Gravity compensation mechanism and mechanical arm with same

Abstract

The utility model discloses a gravity compensation mechanism which is applied to a mechanical arm with a load arm lever, the load arm lever is installed on a holder through a base support, the gravity compensation mechanism comprises a spring guide rod, a linear bearing and a spring, one end of the spring guide rod is rotatably connected to the load arm lever, and the linear bearing and the spring are arranged on the spring guide rod in a sleeved mode. One end of the spring guide rod is connected with a linear bearing, the linear bearing is further connected with a bearing sleeve, at least one protruding shaft rotatably connected to the base support is formed on the outer side wall of the bearing sleeve, the other end of the spring guide rod is connected with a spring end cover, and the spring is located between the bearing sleeve and the spring end cover and can stretch out and draw back when the bearing sleeve rotates. Through cooperation of the linear bearing, the bearing sleeve and the spring guide rod, when the mechanical arm rotates around the pitch shaft, the protruding shaft rotates, the position of the protruding shaft and the position of the base support are not changed, the spring guide rod can move upwards or downwards, and the spring deforms, so that gravity compensation of the mechanical arm is achieved. The utility model further discloses a mechanical arm.

Description

Technical Field

[0001] The utility model relates to the technical field of robot equipment, and more specifically to a gravity compensation mechanism and a mechanical arm with the gravity compensation mechanism. Background Art

[0002] In the prior art, due to the effect of the gravity of the arm, the joints of the robotic arm whose axis is parallel to the ground will generate additional torque at the joints, which reduces the dynamic characteristics of the robotic arm. Therefore, most robotic arms need to be designed with gravity compensation devices.

[0003] At present, the gravity compensation structure of the robotic arm is generally divided into an active gravity compensation structure and a passive gravity compensation structure. The active gravity compensation structure generally uses a motor closed-loop control to offset the torque disturbance of gravity, that is, a sensor is added to the robotic arm, and the control system outputs a compensation torque to offset the influence of gravity on the robotic arm control motor. However, this method cannot be used in scenarios with large loads, because the greater the load, the higher the requirements for the motor, the greater the torque required for the motor, and the greater the size and cost of the motor. The passive gravity compensation structure generally uses a weight balancing method to achieve gravity balance. Its working principle is to add a counterweight to the arm to transfer the center of gravity of the robotic arm to the vicinity of the axis of the rotating joint, thereby reducing the potential energy change of gravity during the rotation of the joint and achieving gravity compensation of the robotic arm. compensation effect; or, adopting the structure described in the Chinese invention patent with application number 201711049846.4 and patent name "A cam spring mechanism for gravity compensation of a mechanical arm", with the help of the cam, tensioning wire rope and tension spring to cooperate to output a torque opposite to gravity, so as to achieve the effect of gravity compensation. However, although the method of balancing the weight is simple to implement, it may cause problems such as the overall volume of the system being too large and the center of gravity being too high. Although the cam spring mechanism does not increase the volume too much, it needs to design and process the cam, which increases the complexity of the design, and the radius of the cam design is a variable that changes with the angle. When the mechanical arm moves quickly, the wire rope will not always remain in the same plane, which may easily cause a stretching gap between the spring and the wire rope, introduce a delay, and reduce the stability of the mechanical arm.

[0004] In view of this, it is necessary to provide a gravity compensation mechanism with a simple structure and which can enable the robot arm to reach a balanced state at any position when in use, and a robot arm having the gravity compensation mechanism to solve the above-mentioned defects. Summary of the invention

[0005] The technical problem to be solved by the utility model is to provide a gravity compensation mechanism which has a simple structure and can make the mechanical arm reach a balanced state at any position when in use, and a mechanical arm having the gravity compensation mechanism.

