Motion Control

Scanning Performance of Air Bearing Equipped Precision Motion Systems

Scanning is a common technique in applications ranging from high-resolution microscopy to industrial material processing. Scanning involves moving either a workpiece or an optic at a constant velocity while a reading or writing operation takes place. Air bearings are used for both purposes, especially when high precision and reliability are vital. While the physical act of writing an image or capturing an image differ by application and industry, all such applications share a common requirement — maintaining a constant velocity.

Posted in: Articles, Motion Control, Imaging and visualization, Automation, Bearings, Reliability
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Four Ways to improve Production by Understanding the Physics of Servos

There is always a need to increase production in automation applications. Sometimes achieving improvements requires breaking the process down to its fundamental basics. The science behind the technology of servo-based motion control systems should be considered when attempting to eliminate inefficiencies. Four fundamentals to examine are inertia, resonance, vibration suppression, and regeneration.

Posted in: Articles, Motion Control, Finite element analysis, Electronic control systems, Automation, Productivity
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Converting from Hydraulic Cylinders to Electric Actuators

Hydraulics are rugged and deliver a low cost per unit of force, but electric rod actuators have attained higher force capacities while becoming more flexible, precise, and reliable.

Advances in motion control technology have prompted a new debate — do hydraulic cylinders or electric linear actuators offer the best solution for a linear motion application? Hydraulic cylinders provide high force at an affordable cost. Hydraulics are rugged, relatively simple to deploy, and deliver a low cost per unit of force. However, electric rod actuators (electric cylinders), particularly those with roller screws, have attained increasingly higher force capacities while becoming more flexible, precise, and reliable.

Posted in: Articles, Motion Control, Electrical systems, Flight control actuators, Hydraulic control, Reliability
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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, 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, 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, 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 and hardware, Hydraulic and pneumatic hybrid power, Productivity, Hydraulic control
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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, Biomechanics
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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, Reliability
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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, Crankshafts, Engine efficiency, Stirling engines
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