A method for cooperative operation of a series-parallel hybrid space operation system

Abstract

The problem addressed by this invention, a cooperative operation method for a serial-parallel hybrid space operating system, is as follows: For the dynamic pose tracking problem of a robotic arm on a moving base during on-orbit operation, a serial-parallel hybrid operating system consisting of a 6-DOF serial robotic arm and a Stewart platform is proposed. The Kane method is used to perform dynamic modeling of the serial-parallel hybrid operating system, analyzing the coupling relationships between the various actuators to obtain explicit dynamic equations. Then, an impedance controller is designed based on these dynamic equations to achieve compliant control of the serial-parallel hybrid operating system. Finally, an IMU located at the end of the serial robotic arm is used to sense the actual attitude of the serial section and compare it with the target attitude to obtain the attitude error. After inverse kinematics solution, the attitude error is compensated using the Stewart platform fixed at the end of the serial robotic arm, achieving more precise attitude tracking.

Description

Technical Field

[0001] This invention relates to a cooperative operation method for a serial-parallel hybrid space operating system, belonging to the field of on-orbit operation of space robots. Background Technology

[0002] In recent years, with the diversification of space-based service demands and the improvement of orbital transportation efficiency, major spacefaring nations have gradually developed the need and capability to operate large on-orbit spacecraft. Truss structures, characterized by high scalability, high specific stiffness, and high specific strength, are widely used in the design of large spacecraft. Limited by the launch vehicle's carrying capacity and fairing envelope size, large space truss structures require deployment through multiple launches and on-orbit assembly. Large trusses inherently possess a degree of flexibility, and during assembly, they are prone to low-frequency reciprocating motions on the base of space operating systems such as robotic arms.

[0003] To address the aforementioned issues, a dynamic analysis of the space operating system on the moving base is required. The space operating system itself needs a large workspace and must achieve rapid and accurate target tracking on the moving base. During operation, the motion of the operating system base can be obtained through vision or sensor measurements. The planner determines the target position in the joint space based on the target pose at the end of the operating system, and then the controller controls the operating system to track the target position in real time. Summary of the Invention

[0004] The problem to be solved by the dynamic modeling and cooperative operation method of the series-parallel hybrid space operating system disclosed in this invention is as follows: A series-parallel hybrid space operating system is proposed. The Kane method is used to perform dynamic analysis on the series-parallel hybrid space operating system on a moving base to obtain explicit dynamic equations. Then, an impedance controller for the series-parallel hybrid operating system is constructed based on the dynamic equations to achieve compliant control of the operating system. Finally, an operation method is designed with a series mechanism for initial tracking and a parallel mechanism for fine compensation. Combining the advantages of the series mechanism's high flexibility and the parallel mechanism's high accuracy, the series mechanism is used for initial tracking of the target pose, and then the Stewart parallel mechanism is used to compensate for the attitude error, ultimately achieving higher attitude tracking accuracy within a larger workspace.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] To ensure sufficient attitude tracking accuracy of the operating system in a large workspace, this invention designs a serial-parallel hybrid spatial operating system and its corresponding operating method. This serial-parallel hybrid operating system consists of a 6-DOF serial manipulator and a parallel Stewart mechanism fixed to the end of the serial manipulator. First, based on the Kane method, a dynamic analysis of the serial-parallel hybrid spatial operating system deployed on a moving base is performed. A suitable generalized velocity is selected, and the partial velocity matrix of the system is obtained. The generalized active force and generalized inertial force are obtained by projecting the active force and inertial force onto the partial velocity matrix. The explicit dynamic equation is obtained from the fact that the sum of the generalized active force and generalized inertial force is 0. Then, each actuator is equivalent to a spring-damped system, and an impedance controller is constructed based on the dynamic model. Finally, the attitude difference that the Stewart mechanism needs to compensate for is obtained through the transitivity of the rotation matrix. The target length of each support is obtained through the position-level inverse kinematics of the Stewart mechanism, and the target length is tracked through the impedance controller.

[0007] This invention discloses a serial-parallel hybrid space operating system and its cooperative operation method, comprising the following steps:

[0008] Step 1: Establish the world coordinate system The linkage coordinate system of the 6-joint robotic arm and the coordinate systems fixed to the parallel platform are determined. The system is kinematically described by selecting a generalized velocity, and then the partial velocity matrix is ​​obtained. The generalized active force and generalized inertial force are further obtained. The dynamic equation is obtained from the fact that the sum of the generalized active force and the generalized inertial force is 0.

