A six-degree-of-freedom piezoelectric active vibration isolation device based on a three-point double-branched chain configuration and a working method thereof

Abstract

The application discloses a refrigerating machine six-degree-of-freedom piezoelectric active vibration isolation device based on a three-point double-branch configuration and a working method thereof. The refrigerating machine six-degree-of-freedom piezoelectric active vibration isolation device based on the three-point double-branch configuration comprises a refrigerating machine, a refrigerating machine mounting platform, a base platform and three three-point double-branches arranged in a triangular array between the two platforms, wherein each three-point double-branch is composed of two piezoelectric actuators, two hookean springs, two feedforward sensors, two feedback sensors, a connecting piece and left and right supports. The vibration isolation device processes signals collected by the sensors through an external controller and generates control signals, the control signals drive the piezoelectric actuators to generate six-degree-of-freedom displacement responses, displacement compensation is performed on the refrigerating machine, the vibration amplitude transmitted from the refrigerating machine to the base platform is attenuated, and active vibration isolation is realized. The application has the advantages of fast response, high precision, anti-interference and the like, and has a significant control effect on low-frequency vibration of the refrigerating machine.

Description

Technical Field

[0001] This invention relates to the fields of piezoelectric drive and mechanical vibration control, and in particular to a six-degree-of-freedom piezoelectric active vibration isolation device for a refrigerator based on a three-point double-branch configuration and its working method. Background Technology

[0002] A refrigerator is a device or system that lowers the temperature of a working space or object below ambient temperature and maintains it at the required low temperature. It is widely used in spacecraft, precision instruments, and medical equipment. However, refrigerators inevitably generate mechanical vibrations and structural noise during operation, which significantly negatively impact equipment performance, lifespan, and the application environment. For example, in the aerospace field, missions such as space remote sensing, astronomical observation, and deep space exploration place extremely high demands on the operating environment of aerospace precision instruments. Vibrations generated by refrigerators during operation can negatively affect the normal use of precision components. To reduce the impact of refrigerator vibration on precision components, passive vibration isolation technologies such as springs and rubber dampers are widely used in existing spacecraft. However, passive vibration isolation technologies have low precision and poor isolation effects in the low-frequency range. Active vibration isolation technology can cancel or isolate vibrations through actuators, has high isolation precision, and can effectively attenuate low-frequency vibrations, making it highly suitable for vibration control of refrigerators. For example, patent CN120667341A discloses an aerospace-grade multi-source, high-capacity, ultra-low-vibration refrigerator device. This refrigerator device uses a vibration isolation unlocking device and an active vibration reduction control circuit to attenuate the vibration of the refrigerator, verifying the feasibility of applying active vibration isolation technology to the vibration isolation of the refrigerator. However, this refrigerator device does not consider the electromagnetic interference of the actuator in space, and it has not conducted in-depth research on the issues of structural lightweighting and response speed, which makes it difficult to apply this technology to the actual vibration control of the refrigerator.

[0003] This invention relates to a six-degree-of-freedom piezoelectric active vibration isolation device for a refrigeration unit based on a three-point double-branch configuration and its operating method. It compensates for refrigeration unit vibration through the displacement response generated by piezoelectric actuators, offering advantages such as lightweight design, fast response, high precision, and anti-interference capabilities. It effectively improves vibration isolation in the low-frequency range, particularly meeting the vibration isolation requirements of refrigeration units. The invention uses an accelerometer to collect signals, an external controller to calculate control signals, and drives six piezoelectric actuators to generate displacement responses, achieving six-degree-of-freedom vibration displacement compensation. Through the above-described vibration isolation device operating method, this invention solves the problem of high-precision control of low-frequency vibration in refrigeration units, while also offering practical advantages such as lightweight design and anti-interference capabilities, meeting the vibration isolation requirements of refrigeration equipment in various scenarios. Summary of the Invention

[0004] This invention addresses the technical problems of existing active vibration isolation devices for refrigeration machines mentioned in the background art by proposing a six-degree-of-freedom piezoelectric active vibration isolation device for refrigeration machines based on a three-point double-branch configuration and its working method.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A six-degree-of-freedom piezoelectric active vibration isolation device for a refrigerator based on a three-point double-branch configuration includes a refrigerator (1), a refrigerator mounting platform (2), a base platform (3), and three three-point double-branch (4) arranged in a triangular array between the two platforms.

