A swing electric cylinder for a humanoid robot

Abstract

The present application relates to the field of humanoid robot joints, and specifically provides a swinging electric cylinder for a humanoid robot. A rack is machined on the lead screw shaft. To eliminate the change in backlash during the gear-rack transmission process, the tooth height of the rack is distributed in a cubic curve along the axial direction. A motor rotor magnetic cylinder made of neodymium iron boron is welded to the outer circle of the nut of the reverse planetary roller screw pair. When the rotor nut rotates, the lead screw moves back and forth. The rack on the lead screw drives the gear to rotate back and forth, and the gear shaft drives the pendulum arm to swing. The swing angle of the pendulum arm is precisely positioned by the forward and backward extension position of the lead screw shaft, and the rotation of the nut drives the axial movement of the lead screw. The encoder detects the angular displacement of the nut and transmits the signal to the controller. The controller controls the angular displacement of the nut through the driver based on the information fed back by the encoder. The swinging electric cylinder of the present application can provide greater torque under the condition of equal weight. It avoids the problem of limited flexibility of humanoid robots due to the influence of size and weight.

Description

Technical Field

[0001] The present application relates to the field of humanoid robot joints, and in particular to a swing electric cylinder for a humanoid robot. Background Art

[0002] As a highly anthropomorphic mechanical system, the joint design of a humanoid robot must precisely replicate the degrees of freedom and flexibility of human limb movement. Guided by bionic principles, the robot's joints must achieve coordinated motion with multiple degrees of freedom, with swinging motion being central to complex tasks such as grasping, walking, and gripping. The swinging motion of the human arm, hip, and finger joints is essentially a rotational-translational compound motion driven by multiple antagonistic muscle groups, and the robot's mechanical structure must emulate this biomechanical characteristic.

[0003] Current mainstream joint designs are divided into two main schools: linear drive and rotary drive. Linear joints often use electric push rods or hydraulic cylinders, driven by servo motors and screw / belt drives. Their advantage lies in intuitive motion trajectories, but they require multiple joints to achieve swing. For example, the parallelogram linkage of a SCARA robotic arm achieves planar swing through two orthogonal linear joints, while a humanoid arm requires a three-degree-of-freedom orthogonal configuration. Rotary joints rely on direct motor drive or harmonic reducers, the latter of which achieve high reduction ratios through the elastic deformation of flexible gears.

[0004] Existing technologies have certain drawbacks in humanoid applications: a single linear joint can only achieve linear movement; two linear joints must be linked together, or an auxiliary linkage mechanism must be added, to achieve swinging motion. The swinging angle is limited to a very small range, such as 90 degrees. This increases the size and weight, hindering the dexterity of humanoid robots. Using a rotary joint to achieve swinging motion requires a speed reducer with a relatively large reduction ratio, such as a harmonic speed reducer. However, harmonic speed reducers are relatively heavy and bulky, and their flexible pulleys have a relatively low fatigue life. Summary of the Invention

[0005] The present application aims to solve the problem that existing joint designs require the addition of auxiliary connecting rod mechanisms or the need for a relatively large speed reducer, which results in an increased size and weight of the humanoid robot, a shorter lifespan, and is not conducive to achieving dexterous movements. The present application provides a swing electric cylinder for a humanoid robot, comprising: a drive module and a transmission module;

[0006] The driving module includes: a housing, a stator, a magnet group and a nut;

[0007] The stator, magnet group and nut are all arranged in the inner cavity of the housing, the magnet group is fixed on the outer circle of the nut, and together with the stator forms a servo motor rotor;

[0008] The transmission module includes: a planetary roller screw pair and a gear pair;

[0009] The planetary roller screw pair includes planetary rollers, a screw and a planet carrier, and the gear pair includes a rack and a gear.

[0010] The rack is machined on the axial surface of the lead screw and meshes with the gear;

[0011] The planetary rollers are arranged between the nut and the lead screw and are in rolling contact with the nut and the lead screw. The planetary carrier is fixed to both ends of the nut and is rotatably connected to the housing.

