Observing Operations | Reviews | Survey Management

Telescope Performance Monitor Real-Time System: Modifications as of 30 Sept 1999

Peregrine M. McGehee
Los Alamos National Laboratory
Last Revision: 30 September 1999

1. Introduction

This report describes enhancements to the SDSS Telescope Performance Monitor Real-Time Displays effective 30 September 1999. Enhancements include access to the MCP and TCC PVT (Position-Velocity-Time) Triplets and simple checks on telescope tracking performance.

No changes have been made to the access methods on sdsshost or to the user environment requirements. With the exception of the MIG readbacks all data is obtained or derived from what the MCP writes into the MCP-TPM shared memory.

This software is maintained by Peregrine M. McGehee.
LANL contact info: peregrine@lanl.gov, (505) 667-3273
APO contact info: peregrin@sdsshost.apo.nmsu.edu, (505) 437-6822

2. Main Display (tpm.dl)

The purpose of the main TPM display is to provide a summary of the telescope configuration. This is accomplished through a number of text and graphical indicators and related display menus.

2.1 Parameters Visible on the Main Display

For the TPM IOC (vxWorks CPU):

Time since last TPM (or MCP) Reboot in Hours

For the Altitude, Azimuth, and Rotator Axes:

Axis Tracking Status (Green=OK,Red=Not OK). See section 2.2.4.2 for details.
Axis Position in Degrees
Servo Error in Encoder Counts
Drive Current in ADC Counts

For the Windscreen:

Altitude LVDT in Counts
Azimuth LVDT in Counts

For the Primary and Secondary Mirror Support Systems (MIG readbacks):

M1 Axial A, B, and C Positions in Inches
M1 Lateral E (East) and Lateral F (West) Positions in Inches
M2 Axial A, B, and C Positions in Inches

2.2 Related Display Menus

2.2.1 About

No change in functionality since last release. The "About" display's purpose is to provide software version and developer contact information.

2.2.2 XY Plots

No change in functionality since last release. This simple utility allows the creation of real-time XY plots of up to three variables against a single variable on the same axis. Implemented in Tcl/Tk with BLT graph widgets and the EPICS Channel Access client interface library.
The menu options are:

Alt/Az Plot - Altitude versus Azimuth
Rot/Az Plot - Rotator Position versus Azimuth
Generic Plot - Template for User-Defined Plots

2.2.3 DETAILS

The Details menu calls up displays that contain detailed information about the state of the telescope and mount.

2.2.3.1 AXIS

No change in functionality since last release. This display provides text update fields of the encoder, current, and voltage readbacks from the altitude, azimuth, and rotator axes.

2.2.3.2 PVTs

This display provides a text readback of the Telescope Control Computer and Mount Control Processor PVT triplets for the Altitude, Azimuth, and Rotator axes. This information is read from the MCP-TPM shared memory at a rate of 5Hz.

The units are:

Position in Encoder Counts
Velocity in Encoder Counts/Second
Time in Milliseconds

2.2.4 SYSTEM CHECKS

This menu provides access to an interlock status display and to the configuration screens for the axis tracking tests. The menu options are:

INTERLOCK
ALT OK?
AZ OK?
ROT OK?

2.2.4.1 INTERLOCK

No change in functionality since last release. The Interlock display is meant to show the axis interlocks that are currently activated.

2.2.4.2 AXIS OK?

The ALT OK?, AZ OK?, and ROT OK? displays are based on the same template screen for configuration of a simple test for axis tracking performance.

The test implemented is:

If the axis servo errors are greater than some limit and
If the axis velocity is less than a certain limit (indicating tracking) then
We should alert the observer to this condition.

The axis servo error is computed as the different between the commanded axis position and the encoder readback. Large errors are possiible when an axis has been moved manually. The servo error is in encoder counts.

The axis velocity is the velocity component of the MCP PVT Triplet and is in encoder counts per second.
The limits on the servo error and the tracking velocity can be entered by the user using the text input fields on the righthand side of the display. The default values are:

Max Tracking Velocity: 10000 counts per second (~135 arcseconds per second)
Max Servo Error: 100 counts (~1.4 arcseconds)

The OK/not-OK state of the test is shown on the far righthand side of the display and is duplicated on the main TPM display. The test is executed at 5Hz within the TPM IOC using an EPICS CALCULATION database record.

