Industrial robot joint zero calibration device and method

Abstract

The invention discloses an industrial robot joint zero position calibration device and method, and belongs to the technical field of industrial robot calibration. The calibration device comprises a zero position calibration mechanism, a tail end reference ball, a tail end tilt angle sensor, a base tilt angle sensor and a support plate; the zero calibration mechanism comprises a mounting base, a control box and three ball rods; a base reference ball is arranged on the mounting base; when the zero position of the joint is calibrated, the tail end reference ball is mounted on the flange plate through the bracket plate; the tail end tilt angle sensor is mounted on the horizontal part of the bracket plate; the base tilt angle sensor is horizontally mounted on the base; in an electrified measurement state, one end of the ball bar magnetically attracts the base reference ball, and the other end of the ball bar magnetically attracts the tail end reference ball; through combined measurement of the zero calibration mechanism, the base tilt angle sensor and the tail end tilt angle sensor, measurement of the actual position and posture of the tail end of the industrial robot is rapidly achieved, so that the error detection precision is improved, and the zero calibration precision and efficiency are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial robot calibration, and in particular relates to a device and method for calibrating the zero position of an industrial robot joint. Background Art

[0002] In industrial automation and manufacturing, industrial robots are increasingly used. Industrial robots can perform tasks such as welding, assembly, handling and spraying, and their working accuracy and efficiency directly affect the overall performance of the production line. Joint zero position calibration is a key step to ensure the working accuracy of the robot, ensuring that the industrial robot has high accuracy and repeatability when performing tasks. The current manual zero position calibration method usually requires complex operating steps and professional technicians, and the calibration process is easily affected by human factors, thereby affecting the calibration accuracy; the visual calibration method uses an external camera to identify the position and posture of the industrial robot through image processing technology, and then calibrates. The visual calibration accuracy is high, but the system is complex, the cost is high, it is easily affected by ambient light, and the scope of use is limited; the laser tracker calibration method has high accuracy, but the equipment is expensive, the operation is complicated, and it is not suitable for large-scale industrial applications. In addition, the existing technology usually takes a long time to adjust and measure. In view of the above problems, it is urgent to propose an industrial robot joint zero position calibration device and method. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a device and method for zero position calibration of an industrial robot joint.

[0004] The present invention provides the following technical solutions:

[0005] In a first aspect, an industrial robot joint zero position calibration device is provided, comprising a zero position calibration mechanism, an end reference ball, an end inclination sensor, a base inclination sensor and a bracket plate;

[0006] The zero calibration mechanism comprises a mounting base, a control box and three ballbars; the mounting base is provided with three base reference balls arranged in a regular triangle; the control box is located on the mounting base and is capable of controlling the power-on state of the ballbar and collecting measurement data of the ballbar;

[0007] When performing joint zero position calibration, the terminal reference ball is installed on the flange of the terminal of the industrial robot through the bracket plate; the terminal inclination sensor is installed on the horizontal part of the bracket plate; the base inclination sensor is horizontally installed on the base of the industrial robot through the extension plate; the zero position calibration mechanism is in a powered-on measuring state, the ballbar corresponds one-to-one with the base reference ball, and one end of the ballbar magnetically attracts the base reference ball, and the other end magnetically attracts the terminal reference ball.

[0008] Optionally, the bracket plate is L-shaped; the first right-angle plate of the bracket plate is detachably mounted on the flange plate and is provided with an external threaded column protruding from the surface, and the terminal reference ball is provided with an internal threaded hole; the terminal reference ball is mounted on the external threaded column through the internal threaded hole; the terminal inclination sensor is mounted on the second right-angle side of the bracket plate;

[0009] The terminal inclination sensor and the base inclination sensor are both dual-axis inclination sensors;

[0010] The ballbar is provided with a liquid crystal display screen which can display the telescopic length of the ballbar;

[0011] The diameters of the spherical parts of the end reference ball and the base reference ball are the same.

[0012] In a second aspect, a method for calibrating the joint zero position of an industrial robot is provided, based on the joint zero position calibration device described in any one of the first aspects, comprising the following steps:

[0013] Install the various components of the joint zero position calibration device at the designated position of the industrial robot, and adjust the joint zero position calibration mechanism to the measuring state;

[0014] Collect the measurement data of each ballbar, the output angle data of the base inclination sensor and the end inclination sensor;

[0015] Multiple test points are randomly selected, and for each test point, the actual position and posture of the robot end corresponding to the test point is obtained based on the collected measurement data and angle data;

[0016] For each test point, the theoretical position and posture of the robot end is obtained through the robot forward kinematics;

[0017] Based on the theoretical and actual positions of all robot ends, the robot kinematic parameter error identification solution is obtained through parameter identification;

[0018] According to the kinematic parameter error identification solution, the robot's joint zero position is corrected.

[0019] Optionally, the steps of installing the components of the joint zero position calibration device at a specified position of the industrial robot specifically include:

[0020] Install the base inclination sensor on the robot base, install the end reference ball on the flange at the end of the robot using the bracket plate, install the end inclination sensor in a horizontal position of the bracket plate, and detachably install the mounting base on the plane of the industrial robot's working area. When installing the end inclination sensor, adjust the posture of the industrial robot so that the output of the two axes of the end inclination sensor is approximately 0.

