Lingchen PLCs Power Ceiling Trolley Applications
In the field of intelligent logistics handling, overhead trolleys serve as core handling equipment, placing extremely high demands on the real-time performance, stability, and safety of their control systems. An overhead trolley handling system developed by a specific client—driven by terminal requirements—needed to transition from its original "Windows + Control Card" architecture to the open-source Linux operating system, while simultaneously contending with the severe constraint of extremely limited available hardware space.
Crucially, given that the overhead track may accommodate multiple transport trolleys—or even human intervention—the control system must possess an exceptionally rapid response speed to facilitate core-level interaction between these entities, thereby preventing accidents and collisions. The equipment architecture is therefore divided into two distinct components: a logic layer and an application layer. The host program manages operational logic and MES integration, while the PLC component is responsible for executing low-level control tasks—such as axis motion, I/O interaction, and status reporting—as directed by the host system.
To address this challenge, Lingchen Technology has developed a comprehensive "computation-and-control-integrated" dual-domain controller solution, built around its LC2000 series PLCs. This solution has successfully enabled high-speed, stable interaction between the host system and the PLC within a Linux operating environment.
1. Client Requirements and Core Challenges
Key Performance Indicators: The client has specified clear performance requirements for the control system:
Communication Speed: The communication latency between the host PC and the PLC must be less than 6 ms.
I/O Response: The rate at which the I/O point status is acquired must be less than 15 ms.
Data Security: Data read and write operations must be separated, and CRC checksums must be applied to all data.
System Architecture: The Linux environment must simultaneously support the execution of both the PLC runtime and the host PC application, while facilitating data exchange between them.
Technical Implementation Challenges: Achieving efficient collaboration between a PLC and a host PC within a Linux environment presents the following technical challenges:
① Real-time Kernel Interaction: When Linux simultaneously runs both the PLC kernel and the host PC application, the two entities must exchange data while meeting strict communication efficiency requirements. Ensuring real-time performance within a non-real-time operating system environment emerges as the primary technical hurdle.
② Separation of Read and Write Operations:** Data read and write operations must not interfere with one another; otherwise, this will lead to data corruption or system anomalies.
③ Data Integrity Assurance: Data exchanged—whether read or written—between the host PC and the PLC must be entirely free of errors. Any inaccuracies would compromise the operational efficiency of the automated cart and could even result in control commands failing to execute.
④ Shared Memory Synchronization: The shared memory regions utilized by both parties must be strictly aligned in terms of location and standardized in terms of size. Furthermore, the timing of signal exchanges must be precisely controlled. Any misalignment in memory location or size could trigger memory overflows or cause the PLC to crash.
⑤ Real-time Data Jitter Handling: Data such as the servo's current position and velocity is subject to real-time jitter. If the timing of data transmission is imprecise, the "current position" data sent may actually reflect the previous cycle's value, resulting in a mismatch with the accompanying CRC checksum data.
⑥ Hardware Compatibility: The I/O modules utilized by the client are custom-designed components. Since certain commercially available PLCs do not natively support communication with these specific modules, targeted software and hardware adaptations are required to ensure compatibility.
2. Lingchen Solutions
To ensure both the open nature and real-time control capabilities of the Ubuntu environment, Lingchen Technology employs a dual-kernel Linux configuration—comprising a standard desktop Linux kernel and a real-time kernel—running on a single CPU hardware platform. This architecture allows for the dynamic allocation of hardware resources between the real-time and non-real-time domains based on specific field application scenarios, thereby guaranteeing the system's real-time performance. In contrast to traditional product configurations—such as the conventional "PLC + Industrial PC" combination—this product facilitates high-speed data exchange between the two domains via shared memory. This communication method enables direct read/write access to data, ensuring a "What You See Is What You Get" (WYSIWYG) experience regarding data visibility. Most importantly, a crash in the desktop Linux kernel does not affect the normal operation of the real-time PLC kernel, thereby achieving a critical security feature through kernel isolation.
