A rope stiffness changing device and active-passive stiffness changing method thereof

Abstract

The present invention is a rope variable stiffness device and an active-passive variable stiffness method thereof, comprising a steel wire rope, a driving motor, a reduction gear, an elastic element, a sliding sleeve, a variable stiffness base, a main shaft and a nut slider; the sliding sleeve comprises an upper and lower part, and ear seats are symmetrically arranged on the upper and lower parts of the sliding sleeve, and the steel wire rope passes through all the ear seats in sequence from one side; a positioning block is arranged on the inner side of the bottom of the sliding sleeve; the variable stiffness base is located at the bottom of the sliding sleeve, and comprises a bottom plate, a bearing seat arranged below the bottom plate, and a cylindrical frame installed on the upper surface of the bottom plate, and the sliding sleeve can move up and down along the variable stiffness base; the nut slider is sleeved on the main shaft, and the nut slider can slide up and down along the variable stiffness base, and an elastic element is arranged between the nut slider and the inner surface of the top of the sliding sleeve. The rope stiffness is decoupled from the rope motion state, and the rope stiffness can not only be passively adjusted, but also actively adjusted, and the stiffness adjustment range is large.

Description

Technical Field

[0001] The invention relates to the technical field of rope-driven robots, and in particular to a rope variable stiffness device and a stiffness adjustment method thereof. Background Art

[0002] Traditional rigid drive devices are easily restricted in complex environments due to their high structural rigidity, and are difficult to flexibly respond to various complex situations. In contrast, rope drives use flexible ropes to transmit motion and force, which can better adapt to irregular or dynamically changing working environments, and also have significant advantages in terms of safety and cost. As a mechanical system with strong flexibility and adaptability, rope-driven robots are widely used in many fields such as medicine, agriculture, and services.

[0003] However, existing rope-driven robots have some technical bottlenecks in practical applications, especially in terms of rope stiffness adjustment. The existing technology adjusts the stiffness of the rope by changing the length of the rope or adding additional support structures. For example, some devices use pulley systems and motors to adjust the tension of the rope to change its stiffness. However, this method takes a long time to adjust the rope tension to change its stiffness, has a slow response speed, and has a complex structure and is not easy to maintain. There are also composite materials or multi-layer structures that adjust the proportion and arrangement of each layer of material to achieve stiffness adjustment. This method is limited by material selection and manufacturing process in practical applications, and it is difficult to achieve high-precision stiffness control. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the present invention provides a novel rope variable stiffness device and a stiffness adjustment method thereof. The device has a wide stiffness adjustment range, and can not only passively adjust the stiffness through the elastic element H, but also actively adjust the stiffness through the driving mechanism F, thereby improving the response speed and stability of the system.

[0005] The technical solution of the present invention to solve the technical problem is:

[0006] In a first aspect, the present invention provides a rope variable stiffness device, the device comprising a rope system, a driving mechanism, a stiffness adjustment mechanism, and an elastic element; the rope system comprises a steel wire rope, the driving mechanism comprises a driving motor and a reduction gear; the stiffness adjustment mechanism comprises a sliding sleeve, a variable stiffness base, a main shaft, and a nut slider;

[0007] The driving motor is installed on one side of the device and fixed to the motor base. The output end of the motor is connected to the reduction gear through a key to transmit the power to the main shaft of the stiffness adjustment mechanism;

[0008] The sliding sleeve comprises an upper and lower part, and ear seats are symmetrically arranged on the upper and lower parts of the sliding sleeve. The steel wire rope passes through all the ear seats in sequence from one side, and one end of the steel wire rope is pulled and the other end is driven;

[0009] A positioning block is provided on the inner side of the bottom of the sliding sleeve;

[0010] The variable stiffness base is located at the bottom of the sliding sleeve, and includes a bottom plate, a bearing seat G2-4 arranged below the bottom plate, and a cylinder frame installed on the upper surface of the bottom plate. A first positioning groove G2-2 is arranged along the height direction of the cylinder frame. The first positioning groove cooperates with the positioning block of the sliding sleeve, so that the sliding sleeve can move up and down along the variable stiffness base;

[0011] A bearing hole G2-8 for installing a bearing is provided at the center of the bottom plate and a first ball bearing G6 is installed thereon. A bearing hole is also provided at a coaxial position of the bearing seat G2-4 and a second ball bearing G5 is installed thereon. The lower end of the spindle G3 is fixed in the bearing seat G2-4 through the second ball bearing, and the upper part passes through the bearing hole on the bottom plate to realize the axial positioning of the spindle G3.

