Motor Load Detection via Current Fluctuation Range
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Solution Overview
Problem
Conventional motor-driven appliances with soft no-load functions face challenges in accurately detecting loaded and unloaded states due to variations in current values caused by individual product differences, power voltage fluctuations, and load conditions, leading to inefficient power consumption and inaccurate state detection.
Innovation Solution
A motor-driven appliance with a control unit that includes a state amount detection unit, fluctuation range derivation unit, load presence/absence detection unit, and drive output unit, which detects the loaded state based on the fluctuation range of the state amount, allowing for accurate differentiation between loaded and unloaded states and optimizing drive output accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a threshold-based current detection method is used to detect loaded and unloaded states, then the control system can implement soft no-load function, but the detection accuracy deteriorates due to current value variations from individual product differences, power voltage fluctuations, and load conditions
Solution Approach 1:
The patent applies dynamics by making the detection threshold adaptive rather than fixed. The control unit dynamically adjusts the threshold based on the relationship between current value and rotational speed. Specifically, the threshold is set to a current value at a rotational speed lower than the rated rotational speed, allowing the system to adapt to varying operating conditions while maintaining accurate loaded state detection.
Solution Approach 2:
The patent changes the detection parameter from a fixed current threshold to a dynamic threshold based on rotational speed characteristics. By detecting whether the current value exceeds the threshold at a rotational speed lower than rated speed, the system accounts for individual product variations and voltage fluctuations, thereby improving detection accuracy while maintaining adaptability.
2Reliability
If the motor rotates at high speed continuously to ensure adequate performance under load, then the motor can meet load requirements, but power consumption increases and efficiency decreases during no-load operation
Solution Approach 1:
The patent implements dynamic speed control based on detected load conditions. When the motor is in an unloaded state, the control unit reduces the rotational speed to a lower level, thereby reducing power consumption. When a load is detected (current exceeds threshold at reduced speed), the motor rotates at high speed to meet performance requirements. This dynamic adjustment resolves the contradiction between reliability and energy efficiency.
Solution Approach 2:
The control unit continuously monitors the current value and rotational speed, periodically adjusting the motor speed based on load conditions. This periodic detection and adjustment mechanism ensures the motor operates at appropriate speeds - low during no-load periods and high during loaded periods - optimizing both performance and energy consumption.
3Use of energy by moving object
If the motor rotates at low speed during no-load operation to reduce power consumption, then energy efficiency improves, but the motor may fail to respond quickly when a load is applied
Solution Approach 1:
The patent employs feedback control by continuously monitoring the current value and comparing it against the dynamically set threshold. When the current exceeds the threshold indicating a loaded state, the control unit immediately responds by increasing motor speed. This feedback mechanism ensures quick response to load changes while maintaining energy efficiency during no-load operation.
Solution Approach 2:
The control unit sets the threshold based on characteristics at rotational speeds lower than rated speed, preparing the system for efficient no-load operation. This preliminary configuration allows the motor to operate at low speed during no-load conditions while being pre-configured to quickly transition to high-speed operation when loading is detected, thus balancing energy efficiency and response speed.
Data Source
AI summary
A motor-driven appliance includes a motor and a control unit that controls a drive output to the motor. The control unit detects a state amount indicating an operational state of the motor to derive a fluctuation range of fluctuation in the state amount. The control unit detects whether the motor is in an unloaded state or in a loaded state, based on the derived fluctuation range to perform the drive output to the motor, based on the detected result.