Predefinition of the maximum permissible speed of robotic devices

Abstract

The invention relates to predefining a maximum allowable speed of a robotic device (1), comprising: predefining a contact point between a human operator and the robotic device (1), a shape of the robotic device (1) at the contact point and spatial boundary conditions of the collision for a collision between the human operator and the robotic device (1) in order to predefine a maximum allowable speed of the robotic device (1) in the most efficient way possible such that a maximum possible maximum allowable speed can be determined, at a speed which ensures that biomechanical limits for preventing injuries are respected; determining, taking into account the spatial boundary conditions, using a computing unit (4) whether the collision is a non-clamping collision or a clamping collision; calculating by the computing unit (4) a maximum allowable speed of the robotic device (1) at the contact point using a free impact model if the collision is a non-clamping collision and using a clamping impact model or using a quasi-static clamping model if the collision is a clamping collision, wherein the models are different in each case; and outputting, using the computing unit (4), a signal which is dependent on the calculated maximum allowable speed of the robotic device (1).

Description

[Technical Field]

[0001] The present invention relates to a computer implementation method for predefining the maximum permissible speed of a robotic device, and a corresponding control unit. [Background technology]

[0002] To prevent or reduce accidents and injuries with robotic devices, it is necessary to protect the mechanical human-machine interface, including moving parts. Such human-machine interfaces exist, for example, in collaborative robotic devices / robots, so-called cobots. In principle, there is a risk of injury resulting from collisions between each moving part of a robotic device (machine) and a part of the human operator's (user's) body. The risk of injury or accidents can be mitigated by limiting the performance of the robotic device to such an extent that the device does not pose a risk of injury or only a mitigated risk of injury.

[0003] Generally, performance limitations can be achieved by limiting the force and / or power of a robotic device. For example, known biomechanical limits quantified in relevant standards indirectly specify, in terms of a safe operating mode for the robotic device, to what extent the power of the robotic device, such as the speed of the moving parts of the robotic device, should be limited so that collisions with humans do not cause unacceptable excessive stress on human tissue and the resulting pain or injury.

[0004] Today, the verification of limits in robotic devices through physical measurement, i.e., adherence to limits, is established. The drawback of this verification is that the corresponding measurements can only be made after the robotic device has been in operation, and therefore, the maximum achievable speed or performance limit can only be determined retrospectively. As a result, the corresponding permissible control signals can also only be generated retrospectively, which leads to long iterative loops and a high degree of uncertainty in the planning process.

[0005] The theoretical understanding of the abstract assessment of collisions between humans and resilient robotic devices was significantly influenced by the article "Fast and "Soft Arm" Tactics" by Bicchi, A. et al., published in IEEE Robot.Automat.Mag.11(2), pages 22-23, in 2004. This article proposed a three-mass oscillator model for assessing the risk of head injury. However, this model is only suitable for hard body parts such as the head.

[0006] The three-mass oscillator model is also used in the article "On Impact the Decoupling Properties of Elastic Robots and Time Optimal Velocity Maximization on Joint Level" by Hadaddin S. et al., published on pages 5089-5096 of the Proceedings of the 2012 IEEE / RSJ-International Conference on Intelligent Robots and Systems. To illustrate the worst-case scenario, the drive inertia is assumed to be infinite mass, which leads to significantly excessive collision forces and, therefore, an unnecessarily reduced maximum allowable velocity in a realistic scenario.

[0007] The article "A New Approach to Estimate the Apparent Mass of Collaborative Robot Manipulators" by Herbster S. et al., published in "Experimental Robotics" (Cham: Springer International Publishing) in 2021 (pages 211-221), also uses a three-mass oscillator model. In it, a linear characteristic curve is assumed to explain the analytical solution for safe speed, i.e., the maximum allowable speed. [Overview of the project] [Problems that the invention aims to solve]

[0008] Therefore, the objective is to specify the maximum permissible speed of the robotic device, ensuring that biomechanical limits to prevent injury are adhered to in the most efficient way possible, so that the highest possible permissible speed can be determined, especially in real-time applications.

[0009] This objective is achieved by the subject matter of the independent claim. Advantageous embodiments may be found in the dependent claims, description, and drawings. [Means for solving the problem]

[0010] One aspect relates to a computer implementation method for predefining the maximum permissible speed of a robotic device / robot device. In this specification, the maximum speed is, in particular, related to one or more points moving at the highest speed among all points on the surface of the robotic device at each point in time along a predefined machine path or trajectory of the robotic device. In particular, the robotic device may be a collaborative robotic device, a so-called cobot. However, in general, the method described may be applied to any machine having a physical interface with a human.

