Vectorable Thrust Control for Multimodal Locomotion of Quadruped Robot SPIDAR

Abstract

In this paper, I present vectorable thrust control for different locomotion modes by a novel quadruped robot, SPIDAR, equipped with vectoring rotor in each link. First, the robot's unique mechanical design, the dynamics model, and the basic control framework for terrestrial/aerial locomotion are briefly introduced. Second, a vectorable thrust control method derived from the basic control framework for aerial locomotion is presented. A key feature of this extended flight control is its ability to avoid interrotor aerodynamics interference under specific joint configuration. Third, another extended thrust control method and a fundamental gait strategy is proposed for special terrestrial locomotion called crawling that requires all legs to be lifted at the same time. Finally, the experimental results of the flight with a complex joint motion and the repeatable crawling motion are explained, which demonstrate the feasibility of the proposed thrust control methods for different locomotion modes.

Figures (11)

• Figure 1: Aerial-terrestrial quadruped robot SPIDAR: (A) change of the joint configuration in the midair; (B) unique crawling motion on the ground by the assistance of vectorable thrust force.
• Figure 2: Kinematics model of the quadruped robot SPIDAR. There are 4 legs ($l \in \{0, 1, 2, 3\}$) with 8 links. A two-DoF joint module, where the yaw axis comes first followed by the pitch axis, connect neighboring links. The joint servo motor generates joint torque $\tau_i$. Each link contains a spherically vectorable rotor apparatus with two vectoring angles ($\phi, \theta$). Thrust $\lambda_i$ combines a pair to forces from the counter rotating dual rotors.
• Figure 3: Basic control framework for terrestrial/aerial locomotion. The vectorable thrust control and the joint control are performed independently. The cost function and the constraints of the optimization-based control allocation would slightly modified according to the locomotion mode (aerial locomotion in Sec. \ref{['sec:flight']} and terrestrial locomotion in Sec. \ref{['sec:crawl']}).
• Figure 4: Vectoring range of $rotor_i$, where green area denotes the valid range, and the red area denotes the invalid range that causes the aerointerference with other rotors.(A) spherical vectoring range expressed in three-dimensional manner; (B) planar vectoring range $S^{'}_i$ expressed in two-dimensional manner.
• Figure 5: Simplified aerointerference model by fixing the vectoring angle $\phi_i$ at $\hat{\phi}_i$.(A) the description of $S^{'}_{ij}$; (B) the description of $S^{"}_{ij}$.