A screw drive fault mechanical redundant travel scaling electromechanical servo

Abstract

The present application relates to a kind of screw failure mechanical redundancy stroke scaling electromechanical servo mechanism, adopt multi-stage drive telescopic trapezoidal screw, as spare connection and transmission component, in the case of reduced reserve transmission efficiency and dynamic torque, ensure basic static bearing capacity, can significantly shorten the zero length of EMA mechanical redundancy scheme, suitable for application in narrow installation space occasion.

Description

TECHNICAL FIELD

[0001] The application relates to an electromechanical servo mechanism, in particular to a screw failure mechanical redundancy stroke scaling electromechanical servo mechanism BACKGROUND

[0002] The commonly used transmission component of a linear electromechanical servo mechanism is a screw, which is driven by high-speed rotation of a servo motor to reduce the speed of the screw through ball or thread contact collision, and then convert the linear motion of the screw nut. Since the transmission screw has the risk of jamming or sticking, the reliability and safety of the EMA are low. If the screw is redundantly designed to improve the reliability of the EMA, a set of screw components must be added, and the normal motion range must be restored after the positive and negative limit strokes. The biggest problem of the redundancy design is that the transmission component is complex, and the zero length of the electromechanical servo mechanism is long, which cannot be adapted to small installation space. Therefore, a short zero length transmission component redundancy electromechanical servo mechanism becomes a key problem. SUMMARY

[0003] The technical problem to be solved by the application is that the application provides a screw failure mechanical redundancy stroke scaling electromechanical servo mechanism. The mechanical transmission adopts a redundant series design, uses a multi-stage driving telescopic trapezoidal screw as a backup connection and transmission component, solves the problem of excessive zero length of the EMA redundancy design, ensures full load output of the main working screw, and reduces the load capacity of the backup transmission to a certain extent.

[0004] The technical scheme adopted by the application is that the application provides a screw failure mechanical redundancy stroke scaling electromechanical servo mechanism, which comprises a servo motor assembly, a roller screw pair assembly, an electromagnetic clutch assembly, a trapezoidal screw pair assembly and a connecting assembly.

[0005] The servo motor assembly is coaxially installed with the roller screw pair assembly, the electromagnetic clutch assembly is installed on the screw rod of the roller screw pair assembly, and the electromagnetic clutch assembly is coaxial with the servo motor assembly and has a reserved attraction gap.

[0006] The roller screw pair assembly is coaxially installed with the trapezoidal screw pair assembly, the electromagnetic clutch assembly is located at the intermediate position of the roller screw pair assembly and the trapezoidal screw pair assembly, and the connecting assembly realizes the connection between the electromechanical servo mechanism and external equipment.

[0007] During normal operation, the servo motor assembly drives the roller screw pair assembly to rotate as a fixed shaft after being powered on, the electromagnetic clutch assembly is powered off, the roller screw pair assembly moves in a reciprocating linear motion under the constraint of the electromagnetic clutch assembly to drive the trapezoidal screw pair assembly to move, the trapezoidal screw pair assembly is connected as a static bearing, and the reciprocating linear motion output of the electromechanical servo mechanism is realized.

[0008] When the roller screw pair assembly fails, the electromagnetic clutch assembly is powered on, the servo motor assembly drives the roller screw pair assembly and the electromagnetic clutch assembly to rotate together, drives the trapezoidal screw pair assembly to move, and realizes the reciprocating linear motion output of the electromechanical servo mechanism.

[0009] Further, the servo motor assembly includes a motor rotor, a motor stator, a motor housing, a motor front end cover, an actuator cylinder, and a clutch connecting tooth disc; the motor rotor is provided with a permanent magnet and a stainless steel sleeve on the surface, the motor rotor is integrated with the long screw nut of the roller screw pair assembly, the clutch connecting tooth disc is installed at one end of the long screw nut, the motor stator and the motor rotor are installed in the inner cavity of the motor housing, the motor stator and the motor rotor cooperate with each other, one end of the motor front end cover is installed at one end of the motor housing, and the other end of the motor front end cover is connected with the actuator cylinder.

[0010] Further, the roller screw pair assembly includes a long screw nut, a composite threaded screw rod, a planetary roller, and a retainer; the long screw nut is installed on the bearing seat in the motor housing and the motor front end cover through the angular contact ball bearings at both ends, a plurality of planetary rollers are installed in the corresponding holes of the retainer, the planetary rollers are installed at one end of the composite threaded screw rod, and the planetary rollers and the composite threaded screw rod constitute an integral moving assembly through planetary rotation and threaded engagement; the planetary rollers are installed in the long screw nut and are in contact and engagement with the threads on the inner surface of the long screw nut; the middle part of the composite threaded screw rod is a flat shaft section.

