A micro servo cylinder for a robot dexterous hand

Abstract

The application discloses a micro servo cylinder for a robot dexterous hand, which comprises a shell, a hollow cup motor, a planetary reducer, a planetary roller screw assembly, a guide anti-rotation structure, a control board and a push rod nut. The motor is directly connected with the push rod nut through the reducer; the screw assembly is connected with the output end of the reducer, and the guide anti-rotation structure inhibits rotation, so that the push rod nut reciprocates along the axial direction; the control board senses the position through inductance change, and realizes double closed-loop control of the pushing force and the position in combination with a pressure sensor. The application adopts an integrated axial structure, is compact in size, adopts plastic guide blocks and round rods to reduce friction, and has the advantages of small volume, high efficiency, high load, high precision and long service life.

Description

Technical Field

[0001] This invention belongs to the field of robot control technology, specifically relating to a miniature servo electric cylinder for a robot's dexterous hand. Background Technology

[0002] With the rapid development of 5G communication, the Internet of Things, and smart terminals, global intelligent manufacturing and robotics technology are entering a period of rapid upgrading. As a core motion component integrating precision mechanics, servo control, and sensing technology, the micro servo electric cylinder is widely used in precision electromechanical equipment fields such as robots, semiconductor manufacturing, and medical devices. In particular, it plays a key role in the finger joint drive of robot dexterity hands, achieving fine movements and precise control. Its performance directly determines the grasping accuracy, movement flexibility, and operational stability of the dexterity hand.

[0003] In existing technologies, the finger joint drive devices of robotic dexterous hands mostly employ traditional miniature electric cylinders. For example, Chinese patent publication number CN203967898U provides a precision electric cylinder designed to reduce component wear and improve control accuracy and reliability. It coaxially integrates the drive motor, lead screw pair, ball spline pair, and hollow piston rod within the cylinder barrel, utilizing the rolling friction of the ball spline pair to replace sliding friction to achieve linear reciprocating motion. Another example is Chinese patent application publication number CN117484483A, which provides a linear drive method for dexterous hands, aiming to achieve flexible linear drive of the finger joints. It employs a rotary drive structure combined with a flexible transmission unit, precisely controlling the rotation angle of the finger joints by pulling and releasing a flexible cable wound around the joint transmission wheel.

[0004] The aforementioned traditional miniature electric cylinders generally suffer from technical defects such as unreasonable structural design and poor compatibility with dexterous fingers. Specifically, traditional miniature electric cylinders typically employ a separate structure for the motor, transmission mechanism, and controller, resulting in an overall bulky cylinder that cannot be adapted to the compact structure and limited installation space of robot dexterous fingers. Furthermore, traditional miniature electric cylinders often use ball screws or trapezoidal screws as core transmission components, which have low load-bearing capacity and limited service life. Under the actual working conditions of high-frequency reciprocating grasping and precise manipulation by robot dexterous hands, component wear is prone to occur, severely affecting drive accuracy. Summary of the Invention

[0005] In view of the above, the present invention provides a miniature servo electric cylinder for robot dexterity hand, which can simultaneously have the advantages of small size, high transmission efficiency, high load, high force control accuracy, high position accuracy, fast linear speed and long service life.

[0006] A miniature servo electric cylinder for a robot's dexterous hand includes a housing. Inside the housing are a coreless motor, a planetary reducer, a planetary roller screw assembly, a guide anti-rotation structure, a pressure sensor, a control board, and a push rod nut. The coreless motor provides input torque and input speed. The planetary reducer drives the coreless motor and the push rod nut coaxially, providing output torque and output speed. The planetary roller screw assembly is connected to the output end of the planetary reducer. The guide anti-rotation structure suppresses the rotational motion of the planetary roller screw assembly, causing the push rod nut to reciprocate linearly along the axial direction, providing push-pull force and linear speed. The pressure sensor detects changes in the load on the electric cylinder in real time, and the control board detects the position of the push rod nut in real time, thus achieving dual control of torque and position.

[0007] Furthermore, the housing is composed of six sections D1 to D6 arranged sequentially along the axial direction from the output end, and a pressure sensor is provided at the end of housing D6.

