Wrist-type device for a robot arm

Abstract

A wrist device of a robot arm includes a first rotation unit, a second rotation unit, and a first brake unit. The first rotation unit includes a first motor, a first rotating shaft rotatable about a first axis, and a first encoder for measuring a rotation angle of the first rotating shaft and capable of feedback controlling the first motor. The second rotation unit includes a second motor and a work platform rotatable about a second axis. The first brake unit includes a first brake pad connected to the first rotating shaft and a first brake disc. When the first brake disc is driven to approach and abut against the first brake pad, the rotation of the first rotating shaft is stopped. The rotation accuracy is improved by measuring the rotation angle of the first rotating shaft by the first encoder and stopping the rotation of the first rotating shaft by the first brake unit.

Description

Technical Field

[0001] This invention relates to a device for use with a robotic arm, and more particularly to a wrist-shaped device for a robotic arm. Background Technology

[0002] See Figure 1 A wrist joint structure for a robotic arm disclosed in Taiwan Patent No. I418452B includes a forearm body 91, a first rotating assembly 92, a wrist body 93, and a second rotating assembly 94. The first rotating assembly 92 is disposed within the forearm body 91 and includes a first motor 921, a first reducer 922, and a transmission mechanism 923. The first motor 921 has an output shaft 924. The first reducer 922 has an input shaft 925 and an output shaft 926. The transmission mechanism 923 includes a first pulley 927, a second pulley 928, and a belt 929. The first pulley 927 is mounted on the output shaft 924 of the first motor 921, and the second pulley 928 is mounted on the input shaft 925 of the first reducer 922. A belt 929 is sleeved between the first pulley 927 and the second pulley 928 to transmit the rotational power of the first motor 921 to the first reducer 922. The wrist body 93 is mounted on the forearm body 91 and connected to the output shaft 926 of the first reducer 922, so that the output shaft 926 of the first reducer 922 drives the wrist body 93 to rotate around a first rotation axis L1. The second rotation assembly 94 includes a second motor 941, a base 942, and a second reducer 943. The second motor 941 is mounted inside the wrist body 93 and has an output shaft 944. The base 942 connects the second motor 941 and the second reducer 943. The rotational power of the second motor 941 is transmitted to the second reducer 943, so that the second reducer 943 can drive a workpiece (not shown) mounted thereon to rotate around a second rotation axis L2.

[0003] However, since the existing robotic arm's wrist joint structure transmits power through the first pulley 927, the second pulley 928, and the belt 929, the belt 929 may become loose or slip during transmission. Furthermore, the belt 929 is susceptible to issues such as poor transmission accuracy due to factors like its elasticity, tension, wear, or uneven tension distribution. This affects the accuracy of the wrist 93 when rotating around the first rotation axis L1. In addition, the structure of the first pulley 927, the second pulley 928, the belt 929, the first reducer 922, and the second reducer 943 results in a large overall device size, which cannot meet the requirements of applications with high precision and miniaturization needs. Summary of the Invention

[0004] The purpose of this invention is to provide a wrist device for a miniaturized robotic arm that improves rotational accuracy.

[0005] The wrist-shaped device of the robotic arm of the present invention includes a housing unit, a first rotating unit, a second rotating unit, and a first braking unit. The first rotating unit includes a first motor disposed within the housing unit, a first rotating shaft connected to the first motor, and a first encoder for measuring the rotation angle of the first rotating shaft. The first motor drives the first rotating shaft to rotate about a first axis. The first encoder can provide feedback control to the first motor. The second rotating unit is disposed on the first rotating shaft and can rotate with the first rotating shaft about the first axis. The second rotating unit includes a second motor and a work platform connected to the second motor. The second motor drives the work platform to rotate about a second axis perpendicular to the first axis. The first braking unit includes a first brake pad connected to the first rotating shaft and a first braking disc that can be driven to move along the first axis to approach or move away from the first brake pad. When the first braking disc is driven to approach and abut against the first brake pad along the first axis, the rotation of the first rotating shaft can be stopped.

