JP5388823B2 - Trajectory measuring device - Google Patents

Description

  The present invention relates to a trajectory measuring apparatus that measures a motion trajectory of a numerically controlled machine tool, a robot, or the like.

  In numerically controlled machine tools and robots, the position of the movable shaft of the machine is controlled as faithfully as possible by driving the motor to the command position. In that case, an error occurs between the command position and the actual machine position due to the influence of the vibration of the machine or the frictional force at the time of reversing the movement direction. When such a problem occurs, the movement locus of the machine is measured to find the cause of the problem, and various parameters of the controller that controls the motor are adjusted. For this purpose, a plurality of methods are known for measuring and displaying the machine motion trajectory.

  In the method disclosed in Patent Document 1, two high-precision steel balls are coupled via a displacement meter, and a movement (arc) is performed to keep the relative distance between the two balls constant. The displacement is read. This method is called the ball bar method and is widely used.

Non-Patent Document 1 discloses a method of measuring a motion trajectory of a machine tool using a measuring instrument called a crossed grid scale (grid encoder). In the measurement using the cross grating scale, two light receiving portions arranged at right angles to each other corresponding to each of the scale having two optical gratings intersecting at right angles on the glass substrate and the optical grating of the scale. It is possible to measure a two-dimensional relative displacement using a detection head having
Patent Document 2 discloses a method of calculating an arc trajectory from a position signal fed back when the machine tool is moved in a circular motion, and displaying an enlarged error from the target trajectory.

JP-A 61-209857 Japanese Patent No. 2504698

Measurement and improvement of motion accuracy of ultra-precise NC machine tool using cross grid scale, Journal of Precision Engineering, Vol. 62, no. 11 (1996) pp. 1612-1616.

  However, the method described in Patent Document 1 has a problem that only a circular arc trajectory having a predetermined radius can be measured, and the cable is easily entangled, making it difficult to measure high-speed motion. In addition, one or more operators have always been required for cable handling and ball bar removal.

  Although the accuracy measurement method using the crossed grid scale described in Non-Patent Document 1 can measure a free shape and high-speed motion, it is necessary to keep the distance between the scale and the head at about 0.5 mm. There was a problem that was easily damaged by collision. In addition, a three-dimensional motion trajectory could not be measured.

  Also, in common with the above method, in order to measure the movement trajectory by attaching a displacement meter to the machine, for example, when a jig or tool is attached to the machine tool, it is necessary to remove them for measurement. there were. For this reason, there has been a problem that it is impossible to measure the motion trajectory of a machine in actual use.

  Furthermore, since the measurement range is limited to a relatively narrow range in common with the above method, the measuring instrument is damaged if the machine moves accidentally beyond the measurement range. In addition, when attempting to measure the motion trajectory of a machine having a large stroke, it was necessary to remove the measuring device once and shift the location. In addition, there are machines that cannot install a measuring instrument, and in such a case, measurement could not be performed.

  In the method described in Patent Document 2, since the motion trajectory is calculated from the machine position obtained from the feedback signal without installing a measuring instrument in the machine, measurement in a free form and within the entire movable range is possible. The vessel is not damaged. However, the actual machine position and the feedback position are not always the same. For example, when the machine is vibrating or there is backlash, the machine movement trajectory cannot be evaluated correctly. There was a problem.

  The present invention has been made in view of the above, and an object of the present invention is to provide a trajectory measuring apparatus capable of accurately measuring a motion trajectory of a machine in actual use without removing a jig or a tool. To do.

  In order to solve the above-described problems and achieve the object, the trajectory measurement apparatus of the present invention is configured to obtain a motion trajectory of a machine whose machine position is controlled so that a detection position of a motor driving a movable shaft follows a command position. A trajectory measuring apparatus for measuring, comprising: an accelerometer that measures the acceleration of the machine; and a motion trajectory analysis unit that analyzes the motion trajectory of the machine based on the command position and / or the detection position and the acceleration. It is characterized by providing.

  According to the present invention, there is an effect that it is possible to accurately measure the motion trajectory of a machine in an actual use state without removing a jig or a tool.