[0011] Further, the electromagnetic clutch assembly includes an outer spline hollow shaft, a moving double-sided spline tooth disc, an electromagnetic attraction coil, a reset spring, a fixed end face tooth disc, a bearing outer ring seat, and a bearing locking nut; the outer spline hollow shaft and the moving double-sided spline tooth disc are coaxially installed through inner and outer spline teeth and can move relative to each other; a pair of deep groove ball bearings are installed on the outer circle of the outer spline hollow shaft, the deep groove ball bearings are fixed by the bearing locking nut installed at the end, the deep groove ball bearings are also installed in the holes of the bearing outer ring seat and fixed by the hole retainer; one end of the fixed end face tooth disc is provided with teeth which cooperate with the teeth of the moving double-sided spline tooth disc, a plurality of reset springs are arranged at one end of the fixed end face tooth disc to reset the moving double-sided spline tooth disc, the electromagnetic attraction coil is installed in the U-shaped hole at the other end of the fixed end face tooth disc to attract the moving double-sided spline tooth disc; the fixed end face tooth disc is sleeved on the bearing outer ring seat, and the flange disc edges of the fixed end face tooth disc and the bearing outer ring seat are fixed on the stepped structure of the inner wall of the motor front end cover by a group of counterbore screws; the center hole of the outer spline hollow shaft is a flat hole, when the middle flat shaft part of the composite threaded screw rod can only translate relative to the flat hole of the outer spline hollow shaft, the planetary roller and the composite threaded screw rod constitute a planetary roller screw pair with the long screw nut and move reciprocally.

[0012] Further, the trapezoidal screw pair assembly includes a first-stage trapezoidal nut, a second-stage trapezoidal screw rod, a second-stage trapezoidal nut, a third-stage trapezoidal screw rod, a third-stage trapezoidal nut, a guide block, and a connecting screw.

[0013] The first-stage trapezoidal nut, the second-stage trapezoidal nut, and the third-stage trapezoidal nut are installed in the actuator cylinder and can reciprocate, the large end outer ring of the first-stage trapezoidal nut, the second-stage trapezoidal nut, and the third-stage trapezoidal nut is provided with a rectangular protrusion, the sidewall of the actuator cylinder is provided with a rectangular groove, the rectangular protrusion on the outer side of the third-stage trapezoidal nut is fixed with the guide block through the connecting screw, and the rectangular protrusions on the first-stage trapezoidal nut, the second-stage trapezoidal nut, and the third-stage trapezoidal nut and the rectangular groove on the sidewall of the actuator cylinder are matched with each other to constrain the rotational movement of the first-stage trapezoidal nut, the second-stage trapezoidal nut, and the third-stage trapezoidal nut.

[0014] The small end of the first-stage trapezoidal nut is inserted into the large end inner hole of the second-stage trapezoidal screw rod, and the threaded segment of the composite screw rod is inserted into the central hole of the first-stage trapezoidal nut and the second-stage trapezoidal screw rod; the small end of the second-stage trapezoidal nut is inserted into the large end inner hole of the third-stage trapezoidal screw rod, the threaded segment of the second-stage trapezoidal screw rod is inserted into the central hole of the second-stage trapezoidal nut and the third-stage trapezoidal screw rod, and the threaded segment of the third-stage trapezoidal screw rod is inserted into the central hole of the third-stage trapezoidal nut.

[0015] The inner surfaces of the first-stage trapezoidal nut and the second-stage trapezoidal nut are uniformly provided with four rectangular protrusions in the circumferential direction, the outer surfaces of the composite screw rod, the second-stage trapezoidal screw rod, and the third-stage trapezoidal screw rod are provided with trapezoidal threads and four rectangular grooves in the circumferential direction, the protrusions on the inner surfaces of the first-stage trapezoidal nut and the second-stage trapezoidal nut are matched with the rectangular grooves of the composite screw rod, the second-stage trapezoidal screw rod, and the third-stage trapezoidal screw rod to drive the first-stage trapezoidal nut, the second-stage trapezoidal nut, and the third-stage trapezoidal nut to reciprocate linearly, and the small end of the third-stage trapezoidal nut extends out of the actuator cylinder.

[0016] Further, the trapezoidal screw pair assembly further includes a shear steel ball and a locking screw, the small end outer surfaces of the first-stage trapezoidal nut and the second-stage trapezoidal nut are provided with two annular grooves, the large end sidewalls of the second-stage trapezoidal screw rod and the third-stage trapezoidal screw rod are provided with locking screw mounting holes, the shear steel ball and the locking screw are limited in the two annular grooves and the locking screw mounting holes to play a shearing bearing role.

