Design principles for six degrees-of-freedom MEMS-based precision manipulators

In the future, the precision manipulation of small objects will become more and more important for appliances such as data storage, micro assembly, sample manipulation in microscopes, cell manipulation, and manipulation of beam paths by micro mirrors. At the same time, there is a drive towards miniaturized systems.\ud Therefore, Micro ElectroMechanical Systems (MEMS), a fabrication technique enabling micron sized features, has been researched for precision manipulation. MEMS devices comprise micro sensors, actuators, mechanisms, optics and fluidic systems. They have the ability to integrate several functions in a small package. MEMS can be commercially attractive by providing cost reduction or enabling new functionality with respect to macro systems. Combining design principles, a mature design philosophy for creating precision machines, and MEMS fabrication, a\ud technology for miniaturization, could lead to micro systems with deterministic behavior and accurate positioning capability. However, in MEMS design trade-offs\ud need to be made between fabrication complexity and design principle requirements.\ud Therefore, the goal of this research has been twofold:\ud 1. Design and manufacture a 6 Degrees-of-Freedom (DOFs) MEMS-based manipulator with nanometer resolution positioning.\ud 2. Derive principle solutions for the synthesis of exact kinematic constraint design and MEMS fabrication technology for multi DOFs precision manipulation in the\ud micro domain

Efficient Collision Detection Method for Flexure Mechanisms Comprising Deflected Leafsprings

When designing and optimizing spatial flexure mechanisms, it is hard to predict collision due to 3D motion and large deformations, which compromises the utilization of spatial freedom. A computationally efficient collision test is desirable to assure that feasible mechanism designs are found when algorithmically optimizing the shape of elastic mechanisms, which are prone to collision. In this paper, a method is presented to test for collision specifically suited for flexure mechanisms by taking advantage of the typical slender aspect ratio and shape of the elastic members. Hereby, an efficient collision test is obtained that allows for the computation of a quantitative value for the severeness of collision. This value can then be used to efficiently converge to collision free solutions without excluding good mechanism designs leading to improved mechanisms, which utilize the maximum spatial design freedom

3D-printed flexure-based finger joints for anthropomorphic hands

Flexure-based finger joints for prosthetic hands have been studied, but until now they lack stiffness and load bearing capacity. In this paper we present a design which combines large range of motion, stiffness and load bearing capacity, with an overload protection mechanism. Several planar and non-planar hinge topologies are studied to determine load capacity over the range of motion. Optimized topologies are compared, in 30 degrees deflected state, in terms of stresses by deflection and grasping forces. Additionally, support stiffnesses were computed for all hinges in the whole range of motion (45 degrees). The Hole Cross Hinge presented the best performance over the range of motion with a grasping force up to 15 N while deflected 30 degrees. A new concept, the Angle Three-Flexure Cross Hinge, provides outstanding performance for deflections from 17.5 up to 30 degrees with a 20 N maximum grasping force when fully deflected. Experimental verification of the support stiffness over the range of motion shows some additional compliances, but the stiffness trend of the printed hinge is in line with the model. The presented joints power grasping capability outperform current state flexure-base hands and are comparable to commercial non-flexure-based prosthetic hands. In the event of excessive loads, an overload protection mechanism is in place to protect the flexure- hinges

Miniature proportional control valve with top-mounted piezo bimorph actuator with millisecond response time

In this paper we demonstrate the realization of a micro control valve with a top-mounted piezoelectric bimorph actuator, to obtain a high-bandwidth proportional control valve for gases in the range of several grams per hour. Dynamic fluidic and mechanical characterization shows that the valve is suitable for high-speed flow control with response times on the order of milliseconds. The microvalve contains an integrated capacitive displacement sensor for position-based control, which can be used to improve the control precision. The microvalve is realized in a straight-forward fabrication process based on a single SOI wafer. A high level of integration of the piezo actuator is achieved using a flexible silicone rubber support between the bimorph and the silicon. This leads to a small volume, high speed device

Modeling of a flexible instrument to study its sliding behavior inside a curved endoscope

Flexible instruments are increasingly used to carry out surgical procedures. The instrument tip is remotely controlled by the surgeon. The flexibility of the instrument and the friction inside the curved endoscope jeopardize the control of the instrument tip. Characterization of the surgical instrument behavior enables the control of the tip motion. A flexible multibody modeling approach was used to study the sliding behavior of the instrument inside a curved endoscope. The surgical instrument was modeled as a series of interconnected planar beam elements. The curved endoscope was modeled as a rigid curved tube. A static friction-based contact model was implemented. The simulations were carried out both for the insertion of the flexible instrument and for fine manipulation. A computer program (SPACAR) was used for the modeling and simulation. The simulation result shows the stick-slip behavior and the motion hysteresis because of the friction. The coefficient of friction has a large influence on the motion hysteresis, whereas the bending rigidity of the instrument has little influence