Variable Stiffness Actuators are at home in the field of robotics and Industry 4.0 as well as the Internet of Things (IoT). They are an important technical development because they make machines and robots much more flexible and safer.
A Variable Stiffness Actuator is a special motor or drive that can change its stiffness. Stiffness means how much a drive "resists" external forces. By changing the stiffness, the robot can either be very stable and powerful or particularly compliant and safe. This is important when robots work together with humans or perform sensitive tasks.
A simple example: a robot arm equipped with Variable Stiffness Actuators can lift heavy car parts (while being stiff and stable) and then carefully hold a pane of glass (while being flexible and gentle). This makes factories safer because robots can "give way" in the event of a collision with humans. At the same time, this increases productivity and opens up new possibilities in automation.