Piezoelectric joint mechanical arm and working method thereof

Abstract

This invention discloses a piezoelectric articulated robotic arm and its operating method, comprising M articulated arms and M-1 connecting components; the M articulated arms are sequentially connected by the M-1 connecting components; each connecting component includes a first and second connecting plate, a first and second bearing, a central shaft, a piezoelectric actuator, and a pre-tensioning mechanism; the piezoelectric actuator includes a stator, a first rotor, and a second rotor; the stator includes a piezoelectric composite beam and a drive ring; the piezoelectric composite beam includes an amplitude beam, a front beam, a rear beam, a first connecting beam, a second connecting beam, a torsional vibration module, a bending vibration module, and pre-tensioning bolts; the pre-tensioning mechanism includes an adjusting nut, a pre-tensioning spring, a first connecting member, a second connecting member, and a pin. This invention achieves the expansion or closure of the robotic arm by applying different harmonic voltage signals to the bending or torsional piezoelectric unit, which is not only simple to control and has a fast response, but also has good environmental adaptability, solving the problem of cantilever warping contact in robotic arm joints and meeting the needs of special environment operations.

Description

Technical Field

[0001] This invention relates to the field of robot joints for special working environments, and more particularly to a device and method for deploying and closing a jointed robotic arm based on piezoelectric drive. Background Technology

