Sandwich-type piezoelectric two-degree-of-freedom robotic arm and its driving method

Abstract

This invention discloses a sandwich-type piezoelectric two-degree-of-freedom robotic arm and its driving method, comprising several sequentially connected unit arm segments; each unit arm segment includes two piezoelectric oscillators and two joint parts; the joint parts of adjacent unit arm segments are spatially orthogonal to each other, and the orthogonal connection between unit arm segments and the application of preload are achieved through the joint parts between unit arm segments. This invention has a compact and simple structure, requires no gear reduction mechanisms, is easy to seal, easy to miniaturize, has low operating noise, easily achieves low speed and high torque, is unaffected by electromagnetic interference, can self-lock upon power failure, and has high control precision.

Description

Technical Field

[0001] This invention relates to the fields of piezoelectric drive and robotics, specifically a sandwich-type piezoelectric two-degree-of-freedom robotic arm and its driving method. Background Technology

[0002] Existing traditional robotic arms use electromagnetic motors and hydraulic presses as drive sources, transmitting the motion of the actuator to the drive joints through gears, pulleys, etc. They have complex structures, large volumes, and are difficult to control in terms of speed and precision. They are difficult to meet the requirements for some special environmental applications, such as deep sea, outer space, high electromagnetic interference, high temperature, and extremely cold environments, and it is also difficult to achieve a miniaturized and compact design.

[0003] In recent years, piezoelectric driven robotic arms have gradually emerged, using the coupling of heterogeneous modes as the driving basis. During the design process, the need to adjust the modal frequency consistency is a large and complex task, and it also imposes many restrictions on the geometry and size of the structure, making it difficult to achieve serialization and modular design. Furthermore, the wear of these piezoelectric actuators during operation can cause two-phase frequency drift, increase the two-phase frequency difference, and reduce the driving performance of the robotic arm.

[0004] Therefore, in most current solutions, the robotic arm is too complex and not compact enough to achieve miniaturization. Summary of the Invention

[0005] To address the problems of existing technologies, this invention provides a sandwich-type piezoelectric two-degree-of-freedom robotic arm and its driving method, which has a simple and compact design and is easy to miniaturize.

[0006] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions:

[0007] In a first aspect, embodiments of the present invention provide a sandwich-type piezoelectric two-degree-of-freedom robotic arm, which consists of at least two sequentially connected unit arm segments, which are connected by a connecting assembly. Each unit arm segment includes two piezoelectric vibrators and two joint parts. The piezoelectric vibrator includes a first metal substrate, a second metal substrate, and a piezoelectric drive assembly. Both the first and second metal substrates are variable-diameter cylinders. The first metal substrate has an external thread at the end near the piezoelectric drive assembly, and the second metal substrate has an internal thread at the end near the piezoelectric drive assembly. The external threads at both ends of the two piezoelectric vibrators of each unit arm segment pass sequentially through through holes on the two ear plates of the joint base and through holes at both ends of the pressure spring, and the piezoelectric vibrator is connected to the joint part by a nut and a washer to complete the threaded engagement. The piezoelectric drive assembly is installed from left to right with: a first electrode plate, a first piezoelectric ceramic plate, a second electrode plate, a second piezoelectric ceramic plate, and a third electrode plate. The third piezoelectric ceramic sheet, the fourth electrode sheet, the fourth piezoelectric ceramic sheet, and the fifth electrode sheet; the first, third, and fifth electrode sheets of the piezoelectric drive assembly are grounded, and the second and fourth electrode sheets are driven by power input signals; the joint part consists of a joint base, a nut, and a washer. One of the joint parts at both ends of the unit arm segment is equipped with a pressure spring. The joint base is a semi-circular hoop structure with an irregular circular cross-section. Through holes are provided at the two ear plates of the joint base; the joint part at the end of one unit arm segment without a pressure spring is connected to the joint part at the end of another unit arm segment with a pressure spring; the joint bases of the joint parts of the two connected unit arm segments are orthogonally arranged in space, and the pressure spring plays the role of applying preload; the two orthogonally arranged joint bases are connected and positioned by nuts and washers and fixed to the two piezoelectric vibrators of their respective unit arm segments; the external threads at both ends of the piezoelectric vibrators are clearance-fitted with the through holes at the ear plates of the stator base; the pressure spring has through holes at both ends corresponding to the ear plates of the joint base.

