Flexible arm attitude optimization method based on joint stiffness model and control system

Abstract

The invention discloses a flexible arm attitude optimization method based on a joint rigidity model, which comprises the following steps: constructing a flexible arm tail end joint rigidity model, calculating the rigidity of the tail end of a flexible arm at a set pose according to the tail end joint rigidity model, and describing the rigidity of the tail end of the flexible arm in each direction by adopting a tail end rigidity ellipsoid; according to a posture optimization algorithm, solving an inverse kinematics solution through bidirectional search, solving the rigidity of each joint group of a posture corresponding to the inverse kinematics solution on the basis of deformation compensation of the mechanical arm, and sorting the rigidity of each joint group according to a sequence from large to small to obtain an optimized posture sequence; establishing a man-machine collaborative optimization mechanism according to the optimized attitude sequence and the working environment image information, and constructing a virtual model of working states of different optimized attitudes in the working environment; and screening out the most reasonable operation attitude under the current working condition according to the environment information and the rigidity information. Accurate expression of the rigidity of the tail end of the flexible hydraulic mechanical arm is achieved, and visual auxiliary reference can be provided for operators in a complex environment.

Description

Technical Field

[0001] The 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 a control system based on a joint stiffness model. Background Art

[0002] Large flexible hydraulic manipulators are important operating equipment in the fields of construction, rescue, and military due to their heavy load and large operating radius. However, the oil compression in the hydraulic power system and the accumulated end deflection of the super-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, the flexible hydraulic arm with redundant degrees of freedom is often in a complex and unstructured working environment. Its posture is difficult to fully consider and thus be selected according to the best. The risk of collision with the surrounding environment is high, which increases the difficulty and safety risk of the operator's operation 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 view of the defects in the prior art, 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 mechanical 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] The joint stiffness model of the flexible hydraulic manipulator end is constructed according to the kinematic information and flexibility information. The stiffness of the flexible hydraulic manipulator end in the set position is calculated according to the joint stiffness model of the flexible hydraulic manipulator end. The stiffness of the flexible hydraulic manipulator end in each direction is described by the end stiffness ellipsoid.

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

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

[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 end of the flexible hydraulic manipulator 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 change in joint angle caused by hydraulic flexibility;

[0013] The stiffness of the joint arm is calculated according to the change value of the joint angle;

[0014] The joint stiffness of each joint is calculated based on the hydraulic stiffness of each joint and the arm stiffness of each joint;

[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 according to 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] Calculate the hydraulic stiffness of each joint based on the equivalent stiffness of the hydraulic cylinder.

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

[0022] According to the end section rotation angle information of each joint hinge point and the end of the arm, calculate the end deflection of each section of the arm;

[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 of solving the kinematic inverse solution through bidirectional search according to 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 robot arm, 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 end ideal 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 solution, 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 terminal force into the terminal joint stiffness model, and obtain the stiffness of each joint group by calculating the terminal 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 acquire kinematic information, flexibility information and working environment image information after the end of the flexible hydraulic mechanical arm 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 mechanical arm according to kinematic information and flexibility information, calculate the stiffness of the terminal of the flexible hydraulic mechanical arm in a set posture according to the terminal joint stiffness model of the flexible hydraulic mechanical arm, and use the terminal stiffness ellipsoid to describe the stiffness of the terminal of the flexible hydraulic mechanical arm in various directions;

[0034] The posture optimization module solves the kinematic inverse solution through bidirectional search according to the posture optimization algorithm of the flexible hydraulic manipulator, solves the stiffness of each joint group corresponding to the posture of the kinematic inverse 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 according to 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 according to 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 building 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 end section rotation angle information of each joint hinge point and 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. A flexible arm posture optimization method based on a joint stiffness model is provided in an embodiment of the present invention. According to the dual elastic effect of the hydraulic chamber and the flexible arm of the flexible hydraulic mechanical arm, the joint stiffness is decoupled into two parts, namely, hydraulic stiffness and arm stiffness, and the two parts are modeled separately, thereby constructing a joint stiffness model of the end of the flexible hydraulic mechanical arm, and introducing a stiffness ellipsoid index to characterize the various stiffness characteristics of the end, so as to achieve an accurate expression of the stiffness of the end of the flexible hydraulic arm. In view of the difficulty of autonomously optimizing stiffness under complex constraints, a flexible arm stiffness collaborative optimization mechanism is constructed with automatic sorting of working postures and sequential screening by operators.

