Flexible cable driven lower limb rehabilitation robot based on multi-stage adjustable variable stiffness device

Abstract

The invention relates to a flexible cable driven lower limb rehabilitation robot based on a multi-stage adjustable variable stiffness device. Comprising a left leg exoskeleton and a right leg exoskeleton which are arranged on the two sides of a control platform, each of the left leg exoskeleton and the right leg exoskeleton comprises a tibia rod, the lower end of each tibia rod is connected with a sole supporting plate through an ankle joint, and the upper end of each tibia rod is connected with a supporting arm through a knee joint; the ankle joint is connected with an ankle joint variable stiffness device, the knee joint is connected with a knee joint variable stiffness device, the ankle joint variable stiffness device is connected with an ankle joint driving device, and the knee joint variable stiffness device is connected with a knee joint driving device. According to the technical scheme, the variable stiffness device is introduced, the strength and stiffness of the driving force can be adjusted in different rehabilitation stages according to specific requirements of patients, and therefore finer rehabilitation training is achieved. And the variable stiffness devices of all the joints are independently adjusted and do not influence each other. And the flexible cable is adopted for driving, so that better safety, flexibility and comfort are achieved.

Description

Technical Field

[0001] The invention relates to the field of rehabilitation robots, and in particular to a flexible cable-driven lower limb rehabilitation robot based on a multi-stage adjustable variable stiffness device. Background Art

[0002] In the field of rehabilitation medicine, with the advent of an aging society, the demand for rehabilitation treatment is increasing, especially for patients with neurological diseases such as stroke and spinal cord injury. Traditional rehabilitation treatment methods mainly rely on manual guidance from physical therapists, but due to problems such as long treatment time, limited treatment effects and large individual differences among patients, more intelligent and automated rehabilitation equipment is urgently needed.

[0003] Current rehabilitation robots have deficiencies in human-machine interaction, compliance and adaptability. For example, some ankle rehabilitation robots have poor human-machine structure matching, poor compliance and weak adaptability, which limits their application in rehabilitation training. In order to solve the above problems, a device that can adjust stiffness is needed to meet the rehabilitation needs of different patients. This device should have a simple and compact structure and high stiffness-tension linear characteristics to improve the range and accuracy of variable stiffness control. As a new type of flexible drive method, flexible cable drive can provide highly flexible control and simulate the natural movement trajectory of human joints. Traditional flexible drive systems mostly rely on fixed stiffness control, which is difficult to accurately adjust according to the rehabilitation progress and needs of different patients, so they have poor adaptability in personalized rehabilitation treatment.

[0004] At present, the research and application of lower limb rehabilitation robots have been very extensive, but there are still some shortcomings waiting to be improved. Patent CN112426327B discloses a variable stiffness cable-driven actuator based on a nonlinear mechanism. The patent uses a motor-driven mechanical action to change the stiffness, which increases the overall weight of the mechanism and increases the burden on the patient's upper body. The response to the safe position cannot be timely, and there are certain safety hazards. Patent CN108606907A proposes a movable parallel cable-driven lower limb rehabilitation robot, which can realize gait training and walking training in passive, assisted and active modes. However, the overall structure is huge, which increases the cost of the machine and has certain requirements for the application scenario. Although safety straps and tension sensors are mentioned, emergency situations that may occur during the patient's use are not considered. Emergency response measures are insufficient, and the patient is pulled by the safety strap, and the comfort of rehabilitation is not high. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned drawbacks and provide a flexible cable-driven lower limb rehabilitation robot based on a multi-stage adjustable variable stiffness device.

[0006] To achieve the above object, the present invention adopts the following technical scheme: comprising a left leg exoskeleton and a right leg exoskeleton symmetrically arranged on both sides of a control platform, wherein the left leg exoskeleton and the right leg exoskeleton each comprise a tibial rod, wherein the lower end of the tibial rod is connected to a foot support plate through an ankle joint, and the upper end of the tibial rod is connected to a support arm fixed on the control platform through a knee joint; The ankle joint is connected to an ankle joint variable stiffness device, and the knee joint is connected to a knee joint variable stiffness device. The ankle joint variable stiffness device and the knee joint variable stiffness device have the same structure and each comprises a shell, and end covers and winding rings are fixed to the two ends of the shell, respectively. A variable stiffness rotating shaft is arranged in the shell, and one end of the variable stiffness rotating shaft close to the end cover is cantilevered outside the shell and is fixedly connected to the electromagnetic brake, and one end of the variable stiffness rotating shaft close to the winding ring is fixedly connected to the ankle joint rotating shaft or the knee joint rotating shaft through a coupling; The variable stiffness shaft is provided with a first magnetic transmission plate, an elastic element group, a second magnetic transmission plate and an electromagnet in sequence from the end cover to the winding ring direction. The first magnetic transmission plate, the elastic element group and the second magnetic transmission plate are connected to form a whole through a connecting rod, and one end of the connecting rod close to the end cover is connected to the end cover through a compression spring. The elastic element group is composed of a plurality of disc springs with the same structure and different elasticity. A key fixed to the elastic element group is provided on the variable stiffness shaft. The circumference of the first magnetic transmission plate and the second magnetic transmission plate are respectively provided with sliders, which cooperate with the slide grooves provided on the inner wall of the shell. The slide grooves are arranged along the axial direction of the shell. When the electromagnet is energized, the second magnetic transmission plate is attracted to move in the direction of the electromagnet, thereby driving the elastic element group to slide in the direction defined by the slide groove. The connection and fixation of each disc spring in the elastic element group with the key are achieved by controlling the current size of the electromagnet. When the electromagnet is powered off, the elastic element group is driven back to its position by the compression spring. The winding ring in the ankle joint variable stiffness device is connected to the ankle joint driving device through a first flexible cable, and the winding ring in the knee joint variable stiffness device is connected to the knee joint driving device through a second flexible cable. The ankle joint driving device and the knee joint driving device have the same structure and each includes a reel connected to the first flexible cable or the second flexible cable. The reel is driven to rotate by a reel motor to achieve the retraction and extension of the corresponding flexible cable.

[0007] The elastic element group includes a first elastic element group consisting of a first disc spring, a second disc spring, and a third disc spring, and a second elastic element group consisting of a fourth disc spring and a fifth disc spring. The key includes a first key that cooperates with the first elastic element group and a second key that cooperates with the second elastic element group. A limiting sleeve is fixed on the connecting rod between the first elastic element group and the second elastic element group. Gaskets are respectively fixed on the connecting rods between the disc springs of the first elastic element group, between the first elastic element group and the first magnetic transmission plate, between the disc springs of the second elastic element group, and between the second elastic element group and the second magnetic transmission plate.

[0008] The ankle joint comprises an ankle joint rotation axis and an ankle joint support frame, the lower end of the tibial rod is fixedly connected to the first ear seat of the ankle joint support frame, the two ends of the ankle joint rotation axis are respectively rotatably connected to the second ear seat of the ankle joint support frame through deep groove ball bearings, a first connecting bracket is coaxially fixed to the ankle joint rotation axis, and the first connecting bracket is fixed to the second connecting bracket on the sole support plate; The knee joint includes a knee joint rotation axis and a knee joint support frame, the third ear seat of the knee joint support frame is fixed to the support arm, the two ends of the knee joint rotation axis are rotatably connected to the fourth ear seat of the knee joint support frame through deep groove ball bearings, a third connecting bracket is coaxially fixed on the knee joint rotation axis, and the third connecting bracket is fixedly connected to the upper end of the tibial rod.