FIG. 1 is a perspective view showing a schematic configuration of a first embodiment of a numerically controlled machine tool to which a trajectory measuring apparatus according to the present invention is applied. FIG. 2 is a side view showing a schematic configuration of the drive mechanism of the numerically controlled machine tool of FIG. FIG. 3 is a block diagram showing a schematic configuration of the first embodiment of the numerically controlled machine tool to which the trajectory measuring apparatus according to the present invention is applied. FIG. 4 is a side view showing an installation error of the accelerometer applied to the trajectory measuring apparatus according to the present invention. FIG. 5 is a block diagram showing a schematic configuration of the motion trajectory analysis unit of FIG. FIG. 6 is a diagram illustrating the relationship between the order of the approximation polynomial of the error waveform approximated by the error waveform approximation unit of FIG. 5 and the approximation error. FIG. 7 is a diagram showing the mechanical end trajectory and the motor end trajectory measured by the trajectory measuring apparatus of FIG. 3 in comparison with the measurement result by the grid encoder. FIG. 8A is a block diagram showing a model of the movable shaft drive mechanism of the second embodiment of the numerically controlled machine tool to which the trajectory measuring apparatus according to the present invention is applied, and FIG. It is a figure explaining generation | occurrence | production of the error by. FIG. 9 is a diagram showing the machine position and the detected position of the numerically controlled machine tool to which the trajectory measuring apparatus according to the present invention is applied in comparison with the measurement result by the grid encoder. FIG. 10 is a side view showing an installation example of the accelerometer 13 for measuring the acceleration of the gantry of the third embodiment of the numerically controlled machine tool to which the trajectory measuring apparatus according to the present invention is applied. FIG. 11 is a perspective view showing an example in which accelerometers are installed on the work table side and the spindle side of the numerical control machine tool to which the trajectory measuring apparatus according to the present invention is applied. FIG. 12 is a flowchart showing an example of an outline of the trajectory measuring method according to the fifth embodiment of the trajectory measuring apparatus according to the present invention. FIG. 13 is a flowchart showing an example of the details of the trajectory measuring method according to the fifth embodiment of the trajectory measuring apparatus according to the present invention. FIG. 14 is a diagram for explaining a method of discriminating an input channel for acceleration signals according to the fifth embodiment of the trajectory measuring apparatus according to the present invention. FIG. 15 is a diagram for explaining a method of discriminating the sign of the acceleration signal in the fifth embodiment of the trajectory measuring apparatus according to the present invention.

  Embodiments of a trajectory measuring apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a perspective view showing a schematic configuration of a first embodiment of a numerically controlled machine tool to which a trajectory measuring apparatus according to the present invention is applied. In FIG. 1, it has a plurality of movable shafts guided in motion in the X-axis, Y-axis, and Z-axis directions, and each movable shaft is driven by a drive mechanism comprising motors 1x, 1y, 1z and feed screws 2x, 2y, 2z. Driven. The rotation angles of the motors 1x, 1y, and 1z are detected by the rotation angle detectors 3x, 3y, and 3z, respectively, and fed back to the motor control device. As a motor driving method, a linear motor may be used instead of the motors 1x, 1y, and 1z and the feed screws 2x, 2y, and 2z, and a linear scale may be used instead of the rotation angle detectors 3x, 3y, and 3z.

  In this numerically controlled machine tool, the work table 4 is driven by the Y-axis drive mechanism, and the column 5 is driven by the X-axis drive mechanism. The spindle head 7 is driven via the ram 6 by the Z-axis drive mechanism attached to the column 5, and as a result, a tool attached to the tip of the spindle head 7 and a workpiece installed on the work table 4. A three-dimensional shape is created between them. The work table 4 and the column 5 are installed on the mount 21.

  FIG. 2 is a side view showing a schematic configuration of the drive mechanism of the numerically controlled machine tool of FIG. In the example of FIG. 2, only the Y-axis drive mechanism is shown for convenience, but the same applies to the X-axis and Z-axis drive mechanisms. In FIG. 2, the rotational motion of the motor 1y is transmitted to the feed screw 2y via the coupling 8y, and is converted into a straight motion via the nut 9y. The straight movement of the feed screw 2y is restricted by the support bearing 10y.

  The command position output from the command generation unit 11 of the motor control device is transmitted to the motor drive unit 12, and the motor drive unit 12 converts the command position and the rotation angle of the motor 1y detected by the rotation angle detector 3y into a position. The motor 1y is driven so that the error from the detection position is as small as possible. The command position and the detection position mean the displacement of each movable shaft with respect to the reference origin position.

In addition to the rotation angle of the motor 1y, a linear scale and a laser displacement meter for detecting the position of the work table 4 may be added to feed back to the motor drive unit 12, and linear may be used instead of the motor 1y and the feed screw 2y. A motor may be used.
In a numerically controlled machine tool, the relative displacement between the tool attached to the tip of the spindle head 7 and the work table 4 is important. The relative displacement is measured in advance, and the command generator 11 or the motor drive unit 12 exists in the machine. It is common practice to correct errors that occur. The cause of the error is a static error such as the perpendicularity between the movable shafts and the pitch error of the feed screw 2y. These are measured and adjusted at the stage of assembling the machine, and rarely change during normal use.

  On the other hand, it is also known that elastic deformation and vibration mainly generated in the coupling 8y, the feed screw 2y, and the support bearing 10y part, the posture change and vibration of the column 5 and the ram 6, and errors due to frictional force occur. The characteristic of the dynamic error varies depending on the use status of the machine, the load mass on the work table 4, the secular change and wear of the machine, and the like. Therefore, it is desirable that the machine motion trajectory can be measured periodically or continuously while the machine is in use, and various correction parameters of the motor control device can be adjusted.

  FIG. 3 is a block diagram showing a schematic configuration of the first embodiment of the numerically controlled machine tool to which the trajectory measuring apparatus according to the present invention is applied. In FIG. 3, the trajectory measuring apparatus measures motion trajectory information necessary for adjusting the parameters of the motor control apparatus. The movement trajectory information includes information necessary for adjustment of the motor control device. Specifically, the presence or absence of mechanical vibration, the period and amplitude of vibration, and a protruding trajectory error ( Information such as the height and width of the quadrant projections, and the size of backlash and lost motion.

