Intelligent calibration device and method for a flexible tactile sensor

Abstract

This invention relates to the field of stress measurement technology, specifically to an intelligent calibration device and method for a flexible tactile sensor. The intelligent calibration device further includes a brushless motor control module, which acquires the compensation force at different tilt angles; acquires the static load current value corresponding to each adjustment of the weight, and obtains a relationship model based on the compensation force; inputs the static load current into the relationship model, and determines the applied force at each initial calibration point based on the compensation force corresponding to the current tilt angle; determines the sensitivity and refinement space quantity based on the applied force and resistance value at each initial calibration point; and determines the number of refinement calibration points based on the sensitivity and refinement space quantity, thereby obtaining the calibration curve of the flexible sensor. This invention, by assessing the sensitivity performance of different force segments, allows for more refined calibration of force segments with high sensitivity and coarser calibration of force segments with low sensitivity, which helps optimize calibration resource allocation and improve calibration efficiency and accuracy.

Description

Technical Field

[0001] This invention relates to the field of stress measurement technology, and more specifically to an intelligent calibration device and method for a flexible tactile sensor. Background Technology

[0002] Flexible tactile sensors are sensors capable of sensing and responding to external physical stimuli such as touch, pressure, temperature, and vibration. As a core technology in robotics, wearable devices, medical devices, and intelligent interactive systems, they have experienced explosive growth in recent years. Their technical principles mainly include piezoresistive, capacitive, and piezoelectric types, with piezoresistive sensors dominating the market due to their low cost and high sensitivity. With the increasing demand for multi-dimensional force sensing in humanoid robots and precision medical equipment, flexible tactile sensors need to achieve higher precision and dynamic response capabilities. Optimizing sensor performance relies on accurate calibration techniques.

[0003] The existing calibration method, which applies a known gravity using weights, converts it into a linear force using a pulley system, and establishes a load-resistance relationship by combining the changes in sensor resistance, has significant bottlenecks in terms of efficiency, accuracy, and applicability. These bottlenecks are mainly reflected in the fact that the magnitude of the applied force depends on the weights, making it difficult to flexibly apply specific forces, and the error is relatively large, especially when calibrating with small forces. Summary of the Invention

[0004] To address the technical problem of large timing errors in the calibration of small forces using existing flexible tactile sensors, the present invention aims to provide an intelligent calibration device and method for flexible tactile sensors. The specific technical solution adopted is as follows:

[0005] One embodiment of the present invention provides an intelligent calibration device for a flexible tactile sensor, including a calibration device body, the calibration device body including a calibrator, and the intelligent calibration device further including a brushless motor control module, the brushless motor control module being mounted on the calibration device body;

[0006] The brushless motor control module is used to obtain the compensation force corresponding to the loading force rod of the calibrator when it is adjusted to different tilt angles; obtain the static load current value corresponding to each adjustment of the weight during the weight test, and combine it with the compensation force corresponding to the initial tilt angle to obtain the relationship model between static load current and bearing capacity; input the brushless motor static load current at each initial calibration point into the relationship model, and combine it with the compensation force corresponding to the current tilt angle to determine the applied force at each initial calibration point;

[0007] Based on the applied force and resistance values ​​at each initial calibration point, the sensitivity of the force segment to which each initial calibration point belongs is determined; the fine-grained space quantity is determined, which is the maximum number of calibration points that can exist between each initial calibration point; based on the sensitivity and the fine-grained space quantity, the number of fine-grained calibration points within the force segment to which each initial calibration point belongs is determined; and the calibration curve of the flexible sensor is obtained through the number of fine-grained calibration points.

[0008] Furthermore, obtaining the compensation force corresponding to different tilt angles when the loading force rod of the calibrator is adjusted includes:

[0009] According to the preset angle step size, the tilt angle of the loading force rod is gradually adjusted to obtain each adjusted tilt angle. The value range of the tilt angle is 0° to 90°.

[0010] At each adjusted tilt angle, the target static load current of the brushless motor is obtained;

[0011] The target static load current is converted into torque using the motor's torque parameters, and the torque is converted into force using the distance from the point of force application to the center of the shaft, denoted as the compensation force, thus obtaining the compensation force corresponding to each adjusted tilt angle.

[0012] Further, obtaining the target static load current of the brushless motor includes:

[0013] Take any adjusted tilt angle as the target tilt angle, repeat the experiment a preset number of times for the target tilt angle, obtain the static load current of the preset number of brushless motors at the target tilt angle, and take the average value of all the static load currents as the target static load current at the target tilt angle.

[0014] Furthermore, the obtained relationship model between static load current and bearing capacity includes:

[0015] Adjust the loading rod to the initial tilt angle and obtain the compensation force corresponding to the initial tilt angle; apply standard weights according to the gradient to cover the sensor range and convert the weight of the weights into gravity to obtain the load-bearing capacity when the weight of the weights is adjusted each time; construct the relationship function between static load current and load-bearing capacity.

[0016] The static load current value corresponding to each adjustment of the weight is used as the independent variable of the relationship function, and the bearing capacity corresponding to each adjustment of the weight is used as the dependent variable of the relationship function. The compensation force corresponding to the initial tilt angle is used to analyze the intercept of the relationship function. The relationship function is solved to obtain the relationship model between static load current and bearing capacity.