[0008] In the first metal matrix: the diameter of the first stepped cylinder is larger than that of the second stepped cylinder;

[0009] Along the axis of the first metal substrate, the length of the first stepped cylinder is less than the length of the second stepped cylinder; for the second metal substrate, except for the internal thread that mates with the external thread at the end near the piezoelectric drive assembly, all other parts are exactly the same as the first metal substrate.

[0010] The first, second, third, and fourth piezoelectric ceramic sheets are all single-section annular piezoelectric ceramic sheets polarized along the thickness direction. In the single-section annular piezoelectric ceramic sheets, the polarization directions of adjacent piezoelectric ceramic sheets are opposite. That is, if the polarization direction of the first piezoelectric ceramic sheet is positive, then the polarization directions of the second and fourth piezoelectric ceramic sheets are negative, and the polarization direction of the third piezoelectric ceramic sheet is positive, and vice versa.

[0011] The first piezoelectric ceramic sheet is in contact with one side of the first electrode sheet and one side of the second electrode sheet; the second piezoelectric ceramic sheet is in contact with the other side of the second electrode sheet and one side of the third electrode sheet; the third piezoelectric ceramic sheet is in contact with the other side of the third electrode sheet and one side of the fourth electrode sheet; the fourth piezoelectric ceramic sheet is in contact with the other side of the fourth electrode sheet and one side of the fifth electrode sheet; the sides of the first and fifth electrodes that are not in contact with the piezoelectric ceramic sheets are respectively in contact with the end face of the first stepped cylinder of the first metal substrate and the end face of the first stepped cylinder of the second metal substrate.

[0012] The first, second, third, fourth, and fifth electrode plates are all annular electrode plates with a round lug.

[0013] The external threads at both ends of the two piezoelectric vibrators in the unit arm section pass through the through holes at the ear plates of the joint base, the through holes at both ends of the pressure spring, and the washers in sequence. Then, the piezoelectric vibrators are assembled and fixed to the joint part by the engagement of the nuts with the external threads at both ends of the piezoelectric vibrators.

[0014] The piezoelectric drive assembly is insulated with waterproof adhesive.

[0015] Secondly, embodiments of the present invention provide a driving process for a sandwich-type piezoelectric two-degree-of-freedom robotic arm, comprising:

[0016] A simple harmonic drive signal is applied to the second and fourth electrode plates of the piezoelectric drive assembly of the two piezoelectric oscillators on the unit arm segment, causing the points in contact between the joint base of the unit arm segment of the piezoelectric oscillator to which the simple harmonic drive signal is applied and the joint base of its adjacent series-connected unit arm segments to produce elliptical motion.

[0017] The simple harmonic drive signal applied to the two piezoelectric oscillators of the same unit arm segment is a simple harmonic drive signal with a specific frequency having a time phase difference of π / 2, wherein the specific frequency is a preset frequency value, and simultaneously excites the two piezoelectric oscillators to have a first-order longitudinal vibration mode with a time phase difference of π / 2.

[0018] Drive signals are applied to the two piezoelectric oscillators of adjacent unit arm sections to trigger the rotation of the unit arm section about the axis of the circular cross section of the joint base of the adjacent unit arm section; drive signals are applied to the piezoelectric oscillators of the two unit arm sections to trigger the two unit arm sections to rotate with two degrees of freedom in the orthogonal plane, wherein the unit arm section and the adjacent unit arm section are orthogonal in space.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. In view of the problems of complex structure and low control precision of traditional electromagnetic and hydraulic press-driven robotic arms, the present invention has a compact and simple structure, does not require gear reduction mechanism, is easy to seal, easy to miniaturize, has low operating noise, is easy to achieve low speed and high torque, is not affected by electromagnetic interference, can self-lock when power is off, and has high control precision.

