Zero calibration device

Abstract

The utility model discloses a zero calibration device, and relates to the field of robots. One end of the tail plug extends into the sleeve and is fixedly connected with the sleeve, and the tail plug is provided with an axial cavity; the magnetic railing ruler is arranged in the axial cavity, and a measuring head of the magnetic railing ruler extends out of the top of the tail plug; a needle bearing is arranged between the outer wall of the magnetic railing ruler and the inner wall of the axial cavity of the tail plug; the limiting ring fixedly sleeves the outer wall of the magnetic railing ruler, and the outer wall of the limiting ring abuts against the inner wall of the sleeve; the first probe is arranged in the sleeve, and one side, far away from the top of the first probe, of the first probe abuts against the step; the limiting cylinder is fixedly arranged at the bottom of the first probe, a measuring head of the magnetic railing ruler extends into the limiting cylinder, and the preset stroke of the measuring head in the limiting cylinder is not smaller than the distance from the bottom of the limiting cylinder to the top of the limiting ring; the two ends of the elastic element abut against the bottom of the first probe and the top of the limiting ring respectively. According to the zero calibration device, the needle bearing isolates the rotation motion of the magnetic railing ruler and the tail plug, and the problem that a cable at the tail of the magnetic railing ruler is broken due to twisting is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of robots, and in particular to a zero point calibration device. BACKGROUND

[0002] In the field of high-precision motion control of industrial robots, the accuracy of zero point calibration directly determines the positioning accuracy of the tool center point (TCP) and the subsequent trajectory motion accuracy.

[0003] The current mainstream technology generally adopts a rotating position feedback scheme in which a magnetic grating ruler is rigidly connected with a tail plug of a joint of a robot. However, since the magnetic grating ruler needs to rotate synchronously with the tail plug, the signal transmission cable connected to the tail of the magnetic grating ruler will continuously accumulate the number of twists in the repeated calibration process, resulting in irreversible spiral winding of the cable. In the long-term operation, the insulation layer of the cable is broken due to mechanical fatigue caused by repeated twisting, and at the same time, the internal conductor contact resistance is easily increased or changed, and even the signal transmission is interrupted. This inherent structural problem seriously restricts the reliability of the calibration process and the service life of the equipment, and becomes a key bottleneck for improving the absolute positioning accuracy of the robot. CONTENT OF THE INVENTION

[0004] The embodiment of the present application provides a zero point calibration device, which solves the technical problems in the background art.

[0005] The embodiment of the application provides a zero point calibration device, which comprises a sleeve, a tail plug, a magnetic grating ruler, a limiting ring, a first probe, an elastic element and a limiting cylinder; a threaded connection mechanism is arranged at the bottom of the sleeve and is used for detachable connection to a zero point stud of a to-be-calibrated shaft of a robot; the top of the sleeve extends into a positioning hole of the to-be-calibrated shaft; the top of the positioning hole is provided with a second probe of the robot; a step is arranged on the inner wall of the sleeve; one end of the tail plug extends into the sleeve and is fixedly connected with the sleeve, and the tail plug has an axial cavity; the magnetic grating ruler is arranged in the axial cavity, and a measuring head of the magnetic grating ruler extends out of the top of the tail plug; a needle bearing is arranged between the outer wall of the magnetic grating ruler and the inner wall of the axial cavity of the tail plug; the magnetic grating ruler is electrically connected to a control system; the limiting ring is fixedly sleeved on the outer wall of the magnetic grating ruler and is located at the top of the tail plug, and the outer wall of the limiting ring abuts against the inner wall of the sleeve; the first probe is arranged in the sleeve, the top of the first probe is used for contact with the second probe of the robot, and the side, away from the top of the first probe, abuts against the step and is used for preventing the first probe from falling off; the limiting cylinder is fixedly arranged at the bottom of the first probe, the measuring head of the magnetic grating ruler extends into the limiting cylinder, and the preset stroke of the measuring head in the limiting cylinder is not less than the distance from the bottom of the limiting cylinder to the top of the limiting ring; the two ends of the elastic element abut against the bottom of the first probe and the top of the limiting ring respectively, so as to provide a pre-tightening force and make the top of the first probe always abut against the second probe of the robot; when the second probe does not reach the zero point position of the to-be-calibrated shaft, the bottom of the first probe always abuts against the measuring head of the magnetic grating ruler.

[0006] In a possible implementation, the preset stroke of the measuring head is 10 mm.

[0007] In a possible implementation, the bottom of the tail plug is in a character type structure and is used for matching a character type nut on the zero point stud of the to-be-calibrated shaft.

[0008] In a possible implementation, the number of the needle bearings is two, and the needle bearings are arranged at the top and the bottom of the axial cavity of the tail plug respectively.

