Rigid-flexible coupling series-parallel main manipulator

Abstract

The invention discloses a rigid-flexible coupling series-parallel main manipulator which comprises a rigid series branch chain as a passive pose sensing branch chain, a flexible parallel mechanism as a force feedback execution branch chain and an operation handle, the operating handle is connected with the far ends of the eight flexible tendon ropes of the flexible parallel platform through the eight symmetrical anchor points, so that the operating handle, the rigid series branch chain and the eight flexible tendon ropes jointly form a rigid-flexible hybrid parallel constraint mechanism with nine branch chains, and structural support and pose recognition are provided through the rigid branch chains. Power interaction is provided through the flexible branch chains. The rigid-flexible coupling design is adopted, force can be directly transmitted to the operation end from the motor through the tendon rope, friction loss is reduced, and the force output efficiency is improved. A rigid branch chain is introduced into a rigid-flexible coupling design framework, so that the overall rigidity of the system is high, meanwhile, a force-position decoupling layout design is adopted, a positioning function is integrated on the rigid branch chain, and the positioning precision can be equivalent to the precision of a rigid structure.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, specifically a rigid-flexible coupled series-parallel hybrid main operator. Background Technology

[0002] Existing master manipulators are mainly divided into three types: series, parallel, and series-parallel hybrid. Specifically: 1. Series master manipulators typically have six degrees of freedom at the end effector. Their main structure is generally mounted on a base and consists of multiple "link-rotation joint" units connected in series. However, they suffer from several drawbacks: errors from each joint accumulate at the end effector, resulting in relatively low precision; poor rigidity (the cantilever structure leads to insufficient rigidity and limited load-bearing capacity); high inertia (the drive motors are distributed across the joints, resulting in large inertia of moving parts and a low load / weight ratio); and a relatively heavy structure with relatively low load-bearing capacity. 2. Parallel-type master manipulators, such as the one with patent number CN117281622A, named "Force Feedback Master Manipulator," employ a multi-branch structure. Typically, the motor is positioned behind the base, achieving higher rigidity and faster response speed. However, they suffer from several drawbacks: ① Small workspace: limited range of motion and singularities within the workspace affecting motion control; ② Complex structure: interference between multiple branches, making design and manufacturing difficult; ③ Complex control: while inverse kinematics solutions are easy, forward kinematics solutions are difficult (often using numerical solutions, which are computationally difficult and slow), and calibration is challenging. 3. Hybrid-type master manipulators employ a hybrid structure, combining series and parallel configurations. However, because the attitude wrist is nested in series at the end of the parallel platform, the center of gravity of the end-effector significantly deviates from the geometric center of the mechanism. During signal transmission and control, the system needs to allocate a large amount of torque to counteract the gravitational effect caused by this center of gravity shift, reducing the output efficiency of effective force feedback. Secondly, because the physical base of the serial wrist moves with the parallel platform, when the parallel branch is at a specific angle, it is very easy to cause spatial physical interference with the wrist structure or the operator's hand, limiting the overall range of motion of the operator's hand. In addition, this hybrid structure does not solve the problem of the difficulty in solving the forward kinematics of the parallel mechanism. The controller still needs to spend a lot of time on numerical solution when calculating the real-time pose of the end effector, which causes delay in signal communication and leads to control lag in the master-slave system.

[0003] This case arose in order to resolve the aforementioned issues. Summary of the Invention

[0004] Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a rigid-flexible coupled series-parallel hybrid main operator, which solves the problems of excessive motion inertia and low torque utilization caused by motor load in traditional series main operators, as well as the limited working space, high risk of branch interference, and lag in positive kinematics numerical calculation in traditional parallel or hybrid main operators.

[0005] Technical solution To achieve the above objectives, the present invention provides the following technical solution: a rigid-flexible coupled series-parallel hybrid main operator, comprising a fixed frame, a rigid series branch mounted on the fixed frame and coupled thereto as a passive posture sensing branch, and a flexible parallel mechanism as a force feedback execution branch, and an operating handle; wherein, the flexible parallel mechanism comprises multiple sets of drive units located at different positions on the fixed frame, each set of drive units comprising a torque motor and a flexible tendon rope connected to the output end of the torque motor, the flexible tendon ropes being radially distributed and respectively clustered and connected to corresponding positions on the operating handle; the rigid series branch comprises multiple connecting rods sequentially connected through rotating joints, a series support rod base supporting the starting end of the connecting rods, the series support rod base being mounted on the fixed frame as a fixed position, and the end being connected to the operating handle, each rotating joint integrating an encoder, which converts the rotation of the rotating joint into an electrical signal for acquisition.

