Estimation of the payload attached to the robot arm

Abstract

The invention discloses a method and a robot, wherein payload information of a payload attached to a robot tool flange of a robot arm is obtained by arranging the robot tool flange in a plurality of different orientations relative to gravity; the force and torque provided to the robot tool flange by gravity acting on the payload are obtained using a force-torque sensor arranged at the robot tool flange; the mass of the payload is obtained based on the obtained forces obtained in at least two of the different orientations. The dependent claims describe possible embodiments of the robot and the method according to the invention.

Description

Technical Field

[0001] The present invention relates to a method of estimating payload information of a payload of a robot tool flange attached to a robot arm, wherein the robot arm comprises a plurality of robot joints connecting a robot base and the robot tool flange. Background Art

[0002] Robotic arms comprising a plurality of robotic joints and links, wherein motors can rotate the joints relative to each other, are known in the field of robotics. Typically, a robotic arm comprises a robot base serving as a mounting base for the robotic arm and a robot tool flange to which various tools can be attached. Typically, a controller is configured to control the robotic joints so as to move the robot tool flange relative to the base, for example, so as to instruct the robot to perform a plurality of work instructions.

[0003] The robot controller is configured to control the robot joints based on a dynamic model of a robot arm known in the prior art, wherein the dynamic model defines the relationship between the forces acting on the robot arm and the resulting acceleration of the robot arm. Typically, the dynamic model includes a kinematic model of the robot arm, which defines the relationship between different parts of the robot arm, such as the robot joints at various joint angles and knowledge about the mass and inertia of the robot arm. The kinematic model includes information about the robot arm, such as the lengths, dimensions of the joints and links, and can be described, for example, by Denavit-Hartenberg parameters. The dynamic model allows the controller to calculate the torque that the joint motors should provide in order to move the robot joints and overcome the effects of gravity on the robot arm.

[0004] On many robot arms, various end effectors may be attached to the robot tool flange, such as grippers, vacuum grippers, magnetic grippers, screwdrivers, welding equipment, dispensing systems, vision systems, etc. When such end effectors are provided, it is necessary to estimate the payload that such end effectors provide to the robot arm. Typically, a user manually inputs the payload information into a kinematic model, which the controller may then take into account when controlling the robot. Typically, the payload information includes information related to the weight and pose of the payload, where the pose of the payload is related to the position and orientation of the payload relative to the robot tool flange. For example, the pose may be indicated at the position of the center of mass of the payload relative to the robot tool flange.

[0005] Many users struggle to set the correct payload, or simply ignore / forget to set the payload. As a result, the controller may not be able to control the robot arm, causing the robot arm to drift, the safety stops to deviate, and the robot arm's safety features to not function properly.

[0006] DE 11 2016 002 797 T5 discloses a calibration unit, which includes: an approximate curve generation unit configured to generate an approximate curve based on position information and force information obtained when a tool part rotates according to a posture command value; a deviation value estimation unit configured to estimate a deviation value of the force information based on the approximate curve, the position information and the force information; a mass / center of gravity position estimation unit configured to remove the deviation value from the force information and calculate the mass and center of gravity position vector of a hand-end load based on the obtained force information; and an external force component calculation unit configured to subtract the deviation value and the gravity action component of the hand-end load from the force information based on the deviation value and the mass and center of gravity position vector. The mass / center of gravity position estimation unit is configured to calculate the mass and center of gravity position vector of the hand-end load based on the obtained force information, which has been obtained by aligning the sensor axis of the force sensor with gravity and rotating the force sensor around an axis perpendicular to gravity. It is difficult for a user to precisely align the sensor axis of the force sensor with gravity and to ensure proper alignment while rotating the force sensor.

[0007] JP 2012 040634 discloses a calibration device and method for a power-controlled robot, which can calibrate necessary parameters in consideration of installation errors even if the installation accuracy of the robot is low, wherein a tool is attached to the front end of a robot arm that acts three-dimensionally via a power sensor. A robot controller causes the robot arm to move in a plurality of postures, and obtains measurement values ​​by the power sensor and obtains posture data of the power sensor when obtaining the measurement values. A calculation device calculates a plurality of parameters including the weight of the tool, a gravity direction vector, and a tool gravity center position vector. Summary of the invention

[0008] The object of the present invention is to solve the above limitations or other problems of the prior art with respect to the prior art. This is achieved by a method and a robot according to the independent claims, wherein payload information of a payload of a robot tool flange attached to a robot arm is obtained by arranging the robot tool flange in a plurality of different orientations relative to gravity; a force-torque sensor arranged at the robot tool flange is used to obtain the force and torque provided to the robot tool flange by gravity acting on the payload; the mass of the payload is obtained based on the obtained forces obtained in at least two of the different orientations, wherein for each of the different orientations, the angle between the robot tool flange and gravity is different. The dependent claims describe possible implementations of the robot and the method according to the present invention. The advantages and beneficial effects of the present invention are described in the specific embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 showing a robotic arm configured to obtain payload information of a payload attached to a robotic tool flange of the robotic arm;

[0010] Figure 2 A flow chart illustrating an embodiment of obtaining payload information of a payload attached to a robotic tool flange of a robotic arm;

[0011] Figure 3 A flow chart illustrating another embodiment of obtaining payload information of a payload attached to a robotic tool flange of a robotic arm;

[0012] Figure 4 A flow chart illustrating an embodiment of the steps of obtaining the mass of a payload attached to a robotic tool flange of a robotic arm;

[0013] Figure 5 A flow chart illustrating an embodiment of the steps of obtaining a pose of a payload attached to a robotic tool flange of a robotic arm;

[0014] Figure 6a and Figure 6b a display screen showing an interface of a robotic arm obtaining payload information;

[0015] Figure 7a and Figure 7b showing different display screens of an interface for a robotic arm obtaining payload information; and

[0016] Figure 8a , Figure 8b and Figure 8c Different display screens of an interface of a robotic arm showing obtaining payload information. DETAILED DESCRIPTION

[0017] The present invention has been described in view of the exemplary embodiments intended only to illustrate the principles of the invention. The skilled person will be able to provide several embodiments within the scope of the claims. Throughout the specification, the reference numerals of similar elements providing similar effects have the same last two digits. In addition, it should be understood that in the case where an embodiment includes multiple identical features, only some of the features may be marked by reference numerals.

[0018] Figure 1A robot arm 101 is shown comprising a plurality of robot joints 103a, 103b, 103c, 103d, 103e connecting a robot base 105 and a robot tool flange 107 to which a payload 109 (shown in phantom) is attached. The base joint 103a is configured to rotate the robot arm around a base axis 111a (shown in dotted lines), as indicated by the rotation arrow 113a; the shoulder joint 103b is configured to rotate the robot arm around a shoulder axis 111b (shown in dotted lines), as indicated by the rotation arrow 113b; the elbow joint 103c is configured to rotate the robot arm around an elbow axis 111c (shown in dotted lines), as indicated by the rotation arrow 113c, the first wrist joint 103d is configured to rotate the robot arm around a first wrist axis 111d (shown in dotted lines), as indicated by the rotation arrow 113d, and the second wrist joint 103e is configured to rotate the robot arm around a second wrist axis 111e (shown in dotted lines), as indicated by the rotation arrow 113e.

