Clamping force global sensing device and calibration method

Abstract

The invention discloses a clamping force global sensing device and a calibration method, and belongs to the technical field of clamping force sensing. Comprising a clamping force sensing module, a clamping force clamping jaw and a clamping device body, the clamping force sensing module is located between the clamping device body and the clamping device clamping jaw, and a parallelogram flexible hinge mechanism is arranged in the clamping force sensing module; a parallelogram flexible hinge moving end and a parallelogram flexible hinge fixed end are arranged in the parallelogram flexible hinge mechanism, and the parallelogram flexible hinge fixed end is fixed to the clamp holder body through the sensing module clamp holder adapter plate. And the moving end of the parallelogram flexible hinge is connected with the clamping jaw of the clamping device through the sensing module clamping jaw adapter plate. According to the clamping force global sensing device and the calibration method, the clamping force is converted into linear infinitesimal displacement in a single direction through the translation characteristic of the flexible hinge structure, and then the magnitude of the clamping force is detected through the piezoelectric / piezoresistive sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of clamping force sensing, and in particular to a clamping force global sensing device and a calibration method. Background Art

[0002] The sensing of clamping force is a core technology in the fields of robots, automation equipment, and precision operations. The clamping force sensing methods are mainly divided into indirect sensing and direct sensing. Indirect sensing measures and analyzes other parameters related to the clamping force, and then estimates the clamping force through a certain algorithm or model. The sensing accuracy of the indirect clamping force sensing method depends on the accuracy of the established model and algorithm, and is greatly affected by factors such as the nonlinearity and uncertainty of the system.

[0003] For some complex working conditions and changing environments, it may be necessary to continuously adjust and optimize the model. In the direct clamping force sensing method, the force sensor is usually installed at the fingertips of the gripper. When an object is clamped, the sensor directly senses the action of the force and converts information such as the magnitude of the force into measurable signals such as electrical signals and optical signals, so as to obtain the value of the clamping force in real time. However, this method has measurement blind spots and is sensitive to the position of the clamping point, and it is difficult to achieve accurate sensing in different grasping modes. Summary of the Invention

[0004] The purpose of the present invention is to provide a clamping force global sensing device and a calibration method, which convert the clamping force into a linear micro-displacement in a single direction through the translational characteristics of a flexible hinge structure, and then use a piezoelectric / piezoresistive sensor to detect the magnitude of the clamping force.

[0005] The present invention provides a clamping force global sensing device and a calibration method, including a clamping force sensing module, a clamping force gripper, and a gripper body. The clamping force sensing module is located between the gripper body and the gripper claw. A parallelogram flexible hinge mechanism is provided in the clamping force sensing module. A parallelogram flexible hinge moving end and a parallelogram flexible hinge fixed end are provided in the parallelogram flexible hinge mechanism. The parallelogram flexible hinge fixed end is fixed to the gripper body through a sensing module gripper adapter plate, and the parallelogram flexible hinge moving end is connected to the gripper claw through a sensing module claw adapter plate. The sensor module in the clamping force sensing module is installed on both sides of the parallelogram flexible hinge moving end.

[0006] Preferably, a gripper mechanical interface is provided above the gripper body, and a gripper electrical interface is provided on one side of the gripper body.

[0007] Preferably, the clamping force sensing module includes a sensor module, a sensing module gripper adapter plate, a parallelogram flexible hinge mechanism, a sensor module preloading support, a sensor module preloading screw, a sensing module jaw adapter plate, and a sensing module side plate; the gripper jaw is connected to the sensing module jaw adapter plate, and the sensing module jaw adapter plate is connected to the sensing module side plate and fixed to the moving end of the parallelogram flexible hinge mechanism by screws; the sensor module is installed on both sides of the moving end of the parallelogram flexible hinge through the sensor module preloading support.

[0008] Preferably, the sensor module includes a piezoelectric / piezoresistive sensor, a sensor module preloading adjustment block, and a sensor module pusher block. The sensor module preloading adjustment block is provided on one side of the piezoelectric / piezoresistive sensor, and the sensor module pusher block is provided on the other side of the piezoelectric / piezoresistive sensor.

[0009] Preferably, the parallelogram flexible hinge mechanism includes a parallelogram flexible hinge, a moving end of the parallelogram flexible hinge, a fixed end of the parallelogram flexible hinge, and a fixing screw hole for the sensing module side plate.