[0017] Further, the connecting assembly includes a front support ear and a rear support ear, the front support ear is connected to the end of the third-stage trapezoidal nut extending out of the actuator cylinder through threads, and the front support ear and the rear support ear are provided with connecting pin holes to be connected to other external parts for bearing.

[0018] Further, the connecting assembly comprises long bolts and nuts; the flange surface and rear support lug of the actuating cylinder are provided with through holes, and the actuating cylinder and the rear support lug are respectively connected with the through holes on the two end surfaces of the motor shell through the long bolts and nuts.

[0019] In normal operation, after the servo motor assembly is powered on, the driving motor rotor and the screw nut of the roller screw pair assembly make fixed shaft rotation, at this time the electromagnetic clutch assembly is powered off, under the fixed constraint of the fixed end surface tooth disc of the electromagnetic clutch assembly and the front end cover of the motor, the flat shaft of the composite screw rod and the flat hole of the outer spline hollow shaft limit the composite screw rod of the roller screw pair assembly to only make reciprocating linear motion with a stroke of (-L, +L), the first stage,

[0020] The second stage and the third stage trapezoidal screw thread are static bearing connections, and reserve a stroke of (-4L / 3, +4L / 3) to drive the front support lug to realize the reciprocating linear motion output of the electromechanical servo mechanism.

[0021] In case of failure, if the thread teeth of the roller screw pair assembly are broken or damaged to cause jamming failure, the electromagnetic clutch assembly is powered on, the electromagnetic attraction coil attracts the moving double-fluted spline disc to combine with the clutch connecting tooth disc, the thread transmission of the roller screw pair assembly becomes a static bearing connection and rotates together, the servo motor assembly drives the composite screw rod to make fixed shaft rotation, drives the first stage trapezoidal nut to make linear motion under the limitation of the side wall groove of the actuating cylinder, the first stage trapezoidal nut pushes the second stage trapezoidal screw rod linearly by using the shear steel ball and the set screw, at the same time, the key groove at the outer thread of the composite screw rod is matched with the key of the second stage trapezoidal screw rod, drives the second stage trapezoidal screw rod to make circular motion, so that the second stage trapezoidal nut makes linear motion under the limitation of the side wall groove of the actuating cylinder, the second stage trapezoidal nut pushes the third stage trapezoidal screw rod linearly by using the shear steel ball and the set screw, the key groove at the outer thread of the second stage trapezoidal screw rod is matched with the key of the third stage trapezoidal screw rod, drives the third stage trapezoidal screw rod to make circular motion, so that the third stage trapezoidal nut makes linear motion under the limitation of the side wall groove of the actuating cylinder, drives the front support lug to make linear motion, finally the three groups of trapezoidal screws make a stroke scaling of (-L / 3, +L / 3), realize the function and performance recovery of the roller screw pair assembly at +L position failure and -L position failure respectively;

[0022] L is the relative distance between the actuating cylinder and the first stage trapezoidal nut.

[0023] Compared with the prior art, the present application has the following advantages:

[0024] (1) The present application provides a screw failure mechanical redundant stroke scaling electromechanical servo mechanism, which uses a multi-stage driving telescopic trapezoidal screw as a backup connection and transmission component, solves the problem of excessive zero length in EMA redundant design, and ensures full load output of the main working screw while the trapezoidal screw backup outputs at a reduced capacity.

[0025] (2) The present application provides a screw failure mechanical redundant stroke scaling electromechanical servo mechanism, which can significantly shorten the zero length and ensure the carrying capacity, and to a certain extent, reduce the carrying capacity of the backup transmission. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a schematic diagram of the internal composition of a screw failure mechanical redundant stroke scaling electromechanical servo mechanism provided by an embodiment of the present application;

[0027] Figure 2 is a schematic diagram of the external shape of the second-stage trapezoidal screw and the third-stage trapezoidal screw provided by an embodiment of the present application;

[0028] Figure 3 is a schematic diagram of the external shape of the composite screw provided by an embodiment of the present application;

[0029] Figure 4 is a schematic diagram of the external shape of the first-stage trapezoidal nut and the second-stage trapezoidal nut provided by an embodiment of the present application;

[0030] Figure 5 is a cross-sectional view of a trapezoidal transmission assembly of a screw failure mechanical redundant stroke scaling electromechanical servo mechanism provided by an embodiment of the present application. DETAILED DESCRIPTION

[0031] The present application is described in conjunction with the drawings.

[0032] As shown in Figures 1-5 , a screw failure mechanical redundant stroke scaling electromechanical servo mechanism includes a servo motor assembly, a roller screw pair assembly, an electromagnetic clutch assembly, a trapezoidal screw pair assembly, and a connection assembly.

