DFM Engineering, Inc.
1035 Delaware Ave. Unit D
Longmont, CO 80501
Phone: 303-678-8143
Fax: 303-772-9411
 
 
 

DFM Engineering
Delivers a Gimbal to the
US Department of Energy Laboratory

 
 

Gimbal Configurations Summary

Model GIM-1-120 Features

In September 2004, DFM Engineering was awarded a contract to provide a gimbal to a laboratory of the US Department of Energy.

The gimbal will support instruments developed by the laboratory for performing various field measurements.

The gimbal is an Altitude over Azimuth (Alt-Az) computer driven two axes mount and provides an instrument mounting plate with standard optical table bolt patterns.

One of the primary concerns of the customer was ease of use and programming.

While the gimbal control system is very similar to those used by DFM Engineering LIDAR scanners, a users interface and command program was provided which communicates with the gimbal control software.

The source code for the user interface command program allows the customer to easily write their own command program incorporating any special features they need.

The command program may be used to perform powerful motions including a user defined raster scan.

 

The word 'Gimbal' is fairly generic and can refer to any configuration of a support that moves in typically two axes. The most common configuration is an altitude over azimuth system where the azimuth axis is attached to the earth (or fixed reference plane).

Gimbal Configurations Summary

  • Alt-Az:
    This configuration consists of a structure where the azimuth axis is attached to the fixed reference point and the altitude (or elevation) axis is attached to the rotating part of the azimuth structure.

    One rotation is about a vertical line (an azimuth rotation) and the second motion is about a horizontal line (the elevation rotation).

    This configuration is used for surveying, landscape camera mounts, gun mounts, and is the typical way a person uses their eyes to look at terrestrial scenes.

  • Alt-Alt:
    This configuration consists of a structure that rotates about a horizontal axis sometimes called the "X" or "Major" axis and, attached to the major axis, is another rotation stage whose axis of rotation is perpendicular to the major axis.

    This axis is sometimes called the "Y" axis or "Minor" axis. Usually the axes are located North-South (for the major axis) and East-West (for the minor axis), but the azimuth alignment can be at any position. Rotation in either axis moves the payload in an up-down motion.

    The typical use for the Alt-Alt configuration is for tracking artificial satellites.

  • Equatorial:
    This configuration is a special alignment case of the previous gimbals where the major (or azimuth) axis is inclined at an angle from the horizontal equal to the site latitude and the azimuth alignment is true North.

    This configuration places the major axis of rotation parallel to the rotation axis of the earth.

    The typical use for the equatorial configuration is for astronomical telescopes because a simple rotation about the "major" axis (called the "polar" axis) counteracts the earth's rotation.

Examining the three configurations leads to the conclusion that they are really the same. Only the orientation of the gimbal referred to the fixed mounting surface (typically the earth's surface) is different.

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DFM Engineering, Inc. designed and manufactured the Model GIM-1-120 for the Department of Energy Laboratory. The table below describes the DFM standard gimbal features and includes the specific features requested by the Department of Energy.

Model GIM-1-120 Toothed Belt Drive Alt-Az Gimbal Features

1.

Altitude over Azimuth configuration

2.

Payload of 120 Lbf. (balanced about the altitude axis)

3.

Payload mounting surface is 18-inches by 24-inches and has †-20 tapped holes on 1-inch x 1-inch centers (same as standard optical tables)

4.

Payload components may be attached to either side of mounting plate

5.

Azimuth Field Of Regard (FOR) +/- 180 degrees-only limited by gimbal and payload cables; Software limit switch set for +/- 180 degrees

6.

Altitude Field Of Regard (FOR) +/- 180 degrees- only limited by payload cables and payload envelope; Typically software limited to -15 to +90 degrees

7.

Slew rate of 10 degrees per second

8.

Tracking rates variable from 0 to slew speed with a velocity resolution of 0.001 degrees per second

9.

Acceleration in both axes of 10 degrees per second squared

10.

Positional Resolution 1 arc second optional

11.

Position Accuracy +/- 0.03 degrees per axis

12.

Position repeatability +/- 0.005 degrees per axis

13.

Torque limited D.C. servo motor driven with high accuracy gear reduction stages

14.

Hybrid digital/analog servo controllers with zero position error integrators

15.

On axis position encoders

16.

Industrial Rack Mount PC controller with position and status display

17.

Keyboard to input commands

18.

Three speed hand paddle (slow, intermediate, and slew speeds) for manual operation from hand paddle

19.

Serial Port (RS-232) interface to allow commands from an external computer

20.

An extensive set of external commands for control by a customer furnished computer

21.

Ethernet interface to allow commands from an external computer

22.

Software and hardware position travel limit switches

23.

Built-in software to perform coordinate and modified raster scans

24.

Sample operations and external command software with source code

25.

Hardware position information latch (from TTL pulse) to accurately time tag position data

26.

Interlock input which may be used for cable take up limit

27.

All wiring uses multiple conductor cables for maximum reliability with gold plated 1-turn connectors

28.

Low power consumption (150 watts average, 350 watts peak)

29.

Altitude and azimuth lock pins to prevent rotation when un-powered

30.

Gimbal environmental temperature-full operation over -10 to + 50 degrees C

31.

Full dust tight covers on drives for outside operation

32.

Reinforced vinyl cover with tie downs

33.

Installation drawing provided

34.

Maintenance and operations manual provided

35.

Gimbal weight of 170 lbf. (unloaded)

36.

Fully operational when cables are plugged in and payload mounted from the keyboard or from the hand paddle

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For more information or examples of the configurations, please visit these pages or contact us with your specific optical system requirements.

• Gimbals

• Siderostats and Coeleostats

• Optical Systems

• Lidar Components