The Design Of MIS Real-Time Control System

The application of minimally invasive surgical robotic technology in the field of medicalsurgery has become an increasing concern. On the one hand, the minimally invasive surgicalrobotic technology has huge potential and broad space for development. Especially to therobotic control system technology which is as an important part of the surgical robot, evenmore people pay attention. Since minimally invasive surgical robot is operating directlyagainst the body, the performance of the surgical robotic system security, stability andaccuracy is particularly important. In the surgery system, each task is mainly in apriority-based scheduling style, however there are still some parallel tasks needing to base ontime-slice schedule, such as tasks needing to be synchronized to perform in the system. Thusrequires a mixture embedded operating system which supports priority-based schedule andtime-slice-based schedule. With the embedded real-time operating system μC/OS-Ⅱ as theobject of study, and modify the surgical robotic system according to its characteristics, thepaper is aimed to develop minimally invasive surgical robotic real-time control system whichhas excellent performance.The study starts by introducing current mainstream RTOS, such as VxWorks,μC/Linux, QNX, μC/OS-Ⅱ etc, and discusses the advantages and disadvantages in detailrespectively. Finally chooseμC/OS-Ⅱ. μC/OS-Ⅱ has the characteristics of open source,preemptive real-time kernel, multi-system services, high stability and high reliability. Choosethe system as the model of the surgical robotic real-time control system to modify. And addtime-slice scheduling mechanism to it without changing its real-time characteristics, alsoextend the number of the tasks that can be scheduled by the original kernel. Divide systemtasks into three task zones, i.e., preemptive scheduling task, time slice scheduling task andsystem task, to be used for tasks with different scheduling demands. Improved kernel is morein line with the requirements of real-time control system of minimally invasive surgical robot.It also provides convenience for function expansion of the system afterward. The hardwareplatform of the system selects a Freescale16-bit dual-core MCU with co-processor. Refer theclock beat function to co-processor dedicatedly to handle. By the advantage that theco-processor is at twice the speed of the main CPU and is parallel performing with the mainCPU, resolve the real-time problem of the system due to a number of tasks, increase the workfrequency of the system, and reduce the CPU load effectively. Also enhance the system’s real-time and timing accuracy to a certain extent. By improving the kernel schedulingmechanism of the system and increasing the number of the tasks that can be scheduled andchanging the manner which the system uses to handle the clock interrupt event, furtherimprove the overall performance of the surgical robot system.Verified by experiment, thedesired design objectives and requirements is achieved.