A flexible arm posture optimization method and control system based on a joint stiffness model

Abstract

The application discloses a flexible arm posture optimization method based on a joint stiffness model, and comprises the following steps: constructing a flexible arm end joint stiffness model, calculating the stiffness of the flexible arm end at a set posture according to the end joint stiffness model, and adopting an end stiffness ellipsoid to describe the stiffness of each direction of the flexible arm end; solving the kinematic inverse solution through bidirectional search according to a posture optimization algorithm, solving the stiffness of each joint group of the posture corresponding to the kinematic inverse solution on the basis of the deformation compensation of the mechanical arm, and sorting the stiffness of each joint group in descending order to obtain an optimized posture sequence; establishing a man-machine collaborative optimization mechanism according to the optimized posture sequence and working environment image information, constructing a virtual model of the working state of different optimized postures in the working environment, and selecting the most reasonable working posture under the current working condition according to the environment information and the stiffness information. The flexible hydraulic mechanical arm end stiffness is accurately expressed, and intuitive auxiliary reference can be provided for the operator in a complex environment.

Description

Technical Field

[0001] The present invention relates to the technical field of large-scale flexible hydraulic mechanical arm control, and in particular to a flexible arm posture optimization method and control system based on a joint stiffness model. Background Art

[0002] Large flexible hydraulic robotic arms are important equipment in the fields of construction, rescue, and military due to their heavy loads and large operating radius. However, the oil compression in the hydraulic power system and the accumulated end deflection of the ultra-long arm make it difficult to characterize the end stiffness of the flexible hydraulic arm, which in turn affects the working performance of the flexible arm. In addition, flexible hydraulic arms with redundant degrees of freedom are often in complex, unstructured working environments. Their posture is difficult to fully consider and thus screen for optimal performance, and the risk of collision with the surrounding environment is high. This increases the operator's operating difficulty and safety risks, and makes it difficult for the flexible hydraulic arm to actively suppress vibration. Therefore, it is very necessary to establish an accurate stiffness model and let the operator understand the stiffness information and working status of all possible postures of the target point. Summary of the Invention

[0003] In response to the defects in the existing technology, the present invention provides a flexible arm posture optimization method and control system based on a joint stiffness model, which realizes the accurate expression of the stiffness of the end of the flexible hydraulic robotic arm and can provide intuitive auxiliary reference for operators in complex environments.

[0004] In a first aspect, an embodiment of the present invention provides a flexible arm posture optimization method based on a joint stiffness model, comprising:

[0005] Obtain kinematic information, flexibility information, and working environment image information after the end of the flexible hydraulic manipulator reaches the target point;

[0006] Based on the kinematic information and flexibility information, a joint stiffness model of the flexible hydraulic manipulator end is constructed. The stiffness of the flexible hydraulic manipulator end in a set position is calculated based on the joint stiffness model of the flexible hydraulic manipulator end. The stiffness of the flexible hydraulic manipulator end in each direction is described using the end stiffness ellipsoid.

[0007] According to the flexible hydraulic manipulator posture optimization algorithm, the kinematic inverse solution is solved through bidirectional search. Based on the deformation compensation of the flexible hydraulic manipulator, the stiffness of each joint group corresponding to the posture of the inverse kinematic solution is solved, and the stiffness of each joint group is sorted in descending order to obtain the optimized posture sequence;

[0008] A human-machine collaborative optimization mechanism is established based on the optimized posture sequence and working environment image information, and a virtual model of the working status of different optimized postures in the working environment is constructed;

[0009] The most reasonable working posture under the current working conditions is selected based on the environmental information and stiffness information provided by the virtual model.

[0010] Furthermore, the specific method of constructing the joint stiffness model of the flexible hydraulic manipulator end according to the kinematic information and the flexibility information includes:

[0011] According to the hydraulic flexibility characteristics and arm flexibility features of the flexible hydraulic manipulator, the joint stiffness of the flexible hydraulic manipulator is decoupled into hydraulic stiffness and arm stiffness.

[0012] Calculate the hydraulic stiffness of each joint, the deflection of each arm end, and the joint angle change caused by hydraulic flexibility;

[0013] Calculate the joint arm stiffness based on the joint angle change value;

[0014] Calculate the joint stiffness of each joint based on the hydraulic stiffness of each joint and the stiffness of each joint arm;

[0015] Calculate the torque and lever arm of the end force at each joint;

[0016] The joint stiffness model of the flexible hydraulic manipulator end is constructed according to the joint stiffness and lever arm of each joint.

[0017] Furthermore, the specific method for calculating the hydraulic stiffness of each joint includes:

[0018] The kinematic information includes joint angle information, and the displacement of the piston rod of each joint hydraulic cylinder is calculated based on the joint angle information;

[0019] Calculate the equivalent stiffness of the hydraulic cylinder based on the displacement of the hydraulic piston rod of each joint;

[0020] The hydraulic stiffness of each joint is calculated based on the equivalent stiffness of the hydraulic cylinder.