[0021] Optionally, obtaining the actual position and posture of the robot end corresponding to the test point based on the collected measurement data and angle data specifically includes:

[0022] A plurality of coordinate systems are defined using the right-hand rule, wherein the plurality of coordinate systems includes the industrial robot base coordinate system F b 、Industrial robot terminal coordinate system F e , measurement coordinate system F c , Base inclination sensor coordinate system F s1 and the end tilt sensor coordinate system F s2 .

[0023] For each test point, the actual position of the robot end is obtained based on the ballbar length data;

[0024] Based on the output angle information of the terminal tilt sensor and the base tilt sensor, the actual posture matrix of the robot terminal is obtained through the coordinate conversion relationship;

[0025] The actual position and posture matrix of the robot end are combined to obtain the actual posture matrix of the robot end.

[0026] Optionally, the industrial robot base coordinate system F b The center of the base of the industrial robot is taken as the coordinate origin, and the Z axis is perpendicular to the installation plane of the industrial robot and points upward; the industrial robot terminal coordinate system F e The center of the flange of the industrial robot is taken as the coordinate origin, and the Z axis is perpendicular to the flange and points outward; the measurement coordinate system F c The center of the mounting base of the zero-position calibration mechanism is taken as the coordinate origin, and the Z axis is perpendicular to the mounting base and upward; the base inclination sensor coordinate system F s1 and the end tilt sensor coordinate system F s2 The center of each sensor base is taken as the coordinate origin, and the coordinate axis direction is consistent with the industrial robot base coordinate system F b The coordinate axes are in the same direction.

[0027] Optionally, the obtaining the actual position of the robot end based on the rod length data of the ballbar specifically includes:

[0028] In the measurement coordinate system F c Next, based on the known rod length data and the coordinates of the three base reference balls P1 (x1, y1, z1), P2 (x2, y2, z2) and P3 (x3, y3, z3), the coordinates P0 (x0, y0, z0) of the end reference ball are obtained;

[0029] The relationship between the coordinates P0 of the end reference sphere and the coordinates P1, P2 and P3 of the three base reference spheres is expressed as:

[0030]

[0031] Among them, R is the radius of the base reference sphere and the end reference sphere, l1, l2 and l3 are the length data of the three ballbars measured respectively;

[0032] According to the end reference ball in the industrial robot end coordinate system F e Transformation Matrix e T q , obtain the actual position of the end of the industrial robot;

[0033] The actual position vector expression of the end of the industrial robot is:

[0034]

[0035] Among them, P r (x r ,y r ,z r ) is the actual position of the robot end.

[0036] Optionally, the actual posture matrix of the robot terminal is obtained through a coordinate transformation relationship based on the collected output angle information of the terminal inclination sensor and the base inclination sensor, specifically including:

[0037] Based on the deflection angle and pitch angle output by the end tilt sensor, the industrial robot base coordinate system F is obtained b Posture matrix R b and the end tilt sensor coordinate system F s2 Posture matrix R2;

[0038] R b =R g 1 R b

[0039] R2=R g 1 R2

[0040] in, 1 R b F is the base inclination sensor coordinate system s1 With the industrial robot base coordinate system F b The attitude transformation matrix, 1 R2 is the base inclination sensor coordinate system F s1 and the end tilt sensor coordinate system F s2 The attitude transformation matrix, R g F is the gravity coordinate system of the end tilt sensor itself g Posture matrix;

[0041] Get the industrial robot base coordinate system Fb and the end tilt sensor coordinate system F s2 Posture conversion relationship;

[0042] R2=R b ( 1 R b ) -11 R2

[0043] According to the industrial robot base coordinate system F b and the end tilt sensor coordinate system F s2 Attitude conversion relationship, end tilt sensor coordinate system F s2 and the industrial robot end coordinate system F e Posture transformation relationship, obtain the industrial robot end coordinate system F e Posture and industrial robot base coordinate system F b The conversion relationship of posture;

[0044] Based on the industrial robot terminal coordinate system F e Posture and industrial robot base coordinate system F b The transformation relationship of posture, obtains the actual posture matrix of the robot end;

[0045] The industrial robot terminal coordinate system F e Posture and industrial robot base coordinate system F b The conversion relationship of posture is:

[0046] R e =R b R r

[0047] R r =( 1 R b ) -11 R2 2 R e

[0048] Among them, R r is the actual posture matrix of the end of the industrial robot, R e F is the industrial robot terminal coordinate system e The posture matrix, 2 R e F is the end tilt sensor coordinate system s2 With the industrial robot end coordinate system F e Posture transformation matrix;

[0049] The actual pose matrix T of the robot end r for:

[0050]

[0051] Among them, P r is the actual position vector of the robot end.

[0052] Optionally, the theoretical pose matrix T of the robot end n for:

[0053]

[0054] Among them, T i n is the theoretical transformation matrix between adjacent coordinate systems of the connecting rod, R n is the theoretical posture matrix, P n is the theoretical position vector;

[0055] The robot kinematic parameter error identification solution is obtained by parameter identification based on the theoretical and actual postures of all robot ends, specifically including:

[0056] For each test point, obtain the posture error matrix ΔT of the industrial robot end i ;

[0057] ΔT i =T r -T n

[0058] Obtain the posture error model ΔE of the industrial robot based on calculus;

[0059]

[0060] Δη=[Δθ Δd Δa Δα Δβ]

[0061] Among them, Δη is the kinematic error vector, H is the Jacobian matrix of the error model, θ, d, a, α and β are the joint angle, joint offset, link length, joint torsion angle and the angle of rotation around the y-axis respectively;

[0062] Construct an overdetermined set of equations based on the pose error matrix of the end of all test points;

[0063] The least square solution of the overdetermined equations is sought as the identification solution of the kinematic parameter errors.

