Rotor assembly and servo motor

Abstract

The invention provides a rotor assembly and a servo motor. The rotor assembly comprises a rotor iron core, permanent magnets and an irradiation light source, the multiple permanent magnets are arranged at intervals in the circumferential direction of the rotor iron core, the rotor iron core is provided with a magnetic isolation gap and an installation groove which are communicated with each other, the installation groove penetrates through at least one end of the rotor iron core in the axial direction, and the magnetic isolation gap is formed between every two adjacent permanent magnets in the radial direction; the installation groove is internally provided with a photosensitive telescopic piece, one end, close to the central axis of the rotor core, of the photosensitive telescopic piece is fixedly connected with the groove wall of the installation groove, and one end, far away from the central axis of the rotor core, of the photosensitive telescopic piece is fixedly connected with the magnetic conduction slip sheet. The irradiation light source is used for irradiating the photosensitive telescopic piece to adjust the telescopic length of the photosensitive telescopic piece. According to the rotor assembly and the servo motor, accurate field weakening control can be achieved, and the rotating speed range of the servo motor is widened.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and more specifically, to a rotor assembly and a servo motor. Background Technology

[0002] Servo motors are widely used in robotics, serving as the power source for robots. Currently, servo motors are generally permanent magnet synchronous motors (PMSMs), which offer high power density and more precise control. PMSMs typically employ high-performance rare-earth permanent magnets to provide a strong magnetic field, thereby achieving efficient and stable operation.

[0003] When a permanent magnet motor is running, its back electromotive force (EMF) is directly related to its rotational speed. According to Faraday's law of electromagnetic induction, the faster the motor speed, the higher the back EMF. Under constant voltage drive, when the motor speed increases to a certain level, the back EMF will reach the output voltage limit of the driver. At this point, the motor will no longer be able to maintain constant torque mode, and the output torque will decrease with increasing speed. This phenomenon is called the "field weakening effect".

[0004] Permanent magnet synchronous motors use high-performance rare-earth permanent magnets, resulting in a fixed and unadjustable magnetic field. The motor's back EMF is proportional to the speed. When the motor's terminal voltage increases with the speed to the maximum voltage value that the driver can output, the motor will no longer be able to operate in constant torque control mode. At this time, it is necessary to reduce the motor's back EMF, i.e., to perform field weakening control, so as to obtain a wider speed range.

[0005] Traditional field weakening control strategies typically involve increasing the direct-axis current of the motor stator to partially counteract the magnetic field generated by the permanent magnets, thereby reducing the back electromotive force. While increasing the direct-axis current is effective, it also increases stator copper losses, leading to decreased motor efficiency. Furthermore, at high speeds, the accuracy and response speed of current control may not meet the demands of high-performance control.

[0006] One related technology provides a method to automatically adjust the magnetic field strength by causing the rotor and stator to be axially misaligned by centrifugal force. Although the magnetic field can be adjusted by using the centrifugal force when the rotor is running at high speed, it cannot achieve the same precise control and adjustment as traditional field weakening schemes. Summary of the Invention

[0007] The main objective of this invention is to provide a rotor assembly and a servo motor that can achieve precise field weakening control and improve the speed range of the servo motor.

[0008] To achieve the above objectives, according to one aspect of the present invention, a rotor assembly is provided, comprising a rotor core, permanent magnets, and an illumination light source. A plurality of permanent magnets are spaced apart circumferentially along the rotor core. The rotor core has interconnected magnetic isolation gaps and mounting slots. The mounting slots axially penetrate at least one end of the rotor core. The magnetic isolation gaps are radially spaced between two adjacent permanent magnets and located on the magnetic force transmission path. A magnetically conductive slide is disposed within the magnetic isolation gap. A photosensitive telescopic member is disposed within the mounting slot. One end of the photosensitive telescopic member near the central axis of the rotor core is fixedly connected to the wall of the mounting slot, and the other end away from the central axis of the rotor core is fixedly connected to the magnetically conductive slide. The illumination light source is used to illuminate the photosensitive telescopic member to adjust its telescopic length.

