Application Cases

Experiment Name: Performance Testing of Soft Robots

Experiment Purpose: The soft actuator, which serves as the trunk of the inchworm-inspired soft robot, is a core component that enables the robot's movement. It not only provides flexible motion but also generates output force. Therefore, studying the movement performance and output force of the soft actuator is highly meaningful. Based on the analysis, the electrostatic adhesive foot requires specific tangential and normal forces, making it necessary to investigate the output performance of the electrostatic adhesive foot.

Testing Equipment: High-voltage amplifier, laser displacement sensor, etc.

Figure: Elongation Characteristic Measurement System

Experiment Process:

When testing the output displacement characteristics of the soft actuator, an elongation characteristic measurement system was set up. The soft actuator was tested on a smooth glass platform, and foot 1 was fixed in the system for convenient measurement of elongation data. Using LABVIEW programming, the controller regulated the high-voltage power supply, and the laser displacement sensor measured the elongation of the robot's foot. The sensor data was transmitted to the computer via the controller.

Initially, direct current (DC) excitation voltage was selected for testing, with the high-level signal VA set at (0.5 kV, 1.0 kV, 1.5 kV, 2.0 kV, 2.5 kV, 3.0 kV, 3.5 kV, 4.0 kV, 4.5 kV, 5.0 kV, 5.5 kV, 6.0 kV), and the low-level signal VF at 0V. The duration of electrification was 60 seconds, and the data acquisition lasted for 100 seconds. Using the aforementioned excitation signals, experiments were conducted on DE films with three different stretch ratios: 300%×400%, 300%×450%, and 300%×500%. As shown in Figure 2, the DE film with a stretch ratio of 300%×500% exhibited the best output displacement performance. Moreover, for different stretch ratios, it can be observed that as the voltage increases, the robot's elongation step length increases in a quadratic curve manner. However, due to the inherent properties of the DE film, there is a risk of breakdown beyond 6 kV. Therefore, in the elongation test, the optimal excitation voltage was selected as 6.0 kV. It can be seen from the figure that when the stretch ratio is 300%×500% and the input voltage high level is 6.0 kV, the bionic soft actuator achieves a maximum output elongation of 16.2 mm in 60 seconds.

Figure 2: Relationship between Elongation Step Length and DC Voltage

In this paper, the elongation performance of the bionic soft actuator made from DE films with a stretch ratio of 300%×500% was tested using sine signals with high-level VA at 3.0 kV, 4.0 kV, 5.0 kV, and 6.0 kV, and low-level VF at 0V as excitation voltages. A series of sine signals with different frequencies (1-30 Hz, with a 1 Hz interval) under these four different amplitude sine voltages were used to test the elongation performance.

Experimental Results:

Figure 3: Variation of Elongation Step Length with Different Sine Amplitudes and Frequencies

The figure above shows the output elongation step length data of the bionic soft actuator, representing the maximum output step elongation of the actuator at different frequencies. It can be seen from the figure that under different voltage amplitudes, as the frequency increases, the robot's elongation step length generally shows a downward trend. However, the lower the voltage amplitude, the less obvious the downward trend; the higher the voltage amplitude, the more pronounced the downward trend and the greater the fluctuation. Therefore, when the application requires a longer step length for the robot, an excitation signal with a higher voltage amplitude and a lower voltage frequency should be selected. When the high-level voltage is 6 kV and the frequency is 1 Hz, the actuator can achieve an output step length of 10.42 mm.

Voltage Amplifier Recommendation: ATA-7020

Figure: Specification Parameters of the ATA-7020 High-Voltage Amplifier

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