Rockwell Automation 1398-PDM-xxx IQ Master Version 3.2.4 for IA-2000 and IQ-5000 Positioning Drive Modules, IQ-55 - Manual (Page 425)

Application Examples • Automated Test Station 403
Publication 1398-PM601A-EN-P — October 2000
APPENDIXES
Automated Test Station
Description
An automated test station is used to perform various tests on a manufactured part or assembly. An oper-
ator loads the part into a mechanical fixture and starts the test. The Allen-Bradley ULTRA Plus or IQ
Positioning Drive Module and brushless motor perform the tests and transmit results to a host computer
through a serial interface. A pass or fail indication is given to allow rejected parts to be directed to a
rework process and good parts to continue on in the manufacturing process. Some tests that can be per-
formed include: measuring torque at a fixed velocity, stress testing an assembly by applying torque at
zero velocity, measuring velocity at a fixed torque, and measuring position deflection at a fixed torque.
Advantages of Servo System
•
RS232 or RS422 serial interface to host computer provides data acquisition of test results for anal-
ysis to aid in statistical process control and quality management, and flexibility of test setup.
• Digital Positioning Drive Module design allows direct current (torque) measurements as well as
velocity and position from within the motion program.
• The operator interface capability allows quick set-up of different test procedures.
Design Considerations
Mechanics
The mechanical fixture(s) and connections to the motor shaft are dependent on the type of tests being
performed, and the physical properties of the parts being tested. If performing torque testing, avoid gear
reductions and couplings that may introduce errors in measurements due to frictional losses. If perform-
ing velocity and/or position testing, use low backlash, high efficiency gear reductions and couplings to
avoid measurement errors.
Test Options
There are four basic test options to consider:
1. Measuring torque at a fixed velocity - This method is used when measuring the running torque of a
rotating assembly such as testing efficiency and frictional losses of a gearbox assembly. The motor
is connected to the input shaft of the assembly and the controller cycles through different velocities
and measures current (ICMD) to the motor at each velocity. The current measurement is then con-
verted to torque by multiplying by the torque constant (KT) of the motor.
2. Stress testing - This method is used when testing the static torque of a fixed part or assembly such
as testing the torque of a screw or nut. The motor is connected to the part and the controller applies
a fixed torque. If the part does not turn, it passes the test. If the part turns more than a preset toler-
ance, it fails the test.
3. Measuring velocity at a fixed torque - This method is similar to option 1, but measures velocity
while applying a fixed torque. This can also be used to measure frictional losses of a rotating
assembly.
4. Measuring position deflection at a fixed torque - This method is used when measuring the amount
of deflection that results from applying a fixed torque to an assembly. An example is testing a
spring clutch mechanism for the proper range of motion. The motor is connected to the assembly
and the controller moves in one direction at a fixed velocity with a preset torque limit. When the
motion is stopped by the mechanism, motor position is captured, and motion is reversed. When
motion stops again, the position is captured and a total position deflection is calculated. This
deflection is compared to a preset tolerance to determine if the part passes or fails. In either direc-
tion, if the assembly does not stop the motion within a preset position tolerance, the part fails.
Torque Measurement Considerations
The ULTRA Plus or IQ PDM controls current to the motor, not torque produced. To convert measured