System Integration & Small Electric Actuators

Submitted by Ric Leyva for Design News Magazine
As the automation and motion control needs of industries using control and drive functions continue to change and progress, the technology that meets those needs must adapt to the growing demand for connectivity, accessibility, and efficiency, all while maintaining a high level of quality and durability. On both the OEM and end-user side, key decision makers have begun to embrace technology that advances the functionality of automation and motion control processes while increasing efficiency and reducing overhead. While each industry uses different configurations of these technologies, there are often clear trends that guide the advancement of the automation and motion control field as a whole.

Two such trends that have recently emerged in the automation and motion control industry include:
  • The integration of safety, vision and motion control systems into one unified platform
  • A large shift from small pneumatic actuators to small electric actuators
This last shift is due to recent technological developments that give electric actuators advantages in terms of energy cost, cleanliness, and controllability. Both of these innovations are driven by the need for increased connectivity and efficiency in control operations.
Electric Actuators
In older automation control systems, multiple aspects of a single operation were driven independently by unique programmable logic controllers (PLCs), vision controllers, safety devices, and motion controllers with little interconnectivity. These controllers would drive the motion, safety, and vision systems separately from one another, only communicating information vital to the success of the operation. This lack of connectivity led to an increased workload for users operating the software and/or machinery when decisions involving multiple systems needed to be made. For example, if a particular component involved in the motion system was not correctly aligned, the user would need to examine the data from the vision system and implement the changes on the motion controller.

With the new development of seamless system integration on one platform, these control decisions can be automated across multiple systems involved in the same process by a single controller that communicates with each system simultaneously. The user is now given real-time control of motion, vision, and safety systems all available via local or remote access with configuration, programming, simulation, and monitoring software available at the touch of a button. The advantage of these new integrated systems can be explained through the analogy of one computer plugged into one printer versus one computer connected to a network with multiple printers available, all of which can be accessed from a single point. Seamlessly integrating each of these control systems into one platform allows for the greatest range of control options available in the industry to date.

This advanced automation platform has been found particularly useful in submicron positioning applications with 4 axes of motion. Operators using the platform were able to use a vision system to determine the target and adjust the position of the motion control system, achieving sub-micron positioning by using the off-the-shelf vision system as an encoder feedback mechanism. This type of integrated control option would not have been available without each system connected on a single network.

Another benefit of an advanced automation platform is the increased flexibility provided by including the safety system on the same network as the rest of the control functions. Previously, safety systems had to use hard I/O inputs separately from the control system. This required hard wiring for connectivity and interaction with any other system component. With the inclusion of the safety system on the same integrated network, hard wiring is no longer needed because the safety system is now connected to every other aspect of the operation. This allows for greater flexibility when involving the safety system in any other vital part of an operation. While the industry has been slow to adopt this system due to the critical importance of safety systems, combined with skepticism over the abilities of the integrated platform, more end users are beginning to utilize the flexibility offered by this approach.

The second trend that has become more apparent recently is the industry moving from small pneumatic actuators to small electric actuators. The benefits of electric actuators have long been underwhelming due to size and cost limitations, but in recent years electric actuators have caught up to pneumatic actuators in terms of size, variety of configurations, and cost, and end users are beginning to take notice.
Integrated Motion Logic Vision System
When it comes to the cost of a pneumatic actuator, there are multiple factors to consider besides the cost of the actuator itself. These include air and electricity costs, and maintenance and operational efficiency. While electric actuators are still more expensive than pneumatic actuators, they have a clear advantage in every other category of cost comparison. Small electric actuators can achieve an efficiency of 70% to 80% while small pneumatic actuators only reach between 20% and 30%. Also, in side-by-side comparisons of rodless air cylinder/slider type pneumatic actuators and cylinder/slider type electric actuators, the electric actuators were proven to average only 28% of the power consumption of pneumatic actuators on an annual basis. This resulted in a 72% reduction in electricity costs. Electric actuators also have the clear advantage of zero air consumption, which immediately reduces a large portion of the overhead associated with pneumatic actuators.

Another area in which small electric actuators are superior is cleanliness. Pneumatic actuators have been known to cause leaks and contamination in sensitive operations, but this is simply not an issue with electric actuators.

Additionally, electric actuators are far superior to pneumatic actuators in terms of controllability. Where pneumatic actuators typically have a motion range limited to two positions (fully extended or home), electric actuators can be configured to achieve any number of positions. Electric actuators feature controllable parameters including position, speed, and acceleration, leading to superior repeatability in comparison to pneumatic actuators. In operating conditions, electric actuators designed to replace pneumatics have been able to achieve a repeatability of 50 microns, while pneumatic actuators have only performed repeatable operations within hundredths of an inch.

Currently, the primary reason many end users are converting to small electric actuators is for the financial benefit. In the automotive industry, compressed air is a large expense on an annual basis, and many manufacturers have made the decision to utilize electric actuators to eliminate that cost. However, some industries also benefit from the additional advantages that small, cost-effective electric actuators offer. In one semiconductor application, electric actuators were used to achieve the necessary precision for an operation, which pneumatic actuators could not accurately perform.

As the industry has grown and adapted to the various types of automation and motion control solutions, achieving the desired result with the least cost and effort on behalf of the user has always been the top priority. With these new trends quickly on the rise, end users can look forward to an ever-improving crop of automation solutions to choose from.

Ric Leyva is business development manager for Valin Corp.

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