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In the recent years a major change in the engineering process of mechatronics and robotics has taken place. In various design oriented laboratories around the world a shift can be recognised from a focus on analysis, simulation and modelling combined with outsourcing hardware design to the use of digital fabrication tools (laser cutter, 3D printer) allowing a cyclic (iterative) design process inside in the lab. This chapter aims to give an overview of the impact of this change, using many examples from various projects, and will share some insights and lessons learned for facilitating and implementing this process.

In this paper, the rotational variable stiffness actuator vsaUT-II is presented. This actuation system is characterized by the property that the apparent stiffness at the actuator output can be varied independently from its position. This behavior is realized by implementing a variable transmission ratio between the internal elastic elements and the actuator output, i.e., a lever arm with variable pivot point position. The pivot point is moved by a planetary gears mechanism, which acquires a straight motion from only rotations, thereby providing a low-friction transmission. The working principle details of the vsaUT-II are elaborated and the design is presented. The actuator dynamics are described by means of a lumped parameter model. The relevant parameters of the actuator are estimated and identified in the physical setup and measurements are used to validate both the design and the derived model.

This paper presents a general design approach for a performance based tuning of a damping injection framework impedance controller by using insights from PID motion control tuning rules. The damping injection framework impedance controller is suitable for human friendly robots as it enhances safety due to the compliance it introduces and guarantees asymptotic stability because of its passive nature. In order to perform successful manipulation with a damping injection framework controlled robot, a performance based analysis and tuning of the controller is essential. By mapping a performance based frequency domain tuning of PID controllers on the framework, the proposed tuning method attempts to analyze and define controller parameters that yield a desired performance requirement given in terms of the maximum allowed position error. The effectiveness of the proposed guideline is illustrated with simulation and experimental results.

In the recent years a major change in the engineering process of mechatronics and robotics has taken place. In various design oriented laboratories around the world a shift can be recognised from a focus on analysis, simulation and modelling combined with outsourcing hardware design to the use of digital fabrication tools (laser cutter, 3D printer) allowing a cyclic (iterative) design process inside in the lab. This chapter aims to give an overview of the impact of this change, using many examples from various projects, and will share some insights and lessons learned for facilitating and implementing this process.

Reading and writing is modelled in CSP using actions containing the symbols ? and !. These reading and writing actions are synchronous and there is a oneto-one relationship between occurrences of pairs of these actions. It is cumbersome to ease the restriction of synchronous execution of the read and write actions. For this reason we introduce the half-asynchronous parallel operator that acts on actions containing the symbols ¿ and ¡ and study the impact on a Vertex Removing Synchronised Product.

Reading and writing is modelled in CSP using actions containing the symbols ? and !. These reading and writing actions are synchronous and there is a oneto-one relationship between occurrences of pairs of these actions. It is cumbersome to ease the restriction of synchronous execution of the read and write actions. For this reason we introduce the half-asynchronous parallel operator that acts on actions containing the symbols ¿ and ¡ and study the impact on a Vertex Removing Synchronised Product.

In the future of the aging society it becomes increasingly difficult to provide personal care to people who are in need of help due to physical impairments caused by various diseases or disorders. The number of caregivers is limited and the cost of individual personal care will increase. Although personal care is desired, the downside is that people in need of care become dependent on caregivers for accomplishing their activities of daily living. This dependence has a big influence on one’s quality of life and self esteem. A solution to this situation is the deployment of assistive robotic aids like multifunctional robotic arms mounted to a table or wheelchair. These systems can aid in various tasks like opening doors and picking up a drinking glass, as well as personal hygiene tasks. Because many of today’s wheelchair mounted robotic arms are based in some aspects on existing designs for industrial applications, they are not safe to be used in human care services. Therefore, there is a need for safe robotic arms that are applicable for this kind of care. This thesis describes various ways of accomplishing safety in robotic arms, and argues that using variable stiffness actuation, which has not been applied before in assistive robotic arms, is a way to accomplish that. These actuators provide the possibility to not only control the position of the actuator output, but also to influence the stiffness that can be perceived at this output. Various concepts of these actuators, using different principles, are investigated in Part I, and Part II treats the modeling of robotic arms that are driven by these actuators. Modularity was a specific goal, because of the large diversity of connections between the actuators and the arm. The result is a model based on graph theory, which consists of vertices and edges, in which the repositioning of an actuator means changing the connections of one or more edges. This thesis also presents a structured method of analyzing an arm's stiffness, and treats the control of the actuator stiffnesses to optimally approximate a desired end effector stiffness.

