Wrist supporting structure of palletizing robot and rigidity calibration method

Abstract

The invention relates to the technical field of industrial robots, in particular to a stacking robot wrist supporting structure and a rigidity calibration method. The structure comprises a forearm and a wrist, and the connecting end of the forearm and the connecting end of the wrist are each of a U-shaped structure. The small arm comprises a left small arm hinge lug and a right small arm hinge lug; the wrist comprises a left wrist hinge lug and a right wrist hinge lug; the left forearm hinge lug and the right forearm hinge lug are located on the inner side of the left wrist hinge lug and the inner side of the right wrist hinge lug respectively, the left forearm hinge lug and the left wrist hinge lug are hinged through a left short shaft assembly, and the right forearm hinge lug and the right wrist hinge lug are hinged through a right short shaft assembly. The supporting rigidity of the wrist is improved, the supporting rigidity can be adjusted while the axial relative position of the wrist and the forearm meets the bearing pre-pressing requirement, and the axial rigidity of the two hinge lugs of the wrist and the two hinge lugs of the forearm is improved.

Description

Technical Field

[0001] This invention relates to the field of industrial robot technology, and in particular to a wrist support structure and stiffness calibration method for a palletizing robot. Background Technology

[0002] In existing industrial robots, the common practice in the industry is to fix one end of the long shaft to the wrist body and then use a clamping cap to press the inner ring of the bearing at the other end. This structure has weak support stiffness and cannot solve the problem of adjusting the support stiffness.

[0003] like Figure 8 As shown, in existing industrial robot connection and support structures between the forearm part 1A and the wrist part 2A, the industry standard is to install two bearings 4A inside the forearm part 1A, with a long shaft 5A passing through the joint. One end of the long shaft 5A is fixed in a hinge lug on one side of the wrist part 2A. The middle of the long shaft 5A forms a hinge kinematic pair with the forearm part 1A through two tapered roller bearings 4A. The outer ring of the tapered roller bearings 4A is axially limited by a bearing cap 6A, and the other end of the long shaft 5A is pressed against the inner ring of the tapered roller bearings 4A by a cup-shaped pressure sleeve 3A. The combination of the cup-shaped pressure sleeve 3A, the long shaft 5A, and the bolts is connected to the other end of the wrist part 2A as a cylindrical pair. The axial support of this cylindrical pair is floating, resulting in insufficient system stiffness. In addition, the structure that provides pre-tightening of the two bearings through the combination of the cup-shaped pressure sleeve 3A, the long shaft 5A, and the bolts cannot adjust the axial relative position of the forearm part 1A and the wrist part 2A, causing significant difficulties for the software in compensating for the rod length. Therefore, there is an urgent need for a palletizing robot wrist support structure and stiffness calibration method that can improve support stiffness and adjust support stiffness. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a wrist support structure and stiffness calibration method for palletizing robots, thereby solving the problems of weak assembly stiffness and inability to adjust axial stiffness in existing industrial robot wrist supports.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The present invention provides a palletizing robot wrist support structure, including a forearm and a wrist, wherein the connection ends of the forearm and the wrist are both U-shaped structures;

[0007] The forearm includes a left forearm hinge and a right forearm hinge;

[0008] The wrist includes a left wrist hinge and a right wrist hinge;

[0009] The left forearm hinge and the right forearm hinge are located inside the left wrist hinge and the right wrist hinge, respectively. The left forearm hinge and the left wrist hinge are hinged together by the left short shaft assembly, and the right forearm hinge and the right wrist hinge are hinged together by the right short shaft assembly.

[0010] In one possible implementation, the left short shaft assembly includes a short shaft, a bearing, a pressure cap, and a gasket. One end of the short shaft is fitted and fixedly connected to the shaft hole of the left forearm hinge, and the other end of the short shaft is connected to the left wrist hinge via the bearing. The outer end face of the left wrist hinge is connected to the pressure cap, which axially limits the bearing. A gasket for adjusting the axial support stiffness is provided between the pressure cap and the bearing.

[0011] The right short axis assembly has the same structure as the left short axis assembly.

