As industry continues to evolve and machines come equipped with a growing number of drives and data-collecting sensors, organizing the automation of every machine component becomes an increasing challenge. Most modern machine automation setups include programmable logic controllers (PLCs) for simple devices, drive controllers for advanced motion control, and personal computers (PCs) or human-machine interface (HMI) terminals for operator visualization of machine components.
As machines become more sophisticated, each automation component relies more on data from others. This necessitates data exchange among the controllers driving each component, which requires design and development integration effort, both initially and throughout the lifecycle. Open controllers, available from multiple vendors, combine many functions into one platform to address these and other issues.
Open Controllers Provide Automation and Visualization
Rather than going through the hassle of establishing and maintaining data exchange among controllers, an open controller blends the functionalities of a standard automation controller, drive controller, and HMI into a single, PC-based platform. This simplifies access to data because the open controller becomes the single repository for tag storage and eliminates the need for data exchange among multiple controllers and an HMI.
In addition to tag storage, open controllers can host the same types of algorithms machine builders and manufacturers are familiar with from standard automation and complex motion controllers — using ladder logic, function block diagram, and structured text routines — as well as high-level language program code like C++ (Figure 1). As compared to standard controllers, open controllers include higher capacities of program and data memory in their cyclic execution routines.
The added memory enables these controllers to integrate directly with data contained by and algorithms processed within the PC operating system (OS) portion of the controller. Recent iterations of open controllers are equipped with quad-core PC processors and 8 gigabytes of random-access memory, optimizing performance with third-party applications such as resource-intensive image processing software.
Because the PC-based software processes run on the same device handling machine I/O and motion control, there is less time required between input detection, OS computation, and output control. This increases machine efficiency because it cuts out time for data exchange between the I/O or motion controller and a separate PC performing computation. With a hybrid controller, all automation software and hardware functions can be programmed in a common development environment, limiting the amount of training required to code routines (Figure 2).
Despite the simplicities offered by consolidation, manufacturers may be concerned about depending on a PC OS for system availability. To address this concern, open controllers are designed to continue cyclic program execution for basic automation and motion control independent of the PC OS, including uninterrupted execution during OS shutdown or reboot.
In case of OS failure, open controllers come with built-in backup and restore procedures to mitigate consequences and get the OS back into operation. Some open controllers also include an integrated web server with pre-compiled hardware diagnostic information to aid in quick recovery following a hardware-related failure, helping reduce downtime.
For further diagnostic and control capability, the most advanced open controllers take functionality beyond automation and motion to include HMI runtime software. This type of integrated device provides standard I/O control and motion control, can execute PC applications and algorithms, and can host operator visualization — all without the need for any additional devices. Furthermore, open controllers typically support communication with Industrial Internet of Things (IIoT) devices and they can control multiple machines and plant operations in a distributed configuration.
Open controllers and their I/O modules — including safety, communication, and motor starter modules — are connected via an integrated backplane bus, providing flexibility to fit a variety of control cabinet spatial layouts (Figure 3). Because open controllers work with many machine types, applications are highly scalable, giving manufacturers the freedom to add new lines and cell areas to existing control schemes.
As plants scale, application code can be reused from one controller to another through global libraries. Additionally, most open controllers ship with a library of ready-to-use objects including safety functions. This eliminates the need for a separate safety controller because it combines standard and fail-safe tasks into its cyclic program routine.
While machine safety is of critical concern, software security cannot be overlooked in today’s age of cybercrime and exploitation. Therefore, open controllers are typically equipped with programming and operation access protection, program manipulation protection, and intellectual property exposure protection.
Motion Control with Open Controllers
In many respects, especially due to its small footprint and modular hardware design, an open controller feels like a standard automation controller with an independent PC OS but motion control capabilities are also included. On top of the single-axis speed and position control included in some standard automation controllers, open controllers usually allow for gearing and camming including:
Synchronization with specification of leading and following axes
Setpoint value coupling
Actual value coupling with extrapolation
Some open controllers also enable kinematic control with up to four interpolating axes to handle applications like pick-and-place machines. These controllers can also conduct cross-controller synchronous operation for expansion and complex line production machine layouts in addition to various other functions — such as pulse-width modulation — by utilizing I/O expansion modules. Motion safety libraries are often included as optional software add-ons.
For programming motion control, the software interface commonly includes a cam editor, a kinematics configuration editor, a kinematics trace, and a tool for coordinating traces among multiple controllers. These tools enhance an open controller’s ability to scale because they allow connection of multiple drive systems to a single controller (Figure 4).
Common open controller motion control application examples include:
Positioning and speed setpoints: palletizers, hoisting and vertical conveyors, feeder and door control systems, conveyor belts, and auxiliary drives.
Coordination (synchronous operation, cams): synchronized axes (including cross-controller coordination), cross cutters, and flying shears.
Kinematics functions with conveyor tracking: cartesian gantries, roll pickers, articulated arms, delta pickers, selective compliance assembly robot arms.
Less is More
While technological advancement drives change on the plant floor, it can be an overwhelming challenge for manufacturers to keep up and maintain a competitive edge. Sensors, robots, drives, and other machine components are constantly improving, accompanied by new data collection mechanisms and control solutions.
If manufacturers continue to rely on complicated networks of yesterday’s controllers to exchange a growing amount of data, messy or incomplete data transactions can hinder productivity. But when manufacturers simplify their machine networks with hybrid PC-based open controllers, it is easier to reintroduce order and capitalize on machine equipment advances.
Savvy manufacturers recognize the benefits of consolidating many tasks into a single, high-performing controller to speed application development, simplify data exchange, and reduce downtime.
This article was written by Kevin Wu, SIMATIC Motion Controllers product marketing manager, at Siemens Industry, Norcross, GA. For more information, visit here .