Amplifier Feedforward Compensation for Accurate Haptic Displacement Sensing
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Solution Overview
Problem
Existing methods for estimating impedance and sensing displacement of electromagnetic transducers, such as haptic actuators, are inefficient and costly, particularly due to the use of Hall sensors, and are affected by variations in transducers and user interactions.
Innovation Solution
An amplifier system with a first feedback loop, a sense resistor, a second control loop outside the feedback loop, and a common-mode feedforward circuit to minimize signal-dependent common-mode feedback, allowing for accurate regulation and sensing of physical quantities associated with the amplifier, including displacement measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall sensors are used for displacement sensing, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces Hall sensors (mechanical/electromagnetic sensing system) with an electrical measurement system that uses voltage division across the sense resistor to determine displacement. The current sensor measures voltage drops which are then used to calculate displacement through established electrical relationships, eliminating the need for complex Hall sensor assemblies.
Solution Approach 2:
The patent introduces a sense resistor as an intermediary element that converts displacement information into measurable voltage signals. This intermediary component enables indirect measurement of displacement through electrical parameters, providing a simpler alternative to direct Hall sensor measurement while maintaining measurement precision.
2Measurement precision
If sample-to-sample variations and temporal component changes are accounted for, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the measured voltage across the sense resistor is continuously monitored and used to adjust the driving signal. This feedback loop compensates for sample-to-sample variations and temporal changes in the haptic transducer characteristics, maintaining measurement precision without requiring complex preprocessing of variation data.
Solution Approach 2:
The system uses the haptic transducer's own electrical characteristics (voltage drops across the sense resistor) to self-diagnose and compensate for variations in its performance. By monitoring its own electrical parameters during operation, the system automatically adjusts for drift and variations without external calibration or complex control algorithms.
3Reliability
If displacement protection algorithms are optimized with accurate measurement, then reliability is improved, but loss of time increases due to measurement processing
Solution Approach 1:
The patent performs preliminary calibration and characterization of the sense resistor and haptic transducer relationship during manufacturing or initial setup. This preliminary action establishes baseline parameters that enable real-time displacement calculation without requiring complex processing during operation, thus improving reliability while minimizing measurement processing time.
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 reduces the disadvantages of existing methods by enabling precise control and measurement of displacement, optimizing haptic feedback, and reducing costs associated with displacement protection algorithms.
Implementation Method 1
a sense resistor for sensing a physical quantity associated with the amplifier
Implementation Method 2
a common-mode feedforward circuit coupled to the sense resistor and configured to minimize effects of a signal-dependent common-mode feedback of the sense resistor
Data Source
AI summary
An amplifier system may include a first feedback loop coupled between an output of an amplifier to an input of a modulator for regulating an output voltage driven at the output of the amplifier to a first terminal of a load of the amplifier system, a sense resistor for sensing a physical quantity associated with the amplifier, a second control loop coupled to the sense resistor such that the sense resistor is outside of the second control loop, the second control loop configured to regulate a common-mode voltage at a second terminal of the load, and a common-mode feedforward circuit coupled to the sense resistor and configured to minimize effects of a signal-dependent common-mode feedback of the sense resistor.