ADwin-Based Real-Time System Tests Six Switches in Parallel
By: CAS DataLoggers
Multi-axis motion control systems are used extensively in manufacturing and laboratory research for positioning purposes. These systems often rely on feedback from position sensors to maintain closed-loop control for improved accuracy. In test and measurement applications, it is often desirable to use additional inputs as part of the feedback loop. For example, in scanning tunneling microscopes, a sample is moved in the X- and Y-axis while a feedback loop drives an actuator to maintain a constant tunneling current between a probe and sample in the Z-axis. The output of this loop can be used to generate a topographic, or height profile of the sample. To achieve the necessary control and accuracy, ADwin data acquisition and control systems (https://www.dataloggerinc.com/
A system based on an ADwin-Gold real-time system, in this case, designed to test the trigger switches of variable-speed power tools, features six stations which allow up to six separate switches in parallel to be tested. Each test station has a stepper motor that drives an actuator to simulate a person pressing the switch. A home sensor and encoder provide information on the position of the switch. The ADwin system, in addition to driving the stepper motor and reading the position information, measures the RMS voltage, RMS current, and duty cycle of the output from the switches.
The ADwin's multitasking capabilities provide independent control of each station. One main, high-priority task implements the main control loop for all six test stations. This control loop includes functions which:
• Find the home position;
• Drive the actuators;
• Move the switch to a specified position;
• Monitor the voltage, current and other input parameters.
Each test station has an individual process associated with it which sequences through the test steps to verify the operation of the switch. These separate processes allow for independent control of each station. These processes run at 100 Hz which is more than fast enough since the RMS data is updated at a line cycle frequency of 60 Hz. A user interface designed with LabView™ controls and monitors the operation of each test station through the use of global data that is automatically synchronized between the ADwin hardware and a PC.
This ADwin-based control system meets or exceeds all of the original design goals, performing substantially better than previous devices which utilized PC-based data acquisition boards to perform the measurement and control functions.
For more information contact a CAS Data Logger Applications Specialist at (800) 956-4437 or request more information (https://www.dataloggerinc.com/