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Dewesoft now interfaces to MTS Flextest Test Bench
Dewesoft now offers easy interface to MTS Flextest durability test bench saving time, costs and reducing chance of an error
Manufacturers in automotive and aerospace industry typically use different instrumentation for in-vehicle and test bench testing. However, thanks to DEWESoft combining two data buses (USB and EtherCAT®) and MTS implementing the EtherCAT® communication on the MTS FlexTest® series controllers, the DEWESoft R8rt instrument can now cover all of the following:
- High channel count test bench data acquisition,
- Real-time signal processing for load analysis feedback (over EtherCAT®)and
- Compact size high performance data logger for in-vehicle use.
Figure 1 – DEWESoft R8rt with up to 8 SIRIUS amplifier slices can easily be taken out of the cabinet and used as an in-vehicle data logger
ABOUT DEWESOFT EQUIPMENT
DEWESoft SIRIUS slices have already been used in many signal conditioning applications for test bench instrumentation, but only as a preamplifier with analogue output of +/-10 V which is used as an input to the controller analogue input stage.
The secondary input stage can now be removed thanks to direct conversion of analogue data to EtherCAT® bus inside the SIRIUS instruments. This significantly improves the user experience due to:
- Lower cost, since there is no need for the additional controller analogue inputs,
- 2-in-1 instrument, since the R8rt can also be used as an in-vehicle data logger,
- Simpler hardware setup due to less cabling (a single cable from the controller to the R8 rt),
- Easy and fast amplifier setup in DEWESoft X software,
- High-speed (200 kS/s) and high-resolution (160 dB dynamic range) data acquisition with the same instrument that is used for the test bench load analysis feedback.
DEWESoft SIRIUS R8rt combines 8 SIRIUS slices (and the SBOX industrial PC) into a compact package featuring:
- up to 64 Dual Core ADC channels with 160 dB dynamic range or
- up to 128 channels in single-ADC (24 bit) configuration.
With DEWESoft X software running on the high performance SBOX PC (Intel i7 CPU, up to 1 TB SSD drive, integrated 100 Hz GPS ), it can be used as an all-around data logger for in-vehicle use or a test bench data acquisition device. With the latest addition of EtherCAT®backplane, the SIRIUS slices also behave as EtherCAT® slaves in parallel to the standard operation in USB mode.
EtherCAT® protocol as a standardised technology enables hardware combinations from different vendors in the overall solution for the customer. But if the user is to run the test bench and also acquire data to DEWESoft X software, the data from the SIRIUS slices needs to be collected by two master systems: the MTS FlexTest (EtherCAT®master) and DEWESoft X on the SBOX. Therefore, additional data bus (USB) is needed besides EtherCAT® to transfer the data at high rate to DEWESoft X. This is achieved in the following way:
- AD converters on the SIRIUS slices run with the rate set in DEWESoft Channel Setup
- SIRIUS firmware copies the sampled data from ADC in real-time to two locations: a buffer for USB transfer and a separate buffer for EtherCAT®
- The EtherCAT®buffer only holds one sample per channel and is constantly updated with the latest values. EtherCAT® master can collect the most recent data at any time.
The exact moment when the EtherCAT® buffer is latched and the data copied to the EtherCAT® bus is controlled by the EtherCAT master, see Figure 2. In this case, the time between those samples copied to EtherCAT® bus depends on the EtherCAT® master jitter which can be up to 100 ps.
Figure 2 – Dual mode clocking diagram (SM sync)
Firstly, the overall system schematic is shown in main picture. Secondly, Test rig actuator control is done with the analogue signals connected straight to the MTS FlexTest. Thirdly, the rest of the input channels that are used for load analysis feedback on the specimen. RPC analysis is acquired by the R8rt, stored on the SBOX and available in real-time to the EtherCAT® bus.
Load cells and accelerometers are typically used to measure the response of the specimen. The setup of the amplifiers is done in DEWESoft Channel Setup,
see Figure 3. The EtherCAT® Network Information (ENI) file is required by MTS HWI File Editor. To be able to add EtherCAT® slaves to the hardware configuration (Figure 4). The ENI file is exported from DEWESoft Channel Setup and copied to the appropriate directory to be accessible by MTS software.
Due to EtherCAT® bus bandwidth usage optimisation of the data from the SIRIUS slices sent over EtherCAT® is raw and unscaled. Scaling factors are obtained from DEWESoft Channel Setup and are exported to a text
Figure 4 – MTS HWI File Editor
file and included in the ENI file for quick import to the MTS Station Manager. The scaled data always represents the same value as displayed in DEWESoft X software: if the user applies custom scaling in DEWESoft, the scaling factor will also change to give the same physical values when applied to the raw data.
RPC® ANALYSIS ON A MULTIAXIS ROAD SIMULATOR
An application of the R8rt was done on a road simulator for testing the durability of car and truck suspension systems. It consisted of 4 corners, each having 6 degrees of freedom. 104 analogue input and output channels which are used by the MTS FlexTest controller for actuator control. An additional 96 channels are used for measuring the response of the specimen. This is to correlate the loads on the test bench to the real road load data. Signals from those channels are acquired by two DEWESoft R8rt systems (each including 6 SIRIUS amplifier slices) and streamed over EtherCAT® to the FlexTest controller.
Figure 5 – one corner of the rig equipped with accelerometers
To compare the performance of the EtherCAT® data transmission to a classical solution used on such rigs (using +-10 V analogue output from the SIRIUS to transmit the data to the controller), a test RPC analysis was performed. Three 3-axial accelerometers were placed on one corner of the rig with input channels distributed between both R8rt instruments. An exemplary drive file was played out on the corner and the response recorded by the R8rt’s. MTS RPC® Pro software was used to create new drive file that replicated the initial run. Therefore, there was no difference in performance and convergence of the RPC Pro compared to the classical analogue data acquisition.
In conclusion, standardised technology adapted by multiple vendors always opens up better solutions for the users. EtherCAT® allows more connectivity with the MTS control system. While the parallel EtherCAT®/USB technology allows the user to use the same hardware for completely different tasks. EtherCAT® solution for connecting the DAQ system with the controller. At the same time the performance of the RPC analysis is the same as with the analogue preamplifiers.
Figure 6 – 2 kilometres of expensive cabling were saved after installing the EtherCAT® DAQ system