Sensorless Anti-Pinch Motor Control via Current Rate of Change

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Solution Overview

Problem

Existing motor control systems for applications like window and seat adjustments in vehicles face challenges in accurately detecting pinch conditions without relying on expensive Hall Effect sensors, necessitating a cost-effective and sensorless solution for obstruction detection.

Innovation Solution

A motor control system that includes a pinch detection module capable of analyzing motor current and its rate of change to generate a pinch signal, using comparators, sample/hold circuits, and current offset calculations to determine pinch conditions, allowing the system to stop or reverse the motor and prevent window closure in case of an obstruction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If Hall Effect sensors and wiring are used to detect pinch conditions, then detection reliability is improved, but system cost increases

Engineering Contradiction:

Improvepinch condition detection reliabilityVSAvoidsystem cost

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the pinch detection function from dedicated Hall Effect sensors and implements it through existing motor control system components (current sensing circuits and control logic), eliminating the need for separate expensive sensors while maintaining detection capability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The motor control system uses its own current sensing capabilities to detect pinch conditions, turning the system's operational parameters into a detection mechanism without requiring external sensing components

Inventive Principle:

Principle #25Self-service

2Measurement precision

If current threshold and rate of change threshold methods are used, then detection precision is improved, but false detection risk increases

Engineering Contradiction:

Improvepinch condition detection precisionVSAvoidfalse detection

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The system pre-estimates the normal current range for each motor based on historical data or manufacturer specifications, establishing a baseline before operation to compare against real-time measurements and reduce false positives

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent employs multiple detection thresholds (current threshold and rate of change threshold) working together, where both conditions must be satisfied to trigger a pinch detection, providing a more robust detection criterion that reduces false positives

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11611297B2Anti-pinch motor control

Publication Date: 2023.03.21 GENTHERM INC

AI summary

A motor control system configured to detect a pinch condition of a structure actuated by a motor includes a pinch detection module configured to receive a current signal indicative of a motor current, determine a rate of change of current based on the current signal, and generate a pinch signal indicative of the pinch condition in response to either one of the motor current being greater than a current threshold and the rate of change of current being greater than a rate of change threshold. The motor control system further includes a position control module configured to control the motor to actuate the structure in response to an input and at least one of stop and reverse the motor in response to the pinch signal.