cs.ROOct 21, 2026

S-Rolling: Steerable Rolling Gaits for Twistable Snake Robots in Low-Clearance Environments

Authors: Qingling Fan, Zhongqiang Ren

Organizations: Global College, Shanghai Jiao Tong University, China

Read PDF
Ask AI
Cite

Copy citation

DOINot available for this paper

Abstract

Snake robots can traverse complex environments with limbless locomotion, but maneuvering in low-clearance environments remains challenging because a gait must maintain a small swept height while also providing planar steering. Existing rolling gaits preserve a low swept height body configuration but generally provide limited steering, whereas steering gaits often introduce vertical undulation and require additional clearance. With that in mind, this paper develops S-rolling, a steerable rolling gait that combines low swept height locomotion with planar maneuverability for twistable snake robots. S-rolling is designed using an S-shaped planar backbone curve, whose head and tail segments roll with independently controlled angular velocities, producing different motion modes. We derive its joint space gait equation, in which a central twist joint realizes the relative rotation between the two segments. We also develop a quasi-static kinematic model relating the segment rolling speeds to the linear and angular velocities of the robot. Real-robot experiments demonstrate the various motion modes, traversal through a 10 cm clearance test track, and maneuvering tasks beneath a large workpiece and a car chassis. In these low-clearance scenarios, S-rolling successfully performs approximately 90∘^\circ and 180∘^\circ heading changes, whereas the baseline rolling arc gait cannot change the robot heading.

Figures & tables

Fig. 1: The T-Snake uses S-rolling to conduct the tests under a car chassis. (a) The joint arrangement of a T-Snake module, and the bottom view of the T-Snake traversing under the chassis. (b) Task sequence: 1) entering beneath the vehicle; 2) turning 180∘180^{\circ} in place to reorient its head; and 3) exiting from beneath the vehicle. (d) The proposed S-rolling gait realizes 180∘180^{\circ} heading change, while (c) the baseline gait, rolling arc, cannot perform.
Fig. 2: Overview of the dorsal reference curve. (a) The dorsal reference frames along the curve c(s)\mathbf{c}(s) . (b) The relative rotation angle ϕij\phi_{i}^{j} from frame Di\mathbf{D}^{i} to frame Dj\mathbf{D}^{j} .
Fig. 3: Develop S-rolling using backbone curve method. (a) The backbone curve consists of two tangential circular arcs. A bellows frame Dr\mathbf{D}^{r} is defined along the curve. We add geometric constraints to determine the unique configuration of the curve. (b) The curve is divided into two segments, and the rolling of each segment is controlled by a different rotation angle. After rotating e^ar\hat{\mathbf{e}}_{a}^{r} , it forms e^ah\hat{\mathbf{e}}_{a}^{h} in frame Dh\mathbf{D}^{h} and e^at\hat{\mathbf{e}}_{a}^{t} in frame Dt\mathbf{D}^{t} .
Fig. 4: Illustration of the discrete mechanism of T-Snake.
Fig. 5: Illustration of the kinematic model of S-rolling on the T-Snake.
Fig. 6: S-rolling locomotion tests under laboratory conditions. (a)-(d) Different motion modes of S-rolling on the T-Snake hardware. (e) Trajectory of the T-Snake traversing the test track.
Fig. 7: Illustration of the T-Snake tests under a large workpiece. (a) The rolling arc gait cannot reach the target exit, while (b) the proposed S-rolling gait completes the task successfully. (c) The bottom view of the T-Snake traversing under the workpiece.
More in this topic

Robot Locomotion

Robot locomotion studies how robots move efficiently and reliably across varied terrains, environments, and movement modes.

See all 233 papers

Explore similar work

CardsList
Oct 21, 2026

Linear Twisting Sidewinding Gaits for Twistable Snake Robot Motion Planning on Complex Terrains

Sidewinding is an efficient gait for snake robots to locomote on various terrains, by undulating the backbone curve and shifting the contact segments along it. However, relying solely on undulatory motion limits the locomotive capability of snake robots, and combining it with twisting motion can improve their speed and robustness. This hypothesis has recently been verified by the rolling vector approach, which locomotes the robot like a differential-drive car. Yet its twisting is concentrated in a short buffer segment, imposing most of the workload on the two twist joints in the middle, which can often overburden the motors and limit its locomotion. With that in mind, this paper develops a new family of twisting sidewinding gaits that distribute the workload over the entire body with our proposed linear twisting function. Under matched turning speed and total output power, our gaits reduce the peak output power of a single twist joint by 42%. Real-robot experiments show that, with the reduced workload, our new gaits can locomote the robot in various terrains that the existing rolling vector approach cannot. Besides, our new gaits can move up to 49% faster than conventional sidewinding without twisting.

Qingling Fan, Zhongqiang Ren

Global College, Shanghai Jiao Tong University, China

Robot Motion GenerationRobot Locomotion
AskPDF
Oct 16, 2026

Rollbot 2: Agile Locomotion by a Single-Actuator Spherical Robot

Reducing actuator count simplifies robot hardware but also removes independent inputs for maneuvering. The original Rollbot steered by modulating a quasi-stable helical orbit, but moved slowly and relied on external motion capture. Rollbot 2 preserves the single-actuator design while its redesigned mass distribution enables near-straight rolling and more direct travel toward commanded paths and beacon targets. Onboard inertial and ultra-wideband sensing support learned steering, beacon seeking, and waypoint following through one motor-velocity command. Rollbot 2 autonomously approaches UWB beacons without motion capture and completes a 468m manually commanded indoor route at 0.87m/s. On the shared 4.8m ``N'' waypoint benchmark, all 16 trials complete the path with a mean traversal time of 10.8s and mean time-averaged deviation of 7cm. Its fastest traversal takes 8.0s, over 70 times faster than the original Rollbot's 564~s run despite minor protocol differences. These results show how mechanical redesign, onboard sensing, and learning-based control improve the agility and autonomy of a single-actuator spherical robot.

Jingxian Wang*, Chen Yu*, Sam Kriegman +1

Northwestern University, Evanston, IL 60208 USA.

Robot LocomotionRobot NavigationRobot Morphology-Control Co-DesignRobot Trajectory Tracking
AskPDF
Jun 21, 2026

SPiralRoll: A Novel Adjustable-Stiffness Underactuated 3-DoF Joint with Torsion Springs for Rolling Robots

Compliant mechanisms are important in robotics because they can improve adaptability, safety, and energy efficiency while reducing hardware complexity. This paper presents SPiralRoll, a novel torsion-spring-based underactuated compliant mechanism for rolling robots and compliant robotic actuation. The mechanism uses arc-distributed elastic members and two motor inputs to realize three physically observable output motions: rotational motion, radial expansion/contraction, and axial spin induced by nonlinear compliant deformation. Two configurations, namely full-arc and single-arc designs, are developed and experimentally evaluated. Beyond benchtop validation, the mechanism is integrated into a spherical rolling robot, where proof-of-concept experiments demonstrate forward rolling and turning. The results show that the full-arc design provides better structural support and smoother deformation, whereas the single-arc design yields larger deformation and stronger inertial excitation, making it more suitable for pendulum-driven rolling locomotion. Overall, SPiralRoll provides a low-cost, compact, and fully 3D-printable solution for underactuated compliant rolling robots and adaptive robotic joints.

Louis Keith, George Ripper, and Seyed Amir Tafrishi

Geometric Mechanics and Mechatronics in Robotics (gm2R) Lab, the School of Engineering, Cardiff University, Cardiff, CF24 3AA, United Kingdom

RoboticsRobot Locomotion
AskPDF