DE102019204564A1 - Determining a parameter of a force acting on a robot - Google Patents

Abstract

According to a method according to the invention for determining a parameter (m, a) of a force (F) acting on a robot (10) on the basis of at least one joint torque (τ2, τ3) of the robot in at least one, in particular stationary, measuring pose of the robot, the Joint torque based on a difference between a drive-side and an output-side position (qab, i- qan, i) of a drive train of the joint and / or a difference between a measurement configuration with the force acting on the robot and at least one previously approached reference configuration without it the force acting on the robot is determined.

Description

The present invention relates to a method for determining a parameter of a force acting on a robot, in particular for operating the robot on the basis of the determined parameter, as well as a system or computer program product for performing the method.

By knowing or taking into account external forces acting on robots, the operation of the robots can be improved, the robots in particular can be precisely (r) controlled and / or (sensitively) interact with their environment.

In particular, if the payload is known, a more precise robot model can be used in a model-based control, and the control or the operation of the robot can be improved as a result.

One object of an embodiment of the present invention is to improve the determination of a parameter of a force acting on a robot, in particular an operation of the robot.

This object is achieved by a method having the features of claims 1 and 10, respectively. Claims 11, 12 provide a system or computer program product for performing a method described here under protection. The subclaims relate to advantageous developments.

According to one embodiment of the present invention, a one or more dimensional parameter of a force acting on a robot is determined on the basis of one or more joint moments of the robot in one or more, in one embodiment (each) stationary, measuring poses of the robot.

In one embodiment, the robot has a robot arm with at least three, in particular at least six, in one embodiment at least seven swivel joints or axes and / or an end flange, in particular an end effector.

With at least three swivel joints, the end flange or end effector can advantageously move to any position, with at least six swivel joints any poses, with at least seven swivel joints the same pose with different (joint or robot) positions. In one embodiment, a pose has a one-, two- or preferably three-dimensional position and / or one, two- or preferably three-dimensional orientation.

In one embodiment, the force acting on the robot acts on the end flange or end effector. As a result, a payload or processing force can be taken into account in one embodiment and the operation of the robot can be improved as a result.

In one embodiment, the robot remains in one or more of the measuring poses (in each case). In this way, exact (re) and / or meaningful (re) values can be determined in one embodiment. In one embodiment, the robot travels through the or one or more of the measurement poses, with a (maximum) speed of its end effector being limited to a maximum of 250 mm / s in a further development. As a result, in one embodiment, values can be determined more quickly and / or loads on a robot-guided payload, in particular with a patient, can be reduced.

In one embodiment, an end effector of the robot has the same orientation in two or more of the, in particular stationary, measuring poses. In this way, in particular, a parameter of a robot-guided payload with a patient can advantageously be determined.

According to one embodiment of the present invention, the or one or more of the joint torques, on the basis of which the parameter is determined, are determined on the basis of a difference between a drive-side and an output-side position, in particular an angular position, in one or a drive train (s) (for Adjustment) of the (respective) robot joint in which the joint torque (in each case) acts or for which the joint torque (in each case) is determined.

This is based on the idea that forces and moments that act in a drive train to adjust a joint on the output side, due to elasticities, play and the like, lead to a difference compared to a drive-side position of this drive train, so that conversely based on such a difference in Forces and / or torques acting on the drive train or joint on the output side can be determined. In one embodiment, a drive-side position of a drive train is a position, in particular an angular position, (within or at a point) of the drive train that is closer to a drive, in particular a motor, of the drive train than (at) an output-side (s) Position.

As a result, joint torques or forces acting on the robot can be advantageously determined in one embodiment, in particular precisely and / or with little expenditure on equipment, in particular in comparison to a (pure) determination based on electrical drive variables, which can be insufficient due to friction, especially in stationary poses.

In one embodiment, one or the drive-side position of the (respective) drive train is a position of a drive and / or in front of or at a transmission input and / or is detected by means of a (first) angle sensor. Additionally or alternatively, one or the output-side position of the (respective) drive train in one embodiment is a position of a robot link or the joint and / or at or after a transmission output and / or is detected by means of a (second) angle sensor.

