Tunas are flexible, high-performance open ocean swimmers that operate at high frequencies to achieve high swimming speeds. Most fish-like robotic systems operate at low frequencies (≤3 Hz) resulting in low swim speeds (≤1.5 body lengths per second), and the cost of transport (COT) is often one to four orders of magnitude higher than that of tunas. Furthermore, the impact of body flexibility on high-performance fish swimming remains unknown. Here we design and test a research platform based on yellowfin tuna (Thunnus albacares) to investigate the role of body flexibility and to close the performance gap between robotic and biological systems. This single-motor platform, termed Tunabot Flex, measures 25.5 cm in length. Flexibility is varied through joints in the tail to produce three tested configurations. We find that increasing body flexibility improves self-propelled swimming speeds on average by 0.5 body lengths per second while reducing the minimum COT by 53%. The most flexible configuration swims 4.60 body lengths per second with a tail beat frequency of 8.0 Hz and a COT measuring 18.4 J kg⁻¹ m⁻¹. We then compare these results in addition to the midline kinematics, stride length, and Strouhal number with yellowfin tuna data. The COT of Tunabot Flex’s most flexible configuration is less than a half-order of magnitude greater than that of yellowfin tuna across all tested speeds. Tunabot Flex provides a new baseline for the development of future bio-inspired underwater vehicles that aim to explore a fish-like, high-performance space and close the gap between engineered robotic systems and fish swimming ability.

金枪鱼是灵活的、高性能的开放海洋游泳者，它们以高频率运行以实现高游泳速度。大多数类鱼机器人系统以低频（≤3 Hz）运行，导致游泳速度低（每秒≤1.5个身体长度），运输成本（COT）通常比金枪鱼高一到四个数量级. 此外，身体柔韧性对高性能鱼类游泳的影响仍然未知。在这里，我们设计并测试了一个基于黄鳍金枪鱼（Thunnus albacares ）的研究平台) 研究身体柔韧性的作用并缩小机器人和生物系统之间的性能差距。这个名为 Tunabot Flex 的单电机平台长 25.5 厘米。通过尾部的接头改变灵活性，以产生三种经过测试的配置。我们发现，增加身体柔韧性可以将自走式游泳速度平均提高 0.5 个身体长度/秒，同时将最小 COT 降低 53%。^{最灵活的配置以 8.0 Hz 的尾拍频率和 18.4 J kg -1} m ^-1的 COT 每秒游动 4.60 个身体长度. 然后，我们将这些结果以及中线运动学、步幅长度和 Strouhal 数与黄鳍金枪鱼数据进行比较。Tunabot Flex 最灵活配置的 COT 在所有测试速度下都比黄鳍金枪鱼大不到半个数量级。Tunabot Flex 为未来仿生水下航行器的开发提供了新的基准，旨在探索类似鱼类的高性能空间，并缩小工程机器人系统与鱼类游泳能力之间的差距。