[0006] The wrist-shaped device of the robotic arm of the present invention further includes a first coil located on the side of the first control turntable opposite to the first brake pad, and a plurality of first elastic members that spring against the first control turntable and move toward the first brake pad. When the first coil is energized, it can attract the first control turntable away from the first brake pad and compress the first elastic members. When the first coil is not energized, the first control turntable is pushed by the first elastic members and moves closer to and against the first brake pad along the first axis.

[0007] The wrist-shaped device of the robotic arm of the present invention further includes a first mounting base fixed to the outer shell unit, a first fixed plate fixed to the first mounting base at intervals along the first axis, and a plurality of first guide posts abutting between the first mounting base and the first fixed plate. The first mounting base is used to accommodate the first coil and the first elastic member. The first brake pad is located between the first fixed plate and the first control turntable, and the first brake pad is spaced apart from the first fixed plate. The first control turntable has a plurality of first grooves through which the first guide posts pass.

[0008] The wrist-shaped device of the robotic arm of the present invention has a first encoder having a first code disk that rotates with the first rotating shaft, and a first reading head disposed in the housing unit for detecting the rotation of the first code disk.

[0009] The wrist device of the robotic arm of the present invention further includes a base, a first side seat and a second side seat spaced apart from the base, a first motor disposed on the first side seat, a first rotating shaft extending through the first side seat and the second side seat along the first axis, and a first encoder connected to the first rotating shaft and located in the second side seat.

[0010] The wrist-shaped device of the robotic arm of the present invention further includes a second braking unit. The second rotation unit further includes a hollow shaft tube connected to the second motor and fixedly inserted through the first rotating shaft along the second axis, a second rotating shaft connected to the work platform and rotatably extending through the hollow shaft tube, and a second encoder for measuring the rotation angle of the second rotating shaft. The second encoder can feed back control of the second motor. The second braking unit is located at the end of the hollow shaft tube opposite to the second motor and includes a second brake pad connected to the second rotating shaft, and a second control turntable that can be driven to move along the second axis to approach or move away from the second brake pad. When the second control turntable is driven to approach and abut against the second brake pad along the second axis, it can stop the rotation of the second rotating shaft.

[0011] The wrist-shaped device of the robotic arm of the present invention further includes a second coil connected to the hollow shaft tube, and a plurality of second elastic elements that spring against the second control turntable and move toward the second brake pad. The second coil and the second elastic elements are located on the side of the second control turntable opposite to the second brake pad. When the second coil is energized, it can attract the second control turntable away from the second brake pad and compress the second elastic elements. When the second coil is not energized, the second control turntable is pushed by the second elastic elements and approaches and abuts against the second brake pad along the second axis.

[0012] The wrist-type device of the robotic arm of the present invention further includes a second mounting base fixed to the hollow shaft tube, a second fixed plate fixed to the second mounting base at intervals along the second axis, and a plurality of second guide posts abutting between the second mounting base and the second fixed plate. The second mounting base is used to accommodate the second coil and the second elastic member. The second brake pad is located between the second fixed plate and the second control disc, and the second brake pad is spaced apart from the second fixed plate. The second control disc has a plurality of second grooves through which the second guide posts pass.

[0013] The wrist device of the robotic arm of the present invention has a second encoder having a second code disk disposed at one end of the second rotating shaft opposite to the working platform, and a second reading head disposed on the second fixed disk for detecting the rotation of the second code disk.

