Online Terminal Force Estimation of Hydraulic Manipulator With Prior Torque Variance

The existing terminal force estimation method based on inverse dynamic parameter identification does not consider the influence of uncertainties, such as dynamic modeling error and dynamic/friction identification error on estimation accuracy. In this article, an estimation method with prior torque variance considering the uncertainties is proposed. First, the dynamic identifiable parameter set of hydraulic manipulator (HM) is established. Second, the dynamic parameters and prior torque variance reflecting those uncertainties are obtained by recursive least square (RLS) method. Then, by minimizing the variance of the terminal force estimation error, a new matrix considering the prior torque variance is established, instead of using the inverse Jacobian matrix of the existing method. Finally, the proposed method is compared with the existing method under the condition of constant and variable load tests. The results show that the average estimation error can be controlled within 1%, which is better than the existing estimation methods.