[0002] Robotic arm joint modules typically achieve movement of the joint module and the entire robotic arm through motors and hydraulic drives. As the application of robotic arms in scientific research continues to expand, certain specialized working environments place higher demands on the drive technology of joint modules, such as resistance to strong magnetic fields, operation in vacuum environments, and miniaturized structures. Electromagnetic motors cannot function properly in strong magnetic fields, and hydraulic drives cannot work effectively in a vacuum environment; furthermore, both methods suffer from mechanical redundancy, hindering miniaturization. With further advancements in the preparation and processing technology of piezoelectric ceramic materials, piezoelectric actuation based on the inverse piezoelectric effect can achieve compact drive structures, direct drive, no electromagnetic interference, and ease of miniaturization, showing broad application prospects in extreme working environments. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the problems mentioned in the background art by providing a piezoelectric joint robotic arm and its working method.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A piezoelectric articulated robotic arm includes M articulated arms and M-1 connecting components; The connecting assembly includes first and second connecting plates, first and second bearings, a central shaft, a piezoelectric actuator, and a pre-tightening mechanism; The piezoelectric actuator includes a stator, a first rotor, and a second rotor; The stator includes a piezoelectric composite beam and a drive ring; The driving ring is circular and has k driving teeth evenly arranged circumferentially on both end faces. The driving teeth on both end faces are symmetrical, and k is a natural number greater than or equal to 3. The piezoelectric composite beam includes an amplitude-changing beam, a front beam, a rear beam, a first connecting beam, a second connecting beam, a torsional vibration module, a bending vibration module, and preload bolts. The torsional vibration module includes a clamping plate and first to fourth torsional vibration piezoelectric ceramic plates; The first to fourth torsional vibration piezoelectric ceramic sheets have the same structure, are square in shape, and have a through hole in the center for cooperating with the pre-tightening bolt. Each sheet contains two torsional vibration units. The dividing line between the two torsional vibration units passes through the center of the torsional vibration piezoelectric ceramic sheet and is parallel to one side of the torsional vibration piezoelectric ceramic sheet. They are polarized along the dividing line and in opposite polarization directions. The clamping plate and the first torsional vibration piezoelectric ceramic plate have the same shape, with a through hole in the center that matches the pre-tightening bolt, and symmetrical lugs on both sides for fixing to the outside. The first torsional vibration piezoelectric ceramic sheet, the second torsional vibration piezoelectric ceramic sheet, the clamping sheet, the third torsional vibration piezoelectric ceramic sheet, and the fourth torsional vibration piezoelectric ceramic sheet are stacked in sequence. The boundary lines of the first and fourth torsional vibration piezoelectric ceramic sheets are coplanar and have opposite polarization directions. The boundary lines of the second and third torsional vibration piezoelectric ceramic sheets are coplanar and have opposite polarization directions. The boundary lines of the first and second torsional vibration piezoelectric ceramic sheets are perpendicular to each other. The bending vibration module includes first to fourth bending vibration piezoelectric ceramic sheets; The first to fourth bending vibration piezoelectric ceramic sheets have the same structure, are square, and have an area less than or equal to that of the first torsional vibration piezoelectric ceramic sheet. They have a through hole in the center for cooperating with the pre-tightening bolt. They are all double-zone piezoelectric ceramic sheets. The dividing line between the two zones passes through the center of the bending vibration piezoelectric ceramic sheet and is parallel to one side of the bending vibration piezoelectric ceramic sheet. They are polarized along the thickness direction and the polarization directions are opposite. The first and second curved piezoelectric ceramic sheets are stacked to form the first curved vibration unit, and the third and fourth curved piezoelectric ceramic sheets are stacked to form the second curved vibration unit. The boundary lines of the first to fourth curved piezoelectric ceramic sheets are coplanar. The polarization directions of the first and second curved piezoelectric ceramic sheets are opposite, the polarization directions of the third and fourth curved piezoelectric ceramic sheets are opposite, and the polarization directions of the second and third curved piezoelectric ceramic sheets are the same. The amplitude beam is a regular square truncated pyramid. The shape of the end face with a larger area is the same as that of the first torsional vibration piezoelectric ceramic sheet. The end with a smaller area is fixed to the side wall of the driving ring. The axis of the amplitude beam passes through the center of the driving ring, and the axis of the driving ring is parallel to one side length of the end face with a larger area of ​​the amplitude beam. Both the front beam and the rear beam are regular square prisms with the same cross-section and shape as the first bending vibration piezoelectric ceramic sheet. The rear beam has a through hole along the axis for engaging with the pre-tightening bolt. One end of the front beam has a threaded blind hole for engaging with the pre-tightening bolt, and the other end is coaxially fixed to the larger end of the amplitude beam. The first connecting beam and the second connecting beam have the same structure, both including a first connecting part and a second connecting part. The first connecting part is a regular square prism with the same cross-section as the first bending vibration piezoelectric ceramic sheet, and the second connecting part is a regular square prism with the same cross-section as the first torsional vibration piezoelectric ceramic sheet. The first connecting part and the second connecting part are coaxially fixed and both are provided with through holes along the axis for cooperating with the pre-tightening bolt. The pre-tightening bolt passes sequentially through the rear beam, the first bending vibration unit, the first connecting part of the first connecting beam, the second connecting part of the first connecting beam, the torsional vibration module, the second connecting part of the second connecting beam, the first connecting part of the second connecting beam, and the second bending vibration unit, and is then threadedly connected to the threaded blind hole on the front beam. This clamps the first bending vibration unit, the first connecting beam, the torsional vibration module, the second connecting beam, the second bending vibration unit, and the front beam between the rear beam and the front beam, so that the first bending vibration unit and the second bending vibration unit are located at the crest or trough of the bending vibration of the piezoelectric composite beam, and the torsional vibration module is located at the node of the torsional vibration of the piezoelectric composite beam. The piezoelectric composite beam is used to output bending or torsional vibration to excite out-of-plane bending vibration of the driving ring. The driving teeth on both ends of the driving ring are not on the peaks, troughs or nodes of the out-of-plane bending vibration. The first rotor and the second rotor have the same structure, are in the shape of a ring, and are symmetrically arranged on both sides of the driving ring, respectively abutting against the driving teeth on the end faces of the driving ring. One end of the articulated arm is provided with a first fixing seat and a second fixing seat, and the other end is provided with a first mounting seat and a second mounting seat; M articulated arms are connected in sequence through M-1 connecting components; Let the joint arms at both ends of the connecting component be the first joint arm and the second joint arm, respectively; One end of the central shaft is fixedly connected to the first mounting seat of the second joint arm, and the other end is fixedly connected to the second mounting seat of the second joint arm; the first bearing is sleeved on the first mounting seat of the second joint arm, and the inner ring is fixedly connected to the first mounting seat of the second joint arm; the second bearing is sleeved on the second mounting seat of the second joint arm, and the inner ring is fixedly connected to the second mounting seat of the second joint arm; the first bearing, the second bearing, and the central shaft are coaxial. The first connecting plate and the second connecting plate are arranged in parallel, with one end of each plate fixedly connected to the end of the first joint arm that has a first fixed seat, and the other end of each plate having a mounting hole; the first connecting plate is fixedly connected to the outer ring of the first bearing through its mounting hole, and the second connecting plate is fixedly connected to the outer ring of the second bearing through its mounting hole, so that the first joint arm and the second joint arm can rotate relative to each other around the central axis; The lugs on both sides of the clamping plate of the piezoelectric actuator are fixedly connected to the first fixed seat and the second fixed seat of the first joint arm, respectively, so that the driving ring, the first rotor and the second rotor are all sleeved outside the central shaft and coaxial with the central shaft; The preload mechanism includes an adjusting nut, a preload spring, a first connecting member, a second connecting member, and a pin; The second connector includes a second connecting disc and a second sleeve. The second connecting disc is a disc with a through hole in the center, and the second sleeve is a hollow cylinder with openings at both ends. One end of the second sleeve is coaxially fixed to the inner wall of the second connecting disc, and the outer wall of the other end is provided with threads for cooperating with the adjusting nut. The second connecting piece is sleeved outside the central shaft. The outer wall of the second connecting disc and the inner wall of the second rotor are coaxially fixed together. The threaded end of the second sleeve passes through the drive ring and the first rotor in sequence. The second sleeve and the central shaft are in clearance fit, and can slide freely relative to the central shaft along the axial direction. The first connector includes a first connecting plate, a first sleeve, and a pre-tightening plate. The first sleeve is a hollow cylinder with openings at both ends, and the first connecting plate and the pre-tightening plate are both discs with a through hole in the center. One end of the first sleeve is coaxially fixed to the inner wall of the first connecting plate, and the other end is coaxially fixed to the inner wall of the pre-tightening plate. The first connecting piece is sleeved outside the second sleeve, and the outer wall of the first connecting plate and the inner wall of the first rotor are coaxially fixedly connected; the first sleeve and the second sleeve are clearance-fitted and can slide freely relative to the central axis along the axial direction; the first rotor is located between the second rotor and the preload plate; The adjusting nut and the second sleeve are threadedly connected at one end; the preload spring is sleeved on the second sleeve, with one end abutting against the adjusting nut and the other end abutting against the preload disc, and is in a compressed state; The adjusting nut is used to adjust the preload between the first rotor, the second rotor, and the drive teeth on both sides of the drive ring; The first sleeve, the second sleeve, and the central shaft are all provided with through grooves parallel to the central shaft axis for engaging with the pin. The pin is parallel to the plane of the driving ring and passes through the through grooves on the first sleeve, the second sleeve, and the central shaft, so that the first sleeve, the second sleeve, and the central shaft are fixed in the circumferential direction and can slide relative to each other in the axial direction.

