A differential mechanism in the form of a cable and pulley

Abstract

The application belongs to the technical field of exoskeleton robots, and particularly discloses a differential mechanism in the form of a flexible cable and a pulley, which comprises a driving wheel, a driven wheel, an output wheel, a cross-shaped connecting piece and a mandrel, wherein the driving wheels are symmetrically arranged on the left and right sides of the output wheel, the driving wheel and the driven wheel are connected through a flexible cable, and the rotation of the driving wheel can drive the driven wheel to move along the circumference of the mandrel; the upper and lower ends of the cross-shaped connecting piece are connected with the driven wheel, and the left and right arms of the cross-shaped connecting piece are connected with the output wheel, and the movement of the driven wheel along the circumference of the mandrel can drive the output wheel to rotate around the mandrel. The application is based on a traditional bevel gear differential mechanism, the pulling force of the flexible cable is used to replace the meshing between the gears, and the cross shaft in the traditional differential mechanism is optimized into the combination of the mandrel and the cross-shaped connecting piece in combination with the characteristics of the flexible cable transmission, the transmission between the flexible cable and the pulley is used to achieve the function of movement synthesis, and the miniaturization and light weight of the differential mechanism are realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of robot exoskeleton, more particularly, relates to a differential mechanism in the form of flexible cable and pulley and its application. BACKGROUND

[0002] In the field of exoskeleton technology, differential mechanism is a commonly used component, which is often used to synthesize different kinematic elements and output to the joint to assist movement. With the miniaturization process of lower limb exoskeleton, although the traditional differential mechanism based on bevel gear can achieve the purpose, it is often large in size, complex in structure, high in cost, and has the problem of heavy weight. These problems will cause the exoskeleton assistance effect to be poor, and even due to the differential mechanism, the energy consumed when wearing the exoskeleton to assist human movement does not decrease but increases, which seriously affects the practical application and popularization of exoskeleton.

[0003] Therefore, there is an urgent need for a small and light differential mechanism suitable for joints. SUMMARY

[0004] In view of the above defects or improvement needs of the prior art, the present application provides a differential mechanism in the form of flexible cable and pulley and its application, which aims to synthesize two independent movements and realize miniaturization and light weight, so as to be suitable for wearable lower limb exoskeleton.

[0005] To achieve the above purpose, according to one aspect of the present application, a differential mechanism in the form of flexible cable and pulley is provided, which includes a driving wheel, a driven wheel, an output wheel, a cross-shaped connecting piece and a mandrel, wherein:

[0006] The cross-shaped connecting piece is sleeved in the middle of the mandrel, the upper and lower ends of the cross-shaped connecting piece are symmetrically connected with the driven wheel, and the left and right ends are symmetrically connected with the output wheel, the driving wheels are symmetrically distributed on the left and right sides of the output wheel, the driving wheels are connected with the driven wheel through flexible cable, the circumferential edge of the driven wheel is located in the fan-shaped hollow of the circumferential edge of the output wheel, and the driving wheel is used to drive the driven wheel to rotate around the mandrel, so as to drive the output wheel to differentially rotate around the mandrel.

[0007] Further, the mandrel is a stepped shaft, the driving wheel is a stepped pulley, and the mandrel is used to axially fix the positions of the driving wheel and the output wheel.

[0008] Further, the driving wheel and the driven wheel have a plurality of cable fixing positions, including a driven wheel cable fixing position at the joint of the driven wheel and the driving wheel, and cable head fixing positions and cable tail fixing positions on the inner and outer circumferential surfaces of the driving wheel at the same horizontal position, the distance between the same horizontal position and the driven wheel cable fixing position being preferably 1 / 8-3 / 8 of a circle.

[0009] According to one embodiment of the present application, the plurality of cable fixing positions include blind holes and threaded holes perpendicular to the blind holes. When the cable is installed, the stability of the cable installation is ensured by screwing a slotted flat end set screw into the threaded hole and tightly nailing the rope end of the cable on the inner wall of the blind hole.

[0010] Further, the cross-shaped connecting piece is plate-shaped, and the sum of the thickness of the cross-shaped connecting piece and the thickness of the output wheel is less than or equal to the diameter of the inner circumference of the driven wheel, so as to ensure that the inner circumferences of the driving wheel and the driven wheel are perpendicular and tangent to each other.

