Grill Platen Position Sensing Using Back-EMF When Motor Is Off
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Solution Overview
Problem
Conventional grills face challenges in accurately detecting the position of the platen assemblies, particularly when the motor is off, which can lead to issues like latch failure and over-travel adjustments, affecting the cooking process.
Innovation Solution
A system that includes a motor with a control mechanism to measure current flow caused by back EMF, allowing for the detection of platen position, latch failure, and over-travel adjustments without the motor being actively powered, using a spring mechanism to bias the platen assembly and a control module to process current samples for precise position tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the motor is turned off after solenoid latch engagement to allow upper platen to rise under spring bias, then energy consumption is reduced and mechanical operation is enabled, but position detection becomes inaccurate or impossible
Solution Approach 1:
The patent replaces traditional mechanical position detection methods with electromagnetic field-based detection. By using the motor's electromagnetic field properties (back EMF) to detect position rather than mechanical sensors, the system maintains detection capability while the motor is off, resolving the contradiction between energy savings and position measurement accuracy.
Solution Approach 2:
The patent changes the detection parameter from requiring active motor operation to utilizing electromagnetic induction principles that work with passive motor coils. By shorting the motor coils and measuring induced currents from platen movement, the system detects position without active motor power, enabling energy-efficient operation while maintaining detection precision.
2Reliability
If a sensor is used to identify when the upper platen is closed for solenoid latch engagement, then latch timing is improved, but the sensor shows false open state after latch engagement when motor is turned off
Solution Approach 1:
The patent replaces mechanical/optical sensors with electromagnetic field-based detection using the motor itself. The motor coils act as sensors through electromagnetic induction, detecting platen position and movement without requiring separate sensor hardware. This eliminates the false reading problem because the detection method works independently of motor power state.
Solution Approach 2:
The patent makes the motor serve dual functions: both as the actuator for moving the platen and as the sensor for detecting platen position and movement. By utilizing the motor coils for both driving and sensing purposes, the system eliminates the need for separate sensors and maintains continuous position information throughout the operation cycle.
3Productivity
If the solenoid latch is engaged immediately when sensor shows closed state, then cooking cycle time is reduced, but the latch may prevent full closing of the platen
Solution Approach 1:
The patent implements continuous feedback monitoring of platen position and movement through electromagnetic detection. The system monitors platen closure progress in real-time and provides feedback to determine the optimal latch engagement moment, ensuring the platen is fully closed before latching occurs. This prevents both premature latching and ensures precise closing.
Solution Approach 2:
The patent performs preliminary detection and monitoring of platen position before initiating latch engagement. By continuously monitoring platen closure through electromagnetic field changes and determining when full closing is achieved, the system prepares for optimal latch timing, ensuring precise closing while maintaining efficient cycle operation.
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 smooth operation of the grill by accurately detecting platen movement and latch engagement, even when the motor is off, preventing over-travel and ensuring consistent cooking results without requiring hardware changes or additional costs.
Implementation Method 1
shorting a motor coil of the 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
Data Source
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.