Parallel platform flexible assembly system for low vortex shaft

Abstract

The application discloses a parallel platform flexible assembly system for a low vortex shaft, which comprises a low vortex shaft auxiliary assembly device and an intelligent assembly platform, the low vortex shaft auxiliary assembly device is used for the movement of a low vortex shaft part, and the intelligent assembly platform is used for the fixation of a cabin section part; wherein the intelligent assembly platform realizes the flexible pose adjustment of the low vortex shaft during assembly; the low vortex shaft axis is aligned with the engine cabin section axis through a laser tracker; the low vortex shaft auxiliary assembly comprises a base, the base is provided with a base rotating shaft in the horizontal direction, the base rotating shaft is used for realizing the rotation of the whole base in the horizontal direction, the base is provided with a low vortex shaft lifting shaft in the vertical direction, and the low vortex shaft lifting shaft is used for realizing the vertical lifting of a lifting arm; the lifting arm is installed on the low vortex shaft lifting shaft; the end of the lifting arm is a parallel platform, the parallel platform is provided with a six-dimensional force sensor and a gripper, the gripper is provided with a low vortex shaft tooling, and the pose of the low vortex shaft tooling is controlled through the sensor and the gripper.

Description

TECHNICAL FIELD

[0001] The application discloses a parallel platform flexible assembly system for a low vortex shaft and relates to the fields of engine assembly and parallel platform compliance control. BACKGROUND

[0002] With the rapid development of society, the mechanical manufacturing industry is constantly progressing, and manufacturing technology is constantly innovating. In the manufacturing process of an aero-engine, the assembly link is an indispensable part, involving all assembly and disassembly from parts, accessories, assemblies, unit bodies, main unit bodies to the whole machine. The traditional engine low vortex shaft assembly usually adopts a manual mode, a crane is used to hoist the low vortex shaft, and multiple operators hold the low vortex shaft to assemble it. The whole process requires the operators to have rich experience and skills, and if there is a slight mistake, the product may be damaged, and in severe cases, the operators may be injured or hurt, etc. On the other hand, the crane only plays an auxiliary supporting role and cannot guarantee the precision of the spline fit. The whole assembly process lacks a safe, high-precision and efficient method. SUMMARY

[0003] The application proposes a parallel platform automatic compliant assembly method for engine low vortex shaft assembly, which can make the assembly process more flexible, efficient and accurate by compliant control of the parallel platform, and changes the traditional manual assembly into automatic assembly.

[0004] To achieve the above purpose, the technical scheme adopted by the application is as follows:

[0005] A parallel platform flexible assembly system for a low vortex shaft, the system comprising: a low vortex shaft auxiliary assembly device and an intelligent assembly platform, the low vortex shaft auxiliary assembly device being used for the movement of the low vortex shaft part, and the intelligent assembly platform being used for the fixation of the cabin section part; wherein,

[0006] The intelligent assembly platform comprises a cabin section tool seat, the cabin section tool seat being provided with a cabin section lifting shaft, the cabin section lifting shaft being provided with a cabin section tool arm, the cabin section tool arm being vertically movable on the cabin section lifting shaft, and the cabin section tool arm being provided with a cabin section tool clamping part;

[0007] The low vortex shaft auxiliary assembly device comprises a clamping and pose adjusting unit, a compliant force control unit and a calibration unit, the clamping and pose adjusting unit being used for all movements except force control in the assembly process; the compliant force control unit being used for the force control movement of the system, and realizing the flexible pose adjustment of the low vortex shaft in assembly by taking the contact force as the input of the impedance control algorithm in the PLC; and the calibration unit realizing the alignment of the low vortex shaft axis and the engine cabin section axis through a laser tracker;

[0008] The low vortex shaft auxiliary assembly comprises a base, the base is provided with a base rotating shaft in the horizontal direction, the base rotating shaft is used for realizing rotation of the whole base in the horizontal direction, the base is provided with a low vortex shaft lifting shaft in the vertical direction, and the low vortex shaft lifting shaft is used for realizing vertical lifting of the boom; the boom is mounted on the low vortex shaft lifting shaft; the end of the boom is a parallel platform, the parallel platform is provided with a six-dimensional force sensor and a gripper, a low vortex shaft tool is mounted on the gripper, and the position and posture of the low vortex shaft tool are controlled through the sensor and the gripper.