[0012] In one possible implementation, the short shaft is a stepped shaft structure, comprising an inner shaft section, an inner shoulder, a sealed shaft section, an outer shoulder, and a bearing shaft section arranged sequentially along the axial direction. The inner shaft section mates with the shaft hole of the left forearm hinge and is axially limited by the inner shoulder. The inner shoulder is fixedly connected to the inner stop positioning surface of the left forearm hinge by screw I. The sealed shaft section is dynamically sealed to the left wrist hinge by a rotating sealing ring. The bearing is mounted on the bearing shaft section, and the back of the inner ring of the bearing is axially limited by the outer shoulder.

[0013] In one possible implementation, the mounting and positioning surface of the pressure cap includes a bearing outer ring back contact surface, a positioning ring surface, and a wrist contact surface arranged sequentially, wherein the bearing outer ring back contact surface presses against the gasket, the positioning ring surface fits against the inner hole of the left wrist hinge, and the wrist contact surface fits against the outer end face of the left wrist hinge and is connected by screw II.

[0014] Another aspect of the present invention provides a method for calibrating the stiffness of the wrist support structure of a palletizing robot as described above, comprising the following steps:

[0015] Step S1: Calibrate the axial stiffness between the left forearm hinge and the left wrist hinge;

[0016] Step S2: Calibrate the axial stiffness between the right forearm hinge and the right wrist hinge;

[0017] Step S3: Assemble the forearm and wrist, and control the axial relative position of the forearm and wrist by distributing the shims of the left and right joints;

[0018] Step S4: Measure whether the support stiffness and rotational torque of the forearm and wrist are up to standard.

[0019] In one possible implementation, the axial stiffness calibration between the left forearm hinge and the left wrist hinge includes the following steps:

[0020] Step S1.1: Measure the axial dimension and tolerance of the outer end face of the left wrist hinge;

[0021] Step S1.2: Measure the axial dimensions and tolerances of the assembly positioning surface of the gland;

[0022] Step S1.3: Measure the axial dimensions and tolerances of the back of the inner and outer rings of the bearing;

[0023] Step S1.4: Measure the axial dimensions and tolerances of the inner and outer shoulders of the short shaft;

[0024] Step S1.5: Measure the axial dimensions and tolerances of the inner stop positioning surface of the left forearm hinge;

[0025] Step S1.6: Based on the cumulative values ​​of the axial dimensions and tolerances of the left wrist hinge, pressure cap, bearing, short shaft and left forearm hinge obtained by measurement, compare them with the standard assembly axial dimension tolerance values ​​to determine the thickness and quantity of the shims in the left joint.

[0026] In one possible implementation, the axial stiffness calibration between the right forearm hinge and the right wrist hinge includes the following steps:

[0027] Step S2.1: Measure the axial dimension and tolerance of the outer end face of the right wrist hinge;

[0028] Step S2.2: Measure the axial dimensions and tolerances of the assembly positioning surface of the gland;

[0029] Step S2.3: Measure the axial dimensions and tolerances of the back of the inner ring and the back of the outer ring of the bearing;

[0030] Step S2.4: Measure the axial dimensions and tolerances of the inner and outer shoulders of the short shaft;

[0031] Step S2.5: Measure the axial dimensions and tolerances of the inner stop positioning surface of the right forearm hinge;

[0032] Step S2.6: Based on the cumulative values ​​of the axial dimensions and tolerances of the right wrist hinge, pressure cap, bearing, short shaft and right forearm hinge obtained by measurement, compare them with the standard assembly axial dimension tolerance values ​​to determine the thickness and quantity of the shims in the right joint.

[0033] In one possible implementation, the assembly process between the forearm and wrist in step S3 includes the following steps:

[0034] Step M1: Install two rotating sealing rings on the inside of the left and right wrist hinges respectively;

[0035] Step M2: Place the left forearm hinge and the right forearm hinge inside the left wrist hinge and the right wrist hinge, respectively;

[0036] Step M3: A short shaft is inserted from the outside to the inside into the left wrist hinge and the left forearm hinge, and the inner end of the short shaft is fixedly connected to the left forearm hinge by a screw I.

[0037] Another short shaft passes through the right wrist hinge and the right forearm hinge from the outside to the inside, and the inner end of the other short shaft is fixedly connected to the right forearm hinge by another screw I.