[0011] In this specification, one method step is to predefine, with respect to a collision between a human operator and a robotic device, at least one contact point between the human operator and the robotic device, the shape of the robotic device at the contact point, and the spatial boundary conditions of the collision. In particular, the shape of the robotic device may include data of the tool and / or workpiece. Thus, the tool used by the robotic device or the workpiece processed by the robotic device may be considered as part of the robotic device. The selection of the contact point between human and machine, i.e., between the operator and the robotic device, and the spatial boundary conditions, e.g., whether the part of the human body belonging to the contact point is captured or free, may be performed manually by the user or (partially) automatically. The user or (partially) automated input may specify one or more contact points in a collision or multiple contact scenario, each including a collision or an associated collision between the operator and the robotic device. The shape of the robotic device associated with the collision may be selected manually by the user, for example, using a list, or automatically, for example, based on a 3D model of the robotic device, which may include the tool and workpiece.

[0012] In a further step of the method, a computing unit is used to determine whether a collision is a non-tightening collision or a tightening collision, taking into account predefined spatial boundary conditions. In the case of collisions with multiple contact points, collisions that are both non-tightening and tightening collisions may occur. In this case, the collision may be divided into, for example, two separate partial collisions for this method, and then the method described is performed individually for each partial collision. At the end of each individual method, different results of the maximum allowable speed may be compared with each other, as well as predefinition of the maximum allowable speed for a robot device with respect to multiple collisions or multiple contact points, as described further below, and an appropriate, for example, lowest maximum speed may be predefined as the maximum allowable speed, i.e., calculated and provided for the output described below.

[0013] Therefore, calculating the maximum permissible speed of the robotic device at the point of contact is a further step in the method. This calculation is performed using a free-impact model if the collision is a non-clamping collision, and using a clamping-impact model and / or a quasi-static-clamping model if the collision is a clamping collision. These models are different in each case. The free-impact model is used herein for "free impact," i.e., a relatively high-speed collision in which the contact point on a body part or a body part belonging to the contact point is not obstructed by any external resistance in the direction of the collision (the direction in which the contact point moves on the robotic device during the collision), i.e., the body part can be avoided. The clamping-impact model relates to a similarly relatively high-speed collision in which the body part assigned to the contact point cannot be avoided, i.e., encounters external resistance and is therefore captured. The quasi-static constriction model is used in this case for low-speed collisions compared to the high-speed collisions described above, in which the contact point on the body part or the body part associated with the contact point is still subjected to external resistance in the direction of the collision, i.e., the body part is unable to avoid the constriction impact.

[0014] In this specification, different models are stored in a computing unit that calculates the maximum permissible speed, and the computing unit may determine each maximum speed specific to the model based on partially identical and partially different input variables, as further described below. In this specification, whether the collision is relatively high-speed or relatively low-speed, i.e., whether a clamping impact model or a quasi-static clamping model is used, may be predefined, for example, by setting corresponding speed limits, by applying both models alternatively or additionally, i.e., by simulating the collision using two different simulations separately and then comparing the results to obtain the maximum permissible speed in each case. For example, the lower of these results may be selected for further parts of the method.

[0015] Finally, the computing unit outputs a control signal that represents the calculated maximum allowable speed of the robot device, which may be selected from a plurality of calculated maximum speeds, and in particular the calculated maximum allowable speed. This control signal may, as herein, be a control signal that can be read directly by the robot device, or alternatively, a control signal that, accordingly, indicates to the human user of the method the maximum speed at which the robot device should be controlled, for example, via a display unit. Thus, the computer implementation method may be implemented in a virtual planning tool, for example, using a virtual robot device that is virtually controlled by the control signal, or directly in the control unit of the robot device as a program sequence. In addition to the tool, safety configuration, kinematic description, mass, inertia, center of gravity, joints, and corresponding motors, the necessary data regarding the torque of the robot device, as well as the limits of body parts affected by collisions, stiffness characteristic curves, and mass, are stored in a corresponding database and provided to this method. The data used is described in more detail below. The signal may be a warning signal, for example, in a real-time application, indicating that the actual speed of the robot device is higher than the maximum allowable speed.

[0016] To calculate the maximum permissible speed, this method accesses parameters stored in a database or model. After the calculation is complete, this method and therefore the algorithm outputs a safe speed, i.e., the maximum permissible speed of the robot device, at which point, if a collision under consideration occurs, the mechanical parts under consideration involved in the collision will not exceed the stored biomechanical limits that are permissible according to standards in effect as of July 2021, such as ISO / TS15066. In the case of multiple pairs of contact points and contact shapes in one or more collisions, the lowest value among the calculated safe speeds may be selected for output.

[0017] Compared to previous methods, the advantages of this specification are, firstly, that clamping impact and quasi-static clamping are combined in a uniform manner but still considered individually. This allows for the precise calculation of which velocities are still safe with a low risk of injury, for both relatively slow and relatively fast collisions.