[0005] As a further optimization of the piezoelectric joint robotic arm of the present invention, k is taken as 8.

[0006] As a further optimization of the piezoelectric joint robotic arm of the present invention, the pre-tightening mechanism also includes an anti-loosening nut, which is threadedly connected to the threaded end of the second sleeve to prevent the adjusting nut from loosening.

[0007] The present invention also discloses a method for operating the piezoelectric joint robotic arm, comprising the following steps: If the first articulated arm needs to rotate positively relative to the second articulated arm about the central axis of the connecting assembly: apply a preset first harmonic voltage signal to the torsional vibration module of the piezoelectric actuator in the connecting assembly to excite the first-order torsional vibration of the piezoelectric composite beam, induce the fourth-order out-of-plane bending vibration A of the driving ring, and then drive the first rotor and the second rotor to rotate positively through the friction of the driving teeth. At this time, the first sleeve and the second sleeve follow the first rotor and the second rotor to rotate positively, and the central axis also follows the first sleeve and the second sleeve to rotate positively through the pin, so that the first articulated arm rotates positively relative to the second articulated arm about the central axis of the connecting assembly. If the first articulated arm needs to rotate in the opposite direction relative to the second articulated arm about the central axis of the connecting assembly: apply a preset second simple harmonic voltage signal to the first bending vibration unit and the second bending vibration unit of the piezoelectric actuator in the connecting assembly to excite the second-order bending vibration of the piezoelectric composite beam, induce the fourth-order out-of-plane bending vibration B of the driving ring, and then drive the first rotor and the second rotor to rotate in the opposite direction through the friction of the driving teeth. At this time, the first sleeve and the second sleeve follow the first rotor and the second rotor to rotate in the opposite direction, while the central axis also follows the first sleeve and the second sleeve to rotate in the opposite direction through the pin, so that the first articulated arm rotates in the opposite direction relative to the second articulated arm about the central axis of the connecting assembly.

[0008] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects: (1) The mechanical arm in this invention uses piezoelectric conversion and friction drive principle to realize direct drive of joints without the need for complex transmission mechanism, realizes integrated design of structure and function, and has the advantage of simple and compact structure.

[0009] (2) The present invention uses a ring-beam sandwich single-phase drive piezoelectric actuator to construct the joint mechanism, which solves the problem of cantilever warping contact of the robotic arm joint.

[0010] (3) In this invention, the opening and closing of the robotic arm joints are driven by a single voltage signal, making the movement of the robotic arm joints easier to control. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure in which the first joint arm, the second joint arm, and the connecting component cooperate in this invention. Figure 2 This is a schematic diagram of the stator structure of the piezoelectric actuator in this invention; Figure 3 This is a schematic diagram of the polarization direction of the piezoelectric ceramic sheet in the torsional vibration module and bending vibration module of this invention; Figure 4 This is a schematic diagram of the structure of the first connecting beam of the piezoelectric actuator in this invention; Figure 5 This is a schematic diagram of the structure of the first connector in this invention; Figure 6 This is a schematic diagram of the structure of the second connector in this invention; Figure 7 This is a half-sectional schematic diagram of the first joint arm, the second joint arm, and the connecting assembly in this invention. Figure 8 This is a schematic diagram comparing the positions of the driving teeth on the driving ring within one wavelength during out-of-plane bending vibration A and out-of-plane bending vibration B in this invention.