[0038] Step M4: Install two bearings on the outer ends of the two short shafts respectively, so that the back of the inner ring of the bearing is close to the outer shoulder of the short shaft;

[0039] Step M5: Place shims of a certain thickness and quantity on the back of the outer rings of the two bearings, then install two pressure caps. The two pressure caps are fixedly connected to the left wrist hinge and the right wrist hinge respectively by screw II, and press the shims tightly.

[0040] The advantages and beneficial effects of this invention are as follows: By placing the bearing 14 in the outer wrist hinge lug, this invention provides greater support stiffness with the characteristics of a simply supported beam compared to existing wrist joint structures, given the same size forearm 4 and wrist 5. Simultaneously, by adding shims 18 to the pressure caps 17 on both sides of the wrist 5 to pre-tighten the bearing stiffness, this structure effectively adjusts the axial relative position of the forearm 4 and wrist 5, avoiding the significant difficulty in software length compensation caused by the rod length accuracy in long-axis structures. This invention employs two short shafts 12, and both hinge lugs of the wrist 5 and forearm 4 form hinge pairs rather than cylindrical pairs; therefore, the system rigidity is relatively good, and it also facilitates wiring in the middle.

[0041] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings.

[0042] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0043] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0044] Figure 1This is a schematic diagram of the connection structure between the forearm and wrist of an existing industrial robot.

[0045] Figure 2 This is an isometric view of a wrist support structure for a palletizing robot according to the present invention.

[0046] Figure 3 This is a schematic diagram of the forearm structure in this invention;

[0047] Figure 4 This is a schematic diagram of the wrist structure in this invention;

[0048] Figure 5 This is a cross-sectional view of a wrist support structure for a palletizing robot according to the present invention.

[0049] Figure 6 for Figure 5 Enlarged view of a portion of point A in the middle;

[0050] Figure 7 for Figure 6 Enlarged view of a section at point B in the middle;

[0051] Figure 8 This is an isometric view of the palletizing robot in an embodiment of the present invention;

[0052] Figure 9 This is a side view of the palletizing robot in an embodiment of the present invention.

[0053] In the diagram: 1-Base, 2-Waist seat, 3-Upper arm, 4-Forearm, 401-Left forearm hinge, 402-Right forearm hinge, 5-Wrist, 501-Left wrist hinge, 502-Right wrist hinge, 6-Flange, 7-Lower swing arm, 8-Rear connecting rod, 9-Outer forearm connecting rod, 10-Triangular connecting rod, 11-Side swing arm, 12-Short shaft, 1201-Inner shaft section, 1202-Inner shaft shoulder, 1203-Sealing chamfer, 1204-Sealing shaft section, 1205-Outer shaft shoulder, 1206-Bearing shaft section, 1207-Process hole, 13-Rotary sealing ring, 14-Bearing, 15-Screw I, 16-Screw II, 17-Gland, 1701-Bearing outer ring back contact surface, 1702-Positioning ring surface, 1703-Wrist contact surface, 18-Gasket. Detailed Implementation

[0054] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0055] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0056] One embodiment of the present invention provides a wrist support structure for a palletizing robot, which improves the wrist support stiffness. The relative axial position of the wrist and forearm allows for adjustment of support stiffness while meeting bearing preload requirements, thereby increasing the axial stiffness of the two hinges of the wrist and the two hinges of the forearm. See also... Figures 2 to 7 As shown, the palletizing robot's wrist support structure includes a forearm 4 and a wrist 5, with both forearm 4 and wrist 5 having a U-shaped connection. The forearm 4 includes a left forearm hinge 401 and a right forearm hinge 402. The wrist 5 includes a left wrist hinge 501 and a right wrist hinge 502. The left forearm hinge 401 and the right forearm hinge 402 are located inside the left wrist hinge 501 and the right wrist hinge 502, respectively, and are hinged together by a left short shaft assembly. The right forearm hinge 402 and the right wrist hinge 502 are hinged together by a right short shaft assembly.

