Electric Pulse Tool Torque Control for Operator Reaction Force
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Solution Overview
Problem
Handheld electric power tools used for fastening operations often subject operators to significant reaction forces, which can be uncomfortable and reduce productivity, as existing pulsed motor control methods do not effectively manage torque delivery to minimize these forces.
Innovation Solution
The electric pulse tool delivers torque in pulses by adjusting the current feed to the motor based on the width of the torque pulses, with wider torque pulses resulting in longer pause intervals and narrower pulses resulting in shorter pause intervals, thereby smoothing the reaction force experienced by the operator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous current is fed to the motor to deliver continuous torque, then the fastening operation is efficient and quick, but the reaction force transferred to the operator becomes large and uncomfortable
Solution Approach 1:
The patent applies periodic action by feeding current to the motor in pulsed intervals rather than continuously. The control unit switches the current on and off in periodic cycles, creating torque pulses that perform the fastening operation while allowing rest periods between pulses. This periodic current feeding pattern reduces the average reaction force on the operator while maintaining sufficient total torque delivery for efficient fastening.
2Ease of operation
If pulsed current is fed to the motor to reduce reaction force, then the operator comfort is improved, but the torque delivery becomes discontinuous and less efficient
Solution Approach 1:
The patent applies dynamics by making the pause interval between current pulses variable rather than fixed. The control unit determines the pause interval dynamically based on the actual torque pulse width and target torque characteristics. This dynamic adjustment optimizes the balance between operator comfort (through adequate pause periods) and fastening efficiency (by adapting pulse timing to actual torque delivery needs).
Solution Approach 2:
The patent applies feedback by using torque sensors to measure actual torque pulses and using this information to control subsequent current pulses. The control unit receives feedback about the torque pulse width and uses this to determine the appropriate pause interval before the next current pulse. This closed-loop feedback ensures optimal balancing of operator comfort and fastening efficiency based on real-time torque conditions.
3Productivity
If the torque pulse width is increased to deliver more torque per pulse, then the fastening efficiency improves, but the reaction force peak becomes larger and more uncomfortable
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting multiple parameters including current pulse width, pause interval duration, and current amplitude. The control unit modifies these parameters based on feedback from torque sensors and position encoders to achieve the desired balance between torque delivery efficiency and reaction force management. This multi-parameter adjustment allows optimization of both productivity and operator comfort.
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 approach reduces the initial reaction force and builds it up more linearly, making the tool more ergonomic and efficient for operators by minimizing discomfort and improving productivity.
Implementation Method 1
an electric motor adapted to drive the output shaft... provide a current pulse to the electric motor
Data Source
AI summary
An electric pulse tool is configured to deliver torque in pulses on an output shaft thereof and includes an electric motor to drive the output shaft. The electric pulse tool is configured to, for each period, provide a current pulse to the electric motor during a current-on time interval, pause a current feed to the electric motor after the current-on time interval until an end of a torque pulse, determine a width of the torque pulse, and continue pausing the current feed to the electric motor during a pause interval from the end of the torque pulse. The pause interval is determined based on the width of the torque pulse such that a wider torque pulse results in a wider pause interval and a narrower torque pulse results in a shorter pause interval.