A Sensorless Haptic Force Estimation Method and Its Application to Uncertain Robotic Manipulators

In this paper, a haptic force estimation scheme without force sensors is proposed for a class of robotic manipulators with multiple disturbances. Different from previous methods, besides haptic force, other disturbances and uncertainties of robotic manipulators are taken into account simultaneously. Motivated by the composite hierarchical anti-disturbance control strategy, a robust haptic force observer (RHOB) is designed by a solution of a linear matrix inequality (LMI), which can extract precise haptic force from multiple disturbances by taking a strategy of compensation and suppression in due course. Moreover, some integral auxiliary signals are regarded as the robust performance indices introduced in the design and analysis. Also, a composite control strategy based on the mentioned design of RHOB guarantees the boundedness of all signals in the augmented closed-loop system and the proposed robust performance indices, and furthermore, the asymptotic convergences of tracking error and force estimation error, in the case of slow-varying haptic force, are successfully achieved. Simulation results demonstrate the effectiveness of the proposed method.