C-1-4 終端誤差を許容した多項式入力型終端状態制御(情報・精密機器のサーポ・スマート制御,口頭発表)

For information devices such as hard disk drives, actuators must be controlled as quickly and precisely as possible. The design of the feedforward input is very important in satisfying these requirements. Therefore, we have proposed design methods based on final-state control so as to reduce its spectrum at the desired frequency points. Furthermore, the final-state control method has been extended to generate the feedforward input using a polynomial. By using a polynomial, the required memory size can be drastically reduced because only the coefficients of the polynomial must be stored. However, when the step number of the input increases, the method may not produce a correct solution because of a numerically ill-posed problem. In this paper, we propose a design method for the final-state control based on a time-symmetric polynomial input. The simulation results show that the proposed method contributes to the improvement of not only the numerically ill-posed problem but also the performance.

For information devices such as hard disk drives, actuators must be controlled quickly and precisely as much as possible. To satisfy these requirements, feedforward input design is very important. For this problem, we have proposed a frequency-shaped final-state control method. This method can obtain a feedforward input that has lower spectrum at desired frequency points so as to reduce residual vibration after positioning. Furthermore, the method has been extended to generate the feedforward input by a polynomial. By using the polynomial, the required memory size can be drastically reduced because it only requires to store the coefficients of polynomial. However, in the frequency-shaped final-state control method by polynomial input, it is not guaranteed that the solution always exist theoretically. In order to solve this problem, final-state control methods in which the feedforward input is generated by both of a polynomial and time-series data are proposed. The effectiveness of the proposed methods are verified by simulation using the plant model of the HDD benchmark problem. The simulation results show that the proposed method outperform the conventional methods.

This paper proposes a new design method of track-seeking trajectory for hard disk drives by using final-state control method. The proposed method can obtain a feedforward control input whose frequency components are minimum at the desired frequency points. In our approach, the control input is evaluated in continuous-time domain, and the frequency components higher than the Nyquist frequency can be also optimized. Simulation and experimental results are shown to evaluate the effectiveness of the proposed method.

We have proposed a frequency-shaped final-state control method that can reduce a residual vibration after positioning by minimizing Fourier gain of feedforward input at desired frequency points. In this method, the feedforward input is obtained as a time series data, therefore, it requires a large memory size to store them in an embedded controller. In this paper, we propose a final-state control method based on a polynomial input. It only requires to store the coefficient of the polynomial, and the required memory size can be drastically reduced. Furthermore, by considering the time symmetry of input, a method to reduce the order of the polynomial without a performance degradation is proposed. The effectiveness is verified by simulations.

In this paper we deal with active control of shock in a collision problem between two objects. In order to make it clear how the deformation of the shock-receiving object can be maximized while minimizing the deformation of the shock-giving object and how energy can be transmitted unilaterally, the relationships among contact stiffness, deformation time, deformation ratio and energy balance are discussed. The final-state control is applied to obtain a feedforward input to deform the shock-receiving object by a desired amount in a predetermined time. Thus, the energy balance and the energy efficiency are verified. Furthermore we examine the conditions necessary to realize a ‘dynamical diode’ that can transmit energy unilaterally from the shock-giving object to the shock-receiving object. It is demonstrated experimentally that the appropriate feedforward input can be obtained by final-state control under specified conditions of contact stiffness and deformation time.

This paper discusses an improvement of final-state control (FSC). FSC is a control method for transferring the state of a dynamic system to specified states at a specified terminal time by using an external input. So far, it is mainly applied to motion control problems such as servo control of hard disk drives. However, FSC cannot deal with time-varying specified states. For example, when an operator pushes a cart and attempts to connect with another stopped cart without any stop, the stopped cart should accelerate to the same velocity as the running cart within a specified time. Here, the velocity of the running cart is time-varying, and a control method which can deal with such time-varying specified states is required. In this paper, in order to deal with the time-varying states, an updating final-state control (UFSC) technique is introduced. UFSC updates the initial and ideal final states at every sample. However, the equation of UFSC algorithm includes inverse matrix computations and the computation process is complicated. Moreover, most computed inputs will not be applied because of updating. So, in order to reduce the computational load, this paper also introduces a device to extract the requisite computation for simple controlled models. The effectiveness of the proposed method is verified by simulations in a case of connection control problem of two carts.

