Embedded rotor structure and linear actuator with same

Abstract

The invention discloses an embedded rotor structure and a linear actuator with the embedded rotor structure. The embedded rotor structure comprises a motor stator, an embedded permanent magnet rotor and a planetary roller screw transmission part. The motor stator comprises a stator iron core and stator three-phase windings arranged in a centralized winding mode, and a high-thermal-conductivity silica gel potting structure is arranged outside the motor stator. The embedded permanent magnet rotor comprises a rotor V-shaped slotted iron core and embedded permanent magnet magnetic steel; the planetary roller lead screw transmission part comprises an outer nut, a thrust lead screw and a planetary roller. The rotor V-shaped slotted iron core is directly attached to the outer nut. Through the design of the embedded V-shaped slotted rotor, a double-flux path is formed, the magnetic circuit impedance is reduced, the flux linkage utilization rate and the reluctance torque are improved, and the thrust density and the output power are enhanced; the permanent magnet embedded structure improves magnetic field distribution and realizes effective field weakening control; the rotor and a transmission part are integrally designed to improve the structural compactness, rigidity and force transmission efficiency, and the robot joint is suitable for humanoid robot joints and other scenes.

Description

Technical Field

[0001] This invention belongs to the field of humanoid robots, and more specifically, relates to an embedded rotor structure and a linear actuator having therein. Background Technology

[0002] Linear actuator technology, with its advantages of high thrust output, compact structure, and high energy efficiency, has been widely used in the power units of various joints of humanoid robots. However, given the stringent size and weight constraints of humanoid robot joints, how to further achieve miniaturization, lightweighting, and high-performance integrated design of actuators remains one of the key technological bottlenecks limiting the overall performance improvement of robot joints.

[0003] To address the issues of large size and low integration in actuators, patent document CN120187561A discloses a linear actuator for humanoid robots and its design method. This solution is the first to propose a design concept based on an integrated layout of an inverted roller screw and motor. By fixing the motor stator to the housing, reversing the nut, and incorporating a slider within the screw, the entire actuator forms a closed linear module structure, achieving a high degree of integration between the coaxial motor and the roller screw. This solution not only significantly reduces assembly volume and mechanical errors but also allows for direct force output via the connecting rod without the need for an additional joint housing, thus theoretically possessing advantages such as high thrust, high rigidity, and long lifespan.

[0004] However, the design of surface-mounting the permanent magnet to the outer wall of the lead screw nut in the structural scheme disclosed in patent document CN120187561A has serious flaws. Since the material of the lead screw nut is typically designed with high hardness and wear resistance as primary goals, its magnetic permeability is extremely low and its magnetic reluctance is high, resulting in a severely discontinuous magnetic circuit in the motor and low magnetic field utilization, leading to high motor losses and low efficiency. Furthermore, under the same size and weight conditions, the output torque of this structure decreases significantly, the speed range is limited, and the thermal performance deteriorates, severely restricting the dynamic performance of the entire linear actuator and making it difficult to meet the requirements of humanoid robot joint systems for high power density, high responsiveness, and wide speed range control. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides an embedded rotor structure and a linear actuator incorporating it. The embedded V-grooved rotor design creates a dual magnetic flux path, reducing magnetic circuit impedance, improving flux linkage utilization and reluctance torque, and enhancing thrust density and output power. The embedded permanent magnet structure improves magnetic field distribution, enabling effective magnetic weakening control, expanding the speed range, and reducing losses. The integrated design of the rotor and transmission components enhances structural compactness, rigidity, and force transmission efficiency, making it suitable for applications such as humanoid robot joints.

[0006] To achieve the above objectives, according to a first aspect of the present invention, an embedded rotor structure is provided, comprising: The motor stator includes a stator core and a three-phase stator winding. The three-phase stator winding adopts a concentrated winding arrangement and each stator tooth is wound with a coil. The three-phase stator winding is provided with a high thermal conductivity silicone potting structure. An embedded permanent magnet rotor includes a rotor V-slotted iron core and permanent magnet steel, with the permanent magnet steel embedded in the rotor V-slotted iron core; The planetary roller screw transmission component includes an outer nut, a thrust screw, planetary rollers, a cage, and bearings. The rotor V-grooved iron core is directly bonded to the outer nut by adhesive bonding or interference fit. Both the stator iron core and the V-grooved rotor iron core are made of stacked high-permeability silicon steel sheets.

