An apparatus and method for robotically automatic polishing of a blade tip radius

Abstract

The application discloses a kind of equipment and method for robot automatic polishing processing blade tip fillet, and polishing tool module is installed at the end of robot module, worktable module is installed in the work radius range that robot end can reach in robot module, workpiece and fixture module are installed on worktable module;Control computer receives the force signal of polishing force acquisition module and outputs control instruction to robot module after processing to realize constant force polishing to workpiece and workpiece in fixture module;Clamp in workpiece and fixture module is clamped to workpiece by pneumatic device module;Pneumatic device module is also connected to polishing tool module, for the clamping of polishing wheel.The present application can realize the fillet machining of the small radius arc of blade complex curved surface workpiece, the size of arc radius and surface quality are controllable, high efficiency can also guarantee the stability and consistency of the appearance of the fillet after processing, and provide a good solution for the automatic machining of the small radius arc of blade tip fillet.

Description

Technical Field

[0001] This invention relates to the field of industrial robot automated processing technology, specifically to a robot-automated grinding and processing equipment and method for the rounded corners of blade tips. Technical Background

[0002] Blades are core components of aero-engines. Due to their harsh operating environment, high surface accuracy and excellent surface quality must be ensured during manufacturing. The blade tip, the sharpest part at the blade's end, is particularly challenging to machine due to its small area and complex profile, especially the rounded corners with minute radii. While dedicated machine tools are primarily used for large-scale production of aero-engine blades, aero-engine blades are typically produced in small batches with diverse designs, making dedicated machine tools unsuitable. For this type of production, CNC machine tools are commonly used to improve processing quality and consistency. CNC machine tools require rigid contact grinding with a corner-forming bonded grinding head for rounded corners with minute radii. However, aero-engine blades are mostly made of highly ductile titanium alloys or high-temperature alloys. Using bonded grinding heads presents challenges in terms of processing accuracy, efficiency, and surface damage, and is also costly, making it unsuitable for rounded corners at aero-engine blade tips. Current processing methods still primarily rely on manual grinding, resulting in lower processing quality and efficiency, and poor consistency in corner size. Therefore, the development of new blade tip rounding grinding equipment and methods has important application value in the field of blade processing. Summary of the Invention

[0003] To address the problem that existing technologies, such as CNC machine tools and other formed rigid grinding tools, are not suitable for grinding the rounded corners of workpieces with a wide variety and small batches, this paper proposes an equipment and method for automatically grinding the rounded corners of blade tips using a robot. By automatically grinding the rounded corners of blade tips using a robot, a small radius arc of the blade tip that meets the processing quality requirements can be obtained, thereby improving processing accuracy and efficiency.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] This invention provides an automated robotic grinding system for machining the rounded corners of blade tips. The system includes a robot module, a grinding tool module, a workpiece and fixture module, a worktable module, a grinding force acquisition module, a control computer, and a pneumatic device module. The grinding tool module is mounted at the end of the robot module. The worktable module is installed within the working radius reachable by the robot's end effector. The workpiece and fixture module is mounted on the worktable module. The control computer receives and processes force signals from the grinding force acquisition module and outputs control commands to the robot module, which in real-time moves the grinding tool module to adjust the grinding force, achieving constant-force grinding of the workpiece in the workpiece and fixture module. The fixture in the workpiece and fixture module clamps the workpiece via the pneumatic device module, which is also connected to the grinding tool module for clamping the grinding wheel.

[0006] The grinding tool module includes a grinding wheel, which is connected to the spindle via a pneumatic chuck. The spindle is driven by an electric motor at the rear end and is mounted on a second flange via a spindle fixing clamp. The second flange is connected to a force sensor in the grinding force acquisition module. The other end of the force sensor is mounted on the robot end of the robot module via a first flange. The output signal line of the force sensor is connected to the control computer via a charge amplifier and acquisition card in the grinding force acquisition module.

