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A subjective evaluation method is generally used to assess ride comfort of cars. However, this method poses many problems as pointed out later. Thus, it is the important task of automobile engineers to establish an objective evaluation method in advancing the development of vehicles, and in fact, research in this area is being actively made. (1),(2),(3),(4) This paper describes research on an objective evaluation method for the phenomenon called harshness among other phenomena related to ride comfort, and introduces a newly developed objective evaluation method since evaluation ratings estimated based on this method correlate well with subjective evaluation ratings given by test drivers and, thus, the method has been verified as sufficiently practical.

Electronics technology has made remarkable progress in recent years, and in the field of automobile noise and vibration control, it has attracted the interest of engineers due to its potential for use in the active control of vibration isolators. This report describes an investigation on reducing automobile vibration caused by engine explosion using a piezo actuator(PA) engine mount. Piezo actuator has a very high speed response but the displacement is generally very small. Therefore PA mount requires an amplitude enlargement mechanism. Here, an active mount with an enlargement mechanism incorporated was developed. For the control system, the adaptive control algorithm proposed by S. J. Elliott et al. was employed as a base, and a control rule against limitation in the power of the actuator was used in combination with it. A significant attenuation of the vibration of the dominant harmonic order in idling was achieved. The results are reported in the following pages.

ER Fluids (Electro-Rheological Fluid) whose solidity or apparent viscosity varies very rapidly and reversibly to changes of electric field strength have been studied for a long time, chiefly in the UK, and the recent remarkable developments of electronics technology have made many engineers interested in its application to control devices, particularly in the automotive field. In this paper, the rhelogical characteristics of ER Fluids are first described on the basis of experimental data measured with the coaxial cylindrical rotatory viscometer that can be operated under electric fields and at different temperatures. Then, the semi-active control mounting system incorporating ER Fluid into a hydraulic mount on the basis of the “Pseudo-Sky Hook Model” is discussed both theoretically using the harmonic linearization method and experimentally, with a one degree of freedom vibration model.

In the first half of this paper, dynamic characteristics of conventional decoupler equipped hydraulic mounts are discussed and the demerits of this type of mounts are clarified particularly in case of superimposed inputs and inputs in a high frequency range, say, 300 Hz or more. It is mentioned that decouplers with weak non-linear structures are more effective against superimposed inputs. Concerning inputs in a high frequency range, our newly developed hydraulic mounts which can achieve low dynamic stiffness up to 800 Hz by utilizing liquid-column-resonance against rubber surging of main elastic bodies are explained in details. In the latter half of this paper, the possibility of semi-actively controlled mounts incorporating electro-rheological (ER) fluids into hydraulic mounts are discussed from the theoretical point of view based upon the experimental results taking a simple one-degree-of-freedom vibrational system for example.

The dynamic properties of tires vary with the running conditions. This fact makes tire vibration analysis of tires difficult. The analytical techniques on both a tire with vehicle weight and a rotating tire are introduced in this paper. First, the constrained modal method is applied and the dynamic characteristics are identified. Then the vibration of the suspension system is simulated and the calculation results are compared with the experimental results. In case of rotating tire, the corrected modal parameters are used. The correct constants are obtained by hammering test and the response of the axle due to a projection or “cleat” is calculated. From the results, we are sure these methods are applicable to the vehicle vibration problems.

In the automotive industry, hydraulic engine mounts have been available for reduction of engine shake, idle shake and noise transmition. The hydraulic mounts have high damping for large motion induced by engine shake and low dynamic stiffness for low amplitude by idle shake or noise transmition. These excellent properties can not be achieved by conventional rubber-mount. However the optimum tuning of the hydraulic mounts is not easy because of the non-linear properties which depend on the frequency and amplitude. To solve these problems, we developed the system analysis which combines the numerical simulation of the hydraulic mount and the modal analysis for the vehicle.