Manipulator clamping force control method and device based on motor driving

Abstract

The invention discloses a manipulator clamping force control method and device based on motor driving, and relates to the field of intelligent manipulators. Comprising the following steps that the mass of a to-be-clamped object is obtained, and basic friction force is calculated; collecting object shape characteristic parameters such as the maximum boundary length, the outer surface area and the volume, and calculating a shape influence coefficient; then, acquiring surface characteristic parameters such as average curvature, irregularity and projection area, calculating a surface concave-convex coefficient, and generating a shape complexity index in combination with the shape influence coefficient; then, acquiring material characteristic parameters such as hardness and elastic modulus, determining and correcting a basic friction coefficient, and calculating friction force; and finally, the instantaneous speed of the clamping task of the manipulator is obtained, the impact load is calculated, the basic friction force is corrected based on the parameters, the accurate clamping force is obtained, and therefore the accurate control over the clamping force of the manipulator is achieved. According to the method, the clamping effect and safety are improved, and the method is suitable for various clamping scenes.

Description

Technical Field

[0001] The present invention relates to the field of intelligent manipulators, and in particular to a motor-driven manipulator clamping force control method and device. Background Art

[0002] With the rapid development of automation technology, robotics, especially industrial robots and manipulators, are increasingly used in all walks of life. As an important component in automated production lines and intelligent manufacturing systems, manipulators are responsible for tasks such as gripping, handling, and assembly, and play an indispensable role in precision manufacturing and material handling. The control of the manipulator's clamping force is the key to its working accuracy and safety, and is directly related to the performance and operation results of the manipulator. Traditional manipulator clamping force control methods usually rely on a fixed basic clamping force, which is difficult to adapt to objects of different shapes, materials, and masses, and cannot be flexibly adjusted to cope with environmental changes, such as humidity, surface characteristics, and other factors.

[0003] In practical applications, the impact of environmental factors on the clamping force cannot be ignored. Environmental humidity, climate change and other factors will have a certain impact on the material properties of the object, especially the friction. For most manipulator systems, the clamping force can usually only be set based on a single friction coefficient, and it is difficult to dynamically adjust this parameter. Therefore, the existing manipulator clamping force control methods often have certain limitations and cannot achieve precise control of the clamping force in a changing working environment, resulting in poor reliability and adaptability of the manipulator when performing tasks.

[0004] In real applications, due to the complexity of the shape, material and surface features of the objects to be clamped, simple clamping force settings often cannot guarantee the ideal effect in all cases. For example, for objects of different masses, the traditional fixed clamping force may cause the clamping to be too tight or too loose, which in turn causes problems such as the object slipping, deformation or damage. In addition, the surfaces of many objects are not only uneven, but also may have different friction coefficients, which further increases the difficulty of clamping force control. If the clamping force is too small, the object may not be firmly grasped; if the clamping force is too large, it may cause damage to the object, especially for fragile or delicate items. Therefore, how to accurately control the clamping force of the manipulator based on factors such as the mass, shape, surface features, and material properties of the object to be clamped has become an important technical problem that needs to be solved in current robotics technology.

[0005] In the prior art, a Chinese patent with the authorization announcement number CN110757463B discloses a method and device for controlling the gripping force of a manipulator, wherein the control method is as follows: a vibration excitation source vibrates the manipulator, so that the vibration sensor obtains the initial vibration excitation response signal, and performs modal analysis on it to obtain the initial inherent modal parameters; the manipulator touches the grasped object, so that the vibration sensor receives the vibration excitation response signal when touching, and performs modal analysis on it to obtain the manipulator touch modal parameters; the manipulator applies force to clamp the grasped object, so that the vibration sensor receives the vibration excitation response signal when applying force, and performs modal analysis on it to obtain the manipulator force clamping modal parameters; the previous step is executed repeatedly, and the modal parameters of two adjacent force clamping are analyzed and compared, until the manipulator continues to apply force to clamp and the manipulator modal parameters no longer change, and the manipulator clamping modal parameters are obtained. However, the clamping force control is not only related to the modal parameters of the manipulator, but also closely related to various factors such as the material properties, shape, and surface characteristics of the object. This solution mainly focuses on the changes in modal parameters, but fails to fully consider that the clamping force of the manipulator is controlled only by the vibration modulus, which reduces the accuracy and effectiveness of the clamping force control.

[0006] The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not constitute the prior art that is already known to one of ordinary skill in the art. Summary of the invention

[0007] The purpose of the present invention is to provide a motor-driven manipulator gripping force control method and device to solve the problems raised in the above-mentioned background technology.

