Design and construction of a novel tribometer with on-line topography and wear measurement

We present a novel experimental platform that links topographical and material changes with the friction and wear behavior of oil-lubricated metal surfaces. This concept combines state-of-the-art methods for the analysis of the surface topography on the micro- and nano-scale with the online measurement of wear. At the same time, it allows for frictional and lateral force detection. Information on the topography of one of the two surfaces is gathered in-situ with a 3D holography microscope at a maximum frequency of 15 fps and higher resolution images are provided at defined time intervals by an atomic force microscope (AFM). The wear measurement is conducted on-line by means of radio nuclide technique (RNT). The quantitative measurement of the lateral and frictional forces is conducted with a custom-built 3D force sensor. The surfaces can be lubricated with an optically transparent oil or water. The stability and precision of the setup have been tested in a model experiment. The results show that the exact same position can be relocated and examined after each load cycle. Wear and topography measurements were performed with a radioactive labeled iron pin sliding against an iron plate

7-DOF Robotic Arm XY-Plane Translational Stability

Robotic arms are traditionally mounted to rigid structures as they perform tasks. As a result, the arm’s movement would not affect the position of its mount and its operational space that it is performing a task within would remain constant. If a robotic arm were to function in orbit, the motion of the arm would cause it to rotate and translate about its center of mass, which changes as the joints of the arm rotate. The purpose of this thesis is to focus on the two-dimensional translational effects of an arm operating on a simulated zero-friction surface and provide a method to anticipate and stabilize these induced forces. By calculating the forces generated by the movement of a 7-DOF Sawyer robotic arm using the arm’s Universal Robotics Description Format (URDF) parameters provided by Spear (2017) and a Denavit-Hartenberg method for the geometric solution of the arm’s kinematics, the induced motion caused by the arm’s movement can be arrested by an efficient control system. Using an XY-table to compensate for the induced motion of the arm, a comparison is made for an open-loop and closed-loop control of a cable driven XY-table. From this analysis, a better understanding of an active mount solution for robotic arms can be identified. The key findings of this research are the validation of open-loop control response based on the calculated reaction force provided by kinematic analysis of the robotic arm’s center of mass. Additionally, a closed-loop control response is assessed based on an applied external force to the system during operation. Both results lead to a controlled system displacement error that does not exceed 1e10-14 meters for the four test cases presented

Dynamic and Control of Air-Bearing Spacecraft Simulator

An air bearing is being designed as a spacecraft rotational motion simulator, featuring the Sawyer Robot and its control box. The objective is to maneuver the robot as desired, performing operations specific to on-orbit servicing operations while maintaining stability of the system. Before the control can be designed, the dynamics of the platform and the robot must be modeled. The dynamics of the robot can be derived utilizing a Newton-Euler recursive approach. By beginning with a simple pendulum, then adding links (degrees of freedom) to more closely resemble the Sawyer arm, the equations of motion for the robot can be developed. After the equations of motion for the robot are derived, the next step is to model the dynamics of the entire platform, which adds three more degrees of freedom to the system. The Newton-Euler recursive approach is not compatible with the system with the addition of the spherical joint; therefore a new approach is adopted to model the attitude dynamics in terms of Euler angles. Once the dynamics are modeled, control design can take place, where an incremental non-linear dynamic inversion controller is designed to reject the disturbances of the robot performing its maneuver, while also actuating the platform to a desired attitude

Human-robot interaction for assistive robotics

This dissertation presents an in-depth study of human-robot interaction (HRI) withapplication to assistive robotics. In various studies, dexterous in-hand manipulation is included, assistive robots for Sit-To-stand (STS) assistance along with the human intention estimation. In Chapter 1, the background and issues of HRI are explicitly discussed. In Chapter 2, the literature review introduces the recent state-of-the-art research on HRI, such as physical Human-Robot Interaction (HRI), robot STS assistance, dexterous in hand manipulation and human intention estimation. In Chapter 3, various models and control algorithms are described in detail. Chapter 4 introduces the research equipment. Chapter 5 presents innovative theories and implementations of HRI in assistive robotics, including a general methodology of robotic assistance from the human perspective, novel hardware design, robotic sit-to-stand (STS) assistance, human intention estimation, and control

Bank-to-turn control technology survey for homing missiles

The potential advantages of bank-to-turn control are summarized. Recent and current programs actively investigating bank-to-turn steering are reviewed and critical technology areas concerned with bank-to-turn control are assessed

Vision technology/algorithms for space robotics applications

The thrust of automation and robotics for space applications has been proposed for increased productivity, improved reliability, increased flexibility, higher safety, and for the performance of automating time-consuming tasks, increasing productivity/performance of crew-accomplished tasks, and performing tasks beyond the capability of the crew. This paper provides a review of efforts currently in progress in the area of robotic vision. Both systems and algorithms are discussed. The evolution of future vision/sensing is projected to include the fusion of multisensors ranging from microwave to optical with multimode capability to include position, attitude, recognition, and motion parameters. The key feature of the overall system design will be small size and weight, fast signal processing, robust algorithms, and accurate parameter determination. These aspects of vision/sensing are also discussed