Brushless Impact Tool Control for Fastener Torque Switching
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Solution Overview
Problem
Impact tools, such as impact drivers and wrenches, often overdrive fasteners or fail to apply sufficient torque when used at full power, leading to stripped threads or slow installation, while using less than full power results in inefficient operation.
Innovation Solution
A brushless impact power tool with a controller that switches between open loop and closed loop control based on motor parameters, adjusting conduction band and advance angle values to optimize torque delivery and prevent component damage, featuring a mode switch for different joint types and operational modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If impact tools are used at full power, then torque delivery is improved, but fasteners may be overdriven or stripped
Solution Approach 1:
The system dynamically switches between open loop and closed loop control modes based on real-time motor parameter monitoring. When motor parameters indicate approaching threshold values, the system transitions to closed loop control to precisely regulate torque delivery, preventing fastener damage while maintaining high torque capability when needed.
Solution Approach 2:
The closed loop control mode continuously monitors motor parameters and adjusts power delivery accordingly. This feedback mechanism allows the system to detect when torque is approaching levels that could damage fasteners and automatically reduces power to maintain safe operating limits, resolving the contradiction between delivering high torque and protecting fastener integrity.
2Reliability
If impact tools are used at less than full power, then fastener damage is prevented, but application speed becomes too slow
Solution Approach 1:
The system dynamically adjusts power delivery based on real-time conditions. During phases where high speed is beneficial and damage risk is low, the system operates in open loop mode at high power. When approaching torque thresholds, it transitions to closed loop mode to maintain safety, thus achieving both high productivity and fastener protection.
Solution Approach 2:
The control system periodically monitors motor parameters and switches between control modes. This periodic action allows the tool to operate at full power during safe phases (high productivity) and switch to protective mode when needed (fastener integrity), resolving the speed-integrity tradeoff through time-based control switching.
3Use of energy by moving object
If impact tools use less than full power, then energy consumption is reduced, but torque may be insufficient for desired fastening
Solution Approach 1:
The system uses partial power (open loop control) during phases where full torque is not yet needed, reducing energy consumption. When torque thresholds are approached, it transitions to closed loop control that delivers precise torque levels, ensuring sufficient fastening force is achieved while minimizing overall energy consumption through intelligent power management.
4Productivity
If impact tools switch between control modes, then operational optimization is improved, but control system complexity increases
Solution Approach 1:
The control system dynamically selects between open loop and closed loop modes based on simple threshold comparisons of motor parameters. This dynamic switching provides operational optimization without requiring complex control algorithms, as the decision logic is based on straightforward parameter monitoring and mode transition rules.
Data Source
AI summary
An impact power tool includes a brushless motor, a power switch, an output spindle, and an impact mechanism configured to selectively apply rotational impacts to the output spindle when a torque on the output spindle exceeds a torque threshold. A controller is configured to control power delivery to the motor to selectively cause the motor to operate in a first mode for installing a fastener or in a second mode for removing a fastener. In the first mode, the controller is configured to control the motor with a first conduction band value and a first advance angle value during a first time period until a first parameter is reached, and to control the motor with a second conduction band value and a second advance angle value, at least one of which is greater than the first conduction band value and the first advance angle value, after the first time period.