  Here, a workpiece 17 is installed on the work table 4, and a tool 16 is attached to the tip of the spindle head 7. The trajectory measuring device includes an accelerometer 13a, 13b that measures the acceleration a of the machine and a motion trajectory analysis unit 14 that analyzes the motion trajectory of the machine based on the command position Pi and / or the detection position Pd and the acceleration a. Is provided. Further, a motion trajectory display unit 15 that displays the motion trajectory of the machine analyzed by the motion trajectory analysis unit 14 may be provided.

  The motion trajectory analysis unit 14 includes an acceleration integration unit 14a that calculates the machine position Pk based on the integration result of the acceleration a, and an error correction that corrects the machine position Pk based on the command position Pi and / or the detection position Pd. A portion 14b is provided. The error correction unit 14b can correct the mechanical position Pk by separating the measurement error and the integration error of the acceleration a by comparing the machine position Pk with the position estimated from the detection position Pd or the command position Pi. it can.

  Then, the command generation unit 11 analyzes the input target position Pm and generates a command position Pi. In the motor drive unit 12, the motor drive voltage Vm is set so that the input command position Pi and the detection position Pd obtained by processing the detection signal Sd transmitted from the rotation angle detectors 3x, 3y, and 3z match as much as possible. Is output to drive the motors 1x, 1y, and 1z.

  Further, the acceleration a, the target position Pm, the command position Pi, and the detection position Pd are input to the motion trajectory analysis unit 14. Then, the machine position Pk is calculated by integrating the acceleration a twice, the machine position Pk is corrected based on the command position Pi and / or the detected position Pd, and the corrected machine position Pk ′ is set to the command position Pi and The detected position Pd is sent to the motion trajectory display unit 15.

  Note that the method of calculating the position by integrating the acceleration a twice is also used for vibration measurement of, for example, an inertial navigation system or a building. However, the measurement accuracy is known to be several meters in the former and several tens of millimeters in the latter, which is 4 to 6 orders of magnitude worse than the accuracy required in the measurement of numerically controlled machine tools. When the position is calculated by integrating the acceleration a twice, the measurement error and the integration error of the acceleration a occur.

  As a cause of the measurement error of the acceleration a, there is an installation error of the accelerometers 13a and 13b. This installation error is that the sensitivity direction of the accelerometers 13a and 13b is deflected with respect to the direction of the movable axis to be measured, and is affected by the movement of a movable axis other than the movable axis to be measured. become. In such a case, the influence of the movable axis other than the movable axis to be measured on the measurement result of the acceleration a or the machine position obtained by integrating the acceleration a twice is obtained analytically or numerically. The acceleration a or the machine position Pk can be corrected by the error.

FIG. 4 is a side view showing an installation error of the accelerometer applied to the trajectory measuring apparatus according to the present invention. In FIG. 4, when measuring the acceleration in the X-axis and Y-axis directions of the XY table using two X-axis accelerometers 18 and Y-axis accelerometers 19 fixed so that the sensitivity directions are orthogonal, the X-axis accelerometer Assuming that the 18 and Y axis accelerometers 19 are installed at an angle θ around the Z axis, the relationship between the true accelerations a _x and a _y and the detected accelerations a _x ′ and a _y ′ is (1) It is expressed as an expression. Therefore, the true accelerations a _x and a _y can be calculated from the tilt angles θ in the sensitivity direction of the X-axis accelerometer 18 and the Y-axis accelerometer 19, and the detected accelerations a _x ′ and a _y ′ can be corrected.

  Further, for example, from the acceleration detected when only the X axis of the XY table is moved and the acceleration detected when only the Y axis is moved, the movement is caused by the movement of a movable axis other than the movable axis to be measured. The influence can be identified in advance, and the result can be used to correct the influence due to the installation error of the accelerometer.

  The integration error that occurs when performing the numerical integration of the acceleration a can analytically or numerically determine the influence of the integration error on the machine position Pk from the command position Pi, and correct the machine position Pk by the calculated error. .

For example, when performing circular motion by moving two movable shafts simultaneously, the motion of each shaft is a sine wave and a cosine wave. Error waveform E _p comprising integral error when the acceleration waveform to determine the position by integrating 2 frequency value by trapezoidal rule at that time is obtained as analytically (2). In equation (2), R is the radius of circular motion, F is the feed rate, and Δt is the data time interval.

  In practice, it is often difficult to calculate and correct the measurement error and integration error of acceleration a separately. Accordingly, an error waveform generated when both the installation error and the integration error of the accelerometers 13a and 13b exist is obtained from the command position Pi as a mathematical expression having a plurality of parameters, and the machine position obtained by integrating the acceleration a twice. By approximating the difference between Pk and the machine position estimated from the detected position Pd or the command position Pi with the equation (2), the installation error and the integration error of the accelerometers 13a and 13b are identified, and the identified error The machine position Pk can be corrected by the amount.

For example, in the case of obtaining the machine position Pk and the acceleration a is integrated twice in the case of performing circular motion, accelerometer 13a, the error waveform E _p is the same period as the circular motion including installation error and the integral error of 13b It becomes a sine wave, and can be reduced to an nth order polynomial as shown in equation (3).

