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Why air bearings are used to test satellites

The number of active satellites in space keeps growing, with more than 10,000 active satellites orbiting our planet. Commercial and academic institutions developing these satellites continuously work on improved test systems and methodologies to fully validate their hardware before launch. Learn why PI's 3-DOF spherical air bearing systems are an important part of this process.
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8 key advantages of torque motors for advanced applications

Electric torque motors drive loads at low speed without additional mechanical transmission systems like gearboxes or speed reducers. They are known for smooth operation with less vibration and backlash. Learn the key benefits that make them a solid choice for many applications.
View this informative Parker blog.

Gear motors with QR codes for product info

NORD DRIVE-SYSTEMS gear motors now come with a QR code sticker on the unit enabling users to access information almost instantly such as product specs, documentation, and service requests via mobile device. The codes can be scanned using a photo app or QR code app and will bring the user to NORD's digital service webpage, which includes a Documentation Center, Spare Parts Shop, customer portal, and more. QR code stickers are now in use at NORD USA's four facilities in Waunakee, WI; Corona, CA; Charlotte, NC; and McKinney, TX.
Learn more.

LM guide actuator with right/left ball screw for symmetrical movement

THK's innovative Type KR-RL Actuator features a driving element that uses right/left threads and enables symmetrical movements with a single motor. Two drive systems are combined into a single package, resulting in a compact overall design. This electric actuator outperforms pneumatic versions by offering precise force control, speed control, a longer life, and energy savings. Applications include gripping, measuring, and positioning for robot hands, screw-tightening machines, cutting equipment, and dispensers.
Learn more.

High-power-density outer-rotor brushless motor

Allied Motion Technologies has released the new KinetiMax High Power Density (HPD) motor series. This outer-rotor brushless motor is designed for high-torque, low-cogging applications like robotics, AGVs, and handheld power tools. With an efficiency rating of over 85% and a high power-to-weight ratio, it's an ideal motor choice for any application where weight and battery life are critical. Available in six frame sizes, with three stack lengths per size and three windings per stack length.
Learn more.

Universal Robots: Seamless integration with Siemens PLCs

Cobot leader Universal Robots has integrated the Standard Robot Command Interface (SRCI) into its software. UR is proud to be among the first cobot vendors to offer this functionality, which is a new standard for robotics manufacturers that aims to create a single interface between PLCs and robots. It will ensure customers a frictionless integration with Siemens Programmable Logic Controllers, since Siemens is the first -- and currently only -- PLC Vendor supporting SRCI in the automation market.
Learn more.

Multi-axis motion control chipset

The Magellan^® MC58000 and MC55000 Motion Control ICs from Performance Motion Devices provide all the advanced motion control required by sophisticated high-precision medical, scientific, automation, industrial, and robotic applications. Available in 1-, 2-, 3-, and 4-axis versions, these programmable devices control brushless DC, DC brush, and step motors and deliver user-selectable profiling modes including S-curve, trapezoidal, velocity contouring, and electronic gearing. High-performance FOC provides high-accuracy, ultra-low noise motor operation.
Learn more.

Wheel drive boosts material handling operations

IDEC Corp.'s new ez-Wheel Assist Wheel Drive (AWD) EW1A Series provides electrical motion assistance for industrial manual material handling equipment. With the help of an EW1A, workers can easily and safely move heavy loads, increasing productivity and efficiency. The modular, all-in-one wheel, gearbox, drive, battery, and control solution is easily integrated into new or existing equipment. Supports a vertical working load up to 400 kg and can transfer loads up to 1,000 kg.
Learn more.

Tech Tip: Have you considered a frameless motor?

With no housing, bearings, or other components beyond the stator and rotor, a frameless motor delivers the most compact, torque-dense motion possible. Instead of its own housing, the motor can be embedded directly within the mechanical design of the machine. Instead of its own bearings, it can use the machine's existing shaft and bearings. Learn from Kollmorgen why a frameless servo motor can be an ideal choice for compact, higher-level assemblies and how to integrate one into your design.
Read this informative Kollmorgen blog.

DURApulse GS30 AC Drives from AutomationDirect

Automation-Direct has added new high-performance DURApulse GS30 drives that support several control modes including sensorless vector control, closed-loop flux vector control, and torque control in a compact package. The GS30 series expands the DURApulse family by adding internal tension control loop expanded parameter sets for greater versatility, as well as optional EtherCAT and single- or dual-port EtherNet/IP communication cards. GS30 drives support up to four independent induction motor parameter sets or control of a single AC permanent magnet motor. Sizes up to 3 hp for a 230-VAC single-phase input, 50 hp for a 230-VAC three-phase input, and 100 hp for a 460-VAC three-phase input. This series offers PID control, built-in PLC functionality, and STO capability typically found with more expensive high-performance AC drives.
Learn more.