[0006] To solve the above technical problems, according to one aspect of the utility model, a gravity compensation mechanism is provided, which is applied to a mechanical arm with a load arm, wherein the load arm is installed on a pan-tilt platform through a base bracket, and the gravity compensation mechanism includes a spring guide rod rotatably connected to the load arm at one end, a linear bearing and a spring sleeved on the spring guide rod, the linear bearing is also connected to a bearing sleeve, the outer side wall of the bearing sleeve is formed with at least one protruding shaft rotatably connected to the base bracket, the other end of the spring guide rod is connected to a spring end cover, the spring is located between the bearing sleeve and the spring end cover, and can be extended and retracted when the bearing sleeve rotates.

[0007] Its further technical solution is: the bearing sleeve includes a cylinder, both sides of the cylinder protrude outward to form two protruding shafts, and the top and bottom of the cylinder are respectively recessed inward to form a first mounting groove and a second mounting groove, and one end of the linear bearing and the spring are respectively located in the first mounting groove and the second mounting groove.

[0008] A further technical solution is as follows: the linear bearing is a flange-type linear bearing, the flange-type linear bearing is located in the first mounting groove, and the mounting flange of the flange-type linear bearing is fixed to the top of the cylinder.

[0009] A further technical solution is as follows: an annular body is formed at one end of the spring guide rod, a rotating shaft is inserted into the annular body, and the annular body is rotatably connected to the load arm rod through the rotating shaft.

[0010] A further technical solution is as follows: two thrust bearings are sleeved on the rotating shaft, the two thrust bearings are arranged on both sides of the annular body, and are both located between the load arm and the annular body.

[0011] To solve the above technical problems, according to another aspect of the utility model, a mechanical arm is provided, which includes a base bracket, a load arm, a drive motor and the above-mentioned gravity compensation mechanism, wherein the load arm is rotatably connected to the base bracket through a connecting shaft, the drive motor is located on one side of the base bracket, and the motor shaft of the drive motor is connected to the connecting shaft, the spring guide rod is rotatably connected to one end of the load arm, and the other end of the load arm is connected to the load, the raised shaft is located below the connecting shaft, and is rotatably connected to the side wall of the base bracket, so that when the load arm rotates under the action of the drive motor, it rotates, so that the spring mounted on the spring guide rod is expanded and contracted, thereby offsetting the gravity of the load arm.

[0012] Its further technical solution is: the base bracket includes a first support plate and a second support plate arranged opposite to each other, the load arm includes a first connecting rod and a connecting arm, the first connecting rod has a ⌒-shaped cross-section, the spring guide rod is rotatably connected to one end of the first connecting rod, one end of the connecting arm passes through the other end of the first connecting rod, the connecting shaft passes through the first support plate, one end of the connecting arm and the second support plate in sequence and is connected to the motor shaft of the driving motor, the other end of the connecting arm is connected to the load, the raised shaft is located directly below the connecting shaft, and is rotatably connected to the first support plate / second support plate.

[0013] Its further technical solution is: a first bearing adapter and a second bearing adapter are respectively installed on the opposite sides of the first support plate and the second support plate, a first bearing and a second bearing are respectively installed on the first bearing adapter and the second bearing adapter, and the protruding shaft passes through the first bearing / second bearing to be rotatably connected with the first support plate / second support plate.

[0014] Its further technical solution is: the base bracket also includes a bottom plate and a motor bracket, the first support plate and the second support plate are respectively fixed on the upper surface of the bottom plate, the motor bracket is located on the outside of the second support plate, the drive motor is located on the motor bracket, and the motor shaft of the drive motor passes through the motor bracket and is connected to the connecting shaft through a third bearing adapter, and a flange bearing and a thrust bearing are sequentially mounted on the connecting shaft, and the flange bearing and the thrust bearing are located between the first support plate and the connecting arm rod.

