Stable grasping force threshold control method, system and manipulator for oil tea tree vibration manipulator

Abstract

The present invention provides a method, system and manipulator for controlling the threshold value of the stable gripping force of a vibration manipulator for oil tea trees, and relates to the field of technical mechanical engineering and automation control. The present invention obtains the friction coefficient of the surface of the oil tea tree and determines the damage threshold, measures the opening angle and clamping pressure of the claw fingers when the manipulator is working, determines the clamping pressure range, calculates the maximum pressure, the minimum pressure and the equivalent pressure, and adjusts the clamping pressure of the manipulator, obtains the natural frequency and the maximum dynamic displacement response of the manipulator claw fingers, and adjusts the opening angle of the claw fingers based on this, calculates the data to generate the gripping force index, and iteratively adjusts to ensure that the gripping force index is less than the damage threshold. The present invention comprehensively utilizes mechanical simulation and actual measurement data, and through feedback adjustment and refined control, successfully solves the problems of manipulator wear and inefficiency caused by excessive pressure and load in the prior art, and improves the service life and production efficiency of the manipulator.

Description

Technical Field

[0001] The present invention relates to the field of mechanical engineering and automation control technology, and in particular to a method, system and manipulator for controlling a threshold value of a stable grasping force of an oil-tea tree vibration manipulator. Background Art

[0002] Fruit picking is a key link in agricultural production, especially in large-scale fruit cultivation. Improving picking efficiency and reducing manpower input has become an urgent need. Although traditional mechanical picking methods can replace manual operations to a certain extent, they still face many challenges due to the different shapes of trees and complex distribution of fruits. The clamps clamp the trunks and the vibration device applies vibration force to the trunks to achieve automatic fruit shedding. This is a relatively efficient method. However, the existing mechanical clamps often show several defects in the process of transmitting vibration force and cannot achieve ideal picking effects.

[0003] In the prior art, a manipulator control method is disclosed with publication number CN116604551A, which obtains several groups of acceleration thresholds according to the load state of the manipulator, determines the acceleration control threshold according to the several groups of acceleration thresholds; determines the output force safety threshold of the driver according to the acceleration control threshold and the mass of the load; and obtains the acceleration threshold of the manipulator according to the maximum acceleration, the minimum acceleration, the acceleration change rate threshold and the motion time in the motion data; controls the acceleration of the manipulator within the output force safety threshold, avoids the servo motor driving the manipulator to transport and move at full load due to the acceleration setting exceeding the design threshold range, and causes the manipulator to be subjected to inertial force exceeding the design threshold during deceleration, causing wear on the manipulator, thereby shortening the service life of the manipulator; and also avoids the servo motor operating unsaturated due to the acceleration setting being less than the equipment design threshold range, thereby reducing production efficiency.

[0004] Insufficient existing technology:

[0005] First, the existing technology fails to fully consider the actual load state of the robot under high acceleration conditions, resulting in the acceleration setting exceeding the design threshold range in some cases. This acceleration beyond the range may cause the servo motor to operate at full load, increase energy consumption, and accelerate the wear of the servo motor and the robot itself, thereby shortening the service life of the robot.

[0006] Secondly, some methods in the prior art fail to effectively balance acceleration and production efficiency. If the acceleration setting is lower than the equipment design threshold range, the servo motor may not operate in a saturated state, which will reduce the overall production efficiency and prevent the equipment from operating at its maximum efficiency, resulting in resource waste and extended production cycles. This inefficiency is particularly evident in large-scale automated production, directly affecting overall production capacity and economic benefits.

[0007] Therefore, it is necessary to provide a method, system and manipulator for controlling the stable grasping force threshold of an oil tea tree vibration manipulator to solve the above problems.

[0008] 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

[0009] The purpose of the present invention is to provide a method, system and manipulator for controlling the stable grasping force threshold of a tea oil tree vibration manipulator, so as to solve the problems raised in the above-mentioned background technology.

[0010] To achieve the above object, the present invention provides the following technical solutions:

[0011] The method for controlling the threshold value of the stable grasping force of the oil tea tree vibration manipulator includes the following specific steps:

[0012] Step 1: Obtain the friction coefficient of the oil tea tree surface through tests at different pressures, and determine the pressure value when the oil tea tree bark is damaged, and use it as the damage threshold of the bark surface;

[0013] Step 2: Use the manipulator to grab the tea tree, and record the clamping pressure of the manipulator and the displacement before and after grabbing, and calculate the equivalent pressure when the manipulator grabs the tea tree, the maximum deformation of the manipulator, the natural frequency of the manipulator's fingers, and the maximum dynamic displacement response, including:

[0014] Conduct static simulation, use finite element software to solve, calculate equivalent pressure, and use the node displacement of the manipulator gripper to calculate the maximum deformation of the gripper under loading conditions;

[0015] Perform dynamic simulation to obtain the natural frequency of the manipulator's fingers, and apply loading conditions of different vibration frequencies to calculate the maximum dynamic displacement response of the manipulator's fingers;

[0016] Step 3: Generate a grasping index based on equivalent pressure, maximum deformation, natural frequency, and maximum dynamic displacement response, and compare the grasping index with the damage threshold. If the grasping index is greater than or equal to the damage threshold, proceed to step 4. If the grasping index is less than the damage threshold, do not adjust the manipulator.

[0017] Step 4: The clamping pressure of the manipulator is adjusted based on the calculated equivalent pressure and maximum deformation, and the opening angle of the manipulator fingers is adjusted based on the calculated maximum dynamic displacement response of the manipulator fingers.

[0018] Furthermore, the damage threshold of the bark surface was determined based on the following method:

[0019] K bark samples were collected from the surface of the same tea oil tree, and the K bark samples were placed one by one on the sliding platforms of different friction testers. Pressure was applied to the bark samples in a direction perpendicular to the bark samples, and the pressure applied to each bark sample was different. The friction force of the bark sample under the corresponding pressure was recorded, and the formula for calculating the friction coefficient was as follows:

[0020]

[0021] Among them, μ k represents the friction coefficient of the oil tea tree surface of the kth bark sample, F k is the pressure on the kth bark sample, N k is the friction force of the kth bark sample, k is the index of the bark sample, and k∈[1,K], μ represents the friction coefficient of the oil tea tree surface;

[0022] The crack length of each bark sample under the corresponding pressure was recorded, and the relationship between the crack length and the corresponding pressure was plotted with pressure as the independent variable and crack length as the dependent variable. The pressure corresponding to the point with the maximum slope in the relationship diagram was taken as the damage pressure σ damage , and the damage pressure is taken as the damage threshold.

