Keeping engineers in the loop

Louise Smyth

Hardware in the loop (HIL) is a type of real-life simulation used to test industrial control systems. Here, Jonathan Wilkins explains how HIL simulation can reduce bugs

In 1945 at Harvard University, a moth was removed from one of the earliest computers, the Mark II Aiken relay calculator.

Taped into the log book with the annotation “first actual case of bug being found”, this was the first time the word bug was used to describe a computer problem.

Debugging, the process of finding and resolving defects that prevent correct operation of a computer system, is quite different nowadays.

HIL is a type of real-life simulation which is used to test industrial control systems.

The control system, instead of being connected to the plant, is connected to the HIL simulator, which accurately mimics the plant in order to test the system’s capabilities.

HIL has many benefits, including its ability to test under conditions that would overload a real plant. It also helps increase the safety and quality of testing, saves time and money and allows for machine control testing in emergency conditions.

When used from an early stage, a simulator can grow with the real plant, allowing control engineers to continuously test the plant and reveal problems or errors before any damage is done.

Usually, errors are detected when the control system and plant are integrated, resulting in a busy and complex communication. Problems discovered here can become very costly as experts are drafted in.

Detecting the same problems early allows for the plant and control system to evolve convergently, reducing both the chance of problems and the associated costs.

In some instances, HIL can allow for more visualisation than the user would typically get during real operation, for example by showing a portion of the machine which is underwater. This results in an increased awareness of the machine, thereby improving safety.

While safety improvements are vital, they are often difficult to achieve. HIL is one way in which to ensure safety standards are as high as possible from the moment the plant is designed.

There are two ways in which hardware in the loop can aid safety. Testing some machinery is dangerous, and may require extensive safety procedures.

Hardware in the loop can allow for testing these machines in a safe and controlled manner, with no risk of harming people or the environment.

In addition, this allows for testing of extreme circumstances which may damage the actual piece of equipment.

The correct action to be taken in emergency situations can also be tested, both the human control and the control system input.

This means any flaws can be detected and processes and procedures improved upon, directly increasing the safety of the machine and plant.

The process of debugging may have become more complicated than removing a physical insect, but removing bugs and errors before they cause problems in the industrial plant remains essential for safety and efficiency.

Jonathan Wilkins is marketing director of industrial obsolete parts supplier, EU Automation