[0014] The beneficial effects of the present invention are as follows: by measuring the rotation angle of the first rotating shaft through the first encoder and feeding back control of the first motor, the accuracy of the first rotating shaft rotating around the first axis can be improved. When the first rotating shaft rotates to the target position, the first brake disc is driven to approach and abut against the first brake pad to stop the first brake pad from rotating around the first axis, which also stops the rotation of the first rotating shaft. This further improves the accuracy of the first rotating shaft rotating around the first axis. In addition, through the control of the first motor in combination with the first encoder and the compact structural design of the first brake unit, the pulleys, belts and reducers used in the prior art are omitted, making the overall device smaller. Attached Figure Description

[0015] Figure 1 This is a three-dimensional exploded view of the wrist joint structure of an existing robotic arm;

[0016] Figure 2 This is a perspective view of an embodiment of the wrist device of the robotic arm of the present invention;

[0017] Figure 3 This is a partial exploded perspective view of a first rotating unit and a first braking unit in the embodiment described above;

[0018] Figure 4 It is similar Figure 3 A partial exploded view;

[0019] Figure 5 This is an exploded perspective view of another part of the first rotating unit and the first braking unit in the embodiment described above;

[0020] Figure 6 It is similar Figure 5 A partial exploded view;

[0021] Figure 7 This is a partial exploded perspective view of a second rotating unit and a second braking unit in the embodiment described above;

[0022] Figure 8 It is similar Figure 7 A partial exploded view;

[0023] Figure 9 This is a cross-sectional view of the embodiment described;

[0024] Figure 10 This is a partially enlarged cross-sectional view of the first braking unit in the embodiment;

[0025] Figure 11 It is similar Figure 10 A partially enlarged sectional view;

[0026] Figure 12 This is a partially enlarged cross-sectional view of the second braking unit in the embodiment; and

[0027] Figure 13 It is similar Figure 12 A partially enlarged sectional view. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] See Figure 2 and Figure 3 An embodiment of the wrist device 1 of the present invention is suitable for mounting on a robotic arm (not shown) and can be controlled by a signal from a servo (not shown). The wrist device 1 of the robotic arm includes a housing unit 2, a first rotating unit 3, a first braking unit 4, a second rotating unit 5, and a second braking unit 6.

[0030] The outer casing unit 2 includes a base 21, a first side seat 22 and a second side seat 23 disposed at a distance from the base 21. The first side seat 22 has a first side shell portion 221 connected to the base 21 and a first cover plate 222 covering one side of the first side shell portion 221. The second side seat 23 has a second side shell portion 231 connected to the base 21 and a second cover plate 232 covering one side of the second side shell portion 231.

[0031] See Figures 3 to 5 The first rotating unit 3 includes a first motor 31 disposed on the first side seat 22 and the second side seat 23 and signal-connected to the servo; a first rotating shaft 32 connected to the first motor 31 and extending through the first side seat 22 and the second side seat 23 along a first axis B; a first ring seat 33 fixed to one end of the first rotating shaft 32 and located in the first side shell 221; a second ring seat 34 fixed to the other end of the first rotating shaft 32 and located in the second side shell 231; a first bearing 35 rotatably abutting between the first ring seat 33 and the first side shell 221; a second bearing 36 rotatably abutting between the second ring seat 34 and the second side shell 231; a first circuit board 37 fixed to the second cover plate 232; and a first encoder 38 located in the second side shell 231.

[0032] See Figures 4 to 6The first motor 31 can be controlled by the signal from the servo to drive the first rotating shaft 32 to rotate around the first axis B. The first encoder 38 is used to measure the rotation angle of the first rotating shaft 32, and has a first code disk 381 fixed to the second ring connector 34 to rotate with the first rotating shaft 32 around the first axis B, and a first read head 382 electrically connected to the first circuit board 37. The first read head 382 is disposed on the side of the first circuit board 37 facing the first code disk 381.

[0033] It is worth noting that, in this embodiment, the first motor 31 is a disc motor. The first encoder 38 is a reflective photoelectric encoder, and the first code disk 381 has multiple staggered reflective and non-reflective areas (not shown). When the first code disk 381 rotates with the second ring connector 34 and the first rotating shaft 32, the first read head 382 continuously emits light towards the first code disk 381. The light is reflected by the reflective areas and received by the first read head 382. When the light shines on the non-reflective areas, the first read head 382 does not receive the reflected light. The first read head 382 can encode the time interval between receiving and not receiving the reflected light, and then calculate the rotation angle of the first rotating shaft 32. The first encoder 38 controls the first motor 31 through feedback from the servo to increase the accuracy of the first motor 31 driving the first rotating shaft 32 to rotate.