[0009] The tibial rod is a split structure, including an upper tibial rod and a lower tibial rod that are plug-fitted together. The upper tibial rod and the lower tibial rod are both integrally formed structures. The upper tibial rod includes a first rod body connected to the knee joint and a second rod body inserted into the lower tibial rod. The lower tibial rod includes a third rod body plug-fitted with the second rod body and a fourth rod body connected to the ankle joint. The cross-sections of the first rod body, the second rod body, the third rod body and the fourth rod body are all square, and the third rod body is a structure with an open top, a hollow interior, a closed bottom end and hollow front and rear end faces. A fixing frame is sleeved near the upper end of the lower tibial rod, and the fixing frame is fixedly connected to the lower tibial rod. A strap for fixing the leg is provided on the fixing frame.

[0010] The length of the tibial rod is adjusted by a length adjusting device between the upper tibial rod and the lower tibial rod, and the length adjusting device comprises a ball screw arranged in a vertical direction and a rotating rod arranged in a horizontal direction, the ball screw is arranged in parallel on the rear side of the tibial rod, the upper end of the ball screw is provided with a screw support seat, the screw support seat is connected to the fixing frame, the lower end of the ball screw is coaxially connected to the first bevel gear, the ball screw is provided with a first nut seat which forms a screw nut movement therewith, and the first nut seat is fixed on the upper tibial rod; one end of the rotating rod is coaxially connected to the second bevel gear, the second bevel gear is meshed with the first bevel gear, the other end of the rotating rod is fixed with a handle rotating disk, the handle rotating disk is connected to a handle, the middle section of the rotating rod is provided with a rotating rod support seat, the rotating rod is fixed in the rotating rod support seat through a rotating rod sleeve, and the rotating rod support seat is fixed to the lower tibial rod through a fourth connecting bracket.

[0011] A spring is provided between the lower tibial rod and the first connecting bracket to provide movement buffer for the ankle joint. Two springs are provided, and the two springs are symmetrically arranged on the front and rear sides of the lower tibial rod. The upper end of the spring is fixed to the upper spring seat connected to the lower tibial rod, and the lower end of the spring is fixed to the lower spring seat on the first connecting bracket.

[0012] The knee joint is provided with a limit device for limiting the rotation angle of the knee joint, and the limit device includes a first limit plate and a second limit plate symmetrically arranged on both sides of the third connecting bracket, the upper ends of the first limit plate and the second limit plate are sleeved on the knee joint rotation axis, and the lower ends of the first limit plate and the second limit plate are fixed to the left and right side surfaces of the upper tibial rod, and the limit device also includes a limit block fixed on the knee joint support frame, and the first limit plate and the second limit plate are provided with a limit surface matching the limit block.

[0013] The output shaft of the drum motor is connected to the drum shaft through a plum blossom coupling, and the two ends of the drum shaft are connected to the first bearing bracket and the second bearing bracket through deep groove ball bearings respectively. The drum motor is fixed on the motor bracket, and a trapezoidal screw is also provided between the first bearing bracket and the second bearing bracket, and the two ends of the trapezoidal screw are rotatably connected to the first bearing bracket and the second bearing bracket respectively, and a second nut seat is provided on the trapezoidal screw to form a screw nut movement therewith, and a first reversing wheel is fixed on the second nut seat, and a second reversing wheel is fixed on the first bearing bracket, the first reversing wheel is parallel to the axle of the second reversing wheel, and the axle of the first reversing wheel is perpendicular to the drum shaft, and a guide rod is provided between the first bearing bracket, the second bearing bracket and the second nut seat, and a three-pulley tension sensor is also provided on the side of the drum.

[0014] A pulley transmission device connecting the drum and the trapezoidal screw is provided between the two. The pulley transmission device includes a first pulley coaxially arranged with the drum, a second pulley coaxially arranged with the trapezoidal screw, and a belt connecting the first pulley and the second pulley, and a tensioning pulley is provided below the belt.

[0015] One end of the first flexible cable is fixedly connected to the drum in the ankle joint driving device, and the other end of the first flexible cable is successively wound around the first reversing wheel, the second reversing wheel, the three-pulley tension sensor, and the first pulley group, and then fixed to the winding ring in the ankle joint variable stiffness device; one end of the second flexible cable is fixedly connected to the drum in the knee joint driving device, and the other end of the second flexible cable is successively wound around the first reversing wheel, the second reversing wheel, the three-pulley tension sensor, and the second pulley group, and then fixed to the winding ring in the knee joint variable stiffness device; The first pulley group includes a first pulley, a second pulley, a first pulley block, a third pulley, a fourth pulley, a fifth pulley, a sixth pulley and a seventh pulley which are arranged in sequence; the second pulley group includes an eighth pulley, a second pulley block, a ninth pulley, a tenth pulley, an eleventh pulley, a twelfth pulley and a thirteenth pulley which are arranged in sequence, wherein: the first pulley is fixed to a first pulley bracket on a side of a second layer plate of the control platform, the second pulley and the eighth pulley are fixed to a second pulley bracket on a side of a first layer plate of the control platform, the third pulley, the fourth pulley, the fifth pulley, the sixth pulley, the seventh pulley, the ninth pulley, the tenth pulley, the eleventh pulley, the twelfth pulley and the thirteenth pulley are all fixed to a pulley support plate, and the pulley support plate, the first pulley block and the second pulley block are all fixed to a bottom plate inside the support arm.

[0016] The beneficial effects of the present invention are: 1. The present invention is provided with an ankle joint variable stiffness device and a knee joint variable stiffness device, which can adjust the stiffness of the driver according to the rehabilitation needs of the rehabilitation patient; at the same time, the elastic element in the variable stiffness device adopts a disc spring structure, so that the variable stiffness device has a lower impedance, can provide a larger elastic force in a smaller volume, and has a higher load-bearing capacity. The disc spring deforms evenly when subjected to force, can provide a stable elastic force, and can improve the stability of rehabilitation training.

[0017] 2. The elastic element group of the present invention provides three stiffness gears through five disc springs, which can achieve the selection of multiple stiffness conditions under one installation condition, greatly enhancing the environmental applicability of the variable stiffness device and achieving one device to meet multiple needs. This modular design can reduce the cost of the equipment.

[0018] 3. In the event of an emergency such as a collision, overload or derailment of the robot, the two sets of disc springs and the electromagnetic brake are used in conjunction to alleviate the impact on the joints and the damage to the mechanical structure, thereby improving the safety of rehabilitation training.

[0019] 4. The present invention adopts a flexible cable drive to make the robot more flexible, avoid rigid contact between the mechanism and the human body, and improve the safety and comfort of rehabilitation training; during the rehabilitation process, a tension sensor is used to monitor the tension of the flexible cable in real time to further improve the safety of rehabilitation training.