[0009] In a possible implementation, the zero point calibration device further comprises a clamping spring; an annular clamping groove is arranged at the bottom of the axial cavity, the clamping spring is arranged in the annular clamping groove and is located at the bottom of the magnetic grating ruler, and the clamping spring is used for limiting the axial displacement of the needle bearing located at the bottom of the tail plug; the bottom of the limiting ring abuts against the needle bearing located at the top of the tail plug.

[0010] In a possible implementation, the zero point calibration device further comprises a fastener; a side wall of the limiting ring is provided with a radial threaded hole; one end of the fastener is screwed into the radial threaded hole and presses the outer wall of the magnetic grating ruler, so as to realize the locking of the limiting ring and the magnetic grating ruler.

[0011] The one or more technical solutions provided in the embodiments of the present application have at least the following technical effects:

[0012] The zero point calibration device provided in the present application needs to be fixed on the robot shaft to be calibrated during installation. The sleeve is stably installed on the zero point stud through the threaded connection mechanism, and the top of the sleeve extends into the positioning hole to ensure the accuracy of the installation position. During the working process of the device, when the shaft to be calibrated starts to rotate, the sleeve, the tail plug and the second probe rotate synchronously. At the same time, the profile of the measuring groove on the robot changes with the rotation of the shaft to be calibrated. This profile change drives the second probe of the robot to produce axial displacement. The axial displacement is pre-tightened by the elastic element, and then transmitted to the first probe, and then the displacement is transmitted to the measuring head of the magnetic grating ruler by the first probe, and finally the measuring head of the magnetic grating ruler moves. The magnetic grating ruler can generate signals corresponding to the displacement in real time, and transmit these signals to the control system. After receiving the signals, the control system draws an "M" type displacement curve, and then automatically identifies the lowest point in the curve, and records the corresponding joint angle value at this time, which is the zero point position of the shaft to be calibrated. In this process, the needle roller bearing can keep the magnetic grating ruler stationary independent of the rotating tail plug, effectively avoiding the cable winding problem caused by the rotation of the tail plug. When the first probe bottom continuously contacts the measuring head of the magnetic grating ruler, the displacement information can be stably transmitted before reaching the zero point position. When the zero point position is reached, the measuring groove will sink, which will trigger a sudden change in displacement, and then the accurate zero point calibration is completed. The zero point calibration device of the present application isolates the rotational motion of the magnetic grating ruler and the tail plug through the needle roller bearing, fundamentally solving the problem of broken tail cable of the magnetic grating ruler due to twisting, and improving the service life of the device; the preset stroke of the measuring head in the limiting cylinder is not less than the distance from the bottom of the limiting cylinder to the top of the limiting ring, and the limiting cylinder can timely block the pressure transmission when the displacement of the measuring head exceeds the preset stroke, effectively avoiding damage to the measuring head of the magnetic grating ruler due to excessive pressure, thereby ensuring the reliability of high-precision measurement. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the present application. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creating any creative labor on the basis of these drawings.

[0014] Figure 1 The structure schematic diagram of the zero point calibration device provided by the embodiment of the present application is shown in the figure;

[0015] Figure 2 The structure schematic diagram of the magnetic grating provided by the embodiment of the present application is shown in the figure;

[0016] Figure 3 The structure schematic diagram of the tail plug provided by the embodiment of the present application is shown in the figure;

[0017] Figure 4 The structure schematic diagram of the sleeve provided by the embodiment of the present application is shown in the figure;

[0018] Figure 5 The structure schematic diagram of the limiting ring provided by the embodiment of the present application is shown in the figure;

[0019] Figure 6 The structure schematic diagram of the clasp provided by the embodiment of the present application is shown in the figure.

[0020] Figure: 1-sleeve; 11-step; 2-tail plug; 21-axial cavity; 22-rectangular structure; 3-magnetic grating; 31-measuring head; 4-limiting ring; 41-radial threaded hole; 5-first probe; 6-elastic element; 7-limiting cylinder; 8-needle bearing; 9-clasp. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0022] In the description of the embodiments of the present application, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limitations on the present application. The terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be a communication between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0023] The embodiment of the present application provides a zero point calibration device, such as Figures 1 to 6 As shown. The zero point calibration device includes a sleeve 1, a tail plug 2, a magnetic scale 3, a limiting ring 4, a first probe 5, an elastic element 6 and a limiting cylinder 7. A threaded connection mechanism is provided at the bottom of the sleeve 1, which is used to be detachably connected to the zero point stud of the axis to be calibrated of the robot. The top of the sleeve 1 extends into the positioning hole of the axis to be calibrated, and the top of the positioning hole is provided with the second probe of the robot. The inner wall of the sleeve 1 is provided with a step 11. One end of the tail plug 2 extends into the sleeve 1 and is fixedly connected to the sleeve 1, and the tail plug 2 has an axial cavity 21. The magnetic scale 3 is arranged in the axial cavity 21, and the measuring head 31 of the magnetic scale 3 extends from the top of the tail plug 2. Specifically, the magnetic scale 3 of the present application is a high-precision displacement measuring component that can sense tiny displacements of its measuring head 31.

