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Motor sizing basics: Balancing torque, speed, and inertia for optimal application performance

Optimizing motor selection for motion control applications can have significant performance, cost, and maintenance benefits. Select too large a motor, and you could overwhelm your actuators and incur unnecessary equipment and energy costs. Select too small a motor, and you may not achieve the torque and speed you need for effective performance. Andrew Skidmore, senior project engineer at Thomson Industries, covers what you need to know to make the proper selection for your application.
Read the Thompson article.

Slip rings for demanding environments

The Orbex Group now offers IP65-rated slip rings for reliable use in demanding industrial or outdoor applications. Constructed from stainless steel, the rugged 200 series resists shock, vibration, and corrosion in salty or washdown environments. It features a wide temp range (-40 to 80 C) and the longest service life of any Orbex slip rings -- up to 80 million revolutions. Units incorporate proprietary channeled brush technology, which creates multiple contact points and reduces contact forces to minimize wear in food processing, packaging, wind turbines, marine cable reels, downhole inspection equipment, and other demanding applications. Mini (300 series) and through-bore (series 500) slip rings also available.
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Multi-axis gimbal system for defense

Cobham Advanced Electronic Solutions has just introduced a new multi-axis gimbal system for military applications such as counter unmanned aerial vehicles (UAV) and air defense operations that offers a great combination of reliability, precision, and affordability. The SPS-1000 is a next-gen sensor positioning system (SPS) that accurately acquires, tracks, and points a variety of sensor payloads in harsh land, sea, and airborne environments. Two key benefits of the modular design approach are integral field-replaceable control electronics (which eliminates all external cables without any sacrifice in performance) and a reconfigurable design allowing for utmost payload flexibility.
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Linear motion guide with built-in encoder

New from THK, the Type SHS-LE integrates the global standard THK Type SHS LM Guide with a THK linear encoder (linear position sensor). This combined model allows for compact machine designs that require less assembly time. THK's Type SHS Caged Ball LM Guide performs with high speed and precision. Each row of balls is arranged at a contact angle of 45°, enabling the SHS to be used in all directions. Its patented THK Caged Technology employs a synthetic resin cage with a patented curvature that cradles each ball and separates it from the next. The spaces between the rolling elements retain grease and act as a lubrication system for long-term, maintenance-free operation. Other benefits include increased speed and accuracy, decreased noise levels, low dust generation, and long life.
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Compact hydraulic/pneumatic position sensors

Novotechnik's TM1 Series of position sensors are designed for use in hydraulic and pneumatic cylinders -- especially in tight-space applications. They are based on magnetostrictive technology and are available in screw flange or plug-in flange models. A ring-shaped magnetic marker moves up and down the sensor's shaft for touchless operation. Specs include stroke lengths from 50 to 2,000 mm (1.9 to 78.7 in.) and accuracy to +/-0.04 percent.
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6 latest trends in direct drive motor technology

Direct drive motors have always been seen as a technological step up from standard transmission devices, with torque and linear motors being seen as the higher end alternative to gearboxes and ball screws. Although the base design has been around for a long time, motor makers are still working on fine-tuning different aspects to increase the overall performance and quality of the product. Here are six advancements that direct drive motor builders are taking to ensure the customer gets the most out of their capabilities. By Brian Zlotorzycki, Business Development Specialist, ETEL Motors
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Small DC motors for lab spectrophotometry

The DeNovix team needed a motion solution for their spectro-photometer application which called for intermittent short, quick motions with micron-level accuracy. After research and testing, they chose FAULHABER small DC motors configured with a high-resolution encoder and an all-plastic planetary gearhead to successfully bring their product to market.
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How to select gearmotors for conveyor applications

If you need to find a gearmotor for your belt-driven conveyor application, Bodine Electric has you covered. This informative and thorough post provides step-by-step instructions for sizing and selection -- complete with examples. Learn about reflected acceleration torque, reflected breakaway torque, and a whole lot more. Also learn the basic set of questions to answer to determine what type of motor will work best.
Read the Bodine blog.

