Control of a robotic manipulator when in contact with a human

Abstract

The present invention relates to a method for controlling a robotic manipulator (1), comprising the following steps: - providing (S1) a database having human body regions, wherein each of the body regions is assigned a corresponding maximum allowable contact pressure value; - determining (S2) a current or future contact event of the robotic manipulator (1) with a human and determining the body region of the human that is contacted; - determining (S3) a reference position fixed relative to the human body, wherein the reference position indicates the starting point of the position path into which human tissue is pressed during the contact event with the human; and - controlling (S4) the robotic manipulator (1) in an impedance-regulated manner such that the determined reference position serves as the zero position of the artificial spring component of the impedance regulation of the robotic manipulator (1) and the maximum allowable contact pressure is not exceeded as a limit value.

Description

Technical Field

[0001] The present invention relates to a method for controlling a robotic manipulator and a control unit for controlling a robotic manipulator. Summary of the Invention

[0002] The object of the present invention is to improve the behavior of a robotic manipulator in the case of a contact event between the robotic manipulator and a human and in particular to make the behavior safer.

[0003] The present invention results from the features of the independent claims. Advantageous improvements and designs are the subject matter of the dependent claims.

[0004] A first aspect of the present invention relates to a method for controlling a robotic manipulator, comprising the following steps:

[0005] - providing a database having body regions of a human, wherein each of the body regions is assigned a corresponding maximum allowable contact pressure value;

[0006] - determining a current or future contact event between the robotic manipulator and the human and determining the body region of the human being contacted;

[0007] - determining a reference position fixed relative to the human body, wherein the reference position indicates the starting point of the position path into which the human tissue is pressed during the contact event with the human; and

[0008] - controlling the robotic manipulator in an impedance regulation manner such that the determined reference position is used as the zero position of the artificial spring component of the impedance regulation of the robotic manipulator and the maximum allowable contact pressure is not exceeded as a limit value.

[0009] The body regions particularly include regions on the surface of the human body, such as regions on the thigh, calf, hand, foot, abdomen, chest, upper back, lower back, face and / or face parts such as the eyes, nose, etc. Alternatively, body regions separate from these body parts are preferably used. The body regions, as stored in the database, are preferably generally valid for humans, so that these body regions are not limited to a specific individual. However, especially when a specific population such as children comes into contact with the robotic manipulator, it is expedient to provide a respective dedicated database having body regions specifically defined for this population.

[0010] Each of these body regions has an associated value according to the database, which indicates the maximum allowable contact pressure at the corresponding body region. Here, the contact pressure is particularly defined in the normal direction of the surface of the body region. The contact pressure refers to the pressure acting on the human body from the outside. Here, the terms "contact pressure" and "contact force" are in principle interchangeable, since pressure is defined by force per unit area. Here, in one embodiment, the term "contact pressure" is always replaced by the term "contact force" above and below. Preferably, in addition to each value of the contact pressure, the database also has a corresponding value of shear stress as the tangential component of the force and / or acting moment acting on the corresponding body region.

[0011] Determining the contact event is preferably carried out by prediction, especially by means of simulation. For this purpose, continuous information about the posture of the robotic manipulator, especially the future posture of the robotic manipulator, and the posture of the person, especially the future posture of the person, is required. In order to infer the future posture of the robotic manipulator or the person from the current posture of the robotic manipulator or the person, the specified target movement path of the robotic manipulator and / or the speed and / or acceleration of the robotic manipulator are particularly used to predict the movement path of the robotic manipulator. Preferably, a similar operation is also performed on the person. In the case of a person, usually the planned trajectory of the person is not started from, because firstly the will of the person is not necessarily known, and in addition, the movement sequence of the person is often unintentionally controlled especially by reflex. Preferably, instead, the current posture of the person and / or the movement of the person (especially speed / acceleration) are detected especially by a camera, and the possible future posture of the person is inferred from the current posture and / or current movement of the person.

[0012] In the case of the currently identified contact event, prediction or simulation is not required, because the current contact event can also be carried out by common collision detection, for example, by determining the external force screw based on the joint torque vector detected by the torque sensor of the robotic manipulator in the joint.

[0013] Regardless of the type of identification of the current or future contact event, this identification particularly also provides information about which or which body regions in the body regions of the person defined in the database are actually affected or will be affected by the contact event. Since a separate maximum allowable contact pressure value is assigned to each of the body regions according to the information in the database, depending on the position of the contact event between the robotic manipulator and the human body, the maximum allowable contact pressure generated from the contact event is also known.

