Automatic tensioning precise flexible cable driving joint and assembling and adjusting method thereof

Abstract

The invention relates to an automatic tensioning precise flexible cable driving joint and an adjusting method thereof, and belongs to the field of optical machines. The joint is driven by the external motor and the two flexible cables, is automatically tensioned by the tensioning device, and is driven by the pulling force of the flexible cables instead of the friction force. The driving device is installed outside the joint, the mass of the driving device can be reduced, rotational inertia is reduced, and the joint is hollow and can pass through a light path. The installation and adjustment method is provided, so that the flexible cable is easy to install and tension, and the driving precision is ensured.

Description

Technical Field

[0001] The invention belongs to the field of optical machinery, and in particular relates to an automatically tensioned precision flexible cable driven joint and an assembly and adjustment method thereof. Background Art

[0002] As a novel transmission form, the flexible cable transmission has been well applied in many fields due to its unique transmission characteristics. First, the flexible cable transmission can effectively reduce the system's rotational inertia and achieve lightweight design, so it is widely used in human-machine interactive robots; secondly, the flexible cable transmission is widely used in minimally invasive surgical robots and surgical end tools due to its flexible layout, long-distance transmission, and light weight; finally, the flexible cable transmission has been widely used in precision rotating platforms due to its high precision, excellent reverse drive performance, and no need for lubrication.

[0003] There are two types of flexible cable transmission: friction transmission and tension transmission. Friction transmission has the advantages of continuous rotation and simple structure, but it requires multiple turns of winding to generate sufficient friction, requires a large axial space, and during use, the flexible cable and the pulley will produce relative sliding, affecting the control accuracy and mechanism stiffness. The travel of tension transmission is limited and requires additional fixing measures, but it has no relative sliding, and the control accuracy and mechanism stiffness are higher.

[0004] Cable drive also has certain disadvantages. After long-term use, the cables will fatigue and deform, and the fixed position will slip. The cables will gradually loosen after long-term use, affecting the drive accuracy and joint stiffness. The more conventional solution is to tighten them regularly during use, which is not applicable in some scenarios where maintenance is not possible. Summary of the invention

[0005] The main purpose of the present invention is to solve the problem of looseness of the existing flexible cable driving mechanism during long-term use, and to provide a precise flexible cable driving joint that can be automatically tensioned, so that the flexible cable is always in a tensioned state.

[0006] The technical solution adopted by the present invention is: an automatically tensioned precision flexible cable driven joint, characterized in that the joint includes a motor, an encoder, an active pulley, a driven pulley, a flexible cable, a base, a bearing, and a tensioning device; wherein the motor is used to drive the active pulley, and drive the flexible cable through the active pulley, and the flexible cable further drives the driven pulley to rotate forward and reversely; the driven pulley is used to install the actuator to be driven; the bearing is used to provide the driven pulley with the degree of freedom to rotate around the axis; the tensioning device is used to tension the flexible cable; the motor is mounted on the base, the active pulley is mounted on the motor shaft, the driven pulley is mounted on the base through the bearing, and an encoder is mounted on the driven pulley to detect the rotation angle of the driven pulley, and the actuator to be driven is fixed to the driven pulley by screws.

[0007] Compared with the existing cable-driven joints, the present invention has the following advantages: the cables in the system can be automatically tensioned; the cables can be driven in both directions with high precision; the joint travel is large, reaching ±165° / transmission ratio; the entire system is hollow and can pass through optical paths and circuits; an installation tool and an installation method are provided, which reduces the difficulty of installing and adjusting the cables. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a three-dimensional diagram of the precision cable-driven joint.

[0009] Figure 2 This is a three-dimensional diagram of the precision cable-driven joint including the installation and adjustment tooling.

[0010] Figure 3 This is a cross-sectional view of the precision cable-driven joint; Figure 4 It is a schematic diagram of the winding and fixing method of the flexible cable; Figure 5 Schematic diagram of the tensioning device.

[0011] In the figure, 1-active pulley, 2-adjusting fixture, 3-flexible cable, 4-spring, 5-bearing, 6-driven pulley, 7-base, 8-encoder, 9-motor, 10-flexible cable fixing head, 11-guide column, 12-anchor screw. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above-mentioned purpose, the present invention adopts the following technical scheme.

