A dual-mode electromechanical actuator based on planetary roller screw pair

Abstract

The application belongs to the technical field of electromechanical actuators, and provides a dual-mode electromechanical actuator based on a planetary roller screw pair. The actuator comprises a planetary roller screw pair and a reverse planetary roller screw pair sharing a redundant screw, which respectively constitute a physically isolated main drive chain and a standby drive chain. The main drive chain drives the redundant screw to rotate through a main motor, so that the drive nut outputs linearly; the standby drive chain drives the drive nut to rotate through a standby motor, so that the redundant screw moves axially, and then drives the drive nut to output. Through the cooperation of displacement sensors and encoders, the system can automatically and undisturbedly switch to the standby chain when the main chain fails, and the output speed is continuous. The application completely eliminates the single-point failure risk of traditional actuators, realizes redundant driving with high reliability and high safety, and is particularly suitable for high-demand fields such as aerospace.

Description

Technical Field

[0001] This application belongs to the field of electromechanical actuator technology, and in particular relates to a dual-mode electromechanical actuator based on a planetary roller screw pair. Background Technology

[0002] A planetary roller screw is a precision mechanical device that converts rotary motion into linear motion. Its core structure consists of a central screw, multiple circumferentially distributed threaded rollers, and an outer nut. During operation, the rotation of the screw drives the rollers to both rotate on their own axis and revolve around a central axis through threaded engagement, mimicking planetary motion, thereby pushing the nut to perform linear motion. Electromechanical actuators (EMAs), with their multiple rollers bearing load in parallel, possess extremely high rigidity, load-bearing capacity, and lifespan. Their advantages include compact structure, high power density, fast response speed, high transmission accuracy, and the elimination of hydraulic oil, significantly improving the reliability, efficiency, and maintainability of EMAs. They are crucial for achieving high-dynamic, high-load, precise linear drive in aerospace, high-end equipment, and other fields.

[0003] In the Chinese patent application with publication number CN112865408A, there is a possibility of a single point of failure at the lead screw nut. When the lead screw nut is stuck and cannot rotate or move linearly, the entire electromechanical actuator system fails.

[0004] In the Chinese utility model patent with announcement number CN219812048U, the main and auxiliary motors are used to drive independent lead screw transmission chains to improve the feasibility of emergency tasks. However, there is still a risk of physical coupling at the mechanical interface level, and there is a lack of closed-loop monitoring and power smoothness guarantee for the path switching process. Summary of the Invention

[0005] In view of the above problems, this invention provides a dual-mode electromechanical actuator based on a planetary roller screw pair, comprising two relatively independent actuation channels. When any single failure occurs in the main channel, the system can immediately detect and automatically switch to the backup channel to continue completing the flight control task. This improves the system's mission reliability by several orders of magnitude.

[0006] This invention discloses a dual-mode electromechanical actuator based on a planetary roller screw pair, including a main drive mechanism, a backup drive mechanism, a redundant screw, a drive nut, a transmission nut, rollers, reverse rollers, an axially connected bearing assembly, a limit mechanism, an external threaded sleeve, and a detection and control system.

[0007] A planetary roller screw pair consists of a redundant lead screw, rollers, and a drive nut.

[0008] The main drive mechanism and the planetary roller screw pair constitute the active path; one end of the redundant screw is engaged with the drive nut through roller threads, and the other end is connected to the main drive mechanism for transmission. The main drive mechanism drives the redundant screw to rotate circumferentially, thereby driving the drive nut to move linearly.

[0009] The redundant lead screw and the drive nut are engaged by roller threads;

[0010] The redundant lead screw is also connected to the transmission nut via an axially connected bearing assembly, a limiting mechanism, an external threaded sleeve, and a reverse roller, forming a reverse planetary roller lead screw pair.

[0011] The backup drive mechanism, the reverse planetary roller screw pair, and the planetary roller screw pair constitute the backup path; the transmission nut is connected to the backup drive mechanism, and the backup drive mechanism drives the redundant screw to move axially, thereby driving the drive nut to move linearly.