[0064] Optionally, the performing of joint zero position correction on the robot according to the kinematic parameter error identification solution specifically includes:

[0065] The kinematic parameters include joint rotation angle, joint offset, link length, joint torsion angle and angle of rotation around the y-axis;

[0066] The identified kinematic parameter errors other than the joint rotation angle are directly compensated to the corresponding kinematic parameters of the industrial robot for correction;

[0067] When correcting the joint angles of each joint of the robot, it is necessary to determine the joint angle compensation value of each joint, and correct the joint angle of the robot according to each joint angle compensation value and the identified joint angle error;

[0068] Specifically, the robot's kinematic parameters other than the joint angles are corrected, and the position and posture T of the robot end after preliminary correction is obtained. c ;

[0069] Based on the theoretical position T of the robot end n and pose T c , establish the partial derivative equation about the deviation ΔT between the two;

[0070]

[0071] in, is the partial derivative of the posture with respect to the i-th joint rotation, δθ i is the compensation value of the i-th joint angle;

[0072] The least squares method is used to solve the partial derivative equation of the deviation ΔT to obtain the compensation value of each joint angle.

[0073] Compared with the prior art, the present invention has the following beneficial effects:

[0074] The industrial robot joint zero position calibration device of the present invention has a simple structure and is easy to disassemble. Through the combined measurement of the zero position calibration mechanism, the base inclination sensor and the terminal inclination sensor, the actual position and posture of the industrial robot terminal can be quickly measured, thereby improving the error detection accuracy and improving the accuracy and efficiency of zero position calibration.

[0075] The industrial robot joint zero-position calibration method of the present invention improves the error detection accuracy and simplifies the zero-position calibration operation steps by means of a zero-position calibration mechanism and a combined measurement through a base inclination sensor and a terminal inclination sensor, thereby effectively improving the accuracy performance of the industrial robot and ensuring the work efficiency of the production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 It is a schematic diagram of the overall structure of the industrial robot joint zero position calibration device of the present invention;

[0077] Figure 2 is a schematic structural diagram of an industrial robot of the present invention;

[0078] Figure 3It is a schematic diagram of the overall structure of the zero position calibration mechanism of the present invention in a non-measurement state;

[0079] Figure 4 is an enlarged schematic diagram of the installation position of the terminal reference ball of the present invention;

[0080] Figure 5 It is a schematic structural diagram of the mounting base of the present invention;

[0081] Figure 6 is a schematic diagram of the structure of the ballbar of the present invention;

[0082] Figure 7 It is an exploded schematic diagram of the installation of the terminal reference ball and the terminal tilt sensor of the present invention;

[0083] Figure 8 It is a schematic diagram of establishing a base coordinate system and a terminal coordinate system of an industrial robot of the present invention;

[0084] Fig. 9 Schematic diagram of establishing the measurement coordinate system;

[0085] Fig.10 It is a schematic diagram of establishing the coordinate systems of two tilt sensors;

[0086] Fig.11 This is the neutral coordinate system of the tilt sensor and the attitude angle measurement model diagram;

[0087] Fig.12 It is a schematic diagram of the measurement principle of the tilt sensor;

[0088] Fig.13 Flowchart for kinematic parameter identification of industrial robot.

[0089] In the figure, the marks are: 1 is the industrial robot body, 2 is the zero position calibration mechanism, 3 is the end reference ball, 4 is the end tilt sensor, 5 is the bracket plate, 6 is the extension plate, and 7 is the base tilt sensor;

[0090] 101 is a base, 102 is a shoulder joint, 103 is an upper arm, 104 is a lower arm, 105 is a first wrist joint, 106 is a second wrist joint, 107 is a flange, and 108 is a servo motor;

[0091] 201 is a mounting base, 202 is a ballbar, 203 is a control box, 204 is a base reference ball, and 205 is a display screen;

[0092] 301 is an internal thread hole, and 501 is an external thread column. DETAILED DESCRIPTION

[0093] The present invention will now be described in further detail with reference to the accompanying drawings.

[0094] It should be noted that the terms such as "upper", "lower", "left", "right", "front", "back", etc. cited in the invention are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments in their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0095] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the components and data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods or devices.

[0096] Example 1

[0097] like Figure 1-Figure 7 As shown, an industrial robot joint zero position calibration device is provided, including a zero position calibration mechanism 2, an end reference ball 3, an end inclination sensor 4, a base inclination sensor 7 and a bracket plate 5.

[0098] The zero calibration mechanism 2 comprises a mounting base 201, a control box 203 and three ballbars 202; the mounting base 201 is provided with three base reference balls 204 arranged in a regular triangle; the control box 203 is located on the mounting base 201 and can control the power-on state of the ballbar 202 and collect the measurement data of the ballbar 202; Figure 3 As shown, in the non-measuring state when powered on, the two ends of the ballbar 202 are magnetically connected to two adjacent base reference balls 204, and the three ballbars 202 are connected end to end; the mounting base 201 is an equilateral triangle in this embodiment; the structure of the ballbar 202 can refer to the prior art.

[0099] Specifically, the control box 203 is embedded in the mounting base 201 and fixed by screws, and the dimensions of the mounting base 201 and the base reference ball 202 are known and fixed.

[0100] When performing joint zero position calibration, the end reference ball 3 is installed on the flange 107 at the end of the industrial robot through the bracket plate 5, and the end inclination sensor 4 is installed on the horizontal part of the bracket plate 5.

