Global competition is pressuring device or machine builders to deliver equipment that increases throughput while reducing operating costs and energy consumption. Responding to this, equipment builders have switched from designing single-purpose machines to creating flexible and effective multipurpose devices by adopting modern control systems. By: Rejwan Ali, Marketing Engineer, National Instruments
Asia is becoming the world’s manufacturing hub. Alongside China, Southeast Asia has also emerged as a strong manufacturing centre, following improvements in infrastructure and technology. Nevertheless, intense global competition is still pressuring device or machine builders to deliver equipment that increases throughput while reducing operating costs. Rising energy costs and environmental awareness are also prompting engineers to design for lower energy consumption as well, as they seek to align with the Paris Agreement goal of keeping average temperature rise as close as possible to 1.5 degrees Celsius maximum. Responding to this, equipment builders have switched from designing single-purpose machines to creating flexible and effective multipurpose devices by adopting modern control systems and sophisticated algorithms and integrating high-end electronics and communication technologies into mechanical structures.
Motion Controller Technology Trends
Motion control is critical to these mechatronic systems. To optimise the mechanical systems, machine builders often substitute mechanical parts with electronic solutions. One example is the elimination of rigid shafts to perform camming operations. These shafts are replaced by a combination of drives and motors that rely on control software to provide camming functionality. Such systems and devices are mechanically more flexible, easier to maintain, and smaller. However, caveat emptor: These machines also contain more electronic components and require complex control and deterministic and reliable communication.
In a typical system, the motion controller takes most of the burden of the increased complexity. By handling multiaxis synchronisation, these controllers offer gearing and camming functionality as well as all the additional safety features such as limits switches, drive enable, and emergency stop. Besides that, the motion controller still needs to provide the traditional functions and run the control algorithms for maximum performance and efficiency.
Traditionally, motion control applications used a dedicated and separate motion controller to handle greater control complexity. The increasing performance of today’s automation controllers, such as programmable automation controllers or programmable logic controllers, is fuelling a trend to integrate the functionality of the motion controller directly into the automation controller and run it as a high-priority task with other automation tasks.
Since the early 1980s, automation systems have been based on digital buses to perform tasks such as transferring process data and performing industrial communication. Compared to analogue buses, they are more reliable and robust, especially for communication via long distances. In addition, digital networks simplified the wiring because they allow connecting multiple elements in a serial fashion instead of connecting each element individually. This results in significantly cheaper cabling and easier-to-maintain systems.
Because of the performance requirements, for many years the motion industry took a different approach and connected to the drives via an analogue bus or specific motion buses. This additional communication scheme increased the complexity of the overall system. With the digital drive trend and high-performance digital buses, it is now possible to simplify the system architecture by using the same bus for motion control and process data and, at the same time, gain significant performance improvements through the advantages of digital buses such as EtherCAT, CANopen, PROFIBUS, Ethernet POWERLINK, or SERCOS.
Especially in applications that perform distributed multiaxis motion control, digital buses offer a lot of advantages. They provide higher flexibility and allow the development of systems with distributed processing power and decision making down to the level of the drives. With common standards, customers can easily combine systems from different vendors and choose the best solution for their individual tasks.
By using digital drives that communicate over digital buses, vendors and manufacturers are able to create drives that use the digital bus to not only exchange control-relevant data but also transfer status information or set up parameters. One of the big questions automation customers ask is, which protocol is right for industrial automation applications in general and motion applications in particular.
The most common Ethernet-based protocols for motion applications are the following:
- SERCOS II/III
- Modbus IDA
- Ethernet POWERLINK
Because of the large number of different bus standards and protocols, customers need to make sure that the components they want to use provide the right interface. This means manufacturers are often forced to develop several different versions of their components. This adds development cost and the requirement to engage in multiple standardisation organisations. With their efforts to provide open systems, companies like National Instruments incorporate interfaces to various bus standards and protocols.
While offering support for all of the major industrial protocols and providing connectivity to all of the standard industrial networks, National Instruments selected EtherCAT as the premiere communication protocol for motion control applications.
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