[0008] To achieve the above object, the present invention provides the following technical solutions: A method for controlling the gripping force of a motor-driven manipulator, the specific steps comprising: Obtaining the mass of the object to be clamped, calculating and generating the basic friction force of the manipulator based on the mass of the object to be clamped, collecting the shape characteristic parameters of the object to be clamped, and calculating the shape influence coefficient of the object to be clamped based on the shape characteristic parameters of the object to be clamped, wherein the shape characteristic parameters include the maximum boundary length, external surface area and volume of the surface of the object to be clamped; Acquire surface feature parameters of the object to be clamped, calculate the surface concavity coefficient of the object to be clamped based on the obtained surface feature parameters, and generate a shape complexity index of the object to be clamped according to the obtained surface concavity coefficient of the object to be clamped and the shape influence coefficient of the object to be clamped, wherein the surface feature parameters of the object to be clamped include surface average curvature, surface roughness and surface projection area; Obtaining material characteristic parameters of the object to be clamped, determining a basic friction coefficient between the object to be clamped and the contacts on the manipulator gripper based on the material characteristic parameters, and correcting the basic friction coefficient according to the ambient humidity and the number of contacts in contact with the object to be clamped to obtain an accurate friction coefficient, and calculating a basic clamping force according to the accurate friction coefficient, wherein the material characteristic parameters of the object to be clamped include the hardness and elastic modulus of the object to be clamped; The instantaneous acceleration of the manipulator when it starts the clamping task and when it stops after completing the clamping task is obtained, and the impact load of the manipulator is calculated based on the instantaneous acceleration. According to the obtained manipulator impact load, combined with the shape complexity index of the object to be clamped, the basic friction force and the material characteristic parameters of the object to be clamped, the basic clamping force of the manipulator is corrected to obtain the precise clamping force of the manipulator, and the clamping force of the manipulator is controlled by this precise clamping force.

[0009] Furthermore, the mass of the object to be clamped is obtained, and based on the mass of the object to be clamped, the basic friction force of the manipulator is calculated and generated, wherein the formula for calculating the basic friction force is: ; In the formula, is the basic friction force of the manipulator, is the mass of the object to be clamped, is the acceleration due to gravity; Based on the shape characteristic parameters of the object to be clamped, the shape influence coefficient of the object to be clamped is calculated, wherein the formula for calculating the shape influence coefficient of the object to be clamped is: ; In the formula, is the shape influence coefficient of the object to be clamped, is the maximum boundary length of the surface of the object to be clamped, is the volume of the object to be clamped, is the surface area of ​​the object to be clamped, where is the shape index, , and are the ratio of the maximum boundary length to the surface area, the ratio of the volume to the surface area of ​​the object to be clamped, and the weight coefficient greater than 0 of the shape index, respectively. ; The shape index The specific calculation is based on the formula: ; In the formula, The minimum boundary length of the surface of the object to be clamped.

[0010] Furthermore, based on the obtained surface feature parameters, the surface concavity coefficient of the object to be clamped is calculated, wherein the surface concavity coefficient of the object to be clamped is calculated based on the formula: ; In the formula, is the surface concave-convex coefficient of the object to be clamped, is the mean curvature of the surface, is the surface roughness, It is the ratio of the surface area of ​​the object to be clamped to the surface projection area. The surface roughness measuring device uses a stylus profilometer. Multiple sampling areas are randomly selected from the surface of the object to be clamped. The sampling areas are measured and analyzed using the stylus profilometer to obtain the surface roughness of each sampling area, and the surface roughness average of all sampling areas is calculated. This average is used as the surface roughness of the object to be clamped. The calculation formula is as follows: ; ; In the formula, Indicates that the stylus profilometer is The sampling length of the sampling area, is the index of the sampling region, and , K is the number of sampling areas, For the The height of the x-th sampling point within the sampling length of the sampling area deviates from the center line, where x is the coordinate of the sampling point within the sampling length. For the The surface roughness of the sampling area, is the surface roughness of the object to be clamped, the center line and The data is obtained by processing the built-in software of the stylus profilometer; The ratio of the surface area of ​​the object to be clamped to the projected surface area , the calculation is based on the formula: ; In the formula, It is the maximum projected area of ​​an object on a plane.

[0011] Furthermore, the obtained surface concave-convex coefficient of the object to be clamped is combined with the shape influence coefficient of the object to be clamped to jointly generate the shape complexity index of the object to be clamped, wherein the formula for calculating the shape complexity index of the object to be clamped is: ; In the formula, is the shape complexity index of the object to be gripped, and are the weight coefficients of the shape influence coefficient of the object to be clamped and the surface concave-convex coefficient of the object to be clamped, respectively. and and Both are greater than 0.

[0012] Furthermore, the basic friction coefficient is corrected according to the ambient humidity and the number of contacts that the object to be clamped contacts, to obtain the precise friction coefficient, wherein the formula for calculating the precise friction coefficient is: ; In the formula, For the exact friction coefficient, is the basic friction coefficient, is the number of contacts in contact, is the ambient humidity, is the attenuation coefficient of the friction coefficient due to the number of contacts in contact, is the gain factor of humidity on friction coefficient, where and and All are greater than 0; The basic clamping force is calculated based on the exact friction coefficient, where the basic clamping force is calculated based on the formula: ; In the formula, is the basic clamping force, is the basic friction force of the manipulator.

