Gravity balancing device for mechanical arm

Abstract

The invention provides a gravity balancing device for a mechanical arm, which is mounted on a base of the mechanical arm, is a mechanical structure for balancing the self gravity of the mechanical arm, aims to solve the problems of energy consumption increase, precision reduction and the like caused by the gravity effect in the movement of the existing mechanical arm, and can remarkably reduce the rotational inertia of the mechanical arm when being mounted on the base. The mechanical arm gravity balance mechanical structure is composed of a transmission mechanism, a fixing mechanism and a balance mechanism. The transmission mechanism is used for transmitting rotation of the mechanical arm joint shaft to the balance mechanism located on the base. And the fixing mechanism is used for fixing the gravity balancing device on the base. The balance mechanism can generate torque completely equal to gravitational torque of the mechanical arm according to the joint angle of the mechanical arm. The invention has the advantages of simple structure, convenience in installation, high precision and the like, and can be widely applied to the fields of industrial automation, robot technology and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of robots, and in particular relates to a gravity balancing device for a robot arm. Background Art

[0002] As the core equipment in the field of industrial automation and robotics, the robotic arm is widely used in various fields such as material handling, assembly, and processing, effectively improving production efficiency and quality. However, when the robotic arm is in operation, due to its large mass and flexible posture, non-constant gravity torque is generated at each joint axis. These torques will consume a considerable amount of the joint motor load capacity and increase the energy consumption of the robotic arm; they will also have a negative impact on the accuracy and stability of the robotic arm's operation process, making it difficult for the robotic arm to meet the expected accuracy requirements. Therefore, in the design process of the robotic arm, it is necessary to consider adding a gravity balance device to offset the gravity torque at the joint axis, reduce the load of the joint motor, reduce the energy consumption of the robotic arm, speed up the response speed, and improve the control accuracy and stability.

[0003] In order to solve the above problems, researchers have conducted in-depth research on the gravity balancing technology of the robotic arm. At present, there are some methods and technologies for gravity balancing, but each method has its limitations and shortcomings.

[0004] For example, the traditional counterweight method balances the gravity torque of the robot arm itself by adding an appropriate counterweight block at the other end of the robot arm joint axis. The gravity torque of the robot arm itself can be balanced by simply making the mass on both sides of the rotation axis equal to the product of the distance from the center of mass to the rotation axis. This method is simple in design and low in cost, but the counterweight block itself will increase the mass and moment of inertia of the robot arm itself, affecting the sensitivity of the robot arm. Larger mass and moment of inertia will also cause greater harm to the human body in an accident.

[0005] The spring method is also a common balancing method. The spring force is used to offset the gravity of the robot arm to achieve a balancing effect. Depending on the fixed positions of the two ends of the spring and the different connection methods, the spring method can also develop many variants. This method does not change the mass and moment of inertia of the robot arm, and does not reduce its sensitivity and safety. However, the balancing device requires a clever structural design, and the stiffness and preload of the spring also need to be accurately calculated to adapt to robots of different sizes and weights.

[0006] In addition, there are some advanced gravity balancing technologies based on sensors and algorithms, such as force feedback control and active balancing systems. These technologies detect the motion state and load changes of the robot arm in real time, and use algorithms to calculate and adjust the output force of the balancing mechanism to achieve dynamic balance. For example, the rotation angle of the robot arm is measured by the sensor, the specific value of the gravity torque at the shaft in this state is calculated, and the compensation torque T is provided by the motor. However, these technologies usually require complex control systems and precise algorithm support, and have high technical and cost requirements. Summary of the invention

[0007] In view of the above technical problems, the present invention proposes a gravity balancing device installed on the base of a robotic arm.