  FIG. 5 is a block diagram showing a schematic configuration of the motion trajectory analysis unit 14 of FIG. In FIG. 5, the motion trajectory analysis unit 14 includes an acceleration integration unit 14a and an error correction unit 14b, and the error correction unit 14b includes subtracters K1 and K2 and an error waveform approximation unit 23.

  When the installation error and integration error of the accelerometers 13a and 13b included in the machine position Pk obtained by integrating the acceleration a twice are identified and corrected, the acceleration a is integrated twice in the subtractor K1. The difference between the obtained machine position Pk and the fed back detected position Pd (FB data) is calculated. This includes both errors caused by error factors of the machine and errors caused by installation errors and integration errors of the accelerometers 13a and 13b.

  Among these, since the error component due to the installation error or integration error of the accelerometers 13a and 13b can be approximated by the polynomial of the equation (3), the machine position Pk obtained by integrating the acceleration a twice and the detected feedback. Of the difference from the position Pd (FB data), a component that can be approximated by a polynomial is an error caused by an installation error or an integration error of the accelerometers 13a and 13b. Therefore, the difference between the machine position Pk obtained by integrating the acceleration a twice and the detected position Pd (FB data) fed back is approximated by a polynomial in the error waveform approximation unit 23. In the subtractor K2, the corrected machine position Pk ′ can be obtained by subtracting the solution obtained by this polynomial from the machine position Pk obtained by integrating the acceleration a twice.

  In the embodiment shown in FIG. 5, the error is identified using the detection position Pd (FB data), but this may be a machine position estimated from the command position Pi. In addition, although circular motion is taken up in the embodiment, when other motion is performed, the installation error and the integration error of the acceleration a may be different from the equation (3).

  When approximating the error waveform, the unknown parameter of the approximate expression may be determined by, for example, the least square method, or a numerical solution method such as the downhill simplex method may be used.

  FIG. 6 is a diagram showing the relationship between the order of the approximation polynomial of the error waveform approximated by the error waveform approximation unit 23 of FIG. 5 and the approximation error. In FIG. 6, the error waveform when the circular motion is measured can be approximated by a polynomial of equation (3), and the approximation accuracy varies depending on the order of the polynomial. As can be seen from FIG. 6, the approximation error becomes smaller as the order of the polynomial is higher, and it can be seen that the approximation error becomes 1 μm or less when the order is 8th or higher.

  When measuring an ordinary machine tool, the measurement accuracy requirement is about 1 μm. Therefore, when measuring circular motion, it is practically sufficient to correct the error by approximating the error with an 8th order polynomial. The machine motion trajectory can be measured with high accuracy.

  FIG. 7 is a view showing the machine end locus and the motor end locus measured by the locus measuring apparatus of FIG. 3 in comparison with the measurement result by the cross grid method (grid encoder). FIG. 7 shows the result of measuring a circular motion with a radius of 25 mm and a feed rate of 3000 mm / min by applying a measurement method using an accelerometer to an actual machine tool. In the example of FIG. 7, 1 div corresponds to 10 μm. In FIG. 7B, in the cross grid method, a deviation of several micrometers is measured between the machine end locus T4 (solid line) and the motor end locus T3 (broken line). Further, in FIG. 7A, also in the trajectory measuring apparatus of FIG. 3, a deviation of several micrometers is present between the machine end trajectory T2 (solid line) and the motor end trajectory T1 (broken line), as in the crossed lattice method. I was able to measure.

  Depending on the measurement target, the measurement accuracy as high as that of the machine tool may not be required. In such a case, the order of the approximate polynomial in the equation (3) may be lowered. On the other hand, when higher-precision measurement is required, the measurement accuracy can be adjusted by increasing the degree of the approximate polynomial in equation (3).

Embodiment 2. FIG.
In the configuration of FIG. 5, when the error waveform due to the error factor of the machine to be measured is expressed by the same equation as the error waveform caused by the installation error and integration error of the accelerometers 13a and 13b, it is originally measured. The target mechanical error is also removed without being distinguished from the installation error and integration error of the accelerometers 13a and 13b.

  Therefore, when the error waveform caused by the installation error and the integration error of the accelerometers 13a and 13b is expressed by the same equation as the error waveform caused by the error factor of the measurement target machine, the command position Pi or the detection position An error amount caused by a machine error factor may be estimated from Pd and added to the machine position Pk.

  Taking circular motion, which is a simultaneous biaxial control motion that controls two movable axes simultaneously, for example, the position command is a sine wave reciprocating motion, and the installation error and integration error of the accelerometers 13a and 13b at this time are circular motion. It is analytically known that it becomes a sine wave shape with the same period. That is, a mechanical error having a fluctuation component for one cycle per round of circular motion is removed without being distinguished from an installation error or an integration error of the accelerometers 13a and 13b.

  FIG. 8A is a block diagram showing the drive mechanism of the movable shaft as a model, and FIG. 8B is a diagram for explaining the generation of an error due to elastic deformation. In FIG. 8A, an example of a mechanical error having a fluctuation component for one cycle per one round of circular motion is an error caused by elastic deformation of the machine. For example, when the driving mechanism of the movable shaft is schematically considered as a spring K (equivalent axial rigidity from the motor end to the machine end) and a mass M (driven body mass), when the mass M is accelerated at a certain acceleration a. Inertia force acts as the product of acceleration a and mass M. When the inertial force acts, elastic deformation occurs as a ratio between the inertial force and the rigidity.

