At the Emerson Exchange Americas Virtual Series, Emerson’s Alec Grainger, Chris Noble and Ajay Rana teamed up to share how to choose the right motion technology—servo vs. variable frequency drive vs. pneumatics. Here is their presentation’s abstract:
All types of machinery rely on some type motion control to perform their functions, whether it is initiated manually by operators or automatically by more advanced control platforms. Original equipment manufacturing (OEM) designers must evaluate several technical and commercial requirements to strike the right balance when selecting these motion control solutions. Two popular technologies for accomplishing OEM equipment motion functionality are pneumatics and servo motors. In very general terms, pneumatic components are often seen as a cost-effective solution, while servo motors and controls are considered more suitable for high-performance applications.
However, each technology features various benefits and some challenges, and there can be overlap situations where either may be suitable. Numerous options can lead to confusion regarding how to select the right products, and end users often need guidance during the decision process. In addition, newer devices are becoming smarter with built-in industrial internet of things (IIoT) capabilities to help users gain access to data needed for improving operations and maintenance. Better data and analytics made possible by the IIoT is also known as a facet of Industry 4.0. OEMs should become familiar with the range of technologies, benefits, and best-fit applications so they can follow a balanced approach in their designs.
The purpose of this presentation is to provide a knowledgebase comparing the use of pneumatics and servos for equipment motion control to help OEMs choose the best options for their systems. Going a step more into Motion control, we will also evaluate where and how to use VFD and Servos as well. Both technologies are electrical motion based and are used based on the performance and degree of precision needed for an application. It is important for OEM to understand the basics of these so that selection criteria are clear, and one should be using only what is really required. By the end of this presentation you will have, a good understanding of pneumatic and servo and VFD technologies. It will also provide the key points where one technology is better than other one and where to use these technologies either solo in conjunction with other to have a better design and a best solution.
Ajay opened highlighting many challenges in assessing the approach, technique and investment in modern motion technology. These include long and complex machine design development, difficulty in integrating with other devices, lack of familiarity with technologies and their associated learning curves, increased costs, lack of machine analytics & troubleshooting, poor overall equipment effectiveness (OEE) and machine performance, lack of scalability & flexibility, and lack of machine accuracy.
Here are the three types of motion driven in two ways:
Servo motion control includes electronic camming, electronic gearing and positioning. Electronic camming controls the slave axis in synchronization with the master axis according to a pre-defined electronic cam table. Electronic gearing is used when one axis, the slave axis, must move incrementally and proportionately to a register, the gear master, which is typically the position or velocity of another axis. Positioning is point-to-point or automatic positioning which combines multiple point to point moves based on various motion profiles. Example applications include constant gap maintenance, rotary knife and material filling.
Alec demonstrated servo control using PACMotion Servo controllers.
Chris described pneumatic control using a PLC or loop controller which sends electric signals to proportional valves that pressurizes each side of an air cylinders piston. It sends a pneumatic signal to set the desired stroke to achieve the right position. This differential pressure control across the cylinder provides precise pneumatic positioning with controlled pressure on one side and constant pressure on the other.
Some industries for servo pneumatic applications include aerospace, agriculture, packaging and food & beverage. Chris focused on packaging applications in a demonstration:
Servo pneumatics are very compact and provide high force to drive the motion required. Applications may include “pick & place” systems and precise & accurate filling operations.
Ajay summed up these motion technologies with assessment criteria:
Visit the Motion Control section on Emerson.com for more on these technologies to meet the demands of your applications.