[0014] This is taken into account according to the present invention. To this end, a reference position is defined, which is considered to be arranged on a person in a body-fixed manner relative to the person, in particular relative to the surface of the human body. Thus, this body-fixed reference position naturally coincides with the position on the surface of the person where the person can feel the contact of the robotic manipulator. During the further movement of the robotic manipulator relative to the surface of the human body with a non-zero normal movement component, tissue indentation of the person occurs, and the person perceives this indentation as contact pressure. The tissue of the person naturally has viscous damping and is also at least partially elastic (and may at least partially be temporarily plastic, which does not represent irreversible deformation of the tissue caused by permanent damage).

[0015] According to the present invention, here, the robotic manipulator is driven in an impedance-regulated manner at least from the starting point of the position path of the tissue indentation of the person during the contact event. Thus, on the one hand, the tissue of the person has an elastic element, and on the other hand, the impedance regulation of the robotic manipulator includes an artificial spring component that virtually builds up an increasing restoring force starting from a reference point at least in the normal component on the surface of the human body and thus reduces the kinetic energy at least in the direction of this normal component.

[0016] Here, the impedance regulation is particularly carried out based on the relative position between the reference position and a predefined position on the robotic manipulator. Here, the length value of this position vector particularly determines the deflection, by which a deflection-related resistance is generated with the help of the artificial spring component.

[0017] Preferably, the impedance regulation is carried out starting from the current position of the position on the robotic manipulator relative to the reference position of the person based on the relative position determined in a two-channel manner. Here, the two-channel function is particularly realized by a sensor set of the robot itself, which on the one hand particularly includes joint angle sensors and on the other hand includes an external sensor unit, preferably a camera unit. Two or more camera units can also be used. This two-channel function particularly results in obtaining position information from at least two sources, and these position information are then particularly checked for data consistency by a comparison unit. If there is an inconsistency between the two sources, at least one of the sensor units fails, and the safe operation of the robotic manipulator can no longer be guaranteed. In this case, preferably, a warning is issued and / or the operation of the robotic manipulator is immediately stopped.

[0018] Preferably, the reference position acts as a zero position for impedance regulation, especially for the zero position of the artificial spring component for impedance regulation, radially symmetrically. In this case, each deflection starting from the zero position is treated equally by the impedance regulation, regardless of the direction of deflection. Alternatively, preferably, the impedance regulation is performed in a direction-dependent manner starting from the reference position as the zero position, especially for the artificial spring component of the impedance regulation. Here, preferably, the artificial spring component of the impedance regulation is applied only in a direction normal to the surface of the affected body area of the person, i.e., at right angles, and preferably a nominal regulation is applied in other directions away from the normal component, which the robotic manipulator has applied until reaching the reference position before applying the impedance regulation. On the one hand, this can be the impedance regulation itself, and on the other hand, it can be force regulation, position regulation, admittance regulation, or other regulation forms known in the prior art.

[0019] Preferably, in addition to the artificial spring component, the impedance regulation of the robotic manipulator further includes an artificial damping component, which naturally generates a velocity-dependent resistance by definition.

[0020] Furthermore, according to the present invention, the force ( / pressure) exerted by the robotic manipulator on a person is limited such that the maximum allowable contact pressure value for the body area affected by the contact event is not exceeded. This is especially within the possibilities of the bandwidth of the actuator of the robotic manipulator, which is usually high enough to ensure such a reaction quickly enough.

[0021] Therefore, the advantageous effect of the present invention is that, in the case of a contact event between the robotic manipulator and a person, the movement of the robotic manipulator is reduced in an elastic manner and especially also in a damped manner on the one hand, such that the person only feels a soft impact in the case of momentum transfer. By limiting the contact pressure generated by the robotic manipulator itself, injury is also advantageously avoided. On the other hand, if the robotic manipulator has no kinetic energy but momentum transfer occurs due to the kinetic energy of the person, in addition to the deflection of the robotic manipulator from the zero position of the impedance regulation in the opposite direction, the same effects as described above exist, where the elasticity of the momentum transfer and especially also the damping characteristics are maintained. Even in the quasi-static force transfer between the person and the robotic manipulator, the subjective soft contact with the robotic manipulator is also advantageous for the person because the impedance regulation causes a deflection-dependent resistance starting from the reference position on the human body surface.

