Biped Robots With Compliant Joints for Walking and Running Performance Growing

This paper deals with the problem of compliance in biped robots locomotion. After a first literature review, we designed and simulated a 3D virtual model of a biped robot conceived with the same link dimensions (and weights) of a standard man. In all simulation, the same input to the robot actuators are proposed, modifying only the compliance of the attached links. We first validated the model and then compared results increasing and reducing compliance on hip, knee and ankle joints. The very good results underline how the robot performances may be increased including the compliant element in the knee. In particular, we noted how including a proper value of the compliance in the knee, power and torque of the actuators may be reduced increasing robot speed

Influence of Compliant Joints in Four-Legged Robots

Legged animals are capable of rapid movements, are efficient from the energy point of view, and are able to adapt their gaits to environmental conditions. Motions like walking, trotting, galloping, and jumping, are difficult to evaluate and replicate due to their being consequences of complex interactions of different systems (such as the musculoskeletal system and the central and peripheral nervous systems, including also the influence of the environment). In this paper, we analyzed the behavior of a four-legged robot constituted by one active DOF in each leg (using commercial servomotors) and one passive DOF in each knee and in the spine (using springs). Our objective was to increase the motion performances of the robot by varying the stiffness of the springs. The results obtained from the simulation underline how the stiffness of the spine influences the performance of the robot by increasing the speed and reducing the energy required by the servomotors

A Comparison between Two Force-Position Controllers with Gravity Compensation Simulated on a Humanoid Arm

The authors propose a comparison between two force-position controllers with gravity compensation simulated on the DEXTER bioinspired robotic arm. The two controllers are both constituted by an internal proportional-derivative (PD) closed-loop for the position control. The force control of the two systems is composed of an external proportional (P) closed-loop for one system (P system) and an external proportional-integrative (PI) closed-loop for the other system (PI system). The simulation tests performed with the two systems on a planar representation of the DEXTER, an eight-DOF bioinspired arm, showed that by varying the stiffness of the environment, with a correct setting of parameters, both systems ensure the achievement of the desired force regime and with great precision the desired position. The two controllers do not have large differences in performance when interacting with a lower stiffness environment. In case of an environment with greater rigidity, the PI system is more stable. The subsequent implementation of these control systems on the DEXTER robotic bioinspired arm gives guidance on the design and control optimisation of the arms of the humanoid robot named SABIAN

Feasibility Study of a Passive Pneumatic Exoskeleton for Upper Limbs Based on a McKibben Artificial Muscle

Exoskeletons are wearable structures or systems designed to enhance human movement and to improve the wearer’s strength or agility, providing auxiliary support aimed at reducing efforts on muscles and joints of the human body. The aim of this work is to discuss on the feasibility of a new passive upper limb exoskeleton, based on the use of pneumatic artificial muscles, and characterized by extreme lightness, cheapness, and ease of use. A broad overview of the state of the art on current exoskeletons is introduced. Then the concept of the new device is presented, and different transmission architectures between pneumatic muscle and limb are discussed. The study demonstrates the potential effectiveness of such a device for supporting an operator in heavy work condition

A passive upper-limb exoskeleton for industrial application based on pneumatic artificial muscles

In recent years, exoskeletons are increasingly spreading into the industrial manufacturing sector to improve productivity and to reduce the incidence of work-related musculoskeletal diseases. The aim of this paper is to present a 2 degrees of freedom (DoF) passive upper-limb exoskeleton, consisting of two McKibben pneumatic artificial muscles (PAMs), and used for assisting workers during activities that require them to keep their hands in a sustained position over the head for a long time. Simulations are performed to test two different commercial PAMs and two different designs of the transmission system used to convey the traction force exerted by the pneumatic muscles to the limb; then the results are discussed. A preliminary assembly of the exoskeleton is also presented. The study confirms that PAMs can be used to realize a passive upper-limb exoskeleton for industrial application and that appropriate working space can be obtained with an accurate design of the transmission system

On the Hardware Feasibility of Nonlinear Trajectory Optimization for Legged Locomotion based on a Simplified Dynamics

Simplified models are useful to increase the computational efficiency of a motion planning algorithm, but their lack of accuracy have to be managed. We propose two feasibility constraints to be included in a Single Rigid Body Dynamicsbased trajectory optimizer in order to obtain robust motions in challenging terrain. The first one finds an approximate relationship between joint-torque limits and admissible contact forces, without requiring the joint positions. The second one proposes a leg model to prevent leg collision with the environment. Such constraints have been included in a simplified nonlinear nonconvex trajectory optimization problem. We demonstrate the feasibility of the resulting motion plans both in simulation and on the Hydraulically actuated Quadruped (HyQ) robot, considering experiments on an irregular terrain

HANDSHAKE: HANDling System for Human Autonomous KEeping

This paper presents a novel biped-wheeled-wearable machine, named HANDSHAKE, and obtained by an evolution of two robots presented in other works: one °exible-wheeled leg and one biped-°exible-wheeled robot. A critical design analysis of these two robots helped the author to propose a novel machine able to revolutionize the lower body exoskeletons' world. Conceptual and functional design, mechanical behavior (kinematics and dynamics), and multibody simulation of the biped-wheeled exoskeleton are presented in this paper, and a ¯rst reduced scale prototype is used to show the feasibility of the proposed solution. The simple control architecture used in this work underlines the enormous advantages to use the HANDSHAKE system for people with a complete absence of mobility, which are completely supported by this machine. This is possible thanks to the wheeled feet of the HANDSHAKE system which allow to support more weights respect to the classical exoskeletons, available on market and literature. The proposed machine increases stability, dynamic balance, autonomy, reducing power supply and complexity in comparison with classical exoskeleton systems because the wheeled feet are always in contact with the ground. These advantages, recognized in humanoid robots, may be used also in exoskeletons

Meccanica dell\u2019equilibratura \u2013 Manuale tecnico-scientifico

Il presente lavoro vuole fornire una sintesi dettagliata sui metodi di equilibratura dei rotori e un accenno sui sistemi di identificazione per la definizione del modello matematico che descrive il comportamento del rotore. Nel testo vengono evidenziate le criticit\ue0 del bilanciamento di rotori e presentate varie soluzioni per risolverle. In alcuni casi, soprattutto quelli in cui non si hanno a disposizione tutti i dati necessari di partenza, i sistemi di identificazione possono essere un utile strumento per ridurre gli errori tra comportamento reale e simulato