Observing Operations | Reviews | Survey Management

Telescope Performance Monitor Real-Time Displays

Peregrine M. McGehee
Los Alamos National Laboratory
Last Revision:  24 January 2000


1. Introduction

1.1 EPICS Overview

This document describes the Experimental Physics and Industrial Control System (EPICS) real-time database that is resident on the SDSS Telescope Performance Monitor VxWorks-based input/output Controller (IOC) and associated operator displays. This software is developed and maintained by Peregrine M. McGehee at Los Alamos National Laboratory who may be contacted by phone at (505) 667-3273, or via e-mail at peregrine@lanl.gov (or peregrin@sdsshost.apo.nmsu.edu on-site).

EPICS is a set of software tools and applications jointly developed by Argonne National Laboratory and Los Alamos National Laboratory for the purpose of controlling Particle Accelerators and Large Experiments. Present and future development is being done cooperatively by Argonne (ANL), Los Alamos National Laboratory (LANL), Lawrence Berkeley Laboratory (LBL), the Jefferson National Laboratory (TJNAF), the Spallation Neutron Source Collaboration,  BESSY (Berliner Elektronenspeicherring-Gesellschaft Fr Synchrotronstrahlung m.b.H.) and DESY (Deutsches Elektronen-Synchrotron).

EPICS provides:

  •      Interfaces to instrumentation from data acquisition, supervisory control, and steady state control through a table entry database.
  •      Operator interface to all control system parameters through interactive displays.
  •      Data logging through a table entry archiving file.
  •      Alarm management through a table entry alarm file.
  •      Sequential control through a state definition language with convenient database interface routines.
  •      Channel access routines for interfacing the control system data to data analysis, third party software packages, adaptive control algorithms and any other functions not provided in the control system.
  • The basic components needed are the Operator Interface (OPI), Input Output Controller (IOC), and a Local Area Network (LAN) which allows the OPI and IOC to communicate. For detailed information about the EPICS toolkit and the channel access protocol please refer to the EPICS homepage at Los Alamos National Laboratory:http://epics.aps.anl.gov/epics/.

    1.2 Access to Operator Displays on sdsshost

    Preliminary real-time displays of SDSS engineering data can be run by entering at the UNIX command line on sdsshost:
    % /usrdevel/peregrin/tpmrt/bin/iris/rt

    Please explore and send me back your comments and suggestions. I need to find out from all of you what type of displays and what information would be most useful to you.

    The data that is available is scanned at 5 Hz rate from the TPM computer and shows information that the MCP writes into shared memory. So any information that is in the shared memory I can have served across the network for you to examine.

    1.3 Implementation Note

    A word on the implementation. The EPICS control system toolkit creates a list of named process variables that clients can connect to over the local network. Any of these displays can be created by staff with knowledge of the specific tools used to build them since it is knowledge of the process variable names that define the interface with the user. At Los Alamos, many of the operations displays in use are created not by the controls staff but by the operators and accelerator physicists.

    For example, to find the name of process variable that is connected to a display widget on the edd/dm screens click on that widget using the middle mouse button. The resultant pop-up display shows the name of the control system process variable. This name can then be typed or pasted with the middle mouse button into the StripTool or Tcl/Tk xyplot tools.

    Figure 1. Example of edd/dm Channel Name Pop-up Display


    1.4 User Environment Requirements

    If you wish to bring up the EPICS operator tools separately, not via the rt script, a number of environmental variables must be first set in the user's shell.

    The execution path must include:

    • /usrdevel/peregrin/epics/extensions/bin/sgi

    • for the EPICS operator applications or extensions including edd/dm, StripTool, and the EPICS-specific et_wish that combines Tcl, Tk, BLT, Tcl-dp, and channel access client library..
    And the standard Tcl/Tk libraries must be defined:
    • TCL_LIBRARY = /p/tcl/v7_4d/lib/tcl7.4
    • TK_LIBRARY = /p/tk/v4_0d/lib/tk4.0
    • DP_LIBRARY = /p/tcldp/v3_2f3/lib/dp

    1.5 Locations

    1.5.1 EPICS

    The EPICS distribution is installed under sdsshost:/usrdevel/peregrin/epics, hereafter referred to as $EPICS.

    $EPICS/base contains the core of the EPICS system, including channel access communications, the tools to create and manage the real-time database, and the standard database recordtypes and device drivers used by the collaboration. EPICS at APO is built using the SGI as a host and the MV162 as the target.