[0012] In the figure, 1-first articulated arm, 2-second articulated arm, 3-first connecting plate, 4-second connecting plate, 5-second mounting base, 6-second bearing, 7-central shaft, 8-first fixed base, 9-piezoelectric actuator, 10-first connecting piece, 11-adjusting nut, 12-preload spring, 13-pin, 14-drive ring, 15-amplitude beam, 16-front beam, 17-rear beam, 18-first connecting beam, 19-second connecting beam, 20-first bending vibration unit, 21-second bending vibration unit, 22-torsional vibration module, 23-preload bolt, 24-preload disc, 25-first sleeve, 26-first connecting disc, 27-second connecting disc, 28-second sleeve, 29-first bearing. Detailed Implementation

[0013] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings: This invention can be implemented in many different forms and should not be considered limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully express the scope of the invention to those skilled in the art. In the drawings, components are enlarged for clarity.

[0014] This invention discloses a piezoelectric articulated robotic arm, comprising M articulated arms and M-1 connecting components; like Figure 1 As shown, the connecting assembly includes first and second connecting plates, first and second bearings, a central shaft, a piezoelectric actuator, and a pre-tightening mechanism; The piezoelectric actuator includes a stator, a first rotor, and a second rotor; like Figure 2 As shown, the stator includes a piezoelectric composite beam and a drive ring; The driving ring is circular and has k driving teeth evenly arranged circumferentially on both end faces. The driving teeth on both end faces are symmetrical, and k is a natural number greater than or equal to 3. The piezoelectric composite beam includes an amplitude-changing beam, a front beam, a rear beam, a first connecting beam, a second connecting beam, a torsional vibration module, a bending vibration module, and preload bolts. The torsional vibration module includes a clamping plate and first to fourth torsional vibration piezoelectric ceramic plates; The first to fourth torsional vibration piezoelectric ceramic sheets have the same structure, are square in shape, and have a through hole in the center for cooperating with the pre-tightening bolt. Each sheet contains two torsional vibration units. The dividing line between the two torsional vibration units passes through the center of the torsional vibration piezoelectric ceramic sheet and is parallel to one side of the torsional vibration piezoelectric ceramic sheet. They are polarized along the dividing line and in opposite polarization directions. The clamping plate and the first torsional vibration piezoelectric ceramic plate have the same shape, with a through hole in the center that matches the pre-tightening bolt, and symmetrical lugs on both sides for fixing to the outside. The first, second, and third torsional piezoelectric ceramic sheets, along with a clamping plate, are stacked sequentially. The boundary lines of the first and fourth torsional piezoelectric ceramic sheets are coplanar and have opposite polarization directions. The boundary lines of the second and third torsional piezoelectric ceramic sheets are also coplanar and have opposite polarization directions. The boundary lines of the first and second torsional piezoelectric ceramic sheets are perpendicular to each other. Figure 3 As shown; The bending vibration module includes first to fourth bending vibration piezoelectric ceramic sheets; The first to fourth bending vibration piezoelectric ceramic sheets have the same structure, are square, and have an area less than or equal to that of the first torsional vibration piezoelectric ceramic sheet. They have a through hole in the center for cooperating with the pre-tightening bolt. They are all double-zone piezoelectric ceramic sheets. The dividing line between the two zones passes through the center of the bending vibration piezoelectric ceramic sheet and is parallel to one side of the bending vibration piezoelectric ceramic sheet. They are polarized along the thickness direction and the polarization directions are opposite. A first bending vibration piezoelectric ceramic sheet and a second bending vibration piezoelectric ceramic sheet are stacked to form a first bending vibration unit. A third bending vibration piezoelectric ceramic sheet and a fourth bending vibration piezoelectric ceramic sheet are stacked to form a second bending vibration unit. The boundary lines between the first and fourth bending vibration piezoelectric ceramic sheets are coplanar. The polarization directions of the first and second bending vibration piezoelectric ceramic sheets are opposite, the polarization directions of the third and fourth bending vibration piezoelectric ceramic sheets are opposite, and the polarization directions of the second and third bending vibration piezoelectric ceramic sheets are the same. Figure 3 As shown; The amplitude beam is a regular square truncated pyramid. The shape of the end face with a larger area is the same as that of the first torsional vibration piezoelectric ceramic sheet. The end with a smaller area is fixed to the side wall of the driving ring. The axis of the amplitude beam passes through the center of the driving ring, and the axis of the driving ring is parallel to one side length of the end face with a larger area of ​​the amplitude beam. Both the front beam and the rear beam are regular square prisms with the same cross-section and shape as the first bending vibration piezoelectric ceramic sheet. The rear beam has a through hole along the axis for engaging with the pre-tightening bolt. One end of the front beam has a threaded blind hole for engaging with the pre-tightening bolt, and the other end is coaxially fixed to the larger end of the amplitude beam. like Figure 4As shown, the first connecting beam and the second connecting beam have the same structure, both including a first connecting part and a second connecting part. The first connecting part is a regular square prism with the same cross-section as the first bending vibration piezoelectric ceramic sheet, and the second connecting part is a regular square prism with the same cross-section as the first torsional vibration piezoelectric ceramic sheet. The first connecting part and the second connecting part are