A continuous force sensation feedback control method based on ToF ranging and voice coil motor driving

Abstract

The application discloses a continuous force sense feedback control method based on ToF ranging and voice coil motor driving, and belongs to the technical field of force sense feedback, which comprises the following steps: collecting distance data of an obstacle in front of a device in real time by using a laser ToF sensor, and performing low-pass filtering to obtain filtered distance data; converting the filtered distance data into target elastic force through a piecewise logarithmic mapping function; converting the target elastic force into target driving current of a voice coil motor; converting the target driving current into a PWM duty cycle; generating electromagnetic thrust under the action of the target driving current, and transmitting the electromagnetic thrust to an external compression spring through a moving part of the voice coil motor, so that the spring generates a compression amount and further transmits the compression amount to a user's finger; and the finger feels the spring elastic force. The application realizes continuous and gradual force sense feedback, does not need an additional sensor, reduces hardware cost and system complexity, and improves the reliability and durability of the system.

Description

Technical Field

[0001] This invention relates to the fields of assistive technology for visually impaired individuals and force and tactile feedback control technology, specifically a continuous force feedback control method based on ToF ranging and voice coil motor drive. Background Technology

[0002] Visually impaired people rely on white canes to perceive obstacles in front of them when walking independently. The white cane transmits tactile information through the physical contact between the cane tip and the ground or obstacle, but the perception distance is extremely short (about 1m), so it cannot provide early warning and is completely ineffective against moving obstacles (such as pedestrians).

[0003] To address the aforementioned issues, smart cane assistive products based on ultrasonic sensors and vibration motors have emerged. These products use ultrasonic ranging to determine the distance to obstacles ahead and control the on / off state or intensity of the vibration motor based on the distance. However, existing solutions have the following drawbacks:

[0004] 1. Discontinuous tactile feedback: The tactile feedback provided by the vibration motor is a step-like binary state of "vibration / no vibration" or discrete intensity levels, which cannot simulate the continuity of distance perception in the real world. When users perceive changes in the distance to obstacles, they can only obtain discrete tactile signals of "present / absent" or "strong / medium / weak", making it difficult to establish a fine distance-force mapping relationship.

[0005] 2. Lack of intuitive physical correspondence between tactile feedback and distance: There is no intuitive physical relationship between changes in vibration intensity and distance to obstacles. Users need to undergo a long period of training to establish a psychological mapping between vibration intensity levels and distance.

[0006] 3. Limited accuracy of ultrasonic ranging: The typical accuracy of ultrasonic ranging is ±10cm, and it is easily affected by ambient temperature, humidity and airflow. In complex environments (such as corridor reflection and open space scattering), the ranging error is large.

[0007] 4. Gear noise and vibration issues in servo motor solutions: Micro servos are used to map distance to the angle of the servo arm, and users can perceive the displacement changes of the arm through their fingers. However, the servo motor has a gear transmission mechanism inside, which generates obvious gear noise during operation; and the PWM signal has high-frequency jitter when the servo motor maintains the angle, causing the user's fingers to feel vibration rather than stable force feedback.

[0008] Furthermore, existing haptic feedback control methods have the following shortcomings:

[0009] Option A: Distance → Vibration Intensity Discrete Mapping – Dividing the distance into several intervals (e.g., 0~1m, 1~3m, 3~5m, >5m), each interval corresponding to a fixed vibration intensity level. While this method is simple to implement, users cannot perceive continuous changes in distance within the same interval, and tactile abrupt changes occur at the interval boundaries, resulting in a poor user experience.

[0010] Option B: Linear mapping of distance to servo angle – This method linearly maps the distance to the servo's 0°~180° angle range. This method suffers from servo gear noise, limited angle resolution (pulse width resolution is typically only 10 bits), and PWM jitter when maintaining the angle.

[0011] Option C: Logarithmic mapping of distance to servo angle – Considering the nonlinearity of human perception, this method uses logarithmic space for distance-angle mapping. While more logically sound, it still fails to address noise and jitter issues at the servo hardware level.

[0012] In summary, the existing solutions suffer from discontinuous force feedback, lack of an intuitive physical correspondence between force and distance, and issues with noise and vibration. Summary of the Invention

[0013] The purpose of this invention is to provide a continuous force feedback control method based on ToF ranging and voice coil motor drive, which realizes continuous progressive force feedback without the need for additional sensors, reduces hardware costs and system complexity, and improves system reliability and durability.

[0014] To achieve the above objectives, the present invention provides a technical solution:

[0015] A continuous force feedback control method based on ToF ranging and voice coil motor drive includes:

[0016] S1, the distance data d of the obstacle directly in front of the device is collected in real time using a laser ToF sensor, and the distance data d is low-pass filtered to obtain filtered distance data. ;

[0017] S2, the filtered distance data Converted into target elastic force through a piecewise logarithmic mapping function The piecewise logarithmic mapping function sets multiple distance segment intervals, and each distance interval is assigned a corresponding elastic range.