[0011] Further, the left and right arms of the cross-shaped connecting piece are symmetrically distributed with two through holes, which are aligned with the through holes of the same diameter on the output wheel, and the cross-shaped connecting piece and the output wheel are fixed and connected by hexagonal head bolts; the upper and lower arms of the cross-shaped connecting piece are symmetrically distributed with two protruding cylinders, and the two driven wheels are installed on the protruding cylinders.

[0012] Further, the output wheel and the external load are connected by another cable, and the inner and outer circumferential surfaces at the same horizontal position of the output wheel have cable head fixing positions and cable tail fixing positions. When the output wheel rotates, the another cable transmits tension along the fixed rope groove and generates the movement of the external load.

[0013] Further, the fixing position is preferably a fixed rope groove, and the external load is a robot exoskeleton.

[0014] According to another aspect of the present application, the present application also provides an application of the differential mechanism in the form of the cable pulley.

[0015] Overall, compared with the prior art, the above technical solutions conceived by the present application mainly have the following technical advantages:

[0016] 1. The differential mechanism in the form of a cable pulley of the present application uses the characteristic of the cable that can transmit tension force to imitate the traditional differential mechanism based on the meshing transmission of bevel gears, and realizes the function of motion synthesis. The overall structure of the differential mechanism is simple, without large parts, and is light in weight and small in size, so that the miniaturization and light weight of the lower limb exoskeleton driving device can be realized, and the differential mechanism is particularly suitable for wearable exoskeleton robots; compared with the traditional differential mechanism, the power is transmitted to one side of the shaft through the cross shaft, so that the differential mechanism is more uniform in stress, and the mandrel will not be bent due to bearing additional bending moment.

[0017] 2. The differential mechanism of the present application uses a mandrel instead of the cross shaft and other parts that need to bear bending moment and torque in the traditional differential mechanism; and uses a pulley that is relatively simple to process instead of a bevel gear that is complex to process. These optimizations make the parts bear more reasonable stress, and reduce the requirements for the material and processing of the parts.

[0018] 3. The cross-shaped connecting piece of the present application is simpler to process than the cross shaft in the traditional differential mechanism, and because it has a certain thickness, in addition to its way of being sleeved with the mandrel, the width of its upper and lower arms can not be limited by the diameter of the mandrel, and its ability to bear torque is greater than the cross shaft which is limited by the diameter of the shaft, so that the requirements for the material of the part are reduced, and the cost of the entire differential mechanism is also reduced. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The structure diagram of the differential mechanism with driving wheels of the embodiment of the present application;

[0020] Figure 2 The function diagram of the differential mechanism in the form of a cable pulley of the embodiment of the present application;

[0021] Figure 3 The principle diagram of the differential mechanism in the form of a cable pulley of the embodiment of the present application.

[0022] Figure 4 The front view of the cable connection of the embodiment of the present application (part of the parts are hidden).

[0023] Figure 5 The right view of the cable connection of the embodiment of the present application (part of the parts are hidden).

[0024] In all the drawings, the same reference signs are used to represent the same elements or structures, in which: driving wheel (01), driven wheel (02), output wheel (03), cross-shaped connecting piece (04), mandrel (05), driving wheel one (06), driving wheel two (07), deep groove ball bearing (08), second cable (09), third cable (10), fourth cable (11), first cable (12), locking screw (13). DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0026] The present application provides a differential mechanism in the form of a flexible cable pulley, as shown in Figures 2 to 4 The present application provides a differential mechanism in the form of a flexible cable pulley, as shown in

[0027] In some embodiments, the heart shaft 05 is a stepped shaft, and the driving wheel 01 is a stepped pulley. The heart shaft 05 is used to axially fix the positions of the driving wheel 01 and the output wheel 03.

[0028] In some embodiments, the driving wheel and the driven wheel have a plurality of flexible cable fixing positions, including a driven wheel flexible cable fixing position at the joint of the driven wheel and the driving wheel, and a flexible cable head fixing position and a flexible cable tail fixing position on the inner and outer circumferential surfaces of the driving wheel at the same horizontal position. The distance between the same horizontal position and the driven wheel flexible cable fixing position is as far as possible. The distance can be 1 / 8-3 / 8 of a circular arc.

[0029] In some embodiments, the plurality of flexible cable fixing positions include a blind hole and a threaded hole perpendicular to the blind hole. When the flexible cable is installed, the slotted flat end set screw is screwed into the threaded hole, and the rope end of the flexible cable is tightly nailed to the inner wall of the blind hole, which ensures the stability of the flexible cable installation.