[0057] See Figure 5 , Figure 7 As shown, in the embodiments of the present invention, the left short shaft assembly includes a short shaft 12, a bearing 14, a pressure cap 17, and a gasket 18. One end of the short shaft 12 is fitted and fixedly connected to the shaft hole of the left forearm hinge 401. The other end of the short shaft 12 is connected to the left wrist hinge 501 through the bearing 14. The outer end face of the left wrist hinge 501 is connected to the pressure cap 17. The pressure cap 17 axially limits the bearing 14, and a gasket 18 for adjusting the axial support stiffness is provided between the pressure cap 17 and the bearing 14.

[0058] Specifically, the right short axis assembly has the same structure as the left short axis assembly.

[0059] See Figure 6 , Figure 7As shown, in this embodiment of the invention, the short shaft 12 is a stepped shaft structure, including an inner shaft section 1201, an inner shaft shoulder 1202, a sealing shaft section 1204, an outer shaft shoulder 1205, and a bearing shaft section 1206 arranged sequentially along the axial direction. A sealing chamfer 1203 is provided between the inner shaft shoulder 1202 and the sealing shaft section 1204. The inner shaft section 1201 mates with the shaft hole of the left forearm hinge lug 401 and is axially limited by the inner shaft shoulder 1202. The inner shaft shoulder 1202 is fixedly connected to the inner stop positioning surface of the left forearm hinge lug 401 by screw I15. The sealing shaft section 1204 is dynamically sealed to the left wrist hinge lug 501 by a rotating sealing ring 13. The bearing 14 is mounted on the bearing shaft section 1206, and the back of the inner ring of the bearing 14 is axially limited by the outer shaft shoulder 1205. A process hole 1207 is provided at the center of the end face of the bearing shaft section 1206.

[0060] In an embodiment of the present invention, the assembly positioning surface of the pressure cap 17 includes a bearing outer ring back contact surface 1701, a positioning ring surface 1702 and a wrist contact surface 1703 arranged sequentially along the axial direction. The bearing outer ring back contact surface 1701 presses against the gasket 18, the positioning ring surface 1702 fits against the inner hole of the left wrist hinge lug 501, and the wrist contact surface 1703 fits against the outer end face of the left wrist hinge lug 501 and is connected by a plurality of screws II16.

[0061] Taking a four-axis palletizing robot with the wrist structure of this invention as an example, see [link to relevant documentation]. Figure 8 , Figure 9 As shown, the four-axis palletizing robot includes a base 1, a waist support 2, an upper arm 3, a forearm 4, a wrist 5, a flange 6, a lower swing arm 7, and a rear connecting rod 8. The base 1 is fixed to the ground. The waist support 2 contains a first drive that allows it to rotate with the base 1 around an axis perpendicular to the mounting surface of the base 1. The waist support 2 contains a second drive that allows the upper arm 3 to rotate with the waist support 2 around two axes, which are orthogonal to the first axis. The waist support 2 contains a third drive that allows one end of the lower swing arm 7 to rotate with the waist support 2 around the second axis. The other end of the lower swing arm 7 is hinged to the lower end of the rear connecting rod 8, and the upper end of the rear connecting rod 8 is hinged to the rear end of the forearm 4. The upper arm 3 and the rear part of the forearm 4 are hinged to three axes, which are parallel to the second axis. The wrist 5 is hinged to the front part of the forearm 4. The lower swing arm 7 moves parallel to the forearm 4, and the rear connecting rod 8 moves parallel to the upper arm 3.

[0062] The four-axis palletizing robot also includes an auxiliary linkage assembly, which comprises an outer forearm link 9, a triangular link 10, and a lateral swing arm 11. One corner of the triangular link 10 is hinged to the forearm 4 along the three axes. The other two corners of the triangular link 11 are hinged to the rear end of the outer forearm link 9 and the upper end of the lateral swing arm 11, respectively. The front end of the outer forearm link 9 is hinged to the wrist 5, and the outer forearm link 9 moves parallel to the forearm 4. The lower end of the lateral swing arm 11 is hinged to the waist support 2, and the lateral swing arm 11 moves parallel to the upper arm 3. All hinge axes are parallel to the second and third axes. The wrist 5 contains a fourth drive that can drive the flange 6 and the wrist 5 to rotate around the four axes, which are parallel to the first axis.

