Fact-checked by Grok 2 weeks ago

Cycloidal drive

A cycloidal drive is a type of mechanical speed reducer that utilizes an eccentrically rotating cycloidal disc with lobes that engage fixed pins to achieve high gear reduction ratios in a single stage, typically ranging from 10:1 to over 100:1, while providing compact size and precise motion transmission.^[1]^[2] Invented by German engineer Lorenz Braren in the 1920s, the cycloidal drive operates on a principle of epicyclic motion where an input shaft drives an eccentric bearing attached to the cycloidal disc; as the disc orbits and rotates, its lobes roll against stationary pins housed in the outer ring, progressively shifting to impart torque to an output shaft connected via additional pins or a carrier.^[3]^[1]^[2] This design distributes load across multiple contact points, enabling the mechanism to handle compressive stresses effectively and achieve gear ratios defined by the difference between the number of disc lobes and housing pins, such as a 10:1 ratio from 10 lobes and 11 pins.^[2]^[1] Cycloidal drives are prized for their high torque density, allowing significant torque output relative to their lightweight and compact form, as well as low backlash for precise positioning, superior shock load resistance due to even load distribution, and high efficiency with minimal noise during operation.^[1]^[4] These attributes make them ideal for demanding applications, including approximately 75% of joints in industrial robots, automation systems, machine tools, packaging machinery, and renewable energy equipment like wind turbine actuators.^[5]^[4]

Fundamentals

Definition and basic principles

A cycloidal drive, also known as a cycloidal speed reducer, is a mechanical transmission device designed to reduce the rotational speed of an input shaft while significantly increasing output torque, achieving this through eccentric motion and rolling contact rather than meshing teeth as in conventional gear systems.^[6] This mechanism enables high gear reduction ratios in a compact footprint, making it suitable for applications requiring precise motion control and high load capacity, such as robotics and industrial automation.^[7] The fundamental principle underlying the cycloidal drive is cycloidal motion, where a cycloid curve is traced by a point on the circumference of a circle that rolls without slipping around the outside of a fixed base circle, generating an epicycloid.^[8] This generates a non-circular profile for the cycloidal disc, which interacts with a set of fixed pins to convert the eccentric input rotation into slower, amplified output rotation via pure rolling contact, minimizing friction and wear compared to sliding or toothed engagements.^[9] In a single-stage configuration, cycloidal drives can deliver reduction ratios exceeding 100:1, allowing substantial torque multiplication within a small volume that is often more compact than equivalent multi-stage alternatives.^[9] This capability stems from the even distribution of load across multiple contact points on the disc, enhancing efficiency and rigidity.^[6] Conceptually, cycloidal drives differ from planetary reducers, which rely on epicyclic arrangements of toothed gears for speed reduction, and from harmonic drives, which employ strain wave deformation of a flexible component; instead, cycloidal systems prioritize rolling action for superior shock load resistance and backlash minimization.^[10]^[11]

Key components

A cycloidal drive consists of several primary components that work together to achieve high reduction ratios in a compact assembly. These include the input shaft with an eccentric cam, the cycloidal disc featuring external lobes, the stationary ring gear equipped with internal pins or rollers, and the output carrier. The input shaft connects to the power source and incorporates an eccentric cam that offsets the rotation to drive the system. The cycloidal disc, often designed with a curtate epicycloid profile for its lobes, serves as the primary motion-transferring element. The stationary ring gear remains fixed and houses the pins or rollers that constrain the disc's movement. The output carrier captures the reduced-speed rotation from the disc and transmits it to the output shaft.^[6]^[12] The lobe-pin interaction is central to load distribution in the drive, where the external lobes of the cycloidal disc engage multiple pins or rollers simultaneously, spreading forces across contact points to enhance durability and efficiency. Typically, about half of the ring gear's pins are in contact under load, allowing for even force transmission. Bearings play a crucial role in supporting the eccentric motion between the input shaft's cam and the cycloidal disc, minimizing friction and ensuring smooth operation while accommodating the offset rotation. These bearings are often integrated into the cam assembly to handle radial and axial loads effectively.^[6]^[12] Design variations in the ring gear components, such as using rollers instead of fixed pins, significantly influence performance. Roller pins, with diameters around 3 mm and spaced evenly (e.g., 30 per gear), convert sliding friction to rolling, which reduces wear and helps minimize backlash to near zero levels in precision applications. Fixed pins, while simpler, can introduce higher backlash due to potential play in the contact zones, making rollers preferable for high-accuracy needs like robotics. Some designs employ dual cycloidal discs for better balance and load sharing, further refining the lobe interactions.^[6]^[13] The components are assembled into a sealed housing that encases the entire mechanism, providing protection from contaminants and enabling lubrication with grease for longevity. This configuration allows for versatile mounting orientations, such as horizontal or vertical, and meets ingress protection standards like IP64 or higher, ensuring reliability in industrial environments. The housing integrates all elements coaxially, maintaining compactness with ratios up to 200:1 in a single stage.^[12]^[13]

