Industrial mechanical arm vibration reduction equipment and method based on adjustable local resonance vibration reduction unit

Abstract

The invention discloses industrial mechanical arm vibration reduction equipment based on adjustable local resonance vibration reduction units, and relates to the technical field of vibration suppression or attenuation devices, the industrial mechanical arm vibration reduction equipment comprises a mechanical arm connecting rod, a plurality of vibrator rings are arranged on the outer side of the mechanical arm connecting rod at equal intervals, and a plurality of two-stage flexible structures are arranged between the vibrator rings and the mechanical arm connecting rod at equal angles; the two-stage flexible structure is adhered to the outer surface of the mechanical arm connecting rod and is connected with the vibrator ring through the adjusting shaft; the invention further provides a using method of the industrial mechanical arm vibration reduction equipment based on the adjustable local resonance vibration reduction unit. The using method comprises the steps that firstly, a simplified model is constructed, and equivalent parameters are obtained; 2, calculating a band gap of a local resonance unit cell structure by using a transfer matrix method; a local resonance structure is additionally arranged on the industrial mechanical arm instead of the tail end of the mechanical arm, and vibration suppression of a mechanical arm body in a specific frequency range is achieved.

Description

Technical Field

[0001] This invention relates to the field of vibration suppression or attenuation devices, specifically to vibration reduction equipment and methods for industrial robotic arms based on adjustable local resonance vibration reduction units. Background Technology

[0002] Industrial robotic arms are typical structures with cantilevered rods and joints connected in series. During operations such as grinding and drilling, they are prone to low-frequency vibrations, which seriously affect positioning accuracy and work efficiency. Therefore, it is necessary to propose corresponding vibration reduction methods based on the vibration characteristics of industrial robotic arms.

[0003] Existing vibration reduction methods for industrial robotic arms mainly include passive vibration control and active / semi-active vibration control. Active / semi-active vibration control offers good targeting, but requires additional electrical components such as sensors and actuators, or reshaping of the control signals for the robotic arm joint motors. The algorithms are complex, the application is cumbersome, and the stability is insufficient. Passive control technologies, such as increasing system stiffness, damping, or adding passive vibration absorbers, offer high stability and are widely used. However, current passive control technologies, even with the addition of damping blocks and vibration absorbers, are only applicable to specific working conditions. Because the natural frequency of the industrial robotic arm changes continuously with its posture during operation, adjusting the mass or spring stiffness requires component replacement, a cumbersome process. Furthermore, these methods are mostly installed at the end of the industrial robotic arm, and there are few methods for controlling the vibration of the robotic arm's links. Therefore, there is an urgent need for innovation in passive control methods. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes an industrial robotic arm vibration damping device based on an adjustable local resonance vibration damping unit. The device includes a robotic arm link, with multiple oscillator rings equidistantly arranged on the outer side of the link. Multiple two-stage flexible structures are arranged at equal angles between the oscillator rings and the robotic arm link. The two-stage flexible structures include a first-stage structure and a second-stage structure. The first-stage structure includes a rectangular frame I with an opening at its bottom, and a periodic sinusoidal curved beam I fixed at the opening end. A boss I is fixed at the bottom of the curved beam I. The second-stage structure includes a rectangular frame II fixed to the bottom of the boss I. The second frame II also has an opening at its bottom, and a periodic sinusoidal curved beam II is fixed at the opening end. A boss II is fixed at the bottom of the curved beam II, and a curved connecting plate is fixed at the bottom of the boss II. Two stops are symmetrically fixed at both ends of the top of the frame II. There are gaps between the two ends of the curved beam I and the stops. The curved connecting plate is bonded to the outer surface of the robotic arm link. The frame I is connected to the oscillator rings via an adjusting shaft.

