Engine servo load torque reduction device

Abstract

The application belongs to the technical field of aerospace engines, and particularly relates to an engine servo load torque reducing device, which comprises a buffer assembly, a compensation assembly and a force bearing assembly; the force bearing assembly is used for sharing the torque of an engine servo brake, and is arranged on a force bearing base of a rocket body; the compensation assembly is used for providing power compensation for the servo brake, and is arranged in the rocket body; the force bearing assembly comprises a fixed base and a lever rocker arm, the fixed base is fixedly installed on the force bearing base of the rocket body, the lever rocker arm is hingedly installed on the fixed base, and the lever rocker arm is hingedly connected with an engine nacelle through an extension piece. Most of the load torques can be transmitted to the force bearing base of the rocket body through the lever rocker arm and the fixed base, and most of the torque loads originally required to be borne by the servo brake can be borne and removed.

Description

Technical Field

[0001] This invention belongs to the field of aerospace engine technology, and specifically relates to an engine servo load torque reduction device. Background Technology

[0002] In aerospace, rocket launch, and other fields, the engine, as the core power unit, directly determines the attitude stability and operational reliability of the entire aircraft through the control precision and load-bearing capacity of its servo brakes. To achieve attitude adjustments such as pitch and yaw, the engine typically needs to drive the casing and exhaust nozzle to make small-angle oscillating movements via servo actuators. During this process, the servo mechanism must continuously withstand the overturning moment generated by the engine operation, the self-weight off-center load moment, and the impact moment brought by aerodynamic loads during flight, forming a significant servo load burden.

[0003] A search revealed that Chinese Patent Publication No. CN116658332B, authorized on January 30, 2026, discloses a device for reducing the servo load torque of a reusable rocket's return stage engine. This device includes a central engine and multiple skirts, which are foldable and evenly arranged circumferentially on the outer wall of the thrust chamber of the central engine. This application offers the following anticipated technical advantages: the device significantly reduces the aerodynamic load torque of the central engine servo system during the return phase, greatly reducing the design difficulty of the central engine servo system and lowering the development cost of the reusable rocket; the skirts are folded during the ascent and return phases, fitting snugly against the outer wall of the central engine's thrust chamber, without affecting the central engine's oscillation operation; the skirts are controlled by linear servos, resulting in a simple structure that can be freely folded and unfolded.

[0004] However, the device still has the following defects: In the process of use, the existing torque reduction device can only achieve static torque sharing by using a rigid load-bearing structure. When subjected to instantaneous impact, it cannot buffer the impact, causing the torque to directly impact the servo brake, affecting the service life of the servo brake and failing to provide protection for the servo brake. Summary of the Invention

[0005] To address the above problems, the present invention provides an engine servo load torque reduction device, comprising a buffer assembly, a compensation assembly, and a load-bearing assembly; The load-bearing component is used to share the torque of the engine servo brake, and the load-bearing component is installed on the load-bearing base of the rocket body; The compensation component is used to provide power compensation for the servo brake, and the compensation component is installed inside the arrow body; The load-bearing component includes a fixed base and a lever rocker arm. The fixed base is fixedly installed on the load-bearing base of the arrow body, and the lever rocker arm is hingedly installed on the fixed base. The lever rocker arm is hinged to the engine casing through a telescopic member.

[0006] In one embodiment of this application, the telescopic member includes a movable rod, a first piston, a first spring, and a fixed tube. The first piston is slidably installed inside the fixed tube. One end of the movable rod is fixedly connected to the first piston, and the other end of the movable rod is provided with a first ball joint. The movable rod is hinged to the engine casing through the first ball joint. One end of the fixed tube is hinged to one end of the lever rocker arm through a first constant level seat. One end of the first spring is fixedly connected inside the fixed tube, and the other end of the first spring is fixedly connected to the first piston.

[0007] In one embodiment of this application, the compensation component includes an air storage tube, a movable tube, a second constant level seat, and a second ball joint. The movable tube is slidably installed inside the movable tube. The air storage tube is connected to the fixed tube. The air storage tube is hinged to the load-bearing base of the rocket body through the second constant level seat. The movable tube is hinged to the engine casing through the second ball joint.

