A manually adjustable variable stiffness module and articulating mechanism

Abstract

This invention relates to a manually adjustable variable stiffness module and joint mechanism, comprising a base, a self-locking mechanism, a stiffness adjustment mechanism, and a cam. Compared with the prior art, this invention, for the first time, places the variable stiffness spring at the output end. The motor output shaft is connected to the cam surface through a transmission structure. The cam follower rotates along the cam surface, thereby driving the spring compression component to compress the spring, achieving variable stiffness characteristics. The structure has good reconfigurability. Secondly, this invention allows for manual adjustment of the joint stiffness value according to the application scenario, which not only reduces the overall size but also allows for real-time adjustment of stiffness according to changes in the living environment, making it more adaptable to real-world application conditions. This design uses a self-locking structure to lock the gear rack, and this unique structure gives it a certain impact resistance. The spring pre-adjustment operation is convenient, the structure is reliable, and the overall structure significantly improves the stability of the variable stiffness process, ensuring human-computer interaction safety. The structure is compact and has a wide range of applications.

Description

Technical Field

[0001] This invention relates to the field of robotics, and in particular to a manually adjustable variable stiffness module and joint mechanism. Background Technology

[0002] With the continuous advancement of technology, robotics, represented by industrial robots, has reached a very high level. Human-computer interaction technology has also made significant progress, human-machine collaboration is becoming increasingly close, and the rehabilitation medicine field is placing greater emphasis on the application of robots. All of these developments have raised requirements for the safety of human-computer interaction.

[0003] In addition, my country's aging population is gradually increasing, and the high incidence of diseases and other issues related to daily living assistance among the elderly are receiving increasing attention, especially for patients with limb dysfunction. To improve their self-care abilities, they need to use compensatory prostheses to replace the affected limbs. Similarly, rehabilitation robots are becoming increasingly common in the field of rehabilitation training. However, using rehabilitation equipment to replace therapist training requires consideration of human-computer interaction and the robot's compliance and compatibility. Furthermore, malfunctions in traditional rigid robots leading to loss of control not only pose a danger to nearby operators but also damage the robot itself.

[0004] To protect people and machines from impacts and adapt to different environments and tasks, as well as meet the requirements for real-time stiffness adjustment, researchers have developed various variable stiffness joints to follow the patient's limb during active and resisted training phases. Different forces need to be applied to the patient's limb to ensure safety and comfort during rehabilitation and enhance the effectiveness of rehabilitation training. Existing active variable stiffness actuators, due to the addition of a new motor as the power source for stiffness adjustment, require the introduction of new controllers and corresponding angle measurement components into the entire joint electromechanical system. This makes the joint structure complex, large in size, and heavy. Furthermore, the introduction of new control signals leads to redundancy in the control system, increasing control difficulty and generally resulting in higher prices. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art by providing a manually adjustable variable stiffness module and joint mechanism.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] According to a first aspect of the present invention, a manually adjustable variable stiffness module is provided, comprising a base, a self-locking mechanism, a stiffness adjustment mechanism, and a cam;

[0008] The cam is rotatably mounted above the base via a bearing, and the top surface of the base is provided with a hyperboloid protrusion.

[0009] The stiffness adjustment mechanism includes a first elastic unit, a second elastic unit, and two sets of motion units. The first and second elastic units have the same structure, including a spring structure, a spring compression block, a guide support frame, a guide rod, a linear bearing, and a cam follower. The first end of the spring compression block is an arc-shaped structure that matches the curvature of the inner wall of the cam. The two ends of the spring structure are respectively connected to the second end of the spring compression block and the first end of the guide support frame. The cam follower is installed at the second end of the guide support frame. The sides of the cam followers of the first and second elastic units respectively contact the curved outer contours of the two sides of the protrusion on the base. The guide rod passes through the side wall of the cam and is connected to the guide support frame. The guide rod and the side wall of the cam are connected by a linear bearing. The spring compression block is slidably connected to the guide rod.

[0010] The motion unit includes a gear and rack housing, a gear, a rack, and a rack guide ring. The gear and rack housings of the two motion units are respectively fixedly connected to both sides of the spring compression block of the first elastic unit. The first end of the rack is a free end and is disposed inside the gear and rack housing. The second end of the rack extends out of the gear and rack housing and is fixedly connected to the spring compression block of the second elastic unit. The rack guide ring is disposed inside the gear and rack housing and is used to guide and position the rack. The racks of the two motion units are arranged in parallel. The gear is placed inside the gear and rack housing and meshes with the rack.

[0011] The self-locking mechanism is adapted to the motion unit and is used to drive the gear to rotate. The rack moves in the opposite direction to the gear, thereby driving the spring compression blocks of the first elastic unit and the second elastic unit to move to change the potential energy of the spring structure of the first elastic unit and the second elastic unit.