In this paper, we analyze in depth the innovative very versatile and energy efficient (V2E2) actuator proposed in Stramigioli et al. (2008). The V2E2 actuator is intended to be used in all kind of robotics and powered prosthetic applications in which energy consumption is a critical issue. In particular, this work focuses on the development of a port-based Hamiltonian model of the V2E2 and presents an optimal control architecture which exploits the intrinsic hybrid characteristics of the actuator design. The optimal control guarantees the minimization of dissipative power losses during torque tracking transients.

Standard methods to model multibody systems are aimed at systems with configuration spaces isomorphic to ${BBR}^n$ . This limitation leads to singularities and other artifacts in case the configuration space has a different topology, for example, in the case of ball joints or a free-floating mechanism. This paper discusses an extension of classical methods that allows for a more general class of joints, including all joints with a Lie group structure as well as nonholonomic joints. The model equations are derived using the Boltzmann–Hamel equations and have very similar structure and complexity as obtained using classical methods. However, singularities are avoided through the use of global non-Euclidean configuration coordinates, together with mappings describing a local Euclidean structure around each configuration. The resulting equations are explicit (unconstrained) differential equations, both for holonomic and nonholonomic joints, which do not require a coordinate atlas and can be directly implemented in simulation software.

In this paper, the accent is on modeling the stick–slip phenomenon of micro devices, where a case shall be presented from the field of scanning probe microactuators. The case is about the lWalker, an electrostatic stepper motor which can deliver forces up to 1.7 mN and has ranges up to 140 lm. For the sake of a reliable operation, it is very important to control the stick–slip effects at the sliding surfaces. In order to introduce the stick–slip effect, a basic model of a mass, spring and sliding surface is presented, accompanied by simulation results. The total model of the device is then shown, again stressing the stick–slip phenomenon at the two sliding surfaces. Simulations from the model presented fit the measurements and can also predict step sizes as a function of varying inputs. Using a model for predictions is very attractive when looking for a way to decrease development cost and time.

In this paper, we present a novel way to approach the interconnection of a continuous and a discrete time physical system first presented in [1][2] [3]. This is done in a way which preserves passivity of the coupled system independently of the sampling time T. This strategy can be used both in the field of telemanipulation, for the implementation of a passive master/slave system on a digital transmission line with varying time delays and possible loss of packets (e.g., the Internet), and in the field of haptics, where the virtual environment should ‘feel’ like a physical equivalent system.

Since their introduction in the early years of this century, variable stiffness actuators (VSA) witnessed a sustained growth of interest in the research community, as shown by the growing number of publications. While many consider VSA very interesting for applications, one of the factors hindering their further diffusion is the relatively new conceptual structure of this technology. When choosing a VSA for their application, educated practitioners, who are used to choosing robot actuators based on standardized procedures and uniformly presented data, would be confronted with an inhomogeneous and rather disorganized mass of information coming mostly from scientific publications. In this paper, the authors consider how the design procedures and data presentation of a generic VSA could be organized so as to minimize the engineer’s effort in choosing the actuator type and size that would best fit the application needs. The reader is led through the list of the most important parameters that will determine the ultimate performance of their VSA robot, and influence both the mechanical design and the controller shape. This set of parameters extends the description of a traditional electric actuator with quantities describing the capability of the VSA to change its output stiffness. As an instrument for the end-user, the VSA datasheet is intended to be a compact, self-contained description of an actuator that summarizes all of the salient characteristics that the user must be aware of when choosing a device for their application. At the end some examples of compiled VSA datasheets are reported, as well as a few examples of actuator selection procedures.

