An underwater flexible mechanical arm system and control method based on rigid folding mechanism

Abstract

The present invention discloses an underwater flexible manipulator system and control method based on a rigid folding mechanism, comprising a waterproof pan-tilt base, a rigid foldable mechanism and a rope-driven control module; the rigid foldable mechanism comprises a plurality of layers of linearly superimposed rigid foldable units, and the rigid foldable units between the layers are hinged by hinges; each layer of rigid foldable units comprises eight deformable modules arranged in a ring, and each deformable module comprises four rigid isosceles trapezoidal pieces, and the sides of the four rigid isosceles trapezoidal pieces are hinged by hinges in sequence to form a deformable module of a quadrangular pyramid structure; the top surface of the quadrangular pyramid structure faces the center of the ring, and the bottom surface of the quadrangular pyramid structure faces away from the center of the ring; the telescopic bending of the rigid foldable mechanism and the opening and closing of the mechanical claw are realized by rope-driven mode. The present invention has the characteristics of high degree of freedom and flexible movement of the flexible manipulator, and at the same time has the advantages of a rigid structure.

Description

Technical Field

[0001] The present invention relates to the field of flexible mechanical arms, and in particular to an underwater flexible mechanical arm system and a control method based on a rigid folding mechanism. Background Art

[0002] In recent years, deep-sea resources, as a huge treasure trove of resources, have been valued by more and more scholars. As deep-diving technology becomes more mature, the demand for the development and scientific research of marine resources continues to increase, and the efficient underwater robotic arm system that can achieve underwater fixed-point sampling has become the focus of academic attention.

[0003] Traditional robotic arms use rigid rod joints, which have limited movement space and are difficult to adapt to complex and narrow space environments, and cannot perform grasping operations. In recent years, emerging continuous robots are all composed of flexible joints, which have infinite degrees of freedom in theory, and can meet the requirements of flexible movement and adapt to complex and narrow working environments.

[0004] For example, a Chinese patent document with publication number CN212445224U discloses a flexible joint robot, including: a driving part; a transmission part, the driving part is detachably connected to one end of the transmission part, and the driving end is located in the transmission part; an action part, one end of the action part is detachably connected to the transmission end of the transmission part; and a manipulator, the manipulator is detachably connected to the other end of the action part.

[0005] A Chinese patent document with publication number CN206840080U discloses an engineering flexible robot system with a series-parallel hybrid structure, including a flexible arm, a drive assembly, and a control device; the flexible arm is composed of a plurality of joint units connected in series, and the flexible arm also includes a universal joint and a steel wire rope; adjacent joint units are connected by a universal joint, which can realize pitch and swing movements.

[0006] However, the underwater working environment is very complex and harsh. Compared with rigid manipulators, flexible manipulators have weak impact resistance and obvious circumferential compression deformation, and cannot adapt to the impact of underwater turbulence and deep water pressure. In addition, the kinematic modeling of flexible manipulators is difficult, and the position of the mechanical claw has great uncertainty. Summary of the invention

[0007] The present invention provides an underwater flexible robotic arm system and control method based on a rigid folding mechanism. The flexible robotic arm has the characteristics of high degree of freedom and flexible movement, and can work normally in a complex environment with multiple obstacles. At the same time, it has the advantages of a rigid structure and can withstand the impact of underwater turbulence, deep water pressure or other sources.