[0008] In one embodiment of this application, a second piston is provided on the side wall of the movable tube, and the second piston slides in cooperation with the inner wall of the gas storage tube.

[0009] In one embodiment of this application, the load-bearing components are provided in at least two sets, and the load-bearing components are arranged in a circular array with respect to the central axis of the engine casing.

[0010] In one embodiment of this application, the compensation components are provided in at least two sets, and the compensation components are arranged in a circular array with respect to the central axis of the engine casing.

[0011] In one embodiment of this application, a second spring is provided inside the gas storage pipe, and one end of the second spring is fixedly connected to the inner wall of the movable pipe.

[0012] In one embodiment of this application, a linkage mechanism is provided on the lever rocker arm, and the linkage mechanism is used to unload the force on the lever rocker arm.

[0013] In one embodiment of this application, the linkage mechanism includes a driven link and a limiting support. One end of the driven link is hinged to one end of the lever rocker arm, and the other end of the driven link is hinged to the limiting support. The limiting support is fixedly installed on the load-bearing base of the arrow body. An engine servo load torque reduction device, the torque reduction method comprising: Multiple load-bearing components are arranged in a circular array on the load-bearing base of the rocket body. When the engine servo drives the casing to swing and generate overturning moment, self-weight moment and aerodynamic moment, most of the load moment of the engine casing is directly transferred to the load-bearing base of the rocket body through the lever rocker arm and driven connecting rod, and the load-bearing base of the rocket body shares the load. A buffer assembly is set between the lever rocker arm and the engine casing. The telescopic structure composed of the fixed tube, the first piston, the first spring, and the movable rod, combined with the universal self-adaptive characteristics of the ball joint and the constant level seat, is used to adapt to the multi-directional compound swing angle of the engine. During the swing of the engine casing, the first spring extends and retracts to absorb energy, absorb impact load and vibration load, and avoid the rigid torque being directly applied to the servo brake, so as to achieve dynamic buffer load reduction. The compensation component, which is connected to the buffer component, allows the movable tube to slide within the air reservoir under the guidance of the second piston when the engine casing tilt angle changes. This, combined with the elastic deformation of the second spring and the communication between the air chamber pressure, provides elastic and pneumatic assistance for the engine tilt reset, reducing the off-center load resistance and the continuous push-pull output force of the servo brake.

[0014] The beneficial effects of this invention are: 1. The lever rocker arm forms a lever force-bearing structure with the fixed base as the hinge fulcrum. One end is flexibly hinged to the engine casing through the telescopic component. It can bear the overturning moment, aerodynamic load moment and self-weight off-center load moment generated during the servo swing of the engine casing in real time. It also transmits most of the load moment to the load-bearing base of the rocket body through the lever rocker arm and the fixed base. It can bear and unload most of the torque load that the servo brake originally needs to bear.

[0015] 2. By using the sliding fit between the first piston and the fixed tube and the elastic deformation of the first spring, the impact load and vibration during the engine swaying process are absorbed, avoiding the direct transmission of rigid torque. With the help of the universal adaptive characteristics of the first ball joint and the first constant level seat, the combined angle generated by the pitch or yaw sway of the engine is compensated in real time, ensuring that the torque transmission direction is adapted to the swaying posture of the engine casing, and without restricting the normal swaying motion of the engine casing. The sliding structure of the first spring and the first piston forms an elastic buffer system. When the engine sways, the first spring softens the instantaneous load by contracting to absorb energy, reducing the impact of torque on the lever rocker arm and servo brake, while avoiding the motion jamming problem caused by rigid connection, thus improving the smoothness of the device operation.