In certain single-core mono-processor configurations, e.g. embedded control systems, like robotic applications, comprising many short processes, process context switches may consume a considerable amount of the available processing power. For this reason it can be advantageous to combine processes, to reduce the number of context switches. Reducing the number of context switches decreases the execution time and thereby increases the performance of the application. As we consider robotic applications only, often consisting of processes with identical periods, release times and deadlines, we restrict these configurations to periodic real-time processes executing on a single-core mono-processor. These processes can be represented by finite directed acyclic labelled multi-graphs. The vertex-removing synchronised product of such graphs gives graphs that represent processes which have less context switches. To reduce the memory occupancy, the vertex-removing synchronised product removes vertices that are not reachable; i.e. represents states that can never occur. By means of a lattice, we show all possible products of a set of graphs, where the number of products is given by the Bell number. We finish with heuristics from which a set of graphs can be calculated that represents a set of processes that will not miss their deadline and which fits in the available memory.

In certain single-core mono-processor configurations, e.g. embedded control systems, like robotic applications, comprising many short processes, process context switches may consume a considerable amount of the available processing power. For this reason it can be advantageous to combine processes, to reduce the number of context switches. Reducing the number of context switches decreases the execution time and thereby increases the performance of the application. As we consider robotic applications only, often consisting of processes with identical periods, release times and deadlines, we restrict these configurations to periodic real-time processes executing on a single-core mono-processor. These processes can be represented by finite directed acyclic labelled multi-graphs. The vertex-removing synchronised product of such graphs gives graphs that represent processes which have less context switches. To reduce the memory occupancy, the vertex-removing synchronised product removes vertices that are not reachable; i.e. represents states that can never occur. By means of a lattice, we show all possible products of a set of graphs, where the number of products is given by the Bell number. We finish with heuristics from which a set of graphs can be calculated that represents a set of processes that will not miss their deadline and which fits in the available memory.

Assistive robotics is an increasingly popular research field, which has led to a large number of commercial and noncommercial systems aimed at assisting physically impaired or elderly users in the activities of daily living. In this article, we propose five criteria based on robotic arm usage scenarios and surveys with which assistive robotic arms can be classified. Different possibilities and implementations to obtain each criterion are treated, and examples of current assistive robotic arms are given. Implementations and systems are discussed and rated qualitatively, which leads to the observation that variable stiffness actuation offers great benefits for assistive robotic systems despite an increase in the overall complexity.

This work presents an energy-based state estimation formalism for a class of dynamical systems with inaccessible/unknown outputs, and systems at which sensor utilization is impractical, or when measurements can not be taken. The power-conserving physical interconnections among most of the dynamical subsystems allow for power exchange through their power ports. Power exchange is conceptually considered as information exchange among the dynamical subsystems and further utilized to develop a natural feedback-like information from a class of dynamical systems with inaccessible/unknown outputs. This information is used in the design of an energy-based state observer. Convergence stability of the estimation error for the proposed state observer is proved for systems with linear dynamics. Furthermore, robustness of the convergence stability is analyzed over a range of parameter deviation and model uncertainties. Experiments are conducted on a dynamical system with a single input and multiple inaccessible outputs (Fig. 1) to demonstrate the validity of the proposed energy-based state estimation formalism.

This work investigates the utilization of microparticles for the wireless sensing of interaction forces in magnetic-based manipulation systems. The proposed force estimation approach allows for using microparticles in sensing the interaction forces at hard-to-reach regions to avoid the mechanical and electronic complexities associated with physical force sensors. Based on the velocity of the microparticle and the applied currents at each of the electromagnets of the magnetic system, an interaction force observer is designed to estimate the contact forces between the microparticle and a soft-tissue simulant with different elasticities. Experimentally, a magnetic system is utilized to steer a microparticle towards a soft-tissue simulant to carry out force sensing. The experimental results show that forces in the range of nano-Newton can be estimated without nano-force sensors. The estimated interaction forces due to this contact can be used either in sensing and diagnosis applications, or in the realization of a force control system.