[0023] Furthermore, the equivalent pressure of the manipulator and the maximum deformation of the manipulator fingers are calculated based on the following method:

[0024] Create a geometric model of the contact interface between the manipulator's claw and the tea tree, and mesh the contact interface for finite element analysis. Obtain the pressure of each network node, and decompose the pressure of each network node into partial pressures in three directions. Filter out the maximum partial pressure, median partial pressure, and minimum partial pressure from the partial pressures of all network nodes to calculate the equivalent pressure. The formula is:

[0025]

[0026] Among them, σ vn represents the equivalent pressure, σ max represents the maximum partial pressure selected from the partial pressures of network nodes, σ min represents the minimum partial pressure selected from the partial pressures of network nodes, σ mid It represents the median of the partial pressures selected from the partial pressures of the network nodes;

[0027] Determine multiple grasping nodes on the manipulator gripper finger, record the coordinates of each grasping node before and after grasping, calculate the displacement change of each grasping node, and select the maximum displacement change as the maximum deformation of the gripper finger under loading conditions δ max .

[0028] Furthermore, the natural frequency of the manipulator fingers is obtained, and loading conditions with different vibration frequencies are applied to calculate the maximum dynamic displacement response of the manipulator fingers, based on the following method:

[0029] Using the equivalent mass and stiffness method, the robot gripper finger is simplified into a single-degree-of-freedom or multi-degree-of-freedom mass-spring system, and the natural frequency is calculated using basic vibration theory. The derivation formula is:

[0030]

[0031] Among them, ω n represents the natural frequency of the robot gripper finger, k eq is the equivalent stiffness of the manipulator gripper system, m eq is the equivalent mass in the manipulator gripper finger system;

[0032] The maximum dynamic displacement response is solved by using the frequency domain analysis method. First, a sinusoidal external force is applied to the robot gripper finger, and its motion is described by the motion equation. Then, the steady-state response is expressed in the frequency domain. When the natural frequency is equal to the excitation frequency, the system displacement response amplitude reaches the maximum. The formula is:

[0033]

[0034]

[0035] Among them, x(t) is the displacement, which describes the displacement of the system at time t. is the velocity, which represents the first-order derivative of displacement x(t) with respect to time, is acceleration, indicating speed The first-order derivative with respect to time, F0 is the external force amplitude, that is, the maximum value of the sinusoidal external force applied to the system, c is the damping coefficient, cos(ω n t) is the cosine function, which describes the change of external force over time, X is the displacement response amplitude, is a cosine function, describing the steady-state response changing over time. is the phase angle, describing the phase shift relative to the external force, F 0 / m eq is the external force amplitude per unit mass, ω is the excitation frequency, and ξ is the damping ratio;

[0036] When n =ω, that is, when the excitation frequency is equal to the natural frequency, the maximum displacement response amplitude is:

[0037]

[0038] Among them, X max is the maximum dynamic displacement response.

[0039] Furthermore, the calculated equivalent pressure, maximum deformation, natural frequency and maximum dynamic displacement response are used to comprehensively generate the grip index, based on the following method:

[0040]

[0041] Where G represents the grip index, σ vn is the equivalent pressure, δ max is the maximum deformation, ω n is the natural frequency, X max is the maximum dynamic displacement response, β0 is a proportional constant used to set the pressure reference value, a is the influence index of equivalent pressure, b is the influence index of maximum deformation, z is the influence index of natural frequency, β2 is the influence index of dynamic displacement response, α1 is the attenuation coefficient, which indicates the attenuation degree of gripping effect with the increase of equivalent pressure; β1 is the influence coefficient of deformation, which indicates the degree of inhibition of maximum deformation on gripping performance, m is the balance coefficient of overall influence, which indicates the power balance of the whole expression. By adjusting m, the influence degree of the comprehensive effect of the four variables on gripping performance can be controlled; ω min ,ω max Indicates the minimum and maximum values ​​of the natural frequency.

[0042] Furthermore, the grasping index and the damage threshold are compared. If the grasping index is greater than or equal to the damage threshold, step 4 is entered. If the grasping index is less than the damage threshold, the manipulator is not adjusted. The logic formula is:

[0043]

[0044] Wherein, Q represents the logical value for judging whether the grasping index exceeds the damage threshold. When Q=0, it means that the damage threshold is not exceeded and there is no need to adjust the claw finger opening angle and clamping pressure. When Q=1, it means that the damage threshold is exceeded and the claw finger opening angle and clamping pressure are adjusted through step 4 until the grasping index is less than the damage threshold. damage Indicates the damage threshold.

[0045] Furthermore, the method for adjusting the clamping pressure of the manipulator based on the equivalent pressure and maximum deformation generated by calculation, and adjusting the opening angle of the manipulator claw based on the maximum dynamic displacement response obtained by calculation is as follows:

[0046] When the equivalent pressure exceeds the expected pressure and the maximum deformation exceeds the expected deformation, the clamping pressure needs to be reduced, but it must not be lower than the minimum safe clamping pressure; otherwise, the clamping pressure is increased, but it must not be higher than the damage threshold. The logic is as follows:

[0047] Δσ=ρ1*(σallow -σ vn )+ρ2*(δ allow -δ max )

[0048] if σ vn >σ allow andδ max >δ allow Then clamp =max(σ clamp -Δσ,σ safe-min )

[0049] else σ vn <σ allow andδ max <δ allow Then clamp =min(σ clamp +Δσ,σ damage )

[0050] Among them, σ clamp is the adjusted clamping pressure, σ safe-min Indicates the minimum safe clamping pressure to prevent unstable grip, σ damage represents the damage threshold, σ allow is the expected pressure, δ allow is the expected deformation, ρ1 and ρ2 are the corresponding proportional coefficients, which are used to indicate the influence of the deviation between the equivalent pressure and the maximum deformation on the clamping pressure, and Δσ indicates the clamping pressure that needs to be adjusted;

[0051] The method for adjusting the opening angle of the manipulator gripper fingers based on the calculated maximum dynamic displacement response is as follows:

[0052] If the maximum dynamic displacement response exceeds the allowable range, it means that the robot gripping deformation is large and the stability is reduced. It is necessary to reduce the opening angle of the claw fingers, but it must not be lower than the minimum opening angle to prevent mechanical damage caused by unstable clamping. If the maximum dynamic displacement is within the allowable range, it means that the gripping stability is good. Increase the opening angle of the claw fingers, but it must not be greater than the maximum opening angle to prevent damage caused by excessive opening. The logic is:

[0053] Δθ=ρ3*(X allow -X max )

[0054] if X max >X allow Then θ adjust =max(θ current -Δθ,θ min )

[0055] else Xmax ≤X allow thenθ adjust =max(θ current +Δθ,θ max )

[0056] Among them, Δθ represents the claw finger opening angle that needs to be adjusted, ρ3 is the corresponding proportional coefficient, which represents the relationship between the maximum displacement dynamic response and the opening angle, and X allow is the desired displacement dynamic response, θ adjust is the adjusted claw opening angle, θ current is the current claw opening angle, θ min is the minimum opening angle of the claw finger, θ max is the maximum opening angle of the claw, X max is the maximum dynamic displacement response.

