Sensor array optimization for the electronic nose via different deep learning methods

A sensor array is a key component of an electronic nose (E-nose). However, the practical applications of the E-nose are often inhibited by its size and energy consumption arising from the number of gas sensors. Achieving a high-performance E-nose with a minimum number of sensors is key and challenging for its practical applications. In this study, different machine learning models have been studied and compared to optimize the performance of the E-nose. The results show that the convolutional neural network (CNN) is the optimal model, which has an accuracy of 0.986 for classification, and an R-square score of 0.979 for concentration prediction, superior to the gated recurrent unit, long short-term memory, multi-layer perceptron neural network, and support vector machine. The performance of the E-nose is slightly changed when the number of sensors that participated in pattern recognition decreases from eight to four, where the CNN model can yield an accuracy of 0.905 for classification and an R-square of 0.972 for concentration prediction. To further quantify the loss and gain of array optimization, a cost-effective metric is designed to reveal the suitable array size under different scenarios. This work can provide valuable guidance in the design of portable E-nose devices with a smaller size and optimal performance.