[0021] Furthermore, the specific method for calculating the deflection of each arm end and the joint angle change value caused by hydraulic flexibility includes:

[0022] Calculate the deflection of each arm end according to the end section rotation angle information of each joint hinge point and the arm end;

[0023] The end displacement changes are mapped to the joints, and the joint angle changes of each arm due to the arm flexibility are calculated.

[0024] Furthermore, the specific method for solving the kinematic inverse solution through bidirectional search based on the flexible hydraulic manipulator posture optimization algorithm includes:

[0025] Set the initial ideal joint angle and the initial ideal end position;

[0026] The ideal joint angle of the first joint is obtained by adding the set value to the initial ideal joint angle;

[0027] According to the inverse kinematics of the manipulator, the ideal joint angles of the corresponding second and third joints are calculated. The obtained joint inverse solution must satisfy the ideal end position and the initial ideal end position. The set value is the search step length. The forward search and reverse search are performed according to the search step length. Two sets of joint angle solutions are obtained each time according to the inverse kinematics solution, and each set of joint angle solutions is recorded.

[0028] The solution process is repeated until both the forward search and the reverse search have no solutions, and all joint angle groups are obtained.

[0029] Furthermore, the specific method for solving the stiffness of each joint group corresponding to the posture of the inverse kinematic solution based on the deformation compensation of the flexible hydraulic manipulator includes:

[0030] Substitute all joint angle groups into the deformation compensation module to obtain the deformation compensation angle of each joint, input the deformation compensation angle and the direction angle of the end force into the end joint stiffness model, and obtain the stiffness of each joint group calculated by the end joint stiffness model.

[0031] In a second aspect, an embodiment of the present invention provides a flexible arm posture optimization control system based on a joint stiffness model, comprising: a data acquisition module, a terminal joint stiffness model construction module, a posture optimization module, a virtual model construction module, and a screening module;

[0032] The data acquisition module is used to obtain kinematic information, flexibility information and working environment image information after the end of the flexible hydraulic manipulator reaches the target point;

[0033] The terminal joint stiffness model construction module is used to construct a terminal joint stiffness model of the flexible hydraulic manipulator according to kinematic information and flexibility information, calculate the stiffness of the flexible hydraulic manipulator terminal in a set posture according to the terminal joint stiffness model of the flexible hydraulic manipulator terminal, and use the terminal stiffness ellipsoid to describe the stiffness of the flexible hydraulic manipulator terminal in various directions;

[0034] The posture optimization module solves the inverse kinematics solution through bidirectional search based on the posture optimization algorithm of the flexible hydraulic manipulator, solves the stiffness of each joint group corresponding to the posture of the inverse kinematics solution on the basis of deformation compensation of the flexible hydraulic manipulator, and sorts the stiffness of each joint group in descending order to obtain an optimized posture sequence;

[0035] The virtual model building module is used to establish a human-machine collaborative optimization mechanism based on the optimized posture sequence and the working environment image information, and to build a virtual model of the working state of different optimized postures in the working environment;

[0036] The screening module is used to screen out the most reasonable working posture under the current working conditions based on the environmental information and stiffness information provided by the virtual model.

[0037] Furthermore, the terminal joint stiffness model construction module decouples the joint stiffness of the flexible hydraulic manipulator into hydraulic stiffness and arm stiffness according to the hydraulic flexibility characteristics and arm flexibility characteristics of the flexible hydraulic manipulator, calculates the hydraulic stiffness of each joint, the end deflection of each arm section, and the joint angle change value caused by hydraulic flexibility, calculates the joint arm stiffness according to the joint angle change value, calculates the joint stiffness of each joint according to the hydraulic stiffness of each joint and the arm stiffness of each joint, calculates the torque and lever arm of the terminal force at each joint, and constructs the terminal joint stiffness model of the flexible hydraulic manipulator according to the joint stiffness and lever arm of each joint.

[0038] Furthermore, the terminal joint stiffness model construction module includes a hydraulic stiffness calculation unit, which calculates the displacement of the hydraulic cylinder piston rod of each joint according to the joint angle information, calculates the equivalent stiffness of the hydraulic cylinder according to the displacement of the hydraulic piston rod of each joint, and calculates the hydraulic stiffness of each joint according to the equivalent stiffness of the hydraulic cylinder.

[0039] Furthermore, the terminal joint stiffness model construction module includes an arm terminal deflection calculation unit and a joint angle change calculation unit, wherein the arm terminal deflection calculation unit is used to calculate the deflection of each arm terminal according to the information of each joint hinge point and the end section rotation angle of the arm terminal;

[0040] The joint angle change calculation unit is used to map the end displacement change to the joint and calculate the joint angle change value of each arm due to the arm flexibility.

