Variable-stiffness series-parallel elastic driver based on variable-stiffness planetary gear reducer unit

Abstract

The invention discloses a variable-stiffness series-parallel elastic driver based on a variable-stiffness planetary gear reducer unit, which is characterized in that a variable-stiffness motor mounting frame of the variable-stiffness planetary gear reducer unit is connected with a driving motor outer sleeve at an input motor end; an inner gear ring positioning frame of the input motor end is connected with an inner gear ring of the variable-rigidity planetary gear reducer unit, the lower end of a sun gear of the variable-rigidity planetary gear reducer unit is inserted into a middle hole of a sun gear driving end of the input motor end, and a lead screw of the variable-rigidity planetary gear reducer unit is inserted into a flange bearing inner hole of the input motor end; a driver shell of the protective shell is connected with the motor outer sleeve, a driver cover plate of the protective shell presses a planet carrier bearing of the variable-rigidity planetary gear reducer unit, and a protruding steel ball of a steel ball linear bearing of the variable-rigidity planetary gear reducer unit is tangent to a conical groove in the inner wall of the driver shell. The invention has the advantages of capability of absorbing external impact and vibration, high energy efficiency and capability of expanding torque output.

Description

Technical Field

[0001] This invention relates to the field of technology, and more specifically to a variable stiffness hybrid elastic actuator based on a variable stiffness planetary gear reducer unit. Background Technology

[0002] Organisms in nature exhibit astonishing adaptability, enabling them to perform diverse tasks in varying environments. This adaptability is largely attributed to the coordinated work of muscular and joint systems, which can adjust stiffness in real time to meet different movement demands. Specifically, joints can increase stiffness through muscle regulation when performing tasks requiring stability and greater force output, such as jumping; conversely, joints can decrease stiffness when performing tasks requiring cushioning and energy storage, such as landing. This dynamic adjustment mechanism is a result of the highly complex and precise control of biological musculoskeletal systems. Inspired by this natural mechanism of muscle and joint stiffness regulation, variable stiffness actuators have been invented.

[0003] Traditional rigid actuators are characterized by simple control, high precision, and theoretically infinite stiffness. However, with the development of robotics technology, traditional rigid actuators can no longer meet the demands. For example, robots frequently experience various impacts during movement, and rigid actuators lack energy absorption and cushioning structures, making them susceptible to damage from instantaneous impacts. Introducing variable stiffness actuators in these applications can effectively solve these problems. Variable stiffness actuators enable smoother joint movements, not only preventing hardware damage from impacts but also continuously storing and releasing energy during robot movement to achieve higher energy efficiency.

[0004] Integrating flexible mechanical components with variable stiffness characteristics into actuators in series or parallel is a simple and effective solution for implementing variable stiffness actuators. Existing variable stiffness actuators can be categorized into series and parallel types based on their structure, and further classified according to their variable stiffness principle, such as spring-preload-based variable stiffness, lever-based variable stiffness, and variable stiffness based on changing the effective length of the elastic element. Each existing variable stiffness actuator has its advantages and disadvantages, and they can demonstrate good performance in their applicable scenarios; however, they do not fully meet all the technical specifications of an ideal actuator in practical applications: compact and simple mechanical design, no range of motion limitations, wide stiffness adjustment range, rapid stiffness change, and high energy efficiency. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a variable stiffness hybrid elastic actuator based on a variable stiffness planetary gear reducer unit. It combines the advantages of variable stiffness series elastic actuators and the disadvantages of variable stiffness parallel elastic actuators, and can better meet the technical specifications of an ideal variable stiffness actuator.

[0006] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0007] A variable stiffness hybrid elastic actuator based on a variable stiffness planetary gear reducer unit includes a protective housing, a variable stiffness planetary gear reducer unit, and an input motor end.

