Automation Of The Lanl Aries Lathe Glovebox

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LA-UR-01-0313 Approved for public release; distribution is unlimited. Title: AUTOMATION OF THE LANL ARIES LATHE GLOVEBOX Author(s): Pete C. Pittman, ESA-EPE Torsten Staab, ESA-EPE Dave Nelson, ESA-EPE Bill Santistevan, ESA-EPE Wendel Brown, NMT-15 Submitted to: The American Nuclear Society Ninth Topical Meeting on Robotics and Remote Systems March 4-8, 2001 Los Alamos NATIONAL LABORATORY Los Alamos National Laboratory, an affirmative action/equal opportunity employer, is operated by the University of California for the U.S. Department of Energy under contract W-7405-ENG-36. By acceptance of this article, the publisher recognizes that the U.S. Government retains a nonexclusive, royaltyfree license to publish or reproduce the published form of this contribution, or to allow others to do so, for U.S. Government purposes. Los Alamos National Laboratory requests that the publisher identify this article as work performed under the auspices of the U.S. Department of Energy. Los Alamos National Laboratory strongly supports academic freedom and a researcher's right to publish; as an institution, however, the Laboratory does not endorse the viewpoint of a publication or guarantee its technical correctness. FORM 836 (10/96) AUTOMATION OF THE LANL ARIES LATHE GLOVEBOX Pete Pittman, Torsten Staab, Dave Nelson, Bill Santistevan, Wendel Brown Los Alamos National Lab Mail Stop J580 Los Alamos, NM 87545 [email protected] 505-667-8340 ABSTRACT This paper presents the design of an automation system required for material handling within a glovebox. The Advanced Recovery and Integration Extraction System (ARIES) located at the Los Alamos National Laboratory (LANL) enables workers to dismantle nuclear weapons, separating the plutonium from other weapon components. The ARIES line consists of several gloveboxes that allow the “pit” or trigger of a nuclear weapon to be dismantled and the plutonium stored in a safe form. The Lathe glovebox is the first step in the ARIES line and is used to cut the pit open to be dismantled. There are several methods for doing this, however there are advantages to using the lathe over other methods for this process. In general, this system will give the ARIES line the capability to handle a wider range of pit types. The system consists of a lathe, a 4 Degree of Freedom (DOF) robot, a glovebox that houses them, and a universal controller that resides outside the glovebox and controls all equipment. This paper will present the design and possible implementation of this lathe automation system. It will cover the system requirements, the mechanical hardware used within the glovebox, the control system and software, and operation procedures for various tasks. 1 INTRODUCTION The ARIES line at LANL is a demonstration system used to prove concept viability and to provide a testbed for the design of new technologies. More information may be found on this project at http://www.lanl.gov:80/aries/. The Pit Disassembly and Conversion Facility (PDCF) to be built at Savannah River will allow the United States (US) to eliminate warheads as defined in START II and START III and will be a much larger production facility to process large numbers of pits as required by the treaties. Dose reduction is the primary justification for implementing automation within the glovebox that houses the lathe. The process currently requires an operator to manually run a lathe or other bisecting mechanism to cut the pit in half. This tends to be a high dose operation LA-UR-01-313 2 because it involves handling the pit directly for extended periods. For some pits, the operator can exceed the 500mrem per operator dose limits set for the PDCF. With the use of this automation system, that dose is essentially eliminated and in most cases, the operator should only be exposed to the background dose levels. In addition, some of the operations were physically challenging due to the weight of the component that had to be handled or the difficult reach or other glovebox limitations. The system design requirements were relatively well defined at the beginning of the project with respect to the overall system architecture. The need for a lathe had already been defined and had been bought previously. The desire was therefore to design the automation to accommodate it. In addition, there was a requirement to use the same controller as the lathe used to provide a uniform interface for the operator, thus making the system simpler to run and maintain in the future. There was an existing glovebox design that had been completed prior to the decision to implement automation, but it had not been fabricated. This was redesigned to accommodate the new system needs. Some of the system task requirements were well defined. These are tasks that must be accomplished by the robot within the glovebox including: · Receiving pits in the glovebox. The pit arrives into the box on a conveyor and the robot is required to retrieve the pit from the tray. The pit is held on a stand on the tray to maintain a repeatable orientation. · Weighing the