Abstract: This paper presents a frog-inspired swimming robot based on articulated pneumatic soft actuator. To realize the miniaturization of the robot and enhance its environmental adaptability, combined with the advantages and characteristics of soft materials, an articulated pneumatic soft actuator is designed based on analysis of a frog’s propulsion characteristics. A structural model is established to analyse the mechanical properties of the soft actuator. With the goal of making full use of the driving torque of the actuator and enhancing the propulsion efficiency of the robot, the motion trajectories of each joint of the robot are planned. Based on the trajectory planning, the control strategy of the soft actuator is determined to realize the frog-like swimming of the robot. The torso size after assembly is 0.175 m × 
0.100 m × 0.060 m, which realizes the miniaturization of the frog-inspired robot. During the movement of the robot, the torso moves stably and flexibly, and can realize continuous linear and turning movements. The rationality of the structure and trajectory planning are verified by prototype experiments.

Key words: bionic robotic frog, articulated pneumatic soft actuator, trajectory planning, prototype experiment