[0016] 3. The second spring undergoes elastic deformation as the movable tube elongates, superimposed with the high pressure in the air chamber to form a dual compensating force. This force is applied along the tangential direction of the casing's swing, which not only offsets part of the inertial resistance and overturning moment generated by the engine's swing, but also assists in the casing's attitude recovery. This can reduce the load resistance that needs to be overcome when the servo brake is driven, and can provide power compensation for the swing of the engine casing. 4. The linkage mechanism transmits the engine swaying torque, overturning torque and aerodynamic load borne by the lever rocker arm to the limit support fixed to the rocket body bearing base through the driven link. This directly shares the core bearing pressure of the lever rocker arm, avoids torque concentration, and prevents overload of the lever rocker arm, thereby indirectly reducing the load on the servo brake.

[0017] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of an embodiment of the present invention is shown.

[0020] Figure 2 An isometric schematic diagram of the compensation component according to an embodiment of the present invention is shown.

[0021] Figure 3 An isometric schematic diagram of a load-bearing component according to an embodiment of the present invention is shown.

[0022] Figure 4 An isometric schematic diagram of the telescopic component according to an embodiment of the present invention is shown.

[0023] Figure 5 An embodiment of the present invention is shown. Figure 4 Enlarged schematic diagram of the structure of section A in the middle.

[0024] Figure 6 A schematic diagram of the lever rocker arm according to an embodiment of the present invention is shown.

[0025] Figure 7 An embodiment of the present invention is shown. Figure 6 Enlarged schematic diagram of section B in the middle.

[0026] Figure 8 A schematic diagram of the driven link according to an embodiment of the present invention is shown.

[0027] In the diagram: 1. Buffer assembly; 2. Compensation assembly; 201. Air storage pipe; 2011. Second spring; 202. Movable pipe; 2021. Second piston; 203. Second normal level seat; 204. Second ball joint; 3. Load-bearing assembly; 301. Fixed base; 302. Lever rocker arm; 303. Telescopic component; 3031. Movable rod; 3032. First piston; 3033. First spring; 3034. Fixed pipe; 3035. First ball joint; 3036. First normal level seat; 304. Linkage mechanism; 3041. Driven link; 3042. Limiting support; 4. Arrow body; 5. Load-bearing base; 6. Engine casing; 7. Servo brake. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention provides an engine servo load torque reduction device, see reference. Figures 1-8 The system includes a buffer assembly 1, a compensation assembly 2, and a load-bearing assembly 3. The load-bearing assembly 3 is used to share the torque of the engine servo brake and is mounted on the load-bearing base of the rocket body. There are at least two sets of load-bearing assemblies 3, which are arranged in a circular array around the central axis of the engine casing. The compensation assembly 2 is used to provide power compensation for the servo brake and is mounted inside the rocket body. There are at least two sets of compensation assemblies 2, which are arranged in a circular array around the central axis of the engine casing. The load-bearing assembly 3 includes a fixed base 301 and a lever rocker arm 302. The fixed base 301 is fixedly mounted on the load-bearing base of the rocket body, and the lever rocker arm 302 is hinged to the fixed base 301. The lever rocker arm 302 is hinged to the engine casing through a telescopic member 303.

[0030] Using the above scheme, the lever rocker arm 302 forms a lever force-bearing structure with the fixed base 301 as the hinge fulcrum. One end is flexibly hinged to the engine casing through the telescopic member 303. It can bear the overturning moment, aerodynamic load moment and self-weight off-center load moment generated during the servo swing of the engine casing in real time. Most of the load moment is transferred and distributed to the load-bearing base of the rocket body through the lever rocker arm 302 and the fixed base 301. It can bear and unload most of the moment load that the servo brake originally needs to bear. Through the lever rocker arm 302, the overturning moment and off-center load moment generated by the swing of the engine casing are directly diverted and transferred to the load-bearing base of the rocket body, and the rocket body bears most of the load. The force of the servo brake is distributed structurally, which can reduce the output load and working load of the servo actuator.

[0031] For example, the telescopic member 303 includes a movable rod 3031, a first piston 3032, a first spring 3033, and a fixed tube 3034. The first piston 3032 is slidably installed in the fixed tube 3034. One end of the movable rod 3031 is fixedly connected to the first piston 3032, and the other end of the movable rod 3031 is provided with a first ball joint 3035. The movable rod 3031 is hinged to the engine casing through the first ball joint 3035. One end of the fixed tube 3034 is hinged to one end of the lever rocker arm 302 through a first constant level seat 3036. One end of the first spring 3033 is fixedly connected in the fixed tube 3034, and the other end of the first spring 3033 is fixedly connected to the first piston 3032.