Operation

Kinematic theory

The kinematic theory of the cycloidal drive is grounded in the relative motions of its core elements: the eccentric input driving the cycloid disc with N_l lobes inside a fixed ring of N_p pins. The speed reduction arises from the constraint that the disc both orbits the central axis and rotates about its own center to maintain meshing with the pins without slipping. To derive the reduction ratio i, consider the angular displacements. Let \theta_{in} be the rotation of the input eccentric, which imparts an orbital motion to the disc center at angular velocity \omega_{in}. The disc's self-rotation \phi relative to the eccentric must satisfy the rolling condition, where the arc length traversed along the effective pitch circle of the ring (proportional to N_p) equals that along the disc (proportional to N_l). Thus, \phi = -\theta_{in} \cdot (N_p / N_l). The absolute rotation of the disc relative to the fixed frame, which drives the output, is \theta_{out} = \theta_{in} + \phi = \theta_{in} (1 - N_p / N_l). Therefore, \omega_{out} = \omega_{in} (1 - N_p / N_l) = \omega_{in} (N_l - N_p) / N_l, and accounting for the direction reversal in standard configurations and the meshing constraint, the magnitude yields the reduction ratio i = \omega_{in} / |\omega_{out}| = N_l / (N_p - N_l).^[14] This ratio ensures that for each input rotation, the disc advances by a fraction determined by the difference in pin and lobe counts, typically with N_p = N_l + 1 for single-stage drives, yielding i = N_l. The paths traced by the lobe tips relative to the fixed pin ring form hypocycloids, while the pin paths relative to the moving disc form epicycloids. These curves ensure smooth, continuous contact during motion. The parametric equations for generating the basic cycloid profile, adapted for the drive's geometry with a base circle of radius R, are:

x = R (\theta - \sin \theta)

y = R (1 - \cos \theta)

where \theta is the parameter representing the roll angle. For the hypocycloid path in the drive, this is modified based on the fixed ring radius a and rolling radius b, but the fundamental form captures the cusp-free, shortened (curtate) cycloid used in lobe design to avoid undercutting.^[15] The input-output velocity relationship follows directly from the reduction ratio, with the output angular velocity \omega_{out} = \omega_{in} (N_l - N_p) / N_l. The disc's orbital velocity contributes \omega_{in} around the main axis, while its rotational velocity relative to the fixed ring is \omega_{disc} = -\omega_{in} (N_p / (N_p - N_l)) to enforce the meshing constraint. This combined motion results in the output shaft, coupled to the disc via output pins in slotted holes, experiencing a reduced and reversed rotation compared to the input. In practice, the eccentricity e influences the instantaneous velocities at contact points, but the average ratio remains fixed by N_p and N_l.^[14] Torque transmission occurs through distributed contact forces at the lobe-pin interfaces, enabling high load capacity despite the compact design. The input torque T_{in} generates an eccentric force F_e = T_{in} / e on the disc, which is balanced by normal and tangential forces at multiple contact points (typically 2–4 per disc). For force balance, the radial components sum to zero: \sum F_r = 0, and tangential components produce the output torque T_{out} = i T_{in} = \sum (F_t \cdot r_p), where F_t is the tangential force at each contact and r_p the pitch radius. Friction at contacts, modeled as F_f = \mu F_n (with \mu the coefficient and F_n the normal force), contributes to efficiency losses but aids in load sharing across points. Hertzian contact theory governs local deformations, ensuring the forces remain below yield limits for durability.^[6]

Mechanism of motion

The mechanism of a cycloidal drive initiates with the rotation of the input shaft, which incorporates an eccentric cam offset from the center. This offset imparts a wobbling orbital motion to the cycloidal disc, causing it to roll continuously inside a fixed annular ring lined with stationary pins, without any slipping at the contact points. The disc's outer profile, shaped with multiple rounded lobes, sequentially engages these pins, with each lobe pushing against a pin to advance the motion while the others maintain rolling contact.^[14]^[1] During one complete rotation of the input shaft, the cycloidal disc completes a full orbit around the ring's center, but the difference between the number of lobes on the disc and pins in the ring—usually one more pin than lobes—results in the disc advancing by only a fractional rotation relative to the pins. This step-by-step engagement emphasizes pure rolling motion, where the disc's cycloidal geometry ensures that each lobe smoothly transitions from disengagement to contact, distributing load across multiple points and minimizing wear.^[14]^[1] The output carrier, which holds output pins that engage slotted holes in the cycloidal disc, plays a crucial role in extracting and transmitting this motion to the output shaft. As the disc wobbles and interacts with the pins, the carrier rotates incrementally, averaging the irregular eccentric path of the disc into a uniform, low-speed rotation at the output. Visualization of this process often involves diagrams illustrating phase shifts in lobe-pin alignments and the progression of contact points, highlighting how sequential engagements create a continuous torque transfer.^[7]^[1]

