Integration of shape memory alloy for microactuation

Shape memory alloy (SMA) actuators in microelectromechanical system (MEMS) have a broad range of applications. The alloy material has unique properties underlying its high working density, simple structures, large displacement and excellent biocompatibility. These features have led to its commercialization in several applications such as micro-robotics and biomedical areas. However, full utilization of SMA is yet to be exploited as it faces various practical issues. In the area of microactuators in particular, fabricated devices suffer from low degrees of freedom (DoF), complex fabrication processes, larger sizes and limited displacement range. This thesis presents novel techniques of developing bulk-micromachined SMA microdevices by applying integration of multiple SMA microactuators, and monolithic methods using standard and unconventional MEMS fabrication processes. The thermomechanical behavior of the developed bimorph SMA microactuator is analyzed by studying the parameters such as thickness of SMA sheet, type and thickness of stress layer and the deposition temperature that affect the displacement. The microactuators are then integrated to form a novel SMA micromanipulator that consists of two links and a gripper at its end to provide three-DoF manipulation of small objects with overall actuation x- and y- axes displacement of 7.1 mm and 5.2 mm, respectively. To simplify the fabrication and improve the structure robustness, a monolithic approach was utilized in the development of a micro-positioning stage using bulk-micromachined SMA sheet that was fabricated in a single machining step. The design consisted of six spring actuators that provided large stage displacement range of 1.2 mm and 1.6 mm in x- and y-axes, respectively, and a rotation of 20° around the z-axis. To embed a self-sensing functionality in SMA microactuators, a novel wireless displacement sensing method based on integration of an SMA spiral-coil actuator in a resonant circuit is developed. These devices have the potential to promote the application of bulk-micromachined SMA actuator in MEMS area

Concept development for lightweight binary-actuated robotic devices, with application to space systems

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001."June 2001."Includes bibliographical references (leaves 66-71).Exploratory space missions of the future will require robotic systems to lead the way by negotiating and mapping very rough terrain, collecting samples, performing science tasks, and constructing facilities. These robots will need to be adaptable and reconfigurable in order to achieve a wide variety of objectives. Conventional designs using gears, motors, bearings, encoders, and many discrete components will be too complex, heavy, and failure-prone to allow highly-reconfigurable systems to be feasible. This thesis develops new concepts that may potentially enable the design of self-transforming space explorers. The vision of this research is to integrate compliant bistable mechanisms with large numbers of binary-actuated embedded smart materials. Compliant mechanisms are lightweight and robust. Binary actuation is the idea of using an actuator in a discrete on/off manner rather than in a continuous manner. A binary actuator is easy to control and robust, and by using tens or hundreds of binary actuators, one can approximate a continuous system, much like a digital computer can approximate an analog system. The first part of this thesis examines the fundamental planning issues involved with systems having large numbers of binary actuators. The notion of a workspace is described and applied to the optimization of a manipulator design. Methods for solving the forward and inverse kinematics are discussed in the context of this application. These methods are extended to the trajectory and locomotion planning problems. Methods for planning systems of substantial complexity are developed in the context of exploratory space robotics. The second part of this thesis presents experimental demonstrations that examine elements of the concept. The results of several design prototypes are discussed.by Matthew D. Lichter.S.M

Surgical Applications of Compliant Mechanisms:A Review

Current surgical devices are mostly rigid and are made of stiff materials, even though their predominant use is on soft and wet tissues. With the emergence of compliant mechanisms (CMs), surgical tools can be designed to be flexible and made using soft materials. CMs offer many advantages such as monolithic fabrication, high precision, no wear, no friction, and no need for lubrication. It is therefore beneficial to consolidate the developments in this field and point to challenges ahead. With this objective, in this article, we review the application of CMs to surgical interventions. The scope of the review covers five aspects that are important in the development of surgical devices: (i) conceptual design and synthesis, (ii) analysis, (iii) materials, (iv) maim facturing, and (v) actuation. Furthermore, the surgical applications of CMs are assessed by classification into five major groups, namely, (i) grasping and cutting, (ii) reachability and steerability, (iii) transmission, (iv) sensing, and (v) implants and deployable devices. The scope and prospects of surgical devices using CMs are also discussed

