Petersen, Ian R.Lanzon, Alexander2026-07-022026-07-021066-033XORCID:/0000-0003-4856-9450/work/219057277https://hdl.handle.net/1885/733812254This paper investigates the robustness of positive-position feedback control of flexible structures with colocated force actuators and position sensors. In particular, the theory of negative-imaginary systems is used to reveal the robustness properties of multi-input, multi-output (MIMO) positive-position feedback controllers and related types of controllers for flexible structures. The negative-imaginary property of linear systems can be extended to nonlinear systems through the notion of counterclockwise input-output dynamics.The authors wish to acknowledge many discussions on the topic of this article with Prof. Reza Moheimani, Dr. Junlin Xiong, Dr. Sourav Patra, and Zhuoyue Song. They also wish to acknowledge financial support from the Australian Research Council, the Engineering and Physical Sciences Research Council, and the Royal Society.19en201010.1109/MCS.2010.93767677956897427