[0012] The external threaded sleeve is located between the transmission nut and the redundant lead screw, and is decoupled from the circumferential rotation of the redundant lead screw through an axially connected bearing assembly;

[0013] The external threaded sleeve and the transmission nut are engaged by multiple reverse roller threads.

[0014] The detection and control system includes a displacement sensor for detecting the actual axial displacement of the drive nut, a main encoder for detecting the rotational speed of the main drive mechanism, and a backup encoder for detecting the rotational speed of the backup drive mechanism.

[0015] The detection and control system is configured to: when the active path is working, determine the fault based on the deviation between the theoretical displacement signal of the drive nut obtained from the motor speed signal of the main encoder and the actual displacement signal of the drive nut collected by the displacement sensor; and when the active path is determined to be faulty, control the backup path to start, and calculate and control the speed of the backup motor based on the speed data before the fault recorded by the main encoder, so as to realize the continuous switching of the output speed of the drive nut.

[0016] Optionally, the main drive mechanism includes a main motor, a main reducer, and a main gear pair; the standby drive mechanism includes a standby motor, a standby reducer, and a standby gear pair.

[0017] Optionally, the limiting mechanism includes a cage and a retaining ring.

[0018] Optionally, one end of the redundant lead screw is an optical shaft, which is connected to the main gear pair via a lead screw spline; the outer wall of the transmission nut is provided with a nut spline, which is connected to the spare gear pair via the nut spline.

[0019] Optionally, the axially connected bearing assembly includes two bearings, with the inner ring fixed to the redundant lead screw and the outer ring fixed inside the external threaded sleeve.

[0020] Optionally, the multiple reverse rollers of the reverse planetary roller screw pair are evenly distributed circumferentially by a cage, and the cage is axially limited between the axially connected bearing assembly and the retaining ring.

[0021] Optionally, the threads of the planetary roller screw pair and the threads of the reverse planetary roller screw pair both satisfy the self-locking condition.

[0022] Optionally, the detection and control system determines an active path fault as follows: the absolute value of the difference between the theoretical displacement signal and the actual displacement signal exceeds a preset threshold.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] (1) The dual-mode electromechanical actuator of the present invention provides a redundant EMA execution scheme. By adopting a planetary roller screw pair (PRSM) and a reverse planetary roller screw pair (IPRSM) structure, the reliability and fault tolerance of the system are effectively improved.

[0025] (2) The dual-mode electromechanical actuator of the present invention achieves physical isolation of the transmission path through a dual-motor, dual-path transmission design, eliminating the risk of system failure due to a single motor, power supply, or control circuit failure. Furthermore, the redundant lead screw isolates the final shared transmission path by employing a clutch structure at the reverse lead screw, eliminating single-point failures. This significantly improves the actuator's operational safety and continuous working capability in high-risk scenarios such as aerospace.

[0026] (3) The dual-mode electromechanical actuator of the present invention has achieved improvements in core performance indicators such as thrust, lifespan and reliability. Attached Figure Description

[0027] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0028] Figure 1 This is a main view of the dual-mode electromechanical actuator based on planetary roller screw pairs of the present invention;

[0029] Figure 2 This is a partial cross-sectional view of the dual-mode electromechanical actuator based on planetary roller screw pairs of the present invention;

[0030] Figure 3 This is another partial cross-sectional view of the dual-mode electromechanical actuator based on planetary roller screw pairs of the present invention.

