Testing Automotive Body Hardware with Virtual Instrumentation

Author(s):
Ken Kinter - VI Engineering

Industry:
Automotive

Products:

The Challenge:
The automotive industry tests all body components for durability in different conditions. Each test differs depending on which components are present, and the number of times each component cycles. The challenge was to develop a generic program to handle any combination of body components with differing amounts of cycles using LabVIEW with a constrained budget.

The Solution:
Implement data acquisition and real-time data analysis using National Instruments LabVIEW based software, a data acquisition (DAQ) board, and SCXI architecture.

Introduction

DaimlerChrysler is a leading automotive company based in Auburn Hills, Michigan who contracted V I Engineering Inc, a Premier National Instruments Alliance Member, to develop a system for durability testing of automotive body components. The system is used to cycle components and collect analog data during a cycle.

The system was required to handle any body component currently available on any of DaimlerChrysler’s automobiles. Because each body component didn’t cycle the same amount of time, they also required that many components maintain an independent cycle count.

During any cycle, analog data is collected on a maximum of 20 channels. Eight of these channels are hardwired to the voltage and current on each of four doors. The remaining 12 channels are inputs to the system. Channel 1 can be calibrated to output a real-time door velocity, which is an important parameter of durability testing. At the conclusion of each test, a summary containing the total counts of each component, and any logged failures is available to the user. Any analog data collected during a test is also available.

Choice of Hardware

A test stand containing 16 DC outputs, 20 Air Outputs, 8 Relay Outputs, 32 Sensor Inputs, and 20 analog inputs was constructed by Candid Logic Inc. A PC containing a PCI-MIO-16E4 card and an SCXI chassis containing seven SCXI modules controlled the stand. Two SCXI-1120 modules were used for 16 of the analog inputs. The other four were input with an SCXI-1121 to allow an input that required excitation. An SCXI-1162HV module was used for the 32 digital sensor inputs. The 16 DC outputs were controlled with an SCXI-1163R. 32 outputs were required for the 16 DC outputs, because each output required a polarity and an enable. Two SCXI-1160 modules were used for the 20 air outputs. 8 of the remaining 12 outputs on one of the SCXI-1160 modules were used for the 8 relay outputs.

Software Implementation

The first step was to develop a body configuration screen, where each body component could be selected. This screen allows the user to select each component to be cycled on the automobile as well as whether the component is manual or electric. Depending on the selected vehicle type, certain components are disabled if they are not available on that vehicle. This screen also contains the failure settings. The user can select from three options if a component fails during a test: halt the test, halt the failed component and continue the test, or set an alarm and continue to cycle the failed component.

The next step was to develop a schedule editor, where the user could input the cycle counts for each component. Along with the component counts, the starting window position can be selected, and the user can select whether the doors will be opened from the inside or outside.

The Run Test screen allows the user to select a component configuration, select a test schedule, and run a test. A standard schedule consists of 5,000 to 10,000 cycles on each component. Data from the 12 analog inputs can be acquired and saved to an ASCII file every specified cycle for comparison throughout the test. This screen also continuously monitors the currents counts during a test as well and the component failures. If a component fails during a test, the test will either pause, continue without cycling the failed component, or continue and keep trying to cycle the failed component. Also when a component fails, the failure is logged to a file along with the cycle count of the failed component, and a time and date stamp.

Challenges

Because each test could be set up to cycle any automotive component, the software had to be capable of running any combination of components. This required the software to continuously monitor component inputs and check failures. Upon a component failure, the component often needed to be removed from cycling.

Summary

By using National Instruments Virtual Instrumentation philosophy, V I Engineering has developed a single computer automated system for DaimlerChrysler, which has the capability of testing all configurations of an automobile for durability. With the new system, DaimlerChrysler can save as many as 50 hours on a full body durability test running 10,000 cycles.

 

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