Motor Drive Signal Shaping for Oscillation Control
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Solution Overview
Problem
Motor-driven systems experience oscillatory behavior known as 'ringing' or 'bounce' due to resonant frequencies, which prolongs settling times and impairs performance in applications like autofocus systems and disk readers.
Innovation Solution
A drive signal is generated using a series of steps based on Pascal's triangle, with each step's size and spacing tailored to the mechanical system's resonant frequency, creating a 'notch' with zero energy at the resonant frequency to minimize oscillations, and additional filtering layers can be applied to accommodate variations in actual resonant frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional drive signals (step or ramp functions) are used to move the mechanical system, then the motor can be controlled to reach new positions, but oscillatory ringing occurs at resonant frequency that prolongs settling time
Solution Approach 1:
The drive signal is structured as a series of periodic steps spaced according to the resonant frequency of the mechanical system. By spacing steps at intervals corresponding to the resonant period, the signal periodically excites and then allows the system to settle, avoiding continuous energy input at the resonant frequency that would sustain oscillations.
Solution Approach 2:
The drive signal parameters (amplitude, timing, spacing) are specifically adjusted based on the known resonant frequency of the mechanical system. The step spacing and duration are modified to create a notch in the frequency spectrum at the resonant frequency, changing the signal characteristics to avoid exciting resonance while maintaining effective position control.
2Loss of time
If the drive signal is optimized to eliminate resonant oscillations, then settling time is reduced, but the drive signal complexity increases due to Pascal's triangle step structure
Solution Approach 1:
The resonant frequency of the mechanical system is measured and stored in advance. Based on this pre-acquired information, the drive signal is pre-configured with appropriate step spacing and timing parameters before actuation begins, eliminating the need for real-time frequency analysis or complex adaptive control during operation.
Solution Approach 2:
The drive signal is segmented into discrete steps rather than being a continuous function. Each step is independently controlled in amplitude and timing, allowing the signal to be constructed from simple discrete elements that collectively achieve the complex goal of avoiding resonant frequency excitation.
Data Source
AI summary
Embodiments of the present invention provide a motor-driven mechanical system with a detection system to measure properties of a back channel and derive oscillatory characteristics of the mechanical system. Uses of the detection system may include calculating the resonant frequency of the mechanical system and a threshold drive DTH required to move the mechanical system from the starting mechanical stop position. System manufacturers often do not know the resonant frequency and DTH of their mechanical systems precisely. Therefore, the calculation of the specific mechanical system's resonant frequency and DTH rather than depending on the manufacturer's expected values improves precision in the mechanical system use. The backchannel calculations may be used either to replace or to improve corresponding pre-programmed values.