[0020] 5. The ankle joint drive device and the knee joint drive device in the present invention are installed on the control platform, which greatly reduces the load on the joints. Combined with the variable stiffness device at the joints, it can realize functions such as driving, braking and stiffness adjustment, thereby increasing the auxiliary torque for patients. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the present invention.

[0022] Figure 2 It is a structural schematic diagram of the control platform of the present invention.

[0023] Figure 3 It is a schematic diagram of the overall structure of the tibial rod of the present invention.

[0024] Figure 4 yes Figure 3 Schematic diagram of the decomposition structure.

[0025] Figure 5 The overall structure of the tibial rod and the length adjustment device of the present invention is shown in FIG. Figure 1 .

[0026] Figure 6 The overall structure of the tibial rod and the length adjustment device of the present invention is shown in FIG. Figure 2 .

[0027] Figure 7 yes Figure 6 Schematic diagram of the decomposition structure.

[0028] Figure 8 This is a schematic diagram of the structure of the left leg exoskeleton of the present invention. Figure 1 .

[0029] Fig. 9 This is a schematic diagram of the structure of the left leg exoskeleton of the present invention. Figure 2 .

[0030] Fig.10 The overall structure of the ankle joint and the lower tibial rod of the present invention is shown in FIG. Figure 1 .

[0031] Fig.11 The overall structure of the ankle joint and the lower tibial rod of the present invention is shown in FIG. Figure 2 .

[0032] Fig.12 yes Fig.11Schematic diagram of the decomposition structure.

[0033] Fig.13 It is a schematic diagram of the connection between the first connecting bracket and the foot support plate of the present invention.

[0034] Fig.14 yes Fig.13 Schematic diagram of the decomposition structure.

[0035] Fig.15 The structure of the ankle joint of the present invention is shown in FIG. Figure 1 .

[0036] Fig.16 The structure of the ankle joint of the present invention is shown in FIG. Figure 2 .

[0037] Fig.17 It is a schematic diagram of the connection between the knee joint and the upper tibial rod of the present invention.

[0038] Fig.18 yes Fig.17 Schematic diagram of the decomposition structure.

[0039] Fig.19 It is a schematic structural diagram of a knee joint of the present invention.

[0040] Fig. 20 It is a structural schematic diagram of the limiting device of the present invention.

[0041] Fig.21 The structure of the ankle joint stiffness changing device of the present invention is shown in FIG. Figure 1 .

[0042] Fig. 22 The structure of the ankle joint stiffness changing device of the present invention is shown in FIG. Figure 2 .

[0043] Fig.23 The schematic diagram of the decomposed structure of the ankle joint stiffness changing device of the present invention is Figure 1 .

[0044] Fig.24 The schematic diagram of the decomposed structure of the ankle joint stiffness changing device of the present invention is Figure 2 .

[0045] Fig.25 It is a structural schematic diagram of the housing of the present invention.

[0046] Fig.26 It is a schematic structural diagram of the first disc spring of the present invention.

[0047] Fig. 27 It is a schematic diagram of the structure of the second layer plate and the ankle joint driving device of the present invention.

[0048] Fig.28 The structure diagram of the ankle joint driving device of the present invention is shown in FIG. Figure 1 .

[0049] Fig.29 The structure diagram of the ankle joint driving device of the present invention is shown in FIG. Figure 2 .

[0050] Fig.30 It is a structural schematic diagram of the support arm of the present invention.

[0051] Fig.31 It is a schematic diagram of the connection of the pulleys on the pulley supporting plate of the present invention.

[0052] Fig.32 It is a schematic diagram of the connection of the pulleys on the first pulley bracket and the second pulley bracket of the present invention.

[0053] The marks in the above drawings are: tibial rod 1, upper tibial rod 11, first rod body 111, second rod body 112, lower tibial rod 12, third rod body 121, fourth rod body 122, fixed frame 13, strap 14, length adjustment device 15, ball screw 151, rotating rod 152, rotating rod sleeve 1521, screw support seat 153, first bevel gear 154, first nut seat 155, second bevel gear 156, handle turntable 157, handle 1571, rotating rod support seat 158, fourth connecting bracket 159, inverted U-shaped base 1591, connecting plate 1592, ankle joint 2, ankle joint rotation axis 21, ankle joint support frame 22, first ear seat 221, second ear seat 222, first connecting bracket 23, spring 24, upper Spring seat 25, lower spring seat 26, first bearing end cover 27, second bearing end cover 28, sole support plate 3, second connecting bracket 31, knee joint 4, knee joint rotating shaft 41, knee joint support frame 42, third ear seat 421, fourth ear seat 422, third connecting bracket 43, first limiting plate 44, second limiting plate 45, limiting block 46, third bearing end cover 47, fourth bearing end cover 48, support arm 5, pulley support plate 51, L-shaped bracket 52, arm body 53, dust cover plate 54, ankle joint variable stiffness device 6, shell 601, end cover 602, winding ring 603, first wire ring 6031, second wire ring 6032, variable stiffness rotating shaft 604, electromagnetic brake 605, first magnetic transmission plate 606, second magnetic transmission plate 607, electromagnet 608, connecting rod 609, compression spring 610, slider 611, slide groove 612, first disc spring 613, keyway 6131, second disc spring 614, third disc spring 615, fourth disc spring 616, fifth disc spring 617, first key 618, second key 619, limiting sleeve 620, gasket 621, bracket 622, connecting ring 6221, ankle joint driving device 7, reel 701, reel motor 702, cylinder shaft 703, first bearing bracket 704, second bearing bracket 705, motor bracket 706, trapezoidal lead screw 707, second nut seat 708, first reversing wheel 709, second reversing wheel 710, guide rod 711, three-pulley tension sensor Device 712, first pulley 713, second pulley 714, belt 715, tensioner 716, first pulley 801, second pulley 802, first pulley block 803, third pulley 804, fourth pulley 805, fifth pulley 806, sixth pulley 807, seventh pulley 808, eighth pulley 809, second pulley block 810, ninth pulley 811, tenth pulley 812, eleventh pulley 813, twelfth pulley 814, thirteenth pulley 815, first pulley bracket 816, second pulley bracket 817, control platform 10, frame body 101, board surface 102, first layer board 103, second layer board 104, left leg exoskeleton 20, right leg exoskeleton 30, first flexible cable 40, second flexible cable 50. DETAILED DESCRIPTION

[0054] The present invention will be further described below in conjunction with the accompanying drawings: like Figure 1 A flexible cable-driven lower limb rehabilitation robot based on a multi-stage adjustable variable stiffness device is shown, comprising a left leg exoskeleton 20 and a right leg exoskeleton 30 symmetrically arranged on both sides of a control platform 10, wherein the left leg exoskeleton 20 and the right leg exoskeleton 30 each comprise a tibial rod 1, wherein the lower end of the tibial rod 1 is connected to a foot support plate 3 via an ankle joint 2, and the upper end of the tibial rod 1 is connected to a support arm 5 fixed on the control platform 10 via a knee joint 4.

[0055] Further, such as Figure 2 As shown, the control platform 10 includes a square frame body 101 , a board surface 102 for a patient to sit on is provided on the top of the frame body 101 , and a first layer board 103 and a second layer board 104 are fixed inside the frame body 101 .

