Admittance Control-based Floating Base Reaction Mitigation for Limbed Climbing Robots

Abstract

Reaction force-aware control is essential for legged climbing robots to ensure a safer and more stable operation. This becomes particularly crucial when navigating steep terrain or operating in microgravity environments, where excessive reaction forces may result in the loss of foot contact with the ground, leading to potential falls or floating over in microgravity. Furthermore, such robots are often tasked with manipulation activities, exposing them to external forces in addition to those generated during locomotion. To effectively handle such disturbances while maintaining precise motion trajectory tracking, we propose a novel control scheme based on position-based impedance control, also known as admittance control. We validated this control method through simulation-based case studies by intentionally introducing continuous and impact interference forces to simulate scenarios such as object manipulation or obstacle collisions. The results demonstrated a significant reduction in both the reaction force and joint torque when employing the proposed method.

Figures (8)

• Figure 1: Limbed climbing robots are helpful in an exploration in steep terrain (left) and autonomous tasks in orbital stations (right). In real missions, the robots are supposed to negotiate with the disturbances when manipulating, carrying, or colliding with other objects.
• Figure 2: Conceptual diagram of an admittance control for the limbed climbing robot's end-effectors (left) and base COM (right).
• Figure 3: Snapshots of loading cargo simulation under (a) Earth and (b) Lunar gravity, comparing the baseline: simple PD control (top) and proposed method (bottom) in each condition. The red and green arrows indicate reaction forces acting on the end-effector and the base, respectively. The light blue curves are trajectories of feet.
• Figure 4: Comparison graphs of maximum reaction force (left) and joint torque (right) between the baseline and proposed method under Earth and Lunar gravity.
• Figure 5: Comparison graphs of the TSM (left axis) and GIAM (right axis) between the baseline and proposed method under Earth and Lunar gravity.