This paper presents an improved version of the insect-mimicking flapping-wing mechanism actuated by LIPCA (Lightweight Piezo-Composite Actuator). As the previous version, the actuation displacement of the actuator is converted into flapping-wing motion by a mechanical linkage system that functioned as displacement amplifier as well. In order to provide feathering motion, the wing is attached to the axis through a hinge system that allows the wing rotation at each end of half-stroke, due to air resistance. In this improved version, the total weight has been reduced to the half of the previous one. The device could produce about 90 degree of flapping angle when it operated at around 10 Hz, which was the natural flapping-frequency. Several flapping tests under different parameter configurations were conducted in order to investigate the characteristic of the generated lift. In addition, the smoke-wire test was also conducted, so that the vortices around the wing can be visually observed. Even though the present wing has smaller wing area, it could produce higher lift then before.
This paper presents a mechanical design, fabrication and test of biomimetic fish robot using the Lightweight Piezocomposite Curved Actuator (LIPCA). We have designed a mechanism for converting actuation of the LIPCA into caudal fin movement. This linkage mechanism consists of rack-pinion system and four-bar linkage. We also have tested four types of caudal fin in order to examine effect of different shape of caudal fin on thrust generation by tail beat.
Subsequently, based on the caudal fin test, four caudal fins which resemble fish caudal fin shapes of ostraciiform, subcarangiform, carangiform and thunniform, respectively, are attached to the posterior part of the robotic fish. The swimming test using 300 Vpp input with 1 Hz to 1.5 Hz frequency was conducted to investigate effect of changing tail beat frequency and shape of caudal fin on the swimming speed of the robotic fish. The maximum swimming speed was reached when the device was operated at its natural swimming frequency. At the natural swimming frequency 1 Hz,
maximum swimming speeds of 1.632 cm/s, 1.776 cm/s, 1.612 cm/s and 1.51 cm/s were reached for ostraciiform-, subcarangiform-, carangiform- and thunniform-like caudal fins, respectively. Strouhal numbers, which are a measure of thrust efficiency, were calculated in order to examine thrust performance of the present biomimetic fish robot. We also approximated the net forward force of the robotic fish using momentum conservation principle.
In this paper, we present our recent progress in LIPCA (Lightweight Piezo-Composite Actuator) application for actuation of flapping wing device. The flapping device uses linkage system that can amplify the actuation displacement of LIPCA. The feathering mechanism is also designed and implemented such that the wing can rotate during flapping. The natural flapping-frequency of the device was 9 Hz, where the maximum flapping angle was reached. The flapping test under 4 Hz to 15 Hz flapping frequency was performed to investigate the flapping performance by measuring the produced lift and thrust. Maximum lift and thrust produced when the flapping device was actuated near the natural flapping-frequency.