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Differential flat underactuated robots have fewer actuators than degrees of freedom (DOFs). This characteristic makes it possible to design light and cost-effective robots with great dexterity. The primary challenge associated with these robots lies in effectively controlling the passive joint, in particular, when collisions with obstacles in the workspace have to be avoided. Most of the previous research focused on point-to-point motions without any control on the actual robot trajectory. In this work, a new method is presented to plan trajectories that include one or more via points. In this way, the underactuated robot can avoid the obstacles in the workspace, similarly to traditional fully actuated robots. First, a trajectory planning strategy is analytically described; then, numerical results are presented. The numerical results show the effects of the via points and of the order of the polynomials adopted to define the motion laws. In addition, experimental tests performed on a two-DOF underactuated robot are presented, and their results validate the proposed method. [ABSTRACT FROM AUTHOR]

Underactuated robots have fewer actuators than degrees of freedom (DOF). Nonactuated joints can be equipped with torsional springs. Underactuated robots can be controlled in a point-to-point motion if they have a particular mass distribution that makes them differentially flat. The trajectory described by the robot moving from the start point to the end point largely depends on the torsional stiffness of the nonactuated joints and on motion time. Thus, the same point-to-point motion can be obtained by sweeping different parts of the workspace. This property increases the dexterity of the robot. This paper focuses on the trajectories of a 3-DOF robot moving in the horizontal plane with two actuators and a torsional spring. Parametric analyses showing the effect of torsional stiffness and motion time are presented. The existence of combinations of torsional stiffness and motion time that minimize the motion torques or the swept area is discussed. The area swept by the underactuated robot is compared with the one swept by an equivalent actuated robot performing the same task. Reductions in the swept area of up to 36% are obtained. Finally, numerical results are validated by means of experimental tests on a simplified prototype. [ABSTRACT FROM AUTHOR]

Collaborative robots are increasingly common in modern production systems, since they allow to merge the productivity of automated systems with the flexibility and dexterity of manual ones. The direct interaction between the human and the robot can be the greatest advantage and the greatest limit of collaborative systems at the same time, depending on how it affects human factors like ergonomics and mental stress. This work presents an overview of collaborative robotics considering three main dimensions: robot features, modern production systems characteristics and human factors. A literature review on how such dimensions interact is addressed and a discussion on the current state of the art is presented, showing the topics that have been already widely explored and the research gaps that should be fulfilled in the future. [ABSTRACT FROM AUTHOR]

Cable robots are widely used in the field of rehabilitation. These robots differ from other cable robots because the cables are rather short and are usually equipped with magnetic hooks to improve the ease of use. The vibrations of rehabilitation robots are dominated by the effects of the hooks and payloads, whereas the cables behave as massless springs. In this paper, a 2D model of the cables of a robot that simulates both longitudinal and transverse vibrations is developed and experimentally validated. Then the model is extended to simulate the vibrations of an actual 3D robot in the symmetry planes. Finally, the calculated modal properties (natural frequencies and modes of vibration) are compared with the typical spectrum of excitation due to the cable's motion. Only the first transverse mode can be excited during the rehabilitation exercise. [ABSTRACT FROM AUTHOR]

Collaborative assembly systems (CAS) are an increasingly important solution to the requests of the current market since they present the flexibility and dexterity of the human operator and the repeatability of the robot. For a CAS to be effective, both agents should carry out the tasks in the workspace without any physical interference. This paper aims to evaluate how the product characteristics influence the interference between the human operator and the robot. To reach the goal, we developed an algorithm that simulates product assembly in the considered workspace. The model also allowed to estimate the makespan achievable for different scenarios, showing a reduction, and thus an increase in the throughput. The makespan depends on several variables, related to the product characteristics and the process ones. Given specific conditions, we have observed that increasing the collaboration parameter from 21.06 to 48.98% led to a reduction in the makespan of about 20%. Lastly, the results obtained by the simulation were verified through a validation test, showing an error of − 2.39%. [ABSTRACT FROM AUTHOR]

In the last decade, robot manufacturers have started to produce collaborative industrial robots, that can work while safely sharing the workspace with a human operator. In this way, robot repeatability, combined with human dexterity, can move automated assembly to a new level of flexibility. The aim of this paper is to investigate the conditions at which such systems, called collaborative assembly systems (CAS), can be better performing than the traditional manual or automated assembly systems. Throughput and unit direct production cost are considered for the comparison. The estimation of such performance figures, which is straightforward in traditional automated assembly systems, becomes more complex in the case of collaborative systems. In fact, both task allocation between the human and the robot, and the way they collaborate/interfere with each other during assembly, affect the throughput of CAS. With the aim of taking into account such parameters, we introduce a set of system variables and a mathematical model which allow to estimate the real convenience of the implementation of CAS in the industrial scenario. In the paper, the model is applied to compare CAS to manual assembly and to noncollaborative automated assembly, both with parameters derived from the literature and in a case study. Finally, a set of implementation conditions is derived, related to the task allocation that maximises CAS performance. [ABSTRACT FROM AUTHOR]