[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, reduce the subjectivity of operators in judging the stiffness of the end of the flexible arm and the difficulty of operation under complex working conditions, and improve the end accuracy of the flexible arm and operational safety.

[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, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual 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 end of a flexible hydraulic manipulator 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;

[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 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 is shown. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

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

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

[0058] like Figure 1 As shown, a flexible arm posture optimization method based on a joint stiffness model provided by a first embodiment of the present invention is shown, 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] The joint stiffness model of the flexible hydraulic manipulator end is constructed according to the kinematic information and flexibility information. The stiffness of the flexible hydraulic manipulator end in the set position is calculated according to the joint stiffness model of the flexible hydraulic manipulator end. The stiffness of the flexible hydraulic manipulator end in each direction is described by the end stiffness ellipsoid.

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

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

[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 embodiment, firstly, a joint stiffness model of the end of the flexible hydraulic mechanical arm is established for the hydraulic elastic characteristics and the elastic characteristics of the long arm, and a stiffness ellipsoid is introduced to characterize the stiffness characteristics of the end in all directions, which can accurately express the stiffness of the end of the flexible hydraulic mechanical arm. Then, a flexible arm posture optimization algorithm is used to improve the end operation stiffness. In addition, a human-machine collaborative optimization mechanism for the operation stiffness of the flexible arm is established, and a virtual model of the operation status of different postures in the working environment is constructed. The most reasonable operation posture under the current working condition is selected according to the environmental information and stiffness information provided by the virtual model, 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 command, 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, the specific method for constructing the joint stiffness model of the end of the flexible hydraulic manipulator according to the kinematic information and the 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 imaxis the maximum displacement of the hydraulic cylinder piston rod corresponding to the i-th joint, V ai is the volume of the rodless cavity, V bi is the volume of the rod cavity, V L1 is the pipe volume of the rodless cavity, V L2 is the pipe volume of the rod cavity. The first joint angle α corresponds to the displacement s of the hydraulic cylinder piston rod. 1 , the second joint angle β and the corresponding hydraulic cylinder piston rod displacement s 2 And the third joint angle γ and the corresponding hydraulic cylinder piston rod displacement s 3 The mathematical relationship between them is shown in formula (3), formula (4) and formula (5) respectively:

[0072]

[0073] In formula (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 section of the 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 section of the arm and the base point of the mechanical arm in the y direction, l 1 is the total length of the hydraulic cylinder, l 10 is the piston rod displacement s 1 =The length of the hydraulic cylinder when 0.

[0074]

[0075] In formula (4), dj is the distance between the hinge points on each robot arm, l 2 is the total length of the hydraulic cylinder, l 20 is the piston rod displacement s 2 =The length of the hydraulic cylinder when 0.

[0076]

[0077] In formula (5), kt is the distance between the hinge points on each robot arm, l 3 is the total length of the hydraulic cylinder, l 30 is the piston rod displacement s 3 =The length of the hydraulic cylinder when 0.

[0078] Assume that the angle of the i-th joint is θ i When the torque τ i Under the action of hi , the corresponding hydraulic cylinder changes in joint angle by Δθ hi Output force F hci for:

[0079] F hci =Khci ·Δs i (6)

[0080] In formula (6), Δs i is Δθ hi The 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 equation (6) and equation (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 of 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 iL is the arm length involved in the arm flexibility calculation, i is the overall length of the i-th boom, L i0 is the length from the hydraulic cylinder driving point to the joint hinge point of the i-th arm, E i is the elastic modulus of the i-th arm material, 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 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] Due to 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 on each joint forms a torque expression as follows:

[0099]

[0100] In formula (16), τ i is the torque formed 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, and the calculation formula is:

[0101]

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

[0103] According to the definition of stiffness, combining 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. Formula (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 stiffness ellipsoid. It is completely derived from theory without the need for joint stiffness calibration, so it can quickly and safely model stiffness. The end stiffness ellipsoid can be used to describe the stiffness of the flexible hydraulic manipulator in all directions under a specific posture.

