Testing device for controllably applying external force to flexible sensor at 0-20Hz

Abstract

The invention discloses a testing device for controllably applying external force to a flexible sensor at 0-20Hz. The main body structure comprises a transmission unit, a numerical control unit, a sensing unit and a power supply unit. The transmission unit adopts a crank sliding block mechanism driven by a stepping motor, and is sequentially connected with a counterweight inertia wheel, a connecting rod and a movable sliding block through two joint bearings, so that the rotary motion of the inertia wheel is converted into the accurate linear reciprocating motion of the movable sliding block. The numerical control unit accurately adjusts the frequency of the reciprocating motion within the range of 0-20 Hz through a programmable stepping motor controller. The sensing unit comprises a fixed sliding block which is coaxially and reversely aligned with the movable sliding block. An embedded rigid pressure sensor and a to-be-tested flexible sensor fixed on the surface of the rigid pressure sensor are assembled on the fixed sliding block. A low-creep polyether block amide elastic block body with a spiral twenty-four-face body structure is installed on the surface, facing the fixed sliding block, of the movable sliding block, and the output value is accurately regulated and controlled within the range of 0-25 N by controlling the deformation quantity of the elastic block body.

Description

Technical Field

[0001] This invention relates to the field of flexible sensor performance testing technology, specifically a testing device for controllably applying external force to a flexible sensor in the range of 0 to 20 Hz. Background Technology

[0002] Flexible sensors, especially flexible pressure sensors, are core sensing devices in personalized medicine, human-computer interaction, the Internet of Things, and intelligent robotics. Their pressure sensing performance, such as sensitivity, response time, hysteresis, and dynamic response range, directly affects the accuracy of signal acquisition. With increasingly complex application scenarios, the demand for sensors capable of accurately capturing human physiological signals (such as arterial pulse, cardiac mechanical vibration, respiration, and gait signals) is constantly increasing. The frequencies of these signals are typically below 20Hz. To comprehensively and accurately evaluate and optimize the performance of flexible sensors, there is an urgent need to develop a testing device capable of stably and accurately dynamically applying external forces within the main human activity frequency range of 0–20Hz.

[0003] However, flexible pressure sensors only began to develop rapidly in the 21st century, and testing instruments for their performance are still immature. Existing testing instruments are usually based on screw / rail transmission mechanisms, which can only detect the performance of flexible sensors under low-frequency (usually no more than 2Hz) pressure. For example, the patent CN115452566A, "A Flexible Mechanical Sensor Testing System," provides a flexible mechanical sensor testing system based on a screw / rail transmission mechanism. Although it has the advantage of high accuracy under low-speed displacement, its transmission principle is essentially designed for precise displacement or static force amplification, and cannot achieve high-frequency reciprocating motion, making it difficult to meet the performance evaluation requirements of flexible sensors in high-frequency dynamic scenarios. In addition, although a vibrator based on electromagnetic induction can apply high-frequency pressure to the flexible pressure sensor, its shortcomings are that the output pressure and unidirectional movement distance of the vibrator head decrease with increasing frequency, resulting in unstable output force of the instrument at different frequencies, and it is not suitable for testing the full-range sensing performance of thicker samples. For example, the patent CN120576927A, entitled "Dynamic and Static Testing Device and Method for Flexible Pressure Sensors," provides a testing device based on the principle of electromagnetic induction and using an exciter as the driving source. Although this device expands the dynamic testing capability to some extent, it still cannot achieve stable output in the high-frequency range (10Hz~20Hz), making it difficult to accurately calibrate the dynamic performance of flexible pressure sensors across the entire operating frequency band. Summary of the Invention

[0004] The problem to be solved by the present invention is that existing mechanical performance testing equipment for flexible sensors generally suffers from insufficient dynamic loading capacity, narrow output frequency range (usually not exceeding 2Hz) or unstable high-frequency output, and difficulty in applying controllable and quantifiable output force to thick flexible sensors. As a result, it is difficult to meet the requirements for accurate, stable and repeatable dynamic mechanical testing of flexible sensors in the main frequency range of human activities (0-20Hz).