[0101] Specifically, the bracket plate 5 is L-shaped; the first right-angle plate of the bracket plate 5 is detachably mounted on the flange 107, and is provided with an external threaded column 501 protruding from the surface, and the end reference ball 3 is provided with an internal threaded hole 301; the end reference ball 3 is mounted on the external threaded column 501 through the internal threaded hole 301; the end inclination sensor 4 is mounted on the second right-angle plate of the bracket plate 5, and the end inclination sensor 4 can be detachably connected to the bracket plate 5 by bolts.

[0102] When performing joint zero position calibration, the base inclination sensor 7 is horizontally installed on the base 101 of the industrial robot through the extension plate 6; the surface of the base 101 of the traditional industrial robot is an inclined surface, which is not suitable for installing the base inclination sensor 7. Using the extension plate 6 to horizontally install the base inclination sensor 7 can ensure that the initial angle output of the base inclination sensor 7 is approximately equal to 0, thereby reducing the difficulty of joint zero position calibration.

[0103] When the joint zero position calibration is performed, the zero position calibration mechanism 2 is in a powered measurement state, the ball bar 202 corresponds to the base reference ball 204 one by one, and one end of the ball bar 202 magnetically attracts the base reference ball 204, and the other end magnetically attracts the terminal reference ball 3, and the spherical parts of the base reference ball 204 and the terminal reference ball 3 are the same size. Specifically, the two ends of the ball bar 202 can be moved to a position where the terminal reference ball 3 and the base reference ball 204 can be attracted by manpower, such as Figure 4 and Figure 6 As shown, the telescopic end of the ballbar 202 is connected to the terminal reference ball 3, and the other end is connected to the base reference ball 204.

[0104] In this embodiment, the terminal inclination sensor 4 and the base inclination sensor 7 are both dual-axis inclination sensors; the dual-axis inclination sensors output angle information including a deflection angle α and a pitch angle β.

[0105] In this embodiment, the ballbar 202 is provided with a liquid crystal display screen 205 which can display the telescopic length of the ballbar 202 . According to the telescopic length of the ballbar 202 , the length data of the ballbar 202 can be obtained.

[0106] In this embodiment, if Figure 2 As shown, the industrial robot body 1 includes a base 101, a shoulder joint 102, an upper arm 103, a lower arm 104, a first wrist joint 105, a second wrist joint 106 and a flange 107. The connection relationship between the various components can refer to the prior art. The industrial robot of the present application has six degrees of freedom, and the six joints are all rotating joints. Each joint can move independently, with high degrees of freedom, flexible joints and accurate movements. The motion drive of the industrial robot adopts a DC servo motor 108 and is equipped with a safety brake.

[0107] The zero position calibration device of the present invention is installed at different positions of the industrial robot when performing joint zero position calibration, and needs to be removed during non-joint zero position calibration to avoid affecting the normal operation of the industrial robot.

[0108] The zero-position calibration device of the present invention has a simple structure and is easy to disassemble. Through the combined measurement of the zero-position calibration mechanism 2, the base inclination sensor 7 and the terminal inclination sensor 4, the actual position and posture of the terminal of the industrial robot can be quickly measured, thereby improving the accuracy and efficiency of the zero-position calibration.

[0109] Example 2

[0110] like Figure 8-Figure 13 As shown, a method for calibrating the zero position of an industrial robot joint comprises the following steps (S1-S6):

[0111] S1: Install the various components of the joint zero position calibration device at the specified position of the industrial robot, and adjust the joint zero position calibration mechanism 2 to the measuring state.

[0112] Specifically, the base inclination sensor 7 is installed on the robot base 101 . Specifically, the base inclination sensor 7 is installed on the surface of the base 101 through the extension plate 6 in a threaded connection manner.

[0113] The end reference ball 3 is installed on the flange 107 at the end of the robot using the bracket plate 5, the end inclination sensor 4 is installed at a horizontal position of the bracket plate 5, and the mounting base 201 is detachably installed on the plane of the working area of ​​the industrial robot, specifically, it can be fixed by screws. Of course, in some other embodiments, the mounting base 201 can also be installed on a tripod, allowing the height of the mounting base 201 to be adjusted.

[0114] When installing the terminal inclination sensor 4, adjust the posture of the industrial robot so that the output of the two axes of the terminal inclination sensor 4 is approximately 0; specifically, during the installation process, adjust the terminal posture of the industrial robot so that the bracket plate 5 is near the horizontal position, install and fix the terminal inclination sensor 4 on the bracket plate 5, and adjust the posture of the industrial robot again so that the output of the two axes of the terminal inclination sensor 4 is basically zero.

[0115] Adjusting the joint zero position calibration mechanism 2 to the measuring state includes: magnetically connecting one end of the ballbar 202 to the base reference ball 204, magnetically connecting the other end to the end reference ball 3, connecting the control box 203 to the control system, etc.

[0116] S2: Collecting the measurement data of each ballbar 202 , and the output angle data of the base inclination sensor 7 and the terminal inclination sensor 4 .

[0117] The measurement data of the ballbar 202 is the telescopic length of the ballbar 202 . The length data of the ballbar 202 during measurement can be obtained based on the telescopic length and the known length of the original ballbar 202 .

[0118] The output angles of the base inclination sensor 7 and the terminal inclination sensor 4 both include a deflection angle α and a pitch angle β.

[0119] S3: Randomly select multiple test points, and for each test point, obtain the actual position and posture of the robot end corresponding to the test point based on the collected measurement data and angle data.