[0032] By adopting the above scheme, the sliding fit between the first piston 3032 and the fixed tube 3034, and the elastic deformation of the first spring 3033, absorb the impact load and vibration during the engine swaying process, avoiding the direct transmission of rigid torque. With the help of the universal adaptive characteristics of the first ball joint 3035 and the first constant level seat 3036, the combined angle generated by the engine pitch or yaw swaying is compensated in real time, ensuring that the torque transmission direction is adapted to the swaying posture of the engine casing, and without restricting the normal swaying motion of the engine casing. The sliding structure of the first spring 3033 and the first piston 3032 forms an elastic buffer system. When the engine sways, the first spring 3033 softens the instantaneous load by contracting and absorbing energy, reducing the impact of torque on the lever rocker arm 302 and the servo brake, while avoiding the motion jamming problem caused by rigid connection, thus improving the smoothness of device operation.

[0033] For example, the compensation component 2 includes an air storage pipe 201, a movable pipe 202, a second constant level seat 203, and a second ball joint 204. The movable pipe 202 is slidably installed inside the movable pipe 202. The air storage pipe 201 is connected to the fixed pipe 3034. The air storage pipe 201 is hinged to the load-bearing base of the arrow body through the second constant level seat 203. The movable pipe 202 is hinged to the engine casing through the second ball joint 204. A second piston 2021 is provided on the side wall of the movable pipe 202. The second piston 2021 slides in cooperation with the inner wall of the air storage pipe 201. A second spring 2011 is provided inside the air storage pipe 201. One end of the second spring 2011 is fixedly connected to the inner wall of the movable pipe 202.

[0034] Using the above scheme, when the engine servo brake drives the engine casing to pitch or yaw around the first constant level seat 3036, the fixed tube 3034, which is sealed and connected to the internal air chamber of the air storage pipe 201, generates a squeezing effect as the lever rocker arm 302 and the movable rod 3031 swing. The sealing gas inside the fixed tube 3034 is synchronously forced into the air chamber of the air storage pipe 201. The gas generates a thrust on the movable tube 202, pushing the movable tube 202 along the inner wall of the air storage pipe 201, and extending it outward under the guidance of the second piston 2021. At the same time, the second constant level seat 203 adaptively adjusts the deflection. The angle and the second ball joint 204 synchronously compensate for the spatial angle deviation caused by the swing of the casing, ensuring that the extension and retraction direction of the movable tube 202 matches the swing direction of the engine casing. During this process, the second spring 2011 undergoes elastic deformation as the movable tube 202 extends, and the superimposed high pressure of the air chamber forms a dual compensation force. This force is applied along the tangential direction of the casing swing, which not only offsets part of the inertial resistance and overturning moment generated by the engine swing, but also provides assistance for the attitude reset of the casing. This can reduce the load resistance that needs to be overcome when the servo brake is driven, and can provide power compensation for the swing of the engine casing.

[0035] For example, a linkage mechanism 304 is provided on the lever rocker arm 302. The linkage mechanism 304 is used to unload the lever rocker arm 302. The linkage mechanism 304 includes a driven link 3041 and a limiting support 3042. One end of the driven link 3041 is hinged to one end of the lever rocker arm 302, and the other end of the driven link 3041 is hinged to the limiting support 3042. The limiting support 3042 is fixedly installed on the load-bearing base of the arrow body.

[0036] By adopting the above scheme, the linkage mechanism transmits the engine swaying torque, overturning torque and aerodynamic load borne by the lever rocker arm 302 to the limiting support 3042 fixed to the rocket body bearing base through the driven link 3041. This directly shares the core bearing pressure of the lever rocker arm 302, avoids torque concentration and overload of the lever rocker arm 302, and indirectly reduces the load burden on the servo brake.

