Van-Tsai Liu

Power converter design for a fuel cell electric vehicle

This research is developed the electric vehicle by the fuel cell. Between fuel cell source and motor controller, we add new power converter, offer steady output voltage to motor controller and drive the direct current hub motor. Converter not only offers steady output voltage but it also combines with coupling inductance technology to battery charger. Besides offers energy to drive motor, and fuel cell charges battery. Micro controller will read the working state of the fuel cell, transmitted by UART interface and show the voltage, current, temperature, gas pressure of the fuel cell in LCD display, reach the function of immediately control the state of electric power system. Verifing via the experiment, the fuel cell electric vehicle that this thesis claimed, even if the fuel cell model in load changing case, the electric converter still can reach the steady output voltage to drive direct current hub motor.

Identification and Control of a Benchmark Flexible Structure using Piezoelectric Actuators and Sensors

In this paper we propose a neural network approach for the identification and control of a benchmark flexible structure: a thin simply-supported plate with bonded piezoelectric film actuators and sensors. A specific linear differential inclusion is developed for a class of multilayer feedforward networks. With this technique, it is shown that the plant model identified by the neural network can be represented as a linear time-invariant system so that traditional or advanced linear control theory can be directly applied to design the stabilizing flexible structure controller.

Robust stabilization for composite observer-based control of discrete systems

Abstract Design criteria of robust observer-based controllers for linear, discrete-time, singularly perturbed systems with slow and fast modes are considered. The developed stability measure complements the quantitative information for unmodeled fast modes that cannot be provided by the usual qualitative robustness analyses. A numerical example is provided to show the analytical results obtained.

Modeling Hysteresis of the Piezoactuators with Prandtl-Ishlinskii Model

The proposed approach is to design a feedforward controller for piezoelectric motion platform. A Prandtl-Ishlinskii(PI) hysteresis model is proposed for the hysteresis behavior of piezoelectric actuators. This model is more mathematically simple when compared to Preisach operator. The PI operator is more efficient phenomenological fit as it is a first order gradient, rather than a step change. The weights of main hysteresis loop are identified by using LMS(LeastMean-Square) algorithm. An inverse feedforward controller is to cascade the inverse PI operator with the actual hysteresis, which is to linearize the hysteresis response. The effectiveness of the proposed method is demonstrated through experimental.

Realization of Stabilizing Network Control Systems with Round-Trip Time Delays

The purpose of this paper is to present a stable network control design with uncertain time-varying communication delays. In the typical networked control systems (NCSs), there are inherent plant delays and network delays. It has been know that time delays may not only degrade the system performance, but also destabilize the controlled plant. To alleviate the influence resulting from time delays while maintaining performance, we propose a compensating scheme which consists of two compensators-a fuzzy-PID controller and a neuron network compensator. The proposed design has also been experimentally verified to show its effectiveness and superiority.

Tracking control of the Z-tilts error compensation stage of the nano-measuring machine using capacitor insertion method

This paper deals with the design of the capacitor insertion method for the three degree-of-freedom (DOF) flexible and deformation mechanisms aimed to eliminate hysteresis effects in piezoelectric actuators. By inserting a capacitor in series with the piezoelectric actuator is applied a 3-DOF nanoprecision platform and laser-measuring systems. The Z-tilts(z, pitch, and roll motion) error compensation stage of the nano-measuring machine is accomplished. In addition, a high resolution laser interferometer is used to measure position accurately. Therefore, above the method is effectively applied to a piezoelectric actuator are presented that compensate substantial improvements in positioning control precision and control performance. With the aid of positioning control, this system provides +/-60nm positioning resolution over the total range of 1000nm and +/-0.1 arcsec angle resolution over the total range of 3 arcsec for the stage along the z-direction.

Development of A four-Degrees-of-Freedom Diffraction Sensor

The development of a diffraction-type four-degrees-of-freedom sensor based on the three-dimensional diffraction method and collimation method is described in this paper. This sensor is designed to be integrated with a linear laser encoder to allow five-degrees-of-freedom measurement. It is composed of a miniature collimation-type sensor, a reflective diffraction grating and a quadrant detector to simultaneously measure a straightness error and three rotational angles. Based on the diffraction method, the reflective diffraction grating reflects the incident laser from the collimation-type sensor to several diffractive laser rays and only the 0 and +1-order diffractive laser rays are detected by the collimation-type sensor and a quadrant detector respectively. According to the changed spot positions of the diffraction laser lights on the collimation-type sensor and the quadrant detector, a straightness error and the three rotational errors can be solved simultaneously.

Realization of Preisach model using adaptive polynomial approximation method

Modeling of systems with hysteresis has received considerable attention recently due to the increasing accuracy requirement in engineering applications. The classical Preisach model (CPM) is the most popular model to characterize hysteresis which can be represented by infinite but countable first order reversal curves (FORC). In practice, one approach to realize the CPM uses data tables; the data of which correspond with the samples of a finite number of FORC. This approach, however, suffers from two drawbacks: it requires a large amount of memory in order to obtain an accurate prediction of hysteresis and it is difficult to derive efficient ways to modify the data table in order to reflect the aging or timing effect of elements with hysteresis. To overcome these drawbacks, this paper proposes to use a set of polynomials instead of data tables for realization of the CPM. The proposed approach reduces the required memory because it only requires to store a small number of polynomial coefficients. Furthermore, the polynomial coefficients can be obtained using the least-square approximation or the adaptive identification algorithm such that the tracking of hysteresis model parameters is possible. The proposed approach has been verified by the computer simulations; the resulting realization compared with the table method yields close effect in model accuracy and has tracking ability for a changed CPM.

Neural Net-based Modeling and Control of a Micro-positioning Platform Using Piezoelectric Actuators

The paper proposes an integrated controller which combines feedforward, PID and a cross-coupling controller to achieve high accuracy for a dual-axis piezoelectric actuated platform. A Preisach model is created to numerically describe the hysteresis behavior of the piezoelectric actuators. On the basis of the Preisach model, a feedforward compensator is developed to compensate for the hysteresis nonlinearity. A PID controller is introduced to further suppress the tracking error due to the modeling inaccuracy and hence to obtain precision tracking control. Finally, a neural net-based cross-coupling control scheme is proposed to reduce the contour errors, which are very typical in dual-axis tracking control problems. The approach developed is numerically and experimentally verified with a variety of operating conditions.

A Novel Micro-positioning Controller for Piezoelectric Actuators

The main purpose of this study is to design a tracking controller for a dual-axes piezoelectric actuated platform. First, a Preisach model is used to numerically describe the hysteresis behavior of piezoelectric actuators. Next, on the basis of the Preisach model, a feed-forward controller is developed to compensate for the hysteresis nonlinearity. Then, a PID controller is introduced to further suppress the tracking error due to the modeling inaccuracy and hence to get precision tracking control. We utilize evolution algorithm to choose three optimality control gain for PID controller. The dual-axes motion control problem for the piezoelectric actuated platform is also investigated. A neural-net based decoupling control scheme is proposed to eliminate the contour error which is typical in dual-axes tracking control problem. The developed approaches are numerically and experimentally verified which demonstrate performance and applicability of the proposed designs under a variety of operating conditions.