Modular piezoelectric driving multi-degree-of-freedom robot arm and working method thereof

Abstract

The application discloses a modular piezoelectric driving multi-freedom mechanical arm and a working method thereof. The mechanical arm comprises M piezoelectric joints and a terminal connecting mechanism. The piezoelectric joint comprises a joint head, a joint piezoelectric vibrator, a joint capsule, first and second pre-tightening bolts, first and second pre-tightening nuts and first to fourth elastic washers. The joint actuators are connected in series through the joint head, and the terminal piezoelectric joint is connected to the terminal connecting mechanism through the joint head. The application utilizes the inverse piezoelectric effect of piezoelectric materials to stimulate the micro-vibration of an elastomer, and drives through friction. The application can adapt to special environments such as strong magnetic fields, narrow spaces and high vacuum, has the characteristics of high structural integration, structural and functional integration, multi-freedom dexterous operation, modular reconfiguration, micron-level positioning accuracy, millimeter-level response and the like, and has the ability of no-power-consumption self-locking attitude keeping, and can meet the dual requirements of precise operation and real-time observation in special environments.

Description

Technical Field

[0001] This invention relates to the field of high-end equipment and intelligent robot technology for special environments, specifically to a modular piezoelectric-driven multi-degree-of-freedom robotic arm and its working method for special environments such as strong magnetic fields, confined spaces, high vacuum, and high and low temperatures, belonging to the field of special environment robots and precision drive technology. Background Technology

[0002] In cutting-edge fields such as nuclear industry, space exploration, high-energy physics, semiconductor manufacturing, and medical imaging, robotic arms often need to perform precision operations in special environments such as strong magnetic fields, high vacuum, confined spaces, and extreme temperatures. For example, in interventional surgery guided by magnetic resonance imaging (MRI), the robotic arm needs to work in a strong magnetic field environment without electromagnetic interference; inside nuclear fusion devices or particle accelerators, the robotic arm needs to complete inspection and maintenance in a high vacuum and strong radiation environment; inside spacecraft cabins or micro-nano operation platforms, the robotic arm needs to achieve multi-degree-of-freedom dexterity operations within a limited space.

[0003] Currently, robotic arms designed for special environments mainly employ the following technical approaches:

[0004] (1) Electromagnetic motor driven robotic arm: Traditional industrial robotic arms generally use servo motors in conjunction with reducers for drive. However, in a strong magnetic field environment, the permanent magnets and electromagnetic coils inside the motor will generate severe electromagnetic interference, which will not only affect the control accuracy of the robotic arm itself, but also cause unacceptable interference to external magnetic field sensitive equipment (such as MRI, electron microscopes, etc.). In addition, electromagnetic motors have problems such as gas release and lubricant volatilization in a high vacuum environment, which limits their long-term reliable operation in a vacuum environment.

[0005] (2) Pneumatic or hydraulic driven robotic arms: Pneumatic and hydraulic drive methods can avoid electromagnetic interference to some extent, but they require complex air or liquid source systems, resulting in a bulky overall structure that is difficult to adapt to operation in confined spaces. At the same time, pneumatic systems have poor controllability and positioning accuracy, while hydraulic systems have leakage risks, limiting their application in high vacuum, clean environments, or strong radiation fields.

[0006] (3) Traditional piezoelectric driven robotic arms: In recent years, piezoelectric drive technology has been gradually introduced into the field of special environment robotic arms due to its advantages such as non-magnetic, fast response, and high precision. However, most existing piezoelectric driven robotic arms adopt a separate structural design—the drive unit, transmission unit, and joint structure are independent of each other, resulting in a large overall size and a limited number of degrees of freedom, making it difficult to achieve dexterous operation with multiple degrees of freedom in confined spaces. In addition, the joints of existing piezoelectric robotic arms are mostly configured with fixed degrees of freedom, with low modularity, making it impossible to flexibly increase or decrease the number of joints or replace functional units according to task requirements, resulting in poor versatility and maintainability.

[0007] (4) End-effector vision and focusing mechanism: In special environment operations, the end-effector of a robotic arm usually needs to be equipped with vision observation equipment to complete precise positioning, detection and operation tasks. However, the focusing mechanism of the existing end-effector of the robotic arm is mostly driven by stepper motors, electromagnetic motors or voice coil motors, which have problems such as large size, complex structure, easy heat generation and serious electromagnetic interference; and due to the limitations of its own structure and driving principle, the focusing accuracy and speed are difficult to meet the high requirements of special environment. In addition, the existing focusing mechanism and the robotic arm body are mostly separate designs with low integration, which further increases the size of the end-effector and is not conducive to operation in a confined space.

[0008] In summary, existing special-environment robotic arms have the following common shortcomings when facing harsh working conditions such as strong magnetic fields, high vacuum, and confined spaces:

[0009] (1) Poor electromagnetic compatibility: Traditional electromagnetic drive methods cannot work normally in strong magnetic field environments and will interfere with sensitive equipment;

[0010] (2) Low structural integration: The separation of the drive and transmission systems results in a large size that is difficult to adapt to small spaces; the separate design of the end focusing mechanism and the robotic arm body further exacerbates the problem of bulky size.

[0011] (3) Insufficient degrees of freedom and flexibility: Due to the limitations of the driving method and structural layout, the existing solutions are difficult to achieve multi-degree-of-freedom agile operation in a compact configuration;

[0012] (4) Poor modularity: The joints and drive units lack standardized and serially modular design, making it impossible to flexibly configure the number of degrees of freedom according to task requirements, and also making it inconvenient to replace and maintain on site.