[0041] Beneficial effects of the present invention:

[0042] 1. This embodiment of the present invention provides a flexible arm posture optimization method based on a joint stiffness model. Based on the dual elastic interaction of the hydraulic chamber and the flexible arm rod of a flexible hydraulic manipulator arm, the joint stiffness is decoupled into two components: hydraulic stiffness and arm rod stiffness. These components are then modeled separately, thereby constructing a joint stiffness model for the flexible hydraulic manipulator end. A stiffness ellipsoid index is introduced to characterize the various stiffness characteristics of the end, achieving an accurate representation of the stiffness of the flexible hydraulic arm end. To address the difficulty of autonomously optimizing stiffness under complex constraints, a collaborative optimization mechanism for flexible arm stiffness is constructed, combining automatic sorting of working postures with sequential selection by the operator.

[0043] 2. A virtual model is also constructed based on the working environment image, which can provide operators with a more intuitive auxiliary reference under complex structural / environmental constraints, reducing the operator's subjectivity in judging the stiffness of the flexible arm end and the difficulty of operation under complex working conditions, and improving the end precision and operation safety of the flexible arm.

[0044] A flexible arm posture optimization control system based on a joint stiffness model provided in an embodiment of the present invention and a flexible arm posture optimization method based on a joint stiffness model provided in an embodiment of the present invention have the same inventive concept and the same beneficial effects, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or parts are generally identified by similar reference numerals throughout the drawings. Elements or parts in the drawings are not necessarily drawn to scale.

[0046] Figure 1 A schematic flow chart of a flexible arm posture optimization method based on a joint stiffness model provided by an embodiment of the present invention is shown;

[0047] Figure 2 A schematic diagram of the process of constructing a joint stiffness model of the flexible hydraulic manipulator end based on kinematic information and flexibility information is shown;

[0048] Figure 3 A flow chart of the posture solving and optimization method is shown;

[0049] Figure 4 A statistical diagram showing the effect of a flexible arm posture optimization method based on a joint stiffness model provided by an embodiment of the present invention is shown;

[0050] Figure 5 A structural block diagram of a flexible arm posture optimization control system based on a joint stiffness model provided by an embodiment of the present invention is shown;

[0051] Figure 6 A structural block diagram of a flexible arm posture optimization visualization interactive system based on a joint stiffness model provided by an embodiment of the present invention is shown;

[0052] Figure 7 A schematic diagram of the workflow of a flexible arm posture optimization visualization interactive system based on a joint stiffness model provided by an embodiment of the present invention is shown;

[0053] Figure 8 The figure shows an interactive interface effect diagram of a flexible arm posture optimization visualization interactive system based on a joint stiffness model provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0054] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0055] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0056] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used in the specification and appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0057] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0058] like Figure 1 FIG. 1 shows a flexible arm posture optimization method based on a joint stiffness model provided by a first embodiment of the present invention, comprising:

[0059] Obtain kinematic information, flexibility information, and working environment image information after the end of the flexible hydraulic manipulator reaches the target point;

[0060] Based on the kinematic information and flexibility information, a joint stiffness model of the flexible hydraulic manipulator end is constructed. The stiffness of the flexible hydraulic manipulator end in a set position is calculated based on the joint stiffness model of the flexible hydraulic manipulator end. The stiffness of the flexible hydraulic manipulator end in each direction is described using the end stiffness ellipsoid.

[0061] According to the flexible hydraulic manipulator posture optimization algorithm, the kinematic inverse solution is solved through bidirectional search. Based on the deformation compensation of the flexible hydraulic manipulator, the stiffness of each joint group corresponding to the posture of the inverse kinematic solution is solved, and the stiffness of each joint group is sorted in descending order to obtain the optimized posture sequence;

[0062] A human-machine collaborative optimization mechanism is established based on the optimized posture sequence and working environment image information, and a virtual model of the working status of different optimized postures in the working environment is constructed;

[0063] The most reasonable working posture under the current working conditions is selected based on the environmental information and stiffness information provided by the virtual model.

[0064] In this example, a combined stiffness model for the end of a flexible hydraulic manipulator arm is first established based on the hydraulic and long arm elastic characteristics. A stiffness ellipsoid is introduced to characterize the stiffness characteristics of the end in all directions, accurately expressing the stiffness of the flexible hydraulic manipulator arm. A flexible arm posture optimization algorithm is then employed to improve the end operating stiffness. Furthermore, a human-machine collaborative optimization mechanism for the flexible arm's operating stiffness is established, and virtual models of the operating states of different postures in the working environment are constructed. Based on the environmental and stiffness information provided by the virtual model, the most reasonable operating posture for the current working conditions is selected, providing an auxiliary reference for the operator.

[0065] Specifically, for a large flexible hydraulic manipulator with three degrees of freedom in the plane, after the operator moves the end of the flexible arm to the specified working point and inputs the optimization instruction, the angle encoder and the inclination sensor transmit the kinematic information and related flexibility information of the flexible arm to the control computer through the information transmission device. Figure 2 As shown in FIG, the specific method for constructing a joint stiffness model of the flexible hydraulic manipulator end according to kinematic information and flexibility information includes the following steps:

[0066] Step 1: According to the hydraulic flexibility characteristics and arm flexibility characteristics of the large flexible hydraulic manipulator, the i-th joint stiffness K of the large flexible hydraulic manipulator is i Decoupled to hydraulic stiffness K hi and arm stiffness K si Two parts:

[0067]

[0068] In formula (1), τ i is the torque on the i-th joint, Δθ hi is the change in joint angle caused by compression deformation of the hydraulic cylinder, Δθ si is the change in joint angle due to displacement of the end of the arm.

