Software motion control
SoftServo's "software motion control" uses software instead of hardware controllers. It originated from the "Next Generation Open CNC System" project at MIT and was granted a US patent (US6826434).
Overview
SoftServo utilizes software to implement all motion control functions, eliminating the need for any motion control cards or dedicated chips. All calculations are performed on the CPU of a general-purpose computer, fully leveraging the ultra-high speed and ultra-precision (double-precision floating-point) computing power of current CPUs. As CPU speed and performance improve, the speed and performance of software motion control systems also increase.
The software motion control algorithm runs on the hardware real-time software RTX. RTX's underlying architecture transforms Microsoft Windows into a real-time operating system. RTX directly manages the hardware, thus eliminating the need for hardware chips like DSPs to guarantee microsecond-level hardware real-time performance. This multi-tasking/multi-threaded real-time software architecture allows even real-time-critical servo motion control programs to run on a single CPU. The SoftServo software motion control system already includes a pre-configured RTX real-time subsystem.
The CPU can simultaneously perform all real-time servo and other control tasks, including closed-loop control, acceleration/deceleration, multi-axis linkage, PLC, G-code execution, and NC path generation. It also provides a graphical user interface, program compilation/loading, file management, data processing, and network communication. The multi-axis high-speed servo loop is closed-loop within a single CPU, achieving high-speed and high-precision motion control. Therefore, customers are not limited by the number of axes in the hardware system, nor do they incur expensive hardware expansion costs; they can achieve real-time motion control of up to 64 axes simply by modifying the software.
Software Architecture
On a single general-purpose CPU, the system software architecture consists of three layers.
1. The lower layer is the real-time layer for motion control. Through the expansion of the real-time subsystem, general-purpose operating systems gain hard real-time capabilities. The real-time layer communicates directly with the CPU and is assigned the highest level of exclusive interrupt priority by the CPU. This layer consists of three real-time modules: the motion control kernel, the PLC kernel, and the interpreter kernel. The motion control kernel is the core of the real-time layer. It is responsible for scheduling all tasks, providing interfaces to other kernels, and handling user data and command exchange with the upper layer, buffering and executing motion data with the interpreter kernel, exchanging PLC input/output data with the PLC kernel, establishing and terminating bus communication with the bus master, and exchanging servo and input/output data.
2. The middle layer is the real-time dynamic link library layer. It provides an interface between the real-time layer and user applications under the general operating system, transmitting user data and instructions to the real-time layer for processing and feeding back the results to the user application layer. This data, feedback, and instructions include equipment control, system initialization, parameter setting, CNC system control instructions, manual operation instructions, automatic operation instructions, test and sampling data, input/output instructions, PLC instructions, CNC and servo status monitoring, etc.
3. The upper layer is the operating system layer. User data and applications run at the operating system layer. Through high-level languages calling motion control and logic function libraries and third-party function libraries, users can develop various control system applications.
operating system
SoftServo's motion control software (including a real-time kernel) can run on Microsoft Windows XP and Windows 7 (32-bit/64-bit). Whether for operation or development, the Windows system provides developers and users with the shortest adaptation and development cycle, offering the most user-friendly interface and maximum scalability.
Real-time subsystem
As is well known, Windows is a non-real-time operating system and cannot be directly used for demanding motion control. RTX can transform Windows into a real-time operating system (RTOS).
By adding a real-time, preemptive multitasking mechanism to the operating system, RTX enables Windows to perform real-time development and handle high-performance, hard real-time critical tasks. Timing accuracy can reach 1 microsecond. Interrupt latency (IST latencies) is less than 10 microseconds. Therefore, on the same computer, the operating system can perform real-time and non-real-time tasks simultaneously, and Windows processes cannot interfere with the execution of real-time processes.
Motion control kernel
The motion control kernel is the foundation and core of the entire software architecture. The position loop and velocity feedback loop can be controlled in a closed loop within the motion control kernel (depending on the control mode and servo control cycle).
●The motion control kernel completes functions such as real-time motion control closed-loop algorithm, path planning, interpolation, acceleration/deceleration curves, compensation, and smoothing.
● The motion control kernel receives instructions from high-level user applications and transmits the commands to servo and I/O devices via the bus.
●This kernel is suitable for the S140M CNC system, the WMX2 general motion control system, and the RMX robot control system.
Soft PLC Core
The soft PLC kernel and motion control kernel are seamlessly integrated and work together to execute PLC sequential programs.
● Compatible with Fanuc PLC instructions and ladder logic.
● Provides deterministic, real-time performance guarantees with scan cycles of 1-5ms.
● It can detect motion status and send motion commands (PLC axis function).
●This kernel is suitable for the S140M CNC system.
Motion interpreter kernel
● High-speed processing of 1000 program segments per second.
● A circular cache containing motion instructions.
●Supports selectable program segment jump, single-step execution, and stop selection (applicable to CNC system S140M).
●Supports subroutine and macro program calls (applicable to CNC system S140M).
●Supports machine coordinates, workpiece coordinates, and relative coordinates (applicable to CNC system S140M).
●Supports robot language (Robot Control System RMX).
Advantages
1. Innovation and economy
● No expensive dedicated processing chip is required; software motion control can easily implement various complex algorithms and communications.
● No motion control board is required; software motion control can perform high-performance closed-loop algorithms for multiple axes within the kernel.
● Minimal, general-purpose hardware offers obvious cost savings, along with simple interfaces and cables, significantly reducing failure rates.
● Installation and integration are very simple and quick, accelerating time to market.
2. Powerful performance
●Fully leverage the ultra-high speed and ultra-precise (double-precision floating-point) computing power of current general-purpose CPUs.
●As CPU speed and performance increase, software motion control processing speed and performance also improve. (Moore's Law: Computer CPU processing power doubles every 18 months.)
●The motion control kernel completes functions such as real-time motion control closed-loop algorithm, feedforward, path planning, interpolation, acceleration/deceleration curves, compensation, and smoothing.
● Seamless integration of motion control kernel and soft PLC kernel for collaborative control.
●Supports multiple motion control modes and numerous optional functions.
3. Customization and scalability
● It provides an open platform and development environment, allowing users to realize their unique product ideas and build the best motion control products with their own technical experience.
● Users can easily integrate third-party applications into a unified motion control platform, such as vision systems, databases, and network applications.
4. Simple and rapid system integration
●Because of the minimal hardware, wiring and connections are very simple.
● Provides setup and testing software.
●Comprehensive technical documentation and international technical support.
● Provides sample programs for various applications.
5. Flexible hardware combinations
●Flexible configuration of the number of axes and I/O points.
● Flexible selection of various EtherCAT bus servo and I/O modules.
● Various general-purpose pulse servos and stepper servos are available.
● You can choose between an EtherCAT bus spindle driver or an analog frequency converter.
● It can control various linear motors and DD motors.
●A variety of general-purpose monitors, keyboards, mice, or PC touchscreens can be selected, or CNC-specific operation panels, monitors, and keyboards can be selected.