[0063] This invention improves the wrist support stiffness of a four-axis palletizing robot. The axial relative position of the wrist 5 and the forearm 4 can adjust the support stiffness while meeting the bearing preload requirements. The axial rigidity of the two hinges of the wrist 5 and the two hinges of the forearm 4 is improved.

[0064] See Figures 2 to 7 As shown, another embodiment of the present invention provides a method for calibrating the stiffness of the wrist support structure of a palletizing robot as described in the above embodiment, comprising the following steps:

[0065] Step S1: Calibrate the axial stiffness between the left forearm hinge 401 and the left wrist hinge 501;

[0066] Step S2: Calibrate the axial stiffness between the right forearm hinge 402 and the right wrist hinge 502;

[0067] Step S3: Assemble the forearm 4 and wrist 5, and control the axial relative position of the forearm 4 and wrist 5 by distributing the shims of the left and right joints.

[0068] Step S4: Measure whether the support stiffness and rotational torque of the forearm 4 and wrist 5 are up to standard.

[0069] In an embodiment of the present invention, the axial stiffness calibration between the left forearm hinge 401 and the left wrist hinge 501 in the left joint includes the following steps:

[0070] Step S1.1: Measure the axial dimension and tolerance of the outer end face of the left wrist hinge lug 501;

[0071] Specifically, the outer end face of the left wrist hinge lug 501 contacts the wrist contact surface 1703 of the pressure cover 17;

[0072] Step S1.2: Measure the axial dimensions and tolerances of the assembly positioning surface of the pressure cap 17;

[0073] Specifically, the axial dimensions and tolerances of the bearing outer ring back contact surface 1701 and the wrist contact surface 1703 are denoted as follows;

[0074] Step S1.3: Measure the axial dimensions and tolerances of the back of the inner ring and the back of the outer ring of bearing 14;

[0075] Step S1.4: Measure the axial dimensions and tolerances of the inner shoulder 1202 and the outer shoulder 1205 of the short shaft 12;

[0076] Step S1.5: Measure the axial dimensions and tolerances of the inner stop positioning surface of the left forearm hinge lug 401;

[0077] Step S1.6: Based on the cumulative values ​​of the axial dimensions and tolerances of the left wrist hinge lug 501, pressure cap 17, bearing 14, short shaft 12 and left forearm hinge lug 401 obtained by measurement, compare them with the standard assembly axial dimension tolerance values ​​(through the coupling calculation of bearing preload calculation and the process dimension chain of mechanical design tolerance fit), determine the thickness and quantity of the shim 18 in the left joint.

[0078] In an embodiment of the present invention, the axial stiffness calibration between the right forearm hinge 402 and the right wrist hinge 502 in the right joint includes the following steps:

[0079] Step S2.1: Measure the axial dimension and tolerance of the outer end face of the right wrist hinge 502;

[0080] Step S2.2: Measure the axial dimensions and tolerances of the assembly positioning surface of the pressure cap 17;

[0081] Step S2.3: Measure the axial dimensions and tolerances of the back of the inner ring and the back of the outer ring of bearing 14;

[0082] Step S2.4: Measure the axial dimensions and tolerances of the inner shoulder 1202 and the outer shoulder 1205 of the short shaft 12;

[0083] Step S2.5: Measure the axial dimensions and tolerances of the inner stop positioning surface of the right forearm hinge lug 402;

[0084] Step S2.6: Based on the cumulative value of the axial dimensions and tolerances of the right wrist hinge lug 502, pressure cap 17, bearing 14, short shaft 12 and right forearm hinge lug 402 obtained by measurement, compare them with the standard assembly axial dimension tolerance value to determine the thickness and quantity of the shim 18 in the right joint.

[0085] In an embodiment of the present invention, the assembly process between the forearm 4 and the wrist 5 in step S3 includes the following steps:

[0086] Step M1: Install two rotating sealing rings 13 on the inner side of the left wrist hinge 501 and the right wrist hinge 502 respectively, with the sealing lips facing inward.

[0087] Step M2: Place the left forearm hinge 401 and the right forearm hinge 402 on the inside of the left wrist hinge 501 and the right wrist hinge 502, respectively.