[0012] Second positioning grooves G2-9 are symmetrically arranged on both sides of the cylinder frame for sliding with the nut slider G4;

[0013] A motor base G2-6 is also provided on the bottom plate outside the cylinder frame, and the output shaft of the driving motor F1 passes downward through the motor base G2-6 and is connected to a spur gear F2 in the reduction gear system; a plurality of gear shafts G2-5 are provided on the lower surface of the bottom plate, each of which is equipped with a spur gear, and a spur gear F5 is also installed on the main shaft between the first ball bearing and the second ball bearing, and all the spur gears are meshed with each other to transmit the power of the driving motor F1 to the main shaft G3 through the reduction gear system composed of all the spur gears;

[0014] The nut slider G4 is mounted on the main shaft, and both ends of the nut slider cooperate with the second positioning grooves so that the nut slider can slide up and down along the variable stiffness base, and an elastic element is arranged between the nut slider and the inner surface of the top of the sliding sleeve.

[0015] Furthermore, the sliding sleeve and the cylindrical frame on the variable stiffness base are both provided with observation windows for reducing weight and observing the status of internal parts;

[0016] Furthermore, four viewing windows are processed on the upper and lower parts of the sliding sleeve respectively; four viewing ports are processed on the cylindrical frame, and the viewing windows and the viewing ports do not block each other in the circumferential direction.

[0017] Furthermore, two upper ear seats and two inclined grooves for guiding the rope are arranged on the outer side of the top of the sliding sleeve, and a circular groove is arranged on the inner side of the top for fixing the elastic element; two lower ear seats are also arranged on the outer side of the top side of the lower part;

[0018] After the driving mechanism F is installed on the variable stiffness base G2, the elastic element H is fixed on the nut slider G4, and then the sliding sleeve F1 is mounted on the outside of the variable stiffness base G2. At this time, the first positioning groove on the variable stiffness base G2 cooperates with the positioning block on the sliding sleeve F1, and the second positioning groove cooperates with the two ends on the nut slider G4; the wire rope passes through the rope hole, the lower ear seat, the two upper ear seats, the other lower ear seat and the rope hole on the other side from one side to complete the installation of the device.

[0019] Furthermore, the elastic element is a linear spring or a variable pitch nonlinear spring.

[0020] Furthermore, one end of the spindle is a lead screw thread G3-2, on which a nut slider G4 is installed; the other end is a three-section stepped shaft, wherein the first section shoulder G3-3 is installed with a first ball bearing G6; the second section shoulder G3-4 is connected to the spur gear F5 for transmission, and is processed with a retaining ring groove G3-5, and the above-mentioned spur gear F5 for transmission is fixed by installing a retaining ring; the third section shoulder G3-6 is used to install a second ball bearing G5; a threaded hole G3-1 is processed on the top of the spindle, which is used to install a limit screw G7 to limit the moving distance of the nut slider G4 on the spindle;

[0021] An annular groove G4-2 is coaxially arranged on the upper surface of the nut slider G4, and the annular groove is used to fix the elastic element H; a threaded hole G4-3 is arranged at the center of the nut slider G4, and the threaded hole on the nut slider cooperates with the screw thread G3-2 of the main shaft.