Fiber Bragg grating sensor is widely used in military, construction, transportation, aviation and other fields due to its advantages in high sensitivity, high precision, high multiplexing and small volume. However, in some special fields such as ultrasonic flaw detection, high-speed vibration and aeroengine monitoring, the signals are rapidly changing, thus requiring high speed sampling. But the demodulation speed of traditional fiber Bragg grating demodulation techniques is hardly to satisfy the requirements, which seriously limits the application of fiber Bragg grating sensor in these fields. To solve this problem, in this paper we propose a dispersion compensation fiber(DCF)-single mode fiber(SMF) dual-channel demodulation method. Based on the SMF and the DCF with the characteristics of positive and negative dispersion coefficients in the anomalous dispersion region respectively, and combining with the optical time domain reflection technology, high speed and high precision demodulation of fiber grating can be realized. This system adopts the whole fiber structure without wavelength scanning, and the grating wavelength and position information can be obtained according to the pulse delay difference under a single optical pulse. There are three factors that quite influence the system accuracy and need to be solved: the grating space disturbance which is caused by the temperature change of the sensor network fiber; the dual-channel length disturbance caused by the DCF-SMF dual-channel temperature change; the dispersion disturbance caused by the inaccurate dispersion difference of the DCF-SMF. By constructing the DCF-SMF dual-channel, adopting the reference grating and introducing the dispersion difference correction model, these influence factors are solved. The case of temperature disturbance elimination is tested by the 5-75℃ temperature experiments. And the results are as follows: when the temperature of the sensor network fiber changes, the standard deviation of this dual-channel demodulation system is 16.8 pm, while only using the DCF single-channel to form the demodulation system, the standard deviation is 3614 pm. And when the DCF-SMF dual-channel is disturbed by temperature, the standard deviation is 11.9 pm. For a long time demodulation under constant temperature, the standard deviation of this system is 6.4 pm. Thus the influences of the sensor network fiber temperature change and the dual-channel temperature change on the system demodulation accuracy are effectively reduced. The feasibility and accuracy of this method are also verified by the strain experiment. Experimental results show that the highest demodulation rate of this method is 1 MHz, while the linearity can be up to 0.9998, and the accuracy is about 8.5 pm. So the system with the dispersion difference correction model has a high precision. Therefore, this novel demodulation method has advantages of high speed and high precision, good stability and large dynamic range, and it is very applicable to quasi-distributed fiber Bragg grating sensing system.

High-precision stages require high-speed and high-precision control to improve their production throughput and quality. However, it is expected that their motion speed and accuracy will reach a limit in the near future if the structure of the conventional high-precision stage is used. Therefore, the authors designed and fabricated a stage called the catapult stage which has a decouplable structure consisting of a fine stage and a coarse stage. This stage is different from conventional dual stages in which the fine stage would be disturbed by the coarse stage since they contact with each other. This paper proposes a novel control system design for the catapult stage, and a settling time shortening control method using final-state control (FSC). So far, FSC is mainly applied to the applications such as hard disk drives whose initial states are the zero. However, it is important to consider the initial states for the catapult stage since the initial position, velocity and acceleration of the catapult stage are not equal to zero. Simulations and experimental results demonstrate the effectiveness of the proposed methods.

This paper addresses the development and applications of the control system based on the real-time operating system (RTOS) RTX which constructs an open architecture control system with real-time performance, flexibility and low cost. In this paper, the RTX-based control system is considered from RTOS evaluation, system-level design, to experiments and applications. A novel software structure consisting of Windows, Labview or Matlab, and RTX is presented, which makes the trade-off between real-time tasks running and data processing or displaying. Finally, the control system is successfully applied in two direct-drive high speed and high precision motion platforms.

The catapult stage is a high-precision dual stage with a new structure which, by allowing contact between fine and coarse parts, is compatible with increasing size and acceleration. Impact force occurs in acceleration and deceleration regions, and may degrade a stage. This paper thus proposes a control method to reduce the impact force that considers the thrust limitation by combining model prediction and final-state control. In the proposed method, the timing to activate the fine stage is automatically determined by solving an optimization problem. Simulation and experimental results demonstrate that the method can significantly reduce the impact force between the fine and coarse parts.

