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Abstract-For maximum maneuverability, terrestrial robots need to be able to turn precisely, quickly, and with a small radius. Previous efforts at turning in legged robots primarily have used leg force or velocity modulation. We developed a palm-sized legged robot, called TAYLRoACH. The tailed robot was able to make rapid, precise turns using only the actuation of a tail appendage. By rapidly rotating the tail as the robot runs forward, the robot was able to make sudden 90• turns at 360• s −1 . Unlike other robots, this is done with almost no change in its running speed. We have also modeled the dynamics of this maneuver, to examine how features, such as tail length and mass, affect the robot's turning ability. This approach has produced turns with a radius of 0.4 body lengths at 3.2 body lengths per second running speed. Using gyro feedback and bang-bang control, we achieve an accuracy of ± 5• for a 60• turn.

Abstract² This paper presents a six-legged, sprawl-tuned autonomous robot (STAR). This novel robot has a variable leg sprawl angle in the transverse plane to adapt its stiffness, height, and leg-to-surface contact angle. The sprawl angle can be varied from nearly positive 60 degrees to negative 90 degrees, enabling the robot to run in a planar configuration, upright, or inverted (see movie). STAR is fitted with spoke wheel-like legs which provide high electromechanical conversion efficiency and enable the robot to achieve legged performance over rough surfaces and obstacles, using a high sprawl angle, and nearly wheel-like performance over smooth surfaces for small sprawl angles. Our model and experiments show that the contact angle and normal contact forces are substantially reduced when the sprawl angle is low, and the velocity increases over smooth surfaces, with stable running at all velocities up to 5.2m/s and a Froude number of 9.8. I. INTRODUCTIONDrawing inspiration from insects, miniature crawling robots possess substantial advantages over wheeled vehicles for off-road locomotion, such as in caves and collapsed buildings, for reconnaissance and search and rescue purposes. Their low weight and cost allow their deployment in large numbers, independently or in swarms, to cover a large work area and increase the odds that some of the robots will succeed in performing a specific task. Some existing examples of comparable robots can crawl at more than 5 (and up and that the sprawled posture is more energy efficient. Full et al. presented a first sprawled robot, SprawlHex [7], which can adjust its sprawl angle, up to 20 degrees, in order to experimentally compare to animal behavior.

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Turning while running at high speeds remains a difficult task for legged robots, but this capability is crucial for maneuvering quickly in a real-world environment. In this work we present a 10 cm long novel robot, SailRoACH, the first running robot that uses aerodynamic forces to turn. We present a scale analysis of aerodynamic steering, showing this steering method is most effective for small robots. Modeling and simulations were performed, and validated with experiments, that showed the robot is capable of stably turning in a 1.2 m radius at 1.6 ms −1 . We also show that aerodynamic steering is superior for high speed turns at high forward velocity, compared to existing methods. Additionally, aerodynamic steering allows us to introduce a constant yaw disturbance to the robot. This is useful for studying legged locomotion, and is difficult to achieve otherwise.