[0009] Further, the clamping and posture adjusting unit comprises a posture adjusting mechanical arm, a cabin section gripper and cabin section rotating motors connected in sequence, five cabin section rotating motors are arranged in the clamping and posture adjusting unit, and are respectively used for realizing lifting of the posture adjusting mechanical arm, rotation of the posture adjusting mechanical arm, translation of the posture adjusting mechanical arm, opening and closing of the gripper and axial rotation of the low vortex shaft, and the low vortex shaft is assembled with the splines and spline grooves on the cabin section through axial rotation.

[0010] Further, the calibration unit is provided with target balls mounted on the cabin section tool and the upper surface of the low vortex shaft respectively, the spatial positions of the target balls are tracked through a laser tracker, so that the relative coordinate system relationship of the low vortex shaft and the cabin section is obtained, a fine displacement angle is output, and the parallel platform is guided to move.

[0011] Further, the compliant force control unit is provided with a PLC, a six-dimensional force sensor and a parallel platform, the PLC takes contact force as input, realizes flexible posture adjustment of the low vortex shaft in assembly through an impedance control algorithm, takes the force value fed back by the six-dimensional force sensor as input, and takes the displacement value of the parallel platform as output.

[0012] As a preferred embodiment of the application, the parallel platform is a parallel robot, a composite motion device composed of six motors, and is electrically connected with the PLC to realize motion of the low vortex shaft in six directions of X, Y, Z, RX, RY and RZ.

[0013] The parallel platform flexible assembly method for the low vortex shaft provided by the embodiment of the application mainly has the following beneficial effects:

[0014] The precision of the parallel platform can reach 0.05 mm, and the precision can be ensured through force control; only one person is needed to control automatic process start and stop, only assembly data needs to be monitored, and the worker does not need to follow the product all the time; the worker does not need to enter the assembly area, and the safety is improved. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0016] Figure 1 This is a flowchart illustrating the coordinate system establishment process in the embodiment.

[0017] Figure 2 A schematic diagram of the rotation center calibration method;

[0018] Figure 3 This is a schematic diagram of the coordinate system;

[0019] Figure 4 Schematic diagram of laser tracker adjustment principle;

[0020] Figure 5 This is a schematic diagram of the hole-shaft mating process;

[0021] Figure 6 Schematic diagram of auxiliary assembly equipment for low-voltage turbine shafts;

[0022] Figure 7 This is a schematic diagram of an intelligent assembly platform;

[0023] Figure 8 This is a schematic diagram of the overall layout of the parallel platform flexible assembly system for low-turbine shafts in this application.

[0024] Figure 9 System topology diagram;

[0025] Figure 10 A cross-sectional view showing the keyway assembly process;

[0026] Figure 11 Diagram of the compliant control model;

[0027] Figure 12 This is a flowchart of the laser tracker's workflow. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention. Other embodiments obtained by those skilled in the art based on the present invention without creative effort are all within the protection scope of the present invention.

[0029] Example 1

[0030] Figure 1 This invention provides a flexible assembly system for a parallel platform oriented towards low-power turboshafts. The system includes: low-power turboshaft auxiliary assembly equipment and an intelligent assembly platform. The low-power turboshaft auxiliary assembly equipment is used for moving the low-power turboshaft section, and the intelligent assembly platform is used for fixing the compartment section.

[0031] The intelligent assembly platform comprises a cabin section tool seat, wherein a cabin section lifting shaft is arranged on the cabin section tool seat, and a cabin section tool arm is arranged on the cabin section lifting shaft; the cabin section tool arm is vertically movable on the cabin section lifting shaft, and the cabin section tool arm is provided with a cabin section tool clamping part;

[0032] The low-vortex shaft auxiliary assembly device comprises a clamping and pose adjusting unit, a compliant force control unit and a calibration unit; the clamping and pose adjusting unit is used for all movements except force control in the assembly process; the compliant force control unit is used for force control movement of the system, and the compliant force control unit realizes flexible pose adjustment of the low-vortex shaft in assembly through an impedance control algorithm in the PLC with contact force as input; and the calibration unit realizes alignment of the low-vortex shaft axis and the engine cabin section axis through a laser tracker.

[0033] The low-vortex shaft auxiliary assembly device comprises a base, wherein a base rotating shaft is arranged on the base in the horizontal direction, the base rotating shaft is used to realize rotation of the whole base in the horizontal direction, and a low-vortex shaft lifting shaft is arranged on the base in the vertical direction, the low-vortex shaft lifting shaft is used to realize vertical lifting of a lifting arm; the lifting arm is mounted on the low-vortex shaft lifting shaft; the end of the lifting arm is a parallel platform, and the parallel platform is provided with a six-dimensional force sensor and a gripper, the gripper is provided with a low-vortex shaft tool, and the pose of the low-vortex shaft tool is controlled through the sensor and the gripper.

