Sensorless Motor End-of-Stroke Detection Using Current Profiles
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Solution Overview
Problem
Existing end-of-stroke detection systems in electronic dispensers require additional components like switches and wiring, increasing costs, and are vulnerable to unauthorized refill units, as they rely on physical sensors to determine the end of stroke and verify refill compatibility.
Innovation Solution
A sensorless method that uses current sensing to determine the end of stroke by analyzing the motor current draw patterns, allowing the motor to continue operation for a calculated additional time based on the measured current draw, and disabling the dispenser if an unauthorized refill unit is detected by comparing measured load profiles with stored profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an end-of-stroke switch is used to detect the end of motor travel, then the motor can be stopped at the correct position, but the cost of the dispenser increases and additional wiring and circuit board space are required
Solution Approach 1:
The patent replaces the mechanical end-of-stroke switch with an electrical sensing method that monitors motor current characteristics. The processor detects changes in current draw patterns to determine when the actuator reaches end of stroke, eliminating the need for mechanical switches and associated wiring while maintaining detection accuracy.
Solution Approach 2:
The motor's own current consumption characteristics are used to provide end-of-stroke detection information. The system leverages the natural electrical signature generated during motor operation to detect position, making the motor self-diagnostic for position feedback without requiring external sensing components.
2Measurement precision
If traditional end-of-stroke detection is used, then the motor can be stopped at the end of stroke, but unauthorized refill units cannot be detected
Solution Approach 1:
The system continuously monitors motor current draw and compares it against expected profiles to detect anomalies. By analyzing the feedback from current sensing during actuator operation, the processor can identify when an unauthorized refill unit is present and prevent dispenser operation, adding security functionality to the existing detection system.
3Device complexity
If current sensing is used to determine end of stroke, then additional hardware is eliminated, but the system must accurately interpret current draw patterns
Solution Approach 1:
The patent replaces mechanical sensing with electrical sensing of motor current. The processor analyzes the electrical characteristics of motor operation to infer mechanical position and load conditions, substituting complex mechanical detection with simpler electrical measurement and digital signal processing.
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 approach reduces costs by eliminating the need for additional hardware and effectively prevents the use of unauthorized refill units by accurately determining the end of stroke and verifying refill compatibility through load profile analysis.
Implementation Method 1
sensing a parameter indicative of current; determining the end of an inrush current and a start point that is after the inrush current and that is at about the beginning of a main current draw
Data Source
AI summary
Embodiments of methods of controlling a motor for driving a load are disclosed herein. Exemplary methods include providing energy to a motor, sensing a parameter indicative of current. Determining the end of an inrush current and a start point that is after the inrush current and that is at about the beginning of a main current draw. Determining an end point at about the end of the main current draw. Continuing to provide energy to the motor for a time period that is a function of the time from the start point to the end point and de-energizing the motor.