[0008] The variable stiffness planetary gear reducer unit includes a planet carrier, a sun gear, a planet carrier bearing, planet shafts, an internal gear ring, a spring mounting bracket, a spring, a ball linear bearing, a variable stiffness motor, a variable stiffness motor end gear, a grooved connecting rod, a lead screw nut, a lead screw, a lead screw end gear, and planet gears. The planet carrier bearing, internal gear ring, and spring mounting bracket are arranged sequentially, with the planet carrier bearing coaxially mounted inside the planet carrier bearing. The upper end of the sun gear is rotatably mounted in the middle of the planet carrier, and the lower end is inserted into the middle of the sun gear drive end of the input motor. One end of three planet shafts is also fixed on the planet carrier, and the other end of each of the three planet shafts is fixed inside a planet gear. The outer wall of the planet gear mates with the inner wall of the internal gear ring. The internal gear ring and the spring mounting bracket are connected by a slider rail. The outer side of the spring mounting bracket is provided with multiple sets of tracks, each set of tracks cooperating with a steel ball linear bearing, and a spring is provided between the spring mounting bracket and the steel ball linear bearing; the variable stiffness motor is mounted on the variable stiffness motor mounting bracket, and the output end of the variable stiffness motor passes through the middle hole of the variable stiffness motor end gear and is fixed; one end of the lead screw, after cooperating with the lead screw nut, passes through the variable stiffness motor mounting bracket and is then fixedly connected to the lead screw end gear, and the other end of the lead screw is inserted into the inner hole of the flange bearing at the input motor end; the lead screw nut is connected to the lead screw nut connector, the round hole of the lead screw nut connector mates with the round hole side of the grooved connecting rod, and is connected by a plug bolt; the groove side of the grooved connecting rod mates with the round hole on the spring mounting bracket, and is also connected by a plug bolt;

[0009] The internal gear ring is connected to the internal gear ring positioning frame at the input motor end;

[0010] The raised steel balls of the ball linear bearing are tangentially fitted to the conical grooves on the inner wall of the drive housing of the protective housing.

[0011] In the above technical solution, the protective housing is formed by connecting the driver cover plate and the driver housing.

[0012] In the above technical solution, the input motor end includes a drive motor, the drive motor is connected to the drive motor outer sleeve, and the drive motor outer sleeve has an embedded flange bearing; the output end of the drive motor is connected to the sun gear drive end, the outer side of the sun gear drive end has a sun gear drive end bearing, one end of the sun gear drive end bearing is fitted with the flange of the sun gear drive end, and the other end is pressed by a screw.

[0013] In the above technical solution, the driver housing is connected to the motor outer sleeve, and the driver cover plate presses down on the planetary carrier bearing.

[0014] In the above technical solution, the variable stiffness motor mounting bracket is connected to the drive motor outer sleeve.

[0015] In the above technical solution, the end of the internal gear ring positioning bracket near the outer sleeve of the drive motor is pressed against the sun gear drive end bearing.

[0016] In the above technical solution, the upper part of the sun gear is installed in the inner hole of the sun gear bearing, and the sun gear bearing is embedded in the through hole in the middle of the planet carrier.

[0017] In the above technical solution, multiple slide rails are evenly installed on the outer side of the internal gear ring, and multiple sliders are evenly installed on the inner side of the spring mounting bracket, with the sliders sliding along the slide rails.

[0018] In the above technical solution, a set of tracks consists of two optical axes, and the steel ball linear bearing moves along the optical axis axially.

[0019] In the above technical solution, both ends of the planetary shaft are fixed by washers and retaining rings.

[0020] The beneficial effects of this invention are as follows:

[0021] (1) The present invention introduces a variable stiffness elastic mechanism (the part of the variable stiffness planetary gear reducer unit excluding the planetary gear reducer, the planetary gear reducer includes the planet carrier, sun gear bearing, sun gear, planet carrier bearing, planet shaft and internal gear ring) into the structural design between the internal gear ring of the planetary gear reducer and the fixed end (protective housing) of the driver, thereby introducing flexibility into the driver, enabling the driver to absorb external impacts and thus protect the driver, as well as to store elastic potential energy during movement and improve energy efficiency.

[0022] (2) By introducing a variable stiffness structure between the internal gear ring and the fixed end of the driver, the present invention enables the driver to simultaneously achieve the characteristics of series elastic drive (such as: absorbing external shocks and vibrations, high energy efficiency, arbitrary adjustment of balance position, and safe human-machine interaction) and parallel elastic drive (such as high output torque and high energy efficiency) and variable stiffness (such as high working bandwidth, strong adaptability, and outstanding bionics). This enriches the applicable scenarios of the driver and solves the problem that series or parallel elastic drives themselves cannot meet all the technical specifications of the ideal variable stiffness drive.

[0023] (3) This invention achieves variable stiffness by adjusting the screw nut to change the curvature of the tangential fit between the steel ball and the conical groove. It has the characteristics of achieving variable stiffness with low energy consumption and maintaining stiffness with zero energy consumption. Furthermore, the conical groove can be customized according to stiffness requirements, and theoretically, the stiffness adjustment range that can be achieved is from a value greater than zero to infinity. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the assembly of the variable stiffness hybrid elastic actuator described in this invention;

[0025] Figure 2 This is an exploded view of the variable stiffness hybrid elastic actuator described in this invention.