[0034] Further, the clamping and pose adjusting unit comprises a pose adjusting mechanical arm, a cabin section gripper and cabin section rotating motors connected in sequence, five cabin section rotating motors are arranged in the clamping and pose adjusting unit, and the five cabin section rotating motors are respectively used to realize lifting of the pose adjusting mechanical arm, rotation of the pose adjusting mechanical arm, translation of the pose adjusting mechanical arm, opening and closing of the gripper and axial rotation of the low-vortex shaft, and the low-vortex shaft realizes assembly with the spline and spline groove on the cabin section through axial rotation.

[0035] Further, the calibration unit is provided with target balls arranged on the surfaces of the cabin section tool and the low-vortex shaft respectively, the spatial positions of the target balls are tracked through a laser tracker, so that the relative coordinate system relationship between the low-vortex shaft and the cabin section is obtained, a fine adjustment displacement angle is output, and the parallel platform is guided to move.

[0036] Further, the compliant force control unit is provided with a PLC, a six-dimensional force sensor and a parallel platform, the PLC takes contact force as input, realizes flexible pose adjustment of the low-vortex shaft in assembly through an impedance control algorithm, takes the force value fed back by the six-dimensional force sensor as input, and takes the displacement value of the parallel platform as output.

[0037] As a preferred embodiment of the application, the parallel platform is a parallel robot, which is a composite motion device composed of six motors, and is electrically connected with the PLC to realize movement of the low-vortex shaft in six directions of X, Y, Z, RX, RY and RZ.

[0038] In order to ensure the reliability and accuracy of the whole automatic process, the difficulties of the whole process are analyzed and solved. The difficulties mainly exist in the alignment of the axis and the spline fit, which can be solved by using the laser tracker, six-dimensional force sensor and parallel platform.

[0039] The specific process of the low-turbine shaft and the engine bay section docking will be introduced below:

[0040] 1. Coordinate system calibration

[0041] The laser tracker can measure the three-dimensional coordinates of the target ball in space, with an accuracy of 0.03 mm. In three-dimensional space, a space coordinate system can be determined by the spatial coordinates of three points. Assuming that the three-dimensional coordinates of three target balls (point O, point A, point B) have been measured, the specific steps to establish the coordinate system are as follows:

[0042] 1) Take point O as the origin of the coordinate system;

[0043] 2) Make a ray from point O to point A, as the positive direction of the X-axis of the coordinate system;

[0044] 3) Make a ray from point O to point B, and the plane formed by the intersection as the XY plane of the coordinate system;

[0045] 4) Take point B as a point on the positive direction of the Y-axis of the coordinate system, and make a ray perpendicular to as the positive direction of the Y-axis of the coordinate system;

[0046] 5) Determine the Z-axis of the coordinate system by the right-hand rule.

[0047] Figure 1 The schematic diagram for determining the coordinate system.

[0048] Install three fixed target seats on the low-turbine shaft tooling and the bay section tooling, respectively, which can be detected by the laser tracker within the calibration range and not on a straight line.

[0049] A precise reference target is needed for calibration, so first use the jog mode to move the mechanical arm and move the low-turbine shaft directly above the bay section and make a part of the low-turbine shaft extend into the hole. Due to the characteristics of the equipment, it can be assumed that the low-turbine shaft radial rotation center and the end rotating motor rotation shaft coincide.

[0050] In order to ensure product safety and avoid collision between the low-turbine shaft and the bay section, use the micrometer to measure. Fix the micrometer on the upper surface of the bay section, the probe contacts the low-turbine shaft, slowly move the end rotating motor, and adjust the parallel platform according to the micrometer reading until the micrometer reading does not fluctuate significantly when rotating, such asFigure 2 As shown.

[0051] Return the rotary motor to the zero position, and move the robotic arm vertically upward to create a distance between the bottom of the low-pressure turbine shaft and the top of the compartment. Use this position as the reference point.

[0052] At the reference position, a laser tracker is used to measure the target point, which is denoted as A on the low-profile worm gear tool. D B D O D The section tooling is marked as A. C B C O C Based on the coordinate system establishment method, establish the low-vortex axis coordinate system {D} and the compartment coordinate system {C}.