pit after entering the glovebox. After the pit is retrieved from the conveyor, the robot moves it to a scale to be weighed. · Loading pits into the lathe chuck. The loading and alignment process is an iterative process that normally increases the dose an operator would receive. · Changing the chuck on the lathe to accommodate different pits. The chuck loading operation requires high precision to ensure proper alignment. This procedure is difficult to do manually, and is particularly difficult given the glovebox environment and the reach that is required with a heavy chuck. · Changing tools or cutters on the lathe tool post. This was automated with the lathe when it was procured, but the mechanism was large and complex. · Handling pit halves. This is a particularly important task as dose is higher when the pit is separated. · Weighing pit components. All components have to be weighed before exiting the glovebox. In addition to these well defined tasks were tasks that were not well defined for a variety of reasons. These tasks were primarily pit disassembly operations once the cutting is complete. The completion of these tasks was ensured by defining general system performance requirements that would guarantee flexibility for future operations. All automation in this environment is required to be proven industrial technology. It must be simple, reliable, and maintainable. 2 MECHANICAL DESCRIPTION The complete system consists of a lathe, the robot, all associated tooling for the lathe and the glovebox that encloses it all. This may be seen in Figure 1. In this figure, the glovebox is shown semi transparent to allow the other equipment to be seen. LA-UR-01-313 3 Figure 1: Model of ARIES Lathe with robot and glovebox. 2.1 Lathe Description The lathe is a large custom air bearing machine tool built by Moore Industries. It is computer controlled including a 2 axis tool post. This may be seen in photos given in Figure 2 and in Figure 3. LA-UR-01-313 4 Figure 2: Photo of ARIES Lathe, spindle on left, tool post in center, and tail stock on right. Figure 3: Photo of ARIES Lathe, spindle on left, tail stock hidden on right. The existing tool changer (which is visible above the tool post in the lathe photos) was removed as the robot is capable of changing the lathe tools. This also freed up space behind the tail stock that can be used for staging other equipment such as scales, etc. Note the flange at the base of LA-UR-01-313 5 the lathe as seen in Figure 3. This is an unusual feature for a glovebox as this allows for the glovebox to be bolted directly to the lathe with the lathe acting as the bottom of the box. The lathe uses a vacuum pot chuck in both the head and tail stock to grip the pit while cutting. The lathe was delivered with a relatively sophisticated controller as described later. 2.2 Robot Description The robot is a 4 DOF gantry system. It is fabricated from off the shelf industrial components and consists of linear modules arranged in a gantry configuration as seen in Figure 4. The X-axis is along the length of the glovebox and the lathe spindle axis. There are dual X-axis rails, both driven. Y-axis cabling Y-axis rails X-axis rails X-axis cabling Z-axis rail Figure 4: ARIES Lathe Robot, top view. The Y-axis axis is across the width of the box. The Z-axis is vertical. The X, Y, and Z axes are Star linear rails with 95.5, 36, and 15 inches of travel respectively. The X-axis is belt driven. The Y and Z axes are ball screw driven. The fourth DOF is provided by a yaw assembly which doubles as an extension to offset the robot envelope. The Yaw axis as seen in Figure 5 has 338 degrees of travel. LA-UR-01-313 6 Yaw-axis Y-axis rails Force Sensor Tool Changer X-axis rail Y-axis cabling Z-axis rail Figure 5: ARIES Lathe Robot, bottom view. The axes were chosen to maximize travel within the glovebox. The robot envelope may be seen in Figure 6. This figure shows the robot envelope, surrounded by a dark area that the robot cannot reach. The lathe, robot tooling, lathe tooling, and pot chucks may also be seen. Figure 6: Robot work envelope. LA-UR-01-313 7 The robot tooling, and some of the lathe tooling is shown in Figure 7. The tooling is as follows from top, left: pot chuck gripper, pit gripper, hemishell gripper, LVDT sensor, slitting saw, lathe tooling gripper, pot chuck, pot chuck interface plate. Figure 7: Robot and Lathe tooling. The robot tooling uses a standard robot tool changer from ATI to allow different tooling to be swapped out and used. The lathe uses a SANDVIK tool changer (clamp) to secure tooling on the tool post. 2.3 Glovebox Description The ARIES Lathe glovebox consists of two sections joined by a flange. The main section will bolt directly to the lathe bed. The other section is an annex for part handling and will be mounted on a stand. An airlock for the introduction of parts connects the annex section to an existing drop box. There are three rows of gloveports on each side of the glovebox. The top row provides access to the robot rails for maintenance. The bottom row allows access to the bellows and rails on the lathe. The middle row of gloveports is at roughly the