The SIMOTION Motion Control System uses high-performance CPUs on which a real-time operating system suitable for fast control processes is implemented.

This real-time operating system organizes an execution system comprising different execution levels.

Execution system

The SIMOTION execution system makes a distinction between system execution levels and user execution levels (tasks):
System tasks process operations that are necessary for general operation of the system. With technology objects, closed-loop position control and characteristic variable calculation is performed in the SERVO, IPO and IPO2 system tasks.

System tasks are regularly executed by the system. The system cycle clock can be specified.

Execution levels with different execution characteristics are available for task-related user programming (user program tasks).

The execution levels define the chronological sequence of programs in the execution system. Each execution level contains one or more tasks. The individual user programs are assigned to these tasks.

All programs – and thus also tasks – can execute PLC, technology and Motion Control tasks.

Task types for task-related execution are:

• Synchronous tasks
• Cyclic tasks
• Sequential tasks
• Time-triggered tasks, and
• Interrupt-driven tasks

Synchronous tasks are synchronized with the system tasks and the control cycle of the drives or the isochronous PROFINET/PROFIBUS.

With the help of these synchronous tasks, the whole application is in isochronous mode (user program в†” Drives в†” I/O). This results in short response times and the application is easily reproducible.

Task structure of a SIMOTION application

Task structure of a SIMOTION application

The following execution levels are available to the application:

StartupTask

The StartupTask is executed once at the operating mode transition from STOP to RUN; it controls the system start-up.

BackgroundTask

The BackgroundTask is executed cyclically and is used for general PLC tasks. Cycle time monitoring checks the maximum processing time of the BackgroundTask. The BackgroundTask can be compared with the OB1 of a SIMATIC controller.

MotionTasks

MotionTasks are used for motion sequences.

Command sequences in the same Motion Task are usually executed sequentially, for example, the next motion command is only started when the previous command has been completed.

The MotionTasks do not require any CPU time during these waiting times, but respond immediately on receipt of the wait event.

SynchronousTasks

In servo-synchronous user tasks, time-critical terminal-toterminal responses for I/Os or fast influencing of setpoints can be implemented on the servo level (synchronous to the system cycle SERVO of the technology objects, e.g. position controllers).

The IPO synchronous user tasks are started synchronously immediately before the interpolator cycle IPO or the slower IPO2.

Fast Motion Control reactions can be implemented here, as well as closed-loop control tasks in which the acquisition of actual values and output of setpoints must be synchronized.

The characteristic variables for the technology objects are calculated in system cycles IPO and IPO2.

The user program is therefore synchronized with the control cycle of the drives and with I/O processing. Synchronization ensures short response times and, above all, deterministic and reproducible machine behavior.

DCC tasks

Drive Control Chart (option) uses the above-mentioned SynchronousTasks. In addition, further synchronous execution levels (special tasks for DCC) can be assigned to the blocks.

TimerInterruptTasks

Several time-triggered tasks are available. The call cycles can be parameterized. Periodically repeated tasks are normally placed here.

InterruptTasks

InterruptTasks are used for a fast response to internal events that are signaled using interrupts. InterruptTasks can be activated by system interrupts, such as alarms and timeouts, or by user interrupts.

ShutdownTask

The ShutdownTask is called when there is a transition to STOP mode. The specific behavior for the transition into this system state can be defined here.

The complete instruction set is available for all user tasks. This allows the current positioning command from a MotionTask to be superimposed with an additional movement which was triggered by a UserInterruptTask, for example.

Runtime levels of the technology packages

The execution cycle can be set object-specifically for Motion Control technology objects.

Technology objects are executed in the execution levels SERVO cycle and IPO cycle or IPO2 cycle that are synchronized with the PROFINET or PROFIBUS cycle.

• Command evaluation and motion control in the IPO/IPO2 cycle
• Position and setpoint control in the SERVO cycle
• IPO/IPO2 cycle can be reduced relative to the SERVO cycle to allow optimization of the system's performance to meet requirements.

IPO/IPO2 cycle can be reduced relative to the SERVO cycle to allow optimization of the system's performance to meet requirements (SERVO_Fast, IPO_Fast).

This additional runtime level enables the performance of the controller to be utilized more efficiently. Electrical and/or hydraulic axes can be distributed over one slow and one fast bus system depending on the dynamic response required.

Electrical positioning drives, for example, can be controlled with cycle times in the millisecond range requiring fewer resources and, at the same time, the pressure-controlled axes of an hydraulic press can be controlled highly dynamically with short cycle times.

The runtime level (SERVO_Fast, IPO_Fast) also enables a particularly fast I/O processing in conjunction with, for example, high-speed PROFINET I/O modules.

Further characteristics of the execution system

• Operating states – Run, Stop, StopU (Stop User Program for test and commissioning functions)
• Process images for inputs/outputs, is separate for BackgroundTask, SynchronousTasks and TimerInterruptTasks
• Debug functions such as
  • Controlling and monitoring of variables
  • Display of the program status
  • Breakpoints and single step
  • Trace functions
• Kernel updates can be implemented with new SCOUT versions.