[0012] The transmission module includes a swing rod, which is fixedly connected to the gear shaft of the gear through a key, and the rotation of the gear drives the swing rod to swing.

[0013] In a feasible implementation, it further includes a control module;

[0014] The control module includes an encoder, a driver and a controller;

[0015] The encoder is fixed to the end face of the nut and is used to detect the angular displacement of the nut. The driver is electrically connected to the stator and the encoder via a cable. The control module is communicatively connected to the driver to form a closed-loop control system.

[0016] The controller is configured to detect the angular displacement of the nut through the encoder, and control the driver to drive the nut to rotate according to the angular displacement.

[0017] In a feasible implementation, the planetary roller screw pair and the gear pair form a reducer, and the reduction ratio A of the reducer satisfies the formula:

[0018] ;

[0019] Among them, m is the gear module, z is the number of gear teeth, is the lead of the planetary roller screw pair;

[0020] The pitch line of the rack is a function of Distribution, Function as follows:

[0021] ;

[0022] Where, is the radial distance from the rack pitch line to the origin, where the pitch line origin is the middle position of the first tooth close to the root of the screw thread, E is the material elastic modulus, I is the neutral axis moment of inertia, l is the total length of the rack, and x is the axial distance from any tooth on the rack to the origin.

[0023] In a feasible implementation, it further includes: a support module;

[0024] The support module includes an angular contact bearing and a deep groove ball bearing;

[0025] The angular contact bearing is fixed to one end of the housing close to the gear, and is used to support the axial movement of the lead screw;

[0026] The deep groove ball bearings are mounted on both ends of the gear shaft of the gear to control the axial displacement of the gear.

[0027] In a feasible implementation, the magnet group of the driving module is fixed in the elliptical groove of the outer circle of the nut by welding, the magnet group is made of neodymium iron boron material, and a magnet is embedded in each of the elliptical grooves.

[0028] In a feasible implementation, the swing angle of the swing rod of the transmission module is controlled by the axial displacement of the lead screw;

[0029] The displacement of the lead screw is driven by the rotation of the nut and is converted into the swing of the rocker through the engagement of the rack and the gear.

[0030] In a feasible implementation, the planetary rollers of the transmission module are evenly distributed in the roller grooves of the planetary carrier, and the planetary carrier is fixed to the inside of the housing by bolts and rollingly cooperates with the internal thread of the nut and the external thread of the screw.

[0031] In a feasible implementation, the housing is a segmented structure, including a motor cavity and a transmission cavity, and the motor cavity is fixedly connected to the stator via a flange;

[0032] The transmission cavity accommodates planetary rollers, a lead screw and a gear, and the motor cavity and the transmission cavity are isolated by a sealing ring.

[0033] In a feasible implementation, the driver of the control module and the controller are integrated on the outside of the housing and connected to the encoder and the stator via a plug-in cable;

[0034] The detection surface of the encoder is in contact with the end surface of the nut.

[0035] In a feasible implementation, an axially extending lubrication groove is provided in the meshing area between the rack and the gear, the lubrication groove is filled with a graphite-based solid lubricant, and the depth of the lubrication groove is 1 / 3 of the rack tooth height.

[0036] The present application provides a swinging electric cylinder for a humanoid robot, which is a swinging electric cylinder driven by a reversed planetary roller screw pair. This swinging electric cylinder is compact and has high torque, enabling the humanoid robot's thigh, upper arm, and finger joints to swing, thereby enabling biomimetic movements such as gripping in the robot's hands, arms, and legs. As a swinging joint for a humanoid robot, the present invention integrates six components: a reversed planetary roller screw pair, a rack and pinion pair, a servo motor, an encoder, a driver, and a controller. A rack is machined onto the screw shaft. To eliminate backlash variations during the rack and pinion transmission, the rack's tooth height is distributed parabolically along the axial direction. A neodymium iron boron motor rotor magnet is welded to the outer diameter of the nut of the reversed planetary roller screw pair. Rotating the rotor nut causes the screw to move back and forth, and the rack on the screw drives the gear to rotate back and forth, which in turn drives the swing arm to swing. The swing arm's swing angle is precisely determined by the forward and backward extension position of the screw shaft. Rotating the nut drives the axial movement of the screw. An encoder is mounted on the end face of the nut, which detects the angular displacement of the nut and transmits the signal to the controller. The controller uses encoder feedback to control the nut's angular displacement through a driver. The oscillating electric cylinder driven by the inverted planetary roller screw pair in this application can provide greater torque for a given weight. This avoids the problem of limited flexibility in humanoid robots due to their size and weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are incorporated into and constitute a part of this specification, illustrate embodiments consistent with the implementation of the present invention, and together with the description, serve to explain the principles of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the implementation of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0038] Figure 1 1 is a schematic structural diagram of a swing electric cylinder for a humanoid robot according to an exemplary embodiment of the present application;

