A robot global safety performance index and safety level evaluation method and system

Abstract

This invention discloses a method and system for evaluating the overall safety performance indicators and safety level of a robot, comprising: Step 1, establishing kinematic, static, and dynamic models of the robot to describe the relationship between the robot's joint spatial displacement, velocity, torque, mass, and end effector velocity, end effector stiffness, and effective mass; Step 2, establishing a physical human-robot interaction model and selecting robot safety performance evaluation indicators to describe the relationship between the robot's joint displacement, velocity, mass, and safety performance evaluation indicators; Step 3, establishing the robot's overall safety performance indicators based on the Monte Carlo method; Step 4, determining the threshold values ​​of human biomechanical limitation indicators according to the task; Step 5, calculating and evaluating the robot's safety level, determining the robot's safety level, and providing safety protection measures. This invention evaluates the overall safety performance of a robot during physical human-robot interaction and guides the design of human-robot interaction systems in flexible manufacturing units under a defined task scenario.

Description

Technical Field

[0001] This invention relates to the field of robotics, specifically to a method and system for evaluating the overall safety performance indicators and safety levels of a robot. Background Technology

[0002] Industrial robots, equipped with intelligent end effectors (welding guns, grinding heads, inspection instruments, spray guns, etc.), can perform high-precision, high-speed, and highly repetitive operations within physical space. With the development of industries such as 3C, power, shipbuilding, and aerospace, flexible manufacturing cells (FMCCs) with human intervention in the environment have become an effective solution for multi-variety, small-batch discrete manufacturing. FMCCs combine their high precision and resilience with human adaptability, featuring human-machine integration, safety and ease of use, sensitivity and precision, and versatility. They not only meet the needs of small-batch, multi-variety, and customized flexible manufacturing in industrial fields but also have potential applications in areas such as social services and rehabilitation medicine for the aging population. Unlike industrial robots that maximize performance and operate in enclosed environments, FMCCs can collaborate with humans in specific areas, transforming the manufacturing model of discrete manufacturing industries. Therefore, the safety performance of industrial robots is a crucial consideration in the design of FMCC systems. Patent CN 106112964B discloses a method for evaluating machine safety levels from an electrical perspective, but it does not consider operator factors. Patent CN 106112964B discloses a collaborative robot collision safety testing system and method. This method measures the contact force of the collaborative robot based on a force sensor, but it cannot measure the robot's overall safety performance. Patents CN 111546331B and CN118009874A disclose a human-robot collaborative robot safety protection system-level safety protection method and a human operator behavior safety detection system and method for industrial robots. These methods use optical motion capture cameras to measure the distance between the robot and the operator to achieve safety control, but they cannot ensure safety during rational interaction between the robot and the human. Currently, robot safety performance evaluation indicators mainly focus on energy, distance, pressure, and force. They typically model the robot and operator as equivalent rigid points, ignoring the pose, stiffness, damping, and other characteristics of the operator and robot, and can only calculate the robot's safety performance under specific poses and velocities. Furthermore, how to classify robot safety levels using robot safety performance indicators and implement different protective measures based on these levels has not been sufficiently studied. Summary of the Invention

[0003] To address the aforementioned issues, the present invention aims to provide a method and system for evaluating the overall safety performance indicators and safety levels of robots. This system enables the comprehensive evaluation of robot safety performance in various operational scenarios. It considers not only the robot's pose, speed, mass, and stiffness, but also the characteristics of the operator's contact points, their mass, and stiffness. By clearly defining the safety level and selecting appropriate human-machine interaction protection measures, this invention provides a reference and foundation for the design of human-machine interaction systems in flexible manufacturing units.

[0004] In a first aspect, the present invention provides a method for evaluating the overall safety performance indicators and safety level of a robot, the method comprising the following steps:

[0005] Step 1: Establish the robot's kinematic model, static model, and dynamic model. The robot's kinematic model represents the mapping between the robot's joint velocities and Cartesian space velocities; the robot's static model represents the mapping between the robot's joint stiffness and Cartesian space stiffness; and the robot's dynamic model represents the mapping between joint torque, mass, damping, and the robot's effective mass and Cartesian space forces.