[0010] Preferably, the piezoelectric / piezoresistive sensor is a thin film sensor, and the output differential voltage signal is: ; , is the voltage value in the initial preloading state; , is the voltage value after clamping force application; The differential voltage signal is mapped to the clamping force value through the Gaussian process regression model, and the model satisfies: ; wherein, is the clamping force mapping function; is the force-voltage conversion function to be fitted; is the mean function; is the covariance function; is the Gaussian process.

[0011] Preferably, the parallelogram flexible hinge mechanism is a symmetric double parallelogram structure, and the moving end of the parallelogram flexible hinge is connected to the fixed end of the parallelogram flexible hinge through a flexible hinge.

[0012] Preferably, it includes the following steps: Step S1: By screwing in the preloading screw, push the preloading adjustment block to move along the preloading direction, apply an initial preloading force to the piezoelectric / piezoresistive sensors on both sides, and record the initial voltage values and ; Step S2: Apply a known clamping force F at different positions of the gripper jaws and collect the corresponding differential voltage signals as follows: ; , is the real-time voltage under force; , is the reference voltage in the pre-tightening state; Data alignment: Generate a cubic spline interpolation function for the collected differential voltage signals and then resample them according to the acquisition frequency of the known clamping force; Normalize the data: ; is the normalized differential voltage; is the mean value of the differential voltage; is the standard deviation of the differential voltage; Denoising and smoothing processing: ; is the filtered voltage signal; is the normalized voltage sequence; n is the half-width parameter of the filtering window; k is the time offset; t is the current time point; Divide the processed data into a training data set and a validation data set; Step S3: Train a Gaussian process model; ; Among them, is the clamping force mapping function; is the force-voltage conversion function to be fitted; is the mean function; is the covariance function; is the Gaussian process; Establish the correlation between the differential input signal and the clamping force through the covariance function; ; Establish the correlation between the differential input signal and the clamping force, is the maximum variance of the sensor output, is the length scale; Use the training data set to train the Gaussian process model and optimize the hyperparameters of the covariance function , its log marginal likelihood function; ; is the known clamping force matrix; is the covariance matrix obtained through training; is the observation noise; is the total covariance matrix; is the input matrix for training; represents the number of samples in the training sample set; By maximizing the marginal likelihood function determine the optimal hyperparameters; Step S4, use the trained Gaussian process regression model, input the new sensor signal, and output the predicted value of the clamping force; ; is the predicted clamping force; is the new input value; is the input matrix for training; is the covariance matrix obtained through training; is the observation noise; is the total covariance matrix; is the known clamping force matrix; Calculate the prediction variance to evaluate the reliability: ; is the covariance of the new input value with itself; is the covariance of the new input value with all training values; is the observation noise; is the total covariance matrix; is the covariance of all training values with the new input value.

[0013] Preferably, the parallelogram flexible hinge mechanism can be replaced with a hinge structure with different stiffness parameters.

[0014] Therefore, the present invention adopts the above-mentioned clamping force global perception device and calibration method, converts the clamping force into a linear micro-displacement in a single direction through the translational characteristics of the flexible hinge structure, and then uses a piezoelectric / piezoresistive sensor to detect the magnitude of the clamping force.

[0015] Next, through the drawings and embodiments, the technical solutions of the present invention will be further described in detail. Description of the Drawings

[0016] Figure 1 is the overall structural schematic diagram of a clamping force global perception device and calibration method of the present invention; Figure 2 is the exploded view of the clamping force perception module structure of a clamping force global perception device and calibration method of the present invention; Figure 3 is the exploded view of the sensor module of a clamping force global perception device and calibration method of the present invention; Figure 4 Schematic structural diagram of the parallelogram flexible hinge mechanism for a clamping force global perception device and a calibration method of the present invention; Figure 5 Another schematic structural diagram of the parallelogram flexible hinge mechanism for a clamping force global perception device and a calibration method of the present invention; Figure 6 Schematic flow diagram of a clamping force global perception device and a calibration method of the present invention.

[0017] Reference numerals

[0018] 1. Clamping force sensing module; 2. Gripper jaw; 3. Gripper body; 4. Gripper electrical interface; 5. Gripper mechanical interface; 11. Sensor module; 12. Transfer board of the sensing module gripper; 13. Parallelogram flexible hinge mechanism; 14. Pre-tightening support for the sensor module; 15. Pre-tightening screw for the sensor module; 16. Transfer board of the gripper jaw of the sensing module; 17. Side plate of the clamping force sensing module; 111. Piezoelectric / piezoresistive sensor; 112. Pre-tightening adjustment block of the sensor module; 113. Pusher block of the sensor module; 131. Parallelogram flexible hinge; 132. Moving end of the parallelogram flexible hinge; 133. Fixed end of the parallelogram flexible hinge; 134. Fixed screw hole of the side plate of the clamping force sensing module; 6. Another parallelogram flexible hinge mechanism; 61. Flexible hinge; 62. Output end of the parallelogram flexible hinge movement; 63. Claw connection platform of the parallelogram flexible hinge; 64. Pre-tightening screw hole. Detailed implementation manners

[0019] The technical solutions of the present invention will be further described below with reference to the drawings and embodiments.

