1,230 research outputs found
Virtual Constraints and Hybrid Zero Dynamics for Realizing Underactuated Bipedal Locomotion
Underactuation is ubiquitous in human locomotion and should be ubiquitous in
bipedal robotic locomotion as well. This chapter presents a coherent theory for
the design of feedback controllers that achieve stable walking gaits in
underactuated bipedal robots. Two fundamental tools are introduced, virtual
constraints and hybrid zero dynamics. Virtual constraints are relations on the
state variables of a mechanical model that are imposed through a time-invariant
feedback controller. One of their roles is to synchronize the robot's joints to
an internal gait phasing variable. A second role is to induce a low dimensional
system, the zero dynamics, that captures the underactuated aspects of a robot's
model, without any approximations. To enhance intuition, the relation between
physical constraints and virtual constraints is first established. From here,
the hybrid zero dynamics of an underactuated bipedal model is developed, and
its fundamental role in the design of asymptotically stable walking motions is
established. The chapter includes numerous references to robots on which the
highlighted techniques have been implemented.Comment: 17 pages, 4 figures, bookchapte
Optimal Kinematic Design of a Robotic Lizard using Four-Bar and Five-Bar Mechanisms
Designing a mechanism to mimic the motion of a common house gecko is the
objective of this work. The body of the robot is designed using four five-bar
mechanisms (2-RRRRR and 2-RRPRR) and the leg is designed using four four-bar
mechanisms. The 2-RRRRR five-bar mechanisms form the head and tail of the
robotic lizard. The 2-RRPRR five-bar mechanisms form the left and right sides
of the body in the robotic lizard. The four five-bar mechanisms are actuated by
only four rotary actuators. Of these, two actuators control the head movements
and the other two control the tail movements. The RRPRR five-bar mechanism is
controlled by one actuator from the head five-bar mechanism and the other by
the tail five-bar mechanism. A tension spring connects each active link to a
link in the four bar mechanism. When the robot is actuated, the head, tail and
the body moves, and simultaneously each leg moves accordingly. This kind of
actuation where the motion transfer occurs from body of the robot to the leg is
the novelty in our design. The dimensional synthesis of the robotic lizard is
done and presented. Then the forward and inverse kinematics of the mechanism,
and configuration space singularities identification for the robot are
presented. The gait exhibited by the gecko is studied and then simulated. A
computer aided design of the robotic lizard is created and a prototype is made
by 3D printing the parts. The prototype is controlled using Arduino UNO as a
micro-controller. The experimental results are finally presented based on the
gait analysis that was done earlier. The forward walking, and turning motion
are done and snapshots are presented.Comment: 21 pages, 10 figures, Submitted for iNaCoMM 2023 conferenc
Feedback Control of an Exoskeleton for Paraplegics: Toward Robustly Stable Hands-free Dynamic Walking
This manuscript presents control of a high-DOF fully actuated lower-limb
exoskeleton for paraplegic individuals. The key novelty is the ability for the
user to walk without the use of crutches or other external means of
stabilization. We harness the power of modern optimization techniques and
supervised machine learning to develop a smooth feedback control policy that
provides robust velocity regulation and perturbation rejection. Preliminary
evaluation of the stability and robustness of the proposed approach is
demonstrated through the Gazebo simulation environment. In addition,
preliminary experimental results with (complete) paraplegic individuals are
included for the previous version of the controller.Comment: Submitted to IEEE Control System Magazine. This version addresses
reviewers' concerns about the robustness of the algorithm and the motivation
for using such exoskeleton
Bio-Inspired Robotics
Modern robotic technologies have enabled robots to operate in a variety of unstructured and dynamically-changing environments, in addition to traditional structured environments. Robots have, thus, become an important element in our everyday lives. One key approach to develop such intelligent and autonomous robots is to draw inspiration from biological systems. Biological structure, mechanisms, and underlying principles have the potential to provide new ideas to support the improvement of conventional robotic designs and control. Such biological principles usually originate from animal or even plant models, for robots, which can sense, think, walk, swim, crawl, jump or even fly. Thus, it is believed that these bio-inspired methods are becoming increasingly important in the face of complex applications. Bio-inspired robotics is leading to the study of innovative structures and computing with sensory–motor coordination and learning to achieve intelligence, flexibility, stability, and adaptation for emergent robotic applications, such as manipulation, learning, and control. This Special Issue invites original papers of innovative ideas and concepts, new discoveries and improvements, and novel applications and business models relevant to the selected topics of ``Bio-Inspired Robotics''. Bio-Inspired Robotics is a broad topic and an ongoing expanding field. This Special Issue collates 30 papers that address some of the important challenges and opportunities in this broad and expanding field
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