FI125511B - Wired distance detector and system based on it to generate robot calibration data - Google Patents

Wired distance detector and system based on it to generate robot calibration data Download PDF

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Publication number
FI125511B
FI125511B FI20145378A FI20145378A FI125511B FI 125511 B FI125511 B FI 125511B FI 20145378 A FI20145378 A FI 20145378A FI 20145378 A FI20145378 A FI 20145378A FI 125511 B FI125511 B FI 125511B
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FI
Finland
Prior art keywords
cable
orientation
points
drum
terminals
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FI20145378A
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Finnish (fi)
Swedish (sv)
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FI20145378A (en
Inventor
Heikki Handroos
Huapeng Wu
Ming Li
Original Assignee
Lappeenrannan Teknillinen Yliopisto
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Application filed by Lappeenrannan Teknillinen Yliopisto filed Critical Lappeenrannan Teknillinen Yliopisto
Priority to FI20145378A priority Critical patent/FI125511B/en
Priority to EP15721756.3A priority patent/EP3134233A1/en
Priority to CN201580021044.5A priority patent/CN106232303A/en
Priority to PCT/FI2015/050272 priority patent/WO2015162335A1/en
Publication of FI20145378A publication Critical patent/FI20145378A/en
Application granted granted Critical
Publication of FI125511B publication Critical patent/FI125511B/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
    • G01B7/026—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring length of cable, band or the like, which has been paid out, e.g. from a reel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J9/00—Programme-controlled manipulators
    • B25J9/16—Programme controls
    • B25J9/1615—Programme controls characterised by special kind of manipulator, e.g. planar, scara, gantry, cantilever, space, closed chain, passive/active joints and tendon driven manipulators
    • B25J9/1623—Parallel manipulator, Stewart platform, links are attached to a common base and to a common platform, plate which is moved parallel to the base
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
    • B25J9/00—Programme-controlled manipulators
    • B25J9/16—Programme controls
    • B25J9/1679—Programme controls characterised by the tasks executed
    • B25J9/1692—Calibration of manipulator
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B3/00—Measuring instruments characterised by the use of mechanical techniques
    • G01B3/11—Chains for measuring length
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/004—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring coordinates of points
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/37—Measurements
    • G05B2219/37126—Wire, tape around cylinder measures displacement, string encoder
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/39—Robotics, robotics to robotics hand
    • G05B2219/39009—Using fixture with potentiometer, wire to end effector, estimate lenght of wire
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00—Program-control systems
    • G05B2219/30—Nc systems
    • G05B2219/39—Robotics, robotics to robotics hand
    • G05B2219/39024—Calibration of manipulator

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  • Engineering & Computer Science (AREA)
  • Robotics (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Orthopedic Medicine & Surgery (AREA)
  • Manipulator (AREA)
  • Numerical Control (AREA)

Description

A system and a method for generating robot calibration data Field of the invention
The invention relates to a system and a method for generating deviation data which is indicative of inaccuracy of kinematic parameters of a robot and is suitable for calibrating the robot.
Background
In many cases there is a need to detect a distance between two points in a three-dimensional space. For example, when calibrating a robot, there is a need to measure the position and orientation, i.e. six degrees-of-freedom “6-DOF”, of an end-effector of the robot. The robot can be for example an industrial robot comprising at least one manipulator that is an arm-like mechanism that consists of links affixed to each other with joints. The manipulator extends from a base frame of the robot to the end-effector. The end-effector is a device at the end of the manipulator where a tool is attached to the manipulator. The exact nature of the end-effector depends on the application of the robot, and in a wider sense, the end effector can be seen as the part of a robot that interacts with the work environment. The position and orientation of the end-effector in a workspace coordinate system fixed to the base frame of the robot is determined by states of the joints of the manipulator. The states of the joints are typically expressed with the aid of joint variables which indicate the instantaneous states, e.g. angles of rotation, of the joints. Estimate position and orientation of the end-effector can be calculated on the basis of prevailing joint variables and the forward-kinematics based on kinematic parameters of the manipulator. Correspondingly, the joint variables needed for setting the end-effector in a desired position and orientation can be calculated on the basis of the desired position and orientation and the inverse-kinematics based on the kinematic parameters.
In order to provide sufficiently accurate operation of the robot, the estimate position and orientation based on the joint variables and the kinematic parameters have to correspond to the real position and orientation of the end-effector with a sufficient accuracy. Thus, the above-mentioned kinematic parameters have to reflect the real kinematics of the manipulator accurately enough. Furthermore, the kinematic parameters should compensate for non-idealities of the joints and possible systematic errors in the joint parameters. In order to maintain the sufficient accuracy of the kinematic parameters, there is in many cases a need to calibrate the kinematic parameters not only during commissioning of the robot but also periodically relating to the course of usage of the robot. The calibration is based on deviation data indicative of inaccuracy in the above-mentioned kinematic parameters. The deviation data can be obtained by comparing the estimate position and orientation based on the joint variables and the kinematic parameters to a reference estimate of the position and orientation of the end-effector. The reference estimate can be obtained by measuring distances from a plurality of base points fixed with respect to the workspace coordinate system to end-effector points fixed with respect to the end-effector and by computing the position and orientation of the end-effector on the basis of known locations of the base-points and the measured distances. The challenge of this approach is related to the need to measure the above-mentioned distances in a sufficiently accurate way.
Summary
The following presents a simplified summary in order to provide a basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention.
In accordance with the invention, there is provided a new system for generating deviation data indicative of inaccuracy in kinematic parameters of a robot. The robot comprises an end-effector whose estimate position and orientation in a workspace coordinate system fixed with respect to a base frame of the robot are determined by joint variables related to the robot and by forward-kinematics based on the kinematic parameters. A system according to the invention comprises: - a distance detector in a fixed position with respect to the base frame of the robot and configured to measure a plurality of distances each being a distance from one of base points of the distance detector to one of end-effector points in fixed positions with respect to the end-effector, and - a controller for computing position and orientation of the end-effector in the workspace coordinate system on the basis of the plurality of the distances and for forming data indicative of a deviation between the computed position and orientation and the estimate position and orientation so as to generate the deviation data.
The distance detector comprises a plurality of cable-based distance detectors so that the cable of each of the cable-based distance detector extends though one of the base points to one of the end-effector points and an encoder signal produced by the cable-based distance detector under consideration is indicative of the distance from the base point under consideration to the end-effector point under consideration.
Each of the above-mentioned cable-based distance detectors comprises: - a winding drum for winding the cable, - a torque generator for directing torque to the winding drum so as to retract the cable, - a measurement drum configured to be rotated by the cable in a first direction response to winding the cable in by the winding drum and in a second direction in response to winding the cable off from the winding drum, and - an encoder connected to the measurement drum and configured to produce the encoder signal indicative of revolutions of the measurement drum and also the length of a portion of the cable caused the revolutions of the measurement drum.