[0008] An underwater flexible manipulator system based on a rigid folding mechanism, comprising a waterproof pan-tilt base, a rigid foldable mechanism and a rope drive control module;

[0009] The rigid foldable mechanism comprises a plurality of layers of linearly superimposed rigid foldable units, wherein the rigid foldable units between the layers are hinged by hinges; each layer of the rigid foldable units comprises eight deformable modules arranged in a ring, wherein each deformable module comprises four rigid isosceles trapezoidal pieces, and the sides of the four rigid isosceles trapezoidal pieces are hinged in sequence by hinges to form a deformable module of a quadrangular pyramid structure; when the eight deformable modules of each layer of the rigid foldable units are arranged in a ring, the top surface of the quadrangular pyramid structure faces the center of the ring, and the bottom surface of the quadrangular pyramid structure faces away from the center of the ring;

[0010] The lower end surface of the bottom rigid foldable unit is fixed on the waterproof pan-tilt base through a mounting plate, and the rope drive control module is arranged inside the waterproof pan-tilt base;

[0011] A first driving rope and a second driving rope are passed through the rigid foldable mechanism, and the lower ends of the first driving rope and the second driving rope are connected to the rope driving control module after passing through the mounting plate; the upper ends of the first driving rope and the second driving rope respectively pass through at least part of the isosceles trapezoidal pieces in each layer of the rigid foldable unit in turn, so as to pull at least one side of the rigid foldable unit to fold and shorten; the bending of the rigid foldable mechanism is achieved by controlling the elongation and shortening of the first driving rope and the second driving rope;

[0012] A mechanical claw is provided at the annular center of the top-level rigid foldable unit, and the mechanical claw is connected to the upper end of the third driving rope. The lower end of the third driving rope passes through the mounting plate and is connected to the rope driving control module. The opening and closing of the mechanical claw is achieved by controlling the extension and shortening of the third driving rope.

[0013] Preferably, the drive rope is a steel rope, which has the capability of transmitting greater force and torque.

[0014] The rope drive control module comprises a single chip microcomputer and three DC reduction motors, and the output shafts of the three DC reduction motors are respectively connected to the lower ends of the first drive rope, the second drive rope and the third drive rope.

[0015] The mechanical claw comprises three clamping jaws, and two mounting holes are arranged at the lower part of each clamping jaw, one of which is hinged to one end of a mounting block, and the other end of the mounting block is hinged to a fixed plate; the other mounting hole is hinged to a fixed block fixed to a control rod; the fixed plate is fixed to the upper end surface of a top-level rigid foldable unit, and the lower end of the control rod passes through the fixed plate and is connected to the upper end of a third driving rope; the control rod is provided with a spring at a position between the mounting plate and the fixed block.

[0016] Furthermore, the deformable modules arranged on the same straight line between adjacent rigid foldable units are grouped into one group, and the first driving rope and the second driving rope are respectively passed through two groups of deformable modules facing each other.

[0017] Furthermore, angle sensors are provided in the deformable modules on the top and bottom rigid foldable units.

[0018] Furthermore, a torsion spring is provided in the hinge structure for keeping the flexible unit in a rigid foldable unit and the deformable module in a stretched state.

[0019] A control method for an underwater flexible mechanical arm system, the control method comprising:

[0020] The forward kinematics modeling of the rigid foldable mechanism is carried out by using the method of coordinate system homogeneous transformation matrix;

[0021] According to the constructed model, the rope drive control module controls the extension and retraction of the first drive rope and the second drive rope so that the rigid foldable mechanism bends until the mechanical claw reaches the grasping position;

[0022] The rope drive control module controls the third drive rope to contract, and the mechanical claw performs grasping.

[0023] Furthermore, the specific process of performing forward kinematic modeling on the rigid foldable mechanism by using the coordinate system homogeneous transformation matrix method is as follows:

[0024] The lower face-to-face angles of the deformable modules in the top and bottom rigid foldable units are measured by angle sensors and are B 11 , B 21 , and further obtain the upper face-face angle B in the corresponding deformable module based on the geometric relationship 12 , B 22 ;

[0025] The coordinates of the position of the mechanical claw in the reference space coordinate system are obtained through the size of these two face-face angles and the corresponding geometric relationship. The formula is:

[0026]

[0027] Among them, P 1 , P 2 is a 4×1 vector containing the coordinates of the two ends of the top layer of the rigid foldable mechanism, i.e., homogeneous coordinates. The midpoint of the line connecting their coordinates is the coordinate of the position of the mechanical claw; T 1 , T 2 is the coordinate system homogeneous transformation matrix of the two ends of the bottom layer of the rigid foldable mechanism relative to the reference space coordinate system;