[0013] (5) Limited end vision function: Existing focusing mechanisms mostly use electromagnetic drive, which cannot work properly in a strong magnetic field environment. They are also large in size and low in precision, making it difficult to integrate them into the end of the robotic arm to achieve high-precision observation and focusing.

[0014] Therefore, to address the problems existing in the prior art, this invention proposes a modular piezoelectric-driven multi-degree-of-freedom robotic arm that can adapt to special environments such as strong magnetic fields, confined spaces, and high vacuum. It features highly integrated structure, integrated structure and function, dexterous multi-degree-of-freedom operation, modular reconfigurability, micron-level positioning accuracy, and millimeter-level response. It also possesses power-free self-locking posture maintenance capabilities. In particular, this invention integrates a piezoelectric-driven focusing mechanism at the end of the robotic arm. A camera can be embedded within this focusing mechanism, enabling high-precision focusing and real-time observation in special environments such as strong magnetic fields and high vacuum, meeting the requirements for precision detection and operation in special environments. Summary of the Invention

[0015] The technical problem to be solved by the present invention is to address the deficiencies mentioned in the background art by providing a modular piezoelectric driven multi-degree-of-freedom robotic arm and its working method.

[0016] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0017] A modular piezoelectric-driven multi-degree-of-freedom robotic arm includes an end effector and M piezoelectric joints, where M is a natural number greater than or equal to 2;

[0018] The piezoelectric joint includes a joint head, a joint piezoelectric vibrator, a joint capsule, first and second preload bolts, first and second preload nuts, and first to fourth elastic washers;

[0019] The articulated head includes a drive head, a connecting rod, a flange, and an articulated threaded rod. The drive head is a spherical cap with a height greater than its radius. The articulated connecting rod is a cylinder with a diameter equal to the diameter of the bottom surface of the drive head. One end of the connecting rod is coaxially fixed to the bottom surface of the drive head, and the other end is coaxially fixed to one end of the flange. One end of the articulated threaded rod is coaxially fixed to the other end of the flange, and the diameter of the articulated threaded rod is smaller than the diameter of the flange.

[0020] The joint piezoelectric vibrator includes an elastic beam, a first fixed lug, a second fixed lug, and first to eighth piezoelectric ceramic plates;

[0021] The elastic beam is a regular square prism, including a first end face, a second end face, and first to fourth side faces connected end to end. The center of the second end face is provided with a drive groove for cooperating with the drive head. The drive groove is a spherical cap with a height less than its radius. The elastic beam is provided with a through hole along its axis that penetrates the bottom of the drive groove and the first end face. The through hole is provided with an internal thread at one end near the first end face for cooperating with the joint threaded rod, forming a joint threaded hole for connection.

[0022] The first to eighth piezoelectric ceramic sheets are all rectangular and polarized along their thickness direction. Specifically, the first and second piezoelectric ceramic sheets are disposed on the first side of the elastic beam with opposite polarization directions; the third and fourth piezoelectric ceramic sheets are disposed on the third side of the elastic beam with opposite polarization directions; the first and third piezoelectric ceramic sheets are symmetrical with the same polarization direction; the second and fourth piezoelectric ceramic sheets are symmetrical with the same polarization direction; the fifth and sixth piezoelectric ceramic sheets are disposed on the second side of the elastic beam with opposite polarization directions; the seventh and eighth piezoelectric ceramic sheets are disposed on the fourth side of the elastic beam with opposite polarization directions; the fifth and seventh piezoelectric ceramic sheets are symmetrical with the same polarization direction; and the sixth and eighth piezoelectric ceramic sheets are symmetrical with the same polarization direction.

[0023] The first and second fixed lugs have the same structure and are symmetrically arranged on the first and third sides of the elastic beam, located at the common node of the first longitudinal vibration mode and the second bending vibration mode of the piezoelectric joint.

[0024] The joint capsule includes a capsule body, a third fixing ear, and a fourth fixing ear. The capsule body is a hollow regular square prism with one open end and the other closed end. The center of the closed end face is provided with a limiting hole for cooperating with the drive head. The diameter of the limiting hole is larger than the bottom diameter of the drive head and the diameter of the flange, but smaller than the diameter of the drive head. The third fixing ear and the fourth fixing ear have the same structure as the first fixing ear and are symmetrically arranged on the two side walls of the open end of the joint capsule.

[0025] The joint capsule is fitted over the end of the elastic beam with the drive groove. The drive head is pressed against the drive groove through the limiting hole, so that the connecting rod, flange, and joint threaded rod are located outside the joint capsule. The third fixing lug corresponds to the first fixing lug, and the fourth fixing lug corresponds to the second fixing lug. The first preload bolt passes through the third fixing lug, the second elastic washer, the first fixing lug, and the first elastic washer in sequence and is threaded to the first preload nut. The second preload bolt passes through the fourth fixing lug, the fourth elastic washer, the third fixing lug, and the third elastic washer in sequence and is threaded to the second preload nut. This is used to adjust the preload force between the drive head and the drive groove.

[0026] The joint thread rod of the (i+1)th piezoelectric joint is threadedly connected to the joint thread hole of the ith piezoelectric joint, so that M piezoelectric joints are connected in series, where i is a natural number greater than or equal to 1 and less than M.

[0027] The end connection mechanism includes a connecting block, first and second built-in cameras, and first and second focusing components;

[0028] The connecting block is rectangular and is used to connect to an external actuator. One end face has a threaded hole at its center for engaging with the threaded rod of the Mth piezoelectric joint, and the other end face has a first observation thread blind hole and a second observation thread blind hole.

[0029] The first and second observation thread blind holes have the same structure.