[0008] Furthermore, the hollow cup motor and the planetary reducer are respectively installed inside the housings D5 and D4. The planetary reducer has at least one stage of planetary gear train, which includes a sun gear, planetary gears, an internal gear ring, and an output frame. The sun gear is fixed to the shaft of the hollow cup motor. When the motor rotates, the sun gear rotates synchronously and drives the planetary gears to rotate. The internal gear ring, which meshes with the planetary gears, is fixed inside the housing D4 and remains stationary. The output frame, which meshes with the planetary gears, rotates synchronously to provide output torque and output speed.

[0009] Furthermore, the planetary roller screw assembly includes a screw, a bearing, and a planetary roller nut. The screw is connected to the output frame of the planetary reducer. The radial support of the screw is provided by the bearing. The bearing is axially limited by the bearing support end faces of housings D4 and D3. The screw and the bearing are axially locked by the nut to limit the inner ring of the bearing. The planetary roller nut and the push rod nut are fixed by a threaded connection, and the planetary roller nut cooperates with the screw. When the output frame drives the screw to rotate, the push rod nut and the planetary roller nut rotate accordingly.

[0010] Furthermore, the bearing seats of housings D4 and D3 are respectively matched with bearings, ensuring the concentricity of housings D4 and D3 and improving the operational stability of the push rod nut.

[0011] Furthermore, the guide anti-rotation structure includes a guide block, a round bar, an O-ring, and a limiting washer. The guide block is mounted on the housing D1, and the inner hole of the guide block matches the outer diameter of the push rod nut, providing radial support for the push rod nut. The round bar is fixed to the housing D2, and the push rod nut matches the round bar, restricting the circumferential movement of the push rod nut. The axial limiting at both ends of the push rod nut is achieved by using O-rings and limiting washers for soft limiting.

[0012] Furthermore, the guide block is made of plastic material, which has good wear resistance, ensuring the stability of the push rod nut during long-term linear reciprocating motion, reducing friction loss, and improving the control accuracy of the electric cylinder.

[0013] Furthermore, the front and rear ends of the control board are fixed to the housing D1 and D6 respectively. When the push rod nut is in linear reciprocating motion, the control board can sense the real-time position of the push rod nut. At the same time, the pressure sensor can sense the load borne by the push rod nut in real time. The control board combines the dual feedback of position and torque to achieve precise closed-loop control of thrust and position by driving the hollow cup motor.

[0014] This invention achieves the following significant and beneficial technical effects through collaborative optimization of structural design: 1. Small size and compact structure: The drive scheme of this invention adopts a hollow cup motor + planetary reducer + planetary roller screw transmission, which is an integrated axial system, reducing radial space; in addition, the volume of the hollow cup motor is only 1 / 3 to 2 / 3 of that of the traditional motor at the same power, and the planetary roller screw is also more compact in overall size compared with the traditional trapezoidal and ball screws under the same load, which further reduces space and is more conducive to assembly into a dexterous hand.

[0015] 2. High efficiency and low loss: The hollow cup motor in this invention adopts a coreless structure to reduce eddy current losses. The planetary reducer improves transmission efficiency through planetary meshing, and the planetary roller screw reduces friction loss through line contact transmission. The entire transmission chain generates little heat during operation, has high energy efficiency, and can achieve long-term continuous operation. This invention uses plastic guide material for the guiding scheme. The material has an extremely low coefficient of friction. The push rod nut contacts the plastic during linear reciprocating motion, which can significantly reduce friction loss and improve efficiency.

[0016] 3. High load and fast linear speed: The planetary roller screw in this invention adopts a multi-roller line contact thread structure, which can achieve high rigidity and large load transmission. Combined with the torque amplification effect of the planetary reducer, the electric cylinder can withstand heavy loads while having a sensitive dynamic response, excellent linear extension and retraction speed and acceleration and deceleration transient characteristics, and can meet the working conditions of high-frequency reciprocating start and stop.

