shape of the engine mount. Keyword: Vibrations, Sensor, Actuator. INTRODUCTION In recent years, various types of ACMs have been developed by many researchers. Y.W. Lee [2] proposed an ACM that used a pneumatic actuator as an active system. The ACMs activated by piezo-electric actuators were developed by M. Hideki and T. Mikasa [3]. The electromagnetic type   INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 5, Issue 8, August (2014), pp. 60-72 © IAEME: www.iaeme.com/IJMET.asp Journal Impact Factor (2014): 7.5377 (Calculated by GISI) www.jifactor.com   IJMET   © I A E M E    International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 60-72 © IAEME   61   ACMs were evolved to utilize their high specific force per unit volume. Recently, Japanese automotive companies such as Toyota, Nissan, and Honda introduced ACMs to the automotive market. They provided the good vehicle tested mount results and highlighted improvements in isolation of force induced by engine roll motion over the low frequency region of interest. This research mainly focuses on development of an ACM designed for low-cost and, yet satisfactory vibration isolation performance. A full loaded ACM system normally requires two sensors: one for measurement of engine vibration or transmitted force through ACM, and the other for position feedback of actuator itself. Without such sensors, the performance of ACM will degrade, compared with the full loaded ACM. In this paper, a model based feed forward algorithm, which consists of a vibration estimation algorithm, a current shaping controller and an improved ACM model, is adopted, in order to compensate for the performance degradation due to absence of the feedback sensors. The engine vibration estimator indirectly monitors the engine vibrations using the signals taken from the existing sensors such as CAM and CAS [12–14]. The current shaping controller compensates for the undesired harmonic distortion in the actuator output due to lack of its position feedback. The improved ACM model is developed to accurately describe the active as well as passive characteristics of ACM. 2. STRUCTURE OF ACM  To isolate the engine-induced vibration, many researchers have developed various kinds of ACMs [6–11], but their basic structures are similar to each other, as illustrated in Fig. 1. These were achieved by different methods from the full loaded ACM system. Undesired harmonics due to the free vibration of actuating system was reduced to some extent by the filter orifice, but it increased the dynamic stiffness of the ACM system in the high frequency region, and then amplified the vibration transfer via the ACM. The low-cost ACMs provided good vibration isolation performance in vehicle tests, but there still remain problems in engine vibration estimation technique, controller of the ACM system and proper mathematical model for design and control. In this paper, three major contributions are made. First, a refined ACM model, which accounts for the actuator model and base motion, is proposed to get the required force information for control and design of ACM actuator. Second, a current shaping algorithm based on the ACM model is suggested in order to compensate for the performance degradation due to absence of feedback sensors without any side effects. Third, an engine vibration estimation algorithm, which uses such existing sensors as CAM and CAS, is extended to construct the gain map easily by applying an in-situ engine vibration estimation method using back EMF (electromotive force) of the actuator coil and engine-mounting system model. The prototype low- cost ACM construction is depicted in Fig. 2, which consists of three components: an ACM device, a current shaping controller and an engine vibration estimator. As a result, main difference between the low-cost ACM and full loaded ACM is absence of two feedback sensors, a displacement sensor for actuator control and a load cell for reference signal. To help understanding, cost comparison between the two is described in Table 1.  International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 60-72 © IAEME   62   Table 1:  Cost comparison between the low-cost ACM and the full loaded ACM. Components Full loaded ACM ($) Low-cost ACM ($) Hydraulic mount 30 30 Current amplifier and micro-processor 100 100 Displacement sensor 2000 0 Load cell 100 0 Total 2230 130 3. DESIGN AND DYNAMIC MODELLING OF ACM 3.1. Design of ACM Many researchers have considered the HEM as the basic structure for various types of active engine mount, mainly because of the inherent reliability in performance and the adaptability to new designs. As shown in Fig. 3, HEM has two force transfer paths: one through the main elastic rubber and another through the fluid in upper chamber. The elastic rubber exerts the force to the chassis, when it is vertically deformed by the engine, supporting the dynamic as well as static loads from the engine. Fluid in the chamber becomes functional when the pressure in the chamber is varied with the decoupler and the inertia track components. The inertia track supplies heavy damping force by resistance to the fluid motion. The decoupler provides amplitude dependent stiffness to compensate for the stiffness increase due to the upper chamber pressure. The ACM, developed in the laboratory, employs the basic structure of the conventional HEM, of which upper chamber is connected to an actuator. The actuator, which essentially replaces the existing decoupler of the conventional passive HEM, actively controls theupper chamber pressure.By controlling the upper chamber pressure, the ACM can cancel the transmitted force from the engine to the chassis. The developed ACM is schematically depicted in Fig. 4. 3.2. Dynamic modeling of ACM For effective design and control of an ACM system, an appropriate mathematical model is essential to describe both passive and active characteristics simultaneously. The passive characteristic means the dynamic behavior of ACM when the actuator is completely turned off. And the active characteristic describes the dynamic relationship between the actuator input and the vibration isolation of ACM. Fig. 1: Structure of the conventional full active control engine mount Fig. 2:  Structure of the active control engine mount without feedback sensors  International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online), Volume 5, Issue 8, August (2014), pp. 60-72 © IAEME   63   Fig. 3:  Conventional hydraulic engine mount Fig. 4:  The developed active control engine mount The conventional HEM model, which has been proposed and optimized in the past by many researchers [26–33], was incorporated into the ACM model to describe the active as well as passive characteristics, accounting for dynamics of the active actuator. Lee and Lee [10] suggested a two-input single-output system as an ACM model, treating the engine vibration and the actuator runner displacement as the two independent inputs and the resulting transmitted force to the chassis as the output. The passive and active transfer functions, defined from the two-input single-output relationship, were extensively used for design and control of the ACM [10]. Sakamoto and Sakai [15] proposed a modified ACM model that reflects the actuator dynamics to explain the passive characteristics more precisely In Fig. 5, Kr and Cb represent the stiffness and volumetric compliance of rubber, respectively; Ac and At denote the cross-sectional areas of the actuator runner and the inertia track, respectively; Ae is the equivalent cross-sectional area of the upper fluid chamber. The fluid flow in the inertia track is modeled as the equivalent mass m t and damping coefficient Rt, and the volumetric compliance of the lower chamber is designated as Kt. Fig. 6:  Conventional dynamic model for active control engine mount Fig. 5:  New dynamic modelfor active control engine mount

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Jul 23, 2017
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