[0006] Step 2: Establish a physical human-machine interaction model and select robot safety performance evaluation indicators. The physical human-machine interaction model describes the forces generated when the operator and the robot make physical contact. The robot safety performance evaluation indicators describe the relationship between the robot's end-effector velocity, effective mass, end-effector stiffness, and safety performance evaluation indicators.

[0007] Step 3: Based on the robot safety performance evaluation index, establish the robot's global safety performance index using the Monte Carlo method;

[0008] Step 4: Determine the threshold value of the human biomechanical limitation index based on the task at hand; the human biomechanical limitation index is the transient impact force generated by physical human-computer interaction; the threshold value of the human biomechanical limitation index is the maximum value of the human biomechanical limitation index that causes injury to a part of the human body.

[0009] Step 5: Based on the robot's overall safety performance indicators and human biomechanical limitation thresholds, calculate and evaluate the robot's safety level, and select safety protection measures according to the safety level selection table.

[0010] Furthermore, the robot's kinematic model is as follows:

[0011]

[0012] Where V represents the robot's end-effector velocity vector, Θ represents the joint displacement vector, and J(Θ) represents the Jacobian matrix. Represents the joint velocity vector;

[0013] The static model of the robot is as follows:

[0014] K(Θ)=J(Θ) -T kJ(Θ) -1

[0015] Where K represents the robot end effector stiffness matrix, and k represents the robot joint stiffness matrix;

[0016] The robot's dynamics model is as follows:

[0017]

[0018] Where M(Θ) is the robot mass matrix, G(Θ) represents the centrifugal force and Coriolis force vectors, G(Θ) represents the gravity vector, and τ represents the joint torque vector. c This represents the external contact torque vector.

[0019] Furthermore, the physical human-computer interaction model is as follows:

[0020]

[0021] Where m c Indicates the effective mass after the collision; v c Indicates the relative velocity between the operator and the robot before the impact; C R The coefficient of restitution represents the ratio of the relative velocity after the impact to the relative velocity before the impact; k c C represents the contact stiffness; Δx represents the compression caused by the contact; C d The damping capacity represents the energy consumed in each cycle.

[0022] Furthermore, the robot's safety performance evaluation indicators are as follows:

[0023]

[0024] Where m H Indicates the effective mass of the part of the human body impacted; m R This indicates the robot's effective mass.

[0025] Furthermore, the robot's overall safety performance indicators are as follows:

[0026]

[0027] Where m represents the number of discrete points in the joint range of motion, and n represents the number of discrete points in the joint velocity range.

[0028] Furthermore, the values ​​of m and n are both greater than 1,000,000.

[0029] Furthermore, the work tasks include welding, grinding, assembly, handling, painting, and inspection. When the work task is welding, the physical contact parts of the human body are the head and hands; when the work task is grinding, painting, or assembly, the physical contact parts of the human body are the forearms and hands; when the work task is handling or inspection, the physical contact parts of the human body are the chest, upper arm, forearm, and hands. The biomechanical limit thresholds for the human head, chest, upper arm, forearm, and hands are 260N, 280N, 300N, 320N, and 280N, respectively.

[0030] Furthermore, the security level is as follows:

[0031]

[0032] Among them, F c The threshold values ​​for human biomechanical limitations are as follows: when α≤1, physical human-computer interaction is inherently safe and requires no safety protection; when 1<α≤2, physical human-computer interaction poses a risk and requires the wearing of protective devices; when α>2, physical human-computer interaction poses a very high risk and requires physical isolation between humans and machines.

[0033] Furthermore, the protective devices include safety helmets, goggles, work gloves, and work clothes, and the human-machine physical isolation includes safety light curtains, protective fences, and distance sensor isolation.