same height as the lowest gloveports on a standard glovebox. These ports can be used for part handling and other operations. The glovebox is shown in Figure 8. LA-UR-01-313 8 Figure 8: ARIES Lathe glovebox. The glovebox is constructed of 5/8” thick 304 stainless steel, which provides more shielding than the standard 7 gage steel and does not require additional lead shielding. Stiffening gussets are not required on a 5/8 inch wall glovebox. The length of the main section is driven by the size of the lathe bed and by the overhang of the lathe headstock. The lathe bed also drives the width of the glovebox. The walls of the box are vertical, rather than tapered inward at the main windows, in order to maximize the space available for the robot rails mounted to the ceiling. The length of the annex box is 33 inches, which is the minimum that will allow a set of gloveports with standard spacing. The height of the box is maximized for Z-axis travel but is limited by the doorway into the room. The overall dimensions of the box and lathe are 140 5/16 inches long, 56 5/16 inches wide, and 92 ¾ inches high. The height measurement is at the top of the flange that joins the two sections of the box. LA-UR-01-313 9 The surface of the lathe table is very low and is cluttered with cables and equipment so a work surface will be placed in the glovebox to act as a false floor. The work surface is a table consisting of aluminum on a frame. This surface is just above the lowest rows of gloveports and is the full width of the inside of the box. This surface is only slightly higher than the floor of a standard glovebox. 3 ELECTRICAL DESCRIPTION All motion within the glovebox is controlled by an AeroTech model U-600 programmable motion control card. This card provides up to sixteen axes of control. Stepper and servo motors are supported in any combination. The card runs an on-board RISC processor, contains its own memory, and operates independently of the host computer on whose bus it resides. The host computer provides the MMI while the U-600 provides the real-time environment necessary for motion control. There is no real-time interaction required between the MMI and motion control. This architecture may be seen in Figure 9. Figure 9: Control system architecture. The controller consists of a 4-axis central card to which additional 4-axis expansion cards are added as needed. Each card can accept analog and digital I/O signals. All digital I/O is passed through OPTO-22 I/O modules for isolation and current-boosting requirements. The control system resides within a personal computer running Windows NT. This computer LA-UR-01-313 10 provides the environment for the Man-Machine Interface (MMI) software and supports the physical environment necessary for the motion controller. All motion on the lathe and robot is generated electrically. Pneumatics (compressed argon & vacuum) are used for part gripping and air-bearing operation. The robot utilizes four servo-controlled drive axes and one stepper-controlled yaw axis. The three cartesian axes, X, Y, & Z, are powered by servo motors. Two servo motors are used on the x-axis in gantry mode for mechanical simplicity. In gantry mode, one motor is defined to be a master and the second motor a slave to the master. To the motion control software, both motors appear as one axis and the motion controller firmware maintains synchronization. The y and z axes are also servo-powered. For simplicity, all servo motors are identical. The Yaw axis consists of a micro stepper motor with a harmonic drive for increased step resolution. A six-axis force-torque transducer is located on the end of the z-axis as seen in Figure 5. The transducer provides three axes each of force and torque data in real time. The transducer provides data used for crash protection during moves through what should be free space. Additionally it provides data for controlling the end of movements where contact occurs with a rigid surface or in force guided moves. The JR3 transducer was chosen for its six-axis capability, digital interface, over-range capability, and its proven history. There are three basic types of safety systems. The first is purely hardware based and the concern here is to provide the E-stop function. Contactors are provided in the AC power circuits feeding the lathe and robot motor amplifiers. In normal operation, the contactors are energized. A series-connected string of normally-closed, emergency-stop switches are located around the perimeter of the glovebox. These switches control the coil of an intermediate relay whose contacts allow the prime power contactors for the motor amplifiers to be energized. Opening any switch removes relay power and the prime power contactors then drop out. The circuit exists purely in hardware and is not influenced by software in any way. The second safety system is hardware and software based. There are several operations that require the operator to put hands in the glovebox between robot operations. The concern is therefore to ensure that the system is not moving when this happens. The glovebox glove ports are protected by a light beam positioned just inside the box. When this beam is broken, a signal is sent to the controller. The controller processes the signal to do one of two things. If the robot is in motion when a hand enters the box, a relay activates the above hardware system and the system comes to an immediate stop as described above. If the robot is not in motion, the controller sets a flag to ensure that no motion occurs while the hand is in the box. The third safety system is purely software based. This includes soft stops, etc. that are used by the operator at the operating console. This allows the robot to be stopped in a controlled manner without the need of recovery routines. In addition, it can include monitoring of the force sensor located at the robot end effector. 