Sensors take a back seat: Actuators are stepping into the smart factory arena

Smart sensors often get a lot of attention in articles and videos that tout the new achievements and future possibilities of Industry 4.0. While sensors are the eyes and ears on the factory floor, giving programmable logic controllers (PLCs) insight, actuators (Figure 1) are the unsung heroes behind the scenes, giving instructions the muscles to get all the work done. The excessive focus on sensors may be because many people don’t realize that making actuators “smart” can pay off big for factory managers. This blog post first explores some of the benefits of smart actuators, then introduces a reference design that demonstrates the benefits of using IO-Link to enable practical smart factory actuator-PLC communication. Click here to read the previous blog post.

Figure 1. Actuators, the unsung heroes of the factory floor, are getting smarter

From mechanical control to electrical control to microelectronic control

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

• Low-power switching: Previously, electric actuators relied on inefficient and unreliable relays, but now on-board electronics enable H-bridge switching, making actuators easier to control with low-level power signals while also reducing the risk of electric shock and improving safety. On-board electronics also allow the use of control components with lower power ratings, helping to simplify the design. In addition, using on-board electronics to manage power can reduce the current on the switch or contacts, resulting in a more efficient and lower-cost system design.

  
  

• Position feedback: One of the great benefits of integrated electronics is knowing exactly where the actuator is at every point in its operating cycle. Advanced position control using encoders allows for a wide range of motion profiles. Any changes in these can trigger adjustments and alarms if necessary, or trigger an automatic shutdown of the system to prevent irreparable damage.

  
  

• Condition Monitoring: By monitoring their own state (condition), smart actuators provide operators with an extra safety net to prevent costly damage and the associated replacement or repair. For example, actuators can monitor temperature (critical for moving parts), voltage and current levels, and take appropriate action to eliminate the hazard or take protective measures when necessary. Actuators also collect data on the number of work cycles performed and send automatic reminders when maintenance is required. Increasingly, actuators are integrating smart algorithms to monitor vibration and noise, which are potential indicators of excessive wear on mechanical components.

  
  

• Real-time communication: Information provided by position feedback, condition monitoring, and other diagnostics can only be truly useful if it is converted into executable solutions. This information must be shared with the PLC via the industrial network. There are many fieldbus protocols and industrial Ethernet versions, and smart actuator designers must carefully decide which protocol and version to use.

Get started quickly with proven smart actuator reference designs

Analog Devices and TMG TE collaborated to design the MAXREFDES278# 8-channel solenoid actuator reference design (Figure 2), which is based on the MAX22200 1A octal integrated serial control solenoid driver IC (with integrated FETs) and the MAX22514 IO-Link transceiver (with integrated protection functions). Designed in an industrial 85mm x 42mm form factor, the MAXREFDES278# includes a dedicated bidirectional terminal block for each solenoid channel and uses an industry-standard M12 connector to support the use of a 4-wire IO-Link cable to connect it to an IO-Link master transceiver (such as the MAX14819).

Figure 2. MAXREFDES278# IO-Link 8-Channel Solenoid Actuator Reference Design

The reference design can be powered in two ways. For example, it can be powered directly by the IO-Link master (supporting a total load of up to 800mA), or an external power supply can be used to provide higher current. The reference design uses the MAX17608 current limiter with overvoltage (OV), undervoltage (UV), and reverse protection to ensure that the IO-Link part is always powered, thereby preventing current from flowing back to the IO-Link master. The advantage of using IO-Link for data communication is that it supports four different types of transmission - process data, diagnostics, configuration, and events. This information can indicate whether the actuator is faulty so that relevant actions can be taken quickly. Another advantage of IO-Link is that it makes the actuator "network-independent", that is, the actuator can work on any industrial network, and engineers do not need to worry about which protocol to choose for the actuator design.