Electric Tool Speed Control Using Battery-Voltage Regression
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Solution Overview
Problem
Conventional electric tools experience unstable motor speed due to abrupt changes when battery voltage shifts between narrow voltage ranges, leading to an unstable rotational speed.
Innovation Solution
Implementing a method that uses regression equations, specifically polynomial, exponential, or logarithmic functions, to calculate duty ratios based on battery voltage, allowing for smoother transitions in motor speed control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a look-up table with voltage ranges is used to maintain constant motor speed, then the motor speed can be maintained under different voltages, but the motor speed becomes unstable with abrupt changes when voltage shifts between ranges
Solution Approach 1:
The patent changes the control parameter from discrete duty ratios in a look-up table to continuous duty ratio values calculated through regression equations. By substituting the actual battery voltage into the regression equation, the system obtains a precise duty ratio that smoothly adjusts with voltage changes, eliminating abrupt transitions and maintaining stable motor speed across the entire voltage range.
2Stability of the object's composition
If narrow voltage ranges are used in the look-up table, then the motor speed change becomes smoother, but the device complexity increases
Solution Approach 1:
The patent replaces the complex mechanical-like structure of a detailed look-up table (which would require numerous discrete voltage ranges and corresponding duty ratio entries) with a simple mathematical regression equation. This equation-based approach provides continuous, smooth control without requiring complex data structures or frequent updates to control parameters, thereby reducing device complexity while maintaining speed smoothness.
Data Source
AI summary
A method of controlling a rotational speed of an electric tool is provided. The electric tool includes a battery, a battery voltage detection circuit, a motor unit, and a controller. The controller stores at least one regression equation of duty ratio on voltage, and detects a voltage of the battery through the battery voltage detection circuit. The controller obtains a duty ratio for a control signal by substituting the voltage of the battery into the at least one regression equation, and outputs the control signal with the duty ratio obtained from the at least one regression equation to the motor unit for controlling operation of the motor unit.