[0022] In a second aspect, the present invention provides an active-passive variable stiffness method, which uses the rope variable stiffness device described in any one of claims 1 to 6, and the specific method is: when the wire rope is tensioned, the wire rope squeezes the sleeve slider and undergoes relative displacement with the variable stiffness base, compresses the elastic element and generates impedance force, thereby realizing the passive variable stiffness function of the wire rope; when the length of the wire rope does not change, the sliding sleeve remains stationary, and at this time the driving motor drives the main shaft to rotate by driving the reduction gear system. Due to the positioning block of the nut slider, the nut slider matched with the main shaft moves axially, actively compresses the elastic element, increases the contact force between the sliding sleeve and the wire rope, and realizes the active variable stiffness function of the wire rope; when the nut slider is in the lowest limit position, the rope stiffness is 0N·mm / rad, and when the nut slider is in the highest limit position, the elastic element reaches the maximum compression amount, and the rope stiffness tends to infinity.

[0023] In a third aspect, the present invention also protects a cable-driven robot using the cable variable stiffness device.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The rope stiffness of the present invention is decoupled from the rope motion state, which can not only passively adjust the rope stiffness, but also actively adjust the stiffness through the driving mechanism F, and the stiffness adjustment range is large (the stiffness variation range of 0 to ∞ can be achieved).

[0026] 2. The stiffness adjustment mechanism adopts screw nut transmission, compact layout, and generates impedance by compressing the elastic element. At the same time, the linear spring has good stability and high stiffness adjustment resolution. This variable stiffness device has a simple structure and is easy to implement.

[0027] 3. The upper and lower ends of the linear spring are clamped in the grooves for fixation, and can be replaced with linear and nonlinear springs according to actual needs. The variable stiffness characteristics of the rope system can be obtained without the need for additional drive.

[0028] 4. The rope variable stiffness device can be directly connected in series with the rope system and can be widely used in various rope-driven robots, achieving the flexibility of the drive and significantly improving the safety and application scope of the rope-driven robots.

[0029] 5. The overall size of the device designed in the embodiment of the present invention is 130mm×90mm×140mm (length×width×height), and the rope stiffness adjustment range is 0N·mm / rad to ∞. When it is infinite, it is regarded as a rigid connection. Compared with the existing rope variable stiffness device, it has the advantages of small size, large stiffness adjustment range, and high stiffness resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the three-dimensional structure of the rope stiffness variable device of the present invention;

[0031] Figure 2 for Figure 1 The main cross-sectional view of

[0032] Figure 3 is a schematic diagram of the three-dimensional structure of the sliding sleeve;

[0033] Figure 4 It is a schematic diagram of the three-dimensional structure of the variable stiffness base;

[0034] Figure 5 A schematic diagram of the three-dimensional structure of the main axis;

[0035] Figure 6 It is a three-dimensional structural schematic diagram of the nut slider;

[0036] Figure 7Schematic diagram of the three-dimensional structure of the device when the rigidity is low (the nut slider is located at a low position);

[0037] Figure 8 Schematic diagram of the three-dimensional structure of the device when the rigidity is high (the nut slider is located at a high position);

[0038] The code names in the figure are: E, rope system; F, driving mechanism; G, stiffness adjustment mechanism; H, elastic element; G1, sliding sleeve; G1-1, upper left ear seat; G1-2, upper right ear seat; G1-3, left inclined slot; G1-4, right inclined slot; G1-5, upper observation window; G1-6, lower left ear seat; G1-7, lower right ear seat; G1-8, positioning block; G1-9, lower observation window; G2, variable stiffness base; G2-1, visual port; G2-2, first positioning slot; G2-3, rope hole; G2-4, bearing seat; G2- 5. Gear shaft; G2-6. Motor base; G2-7. Threaded hole; G2-8. Bearing hole; G2-9. Second positioning groove; G3. Spindle; G3-1. Threaded hole; G3-2. Screw thread; G3-3. First section shoulder; G3-4. Second section shoulder; G3-5. Circlip groove; G3-6. Third section shoulder; G4. Nut slider; G4-1. Left protrusion; G4-2. Groove; G4-3. Threaded hole; G4-4. Right protrusion; G5. Second ball bearing; G6. First ball bearing; G7. Limit screw. DETAILED DESCRIPTION

[0039] The specific embodiments of the present invention are given below. The specific embodiments are only used to further illustrate the present invention in detail and do not limit the protection scope of the present application.