[0006] As a preferred embodiment, the drive unit is further provided in eight groups, and is respectively placed at the eight vertices of the fixed frame to form a matrix spatial layout; in the initial state, the operating handle is located at the geometric symmetry center of the drive unit; The output shaft of the torque motor is equipped with a winding wheel, which is a cylindrical structure with a spiral guide groove of equal diameter on its surface. The flexible tendon rope is wound in the spiral guide groove of equal diameter, with winding redundancy.

[0007] As a preferred embodiment, each of the torque motors is further provided with a conductor unit at an adjacent position, wherein the conductor unit is arranged coaxially with the torque motor and positioned in the direction of rope output. Each group of conductor units includes a conductor unit base mounted on a fixed frame and two V-shaped bearings, large and small, arranged parallel to the conductor unit base. The flexible tendon rope passes around the two V-shaped bearings in an "S" shaped path.

[0008] As a preferred embodiment, one end of the flexible tendon rope is fixedly connected to the end of the operating handle by an adhesive dispensing process, and the other end is connected to the winding reel by an adhesive dispensing process.

[0009] As a preferred embodiment, the encoder is further described as a single-turn absolute magnetic encoder.

[0010] As a preferred embodiment, the rotating joint at the location where the operating handle connects to the flexible tendon rope is provided with a transmission mechanism of equal transmission ratio. The rotating joint has a rotating shaft, and the transmission mechanism includes an active synchronous pulley and a driven synchronous pulley coaxially connected to the rotating joint, as well as a synchronous belt that is enclosed around the active and driven synchronous pulleys. The encoder at this location is off-axis, and a miniature cylindrical magnet is coaxially mounted on the driven synchronous pulley instead of being coaxially mounted at the rotating joint.

[0011] As a preferred embodiment, further, a miniature cylindrical magnet is fixed to the rotating shaft on the remaining rotating joints. The rotation amount of the cylindrical magnet is equal to the rotation angle of the rotating shaft. The cylindrical magnet is located directly above the sensing surface of the magnetic encoder. When the cylindrical magnet rotates with the rotating shaft, the magnetic field above the encoder rotates.

[0012] As a preferred embodiment, the rigid series support is a six-degree-of-freedom passive support. The initial end of the link is installed at the bottom center point of the fixed frame through the conductor unit base. The axes of the first three rotation joints do not coincide with each other, and the axes of the last three rotation joints intersect at one point to form a spherical wrist structure.

[0013] As a preferred embodiment, the connecting rod is further made of a lightweight light-cured resin material, and the connecting rod has a hollow design with a through-hole channel inside.

[0014] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art: A rigid-flexible coupled series-parallel hybrid main operator employs a rigid-flexible coupling design that allows force to be directly transmitted from the motor to the operating end via a tendon cable, reducing friction loss and improving force output efficiency. The rigid-flexible coupling design framework incorporates rigid branches, resulting in high overall system rigidity. Furthermore, the force-position decoupling layout integrates the positioning function onto the rigid branches, enabling positioning accuracy comparable to that of a rigid structure.

[0015] A rigid-flexible coupled series-parallel hybrid main operator mounts all torque motors on the base of a flexible platform, reducing the mass of moving components and resulting in lower moment of inertia during system movement. This reduces operator fatigue and improves system control response speed. Simultaneously, the flexible platform acts as a support, distributing the load of the rigid support, reducing support deformation, and improving positioning accuracy.

[0016] A rigid-flexible coupled serial-parallel hybrid master operator integrates the system's pose perception on a rigid branch of a purely passive structure. That is, the encoder's position is only distributed on the rigid branch, resulting in higher positioning accuracy compared to a purely flexible structure.

[0017] A rigid-flexible coupled series-parallel hybrid main operator employs a passive rigid chain. Due to its low self-weight and low structural stiffness, this chain is designed with a hollow structure and uses lightweight materials (such as PE and aluminum) to further reduce weight and lower the system's moment of inertia. Secondly, the absence of motors on the passive chain results in lower internal stress and structural deformation after assembly, improving structural positioning accuracy. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the rigid series branch structure of the present invention; Figure 3 This is a schematic diagram of the operating handle structure of the present invention; Figure 4 This is a schematic diagram of the structure of the conductor unit (a) and torque motor assembly (b) of the present invention; Figure 5 This is a schematic diagram showing the spatial positions of each structure on the flexible parallel platform of the present invention.