[0034] See Figure 3 , Figure 4 and Figure 9 The first brake unit 4 is located inside the first side seat 22 and includes a first brake mounting disc 41 fixed to the first rotating shaft 32, two first brake pads 42 embedded in the first brake mounting disc 41, a first mounting seat 43 fixed to the first cover plate 222, a first coil 44 housed in the first mounting seat 43, four first elastic elements 45 housed in the first mounting seat 43, a first brake disc 46 that can be driven to move along the first axis B to approach or move away from the first brake pads 42, a first fixing disc 47 fixed to the first mounting seat 43 at intervals along the first axis B, and four first guide posts 48 abutting between the first mounting seat 43 and the first fixing disc 47.

[0035] The first brake mounting disc 41 can carry the first brake pad 42 and rotate with the first rotating shaft 32 around the first axis B. The first brake mounting disc 41 is located between the first fixed disc 47 and the first brake rotating disc 46, and the first brake pad 42 and the first fixed disc 47 maintain a constant distance (see reference). Figure 10 ).

[0036] Reference Figure 9 , wherein the first coil 44 is located on a side of the first braking rotating disc 46 opposite to the first brake mounting disc 41, and can be energized or de-energized under the control of the servo. The first elastic member 45 resiliently urges the first braking rotating disc 46 to constantly move toward the first brake pad 42. Refer to Figure 10 , when the first coil 44 is energized, it can attract the first braking rotating disc 46 to move away from the first brake pad and compress the first elastic member 45, at this time, a gap is maintained between the first braking rotating disc 46 and the first brake pad 42; Refer to Figure 11 , when the first coil 44 is not energized, the first braking rotating disc 46 is pushed by the first elastic member 45 to approach and abut against the first brake pad 42.

[0037] Refer to Figure 3 and Figure 4 , four screws 49 pass through the first fixing disc 47 and the first guiding posts 48 and are screwed to the first mounting seat 43, so that the first fixing disc 47 is fixedly connected to the first mounting seat 43. The first braking rotating disc 46 is provided with four first grooves 461 spaced around the first axis B for the first guiding posts 48 to extend through. Through the limiting fit between the first grooves 461 and the first guiding posts 48, the first guiding posts 48 form tracks for the first braking rotating disc 46 to move along the first axis B, ensuring that the first braking rotating disc 46 can stably move along the first axis B between the first mounting seat 43 and the first fixing disc 47.

[0038] Refer to Figures 7 to 9 , the second rotating unit 5 is disposed on the first rotating shaft 32 and can rotate around the first axis B along with the first rotating shaft 32. The second rotating unit 5 comprises a second motor 51 in signal connection with the servo, a working platform 52 connected to the second motor 51, a hollow shaft tube 53 connected to the second motor 51 and fixedly passing through the first rotating shaft 32 along a second axis T perpendicular to the first axis B, a second rotating shaft 54 connected to the working platform 52 and rotatably extending through the hollow shaft tube 53, an end seat 55 connected to an end of the second rotating shaft 54 opposite to the working platform 52, a second circuit board 56, and a second encoder 57 for measuring the rotation angle of the second rotating shaft 54.

[0039] The second motor 51 is an external rotary motor and has an outer rotor 511 that can rotate about the second axis T under the signal control of the servo. The work platform 52 is connected to the top of the outer rotor 511 and can therefore rotate about the second axis T with the outer rotor 511. The work platform 52 is used to mount the workpiece to be processed or the processing tool. One end of the second rotating shaft 54 ​​is connected to the work platform 52 and can rotate about the second axis T with the work platform 52, and the other end of the second rotating shaft 54 ​​is connected to the end seat 55, which can rotate about the second axis T with the second rotating shaft 54.