[0013] Furthermore, the instantaneous acceleration of the manipulator when it starts the clamping task and stops after completing the clamping task is obtained, and the impact load of the manipulator is calculated based on the instantaneous acceleration, wherein the formula for calculating the impact load of the manipulator is: ; ; In the formula, and are the impact load when the manipulator starts the gripping task and the impact load when the manipulator completes the gripping task, respectively. and are the mass of the object to be gripped and the mass of the manipulator, and They represent the instantaneous acceleration at the beginning and end of the gripping task, and They respectively indicate the start and end time of the gripping task.

[0014] Furthermore, according to the obtained impact load of the manipulator, combined with the shape complexity index of the object to be clamped and the material characteristic parameters of the object to be clamped, the basic clamping force of the manipulator is corrected to obtain the precise clamping force of the manipulator, wherein the formula for calculating the precise clamping force of the manipulator is: ; In the formula, For the precise clamping force of the robot, is the shape complexity index of the object to be gripped, is the material characteristic parameter influence function, , and are the weight coefficients of the impact load, shape complexity index and material characteristic parameter influence function, respectively, where and , and All are greater than 0; The material characteristic parameters affect the function The specific formula is: ; In the formula, is the hardness of the object to be clamped, is the elastic modulus of the object to be clamped.

[0015] The present invention also provides a motor-driven manipulator clamping force control device, which is used to execute the motor-driven manipulator clamping force control method, including: A basic friction force analysis module is used to obtain the mass of the object to be clamped, calculate and generate the basic friction force of the manipulator based on the mass of the object to be clamped, collect the shape characteristic parameters of the object to be clamped, and calculate the shape influence coefficient of the object to be clamped based on the shape characteristic parameters of the object to be clamped, wherein the shape characteristic parameters include the maximum boundary length, external surface area and volume of the surface of the object to be clamped; A shape complexity characterization module is used to obtain surface feature parameters of the object to be clamped, calculate the surface concavity coefficient of the object to be clamped based on the obtained surface feature parameters, and generate a shape complexity index of the object to be clamped based on the obtained surface concavity coefficient of the object to be clamped and the shape influence coefficient of the object to be clamped, wherein the surface feature parameters of the object to be clamped include surface average curvature, surface roughness and surface projection area; A friction force analysis module is used to obtain material characteristic parameters of the object to be clamped, determine the basic friction coefficient between the object to be clamped and the contacts on the manipulator gripper based on the material characteristic parameters, and correct the basic friction coefficient according to the ambient humidity and the number of contacts in contact with the object to be clamped to obtain an accurate friction coefficient, and calculate the basic clamping force according to the accurate friction coefficient, wherein the material characteristic parameters of the object to be clamped include the hardness and elastic modulus of the object to be clamped; The clamping force determination module is used to obtain the instantaneous acceleration of the manipulator when it starts the clamping task and stops after completing the clamping task, and calculate the impact load of the manipulator based on the instantaneous acceleration. According to the obtained manipulator impact load, combined with the shape complexity index of the object to be clamped and the material characteristic parameters of the object to be clamped, the basic clamping force of the manipulator is corrected to obtain the precise clamping force of the manipulator, and the clamping force of the manipulator is controlled by the precise clamping force of the manipulator; A manipulator module, the manipulator module includes a base for fixing, a driving device connected to the base through a connecting block, and a mechanical claw for clamping an object to be clamped, and the driving device drives the mechanical claw to clamp through a connecting rod, and the mechanical claw has a plurality of contacts on one side for clamping the object to be clamped.

[0016] Compared with the prior art, the present invention has the following beneficial effects: By comprehensively considering the mass, shape, surface features and material properties of the object to be clamped, the clamping force can be precisely controlled. First, by obtaining the mass of the object and calculating the basic friction force, a reliable starting point is provided for the clamping process. It can improve the stability of the clamping, and effectively reduce the risk of slipping in actual operation to ensure the safe handling of the object. By comprehensively considering the mass, shape, surface features and material properties of the object to be clamped, the clamping force can be precisely controlled. Secondly, the clamping force correction process takes into account dynamic factors such as the shape complexity index and friction of the object, making the adjustment of the clamping force more scientific and reasonable. The surface concave-convex characteristics, average curvature of the object, and parameters such as the elastic modulus and hardness of the material are fully utilized in the clamping process to ensure the optimal contact between the clamping claw and the object, reducing object damage and production stagnation caused by improper clamping force. At the same time, this method can dynamically adjust the clamping force according to environmental changes (such as humidity, temperature, etc.) and different clamping tasks, thereby improving the adaptability and work efficiency of the manipulator in a changing environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall method flow of the present invention; Figure 2 It is a schematic diagram of the overall device module of the present invention; Figure 3 It is a schematic diagram of the overall structure of the robot of the present invention; Figure 4This is a cross-sectional view of the robot structure of the present invention.

