【正文】 s . The graduation design topic is the liquid level control system based on dde\matlab\simulink\force control, Among them was controlled object for tank level, Communication mode for DDE munications , Matlab is mainly used in the simulation test ,And force control software used for modeling, This system mainly through bination of hardware and software device to achieve precise control of liquid level , In modern industry level control of important ponent, it influence upon production not allow to ignore, in order to ensure safety in production and the product quality and quantity, the level and perform effective control is very necessary, The following is a description of all aspects： 一 PID controller A proportional–integral–derivative controller (PID controller) is a generic .control loop feedback mechanism widely used in industrial control systems. A PID controller attempts to correct the error between a measured process variable and a desired set point by calculating and then outputting a corrective action that can adjust the process accordingly. The PID controller calculation (algorithm) involves three separate parameters。 Industrial enterprises with water, if the drainage water drainage or controlled properly or not, in relation to the workshop of condition。外文翻譯 The liquid level control system based on dde\matlab\simulink Process control is an important application field of automatic technology, it is to point to the level, temperature, flow control process variables, such as in metallurgy, machinery, chemical, electric power, etc can be widely used. Especially liquid level control technology in real life, played an important role in production, for example, the water supply, civil water tower if low water levels, can affect people39。s lives in water。 Boiler drum, if the control level boiler is too low, can make level boiler overheating, possible accident。 the Proportional, the Integral and Derivative values. The Proportional value determines the reaction to the current error, the Integral determines the reaction based on the sum of recent errors and the Derivative determines the reaction to the rate at which the error has been changing. The weighted sum of these three actions is used to adjust the process via a control element such as the position of a control valve or the power supply of a heating element. By tuning the three constants in the PID controller algorithm the PID can provide control action designed for specific process requirements. The response of the controller can be described in terms of the responsiveness of the controller to an error, the degree to which the controller overshoots the set point and the degree of system oscillation. Note that the use of the PID algorithm for control does not guarantee optimal control of the system or system stability. Some applications may require using only one or two modes to provide the appropriate system control. This is achieved by setting the gain of undesired control outputs to zero. A PID controller will be called a PI, PD, P or I controller in the absence of the respective control actions. PI controllers are particularly mon, since derivative action is very sensitive to measurement noise, and the absence of an integral value may prevent the system from reaching its target value due to the control action. loop basics A familiar example of a control loop is the action taken to keep one39。 environment is well suited to rapid prototyping and application development. The interactive programming environment, builtin math functions, toolboxes, editing and debugging tools, and deployment options all contribute to reducing your overall development time. By using the builtin math functions and the many specialized functions contained within our toolboxes, MATLAB can significantly reduce the time it takes you to develop prototypes. In addition to integrated editi ng and debugging tools, MATLAB provides a performance profiler to help you further optimize your code when programming in MATLAB. Building applications around plex algorithms and graphics is easier than ever with the GUI builder, GUIDE. GUIDE was redesigned in MATLAB 6 to save you time. It offers all the drag and drop interface options you would expect, such as text boxes, radio buttons, check boxes, listboxes, sliders, popup menus, frames and more. When you39。 The server application response client applications of data or service request. Client/server applications is both client applications and server application request, it can be and can provide information. Monitor application for debugging purposes. DDE applications can have multiple burst conversation, a service applications can also have multiple client applications, a client applications can to multiple requests data service applications, and an application can also act as client applications and services applications, when don39。 Name in every conversation topics is one and to identify logical data connection string, is the total classification, data it defines a server application conversation theme content, the server application can support one or more theme name。 So, when to change or reconstruct a conversation, just changing the subject name or project name can. 四 force control Introduction Force control is Beijing SANWEI force control technology and soft control strategy software, realtime database and its management system, W