软数控实时任务的时间特性对加工精度的影响

为分析软数控实时任务的不确定性与加工精度的关系，提出一种基于模型的加工误差分析方法。首先研究采样抖动，输入-输出抖动，数控任务可调度性及加工误差评估等相关理论；然后建立二轴数控系统加工误差分析仿真模型；最后对任务抖动、任务不可调度及实时突发任务等与加工误差的相关性进行仿真。结果表明:采样抖动为任务周期的80%，误差达4.7%；输入-输出抖动为任务周期的80%，误差达1.2%；40%的事务不能在时间限内完成，误差达13.4%。该结果体现实时任务的时间特性与加工误差的相关程度，不可调度事务引起较大加工误差。

Effect of time characteristic of soft NC real-time tasks on manufacturing accuracy

For analyzing the relation between uncertainty of soft numerical control(NC) real-time tasks and manufacturing accuracy, a mismachining tolerance analysis method based on model is presented. Firstly, the related theories such as sampling jitter, input-output jitter, NC task schedulability, mismachining tolerance evaluation, etc are deeply researched. Then, a two-axis NC simulation model is established. Finally, the simulation is carried out for the relativity of mismachining tolerance and other factors such as task jitter, task non-schedulability and aperiodic real-time tasks respectively. The results demonstrate that sampling jitter time and input-output jitter time is 80% of task period, error is up to 4.7% and 1.2% respectively, and 40% of jobs are not met the deadline, error is up to 13.4%. So the relativity of time characteristic of real-time tasks and mismachining tolerance is indicated, and the noticeable mismachining tolerance is caused by non-schedulable jobs.