The use of an ultrasound probe or a needle guide during biopsy deforms both the rectal wall and the prostate, resulting in lesion motion. An accurate patient-specific finite element (FE)-based biomechanical model can be used to predict prostate deformations. In this study, an FE model of a prostate phantom is developed using magnetic resonance images, while soft-tissue elasticity is estimated in vivo using an ultrasound-based acoustic radiation force impulse imaging technique. This study confirms that three-dimensional FE-predicted prostate deformation is predominantly dependent on accurate modelling of prostate geometry and boundary conditions. Upon application of various compressive displacements, our results show that a linear elastic FE model can accurately predict prostate deformations. The maximum global error between FE-predicted simulations and experimental results is 0.76 mm. Moreover, the effect of including the urethra, puboprostatic ligament and urinary bladder on prostate deformations is investigated by a sensitivity study.

In this paper, we present the mechanical design and modeling of a manipulation system for unmanned aerial vehicles, which have to physically interact with environments and perform ultrasonic non-destructive testing experiments and other versatile tasks at unreachable locations for humans. The innovation of the prototype lies in the use of a three degrees of freedom Delta robotic manipulator together with a nondestructive testing end-effector, realized by a Cardan gimbal that allows the ultrasonic sensor to compliantly interact with the remote environment. The Cardan gimbal is endowed with a small actuator for the roll motion of the end-effector, a compliant element in the direction of interaction and two passive rotational degrees of freedom with defined equilibria to overcome gravity and to define a stable zero reference. Simulation results of a ducted-fan unmanned aerial vehicle interacting with a wall validate the overall mechanical design

This paper introduces a port-Hamiltonian framework for the design of image-based visual servo control for dynamic mechanical systems. The approach taken introduces the concept of an image effort and provides an interpretation of energy exchange between the dynamics of the physical system and virtual potentials or ‘image Hamiltonians’ posed in the image space. The port-Hamiltonian framework leads to an elegant algorithm to estimate unknown image depth on-line even when the translational velocity of the camera is not measured.

Haptic feedback systems are systems that exert a desired force, to be experienced by the user, to recreate a physical interaction. This type of systems can increase the realism of the interaction with objects that are not in the direct area of influence of the user. The same applies to the interaction with virtual objects. The fundamental problem in the control of these systems is how to maximize the transparency of the system, and related to that the realism of the interaction as perceived by the user, while guaranteeing stability of the interaction under all possible operating conditions. The stability analysis is complicated due to the presence of a closed loop, which can contain multiple unknown, non-linear, and time-varying elements, e.g. the user, a physical environment, and time delays in a possible communication channel. Furthermore, the control algorithm is executed on a discrete medium which, depending on the algorithm, parameter settings, and remaining elements, can have a significant influence on the stability of the interaction. In this thesis a solution is sought to all these factors by means of energy- and portbased reasoning. For both applications an algorithm is derived that is based on the energy exchange between the physical world and the system. By enforcing energy neutrality, in other words passivity, of this exchange a stable interaction is guaranteed. The algorithm for the interaction with virtual environments provides a passive coupling between the physical system and the discrete system. The dynamic behavior of the virtual object is computed with an energy-based integration method. Each iteration the algorithm evaluates the energy that is present in the system. A redistribution of that energy over the energy storing elements is computed based on the model that describes the dynamic behavior of the physical object. This algorithm ensures stability independent of the sample frequency of the algorithm, but adapts the realism of the interaction in such a way that passivity is maintained. The second algorithm divides the control objectives for the passive interaction with physical objects in remote environments by means of a telemanipulation system into two layers that are placed in a hierarchical order. The top layer, the Transparency-layer, contains an arbitrary control algorithm that provides the desired measure of transparency. The Passivity-layer contains an algorithm that guarantees passivity of the interaction and when necessary adapts the desired forces computed by the Transparency-layer to maintain passivity. The implementation of this algorithm also works in the presence of communication delays, by e.g. physical distance, between both locations that are connected by the system, the user and remote environment, respectively.

This video shows the design of a mechanical structure of a miniature pipe inspection robot (MPR) capable of moving trough very small pipes (up to 41 mm inner diameter) as well as a wide range of diameters (63 to 125 mm outer diameter). The requirement to negotiate bends, T-joints and steep inclinations pose another set of strict design constraints. In this video the controlled robot is shown in action.