[0120] Step S3 specifically includes the following sub-steps (S31-S34):

[0121] S31: Use the right-hand rule to define multiple coordinate systems, wherein the multiple coordinate systems include the industrial robot base coordinate system F b 、Industrial robot terminal coordinate system F e , measurement coordinate system F c , Base inclination sensor coordinate system F s1 and the end tilt sensor coordinate system F s2 .

[0122] Specifically, Figure 8-Figure 10 As shown, the industrial robot base coordinate system F b The center of the base 101 of the industrial robot is taken as the coordinate origin, and the Z axis is perpendicular to the installation plane of the industrial robot and points upward.

[0123] Industrial robot terminal coordinate system F e The center of the flange 107 of the industrial robot is taken as the coordinate origin, and the Z axis is perpendicular to the flange 107 and points outward.

[0124] Measuring coordinate system F c The center of the mounting base 201 of the zero-position calibration mechanism 2 is taken as the coordinate origin, and the Z axis is perpendicular to the mounting base 201 and points upward.

[0125] Base inclination sensor coordinate system F s1 and the end tilt sensor coordinate system F s2 The center of the base of each sensor is taken as the coordinate origin, and the direction of the coordinate axis is consistent with the industrial robot base coordinate system F b The coordinate axes are in the same direction.

[0126] S32: For each test point, based on the rod length data of the ballbar 202, the actual position of the robot end is obtained.

[0127] Step S32 includes the following sub-steps (S321-S322):

[0128] S321: In the measurement coordinate system F cNext, based on the known rod length data and the coordinates P1 (x1, y1, z1), P2 (x2, y2, z2) and P3 (x3, y3, z3) of the three base reference spheres 204, the coordinates P0 (x0, y0, z0) of the end reference sphere 3 are obtained.

[0129] Since the size of the mounting base 201 of the zero-position calibration mechanism 2 is known, the positions of the coordinates P1 (x1, y1, z1), P2 (x2, y2, z2) and P3 (x3, y3, z3) of the three base reference spheres 204 are known, and the coordinates of the end reference sphere 3 and the base reference sphere 204 are both sphere center coordinates.

[0130] The relationship between the coordinate P0 of the end reference sphere 3 and the coordinates P1, P2 and P3 of the three base reference spheres 204 is expressed as follows:

[0131]

[0132] Wherein, R is the radius of the base reference sphere 204 and the end reference sphere 3; l1, l2 and l3 are the measured rod length data of the three ballbars 202 respectively.

[0133] S322: According to the end reference ball 3, the industrial robot end coordinate system F e Transformation Matrix e T q , get the actual position of the end of the industrial robot.

[0134] Since the end reference ball 3, the bracket plate 5 and the flange 107 are fixedly connected, the position of the end reference ball 3 in the industrial robot end coordinate system F can be directly obtained. e Transformation Matrix e T q .

[0135] The actual position vector expression of the end of the industrial robot is:

[0136]

[0137] Among them, P r (x r ,y r ,z r ) is the actual position of the robot end.

[0138] S33: Based on the collected output angle information of the terminal inclination sensor 4 and the base inclination sensor 7, the actual posture matrix of the robot terminal is obtained through the coordinate conversion relationship.

[0139] Step S33 includes the following sub-steps (S331-S334):

[0140] S331: Based on the deflection angle and pitch angle output by the end inclination sensor 4, obtain the base coordinate system F of the industrial robot b Posture matrix R b and the end tilt sensor coordinate system F s2 Posture matrix R2.

[0141] According to the attitude angle measurement principle of the inclination sensor, Fig.11 and Fig.12 As shown, Fig.12 (a) is a schematic diagram of the measurement of the tilt sensor in a horizontal state. Fig.12 (b) is a measurement diagram of the inclination sensor in a tilted state; the values ​​of the deflection angle α and pitch angle β output by the inclination sensor are the deflection angle α and pitch angle β of the required attitude angle measurement model. Among them, the deflection angle α is the angle between the sensitive axis X axis at a certain position and the sensitive axis X axis at the initial time, the pitch angle β is the angle between the sensitive axis Y axis at a certain position and the sensitive axis Y axis at the initial time, the OXY plane is the sensitive surface of the inclination sensor, and the O-XYZ coordinate system is the gravity coordinate system of the inclination sensor itself F g The tilt sensor is swung around O0 along the space curve to point O', and the plane coordinate system OXY is swung from the initial position to the position of the plane coordinate system O'X'Y'. The calculation formulas for the deflection angle α and the pitch angle β are as follows:

[0142]

[0143]

[0144] Among them, x is the projection value of O' on the x-axis of the plane coordinate system OXY, y is the projection value of O' on the y-axis of the plane coordinate system OXY, R o is the distance from point O0 to point O.

[0145] Since the end tilt sensor 4 is fixed on the bracket plate 5, the base tilt sensor 7 is fixed on the extension plate 6. Since the deflection angle α and pitch angle β output by the end tilt sensor 4 are in the gravity coordinate system F of the tilt sensor itself g The value below.

[0146] Industrial robot base coordinate system F b Posture matrix R b and the end tilt sensor coordinate system F s2 The posture matrix R2 is:

[0147] R b =R g 1 R b (6)

[0148] R2=R g 1 R2 (7)

[0149] in, 1 R b F is the base inclination sensor coordinate system s1 With the industrial robot base coordinate system F b The attitude transformation matrix, 1 R2 is the base inclination sensor coordinate system F s1 and the end tilt sensor coordinate system F s2 The attitude transformation matrix, R g is the gravity coordinate system F of the end tilt sensor 4 itself g Pose matrix.

