Impact Tool Control Modes for Fastener Torque and Speed
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Solution Overview
Problem
Impact drivers and impact wrenches often either overdrive fasteners, stripping their heads or threads when used at full power, or apply torque too slowly when used at reduced power, failing to meet desired installation speeds or torque levels.
Innovation Solution
A brushless impact power tool with a controller that switches between open loop and closed loop control modes based on motor parameters, adjusting conduction band and advance angle values to optimize torque delivery and prevent component damage, featuring a mode switch for selecting operation modes suited to hard or soft joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the impact tool is used at full power, then the fastening speed is improved, but the fastener may be overdriven or stripped
Solution Approach 1:
The controller dynamically adjusts motor power delivery based on real-time motor parameter feedback (speed, current, temperature). The system transitions between open-loop and closed-loop control modes, continuously modifying conduction band and advance angle values to optimize torque delivery while preventing over-tightening, thus resolving the contradiction between fastening speed and torque control precision
Solution Approach 2:
The closed-loop control mode incorporates feedback from motor parameters (speed, current, temperature) to continuously adjust power delivery. The controller monitors motor performance and modifies conduction band and advance angle values in real-time, enabling precise torque control at high speeds while preventing fastener damage, thereby resolving the speed-precision tradeoff
2Manufacturing precision
If the impact tool is used at reduced power, then the fastener torque control is improved, but the fastening speed becomes too slow
Solution Approach 1:
The system dynamically optimizes motor control parameters (conduction band, advance angle) based on real-time motor performance data. By continuously adjusting these parameters in closed-loop mode, the system achieves precise torque control at reduced power levels while maintaining optimal fastening speed, resolving the contradiction between torque precision and productivity
Solution Approach 2:
The controller changes motor control parameters (conduction band, advance angle, PWM duty cycle) based on motor operating conditions and selected mode of operation. These parameter adjustments enable the system to deliver optimal torque at reduced power levels while maintaining acceptable fastening speeds, resolving the tradeoff between precision and productivity
3Manufacturing precision
If the controller uses closed loop control, then the torque control precision is improved, but the device complexity increases
Solution Approach 1:
The controller implements a dynamic control architecture that can operate in both open-loop and closed-loop modes. The system transitions between these modes based on operating conditions, implementing complex feedback control only when necessary for precise torque control, thereby achieving high precision without permanently increasing system complexity
Solution Approach 2:
The controller is designed to perform multiple functions: open-loop control for high-speed operations, closed-loop control for precision torque applications, and automatic mode selection. This multi-functionality allows the single controller to handle both simple and complex control requirements, achieving precision torque control without requiring separate dedicated control systems
Data Source
AI summary
An impact power tool includes a housing, a motor, a controller, an output member configured to be rotated when the motor is energized, and an impact mechanism configured to rotationally drive the output member. The impact mechanism is configured to selectively apply rotational impacts to the output member when a torque on the output member exceeds a torque threshold. The controller is configured to control the motor during a first phase of operation with open loop control and a baseline conduction band and advance angle setting when a sensed tool operation parameter is one of above or below a threshold value. The controller is configured to control the motor during a second phase of operation with closed speed loop control and an increased conduction band and advance angle setting when the sensed tool operation parameter is the other of above or below the threshold value.