Showing papers by "Jihong Wang published in 2007"

Development of a Multisegment Coal Mill Model Using an Evolutionary Computation Technique

Abstract: This paper presents a multisegment coal mill model that covers the whole milling process from mill startup to shutdown. This multisegment mathematical model is derived through analysis of energy transferring, heat exchange, and mass flow balances. The work presented in the paper focuses on modeling E-type vertical spindle coal mills that are widely used in coal-fired power plants. An evolutionary computation technique is adopted to identify the unknown model parameters using the on-site measurement data. The identified parameters are then validated with different sets of online measured data. Validation results indicate that the model is accurate enough to represent the whole process of coal mill dynamics and can be used for prediction of the mill dynamic performance. Therefore, the model can be used for online monitoring, fault detection, and control to improve the efficiency of combustion.

Tracking control of nonlinear pneumatic actuator systems using static state feedback linearization of the input-output map

Abstract: To achieve more accurate tracking control, a control strategy for servo pneumatic systems based on the feedback linearization theory is presented. The nonlinear pneumatic actuator system is transformed into a linear system description, with a linear input-output map by regular static state feedback and state coordinate transformation. A servo tracking controller is then developed for the system based on the linear system model. Since there exists an inverse trans- formation for the new coordinate system, the designed servo control is transformed back to the original state coordinates with the original input variables. Two different cases are discussed: the pneumatic cylinder is driven (1) by a single five-port proportional valve and (2) by two three-port proportional valves. At the initial stage, for the convenience of analysis, the static friction forces are ignored. They are treated as uncertainties addition to the system in the la ter sections. For on-line implementation, the controller is simplified to require only position and velocity state variables in its feedback. The simulation results show that th e simplified controller can drive the system to achieve the required tracking accuracy.

Development of a Novel Sensorless Longitudinal Road Gradient Estimation Method Based on Vehicle CAN Bus Data

Abstract: The availability of road gradient information will have a big impact upon the quality of vehicle control. This paper presents a novel "sensorless" longitudinal road-gradient estimation method, which was developed in two steps starting from a benchmark system design. The gradient benchmark system consists of an inclinometer sensor and an acceleration-based error correction algorithm, which can be used to verify the accuracy of the road gradient obtained using a sensorless estimation method. The sensorless road-gradient estimation algorithm uses the vehicle data currently available on the vehicle controller area network (CAN) bus. The completed gradient estimation algorithm was successfully tested online in variable road conditions and different driving manners. The test results showed that the resulting longitudinal road-gradient estimation algorithm fulfilled the specified accuracy requirement, and provided a cost effective and reliable way for longitudinal road-gradient estimation in real time.

Motion detection based on accumulative optical flow and double background filtering

Abstract: Moving object detection is very important for video surveillance. In this paper, we present a new real time motion detection algorithm that is based on the integration of accumulative optical flow and double background filtering method (long-term background and short-term background) to achieve better performance. The accumulative optical flow method is used to obtain and keep a stable background image to cope with variations on environmental changing conditions and the double background filtering method is used to eliminate the background information and separate the moving object from it. The biggest advantage of this algorithm is that it does not need to learn the background model from hundreds of images and can handle quick image variations without prior knowledge about the object size and shape. The algorithm has high capability of anti-interference and preserves high accurate rate detection at the same time. The effectiveness of the proposed algorithm for motion detection is demonstrated in a simulation environment and the evaluation results are reported in this paper. required to be stationary when this method is applied. The optical flow is an approximation of the local image motion and specifies how much each image pixel moves between adjacent images. It can achieve success of motion detection in the presence of camera motion or background changing. According to the smoothness constraint, the corresponding points in the two successive frames should not move more than a few pixels. For an uncertain environment, this means that the camera motion or background changing should be relatively small. The method based on optical flow is complex, but it can detect the motion accurately even without knowing the background. The main idea in this paper is to integrate the advantages of these two methods ((9), (10)). In this paper, an integrated accumulative optical flow and double background filtering method is represented. The main goal of the method is to separate the background and foreground effectively and detect the object in motion accurately. In this way, an accumulative optical flow method is used to obtain and keep a stable background image to address variations on environmental changing conditions and use a double background (long-term background and short-term background) method to eliminate the background information and separate the moving object from it. Different from the paper (11), a new strategy is proposed which improves the capability of detecting the object in motion. This paper is organized as follows. In Section II, an overview of the method is presented to explain the whole procedure. In Section III, the optical flow method is introduced and Section IV is dedicated to the double background filtering method. Section V describes a region-based matching method and Section VI presents the experimental results. Section VII concludes the achievement of the paper.

HCCI Engine Modeling for Real-Time Implementation and Control Development

Abstract: A propane-fueled homogeneous charge compression ignition (HCCI) engine model has been developed for the development of new engine control strategies in which a single-zone combustion mathematical model is adopted. The model has a reasonably simple structure and is implemented in a SIMULINK environment for simulation studies. The results of simulation studies show that the model can provide information on autoignition timing, engine work output, gas temperature, and concentrations of in-cylinder species. Model validation has been conducted by comparing the simulated output with experimental results obtained from a single-cylinder HCCI research engine. The comparison shows a fair agreement between the simulation and experimental results.

Energy Efficiency Analysis of a Scroll-type Air Motor Based on a Simplified Mathematical Model.

Abstract: The paper presents a simplified mathematical model for a scroll-type air motor. Through air power/energy analysis, it has shown that a scroll-type air motor with a properly specified structure and suitable pressure of compressed air supply is able to achieve high energy efficiency and satisfies air power requirement. The features of a scroll-type air motor in geometry, mechanical structure, and pneumatic power transmission are studied in the paper. Differential geometry is used as the mathematical tool to parameterise the scroll. In this study, Matlab Symbolic Math Toolbox is found very efficient in finding analytic expressions of scroll chamber volumes and generalised torques. State shifting is employed to solve the dynamic system equations numerically. Energy efficiency of a scroll-type air motor is analysed based on the mathematical model.