[0020] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention belongs.

[0021] The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. The terms such as "including" or "comprising" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. The terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left", "right" are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0022] Embodiment 1

[0023] As shown Figure 1-6 in the figure, a clamping force global perception device and a calibration method of the present invention include a clamping force perception module 1, a clamping force jaw 2 and a gripper body 3. A gripper mechanical interface 5 is provided above the gripper body 3, and a gripper electrical interface 4 is provided on one side of the gripper body 3. The gripper electrical interface 4 completes the electrical connection of the gripper drive and the force sensing sensor, and the gripper mechanical interface 5 completes the connection between the gripper and the robot.

[0024] The clamping force perception module 1 includes a sensor module 11, a perception module gripper adapter plate 12, a parallelogram flexible hinge mechanism 13, a sensor module pre-tightening support 14, a sensor module pre-tightening screw 15, a perception module jaw adapter plate 16, and a perception module side plate 17. The gripper jaw 2 is connected to the perception module jaw adapter plate 16, and the perception module jaw adapter plate 16 is connected to the clamping force perception module side plate 17 and fixed to the moving end 132 of the parallelogram flexible hinge by screws.

[0025] The sensor module 11 is installed on both sides of the moving end 132 of the parallelogram flexible hinge mechanism through the sensor module pre-tightening support 14. The sensor module 11 includes a piezoelectric / piezoresistive sensor 111, a sensor module pre-tightening adjustment block 112, and a sensor module push block 113. A sensor module pre-tightening adjustment block 112 is provided on one side of the piezoelectric / piezoresistive sensor 111, and a sensor module push block 113 is provided on the other side of the piezoelectric / piezoresistive sensor 111. To achieve the pre-tightening of the sensor module 11, the piezoelectric / piezoresistive sensor 111 is subjected to a pre-tightening force and can detect an initial pressure value.

[0026] The clamping force perception module 1 is located between the gripper body 3 and the gripper jaw 2, and a parallelogram flexible hinge mechanism 13 is provided in the clamping force perception module 1. The parallelogram flexible hinge mechanism 13 includes a parallelogram flexible hinge 131, a parallelogram flexible hinge moving end 132, a parallelogram flexible hinge fixed end 133, and a clamping force perception module side plate fixing screw hole 134.

[0027] The parallelogram flexible hinge mechanism 13 is provided with a parallelogram flexible hinge moving end 132 and a parallelogram flexible hinge fixed end 133. The parallelogram flexible hinge fixed end 133 is fixed to the gripper body 3 through the perception module gripper adapter plate 12. The parallelogram flexible hinge moving end 132 is connected to the gripper jaw 2 through the perception module jaw adapter plate 16, and the sensor module 11 in the clamping force perception module 1 is installed on both sides of the parallelogram flexible hinge moving end 132. The parallelogram flexible hinge mechanism 13 is a symmetric double parallelogram structure, and the parallelogram flexible hinge moving end 132 and the parallelogram flexible hinge fixed end 133 are connected by a flexible hinge.

[0028] The parallelogram flexible hinge mechanism 13. When the moving end 132 of the parallelogram flexible hinge is subjected to a force, the parallelogram flexible hinge 131 undergoes a small deformation. On one side of the moving end 132 of the parallelogram flexible hinge, the sensor module push block 113 will be more severely squeezed, and on the other side, the pre-tightening force squeezing the piezoelectric / piezoresistive sensor 111 will be reduced, thus forming a differential pressure signal.

[0029] The piezoelectric / piezoresistive sensor 111 is a thin-film sensor, and the output differential voltage signal is: ; , is the voltage value under the initial pre-tightening state; , is the voltage value after being clamped and stressed; The differential voltage signal is mapped to the clamping force value through the Gaussian process regression model, and the model satisfies: ; Among them, is the mean function; is the covariance function; is the clamping force mapping function; is the force-voltage conversion function to be fitted; is the Gaussian process.

