Low friction rolling contact transmission for an actuator

Abstract

An apparatus with low friction transmission is provided. The apparatus comprises a motor configured to drive an input shaft to have a rotational motion, a cycloidal transmission mechanism configured to convert the rotational motion of the input shaft to a motion of a rotatable output component at a gear ratio, where the cycloidal transmission mechanism has rolling contact between a cycloidal disk and an inner fixed pin thereby reducing friction, and an encoder mounted to the rotatable output component. The output component is located outside of the inner fixed pin.

Description

LOW FRICTION ROLLING CONTACT TRANSMISSION FOR AN ACTUATORCROSS-REFERENCE

[0001] This application claims the benefit of U.S. Provisional Application No. US 63 / 670,000, filed July 11, 2024, which is incorporated herein by reference in its entirety.BACKGROUND

[0002] Actuators are used in robotic systems. One conventional type of actuator is a cycloidal actuator. Cycloidal actuators, also known as cycloidal drives, are mechanical devices that may be used to convert input rotational motion into different output rotational motion, often with a reduction in speed and a corresponding increase in torque. The core components of a cycloidal actuator comprise an input shaft, a motor, a gearbox that comprises a cycloidal disk (or cam), bearings, and an output shaft. The input shaft is connected to an eccentric cam or cycloidal disk that rotates within a fixed actuator housing. As the cycloidal disk rotates, the lobes of the disk engage with the bearings that are mounted in a stationary ring gear, creating a rolling motion. The output shaft is connected to a set of pins that engage with holes on the cycloidal disk. As the disk rotates, the pins follow the motion of the holes, causing the output shaft to rotate at a reduced speed compared to the input shaft. The reduction ratio is determined by the number of lobes on the cycloidal disk and the number of pins or rollers in the ring gear. The output shaft may also be coupled to a load.

[0003] In many robot applications, a system for controlling or measuring the torque generated by the actuator and applied to the load is used to achieve a specific torque, known as torque control. Conventional closed-loop torque control systems require additional sensors, like torque cells, to measure the torque applied by the actuator and calculate errors between the applied and sensed torque.

[0004] In order to address the shortcomings of closed-loop control systems, convention sensorless torque control systems, or open-loop torque control systems were developed. In openloop torque control systems, the systems estimate the applied torque using motor characteristics and current measurements without additional sensors. This method reduces cost, reduces actuator packaging, improves robustness, and typically improves torque bandwidth. However, the overall performance of the conventional open-loop torque-controlled actuators is highly dependent on the relationship between the applied current to the motor and the resulting torque applied to the load. Friction, hysteresis, back-driving torque, and other phenomena of actuators negatively affect this relationship, making many conventional open-loop actuation systemsunsuitable for open-loop torque control. Much of this phenomenon is defined by the mechanical operation of the gearbox.

[0005] Further, traditional cycloidal actuators experience unacceptable levels of internal friction caused by the sliding contact between actuator components, leading to energy loss and wear. Further, the conventional actuators experience backlash due to the gaps required for movement and employ overly complex configurations.SUMMARY

[0006] A need exists for an improved actuator for robotic applications. A further need exists for an actuator suitable for open-loop torque control with improved performance. The present disclosure addresses the above needs by providing a tightly integrated, highly efficient actuator with low friction. The actuator herein may comprise modular hard stops and a large, supported output surface for attaching a load or an actuation load. In some embodiments, the actuator of the present disclosure may be a medium gear ratio (e.g., 20: 1) low friction rolling contact cycloidal actuator. The cycloidal actuator may comprise a fixed inner gearbox and a rotating outer ring which beneficially allows for a compact and / or low-profile encoder arrangement. The actuator uses low-friction components to reduce torque application losses and improve openloop torque control accuracy. The actuator incorporates an asymmetric bearing arrangement for a low-profile encoder configuration and supports an inline interchangeable hard stop for flexible integration.

[0007] The present disclosure also improves upon the relationship between the applied current and the resulting torque in a compact form actuator, making the actuator suitable for open-loop torque control. By reducing friction and mechanical losses, the actuator of the present disclosure enhances the accuracy and efficiency of torque transfer, ensuring smoother and more precise actuator performance.

[0008] In an aspect, the present disclosure provides methods and systems for an apparatus. The apparatus comprises a motor configured to drive an input shaft to have a rotational motion, a cycloidal transmission mechanism configured to convert the rotational motion of the input shaft to a motion of a rotatable output component at a gear ratio, where the cycloidal transmission mechanism has rolling contact between a cycloidal disk and an inner fixed pin thereby reducing friction, and an encoder mounted to the rotatable output component, and wherein the output component is located outside of the inner fixed pin.

