Applying coordinate transformations to multi-DOF shaker control

The dynamic characteristics of test fixtures, test articles and multiple shakers or actuators for multi-degree-of-freedom (MDOF) dynamic testing may cause the number of desired degrees of freedom for MDOF operations to not match the number of exciters or control transducers being used. Thus, it is often necessary to transform the response from multiple control transducers and the capability of multiple exciters that are being used from actuator space to MDOF space and vice-versa to effectively perform such tests. These operations are now capable of being directly performed within the software used for MDOF control to increase test flexibility and greatly reduce test setup time. This article describes current applications of these techniques with multiple shakers and examines the control of torsional motion in large plates as a by-product of coordinate transformation.