[0056] The left leg exoskeleton 20 and the right leg exoskeleton 30 of the present invention have the same structure. Figure 8 , Fig. 9 As shown, the left leg exoskeleton 20 is taken as an example for explanation below, and the structure of the right leg exoskeleton 30 is not repeated.

[0057] Further, such as Figure 3 , Figure 4 As shown, the tibial stem 1 is a split structure, including an upper tibial stem 11 and a lower tibial stem 12 that are plug-fitted together, and both the upper tibial stem 11 and the lower tibial stem 12 are integrally formed structures. Specifically, the upper tibial rod 11 includes a first rod body 111 connected to the knee joint 4 and a second rod body 112 inserted into the lower tibial rod 12, the lower tibial rod 12 includes a third rod body 121 plugged into the second rod body 112 and a fourth rod body 122 connected to the ankle joint 2, the cross-sections of the first rod body 111, the second rod body 112, the third rod body 121 and the fourth rod body 122 are all square, and the third rod body 121 is a structure with an open top, a hollow interior, a closed bottom and hollow front and rear end faces, a fixing frame 13 is sleeved near the upper end of the lower tibial rod 12, the fixing frame 13 is fixedly connected to the lower tibial rod 12, and a strap 14 for fixing the leg is provided on the fixing frame 13, the strap 14 is used to fix the patient's leg during the rehabilitation process to improve the safety of rehabilitation.

[0058] Further, such as Figure 5 , Figure 6 , Figure 7As shown, the length of the tibial rod 1 is adjustable, and the length adjustment of the tibial rod 1 is completed by a length adjustment device 15 between the upper tibial rod 11 and the lower tibial rod 12. The length adjustment device 15 includes a ball screw 151 arranged in the vertical direction and a rotating rod 152 arranged in the horizontal direction. The ball screw 151 is arranged in parallel on the rear side of the tibial rod 1. The upper end of the ball screw 151 is provided with a screw support seat 153, and the screw support seat 153 is connected to the fixed frame 13. The lower end of the ball screw 151 is coaxially connected to a first bevel gear 154, and the ball screw 151 is provided with a screw nut formed therewith. The first nut seat 155 is moved, and the first nut seat 155 is fixed on the upper tibial rod 11; one end of the rotating rod 152 is coaxially connected with the second bevel gear 156, and the second bevel gear 156 is meshed with the first bevel gear 154. The other end of the rotating rod 152 is fixed with a handle rotating disk 157, and the handle rotating disk 157 is connected with a handle 1571. The middle section of the rotating rod 152 is provided with a rotating rod support seat 158, and the rotating rod 152 is fixed in the rotating rod support seat 158 ​​through a rotating rod sleeve 1521. The rotating rod support seat 158 ​​is fixed to the lower tibial rod 12 through a fourth connecting bracket 159. The fourth connecting bracket 159 includes an inverted U-shaped base 1591 fixed to the bottom of the rotating rod support seat 158, and the inverted U-shaped base 1591 is fixed to the upper spring seat 25 through a connecting plate 1592.

[0059] The adjustment principle of the length adjustment device 15 is as follows: when the length of the tibial rod 1 needs to be adjusted, the handle turntable 157 is rotated through the handle 1571, thereby driving the ball screw 151 to rotate through the transmission of the second bevel gear 156 and the first bevel gear 154, and the first nut seat 155 on the ball screw 151 drives the upper tibial rod 11 fixed thereto to move relative to the lower tibial rod 12, thereby completing the adjustment of the length of the tibial rod 1.

[0060] Further, such as Fig.15 , Fig.16 As shown, the ankle joint 2 includes an ankle joint rotation axis 21 and an ankle joint support frame 22. The lower end of the tibial rod 1 is fixedly connected to the first ear seat 221 of the ankle joint support frame 22. The two ends of the ankle joint rotation axis 21 are rotatably connected to the second ear seat 222 of the ankle joint support frame 22 through deep groove ball bearings. The outer side of the second ear seat 222 is respectively fixed with a first bearing end cover 27 and a second bearing end cover 28. The first connecting bracket 23 is coaxially fixed to the ankle joint rotation axis 21. The first connecting bracket 23 is fixed to the second connecting bracket 31 on the sole support plate 3. Specifically, the first connecting bracket 23 is fixedly connected to the ankle joint rotation axis 21 through a key, and rotates synchronously with the ankle joint rotation axis 21, as shown in FIG. Fig.13 , Fig.14As shown, the lower part of the first connecting bracket 23 is fixed to the second connecting bracket 31, and the second connecting bracket 31 is fixed to the transition plate extending from the side of the sole support plate 3 by screws. Preferably, a sole rubber plate 32 is bonded to the sole support plate 3 to provide cushioning for the patient's foot.

[0061] Further, such as Fig.10 , Fig.11 , Fig.12 As shown, a spring 24 is provided between the lower tibial rod 12 and the first connecting bracket 23, and the spring 24 provides a motion buffer for the ankle joint 2 to reduce the impact at the joint. Two springs 24 are provided, and the two springs 24 are symmetrically arranged on the front and rear sides of the lower tibial rod 12, and the upper end of the spring 24 is fixed to the upper spring seat 25 connected to the lower tibial rod 12, and the lower end of the spring 24 is fixed to the lower spring seat 26 on the first connecting bracket 23. Specifically, the upper spring seat 25 is a square frame structure as a whole, and the upper spring seat 25 is sleeved on the lower tibial rod 12 and fixed to the lower tibial rod 12 by screws. The front and rear sides of the upper spring seat 25 are respectively provided with ear seats that match the spring 24, and the lower spring seat 26 is integrally formed with the first connecting bracket 23, which is equivalent to extending an ear seat on the front and rear sides of the first connecting bracket 23 for fixing the spring 24, and the two ends of the spring 24 are respectively fixed to the connecting shaft in the corresponding ear seat.

[0062] Further, such as Fig.17 , Fig.18 , Fig.19 As shown, the knee joint 4 includes a knee joint rotation axis 41 and a knee joint support frame 42, the third ear seat 421 of the knee joint support frame 42 is fixed to the support arm 5, the two ends of the knee joint rotation axis 41 are respectively rotatably connected to the fourth ear seat 422 of the knee joint support frame 42 through deep groove ball bearings, the outer side of the fourth ear seat 422 is respectively fixed with a third bearing end cover 47 and a fourth bearing end cover 48, the third connecting bracket 43 is coaxially fixed on the knee joint rotation axis 41, and the third connecting bracket 43 is fixedly connected to the upper end of the tibial rod 1. Specifically, the third connecting bracket 43 is fixed to the knee joint rotation axis 41 through a key, and rotates synchronously with the knee joint rotation axis 41, and the lower end of the third connecting bracket 43 is fixed to the upper tibial rod 11.