[0005] Furthermore, the adjusting shaft is a two-stage stepped shaft, including a smaller outer diameter optical shaft and a larger outer diameter adjusting handle. The lower section of the optical shaft has an annular groove, in which an elastic retaining ring is installed. The outer surface of the optical shaft has an external thread between the annular groove and the adjusting handle. The optical shaft is threaded to the vibrator ring through the external thread. The end of the optical shaft passes through the first frame, the elastic retaining ring contacts the bottom of the inner wall of the first frame, and the adjusting handle contacts the outer surface of the vibrator ring. The axial relative displacement between the adjusting shaft and the first-stage structure is limited by the elastic retaining ring and the adjusting handle.

[0006] Furthermore, the two-stage flexible structure is 3D printed using photosensitive resin with a density of 1130 kg / m³. 3 The elastic modulus is 2370 MPa, and the Poisson's ratio is 0.41; the oscillator ring and adjusting shaft are made of carbon steel with a density of 7850 kg / m³. 3 Its elastic modulus is 210 GPa and its Poisson's ratio is 0.3.

[0007] Furthermore, the oscillator ring has an inner diameter of 190mm, an outer diameter of 208mm, and a lateral width of 20mm.

[0008] Furthermore, the two-stage flexible structure has a maximum lateral width of 10mm, a frame thickness of 0.75mm, a bending beam thickness of 0.5mm, a period of 20mm, an amplitude of 3mm, a frame thickness of 0.9mm, a bending beam thickness of 0.6mm, a period of 24mm, an amplitude of 3.6mm, a bending connection plate thickness of 1mm, and a distance of 100mm between adjacent vibrator rings.

[0009] Furthermore, there are eight two-stage flexible structures set at equal angles between the individual oscillator ring and the robotic arm link.

[0010] The present invention also proposes a method for using the above-mentioned industrial robotic arm vibration damping device based on the adjustable local resonance vibration damping unit, comprising the following steps: Step 1: Construct a simplified model and obtain equivalent parameters; Extract the local resonant unit structure and robotic arm link of a single oscillator ring period to obtain a simplified local resonant unit cell structure. The robotic arm link of a single oscillator ring period is simplified to a 100mm inner ring. The local resonant unit structure is regarded as a mass spring system. The mass m is calculated through volume and density, m=0.77kg; The equivalent stiffness k is obtained through finite element simulation. With the oscillator ring fixed, a small radial displacement of 0.1mm is applied to the inner ring. The ratio of the inner ring support reaction force to the displacement is calculated to obtain the equivalent stiffness k value. Through compression simulation with different adjustment shaft heights, the stiffness value under different compression amounts is obtained.

[0011] Further, step two: Calculate the bandgap of the locally resonant unit cell structure using the transfer matrix method; a = 10 mm is the structural periodic constant, and the modal functions of the Timoshenko beam with locally resonant units are: in, , , , E is the elastic modulus of the beam, S is the cross-sectional width of the beam, I is the moment of inertia of the cross-section of the beam, G is the shear modulus, κ is the shear coefficient, ρ is the material density, ω is the bending wave frequency, and A, B, C, and D are formula coefficients. Based on the bandgap calculation method using the transfer matrix, the continuity equations for displacement, rotation, bending moment, and shear force are established for a periodic structure, yielding the transfer matrix equations for unit cells j to j+1: in: , , , Using Bloch's theorem, for a given frequency ω, the transfer matrix can be solved. The eigenvalues ​​can be used to obtain the wave vector qa, which can be used to establish the dispersion curve relationship. The bandgap characteristics of the structure can be obtained from the real part Re(qa) of the wave vector. The range that the dispersion curve does not pass through is the bending wave bandgap of the structure, and the bandgap of different compression amounts can be obtained.

[0012] Furthermore, using the natural frequency of the robotic arm as the target value, the dimensions of the two-stage flexible structure are designed accordingly. When the posture of the robotic arm changes, the compression amount is adjusted by adjusting the shaft so that the natural frequency of the equivalent spring mass system is consistent with the natural frequency of the robotic arm, thereby achieving the best vibration reduction effect.

