Transducer Excursion Limiting via Electrical Model Threshold
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Solution Overview
Problem
Haptic transducers face challenges in protecting against excessive excursion, which can lead to damage due to the difficulty in measuring and controlling the maximum excursion, especially in scenarios where direct laser measurement is unsuitable or impractical, such as in the production of mobile devices.
Innovation Solution
A method and controller are introduced to limit the transducer signal based on a stimulus input signal designed to cause the transducer to reach a maximum excursion, determining a threshold electrical response in an electrical model of the transducer to prevent excessive excursion, using a purely electrical model to predict and manage the transducer's behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct laser measurement is used to measure transducer excursion, then measurement precision is improved, but device complexity and ease of manufacture deteriorate due to the need to open the housing and perform difficult measurements on statistical sets of components
Solution Approach 1:
The patent introduces an intermediary electrical model that correlates electrical responses with mechanical excursion. Instead of directly measuring physical displacement with a laser, the system uses electrical measurements (voltage, current) as intermediaries that can be correlated to excursion through a pre-established electrical model, thereby avoiding the complexity of direct optical measurement while maintaining measurement capability
Solution Approach 2:
The patent replaces the mechanical/optical measurement system (laser displacement sensor requiring open housing) with an electrical measurement system. The electrical model allows excursion to be inferred from electrical responses, substituting a complex mechanical measurement approach with a simpler electrical one that can be performed on closed devices
2Ease of operation
If the transducer housing is opened to allow laser measurement, then measurement accessibility is improved, but manufacturing precision and reliability deteriorate due to modifications to the component and inability to mount the modified component in the actual end product
Solution Approach 1:
The electrical model serves as an intermediary that allows measurement without physical access to the moving mass. Electrical responses can be measured through existing terminals on the closed transducer, and the electrical model translates these responses into excursion information, eliminating the need to open the housing and maintain component integrity
Solution Approach 2:
The patent creates an electrical model (a virtual copy of the transducer's behavior) that replicates the relationship between electrical inputs and mechanical outputs. This electrical copy allows measurements to be performed on the electrical domain without affecting the physical transducer structure, preserving manufacturing precision and component integrity
3Measurement precision
If a stimulus input signal is used to determine maximum excursion, then measurement accuracy is improved, but productivity deteriorates due to the time-consuming process of determining threshold electrical response
Solution Approach 1:
The patent performs preliminary action by pre-determining the threshold electrical response through a stimulus signal test during the design or initial calibration phase. This threshold is then stored and used for rapid excursion protection during normal operation, eliminating the need to repeatedly perform time-consuming stimulus tests while maintaining accurate maximum excursion determination
Solution Approach 2:
The electrical model is pre-established with known relationships between electrical responses and excursion. The threshold electrical response corresponding to maximum excursion is determined in advance through stimulus signaling, allowing rapid real-time protection without repeated measurement cycles, thus improving productivity after initial setup
4Reliability
If the transducer signal is limited based on electrical model threshold, then transducer reliability is improved, but device complexity increases due to the need for electrical modeling and signal processing
Solution Approach 1:
The patent implements feedback by continuously monitoring the electrical response (voltage, current) and comparing it against the pre-determined threshold electrical response in the electrical model. When the threshold is approached, the system provides feedback to limit the transducer signal, creating a closed-loop protection system that enhances reliability while using simple comparison logic rather than complex control algorithms
Solution Approach 2:
The electrical model acts as a virtual copy of the transducer's mechanical behavior. By working with this electrical copy rather than directly controlling mechanical parameters, the system achieves reliable excursion protection through electrical domain operations that are computationally simpler and require less complex hardware than direct mechanical sensing and control would demand
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 effectively protects the transducer from over-driving by limiting the electrical response to a predetermined threshold, ensuring the transducer operates within safe excursion limits without the need for direct measurement, facilitating quality control in production environments.
Implementation Method 1
one or more coils of wire 108 may apply electromagnetic force to the magnets, thereby moving the moving mass 102 from the rest position
Implementation Method 2
The moving mass 102 is centred in a rest position by a pair of springs 104a and 104b
Data Source
AI summary
Embodiments described herein relate to methods and apparatus for limiting the excursion of a transducer. The method comprises receiving a transducer signal; and limiting the transducer signal or a signal derived therefrom to generate a limited transducer signal for input into the transducer such that an electrical response caused by the limited transducer signal in an electrical model of the transducer would be less than a threshold electrical response, wherein the threshold electrical response has been determined by: inputting a stimulus input signal into the electrical model of the transducer, wherein the stimulus input signal is designed to cause the transducer to reach a maximum excursion; and determining the threshold electrical response as a maximum of the electrical response caused by the stimulus input signal in the electrical model of the transducer.