[0150] S332: Get the industrial robot base coordinate system F b and the end tilt sensor coordinate system F s2 Posture conversion relationship.

[0151] According to the industrial robot base coordinate system F b Posture matrix R b and the end tilt sensor coordinate system F s2 The posture matrix R2 is derived to obtain the industrial robot base coordinate system F b and the end tilt sensor coordinate system F s2 The posture conversion relationship is:

[0152] R2=R b ( 1 R b ) -11 R2 (8)

[0153] S333: According to the industrial robot base coordinate system F b and the end tilt sensor coordinate system F s2 Attitude conversion relationship, end tilt sensor coordinate system F s2 With the industrial robot end coordinate system F e Posture transformation relationship, obtain the industrial robot end coordinate system F e Posture and industrial robot base coordinate system F b The conversion relationship of posture.

[0154] Specifically, the end tilt sensor 4 is fixedly connected to the industrial robot flange 107 through the bracket plate 5, and the end tilt sensor coordinate system F s2 With the industrial robot end coordinate system F e The posture conversion relationship is:

[0155] R e =R2 2 R e (9)

[0156] Among them, Re F is the industrial robot terminal coordinate system e The posture matrix, 2 R e F is the end tilt sensor coordinate system s2 With the industrial robot end coordinate system F e Pose transformation matrix.

[0157] S334: Based on the industrial robot terminal coordinate system F e Posture and industrial robot base coordinate system F b The transformation relationship of the posture is used to obtain the actual posture matrix of the robot end.

[0158] According to formula (9) and formula (8), the industrial robot end coordinate system F can be deduced e Posture and industrial robot base coordinate system F b The conversion relationship of posture is:

[0159] R e =R b R r (10)

[0160] R r =( 1 R b ) -11 R2 2 R e (11)

[0161] Among them, R r is the actual posture matrix of the industrial robot end.

[0162] S34: Combining the actual position and the actual posture matrix of the robot end, the actual posture matrix of the robot end is obtained.

[0163] Specifically, the obtained industrial robot terminal coordinate system F e and the industrial robot base coordinate system F b The transformation matrix of the actual posture and the actual position P obtained in step S32 r (x r ,y r ,z r ) to obtain the actual posture matrix T of the robot end r for:

[0164]

[0165] Among them, P r is the actual position vector of the robot end.

[0166] S4: For each test point, the theoretical position and posture of the robot end is obtained through the robot forward kinematics.

[0167] According to the known M-DH parameters of the industrial robot (based on the existing M-DH model of the industrial robot), the forward kinematics is derived and the transformation matrix is ​​obtained as follows: b T e = 0 T1(θ1) 1 T2(θ2) 2 T3(θ3) 3 T4(θ4) 4 T5(θ5) 5 T6(θ6). According to the transformation relationship, the theoretical posture matrix of the end of the industrial robot can be obtained as follows:

[0168]

[0169] Among them, T i n is the theoretical transformation matrix between adjacent coordinate systems of the connecting rod, R n is the theoretical posture matrix, P n is the theoretical position vector.

[0170] S5: Based on the theoretical and actual poses of all robot ends, the robot kinematic parameter error identification solution is obtained through parameter identification.

[0171] Step S5 includes the following sub-steps (S51-S54):

[0172] S51: For each test point, obtain the posture error matrix ΔT of the end of the industrial robot i .

[0173]

[0174] S52: Obtaining a posture error model ΔE of the industrial robot according to calculus.

[0175]

[0176] Δη=[Δθ Δd Δa Δα Δβ] (18)

[0177] Among them, Δη is the kinematic error vector, H is the Jacobian matrix of the error model, θ, d, a, α and β are the joint angle, joint offset, link length, joint torsion angle and the angle of rotation around the y-axis respectively; θ, d, a, α and β are the M-DH parameters of the industrial robot.

[0178] S53: Construct an overdetermined set of equations according to the posture error matrices of the ends of all test points.

[0179] S54: The least square solution of the overdetermined equations is sought as the identification solution of the kinematic parameter errors.

[0180] S6: Based on the kinematic parameter error identification solution, the robot joint zero position is corrected.

[0181] The kinematic parameters (M-DH parameters) include joint rotation angle, joint offset, link length, joint torsion angle and the angle of rotation around the y-axis.

[0182] Step S6 includes:

[0183] S61: The identified kinematic parameter errors other than the joint rotation angle are directly compensated to the corresponding kinematic parameters of the industrial robot for correction.

[0184] The joint offset, link length, joint torsion angle and rotation angle around the y-axis are directly compensated according to their respective identification solutions.

[0185] S62: When correcting the joint angles of each joint of the robot, it is necessary to determine the joint angle compensation value of each joint, and correct the joint angle of the robot according to each joint angle compensation value and the identified joint angle error.

[0186] Step S62 specifically includes the following sub-steps:

[0187] S621: After correcting the kinematic parameters of the robot except the joint rotation angle, obtain the initial corrected position and posture T of the robot end c .

[0188] S622: Based on the theoretical position T of the robot end n and pose T c , establish the partial derivative equation about the deviation ΔT between the two;

[0189]

[0190] in, is the partial derivative of the posture with respect to the i-th joint rotation, δθ i is the compensation value of the i-th joint angle.

