Estimation of the digging and payload forces in excavators by means of state observers

•A new method based on the theory of state estimation is proposed for determining the digging and payload forces in excavators, which does not require complex soil-tool interaction models.•Measurements usually available in excavators or very cheap to obtain are exploited.•Gravity compensation of accelerometer measurements through estimated system orientation is addressed.•An estimation regularization is introduced, which allows getting accurate estimates also in the presence of ill-conditioned system models.•A sensitivity analysis at varying level of modeling errors is carried out.