[0018]

[0019] in, The distance segment interval is the current distance. This is the minimum value of the distance segment interval. The maximum value of the distance segment interval; , [This represents the elastic force range corresponding to this segment.] This represents the minimum value of the elastic range. This represents the maximum value within the elastic range.

[0020] S3, based on the linear relationship between the electromagnetic thrust and current of the voice coil motor, the target elastic force... Converted to target drive current for voice coil motor ;

[0021] S4, the target drive current This is converted to a PWM duty cycle D and output to the motor drive circuit to drive the voice coil motor to generate the corresponding electromagnetic thrust. ;

[0022] S5, the voice coil motor is driven by the target current. Electromagnetic thrust is generated under the action of The electromagnetic thrust The compression force is transmitted through the voice coil motor to an external spring, causing the spring to compress by a certain amount (x), which is then transmitted to the user's finger. When the user presses the button assembly, their finger feels the spring's elasticity. The spring force With the target drive current Proportional.

[0023] Furthermore, in S1, the distance data d is low-pass filtered using an exponential moving average filtering method.

[0024] Furthermore, in S2, the piecewise logarithmic mapping function sets multiple distance segmentation intervals as follows:

[0025] The first segment: d>10m, corresponding to an elastic force range of 0.18N, is used to represent unobstructed and minimal tactile sensation;

[0026] The second segment interval: 5m≤d≤10m, corresponding to an elastic force range of 0.18N~0.49N, is used to represent long-distance perception;

[0027] The third segment: 2m≤d<5m, corresponding to an elastic force range of 0.49N~0.80N, is used to represent mid-range perception;

[0028] The fourth segment interval: 0.5m≤d<2m, corresponding to an elastic force range of 0.80N~1.1N, is used to represent close-range perception;

[0029] The fifth segment: d < 0.5m, corresponding to an elastic force range of 1.1N, is used to indicate extremely close and maximum force warning.

[0030] Furthermore, in S3, the target drive current of the voice coil motor

[0031]

[0032] in, This represents the thrust coefficient of the voice coil motor.

[0033] Furthermore, in S4, the PWM duty cycle D is:

[0034]

[0035] in, The resistance of the voice coil motor coil. This is the power supply voltage for the motor drive circuit.

[0036] Furthermore, in S4, during the PWM duty cycle D update process, an anti-jitter strategy is implemented, including: current gradual transition: when the target current... With current When discrepancies exist, the current value is gradually transitioned to the target value over multiple control cycles using linear interpolation, with the current change in each control cycle being... satisfy:

[0037]

[0038] Where S is the transition coefficient.

[0039] Furthermore, the anti-shake strategy also includes:

[0040] After performing a gradual current transition, the elastic dead zone is determined: when the target elastic force... Compared to the elasticity of the last output The absolute value of the difference is less than the dead zone threshold. At this time, the PWM output is not updated, the current PWM is maintained, and the current voice coil motor current remains unchanged;

[0041] When the target elastic force Compared to the elasticity of the last output The absolute value of the difference is equal to or greater than the dead zone threshold. At the same time, the update frequency limit is set to: the maximum update frequency of the PWM duty cycle D is set to not exceed 20Hz.

[0042] Furthermore, in S5, the voice coil motor is driven by the target current. Electromagnetic thrust is generated under the action of for:

[0043]

[0044] Where I is the driving current.

[0045] Furthermore, in S5, the electromagnetic thrust of the voice coil motor and the elastic force of the external compression spring are in mechanical equilibrium.

[0046] =

[0047] The spring force felt by the fingers The spring compression x is determined by the driving current I.

[0048] Furthermore, during the journey, the user autonomously controls the scanning direction, and the detection beam of the laser ToF sensor actively scans the space in front of them as the user autonomously swings the beam. The scanning direction includes the horizontal, downward and upward directions. The user's fingers perceive the force feedback in each scanning direction in real time, and a mental map of the distribution, location and distance of spatial obstacles is constructed during the continuous scanning process.

[0049] Compared with the prior art, the beneficial effects of the present invention are:

[0050] The continuous force feedback control method based on ToF ranging and voice coil motor drive of the present invention can provide continuous progressive force feedback, intuitive physical correspondence between force and distance, noise-free, jitter-free, and fast-response spatial perception force feedback control for visually impaired people.

[0051] 1. Continuous progressive force feedback

[0052] This invention precisely controls the compression of an external compression spring by utilizing the current of a voice coil motor. = The mechanical equilibrium relationship was achieved, resulting in 0.18N. Continuous stepless force feedback within a 1.1N range. Compared with the existing "vibration / non-vibration" binary tactile feedback or servo "angle step", the user's finger perceives a continuously linearly changing force in this invention, establishing an intuitive physical correspondence between the distance to the obstacle and the force felt by the finger: the closer the distance, the greater the resistance felt by the finger.

