VG700M Series User’s Manual Models… VG700MB-200 VG700MB-206 VG700MC-206 VG700MC-208 Moog Crossbow, 1421 McCarthy Blvd., Milpitas, CA 95035 Tel: 408-965-3300, Fax: 408-324-4840 email: info@xbow.com, website: www.xbow.
©2003-2011 Moog Crossbow. All rights reserved. Information in this document is subject to change without notice. Moog Crossbow and SoftSensor are registered trademarks and DMU is a trademark of Moog Crossbow. Other product and trade names are trademarks or registered trademarks of their respective holders.
VG700M User’s Manual Table of Contents 1 Introduction ...............................................................................1 1.1 1.2 2 Quick Start.................................................................................3 2.1 2.1.1 2.1.2 2.2 2.3 2.4 3 3.4.1 3.4.2 3.4.3 3.5 3.5.1 3.6 3.7 3.8 3.9 GyroView Computer Requirements..................................................3 Install GyroView ..............................................................................
VG700M User’s Manual 5.1 6 VG700M Outline Drawing.......................................................... 23 Appendix B. DMU Output Quick Reference ........................24 6.1 Digital Output Conversion .......................................................... 24 7 Appendix C. DMU Command Quick Reference ..................25 8 Appendix D. Troubleshooting Tips........................................26 9 Appendix E. Warranty and Support Information ...............28 9.1 9.2 9.3 9.3.1 9.3.2 9.3.
VG700M User’s Manual About this Manual The following annotations have been used to provide additional information. ; NOTE Note provides additional information about the topic. ; EXAMPLE Examples are given throughout the manual to help the reader understand the terminology. 3 IMPORTANT This symbol defines items that have significant meaning to the user 0 WARNING The user should pay particular attention to this symbol.
VG700M User’s Manual 1 Introduction 1.1 The DMU™ Series Motion and Attitude Sensing Units This manual explains the use of the VG700M Series of products. The VG700M is a six-axis dynamic measurement unit (DMU) designed to measure linear acceleration along three orthogonal axes and rotation rates around three orthogonal axes. It uses three accelerometers and three angular rate sensors to make a complete measurement of the dynamics of your system.
VG700M User’s Manual 1.2 Package Contents In addition to your DMU sensor product you should have: • 1 CD with GyroView Software GyroView (version 2.5 or greater) will allow you to immediately view the outputs of the DMU on a PC running Microsoft® Windows™. You can also download this software from Crossbow’s web site at http://www.xbow.com. • 1 Digital Signal Cable. This links the VG700M directly to a serial port via RS422 to RS232 converter. Only the transmit, receive, power, and ground channels are used.
VG700M User’s Manual 2 Quick Start 2.1 GyroView Software Crossbow includes GyroView software to allow you to use the DMU right out of the box and the evaluation is straightforward. Install the GyroView software, connect the DMU to your serial port, apply power to your unit and start taking measurements. 2.1.
VG700M User’s Manual 2.3 Setup GyroView With the DMU connected to your PC serial port and powered, open the GyroView software. 1. GyroView should automatically detect the DMU and display the serial number and firmware version if it is connected. 2. If GyroView does not connect, check that you have the correct COM port selected. You find this under the “DMU” menu. 3. Select the type of display you want under the menu item “Windows”.
VG700M User’s Manual 3 DMU Details 3.1 DMU Coordinate System The DMU will have a label on one face illustrating the DMU coordinate system. With the connector facing you, and the mounting plate down, the axes are defined as: X-axis – from face with connector through the DMU. Y-axis – along the face with connector from left to right. Z-axis – along the face with the connector from top to bottom. The axes form an orthogonal right-handed coordinate system.
VG700M User’s Manual Table 1.
VG700M User’s Manual The VG700M serial interface connection is standard RS-422. Power is applied to the DMU on pins 4 and 5. Pin 4 is ground; Pin 5 should have 1632 VDC unregulated at 0.5 A. If you are using the cable supplied with the DMU, the power supply wires are broken out of the cable at the DB-9 connector. The red wire is connected to the power supply output; the black wire is connected to the power supply ground. DO NOT REVERSE THE POWER LEADS. 3.
