Flexible low-voltage electrical stimulation system for hand fine tactile feedback

Abstract

The invention provides a flexible low-voltage electrical stimulation system for hand fine tactile feedback, and belongs to the technical field of virtual reality, and the system comprises a main control computer device which is used for rendering a three-dimensional virtual scene, recognizing a user motion, and outputting a tactile control instruction; the tactile control instruction is used for coordinating and controlling tactile feedback; the virtual reality glasses are connected to the main control computer equipment and are used for presenting a three-dimensional virtual scene; the low-voltage driving device is used for outputting a corresponding stimulation signal based on the touch control instruction after receiving the touch control instruction; the voltage of the stimulation signal is lower than a preset voltage threshold; the flexible electrode array is connected to the low-voltage driving device and is used for applying electrical stimulation to the hand skin of the user based on the stimulation signal; the flexible electrode array comprises a plurality of groups of electrode pairs, and each group of electrode pairs are respectively connected to alternating signals which have the same parameters and have a phase difference of 180 degrees. According to the application, the sensory receptor in the skin can be activated through relatively low voltage, and the power utilization safety is guaranteed.

Description

Technical Field

[0001] This application relates to the field of virtual reality technology, and in particular to a flexible low-voltage electrical stimulation system for fine tactile feedback of the hand. Background Technology

[0002] Hand function is central to human interaction with the environment and manipulation of objects, accounting for approximately 90% of upper limb function. Fine motor control and precise manipulation rely heavily on accurate perception of tactile information. Tactile perception is one of the most fundamental human senses, playing a crucial role in exploring the environment, perceiving object characteristics, and achieving precise manipulation. Research shows that providing tactile feedback to users not only significantly improves task completion but also enhances user immersion during interaction. Therefore, hand-based interaction and corresponding tactile rendering have become key areas of development in tactile feedback technology.

[0003] Electrical stimulation, by applying electric current to skin receptors, can induce various tactile sensations such as vibration, touch, tingling, and pressure, offering advantages such as rapid response and high spatial resolution. Furthermore, electrical stimulation devices are lightweight and compact, facilitating high-density deployment in space-constrained areas. However, the limited surface area of ​​the hand restricts electrode size, typically requiring higher voltages for effective stimulation. Therefore, current electrotactile research often relies on high-voltage current pulses directly overcoming the impedance of the stratum corneum to elicit tactile sensations, which poses certain safety risks for users.

[0004] Therefore, how to achieve tactile perception of the hand under low driving voltage has become an urgent technical problem to be solved. Summary of the Invention

[0005] This application provides a flexible low-voltage electrical stimulation system for fine tactile feedback of the hand, which solves the problem of safety hazards caused by the use of high-voltage current pulses in tactile rendering in the prior art.

[0006] This application provides a flexible low-voltage electrical stimulation system for fine tactile feedback in the hand, comprising: The main control computer device is used to render three-dimensional virtual scenes, recognize user actions, and output haptic control commands; the haptic control commands are used to coordinate and control haptic feedback. Virtual reality glasses, connected to the main control computer device, are used to present the three-dimensional virtual scene; A low-voltage drive device is used to receive the tactile control command and output a corresponding stimulation signal based on the tactile control command; the voltage of the stimulation signal is lower than a preset voltage threshold. A flexible electrode array, connected to the low-voltage driving device, is used to apply electrical stimulation to the user's hand skin based on the stimulation signal; the flexible electrode array includes multiple sets of electrode pairs, each set of electrode pairs being connected to an alternating signal with the same parameters but a phase difference of 180°.

[0007] According to the flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application, the flexible electrode array includes: The base layer is made of an insulating material; A conductive layer, wherein the conductive layer is printed on the substrate layer in a preset pattern using stretchable conductive ink, for forming electrode patterns and signal transmission lines; An encapsulation layer, which is adjacent to the conductive layer, is made of insulating material and has openings reserved at the electrode positions; A hydrogel layer is attached to the opening of the encapsulation layer.

[0008] According to the present application, a flexible low-voltage electrical stimulation system for fine tactile feedback of the hand is provided, wherein the base layer is made of thermoplastic polyurethane material.

[0009] According to the present application, a flexible low-voltage electrical stimulation system for fine tactile feedback of the hand is provided, wherein the hydrogel layer is a mixture of N-hydroxyethyl acrylamide and 1 mol sodium chloride solution, and is cross-linked with polyethylene glycol diacrylate to form a three-dimensional ionic network.

