Simulate vehicle doors
One company develops power-control modules for automotive subsystem manufacturers.
Martin Rowe, Senior Technical Editor -- Test & Measurement World, 11/1/2003
A control module for power doors on vans and sport utility vehicles. The DUT consists of digital I/O lines and an ISO 9194 serial port.
The challengeExercise the control module's hardware by simulating input signals, output loads, and serial communications. Test and collect parametric data on six modules over a temperature profile. Minimize investment in test equipment.
The tools- Agilent Technologies Vee test-development software and two 6269B DC power supplies (now discontinued). www.tm.agilent.com.
- Comtrol Rocketport PCI eight-port RS-232 card. www.rocketport.com.
- Keithley Instruments Model 2001 DMM. www.keithley.com.
- Measurement Computing PCI-DIO24 24-channel digital I/O card, two PCI-DIO96 96-channel digital I/O cards, three CIO-ERB48 relay cards, and one PCI-GPIB-300K IEEE 488 interface card. www.mccdaq.com.
- Silicon Engines ISO 9141-to-RS-232 converter. www.siliconengines-ltd.com.
- Thermotron S-32C temperature chamber. www.thermotron.com.
Futaba (Schaumburg, IL; www.futaba.com) develops power-control modules for automotive subsystem manufacturers. Test/software engineer Rick Page developed an automated system that tests a module's digital inputs, digital outputs, and serial communications functions as part of product validation.
 |
|
Engineers at Futaba built a system that tests six power-lift modules in 60 s. |
The test system's 96-channel digital I/O cards (see figure) drive relays that simulate control signals. In a vehicle, these signals originate from switches or buttons that a driver uses to open or close the door. Inductive and resistive loads simulate the motors that open and close a vehicle's doors.
When a test cycle begins, the system activates a relay on the CIO-ERB48 relay card that sends an "enable" signal to the power supplies. Upon receiving the signal, the power supplies apply power to two of the six DUTs. (Because Page used power supplies already on hand, the test system could power two units at a time, but no more.) The system then exercises these two DUTs' inputs and outputs. A complete test simulates the full open-close cycle of the door.
After cycling the second and third DUT pairs through the tests, the system performs a functional test on all of the units (two at a time) where it activates each input and checks that the corresponding output has activated. The DUT's microprocessor monitors each of its outputs and reports on its status through the ISO 9141 serial port, which the system converts to RS-232. The Vee software analyzes the data and stores it in a file.
In addition, Futaba's customer requires that the company expose the DUTs to a specific time-temperature profile with the DUT in both operating and nonoperating states. The Thermotron temperature chamber produces a signal based on the temperature profile. The Keithley DMM monitors the temperature and reports the status to the PC over the IEEE 488 bus. The PC uses the DMM's output to decide when and how to exercise the DUT.
ResultsThe system collects parametric data on the control modules for analysis of DUT performance. When put into use, the new test system doubled test throughput when compared to previous test systems because it simultaneously tests two of six modules in a chamber as opposed to one. The system also met its design goal of testing six DUTs in 60 s.
Page minimized the cost of the test system by using on-hand power supplies and a DMM and by making his own loads for simulating the motor. To make the loads, Page used wood, PVC pipe, insulated wire, and Ni-Cr wire. Page needed to buy the computer, the digital I/O cards, relay cards, and an IEEE-488 interface card. The total cost of new equipment for this project was less than $6000.