Key Advantages of the Integrated Compute-and-Control Dual-Domain Controller
◆ Dual-Domain Shared Memory: Enables high-speed data exchange between the real-time and non-real-time domains via shared memory, ensuring "what you see is what you get" data consistency.
◆ Kernel Isolation: A crash in the desktop Linux kernel does not affect the normal operation of the real-time PLC core, thereby safeguarding the operational safety of the equipment.
◆ Flexible Resource Allocation: Hardware resources can be allocated dynamically based on specific on-site application scenarios to guarantee the real-time performance of the system.
◆ Deep Integration of Compute and Control: Achieves seamless collaboration between high-level computing and low-level control—all on a single hardware platform.
Shared Memory Interaction Scheme
This scheme utilizes a shared memory model for interaction between the host-side C# software and the PLC. The interaction workflow is as follows: A user initiates an operation (e.g., an I/O or axis control command) via the C# UI interface → A dedicated C# interaction class writes the command to the shared memory → The PLC interface reads the command → The PLC executes the corresponding control logic → The hardware is actuated → The PLC retrieves hardware status data and other relevant information → The PLC writes this data back to the shared memory → The C# UI interface retrieves the command execution results, I/O status, and other data. During this operational process, both parties utilize specific flag bits—flag1 and flag2—to synchronize their read/write operations based on the status of these flags. For instance, when the host-side UI detects that flag1 is set to 0, it proceeds to write data; upon completion, it sets flag1 to 1. This mechanism ensures the orderly and accurate exchange of data between the two systems.
Key Technical Implementation
① CRC Verification for Data Integrity: Utilising CRC verification function blocks released via the CODESYS platform—which were thoroughly tested and subsequently integrated into the project program—the system parses and aligns incoming CRC data from the host controller, thereby guaranteeing the accuracy of both transmitted and received data.
② Optimisation of Axis Data and PDO/SDO Operations: For data with less stringent real-time requirements, proprietary PDO write and SDO read function blocks—developed in-house—are employed, triggered by rising-edge signals. Conversely, for data requiring high real-time responsiveness, the system directly retrieves necessary parameters by binding EtherCAT variables to absolute memory addresses, thereby ensuring the real-time integrity of critical data.
③ Adaptation for Custom I/O Modules: Addressing the challenge where certain commercial PLCs do not natively support communication with the client's custom-designed I/O modules, the Lingchen R&D team engaged in close consultation with the client to devise a targeted solution, ensuring seamless integration and compatibility for the machine system.
④ Technical Support and Training: Recognising that the client's engineers were not fully familiar with the PLC programming software, the Lingchen team provided comprehensive software usage training and assisted with on-site debugging, successfully facilitating the handover of the program to the client.
Performance Metrics Verification: Validated through on-site testing, this solution fully meets the client's requirements across all performance metrics:
Communication Speed: The communication latency between the host PC and the PLC is less than 6 ms, satisfying the client's requirements.
I/O Response: The acquisition rate for I/O points is less than 15 ms, with actual performance ranging between 3 ms and 12 ms.
Bus Cycle: A 1 ms scan cycle ensures real-time responsiveness.
System Stability: Kernel isolation has been implemented, ensuring that a crash of the desktop operating system does not affect the core PLC control functions.
3. Solution Highlights and Customer Value
Technical Innovation Highlight: Integrated Control-and-Compute Dual-Domain Architecture** — Runs a dual-kernel Linux system on a single CPU hardware platform. Resources for the real-time and non-real-time domains can be flexibly allocated, thereby preserving the open nature of Ubuntu while simultaneously guaranteeing real-time control performance.
High-Speed Interaction via Shared Memory — The two domains establish a shared memory space for data reading and writing, enabling high-speed data exchange and ensuring "What You See Is What You Get" data consistency. This approach significantly boosts interaction efficiency compared to traditional "PLC + Industrial PC" communication methods.