[0015] Compared with the prior art, when the gravity compensation mechanism of the utility model is applied to a mechanical arm, one end of the spring guide rod can be rotatably connected to the load arm rod of the mechanical arm, and the other end is connected to a spring end cover, and a linear bearing and a spring are sleeved on the spring guide rod, and the linear bearing is connected to a bearing sleeve, and the bearing sleeve is rotatably connected to the base bracket of the mechanical arm through a raised shaft, and the spring is located between the bearing sleeve and the spring end cover. When the mechanical arm performs a pitching motion, through the cooperation of the linear bearing, the bearing sleeve and the spring guide rod, the bearing sleeve rotates and its position with the base bracket remains unchanged, and the spring guide rod can move upward Or move downward, the spring is deformed on the spring guide rod to convert the gravitational potential energy of the mechanical arm and the load and the elastic potential energy of the spring, so that the mechanical arm can reach a balanced state at any position, thereby realizing the gravity compensation of the mechanical arm. It can be seen that the utility model does not require structures such as cams, and can also compensate for the torque of the driving motor of the mechanical arm caused by the gravity on the mechanical arm through gravity compensation, that is, the influence of the gravity on the mechanical arm on the motor drive is eliminated. The structure is simple, and the requirements of the driving load on the motor can be reduced, so that the size of the motor no longer increases due to the increase of the load on the mechanical arm. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a three-dimensional structural schematic diagram of a specific embodiment of the mechanical arm of the utility model.

[0017] Figure 2 yes Figure 1 Schematic diagram of the exploded structure of the robotic arm shown.

[0018] Figure 3 yes Figure 1 The schematic diagram of the structure of the robot arm after removing the first support plate is shown.

[0019] Figure 4 yes Figure 1 Schematic diagram of the structure of the gravity compensation mechanism in the robotic arm shown.

[0020] Figure 5 yes Figure 4 Schematic diagram of the exploded structure of the gravity compensation mechanism shown.

[0021] Figure 6 yes Figure 4 A schematic cross-sectional view of the gravity compensation mechanism shown. DETAILED DESCRIPTION

[0022] In order to enable ordinary technicians in the field to more clearly understand the purpose, technical solutions and advantages of the utility model, the utility model is further explained below in conjunction with the accompanying drawings and embodiments.

[0023] Reference Figures 1 to 6 , Figures 1 to 6A specific embodiment of the mechanical arm 100 of the utility model is shown. In the embodiment shown in the drawings, the mechanical arm 100 includes a base support 20, a load arm 30, a drive motor 40 and a gravity compensation mechanism 10, wherein the load arm 30 is rotatably connected to the base support 20 via a connecting shaft 60, the drive motor 40 is located on one side of the base support 20, and the motor shaft of the drive motor 40 is connected to the connecting shaft 60, and the gravity compensation mechanism 10 includes a spring guide rod 11, a linear bearing 12 and a spring 13 sleeved on the spring guide rod 11, and the linear bearing 12 is also connected to a bearing sleeve 14. In this embodiment, the two sides of the bearing sleeve 14 are respectively protruded outward to form Two raised shafts 15, one end of the spring guide rod 11 is rotatably connected to one end of the load arm 30, the other end of the spring guide rod 11 is connected to a spring end cover 16, the spring 13 is located between the bearing sleeve 14 and the spring end cover 16, the other end of the load arm 30 is connected to the load 33, the two raised shafts 15 are located below the connecting shaft 60, and are rotatably connected to both sides of the base bracket 20 respectively, so that when the load arm 30 rotates under the action of the driving motor 40, the spring guide rod 11 moves upward or downward, so that the spring 13 sleeved on the spring guide rod 11 is expanded and contracted, thereby offsetting the gravity of the load arm 30.