[0009] Furthermore, the circumferential width of the magnetic isolation gap is smaller than the circumferential width of the mounting groove, the magnetic guide plate is T-shaped, the vertical part of the magnetic guide plate is slidably disposed in the magnetic isolation gap, and the horizontal part of the magnetic guide plate is disposed in the mounting groove.

[0010] Furthermore, both the magnetic shielding gap and the cross-section of the mounting groove are rectangular.

[0011] Furthermore, the photosensitive telescopic component is a photoresponsive liquid crystal elastomer; and / or, the mounting groove extends axially through both ends of the rotor core, and the illumination light source is located at both ends of the rotor core, with its position in the radial direction corresponding to the photosensitive telescopic component.

[0012] Furthermore, the output light intensity of the illumination light source is adjustable.

[0013] Furthermore, along the circumferential direction of the rotor core, the two sides of the photosensitive telescopic component are fitted with the groove wall of the mounting slot with clearance.

[0014] Furthermore, the maximum retraction length of the photosensitive telescopic component is less than the length of the magnetically conductive slider within the magnetically isolated gap when it is at its maximum extension length.

[0015] Furthermore, the permanent magnet is attached to the outer circumferential surface of the rotor core.

[0016] According to another aspect of the present invention, a servo motor is provided, including a stator assembly and the aforementioned rotor assembly, wherein the stator assembly is sleeved on the outside of the rotor assembly.

[0017] Furthermore, the servo motor also includes a housing, with the stator assembly fixedly mounted on the inner wall of the housing. A light source circuit board is mounted on the housing, and the illumination light source is mounted on the light source circuit board.

[0018] By applying the technical solution of this invention, a photosensitive expansion joint and a magnetic sliding plate are set in the rotor core. The position of the magnetic sliding plate is adjusted by utilizing the expansion and contraction characteristics of the photosensitive expansion joint under light, thereby changing the magnetic circuit structure of the motor and achieving field weakening control. When the photosensitive expansion joint is irradiated by light of a specific wavelength, a cis-trans isomerization reaction occurs, causing the material to shrink in volume along the orientation direction, thus changing the position of the magnetic sliding plate and affecting the magnetic flux and back electromotive force of the motor. The rotor assembly in this embodiment achieves precise control of the motor's back electromotive force, thereby maintaining the constant torque control mode of the motor at high speeds. This avoids the temperature rise and efficiency reduction problems caused by increasing the direct-axis current in traditional field weakening methods, and also effectively improves the poor control accuracy of mechanical field weakening methods. Since this embodiment achieves field weakening control by adjusting the effective channel area of ​​the magnetic circuit, rather than weakening the permanent magnet magnetic field from the direct-axis current of the motor stator, it avoids increasing the copper loss of the stator and avoiding affecting the motor efficiency. Attached Figure Description

[0019] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0020] Figure 1 A schematic diagram of the servo motor according to an embodiment of the present invention is shown;

[0021] Figure 2 It shows Figure 1 A schematic diagram of the BB-direction cross-section;

[0022] Figure 3 A partially enlarged schematic diagram of the servo motor according to an embodiment of the present invention is shown;

[0023] Figure 4 A schematic diagram of the stator and rotor magnetic circuit structure of a servo motor according to an embodiment of the present invention is shown;

[0024] Figure 5 A schematic diagram of photosensitive field weakening control of a servo motor according to an embodiment of the present invention is shown.