[0019] The robot joint 103f is a tool joint comprising a robot tool flange 107 which is rotatable about a tool axis 111f (shown in dashed lines) as indicated by the rotation arrow 113f. Thus, the robot arm shown is a six-axis robot arm with six degrees of freedom, but it is noted that the present invention may be provided in a robot arm comprising fewer or more robot joints.

[0020] The robot arm is connected to and controlled by a controller 125 which includes an interface device 127 which enables a user to control and program the robot arm. The controller may be provided as a computer with control software installed thereon and may be provided as Figure 1 The interface device may be provided as an external device as shown or as a device integrated into the robot arm. The interface device may be provided, for example, as a teach pendant known in the field of industrial robots, which can communicate with the controller via a wired or wireless communication protocol. The interface device may, for example, include a display 129 and a plurality of input devices 131, such as buttons, sliders, touch pads, joysticks, trackballs, gesture recognition devices, keyboards, etc. The display may be provided as a touch screen that acts as both a display and an input device.

[0021] The controller is configured to control the robot joints based on a kinematic model of the robot arm known in the prior art. In addition, the controller is configured to control the robot arm based on payload information of a payload 109 attached to the robot tool flange, wherein the payload information indicates the mass of the payload and its posture relative to the robot tool flange. In addition, the controller is configured to obtain the mass of the payload and its posture relative to the robot tool flange based on the force and torque provided to the robot tool flange when the payload is attached to the robot tool flange, wherein the controller is configured to obtain the force and torque from a force-torque sensor attached to the robot tool flange and at multiple different orientations of the robot tool flange relative to gravity. The force-torque sensor may be provided as a force-torque sensor disclosed by WO2014 / 110682A1, US4763531, US2015204742. The controller may be configured to utilize the method described below and in combination Figures 2 to 5 The method shown is to obtain the mass and pose of the payload.

[0022] The following paragraphs

[0013] to

[0023] introduce various items for describing the principles of the present invention.

[0023] The robot tool flange coordinate system 115 has an origin at the reference point and defines three coordinate axes x 凸缘 ,y 凸缘 、z 凸缘 In the embodiment shown, the origin of the robot tool flange coordinate system has been arranged on the tool flange axis 111f, wherein one of the axes (z 凸缘 ) is parallel to the tool flange axis and at the outer surface of the robot tool. The position in the robot tool flange coordinate system can be defined as the position vector:

[0024] Equation 1

[0025] where x 凸缘 ,y 凸缘 and z 凸缘 Indicates the position coordinates in the robot tool coordinate system. It should be understood that the robot tool flange coordinate system may be defined relative to the robot base in any desired manner.

[0026] The robot base reference coordinate system 119 has been defined relative to the robot base and consists of three coordinate axes x 基座 ,y 基座 、z 基座 In the embodiment shown, the origin of the base coordinate system has been arranged on the base axis 111a, and one of the axes (z 基座 ) is parallel to the base axis and is at the bottom part of the base. The position in the robot base reference coordinate system can be defined as the position vector:

[0027] Equation 2

[0028] where x 基座 ,y 基座 and z 基座 Indicates the position coordinates in the base coordinate system. It should be understood that the robot base coordinate system can be defined relative to the robot base in any desired manner.

[0029] Based on the kinematic model of the robot, any position coordinate defined in the base reference frame can be transformed using the following equation:

[0030] Equation 3

[0031] in is the transformation matrix that transforms a vector in the robot base coordinate system into a vector in the robot tool flange coordinate system.

[0032] A vector in the robot base coordinate system can be rotated into the robot tool flange coordinate system using the following formula:

[0033] Equation 4

[0034] in is the rotation matrix that rotates the vector in the robot base coordinate system into the vector in the robot tool flange coordinate system. It can be derived based on the kinematic model of the robot and will change as the position of the robot arm changes.

[0035] You can also use the following formula to rotate a vector in the robot tool flange coordinate system into a vector in the robot base coordinate system:

[0036] Equation 5

[0037] The payload 109 has a mass m 载荷 and the pose P relative to the robot tool flange 载荷 The pose of the payload relative to the robot tool flange indicates the position and orientation of the payload relative to the robot tool flange, for example, relative to a robot tool flange reference point. The robot tool flange reference point may be defined at the origin of the robot tool flange reference coordinate system 115. The pose of the payload may be indicated, for example, as a position vector This indicates that the position of the payload's center of mass 117 relative to the robot tool flange reference point is:

[0038] Equation 6

[0039] in and Indicates the coordinates of the center of mass of the payload in the robot's tool flange coordinate system. The payload is shown as an arbitrary box, however it should be understood that the payload can have many different shapes and can be provided as any component that can be attached to the robot's tool flange, such as an end effector, such as a gripper, vacuum gripper, magnetic gripper, tightener, welding equipment, dispensing system, vision system, etc.

[0040] The gravity direction 121 has also been shown as the gravity vector in the robot base coordinate system, which can be defined as:

[0041] Equation 7

[0042] in Indicates the magnitude of gravity along the axis of the robot base coordinate system. In the embodiment shown, the robot arm is arranged in a position where the base axis is aligned with gravity, so gravity only acts on z 基座 The component in the negative direction of the axis acts, so:

[0043] Equation 8

[0044] in To act on Figure 1 It should be understood that the robot arm can be mounted in any orientation relative to gravity, thereby generating different gravity vectors. quantity.

[0045] The gravity vector in the robot base coordinate system can be rotated to the gravity vector defined in the tool flange base coordinate system using the following formula:

[0046] Equation 9

[0047] And the opposite rotation using:

[0048] Equation 10

[0049] The robot tool flange includes a force-torque sensor (not shown) integrated into the robot tool flange. The force-torque sensor is configured to indicate forces and torques applied to the robot tool flange relative to a reference point, which in the present application coincides with the origin of the robot tool flange coordinate system. However, the force-torque sensor may indicate forces-torques applied to the robot tool flange relative to any point connectable to the robot tool flange coordinate system. In one embodiment, the force-torque sensor is a six-axis force-torque sensor configured to indicate forces along three perpendicular axes and torques about three perpendicular axes. For example, the force-torque sensor may indicate a force vector in the robot tool flange coordinate system:

[0050] Equation 11

[0051] in is along x 凸缘 The indicated force of the axis It is along y 凸缘 The indicated force of the axis and It is along z 凸缘 The indicated force of the axis.

[0052] Additionally, the force-torque sensor indicates the torque vector in the robot tool flange coordinate system:

[0053] Equation 12

[0054] in is around x 凸缘 Indicated torque of the axis, is around y 凸缘 The indicated torque of the axis and It is around z 凸缘 Indicated torque of the axis.

