Torque Signal Filtering for Impact Tools
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Solution Overview
Problem
Impact electric tools face inaccuracies in torque measurement due to noise components in the torque value signal generated by torque sensors, which can lead to improper control of driving apparatuses.
Innovation Solution
A signal processing apparatus that determines and adjusts the cut-off frequency of digital low-pass filters based on the number of hits, using approximate equations to filter out noise components from the torque value signal, ensuring accurate torque measurement and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a torque sensor is used to measure torque in impact electric tools, then torque measurement capability is provided, but noise components are introduced into the torque value signal
Solution Approach 1:
The patent segments the torque value signal into multiple frequency components through Fourier transformation, separating the useful torque information from noise components. By dividing the signal into frequency domains, the system can selectively process different components to eliminate noise while preserving measurement accuracy.
Solution Approach 2:
The patent introduces an intermediary processing system that includes Fourier transformation, noise component identification, and inverse Fourier transformation. This intermediary process acts as a mediator between the raw sensor signal and the final torque value, filtering out noise components while maintaining the essential torque measurement information.
2Ease of operation
If noise components are present in the torque value signal, then driving apparatus control accuracy deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the processed torque value signal (after noise removal) is used to control the driving apparatus. The system continuously monitors the torque signal, removes noise components through frequency analysis, and feeds back the cleaned signal for accurate control, ensuring both ease of operation and high control accuracy.
Solution Approach 2:
The patent changes the parameter of the torque value signal by transforming it from the time domain to the frequency domain, identifying and removing noise components, then transforming it back. This parameter transformation process maintains the control capability while significantly improving control accuracy by eliminating signal noise.
Data Source
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AI summary
A signal processing apparatus for an electric tool is provided for generating a motor control signal (Stc) for controlling a motor by performing a smoothing process on a torque value signal (St) from a torque sensor (6) of an electric tool by using a filter (22). The signal processing apparatus includes a half width detector circuit (21) that detects a half width (Bs) of the torque value signal (St); and a calculator circuit (23) that controls a cut-off frequency (fc) of the filter (22) to change the cut-off frequency (fc) according to a number of hits (H) of the electric tool, based on the detected half width of the torque value signal.