阅读说明：本技术 一种基于被动补偿的混联机构系统及其运动分解方法 (Hybrid mechanism system based on passive compensation and motion decomposition method thereof ) 是由 魏延辉 樊雅妮 郭彤旭 谢吉顺 于恬 付敬恒 邵红 王玥玥 于 2020-09-17 设计创作，主要内容包括：本发明提供一种基于被动补偿的混联机构系统,包括混联机构、混联机构末端的压力传感器阵列、波浪被动补偿的运动分配器、混联机构液压系统。所述混联结构包括六自由度并联机构、三自由度串联机构、安装底座；六自由度并联机构由六个液压缸和上平台组成,三自由度串联机构由回转机构、俯仰机构和伸缩机构组成,安装底座用于将混联机构固定在运维船甲板上,三自由度串联机构与六自由度并联机构之间通过铰支座组成。本发明能够在高海况条件下实现海上运维船的被动补偿,保证恶劣天气下的海上平台的运维工作的正常进行。本发明相对于主动海浪补偿系统具有能量消耗小、成本低的优点,适合海上短时、快速运维要求,具有较强实用性。(The invention provides a hybrid mechanism system based on passive compensation, which comprises a hybrid mechanism, a pressure sensor array at the tail end of the hybrid mechanism, a motion distributor for wave passive compensation and a hybrid mechanism hydraulic system. The hybrid structure comprises a six-degree-of-freedom parallel mechanism, a three-degree-of-freedom series mechanism and a mounting base; the six-degree-of-freedom parallel mechanism consists of six hydraulic cylinders and an upper platform, the three-degree-of-freedom series mechanism consists of a swing mechanism, a pitching mechanism and a telescopic mechanism, the mounting base is used for fixing the series-parallel mechanism on a deck of the operation and maintenance ship, and the three-degree-of-freedom series mechanism and the six-degree-of-freedom parallel mechanism are formed by hinged supports. The passive compensation method can realize the passive compensation of the offshore operation and maintenance ship under the condition of high sea condition, and ensure the normal operation and maintenance of the offshore platform under severe weather. Compared with an active sea wave compensation system, the sea wave compensation system has the advantages of low energy consumption and low cost, is suitable for short-time and quick operation and maintenance requirements on the sea, and has strong practicability.)

1. A hybrid mechanism system based on passive compensation is characterized by comprising a hybrid mechanism, a pressure sensor array at the tail end of the hybrid mechanism, a motion distributor for wave passive compensation and a hybrid mechanism hydraulic system.

2. The hybrid mechanism system based on passive compensation as claimed in claim 1, wherein the hybrid structure comprises a six-degree-of-freedom parallel mechanism, a three-degree-of-freedom series mechanism, a mounting base; the six-degree-of-freedom parallel mechanism consists of six hydraulic cylinders and an upper platform, the three-degree-of-freedom series mechanism consists of a swing mechanism, a pitching mechanism and a telescopic mechanism, the mounting base is used for fixing the series-parallel mechanism on a deck of the operation and maintenance ship, and the three-degree-of-freedom series mechanism and the six-degree-of-freedom parallel mechanism are formed by hinged supports.

3. The hybrid mechanism system based on passive compensation as claimed in claim 1, wherein the pressure sensor array at the tail end of the hybrid mechanism is arranged in two directions, the pressure sensor array is uniformly distributed at intervals of every 5 degrees along the semicircular tail end of the hybrid mechanism in the horizontal direction, and the contact force change condition between the advancing direction of the tail end of the hybrid mechanism and the offshore platform is detected; the vertical direction is arranged at the lower end of the tail end of the hybrid mechanism, and the hybrid mechanism is uniformly distributed in a semicircular mode at intervals of every 5 degrees to detect the stress change condition of the lap joint of the tail end of the hybrid mechanism and the offshore platform.

4. The hybrid mechanism system based on passive compensation according to claim 1, wherein the wave passive compensation motion distributor analyzes and decomposes motion according to pressure information detected by a pressure sensor array at the tail end of the hybrid mechanism, forms motion commands of each execution component of the series hybrid mechanism, and drives each hydraulic cylinder and each hydraulic motor of the corresponding hybrid mechanism to move by using the capacity stored by an energy accumulator of a hydraulic system, so as to ensure that the tail end of the hybrid mechanism is in effective contact with the offshore platform, realize the wave motion compensation of the ship, greatly reduce the motion amplitude of the hybrid mechanism of the boarding system compared with the ship, and finally realize reliable butt joint of the boarding platform and the offshore platform under high sea conditions, and ensure safe transportation of personnel.

5. The hybrid mechanism system based on passive compensation as claimed in claim 1, wherein the hybrid mechanism hydraulic system is composed of a power source, an energy accumulator, an execution hydraulic cylinder of a six-degree-of-freedom parallel mechanism, a hydraulic execution element of a three-degree-of-freedom serial mechanism and an oil tank, and the power source is composed of a motor, a hydraulic pump, an overflow valve and a filter; the energy accumulator is provided with a plurality of groups of energy accumulator units according to the system compensation requirement; the actuating element of the six-degree-of-freedom parallel mechanism consists of six hydraulic cylinders; when the hybrid mechanism is in butt joint with an offshore platform, a person manually controls the tail end of the hybrid mechanism to be lapped on the offshore platform, and after passive compensation is performed, pressure energy accumulated by a system energy accumulator is respectively supplied according to the requirements of each executing hydraulic element, so that passive compensation is realized.