[0055] Gravity provides a weight on the payload in the direction of gravity The gravity in the robot base coordinate system can be obtained by the following formula:

[0056] Equation 13

[0057] Where m 载荷 is the mass of the payload and is the gravity vector in the robot base coordinate system and the robot tool flange coordinate system. The gravity can be obtained by the following formula:

[0058] Equation 14

[0059] The gravity on the payload also results in a torque applied to the robot tool flange relative to the robot tool flange coordinate system and this torque can be given by:

[0060] Equation 15

[0061] Where m 载荷 is the mass of the payload, and is the gravity vector in the robot working flange coordinate system.

[0062] The method according to the invention can be implemented via the control software of the robot arm, whereby the payload information of a payload attached to the tool flange of the robot can be determined in a fast, simple and accurate manner. As a result, the robot arm will operate more accurately, since the control software of the robot arm can take the payload into account when controlling the robot. The method according to the invention also makes it possible to determine the payload information of a payload having a complex form.

[0063] Figure 2 A flow chart of a method for obtaining payload information of a payload of a robot tool flange attached to a robot arm according to the present invention is shown. The robot arm includes a plurality of robot joints connecting a robot base and a robot tool flange, and corresponds to Figure 1 The method includes a step 250 of arranging a robot tool flange in a plurality of different orientations, a step 260 of obtaining a mass of a payload, a step 270 of obtaining a posture of the payload, and an optional step 280 of controlling the robot based on the obtained payload information.

[0064] In step 250, the robot tool flange is arranged in a plurality of different orientations, wherein the number n of different orientations of the robot tool flange is 取向 is at least 2. In each of these orientations, a force-torque sensor disposed at the robot tool flange is used to obtain the force and torque provided to the robot tool flange due to gravity acting on the payload.

[0065] In the illustrated embodiment, step 250 includes step 251 of arranging the robot tool flange in a first orientation, for example by: a user manipulating a joint of the robot to arrange the robot tool flange in a first orientation; a user using an interface device 127, an automatic program executed by a controller of the robot, or a combination thereof to control the orientation of the robot tool flange.

[0066] Once the robot tool flange has been arranged in a certain orientation, a step 252 of obtaining the orientation of the robot tool flange 107 (TF) relative to gravity is performed. 凸缘,g,n can be obtained as any parameter from which the orientation of the robot tool flange relative to gravity can be obtained. Orientation O of the robot tool flange 凸缘,g,n It may be stored, for example, in a memory (not shown) of the robot arm. For example, the orientation of the robot tool flange may be obtained by the following operation: 凸缘,g,n:Obtain the angular position of each robot joint in the robot joints; then use the robot's kinematic model and the gravity orientation in the robot base coordinate system to obtain the orientation of the robot tool flange relative to gravity. For example, the orientation of the robot tool flange can be indicated as the origin of the robot tool flange coordinate system and the three coordinate axes x of the robot tool flange coordinate system 凸缘 ,y 凸缘 、z 凸缘 In another embodiment, the orientation of the robot tool flange can be obtained using a gravity sensor arranged at a robot joint, the robot joint including the robot tool flange. Such a gravity sensor can indicate the direction of gravity relative to the robot tool flange, so that the orientation of the robot tool flange can be obtained based on such a gravity sensor. In addition, in an embodiment in which the robot tool flange is automatically arranged in a certain orientation based on a program executed by a controller of the robot, the orientation can be obtained based on program instructions. Orientation of the robot tool flange 凸缘,g It can also be indicated as the gravity vector in the robot tool flange coordinate system at orientation n Gravity vector in n orientation It can be obtained by gravity sensors at the robot joints of the robot tool flange or by using Eq. 9.

[0067] Once the robot tool flange has been arranged in a certain orientation, a force-torque sensor arranged at the robot tool flange is used to obtain the force and torque provided to the robot tool flange due to gravity acting on the payload 253, where the obtained force F in the nth orientation is 传感器,n and the torque T obtained in the nth orientation 传感器,n The force-torque sensor can be stored in the memory of the robot arm. The force-torque sensor can be integrated into the robot tool flange, which ensures that the force-torque sensor is present and properly integrated into the robot arm by the robot arm provider. Alternatively, the force-torque sensor can be provided as an external force-torque sensor that can be attached to the robot tool flange. In such an embodiment, the payload of the force-torque sensor needs to be manually provided into the control software of the robot arm.

[0068] In one embodiment, the force-torque sensor is provided as a six-axis force-torque sensor, which obtains the force and torque provided to the force-torque sensor relative to three base coordinate axes. The force-torque can be aligned with the robot tool flange coordinate system 115, for example, and indicates the force along the axis x. 凸缘 ,y 凸缘 、z 凸缘 The applied forces and applied torques about these axes. Therefore, the forces obtained in orientation n can be indicated as:

[0069] Equation 16

[0070] in is along x in the nth orientation 凸缘 The indicated force of the axis, is along y in the nth orientation 凸缘 The indicated force of the axis and is along z in the nth orientation 凸缘 the indicated force of the axis; and

[0071] The torque obtained in the nth orientation can be indicated as:

[0072] Equation 17

[0073] in is around x in the nth orientation 凸缘 Indicated torque of the axis, is around y in the nth orientation 凸缘 The indicated torque of the axis and Yes, in the nth direction around z 凸缘 Indicated torque of the axis.

[0074] Step 255 is a step of verifying that the force and torque provided to the robot tool flange by gravity have been obtained in at least two different orientations of the robot tool flange relative to gravity. This can be done by incrementing the counter n as the orientations, forces, and torques are obtained in steps 252 and 253. 取向 Increment by 1, then test counter n 取向 Is equal to or greater than the desired number of orientations (in the illustrated embodiment 2) achieved. If the desired number of orientations has not been achieved (indicated by a thumbs down symbol), then at step 254 of changing the orientation of the robot tool flange, otherwise initiated (indicated by a thumbs up symbol), the method continues to the next step.

[0075] The step 254 of changing the orientation of the robot tool flange can be achieved by: the user manipulating the joints of the robot to arrange the robot tool flange in a new orientation; the user controlling the orientation of the robot tool flange using the interface device 127, an automatic program executed by the controller of the robot, or a combination thereof. The orientation of the robot tool flange relative to gravity is changed by rotating the tool flange, which means that the angle between the robot tool flange and gravity is different for a plurality of different orientations. Once the orientation of the robot tool flange has been changed; the orientation of the robot tool flange is obtained, and then the force provided to the robot tool flange of the robot in the new orientation is obtained by repeating steps 252 and 253.

[0076] In one embodiment, the step 254 of changing the orientation of the robot tool flange includes the step of rotating the robot tool flange about an axis that is not parallel and not perpendicular to gravity. This ensures that the angle of the robot tool flange relative to gravity changes.

