A Torque Control Strategy for a Robotic Dolphin Platform Based on Angle of Attack Feedback

Abstract

Biological fish can always sense the state of water flow and regulate the angle of attack in time, so as to maintain the highest movement efficiency during periodic flapping. The biological adjustment of the caudal fin’s angle of attack (AoA) depends on the contraction/relaxation of the tail muscles, accompanying the variation in tail stiffness. During an interaction with external fluid, it helps to maintain the optimal angle of attack during movement, to improve the propulsion performance. Inspired by this, this paper proposes a tail joint motion control scheme based on AoA feedback for the high-speed swimming of bionic dolphins. Firstly, the kinematic characteristics of the designed robot dolphin are analyzed, and the hardware basis is clarified. Second, aiming at the deficiency of the tail motor, which cannot effectively cooperate with the waist joint motor during high-frequency movement, a compensation model for the friction force and latex skin-restoring force is designed, and a joint angle control algorithm based on fuzzy inference is proposed to realize the tracking of the desired joint angle for the tail joint in torque mode. In addition, a tail joint closed-loop control scheme based on angle of attack feedback is proposed to improve the motion performance. Finally, experiments verify the effectiveness of the proposed motion control scheme.

Performance Optimization for Bionic Robotic Dolphin with Active Variable Stiffness Control

“…According to Hooke's law of torsion spring, the torque is proportional to the rotation angle of the joint, namely, τ = K s θ where τ means the torque generated by the flexible component, K s indicates the stiffness coefficient, and θ is the joint angle. To imitate the torsion spring's flexible physical property, we can employ the cycle synchronous torque mode (CST) of the motor driver to control the output torque [30]. As illustrated in Figure 3, a torque control strategy is proposed for the caudal joint to achieve the flexible joint imitation with the capability of active variable stiffness mechanism.…”

Intelligent Fish-Inspired Foraging of Swarm Robots with Sub-Group Behaviors Based on Neurodynamic Models

“…Recently, there has been a trend to develop new systems, algorithms, and robotic strategies inspired by the behavior and intelligence of fish [4,5]. Chen et al [6] proposed an innovative design in the realm of robotic fish, which incorporated a high-frequency oscillation mechanism paired with a compliant and passive system.…”