Micro motion stages with flexure hinges-design and control

The developments in micro and nano technologies brought the need of high precision micropositioning stages to be used in micro/nano applications such as cell manipulation, surgery, aerospace, micro fluidics, optical systems, micromachining and microassembly etc. Micro motion stages with flexible joints called compliant mechanisms are built to provide the needed accuracy and precision. This thesis aims to build compliant planar micro motion stages using flexure hinges to be used as micropositioning devices in x-y directions by applying new control methods. First 3- RRR planar parallel kinematic structure is selected which is also popular in the literature. Then the mechanism is developed to have a new structure which is a 3-PRR mechanism. The necessary geometric parameters are selected by using Finite Element Analysis (FEA). The displacement, stress and frequency behaviors of the mechanisms are compared and discussed. Modeling of the flexure based mechanisms is also studied for 3-PRR compliant stage by using Kinetostatic modeling method which combines the compliance calculations of flexure hinges with kinematics of the mechanism. Piezoelectric actuators and optical 2d position sensor which uses a laser source are used for actuation and measurement of the stages. After the experimental studies it's seen that the results are not compatible with FEA because of the unpredictable errors caused by manufacturing and assembly. We have succeeded to eliminate those errors by implementing a control methodology based on Sliding Mode Control with Disturbance Observer which is also based on Sliding Mode Control using linear piezoelectric actuator models. Finally, we have extracted experimental models for each actuation direction of the stage and used those models instead of piezoelectric actuator models which lowered our errors in the accuracy of our measurement and ready to be used as a high precision micro positioning stage for our micro system applications

The 29th Aerospace Mechanisms Symposium

The proceedings of the 29th Aerospace Mechanisms Symposium, which was hosted by NASA Johnson Space Center and held at the South Shore Harbour Conference Facility on May 17-19, 1995, are reported. Technological areas covered include actuators, aerospace mechanism applications for ground support equipment, lubricants, pointing mechanisms joints, bearings, release devices, booms, robotic mechanisms, and other mechanisms for spacecraft

21st century manufacturing machines: Design, fabrication and controls

Advances in nanotechnology, microfabrication and new manufacturing processes, the revolution of open electronics, and the emerging internet of things will influence the design, manufacture, and control of manufacturing machines in the future. For instance, miniaturization will change manufacturing processes; additive and rapid prototyping will change the production of machine components; and open electronics offer a platform for new control architectures for manufacturing systems that are open, modular, and easy to reconfigure. Combined with the latest trends in cyber-physical systems and the internet of things, open architecture controllers for CNC systems can become platforms, oriented for numerical control as a service (NCaaS) and manufacturing as a service, tailored to the creation of cyber-manufacturing networks of shared resources and web applications. With this potential in mind, this research presents new design-for-fabrication methodologies and control strategies to facilitate the creation of next generation machine tools. It provides a discussion and examples of the opportunities that the present moment offers. The first portion of this dissertation focuses on the design of complex 3D MEMS machines realized from conventional 2.5D microfabrication processes. It presents an analysis of an example XYZ-MEMS parallel kinematics stage as well as of designs of the individual components of the manipulator, integrated into a design approach for PK-XYZ-MEMS stages. It seems likely that this design-for-fabrication methodology will enable higher functionality in MEMS micromachines and result in new devices that interact, in three full dimensions, with their surroundings. Novel and innovative research exemplifies the opportunities new and economical manufacturing technologies offer for the design and fabrication of modern machine tools. The second portion of this dissertation describes the demonstration of a new flexural joint designed with both traditional and additive manufacturing processes. It extrapolates principles based on the design of this joint that alleviate the effects of low accuracy and poor surface finishing, anisotropy, reductions in material properties of components, and small holding forces. Based on these results, the next section presents case examples of the construction of mesoscale devices and machine components using multilayered composites and hybrid flexures for precision engineering, medical training, and machine tools for reduced life applications and tests design-for-fabrication strategies. The results suggest the strategies effectively address existing problems, providing a repertory of creative solutions applicable to the design of devices with hybrid flexures. The implications for medical industry, micro robotics, soft robotics, flexible electronics, and metrology systems are positive. Chapter number five examines to positive impact of open architectures of control for CNC systems, given the current availability of micro-processing power and open-source electronics. It presents a new modular architecture controller based on open-source electronics. This component-based approach offers the possibility of adding micro-processing units and an axis of motion without modification of the control programs. This kind of software and hardware modularity is important for the reconfiguration of new manufacturing units. The flexibility of this architecture makes it a convenient testbed for the implementation of new control algorithms on different electromechanical systems. This research provides general purpose, open architecture for the design of a CNC system based on open electronics and detailed information to experiment with these platforms. This dissertation’s final chapter describes how applying the latest trends to the classical concepts of modular and open architecture controllers for CNC systems results in a control platform, oriented for numerical control as a service (NCaaS) and manufacturing as a service (MaaS), tailored to the creation of cyber-manufacturing networks of shared resources and web applications. Based on this technology, this chapter introduces new manufacturing network for numerical control (NC) infrastructure, provisioned and managed over the internet. The proposed network architecture has a hardware, a virtualization, an operating system, and a network layer. With a new operating system necessary to service and virtualize manufacturing resources, and a micro service architecture of manufacturing nodes and assets, this network is a new paradigm in cloud manufacturing