[0040] See also Figure 1-Figure 2 As shown, a rope variable stiffness device of this embodiment includes a rope system E, a driving mechanism F, a stiffness adjustment mechanism G, and an elastic element H;

[0041] The driving mechanism F is installed on one side of the variable stiffness base G2 and fixed to the motor base G2-6, and is composed of a driving motor F1 and a reduction gear train F2-F5; the driving motor F1 transmits power to the main shaft G3 of the stiffness adjustment mechanism to actively adjust the stiffness of the rope;

[0042] The stiffness adjustment mechanism G comprises a sliding sleeve G1, a variable stiffness base G2, a main shaft G3 and a nut slider G4;

[0043] The sliding sleeve G1 (see Figure 3) comprises an upper and a lower part, the upper and lower parts are an integrated structure, two upper left ear seats G1-1 and upper right ear seats G1-2 and two inclined grooves G1-3 and G1-4 are arranged on the outer side of the top for rope guidance, and a circular groove is processed on the inner side of the top for fixing the elastic element; two lower left ear seats G1-6 and lower right ear seats G1-7 are also arranged on the outer side of the top side of the lower part; in addition, a positioning block G1-8 is arranged on the inner side of the bottom of the sliding sleeve, which cooperates with the positioning groove G2-2 of the variable stiffness base G2 to ensure that the sliding sleeve G1 slides up and down; the upper and lower parts are processed with 4 upper observation windows G1-5 and lower observation windows G1-9 respectively, so as to realize lightweight design and observe the status of internal parts;

[0044] The variable stiffness base G2 is located at the bottom of the rope variable stiffness device, including a bottom plate, a bearing seat G2-4 arranged below the bottom plate, and a cylinder frame installed on the upper surface of the bottom plate. Four visible ports G2-1 are evenly arranged on the side of the cylinder frame, and a first positioning groove G2-2 is arranged between two of the visible ports along the height direction of the cylinder frame, and the first positioning groove cooperates with the positioning block G1-8 on the sliding sleeve; two rope holes G2-3 are symmetrically arranged at the diagonal positions of the bottom plate on the periphery of the cylinder frame, and a bearing hole G2-8 for installing bearings is arranged in the center of the bottom plate, a first ball bearing G6 is installed in the bearing hole G2-8, and a bearing hole is also arranged at the coaxial position of the bearing seat G2-4, in which a second ball bearing G5 is installed, the lower end of the main shaft G3 is fixed in the bearing seat G2-4 through the second ball bearing, and the upper part passes through the bearing hole on the bottom plate to realize the axial positioning of the main shaft G3;

[0045] With the first positioning groove G2-2 as the center, second positioning grooves G2-9 are symmetrically arranged on both sides of the cylinder frame for sliding with the nut slider G4, and the second positioning groove is located between two adjacent viewing ports;

[0046] A motor base G2-6 is also provided on the bottom plate outside the cylinder frame, and a threaded hole G2-7 for installing the drive motor is provided on the motor base G2-6. The output shaft of the drive motor F1 passes downward through the through hole of the motor base G2-6 and is connected with a spur gear F2 in the reduction gear system; a plurality of gear shafts G2-5 are provided on the lower surface of the bottom plate, each of which is equipped with a spur gear, and a spur gear F5 is also installed on the main shaft between the first ball bearing and the second ball bearing, and all the spur gears are meshed with each other to transmit the power of the drive motor F1 to the main shaft G3 through the reduction gear system composed of all the spur gears.

