20 Matching Results

Search Results

Advanced search parameters have been applied.

Kinematically optimal robot placement for minimum time coordinated motion

Description: This paper describes an algorithm for determining the optimal placement of a robotic manipulator within a workcell for minimum time coordinated motion. The algorithm uses a simple principle of coordinated motion to estimate the time of a joint interpolated motion. Specifically, the coordinated motion profile is limited by the slowest axis. Two and six degree of freedom (DOF) examples are presented. In experimental tests on a FANUC S-800 arm, the optimal placement of the robot can improve cycle time of a robotic operation by as much as 25%. In high volume processes where the robot motion is currently the limiting factor, this increased throughput can result in substantial cost savings.
Date: October 1, 1995
Creator: Feddema, J.T.
Partner: UNT Libraries Government Documents Department

Visual Servoing: A technology in search of an application

Description: Considerable research has been performed on Robotic Visual Servoing (RVS) over the past decade. Using real-time visual feedback, researchers have demonstrated that robotic systems can pick up moving parts, insert bolts, apply sealant, and guide vehicles. With the rapid improvements being made in computing and image processing hardware, one would expect that every robot manufacturer would have a RVS option by the end of the 1990s. So why aren`t the Fanucs, ABBs, Adepts, and Motomans of the world investing heavily in RVS? I would suggest four seasons: cost, complexity, reliability, and lack of demand. Solutions to the first three are approaching the point where RVS could be commercially available; however, the lack of demand is keeping RVS from becoming a reality in the near future. A new set of applications is needed to focus near term RVS development. These must be applications which currently do not have solutions. Once developed and working in one application area, the technology is more likely to quickly spread to other areas. DOE has several applications that are looking for technological solutions, such as agile weapons production, weapons disassembly, decontamination and dismantlement of nuclear facilities, and hazardous waste remediation. This paper will examine a few of these areas and suggest directions for application-driven visual servoing research.
Date: May 1, 1994
Creator: Feddema, J. T.
Partner: UNT Libraries Government Documents Department

Parallel Assembly of LIGA Components

Description: In this paper, a prototype robotic workcell for the parallel assembly of LIGA components is described. A Cartesian robot is used to press 386 and 485 micron diameter pins into a LIGA substrate and then place a 3-inch diameter wafer with LIGA gears onto the pins. Upward and downward looking microscopes are used to locate holes in the LIGA substrate, pins to be pressed in the holes, and gears to be placed on the pins. This vision system can locate parts within 3 microns, while the Cartesian manipulator can place the parts within 0.4 microns.
Date: March 4, 1999
Creator: Christenson, T.R. & Feddema, J.T.
Partner: UNT Libraries Government Documents Department

Probability of Detection for Cooperative Sensor Systems

Description: In this paper, the authors quantify how communication increases the effective range of detection of unattended ground sensors. Statistical analysis used to evaluate the probability of detection for multiple sensors using one, two, and infinite levels of cooperation. levels of cooperation are defined as the levels of communication between sensors. One level of cooperation means that one sensor passes its state information to several other sensors within a limited communication range, but this information is not passed beyond this range. Two levels of cooperation means that the state information received by this first set of sensors is relayed to another set of sensors within their communication range. Infinite levels of cooperation means that the state information is further percolated out to all sensors within a communicating group. With large numbers of sensors, every sensor will have state information about every other sensor regardless of communication range. With smaller numbers of sensors, isolated groups may form, thus lowering the probability of information transfer.
Date: March 26, 1999
Creator: Feddema, J.T. & Spletzer, B.L.
Partner: UNT Libraries Government Documents Department

A capacitance-based proximity sensor for whole arm obstacle avoidance

Description: This paper addresses the issue of collision avoidance in unknown or partially modeled environments using a capacitive sensor. An eight channel capacitance-based sensor system which can detect obstacles up to 400 mm (16 inches) away has been developed. This sensor can detect both conductive and non-conductive obstacles of arbitrary color and shape. The sensor hardware is reliable and inexpensive, and it may be fabricated using flexible printed circuit boards to provide whole-arm and joint protection for any robot or manipulator. Simple collision avoidance control algorithms have been implemented on a two-link robot arm. The sensor and control system enable the robot arm to avoid a conductive post and a concrete block. 13 refs., 9 figs.
Date: January 1, 1991
Creator: Novak, J.L. & Feddema, J.T.
Partner: UNT Libraries Government Documents Department