[0191] In order to achieve accurate compensation of errors, the pose T c Partial derivatives of each joint angle The error of the end position of the industrial robot caused by the kinematic parameter error other than the joint angle error is converted into the angle value δθ that needs to be compensated for each joint i .

[0192] S623: Use the least squares method to solve the partial derivative equation of the deviation ΔT to obtain the compensation value of each joint angle.

[0193] S624: Correct the joint angles of the robot according to each joint angle compensation value and the identified joint angle error.

[0194] The theoretical end position T n The corresponding joint angle value θ n Add the joint angle compensation value δθ that needs to be compensated i , plus the identified joint angle error Δθ i , we can get the joint angle value θ of each joint of the robot after correction i , that is, θ i =θ n +Δθ i +δθ i .

[0195] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0196] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. An industrial robot joint zero position calibration device, characterized in that: It comprises a zero position calibration mechanism (2), an end reference ball (3), an end inclination sensor (4), a base inclination sensor (7) and a bracket plate (5); The zero position calibration mechanism (2) comprises a mounting base (201), a control box (203) and three ballbars (202); the mounting base (201) is provided with three base reference balls (204) arranged in a regular triangle; the control box (203) is located on the mounting base (201) and is capable of controlling the power-on state of the ballbar (202) and collecting measurement data of the ballbar (202); When performing joint zero position calibration, the terminal reference ball (3) is mounted on the flange (107) at the terminal of the industrial robot through a bracket plate (5); the terminal inclination sensor (4) is mounted on the horizontal part of the bracket plate (5); the base inclination sensor (7) is horizontally mounted on the base (101) of the industrial robot through an extension plate (6); the zero position calibration mechanism (2) is in a powered measurement state, the ballbar (202) corresponds to the base reference ball (204) one by one, and one end of the ballbar (202) magnetically attracts the base reference ball (204), while the other end magnetically attracts the terminal reference ball (3).

2. The industrial robot joint zero position calibration device according to claim 1, characterized in that: The support plate (5) is L-shaped; the first right-angle plate of the support plate (5) is detachably mounted on the flange (107) and is provided with an external thread column (501) protruding from the surface; the terminal reference ball (3) is provided with an internal thread hole (301); the terminal reference ball (3) is mounted on the external thread column (501) through the internal thread hole (301); the terminal inclination sensor (4) is mounted on the second right-angle side of the support plate (5); The terminal inclination sensor (4) and the base inclination sensor (7) are both dual-axis inclination sensors; The ballbar (202) is provided with a liquid crystal display screen (205) which can display the telescopic length of the ballbar (202); The diameters of the spherical parts of the end reference ball (3) and the base reference ball (204) are the same.

3. A method for calibrating the joint zero position of an industrial robot, based on the joint zero position calibration device according to any one of claims 1 or 2, characterized in that: The following steps are involved: Installing the various components of the joint zero position calibration device at the designated position of the industrial robot, and adjusting the joint zero position calibration mechanism (2) to a measuring state; Collecting measurement data of each ballbar (202), output angle data of the base inclination sensor (7) and the terminal inclination sensor (4); Multiple test points are randomly selected, and for each test point, the actual position and posture of the robot end corresponding to the test point is obtained based on the collected measurement data and angle data; For each test point, the theoretical position and posture of the robot end is obtained through the robot forward kinematics; Based on the theoretical and actual positions of all robot ends, the robot kinematic parameter error identification solution is obtained through parameter identification; According to the kinematic parameter error identification solution, the robot's joint zero position is corrected.

4. The method for zero position calibration of an industrial robot joint according to claim 3, characterized in that: The method of installing the components of the joint zero position calibration device at the designated position of the industrial robot specifically includes: The base tilt sensor (7) is mounted on the robot base (101), the end reference ball (3) is mounted on the flange (107) at the end of the robot using a bracket plate (5), the end tilt sensor (4) is mounted at a horizontal position of the bracket plate (5), and the mounting base (201) is detachably mounted on the plane of the industrial robot working area. When the end tilt sensor (4) is installed, the posture of the industrial robot is adjusted so that the output of the two axes of the end tilt sensor (4) is approximately 0.

5. The method for zero position calibration of industrial robot joints according to claim 3, characterized in that: The actual position and posture of the robot end corresponding to the test point is obtained based on the collected measurement data and angle data, specifically including: A plurality of coordinate systems are defined using the right-hand rule, wherein the plurality of coordinate systems includes the industrial robot base coordinate system F b 、Industrial robot terminal coordinate system F e , measurement coordinate system F c , Base inclination sensor coordinate system F s1 and the end tilt sensor coordinate system F s2 . For each test point, based on the rod length data of the ballbar (202), the actual position of the robot end is obtained; Based on the collected output angle information of the end tilt sensor (4) and the base tilt sensor (7), the actual posture matrix of the end of the robot is obtained through a coordinate conversion relationship; Combine the actual position and actual posture matrix of the robot end to obtain the actual posture matrix of the robot end.

6. The method for zero position calibration of an industrial robot joint according to claim 5, characterized in that: The industrial robot base coordinate system F b The center of the base (101) of the industrial robot is taken as the coordinate origin, and the Z axis is perpendicular to the installation plane of the industrial robot and points upward; the industrial robot terminal coordinate system F e The center of the flange (107) of the industrial robot is taken as the coordinate origin, and the Z axis is perpendicular to the flange (107) and points outward; the measurement coordinate system F c The center of the mounting base (201) of the zero-position calibration mechanism (2) is taken as the coordinate origin, and the Z axis is perpendicular to the mounting base (201) and points upward; the base inclination sensor coordinate system F s1 and the end tilt sensor coordinate system F s2 The center of each sensor base is taken as the coordinate origin, and the coordinate axis direction is consistent with the industrial robot base coordinate system F b The coordinate axes are in the same direction.

