伺服机构的低速爬行

The Jerking Motion of Servomechanism in Low Speed Range

本文讨论具有干摩擦的典型三阶伺服机构的低速爬行问题,给出恒速驱动时的解析解,并由此得到开始滑动的必要条件以及产生爬行的临界条件曲线。最后通过计算实例,阐明了设计这类伺服机构时参数的选择方法。

Some servomechanisms, such as rotating stages, recording instruments, etc. with a low velocity input often show a jerky output response in sliding surfaces of moving part. This phenomenon, usually called a 'Jerking Motion' or a 'Stick-Slip motion', influences the system dynamic qualities greatly. Many authors have investigated it in theoretical analysises and experiments. This paper deals with theoretical analysis of critical conditions of Jerking Motion in a typical thirdorder servomechanism with dry sliding. With the exercise of dimensionless method,thirteen system parameters are combined into four comprehensive dimensionless parameters, which have not only clear sense of physics but also more general representation. To simplify the analysis in calculation, besides, that treatment is of great importance tc choosing parameters conveniently when design of the system. The state equations are solved to employ linear theory to certain time periods, and both a necessary condition for jerking are given. By the aid of computer, critical velocity curves of Jerking Motion are found in digital analysis, and the range of Jerking Motion occurrence is represented graphically in a non-dimensional form. With these curves, it is clear that the Jerking Motion can be prevented by choosing dimensicnless parameters appropriately in given velocity range. Finally, an example is calculated to explain the method of parameters chosen. As a result, smooth motion of the servomechanism in example can remain from stage velocity 0.1 mm/sec to 10 mm/sec.