[0012] Further, the self-locking mechanism includes a screw, a nut, a handle, a spring compression member, a linear spring, and a self-locking housing; the first end of the screw extends into the cam, and the second end of the screw is located outside the cam; the gears of the two sets of motion units are connected to the screw; a through-hole is provided on the side wall of the cam; the self-locking housing is connected to the gear rack housing of the two sets of motion units closest to the through-hole, and the self-locking housing is accommodated in the through-hole; the spring compression member is connected to the screw; the linear spring is sleeved on the screw; the two ends of the linear spring are in contact with the first end of the spring compression member and the gear rack housing, respectively; the spring compression member and the linear spring are located within the accommodating space formed between the self-locking housing and the gear rack housing; the handle and the nut are installed on the second end of the screw and located outside the accommodating space formed between the self-locking housing and the gear rack housing; the nut is not fixedly connected to the handle; the second end of the spring compression member has a locking structure adapted to the handle; the self-locking housing has an opening adapted to the second end of the spring compression member, and the second end of the spring compression member extends out of the self-locking housing through the opening;

[0013] When no external force is applied to the handle, the spring compression member is pressed tightly against the self-locking housing under the action of the linear spring's restoring force, and the rotation angle of the screw is fixed. When the handle is pushed along the screw axis towards the cam direction, the spring compression member moves accordingly and compresses the linear spring, causing the spring compression member to separate from the self-locking housing. When the spring compression member separates from the self-locking housing, the second end of the spring compression member engages with the handle under the action of external force and the linear spring's restoring force. The screw rotates with the rotation of the handle and the spring compression member, and the rotation of the screw drives the gear to rotate.

[0014] Furthermore, in the first elastic unit and the second elastic unit, the spring structure includes two parallel butterfly springs, and the number of guide rods is two, with the two butterfly springs respectively sleeved on the guide rods.

[0015] Furthermore, the cam sidewall is provided with a through hole adapted to the guide rod, the linear bearing is installed in the through hole, the radial outer wall of the linear bearing contacts the through hole, the radial inner wall of the linear bearing contacts the guide rod, one axial side of the linear bearing contacts the inner wall of the through hole, and the other axial side of the linear bearing contacts the linear bearing fixing plate, the linear bearing fixing plate is disposed on the outer wall of the cam.

[0016] Furthermore, in the motion unit, there are multiple rack guide rings, which are connected to the gear rack housing, and the rack is slidably connected to the rack guide rings.

[0017] Furthermore, the handle includes a sleeve and a handle. The sleeve is fitted onto the screw, and the handle is connected to the sleeve. The sleeve end face is provided with a plurality of balls, which are evenly arranged circumferentially along the sleeve end face. The second end of the spring compression member is provided with a concave surface adapted to the size and position of the plurality of balls.

[0018] Furthermore, the screw is a split structure, including a first screw and a second screw. The first end of the first screw and the second end of the second screw are provided with a matching connection structure. The handle is installed on the second end of the first screw, and the gears of the two sets of motion units are respectively connected to the first screw and the second screw.

[0019] Furthermore, the first screw is provided with a protruding part and a retaining ring groove, the gear is disposed between the protruding part and the retaining ring groove, one end of the gear is in contact with the protruding part, and the other end is connected to the first screw through a retaining ring installed in the retaining ring groove, and the protruding part is connected to the gear rack housing through a bearing;

[0020] The second screw has a protruding part and a retaining ring groove. The gear is disposed between the protruding part and the retaining ring groove. One end of the gear is in contact with the protruding part, and the other end is connected to the second screw through a retaining ring installed in the retaining ring groove. The protruding part is connected to the gear rack housing through a bearing.

[0021] Furthermore, the first end of the first screw is provided with an inner hole, and the second end of the second screw is provided with a connecting section adapted to the length and cross-section of the inner hole; or, the second end of the second screw is provided with an inner hole, and the first end of the first screw is provided with a connecting section adapted to the length and cross-section of the inner hole.

[0022] According to a second aspect of the present invention, a manually adjustable variable stiffness joint mechanism is provided, comprising a position control module and the aforementioned variable stiffness module. The position control module includes a motor housing, a position motor, a flange, and a harmonic reducer. The position motor is mounted on the motor housing. The flange is connected to the output shaft of the position motor and the harmonic reducer, respectively. The harmonic reducer is connected to the base of the variable stiffness module. The flange rotates with the output shaft of the position motor. The rotation of the flange drives the harmonic reducer to rotate accordingly. The rotation of the harmonic reducer drives the base of the variable stiffness module to rotate accordingly. When the base rotates, a cam follower that contacts the outer contour of the raised curved surface of the base rolls along the outer contour of the raised curved surface of the base, thereby changing the potential energy of the spring structure of the first elastic unit and the second elastic unit.

