High precision fixture for high temperature fatigue testing machine
By integrating multi-physical quantity sensing and active thermal management, the high-precision fixture solves the positioning accuracy and stability problems of the high-temperature fatigue testing machine fixture, achieving nanometer-level positioning accuracy and high-stability clamping force control, and possessing millisecond-level dynamic response capability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- 广州特种设备检测研究院(广州市特种设备事故调查技术中心广州市电梯安全运行监控中心)
- Filing Date
- 2025-08-15
- Publication Date
- 2026-08-04
AI Technical Summary
The existing high-temperature fatigue testing machine fixtures have problems with low positioning accuracy and poor stability in high-temperature environments. This is mainly due to the nonlinearity and temperature drift effect of the piezoelectric ceramic actuator, as well as the lack of multi-physical quantity sensing and high dynamic response characteristics.
A high-precision fixture integrating multiple physical quantity sensors was designed, including temperature, force, and displacement sensing units. Combined with a piezoelectric ceramic actuator, a flexible transition block and an active thermal management module are used to construct a closed-loop feedback structure to achieve comprehensive compensation for thermal deformation and nonlinear errors.
It achieves nanometer-level positioning accuracy and highly stable clamping force control, possesses millisecond-level dynamic response capability, and can maintain high reliability and high precision in complex environments.
Smart Images
Figure CN224594332U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of fixture technology for high-temperature fatigue testing machines, and in particular to a high-precision fixture for high-temperature fatigue testing machines. Background Technology
[0002] In fields such as high-temperature fatigue testing machines, the clamping stability and accuracy of workpieces play a decisive role in the final machining quality. Traditional mechanical, hydraulic, or pneumatic clamps suffer from slow response speed, low clamping force control accuracy, and complex structure, making it difficult to meet the needs of submicron or even nanometer-level machining.
[0003] To achieve high-precision positioning, piezoelectric ceramic actuators (PCEs) have been introduced into precision fixture design due to their advantages such as high resolution, large output force, and fast response. However, the inherent hysteresis, creep, and nonlinear effects of piezoelectric ceramic materials cause a severe nonlinear relationship between their output displacement and driving voltage, making it impossible to guarantee positioning accuracy under open-loop control.
[0004] Furthermore, during high-temperature fatigue testing, changes in ambient temperature and the heating of the fixture's drive components can cause thermal expansion and contraction of the fixture and workpiece, a phenomenon known as "temperature drift." This thermal deformation directly alters the workpiece's positioning reference and clamping state, and is one of the main sources of machining errors.
[0005] Existing technologies often only compensate for the nonlinearity or single temperature drift problem of piezoelectric actuators, lacking a high-precision fixture structure capable of simultaneously sensing multiple key physical quantities such as temperature, force, and displacement. This results in limited stability and accuracy in high-temperature environments. Therefore, there is an urgent need to develop a novel high-precision fixture for high-temperature fatigue testing machines that integrates multi-physical quantity sensing and high dynamic response characteristics. Utility Model Content
[0006] The present invention aims to at least solve the technical problems existing in the prior art. To this end, the present invention proposes a high-precision fixture for a high-temperature fatigue testing machine, which integrates multiple physical quantity sensors and has high dynamic response characteristics.
[0007] A high-precision fixture for a high-temperature fatigue testing machine according to an embodiment of the present invention includes:
[0008] The clamping body includes a movable clamping block for clamping a workpiece, wherein the movable clamping block has a preset deep hole on the clamping surface near the workpiece.
[0009] A drive execution module is installed on the side of the movable clamping block away from the workpiece, and is used to drive the movable clamping block to produce micro-displacement. The drive execution module includes a piezoelectric ceramic actuator.
[0010] A multi-physical quantity sensing system is electrically connected to the drive execution module. The multi-physical quantity sensing system includes a temperature sensing unit, a force sensing unit, and a displacement sensing unit. The temperature sensing unit is embedded in the preset deep hole, and the opening of the preset deep hole has an epoxy resin layer to seal the opening. The force sensing unit is connected in series between the piezoelectric ceramic actuator and the movable clamping block to measure the actual clamping force of the movable clamping block on the workpiece. The displacement sensing unit is configured to measure the actual displacement of the movable clamping block in a non-contact manner.
[0011] A flexible transition block is disposed between the force sensing unit and the movable clamping block to transmit the output displacement of the piezoelectric ceramic actuator.