[0053] 2. Piecewise logarithmic mappings conform to human perceptual characteristics.

[0054] This invention uses a piecewise logarithmic mapping function to convert distance into force, utilizing the logarithmic perception characteristic of human touch (Weber-Fechner law): in the short distance range (0.5m)... 2m) provides higher force resolution (0.30N / 1.5m=0.20N / m), and in the long distance range (5m) The 10m range offers relatively low force resolution (0.31N / 5m = 0.06N / m). This aligns with users' needs for obstacle perception, namely, a more refined ability to distinguish obstacles at close range and a rough judgment at long range.

[0055] 3. Natural position closed loop, no additional sensors required.

[0056] This invention utilizes the natural mechanical balance between the electromagnetic thrust of a voice coil motor and the elastic force of a spring. The drive current I directly determines the spring compression x, achieving precise force feedback control without the need for additional displacement sensors, position encoders, or force sensors. This not only reduces hardware costs and system complexity but also improves system reliability and durability.

[0057] 4. Triple anti-shake mechanism ensures stable force perception.

[0058] This invention implements a triple anti-shake strategy:

[0059] Elastic dead zone (0.05N): Small changes in force do not trigger updates, avoiding noise felt by the fingers;

[0060] Update frequency limit (20Hz): To match the mechanical response speed of the voice coil motor and avoid excessively fast updates;

[0061] Gradual current transition (S=0.3): The force sensation changes smoothly and continuously, avoiding abrupt changes.

[0062] This invention employs a triple mechanism to ensure that the user feels a stable elastic force while maintaining a pressing state, rather than high-frequency vibration.

[0063] 5. No gear noise

[0064] The voice coil motor of this invention is electromagnetically driven, with the mover moving directly in a magnetic field in a linear motion, eliminating the need for gears, belts, cams, and other mechanical transmission mechanisms. The PWM frequency is set to 20kHz (higher than the upper limit of human hearing), ensuring no audible noise is generated when used in a quiet environment.

[0065] 6. Actively scan and construct spatial mental maps

[0066] Users can autonomously control the scanning direction (horizontal, downward, upward, etc.), and their fingers will perceive force feedback in real time in each scanning direction. Due to the real-time performance (response latency <50ms) and long-range detection capability (up to 10m) of the ToF sensor, users can actively scan to create a spatial mental map, achieving a collision detection distance 5 meters earlier than traditional white canes (1m). Obstacle warnings are 10 times more effective. The laser ToF sensor has strong directivity with a single narrow beam, allowing users to accurately sense the distance to obstacles in a specific direction. Real-time force feedback in the corresponding direction can be obtained through autonomous scanning, without the need to preset a fixed scanning path.

[0067] 7. Flexible Deployment in a Separate Design

[0068] In a separate implementation, the ToF detection unit is worn on the user's head (such as in eyeglass frames or earmuffs), while the force feedback unit is integrated into the cane handle. The advantages of this approach are:

[0069] Autonomous control of detection direction: In the separate solution, the ToF sensor follows the user's head rotation to sense obstacles in the direction the user is facing; in the integrated solution, the user can autonomously control the device's direction (horizontal, downward, upward, etc.). The laser ToF sensor has strong directivity with a single-line narrow beam, which can accurately sense the distance to obstacles in a specific direction.

[0070] Complementing the white cane: The force feedback unit is integrated into the white cane handle, without affecting the user's original white cane operating habits;

[0071] Low latency in wireless communication: Bluetooth BLE has extremely low transmission latency (<10ms), which does not affect the overall system response speed.

[0072] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0073] Figure 1 The flowchart shows the continuous force feedback control method based on ToF ranging and voice coil motor drive of the present invention.

[0074] Figure 2 This is a schematic diagram of the continuous force feedback control method based on ToF ranging and voice coil motor drive of the present invention;

[0075] Figure 3 This is a schematic diagram of the main control loop timing of the present invention;

[0076] Figure 4 This is a piecewise logarithmic mapping curve diagram of the present invention;

[0077] Figure 5 This is a schematic diagram of the current gradual transition timing of the present invention. Detailed Implementation

[0078] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0079] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0080] This invention proposes a continuous force feedback control method based on Time-of-Flight (ToF) ranging and voice coil motor drive. This method relates to the fields of assistive technology for the visually impaired and haptic force feedback control technology. It is a control method that uses a laser ToF sensor to detect the distance to obstacles in front in real time and drives an external compression spring through a voice coil motor (VCM) to generate continuous variable force feedback related to distance.