[0013] like Figure 1 As shown in the figure, an automatic tensioning precision cable drive joint of the present invention is first combined with Figure 1 , Figure 2 and Figure 3 The components and interrelationships of the present invention are further described. The driving joint is composed of an active pulley 1, a flexible cable 3, a tensioning device, a bearing 5, a driven pulley 6, a base 7, an encoder 8, and a motor 9. A mounting fixture 2 is further provided to fix the position between the active pulley 1 and the driven pulley 6 when the flexible cable is installed. The motor 9 is mounted on the base 7, the active pulley 1 is mounted on the motor shaft, the driven pulley 6 is mounted on the base 7 through a bearing, a non-contact encoder 8 is mounted on the driven pulley 6, and the actuator to be driven can be fixed to the driven pulley 6 by screws.

[0014] like Figure 4As shown, the cable-driven joint is driven by two reversely wound cables 3. The cables 3 are made of high-rigidity materials such as single-strand steel wire, multi-strand steel wire or Dyneema rope. The two ends of the cables 3 are respectively a rigid end and a flexible end. The rigid end is fixed to the active pulley 1, and the flexible end is connected to the driven pulley 6 through a tensioning device for bidirectional driving. The rigid end of the cable 3 is fixed to the active pulley 1 by opening a threaded hole radially at the top of the pulley groove and fixing it with a set screw. Alternatively, a threaded hole can be opened axially on the side of the pulley groove and fixed with a set screw. Alternatively, a stop can be machined on the pulley to fix the end of the screw. The tensioning device realizes the tensioning of the cable 3. The tensioning device includes a spring 4, a cable fixing head 10, a plurality of cylindrical guide columns 11 and an anchor screw 12.

[0015] like Figure 5 As shown, the flexible end of the flexible cable 3 is fixed and tensioned by a pre-stretched high-rigidity spring 4, and the tension of the spring 4 is much greater than the joint driving force. The flexible end of one of the flexible cables 3 passes through the hole on the side of the driven pulley 6 from the outside of the driven pulley 6 to the inside of the driven pulley 6, and is connected to one end of the spring 4 through the flexible cable fixing head 10, and the other end of the spring 4 is connected to the anchor screw 12, and the anchor screw 12 is fixed to the inner side of the driven pulley 6. The flexible cable fixing head 10 has a hanging ring at one end to realize the connection with the spring 4, and a hole is set at the other end, and the flexible end is inserted into the hole, and the flexible end is fixed by screwing the screw on the side wall. The connection method of the rigid end of the other flexible cable 3 is the same as that of the flexible cable 3. In addition, a plurality of cylindrical guide posts 11 are provided. The guide posts 11 change the direction of the flexible cable 3 and make its bending radius greater than the minimum bending radius of the material. The guide posts are fixed on the inner side of the driven pulley and are located at a more forward position of the flexible cable fixing head 10. In the working condition where dynamic tensioning is not required, the flexible end of the flexible cable 3 can be locked with screws. The diameter of the guide post 11 determines the turning radius of the flexible cable 3, and then a large end face brim structure is provided at the top to prevent the flexible cable 3 from falling out. The fixing screw is located in the pulley groove. After the flexible cable 3 is screwed, the tensioning mechanism at the rear end is disabled.

[0016] The coverage angle of a single flexible cable 3 on the active and driven pulleys is 180°, so that the joint has the maximum forward and reverse travel; the two flexible cables 3 form a cross in the gap between the active and driven pulleys, so that the fixed point of the driven pulley 6 is closer to the bottom, avoiding its tensioning device from occupying the middle space, and the angle measurement is performed through the hollow encoder 8 without blocking the light path.

[0017] Furthermore, an adjustment method is provided, wherein an adjustment tool 2 is used to limit the relative rotation of the active pulley 1 and the driven pulley 6, so that the active pulley 1 and the driven pulley 6 will not rotate when the flexible cable 3 is installed. The adjustment tool 2 is a trapezoidal structure, which is installed on the outer end surface of the active pulley 1 and the driven pulley 6. Figure 2During installation, the flexible end of the flexible cable 3 is first connected to the spring 4 through the flexible cable fixing head 10, and the flexible end is locked with a screw after the spring 4 is stretched to the maximum stroke, that is, the position where the flexible cable fixing head 10 is attached to the inner surface of the pulley or the guide column 11, and then the flexible cable 3 is tightly wound around the driven pulley 6 and the active pulley 1, and the rigid end is locked on the active pulley with a screw, and finally, the screw at the flexible end is loosened to keep the flexible cable 3 dynamically tensioned.

[0018] The base 7 is a fixed reference system. When driving in the forward direction, the motor 9 rotates clockwise, the active pulley 1 rotates clockwise with the motor, and drives the driven pulley 6 to rotate counterclockwise through the flexible cable 3. The load moves counterclockwise around the base 7 with the driven pulley 6. When driving in the reverse direction, the rotation direction is opposite.

