Pierluigi Rea

A new articulated leg for mobile robots

Purpose – The paper aims to present a new mechanical scheme for a leg to be included in legged vehicles that simplifies the control actuations along the stride.Design/methodology/approach – The scheme includes three four‐bar links grouped in two mechanisms. The first one decouples the vertical and horizontal foot movements. The second one produces a constant horizontal foot velocity when the corresponding motor is given a constant speed. A hybrid robot with wheels at the end of the hind legs has been simulated and constructed to validate the leg performance.Findings – The gait control requires only five commands for the electronic cards to control the leg. Decoupling vertical and horizontal movements allows a more adequate selection of actuators, a reduction of energy consumption, and higher load capacity and robot velocity. Additional mechanical benefits, such as improved robustness and lower inertia, are obtained. The hind legs can also be articulated, allowing the robot to overcome an obstacle and to c...

Mechanics and Simulation of Six-Legged Walking Robots

Legged locomotion is used by biological systems since millions of years, but wheeled locomotion vehicles are so familiar in our modern life, that people have developed a sort of dependence on this form of locomotion and transportation. However, wheeled vehicles require paved surfaces, which are obtained through a suitable modification of the natural environment. Thus, walking machines are more suitable to move on irregular terrains, than wheeled vehicles, but their development started in long delay because of the difficulties to perform an active leg coordination. In fact, as reported in (Song and Waldron, 1989), several research groups started to study and develop walking machines since 1950, but compactness and powerful of the existent computers were not yet suitable to run control algorithms for the leg coordination. Thus, ASV (Adaptive-Suspension-Vehicle) can be considered as the first comprehensive example of six-legged walking machine, which was built by taking into account main aspects, as control, gait analysis and mechanical design in terms of legs, actuation and vehicle structure. Moreover, ASV belongs to the class of “statically stable” walking machines because a static equilibrium is ensured at all times during the operation, while a second class is represented by the “dynamically stable” walking machines, as extensively presented in (Raibert, 1986). Later, several prototypes of six-legged walking robots have been designed and built in the world by using mainly a “technical design” in the development of the mechanical design and control. In fact, a rudimentary locomotion of a six-legged walking robot can be achieved by simply switching the support of the robot between a set of legs that form a tripod. Moreover, in order to ensure a static walking, the coordination of the six legs can be carried out by imposing a suitable stability margin between the ground projection of the center of gravity of the robot and the polygon among the supporting feet. A different approach in the design of six-legged walking robots can be obtained by referring to biological systems and, thus, developing a biologically inspired design of the robot. In fact, according to the “technical design”, the biological inspiration can be only the trivial observation that some insects use six legs, which are useful to obtain a stable support during the walking, while a “biological design” means to emulate, in every detail, the locomotion of a particular specie of insect. In general, insects walk at several speeds of locomotion with a

Cloud E-learning for Mechatronics

This paper describes results of the CLEM project, Cloud E-learning for Mechatronics. CLEM is an example of a domain-specific cloud that is especially tuned to the needs of VET (Vocational, Education and Training) teachers. An interesting development has been the creation of remote laboratories in the cloud. Learners can access such laboratories to support their practical learning of mechatronics without the need to set up laboratories at their own institutions. The cloud infrastructure enables multiple laboratories to come together virtually to create an ecosystem for educators and learners. From such a system, educators can pick and mix materials to create suitable courses for their students and the learners can experience different types of devices and laboratories through the cloud. The paper provides an overview of this new cloud-based e-learning approach and presents the results. The paper explains how the use of cloud computing has enabled the development of a new method, showing how a holistic e-learning experience can be obtained through use of static, dynamic and interactive material together with facilities for collaboration and innovation. We have designed and developed a new customized cloud platform for e-learning.We have designed and developed a new cloud framework to model mechatronic devices.We have evaluated the system with users and teachers in the field.The proposed system is the first cloud based e-learning system for mechatronics.

A Procedure for the Design of Novel Assisting Devices for the Sit-to-Stand

The Sit-to-Stand (STS) is an activity most people perform numerous times daily. Standing up deals with the transition from two stabilized postures, namely seated to standing, with movement of all body segments except the feet. During the STS the body’s Center of Gravity (COG) is moved upward from a sitting position to a standing position without losing balance and requiring a good coordination of many muscles. Three main phases of the STS movement can be recognized. One begins to stand up by inclining the upper body forward, which moves body mass toward the feet in order to maintain balance after lift-off. Prior to leaving the chair, hip and knee extensor muscles are activated to provide antigravity support for these joints, this action is commonly referred to as “weight shift”. Finally, after leaving the chair, the leg and trunk joints are straightened to achieve upright stance. The STS task can be considered of major importance for impaired and elderly people to achieve minimal mobility and independence. In this paper we detail a procedure for the design of assisting devices to be used for the STS. In par-ticular, an experimental procedure is described firstly to track and record point trajectories and the orientation of the trunk during the STS. This analysis is then used to get information for the design of assisting devices. A proposal and simulation results are presented for a novel mechatronic system. In particular, for the case under study experimental tests are used to drive the actuation system for the reported simulation. A functional mechatronic scheme is then proposed to control the device during its operation.

