Sensor-integrating gear wheel for in-situ measurement (SIZA)

Abstract Defects in machine components can result in costly machine downtime. Sensors are widely deployed to prevent this, and intelligent monitoring systems are implemented. However, these solutions are often custom-made, expensive, and difficult to integrate. Technological advances have enabled the development of small, inexpensive sensors and microcontrollers that can be integrated into smaller components. Integrating these into standard machine elements allows modular monitoring systems with sensors close to the vibration source. This paper presents a sensor-integrated gear called SIZA (German abbreviation: “Sensorintegrierendes Zahnrad”, sensor-integrating gear), which incorporates different sensors and a microcontroller, along with software capable of detecting damage and fatigue and communicating this information to a nearby supervisory master system. The electronic system is housed in customized cavities within the gear body, located directly beneath the teeth, with minimal structural weakening. Since the outer dimensions of the gear remain unchanged, it can be used in various systems. Two generations of prototypes have been developed, and the development process and component selection, including benchmarking, are detailed in this paper. Additionally, customized software has been designed to minimize the microcontroller’s energy consumption and computational time, enabling autonomous wireless monitoring. The experimental measurements show the capabilities and advances of sensors close to tooth contact, which is the source of excitation and heat during gear operation. The SIZA is equipped with temperature sensors at multiple positions, accelerometers, microphones, and a hall sensor to provide a comprehensive overview of the gear operation. The temperature sensors give information about absolute temperatures, temperature gradients, and lubrication thickness in the loaded contact. The vibration sensors characterize the vibration behavior of the gear during operation, such as rotating frequencies, gear mesh frequency, and damage-caused frequency amplitudes. The hall sensor is also considered for the measurement of rotating speed in order to evaluate the operation condition and to estimate number of load cycles, which have already been performed. The prototype was developed and built collaboratively by the Institute of Machine Elements (FZG), the Institute of Automation and Information Systems (AIS), and the Chair of Circuit Design (LSE) at the Technical University of Munich (TUM).