[0012] In some embodiments, the temperature sensing unit is an optical fiber temperature sensor, and the aperture of the preset deep hole is in the range of 1.5mm-2.0mm.
[0013] In some embodiments, the movable clamping block has an observation window on its side wall for the displacement sensing unit to pass through the optical path, and the displacement sensing unit is a laser displacement sensor.
[0014] In some embodiments, the flexible transition block is made of beryllium bronze or elastic steel and transmits and guides motion through its own elastic deformation.
[0015] In some embodiments, the drive actuation module further includes a preload application mechanism connected in series with the piezoelectric ceramic actuator, the preload application mechanism being a set of disc springs.
[0016] In some embodiments, an active thermal management module is also included. The active thermal management module is physically attached to the outer surface of the movable clamping block and electrically connected to the temperature sensing unit. The active thermal management module is used to actively adjust the temperature of the movable clamping block according to the signal from the temperature sensing unit.
[0017] In some embodiments, the active thermal management module is one or more semiconductor refrigeration chips.
[0018] In some embodiments, an electromagnetic shielding structure is also included, which is a metal braided mesh or metal foil layer wrapped around the signal transmission cable of the multi-physical quantity sensing system, and the electromagnetic shielding structure is grounded.
[0019] In some embodiments, a vibration damping base is further included, and the clamping body is mounted on the vibration damping base by a high-damping elastomer.
[0020] The high-precision fixture for a high-temperature fatigue testing machine according to the embodiments of the present invention has at least the following beneficial effects:
[0021] 1. Comprehensive Compensation, Extremely High Precision: This device integrates sensing units for three key physical quantities—temperature, force, and displacement—and constructs a complete closed-loop feedback structure. It can acquire the real temperature of the clamping area, the actual clamping force, and the precise position of the grippers in real time. This allows for comprehensive compensation for errors caused by various factors such as thermal drift, piezoelectric nonlinearity, and external force disturbances, achieving nanometer-level positioning accuracy and highly stable clamping force control.
[0022] 2. Active Temperature Control, High Stability: This device innovatively incorporates an active thermal management module (such as a semiconductor cooling chip). Compared to traditional technologies that passively measure temperature and perform post-event compensation, this device actively stabilizes the temperature of the clamping block at a set value, suppressing thermal deformation at its source. This shift from "passive compensation" to "active stabilization" significantly improves the device's thermal stability under long-term, variable operating conditions.
[0023] 3. Optimized structure and excellent dynamic performance: The use of a flexible transition block, utilizing its frictionless and gapless characteristics, ensures the precise and efficient transmission of minute displacements by the piezoelectric actuator. Combined with the high-speed response characteristics of the piezoelectric actuator itself, the entire clamping device possesses millisecond-level dynamic response capabilities.
[0024] Strong anti-interference capability and high reliability: By adding an electromagnetic shielding structure and a vibration-damping base, electromagnetic interference from the drive circuit and mechanical vibration from the external environment are effectively isolated. This ensures the purity of the sensor signals and the accuracy of the measurement, enabling the entire system to maintain high reliability and high precision performance even in complex industrial environments.
[0025] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description
[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:
[0027] Figure 1 This is a schematic diagram of the structure of a high-precision fixture for a high-temperature fatigue testing machine according to some embodiments of the present invention;
[0028] Figure 2 This is a schematic diagram of the signal transmission logic of a high-precision fixture for a high-temperature fatigue testing machine according to some embodiments of the present invention.
[0029] Figure label:
[0030] Upper clamping body 1, lower clamping body 2, movable clamping block 3, piezoelectric ceramic actuator 4, temperature sensing unit 5, force sensing unit 6, displacement sensing unit 7, flexible transition block 8, pre-tightened disc spring assembly 9. Detailed Implementation
[0031] Reference Figure 1 Structural diagram and Figure 2 The schematic diagram illustrates a high-precision clamp for a high-temperature fatigue testing machine. The core design concept of this device is to construct a fully closed-loop feedback control structure based on piezoelectric drive, integrating real-time sensing of multiple physical quantities such as temperature, force, and displacement, supplemented by precision flexible transmission and multiple anti-interference designs. This addresses the fundamental problem of decreased clamping accuracy and stability caused by factors such as thermal drift, piezoelectric nonlinearity, and external force disturbances during high-temperature fatigue testing.