[0025] The above figures include the following reference numerals:

[0026] 1. Rotor core; 2. Permanent magnet; 3. Irradiation light source; 4. Magnetic isolation gap; 5. Mounting slot; 6. Magnetic guide vane; 7. Photosensitive telescopic component; 8. Stator assembly; 9. Housing; 10. Light source circuit board. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] In a conventional permanent magnet servo motor structure, the stator assembly consists of the motor housing, stator core, and winding coils; the rotor assembly consists of the shaft, rotor core, and magnets. The rotor assembly is supported and rotates via two bearings. The position sensor, typically an encoder or resolver, is used to precisely locate the relative position of the magnetic poles and tooth slots for accurate motor rotation control. To improve the motor's power density, high-performance rare-earth permanent magnets are used, with a fixed and unadjustable magnetic field. Since the motor's back electromotive force (EMF) is proportional to speed, once the motor's terminal voltage increases to the maximum output voltage of the driver, the motor can no longer operate in constant torque control mode. At this point, it is necessary to reduce the motor's back EMF, i.e., perform field weakening control, to obtain a wider speed range. Traditional field weakening methods involve adjusting the direct-axis current of the motor stator to weaken the permanent magnet field, thereby reducing the back EMF and increasing the motor's maximum speed. However, this method increases the effective value of the current resulting from the direct-axis current combined with the quadrature-axis current, thus increasing the stator's copper losses and affecting motor efficiency.

[0029] Mechanical field weakening is another method of field weakening. It can reduce the permanent magnet field without increasing the winding current, but it cannot achieve precise control.

[0030] To solve the above problems, see [reference] Figures 1 to 5 As shown, according to an embodiment of the present invention, the rotor assembly includes a rotor core 1, permanent magnets 2, and an illumination light source 3. Multiple permanent magnets 2 are spaced apart circumferentially along the rotor core 1. The rotor core 1 has interconnected magnetic isolation gaps 4 and mounting grooves 5. The mounting groove 5 axially penetrates at least one end of the rotor core 1. The magnetic isolation gaps 4 are radially spaced between two adjacent permanent magnets 2 and located on the magnetic force transmission path. A magnetically conductive slide plate 6 is disposed within the magnetic isolation gap 4. A photosensitive telescopic member 7 is disposed within the mounting groove 5. One end of the photosensitive telescopic member 7 near the central axis of the rotor core 1 is fixedly connected to the groove wall of the mounting groove 5, and the other end away from the central axis of the rotor core 1 is fixedly connected to the magnetically conductive slide plate 6. The illumination light source 3 is used to illuminate the photosensitive telescopic member 7 to adjust its telescopic length.

[0031] This embodiment utilizes a photosensitive expansion joint 7 and a magnetic sliding plate 6 within the rotor core 1. The expansion and contraction of the photosensitive expansion joint 7 under light exposure is used to adjust the position of the magnetic sliding plate 6, thereby altering the motor's magnetic circuit structure and achieving field weakening control. When irradiated with light of a specific wavelength, the photosensitive expansion joint 7 undergoes a cis-trans isomerization reaction, causing the material to shrink in volume along the orientation direction, thus changing the position of the magnetic sliding plate 6 and affecting the motor's magnetic flux and back electromotive force. The rotor assembly in this embodiment achieves precise control of the motor's back electromotive force, maintaining a constant torque control mode at high speeds. This avoids the temperature rise and efficiency reduction problems caused by increased direct-axis current in traditional field weakening methods and effectively improves the poor control accuracy of mechanical field weakening methods. Since this embodiment achieves field weakening control by adjusting the effective channel area of ​​the magnetic circuit, rather than weakening the permanent magnet field through the direct-axis current of the motor stator, it avoids increasing stator copper losses and thus preventing impact on motor efficiency.

[0032] In other embodiments, the accuracy and response speed of the weak magnetic field control can be further optimized by adjusting the material composition of the photosensitive telescopic member 7 and the light intensity control strategy of the irradiation light source, thereby solving the technical problem of accurately controlling the weak magnetic field under different working conditions.

