Parallel Manipulators

In recent years, parallel kinematics mechanisms have attracted a lot of attention from the academic and industrial communities due to potential applications not only as robot manipulators but also as machine tools. Generally, the criteria used to compare the performance of traditional serial robots and parallel robots are the workspace, the ratio between the payload and the robot mass, accuracy, and dynamic behaviour. In addition to the reduced coupling effect between joints, parallel robots bring the benefits of much higher payload-robot mass ratios, superior accuracy and greater stiffness; qualities which lead to better dynamic performance. The main drawback with parallel robots is the relatively small workspace. A great deal of research on parallel robots has been carried out worldwide, and a large number of parallel mechanism systems have been built for various applications, such as remote handling, machine tools, medical robots, simulators, micro-robots, and humanoid robots. This book opens a window to exceptional research and development work on parallel mechanisms contributed by authors from around the world. Through this window the reader can get a good view of current parallel robot research and applications

Using Singularities of Parallel Manipulators for Enhancing the Rigid-body Replacement Design Method of Compliant Mechanisms

International audienceThe rigid-body replacement method is often used when designing a compliant mechanism. The stiffness of the compliant mechanism, one of its main properties, is then highly dependent on the initial choice of a rigid-body architecture. In this paper, we propose to enhance the efficiency of the synthesis method by focusing on the architecture selection. This selection is done by considering the required mobilities and parallel manipulators in singularity to achieve them. Kinematic singularities of parallel structures are indeed advantageously used to propose compliant mechanisms with interesting stiffness properties. The approach is first illustrated by an example, the design of a one degree of freedom compliant architecture. Then the method is used to design a medical device where a compliant mechanism with three degrees of freedom is needed. The interest of the approach is outlined after application of the method

Design of a compensation mechanism for an active cardiac stabilizer based on an assembly of planar compliant mechanisms

Surgical robotics helps to increase the surgeon’s accuracy and limits the invasiveness of the surgery. The complexity of an operation room implies to design surgical devices that are as compact as possible and that can be easily sterilized. One interesting design approach is to combine compliant mechanisms, which have a monolithic structure, and piezoelectric actuators. Based on this approach, a robotic device for minimally invasive coronary artery bypass grafting has been proposed previously in our laboratory. It is composed of a shaft with two fingers in contact with the heart at one end, and an actuated compensation mechanism at the other end. This device successfully helps to increase the stabilization of the heart surface during the surgery but its needs to be increased for an optimal integration in the operation room. One possibility is to reduce the size of the compensation by considering an assembly of planar manufactured structures. This helps to simplify the manufacturing process and may increase the compactness. Parallel architectures constitute interesting solutions for their intrinsic stiffness properties, but in a planar configuration parallel manipulators often exhibit kinematic singularities. Two design approaches for planar parallel compliant mechanisms are presented in this paper. One design approach consists in designing a passive compliant mechanism in a configuration close to the singularity by introducing some asymmetries during the manufacturing process. The second design approach consists in taking advantage of the singularities of parallel manipulators. In fact, in some singular configurations, the end-effector of the manipulator loses stiffness while its actuators are blocked. As compliant mechanisms only work around a given configuration this loss of stiffness is used to produce the required mobilities. The final device, composed of planar compliant mechanisms, is finally presented. Finite element analysis simulations of the whole device during the compensation task give encouraging results

serial and parallel robotics: energy saving systems and rehabilitation devices

This thesis focuses on the design and discussion of robotic devices and their applications. Robotics is the branch of technology that deals with the design, construction, operation, and application of robots as well as computer systems for their control, sensory feedback, and information processing [1]. Nowadays, robotics has been an unprecedented increase in applications of industry, military, health, domestic service, exploration, commerce, etc. Different applications require robots with different structures and different functions. Robotics normally includes serial and parallel structures. To have contribution to two kinds of structures, this thesis consisting of two sections is devoted to the design and development of serial and parallel robotic structures, focused on applications in the two different fields: industry and health