[0031] Figure label:

[0032] 1-Spare gear pair; 2-Spare reducer; 3-Spare motor; 4-Reverse planetary roller screw pair; 5-Main gear pair; 6-Main reducer; 7-Main motor; 8-Planetary roller screw pair; 9-Redundant screw; 10-Nut spline; 11-Transmission nut; 12-Drive nut; 13-Axial connection bearing assembly; 14-Screw spline; 15-External threaded sleeve; 16-Roller; 17-Displacement sensor; 18-Spare encoder; 19-Main encoder; 20-Cage; 21-Retaining ring; 22-Reverse roller. Detailed Implementation

[0033] To better understand the above-described objectives, features, and advantages of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other. Furthermore, the present invention can be implemented in other ways different from those described herein; therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0034] A specific embodiment of the present invention, such as Figures 1-3 A dual-mode electromechanical actuator based on a planetary roller screw pair is disclosed, including a roller 16, a redundant screw 9, a nut spline 10, a screw spline 14, a reverse roller 22, a displacement sensor 17, a spare encoder 18, and a main encoder 19.

[0035] The redundant lead screw 9, roller 16 and drive nut 12 constitute the planetary roller lead screw pair 8;

[0036] The main drive mechanism and the planetary roller screw pair 8 constitute the active path; one end of the redundant screw 9 is indirectly engaged with the drive nut 12 through the thread of the roller 16, and the other end is connected to the main drive mechanism. The main drive mechanism drives the redundant screw 9 to rotate circumferentially, thereby driving the drive nut 12 to move linearly.

[0037] The redundant lead screw 9 is also connected to the transmission nut 11 via the axially connected bearing assembly 13, the limiting mechanism, the external threaded sleeve 15, and the reverse roller 22, forming a reverse planetary roller lead screw pair 4.

[0038] The backup drive mechanism, the reverse planetary roller screw pair 4, and the planetary roller screw pair 8 constitute the backup path; the transmission nut 11 is connected to the backup drive mechanism, and the backup drive mechanism drives the redundant screw 9 to move axially, thereby driving the drive nut 12 to move linearly.

[0039] Furthermore, the main motor 7, the main reducer 6, the main gear pair 5, and the planetary roller screw pair 8 constitute the active path (i.e., the main drive chain); the planetary roller screw pair 8 includes rollers 16 and drive nuts 12; the main gear pair 5 includes two meshing drive gears.

[0040] The spare motor 3, spare reducer 2, spare gear pair 1, reverse planetary roller screw pair 4 and planetary roller screw pair 8 constitute the spare path (i.e., spare transmission chain); the reverse planetary roller screw pair 4 includes a transmission nut 11, a reverse roller 22, an external threaded sleeve 15 and an axially connected bearing assembly 13; the spare gear pair 1 includes two meshing spare gears.

[0041] Furthermore, planetary roller screw pair 8 and reverse planetary roller screw pair 4 share the same redundant screw 9.

[0042] Further, see Figure 3 An axially connected bearing assembly 13 is provided between the redundant lead screw 9 and the external threaded sleeve 15. The inner ring of the axially connected bearing assembly 13 is fixed to the redundant lead screw 9, and the outer ring is fixed to the external threaded sleeve 15. The axially connected bearing assembly 13 achieves circumferential rotational decoupling between the redundant lead screw 9 and the external threaded sleeve 15. The axially connected bearing assembly 13 includes two axially connected bearings. The inner rings of the two axially connected bearings are sleeved on the redundant lead screw 9. Retaining rings 21 are respectively provided on the outer side of the two axially connected bearings. A retainer 20 is clamped between each retaining ring and the axially connected bearing. The retainer 20 is used to hold multiple reverse rollers 22. The multiple reverse rollers 22 are evenly distributed circumferentially on the retainer 20 and are provided between the internal threads of the external threaded sleeve 15 and the transmission nut 11. The multiple reverse rollers 22 are provided with threads. The reverse planetary roller screw pair is formed by the threaded engagement between the multiple reverse rollers 22, the external threaded sleeve 15 and the transmission nut 11.

[0043] Furthermore, multiple rollers 16 are sandwiched between the external thread of the redundant lead screw 9 and the internal thread of the drive nut 12. The multiple rollers 16 are evenly distributed on the cage of the planetary roller screw pair 8. The multiple rollers 16 are provided with threads. The planetary motion transmission pair is formed by the threaded engagement between the multiple rollers 16, the redundant lead screw 9 and the drive nut 12.

