A differential-based parallel force/velocity actuation concept : theory and experiments

textRobots are now moving from their conventional confined habitats such as factory floors to human environments where they assist and physically interact with people. The requirement for inherent mechanical safety is overarching in such human-robot interaction systems. We propose a dual actuator called Parallel Force/Velocity Actuator (PFVA) that combines a Force Actuator (FA) (low velocity input) and a Velocity Actuator (VA) (high velocity input) using a differential gear train. In this arrangement mechanical safety can be achieved by limiting the torque on the FA and thus making it a backdriveable input. In addition, the kinematic redundancy in the drive can be used to control output velocity while satisfying secondary operational objectives. Our research focus was on three areas: (i) scalable parametric design of the PFVA, (ii) analytical modeling of the PFVA and experimental testing on a single-joint prototype, and (iii) generalized model formulation for PFVA-driven serial robot manipulators. In our analysis, the ratio of velocity ratios between the FA and the VA, called the relative scale factor, emerged as a purely geometric and dominant design parameter. Based on a dimensionless parametric design of PFVAs using power-flow and load distributions between the inputs, a prototype was designed and built using commercial-off-the-shelf components. Using controlled experiments, two performance-limiting phenomena in our prototype, friction and dynamic coupling between the two inputs, were identified. Two other experiments were conducted to characterize the operational performance of the actuator in velocity-mode and in what we call ‘torque-limited’ mode (i.e. when the FA input can be backdriven). Our theoretical and experimental results showed that the PFVA can be mechanical safe to both slow collisions and impacts due to the backdriveability of the FA. Also, we show that its kinematic redundancy can be effectively utilized to mitigate low-velocity friction and backlash in geared mechanisms. The implication at the system level of our actuator level analytical and experimental work was studied using a generalized dynamic modeling framework based on kinematic influence coefficients. Based on this dynamic model, three design case studies for a PFVA-driven serial planar 3R manipulator were presented. The major contributions of this research include (i) mathematical models and physical understanding for over six fundamental design and operational parameters of the PFVA, based on which approximately ten design and five operational guidelines were laid out, (ii) analytical and experimental proof-of-concept for the mechanical safety feature of the PFVA and the effective utilization of its kinematic redundancy, (iii) an experimental methodology to characterize the dynamic coupling between the inputs in a differential-summing mechanism, and (iv) a generalized dynamic model formulation for PFVA-driven serial robot manipulators with emphasis on distribution of output loads between the FA and VA input-sets.Mechanical Engineerin

Human-friendly robotic manipulators: safety and performance issues in controller design

Recent advances in robotics have spurred its adoption into new application areas such as medical, rescue, transportation, logistics, personal care and entertainment. In the personal care domain, robots are expected to operate in human-present environments and provide non-critical assistance. Successful and flourishing deployment of such robots present different opportunities as well as challenges. Under a national research project, Bobbie, this dissertation analyzes challenges associated with these robots and proposes solutions for identified problems. The thesis begins by highlighting the important safety concern and presenting a comprehensive overview of safety issues in a typical domestic robot system. By using functional safety concept, the overall safety of the complex robotic system was analyzed through subsystem level safety issues. Safety regions in the world model of the perception subsystem, dependable understanding of the unstructured environment via fusion of sensory subsystems, lightweight and compliant design of mechanical components, passivity based control system and quantitative metrics used to assert safety are some important points discussed in the safety review. The main research focus of this work is on controller design of robotic manipulators against two conflicting requirements: motion performance and safety. Human-friendly manipulators used on domestic robots exhibit a lightweight design and demand a stable operation with a compliant behavior injected via a passivity based impedance controller. Effective motion based manipulation using such a controller requires a highly stiff behavior while important safety requirements are achieved with compliant behaviors. On the basis of this intuitive observation, this research identifies suitable metrics to identify the appropriate impedance for a given performance and safety requirement. This thesis also introduces a domestic robot design that adopts a modular design approach to minimize complexity, cost and development time. On the basis of functional modularity concept where each module has a unique functional contribution in the system, the robot “Bobbie-UT‿ is built as an interconnection of interchangeable mobile platform, torso, robotic arm and humanoid head components. Implementation of necessary functional and safety requirements, design of interfaces and development of suitable software architecture are also discussed with the design

NASA Automated Rendezvous and Capture Review. Executive summary

In support of the Cargo Transfer Vehicle (CTV) Definition Studies in FY-92, the Advanced Program Development division of the Office of Space Flight at NASA Headquarters conducted an evaluation and review of the United States capabilities and state-of-the-art in Automated Rendezvous and Capture (AR&C). This review was held in Williamsburg, Virginia on 19-21 Nov. 1991 and included over 120 attendees from U.S. government organizations, industries, and universities. One hundred abstracts were submitted to the organizing committee for consideration. Forty-two were selected for presentation. The review was structured to include five technical sessions. Forty-two papers addressed topics in the five categories below: (1) hardware systems and components; (2) software systems; (3) integrated systems; (4) operations; and (5) supporting infrastructure