When the cable winds around the winding drum, portions of the cable gets typically a helical form on the winding drum and furthermore the cable overlaps with itself when the winding drum has turned some revolutions. These factors cause variation between the lengths of different turns of the cable on the winding drum. This would cause a measurement error if the measurement were based on the revolutions of the winding drum. As the above-described cable-based distance detector comprises the measurement drum in addition to the winding drum, the variation between the lengths of different turns of the cable on the winding drum does not have any impact on the measurement and thus the length of the cable wound in or off can be measured more accurately.
The cables, the base points, and the end-effector points are advantageously arranged to constitute a 3-2-1 Stewart configuration. The forward kinematics of the 3-2-1 Stewart configuration can be solved analytically, and the six Cartesian coordinates defining the position and orientation of the end-effector can be calculated using the lengths of the six limbs of the 3-2-1 Stewart configuration, i.e. the measured distances from the base points to the end-effector points.
In accordance with the invention, there is provided also a new method for generating deviation data indicative of inaccuracy in kinematic parameters of a robot that comprises an end-effector whose estimate position and orientation in a workspace coordinate system fixed with respect to a base frame of the robot are determined by joint variables related to the robot and by forward-kinematics based on the kinematic parameters, The method comprises: - measuring a plurality of distances each being a distance from one of base points in fixed positions with respect to the base frame to one of end-effector points in fixed positions with respect to the end-effector, and - computing position and orientation of the end-effector in the workspace coordinate system on the basis of the plurality of the distances, and - forming data indicative of a deviation between the computed position and orientation and the estimate position and orientation so as to generate the deviation data.
The above-mentioned distances are measured with cable-based distance detectors of the kind described above. The cable of each of the cable-based distance detectors extends though one of the base points to one of the end-effector points and the encoder signal produced by the cable-based distance detector under consideration is indicative of the distance from the base point under consideration to the end-effector point under consideration.
In accordance with the invention, there is provided also a new calibration method for calibrating a robot. A calibration method according to the invention comprises: - carrying out the above-described method for generating the deviation data, and - updating the kinematic parameters of the robot on the basis of the deviation data.
In a calibration method according to an exemplifying and non-limiting embodiment of the invention, the method for generating the deviation data is carried out at least two times, and more preferably at least three times, so that the position of the end-effector is different at each time. The kinematic parameters are updated on the basis of data containing the deviation data obtained for each of the different positions of the end-effector so as to improve the accuracy of the robot calibration.
A number of exemplifying and non-limiting embodiments of the invention are described in accompanied dependent claims.
Various exemplifying and non-limiting embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying and non-limiting embodiments when read in connection with the accompanying drawings.
The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of unrecited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does not exclude a plurality.
Brief description of the figures
Exemplifying and non-limiting embodiments of the invention and their advantages are explained in greater detail below in the sense of examples and with reference to the accompanying drawings, in which: figures 1a and 1b show schematic illustrations of cable-based distance detector suitable for a system according to an exemplifying and non-limiting embodiment of the invention for generating deviation data indicative of inaccuracy in kinematic parameters of the robot, figure 2a illustrates of a robot and a system according to an exemplifying and nonlimiting embodiment of the invention for generating deviation data indicative of inaccuracy in kinematic parameters of the robot, figure 2b illustrates elements of a system according to an exemplifying and nonlimiting embodiment of the invention, figures 2c and 2d illustrate exemplifying mutual positions and orientations of elements of a system according to an exemplifying and non-limiting embodiment of the invention, figure 3 shows a flowchart of a measurement method suitable for a method according to an exemplifying and non-limiting embodiment of the invention for generating deviation data indicative of inaccuracy in kinematic parameters of a robot, and figure 4 shows a flowchart of a method according to an exemplifying and nonlimiting embodiment of the invention for generating deviation data indicative of inaccuracy in kinematic parameters of a robot.
Description of exemplifying and non-limiting embodiments
Figures 1 a and 1 b show schematic illustrations of cable-based distance detector suitable for a system according to an exemplifying and non-limiting embodiment of the invention for generating deviation data indicative of inaccuracy in kinematic parameters of the robot. The cable-based distance detector comprises a winding drum 101 for winding a cable 110 and a torque generator 102 for directing torque to the winding drum so as to retract the cable. In this exemplifying case, the torque generator 102 comprises a winding spring which stores mechanical energy when the cable is drawn out from the cable-based distance detector and which makes the winding drum to wind the cable in when the cable is allowed to move into the cable-based distance detector. In principle it is also possible that the torque generator comprises e.g. a rotating electrical machine driven with regulated current. The cable-based distance detector comprises a measurement drum 103 configured to be rotated by the cable in a first direction response to winding the cable in by the winding drum 101 and in a second direction in response to winding the cable off from the winding drum. The cable-based distance detector comprises an encoder 104 connected to the measurement drum and configured to produce an encoder signal S indicative of revolutions of the measurement drum. Thus, the encoder signal S is indicative of also the length of a portion of the cable which has caused the above-mentioned revolutions of the measurement drum 103. The encoder 104 can be for example a pulse encoder which produces e.g. 10000 pulses per revolution “PPR”.
The cable-based distance detector may further comprise a press roller 105 and a spring 106 for making the press roller to press the cable 110 against the measurement drum 103 so as to avoid slip between the cable and the measurement drum.
The cable-based distance detector may further comprise a first cable guide 107 for guiding the cable to get in contact with the measurement drum 103 in a given position in the axial direction of the measurement drum when the cable is being wound in by the winding drum. The first cable guide 107 comprises a hole or a slot for guiding the cable. The axial direction of the measurement drum is parallel with the z-direction of a coordinate system 199.
The cable-based distance detector may further comprise a second cable guide 108 for guiding the cable to get in contact with the measurement drum 103 in a given position in the axial direction of the measurement drum when the cable is being wound off from the winding drum. The second cable guide 108 comprises a hole or a slot for guiding the cable.
The measurement drum 103 may comprise a circumferential slot 109 for the cable so as to ensure that the cable contacts the measurement drum in a given position in the axial direction of the measurement drum. The combination of the press roller 105, the slot 109, and the cable guides 107 and 108, provides a significant certainty that the cable travels in and out in the same position. As a result, the travelling length of the cable can be measured accurately on the basis of the rotations of the measurement drum.