[0044] Furthermore, the drive gear and the transmission nut 11, which are connected to the redundant lead screw 9, can be rotated relative to each other.

[0045] Furthermore, the redundant lead screw 9 is configured as a threaded shaft at one end near the spare gear pair 1 and as a smooth shaft at the other end near the main gear pair 5; the smooth shaft of the redundant lead screw 9 is provided with at least one lead screw spline 14 along the axial direction, and is connected to one of the driving gears of the main gear pair 5 through the lead screw spline 14; similarly, the outer wall of the transmission nut 11 is axially machined with a nut spline 10 to achieve a transmission connection with one of the spare gears of the spare gear pair 1.

[0046] When the active path is working, the rotation of the redundant lead screw 9 is isolated by the axial connecting bearing assembly 13, and the standby path other than the redundant lead screw 9 is in a stationary state. When the standby path is working, the transmission nut 11 rotates circumferentially under the drive of the standby drive mechanism, which drives the reverse roller 22 meshing with it to rotate and revolve, thereby driving the external threaded sleeve 15 to move linearly and reciprocally along the axis of the redundant lead screw 9. The axial displacement of the external threaded sleeve 15 is transmitted to the cage 20 through the retaining ring 21, which drives the cage 20 to move axially synchronously. Since the cage 20 and the axial connecting bearing assembly 13 are axially limited and the inner ring of the axial connecting bearing assembly 13 is axially fixed to the redundant lead screw 9, the axial movement of the cage 20 can drive the redundant lead screw 9 to move axially synchronously through the axial connecting bearing assembly 13, and finally drive the drive nut 12 to move synchronously and linearly through the redundant lead screw 9, thus realizing power output.

[0047] Furthermore, the drive nut 12 is the final power output terminal of the entire electromechanical actuator (EMA). A flange structure is provided on the drive nut 12 for connecting to an external actuator, directly outputting linear drive force to an external load, such as ailerons or elevators of aircraft, which require highly reliable linear drive.

[0048] Furthermore, a main gear pair 5 is provided at one end of the transmission nut 11, and a spare gear pair 1 is provided at the other end.

[0049] It is worth noting that the main gear pair 5 is rotatably mounted on one end of the transmission nut 11. That is, the main gear pair 5 is mounted on one end of the optical shaft of the redundant lead screw 9, the redundant lead screw 9 rotates synchronously with the main gear pair 5, and the main gear pair 5 is only mounted on one end of the transmission nut 11 and is not fixedly connected to the transmission nut 11.

[0050] Furthermore, the main reducer 6 and the main motor 7 are connected to one end of the redundant lead screw 9 via the main gear pair 5; the spare reducer 2 and the spare motor 3 are connected to the other end of the transmission nut 11 via the spare gear pair 1.

[0051] Furthermore, both the backup motor 3 and the main motor 7 are equipped with a backup encoder 18 and a main encoder 19 at their tail ends, which are used to monitor the speed and angular position signals of the corresponding motors in real time; a displacement sensor 17 is set on the outer wall of the drive nut 12, which is used to monitor and provide feedback on the linear output displacement of the actuator in real time.

[0052] Furthermore, the detection and control system obtains the theoretical displacement of the drive nut 12 by acquiring the motor speed signal fed back by the main encoder 19 in real time and the transmission ratio of the main reducer 6. Displacement sensor 17 collects the actual displacement of drive nut 12. The system compares the absolute value of the displacement difference between the two. To determine the state of the transmission chain.

[0053] Furthermore, when in active path mode, if the absolute value of the displacement difference is detected... If the preset fault threshold is exceeded, it is determined that the main drive chain has mechanically jammed or the power has been interrupted. The detection and control system immediately executes the switching procedure: shutting down the main motor 7 and activating the backup motor 3.