[0009] In some embodiments, the rolling contact has a coefficient of friction of no greater than 0.1. In some embodiments, the rolling contact has a coefficient of friction of no greater than 0.06. In some embodiments, the rolling contact is provided by a bearing configured to supportthe inner fixed pin thereby reducing a sliding contact between the inner fixed pin and the cycloidal disk. In some embodiments, the bearing comprises a needle roller bearing. In some embodiments, the rolling contact is further provided by a washer. In some embodiments, the cycloidal disk and a ring pin of the rotatable output component has a rolling contact. In some embodiments, the rolling contact between the cycloidal disk and the ring pin is provided by a bearing configured to support the ring pin thereby reducing a sliding contact between the ring pin and the cycloidal disk. In some embodiments, the bearing comprises a needle roller bearing. In some embodiments, the rolling contact between the cycloidal disk and the ring pin is further provided by a washer. In some embodiments, the gear ratio is about 20: 1. In some embodiments, the rotatable output component comprises a housing to house a plurality of ring pins that are engaged with the cycloidal disk via a rolling contact. In some embodiments, the encoder is mounted to the housing. In some embodiments, the encoder comprises an absolute encoder. In some embodiments, the encoder has a low profile comprising an encoder ring and a read head located between the housing of the rotatable output component and a fixed component of the apparatus. In some embodiments, the apparatus further comprises a hard stop mechanism configured to limit a mechanical range of the apparatus. In some embodiments, the hard stop mechanism is swappable. In some embodiments, the hard stop mechanism comprises an output hard stop component and a corresponding fixed portion thereby allowing for an adjustable limit of the mechanical range. In some embodiments, the apparatus has a compact form. In some embodiments, the apparatus is utilized in a robotic system. In some embodiments, the apparatus comprises a controller configured to operate open-loop torque control of the apparatus.

[0010] In another aspect, an apparatus for a robotic system is provided. The apparatus comprises: a motor configured to drive an input shaft to have a rotational motion; a cycloidal transmission mechanism configured to convert the rotational motion of the input shaft to a motion of a rotatable output component at a gear ratio, where the cycloidal transmission mechanism has a rolling contact between components of cycloidal transmission mechanism thereby reducing friction caused by sliding movement; and an encoder mounted to the rotatable output component, where the encoder has a low profile.

[0011] In some embodiments, the gear ratio is in a range of 10: 1 - 30: 1 or is about 20: 1. In some cases, the rotatable output component comprises a housing to house a plurality of ring pins that are engaged with a cycloidal disk via a rolling contact. In some embodiments, the encoder is mounted to the housing. In some cases, the encoder comprises an absolute encoder. In some cases, the encoder comprises an encoder ring and a read head located between the housing of the rotatable output component and a fixed component of the apparatus. In some embodiments, the apparatus further comprises a controller operably coupled to the motor and is configured tooperate an open-loop torque control of the apparatus. In some cases, the open-loop torque control does not use a torque sensor or current sensor to provide a torque feedback.

[0012] Additional aspects and advantages of the present disclosure will become readily apparent to those skilled in this art from the following detailed description, wherein only illustrative embodiments of the present disclosure are shown and described. As will be realized, the present disclosure is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.INCORPORATION BY REFERENCE

[0013] All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. To the extent publications and patents or patent applications incorporated by reference contradict the disclosure contained in the specification, the specification is intended to supersede and / or take precedence over any such contradictory material.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings (also “Figure” and “FIG.” herein), of which:

[0015] FIG. 1 illustrates an exemplary perspective view of a robotic system.

[0016] FIGs. 2A and 2B illustrate an exemplary actuator.

[0017] FIGs. 3A and 3B illustrate an exemplary exploded view of an actuator.

[0018] FIGs. 4A and 4B illustrate an exemplary exploded view of an eccentric shaft.

[0019] FIG. 5 illustrates an exemplary exploded view of an actuator output and encoder assembly.

[0020] FIG. 6 illustrates an exemplary exploded view of a hardstop mechanism.

[0021] FIG. 7 illustrates an exemplary perspective view of a hardstop in an overall assembly.

[0022] FIGs. 8-11 illustrate additional exemplary views of an actuator.DETAILED DESCRIPTION

[0023] While various embodiments of the invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions may occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed.

[0024] Whenever the term “at least,” “greater than,” or “greater than or equal to” precedes the first numerical value in a series of two or more numerical values, the term “at least,” “greater than” or “greater than or equal to” applies to each of the numerical values in that series of numerical values. For example, greater than or equal to 1, 2, or 3 is equivalent to greater than or equal to 1, greater than or equal to 2, or greater than or equal to 3.

[0025] Whenever the term “at most,” “up to,” “no more than,” “less than,” or “less than or equal to” precedes the first numerical value in a series of two or more numerical values, the term “no more than,” “less than,” or “less than or equal to” applies to each of the numerical values in that series of numerical values. For example, less than or equal to 3, 2, or 1 is equivalent to less than or equal to 3, less than or equal to 2, or less than or equal to 1.

[0026] When ranges are present, the ranges include the range endpoints. Additionally, every sub range and value within the range is present as if explicitly written out. The terms “about” and “approximately,” as used herein, when preceding a numerical value indicates the value plus or minus a range of 10%. For example, about 10 may be reasonably understood to convey 9, 10, or 11, or a range of numerical values spanning from 9 to 11. Whenever “about” or “approximately” precedes the first numerical value in a series of two or more numerical values, the term “about” or “approximately” applies to each of the numerical values in that series of numerical values.

