Piezo Linear Drive Control Using Speed-Proportional Variables
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Solution Overview
Problem
Piezo linear drives face challenges with systematic positioning errors and high clamping voltages leading to reduced efficiency and increased response time, especially when positioning heavy objects vertically, due to position-signal-dependent control methods.
Innovation Solution
An operating method that derives control signals from a speed-proportional control variable, approximating linear time dependency of drive travel, and coordinating cycle time and shear stress to reduce permanent voltage loads and control amplifier losses, using a lookup table for interpolated shear stress values to control longitudinal actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If position-signal-dependent control is used for vertical positioning of heavy objects, then positioning capability is achieved, but systematic positioning errors occur and response time increases
Solution Approach 1:
The control method changes the fundamental parameter used for control from position signal to speed-proportional control variable. By deriving control signals from speed rather than position, the system achieves vertical positioning of heavy objects without the systematic errors and slow response characteristic of position-dependent control methods
2Measurement precision
If position-signal-dependent control is used, then positioning control is achieved, but control effort increases and degradation phenomena occur due to high clamping voltages
Solution Approach 1:
The invention changes the control parameter from position signal to speed-proportional control variable. This parameter change fundamentally alters the control signals generated, reducing the need for high clamping voltages during positioning operations and thereby reducing energy losses in control amplifiers and degradation in piezo actuators
Solution Approach 2:
The control method employs periodic activation of piezo stack actuators with coordinated cycle times. By using periodic clamping and feed movements rather than continuous high voltage application, the system reduces permanent voltage loads and associated energy losses while maintaining positioning capability
3Stability of the object's composition
If high clamping voltages are applied over longer periods for position control, then positioning stability is maintained, but functionality of the drive deteriorates
Solution Approach 1:
The control method uses periodic activation of piezo stack actuators with coordinated cycle times instead of continuous high voltage application. This periodic action maintains positioning stability through controlled clamping phases while reducing permanent voltage loads that cause functionality deterioration
Solution Approach 2:
By changing from position-dependent to speed-proportional control, the system alters the temporal pattern of voltage application. This results in reduced duty cycle for high clamping voltages, maintaining stability when needed while preserving actuator functionality through reduced stress
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
This approach enhances positioning accuracy and response behavior while reducing degradation phenomena, allowing for precise and efficient vertical positioning with lower control effort and improved drive performance.
Implementation Method 1
electrical energy is converted into motion by utilizing the electrostrictive effect of one or more piezoelectric elements
Implementation Method 2
If an electrical voltage is applied to the outer electrodes, the piezo foils expand in the direction of the field
Data Source
Figure 1~2
Figure 3~4
AI summary
Operating method of a piezo linear drive (D) with a group of piezo stack actuators which drive a runner (R), wherein the actuators represent a multi-layer ceramic arrangement located on a common substrate (Sa,Sb), wherein within a stack of the multi-layer arrangement a first stack part is designed as a shear or longitudinal actuator (D1,D2) and a second stack part as a clamping actuator (C1,C2) and the latter is at least indirectly in clamping and shearing contact with the runner and at least two identical actuators are located next to each other in order to perform reciprocal clamping and feed movements in stepping mode, for operation in stepping mode for coarse positioning, wherein the adjacent actuators of the group are controlled to perform alternating clamping and feed movements, wherein control signals are derived from a velocity-proportional control variable.