In this paper, a novel concept of integrating an active torque balancing mechanism with a planetary gear reducer is presented. This integrated device is composed of a speed reduction unit and a torque compensation unit. The speed reduction unit, which contains a two-stage planetary gear train, can make the device to transform the speed and torque for meeting the needed requirements of the machine. The torque compensation unit, which consists of a differential gear train and a servo motor, can make the device to balance the input torque fluctuations of the mechanical system. Through an analytical method, an exact control function which can totally eliminate the input torque fluctuation of the driving motor of the machine is derived for the servo motor of the integrated device. At the same time, by adjusting the structure parameters of the differential gear train, the torque fluctuation of the servo motor can be limited too. Besides, in order to obtain a satisfactory tradeoff between the torque fluctuations of the driving motor and the servo motor, an optimization method is developed to find an appropriate control function for the servo motor. In addition, an integrated approach is proposed to optimize both the structure parameters of the differential gear train and the control function of the servo motor. Two numerical examples are given to illustrate the design procedures and to show their feasibilities.

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Pneumatic type anti-vibration apparatuses are used in the field of semiconductor manufacturing and precision measurement. The variation of the supplied air pressure from the air compressor causes the position fluctuation of the isolated table. A control method using a voice coil motor (VCM) as the actuator is proposed in this study to control the position fluctuation of the isolated table caused by the supplied air pressure. The feedforward compensator control scheme is used to provide a proper controlled signal to the VCM. According to the controlled signal, VCM exerts driving force in the opposite direction of the air spring expansion or compression to suppress the vibration of the isolated table.

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In this paper, we propose an autonomous attitude control of a quad tilt wing-unmanned aerial vehicle (QTW-UAV). A QTW-UAV can achieve vertical takeoff and landing; further, hovering flight, which are characteristic of rotary-wing aircraft such as helicopter. And high cruising speeds, which is a characteristic of fixed-wing aircraft, can be also achieved by changing the angle of the rotors and wings by a tilt mechanism. First, we construct an attitude model of the QTW-UAV by using the identification method. We then design the attitude control system with a Kalman filter-based linear quadratic integral (LQI) control method; the experiment results show that a model-based control design is very useful for the autonomous control of a QTW-UAV.

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The method of reducing automotive intake noise can be classified by passive and active control techniques. However, passive control has a limited effect of noise reduction at low frequency range (below 500 Hz) and is limited by the space of the engine room. However, active control can overcome these passive control limitations. The active control technique mostly uses the Least-Mean-Square (LMS) algorithm, because the LMS algorithm can easily obtain the complex transfer function in real-time, particularly when the Filtered-X LMS (FXLMS) algorithm is applied to an active noise control (ANC) system. However, the convergence performance of the LMS algorithm decreases significantly when the FXLMS algorithm is applied to the active control of intake noise under rapidly accelerating driving conditions. Therefore, in this study, the Co-FXLMS algorithm was proposed to improve the control performance of the FXLMS algorithm during rapid acceleration. The Co-FXLMS algorithm is realized by using an estimate of the cross correlation between the adaptation error and the filtered input signal to control the step size. The performance of the Co-FXLMS algorithm is presented in comparison with that of the FXLMS algorithm. Experimental results show that active noise control using Co-FXLMS is effective in reducing automotive intake noise during rapid acceleration.

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Active wave control strategy enables the inactivation of vibration mode, which is valid for suppressing the vibration of a distributed parameter structure. However, when active wave control is applied, new vibration modes are produced in the uncontrolled region. To overcome this problem, this paper proposes a novel control strategy based on a hybrid combination of direct velocity feedback (DVFB) and active wave control. The two control methods have complementary qualities; DVFB is for improving the stability, and active wave control is for its unique control effects. First, a transfer matrix method in the Laplace domain is introduced to describe wave propagation phenomena of an Euler-Bernoulli beam. Then the wave filtering method which uses point sensors is presented. Based on the filtering method, the characteristic equation and control laws of the reflected wave absorbing control are derived. Next, the independence of the two control methods in the proposed hybrid control system is investigated by a numerical simulation. This is followed by the discussion of the stability problem of the hybrid control system via a Nyquist diagram method and three types of root loci. Finally, the control effects of the proposed control system are presented, demonstrating the validity of the proposed method.

