Grill Platen Position Detection Using Back-EMF When Motor Is Off

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Solution Overview

Problem

Conventional grills lack an effective method to detect the position of the platen assembly accurately while the motor is off, which can lead to issues such as incomplete closure, latch failure, and over-travel adjustments, affecting cooking consistency and safety.

Innovation Solution

A system that includes a motor with a control mechanism to measure the current flow caused by back EMF when the motor coil is shorted, allowing for the detection of the platen assembly's position, latch failure, and over-travel adjustments without the motor being active, utilizing a spring mechanism to bias the platen assembly and a control module to process the current data for precise positioning.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the motor is turned off after solenoid latch engagement, then energy consumption is reduced and the platen can rise under spring bias, but the system loses the ability to detect platen position accurately

Engineering Contradiction:

Improvemotor energy consumptionVSAvoidplaten position detection accuracy

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The patent replaces the active motor-driven sensing system with a passive back-EMF sensing system. When the motor is turned off, the system uses the back electromotive force (EMF) generated by motor coil movement to detect platen position, eliminating the need for continuous motor operation while maintaining detection capability. This substitution allows energy savings while preserving measurement functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces back-EMF as an intermediary mechanism to transfer information about platen position to the control system. By measuring the voltage induced in the motor coils during movement, the system can infer position data without requiring the motor to remain active, thus acting as a mediator between mechanical movement and electrical detection.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the sensor shows open state after latch engagement, then the latch can engage properly, but the system cannot detect if the platen has moved from the closed position

Engineering Contradiction:

Improvelatch engagement reliabilityVSAvoidplaten position information

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent implements a feedback mechanism using back-EMF sensing to continuously monitor platen position even after the latch engages and the motor turns off. The control system measures voltage changes in the motor coils that correspond to platen movement, providing real-time feedback about position status without requiring the motor or primary sensor to remain active.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The back-EMF signal serves as an intermediary that carries position information from the mechanical platen movement to the electrical control system. This intermediary mechanism allows the system to track position changes without relying on the primary sensor state, which becomes unreliable after latch engagement.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If no detection method is used while motor is off, then the system is simpler, but latch failure and over-travel adjustments cannot be detected

Engineering Contradiction:

Improvedetection system complexityVSAvoidlatch and position monitoring reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent makes the motor coils serve multiple functions: they act as both actuators for platen movement and as sensors for position detection through back-EMF measurement. This multi-functionality eliminates the need for separate sensing components, maintaining system simplicity while enabling comprehensive monitoring of latch engagement and platen position even when the motor is deactivated.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The motor system performs self-diagnosis by using its own coils to detect position and latch status through back-EMF measurement. The system monitors itself without requiring external sensors or additional complexity, allowing it to detect latch failures and over-travel conditions using resources already present in the motor assembly.

Inventive Principle:

Principle #25Self-service

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

Enables accurate detection of platen assembly movement and latch engagement status, ensuring consistent and safe operation by allowing for precise tracking of the platen's position and preventing over-travel, even when the motor is deactivated, thus improving cooking performance and safety.

Implementation Method 1

shorting a motor coil of a motor operable to move an second platen assembly with respect to a first platen assembly so that back EMF causes current to flow in the motor coil in response to mechanical movement of the upper platen assembly

Methodology Applied

Scientific EffectBack EMF: Electromagnetic Induction

Data Source

PatentUS11051653B2Grill system and method for detecting movement when motor is “off”

Publication Date: 2021.07.06 TAYLOR COMMERCIAL FOODSERVICE LLC

AI summary

A grill including a first platen assembly, an second platen assembly movable with respect to the first platen assembly, a motor operable to move the second platen assembly with respect to the first platen assembly, and a control operable to measure movement of the second platen assembly with respect to the first platen assembly while the motor is off.