[0033] The servo motor assembly includes a motor rotor 1a, a motor stator 1b, a motor housing 1c, a motor front end cover 1d, an actuator cylinder 1e, and a clutch connecting tooth disc 1f. The motor rotor 1a has a permanent magnet and a stainless steel sleeve attached to its surface, and is integrated with a screw pair long nut 2a. The right end of the screw pair long nut 2a is fixedly connected to the clutch connecting tooth disc 1f, and the screw pair long nut 2a has a pair of angular contact ball bearings at both ends. The motor stator 1b is hot-mounted in the inner cavity of the motor housing 1c, and the bearing outer ring is connected to the seat hole of the motor front end cover 1d. One end of the motor front end cover 1d is installed at one end of the motor housing 1c, and the other end of the motor front end cover 1d is connected to the actuator cylinder 1e.

[0034] The roller screw pair assembly includes a screw pair long nut 2a, a composite screw rod 2b, a planetary roller 2c, and a retainer 2d. The screw pair long nut 2a is installed in the bearing seat in the motor housing 1c and the motor front end cover 1d through the angular contact ball bearings at both ends. The left side of the composite screw rod 2b is provided with external threads. A plurality of planetary rollers 2c are installed in the corresponding holes of the retainer 2d. The external threads of the planetary rollers 2c are in contact with the external threads of the composite screw rod 2b. The planetary rollers 2c are installed in the screw pair long nut 2a, and the external threads of the rollers are in contact with and engaged with the threads on the inner surface of the long nut 2a. The middle part of the composite screw rod 2b is a flat shaft section. When the middle flat shaft section of the composite screw rod 2b can only move relative to the flat hole of the external spline hollow shaft 3a, the moving assembly and the long nut 2a form a planetary roller screw pair, and make reciprocating movement.

[0035] The electromagnetic clutch assembly includes an external spline hollow shaft 3a, a moving double-sided spline tooth disc 3b, an electromagnetic attraction coil 3c, a reset spring 3d, a fixed end face tooth disc 3e, a bearing outer ring seat 3f, and a bearing locking nut 3g. The external spline hollow shaft 3a and the moving double-sided spline tooth disc 3b are coaxially installed through the inner and outer spline teeth, and can move relative to each other. A pair of deep groove ball bearings are installed on the outer ring of the external spline hollow shaft 3a, and the inner ring is fixed by the bearing locking nut 3g. The bearings are also installed in the holes of the bearing outer ring seat 3f, and are fixed by the hole retainer. One end of the fixed end face tooth disc 3e is provided with teeth, which can cooperate with the teeth of the moving double-sided spline tooth disc 3b, and a plurality of reset springs 3d are circumferentially arranged to reset the moving double-sided spline tooth disc 3b. The electromagnetic attraction coil 3c is installed in the U-shaped hole at one end of the fixed end face tooth disc 3e by hot installation, and can attract the moving double-sided spline tooth disc 3b. The fixed end face tooth disc 3e is sleeved on the bearing outer ring seat 3f. The flange plate edges of the fixed end face tooth disc 3e and the bearing outer ring seat 3f are fixed to the stepped structure on the inner wall of the motor front end cover 1d by a group of counterbore screws. The center hole of the external spline hollow shaft 3a is a flat hole.