[0081] The method of this invention utilizes the natural mechanical balance between the electromagnetic thrust of the voice coil motor and the elastic force of the external compression spring. The distance to the obstacle is converted into the driving current of the voice coil motor through piecewise logarithmic mapping. The voice coil motor pushes to compress the spring, and the user's finger senses the change in the spring force by pressing the button, thereby establishing a continuous force feedback path from distance to elastic force.

[0082] The continuous force feedback control method based on ToF ranging and voice coil motor drive of the present invention is applicable to the following two implementation methods:

[0083] Integrated implementation: The ToF sensor, microcontroller, motor drive circuit, and voice coil motor are integrated into the same device housing, and the modules are connected via wired means (e.g., UART, PWM). This integrated implementation can be applied to lower-cost, simpler, and more reliable applications because it eliminates the need for wireless connections and separate battery power, resulting in lower hardware costs. The wired signal transmission also simplifies and enhances reliability.

[0084] Separate Implementation: The ToF sensor and remote microcontroller are integrated into the remote detection unit, worn on the user's head (e.g., in eyeglass frames or ear-mounted supports); the voice coil motor, local microcontroller, and motor drive circuit are integrated into the handheld force feedback unit, which can be integrated into the cane handle or other handheld devices. Distance data is transmitted between the remote detection unit and the handheld force feedback unit via a wireless communication module (e.g., Bluetooth BLE), with a transmission latency of less than 10ms. This separate implementation separates ranging and force feedback into two separate devices that communicate wirelessly via Bluetooth or other methods. Each separate device has independent control circuits, wireless transmission antennas, batteries, and charging / discharging controls, resulting in a better user experience. The user only needs one hand to hold the cane (the cane handle integrates the force feedback device), freeing up the other hand. The distance sensor, naturally directional, is worn on the user's head; the direction the user's face is facing indicates the current ranging direction, providing a more intuitive user experience.

[0085] Reference Figures 1-5 As shown, this disclosure provides a continuous force feedback control method based on ToF ranging and voice coil motor drive, including:

[0086] S1, the distance data d of the obstacle directly in front of the device is collected in real time using a laser ToF sensor, and the distance data d is low-pass filtered to obtain the filtered distance data. .

[0087] Specifically, the distance data d of the obstacle directly in front of the device is collected in real time by a laser ToF sensor, with a sampling frequency of not less than 10Hz and a ranging range of 0.05m to 10m.

[0088] In the integrated implementation, the laser ToF sensor directly outputs distance data d to the microcontroller via the UART interface; in the discrete implementation, the laser ToF sensor outputs distance data d to the remote microcontroller via the UART interface, and the remote microcontroller sends the distance data to the local microcontroller of the handheld force feedback unit via a wireless communication module (such as Bluetooth BLE).

[0089] refer to Figure 3 In this step, the distance data d is low-pass filtered using the exponential moving average (EMA) filter to obtain the filtered distance data. .

[0090] (1)

[0091] in, This is a smoothing coefficient, with a value range of 0.1. 0.3, preferred =0.15; This is the distance value after the previous filtering.

[0092] In this step, EMA filtering can eliminate high-frequency noise in the ToF sensor output and prevent high-frequency jitter in force feedback.

[0093] S2, the filtered distance data Converted into target elastic force through a piecewise logarithmic mapping function The piecewise logarithmic mapping function sets multiple distance intervals, with each interval assigned a corresponding elastic range. The piecewise logarithmic function is as follows:

[0094] (2)

[0095] in,[ , [] represents the distance segment interval where the current distance is located. This is the minimum value of the distance segment interval. The maximum value of the distance segment interval; , [This represents the elastic force range corresponding to this segment.] This represents the minimum value of the elastic range. is the maximum value of the elastic force range; i represents the segment number.

[0096] The piecewise logarithmic mapping function of this invention uses different logarithmic interpolation parameters in different distance intervals, and the force perception resolution in the closer distance interval is higher than that in the farther distance interval.

[0097] refer to Figure 4 According to Table 1, this invention divides the ranging range of 0.05m to 10m into 4 effective segments (5m). 10m, 2m 5m, 0.5m The range consists of 2m, <0.5m) and 1 barrier-free section (>10m). Logarithmic interpolation using formula (2) is used within each section. Logarithmic mapping ensures that the force resolution of the near-distance range is higher than that of the far-distance range, which is consistent with the logarithmic perception characteristics of human touch.

[0098] The piecewise logarithmic mapping function sets multiple distance segmentation intervals as follows:

[0099] The first segment: d>10m, corresponding to an elastic force range of 0.18N, is used to represent unobstructed and minimal tactile sensation;

[0100] The second segment interval: 5m ≤ d ≤ 10m, corresponding to an elastic force range of 0.18N. 0.49N is used to represent long-distance sensing;

[0101] The third segment: 2m ≤ d < 5m, corresponding to an elastic force range of 0.49N. 0.80N is used to represent mid-range perception;

[0102] The fourth segment interval: 0.5m ≤ d < 2m, corresponding to an elastic force range of 0.80N. 1.1N is used to represent near-field perception;

[0103] The fifth segment: d < 0.5m, corresponding to an elastic force range of 1.1N, is used to indicate extremely close and maximum force warning.