[0017] 4. High force control precision and high positional precision: The hollow cup motor in this invention has no cogging torque and extremely low moment of inertia, which can achieve smooth and delicate torque output; the planetary reducer has a very small return back clearance, and the planetary roller screw transmission clearance is controllable. The three work together to keep the overall return back clearance of the electric cylinder within a very small range. In addition, the inductive solution senses the real-time position of the push rod nut, and the pressure sensor senses the real-time load. Combined, it can achieve precise thrust closed-loop control and high repeatability positioning accuracy, with excellent compliant force control performance, and is suitable for precision micro-displacement control scenarios.

[0018] 5. Long service life: The hollow cup motor in this invention adopts a coreless structure, eliminating eddy current losses and generating less heat, thus reducing coil aging and component wear. Its characteristics of no cogging torque and extremely low moment of inertia enable smooth motor operation and reduce mechanical losses. The planetary reducer adopts a planetary meshing structure, which can achieve uniform force distribution, effectively dispersing the load during transmission and reducing localized excessive wear. At the same time, the multi-roller structure of the planetary roller screw can achieve uniform force distribution, possessing strong impact resistance and anti-eccentric load capacity, avoiding the cyclic fatigue failure problem of trapezoidal and ball screws. Furthermore, the guide block and round bar have excellent wear resistance, ensuring that the push rod has no significant frictional loss during long-term reciprocating operation, further improving the durability of the electric cylinder. Attached Figure Description

[0019] Figure 1 This is a top view of the miniature servo electric cylinder of the present invention.

[0020] Figure 2 This is a front view of the miniature servo electric cylinder of the present invention (viewed from the output end of the rotary joint module).

[0021] Figure 3 This is a side view of the miniature servo electric cylinder of the present invention.

[0022] Figure 4 This is a rear view of the miniature servo electric cylinder of the present invention.

[0023] Figure 5 For along Figure 2 Cross-sectional view of the AA direction line.

[0024] Figure 6 This is a schematic diagram of the housing structure of the miniature servo electric cylinder of the present invention.

[0025] In the diagram: 1—House, 2—Hollow cup motor, 3—Planetary reducer, 4—Planetary roller screw assembly, 5—Guide anti-rotation structure, 6—Control board, 7—Push rod nut, 101~106—Machine housing, 107—Pressure sensor, 201—Hollow cup motor shaft, 301—Sun gear, 302—Planetary gear, 303—Internal gear ring, 305—Output frame, 401—Screw, 402—Bearing, 403—Nut, 404—Planetary roller nut, 501—Guide block, 502—Round bar, 503—O-ring, 504—Limit washer. Detailed Implementation

[0026] To describe the present invention in more detail, the technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] like Figures 1-6As shown, the miniature servo electric cylinder used in this embodiment for the robot's dexterous hand includes a housing 1, a hollow cup motor 2, a planetary reducer 3, a planetary roller screw assembly 4, a guide anti-rotation structure 5, a control board 6, and a push rod nut 7. The hollow cup motor 2 provides input torque and input speed, while the planetary reducer 3 provides output torque and speed. The planetary roller screw assembly 4 is connected to the output end of the planetary reducer 3. The guide anti-rotation structure 5 suppresses the rotational motion of the planetary roller screw assembly 4, causing the push rod nut 7 to reciprocate linearly along the axial direction, providing push-pull force and linear speed. A pressure sensor 107 is provided at the lower end of the housing 1. The control board 6 uses an inductive scheme to sense the position of the push rod nut 7 in real time, thereby achieving dual control of torque and position, improving the control stability of the electric cylinder.

[0028] like Figure 6 As shown, the housing 1, arranged axially from the output end, includes housing 101, housing 102, housing 103, housing 104, housing 105, housing 106 and pressure sensor 107, forming an integral external structure.

[0029] In the aforementioned housing, a hollow cup motor 2 is installed inside the housing 105, and a planetary reducer 3 structure is contained inside the housing 104. The volume of the hollow cup motor 2 is only 1 / 3 to 2 / 3 of that of a traditional motor at the same power, which can make the entire electric cylinder structure more compact and more suitable for micro electric cylinders.