[0017] Furthermore, determining the applied force at each initial calibration point includes:

[0018] During the application of force to the flexible sensor, several initial calibration points are obtained; a target trajectory is generated based on each initial calibration point, and a brushless motor is driven based on the target trajectory.

[0019] Once the set position is reached, the brushless motor freezes the position loop integral term, switches to the force closed-loop control mode, collects the current steady-state current value of the brushless motor, and obtains the static load current of the brushless motor at each initial calibration point.

[0020] The current tilt angle is obtained by the angle sensor on the support arm of the calibrator, and then the compensation force corresponding to the current tilt angle is obtained.

[0021] Using the static load current of the brushless motor at each initial calibration point as the dependent variable of the relational model, and using the compensation force corresponding to the current tilt angle to analyze the intercept of the relational model, the applied force at each initial calibration point is obtained.

[0022] Furthermore, obtaining several initial calibration points includes:

[0023] During the application of force to the flexible sensor, a maximum loading range is set;

[0024] For the maximum load range, the load is initially divided into stages with a preset loading step size to obtain several initial calibration points.

[0025] Furthermore, the determination of the sensitivity of the force segment to which each initial calibration point of the target belongs includes:

[0026] At each initial calibration point, the resistance value of the flexible tactile sensor is obtained, thus obtaining the resistance value of each initial calibration point;

[0027] Sort all initial calibration points and take the other initial calibration points in the sequence except the first one as the target initial calibration points;

[0028] The applied force change value and resistance change value are determined for each target initial calibration point. The applied force change value is equal to the difference in applied force between the target initial calibration point and its adjacent previous initial calibration point, and the resistance change value is equal to the difference in resistance between the target initial calibration point and its adjacent previous initial calibration point.

[0029] Based on the applied force change value and resistance change value of each target initial calibration point, analyze the degree of increase of resistance change relative to applied force change, and determine the sensitivity of the force segment to which each target initial calibration point belongs. The force segment is the force segment between the target initial calibration point and its adjacent previous initial calibration point.

[0030] Furthermore, determining the refined spatial quantity includes:

[0031] Obtain the initial calibration process and the minimum calibration process during the initial calibration. Based on the ratio of the initial calibration process to the minimum calibration process, determine the fine-grained space quantity.

[0032] Furthermore, determining the number of refined calibration points within the force segment to which each initial calibration point of the target belongs includes:

[0033] For any initial calibration point of a target, calculate the product of the sensitivity of the force segment to which the initial calibration point of the target belongs and the refined spatial quantity;

[0034] The number of fine calibration points within the force segment to which the initial calibration point of the target belongs is determined based on the product of the sensitivity and the fine spatial quantity.

[0035] Another embodiment of the present invention provides an intelligent calibration method for a flexible tactile sensor, comprising:

[0036] Based on the applied force and resistance values ​​at each initial calibration point, determine the sensitivity of the force segment to which each initial calibration point belongs;

[0037] Determine the fine-grained space quantity, which is the maximum number of calibration points that can exist between each initial calibration point;

[0038] Based on the sensitivity and the refined spatial quantity, the number of refined calibration points within the force segment to which each target's initial calibration point belongs is determined.

[0039] The present invention has the following beneficial effects:

[0040] This invention provides an intelligent calibration device and method for a flexible tactile sensor. First, it acquires the compensation force corresponding to different tilt angles, which can compensate for the influence of the load rod's own weight on the applied force, improving calibration accuracy, especially ensuring force measurement precision when force is applied at different angles. Second, it establishes a relationship model between static load current and load-bearing capacity through weight testing, providing precise force feedback control, ensuring the stability and consistency of the applied force, and reducing error accumulation. Next, it performs initial calibration and refined calibration. Based on the sensitivity distribution in the initial calibration results, it distributes calibration points more detailed for different force segments, which helps improve calibration efficiency. Especially in the high-sensitivity force segments, more refined calibration ensures overall calibration accuracy. In summary, this invention, based on the sensitivity performance of the flexible sensor in different force segments, performs more refined calibration for high-sensitivity force segments and coarse calibration for low-sensitivity force segments. This optimizes calibration resource allocation, improves calibration efficiency, and ensures higher calibration accuracy in high-sensitivity force segments, meeting practical application requirements. Attached Figure Description

[0041] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the structure of an intelligent calibration device for a flexible tactile sensor according to an embodiment of the present invention;

[0043] Figure 2 This is an execution flowchart of the brushless motor control module in an embodiment of the present invention;

[0044] The attached figures are labeled as follows:

[0045] 1 represents the base, 2 represents the support arm for adjusting the angle, 3 represents the motor module, 4 represents the support arm for fixing the support, 5 represents the lead screw, 6 represents the brushless motor control module, 7 represents the recording force rod, and 8 represents the placement platform. Detailed Implementation

[0046] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the specific implementation methods, structures, features, and effects of the technical solution proposed according to the present invention are described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0048] The application scenarios targeted by this invention can be:

[0049] Current traditional methods for calibrating flexible sensors involve applying a known weight using weights, converting it into a linear force via a pulley system, and then establishing a load-resistance relationship based on changes in sensor resistance. However, this method is limited by the magnitude of the applied force, making it difficult to flexibly apply specific forces, especially when calibrating with small forces, resulting in significant errors.