[0024] In this embodiment, initially, the load arm 30 is located at the maximum adjustment angle of the pitch axis, one end of the spring guide rod 11 in the gravity compensation mechanism 10 is rotatably connected to the load arm 30, the raised shaft 15 is located directly below the connecting shaft 60, and the spring 13 is in a minimum compression state on the spring guide rod 11. At this time, the mechanical arm 100 is in a balanced state, and the spring coefficient of the spring 13 is K=mgL / h1h2, wherein m is the load mass, L is the length of the load arm 30, h1 is the distance between the end of the spring guide rod 11 connected to the load arm 30 and the connecting shaft 60, and h2 is the distance between the raised shaft 15 and the connecting shaft 60. When the load arm 30 moves downward under the action of the drive motor 40, the spring guide rod 11 moves upward, driving the spring end cover 16 to move upward, thereby compressing the spring 13. In this process, Figure 3As shown, the raised shaft 15 rotates and its position on the base bracket 20 remains unchanged, and its distance h2 from the connecting shaft 60 remains unchanged. Moreover, the connecting shaft 60 rotates and its distance h1 from one end of the spring guide rod 11 connected to the load arm 30 remains unchanged, thereby realizing the conversion of the gravitational potential energy of the robot arm 100 and the load 33 and the elastic potential energy of the spring 13, so that the robot arm 100 can reach a balanced state at any position, and realize gravity compensation of the robot arm 100, thereby compensating the torque of the driving motor 40 caused by the gravity on the robot arm 100 through gravity compensation, eliminating the influence of the gravity on the robot arm 100 on the motor drive, reducing the requirements of the driving load 33 on the motor, so that the size of the motor no longer increases due to the increase of the load 33 on the robot arm 100, the size of the entire robot arm 100 is greatly reduced, and the stability of the robot arm 100 is relatively high; and the operation is simple and flexible.

[0025] In some embodiments, an annular body 111 is formed at one end of the spring guide rod 11, and a rotating shaft 50 is inserted on the annular body 111 to be rotatably connected to the load arm 30 through the rotating shaft 50. Further, two thrust bearings 83 are sleeved on the rotating shaft 50, and the two thrust bearings 83 are respectively arranged on both sides of the annular body 111 and are both located between the load arm 30 and the annular body 111. Preferably, in this embodiment, the rotating shaft 50 is a double-headed internal threaded cylindrical pin, and the connecting rotating shaft 60 is a plug screw.

[0026] Continue to refer to Figures 2 to 6 In some embodiments, the bearing sleeve 14 includes a cylinder 141, the two raised shafts 15 are relatively arranged on the outer wall of the cylinder 141, and the top and bottom of the cylinder 141 are respectively recessed inward to form a first mounting groove 142 and a second mounting groove 143. Preferably, in this embodiment, the linear bearing 12 is a flange-type linear bearing, the flange-type linear bearing is located in the first mounting groove 142, one end of the spring 13 is located in the second mounting groove 143, and the mounting flange 121 of the flange-type linear bearing is fixed to the top of the cylinder 141 by a screw 122. Based on the above design, the raised shaft 15 can rotate when the load arm 30 rotates, h2 remains unchanged, and the linear bearing 12 is conducive to the linear movement of the spring guide rod 11. Combined with the spring end cover 16 and the bearing sleeve 14 connected to the base bracket 20 through the raised shaft 15, the deformation of the spring 13 on the spring guide rod 11 can be ensured, and the conversion of the load arm 30's own gravity and the load 33's gravity and the elastic potential energy of the spring 13 can be realized, thereby maintaining the balance of the robot arm 100.

[0027] In this embodiment, the base bracket 20 includes a first support plate 21 and a second support plate 22 that are arranged opposite to each other, the load arm 30 includes a first connecting rod 31 and a connecting arm 32, the cross section of the first connecting rod 31 is roughly ⌒-shaped, one end of the first connecting rod 31 is provided with a receiving groove 311, the annular body 111 of the spring guide rod 11 is located in the receiving groove 311, the rotating shaft 50 passes through one side of the first connecting rod 31 and enters the receiving groove 311, passes through the annular body 111 and then passes through the other side of the first connecting rod 31, so as to The spring guide rod 11 is rotatably connected to one end of the first connecting rod 31, one end of the connecting arm rod 32 passes through the other end of the first connecting rod 31, and the connecting arm rod 32 and the first connecting rod 31 can be fixed by bolts, the connecting shaft 60 passes through the first support plate 21, one end of the connecting arm rod 32 and the second support plate 22 in sequence and is connected to the motor shaft of the driving motor 40, the other end of the connecting arm rod 32 is connected to the load 33, and the two raised shafts 15 are rotatably connected to the first support plate 21 and the second support plate 22 respectively.