[0030] The first focusing assembly and the second focusing assembly have the same structure, both including a focusing piezoelectric vibrator and a focusing lens;

[0031] The focusing piezoelectric vibrator comprises an externally threaded tube and a focusing piezoelectric ceramic assembly. The inner hole of the externally threaded tube is a hexagonal hole, and the outer thread can cooperate with the inner thread of the first observation thread blind hole. The focusing piezoelectric ceramic assembly comprises a ninth to a fourteenth piezoelectric ceramic sheet. The ninth to fourteenth piezoelectric ceramic sheets have the same rectangular structure, are all polarized along the thickness direction, and are uniformly pasted on the six sides of the inner hole of the externally threaded tube in a circumferential direction. The polarization directions of adjacent piezoelectric ceramic sheets are opposite.

[0032] The focusing lens is a convex lens with the same diameter as the outer diameter of the external threaded tube, and is coaxially fixed to one end of the external threaded tube.

[0033] The first built-in camera and the second built-in camera are respectively installed in the first observation thread blind hole and the second observation thread blind hole. The external thread tube of the first focusing component and the external thread tube of the second focusing component are respectively threadedly connected to the first observation thread blind hole and the second observation thread blind hole. The first focusing component and the second focusing component are respectively used for focusing the first built-in camera and the second built-in camera.

[0034] This invention also discloses a method for operating the modular piezoelectric-driven multi-degree-of-freedom robotic arm, comprising the following steps:

[0035] Step A.1): If it is necessary to drive the drive head of the piezoelectric joint to rotate positively around its central axis, a preset first harmonic voltage signal is applied to the first to fourth piezoelectric ceramic plates in the piezoelectric joint to excite the second-order bending vibration of the joint piezoelectric oscillator. A preset second harmonic voltage signal is applied to the fifth to eighth piezoelectric ceramic plates in the piezoelectric joint. The second harmonic voltage signal is 90 degrees out of phase with the first harmonic voltage signal to excite another second-order bending vibration of the joint piezoelectric oscillator. The two vibration modes are coupled at the drive groove on the second end face of the joint piezoelectric oscillator, and then the drive head of the piezoelectric joint is driven to rotate around its central axis by friction of the drive groove.

[0036] If it is necessary to drive the piezoelectric joint's drive head to rotate in the opposite direction around its central axis, simply adjust the phase difference between the first and second harmonic voltage signals to -90 degrees.

[0037] Step A.2), if the drive head of the piezoelectric joint needs to be driven to rotate forward in the horizontal direction: apply a preset first harmonic voltage signal to the first to fourth piezoelectric ceramic plates in the piezoelectric joint to excite the second-order bending vibration of the joint piezoelectric oscillator; apply a preset second harmonic voltage signal to the fifth and eighth piezoelectric ceramic plates in the piezoelectric joint, and apply a preset third harmonic voltage signal to the sixth and seventh piezoelectric ceramic plates in the piezoelectric joint, wherein the third harmonic voltage signal is 270 degrees out of phase with the first harmonic voltage signal to excite the first-order longitudinal vibration of the joint piezoelectric oscillator; the two vibration modes are coupled at the drive groove on the second end face of the joint piezoelectric oscillator, and then drive the drive head of the piezoelectric joint to rotate in the horizontal direction through the friction of the drive groove;

[0038] If it is necessary to drive the piezoelectric joint's drive head to rotate in the opposite direction in the horizontal direction, simply increase or decrease the phase of the first simple harmonic voltage signal by 180 degrees.

[0039] Step A.3), if the drive head of the piezoelectric joint needs to be driven to rotate forward in the vertical direction: apply a preset first harmonic voltage signal to the fifth to eighth piezoelectric ceramic plates in the piezoelectric joint to excite the second-order bending vibration of the joint piezoelectric oscillator; apply a preset second harmonic voltage signal to the first and fourth piezoelectric ceramic plates, and apply a preset third harmonic voltage signal to the second and third piezoelectric ceramic plates to excite the first-order longitudinal vibration of the joint piezoelectric oscillator; the two vibration modes are coupled at the drive groove on the second end face of the joint piezoelectric oscillator, and then drive the drive head of the piezoelectric joint to rotate forward in the vertical direction through the friction of the drive groove;

[0040] If it is necessary to drive the piezoelectric joint's drive head to rotate in the opposite direction in the vertical direction, the phase of the first simple harmonic signal can be increased or decreased by 180 degrees.

[0041] This invention also discloses a method for the modular piezoelectric-driven multi-degree-of-freedom robotic arm to achieve horizontal and vertical rotation, comprising the following steps:

[0042] Step B.1) If the drive head of the piezoelectric joint needs to be driven to rotate in the horizontal direction: apply a preset first harmonic voltage signal to the first and fourth piezoelectric ceramic plates in the piezoelectric joint, and apply a preset second harmonic voltage signal to the second and third piezoelectric ceramic plates in the piezoelectric joint. The second harmonic voltage signal is 90 degrees out of phase with the first harmonic voltage signal, and simultaneously excites the first-order longitudinal vibration and second-order bending vibration modes of the joint piezoelectric oscillator. The two vibration modes are coupled at the drive groove on the second end face of the joint piezoelectric oscillator, and then the drive head of the piezoelectric joint is driven to rotate in the horizontal direction by the friction of the drive groove.

[0043] If it is necessary to drive the piezoelectric joint's drive head to rotate in the opposite direction in the horizontal direction, simply adjust the phase difference between the first and second simple harmonic voltage signals to -90 degrees.

