Modeling and Control of Flexible Link Manipulators

Autonomous maritime navigation and offshore operations have gained wide attention with the aim of reducing operational costs and increasing reliability and safety. Offshore operations, such as wind farm inspection, sea farm cleaning, and ship mooring, could be carried out autonomously or semi-autonomously by mounting one or more long-reach robots on the ship/vessel. In addition to offshore applications, long-reach manipulators can be used in many other engineering applications such as construction automation, aerospace industry, and space research. Some applications require the design of long and slender mechanical structures, which possess some degrees of flexibility and deflections because of the material used and the length of the links. The link elasticity causes deflection leading to problems in precise position control of the end-effector. So, it is necessary to compensate for the deflection of the long-reach arm to fully utilize the long-reach lightweight flexible manipulators. This thesis aims at presenting a unified understanding of modeling, control, and application of long-reach flexible manipulators. State-of-the-art dynamic modeling techniques and control schemes of the flexible link manipulators (FLMs) are discussed along with their merits, limitations, and challenges. The kinematics and dynamics of a planar multi-link flexible manipulator are presented. The effects of robot configuration and payload on the mode shapes and eigenfrequencies of the flexible links are discussed. A method to estimate and compensate for the static deflection of the multi-link flexible manipulators under gravity is proposed and experimentally validated. The redundant degree of freedom of the planar multi-link flexible manipulator is exploited to minimize vibrations. The application of a long-reach arm in autonomous mooring operation based on sensor fusion using camera and light detection and ranging (LiDAR) data is proposed.publishedVersio

Control of Redundant Flexible Manipulators with Redundancy Resolution

Author's accepted manuscript.© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper deals with the online control of a redundant flexible link manipulator to achieve minimum oscillations using the redundancy resolution technique. Different redundancy resolution techniques proposed and used for rigid link manipulators are tested for their use in the case of flexible link manipulators. The simulation model of a planar three-link flexible manipulator is used in this study. The redundancy resolution using kinetic energy minimization techniques is compared with the local joint acceleration minimization method to show the advantage of achieving minimum vibrations.acceptedVersio

Dynamic Modeling of Planar Multi-Link Flexible Manipulators

A closed-form dynamic model of the planar multi-link flexible manipulator is presented. The assumed modes method is used with the Lagrangian formulation to obtain the dynamic equations of motion. Explicit equations of motion are derived for a three-link case assuming two modes of vibration for each link. The eigenvalue problem associated with the mass boundary conditions, which changes with the robot configuration and payload, is discussed. The time-domain simulation results and frequency-domain analysis of the dynamic model are presented to show the validity of the theoretical derivation.publishedVersio

Static Deflection Compensation of Multi-Link Flexible Manipulators Under Gravity

The static deflection compensation method of a planar multi-link flexible manipulator is proposed using the feedback from inertial sensors mounted at the tip of each link. The proposed compensation technique is validated experimentally using a high-precision laser tracker. The proposed strategy is experimentally verified using a three-link flexible manipulator. A strategy to compensate for the centripetal and tangential acceleration induced on the accelerometer mounted on the rotating link is proposed for correct inclination estimation. The improvement in the inclination estimation using the proposed compensation technique is verified both in simulation and experimental studies.publishedVersio

Knowledge and Perception of Public Towards Medico Legal Autopsy in Nepal

Introduction: Autopsy is an important tool to determine the cause of death. This study was conducted with the objectives to assess the knowledge and perception of Nepalese people towards medico legal autopsy. Methods: It was a questionnaire based cross sectional study performed among the general public of Nepal. A standard pretested questionnaire was used to collect the responses on knowledge and perception of the people about medico legal autopsy. Independent samples t-test was used to compare the mean score of knowledge among the various groups. P value of < 0.05 was considered significant. Results: Mean age of the respondents was 29.06 years (SD = 10.50) and 72.31% were male (n = 188, N = 260). Mean score of knowledge was 6.65 (SD = 1.76) out of a total ten. The score was significantly higher (p = 0.02) among the respondents whose relatives had undergone an autopsy than those whose were not. It was comparable among the educated and uneducated groups.  A total of 75.77% respondents (n = 197, N = 260) would not reject the autopsy of their relatives. Conclusion: People lack knowledge mostly in basic elements of medico legal autopsy. Most of the people showed positive perception towards autopsy and those who were negative, feared of disfigurement of the bodies after an autopsy

Unzipping flood vulnerability and functionality loss:tale of struggle for existence of riparian buildings

Floods pose significant risk to riparian buildings as evidenced during many historical events. Although structural resilience to tsunami flooding is well studied in the literature, high-velocity and debris-laden floods in steep terrains are not considered adequately so far. Historical floods in steep terrains necessitate the need for flood vulnerability analysis of buildings. To this end, we report vulnerability of riparian-reinforced concrete buildings using forensic damage interpretations and empirical/analytical vulnerability analyses. Furthermore, we propose the concept and implications of functionality loss due to flooding in residential reinforced concrete (RC) buildings using empirical data. Fragility functions using inundation depth and momentum flux are presented for RC buildings considering a recent flooding event in Nepal. The results show that flow velocity and sediment load, rather than hydrostatic load, govern the damages in riparian RC buildings. However, at larger inundation depth, hydrostatic force alone may collapse some of the RC buildings

