One of the fundamental requirements for the success of a robot task is the capability to handle interaction between manipulator and environment. The quantity that describes the state of interaction more effectively is the contact force at the manipulator's end effector. High values of contact force are generally undesirable since they may stress both the manipulator and the manipulated object; hence the need to seek for effective force control strategies. The book provides a theoretical and experimental treatment of robot interaction control. In the framework of model-based operational space control, stiffness control and impedance control are presented as the basic strategies for indirect force control; a key feature is the coverage of six-degree-of-freedom interaction tasks and manipulator kinematic redundancy. Then, direct force control strategies are presented which are obtained from motion control schemes suitably modified by the closure of an outer force regulation feedback loop. Finally, advanced force and position control strategies are presented which include passivity-based, adaptive and output feedback control schemes. Remarkably, all control schemes are experimentally tested on a setup consisting of a seven-joint industrial robot with open control architecture and force/torque sensor.

The topic of robot force control is not treated in depth in robotics textbooks, in spite of its crucial importance for practical manipulation tasks. In the few books addressing this topic, the material is often limited to single-degree-of-freedom tasks. On the other hand, several results are available in the robotics literature but no dedicated monograph exists. The book is thus aimed at filling this gap by providing a theoretical and experimental treatment of robot force control.

1. Introduction.- 1. Motion control vs. interaction control.- 2. Indirect vs. direct force control.- 3. Experimental apparatus.- 2. Motion Control.- 1. Modeling.- 1.1 Kinematics.- 1.2 Dynamics.- 2. Tracking control.- 2.1 Dynamic model-based compensation.- 2.2 Euler angles error.- 2.3 Angle/axis error.- 2.4 Quaternion error.- 2.5 Computational issues.- 2.6 Redundancy resolution.- 3. Regulation.- 3.1 Static model-based compensation.- 3.2 Orientation errors.- 4. Further reading.- 3. Indirect Force Control.- 1. Compliance control.- 1.1 Active compliance.- 1.2 Experiments.- 2. Impedance control.- 2.1 Active impedance.- 2.2 Inner motion control.- 2.3 Three-DOF impedance control.- 2.4 Experiments.- 3. Six-DOF impedance control.- 3.1 Euler angles displacement.- 3.2 Angle/axis displacement.- 3.3 Quaternion displacement.- 3.4 Experiments.- 3.5 Nondiagonal six-DOF stiffness.- 4. Further reading.- 4. Direct Force Control.- 1. Force regulation.- 1.1 Static model-based compensation.- 1.2 Dynamic model-based compensation.- 1.3 Experiments.- 2. Force and motion control.- 2.1 Force and position regulation.- 2.2 Force and position control.- 2.3 Moment and orientation control.- 2.4 Experiments.- 3. Force tracking.- 3.1 Contact stiffness adaptation.- 3.2 Experiments.- 4. Further reading.- 5. Advanced Force and Position Control.- 1. Task space dynamics.- 2. Adaptive control.- 2.1 Regulation.- 2.2 Passivity-based control.- 2.3 Experiments.- 3. Output feedback control.- 3.1 Regulation.- 3.2 Passivity-based control.- 3.3 Experiments.- 4. Further reading.- Appendices.- A - Rigid Body Orientation.- 1. Rotation matrix.- 2. Euler angles.- 3. Angle/axis.- 4. Quaternion.- B - Models of Robot Manipulators.- 1. Kinematic models.- 1.1 Six-joint manipulator.- 1.2 Seven-joint manipulator.- 2. Dynamic models.- 2.1 Six-joint manipulator.- 2.2 Seven-joint manipulator.- References.