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

[0024] (1) The base has only a hyperboloid protrusion structure as the input end, and the self-locking mechanism and the variable stiffness module are integrated into the output end. The integration is high, which greatly saves the space of the variable stiffness joint. This modular design is easy to install and remove, simple to maintain, convenient for patients to wear, and has a wide range of applications.

[0025] (2) A self-locking mechanism has been added to the variable stiffness module. By manually adjusting the variable stiffness robot joint, the joint stiffness value can be adjusted in real time according to different application scenarios. It is low in cost and simple in structure.

[0026] (3) The self-locking mechanism compresses the spring by pressing and turning the handle, causing the spring compression part to separate from the self-locking shell, thereby rotating the gear and pre-adjusting the spring stiffness. The spring rebounds and compresses the spring compression part, causing the spring compression part to contact the self-locking shell and generate friction to achieve self-locking. Its unique stiffness adjustment capability gives it a certain impact resistance. In the event of an emergency, it can ensure the safety of human-machine interaction. The stiffness pre-adjustment function is perfect and the operation is simple. Attached Figure Description

[0027] Figure 1A schematic diagram of the overall structure of a manually adjustable variable stiffness joint;

[0028] Figure 2 A schematic diagram of the internal structure of a manually adjustable variable stiffness joint;

[0029] Figure 3 A schematic diagram of the internal structure of a manually adjustable variable stiffness joint;

[0030] Figure 4 A schematic diagram of the internal structure of a manually adjustable variable stiffness joint;

[0031] Figure 5 A schematic diagram of the internal structure of a manually adjustable variable stiffness joint;

[0032] Figure 6 A schematic diagram of the hyperboloid protrusion on the base;

[0033] Figure 7 This is a schematic diagram showing the contact between the cam follower and the outer contour of the curved surface on both sides of the protrusion.

[0034] Figure 8 This is a schematic diagram showing the contact between the cam follower and the outer contour of the curved surface on both sides of the protrusion.

[0035] Figure 9 This is a schematic diagram of the cam structure;

[0036] Figure 10 This is a schematic diagram of the spring compression component;

[0037] Figure 11 This is a schematic diagram of the first screw.

[0038] Figure 12 This is a schematic diagram of the second screw.

[0039] Reference numerals in the attached drawings: 1. Base, 2. Self-locking mechanism, 3. Stiffness adjustment mechanism, 4. Cam, 5. Motor housing, 6. Position motor, 7. Flange, 8. Harmonic reducer;

[0040] 201. Screw; 202. Nut; 203. Handle; 204. Ball bearing; 205. Spring compression component; 206. Linear spring; 207. Self-locking housing; 2011. First screw; 2012. Second screw; 2011a. Protrusion of the first screw; 2011b. Snap ring groove of the first screw; 2012a. Protrusion of the second screw; 2012b. Snap ring groove of the second screw;

[0041] 301. Gear and rack housing; 302. Gear; 303. Rack; 304. Spring structure; 305. Spring compression block; 306. Guide support frame; 307. Guide rod; 308. Linear bearing; 309. Cam follower; 310. Linear bearing fixing plate; 311. Rack guide ring. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, providing detailed implementation methods and specific operating procedures. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them, and the scope of protection of the present invention is not limited to the following embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0043] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer and show the mating relationships between the components, some parts in the drawings have been appropriately scaled down, and the distances between the components have been increased or decreased.

[0044] In the description of the embodiments of this application, it should be understood that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly placed when the product of this application is used, or the orientation or positional relationship commonly understood by those skilled in the art. They are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0045] Furthermore, the terms "first," "second," and "third" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0046] In the description of the embodiments of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0047] Example 1:

[0048] This invention provides a manually adjustable variable stiffness module, including a base 1, a self-locking mechanism 2, a stiffness adjustment mechanism 3, and a cam 4. The cam 4 is rotatably mounted above the base 1 via a bearing, and the structure of the cam 4 is as follows: Figure 8 As shown, the top surface of the base 1 has a hyperboloid protrusion 101; this manually adjustable variable stiffness module is applied to variable stiffness joints.

[0049] (1) The stiffness adjustment mechanism 3 includes a first elastic unit, a second elastic unit, and two sets of motion units, such as Figure 1 , Figure 2 As shown, the first elastic unit and the second elastic unit have the same structure, including a spring structure 304, a spring compression block 305, a guide support frame 306, a guide rod 307, a linear bearing 308, and a cam follower 309. The first end of the spring compression block 305 is an arc-shaped structure that matches the curvature of the inner wall of the cam 4. The two ends of the spring structure 304 are respectively connected to the second end of the spring compression block 305 and the first end of the guide support frame 306. The cam follower 309 is installed at the second end of the guide support frame 306. Figure 7 , Figure 8 As shown, the side surfaces of the cam follower 309 of the first elastic unit and the second elastic unit respectively contact the curved outer contours on both sides of the protrusion 101 on the base 1; the guide rod 307 passes through the side wall of the cam 4 and is connected to the guide support frame 306. The guide rod 307 and the side wall of the cam 4 are connected by a linear bearing 308. The spring compression block 305 is slidably connected to the guide rod 307.

