This paper proposes a vibration control method of an automotive drive system with backlash to maintain stability and control performance under the control period constraint due to an engine's characteristics. Reducing the vibrations of the automotive drive system remains a challenge when improving the riding comfort and driving performance of automobiles. In particular, a vibration control method must be developed to compensate for the backlash of differential gears because this element degrades the vibration control performance. Furthermore, engines used as actuators have a constraint in which control cycles are made longer due to restrictions of the input update. The roughly updated cycles adversely affect not only the high vibration control performance but also the stability. In this study, we validate the control system for an automotive drive system with backlash by considering the input update limitation. First, a basic experimental device, which abstracts actual vehicles to focus on the influence due to backlash while reflecting only the basic structure of an automotive drive system, is created. Then to cope with the control cycle constraint, sampled-data H2 control is applied. The servo system is constructed by applying an approximate integrator and frequency shaping. As an approach to compensate for backlash, we propose a simple and practical control mode switching technique. Finally, the effectiveness of the control system is verified experimentally. The results are compared to the control results with those obtained by the traditional discrete approximation.

In automotive drive systems, differential gear backlash degrades the control performance. Specifically, a shock torque, which is generated when the gear runs freely and collides with the backlash, increases the vibration amplitude. Consequently, it is important to develop a vibration control method to suppress the adverse effect of nonlinearity due to backlash. Furthermore, considering implementations on actual vehicles, design at the development site, and mass production, a simple and practical control method is necessary. This paper describes the configuration of a basic experimental device, which abstracts an actual vehicle to focus on the influence due to backlash while reflecting the basic structure of an automotive drive system. Next, a basic controller is designed using a mixed H2/H∞ control theory, and a servo system is constructed to track the target value. A simple control mode switching algorithm is proposed for backlash compensation. This algorithm is suited to practical applications because it uses only an output without a state estimation and it compensates for performance deteriorations due to the nonlinearity by operating a single linear controller. Finally, simulations and experiments verify the effectiveness of the proposed control system.

Active control of combustion oscillations occurring in a methane-air lean premixed model combustor is accomplished by the method of secondary fuel injection. The main flame is sustained by an axial vane swirler. The central part of the swirler is endowed a function as the secondary fuel injector. The fuel jets from the injector enhance the flame stability by producing rich stable flames in the region of the flame base. Open-loop controls by secondary fuel injection with constant flow rates have been conducted on a naturally unstable condition. The results show sensitivity to the injection amount. It indicates that the flame base is very sensitive to the additional fuel distribution. A similar discussion is made on NOx emission also. Finally, a closed-loop control has been performed by implementing the mixed H-2/H-infinity controller. An obvious effect of the closed-loop control on the suppression of pressure oscillations is found without loosing an advantage for low NOx emissions

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Active vibration control of automotive drivetrains must be developed to compensate for the backlash of gears because it causes undesired responses. In addition, an engine used as an actuator has a constraint which makes the control periods longer and time-varying, resulting in deterioration of the control performance. The contribution of this study is to cope with all the issues described above, backlash and the control period constraint, simultaneously. First, a basic experimental device, which simplifies an actual vehicle to focus on the effect due to backlash, is demonstrated. In the device, the control period constraint, which is equivalent to that of an engine, is reproduced by a digital signal processor. To reduce an adverse effect due to the extension of the control period, the sampled-data controller, which does not require discretization in its implementation, is employed. In this paper, predictive processing using the servo-type sampled-data controller is proposed to compensate for the phase delay of the control input caused by the time-varying control period. In addition, a control mode switching technique included in the prediction suppresses undesired responses due to backlash. Finally, control experiments verify the effectiveness of the control system.

This paper proposes a vibration testing and health monitoring system based on an impulse response excited by a laser ablation. High power YAG pulse laser is used for producing an ideal impulse force on structural surface. It is possible to measure high frequency vibration responses in this system. A health monitoring system is constructed by this vibration testing system and a damage detecting algorithm. A microscopic damage of structures can be extracted by detecting fluctuations of high frequency vibration response with the present health monitoring system. In this study, loosening of bolt tightening torques is defined as the damage of the system. The damage is detected and identified by statistical evaluations with Recognition-Taguchi method.

This paper proposes a vibration testing and health monitoring system based on an impulse response excited by a laser ablation. High power YAG pulse laser is used for producing an ideal impulse force on structural surface. It is possible to measure high frequency vibration responses in this system. A health monitoring system is constructed by this vibration testing system and a damage detecting algorithm. A microscopic damage of structures can be extracted by detecting fluctuations of high frequency vibration response with the present health monitoring system. In this study, loosening of bolt tightening torques is defined as the damage of the system. The damage is detected and identified by statistical evaluations of measured frequency response data with Recognition-Taguchi method. The effectiveness of the present approach is verified by experiment to detect and identify the loosening of bolts installed on an aluminum block structure.