This paper proposes angular velocity vector feedback speed control system, the amplitude and phase signals of diagonal velocity are extracted, and signals are converted into current and voltage vector signals to achieve high efficiency and speed precision. Brushless motor rotational stability on speed and torque are classified, comparative characteristics analysis of dynamic speed and torque between conventional method and proposed method are simulated, results consisting of speed accuracy, the waveform of stator current and back electromotive force of each phase are all compared and analyzed, verifying fitness and validation of the proposed method.

Parallel robotic systems have shown their advantages over the traditional serial robots such as high payload capacity, high speed, and high precision. Their applications are widespread from transportation to manufacturing fields. Therefore, most of the recent studies in parallel robots focus on finding the best method to improve the system accuracy. Enhancing this metric, however, is still the biggest challenge in controlling a parallel robot owing to the complex mathematical model of the system. In this paper, we present a novel solution to this problem with a Type 2 Fuzzy Coherent Controller Network (T2FHC), which is composed of a Type 2 Cerebellar Model Coupling Controller (CMAC) with its fast convergence ability and a Brain Emotional Learning Controller (BELC) using the Lyaponov-based weight updating rule. In addition, the T2FHC is combined with a surface generator to increase the system flexibility. To evaluate its applicability in real life, the proposed controller was tested on a Quanser 2-DOF robot system in three case studies: no load, 180 g load and 360 g load, respectively. The results showed that the proposed structure achieved superior performance compared to those of available algorithms such as CMAC and Novel Self-Organizing Fuzzy CMAC (NSOF CMAC). The Root Mean Square Error (RMSE) index of the system that was 2.20E-06 for angle A and 2.26E-06 for angle B and the tracking error that was -6.42E-04 for angle A and 2.27E-04 for angle B demonstrate the good stability and high accuracy of the proposed T2FHC. With this outstanding achievement, the proposed method is promising to be applied to many applications using nonlinear systems.

Galvano scanners are used as laser beam scanners in laser drilling machines. The galvano scanner requires high-speed and high-precision control for more precise laser processing with high throughput. Heat generated by current amplifiers becomes problematic as the positioning speed of the galvano scanner increases. We propose a final-state control (FSC) method that considers voltage constraint of the current amplifiers. By considering the constraint of the applied voltage on the motor, the power supply voltage of the current amplifier can be lowered. Therefore, the electricity consumption and the heat generated by the current amplifier can be reduced. Experimental results show the effectiveness of the proposed method.Copyright © 2012 by ASME

This paper presents a new method to achieve the requirement of high speed and high precision for ball screw drive. First, a PI controller is adopted to increase the equivalent structural damping in the velocity loop. Next, the design of the position controller is implemented by a two-stage method. The Doubly Coprime Factorization Disturbance Observer (DCFDOB) is developed to suppress disturbance and resist modelling error in the inner loop, while the outer loop is then designed based on method to extend the system bandwidth over first resonant frequency so that high speed and high accuracy can be achieved. Finally, a feedforward controller is implemented to improve tracking performance. The experiment results showed that the proposed method has smaller tracking error and better performance for suppressing disturbance when compared to the conventional cascaded P-PI control.

We propose a noise reduction method for unsteady pressure-sensitive paint (PSP) data based on modal expansion, the coefficients of which are determined from time-series data at optimally placed points. In this study, the proper orthogonal decomposition (POD) mode calculated from the time-series PSP data is used as a modal basis. Based on the POD modes, the points that effectively represent the features of the pressure distribution are optimally placed by the sensor optimization technique. Then, the time-dependent coefficient vector of the POD modes is determined by minimizing the difference between the time-series pressure data and the reconstructed pressure at the optimal points. Here, the coefficient vector is assumed to be a sparse vector. The advantage of the proposed method is a self-contained method, while existing methods use other data, such as pressure tap data for the reduction of the noise. As a demonstration, we applied the proposed method to the PSP data measuring the Kármán vortex street behind a square cylinder. The reconstructed pressure data agreed very well with the pressures independently measured by pressure transducers. This modal-based approach will be applicable not only to PSP data but other types of experimental data.