Snakes on a plan: Toward combining planning and control

Abstract

Highly articulated robot locomotion systems, such as snake robots, present special motion planning challenges. They possess many degrees of freedom, and therefore are modeled by a high dimensional configuration space which must be searched to plan a path. Kinematic and dynamic constraints further complicate the selection of effective controls. Finally, snake robots often have multiple modes of interaction with the terrain as contacts are made and broken, leading to complex and imperfect motion models. We believe that the space of useful controls that provides desirable motions, however, is much smaller. Useful net motions for such systems are often generated via gaits, or cyclic motions in the shape space. Gaits transform a high-dimensional continuum search into a relatively tractable discrete search. In this paper, we put forward a framework which allows a planner to generate paths in a low dimensional work space and select among gaits, preplanned motions in the robot's shape space. The contribution of this paper rests on the "virtual chassis" which is a choice of body frame for the snake robot that allows the planner to efficiently select among and plan with gaits to direct the robot along the work space path. We demonstrate this planner running on a simulated snake robot navigating through a variety of clutter scenarios. The virtual chassis also has the benefit of allowing us to generalize notions of controllability to gait motions.

Maneuvering Control of Planar Snake Robots Using Virtual Holonomic Constraints

“…increases with increasing friction coefficients c n and c t according to (5). This shows the dependence of motor control torques given by (15) on the friction coefficients c n and c t . △ After asymptotically stabilizing Γ 3 , we are left with two control inputs, (u λ , u φ0 ) to solve the direction following problem.…”

“…According to Equation (15), the magnitude of the control torque input depends on u φ0 . According to Equation (19), the magnitude of u φ0 depends on the head angle error.…”

“…In [14], two physical parameters, constraint forces and energy efficiency are introduced as cost functions to optimize, and switching strategies are proposed for generating optimal motion patterns of a snake like robot. In [15], a framework has been put forward which allows a planner to generate paths in a low dimensional work space and select among gaits, pre-planned motions in the robot's shape space. In [16], modal decomposition has been used to modify a snake robots sidewinding gait to orient the head during locomotion.…”

Studying slippage on pushing applications with snake robots

“…Locomotion in planar environments has been probably the main topic of research for snake robots [2][3][4] and has been extended to motion in planar slopes [5,6], motion in 3D-space [7,8], and more broad studies on locomotion [9]. An interesting idea that combines locomotion and interaction with the environment, called obstacle-aided locomotion (OAL), has been proposed in [10] where obstacles in the environment are used as auxiliary sources for propulsion or to avoid jamming.…”

Towards autonomous locomotion: Slithering gait design of a snake-like robot for target observation and tracking

“…The slithering gait has been investigated for wheeled or wheel-less snake robots [8,9,10]. Wu [9] designed a neural controller by adding sensory inputs to achieve self-adaptive steering for collision-free behavior.…”