Model Single Board Computer 75SBC4

The 75SBC4 is a single slot 3U cPCI low-power and high-performance Single Board Computer (SBC) with dual high speed/performance function module slots for configurable multi-function I/O interface expansion. Powered by the Freescale 1.2 GHz QorIQ P2041 Power Architecture® processor, the 75SBC4 offers an extremely low power, cost-conscious SBC solution for today’s demanding, space constrained and resource-limited embedded systems.

Two I/O module slots enable integrators to mix-n-match a variety of I/O and communication functions. This unique, COTS configurable design offers a broad assortment of signal interfaces, including Digital I/O (Discrete, Differential, TTL/CMOS); Analog I/O (A/D, D/A, RTD, Strain Gage); Motion Control and Sensor Interfaces (Synchro/Resolver/LVDT/RVDT Measurement and Simulation, Encoder/Counter) and Communications Interfaces (Serial RS-232/422/423/485, CANBus, MIL-STD-1553 and ARINC 429/575). The 75SBC4 SBC configured with up to two modules allows systems integrators to confidently manage, monitor and process a host of sensor interfacing requirements with NAI’s flexible, leading-edge, fully programmable and continuous background built-in-test (BIT) enabled I/O modules.

North Atlantic Industries (NAI) announces the availability of its latest 3U
rugged VPX power product — the VPX55-3, ideally suited for harsh land, air and sea applications. The VPX55-3
provides up to 300 watts of power with six outputs and is compliant with MIL-STD-704F. Other features include
an option for MIL-STD-1275B transients for operation during +6Vdc cranking conditions and reverse polarity
protection, and a built-in EMI Filter compliant with MIL-STD-461, CE-102— all within a single slot 0.8 pitch,
3U package. The VPX55-3 is designed to meet standard 3U VPX mechanical requirements and has VITA 62
compatible outputs and signaling.
“The VPX55-3 gives our customers the added capability of meeting stringent power requirements in a compact,
rugged COTS package,” said Lino Massafra VP Sales and Marketing. “Many of today’s military systems rely
heavily on power supplies that can support OpenVPX requirements and withstand MIL-STD-704 and
MIL-STD-1275 low and high voltage transients. The VPX55-3 is the first in a complete line of VPX power
converters that supports some of today’s most demanding system power requirements.”

• Ideal for Rugged, 3U VPX Power Applications
• Standard VPX Outputs
• True Single Slot, (0.8″) Plug-In Design
• Utilizes VPX Compatible Connector and I/O per VITA 62
• Integrated EMI Filter per MIL-STD-461F
• Transient Protection per MIL-STD-704F (Standard)
• Transient Protection per Mil-Std-1275B w/ Reverse Polarity protection (optional)
• Ouput Power 300W
• Remote Error Sensing
• Compatible with System Management Bus per VITA 46.11
• Current Share
• BIT
• Short Circuit Protection
• OverVoltage Protection

• Contact ACAL Technology for further information: Quote:GLETBLOG
• Tel : +44 (0) 1189 788878   Fax : +44 (0) 1189 776095   Email : acal@acaltechnology.co.uk

All About Synchros, Resolvers, and Data Acquisition

Converting angular rotation to an electrical signal is the job of an AC transducer. Types of transducers include synchros, resolvers, and linear/rotary variable differential transformers (LVDTs/RVDTs). They can be used in a variety of applications, such as an inertial navigation reference unit (gyro or compass), an automatic direction finder (ADF), an omnirange system, distance measurement equipment, cockpit indicators, and landing-gear positioning and control.

Synchros have been used in a variety of military and commercial systems for many years. Traditionally, they have been the transducer of choice where reliability is important and difficult environment conditions exist. The simplicity of their connection and today’s synchro-to-digital and digital-to-synchro converter boards make the synchro a very attractive component.

In an ADF, for example, the resolver or synchro is used to drive an indicator. As the aircraft turns, the amount of coupling in the transducer changes proportionally. But how do synchros and resolvers work, and what techniques must be used to ensure they produce accurate results?