This paper discusses the design of a mechanical structure of a miniature pipe inspection robot capable of moving through very small pipes (down to 41 mm inner diameter). The requirement to negotiate bends, T-joints and steep inclinations pose another set of strict design constraints. The proposed robot consists of a modular design (7 modules) with a relatively low number of active degrees of freedom. The system is using a novel clamping mechanism with a series-elastic drive. The design of this mechanism has resulted in a high spreading factor allowing the system to operate in a wide diameter range (63 mm to 125 mm outer diameter). In this paper the mechanical design requirements and control system will be discussed. Preliminary test results will be given.

Currently, physicians have no means of correctly estimating the needle tip location during percutaneous needle insertion. A model of needle-tissue interaction that predicts the needle tip location would assist physicians in pre-operative planning and hence improve needle targeting accuracy. This study is aimed to investigate the interactions of bevel-tipped needles and soft tissue in situ, using agarose gel as a soft-tissue simulant. An experimental setup is designed to record the needle-gel interaction forces and torques during needle insertion. Gel rupture during needle insertion is observed using a Laser Scanning Confocal Microscope and recorded in time series and three-dimensional images (Figure). Experimental results show the possibility of observing in situ gel rupture during needle insertion and relating them to the needle-gel interaction forces and torques. Moreover, it is seen that the maximum force along the insertion axis, |Fz max|, is proportional to bevel angle and inversely proportional to insertion speed. The maximum resultant torque, ||Tr max||, is found to be inversely proportional to bevel angle and proportional to insertion speed. However, the influence of the increase in insertion speed in |Fz max| and ||Tr max|| diminishes as insertion speed increases. These results concur with observations noted in gel rupture images.

Currently, physicians have no means of correctly estimating the needle tip location during percutaneous needle insertion. A model of needle-tissue interaction that predicts the needle tip location would assist physicians in pre-operative planning and hence improve needle targeting accuracy. This study is aimed to investigate the interactions of bevel-tipped needles and soft tissue in situ, using agarose gel as a soft-tissue simulant. An experimental setup is designed to record the needle-gel interaction forces and torques during needle insertion. Gel rupture during needle insertion is observed using a Laser Scanning Confocal Microscope and recorded in time series and three-dimensional images (Figure). Experimental results show the possibility of observing in situ gel rupture during needle insertion and relating them to the needle-gel interaction forces and torques. Moreover, it is seen that the maximum force along the insertion axis, |Fz max|, is proportional to bevel angle and inversely proportional to insertion speed. The maximum resultant torque, ||Tr max||, is found to be inversely proportional to bevel angle and proportional to insertion speed. However, the influence of the increase in insertion speed in |Fz max| and ||Tr max|| diminishes as insertion speed increases. These results concur with observations noted in gel rupture images.

In this paper, we propose a generic model and a controller design for a class of underactuated aerial vehicles, namely for unmanned aerial vehicles whose primary support against gravity is thrust. The approach followed is based on energetic consideration and uses the formalisms of port-Hamiltonian systems and bond graphs. The controller is designed for both stabilization during hovering and for trajectory tracking tasks. The competency of the model and the performance of the controller are validated in simulation.

Driven by societal trends, such as aging, and by a desire to drive economic growth and enhance commercial competitiveness, researchers have tried to move robots from structured manufacturing tasks to unstructured professional and personal service applications. As announced in the Falcon project, an example of a possible unstructured professional service task for future robots is found in package-handling tasks in warehouses (distribution centers). The Falcon project aimed to design a new system architecture for a fully automated distribution center and to define, within this architecture, specific critical robotic components, which were then targeted to be researched. The author observed some inherent challenges in following such an application driven research approach. Chapter 2 presents the author’s reflections on the tensions between top-down systems engineering approaches and the classical bottom-up approach for doing research.

