Abstract
In this study, a novel design for a compact, lightweight, agile, omnidirectional three-legged robot involving legs with four degrees of freedom, utilizing an spherical parallel mechanism with an additional non-redundant central support joint for the robot hip structure is proposed. The general design and conceptual ideas for the robot are presented, targeting a close match of the well-known SLIP-model. CAD models, 3d-printed prototypes, and proof-of-concept multi-body simulations are shown, investigating the feasibility to employ a geometrically dense spherical parallel manipulator with completely spherically shaped shell-type parts for the highly force-loaded application in the legged robot hip mechanism. Furthermore, in this study, an analytic expression is derived, yielding the calculation of stress forces acting inside the linkage structures, by directly constructing the manipulator hip Jacobian inside the force domain.
Highlights
Legged robots and their locomotion is an highly active field of research
As can be observed in the diagram, the hip joint at T takes a substantial amount of load forces fR in the vertical and horizontal directions, which are otherwise exerted in the tcp joint for the non-support configuration T
Since forces are transmitted into the tcp joint, the tool-platform has to be carried to the full amount by the outer linkage structure in the T configuration, and the employment of the load support joint highly reduces the overall stress of the manipulator structure
Summary
Regarding the impressive ability of living beings to traverse even and complicated uneven terrain, researchers are motivated to understand and recreate natural locomotion with the development of walking robots. In this regard, remarkable results have been proposed in the past, getting robots to walk over difficult terrain without falling over or being able to stabilize themselves after loosing balance. The SLIP Model Considering natural and energy efficient locomotion, a well known mathematical concept describing the locomotion of animals is the spring-loaded inverted pendulum (SLIP). Regarding a serial arrangement of the motor, the spring, and the leg joint, springs are important for impact reduction at the moment of foot-to-ground contact while walking, acting as a decoupling element [4] between the mechanical structure and the motor inertias
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