[0040] The second encoder 57 is used to measure the rotation angle of the second rotating shaft 54, and has a second code disk 571 disposed on the end base 55, and a second read head 572 electrically connected to the second circuit board 56. The second read head 572 is disposed on the side of the second circuit board 56 facing the second code disk 571.

[0041] It is worth noting that the second encoder 57, like the first encoder 38, is a reflective photoelectric encoder, so the detailed structure and sensing principle of the second encoder 57 will not be described in detail. When the second code disk 571 rotates with the end base 55 and the second rotating shaft 54, the second read head 572 can encode data and calculate the rotation angle of the second rotating shaft 54. The second encoder 57 can control the second motor 51 via feedback from the servo to increase the accuracy of the second motor 51 in driving the rotation of the work platform 52 and the second rotating shaft 54.

[0042] The second braking unit 6 includes a second brake mounting disc 61 connected to the second rotating shaft 54, two second brake pads 62 embedded in the second brake mounting disc 61, a second mounting seat 63 fixed to one end of the hollow shaft tube 53 opposite to the second motor 51, a second coil 64 housed in the second mounting seat 63, four second elastic members 65 housed in the second mounting seat 63, a second brake disc 66 that can be driven to move along the second axis T to approach or move away from the second brake pads 62, a second fixing disc 67 fixed to the second mounting seat 63 at intervals along the second axis T, and four second guide posts 68 abutting between the second mounting seat 63 and the second fixing disc 67.

[0043] The second brake mounting disc 61 can carry the second brake pad 62 and rotate with the second rotating shaft 54 ​​around the second axis T. The second brake mounting disc 61 is located between the second fixed disc 67 and the second brake disc 66, and the second brake pad 62 and the second fixed disc 67 maintain a constant distance (see reference). Figure 12 ).

[0044] Reference Figure 9 , the second coil 64 is located on a side of the second braking rotary disc 66 opposite to the second brake pad 62, and can be energized or de-energized under the signal control of the server. The second elastic member 65 elastically urges the second braking rotary disc 66 to constantly move toward the second brake pad 62. Refer to Figure 12 , when the second coil 64 is energized, it can attract the second braking rotary disc 66 to move away from the second brake pad 62 and compress the second elastic member 65; at this time, the second braking rotary disc 66 and the second brake pad 62 maintain a gap; refer to Figure 13 , when the second coil 64 is not energized, the second braking rotary disc 66 is pushed by the second elastic member 65 to approach and abut against the second brake pad 62.

[0045] Reference Figure 9 , the second circuit board 56 is fixedly connected to the second fixed disc 67.

[0046] Refer to Figure 7 , Figure 8 and Figure 12 , four screws 69 pass through the second fixed disc 67 and the second guide posts 68 and are screwed to the second mounting base 63, so that the second fixed disc 67 is fixedly connected to the second mounting base 63. The second braking rotary disc 66 has four second grooves 661 spaced around the second axis T for the second guide posts 68 to extend through. Through the limiting cooperation of the second grooves 661 and the second guide posts 68, the second guide posts 68 form a track for the second braking rotary disc 66 to move along the second axis T, ensuring that the second braking rotary disc 66 can stably move along the second axis T between the second mounting base 63 and the second fixed disc 67.

[0047] Refer to Figures 9 to 11When the wrist device 1 of the robotic arm of the present invention is in use, the first motor 31 can be controlled by the servo to drive the first rotating shaft 32 to rotate around the first axis B. The first encoder 38 is used to measure the rotation angle of the first rotating shaft 32 and to control the first motor 31 through feedback from the servo to increase the rotation accuracy of the first motor 31 driving the first rotating shaft 32. The first rotating shaft 32 drives the second rotating unit 5 and the first brake mounting plate 41 to rotate together around the first axis B. When the servo controls the first motor 31 to drive the first rotating shaft 32 to rotate, the servo synchronously controls the first coil 44 to be energized, so that the first brake mounting plate 46 is attracted by the first coil 44 and compresses the first elastic member 45, so as to move away from and not contact the first brake pad 42, ensuring that the first brake mounting plate 41 can rotate with the first rotating shaft 32 around the first axis B. When the first rotating shaft 32 rotates to the target position, the servo controls the first coil 44 to be de-energized in real time, so that the first braking disc 46 is no longer attracted by the first coil 44, and the first elastic member 45 pushes the first braking disc 46 closer to and against the first brake pad 42, thereby stopping the first brake mounting disc 41 from rotating around the first axis B, and also stopping the first rotating shaft 32 from rotating around the first axis B. Therefore, the first braking unit 4 can further improve the rotational accuracy and stability of the first rotating shaft 32.