[0069] Step 2: Equivalent stiffness K of the hydraulic cylinder of the i-th joint hci It can be expressed as:

[0070]

[0071] In formula (2), E o is the elastic modulus of the oil, A ai is the rodless cavity area of ​​the hydraulic cylinder corresponding to the i-th joint, A bi is the rod cavity area of ​​the hydraulic cylinder corresponding to the i-th joint, s i is the displacement of the hydraulic cylinder piston rod corresponding to the i-th joint, s imaxV is the maximum displacement of the hydraulic cylinder rod corresponding to the i th joint ai V is the volume of the rodless chamber bi V is the volume of the rod chamber L1 V is the volume of the pipe of the rodless chamber L2 V is the volume of the pipe of the rod chamber. The mathematical relationship between the first joint angle a and the corresponding hydraulic cylinder rod displacement s1, the second joint angle b and the corresponding hydraulic cylinder rod displacement s2, and the third joint angle g and the corresponding hydraulic cylinder rod displacement s3 is shown in equations (3), (4), and (5) respectively:

[0072]

[0073] In equation (3), a is the distance between the fulcrum of the hydraulic cylinder on the base and the base point of the mechanical arm in the x direction, b is the distance between the fulcrum of the hydraulic cylinder on the base and the base point of the mechanical arm in the y direction, c is the distance between the fulcrum of the hydraulic cylinder on the first arm and the base point of the mechanical arm in the x direction, u is the distance between the fulcrum of the hydraulic cylinder on the first arm and the base point of the mechanical arm in the y direction, l1 is the total length of the hydraulic cylinder, l 10 is the length of the hydraulic cylinder when the piston rod displacement s1 = 0.

[0074]

[0075] In equation (4), d-j are the distances between each hinge point on each mechanical arm, l2 is the total length of the hydraulic cylinder, l 20 is the length of the hydraulic cylinder when the piston rod displacement s2 = 0.

[0076]

[0077] In equation (5), k-t are the distances between each hinge point on each mechanical arm, l3 is the total length of the hydraulic cylinder, l 30 is the length of the hydraulic cylinder when the piston rod displacement s3 = 0.

[0078] Assume that the i th joint is at an angle of 0 i when the torque T i acts, due to the hydraulic flexibility characteristics, the joint angle changes by 0 hi , the output force F hi of the corresponding hydraulic cylinder when the joint angle changes by 0 hci is:

[0079] F hci = K hci · 0 i (6)

[0080] In equation (6), 0 i is 0 hiThe corresponding displacement change of the hydraulic cylinder piston rod. Ignoring the friction between the components, according to the principle of moment balance, F hci With τ i The relationship is:

[0081] τ i =F hci ·R hci (7)

[0082] In formula (7), R hci is the hydraulic cylinder output force F hci The force arm to the joint rotation hinge point, substitute equations (6) and (7) into the hydraulic stiffness K hi In the definition, when Δθ hi Approaching infinity (Δθ hi →0), we can get:

[0083]

[0084] According to the law of conservation of kinetic energy, F hci With τ i Another relation is:

[0085] F hci Δs i =τ i Δθ hi =W i (9)

[0086] In formula (9), W i is the torque τ i The total work done is the same as the hydraulic compression energy in the hydraulic cylinder. Combining equations (7), (8) and (9) yields:

[0087]

[0088] Step 3: Assume that the moment on the i-th arm is τ i , the displacement change of the end of the arm is:

[0089]

[0090] In formula (11), Δw i is the end deflection of the i-th arm. When the deflection is small relative to the overall arm length, the deflection can be directly regarded as the end displacement. For the convenience of analysis, Δw is i Directly regarded as the end displacement, l i L is the arm length involved in the arm flexibility calculation, i is the overall length of the i-th arm, L i0 is the length from the hydraulic cylinder driving point to the joint hinge point of the i-th arm, E iis the elastic modulus of the material of the i-th arm, I i is the equivalent section moment of inertia of the i-th arm. Mapping the end displacement change to the joint, the joint angle change of the i-th arm due to the arm flexibility is:

[0091]

[0092] In formula (12), Δθ si To map the end displacement change to the equivalent joint angle change at the joint. According to the definition of arm stiffness, the arm stiffness K of the i-th joint is si for:

[0093]

[0094] Step 3: The stiffness K of the i-th joint of the large flexible hydraulic manipulator i Can be rewritten as:

[0095]

[0096] Because K i Usually much larger than τ i , so Δθ Fi The value of is usually small. Fi Approaching infinity (Δθ Fi →0), the end displacement change and joint angle change can be simplified and approximated:

[0097]

[0098] Assume that a force of magnitude F and direction θ is applied to the end of the flexible hydraulic manipulator. F The external force forms a torque expression at each joint:

[0099]

[0100] In formula (16), τ i is the torque generated by F at the i-th joint, F x and F y are the components of F in the x and y directions, R ix and R iy F x and F y The moment arm to the i-th joint hinge point, assuming that the deformation of each joint caused by F is small, and the moment arm before and after the force is applied is the same, is calculated as:

[0101]

[0102] In formula (17), L 1,2,3are the arm lengths of the first, second and third arms respectively, θ 1,2,3 are the expected joint angles of the first, second, and third joints, respectively.

