A review of shape memory alloy research, applications and opportunities

Medical devices which are currently proposed to use elements made from shape memory alloys may be improved by the use of stress-induced martensite alloy elements instead. The use of stress-induced martensite decreases the temperature sensitivity of the devices, thereby making them easier to install and/or remove.

Medical devices incorporating SIM alloy elements

Provides a summary of recent developments in control of nonholonomic systems. The published literature has grown enormously during the last six years, and it is now possible to give a tutorial presentation of many of these developments. The objective of this article is to provide a unified and accessible presentation, placing the various models, problem formulations, approaches, and results into a proper context. It is hoped that this overview will provide a good introduction to the subject for nonspecialists in the field, while perhaps providing specialists with a better perspective of the field as a whole. The paper is organized as follows: introduction to nonholonomic control systems and where they arise in applications, classification of models of nonholonomic control systems, control problem formulations, motion planning results, stabilization results, and current and future research topics.

Developments in nonholonomic control problems

Gripping and holding of objects are key tasks for robotic manipulators. The development of universal grippers able to pick up unfamiliar objects of widely varying shape and surface properties remains, however, challenging. Most current designs are based on the multifingered hand, but this approach introduces hardware and software complexities. These include large numbers of controllable joints, the need for force sensing if objects are to be handled securely without crushing them, and the computational overhead to decide how much stress each finger should apply and where. Here we demonstrate a completely different approach to a universal gripper. Individual fingers are replaced by a single mass of granular material that, when pressed onto a target object, flows around it and conforms to its shape. Upon application of a vacuum the granular material contracts and hardens quickly to pinch and hold the object without requiring sensory feedback. We find that volume changes of less than 0.5% suffice to grip objects reliably and hold them with forces exceeding many times their weight. We show that the operating principle is the ability of granular materials to transition between an unjammed, deformable state and a jammed state with solid-like rigidity. We delineate three separate mechanisms, friction, suction, and interlocking, that contribute to the gripping force. Using a simple model we relate each of them to the mechanical strength of the jammed state. This advance opens up new possibilities for the design of simple, yet highly adaptive systems that excel at fast gripping of complex objects.

/pdf/universal-robotic-gripper-based-on-the-jamming-of-granular-1lfy77b5w6.pdf

Universal robotic gripper based on the jamming of granular material

https://ris.utwente.nl/ws/files/6561771/Huiskes87adaptive.pdf

Adaptive bone-remodeling theory applied to prosthetic-design analysis

The authors establish a control method for space manipulators taking dynamical interaction between the manipulator arm and the base satellite into account. The kinematics of free-flying multibody systems is investigated by introducing the momentum conservation law into the formulation and a novel Jacobian matrix in generalized form for space robotic arms is derived. The authors develop a control method for space manipulators based on the resolved motion control concept. The proposed method is widely applicable in solving not only free-flying manipulation problems but also attitude-control problems. The validity of the method is demonstrated by computer simulations with a realistic model of a robot satellite. >

Resolved motion rate control of space manipulators with generalized Jacobian matrix

The Development of Soft Gripper for the Versatile Robot Hand

Continuous Path Control of Space Manipulators Mounted on OMV

An analysis of the momentum conservation equations of a redundant free-flying spacecraft/manipulator system acting in a zero-gravity environment is presented. In order to follow a predefined end-effector path, the inverse kinematics at velocity level is considered. The redundancy is solved alternatively in terms of pseudoinverses and null-space components of the manipulator inertia matrix, the manipulator Jacobian matrix, and the generalized Jacobian matrix. A general manipulation task is defined as end-effector continuous path tracking with simultaneous attitude control of the spacecraft. Three subtasks of the general task are considered. The case of manipulator motions that yield no spacecraft attitude disturbance is analyzed in more detail and a special 'fixed-attitude-restricted' (FAR) Jacobian is defined. Through singular-value decomposition of this Jacobian, corresponding FAR dexterity measures (FAR manipulability and FAR condition number) are derived. >

/pdf/analysis-of-a-redundant-free-flying-spacecraft-manipulator-1d5lwrqew9.pdf

Analysis of a redundant free-flying spacecraft/manipulator system

The control problem of multiple manipulators installed on a free-flying space robot is presented. Kinematics and dynamics are studied and the generalized Jacobian matrix is formulated for the motion control of a multiarm system. Individual and coordinated control of dual manipulators is discussed. For the coordinated operation, a new method of controlling two arms simultaneously-one arm traces a given path, while the other arm works both to keep the satellite attitude and to optimize the total operation torque of the system-is developed. By means of this control method, an interesting torque optimum behavior is observed and a practical target capture operation is exhibited by computer simulation. >

Yoji Umetani

Papers

Resolved motion rate control of space manipulators with generalized Jacobian matrix

The Development of Soft Gripper for the Versatile Robot Hand

Continuous Path Control of Space Manipulators Mounted on OMV

Analysis of a redundant free-flying spacecraft/manipulator system

Dual arm coordination in space free-flying robot