[0032] The device mainly includes the following physical structure: an upper clamping body 1, a lower clamping body 2 (which can be configured to have the same structure as the upper clamping body 1), a drive execution module (the core of which is a piezoelectric ceramic actuator 4 and a preload application mechanism), a multi-physical quantity sensing system (including a temperature sensing unit 5, a force sensing unit 6, and a displacement sensing unit 7), a flexible transition block 8, and a drive control circuit, as well as an active thermal management module, an electromagnetic shielding structure, and a vibration damping base as technical solutions in other embodiments.
[0033] The components will be described in detail below.
[0034] like Figure 1 As shown, the clamping body is the foundation for workpiece positioning and fixation, comprising two roughly L-shaped movable clamping blocks 3. The contact surfaces between the movable clamping blocks 3 and the workpiece require precision grinding, with flatness and roughness reaching the micron or even sub-micron level to ensure uniform and reliable contact. The drive execution module provides actuation power to the movable clamping blocks 3, providing precise driving force at the micron or even nanometer level. In this embodiment, the drive execution module uses a stacked piezoelectric ceramic actuator 4, which is composed of hundreds of layers of piezoelectric ceramic sheets stacked in parallel, capable of generating tens of micron-level elongation when a driving voltage of 0-10V or even higher is applied. Its core advantages lie in its fast response speed (down to sub-millisecond level), high resolution (theoretically infinitely small), and large output force. However, its inherent nonlinear characteristics such as hysteresis and creep are the main challenges that the closed-loop system of this device needs to overcome.
[0035] Furthermore, the preload application mechanism is a key structure for ensuring the long-term reliable operation of the piezoelectric ceramic actuator 4. The tensile strength of piezoelectric ceramic materials is much lower than their compressive strength; therefore, the piezoelectric ceramic actuator 4 is easily damaged under tensile force during dynamic operation. Thus, sufficient preload must be applied. This embodiment uses a set of preload disc springs 9 as the preload application mechanism. These springs are installed in series or parallel, providing a large and stable preload within a small space. During assembly, the preload disc springs 9, the piezoelectric ceramic actuator 4, the force sensing unit 6, and the flexible transition block 8 are placed together within a rigid frame. The disc springs are compressed by adjusting the preload bolts, ensuring that all components in the entire force transmission chain are always under pressure.
[0036] Multi-physical quantity sensing systems provide accurate and real-time status feedback for closed-loop control.
[0037] To capture the temperature that best reflects the true thermal state of the workpiece, temperature sensing unit 5 is equipped with a fiber optic temperature sensor. The probe of the fiber optic temperature sensor is inserted into a blind hole with a diameter of 1mm-2.0mm inside the movable clamping block 3. The depth of this blind hole is carefully designed so that its end is as close as possible to the clamping surface, while ensuring sufficient structural strength. Fiber optic sensors were chosen because they are small in size, do not generate heat themselves, and are completely unaffected by the strong electromagnetic field interference generated by the high-voltage drive circuit of the piezoelectric ceramic actuator 4. The opening of the blind hole is potted with high thermal conductivity and high-temperature resistant epoxy resin, which serves three purposes: first, to firmly fix the sensor to the bottom of the hole; second, to fill the air gap with thermally conductive adhesive to ensure that the heat of the clamping block can be efficiently and without delay transferred to the sensor probe; and third, to seal the opening to prevent the intrusion of external dust and other contaminants.
[0038] The force sensing unit 6 can be a high-precision strain gauge sensor, directly connected in series in the force output path of the piezoelectric ceramic actuator 4. This arrangement ensures that its measured value is the force actually applied to the workpiece (transmitted through the flexible transition block 8 and the clamping block), i.e., the actual clamping force F. actual This signal is the core feedback quantity for achieving constant force clamping or precise force control.
[0039] The displacement sensing unit 7 employs a non-contact laser displacement sensor. The laser displacement sensor is installed through a Φ5mm observation window on the side wall of the movable clamping block 3 to measure the distance to a precision-machined reflective reference surface on the outer side of the clamping block. This non-contact measurement method completely avoids interference and wear caused by the contact force of the probe on the micro-displacement system, enabling resolutions of 0.1μm or even higher. The design of the observation window ensures that the laser beam path is unobstructed, and its location is chosen to avoid stress concentration and heat source areas to obtain the most stable displacement readings.