[0039] Figure 2 yes Figure 1 sectional view of

[0040] Figure 3 1 is a schematic structural diagram of a planetary roller screw pair according to an exemplary embodiment of the present application;

[0041] Figure 4 yes Figure 3 sectional view.

[0042] Description of the accompanying drawings:

[0043] 100-housing; 200-stator; 300-magnet assembly; 400-nut; 500-planetary roller; 600-screw; 700-planet carrier; 800-rack; 900-angular contact bearing; 1000-gear; 1100-deep groove ball bearing; 1200-rocker; 1300-driver; 1400-encoder. DETAILED DESCRIPTION

[0044] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the present invention will be more comprehensive and complete and to fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to provide a thorough understanding of the implementation of the example embodiments of the present invention.

[0045] The arms, hip joints, waist joints, and finger joints of humanoid robots all need to swing so that they can perform gripping movements. Traditional robot joints either move in a linear direction or in a rotational direction. If a linear joint is to achieve a swinging motion, two linear joints must be linked together, and an auxiliary connecting rod mechanism must be added. This will increase the size and weight, making it difficult for the humanoid robot to achieve dexterous movements. If a rotary joint is used to achieve a swinging motion, a reducer with a relatively large deceleration rate, such as a harmonic reducer, is required, but the harmonic reducer is relatively heavy. The swinging electric cylinder driven by an inverted planetary roller screw pair can provide greater torque at the same weight.

[0046] To solve the above problems, refer to Figure 1 and Figure 2 As shown, the swing electric cylinder for the humanoid robot provided in this embodiment adopts a composite transmission structure of an inverted planetary roller screw pair and a gear rack. Its mechanical system consists of a drive module and a transmission module. The specific connection relationship and working principle are as follows:

[0047] The drive module is based on the housing 100, whose interior houses the stator 200, magnet assembly 300, and nut 400. The magnet assembly 300 is fixed to the outer cylindrical surface of the nut 400 in a circular array, forming a servo motor rotor structure with the stator 200. When a control current flows through the stator windings, a rotating magnetic field is generated that drives the magnet assembly and nut assembly to rotate around its axis, achieving basic power output.

[0048] The transmission module consists of a two-stage transmission chain consisting of a planetary roller screw pair and a gear pair. The planetary roller screw pair includes planetary rollers 500, a screw 600, and a planetary carrier 700. The planetary rollers 500 are positioned between the inner bore of the nut 400 and the outer surface of the screw 600, achieving rotational-to-linear motion conversion through rolling contact between the rollers and the spiral grooves. The planetary carrier 700 is fixed to both ends of the nut 400 via end flanges. Its bearing outer ring and the housing 100 form a rotational support, ensuring that the screw 600 only moves axially.

[0049] The gear pair transmission is a second-stage transmission in which a rack 800 is directly machined on the surface of the lead screw 600 and meshes with a gear 1000. Gear 1000 is keyed to a rocker 1200 via a journal, converting the linear motion of the rack 800 into reciprocating oscillation of the gear-rocker assembly.

[0050] This application leverages the high load-bearing characteristics of an inverted planetary roller screw and the high efficiency of a rack-and-pinion transmission. Through a two-stage transmission chain, the servo motor's rotational motion is sequentially converted into linear and oscillating motion. The planetary roller screw utilizes a multi-line contact design, enabling a single nut to withstand combined axial and radial loads, improving load-bearing capacity compared to traditional ball screws. The rack-and-pinion utilizes an integrated machining process to eliminate assembly play and ensure transmission accuracy.

