Multi-Spindle Phase Control via Motor Current Analysis
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Solution Overview
Problem
Existing multiple-spindle machines face challenges in reducing vibrations and chatter due to synchronized tooth impacts, which can be costly to address with high-precision position sensors and complex equipment.
Innovation Solution
The method involves measuring motor currents of spindles to determine the time between tooth impacts, calculating a shift angle, and adjusting the angular position of spindles to synchronize cutting teeth out of phase, thereby minimizing vibrations using variable sampling rates and cross-correlation analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-precision rotary encoders are used to sense spindle position, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the position sensing function from external rotary encoders and implements it internally within the motor drive system. The drive unit measures motor current to detect tooth impact timing, eliminating the need for separate position sensors while maintaining measurement precision.
Solution Approach 2:
The motor drive unit performs position measurement functions using its own current sensing capabilities. The system uses the motor's existing current measurement infrastructure to detect cutting tooth impacts, making the system self-sufficient without requiring additional external sensors.
2Measurement precision
If high sampling rates are used to accurately measure spindle position at high rotational speeds, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The system uses feedback from motor current measurements to detect tooth impact timing. By monitoring current variations caused by tooth impacts and using this feedback to determine phase relationships, the system achieves accurate position measurement without requiring high sampling rates.
Solution Approach 2:
The patent leverages the periodic nature of tooth impacts during spindle rotation. By detecting the periodic current variations caused by tooth impacts and analyzing the timing between impacts from different spindles, the system determines phase relationships using the inherent periodicity of the cutting process rather than continuous high-speed sampling.
3Manufacturing precision
If spindles are synchronized to reduce chatter, then manufacturing precision is improved, but object-generated harmful factors increase due to amplified vibrations from synchronized tooth impacts
Solution Approach 1:
The system preliminarily determines the phase relationship between spindles by analyzing tooth impact timing from motor current measurements. By calculating the required phase shift before machining operations begin and adjusting spindle positions in advance, the system optimizes vibration characteristics while maintaining manufacturing precision.
Data Source
AI summary
A method of controlling a multiple spindle machine includes measuring the motor currents provided to a first spindle and a second spindle over a period of time, establishing an amount of time between impacts on a workpiece of a cutting tooth of the first spindle relative to a cutting tooth of the second spindle based on the measured motor currents of the first spindle and the second spindle, determining an angle to shift the second spindle relative to the first spindle, and increasing or decreasing the amount of time between impacts to obtain the determined shift angle for the second spindle.