[0057] The present invention also provides a tea tree vibration manipulator stable grasping force threshold control system, the control system is used to execute any one of the tea tree vibration manipulator stable grasping force threshold control methods described above, including:

[0058] A friction characteristic and damage threshold evaluation module, which is used to obtain the friction coefficient of the oil tea tree surface through tests with different pressures, and to determine the pressure value when the oil tea tree bark is damaged, and use it as the damage threshold of the bark surface;

[0059] The robot grasping performance simulation module is used to grasp the tea tree with the robot, record the clamping pressure of the robot and the clamping angle after grasping, and calculate the equivalent pressure, maximum deformation of the robot, natural frequency of the robot's claws and maximum dynamic displacement response when the robot grasps the tea tree, specifically including:

[0060] Conduct static simulation, use finite element software to solve, calculate equivalent pressure, and use the node displacement of the manipulator gripper to calculate the maximum deformation of the gripper under loading conditions;

[0061] Perform dynamic simulation to obtain the natural frequency of the manipulator's fingers, and apply loading conditions of different vibration frequencies to calculate the maximum dynamic displacement response of the manipulator's fingers;

[0062] A gripping index evaluation module, wherein the gripping index evaluation module comprehensively generates a gripping index based on equivalent pressure, maximum deformation, natural frequency, and maximum dynamic displacement response, and compares the gripping index with a damage threshold. If the gripping index is greater than or equal to the damage threshold, the process proceeds to step 4. If the gripping index is less than the damage threshold, the manipulator is not adjusted.

[0063] A clamping pressure and clamping angle adjustment module, wherein the clamping pressure and clamping angle adjustment module adjusts the clamping pressure of the manipulator based on the calculated equivalent pressure and maximum deformation, and adjusts the opening angle of the manipulator claw based on the calculated maximum dynamic displacement response of the manipulator claw.

[0064] The present invention further provides a tea tree oil vibration manipulator, which comprises the tea tree oil vibration manipulator stable gripping force threshold control system.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] First, by obtaining the friction coefficient of the tea tree surface and the bark damage threshold, measuring the opening angle and clamping pressure of the manipulator's claws when it is working, and recording the clamping pressure on the tree caused by different dragging frequencies, the specific parameters of the manipulator under different loads and operating conditions were determined. These tests and records ensure that the pressure on the tree is within a safe range and will not cause bark damage, thereby extending the service life of the manipulator;

[0067] Secondly, through static and dynamic simulation, finite element analysis is used to obtain the maximum pressure, minimum pressure, equivalent pressure and maximum dynamic displacement response of the manipulator under different operating conditions, and the clamping pressure and claw finger opening angle of the manipulator are adjusted accordingly. This allows the manipulator to operate within the design threshold, avoiding the full load operation of the servo motor or equipment wear caused by the clamping pressure and dynamic response exceeding the design threshold, while ensuring the efficiency and stability of the manipulator system. By constructing a gripping force threshold regression model, the gripping force index is comprehensively generated using the calculated equivalent pressure, maximum deformation, natural frequency and maximum dynamic displacement response, and compared with the damage threshold, the stable gripping function of the manipulator under different operating conditions can be further optimized. The model repeatedly adjusts the claw finger opening angle and clamping pressure to ensure that the manipulator can operate efficiently and safely at different frequencies without causing damage to the manipulator or the tree.

[0068] The present invention makes comprehensive use of mechanical simulation and actual measurement data, and through feedback adjustment and refined control, successfully solves the problems of manipulator wear and inefficiency caused by excessive pressure and load in the prior art, thereby improving the service life and production efficiency of the manipulator. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 It is a schematic diagram of the overall method flow of the present invention.

[0070] Figure 2 It is a schematic diagram of the system module flow of the present invention. DETAILED DESCRIPTION

[0071] 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.

[0072] 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.

[0073] Example:

[0074] See also Figure 1 , a method for controlling the threshold value of the stable grasping force of a vibration manipulator for an oil tea tree, the specific steps comprising:

[0075] Step 1: Obtain the friction coefficient of the oil tea tree surface through tests at different pressures, and determine the pressure value when the oil tea tree bark is damaged, and use it as the damage threshold of the bark surface;

[0076] Step 2: Use the manipulator to grasp the tea tree, and record the clamping pressure of the manipulator and the clamping angle after grasping, and calculate the equivalent pressure when the manipulator grasps the tea tree, the maximum deformation of the manipulator, the natural frequency of the manipulator's fingers, and the maximum dynamic displacement response, including:

[0077] Conduct static simulation, use finite element software to solve, calculate equivalent pressure, and use the node displacement of the manipulator gripper to calculate the maximum deformation of the gripper under loading conditions;

[0078] Perform dynamic simulation to obtain the natural frequency of the manipulator's fingers, and apply loading conditions of different vibration frequencies to calculate the maximum dynamic displacement response of the manipulator's fingers;

[0079] Step 3: Generate a grasping index based on equivalent pressure, maximum deformation, natural frequency, and maximum dynamic displacement response, and compare the grasping index with the damage threshold. If the grasping index is greater than or equal to the damage threshold, proceed to step 4. If the grasping index is less than the damage threshold, do not adjust the manipulator.

[0080] Step 4: The clamping pressure of the manipulator is adjusted based on the calculated equivalent pressure and maximum deformation, and the opening angle of the manipulator fingers is adjusted based on the calculated maximum dynamic displacement response of the manipulator fingers.