[0051] To address the issues of bulky size and high inertia of traditional linear joint linkage systems, this application integrates dual linear drive functions into a single component through the integrated design of a planetary roller screw pair, effectively reducing the overall volume. At the same time, to address the defect of rotary joints relying on heavy reducers, which increases weight, this application adopts a structure in which gear racks directly drive the rocker arm, eliminating bulky components such as harmonic reducers and significantly reducing the weight of a single joint. In addition, the closed-loop control system compensates for nonlinear friction and elastic deformation during the transmission process through real-time feedback, making the swing positioning accuracy better than traditional harmonic reducer applications.

[0052] While maintaining a lightweight design, this oscillating electric cylinder delivers greater torque output and significantly improved power density compared to conventional applications. Its modular design supports coordinated control of multiple joints, bringing the motion envelope of the humanoid robot's waist, hips, and arms closer to natural human motion, significantly reducing overall energy consumption. The integrated structure significantly reduces assembly interfaces and improves system reliability, making it particularly suitable for anthropomorphic work scenarios requiring high loads and high dynamic response.

[0053] In some embodiments of the present application, a control module is further included, which is composed of an encoder 1400, a driver 1300, and a controller.

[0054] Encoder 1400, mounted on the end face of nut 400, detects rotor angular displacement in real time and provides feedback to the controller. Driver 1300 receives commands from the controller and supplies three-phase current to the stator 200 windings through PWM modulation, achieving magnetic field vector control. The controller implements a PID algorithm, dynamically adjusting the drive signal based on encoder feedback to achieve precise control of the swing arm's swing angle.

[0055] In some embodiments of the present application, the planetary roller screw pair and the gear pair form a reducer, and the reduction ratio A of the reducer satisfies the formula:

[0056] .

[0057] Among them, m is the gear module, z is the number of gear teeth, is the lead of the planetary roller screw pair.

[0058] In this embodiment, the calculation formula of the reducer reduction ratio A is used to accurately quantify the torque amplification factor of the transmission system. Among them, the product of the gear module m and the number of teeth z determines the pitch diameter of the gear pair, and the lead of the planetary roller screw pair is This formula reflects the axial displacement per rotation. This formula establishes the coupling relationship between the transmission ratio of gear 1000 and the transmission ratio of lead screw 600, ensuring that the rotary motion output by the drive module achieves the desired swing angle resolution at the output end of pendulum rod 1200 after two-stage transmission.

[0059] Furthermore, the pitch line of the rack 800 is a function of Distribution, Function as follows:

[0060] .

[0061] Where, is the radial distance from the pitch line of the rack 800 to the origin, and the origin of the pitch line is the middle position of the first tooth near the root of the screw 600 thread. E is the elastic modulus of the material, which reflects the ability of the material to resist elastic deformation. I is the neutral axis moment of inertia of the screw section, which characterizes the resistance of the section to bending deformation. l is the total length of the rack 800, which defines the effective working length of the rack 800. x is the axial distance from any tooth on the rack 800 to the origin, and the origin is located at the midpoint of the first tooth at the root of the screw 600 thread. k is the correction coefficient, which is used to compensate for processing errors and assembly deformation.

[0062] This function describes the pitch line distribution through a high-order curve. When the lead screw 600 is subjected to an axial load, elastic bending deformation occurs, causing the actual pitch line of the rack 800 to deviate from the theoretical straight line. The item causes the pitch lines at both ends of the rack to shift in opposite directions, compensating for the pitch line error caused by the deformation of the screw.

[0063] Furthermore, the rack 800 pitch line is pressed After this distribution, the meshing contact line length between gear 1000 and rack 800 automatically adjusts with load changes, maintaining a constant contact ratio and reducing impact loads and noise. Simultaneously, by adjusting parameters such as E and I, the pitch line distribution of rack 800 matches the bending stiffness of screw 600, improving the overall rigidity of the transmission system.

