Mobile sensors: Actuators are entering the smart factory

Smart sensors often steal the spotlight in articles and videos heralding the latest achievements and future possibilities of Industry 4.0. However, while sensors act as the “eyes and ears” that allow programmable logic controllers (PLCs) to understand what’s happening on the factory floor, actuators are the unsung heroes, providing the “muscle” that gets the work done. The unbalanced focus on sensors may be due to many not realizing that making actuators “smart” can deliver significant rewards to factory managers. This blog explores some of those benefits, then introduces a reference design that demonstrates the advantages of using IO-Link to enable practical smart factory actuators to communicate with a PLC.

Mechanical to electrical to microelectronic control

Actuators have traditionally used mechanical principles (pneumatic, hydraulic) to open and close valves, but in many applications, electronically controlled motors have replaced these principles. Still, an actuator will always have moving parts. These create friction and require constant monitoring and maintenance to prevent the types of failures that can cause production to stop unexpectedly. The addition of low-voltage electronics allows plant operators to perform tasks in a smarter way. Some of the advantages that microelectronics bring to actuators include:

Low-power switches: In the past, electric actuators relied on power-inefficient and unreliable relays, but today, on-board electronics implement H-bridge type switches, making them easier to control using low-level power signals, which also improves safety by reducing the risk of electric shock. These also help simplify the design by using control components with lower power ratings. In addition, using on-board electronics to manage power reduces the current at the switch or contacts, allowing for more efficient and lower-cost system designs.

Position Feedback: Knowing exactly where the actuator is at every point in its operating cycle is a significant advantage of using integrated electronics. Advanced position control using encoders enables a wide range of motion profiles. If necessary, any change in these changes can trigger adjustments and alarms or automatically shut down the system, preventing irreparable damage.

Condition-based monitoring: By monitoring their own condition (status), smart actuators provide operators with an additional safety net to prevent costly damage and the associated replacement or repair. For example, they can monitor temperature (an important indicator when it comes to moving parts), voltage and current levels, and take appropriate action to mitigate the cause or apply protective measures when necessary. They also collect data on the number of operating cycles performed and send automatic reminders when maintenance is required. They are also increasingly integrating smart algorithms to monitor vibration and noise as potential indicators of excessive wear on mechanical components.

Real-time communication: Position feedback, condition-based monitoring, and other diagnostics are only useful if they are actionable. Such information must be shared with the PLC over the industrial network. With so many different fieldbus protocols and industrial Ethernet versions, one of the most important decisions for smart actuator designers is which one to use.

Get up and running with proven smart actuator reference designs

Analog Devices and TMG TE have collaborated to design the MAXREFDES22200#1-channel electromagnetic actuator reference design (Figure 22514) based on the MAX278 8A octal integrated serially controlled electromagnetic driver IC (integrated FETs) and the MAX2 IO-Link transceiver (integrated protection). The MAXREFDES278# uses an industrial form factor with a dedicated 2-way terminal block for each solenoid valve channel. The dimensions are 85mm x 42mm and use an industry-standard M12 connector, allowing a 4-wire IO-Link cable to connect to an IO-Link master transceiver such as the MAX14819.

Figure 2. MAXREFDES278# IO-Link 8-channel electromagnetic actuator reference design

The reference design can be powered in two ways. The first, for example, is either directly through the IO-Link master (providing up to 800mA of total load) or using an external power supply for higher currents. The MAX17608 current limiter features overvoltage (OV), undervoltage (UV), and reverse protection to ensure that the IO-Link part is always powered so that current does not flow back to the IO-Link master. The advantage of using IO-Link for data communication is that it carries four different types of transmissions - process data, diagnostics, configuration, and events, and if an actuator fails, it can be flagged for quick processing. Another advantage of using IO-Link is that it makes the actuator "network agnostic", meaning it can work on any industrial network, so engineers don't need to worry about which protocol their actuator design uses.