[0028] T b11 , T b21 , T b12 , T b22 Based on the known face-face angle B 11 , B 21 , B 12 , B 22The coordinate system homogeneous transformation matrix; T n is the coordinate system homogeneous transformation matrix based on the tilt angle between layers, layer is the number of layers, and vector Extract the translation transformation of the position in the coordinate system homogeneous transformation matrix, that is, the coordinates of the position; vector Where x, y, and z are the coordinates of the robot claw.

[0029] T b The matrix is ​​as follows:

[0030]

[0031] m,n,k satisfy:

[0032]

[0033] Among them, a, b, h, and C are the collective sizes of the trapezoidal faces that constitute the deformable module, a is the upper base of the trapezoid, b is the lower base of the trapezoid, h is the height of the trapezoid, and C is the base angle of the trapezoid; m, n, and k are used to obtain the value of the Z axis in the rotation matrix, and B is the corresponding face-to-face angle.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] In the present invention, the robot arm uses a special rigid folding mechanism as a joint, which has a high degree of freedom and flexible movement compared to traditional rigid robot arms. The folding mechanism of the robot arm is composed entirely of rigid components. Compared with traditional flexible robot arms, it can withstand greater impact, has a smaller Poisson's ratio, and is difficult to be compressed in the circumferential direction. In addition, the fully rigid structure can perform more accurate kinematic modeling, making the control of the position of the robot claw more precise. At the same time, using a waterproof gimbal can reduce wiring, reduce the accuracy error caused by wiring problems, and make monitoring and execution of tasks easier. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a structural schematic diagram of an underwater flexible mechanical arm system based on a rigid folding mechanism of the present invention;

[0037] Figure 2 is an overall schematic diagram of the rigid foldable mechanism of the present invention;

[0038] Figure 3 Schematic diagram of the face-face angle on the rigid foldable unit of the present invention;

[0039] Figure 4 It is a schematic diagram of the positions of the single-layer rigid foldable unit and the driving rope in the present invention;

[0040] Figure 5a It is a schematic diagram of the sleeve of the waterproof pan / tilt base;

[0041] Figure 5b It is a schematic diagram of the bottom plate of the waterproof pan / tilt base;

[0042] Figure 5c This is a schematic diagram of waterproofing on the top of the waterproof gimbal base;

[0043] Figure 6a This is a schematic diagram of the third driving rope driving the mechanical claw;

[0044] Figure 6b is a schematic diagram of the mechanical claw closing under the control of the third driving rope;

[0045] Figure 7 The figure is a flow chart for calculating the coordinates of the mechanical claw position at the end of the robot arm relative to the reference coordinate system. DETAILED DESCRIPTION

[0046] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.

[0047] like Figures 1 to 4 As shown, an underwater flexible robotic arm system based on a rigid folding mechanism includes a waterproof pan-tilt base 1, a rigid foldable mechanism 3 and a rope drive control module 2.

[0048] The rigid foldable mechanism 3 includes several layers of linearly stacked rigid foldable units, and the rigid foldable units between the layers are hinged by hinges; each layer of rigid foldable units includes eight deformable modules 4 arranged in a ring, and each deformable module 4 includes four rigid isosceles trapezoidal pieces, and the side surfaces of the four rigid isosceles trapezoidal pieces are hinged in turn by hinges to form a deformable module with a quadrangular pyramid structure; when the eight deformable modules of each layer of rigid foldable units are arranged in a ring, the top surface of the quadrangular pyramid structure faces the center of the ring, and the bottom surface of the quadrangular pyramid structure faces away from the center of the ring.

[0049] The lower end surface of the bottom rigid foldable unit is fixed on the waterproof pan-tilt base 1 through a mounting plate, and the rope drive control module 2 is arranged inside the waterproof pan-tilt base 1.