[0007] The refrigerator (1) is bolted to the refrigerator mounting platform (2) through the bottom through hole; the top surface of the refrigerator mounting platform (2) and the bottom surface of the base platform (3) are both provided with countersunk holes for connecting three-point double chains (4); the three three-point double chains (4) are arranged in a triangular array between the refrigerator mounting platform (2) and the base platform (3), the opening direction of the three-point double chains is outward, they are connected to the refrigerator mounting platform (2) through the top threaded hole, and fixed on the base platform (3) through the bottom threaded hole; the origin of the coordinate system Oxyz is the upper left corner vertex of the base platform (3), the x-axis and y-axis are along the edge direction of the base platform (3), and the z-axis is along the normal direction of the upper plane of the base platform (3).

[0008] The three-point double-branch (4) consists of a connector (41), two Hooke flexures (42), two piezoelectric actuators (43), a left support (44), a right support (45), two feedforward sensors (46), and two feedback sensors (47); the z' axis of the coordinate system Ox'y'z' is inclined upward at a 60° angle to the horizontal plane, and the x' axis and y' axis are symmetrical about the vertical plane passing through the z' axis; the top surface of the connector (41) is parallel to the horizontal plane, and the two bottom planes are orthogonal to each other and perpendicular to the x' axis and y' axis respectively; The oblique side of the left support (44) is perpendicular to the x' axis and parallel to the bottom left plane of the connector (41). The oblique side of the right support (45) is perpendicular to the y' axis and parallel to the bottom right plane of the connector (41). The center lines of the piezoelectric actuator (43) and the Hooke flexure (42) on the left and right supports are parallel to the x' axis and the y' axis, respectively, and are connected by threads. Two feedforward sensors (46) are set on the two orthogonal planes at the bottom of the connector, and two feedback sensors (47) are set on the oblique sides of the left support (44) and the right support (45).

[0009] The connector (41) has three threaded holes on its top surface for connecting to the refrigeration unit mounting platform (2), and two threaded holes on its bottom orthogonal planes for connecting to the Hooke flexible actuator (42). The Hooke flexible actuator (42) is cylindrical in shape. The stud at the top of the cylinder is connected to the threaded hole at the bottom of the connector (41). The cylinder has grooves cut on its side. The grooves can reduce the radial stiffness of the flexible actuator, so that the flexible actuator can produce small deformations under radial force and torque, compensate for the movement gap, and improve the displacement response accuracy of the piezoelectric actuator (43). The piezoelectric actuator (43) is connected to the threaded hole at the bottom of the Hooke flexible actuator (42) through its output end. The actuator contains a piezoelectric stack and a disc spring. The disc spring applies a preload to the piezoelectric stack. The piezoelectric stack is polarized from the d direction. 33 The device is composed of stacked multilayer piezoelectric ceramic sheets. Under voltage signal excitation, it can generate expansion and contraction deformation through the inverse piezoelectric effect, driving the piezoelectric actuator (43) to output a displacement response with corresponding amplitude and frequency in the x' or y' direction. The left support (44) and the right support (45) have through holes at the bottom apex. The center line of the through hole is perpendicular to the inclined side of the base. The bolt passes through the through hole and connects to the threaded hole at the bottom of the piezoelectric actuator (43). Two feedforward sensors (46) collect vibration feedforward signals in the x' and y' directions, respectively, and two feedback sensors (47) collect vibration feedback signals in the x' and y' directions, respectively.

