Dynamics and Control of Robotic Manipulators with Contact and Friction

4Friction Dynamics of Manipulators

4.1 Friction Models of Robot Manipulator Joints

Generally, the robotic arm, an articulated mechanical structure, is an assembly of links interconnected by joints. Industry‐specific robots perform several tasks such as picking, moving, and placing objects. Such robotic arms are also known as robotic manipulators.

A series of jointed links are put together to form an arm‐like manipulator that is capable of automatically moving objects within a given number of degrees of freedom. Every commercial robot manipulator includes a controller and a manipulator arm. The performance of the manipulator depends on its speed, payload weight, and precision. Many manipulator joints consist of roller‐bearing mechanism and transmission as well as seals and covers, in which contact and friction as well as relative motions of interfaces exist. Friction has been experimentally shown to be one of the major sources of performance degradation in motion control system. Robotic manipulators are subject to joint friction that arises in the bearings, transmissions, and seals − in other words, at every point where two surfaces are in relative motion and in contact. Numerous factors, such as surface roughness and topology, lubricant viscosity, load, contaminations, temperature, and velocity influence the friction forces at the contacting surfaces.

In a robot joint, the complex interaction of components such as gears, bearings, and shafts, which are rotating/sliding at different ...