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A testing device for controllably applying external force to a flexible sensor within a 0-20Hz frequency range includes a transmission unit, a numerical control unit, a sensing unit, a power supply unit, and a base bracket. The transmission unit, numerical control unit, sensing unit, and power supply unit are fixed to the base bracket. The transmission unit includes a stepper motor, an inertia wheel, a first joint bearing, a connecting rod, a second joint bearing, a movable slider, a low-creep polyether block amide elastic block with a helical icosahedral structure fixed to the surface of the movable slider, and a linear guide rail. The inertia wheel is mounted on the stepper motor, and the inertia wheel, connecting rod, and movable slider are sequentially connected via the first and second joint bearings. The movable slider can perform linear reciprocating motion on the linear guide rail. The numerical control unit precisely adjusts the frequency of the reciprocating motion within the 0-20Hz range using a programmable stepper motor controller and an operation panel. The sensing unit includes a fixed slider and a rigid pressure sensor embedded in the fixed slider. The fixed slider is used to support the flexible sensor under test. A screw is embedded in the fixed slider to fix it to the base bracket at the target position. The rigid pressure sensor is used to record the pressure value and output frequency applied to the flexible sensor by the transmission unit. The fixed slider and the moving slider are coaxially aligned in opposite directions. Initially, the distance between the moving slider and the fixed slider is at its maximum. Subsequently, as the moving slider approaches the fixed slider, the low-creep polyether block amide elastic block with a helical icosahedral structure contacts and deforms with the flexible sensor under test. By adjusting the position of the fixed slider, the maximum deformation of the low-creep polyether block amide elastic block with a helical icosahedral structure is controlled, achieving precise control of the maximum output force acting on the flexible sensor under test. When the moving slider and the fixed slider are closest, the deformation of the low-creep polyether block amide elastic block with a helical icosahedral structure reaches its maximum, and the output force applied to the flexible sensor reaches its maximum. Subsequently, the distance between the moving slider and the fixed slider gradually increases. When the distance between the moving slider and the fixed slider reaches its maximum again, the testing device completes one working cycle. The power supply unit is electrically connected to the CNC unit and the transmission unit, providing power to the entire testing device.

[0007] Preferably, the surface of the low-creep polyether block amide elastic block with a helical icosahedral structure is hardened and polished to be smooth and flat, ensuring that the applied pressure is evenly distributed; the space filling rate of the low-creep polyether block amide elastic block with a helical icosahedral structure does not exceed 30%, the compression modulus does not exceed 15 kPa, the creep value does not exceed 2%, the deformation recovery rate within 1 ms after pressure removal is not less than 98%, and the precisely adjustable output force range achieved by deformation is 0 to 25 N.

[0008] Furthermore, the inertia wheel has a hollow structure, and its interior can be selectively filled with counterweights according to the requirements of the test frequency and output value to adjust its rotational inertia, thereby reducing motor torque pulsation, eliminating step loss, balancing the vibration generated by high-frequency reciprocating motion, and achieving stable output. Preferably, the counterweights are any one of lead beads or copper beads with a particle size of less than 1mm.

[0009] Preferably, the CNC unit can control the stepper motor to have a microstepping value of not less than 1600 steps / revolution, thereby achieving precise control of the output frequency and output value.

[0010] Preferably, the Young's modulus of the inertia wheel, the first joint bearing, the connecting rod, the second joint bearing, the moving slider, and the fixed slider is not less than 4 GPa.

[0011] Existing devices for applying force to flexible sensors typically only achieve precise, stable, and controllable force output within a low frequency range. When the required force output frequency for dynamic testing exceeds 2Hz, it becomes difficult to apply controllable, stable, and precise force to the flexible sensor, thus failing to meet the dynamic mechanical testing requirements of flexible sensors within the main frequency range of human activity (0–20Hz). This invention, however, couples a crank-slider mechanism with a low-creep elastic block, providing a testing device for controllably applying external force to a flexible sensor within the 0–20Hz range. Compared to existing technologies, the advantages of this invention are as follows.

[0012] 1. Traditional screw / rail-based transmission mechanisms struggle to meet high-frequency reciprocating loading exceeding 2Hz. This invention employs a crank-slider mechanism, achieving smooth reciprocating motion in the high-frequency range. The adjustable counterweight design of the inertia wheel effectively reduces motor torque pulsation and eliminates step loss, ensuring a stable output frequency throughout the 0–20Hz range. Unlike traditional electromagnetic exciters where pressure head displacement and output significantly decrease with increasing frequency, this invention's mechanical output mechanism maintains sufficient stroke and stable output amplitude in the high-frequency range, guaranteeing full-range calibration capability for thick samples or large-deformation flexible sensors.

[0013] 2. This invention utilizes a low-creep polyether block amide elastic block with a helical icosahedral structure. The high elastic recovery, low creep, and controllable deformation characteristics of the polyether block amide elastic block allow for precise setting of the maximum compression amount of the elastic block by adjusting the position of the fixed slider, thereby achieving high-precision, repeatable force control within the range of 0–25 N. The elastic block with the helical icosahedral structure has a low space-filling ratio, low compressive modulus, small creep, and fast deformation recovery. Under high-frequency loading, it can effectively avoid cumulative displacement drift, ensuring stable and highly repeatable loading force. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall structure of the device according to an embodiment of the present invention;

[0015] Figure 2 This is a schematic diagram of the device transmission unit and its components according to an embodiment of the present invention;

[0016] Figure 3 This is a schematic diagram of the numerical control unit and its components in an embodiment of the present invention;

[0017] Figure 4 The diagram (left) and exploded view (right) show the sensing unit and its components of the device according to an embodiment of the present invention. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. The following descriptions are only used to illustrate the technical solutions of the present invention and are not intended to limit it.