According to one embodiment of the present invention, the one or more of the joint torques, on the basis of which the parameter is determined, based on a difference between a measurement configuration in which the force, the parameter of which is to be determined, acts on the robot, and a or several reference configurations approached beforehand, in one embodiment for the determination of the parameter (possibly again), in which this force (in each case) does not act on the robot, determined, in one embodiment on the basis of a difference between the measurement configuration and a reference configuration, in which the robot is load-free or not acted upon by an external force, and / or based on at least one difference between the measurement configuration and a reference configuration in which the robot is (only) acted upon by a known external force in the same way as by the force whose parameters are to be determined.

This is based on the knowledge that the robot's own weight and the like also cause joint torque components that are added to the joint torque components that result from an external force acting on the robot, in particular the force acting on the robot, the parameters of which are to be determined, and the underlying idea of determining these joint torque components resulting from the dead weight of the robot and the like or independent of the force acting on the robot whose parameters are to be determined by means of one or more reference configurations and then subtracting them from the determined total joint torques, so that these parameters can be determined on the basis of the remaining joint torques.

As a result, the parameter of the force acting on the robot can be determined in one embodiment (still) advantageously, in particular precisely and / or with little (re) m, in particular in terms of apparatus, outlay.

The present invention can be used with particular advantage for the identification of a robot-guided payload, with very particular advantage for the identification of a robot-guided payload with a patient (transported and / or positioned by the robot).

In one embodiment, the parameter depends accordingly on a mass and / or center of gravity of a robot-guided payload, in particular a robot-guided payload with a patient (transported and / or positioned by the robot).

In a further development, the parameter depends only on a mass and / or center of gravity of this payload. In one embodiment, a center of gravity comprises a one- or two-dimensional distance from an axis, in particular a distal (st) joint axis.

This is based on the idea that, in contrast to inertial sensors, the mass and center of gravity can be determined (precisely) on the one hand by means of slow (er) robot movements and in particular also stationary or slowly traversing measuring positions and on the other hand in particular for transporting and / or positioning patients sufficient, which in turn should not be moved (er) fast.

Equally, the present invention can also be used with particular advantage to determine a contact force, in particular its direction, its magnitude and / or point of attack, in a contact with the environment of the robot, in particular its end effector, or the parameters, in particular only, of this contact force, in particular their direction, their amount and / or point of attack depend.

In one embodiment, the parameter is determined on the basis of the joint torques of a number of robot joints in the same, in particular stationary, measuring pose of the robot, the number in one embodiment being at least two.

This is based on the idea that both a mass and a center of gravity or both an amount and an application point, in particular a distance from an axis, in particular a distal (st) joint axis, can be determined by at least two joint torques.

Additionally or alternatively, the number is equal to the total number of joints of the robot and / or equal to six. As a result, the parameter (s) can be determined precisely and / or have more components or dimensions in one embodiment.

In an alternative embodiment, the number is less than the total number of joints of the robot and / or less than six. As a result, the parameter of the force acting on the robot can advantageously be determined in one embodiment, in particular with little (more) expenditure on equipment, using the idea explained above, that both a mass and a center of gravity or both an amount and a point of application, in particular a distance from an axis, in particular a distal (st) joint axis, can be determined by two joint moments.

In one embodiment, the parameter is determined on the basis of the joint torques of the same robot joint in two or more, in particular stationary, measuring poses of the robot, the robot or these robot joints in one embodiment having different positions in these measuring poses.

This is based on the idea that the same force acting on the robot, in particular the same robot-guided payload, causes different joint torques in the individual robot joints in different measuring poses or robot positions, so that on the basis of in or for several measuring poses or robot positions determined joint torques of the parameters (still) advantageously (more), in particular precisely (r) and / or with little (re) m, in particular with regard to equipment, can be determined.

In one implementation, the parameter is determined using an equalization problem solving technique. To this end, in one embodiment, more joint torques are determined than the dimension of the parameter is, that is to say in particular in one position joint torques from more robot joints and / or joint moments in more positions or along a path. For example, if the mass and the one-, two- or three-dimensional center of gravity of a robot-guided payload are to be determined (dimension of the parameter = 2, 3 or 4), more joint torques are used in one embodiment, for example at least 3, 4 or 5, in one embodiment, for example, for the mass and the one-dimensional center of gravity distance of a robot-guided payload to an axis, the joint moments of at least two joints in at least two measuring positions or the joint moments of one joint in at least three measuring positions or the joint moments of at least three joints in at least one Measuring pose.