[0047] The main shaft G3 is installed inside the rope stiffness variable device for transmitting power; one end of the main shaft is a screw thread G3-2, and a nut slider G4 is installed on the screw thread G3-2, and the rotation of the main shaft drives the nut slider G4 to move up and down; the other end is a three-section stepped shaft, among which the first section shoulder G3-3 is installed with the first ball bearing G6; the second section shoulder G3-4 is connected to the spur gear F5 for transmission, and is machined with a retaining ring groove G3-5, and the above-mentioned spur gear F5 for transmission is fixed by installing the retaining ring; the third section shoulder G3-6 is used to install the second ball bearing G5; the top of the main shaft is machined with a threaded hole G3-1, which is used to install a limit screw G7 to limit the moving distance of the nut slider G4 on the main shaft.

[0048] The outer end of the nut slider G4 is symmetrically provided with a left protrusion G4-1 and a right protrusion G4-4, which respectively cooperate with the second positioning groove G2-9 of the variable stiffness base to ensure that the nut slider can only move up and down but cannot rotate; an annular groove G4-2 is coaxially provided on the upper surface of the nut slider G4, and the annular groove is used to fix the elastic element H; a threaded hole G4-3 is provided in the center of the nut slider G4, and the threaded hole on the nut slider cooperates with the lead screw thread G3-2 of the main shaft, so that the nut slider moves up and down following the rotation of the main shaft when the main shaft rotates.

[0049] The rope system E includes a steel wire rope and a steel wire rope driving motor (not shown in the figure), one end of the steel wire rope is connected to an external actuator (i.e., the object being towed), and the other end is powered by the steel wire rope driving motor; after the driving mechanism F is installed on the variable stiffness base G2, the elastic element H is fixed on the nut slider G4, and then the sliding sleeve F1 is mounted on the outside of the variable stiffness base G2. At this time, the first positioning groove on the variable stiffness base G2 cooperates with the positioning block on the sliding sleeve F1, and the second positioning groove cooperates with the two protrusions on the nut slider G4; then the steel wire rope is passed from one side through the rope hole, the lower ear seat, the two upper ear seats, the other lower ear seat and the rope hole on the other side to complete the installation of the device.

[0050] One end of the rope system passes through the rope hole of the variable stiffness base, and then passes through the other rope hole of the variable stiffness base via the rope hole of the sliding sleeve. The rope system is subjected to force to cause relative displacement between the sleeve slider and the variable stiffness base, compressing the elastic element and generating impedance force, thereby changing the rope tension characteristics.

[0051] The sliding sleeve has multiple ears for guiding the rope. The number of the ears is an even number and they are arranged symmetrically on the left and right, such as 4, 6, 8, etc., to convert the horizontal displacement of the rope into the vertical displacement of the sliding sleeve.

[0052] A plurality of positioning grooves are arranged on the variable rigidity base to limit the rotation of the nut slider and the sliding sleeve.

[0053] The elastic element is installed between the sliding sleeve and the variable stiffness base, and is compressed or restored in length as the nut slider moves. It can be a linear spring or a variable pitch nonlinear spring, and can be selected according to the stiffness characteristic requirements.

[0054] The active-passive variable stiffness method of the present invention is as follows: when the wire rope is tensioned, the wire rope squeezes the sleeve slider and is relatively displaced with the variable stiffness base, compresses the elastic element and generates impedance force, so that the passive variable stiffness function of the wire rope can be realized. By replacing springs with different stiffnesses, or selecting variable pitch linear springs, the ability of passive variable stiffness can be adjusted; when the length of the wire rope does not change, the sliding sleeve remains stationary, and the driving motor drives the main shaft to rotate by driving the reduction gear system. Due to the protrusion setting of the nut slider, the nut slider matched with the main shaft moves axially, actively compresses the elastic element, and increases the contact force between the sliding sleeve and the wire rope, so that the active variable stiffness function of the wire rope can be realized; when the nut slider is at the lowest limit position, the wire rope stiffness is 0N·mm / rad, and when the nut slider is at the highest limit position, the elastic element reaches the maximum compression amount, and the wire rope stiffness tends to infinity. The stiffness approaching infinity refers to a rigid connection, and the deformation of the wire rope is 0 under the action of external force.