[0018] This is based on the knowledge that the system's behavior is highly nonlinear, i.e., that limitations for a uniform model for all tightening, high-speed and low-speed tightening, tightening impact and quasi-static tightening, result in allowable maximum speeds that deviate significantly from the actual limits for other cases, and are therefore highly inaccurate. In addition, the method described is suitable for both so-called offline (planned) and real-time calculations of each allowable maximum speed of machines, in particular robotic devices with a physical interface with humans. In this specification, specific examples consist of collaborative robotic devices that communicate with humans and operate in power and force limiting modes according to ISO / TS15066. The method described may be used to ensure compliance with predefined limits, such as known biomechanical limits, and thus minimize the risk of unacceptable stresses, i.e., collisions that cause pain and / or injury to the operator.

[0019] The aforementioned method may be used to optimize and verify the allowable speed of the movable parts of a machine along a predefined trajectory, or more precisely, the path (trajectory) of the machine through which a robotic device passes. Different spatial and temporal conditions of collisions can be particularly addressed, which results in the remarkable accuracy of this method.

[0020] Thus, a further insight underlying the present invention is that the use of different models, although the required initial configuration is more complex, is beneficial in terms of overall efficiency than the use of a single model. This method can also take into account the non-linear stiffness characteristic curves at the contact points with respect to both the soft tissue to which the operator's load may be applied and the surface of the machine at the contact points, which may deform in case of a collision, in addition to the various surface shapes at the contact points of the colliding machine parts, including the tool and the workpiece. This method may be particularly applied to various points along the surface of the machine, including the tool and the workpiece, so that a comprehensive assessment of the risk of injury, and thus, in particular, a reliable determination of the maximum allowable speed is achieved.

[0021] In an advantageous embodiment, it is provided that the output control signal represents a position-dependent speed specification along a predefined path of the machine, the trajectory of the robotic device, or one or more parts of the robotic device. The speed specification is position-dependent in that it is predefined along the path of the machine and thus at various positions of each machine part of the robotic device. In particular, a position-dependent speed specification may be generated by changing the magnitude of the originally predefined speed specification with respect to a predefined path of the machine, which is preferably also position-dependent based on the calculated maximum speed. Thus, the original position-dependent speed specification along a path of the machine that may be unsafe can be replaced by an equivalent position-dependent speed specification that ensures that a safe maximum allowable speed is predefined along the predefined path of the machine.

[0022] In this specification, a change in magnitude may include, or may be, a change in magnitude that is uniform, i.e., independent of position, of a predefined maximum speed, or a change in magnitude that is locally adapted to a predefined path of the machine. Thus, in the case of a uniform change in magnitude, a fixed factor is multiplied by the predefined maximum allowable speed according to the position along the path of the machine so as not to exceed the safe speed at which injuries can be excluded as described above at one or more speed extrema of the original speed specification. In the case of a change in magnitude that is locally adapted to a predefined path of the machine, accordingly, the speed may be reduced in the case of a subsection of the path of the machine where the original speed specification exceeds the safe speed, and the speed may be increased in the case of a subsection of the path of the machine where the originally predefined speed specification is below the determined safe maximum speed. In particular, for example, the predefined process speed of the robot device may be taken into account in one or more subsections of the path of the machine in such a way that the originally predefined maximum speed specification is not adjusted there. This is advantageous, for example, in such subsections of the technical process executed by the robot device where the speed may be increased for safety reasons but a low speed is required for the process itself with respect to the calculated maximum allowable speed. This has the advantage that the entire process of the robot device can be safely optimized, i.e., the speed of the robot device can be increased.

[0023] In an alternative embodiment, it is provided that the maximum allowable speed is calculated in real time such that the instantaneous actual speed of the robot device at a predefined contact point is adapted to the instantaneous maximum allowable speed, and the control signal output represents the instantaneous maximum allowable speed of the robot device. This is advantageous, for example, in the case of a device that is manually or semi-automatically controlled, where the instantaneous speed of the robot device is controlled or influenced by an operator.

[0024] In a further advantageous embodiment, it is provided that, if the collision is a clamping collision, the maximum permissible speed is calculated using a clamping impact model and a quasi-static clamping model, and the lower of the calculated maximum speeds is selected as the maximum permissible speed on which the output signal depends. This has the advantage that an implicit distinction is made between faster and slower collisions, i.e., there is no need to set limits from the outset that may be inflexible and incorrect, and priority is given to safer maximum speeds.