[0048] Similarly, see Figure 9 , Figure 12 and Figure 13The second motor 51, controlled by the servo, drives the work platform 52 to rotate around the second axis T. The second rotating shaft 54 ​​rotates along with the work platform 52, and the second brake mounting disc 61 rotates along with the second rotating shaft 54. The second encoder 57 measures the rotation angle of the second rotating shaft 54 ​​and feeds back control of the second motor 51 through the servo to increase the rotational accuracy of the second rotating shaft 54. When the servo controls the second motor 51 to drive the work platform 52 to rotate, the servo synchronously controls the second coil 64 to be energized, causing the second brake disc 66 to be attracted by the second coil 64 and compress the second elastic element 65, so that it moves away from and does not contact the second brake pad 62, ensuring that the second brake mounting disc 61 rotates along with the second rotating shaft 54. When the second rotating shaft 54 ​​rotates to the target position, the servo controls the second coil 64 to be de-energized in real time, so that the second braking disc 66 is no longer attracted by the second coil 64, and the second elastic member 65 pushes the second braking disc 66 closer to and abuts against the second brake pad 62, thereby stopping the second brake mounting disc 61 from rotating around the second axis T, and also stopping the rotation of the second rotating shaft 54 ​​and the working platform 52 around the second axis T. In this way, the second braking unit 6 can further improve the rotational accuracy and stability of the second rotating shaft 54 ​​and the working platform 52.

[0049] In summary, the wrist device 1 of the robotic arm of the present invention can improve the rotational accuracy of the first rotating shaft 32, the second rotating shaft 54 ​​and the working platform 52 by measuring the rotational angle of the first rotating shaft 32 by the first encoder 38 and the rotational angle of the second rotating shaft 54 ​​by the second encoder 57, and by controlling the first motor 31 and the second motor 51 by the feedback from the servo. When the first rotating shaft 32 and the second rotating shaft 54 ​​rotate to the target position, the first braking unit 4 and the second braking unit 6 are controlled by the servo to stop the rotation of the first rotating shaft 32 and the second rotating shaft 54 ​​in real time, which can further improve the rotational accuracy of the first rotating shaft 32 and the second rotating shaft 54. In addition, by controlling the first motor 31 with the first encoder 38, controlling the second motor 51 with the second encoder 57, and the compact arrangement of the first braking unit 4 and the second braking unit 6, the pulleys, belts and reducers used in the prior art are omitted, and the overall device is miniaturized. Therefore, the purpose of the present invention can indeed be achieved.

[0050] However, the above description is merely an embodiment of the present invention and should not be construed as limiting the scope of the present invention. Any simple equivalent changes and modifications made in accordance with the claims and description of the present invention shall still fall within the scope of the present invention.

Claims

1. A wrist-shaped device for a robotic arm, characterized in that: Include: Housing unit; The first rotating unit includes a first motor disposed within the housing unit, a first rotating shaft connected to the first motor, and a first encoder for measuring the rotation angle of the first rotating shaft. The first motor is used to drive the first rotating shaft to rotate around a first axis, and the first encoder can provide feedback control to the first motor. A second rotating unit is disposed on the first rotating shaft and can rotate around the first axis with the first rotating shaft. The second rotating unit includes a second motor and a work platform connected to the second motor. The second motor is used to drive the work platform to rotate around a second axis perpendicular to the first axis. The first braking unit includes a first brake pad connected to the first rotating shaft, and a first braking disc that can be driven to move along the first axis to approach or move away from the first brake pad. When the first braking disc is driven to approach and abut against the first brake pad along the first axis, it can stop the rotation of the first rotating shaft.

