Shared-Coil Inductive Sensing for Transient-Free Actuator Position Estimation
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Solution Overview
Problem
Existing methods for monitoring complex impedances in haptic transducers, such as those used in vibro-haptic systems, face challenges in accurately measuring displacement due to variations in individual transducers and environmental factors, leading to inefficiencies in generating precise vibrations and potentially causing damage to the transducers.
Innovation Solution
A system utilizing an electromagnetic actuator with two coils and an inductance sensing subsystem that alternates between driving and sensing coils to determine displacement based on measured inductance, allowing for precise estimation and application of state variables to maintain accurate impedance monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single coil is used for both driving and sensing in an electromagnetic actuator, then device complexity is reduced, but measurement precision deteriorates due to transient artifacts when switching between driving and sensing modes
Solution Approach 1:
The patent divides the single coil's operational timeline into distinct segments: a driving phase where the coil generates electromagnetic force, and a sensing phase where the same coil measures inductance to determine displacement. This temporal segmentation allows the coil to perform both functions without physical duplication, reducing device complexity while maintaining measurement capability.
Solution Approach 2:
The patent applies preliminary action by implementing a smoothing filter before the inductance measurement to pre-process the signal and remove transient artifacts caused by switching. This preliminary signal processing ensures that the displacement measurement remains precise despite using a shared coil for both driving and sensing functions.
2Measurement precision
If displacement measurement is improved using inductance sensing, then transducer protection and control precision are enhanced, but device complexity increases due to additional sensing coils
Solution Approach 1:
The patent makes the coil universal by enabling it to perform multiple functions: electromagnetic actuation during the driving phase and inductance-based displacement sensing during the sensing phase. This multi-functionality eliminates the need for separate sensing coils, achieving precise displacement measurement without increasing device complexity.
Solution Approach 2:
The patent implements periodic action by alternating between driving and sensing phases in a cyclic manner. The coil periodically switches between generating electromagnetic force and measuring inductance, allowing both actuation and precise measurement functions to be achieved through time-division multiplexing without requiring additional hardware.
3Measurement precision
If the sensing phase duration is extended to improve measurement accuracy, then displacement precision improves, but productivity deteriorates due to reduced driving time
Solution Approach 1:
The patent uses periodic action by establishing a cyclic operation mode where the coil alternates between driving phase and sensing phase. By optimizing the duty cycle and timing of these periodic phases, the system achieves both sufficient measurement accuracy and adequate driving time for effective vibration generation, resolving the trade-off between precision and productivity.
Solution Approach 2:
The patent applies dynamics by making the phase durations adaptive rather than fixed. The controller dynamically adjusts the length of driving and sensing phases based on operational requirements, allowing the system to optimize the balance between measurement precision and vibration generation efficiency in real-time conditions.
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 enables more precise control of haptic transducer displacement, reducing the risk of damage and improving the efficiency of vibration generation by accurately measuring and managing displacement, thus enhancing the performance of vibro-haptic systems.
Implementation Method 1
determine a displacement of the electromagnetic actuator based on a measurement of estimated inductance of the sensing coil
Implementation Method 2
a first coil configured to drive mechanical displacement of the electromagnetic actuator, a second coil configured to drive mechanical displacement of the electromagnetic actuator
Data Source
AI summary
A system may include an electromagnetic actuator, a first coil configured to drive mechanical displacement of the electromagnetic actuator, a second coil configured to drive mechanical displacement of the electromagnetic actuator, and an inductance sensing subsystem having an inductance sensing path coupled to the first coil and the second coil. The inductance sensing subsystem may be configured to select one of the first coil and the second coil for driving mechanical displacement of the electromagnetic actuator, select the other of the first coil and the second coil as a sensing coil for sensing displacement of the electromagnetic actuator, determine a displacement of the electromagnetic actuator based on a measurement of estimated inductance of the sensing coil, and when switching selection of the sensing coil from the first coil to the second coil determine the displacement of the first coil based on a measured inductance of the first coil at approximately the time of switching selection, estimate state variables of the inductance sensing path to be used with the second coil based on the displacement, and apply the state variables to the inductance sensing path after switching selection of the sensing coil from the first coil to the second coil.