[0106] A flexible arm posture optimization method based on a joint stiffness model provided by an 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 end of the flexible hydraulic manipulator 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. After setting the direction parameter θ F After that, the optimized posture can be obtained through the model. Figure 3 As shown, 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 position of the end is P 0 =[x 0 ,y 0 ] T ;

[0110] b. Change the ideal joint angle of the first joint to q 11 =q i0 ±Δq 1 , 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 P 1 =f(q 11 ,q 21 ,q 31 )=P 0 . Where Δq 1 is the search step length, when q 11 =q i0 +Δq 1 When q 11 =q i0 -Δq 1 When , it is recorded as reverse search. According to the inverse kinematics solution, no matter 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. Use the bubble sort algorithm to sort the stiffness of each joint group from large to small, so that the stiffness of the flexible hydraulic manipulator at the fixed operating point θ can be obtained. F Directional stiffness in various postures from large to small.

[0114] like Figure 4 As shown in FIG. 1 , 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 end of the flexible hydraulic arm. Therefore, applying this method to the flexible hydraulic arm can improve the positioning accuracy and anti-interference ability of the end of the flexible hydraulic arm.

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

[0116] 1. The present invention provides a flexible arm posture optimization method based on a joint stiffness model. According to the dual elastic effect of the hydraulic chamber of the flexible hydraulic arm and the flexible arm rod, the joint stiffness is decoupled into two parts, hydraulic stiffness and arm rod stiffness, and the models are separated, so as to construct a joint stiffness model of the end of the flexible hydraulic mechanical arm, and introduce a stiffness ellipsoid index to characterize the various stiffness characteristics of the end, so as to achieve an accurate expression of the stiffness of the end of the flexible hydraulic arm. In view of the difficulty of autonomously optimizing stiffness under complex constraints, a flexible arm stiffness collaborative optimization mechanism is constructed with automatic sorting of working postures and sequential screening by operators.

[0117] 2. Flexible arm posture optimization method to improve terminal stiffness. The terminal 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 terminal stiffness ellipsoid obtained by the stiffness model can describe the stiffness of the flexible arm terminal 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, reduce the subjectivity of operators in judging the stiffness of the end of the flexible arm and the difficulty of operation under complex working conditions, and improve the end accuracy and operation safety of the flexible arm.

[0119] like Figure 5As shown, a flexible arm posture optimization control system based on a joint stiffness model is provided in the second embodiment of the present invention, 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; the data acquisition module is used to obtain kinematic information, flexibility information and working environment image information of the terminal of the flexible hydraulic mechanical arm after the terminal reaches the target point; the terminal joint stiffness model construction module is used to construct a terminal joint stiffness model of the flexible hydraulic mechanical arm according to the kinematic information and flexibility information, calculate the stiffness of the terminal of the flexible hydraulic mechanical arm in a set posture according to the terminal joint stiffness model of the flexible hydraulic mechanical arm, and use the terminal stiffness ellipsoid to describe the flexible The stiffness of the end of the flexible hydraulic manipulator in each direction; the posture optimization module solves the inverse kinematics solution through a two-way search according to 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 the optimized posture sequence; the virtual model construction module is used to establish a human-machine collaborative optimization mechanism according to 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 according to 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 end deflection of each arm according to the end section rotation angle information of each joint hinge and the end of the arm; 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 flexibility of the arm.

[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 corresponding ideal joint angles of the 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 length, and forward search and reverse search are performed according to the search step length. 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 terminal force into the terminal joint stiffness model to obtain the stiffness of each joint group by calculating the terminal joint stiffness model.

[0125] 1. The flexible arm posture optimization system based on the joint stiffness model provided by the present invention decouples the joint stiffness into two parts, namely, hydraulic stiffness and arm stiffness, and models them separately according to the dual elastic effect of the hydraulic chamber of the flexible hydraulic arm and the flexible arm rod, thereby constructing a joint stiffness model of the flexible hydraulic mechanical arm end, and introducing a stiffness ellipsoid index to characterize the various stiffness characteristics of the end, so as to achieve an accurate expression of the stiffness of the flexible hydraulic arm end. In view of the difficulty of autonomously optimizing stiffness under complex constraints, a flexible arm stiffness collaborative optimization mechanism with automatic sorting of working postures and sequential screening by operators is constructed.

[0126] 2. Flexible arm posture optimization method to improve terminal stiffness. The terminal 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 terminal stiffness ellipsoid obtained by the stiffness model can describe the stiffness of the flexible arm terminal 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, reduce the subjectivity of operators in judging the stiffness of the end of the flexible arm and the difficulty of operation under complex working conditions, and improve the end accuracy and operation safety of the flexible arm.

