The high performance demands on commercial computer numerical control (CNC) machine tools have led to the widespread adoption of direct-drive servo axes. In industrial machines, where the workpiece is manipulated by the axis, the plant dynamics seen by the control system may vary widely between different workpieces. These changing plant dynamics have been observed to lead to limit-cycle behavior for a given controller. In such a situation, conventional modeling approximations used by practitioners may fail to predict the onset of instability for these axes. This work demonstrates the failure of conventional modeling approximations to predict the observed instability in an industrial CNC servo axis and investigates the model fidelity required to replicate the observations. This represents an important consideration when designing model-based controllers for direct-drive axes in CNC machines.

References

References
1.
del Re
,
L.
,
Kaiser
,
O.
, and
Pfiffner
,
R.
, 1996, “
Black Box Identification and Predictive Control of High Speed Machine Tools
,”
Proceedings of the IEEE International Conference on Control Applications
, pp.
480
485
.
2.
Erkorkmaz
,
K.
, and
Altintas
,
Y.
, 2001, “
High Speed CNC System Design. Part II: Modeling and Identification of Feed Drives
,”
Int. J. Mach. Tools Manuf.
,
41
(
10
), pp.
1487
1509
.
3.
Zheng
,
J.
,
Zhang
,
M.
, and
Meng
,
Q.
, 2006, “
Modeling and Design of Servo System of CNC Machine Tools
,”
Proceedings of the IEEE International Conference on Mechatronics and Automation
, pp.
1964
1969
.
4.
Younkin
,
G. W.
,
McGlasson
,
W. D.
, and
Lorenz
,
R. D.
, 1991, “
Considerations for Low-Inertia AC Drives in Machine Tool Axis Servo Applications
,”
IEEE Trans. Ind. Appl.
,
27
(
2
), pp.
262
267
.
5.
Poignet
,
P.
,
Gautier
,
M.
, and
Khalil
,
W.
, 1999, “
Modeling, Control and Simulation of High Speed Machine Tool Axes
,”
Proceedings of the IEEE/ASME International Conference on Advanced Intelligent Mechatronics
, pp.
617
622
.
6.
Moscrop
,
J.
,
Cook
,
C.
, and
Moll
,
P.
, 2001, “
Control of Servo Systems in the Presence of Motor-Load Inertia Mismatch
,”
Proceedings of the IEEE Industrial Electronics Society Conference
, Vol.
1
, pp.
351
356
.
7.
Gannel
,
L.
, and
Welch
,
R. H.
, Jr
., 2003, “
Improving the Dynamic Motion Behavior of a Servo System With Low Mechanical Stiffness
,”
Proceedings of the IEEE Industry Applications Society Annual Meeting
, Vol.
1
, pp.
40
44
.
8.
Ellis
,
G.
, and
Lorenz
,
R. D.
, 2000, “
Resonant Load Control Methods for Industrial Servo Drives
,”
Proceedings of the IEEE Industry Applications Society Annual Meeting
, Vol.
3
, pp.
1438
1445
.
9.
Armstrong-Hélouvry
,
B.
,
Dupont
,
P.
, and
de Wit
,
C. C.
, 1994, “
A Survey of Models, Analysis Tools and Compensation Methods for the Control of Machines With Friction
,”
Automatica
,
30
(
7
), pp.
1083
1138
.
10.
Kelly
,
M. J.
, and
Toncich
,
D. J.
, 2000, “
Overcoming Encoder Quantisation Noise in an Adaptive Position Controller
,”
Int. J. Mach. Tools Manuf.
,
40
(
14
), pp.
2031
2046
.
11.
Krishnan
,
R.
, 2001,
Electric Motor Drives: Modeling, Analysis, and Control
,
Prentice-Hall
,
Upper Saddle River, NJ
.
12.
Ebrahimi
,
M.
, and
Whalley
,
R.
, 2000, “
Analysis, Modeling and Simulation of Stiffness in Machine Tool Drives
,”
Comput. Ind. Eng.
,
38
(
1
), pp.
93
105
.
13.
Ljung
,
L.
, 1999,
System Identification: Theory for the User
,
2nd ed.
,
Prentice-Hall
,
Upper Saddle River, NJ
.
14.
Berg
,
M. C.
,
Amit
,
N.
, and
Powell
,
J. D.
, 1988, “
Multirate Digital Control System Design
,”
IEEE Trans. Autom. Control
,
33
(
12
), pp.
1139
1150
.
15.
Tomizuka
,
M.
, 2004, “
Multi-Rate Control for Motion Control Applications
,”
Proceedings of the IEEE International Workshop on Advanced Motion Control
, pp.
21
29
.
16.
Stephens
,
M. A.
,
Manzie
,
C.
, and
Good
,
M. C.
, 2010, “
On the Stability Analysis and Modelling of a Multirate Control Direct-Drive Machine Tool Axis Subject to Large Changes in Load Dynamics
,”
Proceedings of the American Control Conference
, pp.
1550
1555
.
17.
Thomson
,
W. T.
, and
Dahleh
,
M. D.
, 1998,
Theory of Vibration With Applications
,
5th ed.
,
Prentice-Hall
,
Upper Saddle River, NJ
.
You do not currently have access to this content.