Generic data acquisition system for robotic waste characterization

Description: This paper describes a generic data acquisition system for robotic characterization of DOE production facilities and waste sites. While the specific suite of characterization sensors on the end of a robotic arm or vehicle will depend on site needs, many of the data acquisition, display, archival and interpretation requirements of the sites are common. Therefore, the objective is to create a generic, reusable computing and data acquisition system which can accept a multitude of sensors. This paper discusses the progress to date and future plans for the system.
Date: July 1, 1993
Creator: Feddema, J. T. & Spletzer, B. L.
Partner: UNT Libraries Government Documents Department

Whole arm obstacle avoidance for teleoperated robots

Description: This paper describes a collision avoidance system using Whole Arm Proximity (WHAP) sensors on a PUMA 560 robot arm. The capacitance-based sensors generate electric fields which can completely encompass the robot arm and detect obstacles as they approach from any direction. The directional obstacle information gathered by the WHAP sensors together with the sensor geometry and robot configuration is used to scale the commanded joint velocities of the robot. A linearized relationship between the WHAP sensor reading and the distance from the obstacle allows direct transformation of perturbations in VHAP readings to perturbations in joint velocities. The VHAP reading is used to directly reduce the component of the command input velocity along the normal axis of the sensor, allowing graceful reductions in speed as the arm approaches the obstacle. By scaling only the component of the velocity vector in the,direction of the nearest obstacles, the control system restricts motion in the direction of obstacles while permitting unconstrained motion in other directions.
Date: October 1, 1993
Creator: Feddema, J. T. & Novak, J. L.
Partner: UNT Libraries Government Documents Department

Knowledge assistant: A sensor fusion framework for robotic environmental characterization

Description: A prototype sensor fusion framework called the {open_quotes}Knowledge Assistant{close_quotes} has been developed and tested on a gantry robot at Sandia National Laboratories. This Knowledge Assistant guides the robot operator during the planning, execution, and post analysis stages of the characterization process. During the planning stage, the Knowledge Assistant suggests robot paths and speeds based on knowledge of sensors available and their physical characteristics. During execution, the Knowledge Assistant coordinates the collection of data through a data acquisition {open_quotes}specialist.{close_quotes} During execution and post analysis, the Knowledge Assistant sends raw data to other {open_quotes}specialists,{close_quotes} which include statistical pattern recognition software, a neural network, and model-based search software. After the specialists return their results, the Knowledge Assistant consolidates the information and returns a report to the robot control system where the sensed objects and their attributes (e.g. estimated dimensions, weight, material composition, etc.) are displayed in the world model. This paper highlights the major components of this system.
Date: December 1, 1996
Creator: Feddema, J.T.; Rivera, J.J. & Tucker, S.D.
Partner: UNT Libraries Government Documents Department

Ultra-Precise Assembly of Micro-Electromechanical Systems (MEMS) Components

Description: This report summarizes a three year effort to develop an automated microassembly workcell for the assembly of LIGA (Lithography Galvonoforming Abforming) parts. Over the last several years, Sandia has developed processes for producing surface machined silicon and LIGA parts for use in weapons surety devices. Some of these parts have outside dimensions as small as 100 micron, and most all have submicron tolerances. Parts this small and precise are extremely difficult to assembly by hand. Therefore, in this project, we investigated the technologies required to develop a robotic workcell to assembly these parts. In particular, we concentrated on micro-grippers, visual servoing, micro-assembly planning, and parallel assembly. Three different micro-grippers were tested: a pneumatic probe, a thermally actuated polysilicon tweezer, and a LIGA fabricated tweezer. Visual servoing was used to accuracy position two parts relative to one another. Fourier optics methods were used to generate synthetic microscope images from CAD drawings. These synthetic images are used off-line to test image processing routines under varying magnifications and depths of field. They also provide reference image features which are used to visually servo the part to the desired position. We also investigated a new aspect of fine motion planning for the micro-domain. As parts approach 1-10 {micro}m or less in outside dimensions, interactive forces such as van der Waals and electrostatic forces become major factors which greatly change the assembly sequence and path plans. We developed the mathematics required to determine the goal regions for pick up, holding, and release of a micro-sphere being handled by a rectangular tool. Finally, we implemented and tested the ability to assemble an array of LIGA parts attached to two 3 inch diameter wafers. In this way, hundreds of parts can be assembled in parallel rather than assembling each part individually.
Date: April 1, 1999
Creator: Feddema, J.T.; Simon, R.; Polosky, M. & Christenson, T.
Partner: UNT Libraries Government Documents Department