Theory of Operation

Synchros and resolvers, World War II-era technology, still are widely used in modern-day electronic motion-control applications. Essentially, they are transformers. Just like a traditional transformer, they have a primary winding and multiple secondary windings. And just like a transformer, their primary is driven by an AC signal.

Synchros and resolvers are very similar; however, there are some differences. As shown in Figure 1, a synchro has one primary winding and three secondary windings, with each secondary winding mechanically oriented 120º apart. In contrast, as shown in Figure 2, a resolver has two primary windings and two secondary windings oriented at 90º to each other.

While a synchro and a resolver are electrically very similar to a transformer, they are mechanically more like a motor. The primary winding in a synchro or a resolver can be physically rotated with respect to the secondary windings. For this reason, the primary winding is called the rotor. The secondary windings, which are fixed, are called stators.

Synchros are often used to track the rotary output angle of a closed-loop system, which uses feedback to achieve accuracy and repeatability. A synchro can be turned continuously and, since its secondary winding outputs are analog signals, provide infinite resolution output.

As the shaft of a synchro turns, the angular position of its rotor winding changes with respect to its secondary (stator) windings. The relative amplitude of the resulting AC output signals from the secondary windings indicates the rotary position of the synchro’s shaft.

A synchro is excited by an AC reference voltage applied to its rotor winding. Typically, this reference signal is 115 Vrms @ 60 Hz or 400 Hz or 26 Vrms @ 400 Hz.

Synchro-to-Digital Conversion

Synchros generate analog output signals, and those outputs typically must be converted to digital form. This can be accomplished by using a synchro-to-digital converter.

It might seem logical to use a set of conventional analog-to-digital converters to simultaneously sample the AC voltages on the outputs of a synchro. Then, the relative magnitudes of these samples could be used to determine the rotary position of the synchro’s shaft at the time the samples where taken.

However, this does not work well for several reasons:

Synchros have inductive characteristics that must be taken into account.

Synchro output signals can be heavily distorted due to nonlinearities in the synchro and phase-shift of the transducer.

Synchro output signals often contain a lot of noise because of the environment they work in.

In addition, if the inputs and the outputs of a synchro are not galvanically isolated from each other and from signal ground, common-mode noise can dramatically affect the accuracy of conversion. Galvanic isolation implies magnetic, transformer-coupled isolation as opposed to resistive or solid-state isolation.

To avoid these problems, a synchro-to-digital converter must use transformer-isolated inputs and outputs. This significantly reduces the effects of common-mode noise and ground loops.

In terms of signal processing, tracking conversion (closed-loop) is more desirable than successive approximation or direct digitization because of system nonlinearities. Tracking conversion implies a servo mechanism for continuous tracking of the input. On the other hand, direct digitization, such as analog-to-digital (A/D) conversion, and successive approximation are suspect to instantaneous errors that may corrupt the output.

The major benefits of tracking conversion include an error-free output value that tracks the synchro’s angular position up to the maximum tracking speed. Another advantage is high noise immunity and quadrature rejection (the voltage component of an AC signal that is 90° out of phase with the reference and at the fundamental frequency).

A third benefit is the capability to provide tracking over a wide range of excitation frequencies (from 47 Hz to 20 kHz). The reference frequency impacts the overall system dynamic response: the higher the frequency, the higher the bandwidth.

Tracking converters can be classified into three types:

Type 0—with a finite position error even when the rotor is stationary.

Type I—with zero positional error when the rotor is stationary, but a finite positional lag error when the rotor is spinning at a constant angular velocity.

Type II—with zero positional error when the rotor is stationary and when it is spinning at a constant velocity.

Modern resolver-to-digital converters use Type II conversion methodology. It has the best tracking characteristics and minimizes velocity errors accumulating in the position data. As shown in Figure 3, a typical Type II tracking converter consists of the following elements:

An input isolation transformer.

