Brushless Power Tool Motor Control Against Voltage-Limit Wind-Up
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Solution Overview
Problem
Brushless DC motors in hand-held power tools experience wind-up effects and undesirable delayed behavior due to voltage limits, where the control unit cannot impress current into the motor windings, leading to uncorrectable residual faults and suboptimal performance.
Innovation Solution
The control unit adjusts the current request signal based on the voltage difference between the system voltage and the target voltage value, using a difference block, PI controller, and limiting block to avoid wind-up effects, allowing for variable and transformed voltage considerations, thereby optimizing motor control without requiring complex motor parameter measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If field-oriented control is used with integral component for speed control, then control precision is improved, but wind-up effects occur at voltage limit causing delayed motor response
Solution Approach 1:
The control unit calculates the voltage difference between system voltage and target voltage value before generating the current request signal. This preliminary action prevents the integral component from accumulating erroneous values when voltage limit is reached, thereby avoiding wind-up effects and eliminating delayed motor response while maintaining precision control.
2Power
If maximum system voltage is used to meet high speed demand, then power output is improved, but voltage limit causes integral component to accumulate uncorrectable residual faults
Solution Approach 1:
The control unit continuously monitors the voltage difference between system voltage and target voltage value, and uses this feedback to adjust the current request signal. When voltage limit is reached, the feedback mechanism prevents the integral component from accumulating residual faults, ensuring reliable control operation at maximum power output.
3Device complexity
If conventional field-oriented control is used without voltage difference consideration, then device complexity is reduced, but wind-up effects cause suboptimal motor performance
Solution Approach 1:
The control unit modifies the current request signal parameter by calculating and applying the voltage difference between system voltage and target voltage value. This parameter change approach is simple to implement yet effectively prevents wind-up effects, optimizing motor performance without significantly increasing device complexity.
Data Source
AI summary
An electric hand-held power tool, having a brushless DC motor and a control unit for field-oriented control of the DC motor on the basis of a current request signal and a target voltage value derived from the current request signal, wherein the hand-held power tool is further designed to provide a system voltage to supply the DC motor, wherein the control unit is set up to adjust the current request signal taking into account a voltage difference between the system voltage and the target voltage value.