[0027] In some embodiments, the Coefficient of Friction (CoF) may be defined as a dimensionless value that quantifies the frictional force between two surfaces in contact relative to the normal force pressing them together. The CoF may vary depending on the materials in contact, surface conditions, and the type of contact (static or dynamic). In some embodiments, the CoF may range from about 0.01 to about 1.5. In some embodiments, specific values within this range may include a CoF of about 0.01, about 0.05, about 0.1, about 0.2, about 0.5, about 0.8, or higher than about 1.0, representing different levels of frictional interaction. Lower values in this range may indicate smoother surfaces with less friction, while higher values may indicate rougher surfaces with increased frictional resistance.

[0028] In some embodiments, the gear ratio may be defined as the ratio of the rotational speeds of two interlocked gears. The gear ratio may determine the mechanical advantage andspeed of the apparatus. In some embodiments, the gear ratio is in a range of 10: 1 - 30: 1. In some embodiments, the gear ratio may range from about 1 : 1 to about 50: 1. In some embodiments, specific values within this range may include a gear ratio of about 2: 1, about 5: 1, about 10: 1, about 20: 1, or about 30: 1, allowing for various levels of torque amplification and speed reduction depending on the application.

[0029] In some embodiments, a compact form may refer to a configuration where the overall dimensions of an apparatus are minimized while maintaining functionality. In some embodiments, a compact form may indicate dimensions that are less than about 30 centimeters (cm) in length, width, or height. In some embodiments, specific configurations may comprise dimensions that are less than about 25 cm or less than about 20 cm, facilitating integration into space-constrained environments.

[0030] In some embodiments, a low profile may be characterized by a reduced height or thickness of a component or assembly. In some embodiments, a low-profile configuration may feature dimensions that are less than about 15 mm to about 25 mm in height. This configuration may be beneficial in applications requiring height restrictions or where a streamlined appearance is preferred.

[0031] In some embodiments, the mechanical range may refer to the total allowable movement or displacement of a component within an apparatus. In some embodiments, the mechanical range may be defined as being between about 5 degrees to about 180 degrees of rotation or linear movement. In some embodiments, specific values may comprise ranges of about 10 degrees, about 30 degrees, or about 90 degrees, depending on the application requirements.

[0032] In some embodiments, rolling contact may refer to the interaction between two surfaces where one surface rolls over another, minimizing sliding friction. In some embodiments, rolling contact may be characterized by a CoF that is lower than that of sliding contact, typically ranging from about 0.01 to about 0.1. In some embodiments, the effectiveness of rolling contact may be influenced by the surface materials, lubrication, and load applied during operation.

[0033] In some embodiments, torque may be defined as the rotational force applied to an object. The torque may be measured in units such as Newton-meters (Nm) or pound-feet (Ib-ft). In some embodiments, the torque may range from about 0.1 Nm to about 100 Nm. In some embodiments, specific values within this range may comprise torques of about 0.5 Nm, about 1 Nm, about 5 Nm, about 10 Nm, or greater than about 50 Nm, depending on the application and configuration requirements.

[0034] As used herein, the term “actuator” refers to a mechanical device that converts energy into motion and is responsible for moving or controlling a mechanism or system. The actuators may operate using various types of energy sources, including electric, hydraulic, pneumatic, thermal energy, and cycloidal actuators. The electric actuator uses electrical energy to produce motion. The electric actuators may be either linear or rotary, depending on the type of motion required. The hydraulic actuators utilize fluid pressure to generate motion and are typically used in heavy machinery due to their ability to produce high force and precise control. Examples comprise hydraulic cylinders and hydraulic motors. The pneumatic actuators use compressed air to create motion. Examples comprise pneumatic cylinders and air-driven motors. The thermal actuators rely on temperature changes to produce motion. The cycloidal actuators, also known as cycloidal drives, convert rotational motion into a different rotational motion with a reduction in speed and an increase in torque.

[0035] As used herein, the term “low friction” or “low friction component” or “low friction element”, especially in the context of an actuator such as a cycloidal actuator, refer to or comprise elements that are configured to minimize mechanical resistance between interacting parts, thereby enhancing the actuator’s efficiency, durability, and operational smoothness. The components may be integral to reducing the coefficient of friction and wear, facilitating more efficient power transmission and prolonging the lifespan of the actuator. Examples of suitable components may comprise resin washers which may be made from high-performance plastics such as Polytetrafluoroethylene (PTFE) or Ultra-High Molecular Weight Polyethylene (UHMWPE), ball bearings, roller bearings, thrust bearings, roller thrust bearings, bushings such as PTFE bushings, lubricated bronze bushings, ceramic bearings, polymer gears, and selflubricating bushings. The measurement of low friction for these components may be quantified by the coefficient of friction (CoF), which is a dimensionless scalar value which describes the ratio of the force of friction between two bodies to the force pressing them together. The low friction components of the present disclosure have a CoF that is less than 0.1, and preferably less than or equal to 0.06.

[0036] The present disclosure is directed to a low friction, rolling contact cycloidal actuator with a medium gear ratio (e.g., 20: 1). The actuator features a fixed inner gearbox and a rotating outer ring (e.g., low-friction components) to reduce torque application losses and improve openloop torque control accuracy. The actuator also employs an asymmetric bearing arrangement that enables the actuator to have a low-profile encoder configuration. The bearing support of the actuator uses both bearings to support external loads without a third over constraining bearing being employed. The actuator also employs an interchangeable hard stop for flexible integration.

