Application Cases

Experiment Name: Experimental Research on Motor Characteristics

Experiment Purpose: This paper introduces the structure and driving mechanism of a symmetric bimorph piezoelectric linear motor. Based on this, a motion model of the motor is established. The paper discusses in detail the various working modes that the motor can achieve under different driving signals and analyzes the model. The stator form is optimized, and three different types of motors are proposed. Theoretical model analysis is conducted for each type of motor, finite element simulation is used, and the overall structural design and prototype fabrication of the motor are carried out. Performance experimental research is then conducted on the motor.

Testing Equipment: Power amplifier, signal generator, oscilloscope, piezoelectric actuator, laser displacement sensor, etc.

Figure: Diagram of the Experimental Setup

Experiment Process:

I. Continuous Actuation Mode Experiment

By applying sine wave signals with a certain phase difference to four sets of stacked piezoelectric ceramics, the motor's driving foot can perform elliptical motion, which drives the motor rail to output linear motion through friction. For the long flexible hinge piezoelectric motor, adjusting the input voltage and frequency can yield the motor speed characteristic curve shown in the figure below.

Figure: Voltage-Speed Relationship Curve of Long Flexible Hinge Motor at Different Frequencies in Continuous Actuation Mode

As the frequency and voltage increase, the motor speed increases approximately linearly. When the input voltage is 100V and the frequency is 100Hz, the motor speed is 446.4μm/s. In this mode, the motor operates smoothly with low noise. The downside is the relatively low speed.

II. Alternating Stepping Actuation Mode Experiment

When a square wave or triangular wave signal with a certain pattern is applied to the stacked piezoelectric ceramics, the motor's driving foot can move along a rectangular trajectory, thereby driving the rail in linear motion through friction. Compared to the continuous actuation mode, the motor speed is faster in this mode.

Figure: Results of Symmetric Prototype in Stepping Mode

The figure (a) above shows the voltage-speed relationship of the symmetric prototype at different frequencies. The working frequency band of the motor in alternating stepping mode is 10Hz to 120Hz, and the working voltage range is 80-120V. The motor speed increases linearly with the increase of input voltage. When the input signal frequency is 120Hz and the voltage is 120V, the motor speed is 670.22μm/s. Figure (b) above shows the frequency-speed relationship at an input signal voltage of 100V. The motor speed shows a certain linearity with frequency increase, with some errors at certain points. When the frequency exceeds 120Hz, due to the hysteresis effect of the stacked piezoelectric ceramics mentioned in Chapter 2, it is difficult to control the movement timing of the dual driving feet well, resulting in the motor's inability to function properly.

III. Single-Step Actuation Mode Experiment (Resolution Test)

Figure: Single-Step Frequency-Down Resolution Test Results of Symmetric Prototype

The figure above shows the step distance test results of the symmetric prototype. When the input signal voltage is 100V and the frequency is sequentially 100Hz, 50Hz, 10Hz, and 1Hz, the motor's single-step distances are 3.61μm, 3.57μm, 0.65μm, and 0.35μm, respectively. In theoretical analysis, the motor step distance should not change with frequency. However, in the experimental results, the step distance decreases significantly as the frequency decreases. From 100Hz to 50Hz, the error is small, mainly due to test errors and slight differences in the surface morphology of the moving part's test section. From 50Hz to 10Hz and 1Hz, the error increases. From the graph, it can be seen that at low frequencies, the retraction of the moving part is more pronounced. This is because there is a certain difference in the contact state between the dual driving feet of the stator and the moving part, and they cannot achieve perfect contact and separation during movement. The retraction of the moving part directly affects the accuracy of the single-step distance. At higher frequencies, the retraction of the moving part is somewhat mitigated by inertia, and the step distance at this time better represents the performance of the motor. The resolution of the symmetric prototype is 0.35μm.

IV. Load-Carrying Experiment

Figure: Load Characteristic Curve of Symmetric Prototype

The figure above shows the load test results of the symmetric prototype at 100Hz and 200Hz. The motor speed decreases linearly with the increase of load. When the input signal voltage is 100V, the maximum load force is approximately 3N. Since the non-resonant piezoelectric linear motor relies on friction for driving and operates at a lower frequency, its load capacity is generally small.

Experimental Results:

The experiment concludes that the symmetric non-resonant piezoelectric linear motor can achieve motion in three different working modes: continuous actuation mode, alternating stepping mode, and single-step actuation mode. It can be applied to various working scenarios. The combination of multiple working modes can unify large-stroke and high-resolution motion in the same motor.

Power Amplifier Recommendation: ATA-3080C

Figure: Specification Parameters of the ATA-3080C Power Amplifier