Motion Control

Soft Robot “Walks” on Any Terrain

Traditional robots often feature isolated mechanical joints. These discrete components limit a rover’s ability to traverse sand, stone, and other challenging environments. A team at the University of California San Diego has demonstrated a more flexible option: a soft robot that lifts its legs over obstacles and operates on a variety of terrains. The 3D-printed quadrupedal technology may someday support search-and-rescue missions requiring intelligent navigation capabilities.

Posted in: Briefs, Motion Control, Automation, Sensors and actuators, Sensors and actuators, Terrain, Kinematics, Additive manufacturing, Robotics, Autonomous vehicles

High-Temperature Actuators Bend as They “Breathe”

The mechanical components are made from films that expand and contract as they let oxygen in and out.

Extreme temperatures are hard for mechanical components to endure without degrading. To address the problem, researchers at MIT worked with several other universities to develop a new way to make actuators that could be used in exceptionally hot environments.

Posted in: Briefs, Motion Control, Automation, Sensors and actuators, Sensors and actuators, Heat resistant materials, Materials properties, Test equipment and instrumentation

3D-Printed Tensegrity Object Can Change Shape

The technology creates a large, lightweight, strong object that can be flattened and then expanded to its full size when heated.

A team of researchers from the Georgia Institute of Technology has developed a way to use 3D printers to create objects capable of dramatic expansion. The technology could someday be used in applications ranging from space missions to biomedical devices. The new 3D-printed objects use tensegrity, a structural system of floating rods in compression and cables in continuous tension. The researchers fabricated the struts from shape memory polymers that unfold when heated.

Posted in: Briefs, Motion Control, Automation, Thermodynamics, Thermodynamics, Additive manufacturing, Fabrication, Materials properties, Polymers, Smart materials

Flat, Triangular Modules Connect to Form Origami Robot

Using two genderless mechanisms, module sides are connected and folded to create reconfigurable 3D structures.

Origami robots are composed of thin structures that can fold and unfold to change shape. They are compact and lightweight, but have functional restrictions related to size, shape, and how many folds can be created. On the other hand, modular robots use large numbers of individual entities to reconfigure the overall shape and address diverse tasks. These robots are more flexible when it comes to shape and configuration, but they are generally bulky and complex.

Posted in: Briefs, Motion Control, Automation, Sensors and actuators, Sensors and actuators, Fabrication, Robotics, Lightweight materials, Materials properties

Straws Help Create Simple Robot Joints

Plastic drinking straws and inflatable tubing are used to build machines that walk like insects.

Inspired by arthropod insects and spiders, Harvard professor George Whitesides and Alex Nemiroski, a former postdoctoral fellow in Whitesides’ Harvard lab, used ordinary plastic drinking straws to create a type of semi-soft robot capable of standing and walking. The team also created a robotic water strider capable of pushing itself along the liquid surface.

Posted in: Briefs, Motion Control, Automation, Design processes, Robotics, Materials properties, Plastics

Advanced Tool Drive System (ATDS) Camera Positioning Mechanism (CPM)

Robotic servicing of a satellite in low earth orbit (LEO) or geosynchronous Earth orbit (GEO) requires advanced systems capable of meeting the harsh environments of space. To support this effort, the Goddard Space Flight Center Satellite Servicing Capabilities Office (SSCO) has developed a camera positioning mechanism that will be capable of viewing features on a client satellite. Application of the CPM technology would be in multiple areas of spaceflight requiring robotic servicing including space exploration, planetary science, Earth science, and manned spaceflight.

Posted in: Briefs, Mechanical Components, Motion Control, Motors & Drives, Positioning Equipment, Optics, Optics, Maintenance, Repair and Service Operations, Maintenance, repair, and service operations, Robotics, Satellites

Evaluation Standard for Robotic Research

Universal benchmarks can standardize the measurement of robotic manipulation tasks.

The Yale-CMU-Berkeley (YCB) Object and Model Set provides universal benchmarks for labs specializing in robotic manipulation and prosthetics. About two years ago, Aaron Dollar, an associate professor of mechanical engineering and materials science at Yale University, came up with the benchmark idea to bring a level of specificity and universality to manipulation tasks in robotics research. He enlisted the help of two former colleagues in the robotics community, Dr. Siddhartha Srinivasa from Carnegie-Mellon University and Dr. Pieter Abbeel of the University of California, Berkeley.

Posted in: Briefs, Motion Control, Automation, Kinematics, Research and development, Robotics, Quality standards, Quality standards, Biomechanics

Mechanisms for Achieving Non-Sinusoidal Waveforms on Stirling Engines

The current state-of-the-art Stirling engines use sinusoidal piston and displacer motion to drive the thermodynamic cycle and produce power. Research performed at NASA Glenn has shown that non-sinusoidal waveforms have the potential to increase Stirling engine power density, and could possibly be used to tailor engine performance to the needs of a specific application. However, the state-of-the-art Stirling engine design uses gas springs or planar springs that are very nearly linear, resulting in a system that resonates at a single frequency. This means that imposing non-sinusoidal waveforms, consisting of multiple frequencies, requires large forces from the drive mechanism (either the alternator or the crank shaft). These large forces increase losses, and increase the size and requirements of the control system. This innovation aims to reduce the external forcing requirements by introducing internal mechanical components that provide the forces necessary to achieve the desired waveforms.

Posted in: Briefs, Mechanical Components, Mechanics, Motion Control, Alternators, Alternators, Crankshafts, Engine efficiency, Stirling engines

Improving Stirling Engine Performance Through Optimized Piston and Displacer Motion

Stirling engines typically achieve high efficiency, but lack power density. Low power density prevents them from being used in many applications where internal combustion engines are viable competitors, and increases system costs in applications that require Stirling engines. This limits their operating envelope in both terrestrial and space applications. Sinusoidal piston and displacer motion is one of the causes of low power density. Previous work proposed solving this problem by replacing sinusoidal waveforms with waveforms that more closely approximate those of the ideal Stirling cycle. However, when working with real engines, imposing ideal waveforms has been shown to reduce power density and efficiency due to increased pressure drop through the regenerator and heat exchangers.

Posted in: Briefs, Fluid Handling, Mechanical Components, Mechanics, Motors & Drives, Engine efficiency, Pistons, Stirling engines

A Method for Accurate Load/Position Control of Rigidly Coupled Electromechanical Actuators

NASA has developed a technique designed to prevent cross-coupling in systems where two or more linear electro-mechanical actuators (EMA) are rigidly connected and are in danger of becoming cross-coupled. In such systems where the linked EMAs are commanded to achieve two distinct goals, such as position and load control, control problems often arise — especially at higher load and linear velocity levels. Both position and load control become inaccurate and in certain situations, stability of the overall system may be compromised. The NASA-developed approach mitigates the problem and achieves both accurate position following and desired load levels between the two (or more) actuators.

Posted in: Briefs, Mechanical Components, Mechanics, Positioning Equipment, Electronic control systems, Electronic equipment, Sensors and actuators, Electronic control systems, Electronic equipment, Sensors and actuators

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