[0025] In a further advantageous embodiment, the maximum permissible speed is calculated in a quasi-static clamping model based on the following: (a) Predefined kinematic structure of robotic devices, (b) The joint configuration, including the position of one or more axes of the robotic device and the velocity assigned to each axis at the time of collision. (c) Stiffness characteristic curves of human body parts at the point of contact of collision, (d) Stiffness characteristic curve of the machine at the point of contact of the collision, (e) The resulting stiffness curve calculated using the stiffness curves of human body parts and the stiffness curves of machine points, (f) In particular, using biomechanical force thresholds and / or energy thresholds and / or deformation thresholds, or predefined and added maximum deformations, (g) The rigidity curve of the machine at a point and the allowable penetration depth calculated using the resulting rigidity curve, (h) Reaction force of robotic devices, (i) The reaction distance of the robot device calculated using the machine's point stiffness curve and allowable penetration depth. (j) The allowable braking distance of the robot device calculated using predefined maximum allowable deformation and reaction force, and (k) Actual braking distance of robotic devices.

[0026] The predefined kinematic structure of a robotic device according to (a) is expressed herein as the overall arrangement of joints, for example, as Denavitt-Hartenberg parameters. The joint configuration at the time of collision according to (b) transmits the axial position and axial velocity of the robotic device to this method or algorithm, in particular, triggered by human input, for example, by the robotic device or the corresponding control unit of a virtual (offline) planning tool. If the trajectory of the robotic device is transmitted, the joint configuration is calculated and transmitted accordingly for each individual time step. Thus, this method may then be used to calculate the safe velocity for each time step along the trajectory.

[0027] The stiffness curve of a human body part according to (c) depends on the body part affected and the shape of the machine at the contact point. The stiffness curve quantifies the dependency of the forces acting on the body part during the collision on the deformation of the body part in question and is usually distinguished by nonlinear behavior. The stiffness curve of a human body part affected by a collision and associated limits may, in particular according to ISO / TS15066, be selected from a tabular list, determined based on a contact model (simulation), or determined experimentally. Known tabular lists include, for example, the body parts affected and the outlines of the robotic device at the contact point. On the other hand, a contact model may calculate stiffness curves and associated force or energy limits that depend on the contact shape, based on specific material parameters and biomechanical limits for each body part or contact point on a body part.

[0028] The machine point at the contact point according to (d) may have stiffness equivalent to that of the human body part. Similar to the stiffness curve of the human body part, the corresponding stiffness curve may be given by entries in the database, simulations, or experimental data. This stiffness curve may represent nonlinear behavior. The effective stiffness curve according to (e) is obtained from the stiffness curve of the human body part according to (c) and the stiffness curve of the machine point at the contact point according to (d). Such a resulting stiffness curve is shown in Figure 2 and, for example, typically establishes the relationship between the force acting on the human body part at the contact point when a collision with the machine point occurs and the resulting deformation of the human body part at the contact point. In this specification, if the acting force exceeds the allowable biomechanical contact force, the allowable penetration depth is also exceeded, resulting in damage, i.e., injury to the human body part.

[0029] The predefined maximum allowable deformation, as a biomechanical limit, according to (f), is a limit that depends on the body part and contact shape. Therefore, the maximum allowable deformation may exist together with, or as, force thresholds / limits and / or energy thresholds / limits and / or deformation thresholds / limits. In this specification, a distinction may be made between fast (temporary) and slow (quasi-static) values ​​for each impact load and clamping load limit. Quasi-static designations or values ​​are related to quasi-static clamping models, while temporary limits are related to free impact models or clamping impact models. Various force, energy, or deformation limits may be converted to each other using specific stiffness characteristic curves of human body parts. For example, as illustrated in conjunction with Figure 2, this calculation requires a biomechanical force limit.

[0030] The allowable penetration depth according to (g) may be determined from the biomechanical force limits and the resulting stiffness curve. In Figure 2, the allowable penetration depth corresponds to the intersection of the allowable biomechanical contact force and the resulting stiffness curve. The reaction force of the robot device according to (h) is a force limit that can be set on the robot device, and if this force limit is exceeded, the robot device will cause a safe stop. Such a safe stop usually involves asynchronous braking using the maximum deceleration of all axes, in which case path fidelity is not given. Exemplary reaction forces are also shown in Figure 2. The configurable force limits may often be set over specific axes relative to the operating point of the robot device. The force limits may be set in particular as axis-specific force or torque limits, shown for each drive of the robot device. The axis-specific force or torque limits may be converted into an overall force limit using the axis position, the point of the machine at the contact point, i.e., the contact point on the surface of the machine, and the direction of impact.