[0030] In some embodiments, the cross-shaped connecting piece 04 is a plate, and the sum of its thickness and the thickness of the output wheel 03 is less than or equal to the diameter of the inner circumference of the driven wheel 02, so as to ensure that the inner circumference of the driving wheel 01 and the inner circumference of the driven wheel 02 are perpendicular and tangent.

[0031] In some embodiments, the left and right arms of the cross-shaped connector 04 are symmetrically distributed with two through holes, which are aligned with the through holes of the same diameter on the output wheel 03, and the cross-shaped connector 04 is fixedly connected with the output wheel 03 by hexagonal head bolts; the upper and lower arms of the cross-shaped connector are symmetrically distributed with two protruding cylinders, and the two driven wheels 02 are installed on the protruding cylinders.

[0032] In some embodiments, the output wheel 03 can be connected with an external robot skeleton through another flexible cable. The inner and outer circumferential surfaces at the same horizontal position on the circumference of the output wheel 03 are provided with a flexible cable head fixing rope groove and a flexible cable tail fixing rope groove at the same time. When the output wheel rotates, another flexible cable transmits the pulling force along the fixing rope groove and generates the movement of the external robot skeleton.

[0033] In some embodiments, the differential mechanism in the form of a flexible cable pulley has the driving wheel 01 as the input end and the output wheel 03 as the output end.

[0034] The following will add the driving wheel one 06 and the driving wheel two 07 to the differential mechanism in the form of a flexible cable pulley, and specifically describe the motion synthesis function thereof:

[0035] As shown in Figure 1 , the driving wheel one 06 and the driving wheel two 07 are fixedly connected with the driving wheel one 06 and the driving wheel two 07 through the flange and the bolts, and the deep groove ball bearings 08 are installed between the two driving wheels and the mandrel. As shown in Figure 2 , the differential mechanism in the form of a flexible cable pulley can realize the function that when two different rotary motions are input to the two driving wheels of the differential mechanism, the output wheel can output the synthesized rotary motion, and the output rotation speed is half of the sum of the two input rotation speeds.

[0036] As shown in Figure 3 , the principle of the motion synthesis realized by the differential mechanism in the form of a flexible cable pulley is that one end of the flexible cable is fixed on the circumference of the driving wheel 01, and the other end is fixed on the circumference of the driven wheel 02. Since the circumferences of the driving wheel 01 and the driven wheel 02 are perpendicular to each other, the flexible cable can transmit the pulling force between the driving wheel and the driven wheel (similar to the meshing between bevel gears), so the rotation of the driving wheel 01 will drive the rotation of the driven wheel 02 around the mandrel, and this circumferential motion will drive the rotation of the cross-shaped connector 04 around the mandrel 05, and further drive the rotation of the output wheel 03. Therefore, when the two driving wheels rotate at the same time, the differential mechanism in the form of a flexible cable pulley can synthesize the rotary motions of the two driving wheels and output them as the rotary motion of the output wheel around the mandrel.

[0037] The following is a specific embodiment:

[0038] Embodiment 1

[0039] A differential mechanism in the form of a cable pulley, comprising a pair of driving wheels 01, a pair of driven wheels 02, a pair of output wheels 03, a cross-shaped connecting piece 04 and a mandrel 05, wherein the cross-shaped connecting piece 04 is sleeved in the middle of the mandrel 05, the driving wheels 01 are symmetrically distributed on the left and right sides of the cross-shaped connecting piece, the left and right arms of the cross-shaped connecting piece 04 are symmetrically distributed with two through holes, which are aligned with the through holes of the same diameter on the output wheels 03, and the cross-shaped connecting piece 04 is fixed with the output wheels 03 through hexagonal head bolts; the upper and lower arms of the cross-shaped connecting piece 04 are symmetrically distributed with two protruding cylinders, a pair of driven wheels 02 are installed on the protruding cylinders, bearings are installed between the driven wheels 02 and the cylinders, and the center of the cross-shaped connecting piece 04 has a through hole for installation on the stepped mandrel 05.