[0037] The present disclosure pertains to a unique low gear ratio (e.g., 20: 1) low friction rolling contact actuator, such as a cycloidal actuator, that may be configured to enhance torque transfer efficiency and reduce mechanical friction. This is achieved through an arrangement of components and the integration of low friction materials. Specifically, the actuator of the disclosure operates by using a rolling contact cycloidal mechanism with bearings positioned between all sliding surfaces, such as between the cycloid disks and the output pins, as well as the cycloid disks and the ring pins. The inclusion of the low friction components in the actuator protects the bearings and reduces friction further. The configuration of the actuator of the present disclosure allows for efficient torque transfer with minimal energy loss, ensuring smooth and precise motion suitable for applications like legged robots. The actuator comprises the cycloid disks, output pins, ring pins, needle roller bearings, and the incorporation of low friction components such as resin washers or bearings.

[0038] The actuator of the present disclosure employs a cycloidal disk, output pins, ring pins, an eccentric shaft, bearings such as needle type roller bearings, and low friction components such as washers or bearings. The cycloidal disks may be circular disks that move eccentrically within a gearbox of the actuator. The cycloidal disks engage with the ring pins to transmit motion. The output pins are connected to the output shaft and interact with the cycloidal disks to convert the cycloidal motion into rotational output. The ring pins are stationary pins fixed in the housing of the actuator. The cycloidal disks move about or around the ring pins to create the cycloidal motion. The eccentric shaft is the input shaft that drives the cycloidal disks, and is offset from the center, causing the disks to move in a cycloidal path. The needle roller bearings are disposed or positioned around the ring pins and the output pins to facilitate rolling contact, reducing friction. The low friction components (e.g., washers or bearings) are placed between the cycloidal disks and the ring / output.

[0039] The eccentric shaft is driven by a motor and when driven rotates, causing the cycloidal disks to move eccentrically. As the cycloidal disk moves, they engage with the ring pins, causing a rolling motion rather than a sliding motion. The needle roller bearings, in conjunction with the low friction washers or bearings, ensure minimal resistance during this movement. The movement of the cycloidal disks is transferred to the output pins, which are connected to the output shaft. This converts the cycloidal motion into rotational output with a torque multiplication factor based on the current gear ratio (e.g., 20: 1). The actuator may comprise an integrated encoder arrangement that provides precise feedback on the position of the output shaft, enabling accurate control of the actuator. Further, the easily swappable hard stop allows for quick adjustments to the actuator’s range of motion, accommodating various application requirements.

[0040] FIG. 1 is a perspective view of one embodiment of a robotic system that may employ the actuator of the present disclosure. The robotic system may comprise a robot 10 that is comprised of multiple actuators 15. Each actuator 15 employs a torque control technique or method that applies a specified torque on a successor link in the robot. The robot 10 may comprise an arm with an end effector 20 that is gripping any suitable type of implement 25, such with a sander. The robot 10 needs to apply a specified force with the implement 25 onto a target workpiece. Using a control method, a desired force on the end effector 20 may calculate the specified torque needed from each joint in the arm. The present disclosure achieves precise torque application without additional torque-sensing elements, that may be combined and housed in a small and lightweight package or housing.

[0041] As shown for example in FIG. 2A, the illustrated actuator 15 of the present disclosure works by spinning an input shaft 400, which has two eccentric lobes 410, positioned for example 180 degrees apart from each other. The eccentric lobes 410 each spin a cycloidal disk, which are each constrained by the ring pins 350 and the output pins 250. The cycloidal disks contact both the ring and output pins simultaneously and transmit the motion through a rolling contact. Both the ring pins 350 and the output pins 250 employ bearings, such as needle roller bearings 360, to reduce the friction from the cycloid’s contact. The actuator 15 also comprises the cycloidal gearbox 50, motor housing attachment 100, actuator cap 110, small output bearing 175, large output bearing 185, ring pin housing 200, and rotor bearings 450. FIG. 2B shows an alternate embodiment of the actuator of the present disclosure where the low friction element comprises bearings rather than washers.

[0042] FIG. 3A is an exploded view of the actuator 15. The output pin and the ring pin bearing assemblies are exploded, illustrating the use of low friction components, such as washers or bearings. FIG. 4A is an exploded view of the eccentric shaft, both cycloid disks, and low friction components. As shown in FIGS. 3A and 4A, the inclusion of low friction components in the actuator 15 allows for the reduction of transmission losses through the actuator. The low friction components may be comprised in the bearing assembly for the output pins in the form of bearings 260 and the washers 275 and for the ring pins in the form of bearings 360 and washers 375 as shown in FIG. 3A. The low friction components, such as the low friction washer 425 and the low friction washer 475, are also comprised to reduce friction between the cycloidal discs (300) and the eccentric shaft (400) as shown in FIG. 4A. The components work together to create an actuator with a high gear ratio, low friction losses, and back drivability. FIG. 3B shows an alternate embodiment of the actuator of the present disclosure where the low friction element comprises bearings 275B, 375B rather than washers 275, 375. FIG. 4B shows an alternate embodiment of the actuator of the present disclosurewhere the low friction element comprises bearings 425B, 475B rather than washers 425, 475.