[0021] 2. Compared with other piezoelectric actuated robotic arms, since the piezoelectric oscillator uses the first-order longitudinal vibration single mode as the driving basis, there is no need to adjust the frequency consistency of the heterogeneous modes, which reduces the restrictions on the design size and shape of the robotic arm, making it easier to achieve serialized and modular design. Moreover, the adjustable size of the robotic arm varies depending on the engineering application scenario, making it highly applicable to engineering and with important application prospects. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A schematic diagram of a sandwich-type piezoelectric two-degree-of-freedom robotic arm structure provided in an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the unit arm structure provided in an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of a piezoelectric oscillator structure provided in an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of the piezoelectric vibrator metal substrate provided in an embodiment of the present invention;

[0027] Figure 5 A schematic diagram of a piezoelectric drive assembly provided in an embodiment of the present invention;

[0028] Figure 6 This is a schematic diagram of the joint structure provided in an embodiment of the present invention;

[0029] Figure 7 This is a schematic diagram of applying a voltage signal to the piezoelectric drive assembly provided in an embodiment of the present invention;

[0030] Figure 8 This is a schematic diagram of the first-order longitudinal vibration mode of a piezoelectric vibrator along the Z-axis, provided in an embodiment of the present invention.

[0031] In the attached diagram, the labels represent: 1-first unit arm segment, 2-second unit arm segment, 3-third unit arm segment, 4-piezoelectric vibrator, 5-joint portion, 4.1-first metal substrate, 4.2-piezoelectric drive assembly, 4.3-second metal substrate, 4.1.1-first stepped cylinder of the first metal substrate, 4.1.2-second stepped cylinder of the first metal substrate, 4.1.3-internal external thread of the first metal substrate, 4.3.1-first stepped cylinder of the second metal substrate, 4.3.2-second metal substrate. Second stepped cylinder, 4.3.3 Internal thread inside the second metal matrix, 4.2.1 First piezoelectric ceramic sheet, 4.2.2 Second piezoelectric ceramic sheet, 4.2.3 Third piezoelectric ceramic sheet, 4.2.4 Fourth piezoelectric ceramic sheet, 4.2.5 First electrode sheet, 4.2.6 Second electrode sheet, 4.2.7 Third electrode sheet, 4.2.8 Fourth electrode sheet, 4.2.9 Fifth electrode sheet, 5.1 Joint base, 5.2 Nut, 5.3 Washer, 5.4 Pressure spring. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Specifically, such as Figure 1 As shown, the present invention discloses a sandwich-type piezoelectric two-degree-of-freedom robotic arm, comprising a plurality of sequentially connected unit arm segments and connecting components between the arm segments; for illustration, a two-degree-of-freedom piezoelectric driven robotic arm comprising three unit arm segments is taken as an example, the three unit arm segments being the first unit arm segment 1, the second unit arm segment 2, and the third unit arm segment 3.

[0034] like Figure 2 As shown, each unit arm segment contains two piezoelectric oscillators 4 and two joint parts 5.

[0035] like Figure 3 Each piezoelectric oscillator 4 shown includes a first metal substrate 4.1, a second metal substrate 4.3, and a piezoelectric drive assembly 4.2.

[0036] like Figure 4The first metal substrate 4.1 shown is a variable-diameter cylinder with external threads at both ends. The external thread 4.1.3 near the piezoelectric drive assembly 4.2 engages with the internal thread 4.3.3 of the second metal substrate 4.3. The second metal substrate 4.3 is also a variable-diameter cylinder with an internal thread 4.3.3 near one end of the piezoelectric drive assembly 4.2 and an external thread at the other end. The first metal substrate 4.1 and the second metal substrate 4.3 are identical except for the internal and external threads at the end near the piezoelectric drive assembly 4.2. Taking the first metal substrate as an example, the diameter of the first stepped cylinder 4.1.1 of the first metal substrate 4.1 is larger than that of the second stepped cylinder 4.1.2. Along the axis of the first metal substrate 4.1 (or...) Figure 8 The length of the first stepped cylinder 4.1.1 in the Z-axis direction is less than the length of the second stepped cylinder 4.1.2.

