In automotive development, it is important to balance various phenomena with a simplified vehicle body model in the initial design phase. Additionally, idling vibration, engine shake, and road noise are phenomena that affect vehicle ride comfort. Since they have different exciting components and target frequencies, each simplified vehicle model examined in the past report is different. Therefore, it is necessary to represent of each phenomenon in a single vehicle model. Therefore, in recent years, much research has been done in initial design techniques called Model Based Development (MBD) and 1D CAE. We have studied using the Statistical Energy Analysis (SEA) for the initial design. Especially an energy transmissibility parameter of SEA which is called by coupling loss factor (CLF) is focused on describing the phenomenon for various kinds of vibration and noise problem. In this paper, a fundamental study is conducted to examine the balance of multiple phenomena in the initial design phase by the energy transmissibility. At first, a simplified vehicle model that represents each phenomenon is constructed. Next, the energy transmissibility is used to represent each phenomenon, and vibration reduction guidelines are obtained and verified through balance design. The obtained guidelines are then applied numerically to the actual vehicle to confirm vibration reduction.
Overhead cranes are widely used to transport heavy loads, and their efficient operation requires fast and accurate positioning. However, residual vibration which prevents positioning accuracy generally tends to be induced by fast transportation. In previous paper, we proposed a control method which is based on the characteristic that the residual vibration is completely suppressed in a linear undamped system when excited by an external force which does not contain the natural frequency component of the system. To apply this characteristic to nonlinear damped systems, we defined the apparent external force which includes the influence of system nonlinearity and damping. It was confirmed that the residual vibration of a double pendulum type system model of crane can be suppressed by eliminating two natural frequency components from each the apparent external forces. In this paper, in addition, to improve the robustness for a double pendulum type system against the estimation error, new conditions are added to reduce the component around the natural frequencies from each of the two apparent external forces. The effectiveness of these conditions for robustness is verified through numerical simulations. Furthermore, changes in the robustness are examined when the position of the mass point near the support point of the double pendulum is changed. The results showed that the robustness can be improved in many cases except when the control time is short and the mass point is close to the support point.
Overhead traveling cranes are widely used at ports and factories, and they play an important role in mass transportation systems. The main problem with such cranes is that residual vibration of the cargo often occurs at the end of transportation. At present, prevention of residual vibration depends on the skills of the crane operator. Therefore, an automatic operation system for overhead traveling cranes is strongly desired for efficient and safe transportation. In this paper, a new type of open-loop control method is proposed for suppressing the residual vibration. This method is based on the fact that residual vibration is completely suppressed in a linear undamped system excited by an external force that does not contain the natural frequency component of the system. We apply this to a nonlinear damped system and develop an efficient method for determining a trolley trajectory that prevents residual vibration. Numerical simulations confirm that this method can prevent residual vibration. Furthermore, we employ a trigonometric series as well as a power series created by modifying Legendre polynomials in order to construct the trolley trajectory, then examine which is more advantageous for transportation. The results demonstrate that the power series exhibits a better performance in terms of the maximum swing angle of the cargo during transportation and limit of transportation time.
The aim of this study is to develop a systematic method to suppress residual vibration in overhead cranes that lowers operating performance and prevents automation of the system. In the previous paper, we proposed a control method which is based on the fact that residual vibration is completely suppressed in a linear undamped system excited by an external force that does not contain the natural frequency component of the system. The proposed method introduces the concept of the apparent external force which includes the influence of nonlinearity and damping, making it applicable to nonlinear damped systems as well as linear undamped ones. One possible drawback is that it needs the value of the natural frequency of a cargo whose on-site high-precision estimation is generally difficult. Therefore, this paper investigates the influence of the estimation error on the residual vibration, which reveals that the residual vibration increases with the estimation error. To improve the robustness against the estimation error, we employ two types of ways. One is to increase the number of frequency components eliminated from the apparent external force and the other is to make the derivatives of the frequency component zero at the estimated natural frequency. Numerical simulations demonstrate the effectiveness of these approaches, showing that they exhibit similar performance in robustness except in that the latter is easier to use since it does not need additional parameters to be determined.
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