[0043] Unlike conventional cycloidal transmission actuators, the actuator 15 of the present disclosure employs a ring pin housing 200 as the output of the actuator. This enables the use of a high precision, absolute encoder to measure rotational output of the actuator in a small package, enhancing the accuracy of motion control. FIG. 5 is an exploded view of the actuator output and encoder assembly and illustrates the encoder ring 600 and the encoder read head 650. The encoder ring 600 may be mounted to the ring pin housing and the encoder read head 650 may be mounted to a structure fixedly connected to the stationary frame with respect to the actuator housing or stator.

[0044] FIG. 6 is an exploded view of a hardstop mechanism. The illustrated components of the hardstop mechanism allows for quick adjustments to the actuator’s range of motion. The configuration of the hardstop facilitates easy maintenance and customization. The hardstop comprises an output hardstop 700, an output hardstop lobe 725, a fixed portion of the hardstop 750, and a fixed hardstop lobe 775.

[0045] FIG. 7 is a perspective view of the hardstop in an overall assembly and shows the integration of the hardstop mechanism within the overall actuator assembly. The output hardstop 700 and its fixed portion 750 are configured to control the range of motion, while the load 800 represents the part of the actuator that performs the work. FIGs. 8-11 show additional views of the actuator 15 of the present disclosure.

[0046] The actuator of the present disclosure addresses the drawbacks of the conventional actuators through several innovative features. The actuator 15 employs a rolling contact configuration. Unlike traditional cycloidal actuators that rely on sliding contact, the actuator 15 employs rolling contact by incorporating needle roller bearings between all interacting surfaces. This comprises bearings around the cycloid disks, output pins, and ring pins. This reduces friction and wear, leading to more efficient and durable operation. The actuator 15 further comprises low friction elements, such as washers or bearings, disposed between the bearings and the cycloid disks. The low friction components provide an additional layer of friction reduction by ensuring the bearings only roll and do not slide against metal surfaces. This reduces the need for tight machining tolerances and simplifies the assembly process, as precise alignment is less critical.

[0047] The actuator 15 also employs an encoder arrangement where the encoder ring is placed directly between the stator and the ring pin housing. This allows for high-resolution position sensing in a compact package, enhanced precision in motion control, and a reduced overall actuator size. The actuator 15 also comprises an easily swappable hard stop mechanism. This mechanism uses the existing screws for installation, making it lightweight and easy tomodify. This simplifies maintenance and customization of the actuator’s range of motion, reducing costs and improving strength.

[0048] In some embodiments, the components of the actuator may comprise a cycloidal robot arm, cycloidal actuators, an arm end effector, a sanding pad, a cycloid assembly, a motor housing attachment (e.g., fixed), an actuator cap, a small output bearing, a large output bearing, a ring pin housing (e.g., output), fixed pins, fixed pin bearings, low friction washers (e.g., fixed pins), cycloidal discs, ring pins, ring pin bearings, low friction washers (ring pins), an eccentric shaft, eccentric lobes, an eccentric flange spacer, a low friction washer, rotor bearings, a small low friction washer, an encoder ring, an encoder read head, an output hardstop, an output hardstop lobe, a fixed portion of the hardstop, a fixed hardstop lobe, a load, or a combination thereof. In some embodiments, the cycloidal robot arm may provide the primary movement mechanism. In some embodiments, the cycloidal actuators may facilitate the conversion of rotational motion to linear motion. In some embodiments, the arm end effector may be configured to perform specific tasks, such as gripping or manipulating objects. In some embodiments, the sanding pad may be included for surface finishing applications.

[0049] In some embodiments, the cycloid assembly may be integral to the operation of the actuator. In some embodiments, the motor housing attachment (e.g., fixed) may serve as the mounting point for the motor. In some embodiments, the actuator cap may provide protection and support for internal components. In some embodiments, the small output bearing may support the output shaft and reduce friction. In some embodiments, the large output bearing may handle greater loads and maintain stability. In some embodiments, the ring pin housing (e.g., output) may house the ring pins that interact with the cycloidal disk. In some embodiments, the fixed pins may provide structural integrity to the assembly. In some embodiments, the fixed pin bearings may facilitate smooth rotation of the fixed pins. In some embodiments, the low friction washers (e.g., fixed pins) may reduce friction between moving parts and may be complemented by bearings. In some embodiments, the cycloidal discs may be responsible for the primary motion conversion in the actuator. In some embodiments, the ring pins may engage with the cycloidal disks to facilitate rolling contact.