coaxially fixed and both are provided with through holes along the axis for cooperating with the pre-tightening bolt. The pre-tightening bolt passes sequentially through the rear beam, the first bending vibration unit, the first connecting part of the first connecting beam, the second connecting part of the first connecting beam, the torsional vibration module, the second connecting part of the second connecting beam, the first connecting part of the second connecting beam, and the second bending vibration unit, and is then threadedly connected to the threaded blind hole on the front beam. This clamps the first bending vibration unit, the first connecting beam, the torsional vibration module, the second connecting beam, the second bending vibration unit, and the front beam between the rear beam and the front beam, so that the first bending vibration unit and the second bending vibration unit are located at the crest or trough of the bending vibration of the piezoelectric composite beam, and the torsional vibration module is located at the node of the torsional vibration of the piezoelectric composite beam. The piezoelectric composite beam is used to output bending or torsional vibration to excite out-of-plane bending vibration of the driving ring. The driving teeth on both ends of the driving ring are not on the peaks, troughs or nodes of the out-of-plane bending vibration. The first rotor and the second rotor have the same structure, are in the shape of a ring, and are symmetrically arranged on both sides of the driving ring, respectively abutting against the driving teeth on the end faces of the driving ring. One end of the articulated arm is provided with a first fixing seat and a second fixing seat, and the other end is provided with a first mounting seat and a second mounting seat; M articulated arms are connected in sequence through M-1 connecting components; Let the joint arms at both ends of the connecting component be the first joint arm and the second joint arm, respectively; like Figure 1 , Figure 7 As shown, one end of the central shaft is fixedly connected to the first mounting seat of the second joint arm, and the other end is fixedly connected to the second mounting seat of the second joint arm; the first bearing is sleeved on the first mounting seat of the second joint arm, and the inner ring is fixedly connected to the first mounting seat of the second joint arm; the second bearing is sleeved on the second mounting seat of the second joint arm, and the inner ring is fixedly connected to the second mounting seat of the second joint arm; the first bearing, the second bearing, and the central shaft are coaxial. The first connecting plate and the second connecting plate are arranged in parallel, with one end of each plate fixedly connected to the end of the first joint arm that has a first fixed seat, and the other end of each plate having a mounting hole; the first connecting plate is fixedly connected to the outer ring of the first bearing through its mounting hole, and the second connecting plate is fixedly connected to the outer ring of the second bearing through its mounting hole, so that the first joint arm and the second joint arm can rotate relative to each other around the central axis; The lugs on both sides of the clamping plate of the piezoelectric actuator are fixedly connected to the first fixed seat and the second fixed seat of the first joint arm, respectively, so that the driving ring, the first rotor and the second rotor are all sleeved outside the central shaft and coaxial with the central shaft; The preload mechanism includes an adjusting nut, a preload spring, a first connecting member, a second connecting member, and a pin; like Figure 6 As shown, the second connector includes a second connecting disc and a second sleeve. The second connecting disc is a disc with a through hole in the center, and the second sleeve is a hollow cylinder with openings at both ends. One end of the second sleeve is coaxially fixed to the inner wall of the second connecting disc, and the outer wall of the other end is provided with threads for cooperating with the adjusting nut. The second connecting piece is sleeved outside the central shaft. The outer wall of the second connecting disc and the inner wall of the second rotor are coaxially fixed together. The threaded end of the second sleeve passes through the drive ring and the first rotor in sequence. The second sleeve and the central shaft are in clearance fit, and can slide freely relative to the central shaft along the axial direction. like Figure 5 As shown, the first connector includes a first connecting plate, a first sleeve, and a pre-tightening plate. The first sleeve is a hollow cylinder with openings at both ends, and the first connecting plate and the pre-tightening plate are both discs with a through hole in the center. One end of the first sleeve is coaxially fixed to the inner wall of the first connecting plate, and the other end is coaxially fixed to the inner wall of the pre-tightening plate. like Figure 7 As shown, the first connecting piece is sleeved outside the second sleeve, and the outer wall of the first connecting plate and the inner wall of the first rotor are coaxially fixedly connected; the first sleeve and the second sleeve are clearance-fitted and can slide freely relative to the central axis along the axial direction; the first rotor is located between the second rotor and the preload plate; The adjusting nut and the second sleeve are threadedly connected at one end; the preload spring is sleeved on the second sleeve, with one end abutting against the adjusting nut and the other end abutting against the preload disc, and is in a compressed state; The adjusting nut is used to adjust the preload between the first rotor, the second rotor, and the drive teeth on both sides of the drive ring; The first sleeve, the second sleeve, and the central shaft are all provided with through grooves parallel to the central shaft axis for engaging with the pin. The pin is parallel to the plane of the driving ring and passes through the through grooves on the first sleeve, the second sleeve, and the central shaft, so that the first sleeve, the second sleeve, and the central shaft are fixed in the circumferential direction and can slide relative to each other in the axial direction.