[0104] Table 1 Segmented Intervals

[0105] Section 0 d>10m 0.18N Accessible, minimal tactile feedback Section 1 5m≤d≤10m 0.18N~0.49N Long-distance perception Section 2 2m ≤ d < 5m 0.49N~0.80N Mid-range perception Section 3 0.5m ≤ d < 2m 0.80N~1.1N Close-range perception Section 4 d<0.5m 1.1N Extremely close, maximum force warning

[0106] It should be noted that 0.18N is the preload of the external compression spring (corresponding to a preload of 0.5mm), and 1.1N is the maximum thrust of the voice coil motor. These values ​​are adjusted based on the selection of the external compression spring and the voice coil motor.

[0107] This invention uses a piecewise logarithmic mapping function to convert distance into force, utilizing the logarithmic perception characteristic of human touch (Weber-Fechner law): in the short distance range (0.5m)... 2m) provides higher force resolution (0.30N / 1.5m=0.20N / m), and in the long distance range (5m) The 10m sensor provides a lower force resolution (0.31N / 5m=0.06N / m), which meets the user's needs for obstacle perception, namely, more refined discrimination ability is needed at close range, while only a rough judgment is needed at long range.

[0108] S3, based on the linear relationship between the electromagnetic thrust and current of the voice coil motor, the target elastic force... Converted to target drive current for voice coil motor .

[0109] In this invention, the target drive current of the voice coil motor

[0110] (3)

[0111] in, This is the thrust coefficient of the voice coil motor, which is determined by the specific motor selection.

[0112] S4, target drive current This is converted to a PWM duty cycle D and output to the motor drive circuit to drive the voice coil motor to generate the corresponding electromagnetic thrust. .

[0113] In this invention, based on the voice coil motor coil resistance... and the power supply voltage of the drive circuit , target drive current Converted to PWM duty cycle D:

[0114] (4)

[0115] in, The resistance of the voice coil motor coil. This is the power supply voltage for the motor drive circuit.

[0116] In this invention, the PWM signal frequency is set to 20kHz, which is higher than the upper limit of human hearing (20kHz) to ensure no audible noise. The PWM signal drives the voice coil motor through an H-bridge driver circuit. The PWM duty cycle controls the average value of the output voltage, thereby controlling the average current of the voice coil motor coil. The inductive characteristics of the voice coil motor coil naturally provide a low-pass filter for the PWM signal, smoothing the current rather than causing pulsation.

[0117] refer to Figure 5 During the PWM duty cycle D update process, an anti-jitter strategy is implemented, including:

[0118] Gradual current transition:

[0119] When the target current With current When discrepancies exist, the current value gradually transitions to the target value over multiple control cycles using linear interpolation, resulting in a smooth and continuous change in force sensation without abrupt jumps. The current change in each control cycle... satisfy:

[0120] (5)

[0121] Where S is the transition coefficient, with a value ranging from 0.2 to 0.5. Preferably, S = 0.3.

[0122] Elastic dead zone determination:

[0123] refer to Figure 2 After performing a gradual current transition, a spring force dead zone judgment is performed before updating the PWM duty cycle. When the target spring force... Compared to the elasticity of the last output The absolute value of the difference is less than the dead zone threshold. At this time, the PWM duty cycle is not updated; the current PWM is maintained, and the current voice coil motor current remains unchanged. The dead time threshold is specified in the original text. The value range is 0.03N~0.08N.

[0124] Preferred, =0.05N. That is, | When |<0.05N, the PWM output is not updated, and the current voice coil motor current remains unchanged to avoid force jitter caused by minor noise. At this time, minor force changes do not trigger updates, preventing the fingers from feeling noise.

[0125] Update frequency limit:

[0126] The maximum update frequency of the PWM duty cycle D is set to no more than 20Hz, and the time interval between two adjacent PWM updates is ≥50ms, to match the mechanical response speed of the voice coil motor. In other words, the maximum update frequency of the force feedback is no more than 20Hz, meaning the time interval between two adjacent PWM updates is no less than 50ms. This limitation matches the mechanical response speed of the voice coil motor, preventing excessively rapid updates from causing instability in the force feedback.

