Vibration Reduction For Flexible Systems Using A Novel Command Smoothing Technique

For many types of mechanical systems, due to the structure and material of thecomponents, they will present flexible mechanical dynamics. It is a great challenge tothe control system if the mechanical components undergo deflection during the courseof operation. Furthermore, if residual vibration exists after the system reached aset-point, residual vibration will degrade the positioning accuracy and may cause adelay in task completion.This thesis presents a novel command smoothing scheme to suppress vibration toflexible systems. The original driving command is modified by command smoothingcontroller, then drive the system without inducing residual vibration. Robustness tosystem natural frequency analysis shows that controller provides a combination effectof low-past and multi-notch filter. Controller provides more insensitivity to modelingerrors at higher frequency. So it benefits vibration control to multi-mode systems.Additionally, command smoothed by the controller is a smooth profile command,which is easier for actuator to follow. What’s more, the smooth transitions betweenboundary condition help reduce transient vibration. Experiments on bridge cranevalidated the effectiveness and robustness of the controllers.This thesis studies the swing and twisting dynamics of distributed-mass payload,which have not been studied before. The equations of motion of bridge cranetransporting distributed-mass payload are derived. Physical explanation of twistingsuppression is given. A command smoothing scheme is used to suppress payloadswing and twisting. Simulations of a large range of motions and various systemparameters are used to analyze the dynamic behavior and the robustness of the controlscheme. Experimental results obtained from a bridge crane transportingdistributed-mass crate validate the simulated dynamic behavior and the effectivenessof the control scheme.