[0010] According to the present application, a flexible low-voltage electrical stimulation system for fine tactile feedback of the hand is provided, wherein the flexible electrode array integrates 48 electrical tactile stimulation pixels; each pair of adjacent electrical tactile stimulation pixels forms a stimulation electrode pair, and a local current path is formed between the stimulation electrode pairs.

[0011] According to the flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application, the low-voltage driving device includes: The Bluetooth module is used to receive tactile control commands output by the main control computer device; A microcontroller, connected to the Bluetooth module, is used to control the electrical stimulation output circuit based on the tactile control commands; An electrical stimulation output circuit is connected to the microcontroller and is used to output corresponding stimulation signals.

[0012] According to the flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application, the electrical stimulation output circuit includes: A multi-channel digital-to-analog converter chip is connected to the microcontroller to generate multiple biphasic stimulation waveforms; An operational amplifier, connected to the multi-channel digital-to-analog converter chip, includes a non-inverting amplifier module and an inverting amplifier module, which are respectively used to construct a non-inverting amplified signal and an inverting amplified signal based on each of the biphasic stimulation waveforms. A multiplexer, connected to the operational amplifier, includes a first multiplexer module and a second multiplexer module, for outputting a stimulus signal.

[0013] According to the flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application, the electrical stimulation output circuit further includes: A current detection module is connected between the operational amplifier and the microcontroller to monitor the output signal of the operational amplifier. When the output signal is greater than a preset threshold, the microcontroller is instructed to turn off the output of the operational amplifier.

[0014] According to the present application, a flexible low-voltage electrical stimulation system for fine tactile feedback of the hand is provided, wherein the stimulation signal is composed of a high-frequency square wave carrier and a low-frequency sinusoidal modulation signal.

[0015] According to the flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application, the main control computer device is further used for: Using the Kalman filter algorithm, the predicted current at the next moment is estimated based on the real-time sampled current value, and the output voltage of the low-voltage drive device is determined based on the predicted current.

[0016] This application provides a flexible low-voltage electrical stimulation system for fine tactile feedback in the hand, comprising: a main control computer for rendering a three-dimensional virtual scene, recognizing user actions, and outputting tactile control commands; the tactile control commands are used to coordinate and control tactile feedback; virtual reality glasses, connected to the main control computer, for presenting the three-dimensional virtual scene; a low-voltage driving device for receiving the tactile control commands and outputting corresponding stimulation signals based on the tactile control commands; the voltage of the stimulation signals is lower than a preset voltage threshold; and a flexible electrode array connected to the low-voltage driving device for applying electrical stimulation to the user's hand skin based on the stimulation signals; the flexible electrode array includes multiple sets of electrode pairs, each set of electrode pairs being connected to alternating signals with the same parameters but a 180° phase difference. The flexible electrode array of this solution includes multiple sets of electrode pairs, forming local current pathways between the electrode pairs, which can activate sensory receptors in the skin with a relatively low voltage, inducing tactile perception and ensuring electrical safety. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application; Figure 2 This is a schematic diagram of the flexible electrode array provided in this application; Figure 3 This is a schematic diagram of the electrode arrangement array provided in this application; Figure 4 This is a schematic diagram of the low-voltage drive device provided in this application; Figure 5 This is a schematic diagram of the stimulation signal waveform provided in this application; Figure 6 These are schematic diagrams of the six grasping actions provided in this application; Figure 7 This is a schematic diagram of a resistance simulation experiment with voltage and current changes provided in this application; Figure 8 This is a schematic diagram showing the relationship between the threshold voltages that generate sensation, as provided in this application. Figure 9 This is a schematic diagram illustrating the relationship between stimulation frequencies of different hand areas provided in this application; Figure 10 This is a schematic diagram of the confusion matrix for classifying six grasping gestures based on tactile cues, provided in this application; Figure 11 This is a schematic diagram of the average stimulation voltage distribution provided in this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] It should be noted that in the description of the embodiments of this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. The terms "upper," "lower," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly, for example, they can be fixed connections, detachable connections, or integral connections; they can be mechanical connections or electrical connections; they can be direct connections or indirect connections through an intermediate medium; and they can be internal connections between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0021] The terms "first," "second," etc., used in this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, without limiting the number of objects; for example, a first object can be one or more. Furthermore, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects have an "or" relationship.

[0022] The following is combined Figures 1-11 This application describes a flexible low-voltage electrical stimulation system for fine tactile feedback of the hand, as provided in an embodiment of the present application.