[0013] The beneficial effects of this invention are as follows: 1. By adopting the principle of local resonance vibration reduction, a local resonance structure is attached to the industrial robotic arm, rather than to the end of the robotic arm, to suppress vibration within a specific frequency range of the robotic arm body.

[0014] 2. The use of an adjustable stiffness flexible structure can change the bandgap range of the local resonance structure.

[0015] 3. By adjusting the shaft and designing a multi-stage flexible structure, the stiffness adjustment process initially involves deformation of the first-stage structure, which then transforms into deformation of the second-stage structure after the deformation becomes larger. This achieves a larger stiffness adjustment range, allowing the vibration reduction bandgap to match the natural frequency of the robotic arm under different postures. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the connection structure of the robotic arm linkage in this invention; Figure 3 This is a schematic diagram of the local resonance damping unit structure of the oscillator ring in this invention; Figure 4 This is a schematic diagram of the two-stage flexible structure in this invention; Figure 5 This is a schematic diagram of the adjusting shaft in this invention; Figure 6 This is a partial cross-sectional view of the connection between the robotic arm link, the two-stage flexible structure, and the oscillator ring in this invention; Figure 7 This is a schematic diagram of the local resonant unit cell structure of the oscillator ring in Embodiment 3 of the present invention; Figure 8 This is a schematic diagram showing different compression stiffness values ​​in Embodiment 3 of the present invention; Figure 9 This is a bandgap diagram for different compression amounts in Embodiment 3 of the present invention.

[0017] The reference numerals in the attached diagram are explained as follows: 1. Robotic arm link; 2. Vibrator ring; 3. Two-stage flexible structure; 4. Adjustment shaft; 5. Frame 1; 6. Bending beam 1; 7. Boss 1; 8. Frame 2; 9. Stop block; 10. Bending beam 2; 11. Boss 2; 12. Bending connecting plate; 13. Elastic retaining ring; 14. Inner ring. Detailed Implementation

[0018] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0020] The present invention will be further described below with reference to the accompanying drawings: Example 1 Vibration damping equipment for industrial robotic arms based on adjustable local resonance damping units, such as Figure 1 As shown, link 1 of the robotic arm is a typical Comau industrial robotic arm link 1, such as... Figure 2 and Figure 3 As shown, multiple vibrator rings 2 are equidistantly arranged on the outer side of the robotic arm link 1, and multiple two-stage flexible structures 3 are arranged at equal angles between the vibrator rings 2 and the robotic arm link 1.

[0021] like Figure 4 As shown, in this embodiment, the two-stage flexible structure 3 includes a first-stage structure and a second-stage structure; the first-stage structure includes a rectangular frame 5, the bottom of the frame 5 is open and a periodic sinusoidal curved beam 6 is fixed at the open end, and a boss 7 is fixed at the bottom of the curved beam 6.

[0022] The second-level structure includes a rectangular frame 8 fixed to the bottom of boss 7. The bottom of frame 8 is open and a periodic sinusoidal curved beam 10 is fixed at the open end. Boss 11 is fixed to the bottom of curved beam 10. A curved connecting plate 12 is fixed to the bottom of boss 11. Two stops 9 are symmetrically fixed at the top two ends of frame 8. There is a gap between the two ends of curved beam 6 and the stops 9 (0.3mm gap in this embodiment). The curved connecting plate 12 is bonded to the outer surface of the robotic arm link 1. Frame 5 is connected to vibrator ring 2 through adjusting shaft 4.

[0023] It is worth mentioning that, similarly, more levels of flexible structure can be set up to achieve a wider range of stiffness adjustment.

[0024] like Figure 5 As shown, in this embodiment, the adjusting shaft 4 is a two-section stepped shaft, including a smaller outer diameter optical shaft and a larger outer diameter adjusting handle. The lower section of the optical shaft has an annular groove, in which an elastic retaining ring 13 is installed. An external thread (M4 external thread in this embodiment) is formed on the outer surface of the optical shaft between the annular groove and the adjusting handle. The optical shaft is threaded to the vibrator ring 2 via the external thread (the vibrator ring 2 has an M4 threaded hole). Figure 6 As shown, the end of the optical axis passes through frame 5, the elastic retaining ring 13 contacts the bottom of the inner wall of frame 5, and the adjusting handle contacts the outer surface of the vibrator ring 2. The axial relative displacement between the adjusting shaft 4 and the first-stage structure is limited by the elastic retaining ring 13 and the adjusting handle.

