Detecting wake characteristics of moving targets in water by bio-inspired seal whisker array

Abstract:

To detect the wake characteristics of a moving target in water and obtain the information of the target such as trajectory direction and geometric, we proposed a wake detection method by imitating the mechanism of seals using beards to detect prey. First, a whisker model similar to the shape of seal whisker was fabricated with 3D printing technology. Combined with piezoresistive elements and other materials, a sensor array that can sense the wake of a moving target in the water was fabricated. Then, the experimental scheme of wake detection was designed, and simulation analysis was performed under uniform incoming flow of 0.5,1.0,1.5 m/s and non-uniform flow with slight fluctuations to obtain the wake velocity field distribution in different conditions. The lift coefficient and spectral distribution of S₁₁ were analyzed. The wake vortex shedding frequency obtained by theoretical calculation was compared to verify the validity of the experimental scheme. Finally, under laboratory conditions, the sensor array was used to measure the wake characteristics of a target, and the influence of the imitation seal whisker angle on the wake detection was analyzed. Results show that the lift coefficient of the whisker model fluctuated significantly under different incoming flow conditions, and the main frequency obtained by the fast Fourier transform was consistent with the theoretical value of the wake vortex shedding frequency. The average voltage value of the wake signal detected in the wake area was more than 3 times the average voltage value of the non-wake area, so that the wake area and the non-wake area could be accurately identified. On this basis, the gradient direction of the average voltage value attenuation was analyzed to estimate the trajectory direction of the measured target. The maximum response frequency of the wake signal measured by the sensor array was close to the main frequency of the numerical simulation. By inverting the response frequency, the diameter size of the measured target could be estimated. The seal whisker angle could affect the vortex-induced vibration of the sensor and increase the disturbance signal, but it had no significant effect on the estimation of the direction of the motion track and the estimation of the measured target size.