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The modified repetitive control system is a type of servomechanism for the periodic reference input. That is, the modified repetitive control system follows the periodic reference input with small steady state error, even if a periodic disturbance or an uncertainty exists in the plant. Using previously proposed modified repetitive controllers, even if the plant does not include time-delay, transfer functions from the periodic reference input to the output and from the disturbance to the output have infinite numbers of poles. When transfer functions from the periodic reference input to the output and from the disturbance to the output have infinite numbers of poles, it is difficult to specify the input-output characteristic and the disturbance attenuation characteristic. From the practical point of view, it is desirable that the input-output characteristic and the disturbance attenuation characteristic are easily specified. In order to specify the input-output characteristic and the disturbance attenuation characteristic easily, transfer functions from the periodic reference input to the output and from the disturbance to the output are desirable to have finite numbers of poles. From this viewpoint, Yamada et al. proposed the concept of simple repetitive control systems such that the controller works as a modified repetitive controller and transfer functions from the periodic reference input to the output and from the disturbance to the output have finite numbers of poles. In addition, Yamada et al. clarified the parameterization of all stabilizing simple repetitive controllers. However, the method by Yamada et al. cannot be applied for the plant with uncertainty. The purpose of this paper is to propose the parameterization of all robust stabilizing simple repetitive controllers for the plant with uncertainty.

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Active magnetic bearing (AMB) becomes to be widely used in various kinds of rotating machinery. However, as the magnetic force is nonlinear, nonlinear phenomena may occur when the rotational speed becomes higher and the delay of control force relatively increases. In this paper, the magnetic force is modeled by considering both the second order delay of the electric current and the first order delay of the magnetic flux. The AMB force is represented by a power series function of the electric current and shaft displacement. The nonlinear theoretical analysis of the vertical rigid rotor supported by the AMB with the PID control theory is demonstrated. The effects of the gain of the integral feedback on the nonlinear phenomena are clarified theoretically and experimentally.

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A number of structures in industrial facilities are installed on supports, and there have been cases in which damage to such structures has been caused by coupled vibration. In seismic design procedure, the response magnification is obtained from the natural frequency and the modal damping ratio of the coupled system between the structure and the supportive structure. Therefore, the simplified estimation method for calculating the natural frequency and the modal damping ratio of the coupled system is required in the seismic design. In the past study, an equation to calculate the modal damping ratio of a coupled system was presented. The proposed equation was useful for obtaining the modal damping ratio without performing an eigenvalue analysis or a shaking test. In current seismic design procedure, for simplicity, the design response spectrum is used to estimate the acceleration response magnification of a system having one degree of freedom (1-DOF). Though the response magnification of a coupled system can be calculated based on the response magnifications of the 1st mode and the 2nd mode, the participation factor and modal matrix of the coupled system are required. In order to obtain the response magnification, a simpler method that does not involve the participation factor or the modal matrix is proposed, and the characteristics of the proposed method are examined.

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A new optimum design method for dynamic vibration absorbers is proposed for cases when the dynamic characteristics of the primary system vary by a considerable amount and the excitation frequency fluctuates in a small range. When the excitation frequency is constant, it is well known that an undamped dynamic vibration absorber is very effective for attenuating the vibration amplitude of the primary system. However, when the excitation frequency fluctuates in a small range, such an undamped absorber does not always suppress the vibration amplitude. In this paper, we show that the upper limit of the vibration amplitude of the primary system can be easily estimated using the imaginary part of the dynamic stiffness of the absorber. We derive very simple equations that give the optimum natural frequency and damping ratio of the absorber for a given excitation frequency range when the excitation force amplitude is proportional to the square of the frequency and vibration is evaluated using velocity amplitude. Calculation results of the frequency response for some examples of absorbers designed by the proposed method are demonstrated, which show the usefulness of the proposed method.

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New optimum design methods for dynamic vibration absorbers are proposed for the cases when the primary system has some uncertainty in its dynamic characteristics and the excitation frequency fluctuates in a small range. In the previous paper, we derived exact and very simple design equations that give the optimum natural frequency and damping ratio of the absorber for a given excitation frequency range in the special case that the excitation force amplitude is proportional to the square of the frequency and the objective function is the velocity amplitude. In this paper, an approximate design method of dynamic vibration absorbers for a general excitation force and a general objective function is discussed . Two different types of approximate design equation are proposed and calculation results obtained by using the proposed design methods are compared with the exact solution obtained by using a numerical method. Through the discussion, it is demonstrated that the proposed design methods are very useful.

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We develop an importance sampling simulation scheme for estimating extremely small probability of level exceedance with respect to a nonlinear oscillating systems driven by a stationary random noise, where we use a probability measure transformation technique for constructing a simulation scheme based upon the Maruyama-Girsanov theorem. First, a system of Itô random differential equations and the related level exceedance are formulated, where the system nonlinearity is incorporated in terms of a nonlinear restoring force based upon the Masing rule. Next, an importance sampling simulation scheme is constructed, in which the optimal selection of the importance sampling measure is newly proposed. Finally, we give some numerical examples to demonstrate the efficiency of the proposed scheme and quantitatively examine effects of model parameters as well as the nonlinearity.

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