[0050] In the first and second elastic units, the spring structure 304 includes two parallel butterfly springs, and there are two guide rods 307. The two butterfly springs are respectively sleeved on the guide rods 307. The shape of the guide rods 307 matches the shape of the spring compression block 305. There is no direct connection between the spring compression block 305 and the inner wall of the cam 4. The spring compression block 305 reciprocates along the guide rods 307.

[0051] The protrusion 101 on the base 1 is as follows Figure 6 As shown, the protrusion 101 has a hyperboloid structure. A cam follower 309 is mounted on the guide support frame 306 of each elastic unit, and the cam follower 309 contacts the outer contour of the curved surface of the protrusion 101. It is understood that the number of cam followers 309 on each guide support frame 306 is at least one. In other embodiments, the number of cam followers 309 can be adjusted as needed.

[0052] The cam 4 has a through hole on its side wall that matches the guide rod 307. The radial outer wall of the linear bearing 308 contacts the through hole, the radial inner wall of the linear bearing 308 contacts the guide rod 307, one axial side of the linear bearing 308 contacts the inner wall of the through hole, and the other axial side of the linear bearing 308 contacts the linear bearing fixing plate 310. The linear bearing fixing plate 310 is disposed on the outer wall of the cam 4. In this embodiment, corresponding to the two butterfly springs of the spring structure 304, each elastic unit includes two guide rods 307, and the entire variable stiffness module includes four guide rods 307. Each linear bearing fixing plate 310 is used to install the linear bearings 308 of the two guide rods 307 on the same side.

[0053] (2) Figures 1-5 As shown, the motion unit includes a gear and rack housing 301, a gear 302, a rack 303, and a rack guide ring 311. The gear and rack housings 301 of the two motion units are fixedly connected to both sides of the spring compression block 305 of the first elastic unit. The first end of the rack 303 is a free end and is disposed inside the gear and rack housing 301. The second end of the rack 303 extends out of the gear and rack housing 301 and is fixedly connected to the spring compression block 305 of the second elastic unit. The rack guide ring 311 is disposed inside the gear and rack housing 301 and is used to guide and position the rack 303. The racks 303 of the two motion units are arranged in parallel. The gear 302 is placed inside the gear and rack housing 301 and meshes with the rack 303.

[0054] The gear and rack housing 301 is a rectangular shell with a cylindrical protrusion. The rack 303 moves within the rectangular shell, and the gear 302 is located at the cylindrical protrusion and meshes with the rack 303. Multiple rack guide rings 311 are provided, connected to the gear and rack housing 301, and the rack 303 is slidably connected to the rack guide rings 311. In this embodiment, two rack guide rings 311 are provided, installed at both ends of the rectangular shell, to guide the movement of the rack 303.

[0055] In this embodiment, the spring compression block 305 of the second elastic unit is screwed to the rack 303, such as... Figure 1 , Figure 2 As shown, the second end of the spring compression block 305 of the second elastic unit is connected to the spring structure 304, and the two sides of the second end of the spring compression block 305 of the second elastic unit are screwed to the second end of the rack 303 respectively. The second end of the spring compression block 305 of the first elastic unit is connected to the spring structure 304, and the two sides of the second end of the spring compression block 305 of the first elastic unit are screwed to the gear rack housing 301 respectively.

[0056] (3) Figures 1-5As shown, the self-locking mechanism 2 is adapted to the motion unit and is used to drive the gear 302 to rotate. The rack 303 moves towards the gear 302, thereby driving the spring compression block 305 of the first elastic unit and the second elastic unit to move to change the potential energy of the spring structure 304 of the first elastic unit and the second elastic unit.