[0009] The specific implementation method of step one is as follows:

[0010] Step 1.1: The link coordinate system of the 6-joint robotic arm is established using improved DH parameters. Indicate the coordinate system of each link. Let be the origin of the corresponding link coordinate system, where the lower platform of the parallel mechanism and the sixth link of the robotic arm are considered as a whole. Located in the plane of the lower hinge point of the parallel mechanism's support rod. A coordinate system is established at the point where the hybrid robotic arm is fixed to the large truss, i.e., at the robotic arm's base. The origin of the coordinate system is .

[0011] The center of gravity of the parallel mechanism on the platform and Overlap, establish a coordinate system on the upper platform Its coordinate origin Located at the center of the plane where the upper platform and the support rod hinge point are located, the center of mass of the lower platform of the parallel mechanism is... Overlap; establish a coordinate system on the lower platform. Its coordinate origin Located at the center of the plane where the lower platform and the support rod hinge point lie. For the part where the universal joint is fixed to the lower platform, the hinge point is considered the center of the plane. Let O be the origin of the coordinate system. arrive The connection is The axis coincides with the direction of the universal joint's fixed axis. Axis, establish right-handed system For the part connecting the universal joint and the support rod, the hinge point is also used. The origin of the coordinate system is coinciding with the direction of the support rod. The shaft, whose direction coincides with that of the universal joint's moving shaft, is Axis, establish right-handed system The center of gravity of the following support rod is the origin of the coordinate system. Establish a coordinate system Its three-axis direction is the same as Coincident; the center of gravity of the above support rod is the origin of the coordinate system. Establish a coordinate system Its three-axis directions are also the same as coincide.

[0012] Step 1.2: Perform kinematic description of the system.

[0013] Step 1.2.1: Selecting the generalized rate. The generalized rate of this operating system is selected as follows: orders 1-6 are the first derivatives of the six joint angles of the series part, denoted as... ; 7th-9th order is because arrive position vector exist relative derivative in

[0014] exist The component in is denoted as The 10-12 order represents the angular velocity of the upper platform relative to the lower platform in the parallel section. exist The component in is denoted as .

[0015] Step 1.2.2: Considering the characteristics of the series connection, the velocities and angular velocities at each link's coordinate system can be obtained by recursively deriving them step by step outwards. The angular velocities at the origin of each link's coordinate system are:

[0016]

[0017] in, for angular velocity at point in coordinate system The component representation in the coordinate system (hereinafter, the superscript will be used to represent the component representation of a vector in this coordinate system). coordinate system Relative to coordinate system Rotation matrix (hereinafter referred to as rotation matrix) (This represents the rotation matrix of coordinate system A relative to coordinate system B). For the first The orientation of the joint rotation axis in the coordinate system The component representation in the middle, that is Similarly, in the following text... , .

[0018] Step 1.2.3: Differentiating both sides of the equation, we obtain the angular acceleration at the link coordinate system as follows:

[0019]

[0020] Step 1.2.4: Substitute equation (1) into the rigid body velocity calculation formula to obtain the velocity at the link coordinate system:

[0021]

[0022] Taking the derivative of the three equations with respect to time, we obtain the acceleration at the link coordinate system as follows:

[0023]

[0024] In the formula Indicates by arrive The vector in The components are represented in the text.

[0025] Step 1.2.5: Let the center of mass of the i-th link lie in the coordinate system. The position vector in is Then the velocities and accelerations at the center of mass of each link are:

[0026]

[0027]

[0028] Step 1.2.6: Based on the transitivity of angular velocity, the absolute angular velocity of the upper platform is obtained as follows:

[0029]

[0030] Step 1.2.7: Differentiating both sides of the equation with respect to time, we obtain the angular acceleration of the upper platform as follows:

[0031]

[0032] Step 1.2.8: The absolute speed of ascending the platform is:

[0033]

[0034] Step 1.2.9: Differentiating both sides of the equation with respect to time, we obtain the acceleration of the upper platform as:

[0035]

[0036] Step 1.2.10: The parallel mechanism has closed-loop constraints, that is... ,in Let be the vector from the center of mass of the lower platform to the center of mass of the upper platform. The vector from the center of mass of the upper platform to the hinge point. It is the product of the push rod length and the push rod's unit direction vector. Let be the vector from the center of mass of the upper platform to the hinge point. Based on this closed-loop relationship, the vector relationship can be obtained as follows:

[0037]

[0038] in, For the first Total length of each support rod Let its unit direction vector be . The upper and lower hinge points are respectively at and The position vector in the middle.

[0039] Step 1.2.11: From The expression for the total length of the support rod is thus obtained as:

[0040]

[0041] The unit direction vector of the support rod is .