[0077] The optional step 256 of verifying the orientation of the robot tool flange has been shown as part of step 250. In this embodiment, step 256 is performed as part of a loop that includes step 254. Step 256 verifies that the new orientation of the robot tool flange is correct. For example, by checking that the angle between the newly oriented robot tool flange and gravity is different from the angle of the previously oriented robot tool flange. Such verification makes it possible to ensure that payload information can be obtained based on the forces and torques obtained. It should be noted that the verification of the orientation of the robot tool flange can be performed at other locations in the flowchart. For example, when the forces and torques have been obtained at all orientations, step 256 can be provided as a verification performed at the end of step 250. The verification step can then include verification of all orientations and / or the forces and torques obtained.

[0078] Step 250 results in an indication of a plurality of different orientations of the robotic tool flange and, for each of the different orientations, an indication of the forces and torques applied to the robotic tool flange due to gravity acting on a payload attached to the robotic tool flange.

[0079] Then, in step 260, based on the orientation O of the robot tool flange obtained in step 252, 凸缘,g,n and the corresponding force F obtained in step 253 传感器,n To obtain the mass m of the payload 载荷 This can be achieved, for example, by using Equation 13, the resulting force in the nth orientation from Equation 16, and the orientation of gravity in the nth orientation. to achieve this, where the rotation matrix can be obtained based on the kinematic model of the robot and the obtained angles of the robot joints at orientation n. Then, the obtained mass m can be 载荷 Stored in the robot arm's memory.

[0080] Then, in step 270, based on the orientation O of the robot tool flange obtained in step 252, 凸缘,g,n , the corresponding torque T obtained in step 253 传感器,n and the mass m of the payload obtained in step 260 载荷 To obtain the payload posture P 载荷 The pose of the payload can be, for example, the position of the payload's center of mass relative to the robot tool flange. This can be obtained, for example, by using Equation 15, the torque obtained in the nth orientation according to Equation 17 and the gravity orientation in the nth orientation. to achieve this, where the rotation matrix can be obtained based on the kinematic model of the robot and the obtained angles of the robot joints in the orientation n. The pose of the payload is determined based on at least two orientations of the tool flange, which ensures that the pose of the payload can be correctly obtained, because the fact that the non-working orientation in which one axis of the force-torque sensor is parallel to gravity leads to zero torque relative to this axis makes it impossible to determine the position of the center of mass along this axis due to the missing torque.

[0081] The pose of the payload is obtained based on the force-torque measurements in at least two orientations of the robot tool flange relative to gravity, wherein the orientations differ in having different angles relative to gravity, ensuring that the pose of the payload can be determined, such as by changing the angle of the robot tool flange between two of the different orientations, ensuring that the pose about the axis x can be obtained. 凸缘 ,y 凸缘 and z 凸缘 In addition, determining the mass and posture of the payload based on at least two orientations of the robot tool flange allows the use of less expensive force-torque sensors to determine the mass and posture of the payload, which force-torque sensors typically measure forces and torques inaccurately, especially under different operating conditions (such as different temperatures and humidities). This can be achieved as described in the following paragraphs. In addition, by obtaining the force-torque at at least two different orientations of the robot tool flange relative to gravity, it is ensured that the momentum arm, which is defined as a vector from the robot tool flange coordinate system to the center of mass of the payload in at least one orientation, is not parallel to gravity. Therefore, the length of the momentum arm can be obtained based on the force-torque measurements obtained at orientations of the robot tool flange where the momentum arm is not parallel to gravity.

[0082] Step 280 is an optional step of controlling the robot based on the payload information obtained. This can be achieved, for example, by adjusting the kinematic model of the robot taking into account the payload information obtained. Thus, thereafter, the controller can better control the robot arm, preventing deviation of the robot arm and deflection of the safety stop, wherein the robot arm is stopped. The safety functions of the robot arm will also operate as expected.

[0083] Figure 3 A flow chart of a method for obtaining payload information of a payload attached to a robot tool flange of a robot arm according to the present invention is shown. The method is similar to Figure 2 The method shown, and similar steps have been assigned to Figure 2 The same reference numerals are used in the drawings and will not be described in further detail.

[0084] In this embodiment, the step 260 of obtaining the mass of the payload includes a step 361 of obtaining an obtained force difference, wherein the obtained force difference is obtained as a difference between two of the obtained forces obtained at two of the different orientations of the robot tool flange:

[0085] Equation 18 ΔF 传感器，i，j =F 传感器，i -F 传感器，j

[0086] Where ΔF 传感器,i,j is the force F obtained in the nth orientation i 传感器,i and the force F obtained in the nth orientation j 传感器,j The difference in the force obtained between . In vector form and using Equation 16:

[0087] Equation 19

[0088] in and are respectively along x in the n-th orientation i and j 凸缘 The force obtained on the axis, and are respectively along y in the nth orientation i and j 凸缘 The force obtained on the axis, and and are respectively along z in the nth orientation i and j 凸缘 The force obtained on the axis.

[0089] In this embodiment, the mass m of the payload is obtained 载荷 Step 260 includes obtaining a force difference ΔF based on the obtained force difference ΔF. 传感器 and the orientation of the robot tool flange O 凸缘,g,i , O 凸缘,g,j Step 362 of determining the mass of the payload (based on the orientation and the resulting force difference). 凸缘,g,i indicates the orientation of the robot tool flange at the nth orientation i, and O 凸缘,g,i Indicates the orientation of the robot tool flange at the nth orientation j.

[0090] Mass of payload m 载荷 It can be obtained, for example, by using Equation 14 to convert the terms of the forces obtained in the n-th orientation i and j, respectively Replace each item in with the item and item in Indicates the orientation of the gravity vector in the robot tool coordinate system at the nth orientation i and j.

[0091] Obtaining the mass of the payload based on the obtained force difference between two of the obtained forces obtained at two of the different orientations of the robot tool flange allows the use of a less expensive force-torque sensor to obtain the mass of the payload, wherein the absolute accuracy varies under different operating conditions (such as different temperatures and humidity). Assuming that the force measurements made at different orientations are made under the same operating conditions, it can be assumed that the offset relative to the absolute force is the same for the measurements made at two different positions. As an alternative or in addition to obtaining the mass based on the force measurement at a single orientation, the offset can be eliminated to determine the mass of the payload based on the obtained force difference.

[0092] In this embodiment, the step 270 of obtaining the pose of the payload includes the step 371 of obtaining an obtained torque difference, wherein the obtained torque difference is obtained as a difference between two of the obtained torques obtained at two of the different orientations of the robot tool flange:

[0093] Equation 20ΔT 传感器，i，j =T 传感器，i -T 传感器，j

[0094] Where ΔT 传感器 is the torque T obtained in the nth orientation i 传感器,i and the torque T obtained in the nth orientation j 传感器,j The difference in torque obtained between . In vector form and using Equation 17:

[0095] Equation 21

[0096] in and T are respectively around x in the nth orientation i and j 凸缘 The torque obtained on the axis, and are respectively along y in the nth orientation i and j 凸缘 The torque obtained on the axis and and are respectively along z in the nth orientation i and j 凸缘 The torque obtained on the axis.

