A neutron magnetic focusing device control system

Abstract

The present application relates to a kind of neutron magnetic focusing device control system, system includes front-end sensing unit, for the angle of neutron magnetic focusing device, temperature and so on Data acquisition;Core control unit, based on the data of front-end sensing unit acquisition realizes motor and neutron source T0 Signal synchronous control and temperature protection;Feedback compensation unit, real-time feedback equipment state and dynamically compensates phase deviation;Man-machine interaction unit, support local and remote dual-mode control;Through the collaborative work of multiple units, system can realize high-precision synchronous control, real-time state monitoring and fault alarm, effectively improve the operation stability and efficiency of neutron magnetic focusing device, provide reliable technical support for neutron scattering experiment.

Description

Technical Field

[0001] This invention relates to the field of neutron scattering spectrometer control technology, specifically to a neutron magnetic focusing device control system for a small-angle neutron scattering spectrometer, particularly suitable for the small-angle neutron scattering spectrometer at the China Spallation Neutron Source (CSNS), to achieve high-precision synchronous control and real-time protection of the hexapole permanent magnet neutron magnetic focusing device. Background Technology

[0002] The neutron magnetic focusing device is a core component for improving the resolution of neutron scattering spectrometers. It focuses pulsed neutrons using a nested hexapole permanent magnet structure, and its operational stability and control precision directly affect the quality of experimental data. Current control technology for neutron magnetic focusing devices faces the following key challenges:

[0003] Insufficient synchronization accuracy: Traditional control systems rely on manual adjustment of motor phase, which cannot achieve dynamic real-time synchronization with the 25Hz T0 signal of proton target hitting at the China Spallation Neutron Source, resulting in neutron focusing angle matching deviation and reducing spectrometer resolution;

[0004] Temperature monitoring lag: The inner magnetic ring is prone to heat generation due to eddy current effect. Existing manual inspection or single-point temperature measurement has a lag in response, and high temperature can easily cause demagnetization of NdFeB permanent magnets.

[0005] The control mode is limited: it relies heavily on local button operation, making it difficult to connect to the spectrometer's central control system, and it cannot achieve remote cluster management and parameter collaborative adjustment. It is also difficult to adapt to the integrated control requirements of large scientific facilities.

[0006] Passive fault response: The lack of multi-dimensional status monitoring and alarm mechanisms makes it difficult to respond in a timely manner to faults such as motor stall and encoder signal loss.

[0007] With the large-scale application of the China Spallation Neutron Source, the requirements for the control precision and stability of the magnetic focusing device in neutron scattering experiments are becoming increasingly stringent. Therefore, developing a control system for a neutron magnetic focusing device that integrates "high-precision synchronous control, real-time temperature protection, dual-mode interaction, and fault alarm" has become an urgent need to overcome existing technological bottlenecks and support cutting-edge scientific research. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a control system for a neutron magnetic focusing device. Through a four-layer architecture of "front-end sensing - core control - feedback compensation - human-machine interaction", it achieves fully automated control of the entire process and solves the problems of low synchronization accuracy, lagging temperature monitoring, single control mode, and passive fault response.

[0009] The technical solution adopted in this invention is: a control system for a neutron magnetic focusing device, comprising a front-end sensing unit, a core control unit, a feedback compensation unit, and a human-computer interaction unit;

[0010] The front-end sensing unit is installed inside the neutron magnetic focusing device and integrates an absolute angle encoder and a K-type thermocouple. It is used to collect status data such as angle and temperature in real time to achieve comprehensive perception of the equipment's operating status.

[0011] The core control unit is based on an embedded PLC, which connects the servo driver and the motor. Based on the data acquired at the front end, it realizes synchronous control of the motor rotation and the neutron source T0 signal, and at the same time realizes overheat protection based on temperature data.

[0012] The feedback compensation unit calculates the angle deviation and dynamically outputs the compensation amount based on the encoder data triggered by the neutron source T0 signal, ensuring synchronization accuracy.

[0013] The human-machine interaction unit supports local touchscreen operation and remote central control access, enabling equipment control and status monitoring.

[0014] The front-end sensing unit includes one absolute angle encoder and four K-type thermocouples.