[0050] In some embodiments, the ring pin bearings may support the ring pins and reduce friction during operation. In some embodiments, the low friction washers (e.g., ring pins) may enhance the efficiency of the ring pin interactions and may be accompanied by bearings. In some embodiments, the eccentric shaft may provide rotational motion and may be connected to the motor. In some embodiments, the eccentric lobes may convert rotational motion into linear motion. In some embodiments, the eccentric flange spacer may maintain proper spacing between components. In some embodiments, the low friction washer may further reduce friction in theassembly and may be supported by bearings. In some embodiments, the rotor bearings may support the rotor and ensure smooth operation. In some embodiments, the small low friction washer may be used in various locations to minimize friction and may be supported by bearings. In some embodiments, the encoder ring may provide positional feedback for control systems. In some embodiments, the encoder read head may detect position changes and relay information to the control system. In some embodiments, the output hardstop may limit the movement of the actuator. In some embodiments, the output hardstop lobe may engage with other components to prevent over-travel. In some embodiments, the fixed portion of the hardstop may provide a stable reference point. In some embodiments, the fixed hardstop lobe may interact with the output hardstop to limit movement. In some embodiments, the load may refer to the operational weight or force that the actuator is configured to handle.

[0051] In some embodiments, an apparatus may comprise a motor configured to drive an input shaft to have a rotational motion. In some embodiments, the motor may be an electric motor, a pneumatic motor, or a hydraulic motor, or any combination thereof. In some embodiments, the apparatus may further comprise a cycloidal transmission mechanism. The cycloidal transmission mechanism may be configured to convert the rotational motion of the input shaft to a motion of a rotatable output component at a gear ratio. In some embodiments, the gear ratio may be at least about 1 : 1 to at least about 10: 1. In some embodiments, the gear ratio may be configured to be at least about 1 : 1, at least about 2: 1, at least about 3 : 1, at least about 4 : 1 , at least about 5 : 1 , or greater than about 10:1.

[0052] In some embodiments, the cycloidal transmission mechanism may have a rolling contact between a cycloidal disk and an inner fixed pin. In some embodiments, the rolling contact may reduce friction during operation. In some embodiments, the cycloidal disk may be made of materials such as steel, aluminum, or composite materials, or any combination thereof. In some embodiments, the apparatus may further comprise an encoder mounted to the rotatable output component. In some embodiments, the encoder may be an optical encoder, a magnetic encoder, or a capacitive encoder, or any combination thereof. In some embodiments, the output component may be located outside of the inner fixed pin to facilitate the operation of the encoder and enhance accessibility for maintenance or adjustments. In some embodiments, the apparatus may be configured to operate in various applications such as robotics, automotive systems, or industrial machinery, or any combination thereof.

[0053] In some embodiments, the apparatus may have a rolling contact that has a coefficient of friction of no greater than about 0.1. In some embodiments, the coefficient of friction may be configured to be no greater than about 0.1, no greater than about 0.09, no greater than about 0.08, no greater than about 0.07, or no greater than about 0.06. In some embodiments, theapparatus may have a rolling contact that has a coefficient of friction of no greater than about 0.06. In some embodiments, the coefficient of friction may be configured to be no greater than about 0.06, no greater than about 0.05, no greater than about 0.04, or any value in that range. In some embodiments, the rolling contact may be provided by a bearing configured to support the inner fixed pin. In some embodiments, the bearing may reduce a sliding contact between the inner fixed pin and the cycloidal disk. In some embodiments, the bearing may be a ball bearing, a roller bearing, or a sleeve bearing, or any combination thereof. In some embodiments, the configuration of the bearing may enhance the efficiency of the transmission mechanism by minimizing wear and prolonging the operational lifespan of the apparatus. In some embodiments, the apparatus may comprise a bearing that comprises a needle roller bearing. In some embodiments, the needle roller bearing may be configured to provide support while minimizing the space required for the bearing assembly.

[0054] In some embodiments, the apparatus may have the rolling contact that is further provided by a washer. In some embodiments, the washer may be configured to distribute loads and enhance the stability of the rolling contact. The washer may be made of materials such as metal, plastic, or composite materials, or any combination thereof. In some embodiments, the apparatus may comprise a configuration wherein the cycloidal disk and a ring pin of the rotatable output component have rolling contact. In some embodiments, the rolling contact between the cycloidal disk and the ring pin may facilitate efficient power transfer and motion conversion. In some embodiments, the rolling contact between the cycloidal disk and the ring pin may be provided by a bearing configured to support the ring pin. In some embodiments, the bearing may reduce a sliding contact between the ring pin and the cycloidal disk. In some embodiments, the bearing may be a ball bearing, a roller bearing, or a needle bearing, or any combination thereof. The configuration of the bearing may contribute to the overall efficiency and reliability of the apparatus.

[0055] In some embodiments, the apparatus may comprise a bearing that comprises a needle roller bearing. In some embodiments, the needle roller bearing may be configured to provide support while reducing friction in the rolling contact. In some embodiments, the apparatus may have the rolling contact between the cycloidal disk and the ring pin that is further provided by a washer. In some embodiments, the washer may serve to enhance load distribution and stability during operation. In some embodiments, the apparatus may have a gear ratio that is about 20: 1. In some embodiments, the gear ratio may be configured to range from about 10: 1 to about 30: 1. In some embodiments, the gear ratio may be at least about 10: 1, at least about 15: 1, or greater than about 20: 1. In some embodiments, the rotatable output component may comprise a housing that houses a plurality of ring pins. In some embodiments, the ring pins may be engaged with thecycloidal disk via rolling contact. In some embodiments, the configuration of the housing may facilitate the arrangement and support of the ring pins, contributing to the overall performance of the apparatus. In some embodiments, the apparatus may have the encoder mounted to the housing. In some embodiments, the mounting configuration may facilitate efficient data transmission between the encoder and other components of the apparatus.

