SCALER: A Tough Versatile Quadruped Free-Climber Robot (2207.01180v3)

Abstract: This paper introduces SCALER, a quadrupedal robot that demonstrates climbing on bouldering walls, overhangs, ceilings and trotting on the ground. SCALER is one of the first high-degrees of freedom four-limbed robots that can free-climb under the Earth's gravity and one of the most mechanically efficient quadrupeds on the ground. Where other state-of-the-art climbers specialize in climbing, SCALER promises practical free-climbing with payload \textit{and} ground locomotion, which realizes true versatile mobility. A new climbing gait, SKATE gait, increases the payload by utilizing the SCALER body linkage mechanism. SCALER achieves a maximum normalized locomotion speed of $1.87$ /s, or $0.56$ m/s on the ground and $1.0$ /min, or $0.35$ m/min in bouldering wall climbing. Payload capacity reaches $233$ % of the SCALER weight on the ground and $35$ % on the vertical wall. Our GOAT gripper, a mechanically adaptable underactuated two-finger gripper, successfully grasps convex and non-convex objects and supports SCALER.

• The paper introduces SCALER as a high-degree-of-freedom quadruped robot designed for free-climbing in both artificial and natural environments under full gravity.
• It employs a novel SKATE gait and adaptive GOAT gripper for optimized trajectory planning and enhanced load distribution during demanding climbing tasks.
• Benchmarking shows SCALER achieves 0.56 m/s ground speed and climbs at 0.35 m/min while carrying a payload up to 233% of its weight.

An Overview of "SCALER: A Tough Versatile Quadruped Free-Climber Robot" Paper

The paper introduces SCALER, an innovative quadruped robot designed for free-climbing in both artificial and natural environments under Earth's gravitational conditions. SCALER stands out as a high-degree-of-freedom robotic platform capable of performing demanding climbing tasks and demonstrating efficient ground mobility. The authors aim to address the challenges associated with designing legged robots that are not only adaptable to dynamic terrains but can also bear significant payloads—all without compromising operational efficiency.

SCALER’s Design and Capabilities

SCALER exhibits a robust mechanical design characterized by six degrees of freedom (DoF) per limb, made possible through a combination of five-bar linkage mechanisms and sophisticated joint actuation. This design is crucial for achieving dense functionality required for complex tasks like climbing overhangs and ceilings. The paper emphasizes SCALER's adaptability through its novel SKATE gait, improving payload capacity by leveraging its unique body linkage mechanism. This innovative approach allows SCALER to apply translational body motions that enhance stride length and actuator force distribution, making it ideal for challenging environments.

A key aspect of SCALER's functionality is its GOAT gripper, a mechanically adaptive two-fingered device designed for high-tolerance gripping in varied terrains. It integrates spine-tipped fingers for optimal grasping on irregular surfaces, facilitating operations that involve loco-grasping—a combination of locomotion and manipulation—under demanding conditions.

Numerical Performance and Benchmarking

In terms of quantitative results, SCALER achieves a ground locomotion speed of 0.56 m/s and a climbing speed of 0.35 m/min on bouldering walls. Notably, its payload capacity reaches 233% of its own weight on the ground—signaling its potential in real-world applications requiring load-bearing capabilities. These results underscore the robot’s efficiency and mechanical proficiency across diverse scenarios.

When benchmarked against other climbing robotics platforms, SCALER distinguishes itself by operating under Earth's gravity—a feat less often demonstrated in this robotics domain. While robots like LEMUR 3 have been tailored for reduced gravity environments, SCALER's success under full gravity conditions represents a significant engineering accomplishment.

Theoretical and Practical Implications

The practical applications of SCALER are extensive, including infrastructure inspection, exploration, and scientific fieldwork where normal mobile platforms are inadequate. Theoretically, SCALER enhances our understanding of the intersection between robot design, control algorithms, and the dynamics of climbing mechanics—offering substantial insights for future high-DoF robotic systems and their deployment in complex real-world environments.

Future Directions

This research lays the groundwork for further advancements in the field of quadruped climbing robots. Future work might focus on the development of more sophisticated control algorithms, including advanced model predictive control (MPC) for enhanced trajectory planning and autonomous navigation capabilities. There is also potential for integrating more comprehensive sensor fusion and machine learning algorithms to improve environmental interaction and adaptability.

In conclusion, the SCALER platform represents a significant contribution to robotic engineering, addressing the multi-faceted challenges of mobility, manipulation, and load capacity in a single, versatile machine. Its design principles and demonstrated capabilities provide a pathway for future research and development in robotic free-climbing and beyond.