[0042] Step 1.2.12: Equation In coordinate system Taking the first and second derivatives with respect to time, we get:

[0043]

[0044]

[0045] Step 1.2.13: Simultaneous left and right with By performing a cross product, we obtain the support rod. The angular velocity relative to the lower platform is:

[0046]

[0047] again: It can be represented as:

[0048]

[0049] in, .

[0050] Step 1.2.14: Equation Both sides in the coordinate system Take the derivative with respect to time, and then with each time step. Perform dot product and cross product, noting and Orthogonal, after simplification we get:

[0051]

[0052]

[0053] Step 1.2.15: The The angular velocity of each support relative to the world coordinate system is:

[0054]

[0055] The angular acceleration relative to the world coordinate system is:

[0056]

[0057] Step 1.2.16: The velocity and acceleration of the lower support rod's center of mass relative to the world coordinate system, and the velocity and acceleration of the upper support rod's center of mass relative to the world coordinate system are as follows:

[0058]

[0059]

[0060]

[0061]

[0062] Step 1.3 Calculation of Generalized Forces and Writing of Kane Equations

[0063] Step 1.3.1: Represent the generalized rate as a column vector:

[0064]

[0065] Step 1.3.2: For the series connection, the deflection angular velocity and deflection velocity of each link's coordinate system are:

[0066]

[0067]

[0068] Step 1.3.3: The deflection velocity at the center of mass of the connecting rod is:

[0069]

[0070] Step 1.3.4: For the upper platform of the parallel mechanism, the partial velocity at its center of mass is:

[0071]

[0072] Step 1.3.5: The deflection angular velocity is:

[0073]

[0074] In equation (26-30), , .

[0075] Step 1.3.6: For the 6-way support rod, considering that the moment of inertia of the push rod of the actual small drive electric cylinder is very small compared to the moment of inertia of the cylinder body, and that the parallel mechanism uses a UPS configuration, the rotational motion amplitude of the support rod is small. Therefore, only the deflection velocity at the center of mass of the lower support rod is calculated here for the generalized inertial force calculation, ignoring the influence of the rotation of the upper support rod and the support rod as a whole. From the formula... Therefore, for each support rod, its deflection velocity can be written as:

[0076]

[0077] Step 1.3.7: The generalized inertial force of the system can then be calculated using the following expression:

[0078]

[0079] in, ,

[0080]

[0081]

[0082] Form and style The result is consistent; simply replace the deflection velocity at the corresponding position with the deflection angular velocity. Matrix, for matrix ,have:

[0083]

[0084] in:

[0085]

[0086]

[0087] It corresponds to the inertial tensor of the rigid body about its center of mass.

[0088] Step 1.3.8: The generalized active force of the system can be calculated by the following expression:

[0089]

[0090] in, Its components are, in order, the driving torque of joints 1-6 and the driving force of push rods 1-6. Its specific form is as follows:

[0091]

[0092] in, It is the Jacobian matrix of the Stewart mechanism.

[0093] Step 1.3.9: The multi-rigid-body dynamic equations of the hybrid system on the moving base are:

[0094]

[0095] Given the motion states of each joint and strut, substitute... The corresponding driving force and driving torque can then be solved in reverse.

[0096] Step 2: Based on the dynamic model obtained in Step 1, each actuator is equivalent to a spring-damped system, and an impedance controller is constructed in the joint space.

[0097] Step 2.1: Neglecting friction between the actuators, the inverse dynamics of the robotic arm can be written as the following general expression:

[0098]

[0099] in, The driving force or driving torque of the driver. This refers to the forces and torques acting on each actuator when the robotic arm comes into contact with the external environment. Based on the fundamental design principles of an impedance controller, it is desirable for each actuator to exhibit the properties of a spring-damped system when subjected to external forces, i.e.:

[0100]

[0101] Step 2.2: [The formula is missing from the original text.] Substitution ,have:

[0102]

[0103] in, The inverse dynamics of the corresponding multibody system can be expressed by equation Obtain. Formula Can be written as:

[0104]

[0105] Then we have:

[0106]

[0107] The formula Substitution This yields the impedance controller:

[0108]

[0109] Step 3: Taking advantage of the large workspace of the serial robotic arm and the high working accuracy of the parallel mechanism, the serial robotic arm is used to perform preliminary tracking of the target position and pose, and then the Stewart parallel mechanism is used to perform fine compensation of the attitude.