[0007] Furthermore, the permanent magnet is a radially magnetized NS-grade rectangular structure.

[0008] Furthermore, the stator three-phase winding is based on the slot electromotive force star diagram and achieves three-phase phase separation through the 60° phase band phase separation method. The pitch factor and distribution factor of the stator three-phase winding are both 0.966, and the winding factor is 0.933.

[0009] Furthermore, the structural parameters of the motor stator and the embedded permanent magnet rotor are optimized through finite element analysis and multi-objective genetic algorithm. The stator-side optimization parameters include stator yoke width, stator tooth width, stator tooth length, pole shoe width and pole shoe thickness. The rotor-side optimization parameters include rotor yoke width, permanent magnet height, permanent magnet width, V-slot angle and magnetic bridge width.

[0010] Furthermore, the V-groove angle design introduces a difference in magnetic flux paths between the d-axis and q-axis.

[0011] Furthermore, the rotor V-grooved iron core is provided with a magnetic bridge, and the rotor V-grooved iron core provides a low-impedance flow path for the magnetic flux through the top magnetic passage and the bottom magnetic passage.

[0012] Furthermore, the stator core and the rotor V-grooved core are processed by wire cutting, and the air gap between the motor stator and the embedded permanent magnet rotor is designed with high precision control.

[0013] Furthermore, the outer nut, thrust screw, and planetary rollers of the planetary roller screw transmission component are made of high-hardness wear-resistant steel.

[0014] Furthermore, the top and bottom of the rotor V-grooved iron core are provided with magnetic flux passages.

[0015] According to a second aspect of the invention, a linear actuator is provided, including the embedded rotor structure.

[0016] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: 1. The structure of this invention adopts an embedded V-grooved rotor structure, forming a dual magnetic flux path at the top and bottom, which significantly reduces magnetic circuit impedance and improves flux linkage utilization. The V-groove introduces the asymmetry of magnetic flux between the d-axis and q-axis, enhancing the reluctance torque component, enabling the actuator to have higher thrust density and output power under the same size conditions.

[0017] 2. The structure of this invention, with the permanent magnet embedded inside the rotor core, provides a complete magnetic circuit and a uniform magnetic field distribution, enabling effective field weakening control under high-speed conditions and significantly expanding the speed regulation range. Simultaneously, the embedded structure can withstand greater centrifugal force during high-speed rotation, avoiding the risk of surface-mounted magnets detaching at high speeds and improving operational safety and reliability.

[0018] 3. In the structure of this invention, the rotor magnets are covered with high-permeability silicon steel sheets, and the magnetic flux is mainly closed within the stator and rotor cores. The outer nut, due to its poor magnetic permeability, has a lower magnetic flux density, resulting in significantly lower iron losses compared to traditional surface-mounted structures. This optimized magnetic circuit significantly reduces motor losses and improves overall energy efficiency and thermal stability.

[0019] 4. The structure of this invention, due to the high-precision machining of both the rotor and stator, allows for more stable air gap control accuracy through its embedded structure. Compared to surface-mounted rotors, this invention allows for a smaller air gap design, further improving the motor's magnetic field strength and torque output capability, and enhancing force control accuracy and response characteristics.

[0020] 5. The structure of this invention integrates the rotor core and the planetary roller screw outer nut, eliminating the traditional coupling connection, resulting in a more compact structure, a shorter transmission path, and significantly improved system rigidity and force transmission efficiency. Combined with high thermal conductivity silicone potting and wear-resistant steel structural components, the whole machine possesses high reliability, long lifespan, and excellent thermal stability. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view of a linear actuator based on an embedded rotor structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the design of the stator and rotor structural parameters of a linear actuator according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the stator winding arrangement according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the motor magnetic field flow path of the linear actuator in an embodiment of the present invention.