    $EPICS/extensions contains a small number of the numerous add-ons to EPICS as contributed by the many sites. This includes all of the operator display tools.

    1.5.2 TPM application

    The real-time TPM system is under sdsshost:/usrdevel/peregrin/tpm/tpmApp and contains the EPICS database, custom C source code, operator displays, and configuration files.

    2. EPICS Operator Tools

    Three different tools are in use.
    • The main screens are implemented using the EPICS edd/dm display builder developed at LANL.
    • The XY plots are created using a Tcl/Tk program created at LANL using an EPICS interface developed at ANL.
    • The Stripcharts make use of the EPICS StripTool program developed at TJNAF.
    Additional user interface displays can be created quickly using the EPICS edd/dm display manager program. The complete user's guide to edd/dm is available on-line at http://lansce.lanl.gov/organization/EPICSdata/OPI/opintro-1.html.

    Descriptions of the XY plot tool and of the StripTool are given below.

    Additional operations and analysis utilities can be constructed using existing channel access client interfaces to IDL, Mathematica, Java, SDDS, and other software systems.

    2.1 TPM edd/dm Displays

    2.1.1 Main TPM Display

    The main TPM edd/dm display, tpm.dl,  provides a summary of  the three axis positions in degrees and their position errors in encoder counts.

    The row of four pull-down menus, from left to right, bring up:

    • Tcl/Tk XY Plots
      • User configurable XY Plot
      • Altitude versus Azimuth
      • Rotator versus Azimuth
    • Axis Data
      • Encoder, Current, and Voltage data on the three axes
    • Interlock
      • List of active interlocks
    • Time Plot
      • User configurable stripchart
      • Position errors stripchart
      • Rotator data stripchart
      • Altitude data stripchart
      • Azimuth data stripchart
    The "About" pull-down system.

    Figure 2. Main TPM edd/dm Display

    2.1.2 TPM Axis Data Display

    This display provides text update fields of the encoder, current, and voltage readbacks from the altitude, azimuth, and rotator axes.
    Figure 3. TPM Axis Data edd/dm Display

    2.1.3 TPM Interlock Display

    The Interlock display is meant to show the axis interlocks that are currently activated. This is implemented using edd/dm's ability to control widget visibility based on the value of a control system process variable.
    Figure 4. TPM Interlock edd/dm Display

    2.1.4 TPM "About" Display

    The "About" display's purpose is to provide software version and developer contact information.
    Figure 5. TPM "About" edd/dm Display


    2.2 Tcl/Tk-based XY Plots

    This simple utility allows the creation of real-time XY plots of upto three variables against a single variable on the same axis. The variables are EPICS process variables whose names are listed in section 3. of this document.

    The values of the named process variables are fetched every 0.5 seconds. Changing the format of the axes (Min, Max, Nint) does not cause data to be lost.

    The operator input fields are:

    • OPDES - this is the process variable
    • Min - Minimum value for the X (or Y axis)
    • Max - Maximum value for the X (or Y axis)
    • Nint - Number of labeled intervals on the axis. There is a tick mark between every pair of labels.
    The operator controls from left to right are:
    • Start - Start data acquisition and plotting loop
    • Stop - Stop data acquisition and plotting loop
    • Clear - Erase graph and stop
    • Quit - Exit Program

    Figure 6. Sample XYPlot Tcl/Tk Display


    2.3 StripTool

    2.3.1 Program Initialization

    The EPICS StripTool can be started either from the main TPM edd/dm screen or directly from the UNIX shell. The invocation syntax is:
    % StripTool <optional config file name>

    The configuration files presently resident in sdsshost:/usrdevel/peregrin/tpm/tpmApp/opi are:

    • tpm_alt.cfg  - Altitude axis data
    • tpm_az.cfg   - Azimuth axis data
    • tpm_err.cfg  - Altitude, Azimuth, and Rotator position errors
    • tpm_rot.cfg  - Rotator data
    • tpm_ws.cfg - Windscreen LVDT