Kinematic Control of Redundant Manipulators

Treball de Final de Màster Universitari Erasmus Mundus en Robòtica Avançada. Curs acadèmic 2016-2017While most manipulators have enough degrees of freedom (DOFs) to perform tasks in their end-effector task space (desired position and orientation), their workspace is limited due to mechanical joint constraints and obstacles that may be present in the work space. Redundant manipulators have extra DOFs than required for reaching the desired position and orientation of the end-effector. This allows the redundant manipulators to use the extra DOFs to avoid their joint limits and obstacles in the workspace, while still reaching a desired end-effector pose in the task space. The objective of the thesis is to implement and analyze the performance of most common methods for redundancy resolution with respect to algorithmic and kinematic singularity, and incorporation of different additional desired tasks, e.g., joint limit avoidance, singularity avoidance. Moreover, wrist mounted force/torque sensor is calibrated and used to detect the contact with the objects in the environment and for the robust extraction of the object during picking and stowing operations. The thesis is a part of work done for Amazon Robotics Challenge 2017

Modeling and Control of Flexible Link Manipulators

Autonomous maritime navigation and offshore operations have gained wide attention with the aim of reducing operational costs and increasing reliability and safety. Offshore operations, such as wind farm inspection, sea farm cleaning, and ship mooring, could be carried out autonomously or semi-autonomously by mounting one or more long-reach robots on the ship/vessel. In addition to offshore applications, long-reach manipulators can be used in many other engineering applications such as construction automation, aerospace industry, and space research. Some applications require the design of long and slender mechanical structures, which possess some degrees of flexibility and deflections because of the material used and the length of the links. The link elasticity causes deflection leading to problems in precise position control of the end-effector. So, it is necessary to compensate for the deflection of the long-reach arm to fully utilize the long-reach lightweight flexible manipulators. This thesis aims at presenting a unified understanding of modeling, control, and application of long-reach flexible manipulators. State-of-the-art dynamic modeling techniques and control schemes of the flexible link manipulators (FLMs) are discussed along with their merits, limitations, and challenges. The kinematics and dynamics of a planar multi-link flexible manipulator are presented. The effects of robot configuration and payload on the mode shapes and eigenfrequencies of the flexible links are discussed. A method to estimate and compensate for the static deflection of the multi-link flexible manipulators under gravity is proposed and experimentally validated. The redundant degree of freedom of the planar multi-link flexible manipulator is exploited to minimize vibrations. The application of a long-reach arm in autonomous mooring operation based on sensor fusion using camera and light detection and ranging (LiDAR) data is proposed

Control of Redundant Flexible Manipulators with Redundancy Resolution

This paper deals with the online control of a redundant flexible link manipulator to achieve minimum oscillations using the redundancy resolution technique. Different redundancy resolution techniques proposed and used for rigid link manipulators are tested for their use in the case of flexible link manipulators. The simulation model of a planar three-link flexible manipulator is used in this study. The redundancy resolution using kinetic energy minimization techniques is compared with the local joint acceleration minimization method to show the advantage of achieving minimum vibrations

Towards a doctrine of providence : a response to contemporary critiques

<p>This essay is an attempt to find an approach to the Christian doctrine of providence which takes account of modern resistance to traditional formulations even while criticizing some current assumptions that make inevitable --mistakenly, we believe-- a clash between the scientific view of reality and the biblical picture of a governing and intervening God. Our objective is not to develop a doctrine of providence as such, but simply to set in place some of the epistemological and theological conditions that would make such a doctrinal development <em>possible</em> today.</p> <p>Our investigation is set against the foil of a prior analysis of several main currents in Greek and Roman metaphysical theology. We proceed to consider the "anthropological pole" of the Judeo-Christian doctrine of providence. First we examine the term "person"; then we conduct an exegetical and historical-theological study of the doctrine of the <em>imago Dei</em>. We argue that the concept of the <em>personal</em> was undiscoverable by speculation and could only have emerged as a consequence of divine revelation; and that this concept is the key to a proper understanding of the biblical doctrine of the <em>imago Dei</em>, the essence of which is the notion of divine-human relationship. We maintain, moreover, that the definition of man as a <em>rational</em> being makes complete sense only when it is integrated in the more comprehensive conception of man as a <em>personal</em> being.</p> <p>We reinforce this argument by examining the other pole of the doctrine of providence, i.e., the theological. To this end we look at the doctrine of the Trinity. This inquiry forms the basis for the sketch of a theological theory of knowledge in which we apply our relational understanding of the <em>imago Dei</em> to the question of our knowledge of other persons and of things.</p> <p>We conclude by bringing our findings to bear on the "non-interventionist" view of God's relation to the world. This position is critiqued in a final effort to remove some of the theoretical obstacles which have made it difficult to formulate a doctrine of providence faithful both to the biblical picture of God and to modern philosophical and ethical reflection.</p