Piezoelectric Touch Sensing During Haptic Drive
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Solution Overview
Problem
Piezoelectric transducers face challenges in simultaneously providing haptic effects and sensing touch, as the signal produced by user touch is difficult to detect when the transducer is driven with a driving voltage.
Innovation Solution
A device with a piezoelectric transducer mechanically coupled to a touch surface and control circuitry that drives the transducer with a test voltage to measure a response voltage curve, calculates parameters to form a reference voltage curve, and compares it with a driving voltage curve to detect touch, even when the transducer is driven, by analyzing temporal changes, RC time constant, or vibrational amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the piezoelectric transducer is driven with a driving voltage to provide haptic effects, then the haptic feedback performance is improved, but the ability to detect touch signals deteriorates because the touch signal becomes difficult to detect during driving
Solution Approach 1:
The patent applies periodic action by using alternating driving and sensing phases. The piezoelectric transducer is driven with a driving voltage during a first time period to provide haptic feedback, then switched to a sensing phase during a second time period where touch signals are measured. This periodic switching between driving and sensing modes allows both haptic feedback and touch detection to function effectively without mutual interference.
Solution Approach 2:
The patent implements preliminary action by measuring the touch signal before the driving voltage is applied. The sensing phase occurs prior to the driving phase in each cycle, allowing the system to capture touch input signals before the haptic driving voltage is applied to the piezoelectric transducer. This ensures that touch signals are detected when the transducer is not being driven, avoiding signal masking.
2Device complexity
If a single piezoelectric transducer is used for both haptic effects and touch sensing, then device complexity is reduced, but the reliability of simultaneous functionality deteriorates due to signal interference
Solution Approach 1:
The patent uses periodic action to alternate between haptic driving and touch sensing operations with the single piezoelectric transducer. By switching the transducer between driving mode and sensing mode in time-divided manner, the system achieves reliable simultaneous functionality for both haptic feedback and touch detection without requiring multiple transducers.
Solution Approach 2:
The patent applies dynamics by making the operational state of the piezoelectric transducer time-varying. The transducer dynamically switches between being driven with a driving voltage and being used for sensing touch signals. This dynamic state switching allows a single transducer to reliably perform both haptic and sensing functions at different time intervals.
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 efficient detection of touch on the surface, including determining increasing or decreasing forces, even when the transducer is actively providing haptic feedback, by accurately comparing reference and measured voltage curves.
Implementation Method 1
a piezoelectric transducer mechanically coupled to the touch surface
Implementation Method 2
drive the piezoelectric transducer with a driving voltage
Data Source
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AI summary
It is an object to provide an electronic device for sensing and/or for providing a haptic effect. According to an embodiment, a device comprises a touch surface; a piezoelectric transducer mechanically coupled to the touch surface; and a control circuitry electrically coupled to the piezoelectric transducer, configured to: obtain at least one parameter describing a reference response of the piezoelectric transducer; form a reference voltage curve based on the at least one parameter; drive the piezoelectric transducer with a driving voltage; measure a voltage curve over the piezoelectric transducer; compare the reference voltage curve and the measured voltage curve; and detect a touch on the touch surface based on the comparison. A device, a method, and a computer program product are provided.