[0022] According to an advantageous embodiment, the method further has the following steps:

[0023] - determining the edge geometry of the position on the robotic manipulator that comes into contact with a person, wherein the maximum allowable contact pressure is determined or adapted depending on the determined edge geometry.

[0024] Preferably, the database has a value set for each of the body regions, where each element from the value set is assigned to a specific edge geometry of the position on the robotic manipulator that comes into contact with the human or is at least approximately assigned to that edge geometry. Thus, advantageously, not only the sensitivity of the human body region is considered, but also the sensitivity to the edge geometry in contact with the body region. Thus, a thin and sharp profile is naturally more likely to cause injury, even when the contact pressure is not increased compared to a contact event with a blunt surface. Preferably as an alternative to the value set of the database, fixed values for each body region in the database are adapted depending on the determined edge geometry. This is preferably done by multiplying by a factor reflecting the inverse sharpness of the edge geometry, such that a sharper edge is associated with a higher actual contact pressure compared to a constant maximum allowable contact pressure.

[0025] According to another advantageous embodiment, when performing impedance regulation up to the maximum allowable contact pressure, the maximum allowable contact pressure is determined or adapted in a decreasing manner depending on the velocity of the position on the robotic manipulator that comes into contact with the human relative to the human. This embodiment advantageously takes into account the fact that a rapid indentation movement of human tissue is more unpleasant than a slow indentation movement. Thus, similar to the previous embodiment, the velocity is considered instead of the edge geometry in the case of a contact event between the robotic manipulator and the human. Similarly, there can be various entries in the database, which, according to this embodiment, apply to a limited number of velocities or are approximate to these velocities. Alternatively, the respective unique database entry is adapted accordingly, especially by a factor or another function.

[0026] According to another advantageous embodiment, the robotic manipulator is controlled in an impedance regulation manner such that a specified braking distance is not exceeded during the indentation of human tissue. Here, the braking distance depends in particular on the momentum transfer between the robotic manipulator and the human tissue and is related to the indentation depth of the robotic manipulator into the human tissue. What is ensured by the limit value of the braking distance is that the human tissue is not indented beyond the specified limit value. This is done in particular by the corresponding control of the actuators of the robotic manipulator, such that the robotic manipulator performs a retraction movement when the limit value is reached.

[0027] According to another advantageous embodiment, the specified braking distance is determined by predicting at what distance from a reference position the maximum allowable contact pressure is reached during the indentation of human tissue. Thus, advantageously, the actual applied contact pressure is consistent with the maximum allowable contact pressure and is at the same time related to the limit value in the braking distance, such that the behavior of the robotic manipulator that is as natural as possible for the human is utilized throughout the allowable range.

[0028] According to another advantageous embodiment, the control of the robotic manipulator in an impedance-adjusted manner is carried out by impedance adjustment with respect to the earth-fixed coordinate system, such that the relative position vector between the position on the robotic manipulator where contact with a human occurs and the current reference position of the human is determined as the connecting vector in the earth-fixed coordinate system. The earth-fixed coordinate system is in particular a Cartesian coordinate system.

[0029] According to another advantageous embodiment, the method further has the following steps:

[0030] - Determine the hardness and / or modulus of elasticity of the position on the robotic manipulator where contact with a human occurs, wherein the maximum allowable contact pressure is determined or adapted depending on the determined hardness and / or modulus of elasticity. Hardness determines the resistance to penetration of the body and is preferably expressed in Vickers units. On the other hand, the modulus of elasticity describes a stress constant that indicates to what extent the material of the robotic manipulator is stretched under what stress. Advantageously, according to this embodiment, this material property or these material properties of the position on the robotic manipulator where contact with a human occurs are taken into account by a set of data values in a database or by adapting the corresponding valid values from the database, in particular by multiplying by a factor or another function, since this (these) material property (properties) has a significant impact on how a human subjectively perceives the contact event.

[0031] According to another advantageous embodiment, the method further has the following steps:

[0032] - Determine the temperature of the structural element having the position on the robotic manipulator where contact with a human occurs, wherein the maximum allowable contact pressure is determined or adapted depending on the determined temperature. The temperature of the structural element at the position on the robotic manipulator where contact with a human occurs also has a corresponding impact on the subjective perception of the contact event between the human and the robotic manipulator. At extreme temperatures, humans find the contact event rather unpleasant. Similarly, for different temperatures, different values can be stored in the database for the corresponding body regions, or the individual values of the database for each body region can be adapted accordingly.

