Speed Estimation Improvement After Decreasing the Encoder Resolution for a Haptic Interface

A haptic system consists in an articulated mechanical structure with motors and position sensors, as well as embedded electronics allowing force feedback. It is driven by a haptic interface, which enables the user to interact with an image in a virtual reality application through the sense of touch. This paper describes a single degree of freedom haptic interface and particularly presents a low speed estimation method with a reduced resolution encoder, in order to optimize the application cost. It leads to an important relative error of the speed estimation and the deterioration of the obtained stiffness. This paper presents a simple speed estimation method which improves the relative error of the measure and increases the virtual stiffness to almost the value obtained with a high resolution encoder. It keeps the synchronism between the speed and the other variables measurements. Moreover, the measurement accuracy at low speeds using the proposed method is improved, compared to currently known methods.