[0050] To achieve more reliable calibration, one embodiment of the present invention provides an intelligent calibration device for a flexible tactile sensor. The intelligent calibration device includes a calibration device body, which includes a calibrator. The calibrator is generally composed of a base (1), a support arm (2), a lead screw (5), a motor module (3), a support arm (4), a loading force rod (7), and a placement platform (8).

[0051] Among them, the base (1) is used to fix the device; the support arm (2) is connected to the base (1) by a ratchet lock or an electromagnetic brake, and the angle between the support arm (2) and the base (1) can be adjusted; the lead screw (5) can be rotated to adjust the position of the brushless motor control module (6) located on it; the motor module (3) is used to drive the lead screw (5) to rotate; the support arm (4) is used to fix the support motor module (3) and the brushless motor control module (6); the loading rod (7) is used to transmit force and contact the flexible sensor; the placement platform (8) is used to place the flexible sensor and fix the flexible sensor with an adhesive.

[0052] The intelligent calibration device also includes a brushless motor control module (6), which is mounted on the calibration device body. A schematic diagram of the intelligent calibration device is shown below. Figure 1 As shown.

[0053] The execution flowchart of the brushless motor control module is as follows: Figure 2 As shown, it includes:

[0054] S1, obtain the compensation force corresponding to different tilt angles when the loading rod of the calibrator is adjusted to the same tilt angle;

[0055] S2, obtain the static load current value corresponding to each adjustment of the weight during the weight test, and combine it with the compensation force corresponding to the initial tilt angle to obtain the relationship model between static load current and bearing capacity;

[0056] S3, input the static load current of the brushless motor at each initial calibration point into the relational model, and determine the applied force at each initial calibration point by combining the compensation force corresponding to the current tilt angle;

[0057] S4. Based on the applied force and resistance values ​​at each initial calibration point, determine the sensitivity of the force segment to which each initial calibration point belongs;

[0058] S5, determine the fine-grained space quantity, which is the maximum number of calibration points that can exist between each initial calibration point;

[0059] S6. Based on the sensitivity and the refined spatial quantity, determine the number of refined calibration points within the force segment to which each target's initial calibration point belongs; obtain the calibration curve of the flexible sensor through the number of refined calibration points.

[0060] The intelligent calibration device in this embodiment achieves high-precision calibration of flexible tactile sensors through mechatronics design and closed-loop control technology. Its core principle is based on the magnetic field orientation control technology of a brushless motor. Specifically, the brushless motor drives the lead screw to convert rotational motion into linear displacement, pushing the loading rod to apply a precise and controllable force to the sensor. Simultaneously, the motor current feedback is monitored in real time to form closed-loop control. The support arm can flexibly adjust its angle to ensure that the applied force direction is perpendicular. After the sensor's electrical signal and the loading force data are collected synchronously, a force-electric mapping model is established through a fitting algorithm, that is, a relationship model between static load current and load-bearing capacity, to complete the automated calibration. The intelligent calibration device in this embodiment breaks through the limitations of traditional weight calibration, combining the accuracy of micro-force loading, multi-angle adaptability, and efficient automated process.

[0061] Since the final applied force during the calibration of the flexible sensor includes the weight of the loading rod, it is necessary to determine the weight compensation force of the loading rod at different tilt angles to eliminate its influence and improve the accuracy of the calibration results. Since there is a relationship between the weight of the loading rod and its tilt angle, the compensation force corresponding to different tilt angles of the calibrator's loading rod can be determined by analyzing the characteristics of this relationship.

[0062] As one specific implementation method, the sub-steps for implementing step S1 include:

[0063] S10, according to the preset angle step size, gradually adjust the tilt angle of the loading rod to obtain each adjusted tilt angle. The value range of the tilt angle is from 0° to 90°.

[0064] Here, the preset angle step size can be set to 5°. Implementers can set the size of the preset angle step size according to the specific actual situation, without making specific limitations.

[0065] In this embodiment, the loading lever is adjusted to the initial tilt angle, i.e., 0°, ensuring no additional weight. The loading lever is then adjusted to its maximum stroke, with the stroke being gradually adjusted vertically during loading. At this point, the brushless motor is turned on and kept under static load. At the initial tilt angle, the steady-state current value of the brushless motor is recorded. The steady-state current value is sampled at a frequency of 1kHz for 5 seconds, and the average is taken to obtain the static load current value. Collecting the static load current of the brushless motor without additional weight is to obtain the current required to overcome the weight of the loading lever itself. The angle of the loading lever is gradually adjusted, increasing by 5° each time, from 0° to 90°.

[0066] Regarding steady-state current and static load current, static load current refers to the current situation of the brushless motor under static load, while steady current is a mathematical term in the process of obtaining static load current, that is, the method of obtaining static load current, which is the steady-state current within a few seconds after the brushless motor enters static load mode.