[0097] In this embodiment, the posture P of the payload is obtained. 载荷 Step 270 includes obtaining the mass m of the payload based on the obtained 载荷 , the torque difference ΔT obtained 传感器 and the orientation of the robot tool flange O 凸缘,g,i , O 凸缘,g,j Step 372 of determining the attitude of the payload (based on the orientation to obtain the torque difference).

[0098] The payload's posture P 载荷 It can be obtained, for example, by using Equation 15 to convert the terms of the torque obtained in the n-th orientation i and j, respectively, into Replace each item in with the item and item in denotes the orientation (in the form of a gravity vector) of the robot tool flange in the robot tool coordinate system at the nth orientation i and j, and wherein The pose of the payload is indicated as the position of the center of mass of the payload relative to the robot tool flange. and are the same because they refer to the center of mass of the same payload relative to the robot tool flange coordinate system.

[0099] Obtaining the pose of the payload based on the obtained torque difference between two of the obtained torques obtained at two of the different orientations of the robot tool flange allows the use of a less expensive force-torque sensor to obtain the pose of the payload, where the absolute accuracy varies under different operating conditions (such as different temperatures and humidity). Assuming that the torque measurements made at the different orientations are made under the same operating conditions, it can be assumed that the offset relative to the absolute torque is the same for the measurements made at the two different orientations. This offset can be eliminated to determine the pose of the payload based on the obtained torque difference.

[0100] Figure 4 A flow chart showing an embodiment of step 260 of obtaining the mass of the payload is shown. Step 260 is similar to Figure 2 and Figure 3 Step 260 is shown, and similar steps have been assigned to Figure 2 and Figure 3 In this embodiment, step 260 includes:

[0101] Provide an initial guess of the payload mass m 猜测 Step 463.

[0102] For different orientations of the robot tool flange 凸缘,g,i , O 凸缘,g,j at least two orientations, provided by a matrix with a mass corresponding to the initial mass guess m 猜测 The mass of the payload is the expected force F provided to the robot tool flange 预期,i 、F 预期,j Step 464.

[0103] Determine the expected force F in at least two different orientations of the tool flange 预期,i 、F 预期,jThe expected force difference ΔF between at least two expected forces in 预期,i,j Step 465.

[0104] Determine the force error ΔF 误差,i,j At step 466, the force error indicates the force difference ΔF obtained. 传感器,i,j Difference from expected force ΔF 预期,I,j The difference between

[0105] By minimizing the force error ΔF 误差,i,j To provide the mass of the payload m 载荷 Step 467.

[0106] This makes it possible to provide an estimate of the mass of the payload in situations where an exact solution to the equation is not available, for example due to inaccuracies in the force-torque measurements. Furthermore, the method according to the invention can be easily implemented into a controller of a robotic arm using simple logic and digital methods that are easy to implement into standard controllers. Further estimating the mass of the payload by minimizing the force error also makes it possible to estimate how good the obtained mass of the payload is relative to the actual mass of the payload.

[0107] Step 463 of providing an initial mass guess of the payload may be accomplished by providing a random mass guess m of the payload. 猜测 ; Provide a predetermined mass guess of the payload, for example a guess corresponding to half of the allowed payload of the robot arm. In addition, an initial mass guess of the payload can be provided based on one of the force measurements, which initial mass guess can be used as a practical guess even when using a less accurate force-torque sensor.

[0108] The expected force F provided in step 464 预期,i 、F 预期,j The initial mass m can be guessed by using Equation 14 猜测 Instead of m 载荷 to provide, and where the gravity vector is based on the orientation of the robot tool flange as described above. 凸缘,g,i , O 凸缘,g,j Therefore, at least two expected forces F are obtained. 预期,i 、F 预期,j However, it should be appreciated that the expected torque may be obtained for each of the orientations of the robotic tool flange for which the force and torque provided to the robotic tool flange have been obtained (step 250).

[0109] Determine the expected force F in at least two different orientations of the tool flange 预期,i 、F 预期,j The expected force difference ΔF between at least two expected forces in预期,i,j Step 465 can be implemented by the following formula:

[0110] Equation 22ΔF 预期，i.j =F 预期，i -F 预期，j

[0111] In vector form:

[0112] Equation 23

[0113] in and are respectively along x in the n-th orientation i and j 凸缘 Expected force on the axis, and are respectively along y in the nth orientation i and j 凸缘 The expected force on the axis and and are respectively along z in the nth orientation i and j 凸缘 Expected force on the axis.

[0114] Determine the obtained force difference ΔF 传感器 Difference from expected force ΔF 预期 The force error between 误差,i,j Step 466 of can be performed by subtracting one from the other. For example, by:

[0115] Equation 24

[0116] Step 467 of providing the mass of the payload by minimizing the force error may be accomplished by changing the initial mass guess of the payload; and repeating steps 464, 465, 466 using the new initial mass guess of the payload as indicated by ring 468. A new force error may thus be obtained, and by comparing this force error with the previously obtained force error, it may be determined which mass guess results in the minimum torque error. This may be performed multiple times, resulting in a set of torques having corresponding force errors ΔF 误差,k A set of initial mass guesses m 猜测,k , where k is an integer indicating the number of guesses. The mass of the payload m 载荷 Can be set to result in a minimum force error ΔF 误差,min The quality of the guess m 猜测,min Loop 468 may be repeated, for example, a predetermined number of times, wherein the mass guess is changed, for example, at predetermined intervals and within a predetermined mass range. Ideally, when the mass guess m 猜测 The correct mass m of the payload 载荷When matched, the force error is zero. However, this may be difficult to achieve due to inaccuracies in force torque measurements. Loop 468 may then be repeated until an acceptable level of force error has been achieved.

[0117] In embodiments where forces have been obtained for more than three different orientations of the robotic tool flange in step 250, the force error may be provided as the sum of the squares of the force errors between each of the different orientations:

[0118] Equation 25

[0119] Figure 5 FIG. 2 is a flow chart showing an embodiment of step 270 of obtaining the posture of the payload. Step 270 is similar to Figure 2 and Figure 3 Step 270 is shown, and similar steps have been assigned to Figure 2 and Figure 3 In this embodiment, step 270 includes:

[0120] Provide an initial guess of the payload’s pose P 猜测 Step 573.

[0121] For different orientations of the robot tool flange 凸缘,g,i , O 凸缘,g,j at least two orientations, provided by having a guess P corresponding to the initial pose 猜测 The expected torque T provided by the payload to the robot tool flange 预期,i 、T 预期,j Step 574.

[0122] Determine the expected torque T in at least two different orientations of the tool flange 预期,i 、T 预期,j The expected torque difference ΔT between at least two expected torques in 预期,i,j Step 575.

[0123] Determine the torque error ΔT 误差,i,j In step 576, the torque error indicates the torque difference ΔT obtained. 传感器,i,j Difference from expected torque ΔT 预期,I,j The difference between

[0124] By minimizing the torque error ΔT 误差,i,j To provide the payload posture P 载荷 Step 577.