[0025] like Figure 3 In the embodiment shown, there are eight two-stage flexible structures 3 arranged at equal angles between a single oscillator ring 2 and the robotic arm link 1.

[0026] The height of the adjusting shaft 4 is changed by rotating the adjusting handle. Tightening the adjusting handle causes the adjusting shaft 4 to move downwards relative to the threaded hole. Compression adjustment is achieved through the contact between the adjusting shaft 4 and the first-stage structural frame. By simultaneously tightening the two symmetrically distributed adjusting shafts 4 in the circumferential distribution of the vibrator ring 2, the compression of the circumferentially distributed flexible structure remains consistent.

[0027] During compression adjustment, when the compression is small, the main deformation is the deformation of the sinusoidal bending beam 6 of the first-level flexible structure. This deformation leads to a change in the overall stiffness of the flexible structure. When the compression is large, the two ends of the first-level flexible structural frame 5 will contact the second-level structural blocks 9. Then, during the continued compression process, the main deformation will be transformed into the second-level structural bending beam 10. This will cause a large change in the overall stiffness of the flexible structure, thereby achieving stiffness adjustment.

[0028] Example 2 Based on the above embodiment 1, in this embodiment, the two-stage flexible structure 3 is 3D printed using photosensitive resin with a density of 1130 kg / m³. 3 The elastic modulus is 2370 MPa, and the Poisson's ratio is 0.41; the oscillator ring 2 and the adjusting shaft 4 are made of carbon steel with a density of 7850 kg / m³. 3 Its elastic modulus is 210 GPa and its Poisson's ratio is 0.3.

[0029] In this embodiment, the inner diameter of the oscillator ring 2 is 190mm, the outer diameter is 208mm, and the lateral width is 20mm. The maximum lateral width of the two-stage flexible structure 3 is 10mm. The thickness of frame one 5 is 0.75mm, the thickness of bending beam one 6 is 0.5mm, the period is 20mm, and the amplitude is 3mm. The thickness of frame two 8 is 0.9mm, the thickness of bending beam two 10 is 0.6mm, the period is 24mm, and the amplitude is 3.6mm. The thickness of the bending connecting plate 12 is 1mm, and the distance between adjacent oscillator rings 2 is 100mm.

[0030] Example 3 Based on the above embodiment 2, a method for using an industrial robotic arm vibration damping device based on an adjustable local resonance vibration damping unit is proposed, including the following steps: Step 1: Constructing a simplified model and obtaining equivalent parameters; by extracting the local resonant unit structure of a single oscillator ring with 2 periods and the robotic arm link 1, a simplified local resonant unit cell structure can be obtained, such as... Figure 7As shown, the single oscillator ring 2 on the robotic arm link 1 is simplified into an inner ring 14 with a period a = 10 mm. The local resonant unit structure is regarded as a mass spring system. The mass m is obtained by calculating the volume and density, and m = 0.77 kg. The equivalent stiffness k is obtained by finite element simulation. The oscillator ring 2 is fixed, and a small radial displacement of 0.1 mm is applied to the inner ring 14. The ratio of the support reaction force and the displacement of the inner ring 14 is calculated to obtain the equivalent stiffness k value. The stiffness value under different compression amounts is obtained by simulating compression at different heights of the adjusting shaft 4.

[0031] Stiffness values ​​under different compressions, such as Figure 8 As shown.