[0018] In the figure: 1. base; 2. connecting block; 3. driving device; 4. mechanical claw; 5. connecting rod; 6. contact. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0020] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0021] Example: See also Figure 1-4 , the present invention provides a technical solution: A method for controlling the gripping force of a motor-driven manipulator, the specific steps comprising: Step 1: Obtain the mass of the object to be clamped, calculate and generate the basic friction force of the manipulator based on the mass of the object to be clamped, collect the shape characteristic parameters of the object to be clamped, and calculate the shape influence coefficient of the object to be clamped based on the shape characteristic parameters of the object to be clamped, wherein the shape characteristic parameters include the maximum boundary length, external surface area and volume of the surface of the object to be clamped.

[0022] Use a 3D laser scanner or structured light scanner to scan the object to be clamped. This method can obtain a complete 3D model of the object, including boundary features. By processing the scanned data, parameters such as the maximum boundary length, surface area, and volume of the surface can be extracted. Alternatively, during the product design stage, use computer-aided design (CAD) software to create a 3D model of the object. These software can usually directly export parameters such as the maximum boundary length, surface area, and volume of the object.

[0023] The mass of the object to be clamped is obtained, and based on the mass of the object to be clamped, the basic friction force of the manipulator is calculated and generated. The formula for calculating the basic friction force is: ; In the formula, is the basic friction force of the manipulator, is the mass of the object to be clamped, is the acceleration due to gravity; Based on the shape characteristic parameters of the object to be clamped, the shape influence coefficient of the object to be clamped is calculated, wherein the formula for calculating the shape influence coefficient of the object to be clamped is: ; In the formula, is the shape influence coefficient of the object to be clamped, is the maximum boundary length of the surface of the object to be clamped, is the volume of the object to be clamped, is the surface area of ​​the object to be clamped, where is the shape index, , and are the ratio of the maximum boundary length to the surface area, the ratio of the volume to the surface area of ​​the object to be clamped, and the weight coefficient greater than 0 of the shape index, respectively. ; in, It represents the ratio of boundary length to surface area, which is used to reflect the degree of refinement of the shape. The more complex the boundary, the smaller the value. The smaller the value, the more complex the surface of the object to be clamped, the more difficult it is to clamp, and the greater the clamping force required. The influence coefficient of the shape of the object to be clamped Proportional, when When the shape of the object to be clamped decreases, the influence coefficient As it decreases, it means the shape of the object to be gripped is more complex; in, It is used to express the ratio of volume to surface area, and is used to express the thickness or extension of an object, reflecting the surface compactness of an object. The 2 / 3 power of volume is because it is proportional to the surface area. The smaller the value, the more complex the surface structure of the object to be clamped, and the greater the difficulty of clamping. It is proportional to the shape influence coefficient of the object to be clamped.

[0024] The shape index The specific calculation is based on the formula: ; In the formula, The minimum boundary length of the surface of the object to be clamped.

[0025] Among them, when the shape index The larger the shape index is, the greater the difference in the surface structures of the object to be clamped is, that is, the more complex the surface structure is. It is inversely proportional to the shape influence coefficient of the object to be clamped.

[0026] At the same time, since the shape index can comprehensively characterize the shape of the object, its weight coefficient is the largest. Although the ratio of the maximum boundary length to the surface area can reflect the roughness or surface complexity of the object, it can only judge the shape of the object from a single geometric feature. Therefore, the ratio of the maximum boundary length to the surface area has a slightly smaller effect on the shape than the ratio of the volume to the surface area of ​​the object to be clamped. Therefore, the ratio is set to .

[0027] Step 2: Obtain surface feature parameters of the object to be clamped, and calculate the surface concavity coefficient of the object to be clamped based on the obtained surface feature parameters. According to the obtained surface concavity coefficient of the object to be clamped and combined with the shape influence coefficient of the object to be clamped, a shape complexity index of the object to be clamped is jointly generated, wherein the surface feature parameters of the object to be clamped include surface average curvature, surface roughness and surface projection area.

[0028] Based on the obtained surface feature parameters, the surface concave-convex coefficient of the object to be clamped is calculated, wherein the formula for calculating the surface concave-convex coefficient of the object to be clamped is: ; In the formula, is the surface concave-convex coefficient of the object to be clamped, is the mean curvature of the surface, is the surface roughness, It is the ratio of the surface area of ​​the object to be clamped to the projected area of ​​the surface.

[0029] Among them, the surface concave-convex coefficient of the object to be clamped is The larger the value, the more complex the surface shape of the object to be clamped, which means that the object to be clamped is more difficult to clamp, the greater the clamping force required, and the average curvature of the surface It can effectively reflect the overall curvature of a surface at a certain point. When the value is large, it means that the surface around the point is more curved; on the contrary, if A value close to zero indicates that the surface near that point is approximately flat. The degree of change in curvature can also reflect the smoothness of the surface. Smooth surfaces usually have a small average curvature change, while rough or irregular surfaces may have a large curvature change. Therefore, the average curvature of the surface The surface concave-convex coefficient of the object to be clamped Proportional. Through exponential form It shows that the average curvature of the surface has a significant influence on the surface concavity coefficient.