[0044] Step B.2), if it is necessary to drive the drive head of the piezoelectric joint to rotate forward in the vertical direction: apply a preset first simple harmonic voltage signal to the fifth and eighth piezoelectric ceramic plates in the piezoelectric joint, and apply a preset second simple harmonic voltage signal to the sixth and seventh piezoelectric ceramic plates, thereby exciting the longitudinal vibration and second-order bending vibration modes of the joint piezoelectric oscillator; the two vibration modes are coupled at the drive groove on the second end face of the joint piezoelectric oscillator, and then drive the drive head of the piezoelectric joint to rotate forward in the horizontal direction through the friction of the drive groove;

[0045] If it is necessary to drive the piezoelectric joint's drive head to rotate in the opposite direction in the vertical direction, simply adjust the phase difference between the first and second harmonic voltage signals to -90 degrees.

[0046] The present invention also discloses a driving method for the focusing component of the modular piezoelectric driven multi-degree-of-freedom robotic arm, comprising the following steps:

[0047] For the first and second focusing components, if it is necessary to drive them to rotate in the forward direction:

[0048] A preset fourth harmonic voltage signal is applied to the ninth, eleventh, and thirteenth piezoelectric ceramic sheets to excite the third-order in-plane bending vibration of the focusing piezoelectric oscillator; a preset fifth harmonic voltage signal is applied to the tenth, twelfth, and fourteenth piezoelectric ceramic sheets, wherein the fifth harmonic voltage signal and the fourth harmonic voltage signal are 90 degrees out of phase, to excite another third-order in-plane bending vibration of the focusing piezoelectric oscillator; the two third-order in-plane bending vibrations are coupled into a traveling wave and rotate in the forward direction through friction drive;

[0049] If you need to drive it to rotate in the forward direction, simply adjust the phase difference between the fifth and fourth harmonic voltage signals to -90 degrees.

[0050] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0051] (1) The present invention has strong environmental adaptability, not only with good electromagnetic compatibility, but also can be used in environments such as confined spaces, nuclear radiation, high and low temperatures, and high vacuum, and can meet the requirements for maintenance work in special environments;

[0052] (2) The present invention has a highly integrated structure, with drive and transmission integrated, which is not only compact but also has many degrees of freedom and high flexibility, achieving the unity of small size and high flexibility;

[0053] (3) The modular design of each part of the present invention makes it easy to process and assemble. The number of mechanical joints can be freely selected according to the requirements so that the modular piezoelectric drive multi-degree-of-freedom robotic arm can achieve the required indicators and is convenient for replacement and maintenance.

[0054] (4) The present invention integrates a piezoelectric-driven focusing mechanism at the end of the robotic arm, which can be equipped with a built-in camera to achieve high-precision and rapid focusing and real-time observation in special environments such as strong magnetic fields and high vacuum. It overcomes the defects of traditional electromagnetic focusing mechanisms such as poor adaptability and large size, and shares the piezoelectric driving principle with the main body, thereby improving the overall integration of functions. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of the structure of the present invention;

[0056] Figure 2 This is a schematic diagram of the piezoelectric joint in this invention;

[0057] Figure 3 This is a schematic diagram of the joint piezoelectric oscillator in this invention;

[0058] Figure 4 This is a schematic diagram of the joint head structure in this invention;

[0059] Figure 5 This is a schematic diagram of the joint capsule structure in this invention;

[0060] Figure 6 This is a schematic diagram of the focusing component in the actuator of the present invention;

[0061] Figure 7 This is a schematic diagram illustrating the principle of the piezoelectric joint rotating around its central axis in this invention.

[0062] Figure 8 This is a schematic diagram illustrating the principle of vertical rotation of the piezoelectric joint in this invention;

[0063] Figure 9 This is a schematic diagram illustrating the principle of horizontal rotation of the piezoelectric joint in this invention;

[0064] In the figure, 1-piezoelectric joint, 2-actuator, 3-first side of elastic beam, 4-first preload nut, 5-first elastic washer, 6-second elastic washer, 7-first preload bolt, 8-joint capsule, 9-joint head, 10-elastic beam, 11-first fixed lug, 12-drive head, 13-connecting rod, 14-flange, 15-joint threaded rod, 16-external threaded tube, 17-ninth piezoelectric ceramic plate, 18-focusing lens. Detailed Implementation

[0065] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings:

[0066] 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.

[0067] like Figure 1 As shown, this invention discloses a modular piezoelectric-driven multi-degree-of-freedom robotic arm, comprising an end effector and M piezoelectric joints, where M is a natural number greater than or equal to 2;

[0068] like Figure 2 As shown, the piezoelectric joint includes a joint head, a joint piezoelectric vibrator, a joint capsule, first and second preload bolts, first and second preload nuts, and first to fourth elastic washers;

[0069] like Figure 4 As shown, the joint head includes a drive head, a connecting rod, a flange, and a joint threaded rod. The drive head is a spherical cap with a height greater than its radius. The joint connecting rod is a cylinder with a diameter equal to the diameter of the bottom surface of the drive head. One end is coaxially fixed to the bottom surface of the drive head, and the other end is coaxially fixed to one end of the flange. One end of the joint threaded rod is coaxially fixed to the other end of the flange, and the diameter of the joint threaded rod is smaller than the diameter of the flange.

[0070] like Figure 3 As shown, the joint piezoelectric vibrator includes an elastic beam, a first fixed lug, a second fixed lug, and first to eighth piezoelectric ceramic plates;

[0071] The elastic beam is a regular square prism, including a first end face, a second end face, and first to fourth side faces connected end to end. The center of the second end face is provided with a drive groove for cooperating with the drive head. The drive groove is a spherical cap with a height less than its radius. The elastic beam is provided with a through hole along its axis that penetrates the bottom of the drive groove and the first end face. The through hole is provided with an internal thread at one end near the first end face for cooperating with the joint threaded rod, forming a joint threaded hole for connection.