6. A motion decomposition method of a series-parallel mechanism system based on passive compensation is characterized in that a motion coordinate system is respectively established for the positions of each mechanism of a parallel platform and a series gangway ladder, and a homogeneous transformation matrix is solved according to the motion characteristics of joints; pushing down and deriving Jacobian matrixes of the parallel platform and the series gangway ladder in a Cartesian space, and fusing the Jacobian matrixes and the series gangway ladder to obtain a kinematic model of the parallel mechanism in a task space; then, the Jacobian matrix pseudo-inverse method is utilized to carry out basic distribution on the motion quantity of each joint of the parallel platform and the serial gangway ladder, a weight coefficient matrix and a null space item are added into the original Jacobian matrix by combining the limit position of each joint, and then the avoidance of the singular configuration of the gangway ladder is completed by combining the projection gradient method, and the method specifically comprises the following steps:

step 1: establishing a kinematic model of the series-parallel mechanism;

step 2: and designing a motion planning method based on a kinematic model of the hybrid mechanism.

7. The method for decomposing the motion of the hybrid mechanism system based on the passive compensation as claimed in claim 6, wherein the step 1 is specifically as follows:

(1) establishing an integral model of a series-parallel connection mechanism

Setting three attitude angles of the upper platform relative to the base coordinate as alpha, beta and gamma respectively, and setting the position vector of the center of the upper platform in the base coordinate system asThe parallel Stewart platform transforms the matrix into

The rotation angle of the first joint of the series gangway ladder is set as theta₁The second joint rotation angle is theta₂The third joint expansion amount is d₃The homogeneous transformation matrix of the series gangway ladder according to the D-H method is

(2) Establishing a series Gangtai Jacobian matrix

Under the base coordinate system, the motion equation of the gangway ladder with three degrees of freedom in series is

WhereinThe pose vector of the gangway ladder under the base coordinate system is shown, and q is the corner or displacement vector of three joints of the gangway ladder under the joint coordinate system. J. the design is a square_sThe joint space movement speed is converted into the movement speed of a Cartesian space, and the pose quantity of the Cartesian space is converted into the speed quantity of the joint space through the joint space movement speed.

(3) Establishing parallel platform Jacobian matrix

The coordinates of the hinge points of the supporting legs connected with the platform in the corresponding coordinate system can be obtained according to the geometric structures of the movable platform and the static platform, and the coordinates of the hinge points of the upper platform in the movable coordinate system are^AA, coordinates of each hinge point of the lower platform under a static coordinate system are^BB, coordinates of each hinge point of the movable platform under the static coordinate system are as follows:

the vector of each leg under the static coordinate system is then expressed as:

^BL＝[^BL₁ ^BL₂ ^BL₃ ^BL₄ ^BL₅ ^BL₆]

^BL＝^BA-^BB

in order to calculate the working speed of each supporting leg, the derivatives of the two ends of the upper formula are calculated, and the speed vectors of each hinge point of the upper platform are obtained as follows:

let q ═ x y z α β γ]^TGeneralized coordinates representing the motion of the upper platform are:

(4) establishing a Jacobian matrix of a hybrid mechanism under a task space

Defining the speed of each joint of the hybrid mechanism under a motion coordinate system as xi ═ x y z alpha theta gamma theta₁ θ₂ d₃]^TThe pose vector of the tail end of the manipulator under the inertial coordinate system is

The homogeneous transformation matrix of the gangway terminal transformed from the motion coordinate system to the inertia coordinate system is

Wherein the position matrix and the attitude matrix of the gangway end are included.

The position of the tail end of the gangway ladder under an inertial coordinate system can be obtained by derivation

Wherein[ⁱw_v×]Is a diagonally symmetric matrix, i.e. forⁱw_v＝[w_x w_y w_z]^TIs provided with

Two algorithms of [ x ] y- [ y x ] x and x × y-y × x are used in the derivation, where x and y are matrices.

The attitude matrix of the tail end of the gangway ladder under the inertial coordinate system is derived

Whereinⁱw_e＝ⁱw_v+ⁱR_v ^vw_e。

And (3) combining the position matrix and the derivative of the attitude matrix to obtain a kinematic model of the hybrid mechanism:

wherein J_taskIs the Jacobian matrix of the hybrid mechanism under the task space.

8. The method for decomposing the motion of the hybrid mechanism system based on the passive compensation as claimed in claim 6, wherein the step 2 is specifically as follows:

(1) pseudo-inverse solution of Jacobian matrix

According to the kinematic equation under the task space of the hybrid mechanism, the inverse of the kinematic equation can be obtained:

whereinIs the plus inverse of the jacobian matrix, also known as the pseudo-inverse or the mole-pennissl inverse,is the desired speed trajectory of the ramp end, i.e. the amount of compensation for the disturbance of the waves.

Adding a weighted norm matrix to each joint speed of the series-parallel mechanism to obtain a weighted Jacobian matrix plus inverse:

(2) the multitask priority method comprises the following steps:

least square solution of minimum norm of kinematic model under task space of hybrid mechanism

Wherein N is the degree of freedom of the whole series-parallel mechanism,is the velocity and angular velocity vector of any one mechanism or joint,is a joint vector term in the Jacobian matrix null space. Will be provided withThe form-representational-wise-Jacobian-matrix multi-task priority planning algorithm is:

in the formulak is the number of secondary tasks;represents a series of secondary tasks;is the Jacobian matrix in the equation of motion of the corresponding secondary task.

Numerical drift problems may arise when integrating the position for each joint velocity, so a closed loop of error between the desired and planned values is introduced:

and the secondary task I is set as joint limit constraint, three joints are constraint objects for the series gangway ladder, and the moving platform pose of the parallel platform is a constraint object. First, an objective optimization function is defined

Wherein C is_i0 is a constant coefficient used for defining the limiting effect strength of the ith joint; q. q.s_i、q_imaxAnd q is_iminThe angle (position), maximum rotation (movement) boundary value, and minimum rotation (movement) boundary value of the i-th joint, respectively.