[0040] The flexible transition block 8 in this embodiment is integrally formed from beryllium bronze material via wire cutting and is key to achieving ultra-precision motion transmission in this device. The design of the flexible transition block 8 utilizes the elastic deformation of the material. In its design, the structure along the direction of the driving force (such as the thick connecting portion) has extremely high rigidity, ensuring that the output displacement of the piezoelectric ceramic actuator 4 can be transmitted to the movable clamping block 3 with almost no loss. Compared to traditional ball bearing guides or sliders, the flexible transition block 8 has no friction or mechanical backlash, which is crucial for eliminating hysteresis and achieving nanometer-level precise positioning and reciprocating motion.
[0041] The drive control circuit is a physical hardware module, serving as the "brain" of the entire closed-loop system. It receives analog or digital signals from three sensors, processes and calculates them through internal hardware circuit logic, and ultimately outputs a high-voltage signal to drive the piezoelectric ceramic actuator 4. Internally, it implements control logic through operational amplifiers, comparators, filters, and dedicated analog compensation networks (such as analog PID circuits and hysteresis compensation circuits). For example, force and displacement signals can be compared with a reference voltage (representing the target force or displacement) in a differential amplifier. The resulting error signal, after amplification and compensation, directly drives a high-voltage power operational amplifier, ADA4870. The output of this operational amplifier is the drive voltage applied to the piezoelectric ceramic actuator 4.
[0042] For the active thermal management module, to achieve the leap from "passive temperature compensation" to "active temperature control," this embodiment tightly attaches one or more thermoelectric coolers to the non-working outer surface (such as the top) of the movable clamping block 3. The hot and cold surfaces of the thermoelectric coolers are connected to the clamping block and the heat sink via highly thermally conductive silicone grease. The drive control circuit includes a dedicated drive unit that receives signals from the temperature sensing unit 5, compares them with a precise temperature setpoint, and calculates the temperature difference. Based on this temperature difference, the drive unit precisely controls the magnitude and direction of the current flowing through the thermoelectric coolers, thereby achieving rapid cooling or heating of the clamping block and actively locking its temperature within a very small fluctuation range of the setpoint.
[0043] In practical applications, the high-frequency switching noise generated by the piezoelectric ceramic actuator driver can interfere with weak sensor signals. Therefore, all signal cables from the sensors to the drive control circuit use shielded coaxial cables or twisted pairs, with their metal braided shield reliably grounded at a single point on the circuit board, forming a Faraday cage, which effectively isolates electromagnetic interference. Simultaneously, to isolate the influence of mechanical vibrations from the machine tool and the ground on the nanometer-level positioning, the entire clamping body is mounted on a vibration-damping base made of polymer concrete or granite with high mass and high damping characteristics via four high-damping elastomers (such as neoprene pads).
[0044] The entire process of the device is as follows:
[0045] 1. Initialization: The system is powered on, the drive control circuit is set to the initial state, and the user sets the target clamping force or target displacement through the external interface.
[0046] Approach and clamping: The drive control circuit outputs a rising voltage to the piezoelectric ceramic actuator 4, causing it to extend and push the movable clamping block 3 toward the workpiece. During this process, the laser displacement sensor monitors its position in real time.
[0047] 2. Closed-loop steady-state control: When the force sensor reading reaches the target clamping force, the control system enters steady-state closed-loop mode. At this time, the core task of the drive control circuit is to continuously acquire the current operating temperature value T of the fixture. current Actual clamping force F actual The system receives three signals: actual clamping force, actual displacement, and actual clamping force, and maintains the actual clamping force (or actual displacement) constant at the set value.
[0048] 3. Dynamic Disturbance Compensation: In high-temperature fatigue tests, high temperatures cause thermal expansion of the workpiece and clamping block, resulting in a slight increase in the actual clamping force. The force sensor immediately detects this change, and the drive control circuit detects the error that the actual clamping force exceeds the target clamping force. It then instantaneously (within milliseconds) reduces the drive voltage of the piezoelectric ceramic actuator 4, causing it to retract slightly, thus offsetting the force increase caused by thermal expansion and ensuring the actual clamping force accurately returns to the target clamping force. Similarly, for any disturbances caused by temperature changes, such as elongation, creep, or external vibration of the piezoelectric ceramic actuator 4, the system compensates in real time through this high-speed closed-loop feedback mechanism, ensuring the ultimate stability of the clamping state.
[0049] The clamp of this utility model has the following technical effects:
[0050] 1. Comprehensive Compensation, Extremely High Precision: This device integrates sensing units for three key physical quantities—temperature, force, and displacement—and constructs a complete closed-loop feedback structure. The drive control circuit can acquire the real temperature of the clamping area, the actual clamping force, and the precise position of the grippers in real time. This allows for comprehensive compensation for errors caused by various factors such as thermal drift, piezoelectric nonlinearity, and external force disturbances, achieving nanometer-level positioning accuracy and highly stable clamping force control.
