Extended PKM Fixturing System for Micro-Positioning and Vibration Rejection in Machining Application

Area of Science:

• Mechatronics
• Robotics
• Precision Engineering

Background:

• Machining operations often suffer from disturbances affecting workpiece positioning accuracy.
• Existing fixturing platforms may exhibit undesirable coupling effects impacting performance.
• Piezo-actuated mechanisms offer high precision but require robust control strategies.

Purpose of the Study:

• To develop and validate a mechatronic device for precise micro-positioning and disturbance rejection in machining.
• To propose a decoupling method for a 3-Degrees-of-Freedom (DoF) flexure-based piezo-actuated parallel kinematic machine (PKM) fixturing platform.
• To enhance control strategies for improved set-point following and external disturbance containment.

Main Methods:

• Modeling and analysis of the 3-DoF PKM platform's kinematics and dynamics.
• Development of a bump-less switching controller and a fine-tuning procedure for parameter uncertainty estimation and disturbance rejection.
• Implementation of gain scheduling based on a standard ISA form for piezo-actuator controllers to ensure stability.
• Conducting simulations and experimental comparisons, including sensitivity analysis.

Main Results:

• The developed architecture achieves a steady-state error below 1.2 µm.
• Demonstrated vibration reduction of 96% at 1130 Hz.
• Maximum resolving time of 6.60 ms achieved.
• Effective disturbance rejection across an extended broadband frequency range.

Conclusions:

• The proposed mechatronic device and control strategy significantly improve workpiece micro-positioning accuracy.
• The decoupling method effectively mitigates coupling effects in the PKM fixturing platform.
• The system offers robust performance in terms of tracking, disturbance rejection, and stability for precision machining applications.