[0064] The specific motion process is as follows: the stator magnetic field in the drive module drives the nut 400-magnet group 300 to rotate, and the planetary roller screw pair converts the rotational motion into the linear motion of the screw 600, and its displacement is determined by the lead The gear ratio is determined by the gear ratio. A rack 800 machined onto the surface of screw 600 meshes with gear 1000, converting linear motion into rotational motion of gear 1000. The rotation angle is determined by the number of teeth z and the screw displacement. Ultimately, the gear shaft drives pendulum rod 1200 to swing, with the amplitude precisely controlled by reduction ratio A. This formula achieves an optimal balance between transmission efficiency and output torque while maintaining a compact structure by adjusting the parameters of gear 1000 and the lead of screw 600.

[0065] This embodiment establishes a transmission ratio distribution rule through mathematical modeling, leveraging the high-load characteristics of a planetary roller screw and the precise conversion principle of gear transmission. The planetary roller screw utilizes a multi-line contact design, providing a larger contact area within the same volume, thereby increasing load capacity. The rack and pinion utilizes integrated machining to eliminate backlash and ensure transmission accuracy. A formula links the geometric parameters of the two-stage transmission, forming a closed-loop design constraint that minimizes the system's size and weight while still meeting output torque requirements.

[0066] Traditional linear joint linkage systems require multiple components to coordinate, resulting in a large volume, while rotary joints rely on reducers, which increases weight. This embodiment integrates a two-stage transmission into a single component through a reducer design guided by a formula, avoiding the complex linkage of multiple linear joints and eliminating heavy components such as harmonic reducers. At the same time, the modulus m and lead in the formula are As an adjustable parameter, it can be optimized for different joint load requirements. For example, large-load joints use large-module gears and small-lead screws, while high-dynamic joints use small-module gears and large-lead screws.

[0067] In some embodiments of the present application, the swing electric cylinder for a humanoid robot further includes: a support module; the support module includes an angular contact bearing 900 and a deep groove ball bearing 1100.

[0068] The inner ring of angular contact bearing 900 has an interference fit with the outer surface of screw 600, while the outer ring is embedded in the inner wall of housing 100 and positioned axially at the end of housing 100 near gear 1000. This bearing primarily bears the axial load of screw 600. Its contact angle design enables the bearing to withstand both radial and axial forces, ensuring the guiding accuracy of the screw during linear motion.

[0069] Two sets of deep groove ball bearings 1100 are mounted on either end of the gear shaft of gear 1000. The inner ring of the bearing has a clearance fit with the gear shaft, while the outer ring is fixed to the inner surface of housing 100. These bearings limit axial displacement of gear 1000, ensuring a constant meshing clearance between the gear and rack 800 while allowing the gear shaft to rotate about its own axis.

[0070] The torque output by the drive module rotates nut 400, and the planetary roller screw assembly converts this rotational motion into linear motion of screw 600. Screw 600, supported by angular contact bearings 900, translates axially, with its surface rack 800 meshing with gear 1000. Gear 1000 tends to rotate under the meshing force, but because deep groove ball bearings 1100 restrict its axial movement, the gear rotates only about its own axis, thereby driving the swing arm 1200 to oscillate.

[0071] In this embodiment, the angular contact bearing 900 provides axial rigid support to prevent the screw 600 from deflecting under axial load, thereby ensuring the straightness of the pitch line of the rack 800; the deep groove ball bearing 1100 eliminates the axial degree of freedom of the gear 1000, converting the axial component force during the meshing process into a bearing preload force, thereby avoiding changes in the meshing clearance due to axial movement of the gear shaft.

[0072] In conventional oscillating electric cylinders, axial displacement of the leadscrew can easily cause fluctuations in the meshing clearance between the gear and rack, affecting transmission accuracy. This embodiment utilizes angular contact bearings 900 to constrain radial and axial movement of the leadscrew, while deep groove ball bearings 1100 limit axial displacement of the gears, creating a dual-constraint system. This system balances the axial force during meshing with the bearing preload, eliminating gap variations and addressing transmission accuracy stability issues under dynamic loads.