[0125] This makes it possible to provide an estimate of the pose of the payload in situations where an exact solution to the equation is not available, for example due to inaccuracies in the force-torque measurements. Furthermore, the method according to the invention can be easily implemented into a controller of a robotic arm using simple logic and digital methods that are easy to implement into standard controllers. Further estimating the pose of the payload by minimizing the force error also makes it possible to estimate how good the obtained pose of the payload is relative to the actual mass of the payload.

[0126] Step 573 of providing an initial pose guess of the payload may be implemented by providing a random pose guess P of the payload. 猜测 ; Provide a predetermined pose guess of the payload, for example corresponding to the position of the payload's center of mass at a given position in front of the robot tool flange (along z 凸缘 In addition, an initial pose guess of the payload can be provided based on one of the force and torque measurements, which can be used as a practical guess even when a less accurate force-torque sensor is used.

[0127] The expected torque T provided in step 574 预期,i 、T 预期,j The initial pose can be used to guess P by using Equation 15 猜测 Rather than to provide, and where the gravity vector is based on the orientation of the robot tool flange as described above. 凸缘,g,i , O 凸缘,g,j The mass m of the payload obtained in step 260 can be used 载荷 Therefore, at least two expected torques T are obtained. 预期,i 、T 预期,j However, it should be understood that the expected torque may be obtained for each of the orientations of the robotic tool flange for which the force and torque provided to the robotic tool flange have been obtained (step 250).

[0128] Determine the expected torque T in at least two different orientations of the tool flange 预期,i 、T 预期,j The expected torque difference ΔT between at least two expected torques in 预期 Step 575 can be implemented by the following formula:

[0129] Equation 26 ΔT 预期，i.j =T 预期，i -T 预期，j

[0130] In vector form:

[0131] Equation 27

[0132] in and are respectively around x in the nth orientation i and j 凸缘 Expected torque on the axis, and is around y in n-th orientation i and j respectively 凸缘 the expected torque on the axis, and and is around z in nth orientation i and j respectively 凸缘 Expected torque on the axis.

[0133] Determine the torque difference ΔT obtained 传感器,i,j Difference from expected torque ΔT 预期,I,j The torque error ΔT between 误差,i,j Step 576 of can be performed by subtracting one from the other. For example, by:

[0134] Equation 28

[0135] Step 577 of providing a pose of the payload by minimizing the torque error may be accomplished by: changing the initial pose guess of the payload; and repeating steps 574, 575, 576 using the new initial pose guess of the payload as indicated by ring 578. A new torque error may thus be obtained, and by comparing the torque error with the previously obtained torque error, it may be determined which pose guess resulted in the minimum torque error. This may be performed multiple times, resulting in a set of poses with corresponding torque errors ΔT 误差,k A set of initial pose guesses P 猜测,k , where k is an integer indicating the number of guesses. The pose m of the payload 载荷 Can be set to result in a minimum torque error ΔT 误差,min Pose guess P 猜测,min Loop 578 may, for example, repeat a predetermined number of times, wherein the pose guess changes, for example, at predetermined intervals and within a predetermined range of positions. Ideally, when the pose guess m 猜测 Correct posture with payload m 载荷 When matched, the torque error is zero. However, due to inaccuracies in torque measurements, this may be difficult to achieve, and loop 578 may then be repeated until an acceptable level of torque error has been achieved.

[0136] In embodiments where the torques have been obtained for more than three different orientations of the robotic tool flange at step 250, the torque error may be provided as the sum of the squares of the torque errors between each of the different orientations:

[0137] Equation 29

[0138] In one embodiment, the step of changing the orientation of the robot tool flange relative to gravity includes the step of changing the orientation of the robot tool flange by at least 20 degrees relative to at least one other orientation of the robot tool flange. This ensures that the force along the sensing axis of the force-torque sensor and the torque about the sensing axis have been changed within a certain range, and the difference in the obtained force and torque due to the change relative to gravity exceeds the noise and / or measurement error of the force-torque measurement results obtained by the force-torque sensor.

[0139] In one embodiment, the step of arranging the robot tool flange in a plurality of different orientations comprises arranging the robot tool flange in four different orientations relative to gravity. This ensures that in at least one of the different orientations, the sensing axis of the force-torque sensor is not parallel to gravity, thereby avoiding zero torque around the sensing axis parallel to gravity.

[0140] In one embodiment, the step of changing the orientation of the robot tool flange relative to gravity comprises the step of changing the orientation of the robot flange by between 100 and 140 degrees relative to at least one other orientation of the robot flange. It is thereby achieved that the force along at least one of the sensing axes of the force-torque sensor and the torque about the at least one sensing axis have opposite signs, resulting in a more robust determination of the payload information, since the eventual offset in the force-torque sensor along the axis can be eliminated, furthermore, this also ensures that the force along the sensing axis of the force-torque sensor and the torque about the sensing axis have been varied within a range, wherein the difference in the obtained force and torque due to the variation relative to gravity exceeds the measurement error of the force-torque sensor.

[0141] In one embodiment, the step of arranging the robot tool flange in a plurality of different orientations comprises arranging the robot tool flange in four different orientations relative to gravity, wherein the angle between each of the four different orientations is between 100 and 140 degrees relative to the three other orientations. This results in the effect that the obtained forces and torques along the sensing axis of the force-torque sensor are provided over a larger range, wherein at least two of the sensed forces and torques relative to the sensing axis have opposite directions, thereby obtaining a robust method of obtaining payload information. In a more specific embodiment, the angle between each orientation of the robot tool flange is between 110 and 130 degrees, and even more specifically between 115 and 125 or 120 degrees.

[0142] Figure 6a and Figure 6b Shows Figure 1The interface device 127 of the robot arm is shown, and an example of an embodiment is shown, in which the controller is configured to provide user instructions to the user during the estimation of the payload. The user instructions are used to instruct the user to change the orientation of the robot tool flange relative to gravity. Figure 6a In the example of FIG. 6 , a user instruction is provided as a command prompt 690a, instructing the user: “Arrange the robot tool flange in the first orientation!” Once the user has arranged the robot tool flange in the first orientation, the controller is configured to obtain the force-torque provided to the robot tool flange using the force-torque sensor as described above. When the user has arranged the robot tool flange in the first orientation, the user may, for example, press a confirmation icon 691 on the touch screen to instruct the controller to obtain the force and torque provided to the robot tool flange.

[0143] Afterwards, if Figure 6b As shown, a new user instruction is provided as a command prompt 690b, instructing the user: "Change the orientation of the robot tool flange to a second orientation relative to gravity". Once the user has arranged the robot tool flange in the second orientation, the controller is configured to obtain the force-torque provided to the robot tool flange using the force-torque sensor as described above. Similarly, the user can press the confirmation icon 691 on the touch screen to instruct the controller to obtain the force and torque provided to the robot tool flange.

[0144] The above steps may be repeated until the desired number of orientations has been obtained and the controller may obtain the mass and pose of the payload, as previously described. It should be noted that in other embodiments, the user instructions may be provided using different types of interface means, such as voice commands.