[0030] Surface roughness The larger the surface roughness, the rougher the surface. The rougher the surface, the greater the friction generated. The object is less likely to fall off, which means that the object only needs a smaller clamping force, that is, to maintain a stable clamping. Therefore, the surface roughness The surface concave-convex coefficient of the object to be clamped Inversely proportional. In logarithmic form Indicates that when the surface roughness After exceeding a certain range, the influence on the surface roughness coefficient gradually weakens.

[0031] If the surface area of ​​an object is much larger than its projected area, it means that the surface shape of the object is relatively complex, with more bumps, curves or edges. Such objects may require a more sophisticated clamping design to ensure that the clamp can clamp stably. Therefore, the ratio of the surface area of ​​the object to be clamped to its projected area is The surface concave-convex coefficient of the object to be clamped Proportional to Makes the effect smoother and limits the effect on the surface bump factor.

[0032] The surface roughness measuring device uses a stylus profilometer, randomly selects multiple sampling areas from the surface of the object to be clamped, uses the stylus profilometer to measure and analyze the sampling areas to obtain the surface roughness of each sampling area, and calculates the average surface roughness of all sampling areas. This average is used as the surface roughness of the object to be clamped. The calculation formula is as follows: ; ; In the formula, Indicates that the stylus profilometer is The sampling length of the sampling area, is the index of the sampling region, and , K is the number of sampling areas, For the The height of the x-th sampling point within the sampling length of the sampling area deviates from the center line, where x is the coordinate of the sampling point within the sampling length. For the The surface roughness of the sampling area, is the surface roughness of the object to be clamped, the center line and The data is obtained through the built-in software of the stylus profilometer.

[0033] The ratio of the surface area of ​​the object to be clamped to the projected surface area , the calculation is based on the formula: ; In the formula, It is the maximum projected area of ​​an object on a plane.

[0034] According to the obtained surface concave-convex coefficient of the object to be clamped, combined with the shape influence coefficient of the object to be clamped, the shape complexity index of the object to be clamped is jointly generated, wherein the formula for calculating the shape complexity index of the object to be clamped is: ; In the formula, is the shape complexity index of the object to be gripped, and are the weight coefficients of the shape influence coefficient of the object to be clamped and the surface concave-convex coefficient of the object to be clamped, respectively. and and Both are greater than 0.

[0035] Since the shape influences the coefficient The smaller the shape, the more complex the surface of the object to be clamped. It is inversely proportional to the shape complexity index of the object to be gripped and is expressed in logarithmic form. The larger the surface concave-convex coefficient of the object to be clamped, the more complex the surface of the object to be clamped. Therefore, the surface concave-convex coefficient of the object to be clamped is proportional to the shape complexity index of the object to be clamped. It means that when the surface concave-convex coefficient of the object to be clamped exceeds a certain range, it will have a significant impact on the shape complexity index of the object to be clamped.

[0036] At the same time, since the surface concavity coefficient of the object to be clamped is an important reflection of the surface details and morphological complexity of the object, it is usually directly related to the difficulty of grasping the object, the stability of the operation, etc. The uneven surface will increase the difficulty of gripping, and this irregularity may cause sliding, deformation or instability during the grasping process. The shape influence coefficient reflects the complexity of the overall geometric shape of the object, such as volume, structural complexity, etc. Although the overall structure of the shape has an impact on the difficulty of gripping, compared with the surface concavity, the overall influence of the shape usually changes more slowly. Therefore, the setting and and Both are greater than 0.

[0037] Step 3: Obtaining material characteristic parameters of the object to be clamped, determining the basic friction coefficient between the object to be clamped and the contacts on the manipulator gripper based on the material characteristic parameters, and correcting the basic friction coefficient according to the ambient humidity and the number of contacts in contact with the object to be clamped to obtain an accurate friction coefficient, and calculating the basic clamping force according to the accurate friction coefficient, wherein the material characteristic parameters of the object to be clamped include the hardness and elastic modulus of the object to be clamped; The basic friction coefficient is corrected according to the ambient humidity and the number of contacts that the object to be clamped contacts to obtain the precise friction coefficient, where the formula for calculating the precise friction coefficient is: ; In the formula, For the exact friction coefficient, is the basic friction coefficient, is the number of contacts in contact, is the ambient humidity, is the attenuation coefficient of the friction coefficient due to the number of contacts in contact, is the gain factor of humidity on friction coefficient, where and and All are greater than 0; in, Represents the normalized value of ambient humidity, ranging from 0 to 1. Represents the nonlinear effect of the number of contact points on the friction coefficient, which decreases as the number of contacts increases. When humidity increases, the friction coefficient decreases due to lubrication, and the nonlinear correction better reflects this physical phenomenon. An increase in the number of contacts usually increases friction, but the effect is not linear due to material accumulation effects and contact surface wear. Therefore, the exact friction coefficient is inversely proportional to the ambient humidity and directly proportional to the number of contacts.

[0038] The basic clamping force is calculated based on the exact friction coefficient, where the basic clamping force is calculated based on the formula: ; In the formula, is the basic clamping force, is the basic friction force of the manipulator.