[0067] S11, at each adjusted tilt angle, obtain the target static load current of the brushless motor.

[0068] Specifically, any adjusted tilt angle is taken as the target tilt angle. The experiment is repeated a preset number of times for the target tilt angle to obtain the static load current of the brushless motor at the preset number of times. The average value of all static load currents is taken as the target static load current at the target tilt angle. The preset number can be set to 3, with each experiment corresponding to the static load current of one brushless motor. The size of the preset number can be set by the implementer according to the specific actual situation.

[0069] In this embodiment, the static load current of the brushless motor is recorded at each adjusted tilt angle. To ensure the accuracy of the static load current data, the experiment is repeated multiple times for each tilt angle to calculate the average value of all static load currents, which is used as the target static load current for each tilt angle.

[0070] Thus, the data on the correspondence between different tilt angles of the loading rod and the static load current were obtained, that is, the target static load current for each adjusted tilt angle.

[0071] S12: Use the motor's torque parameters to convert each target static load current into torque, and use the distance from the force point to the center of the shaft to convert each torque into force, which is recorded as compensation force, to obtain the compensation force corresponding to each adjusted tilt angle.

[0072] In this embodiment, after obtaining the target static load current for each adjusted tilt angle, the target static load current is converted into torque using the motor's torque parameters. The calculation formula for the torque at each adjusted tilt angle is as follows:

[0073] T = A × Kt; where T represents the torque at each adjusted tilt angle, A represents the target static load current at each adjusted tilt angle, and Kt represents the torque parameter, which is a fixed parameter of the motor and can be directly obtained from the motor design parameter table.

[0074] In this embodiment, after obtaining the torque for each adjusted tilt angle, the torque is converted into a force, i.e., a compensation force. The calculation formula for the compensation force for each adjusted tilt angle is as follows:

[0075] In the formula, F represents the compensation force for each adjusted tilt angle, T represents the torque for each adjusted tilt angle, and L represents the distance from the point of force application to the center of the shaft, which is the radius of the transmission gear on the brushless motor shaft. If it is a gear set, the distance needs to be calculated separately based on the gear set relationship.

[0076] It should be noted that the calculation process for the distance from the point of force application to the center of the shaft is existing technology and is not within the scope of protection of this invention, and will not be elaborated here.

[0077] Thus, the target static load current, torque, and compensation force corresponding to each adjusted tilt angle are obtained, as shown in Table 1:

[0078] Table 1

[0079]

[0080] In Table 1, n represents the number of tilt angles. The above correspondence can be stored in the form of a data table for use in subsequent steps.

[0081] Thus, this embodiment has determined the self-weight compensation force of the loading rod at different tilt angles through calibration experiments, and established a table showing the correspondence between angle, static load current, torque, and compensation force. By compensating for the influence of the loading rod's self-weight on the applied force, the accuracy of calibration can be improved, especially when applying force at different angles, ensuring the accuracy of force measurement.

[0082] When a brushless motor is under static load, if the rotor position changes, the position sensor will detect this change and feed it back to the drive circuit. Upon receiving this information, the drive circuit will adjust the magnitude and direction of the current to counteract the rotor position change, thus achieving torque feedback control. Therefore, based on these characteristics of the brushless motor, a mapping relationship can be established between the static load current and the applied force, providing reference parameters for subsequent closed-loop control and ensuring force loading accuracy.

[0083] As one specific implementation method, the sub-steps for implementing step S2 include:

[0084] S20, adjust the loading rod to the initial tilt angle and obtain the compensation force corresponding to the initial tilt angle.

[0085] In this embodiment, the loading rod is adjusted to the initial tilt angle, i.e., 0°, and the compensation force corresponding to the initial tilt angle of 0° is obtained from Table 1 above. At the same time, the loading rod is rigidly connected to the weight hook to ensure that the direction of the applied force is perpendicular.

[0086] S21, standard weights are applied in a gradient manner to cover the sensor's range, and the weight of the weights is converted into gravity to obtain the load-bearing capacity each time the weight of the weights is adjusted.

[0087] In this embodiment, standard weights are applied in a gradient manner, such as 0.1g, 0.2g, 0.5g, 1g...500g, where g represents the unit gram, covering the sensor's range. The weight of the weights is converted into gravity, calculated as F′=mg, where F′ represents gravity, i.e., bearing capacity, m represents weight, and g represents acceleration gravity, with a standard value of 9.81.

[0088] It is worth noting that under static load, the output torque of the brushless motor needs to balance the weight of the weights and the weight of the loading rod, and the current is proportional to the torque. Therefore, after each weight is added, the steady-state current value is recorded. The steady-state current value is sampled at a frequency of 1kHz for 5 seconds and then averaged.

[0089] S22, construct the relationship function between static load current and bearing capacity.

[0090] In this embodiment, the static load current value corresponding to each adjustment of the weight of the weight also includes the self-weight of the loading rod. Therefore, when constructing the relational function, the compensation force of the loading rod must also be considered in the intercept analysis. The expression corresponding to the relational function is:

[0091] F′=a·I+b-F0; where F′ represents the load-bearing capacity, i.e. the weight of the weight, I represents the static load current value during the weight test, a and b represent the relationship parameters between the load-bearing capacity and the static load current, and F0 represents the compensation force of the loading rod at the initial tilt angle.

