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CN-121994386-A - Flexible touch sensor and pressure touch measurement method thereof

CN121994386ACN 121994386 ACN121994386 ACN 121994386ACN-121994386-A

Abstract

The application provides a flexible touch sensor and a pressure touch measuring method thereof, wherein the flexible touch sensor comprises a piezoelectric micro-mechanical ultrasonic transducer PMUT array layer, a sensor module and a touch sensor, wherein the piezoelectric micro-mechanical ultrasonic transducer PMUT array layer is used for transmitting ultrasonic signals and receiving reflected ultrasonic signals; the flexible ultrasonic coupling layer is arranged between the PMUT array layer and the ultrasonic reflecting layer and is used for conducting ultrasonic signals and responding to external pressure to generate deformation in the thickness direction so as to change the propagation path length of the ultrasonic signals in the flexible ultrasonic coupling layer. According to the application, an ultrasonic reflection mechanism irrelevant to the target acoustic characteristics is realized in the PMUT flexible touch sensor for the first time, the problem of signal-to-noise ratio degradation in a low-impedance/sound-absorption target scene is fundamentally solved, and the universality and measurement consistency of the sensor are obviously improved.

Inventors

  • ZHANG LEI
  • Chen haotian

Assignees

  • 天津大学

Dates

Publication Date
20260508
Application Date
20260213

Claims (10)

  1. 1. A flexible tactile sensor comprising a housing, a first sensor and a second sensor, characterized by comprising the following steps: a piezoelectric micromachined ultrasonic transducer PMUT array layer (4) for transmitting ultrasonic signals and receiving reflected ultrasonic signals; The ultrasonic reflection layer (1) is arranged on the sound wave emission path of the PMUT array layer (4) and is used for reflecting the ultrasonic signals; And the flexible ultrasonic coupling layer (2) is arranged between the PMUT array layer (4) and the ultrasonic reflecting layer (1) and is used for conducting the ultrasonic signals and generating deformation in the thickness direction in response to external pressure so as to change the propagation path length of the ultrasonic signals in the flexible ultrasonic coupling layer (2).
  2. 2. The flexible tactile sensor according to claim 1, wherein the acoustic impedance of the ultrasound reflecting layer (1) is greater than the acoustic impedance of the flexible ultrasound coupling layer (2) to form an ultrasound reflecting interface at the interface between the two.
  3. 3. The flexible tactile sensor according to claim 1, wherein the PMUT array layer (4) comprises a flexible substrate and a plurality of PMUT cells (3) integrated on the flexible substrate, the flexible substrate being a printed circuit board, PCB, or a flexible thin film substrate.
  4. 4. A flexible tactile sensor according to claim 1, wherein the flexible ultrasound coupling layer (2) is made of an acoustically transparent elastomer with a preset elastic modulus for uniformly transforming an external pressure into a linear elastic deformation.
  5. 5. A pressure tactile measurement method based on a flexible tactile sensor according to any one of claims 1 to 4, characterized by comprising the steps of: Driving the PMUT array layer (4) to transmit ultrasonic pulse signals to the flexible ultrasonic coupling layer (2); Receiving an ultrasonic echo signal reflected by the ultrasonic reflecting layer (1) and converting the ultrasonic echo signal into an electric signal; haptic pressure information applied to the sensor is determined from a time of flight ToF between the ultrasonic pulse signal and the ultrasonic echo signal and an amount of change in the time of flight ToF relative to a reference ToF.
  6. 6. A pressure tactile measurement method according to claim 5, wherein the frequency of the ultrasonic pulse signal is matched to the mechanical resonance frequency of the PMUT cell (3), said resonance frequency being in the range of 1-10MHz.
  7. 7. The pressure tactile measurement method according to claim 5, wherein said determining tactile pressure information applied to said sensor from a time of flight ToF between said ultrasonic pulse signal and said ultrasonic echo signal and an amount of change in said time of flight ToF relative to a reference ToF, comprises the steps of: based on a preset ToF variable quantity-pressure mapping model, converting the ToF variable quantity of each PMUT unit (3) in the PMUT array layer (4) into normal pressure components corresponding to sensing positions respectively; and according to the normal pressure components and the spatial arrangement positions of the PMUT array layer (4), calculating pressure spatial distribution information on the contact surface of the sensor.
  8. 8. The method of claim 7, further comprising the steps of, after said calculating the information of the pressure spatial distribution on the sensor contact surface: and according to the pressure space distribution information, solving multidimensional touch information, wherein the multidimensional touch information comprises surface texture morphology information of a contact target and/or a three-dimensional contact force vector acting on the surface of the sensor.
  9. 9. The method of pressure tactile measurement according to claim 5, further comprising the steps of: transmitting a diagnostic pulse signal to at least one PMUT cell (3); receiving at least one characteristic echo signal formed by the diagnosis pulse signal through the internal interface of the ultrasonic coupling layer or the reflection of the ultrasonic reflection layer (1); Extracting at least one characteristic parameter of the amplitude, the center frequency or the waveform distortion rate of the characteristic echo signal, and comparing the characteristic parameter with a preset healthy baseline; and when the degree of the deviation of the characteristic parameter from the preset health baseline exceeds a threshold range, generating a health state degradation early warning signal of a corresponding PMUT unit (3) or a corresponding sensing area.
  10. 10. The method according to claim 5, wherein the determining the tactile pressure information applied to the sensor according to the time of flight ToF between the ultrasonic pulse signal and the ultrasonic echo signal and the amount of change in the time of flight ToF relative to a reference ToF, further comprises the steps of: Acquiring real-time ToF measurement values of at least one non-pressure-acting PMUT unit (3), wherein the non-pressure-acting PMUT unit (3) is a PMUT unit (3) which is judged to not bear external pressure at the current moment; Correlating the real-time ToF measured value of the PMUT unit (3) without pressure effect with sound velocity drift caused by environmental disturbance, and constructing a dynamic sound velocity compensation model; and carrying out sound velocity drift correction on the ToF measured value of the PMUT unit (3) subjected to external pressure based on the dynamic sound velocity compensation model so as to eliminate the influence of environmental temperature, humidity or device aging factors on the tactile pressure measurement result.

