Multiple-Material Topology Optimization of Compliant Mechanisms Created via Polyjet 3D Printing

Compliant mechanisms are able to transfer motion, force, and energy using a monolithic structure without discrete hinge elements. The geometric design freedoms and multi-material capability offered by the PolyJet 3D printing process enables the fabrication of compliant mechanisms with optimized topology. The inclusion of multiple materials in the topology optimization process has the potential to eliminate the narrow, weak, hinge-like sections that are often present in single-material compliant mechanisms. In this paper, the authors propose a design and fabrication process for the realization of 3-phase, multiple-material compliant mechanisms. The process is tested on a 2D compliant force inverter. Experimental and theoretical performance of the resulting 3-phase inverter is compared against a standard 2-phase design.Mechanical Engineerin

TinyTerp: A FULLY AUTONOMOUS MOBILE SMART CENTI-ROBOT

A fully autonomous modular 8 cm3 robot is presented using commercially available off-the-shelf (COTS) components. The robot introduced is called Tiny Terrestrial Robotic Platform (TinyTeRP) which provides an inexpensive, easily assembled, small robotic platform for researchers to study swarm behavior. TinyTeRP can be assembled in 30 minutes and costs $51.50. TinyTeRP is fully autonomous, with approximately 10 minutes of run time, and the ability to travel over 20 cm/s with DC motors and wheels. Communication to other TinyTeRP robots and stationary sensors is performed using a 2.4 GHz IEEE 802.15.4 radio. TinyTeRP has the ability to interface with additional sensors modules and locomotion actuators, including a wheeled locomotion and inertial measurement unit (IMU) module. An additional legged platform module that uses thermally actuated polymer legs with a silver composite acrylic is discussed. Finally, TinyTeRP demonstrates the use of two control algorithms to interact with a fixed beacon using received signal strength indicator (RSSI)

Novel Integrated System Architecture for an Autonomous Jumping Micro-Robot

As the capability and complexity of robotic platforms continue to evolve from the macro to micro-scale, innovation of such systems is driven by the notion that a robot must be able to sense, think, and act [1]. The traditional architecture of a robotic platform consists of a structural layer upon which, actuators, controls, power, and communication modules are integrated for optimal system performance. The structural layer, for many micro-scale platforms, has commonly been implemented using a silicon die, thus leading to robotic platforms referred to as "walking chips" [2]. In this thesis, the first-ever jumping microrobotic platform is demonstrated using a hybrid integration approach to assemble on-board sensing and power directly onto a polymer chassis. The microrobot detects a change in light intensity and ignites 0.21mg of integrated nanoporous energetic silicon, resulting in 246µJ of kinetic energy and a vertical jump height of 8cm

Topology Optimization Algorithms for Additive Manufacturing

Topology optimization is a powerful free-form design tool that couples finite element analysis with mathematical programming to systematically design for any number of engineering problems. Additive manufacturing (AM), specifically 3D printing, is a manufacturing process where material is added through deposition or melting in a layer-by-layer fashion. Additively manufactured parts are `built' from the bottom up, allowing production of intricate designs without extra effort on the part of the engineer or technician -- complexity is often said to be `free'. This dissertation seeks to leverage the full potential of this burgeoning manufacturing technology by developing several new design algorithms based on topology optimization. These include multi-material projection methods appropriate for multiphase 3D printers, an overhang-prevention projection method capable of designing components that do not need sacrificial anchors in metal AM processes, and models for simultaneously optimizing topology and objects embedded in process. These algorithms are demonstrated on several design examples and shown to produce solutions with capabilities that exceed existing designs and/or that require less post-processing in fabrication. Targeting the capabilities of the Polyjet Stratasys 3D printers, a topology optimization algorithm is developed for the design of multi-material compliant mechanisms in which the algorithm ultimately designs both the topology of the part and the placement of each material -- one stiff, one more compliant. Results -- obtained through development of a both a new multi-material model and through development of a robust topology optimization technique for the elimination of one-node hinges -- show the ability to place both soft and stiff material and lead to dramatic improvements in performance of compliant mechanisms. One of the manufacturing challenges in metal powder-based 3D printing technologies is material curling due to internal stress development from the heating and cooling cycle during the printing process. To counteract this phenomena, sacrificial support material is introduced to anchor the part to the build plate, which must then be removed chemically or mechanically in post-production: a time consuming process. Components requiring no post-printing material removal are achieved through development of a topology optimization algorithm to design components to respect a designer-prescribed maximum overhang angle, such that the optimized part can be manufactured without using sacrificial support anchors. Solutions are shown to satisfy the prescribed overhang constraint, along with minimum feature length scale constraints as needed. Finally, an algorithm is developed considering the ability to embed discrete objects such as stiffeners or actuators within a monolithic printed part. Herein, a hybrid continuum-truss topology optimization algorithm is developed to leverage this potential capability, where the algorithm designs not only the continuum phase, but also places discrete truss members within this phase. With an eye towards future AM capabilities, the algorithm is demonstrated on the more contemporary design problem of strut-and-tie models in reinforced concrete design. It is shown that the algorithm is especially useful for designing within complex design domains in which the flow of forces is not obvious. While an exciting direction, it is noted that further advancements in 3D printing technology are needed to allow for such printed topologies