[0008] The technical problem to be solved by the present invention is achieved through the following technical solution: a gravity balancing device applied to a mechanical arm base, the device comprising: a transmission mechanism, a fixing mechanism and a balancing mechanism;

[0009] The transmission mechanism includes a joint connection member and a swing member, wherein the joint connection member is coaxially fixed with the joint of the mechanical arm and rotates with the joint of the mechanical arm, and the swing member is connected to the joint connection member so that the rotation angle of the mechanical arm is halved and transmitted to the swing member;

[0010] The fixing mechanism comprises a rotating shaft, a horizontal rod and a mounting frame, wherein the rotating shaft is located at the top of the mounting member and is connected to the swing member through a bearing so that the swing member rotates along the rotating shaft, the horizontal rod is mounted in the mounting frame, and the mounting frame is mounted on the base of the mechanical arm;

[0011] The balancing mechanism includes an adjustable swing arm, a fixed shell, a translation slider, a steel wire rope and a tension spring. The adjustable swing arm is connected to the swinging member through the fixed shell to control the distance between the adjustable swing arm and the rotation axis, so as to provide a torque that changes with the joint angle to offset the gravity torque at the joint of the robotic arm. The translation slider is installed on the horizontal rod and cooperates with the adjustable swing arm through a pin shaft. The steel wire rope connects the translation slider and the tension spring, and the other end of the tension spring is connected to the base of the robotic arm.

[0012] Furthermore, the swinging member is connected to the joint connecting member by means of gears or synchronous belts. When the gears are used for connection, the tooth density ratio of the joint connecting member and the swinging member is 1:2.

[0013] Furthermore, the bottom of the mounting frame is connected to the mechanical arm by screws, pins, welding or interference fit.

[0014] Furthermore, the adjustable swing arm is mounted on the swing member via a thread, and the distance from the adjustable swing arm to the rotating shaft is controlled by the screwing depth of the thread.

[0015] Furthermore, the horizontal rod includes two, an upper half and a lower half respectively installed in the mounting frame.

[0016] Furthermore, the translation sliders include two, which are respectively installed on different horizontal rods, and the two translation sliders are connected to each other and are provided with vertical grooves.

[0017] Furthermore, the adjustable swing arm is pin-matched through the vertical grooves in the two translation sliders. The pin can move in the vertical grooves on the translation slider. Through this matching mode, the adjustable swing arm and the translation slider are in the same horizontal position, and the direction of the force between the two is horizontal. In this way, the rotational motion of the swing member is converted into horizontal motion.

[0018] Furthermore, the steel wire rope changes direction through the guide wheel, so that the tension spring can be flexibly arranged at any position of the base. Since the steel wire rope can change direction through the guide wheel, the tension spring can be fixed at any position of the base. Therefore, the tension spring can be flexibly arranged at any position of the base, which is convenient for arranging the base components.

[0019] The beneficial effects of the present invention are:

[0020] The invention provides a gravity balancing device installed on the base of a mechanical arm, which uses spring force to offset the mechanical arm gravity moment, thereby reducing the torque required by the mechanical arm joint motor. By compensating for the gravity of the mechanical arm, the energy consumption of the mechanical arm can be effectively reduced, and the dynamic and static performance of the mechanical arm can be improved.

[0021] The gravity moment of the robot arm at the joint will change with the change of the robot arm posture. The present invention uses a combination mechanism of a swing arm and a horizontal sliding link and a reduction device with a 1 / 2 reduction ratio to make the compensation torque generated by the spring elastic force also change with the robot arm posture, and always be equal to the gravity moment of the robot arm in magnitude and opposite in direction.

[0022] The present invention provides a gravity balancing device installed at the base of a robotic arm, which can be installed at the base and provide gravity balance for the joint axis far away from the base. The first advantage is that the space at the base of the robotic arm is relatively open, which is more friendly to the design, processing and assembly of the robotic arm; the second advantage is that the gravity balancing device installed at the joint axis of the robotic arm will introduce mass farther away from the rotation axis, increase the rotational inertia of the robotic arm, and reduce the control performance and safety performance of the robotic arm. The present invention does not need to increase the mass and rotational inertia of the robotic arm itself, and does not need to accurately calculate the stiffness and preload of the spring.