Description

Flexible touch sensor and pressure touch measurement method thereof Technical Field The invention belongs to the technical field of tactile perception and intelligent detection, and particularly relates to a flexible tactile sensor and a pressure tactile measurement method thereof. Background Flexible tactile sensors based on Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) are a research hotspot in the field of robotic electronic skin. The conventional PMUT flexible touch sensor generally adopts a measurement mode that a PMUT array is packaged in a flexible medium, the sensor is in direct contact with a measured target, and the surface of the target is used as an ultrasonic reflection interface. The PMUT transmits ultrasonic pulses to the target, and returns the ultrasonic pulses after being reflected by the surface of the target, and the contact force is calculated by measuring the flight time or amplitude change of ultrasonic signals. However, this mode has technical drawbacks: the echo signal quality of the sensor is highly dependent on the surface acoustic properties of the object being measured. When the target is a low-impedance material (such as human skin, silicone rubber, fabric, foam) or the surface is in a sound absorption structure, the ultrasonic signals are transmitted or dissipated in a large amount at the interface of the target, so that the echo amplitude is weak, the signal-to-noise ratio is suddenly reduced, and even effective reflection cannot be formed. In addition, uncertainty in the contact state (e.g., wetting, contamination, non-conformal contact) further exacerbates fluctuations in the echo signal. The above problems lead to two major bottlenecks faced by existing PMUT flexible tactile sensors in practical applications: The universality is poor, the measurement sensitivity difference of the same sensor to targets with different materials is obvious, and the specific application scene needs to be recalibrated; The signal-to-noise ratio is low, and the effective measurement range is severely limited under the common low-impedance target scenes such as medical rehabilitation, man-machine interaction and the like. Therefore, how to construct an ultrasonic touch sense architecture which is irrelevant to a target and always has high signal to noise ratio on the premise of not depending on the acoustic characteristics of the target is a key technical problem to be solved in the field. Disclosure of Invention In view of the foregoing drawbacks or shortcomings of the prior art, a flexible tactile sensor and a pressure tactile measurement method thereof are provided. In a first aspect, the present application provides a flexible tactile sensor comprising: the piezoelectric micromachined ultrasonic transducer PMUT array layer is used for transmitting ultrasonic signals and receiving reflected ultrasonic signals; the ultrasonic reflection layer is arranged on the sound wave emission path of the PMUT array layer and used for reflecting the ultrasonic signals; The flexible ultrasonic coupling layer is arranged between the PMUT array layer and the ultrasonic reflecting layer and is used for conducting the ultrasonic signals and responding to external pressure to generate deformation in the thickness direction so as to change the propagation path length of the ultrasonic signals in the flexible ultrasonic coupling layer. According to the technical scheme provided by the application, the acoustic impedance of the ultrasonic reflection layer is larger than that of the flexible ultrasonic coupling layer, so that an ultrasonic reflection interface is formed at the interface of the ultrasonic reflection layer and the flexible ultrasonic coupling layer. According to the technical scheme provided by the application, the PMUT array layer comprises a flexible substrate and a plurality of PMUT units integrated on the flexible substrate, and the flexible substrate is a Printed Circuit Board (PCB) or a flexible film substrate. According to the technical scheme provided by the application, the flexible ultrasonic coupling layer is made of an acoustically transparent elastomer with a preset elastic modulus and is used for uniformly converting external pressure into linear elastic deformation. In a second aspect, the present application proposes a pressure tactile measurement method based on the above-mentioned flexible tactile sensor, comprising the steps of: Driving the PMUT array layer to transmit an ultrasonic pulse signal to the flexible ultrasonic coupling layer; receiving an ultrasonic echo signal reflected by the ultrasonic reflecting layer and converting the ultrasonic echo signal into an electric signal; haptic pressure information applied to the sensor is determined from a time of flight ToF between the ultrasonic pulse signal and the ultrasonic echo signal and an amount of change in the time of flight ToF relative to a reference ToF. According to the technical scheme provided by the applic