To support the application of real-time Multi-Agent Control Systems (MACS) for mechatronic systems, a combination between the MACS design approach and OROCOS framework has been implemented: the OROCOS-based Implementation Framework for MACS (OROMACS). This paper presents our research results to make the OROMACS framework be easily applicable to develop realtime safe-guarded controller-agents and to maximize the reusability of safe-guarded MACS designs for various types of mechatronic systems. The approach that we advocate is a combination between OROMACS framework and pattern-based design method. Eleven control system design patterns are formed in which the Safe-Guarded Agent, one of the core design patterns, aims at providing a generic and flexible safe-guarded control solution for mechatronic systems. The design patterns are well organized into two reusable generalized safe-guarded control solutions, one for simple mechatronic systems and one for complex mechatronic systems.

In this work, we present a proof of concept of a novel variable stiffness actuator. The actuator design is based on the conceptual design proposed in earlier work, and is such that the apparent output stiffness of the actuator can be changed independently of the output position and without any energy cost. Experimental results show that the behavior of the prototype is in accordance with the theoretical results of the conceptual design, and thus show that energy efficient variable stiffness actuators can be realized.

We present a novel, simple and effective approach for tele-operation of aerial robotic vehicles with haptic feedback. Such feedback provides the remote pilot with an intuitive feel of the robot's state and perceived local environment that will ensure simple and safe operation in cluttered 3D environments common in inspection and surveillance tasks. Our approach is based on energetic considerations and uses the concepts of network theory and port-Hamiltonian systems. We provide a general framework for addressing problems such as mapping the limited stroke of a `master' joystick to the infinite stroke of a `slave' vehicle, while preserving passivity of the closed-loop system in the face of potential time delays in communications links and limited sensor data.

In this paper, a metric for comparing different designs of variable stiffness actuators is introduced. For the formulation of this metric, we focus on the energy efficiency of the actuators. In particular, we propose a metric that is a measure of how much energy is used by the actuator for changing the output stiffness. In order to facilitate the analysis of the energy usage, we present a port-based modeling framework, from which design criteria are derived for the optimization of the metric. Finally, the metric is interpreted in a comparison between existing actuators.

In this paper, we provide a port-based mathematical framework for analyzing and modeling variable stiffness actuators. The framework provides important insights in the energy requirements and, therefore, it is an important tool for the design of energy efficient variable stiffness actuators. Based on new insights gained from this approach, a novel conceptual actuator is presented. Simulations show that the apparent output stiffness of this actuator can be dynamically changed in an energy efficient way.

This paper describes the design of a motion control algorithm for a humanoid robotic head, which consists of a neck with four degrees of freedom and two eyes (a stereo pair system) that tilt on a common axis and rotate sideways freely. The kinematic and dynamic properties of the head are analyzed and modeled using screw theory. The motion control algorithm is designed to receive, as an input, the output of a vision processing algorithm and to exploit the redundancy of the system for the realization of the movements. This algorithm is designed to enable the head to focus on and to follow a target, showing human-like motions. The performance of the control algorithm has been tested in a simulated environment and, then, experimentally applied to the real humanoid head.

In this work, we present the design and the realization of the motion control algorithm implemented in the Twente hu- manoid head, a seven degrees of freedom (dof) robotic sys- tem. The aim of the project is to have a humanoid head that can serve as a research platform for human-machine interac- tion purposes. The head should not only be able to percieve its environment and track objects, but also be able to move in a human-like way, i.e. to reproduce the motions of human beings and to mime the human expressions.

A consortium of four companies is developing an autonomous inspection system for small diameter, low pressure gas distribution mains. Such a system could eventually replace the current practice of leak survey and improve the assessment of the quality of the mains, being able to investigate the mains from the inside and very closely. A complete system consisting of small robotic platforms, docking stations for battery recharging and data communication, and entrance locks is envisioned. The logistics of such a system seem feasible, although the technological challenge is daunting. Besides the development cost the other major parameter determining the cost of the system is the allowed maximum distance between docking stations. Preliminary analysis of the business case show that a robotic platform driving at a speed of 0.2 km/h and an availability of 50% would earn 160 000 € annually, being the value of its inspection results. This justifies a serious attempt for further evaluation of the vision.

