DMC implemented a real-time program to asynchronously control up to three motors and brakes. The real-time program runs on an NI cRIO and utilizes the cRIO’s hybrid mode, which runs custom FPGA code in tandem with NI’s standard “Scan Engine” for interfacing with several data acquisition modules. The custom FPGA code is used to calculate RMS current and voltage at 50 or 60Hz, depending on the type of AC power that is used for the motor. A Windows-based LabVIEW application runs on a touchscreen and communicates with three cRIOs to enable the operator to configure a test sequence, manually control the motors and brakes, start and stop test sequences, initiate autotuning, view past data, and investigate faults. The Windows application allows for future expansion to up to six cRIOs, for a total of eighteen motors running on one system.
The motor test sequence is designed to simulate real-world motor usage, with varying levels of current being controlled by a PID feedback loop. The program monitors the motor current and temperature and automatically stops the test if the motor stopped performing adequately.
DMC modified NI’s PID toolkit to increase the robustness of the autotuning algorithm and allow multiple motors to be autotuned simultaneously on a single cRIO. The autotuning algorithm saves a lot of time and requires less operator training to configure a new tool because manually tuning a PID control loop for a system with unknown response can be a long and complicated process.