[0054] Furthermore, during the path switching process, the detection and control system uses the main encoder 19 and the backup encoder 18 to perform closed-loop speed control on the main motor 7 and the backup motor 3, thereby controlling the axial movement speed of the drive nut 12 driven by them. Maintaining the same speed as before switching, the closed-loop cooperation of displacement sensor 17, main encoder 19, and backup encoder 18 enables seamless connection of power output and fault self-recovery.

[0055] Specifically, at the moment of switching, the main encoder 19 retrieves the last effective speed data of the main motor 7 before the fault occurred. Based on the proportional relationship between the leads of the main reducer 6, the backup reducer 2, the planetary roller screw pair 8, and the reverse planetary roller screw pair 4, it calculates the required speed of the backup motor 3 and outputs it to the backup encoder 18 to achieve the linear speed of the drive nut 12. To maintain continuity and avoid mechanical impact.

[0056] Specifically, the speed of the main motor 7, after being transmitted through the main reducer 6 and the main gear pair 5, is expressed as the speed of the redundant lead screw 9, which is:

[0057]

[0058] in, The rotational speed of redundant lead screw 9; The last effective speed of the main motor 7 before the main motor failure is provided by the main encoder 19; The transmission ratio of the main reducer (reduction ratio, which is input speed / output speed, with the output speed being lower than the input speed); The transmission ratio of the main gear pair.

[0059] The planetary roller screw pair 8 converts the rotational motion of the redundant screw 9 into the linear motion of the drive nut 12. The linear velocity of the drive nut 12 driven by the planetary roller screw pair 8 is:

[0060]

[0061] in, The lead of planetary roller screw pair 8 is the distance that drives nut 12 to move when redundant screw 9 rotates once.

[0062] The speed of the standby motor 3, after being transmitted through the standby reducer 2 and the standby gear pair 1, is the speed of the transmission nut 11, expressed as:

[0063]

[0064] in, The rotational speed of the transmission nut 11; The required speed of the standby motor; The transmission ratio of the backup reducer; This is the transmission ratio of the spare gear pair.

[0065] The reverse planetary roller screw pair 4 converts the rotational motion of the transmission nut 11 into the linear motion of the redundant screw 9. The linear velocity of the drive nut 12 driven by the reverse planetary roller screw pair 4 is:

[0066]

[0067] in, The lead of the reverse planetary roller screw pair 4 (IPRSM) is the axial displacement of the external threaded sleeve 15 relative to the drive nut for each revolution of the drive nut 11; it is also the thread lead of both the drive nut 11 and the external threaded sleeve 15, and their thread leads are equal.

[0068] When switching paths, it is necessary to ensure that the linear speed of the drive nut remains continuous, i.e. Combining the formulas, we can obtain:

[0069]

[0070] After processing, the formula for calculating the standby motor speed is obtained:

[0071] .

[0072] It is understood that the closed-loop cooperation between displacement sensor 17 and backup encoder 18 in this invention refers to the dynamic cooperation between "input-side high-frequency monitoring" and "output-side actual measurement verification". The specific content of the cooperation is as follows:

[0073] 1. Spatial Dimensional Collaboration (Positioning): The main encoder 19 or the backup encoder 18 is responsible for monitoring the rotational state of the "source" of the power source, while the displacement sensor 17 is responsible for monitoring the linear state of the "end" of the actuator. The combination of these three components solves the problem that traditional EMA cannot determine whether intermediate links in the transmission chain (such as broken gears or stuck lead screws) are broken.

[0074] 2. Time-dimensional collaboration (switching): When a fault is detected and a path switching is required, the displacement sensor 17 provides the precise initial position value at the current moment, while the backup encoder 18 takes over the speed loop control of the backup motor 3 through the data provided by the main encoder 19, ensuring that the speed and direction during the takeover process remain highly consistent with the original path.