[0092] S23, the static load current value corresponding to each adjustment of the weight is used as the independent variable of the relational function, the bearing capacity corresponding to each adjustment of the weight is used as the dependent variable of the relational function, and the compensation force corresponding to the initial tilt angle is used to analyze the intercept of the relational function. Solve the relational function to obtain the relationship model between static load current and bearing capacity.

[0093] In this embodiment, the data measured each time the weight of the weight is adjusted are used to establish a mathematical model of current and force through the least squares method. Thus, the relationship parameters between the load-bearing capacity and the static load current, namely a and b, are determined, and the relationship model between the static load current and the load-bearing capacity is obtained.

[0094] Thus, this embodiment establishes a mathematical model of the relationship between the static load current and the applied force of the brushless motor through experiments, and uses the least squares method to fit the relationship between current and force. By providing precise force feedback control, it helps to ensure the stability and consistency of the applied force and reduce error accumulation.

[0095] After obtaining the relationship model between static load current and load-bearing capacity, the calibration of the flexible sensor can begin. However, before calibration, loading preparation is required, including:

[0096] When calibrating the flexible tactile sensor, the calibration requirements are first collected, including the angle of application (tilt angle), the magnitude of the applied force, or the force curve. Then, the target application angle parameters, such as 0°, 30°, and 60°, are extracted from the calibration task, and the allowable angle error range, such as ±0.5°, is defined. Next, a servo motor drives a harmonic reducer to rotate the support arm to the target angle, with the encoder providing real-time position feedback. An electromagnetic brake or ratchet lock is then engaged to ensure no displacement of the support arm during force application. Finally, a brushless motor is driven to move the loading lever until the flexible sensor displays a resistance value. At this point, the brushless motor stops, and the device reaches its initial loading state.

[0097] After completing the loading preparation, the flexible tactile sensor is calibrated.

[0098] In the calibration of flexible tactile sensors, the mapping relationship between applied force and sensor resistance typically exhibits nonlinear characteristics, and the importance and accuracy requirements for calibration vary significantly across different force ranges, specifically as follows:

[0099] Flexible sensors typically exhibit higher sensitivity at low force levels, but their nonlinearity is also most pronounced.

[0100] The relationship between medium and high force ranges is usually close to linear, and calibration is mainly used to verify linearity and the upper limit of the range.

[0101] When the sensor approaches the upper limit of its range, the sensor material may enter the saturation region due to excessive deformation, and the rate of change of resistance will drop sharply.

[0102] Different flexible tactile sensors have different force range divisions due to differences in structural parameters and other factors. Therefore, when calibrating, it is necessary to combine the relationship between the resistance of different flexible sensors and the applied force to make a more detailed distribution of calibration points for the sensor range, so as to carry out more targeted calibration.

[0103] As one specific implementation method, the sub-steps for implementing step S3 include:

[0104] S30 acquires several initial calibration points during the application of force to the flexible sensor; generates a target trajectory based on each initial calibration point; and drives the brushless motor based on the target trajectory.

[0105] In this embodiment, the initial calibration is first completed by dividing the maximum loading range of the flexible sensor on a large scale. Subsequently, based on the performance characteristics of applied force and resistance in the initial calibration results, a more refined distribution of sampling points can be made to further achieve a more refined and targeted calibration point division.

[0106] The acquisition of initial calibration points includes: setting the maximum loading range during the loading process of the flexible sensor; for the maximum loading range, initially dividing the load into stages with a preset loading step size to obtain several initial calibration points, i.e. displacement requirement points.

[0107] Here, the preset loading step size can be set to 0.3mm, without specific limitation. The implementer can set the size of the preset loading step size according to the specific actual situation. The target trajectory can also be called an S-shaped acceleration / deceleration curve. Its acquisition process is existing technology and is not within the scope of protection of this invention, so it will not be described in detail here.

[0108] S31, when the set position is reached, the brushless motor freezes the position loop integral term, switches to the force closed-loop control mode, collects the current steady-state current value of the brushless motor, and obtains the static load current of the brushless motor at each initial calibration point.

[0109] Here, the set position refers to the corresponding position of different strokes during the index setting process; the frozen position loop integral term is used to prepare for smoothing to force control, keeping the current value of the position integral term unchanged, but retaining the proportional and derivative terms to continue working; for the force closed-loop control mode, the force output of the motor is directly controlled through the current loop, which helps to avoid the position loop from continuously changing when it is obstructed, thus achieving compliant control.

[0110] In this embodiment, the current steady-state current value is sampled at a frequency of 1kHz for 5 seconds, and the average value is taken as the static load current of the brushless motor.

[0111] S32 obtains the current tilt angle through the angle sensor on the support arm of the calibrator, and then obtains the compensation force corresponding to the current tilt angle.

[0112] In this embodiment, the support arm is used to adjust the angle. Since the current steady-state current value includes the weight of the loading rod and the deviation caused by the angle, it is necessary to calculate the force applied to the displacement point by combining the compensation force corresponding to the current tilt angle. The current tilt angle is fixed after it is initially set.