Additionally or alternatively, the parameter is determined in one embodiment on the basis of mean values, in particular the or one or more of the joint torques and / or the differences in the drive train positions and / or measurement and reference configurations. In one embodiment, for this purpose, the measurement pose (s), measurement configuration (s) and / or reference configuration (s) are each approached several times and the joint torque (s), in particular the difference (s), are determined and the joint torque (s) Joint torques are determined on the basis of mean values of the differences ascertained or the parameters are determined on the basis of mean values of the joint torques ascertained, in particular such.

As a result, the parameter can (still) be determined advantageously (more), in particular reliably (more), in one embodiment.

In one embodiment, the measurement configuration and the reference configuration (s) are approached in the same way, in particular by adjusting at least the joints whose joint torques are used in determining the parameter (each or jointly) from or in the same direction.

This is based on the idea that backlash and / or friction effects can be advantageously compensated for.

In one embodiment, the (respective) joint torque is determined on the basis of a difference between a drive-side and an output-side position of the drive train of the (respective) joint and a stiffness of this drive train (between this drive-side and output-side position).

This rigidity can be specified in one embodiment, in particular taken from a machine data record.

In one embodiment, the (respective) stiffness is determined on the basis of a difference between one or more first reference configurations in which a (different, respectively) known, in particular predetermined or measured, first force acts on the robot in a Execution (each) a (different) known payload is attached to its end effector, and one or more second reference configurations are determined in which (each) a (different, possibly different) known, in particular predetermined or measured, second force or payload or no (external) force acts on the robot or the robot is load-free, in one embodiment no payload is attached to its end effector. In one embodiment, the rigidity can thus be determined or predetermined on the basis of one, two or more different known forces acting one after the other on the robot, in particular one, two or more different known payloads attached one after the other to its end effector, in particular on the basis of two different known forces acting one after the other on the robot, in particular payloads attached to its end effector, can be determined or predetermined in certain areas. In one embodiment, based on the determined or specified stiffness values, in one embodiment linear, interpolation and / or extrapolation is performed. In one version, the robot has the or the first and second reference configuration (s) (each) the same (joint) position.

In one embodiment, the (respective) rigidity of the drive train is or is determined for a specific position of the robot or its joints, in particular the position of the robot or its joints in the first and second reference configuration (s) . specified. In one embodiment, the measurement pose (s) are based on several position-specific stiffnesses, in one embodiment linear, interpolated and / or extrapolated.

As a result, in one embodiment, the rigidity of the drive train between the input and output-side position can be currently (more) and / or precisely determined and then based on this rigidity and the determined difference between the input and output-side position in the (respective) measurement pose current joint torque determined, in particular interpolated or extrapolated. In another embodiment, this rigidity can also be determined or be determined in another way.

In one embodiment, the or one or more of the joint torques on the basis of which the parameter is determined are (in each case also) determined on the basis of an electrical drive variable of a drive, in particular an electric motor, of the corresponding drive train, in one embodiment a motor current and / or a Motor voltage, or this drive variable, also taken into account when determining the joint torque (s), in particular by averaging or comparing them to one another in some other way.

As a result, the parameter can (still) be determined advantageously, in particular precisely and / or reliably (more) in one embodiment.

In one embodiment, the robot is operated on the basis of the determined parameter, in one embodiment it is controlled, in particular regulated, and / or monitored and / or a path of the robot is planned.

As a result, the operation of the robot can be improved, the robot can be precisely (r) controlled in one embodiment and / or (sensitively) interact with its environment.

According to one embodiment of the present invention, a system for determining a parameter of a force acting on a robot on the basis of at least one joint torque of the robot in at least one, in particular stationary, measuring pose of the robot, in particular in hardware and / or software, in particular in programming, is for Implementation of a method described here set up and / or comprises: Means for determining the joint torque on the basis of a difference between a drive-side and an output-side position of a drive train of the joint and / or a difference between a measurement configuration with the force acting on the robot and at least a previously approached reference configuration without this force acting on the robot.

