Handheld Power Tool Motor State Detection via Signal Waveform Comparison
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Solution Overview
Problem
Existing methods for detecting the operating state of handheld power tools, such as rotary impact wrenches, are inefficient as they rely on fixed threshold values and additional sensors, which fail to adapt to changing applications and increase the tool's complexity, leading to unreliable operation mode detection.
Innovation Solution
A method that ascertains and compares motor operating quantity signals with state-typical model signals, eliminating the need for additional sensors by using existing motor sensors like Hall sensors, and allowing detection of operating states regardless of target speed, start-up characteristics, or power supply state, using techniques like bandpass filtering and parameter estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fixed threshold values and additional sensors are used for detecting operating state, then detection capability is provided, but device complexity and cost increase
Solution Approach 1:
The patent extracts the operating state detection capability from a separate sensor system and integrates it into the existing motor control system. By utilizing the motor's existing sensors (Hall sensors, current sensors) and processing motor operating quantities (current, speed, acceleration), the patent eliminates the need for additional dedicated sensors while maintaining detection accuracy.
Solution Approach 2:
The motor control system is made multi-functional by enabling it to perform both motor control and operating state detection functions. The existing sensor infrastructure is reused for dual purposes: motor control feedback and impact mode detection, thereby avoiding additional hardware complexity.
2Device complexity
If fixed threshold values are used for impact detection, then detection is simple, but adaptability to different applications is poor
Solution Approach 1:
The patent implements dynamic threshold adaptation by continuously adjusting detection thresholds based on current operating conditions. The system adapts to different applications (self-tapping screws, wood screws, metal screws) by modifying threshold values in real-time according to motor current, speed, and acceleration characteristics, rather than using fixed thresholds.
Solution Approach 2:
The system changes detection parameters (thresholds, evaluation criteria) based on operating conditions. Different application scenarios have different parameter sets that are selected or adjusted dynamically, allowing the same detection system to adapt to various screw types and material conditions without hardware changes.
3Reliability
If additional sensors are added to detect operating state, then detection reliability is improved, but robustness and simplicity are reduced
Solution Approach 1:
The motor system performs self-diagnosis by monitoring its own operating quantities. The existing sensors that serve the motor control function are also used for impact detection, making the system self-sufficient without requiring external or additional sensing infrastructure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides reliable and adaptive detection of operating states, ensuring accurate impact mode identification across various applications without additional sensor costs or complexity, enabling faster reaction times and flexible tool operation.
Implementation Method 1
using existing motor sensors like Hall sensors
Data Source
AI summary
Method for detecting a first operating state of a handheld power tool, wherein the handheld power tool has an electric motor. In this case, the method comprises the steps of: (S1) determining a signal of an operating variable of the electric motor; (S2) comparing the signal of the operating variable with at least one model signal waveform typical of the state, wherein the model signal waveform typical of the state is assigned to the first operating state; (S3) deciding whether the first operating state is present, wherein the decision at least partially depends on whether the model signal waveform typical of the state is identified in the signal of the operating variable in step S2. Additionally disclosed is a handheld power tool, particularly an impact driver, with an electric motor and a control unit, wherein the control unit is designed to execute a method according to the disclosure.