GUARDIANS final report

Emergencies in industrial warehouses are a major concern for firefghters. The large dimensions together with the development of dense smoke that drastically reduces visibility, represent major challenges. The Guardians robot swarm is designed to assist fire fighters in searching a large warehouse. In this report we discuss the technology developed for a swarm of robots searching and assisting fire fighters. We explain the swarming algorithms which provide the functionality by which the robots react to and follow humans while no communication is required. Next we discuss the wireless communication system, which is a so-called mobile ad-hoc network. The communication network provides also one of the means to locate the robots and humans. Thus the robot swarm is able to locate itself and provide guidance information to the humans. Together with the re ghters we explored how the robot swarm should feed information back to the human fire fighter. We have designed and experimented with interfaces for presenting swarm based information to human beings

THE METHODOLOGY FOR INTEGRATING ROBOTIC SYSTEMS IN UNDEGROUND MINING MACHINES

Roof bolting is a critical operation in ensuring the safety and stability of underground mines by securing the roof strata with bolts. The process involves moving and manipulating heavy tools while being vigilant about the safety of the area. During the installation of roof bolts, operators are exposed to hazardous conditions due to challenging working conditions in underground mines, extensive working hours, and demanding shift schedules leading to personnel fatigue and influencing operators to take shortcuts that may increase the risk of injuries and fatal accidents. The successful completion of roof bolting tasks depends heavily on operator judgment and experience to perform these tasks. To mitigate the occupational hazards inherent in roof bolting operations, a six-axis ABB IRB 1600 robotic arm was integrated into the roof bolter machine to imitate human functions during the roof bolting operation. The integration process involves selecting a suitable robot that can perform human activities and has the potential to handle the tasks at hand. The ultimate goal of implementing the robotic system into the roof bolter machine is to minimize human involvement during the roof bolting operation by converting the machine from manual operations to a partially automated roof bolter machine. The integration enhances the safety of personnel by moving humans away from the face where roof bolting takes place to a safe distance. The operator is then assigned a new role to control and supervise all the operational tasks of the automated roof bolting operation via a human-machine interface (HMI). During the laboratory testing of the automation process, the robotic arm cooperates with some novel specialized technologies to imitate human activities during roof bolting operations. The developed systems include the plate feeder, the bolt feeder, and the wrench. These systems were built to support automation and minimize human intervention during roof bolting operations. These components were linked to the Programmable Logic Controller (PLC) and controlled by the HMI touchpad. An HMI was developed for the operator to control and monitor the automated process away from the active face. This study establishes robust communication paths among all the components. The design communication network links the robotic arm and other components of the roof bolter machine, leading to a smooth and sequential roof bolting process. The EtherNet/IP protocol is used to pass messages between the components of the automated roof bolter machine through a Controller Area Network (CAN) bus device installed to enable communication using CAN protocols. Establishing a robust communication network between the components prevents collision and manages the movement of the robotic arm and other developed automated systems during the bolting process. The outcome of the study shows that the robotic arm has the potential to mimic human activities during the roof bolting operation by performing bolt grasping, holding, lifting, placing, and removal of drill steels during the roof bolting operations. As a result, humans can be moved away from hazardous areas to a safe location and control the roof bolting operation through an Human Machine Interface (HMI) touchpad. The HMI controls the bolting process with start and stop buttons from the subroutine of all the components to perform the roof bolting operation. These buttons enable the operator to stop the operation in the event of unsafe acts

Intelligent assist device

In an Intelligent Assist Device (IAD), the human operator is assisted by the power of the servo drives as well as intelligence from this device. Because of the power actuation, the ergonomic injury of the operator using the device can be reduced. A force transducer provides a convenient way for the operator to generate control command by a simple push to move intuition. Therefore, there is minimum required training for using an IAD. Collision of payload with obstacles has always been a major problem in using a lift assist device. Collision might cause damage to the work piece, lift device and sometimes result in operator injury. All these occurrences will significantly increase the total production cost. In this work, a modified collision-avoidance scheme has been proposed, and it has been proven stable both analytically and experimentally. An artificial attractive well is also explored in this research to guide an operator to approach a target along a preferred path. Stability proof is provided and experimental results are given

Robot Manipulators

Robot manipulators are developing more in the direction of industrial robots than of human workers. Recently, the applications of robot manipulators are spreading their focus, for example Da Vinci as a medical robot, ASIMO as a humanoid robot and so on. There are many research topics within the field of robot manipulators, e.g. motion planning, cooperation with a human, and fusion with external sensors like vision, haptic and force, etc. Moreover, these include both technical problems in the industry and theoretical problems in the academic fields. This book is a collection of papers presenting the latest research issues from around the world

Sensor-based navigating mobile robots for people with disabilities

People with severe physical disabilities need help with everyday tasks, such as getting dressed, eating, brushing their teeth, scratching themselves, drinking, etc. They also need support to be able to work. They are usually helped by one or more persona