[0034] Secondly, the present invention provides a robot global safety performance index and safety level assessment system for implementing the method, comprising:

[0035] The robot kinematic model, static model, and dynamic model establishment unit establishes the robot kinematic model, static model, and dynamic model. The robot kinematic model represents the mapping between robot joint velocities and Cartesian space velocities; the robot static model represents the mapping between robot joint stiffness and Cartesian space stiffness; and the robot dynamic model represents the mapping between joint torque, mass, damping, and robot effective mass and Cartesian space forces.

[0036] A physical human-machine interaction model establishment unit establishes a physical human-machine interaction model and selects robot safety performance evaluation indicators. The physical human-machine interaction model describes the forces generated when the operator and the robot make physical contact. The robot safety performance evaluation indicators describe the relationship between the robot's end-effector velocity, effective mass, end-effector stiffness, and safety performance evaluation indicators.

[0037] A robot global safety performance index establishment unit, which establishes robot global safety performance indexes based on the Monte Carlo method;

[0038] The human biomechanical limitation threshold determination unit determines the human biomechanical limitation threshold based on the task at hand; the human biomechanical limitation index is the transient impact force generated by physical human-computer interaction; the human biomechanical limitation threshold is the maximum value of the human biomechanical limitation index that causes injury to a part of the human body.

[0039] The safety level calculation and evaluation unit calculates and evaluates the robot's safety level, and selects safety protection measures based on the safety level selection reference table.

[0040] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0041] (1) The physical human-computer interaction model provided by the present invention not only considers the robot's pose, speed, mass, stiffness and other characteristics, but also the contact parts of the operator, the mass and stiffness of the contact parts and other characteristics.

[0042] (2) The robot safety performance index described in this invention can evaluate the robot safety performance under any pose and joint space velocity in the workspace, and the robot global safety performance index provided can evaluate the overall safety performance of the robot.

[0043] (3) The safety level provided by this invention can provide designers with a reference for safety protection measures and provide a feasible assessment tool to reduce or eliminate risks from the design source. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments are briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a flowchart illustrating a method for evaluating the global safety performance indicators and safety level of a robot, as provided in Embodiment 1 of the present invention.

[0046] Figure 2 This is a comparison diagram of the work tasks and physical contact points provided in Embodiment 1 of the present invention.

[0047] Figure 3 This is a comparison table of security level selection provided in Embodiment 1 of the present invention. Detailed Implementation

[0048] To facilitate understanding of the present invention, a flowchart illustrating a method for evaluating the overall safety performance indicators and safety levels of a robot will be described more fully below with reference to the accompanying drawings. The drawings show a preferred embodiment of the method for evaluating the overall safety performance indicators and safety levels of a robot. However, a method for evaluating the overall safety performance indicators and safety levels of a robot can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of a method for evaluating the overall safety performance indicators and safety levels of a robot more thorough and complete.

[0049] Example 1

[0050] Figure 1 This is a flowchart illustrating a method for evaluating the overall safety performance indicators and safety level of a robot according to the present invention. Exemplarily, this embodiment uses a typical serial industrial robot as an example, and evaluates the overall safety performance indicators and safety level of the robot according to the present invention, with the following steps:

[0051] A: Establishment of robot kinematics, statics, and dynamics models: The robot kinematics model can represent the mapping between robot joint velocities and Cartesian space velocities; the robot statics model can represent the mapping between robot joint stiffness and Cartesian space stiffness; the robot dynamics model can represent the mapping between joint torque, mass, damping, and robot effective mass and Cartesian space forces.

[0052] The robot kinematic model is described as follows:

[0053] Where V represents the robot's end-effector velocity vector, Θ represents the joint angle vector, and J(Θ) represents the Jacobian matrix. This represents the joint velocity vector.

