Special Coverage

Transducer-Actuator Systems for On-Machine Measurements and Automatic Part Alignment
Wide-Area Surveillance Using HD LWIR Uncooled Sensors
Heavy Lift Wing in Ground (WIG) Cargo Flying Boat
Technique Provides Security for Multi-Robot Systems
Bringing New Vision to Laser Material Processing Systems
NASA Tests Lasers’ Ability to Transmit Data from Space
Converting from Hydraulic Cylinders to Electric Actuators
Automating Optimization and Design Tasks Across Disciplines
Vibration Tables Shake Up Aerospace and Car Testing
Supercomputer Cooling System Uses Refrigerant to Replace Water

The Basics of Encoder Selection

Many small motor applications, such as robotics, industrial equipment, and consumer products, employ digital incremental encoders for feedback sensing. Encoder selection is therefore an important part of the system design process. Choosing the best encoder for the job requires knowledge of the most important encoder properties as well as the application’s control requirements.

Posted in: Articles, Motion Control, Electronic control systems, Integrated circuits, Electronic control systems, Integrated circuits, Supplier assessment
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Servo Couplings for High-Tech Systems

Proper coupling ensures a design will meet performance requirements and have a long, trouble-free life.

Couplings are a critical part of system performance in high-tech applications, yet they are often one of the last components to be specified. Selecting the proper coupling ensures the equipment will meet performance requirements and have a long, trouble-free life. Poor coupling selection can lead to high maintenance costs, frequent downtime, and imprecise positioning.

Posted in: Articles, Joining & Assembly, Motion Control, Power Transmission, Sensors and actuators, Sensors and actuators, Materials properties, Fittings, Parts
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Metallic Glass Shatters Gear Limitations

Gears play an essential role in precision robotics, and they can become a limiting factor when the robots must perform in space missions. In particular, the extreme temperatures of deep space pose numerous problems for successful gear operation. At NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, CA, technologist Douglas Hofmann and his collaborators aim to bypass the limitations of existing steel gears by creating gears from bulk metallic glass (BMG).

Posted in: Articles, Aerospace, Manufacturing & Prototyping, Metals, Mechanical Components, Motion Control, Motors & Drives, Power Transmission, Robotics, Robotics, Alloys, Glass, Gears, Durability, Durability, Spacecraft
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Adding SCADA to a Hydraulic Power Unit

With an increased focus on plant productivity and equipment reliability, Supervisory Control and Data Acquisition (SCADA) systems have become vital tools to reduce downtime while increasing asset reliability in hydraulic systems. A SCADA system is a computer system that essentially gathers and analyzes real-time data.

Posted in: Articles, Fluid Handling, Motion Control, Computer software / hardware, Computer software and hardware, Computer software / hardware, Computer software and hardware, Hydraulic and pneumatic hybrid power, Productivity, Hydraulic control
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Control Scheme Improves Motor Operation and Interaction

A team of researchers from the Polytechnic University of Bari, Italy, is working to improve how industrial electric drives operate. They propose a new control scheme that will not only improve motor operation, but also how the motor interacts with other systems.

Posted in: News, Motion Control, Motors & Drives, Mathematical/Scientific Software, Simulation Software
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Tool Helps Design Soft Robots That Can Bend and Twist

Designing a soft robot to move organically — to bend like a finger or twist like a wrist — has always been a process of trial and error. Now, researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences and the Wyss Institute for Biologically Inspired Engineering have developed a method to automatically design soft actuators based on the desired movement.

Posted in: News, Implants & Prosthetics, Motion Control, Robotics, Computer-Aided Design (CAD), Software
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The Basics of Encoder Selection

Positioning: Resolution and Accuracy

An application’s required positioning resolution dictates the choice of encoder resolution. A well-tuned system can maintain the position within one encoder state (quadcount). Therefore, the encoder resolution in quadcounts (states) should at least correspond to the maximum permissible positioning error. Depending on the response time of the system, a higher encoder resolution should be chosen for the controller to detect deviations faster and counteract quicker.

Posted in: Articles, Motion Control, Calibration, Navigation and guidance systems, Navigation and guidance systems, Reliability, Reliability
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How To Substantially Reduce Encoder Cost While Gaining Functionality With Multi-Turn Rotary Position Sensors

Many applications require rotation counters that can measure angles greater than 360º. However the low-cost 10-turn potentiometers most design engineers are familiar with can’t always meet user requirements for resolution and reliability. As an alternative, optical absolute encoders are too expensive for many applications. These solutions require a continuous power supply or they will lose count when power is restored. Also, geared technology/rotation counters are subject to significant wear.

Posted in: White Papers, Motion Control, Automation, Robotics, Data Acquisition, Sensors
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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
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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
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White Papers

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