CN-121989029-A - Intelligent ultrasonic transducer pretightening force assembling equipment and method based on piezoelectric feedback

CN121989029ACN 121989029 ACN121989029 ACN 121989029ACN-121989029-A

Abstract

The invention discloses intelligent ultrasonic transducer pretightening force assembling equipment and method based on piezoelectric feedback, belongs to the technical field of intelligent manufacturing, and constructs a direct feedback closed-loop control system taking a piezoelectric ceramic crystal stack as a force sensing element. A multi-stage self-adaptive control strategy is adopted, idle stroke feeding is sequentially executed to quickly eliminate assembly gaps, an electrical seating point is accurately judged to serve as a loading starting point through synchronous monitoring of piezoelectric voltage and real-time torque, linear loading is carried out, torque rate is calculated in real time to monitor a process state, low-speed micro-progress is carried out when the piezoelectric voltage approaches a target value, finally hardware interruption is triggered at the moment that the voltage reaches a preset threshold value by a hardware comparator, millisecond-level scram is achieved by a drive control unit, and overshoot is eliminated fundamentally. The technical transition from indirect torque control to direct force feedback control is realized, the pretightening force control precision is improved, the consistency and the reliability of high-end ultrasonic transducer products are ensured, and the production efficiency is greatly improved.

Inventors

JU HUI
CHEN CHANGXU
ZHOU FENG
LI MINGAN

Assignees

善彤医疗科技(苏州)有限公司

Dates

Publication Date: 20260508
Application Date: 20260121

Claims (10)

1. Ultrasonic transducer pretightning force intelligence equipment based on piezoelectricity feedback, its characterized in that includes: The mechanical execution unit is used for applying a tightening torque to the pre-tightening bolt of the ultrasonic transducer; The piezoelectric signal acquisition unit is electrically connected with the piezoelectric ceramic crystal stack of the ultrasonic transducer and is used for acquiring an open-circuit voltage signal generated by the piezoelectric ceramic crystal stack due to axial pretightening force; The hardware comparison unit is connected with the piezoelectric signal acquisition unit and is used for comparing the open-circuit voltage signal with a preset reference voltage and generating a trigger signal when the open-circuit voltage signal is more than or equal to the reference voltage, wherein the reference voltage is set based on a target pretightening force value and the piezoelectric parameters of the piezoelectric ceramic crystal stack, and The control unit is respectively in communication connection with the hardware comparison unit and the mechanical execution unit and is used for controlling the mechanical execution unit to run and immediately controlling the mechanical execution unit to stop the current screwing action when responding to the trigger signal; the control unit is configured to control the machine execution unit to sequentially perform a lost motion feed operation at a first speed to eliminate an assembly gap, a linear loading operation at a second speed lower than the first speed until the open circuit voltage signal reaches a switching threshold, and a low speed jog operation (i.e., a motor rotation speed is reduced to a very low speed) at a third speed lower than the second speed, and to immediately control the machine execution unit to terminate a current tightening operation in response to a trigger signal generated by the hardware comparison unit during the low speed jog operation.
2. The intelligent ultrasonic transducer pretightening force assembling device based on piezoelectric feedback according to claim 1, wherein the control unit is configured with a hardware interrupt pin, and the trigger signal generated by the hardware comparing unit is directly connected to the hardware interrupt pin.
3. The intelligent ultrasonic transducer pretension assembling device based on piezoelectric feedback according to claim 1, wherein the piezoelectric signal acquisition unit comprises a voltage follower circuit with high input impedance.
4. The intelligent ultrasonic transducer pretightening force assembling device based on piezoelectric feedback according to claim 1, wherein the mechanical execution unit comprises a motor, a torque sensor and a corner encoder, and the control unit is further used for calculating a torque rate in a screwing process according to a signal of the corner encoder and a signal of the torque sensor and performing process state monitoring or fault diagnosis based on the torque rate.
5. An intelligent ultrasonic transducer pretightening force assembling method based on piezoelectric feedback, which is suitable for the intelligent ultrasonic transducer pretightening force assembling device based on piezoelectric feedback as set forth in any one of claims 1 to 4, and is characterized by comprising: Controlling the mechanical execution unit to rotate at a set first speed so as to quickly eliminate the assembly gap of the pretightening force bolt; Monitoring the open circuit voltage signal and the real-time tightening torque, and judging that the electric seating point is reached when the open circuit voltage signal exceeds a set noise voltage threshold value and the real-time tightening torque exceeds a set contact torque threshold value; A linear loading stage, wherein the mechanical execution unit is controlled to run at a second speed lower than the first speed, and a linearly-increased pretightening force is applied to the piezoelectric ceramic crystal stack; a low-speed micro-advancing stage, wherein when the open-circuit voltage signal reaches a preset switching threshold value, the mechanical executing unit is controlled to operate at a third speed lower than the second speed; And an interrupt triggering stage, namely responding to a triggering signal generated by the hardware comparison unit and controlling the mechanical execution unit to stop suddenly.
6. The method for assembling the intelligent ultrasonic transducer pretensioning force assembling apparatus based on piezoelectric feedback according to claim 5, further comprising, after the interrupt trigger phase: And the elastic compensation stage is to control the mechanical execution unit to reversely rotate by a preset compensation angle.
7. The method for assembling an intelligent ultrasonic transducer pretensioning force assembling apparatus based on piezoelectric feedback according to claim 6, wherein in the elastic compensation phase, the numerical variation of the open-circuit voltage signal is monitored simultaneously, and abnormality diagnosis is performed based on the variation.
8. The method for assembling the intelligent ultrasonic transducer pretightening force assembling device based on piezoelectric feedback according to claim 5, wherein in the sitting point detection stage, when it is determined that the electrical sitting point is reached, the current rotation angle position is recorded as a position control reference zero point.
9. The method for assembling an intelligent ultrasonic transducer pretensioning force assembling apparatus based on piezoelectric feedback according to claim 5, wherein in the linear loading stage, the torque rate is calculated in real time, and when the preset normal range is exceeded, an early warning or a protective shutdown operation is performed.
10. The method for assembling the intelligent ultrasonic transducer pretightening force assembling device based on piezoelectric feedback according to claim 5, wherein in the low-speed micro-advancing stage, the control unit stops software polling judgment of an open-circuit voltage signal, and turns to control the mechanical execution unit to stop suddenly in direct response to a trigger signal generated by the hardware comparison unit.