[0103] According to the definition of stiffness, combined with equations (15) and (16), the combined stiffness model of the “hydraulic-arm” end of the flexible hydraulic manipulator is obtained, and the calculation formula is shown in equation (18):

[0104]

[0105] In formula (18), R i =cos(θ F )R ix +sin(θ F )R iy .K i is the stiffness of the i-th joint calculated according to the joint stiffness model. Equation (18) actually expresses the stiffness of the end of the large flexible hydraulic manipulator in the set position (i.e., Jacobian matrix J) and specific direction (i.e., θ F ) is equivalent to the traditional end-end stiffness ellipsoid. This is derived entirely from theory, eliminating the need for joint stiffness calibration. This allows for fast and secure stiffness modeling. The end-end stiffness ellipsoid can be used to describe the stiffness of the flexible hydraulic manipulator end in all directions under a specific posture.

[0106] The flexible arm posture optimization method based on the joint stiffness model provided by the embodiment of the present invention further includes: establishing a posture optimization algorithm model with the goal of improving the end stiffness as follows:

[0107]

[0108] In formula (19), K(θ F ) is the end of the flexible hydraulic manipulator θ F Stiffness in the direction, P = f(q i ) is the ideal position coordinate of the flexible hydraulic manipulator end calculated according to the ideal angle of each joint, q i (i=1,...,n) is the ideal joint angle of each joint, q imin is the minimum ideal joint angle of each joint, q imax is the maximum value of the ideal joint angle of each joint. F After that, the optimized posture can be obtained through the model. Figure 3 As shown in Figure 2, the specific optimization process is as follows:

[0109] a. Set the initial ideal joint angle to q i0 (i=1, 2, 3), the initial ideal end position is P0=[x0, y0] T ;

[0110] b. Change the ideal joint angle of the first joint to q 11 =q i0 ±Δq1, and calculate the ideal joint angles q of the corresponding second and third joints according to the inverse kinematics of the flexible hydraulic manipulator 21 ,q 31 The obtained joint inverse solution must satisfy the same ideal end position P1=f(q 11 ,q 21 ,q 31 )=P0. Where Δq1 is the search step size, when q 11 =q i0 +Δq1, it is recorded as forward search, when q 11 =q i0 When -Δq1, it is recorded as reverse search. According to the inverse kinematics solution, whether it is forward search or reverse search, each solution will obtain two sets of joint angle solutions, and each set of solutions will be recorded;

[0111] c. Repeat the solution process in step b until both the forward search and the reverse search have no solution;

[0112] d. Substitute all joint angle groups into the deformation compensation module to obtain the deformation compensation angle of each joint, and then add the compensation angle and θ F Substitute them into formula (18) to obtain the stiffness of each joint group calculated by the joint stiffness model of the flexible hydraulic manipulator end;

[0113] e. Using the bubble sorting algorithm, sort the stiffness of each joint group from large to small, so as to obtain the stiffness of the flexible hydraulic manipulator at the fixed working point θ F Directional stiffness in various postures from large to small.

[0114] like Figure 4 As shown in FIG, the experimental effect diagram of a flexible arm posture optimization method based on a joint stiffness model provided by the present invention is shown in FIG. Figure 4 (a) Figure 4 (b) with Figure 4 (c) From the three groups of experiments, it can be seen that the experimental group using this method can reduce the vibration of the flexible hydraulic arm end. Therefore, applying this method to the flexible hydraulic arm can improve the positioning accuracy and anti-interference performance of the flexible hydraulic arm end.

[0115] The working principle and beneficial effects of this solution are:

[0116] 1. This invention provides a flexible arm posture optimization method based on a joint stiffness model. Based on the dual elastic interaction of the hydraulic chamber and the flexible arm rod, the joint stiffness is decoupled into two components: hydraulic stiffness and arm rod stiffness. These components are then modeled separately. This constructs a joint stiffness model for the flexible hydraulic manipulator end. A stiffness ellipsoid index is introduced to characterize the individual stiffness characteristics of the end, achieving an accurate representation of the stiffness of the flexible hydraulic arm end. To address the difficulty of autonomously optimizing stiffness under complex constraints, a collaborative optimization mechanism for flexible arm stiffness is constructed, combining automatic sorting of working postures with sequential selection by the operator.

[0117] 2. Flexible arm posture optimization method to improve end stiffness. The end joint stiffness model is completely derived from theory and does not require calibration of joint stiffness. Therefore, stiffness modeling can be performed quickly and safely. The end stiffness ellipsoid obtained by the stiffness model can describe the stiffness of the flexible arm end in various directions under a specific posture.

