Safety assessment method, device and equipment for operation path of collaborative robot

Abstract

The invention relates to the technical field of robots, in particular to a safety assessment method, device and equipment for an operation path of a collaborative robot, and the method comprises the steps: building an elastic mechanical model based on the deformation energy of a flexible line, the gravitational potential energy and a calculation error; the pose of each robot in the collaborative robot system is obtained, the pose of each robot is input into the elastic mechanical model, and the elastic mechanical model outputs deformation information and stress information of the flexible line; and evaluating the safety of the operation path of each robot according to the deformation information and the stress information. Therefore, the safety problem caused by the fact that the prior art depends on visual hardware, the cost and computing resources are high, and deformation of the flexible wire part or overlarge internal stress is not considered is solved.

Description

Technical Field

[0001] The present application relates to the field of robotics technology, and in particular to a method, device and equipment for evaluating the safety of a collaborative robot operation path. Background Art

[0002] There are a large number of flexible parts such as load-bearing cables, contact wires, and suspension strings (hereinafter referred to as flexible wires) in the railway contact network system. They are prone to deformation, aging and other failures in the natural environment. The replacement and maintenance work is labor-intensive and the ergonomic conditions are poor. Therefore, in order to improve work efficiency, a robot-assisted automated operation system is introduced into the railway contact network maintenance operation system.

[0003] Compared with traditional operating objects such as bolts and rails, linear components in the contact network are more flexible and deform during operation. Therefore, multiple robots are usually required to work together in the automated contact network maintenance system to jointly grasp the flexible wires in order to replace and install such components with high degrees of freedom and prone to deformation. During the maintenance process, two robots usually grasp the two ends of the flexible wire respectively, remove it from the initial position using tooling, and transport it to the storage warehouse with both arms. Then, a new flexible wire is grabbed from the storage warehouse, transported to the designated location on the contact network, and fixed and installed using specific tooling.

[0004] At present, the operational safety strategy of multi-robot collaboration usually focuses on the robot itself. The commonly used safety strategy is to use sensors (such as visual sensors, infrared sensors, lidar, etc.) to monitor the robot's surrounding environment in real time, discretize the collected data of other robots into point clouds, and further fit them into envelope boxes composed of convex polyhedrons. When it is detected that the shortest distance between the envelope boxes exceeds the safety threshold, the safety mechanism is triggered to reduce the robot's speed or trigger an emergency stop to avoid interference, collision and damage. However, due to the high hardware cost and the fact that processing two-dimensional and three-dimensional images consumes more time and computing resources, there is a mismatch between motion control and visual processing efficiency, which affects the working efficiency of the collaborative robot system, and does not take into account the safety issues caused by the deformation of the flexible wire parts themselves or excessive internal stress. Summary of the invention

[0005] The present application provides a method, device and equipment for evaluating the safety of the operation path of a collaborative robot to solve the safety problems caused by the existing technology relying on visual hardware, high cost and computing resources, and not considering the deformation of the flexible wire parts themselves or excessive internal stress.

[0006] The first aspect of the present application provides a method for evaluating the safety of a collaborative robot operation path, comprising the following steps: establishing an elastic mechanics model based on the deformation energy, gravitational potential energy and calculation error of a flexible line, wherein the calculation error is based on the position of each different robot in the collaborative robot system that operates the flexible line grasping the flexible line as the initial point, and calculating the difference between the positions of the same point on the flexible line; obtaining the position and posture of each robot in the collaborative robot system, inputting the position and posture of each robot into the elastic mechanics model, and the elastic mechanics model outputting the deformation information and force information of the flexible line; and evaluating the safety of each robot's operation path based on the deformation information and force information.

[0007] Optionally, the elasticity model is:

[0008]

[0009] F OD =∫||r f (s)-r i (s)||2ds;

[0010]

[0011] dQ(s) / ds=g4(q(s),Q(s),F(s));

[0012]

[0013] Among them, F oE is the total energy, E dtotal is the bending deformation energy of the flexible wire, E g is the gravitational potential energy of the flexible line, ω(s) = [ω1(s), ω2(s), ω3(s)] is the bending vector of any point of the flexible line, r(s) is the shape of the flexible line, ρ is the density of the flexible line, g is the gravitational acceleration, F OD is the calculation error, r f (s) is the coordinates of each point on the flexible line calculated from the position where the first robot in the collaborative robot system grasps the flexible line as the initial point, r i (s) is the coordinates of each point on the flexible line calculated from the position where the second robot in the collaborative robot system grasps the flexible line as the initial point, and r(s) is the coordinate of the center line of the flexible line between the two ends operated by the robot. In the calculation, r is usually taken as i(s) and the average value of rf(s), q(s) = q1(s) - q4(s) is the quaternion that expresses the posture of each microelement on the flexible line, g1 is the functional relationship expression between the coordinates of each point on the flexible line and the posture of each microelement, Q(s) is the result of differentiating the arc length s in q1(s) - q4(s), g2(s) is the functional relationship expression of differentiating the arc length s in q1(s) - q4(s), F(s) = [F1(s), F2(s), F3(s)] T is the force on a point on the flexible line, f(s) is the distributed force on the flexible line except the operating forces at both ends, f1(s)-f3(s) are the components of f(s) in three directions in Euclidean space, g3 is the functional relationship expression that characterizes the relationship between the force on each point on the flexible line and q, Q, F, f, g4 is the functional relationship expression that characterizes the relationship between the quadratic differential of each infinitesimal posture on the flexible line and q, Q, F, s is the arc length of the flexible line between a point on the flexible line and the endpoint of the flexible line.

