Improving Force Control Bandwidth of Flexible-Link Arms Through Output Redefinition

For a constrained flexible beam actuated at one end, we introduce three outputs to achieve fast regulation of the nonminimum phase endpoint force. To this end, three auxiliary signals, i.e., angular displacement, moment, and shear force at the hub are utilized to define new outputs, which are referred to as redefined outputs. Each redefined output is composed of the endpoint force augmented by the time derivative of an auxiliary signal measured at the hub. It is shown that using the redefined outputs along with proper controllers can significantly improve control performance, such as bandwidth, robustness, and error performance. Analytical results are presented that illustrate how bandwidth improvements in a force control loop can be achieved. The results are further verified through simulations and experimental studies.