[0037] like Figure 5 The piezoelectric drive assembly 4.2 shown includes, from left to right, a first electrode plate 4.2.5, a first piezoelectric ceramic plate 4.2.1, a second electrode plate 4.2.6, a second piezoelectric ceramic plate 4.2.2, a third electrode plate 4.2.7, a third piezoelectric ceramic plate 4.2.3, a fourth electrode plate 4.2.8, a fourth piezoelectric ceramic plate 4.2.4, and a fifth electrode plate 4.2.9. The first to fourth piezoelectric ceramic plates are all single-section circular annular piezoelectric ceramic plates polarized along the thickness direction. Adjacent piezoelectric ceramic plates have opposite polarization directions; that is, if the polarization direction of the first piezoelectric ceramic plate 4.2.1 is positive, then the polarization directions of the second piezoelectric ceramic plate 4.2.2 and the fourth piezoelectric ceramic plate 4.2.4 are negative, and the polarization direction of the third piezoelectric ceramic plate 4.2.3 is positive, and vice versa. The first to fourth electrode plates are all circular with a small round lug. The ring-shaped electrode sheet; the first piezoelectric ceramic sheet 4.2.1 is in contact with one side of the first electrode sheet 4.2.5 and one side of the second electrode sheet 4.2.6; the second piezoelectric ceramic sheet 4.2.2 is in contact with the other side of the second electrode sheet 4.2.6 and one side of the third electrode sheet 4.2.7; the third piezoelectric ceramic sheet 4.2.3 is in contact with the other side of the third electrode sheet 4.2.7 and one side of the fourth electrode sheet 4.2.8; the fourth piezoelectric ceramic sheet 4.2.4 is in contact with the other side of the fourth electrode sheet 4.2.8 and one side of the fifth electrode sheet 4.2.9; the sides of the first electrode sheet 4.2.5 and the fifth electrode sheet 4.2.9 that are not in contact with the piezoelectric ceramic sheet are respectively in contact with the end face of the first stepped cylinder 4.1.1 of the first metal substrate and the end face of the first stepped cylinder 4.3.1 of the second metal substrate.

[0038] like Figure 6As shown, the joint portion 5 consists of a joint base 5.1, a nut 5.2, and a washer 5.3. One of the joint portions 5 at both ends of the unit arm segment is equipped with a pressure spring 5.4. The joint base 5.1 is an irregularly shaped circular cross-section semi-circular hoop structure, and through holes are provided at the two ear plates of the joint base 5.1. The joint portion 5 at one end of the unit arm segment without a pressure spring 5.4 is connected to the joint portion 5 at the other end of the unit arm segment with a pressure spring 5.4. The joint bases 5.1 of the joint portions 5 of the two connected unit arm segments are orthogonally arranged in space, and the pressure spring 5.4 serves to apply preload. The two orthogonally arranged joint portions 5... The joint base 5.1 is connected and positioned by nuts 5.2 and washers 5.3 and fixed to the two piezoelectric vibrators 4 of each unit arm section; the external threads at both ends of the piezoelectric vibrator 4 are clearance-fitted with the through holes at the ear plates of the stator base 5.1; the pressure spring 5.4 has through holes at both ends corresponding to the two ear plates of the joint base 5.1. The external threads at both ends of the two piezoelectric vibrators 4 of the unit arm section pass through the through holes at the ear plates of the joint base 5.1, the through holes at both ends of the pressure spring 5.4, and the washer 5.3 in sequence. Then, the piezoelectric vibrator 4 is assembled and fixed to the joint part 5 by the engagement of nuts 5.2 with the external threads at both ends of the piezoelectric vibrator 4.