[0014] Optionally, the safety of each robot operation path is evaluated based on the deformation information and the force information, including: evaluating the interference risk of each robot operation path based on the deformation information; and evaluating the compliance safety of each robot operation path based on the force information.

[0015] Optionally, the interference risk of each robot operation path is evaluated based on the deformation information, including: obtaining the position and posture of each link of each robot; calculating the shortest distance between the deformation information and each link, and generating an interference risk index based on the shortest distance; and evaluating the interference risk of each robot operation path based on the interference risk index.

[0016] Optionally, the compliance safety of each robot operation path is evaluated based on the force information, including: identifying forces and moments in the force information; constructing a compliance safety index based on the forces and moments; and evaluating the compliance safety of each robot operation path based on the compliance safety index.

[0017] Optionally, the interference risk indicator is:

[0018] C1(r(s))=min({r(s)},Robot);

[0019] Among them, r(s) is the arc length between a point on the flexible line and the end point of the flexible line, Robot is the set of the current position and posture of each link of the robot, and C1(r(s)) is the interference risk index.

[0020] Optionally, the compliance safety index is:

[0021] C2(r(s))=w F (||F(s1)||2+||F(s t)||2)+w M (||M(s1)||2+||M(s t )||2);

[0022] Among them, w F and w M are the safety weight coefficients of force and moment, respectively; F(s1) is the force borne by the starting point of the flexible line; F(s t ) is the force on the end of the flexible line, M(s1) is the torque on the starting point of the flexible line, and M(s t ) is the torque borne by one end of the flexible line.

[0023] The second aspect of the present application provides a safety assessment device for a collaborative robot operation path, including: an establishment module for establishing an elastic mechanics model based on the deformation energy, gravitational potential energy and calculation error of a flexible line, wherein the calculation error is based on the position of each different robot in the collaborative robot system that operates the flexible line grasping the flexible line as the initial point, and calculating the difference between the positions of the same point on the flexible line; an input module for obtaining the posture of each robot in the collaborative robot system, inputting the posture of each robot into the elastic mechanics model, and the elastic mechanics model outputs the deformation information and force information of the flexible line; an evaluation module for evaluating the safety of each robot's operation path based on the deformation information and force information.

[0024] Optionally, the elasticity model is:

[0025]

[0026] F OD =∫||r f (s)-r i (s)||2ds;

[0027]

[0028]

[0029] dQ(s) / ds=g4(q(s),Q(s),F(s));

[0030]

[0031] Among them, E OE is the total energy, E dtotal is the bending deformation energy of the flexible wire, E g is the gravitational potential energy of the flexible line, ω(s) = [ω1(s), ω2(s), ω3(s)] is the bending vector of any point of the flexible line, r(s) is the shape of the flexible line, ρ is the density of the flexible line, g is the gravitational acceleration, F ODis the calculation error, r f (s) is the coordinates of each point on the flexible line calculated from the position where the first robot in the collaborative robot system grasps the flexible line as the initial point, r i (s) is the coordinates of each point on the flexible line calculated from the position where the second robot in the collaborative robot system grasps the flexible line as the initial point, and r(s) is the coordinate of the center line of the flexible line between the two ends operated by the robot. In the calculation, r is usually taken as i (s) and r f (s), q(s) = q1(s) - q4(s) is the quaternion that expresses the posture of each microelement on the flexible line, g1 is the functional relationship expression between the coordinates of each point on the flexible line and the posture of each microelement, Q(s) is the result of differentiating the arc length s in q1(s) - q4(s), g2(s) is the functional relationship expression of differentiating the arc length s in q1(s) - q4(s), F(s) = [F1(s), F2(s), F3(s)] T is the force on a point on the flexible line, f(s) is the distributed force on the flexible line except the operating forces at both ends, f1(s)-f3(s) are the components of f(s) in three directions in Euclidean space, g3 is the functional relationship expression that characterizes the relationship between the force on each point on the flexible line and q, Q, F, f, g4 is the functional relationship expression that characterizes the relationship between the quadratic differential of each infinitesimal posture on the flexible line and q, Q, F, s is the arc length of the flexible line between a point on the flexible line and the endpoint of the flexible line.

[0032] Optionally, the evaluation module is further used to: evaluate the interference risk of each robot operation path according to the deformation information; and evaluate the compliance safety of each robot operation path according to the force information.

[0033] Optionally, the evaluation module is further used to: evaluate the interference risk of each robot operation path based on the deformation information, including: obtaining the position and posture of each link of each robot; calculating the shortest distance between the deformation information and each link, and generating an interference risk index based on the shortest distance; and evaluating the interference risk of each robot operation path based on the interference risk index.

[0034] Optionally, the evaluation module is further used to: identify forces and torques in the force information; construct a compliance safety index based on the forces and torques; and evaluate the compliance safety of each robot operation path based on the compliance safety index.

[0035] Optionally, the interference risk indicator is:

[0036] C1(r(s))=min({r(s)},Robot);

[0037] Among them, r(s) is the arc length between a point on the flexible line and the end point of the flexible line, Robot is the set of the current position and posture of each link of the robot, and C1(r(s)) is the interference risk index.