Secondly, defining the weight coefficient of the serial gangway ladder part as follows:

and the secondary task II is set as singular configuration constraint, and the singularity of the parallel platform is distributed in the whole working space, and the great singularity can be avoided only by joint limitation, so that the singular configuration of the gangway ladder is avoided by adopting a method for limiting the operability of the serial mechanism. The degree of operability is used for describing the distance of the mechanism from a singular configuration state, and is defined as

Where J is the Jacobian matrix of the corresponding mechanism.

For the avoidance of singular configuration of the gangway ladder in series, the gradient of the operability of the gangway ladder is calculated by taking the angle (position) of each joint as a variable

(3) Multi-task weighted minimum norm solution based on projection gradient method

The planning method finally adopted by the invention is determined to be a multitask weighted minimum norm solution based on a projection gradient method based on a weighted minimum norm method and a projection gradient method, and the specific expression is

WhereinShowing gangway ladder endThe end of the desired trajectory is,error value, K, for the desired trajectory and the planned trajectory of the ramp end_eIn order to achieve the corresponding gain,represents the jacobian matrix after the constraint of joint constraint is added.

(4) Parallel platform inverse kinematics solution

The motion amount of the series-parallel mechanism obtained by the motion planning method is represented by displacement (rotation) amounts of three joints of the series gangway ladder and a six-degree-of-freedom position attitude amount at the tail end of the parallel platform, wherein the stretching amount corresponding to six connecting rods is required to be further solved by inverse kinematics on the parallel platform.

Parallel platform inverse kinematics solution, knowing the transformation matrix of the upper platform center relative to the lower platform centerThe target determines the amount of expansion and contraction of each rod length. Arbitrary vector R in upper platform coordinate system_aCan be transformed into R in the lower platform coordinate system by means of coordinate transformation_bP is the origin A of the moving coordinate system in the fixed coordinate system B-x_by_bz_bIs determined.

The homogeneous transformation matrix of the parallel platform is as follows:

in the formula:

P＝{X_p Y_p Z_p}^T

Technical Field

The invention relates to a hybrid mechanism system and a motion decomposition method thereof, in particular to a hybrid mechanism system based on passive compensation and a motion decomposition method thereof, and belongs to the technical field of ocean engineering.

Background

With the concept of sustainable development, people pay more attention to the development and use of clean energy and green energy due to the current situation that the traditional energy is high in energy consumption, high in pollution and high in emission and causes irreversible damage to the environment. Based on this, the development and the use of offshore wind energy enter the visual field of all countries, the installation quantity of wind turbines is greatly increased, and all countries are considered to be the most important component in a new energy strategy. The country highly pays attention to the development of offshore wind power, and some guidance documents and regulations are continuously gone out to promote the steady development of offshore wind power. However, the vigorous development of offshore wind resources has also met with some problems. Wind turbine platforms often require repair and maintenance, however, due to sea storms, personnel are at great risk from ship to platform, and it is highly desirable that offshore compensation platforms safely transport personnel and equipment from ship to wind turbine platform. The development of a hybrid based wave compensation system is becoming important in order to maintain stability of the bridge and thus personnel safety.

In the research on the offshore operation compensation system, the heave motion compensation of the offshore operation system is firstly researched and is also researched most, and the problem of offshore replenishment is mainly solved, wherein the research on a heave compensation crane, a robot hand and a winch is mainly used. On the research of the wave compensation platform, a great deal of research work is carried out by the people of Renwei, Chenyangming, WangDongjiao and the like, and on the basis of completing the experimental research of the ancient sunken ship salvage platform of south China sea I, the research idea of the wave compensation platform is further provided. The research on the whole system process from designing and building a test platform to mathematical modeling, computer simulation, control algorithm design and realizing effective control is carried out on the wave compensation platform, and the feasibility of the wave compensation platform is verified through a solid model test. The Lishifai constructs a wave compensation stable platform system with a wave compensation function through a multi-sensor technology, realizes motion compensation opposite to the motion direction of a ship, and constructs a relatively stable platform.

The passive compensation of the hydraulic system actuator is realized by using the hydraulic accumulator of the hybrid mechanism by referring to the research experience of other methods, and the short-time, quick and stable effective compensation of the hybrid mechanism on the sea operation and maintenance ship under the interference of sea waves received by the sea operation and maintenance ship under complex sea conditions is met.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide the wave compensation system of the series-parallel mechanism with good stability and low energy consumption, which can be used for maintenance personnel to safely and smoothly walk onto a fan platform, and can realize the passive compensation of the boarding system by utilizing the energy accumulator of the hydraulic system of the boarding system according to the requirement of the wave compensation system.

The purpose of the invention is realized as follows:

a hybrid mechanism system based on passive compensation comprises a hybrid mechanism, a pressure sensor array at the tail end of the hybrid mechanism, a motion distributor for wave passive compensation and a hybrid mechanism hydraulic system.

The invention also includes such features:

the hybrid structure comprises a six-degree-of-freedom parallel mechanism, a three-degree-of-freedom series mechanism and a mounting base; the six-degree-of-freedom parallel mechanism consists of six hydraulic cylinders and an upper platform, the three-degree-of-freedom series mechanism consists of a swing mechanism, a pitching mechanism and a telescopic mechanism, a mounting base is used for fixing the series-parallel mechanism on a deck of the operation and maintenance ship, and the three-degree-of-freedom series mechanism and the six-degree-of-freedom parallel mechanism consist of hinged supports;

the pressure sensor array at the tail end of the hybrid mechanism is arranged in two directions, the pressure sensor array is uniformly distributed at intervals of 5 degrees in the horizontal direction according to the semicircular tail end of the hybrid mechanism, and the contact force change condition of the advancing direction of the tail end of the hybrid mechanism and the offshore platform is detected; the device is arranged at the lower end of the tail end of the hybrid mechanism in the vertical direction, is uniformly distributed in a semicircular mode at intervals of every 5 degrees, and detects the stress change condition of the lap joint of the tail end of the hybrid mechanism and the offshore platform;