[0088] Step M3: A short shaft 12 is inserted from the outside to the inside into the left wrist hinge 501 and the left forearm hinge 401, and the inner end of the short shaft 12 is fixedly connected to the left forearm hinge 401 by a screw I15.

[0089] Another short shaft 12 is inserted into the right wrist hinge 502 and the right forearm hinge 402 from the outside to the inside, and the inner end of the other short shaft 12 is fixedly connected to the right forearm hinge 402 by another screw I15.

[0090] Step M4: Install two bearings 14 on the outer ends of the two short shafts 12 respectively, so that the back of the inner ring of the bearing 14 is close to the outer shoulder 1205 of the short shaft 12.

[0091] Step M5: Place shims 18 of a certain thickness and number on the back of the outer rings of the two bearings 14, and then install two pressure caps 17. The two pressure caps 17 are fixedly connected to the left wrist hinge lug 501 and the right wrist hinge lug 502 respectively by screws II 16, and press the shims 18 tightly.

[0092] This invention places the bearing 14 in the outer wrist hinge lug, providing greater support stiffness with simple beam characteristics compared to existing wrist joint structures, for the same size forearm 4 and wrist 5. Simultaneously, by adding shims 18 to the pressure caps 17 on both sides of the wrist 5 to pre-tighten the bearing stiffness, this structure effectively adjusts the axial relative position of the forearm 4 and wrist 5, avoiding the significant length compensation difficulties caused by the rod length accuracy in long-axis structures. This invention employs two short shafts 12, and both hinge lugs of the wrist 5 and forearm 4 form hinge pairs rather than cylindrical pairs; therefore, the system rigidity is relatively good, and it also facilitates wiring in the middle.

[0093] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A wrist support structure for a palletizing robot, comprising a forearm (4) and a wrist (5), characterized in that, The connecting ends of the forearm (4) and the wrist (5) are both U-shaped structures; The forearm (4) includes a left forearm hinge (401) and a right forearm hinge (402); The wrist (5) includes a left wrist hinge (501) and a right wrist hinge (502); The left forearm hinge (401) and the right forearm hinge (402) are located inside the left wrist hinge (501) and the right wrist hinge (502) respectively. The left forearm hinge (401) and the left wrist hinge (501) are hinged together by the left short shaft assembly, and the right forearm hinge (402) and the right wrist hinge (502) are hinged together by the right short shaft assembly.

2. The palletizing robot wrist support structure according to claim 1, characterized in that, The left short shaft assembly includes a short shaft (12), a bearing (14), a pressure cap (17), and a gasket (18). One end of the short shaft (12) is fitted and fixedly connected to the shaft hole of the left forearm hinge (401). The other end of the short shaft (12) is connected to the left wrist hinge (501) through the bearing (14). The outer end face of the left wrist hinge (501) is connected to the pressure cap (17). The pressure cap (17) limits the axial movement of the bearing (14). A gasket (18) for adjusting the axial support stiffness is provided between the pressure cap (17) and the bearing (14). The right short axis assembly has the same structure as the left short axis assembly.

3. The palletizing robot wrist support structure according to claim 2, characterized in that, The short shaft (12) is a stepped shaft structure, including an inner shaft section (1201), an inner shaft shoulder (1202), a sealed shaft section (1204), an outer shaft shoulder (1205), and a bearing shaft section (1206) arranged sequentially along the axial direction. The inner shaft section (1201) is engaged with the shaft hole of the left forearm hinge (401) and is axially limited by the inner shaft shoulder (1202). The inner shaft shoulder (1202) is fixedly connected to the inner stop positioning surface of the left forearm hinge (401) by screw I (15). The sealed shaft section (1204) is dynamically sealed to the left wrist hinge (501) by a rotating sealing ring (13). The bearing (14) is mounted on the bearing shaft section (1206), and the back of the inner ring of the bearing (14) is axially limited by the outer shaft shoulder (1205).

4. The palletizing robot wrist support structure according to claim 3, characterized in that, The mounting and positioning surfaces of the pressure cap (17) include a bearing outer ring back contact surface (1701), a positioning ring surface (1702), and a wrist contact surface (1703) arranged sequentially. The bearing outer ring back contact surface (1701) presses against the gasket (18), the positioning ring surface (1702) fits against the inner hole of the left wrist hinge (501), and the wrist contact surface (1703) fits against the outer end face of the left wrist hinge (501) and is connected by screw II (16).