The cable can be arranged to wind one or two circles around the measurement drum 103 without any gap in between and without any overlap to each other so as to avoid any slip between the cable and the measurement drum. In figure 1a, this is illustrated with a dashed line arch 125. The above-mentioned circumferential slot can be designed to allow the cable to wind the one or two circles around the measurement drum 103. Axially directed gaps and overlaps between the circles of the cable can be avoided with a suitable design of the slot and/or with the aid of the cable guides 107 and 108 and the press roller 105 which control how the cable contacts the measurement drum. Furthermore, there can be more than one spring-driven press roller for pressing the cable against the measurement drum.
Figure 2a illustrates of a robot and a system according to an exemplifying and non-limiting embodiment of the invention for generating deviation data indicative of inaccuracy in kinematic parameters related to the robot. The robot can be for example an industrial robot. The robot comprises a manipulator 215 that comprises links 216, 217, 218, and 219 affixed to each other with joints 221, 222, 223, and 224. The manipulator 215 extends from a base frame 220 to an end-effector 232 which is a device at the end of the manipulator where a tool is attached to the manipulator. The exact nature of the end-effector 232 depends on the application of the robot. A robot controller 227 is communicatively connected to the manipulator 215, and the robot controller comprises computing means for controlling the manipulator to operate in a desired way. A teaching board 228 is connected to the ro- bot controller 227, and the teaching board comprises a conventional manual key, whereby an operator may manually operate the robot.
The position and orientation of the end-effector 232 in a workspace coordinate system 299 is determined by states of the joints 221-224. The workspace coordinate system 299 is fixed with respect to the base frame 220 but the origin of the workspace coordinate system does not have to be at the base frame. The states of the joints 221 -224 are typically expressed with the aid of joint variables which indicate the instantaneous states, e.g. the angles of rotation, of the joints. Estimate position and orientation of the end-effector 232 in the coordinate system 299 can be calculated on the basis of prevailing joint variables and the forward-kinematics based on the kinematic parameters of the manipulator. Correspondingly, the joint variables needed for setting the end-effector in a desired position and orientation in the coordinate system 299 can be calculated on the basis of the desired position and orientation and the inverse-kinematics based on the kinematic parameters.
The system for generating the above-mentioned deviation data comprises a distance detector 211 that is mechanically supported to be in a fixed position with respect to the base frame 220 of the robot. The distance detector 211 is configured to measure a plurality of distances each being a distance from one of base points of the distance detector to one of end-effector points in fixed positions with respect to the end-effector 232. In the exemplifying case illustrated in figure 2b, there are the base points 213a, 213b, 213c, 213d, 213e and 213f, and the end-effector points 214a, 214b and 214c. In the exemplifying case illustrated in figure 2a, the end-effector points 214a, 214b and 214c are implemented with the aid of a measurement element 225 that is attached to the end-effector 232.
The system comprises a controller 212 for computing the position and orientation of the end-effector 232 in the workspace coordinate system 299 on the basis of the measured the distances. The controller 212 can be for example an ordinary computer. In this exemplifying case, the controller 212 is communicatively connected to the robot controller 227 via a data switch element 226. In order to generate the deviation data, the controller 212 is configured to form data indicative of the deviation between the computed position and orientation of the end-effector and the estimate position and orientation based on the joint variables and the forward kinematics of the manipulator 215. The controller 212 may have its own means for calculating the estimate position and orientation on the basis of the joint variables and the forward kinematics of the manipulator. Alternatively, the controller 212 can be configured to utilize the robot controller 227 for calculating the estimate position and orientation.
The distance detector 211 comprises a plurality of cable-based distance detectors of the kind described above with reference to figures 1a and 1b. The cable-based distance detectors are inside the distance detector 211 and thus the cable-based distance detectors are not visible in figure 2a. Each of the cable-based distance detectors can be for example such as illustrated in figures 1 a and 1 b. The cables of the cable-based distance detectors extend through apertures representing the above-mentioned base points 213a-213f. The ends of the cables are attached to the above-mentioned end-effector points 214a-214c. The encoder signal produced by each cable-based distance detector is indicative of the distance from the respective base point to the respective end-effector point. In the exemplifying case illustrated in figure 2b, the cables are arranged to constitute a 3-2-1 Stewart configuration where the cables 210b, 210c and 21 Od related to first, second, and third ones of the base points 213b, 213c and 213d are connected to a first one of the end-effector points 214b, the cables 210a and 21 Of related to fourth and fifth ones of the base points 213a and 213f are connected to a second one of the end-effector points 214a, and the cable related to a sixth one of the base points 213e is connected to a third one of the end-effector points 214c. The forward kinematics of the 3-2-1 Stewart configuration can be solved analytically and the six Cartesian coordinates defining the position and orientation of the end-effector can be calculated using the lengths of the six limbs of the 3-2-1 Stewart configuration, i.e. the measured distances from the base points to the end-effector points.
In a system according to another exemplifying and non-limiting embodiment of the invention, the cables are arranged to constitute a 2-2-2 configuration where the cables related to the first and second ones of the base points are connected to the first one of the end-effector points, the cables related to the third and fourth ones of the base points are connected to the second one of the end-effector points, and the cables related to the fifth and sixth ones of the base points are connected to the third one of the end-effector points.
Figure 2b illustrates a distance detector 241 and a measurement element 245 of a system according to an exemplifying and non-limiting embodiment of the invention where the number of the base points is greater than six. In this exemplifying case, the distance detector 241 comprises nine cable-based distance detectors whose cables are drawn through apertures representing the nine base points 213a, 213b, 213c, 213d, 213e, 213f, 213g, 213h and 213i. The cable-based distance detectors are not visible in figure 2b. The measurement element 245 comprises end-effector points 231a, 231 b and 231 c where the cables can be attached to.
In a system according to an exemplifying and non-limiting embodiment of the invention where the number of the base points is greater than six, the controller 212 shown in figure 2a is configured to compute a set of preliminary values for the position and orientation of the end-effector 232 on the basis of encoder signals related to mutually different six-member subsets of the base points and to compute the position and orientation of the end-effector on the basis of the preliminary values. For example, in the case illustrated in figure 2b, a first six-member subset of the base points may comprises e.g. the base points 213a-213f and a second six-member subset may comprise e.g. the base points 213a, 213g, 213c, 213h, 213e and 213i. It is worth noting that there are up to 84 different possibilities to select a six-member subset out of the nine base points.
For example, the controller 212 can be configured to compute numerical values defining the position and orientation of the end-effector to be weighted averages of mutually corresponding numerical values related to the mutually different six-member subsets so as to compute the position and orientation of the end-effector 232 on the basis of the preliminary values. For example, the x-coordinate of the end-effector can be a weighted average of the x-coordinates obtained with the different six-member subsets. The controller can be configured to set a weight for each of the six-member subsets on the basis of a minimum change of the encoder signals related to the six-member subset under consideration and to movement of the end-effector from a previous position and orientation to the position and orien- tation being computed so that a smaller minimum change of the encoder signals corresponds to a smaller weight than a greater minimum change of the encoder signals corresponds to. The purpose of the above-mentioned way of selecting the weights is to suppress the influence of such distance measurements whose relative accuracy may be poorer than that of the other distance measurements.