[0023] The present invention provides a gravity balancing device installed on a base of a mechanical arm, which has a simple structure, low processing cost, and low assembly difficulty, and is suitable for use with various mechanical arms. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of a traditional counterweight balancing method provided in an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of spring balance provided in an embodiment of the present invention;

[0026] Figure 3 A schematic diagram of gravity balancing by using a sensor provided in an embodiment of the present invention;

[0027] Figure 4 It is a schematic diagram of the structure of the device of the present invention in one direction;

[0028] Figure 5 It is a schematic diagram of the structure of the present invention connecting the joint axis of the remote mechanical arm;

[0029] Figure 6 It is a schematic diagram of the connection structure of the translation slider of the present invention;

[0030] Figure 7 This is a force analysis diagram of the gravity of the robotic arm;

[0031] Figure 8 It is the gravity balance principle diagram of the present invention;

[0032] Fig. 9 It is a schematic diagram of the simplified kinematic model of the first two joints of the device of the present invention.

[0033] In the figure: 1. joint connecting part; 2. swinging part; 3. rotating shaft; 4. horizontal rod; 5. mounting frame; 6. fixed shell; 7. adjustable swing arm; 8. translation slider; 9. wire rope; 10. tension spring. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the examples of the present invention clearer, the specific technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings. Obviously, the examples described are part of the examples of the present invention, and all other examples obtained based on the examples in the present invention without creative work belong to the protection scope of the present invention.

[0035] like Figures 1 to 3 As shown in the figure, it is an existing gravity balance method, such as Figure 1 As shown in . Simply make the mass on both sides of the axis equal to the product of the distance from the center of mass to the axis, and the gravitational torque of the robot itself can be balanced. Figure 2 As shown. Depending on the location of the two ends of the spring and the different connection methods, the spring method can also develop many variants. Figure 3A gravity balancing technology is shown, which measures the rotation angle of the robot arm through a sensor, calculates the specific value of the gravity moment at the rotating shaft in this state, and provides a compensation torque T through a motor.

[0036] Different from this, Figure 4 , Figure 5 and Figure 6 As shown, the present invention provides a gravity balancing device that can be installed on the base of a mechanical arm, and the device includes a transmission mechanism, a fixing mechanism, and a balancing mechanism. The transmission mechanism is responsible for transmitting the gravity torque at the joint of the mechanical arm to the balancing mechanism; the fixing mechanism is responsible for limiting the freedom of movement of each part of the device of the present invention, and installing the device of the present invention on the base of the mechanical arm; the balancing mechanism is responsible for providing an adaptive torque to balance the gravity torque at the joint of the mechanical arm.

[0037] The transmission mechanism is described in detail below.

[0038] The transmission mechanism includes: a joint connection member 1 and a swing member 2. The joint connection member 1 is coaxial with the joint of the robot arm and is fixed, and can rotate with the joint of the robot arm. The swing member 2 is installed on the rotating shaft 3 through a bearing and can rotate freely along the rotating shaft 3. The joint connection member 1 and the swing member 2 are connected by a gear (such as Figure 4 As shown), synchronous belt (as Figure 5 The connection method is required to ensure that the rotation angle of the robot arm is halved and transmitted to the swing member 2.

[0039] The fixing mechanism is described in detail below.

[0040] The fixing mechanism includes: a rotating shaft 3, a horizontal rod 4, and a mounting frame 5. The rotating shaft 3 is located at the top of the mounting frame 5, and is responsible for fixing the swinging member 2, allowing the swinging member 2 to rotate along the axis only, and prohibiting the movement of the other five degrees of freedom. The horizontal rod 4 is located in the middle of the mounting frame 5, and the translation slider can only move horizontally through the bearing and the pulley. There are threaded holes at the bottom of the mounting frame 5, and it can be installed on the base of the robot arm by screws. In addition to screw connection, it can also be connected by pins, welding, interference fit, etc.

[0041] The balancing mechanism is described in detail below.