[0015] The preferred value for k is 8.

[0016] The pre-tightening mechanism of the present invention may also include an anti-loosening nut, which is threadedly connected to the threaded end of the second sleeve to prevent the adjusting nut from loosening.

[0017] The present invention also discloses a method for operating the piezoelectric joint robotic arm, comprising the following steps: If the first articulated arm needs to rotate positively relative to the second articulated arm about the central axis of the connecting assembly: apply a preset first harmonic voltage signal to the torsional vibration module of the piezoelectric actuator in the connecting assembly to excite the first-order torsional vibration of the piezoelectric composite beam, induce the fourth-order out-of-plane bending vibration A of the driving ring, and then drive the first rotor and the second rotor to rotate positively through the friction of the driving teeth. At this time, the first sleeve and the second sleeve follow the first rotor and the second rotor to rotate positively, and the central axis also follows the first sleeve and the second sleeve to rotate positively through the pin, so that the first articulated arm rotates positively relative to the second articulated arm about the central axis of the connecting assembly. If the first articulated arm needs to rotate in the opposite direction relative to the second articulated arm about the central axis of the connecting assembly: apply a preset second simple harmonic voltage signal to the first bending vibration unit and the second bending vibration unit of the piezoelectric actuator in the connecting assembly to excite the second-order bending vibration of the piezoelectric composite beam, induce the fourth-order out-of-plane bending vibration B of the driving ring, and then drive the first rotor and the second rotor to rotate in the opposite direction through the friction of the driving teeth. At this time, the first sleeve and the second sleeve follow the first rotor and the second rotor to rotate in the opposite direction, while the central axis also follows the first sleeve and the second sleeve to rotate in the opposite direction through the pin, so that the first articulated arm rotates in the opposite direction relative to the second articulated arm about the central axis of the connecting assembly.

[0018] Out-of-plane bending vibrations A and B are spatially separated by 90 degrees. Their comparison is as follows: Figure 8 As shown.