• - Mittel zum Ermitteln des Parameters auf Basis der Gelenkmomente einer Anzahl von Robotergelenken in derselben, insbesondere stationären, Messpose des Roboters, wobei die Anzahl wenigstens zwei beträgt und/oder kleiner oder gleich der Gesamtzahl der Gelenke des Roboters und/oder kleiner oder gleich sechs ist; und/oder
• - Mittel zum Ermitteln des Parameters auf Basis der Gelenkmomente desselben Robotergelenks in wenigstens zwei, insbesondere stationären, Messposen des Roboters; und/oder
• - Mittel zum Ermitteln des Parameters mithilfe eines Ausgleichsproblemlösungsverfahrens und/oder auf Basis von Mittelwerten; und/oder
• - Mittel zum gleichartigen Anfahren der Messkonfiguration und wenigstens einen Referenzkonfiguration; und/oder
• - Mittel zum Ermitteln des Gelenkmoments auf Basis einer Steifigkeit des Antriebsstrangs, insbesondere zum Ermitteln der Steifigkeit auf Basis einer Differenz zwischen wenigstens einer ersten Referenzkonfiguration mit einer ersten auf den Roboter wirkenden Kraft und wenigstens einer zweiten Referenzkonfiguration mit keiner oder einer zweiten auf den Roboter wirkenden Kraft; und/oder
• - Mittel zum Ermitteln des Gelenkmoments auf Basis einer elektrischen Antriebsgröße; und/oder
• - Mittel zum Betreiben des Roboters auf Basis eines Parameters einer auf den Roboter wirkenden Kraft, wobei der Parameter mittels eines hier beschriebenen Verfahrens bzw. Systems bzw. dessen Mittel ermittelt wird bzw. ist.

In one embodiment, the system or its means has:

• Means for determining the parameter based on the joint torques of a number of robot joints in the same, in particular stationary, measuring pose of the robot, the number being at least two and / or less than or equal to the total number of joints of the robot and / or less than or equal to six ; and or
• - Means for determining the parameter on the basis of the joint moments of the same robot joint in at least two, in particular stationary, measuring poses of the robot; and or
• - Means for determining the parameter with the aid of a compensation problem solving method and / or on the basis of mean values; and or
• - Means for similar approach to the measurement configuration and at least one reference configuration; and or
• Means for determining the joint torque on the basis of a rigidity of the drive train, in particular for determining the rigidity on the basis of a difference between at least one first reference configuration with a first force acting on the robot and at least one second reference configuration with no force or a second force acting on the robot ; and or
• - Means for determining the joint torque on the basis of an electrical drive variable; and or
• Means for operating the robot on the basis of a parameter of a force acting on the robot, the parameter being or being determined by means of a method or system or its means described here.

A means within the meaning of the present invention can be designed in terms of hardware and / or software, in particular a processing, in particular microprocessor unit (CPU), graphics card (GPU), preferably a data or signal connected to a memory and / or bus system, in particular a digital processing unit ) or the like, and / or one or more programs or program modules. The processing unit can be designed to process commands that are implemented as a program stored in a memory system, process, acquire input signals from a data bus and / or deliver output signals to a data bus. A storage system can have one or more, in particular different, storage media, in particular optical, magnetic, solid-state and / or other non-volatile media. The program can be designed in such a way that it embodies or is able to execute the methods described here, so that the processing unit can execute the steps of such methods and thus in particular can determine the parameter or operate the robot. In one embodiment, a computer program product can have, in particular a non-volatile, storage medium for storing a program or with a program stored on it, wherein the execution of this program causes a system or a controller, in particular a computer, to create a to carry out the method described here or one or more of its steps.

In one embodiment, one or more, in particular all, steps of the method are carried out completely or partially automatically, in particular by the system or its means.

In one embodiment, the system has the robot.

• 1: ein System zum Ermitteln eines Parameters einer auf einen Roboter wirkenden Kraft nach einer Ausführung der vorliegenden Erfindung;
• 2: einen Antriebsstrang des Roboters; und
• 3: ein Verfahren zum Ermitteln des Parameters nach einer Ausführung der vorliegenden Erfindung.

Further advantages and features emerge from the subclaims and the exemplary embodiments. This shows, partly schematically:

• 1 : a system for determining a parameter of a force acting on a robot according to an embodiment of the present invention;
• 2 : a drive train of the robot; and
• 3 : a method for determining the parameter according to an embodiment of the present invention.

1 shows a robot 10 with six swivel joints in a first measuring pose (extended in 1 ; α = 0 °) and a second measuring pose (dashed in 1 ; α ≠ 0 °) and a robot controller 20th which carries out the procedure explained below or is set up for this purpose.

Each of the six swivel joints has one in 2 shown drive train with an electric motor 11 and a transmission output 12 which is connected on the one hand to the electric motor or its (output) shaft and on the other hand (rotationally) fixedly to a member of the robot that is actuated or adjusted by the drive train.