[0081] It should be noted that by experimentally measuring the friction coefficient and crack development of the tea tree surface under different pressures, the damage threshold of the bark can be scientifically determined. This process reveals the damage behavior of the bark surface under force by recording the relationship between friction, crack length and applied pressure. The determination of damage pressure and damage intensity provides a quantitative basis for subsequent protective measures and repair strategies, and helps to predict possible damage to the bark when it is subjected to mechanical forces in actual environments.

[0082] Therefore, it is necessary to determine the damage threshold of the bark surface, based on the following method:

[0083] K bark samples were collected from the surface of the same tea oil tree, and the K bark samples were placed one by one on the sliding platforms of different friction testers. Pressure was applied to the bark samples in a direction perpendicular to the bark samples, and the pressure applied to each bark sample was different. The friction force of the bark sample under the corresponding pressure was recorded, and the formula for calculating the friction coefficient was as follows:

[0084]

[0085] Among them, μ k represents the friction coefficient of the oil tea tree surface of the kth bark sample, F k is the pressure on the kth bark sample, N k is the friction force of the kth bark sample, k is the index of the bark sample, and k∈[1,K], μ represents the friction coefficient of the oil tea tree surface;

[0086] The crack length of each bark sample under the corresponding pressure was recorded, and the relationship between the crack length and the corresponding pressure was plotted with pressure as the independent variable and crack length as the dependent variable. The pressure corresponding to the point with the maximum slope in the relationship diagram was taken as the damage pressure σ damage , and the damage pressure is taken as the damage threshold.

[0087] It should be noted that calculating the equivalent pressure and maximum deformation of the manipulator is crucial to ensure the accuracy and safety of the grasping operation. The calculation of the equivalent pressure can reflect the overall force condition when the claw contacts the surface of the tea tree, avoiding excessive local pressure that causes damage to the bark or unstable clamping. By analyzing the pressure distribution of the contact interface, we can quantify the force condition of the manipulator's claw during the grasping process, thereby optimizing the clamping force and avoiding excessive deformation. At the same time, calculating the maximum deformation helps to evaluate the flexibility and stability of the claw, ensuring that the manipulator can stably clamp the target object when grasping, and will not affect the grasping effect or damage the target object due to excessive deformation.

[0088] The grasping node refers to the key position where the robot's claw contacts the tea tree during the grasping process, such as the front end contact point of the claw, which is usually the front end position where the claw contacts the surface of the tea tree. The displacement change of this node can reflect the initial contact between the claw and the bark surface, as well as the deformation caused by clamping force or friction. There are also contact points on both sides of the claw. The specific position is the contact points on both sides of the claw. This node can well feedback the pressure and deformation of the edge position of the robot. There is also the contact depth point of the claw. The contact depth point refers to a certain depth position of the claw. When clamping the bark, the claw enters the point on the bark surface. This node can provide the maximum deformation of the claw during the clamping process.

[0089] Therefore, it is necessary to calculate the equivalent pressure of the manipulator and the maximum deformation of the manipulator's fingers, based on the following method:

[0090] Create a geometric model of the contact interface between the manipulator's claw and the tea tree, and mesh the contact interface for finite element analysis. Obtain the pressure of each network node, and decompose the pressure of each network node into partial pressures in three directions. Filter out the maximum partial pressure, median partial pressure, and minimum partial pressure from the partial pressures of all network nodes to calculate the equivalent pressure. The formula is:

[0091]

[0092] Among them, σ vn represents the equivalent pressure, σ max represents the maximum partial pressure selected from the partial pressures of network nodes, σ min represents the minimum partial pressure selected from the partial pressures of network nodes, σ mid It represents the median of the partial pressure selected from the partial pressures of the network nodes;

[0093] Determine multiple grasping nodes on the manipulator gripper finger, record the coordinates of each grasping node before and after grasping, calculate the displacement change of each grasping node, and select the maximum displacement change as the maximum deformation of the gripper finger under loading conditions δmax .

[0094] It should be noted that obtaining the natural frequency of the manipulator's fingers and analyzing their maximum dynamic displacement response are crucial to ensuring the stability of the manipulator under vibration and external forces. The manipulator may experience external vibration or frequency changes during the actual grasping process. Especially in a high-frequency vibration environment, the dynamic response of the fingers may cause excessive displacement or resonance, which in turn affects the grasping accuracy and object safety. By calculating the natural frequency of the manipulator's fingers and applying loading conditions with different vibration frequencies, the vibration characteristics of the fingers during the working process can be predicted, thereby avoiding the overlap of the resonance frequency and the external excitation frequency, and ensuring the stability and control accuracy of the fingers. At the same time, by calculating the maximum dynamic displacement response, the design of the manipulator can be optimized, the failure risk of the mechanical structure can be reduced, and the operation efficiency and safety can be improved.

[0095] Equivalent mass and equivalent stiffness are important parameters for calculating natural frequency by simplifying the dynamic characteristics of the robot gripper finger system. In a multi-degree-of-freedom system, the stiffness and mass distribution of the robot gripper finger is relatively complex, and it is usually necessary to simplify it into an equivalent mass-spring system for relevant calculations. The equivalent mass can be obtained by weighting the mass of each part of the robot gripper finger according to its position and influence calculation, while the equivalent stiffness is obtained by analyzing the elastic characteristics of the gripper finger structure and considering the stiffness distribution of each component to synthesize a parameter representing the overall stiffness of the system. These simplified equivalent mass and stiffness parameters can effectively describe the inherent vibration characteristics of the system and provide a basis for further calculation of natural frequency and dynamic displacement response.

