Design And Implementation Of Virtual Instrument Of Digital PID Emendation For Second-Order Control System

Modern computer technology and information technology are developing rapidly, which impacted the national economy in various fields and also caused the revolution on measuring apparatus and testing. After the concept of VI (Virtual Instrument) was raised, the VI rapidly occupied the market because of its cost-effective and openness.In the domain of engineering control, the PID is the most widespread control method in the current engineering application because the PID control has flexible structure and is easy for parameter tuning. The PID control is applied particularly to those control objects that have no accurate mathematical model or have big parameter variation. With the development of computer technology, computer system was introduced to perform the PID control. Because of the flexibility of software system, the digital PID control received more and more widespread application.Most of the practical control systems are based on second-order system. Therefore, the article integrates the concept of virtual instrument and digital PID control, a virtual instrument of digital PID emendation was designed and developed based on second-order system. During the development process of the virtual instrument, VB was used to develop the oscillograph module and PID control module. The IO functions that provided by VC were used to establish the DLL of AD/DA, and then VB was used to assembled the DLL into AD/DA module. The virtual instrument of digital PID emendation was constructed with those modules. In order to simplify the further programming, all modules were designed as ActiveX controls, which is easy for the assembly afterwards. In the end, actual application was implemented with the virtual instrument, which achieved the digital PID emendation to a second-order system.The usability and accuracy of the digital PID emendation VI were validated through the actual control of a second-order system. It was also confirmed that the VI of digital PID emendation fully met the design and actual production requirements.