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Über dieses Buch

The advent of new high-speed microprocessor technology together with the need for high-performance robots created substantial and realistic place for control theory in the field of robotics. Since the beginning of the 80's, robotics and control theory have greatly benefited from a mutual fertiliza­ tion. On one hand, robot models (inherently highly nonlinear) have been used as good case studies for exemplifying general concepts of analysis and design of advanced control theory; on the other hand, robot manipulator by using new control algorithms. Fur­ performance has been improved thermore, many interesting robotics problems, e. g. , in mobile robots, have brought new control theory research lines and given rise to the development of new controllers (time-varying and nonlinear). Robots in control are more than a simple case study. They represent a natural source of inspiration and a great pedagogical tool for research and teaching in control theory. Several advanced control algorithms have been developed for different types of robots (rigid, flexible and mobile), based either on existing control techniques, e. g. , feedback linearization and adaptive control, or on new control techniques that have been developed on purpose. Most of those results, although widely spread, are nowadays rather dispersed in different journals and conference proceedings. The purpose of this book is to collect some of the most fundamental and current results on theory of robot control in a unified framework, by editing, improving and completing previous works in the area.



Rigid manipulators


Chapter 1. Modelling and identification

From a mechanical viewpoint, a robotic system is in general constituted by a locomotion apparatus (legs, wheels) to move in the environment and by a manipulation apparatus to operate on the objects present in the environment. It is then important to distinguish between the class of mobile robots and the class of robot manipulators.
W. Khalil, B. Siciliano

Chapter 2. Joint space control

Traditionally, control design in robot manipulators is understood as the simple fact of tuning a PD (Proportional and Derivative) compensator at the level of each motor driving the manipulator joints. Fundamentally, a PD controller is a position and a velocity feedback that has good closed-loop properties when applied to a double integrator. This controller provides a natural way to stabilize double integrators since it can be understood as an additional mechanical (active) spring and damper which reduces oscillations. To this extent, the control of an n-joint manipulator can be interpreted as the control of n independent chains of double integrators for which a PD controller can be designed. In reality, the manipulator dynamics is much more complex than a simple decoupled second-order linear system. It includes coupling terms and nonlinear components such as gravity, Coriolis and centrifugal forces and friction.
B. Brogliato, C. Canudas de Wit

Chapter 3. Task space control

In the above joint space control schemes, it was assumed that the reference trajectory is available in terms of the time history of joint positions, velocities and accelerations. On the other hand, robot manipulator motions are typically specified in the task space in terms of the time history of end-effector position, velocity and acceleration. This chapter is devoted to control of rigid robot manipulators in the task space.
B. Siciliano

Chapter 4. Motion and force control

In this chapter we deal with the motion control problem for situations in which the robot manipulator end effector is in contact with the environment. Many robotic tasks involve intentional interaction between the manipulator and the environment. Usually, the end effector is required to follow in a stable way the edge or the surface of a workpiece while applying prescribed forces and torques. The specific feature of robotic problems such as polishing, deburring, or assembly, demands control also of the exchanged forces at the contact. These forces may be explicitly set under control or just kept limited in a indirect way, by controlling the end-effector position. In any case, force specification is often complemented with a requirement concerning the end-effector motion so that the control problem has in general hybrid (mixed) objectives.
A. De Luca, B Siciliano

Flexible manipulators


Chapter 5. Elastic joints

This chapter deals with modelling and control of robot manipulators with joint flexibility. The presence of such a flexibility is a common aspect in many current industrial robots. When motion transmission elements such as harmonic drives, transmission belts and long shafts are used, a dynamic time-varying displacement is introduced between the position of the driving actuator and that of the driven link.
A. De Luca, P. Tomei

Chapter 6. Flexible links

This chapter is devoted to modelling and control of robot manipulators with flexible links. This class of robots includes lightweight manipulators and/or large articulated structures that are encountered in a variety of conventional and nonconventional settings. From the point of view of applications, we can think about very long arms needed for accessing hostile environments (nuclear sites, underground waste deposits, deep sea, space, etc.) or automated crane devices for building construction. The ultimate challenge is the design of mechanical arms made of light materials that are suitable for typical industrial manipulation tasks, such as pick-and-place, assembly, or surface finishing. Lightweight structures are expected to improve performance of robots with typically low payload-to-arm weight ratio. As opposed to slow and bulky motion of conventional industrial manipulators, such robotic designs are expected to achieve fast and dexterous motion.
A. De Luca, B. Siciliano

Mobile robots


Chapter 7. Modelling and structural properties

The third part of the book is concerned with modelling and control of wheeled mobile robots. A wheeled mobile robot is a wheeled vehicle which is capable of an autonomous motion (without external human driver) because it is equipped, for its motion, with actuators that are driven by an embarked computer.
G. Bastin, G. Campion, B. d’Andrea-Novel

Chapter 8. Feedback linearization

The last two chapters of the book are concerned with state feedback control of wheeled mobile robots.
G. Bastin, G. Campion, B. d’Andrea-Novel

Chapter 9. Nonlinear feedback control

The previous chapter has been devoted to solving point and posture tracking problems by state feedback linearization for the five generic types of wheeled mobile robots. However, as it has been already mentioned, feedback linearization through regular controllers has serious limitations for control of mobile robots. In particular, it does not allow a robot to be stabilized about a fixed point in the configuration space.
C. Canudas de Wit, C. Samson


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