A first angle sensor 1 detects the (position of the electric motor shaft as) the drive-side position q _{an, i of} the i-th drive train, a second angle sensor 2 the (position of the gearbox output or relative position of the robot link to the preceding robot link as) the output-side position q _{ab, i of} the drive train i .

On one end flange 13 a force acts on the robot F. that by a distance a from the axis of rotation of the end flange (vertical in 1 ) is spaced apart. In particular, it can be the weight m · g of a robot-guided payload, the center of gravity of which is the distance a from the axis of rotation of the end flange 13 having.

In a first step S10 (see. 3 ) the in 1 shown measuring poses approached without being at the end flange 13 an external force attacks.

The angle sensors record in these measuring positions 1 , 2 each the drive or driven side positions of the drive trains of at least the third joint, in particular the second and third joint, in one embodiment also further joints.

In one embodiment, the measuring poses are approached several times, the drive train positions are recorded and mean values are formed from this or from the differences Δ _i = (q _{ab, i} - q _{an, i} ) of the input and output positions and these are used further. The repeated approach serves in particular to compensate for any measurement errors, but is not absolutely necessary.

In a second step S20 will the in 1 The measurement poses shown are approached again in the same way, in particular from the same direction, with the end flange 13 now a known external force attacks, in particular a payload with known mass and center of gravity on the end flange 13 is attached. In one embodiment, the measuring poses are approached one after the other with different known external forces, in particular different payloads with different, respectively known masses and / or positions of the center of gravity.

The angle sensors record again 1 , 2 each the drive and output side positions, whereby in one embodiment the measuring positions (with the respectively known external forces, in particular different payloads) are approached several times, the drive train positions are recorded and mean values from this or from the differences between the input and output side positions formed and used further.

mit der transponierten Jacobimatrix J^T, dem Winder h der bekannte externen Kraft und des durch sie bewirkten Drehmoments, dem VektorΔ_L1 der Antriebsstrangstellungsdifferenzen bei der bekannten externen Kraft aus Schritt S20, dem VektorΔ_L0 der Antriebsstrangstellungsdifferenzen aus Schritt S10 ohne externe Kraft und der Steifigkeitsmatrix K mit den Gelenksteifigkeiten c_i. Zusätzlich oder alternativ können die Steifigkeiten in analoger Weise auch auf Basis der unterschiedlichen bekannten Nutzlasten ermittelt werden.Then in a third step S30 Stiffnesses c _{i of} the individual joints are determined on the basis of these differences or mean values, in an embodiment according to $$J^{\text{T}}\cdot H=\tau =K\cdot \left({\Delta }_{\text{L.}1}-{\Delta }_{\text{L.}0}\right)$$

with the transposed Jacobian matrix J ^T , the winder h of the known external force and the torque caused by it, the vector Δ _{L1 of} the drive train position differences at the known external force from step S20 , the vector Δ _{L0 of} the drive train position differences from step S10 without external force and the stiffness matrix K with the joint stiffnesses c _i . Additionally or alternatively, the stiffnesses can also be determined in an analogous manner on the basis of the different known payloads.

This is based on the one hand on the idea of determining joint torques on the basis of drive train position differences (τ- = K · Δ), on the other hand, those joint torques that result from a force acting on the robot, the parameters of which are to be determined, based on the difference between a measurement configuration with this force acting on the robot and a previously approached reference configuration without this force acting on the robot, in particular a load-free reference configuration, to be determined, in particular from total joint torques determined on the basis of drive train position differences, subtracting the joint torque components that are not applied to the robot from this acting force result (τ _L0 = K · Δ _L0 ), the stiffness of the respective drive train taken into account for this in turn based on the difference between the in step S20 first reference configuration approached with the known external (first) force and that in step S10 approached second reference configuration is or is determined without a force acting on the robot or a load-free reference configuration.

In a fourth step S40 will the in 1 The measurement poses shown are approached again in the same way, in particular from the same direction, with the end flange 13 now the (unknown) payload is attached, its mass m and center of gravity distance a is to be determined. The angle sensors record again 1 , 2 each the drive and driven side positions, whereby in one embodiment the measuring poses are approached several times, the drive train positions are recorded and mean values are formed from this or from the differences between the drive and driven side positions and these are used further.

