J. Wang

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

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.

Identification of pneumatic cylinder friction parameters using genetic algorithms

A method for identifying friction parameters of pneumatic actuator systems is developed in this paper, based on genetic algorithms (GA). The statistical expectation of mean-squared errors is traditionally used to form evaluation functions in general optimization problems using GA. However, it has been found that, sometimes, this type of evaluation function does not lead the algorithms to have a satisfactory convergence, that is, the algorithm takes a long period of time or fails to reach the values of parameters to be identified. Different evaluation functions are, therefore, studied in the paper and two types of evaluation functions are found to have the expected rate of convergence and the precision. The algorithm is initially developed and tested using the benchmark data generated by simulations before it is applied for parameter identification using the data obtained from the real system measurement. The results obtained in the paper can provide the manufacturers with the observation to the characteristics inside the pneumatic cylinders.

Measurement of the road gradient using an inclinometer mounted on a moving vehicle

Inclinometers are sensors used to measure the angle of tilt of the surface they are placed upon. Unfortunately inclinometers are very susceptible to noise caused by their movement. Therefore, they are generally only suitable for tilt measurements in static situations. This paper will investigate the inclinometer signal under dynamic conditions. A number of methods of analysing the inclinometer signal will be investigated, with the aim being to develop a method of de-coupling the error signals from the gradient signal. A successful error removal algorithm will enable the errors caused by movement of the sensor to be removed, thus, enabling the inclinometer to be used to measure the angle of tilt of a body under dynamic conditions. For example, the inclinometer can be placed in a vehicle and the gradient of the road can be logged whilst the car is travelling along.

A software tool development for pneumatic actuator system simulation and design

The ready availability of low cost microprocessors and mechantronic components allow industrial users to consider adopting servo-controlled pneumatic actuators with an acceptable cost. This leads to a demand for a software tool in pneumatic actuator system CAS/CAD. Therefore, the paper introduces a software tool developed by the research group in Liverpool for pneumatic actuator system computer aided simulation and design. Pneumatic system components are initially organised into five major classes. Those components are considered as subsystems to a complete pneumatic system and the mathematical models for the individual components are derived which can be combined in different ways to form a complete pneumatic system model. A library is built up to accommodate the five classes of components. Users can pick up different components from the library to formulate a complete pneumatic system based on the design requirements. The complete system dynamic behaviours can then be simulated in different operating modes. The graphic user interface (GUI) and animation techniques are adopted in software design to create a user-friendly environment. The software is still in its early stage and only used for research purpose but it has potential for further development.

Longitudinal road gradient estimation using vehicle CAN bus data

Knowledge of the longitudinal road gradient can be used by Advanced Cruise Control (ACC) and automatic transmission control systems to provide more accurate longitudinal velocity control. This paper presents a method of estimating the longitudinal road gradient just using the available vehicle CAN bus data. This method ensures that no extra sensors need to be added to the vehicle, and therefore there is no added cost to the vehicle. The gradient estimation algorithm is developed combining vehicle modelling techniques and parameter estimation methods. A simple longitudinal acceleration vehicle model is derived using standard vehicle model equations. The unknown longitudinal gradient parameter is then estimated using the data available on the CAN bus.

Energy efficiency analysis and optimal control of servo pneumatic cylinders

The paper presents a method for energy efficiency analysis of servo pneumatic actuator systems. Simulation study indicated that different quantities of compressed air were consumed for one cycle of piston movement when the same controller is adopted but with different profiles for servo pneumatic actuators. This motivated the authors to investigate the profile which leads the system to use the least amount of compressed air, that is, the most energy efficient profile. To avoid solving a set of complicated nonlinear differential equations, the nonlinear system is linearized through input/output state feedback and energy efficient optimal control theory is then applied to the linearized system. An optimal control strategy is developed with respect to the transformed states of the linear system model. The solution of the state trajectory results in an energy efficient profile. Through an inverse transformation, the system is converted back to the original states and control variables. The generalized controller has been proved to be a sub-optimal control with respect to the original nonlinear system model. Simulation study has conducted and the results obtained from linear and nonlinear system models are analysed and compared

Parameter identification for nonlinear pneumatic cylinder actuators

Pneumatic actuators exhibit highly nonlinear characteristics due to air compressibility, significant friction presence and the nonlinearities of control valves. The unknown nonlinear parameters can not be directly measured once the actuators have been manufactured and assembled, which causes a great difficulty in pneumatic system modeling and control. A learning algorithm has been developed in this paper to identify the unknown pneumatic system parameters. The algorithm is initially developed and tested using the data generated by simulations. Then the algorithm has been extended onto the parameter identification using the data obtained from the real system measurement. The results revealed the characteristics of uneven distribution of friction parameters which are position, velocity, moving direction dependent. The results obtained in the paper can provide the manufacturers with the observation to the characteristics inside pneumatic cylinders.

Power System Aggregate Load Area Modeling

This paper presents an aggregate load area model (ALAM) for modeling of an area load in a power system. The loads at different buses within conjunctional areas can be integrated and modeled using this method. The parameters of the ALAM are identified using a genetic algorithm (GA). A two-step identification scheme is employed to reduce the computation cost. The fictitious line impedance and susceptance of the aggregate load area are identified with a modified approach to ALAM. The simulation studies using an IEEE 14-bus and an IEEE 57-bus power system are carried out respectively. Verification results show that the ALAM can represent the area load accurately