[0022] In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 1-Stator core, 2-Stator three-phase winding, 3-Rotor V-slotted core, 4-Permanent magnet, 5-Outer nut, 6-Thrust screw, 7-Planetary roller. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0024] like Figure 1 As shown, taking a 12-slot, 14-pole motor topology as an example, the actuator mainly includes: a motor stator, an embedded permanent magnet rotor, and a planetary roller screw transmission component. The motor stator includes a stator core 1 and a three-phase stator winding 2. The three-phase stator winding 2 adopts a concentrated winding arrangement, with one coil wound on each stator tooth. The three-phase stator winding 2 is externally encapsulated with high thermal conductivity silicone. The embedded permanent magnet rotor includes a rotor V-slotted core 3 and permanent magnets 4, with the permanent magnets 4 embedded within the rotor V-slotted core 3. The planetary roller screw transmission component includes an outer nut 5, a thrust screw 6, planetary rollers 7, a cage, and bearings. The rotor V-slotted core 3 and the outer nut 5 are directly bonded together by adhesive bonding or interference fit. Both the stator core 1 and the V-slotted rotor core 3 are made of stacked high-permeability silicon steel sheets.

[0025] By employing advanced connection processes such as high-precision adhesive bonding or interference fit, the rotor V-grooved iron core 3 and the outer nut 5 of the planetary roller screw are directly bonded at the microscopic level. This innovative connection method breaks through the limitations of traditional motor and transmission mechanism connections via couplings, achieving true integration of the electromagnetic module and mechanical transmission module. This highly integrated assembly scheme not only significantly shortens the force transmission path of the system and reduces potential transmission errors and energy losses, but more importantly, it significantly improves the overall structural compactness of the linear actuator, making it particularly suitable for applications with extremely demanding space requirements, such as humanoid robot joints. In terms of electromagnetic design, the three-phase winding 2 of the motor stator adopts an optimized centralized winding arrangement, with each stator tooth precisely wound with an independent coil. This winding topology not only effectively shortens the winding end length and significantly reduces copper loss and ohmic loss, but also creates favorable conditions for improving slot fill factor, allowing more conductive material to be accommodated within the same slot size, directly increasing the power density of the motor. The winding system is encapsulated entirely in high thermal conductivity silicone. This innovative design not only provides excellent insulation and mechanical fixation, but more importantly, it establishes an efficient heat dissipation path from the inside of the winding to the stator core, improving the thermal conductivity of the winding and significantly enhancing the motor's continuous operating capacity and overload tolerance. Both the stator core 1 and the rotor V-slotted core 3 are made of high-permeability, low-loss silicon steel sheets, manufactured through a precision lamination process. This material selection significantly reduces the total magnetic impedance and iron loss of the motor's magnetic circuit, laying the material foundation for a high-efficiency electromagnetic energy conversion system. In terms of manufacturing process, high-precision wire EDM technology is used to process the key dimensions of the stator and rotor cores, ensuring the dimensional accuracy of the stator slot shape, rotor V-slots, and inner and outer diameters. This precision machining not only guarantees the uniformity of the air gap but also directly affects the consistency of the motor's electromagnetic performance and production efficiency. The permanent magnet 4 is designed as a radially magnetized NS-grade rectangular structure and is embedded in the rotor V-slotted core 3. This embedded design not only effectively protects the permanent magnet from centrifugal force and external impacts, but also optimizes the magnetic field distribution through a reasonable magnetic circuit design, improving the air gap magnetic flux density and back electromotive force waveform quality. Key load-bearing components of the planetary roller screw drive assembly, such as the outer nut 5, thrust screw 6, and planetary rollers 7, are all made of high-strength wear-resistant steel to ensure the linear actuator has high structural rigidity and service life.

[0026] like Figure 2As shown, to further improve the electromagnetic performance of the linear actuator motor and better meet its requirements for power output stability and energy utilization efficiency in scenarios such as humanoid robot joints, the structural shape and dimensions of the motor stator and rotor have undergone refined optimization design. This optimization is not a single-dimensional parameter adjustment, but rather a combination of finite element analysis technology and multi-objective genetic algorithms to achieve synergistic optimization of both electromagnetic characteristics and mechanical performance. This ensures that the motor has strong electromagnetic power output while guaranteeing the mechanical reliability of the stator and rotor structure during long-term operation.

