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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Visual guidance of robot motion

Gu, Lifang January 1996 (has links)
Future robots are expected to cooperate with humans in daily activities. Efficient cooperation requires new techniques for transferring human skills to robots. This thesis presents an approach on how a robot can extract and replicate a motion by observing how a human instructor conducts it. In this way, the robot can be taught without any explicit instructions and the human instructor does not need any expertise in robot programming. A system has been implemented which consists of two main parts. The first part is data acquisition and motion extraction. Vision is the most important sensor with which a human can interact with the surrounding world. Therefore two cameras are used to capture the image sequences of a moving rigid object. In order to compress the incoming images from the cameras and extract 3D motion information of the rigid object, feature detection and tracking are applied to the images. Corners are chosen as the main features because they are more stable under perspective projection and during motion. A reliable corner detector is implemented and a new corner tracking algorithm is proposed based on smooth motion constraints. With both spatial and temporal constraints, 3D trajectories of a set of points on the object can be obtained and the 3D motion parameters of the object can be reliably calculated by the algorithm proposed in this thesis. Once the 3D motion parameters are available through the vision system, the robot should be programmed to replicate this motion. Since we are interested in smooth motion and the similarity between two motions, the task of the second part of our system is therefore to extract motion characteristics and to transfer these to the robot. It can be proven that the characteristics of a parametric cubic B-spline curve are completely determined by its control points, which can be obtained by the least-squares fitting method, given some data points on the curve. Therefore a parametric cubic B–spline curve is fitted to the motion data and its control points are calculated. Given the robot configuration the obtained control points can be scaled, translated, and rotated so that a motion trajectory can be generated for the robot to replicate the given motion in its own workspace with the required smoothness and similarity, although the absolute motion trajectories of the robot and the instructor can be different. All the above modules have been integrated and results of an experiment with the whole system show that the approach proposed in this thesis can extract motion characteristics and transfer these to a robot. A robot arm has successfully replicated a human arm movement with similar shape characteristics by our approach. In conclusion, such a system collects human skills and intelligence through vision and transfers them to the robot. Therefore, a robot with such a system can interact with its environment and learn by observation.

A torso driven walking algorithm for dynamically balanced variable speed biped robots

Sutherland, Alistair James January 2007 (has links)
As a contribution toward the objective of developing useful walking machines, this dissertation considers solutions to some of the problems involved with bipedal robot development. The main area of focus involves control system design and implementation for dynamically balanced walking robots. A new algorithm “Torso Driven Walking” is presented, which reduces the complexity of the control problem to that of balancing the robot’s torso. All other aspects of the system are indirectly controlled by the changing robot state resulting from direct control of the robot’s torso. The result is literally a “top-down” approach to control, where the control system actively balances the top-most component of the robot’s body, leaving the control of the lower limbs to a passive “state-driven” system designed to ensure the robot always keeps at least one leg between the torso and the ground. A series of low-cost robots and simulation systems have been constructed as experimental platforms for testing the proposed new control system. The robots have been designed to balance on “point” feet, and so the control system must be able to dynamically maintain balance, while moving at a variable velocity. The Torso Driven Walking control system achieves a fully dynamic, variable speed walking behaviour that does not rely on maintaining a stable supporting polygon for balance. In addition, the system exhibits a high degree of tolerance for low frequency “bias” or “drift” errors. These measurement errors are commonly encountered when using sensors for detecting torso inclination.

Learning mobile robot control for obstacle avoidance based on motion energy neurons /

Gao, Minqi. January 2009 (has links)
Includes bibliographical references (p. 47-49).

A real-time robot collision avoidance safety system

Herb, Gregory M. 08 June 2009 (has links)
A data structure and update algorithm are presented for a prototype real-time collision avoidance safety system supporting tele-operated robot arms. The data structure is a variant of the octree, which serves as a spatial index. An octree recursively decomposes three dimensional space into eight equal cubic octants (nodes) until each octant meets some decomposition criteria. Our octree stores cylspheres (cylinders with spheres on each end) and rectangular solids as primitives. These primitives make up the two seven-degrees-of-freedom robot arms and environment modeled by the system. Octree nodes containing more than a predetermined number N of primitives are decomposed. This rule keeps the octree small, as the entire environment for our application can be modeled using a few dozen primitives. As robot arms move, the octree is updated to reflect their changed positions. During most update cycles, any given primitive does not change which octree nodes it is in. Thus, modification to the octree is rarely required. Incidents in which one robot arm comes too close to the other arm or· an object in the environment are reported. Cycle time for receiving current joint angles, updating the octree, and detecting/reporting collisions is about 30 milliseconds on an Intel 80386 processor running at 20 MHz. / Master of Science

