高性能連續(xù)軌跡控制系統(tǒng)研究.pdf

1、Contouring control system is one of the fundamental motion control systems inmodern manufacturing industries. This research is motivated by demands of high performancemotion control in contour-following applications. Sin

2、ce there are many factorsthat will influence the performance of the contouring control system, this dissertationstarts from the aspect of control.In the contouring control system, the contour error, which is the shortest

3、 distancefrom the current actual position to the reference contour, gives a better assessment of thecontouring performance than the tracking error, which is is the distance from the currentactual position to the current

4、reference position. As a result, reducing the contour error isof importance in the task of contour following and control law aims to reduce the contourerror directly is desirable.Once the contour error is treated as the

5、control objective, information of the realtimecontour error has to be obtained before performing the control. A typical way isto approximate the reference contour by its tangent line locally and estimate the contourerror

6、 by the distance from the actual position to the tangent line at the referenceposition. However, this approach suffers from a significant error due to line approximation,especially when the curvature of the reference con

7、tour is nonzero. Based on thegeometric interpretation of the contour error and the reference contour, the approach ofapproximating by the osculating circle at the current reference position is proposed. Inthis approach,

8、the estimated contour error can be calculated by the difference betweenthe radius of curvature at the current reference position and the current radius. Furthermore,when an artificial coordinate frame, which is obtained

9、by the transformation ofthe contour-dependent frame at the reference position, is established, the real-time estimatedcontour error becomes the coordinate of the actual position with respect to suchan artificial frame.Af

10、ter the real-time contour error is estimated, it is incorporated in a position loopbasedcross-coupled control (PLCCC) strategy. The PLCCC system ejects the cross compensatedcontrol effort into the position inputs, instea

11、d of the velocity inputs which isadopted in the typical CCC system. In terms of the symmetric structure of the PLCCCsystem, the cross-coupling gains are then determined by the entries of the transformationmatrix which is

12、 employed in contour error estimation and coupled control effort distribution.An equivalent robust control system, established from the contour error transferfunction (CETF), is developed to analyze the stability of the

13、closed-loop PLCCC system.Moreover, a contour error switching control scheme is proposed to improve the contouringaccuracy when the tangent-line approximation is adopted in the PLCCC system.With the fact that the contouri

14、ng performance can be improved by only modifyingthe reference position inputs from the PLCCC system, a direct contour error compensationscheme, with respect to the global fixed coordinate frame, is developed. Interms of

15、a projection map, generated from the unit normal vector of a new coordinateframe, the real-time contour error can then be estimated from the decomposition of thetracking error in the global fixed coordinate frame. As the

16、 consequence, compensationof the contour error is performed directly to the position inputs of the individual axialloops. Moreover, condition for the stability of the closed-loop compensation system isdiscussed. Experime

17、nts performed on a biaxial motion stage show that the accuracy of contourerrors estimation from circular approximation are improved at least 75％, relative to thatestimated from the tangent-line approach. Estimation accur

18、acy of the direct tracking errordecomposition is as precise as the circular approach. In the contour-following experiments,contouring performance is improved more than 50% when the PLCCC strategywith circular approximati

19、on is adopted, relative to the case without any cross-coupledcontrol. Improvements from the contour error switching scheme are still evident. Whenthe direct contour error compensation scheme is applied, contouring accura