[0030] A calibration method for a clamping force global perception device includes the following steps: Step S1: By screwing in the sensor module pre-tightening screw 15, the sensor module pre-tightening adjustment block 112 is pushed to move along the inclined plane. An initial pre-tightening force is applied to the piezoelectric / piezoresistive sensors 111 on both sides, and the initial voltage values and ; Step S2: At different positions of the gripper jaw 2, apply known clamping forces and collect the corresponding differential voltage signals as follows: ; , is the real-time voltage under force; , is the reference voltage under the pre-tightening state; Data alignment: Generate a cubic spline interpolation function for the collected differential voltage signal, and then re-sample it according to the acquisition frequency of the known clamping force; Normalize the data: ; is the normalized differential voltage; is the mean value of the differential voltage; is the standard deviation of the differential voltage; Denoising and smoothing processing: ; is the voltage signal after filtering; is the normalized voltage sequence; n is the half-width parameter of the filtering window; k is the time offset; t is the current time point; Divide the processed data into a training data set and a validation data set; Step S3: Train the Gaussian process model; ; where, is the clamping force mapping function; is the force-voltage conversion function to be fitted; is the mean function; is the covariance function; is the Gaussian process; Establish the correlation between the differential input signal and the clamping force through the covariance function; ; Establish the correlation between the differential input signal and the clamping force, is the maximum variance of the sensor output, is the length scale.

[0031] Use the training data set to train the Gaussian process model and optimize the hyperparameters of the covariance function , its log marginal likelihood function; ; is the known clamping force matrix; is the covariance matrix obtained through training; is the observation noise; is the total covariance matrix; is the input matrix for training; represents the number of samples in the training sample set; By maximizing the marginal likelihood function Determine the optimal hyperparameters.

[0032] Use the validation data set for testing and calculate the error (RMSE / MAE); RMSE (Root Mean Square Error) is the root mean square error; ; MAE (Mean Absolute Error) Mean Absolute Error; ; Step S4: Use the trained Gaussian process regression model to input new sensor signals and output the predicted value of the clamping force; ; is the predicted clamping force; is the new input value; is the trained input matrix; is the covariance matrix obtained through training; is the observation noise; is the total covariance matrix; is the known clamping force matrix; Calculate the prediction variance to evaluate the reliability: .

[0033] is the covariance of the new input value with itself; is the covariance of the new input value with all training values; is the observation noise; is the total covariance matrix; is the covariance of all training values with the new input value.

[0034] The parallelogram flexible hinge mechanism 13 can be replaced with a hinge structure with different stiffness parameters.

[0035] The parallelogram flexible hinge mechanism 13 can be replaced with a hinge mechanism with different stiffness parameters, Figure 5 is the replaceable hinge mechanism. Additionally, the parallelogram flexible hinge mechanism 6 includes a flexible hinge 61, a parallelogram flexible hinge motion output end 62, a parallelogram flexible hinge jaw connection platform 63, and a pre-tightening screw hole 64. The parallelogram flexible hinge jaw connection platform 63 is located at the center of the other parallelogram flexible hinge mechanism 6, and the flexible hinge 61 is located outside the parallelogram flexible hinge jaw connection platform 63. The left side of the parallelogram flexible hinge jaw connection platform 63 is provided with the parallelogram flexible hinge jaw connection platform 63 and the pre-tightening screw hole 64. Through the above replacement, on the premise of maintaining the original installation structure, clamping force detection with higher precision, stronger anti-interference ability, and longer service life can be achieved.

[0036] Therefore, the present invention adopts the above-mentioned clamping force global perception device and calibration method, converts the clamping force into a linear micro-displacement in a single direction through the translational characteristics of the flexible hinge structure, and then uses a piezoelectric / piezoresistive sensor to detect the magnitude of the clamping force. It solves the problems of blind spots in clamping force measurement and sensitivity to the position of the clamping point when using a force sensor installed at the fingertips of the jaws.

[0037] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A clamping force global perception device, characterized in that, It includes a clamping force sensing module, a clamping force jaw, and a gripper body. The clamping force sensing module is located between the gripper body and the gripper jaw. A parallelogram flexible hinge mechanism is provided in the clamping force sensing module. In the parallelogram flexible hinge mechanism, there are a parallelogram flexible hinge moving end and a parallelogram flexible hinge fixed end. The parallelogram flexible hinge fixed end is fixed to the gripper body through the sensing module gripper adapter plate. The parallelogram flexible hinge moving end is connected to the gripper jaw through the sensing module jaw adapter plate. The sensor module in the clamping force sensing module is installed on both sides of the parallelogram flexible hinge moving end.

