CRAB-EDM: A Multi-Modal Underwater Crab-Inspired Robot With Temporally Sequenced Electro-Discharge Modulation

Dielectric elastomer actuators (DEA) have emerged as promising candidates for underwater exploration due to their high energy density and flexibility. However, the accumulation of residual charges compromises actuation efficiency, and conventional single-mode discharge strategies struggle to balance dynamic responsiveness with locomotion stability. Therefore, we present CRAB-EDM, a multi-modal underwater soft robot inspired by crab locomotion and powered by temporally modulated electro-discharge control. By integrating the distributed coordination mechanism of crab-like multi-foot motion with the electromechanical coupling behavior of DEA, we design a six-foot soft robotic architecture coupled with a tri-modal control framework: high-frequency fast discharge enhances dynamic actuation response, medium-frequency delayed discharge improves displacement-frequency synergy, and low-frequency coordinated discharge reinforces gait stability. Through ballast-limb coordination mechanism with a multi-modal control strategy, the nine-gram robot demonstrates versatile behaviors such as turning, jumping, and overing obstacle. Experimental results validate that the synergy between bio-inspired morphology and residual charge modulation significantly improves locomotion efficiency and terrain adaptability, offering a low-noise, highly adaptable solution for constrained underwater exploration.