526 research outputs found
Dynamic Gaits and Control in Flexible Body Quadruped Robot
Legged robots are highly attractive for
military purposes such as carrying heavy loads on uneven
terrain for long durations because of the higher mobility
they give on rough terrain compared to wheeled
vehicles/robots. Existing state-of-the-art quadruped robots
developed by Boston Dynamics such as LittleDog and
BigDog do not have flexible bodies. It can be easily seen that
the agility of quadruped animals such as dogs, cats, and deer
etc. depend to a large extent on their ability to flex their
bodies. However, simulation study on step climbing in 3D
terrain quadruped robot locomotion with flexible body has
not been reported in literature. This paper aims to study the
effect of body flexibility on stability and energy efficiency in
walking mode, trot mode and running (bounding) mode on
step climbing
Master of Science
thesisThis research studies the passive dynamics of an under-actuated trotting quadruped. The goal of this project is to perform three-dimensional (3D) dynamic simulations of a trotting quadruped robot to find proper leg configurations and stiffness range, in order to achieve stable trotting gait. First, a 3D simulation framework that includes all the six degrees of freedom of the body is introduced. Directionally compliant legs together with different leg configurations are employed to achieve passive stability. Compliant legs passively support the body during stance phase and during flight phase a motor is used to retract the legs. Leg configurations in the robot's sagittal and frontal plane are introduced. Numerical experiments are conducted to search the design space of the leg, focusing on increasing the passive stability of the robot. Increased stability is defined as decreased pitching, rolling, and yawing motion of the robot. The results indicate that optimized leg parameters can guarantee passive stable trotting with reduced roll, pitch, and yaw. Studies suggest that a quadruped robot with compliant legs is dynamically stable while trotting. Results indicate that the robot based on a biological model (i.e., caudal inclination of humeri and cranial inclination of femora) has the best performance. Stiff springs at hips and shoulders, soft spring at knees and elbows, and stiff springs at ankles and wrists are recommended. The results of this project provide a conceptual framework for understanding the movements of a trotting quadruped
Fast and Continuous Foothold Adaptation for Dynamic Locomotion through CNNs
Legged robots can outperform wheeled machines for most navigation tasks
across unknown and rough terrains. For such tasks, visual feedback is a
fundamental asset to provide robots with terrain-awareness. However, robust
dynamic locomotion on difficult terrains with real-time performance guarantees
remains a challenge. We present here a real-time, dynamic foothold adaptation
strategy based on visual feedback. Our method adjusts the landing position of
the feet in a fully reactive manner, using only on-board computers and sensors.
The correction is computed and executed continuously along the swing phase
trajectory of each leg. To efficiently adapt the landing position, we implement
a self-supervised foothold classifier based on a Convolutional Neural Network
(CNN). Our method results in an up to 200 times faster computation with respect
to the full-blown heuristics. Our goal is to react to visual stimuli from the
environment, bridging the gap between blind reactive locomotion and purely
vision-based planning strategies. We assess the performance of our method on
the dynamic quadruped robot HyQ, executing static and dynamic gaits (at speeds
up to 0.5 m/s) in both simulated and real scenarios; the benefit of safe
foothold adaptation is clearly demonstrated by the overall robot behavior.Comment: 9 pages, 11 figures. Accepted to RA-L + ICRA 2019, January 201
Development of a quadruped mobile robot and its movement system using geometric-based inverse kinematics
As the main testbed platform of Artificial Intelligence, the robot plays an essential role in creating an environment for industrial revolution 4.0. According to their bases, the robot can be categorized into a fixed based robot and a mobile robot. Current robotics research direction is interesting since people strive to create a mobile robot able to move in the land, water, and air. This paper presents development of a quadruped mobile robot and its movement system using geometric-based inverse kinematics. The study is related to the movement of a four-legged (quadruped) mobile robot with three Degrees of Freedom (3 DOF) for each leg. Because it has four legs, the movement of the robot can only be done through coordinating the movements of each leg. In this study, the trot gait pattern method is proposed to coordinate the movement of the robot's legs. The end-effector position of each leg is generated by a simple trajectory generator with half rectified sine wave pattern. Furthermore, to move each robot's leg, it is proposed to use geometric-based inverse kinematic. The experimental results showed that the proposed method succeeded in moving the mobile robot with precision. Movement errors in the translation direction are 1.83% with the average pose error of 1.33 degrees, means the mobile robot has good walking stability
Perception Based Gait Generation for Quadrupedal Characters
With the rapid expansion of the range of digital characters involved in film and game production, creating a wide variety of expressive characters has become a problem that cannot be solved efficiently through current animation methods. Key-frame animation is time-consuming and requires animation expertise. Motion capture is constrained by equipment and environment requirements and is most applicable to humanoid characters. Simulation can produce physically correct motion but does not account for expressiveness. This thesis focuses on developing a more efficient animation system using a procedural approach in which the skeletal structure and characteristics of motion that communicate weight and age in quadrupeds have been isolated and engineered as user-controlled tools and modifiers to build creature shape and synthesize cyclic gait animation. This new approach accomplished the goal of quick generation of expressive characters. It is also successful in achieving real-time animation playback and adjustment
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