Motion Characteristics of the VIRTTEX Motion System

The motion characteristics of the VIRTTEX motion system were measured using a set of tests similar to those suggested in AGARD Report AR-144. The measurements were devised to measure the performance of existing motion systems, aid in the procurement of new motion systems, and help identify root causes of poor performance. Transfer functions (both within degree-of-freedom and between degree-of-freedom), 1⁄2 Hz noise levels, signal to noise contours, dynamic threshold measurements and hystersis measurements were all conducted. Before these tests, the VIRTTEX motion system was tuned with an emphasis on high bandwidth. The motion system as tuned, has a bandwidth greater than 13Hz on all degrees-of-freedom. The dynamics threshold is 15ms and the motion system has no significant hystersis. The transfer function measurements revealed larger than expected levels of cross talk between degrees-of-freedom. The motion system also exhibits turn-around bump and non-linearity at large velocities and accelerations. Further experience with the complex MTS controller is expected to lead to improvements in both cross talk and non-linearity. This measurement process will be repeated once planned improvements to the system are complete.