Self-Contained and Automatic Calibration of a Multi-Fingered Hand Using Only Pairwise Contact Measurements

A self-contained calibration procedure that can be performed automatically without additional external sensors or tools is a significant advantage, especially for complex robotic systems. Here, we show that the kinematics of a multi-fingered robotic hand can be precisely calibrated only by moving the tips of the fingers pairwise into contact. The only prerequisite for this is sensitive contact detection, e.g., by torque-sensing in the joints (as in our DLR-Hand II) or tactile skin. The measurement function for a given joint configuration is the distance between the modeled fingertip geometries, but the actual measurement is always zero. In an in-depth analysis, we prove that this contact-based calibration determines all quantities needed for manipulating objects with the hand, i.e., the difference vectors of the fingertips, and that it is as sensitive as a calibration using an external visual tracking system and markers. We describe the complete calibration scheme, including the selection of optimal sample joint configurations and search motions for the contacts despite the initial kinematic uncertainties. In a real-world calibration experiment for the torque-controlled four-fingered DLR-Hand II, the maximal error of 17.7mm can be reduced to only 3.7mm.Comment: Presented at the 2023 IEEE-RAS International Conference on Humanoid Robot

Flight telerobot mechanism design: Problems and challenges

Problems and challenges of designing flight telerobot mechanisms are discussed. Specific experiences are drawn from the following system developments: (1) the Force Reflecting Hand Controller, (2) the Smart End Effector, (3) the force-torque sensor, and a generic multi-degrees-of-freedom manipulator

MODELLING AND CONTROL OF MULTI-FINGERED ROBOT HAND USING INTELLIGENT TECHNIQUES

Research and development of robust multi-fingered robot hand (MFRH) have been going on for more than three decades. Yet few can be found in an industrial application. The difficulties stem from many factors, one of which is that the lack of general and effective control techniques for the manipulation of robot hand. In this research, a MFRH with five fingers has been proposed with intelligent control algorithms. Initially, mathematical modeling for the proposed MFRH has been derived to find the Forward Kinematic, Inverse Kinematic, Jacobian, Dynamics and the plant model. Thereafter, simulation of the MFRH using PID controller, Fuzzy Logic Controller, Fuzzy-PID controller and PID-PSO controller has been carried out to gauge the system performance based parameters such rise time, settling time and percent overshoot

Aspects of an open architecture robot controller and its integration with a stereo vision sensor.

The work presented in this thesis attempts to improve the performance of industrial robot systems in a flexible manufacturing environment by addressing a number of issues related to external sensory feedback and sensor integration, robot kinematic positioning accuracy, and robot dynamic control performance. To provide a powerful control algorithm environment and the support for external sensor integration, a transputer based open architecture robot controller is developed. It features high computational power, user accessibility at various robot control levels and external sensor integration capability. Additionally, an on-line trajectory adaptation scheme is devised and implemented in the open architecture robot controller, enabling a real-time trajectory alteration of robot motion to be achieved in response to external sensory feedback. An in depth discussion is presented on integrating a stereo vision sensor with the robot controller to perform external sensor guided robot operations. Key issues for such a vision based robot system are precise synchronisation between the vision system and the robot controller, and correct target position prediction to counteract the inherent time delay in image processing. These were successfully addressed in a demonstrator system based on a Puma robot. Efforts have also been made to improve the Puma robot kinematic and dynamic performance. A simple, effective, on-line algorithm is developed for solving the inverse kinematics problem of a calibrated industrial robot to improve robot positioning accuracy. On the dynamic control aspect, a robust adaptive robot tracking control algorithm is derived that has an improved performance compared to a conventional PID controller as well as exhibiting relatively modest computational complexity. Experiments have been carried out to validate the open architecture robot controller and demonstrate the performance of the inverse kinematics algorithm, the adaptive servo control algorithm, and the on-line trajectory generation. By integrating the open architecture robot controller with a stereo vision sensor system, robot visual guidance has been achieved with experimental results showing that the integrated system is capable of detecting, tracking and intercepting random objects moving in 3D trajectory at a velocity up to 40mm/s

