Rockwell Automation 1398-PDM-xxx IQ Master Version 3.2.4 for IA-2000 and IQ-5000 Positioning Drive Modules, IQ-55 - Manual (Page 426)

404 Application Examples • Automated Test Station
Publication 1398-PM601A-EN-P — October 2000
APPENDIXES
current to torque, the current can be multiplied by the KT of the motor. There are factors that can affect
the accuracy of these results so if high accuracy is needed for torque measurements, some additional
calculations may be necessary.
The first factor is the variation of KT from one motor to another. If multiple stations are performing the
same tests, this can be a concern. This variation should be no more than ±3%, but if necessary, a precise
factory measurement of KT may be obtained.
Another factor is that the KT of a motor is not completely linear with current. At higher current levels,
less torque will be produced per unit current. This can be corrected by determining an equation relating
torque to current or by using a table of torque values measured at specific currents.
A third factor is that the KT of a motor changes slightly with temperature. In this case, a sensor can be
placed in the motor to measure temperature, and an analog signal proportional to temperature may be
connected to the ADC1 input of the PDM. This temperature information can then be used to correct the
torque measurement.
Serial Host Interface
There are two methods of transmitting test data serially to the host computer. The first method is to use
PRINT statements in the program to send data directly to the serial port. This method is not recom-
mended because the host must always be ready to read this data, and also because if a fault occurred
while data was being transmitted, the data would be lost.
The preferred method is for the program to store test results in a group of nonvolatile variables. The host
computer can then request the test results at any time using host commands. Nonvolatile variables
should be used so even if power is removed before the host requests data, the data is preserved so the
host can still request the data once power is restored.
The host computer can optionally run tests without running a program on the PDM. Move commands
can be sent directly to the PDM, and current and velocity measurements can be obtained with direct
serial host commands.
Input/Output Connections
No I/O connections are needed between the PDM and the host computer. The serial interface is used to
pass data and allow the host to control the test process. If an operator terminal is used, no I/O connec-
tions are required either - the operator can control the process using the terminal. The following exam-
ple program assumes the use of a few I/O connections:
Input 3 - Enable
If the Enable function for input 3 is assigned in the PDM parameter setup, this input will enable or dis-
able the PDM. A normally closed push-button should be used. The program will halt, the motor will
decelerate to a stop, and the PDM will be disabled if this input opens.
Input 4 - Start
The Start input is connected to a push-button to allow the operator to start the test after loading the part
into the fixture.
Input 13 - Stop
If the parameters are set to define input 13 as an “X-Killmotion” input, activating this input with a push-
button will Stop motion and program execution but will leave the PDM enabled. This allows a non-
emergency method of stopping the test.
Output 1 - Pass
Output 1 is connected to a light to indicate the part passed the test. It may also be used to fire a solenoid
that moves a gate or conveyor to deflect the part to the proper location to continue in the manufacturing
process.
Output 2 - Fail