Swing electric cylinder for humanoid robot

Abstract

The invention relates to the field of humanoid robot joints, in particular to a swing electric cylinder for a humanoid robot, a rack is machined on a lead screw shaft, and the tooth height of the rack is distributed in a cubic curve mode in the axial direction in order to eliminate the change of a gap in the gear and rack transmission process. A motor rotor magnetic cylinder made of neodymium iron boron is welded to the outer circle of a nut of the reverse planetary roller lead screw pair, the rotor nut rotates, a lead screw moves front and back, a rack on the lead screw pushes a gear to rotate in a reciprocating mode, and a gear shaft drives a swing rod to swing. The swing angle of the swing rod is accurately positioned according to the front-back telescopic position of the lead screw shaft, and the nut rotates to drive the lead screw to move axially. The encoder detects angular displacement of rotation of the nut and transmits a signal to the controller. The controller controls angular displacement of the nut through the driver according to information fed back by the encoder. The swing electric cylinder can provide larger torque under the condition of the same weight. The problem that the flexibility of the humanoid robot is limited due to the fact that the humanoid robot is affected by the size and weight is solved.

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 humanoid robots needs to accurately reproduce the freedom and flexibility of human limb movement. Under the guidance of bionic principles, robot joints need to achieve multi-degree-of-freedom coordinated movement, among which the swinging movement is the core of completing complex tasks such as grasping, walking, and clamping. The swinging movement of human arms, hips, and finger joints is essentially a rotation-translation compound movement driven by multiple groups of antagonistic muscle groups, and robots need to simulate this biomechanical characteristic through mechanical structures.

[0003] The current mainstream joint design is divided into two schools: linear drive and rotary drive. Linear joints mostly use electric push rods or hydraulic cylinders, which are realized by servo motors and screw / belt drives. Their advantage is that the motion trajectory is intuitive, but multiple joints need to be linked to achieve swing. For example, the parallelogram linkage mechanism of the SCARA robot arm achieves planar swing through two orthogonal linear joints, while the humanoid arm requires a three-degree-of-freedom orthogonal configuration. Rotary joints rely on direct motor drive or harmonic reducers, the latter of which achieves a high reduction ratio through the elastic deformation of flexible gears.

[0004] The existing technology still has certain defects in humanoid applications: a single linear joint can only achieve linear movement, and two linear joints must be linked or an auxiliary connecting rod mechanism must be added to achieve swinging, and the swinging angle is limited to a very small range, such as 90 degrees. This will increase the volume and weight, which is not conducive to the humanoid robot to achieve dexterous activities. If a rotary joint is used to achieve the swinging action, a reducer with a relatively large reduction ratio, such as a harmonic reducer, is required, but the weight and volume of the harmonic reducer are relatively large, and the fatigue life of the harmonic reducer flexible wheel is relatively low. Summary of the invention

[0005] The present application aims to solve the problem that the existing joint design needs to add an auxiliary connecting rod mechanism or a reducer with a large reduction ratio, which results in an increase in the size and weight of the humanoid robot, a short service life, and is not conducive to achieving dexterous activities. The present application provides a swing electric cylinder for a humanoid robot, including: a drive module and a transmission module; The driving module comprises: a housing, a stator, a magnet group and a nut; 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; The transmission module comprises: a planetary roller screw pair and a gear pair; The planetary roller screw pair includes: planetary rollers, a screw, and a planetary carrier. The gear pair includes: a rack and a gear; The rack is machined on the axial surface of the screw and meshes with the gear; The planetary rollers are arranged between the nut and the screw and are in rolling contact connection with the nut and the screw. The planetary carrier is fixed at both ends of the nut, and the planetary carrier is rotatably connected to the housing; The transmission module includes a swing rod. The swing rod 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.

[0006] In a feasible implementation manner, a control module is further included; The control module includes an encoder, a driver, and a controller; The encoder is fixed on 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 through a cable, and the control module is communicatively connected to the driver to form a closed-loop control system; Wherein, the controller is configured to: detect the angular displacement of the rotation of the nut through the encoder, and control the driver to drive the nut to rotate according to the angular displacement.