Then in step S50 the winder h of the weight of the payload and the torque caused by it on the basis of the drive train position differences Δ _L0 with a load-free robot from step S10 and the driveline position differences _ΔN in the payload from step S40 determined in an embodiment according to $$H={\left(J^{\text{T}}\right)}^{-1}\cdot \tau ={\left(J^{\text{T}}\right)}^{-1}\cdot K\cdot \left({\Delta }_{\text{N}}-{\Delta }_{\text{L.}0}\right)$$

The difference (Δ _N - Δ _L0 ) between the measurement configuration of the step becomes S40 , in which the unknown force acts on the robot, and the previously approached reference configuration of the step S10 , in which this force does not act on the load-free robot. This means that the robot's own weight can be hidden, so to speak.

In addition, the difference between the drive train positions on the input and output side Δ = [Δ ₁ , ..., Δ _6] ^T , Δ _i = (q _{ab, i} - q _{an, i} ) is used and with the help of the previously in step S30 determined stiffness (s) c _i or K determines the joint moments τ (which result from the payload). In one embodiment, motor currents of the drives of the drive trains can also be used in addition to this, in particular in an analogous manner by determining the motor currents when the robot is load-free (see step S10 ) and with payload (see step S40 ), whereby the joint torques determined on the basis of the drive train position differences and the joint torques determined on the basis of the motor currents can be averaged with one another or compared to one another in some other way.

gelöst werden, in einer Ausführung mit der Nebenbedingung C·h = b, durch die die bekannte Richtung der Gewichtskraft und das daraus resultierende Verschwinden wenigstens einer Kraft- und wenigstens einer Drehmomentkomponente des Winders berücksichtigt werden können, beispielsweise in einem Koordinatensystem mit zur Gravitationsrichtung paralleler bzw. in 1 senkrechter z-Achse und auf der Zeichenebene der 1 senkrecht stehender x-Achse: h = [0, 0, -m·g, -m·g·a,0, 0]^T.In an execution in step S50 with a sufficient number of measurement data, a compensation problem $$\text{min}\Vert J^{\text{T}}\cdot H-\tau \Vert$$

can be solved, in an embodiment with the secondary condition C · h = b, through which the known direction of the weight force and the resulting disappearance of at least one force and at least one torque component of the winder can be taken into account, for example in a coordinate system with or parallel to the gravitational direction . in 1 vertical z-axis and on the plane of the drawing 1 perpendicular x-axis: h = [0, 0, -m · g, -m · g · a, 0, 0] ^T.

In one step S60 will then the robot based on in step S50 determined mass and center of gravity of the currently guided payload operated, for example a path planned, the robot monitors and / or controlled, in particular regulated, preferably based on a model of the payload-guiding robot.

Doing so provide the steps S10 - S30 a calibration, which must be carried out before the steps S40 - S60 can be done, but does not have to be done.

Especially if only the crowd m the payload and its spacing a to the axis of rotation of the end flange 13 are to be determined, for this purpose one joint and two measuring poses or one measuring pose and two joints can be sufficient or taken into account, as follows using the in 1 measurement poses shown and the two in 1 left joints with on the plane of the drawing 1 vertical axes of rotation should be explained.

It is assumed that the rigidity c ₃ and possibly c ₂ as well as the difference Δ _{3, L0} = (q _{ab, 3} - q _{an, 3} ) _L0 and possibly Δ _{2, L0} = (q _{ab, 2} - q _{an, 2} ) _L0 between a drive-side and an output-side position of the drive train of these two joints when the robot is unloaded, as above with reference to steps S10 to S40 have been determined.

$${\mathrm{\tau }}_3={\text{C}}_3\cdot \left({\mathrm{\Delta }}_{\mathrm{3,}\text{N}}-{\mathrm{\Delta }}_{\mathrm{3,}\text{L}0}\right)=\left({\text{I}}_3+\text{a}\right)\cdot \text{m}\cdot \text{g}$$

mit der Gravitationskonstanten g und den mit der Nutzlast in der Messpose ermittelten Antriebsstrangstellungsdifferenzen Δ_2,N, Δ_3,N: $$\text{a}=\left({\text{I}}_2\cdot {\mathrm{\tau }}_3-{\text{I}}_3\cdot {\mathrm{\tau }}_2\right)/\left({\mathrm{\tau }}_2-{\mathrm{\tau }}_3\right)$$

$$\text{m}={\mathrm{\tau }}_3/\left[\left({\text{I}}_3+\text{a}\right)\cdot \text{g}\right]$$