Design and manufacturing

Design parameters

The primary design parameters of a cycloidal drive include the lobe count on the cycloidal disc (typically denoted as z_c or N_l), the pin count in the fixed ring gear ( z_p or N_p), the eccentricity ( e), the disc thickness, and the pin diameter. The lobe count determines the number of cycloidal teeth engaging with the pins, while the pin count sets the fixed reference circle; these are selected to achieve the desired reduction ratio, commonly ranging from 10:1 to 119:1, with the ratio approximated as i \approx z_p - z_c or more precisely i = \frac{z_p}{z_p - z_c}. For instance, a configuration with 30 pins and 29 lobes yields a 30:1 ratio, balancing high reduction with load distribution across multiple contact points to enhance torque capacity.^[6]^[8]^[16] Eccentricity, the offset between the input shaft and cycloidal disc center (e.g., 0.8 mm to 4 mm), directly influences the disc's orbital motion and output torque, with higher values increasing torque capacity but amplifying vibration and unbalance forces. Disc thickness (e.g., 6 mm) and pin diameter (e.g., 1.5 mm for roller pins or 20 mm for fixed pins) are chosen based on load requirements, ensuring sufficient stiffness and contact area to support axial and radial forces without excessive deformation. Guidelines recommend eccentricity not exceeding half the rolling circle diameter (e \leq \delta/2, where \delta = D / N_p and D is the pin reference circle diameter) to maintain smooth engagement.^[6]^[8]^[17] Trade-offs in parameter selection are critical: increasing the lobe count improves motion smoothness by distributing loads more evenly and reducing peak stresses, but it heightens manufacturing complexity due to tighter tolerances on tooth profiles and potentially raises costs. Conversely, balancing eccentricity optimizes torque against vibration, as larger offsets enhance output but necessitate thicker discs or larger pins to mitigate dynamic imbalances. For load capacity, higher pin counts stiffen the system but may slightly reduce efficiency due to increased friction.^[16]^[8]^[17] Stress analysis focuses on contact stresses between lobes and pins, often evaluated using Hertzian contact theory, which models elastic deformation under normal forces to predict maximum Hertzian stress \sigma_H = \sqrt{ \frac{F_E \cdot E^*}{\pi \cdot \rho^* \cdot b} }, where F_E is the equivalent force, E^* the effective modulus, \rho^* the relative curvature, and b the contact width. This approach guides parameter adjustments to keep stresses below material yield limits, particularly at meshing points where geometric deviations can elevate peaks by up to 20%. Modular designs for multi-stage units standardize these parameters (e.g., ratios in 10:1 increments) to allow stacking for higher overall reductions while maintaining compact footprints.^[6]^[16]

Fabrication techniques

The fabrication of cycloidal drives requires high-precision machining to achieve the complex curved profiles essential for smooth operation and minimal backlash. For the cycloidal disc, which features lobes generated from mathematical cycloid curves, primary methods include wire electrical discharge machining (EDM), form grinding, and multi-axis CNC milling. Wire EDM is particularly suited for prototyping and small-batch production, as it uses a thin wire electrode to erode material along the parametric cycloid path, enabling tight tolerances without mechanical stress on the workpiece.^[18] Grinding with dressable CBN worms or specialized cycloidal grinders is the standard for high-volume manufacturing, producing profile deviations below 3 μm by continuously generating the disc's epitrochoid or hypocycloid surfaces relative to an equivalent involute reference.^[19] Five-axis CNC end milling with flat-bottomed tools, oriented at a calculated elevation angle θ derived from lobe count and eccentricity parameters, offers versatility for custom profiles, improving surface quality over traditional hobbing.^[20] The pin ring, which houses the fixed or output pins that interact with the disc lobes, is typically produced through precision drilling or broaching to create evenly spaced holes. Drilling on multi-axis CNC machines ensures concentricity, with holes sized for press-fit or interference insertion of roller bearings to convert sliding to rolling contact, reducing friction. Broaching is employed for larger rings to form semi-cylindrical slots in a single pass, maintaining positional accuracy within 0.01 mm.^[19] Assembly techniques emphasize strict tolerance control to manage eccentricity and alignment, directly impacting backlash. The eccentric shaft is positioned with deviations limited to ±0.005 mm relative to the disc bores, using shims or adjustable bearings for precise offset matching the design eccentricity (often 0.5–2 mm, influenced by lobe count). Pins are inserted into the ring with radial and circumferential tolerances of 0.01 mm, followed by alignment verification to ensure uniform load distribution across lobes. This minimizes backlash to under 0.1° in high-precision units.^[6] Modern advancements include additive manufacturing for rapid prototyping of cycloidal discs and rings, using fused deposition modeling (FDM) with materials like PLA reinforced by steel pins, achieving functional prototypes with stiffness up to 633 Nm/rad at costs below €100. Quality control relies on coordinate measuring machines (CMM) to verify profile accuracy, detecting deviations as low as 10 μm against CAD-generated curves through point-cloud fitting and error mapping.^[21]^[22]