[0042] Fixed shell 6, adjustable swing arm 7, translation slider 8, wire rope 9, tension spring 10. The adjustable swing arm 7 is installed on the swing member 2 through a thread, and the distance from the adjustable swing arm 7 to the rotating shaft 3 can be controlled by the screwing depth of the thread. Figure 6 The adjustable swing arm 7 and the swing member 2 are provided with a square fixed shell (fixed shell 6 is not shown in the figure) to prevent the two from rotating relative to each other, and is used in conjunction with the thread to fix the adjustable swing arm 7 on the swing member 2.

[0043] The adjustable swing arm 7 and the translation slider 8 are matched by a pin shaft, and the pin shaft can move in the vertical groove on the translation slider. Through this matching mode, the adjustable swing arm and the translation slider have the same horizontal position, and the direction of the force between the two is horizontal. In this way, the rotational motion of the swing member is converted into horizontal motion.

[0044] like Figure 6 As shown, the translation slider 8 is connected to one end of the tension spring 10 through a steel wire rope 9. Since the steel wire rope can change direction through a pulley block, the specific routing method and layout strategy of the steel wire rope can be flexibly arranged according to the structure of the robot arm itself without interfering with other components. The other end of the tension spring 10 can be fixed at any position of the base as required without affecting the normal operation of the gravity balance device.

[0045] The principle of the device of the present invention is described in detail below.

[0046] First, the force analysis of the first two connecting rods of the robot arm is carried out, such as Figure 7 When analyzing gravity, it is assumed that the joint axis between the second and third links cannot transmit torque, so the third link and subsequent links are equivalent to applying a downward gravity G at the end of the second link. L3 Similarly, the force exerted by the second connecting rod on the first connecting rod is a downward force G L2 +G L3 .

[0047] Gravity moment T at the first joint of the robot arm G1 The calculation formula is

[0048] T G1 =(G L1 ·L1'+G L2 L1+G L3 ·L1)·sinθ1

[0049] In the formula, G L1 ——is the mass of the first robot arm link;

[0050] G L2 ——is the mass of the second robot arm connecting rod;

[0051] G L3 ——The total mass of the third and subsequent robot arm links;

[0052] L1——The length of the first robot arm link;

[0053] L1'——The distance from the center of mass of the first robot link to the first joint axis;

[0054] θ1——is the rotation angle of the first robot arm link.

[0055] Gravity moment T at the second joint of the robot arm G2 The calculation formula is

[0056] T G2 =(G L2 ·L2'+G L3 ·L2)·sin(θ1+θ2)

[0057] Where, L2 is the length of the second robot arm connecting rod;

[0058] L2'——the distance from the center of mass of the second robot link to the second joint axis;

[0059] θ2——is the rotation angle of the second robot arm link.

[0060] The device of the present invention can be simplified as follows Figure 8 As shown in the schematic diagram, for the elastic force F of the extension spring 10, there is a formula

[0061] F=K·x=K·r·sinθ

[0062] Where, K is the elastic coefficient of the extension spring 10

[0063] x——the elongation of the tension spring 10 (adjust the length of the wire rope 9 so that when the angle θ is 0, the spring is in the original length state);

[0064] θ——rotation angle of swing member 2;

[0065] r——the distance from the adjustable swing arm 6 to the rotating shaft 3;

[0066] The balancing torque T that the gravity balancing device can generate balance It can be derived from the following formula

[0067]

[0068] K is related to the spring and is a fixed parameter; the size of r can be adjusted by the adjustable swing arm.

[0069] According to the above, the transmission ratio of the angle between the joint connecting part 1 and the swinging part 2 is 2:1, that is, θ1=2θ, and the torque transmission ratio is 1:2. Substituting into the above formula, we have

[0070]

[0071] Where G L1 , G L2 , G L3, L1, L1', K are all constant values. Obviously, by adjusting the size of r, the balancing torque T generated by the balancing device can be adjusted. balance The gravitational moment T of the manipulator G1 When the influence of frictional resistance is ignored, the influence of the gravity torque of the robot arm can be offset without error.

[0072] The principle of balancing the gravity moment at the second joint of the device of the present invention is described in detail below.

