A single motor-driven continuum robot that can be designed to deform into a complex shape with curvature distribution

Abstract

This paper proposes a method to deform a continuum robot into a complex shape with distributed curvature using a single motor drive. This continuum robot can be deformed to a desired shape by placing tendon guides at appropriate intervals. We used several target shapes, including clothoid and sin curves, as well as a circular curve of constant curvature and confirmed that the deformed shapes match them both in the simulation and prototype. This paper proposes two models of continuum robots. One is the Plain Model in which the tendons are parallel to the rod and the Penetration Model in which the tendon penetrates to the rod. By placing the penetrating position(s), this continuum robot can be deformed into a shape with inflection point(s). We designed a mathematical model to simulate the deformed shape of the prototype to obtain the proper placement of the guides and penetration point(s). Through the optimization, it was able to find the parameters that, in most cases, result in the error of less than $$4\%$$ 4 % between the target and deformed shapes on simulation. We applied these conditions to the prototype and evaluated the errors, which were approximately $$10\%$$ 10 % , the same as the related works that use a conventional constant curvature model. We think that the results of this paper can be applied to reduce the number of actuators required and the size and weight of continuum or biomimetic robots.

Tendon-Driven Continuum Robots for Aerial Manipulation—A Survey of Fabrication Methods

“…Several strategies have been explored in research to reduce the number of actuators in continuum manipulators. These strategies include: (1) using single motor-driven antagonistic tendon pairs [124,[183][184][185], (2) cross-tendon routing [153,185], (3) helical tendon routing [121], and (4) use of locking mechanisms [166]. Table 4 presents specimen examples for various methods that enable reductions in actuator demand while empowering the motion space.…”

“…To mitigate the risk of tendon entanglement, a practical solution involves designing the driving pulley with two separate grooves or tracks [185]. Each tendon of the pair is then wound on its dedicated groove, ensuring independent motion, and preventing entanglement.…”

“…Technique 2: Cross-Tendon Routing Making use of cross-tendon routing of antagonistic pairs can generate an S-curve in a 2D plane, thereby reducing the actuator requirement by one fourth compared to parallel tendon routing driven by individual motors. In the research [153,185], the antagonistic tendon pair swaps their paths midway through by crossing the backbone either through supports [185], or by avoiding the support and directly penetrating through the backbone [185]. This method produces bending in opposite directions when a tendon is pulled.…”

“…This method produces bending in opposite directions when a tendon is pulled. Furthermore, [185] demonstrated that distributing the disks at various positions can not only produce constant curvature but also variable curvature bending. Therefore, this method can help reduce the additional use of actuators per S-curve.…”

Sensing of Continuum Robots: A Review

“…One of the most common classifications of the continuum robots divides them into three main groups, being cable-driven continuum robots, tubular continuum robots, and soft continuum robots (see Figure 1 ). The cable-driven continuum robots are actuated by shortening or extending the length of cables, embedded within the structure of the robot like in [ 5 , 6 , 7 , 8 , 9 ]. By controlling the length of the cables, the position and shape can be controlled.…”