[0050] The rigid foldable mechanism 3 is provided with a first driving rope 5 and a second driving rope 6, and the lower ends of the first driving rope 5 and the second driving rope 6 are connected to the rope driving control module 2 in the waterproof pan / tilt base 1 after passing through the mounting plate 9. The upper ends of the first driving rope 5 and the second driving rope 6 respectively pass through at least part of the isosceles trapezoidal pieces in each layer of the rigid foldable unit in turn, so as to pull at least one side of the rigid foldable unit to fold and shorten; the bending of the rigid foldable mechanism is achieved by controlling the elongation and shortening of the first driving rope and the second driving rope.

[0051] A mechanical claw 8 is provided at the annular center of the top-level rigid foldable unit. The mechanical claw 8 is connected to the upper end of the third driving rope 7. The lower end of the third driving rope 7 passes through the mounting plate and is connected to the rope driving control module 2. The opening and closing of the mechanical claw 8 is achieved by controlling the extension and shortening of the third driving rope 7.

[0052] like Figure 4 As shown, a layer of rigid foldable unit of a rigid foldable mechanism 3 is shown, wherein the first drive rope 5, the second drive rope 6 and the third drive rope 7 pass through the layer from the position shown in the figure, penetrate the rigid foldable mechanism 3, and are connected to the motor in the rope drive control module 2.

[0053] like Figure 5a As shown, it is a schematic diagram of the sleeve 11 of the waterproof pan-tilt base 1, which is connected to the bottom plate 10 (such as Figure 5b The main connection method is threaded connection. Considering the waterproof problem, a sealing ring is used to perform static sealing treatment on the flange connection between the sleeve and the bottom plate. Figure 5c As shown, the sealing ring is used to perform both static sealing and dynamic sealing.

[0054] like Figure 6a The figure shows a schematic diagram of a mechanical claw 8. Driving the third driving rope 7 to extend and retract can control the opening and closing of the mechanical claw 8. Figure 6b The third driving rope 7 is pulled down to drive the mechanical claw to close. If the third driving rope 7 is loosened, the mechanical claw 8 can be reset to the position by the spring 86 installed on the mechanical claw 8. Figure 6a Open state.

[0055] like Figure 6a As shown, the mechanical claw 8 comprises three clamping jaws 81, and two mounting holes are provided at the lower part of each clamping jaw 81, one of which is hinged to one end of a mounting block 82, and the other end of the mounting block 82 is hinged to a fixing plate 83; the other mounting hole is hinged to a fixing block 85 fixed to a control rod 84. The fixing plate 83 is fixed to the upper end surface of the top rigid foldable unit, and the lower end of the control rod 84 passes through the fixing plate 83 and is connected to the upper end of the third driving rope 7, and the control rod 84 is sleeved with a spring 86 at a position between the fixing plate 83 and the fixing block 85.

[0056] Driving the third driving rope 7 to extend and retract can control the opening and closing action of the mechanical claw 8, such as Figure 6b As shown, the third driving rope 7 is pulled down to drive the clamping claw 81 to close. If the third driving rope 7 is loosened, the mechanical claw can be reset to the position through the spring 86. Figure 6a The open state.

[0057] In the present embodiment, the rope drive control module 2 includes driving components such as Arduino development board and DC reduction motor. The single chip microcomputer used is selected as the expansion board with Arduino as the core board, which has 6-way steering gear interface and 4-way DC reduction motor interface, and can be easily connected. The motor selected is a 360-degree continuous rotation waterproof steering gear, and its torque is 30kg / cm, so it can realize continuous rotation in all directions, and can bear the weight of the whole mechanical arm, and can meet the work demand well. Due to the rope driven mode, 3 DC reduction motors are needed as driving sources, one end of the driving rope is connected to the motor output shaft, and the other end is connected to the actuator, and the driving of the actuator is realized by the contraction and extension of the rope. Wherein 2 motors are used to drive the main structure of the mechanical arm, realize the bending and telescoping of the main structure, and another motor is used to drive the mechanical claw, realize the opening and closing action of the mechanical claw.

