162 J.M. Brown et al. 15.4 Testing Procedure 15.4.1 Single Rotor Testing Procedure To enable supervised learning, data from both healthy and damaged components was collected. The above instrumentation was applied to the single rotor structure as illustrated in Fig. 15.5, and a general testing procedure was developed. A single trial consisted of 10, 5-s measurements at each of five different PWM duty cycles, which control the motor speed. These five duty cycles were kept constant within each trial, and were evenly spaced in ascending and descending order. For each measurement period, data from the sensor network was acquired and recorded. This trial process was repeated five times for each test. In total, the single propeller apparatus was tested with five different motors, three ESCs, and eight 35.56 13.97 cm propellers. Two of these propellers were healthy, and six were in various states of controlled damage. Propeller condition was classified as either symmetric or asymmetric with heavy or light damage. Figure 15.6 displays the varying damage states of the six propellers compared to one of the healthy propellers. Propeller 4 is an example of symmetric heavy damage, while propeller 7 is classified as asymmetric light damage. The three ESCs were tested with no induced damage. A range of motor conditions was used during experimentation: three of the motors were new and undamaged, one was operated extensively but remained undamaged, and the final motor had confirmed damage but was operable. For each motor, all three ESCs were tested with two healthy propellers. In addition, a single ESC was used to test each of the six damaged propellers. In total, 55 tests were performed. As a general procedure, each test was run until the five trials had elapsed, or until the motor stopped unexpectedly. To observe failure during operation and establish a greater understanding of component behavior before, during, and after damage, the system was run at a constant speed until motor or ESC failure was induced. Impact damage to a propeller in Fig. 15.5 Diagram of single rotor structure sensor placement Fig. 15.6 Range of damaged propellers compared to a healthy propeller
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