[0057] The self-locking mechanism 2 includes a screw 201, a nut 202, a handle 203, a spring compression member 205, a linear spring 206, and a self-locking housing 207. The first end of the screw 201 extends into the cam 4, and the second end of the screw 201 is located outside the cam 4. Gears 302 of the two sets of motion units are connected to the screw 201. A through-hole is provided on the side wall of the cam 4. The self-locking housing 207 is connected to the gear rack housing 301 of the two sets of motion units that is closest to the through-hole, and the self-locking housing 207 is accommodated within the through-hole. The structure of the spring compression member 205 is as follows: Figure 10 As shown, the spring compression member 205 is connected to the screw 201, and the linear spring 206 is sleeved on the screw 201. The two ends of the linear spring 206 are not fixed. One end of the linear spring 206 contacts the gear rack housing 301, and the other end of the linear spring 206 contacts the first end of the spring compression member 205. The spring compression member 205 and the linear spring 206 are disposed within the receiving space formed between the self-locking housing 207 and the gear rack housing 301. The handle 203 and the nut 202 are installed on the second end of the screw 201 and are positioned... Outside the receiving space formed between the self-locking housing 207 and the gear rack housing 301, the nut 202 is not fixedly connected to the handle 203. The second end of the spring compression member 205 is provided with a locking structure adapted to the handle 203. The self-locking housing 207 is provided with an opening adapted to the second end of the spring compression member 205. The second end of the spring compression member 205 extends out of the self-locking housing 207 through the opening. The main function of the nut 202 is to limit the handle 203. The range of motion of the handle 203 is between the nut 202 and the spring compression member 205.

[0058] When no external force is applied to the handle 203, the spring compression member 205 adheres tightly to the self-locking housing 207 under the restoring force of the linear spring 206, and the rotation angle of the screw 201 is fixed. When the handle 203 is pushed along the axial direction of the screw 201 towards the cam 4, the spring compression member 205 moves accordingly and compresses the linear spring 206, causing the spring compression member 205 to separate from the self-locking housing 207. When the spring compression member 205 separates from the self-locking housing 207, the second end of the spring compression member 205 engages with the handle 203 under the action of external force and the restoring force of the linear spring 206. The screw 201 rotates with the rotation of the handle 203 and the spring compression member 205, and the rotation of the screw 201 drives the gear 302 to rotate.

[0059] The handle 203 includes a sleeve and a handle. The sleeve is fitted onto the screw 201, and the handle is connected to the sleeve. Multiple balls 204 are evenly distributed around the end face of the sleeve. The second end of the spring compression member 205 has a concave surface adapted to the size and position of the multiple balls 204. In this embodiment, four balls 204 are provided, which can fit into the concave surface of the spring compression member 205, thereby achieving a snap-fit ​​connection between the handle 203 and the spring compression member 205. Compared to other connection methods (such as screw connections or latches), this structure achieves a snap-fit ​​connection between the handle 203 and the spring compression member 205, offering advantages such as high load-bearing capacity and ease of assembly and disassembly.

[0060] The screw 201 has a split structure, including a first screw 2011 and a second screw 2012. The first end of the first screw 2011 and the second end of the second screw 2012 are provided with a matching connection structure. The handle 203 is installed on the second end of the first screw 2011. The gears 302 of the two sets of motion units are respectively connected to the first screw 2011 and the second screw 2012.

[0061] The first screw 2011 has an inner hole at its first end, and the second screw 2012 has a connecting section at its second end that matches the length and cross-section of the inner hole. Alternatively, the second screw 2012 may have an inner hole at its second end, and the first screw 2011 may have a connecting section at its first end that matches the length and cross-section of the inner hole. This allows the first screw 2011 and the second screw 2012 to be assembled at the middle position (between the two gears 302). In this embodiment, the structures of the first screw 2011 and the second screw 2012 are as follows: Figure 11 , Figure 12 As shown.

[0062] like Figure 5 , Figure 11As shown, a protrusion 2011a and a snap ring groove 2011b are provided on the first screw 2011. A gear 302 is disposed between the protrusion 2011a and the snap ring groove 2011b. A keyway is provided between the protrusion 2011a and the snap ring groove 2011b of the first screw 2011 for connecting the gear 302. One end of the gear 302 is fitted to the protrusion 2011a, and the other end is connected to the first screw 2011 via a snap ring installed in the snap ring groove 2011b. The protrusion 2011a and the gear rack housing 301 are connected by a bearing. The second screw 2012 has a protrusion 2012a and a snap ring groove 2012b. A gear 302 is positioned between the protrusion 2012a and the snap ring groove 2012b. A keyway is provided between the protrusion 2012a and the snap ring groove 2012b of the second screw 2012 for connecting the gear 302. One end of the gear 302 is fitted to the protrusion 2012a, and the other end is connected to the second screw 2012 via a snap ring installed in the snap ring groove 2012b. The protrusion 2012a is connected to the gear rack housing 301 via a bearing. The connection between the gear 302 and the screw 201 is achieved through snap rings (2011b, 2012b). The axial positioning of the screw 201 is achieved using the protrusions (2012a, 2011a), the bearing, and the gear rack housing 301. The first screw 2011 is also provided with two symmetrical keyways. The spring compression member 205 is connected to the first screw 2011 through the keyways, ensuring that the spring compression member can only move along the axial direction of the screw 201 and cannot rotate relative to the screw 201.