[0019] In the diagram, 1. Rigid series branch; 1-1. Rotary joint one; 1-2. Rotary joint two; 1-3. Connecting rod; 1-4. Rotary joint six; 1-5. Magnetic encoder; 1-6. Cylindrical magnet; 1-7. Synchronous belt; 2. Fixed frame; 3. Wire unit; 3-1. Small V-bearing; 3-2. Large V-bearing; 3-3. Wire unit base; 4. Torque motor assembly; 4-1. Winding reel; 4-2. Motor base; 4-3. Torque motor; 5. Flexible tendon rope. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0021] like Figure 1 As shown in Figure 4, a rigid-flexible coupled series-parallel hybrid main manipulator includes a fixed frame, a rigid series branch 1 mounted on the fixed frame and coupled thereto as a passive pose sensing branch, a flexible parallel mechanism as a force feedback execution branch, and an operating handle. Specifically, the operating handle is connected to the distal ends of eight flexible tendon ropes 5 of the flexible parallel mechanism through eight symmetrical anchor points. Thus, the operating handle, the rigid series branch 1, and the eight flexible tendon ropes 5 together constitute a rigid-flexible hybrid parallel constraint mechanism with nine branches. The rigid series branch 1 provides structural support and motion guidance, while the flexible parallel mechanism provides power interaction.

[0022] The flexible parallel mechanism includes multiple sets of drive units located at different positions on the fixed frame 2. Each set of drive units includes a torque motor 4-3 and a flexible tendon rope 5 connected to the output end of the torque motor 4-3. The flexible tendon ropes 5 are radially distributed and respectively gathered and connected to the corresponding positions on the operating handle.

[0023] The rigid series branch 1 is a six-degree-of-freedom passive branch, comprising multiple links 1-3 connected in series via rotary joints. The base of the series branch is mounted on a fixed frame 2 (made of aluminum) as a fixed position, and its end is connected to an operating handle. The initial ends of links 1-3 are mounted on the bottom center point of the fixed frame via wire unit bases 3-3. The axes of the first three rotary joints are not coincident, while the axes of the last three rotary joints intersect at a point to form a spherical wrist structure for achieving three-dimensional attitude perception. This pose-decoupled geometric arrangement simplifies the kinematic algorithm logic and reduces the computational load on the control system.

[0024] Because the mechanism employs a purely passive design without a motor, connecting rod 1-3 does not bear the internal stress generated by the feedback torque of torque motor 4-3. Therefore, connecting rod 1-3 can be made of lightweight light-cured resin material combined with a hollow lightweight structure (lightweight PE / polyethylene material to reduce motion inertia). While ensuring sensing accuracy and strength, the motion inertia of the mechanism is significantly reduced. At the same time, the reduction in internal stress reduces the deformation of each component after installation, improving positioning accuracy. In terms of structural and safety design, connecting rod 1-3 has a hollow design with a through-hole channel inside. Power lines and signal lines pass through the hollow channel and converge at the circuit board at the conductor unit base 3-3, achieving embedded protection of the circuitry and avoiding interference from wire pulling.

[0025] Each rotating joint is equipped with an encoder, which converts the rotation of the joint into an electrical signal. The encoder is a single-turn absolute magnetic encoder 1-5 (which uploads angle information to the controller via RS-485 serial communication and identifies angle changes through magnetic field vector transformation based on the Hall effect). The rotational stroke of each joint is limited by the physical structure of the connecting rod 1-3.

[0026] Since it does not go through a reduction gear, the encoder can directly read the absolute angle signal of the output shaft, thereby avoiding errors caused by mechanism backlash and improving the accuracy of position and posture perception.

[0027] To avoid obstructing the anchoring space of the flexible tendon 5 at the end, a transmission mechanism with equal transmission ratio is provided at the rotating joint (i.e., rotating joint 1-4) where the operating handle connects to the flexible tendon 5. The rotating joint has a rotating shaft, and the transmission mechanism includes a driving synchronous pulley and a driven synchronous pulley coaxially connected to the rotating joint, as well as a synchronous belt 1-7 that is enclosed around the driving and driven synchronous pulleys. The encoder at this position is off-axis (designed to optimize the end space layout and reduce structural complexity), and a miniature cylindrical magnet 1-6 is coaxially mounted on the driven synchronous pulley instead of being installed on the coaxial part of the rotating joint. Through this spatially staggered arrangement, while ensuring accurate angle acquisition at the operating handle, sufficient physical space is reserved for the connection of the flexible tendon 5 at the end of the operating handle.