[0023] Figure 1 This is a schematic diagram of the flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application, as shown in the figure. Figure 1 As shown, the system includes the following: The main control computer device is used to render three-dimensional virtual scenes, recognize user actions, and output haptic control commands; the haptic control commands are used to coordinate and control haptic feedback. Virtual reality glasses, connected to the main control computer device, are used to present the three-dimensional virtual scene; A low-voltage drive device is used to receive the tactile control command and output a corresponding stimulation signal based on the tactile control command; the voltage of the stimulation signal is lower than a preset voltage threshold. A flexible electrode array, connected to the low-voltage driving device, is used to apply electrical stimulation to the user's hand skin based on the stimulation signal; the flexible electrode array includes multiple sets of electrode pairs, each set of electrode pairs being connected to an alternating signal with the same parameters but a phase difference of 180°.

[0024] In this embodiment, virtual reality glasses are used to present an immersive three-dimensional virtual environment, providing users with a realistic visual experience and enhancing the immersiveness of the interaction. The main control computer, as the core of the system, is responsible for rendering the virtual scene, recognizing user actions, and coordinating the control of tactile feedback. A low-voltage drive device outputs precise low-voltage stimulation signals to drive the electrode array to generate the required tactile feedback, ensuring effective stimulation while guaranteeing user safety and comfort. The flexible electrode array is attached to the user's hand skin and can apply electrical stimulation to localized skin based on the virtual interactive content, simulating various tactile sensations such as touch and collision, achieving a realistic virtual tactile experience. The entire system works collaboratively, allowing users to experience a highly consistent immersive human-computer interaction in both visual and tactile aspects.

[0025] Here, the haptic control commands are pre-programmed and consistent with the 3D virtual scene. When the corresponding haptic feedback is triggered, the corresponding haptic control commands are output.

[0026] This application provides a flexible low-voltage electrical stimulation system for fine tactile feedback in the hand, comprising: a main control computer for rendering a three-dimensional virtual scene, recognizing user actions, and outputting tactile control commands; the tactile control commands are used to coordinate and control tactile feedback; virtual reality glasses connected to the main control computer for presenting the three-dimensional virtual scene; a low-voltage driving device for receiving the tactile control commands and outputting corresponding stimulation signals based on the tactile control commands; the voltage of the stimulation signals is lower than a preset voltage threshold; and a flexible electrode array connected to the low-voltage driving device for applying electrical stimulation to the user's hand skin based on the stimulation signals; the flexible electrode array includes multiple sets of electrode pairs, each set of electrode pairs being connected to alternating signals with the same parameters but a 180° phase difference. The flexible electrode array of this solution includes multiple sets of electrode pairs, forming local current pathways between the electrode pairs, which can activate sensory receptors in the skin with a relatively low voltage, inducing tactile perception and ensuring electrical safety.

[0027] In an optional embodiment, the flexible electrode array includes: The base layer is made of an insulating material; A conductive layer, wherein the conductive layer is printed on the substrate layer in a preset pattern using stretchable conductive ink, for forming electrode patterns and signal transmission lines; An encapsulation layer, which is adjacent to the conductive layer, is made of insulating material and has openings reserved at the electrode positions; A hydrogel layer is attached to the opening of the encapsulation layer.

[0028] Figure 2 This is a schematic diagram of the flexible electrode array provided in this application, as shown below. Figure 2 As shown, this flexible electrode array consists of four functional layers. The bottom layer is an insulating base layer with a thickness of approximately 50µm. Above this is a conductive layer, approximately 10µm thick, on which stretchable conductive ink (Elasink 990H) is printed into the base layer according to a preset pattern using a screen printing process. This layer forms the electrode pattern and signal transmission lines. To protect the conductive lines and prevent false triggering of non-target areas, the third layer is an encapsulating insulating layer (10µm) with openings at the electrode locations to facilitate electrical stimulation conduction. The hydrogel layer consists of conductive hydrogel patches attached to the openings of the encapsulation layer, effectively reducing the interfacial impedance between the electrodes and the skin.

[0029] In practice, the top of the encapsulation layer is coated with a skin adhesive to fix the patch to the skin of the hand and ensure stable contact.

[0030] The flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application embodiment includes a flexible electrode array comprising an insulating base layer, a conductive layer, an insulating encapsulation layer, and a hydrogel layer. It is externally insulated, and the hydrogel layer at the electrode position reduces the impedance between the electrode and the skin, ensuring the electrical stimulation effect.

[0031] In an optional embodiment, the base layer uses a thermoplastic polyurethane material.

[0032] Alternatively, the encapsulation layer may also be made of stretchable thermoplastic polyurethane (TPU) material.

[0033] The flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application embodiment uses thermoplastic polyurethane to make the encapsulation layer, which has good flexibility and fit.

[0034] In an optional embodiment, the hydrogel layer is formed by mixing N-hydroxyethylacrylamide with 1 mol sodium chloride solution and crosslinking with polyethylene glycol diacrylate to form a three-dimensional ionic network.