[0110] Step 3.1: The robotic arm's serial connection can employ any planning method; here, the RRT planning method is used as an example, and... Origin of the coordinate system An attitude sensor is positioned to measure the attitude of the end of the sixth link in the series connection, i.e., the lower platform of the parallel mechanism, relative to the world coordinate system. The attitude sensor measures... Compared to The rotation matrix is Assuming the set end-point target attitude is relative to... The rotation matrix is Due to the influence of the RRT planner's planning frequency and the target pose tracking deviation of the series controller, there will be a certain deviation between the actual attitude measured by the attitude sensor and the target attitude. This deviation can be expressed as a rotation matrix, i.e.:

[0111]

[0112] Step 3.2: Compensate for the attitude deviation using the parallel mechanism at the end, then the attitude of the upper platform of the parallel mechanism relative to the lower platform is... By specifying the position vector of the upper platform relative to the lower platform in the parallel mechanism, and specifying the relative attitude... Substituting the position-level inverse kinematics equations of the Stewart mechanism (equation) By doing so, the target position of each push rod can be determined.

[0113] Step 3.3: Input the target joint angle of the serial robotic arm obtained from RRT planning and the target position of the push rod of the parallel mechanism obtained from inverse kinematics into the impedance controller for unified control.

[0114] Beneficial effects:

[0115] 1. The present invention discloses a series-parallel hybrid space operating system and its cooperative operation method. The Kane method is used to perform dynamic modeling and analysis of the series-parallel hybrid operating system on the moving base. It can reflect the influence of the operating system of the flexible base during the on-rail assembly of the truss and the coupling relationship between the various drivers of the hybrid system, such as the joint motor of the series robotic arm and the electric cylinders of the various support rods of the parallel mechanism.

[0116] 2. Use an impedance controller with dynamic compensation to uniformly control the series and parallel subsystems of the hybrid operating system. Dynamic compensation can counteract the influence of inertial force and inertial torque on the impedance control of the driver, so that each driver only exhibits compliance with external contact force.

[0117] 3. Combining the advantages of serial robotic arms and parallel mechanisms in terms of workspace and operational precision, the serial subsystem in the hybrid system is responsible for the initial tracking of the target's posture, while the parallel subsystem is responsible for fine compensation. This enables higher attitude tracking accuracy and is more suitable for the on-orbit assembly of trusses. Attached Figure Description

[0118] Figure 1 This is a schematic diagram of the serial-parallel hybrid operating system proposed in this invention;

[0119] Figure 2 A schematic diagram of the coordinate system at the connection point between the end effector of the serial robotic arm and the Stewart parallel mechanism;

[0120] Figure 3 This is a schematic diagram of the coordinate system for the hinge points and supports of the Stewart mechanism.

[0121] Figure 4 This is a schematic diagram of a dynamics simulation verification environment based on Simscape.

[0122] Figure 5 A comparison chart of the calculation results using the Kane method and the simulation results using Simscape;

[0123] Figure 6 This is a schematic diagram of an impedance control simulation environment based on Simscape.

[0124] Figure 7 The compliance response curve of the serial robotic arm to external contact force;

[0125] Figure 8 The compliance response curve of the parallel Stewart mechanism to external contact force;

[0126] Figure 9 This is a schematic diagram of the operation process;

[0127] Figure 10 A simulation scenario for the pose of a robotic arm tracking and capturing points;

[0128] Figure 11 A comparison of Euler rolls before and after compensation by the Stewart mechanism;

[0129] Figure 12 A comparison of Euler angles (pitch) before and after compensation by the Stewart mechanism;

[0130] Figure 13 A comparison of Euler angles (yaw) before and after compensation by the Stewart mechanism. Detailed Implementation

[0131] To better illustrate the purpose and advantages of the present invention, the invention will be further described below with reference to the accompanying drawings.

[0132] This system is a serial-parallel hybrid operating system consisting of a six-degree-of-freedom serial robotic arm and a six-degree-of-freedom Stewart mechanism fixed to the end of the serial robotic arm.

[0133] This invention discloses a cooperative operation method for a serial-parallel hybrid space operating system, which can achieve precise tracking of the pose of the capture point during the assembly task of a space truss, including the following steps:

[0134] Step 1: Establish a dynamic model of the serial-parallel hybrid operating system on a dynamic base using the Kane method. The Kane method is a method that combines the characteristics of vector mechanics and analytical mechanics, with relatively low computational cost, making it suitable for programmatic calculations. The configuration of the serial-parallel hybrid space operating system disclosed in this invention is as follows: Figure 1 As shown, the base of this hybrid system reciprocates with the flexible truss, and the operating mechanism consists of a six-DOF robotic arm and a parallel Stewart mechanism. Before performing dynamic modeling, a coordinate system needs to be established to describe the system. For the series connection, each link directly establishes its coordinate system according to the improved DH parameter establishment rules. Since the sixth link of the robotic arm is fixed to the Stewart mechanism, the lower platform of the Stewart mechanism shares a coordinate system with the sixth link, as shown below. Figure 2 As shown; parallel part, parallel part, establish a coordinate system on the upper platform. Its coordinate origin Located at the center of the plane where the upper platform and the support rod hinge point lie, for the sake of simplifying the calculation, it is assumed that the center of mass of the upper platform is at the center of the plane. Overlapping, lower platform center of gravity and Coincidence. The coordinate systems of the universal joint and the support rod are established as follows: Figure 3 As shown, for the part where the universal joint is fixed to the lower platform, the hinge point is used as the reference point. Let O be the origin of the coordinate system. arrive The connection is The axis coincides with the direction of the universal joint's fixed axis. Axis, establish right-handed system For the part connecting the universal joint and the support rod, the hinge point is also used. The origin of the coordinate system is coinciding with the direction of the support rod. The shaft, whose direction coincides with that of the universal joint's moving shaft, is Axis, establish right-handed system The center of gravity of the following support rod is taken as the origin of the coordinate system. Establish a coordinate system Its three-axis direction is the same as Coincident; the center of gravity of the above support rod is the origin of the coordinate system. Establish a coordinate system Its three-axis directions are also the same as They coincide. At this point, the coordinate system of the system is established.

[0135] After establishing the coordinate system, the generalized rate of the system is selected as... The generalized active force matrix of the system is:

[0136]

[0137] in, Its components are, in order, the driving torque of joints 1-6 and the driving force of push rods 1-6. Its specific form is as follows:

[0138]

[0139] in, It is the Jacobian matrix of the Stewart mechanism.

[0140] The generalized inertial force matrix of the system is:

[0141]

[0142] in, ,

[0143]

[0144]

[0145] Form and style The result is consistent; simply replace the deflection velocity at the corresponding position with the deflection angular velocity. Matrix, for matrix ,have:

[0146]

[0147] in:

[0148]

[0149]

[0150] It corresponds to the inertial tensor of the rigid body about its center of mass.

[0151] In summary, the multi-rigid-body dynamic equations of the hybrid system on the moving base are obtained as follows:

[0152]

[0153] The accuracy of the modeling results was then verified by comparing the results of software simulation with those calculated using the Kane method. Assuming that one end of the truss connected to the serial-parallel hybrid robotic arm reciprocates relative to the other end, let the position vector from the world coordinate system to the base of the serial-parallel hybrid robotic arm be:

[0154]

[0155] in, Specify the joint angle position of joint 1 as... (radians), the joint angle position of joint 3 is (radian), the position of joint 5 joint angle is (Radians), with the remaining joint angles set to 0. Specify the position vector of the upper platform relative to the lower platform of the Stewart mechanism as... Meters. For ease of representation, the pose of the upper platform relative to the lower platform can be represented using 3-2-1 Euler angles, specified. , , The conversion from Euler angles to rotation matrix and from Euler angular velocity to rotational angular velocity can be given by the corresponding formulas. Simulation results are as follows: Figure 5 As shown, the two results agree very well, indicating that the Kane method's modeling results are accurate.

[0156] Step 2: Based on the dynamic model obtained in Step 1, each actuator is equivalent to a spring-damped system, and an impedance controller is constructed within the joint space. The basic principle of impedance control is to treat each actuator as a spring-damped system, hoping that when the operating system interacts with external forces, each actuator will produce a response similar to that of a spring-damped system.

[0157] Neglecting friction between actuators, the inverse dynamics of the robotic arm can be written as the following general expression:

[0158]

[0159] in, The driving force or driving torque of the driver. This refers to the forces and torques acting on each actuator when the robotic arm comes into contact with the external environment. Based on the fundamental design principles of an impedance controller, it is desirable for each actuator to exhibit the properties of a spring-damped system when subjected to external forces, i.e.:

[0160]

[0161] The formula Substitution ,have:

[0162]

[0163] in, The inverse dynamics of the corresponding multibody system can be expressed by equation Obtain. Formula Can be written as:

[0164]

[0165] Then we have:

[0166]

[0167] The formula Substitution This yields the final expressions for the input driving force and driving torque.

[0168] like Figure 6 As shown, when the serial-parallel hybrid robotic arm is in the initial state shown in the figure, when When applying a magnitude of [value] in the direction of the platform on the vertical Stewart mechanism. The duration is The external force was used to verify the compliant response of the hybrid system. The simulation results are as follows: Figure 7 and Figure 8 As shown. By Figure 7 and Figure 8 It can be seen that when no external force is applied, the positions of the joints of the tandem robotic arm and the supports of the Stewart mechanism remain basically stable; when an external force is applied... After the external force is applied, both the tandem robotic arm and the Stewart mechanism move in the direction of the force, exhibiting compliant characteristics. Furthermore, the rate of change of the actuator position over time gradually decreases, demonstrating the characteristics of a spring-damped system. After the external force is unloaded, each joint and push rod gradually converges to its initial position.