[0007] In a feasible implementation manner, the planetary roller screw pair and the gear pair form a speed reducer, and the reduction ratio A of the speed reducer satisfies the formula: ; Wherein, m is the module of the gear, z is the number of teeth of the gear, is the lead of the planetary roller screw pair; The pitch line of the rack is distributed according to the function The function is as follows: ; In the formula, is the radial distance from the pitch line of the rack to the origin. The origin of the pitch line is the middle position of the first tooth close to the root of the screw thread. 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 to the origin.

[0008] In a feasible implementation manner, a support module is further included; The support module includes angular contact bearings and deep groove ball bearings; The angular contact bearings are fixed at one end of the housing close to the gear and are used to support the axial movement of the screw; The deep groove ball bearings are installed at both ends of the gear shaft of the gear and are used to control the axial displacement of the gear.

[0009] In a feasible implementation, the magnet group of the driving module is fixed in the elliptical groove on the outer circle of the nut by welding. The magnet group is made of neodymium iron boron material, and one magnet is embedded in each elliptical groove.

[0010] 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; The displacement of the lead screw is driven by the rotation of the nut and is converted into the swing of the swing rod through the meshing of the rack and the gear.

[0011] In a feasible implementation, the planetary rollers of the transmission module are evenly distributed in the roller grooves of the planet carrier. The planet carrier is fixed inside the housing by bolts and is in rolling cooperation with the internal thread of the nut and the external thread of the lead screw.

[0012] In a feasible implementation, the housing is a segmented structure, including a motor cavity and a transmission cavity. The motor cavity is fixedly connected to the stator through a flange; The transmission cavity houses the planetary rollers, the lead screw and the gear. The motor cavity and the transmission cavity are isolated by a sealing ring.

[0013] In a feasible implementation, the driver of the control module and the controller are integrated outside the housing and are connected to the encoder and the stator through a plug-in cable; The detection surface of the encoder is in contact with the end face of the nut.

[0014] In a feasible implementation, an axially extending lubricating groove is provided in the meshing area of the rack and the gear. The lubricating groove is filled with a graphite-based solid lubricant, and the depth of the lubricating groove is 1 / 3 of the tooth height of the rack.

[0015] The present application provides a swing electric cylinder for a humanoid robot, which belongs to a swing electric cylinder driven by a reverse planetary roller screw pair for a humanoid robot. The swing electric cylinder is small in volume and large in torque, and can enable the thighs, upper arms, and finger joints of the humanoid robot to achieve swing motion, so that the hands, arms, and legs of the humanoid robot can perform bionic actions such as clamping. As a swing joint of a humanoid robot, the present invention has a structure that integrates six components: a reverse planetary roller screw pair, a rack and pinion pair, a servo motor, an encoder, a driver, and a controller. A rack is machined on the screw shaft. In order to eliminate the change in clearance during the transmission of the rack and pinion, the tooth height of the rack is distributed in a parabolic shape along the axial direction. A neodymium iron boron motor rotor magnet cylinder is welded on the outer circle of the nut of the reverse planetary roller screw pair. When the rotor nut rotates, the screw moves back and forth. The rack on the screw pushes the gear to rotate reciprocally, and the gear shaft drives the swing rod to swing. The swing angle of the swing rod is accurately positioned by the position of the forward and backward telescoping of the screw shaft, and the rotation of the nut drives the axial movement of the screw. An encoder is installed on the end face of the nut. The encoder detects the angular displacement of the nut rotation and transmits the signal to the controller. The controller controls the angular displacement of the nut through the driver according to the information fed back by the encoder. The swing electric cylinder driven by the reverse planetary roller screw pair of the present application can provide a larger torque under the same weight. It avoids the problem of limited flexibility of the humanoid robot caused by the influence of volume and weight. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the implementation of the present invention, and are used together with the specification to explain the principles of the embodiments of the present invention. Obviously, the drawings in the following description are only some embodiments of the implementation of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 is a schematic structural diagram of a swing electric cylinder for a humanoid robot shown in an exemplary embodiment of the present application; Figure 2 is Figure 1 the sectional view of Figure 3 is a schematic structural diagram of a planetary roller screw pair shown in an exemplary embodiment of the present application; Figure 4 is Figure 3 the sectional view of

[0018] Description of the reference numerals in the drawings: 100 - housing; 200 - stator; 300 - magnet group; 400 - nut; 500 - planetary roller; 600 - screw; 700 - planet carrier; 800 - rack; 900 - angular contact bearing; 1000 - gear; 1100 - deep groove ball bearing; 1200 - swing rod; 1300 - driver; 1400 - encoder. Detailed Implementation Modes

