Piezoelectric Hydraulic Actuator for Friction-Insensitive Linear Positioning
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Solution Overview
Problem
Existing linear actuators are not precise, resistant to contamination, and suffer from wear issues, particularly when static friction changes due to environmental factors like oil or dirt ingress, limiting their precision and functionality in adjustment tasks.
Innovation Solution
A hydraulic actuator device with two piston elements and piezoelectric control, where the force ratio between the piston elements allows for precise linear movement beyond the range of the piezoelectric actuator, using check valves and a restrictor element to manage fluid flow, independent of static friction, and encapsulating the moving parts to prevent contamination and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromagnetic linear actuators or spindle drives are used, then linear adjustments can be performed, but the devices are complex and not resistant to contamination and wear
Solution Approach 1:
The patent employs a hydraulic actuator consisting of a cylinder, piston, and working fluid to convert piezoelectric actuation into linear motion. The hydraulic system provides smooth, contamination-resistant operation without the mechanical complexity of electromagnetic actuators or spindle drives, directly resolving the contradiction between reliability and device complexity
Solution Approach 2:
The patent replaces traditional electromagnetic or mechanical linear actuators with a hybrid system combining piezoelectric actuation and hydraulic transmission. This substitution eliminates the need for complex electromagnetic components or mechanical spindles, achieving both simplicity and resistance to contamination while maintaining precise linear adjustment capability
2Length of moving object
If piezoelectric actuators operating on the caterpillar or inchworm principle are used for relatively large deflections, then larger movements can be achieved, but three actuators are generally required making the system complex
Solution Approach 1:
The hydraulic mechanism amplifies the piezoelectric element's limited displacement into larger linear movements of the piston rod. The incompressible working fluid transmits force efficiently, allowing a single piezoelectric actuator to achieve large deflections that would otherwise require multiple actuators, thereby reducing system complexity while extending range of motion
Solution Approach 2:
The hydraulic fluid acts as an intermediary between the piezoelectric element and the load, transforming the small, precise movements of the piezoelectric actuator into larger, controlled linear displacements. This intermediary mechanism enables large deflections with a single actuator element, avoiding the complexity of multiple actuators required in inchworm principles
3Device complexity
If a linear drive with clamping device and single actuator element is used, then the system is simpler, but the deflection depends on the magnitude of current static friction which changes due to oil or dirt ingress
Solution Approach 1:
The hydraulic system replaces friction-dependent mechanical clamping with fluid pressure transmission. The incompressible working fluid transmits force from the piezoelectric actuator to the piston without dependence on static friction, eliminating precision errors caused by oil or dirt ingress while maintaining simple system structure
Solution Approach 2:
The patent substitutes friction-based mechanical force transmission with hydraulic force transmission. This replacement eliminates the dependency on static friction magnitude, ensuring that precision remains stable over time even in contaminated environments, while keeping the system structurally simple with minimal components
4Ease of operation
If mechanical systems with two surfaces rubbing against one another are used, then linear movement can be produced, but the system is prone to wear over the long term
Solution Approach 1:
The hydraulic actuator produces linear movement through fluid pressure acting on the piston surface, eliminating direct surface-to-surface rubbing. The working fluid provides smooth, wear-free force transmission, enabling continuous operation over extended periods without the degradation associated with mechanical friction and wear
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
Enables precise, long-range linear movements with reduced wear and energy efficiency, unaffected by static friction changes, ensuring reliable operation over time.
Implementation Method 1
a piezoelectric actuator (36) is provided for exerting a force on the first piston element (14)
Implementation Method 2
a hydraulic actuator having a first piston element (14) for actuating the actuator and a second piston element (18) for producing the linear movement, which piston elements are assigned respective fluidically coupled working chambers
Data Source
AI summary
An actuator device for producing a linear movement, has a hydraulic actuator which includes a first piston element for actuating the actuator and a second piston element for producing the linear movement. The piston elements are assigned respective fluidically coupled working chambers, the volumes of which can be changed by movement of the respective piston element. A piezoelectric actuator is provided for exerting a force on the first piston element.