[0036] The trapezoidal lead screw assembly includes a first-stage trapezoidal nut 4a, a second-stage trapezoidal lead screw 4b, a second-stage trapezoidal nut 4c, a third-stage trapezoidal lead screw 4d, a third-stage trapezoidal nut 4e, a shearing steel ball 4f, a set screw 4g, a guide block 4h, and a connecting screw 4i. The first-stage trapezoidal nut 4a, the second-stage trapezoidal nut 4c, and the third-stage trapezoidal nut 4e are cylindrical in shape and can all be installed inside the actuating cylinder 1e, enabling reciprocating movement. The outer rings of the first-stage trapezoidal nut 4a, the second-stage trapezoidal nut 4c, and the third-stage trapezoidal nut 4e are also provided with rectangular protrusions. A rectangular groove is provided on one side of the actuating cylinder 1e. The rectangular protrusion on the outer side of the third-stage trapezoidal nut 4e is fixed to the guide block 4h by the connecting screw 4i. The protrusions on the first-stage trapezoidal nut 4a, the second-stage trapezoidal nut 4c, and the third-stage trapezoidal nut 4e are aligned with the side wall of the actuating cylinder 1e. The interlocking rectangular grooves constrain the rotational movement of the first-stage trapezoidal nut 4a, the second-stage trapezoidal nut 4c, and the third-stage trapezoidal nut 4e. The small end of the first-stage trapezoidal nut 4a is inserted into the inner hole of the large end of the second-stage trapezoidal screw 4b, and the threaded section of the other end of the compound threaded screw 2b is inserted into the center hole of the first-stage trapezoidal nut 4a and the second-stage trapezoidal screw 4b. The small end of the second-stage trapezoidal nut 4c is inserted into the inner hole of the large end of the third-stage trapezoidal screw 4d, and the threaded section of the second-stage trapezoidal screw 4b is inserted into the center hole of the second-stage trapezoidal nut 4c and the third-stage trapezoidal screw 4d. In the hole, the threaded section of the third-stage trapezoidal screw 4d is inserted into the center hole of the third trapezoidal nut 4e; the outer surface of the small end of the first-stage trapezoidal nut 4a and the second-stage trapezoidal nut 4c is also provided with two annular grooves, and the side wall of the large end of the second-stage trapezoidal screw 4b and the third-stage trapezoidal screw 4d is provided with set screw mounting holes. The shearing steel ball 4f and the set screw 4g are confined within the two annular grooves and the set screw mounting holes, playing a shearing load-bearing role; the inner surface of the first-stage trapezoidal nut 4a and the second-stage trapezoidal nut 4c is provided with four rectangular protrusions around the circumference, and the composite thread... The outer surfaces of rod 2b, second-stage trapezoidal lead screw 4b, and third-stage trapezoidal lead screw 4d are provided with trapezoidal threads, and four rectangular grooves are evenly provided around the circumference. The inner surface protrusions of first-stage trapezoidal nut 4a and second-stage trapezoidal nut 4c and the grooves of composite threaded lead screw 2b, second-stage trapezoidal lead screw 4b, and third-stage trapezoidal lead screw 4d move and cooperate with each other, which can drive the first-stage trapezoidal nut 4a, second-stage trapezoidal nut 4c, and third-stage trapezoidal nut 4e to reciprocate linearly. The other end of the third-stage trapezoidal nut 4e is connected to the front support lug 5a by a thread.

[0037] The connecting assembly includes a front lug 5a, a rear lug 5b, long bolts 5c, and nuts 5d. The flange face of the actuator cylinder 1e and the rear lug 5b each have four through holes, which are threaded together using four sets of long bolts 5c and nuts 5d to the four through holes on both ends of the motor housing 1c. The front lug 5a and rear lug 5b have connecting pin holes for load-bearing connections with other external parts.

[0038] Working principle:

[0039] The servo motor assembly and the roller screw assembly are coaxially mounted, and the rotor of the servo motor assembly and the internal threaded long nut of the roller screw assembly are integrated into one piece to form a hollow structure. One end of the electromagnetic clutch assembly's movable toothed disc can be coaxial with one end of the fixed toothed disc of the servo motor rotor, with a certain engagement gap reserved. The outer ring of the bearing of the electromagnetic clutch assembly is tightly fitted with the composite threaded screw of the roller screw assembly, and a flat shaft and flat hole are provided for movable connection. The roller screw assembly and the trapezoidal screw assembly are coaxially mounted, and the first-stage screw of the trapezoidal screw assembly and the screw of the roller screw assembly share the same part. The electromagnetic clutch assembly is located in the middle position of the roller screw assembly and the trapezoidal screw assembly. The connecting assembly connects the front and rear ends of the above components to form an electromechanical servo mechanism, realizing the connection with the outside.

[0040] During normal operation, after the servo motor assembly is powered on, it drives the rotor 1a and the long nut 2a of the roller screw assembly to rotate on the fixed shaft. At this time, the electromagnetic clutch assembly is de-energized. Under the fixed constraint of the fixed end face toothed plate 3e of the electromagnetic clutch assembly and the front end cover 1d of the motor, the composite thread screw 2b of the roller screw assembly is restricted to reciprocating linear motion with a stroke of (-L, +L) by the flat shaft of the composite thread screw 2b and the flat hole of the external spline hollow shaft 3a. The first, second and third trapezoidal threads of the trapezoidal screw assembly are used as static load connections and are reserved for a stroke of (-4L / 3, +4L / 3), which drives the external support to realize the reciprocating linear motion output of the electromechanical servo mechanism.