[0040] The driving wheels 01 and the driven wheels 02 are provided with a driven wheel cable fixing part at the joint of the driven wheel and the driving wheel, and a cable head fixing part and a cable tail fixing part on the inner and outer circumferential surfaces of the driving wheel respectively, the cable head fixing part and the cable tail fixing part are located at the same horizontal position of the driving wheel, the same horizontal position is 1 / 8 of a circular arc away from the driven wheel cable fixing part, one side of the driving wheel is connected with an external power input system, and the other side is connected with the driven wheel through a plurality of cables in the plurality of cable fixing parts, so that the rotation of the driving wheel can drive the driven wheel to move around the circumference of the mandrel; the output wheel 03 has a fan-shaped hollow on the circumferential edge, and the driven wheel 02 is located in the hollow and combines the movements of the two driving wheels into the rotational movement of the driven wheel around the mandrel.

[0041] When the cable is installed, the slotted flat end set screw 13 is screwed into the threaded hole and the rope end of the cable is tightly nailed to the inner wall of the blind hole, which ensures the stability of the cable installation.

[0042] The edge of the driven wheel 02 is perpendicular to the edge of the driving wheel, the driving wheel 01 is a stepped pulley, and the last stage is provided with a flange plate, which is uniformly distributed with a plurality of threaded holes to ensure the connection of the driven wheel and the driving wheel.

[0043] The installation method of the cable on the output wheel 03 is the same as that of the cable on the driving wheel and the driven wheel. When the output wheel 03 rotates, the cable transmits tension along the rope groove and generates movement.

[0044] Application example

[0045] Take the output of the knee joint rotation movement at a certain moment in walking as an example, first, the upper drive device of the exoskeleton robot outputs the rotation movement 1 (x rad / s) of the knee joint at this moment in the first movement primitive and the rotation movement 2 (y rad / s) of the knee joint at this moment in the second movement primitive according to the walking stage it is in, the two rotation movements drive the drive wheel one 06 and the drive wheel two 07 through the flexible cable, so that the drive wheel one 06 and the drive wheel two 07 rotate at the rotational speed of x rad / s and y rad / s respectively. The driving wheel of the differential mechanism in the form of flexible cable pulley is fixed with the two drive wheels through the flange, since the circumferences of the driving wheel 01 and the driven wheel 02 are perpendicular to each other, and one end of the flexible cable is fixed on the circumference of the driving wheel 01, and the other end is fixed on the circumference of the driven wheel 02. By using the characteristics of the flexible cable that can transmit tension, the tension of the flexible cable is used to replace the interdental pressure generated by the meshing of the bevel gear in the traditional differential mechanism.

[0046] Take the left driving wheel as an example, the right driving wheel is static (x>0, y=0): the connection mode of the flexible cable is shown in the right view Figure 5 As shown, the first flexible cable 12 is connected to the left driving wheel flexible cable fixing part 1, first wraps around three-quarters of the circumference and then wraps around the larger diameter circumference surface of the left driving wheel, and then wraps around the larger diameter circumference surface of the upper driven wheel at the tangent position, and then wraps around three-quarters of the circumference and is fixed to the upper driven wheel flexible cable fixing part 1; the second flexible cable 09 is connected to the left driving wheel flexible cable fixing part 2, first wraps around three-quarters of the circumference and then wraps around the smaller diameter circumference surface of the left driving wheel, and then wraps around the smaller diameter circumference surface of the lower driven wheel at the tangent position, and then wraps around three-quarters of the circumference and is fixed to the lower driven wheel flexible cable fixing part 2; the third flexible cable 10 and the fourth flexible cable 11 wrap around the right driving wheel, and the wrapping mode is similar to that of the first flexible cable 12 and the second flexible cable 09, since Figure 5As the two cables are not visible in the right view, they are not shown here. Taking the clockwise direction as positive, when the left driving wheel rotates clockwise, the first cable 12 is pulled tight because its end is fixed to the circumference of the left driving wheel. The tension is transmitted along the cable to the other end of the cable, which is fixed to the circumference of the upper driven wheel, thus driving the upper driven wheel to rotate. Since the other end of the third cable 10 is fixed to the circumference of the upper driven wheel, the rotation of the driven wheel will cause the third cable 10 to be pulled tight. However, since the right driving wheel is stationary, the tension of the third cable 10 and the first cable 12 together pull the upper driven wheel to rotate clockwise around the central shaft. Similarly, when the left driving wheel rotates anticlockwise and the right driving wheel is stationary (x = 0, y = 0), the second cable 09 is pulled tight because its end is fixed to the circumference of the left driving wheel. The tension is transmitted along the cable to the other end of the cable, which is fixed to the circumference of the lower driven wheel, thus driving the lower driven wheel to rotate. Since the other end of the fourth cable 11 is fixed to the circumference of the lower driven wheel, the rotation of the driven wheel will cause the fourth cable 11 to be pulled tight. However, since the right driving wheel is stationary, the tension of the fourth cable 11 and the second cable 09 together pull the lower driven wheel to rotate anticlockwise around the central shaft. Similarly, when the right driving wheel rotates clockwise or anticlockwise and the left driving wheel is stationary, the same applies, which is not shown here.