[0063] Further, such as Fig. 20As shown, the knee joint 4 is provided with a limit device for limiting the rotation angle of the knee joint 4, and the limit device includes a first limit plate 44 and a second limit plate 45 symmetrically arranged on both sides of the third connecting bracket 43, the upper ends of the first limit plate 44 and the second limit plate 45 are sleeved on the knee joint rotation axis 41, and the lower ends of the first limit plate 44 and the second limit plate 45 are fixed to the left and right sides of the upper tibial rod 11, and the limit device also includes a limit block 46 fixed on the knee joint support frame 42, and the first limit plate 44 and the second limit plate 45 are provided with a limit surface that matches the limit block 46. When the knee joint rotation axis 41 rotates, the upper tibial rod 11 rotates synchronously, and the first limit plate 44 and the second limit plate 45 fixed on the upper tibial rod 11 also rotate accordingly. When the limit surfaces in the first limit plate 44 and the second limit plate 45 rotate to contact with the limit block 46, the knee joint rotation axis 41 will no longer rotate, thereby safely limiting the movement angle of the knee joint.

[0064] Furthermore, the ankle joint 2 is connected to an ankle joint stiffness varying device 6, and the knee joint 4 is connected to a knee joint stiffness varying device. The ankle joint stiffness varying device 6 and the knee joint stiffness varying device have the same structure. The ankle joint stiffness varying device 6 is taken as an example for explanation below, and the knee joint stiffness varying device will not be described in detail.

[0065] Specifically, Fig.21 , Fig. 22 , Fig.23 , Fig.24 As shown, the ankle joint variable stiffness device 6 includes a shell 601, and end covers 602 and a winding ring 603 are respectively fixed at both ends of the shell 601. A variable stiffness shaft 604 is provided in the shell 601. One end of the variable stiffness shaft 604 close to the end cover 602 is cantilevered outside the shell 601 and the end is fixedly connected to the electromagnetic brake 605. One end of the variable stiffness shaft 604 close to the winding ring 603 is fixedly connected to the ankle joint rotation axis 21 through a coupling. A first magnetic transmission plate 606, an elastic element group, a second magnetic transmission plate 607 and an electromagnet 608 are sequentially provided on the variable stiffness shaft 604 from the end cover 602 to the winding ring 603. The first magnetic transmission plate 606, the elastic element group and the second magnetic transmission plate 607 are connected to form a whole through a connecting rod 609. The electromagnet 608 is fixedly connected to the variable stiffness shaft 604 through a key. One end of the connecting rod 609 close to the end cover 602 is connected to the end cover 602 through a compression spring 610. One end of the compression spring 610 is connected to a first spring fixing hole provided at the end of the connecting rod 609, and the other end of the compression spring 610 is connected to a second spring fixing hole provided on the end cover 602.

[0066] The elastic element group is composed of a plurality of disc springs with the same structure and different elasticity. A key fixed to the elastic element group is provided on the variable stiffness shaft 604. Slide blocks 611 are respectively provided on the circumference of the first magnetic transmission plate 606 and the second magnetic transmission plate 607. The slide blocks 611 are semi-cylindrical protrusions. The slide blocks 611 cooperate with the slide grooves 612 provided on the inner wall of the housing 601. Fig.25 As shown, the slide groove 612 is arranged along the axial direction of the housing 601 .

[0067] In this embodiment, four groups of sliders 611, slide slots 612, connecting rods 609 and compression springs 610 are provided. The winding ring 603 in this embodiment is a split structure, including a first wire ring 6031 fixed to the housing 604 and a second wire ring 6032 fixed to the first wire ring 6031.

[0068] The ankle joint variable stiffness device 6 is fixed to the ankle joint support frame 22 through a bracket 622. Specifically, the bracket 622 is arranged below the shell 601. The bracket 622 is semicircular in shape as a whole. One end of the bracket 622 is fixedly connected to the ankle joint support frame 22, and the other end of the bracket 622 is provided with a connecting ring 6221 that is engaged and fixed with the step surface of the electromagnetic brake 605.

[0069] Preferably, the elastic element groups in this embodiment are provided with two groups, including a first elastic element group consisting of a first disc spring 613, a second disc spring 614, and a third disc spring 615, and a second elastic element group consisting of a fourth disc spring 616 and a fifth disc spring 617, the key includes a first key 618 matched with the first elastic element group and a second key 619 matched with the second elastic element group, each disc spring in the first elastic element group is provided with a key slot matched with the first key 618 at the same position, and the first disc spring 613 has an inner wall provided with a key slot 6131 matched with the first key 618, as shown in FIG. Fig.26 As shown. Each disc spring in the second elastic element group is provided with a keyway matched with the second key 619 at the same position, and the variable stiffness shaft 604 is driven to rotate by the cooperation between the key and the keyway. A limiting sleeve 620 is fixed on the connecting rod 609 between the first elastic element group and the second elastic element group, and a gasket 621 is fixed on the connecting rod 609 between each disc spring of the first elastic element group, between the first elastic element group and the first magnetic transmission plate 606, between each disc spring of the second elastic element group, and between the second elastic element group and the second magnetic transmission plate 607.

[0070] When working, the electromagnet 608 is energized, and different magnetic forces are generated according to the current size to attract the second magnetic transmission plate 607 to move toward the electromagnet 608, thereby driving the first elastic element group and the second elastic element group to slide along the direction defined by the slide slot 612. During the sliding process, the current size of the electromagnet 608 is controlled to realize the connection and fixation of each disc spring in the elastic element group with the key. In this embodiment, each disc spring has three gear combinations during the movement process: the first gear is that the third disc spring 615 is fixed to the first key 618 alone; the second gear is that the second disc spring 614 is fixed to the first key 618, and the fifth disc spring 617 is fixed to the second key 619 at the same time; the third gear is that the first disc spring 613 is fixed to the first key 618, and the fourth disc spring 616 is fixed to the second key 619 at the same time. The stiffness of the above three gear combinations is from small to large, that is, the stiffness of the first gear is the smallest, and the stiffness of the third gear is the largest. When in use, different stiffness gears can be selected according to the actual situation of the patient. After the electromagnet 608 is powered off, the elastic element group is driven back to its original position through the compression spring 610. In the initial state, the first elastic element group and the second elastic element group are not matched with the corresponding keys, that is, the rotation of the housing 601 will not drive the variable stiffness shaft 604 and the ankle joint rotation shaft 21 to rotate, which is the neutral gear position.

[0071] The working principle of the ankle joint variable stiffness device 6 is as follows: when the patient's rehabilitation exercise needs to be adjusted to the maximum stiffness, the electromagnet 608 is energized, and the second magnetic transmission plate 607 drives the second elastic element group and the first elastic element group to move a certain distance in the direction of the electromagnet 608 to the matching state of the third gear, that is, the first disc spring 613 is combined with the first key 618, and the fourth disc spring 616 is combined with the second key 619, and the compression spring 610 is stretched at this time; when the stiffness needs to be reduced, the current passed into the electromagnet 608 is reduced, thereby reducing the suction force on the second magnetic transmission plate 607, and the stretching length of the compression spring 610 is reduced at this time, and the compression spring 610 pulls the first elastic element group and the second elastic element group back to the matching state of the second gear or the first gear to complete the switching of different gear stiffness. That is, the stiffness is switched by changing the size of the current passed through the electromagnet 608. When the ankle joint variable stiffness device 6 is in the initial state, the first elastic element group and the second elastic element group are not combined with the key on the variable stiffness shaft 604, that is, it is in the neutral position. At this time, the winding ring 603 will not drive the ankle joint 2 to rotate. At the same time, the electromagnetic brake 605 provided on the ankle joint variable stiffness device 6 can respond to emergencies, brake in time, and reduce the chance of injury to the wearer.