[0038] Optionally, the compliance safety index is:

[0039] C2(r(s))=w F (||F(s1)||2+||F(s t )||2)+w M (||M(s1)||2+||M(s t )||2);

[0040] Among them, w F and w M are the safety weight coefficients of force and moment, respectively; F(s1) is the force borne by the starting point of the flexible line; F(s t ) is the force on the end of the flexible line, M(s1) is the torque on the starting point of the flexible line, and M(s t ) is the torque borne by one end of the flexible line.

[0041] The third aspect of the present application provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to perform a safety assessment method for an operation path of a collaborative robot as in the above-mentioned embodiment.

[0042] The fourth aspect of the present application provides a computer-readable storage medium having a computer program or instructions stored thereon, and the computer program or instructions are executed by a processor to perform a safety assessment method for the operation path of a collaborative robot as in the above-mentioned embodiment.

[0043] Therefore, this application has at least the following beneficial effects:

[0044] The embodiment of the present application can establish an elastic mechanics model based on the deformation energy, gravitational potential energy and calculation error of the flexible line. The elastic mechanics model can be used to predict the deformation information and force information of the flexible line only when the robot's position and posture are known, and then the safety of the robot's operation path is evaluated based on the deformation information and force information. There is no need to introduce additional visual hardware, which reduces computing resources and hardware costs, and avoids interference collisions caused by missed detection of the operating object due to visual hardware occlusion and fitting registration failure during operation. Therefore, the existing technology relies on visual hardware, has high costs and computing resources, and does not take into account the safety problems caused by the deformation of the flexible line parts themselves or excessive internal stress.

[0045] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0047] Figure 1 A flowchart of a method for evaluating the safety of a collaborative robot operation path according to an embodiment of the present application;

[0048] Figure 2 A schematic diagram of the relationship between the postures of the two ends of the flexible wire and the postures of the robots 1 and 2 provided according to an embodiment of the present application;

[0049] Figure 3 A schematic diagram of the calculation relationship between the position and posture of a certain point on the flexible line provided according to an embodiment of the present application;

[0050] Figure 4 A specific flow chart of a method for evaluating the safety of a collaborative robot operation path according to an embodiment of the present application;

[0051] Figure 5 This is an example diagram of a safety assessment device for a collaborative robot operation path provided according to an embodiment of the present application;

[0052] Figure 6 It is a schematic diagram of the structure of an electronic device provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0053] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0054] Before describing the solution of this application, we first briefly introduce how the relevant technology can achieve the safety assessment of the operation path of the collaborative robot, as follows:

[0055] In the related technologies, the technical solution of collaborative robot safety strategy is based on the safety judgment of the measurement results of the operation object and the robot by sensors, which requires the introduction of a large number of sensors, including plane cameras, depth cameras, etc. The hardware cost of this solution is relatively high, and the processing of two-dimensional and three-dimensional images consumes a lot of time and computing resources. There is a problem of mismatch between motion control and visual processing efficiency, which affects the working efficiency of the collaborative robot system.

[0056] On the basis of obtaining the visual image data of the robot and the operating object, it is necessary to fit the point cloud or pixel set according to the prior information of the above objects, process it into a regular envelope sphere or convex polyhedron envelope box, and then calculate the distance between the above envelopes. However, in the railway contact network maintenance scenario, the operating objects such as suspension strings and contact wires are linear flexible bodies, and their shapes change with the robot's operation process. It is difficult to use templates for visual recognition. Moreover, such objects usually appear in curved shapes, which are difficult to fit with convex polyhedrons or spheres. Therefore, the recognition results of such operating objects may be missed. In the working environment, such linear components occupy a large space in the axial direction, which is extremely prone to obstruction and interference between robots and operating objects in multi-machine collaborative systems.

[0057] Related technologies mainly rely on visual information, and only use the physical distance between the operating object and the robot as a safety criterion. When the flexible linear parts grasped by the robot are twisted, their deformation stress will rise rapidly, and the probability of instability will increase. Even in the absence of interference, there may be sudden changes in shape and collision with other robots, or excessive internal stress may cause self-injury, which is a point not taken into account in the current collaborative robot safety operation strategy.

[0058] In addition, it should be noted that during the maintenance of the contact network, a collaborative robot system consisting of N robotic arms (usually N=2) is usually required to grasp the two ends of a flexible line and transport it from the initial position to the target position according to a certain posture and trajectory. During the transportation process, there should be no collision or interference between the flexible line and the robot, and the flexible line should not be over-stretched or over-twisted. Therefore, the embodiments of the present application take into account the flexibility and safety requirements during the operation process. Before the robot is executed to operate according to the set trajectory and posture, the robot operation path needs to be evaluated. If there is interference with the operating object and excessive operating force in the operation task, an early warning is required.

[0059] Specifically, the present application provides a safety assessment method for collaborative robot operation paths, in which the safety of the collaborative robot operating flexible parts is assessed based on the deformation prediction of the operation object, so as to provide early warning of potentially dangerous robot operation paths before the operation is performed. This solves the problem that the existing technology relies on visual hardware, has high costs and computing resources, and does not take into account the safety issues caused by the deformation of the flexible wire parts themselves or excessive internal stress.

[0060] Figure 1 A flowchart of a method for assessing the safety of a collaborative robot operation path provided in an embodiment of the present application.

[0061] like Figure 1As shown, the safety assessment method of the collaborative robot operation path includes the following steps:

[0062] In step S101 , an elastic mechanics model is established based on the deformation energy, gravitational potential energy and calculation error of the flexible wire.

