Double-Wound Haptic Actuator Coil for Temperature-Independent Velocity Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional haptic engines face challenges in accurately sensing the velocity of a haptic actuator's moving mass due to temperature variations, which affect coil resistance, leading to errors in back EMF voltage measurement, and existing solutions either require real-time impedance measurement, add audible tones, or waste volume by using a dummy coil.
Innovation Solution
A haptic engine with a double-wound driving coil, where both coils are thermally and mechanically coupled, allowing velocity sensing independently of coil resistance, eliminating the need for real-time impedance measurement and avoiding additional volume usage by utilizing both coils for driving.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single-coil haptic actuators are used for velocity sensing, then the structure is simple, but temperature variations cause coil resistance changes that lead to measurement errors
Solution Approach 1:
The single coil is segmented into two separate coils wound around the same core. One coil serves as the driving coil while the other serves as the sensing coil. This segmentation allows independent optimization of each coil's function, with the sensing coil specifically designed to measure back EMF without being affected by resistance changes in the driving coil.
Solution Approach 2:
A second coil is introduced as an intermediary sensing element that indirectly measures the magnetic field changes caused by mass velocity. This intermediary coil allows velocity sensing without directly exposing the measurement process to temperature-induced resistance variations in the primary driving coil.
2Measurement precision
If real-time impedance measurement is implemented to compensate for temperature effects, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The sensing coil generates its own back EMF signal that directly reflects mass velocity. This self-service approach eliminates the need for external impedance measurement circuits or complex compensation algorithms, as the sensing coil inherently provides temperature-independent velocity information through its back EMF output.
3Measurement precision
If a dummy coil is added for temperature compensation, then measurement accuracy improves, but volume increases
Solution Approach 1:
The sensing coil is merged with the driving coil by winding both coils around the same magnetic core in close proximity. This merging allows the sensing function to be integrated into the existing actuator structure without requiring additional space, as both coils share the same magnetic path and physical envelope.
Solution Approach 2:
The second coil serves multiple functions: it acts as a sensing element for velocity measurement, utilizes the existing magnetic field generated by the driving coil, and shares the same magnetic core structure. This multi-functionality eliminates the need for separate dedicated sensing components that would increase actuator volume.
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 solution robustly addresses temperature variations, reduces the need for factory calibration, eliminates acoustic noise and power consumption, and ensures effective driving of the haptic actuator's mass by utilizing both windings for driving.
Implementation Method 1
a back electromotive force voltage, or simply bEMF, induced in the driving coil, or simply coil, is related to the velocity of the moving mass
Implementation Method 2
A haptic actuator in which a mass is driven using electromagnetic forces to move relative the haptic actuator's frame
Data Source
AI summary
A haptic engine includes a linear resonant actuator having a double-wound driving coil which is used for sensing a back electromotive force (EMF) voltage independently of the coil resistance, thus minimizing the back EMF voltage's sensitivity to temperature.