[0118] 3. A virtual model is also constructed based on the working environment image, which can provide operators with a more intuitive auxiliary reference under complex structural / environmental constraints, reducing the operator's subjectivity in judging the stiffness of the flexible arm end and the difficulty of operation under complex working conditions, and improving the end precision and operation safety of the flexible arm.

[0119] like Figure 5 As shown, the second embodiment of the present invention provides a flexible arm posture optimization control system based on a joint stiffness model, including: a data acquisition module, a terminal joint stiffness model construction module, a posture optimization module, a virtual model construction module and a screening module; the data acquisition module is used to obtain the kinematic information, flexibility information and working environment image information of the terminal of the flexible hydraulic manipulator after the terminal reaches the target point; the terminal joint stiffness model construction module is used to construct a joint stiffness model of the terminal of the flexible hydraulic manipulator according to the kinematic information and flexibility information, calculate the stiffness of the terminal of the flexible hydraulic manipulator in the set posture according to the joint stiffness model of the terminal of the flexible hydraulic manipulator, and use the terminal stiffness ellipsoid to describe the flexible The stiffness of the end of the flexible hydraulic manipulator in each direction is calculated; the posture optimization module solves the inverse kinematics solution through a bidirectional search based on the posture optimization algorithm of the flexible hydraulic manipulator, solves the stiffness of each joint group of the posture corresponding to the inverse kinematics solution on the basis of deformation compensation of the flexible hydraulic manipulator, and sorts the stiffness of each joint group in order from large to small to obtain an optimized posture sequence; the virtual model construction module is used to establish a human-machine collaborative optimization mechanism based on the optimized posture sequence and the working environment image information, and construct a virtual model of the working status of different optimized postures in the working environment; the screening module is used to screen out the most reasonable working posture under the current working conditions based on the environmental information and stiffness information provided by the virtual model.

[0120] The terminal joint stiffness model construction module decouples the joint stiffness of the flexible hydraulic manipulator into hydraulic stiffness and arm stiffness according to the hydraulic flexibility characteristics and arm flexibility characteristics of the flexible hydraulic manipulator, calculates the hydraulic stiffness of each joint, the end deflection of each arm section, and the joint angle change value caused by hydraulic flexibility, calculates the joint arm stiffness according to the joint angle change value, calculates the joint stiffness of each joint according to the hydraulic stiffness of each joint and the arm stiffness of each joint, calculates the torque and lever arm of the terminal force at each joint, and constructs the terminal joint stiffness model of the flexible hydraulic manipulator according to the joint stiffness and lever arm of each joint.

[0121] The terminal joint stiffness model construction module includes a hydraulic stiffness calculation unit, which calculates the displacement of the hydraulic cylinder piston rod of each joint according to the joint angle information, calculates the equivalent stiffness of the hydraulic cylinder according to the displacement of the hydraulic piston rod of each joint, and calculates the hydraulic stiffness of each joint according to the equivalent stiffness of the hydraulic cylinder.

[0122] The terminal joint stiffness model construction module includes an arm terminal deflection calculation unit and a joint angle change calculation unit. The arm terminal deflection calculation unit is used to calculate the deflection of each arm terminal according to the end section rotation angle information of each joint hinge point and the arm terminal; the joint angle change calculation unit is used to map the terminal displacement change to the joint and calculate the joint angle change value of each arm due to the arm flexibility.

[0123] The posture optimization module includes a joint angle calculation unit, which pre-sets the initial ideal joint angle and the initial ideal end position; the ideal joint angle of the first joint is obtained by adding the set value to the initial ideal joint angle; the ideal joint angles of the corresponding second and third joints are calculated according to the inverse kinematics of the robot arm, and the obtained joint inverse solution must satisfy the ideal end position and the initial ideal end position. Among them, the set value is the search step size, and forward search and reverse search are performed according to the search step size. Two groups of joint angle solutions are obtained each time according to the inverse kinematics solution, and each group of joint angle solutions is recorded; the solution process is repeated until there is no solution in both the forward search and the reverse search, and all joint angle groups are obtained.

[0124] The posture optimization module includes a joint stiffness calculation unit, which substitutes all joint angle groups into the deformation compensation module to obtain the deformation compensation angle of each joint, and inputs the deformation compensation angle and the direction angle of the end force into the end joint stiffness model to obtain the stiffness of each joint group calculated by the end joint stiffness model.

[0125] 1. This invention provides a flexible arm posture optimization system based on a joint stiffness model. By leveraging the dual elasticity of the hydraulic chamber and the flexible arm rod, the system decouples joint stiffness into hydraulic stiffness and arm rod stiffness, modeling them separately. This system then constructs a joint stiffness model for the flexible hydraulic manipulator end. A stiffness ellipsoid index is introduced to characterize the individual stiffness characteristics of the end, enabling accurate representation of the stiffness of the flexible hydraulic arm end. To address the difficulty of autonomously optimizing stiffness under complex constraints, a collaborative optimization mechanism for flexible arm stiffness is constructed, combining automatic sorting of working postures with sequential selection by the operator.