[0047] More generally, when both the left driving wheel and the right driving wheel rotate (x ≠ 0, y ≠ 0), since the driven wheels are affected by two independent motions, they can be regarded as dynamic pulleys rotating around the central shaft. According to the dynamic pulley principle, the angular velocity v of the driven wheels rotating around the central shaft is

[0048]

[0049] where x is the angular velocity of the left driving wheel and y is the angular velocity of the right driving wheel. The effect of the differential mechanism is shown in Figure 2

[0050] In summary, the differential mechanism in the form of cable pulleys can realize the function of motion synthesis. Its miniaturization and light weight make it particularly suitable for wearable exoskeleton robots to synthesize multiple motion primitives obtained from motion experiments to generate human-like and natural joint movements.

[0051] Those skilled in the art will readily understand that the above description is only the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A differential mechanism in the form of a flexible cable and pulley, characterised in that, The differential mechanism comprises a driving wheel (01), a driven wheel (02), an output wheel (03), a cross-shaped connecting piece (04) and a mandrel (05), wherein: The cross-shaped connecting piece (04) is sleeved in the middle of the mandrel (05), the upper and lower ends of the cross-shaped connecting piece (04) are symmetrically connected with the driven wheel (02), the left and right ends of the cross-shaped connecting piece (04) are symmetrically connected with the output wheel (03), the driving wheels (01) are symmetrically distributed on the left and right sides of the output wheel (03), the driving wheels (01) are connected with the driven wheel (02) through flexible ropes, the circumferential edge of the driven wheel (02) is located in the sector hollow of the circumferential edge of the output wheel (03), the driving wheels (01) are used to drive the driven wheel (02) to move circumferentially around the mandrel (05), so as to drive the output wheel (03) to differentially rotate around the mandrel; The mandrel (05) is a stepped shaft, the driving wheels (01) are stepped pulleys, and the mandrel (05) is used to axially fix the positions of the driving wheels (01) and the output wheel (03); The left and right arms of the cross-shaped connecting piece (04) are symmetrically distributed with two through holes, the through holes are aligned with the through holes with the same diameter on the output wheel (03), and the cross-shaped connecting piece (04) and the output wheel (03) are fixedly connected through hexagonal head bolts; the upper and lower arms of the cross-shaped connecting piece (04) are symmetrically distributed with two protruding cylinders, and the two driven wheels (02) are installed on the protruding cylinders.

2. The differential mechanism of claim 1, wherein, The driving wheels (01) and the driven wheels (02) have a plurality of flexible rope fixing positions, the plurality of flexible rope fixing positions comprise a driven wheel flexible rope fixing position at the joint of the driven wheel (02) and the driving wheel (01), and a flexible rope head fixing position and a flexible rope tail fixing position on the inner and outer circumferential surfaces at the same horizontal position of the driving wheel, respectively, the distance between the same horizontal position and the driven wheel flexible rope fixing position is 1 / 8-3 / 8 of a circle.

3. The differential mechanism of claim 2, wherein, The plurality of flexible rope fixing positions comprise blind holes and threaded holes perpendicular to the blind holes.

4. The differential mechanism of claim 1, wherein, The cross-shaped connecting piece (04) is plate-shaped, the sum of the thickness of the cross-shaped connecting piece (04) and the thickness of the output wheel is less than or equal to the diameter of the inner circumference of the driven wheel (02), so as to ensure that the inner circumference of the driving wheel (01) is perpendicular to and tangent to the inner circumference of the driven wheel (02).

5. The differential mechanism of claim 1 wherein, The output wheel (03) is connected with an external load through another flexible rope.

6. The differential mechanism of claim 5, wherein, The external load is a robot exoskeleton.

7. Application of the differential mechanism in a robot exoskeleton according to any one of claims 1-6.

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