[0030] To further optimize space, the planetary reducer 3 uses planetary transmission, ensuring that the hollow cup motor 2 and the push rod nut 7 are coaxially and directly connected, reducing the lateral space required and making it more suitable for dexterous hands. Compared with traditional single-tooth parallel transmission, the planetary reducer 3 has higher torque capacity, stronger rigidity, better wear resistance, and a significantly longer service life. Specifically, the planetary reducer 3 has a single-stage or multi-stage planetary gear train (in this embodiment, the planetary reducer 3 has a single-stage planetary gear train). As the number of planetary gear trains used in the planetary reducer 3 increases, the movement speed of the push rod nut 7 can decrease, while the thrust can increase. The specific adjustment can be made according to the actual application conditions.

[0031] The planetary reducer 3 includes a sun gear 301, planetary gears 302, an internal gear ring 303, and an output frame 305. The sun gear 301 is fixed to the hollow cup motor shaft 201. When the motor rotates, the sun gear 301 rotates synchronously, driving the planetary gears 302 to rotate. The internal gear ring 303, which meshes with the planetary gears 302, is fixed inside the housing 104 and remains stationary. At this time, the output frame 305, which cooperates with the planetary gears 302, rotates synchronously, providing output torque and speed.

[0032] The planetary roller screw assembly 4 includes a screw 401, a bearing 402, and a planetary roller nut 404. The screw 401 is connected to the output frame 305. The radial support of the screw 401 is provided by the bearing 402. The bearing 402 has small clearance, high rigidity, and strong axial load capacity, which can improve the service life of the electric cylinder, improve the operating stability of the electric cylinder, and ensure control accuracy.

[0033] Bearing 402 is axially limited by the bearing support end faces of housing 104 and housing 103. The lead screw 401 and bearing 402 are axially locked by the inner ring of the bearing via nut 403, ensuring no axial movement of the lead screw 401, reducing the return backlash of the push rod nut 7, and further improving control accuracy. Furthermore, the bearing seats of housing 104 and housing 103 respectively mate with bearing 402, ensuring the concentricity of housing 104 and housing 103 and improving the operational stability of the push rod nut 7.

[0034] The planetary roller nut 404 and the push rod nut 7 are fixed together by a threaded connection. The planetary roller nut 404 cooperates with the lead screw 401. When the output frame 305 drives the lead screw 401 to rotate, the push rod nut 7 and the planetary roller nut 404 rotate accordingly. Compared with traditional trapezoidal lead screws and ball screws, the planetary roller lead screw assembly 4 has increased transmission efficiency, enhanced impact resistance, and significantly improved load-bearing capacity, thus improving both the control stability and service life of the electric cylinder.

[0035] The guide anti-rotation structure 5 includes a guide block 501, a round bar 502, an O-ring 503, and a limiting washer 504. The guide block 501 is mounted on the housing 101, which is fixed to the housing 102. The inner hole of the guide block 501 in the housing 101 matches the outer diameter of the push rod nut 7, providing radial support for the push rod nut 7. The round bar 502 is fixed to the housing 102, and the push rod nut 7 matches the round bar 502, restricting the circumferential motion of the push rod nut 7, thus converting it into linear motion. The guide block 501 is made of plastic. Plastic materials have a low coefficient of friction, excellent high-temperature resistance, and good wear resistance, which can ensure the stability of the push rod nut 7 during long-term linear reciprocating motion, reduce friction loss, and improve the control accuracy of the electric cylinder. The round bar has a low coefficient of friction, good wear resistance, high rigidity, stable dimensions, high temperature resistance, and no magnetic interference. It can also ensure the stability of the push rod nut 7 during long-term linear reciprocating motion, greatly improving the durability and control accuracy of the electric cylinder.

[0036] The axial limit at both ends of the push rod nut 7 is achieved by using O-rings 503 and limit washers 504 for soft limiting, which avoids hard collisions at high speeds of the electric cylinder, ensuring that core components such as bearings, reducers, and motors are not subjected to huge impacts, improving the service life of the electric cylinder, and preventing the electric cylinder from jamming at its limit stroke, which would lead to cylinder failure.