[0072] When the ankle joint variable stiffness device 6 is in effect, at least one group of disc springs in the first elastic element group and the second elastic element group is fixed with the key on the variable stiffness shaft 604, so the winding ring 603 will drive the ankle joint rotation axis 21 to rotate through the variable stiffness shaft 604 to complete the rehabilitation movement of the ankle joint.

[0073] Furthermore, the winding ring 603 in the ankle joint variable stiffness device 6 is connected to the ankle joint drive device 7 via the first flexible cable 40, and the winding ring in the knee joint variable stiffness device is connected to the knee joint drive device via the second flexible cable 50. The ankle joint drive device 7 is fixed on the second layer board 104 of the control platform 10, as shown in FIG. Fig. 27 As shown, the knee joint drive device is fixed on the first layer 103 of the control platform 10. The ankle joint drive device 7 and the knee joint drive device in the present invention have the same structure, and the ankle joint drive device 7 is used as an example for description below, and the knee joint drive device is not repeated here.

[0074] Specifically, Fig.28 , Fig.29 As shown, the ankle joint driving device 7 includes a reel 701 connected to the first flexible cable 40, and the reel 701 is driven to rotate by a reel motor 702 to realize the retraction and extension of the first flexible cable 40. The output shaft of the reel motor 702 is connected to the barrel shaft 703 of the reel 701 through a plum blossom coupling, and the two ends of the barrel shaft 703 are respectively connected to the first bearing bracket 704 and the second bearing bracket 705 through deep groove ball bearings. The reel motor 702 is fixed to the motor bracket 706, and a trapezoidal lead screw 707 is further provided between the first bearing bracket 704 and the second bearing bracket 705. The two ends of the trapezoidal lead screw 707 are respectively rotatably connected to the first bearing bracket 704 and the second bearing bracket 705. The trapezoidal lead screw 707 is provided with a second nut seat 708 that forms a lead screw nut movement therewith, and a first reversing wheel 709 is fixed to the second nut seat 708, and a second reversing wheel 709 is fixed to the first bearing bracket 704. 10. The axles of the first reversing wheel 709 and the second reversing wheel 710 are parallel, and the axle of the first reversing wheel 709 is perpendicular to the barrel axis 703 of the reel 701. A guide rod 711 is provided between the first bearing bracket 704, the second bearing bracket 705 and the second nut seat 708, and a three-pulley tension sensor 712 is also provided on the side of the reel 701. The three-pulley tension sensor 712 is used to measure the tension of the first flexible cable 40, and transmit the detected flexible cable tension to the controller in real time. If a large change in tension is detected, or the tension is 0, etc., the controller energizes the electromagnetic brake, which will jam the variable stiffness shaft 604 to stop working, thereby reducing the risk of injury to the wearer.

[0075] A pulley transmission device connecting the drum 701 and the trapezoidal lead screw 707 is provided between the drum 701 and the trapezoidal lead screw 707. The pulley transmission device includes a first pulley 713 coaxially arranged with the drum 701, a second pulley 714 coaxially arranged with the trapezoidal lead screw 707, and a belt 715 connecting the first pulley 713 and the second pulley 714. A tensioning wheel 716 is provided below the belt 715. The drum motor 702 drives the drum 701 to rotate through the drum shaft 703, the first pulley 713 connected to the drum shaft 703 rotates synchronously and drives the second pulley 714 to rotate, and the second pulley 714 drives the trapezoidal lead screw 707 to rotate, thereby causing the second nut seat 708 to shift, so as to ensure that the cable exit point of the first flexible cable 40 on the drum 701 is always tangent to the first reversing wheel 709.

[0076] The working principle of the ankle joint driving device 7 is as follows: the drum motor 702 drives the drum 701 to rotate, and the first pulley 713 fixed on the drum shaft 703 drives the second pulley 714 to rotate through the belt 715, so that the second nut seat 708 on the trapezoidal lead screw 707 is displaced, so that the cable outlet point of the first flexible cable 40 wound on the drum 701 is always tangent to the first reversing wheel 709. When the drum 701 rotates, the first flexible cable 40 wound on the drum 701 is correspondingly retracted and released, thereby transmitting power to the winding ring 603, driving the winding ring 603 to rotate.

[0077] In the present invention, one end of the first flexible cable 40 is fixedly connected to the drum 701 in the ankle joint driving device 7, and the other end of the first flexible cable 40 is fixed to the winding ring 603 in the ankle joint variable stiffness device 6 after winding through the first reversing wheel 709, the second reversing wheel 710, the three-pulley tension sensor 712, and the first pulley group. One end of the second flexible cable 50 is fixedly connected to the drum in the knee joint driving device, and the other end of the second flexible cable 50 is fixed to the winding ring in the knee joint variable stiffness device after winding through the first reversing wheel, the second reversing wheel, the three-pulley tension sensor, and the second pulley group. Specifically, the first pulley group includes a first pulley 801, a second pulley 802, a first pulley block 803, a third pulley 804, a fourth pulley 805, a fifth pulley 806, a sixth pulley 807 and a seventh pulley 808, which are arranged in sequence; the second pulley group includes an eighth pulley 809, a second pulley block 810, a ninth pulley 811, a tenth pulley 812, an eleventh pulley 813, a twelfth pulley 814 and a thirteenth pulley 815, which are arranged in sequence, wherein: the first pulley 801 is fixed on a first pulley bracket 816 on the side of the second layer board 104 of the control platform 10, and the second pulley 802 and the eighth pulley 809 are fixed on a second pulley bracket 817 on the side of the first layer board 103 of the control platform 10, as shown in FIG. Fig.32The third pulley 804, the fourth pulley 805, the fifth pulley 806, the sixth pulley 807, the seventh pulley 808, the ninth pulley 811, the tenth pulley 812, the eleventh pulley 813, the twelfth pulley 814 and the thirteenth pulley 815 are all fixed on the pulley support plate 51, and the pulley support plate 51, the first pulley block 803 and the second pulley block 810 are all fixed on the bottom plate inside the support arm 5, as shown. Fig.31 In this embodiment, the support arm 5 includes a U-shaped arm body 53 and a dust cover plate 54. The arm body 53 is fixed to the side of the control platform 10 through an L-shaped bracket 52, and the front end of the support arm 5 is fixed to the third ear seat 421 on the knee joint support frame 42. Fig.30 shown.

[0078] The route of the first flexible cable 40 is as follows: one end of the first flexible cable 40 is fixed to the reel 701 in the ankle joint driving device 7, and the other end of the first flexible cable 40 is successively wound around the first reversing wheel 709, the second reversing wheel 710, the pulley in the three-pulley tension sensor 712, the first pulley 801, the second pulley 802, the first pulley block 803, the third pulley 804, the fourth pulley 805, the fifth pulley 806, the sixth pulley 807 and the seventh pulley 808, and then fixed to the winding ring 603 on the ankle joint variable stiffness device 6.