[0015] The core control unit includes one embedded PLC, one servo driver A (EtherCAT bus type), and one servo motor (rated power 7.5kW, rated torque 48N). m, speed 1500rpm, transmission ratio 3:1, load speed 500rpm), 1 servo drive B (supporting EnDat2.2 protocol and position latching function).

[0016] The core control unit adopts a "dual virtual axis + closed-loop compensation" synchronization algorithm. The speed of virtual axis 1 is set to 3000° / s (matching the frequency of the 25Hz T0 signal). Virtual axis 2 dynamically outputs compensation based on the difference between the latched position and the target position of the feedback unit. The motor command position = virtual axis 1 position + virtual axis 2 compensation position, and the synchronization accuracy is better than ±1°.

[0017] In the feedback compensation unit, after receiving the 25Hz T0 signal, the servo driver B triggers the encoder position latch (response time < 1μs). Every 10ms, the latched data is uploaded to the PLC. The PLC calculates the difference between the latched angle and the target angle and sends a compensation command to the servo driver A through the EtherCAT bus.

[0018] The human-machine interface unit includes a touch screen (7-inch, 800×480 resolution), with an interface including a main interface (displaying real-time operating parameters and buttons such as "Start / Stop" and "Alarm Reset"), a manual interface (motor jog forward / reverse buttons, jog speed settings, etc.), a parameter interface (setting T0 synchronization angle, temperature over-limit threshold, etc.), an alarm interface (displaying fault records in reverse chronological order), a monitoring interface (displaying latch position and compensation records), and a temperature interface (displaying the current temperature value of the thermocouple). Remote control is connected to the spectrometer master control system based on EPICS via the Modbus TCP protocol, and the mode is switched by the BOOL variable "MOD_B_modbus_remote" (0=local control, 1=remote control). The remote end can be monitored and operated through the ControlSystemStudio (CSS) client.

[0019] The core control unit has a temperature interlock function. When the temperature detected by the thermocouple is greater than or equal to the set over-limit threshold (such as 100℃), the PLC immediately issues a "motor stop" command and displays the corresponding alarm information.

[0020] The wiring of the front-end sensing unit uses flame-retardant or fire-resistant insulated wires, and the motor drive line and encoder signal line use twisted pair double shielded cables. The shielding layer is grounded inside the control chassis. The core control device is placed in a 19-inch 4U standard chassis, with power lines, signal lines, control lines and grounding lines arranged reasonably, and spare terminals reserved for expansion.

[0021] A method for operating a control system for a neutron magnetic focusing device includes the following steps:

[0022] The front-end sensing unit collects angle and temperature data in real time and transmits it to the core control unit.

[0023] The core control unit initializes the parameters and, after startup, controls the motor operation according to the "dual virtual axis + closed-loop compensation" algorithm, receives feedback data and dynamically compensates for it.

[0024] The feedback compensation unit uploads encoder latch data in real time, calculates angle deviation, and outputs compensation amount.

[0025] The human-computer interaction unit enables local / remote control and status monitoring;

[0026] When the temperature exceeds the limit, the core control unit immediately shuts down and issues an alarm.

[0027] This invention provides a control system for a neutron magnetic focusing device. Through an innovative four-layer architecture design of "front-end sensing - core control - feedback compensation - human-machine interaction," it significantly improves the control accuracy and operational stability of the neutron magnetic focusing device. The specific beneficial effects are reflected in the following aspects:

[0028] This invention employs a "dual virtual axis + closed-loop compensation" synchronization control algorithm, which strictly controls the synchronization error within ±1°, far exceeding the accuracy of traditional control systems. It effectively solves the problem of neutron focusing angle matching deviation, significantly improves the resolution of the neutron scattering spectrometer, and provides a reliable guarantee for high-precision scientific experiments.

[0029] This invention constructs a multi-dimensional temperature monitoring network by embedding four K-type thermocouples at key locations within the inner magnetic coil, enabling real-time and accurate monitoring of equipment temperature. Once an excessive temperature is detected, the system immediately triggers a shutdown protection and alarm, with a response time of less than one second. This effectively prevents the NdFeB permanent magnet from demagnetizing due to high temperatures, extending the equipment's service life.