[0041] During malfunction, the thread teeth of the roller screw assembly break or become damaged, causing a jamming / sticking fault. After the electromagnetic clutch assembly is energized, its electromagnetic engagement coil 3c engages the double-sided splined toothed disc 3b, which then engages with the clutch connecting toothed disc 1f. The threaded transmission of the roller screw assembly becomes a static load connection, and they rotate together. The servo motor assembly drives the first-stage trapezoidal screw (i.e., the compound threaded screw 2b) of the trapezoidal screw assembly to rotate on a fixed axis. This causes the first-stage trapezoidal nut 4a to send linear motion under the rotational constraint of the side wall groove of the actuator cylinder 1e. The shearing steel ball 4f and the set screw 4g push the second-stage trapezoidal screw 4b to move linearly. At the same time, the external thread of the first-stage trapezoidal screw has a keyway that passes through the inner cavity of the second-stage trapezoidal screw and engages with the key of the second-stage trapezoidal screw 4b, causing the second-stage trapezoidal screw 4b to rotate. The rotational motion causes the second-stage trapezoidal nut 4c to move linearly under the rotational constraint of the protrusion on the actuator cylinder 1e. Similarly, the second-stage trapezoidal nut 4c uses the shear steel ball 4f and the set screw 4g to drive the third-stage trapezoidal screw 4d to move linearly. The keyway at the external thread of the second-stage trapezoidal screw 4b engages with the key of the third-stage trapezoidal screw 4d, causing the third-stage trapezoidal screw 4d to rotate. This causes the third-stage trapezoidal nut 4e to move linearly under the constraint of the side wall groove of the actuator cylinder 1e. The first-stage trapezoidal screw and nut drive the front support lug 5a to move linearly. Finally, the three sets of trapezoidal screws experience a stroke scaling of (-L / 3, +L / 3), realizing the functional and performance recovery of the roller screw assembly in the +L and -L position faults, respectively. L is the relative distance between the actuator cylinder 1e and the first-stage trapezoidal nut 4a.

[0042] The parts of this invention not described in detail are well-known to those skilled in the art.

Claims

1. A lead screw failure mechanical redundancy stroke scaling electromechanical servo mechanism, characterized in that, include: Servo motor assembly, roller screw assembly, electromagnetic clutch assembly, trapezoidal screw assembly, connecting assembly; The servo motor assembly and the ball screw assembly are mounted coaxially. The electromagnetic clutch assembly is mounted on the lead screw of the ball screw assembly. The electromagnetic clutch assembly is coaxial with the servo motor assembly and has a reserved engagement gap. The roller screw assembly and the trapezoidal screw assembly are coaxially mounted. The electromagnetic clutch assembly is located in the middle of the roller screw assembly and the trapezoidal screw assembly. The connecting assembly enables the electromechanical servo mechanism to connect with external equipment. During normal operation, when the servo motor assembly is powered on, it drives the roller screw assembly to rotate on a fixed axis. When the electromagnetic clutch assembly is de-energized, the roller screw assembly reciprocates linearly under the constraint of the electromagnetic clutch assembly, driving the trapezoidal screw assembly to move. The trapezoidal screw assembly acts as a static load-bearing connection, realizing the reciprocating linear motion output of the electromechanical servo mechanism. When the roller screw assembly fails, the electromagnetic clutch assembly is energized, and the servo motor assembly drives the roller screw assembly and the electromagnetic clutch assembly to rotate together, driving the trapezoidal screw assembly to move and realizing the reciprocating linear motion output of the electromechanical servo mechanism. During normal operation, after the servo motor assembly is powered on, the drive motor rotor (1a) together with the long nut (2a) of the ball screw assembly rotates on the fixed shaft. At this time, the electromagnetic clutch assembly is de-energized. Under the fixed constraint of the fixed end face toothed plate (3e) of the electromagnetic clutch assembly and the front end cover (1d) of the motor, the composite threaded screw (2b) of the ball screw assembly is restricted to only perform reciprocating linear motion with a stroke of (-L, +L) by the flat shaft of the composite threaded screw (2b) and the flat hole of the external spline hollow shaft (3a). The first, second and third trapezoidal threads of the trapezoidal screw assembly are used as static load connections and are reserved for a stroke of (-4L / 3, +4L / 3), which drives the front support (5a) to realize the reciprocating linear motion output of the electromechanical servo mechanism. When the roller screw assembly malfunctions, the thread teeth of the roller screw pair may break or be damaged, causing a jamming / sticking fault. The electromagnetic clutch assembly is energized, and its electromagnetic engagement coil (3c) engages the moving double-sided splined toothed disc (3b) with the clutch connecting toothed disc (1f). The threaded transmission of the roller screw pair assembly becomes a static load connection and rotates together. The servo motor assembly drives the composite threaded screw (2b) to perform fixed-axis rotation, causing the first-stage trapezoidal nut (4a) to move linearly under the constraint of the side wall groove of the actuator cylinder (1e). The first-stage trapezoidal nut (4a) uses the shearing steel ball (4f) and the set screw (4g) to push the second-stage trapezoidal screw (4b) to move linearly. At the same time, the keyway at the external thread of the composite threaded screw (2b) engages with the key of the second-stage trapezoidal screw (4b), driving the second-stage... The trapezoidal screw (4b) rotates, causing the second-stage trapezoidal nut (4c) to move linearly under the constraint of the side wall groove of the actuator (1e). The second-stage trapezoidal nut (4c) uses the shearing steel ball (4f) and the set screw (4g) to push the third-stage trapezoidal screw (4d) to move linearly. The keyway at the external thread of the second-stage trapezoidal screw (4b) engages with the key of the third-stage trapezoidal screw (4d), causing the third-stage trapezoidal screw (4d) to rotate. This causes the third-stage trapezoidal nut (4e) to move linearly under the constraint of the side wall groove of the actuator (1e), which in turn causes the front support (5a) to move linearly. Finally, the three sets of trapezoidal screws experience a stroke scaling of (-L / 3, +L / 3), realizing the functional and performance recovery of the roller screw assembly in the +L position fault and the -L position fault, respectively. L is the relative distance between the actuator (1e) and the first-stage trapezoidal nut (4a).