[0010] The aforementioned six-degree-of-freedom piezoelectric active vibration isolation device for a refrigeration unit based on a three-point double-branch configuration has the following vibration isolation methods:

[0011] Starting with the piezoelectric actuator (43) on the three-point double-branch left support (44) with its opening facing the negative x-axis, six piezoelectric actuators (43) are sequentially designated as the first to sixth piezoelectric actuators in a clockwise direction. The vibration isolation device drives the first to sixth piezoelectric actuators to output displacement responses of different magnitudes through an external controller, compensating for the vibration of the refrigerator in the three translational degrees of freedom along the x, y, and z axes and the three rotational degrees of freedom around the x, y, and z axes. Through the above method, the vibration isolation device effectively attenuates the vibration amplitude transmitted from the refrigerator (1) to the base platform (3).

[0012] The aforementioned six-degree-of-freedom piezoelectric active vibration isolation device for a refrigerator based on a three-point double-branch configuration has the following control method:

[0013] Six feedforward sensors (46) are installed on two orthogonal planes below the three-point double-branch connector (41) to collect feedforward signals; six feedback sensors (46) are installed on the left support (44) and right support (45) of the three-point double-branch connector to collect feedback signals; the vibration isolation device processes the feedforward and feedback signals through an external controller and calculates the control signal to drive the piezoelectric actuator (43) on the corresponding support to output displacement response. For the first to sixth piezoelectric actuators, taking the first piezoelectric actuator as an example, the specific control method is as follows:

[0014] Step 1), signal acquisition; the original vibration of the refrigerator (1) during operation is transmitted to the three-point double-branch connector (41), and the feedforward sensor (46) collects the feedforward signal and inputs it into the external controller;

[0015] Step 2), vibration isolation; the external controller inputs the feedforward signal into the identified control channel frequency response function, generates the Filtered-x signal for subsequent signal optimization, and simultaneously inputs the feedforward signal into the adaptive filter to calculate the control signal; the first piezoelectric actuator generates a displacement response under the drive of the control signal to compensate for the original vibration; the feedback sensor (47) senses the residual vibration of the support and collects the feedback signal to input into the external controller;

[0016] Step 3), signal optimization; the Fx-LMS algorithm dynamically adjusts the adaptive filter weight coefficients based on the feedback signal, with the goal of minimizing residual vibration energy, and corrects the phase error based on the Filtered-x signal to optimize the control signal, so that the amplitude, frequency and phase of the piezoelectric actuator displacement response are consistent with the original vibration, thus achieving accurate compensation. The optimized control signal drives the first piezoelectric actuator to generate a new displacement response to compensate for the original vibration. The feedback sensor (47) senses the residual vibration and generates a new feedback signal to input the iterative loop, forming a complete closed loop of vibration isolation, acquisition, optimization and vibration isolation;

[0017] The aforementioned six-degree-of-freedom piezoelectric active vibration isolation device for a refrigerator based on a three-point double-branch configuration controls six piezoelectric actuators (43) to generate displacement responses along the x, y, and z axes (three translational degrees of freedom) and around the x, y, and z axes (three rotational degrees of freedom) to compensate for the original vibration of the refrigerator and achieve active vibration isolation.

[0018] Compared with the prior art, the above technical solutions of the present invention have the following technical effects:

[0019] 1. This invention is based on a three-point double-branch configuration design for an active vibration isolation device, which drives multiple piezoelectric actuators in a coordinated manner to achieve a six-degree-of-freedom displacement response and effectively attenuate the complex six-degree-of-freedom vibrations generated by the refrigerator.

