UHF-RFID-sensors for online measurements in washing machines

Industrial cleaning of textiles depend, as most cleaning processes, on the four parameters of the ""Sinner's Circle"": chemicals, mechanics, temperature and time. State of the art washing machines are only able to measure the time and the temperature. The latter is arguably imprecise, as the temperature sensor is oftentimes located outside of the drum. For this reason, the machines are not able to work efficiently, as they use incorrect amounts of chemicals, heat and mechanical force, resulting in either insufficiently cleaned or stressed textiles. To increase the efficiency, an RFID-based approach is proposed to employ wireless sensors in the washing machine drum, which could be used to collect the data of interest. In order to overcome the severe influences from water, metal and the rotating drum, a broadband circularly polarized reader antenna, rotation symmetric contactless coupler and tag harvesting method are considered in this paper. The limitations and design considerations are discussed and first results are shown.