    2.3.2 Example StripTool display

    The following figure shows a StripTool chart display. The operator control features are:
    • The names of the EPICS process variables being plotted are shown in the column on the right-hand side. These names are enclosed in boxes that indicate the data color. Other information listed are the units and the display min and max for that channel. Clicking on that box changes the vertical axis on the left-hand side to reflect those limits.
    • The buttons along bottom of the display have the following functions (given from left to right): Pan Left, Pan Right, Zoom In, Zoom Out, and Auto Scroll.
    • The control menu can be accessed by clicking and holding down the right mouse button on the main part of the display. The options in this menu are:
      • Controls Dialog - see below.
      • Toggle Scroll Buttons - on and off.
      • Print - defaults to the printer hdraper at APO.
      • Snapshot - screen capture.
      • Dump - to an ASCII file.
      • Dismiss - close display.
      • Quit - exit program.
    Figure 7. Example StripTool Chart


    2.3.3 StripTool Controls Dialog

    The Controls Dialog for the StripTool utility is divided into the following five regions:
    • Signal Connect
    • Time Controls
    • Graph Options
    • Curves
    • Application Controls
    In addition, the File pull-down menu allows you to save the present configuration as a named file, or to load an existing configuration file. Signal Connect

    The name of an EPICS process variable is typed or pasted into the text entry box and the Connect button is pushed. If the process variable can be located, a row is added in the Curves section. Time Controls

    The user can modify the data sample interval and the redraw interval. The practical limits to these are based on the workstation and network performance since the shorter intervals pose more of a load on the system performance. Graph Options

    These allow the user to alter the color and general appearance of the stripcharts. Curves

    Here you may change the display limits of each channel and to remove them from the stripchart. Application Control

    The control buttons from left to right allow the user to:
    • Show stripchart
    • Clear the stripchart - removes all process variables
    • Dismiss the controls dialog window
    • End program
    • Figure 8. Example StripTool Dialog Window


    3. Real-Time EPICS Database

    3.1 Database Descriptions

    Each record in the real-time EPICS database is described by a number of fields (see the EPICS Record Reference Manual). For the purpose of this document we will list the following set of attributes:
  • Name - the location of the record in the EPICS global namesake implemented on the local SDSS Internet. This is the string that clients across the network use to access this record. The name is what can be used by any operator tool including the display manager, Strip Tool, and Tcl/Tk applications.
  • Description - the information contained in the record.
  • Type - the nature of the database record.
  • Units - the units that the record value is in.
  • Scan Rate - the frequency at which the record is updated.
  • 3.2 Shared Memory Access

    The EPICS database on the TPM primarily serves data that is written by the SDDS Mount Control Processor (MCP) across a shared memory interface.

    3.2.1 Data Transfer

    The tpm_getdata subroutine record is the first to be processed as part of the Hz scanning. It's purpose to to copy data from the MCP-TPM shared memory into a number of global vxWorks variables. These variables are then tied to EPICS database records using the "vxWorks Variable" or symbolic device support.
    Name Description Type Units Scan Rate
    tpm_getdata Load Data Into Global Variables General Subroutine None 5 Hz

    3.2.2 Altitude Axis

    Name Description Type Units Scan Rate
    tpm_ALCPOS Altitude Position Command LongIn Encoder counts 5 Hz
    tpm_ALCVOLT  Altitude Voltage Command LongIn ADC counts 5 Hz
    tpm_ALENC1 First Altitude Encoder LongIn Encoder counts 5 Hz
    tpm_ALENC2 Secon LongIn Encoder counts 5 Hz
    tpm_ALMTRV1 Altitude First Motor Voltage LongIn ADC counts 5 Hz
    tpm_ALMTRV2 Altitude Second Motor Voltage LongIn ADC counts 5 Hz
    tpm_ALMTRC1 Altitude First Motor Current LongIn ADC counts 5 Hz
    tpm_ALMTRC2 Altitude Second Motor Current LongIn ADC counts 5 Hz

    3.2.3 Azimuth Axis

    Name Description Type Units Scan Rate
    tpm_AZCPOS Azimuth Position Command LongIn Encoder counts 5 Hz
    tpm_AZCVOLT  Azimuth Voltage Command LongIn DAC counts 5 Hz
    tpm_AZENC1 First Azimuth Encoder LongIn Encoder counts 5 Hz
    tpm_AZENC2 Second Azimuth Encoder LongIn Encoder counts 5 Hz
    tpm_AZMTRV1 Azimuth First Motor Voltage LongIn ADC counts 5 Hz
    tpm_AZMTRV2 Azimuth Second Motor Voltage LongIn ADC counts 5 Hz
    tpm_AZMTRC1 Azimuth First Motor Current LongIn ADC counts 5 Hz
    tpm_AZMTRC2 Azimuth Second Motor Current LongIn ADC counts 5 Hz