A digital-to-analog converter that is used to multiply the analog SIN input by a digitally generated COS function and the analog COS input by a digitally generated SIN function.

A summing amplifier which still contains harmonics and quadrature at its output.

A phase-sensitive synchronous demodulator to clean the error voltage.

An integrator so there is no lag error associated with the rotor revolving at a constant angular velocity.

A voltage-controlled oscillator to generate a constant frequency to track the input.

An up-down counter with function generator ROMs on its output to evaluate polarity to count up for forward rotation and down for backward rotation.

A phase shifter and reference squarer that drive the demodulator.

This methodology is similar to that used by a phase-locked loop, which generates a local frequency and then adjusts that frequency to track the frequency of an input signal. As such, the Type II converter is a self-contained servo-mechanism for data acquisition and conversion, uniquely tailored to the properties of the input signals.

LVDTs and RVDTs

LVDTs and RVDTs are electromagnetic displacement transducers designed to provide output voltages proportional to linear and rotary displacement, respectively. These transducers consist of a primary winding, two secondary windings, and a movable armature made of a soft ferromagnetic material, as illustrated in Figure 4.

This transducer type would be typical of flight-surface measurement, such as flaps, slats, rudder, and aileron, or landing-gear positioning and control. As differential or ratiometric devices, they are particularly insensitive to common-mode noise and temperature effects, making them ideal for use in harsh environments.

Like synchros, LVDTs have front-end configuration and inductive characteristics that must be considered. The output signals can be heavily distorted because of nonlinearities and phase-shift in the transducer. And, output signals often contain a lot of noise because of the environment they work in.

Like synchros, if the inputs and the outputs of an LVDT are not galvanically isolated from each other and from signal ground, common-mode noise can dramatically affect the accuracy of conversion. Multichannel implementations are typical, and hardware is tailored to meet voltage and frequency requirements. Such instruments are essential tools to the measurement, control, simulation, and test of motion electronics.

Testing and Troubleshooting

Synchro and LVDT signals require specialized test equipment for accurate measurement and calibration. Many parameters must be considered since all of these invariably will affect the performance and integrity of the system as a whole. The list includes accuracy, phase shift and quadrature effects, resolution, dynamic characteristics, and distortion and noise.

Accuracy of the synchro/resolver signals are most easily verified using an angle position indicator (API). These instruments can read the synchro signal directly in degrees. APIs automatically compensate for phase shift, noise, and distortion. Due to their transformer-coupled inputs, common-mode effects are minimized.

For calibration-grade accuracy up to 2 arc seconds, a synchro/resolver bridge and phase angle voltmeter (PAV) are required. The PAV also measures phase shift and total rms and fundamental, quadrature, and in-phase voltages. It is designed to measure these parameters accurately in the presence of highly distorted and noisy signals.

To accurately simulate a synchro/resolver signal or to drive a synchro/resolver, a synchro/resolver standard is required. It is important to understand the load requirements of the unit-under-test and to make sure that these fall within the output drive capability and rated accuracy of the simulator.

These simulators are designed to generate signals with enough resolution, speed, and drive capability to dynamically and statically test most common devices that accept three (synchro) or four (resolver) wire inputs. Typically, accuracy will be 2 arc seconds and traceable to the National Institute of Standards and Testing (NIST).

Conclusion

Synchros, resolvers, and LVDT/RVDTs are important and reliable elements of avionics systems. The operation and interface of these transducers enable navigation and flight-surface control feedback. Consequently, the operational characteristics, typical failure mechanisms, and available equipment for measurement, control, simulation, and test of these transducer types are important elements to the design of aircraft systems, flight simulators, and ATE. Transformer isolation of input signals and tracking conversion techniques are essential to the accurate handling of data acquisition and signal processing.

References

1. Johnson, M. and Salz, K., “Synchros and Resolvers, Motion Electronics in Avionics,” Avionics Test Equipment Handbook and Directory, ISBN1-885544-09-X, 1998, pp. 1-19 to 1-24.

