This paper is concerned with the design of a robotic fish and its motion control algorithms. A radio-controlled, four-link biomimetic robotic fish is developed using a flexible posterior body and an oscillating foil as a propeller. The swimming speed of the robotic fish is adjusted by modulating joint's oscillating frequency, and its orientation is tuned by different joint's deflections. Since the motion control of a robotic fish involves both hydrodynamics of the fluid environment and dynamics of the robot, it is very difficult to establish a precise mathematical model employing purely analytical methods. Therefore, the fish's motion control task is decomposed into two control systems. The online speed control implements a hybrid control strategy and a proportional-integral-derivative (PID) control algorithm. The orientation control system is based on a fuzzy logic controller. In our experiments, a point-to-point (PTP) control algorithm is implemented and an overhead vision system is adopted to provide real-time visual feedback. The experimental results confirm the effectiveness of the proposed algorithms.
Along
with ultralow-energy delay products and symmetric complementary
polarities, carbon nanotube field-effect transistors (CNT FETs) are
expected to be promising building blocks for energy-efficient computing
technology. However, the work frequencies of the existing CNT-based
complementary metal-oxide-semiconductor (CMOS) integrated circuits
(ICs) are far below the requirement (850 MHz) in state-of-art wireless
communication applications. In this work, we fabricated deep submicron
CMOS FETs with considerably improved performance of n-type CNT FETs
and hence significantly promoted the work frequency of CNT CMOS ICs
to 1.98 GHz. Based on these high-speed and sensitive voltage-controlled
oscillators, we then presented a wireless sensor interface circuit
with working frequency up to 1.5 GHz spectrum. As a preliminary demonstration,
an energy-efficient wireless temperature sensing interface system
was realized combining a 150 mAh flexible Li-ion battery and a flexible
antenna (center frequency of 915 MHz). In general, the CMOS-logic
high-speed CNT ICs showed outstanding energy efficiency and thus may
potentially advance the application of CNT-based electronics.
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