[0024] The magnetic scale 3 is electrically connected to the control system. Specifically, the tail cable of the magnetic scale 3 is connected to the control system. A needle roller bearing 8 is positioned between the outer wall of the magnetic scale 3 and the inner wall of the axial cavity 21 of the tail plug 2. This needle roller bearing 8 isolates the magnetic scale 3 from the tail plug 2, allowing relative rotation between the two.

[0025] The first probe 5 is disposed within the sleeve 1, with its top contacting the robot's second probe. The side of the probe 5 facing away from the top abuts against a step 11, preventing the first probe 5 from falling off. A stopper 7 is fixed to the bottom of the first probe 5, and the measuring head 31 of the magnetic scale 3 extends into the stopper 7. The preset travel of the measuring head 31 within the stopper 7 is no less than the distance from the bottom of the stopper 7 to the top of the stop ring 4.

[0026] If the displacement of the measuring head 31 exceeds its preset stroke, the measuring head 31 of the magnetic grating ruler 3 will be crushed due to excessive pressure. In the design of the present application, when the displacement of the measuring head 31 continues to increase until the limiting cylinder 7 contacts the limiting ring 4, the limiting cylinder 7 will play a role to prevent the bottom of the first probe 5 from continuing to compress the measuring head 31 of the magnetic grating ruler 3, thereby effectively avoiding the damage of the measuring head 31 due to excessive pressure, and providing reliable protection for the magnetic grating ruler 3.

[0027] The two ends of the elastic element 6 respectively abut against the bottom of the first probe 5 and the top of the limiting ring 4, for providing a pre-tightening force to make the top of the first probe 5 always press against the second probe of the robot. When the second probe does not reach the zero position of the axis to be calibrated, the bottom of the first probe 5 always abuts against the measuring head 31 of the magnetic grating ruler 3. The second probe of the present application always maintains a close contact state with the measuring groove on the robot. The position of the measuring groove on the robot is fixed and unchangeable.

[0028] It should be noted that when installing the zero point calibration device, it needs to be fixed on the robot shaft to be calibrated. The sleeve 1 is installed on the zero point stud through a threaded connection mechanism, and the top of the sleeve 1 extends into the positioning hole to ensure the accuracy of the installation position. During the operation of the device, when the shaft to be calibrated starts to rotate, the sleeve 1, the tail plug 2 and the second probe rotate synchronously. At the same time, the profile of the measuring groove on the robot changes with the rotation of the shaft to be calibrated. This profile change drives the second probe of the robot to produce axial displacement. The axial displacement is pre-tightened by the elastic element 6, and then transmitted to the first probe 5, and then transmitted to the measuring head 31 of the magnetic grating ruler 3 by the first probe 5, and finally drives the measuring head 31 of the magnetic grating ruler 3 to move. The magnetic grating ruler 3 can generate signals corresponding to the displacement in real time, and transmit these signals to the control system. After receiving the signals, the control system draws an "M" type displacement curve, and then automatically identifies the lowest point in the curve, and records the corresponding joint angle value at this time, which is the zero point position of the shaft to be calibrated. In this process, the needle bearing 8 can keep the magnetic grating ruler 3 stationary independent of the rotating tail plug 2, effectively avoiding the problem of cable entanglement caused by the rotation of the tail plug 2. When not reaching the zero point position, the bottom of the first probe 5 will continuously contact the measuring head 31 of the magnetic grating ruler 3, so as to stably transmit the displacement information. When reaching the zero point position, the measuring groove will be sunken, which will trigger the displacement mutation, and then the accurate zero point calibration is completed. The zero point calibration device of the present application isolates the rotational motion of the magnetic grating ruler 3 and the tail plug 2 through the needle bearing 8, fundamentally solving the problem of breakage of the tail cable of the magnetic grating ruler 3 due to twisting, and improving the service life of the device; the preset stroke of the measuring head 31 in the limiting cylinder 7 is not less than the distance from the bottom of the limiting cylinder 7 to the top of the limiting ring 4, and the limiting cylinder 7 can timely block the pressure transmission when the displacement of the measuring head 31 exceeds the preset stroke, effectively avoiding damage to the measuring head 31 of the magnetic grating ruler 3 due to excessive pressure, thereby ensuring the reliability of high-precision measurement.