[0113] The compensation force corresponding to the current tilt angle can be directly obtained from Table 1 in step S1 above. If the current tilt angle is not in Table 1, the compensation force corresponding to the current tilt angle is re-determined by referring to steps S10 to S12.

[0114] S33, the static load current of the brushless motor at each initial calibration point is used as the dependent variable of the relational model, and the compensation force corresponding to the current tilt angle is used to analyze the intercept of the relational model to obtain the applied force at each initial calibration point.

[0115] As an example, the formula for calculating the applied force at the i-th initial calibration point is as follows:

[0116] F i =a·I i +bF g In the formula, F i This represents the applied force at the i-th initial calibration point, i.e., the actual applied force. a and b represent the relationship parameters between bearing capacity and static load current. i F represents the static load current of the brushless motor at the i-th initial calibration point. g This represents the compensation force corresponding to the current tilt angle.

[0117] By referring to the calculation process of the applied force at the i-th initial calibration point, the applied force at each initial calibration point can be obtained.

[0118] The distribution of different force segments reveals that the higher the sensitivity of the flexible tactile sensor during the calibration stroke, the more directly it relates to the accuracy requirements of actual applications, and thus the higher the calibration accuracy requirement for this segment. Conversely, the lower the sensitivity of the calibration stroke, the closer it is to the saturation region, and the lower the correlation between this segment and actual applications. At the same time, the corresponding sensor resistance change is smaller, and thus the required accuracy during calibration is lower.

[0119] In this embodiment, the sensitivity can be obtained by the ratio of the applied force change to the resistance change. The greater the resistance change relative to the applied force change, the higher the sensitivity of the sensor. Therefore, the sensitivity of different applied force segments is calculated by applying the applied force and obtaining the resistance value at each initial calibration point.

[0120] As one specific implementation method, the sub-steps for implementing step S4 above include:

[0121] S40: At each initial calibration point, obtain the resistance value of the flexible tactile sensor to obtain the resistance value of each initial calibration point.

[0122] The sensitivity in this embodiment is obtained by the ratio of the applied force change to the resistance change, so it is necessary to collect the resistance values ​​at each initial calibration point.

[0123] S41, sort all the initial calibration points and take the other initial calibration points in the sequence except the first initial calibration point as the target initial calibration points.

[0124] Specifically, all initial calibration points are sorted by stroke size to obtain the sorting results of the initial calibration points. Since the object of sensitivity analysis is force segment, in order to facilitate the determination of force segment, the other initial calibration points in the sorting results except the first initial calibration point are limited to the target initial calibration points, because the stroke of the first initial calibration point is 0. The force segment here is the force segment between the target initial calibration point and its adjacent previous initial calibration point.

[0125] S42, determine the applied force change value and resistance change value at each target's initial calibration point.

[0126] In this embodiment, the applied force change value is equal to the difference in applied force between the target initial calibration point and its adjacent previous initial calibration point, while the resistance change value is equal to the difference in resistance between the target initial calibration point and its adjacent previous initial calibration point.

[0127] S43. Based on the applied force change value and resistance change value of each target initial calibration point, analyze the degree of increase of resistance change relative to applied force change, and determine the sensitivity of the force segment to which each target initial calibration point belongs.

[0128] As an example, the formula for calculating the sensitivity of the force segment to which the initial calibration point of the i-th target belongs is as follows:

[0129] In the formula, M i Represents the sensitivity of the force segment to which the initial calibration point of the i-th target belongs, Norm represents the linear normalization function, and R i R represents the resistance value of the initial calibration point of the i-th target. i-1 R represents the resistance value of the previous initial calibration point adjacent to the i-th target initial calibration point. i -R i-1 F represents the change in resistance at the initial calibration point of the i-th target. i F represents the applied force at the initial calibration point of the i-th target. i-1 F represents the applied force at the previous initial calibration point adjacent to the i-th target initial calibration point. i -F i-1 γ represents the change in applied force at the initial calibration point of the i-th target, and γ represents a non-zero constant used to avoid the denominator of the fraction being zero. Its empirical value can be 0.01.

[0130] As a specific implementation method, the sub-steps for implementing step S5 above include:

[0131] S50: Obtain the setting process and the minimum process of the historical calibration during the initial calibration. Based on the ratio of the setting process to the minimum process, determine the fine-tuning space quantity.

[0132] In this embodiment, the minimum process of historical calibration is the minimum process that the current intelligent calibration device can complete with high accuracy. The minimum process can be set to 0.05mm. Compared with the set process during the initial calibration, the set process can be taken from empirical values ​​in the range of 0.3 to 0.5mm. The fine space of the calibration points can be calculated, that is, the interpolation space between each calibration point during the initial calibration process.

[0133] As an example, the formula for calculating the refined spatial quantity can be:

[0134] In the formula, P represents the refinement space quantity, that is, the maximum number of calibration points that can exist between each initial calibration point during the initial calibration process; rounddown represents the floor function; d0 represents the setting process during the initial calibration; d min This represents the minimum process of historical calibration. The -1 is due to the relationship between the data segment and the partition point, that is, when a data segment needs to be divided into two segments, the number of partition points required is 1.

