Piezo Actuator Pre-tightening with Capacitive Sensor
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Solution Overview
Problem
Existing precision-positioning systems, particularly those using piezoelectric ceramic actuators, face challenges in maintaining pre-tightening precision and stability due to undetectable pre-tightening displacement, lateral forces, and bending moments, especially during high-frequency motions, which affect the accuracy and stability of the actuator's output displacement.
Innovation Solution
A precision-positioning drive end pre-tightening device incorporating a two-stage pre-tightening mechanism with roller balls and jack screws for face and point contacts, coupled with a capacitive sensor and film force sensor to monitor and adjust pre-tightening forces, ensuring precise and stable displacement, and utilizing a reflective mirror and laser interferometer for precise displacement measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a wedge block mechanism is used for pre-tightening, then pre-tightening force can be applied to the piezoelectric ceramic actuator, but pre-tightening displacement cannot be detected and lateral forces and bending moments are produced
Solution Approach 1:
A capacitive sensor is introduced as an intermediary measurement device between the pre-tightening block and the actuator. The sensor non-contactively measures the displacement of the pre-tightening block, eliminating the need for mechanical contact that would produce lateral forces. The sensor bracket with connecting rods transmits only axial movement to the sensor while isolating lateral forces.
Solution Approach 2:
The patent replaces traditional mechanical displacement measurement methods (such as contact式 sensors or direct reading mechanisms) with a capacitive sensor system. This substitution eliminates mechanical friction and lateral forces while providing precise non-contact measurement of pre-tightening displacement.
2Object-affected harmful factors
If a fixing block with pressing screw is used, then lateral forces are avoided, but torque during rotation and inability to measure pre-tightening amount remain
Solution Approach 1:
The capacitive sensor acts as an intermediary that measures pre-tightening displacement without requiring rotational adjustment mechanisms. The sensor bracket system converts the linear movement of the pre-tightening block into a measurable capacitive change, eliminating the need for rotating screws and associated torque issues.
Solution Approach 2:
The capacitive sensor provides real-time feedback on the pre-tightening displacement, allowing the control system to monitor and maintain the desired pre-tightening amount. This feedback mechanism enables precise control without relying on open-loop mechanical adjustment methods.
3Force
If inclined face contact between wedge blocks is used, then pre-tightening force transmission is achieved, but manufacturing precision difficulties and undetermined force location occur
Solution Approach 1:
The patent replaces the inclined plane contact mechanism with a vertical pressing mechanism using a pre-tightening block with a horizontal pressing surface. This eliminates the need for precision-machined inclined faces and their associated manufacturing difficulties, while still achieving effective pre-tightening force transmission through the actuator.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution ensures sub-micrometer level stability and precision of pre-tightening, eliminates lateral forces and torque, and provides real-time feedback for maintaining accurate displacement, enhancing the overall precision and stability of the actuator's output displacement.
Implementation Method 1
a capacitive sensor 4, a capacitive sensor bracket 3... an end surface of the capacitive sensor 4 and an upper side surface of the pre-tightening block 12 are parallel to each other, and a gap exists therebetween
Implementation Method 2
a film force sensor 13... a two-stage pre-tightening device for pre-tightening the actuator 14 is also provided on said positioning platform 6
Implementation Method 3
A piezoelectric ceramic actuator has a sub-nanometer resolution and a millisecond response, and a larger driving force, linear motion range and stiffness etc.
Data Source
AI summary
Disclosed is a precision-positioning drive end pre-tightening device, which comprises a positioning platform (6), an actuator (14), a capacitive sensor (4), a capacitive sensor bracket (3), a pre-tightening block (12) and a film force sensor (13), wherein a sliding groove is provided in the middle of the positioning platform (6), and said pre-tightening block (12), said film force sensor (13) and said actuator (14) are provided in the sliding groove in sequence; the capacitive sensor bracket (3) is fixed on the positioning platform (6), and three connecting rods (3-1) which are connected in sequence via compliant hinges are axially provided at one end of the bracket body of the capacitive sensor bracket (3); an end surface of the capacitive sensor (4) and an upper side surface of the pre-tightening block (12) are parallel to each other, and a gap exists therebetween; and a two-stage pre-tightening device for pre-tightening the pre-tightening block (12) are also provided on the positioning platform (6). The technical means of the device is simple and easy, and the device can satisfy the requirements in related fields of precision positioning, precision and ultra-precision machining, precision operating, precision measurement, micro-electro-mechanical system, etc. for the precision-locating drive end pre-tightening device.