[0063] Specifically, the manual adjustment of the module stiffness is as follows: Slightly press the handle 203 towards the cam 4. The handle 203 engages with the spring compression member 205. The ball bearing 204 embeds into the concave surface of the second end of the spring compression member 205. The spring compression member 205 compresses the linear spring 206, separating the spring compression member 205 from the self-locking housing. The self-locking housing's restriction on the spring compression member 205 disappears. Rotating the handle 203 causes the spring compression block 305 to rotate. The spring compression block 305 connects to the screw 201, thereby causing the screw 201 to rotate. The gear 302 connected to the screw 201 then rotates accordingly. When the handle 203 is rotated, the rack 303, which meshes with the gear 302, also begins to move. Simultaneously, since the overall position of the self-locking mechanism 2 is not fixed, when the handle 203 rotates the gear 302, the gear 302 does not rotate 360° around an axis, but rather rolls. At this time, the self-locking housing 207 also translates within the passage, and the rack and pinion housing 301 connected to the self-locking housing 207 moves accordingly. Since there is no fixed connection between the rack 303 and the rack and pinion housing 301, they move in opposite directions, moving away from each other. Similarly, when the handle 203 is rotated at a different angle, the direction of rotation of the gear 302 changes, causing the rack 303 and the rack and pinion housing 301 to move in opposite directions, moving closer together. In this way, the spring structures 304 of the first and second elastic units can synchronously achieve compression and recovery, thereby simultaneously changing the potential energy of the spring structures 304 of both the first and second elastic units. Once the potential energy of the spring structure 304 reaches the required level when the handle 203 is rotated, rotation of the handle 203 is stopped, and the rotation angle of the handle 203 remains unchanged. The handle 203 is no longer pressed down, and under the restoring force of the linear spring 206, the spring compression component 205 is pressed tightly against the self-locking housing 207 and cannot rotate, thus fixing the rotation angle of the screw 201. In this way, the pre-compression of the spring structure 304 in the variable stiffness module is changed through the self-locking mechanism 2, thereby adjusting the stiffness of the module.

[0064] Since the spring compression member 205 is pressed against the self-locking housing 207 by the restoring force of the linear spring 206 after the handle 203 is released, in order to further prevent the spring compression member 205 from rotating after the handle 203 is released, anti-slip textures can be provided on the self-locking housing 207 and the spring compression member 205 to prevent the spring compression member 205 from rotating.

[0065] In the design of the self-locking mechanism 2 of the present invention, the spring is compressed by pressing and rotating the handle 203, causing the spring compression member 205 to separate from the self-locking housing 207, thereby rotating the gear 302 to pre-adjust the spring stiffness. The spring rebounds and compresses the spring compression member 205, causing the spring compression member 205 to contact the self-locking housing 207 and generate friction to achieve self-locking. The unique stiffness adjustment capability gives it a certain impact resistance, ensuring the safety of human-machine interaction in the event of an emergency. The stiffness pre-adjustment function is perfect and the operation is simple.

[0066] This invention also provides a manually adjustable variable stiffness joint mechanism, including a position control module and the aforementioned variable stiffness module. The position control module includes a motor housing 5, a position motor 6, a flange 7, and a harmonic reducer 8. The position motor 6 is mounted on the motor housing 5. The flange 7 is connected to the output shaft of the position motor 6 and the harmonic reducer 8, respectively. The harmonic reducer 8 is connected to the base 1 of the variable stiffness module. The flange 7 rotates with the output shaft of the position motor 6. The rotation of the flange 7 drives the harmonic reducer 8 to rotate accordingly. The rotation of the harmonic reducer 8 drives the base 1 of the variable stiffness module to rotate accordingly. When the base 1 rotates, the cam follower 309, which is in contact with the outer contour of the curved surface of the protrusion 101 of the base 1, rolls and reciprocates along the outer contour of the curved surface of the protrusion 101 of the base 1, driving the cam 4 to rotate. The external load connected to the cam 4 moves accordingly. During the movement, the different positions of the cam follower 309 will change the potential energy of the spring structure 304 of the first elastic unit and the second elastic unit, realizing the variable stiffness characteristic. The structure is compact, easy to maintain, low in cost, and widely applicable.