[0019] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0020] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A piezoelectric jointed robotic arm, characterized by, It includes M articulated arms and M-1 connecting components; The connecting assembly includes first and second connecting plates, first and second bearings, a central shaft, a piezoelectric actuator, and a pre-tightening mechanism; The piezoelectric actuator includes a stator, a first rotor, and a second rotor; The stator includes a piezoelectric composite beam and a drive ring; The driving ring is circular and has k driving teeth evenly arranged circumferentially on both end faces. The driving teeth on both end faces are symmetrical, and k is a natural number greater than or equal to 3. The piezoelectric composite beam includes an amplitude-changing beam, a front beam, a rear beam, a first connecting beam, a second connecting beam, a torsional vibration module, a bending vibration module, and preload bolts. The torsional vibration module includes a clamping plate and first to fourth torsional vibration piezoelectric ceramic plates; The first to fourth torsional vibration piezoelectric ceramic sheets have the same structure, are square in shape, and have a through hole in the center for cooperating with the pre-tightening bolt. Each sheet contains two torsional vibration units. The dividing line between the two torsional vibration units passes through the center of the torsional vibration piezoelectric ceramic sheet and is parallel to one side of the torsional vibration piezoelectric ceramic sheet. They are polarized along the dividing line and in opposite polarization directions. The clamping plate and the first torsional vibration piezoelectric ceramic plate have the same shape, with a through hole in the center that matches the pre-tightening bolt, and symmetrical lugs on both sides for fixing to the outside. The first torsional vibration piezoelectric ceramic sheet, the second torsional vibration piezoelectric ceramic sheet, the clamping sheet, the third torsional vibration piezoelectric ceramic sheet, and the fourth torsional vibration piezoelectric ceramic sheet are stacked in sequence. The boundary lines of the first and fourth torsional vibration piezoelectric ceramic sheets are coplanar and have opposite polarization directions. The boundary lines of the second and third torsional vibration piezoelectric ceramic sheets are coplanar and have opposite polarization directions. The boundary lines of the first and second torsional vibration piezoelectric ceramic sheets are perpendicular to each other. The bending vibration module includes first to fourth bending vibration piezoelectric ceramic sheets; The first to fourth bending vibration piezoelectric ceramic sheets have the same structure, are square, and have an area less than or equal to that of the first torsional vibration piezoelectric ceramic sheet. They have a through hole in the center for cooperating with the pre-tightening bolt. They are all double-zone piezoelectric ceramic sheets. The dividing line between the two zones passes through the center of the bending vibration piezoelectric ceramic sheet and is parallel to one side of the bending vibration piezoelectric ceramic sheet. They are polarized along the thickness direction and the polarization directions are opposite. The first and second curved piezoelectric ceramic sheets are stacked to form the first curved vibration unit, and the third and fourth curved piezoelectric ceramic sheets are stacked to form the second curved vibration unit. The boundary lines of the first to fourth curved piezoelectric ceramic sheets are coplanar. The polarization directions of the first and second curved piezoelectric ceramic sheets are opposite, the polarization directions of the third and fourth curved piezoelectric ceramic sheets are opposite, and the polarization directions of the second and third curved piezoelectric ceramic sheets are the same. The amplitude beam is a regular square truncated pyramid. The shape of the end face with a larger area is the same as that of the first torsional vibration piezoelectric ceramic sheet. The end with a smaller area is fixed to the side wall of the driving ring. The axis of the amplitude beam passes through the center of the driving ring, and the axis of the driving ring is parallel to one side length of the end face with a larger area of ​​the amplitude beam. Both the front beam and the rear beam are regular square prisms with the same cross-section and shape as the first bending vibration piezoelectric ceramic sheet. The rear beam has a through hole along the axis for engaging with the pre-tightening bolt. One end of the front beam has a threaded blind hole for engaging with the pre-tightening bolt, and the other end is coaxially fixed to the larger end of the amplitude beam. The first connecting beam and the second connecting beam have the same structure, both including a first connecting part and a second connecting part. The first connecting part is a regular square prism with the same cross-section as the first bending vibration piezoelectric ceramic sheet, and the second connecting part is a regular square prism with the same cross-section as the first torsional vibration piezoelectric ceramic sheet. The first connecting part and the second connecting part are coaxially fixed and both are provided with through holes along the axis for cooperating with the pre-tightening bolt. The pre-tightening bolt passes sequentially through the rear beam, the first bending vibration unit, the first connecting part of the first connecting beam, the second connecting part of the first connecting beam, the torsional vibration module, the second connecting part of the second connecting beam, the first connecting part of the second connecting beam, and the second bending vibration unit, and is then threadedly connected to the threaded blind hole on the front beam. This clamps the first bending vibration unit, the first connecting beam, the torsional vibration module, the second connecting beam, the second bending vibration unit, and the front beam between the rear beam and the front beam, so that the first bending vibration unit and the second bending vibration unit are located at the crest or trough of the bending vibration of the piezoelectric composite beam, and the torsional vibration module is located at the node of the torsional vibration of the piezoelectric composite beam. The piezoelectric composite beam is used to output bending or torsional vibration to excite out-of-plane bending vibration of the driving ring. The driving teeth on both ends of the driving ring are not on the peaks, troughs or nodes of the out-of-plane bending vibration. The first rotor and the second rotor have the same structure, are in the shape of a ring, and are symmetrically arranged on both sides of the driving ring, respectively abutting against the driving teeth on the end faces of the driving ring. One end of the articulated arm is provided with a first fixing seat and a second fixing seat, and the other end is provided with a first mounting seat and a second mounting seat; M articulated arms are connected in sequence through M-1 connecting components; Let the joint arms at both ends of the connecting component be the first joint arm and the second joint arm, respectively; One end of the central shaft is fixedly connected to the first mounting seat of the second joint arm, and the other end is fixedly connected to the second mounting seat of the second joint arm; the first bearing is sleeved on the first mounting seat of the second joint arm, and the inner ring is fixedly connected to the first mounting seat of the second joint arm; the second bearing is sleeved on the second mounting seat of the second joint arm, and the inner ring is fixedly connected to the second mounting seat of the second joint arm; the first bearing, the second bearing, and the central shaft are coaxial. The first connecting plate and the second connecting plate are arranged in parallel, with one end of each plate fixedly connected to the end of the first joint arm that has a first fixed seat, and the other end of each plate having a mounting hole; the first connecting plate is fixedly connected to the outer ring of the first bearing through its mounting hole, and the second connecting plate is fixedly connected to the outer ring of the second bearing through its mounting hole, so that the first joint arm and the second joint arm can rotate relative to each other around the central axis; The lugs on both sides of the clamping plate of the piezoelectric actuator are fixedly connected to the first fixed seat and the second fixed seat of the first joint arm, respectively, so that the driving ring, the first rotor and the second rotor are all sleeved outside the central shaft and coaxial with the central shaft; The preload mechanism includes an adjusting nut, a preload spring, a first connecting member, a second connecting member, and a pin; The second connector includes a second connecting disc and a second sleeve. The second connecting disc is a disc with a through hole in the center, and the second sleeve is a hollow cylinder with openings at both ends. One end of the second sleeve is coaxially fixed to the inner wall of the second connecting disc, and the outer wall of the other end is provided with threads for cooperating with the adjusting nut. The second connecting piece is sleeved outside the central shaft. The outer wall of the second connecting disc and the inner wall of the second rotor are coaxially fixed together. The threaded end of the second sleeve passes through the drive ring and the first rotor in sequence. The second sleeve and the central shaft are in clearance fit, and can slide freely relative to the central shaft along the axial direction. The first connector includes a first connecting plate, a first sleeve, and a pre-tightening plate. The first sleeve is a hollow cylinder with openings at both ends, and the first connecting plate and the pre-tightening plate are both discs with a through hole in the center. One end of the first sleeve is coaxially fixed to the inner wall of the first connecting plate, and the other end is coaxially fixed to the inner wall of the pre-tightening plate. The first connecting piece is sleeved outside the second sleeve, and the outer wall of the first connecting plate and the inner wall of the first rotor are coaxially fixedly connected; the first sleeve and the second sleeve are clearance-fitted and can slide freely relative to the central axis along the axial direction; the first rotor is located between the second rotor and the preload plate; The adjusting nut and the second sleeve are threadedly connected at one end; the preload spring is sleeved on the second sleeve, with one end abutting against the adjusting nut and the other end abutting against the preload disc, and is in a compressed state; The adjusting nut is used to adjust the preload between the first rotor, the second rotor, and the drive teeth on both sides of the drive ring; The first sleeve, the second sleeve, and the central shaft are all provided with through grooves parallel to the central shaft axis for engaging with the pin. The pin is parallel to the plane of the driving ring and passes through the through grooves on the first sleeve, the second sleeve, and the central shaft, so that the first sleeve, the second sleeve, and the central shaft are fixed in the circumferential direction and can slide relative to each other in the axial direction.