[0007] The polishing tool is an elastic polishing wheel, which adopts a structure of overlapping circumferential layers of substrate, with abrasive particles coated on the surface of each substrate layer.

[0008] It also includes a calibration tool with a mounting sleeve and three positioning rods on one side of the mounting sleeve. The mounting sleeve is fitted onto the spindle fixing fixture. The axes of the three positioning rods are parallel to each other, and the lines connecting the points of the three positioning rods on the tangent plane perpendicular to the axis of the positioning rods form a right triangle. The three positioning points at the lower end of the positioning rods are used to determine the initial point, a point in the positive X-axis direction, and a point in the negative Y-axis direction, respectively.

[0009] This invention also provides a method for automatically grinding and processing the tip radius of blades using a robot, comprising the following steps:

[0010] 1) Calibrate the tool coordinate system of the grinding tool in the robot module, the workpiece coordinate system in the worktable module, and the force sensor coordinate system. Transform the three coordinate systems relative to the base coordinates of the robot module to achieve coordinate unification of the equipment system.

[0011] 2) Import the 3D model of the blade into the trajectory generation software, select the top surface of the blade tip, extract the right-angle vertex contour curve of the blade tip, and set the feed direction. Set the step size according to the magnitude of the curve curvature change, and discretize along the feed direction to obtain multiple discrete points;

[0012] 3) Read the coordinates of each discrete point, set the direction of the angle between the discrete point and the top surface as the normal direction, combine the feed setting direction, and generate and read the position coordinates and attitude angles of all discrete points according to the right-hand coordinate rule, and generate the trajectory coordinates of all discrete points (including position and attitude).

[0013] 4) According to the feed setting direction, the discrete data of the discrete points in the feed direction are converted into continuous data using the spline interpolation method, and the feed direction of the machining trajectory is smoothed.

[0014] 5) The pose control method of adjusting the tool coordinate system deflection angle by adjusting the trajectory between rows is used to achieve rounded corner centering and reduce interference when grinding the leaf basin and leaf back;

[0015] 6) Automatically generate a robot-recognizable trajectory code program from the smoothed and offset machining trajectory and add pre-guided code, then import the generated trajectory code program into the robot controller;

[0016] 7) Set the entry and exit methods. The entry and exit directions are based on the tangent direction of the right-angle vertex contour curve of the leaf tip. The initial point is set at the negative X-axis of the tool coordinate system, and the end point is set at the positive X-axis of the tool coordinate system, and the exit point is set at the positive X-axis of the tool coordinate system.

[0017] 8) Set process parameters, grind the right angle of the blade, and adjust and optimize the process parameters and processing trajectory based on the test results such as the morphology and fillet size after grinding;

[0018] 9) Select optimized grinding force, grinding speed, feed rate, grit size, tool coordinate deflection angle and other combined process parameters to grind the right angle of the blade tip, and process the right angle of the blade tip into a rounded corner with a small radius arc;

[0019] 10) Scan and measure the shape of the rounded corners of the processed blade tip to determine whether the radius of the rounded corners meets the processing quality requirements.

[0020] Step 1) includes the calibration of the grinding tool coordinate system and the workpiece coordinate system, which includes:

[0021] 101) The coordinate system calibration of the grinding tool is performed by determining the origin and direction of the coordinate system using the four-point method and the ABC two-point method respectively. When using the ABC two-point method for calibration, the calibration tool is used to determine the initial point, a point in the positive X-axis direction, and a point in the negative Y-axis direction, thereby completing the establishment of the tool coordinate system.

[0022] 102) The workpiece coordinate system is measured using an indirect method. Four positioning points on the worktable are selected, and the coordinate values ​​of these positioning points are input into the robot controller to calculate and form the workpiece coordinate system.

[0023] In step 5), the grinding wheel axis is deflected by 15 degrees around the tool coordinate system Y-axis, and the tool coordinate system Z-axis forms a 45-degree angle with the top surface of the blade tip, so as to achieve rounded corner centering and reduce interference during grinding of the blade basin and blade back.