[0127] In summary, this invention outputs the calculated PWM duty cycle to the motor drive circuit (H-bridge drive) to drive the voice coil motor to generate the corresponding electromagnetic thrust. During the PWM update process, the following triple anti-jitter mechanism is implemented:

[0128] (1) Elastic dead zone: | |< PWM is not updated intermittently to avoid force feedback jitter caused by minor noise;

[0129] (2) Update frequency limit: The time interval between two adjacent PWM updates is ≥50ms (update frequency ≤20Hz), which matches the mechanical response speed of the voice coil motor;

[0130] (3) Gradual current transition: The amount of current change in each control cycle

[0131] (Preferred value: S=0.3) The force sensation changes smoothly and continuously, without any abrupt changes.

[0132] This invention works in concert through the above three mechanisms to ensure that the user feels a stable elastic force when maintaining the pressing state, rather than high-frequency vibration.

[0133] S5, the voice coil motor at the target drive current Electromagnetic thrust is generated under the action of electromagnetic thrust The compression force is transmitted through the voice coil motor to an external spring, causing the spring to compress by a certain amount x, which is then transmitted to the user's finger. When the user presses the button assembly, the finger feels the spring's elasticity. Spring elasticity With target drive current Proportional.

[0134] In this invention, the voice coil motor is driven by the target current. Electromagnetic thrust is generated under the action of for:

[0135] (6)

[0136] Where I is the driving current.

[0137] The target drive current is discussed below. The driving current I will be explained.

[0138] The thrust currently perceived by the user comes from the current electromagnetic thrust, which is proportional to the current current value I; while the target current value is calculated based on the currently measured distance. This refers to the desired or future change in current value to the target value (considering the microscopic time required for program execution and calculation). If the microscopic delay consumed by program execution and calculation is ignored, the two can be considered equal. However, if the delay is strictly considered, there is a certain microsecond delay between them. This microsecond delay is on the order of milliseconds, imperceptible to the human body, and does not affect the user experience. In actual testing with the prototype, the corresponding change in force can be felt instantly when pointing at an obstacle, with no perceptible delay.

[0139] That is, the current electromagnetic thrust is proportional to the current value I. If we choose to ignore the time delay between the target driving current Itarget and the current current I, we assume that the current Itarget to be driven (after a very small time delay, which can be ignored in actual measurement) will be equal to the current value I.

[0140] Accordingly, the spring force of the present invention With target drive current They are directly proportional. If it is the current elastic force, it is directly proportional to the current current value I; if it is the target elastic force, it is directly proportional to the target current value Itarget. If the calculation delay is ignored, there is no need to make a strict distinction.

[0141] The thrust The electromagnetic thrust of the voice coil motor is transmitted to an external compression spring, causing the spring to compress by a certain amount (x). When the system reaches mechanical equilibrium, the electromagnetic thrust of the voice coil motor and the elastic force of the external compression spring are in a state of mechanical equilibrium.

[0142] = (7)

[0143] in, This is the stiffness coefficient of the external compression spring (e.g., k_spring≈0.37N / mm). This represents the spring compression. The spring force felt by the finger. The spring compression x is determined by the driving current I.

[0144] When a user presses the button component, the force felt by the finger is the spring force. .because The force felt by the fingers is directly determined by the driving current of the voice coil motor.

[0145] Mechanical equilibrium position closed loop: electromagnetic thrust of voice coil motor The elastic force of the external compression spring = They are equal in steady state, that is = .

[0146] Therefore, driving current The only factor that determines the spring compression is The amount of spring compression is the sole determinant of the elastic force perceived by the user's finger. This mechanical balance naturally forms a closed-loop positional feedback loop, eliminating the need for additional displacement sensors, encoders, or force sensors.

[0147] The electromagnetic thrust of the voice coil motor and the elastic force of the external compression spring form a mechanical balance. The drive current uniquely determines the spring compression, enabling precise force feedback control without the need for additional displacement sensors, position encoders, or force sensors. This not only reduces hardware costs and system complexity but also improves system reliability and durability.

[0148] This invention precisely controls the compression of an external compression spring by utilizing the current of a voice coil motor. = The mechanical equilibrium relationship enables continuous stepless force feedback within the range of 0.18N to 1.1N. Compared with the existing "vibration / non-vibration" binary haptic feedback or the "angle step" of the servo motor, the user's finger perceives a continuously linearly changing force, and an intuitive physical correspondence is established between the distance to the obstacle and the force felt by the finger: the closer the distance, the greater the resistance felt by the finger.

[0149] This invention realizes a continuous force feedback control method based on the mechanical balance of a voice coil motor and a spring, utilizing the natural mechanical balance relationship between the electromagnetic thrust of the voice coil motor and the elastic force of the external compression spring. = The distance to the obstacle is converted into the driving current of the voice coil motor through piecewise logarithmic mapping. The voice coil motor pushes to compress the spring, and the user's finger senses the change in the spring force by pressing the button, thus establishing a continuous force feedback path of "distance → force".