[0039] Step 4: Obtain the instantaneous acceleration of the manipulator when it starts the clamping task and when it stops after completing the clamping task, calculate the impact load of the manipulator based on the instantaneous acceleration, and according to the obtained manipulator impact load, combined with the shape complexity index of the object to be clamped, the basic friction force and the material characteristic parameters of the object to be clamped, correct the basic clamping force of the manipulator to obtain the precise clamping force of the manipulator, and use this precise clamping force to complete the control of the manipulator's clamping force.

[0040] The instantaneous acceleration of the manipulator when it starts the gripping task and stops after completing the gripping task is obtained, and the impact load of the manipulator is calculated based on the instantaneous acceleration. The formula for calculating the impact load of the manipulator is: ; ; In the formula, and are the impact load when the manipulator starts the gripping task and the impact load when the manipulator completes the gripping task, respectively. and are the mass of the object to be gripped and the mass of the manipulator, and They represent the instantaneous acceleration at the beginning and end of the gripping task, and They respectively indicate the start and end time of the gripping task.

[0041] When starting, the acceleration of the robot will cause the clamped object to be subjected to additional upward force, which may cause an instantaneous change in the clamping force. If the clamping force is insufficient, the object may slip. When stopping, the inertia of the object causes it to continue to move forward. If the clamping force is insufficient, the object may be disengaged due to impact.

[0042] According to the obtained impact load of the manipulator, combined with the shape complexity index of the object to be clamped and the material characteristic parameters of the object to be clamped, the basic clamping force of the manipulator is corrected to obtain the precise clamping force of the manipulator. The formula for calculating the precise clamping force of the manipulator is: ; In the formula, For the precise clamping force of the robot, is the shape complexity index of the object to be gripped, is the material characteristic parameter influence function, , and are the weight coefficients of the impact load, shape complexity index and material characteristic parameter influence function, respectively, where and , and All are greater than 0; The material characteristic parameters affect the function The specific formula is: ; In the formula, is the hardness of the object to be clamped, is the elastic modulus of the object to be clamped.

[0043] The greater the impact load, the greater the clamping force required to fix the object. Therefore, the impact load is proportional to the precise clamping force of the manipulator. The maximum impact load is selected. The clamping force is modified. As the impact load increases, the clamping force requirement will also increase to ensure that the object to be clamped will not fall off under impact. This effect will be amplified.

[0044] The increase in shape complexity usually leads to an increase in the clamping force, which is used to stabilize and fix the object. The greater the shape complexity, the more complex the shape of the object to be clamped, the more difficult it is to clamp, and the greater the clamping force required. Therefore, the shape complexity is proportional to the precise clamping force of the manipulator. Indicates that when As the force increases, the influence on the precise clamping force of the robot gradually weakens.

[0045] Material characteristic parameter influence function It is inversely proportional to the precise gripping force of the manipulator, because the greater the hardness and elastic modulus of the object to be gripped, The smaller it is, the less likely the object to be clamped will be damaged, and the weaker the effect on the precise clamping force of the robot will be.

[0046] The present invention also provides a motor-driven manipulator clamping force control device, which is used to execute the motor-driven manipulator clamping force control method, including: A basic friction force analysis module is used to obtain the mass of the object to be clamped, calculate and generate the basic friction force of the manipulator based on the mass of the object to be clamped, collect the shape characteristic parameters of the object to be clamped, and calculate the shape influence coefficient of the object to be clamped based on the shape characteristic parameters of the object to be clamped, wherein the shape characteristic parameters include the maximum boundary length, external surface area and volume of the surface of the object to be clamped; A shape complexity characterization module is used to obtain surface feature parameters of the object to be clamped, calculate the surface concavity coefficient of the object to be clamped based on the obtained surface feature parameters, and generate a shape complexity index of the object to be clamped based on the obtained surface concavity coefficient of the object to be clamped and the shape influence coefficient of the object to be clamped, wherein the surface feature parameters of the object to be clamped include surface average curvature, surface roughness and surface projection area; A friction force analysis module is used to obtain material characteristic parameters of the object to be clamped, determine the basic friction coefficient between the object to be clamped and the contacts on the manipulator gripper based on the material characteristic parameters, and correct the basic friction coefficient according to the ambient humidity and the number of contacts in contact with the object to be clamped to obtain an accurate friction coefficient, and calculate the basic clamping force according to the accurate friction coefficient, wherein the material characteristic parameters of the object to be clamped include the hardness and elastic modulus of the object to be clamped; The clamping force determination module is used to obtain the instantaneous acceleration of the manipulator when it starts the clamping task and stops after completing the clamping task, and calculate the impact load of the manipulator based on the instantaneous acceleration. According to the obtained manipulator impact load, combined with the shape complexity index of the object to be clamped and the material characteristic parameters of the object to be clamped, the basic clamping force of the manipulator is corrected to obtain the precise clamping force of the manipulator, and the clamping force of the manipulator is controlled by the precise clamping force of the manipulator; The manipulator module includes a base 1 for fixing, a driving device 3 connected to the base 1 through a connecting block 2, and a mechanical claw 4 for clamping the object to be clamped. The driving device 3 drives the mechanical claw 4 to clamp the object to be clamped through a connecting rod 5, and the mechanical claw 4 has a plurality of contacts 6 on one side for clamping the object to be clamped. There are two mechanical claws 4 distributed on both sides of the driving device 3. For details, please refer to Figure 3 and Figure 4 .