[0063] The calculation error is based on the position of the flexible wire grasped by different robots in the collaborative robot system operating the flexible wire as the initial point, and the difference between the positions of the same point on the flexible wire is calculated.

[0064] It can be understood that the embodiment of the present application can establish an elastic mechanics model based on the deformation energy, gravitational potential energy and calculation error of the flexible line, wherein the calculation error is the difference between the positions of the same point on the flexible line calculated by each robot in the collaborative robot system of the flexible line F OD .

[0065] Taking a collaborative robot system with two robots as an example, the calculation error is the difference between the position of a point on the flexible line calculated forward from the operating end of robot 1 and the position of the same point on the flexible line calculated reversely from the operating end of robot 2.

[0066] In the embodiment of the present application, the elastic mechanics model is:

[0067]

[0068] F OD =∫||r f (s)-r i (s)||2ds;

[0069]

[0070] dQ(s) / ds=g4(q(s),Q(s),F(s));

[0071]

[0072] Among them, E OE is the total energy, E dtotal is the bending deformation energy of the flexible wire, E g is the gravitational potential energy of the flexible line, ω(s) = [ω1(s), ω2(s), ω3(s)] is the bending vector of any point of the flexible line, r(s) is the shape of the flexible line, ρ is the density of the flexible line, g is the gravitational acceleration, F OD is the calculation error, r f (s) is the coordinates of each point on the flexible line calculated from the position where the first robot (i.e., robot 1) in the collaborative robot system grasps the flexible line as the initial point, r i(s) is the coordinates of each point on the flexible line calculated from the position where the second robot (i.e., robot 2) in the collaborative robot system grasps the flexible line as the initial point, and r(s) is the coordinate of the center line of the flexible line between the two ends operated by the robot. In the calculation, r is usually taken as i (s) and r f (s), q(s) = q1(s) - q4(s) is the quaternion that expresses the posture of each microelement on the flexible line, g1 is the functional relationship expression between the coordinates of each point on the flexible line and the posture of each microelement, Q(s) is the result of differentiating the variable (arc length s) in q1(s) - q4(s), g2(s) is the functional relationship expression of differentiating the variable (arc length s) in q1(s) - q4(s), F(s) = [F1(s), F2(s), F3(s)] T is the force on a point on the flexible line, f(s) is the distributed force on the flexible line except the operating forces at both ends, f1(s)-f3(s) are the components of f(s) in three directions in Euclidean space, g3 is the functional relationship expression that characterizes the relationship between the force on each point on the flexible line and q, Q, F, f, g4 is the functional relationship expression that characterizes the relationship between the quadratic differential of each infinitesimal posture on the flexible line and q, Q, F, s is the arc length of the flexible line between a point on the flexible line and the endpoint of the flexible line.

[0073] Among them, g1~g4 are used to express that the differential term on the far left is only related to several variables in the brackets after g, and a system of differential equations can be constructed to solve it.

[0074] Specifically, the process of constructing the elastic mechanics model in the embodiment of the present application, taking two robots as an example, is as follows:

[0075] In the collaborative robot system, the end effector path of robot 1 is set to P1 = {p1 1 ,p2 1 ,…,p n 1}, the end effector path of robot 2 is P2 = {p1 2 ,p2 2 ,…,p n 2}, where p i j =[r i j ,θ i j ],t i j is the robot end position vector, θ i j is the posture vector of the robot end effector, expressed as a quaternion. The posture sequences at both ends of the flexible line are also determined by the robot actuator, which are T0 = {t10 ,t2 0 ,…,t n 0 =P1,T t ={t1 t ,t2 t ,…,t n t}=P2.

[0076] Under the conditions of the positions and postures of the two ends of a straight flexible line, an elastic mechanics model can be established based on Cosserat elastic rod theory.

[0077] Assume that the linear density of the flexible wire is ρ, the bending stiffness is C1, and the torsional stiffness is C3.

[0078] At time i, the positions of robot 1 and robot 2 are given as p i 1 =[r i 1 ,θ i 1 ] and p i 2 =[r i 2 ,θ i 2 ], the positions of the two ends of the flexible line are t i 0 =[r0,q0]=p i 1 and t i t =[r t ,q t ]=p i 2 The coordinates of the center line of the flexible line between the two ends are r(s), where r(0) = r0, r(L) = r t , s∈[0,L] is the length variable of the flexible line, and L is the total length of the flexible line. The posture of each microelement on the flexible line is q(s)=[q1(s),q2(s),q3(s),q4(s)], where q(0)=q0, q(L=q t , where the relationship between the postures of the two ends of the flexible line and the postures of robot 1 and robot 2 is as follows: Figure 2 shown.

[0079] Assume that the bending vector at any point on the flexible line is ω(s) = [ω1(s), ω2(s), ω3(s)], and the derivation formula is as shown in (1).

[0080]

[0081] Flexible wire bending deformation energy C=diag(C1,C1,C3). The gravitational potential energy of the flexible line is E g =∫r(s)ρgds=∫∫(dr(s) / ds)ρgds 2 For stability considerations, the shape of the flexible line after the operation should be the lowest point of the comprehensive potential energy. Therefore, when calculating the shape of the flexible line, the q(s) function is obtained so that F OE Minimum.

