Browsing by Author "Ghorbel, Fathi H"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Analysis and Design of an In-line Pump as a Thruster for Swimming Robots
    (2018-04-19) Deng, Hankun; Ghorbel, Fathi H
    With the development of science and technology, human labors have been greatly liberated from tedious and dangerous work. In recent several decades, different kinds of robots start playing important roles in people’s lives. Among those robots, the swimming robot is special and still in the beginning of its development. Swimming robots have been served in many aspects. However, establishing precise control system is always a challenge for the design and use of swimming robots. Unlike robot arms that are well understood, mechanism of thrust generators is more complicated and their performance is unpredictable compared with DC motors. The purpose of this project is to design a thrust generator which is amenable to feedback control. When the feedback signal is the angular velocity of the impeller, the relationship between angular velocity and generated thrust force should be clear and reliable. Thrust force can be calculated by the flow-rate of the pump. Hence, finding a relationship between flow-rate and angular velocity is of the first priority. In this thesis, a new pump is designed and analyzed based on the IL-500P pump that is currently served as a thrust generator in RiSYS swimming robot. Then, the mathematical model simulation and finite element analysis are implemented for its performance.
  • Thumbnail Image
    Item
    Analytical investigation of vibration attenuation with a nonlinear tuned mass damper
    (2015-04-24) Atzil, Aaron M; Dick, Andrew J; Ghorbel, Fathi H; O'Malley, Marcia K; Nagarajaiah, Satish
    Vibration attenuation devices are used to reduce the vibrations of various mechanical systems and structures. In this work, an analytical method is proposed to provide the means to investigate the influence of system parameters on the dynamic response of a system. The method of multiple scales is used to calculate an approximate broadband solution for a two degree-of-freedom system consisting of a linear primary structure and a nonlinear tuned mass damper. The model is decoupled, approximate analytical solutions are calculated, and then they are combined to produce the desired frequency-response information. The approach is initially applied to a linear two degree-of-freedom system in order to verify its performance. The approach is then applied to the nonlinear system in order to study how varying the values of parameters associated with the nonlinear absorber affect its ability to attenuate the response of the primary structure. Finally, the analytical solution is compared to a numerical solution in order to determine how well it approximates the nonlinear system frequency-response.
  • Thumbnail Image
    Item
    Digital Twin for Prognostics: Analysis, Simulation, and Experiment
    (2023-04-21) Brownell, Kenneth Clay; Ghorbel, Fathi H
    The emerging research on Digital Twins (DTs) for prognostics has been vital to the future of Industry 4.0. These DTs can be utilized to increase the accuracy and efficiency for prognostics and health management (PHM) for complex industrial equipment. This is based on the approximation of the Remaining Useful Life (RUL) which requires an accurate digital twin that represents the dynamics of the physical system. However, the dynamics for the physical system do not remain constant due to structural changes over time. Research by our group on the application of an equation discovery technique known as Model Error Discovery with Interpretability and Data Assimilation (MEDIDA) for DTs has proven feasible for structural identification and model updates. This thesis analyzes the elements of a DT for prognostics through structural identification for an Industrial Emulator (IE) experimental setup. A closed-loop system was determined necessary for structural identification and was used to successfully identify a single nonlinearity and a nonlinearity caused by frictional dynamics of the LuGre friction model with an additional unmeasurable state. These elements are crucial to obtain a DT that replicates the physical system and provides a more accurate RUL calculation for prognostics.
  • Thumbnail Image
    Item
    Hardware- versus Human-centric Assessment of Rehabilitation Robots
    (2015-04-20) Rose, Chad Gregory; O'Malley, Marcia K.; Ghorbel, Fathi H; Dick, Andrew J
    Individuals with disabilities arising from neurological injury require rehabilitation of the distal joints of the upper extremities to regain the ability to independently perform activities of daily living (ADL). Robotic rehabilitation has been shown to effectively conduct high intensity, long duration therapy and quantitatively assess the effects of therapy. This thesis presents methods and results for validating rehabilitation devices for training and assessment. Traditionally, methods for validating rehabilitation robots relied on robotic characterizations, which enables comparison of different designs' performance independent of a human user. An example of this method is presented here, in particular quantifying the torque output, range of motion, closed loop position performance, and high spatial resolution of two rehabilitation devices. However, these traditional validation methods do not assess the effect wearing the robot has on the user, and a new assessment method has been developed to address this shortcoming of traditional methods. A novel hand and wrist device was assessed through kinematic analysis of synergistic movements, as quantified by velocity- and position-dependent metrics. This experimental approach is promising for the characterization of multi-articular wearable robots as measurement tools in robotic rehabilitation. Together, the two methods presented can be used to validate rehabilitation robotic devices.
  • Thumbnail Image
    Item
    Myoelectric Control of a Robotic Exoskeleton for Rehabilitation
    (2015-04-21) Artz, Edward J; O'Malley, Marcia K.; Ghorbel, Fathi H; McLurkin, James
    A primary challenge in the design of human-robot interfaces for rehabilitation after neurological injury, such as stroke or spinal cord injury, is the detection of user intent, needed to maximize the efficacy of the therapy. Common approaches to rehabilitation robot interfaces, including the current implementation of the MAHI Exo-II upper extremity therapeutic exoskeleton at Rice University, rely on impedance control schemes. Another approach, surface electromyography (sEMG), is gaining attention. This interface is appealing as the recorded signal is related to the individual's desired torque about the joint the muscle actuates. In this thesis, an sEMG interface and associated control schemes are proposed and investigated for the MAHI Exo-II. A known drawback of sEMG interfaces are lengthy subject- and session-dependent calibration procedures to develop muscle-force mappings. In this thesis, a relaxed calibration procedure and various control schemes are proposed to enable practical integration into therapy protocols. Agonist-antagonist muscle groups were related following normalization based on sub-maximal isometric contraction in the exoskeleton. Pilot experiments were conducted on healthy subjects to assess the usability of the exoskeleton in the proposed control modes of operation given simple sEMG interface. The results of these experiments support the implementation of the proposed sEMG interface. Future experiments will focus on validation in impaired populations.