[0073] In some embodiments of the present application, reference Figure 3 and Figure 4 As shown, the outer surface of nut 400 is machined with several oval grooves evenly distributed along the circumference. Each groove is embedded with a neodymium iron boron magnet, which is fixed in place by laser welding. Neodymium iron boron has a high magnetic energy product and coercive force, providing a magnetic field strength several times stronger than that of traditional ferrite magnets of the same volume.

[0074] The design of the elliptical groove allows the magnet group 300 to fit tightly with the outer curved surface of the nut 400, and the welding process ensures that the magnet does not fall off under high-speed rotation and vibration conditions.

[0075] Traditional electromagnetic drive systems suffer from low magnetic field utilization and large thrust fluctuations. This embodiment utilizes the high coercivity of the neodymium iron boron material to reduce hysteresis losses in the alternating magnetic field. The elliptical slot design increases the contact area between the magnet assembly 300 and the nut 400, improving heat conduction efficiency. Furthermore, welding eliminates the air gap associated with traditional glue bonding, improving magnetic field closure.

[0076] In some embodiments of the present application, the swing angle of the rocker arm 1200 of the transmission module is controlled by the axial displacement of the screw 600; the displacement of the screw 600 is driven by the rotation of the nut 400 and is converted into the swing of the rocker arm 1200 through the engagement of the rack 800 and the gear 1000.

[0077] The drive module outputs rotational torque, causing the nut 400 to rotate under electromagnetic force, and its internal threads propel the lead screw 600 in axial translation. The movement of the lead screw 600 generates relative motion between the surface rack 800 and the gear 1000. The geometric constraints of the gear 1000's tooth profile convert the linear motion of the rack 800 into rotational motion of the gear. The rotation axis of the gear 1000 is fixedly connected to the pendulum rod 1200, enabling the pendulum rod to oscillate around its rotation axis.

[0078] The threaded engagement of nut 400 and lead screw 600 achieves rotational-linear motion conversion, while the meshing of rack 800 and gear 1000 achieves linear-rotational motion conversion. This embodiment employs a two-stage transmission structure: rotational-linear-rotational, minimizing errors in intermediate links. Position feedback control is achieved by precisely linking displacement and swing angle through the lead screw. Furthermore, the helix angle of lead screw 600 matches the module of gear 1000 to prevent self-locking.

[0079] In some embodiments of the present application, a planetary roller screw assembly includes a planet carrier 700, a plurality of planetary rollers 500, a screw 600, and a nut 400. The planet carrier 700 is secured to the transmission cavity within the housing 100 via a bolt assembly. Multiple roller grooves are evenly distributed around the planet carrier 700. Each groove houses a planetary roller 500. The outer surfaces of the rollers form a rolling friction pair with the internal threads of the nut 400 and the external threads of the screw 600. This structure enables the rotational motion of the nut 400 to drive the linear motion of the screw 600 through the revolution of the planetary rollers 500.

[0080] The drive module outputs torque to rotate the nut 400, causing the planetary rollers 500 to both rotate and revolve within their grooves, converting the rotational motion into axial translation of the lead screw 600. The fixed constraint of the planetary carrier 700 ensures that all rollers move synchronously, achieving multi-line contact transmission.

[0081] This embodiment utilizes a multi-roller design to distribute contact stress across multiple planetary rollers 500, extending the life of the structure and increasing the rated load. Furthermore, rolling friction reduces energy loss, vibration shock, and adapts to high-frequency reciprocating motion.

[0082] In some embodiments of the present application, the housing 100 is a segmented structure, including a motor cavity and a transmission cavity. The motor cavity is fixedly connected to the stator 200 through a flange; the transmission cavity accommodates the planetary rollers 500, the lead screw 600 and the gear 1000, and the motor cavity and the transmission cavity are isolated by a sealing ring.

[0083] The stator 200 in the motor cavity generates a rotating magnetic field, which drives the nut 400 in the transmission cavity to rotate. The magnetic field energy is transferred to the transmission cavity through the air gap, achieving contactless power transmission. The sealing ring prevents the cooling lubricant in the motor cavity from entering the transmission cavity.