[0033] In one embodiment, the circumferential width of the magnetic isolation gap 4 is smaller than the circumferential width of the mounting groove 5, the magnetic guide plate 6 is T-shaped, the vertical part of the magnetic guide plate 6 is slidably disposed in the magnetic isolation gap 4, and the horizontal part of the magnetic guide plate 6 is disposed in the mounting groove 5.

[0034] In the rotor core 1, the circumferential width of the magnetic isolation gap 4 is designed to be narrower than the width of the mounting slot 5, allowing the vertical portion (i.e., the vertical part) of the T-shaped magnetic guide vane 6 to be tightly and slidably placed within the magnetic isolation gap 4, while the horizontal portion (i.e., the horizontal part) is stably positioned within the mounting slot 5. When the photosensitive telescopic component 7 is irradiated by the illumination source 3 and retracts, it pulls the horizontal portion of the magnetic guide vane 6 to move radially inward, and the vertical portion slides within the magnetic isolation gap 4 accordingly. This increases the magnetic isolation space within the magnetic isolation gap 4, reduces the magnetic cross-sectional area of ​​the magnetic circuit, and effectively weakens the magnetic field generated by the permanent magnet 2. This allows the motor to reduce back EMF at high speeds, maintain constant torque control, and simultaneously reduce efficiency losses due to additional current consumption, significantly improving the motor's speed range and operating efficiency.

[0035] Furthermore, the magnetic sliding piece 6 adopts a T-shaped structure, which can limit the sliding position of the magnetic sliding piece 6 within the mounting groove 5 using the horizontal part, avoiding damage to the thinner vertical part of the magnetic sliding piece 6 due to impact, and extending the service life of the magnetic sliding piece 6. The T-shaped structure of the magnetic sliding piece 6 can increase the bonding surface when bonding the magnetic sliding piece 6 with the photosensitive telescopic component 7, thereby improving the bonding force between the magnetic sliding piece 6 and the photosensitive telescopic component 7.

[0036] In one embodiment, the magnetic slider 6 is made of a soft magnetic material.

[0037] In one embodiment, both the magnetic shielding gap 4 and the mounting groove 5 have rectangular cross-sections.

[0038] The magnetic isolation gap 4 and the mounting groove 5 adopt a rectangular cross-section design to ensure the stability and alignment accuracy of the magnetic guide slider 6 during radial movement. When the photosensitive telescopic component 7 changes size due to illumination from the light source 3, the rectangular cross-section mounting groove 5 provides precise guidance for the photosensitive telescopic component 7, while the rectangular cross-section magnetic isolation gap 4 provides a clear path for the displacement of the magnetic guide slider 6, which helps to reduce friction during sliding, ensures the smoothness of slider movement and the accuracy of positioning, and further optimizes the field weakening control efficiency of the motor under different operating conditions.

[0039] In one embodiment, the widths of the magnetic isolation gap 4 and the mounting groove 5 can be the same, and the widths between the photosensitive telescopic component 7 and the magnetic guide slider 6 can be the same or different, depending on the specific requirements.

[0040] In one embodiment, the photosensitive extensor 7 is a photoresponsive liquid crystal elastomer (LCE). The photosensitive extensor 7 is made of LCE material, a special type of smart material that combines the anisotropic properties of liquid crystal molecules with the flexible deformation properties of elastomers. This material can produce significant shape changes under external stimuli such as light, heat, and electric fields, thus showing great application potential in soft robotics, micromechanics, sensors, and actuators. The deformation mechanism of LCE is mainly based on the rearrangement of its internal liquid crystal molecules. When the material is stimulated by light or heat, the state of the liquid crystal molecules changes, leading to a redistribution of intermolecular forces and thus inducing macroscopic deformation of the material. For example, in a photoresponsive LCE, light of a specific wavelength can trigger intramolecular chemical reactions, causing the liquid crystal molecules to change from an ordered state to a disordered state, resulting in the material contracting along a specific direction. When the light source is removed, or the temperature rises above a certain threshold, the liquid crystal molecules rearrange back to an ordered state, restoring the material to its original shape.

