A velocity command stepper motor for CSI application

Original publisher: Hampton, Va. : NASA Langley Research Center, [1991] OCLC Number: (OCoLC)63049746 Excerpt: ... The second test article used was the NASA Mini-Mast, which is a 20 meter vertically cantilevered near-flight quality truss beam. For these tests two linear motors were used to provide two axis control. Tile linear motors were mounted on the tip plate to provide control forces along the Mini-Mast global X and Y bending axis ( see next chart ). The first five modes of the Mini-Mast are as follows: 1st X & Y bending ( 0.85 Hz ), ist Torsion ( 4.2 Hz ), and 2nd X & Y bending ( 6.2 Hz ). A interesting comparison between the two types of actuators shown ( reaction wheel vs. reaction mass ) can be made. Given the 50 ft-lbf torque output of the reaction wheels and the 0.7 ibf force output of the linear step motor, the torque available for application to the structure is equivalent, but the weight of the reaction wheels is 13 times that of the reaction mass actuator. MIN !-MASTTIP PLATE 13 G_-" F'C_C > RQti.tt_l.IT7