[0073] The simplified kinematic models of the first two joints are as follows Fig. 9 As shown, the second joint is driven by a synchronous wheel and synchronous belt mechanism (or other long-distance transmission mechanism), and the radius R of the two synchronous wheels is equal. The thick solid line in the figure represents the synchronous belt. As the synchronous belt is not stretchable, the thick solid lines in the left and right figures are equal. From the relative position of the meshing point of the synchronous wheel and synchronous belt, it can be seen that when the first connecting rod rotates θ1 and the second connecting rod rotates θ2, the rotation angle of the synchronous wheel at the first joint is θ1+θ2.

[0074] Fix the joint connection part 1 to the synchronous wheel at the first joint. According to the above, the transmission ratio of the angle between the joint connection part 1 and the swing part 2 is 2:1, that is, θ1+θ2=2θ'. Substitute it into the calculation formula of the gravity moment of the second joint, and we can get

[0075]

[0076] Where G L2 , G L3 , L2, L2', K are all constant values. Obviously, by adjusting the size of r, the balancing torque T generated by the balancing device can be adjusted. balance The gravitational moment T of the manipulator G2 When the influence of frictional resistance is ignored, the influence of the gravity torque of the robot arm can be offset without error.

[0077] For other joints with parallel axis directions, the gravity balancing device can be designed using the same principle.

[0078] The above embodiments are used to illustrate the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A gravity balancing device applied to a robotic arm base, characterized in that: The device comprises: a transmission mechanism, a fixing mechanism and a balancing mechanism; The transmission mechanism includes a joint connection member and a swing member, wherein the joint connection member is coaxially fixed with the joint of the mechanical arm and rotates with the joint of the mechanical arm, and the swing member is connected to the joint connection member so that the rotation angle of the mechanical arm is halved and transmitted to the swing member; The fixing mechanism comprises a rotating shaft, a horizontal rod and a mounting frame, wherein the rotating shaft is located at the top of the mounting member and is connected to the swing member through a bearing so that the swing member rotates along the rotating shaft, the horizontal rod is mounted in the mounting frame, and the mounting frame is mounted on the base of the mechanical arm; The balancing mechanism includes an adjustable swing arm, a fixed shell, a translation slider, a steel wire rope and a tension spring. The adjustable swing arm is connected to the swinging member through the fixed shell to control the distance between the adjustable swing arm and the rotating axis. The translation slider is installed on the horizontal rod and cooperates with the adjustable swing arm through a pin shaft. The steel wire rope connects the translation slider and the tension spring, and the other end of the tension spring is connected to the base of the mechanical arm.

2. A gravity balancing device applied to a robot arm base according to claim 1, characterized in that: The swinging member and the joint connecting member are connected in a manner including a gear or a synchronous belt connection. When the gear connection is used, the tooth density ratio of the joint connecting member and the swinging member is 1:

2.

3. A gravity balancing device applied to a robot arm base according to claim 1, characterized in that: The bottom of the mounting frame is connected to the mechanical arm by screws, pins, welding or interference fit.

4. A gravity balancing device applied to a robot arm base according to claim 1, characterized in that: The adjustable swing arm is installed on the swing member through a thread, and the distance from the adjustable swing arm to the rotating shaft is controlled by the screwing depth of the thread.

5. The gravity balancing device used in a robot arm base according to claim 1, characterized in that: The horizontal rods include two, an upper half and a lower half respectively mounted in the mounting frame.

6. A gravity balancing device applied to a robot arm base according to claim 5, characterized in that: The translation sliding blocks include two, which are respectively installed on different horizontal rods. The two translation sliding blocks are connected to each other and are provided with vertical grooves.

7. A gravity balancing device applied to a robot arm base according to claim 6, characterized in that: The adjustable swing arm is pin-matched through vertical grooves in two translation slide blocks.

8. The gravity balancing device used in a robot arm base according to claim 1, characterized in that: The steel wire rope changes direction through the guide wheel, so that the tension spring can be flexibly arranged at any position of the base.

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