Since the change in the acceleration a during the sine wave reciprocation is a second derivative of the command position Pi, the acceleration a has a waveform with the sign of the command position Pi reversed. That is, it can be seen that the change in the amount of elastic deformation due to the change in the acceleration a becomes a sine wave having the same cycle as the change in the command position Pi, as shown in FIG. For example, when represented by a sine wave motor shaft displacement x _m is the arc radius R and the amplitude, the machine end displacement x _t is represented by a sine wave having the same period as the motor shaft displacement x _m, amplitude arc radius A value obtained by adding the elastic deformation amount D to R.

  The elastic deformation amount D can be easily calculated if the rigidity, mass, and acceleration waveform of the drive mechanism are known. As the acceleration waveform, the measurement result by the accelerometers 13a and 13b installed in the machine may be used, or the acceleration waveform may be calculated from the command position Pi or the detection position Pd. Also, the elastic deformation amount D can be calculated by using the natural frequency determined by the ratio of the stiffness and the mass instead of the stiffness and the mass of the drive mechanism.

  FIG. 9 is a diagram showing the machine position and the detected position of the numerically controlled machine tool to which the trajectory measuring apparatus according to the present invention is applied in comparison with the measurement result by the grid encoder. In the example of FIG. 9, 1 div corresponds to 5 μm. Further, the XY table to be measured has a structure in which the rigidity in the X-axis direction is lower than that in the Y-axis direction. In FIG. 9, when a trajectory error due to elastic deformation appears prominently, the machine position Pk ′ is measured without distinction from an installation error or an integration error of the accelerometers 13a and 13b. In the measurement result according to the second embodiment of the present invention, as shown in FIG. 9A, the trajectory T7 obtained from the detected position Pd and the machine position Pk measured using the accelerometers 13a and 13b. The motion trajectory T6 is displayed in an overlapping manner. Further, as shown in FIG. 9B, only the mechanical movement trajectory T8 is shown in the cross lattice method.

  According to FIG. 9A, the mechanical movement trajectory T6 has an elliptical shape having a long axis in the horizontal axis direction, which is a trajectory error due to elastic deformation caused by low rigidity in the X-axis direction. Even when the measurement result by the grid encoder in FIG. 9B is seen, a trajectory error similar to that in FIG. 9A is generated in the mechanical motion trajectory T8, and the method of the present embodiment shown in FIG. The effectiveness was confirmed.

Embodiment 3 FIG.
FIG. 10 is a side view showing an installation example of the accelerometer 13 for measuring the acceleration of the gantry of the third embodiment of the numerically controlled machine tool to which the trajectory measuring apparatus according to the present invention is applied. In FIG. 10, a reaction force accompanying the movement of the work table 4 acts on the gantry 21 that supports the movable shaft, and vibration is generated. In such a case, since the acceleration measured by the accelerometer 13b is an absolute acceleration, the information includes the vibration acceleration of the gantry 21, and the displacement of the movable shaft cannot be analyzed correctly.

  Therefore, an accelerometer 13c for measuring the acceleration of the gantry 21 that supports the movable axis of the machine is provided, and the sensitivity direction of the accelerometer 13c is installed so as to substantially coincide with the movement direction of the movable axis. The analysis unit 14 may calculate the relative acceleration between the acceleration of the movable axis and the acceleration of the gantry 21 and integrate the relative acceleration twice to obtain the relative displacement between the gantry 21 and the movable axis. Thereby, even when the vibration of the gantry 21 is so large that it cannot be ignored, the mechanical motion trajectory can be accurately measured.

Embodiment 4 FIG.
FIG. 11 is a perspective view showing an example in which accelerometers are installed on the work table side and the spindle side of the numerical control machine tool to which the trajectory measuring apparatus according to the present invention is applied. In FIG. 11, when three-dimensional relative motion becomes a problem as in a machine tool, accelerometers 22a and 22b for measuring accelerations in three directions orthogonal to two machine elements that perform relative motion are provided. The accelerometers 22a and 22b installed on the two machine elements are installed so that the sensitivity directions thereof substantially coincide with each other, and the motion trajectory analysis unit 14 in FIG. 3 calculates the relative acceleration from the acceleration in each direction of the two machine elements. By calculating and integrating the relative acceleration twice to obtain the relative displacement between the two machine elements, the three-dimensional relative displacement between the two machine elements can be measured more accurately.

  In the example of FIG. 11, an example in which triaxial accelerometers 22a and 22b capable of measuring acceleration in three axial directions are installed on the main spindle side and the work table 4 side, respectively, but a normal uniaxial accelerometer is used. You may install 3 each and a 1 axis | shaft accelerometer may be installed only in the direction to measure.

Embodiment 5 FIG.
In FIG. 3, when the accelerometers 13a and 13b are installed in the machine, the sensitivity of the accelerometers 13a and 13b is not always correctly calibrated in advance, and the positive and negative directions of the accelerometers 13a and 13b are movable. It does not necessarily coincide with the positive / negative direction of the axis. Furthermore, a plurality of cables for transmitting a plurality of acceleration signals are not necessarily connected to the input channel in the correct order.