[0028] It is understandable that a long strip groove 321 can be provided at the connection between the connecting arm 32 and the first connecting rod 31 and the connection between the connecting arm 32 and the load 33. When the mass m of the load 33 changes and the spring coefficient K remains unchanged, the user can maintain the balance of the robot arm 100 by changing the position of the connecting arm 32 and the first connecting rod 31, that is, changing h1 and h2. This method is simple and convenient to operate; or the balance of the robot arm 100 can be maintained by changing the position of the load 33, that is, by changing L by moving the position of the bolt in the long strip groove 321. As another embodiment, when the mass m of the load 33 changes, the spring 13 whose spring coefficient satisfies K=mgL / h1h2 can also be replaced to maintain the balance of the robot arm 100. This method does not require changing the structure of the robot arm, is flexible to operate, and provides more options.

[0029] Specifically, Figure 2As shown, the base bracket 20 also includes a bottom plate 23 and a motor bracket 24, the first support plate 21 and the second support plate 22 are respectively fixed to the upper surface of the bottom plate 23, and a first bearing adapter 25 and a second bearing adapter 26 are respectively installed on the opposite sides of the first support plate 21 and the second support plate 22, and a first bearing 27 and a second bearing 28 are respectively installed on the first bearing adapter 25 and the second bearing adapter 26 corresponding to the two protruding shafts 15, and the two protruding shafts 15 are respectively penetrated by the first bearing 27 and the second bearing 28 to be rotatably connected with the first support plate 21 and the second support plate 22, and the motor bracket 2 4 is located outside the second support plate 22, the drive motor 40 is located on the motor bracket 24, and the motor shaft of the drive motor 40 passes through the motor bracket 24 and is connected to the connecting shaft 60 through a third bearing adapter 90, a flange bearing 81 and a thrust bearing 82 are sleeved on the connecting shaft 60 in sequence, and a thrust bearing adapter 70 is also connected to the end of the connecting shaft 60, the flange bearing 81, the thrust bearing 82 and the thrust bearing adapter 70 are located between the first support plate 21 and the connecting arm 32, and the thrust bearing adapter 70 passes through the connecting arm 32 and is connected to the third bearing adapter 90. Preferably, the flange bearing 81 and the thrust bearing 82 can also be sleeved between the third bearing adapter 90 and the motor shaft to facilitate rotation transmission.

[0030] It can be understood that when the robotic arm 100 of the present embodiment is applied to a gimbal, it can be installed on the surface of the gimbal through the base plate 23. When the robotic arm 100 rotates around the pitch axis, the connecting arm rod 32 and the first connecting rod 31 rotate, thereby driving the gravity compensation mechanism 10 to work. At this time, the two protruding shafts 15 in the gravity compensation mechanism 10 rotate, the spring guide rod 11 moves upward, and the spring 13 is compressed, thereby realizing the conversion of the gravitational potential energy of the robotic arm 100 and the load 33 and the elastic potential energy of the spring 13, and compensating the torque of the driving motor 40 of the robotic arm 100 caused by the gravity on the robotic arm 100, so that the robotic arm 100 can reach a balanced state at any position, realizing the gravity compensation of the robotic arm 100, and when the robotic arm 100 returns to its original position, the protruding shaft 15 rotates, the spring guide rod 11 moves downward, the spring 13 stretches and returns to its initial state, and the robotic arm 100 maintains balance.

[0031] In summary, the utility model does not require structures such as cams, and can also compensate for the torque of the driving motor of the robotic arm caused by the gravity on the robotic arm through gravity compensation, thereby eliminating the influence of the gravity on the robotic arm on the motor drive. The structure is simple, and the requirements of the driving load on the motor can be reduced, so that the size of the motor no longer increases due to the increase in the load on the robotic arm, and a smaller motor can be used, and the size of the entire robotic arm is greatly reduced.