Kernel Isolation Security Mechanism — A crash in the desktop-environment Linux kernel does not affect the normal operation of the real-time PLC kernel, thereby fundamentally safeguarding the operational safety of the device.
Flexible PDO/SDO Read-Write Strategies — To accommodate varying real-time requirements, two distinct methods are employed: functional block encapsulation and absolute address binding. This approach strikes an optimal balance between operational efficiency and real-time responsiveness.
CRC Verification for Data Integrity — All data is subject to CRC verification to ensure the accuracy and integrity of transmitted and received data, thereby preventing instruction failures or operational anomalies caused by data errors.
Value Creation for Clients—Solving System Migration Challenges: Successfully assisted the client in migrating from a Windows-based control card solution to the open-source Linux operating system, thereby meeting terminal requirements while effectively overcoming hardware constraints related to limited available storage space.
Ensuring Equipment Operational Safety: Under complex operating conditions—such as multiple carts sharing a single track or scenarios involving manual intervention—the system's high-speed kernel interaction capabilities effectively prevent accidents and collisions.
Lowering Development Barriers: Through technical training and on-site support, we enabled the client's engineers to rapidly master PLC programming, facilitating a smooth and successful program handover.
Enhancing System Reliability: Multiple layers of safeguards—including data read-write separation, CRC verification, and kernel isolation—ensure the system's long-term stability and reliable operation.
4. Summarise
In the field of industrial automation, driven by shifts in the global landscape and the widespread adoption of open-source technologies, the demand for migrating from Windows to Linux-based systems is steadily on the rise. Centred around its LC2000 series PLCs, Lingchen Technology has developed an integrated compute-and-control dual-domain controller solution that successfully resolves the technical challenges associated with kernel-level interaction between PLCs and host computers within a Linux environment. Through a series of technical innovations—including dual-domain shared memory, 1ms bus cycles, CRC verification, and kernel isolation—this solution achieves exceptional performance, boasting a host-to-PLC communication latency of less than 6ms and an I/O response time of under 15ms, while simultaneously ensuring data accuracy and system reliability. This represents far more than a simple product substitution; it is a deeply integrated, field-proven solution that seamlessly combines computing and control capabilities. From kernel-level interaction to data synchronisation, and from hardware adaptation to technical training, every facet of this solution reflects Lingchen Technology’s profound understanding of the convergence between industrial control and open-source technologies.
About Us
Established in 2006, Suzhou Lingchen Data Acquisition & Computer Co., Ltd. operates under a business philosophy centered on creating value for clients and fostering win-win partnerships. The company provides customers with core components and system solutions for a wide range of automation equipment, including industrial computers, motion control systems, test and measurement instruments, machine vision systems, and robotics. Currently, Lingchen oversees two wholly-owned subsidiaries: Suzhou Xun'ya Automation Technology Co., Ltd. and T.O.K. Robotics (Suzhou) Co., Ltd., which specialize in the sales of robotic systems and the R&D, manufacturing, and sales of linear motion products, respectively.
Product System Network
Within the hierarchical structure of automated control networks, Lingchen Technology offers a comprehensive range of products spanning the device, control, and information layers.
01 Industrial Computers
Lingchen Industrial Chassis provides comprehensive physical protection for critical computing cores through its industrial-grade robust structure, exceptional thermal management, and dust-proof design, ensuring enduring and stable operation even in harsh industrial environments characterized by vibration, dust, and extreme temperatures.
02 Embedded Industrial PC
Lingchen Embedded Industrial PCs feature a compact and rugged industrial design, integrating high-performance computing, extensive I/O interfaces, and broad tolerance for wide temperature and voltage ranges. Specifically engineered for embedded applications—such as machine vision, edge computing, and automation equipment—these systems provide a stable and reliable intelligent core within limited spaces, empowering smart manufacturing and IoT applications.