[0028] Miniature cylindrical magnets 1-6 are fixed to the rotating shafts of the remaining rotating joints. The rotation of the cylindrical magnets 1-6 is equal to the rotation angle of the rotating shaft, ensuring accurate sensing of related motion characteristics. The cylindrical magnets 1-6 are located directly above the sensing surface of the magnetic encoder 1-5. As the cylindrical magnets 1-6 rotate with the rotating shaft, the magnetic field above the encoder rotates, allowing the magnetic encoder 1-5 to read the change in angular displacement. A similar "magnet-shaft-encoder" structure is implemented to read the real-time rotation angles of the joints in a rigid chain.

[0029] The drive unit comprises eight groups, each positioned at one of the eight vertices of the fixed frame 2, forming a matrix spatial layout. Initially, the operating handle is located at the geometric center of the drive unit. The output shaft of the torque motor 4-3 is fitted with a winding wheel 4-1, which is a cylindrical structure with helical guide grooves of equal diameter on its surface. Depending on the installation position, it can rotate clockwise or counterclockwise. Flexible tendon ropes 5 are wound in the helical guide grooves of equal diameter, ensuring that the tendon rope experiences constant force under the same output torque, thus eliminating the nonlinear influence of changes in the wheel diameter on the feedback force.

[0030] Each torque motor 4-3 is equipped with a conductor unit 3 adjacent to it. The conductor unit 3 is coaxially arranged with the torque motor 4-3 and positioned in the direction of rope output. Each conductor unit 3 includes a conductor unit base 3-3 mounted on the fixed frame 2 and two V-shaped bearings, one large and one small, arranged parallel to the conductor unit base 3-3. The flexible tendon rope 5 passes around the two V-shaped bearings in an "S" shaped path. Its physical constraint ensures that the direction of rope output of the flexible tendon rope 5 is always fixed in the preset position, thereby stabilizing the force vector direction of the flexible tendon rope 5 and improving the stability of power transmission.

[0031] In terms of transmission principle, this scheme eliminates the mechanical backlash and frictional loss of multi-stage transmission through direct connection of the flexible tendon cord 5, and reduces the system's additional inertia by utilizing the lightweight characteristics of the flexible tendon cord 5. For sensing requirements, the platform calculates pose through rigid series passive branches, with the force feedback function independently handled by a parallel platform, avoiding interference with positional accuracy caused by the elastic deformation of the tendon cord. Addressing the unidirectional driving characteristics of the flexible tendon cord 5, this embodiment employs an eight-cord, six-degree-of-freedom redundant configuration, achieving omnidirectional force feedback through spatial tension synthesis, thereby avoiding type II singular configurations caused by linear correlation of the driving degrees of freedom and ensuring the continuity of the force feedback output.

[0032] Rigidly connected branch 1, without an active drive unit, is defined as a passive branch. It captures joint variables in real time and uploads them to the controller. The controller then uses forward kinematics formulas to analyze and obtain the real-time pose of the master hand's end effector, providing a data foundation for subsequent force feedback output control and slave hand motion mapping. The forward kinematics formulas are shown below: The flexible parallel mechanism is connected to the end actuator of the rigid series branch 1 through eight flexible tendon ropes 5. One end of the flexible tendon rope 5 is fixedly connected to the end of the operating handle through a dispensing process, and the other end is connected to the winding wheel 4-1 through dispensing and directly coupled to the torque motor assembly 4. The torque motor assembly 4 is fixed on the fixed frame 2.

[0033] The winding reel 4-1 is coaxially mounted with the torque motor 4-3, and its surface is engraved with clockwise or counterclockwise helical guide wire grooves of equal diameter. The direction of rotation of the guide wire grooves is determined by the mounting position of the torque motor 4-3 to ensure that the lower flexible tendon rope 5 is always wound from below the winding reel 4-1, while the upper flexible tendon rope 5 is always wound from above the winding reel 4-1. The helical guide wire grooves on the winding reel 4-1 guide the flexible tendon rope 5 to always be wound on the hub with a constant diameter, so that when the torque motor 4-3 outputs torque, the lever arm acting on the flexible tendon rope 5 remains constant, which is beneficial to the stable output of the tension of the flexible tendon rope 5.

[0034] The direction vectors of each flexible tendon cord 5 in the flexible parallel mechanism can be defined by the connection point at the end of the operating handle and the exit point of the guide wire unit 3. The pose of the end of the operating handle can be calculated by the forward kinematics algorithm of the rigid series branch 1, as shown in Equation 3, thereby obtaining the specific spatial coordinates of the flexible tendon cord connected to the end of the operating handle, as shown in Equation 3. Figure 5 (a) A i Location shown.