In a system according to another exemplifying and non-limiting embodiment of the invention where the number of the base points is greater than six, the controller 212 is configured to select six ones of the base points so that such one or more of the base points, relating to which there are smallest changes of the encoder signals when the end-effector is moved from a previous position and orientation to the position and orientation being computed, are left out from the selected six ones of the base points. The controller is configured to compute the position and orientation of the end-effector 232 on the basis of the encoder signals related to the selected six ones of the base points. In this case, such distance measurements whose relative accuracy may be poorer than that of the other distance measurements are left out from the consideration.
Figures 2c and 2d illustrate exemplifying mutual positions and orientations of the distance detector 211 and the measurement element 225. Figure 2c shows a situation where the measurement element 225 is mated with the distance detector 211. The mutual position and orientation of the measurement element 225 and the distance detector 211 shown in figure 2c can be regarded as absolute zero position and orientation and all the mechanical and cable dimensions can be calibrated in advance in this situation so as to improve the measurement accuracy. When the measurement element 225 has been mounted to the end-effector 232, the new particular position and orientation shown in figure 2d can be regarded as new zero position and orientation according to case-specific needs, and all the measurement thereafter conducted can be referred to the new zero position and orientation.
A system according to an exemplifying and non-limiting embodiment of the invention comprises a temperature sensor 230 and the controller 212 is configured to correct the encoder signals on the basis of the thermal expansion coefficient of the material of the cables and a measured change of temperature. When the temperature is changing, the encoder signals related to a given position and orientation of the end-effector may change because the cables get deformed due to the temperature change. For example, the encoder signals corresponding to the above-mentioned new zero position and orientation shown in figure 2d may change due to temperature changes.
In a system according to an exemplifying and non-limiting embodiment of the invention, the controller 212 is configured to correct the encoder signals on the basis of elasticity of the cables and estimates of tensions acting on the cables. An estimate for the tension can be obtained for example on the basis of known properties of a cable-based distance detector, e.g. the force generated by a winding spring as a function of the measured distance, i.e. the amount of the cable drawn out.
The deviation data indicative of the inaccuracy in the kinematic parameters can be used as input data for a suitable calibration algorithm which updates the kinematic parameters. In a system according an exemplifying and non-limiting embodiment of the invention, the controller 212 is configured to update the kinematic parameters on the basis of the deviation data. The format of the deviation data and the way how the deviation data has to express the deviation between the computed position and orientation and the estimate position and orientation based on the joint variables depend typically on the calibration algorithm being used. In a system according an exemplifying and non-limiting embodiment of the invention, the controller 212 is configured to carry out the above-described process for obtaining the deviation data at least two times, and more preferably at least three times, so that the position of the end-effector 232 is different at each time. The kinematic parameters are updated on the basis of data containing the deviation data obtained for each of the different positions of the end-effector.
Figure 3 shows a flowchart of a measurement method for measuring a length of a portion of a cable wound in by, or off from, a winding drum of a cable-based distance detector. The measurement method comprises the following actions: - action 301: arranging the cable to rotate a measurement drum when the cable is wound in by, or off from, the winding drum, the measurement drum being separate with respect to the winding drum, and - action 302: producing an encoder signal indicative of revolutions of the measurement drum when the cable is wound in by, or off from, the winding drum, the encoder signal being indicative of also the length of the portion of the cable wound in by, or off from, the winding drum.
The measurement method may further comprise pressing the cable against the measurement drum with a spring-driven press roller so as to avoid slip between the cable and the measurement drum.
The measurement method may further comprise guiding the cable with a first cable guide to get in contact with the measurement drum in a given position in the axial direction of the measurement drum when the cable is wound in by the winding drum.
The measurement method may further comprise guiding the cable with a second cable guide to get in contact with the measurement drum in a given position in the axial direction of the measurement drum when the cable is wound off from the winding drum.
The measurement drum may comprise a circumferential slot for the cable so as to ensure that the cable contacts the measurement drum in a given position in the axial direction of the measurement drum.
The cable can be arranged to wind one or two circles around the measurement drum without any gap in between and without any overlap to each other so as to avoid any slip between the cable and the measurement drum. The above-mentioned circumferential slot can be designed to allow the cable to wind the one or two circles around the measurement drum. Overlaps and axially directed gaps between the circles of the cable can be avoided with a suitable design of the slot and/or with the aid of the above-mentioned first and second cable guides and the spring-driven press roller which control how the cable contacts the measurement drum. Furthermore, there can be more than one spring-driven press roller for pressing the cable against the measurement drum.
Figure 4 shows a flowchart of a method according to an exemplifying and nonlimiting embodiment of the invention for generating deviation data indicative of inaccuracy in kinematic parameters of a robot. The robot comprises an end-effector whose estimate position and orientation in a workspace coordinate system fixed with respect to a base frame of the robot are determined by joint variables related to the robot and by the forward-kinematics based on the kinematic parameters. The method comprises the following actions: - action 401: measuring a plurality of distances each being a distance from one of base points in fixed positions with respect to the base frame to one of end-effector points in fixed positions with respect to the end-effector, and - action 402: computing position and orientation of the end-effector in the workspace coordinate system on the basis of the plurality of the distances, and - action 403: forming data indicative of a deviation between the computed position and orientation and the estimate position and orientation so as to generate the deviation data.
Each of the distances is measured with the above-described measurement method 301-302 so that the cable of each of the cable-based distance detectors extends though one of the base points to one of the end-effector points and the encoder signal produced by the cable-based distance detector under consideration is indicative of the distance from the base point under consideration to the end-effector point under consideration.
In a method according to an exemplifying and non-limiting embodiment of the invention, the cables related to first, second, and third ones of the base points are connected to a first one of the end-effector points, the cables related to fourth and fifth ones of the base points are connected to a second one of the end-effector points, and the cable related to a sixth one of the base points is connected to a third one of the end-effector points so as to constitute a 3-2-1 Stewart configuration for the position and orientation detection.
In a method according to another exemplifying and non-limiting embodiment of the invention, the cables related to first and second ones of the base points are connected to a first one of the end-effector points, the cables related to third and fourth ones of the base points are connected to a second one of the end-effector points, and the cables related to fifth and sixth ones of the base points are connected to a third one of the end-effector points so as to constitute a 2-2-2 configuration for the position and orientation detection.