[0145] A first representation 692a of the robotic tool flange is shown on the display and indicates at least one of the different orientations of the robotic tool flange. Figure 6a In FIG. 6 , a first representation 692a indicates a desired orientation of the robot tool flange in the first orientation and is provided as an image 693a showing a possible configuration of the robot arm with the robot tool flange arranged in the first orientation. Additionally, an orientation symbol 694a indicating the orientation of the robot tool flange is shown. A gravity symbol indicating a gravity orientation 695 may also be provided at the display. Figure 6b , a first representation 692b indicates a desired orientation of the robot tool flange in the second orientation and is provided as an image 693b showing a possible configuration of the robot arm with the robot tool flange arranged in the second orientation and symbol 694b indicates the orientation of the robot tool flange in the second orientation.

[0146] The user instructions are used to assist the user when configuring the robot arm controller with the payload information and to make it easier for the user to ensure that the payload information is correctly determined. It should be noted that more than one graphical representation of the desired orientation of the robot tool flange may be shown together on the screen in order to provide an overview of the orientations that are needed to obtain the forces and torques.

[0147] Figure 7a and Figure 7b Shows Figure 1 An interface device 127 of a robotic arm is shown, and an example of an embodiment is shown in which the controller is configured to provide user instructions to a user during estimation of the payload. Figure 7a and Figure 7b The screen shown in corresponds to Figure 6a and Figure 6b , and only the differences will be described.

[0148] In this embodiment, a second representation 796 of the robot tool flange is shown on the display and indicates at least one of the different orientations of the robot tool flange. Figure 6a In FIG. 6 , a first representation 692a indicates a desired orientation of the robot tool flange in the first orientation and is provided as an image 693a showing a possible configuration of the robot arm with the robot tool flange arranged in the first orientation. Additionally, an orientation symbol 694a indicating the orientation of the robot tool flange is shown. A gravity symbol indicating a gravity orientation 695 may also be provided at the display. Figure 6b , a first representation 692b indicates a desired orientation of the robot tool flange in the second orientation and is provided as an image 693b showing a possible configuration of the robot arm with the robot tool flange arranged in the second orientation and symbol 694b indicates the orientation of the robot tool flange in the second orientation.

[0149] In this embodiment, the second representation 796 indicates the actual orientation of the robot tool flange and is provided as an image 797, which shows the actual configuration of the robot arm. In the illustrated embodiment, the image 797 is shown as a portion of the robot arm, however it should be noted that the image could also show the entire robot. If the configuration of the robot is changed, the image of the robot in the actual configuration changes.

[0150] In this embodiment, the first representations 792a, 792b of the robot tool flange in the first orientation and the second orientation, respectively, are provided in phantom lines to distinguish the first representation from the second representation.

[0151] This provides assistance to the user when arranging the robot tool flange in a desired orientation, as the user can associate the second representation of the actual robot position with the representation of the desired orientation, thereby being guided in which orientation the robot tool flange should be arranged.

[0152] Figure 8a , Figure 8b and Figure 8c Shows Figure 1 The interface device 127 of the robot arm is shown, and an example of an embodiment is shown, in which the controller is configured to provide user instructions to the user during the estimation of the payload. Figure 8a and Figure 8b , a user instruction is provided as a command prompt 890a, instructing the user: "Rotate the robot tool flange as indicated by the arrow!". A second representation 796 indicates the actual orientation of the robot tool flange and is provided as an image 797, which shows the actual configuration of the robot arm. An arrow 898 indicates the rotation direction that the user should rotate the robot tool flange in order to arrange the robot tool flange in one of the desired orientations. The direction of the arrow is determined based on the actual configuration of the robot arm and information related to the desired orientation of the robot tool flange, such as the actual orientation of the robot arm, the orientation relative to the previous orientation of the forces and torques obtained. For example, Figure 8a and Figure 8b As shown, Figure 8a The arrow 898a in FIG. 8 has changed to responsive to the change in the actual orientation of the robot arm. Figure 8b Arrow 898b in.

[0153] exist Figure 8c In the embodiment of the present invention, the robot tool flange has been arranged in the desired orientation, and a command prompt 890b indicating "the orientation of the robot tool flange is correct" is displayed on the display. The user is informed that the robot tool flange is arranged in a certain orientation for obtaining the payload information of the payload. The user can then confirm the orientation after the controller continues.

[0154] The illustrated screens of the interface device are only used to illustrate possible implementations of user instructions, a first representation, a second representation of the robot tool flange, which can be used to assist the user in obtaining payload information of a payload attached to the robot tool flange using the robot and method according to the present invention. It should be noted that the illustrated screens have been simplified and the skilled person will be able to provide additional elements to the screens, such as control icons, menu additional graphics.

[0155] Brief Description of Figure Numbers

[0156] 101: Robotic Arm

[0157] 103a-103e: Robotic joints

[0158] 105: Robot base

[0159] 107: Robot tool flange

[0160] 109: Payload

[0161] 111a-111f: Rotation axis

[0162] 113: Rotation Arrow

[0163] 115: Robot tool flange coordinate system

[0164] 117: Center of mass of payload

[0165] 119: Robot base coordinate system

[0166] 121: Direction of gravity

[0167] 125: Controller

[0168] 127: Interface Device

[0169] 129: Display

[0170] 131: Input device

[0171] 250: Arranging the robot tool flange in multiple orientations

[0172] 251: Arrange the robot tool flange in a first orientation

[0173] 252: Get the orientation of the robot tool flange

[0174] 253: Obtain the force and torque provided to the robot tool flange

[0175] 254: Changing the orientation of the robot tool flange

[0176] 255: Verify that force-torque has been obtained in at least two different orientations

[0177] 256: Verify the orientation of the robot tool flange

[0178] 260: Get the mass of the payload

[0179] 270: Get the payload posture

[0180] 280: Controlling a robot based on the mass and pose of the payload

[0181] 361: Obtaining the force difference between two different orientations

[0182] 362: Obtain the mass of the payload based on the force difference obtained

[0183] 371: Get the torque difference between two orientations

[0184] 372: Obtaining the payload posture based on the torque difference obtained

[0185] 463: Provides a guess at the mass of the payload 464: Provides expected forces in two orientations based on the guess at the mass

[0186] 465: Determine the expected force difference between two expected forces in the expected force

[0187] 466: Determine force error based on obtained force difference and expected force difference

[0188] 467: Providing Payload Mass by Minimizing Force Error

[0189] 468: Ring

[0190] 573: Provide a guess about the payload's pose

[0191] 574: Providing expected torque in two orientations based on a guess about the pose

[0192] 575: Determine the expected torque difference between two expected torques in the expected torque

[0193] 576: Determine torque error based on obtained torque difference and expected torque difference

[0194] 577: Providing payload posture by minimizing torque error

[0195] 578: Ring

[0196] 690a: Command prompt: "Place the robot flange in the 1st orientation!".