[0082]

[0083] In order to reduce the impact of discrete errors, the error term F is added to the objective function. OD As shown in (3). That is, the difference between the position of a point on the flexible line calculated from the robot 1 operating end and the position of the same point on the flexible line calculated from the robot 2 operating end. Where d3 is the axis direction vector of the flexible line, and the calculation relationship between the position of a point on the flexible line and the posture is as follows: Figure 3 shown.

[0084] F OD =∫||r f (s)-r i (s)||2ds; (3)

[0085]

[0086] By optimizing and calculating the minimum q(s) value of FOE+FOD and combining it with formula (4), the shape of the entire flexible line and the posture of any point, i.e., r(s) and q(s), can be predicted and calculated under the condition that the robot operation conditions at both ends of the flexible line are known.

[0087] Under the premise of obtaining the shape of the flexible line, assume that the moment at any point on the line is M(s) = [M1(s), M2(s), M3(s)] T , M(s)=[c1ω1(s), c1ω2(s), c3ω3(s)]. F(s)=[F1(s),F2(s),F3(s)] T is the force on a point on the flexible line. Combining Kirchhoff theory, the differential equation that characterizes the relationship between the deformation and force of the flexible line is established as shown in (6). The force F(s) of the flexible line can be obtained according to equation (6.3).

[0088]

[0089] dQ(s) / ds=g4(q(s),Q(s),F(s)); (6.4)

[0090]

[0091] In step S102, the position and posture of each robot in the collaborative robot system is obtained, and the position and posture of each robot is input into the elastic mechanics model, and the elastic mechanics model outputs the deformation information and force information of the flexible line.

[0092] Among them, deformation information can also be understood as morphological information.

[0093] It can be understood that the embodiment of the present application can obtain the robot posture of each person in the collaborative robot system, and input the posture of each robot into the elastic mechanics model, and the elastic mechanics model outputs the deformation information and force information of the flexible line.

[0094] In step S103, the safety of each robot operation path is evaluated based on the deformation information and the force information.

[0095] It can be understood that the embodiments of the present application can evaluate the safety of each robot's operating path based on the deformation information and force information, thereby preventing the occurrence of dangerous phenomena such as flexible line collision, over-stretching, and over-twisting during maintenance operations. The deformation information and force information of the flexible line can be obtained using the elastic mechanics model only by the robot's posture, without the need to use visual hardware, thereby reducing computing resources and hardware costs.

[0096] In an embodiment of the present application, the safety of each robot operation path is evaluated based on deformation information and force information, including: evaluating the interference risk of each robot operation path based on deformation information; and evaluating the compliance safety of each robot operation path based on force information.

[0097] It can be understood that the embodiments of the present application can evaluate the interference risk of each robot operation path based on deformation information, and evaluate the compliance safety of each robot operation path based on force information. The specific evaluation method is as follows.

[0098] In an embodiment of the present application, the interference risk of each robot operation path is evaluated based on the deformation information, including: obtaining the position and posture of each link of each robot; calculating the shortest distance between the deformation information and each link, and generating an interference risk index based on the shortest distance; and evaluating the interference risk of each robot operation path based on the interference risk index.

[0099] It is understandable that the embodiment of the present application can design an interference risk index based on deformation information, specifically: determine the current position and posture of each link of the robot through the robot joint encoder, and record the collection as Robot. By calculating the distance between the flexible line curve and the link, the interference risk criterion C1 of the flexible line at the current moment can be obtained, and then the interference risk of each robot operation path can be evaluated based on the interference risk. If C1 <T D(safety threshold), it means that during the operation, there is a high risk of collision and interference between the flexible line and the robot, and the robot's operating path needs to be adjusted.

[0100] In the embodiment of the present application, the interference risk index is:

[0101] C1(r(s))=min({r(s)},Robot); (7)

[0102] Among them, r(s) is the arc length between a point on the flexible line and the end point of the flexible line, Robot is the set of the current position and posture of each link of the robot, and C1(r(s)) is the interference risk index.

[0103] In an embodiment of the present application, the compliance safety of each robot operation path is evaluated based on the force information, including: identifying the forces and moments in the force information; constructing a compliance safety index based on the forces and moments; and evaluating the compliance safety of each robot operation path based on the compliance safety index.

[0104] It should be noted that since another requirement for robot operation safety is that the operating force must not exceed the limit during the maintenance process, which would cause over-stretching or over-twisting of the operated object, the embodiment of the present application designs a compliance safety index C2 that characterizes compliance safety. By identifying the force and torque in the force information, a compliance safety index is constructed based on the force and torque, and the compliance safety of each robot operation path is evaluated based on the compliance safety index.

[0105] For the planned robot operation path, it is required to satisfy C2(r(s)) <T S ,max(||F(s1)||2,||F(s t )||2)≤T F and max(||M(s1)||2,||M(s t )||2)≤M F , otherwise there is a risk of damage to the robot and the object being operated due to excessive force. s is the comprehensive stress safety threshold, T F is the safety threshold of force component, M F is the torque component safety threshold, w f and w M are the safety weight factors of force and moment respectively.

[0106] In the embodiment of the present application, the compliance safety index is:

[0107] C2(r(s))=w F (||F(s1)||2+||F(s t )||2)+w M(||M(s1)||2+||M(s t )||2);(8)

[0108] Among them, w F and w M are the safety weight coefficients of force and moment, respectively; F(s1) is the force borne by the starting point of the flexible line; F(s t ) is the force on the end of the flexible line, M(s1) is the torque on the starting point of the flexible line, and M(s t ) is the torque borne by one end of the flexible line.