In a method according to an exemplifying and non-limiting embodiment of the invention, the number of the base points is greater than six and the method comprises computing a set of preliminary values for the position and orientation of the end-effector on the basis of encoder signals related to mutually different six-member subsets of the base points and computing the position and orientation of the end-effector on the basis of the preliminary values.
The position and orientation of the end-effector can be computed on the basis of the preliminary values for example by computing numerical values defining the position and orientation of the end-effector as weighted averages of mutually corresponding numerical values related to the mutually different six-member subsets. The weight for a given one of the six-member subsets can be set for example on the basis of a minimum change of the encoder signals related to the six-member subset under consideration and to movement of the end-effector from a previous position and orientation to the position and orientation being computed so that a smaller minimum change of the encoder signals corresponds to a smaller weight than a greater minimum change of the encoder signals corresponds to.
In a method according to an exemplifying and non-limiting embodiment of the invention where the number of the base points is greater than six, six ones of the base points are selected so that such one or more of the base points, relating to which there are smallest changes of the encoder signals when the end-effector is moved from a previous position and orientation to the position and orientation being computed, are left out from the selected six ones of the base points. The method further comprises computing the position and orientation of the end-effector on the basis of the encoder signals related to the selected six ones of the base points.
A method according to an exemplifying and non-limiting embodiment of the invention comprises correcting the encoder signals on the basis of the thermal expansion coefficient of the material of the cables and a measured change of temperature.
A method according to an exemplifying and non-limiting embodiment of the invention comprises correcting the encoder signals on the basis of elasticity of the cables and estimates of tensions acting on the cables.
A calibration method according to an exemplifying and non-limiting embodiment of the invention comprises: - the above-described sequence of actions 401-403 for generating the deviation data, and - action 404: updating the kinematic parameters of the robot on the basis of the deviation data.
In a calibration method according to an exemplifying and non-limiting embodiment of the invention, the sequence of the actions 401-403 for generating the deviation data is carried out at least two times, and more preferably at least three times, so that the position of the end-effector is different at each time. The kinematic parameters are updated on the basis of data containing the deviation data obtained for each of the different positions of the end-effector.
The specific examples provided in the description given above should not be construed as limiting the scope and/or the applicability of the appended claims.

Claims (27)

1. Järjestelmä robotin kinemaattisten parametrien epätarkkuuden osoittavan poikkeamadatan generoimiseksi, joka robotti käsittää päätetyökalun, jonka likimääräinen asento ja orientaatio robotin jalustarungon suhteen kiinteässä työskentelytilan koordinaatistossa määritellään robottikohtaisilla niveltilamuuttujilla ja kinemaattisiin parametreihin perustuvalla suoralla kinematiikalla, joka järjestelmä käsittää: - etäisyysilmaisimen (211) kiinteässä asennossa robotin jalustarunkoon nähden ja konfiguroituna mittaamaan joukko välimatkoja, joista kukin on välimatka yhdestä etäisyysilmaisimen peruspisteiden (213a-213f) joukosta yhteen päätetyökaluun nähden kiinteästi sijaitsevista päätetyökalun pisteistä (214a-214c), ja - kontrollerin (212) päätetyökalun asennon ja orientaation laskemiseksi työskentelytilan koordinaatistossa kyseisen välimatkojen joukon perusteella ja lasketun asennon ja orientaation ja likimääräisen asennon ja orientaation välisen poikkeaman osoittavan datan muodostamiseksi poikkeamadatan generoimista varten, tunnettu siitä, että etäisyysilmaisin käsittää joukon kaapelipohjaisia etäisyysil-maisimia siten, että kunkin kaapelipohjaisen etäisyysilmaisimen kaapeli (210a-21 Of) ulottuu peruspisteistä yhden kautta yhteen päätetyökalun pisteistä ja kyseessä olevan kaapelipohjaisen etäisyysilmaisimen tuottama kooderisignaali osoittaa välimatkan kyseessä olevasta peruspisteestä kyseessä olevaan päätetyökalun pisteeseen, kunkin kaapelipohjaisen etäisyysilmaisimen käsittäessä: kelausrum-mun (101) kyseisen kaapelipohjaisen etäisyysilmaisimen kaapelin (110) kelaami-seksi, vääntömomenttigeneraattorin (102) vääntömomentin suuntaamiseksi ke-lausrumpuun kaapelin vetämiseksi sisään, mittausrummun (103), joka on konfigu-roitu pyöritettäväksi kaapelin toimesta ensimmäiseen suuntaan vasteena sille, että kelausrumpu kelaa kaapelin sisään, ja toiseen suuntaan vasteena sille, että kaapeli tulee kelatuksi pois kelausrummulta, ja kooderin (104), joka on kytketty mitta-usrumpuun ja konfiguroitu tuottamaan mittausrummun kierrokset osoittava kooderisignaali.1. A system for generating inaccurate deviation data for a robot's kinematic parameters, comprising a terminal tool whose approximate position and orientation with respect to the robot base frame in a fixed working space coordinate system is determined by a robot-specific articulation variable and configured to measure a plurality of distances, each of which is a distance from one of a plurality of detector datum points (213a-213f) to one of a plurality of terminal tool points (214a-214c) fixed to one end tool, and and between the calculated position and orientation and the approximate position and orientation generating offset data for generating offset data, characterized in that the distance detector comprises a plurality of cable-based distance detectors such that the cable (210a-21 Of) of each cable-based distance detector extends from the base points to one of the terminals of the from the base point to the respective end tool point, each cable distance detector comprising: a coil drum (101) for winding the cable (110) of said cable distance detector, for applying a torque generator (102) to a rotating drum 103, -buckled for rotation by the cable in the first direction in response to the winding drum winding in the cable and in the other direction in response to the cable i.e., winding out of the winding drum, and an encoder (104) coupled to the measuring drum and configured to produce an encoder signal indicative of the revolutions of the measuring drum. 2. Patenttivaatimuksen 1 mukainen järjestelmä, jossa peruspisteistä (213b, 213c, 213d) ensimmäiseen, toiseen ja kolmanteen liittyvät kaapelit on yhdistetty ensimmäiseen päätetyökalun pisteistä (214b), peruspisteistä (213a, 213f) neljänteen ja viidenteen liittyvät kaapelit on yhdistetty toiseen päätetyökalun pisteistä (214a), ja peruspisteistä (213e) kuudenteen liittyvä kaapeli on yhdistetty kolmanteen päätetyökalun pisteistä (214c) 3-2-1 Stewart konfiguraation muodostamiseksi asennon ja orientaation ilmaisemista varten.The system of claim 1, wherein the cables connected to the first, second and third of the base points (213b, 213c, 213d) are connected to the first terminals (214b), the fourth and fifth cables of the base points (213a, 213f) connected to the second terminals (214a). ), and a cable associated with a sixth of the base points (213e) is connected to the third end tool points (214c) to form a 3-2-1 Stewart configuration for indicating position and orientation. 