[0033] According to another advantageous embodiment, the impedance adjustment has a non-linear artificial spring component, such that as the deflection increases, a reaction force that rises disproportionately with the deflection acts on the robotic manipulator. Since human tissue in particular also has non-linear mechanical properties (thus, blood is a non-Newtonian fluid, and when tendons and / or bones and / or ligaments are struck, the resistance during tissue indentation suddenly increases), this property of the human body is in particular also reflected by the impedance adjustment. Thereby, advantageously, the behavior of the robotic manipulator during the contact event is perceived by humans as significantly more pleasant.

[0034] Another aspect of the present invention relates to a control unit for controlling a robotic manipulator, having: an interface to a database having human body regions, wherein each of the body regions is assigned a corresponding maximum allowable contact pressure value; and a calculation unit, wherein the calculation unit is configured to: determine a current or future contact event between the robotic manipulator and a human and determine the body region of the human being contacted; determine a reference position fixed relative to the human body, wherein the reference position indicates the starting point of the position path along which the human tissue is pressed in during the contact event with the human; and control the robotic manipulator in an impedance regulation manner such that the determined reference position serves as the zero position of the artificial spring component of the impedance regulation of the robotic manipulator and the maximum allowable contact pressure is not exceeded as a limit value.

[0035] The advantages and preferred improvements of the proposed control unit result from a similar and meaningful transfer of the above-described embodiments made in connection with the proposed method.

[0036] Further advantages, features and details result from the following description, in which at least one embodiment is described in detail, where necessary with reference to the drawings. Identical, similar and / or functionally identical parts are provided with the same reference numerals. Description of the Drawings

[0037] Figure 1 shows a method for controlling a robotic manipulator according to an embodiment of the present invention; and

[0038] Figure 2 shows a control unit for performing the method according to Figure 1 .

[0039] The illustrations in the drawings are schematic and not drawn to scale. Detailed Description of the Invention

[0040] Figure 1 shows a method for controlling a robotic manipulator 1. The method is executed on a control unit 3. Thus, the method steps shown below can also be transferred to Figure 2 and can be applied Figure 2 with the reference numerals. The method has the following steps:

[0041] - Provide S1 a database having human body regions, wherein each of the body regions is assigned a corresponding maximum allowable contact pressure value;

[0042] - Determine S2 a current or future contact event between the robotic manipulator 1 and a human and determine the body region of the human being contacted;

[0043] - Determine S3 a reference position fixed relative to the human body, wherein the reference position indicates the starting point of the position path along which the human tissue is pressed in during the contact event with the human;

[0044] - Determine the edge geometry of the position on the S5 robot manipulator 1 that comes into contact with a human, wherein the maximum allowable contact pressure is adapted depending on the determined edge geometry;

[0045] - Determine the hardness and / or modulus of elasticity of the position on the S6 robot manipulator 1 that comes into contact with a human, wherein the maximum allowable contact pressure is adapted depending on the determined hardness and / or modulus of elasticity;

[0046] - Determine the temperature of the structural element at the position on the S7 robot manipulator 1 that comes into contact with a human, wherein the maximum allowable contact pressure is adapted depending on the determined temperature; and

[0047] - Control the S4 robot manipulator 1 in an impedance regulation manner such that the determined reference position serves as the zero position of the artificial spring component for impedance regulation of the robot manipulator 1 and the maximum allowable contact pressure is not exceeded as a limit value.

[0048] Figure 2 A control unit 3 for controlling a robot manipulator 1 is shown, which has: an interface 5 to a database with body regions of a human, wherein each of the body regions is assigned a corresponding maximum allowable contact pressure value; and a calculation unit 7, wherein the calculation unit 7 is configured to determine a current or future contact event of the robot manipulator 1 with a human and to determine the body region of the human that is contacted. Furthermore, the calculation unit 7 determines a reference position fixed relative to the human body, wherein the reference position indicates the starting point of the position path into which the human tissue is pressed during the contact event with the human. This is done by extrapolating the current movement processes of not only the human but also the robot manipulator 1 to simulate future movement processes. Furthermore, the calculation unit 7 controls the robot manipulator 1 in an impedance regulation manner such that the determined reference position serves as the zero position of the artificial spring component for impedance regulation of the robot manipulator 1 and the maximum allowable contact pressure is not exceeded as a limit value.

