Creating Railway Laboratory Test Benches Based on NI LabVIEW, PXI, and CompactRIO

Eduardo Elizalde, CETEST S.L.

"We chose systems based on NI platforms to develop control software and data acquisition systems for our railway rolling stock integral laboratory."

- Eduardo Elizalde, CETEST S.L.

The Challenge:

Developing acquisition and control solutions for a railway rolling stock integral laboratory.

The Solution:

Using the NI LabVIEW Real-Time Module, the NI LabVIEW FPGA Module, and NI CompactRIO, NI Single-Board RIO, and NI PXI hardware to create a custom acquisition and control solution to meet our test requirements.

CETEST S.L. is a fully accredited independent test laboratory that offers services for design verification and homologation of systems and components. We focus on the railway rolling stock (vehicles and components) field, for which our company is recognized for throughout Europe. Due to the variety of test scenarios required by the sector, we develop, both internally and in collaboration with other companies, specific testing systems with advanced mechatronics solutions. Among other activities, we conduct structural integrity, fatigue resistance, performance, and durability tests on laboratory components. Additionally, we measure noise, vibration, and perform field dynamic behavior tests.


In recent years, our customers’ testing needs have increased along with the need for new test benches and new acquisition and control equipment. Due to the versatility of National Instruments products, we performed many of these updates using NI architectures.



Big Structure Test

We have a specific test bench for the structural integrity test of big structures. This bench can test structures up to 35 m long with different load combinations, simulating both exceptional and service loads. A pneumatic line used for applying vertical loads (values up to 100 tons) is managed with an interface based on LabVIEW (see Figure 1). The rest of the load hypotheses (different height compressions or traction) are applied by hydraulic actuators, up to 400 tons. These tests monitor displacement and load readings of 20 actuators, as well as all signals coming from the hydraulic and pneumatic system. With the aim of creating a versatile test bench, we defined different control loops. Therefore, the system can control actuators independently or combined, both in displacement and in load. Moreover, the user can manually control the test bench, if required.



Integrity and Fatigue-Resistance Test

To check the integrity and fatigue resistance of a structure, we use strain gages and displacement sensor measurements in different points of the structure, which requires a multichannel acquisition system. For this purpose, we customized two NI PXIe-8108 embedded controller acquisition systems by combining an NI PXIe-4330 simultaneous bridge input module with an NI PXI-6225 multifunction M Series module. When used independently, each system can contain up to 18 cards. Nevertheless, if more channels are needed, the user can implement communication between both systems. With the aim of adapting the system to test needs, we developed configuration, visualization, and acquisition software using the LabVIEW Real-Time and LabVIEW FPGA modules.




High-Static or Quasistatic Load Testing

The variety of tests under load conditions on other kinds of structures and components makes it impossible to establish a standard configuration. For cases with high-static or quasistatic loads, we have 700 bar hydraulic systems and actuators. We can control these both in load and displacement. To perform these applications, we programmed an NI cRIO-9076 real-time processor with an FPGA-based system to remotely control user-defined load sequences. Additionally, the system can measure, evaluate, and acquire signals from sensors.




Testing Rolling Stock Rotating Elements

To test specific rolling stock rotating elements (such as gearboxes and bearings), we developed acquisition and control systems based on NI products. Two examples include a test bench under variable rotation speed and torque for gearboxes in a four-square configuration and two functional performance tests for railway axleboxes. The aim of these test benches is to study different working order variables and temperatures, and grease and oil distribution.




Gearbox Test Bench With Load Application

In the gearbox test bench with load application, we can test gearboxes with up to 1 MW power by controlling a 350 kW engine. We can achieve speeds of up to 6,000 rpm and torque of up to 10 kN per m. Test bench control with the NI PXI-8102 embedded controller offers user-defined torque and speed cycles. Additionally, the system can measure, evaluate, and acquire signals coming from sensors (torque, speed, and temperature) and variator parameters.


Railway Bearing Axleboxes

With railway bearing axlebox test benches, we can create user-defined axial load and speed cycles. Additionally, the system can measure, evaluate, and acquire signals coming from sensors (load cells, speed, and temperature) and variator parameters. In this case, the control of one of the test benches is based on an NI cRIO-9022 embedded real-time controller and the other on an NI PXI-8102 embedded controller.


Rotational Resistance Static Characterization

As a final example of our capacities, we own a test bench for rotational resistance static characterization of the bogie-car body joint. This resistance measurement is a key issue for contrasting theoretical models as well as for curve circulation security analysis. The control, based on an NI sbRIO-9631 embedded control and acquisition device, manages a 210 bar hydraulic system, sets alarms, and limits and generates waveforms for the relative rotation speed control. Moreover, the system can acquire displacement and torque sensor signals.


We chose systems based on NI platforms to develop control software and data acquisition systems for our railway rolling stock integral laboratory. So far, we have used CompactRIOPXI, and NI Single-Board RIO programmed with LabVIEW Real-Time or LabVIEW FPGA. We also chose a multichannel acquisition system for acquiring both strain gages and high-level signals as an alternative to the usual acquisition systems used for structural tests.


Author Information:

Eduardo Elizalde

Figure 1. Big Structures Test Bench GUI
Figure 2. Multichannel Acquisition System Visualization Screen
Figure 3. Particular load Application Hydraulic System Control Screen
Figure 4. Railway Axle Boxes Performance Test Bench
Figure 5. Rotational Resistance Test Bench Schema