Revamping a Test Bench for Automotive Transmission Parts

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"The program allows you to calibrate the signals from the sensors by applying, thanks to a reference device, a known value and perform the calibration of the entire system."

- Luca Cambiaso, SITEM

The Challenge:
Upgrading both the hardware (data acquisition system, control panels, and signal wiring) and the software of an old test bench for automotive transmission parts, and completely redesigning the program for test management.

The Solution:
Using a data acquisition and control system based on the CompactRIO platform to effectively monitor test bench safety requirements, and designing and developing a LabVIEW software program to manage HMI, acquire and control signals, and perform data post processing.

Author(s):
Luca Cambiaso - SITEM
Alessandro Lugli - SITEM
Marco Scarpa - SITEM

Software and Instrumentation for Test and Measurement (SITEM) is an Italian private company, UNI EN ISO 9001:2008 certified, that has been active since 1999 in test and measurement, industrial automation, and imaging systems markets.

SITEM developed this system according to customer requirements. The customer, a worldwide leading company in the automotive market, runs different kinds of tests for automotive transmission parts.

We physically divided the test bench into two sections:
• The test cell houses the electric motor simulating the car engine and the system for engagement and disengagement of the device under test (DUT)
• The supervision console, external to the cell, houses the hardware devices for signal conditioning and acquisition and the part of the supervisory interface with the operator

The system can interact and control:
• the driver for a brushless motor that simulates the motor vehicle
• two solenoid valves for the movement of a mechanical piston, which simulates transmission engagement and disengagement and the proximity switches
• two solenoid valves and proximity switches for the actuation of a mechanical brake

Hardware
We based the control and data acquisition system on the CompactRIO platform. Our system consists of: a cRIO-9112 chassis, a cRIO-9022 real-time controller, an NI 9205 acquisition module (takes care of four preconditioned thermocouples), an NI 9237 acquisition module (torque acquisition), an NI 9215 acquisition module (sensor of the phonic wheel), an NI 9269 module (generates the reference voltage to the inverter to adjust engine speed), an NI 9425 acquisition module for digital signals (proximity switches and buttons on the manual control panel in the cell), and an NI 9476 digital signal generation module (various signals to the system).

Software
We used LabVIEW for software development. Our software comprises three parts:
• Low-level software, programming FPGA electronics , which is used for data acquisition and generation modules
• Real-time software, which deals with measurements management and with the equipment and safety devices control
• Supervision software, running on the supervisor PC, which helps the operator interact with the system for all operations and calibration, and manages the automatic measurements procedures for which the system was designed

The software handles two test sets. The first test set performs a number of engagement/disengagement cycles at different engine speeds. Between one cycle and the next, the system waits for the DUT returning to the expected predefined temperature. The system stores data for all cycles performed (disk temperature, torque, power, RPM). The second test set runs a number of cycles of engagement/ disengagement at different engine speeds, but without waiting, between one cycle and the next to return to the defined temperature. In this way, the DUT reaches a very high temperature. The system stores data of the final cooling (disk temperature and carter  temperature).

Using this program, the operator can store different setups for different DUT models. The program can handle up to 20 different energy levels and can automatically generate test reports based on Excel macros.

We specifically designed a panel for users to review graphs (temperature, energy, and the number of revolutions) of all the cycles performed (about some thousands/year) for a given test set. They can also use the same panel to export data of a certain cycle to Excel. Finally, users can calibrate the signals from the sensors by applying, thanks to a reference device, a known value and calibrate the entire system.

RESULTS
We have tested the test bench with very good results in terms of flexibility and functionality, so we are going to upgrade a second test bench.

Author Information:
Luca Cambiaso
SITEM

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