Piezoelectric Drive Device Symmetrical Actuator Groups

Solution Overview

Problem

Existing piezoelectric drive devices face issues with vibrations and backlash due to the coordination of multiple actuators, which are not adequately addressed in existing technologies.

Innovation Solution

The use of multiple piezoelectric drive units arranged in symmetrical groups with synchronized or staggered contact timings and positions to minimize vibrations and backlash, where each group's contact members press the driven member at specific symmetrical positions around the center axis, ensuring that forces are applied only in the rotational direction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If multiple piezoelectric actuators are used to drive a driven body, then the driving force is improved, but vibrations and backlash occur

Engineering Contradiction:

Improvedriving forceVSAvoidvibrations and backlash

Core Design Contradiction:

ForceVSObject-affected harmful factors

Solution Approach 1:

The patent applies asymmetry by dividing the multiple piezoelectric actuators into two distinct groups (first and second piezoelectric drive unit groups) with different operational characteristics. The first group operates during a first half cycle while the second group operates during a second half cycle, creating an asymmetric driving pattern that prevents simultaneous operation. This asymmetric control strategy eliminates the vibrations and backlash that occur when multiple actuators operate simultaneously, while still providing sufficient driving force through the coordinated action of both groups.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent implements periodic action by alternating the operation of the first and second piezoelectric drive unit groups in a cyclic manner. The first group operates during a first half cycle and the second group operates during a second half cycle, creating a periodic driving pattern. This periodic alternation ensures that only one group is active at any given time, preventing the harmful vibrations and backlash that result from simultaneous operation of multiple actuators, while maintaining continuous driving force through the cyclical switching between groups.

Inventive Principle:

Principle #19Periodic action

2Speed

If multiple actuators operate simultaneously, then the driving speed is improved, but vibrations and backlash increase

Engineering Contradiction:

Improvedriving speedVSAvoidvibrations and backlash

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The patent implements periodic action by alternating the operation of the first and second piezoelectric drive unit groups in a cyclic manner. The first group operates during a first half cycle and the second group operates during a second half cycle, creating a periodic driving pattern. This periodic alternation ensures that only one group is active at any given time, preventing the harmful vibrations and backlash that result from simultaneous operation of multiple actuators, while maintaining continuous driving force through the cyclical switching between groups.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies dynamics by making the operational state of the piezoelectric actuator groups time-dependent and continuously changing. The system dynamically switches between the first and second groups based on the oscillation cycle phase, with the first group active during the first half cycle and the second group active during the second half cycle. This dynamic control strategy allows the system to maintain high driving speed through continuous operation while avoiding vibrations and backlash by ensuring only one group operates at any moment.

Inventive Principle:

Principle #15Dynamics

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 configuration effectively reduces vibrations and backlash by ensuring that forces applied to the driven member are purely rotational, enhancing the precision and stability of the drive mechanism.

Implementation Method 1

a piezoelectric vibrating body which is disposed on the vibrating plate

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentEP3051688B1Piezoelectric drive device, robot, and drive method of robot

Publication Date: 2019.03.06 SEIKO EPSON CORP

Figure 1A~1B
Figure 2~3
Figure 4A~4B

AI summary

A piezoelectric drive device includes multiple piezoelectric drive units that drive a driven member. Each of the multiple piezoelectric drive units has a vibrating plate, a piezoelectric vibrating body which is disposed in the vibrating plate, and a contact member which can come into contact with the driven member. The multiple piezoelectric drive units belong to a first piezoelectric drive unit group and a second piezoelectric drive unit group. The respective contact members of the multiple piezoelectric drive units belonging to the first piezoelectric drive unit group are arranged at a position which is symmetrical to a movement center axis or a movement center line of the driven member. The respective contact members of the multiple piezoelectric drive units belonging to the second piezoelectric drive unit group are arranged at a position which is symmetrical to a movement center axis or a movement center line of the driven member. A timing when the respective contact members of the first piezoelectric drive unit group press the driven member is different from a timing when the respective contact members of the second piezoelectric drive unit group press the driven member.