[0035] In this embodiment, the hydrogel layer is 1 mm thick and is made by mixing N-hydroxyethyl acrylamide (NHEAA) with 1 mol sodium chloride solution and cross-linking with polyethylene glycol diacrylate (PEGDA) to form a three-dimensional ionic network.

[0036] The flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application embodiment mixes NHEAA with sodium chloride solution and crosslinks with PEGDA to form a three-dimensional ionic network, which not only improves conductivity but also enhances adhesion and softness to the skin, thereby further optimizing the electrical stimulation effect and user experience.

[0037] In an optional embodiment, the flexible electrode array integrates 48 electrotactile stimulation pixels; each pair of adjacent electrotactile stimulation pixels forms a stimulation electrode pair, and a local current path is formed between the stimulation electrode pairs.

[0038] Figure 3 This is a schematic diagram of the electrode arrangement array provided in this application, such as... Figure 3 As shown, the hydrogel patch integrates 48 electrotactile stimulation pixels, covering the entire hand. Each pair of adjacent pixels forms a stimulation electrode pair, creating a local current pathway between them, thereby activating sensory receptors in the skin and inducing tactile perception. Spatially, the stimulation electrodes are divided into six regions based on anatomical structure: fingertips, phalanges, distal palm, thenar eminence, hypothenar eminence, and central palm. Stimulation parameters can be set individually for each region, enabling independent control of multiple regions. To simplify circuit design and reduce manufacturing complexity, electrodes within the same region are partially interconnected.

[0039] The flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application embodiment achieves a high electrode density radio tactile feedback system through 48 electrode pairs, enabling refined control of tactile sensation in the hand.

[0040] In an optional embodiment, the low-voltage drive device includes: The Bluetooth module is used to receive tactile control commands output by the main control computer device; A microcontroller, connected to the Bluetooth module, is used to control the electrical stimulation output circuit based on the tactile control commands; An electrical stimulation output circuit is connected to the microcontroller and is used to output corresponding stimulation signals.

[0041] Figure 4 This is a schematic diagram of the low-voltage drive device provided in this application, as shown below. Figure 4 As shown, the core of the low-voltage drive device is a microcontroller (single-chip microcomputer), which receives tactile control commands from the host computer via a Bluetooth module. Based on the received commands, it controls the electrical stimulation output circuit to output corresponding stimulation signals.

[0042] Optionally, the microcontroller is a 32-bit STM32RCT6 microcontroller.

[0043] Optionally, the Bluetooth module is an HC-05 Bluetooth module.

[0044] Optionally, the low-voltage drive is powered by a 12V lithium battery and regulates the input voltage to 3.3V, ±15V and ±40V respectively according to the module requirements to power different functional units.

[0045] The flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application embodiment receives tactile control commands from the host computer device via a Bluetooth module, and outputs corresponding stimulation signals accordingly. The current is then transmitted to the user's hand through a flexible electrode array to achieve tactile rendering.

[0046] In an optional embodiment, the electrical stimulation output circuit includes: A multi-channel digital-to-analog converter chip is connected to the microcontroller to generate multiple biphasic stimulation waveforms; An operational amplifier, connected to the multi-channel digital-to-analog converter chip, includes a non-inverting amplifier module and an inverting amplifier module, which are respectively used to construct a non-inverting amplified signal and an inverting amplified signal based on each of the biphasic stimulation waveforms. A multiplexer, connected to the operational amplifier, includes a first multiplexer module and a second multiplexer module, for outputting a stimulus signal.

[0047] In this embodiment, a microcontroller controls a multi-channel digital-to-analog converter chip (DAC60508, Texas Instruments) to generate six biphasic stimulation waveforms. Each waveform is amplified by inverting and non-inverting amplifier circuits constructed from operational amplifiers (OPA455, Texas Instruments), forming two AC signals with opposite phases. These signals are fed into two 16-channel analog multiplexers (TMUX9616, Texas Instruments), thus achieving a total of 32 independent stimulation output channels. The patch is connected to the drive control module via a 32-channel flexible circuit cable, maintaining high system integration while ensuring flexibility and wearing comfort. The microcontroller can independently control the switching state of each multiplexer channel.

[0048] The flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application generates multiple AC signals with opposite phases through a multi-channel digital-to-analog converter chip, an operational amplifier, and a multiplexer, and outputs them to control a flexible electrode array to achieve fine control of hand tactile sensation.