[0027] In the specific optimization process, a two-dimensional electromagnetic field finite element model closely matching actual working conditions was first constructed. This model fully includes core components such as the stator, rotor, permanent magnets, and air gap, while fully considering the actual conduction characteristics of the magnetic circuit under different working conditions, providing an accurate simulation foundation for subsequent analysis. Subsequently, through parametric modeling, key dimensions affecting the magnetic circuit distribution and winding performance on the stator side, as well as core parameters related to permanent magnet installation and reluctance characteristics on the rotor side, were all included in the scope of optimization variables, and the reasonable adjustment range of each variable was clearly defined to ensure that the variable settings can comprehensively cover the core dimensions affecting the overall performance of the motor. Based on this, combined with the actual application requirements of the linear actuator, a multi-objective optimization function was constructed with the core optimization objectives of maximizing the output torque to enhance power output intensity, minimizing torque pulsation to ensure smooth operation, achieving high flux utilization to improve energy efficiency, and reducing iron loss to minimize energy consumption. By leveraging the global optimization capability of the genetic algorithm, the limitations of single optimization methods in balancing multiple objectives were overcome. Finally, under multiple constraints such as rotor structural mechanical strength and stator assembly compatibility, the optimal parameter combination that can balance electromagnetic performance and mechanical stability was selected.

[0028] To further optimize magnetic circuit efficiency, dedicated magnetic flux paths are designed at both the top and bottom of the rotor core. The structural design of these paths fully incorporates the laws of magnetic circuit conduction, providing a low-impedance flow path for the magnetic flux linkage. This effectively reduces flux loss on unnecessary paths, promoting more efficient formation of closed loops and significantly reducing magnetic leakage, thereby improving the effective utilization rate of the air gap magnetic field. Simultaneously, the V-groove angle design has been carefully considered. By rationally setting the embedding angle of the permanent magnet, a significant difference in the magnetic flux paths between the d-axis and q-axis is intentionally introduced. This differentiated design specifically enhances the contribution ratio of reluctance torque to the total torque, enabling the motor to maintain stable and strong power output across different speed ranges, including low-speed start-up and high-speed operation, better adapting to the operational needs of linear actuators under complex conditions such as start-stop and speed regulation.

[0029] Furthermore, the optimized magnetic bridge structure also plays a crucial role. While ensuring the overall structural integrity of the rotor and preventing deformation and damage during high-speed rotation or load impacts, it also optimizes the magnetic flux conduction capability, preventing the magnetic bridge from becoming a bottleneck in the magnetic circuit. This design allows for the maintenance of excellent electromagnetic conversion efficiency and mechanical stability even under harsh operating conditions such as high-speed motor operation or heavy loads, providing strong support for the long-term reliable operation of the linear actuator.

[0030] like Figure 3 As shown, this invention addresses the dual requirements of compact structure and efficient power output for linear actuators in humanoid robot joints and other applications. It employs a motor topology combining a 12-slot stator and a 14-pole rotor. This pole-slot configuration has been validated through multiple rounds of electromagnetic simulation and real-world testing. It provides ample space for the stator windings within the slots, preventing excessive wire congestion from affecting insulation and heat dissipation. Furthermore, the 14-pole rotor design enables high-frequency alternation of the magnetic field within a limited radial dimension, providing continuous and stable torque output to the linear actuator. This perfectly balances structural compactness and power performance.

[0031] In the stator winding design, this invention adopts a concentrated winding scheme with a pitch of 1. Compared to the traditional distributed winding design that requires winding wires across multiple stator slots, the concentrated winding eliminates the need for cross-slot wiring, significantly shortening the length of the winding ends. As the non-effective area that does not participate in electromagnetic energy conversion, the shortened length of the winding ends not only directly reduces the amount of copper used and lowers material costs, but more importantly, it reduces end copper losses caused by wire resistance when current flows through, thus reducing energy loss during motor operation from the source. Simultaneously, the concentrated winding method facilitates closer arrangement of wires within the stator slots, effectively improving the slot fill factor. Increased slot fill factor means that more conductive wires can be accommodated in the stator slots, significantly increasing the motor's output power under the same current density, thereby enhancing the overall power density. This is a key design feature for improving the dynamic performance of humanoid robot joints that need to achieve high power output in confined spaces. In addition, shorter winding ends can reduce heat accumulation in the end area. Combined with the high thermal conductivity silicone potting structure outside the stator three-phase windings, the heat dissipation efficiency of the motor can be further optimized, avoiding the impact of local overheating on the winding insulation performance and extending the service life of the motor.