Should only the in 1 The measurement pose shown in solid lines are used (if necessary with multiple approaches and averaging), then results from $${\mathrm{<figure-callout\; id="2"\; label="\tau "\; filenames="DE102019204564A1\_0012.png"\; state="\{\{state\}\}">\tau </figure-callout>}}_2={\text{C.}}_2\cdot \left({\mathrm{<figure-callout\; id="2"\; label="\Delta "\; filenames="DE102019204564A1\_0012.png"\; state="\{\{state\}\}">\Delta </figure-callout>}}_{\mathrm{2,}\text{N}}-{\mathrm{<figure-callout\; id="2"\; label="\Delta "\; filenames="DE102019204564A1\_0012.png"\; state="\{\{state\}\}">\Delta </figure-callout>}}_{\mathrm{2,}\text{L.}0}\right)=\left({\text{I.}}_2+\text{a}\right)\cdot \text{m}\cdot \text{G}$$

$${\mathrm{\tau }}_3={\text{C.}}_3\cdot \left({\mathrm{\Delta }}_{\mathrm{3,}\text{N}}-{\mathrm{\Delta }}_{\mathrm{3,}\text{L.}0}\right)=\left({\text{I.}}_3+\text{a}\right)\cdot \text{m}\cdot \text{G}$$

with the gravitational constant g and the drive train position differences Δ _{2, N} , Δ _{3, N} determined with the payload in the measuring pose: $$\text{a}=\left({\text{I.}}_2\cdot {\mathrm{\tau }}_3-{\text{I.}}_3\cdot {\mathrm{\tau }}_2\right)/\left({\mathrm{\tau }}_2-{\mathrm{\tau }}_3\right)$$

$$\text{m}={\mathrm{\tau }}_3/\left[\left({\text{I.}}_3+\text{a}\right)\cdot \text{G}\right]$$

$${\mathrm{\tau }}_{\mathrm{3,}\mathrm{\alpha }\ne 0°}={\text{C}}_3\cdot {\left({\mathrm{\Delta }}_{\mathrm{3,}\text{N}}-{\mathrm{\Delta }}_{\mathrm{3,}\text{L}0}\right)}_{\mathrm{\alpha }\ne 0°}=\left(\text{cos}\mathrm{\alpha }\cdot {\text{I}}_3+\text{a}\right)\cdot \text{m}\cdot \text{g}$$

mit den Werten α=0° für die in 1 ausgezogen dargestellte Messpose und α≠0° für die in 1 gestrichelt dargestellte Messpose: $$\text{m}=\left({\mathrm{\tau }}_{\mathrm{3,}\mathrm{\alpha }=0°}-{\mathrm{\tau }}_{\mathrm{3,}\mathrm{\alpha }\ne 0°}\right)/\left[\text{g}\cdot {\text{I}}_3\cdot \left(1-\text{cos}\mathrm{\alpha }\right)\right]$$

$$\text{a}={\mathrm{\tau }}_{\mathrm{3,}\mathrm{\alpha }=0°}/\left(\text{m}\cdot \text{g}\right)-{\text{I}}_3$$

If, on the other hand, only one joint is to be used (if necessary, with multiple approaches and averaging), the result for the two is in 1 represented measuring poses $${\mathrm{\tau }}_{\mathrm{3,}\mathrm{\alpha }=0°}={\text{C.}}_3\cdot {\left({\mathrm{\Delta }}_{\mathrm{3,}\text{N}}-{\mathrm{\Delta }}_{\mathrm{3,}\text{L.}0}\right)}_{\mathrm{\alpha }=0°}=\left({\text{I.}}_3+\text{a}\right)\cdot \text{m}\cdot \text{G}$$

$${\mathrm{\tau }}_{\mathrm{3,}\mathrm{\alpha }\ne 0°}={\text{C.}}_3\cdot {\left({\mathrm{\Delta }}_{\mathrm{3,}\text{N}}-{\mathrm{\Delta }}_{\mathrm{3,}\text{L.}0}\right)}_{\mathrm{\alpha }\ne 0°}=\left(\text{cos}\mathrm{\alpha }\cdot {\text{I.}}_3+\text{a}\right)\cdot \text{m}\cdot \text{G}$$

with the values α = 0 ° for the in 1 Measuring pose shown in solid lines and α ≠ 0 ° for the in 1 dashed measuring pose: $$\text{m}=\left({\mathrm{\tau }}_{\mathrm{3,}\mathrm{\alpha }=0°}-{\mathrm{\tau }}_{\mathrm{3,}\mathrm{\alpha }\ne 0°}\right)/\left[\text{G}\cdot {\text{I.}}_3\cdot \left(1-\text{cos}\mathrm{\alpha }\right)\right]$$

$$\text{a}={\mathrm{\tau }}_{\mathrm{3,}\mathrm{\alpha }=0°}/\left(\text{m}\cdot \text{G}\right)-{\text{I.}}_3$$

Although exemplary embodiments have been explained in the preceding description, it should be pointed out that a large number of modifications are possible.