[0037] The control board 6 is fixed to the housing 101 and housing 106 by screws at both ends. The control board 6 can sense the real-time position of the push rod nut 7 during its linear reciprocating motion, thereby achieving non-contact, high-precision closed-loop position control. In addition, the pressure sensor 107 is connected to the housing 106. When the push rod nut 7 performs linear reciprocating motion, the pressure sensor 107 can also sense the load borne by the push rod nut 7 in real time, ultimately achieving dual control of position and torque sensing.

[0038] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. Those skilled in the art can readily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A miniature servo electric cylinder for a robot dexterous hand, characterized in that, The system includes a housing, within which are housed a coreless motor, a planetary reducer, a planetary roller screw assembly, a guide anti-rotation structure, a pressure sensor, a control board, and a push rod nut. The coreless motor provides input torque and input speed. Through the planetary reducer, the coreless motor and push rod nut are coaxially connected, providing output torque and output speed. The planetary roller screw assembly is connected to the output end of the planetary reducer. The guide anti-rotation structure suppresses the rotational movement of the planetary roller screw assembly, causing the push rod nut to reciprocate linearly along the axial direction, providing push-pull force and linear speed. The pressure sensor detects changes in the load on the electric cylinder in real time, and the control board detects the position of the push rod nut in real time, thus achieving dual control of torque and position.

2. The miniature servo electric cylinder for a robot dexterous hand according to claim 1, characterized in that: The housing is composed of six sections D1 to D6 arranged axially from the output end, and a pressure sensor is installed at the end of housing D6.

3. The miniature servo electric cylinder for a robot dexterous hand according to claim 2, characterized in that: The hollow cup motor and the planetary reducer are respectively installed inside the housings D5 and D4. The planetary reducer has at least one stage of planetary gear train, which includes a sun gear, planetary gears, an internal gear ring, and an output frame. The sun gear is fixed to the shaft of the hollow cup motor. When the motor rotates, the sun gear rotates synchronously and drives the planetary gears to rotate. The internal gear ring, which meshes with the planetary gears, is fixed inside the housing D4 and remains stationary. The output frame, which meshes with the planetary gears, rotates synchronously to provide output torque and output speed.

4. The miniature servo electric cylinder for a robot dexterous hand according to claim 2, characterized in that: The planetary roller screw assembly includes a screw, a bearing, and a planetary roller nut. The screw is connected to the output frame of the planetary reducer. The radial support of the screw is provided by the bearing. The bearing is axially limited by the bearing support end faces of housings D4 and D3. The screw and the bearing are axially locked by the nut to limit the inner ring of the bearing. The planetary roller nut and the push rod nut are fixed by a threaded connection, and the planetary roller nut cooperates with the screw. When the output frame drives the screw to rotate, the push rod nut and the planetary roller nut rotate accordingly.

5. The miniature servo electric cylinder for a robot dexterous hand according to claim 4, characterized in that: The bearing seats of housings D4 and D3 are respectively matched with bearings to ensure the concentricity of housings D4 and D3 and improve the operational stability of the push rod nut.

6. The miniature servo electric cylinder for a robot dexterous hand according to claim 2, characterized in that: The guide anti-rotation structure includes a guide block, a round bar, an O-ring, and a limiting washer. The guide block is installed on the housing D1, and the inner hole of the guide block matches the outer diameter of the push rod nut to provide radial support for the push rod nut. The round bar is fixed to the housing D2, and the push rod nut matches the round bar to restrict the circumferential movement of the push rod nut. The axial limiting at both ends of the push rod nut is achieved by using O-rings and limiting washers for soft limiting.

7. The miniature servo electric cylinder for a robot dexterous hand according to claim 2, characterized in that: The control board is fixed to the housing D1 and D6 at its front and rear ends, respectively. When the push rod nut is in linear reciprocating motion, the control board can sense the real-time position of the push rod nut. At the same time, the pressure sensor can sense the load borne by the push rod nut in real time. The control board combines the dual feedback of position and torque to achieve precise closed-loop control of thrust and position by driving the hollow cup motor.

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