Design And Application Research Of Network Latency Device Based On Nios â…¡ Soft Core

Along with the continuously progress of the networked control system theory and application research, the influences of network delay are also becoming more seriously. It may deteriorate the system performance and cause the information latency, and even cause system instability. But at this stage of the research mainly focus on the theoretical simulation, lack of specific equipment to verify actual effect of control algorithm. This network latency device is a good way to solve this problem.The whole system consists of a computer, a network latency device, and a controlled object. Computer acts as the master controller, to achieve human-computer interaction through Visual Basic and validates control algorithm by calling MATLAB. The network latency device is constructed by implanting the Nios â…¡ soft core to the FPGA via SOPC technology. The software program is base on MicroC/OS â…¡ real-time operating system, and the network protocol is realized through the NicheStack TCP/IP protocol stack, and we choose DM9000A as the network interface card. There are three work modes of network latency device:fixed delay time mode, stochastic time delay mode and random packet loss mode. By setting a receiver FIFO to receive the sensor signal, when working at the time delay work mode, the signal after the given delay will be sent to the computer; When work at random packet loss mode, signals will be sent or not depend on the set of packet loss probability. A similar send FIFO is also set up to control the signal output in control signal output terminal.The main work of this paper are as follows:firstly, we briefly introduce the existing situation of networked control systems at home and abroad; secondly, the designing scheme and technical background of network delay is introduced in detail; thirdly, the development procedure of network latency machine is presented in detail, including the design of the hardware and software; finally, in view of the networked control systems with random time delay, dc motor is chosen as the controlled object, and we compare the ordinary PID and fuzzy PID control effect, and then research the different effect to the performance of the system caused by different random time delay.