2. The clamping force global perception device according to claim 1, characterized in that A gripper mechanical interface is provided above the gripper body, and a gripper electrical interface is provided on one side of the gripper body.

3. The clamping force global perception device according to claim 1, wherein The clamping force sensing module includes a sensor module, a sensing module gripper adapter plate, a parallelogram flexible hinge mechanism, a sensor module pre-tightening support, a sensor module pre-tightening screw, a sensing module jaw adapter plate, and a sensing module side plate. The gripper jaw is connected to the sensing module jaw adapter plate. The sensing module jaw adapter plate is connected to the sensing module side plate and fixed to the parallelogram flexible hinge moving end by screws. The sensor module is installed on both sides of the parallelogram flexible hinge moving end through the sensor module pre-tightening support.

4. The clamping force global perception device according to claim 1, characterized in that, The sensor module includes a piezoelectric / piezoresistive sensor, a sensor module pre-tightening adjustment block, and a sensor module pusher. A sensor module pre-tightening adjustment block is provided on one side of the piezoelectric / piezoresistive sensor, and a sensor module pusher is provided on the other side of the piezoelectric / piezoresistive sensor.

5. The clamping force global perception device according to claim 1, characterized in that The parallelogram flexible hinge mechanism includes a parallelogram flexible hinge, a parallelogram flexible hinge moving end, a parallelogram flexible hinge fixed end, and a sensing module side plate fixing screw hole.

6. The clamping force global perception device according to claim 4, wherein The piezoelectric / piezoresistive sensor is a thin-film sensor, and the output differential voltage signal is: ； , is the voltage value in the initial pre-tightening state; , is the voltage value after clamping force is applied; Differential voltage signal is mapped to the clamping force value through a Gaussian process regression model, and the model satisfies: ； Among them, is the mean function; is the covariance function; is the clamping force mapping function; is the force-voltage conversion function to be fitted; is the Gaussian process.

7. The clamping force global perception device according to claim 3, wherein The parallelogram flexible hinge mechanism is a symmetric double-parallelogram structure. The parallelogram flexible hinge moving end and the parallelogram flexible hinge fixed end are connected by a flexible hinge.

8. A calibration method for a clamping force global perception device according to any one of claims 1-7, characterized in that, It includes the following steps: Step S1: By screwing in the pre-tightening screw, the pre-tightening adjustment block is pushed to move along the pre-tightening direction, applying an initial pre-tightening force to the piezoelectric / piezoresistive sensors on both sides, and recording the initial voltage value and ; Step S2: Apply a known clamping force F at different positions of the gripper jaw, and collect the corresponding differential voltage signals as follows: ； , is the real-time voltage under stress; , is the reference voltage in the pre-tightening state; Data alignment: Generate a cubic spline interpolation function for the collected differential voltage signals, and then resample it according to the acquisition frequency of the known clamping force. Normalize the data: ； is the normalized differential voltage; is the mean value of the differential voltage; is the standard deviation of the differential voltage; Denoising and smoothing processing: ； is the voltage signal after filtering; is the standardized voltage sequence; n is the half-width parameter of the filtering window; k is the time offset; t is the current time point; Divide the processed data into a training data set and a validation data set. Step S3: Train a Gaussian process model. ； Among them, is the clamping force mapping function; is the force-voltage conversion function to be fitted; is the mean function; is the covariance function; is the Gaussian process; Establish the correlation between the differential input signal and the clamping force through the covariance function. ； is the maximum variance of the sensor output, is the length scale; Train a Gaussian process model using a training dataset and optimize the hyperparameters of the covariance function , its log marginal likelihood function; ； is the known clamping force matrix; is the covariance matrix obtained through training; is the observation noise; is the total covariance matrix; is the input matrix for training; represents the number of samples in the training sample set; By maximizing the marginal likelihood function Determine the optimal hyperparameters; Step S4: Use the trained Gaussian process regression model to input a new sensor signal and output the predicted value of the clamping force. ； is the predicted clamping force; is the new input value; is the trained input matrix; is the covariance matrix obtained through training; is the observation noise; is the total covariance matrix; is the known clamping force matrix; Calculate the prediction variance to evaluate the reliability: ； is the covariance of the new input value with itself; is the covariance of the new input value with all training values; is the observation noise; is the total covariance matrix; is the covariance of all training values with the new input value.

9. A clamping force global perception device according to claim 1, characterized in that The parallelogram flexible hinge mechanism can be replaced with a hinge structure with different stiffness parameters.

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