Affordable flexible hybrid manipulator for miniaturised product assembly

Miniaturised assembly systems are capable of assembling parts of a few millimetres in size with an accuracy of a few micrometres. Reducing the size and the cost of such a system while increasing its flexibility and accuracy is a challenging issue. The introduction of hybrid manipulation, also called coarse/fine manipulation, within an assembly system is the solution investigated in this thesis. A micro-motion stage (MMS) is designed to be used as the fine positioning mechanism of the hybrid assembly system. MMSs often integrate compliant micro-motion stages (CMMSs) to achieve higher performances than the conventional MMSs. CMMSs are mechanisms that transmit an output force and displacement through the deformation of their structure. Although widely studied, the design and modelling techniques of these mechanisms still need to be improved and simplified. Firstly, the linear modelling of CMMSs is evaluated and two polymer prototypes are fabricated and characterised. It is found that polymer based designs have a low fabrication cost but not suitable for construction of a micro-assembly system. A simplified nonlinear model is then derived and integrated within an analytical model, allowing for the full characterisation of the CMMS in terms of stiffness and range of motion. An aluminium CMMS is fabricated based on the optimisation results from the analytical model and is integrated within an MMS. The MMS is controlled using dual-range positioning to achieve a low-cost positioning accuracy better than 2µm within a workspace of 4.4×4.4mm2. Finally, a hybrid manipulator is designed to assemble mobile-phone cameras and sensors automatically. A conventional robot manipulator is used to pick and place the parts in coarse mode while the aluminium CMMS based MMS is used for fine alignment of the parts. A high-resolution vision system is used to locate the parts on the substrate and to measure the relative position of the manipulator above MMS using a calibration grid with square patterns. The overall placement accuracy of the assembly system is ±24µm at 3σ and can reach 2µm, for a total cost of less than £50k, thus demonstrating the suitability of hybrid manipulation for desktop-size miniaturised assembly systems. The precision of the existing system could be significantly improved by making the manipulator stiffer (i.e. preloaded bearings…) and adjustable to compensate for misalignment. Further improvement could also be made on the calibration of the vision system. The system could be either scaled up or down using the same architecture while adapting the controllers to the scale.Engineering and Physical Sciences Research Council (EPSRC

Design and modeling of a compliant mechanism

Compliant mechanisms are widely used in high precision systems, because they provide high resolution, frictionless, smooth and continuous motion. These kinds of mechanisms are also cheaper than the other types of high precision mechanisms. The main idea of this kind of mechanism is that no additional joints are used for creating the motion, the deflection of the flexible elements are used to create the desired motion. In this thesis, a planar parallel compliant mechanism is designed. The mechanism is actuated from three ends by using piezo mike micromotors to create motion in XY plane. The mathematical model of the mechanism is derived by using Euler Bernoulli dynamic equation for the three beams on the mechanism. The separation of variables technique is used to solve the dynamic equations. Necessary transformations are calculated for defining the center position of the stage in terms of the deflections of the beam. The mathematical model is represented in state space form and it is simulated in MATLAB Simulink. The position results are compared with another simulation called COMET. The mathematical model is reduced to two input and two output system in order to make the XY position control of the mechanism by using PID control. Finally, the mechanism is manufactured by using laser cutting and water jet cutting techniques, open loop experiments of the mechanism are verified by actuating the piezo motors manually and by giving voltage signal

A Review of SMA-Based Actuators for Bidirectional Rotational Motion: Application to Origami Robots

Shape memory alloys (SMAs) are a group of metallic alloys capable of sustaining large inelastic strains that can be recovered when subjected to a specific process between two distinct phases. Regarding their unique and outstanding properties, SMAs have drawn considerable attention in various domains and recently became appropriate candidates for origami robots, that require bi-directional rotational motion actuation with limited operational space. However, longitudinal motion-driven actuators are frequently investigated and commonly mentioned, whereas studies in SMA-based rotational motion actuation is still very limited in the literature. This work provides a review of different research efforts related to SMA-based actuators for bi-directional rotational motion (BRM), thus provides a survey and classification of current approaches and design tools that can be applied to origami robots in order to achieve shape-changing. For this purpose, analytical tools for description of actuator behaviour are presented, followed by characterisation and performance prediction. Afterward, the actuators’ design methods, sensing, and controlling strategies are discussed. Finally, open challenges are discussed