[0032] In the winding arrangement stage, an in-depth analysis of the slot electromotive force (EMF) star diagram provides an intuitive visual basis for winding phase planning. The slot EMF star diagram clearly shows the phase distribution of the EMF generated by the conductors in each stator slot, helping to accurately determine the connection method of conductors in different slots. This effectively avoids mutual cancellation or interference of magnetic fields in each winding due to phase misalignment, ensuring that magnetic field energy is concentrated for torque output. Based on this, the three-phase windings are arranged using a 60° phase band splitting method, so that the U, V, and W phase windings correspond to slot areas with a 60° electrical angle on the stator circumference. This phase splitting method strictly ensures that the three-phase windings are symmetrically distributed in space with a 120° electrical angle difference. When the three-phase AC current is applied to the windings according to a specific phase difference, the magnetic fields generated by the three phase currents can be superimposed in the air gap to form a continuous and uniform rotating magnetic field. This provides a stable magnetic field driving force for the smooth rotation of the rotor, avoiding problems such as jamming and shaking during rotor rotation due to uneven magnetic field distribution, laying a solid foundation for the subsequent smooth operation of the linear actuator.

[0033] Based on the structural characteristics of the 14-pole rotor, electromagnetic theory calculations and simulation analysis revealed that both the winding pitch factor and distribution factor are at a high level, and the final synthesized winding factor also reaches an excellent range. This high winding factor is an important verification of the rationality of the 12-slot 14-pole configuration, indicating that this scheme can effectively suppress high-order harmonic components in the air gap magnetic field. High-order harmonic magnetic fields not only cannot participate in the generation of effective torque, but also generate additional iron losses in the stator and rotor cores, while also causing motor vibration and noise. In severe cases, they can even accelerate core wear and affect the service life of the motor. A high winding factor can significantly increase the content of the fundamental magnetic field in the air gap magnetic field, allowing more magnetic field energy to be used for effective torque output and reducing unnecessary energy waste.

[0034] The advantages of this optimized design are manifested in several dimensions: From the perspective of energy conversion efficiency, a higher winding factor significantly reduces losses during electromagnetic energy conversion. Current flowing through the windings is more efficiently converted into magnetic field energy, which in turn generates mechanical torque in the rotor, directly improving the overall energy efficiency of the motor. For battery-powered humanoid robots, this effectively reduces energy consumption and extends battery life after a single charge. From the perspective of back electromotive force (EMF) characteristics, a high winding factor results in a higher amplitude and a waveform closer to a standard sine wave. A high back EMF amplitude means that at the same speed, the motor can output a larger induced EMF, which can offset voltage drops to some extent and improve torque output capability. A sinusoidal back EMF waveform reduces distortion of the current waveform, avoiding additional losses due to current harmonics and further optimizing energy efficiency. From the perspective of operational stability, the optimized electromagnetic design effectively suppresses torque pulsation. Even under different operating conditions such as low-speed start-up, high-speed operation, or sudden load changes, the motor maintains stable torque output, ensuring low noise and minimal vibration during operation. This is particularly important for scenarios where humanoid robot joints require precise motion control, preventing torque fluctuations from causing decreased joint motion accuracy or abnormal noises, thus affecting the robot's motion coordination. From a control performance perspective, the near-sine wave back EMF waveform creates favorable conditions for the implementation of advanced control strategies such as vector control. Vector control requires establishing a precise mathematical model based on the motor's electromagnetic parameters. The sinusoidal back EMF waveform allows the model to better reflect the actual operating state of the motor, enabling the controller to more accurately decouple the motor's flux linkage and torque, thereby improving the system's control accuracy. Simultaneously, this also accelerates the motor's dynamic response speed. When the linear actuator needs to cope with sudden load changes or rapid motion adjustments, it can quickly perform torque compensation or speed adjustments, avoiding motion deviations caused by response lag. This comprehensive optimization of the linear actuator's performance makes it more suitable for the stringent requirements of humanoid robot joints.

