Field-Oriented Control (FOC); Generated by Gemini

This article explains Field-Oriented Control for AC motors, covering torque, flux, efficiency, and precise variable-speed drive performance.

Field Oriented Control (FOC) for AC Motors

<h2 id="isPasted">Introduction</h2>Once the design is finalized and the technical specifications are defined, the next step is selecting the right gearbox. Factors like compatibility with the motor interface and cost efficiency in drive technology also play a role. Nabtesco Precision Europe GmbH, <a href="https://www.nabtesco.de/en/" target="_blank">a global leader in precision gear technology</a>, provides expertise in these areas.With over 35 years of experience in <a href="https://www.nabtesco.de/en/industries/robotics" target="_blank">robotics</a> and automation, the company specializes in precision gear technology. Its product range includes both strain wave gears and cycloidal gears, making it one of the most comprehensive selections of precision gear solutions on the market.<h2>Gearboxes for All Applications With Precision Across the Board</h2>High-precision gears are essential in applications that demand accuracy and efficiency. Whether in robotics, automation, or aerospace, choosing the right gearbox ensures smooth operation and optimal torque transmission.Christian Otto, Senior Application Engineer at Nabtesco Precision Europe GmbH, explains: “Our portfolio includes both cycloidal and strain wave gear technologies, each offering distinct advantages while complementing each other. This allows for a scalable product range covering torque values from 7 to 70,000 Nm.”With just one dedicated point of contact for all gear solutions, Nabtesco helps optimize design processes, enhances compatibility, and accelerates development cycles.<h2>Cycloidal and Strain Wave Gears: A Winning Pair</h2>Cycloidal gearboxes are highly rigid and ideal for handling higher torque. On the other hand, zero-backlash strain wave gears perform best in low-torque applications, especially where high performance is needed in compact spaces. The combination of these two gearboxes offers significant advantages for <a href="https://www.nabtesco.de/en/applications/automation" target="_blank">automation</a> applications. The key factors include exceptional transmission and repeatability, high single-stage reduction ratios, exceptional shock load capacity (up to 500% of rated torque), compact design, and long operational lifespan.On top of it, there’s more to what makes it so effective. Christian Otto explains: "In terms of precision, torque capacity, and torque density, these two technologies deliver superior performance. By equipping the larger axes of a robot or machine with cycloidal gearboxes and using strain wave gears in the end-effector area, the entire axis chain achieves maximum precision."<h2>How Backlash Defines Precision in Gearboxes?</h2>Not all industry experts may readily agree that cycloidal and strain wave gears are the only true precision gear solutions. Here, accurately defining a "precision gearbox" helps clarify the debate, as opinions on its definition often differ.The accuracy of a gearbox is largely determined by its backlash and hysteresis loss. The lower these values, the more precisely the gearbox operates. In this regard, cycloidal and strain wave gears lead by a considerable margin.Here are a few key points to put things in perspective:<ul><li>Strain wave gears are backlash-free.</li><li>Cycloidal gears have exceptionally low backlash, typically in the range of 0.1–0.2 arcmin.</li><li>Both technologies feature a maximum hysteresis loss of 1 arcmin.</li></ul>In comparison:<ul><li>Conventional low-backlash planetary gearboxes typically have backlash of 1-3 arcmin.</li><li>Standard planetary gearboxes usually have backlash values of 7 arcmin or higher.</li></ul>This stark contrast highlights why cycloidal and strain-wave gears lead the precision gearing technology.<h2>High-Torque Operation with Cycloidal Gears</h2>A typical application of the cycloidal and strain-wave gear combination is in a 6-axis robot. In most cases, axes 1 to 3 are equipped with cycloidal gearboxes, where high torsional rigidity, robustness, and durability are essential. This makes Nabtesco’s cycloidal precision gear technology a great fit.The <a href="https://www.nabtesco.de/en/technology/cycloidal-gears" target="_blank">two-stage reduction principle</a> of the cycloidal gears delivers exceptional dynamics and smooth operation, ensuring high repeatability and precise path accuracy. Integrated angular contact ball bearings absorb axial and radial loads, as well as bending moments, resulting in high moment rigidity and superior resistance to shock and overload conditions, up to 500% of the rated torque.The cam-and-roller power transmission mechanism enables nearly full-surface contact, ensuring uniform force distribution within the gearbox. This design results in enhanced rigidity, allowing for smooth transmission of extremely high torques.