MELSEC iQ-R Series Motion Module (RD78G) - System overview

MELSEC iQ-R Series Motion Module (RD78G) - System overview

MELSEC iQ-R Series Motion Module (RD78G) - System overview

This is an introductory article to the series Melsec iQ-R Series Motion Module (RD78G) Quick Start Guide. 

This article is dedicated to introduction of MELSEC iQ-R Series Motion Module RD78G(H).
It will introduce its functionalities, available programming methods and a sample hardware system configuration. 

1. Features of MELSEC iQ-R Series Motion Module RD78G(H)


MELSEC iQ-R series Motion module RD78G(H) is a servo system controller supporting CC-Link IE TSN that enables mixing of real-time control communication required for motion control and non-real time information communication utilized by the IT systems. By supporting the network, the Motion module can flexibly connect various devices including servo amplifiers, I/O modules, and high-speed counters.

Main features of RD78G(H)
• High-speed processing with multi-core processor
• Up to 256 control axes
• Programming with the PLCopen® Motion Control FB (function block) for positioning control, etc.



2. Programming methods


There are two proramming methods for a servo system using RD78G(H): programming by a PLC CPU only and programming by a PLC CPU and the Motion module. Selectable programming languages vary depending on the controller. 

• Motion module : structured text language (ST)
• PLC CPU : ladder diagram (ladder), function block diagram/ladder diagram (FBD/LD), sequential function chart (SFC), and structured text language (ST)





Programming by a PLC CPU only
• Advantages : Easy program management by programming with only one CPU.
• Disadvantages : Longer scan time due to processing by one CPU.

Programming by a PLC CPU and the Motion module
• Advantages : Reduced scan time because motion control is programmed to the Motion module, not affecting other processing in a sequence program.
• Disadvantages : Necessary to manage programs of both the PLC CPU and the Motion module.

3. Sample hardware system configuration


The following shows a system configuration example using a Motion module (RD78G), a servoamplifier (MR-J5-G), and a servo motor (HK-KT series).



The other articles in the Melsec iQ-R Series Motion Module (RD78G) Quick Start Guide series detail the project set up, parameter setting, homing execution, and examples of programs - speed control, torque control, positioning, interpolation, synchronization etc. The articles are divided into Motion side programming and PLC side programming (indicated in the title of each article). The tags (Motion side programming, PLC side programming) make it easy to navigate through them.