FPGA Technology Replaces Multiple In-Vehicle Test Systems

Automotive manufacturers test every single aspect of a car. Performing temperature testing on seat warmers, monitoring chassis vibration during harsh test runs, and measuring the G forces exuded on the passenger during crash tests are a few examples of different test procedures car manufacturers complete to ensure safe product deliveries to the consumer. Unfortunately, running numerous tests correlates to learning and using a variety of new test equipment. The National Instruments CompactRIO platform represents a huge leap forward for in-vehicle testing. NI CompactRIO is a rugged, high-performance system that incorporates an embedded field-programmable gate array (FPGA) so engineers can customize a single hardware platform to meet a variety of in-vehicle application challenges.

The Need for Custom Hardware and Multiple Test Systems
The different technical requirements of each in-vehicle application, such as sampling rates, signal conditioning, signal processing, signal analysis, and response times, have resulted in a variety of custom in-vehicle test systems. Sampling rates alone for in-vehicle applications represent a large range -- between 20 S/s for temperature logging and 200 kS/s for crash tests (see Figure 1).

Figure 1. Sampling rates alone for in-vehicle applications represent a large range -- between 20 S/s for temperature logging and 200 kS/s for crash tests.

FPGA technology makes it possible for CompactRIO to meet each of these in-vehicle application requirements, eliminating the need for custom hardware and multiple test systems. Engineers can use CompactRIO for low-speed, accurate temperature measurements and then reprogram the system in minutes to meet the performance and control needs of rapid prototyping. Additionally, they can perform low- and high-speed measurements within the same system to perform different tests in parallel. Before the introduction of CompactRIO, no single system could meet the requirements for all these applications.

A Look into the FPGA
An FPGA is a device that contains a matrix of reconfigurable gate array logic circuitry. When an engineer configures an FPGA, the internal circuitry is connected in a way that creates a hardware implementation of the software application. Unlike processors, FPGAs use dedicated hardware for processing logic and do not have an operating system. FPGA technology offers many advantages, including custom I/O timing and synchronization, 20 MHz control loop rates, the reliability of dedicated hardware, and digital signal processing and analysis.

Traditionally, engineers needed extensive knowledge of hardware design tools and languages such as VHDL to program FPGAs. The FPGA in CompactRIO is programmed with National Instruments LabVIEW graphical development tools so engineers can customize and reconfigure the FPGA within CompactRIO in a short amount of time. When the system functionality needs to change, developers simply download new NI LabVIEW code to the FPGA and change the personality of CompactRIO.

FPGA Flexibility and Performance for In-Vehicle I/O
CompactRIO provides a wide range of I/O modules for connecting to any in-vehicle sensor, actuator, and network. Engineers can completely customize the timing, synchronization, processing, and control rates of the I/O for each application.

I/O	Sensor and Signal Type	Module	Channels	Special Features
Temperature	Thermocouple	NI 9211	4	24-bit resolution, 15 S/s
	RTD	NI 9217	4	24-bit resolution, 100 S/s
Sound and vibration	IEPE sensors (accelerometer/microphone)	NI 9233	4	24-bit resolution, 50 kS/s per ch, simultaneous, IEPE conditioning, antialiasing
Strain	Bridge-based sensors (strain gages, load cells)	NI 9237	4	24-bit resolution, 50 kS/s per ch, simultaneous, full-/half-bridge
Voltage	±200 mV to ±10 V	NI 9205	32	16-bit resolution, 250 kS/s
	±60 V	NI 9221	8	12-bit resolution, 800 kS/s
Fuel cell	±200 mV to ±10 V	NI 9206	32	16-bit resolution, 250 kS/s, 600 V DC CAT I isolation
CAN communication	Two-port high-speed CAN interface	NI 9583	2	Two-port, high-speed CAN module

¹Coming Soon

Table 1. CompactRIO In-Vehicle I/O

Sampling Rate Flexibility
Because the FPGA is connected directly to each I/O module, engineers can customize the sampling rates of CompactRIO on a per-module basis. This provides unmatched timing flexibility for the system. Within a single CompactRIO system, engineers can acquire temperature measurements at 10 S/s while also monitoring vibration measurements at 50 kS/s. Engineers also can program different channels within the same I/O module for different rates by implementing decimation directly on the FPGA.

