1. Fraunhofer Institute for Manufacturing Engineering and Automation IPA, Nobelstraße 12, 70569 Stuttgart, Germany
2. Hochschule Reutlingen, ESB Business School, Alteburgstraße 150, 72762 Reutlingen, Germany
3. Institute for Energy Efficiency in Production EEP, University of Stuttgart, Nobelstraße 12, D 70569 Stuttgart, Germany