Towards Rich Motion Skills with the Lightweight Quadruped Robot Serval - A Design, Control and Experimental Study

Abstract

Bio-inspired robotic designs introducing and benefiting from morphological aspects present in animals allowed the generation of fast, robust and energy efficient locomotion. We used engineering tools and interdisciplinary knowledge transferred from biology to build low-cost robots able to achieve a certain level of versatility. Serval, a compliant quadruped robot with actuated spine and high range of motion in all joints was developed to address the question of what mechatronic complexity is needed to achieve rich motion skills. In our experiments, the robot presented a high level of versatility (number of skills) at medium speed, with a minimal control effort and, in this article, no usage of its spine. Implementing a basic kinematics-duplication from dogs, we found strengths to emphasize, weaknesses to correct and made Serval ready for future attempts to achieve more agile locomotion. In particular, we investigated the following skills: trot, bound (crouched), sidestep, turn with a radius, ascend slopes including flat ground transition, perform single and double step-downs, fall, trot over bumpy terrain, lie/sit down, and stand up.

Small-Sized Reconfigurable Quadruped Robot With Multiple Sensory Feedback for Studying Adaptive and Versatile Behaviors

“…However, despite the performance of the robots shedding significant light on legged robotic applications in the transport field, thus far, they have not been used to investigate the mechanisms of self-organized locomotion generation and basic research. Moreover, their heavy weight and large size may result in a high-operation complexity as well as pose dangers for handlers or researchers who may use them as a legged platform for studying bio-inspired locomotion control (Eckert et al, 2018).…”

“…These robots have exhibited such stable and dynamic locomotor capabilities that they are quite suitable for studying high-level application techniques (for example, path planning, navigation, and transportation). However, it remains somewhat challenging to use these robots for investigating middlelevel locomotion control (such as self-organized locomotion generation, reflex mechanisms, and compliant control), because their powerful actuators [that of the MIT Cheetah is ∼230 Nm (Bledt et al, 2018)] still pose a danger to single researchers while directly manipulating their joints (Eckert et al, 2018). Furthermore, the development and hardware costs of these robots are quite high.…”

Structural Design and Crawling Pattern Generator of a Planar Quadruped Robot for High-Payload Locomotion

“…The design of bionic robots has benefited from the introduction of robust and energy-saving movements based on those of animals. When compared with wheeled robots and other types of legged robots, quadruped robots can perform in response to external stimulation in an accurate and ideal manner of conditioned reflection and have the natural advantages of trafficability and agility on complex outdoor terrain [ 1 , 2 ]. At the same time, these robots offer further advantages in terms of dynamic locomotion, stability and manufacturing cost.…”

Learning Active Spine Behaviors for Dynamic and Efficient Locomotion in Quadruped Robots

“…There have been quite a few quadruped robots having passive or active spine in their structure, namely, BobCat, Sevel, MIT Cheetah, INU [2], [3], [4], [5], [6]. There is a large body of work over planer spine models with one DOF revolute [7], [8], [9], and prismatic [10] joints.…”

“…Apart from the one DOF model, the spines were modeled as point masses in these works. On the other hand, robots such as Sevel [3], INU [2] be longer while maintaining its orientation during bounding. However, reduced order models were used when constructing the empirical model of the robot.…”