03 Motion Control Card
The Lingchen motion control card is capable of controlling up to 32 motion axes and simultaneously supports the control of up to 512 DI points and 512 DO points, with a maximum bus communication cycle of 250 µs. In terms of motion control, it supports functions such as single-axis relative motion, absolute motion, jogging, and drive-based homing; multi-axis interpolation; multi-axis point table motion; and electronic gearing.
04 LMC Series Motion Controllers
The Lingchen LMC series motion controllers are designed around an open, hard real-time kernel (with jitter < ±0.3 µs). This design thoroughly resolves the non-real-time limitations inherent in traditional Windows-based platforms, ensuring both determinism and instantaneous response for multi-axis commands. Installation is remarkably simple, requiring only a single Ethernet cable for connection; furthermore, utilizing highly efficient asynchronous communication technology, the system enables the synchronized issuance and control of motion commands for up to 12 axes within just 1 millisecond.
05 NAC Series High-Performance Motion Controllers
At the core of the Lingchen NAC controller lies a powerful bus expansion capability, supporting four EtherCAT masters to enable the precise control of 256 axes per station—totaling 4,096 I/O channels. Its motion control capabilities are both comprehensive and robust: beyond standard point-to-point, linear, and circular interpolation, it features advanced functions such as 5-axis interpolation, spline-based trajectory smoothing, and dynamic coordinate systems. Furthermore, it integrates vibration suppression, "soft landing" capabilities, and high-precision position comparison outputs; combined with eight independent interpolation groups and continuous interpolation functionality, it effectively meets the demands of complex trajectories and high-speed synchronization. The development environment is open and flexible, supporting multiple programming languages—including C++, C#, and Python—and allows for direct programming within the real-time operating system, thereby significantly enhancing integration and debugging efficiency.
06 PLC Motion Controller
Lingchen PLC controllers strictly adhere to PLCopen specifications and the IEC 61131-3 international standard, combining high performance, a compact footprint, and a modular design to facilitate easy development and flexible deployment. Widely applicable to automation equipment and production line systems across sectors such as 3C electronics, lithium-ion batteries, packaging, and printing, these controllers can also be extended to serve as network communication nodes within integrated production lines for logistics, automotive, and consumer goods industries. By meeting requirements for internal/external network isolation, high-speed bus communication, and real-time data processing, they provide a stable and reliable control core for a diverse range of industrial environments.
07 Industrial Network Cards
Lingchen industrial network cards are specifically engineered for harsh industrial environments, featuring 10/100/1000Mbps auto-negotiation capabilities to deliver stable and reliable high-speed network connectivity. Characterized by robust anti-interference, surge protection, and wide-temperature operation, these cards are widely deployed in critical applications such as motion control, machine vision, and automation systems. The products feature a flexible installation design—including a standard full-height bracket and an optional half-height bracket—enabling seamless integration into a wide range of smart manufacturing equipment and industrial networks.
08 IO Module
Lingchen Technology offers a comprehensive range of I/O module solutions, designed to meet the diverse requirements of industrial automation flexibly.
LC/LD Series Expandable I/O Modules: Supporting multiple protocols—including EtherCAT, Profinet, Ethernet/IP, and Modbus TCP—these modules allow for the flexible expansion of data acquisition capabilities covering digital signals, analog signals, temperature, pressure, and pulses. They are widely applied across sectors such as 3C electronics, lithium-ion batteries, semiconductors, automotive manufacturing, and medical equipment.
MINI Series I/O Modules: Characterized by their compact size and high real-time performance, this series encompasses digital I/O, analog I/O, temperature modules, and communication modules. They are ideally suited for control and data acquisition scenarios where space constraints and real-time responsiveness are critical requirements.
GWS Series Cabinet-Free I/O Modules: Featuring exceptional stability and convenient network cabling capabilities, these modules are designed for distributed system layouts, enabling significant reductions in both system integration time and costs.
Our entire product portfolio is dedicated to providing users with reliable, easy-to-integrate, and adaptable I/O module support for a wide variety of application scenarios.
