A gravity balancing device for a robotic arm

Abstract

The present invention proposes a gravity balancing device for a robotic arm, which is installed on the base of the robotic arm. It is a mechanical structure used to balance the gravity of the robotic arm itself. It aims to solve the problems of increased energy consumption and reduced precision caused by gravity during the movement of existing robotic arms. At the same time, it can significantly reduce the rotational inertia of the robotic arm when installed on the base. The mechanical structure of the robotic arm gravity balance is composed of a transmission mechanism, a fixing mechanism and a balancing mechanism. The transmission mechanism is used to transmit the rotation of the robotic arm joint axis to the balancing mechanism located on the base. The fixing mechanism is used to fix the gravity balancing device on the base. The balancing mechanism can generate a torque that is completely equivalent to the gravity torque of the robotic arm according to the joint angle of the robotic arm. The present invention has the advantages of simple structure, easy installation, high precision, etc., and can be widely used in industrial automation, robotics and other fields.

Description

Technical Field

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

[0002] As core equipment in industrial automation and robotics, robotic arms are widely used in various fields, including material handling, assembly, and processing, effectively improving production efficiency and quality. However, during operation, the large mass and flexible posture of the robotic arm generate non-constant gravitational torques at each joint axis. These torques not only consume a considerable amount of the joint motor load capacity, increasing the robotic arm's energy consumption, but also negatively impact the accuracy and stability of the robotic arm's operation, making it difficult for the robotic arm to achieve the desired precision. Therefore, during the robotic arm design process, it is necessary to consider incorporating a gravity balancing device to offset the gravitational torque at the joint axis, reduce the load on the joint motor, reduce the robotic arm's energy consumption, speed up response, and improve control accuracy and stability.

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

[0004] For example, the traditional counterweight method balances the arm's inherent gravitational torque by adding an appropriate counterweight to the other end of the arm's joint axis. This counterweight is simply equalized by multiplying the mass on either side of the axis by the distance from the center of mass to the axis. This method is simple and inexpensive, but the counterweight itself increases the arm's mass and moment of inertia, affecting its agility. Greater mass and moment of inertia can also pose a greater risk of harm to the human body in the event of an accident.

[0005] The spring method is also a common balancing method. It uses spring force to offset the weight of the robotic arm, achieving balance. Numerous variations of the spring method can be developed, depending on the locations of the spring ends and the connection method. This method does not change the mass or moment of inertia of the robotic arm, nor does it reduce its sensitivity or safety. However, the balancing device requires ingenious structural design, and the spring stiffness and preload must be precisely calculated to accommodate robotic arms of varying sizes and weights.

[0006] There are also advanced sensor- and algorithm-based gravity balancing technologies, such as force feedback control and active balancing systems. These technologies achieve dynamic balance by detecting the robot's motion state and load changes in real time, using algorithms to calculate and adjust the balancing mechanism's output force. For example, sensors measure the robot's rotation angle, calculate the specific gravity torque at the axis in this state, and use the motor to provide compensating torque T. However, these technologies typically require complex control systems and precise algorithms, placing high demands on both technology and cost. Summary of the Invention

[0007] In response to the above technical problems, the present invention proposes a gravity balancing device installed at 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 robotic arm base, the device comprising: a transmission mechanism, a fixing mechanism and a balancing mechanism;

[0009] The transmission mechanism includes a joint connecting member and a swinging member. The joint connecting member is coaxially fixed with the joint of the robotic arm and rotates with the joint of the robotic arm. The swinging member is connected to the joint connecting member so that the rotation angle of the robotic arm is halved and transmitted to the swinging member.

[0010] The fixing mechanism includes a rotating shaft, a horizontal rod and a mounting frame. 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 installed in the mounting frame, and the mounting frame is installed at the base of the robotic 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 part through the fixed shell to control the distance between the adjustable swing arm and the rotation axis, and is used to provide a torque that changes with the joint angle to offset the gravitational 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 and the joint connecting member are connected by 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 bracket is connected to the robotic 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 rods include two, which are respectively installed in the upper half and the lower half of 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 pinned via vertical grooves in the two translating sliders. The pins are movable within the vertical grooves of the translating sliders. This arrangement ensures that the adjustable swing arm and the translating sliders are aligned horizontally, and the force acting between them is horizontal. This converts the swing member's rotational motion into horizontal movement.

[0018] Furthermore, the wire rope is redirected by the guide pulley, allowing the tension spring to be flexibly arranged at any position on the base. Since the wire rope can be redirected by the guide pulley, the tension spring can be fixed at any position on the base. Therefore, the tension spring can be flexibly arranged at any position on the base, facilitating the arrangement of base components.

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

[0020] The present invention provides a gravity balancing device mounted on the base of a robotic arm. This device uses spring force to offset the arm's gravitational torque, thereby reducing the torque required by the arm's joint motors. By compensating for the arm's gravity, it effectively reduces the arm's energy consumption and improves its dynamic and static performance.

[0021] The magnitude of the gravitational torque at the joints of the robotic arm changes with the arm's posture. This invention utilizes a combination of a swing arm and a horizontal sliding link, along with a reduction gear with a 1 / 2 reduction ratio, to ensure that the compensating torque generated by the spring force also changes with the arm's posture, always being equal in magnitude and opposite in direction to the gravitational torque of the robotic arm.

[0022] The present invention provides a gravity balancing device for installation at the base of a robotic arm. This device can be installed at the base and provide gravity balancing for joint axes that are far from the base. This has the following advantages: first, the base of the robotic arm is relatively spacious, making the design, processing, and assembly of the robotic arm more user-friendly; second, the gravity balancing device installed at the joint axis of the robotic arm introduces mass farther from the rotational axis, increasing the robotic arm's moment of inertia and reducing its control and safety performance. This invention eliminates the need to increase the mass and moment of inertia of the robotic arm itself, or to precisely calculate the spring stiffness and preload.