Doctor of Philosophy

dissertationIn this dissertation, we present methods for intuitive telemanipulation of manipulators that use piezoelectric stick-slip actuators (PSSAs). Commercial micro/nano-manipulators, which utilize PSSAs to achieve high precision over a large workspace, are typically controlled by a human operator at the joint level, leading to unintuitive and time-consuming telemanipulation. Prior work has considered the use of computer-vision-feedback to close a control loop for improved performance, but computer-vision-feedback is not a viable option for many end users. We discuss how open-loop models of the micro/nano-manipulator can be used to achieve desired end-effector movements, and we explain the process of obtaining open-loop models. We propose a rate-control telemanipulation method that utilizes the obtained model, and we experimentally quantify the effectiveness of the method using a common commercial manipulator (the Kleindiek MM3A). The utility of open-loop control methods for PSSAs with a human in the loop depends directly on the accuracy of the open-loop models of the manipulator. Prior research has shown that modeling of piezoelectric actuators is not a trivial task as they are known to suffer from nonlinearities that degrade their performance. We study the effect of static (non-inertial) loads on a prismatic and a rotary PSSA, and obtain a model relating the step size of the actuator to the load. The actuator-specific parameters of the model are calibrated by taking measurements in specific configurations of the manipulator. Results comparing the obtained model to experimental data are presented. PSSAs have properties that make them desirable over traditional DC-motor actuators for use in retinal surgery. We present a telemanipulation system for retinal surgery that uses a full range of existing disposable instruments. The system uses a PSSA-based manipulator that is compact and light enough that it could reasonably be made head-mounted to passively compensate for head movements. Two mechanisms are presented that enable the system to use existing disposable actuated instruments, and an instrument adapter enables quick-change of instruments during surgery. A custom stylus for a haptic interface enables intuitive and ergonomic telemanipulation of actuated instruments. Experimental results with a force-sensitive phantom eye show that telemanipulated surgery results in reduced forces on the retina compared to manual surgery, and training with the system results in improved performance. Finally, we evaluate operator efficiency with different haptic-interface kinematics for telemanipulated retinal surgery. Surgical procedures of the retina require precise manipulation of instruments inserted through trocars in the sclera. Telemanipulated robotic systems have been developed to improve retinal surgery, but there is not a unique mapping of the motions of the surgeon's hand to the lower-dimensional motions of the instrument through the trocar. We study operator performance during a precision positioning task on a force-sensing phantom retina, reminiscent of telemanipulated retinal surgery, with three common haptic-interface kinematics implemented in software on a PHANTOM Premium 6DOF haptic interface. Results from a study with 12 human subjects show that overall performance is best with the kinematics that represent a compact and inexpensive option, and that subjects' subjective preference agrees with the objective performance results

Master of Science

thesisParkinson Disease (PD) is a progressive and chronic movement disorder that affects an individual's ability to walk and move naturally. Research shows that training using virtual reality can offer improvements over traditional therapy and decrease the effects of some PD symptoms. In an effort to address the need for such therapeutic intervention, a Virtual Reality (VR) rehabilitation simulator was developed using 3D graphical displays in concert with haptic Smart Shoes. The system creates challenging virtual terrain to safely train participants in situations that demand greater balance and neuromuscular control. As part of this effort, an Ankle Foot Simulator (AFS) was created to mimic human gait, including ankle and foot response to a variety of terrain features. This thesis describes the development and testing of a novel AFS robot designed to mimic human gait and evaluate Smart Shoe behavior and response to perturbations. The major design requirement for the AFS robot is to reproduce natural gait dynamics by: 1) matching complex trajectories of the ankle, 2) generating Ground Reaction Forces (GRF) during normal walking gait, and 3) mimicking foot/ankle dynamics such as ankle roll over. This thesis focuses on the design and control of the AFS to achieve sufficient Range of Motion (ROM) to mimic human gait, including extreme ankle rollover, while providing appropriately fast dynamics, sufficient load capacity, and high repeatability. Design aspects of the AFS include 1) forward and inverse kinematic derivations of the ankle mechanism, 2) derivations of feedforward components of the control algorithms, and 3) mapping ankle mechanism actuator forces to ankle moments. The AFS robot tracks ankle position and orientation data to within 5.5 mm and 5.5 degrees. The AFS is also able to reproduce GRFs, including dorsal/plantar flexion and inversion/eversion ankle moments with an r2 value of 0.82 or more. The AFS also demonstrates passive ankle stiffness. To improve performance of the AFS, an iterative learning controller is suggested for future work