<h2>Compact Strain Wave Gears with Zero Backlash</h2><a href="https://www.nabtesco.de/en/technology/strain-wave-gears" target="_blank">Strain wave gears</a> are commonly used in wrist axes 4 to 6, and in smaller cobots, they are often integrated into all axes. These compact precision gearboxes offer absolute zero backlash, high repeatability, and maintenance-free operation. They also provide up to 15% higher torque capacity compared to conventional strain wave gearboxes. All this comes in a compact and lightweight design.Manufactured to automotive industry standards at Ovalo GmbH in Limburg (Lahn), these gearboxes meet strict quality requirements. Each unit can be customized to match specific performance, geometry, material, and interface requirements. If needed, customization can also extend to function, component, and system integration.The gearboxes are based on a modular product platform with a wide range of sizes, designs, and materials. Additional components such as motors, bearings, seals, housings, sensors, brakes, and ECUs can be integrated. The key properties, such as traceability, transmission accuracy, efficiency, and moment of inertia, can be adapted to suit application needs. This flexibility enables engineers to design machines and robots without compromising on performance.<h2>Perfect Team for Tool Head and Worktable</h2>In <a href="https://www.nabtesco.de/en/industries/machine-tool-construction" target="_blank">machine tool manufacturing</a>, high-reduction precision gearboxes ensure exceptional accuracy. Cycloidal gearboxes provide precise positioning in swivel tables, while zero-backlash strain wave gears in tool heads guarantee precision during machining.A high reduction ratio minimizes the moment of inertia between the application and motor, improving control accuracy, reducing drivetrain vibrations, and enabling dynamic positioning. This results in shorter auxiliary times and a more cost-effective machining process.The same principle applies to laser and waterjet cutting machines. Cycloidal gearboxes are ideal for large axes beneath worktables, while compact strain wave gears excel in cutting heads for precise laser or waterjet control. This combination maximizes precision, dynamics, and efficiency.Other applications, including C-arm scanners in <a href="https://www.nabtesco.de/en/applications/medical-technology" target="_blank">medical technology</a>, antennas, <a href="https://www.nabtesco.de/en/products/rotary-indexers" target="_blank">rotary tables</a>, milling machines, and welding positioners, also benefit from these technologies.<h2>Modular Steer-by-Wire Platform for Autonomous Driving</h2>Nabtesco’s CV-EPS (Commercial Vehicle Electronic Power Steering) is a modular steer-by-wire platform designed for autonomous driving. It features a high-voltage system (AxCu – Axle Steering Control Unit) and a low-voltage solution (24 to 48 volts) for trucks, lorries, and buses. A cycloidal gearbox transmits the main steering torque, while a strain wave gear acts as a preliminary stage between the steering wheel and the cycloidal gearbox.“Electromechanical solutions like CV-EPS offer significant advantages over hydraulic systems. They eliminate oil, pumps, and hydraulic lines, allow for integrated assistance functions, and enable customer-specific adjustments such as steering feel. The combination of strain wave and cycloidal gear technology ensures power transmission in a compact space with maximum rigidity and accuracy,” explains Jonas Kinzel, Product Manager Wave Gears at Nabtesco.<h2>Engineering Support at Every Stage of Development</h2>Nabtesco’s cycloidal and strain wave gears don't always need to be used together. Each offers distinct advantages on its own. In most cases, geometric size determines the choice between the two technologies, but there is an overlap where both are viable.Jonas Kinzel explains, "For outer diameters between 100 and 150 mm or torques from 250 to 450 Nm, we offer solutions using either cycloidal or strain wave gears. The choice depends on the application. Cycloidal gearboxes are ideal for high torque, while strain wave gears are best for zero-backlash requirements."He further adds that many customers lack the time or resources to explore gearbox technologies in detail. That's why Nabtesco offers tailored solutions based on customer requirements regarding cost, performance, weight, and space constraints. The company also provides comprehensive engineering support from design to assembly to help customers streamline their processes.<h2>Delivering High Performance Solutions Across Industries</h2>Precision gearboxes play a crucial role across <a href="https://www.nabtesco.de/en/solutions" target="_blank">industries</a>, including robotics, machine tools, medical technology, logistics, and mobility. Whether it is pick-and-place, handling, or positioning, almost every system requires a combination of large and small axes. Nabtesco Precision Europe's cycloidal and strain wave gears work together to deliver greater <a href="https://www.nabtesco.de/en/service/added-value" target="_blank">efficiency, flexibility, and cost-effectiveness.</a>

Nabtesco provides strain wave and cycloidal gears with a torque range from 7 to 70,000 Nm, enabling consistent performance, seamless compatibility, and cost-effective operation across different applications.

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