[0150] This invention achieves the following technical effects:

[0151] 1. Continuous stepless force feedback: continuously adjustable within the range of 0.18N~1.1N, with non-discrete levels;

[0152] 2. Intuitive force-distance correspondence: By utilizing the mapping relationship between spring force and distance, users can intuitively understand it without any learning;

[0153] 3. No additional feedback sensors required: The mechanical equilibrium relationship naturally forms a closed position loop, eliminating the need for displacement or force sensors;

[0154] 4. Triple anti-shake: Elastic dead zone + update frequency limit + current gradual transition, ensuring force perception stability.

[0155] Users can actively scan by autonomously controlling the scanning direction, and the detection beam of the laser ToF sensor will actively scan the space in front of them by autonomously swinging the beam.

[0156] In this invention, the scanning direction includes the horizontal direction (sensing pedestrians, walls, etc.), the downward direction (sensing stairs, steps, ground obstacles, etc.), and the upward direction (sensing the entrance of a shopping mall escalator, hanging obstacles, etc.).

[0157] Specifically, as the user swings the device while walking, the detection beam of the laser ToF sensor sweeps across the space in front of them, with the scanning direction being horizontal, downward, or upward. The finger provides real-time force feedback in each scanning direction.

[0158] When the beam of light is directed in an open area, the finger feels a minimum pre-force of 0.18N;

[0159] When the beam of light is directed toward the obstacle, the finger feels a relatively large elastic force corresponding to the distance from the obstacle;

[0160] During continuous scanning, users connect the force feedback from different directions, naturally forming a mental map in their minds showing the distribution and distance of obstacles ahead.

[0161] The Time-of-Flight (ToF) sensor scans space along its scanning direction, allowing the user's fingers to perceive force feedback in real time along each scanning direction. During continuous scanning, the user constructs a mental map of the location and distance of obstacles in the space. Due to the system's low response latency (<50ms) and high force feedback update frequency (20Hz), the user can chain the force feedback from different directions during continuous scanning, building a mental map of the location and distance of obstacles in the space. The laser ToF sensor features strong directivity with a single-line narrow beam, allowing users to accurately perceive the distance to obstacles in specific directions. By autonomously controlling the scanning direction, users can obtain real-time force feedback in the corresponding direction. Users do not need to preset a fixed scanning path and can adjust the scanning direction as needed to obtain information about the region of interest.

[0162] Users swing their fingers along a laser ToF sensor, which then sends the measured distance to the controller, providing force feedback to the user's fingers. Users can then independently assess the force feedback in different swing directions to determine the location and distance of obstacles, and ultimately choose their walking direction.

[0163] Specifically, the user points the laser ToF sensor in the direction they want to detect. The specific implementation is as follows: the laser ToF sensor emits a laser beam that illuminates a point on the obstacle to measure distance. The beam and the point are invisible to the naked eye in the infrared band, and the power strictly meets safety requirements to ensure no damage to other people's eyes or cameras.

[0164] The laser ToF sensor measures the distance from the obstacle in the current direction and sends it to the controller. The controller maps the distance to the magnitude of the force and drives the voice coil motor so that the user's finger can feel the corresponding pressure in real time. For example, the greater the distance, the smaller the pressure, and the smaller the distance, the greater the pressure. Moreover, the real-time performance of the above process can be very high (far less than the time delay that humans can perceive).

[0165] For example, if there is a tree in front of you, when the laser sweeps across the tree trunk, you can sense the process of pressure increasing and then decreasing again. The pressure is high when the laser beam points to the tree trunk at a certain angle (when the laser beam hits the tree trunk). Thus, the user can mentally perceive an obstacle with a certain width and approximate distance in that direction.

[0166] For example, using a laser ToF sensor to detect an open door in the middle of a continuous wall means that users don't need to walk to within 1 meter of a cane to know there's a door. Instead, laser scanning feedback allows them to perceive the approximate distance and location of their surroundings from about 10 meters in advance. This helps users mentally establish a general distribution of nearby obstacles (distance, location), enhancing their perception of their environment and aiding in the autonomous selection of their walking direction.

[0167] In summary, users can autonomously control the scanning direction (horizontal, downward, upward, etc.), and their fingers can perceive force feedback in each scanning direction in real time. Due to the real-time performance (response latency <50ms) and long-range detection capability (up to 10m) of the ToF sensor, users can actively scan to create a spatial mental map, receiving obstacle warnings 5-10 times earlier than the ~1m collision detection distance of traditional white canes. The laser ToF sensor has strong directivity with a single-line narrow beam, allowing users to accurately perceive the distance to obstacles in specific directions and obtain real-time force feedback in those directions through autonomous scanning, without needing to preset a fixed scanning path.

[0168] In the description of this invention, it should be understood that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description, and is not intended to 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 invention.

