Motion controller
Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules controller
MELSEC iQ-R motion modules for CC-Link IE TSN servo networks controlling 1 to 256 axes, with minimum operation cycles of 62.5 µs (RD78G) and 31.25 µs (RD78GH).
Key specifications
| Fieldbus | CC-Link IE TSN 1 Gbps |
|---|---|
| Axes | 1–256 |
| Axes max | 256 |
| Operation cycle | 62.5 µs min (RD78G), 31.25 µs (RD78GH); 250 µs min in Simple Motion mode for RD78G4/8/16 |
| Functions | position, speed, torque, synchronous and cam control; linear (4-axis), circular and helical interpolation |
| Programming | GX Works3: ladder, SFC, FBD/LD |
Summarised in our own words from Mitsubishi Electric Corporation's published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1 · Source 2
Specify Motion is not affiliated with Mitsubishi Electric Corporation. Mitsubishi Electric and MELSEC iQ-R RD78G / RD78GH motion modules are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Typical applications
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Speak to our engineers about your project
Our experienced engineers are on hand, ready to help with your project. Whether you need the Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules itself, help sourcing it, or a modified or custom design built around your load, speed and space, tell us what the machine has to do and we'll come back with the right option.
- Help sourcing MELSEC iQ-R RD78G / RD78GH motion modules and spares for installed machines
- Modified and custom designs when a catalogue part doesn't fit
- Complete axis: motor, drive, gearing and feedback matched together
What a motion controller is
A motion controller plans and coordinates movement for one or more axes, sending position, velocity or torque commands to servo or stepper drives. It generates trajectories with defined acceleration and jerk, synchronises axes for interpolation, electronic gearing and camming, and handles homing, limits and registration inputs. Commands reach drives over pulse, analogue or, most commonly now, EtherCAT and other real-time networks. Many controllers also include PLC functions to IEC 61131-3, combining logic and motion.
When engineers choose a motion controller
Choose a dedicated motion controller when a machine needs coordinated multi-axis motion beyond basic point-to-point moves, such as robots, gantries, packaging and CNC. It gives deterministic timing and motion libraries. The trade-offs are cost, programming effort and ecosystem lock-in. For simple machines with a few independent axes, a PLC with motion function blocks or intelligent drives with stored moves may be enough.
How to specify the Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules
Send these with your enquiry and an engineer can confirm the right MELSEC iQ-R RD78G / RD78GH motion modules variant or an equivalent:
- Number of axes and drives
- Network and cycle time (ms)
- Motion functions: interpolation, camming, robotics
- Programming environment and languages
- I/O and expansion
- HMI and connectivity
- Safety integration
Common mistakes to avoid
- Choosing a controller that does not support the drives' network
- Underestimating cycle time needs for many axes
- Ignoring programming tools and skills in the team
- Not planning for future axis count
Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules: frequently asked questions
What is the Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules?
MELSEC iQ-R motion modules for CC-Link IE TSN servo networks controlling 1 to 256 axes, with minimum operation cycles of 62.5 µs (RD78G) and 31.25 µs (RD78GH). It is made by Mitsubishi Electric Corporation; Specify Motion can help source it or propose an equivalent.
Who makes the Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules?
The Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules is made by Mitsubishi Electric (Mitsubishi Electric Corporation) and is listed here for engineers comparing options. Specify Motion is not affiliated with Mitsubishi Electric Corporation; brand names are used only to identify the product.
Is there an alternative to the Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules?
Yes. Our engineers can propose an equivalent built around your load, speed and environment. An engineer confirms the fit against your application before recommending anything.
What is the difference between a motion controller and a PLC?
A PLC handles machine logic, sequencing and I/O. A motion controller specialises in trajectory planning and coordinating axes. Many modern controllers combine both, running PLC logic and motion libraries on one CPU. Choose based on axis count, motion complexity and timing requirements.
Why is EtherCAT common for motion control?
EtherCAT offers short cycle times, precise synchronisation using distributed clocks and simple cabling, which suit coordinated multi-axis motion. Many drives and I/O devices support it. Other real-time networks such as PROFINET IRT and Sercos are also used, so check what the drives and controller support.
Further reading: How to select a motion controller or plc · Controllers and PLCs
Other motion controller series
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Tell us about your project and how you use the Mitsubishi Electric MELSEC iQ-R RD78G / RD78GH motion modules: the load, speed, duty and environment. An experienced engineer will review it and reply, normally within one working day.
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