[0019] Example implementation modes will now be described more fully with reference to the accompanying drawings. However, the example implementation modes can be implemented in various forms and should not be construed as limited to the examples set forth herein; rather, these implementation modes are provided so that the embodiments of the present invention will be more complete and comprehensive, and the concept of the example implementation modes will be fully conveyed to those skilled in the art. The described features, structures, or characteristics can be combined in any suitable manner in one or more implementation modes. In the following description, numerous specific details are provided to give a thorough understanding of the implementation modes of the embodiments of the present invention.

[0020] The arm, hip joint, waist joint, and finger joints of a humanoid robot all need to perform swinging motions, so that grasping motions can be achieved. Traditional robot joints either move linearly or rotate. If a linear joint is to achieve a swinging motion, two linear joints must be linked together, and an auxiliary link mechanism must be added, so that both the volume and weight will increase, which is not conducive to the humanoid robot achieving dexterous movements. If a rotary joint is used to achieve a swinging motion, a speed reducer with a relatively large reduction ratio, such as a harmonic speed reducer, is required, but the harmonic speed reducer is relatively heavy. The swinging electric cylinder driven by a reverse planetary roller screw pair can provide a greater torque under the same weight.

[0021] To solve the above problems, referring to Figure 1 and Figure 2 as shown, the swinging electric cylinder for a humanoid robot provided in this embodiment adopts a composite drive structure of a reverse planetary roller screw pair and a gear rack. Its mechanical system is composed of a drive module and a transmission module. The specific connection relationship and operating principle are as follows: The drive module is based on the housing 100. Its inner cavity integrates a stator 200, a magnet group 300, and a nut 400. The magnet group 300 is fixed on the outer cylindrical surface of the nut 400 by an annular array, forming a servo motor rotor structure with the stator 200. When a control current is applied to the stator winding, a rotating magnetic field is generated to drive the magnet group-nut assembly to rotate around its own axis, realizing the output of basic power.

[0022] The transmission module consists of a planetary roller screw pair and a gear pair to form a two-stage transmission chain. Among them, the planetary roller screw pair includes: planetary rollers 500, a lead screw 600, and a planetary carrier 700. The planetary rollers 500 are located between the inner hole of the nut 400 and the outer surface of the lead screw 600, and the rotation-linear motion conversion is realized through the rolling contact between the rollers and the spiral grooves. The planetary carrier 700 is fixed to both ends of the nut 400 through an end face flange, and the outer ring of its bearing forms a rotating support with the housing 100 to ensure that the lead screw 600 only makes axial translation.

[0023] The gear pair transmission directly processes a rack 800 on the surface of a lead screw 600, which meshes with a gear 1000 to form a second-stage transmission. The gear 1000 is key-connected to a swing rod 1200 through a journal, converting the linear motion of the rack 800 into the reciprocating swing of the gear-swing rod assembly.

[0024] Based on the high load-bearing characteristics of the reverse planetary roller screw pair and the high efficiency of the gear-rack transmission, this application sequentially converts the rotational motion of a servo motor into linear motion and swing motion through a two-stage transmission chain. Among them, the planetary roller screw pair adopts a multi-line contact design, enabling a single nut to bear axial / radial composite loads, and improving the load-bearing capacity compared with traditional ball screws; the gear-rack adopts an integrated processing technology to eliminate assembly gaps and ensure transmission accuracy.

[0025] Aiming at the problems of large volume and high moment of inertia existing in traditional linear joint linkage systems, this application effectively reduces the overall volume through the integrated design of the planetary roller screw pair, integrating the dual linear drive functions into a single component. At the same time, aiming at the defect that the rotary joint relies on a heavy reducer, resulting in an increase in weight, this application adopts a structure in which the gear-rack directly drives the swing rod, eliminating heavy components such as harmonic reducers and significantly reducing the weight of a single joint. In addition, the closed-loop control system compensates for the non-linear friction and elastic deformation during the transmission process through real-time feedback, making the swing positioning accuracy better than that of traditional harmonic reducer applications.