[0035] As shown in Figure 4, under the rated operating conditions of the motor, this is the most crucial working state when the linear actuator drives the joints of the humanoid robot. At this time, the motor needs to continuously and stably output rated torque and speed. The operating efficiency and stability of the magnetic circuit directly determine the reliability and energy consumption of the joint's power output. The motor's magnetic circuit strictly follows the principle of minimum magnetic reluctance in electromagnetism. The core of this principle is that magnetic flux, as the carrier of magnetic field energy, will spontaneously choose the path of lowest magnetic reluctance to flow. The permeability of a material is inversely proportional to its magnetic reluctance; the higher the permeability of a material, the lower its magnetic reluctance, and the easier it is to become a channel for magnetic flux to pass through preferentially.

[0036] In this invention, both the stator core 1 and the V-grooved rotor core 3 of the motor are made of high-permeability silicon steel sheets, processed by a precision lamination process. This combination of materials and processes has two key advantages: firstly, the high permeability of the silicon steel sheets results in a magnetic reluctance far lower than that of ordinary metal materials, creating a low-impedance foundation for magnetic flux flow and guiding the flux through efficiently; secondly, the lamination structure, by setting an insulating coating between the silicon steel sheets, can effectively cut off the eddy current loop formed by alternating magnetic flux inside the core, reducing the eddy current loss of the core itself from the source and further improving the energy utilization efficiency of the magnetic circuit. In contrast, the outer nut 5 of the planetary roller screw is made of high-hardness wear-resistant steel to meet the requirements for wear resistance and impact resistance during transmission. The core advantage of this type of material lies in its mechanical properties, capable of withstanding high-frequency friction and load impacts, but its permeability is only a fraction of that of silicon steel sheets, or even lower, resulting in extremely high magnetic reluctance. Therefore, under rated operating conditions, most of the magnetic flux generated by the motor is confined within the stator core and the V-slotted rotor core, forming a closed main magnetic flux path. This path directly connects the permanent magnet, rotor core, air gap, and stator core, and is the core channel for converting electromagnetic energy into mechanical torque, ensuring that energy is precisely applied to the power output stage.

[0037] In contrast, the area where the outer nut 5 is located has low material permeability, resulting in only a very small amount of magnetic flux flowing through it. This magnetic flux distribution characteristic brings two key benefits: From the perspective of energy loss control, the eddy current losses generated by alternating magnetic flux in a conductor are proportional to the square of the material's permeability and magnetic flux density. The low magnetic flux density in the outer nut area significantly reduces the eddy current losses generated within it, while iron losses (including hysteresis losses and eddy current losses) are also reduced, avoiding ineffective energy consumption in non-core components; From the perspective of energy utilization efficiency, minimal magnetic flux leakage means that almost all magnetic field energy is concentrated in the main magnetic flux path to participate in the generation of effective torque, without being wasted due to magnetic flux dissipating to non-power conversion areas such as the outer nut, significantly improving the overall energy conversion efficiency of the motor.

[0038] To further optimize magnetic circuit performance, the rotor V-slotted core 3 features dedicated magnetic flux paths at both the top and bottom. These two paths are not simply structural additions, but rather precise designs tailored to the flow requirements of different types of magnetic flux within the motor. During motor operation, two types of critical magnetic flux exist: one is the excitation flux generated by the permanent magnets, which is the core source of the motor's magnetic field and determines its fundamental strength; the other is the armature reaction flux generated after load current is applied to the stator windings, primarily used to adjust the strength and direction of the magnetic field to adapt to torque requirements under different loads. These two magnetic flux paths together provide a continuous, uninterrupted, low-resistivity flow path for both types of magnetic flux, ensuring efficient flux transmission. The top passage's structural design better suits the conduction requirements of the main magnetic flux. Its cross-sectional shape and orientation have been optimized through electromagnetic simulation, enabling efficient convergence of the excitation flux output from the permanent magnet and precise guidance to the air gap before smoothly transmitting it to the stator core, minimizing losses during the main magnetic flux conduction process. The bottom passage focuses on enhancing the conductivity of the magnetic circuit in the quadrature axis direction. The magnetic flux in the quadrature axis direction is closely related to the motor's reluctance torque. The low reluctance of the bottom passage allows for smoother flow of the quadrature axis flux, further strengthening the contribution of reluctance torque to the total torque. The two passages work together to reduce the total reluctance of the entire magnetic circuit in both axial and radial dimensions, forming a symmetrical and balanced magnetic circuit structure.