[0041] As a photosensitive expansion joint, the photoresponsive liquid crystal elastomer (LCE) utilizes its photothermal coupling strain characteristics to achieve active deformation through irradiation by the light source 3, thereby controlling the position of the magnetically conductive slider 6. When the LCE material is irradiated with light of a specific wavelength, the photosensitive groups inside undergo cis-trans isomerization reactions, causing the material volume to shrink, which in turn changes the position of the magnetically conductive slider, affecting the motor's magnetic flux and back EMF. This enables precise adjustment of the motor's field weakening control, improving the motor's speed range and operating efficiency, while avoiding the additional losses caused by the increased direct-axis current in traditional field weakening methods.

[0042] In one embodiment, the mounting groove 5 extends axially through both ends of the rotor core 1, and the illumination light source 3 is disposed at both ends of the rotor core 1, with its radial position corresponding to the photosensitive telescopic component 7.

[0043] By setting axially penetrating mounting slots 5 at both ends of the rotor core 1 and radially arranging illumination light sources 3 at the corresponding positions, a dual-sided illumination condition for the photosensitive telescopic component 7 is formed. This structural design ensures that the photosensitive telescopic component 7 receives illumination light from the illumination light source 3 uniformly along its entire axial length, guaranteeing its uniform contraction and recovery along the axial direction. This, in turn, allows for precise adjustment of the position of the magnetic guide vane 6, achieving a uniform and controllable magnetic weakening effect on the motor's magnetic circuit. The dual-sided light source effectively avoids the problem of uneven response of the photosensitive telescopic component 7 caused by the angle or distance of the light source, enhancing the stability and consistency of magnetic field adjustment.

[0044] In one embodiment, the output light intensity of the illumination light source 3 is adjustable.

[0045] The adjustable light source 3 allows the motor to adjust the degree of contraction of the photosensitive telescopic component according to actual needs, thereby precisely controlling the position of the magnetic sliding plate. The adjustment of the light intensity directly affects the photoinduced contraction intensity of the LCE material, which in turn affects the displacement of the magnetic sliding plate 6, achieving precise control of the motor's magnetic flux and back EMF. This improves the flexibility and accuracy of field weakening control, enabling the motor to maintain optimal operating conditions at different speeds, and improving the motor's operating efficiency and speed range.

[0046] In one embodiment, the illumination light source 3 is UV or the like.

[0047] In other embodiments, other types of light sources, such as LED light sources, can be used, combined with temperature sensors and intelligent control algorithms, to further optimize the light intensity control strategy and solve the technical problem of achieving efficient and accurate magnetic weakening control under complex working conditions.

[0048] In one embodiment, along the circumferential direction of the rotor core 1, the two sides of the photosensitive telescopic member 7 are fitted with the groove wall of the mounting groove 5 with a clearance.

[0049] The clearance fit design between the photosensitive telescopic component 7 and the mounting groove 5 ensures the freedom of the photosensitive telescopic component 7 during contraction and expansion, avoiding the influence of mechanical constraints on displacement control. This clearance fit design helps maintain the stability of the photosensitive telescopic component 7 during movement, ensuring its accurate response to changes in light intensity and enabling precise control of the position of the magnetic sliding plate 6. This improves the accuracy and reliability of the weak magnetic control, allowing the motor to more effectively maintain constant torque control at high speeds, thus improving the motor's operating efficiency and speed range.

[0050] In one embodiment, the maximum retracted length of the photosensitive telescopic member 7 is less than the length of the magnetically conductive slider 6 within the magnetically insulating gap 4 when it is at its maximum extended length.