[0020] 2. This invention adopts the piezoelectric active vibration isolation principle to solve the problem of insufficient low-frequency performance of traditional passive vibration isolation technology, and has the characteristics of fast response and high precision;

[0021] 3. This invention uses a piezoelectric actuator to actively compensate for the vibration of the refrigeration unit, which has a certain anti-interference capability in complex electromagnetic environments and effectively improves the reliability of the vibration isolation device; Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the present invention;

[0023] Figure 2 This is a schematic diagram of the positional distribution of the three-point double-branched structure in this invention;

[0024] Figure 3 This is a schematic diagram of the three-point double-branch structure in this invention;

[0025] Figure 4 This is a bottom schematic diagram of the three-point double-branched chain in this invention;

[0026] Figure 5 This is a schematic diagram of the three-point double-branch connector in this invention;

[0027] Figure 6 This is a schematic diagram of the three-point double-branch flexible hinge in this invention;

[0028] Figure 7 This is a cross-sectional view of the three-point double-branch piezoelectric actuator in this invention;

[0029] Figure 8 This is a schematic diagram of the left and right supports of the three-point double-branched chain in this invention;

[0030] Figure 9 This is a schematic diagram of displacement compensation when the refrigeration unit vibrates along the x-direction.

[0031] Figure 10 This is a schematic diagram of displacement compensation when the refrigeration unit vibrates along the y-direction.

[0032] Figure 11 This is a schematic diagram of displacement compensation when the refrigeration unit vibrates along the z-direction.

[0033] Figure 12 This is a schematic diagram of displacement compensation when the refrigeration unit vibrates and rotates around the x-direction;

[0034] Figure 13 This is a schematic diagram of displacement compensation when a refrigeration unit vibrates and rotates around the y-direction;

[0035] Figure 14 This is a schematic diagram of displacement compensation when the refrigeration unit vibrates and rotates around the z-direction;

[0036] Figure 15 This is the control route diagram of the present invention;

[0037] In the diagram, the following coordinates are marked: Oxyz - global coordinate system, Ox'y'z' - local coordinate system, 1 - refrigerator, 2 - refrigerator mounting platform, 3 - base platform, 4 - three-point double-branch, 41 - connector, 42 - flexible hinge, 43 - piezoelectric actuator, 44 - left support, 45 - right support, 46 - feedforward sensor, 47 - feedback sensor. Detailed Implementation

[0038] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings:

[0039] 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.

[0040] like Figure 1 , Figure 2 As shown, a six-degree-of-freedom piezoelectric active vibration isolation device for a refrigerator based on a three-point double-branch configuration includes a refrigerator (1), a refrigerator mounting platform (2), a base platform (3), and three three-point double-branch (4) arranged in a triangular array between the two platforms.

[0041] The refrigerator (1) is bolted to the refrigerator mounting platform (2) through the bottom through hole; the top surface of the refrigerator mounting platform (2) and the bottom surface of the base platform (3) are both provided with countersunk holes for connecting three-point double branches (4); the three three-point double branches (4) are arranged in a triangular array between the refrigerator mounting platform (2) and the base platform (3), with the opening direction of the three-point double branches facing outward, connected to the refrigerator mounting platform (2) through the top threaded hole, and fixed to the base platform (3) through the bottom threaded hole; the origin of the coordinate system Oxyz is the upper left corner vertex of the base platform (3), the x-axis and y-axis are along the edge direction of the base platform (3), and the z-axis is along the normal direction of the upper plane of the base platform (3).

[0042] like Figure 3 , Figure 4As shown, the three-point double-branch (4) consists of a connector (41), two Hooke flexures (42), two piezoelectric actuators (43), a left support (44), a right support (45), two feedforward sensors (46), and two feedback sensors (47); the z' axis of the coordinate system Ox'y'z' forms a 60° angle with the horizontal plane and is obliquely upward, and the x' axis and y' axis are symmetrical about the vertical plane passing through the z' axis; the top surface of the connector (41) is parallel to the horizontal plane, and the two bottom planes are orthogonal to each other and perpendicular to the x' axis and y' axis, respectively. The left support (44) has a sloping side perpendicular to the x' axis and parallel to the bottom left plane of the connector (41). The right support (45) has a sloping side perpendicular to the y' axis and parallel to the bottom right plane of the connector (41). The center lines of the piezoelectric actuator (43) and the Hooke flexure (42) on the left and right supports are parallel to the x' axis and the y' axis, respectively, and are connected by threads. Two feedforward sensors (46) are set on the two orthogonal planes at the bottom of the connector, and two feedback sensors (47) are set on the sloping sides of the left support (44) and the right support (45).