[0169] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0170] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A continuous force feedback control method based on ToF ranging and voice coil motor drive, characterized in that, include: S1, the distance data d of the obstacle directly in front of the device is collected in real time using a laser ToF sensor, and the distance data d is low-pass filtered to obtain filtered distance data. ; S2, the filtered distance data Converted into target elastic force through a piecewise logarithmic mapping function The piecewise logarithmic mapping function sets multiple distance segment intervals, and each distance interval is assigned a corresponding elastic range. in,[ , [] represents the distance segment interval where the current distance is located. This is the minimum value of the distance segment interval. The maximum value of the distance segment interval; , [This represents the elastic force range corresponding to this segment.] This represents the minimum value of the elastic range. This represents the maximum value within the elastic range. S3, based on the linear relationship between the electromagnetic thrust and current of the voice coil motor, the target elastic force... Converted to target drive current for voice coil motor ; S4, the target drive current This is converted to a PWM duty cycle D and output to the motor drive circuit to drive the voice coil motor to generate the corresponding electromagnetic thrust. ; S5, the voice coil motor is driven by the target current. Electromagnetic thrust is generated under the action of The electromagnetic thrust The compression force is transmitted through the voice coil motor to an external spring, causing the spring to compress by a certain amount (x), which is then transmitted to the user's finger. When the user presses the button assembly, their finger feels the spring's elasticity. The spring force With the target drive current Proportional.

2. The continuous force feedback control method based on ToF ranging and voice coil motor drive according to claim 1, characterized in that, In S1, the distance data d is low-pass filtered using an exponential moving average filtering method.

3. The continuous force feedback control method based on ToF ranging and voice coil motor drive according to claim 1, characterized in that, In S2, the piecewise logarithmic mapping function sets multiple distance segmentation intervals as follows: The first segment: d>10m, corresponding to an elastic force range of 0.18N, is used to represent unobstructed and minimal tactile sensation; The second segment interval: 5m≤d≤10m, corresponding to an elastic force range of 0.18N~0.49N, is used to represent long-distance perception; The third segment: 2m≤d<5m, corresponding to an elastic force range of 0.49N~0.80N, is used to represent mid-range perception; The fourth segment interval: 0.5m≤d<2m, corresponding to an elastic force range of 0.80N~1.1N, is used to represent close-range perception; The fifth segment: d < 0.5m, corresponding to an elastic force range of 1.1N, is used to indicate extremely close and maximum force warning.

4. The continuous force feedback control method based on ToF ranging and voice coil motor drive according to claim 1, characterized in that, In S3, the target drive current of the voice coil motor in, This represents the thrust coefficient of the voice coil motor.

5. The continuous force feedback control method based on ToF ranging and voice coil motor drive according to claim 1, characterized in that, In S4, the PWM duty cycle D is: in, The resistance of the voice coil motor coil. This is the power supply voltage for the motor drive circuit.

6. The continuous force feedback control method based on ToF ranging and voice coil motor drive according to claim 1, characterized in that, In S4, during the PWM duty cycle D update process, an anti-jitter strategy is implemented, including: current gradual transition: when the target current... With current When discrepancies exist, the current value is gradually transitioned to the target value over multiple control cycles using linear interpolation, with the current change in each control cycle being... satisfy: Where S is the transition coefficient.

7. The continuous force feedback control method based on ToF ranging and voice coil motor drive according to claim 1, characterized in that, The anti-shake strategy also includes: After performing a gradual current transition, the elastic dead zone is determined: when the target elastic force... Compared to the elasticity of the last output The absolute value of the difference is less than the dead zone threshold. At this time, the PWM output is not updated, the current PWM is maintained, and the current voice coil motor current remains unchanged; When the target elastic force Compared to the elasticity of the last output The absolute value of the difference is equal to or greater than the dead zone threshold. At the same time, the update frequency limit is set to: the maximum update frequency of the PWM duty cycle D is set to not exceed 20Hz.

8. The continuous force feedback control method based on ToF ranging and voice coil motor drive according to claim 1, characterized in that, In S5, the voice coil motor is in the target drive current Electromagnetic thrust is generated under the action of for: Where I is the driving current.

9. The continuous force feedback control method based on ToF ranging and voice coil motor drive according to claim 1, characterized in that, In S5, the electromagnetic thrust of the voice coil motor and the elastic force of the external compression spring are in mechanical equilibrium. = The spring force felt by the fingers The spring compression x is determined by the driving current I.

10. The continuous force feedback control method based on ToF ranging and voice coil motor drive according to claim 1, characterized in that, During the journey, the user autonomously controls the scanning direction, and the detection beam of the laser ToF sensor actively scans the space in front of them as the user swings it. The scanning direction includes the horizontal, downward and upward directions. The user's fingers perceive the force feedback in each scanning direction in real time, and a mental map of the distribution, location and distance of obstacles in the space is constructed during the continuous scanning process.

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