[0026] Figure 3(a) is a schematic diagram of the protective shell structure of the present invention;

[0027] Figure 3(b) is a rear view of the protective casing described in this invention;

[0028] Figure 4(a) is a schematic diagram of the variable stiffness planetary gear reducer unit structure of the present invention;

[0029] Figure 4(b) is a bottom view of the variable stiffness planetary gear reducer unit of the present invention;

[0030] Figure 5 This is an assembly diagram of the input motor end of the present invention;

[0031] In the diagram: 1-Protective housing, 2-Variable stiffness planetary gear reducer unit, 3-Input motor end, 4-Driver cover plate, 5-M3 countersunk screw, 6-Driver housing, 7-Planet carrier, 8-Sun gear bearing, 9-Sun gear, 10-Planet carrier bearing, 11-Planet shaft, 12-8mm snap ring, 13-8mm washer, 14-Internal gear ring, 15-Slide rail, 16-M2 screw, 17-Slider, 18-Spring mounting bracket, 19-Spring, 20-3mm optical shaft, 21-Steel ball linear bearing, 22-Variable stiffness motor, 23-Variable stiffness motor mounting bracket, 24 - M3 flat head screw, 25- lead screw nut connector, 26- variable stiffness motor end gear, 27- slotted connecting rod, 28- lead screw nut, 29- lead screw, 30- plug bolt, 31- lead screw end gear, 32- M3 washer, 33- planetary gear, 34- flange bearing, 35- drive motor outer sleeve, 36- sun gear drive end bearing, 37- internal gear ring positioning bracket, 38- M4 screw, 39- sun gear drive end, 40- M2.5 screw, 41- M2 flat head screw, 42- bearing pressure ring, 43- drive motor, 44- M3 screw, 45- conical groove. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0033] like Figure 1 , 2 As shown in Figures 3(a), 3(b), 4(a), 4(b), and 5, the variable stiffness hybrid elastic actuator based on a variable stiffness planetary gear reducer unit of the present invention consists of a protective housing 1, a variable stiffness planetary gear reducer unit 2, and an input motor end 3. The variable stiffness motor mounting bracket 23 of the variable stiffness planetary gear reducer unit 2 is connected to the drive motor outer sleeve 35 of the input motor end 3 by M3 screws 44. An M2.5 screw 40 passes through the reserved hole of the internal gear ring positioning bracket 37 of the input motor end 3 and is connected to the internal gear ring 14 of the variable stiffness planetary gear reducer unit 2. The actuator housing 6 of the protective housing 1 is connected to the motor outer sleeve 35 of the input motor end 3 by M3 screws 44, and the actuator cover plate 4 of the protective housing 1 presses against the planetary carrier bearing 10 of the variable stiffness planetary gear reducer unit 2. The raised steel balls of the three steel ball linear bearings 21 of the variable stiffness planetary gear reducer unit 2 are tangentially engaged with the conical groove 45 on the inner wall of the actuator housing 6 of the protective housing 1. The D-shaped shaft at the lower end of the sun gear 9 of the variable stiffness planetary gear reducer unit 2 is inserted into the middle D-shaped hole of the sun gear drive end 39 of the input motor end 3. The lower end of the lead screw 29 of the variable stiffness planetary gear reducer unit 2 is inserted into the inner hole of the flange bearing 34 of the input motor end 3.

[0034] like Figure 3(a) , 3(b) As shown in the diagram, the protective housing 1 is assembled with the driver cover 4 connected to one side of the driver housing 6 by ten M3 countersunk screws 5.