Power steering systems for warehouse and autonomous vehicles

Allied Motion has introduced the electric power steering (EPS) series for steer-by-wire warehouse vehicles, autonomous AGVs, and similar material transport vehicles. This compact system includes a fully integrated motor, gearbox, controller, and optional output pinion. It is available in three frame sizes and 16 models to cover virtually any electric steering requirement in applications from small pallet lifters to AGVs/AGCs to multi-ton reach trucks. An optional, patent-pending feature, Turning Wheel Absolute Position Control, allows the controller to know the turning wheel position without external sensors.
Learn more.

New brushless motors maximize power density

Allied Motion Technologies has introduced the KinetiMax 95 High Power Drive (HPD), an outer-rotor brushless motor. This frameless motor is designed to maximize power density for its volume with a nominal output torque of 2 Nm at 2,300 RPM, resulting in 480 W of continuous output power. At only 37 mm axial length, this compact stator-rotor set is an ideal solution for applications such as material handling systems, AGVs, mobile robots, handheld power tools, and more.
Learn more.

Compact rod motors: Effective linear thrust generation

RDM-A Series rod motors from Akribis Systems are great for space-constrained applications requiring high motor forces and smooth linear motion. These compact motors feature a tubular design to distribute magnetic flux evenly along the circumference of the stator. They achieve continuous forces from 2.1 to 137.8 N and peak forces from 6.2 to 413.4 N. An air gap between the coil and magnet track enables non-contact axial linear movement and steady force production over the length of the stroke, and ironless construction ensures cog-free motion.
Learn more.

NORD's heavy-duty drive systems tackle tough industrial applications

Industrial gear units from NORD DRIVE-SYSTEMS are used for a variety of heavy-duty applications, providing high output torques and long service life with minimal maintenance. Combining high-efficiency motors and dynamic VFDs, users get high performance and smooth operation. Learn which drive systems are used for which real-world applications in industries including grain, cranes and hoists, wastewater, food and beverage, and bulk material handling. Good info here.
Read the full article.

XYZ nanopositioning stage for scanning and positioning in photonics and microscopy

PI's P-616 XYZ Piezo Nanoposition-ing Stage, based on a parallel-kinematic design, features a single, lightweight moving platform for all three axes. It offers high precision (sub-nanometer resolution) and dynamics in a compact package. Known as the NanoCube^®, it is the smallest and lightest system with capacitive feedback, providing a 100-µm linear travel range in three degrees of freedom.
Learn more.

What's a unified momentum model? New theory could improve the design and operation of wind farms

Engineers at MIT have developed a comprehensive model that accurately represents the airflow around rotors even under extreme conditions, such as when the blades are operating at high forces and speeds, or are angled in certain directions. [Credit: Image courtesy of the researchers]

 

 

 

 

The first comprehensive model of rotor aerodynamics could improve the way turbine blades and wind farms are designed and how wind turbines are controlled.

By David L. Chandler, MIT

The blades of propellers and wind turbines are designed based on aerodynamics principles that were first described mathematically more than a century ago. However, engineers have long realized that these formulas don't work in every situation. To compensate, they have added ad-hoc "correction factors" based on empirical observations.

Now, for the first time, engineers at MIT have developed a comprehensive, physics-based model that accurately represents the airflow around rotors even under extreme conditions, such as when the blades are operating at high forces and speeds, or are angled in certain directions. The model could improve the way rotors themselves are designed, but also the way wind farms are laid out and operated. The new findings are described in the journal Nature Communications, in an open-access paper by MIT postdoc Jaime Liew, doctoral student Kirby Heck, and Michael Howland, the Esther and Harold E. Edgerton Assistant Professor of Civil and Environmental Engineering.

"We've developed a new theory for the aerodynamics of rotors," Howland says. This theory can be used to determine the forces, flow velocities, and power of a rotor, whether that rotor is extracting energy from the airflow, as in a wind turbine, or applying energy to the flow, as in a ship or airplane propeller. "The theory works in both directions," he says.

Because the new understanding is a fundamental mathematical model, some of its implications could potentially be applied right away. For example, operators of wind farms must constantly adjust a variety of parameters, including the orientation of each turbine as well as its rotation speed and the angle of its blades, in order to maximize power output while maintaining safety margins. The new model can provide a simple, speedy way of optimizing those factors in real time.

"This is what we're so excited about, is that it has immediate and direct potential for impact across the value chain of wind power," Howland says.

Modeling the momentum
Known as momentum theory, the previous model of how rotors interact with their fluid environment -- air, water, or otherwise -- was initially developed late in the 19th century. With this theory, engineers can start with a given rotor design and configuration, and determine the maximum amount of power that can be derived from that rotor -- or, conversely, if it's a propeller, how much power is needed to generate a given amount of propulsive force.