A consortium of four companies is developing an autonomous inspection system for small diameter, low pressure gas distribution mains. Such a system could eventually replace the current practice of leak survey and improve the assessment of the quality of the mains, being able to investigate the mains from the inside and very closely. A complete system consisting of small robotic platforms, docking stations for battery recharging and data communication, and entrance locks is envisioned. The logistics of such a system seem feasible, although the technological challenge is daunting. Besides the development cost the other major parameter determining the cost of the system is the allowed maximum distance between docking stations. Preliminary analysis of the business case show that a robotic platform driving at a speed of 0.2 km/h and an availability of 50% would earn 160 000 € annually, being the value of its inspection results. This justifies a serious attempt for further evaluation of the vision.

Questo libro presenta una raccolta organizzata di esercizi e quiz per il completamento della preparazione di esami di Controlli Automatici e Teoria dei Sistemi. Il contenuto del libro deriva dall'attività didattica che gli autori svolgono da diversi anni nell'ambito del corso di "Controlli Automatici LS" per la Laurea Specialistica in Ingegneria Informatica presso la Facoltà di Ingegneria dell'Università di Bologna, pertanto rispecchia il programma e gli argomenti sviluppati in tale corso e non intende certamente coprire tutti gli aspetti di queste discipline. I diversi argomenti sono organizzati in capitoli, ognuno dei quali è suddiviso in una parte introduttiva corredata da diversi esempi, volta a completare e rafforzare quanto illustrato a lezione e disponibile nelle dispense del corso, da una parte di esercizi e da una di quiz a risposta multipla.

This paper presents a simple and fast solution to the problem of finding the time variation of n contact forces that keep an object under equilibrium while one of the n contact forces is removed/added from/to the grasp. The object is under a constant perturbation force, like for instance its own weight. It is assumed no acceleration of the object during the regrasp operation, as well as the knowledge of the starting and ending grasp configurations. The procedure returns the set points of the n contact forces for a feed-forward control system of a manipulator device in a regrasping action. The procedure was implemented and an illustrative numerical example is included in the paper.

In this paper, we present a software architecture, based on RTAI-Linux, for the real-time simulation of dynamic systems and for the rapid prototyping of digital controllers. Our aim is to simplify the testing phase of digital controllers by providing the real-time simulation of the plant with the same interface used for the communication between the control applications and real plant. This unified interface, based on the COMEDI library, allows to switch the controller from the simulated to the real plant without any modification of the control software. Moreover, a set of tools for helping the users in the development of the real-time simulation tasks of the plants have been developed. A great attention has been posed in the automatic generation of symbolic kinematic and dynamic models of robotic manipulators from a description of the robot in terms of kinematic parameters and inertia/center of mass of each link. The system, besides being useful for rapid prototyping of mechatronic control systems, may be used for fault detection, and also as a teaching tool in Mechatronic/Digital Control Courses. A case study, the real-time simulation and control of the PUMA 560 manipulator, is presented and discussed.

In robotics, the manipulation of a priori unknown objects involves several steps and problems that must be carefully considered and solved by proper planning and control algorithms. For example, once suitable contact points have been computed, the control system should be able to track them in the approach phase, i.e., while the relative position/ orientation of the object and the gripper of the robotic system change due to the approaching movement of the robot toward the object. This correspondence paper proposes a practicalmethod for the tracking of grasp points in image space that is based on transferring previously computed grasp points from an initial image to subsequent ones and on the analysis of the new grasp configuration. Three different options are proposed for this transference. Experimental results show the interesting practical performance of the general procedure

A bilateral telemanipulator is a robotic system that allows the interaction with remote environments and it is composed by a controlled local robot (the master) and a controlled remote robot (the slave) interconnected through a communication channel. The motion imposed to the master by the human is transmitted to the slave which moves accordingly; when the slave interacts with a remote environment, the interaction force is fed back to the master side in order to improve the perception of the remote environment felt by the user. Passivity theory is a very suitable tool for the implementation of bilateral telemanipulation schemes over delayed communication channels. In passivity based telemanipulation, both master and slave are controlled by means of passive impedance controllers and master and slave sides are interconnected through a scattering based communication channel [1, 8] which allows an exchange of information which is passive independently of any constant communication delay. In this way, the overall telemanipulation system is passive and, consequently, its behavior is stable both in case of free motion and in case of interaction with any passive environment. In [12, 11], a generic framework for geometric telemanipulation of port-Hamiltonian systems [13] has been proposed; master and slave are interconnected through intrinsically passive port-Hamiltonian impedance controllers which allow to shape the energetic behavior of the robots and to achieve desired dynamic properties at master and slave sides. Local and remote sides are interconnected through a scattering based communication channel that allows a lossless exchange of energy.