Marathon stainless steel and jet pump motors from AutomationDirect

New Marathon Powerwash SXT washdown duty motors are designed for use in food and beverage processing and other washdown environments. The all stainless steel, totally enclosed motors are available in single and three-phase. C-face with rigid base (footed) and C-face footless mounting options are available. Jet pump motors are commonly used in commercial and industrial water treatment and processing applications to power centrifugal and hydraulic pumps. Marathon jet pump motors are available in single and three-phase, and in TEFC and Open Drip Proof (ODP) designs. The ODP design allows air to circulate through the motor windings for cooling, but prevents drops of liquid from falling into the motor. The increased air flow means lower operating temperatures and increased efficiency when compared to TEFC or TENV motors.
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Emergency braking in power outages, long holding power

Miki Pulley's BXW Spring Actuated Electromag-netic Brakes utilize internal compression springs to provide power-off, fail-safe braking. The primary moving part in this robust but simple brake design is the armature plate. When actuated, the brake compression springs push the armature plate into the friction disc when power is disengaged. This feature provides fail-safe braking and allows the brake to maintain position over long periods of time, thus preventing machinery from "coasting" when powered off. Brakes are ideal for small and large applications, including use with servo motors. Additional features: quiet operation, high holding torque, space savings, long service life, stable and reliable braking power, and manual release mechanisms.
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First subsea actuator to have advantages of both electro-mechanical and electro-hydraulic systems

The Subsea Valve Actuator (SVA) from Rexroth is an electro-mechanical actuator with hydrostatic drive designed to complete the range of traditional hydraulic and all-electric subsea actuators for subsea control and production systems. It achieves the same safety performance as hydraulic actuators, but with much better reliability. It also provides a simple electric interface similar to those in all-electric actuators (without umbilicals for hydraulic fluid power). The SVA is compatible with Industry 4.0 technology and includes integrated sensors for monitoring position, pressure, temperature, and more. Operates up to a depth of 3,000 m.
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Engineer's Toolbox:
Microstepping's myths and realities

There are compelling reasons other than high resolution for microstepping, but there are also real tradeoffs to consider. Engineers at FAULHABER MICROMO discuss the drawbacks and benefits of microstepping technologies -- and how to make the most of them for your given application.
Read the full article.

Next-gen angle encoder for motion feedback

RSF Elektronik is now offering a next-generation kit angle encoder for motion feedback best suited for applications in robotics, semiconductor, medical, and machine tool. Offered through parent company Heidenhain in North America, this new encoder is available in both absolute (MCR 15) and incremental (MSR 15) versions. Both models consist of an optical scanning unit and a separate full circle drum with the graduation on the outer diameter. The new encoders are available in several sizes of drums that come with accuracies starting at 20 arc sec with up to 10 arc sec, depending upon diameter. Resolutions are also diameter-based and range from 22 to 25 bits for the absolute versions. The resolutions of the incremental versions start at 4,740 lines per 360 degrees all the way up to 27,540 for the largest diameter.
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New Orbex brushless servo motors enhance efficiency

The Orbex Group, a leading manufacturer of high-performance electric motors and slip rings, now offers brushless servo motors that combine high torque, low inertia, and various customizable options to improve efficiency in dynamic servo-driven applications. Available in a range of frame sizes (60 to 176 mm), NdFeB-based brushless servo motors include incremental encoders for position feedback and electrical commutation -- enhancing motor efficiency, minimizing maintenance requirements, and increasing throughput. Customizable windings make it easy to meet your technical requirements, while integrated gear reducers reduce package size and lower overall costs. Other customizable features include brakes, additional feedback options, connectors, and custom mounting options.
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New OnRobot converter kit unifies cobot tool connections

In a bid to make robotic applications faster and easier to implement, OnRobot has created a unified mechanical and electrical interface for any OnRobot end-of-arm tooling (EoAT). The innovation dramatically simplifies automation. The Digital I/O Converter Kit allows OnRobot end-of-arm tools to work with a full range of leading collaborative and light industrial robot brands including Universal Robots, KUKA, FANUC, Doosan, Techman, Yaskawa, Mitsubishi, Kawasaki, and Nachi. Use one tool easily on two different cobots, or even use two tools in one cycle.
Read the full article.

Small but mighty: Mini plasma-powered satellite may launch new era in space exploration

By John Greenwald, Princeton Plasma Physics Laboratory

A tiny satellite under construction at the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) could open new horizons in space exploration. Princeton University students are building the device, called a cubic satellite, or CubeSat, as a testbed for a miniaturized rocket thruster with unique capabilities being developed at PPPL.

The thruster, whose development is led by PPPL physicist Yevgeny Raitses, holds the promise of increased flexibility for the mission of CubeSats, more than 1,000 of which have been launched by universities, research centers, and commercial interests around the world. The proposed propulsion device -- powered by plasma -- could raise and lower the orbits of CubeSats circling the Earth, a capability not broadly available to small spacecraft today, and would hold the potential for exploration of deep space. "Essentially, we will be able to use these miniature thrusters for many missions," Raitses said.