[0031] In principle, force limits may be defined for any point on the machine, i.e., for any contact point on the surface of the machine. A force limit set at a point on the machine, for example, the end effector of a robotic device, can usually be converted to a force limit for any other point on the machine. Then, axis-specific force or torque limits do not need to be given for all axes. If the position of an axis is unfavorable, the robotic device may not detect a collision in such cases. This is the case when, in the event of a collision, none of the monitored axis-specific forces or torques are addressed by the input force. Both force limits at the operating point and axis-specific force or torque limits, both generally called monitored limits, are often both set, i.e., predefined and enabled in the robotic device. In such cases, the lower of the two resulting limits must be considered as a reaction force in the robotic device for further consideration.

[0032] The calculated reaction distance of a robotic device according to (i) may be obtained from the reaction force set at the machine's operating point and the resulting stiffness characteristic curve. Then, as also shown in Figure 2, the intersection of the limit and the characteristic curve corresponds to the length of the reaction distance. The allowable braking distance of a robotic device according to (j) is obtained from the allowable penetration depth minus the machine's reaction distance. An exemplary allowable braking distance is also shown in Figure 2. If the reaction force on the robotic device is greater than the allowable contact force at each body position, there is no safe speed. In this case, the robotic device must not move until the affected body part is outside the hazard zone.

[0033] In the event of a safety stop, the robotic device typically performs asynchronous braking, in which case all axes are decelerated to the maximum extent, and a loss of path accuracy is accepted. Herein, the axis positions of the robotic device after such a braking process are calculated from the axis velocity at the time of impact, the axis position from which the reach can be determined, the additional load at the point of application or tool, and the braking angle moved. The braking angle may be selected from the manufacturer's specifications, calculated based on possible deceleration, or determined experimentally. The deceleration is then obtained from the available force or torque on the axes of the robotic device and the dynamics of the robotic device, considered as a mechanical system. Using known kinematic structures and considering the difference in distance at the impact point before and after the end of the braking process, the distance moved in the direction of impact may be calculated with respect to any point on the machine, i.e., for each point on the machine as a point of contact at impact. This distance then corresponds to the actual braking distance of the machine according to (k).

[0034] In an advantageous embodiment, the maximum permissible speed may be determined iteratively based on the reaction force of the robotic device until the actual braking distance corresponds to the permissible braking distance. In this specification, the bisection method is particularly suitable. The maximum permissible speed can be calculated particularly quickly using the aforementioned variables due to fewer iterative steps.

[0035] In another advantageous embodiment, if the collision involves contact points at different parts of the human body, the control signal output depends on the maximum permissible speed corresponding to the shortest actual braking distance, based on a predefined maximum permissible deformation and the resulting stiffness curve. This maximum permissible speed does not necessarily have to be the lowest maximum permissible speed at the various contact points. This has the advantage that injuries are avoided particularly effectively because it is each contact point of the collision that is evaluated in relation to the required braking distance, rather than the maximum speed itself.

[0036] In a further advantageous embodiment, if the collision involves contact points at different machine points, it is provided that the maximum permissible speed at all contact points is calculated and the output signal depends on the lowest maximum permissible speed. In contrast to what was described in the previous paragraph, it has been found that, with respect to different machine points, the maximum speed itself, rather than the actual braking distance, is best suited to limiting the risk of injury.

[0037] In a further advantageous embodiment, it is provided that, in the case of the free impact model and the clamping impact model, the maximum permissible speed in each case is calculated based on the following: (a) Predefined kinematic structure of robotic devices, (b) The joint configuration, including the position of one or more axes of the robotic device and the velocity assigned to each axis at the time of collision. (c) Stiffness characteristic curves of human body parts at the point of contact of collision, (d) Stiffness characteristic curve of the machine at the point of contact of the collision, (e) The resulting stiffness curves calculated using the stiffness characteristic curves of human body parts and the stiffness curves of machine points, and (f) A predefined maximum allowable deformation using a biomechanical force threshold and / or biomechanical energy threshold.

[0038] The stated values ​​correspond to those already explained above regarding the quasi-static tightening model.

[0039] In addition, in this specification, an additional maximum speed is calculated based on the following: (l) the effective mass of the machine at the point of contact of the collision, and (m) Effective rigidity of robotic devices.

[0040] Using only the free-impact model, the maximum velocity is calculated based on the following: (n) The effective mass of the human body part at the point of contact of the collision.

