Abstract
Snake robot locomotion in a cluttered environment where the snake robot utilises a sensory-perceptual system to perceive the surrounding operational environment for means of propulsion is defined as perception-driven obstacle-aided locomotion (POAL). From a control point of view, achieving POAL with traditional rigidly-actuated robots is challenging because of the complex interaction between the snake robot and the immediate environment. To simplify the control complexity, compliant motion and fine torque control on each joint is essential. Accordingly, intrinsically elastic joints have become progressively prominent over the last years for a variety robotic applications. Commonly, elastic joints are considered to outperform rigid actuation in terms of peak dynamics, robustness, and energy efficiency. Even though a few examples of elastic snake robots exist, they are generally expensive to manufacture and tailored to custom-made hardware/software components that are not openly available off-the-shelf. In this work, Serpens, a newly-designed low-cost, open-source and highly-compliant multi-purpose modular snake robot with series elastic actuator (SEA) is presented. Serpens features precision torque control and stereoscopic vision. Only low-cost commercial-off-the-shelf (COTS) components are adopted. The robot modules can be 3D-printed by using Fused Deposition Modelling (FDM) manufacturing technology, thus making the rapid-prototyping process very economical and fast. A screw-less assembly mechanism allows for connecting the modules and reconfigure the robot in a very reliable and robust manner. The concept of modularity is also applied to the system architecture on both the software and hardware sides. Each module is independent, being controlled by a self-reliant controller board. The software architecture is based on the Robot Operating System (ROS). This paper describes the design of Serpens and presents preliminary simulation and experimental results, which illustrate its performance.
Highlights
In nature, limbless organisms such as snakes may exploit rocks, stones, branches, obstacles, or other irregularities in the terrain as a means of propulsion to achieve locomotion [1]
Snake robot locomotion in a cluttered environment where the snake robot utilises a sensory-perceptual system to exploit the surrounding operational space and identifies walls, obstacles, or other external objects for means of propulsion can be defined as perception-driven obstacle-aided locomotion (POAL) [4,5]
This characteristic is adequate for industrial automation because it allows robots for tracking trajectories in static or mapped environments, i.e., pick-and-place applications, but it is not suitable for robots that interact with unmapped and dynamic environments or need to navigate terrains cluttered with obstacles, such as snake robots
Summary
Limbless organisms such as snakes may exploit rocks, stones, branches, obstacles, or other irregularities in the terrain as a means of propulsion to achieve locomotion [1]. From a control point of view, achieving POAL requires precisely identifying potential push-points and to accurately determine achievable contact reaction forces Accomplishing this with traditional rigidly-actuated robots is extremely demanding because of the absence of compliance. Actuated robots are characterised by having a high bandwidth, which forces them to promptly move to commanded positions regardless of what external forces act on their joints This characteristic is adequate for industrial automation because it allows robots for tracking trajectories in static or mapped environments, i.e., pick-and-place applications, but it is not suitable for robots that interact with unmapped and dynamic environments or need to navigate terrains cluttered with obstacles, such as snake robots. When considering POAL, the high reflected inertia of traditional gear-motor-driven actuators can cause potential collisions that may damage both the robot and the environment.
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