Performance characteristics

Advantages

Cycloidal drives exhibit high torque density, enabling significant torque output in a compact form factor, primarily due to the distribution of load across multiple contact points between the cycloidal disc and output pins. This design allows for reduction ratios typically ranging from 10:1 to over 100:1 in a single stage, surpassing the capabilities of many traditional gear systems and reducing the need for multi-stage configurations.^[23]^[1] A key advantage is the exceptional overload capacity, often up to 500% of the rated torque momentarily, which stems from the even load sharing across at least 30% of the disc profile, preventing localized stress concentrations. This feature enhances reliability in demanding environments where sudden load spikes occur.^[24]^[23] Cycloidal drives provide minimal backlash, typically less than 1 arcminute, which ensures high positional accuracy and repeatability essential for precision tasks. The cycloidal motion eliminates the play typical in meshed gear pairs, making these drives superior for applications requiring exact positioning.^[25]^[23]^[3] Furthermore, their compact footprint facilitates integration into space-constrained systems while maintaining robustness. Cycloidal drives demonstrate superior durability under shock loads and enhanced vibration resistance compared to traditional involute gears, owing to the primarily rolling contact mechanism that minimizes wear and oscillatory forces.^[26]^[27]^[28]

Disadvantages

Cycloidal drives incur higher manufacturing and material costs primarily due to the precision machining required for their complex cycloidal disc profiles and pin arrangements, which demand tight tolerances to ensure proper meshing and load distribution.^[29] This precision often involves specialized cutting tools and processes that are more time-consuming and expensive compared to standard gear fabrication.^[29] Additionally, the need for high-quality materials to withstand contact stresses further elevates production expenses, making cycloidal drives less economical for cost-sensitive applications.^[1] Efficiency in cycloidal drives typically ranges from 80% to 95%, depending on load and design, with losses owing to friction at the lobe-pin contact points despite primarily rolling motion.^[30]^[28] This friction arises from minimal sliding components in the contact, contrasting with pure rolling in other gear types, and can reduce overall power transmission effectiveness, particularly under load.^[28] The resulting heat buildup necessitates careful thermal management to prevent performance degradation.^[30] At high speeds, cycloidal drives exhibit potential for vibrations and noise due to the eccentric motion of the cycloidal disc, which can induce dynamic imbalances if not adequately balanced.^[30] Over time, this leads to wear on the contact surfaces, such as uniform abrasion on the lobes, which may require break-in periods to stabilize but still contributes to long-term maintenance needs.^[30] Their speed ratings are limited, with input speeds typically up to 2000-3000 rpm depending on the model, lower than those of helical gears that can operate at 10,000 rpm or more, restricting use in high-velocity scenarios.^[31]^[32]^[33] Lubrication and sealing in cycloidal drives present added complexity, as the enclosed design requires specialized grease to minimize friction losses while maintaining separation of internal components from external environments.^[30] Effective sealing is critical to retain lubricant and prevent contamination, but the intricate geometry complicates maintenance and increases the risk of leaks under operational stresses.^[34] This design complexity, stemming from precise parameter selection for disc eccentricity and pin positioning, further amplifies challenges in assembly and servicing.

Applications

Industrial machinery

Cycloidal drives are extensively employed in industrial machinery for their ability to deliver reliable torque transmission in demanding conditions, such as conveyors, mixers, and crushers operating in harsh environments like mining and cement production. In conveyor systems, these drives facilitate smooth power transfer for both continuous and intermittent operations, enabling efficient material handling in sectors including manufacturing and mining, where exposure to dust, vibration, and heavy loads is common.^[4]^[35] Their epicycloidal motion distributes loads evenly across multiple pins, enhancing durability under abrasive conditions typical of these applications.^[36] In mixers and crushers, cycloidal drives provide high torque at low speeds, essential for processing tough materials in industries like chemicals, cement, and mining. For instance, they power heavy-duty mixers in rubber and chemical processing, where consistent agitation is required despite variable loads and potential shock impacts.^[37]^[38] This reliability stems from their capacity to handle overloads up to 500% of rated torque, as exemplified by Sumitomo's Cyclo® series, which has been a staple in industrial reducers since the early 1930s, based on the 1925 invention of the cycloidal principle.^[36]^[39] Packaging machines and food processing equipment benefit from cycloidal drives' smooth, backlash-free operation, ensuring precise and hygienic motion control. In packaging lines, they drive indexing mechanisms for accurate positioning of products, while in food processing, their sealed, washdown-compatible designs meet stringent sanitation standards, supporting applications like filling and conveying.^[40]^[41] Nabtesco's Neco series, for example, integrates seamlessly into these systems for reliable performance under frequent start-stop cycles.^[42] Cycloidal drives are also integrated into wind turbine yaw systems and industrial pumps, where high overload handling is critical for operational stability. In yaw drives, they enable precise nacelle orientation against varying wind forces, used in offshore and onshore turbines, though failure analyses have shown potential issues like fatigue under extreme loads.^[43] For pumps, particularly in mining and water management, they provide robust drive mechanisms for high-pressure fluid transfer, resisting shocks from irregular flows.^[44] Sumitomo Cyclo® units, with their proven shock load resistance, continue to exemplify this capability in such heavy-duty setups dating back to the early 1930s.^[36]^[45]