[0056] In some embodiments, the encoder may comprise an absolute encoder. In some embodiments, the absolute encoder may provide precise position feedback and enhance the control capabilities of the apparatus. In some embodiments, the encoder may have a low profile that comprises an encoder ring and a read head. In some embodiments, the read head may be located between the housing of the rotatable output component and a fixed component of the apparatus. This configuration may help minimize the overall size of the apparatus while maintaining functionality. In some embodiments, the apparatus may further comprise a hard stop mechanism configured to limit a mechanical range of the apparatus. In some embodiments, the hard stop mechanism may be implemented to prevent excessive movement of the components, thereby protecting the apparatus from damage. The hard stop mechanism may be constructed from materials such as metal, plastic, or rubber, or any combination thereof. In some embodiments, the apparatus may have a hard stop mechanism that is swappable. In some embodiments, the swappable configuration may allow for easy replacement or adjustment of the hard stop mechanism as needed.

[0057] In some embodiments, the hard stop mechanism may comprise an output hard stop component and a corresponding fixed portion. In some embodiments, this configuration may allow for an adjustable limit of the mechanical range. The adjustability may enhance the versatility of the apparatus in various applications. In some embodiments, the apparatus may have a compact form. In some embodiments, the compact form may facilitate integration into space-constrained environments or applications where size reduction is beneficial. In some embodiments, the apparatus may be utilized in a robotic system. In some embodiments, the robotic system may comprise applications such as automation, material handling, or robotic arms, or any combination thereof. In some embodiments, the apparatus may comprise a controller configured to operate open-loop torque control of the apparatus. Open-loop torque control may be conducted without requiring a feedback sensor (e.g., torque sensor, current sensor) to generate a torque feedback. In some embodiments, the controller may be configured to manage the torque output without feedback, simplifying the control scheme while maintaining functionality. The controller may be implemented using various electronic components such as microcontrollers, programmable logic controllers, or digital signal processors, or any combination thereof. The controller may be operably coupled to the actuator or incommunication with the actuator.

[0058] In an aspect, the present disclosure provides methods and systems for an apparatus. The apparatus comprises a motor configured to drive an input shaft to have a rotational motion, a cycloidal transmission mechanism configured to convert the rotational motion of the input shaft to a motion of a rotatable output component at a gear ratio, where the cycloidal transmission mechanism has rolling contact between a cycloidal disk and an inner fixed pin thereby reducing friction, and an encoder mounted to the rotatable output component, and wherein the output component is located outside of the inner fixed pin.

[0059] In some embodiments, the rolling contact has a coefficient of friction of no greater than 0.1. In some embodiments, the rolling contact has a coefficient of friction of no greater than 0.06. In some embodiments, the rolling contact is provided by a bearing configured to support the inner fixed pin thereby reducing a sliding contact between the inner fixed pin and the cycloidal disk. In some embodiments, the bearing comprises a needle roller bearing. In some embodiments, the rolling contact is further provided by a washer. In some embodiments, the cycloidal disk and a ring pin of the rotatable output component has a rolling contact. In some embodiments, the rolling contact between the cycloidal disk and the ring pin is provided by a bearing configured to support the ring pin thereby reducing a sliding contact between the ring pin and the cycloidal disk. In some embodiments, the bearing comprises a needle roller bearing. In some embodiments, the rolling contact between the cycloidal disk and the ring pin is further provided by a washer. In some embodiments, the gear ratio is about 20: 1. In some embodiments, the rotatable output component comprises a housing to house a plurality of ring pins that are engaged with the cycloidal disk via a rolling contact. In some embodiments, the encoder is mounted to the housing. In some embodiments, the encoder comprises an absolute encoder. In some embodiments, the encoder has a low profile comprising an encoder ring and a read head located between the housing of the rotatable output component and a fixed component of the apparatus. In some embodiments, the apparatus further comprises a hard stop mechanism configured to limit a mechanical range of the apparatus. In some embodiments, the hard stop mechanism is swappable. In some embodiments, the hard stop mechanism comprises an output hard stop component and a corresponding fixed portion thereby allowing for an adjustable limit of the mechanical range. In some embodiments, the apparatus has a compact form. In some embodiments, the apparatus is utilized in a robotic system. In some embodiments, the apparatus comprises a controller configured to operate open-loop torque control of the apparatus.

[0060] In another aspect, an apparatus for a robotic system is provided. The apparatus comprises: a motor configured to drive an input shaft to have a rotational motion; a cycloidal transmission mechanism configured to convert the rotational motion of the input shaft to amotion of a rotatable output component at a gear ratio, where the cycloidal transmission mechanism has a rolling contact between components of cycloidal transmission mechanism thereby reducing friction caused by sliding movement; and an encoder mounted to the rotatable output component, where the encoder has a low profile.