[0039] This symmetrical, low-resistance magnetic circuit design brings multi-dimensional performance improvements: Regarding permanent magnet utilization efficiency, the low-resistance path reduces excitation flux losses, allowing the magnetic field energy released by the permanent magnet to be more fully converted into the air gap magnetic field, directly enhancing the air gap magnetic flux density. Air gap magnetic flux density is a key parameter determining motor torque output; its improvement means that, with the same motor size, it can output greater torque, providing stronger power support for the linear actuator. Regarding magnetic circuit stability, the low-resistance design effectively suppresses magnetic circuit saturation. Magnetic circuit saturation can cause a non-linear decrease in motor torque output and even lead to core overheating. This design, by widening the motor's linear operating range, ensures that the motor maintains stable torque output and energy efficiency even under load fluctuations or speed changes, avoiding power interruptions or sudden efficiency drops due to changes in operating conditions. Regarding dynamic performance, the optimized magnetic circuit structure not only improves the motor's torque output capability and operating efficiency but also enhances field weakening speed-enhancing performance. Field weakening for speed enhancement is a key technology for motors to achieve higher speeds under high-speed conditions by adjusting the magnetic field. Effective field weakening allows linear actuators to operate smoothly across a wide speed range, adapting readily to both the low-speed, precise movements required by humanoid robot joints and rapid dynamic adjustments to handle unexpected situations. Ultimately, this magnetic circuit design fundamentally enhances the overall electromagnetic performance and dynamic response characteristics of linear actuators under complex conditions, providing a core guarantee for the stable and efficient actuation of robot joints.

[0040] In another embodiment of the present invention, a linear actuator is provided, which utilizes the aforementioned embedded rotor structure. This linear actuator employs a coaxial, compact layout and, in addition to the core embedded rotor structure, is equipped with a high-strength, lightweight housing, a high-precision position feedback component, an efficient heat dissipation system, and an integrated drive control unit. All components form a collaborative, organic whole surrounding the embedded rotor structure. The outer shell is made of high-quality materials with both high strength and low weight, and is precision-machined. It not only provides a stable mounting base for the stator core, ensuring the structural stability of the electromagnetic module during operation, but also, through the optimized heat dissipation design on the shell surface and the built-in heat-conducting auxiliary structure, constructs a complete heat dissipation path from the windings to the stator core and then to the shell. This, combined with the high thermal conductivity silicone potting structure on the stator three-phase windings, further enhances the thermal stability of the entire machine, preventing heat accumulation from affecting the actuator's operating efficiency and lifespan. The position feedback component uses a high-resolution detection element, directly integrated into the end of the thrust screw, which can capture the linear displacement of the screw and the rotational speed signal of the rotor in real time, accurately transmitting the data to the drive control unit, providing a reliable basis for the high-precision force control and position control of the actuator. The drive control unit has undergone special optimization of the vector control algorithm for the unique electromagnetic characteristics of the embedded permanent magnet rotor, which can give full play to the synergistic effect of reluctance torque and permanent magnet torque, ensuring that the actuator can achieve smooth speed regulation and rapid dynamic response under different operating conditions.

[0041] At the assembly level, this linear actuator adopts a modular design approach, achieving precise matching and efficient assembly of each component. The stator core and the outer shell are connected by a stable fixing method, ensuring the structural stability of the electromagnetic module during long-term operation. The rotor V-grooved core and the outer nut of the planetary roller screw are integrated using a high-precision connection process, completely eliminating the transmission gaps and errors caused by couplings in traditional structures. This allows the torque generated by the motor to be directly transmitted to the screw drive components, significantly optimizing force transmission efficiency. The air gap is controlled through the precision machining of the stator and rotor cores, combined with positioning and calibration using specialized assembly tooling, ensuring uniform air gap distribution and maximizing magnetic field utilization and torque output capability.

