Work Machine Torque Control via Duty-Voltage Mode Switching
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Solution Overview
Problem
Existing driver drills face challenges in maintaining high torque precision due to variations in tightening torque, which is estimated based on motor current.
Innovation Solution
The work machine incorporates a control system that adjusts the motor's duty ratio and application voltage based on detected current and torque conditions, allowing for precise torque control during tightening and loosening operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If tightening torque is estimated based on motor current, then mechanical configuration can be simplified, but variation in tightening torque becomes large
Solution Approach 1:
The patent changes the control parameters by switching between constant duty ratio mode (for speed control) and constant voltage mode (for torque control). By detecting motor current and comparing it with threshold values, the system transitions from PWM duty ratio control to direct voltage control, thereby achieving precise torque control while maintaining simplified mechanical configuration.
Solution Approach 2:
The patent implements dynamic control mode switching based on real-time motor current detection. The control part dynamically transitions between constant duty ratio drive and constant voltage drive modes, allowing the system to adapt to different operational phases (acceleration vs. torque control) and achieve both simplified mechanics and precise torque control.
2Ease of operation
If constant duty ratio is maintained after current reaches threshold, then motor control is simplified, but torque precision deteriorates
Solution Approach 1:
The control system dynamically switches between constant duty ratio mode during acceleration phase and constant voltage mode during torque control phase. This dynamic transition ensures simplified control during speed buildup while achieving high torque precision during the tightening operation by maintaining constant voltage after current threshold is reached.
Solution Approach 2:
The motor control process is segmented into two distinct phases: acceleration phase (constant duty ratio) and torque control phase (constant voltage). By dividing the control process into segments with different control strategies, the system achieves both ease of operation during acceleration and high torque precision during the tightening operation.
3Device complexity
If motor is stopped based on current threshold, then control is simplified, but torque variation increases
Solution Approach 1:
The patent changes the stopping criterion from current-based control to voltage-based control. By maintaining constant voltage after the current threshold is reached and detecting torque completion through voltage effective value comparison, the system achieves more consistent torque control and reduces torque variation while keeping the control system relatively simple.
Solution Approach 2:
The system implements feedback control by continuously monitoring motor current, comparing it with threshold values, and switching control modes accordingly. The control part uses feedback from current detection to determine when to transition from duty ratio control to voltage control, and further uses voltage effective value feedback to detect torque completion, thereby reducing torque variation.
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 enables the work machine to achieve high torque precision by stabilizing the effective value of the motor application voltage and controlling the motor's state based on predetermined conditions, thereby suppressing variations in tightening torque.
Implementation Method 1
a motor (12)
Implementation Method 2
decrease an effective value of an application voltage applied to the motor to set as a completion effective value
Data Source
AI summary
A work machine has high torque precision. When a prescribed condition pertaining to torque that acts on a tip tool is satisfied during one ON operation of a slide switch (YES in S18 or YES in S19), a microcomputer lowers the duty to d1, which corresponds to a set torque, and sets an effective value for a motor-applied voltage to a completion effective value, which corresponds to a set torque (S25, S13, S14). When a completion condition is satisfied when the duty has been set to d1, the microcomputer sets the effective value for the motor-applied voltage to zero even when the slide switch is in an ON operation, thereby stopping the motor (NO in S20, YES in S21, S25).