Power Tool Motor Control Using Battery Current Cycle Detection
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Solution Overview
Problem
Battery powered hydraulic tools require a pressure sensor for hydraulic cycle control, which increases complexity, cost, and space requirements.
Innovation Solution
A firmware algorithm that uses battery current as feedback to determine when a hydraulic cycle is complete, eliminating the need for a pressure sensor by monitoring motor revolutions and current draw to control the hydraulic cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pressure sensor is used to control hydraulic cycles, then hydraulic cycle control accuracy is improved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the pressure sensor from the hydraulic control system. Instead of using a pressure sensor to directly measure hydraulic pressure, the system uses a current sensor to measure motor current, which indirectly reflects pressure conditions. This extraction removes the complex pressure sensing mechanism while maintaining control functionality through electrical parameter monitoring.
Solution Approach 2:
The patent introduces motor current as an intermediary parameter between the control system and hydraulic pressure. Rather than directly sensing pressure, the system measures current draw which correlates with pressure conditions through the motor-hydraulic pump connection. This intermediary approach allows indirect pressure monitoring using simpler electrical sensors.
2Measurement precision
If a pressure sensor is used to control hydraulic cycles, then hydraulic cycle control accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive pressure sensors with cheaper current sensors and control algorithms. The current sensor is a standard component in motor control systems, significantly reducing component cost. The solution accepts that the current-based method requires more complex control logic but gains substantial cost savings in hardware components.
Solution Approach 2:
The patent substitutes mechanical pressure sensing with electrical current measurement and digital signal processing. Instead of using mechanical pressure sensors that convert pressure to electrical signals, the system uses electrical parameters (current, voltage, frequency) already present in the motor control system to infer pressure conditions, eliminating the need for separate mechanical sensing hardware.
3Measurement precision
If a pressure sensor is used to control hydraulic cycles, then hydraulic cycle control accuracy is improved, but space requirements increase
Solution Approach 1:
The patent merges the pressure sensing function with the existing motor control system. The current sensor that is already part of the motor control circuitry is used to infer pressure conditions, eliminating the need for a separate pressure sensor module. This merging of functions reduces the overall space required for sensing components while maintaining control capability.
Data Source
AI summary
A method of determining when a cycle of a power tool is complete includes calculating an average current draw of a battery while a motor is running, determining a number of revolutions of the motor, and determining that the cycle is complete when the average current draw exceeds a threshold current value and the number of motor revolutions exceeds a threshold number of motor revolutions.