2. The lead screw fault mechanical redundancy stroke scaling electromechanical servo mechanism according to claim 1, characterized in that, The servo motor assembly includes a motor rotor (1a), a motor stator (1b), a motor housing (1c), a motor front end cover (1d), an actuator cylinder (1e), and a clutch connecting sprocket (1f). The surface of the motor rotor (1a) is covered with a permanent magnet and a stainless steel sleeve. The motor rotor (1a) is integrated with the lead screw pair long nut (2a) of the roller lead screw pair assembly. The clutch connecting sprocket (1f) is installed at one end of the lead screw pair long nut (2a). The motor stator (1b) and the motor rotor (1a) are installed in the inner cavity of the motor housing (1c). The motor stator (1b) and the motor rotor (1a) cooperate with each other. One end of the motor front end cover (1d) is installed at one end of the motor housing (1c), and the other end of the motor front end cover (1d) is connected to the actuator cylinder (1e).

3. The lead screw fault mechanical redundancy stroke scaling electromechanical servo mechanism according to claim 2, characterized in that, The ball screw assembly includes a ball screw pair nut (2a), a composite threaded ball screw (2b), planetary rollers (2c), and a cage (2d). The ball screw pair nut (2a) is mounted on bearing seats in the motor housing (1c) and the motor front end cover (1d) respectively through angular contact ball bearings at both ends. Several planetary rollers (2c) are installed in corresponding holes in the cage (2d). The planetary rollers (2c) are installed at one end of the composite threaded ball screw (2b), forming an integral moving assembly through planetary rotation and threaded meshing motion. The planetary rollers (2c) are installed in the ball screw pair nut (2a) and contact and mesh with the threads on the inner surface of the ball screw pair nut (2a). The middle part of the composite threaded ball screw (2b) is a flat shaft section.

4. The lead screw fault mechanical redundancy stroke scaling electromechanical servo mechanism according to claim 3, characterized in that, The electromagnetic clutch assembly includes an external spline hollow shaft (3a), a movable double-spline toothed sprocket (3b), an electromagnetic engagement coil (3c), a return spring (3d), a fixed end face toothed sprocket (3e), a bearing outer ring seat (3f), and a bearing lock nut (3g). The external spline hollow shaft (3a) and the movable double-spline toothed sprocket (3b) are coaxially mounted via internal and external spline teeth, allowing relative movement between them. A pair of deep groove ball bearings are mounted on the outer ring of the external spline hollow shaft (3a), and the inner ring of the deep groove ball bearings is fixed by the bearing lock nut (3g) installed at the end. The deep groove ball bearings are also installed in the holes of the bearing outer ring seat (3f) and fixed by retaining rings. One end of the fixed end face toothed sprocket (3e) has teeth that engage with the teeth of the movable double-spline toothed sprocket (3b), and several teeth are set around one end of the circumference. A return spring (3d) resets the movable double-sided splined toothed plate (3b). An electromagnetic attraction coil (3c) is installed in the U-shaped hole at the other end of the fixed end face toothed plate (3e) to attract the movable double-sided splined toothed plate (3b). The fixed end face toothed plate (3e) is fitted on the outer ring seat of the bearing (3f). The flange edges of the fixed end face toothed plate (3e) and the outer ring seat of the bearing (3f) are fixed to the stepped structure on the inner wall of the motor front end cover (1d) by a set of countersunk screws. The center hole of the hollow external spline shaft (3a) is a flat hole. When the middle flat shaft part of the composite thread screw (2b) can only translate relative to the flat hole of the hollow external spline shaft (3a), the planetary roller (2c) and the composite thread screw (2b) and the screw pair long nut (2a) constitute a planetary roller screw pair and reciprocate.