[0032] Step 2: Calculate the bandgap of the locally resonant unit cell structure using the transfer matrix method; a = 10 mm is the structural periodic constant. The modal functions of the Timoshenko beam with locally resonant units are: in, , , , E is the elastic modulus of the beam, S is the cross-sectional width of the beam, I is the moment of inertia of the cross-section of the beam, G is the shear modulus, κ is the shear coefficient, ρ is the material density, ω is the bending wave frequency, and A, B, C, and D are formula coefficients. Based on the bandgap calculation method using the transfer matrix, the continuity equations for displacement, rotation, bending moment, and shear force are established for a periodic structure, yielding the transfer matrix equations for unit cells j to j+1: in: , , , Using Bloch's theorem, for a given frequency ω, the transfer matrix can be solved. The eigenvalues ​​can be used to obtain the wave vector qa, which can be used to establish the dispersion curve relationship. The bandgap characteristics of the structure can be obtained from the real part Re(qa) of the wave vector. The range that the dispersion curve does not pass through is the bending wave bandgap of the structure, and the bandgap of different compression amounts can be obtained.

[0033] Different compression band gaps, such as Figure 9 As shown, Figure 9 The three compressed data are as follows: (a) Compression 0mm, 28.10-31.87Hz; (b) Compression 0.5mm, 31.93-36.22Hz; (c) Compression 1.5mm, 44.05-49.96Hz.

[0034] In this embodiment, the natural frequency of the robotic arm is used as the target value to design the dimensions of the two-stage flexible structure. When the posture of the robotic arm changes, the compression amount is adjusted by adjusting the shaft so that the natural frequency of the equivalent spring mass system is consistent with the natural frequency of the robotic arm, thereby achieving the best vibration reduction effect.

[0035] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. An industrial robotic arm vibration damping device based on an adjustable local resonance vibration damping unit, comprising a robotic arm link (1), characterized in that: Multiple vibrating rings (2) are equidistantly arranged on the outer side of the robotic arm link (1), and multiple two-stage flexible structures (3) are arranged at equal angles between the vibrating rings (2) and the robotic arm link (1). The two-stage flexible structure (3) includes a first-stage structure and a second-stage structure. The first-stage structure includes a rectangular frame (5), with an opening at the bottom of the frame (5) and a periodic sinusoidal curved beam (6) fixed at the opening end. A boss (7) is fixed at the bottom of the curved beam (6). The second-stage structure includes a rectangular frame (8) fixed at the bottom of the boss (7), with an opening at the bottom of the frame (8) and a periodic sinusoidal curved beam (10) fixed at the opening end. A boss (11) is fixed at the bottom of the curved beam (10), and a curved connecting plate (12) is fixed at the bottom of the boss (11). Two stops (9) are symmetrically fixed at the top two ends of the frame (8). There is a gap between the two ends of the curved beam (6) and the stops (9). The curved connecting plate (12) is bonded to the outer surface of the robotic arm link (1). The frame (5) is connected to the vibrator ring (2) through the adjusting shaft (4).

2. The industrial robotic arm vibration reduction device based on an adjustable local resonance vibration reduction unit according to claim 1, characterized in that: The adjusting shaft (4) is a two-section stepped shaft, including a light shaft with a smaller outer diameter and an adjusting handle with a larger outer diameter. The lower section of the light shaft has an annular groove, in which an elastic retaining ring (13) is installed. The outer surface of the light shaft has an external thread between the annular groove and the adjusting handle. The light shaft is threaded to the vibrator ring (2) through the external thread. The end of the light shaft passes through the frame (5). The elastic retaining ring (13) contacts the bottom of the inner wall of the frame (5). The adjusting handle contacts the outer surface of the vibrator ring (2). The axial relative displacement between the adjusting shaft (4) and the first-stage structure is limited by the elastic retaining ring (13) and the adjusting handle.

3. The industrial robotic arm vibration reduction device based on an adjustable local resonance vibration reduction unit according to claim 1, characterized in that: The two-stage flexible structure (3) is 3D printed using photosensitive resin with a density of 1130 kg / m³. 3 The elastic modulus is 2370 MPa and the Poisson's ratio is 0.41; the oscillator ring (2) and the adjusting shaft (4) are made of carbon steel with a density of 7850 kg / m³. 3 Its elastic modulus is 210 GPa and its Poisson's ratio is 0.