the motion distributor for wave passive compensation analyzes and decomposes motion according to pressure information detected by a pressure sensor array at the tail end of the hybrid mechanism, forms motion instructions of each execution part of the series of hybrid mechanisms, and drives each hydraulic cylinder and each hydraulic motor of the corresponding hybrid mechanism to move by using the capacity stored by an energy accumulator of a hydraulic system, so that the tail end of the hybrid mechanism is ensured to be in effective contact with an offshore platform, and the compensation of the wave motion of a ship is realized, the motion amplitude of the hybrid mechanism of a boarding system is greatly reduced compared with that of the ship, the boarding platform is reliably butted with the offshore platform under a high sea condition, and the safe transportation of personnel is guaranteed;

the hydraulic system of the parallel-serial mechanism consists of a power source, an energy accumulator, an execution hydraulic cylinder of a six-degree-of-freedom parallel mechanism, a hydraulic execution element of a three-degree-of-freedom serial mechanism and an oil tank, wherein the power source consists of a motor, a hydraulic pump, an overflow valve and a filter; the energy accumulator is provided with a plurality of groups of energy accumulator units according to the system compensation requirement; the actuating element of the six-degree-of-freedom parallel mechanism consists of six hydraulic cylinders; when the hybrid mechanism is butted with an offshore platform, the tail end of the hybrid mechanism is manually controlled by a person to be lapped on the offshore platform, and after passive compensation is carried out, pressure energy accumulated by a system energy accumulator is respectively supplied according to the requirements of each executing hydraulic element, so that passive compensation is realized;

a motion decomposition method of a series-parallel mechanism system based on passive compensation comprises the steps of firstly, respectively establishing a motion coordinate system for each mechanism position of a parallel platform and a series gangway ladder, and solving out a homogeneous transformation matrix according to joint motion characteristics; pushing down and deriving Jacobian matrixes of the parallel platform and the series gangway ladder in a Cartesian space, and fusing the Jacobian matrixes and the series gangway ladder to obtain a kinematic model of the parallel mechanism in a task space; then, the Jacobian matrix pseudo-inverse method is utilized to carry out basic distribution on the motion quantity of each joint of the parallel platform and the serial gangway ladder, a weight coefficient matrix and a null space item are added into the original Jacobian matrix by combining the limit position of each joint, and then the avoidance of the singular configuration of the gangway ladder is completed by combining the projection gradient method, and the method specifically comprises the following steps:

step 1: establishing a kinematic model of the series-parallel mechanism;

step 2: and setting a motion planning method based on the kinematic model of the series-parallel mechanism.

The step 1 specifically comprises the following steps:

(1) establishing an integral model of a series-parallel connection mechanism

Setting three attitude angles of the upper platform relative to the base coordinate as alpha, beta and gamma respectively, and setting the position vector of the center of the upper platform in the base coordinate system asThe parallel Stewart platform transforms the matrix into

The rotation angle of the first joint of the series gangway ladder is set as theta₁The second joint rotation angle is theta₂The third joint expansion amount is d₃The homogeneous transformation matrix of the series gangway ladder according to the D-H method is

(2) Establishing a series Gangtai Jacobian matrix

Under the base coordinate system, the motion equation of the gangway ladder with three degrees of freedom in series is

WhereinThe pose vector of the gangway ladder under the base coordinate system is shown, and q is the corner or displacement vector of three joints of the gangway ladder under the joint coordinate system. J. the design is a square_sThe joint space movement speed is converted into the movement speed of a Cartesian space, and the pose quantity of the Cartesian space is converted into the speed quantity of the joint space through the joint space movement speed.

(3) Establishing parallel platform Jacobian matrix

The coordinates of the hinge points of the supporting legs connected with the platform in the corresponding coordinate system can be obtained according to the geometric structures of the movable platform and the static platform, and the coordinates of the hinge points of the upper platform in the movable coordinate system are^AA, coordinates of each hinge point of the lower platform under a static coordinate system are^BB, coordinates of each hinge point of the movable platform under the static coordinate system are as follows:

the vector of each leg under the static coordinate system is then expressed as:

^BL＝[^BL₁ ^BL₂ ^BL₃ ^BL₄ ^BL₅ ^BL₆]

^BL＝^BA-^BB

in order to calculate the working speed of each supporting leg, the derivatives of the two ends of the upper formula are calculated, and the speed vectors of each hinge point of the upper platform are obtained as follows:

let q ═ x y z α β γ]^TGeneralized seat representing upper platform motionThe label, there are:

(4) establishing a Jacobian matrix of a hybrid mechanism under a task space

Defining the speed of each joint of the hybrid mechanism under a motion coordinate system as xi ═ x y z alpha theta gamma theta₁ θ₂ d₃]^TThe pose vector of the tail end of the manipulator under the inertial coordinate system is

The homogeneous transformation matrix of the gangway terminal transformed from the motion coordinate system to the inertia coordinate system is

Wherein the position matrix and the attitude matrix of the gangway end are included.

The position of the tail end of the gangway ladder under an inertial coordinate system can be obtained by derivation

Wherein[ⁱw_v×]Is a diagonally symmetric matrix, i.e. forⁱw_v＝[w_x w_y w_z]^TIs provided with

Two algorithms of [ x ] y- [ y x ] x and x × y-y × x are used in the derivation, where x and y are matrices.

The attitude matrix of the tail end of the gangway ladder under the inertial coordinate system is derived

Whereinⁱw_e＝ⁱw_v+ⁱR_v ^vw_e。

And (3) combining the position matrix and the derivative of the attitude matrix to obtain a kinematic model of the hybrid mechanism:

wherein J_taskIs the Jacobian matrix of the hybrid mechanism under the task space.