[0039] like Figure 7 As shown, a simple harmonic drive signal is applied to the second electrode plate 4.2.6 and the fourth electrode plate 4.2.8 of the piezoelectric drive assembly 4.2 of the two piezoelectric oscillators 4 on the unit arm segment. The simple harmonic drive signal applied to the two piezoelectric oscillators 4 in the same unit arm segment is a simple harmonic drive signal with a specific frequency having a time phase difference of π / 2, wherein the specific frequency is a preset frequency value, and simultaneously excites the two piezoelectric oscillators 4 to have a time phase difference of π / 2, as shown in the figure. Figure 8 The first-order longitudinal vibration mode shown causes the joint base 5.1 of the unit arm segment of the piezoelectric oscillator 4, which is subjected to a simple harmonic driving signal, to produce a small-amplitude elliptical motion at each point in contact with the joint base 5.1 of its adjacent unit arm segments connected in series, and generates a driving force through friction.

[0040] During operation, driving signals can be applied to the two piezoelectric vibrators 4 of adjacent unit arms to trigger the rotation of the unit arm about the axis of the circular section of the contact part of the joint base 5.1 of the adjacent unit arm. Applying driving signals to the piezoelectric vibrators 4 of the two unit arms can trigger the two unit arms to rotate with two degrees of freedom in an orthogonal plane, wherein the unit arm and the adjacent unit arm are orthogonal in space.

[0041] Furthermore, since the unit arm segment and its adjacent unit arm segment are orthogonal in space, applying a driving signal to the corresponding piezoelectric oscillator of the two unit arm segments can realize two-degree-of-freedom rotation of the two unit arm segments in the orthogonal plane.

[0042] This embodiment discloses a sandwich-type piezoelectric two-degree-of-freedom robotic arm and its driving method. The robotic arm includes several sequentially connected unit arm segments and connecting components between the arm segments. Each unit arm segment includes two piezoelectric vibrators 4 and a joint portion 5. The joint portions 5 of each unit arm segment and adjacent unit arm segments are spatially orthogonal to each other. Two orthogonally arranged joint bases 5.1 are connected and positioned by nuts 5.2 and washers 5.3 and fixed to the two piezoelectric vibrators 4 of their respective unit arm segments. A pressure spring 5.4 applies preload. During operation, the simple harmonic driving signal applied to the two piezoelectric vibrators of the same unit arm segment is a simple harmonic driving signal with a specific frequency having a time phase difference of π / 2, wherein the specific frequency is preset. The frequency value can simultaneously excite the first-order longitudinal vibration mode of two piezoelectric oscillators 4 with a phase difference of π / 2 in time. This causes the points where the joint base 5.1 of the unit arm segment of the piezoelectric oscillator 4, which is subjected to a simple harmonic driving signal, contacts the joint base 5.1 of its adjacent series-connected unit arm segments to produce micro-amplitude elliptical motion. Through friction, a driving force is generated, which applies driving signals to the two piezoelectric oscillators 4 of the adjacent unit arm segments respectively, triggering the unit arm segments to rotate about the axis of the circular cross section of the contact part of the joint base 5.1 of the adjacent unit arm segments. Since the unit arm segment and its adjacent unit arm segment are orthogonal in space, applying driving signals to the corresponding piezoelectric oscillators of the two unit arm segments can realize two-degree-of-freedom rotation of the two unit arm segments in the orthogonal plane.

[0043] The piezoelectric vibrator 4 of this invention uses a first-order longitudinal vibration single mode as the driving basis, eliminating the need for frequency consistency adjustment of heterogeneous modes, reducing restrictions on the design size and shape of the robotic arm, and making it easier to achieve serialization and modular design. It has important application prospects in different engineering applications.

[0044] Compared with the prior art, this embodiment has the following advantages:

[0045] Compared to traditional electromagnetic and hydraulic press-driven robotic arms, it has a simple structure, light weight, no need for gear reduction mechanisms, is easy to seal, easy to miniaturize, has low operating noise, is easy to achieve low speed and high torque, is not affected by electromagnetic interference, can self-lock when power is off, and has high control precision.

