Design And Implementation Of Embedded Real-time Robot Communication System Compatible With ROS

With the tremendous development of robot industry,the long development cycle of robot product becomes the contradiction between supply and demand.ROS(Robot Operating System)takes advantage of modularity of code and shorten the development cycle of robot products,so it occupies an important position in robot industry.However,ROS is based on Linux kernel,so it has a high hardware requirement.Because of that,low-end and low-cost hardware platform can hardly be a part of ROS distributed communication system.Starting with that,this paper design and implement a low-cost and low-power embedded real-time robot communication system compatible with ROS based on STM32.This system is compatible with the publish/subcribe mode of ROS and can be integrated in ROS distributed communication system seamlessly.And it provides ROS application developers with APIs similar to that of ROS in order to be friendly to the developers.To be compatible with ROS,this paper design and implement the system from the bottom up based on the full analysis on the work mechanism and implementation details.Low-cost and low-power STM32 is selected to be the hardware platform of the system.And one of the most popular embedded real-time operating system Free RTOS is selected to be the operating of this system,because it is suitable for the hardware and can guarantee the real-time of the system.LWIP is selected to be the TCP/IP stack for the system,considering the function and requirements of it.After the porting of Free RTOS and LWIP this paper design and implement a message middleware compatible with ROS.Considering the efficiency and stability of the middleware,this paper implement the decoupling with the Free RTOS message queue.And this system has the feature of asynchronization.Considering the ability to handle messages and resource utilization of the system,the message middeware is designed as a multitask model so that this system is concurrent.Because this system is drived by messages completely,callback mechanism is selected to handle messages.The detail of the message middleware is encapsulated as APIs similar to ROS for developers.Based on those APIs,two demos are implemented for testing and verifying the system.In the functional test,two demos achieve ROS publishing and subscribing and communicate with ROS on the host computer.In the non-functional test,Free RTOS debugging interfaces and embedded system debugging tool Tracealyzer are used to test the stack usage and task s cheduling in detail.The test result shows the system runs steadily.The timestamp provided by Tracealyzer is used to test the real-time of the system.The time cost in the process of handling ROS messages is about several dozens of microseconds.The real-time of this system is enough for most of applications.In summary,this system provides a solution to integrate low-end and low-cost hardware platform in ROS distributed communication system seamlessly.In the situation of low-cost and low-power requirement,this system has highly pratical value.