Electric Tool Kickback Detection Using Speed-Torque Balance
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Solution Overview
Problem
Existing electric tools face challenges in accurately detecting unstable behavior that could lead to kickback and other inconveniences, as they rely on simplistic methods like inertial torque calculation and current detection thresholds, which are not sufficient for precise motor control.
Innovation Solution
The electric tool incorporates a number of revolutions detection unit and a torque detection unit, which work in conjunction with a drive control unit to accurately detect unstable behavior by analyzing the balance between the number of revolutions and load torque, allowing for timely deceleration or stoppage of the motor to prevent kickback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current detection threshold methods are used to detect unstable behavior, then the detection process is simple, but the detection precision is insufficient leading to inaccurate kickback detection
Solution Approach 1:
The patent combines multiple detection parameters (motor current, rotation speed, and torque) into a unified unstable behavior detection system. By merging these parameters and analyzing their relationships, the system achieves comprehensive detection of kickback conditions without requiring separate complex detection circuits for each parameter.
Solution Approach 2:
The system continuously monitors motor current and rotation speed, compares actual values against reference values, and adjusts control based on the detected deviations. This feedback mechanism enables dynamic detection of unstable behavior by analyzing the relationship between current increase and rotation speed decrease, improving detection accuracy over static threshold methods.
2Measurement precision
If inertial torque calculation is used to detect kickback, then the detection method is straightforward, but the detection accuracy is insufficient for precise motor control
Solution Approach 1:
The patent transitions from single-parameter inertial torque calculation to multi-dimensional analysis by incorporating both motor current and rotation speed measurements. By analyzing the coordinated changes in these two dimensions, the system achieves more accurate kickback detection that accounts for the dynamic relationship between electrical and mechanical parameters.
Solution Approach 2:
The detection system serves multiple functions simultaneously: it monitors motor current, tracks rotation speed, calculates torque, and detects unstable behavior. This multi-functional approach eliminates the need for separate detection mechanisms while improving overall detection accuracy through integrated parameter analysis.
3Reliability
If the motor is stopped or decelerated upon detecting unstable behavior, then user safety is improved, but productivity is reduced due to operational interruptions
Solution Approach 1:
The system performs preliminary detection of unstable behavior by monitoring the relationship between motor current increase and rotation speed decrease before kickback fully occurs. By detecting early signs of instability and taking preventive control actions, the system prevents severe kickback events while maintaining operational continuity when conditions are normal.
Solution Approach 2:
The control system dynamically adjusts motor operation based on real-time detection of unstable behavior. Rather than continuous stopping, the system applies selective deceleration or stopping only when unstable behavior is detected, and maintains normal operation during stable conditions. This dynamic control approach balances safety requirements with productivity maintenance.
Data Source
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AI summary
The problem to be overcome by the present disclosure is to detect an unstable behavior accurately. An electric tool (1) includes: a motor (2); an attachment unit to receive a tip tool attached thereto; a drive control unit (64) to control the motor (2); a number of revolutions detection unit (62); and a torque detection unit (63). The number of revolutions detection unit (62) detects a number of revolutions of a first detection target shaft. The torque detection unit (63) detects a load torque of a second detection target shaft. The drive control unit (64) detects, based on the number of revolutions and load torque detected, an unstable behavior of at least one of the tip tool, the first detection target shaft, or the second detection target shaft and either decelerates, or stops running, the motor (2) when detecting the unstable behavior.