In the exemplary embodiment, the mass and center of gravity of a robot-guided payload was determined, which is particularly advantageous for robot-assisted patient positioning or the like due to the limited adjustment options for parameter identification. Nevertheless, parameters of contact forces that act on the robot can also be determined instead.

It should also be pointed out that the exemplary designs are merely examples that are not intended to restrict the scope of protection, the applications and the structure in any way. Rather, the preceding description provides a person skilled in the art with guidelines for the implementation of at least one exemplary embodiment, with various changes, in particular with regard to the function and arrangement of the components described, being able to be made without departing from the scope of protection as it emerges from the claims and these equivalent combinations of features.

List of reference symbols

1

drive-side angle sensor

2

output-side angle sensor

10

robot

11

Electric motor

12th

Gearbox output

13

End flange

20th

Robot control

q _an, i

drive-side position of the i . Joint

qab, i

output side position of i . Joint

τ _i

Joint moment of the i. Joint (i = 1,2, ..., 6)

I ₂ , I ₃

Distances (known from robot kinematics)

a

Distance F to axis 6th (Center of gravity payload)

F.

Force acting on the robot (end flange) (mg)

m

Mass of the payload

Claims (12)

Method for determining a parameter (m, a) of a force (F) acting on a robot (10) on the basis of at least one joint moment (τ ₂ , τ ₃ ) of the robot in at least one, in particular stationary, measuring pose of the robot, the joint moment on the basis of a difference between a drive-side and an output-side position (q _{ab, i} - q _{an, i} ) of a drive train of the joint and / or a difference between a measurement configuration with the force acting on the robot and at least one previously approached reference configuration without it force acting on the robot is determined. Procedure according to Claim 1 , characterized in that the parameter, in particular only, depends on a mass (m) and / or center of gravity (a) of a robot-guided payload, in particular with a patient, or a contact force in an environmental contact of the robot. Method according to one of the preceding claims, characterized in that the parameter is determined on the basis of the joint torques (τ ₂ , τ ₃ ) of a number of robot joints in the same, in particular stationary, measuring pose of the robot, the number being at least two and / or less or equal to the total number of joints of the robot and / or less than or equal to six. Method according to one of the preceding claims, characterized in that the parameter is determined on the basis of the joint moments (τ ₃ ) of the same robot joint in at least two, in particular stationary, measurement poses of the robot. Method according to one of the preceding claims, characterized in that the parameter is determined with the aid of a compensation problem-solving method and / or on the basis of mean values. Method according to one of the preceding claims, characterized in that the joint torque is determined on the basis of a rigidity of the drive train. Method according to the preceding claim, characterized in that the rigidity is determined on the basis of a difference between at least one first reference configuration with a first force acting on the robot and at least one second reference configuration with no force or a second force acting on the robot. Method according to one of the preceding claims, characterized in that the measurement configuration and at least one reference configuration are approached in the same way. Method according to one of the preceding claims, characterized in that the joint torque is determined on the basis of an electrical drive variable. Method for operating (S60) a robot (10) on the basis of a parameter of a force acting on the robot, characterized in that the parameter is determined by means of a method according to one of the preceding claims (S10-S50). System for determining a parameter (m, a) of a force (F) acting on a robot (10) based on at least one joint moment (τ ₂ , τ ₃ ) of the robot in at least one, in particular stationary, measuring pose of the robot, the system is set up to carry out a method according to one of the preceding claims and / or has: means for determining the joint torque on the basis of a difference between a drive-side and an output-side position (q _{ab, i} - q _{an, i} ) of a drive train of the joint and / or a difference between a measurement configuration with the force acting on the robot and at least one reference configuration approached beforehand without this force acting on the robot. Computer program product with a program code, which is stored on a medium readable by a computer, for carrying out a method according to one of the preceding claims.

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