[0084] This embodiment physically separates the motor from the transmission system to avoid electromagnetic interference, and the independent cavity design facilitates separate disassembly and maintenance. The segmented structure increases the heat dissipation area and optimizes the temperature field distribution. The independently sealed cavity prevents cross contamination and improves system reliability.

[0085] In some embodiments of the present application, the control module includes a driver 1300 and a controller, integrated into the outer surface of the housing 100. The driver output is connected to the stator 200 winding via a plug-in cable, and the controller communicates with the encoder 1400 via a dedicated interface. The detection surface of the encoder 1400 aligns with the end face of the nut 400 to provide position feedback.

[0086] The controller sends motion instructions to the driver 1300, which drives the stator 200 to generate a rotating magnetic field. The encoder 1400 detects the displacement of the nut 400 in real time, forming a closed-loop control system.

[0087] This embodiment is based on the principle of mechatronics, and reduces electromagnetic interference by designing the driver and controller to share a common housing, and reduces signal delay by short-distance cable transmission.

[0088] In some embodiments of the present application, an axial lubrication groove is machined into the meshing area between rack 800 and gear 1000, and the groove is filled with a graphite-based solid lubricant. The groove depth is 1 / 3 of the rack tooth height, ensuring continuous lubricant deposition during meshing. As gear 1000 rotates, the tooth surfaces come into contact with the graphite particles in the lubrication groove, and the solid lubricant is micro-melted onto the meshing surfaces through frictional heat, forming a lubricating film.

[0089] Traditional grease lubrication has the risk of rapid loss and contamination. This embodiment achieves targeted lubrication by embedding solid lubricants into the meshing area. The lubrication groove design controls the amount of lubricant released and avoids excessive contamination.

[0090] The present application provides a swinging electric cylinder for a humanoid robot. This type of cylinder utilizes an inverted planetary roller screw drive. It integrates six components: an inverted planetary roller screw, a rack and pinion, a servo motor, an encoder, a driver, and a controller. A rack is machined onto the screw shaft. To eliminate backlash variations during the rack and pinion transmission, the rack's tooth height is distributed parabolically along the axial direction. A neodymium iron boron motor rotor magnet is welded to the outer diameter of the nut of the inverted planetary roller screw. Rotating the rotor nut causes the screw to move back and forth, and the rack on the screw drives the gear to rotate back and forth, which in turn drives the swing arm. The swing arm's swing angle is precisely determined by the forward and backward extension position of the screw shaft. Rotation of the nut drives axial movement of the screw. An encoder is mounted on the end face of the nut. The encoder detects the angular displacement of the nut and transmits a signal to a controller. Based on the encoder feedback, the controller controls the angular displacement of the nut through the driver. The inverted planetary roller screw drive of the present application can provide greater torque for a given weight. This avoids the problem of limited flexibility of humanoid robots due to their size and weight.

[0091] Those skilled in the art will readily conceive of other embodiments of the present disclosure after considering the disclosure of the specification and examples. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art that are not disclosed in this disclosure.

Claims

1. A swing electric cylinder for a humanoid robot, characterized in that: include: Drive module and transmission module; The driving module comprises: a housing (100), a stator (200), a magnet group (300) and a nut (400); The stator (200), the magnet group (300) and the nut (400) are all arranged in the inner cavity of the housing (100); the magnet group (300) is fixed on the outer circle of the nut (400) and forms a servo motor rotor with the stator (200); The transmission module includes: a planetary roller screw pair and a gear pair; The planetary roller screw pair comprises: planetary rollers (500), a screw (600) and a planetary carrier (700); the gear pair comprises: a rack (800) and a gear (1000); The rack (800) is machined on the axial surface of the lead screw (600) and meshes with the gear (1000); The planetary roller (500) is provided between the nut (400) and the lead screw (600), and is connected to the nut (400) and the lead screw (600) in rolling contact, the planetary carrier (700) is fixed to both ends of the nut (400), and the planetary carrier (700) is rotationally connected to the housing (100); The transmission module comprises a swing rod (1200), wherein the swing rod (1200) is fixedly connected to the gear shaft of the gear (1000) via a key, and the rotation of the gear (1000) drives the swing rod (1200) to swing; The pitch line of the rack (800) is a function of Distribution, Function as follows: ； Where, is the radial distance from the pitch line of the rack (800) to the origin, the pitch line origin is the middle position of the first tooth close to the root of the thread of the screw (600), E is the elastic modulus of the material, I is the moment of inertia of the neutral axis, l is the total length of the rack, and x is the axial distance from any tooth on the rack (800) to the origin.