[0049] In an optional embodiment, the electrical stimulation output circuit further includes: A current detection module is connected between the operational amplifier and the microcontroller to monitor the output signal of the operational amplifier. When the output signal is greater than a preset threshold, the microcontroller is instructed to turn off the output of the operational amplifier.

[0050] In this embodiment, a current monitoring module is integrated to achieve real-time and accurate control and monitoring of the current flowing through the human body. The current is converted into a voltage signal through a shunt resistor and amplified by a differential amplifier (INA149, Texas Instruments). Subsequently, the signal is processed by hardware rectification and envelope detection circuitry and sampled by the analog-to-digital converter (ADC) inside the microcontroller. When the current exceeds a preset threshold (e.g., 3mA), the microcontroller immediately shuts off the amplifier output to ensure user safety.

[0051] The flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application embodiment monitors the system output current through a current monitoring module. When the output current exceeds a preset threshold, the current output is turned off to ensure electrical safety.

[0052] In an optional embodiment, the stimulation signal consists of a high-frequency square wave carrier and a low-frequency sinusoidal modulation signal.

[0053] Figure 5 This is a schematic diagram of the stimulation signal waveform provided in this application, such as... Figure 5 As shown, in each pair of electrodes, two adjacent stimulation pixels are connected to alternating signals with identical parameters but 180° out of phase. The stimulation signal consists of a high-frequency square wave carrier and a low-frequency sinusoidal modulation signal. The high-frequency square wave can effectively penetrate the skin's impedance interface, while the low-frequency sinusoidal signal is used to modulate different tactile sensations. The frequency of the high-frequency carrier can be adjusted from 1Hz to 10kHz, and the frequency range of the low-frequency modulation signal is from 1Hz to 500Hz, covering the sensitive frequency band of human tactile perception. The voltage signal can be finely adjusted, with a minimum adjustment step of 0.1V, basically covering the skin sensitivity range of most users.

[0054] The flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application uses a high-frequency square wave as the carrier wave and a low-frequency sinusoidal signal to modulate the signal, covering the sensitive frequency band of human tactile perception and realizing different tactile sensations.

[0055] In an optional embodiment, the main control computer device is further configured to: Using the Kalman filter algorithm, the predicted current at the next moment is estimated based on the real-time sampled current value, and the output voltage of the low-voltage drive device is determined based on the predicted current.

[0056] In this embodiment, due to changes in skin impedance and contact conditions, the current flowing through the skin fluctuates over time, thus affecting the induced tactile intensity. To achieve a stable electrical stimulation effect, a Kalman filter is used to predict future current changes based on real-time measured current values. The Kalman filter is a widely used optimal state estimation algorithm that can achieve real-time updates and predictions of the system state even in the presence of uncertainty and noise. Its estimation process can be expressed by the following formula: ; in, Let A represent the prior predicted current value at time k; let B represent the state transition matrix; and let B represent the control input matrix. This represents the posterior predicted current value at time k; This represents the prior error covariance; This represents the posterior error covariance; Represents the observation matrix; Represents the process noise covariance matrix; It is the identity matrix; This represents the current value measured at time k.

[0057] In this embodiment, the current cycle (e.g., 1ms) is sampled and transmitted to the host system. The Kalman filter algorithm predicts the current change trend at the next moment based on these measurements and calculates the required voltage to maintain the desired stimulation current intensity. To ensure user safety, the system limits the voltage adjustment range: if the adjusted voltage exceeds 20% of the initial setting, the system will automatically stop outputting to prevent potential risks.

[0058] The flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application uses a Kalman filter algorithm to predict the current output at the next moment, thereby controlling the voltage to not exceed the set value to ensure system safety.

[0059] To verify the potential of the proposed tactile system in wearable and interactive applications, the following section describes the effects of the flexible low-voltage electrical stimulation system for fine tactile feedback of the hand provided in this application, based on specific experiments.

[0060] In the experiment, each participant was required to complete the following four experiments: threshold voltage test, hand area tactile sensitivity assessment, virtual tactile information recognition experiment, and virtual reality (VR) demonstration experiment.

[0061] First, a threshold voltage test experiment was conducted to evaluate the system's effectiveness in inducing fine tactile perception within a skin-safe voltage range. In this experiment, an unmodulated square wave signal was applied to each stimulation channel to avoid interference from sinusoidal modulation. The initial signal amplitude was set low and gradually increased in 0.1V increments until the subject clearly reported feeling tactile sensation; the corresponding voltage was recorded as the tactile threshold. Each subject underwent the test three times. The square wave frequency was adjusted from 10Hz to 10kHz (including 10Hz, 1kHz, 2kHz, 4kHz, 6kHz, 8kHz, and 10kHz). Each channel was tested individually, and the results were averaged to obtain the overall threshold voltage distribution of the palm at each frequency.