[0024] Between steps 5 and 6, the process further includes: based on the diameter of the elastic grinding wheel and the fact that during the grinding process, while the elastic grinding wheel is feeding along the positive X direction of the tool coordinate system, it also shifts along the negative Z direction of the tool coordinate system. The shift distance is 80% of the axial length of the grinding wheel, so that the grinding line is spiral-shaped, increasing the contact length between the grinding wheel and the workpiece.

[0025] In step 7), a feed method with a set distance for cutting in and cutting out is adopted, and the feed direction and normal direction for grinding are selected, namely, the feed direction along the tangent of the right-angle contour line of the blade tip and the normal direction along the axis of the elastic grinding wheel.

[0026] Step 8) involves adjusting and optimizing the process parameters and machining trajectory, including:

[0027] 801) Adjustment and optimization of process parameters, including grinding force, grinding speed, feed rate, abrasive type, grit size, and tool coordinate deflection angle. Based on feedback of the radius of the fillet, different combinations of process parameters are selected for grinding to determine the optimal combination of process parameters.

[0028] 802) Adjustment and optimization of the processing trajectory: Adjust the deflection angle of the grinding wheel and increase the deflection angle of the grinding wheel axis along the Y-axis of the tool coordinate system to reduce interference to the blade basin and blade back during the grinding process.

[0029] The present invention has the following beneficial effects and advantages:

[0030] 1. The automated processing solution proposed in this invention can replace manual grinding operations, reducing labor intensity and grinding costs, and improving the accuracy and consistency of the radius of curvature of the blade tips (currently, blade tip curvature is manually ground). Furthermore, considering the deterministic contact characteristics of rigid molds formed by CNC machine tools, the processing method proposed in this invention avoids problems related to processing accuracy and surface damage, providing a reference for the automated processing of small-radius curvatures at the tips of various types of aerospace blades in small batches.

[0031] 2. This invention utilizes the compliant characteristics of multi-degree-of-freedom robots to automatically grind and process the right-angled vertex contour curve of the blade tip into a rounded corner, thereby reducing blade tip eddies and improving work efficiency. At the same time, this process is applicable to a variety of aerospace blade materials and types, and can be widely used in the field of aerospace blade processing and manufacturing.

[0032] 3. This invention uses a six-dimensional force / torque sensor to measure the grinding force in real time. Compared with one-dimensional and three-dimensional force sensors, the six-dimensional force sensor can provide more accurate force feedback information and detect the force and torque of the robot in three directions in real time. It can adaptively adjust the smoothness of the grinding process to adapt to the complexity and irregularity of the workpiece surface, improve the grinding efficiency, and reduce the workpiece damage rate.

[0033] 4. The elastic grinding wheel used in this invention will undergo adaptive envelope deformation during the grinding process. Due to the grinding force, the surface of the grinding wheel will undergo concave elastic deformation, and through its own deformation, it will adaptively envelope the right-angled surface of the blade tip. A tiny envelope surface will be formed between the right-angled surface and the grinding wheel, realizing "micro-surface contact cutting". This achieves the rounding of small-radius arcs. Compared with the poor dimensional accuracy stability and surface damage caused by traditional rigid tool processing or sandpaper grinding, the elastic deformation of the elastic grinding wheel can better adapt to the curvature changes of the blade, reduce surface damage, and thus improve processing accuracy and ensure the dimensional accuracy and shape accuracy stability requirements of the grinding process. At the same time, the elastic matrix material such as polyester fiber used in the elastic grinding wheel can better adapt to blade materials with different curvatures and hardness, such as titanium alloys and high-temperature alloys, thereby increasing the applicability of the grinding wheel.

[0034] 5. This invention employs offline trajectory generation software for trajectory planning and automatic generation. The robot will strictly follow the digital grinding and processing trajectory, working based on the 3D design model. This ensures accuracy while significantly improving the consistency of processing quality. Furthermore, the trajectory generation program can be modified and updated according to different types of blades to meet the changing needs of aerospace blade production. This flexibility and programmability better adapt to the changing demands of multi-variety, small-batch production, while improving production efficiency and applicability. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall structure of the equipment for automatically grinding and processing the blade tip radius of the present invention.