[0067] In use, the manually adjustable variable stiffness joint mechanism is employed in upper and lower limb rehabilitation equipment, exoskeletons, and prostheses. The position control module is located at the joint input end, and the variable stiffness module at the joint output end. A limit switch is installed on the motor housing 5 of the position control module to measure the mechanical zero position between the joint input end and the modular flexible variable stiffness drive mechanism. The variable stiffness module, mimicking the process of the human body changing stiffness through muscle contraction, can follow the patient's limbs during resistance training. By adjusting the compression of the spring structure 304, the stiffness characteristics of the entire variable stiffness module are altered, achieving compliance in the interaction with the external environment and applying different forces to the patient's limbs to enhance the rehabilitation effect. In different application scenarios, the pre-compression of the spring structure 304 can be manually adjusted before use via the self-locking mechanism 2, resulting in different initial stiffnesses when the motor drives the base 1 and subsequently the cam 4 to rotate. This allows for real-time adjustment of the joint stiffness value, resulting in a low-cost and simple structure.

[0068] In the joint mechanism, the position motor 6 is connected to the base 1 via the flange 7 and the harmonic reducer 8. The base 1 has only a hyperboloid protrusion structure 101 as the input end. The self-locking mechanism 2 and the variable stiffness module are both integrated into the output end. The integration is high, which greatly saves the space of the variable stiffness joint. This modular design is easy to install and remove, simple to maintain, convenient for patients to wear, and has a wide range of applications.

[0069] Manually adjustable variable stiffness joint mechanisms have a wide range of applications. For example, they can be used in variable stiffness structures of upper and lower limb exoskeletons to improve joint compliance and the safety of human-machine interaction; they are suitable for variable stiffness structures in collaborative robots to provide them with sufficient rigidity and flexibility of joint movement; they are suitable for variable stiffness structures in surgical robotic arms to achieve a balance between rigidity and flexibility in flexible instruments, which is key to balancing operational precision and force output; they are suitable for variable stiffness structures in bionic robot joints to improve the compliance of human-machine interaction and achieve better human-machine collaboration; and they are suitable for variable stiffness structures in soft actuators to give them greater adaptability.

[0070] Compared with the prior art, this invention places the variable stiffness spring at the output end for the first time. The motor output shaft is connected to the curved surface of cam 4 through a transmission structure. The follower cam 309 rotates along the curved surface of cam 4, thereby driving the spring compression component 205 to compress the spring, realizing the variable stiffness characteristic. The structure has good reconfigurability. Secondly, according to the application scenario, the stiffness value of the joint can be manually adjusted, which not only reduces the overall size, but also allows for real-time adjustment of stiffness according to changes in life scenarios, making it more adaptable to real application conditions. This design uses a self-locking structure to lock the gear 302 and rack 303. This unique structure gives it a certain impact resistance. The spring pre-adjustment operation is convenient, the structure is reliable, and the overall structure significantly improves the stability of the variable stiffness process, ensures the safety of human-computer interaction, and has a compact structure with a wide range of applications.

[0071] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A manually adjustable variable stiffness module, characterized in that, Includes a base, a self-locking mechanism, a stiffness adjustment mechanism, and a cam; The cam is rotatably mounted above the base via a bearing, and the top surface of the base is provided with a hyperboloid protrusion. The stiffness adjustment mechanism includes a first elastic unit, a second elastic unit, and two sets of motion units. The first and second elastic units have the same structure, including a spring structure, a spring compression block, a guide support frame, a guide rod, a linear bearing, and a cam follower. The first end of the spring compression block is an arc-shaped structure that matches the curvature of the inner wall of the cam. The two ends of the spring structure are respectively connected to the second end of the spring compression block and the first end of the guide support frame. The cam follower is installed at the second end of the guide support frame. The sides of the cam followers of the first and second elastic units respectively contact the curved outer contours of the two sides of the protrusion on the base. The guide rod passes through the side wall of the cam and is connected to the guide support frame. The guide rod and the side wall of the cam are connected by a linear bearing. The spring compression block is slidably connected to the guide rod. The motion unit includes a gear and rack housing, a gear, a rack, and a rack guide ring. The gear and rack housings of the two motion units are respectively fixedly connected to both sides of the spring compression block of the first elastic unit. The first end of the rack is a free end and is disposed inside the gear and rack housing. The second end of the rack extends out of the gear and rack housing and is fixedly connected to the spring compression block of the second elastic unit. The rack guide ring is disposed inside the gear and rack housing and is used to guide and position the rack. The racks of the two motion units are arranged in parallel. The gear is placed inside the gear and rack housing and meshes with the rack. The self-locking mechanism is adapted to the motion unit and is used to drive the gear to rotate. The rack moves in the opposite direction to the gear, thereby driving the spring compression block of the first elastic unit and the second elastic unit to move to change the potential energy of the spring structure of the first elastic unit and the second elastic unit. The self-locking mechanism includes a screw, a nut, a handle, a spring compression member, a linear spring, and a self-locking housing. The first end of the screw extends into the cam, and the second end of the screw is located outside the cam. The gears of the two sets of motion units are connected to the screw. A through-hole is provided on the side wall of the cam. The self-locking housing is connected to the gear rack housing closest to the through-hole in the two sets of motion units, and the self-locking housing is accommodated within the through-hole. The spring compression member is connected to the screw, and the linear spring is sleeved on the screw. The two ends of the linear spring contact the first end of the spring compression member and the gear rack housing, respectively. The spring compression member and the linear spring are located within the accommodating space formed between the self-locking housing and the gear rack housing. The handle and the nut are installed at the second end of the screw and located outside the accommodating space formed between the self-locking housing and the gear rack housing. The nut is not fixedly connected to the handle. The second end of the spring compression member has a locking structure adapted to the handle. The self-locking housing has an opening adapted to the second end of the spring compression member, and the second end of the spring compression member extends out of the self-locking housing through the opening. When no external force is applied to the handle, the spring compression member is pressed tightly against the self-locking housing under the action of the linear spring's restoring force, and the rotation angle of the screw is fixed. When the handle is pushed along the screw axis towards the cam direction, the spring compression member moves accordingly and compresses the linear spring, causing the spring compression member to separate from the self-locking housing. When the spring compression member separates from the self-locking housing, the second end of the spring compression member engages with the handle under the action of external force and the linear spring's restoring force. The screw rotates with the rotation of the handle and the spring compression member, and the rotation of the screw drives the gear to rotate.

