Digital Material Assembly by Passive Means and Modular Isotropic Lattice Extruder System

A set of machines and related systems build structures by the additive assembly of discrete parts. These digital material assemblies constrain the constituent parts to a discrete set of possible positions and orientations. In doing so, the structures exhibit many of the properties inherent in digital communication such as error correction, fault tolerance and allow the assembly of precise structures with comparatively imprecise tools. Assembly of discrete cellular lattices by a Modular Isotropic Lattice Extruder System (MILES) is implemented by pulling strings of lattice elements through a forming die that enforces geometry constraints that lock the elements into a rigid structure that can then be pushed against and extruded out of the die as an assembled, loadbearing structure

Discrete Assemblers Utilizing Conventional Motion Systems

An alternative to additive manufacturing is disclosed, introducing an end-to-end workflow in which discrete building blocks are reversibly joined to produce assemblies called digital materials. Described is the design of the bulk-material building blocks and the devices that are assembled from them. Detailed is the design and implementation of an automated assembler, which takes advantage of the digital material structure to avoid positioning errors within a large tolerance. To generate assembly sequences, a novel CAD/CAM workflow is described for designing, simulating, and assembling digital materials. The structures assembled using this process have been evaluated, showing that the joints perform well under varying conditions and that the assembled structures are functionally precise

Design and evaluation of a reaction-force series elastic actuator configurable as biomimetic powered ankle and knee prostheses

Thesis: Ph. D., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, February, 2020Cataloged from the official PDF of thesis.Includes bibliographical references (pages 179-190).All commercial leg powered prostheses have been, up to this point, a one-size fits-all design, and of those existing systems, none has yet managed to fully achieve biological walking range of motion, torque and power. Yet, no human body is the same as the next. A configurable prosthesis potentially offers improvements in battery run-time, prosthesis mass, acoustic noise, user comfort, and even enables sport and economy modes within the same fundamental hardware. In this thesis, a reaction-force, series-elastic actuator (RFSEA) is presented that is capable of achieving biomimetic ankle and knee kinetics and kinematics during level-ground walking across a range of body masses, heights and walking styles. The platform is configurable to inertial load by swapping a simple-to-manufacture flat-plate composite spring that allows tuning the actuator dynamics to match different user requirements. The RFSEA also comprises a high torque and pole-count drone motor that directly drives a ball screw with a tunable, low-gear ratio lead. The design enables high dynamic range providing a closed-loop, torque-controlled joint that can demonstrate arbitrary levels of impedance. This control fidelity is important to support smooth control in free-space and high-inertial output conditions, such as the swing and late-stance phases of walking, respectively. A simulation framework is presented that defines mechatronic design specifications for the motor, spring, and gear-reduction components. The optimization procedure clamps output joint dynamics to subject-specific biological gait data, and searches for minimum electric energy solutions across the motor, gear-reduction and spring component space. A second optimization procedure then searches for optimal linkage and spring geometry to best approach the design targets as constrained by the availability of discrete drivetrain components. In this thesis, ankle and knee designs are presented with optimized components using biological joint data from a non-amputee subject walking at 2.0m/sec with a body mass equal to 90Kg. For these designed biomimetic joints, system specifications are verified using bench test evaluations, and preliminary human gait studies.With a minimum viable actuator mass of 1.4Kg, the platform has a nominal torque control bandwidth of 6Hz at 82Nm, a repeated peak torque capacity of 175Nm, peak demonstrated power over 400W (with theoretical limits over 1kW), a 110 degree range of motion, as well as torque and power densities of 125Nm/kg and 286W/kg, respectively. Configured as an ankle-foot prosthesis, there are 35 degrees of dorsifiexion and 75 degrees of plantar flexion, and as a knee the full 110 degrees of flexion are available to enable activities on varied terrain such as stairs and inclines. Walking dynamics are evaluated with a finite state-machine ankle controller piloted by N=3 subjects with below-knee amputation walking at 1.5m/sec on an instrumented treadmill and one subject walking on stairs. In preliminary experiments, net positive work of 0.2J/Kg, peak joint torque of 1.5Nm/Kg, and peak mechanical power of 4.3W/Kg all fall within one standard deviation of the intact-limb biological mean. Configured as an ankle-foot prosthesis, the system mass is 2.2Kg including battery and electronics, and as a knee the system mass is 1.6Kg, making the RFSEA platform the lightest, most adaptable, and most biomimetic leg system yet published.by Matthew E. Carney.Ph. D.Ph. D. Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Science

Discrete cellular lattice assembly

Thesis: S.M., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2015.Cataloged from PDF version of thesis.Includes bibliographical references (pages 109-113).Robotic assembly of discrete cellular lattices at super-hertz (>1Hz) assembly rates is shown to be possible by integrating the design of a modular robotic assembler with the specified lattice topology such that the lattice can itself be removed from the incremental assembly process. Limits to assembly rates are ultimately dependent on allowable error, system stiffness, and damping characteristics. Vibrations due to cyclical motions of the end-effector, locomotion system, and the dynamic response of an incrementally varying lattice must settle to acceptable ranges to enable engagement between end-effectors, discrete elements, and their affixing features to adjacent cells. For given system dynamics, longer settling times enables greater energy dissipation, and less error. With a greater allowable error at the interface, a shorter assembly cycle period can be attained. Passive alignment features designed into the robot end-effectors, locomotion systems, and the discrete lattice elements reduce the precision requirements of the assembly process by opening up the acceptable error range, thereby, enabling higher assembly cycle-rates. An experiment was performed to evaluate how an assembler locally referencing a lattice performed in comparison to a globally referenced assembler. The two assemblers were of similar kinematic form: both gantry-type CNC machines: a ShopBot and a custom built relative robotic assembler. The results showed superior performance by the global coordinate frame system. An error budget analysis of the two systems showed that the locally referenced, lattice based system had a larger more variable structural loop than the global coordinate frame ShopBot. The control experiment, demonstrated 0.1Hz assembly rates, while first order approximations predict a maximum 4Hz cycle for the specified interface geometry. Results show that in order to successfully assemble discrete cellular lattices at super-hertz rates the robot must itself become the local, instantaneous global coordinate frame such that the structural loop is absolutely minimized, while stiffness is maximized; at the instantaneous moment of assembly the structural loop of the robot must reference only itself.by Matthew Eli Carney.S.M