[0054] The static model of the robot is expressed as K = J(Θ). -T kJ(Θ) -1 ;

[0055] Where K represents the robot end effector stiffness vector, and k represents the robot joint space stiffness matrix;

[0056] The robot dynamics model is expressed as follows:

[0057] Where M(Θ) is the mass matrix, G(Θ) represents the centrifugal force and Coriolis force vectors, G(Θ) represents the gravity vector, and τ represents the joint torque vector. c Represents the external contact torque vector;

[0058] B: Establishment of a physical human-machine interaction model and selection of robot safety performance evaluation indicators: The physical human-machine interaction model can describe the forces generated when the operator and the robot make physical contact; The robot safety performance evaluation indicators can describe the relationship between the robot's end-effector velocity, effective mass, end-effector stiffness and safety performance evaluation indicators.

[0059] The modeling process of the physical human-computer interaction model is as follows: the kinetic energy transferred by the robot during the physical human-computer interaction process is expressed as... Where m c The effective mass after the collision is represented by the following calculation process:

[0060]

[0061] Where m H The effective mass of the impact site is indicated by the following values: head, chest, upper arm, lower arm, and hand. The effective masses are 4.4 kg, 40 kg, 3 kg, 2 kg, and 0.6 kg, respectively. R The effective mass of the robot is represented by the following calculation process:

[0062]

[0063] During human-machine interaction collisions, the transferred kinetic energy can be converted into viscous loss and elastic potential energy. The relationship between the three is as follows:

[0064]

[0065] k H The coefficient of elasticity represents the impact point on the human body. The coefficients of elasticity for the head, chest, upper arm, lower arm, and hand are 150 N / mm, 25 N / mm, 30 N / mm, 40 N / mm, and 75 N / mm, respectively. R Let F represent the end effector stiffness of the robot in the direction u, and let F represent the physical human-robot interaction contact force.

[0066]

[0067] The physical human-computer interaction model is described as follows:

[0068]

[0069] Transformed into:

[0070] Where m c Indicates the effective mass after the collision; v c Indicates the relative velocity between the operator and the robot before the impact; C R The coefficient of restitution represents the ratio of the relative velocity after the impact to the relative velocity before the impact; k cC represents the contact stiffness; Δx represents the compression caused by the contact; C d The damping capacity represents the energy consumed in each cycle.

[0071] The physical human-robot interaction contact force is selected as an evaluation index for robot safety performance, and is expressed as follows:

[0072]

[0073] C: Establishing robot global safety performance indicators based on the Monte Carlo method

[0074] The robot's global safety performance index is the average value of safety performance evaluation indicators across the robot's joint range of motion and joint velocity. It measures the robot's safety performance throughout the entire workspace. The mathematical expression of the robot's global safety performance index is as follows:

[0075]

[0076] Where m represents the number of discrete points in the joint range of motion, and n represents the number of discrete points in the joint acceleration range. Both m and n must be greater than 1,000,000.

[0077] D: Based on the task at hand, determine the threshold values ​​for human biomechanical limitations.

[0078] like Figure 2 As shown, the work tasks include welding, grinding, assembly, handling, painting, and inspection. The parts of the body that come into physical contact with the human body during these tasks are the head, chest, upper arm, lower arm, and hand. Specifically, when the task is welding, the parts of the body that come into physical contact with the human body are the head and hand; when the task is grinding, painting, or assembly, the parts of the body that come into physical contact with the human body are the lower arm and hand; and when the task is handling or inspection, the parts of the body that come into physical contact with the human body are the chest, upper arm, lower arm, and hand. The human biomechanical limiting index is the transient impact force generated by physical human-machine interaction. The threshold value of the human biomechanical limiting index is the maximum value of the human biomechanical limiting index that causes injury to any part of the human body, and its mathematical expression is F. C The biomechanical limiting thresholds for the human head, chest, upper arm, lower arm, and hand are 260N, 280N, 300N, 320N, and 280N, respectively.