[0029] In the embodiment of the present application, the preset stroke of the measuring head 31 is 10mm.

[0030] In the embodiment of the present application, the bottom of the tail plug 2 is a character-shaped structure 22, which is used to match with a character-shaped nut on the zero point stud of the shaft to be calibrated.

[0031] In the embodiment of the present application, the number of needle bearings 8 is two, which are respectively arranged at the top and bottom of the axial cavity 21 of the tail plug 2, so that the top and bottom of the tail plug 2 can obtain stable and accurate support during rotation, effectively dispersing the stress generated during rotation.

[0032] In this embodiment of the present application, the zero point calibration device further includes a retaining spring 9. An annular retaining groove is provided at the bottom of the axial cavity 21. The retaining spring 9 is disposed within the annular retaining groove and is located at the bottom of the magnetic scale 3. The retaining spring 9 is used to limit the axial displacement of the needle roller bearing 8 located at the bottom of the tail plug 2. The bottom of the limiting ring 4 abuts against the needle roller bearing 8 located at the top of the tail plug 2.

[0033] In the embodiment of the present application, the zero point calibration device further includes a fastener. The side wall of the limit ring 4 is provided with a radial threaded hole 41. One end of the fastener is screwed into the radial threaded hole 41 and presses against the outer wall of the magnetic scale 3 to achieve locking of the limit ring 4 and the magnetic scale 3.

[0034] It should be noted that the present application isolates the top cross-section of the tail plug 2 by means of a needle roller bearing 8 located at the top of the tail plug 2, so that when the sleeve 1 and the tail plug 2 rotate, the magnetic scale 3 and the retaining ring 4 remain stationary. Specifically, the retaining ring 4 is sleeved onto the outer circumference of the magnetic scale 3, and the two are assembled and positioned using a clearance fit, and are ultimately fixedly connected by fasteners.

[0035] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0036] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A zero point calibration device, characterized in that: It includes a sleeve, a tail plug, a magnetic scale, a limiting ring, a first probe, an elastic element and a limiting cylinder; The bottom of the sleeve is provided with a threaded connection mechanism for detachably connecting to the zero-point stud of the axis to be calibrated of the robot. The top of the sleeve extends into the positioning hole of the axis to be calibrated. The top of the positioning hole is provided with the second probe of the robot. The inner wall of the sleeve is provided with a step. One end of the tail plug extends into the sleeve and is fixedly connected to the sleeve, and the tail plug has an axial cavity; The magnetic scale is arranged in the axial cavity, and the measuring head of the magnetic scale extends from the top of the tail plug; A needle bearing is provided between the outer wall of the magnetic scale and the inner wall of the axial cavity of the tail plug; the magnetic scale is electrically connected to the control system; The limiting ring is fixedly sleeved on the outer wall of the magnetic scale and is located on the top of the tail plug, with its outer wall abutting against the inner wall of the sleeve; The first probe is disposed in the sleeve, with its top being used to contact the second probe of the robot, and its side away from the top of the first probe abutting against the step to prevent the first probe from falling off; The limiting cylinder is fixedly arranged at the bottom of the first probe, the measuring head of the magnetic scale extends into the limiting cylinder, and the preset stroke of the measuring head in the limiting cylinder is not less than the distance from the bottom of the limiting cylinder to the top of the limiting ring; The two ends of the elastic element are respectively in contact with the bottom of the first probe and the top of the limiting ring, so as to provide a pre-tightening force so that the top of the first probe always presses against the second probe of the robot; When the second probe has not reached the zero position of the shaft to be calibrated, the bottom of the first probe always abuts against the measuring head of the magnetic scale.

2. The zero point calibration device according to claim 1, characterized in that: The preset stroke of the measuring head is 10 mm.

3. The zero point calibration device according to claim 1, characterized in that: The bottom of the tail plug is a straight-shaped structure, which is used to match the straight-shaped nut on the zero point stud of the shaft to be calibrated.

4. The zero point calibration device according to claim 1, characterized in that: There are two needle roller bearings, which are respectively arranged at the top and bottom of the axial cavity of the tail plug.

5. The zero point calibration device according to claim 4, characterized in that: Also includes a circlip; An annular groove is provided at the bottom of the axial cavity, and the retaining spring is provided in the annular groove and located at the bottom of the magnetic scale, for limiting the axial displacement of the needle bearing located at the bottom of the tail plug; The bottom of the limiting ring abuts against the needle bearing located on the top of the tail plug.

6. The zero point calibration device according to claim 1, characterized in that: Also included are fasteners; The side wall of the limiting ring is provided with a radial threaded hole; One end of the fastener is screwed into the radial threaded hole and presses the outer wall of the magnetic scale to achieve locking of the limit ring and the magnetic scale.

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