Precision robotics and automation

Cycloidal drives are widely integrated into robotic joints, particularly in collaborative robots, where their zero-backlash motion enables precise, smooth operation without positional errors during human-robot interactions.^[46] This design facilitates compact integration into joint actuators, allowing for high torque density in limited spaces while maintaining structural integrity under dynamic loads.^[47] For instance, manufacturers like Cone Drive incorporate cycloidal gearing, such as the Spinea series, into robotic arms to achieve low backlash and high positioning accuracy, supporting applications in assembly and manipulation tasks.^[46] In precision automation, cycloidal drives enhance repeatable accuracy in systems like CNC machines, automated guided vehicles (AGVs), and semiconductor handling equipment. Their ability to provide high reduction ratios—often exceeding 100:1 in a single stage—ensures consistent torque amplification and minimal vibration, critical for micron-level positioning in machining and wafer transport.^[23] Sumitomo's cycloidal technology, for example, is employed in machine tools for efficient speed reduction, while HSOAR's implementations in AGVs demonstrate superior load handling for material transport in cleanroom environments.^[23]^[48] Compared to harmonic drives commonly used in servo reducers, cycloidal drives offer superior torsional rigidity due to their rigid disc construction and multi-point contact, which distributes loads more evenly and reduces deflection under torque.^[49] This rigidity advantage makes cycloidal systems preferable for robotics applications demanding high stiffness, such as joint actuators where harmonic drives may exhibit elasticity in the flexspline.^[50] Emerging applications include exoskeletons and medical devices, where the lightweight, high-ratio design of cycloidal drives supports back-drivable joints for natural human augmentation. In wearable exoskeletons, such as those prototyped with cycloidal mechanisms, the drives provide compact, efficient power transmission for lower-back support, enabling flexible human-robot interaction without excessive bulk.^[51] SPINEA's TwinSpin® series, with rated torques up to 18 Nm, exemplifies this in exoskeleton units paired with compact motors for rehabilitation.^[52] In medical robotics, Nabtesco's cycloidal servo gears contribute to precise patient handling and imaging systems, leveraging their high load capacity and minimal backlash for safe, accurate motion.^[53]

Historical development

Invention and early patents

The invention of the cycloidal drive is credited to German engineer Lorenz Konrad Braren, who developed the core principle in 1925 while working as chief designer at Friedrich Deckel in Munich.^[45] Inspired by precision mechanisms like the "COMPUR" camera shutter, Braren created an innovative gearbox utilizing an eccentric disc mechanism to achieve high-ratio speed reduction through cycloidal motion, offering a compact alternative to existing technologies.^[45] This design distributed load evenly across multiple contact points, enhancing durability and efficiency for industrial applications.^[3] The foundational concepts for Braren's invention drew from the mathematical study of cycloid geometry, a curve first described in the 16th century and extensively analyzed in the 17th century for its properties in generating smooth, low-friction profiles suitable for mechanical transmissions.^[3] While cycloidal profiles had been applied in clock gears and other precision devices since the 17th century, Braren's work marked the first practical implementation as a high-reduction gearbox, addressing key limitations of worm gears such as lower efficiency (often below 70%) and higher wear due to sliding contact. His mechanism used an eccentrically driven cycloidal disc rolling within a ring of pins, enabling ratios up to 100:1 in a single stage without the backlash common in spur or helical gears. In 1931, Braren founded Cyclo GmbH in Munich to produce the drives commercially. Braren filed the initial German patent application on December 5, 1925, establishing priority for the Cyclo® principle, which described the eccentric disc and pin-ring configuration in detail.^[54] This was followed by related German patents, including DRP 459,025 and its addition DRP 464,992, which refined the cycloidal curve generation and empirical corrections for optimal meshing.^[55] The corresponding U.S. patent, No. 1,694,031, was granted on December 4, 1928, for the "Gear Transmission," detailing prototypes tested in the late 1920s for industrial speed reduction in machinery like mills and conveyors. These early tests demonstrated superior torque capacity and reduced vibration compared to worm drives, validating the design's potential despite manufacturing challenges with precise cycloid profiling.^[56]

