Selecting the right robot controller for the job

The current trend of robot control is changing, with PLC-based solutions offering advantages over the traditional dedicated robot controller. So, what needs consideration when chosing the right solution for the application? Mitsubishi Electric’s Product Manager Barry Weller considers how to determine which robot control option is best.

Although the choice of robot controller may appear simple, it influences the machine capabilities and ease of set-up and operation. Getting it right improves system flexibility, avoids compromising performance and improves productivity. It also simplifies commissioning for machine builders and integrators and reduces changeover time for operators. Following best practices and principles, supports controller selection to meet their application requirements and maximise productivity and Return on Investment.

Benefits of a PLC-based controller

PLC based control options empower robot integrators to develop bespoke systems using the many PLC or motion control products available. One example is Mitsubishi Electric’s iQ-R PLC based robot controller which includes kinematics to control many different types of system. It enables an Original Equipment Manufacturer (OEM) to design and build a bespoke robotic solution. For example; a 2-axis gantry pick and place or a 4-axis delta arm for packaging.

An example of an application like this would be the control of a bakery tin store. The motion profile of this application is a simple pick and place operation with 2 or 3 axes of control. But the mechanics can be very large, often having to span tens of metres of the store. Using the built-in kinematics of the iQ-R PLC system reduces the setup times and programming of the control system, either by teaching the tin positions, or using the co-ordinates calculated in the control system. This system also allows the simple integration of other axes into the system; for example, system expansion could include the control of the delivery system, bringing the tins into, or away from the store.

Choosing a PLC-based robot control option may seem like the most cost-effective choice. Designing a bespoke system may offer a price advantage as it is often cheaper to buy a kit of parts and build the system from scratch than invest in a traditional robot arm. The application will determine the best approach but designing in this way allows the OEM to create a tailor-made solution.

Benefits of dedicated robot controllers?

Yet, it is important to consider the design time of the mechanical system, the flexibility required from the manufacturing cell, the cell footprint and the configuration and engineering time. It is often the case with an OEM having many identical systems to build and would show cost savings.

Selecting an off-the-shelf dedicated robotic system addresses this. For example, a typical 4-axis SCARA (Selective Compliance Articulated Robot Arm) system is available at a very competitive price. Importing the design of the robot mechanical system and its CAD model into the machine design saving time and cost. During constriction, the robot is also simple to install and needs four bolts to mount it into a machine. Programming is also fast, taking less than an hour for a simple operation.

The controllers contain hundreds of dedicated instructions that make the more complex functions such as tracking a product along a moving conveyor or complying with an external force, easy to integrate as they are already built into the system.

Further benefits come when considering machine safety. Dedicated robot controllers must conform to industry standards that cover their design, which includes safety. This makes it simpler for the system designer to integrated safety system for the total machine by using compliant components.

Selecting robot controller

If the choice between dedicated or PLC-based robot controller is still in the balance, Mitsubishi Electric can support machine builders and robot integrators alike in selecting the most suitable alternative. Customers can choose between state-of-the-art PLCs and dedicated robot controllers to match the requirements of their systems.

Mitsubishi Electric offers advanced MELFA robot controllers that allow users to programme the robots with Mitsubishi’s RT-Toolbox engineering environment. For PLC-based control, Mitsubishi Electric’s iQ Monozukuri Handling Suite empowers users to take control of movement and information management tasks. It also integrates the company’s high-performance controllers with robots, HMIs and other compatible automation components.

When the choice of robot controller is unclear, Mitsubishi Electric offers the unique option of integrating a dedicated robot controller into the PLC rack. The controller is compatible with their iQ modular PLC platform including many functional controllers, I/O and networking options.

Finally, the control requirements and the physical attributes of the application often dictate which option is best. For machine builders and integrators, it seems sensible to adopt a flexible, integrated automation solution that offers choice and scalability.

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