As system integrators, we’re the ones responsible for delivering process control systems to manufacturers. We focus on understanding the process design, making sure that the process is automated well, and that operators are alerted to process upsets. The process I’m talking about here is what makes the products that get shipped out the door. No matter if it’s grains or garden hoses, that process was developed by people, then refined and perfected over time and is controlled by a computerized system.
Or is it?
While some people initially designed the process, different people run the process day-to-day. These people get help from the control system, of course, but they are the ones responsible for making the products and getting them out the door.
When you consider this there are two processes involved in producing your product(s). There is the process employees go through of parking their car, badging in, having a shift change meeting, getting pallets in the door, getting products out the door, having another shift change meeting, and getting back in their car. These processes are separate from the designed production process but need to be considered in the overall process.
To approach this consideration correctly, ask these kinds of questions: How much of the employee’s work day is spent at a computer? How much of their time is spent starting sequences, checking interlocks, clicking buttons and/or browsing 10 different HMI displays? How much of the operator’s attention is on the control system and how much attention is on the process that’s running on the plant floor? Is their control system requiring too much attention when they could be accomplishing more important things?
While the systems integrator’s primary goal is automating the production process, the integrator must also understand that the control system is just one of the many tools used in an employee’s overall workday.
When designing the process control system, integrators need to consider all aspects of the operator or technicians workday processes. Integrators should think about: How can we reduce the number of HMI screens they need to be browsing? How can we reduce the number of clicks and keystrokes required? How can we reduce the number of decisions and attention required to get product out the door?
Such questions are important because it’s the integrator’s job to design the system in a way that the operator can glance at an HMI, see what they need at just the right time and go elsewhere to continue doing their job.
Dashboards (controls overview screens) can help with this. Since many operators are in the habit of monitoring the production process from the HMI, integrator should help build-in situational awareness as a key component of the operator’s daily processes. This can be achieved by showing key performance indicators on the HMI in a way that grabs attention only when it’s required. Integrators should strive for 90% of the operator’s typical HMI interactions to be done from the dashboard on a good day.
When the inevitable production process upsets occur, is it reasonable for the automation system to be required to handle it alone, or will operators be required to make decisions to get the system back on track? This point is sometimes overlooked when developing automation systems.
Integrators must give operators the access to intervene as needed to and provide the controls to do so in a way that will not override their decisions. For example, modern control systems give the operator the ability to “lock” a motor in manual mode using software. The operator had a good reason for putting it in manual mode, so the supporting control system should leave it in manual. Of course, a device left in manual mode should be mitigated with permissives, interlocks and alerting instead of allowing the program to force it back to auto. This type of design is much more effective for the operator.
Designing control systems to help with an operator’s daily processes doesn’t happen overnight. It takes time and effort to understand how operators and technicians will use automation in their daily lives. That’s why integrators should focus on making their daily processes easier.
Tim Garnett is senior systems engineer at Malisko Engineering, a certified member of the Control System Integrators Association (CSIA). See Malisko Engineering’s profile on the CSIA Industrial Automation Exchange.