[0053] A parallel platform coordinate system and a TCP coordinate system are established using a laser tracker, during which the laser tracker tracks O in real time. D :

[0054] 1) Move the parallel platform a certain distance in the positive X-axis direction, and measure the position after it comes to rest. Record this position as O. DX ;

[0055] 2) Move the parallel platform a certain distance in the positive Y-axis direction, and measure the position after it comes to rest. Record this position as O. DY ;

[0056] 3) The parallel platform returns to the reference position, causing the end rotary motor to move. After rotating a certain angle, record the position at that point. Repeat n (≥2) times, and record it as O. D1 O Dn ;

[0057] 4) Utilizing O D O D1 O Dn Create a spatial circle I, with the center of circle I as the origin. As the X-axis Establish the gripper coordinate system {J} with the Y-axis as the Y-axis;

[0058] 5) Fix the target seat at the end of the low-level vortex shaft and measure it, denoted as E. Calculate the distance from point E to circle I, denoted as L1. After removing the target seat thickness δ1 and the target ball thickness δ2, obtain the length L2 of the end of the low-level vortex shaft (=L1-δ1-δ2). Translate L2 with the positive direction of the Z-axis of the parallel platform coordinate system as the direction of movement to obtain the TCP coordinate system {H};

[0059] 6) Adjust the attitude of the parallel platform and measure the target position and the value of the six-dimensional force sensor when it is stationary. Repeat this process m (≥3) times, and record the points as E1, ..., E m The force values ​​are denoted as F1, ..., F m(1x3 matrix), and the torque values are denoted as T1, T2, and T3. m (1x3 matrix). The E, E1, E2, and E3 are used to denote the position values of the four joints of the parallel platform. m A space ball Q is established, and the origin of the jaw coordinate system {J} is translated to the center of the ball Q to establish the parallel platform coordinate system {P}.

[0060] The relationship between the coordinate systems is shown in the following figure. Figure 3

[0061] The parallel platform motion coordinate system is converted from {P} to the TCP coordinate system {H}, which ensures that the amplitude of the low vortex shaft bottom is not large when the parallel platform rotates, and avoids collision when inside the cabin section.

[0062] 2. Axis alignment

[0063] During formal assembly, due to gear clearance and other reasons, there will be a certain error in the axis of the cabin section, so it is necessary to correct it according to the actual measurement results. When the low vortex shaft reaches the reference position, a laser tracker is used to establish the measurement coordinate systems of the low vortex shaft and the cabin section, denoted as {D'} and {C'}, and the homogeneous transformation matrix between them is denoted as (4x4 matrix). According to the calibration results, the homogeneous transformation matrix between the low vortex shaft coordinate system {D} and the cabin coordinate system {C} can be obtained That is,

[0064]

[0065]

[0066] If {D'} and {D} are considered as the same coordinate system, then we can get:

[0067]

[0068] After sorting, we get:

[0069]

[0070] Convert to pose adjustment, i.e. the parallel platform pose adjustment amount, Figure 4 is the adjustment principle diagram.

[0071] 2.3 spline cooperation

[0072] Due to the special shape of the spline, a specific angle is needed to realize the cooperation of the spline and the keyway. Assuming that there are 60 teeth on the spline, a maximum axial rotation of ±3° is needed to realize the alignment of the spline and the keyway. Therefore, during assembly, the motor needs to be rotated to find the appropriate angle.

[0073] ​On the other hand, since the low-profile turbine shaft needs to be assembled at the bottom of the compartment, the observation space is narrow and it is impossible to determine the completion of the keyway mating by visual means. Therefore, in order to ensure the safety of the assembly, a six-dimensional force sensor installed at the end is used to control the parallel platform with impedance to monitor and control the assembly force.

[0074] Impedance control is a type of compliant control. This method simulates the end of the parallel platform as a mass-spring-damped system, and its control law is:

[0075]

[0076] Where M, B, and K represent mass (inertia), damping, and stiffness, respectively, and the subscript d indicates the desired value of the system, f e This indicates the force applied to the end of the parallel platform, and the parameters are calibrated according to the actual environment.

[0077] Impedance control uses external contact force as input, therefore it requires identification of the external force. A six-dimensional force sensor can measure force and torque in three directions, and its components are as follows:

[0078]

[0079]

[0080] Where F and T are the measured values ​​from the six-dimensional force sensor, and G and T are the measured values ​​from the force sensor. g The force and torque exerted by the load gravity on the six-dimensional force sensor are represented by F0 and T0, respectively, where F0 and T0 are the zero points of the six-dimensional force sensor. w T w This represents the forces and torques acting on the six-dimensional force sensor. Gravity compensation is performed using the least squares method, utilizing F1, ..., F... m and T1, ..., T m By performing calculations, we can obtain G and T. g Given F0 and T0, the external force can be obtained using the following formula:

[0081] F w =FG-F0;

[0082] T w =TT g -T0.