[0061] In some embodiments, the gear ratio is in a range of 10: 1 - 30: 1 or is about 20: 1. In some cases, the rotatable output component comprises a housing to house a plurality of ring pins that are engaged with a cycloidal disk via a rolling contact. In some embodiments, the encoder is mounted to the housing. In some cases, the encoder comprises an absolute encoder. In some cases, the encoder comprises an encoder ring and a read head located between the housing of the rotatable output component and a fixed component of the apparatus. In some embodiments, the apparatus further comprises a controller operably coupled to the motor and is configured to operate an open-loop torque control of the apparatus. In some cases, the open-loop torque control does not use a torque sensor or current sensor to provide a torque feedback.

[0062] While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. It is not intended that the invention be limited by the specific examples provided within the specification. While the invention has been described with reference to the aforementioned specification, the descriptions and illustrations of the embodiments herein are not meant to be construed in a limiting sense. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. Furthermore, it shall be understood that all aspects of the invention are not limited to the specific depictions, configurations or relative proportions set forth herein which depend upon a variety of conditions and variables. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is therefore contemplated that the invention shall also cover any such alternatives, modifications, variations or equivalents. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.

Claims

CLAIMSWHAT IS CLAIMED IS:

1. An apparatus comprising: a motor configured to drive an input shaft to have a rotational motion; a cycloidal transmission mechanism configured to convert the rotational motion of the input shaft to a motion of a rotatable output component at a gear ratio, wherein the cycloidal transmission mechanism has a rolling contact between a cycloidal disk and an inner fixed pin thereby reducing friction; and an encoder mounted to the rotatable output component, and wherein the output component is located outside of the inner fixed pin.

2. The apparatus of claim 1, wherein the rolling contact has a coefficient of friction of no greater than 0.1.

3. The apparatus of claim 1, wherein the rolling contact has a coefficient of friction of no greater than 0.06.

4. The apparatus of claim 1, wherein the rolling contact is provided by a bearing configured to support the inner fixed pin thereby reducing a sliding contact between the inner fixed pin and the cycloidal disk.

5. The apparatus of claim 4, wherein the bearing comprises a needle roller bearing.

6. The apparatus of claim 4, wherein the rolling contact is further provided by a washer.

7. The apparatus of claim 1, wherein the cycloidal disk and a ring pin of the rotatable output component has a rolling contact.

8. The apparatus of claim 7, wherein the rolling contact between the cycloidal disk and the ring pin is provided by a bearing configured to support the ring pin thereby reducing a sliding contact between the ring pin and the cycloidal disk.

9. The apparatus of claim 8, wherein the bearing comprises a needle roller bearing.

10. The apparatus of claim 8, wherein the rolling contact between the cycloidal disk and the ring pin is further provided by a washer.

11. The apparatus of claim 1, wherein the gear ratio is in a range of 10: 1-30: 1.

12. The apparatus of claim 1, wherein the rotatable output component comprises a housing to house a plurality of ring pins that are engaged with the cycloidal disk via a rolling contact.

13. The apparatus of claim 12, wherein the encoder is mounted to the housing.

14. The apparatus of claim 13, wherein the encoder comprises an absolute encoder.

15. The apparatus of claim 12, wherein the encoder has a low profile comprising an encoder ring and a read head located between the housing of the rotatable output component and a fixed component of the apparatus.

16. The apparatus of claim 1, further comprising a hard stop mechanism configured to limit a mechanical range of the apparatus.

17. The apparatus of claim 16, wherein the hard stop mechanism is swappable.

18. The apparatus of claim 16, wherein the hard stop mechanism comprises an output hard stop component and a corresponding fixed portion thereby allowing for an adjustable limit of the mechanical range.

19. The apparatus of claim 1, wherein the apparatus has a compact form.

20. The apparatus of claim 1, wherein the apparatus is utilized in a robotic system.

21. The apparatus of claim 1, further comprising a controller configured to operate openloop torque control of the apparatus.

22. An apparatus for a robotic system, the apparatus comprising: a motor configured to drive an input shaft to have a rotational motion; a cycloidal transmission mechanism configured to convert the rotational motion of the input shaft to a motion of a rotatable output component at a gear ratio, wherein the cycloidal transmission mechanism has a rolling contact between components of cycloidal transmission mechanism thereby reducing friction caused by sliding movement; and an encoder mounted to the rotatable output component, wherein the encoder has a low profile.

23. The apparatus of claim 22, wherein the gear ratio is in a range of 10: 1 - 30: 1.

24. The apparatus of claim 22, wherein the gear ratio is about 20: 1.

25. The apparatus of claim 22, wherein the rotatable output component comprises a housing to house a plurality of ring pins that are engaged with a cycloidal disk via a rolling contact.

26. The apparatus of claim 25, wherein the encoder is mounted to the housing.

27. The apparatus of claim 26, wherein the encoder comprises an absolute encoder.

28. The apparatus of claim 25, wherein the encoder comprises an encoder ring and a read head located between the housing of the rotatable output component and a fixed component of the apparatus.

29. The apparatus of claim 22, further comprising a controller operably coupled to the motor and is configured to operate an open-loop torque control of the apparatus.

30. The apparatus of claim 29, wherein the open-loop torque control does not use a torque sensor or current sensor to provide a torque feedback.

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