On the development of a cybernetic prosthetic hand

The human hand is the end organ of the upper limb, which in humans serves the important function of prehension, as well as being an important organ for sensation and communication. It is a marvellous example of how a complex mechanism can be implemented, capable of realizing very complex and useful tasks using a very effective combination of mechanisms, sensing, actuation and control functions. In this thesis, the road towards the realization of a cybernetic hand has been presented. After a detailed analysis of the model, the human hand, a deep review of the state of the art of artificial hands has been carried out. In particular, the performance of prosthetic hands used in clinical practice has been compared with the research prototypes, both for prosthetic and for robotic applications. By following a biomechatronic approach, i.e. by comparing the characteristics of these hands with the natural model, the human hand, the limitations of current artificial devices will be put in evidence, thus outlining the design goals for a new cybernetic device. Three hand prototypes with a high number of degrees of freedom have been realized and tested: the first one uses microactuators embedded inside the structure of the fingers, and the second and third prototypes exploit the concept of microactuation in order to increase the dexterity of the hand while maintaining the simplicity for the control. In particular, a framework for the definition and realization of the closed-loop electromyographic control of these devices has been presented and implemented. The results were quite promising, putting in evidence that, in the future, there could be two different approaches for the realization of artificial devices. On one side there could be the EMG-controlled hands, with compliant fingers but only one active degree of freedom. On the other side, more performing artificial hands could be directly interfaced with the peripheral nervous system, thus establishing a bi-directional communication with the human brain

Telerobotic Sensor-based Tool Control Derived From Behavior-based Robotics Concepts

@font-face { font-family: TimesNewRoman ; }p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: Times New Roman ; }div.Section1 { page: Section1; } Teleoperated task execution for hazardous environments is slow and requires highly skilled operators. Attempts to implement telerobotic assists to improve efficiency have been demonstrated in constrained laboratory environments but are not being used in the field because they are not appropriate for use on actual remote systems operating in complex unstructured environments using typical operators. This work describes a methodology for combining select concepts from behavior-based systems with telerobotic tool control in a way that is compatible with existing manipulator architectures used by remote systems typical to operations in hazardous environment. The purpose of the approach is to minimize the task instance modeling in favor of a priori task type models while using sensor information to register the task type model to the task instance. The concept was demonstrated for two tools useful to decontamination & dismantlement type operations—a reciprocating saw and a powered socket tool. The experimental results demonstrated that the approach works to facilitate traded control telerobotic tooling execution by enabling difficult tasks and by limiting tool damage. The role of the tools and tasks as drivers to the telerobotic implementation was better understood in the need for thorough task decomposition and the discovery and examination of the tool process signature. The contributions of this work include: (1) the exploration and evaluation of select features of behavior-based robotics to create a new methodology for integrating telerobotic tool control with positional teleoperation in the execution of complex tool-centric remote tasks, (2) the simplification of task decomposition and the implementation of sensor-based tool control in such a way that eliminates the need for the creation of a task instance model for telerobotic task execution, and (3) the discovery, demonstrated use, and documentation of characteristic tool process signatures that have general value in the investigation of other tool control, tool maintenance, and tool development strategies above and beyond the benefit sustained for the methodology described in this work

Whole-hand input

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Architecture, 1992.Includes bibliographical references (p. 219-233).by David Joel Sturman.Ph.D