[0030] This invention supports dual-mode interaction between local touchscreen control and remote EPICS-based spectrometer control system, allowing maintenance personnel to flexibly choose the control method according to actual needs. In remote control mode, the system seamlessly integrates with the spectrometer control system, supporting remote monitoring and operation via the ControlSystemStudio (CSS) client, significantly reducing on-site maintenance costs and adapting to the cluster control requirements of large scientific facilities.

[0031] The system of this invention has a built-in fault alarm mechanism that can clearly display alarm information on the interface, including key data such as fault type and occurrence time, which makes it easy for maintenance personnel to quickly locate problems and take corresponding measures, effectively reducing downtime and improving experimental efficiency.

[0032] This invention uses twisted-pair, double-shielded cables and flame-retardant wires for equipment connection, with the shielding layer grounded at one end, effectively reducing signal interference and ensuring the stability and safety of system operation. Simultaneously, the wiring design complies with industrial safety standards, providing strong support for the long-term stable operation of the equipment. Attached Figure Description

[0033] Figure 1 This is an architecture diagram of the system of the present invention.

[0034] Figure 2 This is a hardware layout diagram of the main controller chassis in this invention.

[0035] Figure 3 This is a hardware layout diagram of the driver chassis in this invention.

[0036] Figure 4 This is a flowchart of the synchronization control algorithm in this invention.

[0037] Figure 5 This is a schematic diagram of the main interface of the touch screen in this invention.

[0038] Figure 6 This is a schematic diagram of the installation position of the absolute angle encoder in this invention. Detailed Implementation

[0039] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings:

[0040] like Figure 1-6 As shown, where Figure 1 The overall architecture of the neutron magnetic focusing device control system of the present invention is shown, including a front-end sensing unit, a core control unit, a feedback compensation unit, and a human-machine interaction unit; the units communicate with each other through a data bus to jointly realize high-precision synchronous control and real-time protection of the neutron magnetic focusing device. Figure 4 The invention demonstrates the "dual virtual axis + closed-loop compensation" synchronous control algorithm flow. This algorithm uses virtual axis 1, matched with the 25Hz T0 signal frequency, as a reference for motor motion; virtual axis 2 dynamically outputs compensation based on the feedback angle difference, achieving precise adjustment of the motor's commanded position and ensuring synchronization accuracy better than ±1°. More specifically, a neutron magnetic focusing device control system, mainly comprising a front-end sensing unit, a core control unit, a feedback compensation unit, and a human-machine interface unit, is applied to the six-pole permanent magnet neutron magnetic focusing device of the small-angle neutron scattering spectrometer at the China Spallation Neutron Source (CSNS). This device has an inner magnetic ring diameter of 20mm and an outer magnetic ring diameter of 40mm. The outer magnetic ring needs to rotate at 500rpm and maintain synchronization with the rising edge of the 25Hz T0 signal (synchronization angle cycles from 0° to 120° to 240° to 0°), with synchronization accuracy better than ±1°. Simultaneously, the operating temperature of the inner magnetic ring needs to be controlled below 100℃ to prevent demagnetization of the permanent magnet.

[0041] I. Hardware Deployment

[0042] (a) Chassis layout

[0043] Based on the placement location and equipment type, the main hardware is housed in two chassis: the main controller chassis and the drive chassis. The main controller chassis is located in the cabinet space, while the drive chassis is placed next to the neutron magnetic focusing device. The two chassis are connected via an EtherCAT bus.

[0044] The main controller chassis uses a 19-inch 4U standard chassis, with the internal layout arranged according to functional zones, as follows:

[0045] Upper layer area: Auxiliary equipment is arranged, including a power filter, a 24V DC power module and an Ethernet switch, etc.

[0046] Lower layer: The core control unit is installed, mainly consisting of one embedded PLC and several terminal blocks. Through reasonable layout, electromagnetic interference is reduced.

[0047] The drive enclosure is a non-standard custom design, measuring 600mm high, 500mm wide, and 300mm deep. It primarily houses the drive and temperature acquisition module, and includes:

[0048] One servo driver A (EtherCAT bus type, compatible with 7.5kW motor), one servo driver B (supporting EnDat2.2 protocol and position latching function), and one 4-channel thermocouple input module.