[0079] The route of the second flexible cable 50 is as follows: one end of the second flexible cable 50 is fixed to the reel in the knee joint driving device, and the other end of the second flexible cable 50 is successively wound around the first reversing wheel, the second reversing wheel, the pulley in the three-pulley tension sensor, the eighth pulley 809, the second pulley block 810, the ninth pulley 811, the tenth pulley 812, the eleventh pulley 813, the twelfth pulley 814 and the thirteenth pulley 815, and then fixed to the winding ring on the knee joint stiffness variable device.

[0080] The present invention has two situations when conducting rehabilitation training: active rehabilitation mode and passive rehabilitation mode. The active rehabilitation mode is mainly for patients with certain autonomous movement ability but weak muscle strength. The robot will provide auxiliary torque according to the patient's active movement intention, enhance muscle activity ability, and promote neuromuscular remodeling. The patient's movement intention is detected and analyzed by the change of the flexible cable force of the three-pulley tension sensor, and the joint stiffness is adjusted according to the detected movement intention and joint state. When the stiffness is low, the robot provides less resistance, allowing rehabilitation patients to move with greater freedom; when the stiffness is high, the robot provides stronger support or constraint to stabilize the patient's movement trajectory.

[0081] The passive rehabilitation mode is mainly for patients who have completely lost their ability to move or are in the early stages of rehabilitation. The robot leads the movement process and drives the patient's limbs to move along the preset trajectory to maintain joint mobility and prevent muscle atrophy. First, preset the training trajectory, such as joint flexion and extension, or generate a personalized movement trajectory based on the patient's historical data, control the robot to drive the patient's limbs to move, and perform rehabilitation training according to the set trajectory. During the rehabilitation process, monitor the patient's physiological feedback (such as muscle tension, heart rate, etc.) and adjust the training intensity and stiffness in a timely manner.

[0082] These two modes can be used in combination, for example, the patient starts with the passive mode and gradually transitions to the active mode as muscle strength recovers, thereby improving the rehabilitation effect.

[0083] The embodiments described above are merely descriptions of preferred implementation modes of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A cable-driven lower limb rehabilitation robot based on a multi-level adjustable variable stiffness device, characterized in that: The device comprises a left leg exoskeleton (20) and a right leg exoskeleton (30) symmetrically arranged on both sides of a control platform (10), wherein the left leg exoskeleton (20) and the right leg exoskeleton (30) each comprise a tibial rod (1), wherein the lower end of the tibial rod (1) is connected to a foot support plate (3) via an ankle joint (2), and the upper end of the tibial rod (1) is connected to a support arm (5) fixed to the control platform (10) via a knee joint (4); The ankle joint (2) is connected to an ankle joint variable stiffness device (6), and the knee joint (4) is connected to a knee joint variable stiffness device. The ankle joint variable stiffness device (6) and the knee joint variable stiffness device have the same structure and each comprises a shell (601). End covers (602) and a winding ring (603) are fixed to two ends of the shell (601). A variable stiffness rotating shaft (604) is arranged inside the shell (601). One end of the variable stiffness rotating shaft (604) close to the end cover (602) is cantilevered outside the shell (601) and the end is fixedly connected to the electromagnetic brake (605). One end of the variable stiffness rotating shaft (604) close to the winding ring (603) is fixedly connected to the ankle joint rotating shaft (21) or the knee joint rotating shaft (41) via a coupling. The variable stiffness rotating shaft (604) is provided with a first magnetic transmission plate (606), an elastic element group, a second magnetic transmission plate (607) and an electromagnet (608) in sequence from the end cover (602) to the winding ring (603); the first magnetic transmission plate (606), the elastic element group and the second magnetic transmission plate (607) are connected to form a whole through a connecting rod (609); one end of the connecting rod (609) close to the end cover (602) is connected to the end cover (602) through a compression spring (610); the elastic element group is composed of a plurality of disc springs with the same structure and different elasticity; the variable stiffness rotating shaft (604) is provided with a key fixed to the elastic element group; The first magnetic transmission plate (606) and the second magnetic transmission plate (607) are respectively provided with sliders (611) in the circumferential direction, and the sliders (611) cooperate with the slide grooves (612) provided on the inner wall of the housing (601), and the slide grooves (612) are provided along the axial direction of the housing (601). When the electromagnet (608) is energized, it attracts the second magnetic transmission plate (607) to move in the direction of the electromagnet (608), thereby driving the elastic element group to slide along the direction defined by the slide grooves (612), and the connection and fixation of each disc spring in the elastic element group with the key are achieved by controlling the current of the electromagnet (608). When the electromagnet (608) is powered off, the elastic element group is driven to return to its original position by compressing the spring (610); The winding ring (603) in the ankle joint variable stiffness device (6) is connected to the ankle joint drive device (7) via a first flexible cable (40), and the winding ring in the knee joint variable stiffness device is connected to the knee joint drive device via a second flexible cable (50). The ankle joint drive device (7) and the knee joint drive device have the same structure and each comprises a reel (701) connected to the first flexible cable (40) or the second flexible cable (50). The reel (701) is driven to rotate by a reel motor (702) to achieve the retraction and extension of the corresponding flexible cable.

2. The flexible cable-driven lower limb rehabilitation robot based on a multi-level adjustable variable stiffness device according to claim 1, characterized in that: The elastic element group comprises a first elastic element group consisting of a first disc spring (613), a second disc spring (614), and a third disc spring (615), and a second elastic element group consisting of a fourth disc spring (616) and a fifth disc spring (617). The key comprises a first key (618) matched with the first elastic element group and a second key (619) matched with the second elastic element group. A limiting sleeve (620) is fixed on the connecting rod (609) between the first elastic element group and the second elastic element group. Gaskets (621) are respectively fixed on the connecting rods (609) between the disc springs of the first elastic element group, between the first elastic element group and the first magnetic transmission plate (606), between the disc springs of the second elastic element group, and between the second elastic element group and the second magnetic transmission plate (607).

3. The cable-driven lower limb rehabilitation robot based on a multi-level adjustable variable stiffness device according to claim 1, characterized in that: The ankle joint (2) comprises an ankle joint rotation axis (21) and an ankle joint support frame (22); the lower end of the tibial rod (1) is fixedly connected to a first ear seat (221) of the ankle joint support frame (22); the two ends of the ankle joint rotation axis (21) are rotatably connected to a second ear seat (222) of the ankle joint support frame (22) via deep groove ball bearings; a first connecting bracket (23) is coaxially fixed to the ankle joint rotation axis (21); the first connecting bracket (23) is fixed to a second connecting bracket (31) on the sole support plate (3); The knee joint (4) comprises a knee joint rotation axis (41) and a knee joint support frame (42); a third ear seat (421) of the knee joint support frame (42) is fixed to the support arm (5); two ends of the knee joint rotation axis (41) are rotatably connected to a fourth ear seat (422) of the knee joint support frame (42) via deep groove ball bearings; a third connecting frame (43) is coaxially fixed to the knee joint rotation axis (41); and the third connecting frame (43) is fixedly connected to the upper end of the tibial rod (1).