Commercial evolution

Following the invention of the cycloidal drive in the early 20th century, commercialization accelerated in the 1930s through licensing agreements that enabled widespread production and branding. In 1938, Sumitomo Heavy Industries signed a license agreement with Cyclo GmbH in Germany for the Cyclo Reducer technology, leading to domestic production starting in 1939 at the Niihama Works in Japan.^[57] This marked the establishment of the Cyclo® brand, which Sumitomo expanded globally, with subsidiaries formed in the United States in 1966, Canada in 1984, and China in 1994, facilitating international distribution for industrial applications.^[57] By 2003, cumulative production of Cyclo Reducers reached 10 million units, solidifying Sumitomo's role in the market.^[57] Mid-20th-century developments shifted focus toward precision applications, particularly through Nabtesco's innovations. In 1980, Nabtesco manufactured its first cycloidal gearbox for excavator power drives, initially without precision features but providing robust performance in heavy machinery.^[3] Collaborations with Japanese robot manufacturers in the early 1980s spurred further refinement, with precision gear development beginning in 1983 and the launch of the RV (rotor vector) gearbox in 1985, optimized for high torque, rigidity, and low backlash in robotics.^[3] By the late 1980s, integrations like the main bearing enhanced efficiency, reducing the need for external components and enabling broader adoption in automated systems.^[3] In the 21st century, advancements emphasized compactness and seamless integration with electric motors to meet demands in automation and robotics. Designs evolved to fit within brushless DC motor stators, minimizing footprint while maintaining high torque density, as demonstrated in custom actuators for precise motion control.^[58] These integrated units support applications in electric vehicles and industrial servos, with backlash reduced to 0.1–0.2 arcminutes for enhanced accuracy.^[3] The year 2025 marked the centennial of cycloidal gear technology, celebrated by Sumitomo Drive Technologies with events highlighting a century of engineering influence on global drive systems.^[45] The evolution of multi-stage units and hybrid variants further expanded cycloidal drives from heavy industrial uses to precision markets. Multi-stage configurations, combining two or more cycloidal stages, achieve higher reduction ratios (up to 1000:1) with improved load distribution, ideal for compact automation where single-stage limits torque capacity.^[7] Hybrid variants, such as quasi-direct drives pairing cycloidal gears with frameless motors, emerged in the 2020s for legged robotics, offering low inertia and adaptive control while bridging industrial robustness with precision dynamics.^[59] This progression broadened market penetration, with precision models now dominating robotics and evolving industrial segments.^[3]