3. Patenttivaatimuksen 1 mukainen järjestelmä, jossa peruspisteistä ensimmäiseen ja toiseen liittyvät kaapelit on yhdistetty ensimmäiseen päätetyökalun pisteistä, peruspisteistä kolmanteen ja neljänteen liittyvät kaapelit on yhdistetty toiseen päätetyökalun pisteistä, ja peruspisteistä viidenteen ja kuudenteen liittyvät kaapelit on yhdistetty kolmanteen päätetyökalun pisteistä 2-2-2 konfiguraation muodostamiseksi asennon ja orientaation ilmaisemista varten.The system of claim 1, wherein the cables connected to the first and second base points are connected to the first terminals of the terminal tool, the cables connected to the third and fourth base points are connected to the second terminals of the terminal tool and the cables related to the fifth and sixth terminals are connected from 2-2-2 of the configuration to form a position and orientation. 4. Jonkin patenttivaatimuksen 1-3 mukainen järjestelmä, jossa peruspisteiden lukumäärä on suurempi kuin kuusi ja kontrolleri on konfiguroitu laskemaan joukko ennakkoarvoja päätetyökalun asennolle ja orientaatiolle peruspisteiden keskenään erilaisiin kuusijäsenisiin osajoukkoihin liittyvien kooderisignaalien perusteella ja laskemaan päätetyökalun asento ja orientaatio kyseisten ennakkoarvojen perusteella.The system of any one of claims 1 to 3, wherein the number of datum points is greater than six and the controller is configured to compute a plurality of predetermined values for the position and orientation of the terminal tool based on encoder signals associated with different six-member subsets. 5. Patenttivaatimuksen 4 mukainen järjestelmä, jossa kontrolleri on konfiguroitu laskemaan päätetyökalun asennon ja orientaation määrittävät numeeriset arvot olemaan keskenään erilaisiin kuusijäsenisiin osajoukkoihin liittyvien keskenään vastaavien numeeristen arvojen painotettuja keskiarvoja päätetyökalun asennon ja orientaation laskemiseksi ennakkoarvojen perusteella, ja kontrolleri on konfiguroitu asettamaan kuusijäsenisistä osajoukoista kunkin paino kyseessä olevaan kuusijäseniseen osajoukkoon ja päätetyökalun liikkeeseen edellisestä asennosta ja orientaatiosta laskettavaan asentoon ja orientaatioon liittyvien kooderignaalien minimi-muutoksen perusteella siten, että kooderisignaalien pienempi minimimuutos vastaa pienempää painoa kuin se, jota kooderisignaalien suurempi minimuutos vastaa.The system of claim 4, wherein the controller is configured to compute numerical values defining the position and orientation of the terminal tool to be weighted averages of corresponding numerical values associated with different six-member subsets based on the predefined values, and the controller is configured to determine based on the minimum change in encoder signals associated with the six-member subset and the movement of the terminal tool relative to the position and orientation calculated from the previous position and orientation such that the smaller minimum change in the encoder signals corresponds to less weight than the higher minimum change in the encoder signals. 6. Jonkin patenttivaatimuksen 1-5 mukainen järjestelmä, jossa peruspisteiden lukumäärä on suurempi kuin kuusi ja kontrolleri on konfiguroitu valitsemaan peruspisteiden joukosta kuusi kappaletta siten, että sellainen yksi tai useampi perus-pisteistä, johon kooderisignaalien pienimmät muutokset liittyvät silloin kun pääte-työkalu tulee liikutetuksi edellisestä asennosta ja orientaatiosta laskettavaan asentoon ja orientaatioon, jätetään pois peruspisteistä valittujen kuuden kappaleen joukosta, ja kontrolleri on konfiguroitu laskemaan päätetyökalun asento ja orientaatio peruspisteistä valittuihin kuuteen kappaleeseen liittyvien kooderisignaalien perusteella.The system of any one of claims 1 to 5, wherein the number of datum points is greater than six and the controller is configured to select from six datum points such that one or more of the datum points to which the smallest changes in encoder signals are associated when the terminal tool is moved from position and orientation to calculated position and orientation, is omitted from the six points selected from the datums, and the controller is configured to calculate the position and orientation of the terminal tool based on the encoder signals associated with the six paragraphs selected from the datums. 7. Jonkin patenttivaatimuksen 1-6 mukainen järjestelmä, jossa järjestelmä käsittää lämpötila-anturin (230) ja kontrolleri on konfiguroitu korjaamaan kooderisignaa-lit kaapelien materiaalin lämpölaajenemiskertoimen ja lämpötilan mitatun muutoksen perusteella.The system of any one of claims 1 to 6, wherein the system comprises a temperature sensor (230) and the controller is configured to correct the encoder signals based on the thermal expansion coefficient of the cable material and the measured change in temperature. 8. Jonkin patenttivaatimuksen 1-7 mukainen järjestelmä, jossa kontrolleri on konfiguroitu korjaamaan kooderisignaalit kaapelien elastisuuden ja kaapeleihin vaikuttavien jännitysten arvioiden perusteella.The system of any one of claims 1 to 7, wherein the controller is configured to correct the encoder signals based on estimates of cable elasticity and stress applied to the cables. 9. Jonkin patenttivaatimuksen 1-8 mukainen järjestelmä, jossa kontrolleri on konfiguroitu päivittämään kinemaattiset parametrit poikkeamadatan perusteella.The system of any one of claims 1 to 8, wherein the controller is configured to update kinematic parameters based on the offset data. 10. Jonkin patenttivaatimuksen 1-9 mukainen järjestelmä, jossa kukin kaapeli-pohjainen etäisyysilmaisin käsittää lisäksi puristustelan (105) ja jousen (106) puris-tustelan saattamiseksi puristamaan kaapeli mittausrumpua vasten kaapelin ja mit-tausrummun välisen luiston välttämiseksi.The system of any one of claims 1 to 9, wherein each cable-based distance detector further comprises a press roll (105) and a spring (106) for causing the press roll to press the cable against the measuring drum to prevent slip between the cable and the measuring drum. 11. Jonkin patenttivaatimuksen 1-10 mukainen järjestelmä, jossa kukin kaapeli-pohjainen etäisyysilmaisin käsittää lisäksi ensimmäisen kaapeliohjaimen (107) kaapelin ohjaamiseksi tulemaan kontaktiin mittausrummun kanssa tietyssä asemassa mittausrummun aksiaalisessa suunnassa silloin kun kelausrumpu on kelaamassa kaapelia.The system of any one of claims 1 to 10, wherein each cable-based distance detector further comprises a first cable guide (107) for guiding the cable to contact the measuring drum at a particular position in the axial direction of the measuring drum while the winding drum is winding the cable. 