Move Over Sensors: Actuators Are Entering The Smart Factory Stage

by Michael Jackson, Brian Condell, and Konrad Scheuer

Smart sensors often steal the limelight 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 a programmable logic controller (PLC) to know what's happening on the factory floor, actuators (Figure 1) are the unsung heroes that provide the 'muscle' that gets things done. The unbalanced focus on sensors could be attributable to the fact that many people aren’t aware that making actuators ‘smart’ can deliver significant rewards for factory managers. This blog explores some of these benefits before presenting a reference design demonstrating the advantages of using IO-Link to enable a practical smart factory actuator to communicate with a PLC. To catch up on the previous blog post find it here.

Figure 1 Actuators - the unsung heroes on the factory floor - are becoming smarter

Mechanical to Electrical to Microelectronic Control

Actuators traditionally used mechanical principles (pneumatic, hydraulic) to open and close valves, but electrically controlled motors have replaced these in many applications. Nonetheless, actuators will always have moving parts. These create friction and require ongoing monitoring and maintenance to prevent the type of failure that could cause production to stop unexpectedly. The addition of low-voltage electronics allows factory operators to perform their tasks in much cleverer ways. Some of the advantages microelectronic technology brings to actuators include the following:

• Low power switching: Historically, electrical actuators relied on power-inefficient and unreliable relays, but nowadays, onboard electronics implement H-bridge-type switching, making them easier to control using low-level power signals that also improve safety by reducing the risk of electric shock. These also help to simplify the design by enabling the use of control components with lower power ratings. In addition, using onboard electronics to manage power reduces current at the switches or contacts, allowing a more efficient and lower-cost system design.
• Position feedback: Understanding exactly where an actuator is at every point in a cycle of operation is a significant benefit of using integrated electronics. Advanced position control, using encoders, enables a wide range of movement profiles. Any variations in these can trigger adjustments and alarms or an automatic system shutdown if required, safeguarding against irreparable damage.
• Condition-based monitoring: By monitoring their own state (condition), smart actuators provide operators with an additional safety net against costly damage and associated replacement or repair. For example, they can monitor temperature (a vital metric where moving parts are concerned), voltage, and current levels and act accordingly to mitigate the cause or, if necessary, take protective measures. They also collect data about the number of operating cycles they have performed and send automatic reminders when maintenance is required. Increasingly they are also integrating intelligent algorithms to monitor vibrations and noise as potential indicators of excessive wear and tear in mechanical components.
• Real-time communications: Position feedback, condition-based monitoring, and other diagnostics are only useful if they are actionable. Such information must be shared with a PLC across an industrial network. With so many different Fieldbus protocols and versions of industrial Ethernet, one of the most significant decisions for smart actuator designers is which one to use.

Get Up and Running with a Proven Smart Actuator Reference Design

Analog Devices and TMG TE collaborated to design the MAXREFDES278# 8-Channel Solenoid Actuator reference design (Figure 2), based on the MAX22200 1A Octal Integrated Serial-Controlled Solenoid Driver IC (with integrated FETs) and the MAX22514 IO-Link transceiver (with integrated protection). The MAXREFDES278# has an industrial form factor, with each solenoid channel having a dedicated 2-way terminal block. It measures 85mm x 42mm and uses an industry-standard M12 connector, allowing a 4-wire IO-Link cable to connect it to an IO-Link master transceiver like the MAX14819.

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

This reference design can be powered in two ways. For example, the first is through the IO-Link master directly (delivering up to 800mA total load) or using an external power source to provide higher currents. The MAX17608 current limiter is used, with over-voltage (OV), under-voltage (UV), and reverse protection to ensure that the IO-Link portion is always powered and so that no current can 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 which can flag if the actuator malfunctions allowing it to be quickly attended. Another advantage of using IO-Link is that it makes the actuator 'network agnostic', meaning it will work on any industrial network, so engineers don't need to worry about which protocol their actuator design uses.

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