[0109] The following is a specific example to describe the safety assessment method of the collaborative robot operation path of the embodiment of the present application. The specific process is as follows: Figure 4 As shown, including:

[0110] In the collaborative robot system, the end effector path of robot 1 is set to P1 = {p1 1 ,p2 1 ,…,p n 1}, the end effector path of robot 2 is P2 = {p1 2 ,p2 2 ,…,p n 2}, where p i j =[r i j ,θ i j ],t i j is the robot end position vector, θ i j is the posture vector of the robot end effector, expressed as a quaternion. The posture sequences at both ends of the flexible line are also determined by the robot actuator, which are T0 = {t1 0 ,t2 0 ,…,t n 0 =P1,T t ={t1 t ,t2 t ,…,t n t}=P2.

[0111] Under the condition that the positions and postures of the two ends of the flexible line are known, an optimization model can be established based on the Cosserat elastic rod theory to predict and calculate the shape and force conditions of the flexible line during robot operation, and then an evaluation index function can be designed to evaluate the safety of each step in the collaborative robot operation. If the index function deviates from the threshold, the path planning is re-performed to prevent the occurrence of dangerous phenomena such as collision, over-stretching, and over-twisting of the flexible line during maintenance operations.

[0112] Assume that the linear density of the flexible wire is ρ, the bending stiffness is C1, and the torsional stiffness is C3.

[0113] At time i, the positions of robot 1 and robot 2 are given as p i 1 =[r i 1 ,θ i 1 ] and p i 2 =[r i 2 ,θ i 2 ], the positions of the two ends of the flexible line are t i 0 =[r0,q0]=p i 1 and t i t =[r t ,q t ]=p i 2 The coordinates of the center line of the flexible line between the two ends are r(s), where r(0) = r0, r(L) = r t , s∈[0,L] is the length variable of the flexible line, and L is the total length of the flexible line. The posture of each microelement on the flexible line is q(s)=[q1(s),q2(s),q3(s),q4(s)], where q(0)=q0, q(L=q t .

[0114] Minimize the objective function FOE+FOD, and predict and calculate the shape of the entire flexible line and the posture of any point, i.e., r(s) and q(s), through formulas (1)-(5).

[0115] Under the premise of obtaining the shape of the flexible line, assume that the moment at any point on the line is M(s) = [M1(s), M2(s), M3(s)] T , M(s)=[c1ω1(s), c1ω2(s), c3ω3(s)]. F(s)=[F1(s),F2(s),F3(s)] Tis the force on a point on the flexible line. Combining Kirchhoff theory, the differential equation that characterizes the relationship between the deformation and force of the flexible line is established as shown in formula (6). The force F(s) of the flexible line can be obtained according to formula (6.3), where f(s) is the distributed force on the flexible line except the operating forces at both ends, which is usually the gravity caused by the density of the flexible line.

[0116] The safety of the robot's operation path is evaluated through C1(r(s)) and C2(r(s)). If C1(r(s)) is less than TD, or C2(r(s)) is greater than or equal to TS, an alarm message is issued and the robot's operation path is replanned.

[0117] In summary, the embodiment of the present application establishes an elastic mechanics model, takes into account the deformation energy, gravitational potential energy and calculation errors, models the flexible lines in the maintenance process, predicts their shape and force conditions, and designs interference and force criteria to characterize the safety of the operation based on the modeling prediction results. It can determine whether there will be collisions and damage to the operation object during the operation when only the robot operation path is known. The safety of the task can be evaluated before the operation path planning is completed and executed, avoiding interference collisions caused by missed detection of the operation object due to occlusion of the visual sensor and fitting and registration failure during the operation. Compared with the prior art, there is no need to introduce visual sensors, the cost is lower, and there is no need to process images and point cloud data, which consumes less computing resources.

[0118] According to the safety assessment method of the collaborative robot operation path proposed in the embodiment of the present application, an elastic mechanics model can be established based on the deformation energy, gravitational potential energy and calculation error of the flexible line. The elastic mechanics model can be used to predict the deformation information and force information of the flexible line only when the robot's position and posture are known, and then the safety of the robot's operation path can be assessed based on the deformation information and force information. There is no need to introduce additional visual hardware, thus reducing computing resources and hardware costs, and avoiding interference collisions caused by missed detection of the operation object due to occlusion of visual hardware and failure of fitting and registration during operation.

[0119] Next, a safety assessment device for the operation path of a collaborative robot proposed in an embodiment of the present application will be described with reference to the accompanying drawings.

[0120] Figure 5 It is a block diagram of a safety assessment device for a collaborative robot operation path according to an embodiment of the present application.

[0121] like Figure 5 As shown, the safety assessment device 10 for the collaborative robot operation path includes: an establishment module 100, an input module 200 and an assessment module 300.

[0122] Among them, the establishment module 100 is used to establish an elastic mechanics model based on the deformation energy, gravitational potential energy and calculation error of the flexible line, wherein the calculation error is to start from the position of each different robot in the collaborative robot system that operates the flexible line grasping the flexible line as the initial point, and calculate the difference between the positions of the same point on the flexible line; the input module 200 is used to obtain the posture of each robot in the collaborative robot system, and input the posture of each robot into the elastic mechanics model, and the elastic mechanics model outputs the deformation information and force information of the flexible line; the evaluation module 300 is used to evaluate the safety of each robot's operating path based on the deformation information and force information.