[0032] The above description is only a preferred embodiment of the utility model, and does not limit the utility model in any form. Those skilled in the art can make various equivalent changes and improvements based on the above embodiments, and all equivalent changes or modifications made within the scope of the claims should fall within the protection scope of the utility model.

Claims

1. A gravity compensation mechanism, applied to a mechanical arm having a load arm, wherein the load arm is mounted on a pan / tilt platform via a base bracket, characterized in that: The gravity compensation mechanism includes a spring guide rod with one end rotatably connected to the load arm rod, a linear bearing and a spring sleeved on the spring guide rod, the linear bearing is also connected to a bearing sleeve, the outer wall of the bearing sleeve is formed with at least one raised shaft rotatably connected to the base bracket, the other end of the spring guide rod is connected to a spring end cover, the spring is located between the bearing sleeve and the spring end cover, and can be extended and retracted when the bearing sleeve rotates.

2. The gravity compensation mechanism according to claim 1, characterized in that: The bearing sleeve includes a cylinder, both sides of which protrude outward to form two protruding shafts, and the top and bottom of the cylinder are respectively recessed inward to form a first mounting groove and a second mounting groove, and one end of the linear bearing and the spring are respectively located in the first mounting groove and the second mounting groove.

3. The gravity compensation mechanism according to claim 2, characterized in that: The linear bearing is a flange-type linear bearing, which is located in the first mounting groove, and the mounting flange of the flange-type linear bearing is fixed to the top of the cylinder.

4. The gravity compensation mechanism according to claim 1, characterized in that: An annular body is formed at one end of the spring guide rod, and a rotating shaft is inserted into the annular body so as to be rotatably connected to the load arm rod through the rotating shaft.

5. The gravity compensation mechanism according to claim 4, characterized in that: Two thrust bearings are sleeved on the rotating shaft. The two thrust bearings are arranged on both sides of the annular body and are both located between the load arm and the annular body.

6. A robotic arm, characterized in that: It comprises a base support, a load arm, a drive motor and the gravity compensation mechanism as described in any one of claims 1 to 5, wherein the load arm is rotatably connected to the base support via a connecting shaft, the drive motor is located at one side of the base support, and the motor shaft of the drive motor is connected to the connecting shaft, the spring guide rod is rotatably connected to one end of the load arm, and the other end of the load arm is connected to the load, the raised shaft is located below the connecting shaft and is rotatably connected to the side wall of the base support so that when the load arm rotates under the action of the drive motor, the spring sleeved on the spring guide rod is expanded and contracted, thereby offsetting the gravity of the load arm.

7. The robot arm according to claim 6, characterized in that: The base bracket includes a first support plate and a second support plate arranged opposite to each other, the load arm includes a first connecting rod and a connecting arm, the first connecting rod has a ⌒-shaped cross-section, the spring guide rod is rotatably connected to one end of the first connecting rod, one end of the connecting arm passes through the other end of the first connecting rod, the connecting shaft passes through the first support plate, one end of the connecting arm and the second support plate in sequence and is connected to the motor shaft of the driving motor, the other end of the connecting arm is connected to the load, the raised shaft is located directly below the connecting shaft, and is rotatably connected to the first support plate / second support plate.

8. The robot arm according to claim 7, characterized in that: A first bearing adapter and a second bearing adapter are respectively installed on the opposite sides of the first support plate and the second support plate, and a first bearing and a second bearing are respectively installed on the first bearing adapter and the second bearing adapter, and the protruding shaft passes through the first bearing / second bearing to be rotatably connected with the first support plate / second support plate.

9. The mechanical arm according to claim 7, characterized in that: The base bracket also includes a bottom plate and a motor bracket, the first support plate and the second support plate are respectively fixed to the upper surface of the bottom plate, the motor bracket is located on the outer side of the second support plate, the drive motor is located on the motor bracket, and the motor shaft of the drive motor passes through the motor bracket and is connected to the connecting shaft through a third bearing adapter, and a flange bearing and a thrust bearing are sequentially sleeved on the connecting shaft, and the flange bearing and the thrust bearing are located between the first support plate and the connecting arm rod.

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