[0026] While maintaining a lightweight design, this swing cylinder can output a larger torque, and the power density is significantly improved compared with traditional applications. The modular design supports the coordinated control of multiple joints, making the motion envelopes of joints such as the waist, hip, and arm of a humanoid robot closer to the natural motion characteristics of humans, and effectively reducing the overall energy consumption of the machine. The integrated structure significantly reduces the assembly interface and improves the reliability of the system, especially suitable for anthropomorphic operation scenarios that require high load and high dynamic response.

[0027] In some embodiments of this application, it further includes a control module. The control module consists of an encoder 1400, a driver 1300, and a controller.

[0028] The encoder 1400 is installed on the end face of the nut 400, real-time detecting the rotor angular displacement and feeding it back to the controller. The driver 1300 receives the controller's instruction, supplies three-phase current to the stator 200 winding through PWM modulation, and forms a magnetic field vector control. The controller executes the PID algorithm, dynamically adjusts the drive signal according to the encoder feedback value, and realizes the precision control of the swing angle of the swing rod.

[0029] In some embodiments of this application, the planetary roller screw pair and the gear pair form a reducer, and the reduction ratio A of the reducer satisfies the formula: .

[0030] where m is the module of the gear, z is the number of teeth of the gear, is the lead of the planetary roller screw pair.

[0031] In this embodiment, the calculation formula of the reduction ratio A of the reducer 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 reflects its axial displacement per revolution. Through this formula, the coupling relationship between the transmission ratio of gear 1000 and the transmission ratio of screw 600 can be established, ensuring that after two-stage transmission of the rotational motion output by the drive module, the expected swing angle resolution is obtained at the output end of the swing rod 1200.

[0032] Furthermore, the pitch line of the rack 800 is distributed according to the function The function is as follows: .

[0033] In the formula, is the radial distance from the pitch line of the rack 800 to the origin. The origin of the pitch line 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, reflecting the ability of the material to resist elastic deformation; I is the moment of inertia of the neutral axis of the screw cross-section, characterizing the resistance of the cross-section to bending deformation; l is the total length of the rack 800, defining 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 thread of the screw 600; k is a correction factor used to compensate for machining errors and assembly deformations.

[0034] This function describes the pitch line distribution through a high-order curve. Since when the screw 600 bears an axial load, it will produce elastic bending deformation, resulting in the actual pitch line of the rack 800 deviating from the theoretical straight line, and the term in the function causes the pitch lines at both ends of the rack to deflect in opposite directions, compensating for the pitch line error caused by the screw deformation.

[0035] Furthermore, after the pitch line of the rack 800 is distributed according to the meshing contact line length between the gear 1000 and the rack 800 is automatically adjusted with the change of the load, maintaining a constant contact ratio, reducing the impact load and noise. At the same time, by adjusting parameters such as E and I, the pitch line distribution of the rack 800 is matched with the flexural rigidity of the screw 600, improving the overall rigidity of the transmission system.

[0036] 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 Decision; The rack 800 machined on the surface of the lead screw 600 meshes with the gear 1000, converting linear motion into the rotational motion of the gear 1000. The rotation angle is jointly determined by the number of teeth z and the displacement of the lead screw. Finally, the gear shaft drives the swing rod 1200 to achieve swinging, and the swinging amplitude is precisely controlled by the reduction ratio A. This formula can adjust the parameters of the gear 1000 and the lead of the lead screw 600 to achieve the optimal balance between transmission efficiency and output torque while maintaining the structural compactness.

[0037] This embodiment is based on the high load-bearing characteristics of the planetary roller screw pair and the precise conversion principle of gear transmission, and establishes a transmission ratio distribution rule through mathematical modeling. The planetary roller screw pair adopts a multi-threaded contact design, providing a larger contact area under the same volume and enhancing the load capacity; the gear-rack pair adopts integrated machining to eliminate clearance and ensure transmission accuracy. The formula correlates the geometric parameters of the two-stage transmission to form a closed-loop design constraint, minimizing the structural size and weight of the system while meeting the output torque requirements.

[0038] Traditional linear joint linkage systems require multiple components to cooperate, resulting in a large volume, while rotary joints rely on reducers, increasing the weight. This embodiment integrates the two-stage transmission into a single component through the reducer design guided by the formula, avoiding the complex linkage of multiple linear joints and eliminating heavy components such as harmonic reducers. At the same time, the module m and lead in the formula As adjustable parameters, they can be optimized according to different joint load requirements. For example, large-load joints use large-module gears and small-lead lead screws, and high-dynamic joints use small-module gears and large-lead lead screws.

