The hottest Rockwell IEEE1588 in the decentralized

Application of Rockwell IEEE1588 in distributed motion control system

Abstract: This paper describes the application of IEEE1588 in a distributed motion control system. The current solution relies on the special realization of time synchronization by decentralized moving parts. With the emergence of IEEE1588 standard, a motion control solution using commercial technology on standard networks (such as Ethernet) can be developed. This paper illustrates the basic operation of IEEE1588 and motion in a network through an example. This is the result of developing CIP sync synchronization principle

introduction

this paper describes the application of IEEE1588 in a decentralized motion control system. The current solution relies on the special realization of time synchronization by decentralized moving parts. With the emergence of IEEE1588, a motion control solution using commercial technology on standard networks (such as Ethernet) can be developed. This article will explain the basic operation of IEEE1588 and motion in a network example

decentralized motion control requires close synchronization between system nodes, which usually requires that the fluctuation between clocks in the system is in the order of microseconds. Higher performance application drivers will improve this performance to a few minutes a microsecond range. The current solution is to use appropriate network and interface components to achieve close synchronization between nodes in the decentralized system. The customized interface card controls the distribution and synchronization of the clock of the whole system and the timing transmission of control data

ieee1588 precise time protocol provides a standardized synchronization mechanism on the distributed network. By using IEEE1588 protocol, standardized solutions can replace special solutions on the standard network. Ready made components can be used to replace special network interface components

now a simple distributed motion control system is implemented using IEEE1588 protocol and Ethernet to demonstrate this principle

example description

example motion system is composed of three controllers, each of which is connected to a driver through a SERCOS adapter. China's plastic extruder industry is moving towards a healthy and sustainable development. SERCOS is the industrial standard for connecting digital drivers. All motion nodes are connected to standard Ethernet with Ethernet card

the "motion planner" in the regulator manages the position information of each drive to control inching, movement, and linkage operations. Each driver acts as a moving shaft, one of which is the main shaft and the other two are driven shafts. Each driven shaft is linked with the main shaft at a ratio of 1:1. The controller connected to the spindle sends the position reference to the controller connected to the driven shaft at certain intervals

the clocks of all nodes in the system are synchronized. It uses IEEE1588 protocol to achieve clock synchronization of Ethernet. The clock synchronization on the backplane is realized by a special protocol with IEEE1588 first

system clock synchronization

network clock synchronization is realized on the Ethernet adapter card, which contains an FPGA hardware auxiliary circuit, which is used to time stamp the incoming and outgoing IEEE1588 protocol messages. This FPGA contains a 64 bit, 25 nanosecond high-resolution tunable clock

this adapter also contains an interface chip connected to the base plate. The clock of the base plate chip is synchronized with the 1588 clock that also provides the maximum experimental force. The base plate interface on this adapter acts as the master clock, and other clocks on the base plate are synchronized with the master clock on this adapter. A simple algorithm is used to synchronize the base clock with the 1588 clock. This adapter represents a 1588 boundary clock node, while the base clock is classified as an "external" clock

motion synchronization

basic motion control requires that the running of motion tasks at one node should be synchronized with all other nodes. All transactions between nodes are based on synchronous refresh cycles. The two transactions between controller and drive and between controller and controller are the same

controller to drive transaction: at the beginning of the cycle, the controller sends the interpolation position to refresh each drive. The drive uses this position refresh value to control the closed-loop position and speed of the motor. Each drive returns its actual position to the controller. The controller calculates a new position and repeats it periodically. This operation lasts for a position refresh cycle

controller to controller transactions: at the beginning of the cycle, the spindle controller sends a position reference to each driven shaft, and the controller of each driven shaft plans the movement of the shaft with this position reference

in order to synchronize the movement of the whole system, the refresh of the movement task and position should be synchronized with the 1588 clock. A small circuit in the FPGA provides a cycle interrupt to the CPU to trigger this position refresh cycle. This circuit compares the time of loading a target register with the current 1588 clock time, and generates an interrupt when the current time matches the target time. In this interrupt subroutine, the CPU will also load a figure: I) the new target time of the filling structure inside various 3D print tubes, which is equal to the current target time plus the cycle time, and then repeat the process. The cycle time and phase are set during node configuration

1588

1588 protocol is a c/c++ tool running on the adapter. The implementation of most 1588 protocols includes synchronization, diagnosis, delay request, delay response and message management

1588 boot protocol is used to speed up the clock synchronization of the time slave at startup. Realize the guidance of 8 synchronous messages

the "best master" algorithm is not provided here. The system uses the "recommended" master selection method to determine the master clock of the sub network. At startup, the slave clock listens to the master clock indefinitely. This means that the slave clock will never become the master clock. Nor will more than one "recommended" master station be appointed

some support is provided for monitoring the integrity of the master clock. If a slave clock finds that it has lost the master clock, it will stop its master clock, which will cause the SERCOS adapter to close the SERCOS loop and stop all movements

output synchronization

in example application