[0047] The above formulas are all dimensionless and numerical calculations. The formula is a formula for the most recent real situation obtained by collecting a large amount of data and performing software simulation. The preset parameters in the formula are set by technicians in this field according to actual conditions.

[0048] The above embodiments may be implemented in whole or in part by software, hardware, firmware or any other combination thereof. When implemented by software, the above embodiments may be implemented in whole or in part in the form of a computer program product. Those skilled in the art may appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein may be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed by hardware or software methods depends on the specific application and design constraints of the technical solution.

[0049] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, and may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0050] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A motor-driven manipulator gripping force control method, characterized in that: The specific steps include: Obtaining the mass of the object to be clamped, calculating and generating the basic friction force of the manipulator based on the mass of the object to be clamped, collecting the shape characteristic parameters of the object to be clamped, and calculating the shape influence coefficient of the object to be clamped based on the shape characteristic parameters of the object to be clamped, wherein the shape characteristic parameters include the maximum boundary length, external surface area and volume of the surface of the object to be clamped; Acquire surface feature parameters of the object to be clamped, calculate the surface concavity coefficient of the object to be clamped based on the obtained surface feature parameters, and generate a shape complexity index of the object to be clamped according to the obtained surface concavity coefficient of the object to be clamped and the shape influence coefficient of the object to be clamped, wherein the surface feature parameters of the object to be clamped include surface average curvature, surface roughness and surface projection area; Obtaining material characteristic parameters of the object to be clamped, determining a basic friction coefficient between the object to be clamped and the contacts on the manipulator gripper based on the material characteristic parameters, and correcting the basic friction coefficient according to the ambient humidity and the number of contacts in contact with the object to be clamped to obtain an accurate friction coefficient, and calculating a basic clamping force according to the accurate friction coefficient, wherein the material characteristic parameters of the object to be clamped include the hardness and elastic modulus of the object to be clamped; The instantaneous acceleration of the manipulator is obtained when it starts the clamping task and when it stops after completing the clamping task. The impact load of the manipulator is calculated based on the instantaneous acceleration. According to the obtained manipulator impact load, combined with the shape complexity index of the object to be clamped and the material characteristic parameters of the object to be clamped, the basic clamping force of the manipulator is corrected to obtain the precise clamping force of the manipulator. The precise clamping force of the manipulator is used to control the clamping force of the manipulator.

2. According to the motor-driven manipulator gripping force control method of claim 1, it is characterized in that: The mass of the object to be clamped is obtained, and based on the mass of the object to be clamped, the basic friction force of the manipulator is calculated and generated. The formula for calculating the basic friction force is: ； In the formula, is the basic friction force of the manipulator, is the mass of the object to be clamped, is the acceleration due to gravity; Based on the shape characteristic parameters of the object to be clamped, the shape influence coefficient of the object to be clamped is calculated, wherein the formula for calculating the shape influence coefficient of the object to be clamped is: ； In the formula, is the shape influence coefficient of the object to be clamped, is the maximum boundary length of the surface of the object to be clamped, is the volume of the object to be clamped, is the surface area of ​​the object to be clamped, where is the shape index, , and are the ratio of the maximum boundary length to the surface area, the ratio of the volume to the surface area of ​​the object to be clamped, and the weight coefficient greater than 0 of the shape index, respectively. ; The shape index The specific calculation is based on the formula: ； In the formula, The minimum boundary length of the surface of the object to be clamped.

3. The method for controlling the gripping force of a motor-driven manipulator according to claim 2, characterized in that: Based on the obtained surface feature parameters, the surface concave-convex coefficient of the object to be clamped is calculated, wherein the formula for calculating the surface concave-convex coefficient of the object to be clamped is: ； In the formula, is the surface concave-convex coefficient of the object to be clamped, is the mean curvature of the surface, is the surface roughness, is the ratio of the surface area of ​​the object to be clamped to the surface projection area, wherein the surface roughness calculation formula of the object to be clamped is as follows: ； ； In the formula, Indicates that the stylus profilometer is The sampling length of the sampling area, is the index of the sampling region, and , K is the number of sampling areas, For the The height of the x-th sampling point within the sampling length of the sampling area deviates from the center line, where x is the coordinate of the sampling point within the sampling length. For the The surface roughness of the sampling area, is the surface roughness of the object to be clamped, the center line and The data is obtained by processing the built-in software of the stylus profilometer; The ratio of the surface area of ​​the object to be clamped to the projected surface area , the calculation is based on the formula: ； In the formula, It is the maximum projected area of ​​an object on a plane.