[0062] Secondly, the regional assessment experiment aimed to investigate the effects of different stimulus frequencies and voltage amplitudes on tactile perception in different areas of the hand. To quantify the intensity of perception, five predefined tactile levels were established: no sensation, slight sensation, noticeable sensation, strong sensation, and discomfort. The stimulus signal was a 10kHz square wave, superimposed with sinusoidal modulated signals of different frequencies (25Hz, 50Hz, 100Hz, and 200Hz). The initial signal amplitude was set low and gradually increased in increments of 0.1V. Subjects participated in the experiment unknowingly and selected the tactile level option that best matched their perception. When subjects reported changes in their perception level, the corresponding voltage and current values ​​were recorded. This process was repeated three times for each subject.

[0063] Subsequently, a virtual tactile information recognition experiment was conducted to evaluate the system's ability to transmit fine tactile information. Six common grasping actions in daily life were selected for the experiment, including: pinch grasp, three-finger grasp, parallel open grasp, fixed hook grasp, master grasp, and ball grasp (e.g., ...). Figure 5 (As shown). These movements are commonly used to grasp objects of different shapes and are representative in virtual interaction. Furthermore, they involve coordinated movements of the palm and fingers, effectively assessing the system's spatial accuracy in whole-hand tactile stimulation. Each grasping movement is coded with personalized stimulation parameters to simulate the corresponding tactile experience. The amplitude and frequency of the stimulation waveform are personalized based on the subject's threshold voltage map, and the stimulation location is determined by the contact area between the hand and the virtual object. Each tactile pattern is applied to the subject in a random order, and the subject must determine its corresponding grasping movement. Each stimulus is repeated 5 times, for a total of 30 tests.

[0064] Finally, to verify the feasibility of the system in immersive virtual interaction scenarios, a VR demonstration experiment was conducted. The system supports real-time adjustment of tactile stimuli in terms of spatial location and intensity, providing synchronous tactile feedback to the hand during VR interaction. An immersive virtual environment simulating an insect crawling on the user's palm was constructed in the experiment. During the interaction, the tactile system applied tactile stimulation to the hand in real time, enhancing the realism of the tactile experience. The insect started from the tip of the index finger, passed through the palm, and finally reached the tip of the ring finger, a process that lasted 6 seconds. Each subject repeated this cycle 5 times. The tactile sensation generated during the insect's movement was defined as the level of perceived awareness, consistent with the standards in the previous experiment. Different stimulation parameters were applied to different locations along the path, and the system automatically switched the corresponding stimulation channels to achieve spatiotemporal synchronous tactile feedback.

[0065] To verify the effectiveness of the control strategy, a simulation experiment was designed in which the load resistance was continuously varied from 10kΩ to 20kΩ.

[0066] Figure 7 This is a schematic diagram of a resistance simulation experiment involving voltage and current changes provided in this application, such as... Figure 7 As shown, the average variation trends of load voltage and current are observed in ten sets of simulation experiments conducted under feedback control conditions. In the experiments, the target current was calculated based on the preset voltage and the real-time measured impedance. The initial voltage was set to 10V, corresponding to an output current of 1mA, which the system maintained throughout the experiment. Despite significant changes in load impedance, the Kalman filter-based feedback control strategy effectively maintained stable current output, with a root mean square error (RMSE) of only 0.011mA, demonstrating high accuracy. Furthermore, the current value calculated using known voltage and resistance values ​​closely matched the actual measurement results, further verifying the accuracy and real-time performance of the current monitoring module. In summary, the Kalman filter-based feedback strategy can accurately predict the load current and adjust the output voltage in real time, thereby ensuring the stability of the current output and the consistency of tactile perception.

[0067] Figure 8 This is a schematic diagram illustrating the relationship between the threshold voltages that generate sensation, as provided in this application. Figure 8As shown, to investigate the relationship between stimulation frequency and voltage threshold, this experiment recorded and analyzed the tactile detection voltage threshold at different square wave frequencies. For each participant, the thresholds of multiple stimulation channels were averaged to represent the voltage threshold of the entire hand at that frequency. Overall, the detection voltage threshold remained at a low level, and tactile perception could be reliably induced at voltages below 20V. This result is mainly attributed to the use of hydrogel-based electrode patches, which significantly reduced the contact impedance between the skin and the electrodes. Furthermore, the voltage threshold showed a significant decreasing trend with increasing stimulation frequency. Specifically, the average voltage threshold decreased from 18.5V at 10Hz to 12.5V at 10kHz, a decrease of approximately 30%. This phenomenon can be attributed to the capacitive properties of the skin and the skin-electrode interface: higher frequency AC signals can generate higher current densities at the interface and achieve deeper skin penetration. The experimental results indicate that, under low voltage conditions, a high-frequency electrical stimulation strategy is an effective method for inducing electrotactile sensation.