7. The method for zero position calibration of an industrial robot joint according to claim 5, characterized in that: The obtaining of the actual position of the robot end based on the rod length data of the ballbar (202) specifically includes: In the measurement coordinate system F c Next, based on the known rod length data and the coordinates P1 (x1, y1, z1), P2 (x2, y2, z2) and P3 (x3, y3, z3) of the three base reference spheres (204), the coordinates P0 (x0, y0, z0) of the end reference sphere (3) are obtained; The relationship between the coordinate P0 of the end reference sphere (3) and the coordinates P1, P2 and P3 of the three base reference spheres (204) is expressed as follows: Wherein, R is the radius of the base reference sphere (204) and the end reference sphere (3), and l1, l2 and l3 are the measured rod length data of three ballbars (202); According to the end reference ball (3), in the industrial robot end coordinate system F e Transformation Matrix e T q , obtain the actual position of the end of the industrial robot; The actual position vector expression of the end of the industrial robot is: Among them, P r (x r ,y r ,z r ) is the actual position of the robot end.

8. The method for zero position calibration of industrial robot joints according to claim 5, characterized in that: The method of obtaining the actual posture matrix of the robot terminal through a coordinate conversion relationship based on the collected output angle information of the terminal tilt sensor (4) and the base tilt sensor (7) specifically includes: Based on the deflection angle and pitch angle output by the end tilt sensor (4), the base coordinate system F of the industrial robot is obtained. b Posture matrix R b and the end tilt sensor coordinate system F s2 Posture matrix R2; R b =R g 1 R b R2=R g 1 R2 in, 1 R b F is the base inclination sensor coordinate system s1 With the industrial robot base coordinate system F b The attitude transformation matrix, 1 R2 is the base inclination sensor coordinate system F s1 and the end tilt sensor coordinate system F s2 The attitude transformation matrix, R g is the gravity coordinate system F of the end tilt sensor (4) itself g Posture matrix; Get the industrial robot base coordinate system F b and the end tilt sensor coordinate system F s2 Posture conversion relationship; R2=R b ( 1 R b ) -11 R2 According to the industrial robot base coordinate system F b and the end tilt sensor coordinate system F s2 Attitude conversion relationship, end tilt sensor coordinate system F s2 With the industrial robot end coordinate system F e Posture transformation relationship, obtain the industrial robot end coordinate system F e Posture and industrial robot base coordinate system F b The conversion relationship of posture; Based on the industrial robot terminal coordinate system F e Posture and industrial robot base coordinate system F b The transformation relationship of posture, obtains the actual posture matrix of the robot end; The industrial robot terminal coordinate system F e Posture and industrial robot base coordinate system F b The conversion relationship of posture is: R e =R b R r R r =( 1 R b ) -11 R2 2 R e Among them, R r is the actual posture matrix of the end of the industrial robot, R e F is the industrial robot terminal coordinate system e The posture matrix, 2 R e F is the end tilt sensor coordinate system s2 With the industrial robot end coordinate system F e Posture transformation matrix; The actual posture matrix Tr of the robot end is: Among them, P r is the actual position vector of the robot end.

9. The method for zero position calibration of an industrial robot joint according to claim 3, characterized in that: The theoretical pose matrix Tn of the robot end is: Among them, T i n is the theoretical transformation matrix between adjacent coordinate systems of the connecting rod, R n is the theoretical posture matrix, P n is the theoretical position vector; The robot kinematic parameter error identification solution is obtained by parameter identification based on the theoretical and actual postures of all robot ends, specifically including: For each test point, obtain the posture error matrix ΔT of the industrial robot end i ; ΔT i =T r -T n Obtain the posture error model ΔE of the industrial robot based on calculus; Δη=[ΔθΔdΔaΔαΔβ] Among them, Δη is the kinematic error vector, H is the Jacobian matrix of the error model, θ, d, a, α and β are the joint angle, joint offset, link length, joint torsion angle and the angle of rotation around the y-axis respectively; Construct an overdetermined set of equations based on the pose error matrix of the end of all test points; The least square solution of the overdetermined equations is sought as the identification solution of the kinematic parameter errors.

10. The method for zero position calibration of industrial robot joints according to claim 3, characterized in that: The method of performing joint zero position correction on the robot according to the kinematic parameter error identification solution specifically includes: The kinematic parameters include joint rotation angle, joint offset, link length, joint torsion angle and angle of rotation around the y-axis; The identified kinematic parameter errors other than the joint rotation angle are directly compensated to the corresponding kinematic parameters of the industrial robot for correction; When correcting the joint angles of each joint of the robot, it is necessary to determine the joint angle compensation value of each joint, and correct the joint angle of the robot according to each joint angle compensation value and the identified joint angle error; Specifically, the robot's kinematic parameters other than the joint angle are corrected, and the position and posture T of the robot end after preliminary correction is obtained. c ; Based on the theoretical pose Tn and pose T of the robot end c , establish the partial derivative equation about the deviation ΔT between the two; in, is the partial derivative of the posture with respect to the i-th joint rotation, δθ i is the compensation value of the i-th joint angle; The least squares method is used to solve the partial derivative equation of the deviation ΔT to obtain the compensation value of each joint angle.

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