7-degree-of-freedom hybrid-manipulator exoskeleton for lower-limb motion capture

Lower-limb exoskeletons are wearable robotic systems with a kinematic structure closely matching that of the human leg. In part, this technology can be used to provide clinical assessment and improved independent-walking competency for people living with the effects of stroke, spinal cord injury, Parkinson’s disease, multiple sclerosis, and sarcopenia. Individually, these demographics represent approximately: 405 thousand, 100 thousand, 67.5 thousand, 100 thousand, and 5.9 million Canadians, respectively. Key shortcomings in the current state-of-the-art are: restriction on several of the human leg’s primary joint movements, coaxial joint alignments at the exoskeleton-human interface, and exclusion of well-suited parallel manipulator components. A novel exoskeleton design is thus formulated to address these issues while maintaining large ranges of joint motion. Ultimately, a single-leg unactuated prototype is constructed for seven degree-of-freedom joint angle measurements; it achieves an extent of motion-capture accuracy comparable to a commercial inertial-based system during three levels of human mobility testing

Using Engineering to Create an Adaptive Self-Feeding System for Patients with Upper Body Disabilities

This research project aims to provide a self-feeding manipulator system to accommodate those who have upper-body motor disabilities. The purpose of the device is to allow patients to rely less on their caregivers during a meal. The patient's safe feeding without injury or malfunction at home or in a public setting will successfully achieve this form of assistance. The target cost is USD 1096 with a minimum of six months to make it a marketable product and nine months to develop a prototype. People have created similar devices such as the Neater Eater, Mealtime Partners, and the Obi Robotic Feeder in the past. These devices stem from one general need: provide a means to assist people with disabilities in feeding themselves. However, the disadvantage to all the existing products is that they are very costly, ranging between 4000 – 8000 USD apiece. In addition, they are inaccessible to people in Qatar due to their production and market being overseas. We use engineering methods to create a device that is more versatile and accessible. This thesis discusses all the alternatives created to build the manipulator. The manipulator's design is one with four degrees of freedom, and the actuators used to mobilize the joints were Servo Motors. The manipulator is to work automatically using Denavit-Hartenberg, Forward Kinematics, and Jacobian robotics methods. Some parts of the manipulator require 3D printing and CNC machining, which will be accessible in the TAMUQ building. In addition, some parts will be bought based on our requirements calculations. Another engineering method used to control the manipulation of the system is by using an Arduino board. The device consists of four main subsystems. Firstly, there is the base which mounts on any flat surface. Also, a plate, divided into four sections, that attaches to the base and can rotate. The manipulator is also attached to the base, along with a spoon attached to the manipulator. Finally, the user-interface is a critical component of the system to allow easy communication between the user and the device. Since this device targets patients with upper-body disabilities, a user-interface that functions using the patient's feet would be suitable. We aim to have the device ready to test by the end of April 2021 and allow patients from Sidra Hospital to test the device

Safe Human-Robot Interaction Using Variable Stiffness, Hyper-Redundancy, and Smart Robotic Skins

In service robotics, safe human-robot interaction (HRI) is still an open research topic, requiring developments both in hardware and in software as well as their integration. In UMAY1 and MEDICARE-C2projects, we addressed both mechanism design and perception aspects of a framework for safe HRI. Our first focus was to design variable stiffness joints for the robotic neck and arm to enable inherent compliance to protect a human collaborator. We demonstrate the advantages of variable stiffness actuators (VSA) in compliancy, safety, and energy efficiency with applications in exoskeleton and rehabilitation robotics. The variable-stiffness robotic neck mechanism was later scaled down and adopted in the robotic endoscope featuring hyper-redundancy. The hyper-redundant structures are more controllable, having efficient actuation and better feedback. Lastly, a smart robotic skin is introduced to explain the safety support via enhancement of tactile perception. Although it is developed for a hyper-redundant endoscopic robotic platform, the artificial skin can also be integrated in service robotics to provide multimodal tactile feedback. This chapter gives an overview of systems and their integration to attain a safer HRI. We follow a holistic approach for inherent compliancy via mechanism design (i.e., variable stiffness), precise control (i.e., hyper-redundancy), and multimodal tactile perception (i.e., smart robotic-skins)