We present an innovative hybrid control strategy for contact detection and force regulation of robotic manipulators. This hybrid architecture controls the robotic manipulator during the following stages of interaction with the work environment: the free motion, the transition phase, and the constrained motion. The proposed control strategy is to switch between a position and a force controller with hysteresis relying only on contact force measurements. We implement this strategy in a hybrid controller and provide a design procedure which depends on the viscoelastic parameters of the work environment. Our controller guarantees contact detection and force regulation without bounce-off effects between the robotic manipulator and the work environment from compact sets of initial conditions. Additionally, the resulting closed-loop system is robust to measurement noise. We include simulations that show how the proposed hybrid control strategy guarantees good performance in the cases of stiff and compliant work environments, and in the presence of measurement noise. © 2007 IEEE.

One of the basic requirements in grasping and manipulation of objects is the determination of a suitable set of grasping forces such that the external forces and torques applied on the object are balanced and the object remains in equilibrium. This paper presents a new mathematical approach to efficiently obtain the optimal solution of this problem using the dual theorem of non-linear programming. The problem is modeled such that the basic convexity property necessary to apply the dual theorem is satisfied and, then, it is transformed into another one much easier to be solved. Three examples showing the efficiency and accuracy of the proposed methodology are included in the paper.

The goal of this paper is to introduce a methodology to preserve the passivity of a continuous time system under discretization. The authors define a new output that allows to preserve the passivity of the continuous system in its discrete counterpart with the same sto-rage function. First the authors give a general definition of the output and then they specialize it for linear systems. The result proposed in the first part of the paper is very interesting and very general.

The Cayley-Hamilton theorem is an important theorem of linear algebra which is well known and used in system theory. Unfortunatelly, this powerful result is practically never used in robotics even though it is of extreme relevance. This article is a review of the use of this result for the calculation of general matrix functions which are very common in robotics. It will be shown how any analytic matrix function like exponential, logarithm and more complicated expressions in robotics, can be easily and analytically calculated in an explicit form. Examples are given for the exponential map, inverse of the exponential map, and the derivative of the exponential map. For the first two examples there exist well known expressions in the literature, but the last one is not as easy to compute without the presented methods.

Passivity based bilateral telemanipulation schemes are often subject to a position drift between master and slave if the communication channel is implemented using scattering variables. The magnitude of this position mismatch can be significant during interaction tasks. In this paper we propose a passivity preserving scheme for compensating the position drift arising during contact tasks in port-Hamiltonian based telemanipulation improving the kinematic perception of the remote environment felt by the human operator.

This paper structures existing modelling techniques and theories into a systematic stepwise design trajectory with the goal to facilitate a less error-prone path from model to realization. It is a model-driven approach, whereby simulation is used to check whether refinement updates leave the model compliant with the requirements. Via various “in-the-loop simulations‿, the design trajectory runs from complete simulation to full realization. Tests on a basic experimental set up showed that the design trajectory is feasible, although it is expected that all stages are really necessary when complex controller behavior is to be implemented on distributed embedded computers.

One of the basic requirements in grasping and manipulation of objects is the determination of a suitable set of grasping forces such that the external forces and torques applied on the object are balanced and the object remains in equilibrium. This paper presents a new mathematical approach to efficiently obtain the optimal solution of this problem using the dual theorem of non-linear programming. The problem is modeled such that the basic convexity property necessary to apply the dual theorem is satisfied and, then, it is transformed into another one much easier to be solved. Three examples showing the efficiency and accuracy of the proposed methodology are included in the paper.

In this paper an extension of the basic Command Governor approach for manipulation of dynamic systems is proposed. This work presents a way to incorporate kinetostatic feedback to the operator maintaining the passivity of the closed-loop system. Preliminary simulation results, without time-delay, are presented showing the theoretically expected effectiveness of the proposed method.