[0169] Step 3: Leveraging the advantages of a large workspace for the serial robotic arm and the high precision of the parallel mechanism, the serial robotic arm is used for initial target pose tracking, followed by fine-tuning of the pose using the Stewart parallel mechanism. The serial part of the robotic arm can employ any planning method; here, the RRT planning method is used as an example. Origin of the coordinate system An attitude sensor is positioned to measure the attitude of the end of the sixth link in the series connection, i.e., the lower platform of the parallel mechanism, relative to the world coordinate system. The attitude sensor measures... Compared to The rotation matrix is Assuming the set end-point target attitude is relative to... The rotation matrix is Due to the influence of the RRT planner's planning frequency and the target pose tracking deviation of the series controller, there will be a certain deviation between the actual attitude measured by the attitude sensor and the target attitude. This deviation can be expressed as a rotation matrix, i.e.:

[0170]

[0171] By using the parallel mechanism at the end to compensate for this attitude deviation, the attitude of the upper platform relative to the lower platform of the parallel mechanism is then determined. By specifying the position vector of the upper platform relative to the lower platform in the parallel mechanism, and specifying the relative attitude... Substituting the position-level inverse kinematics equations of the Stewart mechanism (equation) This allows for the inverse kinematics solution to determine the target positions of each push rod. The target joint angles of the serial robotic arm obtained from the RRT planning and the target positions of the push rods of the parallel mechanism obtained from the inverse kinematics solution are then fed into the impedance controller for unified control.

[0172] Overall control and operation methods such as Figure 9 As shown.

[0173] Figure 10 For a hypothetical truss grasping scenario, the red coordinates represent the preset grasping point pose, which is also the target pose at the end of the hybrid robotic arm. The process of the hybrid robotic arm tracking the target pose is simulated. The base of the serial-parallel hybrid robotic arm performs the same motion as in equation (57). The target position and pose are fixed relative to the world coordinate system, and the roll, pitch, and yaw angles of the target pose relative to the world coordinate system are all set to 0. The target joint angles of each joint of the robotic arm are planned using the RRT planning method, with a planning frequency of... An impedance controller is used to track the target joint angle; simultaneously, the deviation of the end effector posture of the serial robotic arm relative to the target posture is measured at a frequency of [frequency missing]. At the same time, add to the measurement results To mitigate random noise, a Stewart end effector is used to compensate for attitude deviations. The attitude tracking performance is compared between the cases with and without Stewart attitude compensation. Simulation results are as follows: Figures 11 to 13 As shown in the figure, the overall comparison reveals that, within the adjustment time, when the attitude deviation enters the compensation range of the Stewart mechanism, the attitude of the Stewart platform converges faster than that of the end effector of the serial manipulator. After entering steady state, the attitude of the Stewart platform is more stable and has smaller errors compared to the end effector of the serial manipulator. Since the base posture of the hybrid system changes continuously over time, and the RRT planning frequency is relatively low, and the serial manipulator's target tracking speed is worse than that of the parallel mechanism, the end effector of the serial manipulator exhibits a certain degree of periodic fluctuations near the target attitude angle. However, the end effector's attitude measurement frequency is higher than that of the RRT planning frequency, providing more practical attitude information. Furthermore, the parallel mechanism itself has a faster response speed than the serial manipulator, resulting in a significantly smaller amplitude of the attitude angle deviation after attitude compensation. These results demonstrate that the hybrid serial-parallel configuration effectively addresses the drawback of the low planning frequency of the RRT planner, achieving collision avoidance planning while maintaining relatively high end effector attitude tracking accuracy in time-varying environments.

[0174] The technical contents not described in detail in this invention are common knowledge to those skilled in the art.

[0175] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is merely a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for cooperative operation of a series-parallel hybrid space operation system, characterized in that: Includes the following steps, Step 1: Establish the world coordinate system The linkage coordinate system of the 6-joint robotic arm and the coordinate systems fixed to the parallel platform are determined. The system is kinematically described by selecting a generalized velocity, and then the partial velocity matrix is ​​obtained. The generalized active force and generalized inertial force are further obtained. The dynamic equation is obtained from the fact that the sum of the generalized active force and the generalized inertial force is 0. Step 2: Based on the dynamic equations obtained in Step 1, each actuator is equivalent to a spring-damped system, and an impedance controller is constructed in the joint space. Step 3: Start the hybrid operating system under the control of the impedance controller, use the serial robotic arm to perform initial tracking of the target pose, and then use the Stewart parallel mechanism to perform fine compensation of the attitude, so as to realize the coordinated operation of the serial and parallel mechanisms.