[0036] Figure 2 This is a schematic diagram of the blade structure in this invention;

[0037] Figure 3 This is a schematic diagram of the polishing tool module in this invention;

[0038] Figure 4 This is a schematic diagram of the elastic grinding wheel structure in this invention;

[0039] Figure 5 This is a schematic diagram showing the relative positions of the tool and the workpiece in this invention;

[0040] Figure 6This is a schematic diagram of the calibration tool structure in this invention;

[0041] Figure 7A This is a schematic diagram of the morphological changes of the leaf tip before polishing in this invention;

[0042] Figure 7B This is a schematic diagram illustrating the morphological changes of the leaf tip after grinding in this invention;

[0043] Figure 8A This is a schematic diagram (a) of the grinding offset of the elastic grinding wheel in this invention;

[0044] Figure 8B This is a schematic diagram (II) of the grinding offset of the elastic grinding wheel in this invention;

[0045] Figure 9 This is a schematic diagram of the system communication scheme in this invention;

[0046] Figure 10 This is a schematic diagram of the grinding process in this invention.

[0047] Among them, 1 is the robot module, 2 is the grinding tool module, 21 is the electric motor, 22 is the spindle fixing fixture, 23 is the spindle, 24 is the pneumatic chuck, 25 is the grinding wheel, 26 is the force sensor, 27 is the first flange, 28 is the second flange, 3 is the workpiece and fixture module, 31 is the blade tip, 32 is the right-angle vertex contour curve of the blade tip, 33 is the top surface of the blade tip, 4 is the worktable module, 5 is the control computer, 6 is the pneumatic device module, 7 is the calibration tool, 71 is the first positioning rod, 72 is the second positioning rod, 73 is the third positioning rod, and 74 is the mounting sleeve. Detailed Implementation

[0048] The present invention will now be further described with reference to the accompanying drawings.

[0049] This invention provides equipment for automatically grinding and machining the rounded corners of blade tips using a robot. It achieves automated grinding and machining of blade tip rounded corners using an industrial robot as the base. Figure 1As shown. This equipment includes a robot module 1, a grinding tool module 2, a workpiece and fixture module 3, a worktable module 4, a grinding force acquisition module, a control computer 5, and a pneumatic device module 6. The grinding tool module 2 is installed at the end of the robot module 1, the worktable module 4 is installed within the working radius reachable by the end of the robot in the robot module 1, and the workpiece and fixture module 3 is installed on the worktable module 4. The control computer 5 receives the force signal from the grinding force acquisition module, processes it, and outputs control commands to the robot module 1, which drives the grinding tool module 2 to move in real time to adjust the grinding force, so as to achieve constant force grinding of the workpiece in the workpiece and fixture module 3. The fixture in the workpiece and fixture module 3 clamps the workpiece through the pneumatic device module 6. The pneumatic device module 6 is also connected to the grinding tool module 2 to realize the opening and closing of the pneumatic chuck (24) for clamping the grinding wheel (25).

[0050] The grinding force acquisition module includes a force sensor 26, a charge amplifier, and a data acquisition card. The force sensor 26 acquires the grinding force, and the acquired force data is transmitted from the charge amplifier to the signal input terminal of the control computer via the data acquisition card. The force control software running on the control computer controls the actual grinding force according to the grinding force setting value, and the control computer outputs the data to the robot module 1 for compensation and adjustment of the robot's movement. The grinding force acquisition module is existing technology.

[0051] Blade morphology and polished areas, such as Figure 2 As shown.