12. Jonkin patenttivaatimuksen 1-11 mukainen järjestelmä, jossa kukin kaapeli-pohjainen etäisyysilmaisin käsittää lisäksi toisen kaapeliohjaimen (108) kaapelin ohjaamiseksi tulemaan kontaktiin mittausrummun kanssa tietyssä asemassa m it- tausrummun aksiaalisessa suunnassa silloin kun kaapelia kelataan erilleen ke-lausrummulta.The system of any one of claims 1 to 11, wherein each cable-based distance detector further comprises a second cable guide (108) for guiding the cable to contact the measuring drum at a certain position in the axial direction of the measuring drum when the cable is wound apart from the reel. 13. Jonkin patenttivaatimuksen 1-12 mukainen järjestelmä, jossa mittausrumpu käsittää kehän suuntaisen hahlon (109) kaapelia varten sen seikan varmistamiseksi, että kaapeli tulee kontaktiin mittausrummun kanssa tietyssä asemassa mit-tausrummun aksiaalisessa suunnassa.The system of any one of claims 1 to 12, wherein the measuring drum comprises a circumferential slot (109) for the cable to ensure that the cable is in contact with the measuring drum at a certain position in the axial direction of the measuring drum. 14. Menetelmä robotin kinemaattisten parametrien epätarkkuuden osoittavan poikkeamadatan generoimiseksi, joka robotti käsittää päätetyökalun, jonka likimääräinen asento ja orientaatio robotin jalustarungon suhteen kiinteässä työskentelytilan koordinaatistossa määritellään robottikohtaisilla niveltilamuuttujilla ja kinemaattisiin parametreihin perustuvalla suoralla kinematiikalla, jossa menetelmässä: - mitataan (401) joukko välimatkoja, joista jokainen on välimatka yhdestä ja-lustarunkoon nähden kiinteästi sijaitsevista peruspisteistä yhteen päätetyö-kaluun nähden kiinteästi sijaitsevista päätetyökalun pisteistä, ja - lasketaan (402) päätetyökalun asento ja orientaatio työskentelytilan koordinaatistossa välimatkojen kyseisen joukon perusteella, ja - muodostetaan (403) lasketun asennon ja orientaation ja likimääräisen asennon ja orientaation välisen poikkeaman osoittava data poikkeamadatan generoimiseksi, tunnettu siitä, että välimatkat mitataan kaapelipohjaisilla etäisyysilmaisimilla siten, että kunkin kaapelipohjaisen etäisyysilmaisimen kaapeli ulottuu peruspisteistä yhden kautta yhteen päätetyökalun pisteistä ja kyseessä olevan kaapelipohjaisen etäisyysilmaisimen tuottama kooderisignaali osoittaa välimatkan kyseessä olevasta peruspisteestä kyseessä olevaan päätetyökalun pisteeseen, kunkin kaapelipohjaisen etäisyysilmaisimen kelausrummulle tai rummulta pois kelaaman kaapelin osan pituuden mittaamisen käsittäessä: kaapelin järjestämisen (301) pyörittämään kelausrumpuun nähden erillistä mittausrumpua kun kaapelia kelataan kelausrummulle tai rummulta pois, ja mittausrummun kierrokset osoittavan kooderisignaalin tuottamisen (302) kun kaapelia kelataan kelausrummulle tai rummulta pois, jolloin kooderisignaali osoittaa myös kaapelin sen osan pituuden, joka on kelattu kelaus-rummulle tai rummulta pois.A method for generating inaccurate deviation data for a robot's kinematic parameters, the robot comprising a terminal tool whose approximate position and orientation with respect to the robot base frame in a fixed working space coordinate system is defined by a series of is the distance from one of the base points fixedly perpendicular to the chassis frame to the terminals of a fixed tool perpendicular to one end tool, and - calculating (402) the position and orientation of the terminal and orientation deviation data to generate the deviation data, characterized in that the distances m plotting the cable-based distance detectors so that the cable of each cable-based distance detector extends one of the base points through one of the terminals of the end tool and the encoder signal produced by the cable-based distance detector indicates the distance from the reference base (301) rotating a measuring drum separate from the winding drum when the cable is wound on or off the winding drum and producing (302) a coding signal indicative of revolutions of the measuring drum, wherein the encoder signal also indicates the length of the cable off. 15. Patenttivaatimuksen 14 mukainen menetelmä, jossa peruspisteistä ensimmäiseen, toiseen ja kolmanteen liittyvät kaapelit yhdistetään ensimmäiseen pääte-työkalun pisteistä, peruspisteistä neljänteen ja viidenteen liittyvät kaapelit yhdistetään toiseen päätetyökalun pisteistä, ja peruspisteistä kuudenteen liittyvä kaapeli yhdistetään kolmanteen päätetyökalun pisteistä 3-2-1 Stewart konfiguraation muodostamiseksi asennon ja orientaation ilmaisemista varten.The method of claim 14, wherein the cables connecting the first, second, and third terminals are connected to the first terminals of the terminal tool, the cables connected to the fourth and fifth bases are connected to the second terminals, and the sixth connected cable is connected to terminals 3-2-1 of the third terminal. to form a position and orientation. 16. Patenttivaatimuksen 14 mukainen menetelmä, jossa peruspisteistä ensimmäiseen ja toiseen liittyvät kaapelit yhdistetään ensimmäiseen päätetyökalun pisteistä, peruspisteistä kolmanteen ja neljänteen liittyvät kaapelit yhdistetään toiseen päätetyökalun pisteistä, ja peruspisteistä viidenteen ja kuudenteen liittyvät kaapelit yhdistetään kolmanteen päätetyökalun pisteistä 2-2-2 konfiguraation muodostamiseksi asennon ja orientaation ilmaisemista varten.The method of claim 14, wherein connecting cables from the base points to the first and second terminals are connected to the first terminals of the terminal tool, cables connecting the base points to the third and fourth terminals are connected to the second terminals, and connecting cables from the base points to the fifth and sixth terminals. for expressing orientation. 