[0043] The connector (41) has three threaded holes on its top surface for connecting to the refrigeration unit mounting platform (2), and two threaded holes on its bottom orthogonal planes for connecting to the Hooke flexible actuator (42). The Hooke flexible actuator (42) is cylindrical in shape. The stud at the top of the cylinder is connected to the threaded hole at the bottom of the connector (41). The cylinder has grooves cut on its side. The grooves can reduce the radial stiffness of the flexible actuator, so that the flexible actuator can produce small deformations under radial force and torque, compensate for the movement gap, and improve the displacement response accuracy of the piezoelectric actuator (43). The piezoelectric actuator (43) is connected to the threaded hole at the bottom of the Hooke flexible actuator (42) through its output end. The actuator contains a piezoelectric stack and a disc spring. The disc spring applies a preload to the piezoelectric stack. The piezoelectric stack is polarized from the d direction. 33 The device is composed of stacked multilayer piezoelectric ceramic sheets. Under voltage signal excitation, it can generate expansion and contraction deformation through the inverse piezoelectric effect, driving the piezoelectric actuator (43) to output a displacement response with corresponding amplitude and frequency in the x' or y' direction. The left support (44) and the right support (45) have through holes at the bottom apex. The center line of the through hole is perpendicular to the inclined side of the base. The bolt passes through the through hole and connects to the threaded hole at the bottom of the piezoelectric actuator (43). Two feedforward sensors (46) collect vibration feedforward signals in the x' and y' directions, respectively, and two feedback sensors (47) collect vibration feedback signals in the x' and y' directions, respectively.

[0044] The aforementioned six-degree-of-freedom piezoelectric active vibration isolation device for a refrigeration unit based on a three-point double-branch configuration has the following vibration isolation methods:

[0045] Starting with the piezoelectric actuator (43) on the three-point double-branch left support (44) with its opening facing the negative x-axis, six piezoelectric actuators (43) are sequentially designated as the first to sixth piezoelectric actuators in a clockwise direction. The vibration isolation device drives the first to sixth piezoelectric actuators to output different displacement responses through an external controller, compensating for the vibration of the refrigerator in the three translational degrees of freedom along the x, y, and z axes and the three rotational degrees of freedom around the x, y, and z axes. Through the above method, the vibration isolation device effectively attenuates the vibration amplitude transmitted from the refrigerator (1) to the base platform (3). The specific vibration isolation method is as follows:

[0046] like Figure 9 As shown, when the refrigerator generates a unit vibration along the x-direction of translation, the magnitudes of the output displacements of the first to sixth piezoelectric actuators are -0.3534, -0.3534, -0.4405, 0.7927, 0.7927, and -0.4405, respectively, thereby generating a unit displacement response along the x-direction of translation to compensate for the vibration of the refrigerator. The negative sign indicates that the direction of the actuator output displacement is opposite.

[0047] like Figure 10 As shown, when the refrigerator generates a unit vibration along the y-direction, the magnitudes of the output displacements of the first to sixth piezoelectric actuators are 0.7903, -0.7903, -0.6595, 0.0555, -0.0555, and 0.6595, respectively, thereby generating a unit displacement response along the y-direction to compensate for the refrigerator vibration. The negative sign indicates that the direction of the actuator output displacement is opposite.

[0048] like Figure 11 As shown, when the refrigerator generates a unit vibration along the z-direction, the magnitudes of the output displacements of the first to sixth piezoelectric actuators are 0.6103, 0.6103, 0.6092, 0.6073, 0.6073, and 0.6092, respectively, thereby generating a unit displacement response along the z-direction to compensate for the refrigerator vibration. The negative sign indicates that the direction of the actuator output displacement is opposite.