[0075] 3. Security Collaboration (Self-Recovery): This collaboration mechanism forms a closed loop of "monitoring-judgment-execution", enabling the system to autonomously complete the smooth transition to the backup channel by utilizing the redundant information flow of the sensor group without the need for external command intervention.

[0076] When the active path is active (alternate path is disabled):

[0077] The main motor 7 drives the main gear pair 5 to rotate, which in turn drives the redundant lead screw 9 to rotate via the lead screw spline 14. At this time, the roller-drive nut assembly of the planetary roller screw pair 8 (PRSM) only moves axially. The drive nut 12 can be designed with a flange structure or replaced with a flange-shaped nut to connect and output thrust.

[0078] Meanwhile, since the axially connected bearing assembly 13 achieves rotational decoupling in the circumferential direction, the rotational motion of the redundant lead screw 9 is not transmitted to the external threaded sleeve 15. Therefore, the external threaded sleeve 15 remains stationary, and the transmission nut 11 connected to it does not move at all. In this state, the planetary roller screw pair 8 converts the rotation of the redundant lead screw 9 into the axial linear motion of the drive nut 12, thereby outputting thrust normally.

[0079] When the backup path is active (active path is disabled):

[0080] The standby motor 3 drives the standby gear pair 1 to rotate, and transmits torque to the drive nut 11 through the nut spline 10. Based on the working principle of the reverse planetary roller screw pair 4 (IPRSM), the redundant screw 9 generates axial movement, which drives the roller-drive nut assembly of the PRSM to move axially as a whole, thereby causing the drive nut 12 to output thrust.

[0081] During this process, the redundant lead screw 9 slides freely axially on the keyway in the main gear pair 5 via the lead screw spline 14, while the position of the main gear pair 5 remains fixed.

[0082] Understandably, during the main path operation, the planetary roller screw pair 8 works by converting the rotational motion of the redundant screw 9 into the linear motion of the drive nut 12 through multi-point contact between multiple rollers, the screw, and the nut. Therefore, the drive nut 12 has thrust. During the standby path operation, the reverse planetary roller screw pair works by converting the rotational motion of the transmission nut 11 into the axial motion of the external threaded sleeve 15 and the redundant screw 9. Because of the self-locking thread, the redundant screw 9 drives the drive nut 12 of the planetary roller screw pair 8 to output axial thrust.

[0083] Furthermore, the threads of the planetary roller screw pair 8 and the threads of the reverse planetary roller screw pair 4 both meet the self-locking condition.

[0084] In the planetary roller screw pair 8, the external threads of the redundant screw 9, the external threads of the roller 16, and the internal threads of the drive nut 12 have matched thread parameters and all satisfy the aforementioned self-locking conditions. When the active path fails and the backup path is put into operation, the main gear pair 5 driving the redundant screw 9 on the active path stops rotating, and the circumferential degree of freedom of the redundant screw 9 is locked, but the drive nut 12 still bears the external load force. This self-locking thread design can prevent relative rotation or axial slippage between the drive nut 12 and the redundant screw 9 due to the load force, ensuring that the axial displacement of the redundant screw 9 can be transmitted to the drive nut 12 without loss, so that the backup path can output a smooth, non-slip linear thrust.

[0085] In the reverse planetary roller screw pair 4, the internal thread of the transmission nut 11, the external thread of the reverse roller 22, and the external thread of the external threaded sleeve 15 have matched thread parameters and all satisfy the aforementioned self-locking conditions. On the one hand, when the active path is working normally, the circumferential rotation of the redundant screw 9 is circumferentially decoupled from the external threaded sleeve 15 through the axial connecting bearing group 13. This self-locking thread design can prevent accidental relative rotation or axial slippage between the transmission nut 11 and the external threaded sleeve 15, ensuring that the backup path is in a static locked state throughout and does not interfere with the main drive chain. On the other hand, when the backup path is working, this self-locking thread design can ensure that the rotational motion of the transmission nut 11 is accurately converted into the axial linear displacement of the external threaded sleeve 15, with no transmission slippage, ensuring that the axial movement speed and displacement of the redundant screw 9 are accurately controllable, and further ensuring the continuity of the output speed of the drive nut 12 during path switching.