[0055] The overall dimensions of the rope variable stiffness device of this embodiment are 130mm×90mm×140mm (length×width×height), and the torque of the drive motor is 0.8N·m; the elastic element is a linear spring with a spring wire diameter of 3mm, a middle diameter of 36mm, and 19 turns, and the spring material is carbon spring steel wire; the upper part of the sliding sleeve G1 is a cylindrical sleeve with an outer diameter of 73mm, a height of 70mm, and a thickness of 4mm; the lower part has an outer diameter of 90mm, a height of 50mm, and a thickness of 4mm; the lead screw of the main shaft G3 has a thread of M12×1.25, and the stiffness adjustment range of the wire rope is 0N·mm / rad to ∞.

[0056] The present invention can be applied to applications that require precise control and adjustment of the stiffness of the rope, such as rope-driven robots, rope-driven rehabilitation robots, medical devices, robotic arms and other fields, and has broad application prospects. In particular, the rope variable stiffness device is applied to a rope-driven variable stiffness robot. The rope variable stiffness device is connected in series with the rope system, and can adjust the stiffness of the rope in both passive and active modes, so that the rope drive has a certain degree of flexibility. When in use, one end of the rope is fixed, and the other end is pulled and moves axially. The stiffness adjustment mechanism is used to compress the internal elastic element to achieve passive stiffness adjustment of the rope. In addition, the drive motor can also be used to actively compress the spring to achieve active stiffness adjustment of the rope.

[0057] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A rope stiffness varying device, characterized in that: The device comprises a rope system, a driving mechanism, a stiffness adjustment mechanism, and an elastic element; the rope system comprises a steel wire rope, the driving mechanism comprises a driving motor and a reduction gear; the stiffness adjustment mechanism comprises a sliding sleeve, a variable stiffness base, a main shaft, and a nut slider; The driving motor is installed on one side of the device and fixed to the motor base. The output end of the motor is connected to the reduction gear through a key to transmit the power to the main shaft of the stiffness adjustment mechanism; The sliding sleeve comprises an upper and lower part, and ear seats are symmetrically arranged on the upper and lower parts of the sliding sleeve. The steel wire rope passes through all the ear seats in sequence from one side, and one end of the steel wire rope is pulled and the other end is driven; A positioning block is provided on the inner side of the bottom of the sliding sleeve; The variable stiffness base is located at the bottom of the sliding sleeve, and includes a bottom plate, a bearing seat arranged below the bottom plate, and a cylinder frame installed on the upper surface of the bottom plate. A first positioning groove is arranged along the height direction of the cylinder frame. The first positioning groove cooperates with the positioning block of the sliding sleeve, so that the sliding sleeve can move up and down along the variable stiffness base; A bearing hole for mounting a bearing is provided at the center of the bottom plate and a first ball bearing is installed thereon. A bearing hole is also provided at a coaxial position of the bearing seat and a second ball bearing is installed thereon. The lower end of the main shaft is fixed in the bearing seat through the second ball bearing, and the upper part passes through the bearing hole on the bottom plate to realize the axial positioning of the main shaft. Second positioning grooves are symmetrically arranged on both sides of the cylinder frame for sliding with the nut slider; A motor base is also arranged on the bottom plate outside the cylinder frame, and the output shaft of the driving motor passes downward through the motor base and is connected to a spur gear in the reduction gear system; a plurality of gear shafts are arranged on the lower surface of the bottom plate, each of which is equipped with a spur gear, and a spur gear is also arranged on the main shaft between the first ball bearing and the second ball bearing, and all the spur gears are meshed with each other to transmit the power of the driving motor to the main shaft through the reduction gear system composed of all the spur gears; The nut slider is sleeved on the main shaft, and both ends of the nut slider are matched with the second positioning grooves, so that the nut slider can slide up and down along the variable stiffness base, and an elastic element is arranged between the nut slider and the inner surface of the top of the sliding sleeve; When the wire rope is tensioned, the wire rope squeezes the sleeve slider and moves relative to the variable stiffness base, compressing the elastic element and generating impedance force, thereby realizing the passive variable stiffness function of the wire rope; when the length of the wire rope does not change, the sliding sleeve remains stationary. At this time, the driving motor drives the main shaft to rotate by driving the reduction gear system. Due to the positioning block of the nut slider, the nut slider matched with the main shaft moves axially, actively compressing the elastic element, increasing the contact force between the sliding sleeve and the wire rope, and realizing the active variable stiffness function of the wire rope; when the nut slider is at the lowest limit position, the rope stiffness is 0 N•mm / rad, and when the nut slider is at the highest limit position, the elastic element reaches the maximum compression amount, and the rope stiffness tends to infinity.