2. The serial-parallel hybrid space operating system and its cooperative operation method as described in claim 1, characterized in that: The link coordinate system of the 6-joint robotic arm described in step one is established using improved DH parameters. Indicate the coordinate system of each link. Let be the origin of the corresponding link coordinate system, where the lower platform of the parallel mechanism and the sixth link of the robotic arm are considered as a whole. Located in the plane of the lower hinge point of the parallel mechanism support; a coordinate system is established at the point where the hybrid robotic arm is fixed to the large truss, i.e., at the base of the robotic arm. The origin of the coordinate system is .

3. The serial-parallel hybrid space operating system and its cooperative operation method as described in claim 1, characterized in that: The coordinate systems fixed to the parallel platform as described in step one include , , , , and The definitions of each coordinate system are detailed below; The center of gravity of the parallel mechanism on the platform and Overlap, establish a coordinate system on the upper platform Its coordinate origin Located at the center of the plane where the upper platform and the support rod hinge point are located, the center of mass of the lower platform of the parallel mechanism is... Overlap; establish a coordinate system on the lower platform. Its coordinate origin Located at the center of the plane where the lower platform and the support rod hinge point lie; for the part where the universal joint is fixed to the lower platform, the hinge point is considered the center of the plane. Let O be the origin of the coordinate system. arrive The connection is The axis coincides with the direction of the universal joint's fixed axis. Axis, establish right-handed system For the part connecting the universal joint and the support rod, the hinge point is also used. The origin of the coordinate system is coinciding with the direction of the support rod. The shaft, whose direction coincides with that of the universal joint's moving shaft, is Axis, establish right-handed system The center of gravity of the following support rod is the origin of the coordinate system. Establish a coordinate system Its three-axis direction is the same as Coincident; the center of gravity of the above support rod is the origin of the coordinate system. Establish a coordinate system Its three-axis directions are also the same as coincide.

4. The serial-parallel hybrid space operating system and its cooperative operation method as described in claim 1, characterized in that: The method for kinematically describing the system described in step one is as follows: Step 1.1: Select the generalized rate; the first derivatives of orders 1-6 are the magnitudes of the six joint angles of the series part, denoted as... The 7th to 9th orders are based on arrive position vector exist relative derivative in exist The component in is denoted as ; For orders 10-12, the angular velocity of the upper platform relative to the lower platform in the parallel section is... exist The component in is denoted as ; Step 1.2: Based on the characteristics of the series connection, the angular velocity and velocity at each link coordinate system can be obtained by recursively deriving them step by step outwards; The angular velocities at the origin of each link's coordinate system are: ,in, for angular velocity at point in coordinate system The component representation in the coordinate system (hereinafter, the superscript will be used to represent the component representation of a vector in this coordinate system). coordinate system Relative to coordinate system Rotation matrix (hereinafter referred to as rotation matrix) (This represents the rotation matrix of coordinate system A relative to coordinate system B). For the first The orientation of the joint rotation axis in the coordinate system The component representation in the middle, that is ; The velocities at each link's coordinate system are: In the formula Indicates by arrive The vector in Component representation in; Step 1.3: Differentiating both sides of the equation, we obtain the angular acceleration at the link coordinate system as follows: Step 1.4: Substitute equation (1) into the rigid body velocity calculation formula and differentiate with respect to time to obtain the acceleration at the link coordinate system as follows: Step 1.5: Let the first... The center of mass of each link is in the coordinate system The position vector in is Then the velocities and accelerations at the center of mass of each link are: , Step 1.6: Based on the transitivity of angular velocity, the absolute angular velocity of the upper platform is obtained as follows: Step 1.7: Differentiating both sides of the equation with respect to time, we obtain the angular acceleration of the upper platform as follows: Step 1.8: The absolute speed of going up the platform is: Step 1.9: Differentiating both sides of the equation with respect to time, we obtain the acceleration of the upper platform as: Step 1.10: The parallel mechanism has a closed-loop constraint condition, that is... ,in Let be the vector from the center of mass of the lower platform to the center of mass of the upper platform. The vector from the center of mass of the upper platform to the hinge point. It is the product of the push rod length and the push rod's unit direction vector. Let be the vector from the center of mass of the upper platform to the hinge point; based on this closed-loop relationship, the vector relationship can be obtained as follows: ,in, For the first Total length of each support rod Let its unit direction vector be . The upper and lower hinge points are respectively at and The position vector in; Step 1.11: From The expression for the total length of the support rod is thus obtained as: The unit direction vector of the support rod is... ; Step 1.12: Formula In coordinate system Taking the first and second derivatives with respect to time, we get: , Step 1.13: Simultaneous left and right with By performing a cross product, we obtain the support rod. The angular velocity relative to the lower platform is: ,again: It can be represented as: ,in, ; Step 1.14: Formula Both sides in the coordinate system Take the derivative with respect to time, and then with each time step. Perform dot product and cross product, noting and Orthogonal, after simplification we get: , Step 1.15: The angular velocity of each support relative to the world coordinate system is: The angular acceleration relative to the world coordinate system is: Step 1.16: The velocity and acceleration of the lower support rod's center of mass relative to the world coordinate system, and the velocity and acceleration of the upper support rod's center of mass relative to the world coordinate system are as follows: ， ， ， 。 5. The serial-parallel hybrid space operating system and its cooperative operation method as described in claim 1, characterized in that: The generalized inertial force of the system described in step one can be calculated by the following expression: in, , It is a partial velocity matrix. This is the deflection angular velocity matrix; The inertial force matrix, The moment of inertia matrix; In the figure, rows 1-18 show the deflection velocity at the center of mass of each link in the series mechanism, corresponding to equation (36); rows 19-21 show the deflection velocity of the upper platform in the parallel mechanism, corresponding to equation (37); rows 22-39 show the deflection velocity at the center of mass of the lower link in the parallel mechanism, corresponding to equation (39). Form and The result is consistent; simply replace the deflection velocity at the corresponding position with the deflection angular velocity. Matrix, for matrix ,have: in: It corresponds to the inertial tensor of a rigid body about its center of mass; The generalized active force of the system can be calculated by the following expression: in, Its components are, in order, the driving torque of joints 1-6 and the driving force of push rods 1-6. Its specific form is as follows: in, It is the Jacobian matrix of the Stewart mechanism; The multi-rigid-body dynamic equations of the hybrid system on the moving base are: Given the motion states of each joint and strut, substitute... The corresponding driving force and driving torque can then be solved in reverse.