3.

4. The industrial robotic arm vibration reduction device based on an adjustable local resonance vibration reduction unit according to claim 1, characterized in that: The oscillator ring (2) has an inner diameter of 190mm, an outer diameter of 208mm, and a transverse width of 20mm.

5. The industrial robotic arm vibration reduction device based on an adjustable local resonance vibration reduction unit according to claim 1, characterized in that: The two-stage flexible structure (3) has a maximum transverse width of 10mm, frame one (5) has a thickness of 0.75mm, bending beam one (6) has a thickness of 0.5mm, a period of 20mm, an amplitude of 3mm, frame two (8) has a thickness of 0.9mm, bending beam two (10) has a thickness of 0.6mm, a period of 24mm, an amplitude of 3.6mm, bending connecting plate (12) has a thickness of 1mm, and the distance between adjacent vibrator rings (2) is 100mm.

6. The industrial robotic arm vibration reduction device based on an adjustable local resonance vibration reduction unit according to claim 1, characterized in that: The number of two-stage flexible structures (3) set at equal angles between a single oscillator ring (2) and a robotic arm link (1) is eight.

7. A method of using an industrial robotic arm vibration damping device based on an adjustable local resonance vibration damping unit according to any one of claims 2-6, characterized in that: Includes the following steps: Step 1: Construct a simplified model and obtain equivalent parameters; Extract the local resonance unit structure of a single oscillator ring (2) cycle and the robotic arm link (1) to obtain a simplified local resonance unit cell structure. The robotic arm link (1) of a single oscillator ring (2) cycle is simplified to an inner ring (14) of 100mm. The local resonance unit structure is regarded as a mass spring system. The mass m is obtained by calculating the volume and density, m=0.77kg. The equivalent stiffness k is obtained by finite element simulation. The oscillator ring (2) is fixed, and a radial displacement of 0.1mm is applied to the inner ring (14). The ratio of the support reaction force and displacement of the inner ring (14) is calculated to obtain the equivalent stiffness k value. The stiffness value under different compression amounts is obtained by compression simulation of different adjustment shafts (4).

8. The method of using an industrial robotic arm vibration damping device based on an adjustable local resonance vibration damping unit according to claim 7, characterized in that: Step 2: Calculate the bandgap of the locally resonant unit cell structure using the transfer matrix method; a = 10 mm is the structural periodic constant. The modal functions of the Timoshenko beam with locally resonant units are: in, ， ， ， E is the elastic modulus of the beam, S is the cross-sectional width of the beam, I is the moment of inertia of the cross-section of the beam, G is the shear modulus, κ is the shear coefficient, ρ is the material density, ω is the bending wave frequency, and A, B, C, and D are formula coefficients. Based on the bandgap calculation method using the transfer matrix, the continuity equations for displacement, rotation, bending moment, and shear force are established for a periodic structure, yielding the transfer matrix equations for unit cells j to j+1: in: ， ， ， Using Bloch's theorem, for a given frequency ω, the transfer matrix can be solved. The eigenvalues ​​can be used to obtain the wave vector qa, which can be used to establish the dispersion curve relationship. The bandgap characteristics of the structure can be obtained from the real part Re(qa) of the wave vector. The range that the dispersion curve does not pass through is the bending wave bandgap of the structure, and the bandgap of different compression amounts can be obtained.

9. The method of using an industrial robotic arm vibration damping device based on an adjustable local resonance vibration damping unit according to claim 8, characterized in that: Using the natural frequency of the robotic arm as the target value, the dimensions of the two-stage flexible structure (3) are designed accordingly. When the posture of the robotic arm changes, the compression amount is adjusted by adjusting the shaft (4) so ​​that the natural frequency of the equivalent spring mass system is consistent with the natural frequency of the robotic arm, thereby achieving the best vibration reduction effect.

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