VG700M User’s Manual To convert the acceleration data into G’s, use the following conversion: accel = data*(GR * 1.5)/(215-1) where accel is the actual measured acceleration in G’s, data is the digital data sent by the DMU, and GR is the G Range for your DMU. (The data is scaled so that1 G = 9.80 m s-2.) The G range of your DMU is the range of accelerations your DMU will measure. For example, if your DMU uses a ±4 G accelerometer, then the G range is 4.
VG700M User’s Manual the erection rate should always be greater than the drift rate of the rate gyros. The erection rate is discussed in section 4.2 in more detail. The VG700M outputs the pitch, roll and relative heading in the digital data packet in angle mode.
VG700M User’s Manual Character(s) Sent c Response C Description Changes measurement type to Scaled Mode. DMU outputs measurements in scaled engineering units. Command Angle Mode Character(s) Sent a Response A Description Changes measurement type to Angle (VG) Mode. DMU calculates stabilized pitch and roll. Also outputs sensor measurements in scaled engineering units. Command Polled Mode Character(s) Sent P Response none Description Changes data output mode to Polled Mode.
VG700M User’s Manual Description "G" requests a single data packet. DMU will respond with a data packet. The format of the data packet will change with the measurement mode (Raw, Scaled, or Angle). Sending the DMU a "G" while it is in Continuous Mode will place the DMU in Polled Mode. Command Set Erection Rate Character(s) Sent T Response none Description The T command sets the vertical gyro erection rate.
VG700M User’s Manual Description This queries the DMU firmware and will tell you the DMU type and firmware version. The response is an ASCII string. The exact string will vary according to the DMU type and version. Command Query Serial Number Character(s) Sent S Response Serial number packet Description This queries the DMU for its serial number. The DMU will respond with a serial number data packet that consists of a header byte (FF), the serial number in 4 bytes, and a checksum byte.
VG700M User’s Manual Table 2 Bit Message Definition (VG700MB-206 Only) BIT Data Description Bit Location Accelerometer Failure Gyro Zeroing Validity Gyro Zeroing Process Algorithm Validity Status Accelerometer outputs are incorrect Bit 2 Gyro Zeroing invalid Bit 4 Gyro Zeroing in process Bit 5 Not valid Bits 6,7: 00 Pitch and Roll outputs computed using only accelerometers Not used Bits 6,7: 10 Full accuracy data using gyros and accelerometers Bits 6,7: 11 Bits 6,7: 01 Notes: 1) The Algori
VG700M User’s Manual 3.6 Data Packet Format In general, the digital data representing each measurement is sent as a 16-bit number (two bytes). The data is sent MSB first then LSB. In voltage mode, the data is sent as unsigned integers to represent the range 0 – 5 V. In scaled and angle mode, the data generally represents a quantity that can be positive or negative. These numbers are sent as a 16-bit signed integer in 2's complement format. The data is sent as two bytes, MSB first then LSB.
VG700M User’s Manual Table 3.
VG700M User’s Manual Table 4.
VG700M User’s Manual 3.7 Timing In some applications, using the DMU’s digital output requires a precise understanding of the internal timing of the device. The processor internal to the DMU runs in a loop - collecting data from the sensors, processing the data, then collecting more data. The data is reported to the user through a parallel process. In continuous mode, the system processor activity is repeatable and accurate timing information can be derived based purely on the overall loop rate.
VG700M User’s Manual 3.9 Adaptive-T Algorithm (installed at Crossbow factory) There is no one optimal erection rate for all environments. A high erection rate is better when you are closer to a static situation, and a low erection rate is better when you are in a dynamic situation. Crossbow has developed an algorithm to automatically switch the erection rate (the T parameter) based on the dynamics measured by the DMU. This algorithm is referred to as adaptive-T and is implemented as default at the factory.
