BLDC Power Tool Battery Pack Identification for Adaptive Power Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power tools are inefficient when using battery packs with different rated capacities, as they are not optimized for a wide range of power and performance characteristics, leading to unsuitable operation with either low or high capacity battery packs.
Innovation Solution
A power tool system that includes a BLDC motor, a power switch circuit, and a controller capable of identifying the capacity of a battery pack by measuring motor phase current values and applying voltage pulses to determine the rotor position and impedance, allowing for optimal power regulation across various battery pack capacities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a power tool is designed to operate with a specific battery pack capacity, then it achieves optimal efficiency with that capacity, but it becomes incompatible or inefficient with battery packs of different capacities
Solution Approach 1:
The power tool employs dynamic control parameters that automatically adjust based on the detected battery pack capacity. The controller modifies motor current limits, switching frequencies, and power output thresholds in real-time according to the identified battery characteristics, enabling optimal efficiency across different battery capacities without requiring multiple tool configurations
Solution Approach 2:
The system changes operational parameters such as maximum current draw, PWM duty cycle limits, and motor speed thresholds based on the detected battery pack capacity. When a high-capacity battery is detected, the tool permits higher current and power output; when a low-capacity battery is detected, the tool reduces maximum power limits to prevent overheating and ensure safe operation
2Power
If a power tool uses a high capacity battery pack, then it provides greater power capability, but it may be harmful to the battery pack due to high current draw
Solution Approach 1:
The controller continuously monitors battery pack parameters including voltage, current draw, and temperature during operation. Based on this feedback and the identified battery capacity, the controller dynamically adjusts the maximum permissible current draw to stay within safe operating limits for the specific battery pack, preventing overheating and damage while still utilizing available power capacity
Solution Approach 2:
The system performs preliminary identification of the battery pack capacity and characteristics before full operation begins. This preliminary detection allows the controller to pre-configure safe operating parameters and current limits specific to the connected battery pack, preventing harmful conditions before they occur rather than reacting to them during operation
3Reliability
If a power tool uses a low capacity battery pack, then it ensures safety with high current draw, but it does not utilize the full power capability of the battery pack
Solution Approach 1:
The controller adjusts operational parameters to match the actual battery pack capacity. When a low-capacity battery is detected, the system configures appropriate current limits and power thresholds that ensure safe operation while still utilizing the full available capacity of the smaller battery pack, preventing both underutilization and overloading
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
Enables efficient use of battery packs with different capacities by accurately identifying and configuring power output, ensuring compatibility and safety across a range of power tools with diverse performance characteristics.
Implementation Method 1
applies a series of voltage pulses to the motor and measures a corresponding series of motor phase current values to identify an initial position of the rotor relative to the stator
Implementation Method 2
calculate a battery identifier as a function of a sum of the phase current values divided by the bus voltage
Implementation Method 3
identify at least one of an impedance or a capacity of the battery pack as a function of the high-magnitude current value
Data Source
AI summary
A power tool is provided including: a housing including a battery receiving portion configured to receive a removeable power tool battery pack and a motor housing; a brushless direct-current (BLDC) motor disposed within the motor housing, the motor including a stator and a rotor; a power switch circuit disposed between the battery receiving portion and the motor; and a controller that controls a switching operation of the power switch circuit to regulate a supply of power from the battery pack to the motor. At tool start-up, the applies a series of voltage pulses to the motor and measures a corresponding series of motor phase current values to identify an initial position of the rotor relative to the stator. Further, the controller identifies at least one of an impedance or a capacity of the battery pack as a function of the motor phase current values.