2. The oscillating electric cylinder for a humanoid robot according to claim 1, characterized in that: Also includes: Control module; The control module includes an encoder (1400), a driver (1300) and a controller; The encoder (1400) is fixed to the end face of the nut (400) and is used to detect the angular displacement of the nut (400); the driver (1300) is connected to the stator (200) and the encoder (1400) via a cable; and the control module is communicatively connected to the driver (1300) to form a closed-loop control system; The controller is configured to detect the angular displacement of the nut (400) through the encoder (1400), and control the driver (1300) to drive the nut (400) to rotate according to the angular displacement.

3. The oscillating electric cylinder for a humanoid robot according to claim 1, characterized in that: The planetary roller screw pair and the gear pair form a reducer, and the reduction ratio A of the reducer satisfies the formula: ； Among them, m is the gear module, z is the number of gear teeth, is the lead of the planetary roller screw pair.

4. The oscillating electric cylinder for a humanoid robot according to claim 1, characterized in that: Also includes: Support module; The support module comprises an angular contact bearing (900) and a deep groove ball bearing (1100); The angular contact bearing (900) is fixed to one end of the housing (100) close to the gear (1000) and is used to support the axial movement of the lead screw (600); The deep groove ball bearings (1100) are mounted on both ends of the gear shaft of the gear (1000) and are used to control the axial displacement of the gear (1000).

5. The oscillating electric cylinder for a humanoid robot according to claim 1, characterized in that: The magnet group (300) of the driving module is fixed in the elliptical groove of the outer circle of the nut (400) by welding. The magnet group (300) is made of neodymium iron boron material, and a magnet is embedded in each of the elliptical grooves.

6. The oscillating electric cylinder for a humanoid robot according to claim 1, characterized in that: The swing angle of the swing rod (1200) of the transmission module is controlled by the axial displacement of the lead screw (600); The displacement of the lead screw (600) is driven by the rotation of the nut (400) and is converted into the swing of the swing rod (1200) through the engagement of the rack (800) and the gear (1000).

7. The oscillating electric cylinder for a humanoid robot according to claim 1, characterized in that: The planetary rollers (500) of the transmission module are evenly distributed in the roller grooves of the planetary carrier (700). The planetary carrier (700) is fixed to the inside of the housing (100) by bolts and is rolling-matched with the internal thread of the nut (400) and the external thread of the lead screw (600).

8. The oscillating electric cylinder for a humanoid robot according to claim 1, characterized in that: The housing (100) is a segmented structure, comprising a motor cavity and a transmission cavity, the motor cavity being fixedly connected to the stator (200) via a flange; The transmission cavity accommodates the planetary roller (500), the lead screw (600) and the gear (1000), and the motor cavity and the transmission cavity are isolated by a sealing ring.

9. The oscillating electric cylinder for a humanoid robot according to claim 2, characterized in that: The driver (1300) of the control module and the controller are integrated on the outside of the housing (100), and are connected to the encoder (1400) and the stator (200) via a plug-in cable; The detection surface of the encoder (1400) is in contact with the end surface of the nut (400).

10. The oscillating electric cylinder for a humanoid robot according to claim 1, characterized in that: An axially extending lubrication groove is provided in the meshing area between the rack (800) and the gear (1000), wherein the lubrication groove is filled with a graphite-based solid lubricant, and the depth of the lubrication groove is 1 / 3 of the tooth height of the rack (800).

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