[0049] Wiring specifications: All internal wiring uses flame-retardant insulated wires, and motor power lines and encoder signal lines are laid separately; each terminal can be connected to no more than 2 wires, and 10% of the terminals are reserved for future expansion.

[0050] (ii) Front-end equipment installation

[0051] Angle sensing device: One absolute angle encoder is installed on the outer magnetic ring shaft end; the encoder cable uses EnDat2.2 dedicated twisted pair double shielded cable, and the shielding layer is grounded at one end in the driver chassis to avoid signal interference causing angle acquisition deviation.

[0052] Temperature sensing equipment: 4 K-type thermocouples are embedded in key positions of the inner magnetic coil; thermocouple cables are connected to the PLC through the thermocouple input module.

[0053] II. Software Configuration

[0054] (I) PLC Program Development

[0055] The control program is developed based on TwinCAT software and adopts a modular design. The core module functions are as follows:

[0056] Initialization module: Executed automatically after system startup, it completes parameter loading and device communication detection; if a communication abnormality is detected, an "initialization failure" alarm is immediately triggered, and the motor is prevented from starting.

[0057] Synchronous control module: Implements the "dual virtual axis + closed-loop compensation" algorithm, calling the TwinCAT MC_GearInMultiMaster function block:

[0058] Virtual axis 1 configuration: The speed is set to 3000° / s, which is matched with the 25Hz T0 signal frequency and serves as the reference for motor motion;

[0059] Virtual axis 2 configuration: dynamically outputs compensation amount based on the difference between the latched angle uploaded by servo driver B and the target angle;

[0060] Motor command calculation: The final command position of the motor = position of virtual axis 1 + compensation position of virtual axis 2, and is sent to the servo driver A in real time via EtherCAT bus to ensure synchronization accuracy.

[0061] Temperature interlock module: Reads data from 4 thermocouples in real time. When the temperature of any thermocouple is greater than or equal to the over-limit threshold (e.g., 100℃), it immediately triggers protection: ① issues a generator stop command; ② cuts off the servo drive enable; ③ displays alarm information on the local interface and reports it to the spectrometer master control based on EPICS via ModbusTCP.

[0062] Fault handling module: Records fault information, such as fault type and occurrence time; supports fault reset (locally via touch screen button, or remotely via EPICS-based spectrometer master control command).

[0063] (II) Touchscreen Programming

[0064] Develop 6 types of functional interfaces based on a touchscreen (7-inch, 800×480 resolution), with an interface switching response time of ≤1 second:

[0065] Main interface: The left side displays real-time operating parameters (probe latch position record, error record, current angle of magnetic coil, etc.), and the right side has "Start / Stop" and "Alarm Reset" buttons.

[0066] Manual interface: Supports motor jogging control (forward / reverse button, jogging speed adjustable), real-time display of the position of the virtual axis 1 / 2, which is convenient for on-site debugging.

[0067] Parameter interface: You can set the synchronization angle, temperature over-limit threshold, and compensation cycle.

[0068] Alarm interface: Displays fault records in reverse chronological order, with each record including the fault type and the time of occurrence.

[0069] Monitoring interface: Displays 21 historical records of encoder latch position and error, facilitating analysis of synchronization deviation trends.

[0070] Temperature interface: Displays the current temperature value of each thermocouple.

[0071] (III) Remote Access Configuration

[0072] Following the "Modbus Variable Programming Specifications in Beckhoff PLCs for Micro-Angle Spectrometers", configure ModbusTCP variables to achieve communication with the spectrometer master control based on EPICS:

[0073] Variable definition: BOOL type variables are prefixed with "MOD_B_" (e.g., MOD_B_modbus_remote, 0 = local control, 1 = remote control), and REAL type variables are prefixed with "MOB_R_" (e.g., MOB_R_encoder_angle, which stores the real-time angle of the encoder); variable addresses only use the M area (register addresses 12289~24576), and the starting address is an even number (e.g., MB2, MB4) to avoid address misalignment.

