A novel spherical actuator: Design and control

The paper describes the design and control of a novel spherical permanent magnet actuator which is capable of two-degrees-freedom and a high specific torque. Based on an analytical actuator model, an optimal design procedure is developed to yield maximum output torque or maximum system acceleration for a given payload. The control of the actuator, whose dynamics are similar to those of robotic manipulators, is facilitated by the establishment of a complete actuation system model. A robust control law is applied, and its effectiveness is demonstrated by computer simulatio

A novel spherical permanent magnet actuator with three degrees-of-freedom

The paper describes a new version of spherical actuator, which is capable of three degrees-of-freedom and a high specific torque. The three-dimensional magnetic field distribution is established using an analytical technique formulated in spherical co-ordinates, and enables the torque vector and back-emf to be derived in closed forms. This facilitates the characterisation of the actuator, and provides the foundation for design optimisation, actuator dynamic modelling and servo control developmen

Part clamping and fixture geometric adaptability for reconfigurable assembly systems.

Masters of Science in Mechanical Engineering. University of KwaZulu-Natal. Durban, 2017.The Fourth Industrial Revolution is leading towards cyber-physical systems which justified research efforts in pursuing efficient production systems incorporating flexible grippers. Due to the complexity of assembly processes, reconfigurable assembly systems have received considerable attention in recent years. The demand for the intricate task and complicated operations, demands the need for efficient robotic manipulators that are required to manoeuvre and grasp objects effectively. Investigations were performed to understand the requirements of efficient gripping systems and existing gripping methods. A biologically inspired robotic gripper was investigated to establish conformity properties for the performance of a robotic gripper system. The Fin Ray Effect® was selected as a possible approach to improve effective gripping and reduce slippage of component handling with regards to pick and place procedures of assembly processes. As a result, the study established the optimization of self-adjusting end-effectors. The gripper system design was simulated and empirically tested. The impact of gripping surface compliance and geometric conformity was investigated. The gripper system design focused on the response of load applied to the conformity mechanism called the Fin Ray Effect®. The appendages were simulated to determine the deflection properties and stress distribution through a finite element analysis. The simulation proved that the configuration of rib structures of the appendages affected the conformity to an applied force representing an object in contact. The system was tested in real time operation and required a control system to produce an active performance of the system. A mass loading test was performed on the gripper system. The repeatability and mass handling range was determined. A dynamic operation was tested on the gripper to determine force versus time properties throughout the grasping movement for a pick and place procedure. The fluctuating forces generated through experimentation was related to the Lagrangian model describing forces experienced by a moving object. The research promoted scientific contribution to the investigation, analysis, and design of intelligent gripping systems that can potentially be implemented in the operational processes of on-demand production lines for reconfigurable assembly systems

Locomotion of circular robots with diametrically translating legs: Design, analysis, and fabrication

This work develops an analytical basis for designing the locomotion of mobile robots with a circular core and equispaced diametral legs which actuate linearly. Two elementary regimes of motion are first developed using the intrinsic geometry of the mechanism, then combined for fluid motion. The first and primary gait has a path trajectory defined by its kinematic constraints. Dynamics are explored to assist actuator design and understand the mechanism\u27s constraint forces. Simulation results are provided in support of the design concept and geometric optimization. The proposed robot, or Locomotive Amoebic Device (LAD), bears resemblance with certain cellular locomotion, and thus miniaturization is a possibility. A prototype of LAD is constructed which supports the design theory and simulation by executing the primary motion regime with appropriate speed and current settings. Future work is promising for extending the design to a spherical concept, generalizing the theory in terms of the number of legs, creating a variety of control schemes for maneuvers such as dampening phase transitions or pure rolling, equipping and justifying the design for applications such as Planetary Exploration or Medical Procedures, and potentially creating a millimeter scale version or smaller of spherical LAD. This thesis theorizes a unique mode of locomotion and proffers simulation and experimental support

Ultra-High Field Strength MR Image-Guided Robotic Needle Delivery Device for In-Bore Small Animal Interventions

Current methods of accurate soft tissue injections in small animals are prone to many sources of error. Although efforts have been made to improve the accuracy of needle deliveries, none of the efforts have provided accurate soft tissue references. An MR image-guided robot was designed to function inside the bore of a 9.4T MR scanner to accurately deliver needles to locations within the mouse brain. The robot was designed to have no noticeable negative effects on the image quality and was localized in the MR images through the use of an MR image visible fiducial. The robot was mechanically calibrated and subsequently validated in an image-guided phantom experiment, where the mean needle targeting accuracy and needle trajectory accuracy were calculated to be 178 ± 54µm and 0.27 ± 0.65º, respectively. Finally, the device successfully demonstrated an image-guided needle targeting procedure in situ