The step 2 specifically comprises the following steps:

(1) pseudo-inverse solution of Jacobian matrix

According to the kinematic equation under the task space of the hybrid mechanism, the inverse of the kinematic equation can be obtained:

whereinIs the plus inverse of the jacobian matrix, also known as the pseudo-inverse or the mole-pennissl inverse,is the desired speed trajectory of the ramp end, i.e. the amount of compensation for the disturbance of the waves.

Adding a weighted norm matrix to each joint speed of the series-parallel mechanism to obtain a weighted Jacobian matrix plus inverse:

(2) the multitask priority method comprises the following steps:

least square solution of minimum norm of kinematic model under task space of hybrid mechanism

Wherein N is the degree of freedom of the whole series-parallel mechanism,is the velocity and angular velocity vector of any one mechanism or joint,is a joint vector term in the Jacobian matrix null space. Will be provided withThe form-representational-wise-Jacobian-matrix multi-task priority planning algorithm is:

wherein k is the number of secondary tasks;represents a series of secondary tasks;is the Jacobian matrix in the equation of motion of the corresponding secondary task.

Numerical drift problems may arise when integrating the position for each joint velocity, so a closed loop of error between the desired and planned values is introduced:

and the secondary task I is set as joint limit constraint, three joints are constraint objects for the series gangway ladder, and the moving platform pose of the parallel platform is a constraint object. First, an objective optimization function is defined

Wherein C is_i0 is a constant coefficient used for defining the limiting effect strength of the ith joint; q. q.s_i、q_imaxAnd q is_iminThe angle (position), maximum rotation (movement) boundary value, and minimum rotation (movement) boundary value of the i-th joint, respectively.

Secondly, defining the weight coefficient of the serial gangway ladder part as follows:

and the secondary task II is set as singular configuration constraint, and the singularity of the parallel platform is distributed in the whole working space, and the great singularity can be avoided only by joint limitation, so that the singular configuration of the gangway ladder is avoided by adopting a method for limiting the operability of the serial mechanism. The degree of operability is used for describing the distance of the mechanism from a singular configuration state, and is defined as

Where J is the Jacobian matrix of the corresponding mechanism.

For the avoidance of singular configuration of the gangway ladder in series, the gradient of the operability of the gangway ladder is calculated by taking the angle (position) of each joint as a variable

(3) Multi-task weighted minimum norm solution based on projection gradient method

The planning method finally adopted by the invention is determined to be a multitask weighted minimum norm solution based on a projection gradient method based on a weighted minimum norm method and a projection gradient method, and the specific expression is

WhereinTo indicate the desired trajectory of the end of the gangway,error value, K, for the desired trajectory and the planned trajectory of the ramp end_eIn order to achieve the corresponding gain,represents the jacobian matrix after the constraint of joint constraint is added.

(4) Parallel platform inverse kinematics solution

The motion amount of the series-parallel mechanism obtained by the motion planning method is represented by displacement (rotation) amounts of three joints of the series gangway ladder and a six-degree-of-freedom position attitude amount at the tail end of the parallel platform, wherein the stretching amount corresponding to six connecting rods is required to be further solved by inverse kinematics on the parallel platform.

Parallel platform inverse kinematics solution, knowing the transformation matrix of the upper platform center relative to the lower platform centerThe target determines the amount of expansion and contraction of each rod length. Arbitrary vector R in upper platform coordinate system_aCan be transformed into R in the lower platform coordinate system by means of coordinate transformation_bP is the origin A of the moving coordinate system in the fixed coordinate system B-x_by_bz_bIs determined.

The homogeneous transformation matrix of the parallel platform is as follows:

in the formula:

P＝{X_p Y_p Z_p}^T

compared with the prior art, the invention has the beneficial effects that:

(1) the passive compensation method can realize the passive compensation of the offshore operation and maintenance ship under the condition of high sea condition, and ensure the normal operation and maintenance of the offshore platform under severe weather.

(2) Compared with an active sea wave compensation system, the sea wave compensation system has the advantages of low energy consumption and low cost, is suitable for short-time and quick operation and maintenance requirements on the sea, and has strong practicability.

(3) Compared with an active sea wave compensation system, the sea wave passive compensation system utilizes the energy accumulator to accumulate energy, can more quickly realize attitude compensation of the offshore operation and maintenance ship, overcomes the defects of sensor noise, active compensation calculation errors and actuating mechanism motion errors, and can more accurately realize sea wave passive compensation.

Drawings

FIG. 1 is a diagram of a passive compensation system for sea waves;

FIG. 2 is a schematic diagram of a series-parallel mechanism of a wave compensation system;

FIGS. 3a-b are diagrams of a series-parallel mechanism end pressure sensor profile, wherein (a) is a top view; (b) a side view;

FIG. 4 is a schematic diagram of a passive compensated motion distributor;

FIG. 5 is a hydraulic system of the series-parallel mechanism;

FIG. 6 is a flow chart of a series-parallel mechanism motion planning;

FIG. 7 is a model diagram of a series-parallel mechanism of the sea wave compensation system.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

The invention provides a hybrid mechanism system based on passive compensation and a motion decomposition method thereof. The principle is that the contact force of the tail end of the on-board hybrid mechanism and the offshore platform on the sea, which is interacted in the automatic compensation stage, is used as reference, the position and posture change of the hybrid mechanism relative to the landing platform, which is caused by the influence of sea waves on the operation and maintenance ship, is indirectly detected, the passive compensation of the hydraulic system executing mechanism is realized through the hydraulic energy accumulator of the hybrid mechanism, and the short-time, quick and stable effective compensation of the hybrid mechanism on the offshore operation and maintenance ship under the interference of the sea waves under the complex sea condition is met.