[0049] like Figure 12 As shown, when the refrigerator generates a unit vibration about the x-direction, the magnitudes of the output displacements of the first to sixth piezoelectric actuators are -0.2114, 0.2114, 0.8928, 0.6803, -0.6803, and -0.8928, respectively, thereby generating a unit displacement response to compensate for the refrigerator vibration about the x-direction. The negative sign indicates that the direction of the actuator output displacement is opposite.

[0050] like Figure 13As shown, when the refrigerator generates a unit vibration about the y-direction, the magnitudes of the output displacements of the first to sixth piezoelectric actuators are -0.9103, -0.9103, 0.2706, 0.6342, 0.6342, and 0.2706, respectively, thereby generating a unit displacement response about the y-direction to compensate for the refrigerator vibration. The negative sign indicates that the direction of the actuator output displacement is opposite.

[0051] like Figure 14 As shown, when the refrigerator generates a unit vibration about the z-axis, the magnitudes of the output displacements of the first to sixth piezoelectric actuators are 0.9350, -0.9350, 0.9386, -0.9456, 0.9456, and -0.9386, respectively, thereby generating a unit displacement response about the z-axis to compensate for the refrigerator vibration. The negative sign indicates that the direction of the actuator output displacement is opposite.

[0052] The aforementioned six-degree-of-freedom piezoelectric active vibration isolation device for a refrigerator based on a three-point double-branch configuration has the following control method:

[0053] Six feedforward sensors (46) are installed on two orthogonal planes below the three-point double-branch connector (41) to collect feedforward signals; six feedback sensors (46) are installed on the left support (44) and right support (45) of the three-point double-branch connector to collect feedback signals; the vibration isolation device processes the feedforward and feedback signals through an external controller and calculates the control signal to drive the piezoelectric actuator (43) on the corresponding support to output displacement response. For the first to sixth piezoelectric actuators, taking the first piezoelectric actuator as an example, the specific control method is as follows:

[0054] like Figure 15 As shown, X(n) is the feedforward signal, W(z) is the adaptive filter in the external controller, u(n) is the control signal, H(z) is the frequency response function of the control channel, i.e., the frequency response function of the piezoelectric actuator, y(n) is the displacement response of the piezoelectric actuator output, and δ d (n) represents the original vibration of the refrigerator, e(n) is the feedback signal, Ĥ(z) is the identified frequency response function of the control channel, v(n) is the filtered-x signal, and Fx-LMS is the adaptive control algorithm.

[0055] Step 1), signal acquisition; original vibration δ of the refrigerator (1) during operation d1 (n) is transmitted to the three-point double-branch connector (41), and the feedforward sensor (46) collects the feedforward signal X1(n) and inputs it into the external controller;

[0056] Step 2), vibration isolation; the external controller inputs the feedforward signal X1(n) into the identified control channel frequency response function Ĥ1(z), generating a filtered-x signal v1(n) for subsequent signal optimization, and simultaneously inputs the feedforward signal X1(n) into the adaptive filter W1(z) to calculate the control signal u1(n); the first piezoelectric actuator H1(z) generates a displacement response y1(n) under the drive of the control signal, which is related to the original vibration δ d1 (n) performs compensation; the feedback sensor (47) senses the residual vibration of the support and collects the feedback signal e1(n) and inputs it into the external controller;

[0057] Step 3), signal optimization: The Fx-LMS algorithm dynamically adjusts the weight coefficients of the adaptive filter W1(z) based on the feedback signal e1(n), with the goal of minimizing residual vibration energy. It also corrects the phase error based on the filtered-x signal v1(n) and optimizes the control signal u1(n) so that the amplitude, frequency, and phase of the piezoelectric actuator displacement response y1(n) are consistent with the original vibration δ. d1 (n) Maintain consistency to achieve precise compensation. The optimized control signal drives the first piezoelectric actuator to generate a new displacement response to compensate for the original vibration. The feedback sensor (47) senses the residual vibration and generates a new feedback signal to input the iterative cycle, forming a complete closed loop of vibration isolation, acquisition, optimization, and vibration isolation.