[0123] In the embodiment of the present application, the elastic mechanics model is:

[0124]

[0125] F OD =∫||r f (s)-r i (s)||2ds;

[0126]

[0127]

[0128] dQ(s) / ds=g4(q(s),Q(s),F(s));

[0129]

[0130] Among them, E OE is the total energy, E dtotal is the bending deformation energy of the flexible wire, E g is the gravitational potential energy of the flexible line, ω(s) = [ω1(s), ω2(s), ω3(s)] is the bending vector of any point of the flexible line, r(s) is the shape of the flexible line, ρ is the density of the flexible line, g is the gravitational acceleration, F OD is the calculation error, r f (s) is the coordinates of each point on the flexible line calculated from the position where the first robot in the collaborative robot system grasps the flexible line as the initial point, r i(s) is the coordinate of each point on the flexible line calculated from the position where the second robot in the collaborative robot system grasps the flexible line as the initial point, r(s) is the coordinate of the center line of the flexible line between the two ends operated by the robot, q(s) = q1(s) - q4(s) is the quaternion expressing the posture of each microelement on the flexible line, g1 is the functional relationship expression between the coordinates of each point on the flexible line and the posture of each microelement, Q(s) is the result of differentiating the arc length s in q1(s) - q4(s), g2(s) is the functional relationship expression representing the differential of the arc length s in q1(s) - q4(s), F(s) = [F1(s), F2(s), F3(s)] T is the force on a point on the flexible line, f(s) is the distributed force on the flexible line except the operating forces at both ends, f1(s)-f3(s) are the components of f(s) in three directions in Euclidean space, g3 is the functional relationship expression that characterizes the relationship between the force on each point on the flexible line and q, Q, F, f, g4 is the functional relationship expression that characterizes the relationship between the quadratic differential of each infinitesimal posture on the flexible line and q, Q, F, s is the arc length of the flexible line between a point on the flexible line and the endpoint of the flexible line.

[0131] In the embodiment of the present application, the evaluation module 300 is further used to: evaluate the interference risk of each robot operation path according to the deformation information; and evaluate the compliance safety of each robot operation path according to the force information.

[0132] In an embodiment of the present application, the evaluation module 300 is further used to: evaluate the interference risk of each robot operation path based on the deformation information, including: obtaining the position and posture of each link of each robot; calculating the shortest distance between the deformation information and each link, and generating an interference risk index based on the shortest distance; and evaluating the interference risk of each robot operation path based on the interference risk index.

[0133] In the embodiment of the present application, the evaluation module 300 is further used to: identify the forces and moments in the force information; construct a compliance safety index based on the forces and moments; and evaluate the compliance safety of each robot operation path based on the compliance safety index.

[0134] In the embodiment of the present application, the interference risk index is:

[0135] C1(r(s))=min({r(s)},Robot);

[0136] Among them, r(s) is the arc length between a point on the flexible line and the end point of the flexible line, Robot is the set of the current position and posture of each link of the robot, and C1(r(s)) is the interference risk index.

[0137] In the embodiment of the present application, the compliance safety index is:

[0138] C2(r(s))=w F (||F(s1)||2+||F(s t )||2)+w M (||M(s1)||2+||M(s t )||2);

[0139] Among them, w F and w M are the safety weight coefficients of force and moment, respectively; F(s1) is the force borne by the starting point of the flexible line; F(s t ) is the force on the end of the flexible line, M(s1) is the torque on the starting point of the flexible line, and M(s t ) is the torque borne by one end of the flexible line.

[0140] It should be noted that the aforementioned explanation of the embodiment of the method for safety assessment of the operation path of a collaborative robot is also applicable to the device for safety assessment of the operation path of a collaborative robot of this embodiment, and will not be repeated here.

[0141] According to the safety assessment device for the operating path of a collaborative robot proposed in the embodiment of the present application, an elastic mechanics model can be established based on the deformation energy, gravitational potential energy and calculation error of the flexible line. The elastic mechanics model can be used to predict the deformation information and force information of the flexible line only when the position and posture of the robot is known, and then the safety of the operating path of the robot can be assessed based on the deformation information and force information. There is no need to introduce additional visual hardware, thus reducing computing resources and hardware costs, and avoiding interference collisions caused by missed detection of the operating object due to occlusion of visual hardware and failure of fitting and registration during operation.

[0142] Figure 6 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. The electronic device may include:

[0143] A memory 601 , a processor 602 , and a computer program stored in the memory 601 and executable on the processor 602 .

[0144] When the processor 602 executes the program, the safety assessment method of the collaborative robot operation path provided in the above embodiment is implemented.

[0145] Furthermore, the electronic device further comprises:

[0146] The communication interface 603 is used for communication between the memory 601 and the processor 602 .

[0147] The memory 601 is used to store computer programs that can be executed on the processor 602 .

[0148] The memory 601 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0149] If the memory 601, the processor 602 and the communication interface 603 are implemented independently, the communication interface 603, the memory 601 and the processor 602 can be connected to each other through a bus and communicate with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 6 Only one thick line is used in the diagram, but this does not mean that there is only one bus or only one type of bus.

[0150] Optionally, in a specific implementation, if the memory 601, the processor 602 and the communication interface 603 are integrated on a chip, the memory 601, the processor 602 and the communication interface 603 can communicate with each other through an internal interface.

[0151] The processor 602 may be a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0152] An embodiment of the present application also provides a computer-readable storage medium having a computer program or instructions stored thereon. When the computer program or instructions are executed by a processor, the safety assessment method for the collaborative robot operation path as described above is implemented.

