John P. H. Steele

Modeling and control of the stanford/JPL hand

Improved dexterity is an area of current research in robotics. At Sandia National Laboratories and the University of New Mexico we are pursuing research in this area with the aid of a Stanford/JPL hand from Salisbury Robotics. In this paper we present some of the issues raised in studying the characteristics and control of a single finger of the dexterous hand. The issues we present are dynamic modeling, friction based hysteresis, and identification of the finger system. We also discuss our present method for sensing and control.

Control and scale model simulation of sensor-guided LHD mining machines

Work has been underway on the development of autonomous (tele-managed) LHD (load, haul, and dump) mining machines. Previous work has shown that ultrasonic sensors exhibit several characteristics which make them a reasonable choice for sensor-based navigation in underground mining operations. The authors discuss recent work done to develop control algorithms for use with these sensors, experiments with a scale model of an LHD miner to verity the ultrasonic-based control and modeling methods, and approaches to developing real-time task level control models. Experimental testing of a scale-model system indicates that acceptable behavior can be achieved if the speed is kept low and a deadband is introduced into the control algorithm. Transition logic appears to be a useful tool for describing the control system at a task level.<<ETX>>

Development of closed‐loop control of robotic welding processes

Purpose – The purpose of this research is to develop closed‐loop control of robotic welding processes.Design/methodology/approach – The approach being developed is the creation of three‐dimensional models of the weld pool using stereo imagining. These models will be used in a model‐based feedback control system. Fusion of more than one sensor type in the controller is used.Findings – Three‐dimensional images can be produced from stereo images of GMAW‐p weld pools. This requires coordinating the image capture with the arc pulse to allow observation of the pool.Research limitations/implications – This is a work in progress. The imaging is not being done in real time at this point in time. Future work will address this issue. Also, how the image information is to be used to make corrections within the controller is future work.Practical implications – Closing the loop on GMAW welding will allow robotic automation of welding to proceed to a much broader degree of application.Originality/value – This paper dem...

Stereo vision in LHD automation

This paper details work in applying stereo vision for the enhancement of safety and productivity in the operation of a load-haul-dump (LHD) vehicle in underground mining. The primary goal of this portion of the research is to provide 3D models of the LHDs environment. Availability of these models facilitates performance of automated or teleoperated loading tasks and enhances safety through identification and location of humans in the path of the vehicle. Generation of an accurate 3D model of the immediate surroundings of the LHD is accomplished through processing of stereo visual imagery. Stereo video is acquired using a pair of digital cameras mounted above the cab of the LHD. The video data is processed into a dense depth map plus confidence information. These depths and the stereo rig calibration data are then used to construct a 3D surface model. We demonstrate useful models obtained under both well-illuminated and low-light conditions.

An algorithm with real-time response for avoiding moving obstacles

A method is presented for modeling the trajectories of a robot and obstacles in three spaces (x, y, and time) such that potential collisions can be detected in a direct manner; no a priori knowledge of the obstacles trajectory is required. Having determined that a collision will occur, a method for avoiding such collisions by altering the time and space trajectory for the robot is presented. The modeling has been intentionally designed to be succinct enough that the collision avoidance algorithm can run in real-time, thus making it suitable for inclusion as part of a robot navigation system for a real mobile robot. Results of simulations are presented and discussed.<<ETX>>

Mobile Robot Path Planning In Dynamic Environments

This paper presents our approach to the problem of, controlling a mobile robot which must travel in dynamic environments. A dynamic environment is one which has obstacles, both stationary and moving, of which the robot is unaware at the time the original path plan is developed. There exists a natural decomposition of the path planning problem which provides the basis for dealing with such environments. The decomposition consists of (1) planning a path which avoids all the known static obstacles prior to initiating any motion, and (2) as the path motion is executed, the motion control is updated in real-time to avoid collisions with any unforseen obstacles either stationary or moving. The algorithms for both the static and the dynamic avoidance of obstacles is presented.

WiFi based communication and localization of an autonomous mobile robot for refinery inspection

Oil and gas refineries can be a dangerous environment for numerous reasons, including heat, toxic gasses, and unexpected catastrophic failures. In order to augment how human operators interact with this environment, a mobile robotic platform is developed. This paper focuses on the use of WiFi for communicating with and localizing the robot. More specifically, algorithms are developed and tested to minimize the total number of WiFi access points (APs) and their locations in any given environment while taking into consideration the throughput requirements and the need to ensure every location in the region can reach at least k APs. When multiple WiFi APs are close together, there is a potential for interference. A graph-coloring heuristic is used to determine AP channel allocation. In addition, WiFi fingerprinting based localization is developed. All the algorithms implemented are tested in real world scenarios with the robot developed and results are promising.

Contaminant classification in robotic gas metal arc welding via image based spatter tracking

This paper presents a new method for measuring and classifying spatter in gas metal arc welding (GMAW) by optical monitoring of the weld pool and surrounding area via a high-frame-rate camera. Image processing and tracking algorithms are described that extract and classify individual spatter events from raw camera images. This new sensor is then used to investigate the relationship between workpiece contamination and weld spatter.

Development of an Oil and Gas Refinery Inspection Robot

Oil and gas refineries present challenging environments in which to work and operate, especially in places like the Middle East where temperatures can reach 50 C and sand storms which can reduce visibility to a few meters. In addition, there can be gas or steam leaks which present health and safety hazards to the workers. At present, continuous operation of these plants requires that human workers venture out into these conditions in order to observe and report on the conditions within the plant. The goal of this work is to design, fabricate, assemble, and test an inspection robot in an effort to reduce the exposure and risks to human operators while increasing the flexibility and range of remote observations provided by a mobile robot. In this paper, we will report on the design approach taken, the subsystems identified and developed, the software environment chosen, and the application tasks envisioned. We will also report on the challenges of developing a robust localization algorithm for use in the challenging environment of a refinery as well as the needs for robust wireless communications in order to maintain command and control from the operators control room. An overview of the fivedegree-of-freedom arm designed and fabricated, and its realtime control will also be presented. Results from GPS navigation and localization experiments will be presented. While average errors during parked operations were often less than one meter for the WAAS enabled GPS system, locational errors during dynamic operations were often more than three meters. This is due to multi-path signals near building structures and piping infrastructure. Real-time arm control has been implemented using FPGAs and while tuning presented some challenge, the FPGA has provided smooth and repeatable operation. Sensors include gas detectors, acoustic sensors, thermal imaging, and video camera streaming. In addition, we will report on a multi-faceted approach to localization using three different sensor technologies and integrated using a Kalman filter. NOMENCLATURE DOF Degrees-of-Freedom GPS Global Positioning System FPGA Field Programmable Gate Array PWM Pulse Width Modulation

Design Considerations for Development of a Wire-Based Rock Cutting Mechanism for Space Exploration

Exploration and understanding of other celestial bodies will involve the same type of science used to understand our own planet earth. Specifically, much can be learned from studying the geology of the rocks present in a region of interest. One of the important tools used by geologists to understand and interpret rocks is a specimen called thin section. A thin section is produced by slicing a thin (typically 30 μm thick) plate or tablet from the rock. In this paper, the design of an autonomous rough cutter, used to produce the first stage of the specimen preparation, that is, a tablet (20 × 20 × 5 mm 3 ), is presented. Attention is given to the functional specification, the selection of cutting mechanism, in this case, diamond wire, and the design of the wire handling system. Also included are considerations of power usage, wire wear, and system configuration.