[0058] In the present invention, the main function of the rotatable waterproof pan-tilt base is to help the robot arm achieve all-round grasping. The pan-tilt and the robot arm body and the mechanical claw on it are all driven by a waterproof steering gear and supported by bearings. Therefore, in order to reduce weight, except for the bearing support part and the steering gear installation part, the rest are made of 3D printed materials.

[0059] like Figure 2 As shown, the structure can be modeled by forward kinematics using the coordinate system homogeneous transformation matrix.

[0060] like Figure 3 As shown in the figure, the lower face-face angles of the deformable modules in the top and bottom rigid foldable units are measured by the angle sensor as B 11 , B 21 , and further obtain the upper face-face angle B in the corresponding deformable module based on the geometric relationship 12 , B 22 .

[0061] The coordinates of the position of the mechanical claw in the reference space coordinate system are obtained through the size of these two face-face angles and the corresponding geometric relationship. The formula is:

[0062]

[0063] Among them, P 1 , P 2 is a 4×1 vector containing the coordinates of the two ends of the top layer of the rigid foldable mechanism. The midpoint of the line connecting their coordinates is the coordinate of the position of the mechanical claw. 1 、T 2 is the coordinate system homogeneous transformation matrix of the two ends of the bottom layer of the rigid foldable mechanism relative to the reference space coordinate system;

[0064] Tb11 , T b21 , T b12 , T b22 Based on the known face-face angle B 11 , B 21 , B 12 , B 22 The coordinate system homogeneous transformation matrix; T n is the coordinate system homogeneous transformation matrix based on the tilt angle between layers, layer is the number of layers, and vector Extract the translation transformation of the position in the coordinate system homogeneous transformation matrix, that is, the coordinates of the position; vector Where x, y, and z are the coordinates of the robot claw.

[0065] T b The matrix is ​​as follows:

[0066]

[0067] m,n,k satisfy:

[0068]

[0069] Among them, a, b, h, and C are the collective sizes of the trapezoidal faces that constitute the deformable module, a is the upper base of the trapezoid, b is the lower base of the trapezoid, h is the height of the trapezoid, and C is the base angle of the trapezoid; m, n, and k are used to obtain the value of the Z axis in the rotation matrix, and B is the corresponding face-to-face angle.

[0070] In the modeling process, the default coordinates of the position of the mechanical claw at the end of the robot arm in the coordinate system with it as the origin are (0,0,0). According to the geometric relationship of the structure, the rotation matrix and displacement matrix between this coordinate system and the corresponding coordinate system of the next layer can be obtained, thereby obtaining the coordinate system transformation matrix and the coordinates of the mechanical claw position in the coordinate system of the next layer (x 1 ,y 1 ,z 1 ). Through continuous matrix transformation, the coordinates (x n ,y n ,z n ), the process is as follows Figure 7 shown.

