SEDL / STP / STP1303-EB / STP11547S

Control of a Biaxial Test Using Calculated Input Signals and Cascade Control

Albright, FJ
Senior staff scientist and senior project manager, MTS Systems Corp., Eden Prairie, MN

Johnson, LE
Senior staff scientist and senior project manager, MTS Systems Corp., Eden Prairie, MN

Pages: 11    Published: Jan 1997

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Abstract

Control of a single-channel material test is relatively straightforward with modern servocontrollers. During this type of test, the center of the specimen moves as the specimen length changes. Although normally not a problem, this motion is not acceptable for some tests, such as planar biaxial tests. Relative motion of the specimen center will introduce unwanted stresses in the test piece and make visual monitoring of the specimen difficult.

This paper describes a control technique to minimize specimen motion in the planar biaxial test application. It utilizes calculated input signals for the feedback. The control architecture is a cascade control loop. Description of the basic control method is provided and actual test results showing specimen motion with and without the control are presented.