[0058] The aforementioned six-degree-of-freedom piezoelectric active vibration isolation device for a refrigerator based on a three-point double-branch configuration controls six piezoelectric actuators (43) to generate displacement responses along the x, y, and z axes (three translational degrees of freedom) and around the x, y, and z axes (three rotational degrees of freedom) to compensate for the original vibration of the refrigerator and achieve active vibration isolation.

Claims

1. A six-degree-of-freedom piezoelectric active vibration isolation device for a refrigerator based on a three-point double-branch configuration, characterized in that: It includes a refrigeration unit (1), a refrigeration unit mounting platform (2), a base platform (3), and three three-point double-branched chains (4) arranged in a triangular array between the two platforms.

2. The six-degree-of-freedom piezoelectric active vibration isolation device for a refrigerator based on a three-point double-branch configuration according to claim 1, characterized in that: The refrigerator (1) is bolted to the refrigerator mounting platform (2) through the bottom through hole; the top surface of the refrigerator mounting platform (2) and the bottom surface of the base platform (3) are both provided with countersunk holes for connecting three-point double chains (4); the three three-point double chains (4) are arranged in a triangular array between the refrigerator mounting platform (2) and the base platform (3), the opening direction of the three-point double chains is outward, they are connected to the refrigerator mounting platform (2) through the top threaded hole, and fixed to the base platform (3) through the bottom threaded hole; the origin of the coordinate system Oxyz is the upper left corner vertex of the base platform (3), the x-axis and y-axis are along the edge direction of the base platform (3), and the z-axis is along the normal direction of the upper plane of the base platform (3); The three-point double-branch (4) consists of a connector (41), two Hooke flexures (42), two piezoelectric actuators (43), a left support (44), a right support (45), two feedforward sensors (46), and two feedback sensors (47); the z' axis of the coordinate system Ox'y'z' is inclined upward at a 60° angle to the horizontal plane, and the x' axis and y' axis are symmetrical about the vertical plane passing through the z' axis; the top surface of the connector (41) is parallel to the horizontal plane, and the two bottom planes are orthogonal to each other and perpendicular to the x' axis and y' axis respectively; The oblique side of the left support (44) is perpendicular to the x' axis and parallel to the bottom left plane of the connector (41). The oblique side of the right support (45) is perpendicular to the y' axis and parallel to the bottom right plane of the connector (41). The center lines of the piezoelectric actuator (43) and the Hooke flexure (42) on the left and right supports are parallel to the x' axis and the y' axis, respectively, and are connected by threads. Two feedforward sensors (46) are set on the two orthogonal planes at the bottom of the connector, and two feedback sensors (47) are set on the oblique sides of the left support (44) and the right support (45). The connector (41) has three threaded holes on its top surface for connecting to the refrigeration unit mounting platform (2), and two threaded holes on its bottom orthogonal planes for connecting to the Hooke flexible actuator (42). The Hooke flexible actuator (42) is cylindrical in shape. The stud at the top of the cylinder is connected to the threaded hole at the bottom of the connector (41). The cylinder has grooves cut on its side. The grooves can reduce the radial stiffness of the flexible actuator, so that the flexible actuator can produce small deformations under radial force and torque, compensate for the movement gap, and improve the displacement response accuracy of the piezoelectric actuator (43). The piezoelectric actuator (43) is connected to the threaded hole at the bottom of the Hooke flexible actuator (42) through its output end. The actuator contains a piezoelectric stack and a disc spring. The disc spring applies a preload to the piezoelectric stack. The piezoelectric stack is polarized from the d direction. 33 The device is composed of stacked multilayer piezoelectric ceramic sheets. Under voltage signal excitation, it can generate expansion and contraction deformation through the inverse piezoelectric effect, driving the piezoelectric actuator (43) to output a displacement response with corresponding amplitude and frequency in the x' or y' direction. The left support (44) and the right support (45) have through holes at the bottom apex. The center line of the through hole is perpendicular to the inclined side of the base. The bolt passes through the through hole and connects to the threaded hole at the bottom of the piezoelectric actuator (43). Two feedforward sensors (46) collect vibration feedforward signals in the x' and y' directions, respectively, and two feedback sensors (47) collect vibration feedback signals in the x' and y' directions, respectively.

