Abstract
This paper proposes the concept of full configuration state of metamorphic mechanism. Based on the concept, the configuration synthesis principle of metamorphic parallel mechanism is put forward. Firstly, a metamorphic parallel mechanism in full configuration state is synthesized, and then full configuration state evolves into a specific configuration state by increasing constraints or decreasing degrees of freedom. A reconfigurable moving platform based on the triple symmetric Bricard spatial closed-loop mechanism with a single degree of freedom is proposed. Based on this, a new method for switching motion configuration states of the metamorphic parallel mechanism is constructed. According to the configuration synthesis principle presented above, a novel metamorphic parallel mechanism that can switch between three- and four-degree-of-freedom is synthesized, and then the triple symmetric Bricard spatial closed-loop mechanism is used as the reconfigurable moving platform (that is, the reconfigurable foot of a walking robot) of the metamorphic mechanism, and thus, a novel metamorphic parallel leg mechanism is created. The screw theory is used to verify the degrees of freedom of the new type of metamorphic parallel leg. The proposed metamorphic parallel leg mechanism is expected to improve flexibility and adaptability of walking robots in unstructured environment.
Highlights
Analysis of Degree of Freedom for Metamorphic Parallel Leg MechanismTo realize discontinuous contacts with three-dimensional terrains for a walking robot, a walking leg mechanism should have at least three spatial degrees of freedom, which should include at least one prismatic degree of freedom in order to adapt to the terrain well and decrease foot-ground impact [13]
Mathematical Problems in Engineering components, the number of kinematic pairs changed by locking and releasing of kinematic pairs, the characteristics of components changed by different stiffnesses or flexibilities, the characteristics of kinematic pairs changed by different types and axes geometric relationship, and the adjacency relationship between component modules changed by reorganization of the same or similar units
Research hotspots of parallel metamorphic mechanisms mainly focus on configuration synthesis and metamorphic characteristic analysis
Summary
To realize discontinuous contacts with three-dimensional terrains for a walking robot, a walking leg mechanism should have at least three spatial degrees of freedom, which should include at least one prismatic degree of freedom in order to adapt to the terrain well and decrease foot-ground impact [13]. E leg with such 2R1T (where R denotes a rotational degree of freedom and T denotes a translational degree of freedom) degrees of freedom is easy to control and can walk quickly but is not flexible enough to turn; it may lead to the overall instability of the robot. Aiming at the requirements of degrees of freedom for walking robots in complex and variable environments, this paper proposes a new concept of metamorphic parallel leg mechanism with a reconfigurable moving platform (as the reconfigurable foot of the robot).
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