[0086] Specifically, the thread self-locking condition is: the thread helix angle (lead angle) is less than or equal to its equivalent friction angle, expressed as:

[0087]

[0088] in, Indicates the thread helix angle (lead angle); This represents the equivalent friction angle.

[0089] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A dual-mode electromechanical actuator based on a planetary roller screw pair, characterized in that, It includes a main drive mechanism, a backup drive mechanism, a redundant lead screw, a drive nut, a transmission nut, rollers, reverse rollers, an axially connected bearing assembly, a limit mechanism, an external threaded sleeve, and a detection and control system. A planetary roller screw pair consists of a redundant lead screw, rollers, and a drive nut. The main drive mechanism and the planetary roller screw pair constitute the active path; one end of the redundant screw is engaged with the drive nut through roller threads, and the other end is connected to the main drive mechanism for transmission. The main drive mechanism drives the redundant screw to rotate circumferentially, thereby driving the drive nut to move linearly. The redundant lead screw is also connected to the transmission nut via an axially connected bearing assembly, a limiting mechanism, an external threaded sleeve, and a reverse roller, forming a reverse planetary roller lead screw pair. The backup drive mechanism, the reverse planetary roller screw pair, and the planetary roller screw pair constitute the backup path; the transmission nut is connected to the backup drive mechanism, and the backup drive mechanism drives the redundant screw to move axially, thereby driving the drive nut to move linearly. The external threaded sleeve is located between the transmission nut and the redundant lead screw, and is decoupled from the circumferential rotation of the redundant lead screw through an axially connected bearing assembly; The external threaded sleeve and the transmission nut are engaged by multiple reverse roller threads; The detection and control system includes a displacement sensor for detecting the actual axial displacement of the drive nut, a main encoder for detecting the rotational speed of the main drive mechanism, and a backup encoder for detecting the rotational speed of the backup drive mechanism. The detection and control system is configured to: when the active path is working, determine the fault by the deviation between the theoretical displacement signal of the drive nut obtained from the motor speed signal of the main encoder and the actual displacement signal of the drive nut collected by the displacement sensor; and when the active path is determined to be faulty, control the backup path to start, and calculate and control the speed of the backup motor based on the speed data before the fault recorded by the main encoder, so as to realize the continuous switching of the output speed of the drive nut.

2. The dual-mode electromechanical actuator according to claim 1, characterized in that, The main drive mechanism includes a main motor, a main reducer, and a main gear pair; the standby drive mechanism includes a standby motor, a standby reducer, and a standby gear pair.

3. The dual-mode electromechanical actuator according to claim 1, characterized in that, The limiting mechanism includes a cage and a retaining ring.

4. The dual-mode electromechanical actuator according to claim 2, characterized in that, One end of the redundant lead screw is an optical shaft, which is connected to the main gear pair via a lead screw spline; the outer wall of the transmission nut is provided with a nut spline, which is connected to the spare gear pair via the nut spline.

5. The dual-mode electromechanical actuator according to claim 1, characterized in that, The axially connected bearing assembly includes two bearings, with the inner ring fixed to the redundant lead screw and the outer ring fixed inside the external threaded sleeve.

6. The dual-mode electromechanical actuator according to claim 3, characterized in that, The multiple reverse rollers of the reverse planetary roller screw pair are evenly distributed circumferentially by a cage, and the cage is axially limited between the axially connected bearing assembly and the retaining ring.

7. The dual-mode electromechanical actuator according to claim 1, characterized in that, The threads of both the planetary roller screw pair and the reverse planetary roller screw pair satisfy the self-locking condition.

8. The dual-mode electromechanical actuator according to claim 1, characterized in that, The detection and control system determines an active path fault when the absolute value of the difference between the theoretical displacement signal and the actual displacement signal exceeds a preset threshold.

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