[0074] Communication logic: When MOD_B_modbus_remote=1, the PLC receives control commands (such as motor start / stop, parameter modification) from the EPICS-based spectrometer master control and reports operating data in real time; in remote mode, the touch screen operation buttons are automatically deenabled, allowing only status viewing to prevent permission conflicts.

[0075] Client adaptation: The spectrometer master control terminal based on EPICS adopts the ControlSystemStudio (CSS) client to develop a dedicated monitoring interface that supports real-time display of information such as angle, temperature, and rotation speed.

[0076] III. System Debugging and Performance Verification

[0077] (I) Debugging process

[0078] Hardware debugging: Before powering on, check the wiring for correctness. After confirming that everything is correct, power on the control box and ensure that the indicator lights of the PLC and driver are normal.

[0079] Software debugging: Load the initialization program, test the motor jogging function in manual mode, and observe whether the encoder angle acquisition is continuous; in synchronous mode, connect the analog 25Hz T0 signal, test the "dual virtual axis + closed loop compensation" algorithm, adjust the compensation period to 10ms, and ensure that the synchronization error is stable within ±1°.

[0080] Protection function debugging: Test the temperature interlock function by modifying the temperature over-limit threshold: When the temperature rises to the over-limit threshold, the PLC should stop the machine and alarm within 1 second; simulate encoder cable disconnection to test the fault detection function. The PLC should immediately trigger the alarm and prevent the motor from starting.

[0081] (ii) Results of multiple performance verifications

[0082] Synchronization accuracy verification: During the synchronous operation of the system, 2500 sets of encoder angle data corresponding to the rising edge of the T0 signal were collected, and all of them met the accuracy requirement of ±1°; among them, more than 95% of the data error was ≤ ±0.1°, and the synchronization stability was good.

[0083] Temperature control verification: Simulating eddy current heating in the internal magnetic coil, when the temperature monitored by the thermocouple rises from 25℃ to the over-limit threshold, the PLC issues a shutdown command within 0.5s and simultaneously issues an alarm message, demonstrating timely protection response.

[0084] Example: Application of the CSNS Small Angle Neutron Scattering Spectrometer

[0085] This embodiment applies the above-mentioned neutron magnetic focusing device control system to the small-angle neutron scattering spectrometer at the China Spallation Neutron Source (CSNS). The specific application scenarios and effects are as follows:

[0086] The spectrometer in this embodiment is mainly used to study the structure and dynamic processes of materials at the nanometer to micrometer scale. It requires a neutron magnetic focusing device to focus pulsed neutrons onto the detector to improve experimental resolution. The control system needs to achieve the following:

[0087] Synchronized with the 25Hz T0 signal of CSNS proton target, ensuring that the neutron focusing angle matches the pulsed neutron arrival time;

[0088] Real-time monitoring of the inner magnetic ring temperature prevents the permanent magnet from demagnetizing due to high temperature, which would affect the focusing effect;

[0089] Remote operation and maintenance is supported, and maintenance personnel can monitor the equipment status from the CSNS spectrometer control room.

[0090] Based on the spectrometer's on-site layout, the main controller chassis is installed in a cabinet room approximately 25m away from the magnetic focusing device, communicating with the equipment in the field driver chassis via EtherCAT bus. The encoder cables are shielded and reinforced to withstand the complex electromagnetic environment of the site. The spectrometer's central control terminal, based on EPICS, is connected to the system via ModbusTCP protocol to achieve coordinated control with other spectrometer equipment.

[0091] Multiple experiments have proven that the synchronization accuracy of this invention is within ±1°, significantly optimizing the neutron focusing effect. Simultaneously, temperature interlocking and precise synchronization control prevent demagnetization of the inner magnetic ring permanent magnet and motor overload.

[0092] In summary, this invention, through a four-layer architecture of "front-end perception - core control - feedback compensation - human-computer interaction," effectively solves the problems of low synchronization accuracy, temperature interlock lag, and inconvenient operation and maintenance of neutron magnetic focusing devices. It provides reliable technical support for the efficient operation of the CSNS small-angle neutron scattering spectrometer and can also serve as a reference for the control of magnetic focusing equipment in other large scientific facilities.

