Dynamic load fixture for application of torsion loads for rotary mechanical systems

Abstract

A dynamic load fixture (DLF) applies a torsion load to a unit under test (UUT) to achieve the demanding aerodynamic load exposures encountered by a control actuation system (CAS) in flight. Instead of fixing the end of the torsion bar, the DLF controls the application of torque to the torsion bar, hence the UUT via a DLF motor. The dynamic load can be independent of the angular rotation of the UUT, which allows the DLF to more effectively reproduce desired acceptance tests such as torque-at-rate and nonlinear loads. Furthermore, application of the loads through a torsion bar allows the system the compliance needed to generate precise loads while allowing for the flexibility of changing torsion bars to test a wide variety of UUT on one test platform. To achieve the demanding aerodynamic load exposures encountered by a CAS in flight, the controller must be able to respond both very fast and very precisely. Control is enhanced by the thorough characterization of the DLF and application of either 'classic' negative feedback control or 'modern' state-space control methods of linear observers and quadratic optimum control.