[0079] E: Robot safety level calculation and assessment, based on the safety level selection reference table, the safety protection measures are selected. The safety level is expressed as follows:

[0080]

[0081] like Figure 3As shown, when α≤1, physical human-computer interaction is inherently safe and requires no safety protection; when 1<α≤2, physical human-computer interaction is risky and requires the wearing of protective devices, such as safety helmets, goggles, and work gloves, to protect the operator's safety; when α>2, physical human-computer interaction is extremely risky and requires physical isolation between the human and the machine, which can be achieved through safety light curtains, protective fences, distance sensors, etc.

[0082] The protective devices provided by this invention mainly include safety helmets, goggles, work gloves, and work clothes. The human-machine physical isolation method provided by this invention includes safety light curtains, protective fences, and distance sensors.

[0083] This embodiment also provides a robot global safety performance index and safety level assessment system for implementing the method, including:

[0084] The robot kinematic model, static model, and dynamic model establishment unit establishes the robot kinematic model, static model, and dynamic model. The robot kinematic model represents the mapping between robot joint velocities and Cartesian space velocities; the robot static model represents the mapping between robot joint stiffness and Cartesian space stiffness; and the robot dynamic model represents the mapping between joint torque, mass, damping, and robot effective mass and Cartesian space forces.

[0085] A physical human-machine interaction model establishment unit establishes a physical human-machine interaction model and selects robot safety performance evaluation indicators. The physical human-machine interaction model describes the forces generated when the operator and the robot make physical contact. The robot safety performance evaluation indicators describe the relationship between the robot's end-effector velocity, effective mass, end-effector stiffness, and safety performance evaluation indicators.

[0086] A robot global safety performance index establishment unit, which establishes robot global safety performance indexes based on the Monte Carlo method;

[0087] The human biomechanical limitation threshold determination unit determines the human biomechanical limitation threshold based on the task at hand; the human biomechanical limitation index is the transient impact force generated by physical human-computer interaction; the human biomechanical limitation threshold is the maximum value of the human biomechanical limitation index that causes injury to a part of the human body.

[0088] The safety level calculation and evaluation unit calculates and evaluates the robot's safety level, and selects safety protection measures based on the safety level selection reference table.

[0089] This invention provides a feasible robot safety performance evaluation tool to assess the overall safety performance of robots during physical human-robot interaction and guide the design of human-robot interaction systems in flexible manufacturing units under specific operational scenarios.

[0090] Matters not covered in this invention are common knowledge. The above embodiments are only for illustrating the technical concept and features of this invention, and are intended to enable those skilled in the art to understand the content of this invention and implement it accordingly. They should not be construed as limiting the scope of protection of this invention. All equivalent changes or modifications made in accordance with the spirit and essence of this invention should be covered within the scope of protection of this invention.

Claims

1. A method for assessing the safety level of a robot, characterized in that, The method includes the following steps: Step 1: Establish the robot's kinematic model, static model, and dynamic model. The robot's kinematic model represents the mapping between the robot's joint velocities and Cartesian space velocities; the robot's static model represents the mapping between the robot's joint stiffness and Cartesian space stiffness; and the robot's dynamic model represents the mapping between joint torque, mass, damping, and the robot's effective mass and Cartesian space forces. Step 2: Establish a physical human-machine interaction model and select robot safety performance evaluation indicators. The physical human-machine interaction model describes the forces generated when the operator and the robot make physical contact. The robot safety performance evaluation indicators describe the relationship between the robot's end-effector velocity, effective mass, end-effector stiffness, and safety performance evaluation indicators. Step 3: Based on the robot safety performance evaluation index, establish the robot's global safety performance index using the Monte Carlo method; Step 4: Determine the threshold value of the human biomechanical limitation index based on the task at hand; the human biomechanical limitation index is the transient impact force generated by physical human-computer interaction; the threshold value of the human biomechanical limitation index is the maximum value of the human biomechanical limitation index that causes injury to a part of the human body. Step 5: Based on the robot's overall safety performance indicators and human biomechanical limitation thresholds, calculate and evaluate the robot's safety level, and select safety protection measures according to the safety level selection table. The physical human-computer interaction model is as follows: in Indicates the effective mass after the collision; This indicates the relative speed between the operator and the robot before the impact. The coefficient of restitution represents the ratio of the relative velocity after the impact to the relative velocity before the impact. For contact stiffness; The amount of compression generated by contact; The damping capacity represents the energy consumed in each cycle. The robot safety performance evaluation indicators are as follows: in Indicates the effective mass of the part of the human body that impacts; Indicates the effective mass of the robot; The robot's overall safety performance indicators are as follows: Where m represents the number of discrete points in the range of joint motion, and n represents the number of discrete points in the range of joint velocity. The security level is: Among them, F c The threshold value is the human biomechanical limiting index. At this time, physical human-computer interaction is inherently safe and requires no security protection; Physical human-computer interaction carries risks and requires the wearing of protective devices. At that time, physical human-computer interaction poses a great risk and physical isolation between humans and machines is required.