Claims

1. A control system for a neutron magnetic focusing device, characterized in that: It includes a front-end sensing unit, a core control unit, a feedback compensation unit, and a human-computer interaction unit; among which: The front-end sensing units are distributed inside the neutron magnetic focusing device to build a multi-dimensional state monitoring network, including angle sensing and temperature sensing. The core control unit serves as the system's control center, realizing motion control and safety interlocking; the core control unit includes: Hardware configuration: 1 embedded PLC supporting EtherCAT bus and ModbusTCP protocol; 1 servo drive A with a 7.5kW servo motor to drive the magnetic coil rotation; 1 servo drive B receives a 25Hz T0 signal and triggers encoder latching. Synchronization Algorithm: Employing a "dual virtual axis + closed-loop compensation" logic, virtual axis 1 is frequency-matched to the 25Hz T0 signal and set to a speed of 3000° / s, serving as the motor motion reference; virtual axis 2 dynamically outputs compensation based on the feedback angle difference. The motor command position = virtual axis 1 position + virtual axis 2 compensation position, with a synchronization accuracy better than ±1°. Virtual axis 1 and virtual axis 2 in the synchronization algorithm are implemented through a PLC program. Virtual axis 1 is configured with a speed set to 3000° / s, matching the 25Hz T0 signal frequency; virtual axis 2 dynamically outputs compensation based on the difference between the latched angle uploaded by the servo driver B and the target angle. Safety interlock: If the temperature detected by the thermocouple is greater than or equal to the set over-limit threshold, the machine will immediately stop and an alarm will sound; The feedback compensation unit achieves full closed-loop feedback of position and phase; The human-computer interaction unit supports both local and remote dual-mode control.

2. The control system for the neutron magnetic focusing device according to claim 1, characterized in that: The front-end sensing unit includes: Angle sensing module: includes one absolute angle encoder, installed on the outer magnetic ring shaft, which collects angle data in real time via the EnDat2.2 protocol, with a resolution of 1342 x 17728. Temperature sensing module: Includes 4 K-type thermocouples, embedded in key positions of the inner magnetic coil, for multi-point temperature monitoring.

3. The control system for the neutron magnetic focusing device according to claim 1, characterized in that: The feedback compensation unit includes: After receiving the 25Hz T0 signal, the servo driver B triggers the encoder position latch with a response time of <1μs. Data is uploaded to the PLC every 10ms. The PLC calculates the difference between the latched angle and the target angle, and sends a compensation command via the EtherCAT bus to dynamically adjust the motor phase.

4. The control system for the neutron magnetic focusing device according to claim 1, characterized in that: The human-computer interaction unit includes: Local control module: Enables automatic start / stop of equipment, motor jogging, parameter setting, and status monitoring via touch screen; Remote control module: Connects to the EPICS-based spectrometer control system via the Modbus protocol, supporting remote monitoring and operation via the ControlSystemStudio (CSS) client.

5. The control system for the neutron magnetic focusing device according to claim 4, characterized in that: The touchscreen interface of the local control module includes a main interface, a manual interface, a parameter interface, an alarm interface, a monitoring interface, and a temperature interface, with an interface switching response time of ≤1s.

6. The control system for the neutron magnetic focusing device according to claim 1, characterized in that: The system also includes a fault alarm module, which clearly displays alarm information on the interface, including the fault type and occurrence time, and supports fault reset operations.

7. The control system for the neutron magnetic focusing device according to claim 1, characterized in that: The system uses twisted-pair double-shielded cables and flame-retardant wires for wiring, with the shielding layer grounded at one end to reduce signal interference and meet industrial safety standards.

8. The control system for the neutron magnetic focusing device according to any one of claims 1 to 7, characterized in that: The system is applied to the hexapole permanent magnet neutron focusing device of the small-angle neutron scattering spectrometer at the China Spallation Neutron Source (CSNS). It enables the outer magnetic ring to rotate at 500 rpm and keep synchronized with the rising edge of the 25 Hz T0 signal. The synchronization angle cycles from 0° to 120° to 240° to 0°, with a synchronization accuracy better than ±1°. Meanwhile, the operating temperature of the inner magnetic ring is controlled below 100°.

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