EtherCAT Function Blocks that Work with Drive Parameters
These function blocks
A function block groups an algorithm and a set of private data.
It has inputs and outputs. are used to work with drive In electrical engineering, a drive is an electronic device to provide power to a motor or servo.
Control device for regulating the speed, torque and position of a motor.
A unit controlling a motor using the current and timing in its coils. parameters not supported by ML and MC function A function calculates a result according to the current value of its inputs.
A function has no internal data and is not linked to declared instances. blocks.
- They support reading and writing drive parameters using the non-cyclic SDO channel in the EtherCAT Ethernet ofr Control Automation Technology.
EtherCAT® is an open, high-performance Ethernet-based fieldbus system.
The development goal of EtherCAT is to apply Ethernet to automation applications which require short data update times (also called cycle times) with low communication jitter (for synchronization purposes) and low hardware costs. network.
- The ASCII American Standard Code for Information Interchange - ASCII provides a one-to-one mapping between alphanumeric characters and a digital one-byte word. name for the parameter is used as an input.
Execution Time
These function blocks typically take a longer time to execute (up to ten cycles to finish executing).
It takes the same amount of time to Read or Write a parameter.
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It takes more than one cycle to execute these function blocks (but less than 100 ms).
See When can I expect my SDO command to be completed? in the FAQs on how to set up the update rate for SDO communication.
Reason
It is not only linked to the ASCII SDO communication. Because these FBs are waiting for the AKD drive to responds, the execution time can also increase due to the load of the AKD firmware at the time you call them.
Result
The PLC Programmable Logic Controller - A digital computer used for automation of industrial processes, such as control of machinery on factory assembly lines.
Used to synchronize the flow of inputs from (physical) sensors and events with the flow of outputs to actuators and events. code is overrunning the cycle duration. as explained in Tasking Model / Scheduling.
As a consequence, you can see this message in the Controller Log window:
The Virtual Machine
Solution
When this happens we recommend:
- Use these function blocks sparingly in programs The act of performing a sequence of instructions or commands.
- Rely on the EtherCAT read/write SDO function blocks
- Smooth the load of the PLC code by executing these function blocks at the required update rate.
Stats about the FB Execution Time
- There is a small difference in timing when running EtherCAT at 2ms compared to other frequencies.
0.25, 0.5, 1ms 2ms Mean 9ms 14ms Min 3ms 8ms Max 16ms 24ms - Max time to consider when executing a single SDO command, (i.e., before the Done output becomes TRUE): 24ms.
- Max time to consider when executing a single Drive Parameter command (i.e. before the Done output becomes TRUE): 60 ms.
4 kHz 1 kHz Mean 20 ms 11 ms Min 15 ms 9 ms Max 45 ms 58 ms - When sending multiple commands to a single drive, only one command can be sent at a time.
- The time to execute multiple commands is:
Number of commands x Execution time of a single command
- The time to execute multiple commands is:
- When commands are sent to different AKD drives at the same time, the requests do not interfere with each other.
- The function finishes execution in the same maximum time as one drive.
