Research On Optimization Of DDS Data Transmission Based On DPDK

In the era of Industry 4.0,intelligent manufacturing,the core of which is digitization,networking and intelligence,undertakes the heavy responsibility of leading the country’s industrial technological transformation.The communication system composed of distributed heterogeneous devices in intelligent factories has the characteristics of large-scale,dynamic change and time-sensitive.Data Distribution Service(DDS)communication middleware based on publish-subscribe architecture can provide a loosely coupled and flexible data interaction mechanism,which solves the problems of data transmission between distributed nodes.However,the introduction of the middle layer inevitably increases the transmission delay.And as the number of production line equipment increases,a large number of network data packets will bring serious performance bottlenecks to the DDS transmission system.This paper studies the DDS data transmission processing flow and analyzes the main reasons for their performance bottlenecks,including frequent hardware interrupting,thread scheduling and data copying from kernel mode to user mode,which bring a lot of system cost in kernel packet processing.In response to the above problems,this paper combines Data Plane Development Kit(DPDK)technology with DDS communication middleware.This paper uses the user mode driver,polling and thread binding CPU core technologies of DPDK to reduce DDS data transmission delay.The main research works are as follows.Firstly,aiming at the original DDS transmission delay,this paper researches and designs the DDS transport layer based on DPDK to optimize.On the one hand,DPDK user mode protocol stack is used to realize the DDS communication mechanism,which is compatible with the original DDS system.On the other hand,the kernel transmission or DPDK transmission is selected by setting the QoS transmission strategy.Through the experimental tests to transmit 1KB data samples,the results show that the DDS transmission based on DPDK can communicate with the original DDS and the transmission delay is reduced by about 30%,which significantly improves the DDS data processing efficiency.Secondly,in order to take advantage of the highly configurable QoS mechanism and multiple transmission methods,this paper designs a set of multi-protocol stack DDS configuration tool software.The interface provides functions for configurating QoS policy attributes and transmission methods.Experimental results show that the tool can configure QoS attributes and DDS transmission methods according to user input,which simplifies configuration operations.Finally,aiming at the problem of some memory waste in DPDK,this paper researches in the field of industrial equipment status monitoring and formulates six types of robot equipment status metadata.It can standardize the data format which assists configuration to the DPDK network frame length to reduce memory waste.This paper uses the above methods to build a set of industrial equipment status information monitoring system based on RDCS middleware.This paper applies it to the actual robot collaborative welding scene to monitor the real-time status information of two six-axis robots and calculates the transmission delay using the two methods including kernel transmission and DPDK transmission.The results further verifies that DPDK can reduce the transmission delay of the DDS system.