[0023] The present invention provides a gravity balancing device installed on the base of a robotic arm, which has a simple structure, low processing cost, and low assembly difficulty, and is suitable for use with various robotic 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 a spring balance method provided in an embodiment of the present invention;

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

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

[0028] Figure 5 This is a schematic diagram of the structure of the present invention connecting the joint axis of the remote robotic 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 a diagram of the gravity balance principle of the present invention;

[0032] Figure 9 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 connection; 2. Swinging member; 3. Rotating axis; 4. Horizontal rod; 5. Mounting frame; 6. Fixed shell; 7. Adjustable swing arm; 8. Translation slider; 9. Steel wire rope; 10. Tension spring. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions, and advantages of the examples of the present invention more clear, the specific technical solutions of the present invention are clearly and completely described below with reference to the accompanying drawings. Obviously, the examples described are only part of the examples of the present invention. All other examples based on the examples of the present invention, which are not obtained through creative work, fall within the scope of protection 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. 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. According to the different fixed positions and connection methods of the two ends of the spring, the spring method can also develop many variations. Figure 3A gravity balancing technology shown in the figure measures the rotation angle of the robot arm through a sensor, calculates the specific value of the gravity torque at the rotation shaft in this state, and provides a compensation torque T through the 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 at the base of a robotic arm. The device includes a transmission mechanism, a fixing mechanism, and a balancing mechanism. The transmission mechanism is responsible for transmitting the gravitational torque at the robotic arm joints to the balancing mechanism; the fixing mechanism is responsible for limiting the degrees of freedom of movement of the various components of the device and for mounting the device at the robotic arm base; and the balancing mechanism is responsible for providing an adaptive torque to balance the gravitational torque at the robotic arm joints.

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

[0038] The transmission mechanism includes: a joint connection part 1 and a swing part 2. The joint connection part 1 is coaxial with the robot arm joint and fixed, and can rotate with the robot arm joint. The swing part 2 is installed on the rotating shaft 3 through a bearing and can rotate freely along the rotating shaft 3. The joint connection part 1 and the swing part 2 are connected by a gear (such as Figure 4 As shown), synchronous belt (as Figure 5 The connection method needs 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 comprises a rotating shaft 3, a horizontal rod 4, and a mounting bracket 5. The rotating shaft 3, located at the top of the mounting bracket 5, secures the oscillating member 2, allowing only rotation along its axis and prohibiting movement in the remaining five degrees of freedom. The horizontal rod 4, located in the middle of the mounting bracket 5, restricts the translational slider to horizontal motion via bearings and pulleys. The mounting bracket 5 has threaded holes at its bottom, allowing it to be screwed to the base of the robotic arm. In addition to screw connections, other possible attachment methods include pins, welding, and interference fits.

[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. Among them, 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, such as 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 to be used in conjunction with the thread to fix the adjustable swing arm 7 to the swing member 2.

[0043] The adjustable swing arm 7 and the translating slider 8 are mated via a pin that moves within a vertical groove on the translating slider. This arrangement ensures that the adjustable swing arm and the translating slider are aligned horizontally, and the force acting between them is horizontal. This converts the swing member's rotational motion into horizontal movement.

[0044] like Figure 6 As shown, the translation slider 8 is connected to one end of a tension spring 10 via a wire rope 9. Because the wire rope can be redirected via a pulley system, the specific routing and layout of the wire rope can be flexibly adapted to the robot arm's structure without interfering with other components. The other end of the tension spring 10 can be fixed to any position on the base as needed, 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. Therefore, 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 link on the first link is the downward force G L2 +G L3 .

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

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

[0049] Where G L1 ——is the mass of the first robot arm link;

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

[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——The rotation angle of the first robot arm link.

[0055] Gravity torque T at the second joint of the robotic 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 link;

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

[0059] θ2——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 neglected, the influence of the gravitational torque of the manipulator 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 Figure 9 As shown, the second joint is driven by a synchronous wheel and belt mechanism (or other remote transmission mechanism), with the radii R of the two synchronous wheels being equal. The thick solid line in the figure represents the synchronous belt. Because the synchronous belt is not stretchable, the thick solid lines in the left and right figures are equal in length. The relative positions of the meshing points of the synchronous wheels and belt indicate that when the first link rotates θ1 and the second link rotates θ2, the synchronous wheel at the first joint rotates by an angle equal to θ1 + θ2.

[0074] Fix the joint connector 1 to the synchronous wheel at the first joint. According to the above, the transmission ratio of the angle between the joint connector 1 and the swing member 2 is 2:1, that is, θ1+θ2=2θ'. Substitute it into the calculation formula of the gravity torque 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 neglected, the influence of the gravitational torque of the manipulator 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 modifications and changes 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. The joint connection member is coaxially fixed with the joint of the robotic arm and rotates with the joint of the robotic arm. The swing member is connected to the joint connection member so that the rotation angle of the robotic arm is halved and transmitted to the swing member. The fixing mechanism includes a rotating shaft, a horizontal rod and a mounting frame. 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 installed in the mounting frame, and the mounting frame is installed at the base of the robotic 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 rotation 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 robotic arm.

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

4. The gravity balancing device applied to a robotic arm base according to claim 1, characterized in that: 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.

5. The gravity balancing device applied to a robotic arm base according to claim 1, characterized in that: The horizontal rods include two, the upper half and the lower half of which are respectively installed in the mounting frame.

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

7. The gravity balancing device applied to a robotic arm base according to claim 6, characterized in that: The adjustable swing arm is pin-coupled via vertical grooves in the two translation slide blocks.

8. The gravity balancing device applied to a robotic 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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