[0037] The above embodiments have the following beneficial effects: 1. The lever rocker arm 302 forms a lever force-bearing structure with the fixed base 301 as the hinge fulcrum. One end is flexibly hinged to the engine casing through the telescopic member 303. It can bear the overturning moment, aerodynamic load moment and self-weight off-center load moment generated during the servo swing of the engine casing in real time. It also transmits most of the load moment to the load-bearing base of the rocket body through the lever rocker arm 302 and the fixed base 301. It can bear and unload most of the torque load that the servo brake originally needs to bear.

[0038] 2. By using the sliding fit between the first piston 3032 and the fixed tube 3034, and the elastic deformation of the first spring 3033, the impact load and vibration during the engine swaying process are absorbed, avoiding the direct transmission of rigid torque. With the help of the universal adaptive characteristics of the first ball joint 3035 and the first constant level seat 3036, the combined angle generated by the pitch or yaw sway of the engine is compensated in real time, ensuring that the torque transmission direction is adapted to the swaying posture of the engine casing, and without restricting the normal swaying motion of the engine casing. The sliding structure of the first spring 3033 and the first piston 3032 forms an elastic buffer system. When the engine sways, the first spring 3033 softens the instantaneous load by contracting and absorbing energy, reducing the impact of torque on the lever rocker arm 302 and the servo brake, while avoiding the motion jamming problem caused by rigid connection, thus improving the smoothness of the device operation.

[0039] 3. The second spring 2011 undergoes elastic deformation as the movable tube 202 elongates, superimposed with the high pressure in the air chamber to form a dual compensating force. This force is applied along the tangential direction of the casing's swing, which not only offsets part of the inertial resistance and overturning moment generated by the engine's swing, but also assists in the casing's attitude recovery. This can reduce the load resistance that needs to be overcome when the servo brake is driven, and can provide power compensation for the swing of the engine casing. 4. The linkage mechanism transmits the engine swaying torque, overturning torque and aerodynamic load borne by the lever rocker arm 302 to the limit support 3042 fixed to the rocket body bearing base through the driven link 3041. This directly shares the core bearing pressure of the lever rocker arm 302, avoids torque concentration and overload of the lever rocker arm 302, and indirectly reduces the load burden on the servo brake.

[0040] Based on the aforementioned engine servo load torque reduction device, this embodiment of the invention also provides a torque reduction method for the engine servo load torque reduction device. For example, the torque reduction method includes: Multiple load-bearing components are arranged in a circular array on the load-bearing base of the rocket body. When the engine servo drives the casing to swing and generate overturning moment, self-weight moment and aerodynamic moment, most of the load moment of the engine casing is directly transferred to the load-bearing base of the rocket body through the lever rocker arm and driven connecting rod, and the load-bearing base of the rocket body shares the load. A buffer assembly is set between the lever rocker arm and the engine casing. The telescopic structure composed of the fixed tube, the first piston, the first spring, and the movable rod, combined with the universal self-adaptive characteristics of the ball joint and the constant level seat, is used to adapt to the multi-directional compound swing angle of the engine. During the swing of the engine casing, the first spring extends and retracts to absorb energy, absorb impact load and vibration load, and avoid the rigid torque being directly applied to the servo brake, so as to achieve dynamic buffer load reduction. The compensation component, which is connected to the buffer component, allows the movable tube to slide within the air reservoir under the guidance of the second piston when the engine casing tilt angle changes. This, combined with the elastic deformation of the second spring and the communication between the air chamber pressure, provides elastic and pneumatic assistance for the engine tilt reset, reducing the off-center load resistance and the continuous push-pull output force of the servo brake.

[0041] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An engine servo load torque reduction device, characterized in that: It includes a buffer component (1), a compensation component (2), and a load-bearing component (3); The load-bearing component (3) is used to share the torque of the engine servo brake, and the load-bearing component (3) is set on the load-bearing base of the arrow body; The compensation component (2) is used to provide power compensation for the servo brake, and the compensation component (2) is disposed in the arrow body; The load-bearing component (3) includes a fixed base (301) and a lever rocker arm (302). The fixed base (301) is fixedly installed on the load-bearing base of the arrow body. The lever rocker arm (302) is hinged on the fixed base (301). The lever rocker arm (302) is hinged to the engine casing through a telescopic member (303).