  Therefore, the detected acceleration obtained by differentiating the detected position of the same movable axis with the acceleration of the movable axis twice, or the machine speed obtained by integrating the acceleration once and the detected speed obtained by differentiating the detected position once, Or the machine position obtained by integrating acceleration twice and the detected position are compared, and the amplitude in the waveform of acceleration and detected acceleration, the amplitude in waveform of machine speed and detected speed, or the amplitude in waveform of machine position and detected position The amplitude of the acceleration of the movable axis, the amplitude of the machine speed, or the amplitude of the machine position may be corrected so that the two coincide. This eliminates the need to calibrate the sensitivity of the accelerometers 13a and 13b in advance.

  Further, the detected acceleration obtained by differentiating the detected position of the same movable axis with the acceleration of the movable axis twice, or the machine speed obtained by integrating the acceleration once and the detected speed obtained by differentiating the detected position once, Or, the error between the machine position obtained by integrating acceleration twice and the detected position is obtained, and the amplitude of the error is calculated from the acceleration amplitude calculated from the command position or the detected position, or from the previous position or the detected position. If the velocity amplitude is larger than the amplitude of the command position or the detection position, the acceleration of the movable axis, the machine speed, or the sign of the machine position may be reversed. This eliminates the need to calibrate the accelerometer sign in advance.

  Furthermore, the acceleration obtained by differentiating the acceleration of the plurality of movable axes and the detection positions of the plurality of movable axes twice, or the machine speed obtained by integrating the acceleration once and the detection position obtained by differentiating once. The machine position obtained by integrating twice the detected speed or acceleration is compared with the detected position, and the acceleration and detected acceleration of the Nth movable axis (N is a positive integer) or the machine of the Nth movable axis. If there is a phase difference between the speed and the detected speed, or the machine position of the Nth movable shaft and the fluctuation waveform of the detected position, the Nth machine speed data and the N + 1th machine speed data are switched. You may do it. As a result, even when the input channel of the acceleration signal is wrong, the mechanical motion trajectory can be measured correctly.

  FIG. 12 is a flowchart showing an example of an outline of the trajectory measuring method according to the fifth embodiment of the trajectory measuring apparatus according to the present invention. In FIG. 12, the sensitivity, input channel, and sign of the accelerometers 13a and 13b are calibrated from the speed obtained by integrating the acceleration a once and the speed obtained by differentiating the detection position Pd (steps S1 to S3). . Further, the machine position Pk is obtained by integrating the velocity waveforms after calibrating them (step S4), and the integration error and the installation errors of the accelerometers 13a and 13b are compared by comparing the machine position Pk and the detection position Pd. Is corrected (step S5), and for example, the result of estimating the amount of elastic deformation is added to display the mechanical motion trajectory (steps S6 and S7).

  FIG. 13 is a flowchart showing an example of the details of the trajectory measuring method according to the fifth embodiment of the trajectory measuring apparatus according to the present invention. In the example of FIG. 13, the case of measuring circular motion is taken as an example. The analysis is performed for each movable axis, but in the example of FIG. 13, only the processing for one axis is shown for convenience.

  In FIG. 13, in this locus measurement method, sensitivity calibration processing 30, code calibration processing 31, input channel correction processing 32, error correction processing 33, and elastic deformation estimation processing 34 are performed. In the sensitivity calibration process 30, the amplitude Avfb [m / s] (steps S11 and S12) of the velocity Vfb [m / s] obtained by differentiating the feedback position once and the velocity Va obtained by integrating the acceleration once. A ratio R of [m / s] to amplitude Ava [m / s] (steps S13 and S14) is calculated (step S15). The velocity amplitude Ava can be obtained as a difference between the maximum value and the minimum value of the velocity Va. However, when the velocity Va is extremely small or the resolution is low, the velocity amplitude Ava cannot be calculated correctly. However, in such a low-speed motion, since the trajectory cannot be measured by the accelerometers 13a and 13b, the accelerometers 13a, 13a, If the motion trajectory can be measured by the method according to 13b, the velocity amplitude Ava can be obtained without any problem.

  Further, the velocity amplitude Ava during the circular motion corresponds to the command speed (F value) of the circular motion, and there is no difference between the motor end and the machine end except for the influence of microscopic vibration. Therefore, the velocity amplitude ratio R can be regarded as an acceleration sensitivity error, and the measurement sensitivity of the accelerometers 13a and 13b can be calibrated by multiplying the velocity Va obtained by integrating the acceleration once by the velocity amplitude ratio R ( Step S16). Since the sensitivity of the accelerometers 13a and 13b is calibrated from the velocity amplitude Ava, the result is not affected even if the input channel or sign of acceleration is reversed.

  FIG. 14 is a diagram for explaining a method of discriminating an input channel for acceleration signals according to the fifth embodiment of the trajectory measuring apparatus according to the present invention. 14 shows the X-axis velocity waveform when the feed rate is 3000 mm / min and the radius is 10 mm. Also, when FIG. 14A is connected to the correct channel, FIG. This is the result when the channels are reversed. In FIG. 14, in the circular motion, the two axes perform a sine wave motion and a cosine wave motion, respectively, and their phases are 90 °. As shown in FIG. 14A, when the acceleration signal is input to the correct channel, the phase of the velocity Va ′ obtained by integrating the acceleration and the velocity Vfb obtained by differentiating the feedback position are the same. To do. However, as shown in FIG. 14B, when the acceleration input channels are reversed, the phases of the velocities Va ′ and Vfb are shifted by the phase difference P.