[0039] In some embodiments of the present application, the swing 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.

[0040] The inner ring of the angular contact bearing 900 is in interference fit with the outer surface of the lead screw 600, and the outer ring is embedded in the inner wall of the housing 100 and axially positioned at one end of the housing 100 close to the gear 1000. This bearing mainly bears the axial load of the lead screw 600, and its contact angle design enables the bearing to bear both radial and axial forces simultaneously, ensuring the guiding accuracy of the lead screw during linear motion.

[0041] There are two groups of deep groove ball bearings 1100, which are respectively installed at both ends of the gear shaft of the gear 1000. The inner ring of the bearing is in clearance fit with the gear shaft, and the outer ring is fixed to the inner surface of the housing 100. This bearing is used to limit the axial displacement of the gear 1000, ensure a constant meshing clearance between the gear and the rack 800, and at the same time allow the gear shaft to rotate around its own axis.

[0042] The torque output by the driving module drives the nut 400 to rotate, and the planetary roller screw pair converts the rotational motion into the linear motion of the screw 600. The screw 600 translates axially under the support of the angular contact bearing 900, and the surface rack 800 on it meshes with the gear 1000. Under the action of the meshing force, the gear 1000 has a tendency to rotate, but due to the deep groove ball bearing 1100 restricting its axial movement, the gear only rotates around its own axis, thereby driving the swing rod 1200 to swing.

[0043] In this embodiment, the angular contact bearing 900 provides axial rigid support to prevent the screw 600 from skewing under axial load and ensure the straightness of the pitch line of the rack 800; the deep groove ball bearing 1100 eliminates the axial freedom of the gear 1000, so that the axial component force during the meshing process is converted into the bearing preload force, avoiding the change of the meshing clearance caused by the axial movement of the gear shaft.

[0044] In the traditional swing cylinder, the axial displacement of the screw easily causes the fluctuation of the meshing clearance between the gear and the rack, affecting the transmission accuracy. In this embodiment, the radial and axial movements of the screw are restricted by the angular contact bearing 900, and the axial displacement of the gear is restricted in cooperation with the deep groove ball bearing 1100, forming a double constraint system. This system balances the axial force during the meshing process with the bearing preload force, eliminates the change of the clearance, and solves the problem of the stability of the transmission accuracy under dynamic load.

[0045] In some embodiments of the present application, with reference to Figure 3 and Figure 4 As shown, a number of elliptical grooves are machined on the outer circumferential surface of the nut 400 and are evenly distributed along the circumferential direction. Each groove is embedded with a magnet made of neodymium iron boron, and the magnet is fixed in the groove by laser welding technology. The neodymium iron boron material has a high magnetic energy product and coercivity, and can provide a magnetic field strength several times stronger than that of traditional ferrite magnets under the same volume.

[0046] The design of the elliptical groove makes the magnet group 300 closely fit the outer circumferential surface of the nut 400, and the welding technology ensures that the magnet does not fall off under the conditions of high-speed rotation and vibration.

[0047] The traditional electromagnetic drive system has problems such as low magnetic field utilization rate and large thrust fluctuation. In this embodiment, the high coercivity of the neodymium iron boron material reduces the hysteresis loss of the magnet group 300 in the alternating magnetic field; the design of the elliptical groove increases the contact area between the magnet group 300 and the nut 400, improving the heat conduction efficiency. Further, the welding fixation method also eliminates the air gap of the traditional glue bonding, improving the magnetic field closure.

[0048] In some embodiments of the present application, the swing angle of the swing rod 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 swing rod 1200 through the meshing of the rack 800 and the gear 1000.

[0049] The driving module outputs rotational torque, and the nut 400 rotates under the action of electromagnetic force. Its internal thread pushes the lead screw 600 to translate axially. The movement of the lead screw 600 causes relative movement between the surface rack 800 and the gear 1000. The geometric constraint of the tooth profile of the gear 1000 converts the linear movement of the rack 800 into the rotational movement of the gear. The rotation axis of the gear 1000 is fixedly connected to the swing rod 1200, thereby realizing the swing of the swing rod around the rotation axis.