[0041] The effective mass of a point in a machine according to (l) is calculated herein according to Khatib O., and accordingly can be found in the article "A Unified Approach for Motion and Force Control of Robotic Manipulators: The Operational Space Formulation," published in 1987 on pages 43-53 of the IEEE Journal of Robotics and Automation 3(1), and in the article "Inertial Properties in Robotic Manipulation: An Object-Level Framework," published in 1995 on pages 19-36 of the International Journal of Robotics Research 14(1), as follows: the arrangement of the machine parts at the time of collision (axis positions), dynamic mass properties, kinematic structure of the robot device (geometric arrangement of axes, etc.), collision direction, and collision point. The dynamic mass properties of the robot device may be calculated with or without drive inertia. This yields either the effective mass of the robot device without considering drive inertia, or the effective mass of the robot device considering drive inertia, and the effective drive mass is calculated from the difference between the two effective masses. When calculating while considering drive inertia, the transmission rate of individual drives in robotic devices must be taken into account. Khatib's method is particularly suitable for calculating the series configuration of different elements of a robotic chain in an articulated robot, where mechanical parts move relative to each other. However, this method can also be used for parallel kinematic chains and mixed configurations.

[0042] The effective stiffness (n) of a robotic device may be calculated according to J.-K. Salisbury, "Active stiffness control of a manipulator in cartesian coordinates," published in 1980 in the Proceedings of the Conference on Decision and Control including the Symposium on Adaptive Processes, pp. 95-100, and A. Albu-Schaffer, M. Fischer, G. Schreiber, F. Schoeppe, and G. Hirszinger, "Soft robotics: what cartesian stiffness can obtain with passively compliant, uncoupled joints?", published in Volume 4, pp. 3295-3301, Proceedings of the 2004 IEEE / RSJ International Conference on Intelligent Robots and Systems (IROS), held in Sendai, Japan in February 2004. In these articles, following the equivalent model, the effective drive mass is elastically coupled to the effective mass of the shaft, for example, as shown in Figure 3 accordingly. The stiffness between these masses then results in effective stiffness.

[0043] To determine the forces in the case of a free impact (non-compressive collision) under spatial conditions, the effective mass of a human being according to (n) is required. The effective mass of a human being is calculated herein using a dynamic mass model of a human being or selected from a tabular list, for example, according to ISO / TS15066. The dynamic mass model typically considers dynamic mass properties such as body posture (i.e., the position of individual joints), dynamic mass properties depending on, for example, sex, height, and weight, the direction of impact, and the point of impact. The tabular list typically includes the affected body segments and body postures. In the case of a compressive impact, the body parts (body tissues) cannot escape the applied force, i.e., cannot recoil. Therefore, in the equivalent model, the body parts must be considered to be rigidly trapped.

[0044] Simulation models for free impact or constriction impact models may be constructed using specific variables as parameters, as shown, for example, in Figure 3. Thus, the free impact model may include or be a three-mass oscillator model, and / or the constriction impact model may include or be a two-mass oscillator model. These models are suitable for drawing conclusions about the force curve at the point of contact based on the impact velocity. The transmitted energy and maximum force may be determined from the force curve and then used to draw conclusions about expected injuries via the resulting stiffness characteristic curve, and accordingly, the safe velocity may be predefined as the maximum permissible velocity.

[0045] The calculation of the safe speed as the maximum permissible speed is, as specified herein, analytically possible if the resulting stiffness curve at the contact point is linear, and numerically only if the resulting stiffness curve at the contact point is nonlinear. To accelerate this method, as specified herein, it may also be possible to linearize the resulting stiffness curve at the intersection of the resulting stiffness curve and the biomechanical force limit. In this case, for example, an initial estimate of the maximum permissible speed may be derived based on the analytical solution and subsequently used as an initial value for the numerical method.

[0046] It should be noted in this specification that, in the case of transient, i.e., relatively fast collisions, the drive controller of the robotic device may be ignored because the collision duration is usually too short for the drive controller to intervene. Therefore, the reaction force set and monitored on the machine usually does not affect the impact. If an impact occurs, a biomechanical limit value smaller than the reaction force set and monitored on the robotic device may usually be observed.

[0047] Another aspect relates to a control unit for predefining the maximum permissible speed of a robotic device. Such a control unit includes a detection unit for detecting the contact point between a human operator and the robotic device, for detecting the shape of the robotic device at the contact point, and for detecting the spatial boundary conditions of the collision. Furthermore, the control unit includes a computing unit for determining whether the collision is a non-tightening collision or a tightening collision, taking into account the physical boundary conditions, and for calculating the maximum permissible speed of the robotic device at the contact point, using a free impact model if the collision is a non-tightening collision, and using a tightening impact model or a quasi-static tightening model if the collision is a tightening collision. These models are different in each case. The computing unit is also configured to output a control signal that depends on the calculated maximum permissible speed of the robotic device. Further aspects relate to a robotic device having such a control unit.

[0048] The advantages and favorable embodiments of the control unit and robotic devices equipped with the control unit are described herein in relation to the advantages and favorable embodiments of the method described.