    3.2.4 Instrument Rotator

    Name Description Type Units Scan Rate
    tpm_ROCPOS Rotator Position Command LongIn Encoder counts 5 Hz
    tpm_ROCVOLT  Rotator Voltage Command LongIn DAC counts 5 Hz
    tpm_ROCENC Rotator Encoder LongIn Encoder counts 5 Hz
    tpm_ROMTRV Rotator Motor Voltage LongIn ADC counts 5 Hz
    tpm_ROMTRC Rotator Motor Current LongIn ADC counts 5 Hz

    3.2.5 Windscreen

    Name Description Type Units Scan Rate
    tpm_ALWSPOS Altitude/Windscreen LVDT  LongIn Encoder counts 5 Hz

    3.2.6 Interlocks

    Name Description Type Units Scan Rate
    tpm_ALLWC Alitude/Windscreen Lower Collision BinaryIn Triggered=1/OK=0 5 Hz
    tpm_ALP100  Altitude 100 Degree Limit BinaryIn Triggered=1/OK=0 5 Hz
    tpm_ALP20 Altitude 20 Degree Limit BinaryIn Triggered=1/OK=0 5 Hz
    tpm_ALP_2 Altitude -2 Degree Limit BinaryIn Triggered=1/OK=0 5 Hz
    tpm_ALRWC Altitude/Wind Screen Raise Collision BinaryIn Triggered=1/OK=0 5 Hz
    tpm_ALSTOW Altitude Stow Position BinaryIn Triggered=1/OK=0 5 Hz
    tpm_AZCCWC Azimuth/Windscreen CCW Limit BinaryIn Triggered=1/OK=0 5 Hz
    tpm_AZCCWHL Azimuth/Windscreen CCW Hard Limit BinaryIn Triggered=1/OK=0 5 Hz
    tpm_AZCCWSL Azimuth/Windscreen CCW Soft Limit BinaryIn Triggered=1/OK=0 5 Hz
    tpm_AZCWC Azimuth/Windscreen CW Limit BinaryIn Triggered=1/OK=0 5 Hz
    tpm_AZCWHL Azimuth/Windscreen CW Hard Limit BinaryIn Triggered=1/OK=0 5 Hz
    tpm_AZCWSL Azimuth/Windscreen CW Soft Limit BinaryIn Triggered=1/OK=0 5 Hz
    tpm_ROCCWHL Rotator CCW Hard Limit BinaryIn Triggered=1/OK=0 5 Hz
    tpm_ROCCWSL Rotator CCW Soft Limit BinaryIn Triggered=1/OK=0 5 Hz
    tpm_ROCWHL Rotator CW Hard Limit BinaryIn Triggered=1/OK=0 5 Hz
    tpm_ROCWSL Rotator CW Soft Limit BinaryIn Triggered=1/OK=0 5 Hz
    tpm_ROICHG Rotator at Instrument Change BinaryIn Triggered=1/OK=0 5 Hz

    3.3 Derived Quantities

    The raw data obtained from the shared memory interface can be transformed into other forms by use of EPICS Calculation records. For each axis we scale the encoder readings into degrees on the sky and compute the differences between the axis encoder and commanded positions.
    Name Description Type Units Scan Rate
    tpm_altitude Altitude Position Calculation Degrees 5 Hz
    tpm_azimuth Azimuth Position Calculation Degrees 5 Hz
    tpm_rotator Rotator Position Calculation Degrees 5 Hz
    tpm_alterr Altitude Servo Error Calculation Encoder Counts 5 Hz
    tpm_azerr Azimuth Servo Error Calculation Encoder Counts 5 Hz
    tpm_roterr Rotator Servo Error Calculation Encoder Counts 5 Hz

    3.4 Other

    For informational purposes we compute the time since last reboot of the TPM IOC. This is available from the system as clock ticks and we use a Calculation record to translate that into hours.
    Name Description Type Units Scan Rate
    tpm_uptime TPM IOC up-time Calculation Hours 0.1 Hz
    tpm_vxTicks vxWorks clock ticks LongIn Ticks Passive

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