3. The working method of a six-degree-of-freedom piezoelectric active vibration isolation device for a refrigerator based on a three-point double-branch configuration according to claim 1, characterized in that, The following vibration isolation methods are available: Starting with the piezoelectric actuator (43) on the left support (44) of the three-point double-branch type with the opening facing the negative x-axis, six piezoelectric actuators (43) are sequentially designated as the first to sixth piezoelectric actuators in a clockwise direction. The vibration isolation device drives the first to sixth piezoelectric actuators to output displacement responses of different magnitudes through an external controller, and performs displacement compensation for the vibration of the refrigerator in the three translational degrees of freedom along the x, y, and z axes and the three rotational degrees of freedom around the x, y, and z axes. The vibration isolation device effectively attenuates the vibration amplitude transmitted from the refrigeration unit (1) to the base platform (3) through the above method.

4. The working method of a six-degree-of-freedom piezoelectric active vibration isolation device for a refrigerator based on a three-point double-branch configuration according to claim 1, characterized in that, It has the following control methods: Six feedforward sensors (46) are installed on two orthogonal planes below the three-point double-branch connector (41) to collect feedforward signals; six feedback sensors (46) are installed on the left support (44) and right support (45) of the three-point double-branch connector to collect feedback signals; the vibration isolation device processes the feedforward and feedback signals through an external controller and calculates the control signal to drive the piezoelectric actuator (43) on the corresponding support to output displacement response. For the first to sixth piezoelectric actuators, taking the first piezoelectric actuator as an example, the specific control method is as follows: Step 1), signal acquisition; the original vibration of the refrigerator (1) during operation is transmitted to the three-point double-branch connector (41), and the feedforward sensor (46) collects the feedforward signal and inputs it into the external controller; Step 2), vibration isolation; the external controller inputs the feedforward signal into the identified control channel frequency response function, generates the Filtered-x signal for subsequent signal optimization, and simultaneously inputs the feedforward signal into the adaptive filter to calculate the control signal; the first piezoelectric actuator generates a displacement response under the drive of the control signal to compensate for the original vibration; the feedback sensor (47) senses the residual vibration of the support and collects the feedback signal to input into the external controller; Step 3), signal optimization; the Fx-LMS algorithm dynamically adjusts the adaptive filter weight coefficients based on the feedback signal, with the goal of minimizing residual vibration energy, and corrects the phase error based on the Filtered-x signal to optimize the control signal, so that the amplitude, frequency and phase of the piezoelectric actuator displacement response are consistent with the original vibration, thus achieving accurate compensation. The optimized control signal drives the first piezoelectric actuator to generate a new displacement response to compensate for the original vibration. The feedback sensor (47) senses the residual vibration and generates a new feedback signal to input the iterative loop, forming a complete closed loop of vibration isolation, acquisition, optimization and vibration isolation; The aforementioned six-degree-of-freedom piezoelectric active vibration isolation device for a refrigerator based on a three-point double-branch configuration controls six piezoelectric actuators (43) to generate displacement responses along the x, y, and z axes (three translational degrees of freedom) and around the x, y, and z axes (three rotational degrees of freedom) to compensate for the original vibration of the refrigerator and achieve active vibration isolation.

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