Dynamic Notch Filtering for Multi-Axis Oscillation Control
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Solution Overview
Problem
Mechanical oscillations in multi-axis control systems, such as robots, due to backlash, compliant couplings, and flexing of mechanical linkages, lead to increased settling time and reduced throughput.
Innovation Solution
Implement a dynamic notch filter in each motor drive of the multi-axis control system, updating its operation based on position and loading, with faster update rates for generating output voltage to reduce oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional control methods are used without dynamic notch filter, then system simplicity is maintained, but mechanical oscillations increase leading to longer settling time
Solution Approach 1:
A dynamic notch filter is introduced as an intermediary component in the control signal path between the motion controller and motor drives. This filter selectively attenuates oscillation frequencies while allowing other control signals to pass through, thereby reducing mechanical oscillations and settling time without fundamentally redesigning the entire control system
Solution Approach 2:
The notch filter parameters (center frequency and bandwidth) are made dynamic rather than fixed. The filter continuously adapts its characteristics based on real-time feedback from position sensors and loading conditions, allowing it to track varying oscillation frequencies that occur during different robot operating conditions such as different positions, speeds, and payload configurations
2Productivity
If high acceleration and deceleration rates are used, then productivity is improved, but mechanical oscillations increase due to spring-mass system excitation
Solution Approach 1:
The dynamic notch filter proactively counteracts mechanical oscillations by attenuating excitation frequencies before they can fully develop. By continuously monitoring system state and adjusting filter parameters in real-time, the filter prevents oscillation buildup during high acceleration and deceleration events, enabling aggressive motion profiles without stability compromises
3Manufacturing precision
If rigid couplings are used to reduce backlash, then mechanical precision is improved, but system complexity and potential for oscillation increase
Solution Approach 1:
The patent replaces complex mechanical coupling solutions (such as precision rigid couplings or anti-backlash mechanisms) with a control-based approach using dynamic notch filtering. This substitution maintains positioning precision by electronically compensating for oscillations caused by simpler, more compliant mechanical couplings, thereby reducing overall system complexity
Data Source
AI summary
A system and method for reducing mechanical oscillations in a multi-axis control system provides a first command for a dynamic notch filter at a first update rate to at least one motor drive. Each motor drive is connected to a motor for an axis in the multi-axis control system. Each motor drive receives a second command for desired operation of the motor at a second update rate. Operation of the dynamic notch filter in each motor drive is changed as a function of the first command at the first update rate, and each motor drive generates a desired output voltage for operation of the motor at a third update rate. The third update rate is faster than the second update rate, the second command is passed through the dynamic notch filter to generate a filtered command, and the desired output voltage is generated as a function of the filtered command.