[0068] Because the distribution density of mechanoreceptors varies across different regions of the skin, different areas will produce different tactile sensations even when using the same electrical stimulation parameters. In this study, based on the anatomical structure of the hand, six main regions were analyzed: the fingertips, the middle and proximal phalanges of the fingers, the distal palmar region, the central palmar region, the thenar eminence, and the hypothenar eminence. Within each region, the voltage thresholds of all stimulation channels were averaged to assess the perceptual response at different stimulation frequencies.

[0069] Figure 9 This is a schematic diagram illustrating the relationship between stimulation frequencies of different hand areas provided in this application, such as... Figure 9 As shown, the results indicate that there are significant differences in the sensitivity of different areas of the hand to stimulation voltage. The voltage threshold of the finger areas is generally lower than that of the palm areas, meaning that they are more likely to perceive touch under the same stimulation conditions. Among them, the fingertips are the most sensitive areas, requiring only 10.7V to elicit significant tactile sensation at a modulation frequency of 25Hz; while the thenar eminence is the least sensitive area, with a maximum acceptable stimulation voltage as high as 33.8V. In addition, finger areas (such as fingertips and phalanges) have a smaller tolerance range to electrical stimulation, showing higher tactile sensitivity; while palm areas (such as the palm center, thenar eminence, and hypothenar eminence) have a larger voltage tolerance range. This finding is consistent with previous research results and can be attributed to the differences in the distribution of mechanoreceptors in the skin of the hand.

[0070] The modulation frequency of the stimulus waveform also affects the intensity and threshold of tactile perception. Experiments showed that, regardless of the anatomical region, the voltage threshold required to perceive different levels of tactile sensation increased with increasing modulation frequency. At low frequencies, subjects could perceive slight tactile sensations at lower voltages; while high-frequency stimuli required higher voltages to produce similar sensations and were more likely to induce strong or even uncomfortable tactile experiences. Increasing the frequency also broadened the perceptible voltage range, allowing for more precise modulation of tactile intensity. However, it is noteworthy that the modulation frequency had almost no effect on the relative sensitivity between different hand regions; that is, the sensitivity ranking of each region remained stable across all frequencies. In summary, the modulation frequency primarily affects the intensity and threshold of tactile perception, but has a relatively small impact on the spatial distribution pattern of tactile perception.

[0071] To evaluate the proposed electrotactile system's ability to induce fine and localized tactile perception, participants were asked to identify different grasping motions using only virtual tactile cues. Based on personalized threshold maps obtained from previous experiments, the system applied electrical stimulation with different frequencies and amplitudes to different regions to ensure consistent and clear tactile perception. For highly sensitive regions such as fingertips and knuckles, a higher stimulation frequency (100 Hz) was used to broaden the adjustable voltage range; while for less sensitive regions such as the palm, a lower frequency (50 Hz) was used to reduce the required stimulation voltage. By jointly modulating the frequency and amplitude of the stimulation, the system can be finely tuned according to the characteristics of different regions, thereby reliably inducing stable and significant tactile sensations.

[0072] Figure 10 This is a schematic diagram of the confusion matrix for classifying six grasping gestures based on tactile cues, as provided in this application. Figure 10 As shown, the overall recognition accuracy of the participants reached 97.2%, demonstrating a high level of recognition ability. The confusion matrix revealed that "grip grip" and "spherical grip" were misjudged in a few cases. This was mainly due to the small difference in tactile feedback between these two gripping methods, with the differences primarily concentrated in subtle changes in the palm. Overall, the high recognition accuracy exhibited by the participants fully validates the effectiveness and practical value of the system in providing accurate and well-defined electro-tactile feedback.

[0073] In addition to transmitting coded tactile information of static grasping movements, the proposed electro-tactile stimulation system also possesses the ability to provide real-time dynamic tactile feedback in an immersive virtual environment. In this application, an immersive virtual scene was constructed to simulate the process of an insect crawling on a user's palm. Simultaneously, the tactile feedback system provided tactile stimulation corresponding to the visual scene. This tactile feedback method is consistent with the aforementioned experiments: a high-frequency stimulation of 100Hz was used for the finger area, and a low-frequency stimulation of 50Hz was used for the palm area. Finally, the system adjusted the voltage according to the sensitivity of each area, ensuring that the entire hand maintained a "light touch" level of sensory intensity throughout the stimulation process. Figure 11 The average stimulation voltage distribution for all participants throughout the experiment is shown. As the insect moved along its path in the virtual scene, the location of the hand stimulation dynamically changed. The figure clearly illustrates the differences in current intensity required to induce the same tactile perception in different areas. All participants reported that combining visual information from the virtual environment with high-resolution tactile stimulation significantly enhanced immersion and realism. This demonstration validates that the proposed system can effectively transmit tactile information of virtual objects to users through precisely controlled spatiotemporal distribution and intensity-modulated electrical stimulation, providing reliable tactile support for immersive human-computer interaction.

