Grill Platen Movement Detection Using Motor Back-EMF
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Solution Overview
Problem
Conventional grill systems face challenges in accurately detecting the position and movement of the platen assembly when the motor is turned off, particularly in identifying latch failures and over-travel adjustments, which can affect the cooking process and food placement.
Innovation Solution
A system that includes a motor with a control mechanism to measure current flow caused by back EMF when the motor coil is shorted, allowing for the detection of the platen assembly's position and movement without the motor being active, using a spring mechanism to bias the platen assembly and a latch mechanism for coupling, enabling identification of latch failures and over-travel adjustments.
Engineering Contradictions & Design Principles
Engineering 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 latch can hold the platen position, but the system cannot detect platen movement or position changes
Solution Approach 1:
The patent replaces continuous motor operation with an intermittent measurement system. The motor is turned off to save energy, and position detection is achieved by momentarily shorting the motor coil to measure back EMF generated during platen movement, substituting continuous power consumption with periodic measurement pulses.
Solution Approach 2:
The control system implements periodic measurement by intermittently shorting the motor coil at specific intervals or events (such as during latch operation or when position changes are expected). This periodic measurement approach maintains detection capability while minimizing energy consumption compared to continuous monitoring.
2Reliability
If the hall effect sensor is adjusted to show closed state when solenoid is engaged, then latch engagement is detected, but the sensor shows open state when motor is off, preventing accurate position detection
Solution Approach 1:
The patent introduces back EMF measurement as an intermediary method for position detection. Instead of relying solely on the hall effect sensor which has state transition issues, the system uses the motor coil itself as a sensor by measuring the back EMF generated during platen movement, providing an alternative and more reliable position indication method.
Solution Approach 2:
The motor coil serves dual purposes: it acts as both the actuator for moving the platen and as the sensor for detecting platen position through back EMF measurement. This self-service approach eliminates the need for separate sensing hardware and resolves the hall effect sensor's state ambiguity problem.
3Measurement precision
If additional sensors or hardware are added to detect motor-off movement, then position detection accuracy improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent makes the motor coil multi-functional by using it both for actuation and for sensing. The same motor coil that drives the platen is also used to detect position through back EMF measurement during intermittent shorting, eliminating the need for additional sensors or hardware components.
Solution Approach 2:
The patent merges the actuator and sensor functions into a single component - the motor coil. By combining the motor's electrical coil with the sensing function through back EMF measurement, the system reduces hardware complexity while maintaining detection precision.
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 precise tracking of platen assembly movement and position, ensuring smooth closing, detecting latch failures, and adjusting for over-travel without requiring hardware changes or additional costs, thereby improving the cooking process and food placement accuracy.
Implementation Method 1
shorting a motor coil of the motor 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.