[0042] In terms of performance, this linear actuator leverages the core advantages of its embedded rotor structure to achieve multi-dimensional performance improvements: Optimized magnetic flux paths through the V-groove design, combined with adjusted pole-slot configurations and winding parameters, effectively enhance thrust density, enabling stronger thrust output within a limited volume to meet the load-bearing drive requirements of humanoid robot joints; the embedded permanent magnet structure avoids the risk of magnet detachment during high-speed rotation, and a targeted, optimized field-weakening control strategy significantly widens the speed range, achieving both precise positioning during slow joint operation and dynamic response in fast-moving scenarios; optimized magnetic circuit design drastically reduces motor losses, and combined with a high-efficiency cooling system, effectively improves overall energy efficiency and reduces energy consumption; the integrated structural design significantly optimizes the actuator's overall size and weight while significantly improving structural rigidity, enabling it to withstand frequent start-stop cycles and impact loads, meeting the reliability and long-life requirements of humanoid robot joints during long-term, high-frequency operation.

[0043] In terms of application scenarios, this linear actuator can be directly used as the power unit for core joints such as the hip, knee, and shoulder joints of humanoid robots, providing power support for the flexible movement and stable load-bearing of robot joints. In addition, it can also be extended to industrial robots, precision automation equipment and other fields, providing solutions for components in these devices that require high-precision linear drive. Its integrated design concept and excellent comprehensive performance provide a new direction for the technological upgrading and application expansion of linear actuators.

[0044] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An interior rotor structure, characterized by, It comprises: a motor stator comprising a stator core (1) and a stator three-phase winding (2), the stator three-phase winding (2) is arranged in a concentrated winding and one coil is wound on each stator tooth, and the stator three-phase winding (2) is provided with a high-thermal-conductivity silicone potting structure; an embedded permanent magnet rotor comprising a rotor V-shaped slotted core (3) and a permanent magnet magnetic steel (4), and the permanent magnet magnetic steel (4) is embedded in the rotor V-shaped slotted core (3); and a planetary roller screw transmission component comprising an outer nut (5), a thrust screw (6), a planetary roller (7), a retainer and a bearing, the rotor V-shaped slotted core (3) is directly attached to the outer nut (5) through gluing or interference fit, and the stator core (1) and the V-shaped slotted rotor core (3) are both made of high magnetic permeability silicon steel sheets.

2. An insert rotor structure according to claim 1, wherein The stator three-phase winding (2) realizes three-phase separation through a 60° phase belt separation method based on a slot electromotive force star chart, and the pitch factor and the distribution factor of the stator three-phase winding (2) are both 0.966, and the winding factor is 0.

933.

3. An insert rotor structure according to claim 1, wherein The permanent magnet magnetic steel (4) is an NS level rectangular structure with radial magnetization.

4. An insert rotor structure according to claim 1, wherein The structural parameters of the motor stator and the embedded permanent magnet rotor are obtained through finite element analysis and multi-objective genetic algorithm optimization. The structural parameters include stator yoke width, stator tooth width, stator tooth length, pole shoe width and pole shoe thickness, and the rotor side optimization parameters include rotor yoke width, permanent magnet height, permanent magnet width, V-shaped slot angle and magnetic bridge width.

5. An insert rotor structure according to any one of claims 1-4, characterized in that The angle design of the V-shaped slotted core (3) introduces the difference between the d-axis and q-axis magnetic flux paths.

6. An insert rotor structure according to claim 5, wherein The rotor V-shaped slotted core (3) is provided with a magnetic bridge, and the rotor V-shaped slotted core (3) provides a low impedance flow path for the flux linkage through the top magnetic flux path and the bottom magnetic flux path.

7. An insert rotor construction as claimed in claim 6, characterised in that The top and bottom of the rotor V-shaped slotted core (3) are provided with magnetic flux paths.

8. An insert rotor structure according to claim 7, wherein The stator core (1) and the rotor V-shaped slotted core (3) are processed by wire cutting process, and the air gap between the motor stator and the embedded permanent magnet rotor is designed with high precision control.

9. An insert rotor structure according to any one of claims 1-4, characterized in that The outer nut (5), the thrust screw (6) and the planetary roller (7) of the planetary roller screw transmission component are made of high-hardness wear-resistant steel material.

10. A linear actuator characterized by, It comprises an embedded rotor structure as claimed in any one of claims 1-9. It comprises an embedded rotor structure as claimed in any one of claims 1-9.

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