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Caterpillar Inspired Soft Crawling Robot

Nature’s Inspiration

Earthworms, caterpillars, and many species of snakes use what is called rectilinear motion which uses radial and longitudinal muscles to propel themselves forward. In this type of motion the radial muscles contract in order to create a gap between the surface and the animal's body while also lengthening the body segment, allowing it to push the body forward without creating drag, alternatively the longitudinal muscles constrict to make that segment fatter, increasing contact with the ground and creating an anchor the rest of the body can push against to move forward. By alternating between these two muscles in each segment of the body, these animals create forward propulsion. This type of locomotion is idea for compact spaces.

BAM Approach

The Kresling pattern has been chosen by this project to convert rotational motion from a servo into lateral motion. By using two of these towers in a single robot, we are able to achieve 2-D motion. In order to allow the robot to move forward using an expansion and contraction motion, similar to the expansion and contraction of the rectilinear motion) this robot uses anisotropic frictional feet which allow movement in one direction while resisting motion in the other resulting in the front and back plate alternating as an anchor as the robot moves forward. The feet are designed using a ratcheting system which means they roll in the forward direction while the ratchet prevents them from rolling in the backward direction. This allows the friction from the wheels to prevent backsliding. 

The current OSCAR design showing (a) the main components, (b) a side view, and (c) an exploded CAD view

Using small scale Arduinos (previous work has used TinyDuino) and batteries it is possible to allow this robot to crawl untethered. The current work in this project is to connect multiple together in order to better understand their ideal walking gate and to study the dynamics of the peristaltic motion which occurs in nature when using rectilinear locomotion.

Sliding ratchet feet function for a) forward and b) backwards direction

Recent Results

Adding compliance to robots adds many benefits, however alongside this, soft robots tend to be under-actuated meaning that their motion has high uncertainty. Compared to other soft crawling robots, OSCAR has the following advantages. First, OSCAR uses two origami towers with simple actuation using servo motors. Second, the components of OSCAR allow for mass manufacturing which means that when damaged parts can be replaced easily and quickly. Thirdly, OSCAR is modular which means that it can operate in single and multi-segment configurations. OSCAR has been designed to reduce these uncertainties and to allow for open and closed loop control. One method of achieving this is the redesign of the an-isotropic frictional feet. Originally designed as a wedge with a smooth front face and rough back face, this design which resulted in inconsistent friction was replaced with a ratcheting foot design in order to improve predictability. In order to ensure even contact between OSCARs feet and the ground OSCAR has been built using an assembly guide which enforces even and consistent placement of the towers. Finally, using an uncertainty assessment, it was possible to correct for many of the uncertainties in the OSCAR robot which were consistent throughout the OSCAR robot movement. This has resulted in OSCAR being controllable using a basic open loop control mechanism. Through this OSCAR is able to follow paths and avoid obstacles both as a single OSCAR unit and a two OSCAR robot.

2D navigation in the presence of static obstacles showing: (a) the planned path and combined experimental results. Solid and dashed-line boxes indicate the robot orientation in the reference path and the experiment, respectively. Shaded areas corre- spond to the robot body motion, (b) and (c) the trajectory repeatability for four trials in settings of part 1 and part 2 experiments, respectively

Engineering Impact

Most mobile robots lack the ability to traverse complex terrains and compact spaces due to the inability to adapt to their surroundings. Traditionally, robots have consisted largely of mechanical hardware, making them large, bulky, and generally unsuitable for harsh and unpredictable environments. While the development of soft robotics has provided means for increased maneuverability and adaptability, it has brought new challenges such as decreased durability and lack of autonomy due to modeling complexity. For a mobile robot to be useful for applications such as search and rescue, intelligence, and surveillance missions, it must be autonomous and able to withstand harsh and complex terrains. The ability of a robot to autonomously segment in the field would allow missions to continue even if part of the robot were stuck or disabled and prevented from continuing.


  • Angatkina, O., Alleyne, A. G., & Wissa, A. (2023). Robust design and evaluation of a novel modular origami-enabled mobile robot (OSCAR). Journal of Mechanisms and Robotics, 15(2), 021015.

  • Angatkina, O., K. Gustafson, A. Wissa, & A. Alleyne. "Path Following for the Soft Origami Crawling Robot." Proceedings of the ASME 2019 Dynamic Systems and Control Conference, Park City, Utah, USA. October 8–11, 2019. V003T20A009. ASME. (Vol. 59162, p. V003T20A009). 

  • Angatkina, O, B. Chien, A. Pagano, T. Yan, A. Alleyne, S. Tawfick, & A. Wissa . "A Metameric Crawling Robot Enabled by Origami and Smart Materials," Proc. Smart Materials, Adaptive Structures and Intelligent Systems Conf. 2017-3836, Snowbird, UT. (Abstract and full draft paper were subject to peer review)

  • Pagano, A., Yan, T., Chien, B., Wissa, A., & Tawfick, S. (2017). A crawling robot driven by multi-stable origami. Smart Materials and Structures, 26(9), 094007.

  • Pagano, A., Leung, B., Chien, B., Yan, T., Wissa, A., & Tawfick, S. (2016, September). Multi-stable origami structure for crawling locomotion. In Smart Materials, Adaptive Structures and Intelligent Systems (Vol. 50497, p. V002T06A005). American Society of Mechanical Engineers.


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