[0083] Based on the impedance control of the parallel platform by external force, if a keyway misfit occurs when the parallel platform moves downwards, F wz It will increase, at this time maintain the contact force and use the rotary motor to rotate the low vortex shaft, when monitoring F wz When the speed decreases, the keyway fit is considered complete, and rotation stops. Simultaneously, impedance control is adjusted according to T. wz Rotating Parallel Platform Rz , avoid the too large fitting moment between the tooth groove.

[0084] On the other hand, the spline itself has a certain height, and if the low vortex shaft and the spline groove axis deviation is too large, it will appear to be blocked, and in serious cases it will cause product damage, such as Figure 5 (a) shown. In order to ensure that the contact force between the shaft hole is stable within a certain range during this process, monitor F wx , F wy , T wx , T wy , respectively control the X, Y, R x , R y in the TCP coordinate system {H} movement, so that the parallel platform can automatically adjust the position of the shaft according to the end force, as shown in Figure 5 (b) shown.

[0085] It can be listed by comparison, such as, the previous processing speed is seconds, and after using the patent, it is milliseconds.

[0086]

[0087] The above examples only illustrate the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the present application.

Claims

1. A low-vortex axial oriented parallel platform flexible assembly system, characterized in that, The system comprises: A low vortex shaft auxiliary assembly device for movement of a low vortex shaft part and an intelligent assembly platform for fixation of a cabin section part; wherein The intelligent assembly platform comprises a cabin section tool seat, the cabin section tool seat being provided with a cabin section lifting shaft, the cabin section lifting shaft being provided with a cabin section tool arm, the cabin section tool arm being vertically movable on the cabin section lifting shaft, and the cabin section tool arm being provided with a cabin section tool clamping part; The low vortex shaft auxiliary assembly device comprises a clamping and pose adjusting unit, a compliant force control unit and a calibration unit, the clamping and pose adjusting unit being used for all movements except force control in the assembly process, the compliant force control unit being used for force control movement of the system, and the calibration unit being used for alignment of the low vortex shaft axis and the engine cabin section axis through a laser tracker; The low vortex shaft auxiliary assembly comprises a base, the base being provided with a base rotating shaft in the horizontal direction, the base rotating shaft being used for rotation of the whole base in the horizontal direction, the base being provided with a low vortex shaft lifting shaft in the vertical direction, the low vortex shaft lifting shaft being used for vertical lifting of a lifting arm, the lifting arm being mounted on the low vortex shaft lifting shaft, the lifting arm being provided with a parallel platform at the end, the parallel platform being provided with a six-dimensional force sensor and a clamping jaw, the clamping jaw being provided with a low vortex shaft tool, the pose of the low vortex shaft tool being controlled through the sensor and the clamping jaw, the clamping and pose adjusting unit comprising a pose adjusting mechanical arm, a cabin section clamping jaw and a cabin section rotating motor connected in sequence, the clamping and pose adjusting unit being provided with five cabin section rotating motors, respectively used for realizing lifting of the pose adjusting mechanical arm, rotation of the pose adjusting mechanical arm, translation of the pose adjusting mechanical arm, opening and closing of the clamping jaw and axial rotation of the low vortex shaft, and the low vortex shaft being assembled with a spline and a spline groove on the cabin section through axial rotation; The compliant force control unit is provided with a PLC, a six-dimensional force sensor and a parallel platform, the PLC taking contact force as input, realizing flexible pose adjustment of the low vortex shaft in assembly through an impedance control algorithm, taking the force value fed back by the six-dimensional force sensor as input and taking the displacement value of the parallel platform as output.

2. The low vortex shaft oriented parallel kinematic platform flexible assembly system of claim 1, wherein, The calibration unit is provided with target balls mounted on the cabin section tool and the surface of the low vortex shaft, respectively, and the spatial positions of the target balls are tracked through a laser tracker, so as to obtain the relative coordinate system relationship of the low vortex shaft and the cabin section, output a fine adjustment displacement angle and guide movement of the parallel platform.

3. The low vortex shaft oriented parallel kinematic platform flexible assembly system of claim 1, wherein, The parallel platform is a parallel robot, which is a composite motion device composed of six motors and is electrically connected with the PLC to realize movement of the low vortex shaft in six directions of X, Y, Z, RX, RY and RZ.

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