[0126] 2. Flexible arm posture optimization method to improve end stiffness. The end joint stiffness model is completely derived from theory and does not require calibration of joint stiffness. Therefore, stiffness modeling can be performed quickly and safely. The end stiffness ellipsoid obtained by the stiffness model can describe the stiffness of the flexible arm end in various directions under a specific posture.

[0127] 3. A virtual model is also constructed based on the working environment image, which can provide operators with a more intuitive auxiliary reference under complex structural / environmental constraints, reducing the operator's subjectivity in judging the stiffness of the flexible arm end and the difficulty of operation under complex working conditions, and improving the end precision and operation safety of the flexible arm.

[0128] like Figure 6 As shown, another embodiment of the present invention provides a visual interactive system for optimizing the posture of a flexible arm based on a joint stiffness model, comprising: an input device, an information display, a control system, an information transmission device, and an execution device. The control system is the flexible arm posture optimization control system based on the joint stiffness model described in the second embodiment above, and the execution device includes a flexible hydraulic manipulator arm, an angle encoder, an inclination sensor, and a camera in an actual working scenario. The information transmission device is used to facilitate information exchange between the control system and the execution device.

[0129] The system workflow includes the following: For a large, flexible hydraulic manipulator with three degrees of freedom (DOF) in a planar configuration, the operator controls the end of the flexible hydraulic manipulator to reach the target point and then inputs a posture optimization command through an input device. The angle encoder measures the joint angle change caused by the hydraulic flexibility, and the tilt sensor measures the end cross-sectional rotation angle at the joint hinge and the end of the arm, which is then transmitted to the control system via an information transmission device for calculation of the end joint stiffness. Based on this, the flexible arm posture optimization algorithm solves the inverse kinematics solution through a bidirectional search. The inverse kinematics solution is then solved based on flexible arm deformation compensation, and the end stiffness of the postures corresponding to the inverse kinematics solution is sorted, thereby selecting a flexible arm posture sequence sorted by stiffness. The control system establishes a human-machine collaborative optimization mechanism based on the flexible arm posture sequence and the working environment image information captured by the camera, displaying a virtual model of the working state of different optimized postures in the working environment on the monitor.

[0130] like Figure 7 As shown, the control system generates a virtual model image of the flexible arm operating in the working environment with an optimized posture based on the working environment image information obtained by the camera and the flexible arm posture sequence. The operator can judge whether the optimized posture will have the risk of interference and collision with the surrounding environment based on the virtual model image, and then select the most reasonable working posture in the stiffness optimization posture sequence.

[0131] like Figure 8 As shown, the interactive interface rendering of the flexible arm posture optimization visualization interactive system based on the joint stiffness model is shown, where the right side shows the currently selected posture information and the optimized posture sequence, and the left side shows the virtual modeling screen of the selected posture and the working environment. The operator can intuitively feel the construction situation based on the virtual modeling screen, and then select the most reasonable working posture.

[0132] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method 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 in the scope of protection of the present invention.

Claims

1. A flexible arm posture optimization method based on a joint stiffness model, characterized in that: include: Obtain kinematic information, flexibility information, and working environment image information after the end of the flexible hydraulic manipulator reaches the target point; Based on the kinematic information and flexibility information, a joint stiffness model of the flexible hydraulic manipulator end is constructed. The stiffness of the flexible hydraulic manipulator end in a set position is calculated based on the joint stiffness model of the flexible hydraulic manipulator end. The stiffness of the flexible hydraulic manipulator end in each direction is described using the end stiffness ellipsoid. According to the flexible hydraulic manipulator posture optimization algorithm, the kinematic inverse solution is solved through bidirectional search. Based on the deformation compensation of the flexible hydraulic manipulator, the stiffness of each joint group corresponding to the posture of the inverse kinematic solution is solved, and the stiffness of each joint group is sorted in descending order to obtain the optimized posture sequence; A human-machine collaborative optimization mechanism is established based on the optimized posture sequence and working environment image information, and a virtual model of the working status of different optimized postures in the working environment is constructed; The most reasonable working posture under the current working conditions is selected based on the environmental information and stiffness information provided by the virtual model; The specific method for constructing a joint stiffness model of the flexible hydraulic manipulator end according to kinematic information and flexibility information includes: According to the hydraulic flexibility characteristics and arm flexibility features of the flexible hydraulic manipulator, the joint stiffness of the flexible hydraulic manipulator is decoupled into hydraulic stiffness and arm stiffness. Calculate the hydraulic stiffness of each joint, the deflection of each arm end, and the joint angle change caused by hydraulic flexibility; Calculate the joint arm stiffness based on the joint angle change value; Calculate the joint stiffness of each joint based on the hydraulic stiffness of each joint and the stiffness of each joint arm; Calculate the torque and lever arm of the end force at each joint; The joint stiffness model of the flexible hydraulic manipulator end is constructed according to the joint stiffness and lever arm of each joint.