[0135] The sensitivity calculated in step S4 lies between the initial calibration points in the preliminary calibration. Therefore, the number of fine calibration points for each force segment can be calculated using the sensitivity and the fine space quantity.

[0136] As a specific implementation method, the sub-steps for implementing step S5 above include:

[0137] S50, for any initial calibration point of the target, calculate the product of the sensitivity of the force segment to which the initial calibration point of the target belongs and the refined spatial quantity.

[0138] S51, based on the product of sensitivity and fine-grained space quantity, determine the number of fine-grained calibration points within the force segment to which the initial calibration point of the target belongs.

[0139] In this embodiment, the greater the sensitivity of a certain force segment, the more closely the force segment fits the actual application process, the higher the calibration accuracy requirement of the force segment, and the higher the number of fine calibration points; the larger the fine space, the more calibration points can exist between the initial calibration points, and the higher the number of fine calibration points.

[0140] As an example, the formula for calculating the number of refined calibration points within the force segment to which the i-th initial calibration point belongs is as follows:

[0141] N i =round(P×M) i )-1; where N i This indicates the number of refined calibration points within the force segment to which the initial calibration point of the i-th target belongs; round represents the rounding function, specifically the rounding-to-float function; P represents the refined spatial quantity; M... i This represents the sensitivity of the force segment to which the initial calibration point of the i-th target belongs. The -1 is due to the relationship between the data segment and the division point, that is, when a data segment needs to be divided into two segments, the number of division points required is 1.

[0142] Referring to the calculation process of the number of refined calibration points within the force segment to which the i-th target initial calibration point belongs, the number of refined calibration points within the force segment to which each target initial calibration point belongs is obtained.

[0143] As a specific implementation method, the sub-steps for implementing step S6 above include:

[0144] S60 divides the stress segment into fine calibration points by using the number of fine calibration points within the force segment to which each target's initial calibration point belongs.

[0145] In this embodiment, for all target initial calibration points, the range of each target initial calibration point and its adjacent previous initial calibration point is obtained. For example, the range of the i-th target initial calibration point is denoted as [S]. i-1 ,S i The range is evenly divided by the number of fine calibration points within the force segment to which the initial calibration point of the target belongs, thus obtaining the required points for fine calibration, namely each fine calibration point.

[0146] S61, For each fine calibration point, repeat the implementation sub-step of step S3 above to obtain the applied force at each fine calibration point and obtain the resistance value of the flexible sensor at each fine calibration point.

[0147] S62 inputs the applied force and resistance values ​​at each fine calibration point into the least squares method for fitting, and obtains the calibration curve of the flexible sensor.

[0148] Thus far, this embodiment has performed initial calibration and fine-tuning calibration. Based on the sensitivity distribution in the initial calibration results, a more detailed calibration point distribution is performed for different force segments, which can improve calibration efficiency, especially for the high-sensitivity force segments, to ensure overall calibration accuracy. In addition, this embodiment also performs fine-tuning calibration for high-sensitivity force segments and coarse calibration for low-sensitivity force segments based on the sensitivity performance of the flexible sensor in different force segments. This can optimize the allocation of calibration resources, improve calibration efficiency, and ensure higher calibration accuracy in the high-sensitivity force segments to meet practical application requirements.

[0149] An embodiment of the present invention also provides an intelligent calibration method for a flexible tactile sensor, comprising:

[0150] Based on the applied force and resistance values ​​at each initial calibration point, determine the sensitivity of the force segment to which each initial calibration point belongs;

[0151] Determine the fine-grained space quantity, which is the maximum number of calibration points that can exist between each initial calibration point;

[0152] Based on sensitivity and refinement space quantity, determine the number of refinement calibration points within the force segment to which each target's initial calibration point belongs.

[0153] It should be noted that the detailed implementation process of the intelligent calibration method for a flexible tactile sensor can be referred to the implementation sub-steps of steps S4 to S5 above, and the same content will not be repeated here.

