Mixed Position and Twist Space Synthesis of 3R Chains

Mixed-position kinematic synthesis is used to not only reach a certain number of precision positions, but also impose certain instantaneous motion conditions at those positions. In the traditional approach, one end-effector twist is defined at each precision position in order to achieve better guidance of the end-effector along a desired trajectory. For one-degree-of-freedom linkages, that suffices to fully specify the trajectory locally. However, for systems with a higher number of degrees of freedom, such as robotic systems, it is possible to specify a complete higher-dimensional subspace of potential twists at particular positions. In this work, we focus on the 3R serial chain. We study the three-dimensional subspaces of twists that can be defined and set the mixed-position equations to synthesize the chain. The number and type of twist systems that a chain can generate depend on the topology of the chain; we find that the spatial 3R chain can generate seven different fully defined twist systems. Finally, examples of synthesis with several fully defined and partially defined twist spaces are presented. We show that it is possible to synthesize 3R chains for feasible subspaces of different types. This allows a complete definition of potential motions at particular positions, which could be used for the design of precise interaction with contact surfaces.Peer ReviewedPostprint (author's final draft

Dimensional Synthesis of Wristed Binary Hands

The kinematic synthesis applied to tree topologies is a tool for the design of multi-fingered robotic hands, for a simultaneous task of all fingertips. Even though traditionally wrists and hands have been designed separately, the wrist usually being part of the robot manipulator arm, it makes sense to consider the wrist as a part of the hand, as many grasping and manipulation actions are a coordinated action of wrist and fingers. The manipulation capabilities of robotic hands mayalso beenhancedbyconsidering more than one splitting stage, as opposed to the single-palm traditional hand. In this work we present the dimensional synthesis for a family of multi-fingered hands, the binary hands, which have a 2R wrist and several splitting stages, each of them spanning two branches consisting f a revolute joint for each edge. For these topologies, it is proved that a three-position task can be defined for each fingertip, regardless of the number of fingers. One example is presented to show the possible design strategies and uses for this family of hands.Postprint (published version

Mixed Position and Twist Space Synthesis of 3R Chains

Mixed-position kinematic synthesis is used to not only reach a certain number of precision positions, but also impose certain instantaneous motion conditions at those positions. In the traditional approach, one end-effector twist is defined at each precision position in order to achieve better guidance of the end-effector along a desired trajectory. For one-degree-of-freedom linkages, that suffices to fully specify the trajectory locally. However, for systems with a higher number of degrees of freedom, such as robotic systems, it is possible to specify a complete higher-dimensional subspace of potential twists at particular positions. In this work, we focus on the 3R serial chain. We study the three-dimensional subspaces of twists that can be defined and set the mixed-position equations to synthesize the chain. The number and type of twist systems that a chain can generate depend on the topology of the chain; we find that the spatial 3R chain can generate seven different fully defined twist systems. Finally, examples of synthesis with several fully defined and partially defined twist spaces are presented. We show that it is possible to synthesize 3R chains for feasible subspaces of different types. This allows a complete definition of potential motions at particular positions, which could be used for the design of precise interaction with contact surfaces

Synthesis of Spatial 3R Chains with Configuration-Specific Twist System

Mixed-position synthesis of linkages has been used to define local contact conditions and for better adjusting a mechanism to its desired trajectory. In this work, multiple velocities are defined at a configuration in order to fully specify the subspace of twists of the end-effector at that point, and also to specify lowerdimensional subspaces of twists. This is applied to the spatial 3R chain, for which the equations are developed in detail.Peer ReviewedPostprint (author's final draft

A Design Implementation Process for Robotic Hand Synthesis

Peer ReviewedPostprint (author's final draft

Design of a Dexterous Hand for a Multi-Hand Task

Kinematic synthesis applied to tree topologies is a tool for the design of multi-fingered robotic hands, for a simultaneous task of all fingertips. Dexterous multi-fingered robotic hands can be designed to perform collaborative tasks that are traditionally performed by more than one robotic manipulator. Such collaborative tasks require multiple robotic arms and a method to control their coordinate operation. In this work, the synthesis process for the design of a single robotic hand for a bimanual task is discussed, with application to the task of holding and peeling an orange.Peer ReviewedPostprint (author's final draft

In-Hand Manipulative Synthesis Using Velocity Subspaces

The kinematic design of robots for tasks involving positions and its derivatives has been explored in the past in order to shape the trajectory of the robot at a given set of points. This approach has been successful for the synthesis of linkages; however defining a single velocity in the vicinity of a specified location might not be enough for a desired task. In the design of multi-fingered robotic hands, it is interesting to ask whether a hand can be designed for a certain in-hand manipulation that ensures contact and at the same time relative motion of the fingertips on the object surface. In this article we define a method for designing robotic hands that guide an object through a kinematic task with velocity specifications in the vicinity of key task positions. Given the mobility for a hand topology, the necessary velocities are derived at each task position to fully define the subspace of allowable directions for object manipulation. As an example, a multi-fingered robotic hand for grasping and manipulating an object with a known geometry has been designed. The proposed synthesis technique can be used to create a velocity field associated to a desired trajectory, or to fully specify the allowable velocities, or the tangent space at each position, to successfully guide the object with specified constraints.Peer ReviewedPostprint (author's final draft

Design of a Multi-palm Robotic Hand for Assembly Tasks

Some robotic tasks, especially those in which there are interactions between manipulated objects, require the collaborative work of two robotic arms equipped with end-effector grippers or robotic hands. Most of the current applications in which a bimanual task is attempted by a robot use two robot arm manipulators with simple grippers, in which the end-effectors are used for grasping and the remaining motion is performed by the robotic arms. In this work, we propose the design of a highly dexterous multi-fingered robotic hand, able to perform the bimanual task when attached to a simple arm manipulator. Dexterous robotic hands can be designed with more than one splitting stage; their design for a task can be done using kinematic synthesis for tree topologies. The synthesis process is applied in this case to the design of a robotic hand with three palms for a bimanual task consisting of assembling an emergency stop button.Peer ReviewedPostprint (author's final draft

COVID-19 and multiorgan failure: A narrative review on potential mechanisms

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) in December 2019 form Wuhan, China leads to coronavirus disease 2019 (COVID-19) pandemic. While the common cold symptoms are observed in mild cases, COVID-19 is accompanied by multiorgan failure in severe patients. The involvement of different organs in severe patients results in lengthening the hospitalization duration and increasing the mortality rate. In this review, we aimed to investigate the involvement of different organs in COVID-19 patients, particularly in severe cases. Also, we tried to define the potential underlying mechanisms of SARS-CoV2 induced multiorgan failure. The multi-organ dysfunction is characterized by acute lung failure, acute liver failure, acute kidney injury, cardiovascular disease, and as well as a wide spectrum of hematological abnormalities and neurological disorders. The most important mechanisms are related to the direct and indirect pathogenic features of SARS-CoV2. Although the presence of angiotensin-converting enzyme 2, a receptor of SARS-CoV2 in the lung, heart, kidney, testis, liver, lymphocytes, and nervous system was confirmed, there are controversial findings to about the observation of SARS-CoV2 RNA in these organs. Moreover, the organ failure may be induced by the cytokine storm, a result of increased levels of inflammatory mediators, endothelial dysfunction, coagulation abnormalities, and infiltration of inflammatory cells into the organs. Therefore, further investigations are needed to detect the exact mechanisms of pathogenesis. Since the involvement of several organs in COVID-19 patients is important for clinicians, increasing their knowledge may help to improve the outcomes and decrease the rate of mortality and morbidity.</p