Optimized inchworm motion planning for a novel in-pipe robot

Abstract

Modern society is fueled by very comprehensive grids of gas and liquid supply pipelines. The frequent inspection and maintenance of such pipeline grids is not a trivial task. It has been demonstrated that such task is best performed by using in-pipe robots. In this paper, a novel inchworm robot design and its optimized motion planning are presented. The proposed design uses a helical drive for both gripping and locomotion of the robot. The extension and retraction between inchworm segments are facilitated by conic springs as they can store strain energy. The proposed inchworm robot can also be made very compact without sacrificing stroke length as conic springs can be easily designed with telescopic feature. To generate inchworm motion, a sinusoidal velocity pattern is planned for each segment. The frequency of the velocity pattern is optimized using a genetic algorithm (GA). The optimization result from the GA method has been validated using a traditional gradient based method.

Mathematical model of inchworm locomotion

“…Some papers use terms like "inchworm-like robots", "inchworm robot", or "inchworm motion" in their titles, but involve robots that crawl and do not exhibit any or much arching [35][36][37][38][39][40]. Some robots exhibit arching behavior but are not soft, often containing rigid segments connected by joints [18,[41][42][43][44][45][46][47].…”

“…Further papers describing robots and other devices inspired by inchworm locomotion include [48][49][50][51][52]. Some robots resembling earthworms or caterpillars are used for purposes such as endoscopies, colonoscopies, and inspection of pipes [37,39,[53][54][55][56][57]. A discussion of the effect of friction on earthworm-type robots is presented in [58].…”

Driving Mechanisms, Motion, and Mechanics of Screw Drive In-Pipe Robots: A Review

“…Ma et al studied a differential-driven screw in-pipe robot [34,35] and an ASDIR that can travel in circular and square pipes [36]. Ren et al proposed an ASDIR based on compound planetary gearing [37,38], a variable-pitch SDIR [39], an inchworm SDIR [40], and a helical-contact deformation measuring method in pipelines [41]. The abovementioned SDIRs have different structures and driving principles, and each has its own advantages and application scope.…”

Variable Pitch Helical Drive in-Pipe Robot

“…If a single module of the aforementioned modular in-pipe robot is slightly long, then getting stuck in curves is easy. Most turning principles, including those in the previous works of the authors, are passive [15], [16]. Thus, the structure of the robot itself cannot compliantly solve the problem of passing through curved pipes.…”