5. A method for calibrating the stiffness of the wrist support structure of a palletizing robot as described in claim 4, characterized in that, Includes the following steps: Step S1: Calibrate the axial stiffness between the left forearm hinge (401) and the left wrist hinge (501): Step S2: Calibrate the axial stiffness between the right forearm hinge (402) and the right wrist hinge (502); Step S3: Assemble the forearm (4) and wrist (5), and control the axial relative position of the forearm (4) and wrist (5) by allocating the shims of the left and right joints; Step S4: Measure whether the support stiffness and rotational torque of the forearm (4) and wrist (5) are qualified.

6. The stiffness calibration method according to claim 5, characterized in that, The axial stiffness calibration between the left forearm hinge (401) and the left wrist hinge (501) includes the following steps: Step S1.1: Measure the axial dimension and tolerance of the outer end face of the left wrist hinge (501); Step S1.2: Measure the axial dimensions and tolerances of the assembly positioning surface of the gland (17); Step S1.3: Measure the axial dimensions and tolerances of the back of the inner ring and the back of the outer ring of the bearing (14); Step S1.4: Measure the axial dimensions and tolerances of the inner shoulder (1202) and outer shoulder (1205) of the short shaft (12); Step S1.5: Measure the axial dimensions and tolerances of the inner stop positioning surface of the left forearm hinge (401); Step S1.6: Based on the cumulative value of the axial dimensions and tolerances of the left wrist hinge (501), pressure cap (17), bearing (14), short shaft (12) and left forearm hinge (401) obtained by measurement, compare them with the standard assembly axial dimension tolerance value to determine the thickness and quantity of the shim (18) in the left joint.

7. The stiffness calibration method according to claim 5, characterized in that, The axial stiffness calibration between the right forearm hinge (402) and the right wrist hinge (502) includes the following steps: Step S2.1: Measure the axial dimensions and tolerances of the outer end face of the right wrist hinge (502); Step S2.2: Measure the axial dimensions and tolerances of the assembly positioning surface of the gland (17); Step S2.3: Measure the axial dimensions and tolerances of the back of the inner ring and the back of the outer ring of the bearing (14); Step S2.4: Measure the axial dimensions and tolerances of the inner shoulder (1202) and outer shoulder (1205) of the short shaft (12); Step S2.5: Measure the axial dimensions and tolerances of the inner stop positioning surface of the right forearm hinge (402); Step S2.6: Based on the cumulative value of the axial dimensions and tolerances of the right wrist hinge (502), pressure cap (17), bearing (14), short shaft (12) and right forearm hinge (402) obtained by measurement, compare them with the standard assembly axial dimension tolerance value to determine the thickness and quantity of the shim (18) in the right joint.

8. The stiffness calibration method according to claim 5, characterized in that, In step S3, the assembly process between the forearm (4) and the wrist (5) includes the following steps: Step M1: Install two rotating sealing rings (13) on the inner side of the left wrist hinge (501) and the right wrist hinge (502) respectively; Step M2: Place the left forearm hinge (401) and the right forearm hinge (402) inside the left wrist hinge (501) and the right wrist hinge (502) respectively; Step M3: A short shaft (12) is inserted from the outside to the inside into the left wrist hinge (501) and the left forearm hinge (401), and the inner end of the short shaft (12) is fixedly connected to the left forearm hinge (401) by a screw I (15). Another short shaft (12) is inserted into the right wrist hinge (502) and the right forearm hinge (402) from the outside to the inside, and the inner end of the other short shaft (12) is fixedly connected to the right forearm hinge (402) by another screw I (15); Step M4: Install two bearings (14) on the outer ends of the two short shafts (12) respectively, so that the back of the inner ring of the bearing (14) is close to the outer shoulder (1205) of the short shaft (12); Step M5: Place shims (18) of a certain thickness and number on the back of the outer rings of the two bearings (14), and then install two pressure caps (17). The two pressure caps (17) are fixedly connected to the left wrist hinge (501) and the right wrist hinge (502) respectively by screw II (16), and press the shims (18) tight.

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