2. The robot safety level assessment method according to claim 1, characterized in that, The robot's kinematic model is as follows: in This represents the end-effector velocity vector of the robot. Represents the joint displacement vector. Represents the Jacobian matrix, Represents the joint velocity vector; The static model of the robot is as follows: in Represents the stiffness matrix of the robot's end effector. Represents the joint stiffness matrix of the robot; The robot's dynamics model is as follows: in For the robot mass matrix, For the centrifugal force and Coriolis force vectors, It is the gravity vector. Represents the joint torque vector. This represents the external contact torque vector.

3. The robot safety level assessment method according to claim 1, characterized in that, The values ​​of m and n are both greater than 1,000,000.

4. The robot safety level assessment method according to claim 1, characterized in that, The work tasks include welding, grinding, assembly, handling, painting, and inspection. When the work task is welding, the physical contact parts of the human body are the head and hands; when the work task is grinding, painting, or assembly, the physical contact parts of the human body are the forearms and hands; when the work task is handling or inspection, the physical contact parts of the human body are the chest, upper arm, forearm, and hands. The biomechanical limit thresholds for the human head, chest, upper arm, forearm, and hands are 260N, 280N, 300N, 320N, and 280N, respectively.

5. The robot safety level assessment method according to claim 4, characterized in that, The protective devices include safety helmets, goggles, work gloves, and work clothes, and the human-machine physical isolation includes safety light curtains, protective fences, and distance sensor isolation.

6. A robot safety level assessment system for implementing the method of any one of claims 1-5, characterized in that, include: The robot kinematic model, static model, and dynamic model establishment unit establishes the robot kinematic model, static model, and dynamic model. The robot kinematic model represents the mapping between robot joint velocities and Cartesian space velocities; the robot static model represents the mapping between robot joint stiffness and Cartesian space stiffness; and the robot dynamic model represents the mapping between joint torque, mass, damping, and robot effective mass and Cartesian space forces. A physical human-computer interaction model establishment unit is used to establish a physical human-computer interaction model and select robot safety performance evaluation indicators. The physical human-computer interaction model describes the forces generated when the operator and the robot make physical contact. The robot safety performance evaluation index describes the relationship between the robot's end-effector velocity, effective mass, end-effector stiffness, and safety performance evaluation index. A robot global safety performance index establishment unit, which establishes robot global safety performance indexes based on the Monte Carlo method; The human biomechanical limitation threshold determination unit determines the human biomechanical limitation threshold based on the task at hand; the human biomechanical limitation index is the transient impact force generated by physical human-computer interaction; the human biomechanical limitation threshold is the maximum value of the human biomechanical limitation index that causes injury to a part of the human body. The safety level calculation and evaluation unit calculates and evaluates the robot's safety level, and selects safety protection measures based on the safety level selection reference table.

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