CHRNS: HFBS PLC

Core components of the High Flux Back Scattering (HFBS) spectrometer include the Phase Space Transformation (PST) chopper, Doppler Drive with a Si(111) monochromator, analyzers, and detectors and associated electronics. These components are controlled in real-time with a Programmable Logic Controller (PLC) system. Moving components such as the PST and the Doppler Drive go through regular and required maintenance for increased reliability. However, the PLC system was still in its original form with legacy components from when the instrument was commissioned 20 years ago. We are utilizing the unexpected outage to upgrade this system Here is a list of the upgrades.

• The PLC upgrade will provide better reliability and a more modern design. The PLC controls the servo amplifiers and 3He tube high voltage. It also monitors critical instrument variables such as temperatures, pressures, water flows, oil flows, and motor speeds. Its status can be queried by the instrument control PC via Modbus using TCP protocol. The PLC system upgrade has been completed. The New PLC system controls and monitors the core components via a human machine interface (HMI) touchscreen panel. The new HMI panel displays sensor data, alarm flags, and control setpoints for the PST and Doppler drive as well as enables/disables high voltage to the detectors. The HMI interfaces directly with the PLC and makes the control and monitoring smooth and reliable.

• A detailed documentation package for the PLC design and operation allows for more approachable maintenance and upgrades in the future.
• The new PLC has been programmed to control various components more actively for improved reliability and safety e.g. new PLC also monitors water temperature and its flow rate to the PST and can shut down the PST in unsafe conditions. The new PLC system also controls PST coil temperature more aggressively for longevity.
• New compact servo drives have been purchased to replace the current open-loop and analog-controlled design. The drives are being relocated to the front of the electronic rack for easier access as well as to manage the heat produced. A second drive is being planned to accommodate a noise-reducing chopper without having to reconfigure the whole system when the chopper is implemented. A postponement in delivery of servo drives has delayed this project. The major parts needed to implement the new PST drive are now in hand and the packaging details are gradually being designed and installed. The installation is expected to be completed before the reactor startup.  ·
• Due to the unfortunate semiconductor shortage, we are now looking into field-oriented control of the currents to the motor. This approach will allow us to control induction motors, which previously could only be speed controlled, like a servo motor. As the Doppler motor currently is driven by a speed-controlled induction motor, we may be able to operate it in a position-controlled mode as well. This should remove any discrepancies in the data that occur when Doppler is run between two elastic scans. Testing of the spare induction motor is in progress and is expected to be completed later in CY2023.