[0019] The pre-tensioning force of the tensioning device is much greater than the driving force of the joint, so as to improve the system control bandwidth. The encoder 8 is a non-contact hollow encoder.

[0020] In summary, the cable-driven joint has the advantages of being simple and reliable, highly practical, having a large stroke, being hollow to allow light paths and circuits to pass through, being able to be driven bidirectionally with high precision, having a wide control bandwidth, being able to be automatically tensioned, being easy to assemble and adjust, having little wear, and having a long service life. The principle and feasibility of the invention have also been verified through experiments, and other similar principles and configurations are also considered to be within the scope of protection of the invention.

Claims

1. An automatically tensioned precision cable-driven joint, characterized in that: The joint includes a motor, an encoder, an active pulley, a driven pulley, a flexible cable, a base, a bearing, and a tensioning device; wherein the motor is used to drive the active pulley, and drive the flexible cable through the active pulley, and the flexible cable further drives the driven pulley to rotate forward and reversely; the driven pulley is used to install the actuator to be driven; the bearing is used to provide the driven pulley with the degree of freedom to rotate around the axis; the tensioning device is used to tension the flexible cable; the motor is installed on the base, the active pulley is installed on the motor shaft, the driven pulley is installed on the base through the bearing, and an encoder is installed on the driven pulley to detect the rotation angle of the driven pulley, and the actuator to be driven is fixed to the driven pulley by screws.

2. The joint according to claim 1, characterized in that: The flexible cable is two flexible cables wound in opposite directions, with two ends of the flexible cable being a rigid end and a flexible end respectively. The rigid end is fixed on the active pulley, and the flexible end is connected to the driven pulley through a tensioning device for bidirectional driving.

3. The joint according to claim 1, characterized in that: The flexible rope is made of single-strand steel wire, multiple-strand steel wire or Dyneema rope.

4. The joint according to claim 2, characterized in that: The rigid end of the flexible cable is fixed to the active pulley by: opening a threaded hole radially at the top of the pulley groove and fixing it with a set screw, or opening a threaded hole axially at the side of the pulley groove and fixing it with a set screw, or processing a stop on the pulley for fixing the end of the screw.

5. The joint according to claim 1, characterized in that: The coverage angle of a single flexible cable on the active and driven pulleys is 180°, so that the joint has the maximum forward and reverse travel.

6. The joint according to claim 1, characterized in that: The two flexible cables cross each other in the gap between the master and slave pulleys.

7. The joint according to claim 4, characterized in that: The tensioning device includes a spring, a flexible cable fixing head, a plurality of cylindrical guide columns and anchor screws; the flexible end of the flexible cable is fixed with a pre-stretched high-rigidity spring for tensioning, and the spring tension is much greater than the joint driving force.

8. The joint according to claim 1, characterized in that: The flexible end of one of the flexible cables passes through a hole on the side of the driven pulley and enters the inner side of the driven pulley from the outside of the driven pulley, and is connected to one end of the spring through a flexible cable fixing head, and the other end of the spring is connected to an anchor screw, which is fixed to the inner side of the driven pulley. One end of the flexible cable fixing head has a hanging ring to achieve connection with the spring, and the other end is provided with a hole, and the flexible end is inserted into the hole, and the flexible end is fixed by turning the screw on the side wall; the connection method of the flexible and rigid end of the other flexible cable is the same as that of the flexible cable. In addition, a plurality of cylindrical guide columns are provided, which change the direction of the flexible cable and make its bending radius greater than the minimum bending radius of the material. The guide column is fixed on the inner side of the driven pulley and is located at a front end of the flexible cable fixing head; the diameter of the guide column determines the turning radius of the flexible cable, and a large end face brim structure is provided on the top of the guide column to prevent the flexible cable from falling out.

9. A method for adjusting the size of a product according to any one of claims 1 to 8, characterized in that: The relative rotation of the active pulley and the driven pulley is limited by a trapezoidal adjustment fixture, and the flexible end of the cable is connected to the spring through the cable fixing head. After the spring is stretched to the maximum stroke, the flexible end is locked with a screw. The maximum stroke is the position where the cable fixing head is attached to the inner surface of the pulley or the guide column. The cable is then tightly wound around the driven pulley and the active pulley, and the rigid end is locked on the active pulley with a screw. Finally, the screw at the flexible end is loosened to keep the cable dynamically tensioned.

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