[0051] 2. Active Temperature Control, High Stability: This device innovatively incorporates an active thermal management module (such as a semiconductor cooling chip). Compared to traditional technologies that passively measure temperature and perform post-event compensation, this device actively stabilizes the temperature of the clamping block at a set value, suppressing thermal deformation at its source. This shift from "passive compensation" to "active stabilization" significantly improves the device's thermal stability under long-term, variable operating conditions.
[0052] 3. Optimized structure and excellent dynamic performance: The use of a flexible transition block, utilizing its frictionless and gapless characteristics, ensures the precise and efficient transmission of minute displacements by the piezoelectric actuator. Combined with the high-speed response characteristics of the piezoelectric actuator itself, the entire clamping device possesses millisecond-level dynamic response capabilities.
[0053] 4. Strong anti-interference capability and high reliability: By adding an electromagnetic shielding structure and a vibration-damping base, electromagnetic interference from the drive circuit and mechanical vibration from the external environment are effectively isolated. This ensures the purity of the sensor signals and the accuracy of the measurements, enabling the entire system to maintain high reliability and high precision performance even in complex industrial environments.
[0054] Examples of the embodiments described above are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described above with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.
[0055] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.
[0056] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. If "first" or "second" is used in the description, it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.
[0057] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.
[0058] The embodiments of the present utility model have been described in detail above with reference to the accompanying drawings. However, the present utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present utility model.
Claims
1. A high-precision clamp for a high-temperature fatigue testing machine, characterized by, include: The clamping body includes a movable clamping block for clamping a workpiece, wherein the movable clamping block has a preset deep hole on the clamping surface near the workpiece. A drive execution module is installed on the side of the movable clamping block away from the workpiece, and is used to drive the movable clamping block to produce micro-displacement. The drive execution module includes a piezoelectric ceramic actuator. A multi-physical quantity sensing system is electrically connected to the drive execution module. The multi-physical quantity sensing system includes a temperature sensing unit, a force sensing unit, and a displacement sensing unit. The temperature sensing unit is embedded in the preset deep hole, and the opening of the preset deep hole has an epoxy resin layer to seal the opening. The force sensing unit is connected in series between the piezoelectric ceramic actuator and the movable clamping block to measure the actual clamping force of the movable clamping block on the workpiece. The displacement sensing unit is configured to measure the actual displacement of the movable clamping block in a non-contact manner. A flexible transition block is disposed between the force sensing unit and the movable clamping block to transmit the output displacement of the piezoelectric ceramic actuator.
2. The high-precision jig for a high-temperature fatigue testing machine according to claim 1, characterized by The temperature sensing unit is an optical fiber temperature sensor, and the aperture of the preset deep hole is in the range of 1.5mm-2.0mm.
3. The high-precision clamp for a high-temperature fatigue testing machine according to claim 1, characterized by The movable clamping block has an observation window on its side wall for the displacement sensing unit to pass through the optical path. The displacement sensing unit is a laser displacement sensor.
4. The high-precision clamp for a high-temperature fatigue testing machine according to claim 1, characterized by The flexible transition block is made of beryllium bronze or elastic steel and transmits and guides motion through its own elastic deformation.
5. The high-precision clamp for a high-temperature fatigue testing machine according to claim 1, characterized by The drive execution module also includes a preload application mechanism connected in series with the piezoelectric ceramic actuator, which is a set of disc springs.
6. The high-precision clamp for a high-temperature fatigue testing machine according to claim 1, characterized by It also includes an active thermal management module, which is physically attached to the outer surface of the movable clamping block and electrically connected to the temperature sensing unit.
7. The high-precision clamp for a high-temperature fatigue testing machine according to claim 6, characterized by The active thermal management module is one or more semiconductor cooling chips.
8. The high precision clamp for a high temperature fatigue testing machine of claim 1, wherein, It also includes an electromagnetic shielding structure, which is a metal braided mesh or metal foil layer wrapped around the signal transmission cable of the multi-physical quantity sensing system, and the electromagnetic shielding structure is grounded.
9. The high precision clamp for a high temperature fatigue testing machine of claim 1, wherein, It also includes a vibration damping base, and the clamping body is mounted on the vibration damping base by a high-damping elastomer.