[0072] The first to eighth piezoelectric ceramic sheets are all rectangular and polarized along their thickness direction. Specifically, the first and second piezoelectric ceramic sheets are disposed on the first side of the elastic beam with opposite polarization directions; the third and fourth piezoelectric ceramic sheets are disposed on the third side of the elastic beam with opposite polarization directions; the first and third piezoelectric ceramic sheets are symmetrical with the same polarization direction; the second and fourth piezoelectric ceramic sheets are symmetrical with the same polarization direction; the fifth and sixth piezoelectric ceramic sheets are disposed on the second side of the elastic beam with opposite polarization directions; the seventh and eighth piezoelectric ceramic sheets are disposed on the fourth side of the elastic beam with opposite polarization directions; the fifth and seventh piezoelectric ceramic sheets are symmetrical with the same polarization direction; and the sixth and eighth piezoelectric ceramic sheets are symmetrical with the same polarization direction.

[0073] The first and second fixed lugs have the same structure and are symmetrically arranged on the first and third sides of the elastic beam, located at the common node of the first longitudinal vibration mode and the second bending vibration mode of the piezoelectric joint.

[0074] like Figure 5 As shown, the joint capsule includes a capsule body, a third fixing ear, and a fourth fixing ear. The capsule body is a hollow regular square prism with one open end and the other closed end. The center of the closed end face is provided with a limiting hole for cooperating with the drive head. The diameter of the limiting hole is larger than the bottom diameter of the drive head and the diameter of the flange, but smaller than the diameter of the drive head. The third fixing ear and the fourth fixing ear have the same structure as the first fixing ear and are symmetrically arranged on the two side walls at the open end of the joint capsule.

[0075] The joint capsule is fitted over the end of the elastic beam with the drive groove. The drive head is pressed against the drive groove through the limiting hole, so that the connecting rod, flange, and joint threaded rod are located outside the joint capsule. The third fixing lug corresponds to the first fixing lug, and the fourth fixing lug corresponds to the second fixing lug. The first preload bolt passes through the third fixing lug, the second elastic washer, the first fixing lug, and the first elastic washer in sequence and is threaded to the first preload nut. The second preload bolt passes through the fourth fixing lug, the fourth elastic washer, the third fixing lug, and the third elastic washer in sequence and is threaded to the second preload nut. This is used to adjust the preload force between the drive head and the drive groove.

[0076] The joint thread rod of the (i+1)th piezoelectric joint is threadedly connected to the joint thread hole of the ith piezoelectric joint, so that M piezoelectric joints are connected in series, where i is a natural number greater than or equal to 1 and less than M.

[0077] The end connection mechanism includes a connecting block, first and second built-in cameras, and first and second focusing components;

[0078] The connecting block is rectangular and is used to connect to an external actuator. One end face has a threaded hole at its center for engaging with the threaded rod of the Mth piezoelectric joint, and the other end face has a first observation thread blind hole and a second observation thread blind hole.

[0079] The first and second observation thread blind holes have the same structure.

[0080] like Figure 6 As shown, the first focusing assembly and the second focusing assembly have the same structure, both including a focusing piezoelectric vibrator and a focusing lens;

[0081] The focusing piezoelectric vibrator comprises an externally threaded tube and a focusing piezoelectric ceramic assembly. The inner hole of the externally threaded tube is a hexagonal hole, and the outer thread can cooperate with the inner thread of the first observation thread blind hole. The focusing piezoelectric ceramic assembly comprises a ninth to a fourteenth piezoelectric ceramic sheet. The ninth to fourteenth piezoelectric ceramic sheets have the same rectangular structure, are all polarized along the thickness direction, and are uniformly pasted on the six sides of the inner hole of the externally threaded tube in a circumferential direction. The polarization directions of adjacent piezoelectric ceramic sheets are opposite.

[0082] The focusing lens is a convex lens with the same diameter as the outer diameter of the external threaded tube, and is coaxially fixed to one end of the external threaded tube.

[0083] The first built-in camera and the second built-in camera are respectively installed in the first observation thread blind hole and the second observation thread blind hole. The external thread tube of the first focusing component and the external thread tube of the second focusing component are respectively threadedly connected to the first observation thread blind hole and the second observation thread blind hole. The first focusing component and the second focusing component are respectively used for focusing the first built-in camera and the second built-in camera.

[0084] This invention also discloses a method for operating the modular piezoelectric-driven multi-degree-of-freedom robotic arm, comprising the following steps:

[0085] Step A.1), as follows Figure 7 As shown, if it is necessary to drive the drive head of the piezoelectric joint to rotate positively around its central axis, a preset first harmonic voltage signal is applied to the first to fourth piezoelectric ceramic plates in the piezoelectric joint to excite the second-order bending vibration of the joint piezoelectric oscillator. A preset second harmonic voltage signal is applied to the fifth to eighth piezoelectric ceramic plates in the piezoelectric joint. The second harmonic voltage signal is 90 degrees out of phase with the first harmonic voltage signal to excite another second-order bending vibration of the joint piezoelectric oscillator. The two vibration modes are coupled at the drive groove on the second end face of the joint piezoelectric oscillator, and then the drive head of the piezoelectric joint is driven to rotate around its central axis through the friction of the drive groove.