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

[0129] The system workflow includes: for a large flexible hydraulic manipulator with three degrees of freedom in the plane, after the operator controls the end of the flexible hydraulic manipulator to reach the target point, the operator inputs the posture optimization command through the input device, and the angle encoder measures the joint angle change information caused by the hydraulic flexibility and the end section rotation angle information at the joint hinge and the end of the arm measured by the inclination sensor. The information is transmitted to the control system through the information transmission device for the calculation of the end joint stiffness. The flexible arm posture optimization algorithm based on this solves the kinematic inverse solution through a two-way search, and sorts the end stiffness of the corresponding posture of the kinematic inverse solution based on the deformation compensation of the flexible arm, so as to select the 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 obtained by the camera, and displays the virtual model screen of the working status of different optimized postures in the working environment on the display.

[0130] like Figure 7 As shown, the control system generates a virtual model screen 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 screen, 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; The joint stiffness model of the flexible hydraulic manipulator end is constructed according to the kinematic information and flexibility information. The stiffness of the flexible hydraulic manipulator end in the set position is calculated according to the joint stiffness model of the flexible hydraulic manipulator end. The stiffness of the flexible hydraulic manipulator end in each direction is described by the end stiffness ellipsoid. According to the flexible hydraulic manipulator posture optimization algorithm, the kinematic inverse solution is solved through bidirectional search. On the basis of the deformation compensation of the flexible hydraulic manipulator, the stiffness of each joint group corresponding to the posture of the kinematic inverse solution is solved, and the stiffness of each joint group is sorted in descending order to obtain the optimized posture sequence. Establish a human-machine collaborative optimization mechanism based on the optimized posture sequence and working environment image information, and construct a virtual model of the working status of different optimized postures in the working environment; 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.

2. The method according to claim 1, characterized in that The specific method for constructing the joint stiffness model of the end of the flexible hydraulic mechanical arm according to the kinematic information and the 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 change in joint angle caused by hydraulic flexibility; The stiffness of the joint arm is calculated according to the change value of the joint angle; The joint stiffness of each joint is calculated based on the hydraulic stiffness of each joint and the arm stiffness of each joint; 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.

3. The method according to claim 2, characterized in that 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 according to the joint angle information; Calculate the equivalent stiffness of the hydraulic cylinder based on the displacement of the hydraulic piston rod of each joint; Calculate the hydraulic stiffness of each joint based on the equivalent stiffness of the hydraulic cylinder.

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

5. The method according to claim 4, characterized in that 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 robot arm, 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 end ideal 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 solution, and all joint angle groups are obtained.

6. The method according to claim 5, characterized in that 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 terminal force into the terminal joint stiffness model, and obtain the stiffness of each joint group by calculating the terminal joint stiffness model.

7. A flexible arm posture optimization control system based on a joint stiffness model, characterized in that: include: Data acquisition module, terminal joint stiffness model building module, posture optimization module, virtual model building module and screening module; The data acquisition module is used to acquire kinematic information, flexibility information and working environment image information after the end of the flexible hydraulic mechanical arm reaches the target point; The terminal joint stiffness model construction module is used to construct a terminal joint stiffness model of the flexible hydraulic mechanical arm according to kinematic information and flexibility information, calculate the stiffness of the terminal of the flexible hydraulic mechanical arm in a set posture according to the terminal joint stiffness model of the flexible hydraulic mechanical arm, and use the terminal stiffness ellipsoid to describe the stiffness of the terminal of the flexible hydraulic mechanical arm in various directions; The posture optimization module solves the kinematic inverse solution through bidirectional search according to the posture optimization algorithm of the flexible hydraulic manipulator, solves the stiffness of each joint group corresponding to the posture of the kinematic inverse 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 according to 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 according to the environmental information and stiffness information provided by the virtual model.

8. The system according to claim 7, characterized in that The terminal joint stiffness model construction module decouples the joint stiffness of the flexible hydraulic mechanical arm into hydraulic stiffness and arm stiffness according to the hydraulic flexibility characteristics and arm flexibility characteristics of the flexible hydraulic mechanical 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 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 mechanical arm according to the joint stiffness and lever arm of each joint.

9. The system according to claim 8, characterized in that The terminal joint stiffness model building 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.

10. The system according to claim 9, characterized in that The terminal joint stiffness model building 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 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 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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