4. The method for controlling the gripping force of a motor-driven manipulator according to claim 3 is characterized in that: According to the obtained surface concave-convex coefficient of the object to be clamped, combined with the shape influence coefficient of the object to be clamped, the shape complexity index of the object to be clamped is jointly generated, wherein the formula for calculating the shape complexity index of the object to be clamped is: ； In the formula, is the shape complexity index of the object to be gripped, and are the weight coefficients of the shape influence coefficient of the object to be clamped and the surface concave-convex coefficient of the object to be clamped, respectively. and and Both are greater than 0.

5. The method for controlling the gripping force of a motor-driven manipulator according to claim 1, characterized in that: The basic friction coefficient is corrected according to the ambient humidity and the number of contacts that the object to be clamped contacts to obtain the precise friction coefficient, where the formula for calculating the precise friction coefficient is: ； In the formula, For the exact friction coefficient, is the basic friction coefficient, is the number of contacts in contact, is the ambient humidity, is the attenuation coefficient of the friction coefficient due to the number of contacts in contact, is the gain factor of humidity on friction coefficient, where and and All are greater than 0; The basic clamping force is calculated based on the exact friction coefficient, where the basic clamping force is calculated based on the formula: ； In the formula, is the basic clamping force, is the basic friction force of the manipulator.

6. The method for controlling the gripping force of a motor-driven manipulator according to claim 2, characterized in that: The instantaneous acceleration of the manipulator when it starts the gripping task and stops after completing the gripping task is obtained, and the impact load of the manipulator is calculated based on the instantaneous acceleration. The formula for calculating the impact load of the manipulator is: ； ； In the formula, and are the impact load when the manipulator starts the gripping task and the impact load when the manipulator completes the gripping task, respectively. and are the mass of the object to be gripped and the mass of the manipulator, respectively. and They represent the instantaneous acceleration at the beginning and end of the gripping task, and They respectively indicate the start and end time of the gripping task.

7. The method for controlling the gripping force of a motor-driven manipulator according to claim 6, characterized in that: According to the obtained impact load of the manipulator, combined with the shape complexity index of the object to be clamped and the material characteristic parameters of the object to be clamped, the basic clamping force of the manipulator is corrected to obtain the precise clamping force of the manipulator. The formula for calculating the precise clamping force of the manipulator is: ； In the formula, For the precise clamping force of the robot, is the shape complexity index of the object to be gripped, is the material characteristic parameter influence function, , and are the weight coefficients of the impact load, shape complexity index and material characteristic parameter influence function, respectively, where and , and All are greater than 0; The material characteristic parameters affect the function The specific formula is: ； In the formula, is the hardness of the object to be clamped, is the elastic modulus of the object to be clamped.

8. A motor-driven manipulator gripping force control device, characterized in that: The motor-driven manipulator gripping force control device is used to execute the motor-driven manipulator gripping force control method according to any one of claims 1 to 7, comprising: A basic friction force analysis module is used to obtain the mass of the object to be clamped, calculate and generate the basic friction force of the manipulator based on the mass of the object to be clamped, collect the shape characteristic parameters of the object to be clamped, and calculate the shape influence coefficient of the object to be clamped based on the shape characteristic parameters of the object to be clamped, wherein the shape characteristic parameters include the maximum boundary length, external surface area and volume of the surface of the object to be clamped; A shape complexity characterization module is used to obtain surface feature parameters of the object to be clamped, calculate the surface concavity coefficient of the object to be clamped based on the obtained surface feature parameters, and generate a shape complexity index of the object to be clamped based on the obtained surface concavity coefficient of the object to be clamped and the shape influence coefficient of the object to be clamped, wherein the surface feature parameters of the object to be clamped include surface average curvature, surface roughness and surface projection area; A friction force analysis module is used to obtain material characteristic parameters of the object to be clamped, determine the basic friction coefficient between the object to be clamped and the contacts on the manipulator gripper based on the material characteristic parameters, and correct the basic friction coefficient according to the ambient humidity and the number of contacts in contact with the object to be clamped to obtain an accurate friction coefficient, and calculate the basic clamping force according to the accurate friction coefficient, wherein the material characteristic parameters of the object to be clamped include the hardness and elastic modulus of the object to be clamped; The clamping force determination module is used to obtain the instantaneous acceleration of the manipulator when it starts the clamping task and stops after completing the clamping task, and calculate the impact load of the manipulator based on the instantaneous acceleration. According to the obtained manipulator impact load, combined with the shape complexity index of the object to be clamped and the material characteristic parameters of the object to be clamped, the basic clamping force of the manipulator is corrected to obtain the precise clamping force of the manipulator, and the clamping force of the manipulator is controlled by the precise clamping force of the manipulator; A manipulator module, the manipulator module comprising a base (1) for fixing, a driving device (3) connected to the base (1) via a connecting block (2), and a mechanical claw (4) for clamping an object to be clamped, wherein the driving device (3) drives the mechanical claw (4) to clamp the object to be clamped via a connecting rod (5), and the mechanical claw (4) has a plurality of contacts (6) on one side thereof for clamping the object to be clamped.

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