UBC Theses and Dissertations
Vibration avoidance and contour error compensation in high speed five-axis machine tools using command shaping techniques Rezayi Khoshdarregi, Mohammad
The present machine tools travel at high velocities with large acceleration and jerk, which creates large inertial loads with wide frequency content, resulting in excitation of the natural frequencies of the machine. This thesis presents a command shaping module which avoids structural vibrations and improves contouring accuracy in five-axis machine tools. Inertial-induced vibrations of feed drives are avoided by applying a sequence of input shaping impulses on the axis position commands as a function of natural frequencies of the machine. Input shapers block those harmonics of the command which can excite the modes of the machine. While command shaping avoids the excitation of transient vibrations caused by inertial loads, it introduces a time delay which increases the contouring errors in multi-axis motion control systems. Although input shaping can effectively avoid vibrations, it distorts the toolpath in multi-axis contouring due to added time delays. The distortion increases the contour errors caused by the limited bandwidth of axis servo drives, resulting in relatively large geometric errors and violation of the required tolerance. The transfer function of the axis drives and kinematic configuration of the machine tool are used to estimate the contouring error, which is decoupled into axis components, and compensated prior to sending the position commands to each drive. The proposed integrated input shaping and contour error compensation module can be applied on any arbitrary trajectory, and the shaped-compensated command results in vibration-free and accurate contouring of the desired path. The input shaping and contouring error compensation techniques introduced in the thesis have been experimentally validated in single, two and five axis machine tools.
Item Citations and Data
Attribution-NonCommercial-NoDerivatives 4.0 International