[0035] like Figure 4(a) , 4(b)As shown in the diagram, the planetary gear reducer unit 2 is assembled with the planetary carrier bearing 10 coaxially mounted with the planetary carrier 7, and the planetary carrier bearing 10 fitting into the outer wall of the planetary carrier 7; the sun gear bearing 8 is embedded in the through hole in the middle of the planetary carrier 7; the protruding shaft on the upper part of the sun gear 9 is installed in the inner hole of the sun gear bearing 8; one end of the three planetary shafts 11 passes through the pre-drilled holes in the planetary carrier 7 and is fixed by an 8mm washer 13 and an 8mm snap ring 12, and the other end of the planetary shafts 11 passes through the planetary gears 33 and is also fixed by an 8mm washer 13 and an 8mm snap ring 12; the internal gear ring 14 meshes with the three planetary gears 33. The system consists of three evenly distributed slide rails 15 installed on the outer side of the internal gear ring 14, each slide rail 15 fixed to the internal gear ring 14 by two M2 screws 16; three sliders 17 installed on the inner side of the spring mounting bracket 18, each slider 17 fixed by two M2 screws 16, the three sliders 17 respectively cooperating with the three slide rails 15 and movable along the slide rails 15; six 3mm optical shafts 20 inserted into the reserved holes of the spring mounting bracket 18, each 3mm optical shaft 20 fixed by one M2 screw 16, forming three sets of tracks; three ball bearings 21 respectively cooperating with the three sets of tracks, and the ball bearings 21... 1. It can move freely along the axial direction of the 3mm optical axis 20; the spring 19 is embedded between the spring mounting bracket 18 and the steel ball linear bearing 21; the lead screw nut 28 is engaged with the lead screw 29, and when the lead screw 29 rotates, the lead screw nut 28 will move up and down along the lead screw 29; one end of the lead screw 29 passes through the variable stiffness motor mounting bracket 23 and then through the lead screw end gear 31, and is connected to the lead screw 29 by the M3 washer 32 and the M3 flat head screw 24; the variable stiffness motor 22 is mounted on the variable stiffness motor mounting bracket 23 by three M3 screws 24; the output end of the variable stiffness motor 22 passes through the variable stiffness motor... The middle hole of the end gear 26 is connected together by an M3 washer 32 and an M3 flat-head screw 24, and is fixed on the shaft side by an M3 flat-head screw 24; the lead screw nut connector 25 is connected to the lead screw nut 28 by four M3 flat-head screws 24; the round hole side of the grooved connecting rod 27 mates with the round hole of the lead screw nut connector 25, and is penetrated by a plug bolt 30, allowing the grooved connecting rod 27 to rotate freely around the plug bolt 30; the slot side of the grooved connecting rod 27 mates with the round hole on the spring mounting bracket 18, and is also penetrated by a plug bolt 30, allowing the grooved connecting rod 27 and the plug bolt 30 to mate through the slot.

[0036] like Figure 5As shown in the diagram, the input motor end 3 is assembled with the drive motor 43 connected to the drive motor outer sleeve 35 by ten M2.5 screws 40; the sun gear drive end 39 is connected to the output end of the drive motor 43 by three M4 screws 38; the inner wall of the sun gear drive end bearing 36 is embedded in the outer wall of the sun gear drive end 39, one end of the sun gear drive end bearing 36 is in contact with the flange of the sun gear drive end 39, and the other end is pressed by six M3 flat-head screws 24; the internal gear ring positioning bracket 37 is concentrically mounted on the internal gear ring 14, and the end of the internal gear ring positioning bracket 37 near the drive motor outer sleeve 35 is pressed by the bearing pressure ring 42 and eight M2 flat-head screws 41 to the sun gear drive end bearing 36; the flange bearing 34 is embedded in the reserved hole of the drive motor outer sleeve 35.

[0037] The working principle of a variable stiffness hybrid elastic actuator based on a variable stiffness planetary gear reducer unit is as follows:

[0038] Variable stiffness principle: The rotation of the variable stiffness motor 22 causes the spring mounting bracket 18, which indirectly cooperates with the lead screw nut 28, to move axially along the lead screw 29, thereby changing the mating position between the steel ball linear bearing 21 and the conical groove 45, i.e., changing the curvature of the tangential mating surface of the steel balls, thus realizing variable stiffness adjustment. The conical surface of the groove can be customized according to requirements to achieve different stiffness ranges. In this invention, the stiffness range of the actuator is from a value greater than zero to infinity.

[0039] Drive principle: Assuming that the spring mounting bracket 18 is fixed along the axial position of the lead screw 29, when the external load is zero, the spring mounting bracket 18 will not deflect, the spring 19 will not deform, and the drive motor 43 will drive the sun gear 9 to rotate, thereby driving the output end (i.e., the planetary carrier 7) to rotate; when the external load is not zero, the load force is transmitted to the internal gear ring 14 and the sun gear 9 in a certain proportion. The spring mounting bracket 18, which is fixed to the internal gear ring 14, will deflect under the force, causing the spring 19 to be compressed, forming a buffer effect.

[0040] In this invention, a lead screw 29 is used as a mechanism to achieve variable stiffness. When there is no load, the variable stiffness motor 22 can achieve stiffness change with a very small force, and when driven, the variable stiffness motor 22 does not need to output force to maintain stiffness.