[0049] In the description and in the introduction, in addition to the features and feature combinations mentioned above, the features and feature combinations described later in the description of the figures and / or the features and feature combinations shown in the figures alone may be used not only in the combinations shown in each example, but also in other combinations, without departing from the scope of the invention. Accordingly, embodiments that are not explicitly shown and described in the figures but become apparent from the described embodiments and can be produced by separate combinations of features should also be considered included and disclosed by the invention. Accordingly, embodiments and feature combinations that do not include all the features of the originally formed independent claims should also be considered disclosed. Furthermore, embodiments and feature combinations that exceed or deviate from the scope of the feature combinations presented in reference to the claims should be considered disclosed, in particular by the embodiments presented above.

[0050] Without intending to limit ourselves to the specific embodiments shown herein, the subject matter according to the present invention will be described in further detail based on the following figures and schematic diagrams. [Brief explanation of the drawing]

[0051] [Figure 1] This is a diagram of an exemplary robotic device, including an exemplary embodiment of a control unit for predefining the maximum permissible speed of the robotic device. [Figure 2] This figure shows the stiffness characteristic curve obtained as an example result at the contact point. [Figure 3] This is a diagram of an exemplary free impact model and an exemplary clamping impact model, showing alternative models. [Modes for carrying out the invention]

[0052] In different diagrams, elements that are similar or functionally similar are given similar reference symbols.

[0053] Figure 1 shows a robot device (1) including a control unit 2 for predefining the maximum permissible speed of the robot device (1). In this case, the control unit 2 includes a detection unit 3 to detect the contact point between the human operator and the robot device 1, the shape of the robot device at the contact point, and the spatial boundary conditions of the collision with respect to the collision between the human operator and the robot device 1. In the example shown, the contact point a, spatial condition b, and shape c are predefined by the user 5 of the control unit 2.

[0054] The control unit 2 also includes a computing unit 4 to determine whether the collision is a non-tightening collision or a tightening collision, taking into account the spatial boundary conditions b of the collision, and to calculate the maximum allowable speed of the robot device 1 at contact point a, using a free impact model if the collision is a non-tightening collision, and using a tightening impact model or a quasi-static tightening model if the collision is a tightening collision.

[0055] These models are different in each case. Computing unit 4 is also configured, as herein, to output a signal g that depends on the calculated maximum allowable speed of robotic device 1.

[0056] In the example shown, the control unit 2 extracts the joint configuration d from the robot device 1 with respect to the time of the collision and the tool data e representing the tool of the robot device 1. In addition, a torque or force threshold f is also extracted from the robot device. In the example shown, the computing unit 4 extracts, from the machine database 5, in addition to the pre-defined kinematic structure of the robot device 1, other data of the robot device, such as the mass, inertia, and center of gravity of the joints and motors of the robot device in the example shown. In this specification, torque data is also extracted. The stored models, namely, the free impact model, the clamping impact model, and the quasi-static clamping model, are retrieved accordingly from the model database 6 and the associated biomechanical database 7, together with the relevant values such as the limit values, stiffness characteristic curves, and mass of the human body parts affected by the collision.

[0057] Figure 2 shows an example of the resulting stiffness characteristic curve h as a function of the force F for the formation D. The allowable penetration depth x2 corresponds to the deformation D at the intersection of the allowable biomechanical contact force y2 and the resulting stiffness characteristic curve h. The reaction distance x1 of the robot device is obtained from the set reaction force y1 of the robot device and the resulting stiffness characteristic curve h. Next, the allowable braking distance of the robot device is obtained from the value obtained by subtracting the reaction distance x1 from the allowable penetration depth x2.

[0058] Figure 3 is an alternative model to the free impact model and the clamping impact model. In both cases, it is assumed that the robot device 1 moves at the collision point with the collision velocity v C Herein, the effective driving mass m D is coupled to and moves with the effective mass m T of the shaft via the effective stiffness c L of the drive system, and then transmits the contact force F(t) via the effective stiffness c M at the surface of the machine. Herein, the effective masses m D , m L may move different distances x D , x L only.

[0059] In the three-mass oscillator model, as shown in the upper right of Figure 3, the operator has a finite effective mass m. H However, human rigidity c H It is coupled with the contact force F(t) via [a certain mechanism]. Therefore, in the example shown, the free impact model is based on the mass m D , m L , and m H This is a three-mass oscillator model including [the specified component]. In the case of a tightening shock, it is assumed that operator 5 does not move, as shown in the lower right of Figure 3. Therefore, the stiffness of human soft tissue c H This absorbs the entire contact force F(t). In this method, two masses m D , m L Since only one factor is considered, the shock model being tightened is the two-mass oscillator model.