2. The piezoelectric joint robotic arm of claim 1, wherein, The value of k is 8.

3. The piezoelectric jointed robotic arm of claim 1, wherein, The pre-tightening mechanism also includes an anti-loosening nut, which is threadedly connected to the threaded end of the second sleeve to prevent the adjusting nut from loosening.

4. The method of operating a piezoelectric jointed robotic arm according to claim 1, wherein, Includes the following steps: If the first articulated arm needs to rotate positively relative to the second articulated arm about the central axis of the connecting assembly: apply a preset first harmonic voltage signal to the torsional vibration module of the piezoelectric actuator in the connecting assembly to excite the first-order torsional vibration of the piezoelectric composite beam, induce the fourth-order out-of-plane bending vibration A of the driving ring, and then drive the first rotor and the second rotor to rotate positively through the friction of the driving teeth. At this time, the first sleeve and the second sleeve follow the first rotor and the second rotor to rotate positively, and the central axis also follows the first sleeve and the second sleeve to rotate positively through the pin, so that the first articulated arm rotates positively relative to the second articulated arm about the central axis of the connecting assembly. If the first articulated arm needs to rotate in the opposite direction relative to the second articulated arm about the central axis of the connecting assembly: apply a preset second simple harmonic voltage signal to the first bending vibration unit and the second bending vibration unit of the piezoelectric actuator in the connecting assembly to excite the second-order bending vibration of the piezoelectric composite beam, induce the fourth-order out-of-plane bending vibration B of the driving ring, and then drive the first rotor and the second rotor to rotate in the opposite direction through the friction of the driving teeth. At this time, the first sleeve and the second sleeve follow the first rotor and the second rotor to rotate in the opposite direction, while the central axis also follows the first sleeve and the second sleeve to rotate in the opposite direction through the pin, so that the first articulated arm rotates in the opposite direction relative to the second articulated arm about the central axis of the connecting assembly.

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