Global electronics brand Xiaomi recently revealed its first fully automated manufacturing plant in Beijing. Dubbed as a ‘dark factory,’ this facility entirely relies on AI and robotics to create one smartphone every second. The term stems from the fact that it operates in total darkness, as robots don’t require lights to see.
It’s a glimpse into the future of factories, though whether this will be the case remains to be seen. Full automation remains a prototype owing to challenges ranging from high costs to the risks of single points of failure. Nevertheless, industry experts agree that industrial automation systems are rapidly becoming the new norm.
Factories and other heavy industries are urged to embrace automation, lest they lose their advantages to rivals in today’s economy. One step in the right direction involves integrating safety programmable logic controllers (PLCs) into their automation systems.
Safety PLCs Explained
PLCs succeeded mechanical means of automation (e.g., drum sequences, closed-loop controllers) due to the latter’s rigid nature. Whereas updating legacy control logics required rewiring the hardware and updating their documentation, PLCs harness real-time data gathering and update their assigned automated functions based on said data.
As PLCs grew more widespread across the manufacturing sector, calls for stringent safety requirements necessitated their evolution. This gave birth to a new breed of PLC: the safety PLC (sometimes called a programmable safety controller).
While carrying the same functions as normal PLCs, safety PLCs from suppliers like Venus Automation also carry safety functions that ensure a factory or plant’s functionality. Some of these include the following:
- Dual-channel redundancy: The safety PLC comes equipped with two channels or input/output (I/O) points. In the event of one channel suffering a technical problem, the other channel can temporarily take over operations.
- Self-diagnostic capability: The safety PLC continuously run self-diagnostics to identify issues and, if confirmed, revert the system to a safe state. Such a response reduces the risk of industrial equipment suffering costly damage due to continuous operation.
- SIL-3-compliant design: A safety PLC is required to achieve a Safety Integrity Level (SIL) of 3 based on values specified under IEC 61508. In this case, the probability of failure on demand should be within 0.001 and 0.0001.
Safety PLCs are essentially early warning systems. Upon detecting an anomaly or problem with the equipment, they initiate protective measures until the problem can be addressed. They’re used in many industries—from automotive to mechanical engineering.
Significance in Robotics
As mentioned earlier, industrial automation is an inevitability moving forward, and recent numbers back it up. In a study of manufacturers in Germany, Malaysia, and the U.S., over half are already integrating robotic hardware. Roughly a fifth of them are also considering adopting robotics within the next five years.
In another study, India’s industrial sector posted a record-high rate of robot installations in 2023 at 59%. The automotive market fueled its growth the most, with the demand for robot installations more than doubling for automotive assembly and parts manufacturing.
Industrial automation has been on the rise throughout the decade, but it was only after the pandemic that the writing was finally on the wall. The loss of human labor to absences due to disease and quarantine measures prompted factories to invest in robotic systems. The ongoing global labor shortage has only furthered such decisions.
However, increased adoption of robotics in manufacturing isn’t without its share of risks. Outside of the possibility of layoffs, the more prevalent risks include:
- Unexpected movement: Sophisticated programming carries the risk of the robot performing unexpected or unwanted actions. These account for a large number of work-related injuries, ranging from fractures to finger amputations.
- Electrical hazards: A robotic system’s delicate circuits are susceptible to power surges, which can result in critical hardware failure. Similarly, nearby workers are vulnerable to electrical currents running through the wiring.
- Collision hazards: Inadequate spacing between robotic systems risks them hitting one another (or a worker unknowingly stepping within their space) during operation. Mobile robots are especially prone to this due to their constant movement.
- System errors: No robotic system works flawlessly. Besides unexpected actions, it can also suffer from errors due to inconsistent, if not anomalous, input. Such problems can prompt the whole system to cease operations for safety reasons.
While safety features like I/O processing are inherent in automated systems, they aren’t designed for environments that use multiple I/O points. According to the Association for Advancing Automation, PLCs are highly recommended for better coordination between equipment and data handling.
Take robotic arms, for example. Their typical system architecture, a two-vendor setup, necessitates working with PLCs. The arms’ control module facilitates their range of motion, whereas the PLC manages the wider system. Connectivity is provided through a range of protocols, such as Ethernet, serial communication, or I/O signals.
Compliance with Safety Standards
A key advantage safety PLCs possess over their conventional counterparts is their design’s compliance with international safety standards. Factories and other facilities seeking ISO or other forms of accreditation would benefit from investing in compliant hardware.
Most standards that safety PLCs comply with fall under the purview of the International Electrotechnical Commission (IEC). General requirements are outlined under IEC 61508. As a safety-related system, safety PLCs under this standard must function as intended or fail to do so predictably.
The application of other IEC standards depends on the application. For instance:
- IEC 61131 – recognized programming languages for logic systems in safety PLCs
- IEC 61511 – practices for designing safety PLCs in Safety Instrumented Systems
- IEC 62061 – requirements for the implementation of safety PLCs in machinery
On the ISO side, safety PLC design and construction also adhere to guidelines under ISO 13849. This standard defines principles for the design and construction of safety-related parts in machinery. It’s the ISO equivalent to IEC 61508, though it features a different focus and set of compliance metrics.
Integrating Safety PLCs
It goes without saying that safety PLCs are a staple of industrial environments. Their value in regulating the actions of robotic systems is proof enough, but manufacturing integrates them in other ways.
One application as common as robotic safety systems is an emergency shutdown routine. An emergency stop button enables a factory or plant to stop normal operations quickly in case of hazardous conditions (e.g., gas leaks). Also called process shutdown systems, these features are a must in facilities that handle hazardous materials like oil and gas.
Another application involves sensors in machine guarding systems. Sensor inputs by safety PLCs can prevent machinery and robotic equipment from operating unless all factors have been satisfied (i.e., no obstructions within the vicinity). Such systems reduce the risk of costly equipment damage and worker injury.
In Conclusion
As industrial robotic integration grows, efficiency and safety have also escalated in priority. Whether for a dark factory or one with more robots than people, safety PLCs should be no less a part of the evolution. Their ability to limit or manage automation in critical processes can mean the difference between significant gains and crippling losses.