[0051] This design limits the maximum retraction range of the photosensitive telescopic component 7, ensuring that the magnetic circuit maintains a certain magnetic permeability even under maximum magnetic weakening conditions, thus avoiding abnormal motor operation caused by completely cutting off the magnetic circuit. By limiting the maximum retraction length of the photosensitive telescopic component 7, it is ensured that the motor maintains an appropriate magnetic flux under different operating conditions, avoiding performance degradation due to excessively low magnetic flux, improving the stability and reliability of the motor under magnetic weakening control, enabling the motor to maintain good operating conditions at high speeds, and avoiding performance fluctuations caused by unstable magnetic circuit structure.

[0052] In addition, this design can also avoid the problem that the photosensitive telescopic component 7 cannot quickly align with the magnetic isolation gap 4 and thus cannot extend smoothly when it is fully retracted into the mounting groove 5, thereby improving the stability and reliability of the telescopic movement of the photosensitive telescopic component 7.

[0053] In one embodiment, the permanent magnet 2 is attached to the outer peripheral surface of the rotor core 1.

[0054] The permanent magnet 2 is surface-mounted on the outer circumference of the rotor core 1, which simplifies the motor's structural design and reduces manufacturing costs. The surface-mount design of the permanent magnet allows magnetic lines of force to pass more directly through the rotor core 1 and the magnetic sliding plate 6, improving the efficiency of the magnetic circuit and thus the operating efficiency of the motor. This simplifies the motor's manufacturing process, reduces costs, and simultaneously improves the motor's operating efficiency and speed range.

[0055] In one embodiment, the rotor core 1 may also have a magnetic groove opened on the inner side of the outer circle, and the permanent magnet 2 may be placed in the magnetic groove opened on the rotor core 1.

[0056] The permanent magnet 2 can be arranged in a straight line or a V-shape, etc.

[0057] According to an embodiment of the present invention, the servo motor includes a stator assembly 8 and the rotor assembly described above, with the stator assembly 8 sleeved on the outside of the rotor assembly.

[0058] The coordinated design of the stator assembly 8 and rotor assembly of the servo motor ensures efficient operation and precise control. When energized, the winding coils of the stator assembly 8 generate a magnetic field, which interacts with the permanent magnets in the rotor assembly, driving the motor to rotate. Meanwhile, the photosensitive telescopic element 7 and the magnetically conductive sliding plate 6 in the rotor assembly achieve field weakening control of the motor's magnetic flux and back EMF. Through this structure, this embodiment of the invention provides a novel servo motor that, through the field weakening control scheme of the photosensitive telescopic element, improves the motor's speed range and operating efficiency, while avoiding the additional losses caused by the increased direct-axis current in traditional field weakening methods.

[0059] In one embodiment, the servo motor further includes a housing 9, a stator assembly 8 is fixedly disposed on the inner wall of the housing 9, a light source circuit board 10 is disposed on the housing 9, and an illumination light source 3 is disposed on the light source circuit board 10.

[0060] The housing 9 provides protection for the stator assembly 8 and the light source circuit board 10, while also fixing the position of the illumination light source 3, ensuring accurate illumination of the photosensitive telescopic component 7 by the illumination light source 3. The illumination light source 3 on the light source circuit board 10, through circuit control, can precisely adjust the light intensity, thereby controlling the degree of contraction of the photosensitive telescopic component 7, achieving precise control of the position of the magnetic guide slider 6. This improves the structural stability of the servo motor and the accuracy of the field weakening control, enabling the motor to maintain good operating conditions at high speeds, and improving the motor's operating efficiency and speed range.

[0061] See also Figure 4 The diagram shown is a schematic diagram of the stator and rotor magnetic circuits of a servo motor according to an embodiment of this application.

[0062] Magnetic field lines originate from the N pole of the first permanent magnet 2, pass through the rotor core 1, the magnetic sliding plate 6, and the rotor core 1, reaching the S pole of the second permanent magnet 2 and its interior. They then exit from the N pole of the second permanent magnet 2, pass through the stator-rotor air gap, reach the stator teeth, yoke, and stator teeth, and then exit from the stator assembly 8, pass through the stator-rotor air gap again, reach the S pole of the first permanent magnet 2 and its interior, and exit from the N pole, forming a complete magnetic circuit. The density of the magnetic field lines in the diagram can be visualized as the magnitude of the magnetic field in the circuit.