[0153] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0154] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0155] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or N executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0156] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above embodiment, the N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one or a combination of multiple of the following technologies known in the art: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0157] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

Claims

1. A safety assessment method for a collaborative robot operation path, characterized in that: The following steps are involved: An elastic mechanics model is established based on the deformation energy, gravitational potential energy and calculation error of the flexible wire, wherein the calculation error is the difference between the positions of the same point on the flexible wire calculated from the positions of different robots grasping the flexible wire in the collaborative robot system operating the flexible wire as the initial point; Acquire the position and posture of each robot in the collaborative robot system, input the position and posture of each robot into the elastic mechanics model, and the elastic mechanics model outputs the deformation information and force information of the flexible line; The safety of each robot operation path is evaluated according to the deformation information and the force information.

2. The method for safety assessment of collaborative robot operation paths according to claim 1, characterized in that: The elastic mechanics model is: F OD =∫||r f (S)-r i (s)||2ds; dQ(s) / ds=g4(q(s),Q(s),F(s)); Among them, F OE is the total energy, E dtotal is the bending deformation energy of the flexible wire, E g is the gravitational potential energy of the flexible line, ω(s)=[ω1(s),ω2(s),ω3(s)] is the bending vector of any point of the flexible line, r(s) is the shape of the flexible line, ρ is the density of the flexible line, g is the gravitational acceleration, F OD is the calculation error, r f (s) is the coordinates of each point on the flexible line calculated from the position where the first robot in the collaborative robot system grasps the flexible line as the initial point, r i (s) is the coordinate of each point on the flexible line calculated from the position where the second robot in the collaborative robot system grasps the flexible line as the initial point, r(s) is the coordinate of the center line of the flexible line between the two ends operated by the robot, q(s) = q1(s) - q4(s) is the quaternion expressing the posture of each microelement on the flexible line, g1 is the functional relationship expression between the coordinates of each point on the flexible line and the posture of each microelement, Q(s) is the result of differentiating the arc length s in q1(s) - q4(s), g2(s) is the functional relationship expression representing the differential of the arc length s in q1(s) - q4(s), F(s) = [F1(s), F2(s), F3(s)] T is the force on a point on the flexible line, f(s) is the distributed force on the flexible line except the operating forces at both ends, f1(s)-f3(s) are the components of f(s) in three directions in Euclidean space, g3 is the functional relationship expression that characterizes the relationship between the force on each point on the flexible line and q, Q, F, f, g4 is the functional relationship expression that characterizes the relationship between the quadratic differential of each infinitesimal posture on the flexible line and q, Q, F, s is the arc length of the flexible line between a point on the flexible line and the endpoint of the flexible line.

3. The safety assessment method for the collaborative robot operation path according to claim 1, characterized in that: The evaluating the safety of each robot operation path according to the deformation information and the force information includes: Evaluate the interference risk of each robot operation path according to the deformation information; The compliance safety of each robot operation path is evaluated according to the force information.

4. The method for safety assessment of collaborative robot operation paths according to claim 3, characterized in that: The step of evaluating the interference risk of each robot operation path according to the deformation information comprises: Obtaining the position and posture of each connecting rod of each robot; calculating the shortest distance between the deformation information and each connecting rod, and generating an interference risk index based on the shortest distance; The interference risk of each robot operation path is evaluated based on the interference risk index.

5. The method for safety assessment of collaborative robot operation paths according to claim 3, characterized in that: The step of evaluating the compliance safety of each robot operation path according to the force information includes: identifying forces and moments in the force information; constructing the compliance safety index based on the force and the moment; The compliance safety of each robot operation path is evaluated based on the compliance safety index.

6. The method for safety assessment of collaborative robot operation paths according to claim 4, characterized in that: The interference risk index is: C1(r(s))=min({r(s)},Robot); Among them, r(s) is the arc length between a point on the flexible line and the end point of the flexible line, Robot is the set of the current position and posture of each link of the robot, and C1(r(s)) is the interference risk index.

7. The method for safety assessment of collaborative robot operation paths according to claim 5, characterized in that: The compliance safety index is: C2(r(s))=w F (||F(s1)||2+||F(s t )||2)+w M (||M(s1)||2+||M(s t )||2); Among them, w F and w M are the safety weight coefficients of force and moment, respectively; F(s1) is the force borne by the starting point of the flexible line; F(s t ) is the force on the end of the flexible line, M(s1) is the torque on the starting point of the flexible line, and M(s t ) is the torque borne by one end of the flexible line.

8. A safety assessment device for a collaborative robot operation path, characterized in that: include: Establishing a module for establishing an elastic mechanics model based on the deformation energy, gravitational potential energy and calculation error of the flexible line, wherein the calculation error is to calculate the difference between the positions of the same point on the flexible line starting from the position where each different robot in the collaborative robot system operating the flexible line grasps the flexible line as the initial point; An input module, used for acquiring the position and posture of each robot in the collaborative robot system, inputting the position and posture of each robot into the elastic mechanics model, and the elastic mechanics model outputs deformation information and force information of the flexible line; An evaluation module is used to evaluate the safety of each robot operation path according to the deformation information and the force information.

9. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the safety assessment method for the collaborative robot operation path as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program or instruction stored thereon, characterized in that: The computer program or instructions are executed by a processor to implement the safety assessment method for the collaborative robot operation path as described in any one of claims 1-7.

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