Hongen Wu

Fuzzy Logic Thermal Error Compensation for Computer Numerical Control Noncircular Turnning System

With the new emerging technologies of high performance machining and the increasing demand for improved machining accuracy in recent years, the problem of thermal deformation of machine tool structures is becoming more critical than ever. The computer numerical control (CNC) turning system for noncircular section pistons is designed with giant magnetostrictive actuator (GMA) as the turning module. When the temperature of the cooler system of the GMA varies for about 6degC, the dimension error of the surface contour varies for about 20 micron, and cannot meet the precision requirement of the pistons contour dimension. In this paper, a method using fuzzy logic control for the compensation of the thermally induced error is developed. The fuzzy rule is used to compensate directly for the nonlinearity and uncertainty of the cooler system. The rule development strategy for the compensation system is to change the feed quantity of GMA to control the tool the pistons dimension. The fuzzy logic control developed here is a two-input single-output controller. The two inputs are the temperature deviation from setpoint error, and error rate. The output is the compensated value of the feed system. The triangular membership functions are used to define the input linguistic variables and the output linguistic variables. The fuzzy logic approach incorporates many advantages of using fuzzy logic such as the incorporation of heuristic knowledge, ease of implementation and the lack of a need for an accurate mathematical model. The experimental results are presented and the effectiveness of the fuzzy thermal error compensation control technique is discussed. Accuracy is greatly improved using the developed error compensation system

Realization of CNC System on Middle-Convex and Varying Oval Piston Machining

To machine non-circular middle-convex and varying oval (NMVO) pistons with computer numerical control (CNC) turning system, the cutter must reciprocate in X-axis with high-speed and high-precision to tracking the rotating of spindle. A CNC turning system for NMVO piston machining is designed. The CNC system consisted of a normal turning system and an ellipse section turning module. The turning system is Simense 802C which controls X, Z axes and spindle just as general CNC system. A U-axis (ellipse section turning module) is attached to X-axis of the CNC system to implement the function of spindle tracking. The U-axis is made up of a giant magnetostrictive actuator (GMA), a PC and software for piston design and control. By adopting modulization idea, with the method of object oriented analysis, piston design and control software for NMVO piston turning was developed on Windows XP platform. A DSP controller is designed as the core processor of the ellipse turning module to meet the real-time requirement of the control system.

A Novel Design of Distributed Servo System Based on Rearranging Functions between Host Controller and Servo Driver

Distributed control system (DCS) and field-bus control system (FCS) become the mainstream in manufacture and processing control applications nowadays. This paper provides a novel DCS scheme for multi-axis motion control with synchronization ability, which is just needed for motion control with interpolation. To make use of DCS advantage and optimize the cost and performance, the scheme adopted a very different structure to arrange function modules of servo system between the host and the distributed driver. Considering that the baud rates of serial bus is high enough with todays technology and that host computer is of powerful data processing ability, the velocity-loop is migrated up to the host. An experiment was carried out to check the feasibility of the design.

Digital platform design for Magnetically suspended Bearings equipped for wind turbine based on DSP28335+FPGA

In order to use the wind energy more efficiently in wind turbine system, Active Magnetically suspended Bearings (AMBs) are equipped to eliminate the friction of the mechanical bearings. In the traditional analogue PID controller of AMBs control system, it has the shortcomings of inconvenient in parameters adjustment, low control resolution, difficulty to change hardware structure and realize advanced control algorithms. This digital platform is to enable the implementation of new and more complex control algorithms for Active Magnetically suspended Bearings (AMBs) equipped for wind turbine generator. This paper presents the design, implementation of a novel real-time controller for AMBs equipped for wind turbine based on a floating-point Digital Signal Processor (DSP) and on a Field-Programmable Gate Array (FPGA), by operating in a cooperative way. The platform combines the flexibility and processing power from both devices and this digital controller solution will result in an improvement in the control performance and a remarkable reduction in software development time.

A Novel Speed Control Algorithm with Programmable Timer for Embedded Motion Control System

The goal of this work is to present a useful speed control algorithm applied for embedded motion control system. A programmable timer is employed to generate pulses for controlling a stepping motor or a servo motor with pulse interface driver. The pulse frequency, which determines the motor speed, is adjusted by modifying the setting value of timers period register with the proposed algorithm in the paper. And by adopting a hardware timer, the method can achieve a fine performance but a very little cost in computing. A simulation on the method was carried out with Matlab, and the results show that the speed-time plot is very smooth during acceleration and deceleration stages, thus the dynamic shock in working mechanism excitated by speed turning points can be eliminated a lot. Furthermore, based on the algorithm, a prototype controller with DSP TMS320LF2407A was implemented, and the experiment results on the prototype controller are identical with the simulation analysis. Therefore, the algorithm provides a practical speed control solution for embedded servo system with low cost and high performance.

Adaptive Fuzzy Control for Adjusting of Plumb Attitude of Upper Air Manipulator Frame Suspended by Steel Ropes

This paper discussed the attitude control problem of a manipulator frame which is suspended by 2 ropes hitched on its both sides. The dynamic disturbance, which induced by manipulator changing its arm status or by the arms load varying, will results in the frame swing. To adjust the attitude of the frame and keep it in plumb, a dynamic adjusting mechanism is introduced, and the control model of the mechanism, which employ the adaptive FLC (fuzzy logic control), is discussed. The FLC algorithm is concise and robust, and can avoid the difficulties caused by uncertain parameters and the nonlinear characteristic of the adjusting mechanism. The simulation results of the control model show that the adaptive FLC is feasible and satisfied for this objects attitude control.