[0096] Therefore, it is necessary to obtain the natural frequency of the manipulator's gripper finger and apply loading conditions of different vibration frequencies to calculate the maximum dynamic displacement response of the manipulator's gripper finger. The method is as follows:

[0097] Using the equivalent mass and stiffness method, the robot gripper finger is simplified into a single-degree-of-freedom or multi-degree-of-freedom mass-spring system, and the natural frequency is calculated using basic vibration theory. The derivation formula is:

[0098]

[0099] Among them, ω n represents the natural frequency of the robot gripper finger, k eq is the equivalent stiffness of the manipulator gripper system, m eq is the equivalent mass in the manipulator gripper finger system;

[0100] The maximum dynamic displacement response is solved by using the frequency domain analysis method. First, a sinusoidal external force is applied to the robot gripper finger, and its motion is described by the motion equation. Then, the steady-state response is expressed in the frequency domain. When the natural frequency is equal to the excitation frequency, the system displacement response amplitude reaches the maximum. The formula is:

[0101]

[0102] Among them, x(y) is the displacement, which describes the displacement of the system at time t. is the velocity, which represents the first-order derivative of displacement x(t) with respect to time, is acceleration, indicating speed The first-order derivative with respect to time, F0 is the external force amplitude, that is, the maximum value of the sinusoidal external force applied to the system, c is the damping coefficient, cos(ω n t) is the cosine function, which describes the change of external force over time, X is the displacement response amplitude, is a cosine function, describing the steady-state response changing over time. is the phase angle, describing the phase shift relative to the external force, F0 / m eq is the external force amplitude per unit mass, ω is the excitation frequency, and ξ is the damping ratio;

[0103] When n =ω, that is, when the excitation frequency is equal to the natural frequency, the maximum displacement response amplitude is:

[0104]

[0105] Among them, X max is the maximum dynamic displacement response.

[0106] It should be noted that in the grasping process of the manipulator's fingers, the grasping index is a key parameter to measure the grasping effect and grasping stability. The grasping performance of the manipulator depends not only on the externally applied pressure, but also on the deformation, natural frequency and dynamic response of the manipulator's fingers. In order to effectively evaluate the grasping performance, these factors must be considered comprehensively. The grasping effect can be comprehensively evaluated by calculating the equivalent pressure, maximum deformation, natural frequency and maximum dynamic displacement response. The grasping index can quantify the combined impact of these different factors and help designers optimize the grasping ability of the manipulator. For example, too high deformation or too large dynamic displacement may lead to unstable grasping and reduce pressure efficiency, while natural frequency and vibration response are closely related to the stability and accuracy of the manipulator. Establishing a comprehensive grasping index is an important means to ensure that the manipulator can provide the best grasping effect, reduce errors and improve work efficiency in the actual grasping process.

[0107] The formula for calculating the gripping index is to calculate the gripping index of the robot gripper through a variety of factors. Its composition can be divided into several parts, each of which reflects different influencing factors and their mutual relationship. For the equivalent pressure relationship part This reflects the effect of equivalent pressure on gripping performance. The greater the pressure, the stronger the gripping force, but too high pressure may lead to attenuation of the gripping effect, so the attenuation factor is introduced. It means that as the pressure increases, the gripping effect may decrease, especially in some materials or structures, excessive pressure may cause problems such as sliding or deformation. a is the pressure influence index, which is used to adjust the influence of equivalent pressure on the pressure index. For the maximum deformation part of the relationship Where β1 represents the degree of suppression of deformation, b is the influence index of deformation on gripping performance. When the deformation increases, the value of this item approaches 0, thereby reducing the value of the pressure index, indicating that the gripping effect decreases. For the natural frequency relation part This term is used to represent the response change of the natural frequency within a specific frequency range, aiming to quantify the effect of the natural frequency on the gripping pressure. This term reflects the change in the gripping effect of the manipulator at different frequencies, where ω max ,ω min is the maximum and minimum value of the frequency, which controls the change of the gripping effect within the frequency range; for the maximum dynamic displacement response part This term is used to consider the attenuation effect of dynamic displacement on the grasping performance. β2 is the attenuation coefficient of dynamic displacement to the pressure index, which indicates the degree of reduction in grasping performance when the displacement response increases.

[0108] Therefore, it is necessary to use the calculated equivalent pressure, maximum deformation, natural frequency and maximum dynamic displacement response to comprehensively generate the grip index, based on the following method:

[0109]

[0110] Where G represents the grip index, σ vn is the equivalent pressure, δ max is the maximum deformation, ω n is the natural frequency, X maxis the maximum dynamic displacement response, β0 is a proportional constant used to set the pressure reference value, a is the influence index of equivalent pressure, b is the influence index of maximum deformation, z is the influence index of natural frequency, β2 is the influence coefficient of dynamic displacement response, α1 is the attenuation coefficient, which indicates the attenuation degree of grasping effect as the equivalent pressure increases; β1 is the influence coefficient of deformation, which indicates the degree of inhibition of maximum deformation on grasping performance, m is the balance coefficient of overall influence, which indicates the power balance of the whole expression. By adjusting m, the influence degree of comprehensive effect of four variables on grasping performance can be controlled; in the above formula, the influence index size is arranged as a>b>z>0, because the equivalent pressure directly determines the gripping force of the manipulator on the target object, and the strength of gripping force is usually closely related to pressure. When the pressure increases, the gripping ability of the manipulator increases, so the influence on gripping performance is usually the most significant, so the highest weight ratio a is given; the maximum deformation reflects the deformation that may occur in the manipulator during the process of grasping the object. Too much deformation will affect the stability of the gripping force, resulting in loose clamping or even damage to the grasped object. Large deformation will directly inhibit the gripping force and reduce the gripping index, so the second weight ratio b is assigned; the change of natural frequency will affect the amplitude of vibration, but it will not directly affect the size of the gripping force like equivalent pressure or deformation, so the minimum weight ratio z is assigned, and the range of β1 and β2 is [0,1], because by limiting the range of β1 and β2 to [0,1], the influence of these factors on the gripping performance can be flexibly adjusted. If the influence of a certain factor needs to be weaker, the coefficient can be set to close to 0; if the role of a certain factor needs to be emphasized, the coefficient can be set to close to 1. In this way, the gripping performance can be finely controlled by adjusting these coefficients during the design process. m is usually a positive real number in [5,10]. If m is less than 1, it is believed that the influencing factors in the formula, such as pressure and deformation, contribute more to the gripping performance. The gripping index will respond more strongly to changes in these factors, which will lead to system instability. When m is greater than 5 and less than 10, the response to each factor is weaker, and the gripping performance will become more stable. Even if the input parameters change significantly, the fluctuation of the gripping index will not be particularly drastic. The β0 value range is set to (0,1] because limiting the value of the β0 proportional constant to less than 1 can ensure that the calculation of the gripping index will not result in an excessively large result due to this benchmark value. An excessively large gripping index may lead to an over-evaluation of the gripping performance and generate unnecessary excitations in the control system. At the same time, it is necessary to ensure that the gripping index is positive in value. The gripping performance is a physical quantity and should not be negative, so it must be set to a value greater than zero.