Improvements in the control of robotic motion simulations using the ATB model

Barineau, Daniel W. January 1988 (has links)
Modifications were made to the control model for torque generation in the Air Force Articulated Total Body (ATS) simulation computer program. Limb motion stability was improved by introducing integral control in the existing feedback control equation. Motion studies were performed using a Merlin robot model to determine control equation gains for single and multi-joint rotations up to 180 degrees. The robotic motion was made to resemble coordinated angular motion profiles that had previously been determined for similar human arm motion. The control equation gains for the six joints examined were added to the input description as a tabular set of data, which the program could access depending on the joint target angles prescribed by the user. Simultaneous multi-joint rotations were also studied using the same controlling values as were used for single joint rotations. These numbers produced accurate results for all joint rotations, as long as either the shoulder or elbow joints were held at their initial angular positions. The errors produced when the target angles for both the shoulder and elbow were non-zero were less than two degrees of arc. / Master of Science

Biped robot with a vestibular system

Huang, Chuen-Chane 13 October 2005 (has links)
The kinematics and dynamics of two legged or biped walking is considered. The resulting governing equations include actuator torques for a robot and muscle generated torques for a human. These torques are those necessary at each joint of a leg, including the foot, for a successful stride. The equations are developed from a consistent set variables with respect to a single inertial reference frame. This single reference frame approach has not been used by previous investigators. Control of the joint torques makes biped walking an extraordinary complex problem from a dynamics and control viewpoint. The control scheme that is developed incorporates the use of the direction of gravity as an important element in the overall control. The inclusion of gravity in biped robot walking has not previously been properly considered in other works. A way is described to separate gravity and acceleration which are measured by an accelerometer which is on the robot. This system incorporates the use of angular motion sensing of the robot segment that contains the linear accelerometers. This system was formulated based on human motion sensing and what probably is present in the human central nervous system for processing these signals. / Ph. D.

Galloping, bounding and wheeled-leg modes of locomotion on underactuated quadrupedal robots

Smith, James Andrew. January 2006 (has links)
No description available.

Controller estimation for the adaptive control of robotic manipulators

Guo, Lin, 1962- January 1987 (has links)
No description available.

Vision-Based Motion for a Humanoid Robot

Alkhulayfi, Khalid Abdullah 13 July 2016 (has links)
The overall objective of this thesis is to build an integrated, inexpensive, human-sized humanoid robot from scratch that looks and behaves like a human. More specifically, my goal is to build an android robot called Marie Curie robot that can act like a human actor in the Portland Cyber Theater in the play Quantum Debate with a known script of every robot behavior. In order to achieve this goal, the humanoid robot need to has degrees of freedom (DOF) similar to human DOFs. Each part of the Curie robot was built to achieve the goal of building a complete humanoid robot. The important additional constraints of this project were: 1) to build the robot from available components, 2) to minimize costs, and 3) to be simple enough that the design can be replicated by non-experts, so they can create robot theaters worldwide. Furthermore, the robot appears lifelike because it executes two main behaviors like a human being. The first behavior is tracking where the humanoid robot uses a tracking algorithm to follow a human being. In other words, the tracking algorithm allows the robot to control its neck using the information taken from the vision system to look at the nearest human face. In addition, the robot uses the same vision system to track labeled objects. The second behavior is grasping where the inverse kinematics (IK) is calculated so the robot can move its hand to a specific coordinate in the surrounding space. IK gives the robot the ability to move its end-effector (hand) closer to how humans move their hands.

Biomimetic Design and Construction of a Bipedal Walking Robot

Steele, Alexander Gabriel 15 June 2018 (has links)
Human balance and locomotion control is highly complex and not well understood. To understand how the nervous system controls balance and locomotion works, we test how the body responds to controlled perturbations, the results are analyzed, and control models are developed. However, to recreate this system of control there is a need for a robot with human-like kinematics. Unfortunately, such a robotic testbed does not exist despite the numerous applications such a design would have in mobile robotics, healthcare, and prosthetics. This thesis presents a robotic testbed model of human lower legs. By using MRI and CT scans, I designed joints that require lower force for actuation, are more wear resistant, and are less prone to catastrophic failure than a traditional revolute (or pinned) joints. The result of using this process is the design, construction, and performance analysis of a biologically inspired knee joint for use in bipedal robotics. For the knee joint, the design copies the condylar surfaces of the distal end of the femur and utilizes the same crossed four-bar linkage design the human knee uses. The joint includes a changing center of rotation, a screw-home mechanism, and patella; these are characteristics of the knee that are desirable to copy for bipedal robotics. The design was calculated to have an average sliding to rolling ratio of 0.079, a maximum moment arm of 2.7 inches and a range of motion of 151 degrees. This should reduce joint wear and have kinematics similar to the human knee. I also designed and constructed novel, adjustably-damped hip and ankle joints that use braided pneumatic actuators. These joints provide a wide range of motion and exhibit the same change in stiffness that human joints exhibit as flexion increases, increasing stability, adaptability, and controllability. The theoretical behaviors of the joints make them desirable for use in mobile robotics and should provide a lightweight yet mechanically strong connection that is resistant to unexpected perturbations and catastrophic failure. The joints also bridge the gap between completely soft robotics and completely rigid robotics. These joints will give researchers the ability to test different control schemes and will help to determine how human balance is achieved. They will also lead to robots that are lighter and have lower power requirements while increasing the adaptability of the robot. When applying these design principles to joints used for prosthetics, we reduce the discomfort of the wearer and reduce the effort needed to move. Both of which are serious issues for individuals who need to wear a prosthetic device.

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