Automation is a powerful way to reduce production costs. The growing market demand for a wide set of models and small batch production make flexible automated production systems an emerging need in several industries. The aim of this paper is to analyze and to maximize the performance of robotized flexible production systems consisting of a robot, feeder, working station, and unloading station, where the operations of the working cycle are scheduled using a sequencing algorithm based on priority rules. Since the working cycle is not predefined, the cycle time is strongly influenced by the parameters characterizing the workcell such as the workcell layout, the robot transfer movements, the feeder, the working operations, and the presence of a buffer between stations. In this work, we modeled the working cycle of a simple but representative layout of an industrial robotized flexible production system with and without buffer, and we implemented a recursive algorithm to estimate the cycle time. The analytical model derived was compared to the experimental results, obtained by using a prototype of the flexible production workcell. The results show that the analytical model is a powerful tool to estimate the performance of the workcell and to identify the design variables or their combinations that maximize the throughput. [ABSTRACT FROM AUTHOR]

Sophia-3 (string-operated planar haptic interface for arm rehabilitation) is a planar cable-driven device with a tilting working plane. It represents the first application of the adaptive cable-driven design paradigm recently introduced by the authors, featuring a moving pulley-block that allows the robot to achieve excellent force capabilities, despite the low number of cables. This study presents the design, kinematics, and control of the device and results of experimental validation on healthy subjects. [ABSTRACT FROM PUBLISHER]

This paper presents the development of and clinical tests on NeReBot (NEuroREhabilitation roBOT): a three degrees-of-freedom (D0F), wire-driven robot for poststroke upper-limb rehabilitation. Basically, the robot consists of a set of three wires independently driven by three electric motors. The wires are connected to the patient's upper limb by means of a splint and are supported by a transportable frame, located above the patient. By controlling wire length, rehabilitation treatment (based on the passive or active-assistive spatial motion of the limb) can be delivered over a wide working space. The arm trajectory is set by the therapist through a very simple teaching-by-showing procedure, enabling most common "hands on" therapy exercises to be reproduced by the robot. Compared to other rehabilitation robots, NeReBot offers the advantages of a low-cost mechanical structure, intrinsically safe treatment thanks to the use of wires, high acceptability by the patient, who does not feel constrained by an "industrial-like" robot, transportability (it can be easily placed aside a hospital bed and/or a wheelchair), and a good trade-off between low number of DoF and spatial performance. These features and the very encouraging results of the first clinical trials make the NeReBot a good candidate for adoption in the rehabilitation treatment of subacute stroke survivors. Clinical trials were performed with a 12-patient experimental group and a 12-patient control group. Resulted that the patients who received robotic therapy in addition to conventional therapy showed greater reductions in motor impairment (in terms of Medical Research Council score, the upper limb subsection of the Fugl-Meyer score, and the Motor Status Score) and improvements in functional abilities (as measured by the Functional Independence Measure and its motor component). No adverse effects occurred and the robotic approach was very well accepted. According to these results, the NeReBot therapy may efficaciously complement standard poststroke multidisciplinary rehabilitation and offer novel therapeutic strategies for neurological rehabilitation. [ABSTRACT FROM AUTHOR]

Moving from a given position to another with an industrial robot can be a challenging problem when the task is redundant around the tool axis. In this case, there are infinite ways of choosing both the starting and the ending configurations, so that the movement between the given points is not uniquely defined. In this paper, an algorithm that calculates the suboptimal movement between two positions is proposed, which automatically generates a cloud of safe via points around the workpiece and then by exploiting such points finds the suboptimal safe path between the two positions that minimizes movement time. The proposed method, in which the search of the suboptimal path is based on graph theory and the Dijkstra algorithm, can iteratively evaluate a high number of starting and ending configurations in low computational time, allowing performing a reasonably wide search of the suboptimal path within the infinite possible motions between the given points. [ABSTRACT FROM AUTHOR]

This paper provides an overview of collaborative robotics towards manufacturing applications. Over the last decade, the market has seen the introduction of a new category of robots—collaborative robots (or "cobots")—designed to physically interact with humans in a shared environment, without the typical barriers or protective cages used in traditional robotics systems. Their potential is undisputed, especially regarding their flexible ability to make simple, quick, and cheap layout changes; however, it is necessary to have adequate knowledge of their correct uses and characteristics to obtain the advantages of this form of robotics, which can be a barrier for industry uptake. The paper starts with an introduction of human–robot collaboration, presenting the related standards and modes of operation. An extensive literature review of works published in this area is undertaken, with particular attention to the main industrial cases of application. The paper concludes with an analysis of the future trends in human–robot collaboration as determined by the authors. [ABSTRACT FROM AUTHOR]

In robotics, the risk of collisions is present both in industrial applications and in remote handling. If a collision occurs, the impact may damage both the robot and external equipment, which may result in successive imprecise robot tasks or line stops, reducing robot efficiency. As a result, appropriate collision avoidance algorithms should be used or, if it is not possible, the robot must be able to react to impacts reducing the contact forces. For this purpose, this paper focuses on the development of a special end-effector that can withstand impacts. It is able to protect the robot from impulsive forces caused by collisions of the end-effector, but it has no effect on possible collisions between the links and obstacles. The novel end-effector is based on a bi-stable mechanism that decouples the dynamics of the end-effector from the dynamics of the robot. The intrinsically nonlinear behavior of the end-effector is investigated with the aid of numerical simulations. The effect of design parameters and operating conditions are analyzed and the interaction between the functioning of the bi-stable mechanism and the control system is studied. In particular, the effect of the mechanism in different scenarios characterized by different robot velocities is shown. Results of numerical simulations assess the validity of the proposed end-effector, which can lead to large reductions in impact forces. Numerical results are validated by means of specific laboratory tests. [ABSTRACT FROM AUTHOR]