Frequency-Selective Motion Control via Spectral Shaping
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Solution Overview
Problem
Conventional motion control techniques fail to balance rapid motion execution, spectral content control, and robustness to frequency variations in mechanical systems, often resulting in excessive energy at critical frequencies or prolonged execution times due to limitations in controlling vibrational responses.
Innovation Solution
A control technique that generates acceleration data using a prototype pulse with a defined attenuation band to inhibit undesired responses, scaling the pulse amplitude based on initial and final boundary conditions, and shaping the spectral content to achieve efficient motion control without exciting unwanted vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If smooth command profiles are used to limit acceleration bandwidth, then vibrational response is reduced, but motion execution time increases
Solution Approach 1:
The patent transforms the command profile from time-domain smoothing to frequency-domain spectral shaping. By defining the acceleration command through its frequency spectrum characteristics (attenuation bands at resonant frequencies) rather than time-domain continuity, the system achieves vibration suppression without excessive motion duration. The spectral content is explicitly controlled to concentrate energy away from critical frequencies while maintaining rapid execution.
Solution Approach 2:
The invention shifts the control approach from the time dimension to the frequency dimension. Instead of constraining the command in the time domain (continuous derivatives), the patent formulates the command by specifying its frequency spectrum characteristics, including attenuation bands at resonant frequencies and concentration of energy in non-critical bands. This dimensional transformation allows simultaneous achievement of rapid execution and vibration suppression.
2Object-affected harmful factors
If timing is matched to natural vibration period, then vibrational energy is removed, but robustness to frequency variations deteriorates
Solution Approach 1:
The patent replaces time-domain timing parameters (synchronized with natural period) with frequency-domain spectral parameters. The acceleration command is defined by its frequency spectrum, including specific attenuation bands at resonant frequencies and energy concentration in non-critical bands. This spectral formulation maintains effectiveness across frequency variations without requiring precise timing synchronization.
Solution Approach 2:
The invention preemptively shapes the acceleration spectrum to prevent excitation of resonant frequencies rather than attempting to cancel vibrations after they occur. By incorporating attenuation bands at critical frequencies in the spectral definition of the command, the system proactively avoids exciting unwanted vibrations, making the control robust to frequency variations.
3Object-affected harmful factors
If notch filtering is applied to remove frequency content, then resonant vibration is suppressed, but commanded duration increases
Solution Approach 1:
The patent formulates the acceleration command by explicitly specifying its frequency spectrum characteristics, including attenuation bands at resonant frequencies and concentration of energy in non-critical frequency bands. This spectral shaping approach achieves resonant vibration suppression without the transient response delays inherent in traditional notch filtering, maintaining the originally intended motion duration.
Data Source
AI summary
A motion command is constructed based on an optimized acceleration pulse designed to control the spectral content of the commanded acceleration. By way of judicious design of the pulse shape, the majority of the energy in the command is contained in a narrow baseband and rolls off rapidly in frequencies outside that band. Additionally, the command can be constructed to suppress selected frequency content in one or more attenuation bands outside the baseband. The resulting motion command permits rapid motion control, while avoiding the excitation of unwanted resonant response in the system while remaining tolerant of system uncertainty.