[0063] As mentioned earlier, the maximum speed of a motor is affected by the back electromotive force (EMF). For a conventional permanent magnet motor, the formula for the back EMF is:

[0064]

[0065] Where k ω Here, N is the winding factor, f is the number of turns per phase in series, Φ is the power supply frequency, and Φ is the flux per pole. Additionally:

[0066] in

[0067] Where F m It is the magnetomotive force (constant) of a permanent magnet, R g L is the air gap reluctance (constant), μ is the material's permeability (constant), and L is the permeability. core The core length is constant, and the core cross-sectional area A core When it decreases, the magnetic reluctance R of the iron core core Increasing the total magnetic reluctance leads to a decrease in magnetic flux Φ, which in turn leads to a decrease in back electromotive force. Similarly, the cross-sectional area A of the iron core... core As the voltage increases, the back electromotive force of the motor rises.

[0068] The photosensitive magnetic weakening control principle of this application is as follows:

[0069] The weak magnetic actuator used in this invention is based on the reversible variation properties of photoresponsive liquid crystal elastomer (LCE) material. Through external UV (ultraviolet light) excitation and temperature control, it achieves the driving and displacement output of an external load. Its working principle can be divided into the following two stages, as follows: Figure 5 As shown:

[0070] 1. Photo-induced contraction stage (driving stage)

[0071] When a photosensitive elastomer is irradiated with ultraviolet light of a specific wavelength (such as 365 nm), the photosensitive groups containing azobenzene structures inside the material undergo cis-trans isomerization, leading to the disruption of the ordered liquid crystal structure. Macroscopically, this manifests as volume shrinkage along the orientation direction. This photoinduced phase transition generates active strain, enabling the actuator to contract controllably without mechanical contact. During contraction, it overcomes an external force F aligned with its direction of motion, causing the actuator to contract from its initial position to a preset target displacement ΔL. target The mechanical equilibrium relationships in this process are as follows:

[0072]

[0073] Where ε is the total strain (ΔL) target =ε·L), f is the external reverse load (i.e., the centrifugal force of the magnetically conductive slider f = mω). 2 r, f are linearly related to ω), E is the Young's modulus of the LCE, A is the cross-sectional area of ​​the LCE, ε act It is an active strain induced by light and temperature.

[0074] Active strain ε act Follows the following control model:

[0075]

[0076] Where ε maxLet I0 represent the maximum strain of the LCE, I0 represent the characteristic saturation light intensity of the LCE, T represent the external temperature control variable, T0 represent the response failure threshold of the LCE, and ΔT represent the temperature sensitivity of the LCE. This model illustrates the effect of UV light intensity I0. UV The photo-induced shrinkage intensity is determined; temperature T controls the material's recovery tendency (the higher the temperature, the faster the recovery and the smaller the strain), and this temperature is provided by the heat generated when the motor is working.

[0077] Using the above function form, it is possible to: precisely control the degree of contraction by controlling the light intensity and temperature, so that the final deformation can accurately stop at the set position while overcoming the centrifugal force of the magnetic sliding plate, and control the cross-sectional area of ​​the magnetic circuit to precisely control the back electromotive force of the motor, thereby obtaining a controllable magnetic weakening method.

[0078] In the above adjustment process, the control logic ultimately forms a closed loop through the feedback of the demand for magnetic weakening. That is, the light intensity is ultimately controlled according to the rate of change of rotation speed. For example, if the rate of change of rotation speed is too small, it means that the magnetic weakening is insufficient, so the light intensity is increased; if the rate of change of rotation speed is too large, the light intensity is decreased. By controlling the influence of light intensity and temperature on the LCE, the LCE is made to contract or expand as needed, thereby achieving control of magnetic weakening.