[0071] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A control method for an underwater flexible robotic arm system, It is characterized in that Used to control an underwater flexible manipulator system based on a rigid folding mechanism, the underwater flexible manipulator system comprising a waterproof pan-tilt base, a rigid foldable mechanism and a rope drive control module; The rigid foldable mechanism comprises a plurality of layers of linearly superimposed rigid foldable units, wherein the rigid foldable units between the layers are hinged by hinges; each layer of the rigid foldable units comprises eight deformable modules arranged in a ring, wherein each deformable module comprises four rigid isosceles trapezoidal pieces, and the sides of the four rigid isosceles trapezoidal pieces are hinged in sequence by hinges to form a deformable module of a quadrangular pyramid structure; when the eight deformable modules of each layer of the rigid foldable units are arranged in a ring, the top surface of the quadrangular pyramid structure faces the center of the ring, and the bottom surface of the quadrangular pyramid structure faces away from the center of the ring; angle sensors are provided in the deformable modules on the top and bottom rigid foldable units; The lower end surface of the bottom rigid foldable unit is fixed on the waterproof pan-tilt base through a mounting plate, and the rope drive control module is arranged inside the waterproof pan-tilt base; A first driving rope and a second driving rope are passed through the rigid foldable mechanism, and the lower ends of the first driving rope and the second driving rope are connected to the rope drive control module after passing through the mounting plate; the upper ends of the first driving rope and the second driving rope respectively pass through at least part of the isosceles trapezoidal pieces in each layer of the rigid foldable unit in turn, so as to pull at least one side of the rigid foldable unit to fold and shorten; The bending of the rigid foldable structure is achieved by controlling the elongation and shortening of the first drive rope and the second drive rope; A mechanical claw is provided at the annular center of the top rigid foldable unit, the mechanical claw is connected to the upper end of the third driving rope, the lower end of the third driving rope passes through the mounting plate and is connected to the rope driving control module, and the opening and closing of the mechanical claw is realized by controlling the extension and shortening of the third driving rope; The control method comprises: The forward kinematics modeling of the rigid foldable mechanism is carried out by using the coordinate system homogeneous transformation matrix method; the specific process is as follows: The lower face-to-face angles of the deformable modules in the top and bottom rigid foldable units are measured by angle sensors and are B 11 , B 21 , and further obtain the upper face-face angle B in the corresponding deformable module based on the geometric relationship 12 , B 22 ; The coordinates of the position of the mechanical claw in the reference space coordinate system are obtained through the size of these two face-face angles and the corresponding geometric relationship. The formula is: Among them, P 1 , P 2 is a 4×1 vector containing the coordinates of the two ends of the top layer of the rigid foldable mechanism, i.e., homogeneous coordinates. The midpoint of the line connecting their coordinates is the coordinate of the position of the mechanical claw; T 1 , T 2 is the coordinate system homogeneous transformation matrix of the two ends of the bottom layer of the rigid foldable mechanism relative to the reference space coordinate system; T b11 , T b21 , T b12 , T b22 Based on the known face-face angle B 11 , B 21 , B 12 , B 22 The coordinate system homogeneous transformation matrix; T n is the coordinate system homogeneous transformation matrix based on the tilt angle between layers, layer is the number of layers, and vector Extract the translation transformation of the position in the coordinate system homogeneous transformation matrix, that is, the coordinates of the position; vector x, y, z are the coordinates of the position of the robot claw; According to the constructed model, the rope drive control module controls the extension and retraction of the first drive rope and the second drive rope so that the rigid foldable mechanism bends until the mechanical claw reaches the grasping position; The rope drive control module controls the third drive rope to contract, and the mechanical claw performs grasping.

2. The control method of the underwater flexible manipulator system according to claim 1, It is characterized in that The rope drive control module comprises a single chip microcomputer and three DC reduction motors, and the output shafts of the three DC reduction motors are respectively connected to the lower ends of the first drive rope, the second drive rope and the third drive rope.

3. The control method of the underwater flexible manipulator system according to claim 1, It is characterized in that The mechanical claw comprises three clamping jaws, and two mounting holes are arranged at the lower part of each clamping jaw, one of which is hinged to one end of a mounting block, and the other end of the mounting block is hinged to a fixed plate; the other mounting hole is hinged to a fixed block fixed to a control rod; the fixed plate is fixed to the upper end surface of a top-level rigid foldable unit, and the lower end of the control rod passes through the fixed plate and is connected to the upper end of a third driving rope; the control rod is provided with a spring at a position between the mounting plate and the fixed block.

4. The control method of the underwater flexible manipulator system according to claim 1, It is characterized in that Each deformable module arranged on the same straight line between adjacent rigid foldable units is divided into one group, and two groups of deformable modules facing each other are respectively provided with a first driving rope and a second driving rope.

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