Princeton graduate and undergraduate students gather with advisors around a model of the CubeSat chassis inside a sphere. From left: Jacob Simmonds; Jerry Xiang; Nirbhav Chopra; Daniel Marlow, Evans Crawford 1911 Professor of Physics at Princeton; Yevgeny Raitses, PPPL physicist; Seth Freeman; Matthew Bledsoe; Daniel Piatek (Seton Hall student). [Photo by Elle Starkman/Office of Communications]

 

 

 

 

Hundreds of micropowered CubeSats
One example: Hundreds of such micropowered CubeSats are envisioned by physicist Masaaki Yamada, principal investigator of the PPPL Magnetic Reconnection Experiment (MRX), which studies magnetic reconnection -- the separation and explosive snapping together of magnetic field lines in plasma that triggers auroras, solar flares, and geomagnetic storms that can disrupt cell phone service and power grids on Earth. Such CubeSat fleets could capture in fine detail the reconnection process in the magnetosphere, the magnetic field that surrounds the Earth, Yamada said.

The miniaturized engine scales down a cylindrical thruster with a high volume-to-surface geometry developed at the PPPL Hall Thruster Experiment (HTX), which Raitses leads and launched with PPPL physicist Nat Fisch in 1999. The experiment investigates the use of plasma -- the state of matter composed of free-floating electrons and atomic nuclei, or ions -- for space propulsion.

Key advantage
A key advantage of the miniaturized cylindrical Hall thruster will be its ability to produce a higher density of rocket thrust than existing plasma thrusters used for most CubeSats now orbiting Earth. The miniaturized thruster can achieve both increased density and a high specific impulse -- the technical term for how efficiently a rocket burns fuel -- that will be many times greater than that produced by chemical rockets and cold-gas thrusters typically used on small satellites.

High specific-impulse thrusters use much less fuel and can lengthen satellite missions, making them more cost effective. Equally important is the fact that a high specific impulse can produce a large enough increase in a satellite's momentum to enable the spacecraft to change orbits -- a feature not available on currently orbiting CubeSats. Finally, high thrust density will enable satellites to accomplish complex fuel-optimized orbits in a reasonable time.

These capabilities provide many benefits. For example, a CubeSat might descend to lower orbit to track hurricanes or monitor shoreline changes and return to a higher orbit where the drag force on a satellite is weaker, requiring less fuel for propulsion.

The roughly foot-long CubeSat, which Princeton has dubbed a "TigerSat," consists of three nearly 4-in. aluminum cubes stacked vertically together. Sensors, batteries, radio equipment, and other instruments will fill the CubeSat, with a miniaturized thruster roughly equal in diameter to two U.S. quarters housed at either end. A thruster will fire to change orbits when the satellite passes the Earth's equator.

Mechanical and aerospace engineering students
Building the CubeSat are some 10 Princeton graduate and undergraduate students in the Department of Mechanical and Aerospace Engineering, with Daniel Marlow, the Evans Crawford 1911 Professor of Physics, serving as faculty advisor. Undergraduates include Andrew Redd, who leads design and construction of the CubeSat, and Seth Freeman, who is working full time on the project over the summer. Working on thruster development is Jacob Simmonds, a third-year graduate engineering student, whose thesis advisors are Raitses and Yamada. "This project began as a prototype of Yamada's CubeSat and has evolved into its own project as a testbed for the plasma thruster," Simmonds said.

Also under construction at PPPL is a test facility designed to simulate key aspects of the CubeSat's operation. Undergraduates working on their own time are building the satellite and this facility. "To the extent that students and their advisors have identified well-defined questions associated with the TigerSat project, they can get independent work credit," Marlow said. "Also, some problem sets in the introductory physics course for undergraduates that I teach have questions related to the TigerSat flight plan."

Simmonds, while working on the thruster, is drafting a proposal for NASA's Cubic Satellite Launch Initiative (CSLI) that is due in November. Projects selected by the initiative, which promotes public-private technology partnerships and low-cost technology development, have launch costs covered on commercial and NASA vehicles. Plans call for a TigerSat launch in the fall of 2021.

Value of collaboration
For Raitses, this project demonstrates the value of Princeton engineering students collaborating with PPPL and of University faculty cooperating with the Laboratory. "This is something that is mutually beneficial," he said, "and something that we want to encourage."

Support for the thruster work comes from Laboratory Directed Research and Development (LDRD) funds made available through the DOE Office of Science (FES). Basic science aspects of the novel thruster based on low-temperature magnetized plasma is supported by the Air Force Office of Scientific Research. Princeton University supports construction of the CubeSat and the test facility.

PPPL, on Princeton University's Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas -- ultra-hot, charged gases -- and to developing practical solutions for the creation of fusion energy. The Laboratory is managed by the University for the U.S. Department of Energy's Office of Science, which is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time.

Published August 2019

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