Dynamic characteristics of electronic expansion valve principle

Aiming at the model of the relation between the degree of superheat of the evaporator of the refrigeration system and the opening degree of the EDM electronic expansion valve, the electric expansion of the electronic expansion valve is driven by the electric pulse to obtain the superheat degree of the evaporator as a dynamic response. System identification method to identify the refrigeration system.After comparing the identification results of various identification methods, the identification accuracy of various identification methods in dealing with this kind of problems is given, as well as the characteristics in the specific process, given Which is suitable for the identification of this kind of model.At the same time, it also shows that the link described by a third-order link is closer to the actual situation, which lays a good foundation for the simulation and simulation of the refrigeration system in the future. At present, due to the complexity and strong coupling of internal systems, it is difficult to establish accurate system models by the usual mechanistic methods. It is difficult to achieve good control performance by using conventional proportional integral derivative (PID) regulators , Such as the initial operation and changes in conditions, the need to readjust the PID parameters, and sometimes can not even meet the basic requirements.Real analysis and application experience shows that the structure of refrigeration systems such as the known part of the unknown parameters but changes slowly Control object, especially suitable for adaptive control. Process control is the primary problem facing the process of modeling, modeling methods are usually organic methods and system identification methods. System identification method is through the input and output data to create a mathematical model, which is the basis of self-tuning control system. There are many systematic identification methods , The most commonly used method is the least squares method, in addition to the auxiliary variable method, gradient correction method and maximum likelihood method, etc. But not every identification method for all problems are applicable.Then give a random search The method and practice show that this method is very suitable for the identification of refrigeration system. Using several of the identification methods to identify the test data and comparing the results with the online real-time requirements of these methods in order to obtain a suitable identification method for this type of model. Many of these methods give a more detailed derivation There are some explanations for the selection of certain parameters in the identification method. However, according to the parameters in the literature, the identification results of this paper are often biased estimates. Therefore, in the specific model, the setting of these parameters is given in this paper.

5 Axis Cnc Router Machine

In the simplest terms, 5-axis machining involves using a CNC to move a part or cutting tool along five different axes simultaneously. This enables the machining of very complex parts, which is why 5-axis is especially popular for aerospace applications. However, several factors have contributed to the wider adoption of 5-axis machining. These include: A push toward single-setup machining (sometimes referred to as [Done-in-One") to reduce lead time and increase efficiency

The ability to avoid collision with the tool holder by tilting the cutting tool or the table, which also allows better access to part geometry
Improved tool life and cycle time as a result of tilting the tool/table to maintain optimum cutting position and constant chip load

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