2. The method according to claim 1, wherein The specific method for calculating the hydraulic stiffness of each joint includes: The kinematic information includes joint angle information, and the displacement of the piston rod of each joint hydraulic cylinder is calculated based on the joint angle information; Calculate the equivalent stiffness of the hydraulic cylinder based on the displacement of the hydraulic piston rod of each joint; The hydraulic stiffness of each joint is calculated based on the equivalent stiffness of the hydraulic cylinder.

3. The method according to claim 2, wherein The specific method for calculating the deflection of each arm end and the change in joint angle caused by hydraulic flexibility includes: Calculate the deflection of each arm end according to the end section rotation angle information at each joint hinge point and the arm end; The end displacement changes are mapped to the joints, and the joint angle changes of each arm due to the arm flexibility are calculated.

4. The method according to claim 3, wherein The specific method for solving the kinematic inverse solution through bidirectional search according to the flexible hydraulic manipulator posture optimization algorithm includes: Set the initial ideal joint angle and the initial ideal end position; The ideal joint angle of the first joint is obtained by adding the set value to the initial ideal joint angle; According to the inverse kinematics of the manipulator, the ideal joint angles of the corresponding second and third joints are calculated. The obtained joint inverse solution must satisfy the ideal end position and the initial ideal end position. The set value is the search step length. The forward search and reverse search are performed according to the search step length. Two sets of joint angle solutions are obtained each time according to the inverse kinematics solution, and each set of joint angle solutions is recorded. The solution process is repeated until both the forward search and the reverse search have no solutions, and all joint angle groups are obtained.

5. The method according to claim 4, wherein The specific methods for solving the stiffness of each joint group corresponding to the posture of the inverse kinematic solution based on the deformation compensation of the flexible hydraulic manipulator include: Substitute all joint angle groups into the deformation compensation module to obtain the deformation compensation angle of each joint, input the deformation compensation angle and the direction angle of the end force into the end joint stiffness model, and obtain the stiffness of each joint group calculated by the end joint stiffness model.

6. A flexible arm posture optimization control system based on a joint stiffness model, characterized in that: include: Data acquisition module, end joint stiffness model construction module, posture optimization module, virtual model construction module and screening module; The data acquisition module is used to obtain kinematic information, flexibility information and working environment image information after the end of the flexible hydraulic manipulator reaches the target point; The terminal joint stiffness model construction module is used to construct a terminal joint stiffness model of the flexible hydraulic manipulator according to kinematic information and flexibility information, calculate the stiffness of the flexible hydraulic manipulator terminal in a set posture according to the terminal joint stiffness model of the flexible hydraulic manipulator terminal, and use the terminal stiffness ellipsoid to describe the stiffness of the flexible hydraulic manipulator terminal in various directions; The posture optimization module solves the inverse kinematics solution through bidirectional search based on the posture optimization algorithm of the flexible hydraulic manipulator, solves the stiffness of each joint group corresponding to the posture of the inverse kinematics solution on the basis of deformation compensation of the flexible hydraulic manipulator, and sorts the stiffness of each joint group in descending order to obtain an optimized posture sequence; The virtual model building module is used to establish a human-machine collaborative optimization mechanism based on the optimized posture sequence and the working environment image information, and to build a virtual model of the working state of different optimized postures in the working environment; The screening module is used to screen out the most reasonable working posture under the current working conditions based on the environmental information and stiffness information provided by the virtual model; The terminal joint stiffness model construction module decouples the joint stiffness of the flexible hydraulic robotic arm into hydraulic stiffness and arm stiffness according to the hydraulic flexibility characteristics and arm flexibility characteristics of the flexible hydraulic robotic arm, calculates the hydraulic stiffness of each joint, the end deflection of each arm section, and the joint angle change value caused by hydraulic flexibility, calculates the joint arm stiffness according to the joint angle change value, calculates the joint stiffness of each joint according to the hydraulic stiffness of each joint and the joint arm stiffness of each joint, calculates the torque and lever arm of the terminal force at each joint, and constructs the terminal joint stiffness model of the flexible hydraulic robotic arm according to the joint stiffness and lever arm of each joint.

7. The system according to claim 6, wherein: The terminal joint stiffness model construction module includes a hydraulic stiffness calculation unit, which calculates the displacement of the hydraulic cylinder piston rod of each joint according to the joint angle information, calculates the equivalent stiffness of the hydraulic cylinder according to the displacement of the hydraulic piston rod of each joint, and calculates the hydraulic stiffness of each joint according to the equivalent stiffness of the hydraulic cylinder.

8. The system according to claim 7, wherein: The terminal joint stiffness model construction module includes an arm terminal deflection calculation unit and a joint angle change calculation unit. The arm terminal deflection calculation unit is used to calculate the deflection of each arm terminal according to the end section rotation angle information at each joint hinge point and the arm terminal; The joint angle change calculation unit is used to map the end displacement change to the joint and calculate the joint angle change value of each arm caused by the arm flexibility.

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