4. The cable-driven lower limb rehabilitation robot based on a multi-level adjustable variable stiffness device according to claim 1, characterized in that: The tibial rod (1) is a split structure, comprising an upper tibial rod (11) and a lower tibial rod (12) that are plugged together. The upper tibial rod (11) and the lower tibial rod (12) are both integrally formed structures. The upper tibial rod (11) comprises a first rod body (111) connected to the knee joint (4) and a second rod body (112) inserted into the lower tibial rod (12). The lower tibial rod (12) comprises a third rod body (121) plugged with the second rod body (112) and a third rod body (122) plugged with the ankle joint (2). A fourth rod (122) is connected to the lower tibial rod (12), the cross-sections of the first rod (111), the second rod (112), the third rod (121) and the fourth rod (122) are all square, and the third rod (121) is a structure with an open top, a hollow interior, a closed bottom and hollow front and rear end surfaces, a fixing frame (13) is sleeved near the upper end of the lower tibial rod (12), the fixing frame (13) is fixedly connected to the lower tibial rod (12), and a strap (14) for fixing the leg is provided on the fixing frame (13).

5. The cable-driven lower limb rehabilitation robot based on a multi-level adjustable variable stiffness device according to claim 4, characterized in that: The length of the tibial rod (1) is adjusted by a length adjustment device (15) between the upper tibial rod (11) and the lower tibial rod (12). The length adjustment device (15) comprises a ball screw (151) arranged in a vertical direction and a rotating rod (152) arranged in a horizontal direction. The ball screw (151) is arranged in parallel on the rear side of the tibial rod (1). The upper end of the ball screw (151) is provided with a screw support seat (153). The screw support seat (153) is connected to the fixed frame (13). The lower end of the ball screw (151) is coaxially connected to a first bevel gear (154). The ball screw (151) is provided with a first nut seat (152) which forms a screw nut movement with the ball screw (151). 155), the first nut seat (155) is fixed on the upper tibial rod (11); one end of the rotating rod (152) is coaxially connected to the second bevel gear (156), the second bevel gear (156) is meshed with the first bevel gear (154), the other end of the rotating rod (152) is fixed with a handle rotating disk (157), the handle rotating disk (157) is connected to a handle (1571), the middle section of the rotating rod (152) is provided with a rotating rod support seat (158), the rotating rod (152) is fixed in the rotating rod support seat (158) through a rotating rod sleeve (1521), and the rotating rod support seat (158) is fixed to the lower tibial rod (12) through a fourth connecting bracket (159).

6. The flexible cable-driven lower limb rehabilitation robot based on a multi-level adjustable variable stiffness device according to claim 4, characterized in that: A spring (24) for providing movement buffer for the ankle joint (2) is provided between the lower tibial rod (12) and the first connecting bracket (23). Two springs (24) are provided, and the two springs (24) are symmetrically arranged on the front and rear sides of the lower tibial rod (12). The upper end of the spring (24) is fixed to an upper spring seat (25) connected to the lower tibial rod (12), and the lower end of the spring (24) is fixed to a lower spring seat (26) on the first connecting bracket (23).

7. The cable-driven lower limb rehabilitation robot based on a multi-level adjustable variable stiffness device according to claim 1, characterized in that: The knee joint (4) is provided with a limit device for limiting the rotation angle of the knee joint (4), the limit device comprising a first limit plate (44) and a second limit plate (45) symmetrically arranged on both sides of the third connecting bracket (43), the upper ends of the first limit plate (44) and the second limit plate (45) are sleeved on the knee joint rotation axis (41), the lower ends of the first limit plate (44) and the second limit plate (45) are fixed to the left and right side surfaces of the upper tibial rod (11), the limit device also comprises a limit block (46) fixed to the knee joint support frame (42), and the first limit plate (44) and the second limit plate (45) are provided with a limit surface that matches the limit block (46).

8. The cable-driven lower limb rehabilitation robot based on a multi-level adjustable variable stiffness device according to claim 1, characterized in that: The output shaft of the reel motor (702) is connected to the shaft (703) of the reel (701) via a plum blossom coupling, and the two ends of the shaft (703) are connected to the first bearing bracket (704) and the second bearing bracket (705) via deep groove ball bearings, respectively. The reel motor (702) is fixed to the motor bracket (706), and a trapezoidal lead screw (707) is provided between the first bearing bracket (704) and the second bearing bracket (705), and the two ends of the trapezoidal lead screw (707) are rotatably connected to the first bearing bracket (704) and the second bearing bracket (705), respectively. The trapezoidal lead screw (707) is provided with a lead screw A second nut seat (708) for nut movement, a first reversing wheel (709) is fixed on the second nut seat (708), a second reversing wheel (710) is fixed on the first bearing bracket (704), the axles of the first reversing wheel (709) and the second reversing wheel (710) are parallel, and the axle of the first reversing wheel (709) is perpendicular to the cylinder axis (703) of the reel (701), a guide rod (711) is provided between the first bearing bracket (704), the second bearing bracket (705) and the second nut seat (708), and a three-pulley tension sensor (712) is also provided on the side of the reel (701).

9. The flexible cable-driven lower limb rehabilitation robot based on a multi-level adjustable variable stiffness device according to claim 8, characterized in that: A pulley transmission device connecting the drum (701) and the trapezoidal lead screw (707) is provided between the two. The pulley transmission device comprises a first pulley (713) coaxially arranged with the drum (701), a second pulley (714) coaxially arranged with the trapezoidal lead screw (707), and a belt (715) connecting the first pulley (713) and the second pulley (714), and a tensioning pulley (716) is provided below the belt (715).

10. The cable-driven lower limb rehabilitation robot based on a multi-level adjustable variable stiffness device according to claim 1, characterized in that: One end of the first flexible cable (40) is fixedly connected to the drum (701) in the ankle joint driving device (7), and the other end of the first flexible cable (40) is successively wound around the first reversing wheel (709), the second reversing wheel (710), the three-pulley tension sensor (712), and the first pulley group, and then fixed to the winding ring (603) in the ankle joint variable stiffness device (6); one end of the second flexible cable (50) is fixedly connected to the drum in the knee joint driving device, and the other end of the second flexible cable (50) is successively wound around the first reversing wheel, the second reversing wheel, the three-pulley tension sensor, and the second pulley group, and then fixed to the winding ring in the knee joint variable stiffness device; The first pulley block comprises a first pulley (801), a second pulley (802), a first pulley block (803), a third pulley (804), a fourth pulley (805), a fifth pulley (806), a sixth pulley (807) and a seventh pulley (808) arranged in sequence; the second pulley block comprises an eighth pulley (809), a second pulley block (810), a ninth pulley (811), a tenth pulley (812), an eleventh pulley (813), a twelfth pulley (814) and a thirteenth pulley (815) arranged in sequence, wherein: the first pulley (801) is fixed to a first pulley bracket (814) on the side of the second layer board of the control platform (10); 6), the second pulley (802) and the eighth pulley (809) are fixed on the second pulley bracket (817) on the side of the first layer plate of the control platform (10), the third pulley (804), the fourth pulley (805), the fifth pulley (806), the sixth pulley (807), the seventh pulley (808), the ninth pulley (811), the tenth pulley (812), the eleventh pulley (813), the twelfth pulley (814) and the thirteenth pulley (815) are all fixed on the pulley support plate (51), and the pulley support plate (51), the first pulley block (803) and the second pulley block (810) are all fixed on the bottom plate inside the support arm (5).

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