When it comes to motion control, there are usually two main types of controllers: PLCs and PC-based controllers. PLCs have been the go-to option for motion control in industrial automation for decades, thanks to their reliability, redundancy, and ruggedness. On the other hand, PC-based controllers have become increasingly popular due to their flexibility, additional features, and IoT capabilities. In this article, we’ll discuss the pros and cons for each, and provide context for LabVIEW users for considering motion control for test and measurement systems.
PLCs (Programmable Logic Controllers)
PLCs have long been popular in the field of industrial automation control since the 1970s, providing highly reliable control applications for various automation control equipment. This is primarily due to their ability to offer safe, dependable, and comprehensive solutions for automation control applications that meet the current needs of industrial enterprises. Some popular brands of PLCs for motion control include Allen-Bradley, Siemens, Mitsubishi, and Omron. Here are some pros and cons about using PLCs:
Pros -
- PLCs are easily accessible in the industrial automation space. Prices start from $2-300 USD, to PLCs with more functionality priced at $500-$1000 USD.
- PLCs have good reliability, redundancy, and ruggedness ratings.
- PLCs can support standalone operation, no need for other HMI inputs such as mouse and keyboard.
- Most vocational schools and technical institutes offer PLC courses, making it easy to find PLC engineers.
Cons -
- Each vendor may have proprietary protocols for communication and data export from PLC.
- Processing power of PLC may be limited*
Note: Early PLCs were microcontroller-based with limited memory, but moderns PLCs have evolved to take advantage of more powerful CPUs.
PC-based controllers
With the advent of the PC and the Internet era, PC-based controllers for industrial automation have been able to fully integrate into the IT systems of the Internet age. They have the basic characteristics of a network system, such as high performance, open system, and a rich talent base. However, PC-based programming is typically more complex than PLC programming. As a result, it can be difficult for an engineer to become proficient in both tools simultaneously. (This may also be why there is an ongoing debate about which is better, PLCs or PC-based systems. 😀)
Here are pros and cons about using PC-based controllers:
Pros -
- Very flexible with open architecture
- Variety of tools at your disposal, including vision analysis. machine learning, and databases.
- Open networking protocols
Cons -
- General purpose OS such as Windows may crash at times.
- Rapidly evolving software stack, need to update and maintain software
What does this mean for LabVIEW users?
For LabVIEW users, the choice between PLCs and PC-based motion controllers will depend on several factors. LabVIEW is an excellent choice for motion control applications that involve acquiring measurement data, as it has strong data acquisition capabilities. Additionally, for research applications, LabVIEW allows researchers to quickly prototype complex algorithms and modify according to new discoveries, making it a preferred choice amongst the scientific community.
On the flip side, if your application does not involve measurements and the motion control is simple (like repetitive back and forth motion), then LabVIEW may not show its value. In such cases, it may not matter much whether you use LabVIEW for motion control or not. You could write a simple PLC program for the motion aspect and use LabVIEW to control the PLC using RS-232 or Modbus commands.
However! There is one downside to the LabVIEW & PLC approach. Now you have two tools and two sets of programs to maintain. For teaching or maintenance purposes, this extra layer of complexity is also something to be considered.
- You need analog measurements and sensor readings.
- You need a GUI for your application.
- You want to keep everything under LabVIEW, and don’t want to use/maintain another tool.
- You need other analysis capabilities, such as Vision
For other motion control scenarios, using LabVIEW becomes a matter of convenience, preference, and/or habit.
Conclusion
As with any tool, it’s important to weigh the pros and cons of each approach. For LabVIEW users, it’s good to clearly know the strong aspects, so that you can take full advantage of LabVIEW for test and measurement. For more information on integrating motion control with LabVIEW, download our free 33-page presentation here:
Integrating Motion Control with LabVIEW - TENET.pdf