References

[1]
Cycloidal Drive Working Principle | Archimedes Drive - IMSystems
A cycloidal drive operates through a unique motion mechanism. The input shaft is connected to an eccentric bearing, which is not positioned at the center of ...
[2]
Let Stagnoli explain what cycloidal drives are and how they work
Feb 12, 2024 · Cycloidal drives are sophisticated mechanical components, which use intelligent planetary motion to provide precise and efficient speed reduction.
[3]
News | History: 100 years of cycloidal gears
Aug 7, 2025 · In the late 1920s, the German engineer and entrepreneur Lorenz Braren developed an entirely new technology: the cyclo gear. For the transmission ...
[4]
10 uses of cycloidal gears in engineering - Cone Drive
What are the advantages of cycloidal drives? · High Torque Capacity – Cycloidal gears are known for their ability to transmit high torque with minimal stress on ...Missing: definition | Show results with:definition
[5]
Fault Diagnosing of Cycloidal Gear Reducer Using Statistical ... - NIH
Feb 2, 2023 · Cycloidal drives [1] are used in around 75% of the joints of industrial robots. The second most commonly used gearbox is Harmonic Drive with ...
[6]
Design principle and numerical analysis for cycloidal drive ...
Cycloidal drives are a high-performance precise transmission technology characterized by compact size, rigidity, high reduction ratio, and high load capacity.
[7]
Understanding Cycloidal Gearboxes | Single-stage vs Multi-stage
Mar 13, 2024 · This unique mechanism allows for the efficient transmission of torque with a high reduction ratio in a single stage. Components: Key components ...
[8]
Construction of the cycloidal disc of a cycloidal drive - tec-science
Jan 14, 2019 · The basic shape of the cycloidal disc is a cycloid. Such a cycloidal shape is obtained by a rolling circle that rolls on a base circle.Missing: definition | Show results with:definition
[9]
Benefits of Cyclo gears - Sumitomo Drive Technologies
High Reduction Ratios. Cycloidal gearboxes are capable of providing very high reduction ratios in a single stage, often ranging from 30:1 to over 100:1, and ...
[10]
Planetary vs Cycloidal Gearboxes - Transcyko
Mar 8, 2023 · Although a cycloidal gearbox is more durable and can resist very high torque loadings, it is not able to transmit as much torque as a planetary ...
[11]
What Is the Difference Between Strain Wave & Cycloidal Drives
Mar 6, 2024 · Cycloidal Gearboxes: Typically exhibit slightly higher backlash compared to strain wave gearboxes but still offer low backlash options suitable ...
[12]
Cycloidal Drives & Gearboxes
In a typical cycloidal gear, the input shaft is designed with an eccentric profile that gets pressed into a bearing. The bearing is assembled into an outer ...Missing: key | Show results with:key
[13]
Cycloidal gearbox design: principles, structure, and ... - Bonsystems
Apr 30, 2025 · This article introduces fundamental concepts that are helpful for designing a cycloidal gearbox and shares actual test results.
[14]
How does a cycloidal drive work? - tec-science
Jan 14, 2019 · The transmission ratio of a cycloidal drive is determined by the number of the fixed ring pins N and the number of the lobes of the cycloidal ...
[15]
Hypocycloid Gear Calculator - Otvinta.com
The following online calculator computes the parametric equations of the cycloid disk of a hypocycloid drive. A hypocycloid drive is defined by just four easy- ...
[16]
[PDF] The Working Principle and Parameter Design Method of Cycloidal ...
Sep 28, 2022 · Hypocycloid: a hypocycloid or luffing hypocycloid when the base line is pure rolling in a fixed ... Figure 3: Diagram of parametric equation of ...
[17]
(PDF) Influence of design parameters on cyclo drive efficiency
### Design Parameters of Cyclo Drive
[18]
Impacts of a Profile Failure of the Cycloidal Drive of a Planetary Gear ...
Oct 15, 2025 · The analysis of load distribution was calculated on the cogs of a planetary gear made with a wire EDM machine. On the other hand, we investigate ...
[19]
[PDF] CYCLOIDAL GEARBOXES - KAPP NILES
In cycloidal gearboxes two or more profiled cycloidal discs roll off in excentrical motion with ring gear pins inside a ring gear housing.
[20]
CN105665838A - Machining method for cycloid gear - Google Patents
At present, precision machining can only be processed by grinding technology, which is processed by a special cycloidal grinder. Due to the special tooth shape ...
[21]
[PDF] 3D-printable low-reduction cycloidal gearing for robotics
The basic working principle of a cycloidal drive is that of a disk rolling about an outer ring of larger radius. As it rolls, the disk rotates at a velocity ...Missing: kinematics derivation
[22]
Comprehensive Measurement of Cycloid Gear Accuracy Based on ...
Jun 25, 2023 · Compared with the cycloid profile measured by CMM, the difference of cycloid profile obtained is 10μm. According to the tooth profile equation ...
[23]
The Benefits of Cycloidal Gear Technology
Cycloidal drives and gearmotors offer outstanding performance, reliability and a long lifetime, even in the toughest operating conditions.Missing: definition engineering
[24]
Cycloidal gears versus planetary gears | Nabtesco
In addition, they offer 500% higher overload protection. Learn more about cycloidal gears. The advantages of cycloidal gears over planetary gears: More ...
[25]
Cycloidal Reducer Technology Provides High-Precision Control
Apr 20, 2023 · Cycloidal reducers also provide higher axial and radial loading capacity, lower input inertia, higher overloading capacity, and greater ...
[26]
Cycloidal Gears - Precise, Robust, Compact | Nabtesco
They feature high overload capability and extreme ... The high torque density of the low-backlash precision gears enables an extremely compact design.Missing: capacity | Show results with:capacity
[27]
Why Are Precision Cycloidal Gearboxes Preferred Over Traditional ...
May 17, 2024 · The design of cycloidal gear systems allows for continuous rolling contact, which reduces vibration and noise compared to traditional gear ...
[28]
Analysis of Energy Efficiency in Spur Gear Transmissions - MDPI
Dec 20, 2024 · The main disadvantages of the cycloidal profile in comparison with the involute profile are: The cutting tools (rack) for manufacturing the ...
[29]
[PDF] Cycloidal Geartrain In-Use Efficiency Study - MAHI Lab
Cycloidal drives achieve reductions that would require three or more stages in a traditional planetary drive. In situations where small backlash is acceptable, ...
[30]
Efficiency of the eccentric rolling transmission - ScienceDirect.com