[0111] It should be noted that by comparing the grip index with the damage threshold, the clamping strength of the manipulator can be dynamically adjusted to ensure that the object can be effectively controlled during the gripping process without causing damage to the object or system failure due to excessive pressure. When the grip index exceeds the damage threshold, the system automatically triggers the adjustment mechanism and resets the clamping force until the pressure returns to a safe range.

[0112] Therefore, it is necessary to compare the grasping index and the damage threshold. If the grasping index is greater than or equal to the damage threshold, proceed to step 4. If the grasping index is less than the damage threshold, the manipulator is not adjusted. The logic formula is:

[0113]

[0114] Wherein, Q represents the logical value for judging whether the grasping index exceeds the damage threshold. When Q=0, it means that the damage threshold is not exceeded and there is no need to adjust the claw finger opening angle and clamping pressure. When Q=1, it means that the damage threshold is exceeded and the claw finger opening angle and clamping pressure are adjusted through step 4 until the grasping index is less than the damage threshold. damage Indicates the damage threshold.

[0115] It should be noted that by precisely adjusting the clamping pressure based on the equivalent pressure and the maximum deformation, the manipulator can provide sufficient gripping force during the grasping process, while avoiding damage to the object or unstable grasping due to excessive or insufficient clamping. At the same time, the opening angle of the claw fingers is adjusted in real time in combination with the maximum dynamic displacement response, and the displacement error is corrected through the feedback control strategy to ensure stability and accuracy during the grasping process. These adjustment mechanisms enable the manipulator to adapt to different working environments and task requirements, and improve the safety, reliability and intelligence level of the grasping system.

[0116] Therefore, it is necessary to adjust the clamping pressure of the manipulator based on the equivalent pressure and maximum deformation generated by calculation, and adjust the opening angle of the manipulator claw based on the maximum dynamic displacement response obtained by calculation. The method is as follows:

[0117] When the equivalent pressure exceeds the expected pressure and the maximum deformation exceeds the expected deformation, the clamping pressure needs to be reduced, but it must not be lower than the minimum safe clamping pressure; otherwise, the clamping pressure is increased, but it must not be higher than the damage threshold. The logic is as follows:

[0118] Δσ=ρ1*(σ allow -σ vn )+ρ2*(σ allow -δ max )

[0119] if σ vn >σ allow and δmax >δ allow Then clamp =max(σ clamp -Δσ,σ safe-min )

[0120] else σ vn <σ allow and δ max <δ allow Then clamp =min(σ clamp +Δσ,σ damage )

[0121] Among them, σ clamp is the adjusted clamping pressure, σ safe-min Indicates the minimum safe clamping pressure to prevent unstable grip, σ damage represents the damage threshold, σ allow is the expected pressure, δ allow is the expected deformation, ρ1 and ρ2 are corresponding proportional coefficients, which are used to indicate the influence of the deviation between the equivalent pressure and the maximum deformation on the clamping pressure, and Δσ indicates the clamping pressure that needs to be adjusted. In the above formula, the proportional coefficients of ρ1 and ρ2 are set to ρ1>ρ2>0 because the equivalent pressure directly affects the clamping effect of the manipulator and the safety of the target object. Excessive pressure may not only cause damage to the object, but also cause unstable clamping. Therefore, a higher weight should be given when adjusting the clamping pressure. The maximum deformation has a relatively small influence. If the object is deformed greatly but does not reach the damage threshold, it may still be acceptable. Therefore, the adjustment of the deformation has a relatively low influence, so a lower weight is given.

[0122] The method for adjusting the opening angle of the manipulator gripper fingers based on the calculated maximum dynamic displacement response is as follows:

[0123] If the maximum dynamic displacement response exceeds the allowable range, it means that the robot gripping deformation is large and the stability is reduced. It is necessary to reduce the opening angle of the claw fingers, but it must not be lower than the minimum opening angle to prevent mechanical damage caused by unstable clamping. If the maximum dynamic displacement is within the allowable range, it means that the gripping stability is good. Increase the opening angle of the claw fingers, but it must not be greater than the maximum opening angle to prevent damage caused by excessive opening. The logic is:

[0124] Δθ=ρ3*(X allow -X max )

[0125] if X max >X allow Then θ adjust =max(θ current -Δθ,θmin )

[0126] else X max ≤X allow Then θ adjust =max(θ current +Δθ,θ max )

[0127] Among them, Δθ represents the claw finger opening angle that needs to be adjusted, ρ3 is the corresponding proportional coefficient, which represents the relationship between the maximum displacement dynamic response and the opening angle, and X allow is the desired displacement dynamic response, θ adjust is the adjusted claw opening angle, θ current is the current claw opening angle, θ min is the minimum opening angle of the claw finger, θ max is the maximum opening angle of the claw, X max is the maximum dynamic displacement response; in the above formula, the value range of ρ3 is set to (0,1], and ρ3 should be a positive value, indicating that there is a positive correlation between the adjustment angle and the displacement response. When the maximum dynamic displacement exceeds the allowable range, the opening angle of the claw finger should be reduced accordingly, and vice versa; and it is less than or equal to 1 because when ρ3≤1, the system can ensure that the amplitude of each adjustment will not be too large, thereby avoiding unstable grasping due to excessive adjustment. For example, setting ρ3=0.5 means that the angle of each adjustment is half of the dynamic displacement deviation, which can make the adjustment of the claw finger smoother and avoid mechanical damage caused by mutations; ρ3 must be greater than 0 to ensure that the adjustment caused by the dynamic displacement response is effective. If ρ3=0, it means that there is no adjustment, which will cause the system to be unable to respond to dynamic changes and unable to achieve effective control.

[0128] See also Figure 2 The present invention also provides a tea tree vibration manipulator stable grasping force threshold control system, the control system is used to execute any one of the tea tree vibration manipulator stable grasping force threshold control methods, including:

[0129] A friction characteristic and damage threshold evaluation module, which is used to obtain the friction coefficient of the oil tea tree surface through tests with different pressures, and to determine the pressure value when the oil tea tree bark is damaged, and use it as the damage threshold of the bark surface;

[0130] The robot grasping performance simulation module is used to grasp the tea tree with the robot, record the clamping pressure of the robot and the clamping angle after grasping, and calculate the equivalent pressure, maximum deformation of the robot, natural frequency of the robot's claws and maximum dynamic displacement response when the robot grasps the tea tree, specifically including:

[0131] Conduct static simulation, use finite element software to solve, calculate equivalent pressure, and use the node displacement of the manipulator gripper to calculate the maximum deformation of the gripper under loading conditions;

[0132] Perform dynamic simulation to obtain the natural frequency of the manipulator's fingers, and apply loading conditions of different vibration frequencies to calculate the maximum dynamic displacement response of the manipulator's fingers;

[0133] A gripping index evaluation module, wherein the gripping index evaluation module comprehensively generates a gripping index based on equivalent pressure, maximum deformation, natural frequency, and maximum dynamic displacement response, and compares the gripping index with a damage threshold. If the gripping index is greater than or equal to the damage threshold, the process proceeds to step 4. If the gripping index is less than the damage threshold, the manipulator is not adjusted.