2. The wrist device of the robotic arm according to claim 1, characterized in that: The first braking unit further includes a first coil located on the side of the first braking disc opposite to the first brake pad, and a plurality of first elastic members that spring against the first braking disc and move toward the first brake pad. When the first coil is energized, it can attract the first braking disc away from the first brake pad and compress the first elastic members. When the first coil is not energized, the first braking disc is pushed by the first elastic members and moves closer to and against the first brake pad along the first axis.

3. The wrist device of the robotic arm according to claim 2, characterized in that: The first braking unit further includes a first mounting base fixed to the housing unit, a first fixed plate fixed to the first mounting base at intervals along the first axis, and a plurality of first guide posts abutting between the first mounting base and the first fixed plate. The first mounting base is used to accommodate the first coil and the first elastic member. The first brake pad is located between the first fixed plate and the first brake disc, and the first brake pad is spaced apart from the first fixed plate. The first brake disc has a plurality of first grooves through which the first guide posts pass.

4. The wrist-shaped device of the robotic arm according to claim 1, characterized in that: The first encoder has a first code disk that rotates with the first rotating shaft, and a first reading head disposed in the housing unit for detecting the rotation of the first code disk.

5. The wrist-shaped device of the robotic arm according to claim 1, characterized in that: The housing unit further includes a base, a first side seat and a second side seat spaced apart from the base, a first motor disposed on the first side seat, a first rotating shaft extending through the first side seat and the second side seat along the first axis, and a first encoder connected to the first rotating shaft and located inside the second side seat.

6. The wrist device of the robotic arm according to claim 1, characterized in that: It also includes a second braking unit. The second rotating unit further includes a hollow shaft tube connected to the second motor and fixedly inserted through the first rotating shaft along the second axis, a second rotating shaft connected to the working platform and rotatably extending through the hollow shaft tube, and a second encoder for measuring the rotation angle of the second rotating shaft. The second encoder can feed back control of the second motor. The second braking unit is located at the end of the hollow shaft tube opposite to the second motor and includes a second brake pad connected to the second rotating shaft, and a second control turntable that can be driven to move along the second axis to approach or move away from the second brake pad. When the second control turntable is driven to approach and abut against the second brake pad along the second axis, it can stop the rotation of the second rotating shaft.

7. The wrist-shaped device of the robotic arm according to claim 6, characterized in that: The second braking unit further includes a second coil connected to the hollow shaft tube, and a plurality of second elastic elements that spring against the second braking disc and move toward the second brake pad. The second coil and the second elastic elements are located on the side of the second braking disc opposite to the second brake pad. When the second coil is energized, it can attract the second braking disc away from the second brake pad and compress the second elastic elements. When the second coil is not energized, the second braking disc is pushed by the second elastic elements and moves closer to and abuts against the second brake pad along the second axis.

8. The wrist device of the robotic arm according to claim 7, characterized in that: The second braking unit further includes a second mounting base fixed to the hollow shaft tube, a second fixed plate fixed to the second mounting base at intervals along the second axis, and a plurality of second guide posts abutting between the second mounting base and the second fixed plate. The second mounting base is used to accommodate the second coil and the second elastic member. The second brake pad is located between the second fixed plate and the second brake disc, and the second brake pad is spaced apart from the second fixed plate. The second brake disc has a plurality of second grooves through which the second guide posts pass.

9. The wrist device of the robotic arm according to claim 8, characterized in that: The second encoder has a second code disk disposed at one end of the second rotating shaft opposite to the working platform, and a second reading head disposed on the second fixed disk for detecting the rotation of the second code disk.

Images