Mohammad Reza Jafari attended Shahid Fahmide High school in Qom and received his B.Sc. and M.Sc. degree in Electrical Engineering from Sharif University of Technology in 2014 and 2016 respectively.He is currently pursuing a PhD in control engineering at K.N. Toosi University. His current research interests include control of underactuated systems with first or second order nonholonomic constraint especially underactuated cable-driven robots.
In ARAS research groups, development of many robots such as hydraulic shoulder parallel robot, delta robot, wheeled mobile robot, cable driven redundant parallel manipulator, etc., has been carefully accomplished. Some of them like UAV and UGV are naturally under-actuated, meaning that the number of actuators are less than the degrees of freedom. Moreover, cable driven robot in the suspended mode may be designed under-actuated.
Over recent decades, control of these systems is one of the attractive fields for researchers. Despite of several works in this field, there are some open problems that are the focus of our research. Under-actuation leads to some constraints on configuration variables. In some cases velocity of robot is in a subset of overall space. These robots have velocity constraint and are called to have first order or velocity non-holonomic constraints. Examples of these robots are wheeled mobile robot and (nS)-2SP under-actuated wrist robot which is shown in fig 1. In other cases acceleration of robot is in a subset of space which leads to second order or acceleration nonholonomic. UAV and underactuated cable robot are examples of second order nonholonomic systems.
There are some methods to control first order nonholonomic systems such as changing the equation of motion to chained form by which several robust and adaptive algorithm has been proposed for stabilization and trajectory tracking on them in literature. For controlling second order non-holonomic systems, changing the equation to strict feedback form is a possible and common method. Therefore, one of the main objects of our team is to further develop these methods and derive adaptive and robust control law based on this structure.