2. The rope stiffness varying device according to claim 1, characterized in that: The sliding sleeve and the cylindrical frame on the variable stiffness base are both provided with observation windows for reducing weight and observing the status of internal parts.

3. The rope stiffness varying device according to claim 2, characterized in that: Four viewing windows are respectively processed on the upper and lower parts of the sliding sleeve; four viewing ports are processed on the cylindrical frame, and the viewing windows and the viewing ports do not block each other in the circumferential direction.

4. The rope stiffness varying device according to claim 1, characterized in that: Two upper ear seats and two inclined grooves for guiding the rope are arranged on the outer side of the top of the sliding sleeve, and a circular groove is arranged on the inner side of the top for fixing the elastic element; two lower ear seats are also arranged on the outer side of the top side of the lower part; After the driving mechanism is installed on the variable stiffness base, the elastic element is fixed on the nut slider, and then the sliding sleeve is put on the outside of the variable stiffness base. At this time, the first positioning groove on the variable stiffness base cooperates with the positioning block on the sliding sleeve, and the second positioning groove cooperates with the two ends on the nut slider for installation; the wire rope passes through the rope hole, the lower ear seat, the two upper ear seats, the other lower ear seat and the rope hole on the other side from one side to complete the installation of the device.

5. The rope stiffness varying device according to claim 1, characterized in that: The elastic element is a linear spring or a variable pitch nonlinear spring.

6. The rope stiffness varying device according to claim 1, characterized in that: One end of the spindle is a lead screw thread, on which a nut slider is installed; the other end is a three-section stepped shaft, wherein the first section shoulder is installed with a first ball bearing; the second section shoulder is connected to a spur gear for transmission and is processed with a retaining ring groove, and the above-mentioned spur gear for transmission is fixed by installing a retaining ring; the third section shoulder is used to install a second ball bearing; the top of the spindle is processed with a threaded hole for installing a limit screw to limit the moving distance of the nut slider on the spindle; An annular circular groove is coaxially arranged on the upper surface of the nut slider, and the annular circular groove is used to fix the elastic element; a threaded hole is arranged at the center of the nut slider, and the threaded hole on the nut slider cooperates with the lead screw thread of the main shaft.

7. An active-passive variable stiffness method, characterized in that: The method uses the rope variable stiffness device described in any one of claims 1 to 6, and the specific method is: when the wire rope is tensioned, the wire rope squeezes the sleeve slider and relatively displaces with the variable stiffness base, compresses the elastic element and generates impedance force, thereby realizing the passive variable stiffness function of the wire rope; when the length of the wire rope does not change, the sliding sleeve remains stationary, and the driving motor drives the main shaft to rotate by driving the reduction gear system. Due to the positioning block of the nut slider, the nut slider matched with the main shaft moves axially, actively compresses the elastic element, increases the contact force between the sliding sleeve and the wire rope, and realizes the active variable stiffness function of the wire rope; when the nut slider is at the lowest limit position, the rope stiffness is 0 N•mm / rad, and when the nut slider is at the highest limit position, the elastic element reaches the maximum compression amount, and the rope stiffness tends to infinity.

8. A rope-driven robot, characterized in that: The robot uses the rope variable stiffness device described in any one of claims 1-6.

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