Motion Control

Analyzing 6-Pulse Drive Harmonic Mitigation Techniques for Industrial Automation

Contemporary industrial automation control systems are employing variable frequency drives (VFDs) in ever-increasing numbers. VFDs give control engineers flexibility to precisely regulate the speed and torque of motors in a wide array of applications. The proliferation of these VFDs has brought increased attention to harmonic distortion created by these drives and their effects on the power system. A standard-pulse drive with no built-in harmonic mitigation controls may interfere with neighboring equipment, reduce equipment life, and create a serious negative impact on the quality of utility power. Looking at the theory of operation for the following harmonic mitigation techniques and their typical performance levels may help take the guesswork out of harmonic reduction for these power systems.

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Reliable Locking in High-Vibration Environments

Today’s PCB plug-in connectors must accommodate many trends, including increasing miniaturization, rising levels of performance of electronic components, and growing complexity in machine and system engineering.

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Selecting the Proper Motor for Linear Motion Applications

Linear motion systems are found inside countless machines including precision laser cutting systems, laboratory automation equipment, semiconductor fabrication machines, CNC machines, factory automation, and many others too numerous to list. They range from the relatively simple such as an inexpensive seat actuator in a passenger vehicle, to a complex, multi-axis coordinate system complete with control and drive electronics for closed-loop positioning. No matter how simple or complex the linear motion system, at the most basic level, they all have one thing in common: moving a load through a linear distance in a specific amount of time.

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Design Considerations for Gearmotors in Long-Life Applications

At first glance, the photo at the top is not appealing to any market — a pallet full of old gearmotors is not something one wants to think about after purchasing the necessary gearmotor/motor for their application. But think of it this way instead: these gearmotors were removed from their installation for a refurbishment project after being in service for 30 years. Sandia National Laboratories placed these gearmotors into service in their Heliostat Field in New Mexico in the 1970s. The gearmotors were used to position solar reflectors to concentrate light from all of the individual panels towards one point at the top of a tower. After 30 years, Sandia decided to upgrade the field with a new control system, and they decided to replace the still-operating gearmotors at the same time.

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Redundant Sensors Improve Precision and Reliability

Some machine processes, such as presses, can require extreme accuracy in applying and holding force on an object. A popular way to measure force is via load cells. But what do you do when the accuracy required by a particular application is higher than that guaranteed by the load cell manufacturer?

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Compact Active Vibration Control System

A highly directional actuator can be shaped so that it couples to the response of a flexible structure in the same manner as point sensors. Langley Research Center, Hampton, Virginia This innovation consists of an analog controller, diamond-shaped patch actuator, and point sensors (such as accelerometers). The actuator is designed to couple to the flexural response of the structure in the same manner as a group of point sensors. This results in a co-located transducer pair. The signals from all sensors are combined, filtered, and amplified within the analog controller. The resulting signal is then applied to the actuator, which generates a control force out-of-phase with the measured response. Because the transducers are co-located, the vibration control system is inherently robust to variations in properties of the underlying structure that is being controlled. This type of control system actively suppresses the vibration of a flexible structure using surface-mounted transducers without any external mechanical connections.

Posted in: Briefs, TSP, Motion Control

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Deep Throttling Turbopump

Marshall Space Flight Center, Alabama Advancement in space exploration necessitates deep throttling of liquid cryogenic rocket engines. Both lunar and Martian robotic and human exploration require engines that can be deep throttled,can start and restart, have a long life, and require minimal maintenance. An engine that is capable of deep throttling at low thrust levels and is versatile enough to accommodate multiple applications would advance the state of the art and enable NASA to meet space exploration objectives. An advanced partial emission turbo pump design is an enabling technology for developing such low thrust level engines. This will complement the current state-of-the-art full emission pump technology.

Posted in: Briefs, Motion Control

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