Position Sensor Speed Indication for Anti-Trap Detection
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Solution Overview
Problem
Existing speed indication methods using position sensors in electric drive units, such as power windows, suffer from low temporal resolution at low speeds, leading to inadequate reaction time for anti-trap functions, which is critical for safety and legal compliance.
Innovation Solution
A method and device that provide continuous speed indication by determining pulse duration between sensor signal edges and updating movement information at regular intervals, even when no new edges are detected, ensuring accurate and timely movement information at low speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a position encoder is used to determine speed based on time intervals between edges, then the device complexity is reduced and cost is lowered, but the temporal resolution of speed information deteriorates at low speeds
Solution Approach 1:
The patent applies preliminary action by pre-defining a fixed evaluation period (first time period) during which speed is calculated based on a predetermined number of edges (first number of edges). This allows the system to continuously provide speed information at regular intervals regardless of the actual time between edges, ensuring temporal resolution is maintained even at low speeds where edge intervals would naturally be longer.
Solution Approach 2:
The patent implements periodic action by evaluating speed at fixed time intervals (first time period) rather than only when edges occur. This periodic evaluation ensures that speed information is continuously available at predictable intervals, improving temporal resolution compared to waiting for natural edge occurrences, especially at low speeds.
2Ease of operation
If speed is determined from time intervals between position encoder edges, then the measurement method is simple, but the reaction time for anti-trap functions is insufficient at low speeds
Solution Approach 1:
The system performs preliminary action by pre-calculating and storing speed values based on predetermined edge counts within fixed time periods. This allows the control unit to immediately access current speed information without waiting for the next edge event, significantly reducing reaction time for anti-trap functions while maintaining simple measurement methodology.
Solution Approach 2:
The patent ensures continuity of useful action by continuously providing speed information at regular intervals (every first time period) rather than intermittently based on edge occurrences. This continuous availability of speed data ensures that anti-trap detection can respond promptly regardless of the drive unit's current speed, eliminating gaps in monitoring that would occur with edge-based timing.
3Measurement precision
If the evaluation period is extended to capture more edges at low speeds, then measurement accuracy improves, but the response time for safety-critical detection deteriorates
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the evaluation parameters: it uses a fixed time period (first time period) combined with a predetermined number of edges (first number of edges) to calculate speed. This approach maintains measurement accuracy by ensuring sufficient edge samples are collected while limiting the maximum evaluation duration, thus preserving fast response capability for safety-critical detection.
Solution Approach 2:
The system implements dynamics by adapting the speed evaluation to work effectively across varying speed conditions. By using a fixed time period rather than a fixed number of edges, the system automatically adjusts the effective measurement window based on current speed - at low speeds it captures fewer edges within the fixed period but still provides timely updates, while at high speeds it captures more edges for accurate measurement, maintaining both accuracy and response speed across all operating conditions.
Data Source
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AI summary
The invention relates to a method for providing an indication of movement from a sensor signal from a position transmitter (9), wherein the indication of movement indicates a speed of movement, wherein the sensor signal from the position transmitter (9) generates an edge following a movement via a particular path range having the following steps: - a pulse duration (dT) is ascertained (S1) as the interval of time between the last two provided edges of the sensor signal; - depending on whether a period which corresponds to the pulse duration (dT) has elapsed since the last provided edge of the sensor signal, an indication which is dependent on the pulse duration (dT) or an indication which is dependent on the period since the last edge of the sensor signal is provided (S4, S6) as an indication of movement.