Overall design of Ca.U.M.Ha. robotic hand for harvesting horticulture products

The overall design of Ca.U.M.Ha. (Cassino-Underactuated-Multifinger-Hand) for harvesting horticulture products is presented. Ca.U.M.Ha. shows an anthropomorphic design incorporating four underactuated finger mechanisms and a simplified contrasting thumb, which are all joined to a rigid palm. The pneumatic cylinders of the articulated fingers are operated in parallel in order to give an additional auto-adaptability on the object to grasp. An application of Ca.U.M.Ha. for grasping different shapes of apples is presented.

Mechanical Design of a Novel Biped Climbing and Walking Robot

The present paper deals with the mechanical design of a novel biped climbing and walking robot, which is provided of a 2 (3-RPS) leg mechanism with 6 d.o.f.s. and which makes use of suction-cups for climbing on flat and rigid vertical surfaces. The serial-parallel kinematic structure of each leg mechanism, along with the climbing and walking motions of the proposed biped robot, are analyzed.

The Synthesis of the Axodes of RCCC Linkages

As the coupler link of an RCCC linkage moves, its instant screw axis (ISA) sweeps a ruled surface on the fixed link; by the same token, the ISA describes on the coupler link itself a corresponding ruled surface. These two surfaces are the axodes of the linkage, which roll while sliding and maintaining line contact. The axodes not only help to visualize the motion undergone by the coupler link but also can be machined as spatial cams and replace the four-bar linkage, if the need arises. Reported in this paper is a procedure that allows the synthesis of the axodes of an RCCC linkage. The synthesis of this linkage, in turn, is based on dual algebra and the principle of transference, as applied to a spherical four-bar linkage with the same input–output function as the angular variables of the RCCC linkage. Examples of RCCC linkages are included. Moreover, to illustrate the generality of the synthesis procedure, it is also applied to a spherical linkage, namely, the Hooke joint, and to the Bennett linkage.

Effects of the design parameters on the synthesis of Geneva mechanisms

A general algorithm for the kinematic synthesis of Geneva mechanisms with curved slots is introduced here, when a suitable displacement program is given with the aim of avoiding the typical shock-loading problems of conventional Geneva mechanisms. Moreover, the effects of the design parameters are analyzed through significant numerical examples. These parameters are: number of driving cranks; number of slots; imposed displacement program; and pin radius of the driving crank for the Geneva mechanism.

An Ecosystem for E-Learning in Mechatronics: The CLEM Project

This paper describes some results of the FP7 CLEM project, Cloud E-learning for Mechatronics. An interesting development has been the creation of remote laboratories in the cloud. Learners can access such laboratories to help with their practical learning about mechatronics without need to set up laboratories at their own institutions. On the other hand the cloud infrastructure enables multiple laboratories to come together virtually to create an ecosystem for educators and learners. From such a system, educators can pick and mix materials to create suitable courses for their students. This means that learners can experience different types of devices and laboratories through the cloud. The paper provides an overview of the CLEM project, presenting results so far. In addition to the remote laboratories set up using a Raspberry Pi and Arduino microprocessor structure, this paper also presents information on the results of a survey and the development of static learning material. It also explains how a holistic e-learning experience can be obtained through use of static and dynamic material together with facilities for collaboration and innovation.

The Synthesis of the Axodes of Spatial Four-Bar Linkages

The paper introduces a procedure for the motion analysis of a four-bar linkage by means of dual algebra and the Principle of Transference. This procedure allows the mapping of the motion from the Euclidean to the spherical dual space. In particular, the position analysis of a spatial four-bar linkage is formulated by referring to a spherical four-bar linkage, which moves on the dual unit sphere. Moreover, both fixed and moving axodes of the coupler link are obtained, as traced by the spatial motion of the instant screw axis (ISA) with respect to the fixed and moving frames. These ruled surfaces reproduce the spatial motion of the coupler link upon relatively rolling and sliding around and along the ISA. Finally, the proposed procedure has been implemented in MatLab, in order to analyze the motion of the different types of four-bar linkages, including the Bennett mechanism and the Hooke joint. The motion is illustrated by means of animations of the four-bar linkages and their axodes.Copyright