[0134] A clamping pressure and clamping angle adjustment module, wherein the clamping pressure and clamping angle adjustment module adjusts the clamping pressure of the manipulator based on the calculated equivalent pressure and maximum deformation, and adjusts the opening angle of the manipulator claw based on the calculated maximum dynamic displacement response of the manipulator claw.

[0135] The present invention further provides a tea tree oil vibration manipulator, which comprises the tea tree oil vibration manipulator stable gripping force threshold control system.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] 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 method for controlling the threshold value of the stable gripping force of a vibration manipulator for an oil tea tree, characterized in that: The specific steps include: Step 1: Obtain the friction coefficient of the oil tea tree surface through tests at different pressures, and determine the pressure value when the oil tea tree bark is damaged, and use it as the damage threshold of the bark surface; Step 2: Use the manipulator to grab the tea tree, and record the clamping pressure of the manipulator and the displacement before and after grabbing, and calculate the equivalent pressure when the manipulator grabs the tea tree, the maximum deformation of the manipulator, the natural frequency of the manipulator's fingers, and the maximum dynamic displacement response, including: Conduct static simulation, use finite element software to solve, calculate equivalent pressure, and use the node displacement of the manipulator gripper to calculate the maximum deformation of the gripper under loading conditions; Perform dynamic simulation to obtain the natural frequency of the manipulator's fingers, and apply loading conditions of different vibration frequencies to calculate the maximum dynamic displacement response of the manipulator's fingers; Step 3: Generate a grasping index based on equivalent pressure, maximum deformation, natural frequency, and maximum dynamic displacement response, and compare the grasping index with the damage threshold. If the grasping index is greater than or equal to the damage threshold, proceed to step 4. If the grasping index is less than the damage threshold, do not adjust the manipulator. Step 4: The clamping pressure of the manipulator is adjusted based on the calculated equivalent pressure and maximum deformation, and the opening angle of the manipulator fingers is adjusted based on the calculated maximum dynamic displacement response of the manipulator fingers.

2. The method for controlling the stable gripping force threshold of the oil tea tree vibration manipulator according to claim 1 is characterized in that: The damage threshold for the bark surface is determined based on the following method: K bark samples were collected from the surface of the same tea oil tree, and the K bark samples were placed one by one on the sliding platforms of different friction testers. Pressure was applied to the bark samples in a direction perpendicular to the bark samples, and the pressure applied to each bark sample was different. The friction force of the bark sample under the corresponding pressure was recorded, and the formula for calculating the friction coefficient was as follows: Among them, μ k represents the friction coefficient of the oil tea tree surface of the kth bark sample, F k is the pressure on the kth bark sample, N k is the friction force of the kth bark sample, k is the index of the bark sample, and k∈[1,K], μ represents the friction coefficient of the oil tea tree surface; The crack length of each bark sample under the corresponding pressure was recorded, and the relationship between the crack length and the corresponding pressure was plotted with pressure as the independent variable and crack length as the dependent variable. The pressure corresponding to the point with the maximum slope in the relationship diagram was taken as the damage pressure σ damage , and the damage pressure is taken as the damage threshold.

3. The method for controlling the stable gripping force threshold of the oil tea tree vibration manipulator according to claim 1 is characterized in that ,The equivalent pressure of the manipulator and the maximum deformation of the manipulator fingers are calculated based on the following method: Create a geometric model of the contact interface between the manipulator's claw and the tea tree, and mesh the contact interface for finite element analysis. Obtain the pressure of each network node, and decompose the pressure of each network node into partial pressures in three directions. Filter out the maximum partial pressure, median partial pressure, and minimum partial pressure from the partial pressures of all network nodes to calculate the equivalent pressure. The formula is: Among them, σ vn represents the equivalent pressure, σ max represents the maximum partial pressure selected from the partial pressures of network nodes, σ min represents the minimum partial pressure selected from the partial pressures of network nodes, σ mid It represents the median of the partial pressure selected from the partial pressures of the network nodes; Determine multiple grasping nodes on the manipulator gripper finger, record the coordinates of each grasping node before and after grasping, calculate the displacement change of each grasping node, and select the maximum displacement change as the maximum deformation of the gripper finger under loading conditions δ max .

4. The method for controlling the stable gripping force threshold of the oil tea tree vibration manipulator according to claim 1 is characterized in that: The natural frequency of the manipulator fingers is obtained, and loading conditions with different vibration frequencies are applied to calculate the maximum dynamic displacement response of the manipulator fingers. The method is based on: Using the equivalent mass and stiffness method, the robot gripper finger is simplified into a single-degree-of-freedom or multi-degree-of-freedom mass-spring system, and the natural frequency is calculated using basic vibration theory. The derivation formula is: Among them, ω n represents the natural frequency of the robot gripper finger, k eq is the equivalent stiffness of the manipulator gripper system, m eq is the equivalent mass in the manipulator gripper finger system; The maximum dynamic displacement response is solved by using the frequency domain analysis method. First, a sinusoidal external force is applied to the robot gripper finger, and its motion is described by the motion equation. Then, the steady-state response is expressed in the frequency domain. When the natural frequency is equal to the excitation frequency, the system displacement response amplitude reaches the maximum. The formula is: Among them, x(t) is the displacement, which describes the displacement of the system at time t. is the velocity, which represents the first-order derivative of displacement x(t) with respect to time, is acceleration, indicating speed The first-order derivative with respect to time, F0 is the external force amplitude, that is, the maximum value of the sinusoidal external force applied to the system, c is the damping coefficient, cos(ω n t) is the cosine function, which describes the change of external force over time, X is the displacement response amplitude, is a cosine function, describing the steady-state response changing over time. is the phase angle, describing the phase shift relative to the external force, F0 / m eq is the external force amplitude per unit mass, ω is the excitation frequency, and ξ is the damping ratio; When n =ω, that is, when the excitation frequency is equal to the natural frequency, the maximum dynamic displacement response is: Among them, X max is the maximum dynamic displacement response.