CAD-driven microassembly and visual servoing

Description: This paper describes current research and development on a robotic visual servoing system for assembly of LIGA (Lithography Galvonoforming Abforming) parts. The workcell consists of an AMTI robot, precision stage, long working distance microscope, and LIGA fabricated tweezers for picking up the parts. Fourier optics methods are used to generate synthetic microscope images from CAD drawings. These synthetic images are used off-line to test image processing routines under varying magnifications and depths of field, They also provide reference image features which are used to visually servo the part to the desired position.
Date: March 10, 1998
Creator: Feddema, J.T. & Simon, R.W.
Partner: UNT Libraries Government Documents Department

Efficient Control Law Simulation for Multiple Mobile Robots

Description: In this paper we consider the problem of simulating simple control laws involving large numbers of mobile robots. Such simulation can be computationally prohibitive if the number of robots is large enough, say 1 million, due to the 0(N2 ) cost of each time step. This work therefore uses hierarchical tree-based methods for calculating the control law. These tree-based approaches have O(NlogN) cost per time step, thus allowing for efficient simulation involving a large number of robots. For concreteness, a decentralized control law which involves only the distance and bearing to the closest neighbor robot will be considered. The time to calculate the control law for each robot at each time step is demonstrated to be O(logN).
Date: October 6, 1998
Creator: Driessen, B. J.; Feddema, J. T.; Kotulski, J. D. & Kwok, K. S.
Partner: UNT Libraries Government Documents Department

Assembly planning at the micro scale

Description: This paper investigates a new aspect of fine motion planning for the micro domain. As parts approach 1--10 {micro}m or less in outside dimensions, interactive forces such as van der Waals and electrostatic forces become major factors which greatly change the assembly sequence and path plans. It has been experimentally shown that assembly plans in the micro domain are not reversible, motions required to pick up a part are not the reverse of motions required to release a part. This paper develops the mathematics required to determine the goal regions for pick up, holding, and release of a micro-sphere being handled by a rectangular tool.
Date: May 14, 1998
Creator: Feddema, J.T.; Xavier, P. & Brown, R.
Partner: UNT Libraries Government Documents Department

Experiments in micromanipulation and CAD-driven microassembly

Description: This paper discusses recent experiments in the manipulation and assembly of parts with 100 micron outside dimensions and submicron tolerances. The objective of this work is to develop a micromanipulation workcell which can automatically assemble LIGA (Lithography Galvonoforming Abforming) parts using an assembly plan and a CAD drawing of each of the components. The workcell consists of an AdeptOne robot, precision stages, long distance microscope, and a high aspect ratio modeled polysilicon tweezers for picking up the parts. Fourier optics methods are used to generate synthetic microscope images from CAD drawings. These synthetic images are used off-line to test image processing routines under varying magnifications an depths of field. They also provide reference image features which are used to visually servo the true part to the desired position.
Date: October 1, 1997
Creator: Feddema, J.T.; Keller, C.G. & Howe, R.T.
Partner: UNT Libraries Government Documents Department

Miniature Autonomous Robotic Vehicle (MARV)

Description: Sandia National Laboratories (SNL) has recently developed a 16 cm{sup 3} (1 in{sup 3}) autonomous robotic vehicle which is capable of tracking a single conducting wire carrying a 96 kHz signal. This vehicle was developed to assess the limiting factors in using commercial technology to build miniature autonomous vehicles. Particular attention was paid to the design of the control system to search out the wire, track it, and recover if the wire was lost. This paper describes the test vehicle and the control analysis. Presented in the paper are the vehicle model, control laws, a stability analysis, simulation studies and experimental results.
Date: December 31, 1996
Creator: Feddema, J.T.; Kwok, K.S.; Driessen, B.J.; Spletzer, B.L. & Weber, T.M.
Partner: UNT Libraries Government Documents Department