The passive compensation-based hybrid mechanism system and the motion decomposition method thereof are characterized in that based on the contact force of the tail end of an onboard hybrid mechanism and an offshore platform on which the onboard hybrid mechanism is landed and interacted in an automatic compensation stage as reference, the position and posture change of the hybrid mechanism relative to the landing platform caused by the influence of sea waves on an operation and maintenance ship is indirectly detected, the passive compensation of a hydraulic system executing mechanism is realized through a hydraulic energy accumulator of the hybrid mechanism, the short-time, quick and stable effective compensation of the hybrid mechanism on the offshore operation and maintenance ship under the interference of the sea waves under complex sea conditions is met, and the problems that the active compensation of the boarding system consumes a large amount of energy of the system and supplies power to the ship are greatly solved. And has more safety and practicability.

The concrete solving method is as follows:

the passive compensation system of the series-parallel mechanism system consists of a series-parallel mechanism, a pressure sensor array at the tail end of the series-parallel mechanism, a motion distributor for wave passive compensation and a hydraulic system of the series-parallel mechanism.

The series-parallel mechanism mainly comprises a six-degree-of-freedom parallel mechanism, a three-degree-of-freedom series mechanism and an installation base: the six-degree-of-freedom parallel mechanism consists of six hydraulic cylinders and an upper platform and is mainly used for compensating the three-dimensional attitude (pitching, rolling and course) of the operation and maintenance ship influenced by sea waves; the three-degree-of-freedom series mechanism consists of a swing mechanism, a pitching mechanism and a telescopic mechanism and can compensate three-dimensional direction displacement of the operation and maintenance ship influenced by sea waves; the mounting base is used for fixing the hybrid mechanism on the operation and maintenance ship deck. The three-freedom-degree series mechanism and the six-freedom-degree parallel mechanism are formed by a hinged support.

The pressure sensor array at the tail end of the hybrid mechanism of the boarding system is arranged in two directions, the pressure sensor array is uniformly distributed at intervals of 5 degrees in the horizontal direction according to the semicircular tail end of the hybrid mechanism, and the contact force change condition of the tail end advancing direction of the hybrid mechanism and the offshore platform is mainly detected; the vertical direction is arranged at the lower end of the tail end of the hybrid mechanism, and the hybrid mechanism is uniformly distributed in a semicircular mode at intervals of every 5 degrees to detect the stress change condition of the lap joint of the tail end of the hybrid mechanism and the offshore platform.

The motion distributor for wave passive compensation analyzes and decomposes motion according to pressure information detected by a pressure sensor array at the tail end of the hybrid mechanism, forms motion instructions of each execution part of the series hybrid mechanism, and drives each part of hydraulic cylinders and hydraulic motors of the corresponding hybrid mechanism to move by using the capacity stored by an energy accumulator of a hydraulic system, so that the tail end of the hybrid mechanism is ensured to be effectively contacted with an offshore platform, and the compensation of ship wave motion (rolling, pitching and heaving) is realized, so that the motion amplitude of the hybrid mechanism of the boarding system is greatly reduced compared with that of a ship, the boarding platform is reliably butted with the offshore platform under a high sea condition, and the safe transportation of personnel is ensured.

The hydraulic system of the series-parallel mechanism consists of a power source, an energy accumulator, an execution hydraulic cylinder of a six-degree-of-freedom parallel mechanism, a hydraulic execution element (a hydraulic cylinder and a hydraulic motor) of a three-degree-of-freedom series mechanism and an oil tank. The power source consists of a motor, a hydraulic pump, an overflow valve and a filter; the energy accumulator is provided with a plurality of groups of energy accumulator units according to the system compensation requirement; the actuating element of the six-degree-of-freedom parallel mechanism consists of six hydraulic cylinders; the hydraulic element of the three-degree-of-freedom series mechanism consists of two high-power hydraulic motors and a hydraulic cylinder. When the hybrid mechanism is in butt joint with the offshore platform, a person manually controls the tail end of the hybrid mechanism to be lapped on the offshore platform, after passive compensation is carried out, pressure energy gathered by the system energy accumulator is respectively supplied according to the requirements of each execution hydraulic element, and passive compensation is realized.

The method comprises the steps of firstly establishing a motion coordinate system aiming at the positions of mechanisms of a parallel platform and a series gangway ladder respectively and solving a homogeneous transformation matrix according to the motion characteristics of joints based on the kinematic distribution of a series-parallel mechanism with contact force change. And pushing down and deriving Jacobian matrixes of the parallel platform and the series gangway ladder in the Cartesian space, and fusing the Jacobian matrixes and the series gangway ladder to obtain a kinematic model of the parallel mechanism in the task space. And then, the motion amount of each joint of the parallel platform and the serial gangway ladder is basically distributed by utilizing a Jacobi matrix pseudo-inverse method. In order to meet the requirements on performance indexes and realize the optimization of constraint, the invention combines the limit positions of all joints to add a weight coefficient matrix and a zero space item into the original Jacobian matrix, and combines a projection gradient method to finish the avoidance of the singular configuration of the gangway ladder.

Implementation 1: as shown in fig. 1, the passive compensation system of the series-parallel mechanism system is composed of a series-parallel mechanism, a pressure sensor array at the tail end of the series-parallel mechanism, a motion distributor for wave passive compensation, and a hydraulic system of the series-parallel mechanism.

Implementation 2: as shown in fig. 2, the parallel-serial mechanism mainly comprises a six-degree-of-freedom parallel mechanism, a three-degree-of-freedom serial mechanism and an installation base: the six-degree-of-freedom parallel mechanism consists of six hydraulic cylinders and an upper platform and is mainly used for compensating the three-dimensional attitude (pitching, rolling and course) of the operation and maintenance ship influenced by sea waves; the three-degree-of-freedom series mechanism consists of a swing mechanism, a pitching mechanism and a telescopic mechanism and can compensate three-dimensional direction displacement of the operation and maintenance ship influenced by sea waves; the mounting base is used for fixing the hybrid mechanism on the operation and maintenance ship deck. The three-freedom-degree series mechanism and the six-freedom-degree parallel mechanism are formed by a hinged support.

