A fault-tolerant intelligent robotic control system

This paper describes the concept, design, and features of a fault-tolerant intelligent robotic control system being developed for space and commercial applications that require high dependability. The comprehensive strategy integrates system level hardware/software fault tolerance with task level handling of uncertainties and unexpected events for robotic control. The underlying architecture for system level fault tolerance is the distributed recovery block which protects against application software, system software, hardware, and network failures. Task level fault tolerance provisions are implemented in a knowledge-based system which utilizes advanced automation techniques such as rule-based and model-based reasoning to monitor, diagnose, and recover from unexpected events. The two level design provides tolerance of two or more faults occurring serially at any level of command, control, sensing, or actuation. The potential benefits of such a fault tolerant robotic control system include: (1) a minimized potential for damage to humans, the work site, and the robot itself; (2) continuous operation with a minimum of uncommanded motion in the presence of failures; and (3) more reliable autonomous operation providing increased efficiency in the execution of robotic tasks and decreased demand on human operators for controlling and monitoring the robotic servicing routines

Adaptive Constrained Kinematic Control using Partial or Complete Task-Space Measurements

Recent advancements in constrained kinematic control make it an attractive strategy for controlling robots with arbitrary geometry in challenging tasks. Most current works assume that the robot kinematic model is precise enough for the task at hand. However, with increasing demands and safety requirements in robotic applications, there is a need for a controller that compensates online for kinematic inaccuracies. We propose an adaptive constrained kinematic control strategy based on quadratic programming, which uses partial or complete task-space measurements to compensate online for calibration errors. Our method is validated in experiments that show increased accuracy and safety compared to a state-of-the-art kinematic control strategy.Comment: Accepted on T-RO 2022, 16 Pages. Corrected a few typos and adjusted figure placemen

A laboratory breadboard system for dual-arm teleoperation

The computing architecture of a novel dual-arm teleoperation system is described. The novelty of this system is that: (1) the master arm is not a replica of the slave arm; it is unspecific to any manipulator and can be used for the control of various robot arms with software modifications; and (2) the force feedback to the general purpose master arm is derived from force-torque sensor data originating from the slave hand. The computing architecture of this breadboard system is a fully synchronized pipeline with unique methods for data handling, communication and mathematical transformations. The computing system is modular, thus inherently extendable. The local control loops at both sites operate at 100 Hz rate, and the end-to-end bilateral (force-reflecting) control loop operates at 200 Hz rate, each loop without interpolation. This provides high-fidelity control. This end-to-end system elevates teleoperation to a new level of capabilities via the use of sensors, microprocessors, novel electronics, and real-time graphics displays. A description is given of a graphic simulation system connected to the dual-arm teleoperation breadboard system. High-fidelity graphic simulation of a telerobot (called Phantom Robot) is used for preview and predictive displays for planning and for real-time control under several seconds communication time delay conditions. High fidelity graphic simulation is obtained by using appropriate calibration techniques

An 8-DOF dual-arm system for advanced teleoperation performance experiments

This paper describes the electro-mechanical and control features of an 8-DOF manipulator manufactured by AAI Corporation and installed at the Jet Propulsion Lab. (JPL) in a dual-arm setting. The 8-DOF arm incorporates a variety of features not found in other lab or industrial manipulators. Some of the unique features are: 8-DOF revolute configuration with no lateral offsets at joint axes; 1 to 5 payload to weight ratio with 20 kg (44 lb) payload at a 1.75 m (68.5 in.) reach; joint position measurement with dual relative encoders and potentiometer; infinite roll of joint 8 with electrical and fiber optic slip rings; internal fiber optic link of 'smart' end effectors; four-axis wrist; graphite epoxy links; high link and joint stiffness; use of an upgraded JPL Universal Motor Controller (UMC) capable of driving up to 16 joints. The 8-DOF arm is equipped with a 'smart' end effector which incorporates a 6-DOF forcemoment sensor at the end effector base and grasp force sensors at the base of the parallel jaws. The 8-DOF arm is interfaced to a 6 DOF force reflecting hand controller. The same system is duplicated for and installed at NASA-Langley

Human Motion Mapping to a Robot Arm with Redundancy Resolution

The problem of image based visual servoing for robots working in a dynamic environment is addressed in this paper. It is assumed that the environment is observed by depth sensors which allow to measure the distance between any moving obstacle and the robot. The main idea is to control suitable image moments during the interaction phase to relax a certain number of robot’s degrees of freedom. If an obstacle approaches the robot, the main visual servoing task is attenuated or completely abandoned while the image features are kept in the camera field of view by controlling the image moments. Fuzzy rules are used to set the reference values for the controller. Beside that, the relaxed redundancy of the robot is exploited to avoid collisions as well. After removing the risk of collision, the main visual servoing task is resumed. The effectiveness of the algorithm is shown by several case studies on a KUKA LWR 4 robot arm

Industrial automation and control in hazardous nuclear environments

textThis report discusses the design and implementation of an automated system for use in geometrically-constrained, hazardous glovebox environments. This system’s purpose is to reduce a hemispherical plutonium pit into smaller pieces that fit inside of a crucible. The size reduction of plutonium pits supports stockpile stewardship efforts by the United States Department of Energy. The automation of this process increases the safety of radiation workers by handling radioactive nuclear material. This decreases glovebox worker dose and exposure to tools, sharps, and fines. This effort examines the hardware and software framework developed to support the use of a Port Deployed Manipulator (PDM) for a contact task. This research effort uses a 7 Degree-of-Freedom (DOF) PDM and a micropunch to reduce hemispherical pit surrogates. Formulation of the material reduction execution algorithm involved addressing a variety of topics related to industrial automation: 1. Collision detection and object recognition based on user-specified parameters. 2. Joint torque monitoring 3. Online motion planning for contact tasks 4. Object-in-hand industrial manufacturing 5. Grasping and handling of nuclear material 6. Software compliance via robust nonlinear control methods A high-bandwidth collision detection algorithm involving joint torque monitoring was developed to increase robot safety during operation. The motion planning algorithm developed for this effort takes variable geometric properties to be used with a range of hemishells. The algorithm’s feasibility was validated on a hardware test bed in a laboratory setting. Hardware cold tests conclude that mechanical compliance is sufficient for task completion. However, software compliance would increase performance, ef- ficiency, and safety during task execution. Two different nonlinear force control laws (feedback linearization and sliding mode control) that minimize object shear forces were developed using a simplified material reduction simulation. It is recommended that glovebox automation research continue to increase worker safety throughout the DOE complex.Mechanical Engineerin

The KALI multi-arm robot programming and control environment

The KALI distributed robot programming and control environment is described within the context of its use in the Jet Propulsion Laboratory (JPL) telerobot project. The purpose of KALI is to provide a flexible robot programming and control environment for coordinated multi-arm robots. Flexibility, both in hardware configuration and software, is desired so that it can be easily modified to test various concepts in robot programming and control, e.g., multi-arm control, force control, sensor integration, teleoperation, and shared control. In the programming environment, user programs written in the C programming language describe trajectories for multiple coordinated manipulators with the aid of KALI function libraries. A system of multiple coordinated manipulators is considered within the programming environment as one motion system. The user plans the trajectory of one controlled Cartesian frame associated with a motion system and describes the positions of the manipulators with respect to that frame. Smooth Cartesian trajectories are achieved through a blending of successive path segments. The manipulator and load dynamics are considered during trajectory generation so that given interface force limits are not exceeded