2.2.5 TIME SERIES

This menu allows selection of a number of EPICS StripTool configurations to proviide for time-series plots of telescope engineering parameters.
The menu options are:

GENERIC - Template for User-Defined Stripcharts.
POSITION ERRORS - Altitude, Azimuth, and Rotator servo errors.
ROTATOR - Encoder, Motor Current, Motor Voltage.
ALTITUDE - Encoders 1 and 2, Motor Currents 1 and 2, Motor Voltages 1 and 2.
AZIMUTH - Encoders 1 and 2, Motor Currents 1 and 2, Motor Voltages 1 and 2.
CURRENTS - Altoitude Motor Current 1, Azimuth Motor Current 2, Rotator Motor Current.

3. Additions to the 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 MIG Channels

Name	Description	Type	Units	Scan Rate
tpm_MIG1	MIG: M1 Axial A	AnalogIn	Inches	5Hz
tpm_MIG2	MIG: M1 Axial B	AnalogIn	Inches	5Hz
tpm_MIG3	MIG: M1 Axial C	AnalogfIn	Inches	5Hz
tpm_MIG4	MIG: M2 Axial A	AnalogIn	Inches	5Hz
tpm_MIG5	MIG: M1 Lateral E (East)	AnalogIn	Inches	5Hz
tpm_MIG6	MIG: M1 Lateral F (West)	AnalogIn	Inches	5Hz
tpm_MIG7	MIG: M2 Axial B	AnalogIn	Inches	5Hz
tpm_MIG8	MIG: M2 Axial C	AnalogIn	Inches	5Hz

3.2 TCC PVT Triplets

Name	Description	Type	Units	Scan Rate
tpm_ALTCCPOS	TCC Alt Position	LongIn	Counts	5Hz
tpm_ALTCCVEL	TCC Alt Velocity	LongIn	Counts/Sec	5Hz
tpm_ALTCCTIM	TCC Alt Time	LongIn	Milliseconds	5Hz
tpm_AZTCCPOS	TCC Az Position	LongIn	Counts	5Hz
tpm_AZTCCVEL	TCC Az Velocity	LongIn	Counts/Sec	5Hz
tpm_AZTCCTIM	TCC Az Time	LongIn	Milliseconds	5Hz
tpm_ROTCCPOS	TCC Rotator Position	LongIn	Counts	5Hz
tpm_ROTCCVEL	TCC Rotator Velocity	LongIn	Counts/Sec	5Hz
tpm_ROTCCTIM	TCC Rotator Time	LongIn	Milliseconds	5Hz

3.3 MCP PVT Triplets

Name	Description	Type	Units	Scan Rate
tpm_ALMCPPOS	MCP Alt Position	LongIn	Counts	5Hz
tpm_ALMCPVEL	MCP Alt Velocity	LongIn	Counts/Sec	5Hz
tpm_ALMCPTIM	MCP Alt Time	LongIn	Milliseconds	5Hz
tpm_AZMCPPOS	MCP Az Position	LongIn	Counts	5Hz
tpm_AZMCPVEL	MCP Az Velocity	LongIn	Counts/Sec	5Hz
tpm_AZMCPTIM	MCP Az Time	LongIn	Milliseconds	5Hz
tpm_ROMCPPOS	MCP Rotator Position	LongIn	Counts	5Hz
tpm_ROMCPVEL	MCP Rotator Velocity	LongIn	Counts/Sec	5Hz
tpm_ROMCPTIM	MCP Rotator Time	LongIn	Milliseconds	5Hz

3.4 Tracking Checks

The Calculation record fields used for the tracking checks are:

INPA - Link to Axis Velocity (from MCP PVT Triplet)
B - Maximum Tracking Velocity (user input)
INPC - Link to Axis Servo Error (computed)
D - Maximum Servo Error (user input)
CALC - (ABS(A)<B)&(ABS(C)>D)

Name	Description	Type	Units	Scan Rate
tpm_altok	Altitude Tracking Check	Calculation	0=OK/1=Not OK	5Hz
tpm_azok	Azimuth Tracking Check	Calculation	0=OK/1=Not OK	5Hz
tpm_rotok	Rotator Tracking Check	Calculation	0=OK/1=Not OK	5Hz