[0046] Compared to other piezoelectrically actuated robotic arms, the piezoelectric oscillator 4 uses a first-order longitudinal vibration single mode as the driving basis, eliminating the need for mode coupling frequency consistency adjustment between different phase modes. This reduces the limitations on the design size and shape of the robotic arm, making it easier to achieve serialized and modular designs. Furthermore, the robotic arm has a wide range of adjustable dimensions depending on the engineering application scenario, making it highly applicable in engineering and possessing significant application prospects.

[0047] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. In particular, for the device embodiments, the above descriptions are merely preferred embodiments of the present invention. Since they are fundamentally similar to the method embodiments, the descriptions are relatively simple, and relevant parts can be referred to the descriptions of the method embodiments. The above descriptions are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention, without departing from the principle of the present invention, should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A sandwich-type piezoelectric two-degree-of-freedom robotic arm, characterized in that: It includes at least two sequentially connected unit arms, with adjacent unit arms connected by joint portions (5). Each unit arm includes two piezoelectric oscillators (4) and two joint portions (5) located at both ends of the piezoelectric oscillators respectively. The piezoelectric vibrator (4) includes a first metal substrate (4.1), a piezoelectric drive assembly (4.2), and a second metal substrate (4.3) connected sequentially by a threaded structure. The first metal substrate (4.1) and the second metal substrate (4.3) are both cylinders with variable diameters. The piezoelectric drive assembly (4.2) is installed from left to right with the following components: a first electrode plate (4.2.5), a first piezoelectric ceramic plate (4.2.1), a second electrode plate (4.2.6), and a second piezoelectric ceramic plate (4.2.5). 2.2), third electrode (4.2.7), third piezoelectric ceramic sheet (4.2.3), fourth electrode (4.2.8), fourth piezoelectric ceramic sheet (4.2.4), and fifth electrode (4.2.9); the first electrode (4.2.5), third electrode (4.2.7), and fifth electrode (4.2.9) of the piezoelectric drive assembly (4.2) are grounded, and the second electrode (4.2.6) and fourth electrode (4.2.8) are driven by a power supply input signal; The joint part (5) is a joint base (5.1) with an irregular circular cross-section and a semi-circular hoop structure. The joint base (5.1) has through holes at the two ear plates. The first metal base (4.1) and the second metal base (4.3) of the piezoelectric vibrator (4) are fixedly connected to the joint base (5.1) at both ends respectively. One of the joint parts (5) at both ends of the unit arm segment is equipped with a pressure spring (5.4). In two adjacent unit arm segments, the joint part (5) at the end without the pressure spring (5.4) is connected to the joint part (5) at the end of the other unit arm segment equipped with the pressure spring (5.4). The joint bases (5.1) of the joint parts (5) of the two connected unit arm segments are orthogonally arranged in space. The pressure spring (5.4) applies preload to the two joint bases (5.1).

2. The sandwich-type piezoelectric two-degree-of-freedom robotic arm according to claim 1, characterized in that: The first metal substrate (4.1) includes a first stepped cylinder (4.1.1) and a second stepped cylinder (4.1.2). The diameter of the first stepped cylinder (4.1.1) is greater than that of the second stepped cylinder (4.1.2) along the axis of the first metal substrate (4.1), and the length of the first stepped cylinder (4.1.1) is less than that of the second stepped cylinder (4.1.2).

3. The sandwich-type piezoelectric two-degree-of-freedom robotic arm according to claim 1, characterized in that: The first piezoelectric ceramic sheet (4.2.1), the second piezoelectric ceramic sheet (4.2.2), the third piezoelectric ceramic sheet (4.2.3), and the fourth piezoelectric ceramic sheet (4.2.4) are all single-partitioned annular piezoelectric ceramic sheets polarized along the thickness direction; among the above piezoelectric ceramic sheets, the polarization directions of two adjacent piezoelectric ceramic sheets are opposite.