VG700M User’s Manual 4 DMU Operating Tips 4.1 The “Zero” Command The “z” command is used to zero the angular rate sensor biases. This command does not “zero” the angle output! This should be an essential part of your strategy in using the DMU effectively. Stabilized pitch and roll angles are calculated by integrating the output of the angular rate sensors. Rate sensors are subject to small offsets in the angular rate measurement.
VG700M User’s Manual drift rate of the rate gyros, or the calculated angles will drift off with increasing error. If the erection rate is too high, however, the calculated angles will be forced to follow the accelerometers too closely. This will lead to inaccuracies when the unit is under dynamic conditions. One way to start is to set the erection rate about twice as fast as the worst rate gyro drift rate. This is appropriate for a dynamic environment, when the unit will be under significant acceleration.
VG700M User’s Manual 4.3 Mounting the DMU The DMU should be mounted as close to the center of gravity (CG) of your system as possible. This will minimize any “lever effect”. If it is not mounted at the center of gravity, then rotations around the center of gravity will cause the DMU accelerometers to measure acceleration proportional to the product of the angular rate squared and the distance between the DMU and the CG. The DMU will measure rotations around the axes of its sensors.
VG700M User’s Manual 4.5 Advanced Strategies for Adjusting the Erection Rate The DMU attitude estimation algorithm is divided into two separate entities. Gyro angular rate information is integrated in time to propagate the DMU body attitude with respect to the tangent plane. If the initial attitude of the vehicle was known exactly and if the gyros provided perfect readings then this integration process would suffice.
VG700M User’s Manual 5 5.1 Appendix A. Mechanical Specifications Outline Drawing NOTE: The VG700MC-208 includes one (1) set of captive mounting fasteners and washers (not shown) Doc.# 7430-0280-01 Rev.
VG700M User’s Manual 6 Appendix B. DMU Output Quick Reference GR is the G-range of the accelerometers. For example, if your DMU has ±4 G accelerometers, GR = 4. RR is the rate range of the rate sensors. For example, if your DMU has ±200°/s rate sensors, RR = 200. 6.1 Digital Output Conversion Data is sent as 16-bit signed integer for all but Temperature. Temperature sensor data is sent as unsigned integer. Roll, Pitch, Relative Heading Acceleration (Angle Mode) Accel (G) = data * GR * 1.
VG700M User’s Manual 7 Appendix C. DMU Command Quick Reference Command (ASCII) Response Description R H Ping: Pings DMU to verify communications. r R Change to Voltage Mode. c C Change to Scaled Sensor Mode. a A Change to Angle Mode (VG Mode). P None Change to polled mode. Data packets sent when a G is received by the DMU. C None Change to continuous data transmit mode. Data packets streamed continuously. Packet rate is dependent on operating mode. Sending "G" stops data transmission.
VG700M User’s Manual 8 Appendix D. Troubleshooting Tips Is the supply voltage and connections okay? The VG700M needs at least a 16V power supply for proper operation. Verify that your power supply is regulated and not current limited. Ensure that the supply does not fall below 16V or go above 32V. Make sure that all the connections are intact.
VG700M User’s Manual Is the vibration isolation adequate? Large amounts of vibration will make the accelerometer readings noisy and thereby may affect the angle calculations. In addition, if the magnitude of the vibration exceeds the range of the accelerometer, the accelerometer output can saturate. This can cause errors in the accelerometer output and in turn the estimated angles.
VG700M User’s Manual 9 Appendix E. Warranty and Support Information 9.1 Customer Service As a Moog Crossbow customer you have access to product support services, which include: 9.
VG700M User’s Manual 9.3.2 Identification and Protection If the equipment is to be shipped to Crossbow for service or repair, please attach a tag TO THE EQUIPMENT, as well as the shipping container(s), identifying the owner. Also indicate the service or repair required, the problems encountered, and other information considered valuable to the service facility such as the list of information provided to request the RMA number.
Moog Crossbow 1421 McCarthy Blvd. Milpitas, CA 95035 Phone: 408.965.3300 Fax: 408.324.4840 Email: info@xbow.com Website: www.xbow.
