In the world of technology, people often speak of real-time capability. Real-time processing is indispensable in many areas – from computer technology, automation, to fieldbus systems and mobile telephony. But what exactly does real-time capability mean in this context, and why is it so important?
Real-time capability relates to systems that respond to external events or data in a defined, predictable time. The reaction time is so short that the system virtually “immediately” reacts to the events. A distinction is made here between three types of real time, which must be implemented depending on the application requirements:
Hard real time
Strict time conditions must be adhered to here. Any exceedance of the time limit can lead to critical malfunctions. A good example of this is the anti-lock braking system (ABS) in cars. If you step on the brake, the ABS must respond immediately to prevent the wheels from locking up. Any delay, even in the millisecond range, could have serious consequences, such as an accident. In systems like this, any delay beyond the defined time limit is considered a malfunction.
Soft real time
These are systems where occasional delays are acceptable, as long as the performance remains good on average. A good example is streaming videos. If the video usually runs smoothly, but occasionally buffers, that is OK. The user experience is not significantly impaired. Soft real-time systems are therefore more flexible, because they tolerate small delays, as long as the overall performance remains within an acceptable range.
Fixed real time
Fixed real time is less strict than hard real time. Even though time specifications are important, exceeding the time limits does not necessarily lead to serious consequences. In systems like this, the result or a message is irrelevant or useless after the set time expires.
From the second to the millisecond range
Real-time requirements in technology vary greatly depending on the application, where the time specifications span from seconds down to the millisecond range. In logistics, in automated warehouses for example, robots and conveyor systems can be timed based on seconds. The real-time movement of goods from one point to another is important, but delays of a few seconds can usually be tolerated.
In the event of a vehicle collision, however, the acceleration sensor data must be used to deploy the airbags as quickly as possible, while taking the force and position of the impact into consideration. This decision is made within 20-30 milliseconds to ensure effective protection. Any delays could put the safety of the passengers at great risk.
Modern Industrial Ethernet networks are often used in the field of industrial networking of devices. People also often speak of a real-time capability of networks here. One example of this is EtherCAT. During its development, particular attention was paid to short cycle times (≤ 100 µs) and a low jitter. When designing a real-time capable complete system, all subcomponents are crucial, from the networking of sensors and actuators and data transmission to the data processing.
In summary, it is evident that real-time processing is a key aspect in many technical areas, from automation technology, computer technology, to mobile telephony. Real-time processing refers to the capability of systems to respond quickly to external events. Depending on the application requirement, a distinction is made between hard real time, where strict time conditions must be observed (as with ABS in cars), soft real time, which tolerates occasional delays (as with video streaming), and fixed real time, which has less strict time specifications. The time requirements vary greatly depending on the application, from seconds to milliseconds or beyond.