Implementation 3: as shown in the attached figure 3, the pressure sensor array at the tail end of the hybrid mechanism of the boarding system is arranged in two directions, the pressure sensor array is uniformly distributed at intervals of 5 degrees in the horizontal direction according to the semicircular tail end of the hybrid mechanism, and the pressure sensor array is mainly used for detecting the contact force change condition of the advancing direction of the tail end of the hybrid mechanism and an offshore platform; the vertical direction is arranged at the lower end of the tail end of the hybrid mechanism, and the hybrid mechanism is uniformly distributed in a semicircular mode at intervals of every 5 degrees to detect the stress change condition of the lap joint of the tail end of the hybrid mechanism and the offshore platform.

Implementation 4: as shown in fig. 4, the motion distributor for wave passive compensation analyzes and decomposes motion according to pressure information detected by a pressure sensor array at the tail end of the hybrid mechanism, forms motion instructions of each execution component of the series of hybrid mechanisms, and drives each hydraulic cylinder and each hydraulic motor of the corresponding hybrid mechanism to move by using the capacity stored by an energy accumulator of a hydraulic system, so as to ensure that the tail end of the hybrid mechanism is effectively contacted with an offshore platform, and realize the compensation of ship wave motion (rolling, pitching and heaving), thereby greatly reducing the motion amplitude of the hybrid mechanism of the boarding system compared with a ship, and finally realizing the reliable butt joint of the boarding platform and the offshore platform under high sea conditions and ensuring the safe transportation of personnel.

Implementation 5: as shown in fig. 5, the hydraulic system of the parallel-serial mechanism is composed of a power source, an energy accumulator, an actuating hydraulic cylinder of the six-degree-of-freedom parallel mechanism, hydraulic actuating elements (a hydraulic cylinder and a hydraulic motor) of the three-degree-of-freedom serial mechanism, and an oil tank. The power source consists of a motor, a hydraulic pump, an overflow valve and a filter; the energy accumulator is provided with a plurality of groups of energy accumulator units according to the system compensation requirement; the actuating element of the six-degree-of-freedom parallel mechanism consists of six hydraulic cylinders; the hydraulic element of the three-degree-of-freedom series mechanism consists of two high-power hydraulic motors and a hydraulic cylinder. When the hybrid mechanism is in butt joint with the offshore platform, a person manually controls the tail end of the hybrid mechanism to be lapped on the offshore platform, after passive compensation is carried out, pressure energy gathered by the system energy accumulator is respectively supplied according to the requirements of each execution hydraulic element, and passive compensation is realized.

Implementation 6: referring to fig. 6, in the kinematic distribution of the series-parallel mechanism based on the contact force variation, a motion coordinate system is established for each mechanism position of the parallel platform and the series gangway ladder, and a homogeneous transformation matrix is solved according to the joint motion characteristics. And pushing down and deriving Jacobian matrixes of the parallel platform and the series gangway ladder in the Cartesian space, and fusing the Jacobian matrixes and the series gangway ladder to obtain a kinematic model of the parallel mechanism in the task space. And then, the motion amount of each joint of the parallel platform and the serial gangway ladder is basically distributed by utilizing a Jacobi matrix pseudo-inverse method. In order to meet the requirements on performance indexes and realize the optimization of constraint, the invention combines the limit positions of all joints to add a weight coefficient matrix and a zero space item into the original Jacobian matrix, and combines a projection gradient method to finish the avoidance of the singular configuration of the gangway ladder.

Step 1: with reference to FIG. 7, a kinematic model of the series-parallel mechanism is established

(1) Establishing an integral model of a series-parallel connection mechanism

Setting three attitude angles of the upper platform relative to the base coordinate as alpha, beta and gamma respectively, and setting the position vector of the center of the upper platform in the base coordinate system asThe parallel Stewart platform transforms the matrix into

The rotation angle of the first joint of the series gangway ladder is set as theta₁The second joint rotation angle is theta₂The third joint expansion amount is d₃The homogeneous transformation matrix of the series gangway ladder according to the D-H method is

(2) Establishing a series Gangtai Jacobian matrix

Under the base coordinate system, the motion equation of the gangway ladder with three degrees of freedom in series is

WhereinThe pose vector of the gangway ladder under the base coordinate system is shown, and q is the corner or displacement vector of three joints of the gangway ladder under the joint coordinate system. J. the design is a square_sThe joint space movement speed is converted into the movement speed of a Cartesian space, and the pose quantity of the Cartesian space is converted into the speed quantity of the joint space through the joint space movement speed.

(3) Establishing parallel platform Jacobian matrix

The coordinates of the hinge points of the supporting legs connected with the platform in the corresponding coordinate system can be obtained according to the geometric structures of the movable platform and the static platform, and the coordinates of the hinge points of the upper platform in the movable coordinate system are^AA, coordinates of each hinge point of the lower platform under a static coordinate system are^BB, coordinates of each hinge point of the movable platform under the static coordinate system are as follows:

the vector of each leg under the static coordinate system is then expressed as:

^BL＝[^BL₁ ^BL₂ ^BL₃ ^BL₄ ^BL₅ ^BL₆]

^BL＝^BA-^BB

in order to calculate the working speed of each supporting leg, the derivatives of the two ends of the upper formula are calculated, and the speed vectors of each hinge point of the upper platform are obtained as follows:

let q ═ x y z α β γ]^TGeneralized coordinates representing the motion of the upper platform are:

(4) establishing a Jacobian matrix of a hybrid mechanism under a task space

Defining the speed of each joint of the hybrid mechanism under a motion coordinate system as xi ═ x y z alpha theta gamma theta₁ θ₂ d₃]^TThe pose vector of the tail end of the manipulator under the inertial coordinate system is

The homogeneous transformation matrix of the gangway terminal transformed from the motion coordinate system to the inertia coordinate system is

Wherein the position matrix and the attitude matrix of the gangway end are included.