Description

Intelligent ultrasonic transducer pretightening force assembling equipment and method based on piezoelectric feedback Technical Field The invention relates to the technical field of intelligent manufacturing, in particular to ultrasonic transducer pretightening force intelligent assembly equipment and method based on piezoelectric feedback. Background Ultrasonic transducers serve as a core component of ultrasonic surgical equipment and serve the key function of converting electrical energy into mechanical vibrations. The performance and service life of the piezoelectric ceramic stack is greatly dependent on the axial pre-tightening force applied to the piezoelectric ceramic stack during assembly. And an accurate and stable pretightening force can ensure that the piezoelectric ceramic, the metal electrode and the structural member always keep close contact under high-speed vibration, thereby obtaining optimal energy transmission efficiency and working stability. Otherwise, insufficient pre-tightening force can directly lead to the increase of the electric shock resistance between the components, thereby causing abnormal heating and energy loss and seriously reducing the working efficiency of the transducer. And the excessive pretightening force can directly lead to the breakage of brittle piezoelectric ceramics, thereby causing the immediate failure of the whole transducer function and seriously affecting the reliability and safety of ultrasonic surgical equipment. Currently, the control of the pretightening force of an ultrasonic transducer in the industry mainly depends on the use of a manual torque wrench by an operator. This method indirectly desires to achieve the target preload by controlling the torque at which the bolt is tightened. However, the conversion relationship between torque and pretightening force is significantly affected by factors such as the friction coefficient of the thread pair and the supporting surface, and the factors have great variability in actual production due to machining tolerance, lubrication state and the like. This results in the eventual actual pretension force being generated, even with the same set torque applied, with deviations of up to twenty-five to thirty percent. The inherent precision defect not only ensures that the product quality highly depends on personal experience of operators, so that the consistency of different batches of products and even the same batch of products is extremely poor, and the mass production qualification rate and the mass production level of the high-end ultrasonic transducer are more seriously restricted. In order to improve the automation level of the assembly process, the prior art proposes some improvements. One of them is to integrate a dedicated pressure sensor and a micro motor inside the transducer, so that force control is realized by direct feedback of the sensor. However, the method places the sensor in the stress path of the core, and the rigidity, hysteresis and temperature drift characteristics of the sensor inevitably interfere with and deteriorate the high-frequency vibration performance of the transducer, thereby deviating from the original purpose of pursuing high-precision resonance performance and obviously increasing the complexity of the structure and the manufacturing cost. Another solution uses the physical characteristics of piezoelectric ceramics, namely, the oscilloscopes are used for observing the voltage changes generated at two ends of the piezoelectric ceramics during pre-tightening, and the piezoelectric ceramics are stopped manually when the voltage curve enters a nonlinear region. Although the method directly reflects the pretightening force state, the judgment of the pretightening force state completely depends on human eyes to observe and react, has hundreds of milliseconds of delay, cannot prevent inertial overshoot in a high-speed tightening stage, is basically unreliable open-loop control, and cannot realize high-precision automation in a true sense. Although theoretical research shows that the open-circuit voltage generated by the piezoelectric ceramic crystal stack when the piezoelectric ceramic crystal stack is compressed by the pretightening force has a definite linear proportional relation with the pretightening force, and a solid theoretical basis is provided for directly and accurately controlling the mechanical quantity through an electric signal. However, none of the prior art has translated this principle into a closed loop control system that enables real-time, automatic, fast response and has substantial overshoot prevention capability. The technical blank directly causes that the high-end ultrasonic transducer assembly process is difficult to break through the bottleneck in the aspects of precision, efficiency and consistency for a long time. Therefore, a brand new technical scheme is urgently needed in the field to fundamentally overcome the defects of the prior art, and high precis