[0035] Figure 5 (a) B i The spatial position of conductor element 3 is determined by its normal vector and can be obtained by equation (4). The exit point of the flexible tendon rope at conductor element 3 is as follows: Figure 5 As shown in (b), the point of tangency of the winding reel is defined as... The tangent point The precise spatial coordinates can be determined by equation (5) based on the geometric constraint relationship of the traverse element 3.

[0036]

[0037] Finally, the direction vectors of each tendon can be obtained by equation (6). Based on the obtained tendon vector relationship, the controller allocates the target output torque to each torque motor 4-3 according to the preset force feedback algorithm, thereby obtaining the required force feedback effect.

[0038]

[0039] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A rigid-flexible coupled serial-parallel hybrid master operator, characterized in that: It includes a fixed frame, a rigid series branch mounted on the fixed frame and coupled together to form a passive pose sensing branch, and a flexible parallel mechanism to form a force feedback execution branch, and an operating handle; wherein, The flexible parallel mechanism includes multiple sets of drive units located at different positions on the fixed frame. Each set of drive units includes a torque motor and a flexible tendon rope connected to the output end of the torque motor. The flexible tendon ropes are radially distributed and converge to the corresponding positions on the operating handle. Each torque motor is provided with a wire unit at an adjacent position. The wire unit is arranged coaxially with the torque motor, located in the rope output direction, and constrains the output position. The rigid series support chain includes multiple connecting rods connected in series via rotating joints, a series support rod base supporting the starting end of the connecting rods, the series support rod base being installed on a fixed frame as a fixed position, and the end being connected to an operating handle. Each rotating joint is integrated with an encoder, which converts the rotation of the rotating joint into an electrical signal for acquisition.

2. The rigid-flexible coupled serial-parallel hybrid main operator according to claim 1, characterized in that: The drive unit is provided in eight groups and is placed at the eight vertices of the fixed frame to form a matrix spatial layout; in the initial state, the operating handle is located at the geometric symmetry center of the drive unit; The output shaft of the torque motor is equipped with a winding wheel, which is a cylindrical structure with a spiral guide groove of equal diameter on its surface. The flexible tendon rope is wound in the spiral guide groove of equal diameter, with winding redundancy.

3. The rigid-flexible coupled serial-parallel hybrid main operator according to claim 2, characterized in that: Each set of conductor units includes a conductor unit base mounted on a fixed frame and two V-shaped bearings, large and small, arranged in parallel on the conductor unit base. The flexible tendon rope passes around the two V-shaped bearings in an "S" shaped path.

4. The rigid-flexible coupled serial-parallel hybrid main operator according to claim 2, characterized in that: One end of the flexible tendon rope is fixedly connected to the end of the operating handle by an adhesive dispensing process, and the other end is connected to the winding reel by an adhesive dispensing process.

5. The rigid-flexible coupled serial-parallel hybrid main operator according to claim 2, characterized in that: The encoder is a single-turn absolute magnetic encoder.

6. The rigid-flexible coupled serial-parallel hybrid main operator according to claim 5, characterized in that: The rotating joint at the location where the operating handle connects to the flexible tendon rope is provided with a transmission mechanism with equal transmission ratio. The transmission mechanism includes an active synchronous pulley and a driven synchronous pulley coaxially connected to the rotating joint, as well as a synchronous belt that is closed around the active synchronous pulley and the driven synchronous pulley. The encoder at this location is off-axis, the rotating joint has a rotating shaft, and a cylindrical magnet is coaxially mounted on the driven synchronous pulley instead of being mounted on the rotating shaft of the rotating joint.

7. The rigid-flexible coupled serial-parallel hybrid main operator according to claim 6, characterized in that: The remaining rotating joints have a rotating shaft fixed with a cylindrical magnet. The rotation of the cylindrical magnet is equal to the rotation angle of the rotating shaft. The cylindrical magnet is located directly above the sensing surface of the magnetic encoder. When the cylindrical magnet rotates with the rotating shaft, the magnetic field above the encoder rotates.

8. The rigid-flexible coupled serial-parallel hybrid main operator according to claim 1, characterized in that: The rigid series support is a six-degree-of-freedom passive support. The initial end of the link is installed at the bottom center point of the fixed frame through the wire unit base. The axes of the first three rotation joints do not coincide with each other, and the axes of the last three rotation joints intersect at one point to form a spherical wrist structure.

9. The rigid-flexible coupled serial-parallel hybrid main operator according to claim 8, characterized in that: The connecting rod is made of lightweight light-cured resin material, and the connecting rod has a hollow design with a through-hole channel inside.

Images