[0079] 2. Thermal recovery phase (reset phase)

[0080] When the motor does not need to weaken the magnet or the degree of weakening needs to be reduced, it can be achieved by turning off the ultraviolet light or reducing the intensity of the ultraviolet light. Since the motor generates heat when it is running, there is no need to add an additional heat source to LCE. When the temperature of LCE material exceeds the photointensity-induced change threshold, its photoinduced cis-trans isomers are rearranged, the liquid crystal state is restored, and the material elongates.

[0081] The response of the aforementioned thermally induced process can also be expressed through the aforementioned active strain model, achieving a controllable recovery speed and degree, and enabling the actuator to possess good closed-loop drive-reset cycle characteristics.

[0082] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0083] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in sequences other than those illustrated or described herein.

[0084] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A rotor assembly, characterized in that, The device includes a rotor core (1), permanent magnets (2), and an illumination source (3). A plurality of permanent magnets (2) are arranged circumferentially around the rotor core (1). The rotor core (1) has interconnected magnetic isolation gaps (4) and mounting grooves (5). The mounting grooves (5) extend axially through at least one end of the rotor core (1). The magnetic isolation gaps (4) are radially located between two adjacent permanent magnets (2) and on the magnetic force transmission path. A magnetic guide vane (6) is provided in the magnetic isolation gaps (4). A photosensitive telescopic member (7) is provided in the mounting grooves (5). One end of the photosensitive telescopic member (7) near the central axis of the rotor core (1) is fixedly connected to the groove wall of the mounting groove (5), and the other end away from the central axis of the rotor core (1) is fixedly connected to the magnetic guide vane (6). The illumination source (3) is used to illuminate the photosensitive telescopic member (7) to adjust the telescopic length of the photosensitive telescopic member (7).

2. The rotor assembly according to claim 1, characterized in that, The circumferential width of the magnetic isolation gap (4) is smaller than the circumferential width of the mounting groove (5). The magnetic guide plate (6) is T-shaped. The vertical part of the magnetic guide plate (6) is slidably disposed in the magnetic isolation gap (4), and the horizontal part of the magnetic guide plate (6) is disposed in the mounting groove (5).

3. The rotor assembly according to claim 2, characterized in that, The cross-sections of the magnetic shielding gap (4) and the mounting groove (5) are both rectangular.

4. The rotor assembly according to claim 1, characterized in that, The photosensitive telescopic component (7) is a photoresponsive liquid crystal elastomer; and / or, the mounting groove (5) passes through both ends of the rotor core (1) axially, and the irradiation light source (3) is disposed at both ends of the rotor core (1), and its position in the radial direction corresponds to that of the photosensitive telescopic component (7).

5. The rotor assembly according to claim 1, characterized in that, The output light intensity of the illumination light source (3) is adjustable.

6. The rotor assembly according to claim 1, characterized in that, Along the circumferential direction of the rotor core (1), the two sides of the photosensitive telescopic member (7) are fitted with the groove wall of the mounting groove (5) with a clearance.

7. The rotor assembly according to claim 1, characterized in that, The maximum retraction length of the photosensitive telescopic component (7) is less than the length of the magnetically conductive slider (6) within the magnetically insulating gap (4) when it is at its maximum extension length.

8. The rotor assembly according to claim 1, characterized in that, The permanent magnet (2) is attached to the outer circumferential surface of the rotor core (1).

9. A servo motor, characterized in that, It includes a stator assembly (8) and a rotor assembly according to any one of claims 1 to 8, wherein the stator assembly (8) is sleeved on the outside of the rotor assembly.

10. The servo motor according to claim 9, characterized in that, The servo motor also includes a housing (9), the stator assembly (8) is fixedly disposed on the inner wall of the housing (9), a light source circuit board (10) is disposed on the housing (9), and the illumination light source (3) is disposed on the light source circuit board (10).

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