Online Estimation Method and Verification of Sampling Mass for Lunar Drilling in the Chang’E-6 Mission

The Chang’E-6 lunar mission successfully collected the lunar back surface and subsurface lunar regolith by excavating and drilling and returned the lunar regolith samples to the earth. Drilling–sampling system exhibits highly nonlinear characteristics due to the stratified structure of lunar regolith and unknown physical property parameters, making it prone to abnormal operating conditions and sampling disturbances. Furthermore, constrained by extraterrestrial environmental limitations, the system can only obtain health parameters, operational protocol parameters, and drilling status parameters while lacking direct measurement data on sampling mass. The development of online estimation methods for sampling mass under nonlinear and under-sensing characteristics poses significant technical challenges. Based on the mechanism of machine–regolith interaction and the experimental data of ground drilling and sampling, this paper constructs a sampling status identification model and a fuzzy pre-judgment model of sampling mass based on the downhole WOB based on the response characteristic parameters of the drilling–sampling stage. According to the telemetry data of Chang’E-6 lunar surface drilling–coring operation, the drilling–sampling mass is predicted to be 292.4 g, and the error between the predicted result and the actual sampling mass of 320 g is within 10%. This estimation method provides a new idea for the prediction of the fidelity sampling efficiency of extraterrestrial objects.