2. The manually adjustable variable stiffness module according to claim 1, characterized in that, In the first elastic unit and the second elastic unit, the spring structure includes two parallel butterfly springs, and there are two guide rods, with the two butterfly springs respectively sleeved on the guide rods.

3. The manually adjustable variable stiffness module according to claim 1, characterized in that, The cam sidewall is provided with a through hole adapted to the guide rod. The linear bearing is installed in the through hole. The radial outer wall of the linear bearing contacts the through hole, the radial inner wall of the linear bearing contacts the guide rod, one axial side of the linear bearing contacts the inner wall of the through hole, and the other axial side of the linear bearing contacts the linear bearing fixing plate. The linear bearing fixing plate is disposed on the outer wall of the cam.

4. A manually adjustable variable stiffness module according to claim 1, characterized in that, In the motion unit, there are multiple rack guide rings, which are connected to the gear rack housing, and the rack is slidably connected to the rack guide rings.

5. A manually adjustable variable stiffness module according to claim 1, characterized in that, The handle includes a sleeve and a handle. The sleeve is fitted onto the screw, and the handle is connected to the sleeve. Multiple balls are provided on the end face of the sleeve, and the multiple balls are evenly arranged circumferentially along the end face of the sleeve. The second end of the spring compression member is provided with a concave surface adapted to the size and position of the multiple balls.

6. A manually adjustable variable stiffness module according to claim 1, characterized in that, The screw has a split structure, including a first screw and a second screw. The first end of the first screw and the second end of the second screw are provided with a matching connection structure. The handle is installed on the second end of the first screw. The gears of the two sets of motion units are respectively connected to the first screw and the second screw.

7. A manually adjustable variable stiffness module according to claim 6, characterized in that, The first screw has a protruding part and a retaining ring groove. The gear is disposed between the protruding part and the retaining ring groove. One end of the gear is in contact with the protruding part, and the other end is connected to the first screw through a retaining ring installed in the retaining ring groove. The protruding part is connected to the gear rack housing through a bearing. The second screw has a protruding part and a retaining ring groove. The gear is disposed between the protruding part and the retaining ring groove. One end of the gear is in contact with the protruding part, and the other end is connected to the second screw through a retaining ring installed in the retaining ring groove. The protruding part is connected to the gear rack housing through a bearing.

8. A manually adjustable variable stiffness module according to claim 6, characterized in that, The first end of the first screw is provided with an inner hole, and the second end of the second screw is provided with a connecting section adapted to the length and cross-section of the inner hole; or, the second end of the second screw is provided with an inner hole, and the first end of the first screw is provided with a connecting section adapted to the length and cross-section of the inner hole.

9. A manually adjustable variable stiffness joint mechanism, characterized in that, The system includes a position control module and a variable stiffness module as described in any one of claims 1-8. The position control module includes a motor housing, a position motor, a flange, and a harmonic reducer. The position motor is mounted on the motor housing. The flange is connected to the output shaft of the position motor and the harmonic reducer. The harmonic reducer is connected to the base of the variable stiffness module. The flange rotates with the output shaft of the position motor. The rotation of the flange drives the harmonic reducer to rotate. The rotation of the harmonic reducer drives the base of the variable stiffness module to rotate. When the base rotates, the cam follower that contacts the outer contour of the raised curved surface of the base rolls along the outer contour of the raised curved surface of the base, thereby changing the potential energy of the spring structure of the first elastic unit and the second elastic unit.

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