Alicja Mazur

Hybrid adaptive control laws solving a path following problem for non-holonomic mobile manipulators

In this paper a general solution to the path following problem for mobile manipulators with non-holonomic mobile platform has been presented. New proposed control algorithms — for mobile manipulators with fully known dynamics or with parametric uncertainty in the dynamics — take into considerations the kinematics as well as the dynamics of the non-holonomic mobile manipulator. The convergence of the control algorithms is proved using the LaSalles invariance principle.

On path following control of nonholonomic mobile manipulators

On path following control of nonholonomic mobile manipulators This paper describes the problem of designing control laws for path following robots, including two types of nonholonomic mobile manipulators. Due to a cascade structure of the motion equation, a backstepping procedure is used to achieve motion along a desired path. The control algorithm consists of two simultaneously working controllers: the kinematic controller, solving motion constraints, and the dynamic controller, preserving an appropriate coordination between both subsystems of a mobile manipulator, i.e. the mobile platform and the manipulating arm. A description of the nonholonomic subsystem relative to the desired path using the Frenet parametrization is the basis for formulating the path following problem and designing a kinematic control algorithm. In turn, the dynamic control algorithm is a modification of a passivity-based controller. Theoretical deliberations are illustrated with simulations.

Trajectory tracking control in workspace-defined tasks for nonholonomic mobile manipulators

This paper considers a problem of tracking control design for different types of nonholonomic mobile manipulators. The mobile platform is in form of a unicycle. In the first step, an input–output decoupling controller is developed. The proposed selection of output functions is in more general form than the output functions previously introduced by others [Yamamoto and Yun]. It makes possible to move simultaneously, the mobile platform and the manipulator built on it. Regularity conditions that guarantee the existence of the input–output decoupling control law are presented. In the second step, trajectory and path tracking controllers are formulated and presented. Theoretical considerations are illustrated with simulations for the mobile manipulator consisting of a vertical, three degree of freeedom (DOF) pendulum (with holonomic or nonholonomic drives) mounted atop of a unicycle.

Towards Practical Implementation of an Artificial Force Method for Control of the Mobile Platform Rex

The article describes skid steering mobile platform, which is a nonholonomic robot. For controlling such a robot artificial force method has been used. This method assumes that the number of control inputs is the same as the number of controlled variables. Simultaneously additional control signal is equal to zero equivalently. Considerable attention is paid to possibility of practical application of the described algorithm in the physical equipment.

Virtual Force Concept in Steering Mobile Manipulators with Skid-Steering Platform Moving in Unknown Environment

Underactuated control system, namely mobile manipulator mounted on skid-steering platform has been considered in the paper. As a control scheme the concept of virtual force is presented and discussed. In such concept, full rank of input matrix, describing relationship between controlled variables and number of actuators, has been assumed. The signal of the assumed additional actuator is equal to zero equivalently (because this force is “virtual” and it does not exist in practice) but in this way the invertibility of input matrix can be achieved. The equation of the implicit function generates the reference signals needed in control algorithm. Mathematical proof of proper action of such control law has been presented using Lyapunov-like function. Efficiency and robustness of control scheme on parametric uncertainty of terrain, which the mobile manipulator is moving on, have been tested in numerous simulations.

New approach to the control problem of mobile manipulators

In the paper a new solution to the trajectory tracking problem of a nonholonomic mobile manipulator with a (2, 0) class mobile platform has been presented. A new control algorithm for the mobile manipulator is introduced and proved.

Robust Control of Differentially Driven Mobile Platforms

Wheeled mobile platforms constitute an important group of robotic objects. They can be treated as independent robots or as a transportation part of a composite robotic assembly, for instance mobile manipulators. Depending on the kind of the wheels and the way in which they are fixed to the cart, motion of wheeled mobile platforms can be realized with or without slippage phenomenon. If no slippage effect between the wheels and the surface occurs, then there exists some equation describing forbidden directions of realized velocities of the system. Such a relationship is called the nonholonomic constraint in the platform’s motion.

Path Following for Nonholonomic Mobile Manipulators

In the paper a new control algorithm preserving a path following for special class of mobile manipulators, namely for nonholonomic mobile manipulators, is presented. The mobile manipulator is a robotic system consisting of a mobile platform equipped with non-deformable wheels and a manipulator mounted on this platform. Such a composed system is able to realize manipulation tasks in a much larger workspace than a manipulator with a fixed base. Taking into account the type of constraints of both subsystems, there are 4 possible configurations of mobile manipulators: type (h, h) - a holonomic manipulator on a holonomic platform, type (h, nh) - a holonomic platform with a nonholonomic manipulator, type (nh, h) - a nonholonomic platform with a holonomic manipulator, and finally type (nh, nh) - both the platform and the manipulator nonholonomic. In our considerations we focus on the nonholonomic mobile manipulator of the (nh, h) type.

Trajectory Tracking Control for Nonholonomic Mobile Manipulators

In the paper we present new control algorithms for a special class of mobile manipulators, namely for nonholonomic mobile manipulators. A mobile manipulator is defined as a robotic system composed of a mobile platform and a manipulator mounted on the platform equipped with non-deformable wheels. Such a combined system is able to perform manipulation tasks in a much larger workspace than a fixed-base manipulator. Taking into account the type of mobility of their components, there are 4 possible configurations: type (h, h) — with both the platform and the manipulator holonomic, type (h, nh) — a holonomic platform with a nonholonomic manipulator, type (nh, h) — a nonholonomic platform with a holonomic manipulator, and finally type (nh, nh) — both the platform and the manipulator nonholonomic. The notion doubly nonholonomic manipulator was introduced in [13] for the type (nh,nh). The rigid manipulator can be a holonomic or a nonholonomic system depending on its construction.

Compliance force control for Polish cardiosurgical manipulator RobIn Heart

In the paper hybrid control for Polish cardiosurgical robot RobIn Heart 3 has been presented. Classical position-force control with modification introduced by Fisher and Mujtaba has been simulated with dynamics model of this robot. It has been conducted extensive simulation study, which should give an answer to the question, if selected motion patterns, so-called “motion primitives”, could be prepared to support human reactions. Such patterns could give surgeon possibility to make a process of cutting or needling more precisely and with precise force of pressure. Simulation research has confirmed correctness of assumed control solution. It is a point of departure to practical implementation of such control scheme in robot RobIn Heart.