[0050] Among them, the thread fit between the nut 400 and the lead screw 600 realizes the conversion of rotational-linear movement, and the meshing between the rack 800 and the gear 1000 realizes the conversion of linear-rotational movement. This embodiment adopts a two-stage transmission structure of rotational-linear-rotational, reduces the error of intermediate links, and precisely correlates the displacement and swing angle through the lead of the lead screw to achieve position feedback control. At the same time, the helix angle of the lead screw 600 is designed to match the module of the gear 1000 to avoid the self-locking effect.

[0051] In some embodiments of the present application, the planetary roller screw assembly includes a planet carrier 700, a plurality of planetary rollers 500, a lead screw 600, and a nut 400. The planet carrier 700 is fixed to the internal transmission cavity of the housing 100 through a bolt group, and a plurality of roller grooves are evenly distributed on its circumference. Each groove is installed with a planetary roller 500, and the outer surface of the roller forms a rolling friction pair with the internal thread of the nut 400 and the external thread of the lead screw 600. This structure enables the rotational movement of the nut 400 to drive the lead screw 600 to make a linear movement through the revolution of the planetary roller 500.

[0052] The driving module outputs torque to drive the nut 400 to rotate. The planetary roller 500 rotates and revolves in the roller groove, converting the rotational movement into the axial translation of the lead screw 600. The fixed constraint of the planet carrier 700 ensures the synchronous movement of all rollers, realizing multi-line contact transmission.

[0053] In this embodiment, through the multi-roller design, the contact stress is dispersed to a plurality of planetary rollers 500, extending the service life of the structure and also increasing the rated load. At the same time, the rolling friction reduces energy loss, reduces vibration and shock, and is suitable for high-frequency reciprocating motion.

[0054] 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 houses 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.

[0055] The stator 200 in the motor cavity generates a rotating magnetic field to drive the nut 400 in the transmission cavity to rotate. The magnetic field energy is transmitted to the transmission cavity through the air gap to achieve non-contact power transmission. The sealing ring prevents the cooling and lubricating fluid in the motor cavity from entering the transmission cavity.

[0056] In this embodiment, the motor is physically separated from the drive system to avoid electromagnetic interference, and the independent cavity design facilitates separate disassembly and repair. The heat dissipation area is increased through a segmented structure, and the temperature field distribution is also optimized. The independent sealed cavity prevents cross-contamination and improves the system reliability.

[0057] In some embodiments of the present application, the control module includes a driver 1300 and a controller, which are integrated on the outer surface of the housing 100. The output end of the driver is connected to the winding of the stator 200 through a plug-in cable, and the controller communicates with the encoder 1400 through a dedicated interface. The detection surface of the encoder 1400 is flush with the end face of the nut 400 to achieve position feedback.

[0058] The controller sends a motion command to the driver 1300 to drive the stator 200 to generate a rotating magnetic field. The encoder 1400 continuously detects the displacement of the nut 400 to form a closed-loop control system.

[0059] This embodiment is based on the principle of mechatronics. By designing the driver and the controller to share the same housing, electromagnetic interference is reduced, and the short-distance cable transmission reduces signal delay.

[0060] In some embodiments of the present application, axial lubricating grooves are machined in the meshing area between the rack 800 and the gear 1000, and the grooves are filled with a graphite-based solid lubricant. The depth of the lubricating groove is 1 / 3 of the tooth height of the rack to ensure continuous precipitation of the lubricant during meshing. When the gear 1000 rotates, the tooth surface contacts the graphite particles in the lubricating groove, and the solid lubricant is micro-melted onto the meshing surface through frictional heat to form a lubricating film.

[0061] Traditional grease lubrication has the problems of fast loss and pollution risk. In this embodiment, by embedding the solid lubricant in the meshing area, fixed-point lubrication is achieved. The design of the lubricating groove controls the release amount of the lubricant and also avoids excessive pollution.