5. The lead screw fault mechanical redundancy stroke scaling electromechanical servo mechanism according to claim 4, characterized in that, The trapezoidal lead screw assembly includes a first-stage trapezoidal nut (4a), a second-stage trapezoidal lead screw (4b), a second-stage trapezoidal nut (4c), a third-stage trapezoidal lead screw (4d), a third-stage trapezoidal nut (4e), a guide block (4h), and a connecting screw (4i). The first-stage trapezoidal nut (4a), the second-stage trapezoidal nut (4c), and the third-stage trapezoidal nut (4e) are all installed inside the actuator cylinder (1e) and can reciprocate. The outer ring of the large end of the first-stage trapezoidal nut (4a), the second-stage trapezoidal nut (4c), and the third-stage trapezoidal nut (4e) is provided with a rectangular protrusion, and a rectangular groove is provided on the side wall of the actuator cylinder (1e). The rectangular protrusion on the outer side of the third-stage trapezoidal nut (4e) is fixed to the guide block (4h) by the connecting screw (4i). The rectangular protrusion on the first-stage trapezoidal nut (4a), the second-stage trapezoidal nut (4c), and the third-stage trapezoidal nut (4e) and the rectangular groove on the side wall of the actuator cylinder (1e) cooperate with each other to constrain the rotational movement of the first-stage trapezoidal nut (4a), the second-stage trapezoidal nut (4c), and the third-stage trapezoidal nut (4e). The small end of the first-stage trapezoidal nut (4a) is inserted into the inner hole of the large end of the second-stage trapezoidal screw (4b), and the threaded section of the other end of the compound threaded screw (2b) is inserted into the center hole of the first-stage trapezoidal nut (4a) and the second-stage trapezoidal screw (4b); the small end of the second-stage trapezoidal nut (4c) is inserted into the inner hole of the large end of the third-stage trapezoidal screw (4d), the threaded section of the second-stage trapezoidal screw (4b) is inserted into the center hole of the second-stage trapezoidal nut (4c) and the third-stage trapezoidal screw (4d), and the threaded section of the third-stage trapezoidal screw (4d) is inserted into the center hole of the third-stage trapezoidal nut (4e); The inner surfaces of the first-stage trapezoidal nut (4a) and the second-stage trapezoidal nut (4c) are uniformly provided with four rectangular protrusions around the circumference. The outer surfaces of the composite threaded screw (2b), the second-stage trapezoidal screw (4b), and the third-stage trapezoidal screw (4d) are provided with trapezoidal threads and four rectangular grooves uniformly provided around the circumference. The inner surface protrusions of the first-stage trapezoidal nut (4a) and the second-stage trapezoidal nut (4c) and the rectangular grooves of the composite threaded screw (2b), the second-stage trapezoidal screw (4b), and the third-stage trapezoidal screw (4d) move and cooperate with each other, which can drive the first-stage trapezoidal nut (4a), the second-stage trapezoidal nut (4c), and the third-stage trapezoidal nut (4e) to reciprocate linearly. The small end of the third-stage trapezoidal nut (4e) extends out from the actuator (1e).

6. The lead screw fault mechanical redundancy stroke scaling electromechanical servo mechanism according to claim 5, characterized in that, The trapezoidal lead screw assembly also includes a shearing steel ball (4f) and a set screw (4g). Two annular grooves are provided on the outer surface of the small end of the first-stage trapezoidal nut (4a) and the second-stage trapezoidal nut (4c). Set screw mounting holes are provided on the side wall of the large end of the second-stage trapezoidal lead screw (4b) and the third-stage trapezoidal lead screw (4d). The shearing steel ball (4f) and the set screw (4g) are confined within the two annular grooves and the set screw mounting holes, thus playing a shearing and bearing role.

7. The lead screw fault mechanical redundancy stroke scaling electromechanical servo mechanism according to claim 6, characterized in that, The connecting assembly includes a front support lug (5a) and a rear support lug (5b). The front support lug (5a) is connected to the end of the actuator cylinder (1e) by a threaded connection with a third trapezoidal nut (4e). The front support lug (5a) and the rear support lug (5b) are provided with connecting pin holes for load-bearing connection with other external parts.

8. The lead screw fault mechanical redundancy stroke scaling electromechanical servo mechanism according to claim 7, characterized in that, The connecting assembly includes a long bolt (5c) and a nut (5d); the flange face and rear support lug (5b) of the actuator (1e) are provided with through holes, and the actuator (1e) and the rear support lug (5b) are threadedly connected to the through holes on both ends of the motor housing (1c) by the long bolt (5c) and the nut (5d).

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