[0019] Example

[0020] like Figure 1 As shown in the figure, the present invention provides a test device for controllably applying external force to a flexible sensor in the range of 0 to 20 Hz, which mainly includes a transmission unit 1, a numerical control unit 2, a sensing unit 3, a power supply unit 4, and a base bracket 5 supporting the entire device.

[0021] Specifically, such as Figure 2As shown, the transmission unit 1 includes a stepper motor 6, an inertia wheel 7, a first joint bearing 8, a connecting rod 9, a second joint bearing 10, a movable slider 11, a low-creep polyether block amide elastic block 12 with a helical icosahedral structure fixed to the surface of the movable slider 11, and a linear guide rail 13. The inertia wheel 7 is mounted on the stepper motor 6, and the inertia wheel 7, connecting rod 9, and movable slider 11 are connected sequentially through the first joint bearing 8 and the second joint bearing 10. The movable slider 11 can perform linear reciprocating motion on the linear guide rail 13. The surface of the low-creep polyether block amide elastic block 12 with a helical icosahedral structure is hardened and polished, making it smooth and flat to ensure uniform pressure distribution. The space filling rate of the low-creep polyether block amide elastic block 12 with a helical icosahedral structure is 30%, its compressive modulus is 15 kPa, its creep value is 2%, and its deformation recovery rate within 1 ms after pressure removal is 98%. The precisely adjustable output force range achieved through deformation is 0–25 N. The inertia wheel 7 has a hollow structure, and its interior can be selectively filled with counterweights according to the test frequency and output force requirements to adjust its rotational inertia, thereby reducing motor torque pulsation, eliminating step loss, balancing the vibration generated by high-frequency reciprocating motion, and achieving stable output. The counterweights are lead beads with a particle size of less than 1 mm. The Young's modulus of the inertia wheel 7, connecting rod 9, and moving slider 11 is 4 GPa, and the Young's modulus of the first joint bearing 8 and the second joint bearing 10 is 15 GPa.

[0022] Specifically, such as Figure 3 As shown, the CNC unit 2 precisely adjusts the reciprocating motion frequency within the range of 0-20Hz via the programmable stepper motor controller 14 and the operation panel 15. The CNC unit 2 can control the stepper motor 6 to have a microstepping value of 1600 steps / revolution, thereby achieving precise control over the output frequency and output value. The programmable stepper motor controller 14 is electrically connected to the stepper motor 6, and the user can precisely set and adjust the rotational speed of the stepper motor 6 and the inertia wheel 7 through the operation panel 15, thereby controlling the reciprocating motion frequency of the moving slider 11.

[0023] Specifically, such as Figure 4 As shown, the sensing unit 3 includes a fixed slider 16 and a rigid pressure sensor 17 embedded in the fixed slider 16. The rigid pressure sensor 17 is embedded in a groove on the side of the fixed slider 16 facing the movable slider 11, and is used to collect and output the pressure value and output frequency applied to the flexible sensor 18 under test in real time and accurately. The fixed slider 16 and the movable slider 11 are coaxially aligned in opposite directions. The Young's modulus of the fixed slider 16 is 4 GPa. The fixed slider 16 is used to support the flexible sensor 18 under test, which is adhered to the fixed slider 16 with adhesive. The fixed slider 16 is fixed to the base bracket 5 at the target position by embedding screws in the fixed slider 16.

[0024] Specifically, the power supply unit 4 adopts an integrated power module, which is electrically connected to the CNC unit 2 and the transmission unit 1 to provide power to the entire testing device.

[0025] Specifically, the transmission unit 1, the sensing unit 3, and the power supply unit 4 are all fixedly installed on the base bracket 5 by bolts and nuts, forming a compact and stable integrated device.

[0026] The working principle of the test device for controllably applying external force to the flexible sensor is explained in detail below.