[0074] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A flexible low-voltage electrical stimulation system for fine tactile feedback for hand, characterized by, The application relates to a device for rendering a three-dimensional virtual scene, identifying user actions and outputting haptic control instructions; the haptic control instructions are used for coordinating control of haptic feedback. A virtual reality glasses connected to the host computer device is used for presenting the three-dimensional virtual scene. A low-voltage driving device is used for receiving the haptic control instructions and outputting corresponding stimulation signals based on the haptic control instructions; the voltage of the stimulation signals is lower than a preset voltage threshold. A flexible electrode array connected to the low-voltage driving device is used for applying electrical stimulation to the skin of a user's hand based on the stimulation signals; the flexible electrode array comprises a plurality of electrode pairs, and each electrode pair is connected to an alternating signal with the same parameters but a phase difference of 180 degrees. The flexible electrode array comprises:

2. The flexible low-voltage electrostimulation system for fine haptic feedback for hands of claim 1, wherein, A base layer made of insulating material; A conductive layer printed on the base layer in a preset pattern using stretchable conductive ink, used for forming an electrode pattern and a signal transmission line; An encapsulation layer adjacent to the conductive layer, made of insulating material and having openings at electrode positions; A hydrogel layer attached to the opening positions of the encapsulation layer. The base layer uses thermoplastic polyurethane material.

3. The flexible low-voltage electrostimulation system for fine haptics feedback for hands of claim 2, wherein, The hydrogel layer is formed by mixing N-hydroxyethyl acrylamide with a 1Mol sodium chloride solution and cross-linking by polyethylene glycol diacrylate to form a three-dimensional ionic network.

4. The flexible low-voltage electrostimulation system for fine haptics feedback for hand according to claim 2, characterized in that, The flexible electrode array integrates 48 electrohaptic stimulation pixels; every two adjacent electrohaptic stimulation pixels form an stimulation electrode pair, and a local current path is formed between the stimulation electrode pair.

5. The flexible low-voltage electrostimulation system for fine haptic feedback of hand according to any of claims 1-4, characterized in that, The low-voltage driving device comprises:

6. The flexible low-voltage electrostimulation system for fine haptic feedback for hands of claim 1, wherein, A Bluetooth module used for receiving the haptic control instructions output by the host computer device; A microcontroller connected to the Bluetooth module and used for controlling an electrical stimulation output circuit based on the haptic control instructions; An electrical stimulation output circuit connected to the microcontroller and used for outputting corresponding stimulation signals. The electrical stimulation output circuit comprises:

7. The flexible low-voltage electrostimulation system for fine haptic feedback for hands of claim 6, wherein, A multi-channel digital-to-analog conversion chip connected to the microcontroller and used for generating a plurality of bi-phase stimulation waveforms; An operational amplifier connected to the multi-channel digital-to-analog conversion chip and comprising a same-phase amplifier module and an inverse-phase amplifier module, which are respectively used for constructing same-phase amplified signals and inverse-phase amplified signals based on each of the bi-phase stimulation waveforms; A multiplexer connected to the operational amplifier and comprising a first multiplexer module and a second multiplexer module, which are used for outputting stimulation signals. The electrical stimulation output circuit further comprises:

8. The flexible low-voltage electrostimulation system for fine haptic feedback for hands of claim 7, wherein, A current detection module connected between the operational amplifier and the microcontroller and used for monitoring the output signal of the operational amplifier; when the output signal is greater than a preset threshold, the microcontroller is instructed to close the output of the operational amplifier. The stimulation signal is composed of a high-frequency square wave carrier and a low-frequency sine modulation signal.

9. The flexible low-voltage electrostimulation system for fine haptic feedback for hands of claim 1, wherein, The host computer device is further used for:

10. The flexible low-voltage electrostimulation system for fine haptic feedback for hands of claim 1, wherein, Using a Kalman filtering algorithm to estimate a predicted current at the next moment based on real-time sampled current values and determine the output voltage of the low-voltage driving device based on the predicted current. ​

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