[0062] The present application provides a swing electric cylinder for a humanoid robot, which belongs to a swing electric cylinder for the transmission of a reverse planetary roller screw pair of a humanoid robot, and has a structure that integrates six components: a reverse planetary roller screw pair, a gear rack pair, a servo motor, an encoder, a driver, and a controller. A rack is machined on the screw shaft. In order to eliminate the change in clearance during the gear rack transmission, the tooth height of the rack is distributed in a parabolic shape along the axial direction. A neodymium iron boron motor rotor magnet cylinder is welded on the outer circle of the nut of the reverse planetary roller screw pair. When the rotor nut rotates, the screw moves back and forth. The rack on the screw pushes the gear to rotate reciprocally, and the gear shaft drives the swing rod to swing. The angle of swing of the swing rod is accurately positioned by the position of the forward and backward telescoping of the screw shaft, and the rotation of the nut drives the axial movement of the screw. An encoder is installed on the end face of the nut. The encoder detects the angular displacement of the nut rotation and transmits the signal to the controller. The controller controls the angular displacement of the nut through the driver according to the information fed back by the encoder. The swing electric cylinder with the transmission of the reverse planetary roller screw pair in the present application can provide a larger torque under the same weight. It avoids the problem of limited flexibility of the humanoid robot caused by the influence of volume and weight.

[0063] After considering the specification and the disclosure of the embodiments, those skilled in the art will readily conceive of other embodiments of the present disclosure. This application is intended to cover any variations, uses, or adaptations of the present disclosure, which follow the general principles of the present disclosure and include well-known common general knowledge or conventional technical means in the technical field not disclosed in the present disclosure.

Claims

1. A swinging electric cylinder for a humanoid robot, characterized in that, Including: A driving module and a transmission module; The driving module includes: 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 includes: planetary rollers (500), a screw (600), and a planetary carrier (700). The gear pair includes: a rack (800) and a gear (1000); The rack (800) is machined on the axial surface of the screw (600) and meshes with the gear (1000); The planetary rollers (500) are arranged between the nut (400) and the screw (600) and are in rolling contact connection with the nut (400) and the screw (600). The planetary carrier (700) is fixed at both ends of the nut (400), and the planetary carrier (700) is rotatably connected to the housing (100); The transmission module includes a swing rod (1200). The swing rod (1200) is fixedly connected to the gear shaft of the gear (1000) by a key, and the rotation of the gear (1000) drives the swing rod (1200) to swing.

2. The swinging electric cylinder for a humanoid robot according to claim 1, wherein, Also including: A control module; The control module includes an encoder (1400), a driver (1300), and a controller; The encoder (1400) is fixed on the end face of the nut (400) for detecting the angular displacement of the nut (400). The driver (1300) is connected to the stator (200) and the encoder (1400) through a cable. The control module is communicatively connected to the driver (1300) to form a closed-loop control system; Wherein, the controller is configured to: detect the angular displacement of the rotation 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 swinging electric cylinder for a humanoid robot according to claim 1, wherein The planetary roller screw pair and the gear pair form a reducer, and the reduction ratio A of the reducer satisfies the formula: ； where m is the module of the gear, z is the number of teeth of the gear, is the lead of the planetary roller screw pair; The pitch line of the rack (800) is in accordance with the function distributes, and the function is as follows: ； In the formula, is the radial distance from the pitch line of the rack (800) to the origin, where the origin of the pitch line is the middle position of the first tooth close to the root of the thread of the lead 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.

4. The swinging electric cylinder for a humanoid robot according to claim 1, wherein Also including: A support module; The support module includes angular contact bearings (900) and deep groove ball bearings (1100); The angular contact bearings (900) are fixed at one end of the housing (100) close to the gear (1000) for supporting the axial movement of the screw (600); The deep groove ball bearings (1100) are installed at both ends of the gear shaft of the gear (1000) for controlling the axial displacement of the gear (1000).

5. The swing 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 oval groove on the outer circle of the nut (400) by welding. The magnet group (300) is made of neodymium iron boron material, and one magnet is embedded in each oval groove.

6. The swinging 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 meshing of the rack (800) and the gear (1000).

7. The swinging 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 planet carrier (700). The planet carrier (700) is fixed inside the housing (100) by bolts and is in rolling cooperation with the internal thread of the nut (400) and the external thread of the lead screw (600).

8. The swinging electric cylinder for a humanoid robot according to claim 1, characterized in that, 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 houses the planetary rollers (500), the lead screw (600) and the gear (1000). The motor cavity and the transmission cavity are isolated by a sealing ring.

9. The swing electric cylinder for a humanoid robot according to claim 1, characterized in that, The driver (1300) of the control module and the controller are integrated outside the housing (100) and are connected to the encoder (1400) and the stator (200) through a plug-in cable. The detection surface of the encoder (1400) is in contact with the end face of the nut (400).

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

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