Impact Fault Detection for Linear Vapor Compressor Using RISE Observer

In some applications, an indicator is needed for sudden system state changes, where the direct measurement of the system states is neither possible nor practical. In this brief, it is shown that the error of robust integral of the sign of the error observer can be used as an indicator of sudden system state changes. The application of this method for collision detection in a linear vapor compressor is investigated. Linear vapor compressors are becoming more widely utilized in cooling appliances, such as household refrigerators and portable coolers due to their high efficiency. The fact that the piston is free in a linear vapor compressor allows for the possibility of collisions between the compressor piston and other components of the linear vapor compressor within the compression chamber. Sensorless crash detection is preferred for purposes of reliability, ease of production, and cost effectiveness. For this purpose, a novel head crash detection scheme applying a nonlinear observer is developed. This scheme not only detects all head crashes accurately, but also provides an indicator proportional to the piston velocity at the time of impact. This indicator can be used to estimate how much the force command needs to be reduced to prevent further collision. A set of simulation and experimental test results validate the performance of the head crash detection scheme.