[0197] 690b: Command prompt: "Change the orientation of the robot tool flange to a second orientation relative to gravity"

[0198] 691: Confirm icon

[0199] 692a-692b: First representation of the robot tool flange

[0200] 693a: Image showing a possible configuration of a portion of a robotic arm with the robotic tool flange arranged in a 1st orientation

[0201] 693b: Image showing a possible configuration of a portion of a robotic arm with the robotic tool flange arranged in a second orientation

[0202] 694a-694b: Symbols indicating the orientation of the robot tool flange

[0203] 695: Gravity Orientation

[0204] 792a-792b: First representation of the robot tool flange

[0205] 796: Second representation of the robot tool flange

[0206] 797: Image showing actual configuration of a portion of a robot

[0207] 890a: Command prompt: "Rotate the robot tool flange as shown by the arrow!".

[0208] 890b: Command prompt: "The orientation of the robot tool flange is correct"

[0209] 898a-898b: Arrow indicating direction of rotation

Claims

1. A method for obtaining payload information of a payload of a robot tool flange attached to a robot arm, wherein the robot arm comprises a plurality of robot joints connecting a robot base and the robot tool flange, characterized in that The method comprises: the step of arranging said robotic tool flange in a plurality of different orientations, including the step of changing said orientation of said robotic tool flange relative to gravity; the step of obtaining, in each of said different orientations, a force and torque provided to said robotic tool flange by gravity acting on said payload using a force-torque sensor arranged at said robotic tool flange; deriving a mass of the payload based on the derived forces obtained in at least two of the different orientations, and deriving a pose of the payload relative to the robotic tool flange based on the mass of the payload and the derived torque in at least two of the different orientations; wherein the step of changing the orientation of the robotic tool flange comprises the step of rotating the tool flange relative to gravity such that the angle between the robotic tool flange and gravity is different for each of the plurality of different orientations, and The step of arranging the robotic tool flange in the plurality of different orientations relative to gravity includes the step of rotating the robotic tool flange about an axis that is non-parallel and non-perpendicular to gravity.

2. The method according to claim 1, characterized in that The step of obtaining the mass of the payload based on the obtained forces in the at least two different orientations comprises the following steps: obtaining at least one obtained force difference, wherein the obtained force difference is obtained as a difference between two of the obtained forces obtained at two of the different orientations of the robot tool flange; and - Determining the mass of the payload based on the derived force difference.

3. The method according to claim 2, characterized in that The step of obtaining the mass of the payload based on the obtained forces at the at least two different locations comprises the following steps: Providing an initial guess of the mass of the payload; providing, for at least two of the different orientations of the robotic tool flange, an expected force provided to the robotic tool flange by a payload having a mass corresponding to the initial guess of the mass; determining an expected force difference between at least two of the expected forces in at least two of the different orientations of the tool flange; determining a force error, the force error being indicative of a difference between the achieved force difference and the expected force difference; - Providing the mass of the payload by minimizing the force error.

4. The method according to any one of claims 1 to 3, characterized in that The step of obtaining the pose of the payload relative to the robot tool flange comprises the following steps: obtaining at least one obtained torque difference, wherein the obtained torque difference is obtained as a difference between two of the obtained torques obtained at two of the different orientations of the tool flange; and - Determining the posture of the payload relative to the tool flange based on the derived torque difference and the mass of the payload.

5. The method according to claim 4, characterized in that The step of obtaining the pose of the payload relative to the robot tool flange comprises the following steps: Providing an initial guess of the pose of the payload; providing, for at least two of the different orientations of the robotic tool flange, an expected torque provided to the robotic tool flange by a payload having a pose corresponding to the initial guess of the pose of the payload; determining an expected torque difference between at least two of the expected torques in at least two of the different orientations of the robotic tool flange; determining a torque error, the torque error being indicative of a difference between the achieved torque difference and the expected torque difference; • Providing the pose of the payload by minimizing the torque error.

6. The method according to any one of claims 1 to 3, characterized in that The step of changing the orientation of the robotic tool flange relative to gravity includes the step of changing the orientation of the robotic tool flange by at least 20 degrees relative to at least one other orientation of the robotic tool flange.

7. The method according to any one of claims 1 to 3, characterized in that The step of changing the orientation of the robotic tool flange relative to gravity includes the step of changing the orientation of the robotic tool flange by between 110 degrees and 130 degrees relative to at least one other orientation of the robotic tool flange.

8. The method according to any one of claims 1 to 3, characterized in that The step of arranging the robotic tool flange in a plurality of different orientations includes arranging the robotic tool flange in four different orientations relative to gravity.

9. A method of controlling a robot arm, the robot arm comprising a plurality of robot joints connecting a robot base and a robot tool flange, the method comprising the step of controlling the robot joints based on a kinematic model of the robot and payload information of a payload attached to the robot tool flange, wherein the payload information indicates the mass of the payload and its posture relative to the robot tool flange, characterized in that The method comprises the step of obtaining the mass and the pose of the payload, said step comprising the method according to any one of claims 1 to 8.

10. A robot arm, comprising a plurality of robot joints connecting a robot base and a robot tool flange, the robot arm comprising at least one controller, the at least one controller being configured to control the robot joints based on a kinematic model of the robot and payload information of a payload attached to the robot tool flange, wherein the payload information indicates the mass of the payload and the posture thereof relative to the robot tool flange, the controller being configured to obtain the mass of the payload and the posture thereof relative to the robot tool flange based on a force and torque provided to the robot tool flange when the payload is attached to the robot tool flange, wherein the controller is configured to obtain the force and torque from a force-torque sensor attached to the robot tool flange and at a plurality of different orientations of the robot tool flange relative to gravity, characterized in that For each of the plurality of different orientations, the angle between the robot tool flange and gravity is different, and the controller is configured to obtain the mass of the payload and the posture thereof relative to the robot tool flange by executing the method according to any one of claims 1 to 8.

11. The robot arm according to claim 10, characterized in that: The controller is configured to provide user instructions to a user, the user instructions instructing the user to change the orientation of the robotic tool flange relative to gravity.

12. The robot arm according to claim 11, characterized in that: The user instructions instruct a user to rotate the robotic tool flange about an axis that is non-parallel and non-perpendicular to gravity.

13. The robot arm according to any one of claims 10 to 12, characterized in that: The robot arm comprises an interface device comprising a display device on which a first representation of the robot tool flange is shown, the first representation indicating at least one of the different orientations of the robot tool flange.

14. The robot arm according to claim 13, characterized in that: A second representation of the robot tool flange is shown, the second representation indicating an actual orientation of the robot tool flange relative to the first representation of the robot tool flange.

15. The robot arm according to claim 11 or 12, characterized in that: The robot arm comprises an interface device comprising a display device on which a representation of the robot tool flange is shown, wherein the representation indicates an actual orientation of the robot tool flange, and wherein an arrow is shown by the display device, wherein the arrow indicates a rotational direction in which the user should rotate the robot tool flange.

Images