  Therefore, in the code calibration process 31, the half-period T of the speed Vfb and the phase difference P between the speeds Va ′ and Vfb are obtained (step S17), and if there is this phase difference P, the accelerometers 13a and 13b are in the opposite channels. And the data on the first and second axes are exchanged (step S18). The phase difference P is calculated as a difference between a time Ta at which the sign of the velocity Va ′ obtained from the acceleration is inverted and a time Tfb at which the sign of the velocity Vfb obtained from the feedback position is inverted.

  FIG. 15 is a diagram for explaining a method of discriminating the sign of the acceleration signal in the fifth embodiment of the trajectory measuring apparatus according to the present invention. In the example of FIG. 15, the speed obtained from the feedback position and the acceleration when a circular motion with a feed speed of 3000 mm / min and a radius of 10 mm is performed, and the difference between the two are shown. FIG. 15A shows the result when the signs of the two data match, and FIG. 15B shows the result when the sign of the acceleration is reversed with respect to the feedback.

  In FIG. 15A, when the signs of the two data match, the speed difference between the two speeds Va ′ and Vfb is smaller than 3000 mm / min, which is the amplitude Avfb of the feed speed of the circular motion. . On the other hand, as shown in FIG. 15B, when the sign of acceleration is reversed with respect to feedback, the maximum value Dif of the difference between the two velocities Va ′ and Vfb is larger than the amplitude Avfb of the feed speed. I understand that

  Therefore, in the input channel correction process 32, the maximum value Dif of the difference between the two speeds Va ′ and Vfb is obtained (step S19), and the maximum value Dif of the difference between the two speeds Va ′ and Vfb is obtained from the amplitude Avfb of the feed speed. If it is larger, the sign of the acceleration Va is calibrated by inverting the sign of the velocity Va obtained by integrating the acceleration (step S20).

  Next, the machine position Pa is obtained by integrating the speed after the calibration in the above process (step S21), and the difference between the machine position Pa after the calibration and the detected position Pd (FB data) fed back is calculated. (Step S22). Then, the difference between the calibrated machine position Pa and the fed back detected position Pd (FB data) is approximated by a polynomial expression (3) (step S23). Then, the solution obtained by this polynomial is subtracted from the calibrated machine position Pa (step S24), and the result of estimating the amount of elastic deformation is added to display the machine motion trajectory (steps S25 and S26).

  In the embodiment shown in FIGS. 12 to 15, the sensitivity, sign, and input channel of the accelerometer are determined from the speed obtained by integrating the acceleration once and the speed obtained by differentiating the detected position once. I am calibrating. However, the sensitivity, sign and input channel can be calibrated in the same way even if acceleration or position is used instead of velocity.

  By the above method, the sensitivity, input channel and sign of the accelerometer can be automatically recognized and calibrated. If the circular motion trajectory is measured once and the calibration result at that time is stored, the calibration result can be used when measuring the freeform. That is, the accelerometer can be calibrated simultaneously by measuring the circular motion trajectory.

  As described above, the trajectory measuring apparatus according to the present invention compares the machine position obtained by integrating acceleration twice with the machine position estimated from the detected position or the command position, thereby measuring the acceleration and integrating it. It is suitable for a method for accurately measuring the motion trajectory of a machine in an actual use state without removing a jig or a tool.

1x, 1y, 1z Motor 2x, 2y, 2z Feed screw 3x, 3y, 3z Rotation angle detector 4 Work table 5 Column 6 Ram 7 Spindle head 8y Coupling 9y Nut 10y Support bearing 11 Command generator 12 Motor drive unit 13a ~ 13c accelerometer 14 motion trajectory analysis unit 14a acceleration integration unit 14b error correction unit 15 motion trajectory display unit 16 tool 17 workpiece 18 X-axis accelerometer 19 Y-axis accelerometer 21 mount 22a, 22b 3-axis accelerometer 23 error waveform approximation unit K1, K2 Subtractor 30 Sensitivity calibration process 31 Sign calibration process 32 Input channel correction process 33 Error correction process 34 Elastic deformation estimation process

Claims (11)