[0086] If it is necessary to drive the piezoelectric joint's drive head to rotate in the opposite direction around its central axis, simply adjust the phase difference between the first and second harmonic voltage signals to -90 degrees.

[0087] Step A.2), as follows Figure 8As shown, if it is necessary to drive the drive head of the piezoelectric joint to rotate in the horizontal direction: a preset first harmonic voltage signal is applied to the first to fourth piezoelectric ceramic plates in the piezoelectric joint to excite the second-order bending vibration of the joint piezoelectric oscillator; a preset second harmonic voltage signal is applied to the fifth and eighth piezoelectric ceramic plates in the piezoelectric joint, and a preset third harmonic voltage signal is applied to the sixth and seventh piezoelectric ceramic plates in the piezoelectric joint. The third harmonic voltage signal is 270 degrees out of phase with the first harmonic voltage signal to excite the first-order longitudinal vibration of the joint piezoelectric oscillator; the two vibration modes are coupled at the drive groove on the second end face of the joint piezoelectric oscillator, and then the drive head of the piezoelectric joint is driven to rotate in the horizontal direction by the friction of the drive groove;

[0088] If it is necessary to drive the piezoelectric joint's drive head to rotate in the opposite direction in the horizontal direction, simply increase or decrease the phase of the first simple harmonic voltage signal by 180 degrees.

[0089] Step A.3), as follows Figure 9 As shown, if it is necessary to drive the drive head of the piezoelectric joint to rotate forward in the vertical direction: a preset first harmonic voltage signal is applied to the fifth to eighth piezoelectric ceramic plates in the piezoelectric joint to excite the second-order bending vibration of the joint piezoelectric oscillator; a preset second harmonic voltage signal is applied to the first and fourth piezoelectric ceramic plates, and a preset third harmonic voltage signal is applied to the second and third piezoelectric ceramic plates to excite the first-order longitudinal vibration of the joint piezoelectric oscillator; the two vibration modes are coupled at the drive groove on the second end face of the joint piezoelectric oscillator, and then the drive head of the piezoelectric joint is driven to rotate forward in the vertical direction by the friction of the drive groove;

[0090] If it is necessary to drive the piezoelectric joint's drive head to rotate in the opposite direction in the vertical direction, the phase of the first simple harmonic signal can be increased or decreased by 180 degrees.

[0091] This invention also discloses a method for the modular piezoelectric-driven multi-degree-of-freedom robotic arm to achieve horizontal and vertical rotation, comprising the following steps:

[0092] Step B.1) If the drive head of the piezoelectric joint needs to be driven to rotate in the horizontal direction: apply a preset first harmonic voltage signal to the first and fourth piezoelectric ceramic plates in the piezoelectric joint, and apply a preset second harmonic voltage signal to the second and third piezoelectric ceramic plates in the piezoelectric joint. The second harmonic voltage signal is 90 degrees out of phase with the first harmonic voltage signal, and simultaneously excites the first-order longitudinal vibration and second-order bending vibration modes of the joint piezoelectric oscillator. The two vibration modes are coupled at the drive groove on the second end face of the joint piezoelectric oscillator, and then the drive head of the piezoelectric joint is driven to rotate in the horizontal direction by the friction of the drive groove.

[0093] If it is necessary to drive the piezoelectric joint's drive head to rotate in the opposite direction in the horizontal direction, simply adjust the phase difference between the first and second simple harmonic voltage signals to -90 degrees.

[0094] Step B.2), if it is necessary to drive the drive head of the piezoelectric joint to rotate forward in the vertical direction: apply a preset first simple harmonic voltage signal to the fifth and eighth piezoelectric ceramic plates in the piezoelectric joint, and apply a preset second simple harmonic voltage signal to the sixth and seventh piezoelectric ceramic plates, thereby exciting the longitudinal vibration and second-order bending vibration modes of the joint piezoelectric oscillator; the two vibration modes are coupled at the drive groove on the second end face of the joint piezoelectric oscillator, and then drive the drive head of the piezoelectric joint to rotate forward in the horizontal direction through the friction of the drive groove;

[0095] If it is necessary to drive the piezoelectric joint's drive head to rotate in the opposite direction in the vertical direction, simply adjust the phase difference between the first and second harmonic voltage signals to -90 degrees.

[0096] The present invention also discloses a driving method for the focusing component of the modular piezoelectric driven multi-degree-of-freedom robotic arm, comprising the following steps:

[0097] For the first and second focusing components, if it is necessary to drive them to rotate in the forward direction:

[0098] A preset fourth harmonic voltage signal is applied to the ninth, eleventh, and thirteenth piezoelectric ceramic sheets to excite the third-order in-plane bending vibration of the focusing piezoelectric oscillator; a preset fifth harmonic voltage signal is applied to the tenth, twelfth, and fourteenth piezoelectric ceramic sheets, wherein the fifth harmonic voltage signal and the fourth harmonic voltage signal are 90 degrees out of phase, to excite another third-order in-plane bending vibration of the focusing piezoelectric oscillator; the two third-order in-plane bending vibrations are coupled into a traveling wave and rotate in the forward direction through friction drive;

[0099] If you need to drive it to rotate in the forward direction, simply adjust the phase difference between the fifth and fourth harmonic voltage signals to -90 degrees.

[0100] 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.