5. The method for controlling the stable gripping force threshold of the oil tea tree vibration manipulator according to claim 1 is characterized in that: The grip index is generated by using the calculated equivalent pressure, maximum deformation, natural frequency and maximum dynamic displacement response, based on the following method: Where G represents the grip index, σ vn is the equivalent pressure, δ max is the maximum deformation, ω n is the natural frequency, X max is the maximum dynamic displacement response, β0 is a proportional constant used to set the pressure reference value, a is the influence index of equivalent pressure, b is the influence index of maximum deformation, z is the influence index of natural frequency, β2 is the influence index of dynamic displacement response, α1 is the attenuation coefficient, which indicates the attenuation degree of gripping effect with the increase of equivalent pressure; β1 is the influence coefficient of deformation, which indicates the degree of inhibition of maximum deformation on gripping performance, m is the balance coefficient of overall influence, which indicates the power balance of the whole expression. By adjusting m, the influence degree of comprehensive effect of four variables on gripping performance can be controlled; ω min ,ω max Indicates the minimum and maximum values ​​of the natural frequency.

6. The method for controlling the stable gripping force threshold of the oil tea tree vibration manipulator according to claim 5 is characterized in that: Compare the grasping index and the damage threshold. If the grasping index is greater than or equal to the damage threshold, go to step 4. If the grasping index is less than the damage threshold, do not adjust the manipulator. The logic formula is: Wherein, Q represents the logical value for judging whether the grasping index exceeds the damage threshold. When Q=0, it means that the damage threshold is not exceeded and there is no need to adjust the claw finger opening angle and clamping pressure. When Q=1, it means that the damage threshold is exceeded and the claw finger opening angle and clamping pressure are adjusted through step 4 until the grasping index is less than the damage threshold. damage Indicates the damage threshold.

7. The method for controlling the stable gripping force threshold of the oil tea tree vibration manipulator according to claim 3 is characterized in that: The method for adjusting the clamping pressure of the manipulator based on the equivalent pressure and maximum deformation generated by calculation, and adjusting the opening angle of the manipulator claw based on the maximum dynamic displacement response obtained by calculation is as follows: When the equivalent pressure exceeds the expected pressure and the maximum deformation exceeds the expected deformation, the clamping pressure needs to be reduced, but it must not be lower than the minimum safe clamping pressure; otherwise, the clamping pressure is increased, but it must not be higher than the damage threshold. The logic is as follows: Δσ=ρ1*(σ allow -s vn )+ρ2*(δ allow -d max ) if s vn >s allow and d max >d allow then s clamp =max(σ clamp -Ds,s safe-min ) else s vn <s allow and d max <d allow then s clamp =min(σ clamp +Ds,s damage ) Among them, σ clamp is the adjusted clamping pressure, σ safe-min Indicates the minimum safe clamping pressure to prevent unstable grip, σ damage represents the damage threshold, σ allow is the expected pressure, δ allow is the expected deformation, ρ1 and ρ2 are the corresponding proportional coefficients, which are used to indicate the influence of the deviation between the equivalent pressure and the maximum deformation on the clamping pressure, and Δσ indicates the clamping pressure that needs to be adjusted; The method for adjusting the opening angle of the manipulator gripper fingers based on the calculated maximum dynamic displacement response is as follows: If the maximum dynamic displacement response exceeds the allowable range, it means that the robot gripping deformation is large and the stability is reduced. It is necessary to reduce the opening angle of the claw fingers, but it must not be lower than the minimum opening angle to prevent mechanical damage caused by unstable clamping. If the maximum dynamic displacement is within the allowable range, it means that the gripping stability is good. Increase the opening angle of the claw fingers, but it must not be greater than the maximum opening angle to prevent damage caused by excessive opening. The logic is: Δθ=ρ3*(X allow -X max ) if X max >X allow then I adjust =max(θ current -Dθ,θ min ) else X max ≤X allow then I adjust =max(θ current +Δθ,θ max ) Among them, Δθ represents the claw finger opening angle that needs to be adjusted, ρ3 is the corresponding proportional coefficient, which represents the relationship between the maximum displacement dynamic response and the opening angle, and X allow is the desired displacement dynamic response, θ adjust is the adjusted claw opening angle, θ current is the current claw opening angle, θ min is the minimum opening angle of the claw finger, θ max is the maximum opening angle of the claw, X max is the maximum dynamic displacement response.

8. A stable grasping force threshold control system for a tea tree vibration manipulator, characterized in that: The control system is used to execute the method for controlling the stable grasping force threshold of the oil tea tree vibration manipulator according to any one of claims 1 to 7, comprising: A friction characteristic and damage threshold evaluation module, which is used to obtain the friction coefficient of the oil tea tree surface through tests with different pressures, and to determine the pressure value when the oil tea tree bark is damaged, and use it as the damage threshold of the bark surface; The robot grasping performance simulation module is used to grasp the tea tree with the robot, record the clamping pressure of the robot and the clamping angle after grasping, and calculate the equivalent pressure, maximum deformation of the robot, natural frequency of the robot's claws and maximum dynamic displacement response when the robot grasps the tea tree, specifically including: Conduct static simulation, use finite element software to solve, calculate equivalent pressure, and use the node displacement of the manipulator gripper to calculate the maximum deformation of the gripper under loading conditions; Perform dynamic simulation to obtain the natural frequency of the manipulator's fingers, and apply loading conditions of different vibration frequencies to calculate the maximum dynamic displacement response of the manipulator's fingers; A gripping index evaluation module, wherein the gripping index evaluation module comprehensively generates a gripping index based on equivalent pressure, maximum deformation, natural frequency, and maximum dynamic displacement response, and compares the gripping index with a damage threshold. If the gripping index is greater than or equal to the damage threshold, the process proceeds to step 4. If the gripping index is less than the damage threshold, the manipulator is not adjusted. A clamping pressure and clamping angle adjustment module, wherein the clamping pressure and clamping angle adjustment module adjusts the clamping pressure of the manipulator based on the calculated equivalent pressure and maximum deformation, and adjusts the opening angle of the manipulator claw based on the calculated maximum dynamic displacement response of the manipulator claw.

9. A tea tree vibration manipulator, characterized in that: The manipulator is used to implement the stable grasping force threshold control system of the oil tea tree vibration manipulator as described in claim 8.

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