[0041] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A variable stiffness hybrid elastic drive based on a variable stiffness planetary gear reducer unit, characterized in that: It comprises a protective housing (1), a variable stiffness planetary gear reducer unit (2) and an input motor end (3); The variable stiffness planetary gear reducer unit (2) comprises a planet carrier (7), a sun gear (9), a planet carrier bearing (10), a planet shaft (11), an inner gear ring (14), a spring mounting frame (18), a spring (19), a steel ball linear bearing (21), a variable stiffness motor (22), a variable stiffness motor end gear (26), a grooved connecting rod (27), a screw nut (28), a screw (29), a screw end gear (31) and a planet gear (33); the planet carrier bearing (10), the inner gear ring (14) and the spring mounting frame (18), a spring (19), a steel ball linear bearing (21), a variable stiffness motor (22), a variable stiffness motor end gear (26), a grooved connecting rod (27), a screw nut (28), a screw (29), a screw end gear (31) and a planet gear (33); The mounting frames (18) are arranged in sequence, and the planetary frame (7) is coaxially mounted inside the planetary frame bearing (10); the upper end of the sun gear (9) is rotatably mounted in the middle of the planetary frame (7), and the lower end is inserted into the middle of the sun gear driving end (39) of the input motor end (3); one end of three planetary shafts (11) is also fixed on the planetary frame (7), and the other ends of the three planetary shafts (11) are respectively fixed inside a planetary wheel (33), and the outer wall of the planetary wheel (33) is matched with the inner wall of the inner gear ring (14); the inner gear ring (14) is connected to the spring The mounting frames (18) are matched with each other through sliders and rails; a plurality of rails are arranged outside the spring mounting frame (18), each rail is matched with a steel ball linear bearing (21), and a spring (19) is arranged between the spring mounting frame (18) and the steel ball linear bearing (21); the variable stiffness motor (22) is mounted on the variable stiffness motor mounting frame (23), and the output end of the variable stiffness motor (22) passes through the middle hole of the variable stiffness motor end gear (26) and is fixed; one end of the lead screw (29) is matched with the lead screw nut (28) After being assembled, the screw (29) passes through the variable stiffness motor mounting frame (23) and is fixedly connected to the screw end gear (31). The other end of the screw (29) is inserted into the inner hole of the flange bearing (34) of the input motor end (3). The screw nut (28) is connected to the screw nut connecting piece (25). The round hole of the screw nut connecting piece (25) matches with the round hole side of the grooved connecting rod (27) and is penetrated by a plug bolt. The notch side of the grooved connecting rod (27) matches with the round hole on the spring mounting frame (18) and is also penetrated by a plug bolt. The inner gear ring (14) is connected to the inner gear ring positioning frame (37) of the input motor end (3); The protruding steel ball of the steel ball linear bearing (21) is tangentially matched with the conical groove (45) on the inner wall of the driver housing (6) of the protective housing (1).

2. The variable stiffness hybrid elastic actuator according to claim 1, characterized in that: The protective housing (1) is formed by connecting a driver cover plate (4) and a driver housing (6).

3. The variable stiffness hybrid elastic actuator according to claim 2, characterized in that: The input motor end (3) comprises a drive motor (43), the drive motor (43) is connected to an outer sleeve (35) of the drive motor, and a flange bearing (34) is embedded in the outer sleeve (35) of the drive motor; the output end of the drive motor (43) is connected to a sun gear drive end (39), a sun gear drive end bearing (36) is embedded on the outer side of the sun gear drive end (39), one end of the sun gear drive end bearing (36) is in contact with a flange of the sun gear drive end (39), and the other end is tightened by a screw.

4. The variable stiffness hybrid elastic actuator according to claim 3, characterized in that: The drive housing (6) is connected to the motor outer sleeve (35), and the drive cover plate (4) presses the planetary carrier bearing (10).

5. The variable stiffness hybrid elastic actuator according to claim 3, characterized in that: The variable stiffness motor mounting frame (23) is connected to the outer sleeve (35) of the driving motor.

6. The variable stiffness hybrid elastic actuator according to claim 3, characterized in that: One end of the inner gear ring positioning frame (37) close to the outer sleeve (35) of the driving motor is pressed against the sun gear driving end bearing (36).

7. The variable stiffness hybrid elastic actuator according to claim 1, characterized in that: The upper part of the sun gear (9) is installed in the inner hole of the sun gear bearing (8), and the sun gear bearing (8) is embedded in the through hole in the middle of the planet carrier (7).

8. The variable stiffness hybrid elastic actuator according to claim 1, characterized in that: A plurality of slide rails (15) are evenly installed on the outer side of the inner gear ring (14), and a plurality of slide blocks (17) are evenly installed on the inner side of the spring mounting frame (18), and the slide blocks (17) slide along the slide rails (15).

9. The variable stiffness hybrid elastic actuator according to claim 1, characterized in that: A set of tracks is composed of two optical axes (20), and the steel ball linear bearing (21) moves axially along the optical axis (20).

10. The variable stiffness hybrid elastic actuator according to claim 1, characterized in that: Both ends of the planetary shaft (11) are fixed by means of gaskets and retaining springs.

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