A trajectory measuring device that measures a motion trajectory of a machine whose machine position is controlled so that a detection position of a motor that drives a movable shaft follows a command position,
An accelerometer for measuring the acceleration of the machine;
E Bei and said command position or the detection position or motion trajectory analysis unit for analyzing the movement trajectory of the machine based on the acceleration and both,
The motion trajectory analysis unit
An acceleration integrator that calculates a machine position based on the integration result of the acceleration;
An error correction unit that corrects the machine position based on the command position or the detection position or both,
Further, the error correction unit corrects the machine position by separating the acceleration measurement error and the integration error by comparing the machine position with a position estimated from the detection position or the command position. Trajectory measuring device characterized by   A trajectory measuring device that measures a motion trajectory of a machine whose machine position is controlled so that a detection position of a motor that drives a movable shaft follows a command position,
  An accelerometer for measuring the acceleration of the machine;
  A motion trajectory analysis unit that analyzes the motion trajectory of the machine based on the command position or the detection position or both and the acceleration;
  The motion trajectory analyzer generates a measurement error due to the movement of a movable axis other than the movable axis to be measured because the sensitivity direction of the accelerometer is deflected with respect to the direction of the movable axis to be measured. In this case, the trajectory measuring apparatus is characterized in that the measurement error is obtained analytically or numerically, and the acceleration or the machine position is corrected by the obtained error.   A trajectory measuring device that measures a motion trajectory of a machine whose machine position is controlled so that a detection position of a motor that drives a movable shaft follows a command position,
  An accelerometer for measuring the acceleration of the machine;
  A motion trajectory analysis unit that analyzes the motion trajectory of the machine based on the command position or the detection position or both and the acceleration;
  The motion trajectory analysis unit integrates acceleration twice to determine a machine position, and when an integration error due to numerical integration occurs, the integration error is analytically or numerically determined from a command position, and the error is calculated by the calculated error. A trajectory measuring apparatus that corrects a machine position.   A trajectory measuring device that measures a motion trajectory of a machine whose machine position is controlled so that a detection position of a motor that drives a movable shaft follows a command position,
  An accelerometer for measuring the acceleration of the machine;
  A motion trajectory analysis unit that analyzes the motion trajectory of the machine based on the command position or the detection position or both and the acceleration;
  The machine position and the detection position obtained by calculating the error waveform generated when both the installation error and the integration error of the accelerometer exist from the command position as a mathematical expression having a plurality of parameters and integrating the acceleration twice. Alternatively, by approximating the difference from the machine position estimated from the command position with the mathematical formula, the accelerometer installation error and integration error are identified, and the machine position is corrected by the identified error. Trajectory measuring device. When an error waveform caused by an installation error and an integration error of the accelerometer is expressed as the same mathematical expression as an error waveform caused by an error factor of a machine that is a measurement target, the machine is determined from the command position or the detection position. The trajectory measuring apparatus according to claim 4 , wherein an error amount caused by an error factor is estimated and added to the machine position. The trajectory measuring apparatus according to claim 5 , wherein the error waveform is expressed by an nth-order polynomial that approximates a sine wave having the same period as a circular motion. A second accelerometer that measures the acceleration of the cradle that supports the movable axis of the machine;
The second accelerometer is installed such that its sensitivity direction substantially coincides with the movement direction of the movable shaft,
2. The motion trajectory analysis unit calculates a relative acceleration between the acceleration of the movable shaft and the acceleration of the gantry, and analyzes the motion trajectory of the machine using the relative acceleration as the acceleration of the machine. The trajectory measuring apparatus according to any one of 1 to 6 . The accelerometer measures accelerations in three orthogonal directions, and is installed so that the sensitivity directions of the accelerometers substantially coincide with each of two mechanical elements that perform relative motion,
2. The motion trajectory analysis unit calculates a relative acceleration from acceleration in each direction in the two machine elements, and analyzes the motion trajectory of the machine using the relative acceleration as the acceleration of the machine. The trajectory measuring apparatus according to any one of 6 . Detected acceleration obtained by differentiating twice the detection position of the same movable axis as the acceleration of the movable axis, or detected speed obtained by differentiating the mechanical speed obtained by integrating the acceleration once and the detection position once. Or the machine position obtained by integrating the acceleration twice and the detected position are compared, and the amplitude in the waveform of the acceleration and the detected acceleration, or the amplitude in the waveform of the machine speed and the detected speed, or the machine so that the amplitude at the position and the detection position of the waveform match, the acceleration of the movable shaft amplitude or the machine velocity amplitude, or of claims 1 to 8, characterized in that to correct the amplitude of the machine position, The trajectory measuring apparatus according to any one of the above. Detected acceleration obtained by differentiating twice the detection position of the same movable axis as the acceleration of the movable axis, or detected speed obtained by differentiating the mechanical speed obtained by integrating the acceleration once and the detection position once. Or an error between the mechanical position obtained by integrating the acceleration twice and the detected position, and the amplitude of the error is the amplitude of the acceleration calculated from the command position or the detected position, or the command position or The acceleration of the movable shaft, the machine speed, or the sign of the machine position is inverted when the amplitude of the speed calculated from the detection position is greater than the amplitude of the command position or the detection position. The trajectory measuring device according to any one of claims 1 to 8 . Detected acceleration obtained by differentiating the acceleration of a plurality of movable axes and detection positions of the plurality of movable axes twice, or obtained by differentiating the machine speed obtained by integrating the acceleration once and the detection position once. The detected position or the machine position obtained by integrating the acceleration twice is compared with the detected position, and the acceleration and detected acceleration of the N-th movable axis (N is a positive integer) or the N-th movable position. If there is a phase difference between the machine speed of the shaft and the detection speed, or between the machine position of the Nth movable axis and the fluctuation waveform of the detection position, the Nth machine speed data and the N + 1th machine speed locus measuring device according to any one of claims 1 8, characterized in that to replace the data.

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