Abstract This paper presents the design, dynamic modeling, and integration of a single degree of freedom (DOF) robotic leg mechanism intended for tailed quadruped locomotion. The design employs a lightweight six-bar linkage that couples the hip and knee flexion/extension joints mechanically, requiring only a single degree of actuation. By utilizing a parametric optimization, a unique topological arrangement is achieved that results in a foot trajectory that is well suited for dynamic gaits including trot-running, bounding, and galloping. Furthermore, a singular perturbation is introduced to the hybrid dynamic framework to address the lack of robust methods that provide a solution for the differential algebraic equations (DAEs) that characterize closed kinematic chain (CKC) structures as well as the hybrid nature of legged locomotion. By approximating the system dynamics as ordinary differential equations (ODEs) and asymptotically driving the constraint error to zero, CKCs can adopt existing real-time model-based/model-predictive/hybrid-control frameworks. The dynamic model is verified through simulations and the foot trajectory was experimentally validated. Preliminary open-loop planar running demonstrated speeds up to 3.2 m/s. These advantages, accompanied by low-integration costs, warrant this leg as a robust, effective platform for future tailed quadruped research.
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Feedback Control of the Locomotion of a Tailed Quadruped Robot
The traditional locomotion paradigm of quadruped robots is to use dexterous (multi degrees of freedom) legs and dynamically optimized footholds to balance the body and achieve stable locomotion. With the introduction of a robotic tail, a new locomotion paradigm becomes possible as the balancing is achieved by the tail and the legs are only responsible for propulsion. Since the burden on the leg is reduced, leg complexity can be also reduced. This paper explores this new paradigm by tackling the dynamic locomotion control problem of a reduced complexity quadruped (RCQ) with a pendulum tail. For this specific control task, a new control strategy is proposed in a manner that the legs are planned to execute the open-loop gait motion in advance, while the tail is controlled in a closed-loop to prepare the quadruped body in the desired orientation. With these two parts working cooperatively, the quadruped achieves dynamic locomotion. Partial feedback linearization (PFL) controller is used for the closed-loop tail control. Pronking, bounding, and maneuvering are tested to evaluate the controller’s performance. The results validate the proposed controller and demonstrate the feasibility and potential of the new locomotion paradigm.
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- Award ID(s):
- 1906727
- NSF-PAR ID:
- 10326665
- Date Published:
- Journal Name:
- ASME 2021 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, 45TH MECHANISMS AND ROBOTICS CONFERENCE (MR)
- Volume:
- Volume 8B
- Issue:
- V08BT08A009
- Page Range / eLocation ID:
- 1-8
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1115/DETC2021-71611