2. The engine servo load torque reduction device according to claim 1, characterized in that: The telescopic component (303) includes a movable rod (3031), a first piston (3032), a first spring (3033), and a fixed tube (3034). The first piston (3032) is slidably installed in the fixed tube (3034). One end of the movable rod (3031) is fixedly connected to the first piston (3032), and the other end of the movable rod (3031) is provided with a first ball joint (3035). The movable rod (3031) is hinged to the engine casing through the first ball joint (3035). One end of the fixed tube (3034) is hinged to one end of the lever rocker arm (302) through a first constant level seat (3036). One end of the first spring (3033) is fixedly connected in the fixed tube (3034), and the other end of the first spring (3033) is fixedly connected to the first piston (3032).

3. The engine servo load torque reduction device according to claim 2, characterized in that: The compensation component (2) includes an air storage pipe (201), a movable pipe (202), a second normal level seat (203), and a second ball joint (204). The movable pipe (202) is slidably installed inside the movable pipe (202). The air storage pipe (201) is connected to the fixed pipe (3034). The air storage pipe (201) is hinged to the load-bearing base of the rocket body through the second normal level seat (203). The movable pipe (202) is hinged to the engine casing through the second ball joint (204).

4. The engine servo load torque reduction device according to claim 3, characterized in that: A second piston (2021) is provided on the side wall of the active tube (202), and the second piston (2021) slides in cooperation with the inner wall of the gas storage tube (201).

5. The engine servo load torque reduction device according to claim 1, characterized in that: The load-bearing components (3) are provided in at least two sets, and the load-bearing components (3) are arranged in a ring array with the central axis of the engine casing.

6. The engine servo load torque reduction device according to claim 1, characterized in that: The compensation components (2) are provided in at least two sets, and the compensation components (2) are arranged in a circular array with the central axis of the engine casing.

7. The engine servo load torque reduction device according to claim 3, characterized in that: A second spring (2011) is provided inside the gas storage pipe (201), and one end of the second spring (2011) is fixedly connected to the inner wall of the movable pipe (202).

8. The engine servo load torque reduction device according to claim 1, characterized in that: The lever rocker arm (302) is provided with a linkage mechanism (304), which is used to unload the force on the lever rocker arm (302).

9. The engine servo load torque reduction device according to claim 8, characterized in that: The linkage mechanism (304) includes a driven link (3041) and a limiting support (3042). One end of the driven link (3041) is hinged to one end of the lever rocker arm (302), and the other end of the driven link (3041) is hinged to the limiting support (3042). The limiting support (3042) is fixedly installed on the load-bearing base of the arrow body.

10. A torque reduction method applied to the engine servo load torque reduction device according to any one of claims 1-9, characterized in that: The torque reduction method includes: Multiple load-bearing components are arranged in a circular array on the load-bearing base of the rocket body. When the engine servo drives the casing to swing and generate overturning moment, self-weight moment and aerodynamic moment, most of the load moment of the engine casing is directly transferred to the load-bearing base of the rocket body through the lever rocker arm and driven connecting rod, and the load-bearing base of the rocket body shares the load. A buffer assembly is set between the lever rocker arm and the engine casing. The telescopic structure composed of the fixed tube, the first piston, the first spring, and the movable rod, combined with the universal self-adaptive characteristics of the ball joint and the constant level seat, is used to adapt to the multi-directional compound swing angle of the engine. During the swing of the engine casing, the first spring extends and retracts to absorb energy, absorb impact load and vibration load, and avoid the rigid torque being directly applied to the servo brake, so as to achieve dynamic buffer load reduction. The compensation component, which is connected to the buffer component, allows the movable tube to slide within the air reservoir under the guidance of the second piston when the engine casing tilt angle changes. This, combined with the elastic deformation of the second spring and the communication between the air chamber pressure, provides elastic and pneumatic assistance for the engine tilt reset, reducing the off-center load resistance and the continuous push-pull output force of the servo brake.

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