Other well-knowns examples are cycloidal transmissions, with an efficiency of 60–96% [6], or ball-type continuously variable transmissions (CVTs), with an ...
[31]
DARALI CYCLOIDAL REDUCERS ±o¼Ö§Qºë±K¾÷±ñ Concentric ...
We recommend input speed to the DARALI DRIVES not to exceed 1800 rpm. Some larger models (i.e. B23~B27, A91~A93) have input speed limit capped at 1200 rpm.
[32]
[PDF] Double Helical Gear Performance Results in High Speed Gear Trains
The double helical, inward or outward pumping gears, had a similar result for temperature difference at 15000 rpm as the single helical at 12500 rpm.
[33]
(PDF) A comparative calculation of cycloid drive efficiency
The paper aims to compare the results obtained based on two so far the most recognized and acceptable theoretical models (Malhotra model and Kudryavtsev model).Missing: disadvantages | Show results with:disadvantages
[34]
Cycloidal Gearboxes for Mining: Maximizing Efficiency & Durability
Nov 30, 2023 · Transcyko cycloidal gearboxes are an excellent choice for heavy and light duty mining industry applications above and below ground.
[35]
Cyclo® 6000 Speed Reducer - Sumitomo Drive Technologies
This Gearmotor features a 500% shock load rating, high strength, and exceptional reliability thanks to the unique Cyclo® mechanism.
[36]
Sumitomo cyclo gear reducer - SDT Transmission
Common Applications: They are widely used in metallurgy, mining, lifting, transportation, cement, construction, chemical, and food processing industries. ...
[37]
Cycloidal Reducer in Mixer Industry - Yongzhuan Motor
Apr 24, 2025 · Cycloidal reducers have become indispensable in the mixer industry, offering unmatched performance and reliability across various applications.Missing: crushers | Show results with:crushers
[38]
100 years of the Cyclo® gear | Sumitomo Drive Technologies
Sumitomo Cyclo Gears are proven in applications including robust industrial gears, robotics, machine tools and medical technology.
[39]
Precision gears for the food industry | Nabtesco
Jun 20, 2024 · The gears of the Neco and RD-C series from Nabtesco combine precision with a hygienic design – ideal for the food industry.
[40]
Cycloidal Gearboxes For Conveyor Systems - Transcyko
Jan 16, 2023 · Cycloidal gearboxes are also perfectly suited for automated stop-start assembly lines and food processing conveyors, which demand a high degree ...
[41]
High performance cycloidal gears for food industry applications
Jun 20, 2024 · These gear systems feature high precision, efficiency and reliability and optimally fulfil the specific hygiene standards of the food industry.
[42]
Fracture Analysis of a Cycloidal Gearbox as a Yaw Drive on a Wind ...
Due to the importance of the yaw drives for wind turbines, this paper aims to evaluate a failure that occurred on a cycloidal gearbox used in a drive of this ...Missing: pumps | Show results with:pumps
[43]
Ventilation & Pumping Applications of Cyclo Drives in Coal Mining ...
May 21, 2024 · Cyclo drives are used for ventilation fans, pumping groundwater, and potentially for coal slurry transport in coal mining.
[44]
100 Years of Cyclo® - Sumitomo Drive Technologies | EMEIA
Feb 7, 2025 · With a spirit of innovation, Lorenz Konrad Braren laid the foundation for the success story of cycloidal gears in 1925. The engineer, born in ...
[45]
Cone Drive adds cycloidal gearing technology to its robotics lineup
Oct 1, 2025 · Cone Drive says its new Spinea cycloidal gearing series provides both precision and high torque density for industrial applications.<|control11|><|separator|>
[46]
Cycloidal Gear : Benefits, Applications & Top Gear Manufacturers
Explore cycloidal gears: compact, durable & precise solutions. Learn key benefits, applications in robotics & automation, and top gear manufacturers.
[47]
HSOAR Group Reveals How Cycloidal Drives Revolutionize AGV ...
Jun 28, 2024 · The company's latest research highlights the significant advantages of cycloidal drives in heavy-load AGV/AMR applications across various ...<|separator|>
[48]
Harmonic Drive Vs Cycloidal
Cycloidal and harmonic drives are both suitable for creating high ratio transmissions in small spaces. This makes them ideal for use in robotics and automation ...
[49]
https://conedrive.com/cycloidal-gears-vs-harmonic-gears/
[50]
Cycloidal-drive joint design for wearable exoskeletons
A compact cycloidal gear transmission was designed to satisfy the compactness requirement while ensuring the minimum torque is required for backdriving the ...
[51]
Compact unit for exoskeletons. TwinSpin® gearbox from SPINEA ...
SPINEA® has the smallest cycloid gearbox on the market in its portfolio. The TS 050 M-series has a rated torque of 18 Nm and a peak torque of up to 36 Nm at a ...
[52]
Medical technology - Nabtesco Precision Europe GmbH
Motorised drives provide for extreme precision in the handling of patients and in imaging processes such as X-ray, MRI or ultrasonic examinations.
[53]
Cycloid gear - Wikipedia
A cycloidal gear is a toothed gear with a cycloidal profile. Such gears are used in mechanical clocks and watches, rather than the involute gear form used ...<|control11|><|separator|>
[54]
US1817405A - Production of cycloidal curves - Google Patents
In a device for producing cycloidal curves, a tool a work carrier, a drive for causing a bodily circular movement of said tool and said work carrier in ...<|control11|><|separator|>
[55]
US4050331A - Cycloidal gears - Google Patents
The present invention relates to cycloidal gears. Planetary gears are known ... Lorenz Braren Transmission gear with eccentrically moved intermediate links.
[56]
A new method to estimate effective elastic torsional compliance of ...
... Cycloidal drive namely “Gear Transmission” (1928 US Patent No. 1,694,031), by Lorenz K. Braren [1]. He has thoroughly described the construction of his ...
[57]
Our History - Sumitomo Drive Technologies | Japan
1938: License agreement between Cyclo GmbH and Sumitomo. 1939: Began domestic production of the Cyclo reducer manufactured in Niihama Works, Japan. Niihama ...Missing: 1930s | Show results with:1930s
[58]
Compact Cycloidal Drive Lives Inside This Custom Brushless Motor
Feb 16, 2024 · 3D printed cycloidal gearbox is designed to fit inside the stator of a BLDC motor. And not just any BLDC motor, but one built mostly from scratch.
[59]
Cycloidal Quasi-Direct Drive Actuator Designs with Learning-based ...
Oct 22, 2024 · This paper presents a novel approach through the design and implementation of Cycloidal Quasi-Direct Drive actuators for legged robotics.