[0027] In the operation of this device, assuming the initial stage is when the distance between the movable slider 11 and the fixed slider 16 is at its maximum, as the inertia wheel 7 drives the connecting rod 9 to move the movable slider 11, as the movable slider 11 approaches the fixed slider 16, the low-creep polyether block amide elastic block 12 with a helical icosahedral structure contacts and deforms with the flexible sensor 18 under test. By adjusting the position of the fixed slider 16, the maximum deformation of the low-creep polyether block amide elastic block 12 with a helical icosahedral structure is controlled, thereby achieving precise control of the maximum output force applied to the flexible sensor 18 under test. When the distance between the movable slider 11 and the fixed slider 16 is closest, the deformation of the low-creep polyether block amide elastic block 12 with a helical icosahedral structure reaches its maximum, and the output force applied to the flexible sensor 18 under test reaches its maximum. Subsequently, the distance between the movable slider 11 and the fixed slider 16 gradually increases. When the distance between the movable slider 11 and the fixed slider 16 reaches its maximum again, the testing device completes one working cycle. As the inertia wheel 7 continues to move, a new working cycle begins. The motion trajectory and speed of the inertial wheel 7 are controlled by the numerical control unit 2.

[0028] This invention has been described through preferred embodiments. Those skilled in the art should understand that various modifications, variations, or equivalent substitutions can be made to the above features and implementation methods without departing from the spirit and scope defined by the claims. This invention is not limited to the specific embodiments disclosed in this specification; all technical solutions falling within the scope of protection of the claims of this application should be considered as falling within the protection scope of this invention.

Claims

1. A testing device for controllably applying an external force to a flexible sensor in the range of 0-20 Hz, characterized by: The application relates to a flexible sensor test device, which comprises a transmission unit (1), a numerical control unit (2), a sensing unit (3), a power supply unit (4) and a bottom bracket (5). The transmission unit (1) comprises a stepping motor (6), an inertial wheel (7), a first joint bearing (8), a connecting rod (9), a second joint bearing (10), a moving slider (11), a low-creep polyether block amide elastic block body (12) with a chiral 24-faced structure fixed on the surface of the moving slider (11) and a linear guide rail (13). The inertial wheel (7) is installed on the stepping motor (6) and is sequentially connected with the moving slider (11) through the first joint bearing (8) and the second joint bearing (10). The moving slider (11) can make linear reciprocating motion on the linear guide rail (13). The numerical control unit (2) can accurately adjust the frequency of the reciprocating motion in the range of 0-20 Hz through a programmable stepping motor controller (14) and an operation panel (15). The sensing unit (3) comprises a fixed slider (16) and a rigid pressure sensor (17) embedded in the fixed slider (16). The fixed slider (16) is used for bearing a flexible sensor (18) to be tested, the fixed slider (16) is fixed on the bottom bracket (5) at a target position by embedding a screw in the fixed slider (16); the rigid pressure sensor (17) is used for recording the pressure value and the output frequency of the transmission unit (1) applied to the flexible sensor (18) to be tested. The fixed slider (16) and the moving slider (11) are coaxially and oppositely aligned, in the process that the moving slider (11) approaches the fixed slider (16), the low-creep polyether block amide elastic block body (12) with the chiral 24-faced structure is in contact with the flexible sensor (18) to be tested and is deformed, the maximum deformation of the low-creep polyether block amide elastic block body (12) with the chiral 24-faced structure is adjusted by adjusting the position of the fixed slider (16), and the maximum output value acting on the flexible sensor (18) to be tested is accurately controlled.

2. The testing device for controllably applying an external force to a flexible sensor at 0-20 Hz according to claim 1, characterized in that: The surface of the low-creep polyether block amide elastic block body (12) with the chiral 24-faced structure is hardened and polished, and is smooth and flat; the space filling rate of the low-creep polyether block amide elastic block body (12) with the chiral 24-faced structure is not more than 30%, the compression modulus is not more than 15 kPa, the creep value is not more than 2%, the deformation recovery rate within 1 ms after pressure removal is not less than 98%, and the accurately adjustable output value range realized through deformation is 0-25 N.

3. The testing device of claim 1, wherein the testing device is configured to controllably apply an external force to the flexible sensor in a range of 0-20 Hz. The inertial wheel (7) is of a hollow structure, the inside of the inertial wheel (7) can be selectively filled with a counterweight according to the requirements of test frequency and output value, so as to adjust the rotational inertia, thereby weakening the motor torque pulsation, eliminating step loss, balancing the vibration generated by high-frequency reciprocating motion and realizing smooth output.

4. The testing device of claim 1, wherein the testing device is capable of applying an external force to the flexible sensor in a controllable manner in the frequency range of 0-20 Hz. The numerical control unit (2) can control the subdivision value of the stepping motor (6) to be not less than 1600 steps / revolution, so as to realize accurate control of the output frequency and the output value.

5. The testing device of claim 1, wherein the testing device is capable of applying an external force to the flexible sensor in a controllable manner in the frequency range of 0-20 Hz. The Young's modulus of the inertial wheel (7), the first joint bearing (8), the connecting rod (9), the second joint bearing (10), the movable slider (11) and the fixed slider (16) is not less than 4 GPa.

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