17. Jonkin patenttivaatimuksen 14-16 mukainen menetelmä, jossa peruspistei-den lukumäärä on suurempi kuin kuusi ja menetelmässä lasketaan joukko ennak-koarvoja päätetyökalun asennolle ja orientaatiolle peruspisteiden keskenään erilaisiin kuusijäsenisiin osajoukkoihin liittyvien kooderisignaalien perusteella ja lasketaan päätetyökalun asento ja orientaatio kyseisten ennakkoarvojen perusteella.The method of any one of claims 14 to 16, wherein the number of datum points is greater than six and the method calculates a plurality of predetermined values for the position and orientation of the terminal tool based on encoder signals associated with different six-member subsets of the terminals and calculates the position and orientation of the terminal tool. 18. Patenttivaatimuksen 17 mukainen menetelmä, jossa menetelmässä lasketaan päätetyökalun asennon ja orientaation määrittävät numeeriset arvot olemaan keskenään erilaisiin kuusijäsenisiin osajoukkoihin liittyvien keskenään vastaavien numeeristen arvojen painotettuja keskiarvoja päätetyökalun asennon ja orientaation laskemiseksi ennakkoarvojen perusteella, ja menetelmässä asetetaan kuusijäsenisistä osajoukoista kunkin paino kyseessä olevaan kuusijäseniseen osajoukkoon ja päätetyökalun liikkeeseen edellisestä asennosta ja orientaatiosta laskettavaan asentoon ja orientaatioon liittyvien kooderignaalien minimimuutoksen perusteella siten, että kooderisignaalien pienempi minimimuutos vastaa pienempää painoa kuin se, jota kooderisignaalien suurempi minimuutos vastaa.The method of claim 17, wherein the method calculates numerical values defining the position and orientation of the terminal tool to be weighted averages of mutually equivalent numerical values associated with different six-member subsets, based on predictions, based on the minimum change in encoder signals associated with the position and orientation calculated from the previous position and orientation, such that the smaller minimum change in the encoder signals corresponds to a lower weight than the smaller change in the encoder signals. 19. Jonkin patenttivaatimuksen 14-16 mukainen menetelmä, jossa peruspistei-den lukumäärä on suurempi kuin kuusi ja menetelmässä valitaan peruspisteiden joukosta kuusi kappaletta siten, että sellainen yksi tai useampi peruspisteistä, johon kooderisignaalien pienimmät muutokset liittyvät silloin kun päätetyökalu tulee liikutetuksi edellisestä asennosta ja orientaatiosta laskettavaan asentoon ja orientaatioon, jätetään pois peruspisteistä valittujen kuuden kappaleen joukosta, ja menetelmässä lasketaan päätetyökalun asento ja orientaatio peruspisteistä valittuihin kuuteen kappaleeseen liittyvien kooderisignaalien perusteella.The method of any one of claims 14-16, wherein the number of datum points is greater than six and the method comprises selecting from six datum points one or more of the datum points to which the smallest changes in the encoder signals are associated when the terminal tool is moved from its previous position position and orientation, omitting the six points selected from the datum, and calculating the position and orientation of the terminal tool based on the encoder signals associated with the six paragraphs selected from the datum. 20. Jonkin patenttivaatimuksen 14-19 mukainen menetelmä, jossa menetelmässä korjataan kooderisignaalit kaapelien materiaalin lämpölaajenemiskertoimen ja lämpötilanmitatun muutoksen perusteella.A method according to any one of claims 14 to 19, wherein the method corrects the encoder signals based on the thermal expansion coefficient of the cable material and the measured change in temperature. 21. Jonkin patenttivaatimuksen 14-20 mukainen menetelmä, jossa menetelmässä korjataan kooderisignaalit kaapelien elastisuuden ja kaapeleihin vaikuttavien jännitysten arvioiden perusteella.The method of any one of claims 14 to 20, wherein the method corrects encoder signals based on estimates of cable elasticity and stresses applied to the cables. 22. Jonkin patenttivaatimuksen 14-21 mukainen menetelmä, jossa menetelmässä lisäksi puristetaan kaapeli mittausrumpua vasten jousikäyttöisellä puristustelalla kaapelin ja mittausrummun välisen luiston välttämiseksi.The method of any one of claims 14 to 21, further comprising compressing the cable against the measuring drum by means of a spring-driven compression roller to prevent slipping between the cable and the measuring drum. 23. Jonkin patenttivaatimuksen 14-22 mukainen menetelmä, jossa menetelmässä lisäksi ohjataan kaapeli ensimmäisellä kaapeliohjaimella tulemaan kontaktiin mittausrummun kanssa tietyssä asemassa mittausrummun aksiaalisessa suunnassa silloin kun kaapeli tulee kelatuksi sisään kelausrummun toimesta.The method of any one of claims 14 to 22, further comprising directing the cable with the first cable guide to contact the measuring drum at a certain position in the axial direction of the measuring drum when the cable is wound in by the winding drum. 24. Jonkin patenttivaatimuksen 14-23 mukainen menetelmä, jossa menetelmässä lisäksi ohjataan kaapeli toisella kaapeliohjaimella tulemaan kontaktiin mittaus-rummun kanssa tietyssä asemassa mittausrummun aksiaalisessa suunnassa silloin kun kaapeli tulee kelatuksi pois kelausrummulta.The method of any one of claims 14 to 23, further comprising controlling the cable with a second cable guide to contact the measuring drum at a certain position in the axial direction of the measuring drum when the cable is wound off the winding drum. 25. Jonkin patenttivaatimuksen 14-24 mukainen menetelmä, jossa mittausrumpu käsittää kehän suuntaisen hahlon kaapelia varten sen seikan varmistamiseksi, että kaapeli tulee kontaktiin mittausrummun kanssa tietyssä asemassa mittausrummun aksiaalisessa suunnassa.The method of any one of claims 14 to 24, wherein the measuring drum comprises a circumferential slot for the cable to ensure that the cable is in contact with the measuring drum at a certain position in the axial direction of the measuring drum. 26. Jonkin patenttivaatimuksen 14-25 mukainen menetelmä, jossa menetelmässä lisäksi päivitetään (404) kinemaattiset parametrit poikkeamadatan perusteella.The method of any one of claims 14 to 25, further comprising updating (404) the kinematic parameters based on the offset data. 27. Kalibrointimenetelmä robotin kalibroimiseksi, jossa kalibrointimenetelmässä: - suoritetaan jonkin patenttivaatimuksen 14-25 mukainen menetelmä (401 -403) robotin kinemaattisten parametrien epätarkkuuden osoittavan poikkeamadatan generoimiseksi, ja - päivitetään (404) kinemaattiset parametrit kyseisen poikkeamadatan perusteella.A calibration method for calibrating a robot, the method comprising: - performing (401 -403) a method (401 -403) according to any one of claims 14 to 25 for generating an error data indicating an inaccuracy of the kinematic parameters of the robot, and updating (404) based on said error data.
FI20145378A 2014-04-23 2014-04-23 Wired distance detector and system based on it to generate robot calibration data FI125511B (en)

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EP15721756.3A EP3134233A1 (en) 2014-04-23 2015-04-21 A cable-based distance detector and a system based on it for generating robot calibration data
CN201580021044.5A CN106232303A (en) 2014-04-23 2015-04-21 Distance detector based on cable and generate the system of robot calibration data based on it
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