Piezoelectric Stick-Slip Drive for High-Resolution Positioning
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Solution Overview
Problem
Existing stick-slip drives in linear or rotary positioning devices suffer from disruptive backlash, vibrations, and limited precision due to incomplete forced slip between friction members, leading to alternating speed and increased vibrations, especially at small step sizes, which hinder high-precision positioning.
Innovation Solution
A drive system comprising two piezoelectric or electrostrictive actuator groups with a common electrical control signal, including an inertia drive signal portion with varying gradients and a semi-static scan signal portion, allowing for non-resonant linear or rotary positioning by alternatingly applying sawtooth voltage waveforms to achieve both macroscopic and microscopic movements without enlarging the actuator or increasing its stroke, thereby reducing vibrations and enhancing precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the step size is reduced to achieve higher positioning precision, then the positioning resolution is improved, but the backlash and vibrations increase disrupting the uniform movement
Solution Approach 1:
The patent applies periodic stick-slip cycles with alternating flat and steep signal edges to achieve controlled movement. The periodic activation and deactivation of the friction member creates regular stick-slip phases that enable precise positioning while minimizing disruptive backlash through controlled periodic motion rather than continuous movement
Solution Approach 2:
The patent dynamically adjusts the signal waveform characteristics (flat edge duration, steep edge slope) to optimize the stick-slip behavior. By making the friction member dynamically capable of entraining the runner during stick phase and allowing controlled slip during slip phase, the system adapts to achieve uniform movement at small step sizes without excessive backlash
2Length of moving object
If the actuator stroke is increased to enlarge the scanning range, then the working range is expanded, but the actuator mass and capacity increase making it more difficult to drive and causing greater vibrations
Solution Approach 1:
The patent segments the positioning task into multiple small stick-slip steps rather than using a single large actuator stroke. By accumulating many small precise steps to achieve the desired scanning range, the system avoids the need for a large-stroke actuator that would have greater mass and generate more vibrations, thus expanding scanning range without increasing actuator size
Solution Approach 2:
The patent transitions from a single-dimension approach (large actuator stroke) to a multi-dimensional approach by combining temporal dimension (multiple sequential stick-slip cycles) with spatial dimension (accumulated small steps). This allows achieving large scanning ranges through many small steps over time rather than requiring a physically large actuator stroke
3Force
If the actuator mass is increased to provide greater force for overcoming friction, then the driving force is improved, but the inertia increases leading to greater vibrations and slower response
Solution Approach 1:
The patent uses periodic stick-slip cycles where the actuator is only actively driven during the stick phase, and the runner coasts during the slip phase. This periodic operation allows using a lightweight actuator that provides sufficient force during the active stick phase, while the periodic nature of the cycles prevents continuous vibration and allows the system to settle between cycles
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 provides a larger scanning range with reduced vibrations and improved precision, allowing for high-resolution positioning without the need for larger actuators or increased mass, thus overcoming the limitations of traditional stick-slip drives in achieving uniform movement and minimizing unwanted oscillations.
Implementation Method 1
a first piezoelectric or electrostrictive actuator group (42), each consisting of at least one actuator (D)... a second piezoelectric or electrostrictive actuator group (44), each consisting of at least one actuator
Implementation Method 2
a first piezoelectric or electrostrictive actuator group (42), each consisting of at least one actuator (D)... a second piezoelectric or electrostrictive actuator group (44), each consisting of at least one actuator
Implementation Method 3
the friction member fixed to the actuator entrains the runner... When the steep edge is active, slip occurs between the friction member and the runner
Data Source
AI summary
The disclosure relates to a drive means for non-resonant linear and/or rotary positioning of an object, comprising at least two piezoelectric or electrostrictive actuator groups, where-in a first actuator group moves a first runner portion relative to a stationary base of the drive means according to the principle of an inertia drive, and by means of the second actuator group a second runner portion is moved relative to the first runner portion with a limited range of movement in the high-resolution scan mode, wherein a common electrical control signal is applied to the first and second actuator groups.