Motor Current Pinch Detection for Window Actuators
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Solution Overview
Problem
Existing anti-pinch technologies for motor-actuated closing members, such as power windows, face challenges in reliably detecting pinches during transient states, particularly when the window starts up after being temporarily stopped in an intermediate position, due to dynamic changes in motor current and speed influenced by factors like supply voltage, temperature, and window position.
Innovation Solution
A pinch detector that measures motor current during a blind time period at the start of the motor's closing movement, determines a reference value, and compares subsequent current values to a threshold value, set by adding a margin value to the reference value, to detect pinches during the detection time period, effectively addressing the challenge of pinch detection in transient states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional sensors (force or speed sensors) are used for pinch detection, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The motor itself serves as the sensing element by monitoring its own current consumption. The control unit analyzes current variations during motor operation to detect pinches, eliminating the need for external force or speed sensors. This self-service approach maintains high detection accuracy while reducing system complexity and cost.
Solution Approach 2:
The patent replaces mechanical sensing systems (force sensors, speed sensors) with an electrical measurement system that monitors motor current. This substitution uses electrical signals instead of mechanical components to detect pinches, achieving the same functional goal with simpler and less expensive equipment.
2Speed
If pinch detection is performed during motor start-up transient state, then response speed is improved, but reliability deteriorates due to dynamic current changes
Solution Approach 1:
The control unit performs preliminary actions by continuously monitoring motor current from the start of operation. It establishes a reference current value before pinch detection begins and uses this baseline to detect current increases indicating pinches. This preliminary current characterization enables reliable detection during the critical transient start-up phase.
Solution Approach 2:
The patent implements dynamic pinch detection by continuously adapting the current threshold based on real-time motor operation conditions. The control unit adjusts detection parameters dynamically during motor start-up and steady-state operation, allowing reliable pinch detection across varying operating conditions rather than using fixed thresholds.
3Productivity
If the anti-pinch algorithm is deactivated before the window seal is reached, then productivity is improved, but safety deteriorates
Solution Approach 1:
The control unit applies different detection strictness levels at different window positions. During the approach to the seal, the system maintains relaxed detection to ensure complete closing (productivity). When the seal is reached and further closing would cause damage, the system switches to strict detection mode to prevent pinches and damage (safety). This local differentiation of detection quality resolves the contradiction.
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
This solution allows for efficient and reliable detection of pinches during motor start-up, even in difficult scenarios, ensuring the window closes without exceeding the safe pinch force limit, while being simple, fast, and robust to external conditions like supply voltage and obstacle stiffness.
Implementation Method 1
a measuring circuit to measure a motor current
Data Source
AI summary
The pinch detector is suitable to detect a pinch at a closing member actuated by a motor equipped with a measuring circuit to measure a motor current. It includes a first portion that, when the motor starts closing the member, obtains a reference value of the motor current measured at the end of a blind time period having a predetermined duration from the moment the motor starts to close the member; a second portion that compares current values of the measured motor current to a threshold value depending on said reference value, during a detection time period, following the blind time period and preceding a steady state time period of the motor, in order to detect a pinch at the closing member based on a comparison result.