4 SOFTWARE DESCRIPTION LA-UR-01-313 11 Figure 10 depicts the system architecture of the Aerotech U600 motion control board. The U600 axis processor supports up to four independent tasks. Each task is capable of executing any program stored in the U600-internal CNC program pool. Figure 10: Controller system architecture. Task synchronization and access to external hardware (e.g., force sensor) can be achieved via global variables, I/O registers, and Virtual I/Os. The U600 board also enables each motion control task to access axes parameters, which contain valuable information, such as feed rates and dimensions. Task 1 will be used to execute robot-specific CNC routines. Task 2 will run the lathe CNC software. Task 3 will continuously execute system-wide monitoring routines to ensure system safety. Task 4 will not be used in the ARIES Lathe project. There will be a dedicated CNC main program for each of the three tasks being used. The Aerotech provides a MMI. It is limited in how it can be modified, but still allows for all necessary functions to be included. The Run Page that is accessed after startup will provide a number of customized push keys, such as F7 “Go to Robot” and F8 “Go to Lathe” as seen in Figure 11. LA-UR-01-313 12 Figure 11: Controller Run Page startup screen. By pushing the F7 key, the user will be automatically transferred to the robot control startup screen. There will be a total of three robot control screens available to the user. Each of the robot control screens will provide an ESTOP (Emergency Stop) key (i.e., F7), a lathe control screen toggle key (F8) that enables the user to switch back and forth between robot and lathe control screens, and a number of other robot-specific function keys. A couple Robot control screens may be seen in Figure 12. Figure 12: Controller robot control screens. By pushing the F8 “Go to Lathe” key in the Run Page screen (see Figure 11), the user will be automatically transferred to the lathe control startup screen. There will be a total of three lathe control screens available to the user. Similar to the robot control screens, each lathe control LA-UR-01-313 13 screen will provide an ESTOP (Emergency Stop) key (i.e., F7), a robot control screen toggle key (F8), and a number of other lathe-specific functions keys. A couple Lathe control screens may be seen in Figure 13. Figure 13: Controller lathe control screens. Recovery from abnormal situations is a manual process. This will require the operator to intervene and move the equipment manually via a mechanical joystick or through manual control screens as seen in Figure 14. Figure 14: Controller manual control screens. 5 PROJECT CONTROL DESCRIPTION Project control has also been a focus in this project. All work has been thoroughly documented including the following documents: · Project Plan: provides overall project structure and an outline. · Schedule: detailed MS Project schedule. Individual team members also maintain schedules to track their work. · Design Requirements Specification: signed document to outline the system operating, mechanical, and electrical requirements. · Software Requirements Specification: signed document to outline the system software requirements. LA-UR-01-313 14 · · · · · · 6 Safety/Failure Analysis: document that covers all potential system failures. System Design Description: design document that describes the mechanical and electrical design of the system. Mechanical Design Drawings: detailed fabrication drawings. Electrical Design Drawings: detailed fabrication drawings. Maintenance Guide: provides operators with a detailed description of how individual components are removed from the glovebox for maintenance. Acceptance Test Plan: outline of acceptance requirements and tests that each system is run though. CONCLUSIONS The design goals here have been to make this an industrial type system, capable of operating in a plant environment for extended periods. This has been accomplished. The system is currently being fabricated with the robot expected to be running in 06/01. Cold testing with a fully integrated system should happen in 01/02 and the system should be installed and operating by 07/02. 7 ACKNOWLEDGEMENTS Funding for the work described in this paper was supplied by the US Department of Energy under contract to the University of California, operator of the Los Alamos National Laboratory. LA-UR-01-313 15