2. Salz, K., “How Synchros and Resolvers Work, and How You Can Use Them to Build High-Performance Motion Control Systems,” VMEbus Systems, February 1998/1.

About the Author

Michael W. Johnson is a regional sales manager at North Atlantic Instruments. He has written several articles on topics including motion control, electronics, and chemical processing. Mr. Johnson holds a B.S. in engineering chemistry and an M.A. in electrical engineering and industrial management from the State University of New York at Stony Brook. North Atlantic Instruments, 170 Wilbur Place, Bohemia, NY 11716, (516) 218-1233.

• Contact ACAL Technology for further information: Quote:GLETBLOG
• Tel : +44 (0) 1189 788878      Email: acal@acaltechnology.co.uk

Model VME 64E3

The 64E3 is a single slot, 6U VME, low-power/high-performance, high-density, multi-function I/O board. Five I/O module slots enable integrators to mix and match a variety of I/O and communication functions.

The 64E3 supports an extended module slot that can be populated from a selection of especially high-density I/O, a 12-port unmanaged Gigabit Ethernet switch, high-speed, full hand-shaking modem control, serial communications or a 48-channel, fully programmable discrete module. Configured with up to five modules system integrators can confidently manage, monitor and control a host of sensor interfacing requirements using NAI’s flexible, leading-edge, fully programmable and continuous background built-in-test (BIT) enabled function modules.

Model DC/DC 44LS1

The NAI 44LS1 is a +28VDC IN power line conditioner with holdup capability. The 44LS1 protects downstream DC-DC converters Mil-Std 704 and Mil-Std 1275 transients, low voltage conditions and power interruptions; providing up to 50 milliseconds of holdup time (at full power). The 44LS1 is designed to meet standard 3U cPCI mechanical requirements and is a perfect companion unit for all NAI DC/DC converters.

Power Supply Reference Guide

Power Supply Configuration Wizard

Bohemia NY, September 28, 2011– North Atlantic Industries (NAI) has announced the availability of a rugged 12-port Gigabit Ethernet Switch Module. The H2 is an extremely low power, high performance Ethernet switch. It supports 16 KB jumbo frames, 802.1P QoS or DiffServ/ToS priority queues, 802.1Q VLAN, Port Aggregation, Spanning Tree, Rapid & Multiple Spanning Tree, NAT, Port Forwarding, DNS, DHCP, and Firewalling. The module can be mounted on a 3U cPCI or 6U VME rugged board. When mounted on a 6U VME board, single board computer and/or additional I/O functions can be added to support system level requirements for processing and sensor interfacing.
The H2 implements standard Ethernet switching functions via Broadcom® technology and features:

 6.6 W (12 x Gig-E ports active) at 85°C
 IPv4 and IPv6 traffic class support
 Automatic learning and aging tags
 True non-blocking Gig-E integrated switch fabric w/4Mb packet buffer memory (for L2 functionality)
 High performance look-up engine with support for up to 8K unicast MAC addresses

“The H2 module switch enables system integrators to link Ethernet-based communications, control systems and sensor data across a broad range of application-ready subsystems,” said Lino Massafra VP Sales and Marketing. “Customers looking forward to the next generation of Unmanned Aircraft Systems (UAS) and other autonomous robotic systems will take advantage of the high channel density and extremely low power features our H2 has to offer.”
In addition, based on NAI’s COTS, multi-function, high-density I/O and processor platforms (i.e. 75D3, 64DP3, 64E3), multi-board systems can be configured combining the H2 multi-port Gig-E switch capability with application specific processing and I/O.
North Atlantic Industries (NAI) is a leading independent supplier of Embedded I/O Boards, Single Board Computers, Rugged Power Supplies, Embedded Systems, Motion Simulation and Measurement Instruments for the Military, Aerospace and Industrial Industries. NAI provides the highest quality COTS and modified COTS products in Commercial, Extended Temperature and Rugged versions. Information about NAI and its products can be found at www.naii.com.

Gigabit Ethernet Switch Module