Ultrasound Guided Robot for Human Liver Biopsy using High Intensity Focused Ultrasound for Hemostasis

Percutaneous liver biopsy is the gold standard among clinician\u27s tool to diagnose and guide subsequent therapy for liver disease. Ultrasound image guidance is being increasingly used to reduce associated procedural risks but post–biopsy complications still persist. The major and most common complication is hemorrhage, which is highly unpredictable and may sometimes lead to death. Though the risk of mortality is low, it is too high for a diagnostic procedure. Post-biopsy care and additional surgical intervention to arrest hemorrhage make liver biopsy a costly procedure for health care delivery systems. Non-invasive methods to stop bleeding exist like electro–cautery, microwave, lasers, radio frequency, argon–beam, and High Intensity Focused Ultrasound (HIFU). All the methods except HIFU require direct exposure of the needle puncture site for hemostasis. HIFU is an ultrasound modality and uses mechanical sound waves for focused energy delivery. Ultrasound waves are minimally affected by tissue attenuation and focus internal targets without direct exposure. Human error in focusing HIFU renders it unusable for a medical procedure especially when noninvasive. In this project we designed and developed an ultrasound guided prototype robot for accurate HIFU targeting to induce hemostasis. The robotic system performs percutaneous needle biopsy and a 7.5 cm focal length HIFU is fired at the puncture point when the needle tip retracts to the liver surface after sample collection. The robot has 4 degrees of freedom (DOF) for biopsy needle insertion, HIFU positioning, needle angle alignment and US probe image plane orientation. As the needle puncture point is always in the needle path, mechanically constraining the HIFU to focus on the needle reduced the required functionality significantly. Two mini c-arms are designed for needle angle alignment and US probe image plane orientation. This reduced the contact foot print of the robot over the patient providing a greater dexterity for positioning the robot. The robot is validated for HIFU hemostasis by a series of experiments on chicken breasts. HIFU initiated hemorrhage control with robotic biopsy ensures arrest of post-biopsy hemorrhage and decreases patient anxiety, hospital stay, morbidity, time of procedure, and cost. This can also be extended to other organs like kidneys, lungs etc. and has widespread implications such as control of hemorrhage in post-biopsies in patients with reduced ability for hemostasis. This research opens a greater scope for research for automation and design making it a physician friendly tool for eventual clinical use

AUTONOMOUS ROBOTIC SYSTEM: POINT-TO-POINT MOBILE ROBOT

Autonomous robots are defined as robots which can perform desired tasks in unstructured environments on their own without continuous human guidance. Different robots can be autonomous in different ways. The main difference between these robots is the task they have been programmed to do. This project is initiated for educational purpose in order to increase awareness and enthusiasm among students regarding the autonomous robotic system. The first task to ensure this project meet its objective is by doing extensive literature reviews on the subject (autonomous robotic system). Based on the reviews, the general structure and design block (consists of main system and sub-systems) can be constructed. This is referred as the foundation for the project to start with. The scope of study for this project is to focus on theoretical aspects of the system. It divided into several scopes, which are electronics circuitry (for sensors and motors), Programmable Logic Controller (PLC) programming, and some mechanical aspects regard to the physical parts of the robot. These areas are vital in order to develop and implement the theoretical aspects into a working prototype of autonomous robotic system. The project is planned to develop based on the process flowchart approach where every detail of tasks from starting to the end is shown in sequential order. The results on this project mainly present the selection and implementation of prototype sub-systems like locomotion, navigation and control system. The discussions are focus on process and problems occurred during the prototype development. Finally, this project is about fulfilling its objective which primarily is to deliver a working prototype of an autonomous robotic system with the ability to move from one point to another in precise manner

Motor Eyes: Mechanical Platform for a Binocular Robotic Vision System

Stereoscopic vision systems require high computational power to perform image processing for 3D reconstruction of a scene. Synchronizing eye movements through mechanical coupling can reduce this processing power. To investigate this potential, the project team developed a mechanical platform for a binocular robotic vision system that uses stepper motors and slider linkages to achieve coupled pan, coupled tilt and coupled vergence eye movements. A prototype, controlled by an Arduino Uno, was constructed. The prototype achieved eye rotation speeds comparable to human saccadic eye motion and was capable of focusing on specified points with some position error caused by the prototype’s high sensitivity to misalignments of mechanical parts