Modeling and slipping control of a planar slider

The paper presents a novel strategy to control the instantaneous rotational velocity of a planar slider subject to a soft contact with friction and to external loads, including gravity. The approach is based on a novel model that combines the LuGre dynamic friction model with the limit surface concept for two main reasons. First, the limit surface allows considering both translational and rotational sliding motions. Secondly, the actual friction provided at the contact by the LuGre dynamic model exhibits dependence on the rate of variation of the external loads and, thus, it is worthwhile in dynamic conditions. Slipping control is realized by acting on the friction forces through the normal load so as to stably regulate the velocity of the slider to zero. The control law exploits a nonlinear observer, based on the proposed model, to estimate the instantaneous rotational velocity of the slider, which is used to compute the normal load necessary to ensure a globally asymptotically stable equilibrium of the slider. Experimental results show the effectiveness of the approach in an application of robotic manipulation using an industrial gripper sensorized with force/tactile sensors