4. The sandwich-type piezoelectric two-degree-of-freedom robotic arm according to claim 3, characterized in that: The first piezoelectric ceramic sheet (4.2.1) is in contact with one side of the first electrode sheet (4.2.5) and one side of the second electrode sheet (4.2.6); The second piezoelectric ceramic sheet (4.2.2) is in contact with the other side of the second electrode sheet (4.2.6) and one side of the third electrode sheet (4.2.7); The third piezoelectric ceramic sheet (4.2.3) is in contact with the other side of the third electrode sheet (4.2.7) and one side of the fourth electrode sheet (4.2.8); The fourth piezoelectric ceramic sheet (4.2.4) is in contact with the other side of the fourth electrode sheet (4.2.8) and one side of the fifth electrode sheet (4.2.9); The sides of the first electrode (4.2.5) and the fifth electrode (4.2.9) that are not in contact with the piezoelectric ceramic sheet are respectively in contact with the first stepped cylinder of the first metal substrate. The end face of 4.1.1) contacts the end face of the first stepped cylinder (4.3.1) of the second metal substrate.

5. The sandwich-type piezoelectric two-degree-of-freedom robotic arm according to claim 1 or 4, characterized in that: The first electrode (4.2.5), the second electrode (4.2.6), the third electrode (4.2.7), the fourth electrode (4.2.8), and the fifth electrode (4.2.9) are all annular electrode plates with a round lug.

6. The sandwich-type piezoelectric two-degree-of-freedom robotic arm according to claim 1, characterized in that: The two piezoelectric vibrators (4) of the unit arm section are provided with external threads at both ends. The external threads pass through the through holes at the ear plate of the joint base (5.1) and the through holes at both ends of the pressure spring (5.4) in sequence. Then, the piezoelectric vibrator (4) and the joint part (5) are assembled and fixed by the external threads at both ends of the piezoelectric vibrator (4) through the engagement of the nut (5.2). A washer (5.3) is provided between the pressure spring (5.4) and the nut (5.2).

7. The sandwich-type piezoelectric two-degree-of-freedom robotic arm according to claim 1, characterized in that: The piezoelectric drive assembly (4.2) is insulated with waterproof adhesive.

8. A driving method for a sandwich-type piezoelectric two-degree-of-freedom robotic arm as described in any one of claims 1-7, characterized in that... Includes the following steps: A simple harmonic drive signal is applied to the second electrode plate (4.2.6) and the fourth electrode plate (4.2.8) of the piezoelectric drive assembly (4.2) of the two piezoelectric oscillators (4) on the unit arm segment, so that the joint base (5.1) of the unit arm segment of the piezoelectric oscillator (4) to which the simple harmonic drive signal is applied generates elliptical motion at each point in contact with the joint base (5.1) of the adjacent unit arm segment connected in series.

9. The driving method for the sandwich-type piezoelectric two-degree-of-freedom robotic arm according to claim 8, characterized in that: The simple harmonic drive signal applied to the two piezoelectric oscillators of the same unit arm segment is a simple harmonic drive signal with a specific frequency having a time phase difference of π / 2, wherein the specific frequency is a preset frequency value, and simultaneously excites the two piezoelectric oscillators (4) to have a first-order longitudinal vibration mode with a time phase difference of π / 2.

10. The driving method for the sandwich-type piezoelectric two-degree-of-freedom robotic arm according to claim 8, characterized in that: Drive signals are applied to the two piezoelectric oscillators (4) of the adjacent unit arm sections respectively, triggering the rotation of the unit arm section around the circular cross-section axis of the contact part of the joint base (5.1) of the adjacent unit arm section; drive signals are applied to the piezoelectric oscillators (4) of the two unit arm sections respectively, triggering the two unit arm sections to rotate in two degrees of freedom in the orthogonal plane, wherein the unit arm section and the adjacent unit arm section are orthogonal in space.

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