[0101] 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 modular piezoelectric-driven multi-degree-of-freedom robotic arm, characterized in that, It includes an end-connection mechanism and M piezoelectric joints, where M is a natural number greater than or equal to 2; The piezoelectric joint includes a joint head, a joint piezoelectric vibrator, a joint capsule, first and second preload bolts, first and second preload nuts, and first to fourth elastic washers; The articulated head includes a drive head, a connecting rod, a flange, and an articulated threaded rod. The drive head is a spherical cap with a height greater than its radius. The articulated connecting rod is a cylinder with a diameter equal to the diameter of the bottom surface of the drive head. One end of the connecting rod is coaxially fixed to the bottom surface of the drive head, and the other end is coaxially fixed to one end of the flange. One end of the articulated threaded rod is coaxially fixed to the other end of the flange, and the diameter of the articulated threaded rod is smaller than the diameter of the flange. The joint piezoelectric vibrator includes an elastic beam, a first fixed lug, a second fixed lug, and first to eighth piezoelectric ceramic plates; The elastic beam is a regular square prism, including a first end face, a second end face, and first to fourth side faces connected end to end. The center of the second end face is provided with a drive groove for cooperating with the drive head. The drive groove is a spherical cap with a height less than its radius. The elastic beam is provided with a through hole along its axis that penetrates the bottom of the drive groove and the first end face. The through hole is provided with an internal thread at one end near the first end face for cooperating with the joint threaded rod, forming a joint threaded hole for connection. The first to eighth piezoelectric ceramic sheets are all rectangular and polarized along their thickness direction. Specifically, the first and second piezoelectric ceramic sheets are disposed on the first side of the elastic beam with opposite polarization directions; the third and fourth piezoelectric ceramic sheets are disposed on the third side of the elastic beam with opposite polarization directions; the first and third piezoelectric ceramic sheets are symmetrical with the same polarization direction; the second and fourth piezoelectric ceramic sheets are symmetrical with the same polarization direction; the fifth and sixth piezoelectric ceramic sheets are disposed on the second side of the elastic beam with opposite polarization directions; the seventh and eighth piezoelectric ceramic sheets are disposed on the fourth side of the elastic beam with opposite polarization directions; the fifth and seventh piezoelectric ceramic sheets are symmetrical with the same polarization direction; and the sixth and eighth piezoelectric ceramic sheets are symmetrical with the same polarization direction. The first and second fixed lugs have the same structure and are symmetrically arranged on the first and third sides of the elastic beam, located at the common node of the first longitudinal vibration mode and the second bending vibration mode of the piezoelectric joint. The joint capsule includes a capsule body, a third fixing ear, and a fourth fixing ear. The capsule body is a hollow regular square prism with one open end and the other closed end. The center of the closed end face is provided with a limiting hole for cooperating with the drive head. The diameter of the limiting hole is larger than the bottom diameter of the drive head and the diameter of the flange, but smaller than the diameter of the drive head. The third fixing ear and the fourth fixing ear have the same structure as the first fixing ear and are symmetrically arranged on the two side walls of the open end of the joint capsule. The joint capsule is fitted over the end of the elastic beam with the drive groove. The drive head is pressed against the drive groove through the limiting hole, so that the connecting rod, flange, and joint threaded rod are located outside the joint capsule. The third fixing lug corresponds to the first fixing lug, and the fourth fixing lug corresponds to the second fixing lug. The first preload bolt passes through the third fixing lug, the second elastic washer, the first fixing lug, and the first elastic washer in sequence and is threaded to the first preload nut. The second preload bolt passes through the fourth fixing lug, the fourth elastic washer, the third fixing lug, and the third elastic washer in sequence and is threaded to the second preload nut. This is used to adjust the preload force between the drive head and the drive groove. The joint thread rod of the (i+1)th piezoelectric joint is threadedly connected to the joint thread hole of the ith piezoelectric joint, so that M piezoelectric joints are connected in series, where i is a natural number greater than or equal to 1 and less than M. The end connection mechanism includes a connecting block, first and second built-in cameras, and first and second focusing components; The connecting block is rectangular and is used to connect to an external actuator. One end face has a threaded hole at its center for engaging with the threaded rod of the Mth piezoelectric joint, and the other end face has a first observation thread blind hole and a second observation thread blind hole. The first and second observation thread blind holes have the same structure. The first focusing assembly and the second focusing assembly have the same structure, both including a focusing piezoelectric vibrator and a focusing lens; The focusing piezoelectric vibrator comprises an externally threaded tube and a focusing piezoelectric ceramic assembly. The inner hole of the externally threaded tube is a hexagonal hole, and the outer thread can cooperate with the inner thread of the first observation thread blind hole. The focusing piezoelectric ceramic assembly comprises a ninth to a fourteenth piezoelectric ceramic sheet. The ninth to fourteenth piezoelectric ceramic sheets have the same rectangular structure, are all polarized along the thickness direction, and are uniformly pasted on the six sides of the inner hole of the externally threaded tube in a circumferential direction. The polarization directions of adjacent piezoelectric ceramic sheets are opposite. The focusing lens is a convex lens with the same diameter as the outer diameter of the external threaded tube, and is coaxially fixed to one end of the external threaded tube. The first built-in camera and the second built-in camera are respectively installed in the first observation thread blind hole and the second observation thread blind hole. The external thread tube of the first focusing component and the external thread tube of the second focusing component are respectively threadedly connected to the first observation thread blind hole and the second observation thread blind hole. The first focusing component and the second focusing component are respectively used for focusing the first built-in camera and the second built-in camera.

