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High-pressure Cylinder Tester for Airbag Inflator

2/21/2012

Project Introduction:
In 1951 the first airbag was invented, but it wasn’t until 1967, when a practical component for crash detection was developed: An electromechanical sensor with a steel ball attached to a tube by a magnet that could inflate the airbag in under 30ms, so that it could be utilized.

Our customer is an airbag inflator automated test equipment (ATE) manufacturer. The key technology of an ATE is to test an airbag inflator’s life under high pressure. The testing is a two stage process: one is a maximum pressure test, and another is the life cycle test. The maximum pressure test examines the maximum pressure under which the inflator will crack. The life cycle test is to cyclically test the inflator endurance capability 100,000 times under variable pressures.

To ensure the quality of the airbag inflators, the inflator life testing procedures require reliable industrial controllers that control the injection of high pressure water into the inflator to test the life & high speed recording the test data for testing data analysis.

System Requirements:
The airbag inflator ATE includes two major functions:

  1. Hydraulic cylinder control and high speed measurement function
  2. High speed data log, analysis & reporting, and operation parameter setting

A standalone controller with local operator panel is required for hydraulic control and high speed measurement functions. For hydraulic pressure and flow control, the controller must measure the outlet pressure of the cylinder as a set point to control inlet pressure and flow of air from the cylinder, which is amplified generating a high pressure of water into the inflator. It must also have a high speed control loop function to control the pressure, flow & valve action and air cylinder direction.

Furthermore, for the maximum pressure test and cyclical test, the controller must have a ramp-soak function, which is a time-based pressure set point profile. In the maximum pressure profile, the profile is a ramp function to increase the pressure value to a maximum of 1500 kg/cm3. In the cyclical test, the pressure ramp-soak-ramp function must be repeated 100,000 times.

A high speed sampling analog module is also needed to measure the pressure response for analysis & reporting. The sampling rate should be at a sampling rate of 1000 to record 1ms pressure response and collect the data with a time stamp for use with the reporting and analysis software installed on the PC.

Pressure drop off detection is required to detect the maximum pressure of inflators. This maximum pressure is designed by inflator manufacturers and to be verified by safety requirement. The inflators will show a pressure drop if they are manufactured incorrectly and this will lead to cracks in the inflator. The controllers then detect the crack and record the maximum pressure to finish the control cycle.

A color LCD operator monitor with touch screen is equipped with an alarm summary, control devices status, two operating modes, parameter setting display and pressure profile operation display functions.

For high speed data logs, analysis and recording functions, industrial PCs are needed to connect to the controllers to set testing parameters, alarms, devices status and profiles. High speed analog input modules are required to measure the testing pressure values for data logs and records.

Project Implementation:

Product Description
WebOP-2057V 5.7" QVGA Operator Panel with WebOP Designer 2.0 Software
APAX-5520KW PAC with AMD Geode GX CPU
APAX-5017H 12-ch High Speed Analog Input Module
APAX-5028 8-ch Analog Output Module
APAX-5040 24-ch Digital Input Module
APAX-5046 24-ch Digital Output Module
UNO-3084 Intel® Core™ 2 Duo Automation Computer with Dual DVI, 1 x PCIe, 3 x PCI and FireWire
PCI-1712 1 MS/s, 12-bit, 16-ch PCI Multifunction Card

System Diagram:

System Description:
For this application, the customer chose a solution that utilized Advantech’s PAC (Programmable Automation Controller), because it combines PLC and PC features, providing both high speed pressure control and analysis functions, including high speed analog measurement (1ms sample rate), closed loop control, batch functions of ramp soak curve profile configuration, and data log & reporting functions. Test pressure profile generation and alarm detection on all device statuses are also included in the system.

Furthermore, IEC 61131-3 international standard control and engineering language is installed in the APAX-5000 system with the Ladder diagram program, allowing engineers easily implement logic functions such as alarm handling and on-off valve control. The ramp/soak profile configuration function block enables easy implementation of pressure profiles, process control, pressure PID, and flow and temperature control.

The system uses the following devices: Advantech’s APAX-5520KW, PAC controller with IEC 61131-3 control language, is used for control functions; a high speed APAX-5017H AI module, is used to measure the high speed pressure and flow status; an APAX-5028 8-ch analog output , is used to control hydraulic proportional valve; an APAX-5040 24-ch DI module, is used to monitor and detect the devices status; and an APAX-5060, 12-ch relay output module, controls the on/off of inflator ATE devices.

To perform testing, analysis and real-time data logs two systems are used: a high performance vibration and shock resistant UNO-3084 embedded platform is used; and a PCI-1712 is installed to measure high speed pressure values, and log real time data into the analysis and log file database.

With support of a color display and touch screen, Advantech’s WebOP-2000 operator panel, is the most suitable for this application allowing operators to easily monitor and control parameter settings. The WebOP series also supports Ethernet ports or RS-485 interfaces to connect to the APAX system.

Conclusion:
Under the premise of safety, the test machine with Advantech’s products in this project not only became the first and original high-pressure cylinder tester in that facility but also a set of precise verification and test machines. Through Advantech’s solutions, the tester can smoothly operate this testing equipment and quickly collect the pressure signals, ensuring the customer carries out accurate analysis of the inflator with detailed information as well as greatly enhancing the product manufacturing quality.