Design, Modeling, and Motion Analysis of a Novel Fluid Actuated Spherical Rolling Robot

Abstract

This paper studies a novel fluid actuated system for a spherical mobile robot. The robot’s mechanism consists of two essential parts: circular pipes to lead spherical moving masses (cores) and an internal driving unit to propel the cores. The spherical shell of the robot is rolled by displacing the cores in the pipes filled with fluid. First, we describe the structure of the robot and derive its nonlinear dynamics using the D’Alembert principle. Next, we model the internal driving unit that actuates the core inside the pipe. The simulated driving unit is studied with respect to three important parameters—the input motor torque, the actuator size, and the fluid properties. The overall model of the robot is then used for analyzing motion patterns in the forward direction. Analytical studies show that the modeled robot can be implemented under the given design specifications.

Inverse Dynamics-Based Motion Control of a Fluid-Actuated Rolling Robot

“…Having established the motion of the robot, θ(t) and γ(t) (by integrating (3.1) or (3.3), depending on the chosen case) and having computed the driving torque τ γ (t), one can then define the fluid pressure P p in the circular pipe. Note that the driving torque τ γ is related to P p as [11] τ…”

“…This actuation principle can be realized by moving internal weights connected to rods. Rotating a mass within the sphere is another alternative way to actuate a rolling robot [8][9][10][11]. Trajectory tracking for pendulum-actuated robots was considered in [4,12,13,25].…”

“…In our previous work, we introduced a novel fluid-actuated spherical robot [11,19]. This robot employs the mass-imbalance principle based on rotating a spherical mass (core) inside circular pipes.…”

“…Let θ be the rotation angle of the sphere, and let γ be the relative angle of the mass point. By means of the Lagrange -Euler formalism, the nonlinear dynamics of this rolling system can be established as follows [11,19]:…”

“…The input fluid pressure to the pipe, P p , can be found with the use of the Bernoulli equation. It is obtained as [11,20]…”