Application Cases

Experiment Title: Testing of Driver Characteristics

Testing Purpose:A test platform was built based on the structural characteristics and driving requirements of the balloon-shaped DEA. The MATLAB software was used to control the high voltage amplifier to electrically drive the balloon-type DEA, and a pressure sensor was used to record the pressure changes inside the DEA balloon. As an anchoring structure, the size of the balloon in the driven state is a key performance parameter. An AVT industrial camera was used to record the experimental process and obtain the maximum radius of the balloon at each stage. The critical voltage of the balloon-shaped DEA was obtained through testing. The changes in the maximum radius of the balloon when the applied voltage and initial pressure were used as single variables were studied. The role of the external gas chamber in stabilizing the pressure supply and increasing the deformation of the DEA balloon was verified, and an ideal pressure-voltage matching relationship was summarized.

Testing Equipment: High Voltage Amplifier, Pressure Sensor, Signal Acquisition Card, Industrial Camera, Computer, etc.

Figure 1: Schematic Diagram of the Driver Test Platform

Experiment Process:

The driver test platform is shown in Figure 1 and mainly consists of voltage control, pressure measurement, and balloon deformation measurement. The driver sample was placed flat on a test platform supported by columns. The aluminum electrode was connected to the voltage output terminal of the high voltage amplifier, and the bottom of the driver was connected to a flexible air hose leading to a three-way valve. The other two outlets of the three-way valve were connected to a pressure sensor and a check valve, respectively. The check valve was used to inject gas into the driver while preventing gas leakage. An industrial camera was positioned directly above the driver to record the deformation of the balloon during the experiment. To improve imaging quality, lighting equipment was used. The computer was connected to the signal acquisition card, which was used to control the output voltage of the high voltage amplifier and to collect signals from the pressure sensor and the high voltage amplifier. The collected experimental data were analyzed using computer software.

Dielectric elastomer materials typically require thousands of volts of external voltage for activation, which ordinary power supplies cannot meet. A high voltage power amplifier was used, which can be controlled by a computer to output voltage parameters such as magnitude and waveform. The output voltage can reach 5kV (DC) or the corresponding peak AC, and the power supply can be remotely controlled to ensure the safety of the experiment. Additionally, the high voltage amplifier has measurement capabilities, allowing real-time detection and recording of current and voltage changes, which are then uploaded to the computer via the signal acquisition card. MATLAB software was used to control the experimental process. MATLAB can send command streams to the high voltage amplifier to control its on-off according to a given time schedule. It can also read electrical signals transmitted by the signal acquisition card, plot the relationship curves between time, voltage, and current, and analyze the electrical characteristics of the driver during the electrification process.

Since the driver is designed as a sealed balloon, the total amount of gas inside the device can be considered constant in an ideal state. According to the ideal gas law PV=nRT, the pressure change is inversely related to the volume change at constant temperature. Therefore, pressure changes can be used to reflect the volume changes of the balloon. Thus, pressure changes are also one of the important parameters of the experiment.

Figure 2: Pressure Measurement Equipment (a) Pressure Sensor (b) Pressure Sensor Power Supply

A pressure sensor was selected, as shown in Figure 2(a). The sensor's power supply is a direct current of 5V, provided by a small power supply shown in Figure 2(b). The power and signal lines were connected according to the product manual, and the signal line was connected to the signal acquisition card to convert and transmit the signals collected by the pressure sensor to the computer. The sensor has a range of ±5PSI (i.e., ±34.475kPa) and a measurement error of ±0.01kPa, which meets the experimental requirements in terms of range and accuracy. The pressure sensor measures the pressure difference between two ports. During the experiment, only one port was used, and the measured pressure value was the difference between atmospheric pressure and the internal pressure of the balloon.

Experimental Results:

Figure 3: AVT Industrial Camera

Pressure changes can reflect the overall volume changes, but it is also necessary to measure the radius changes of the driver balloon before and after electrification as a reference for the driver's anchoring performance. An AVT industrial camera was used to record the electrification process from a top view, as shown in Figure 3. The camera was programmed to start recording simultaneously with the start of electrification by the high voltage amplifier and to stop recording 2 seconds after the power was cut off.

The collected experimental images were processed as follows: First, images of the balloon before and after electrification in a stable state were selected. Photoshop software was used to batch process and crop images of the same position and size, which should include the entire balloon shape. Then, ImageJ software was used to binarize the images, creating a clear grayscale contrast between the balloon edge and the non-balloon part. The balloon boundary area was selected using the tool, as shown in Figure 4. The total number of pixels in the area enclosed by the yellow line can be calculated using ImageJ's grayscale statistics function. By comparing this with the total number of pixels in the central magnet area, the ratio of the balloon area to the central magnet area can be obtained. Knowing that the actual area of the magnet is 16π mm², the actual area of the balloon can be easily calculated, and thus the estimated radius of the balloon can be obtained.

High Voltage Amplifier Recommendation: ATA-7050

Figure: Specifications of the ATA-7050 High Voltage Amplifier

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