Application Cases

Experiment Name: Study on Electrical Signal Response of Minimum Energy Structures

Research Direction:
The working stroke and output torque of the actuator directly determine the performance of pipeline robots, and electrical signals have a direct impact on the actuator's working stroke. Additionally, the forward movement of soft pipeline robots differs from that of traditional rigid pipeline robots, with displacement exhibiting a certain hysteresis effect relative to the electrical signal. Therefore, it is necessary to investigate the influence of electrical signals on the deformation angle of the actuator and make corresponding optimizations to enhance the load capacity and expand the driving stroke of the actuator.

Experimental Objective:
To study the dynamic characteristics of the Dielectric Elastomer Minimum Energy Structure (DEMES), specifically the effects of the waveform, frequency, and peak value of electrical signals on the electrically induced deformation of DEMES. In these experiments, a pre-optimized static configuration was used: material stretch ratios of 380% × 300%; circular cut-out parameters r, b, and h of 15 mm, 8 mm, and 4 mm, respectively; and a material thickness of 0.21 mm.

Test Equipment:
Signal generator, high-voltage amplifier, displacement sensor, digital oscilloscope, etc.

Experimental Process:
A signal generator and an ATA-7050 high-voltage amplifier were used to generate the driving voltage. The measurement distance was set to 15 cm, and a displacement sensor was employed to measure the deformation of the DEMES, maintaining the measurement range between 15–20 cm. A digital oscilloscope recorded the measured data at a sampling frequency of 500 Hz. The experimental setup connection diagram and the actual experimental setup are shown in Figure 4-1 (left and right, respectively).

Figure 4-1: Experimental Setup Diagram

For convenience, the change in distance between the two ends of the actuator was measured.

Experimental Results:
To study the dynamic response of DEMES at different frequencies, the voltage signals were configured as shown in Table 4-1.

The experimental results are shown in Figure 4-2. It can be observed that the deformation of DEMES varies significantly at different frequencies, with the general trend being that deformation decreases as frequency increases. This is determined by the viscoelastic nature of the DE material itself. The deformation of DEMES lags behind the application of the electrical signal. At higher frequencies, within one cycle, the DE material is subjected to voltage and deforms, but the DEMES does not reach its maximum deformation before the voltage is removed. Similarly, during the period when the voltage is off, the DEMES recovers from its deformed state but does not fully return to its original state before the next cycle begins. This phenomenon becomes more pronounced at higher frequencies.

To study the dynamic response of DEMES under different peak voltages, sinusoidal waves with a frequency of 1 Hz and a duty cycle of 50% were applied, with maximum voltages of 3 kV, 4 kV, and 5 kV. The deformation of DEMES was measured, and the curves are plotted in Figure 4-3.

The maximum deformation of DEMES is positively correlated with the maximum voltage. However, the difference in deformation between 5 kV and 4 kV is greater than that between 4 kV and 3 kV at the same time point. This indicates that the deformation of DEMES does not simply increase linearly with voltage but rather increases at a greater gradient as the voltage rises. Within the allowable frequency range, as the peak voltage increases, the deformation increases, and the magnitude of the increase also becomes larger.

To investigate the dynamic response of DEMES under different voltage waveforms, experiments were conducted using square, triangular, and sinusoidal waves generated by the signal generator. To minimize errors caused by fabrication, temperature, and time, these waveforms were applied to the same actuator. To avoid changes in material properties due to repeated actuation under high voltage, a lower voltage of 4.5 kV was used, with a duty cycle of 50% and a signal frequency of 5 Hz.

Figure 4-4 shows the electrically induced deformation of DEMES under the three different voltage waveforms.

Figure 4-4: Electrically Induced Deformation of DEMES under Square, Triangular, and Sinusoidal Waves

Under the square wave signal, the actuator deforms after the voltage is applied, with the deformation speed gradually slowing until the voltage signal stops, at which point it begins to recover to its initial state at a certain speed, which also gradually slows. This results in sharp peaks in the graph, with a slight hysteresis in the 50% deformation increase cycle relative to the duty cycle. Due to the viscoelastic nature of the DE material, its deformation exhibits a hysteresis effect compared to the voltage signal.

Under the triangular wave signal, during the half-cycle when the voltage increases, the actuator deforms after the voltage is applied, with the deformation speed slowing down before the voltage signal reaches its maximum. At the moment the voltage signal peaks, the deformation speed is almost zero.

Under the sinusoidal wave signal, except for the first cycle, the deformation curve of the actuator follows a sinusoidal pattern. Due to the hysteresis effect, the entire waveform lags slightly behind the electrical signal.

Recommended High-Voltage Amplifier: ATA-7050

Figure: ATA-7050 High-Voltage Amplifier Specifications

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