The position of the tail end of the gangway ladder under an inertial coordinate system can be obtained by derivation

Wherein[ⁱw_v×]Is a diagonally symmetric matrix, i.e. forⁱw_v＝[w_x w_y w_z]^TIs provided with

Two algorithms of [ x ] y- [ y x ] x and x × y-y × x are used in the derivation, where x and y are matrices.

The attitude matrix of the tail end of the gangway ladder under the inertial coordinate system is derived

Whereinⁱw_e＝ⁱw_v+ⁱR_v ^vw_e。

And (3) combining the position matrix and the derivative of the attitude matrix to obtain a kinematic model of the hybrid mechanism:

wherein J_taskIs the Jacobian matrix of the hybrid mechanism under the task space.

Step 2: kinematic model based on series-parallel mechanism and design motion planning method

(1) Pseudo-inverse solution of Jacobian matrix

According to the kinematic equation under the task space of the hybrid mechanism, the inverse of the kinematic equation can be obtained:

whereinIs the plus inverse of the jacobian matrix, also known as the pseudo-inverse or the mole-pennissl inverse,is the desired speed trajectory of the ramp end, i.e. the amount of compensation for the disturbance of the waves.

Adding a weighted norm matrix to each joint speed of the series-parallel mechanism to obtain a weighted Jacobian matrix plus inverse:

(2) the multitask priority method comprises the following steps:

least square solution of minimum norm of kinematic model under task space of hybrid mechanism

Wherein N is the degree of freedom of the whole series-parallel mechanism,is the velocity and angular velocity vector of any one mechanism or joint,is a joint vector term in the Jacobian matrix null space. Will be provided withThe form-representational-wise-Jacobian-matrix multi-task priority planning algorithm is:

wherein k is the number of secondary tasks;represents a series of secondary tasks;is the Jacobian matrix in the equation of motion of the corresponding secondary task.

Numerical drift problems may arise when integrating the position for each joint velocity, so a closed loop of error between the desired and planned values is introduced:

and the secondary task I is set as joint limit constraint, three joints are constraint objects for the series gangway ladder, and the moving platform pose of the parallel platform is a constraint object. First, an objective optimization function is defined

Wherein C is_i0 is a constant coefficient used for defining the limiting effect strength of the ith joint; q. q.s_i、q_imaxAnd q is_iminAre respectively provided withAre the angle (position), maximum rotation (movement) boundary value and minimum rotation (movement) boundary value of the ith joint.

Secondly, defining the weight coefficient of the serial gangway ladder part as follows:

and the secondary task II is set as singular configuration constraint, and the singularity of the parallel platform is distributed in the whole working space, and the great singularity can be avoided only by joint limitation, so that the singular configuration of the gangway ladder is avoided by adopting a method for limiting the operability of the serial mechanism. The degree of operability is used for describing the distance of the mechanism from a singular configuration state, and is defined as

Where J is the Jacobian matrix of the corresponding mechanism.

For the avoidance of singular configuration of the gangway ladder in series, the gradient of the operability of the gangway ladder is calculated by taking the angle (position) of each joint as a variable

(3) Multi-task weighted minimum norm solution based on projection gradient method

The planning method finally adopted by the invention is determined to be a multitask weighted minimum norm solution based on a projection gradient method based on a weighted minimum norm method and a projection gradient method, and the specific expression is

WhereinTo indicate the desired trajectory of the end of the gangway,error value, K, for the desired trajectory and the planned trajectory of the ramp end_eIn order to achieve the corresponding gain,represents the jacobian matrix after the constraint of joint constraint is added.

(4) Parallel platform inverse kinematics solution

The motion amount of the series-parallel mechanism obtained by the motion planning method is represented by displacement (rotation) amounts of three joints of the series gangway ladder and a six-degree-of-freedom position attitude amount at the tail end of the parallel platform, wherein the stretching amount corresponding to six connecting rods is required to be further solved by inverse kinematics on the parallel platform.

Parallel platform inverse kinematics solution, knowing the transformation matrix of the upper platform center relative to the lower platform centerThe target determines the amount of expansion and contraction of each rod length. Arbitrary vector R in upper platform coordinate system_aCan be transformed into R in the lower platform coordinate system by means of coordinate transformation_bP is the origin A of the moving coordinate system in the fixed coordinate system B-x_by_bz_bIs determined.

The homogeneous transformation matrix of the parallel platform is as follows:

in the formula:

P＝{X_p Y_p Z_p}^T

in summary, the following steps: the invention provides a hybrid mechanism system based on passive compensation and a motion decomposition method thereof. The passive compensation of the hydraulic system executing mechanism is realized through the hydraulic energy accumulator of the hybrid mechanism based on the reference of the contact force of the tail end of the on-board hybrid mechanism and the offshore platform on the sea, which is interacted in the automatic compensation stage, of the operation and maintenance ship, so that the position and posture change of the hybrid mechanism relative to the landing platform caused by the influence of sea waves is indirectly detected, and the short-time, quick and stable effective compensation of the hybrid mechanism on the offshore operation and maintenance ship under the interference of the sea waves under the complex sea conditions is met. The passive compensation system of the series-parallel mechanism system consists of a series-parallel mechanism, a pressure sensor array at the tail end of the series-parallel mechanism, a motion distributor for wave passive compensation and a hydraulic system of the series-parallel mechanism. The invention also provides a motion decomposition method of the passively compensated parallel-serial mechanism. The invention effectively solves the problems that the active compensation of the boarding system has higher energy consumption on the system and higher requirement on the power supply for the ship, can greatly save the cost of system devices, realizes the real-time, quick, effective and stable compensation, and has safety and practicability.