6. The serial-parallel hybrid space operating system and its cooperative operation method as described in claim 5, characterized in that: The matrix described in step one The parameters are obtained through the following method: The generalized rate can be written as a column vector: For the series connection, the angular velocity and deflection velocity of each link's coordinate system are: The deflection velocity at the center of mass of the connecting rod is: For the upper platform of a parallel mechanism, its partial velocity at the center of mass is: The angular velocity is: For a 6-way support rod, the formula is... Therefore, for each support rod, its deflection velocity can be written as: The angular velocity is 0; In equation (35-40), , .

7. The method as described in claim 1, characterized in that: The second step is implemented as follows: Step 2.1: Equation (32) can be written as the following general expression: in, The driving force or driving torque of the driver. This refers to the forces and torques acting on each actuator when the robotic arm comes into contact with the outside world. Based on the basic design principles of an impedance controller, it is desirable that each actuator exhibits the properties of a spring-damped system when subjected to external forces. Step 2.2: Substitute equation (42) into equation ,have: in, The inverse dynamics of the corresponding multibody system can be expressed by equation Obtain; formula Can be written as: Then we have: Substituting equation (45) into equation This yields the final expressions for the input driving force and driving torque, which is the impedance controller.

8. The method as described in claim 1, characterized in that: The method for implementing step three is as follows: Step 3.1: Use the RRT planning method to plan the serial part of the robotic arm, and in Origin of the coordinate system An attitude sensor is positioned to measure the attitude of the end of the sixth link in the series connection, i.e., the lower platform of the parallel mechanism, relative to the world coordinate system. The attitude sensor measures... Compared to The rotation matrix is The set end-point target attitude is relative to The rotation matrix is Due to the influence of the RRT planner's planning frequency and the target pose tracking deviation of the series controller, there will be a certain deviation between the actual attitude measured by the attitude sensor and the target attitude. This deviation can be expressed as a rotation matrix, i.e.: Step 3.2: Use the Stewart parallel mechanism at the end to compensate for the attitude deviation. The attitude of the upper platform relative to the lower platform of the parallel mechanism is then determined. By specifying the position vector of the upper platform relative to the lower platform of the parallel mechanism, and specifying the relative attitude... Substituting the position-level inverse kinematics equations of the Stewart mechanism (equation) By using this method, the target position of each pusher can be determined; Step 3.3: Input the target joint angle of the serial robotic arm obtained from RRT planning and the target position of the push rod of the parallel mechanism obtained from inverse kinematics into the impedance controller for unified control, so as to realize the coordinated operation of the serial and parallel mechanisms.

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