Claims

1. A method for predefining the maximum permissible speed of a robotic device, A method for predefining the contact point between a human operator and the robot device, the shape of the robot device at the contact point, and the spatial boundary conditions of the collision between a human operator and the robot device, A method step of determining whether the collision is a non-tightening collision or a tightening collision, taking into account the aforementioned spatial boundary conditions and using a computing unit, A method step in which the computing unit calculates the maximum allowable velocity of the robot device at the contact point, using a free impact model if the collision is a non-tightening collision, and using a tightening impact model or a quasi-static tightening model if the collision is a tightening collision, wherein the model is different in each case. A method step of outputting a signal dependent on the calculated maximum allowable speed of the robotic device using the computing unit, Methods that include...

2. The method according to claim 1, characterized in that the output signal represents a position-dependent velocity specification along a predefined machine path with respect to the robot device, the velocity specification is generated by changing the magnitude of an originally predefined velocity specification with respect to the predefined machine path based on the calculated maximum allowable velocity, preferably the magnitude change includes a uniform magnitude change or a magnitude change locally adapted to the predefined machine path, taking into account the predefined process velocity of the robot device in one or more subsections of the machine path.

3. The method according to claim 1, characterized in that the allowable maximum speed is calculated in real time, and the output signal represents the instantaneous allowable maximum speed of the robot device.

4. The method according to claim 1 or 2, characterized in that, if the collision is a clamping collision, the maximum permissible speed is calculated using the clamping impact mode and the quasi-static clamping model, and the lower of the calculated maximum permissible speeds is selected as the maximum permissible speed for the output.

5. In the aforementioned quasi-static tightening model, the allowable maximum speed is (a) The predefined kinematic structure of the robot device, (b) The joint configuration, including, in particular, the position of one or more axes of the robot device and the velocity assigned to each axis, at the time of the collision. (c) Stiffness characteristic curve of the human body part at the contact point of the collision, (d) Stiffness characteristic curve of the machine at the contact point of the collision, (e) The resulting stiffness curve calculated using the stiffness curve of the human body part and the stiffness curve of the points of the machine, (f) In particular, a predefined maximum allowable deformation using force thresholds and / or energy thresholds and / or deformation thresholds, (g) Allowable penetration depth calculated using the stiffness characteristic curve of the machine point and the resulting stiffness characteristic curve, (h) Reaction force of the robot device, (i) The reaction distance of the robot device calculated using the stiffness characteristic curve of the machine point and the allowable penetration depth, (j) The allowable braking distance of the robot device calculated using the predefined maximum allowable deformation and the reaction force, and (k) The actual braking distance of the robot device The method according to claim 1 or 2, characterized in that it is calculated based on the method.

6. The method according to claim 5, characterized in that the maximum permissible speed of the robot device is determined iteratively until the actual braking distance matches the permissible braking distance, and in particular, is determined iteratively using a bisection method.

7. The method according to claim 5, characterized in that, if the collision involves contact points at different parts of the human body, the output signal depends on the allowable maximum speed corresponding to the shortest actual braking distance.

8. The method according to claim 5, characterized in that, if the collision includes contact points at different machine points, the maximum permissible speed for all contact points is calculated and the output signal depends on the lowest maximum permissible speed.

9. In the case of the free impact model and the clamping impact model, (a) The predefined kinematic structure of the robot device, (b) The joint configuration, including, in particular, the position of one or more axes of the robot device and the velocity assigned to each axis, at the time of the collision. (c) Stiffness characteristic curve of the human body part at the contact point of the collision, (d) Stiffness characteristic curve of the machine at the contact point of the collision, (e) The resulting stiffness curve calculated using the stiffness curve of the human body part and the stiffness curve of the points of the machine, (f) Predefined maximum allowable deformation using force thresholds and / or energy thresholds, (l) The effective mass of the machine at the point of contact of the collision, (m) The effective stiffness of the robot device, and only in the case of the free impact model, (n) Effective mass of the human body part at the point of contact of the collision The method according to claim 1 or 2, characterized in that the maximum permissible speed is calculated in each case based on the following.

10. The method according to claim 9, characterized in that the free shock model includes or is a three-mass oscillator model, and / or the clamping shock model includes or is a two-mass oscillator model.

11. A control unit for predefining the maximum permissible speed of a robotic device, A detection unit for detecting the contact point between a human operator and a robotic device, the shape of the robotic device at the contact point, and the spatial boundary conditions of the collision between a human operator and a robotic device, A control unit comprising: a computing unit for determining whether the collision is a non-tightening collision or a tightening collision, taking into account the spatial boundary conditions, and for calculating the allowable maximum velocity of the robot device at the contact point, using a free impact model if the collision is a non-tightening collision, and using a tightening impact model or a quasi-static tightening model if the collision is a tightening collision, wherein the model is different in each case, and a computing unit for outputting a signal dependent on the calculated allowable maximum velocity of the robot device.

12. A robotic device comprising the control unit described in claim 11.

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