Decentralized fuzzy control of multiple nonholonomic vehicles

Description: This work considers the problem of controlling multiple nonholonomic vehicles so that they converge to a scent source without colliding with each other. Since the control is to be implemented on simple 8-bit microcontrollers, fuzzy control rules are used to simplify a linear quadratic regulator control design. The inputs to the fuzzy controllers for each vehicle are the (noisy) direction to the source, the distance to the closest neighbor vehicle, and the direction to the closest vehicle. These directions are discretized into four values: Forward, Behind, Left, and Right, and the distance into three values: Near, Far, Gone. The values of the control at these discrete values are obtained based on the collision-avoidance repulsive forces and the change of variables that reduces the motion control problem of each nonholonomic vehicle to a nonsingular one with two degrees of freedom, instead of three. A fuzzy inference system is used to obtain control values for inputs between the small number of discrete input values. Simulation results are provided which demonstrate that the fuzzy control law performs well compared to the exact controller. In fact, the fuzzy controller demonstrates improved robustness to noise.
Date: September 1, 1997
Creator: Driessen, B.J.; Feddema, J.T. & Kwok, K.S.
Partner: UNT Libraries Government Documents Department

Explaining finite state machine characteristics using variable structure control

Description: This paper describes how variable structure control can be used to describe the overall behavior of multiple autonomous robotic vehicles with simple finite state machine rules. The importance of this result is that it allows for the design of provably asymptotically stable group behaviors from a set of simple control laws and appropriate switching points with variable structure control. The ability to prove convergence to a goal is especially important for applications such as locating military targets or land mines.
Date: October 1, 1997
Creator: Feddema, J. T.; Robinett, R. D. & Driessen, B. J.
Partner: UNT Libraries Government Documents Department

Designing stable finite state machine behaviors using phase plane analysis and variable structure control

Description: This paper discusses how phase plane analysis can be used to describe the overall behavior of single and multiple autonomous robotic vehicles with finite state machine rules. The importance of this result is that one can begin to design provably asymptotically stable group behaviors from a set of simple control laws and appropriate switching points with decentralized variable structure control. The ability to prove asymptotically stable group behavior is especially important for applications such as locating military targets or land mines.
Date: March 10, 1998
Creator: Feddema, J.T.; Robinett, R.D. & Driessen, B.J.
Partner: UNT Libraries Government Documents Department

Minimum-time trajectory control of a two-link flexible robotic manipulator

Description: This paper analyzes the experimental and simulation results of a minimum-time trajectory control scheme for a two-link flexible robot. An off-line optimization routine determines a minimum-time, straight line tip trajectory which stays within the torque constraints of the motors and ends in a quiescent state, i.e., no vibrational transients. An efficient finite-element model is used in the optimization to approximate the flexible arm dynamics. The control strategy described here is used to determine the feedback gains for the position, velocity, and strain gage signals from a quadratic cost criterion based on the finite-element model linearized about the straight line tip trajectory. These feedback signals are added to the modeled torque obtained from the optimization routine and used to control the robot arm actuators. The results indicate that this combination of model-based and error-driven control strategies achieves a closer tracking of the desired trajectory and a better handling of modeling errors (such as tip payloads) than either strategy alone.
Date: January 1, 1990
Creator: Schoenwald, D.A.; Feddema, J.T.; Eisler, G.R. & Segalman, D.J.
Partner: UNT Libraries Government Documents Department

Techniques for controlling a two-link flexible arm

Description: The long length and relatively small cross sectional area of the robotic arms envisioned for use inside of the underground nuclear waste storage tanks will require the control of flexible structures. This will become an important problem in the characterization and remediation of these tanks. We are developing control strategies to actively damp residual vibrations in flexible robotic arms caused by high speed motion and abrupt external forces. A planar, two-link flexible arm is currently being used to test these control strategies. In this paper, two methods of control are discussed. The first is a minimum-time control approach which utilizes a finite element model and and optimization program. These tools plan the motor torque profiles necessary for the tip of the arm to move along a straight line, in minimum time, within the motors' torque constraints, and end in a quiescent state. To account for modeling errors in the finite element model, errors in joint angles, velocities, and link curvatures are added to the optimal torque trajectory. Linear quadratic Gaussian (LQG) regulatory design theory is used to determine the feedback gains. The second method of control is a teleoperated joystick controller which uses an input shaping technique to alter the commands of the joystick so as to reduce the residual vibration of the fundamental modes. Approximating the system as linear, the natural frequency and damping ratio are estimated on-line for the complete system, which includes the structure plus a lower level proportional derivative controller. An input shaping filter is determined from the estimated natural frequency, estimated damping ratio, and the desired transfer function of the system. 11 reps., 9 figs.
Date: January 1, 1990
Creator: Feddema, J.T.; Eisler, G.R.; Segalman, D.J.; Robinett, R.D. III; Morimoto, A.K. & Schoenwald, D.A.
Partner: UNT Libraries Government Documents Department