[0154] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention 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 scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. An intelligent calibration device for a flexible tactile sensor, comprising a calibration device body, the calibration device body including a calibrator, the calibrator comprising a base, a support arm, a lead screw, a motor module, a support arm, a loading rod, and a placement platform; the base is used to fix the device; the support arm is connected to the base via a ratchet lock or an electromagnetic brake for adjusting the angle; the lead screw adjusts the position of the brushless motor control module by rotation; The motor module is used to drive the lead screw to rotate; the support arm is used to fix and support the motor module and the brushless motor control module; the loading rod is used to transmit force and contact the flexible sensor; the placement platform is used to place the flexible sensor and fix the flexible sensor with an adhesive; characterized in that... The intelligent calibration device also includes a brushless motor control module, which is mounted on the calibration device body. The brushless motor control module is used to obtain the compensation force corresponding to the loading force rod of the calibrator when it is adjusted to different tilt angles; obtain the static load current value corresponding to each adjustment of the weight during the weight test, and combine it with the compensation force corresponding to the initial tilt angle to obtain the relationship model between static load current and bearing capacity; input the brushless motor static load current at each initial calibration point into the relationship model, and combine it with the compensation force corresponding to the current tilt angle to determine the applied force at each initial calibration point; Based on the applied force and resistance values ​​at each initial calibration point, the sensitivity of the force segment to which each initial calibration point belongs is determined; Determine the fine-grained space quantity, which is the maximum number of calibration points that can exist between each initial calibration point; based on the sensitivity and the fine-grained space quantity, determine the number of fine-grained calibration points within the force segment to which each initial calibration point of the target belongs; The calibration curve of the flexible sensor is obtained by refining the number of calibration points. The obtained relationship model between static load current and bearing capacity includes: Adjust the loading rod to the initial tilt angle and obtain the compensation force corresponding to the initial tilt angle; load standard weights according to the gradient to cover the sensor range and convert the weight of the weights into gravity to obtain the load-bearing capacity when the weight of the weights is adjusted each time; construct the relationship function between static load current and load-bearing capacity. The static load current value corresponding to each adjustment of the weight is used as the independent variable of the relationship function, and the bearing capacity corresponding to each adjustment of the weight is used as the dependent variable of the relationship function. The compensation force corresponding to the initial tilt angle is used to analyze the intercept of the relationship function. The relationship function is solved to obtain the relationship model between static load current and bearing capacity.

2. The intelligent calibration device for a flexible tactile sensor according to claim 1, characterized in that, The acquisition of the compensation force corresponding to the adjustment of the loading force rod of the calibrator to different tilt angles includes: According to the preset angle step size, the tilt angle of the loading force rod is gradually adjusted to obtain each adjusted tilt angle. The value range of the tilt angle is 0° to 90°. At each adjusted tilt angle, the target static load current of the brushless motor is obtained; The target static load current is converted into torque using the motor's torque parameters, and the torque is converted into force using the distance from the point of force application to the center of the shaft, denoted as the compensation force, thus obtaining the compensation force corresponding to each adjusted tilt angle.

3. The intelligent calibration device for a flexible tactile sensor according to claim 2, characterized in that, The process of obtaining the target static load current of the brushless motor includes: Take any adjusted tilt angle as the target tilt angle, repeat the experiment a preset number of times for the target tilt angle, obtain the static load current of the preset number of brushless motors at the target tilt angle, and take the average value of all the static load currents as the target static load current at the target tilt angle.

4. The intelligent calibration device for a flexible tactile sensor according to claim 1, characterized in that, The determination of the applied force at each initial calibration point includes: During the application of force to the flexible sensor, several initial calibration points are obtained; a target trajectory is generated based on each initial calibration point, and a brushless motor is driven based on the target trajectory. Once the set position is reached, the brushless motor freezes the position loop integral term, switches to the force closed-loop control mode, collects the current steady-state current value of the brushless motor, and obtains the static load current of the brushless motor at each initial calibration point. The current tilt angle is obtained by the angle sensor on the support arm of the calibrator, and then the compensation force corresponding to the current tilt angle is obtained. Using the static load current of the brushless motor at each initial calibration point as the dependent variable of the relationship model, and using the compensation force corresponding to the current tilt angle to analyze the intercept of the relationship model, the applied force at each initial calibration point is obtained.

5. The intelligent calibration device for a flexible tactile sensor according to claim 4, characterized in that, The acquisition of several initial calibration points includes: During the application of force to the flexible sensor, a maximum loading range is set; For the maximum load range, the load is initially divided into stages with a preset loading step size to obtain several initial calibration points.

6. The intelligent calibration device for a flexible tactile sensor according to claim 1, characterized in that, The sensitivity determination of the force segment to which each target's initial calibration point belongs includes: At each initial calibration point, the resistance value of the flexible tactile sensor is obtained, thus obtaining the resistance value of each initial calibration point; Sort all initial calibration points and take the other initial calibration points in the sequence except the first one as the target initial calibration points; The applied force change value and resistance change value are determined for each target initial calibration point. The applied force change value is equal to the difference in applied force between the target initial calibration point and its adjacent previous initial calibration point, and the resistance change value is equal to the difference in resistance between the target initial calibration point and its adjacent previous initial calibration point. Based on the applied force change value and resistance change value of each target initial calibration point, analyze the degree of increase of resistance change relative to applied force change, and determine the sensitivity of the force segment to which each target initial calibration point belongs. The force segment is the force segment between the target initial calibration point and its adjacent previous initial calibration point.

7. The intelligent calibration device for a flexible tactile sensor according to claim 1, characterized in that, The determination of the refined spatial quantity includes: Obtain the initial calibration process and the minimum calibration process during the initial calibration. Based on the ratio of the initial calibration process to the minimum calibration process, determine the fine-grained space quantity.

8. The intelligent calibration device for a flexible tactile sensor according to claim 1, characterized in that, Determining the number of refined calibration points within the force segment to which each initial calibration point of the target belongs includes: For any initial calibration point of a target, calculate the product of the sensitivity of the force segment to which the initial calibration point of the target belongs and the refined spatial quantity; The number of fine calibration points within the force segment to which the initial calibration point of the target belongs is determined based on the product of the sensitivity and the fine spatial quantity.

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