2. The working method of the modular piezoelectric driven multi-degree-of-freedom robotic arm according to claim 1, characterized in that, Includes the following steps: Step A.1): If it is necessary to drive the drive head of the piezoelectric joint to rotate positively around its central axis, a preset first harmonic voltage signal is applied to the first to fourth piezoelectric ceramic plates in the piezoelectric joint to excite the second-order bending vibration of the joint piezoelectric oscillator. A preset second harmonic voltage signal is applied to the fifth to eighth piezoelectric ceramic plates in the piezoelectric joint. The second harmonic voltage signal is 90 degrees out of phase with the first harmonic voltage signal to excite another second-order bending vibration of the joint piezoelectric oscillator. The two vibration modes are coupled at the drive groove on the second end face of the joint piezoelectric oscillator, and then the drive head of the piezoelectric joint is driven to rotate around its central axis by friction of the drive groove. If it is necessary to drive the piezoelectric joint's drive head to rotate in the opposite direction around its central axis, simply adjust the phase difference between the first and second harmonic voltage signals to -90 degrees. Step A.2), if it is necessary to drive the drive head of the piezoelectric joint to rotate in the horizontal direction: apply a preset first simple harmonic voltage signal to the first to fourth piezoelectric ceramic sheets in the piezoelectric joint to excite the second-order bending vibration of the joint piezoelectric oscillator; A preset second harmonic voltage signal is applied to the fifth and eighth piezoelectric ceramic plates in the piezoelectric joint, and a preset third harmonic voltage signal is applied to the sixth and seventh piezoelectric ceramic plates in the piezoelectric joint. The third harmonic voltage signal is 270 degrees out of phase with the first harmonic voltage signal, which excites the first-order longitudinal vibration of the joint piezoelectric oscillator. The two vibration modes are coupled at the drive groove on the second end face of the joint piezoelectric oscillator, and then the drive head of the piezoelectric joint is driven to rotate horizontally through the friction of the drive groove. If it is necessary to drive the piezoelectric joint's drive head to rotate in the opposite direction in the horizontal direction, simply increase or decrease the phase of the first simple harmonic voltage signal by 180 degrees. Step A.3), if it is necessary to drive the drive head of the piezoelectric joint to rotate in the vertical direction: apply a preset first simple harmonic voltage signal to the fifth to eighth piezoelectric ceramic plates in the piezoelectric joint to excite the second-order bending vibration of the joint piezoelectric oscillator; A preset second harmonic voltage signal is applied to the first and fourth piezoelectric ceramic sheets, and a preset third harmonic voltage signal is applied to the second and third piezoelectric ceramic sheets, which excites the first-order longitudinal vibration of the joint piezoelectric oscillator; the two vibration modes are coupled at the drive groove on the second end face of the joint piezoelectric oscillator, and then the drive head of the piezoelectric joint is driven to rotate in the vertical direction through the friction of the drive groove. If it is necessary to drive the piezoelectric joint's drive head to rotate in the opposite direction in the vertical direction, the phase of the first simple harmonic signal can be increased or decreased by 180 degrees.

3. The working method of the modular piezoelectric driven multi-degree-of-freedom robotic arm according to claim 1, characterized in that, Modular piezoelectric-driven multi-degree-of-freedom robotic arms can also achieve horizontal and vertical rotation using the following working methods, including the following steps: Step B.1) If the drive head of the piezoelectric joint needs to be driven to rotate in the horizontal direction: apply a preset first harmonic voltage signal to the first and fourth piezoelectric ceramic plates in the piezoelectric joint, and apply a preset second harmonic voltage signal to the second and third piezoelectric ceramic plates in the piezoelectric joint. The second harmonic voltage signal is 90 degrees out of phase with the first harmonic voltage signal, and simultaneously excites the first-order longitudinal vibration and second-order bending vibration modes of the joint piezoelectric oscillator. The two vibration modes are coupled at the drive groove on the second end face of the joint piezoelectric oscillator, and then the drive head of the piezoelectric joint is driven to rotate in the horizontal direction by the friction of the drive groove. If it is necessary to drive the piezoelectric joint's drive head to rotate in the opposite direction in the horizontal direction, simply adjust the phase difference between the first and second simple harmonic voltage signals to -90 degrees. Step B.2), if it is necessary to drive the drive head of the piezoelectric joint to rotate forward in the vertical direction: apply a preset first simple harmonic voltage signal to the fifth and eighth piezoelectric ceramic plates in the piezoelectric joint, and apply a preset second simple harmonic voltage signal to the sixth and seventh piezoelectric ceramic plates, thereby exciting the longitudinal vibration and second-order bending vibration modes of the joint piezoelectric oscillator; the two vibration modes are coupled at the drive groove on the second end face of the joint piezoelectric oscillator, and then drive the drive head of the piezoelectric joint to rotate forward in the horizontal direction through the friction of the drive groove; If it is necessary to drive the piezoelectric joint's drive head to rotate in the opposite direction in the vertical direction, simply adjust the phase difference between the first and second harmonic voltage signals to -90 degrees.

4. The focusing assembly driving method for a modular piezoelectric-driven multi-degree-of-freedom robotic arm as described in claim 1, characterized in that, Includes the following steps: For the first and second focusing components, if it is necessary to drive them to rotate in the forward direction: A preset fourth harmonic voltage signal is applied to the ninth, eleventh, and thirteenth piezoelectric ceramic sheets to excite the third-order in-plane bending vibration of the focusing piezoelectric oscillator; a preset fifth harmonic voltage signal is applied to the tenth, twelfth, and fourteenth piezoelectric ceramic sheets, wherein the fifth harmonic voltage signal and the fourth harmonic voltage signal are 90 degrees out of phase, to excite another third-order in-plane bending vibration of the focusing piezoelectric oscillator; the two third-order in-plane bending vibrations are coupled into a traveling wave and rotate in the forward direction through friction drive; If you need to drive it to rotate in the forward direction, simply adjust the phase difference between the fifth and fourth harmonic voltage signals to -90 degrees.

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