[0049] Although the present invention has been illustrated and described in more detail by preferred embodiments, the present invention is not limited to the disclosed embodiments, and those skilled in the art can derive other variants therefrom without departing from the scope of protection of the present invention. Therefore, it is obvious that there are various possible variants. It is also obvious that the embodiments cited by way of example actually only represent examples and should not be understood in any way as, for example, a limitation on the scope of protection of the present invention, possible applications or configurations. On the contrary, the foregoing description and the description of the drawings enable those skilled in the art to specifically implement the exemplary embodiments, wherein those skilled in the art, having understood the disclosed inventive concept, can make various changes, for example, to the functions or arrangements of the individual elements mentioned in the exemplary embodiments, without departing from the scope of protection defined by the claims and their legal equivalents, such as further explanations in the specification.

[0050] Description of reference numerals:

[0051] 1 Robot manipulator

[0052] 3 Control unit

[0053] 5 Interface

[0054] 7 Computing unit

[0055] S1 Provide

[0056] S2 Determine

[0057] S3 Determine

[0058] S4 Determine

[0059] S5 Determine

[0060] S6 Determine

[0061] S7 Determine

Claims

1. A method for controlling a robotic manipulator (1), comprising the following steps: - Provide (S1) a database with human body regions, wherein, Each of said body regions is assigned a corresponding maximum allowable contact pressure value; - determining (S2) a current or future contact event between the robotic manipulator (1) and the person and determining the body region of the person being contacted; - determining (S3) a reference position fixed relative to the person's body, wherein the reference position indicates the starting point of the position path along which the person's tissue is pressed in during the contact event with the person; and - controlling (S4) the robotic manipulator (1) in an impedance regulation manner such that the determined reference position serves as the zero position of the artificial spring component of the impedance regulation of the robotic manipulator (1) and the maximum allowable contact pressure is not exceeded as a limit value.

2. The method according to claim 1, further comprising the following steps: - determine (S5) the edge geometry of the position on the robotic manipulator (1) that comes into contact with the person, wherein, determining or adapting the maximum allowable contact pressure depending on the determined edge geometry.

3. The method according to any one of the preceding claims, wherein When performing impedance regulation until the maximum allowable contact pressure, determining or adapting the maximum allowable contact pressure depending on the speed of the position of the robotic manipulator (1) in contact with the person relative to the person.

4. The method according to claim 1 or 2, wherein Controlling the robotic manipulator (1) in an impedance regulation manner such that a specified braking distance is not exceeded during the pressing-in of the person's tissue.

5. The method according to claim 4, wherein The specified braking distance is determined by predicting at what distance from the reference position the maximum allowable contact pressure is reached during the pressing-in of the person's tissue.

6. The method according to claim 1 or 2, wherein Controlling the robotic manipulator (1) in an impedance regulation manner is performed by impedance regulation with respect to a ground-fixed coordinate system such that the relative position vector between the position on the robotic manipulator (1) in contact with the person and the current reference position of the person is determined as the connecting vector in the ground-fixed coordinate system.

7. The method according to claim 1 or 2, further comprising the following steps: - determining (S6) the hardness and / or modulus of elasticity of the position on the robotic manipulator (1) that comes into contact with the person, wherein, determining or adapting the maximum allowable contact pressure depending on the determined hardness and / or elastic modulus.

8. The method according to claim 1 or 2, further comprising the following steps: - Determine (S7) the temperature of a structural element having a position on the robotic manipulator (1) in contact with the person, wherein, determining or adapting the maximum allowable contact pressure depending on the determined temperature.

9. The method according to claim 1 or 2, wherein The impedance regulation has a non-linear artificial spring component such that as the deflection increases, a reaction force that rises disproportionately with the deflection acts on the robotic manipulator (1).

10. A control unit (3) for controlling a robotic manipulator (1), having: an interface (5) to a database with human body regions, wherein, Each of said body regions is assigned a corresponding maximum allowable contact pressure value; and a calculation unit (7), wherein the calculation unit is configured to: determine a current or future contact event between the robotic manipulator (1) and the person and determine the body region of the person being contacted; determine a reference position fixed relative to the person's body, wherein the reference position indicates the starting point of the position path along which the person's tissue is pressed in during the contact event with the person; and control the robotic manipulator (1) in an impedance regulation manner such that the determined reference position serves as the zero position of the artificial spring component of the impedance regulation of the robotic manipulator (1) and the maximum allowable contact pressure is not exceeded as a limit value.

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