I/O Synchronization
One benefit of FPGA technology for in-vehicle data acquisition and testing is the ability to achieve deterministic hardware synchronization between any I/O module. For example, the NI 9853 CAN interface module and any analog or digital input module both can perform read actions to obtain simultaneous measurements with nanosecond resolution. With this synchronization, a test engineer can read values from a specific CAN device, such as an electronic control unit (ECU) or actuator, and compare it against data from a simultaneous analog or digital input.

40 MHz Decision Making
For control applications such as rapid prototyping, the custom hardware performance of the onboard FPGA facilitates closed-loop control at extremely fast rates. Using any of the I/O modules, engineers can program CompactRIO to respond to incoming CAN, analog, or digital data with decisions at rates up to 40 MHz. Traditionally these applications required the performance of costly custom hardware.

Sensor-Level Signal Processing and Analysis
The FPGA in CompactRIO acts as a parallel processing engine so engineers can perform advanced signal processing and analysis on any sensor signal. For instance, decoding tachometer signals is normally a processor-intensive task. Engineers can program the FPGA to decode a variety of sensor signals in hardware, allowing a networked CPU to take on other processing tasks. Additionally, engineers easily can implement advanced digital filters in FPGA hardware using the LabVIEW Digital Filter Design Toolkit.

Stand-Alone and Networked Operation
The CompactRIO controller contains an embedded real-time processor for intelligent, stand-alone operation; includes Ethernet and serial ports for connection to host computers and peripherals; and runs LabVIEW Real-Time software for deterministic control, data logging, and analysis. In addition, you can combine the Ethernet port with the included Web and file servers so operators easily can interface to the embedded program running on the controller. Because of its dual 9 to 35 V (6 to 35 V during operation) power supply inputs, engineers can power CompactRIO directly from a vehicle battery. The controller contains up to 512 MB of nonvolatile memory for in-vehicle data logging.

Figure 2. CompactRIO performs stand-alone or networked operation for in-vehicle applications.

Small, Rugged Package for Any In-Vehicle Environment
The mechanical design of CompactRIO creates a system that withstands the rigors of any in-vehicle testing environment, such as the dry heat of the Arizona proving grounds. CompactRIO maintains a small size, low power consumption, and a wide -40 to 70 ºC operating temperature range along with a variety of industrial certifications and ratings. A four-slot reconfigurable embedded system measures 179.6 by 88.1 by 88.1 mm (7.07 by 3.47 by 3.47 in.) and weighs just 1.58 kg (3.47 lb). An eight-slot system filled with 32-channel I/O modules delivers up to 256 I/O channels per system. The platform is rated for up to 50 g of shock and up to 2,300 V_rms isolation (withstand) and has international safety, EMC, and environmental certifications.

Create Customized In-Vehicle I/O
With the openness of the CompactRIO system, engineers quickly can develop custom modules to meet specific in-vehicle I/O needs. The CompactRIO module development kit provides license rights, design guidelines, and access to LabVIEW FPGA software tools for creating a custom module. Third-party companies have created custom modules for in-vehicle acquisition and control by adding the following capabilities to CompactRIO:

“LabVIEW and the reconfigurable I/O FPGA technology enabled quick development for our Gxxx mobile modules. The resulting system offers a level of reliability that would not have been possible without the CompactRIO architecture. Now customers can easily create remotely operated and supervised mobile systems with wireless communication, timing, and global positioning capabilities.”
- Wolfram Koerver, CEO, S.E.A. Datentechnik GmbH


With an embedded FPGA and a common programming environment, engineers can use CompactRIO and LabVIEW to create any in-vehicle test, control, and design application. The high speed and synchronization capabilities of the FPGA, combined with a rugged form factor and a wide range of I/O modules, make CompactRIO the ideal platform for any in-vehicle application.

Joel Shapiro
Product Marketing Manager, Industrial Communications
joel.shapiro@ni.com

Todd Dobberstein
Product Marketing Manager, CompactRIO
todd.dobberstein@ni.com

This article first ran in the December 20, 2005, issue of NI News.

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