SUMMARY

Flexible systems vibrate or oscillate when moved. This behavior results in decreased performance in the form of inaccurate positioning, transient deflection, and residual vibration. In a backdrivable flexible system, coupling between flexible and rigid-body modes also leads to degraded performance of the rigid-body motion. For example, sway of a massive payload can backdrive the position of a crane trolley. Other examples of backdrivable flexible systems include helicopters carrying suspended loads and spacecraft with flexible appendages.

This research will investigate dynamic models that capture the fundamental behavior of a variety of backdrivable flexible systems. These models will be used to understand and illustrate the conditions under which a system can be classified as backdrivable. Then, the models will be studied to identify the range o system parameters that can lead to significant backdrivability and degraded performance.

The fundamental models will also be used to develop and analyze control methods that can mitigate or suppress the performance degradation seen in both the flexible mode(s) and the backdriven rigid-body mode(s). The proposed control methods will be illustrated using two motivating case studies: experiments and simulations of helicopters carrying suspended loads, and as part of an attitude control system for a spacecraft with flexible appendages driven by stepper motors.