Momentum theory equations "are the first thing you would read about in a wind energy textbook, and are the first thing that I talk about in my classes when I teach about wind power," Howland says. From that theory, physicist Albert Betz calculated in 1920 the maximum amount of energy that could theoretically be extracted from wind. Known as the Betz limit, this amount is 59.3% of the kinetic energy of the incoming wind.

Just a few years later, however, others found that the momentum theory broke down "in a pretty dramatic way" at higher forces that correspond to faster blade rotation speeds or different blade angles, Howland says. It fails to predict not only the amount, but even the direction of changes in thrust force at higher rotation speeds or different blade angles: Whereas the theory said the force should start going down above a certain rotation speed or blade angle, experiments show the opposite -- that the force continues to increase. "So, it's not just quantitatively wrong, it's qualitatively wrong," Howland says.

The theory also breaks down when there is any misalignment between the rotor and the airflow, which Howland says is "ubiquitous" on wind farms, where turbines are constantly adjusting to changes in wind directions. In fact, in an earlier paper in 2022, Howland and his team found that deliberately misaligning some turbines slightly relative to the incoming airflow within a wind farm significantly improves the overall power output of the wind farm by reducing wake disturbances to the downstream turbines.

In the past, when designing the profile of rotor blades, the layout of wind turbines in a farm, or the day-to-day operation of wind turbines, engineers have relied on ad-hoc adjustments added to the original mathematical formulas, based on some wind tunnel tests and experience with operating wind farms, but with no theoretical underpinnings.

Instead, to arrive at the new model, the team analyzed the interaction of airflow and turbines using detailed computational modeling of the aerodynamics. They found that, for example, the original model had assumed that a drop in air pressure immediately behind the rotor would rapidly return to normal ambient pressure just a short way downstream. However, it turns out, Howland says, that as the thrust force keeps increasing, "that assumption is increasingly inaccurate."

And the inaccuracy occurs very close to the point of the Betz limit that theoretically predicts the maximum performance of a turbine -- and therefore is just the desired operating regime for the turbines. "So, we have Betz's prediction of where we should operate turbines, and within 10 percent of that operational set point that we think maximizes power, the theory completely deteriorates and doesn't work," Howland says.

Through their modeling, the researchers also found a way to compensate for the original formula's reliance on a one-dimensional modeling that assumed the rotor was always precisely aligned with the airflow. To do so, they used fundamental equations that were developed to predict the lift of three-dimensional wings for aerospace applications.

The researchers derived their new model, which they call a unified momentum model, based on theoretical analysis, and then validated it using computational fluid dynamics modeling. In follow-up work not yet published, they are doing further validation using wind tunnel and field tests.

Fundamental understanding
One interesting outcome of the new formula is that it changes the calculation of the Betz limit, showing that it's possible to extract a bit more power than the original formula predicted. Although it's not a significant change -- on the order of a few percent -- "it's interesting that now we have a new theory, and the Betz limit that's been the rule of thumb for a hundred years is actually modified because of the new theory," Howland says, "and that's immediately useful." The new model shows how to maximize power from turbines that are misaligned with the airflow, which the Betz limit cannot account for.

The aspects related to controlling both individual turbines and arrays of turbines can be implemented without requiring any modifications to existing hardware in place within wind farms. In fact, this has already happened, based on earlier work from Howland and his collaborators two years ago that dealt with the wake interactions between turbines in a wind farm, and was based on the existing, empirically based formulas.

"This breakthrough is a natural extension of our previous work on optimizing utility-scale wind farms," he says, because in doing that analysis, they saw the shortcomings of the existing methods for analyzing the forces at work and predicting power produced by wind turbines. "Existing modeling using empiricism just wasn't getting the job done," he says.

In a wind farm, individual turbines will sap some of the energy available to neighboring turbines because of wake effects. Accurate wake modeling is important both for designing the layout of turbines in a wind farm, and also for the operation of that farm, determining moment to moment how to set the angles and speeds of each turbine in the array.

Until now, Howland says, even the operators of wind farms, the manufacturers, and the designers of the turbine blades had no way to predict how much the power output of a turbine would be affected by a given change such as its angle to the wind without using empirical corrections. "That's because there was no theory for it. So, that's what we worked on here. Our theory can directly tell you, without any empirical corrections, for the first time, how you should actually operate a wind turbine to maximize its power," he says.

Because the fluid flow regimes are similar, the model also applies to propellers, whether for aircraft or ships, and also for hydrokinetic turbines such as tidal or river turbines. Although they didn't focus on that aspect in this research, "it's in the theoretical modeling naturally," he says.

The new theory exists in the form of a set of mathematical formulas that a user could incorporate in their own software, or as an open-source software package that can be freely downloaded from GitHub. "It's an engineering model developed for fast-running tools for rapid prototyping and control and optimization," Howland says. "The goal of our modeling is to position the field of wind energy research to move more aggressively in the development of the wind capacity and reliability necessary to respond to climate change."

Published September 2024

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