[0052] like Figure 3 As shown, the grinding tool module 2 includes a grinding wheel 25, which is connected to the spindle 23 via a pneumatic chuck 24. The spindle 23 is mounted on a second flange 28 via a rear-end electric motor 21 and a spindle fixing clamp 22. The second flange 28 is connected to a force sensor 26. The other end of the force sensor 26 is mounted on the robot end of the robot module 1 via a first flange 27. The output signal line of the force sensor 26 is connected to the control computer via a charge amplifier and a data acquisition card in the grinding force acquisition module.

[0053] Grinding wheel 25 is an elastic grinding wheel, which adopts a layered substrate structure with circumferentially stacked layers. Abrasive particles are coated on the surface of each substrate layer. Figure 4As shown. The equipment of this invention also includes an electric motor 21, a cooling system, a pneumatic device module 6, and a motor speed control system (i.e., the speed of the electric motor is controlled by a control computer via a PLC). Since the spindle 23 is connected to the second flange 28 via the spindle fixing clamp 22, and the second flange 28 is equipped with a force sensor 26, which is connected to the robot end effector via the first flange 27, the grinding force can be measured in real time during the grinding process. The cooling system uses water cooling and includes components such as a water pump, radiator, water pipes, and water tank installed on the periphery. The water pump draws coolant from the water tank and delivers it to the electric motor 21 via water pipes (the electric motor 21 has a cooling circulating water inlet interface, which the water pipes directly connect to). When the coolant flows through the electric motor, it absorbs the heat generated by the electric motor and flows back to the radiator. In the radiator, the coolant dissipates heat into the surrounding air through the radiator fins. Afterward, the coolant flows back to the water tank and is recycled to maintain the stable temperature of the electric motor.

[0054] like Figure 6 As shown, the equipment of the present invention also includes a calibration tool, having a mounting sleeve 74 and first to third positioning rods 71 ​​to 73 disposed on one side of the mounting sleeve 74. The mounting sleeve 74 is fitted onto the spindle fixing fixture 22. The axes of the three positioning rods are parallel to each other, and the line connecting the points of the three positioning rods on the tangent plane perpendicular to the axis of the positioning rods forms a right triangle. The three positioning points at the lower end of the positioning rods are used to determine the initial point, a point in the positive X-axis direction, and a point in the negative Y-axis direction, respectively. The Z-direction is determined according to the right-hand coordinate rule.

[0055] In this embodiment, robot module 1 uses a KUKA robot. The KUKA robot tool coordinate system calibration using the ABC two-point method is as follows: select two points A and B in the tool coordinate system at the robot end effector, then move the robot end effector to align point A of the tool with a known marker point; then move the robot end effector to another position and align point B of the tool with the known marker point; by measuring the attitude and displacement of the robot end effector at the two positions, the position and orientation of the two points in the robot end effector flange coordinate system relative to the tool coordinate system can be calculated; finally, the position and orientation of the tool coordinate system are calculated based on these data.

[0056] In the equipment of this invention, the control communication scheme includes: communication between the control computer and the robot controller, and communication between the control computer and the force sensor. The working threads are as follows: Figure 9As shown, communication between the control computer and the robot is achieved via Ethernet, using the TCP / IP communication protocol for data transmission. During the robot's automatic grinding process, the control computer transmits control command data to the robot controller via Ethernet using standard network protocols, sending commands to the robot such as start, stop, and move commands. It can also receive the robot's status information, such as position, speed, and attitude. The spindle 23 is driven by an electric motor 21, with the electrical control cabinet providing the power source. The rotational speed is controlled by a motor controller, which is connected to the control computer via a PLC for communication and control.

[0057] To control the robot in completing the blade grinding task, this invention employs a standard TCP / IP communication protocol to transmit the planned processing trajectory from the trajectory generation software to the robot controller. Communication is conducted via data stream, with output in XML format to ensure data transmission security and stability. Data collected by force sensor 26 is connected to the control computer via Modbus communication protocol, allowing real-time reading of the grinding force measured by force sensor 26. The control computer 5 adjusts the robot's movement based on the set and measured grinding force values, regulating the normal grinding force between the grinding wheel and the blade tip 31 to achieve constant force grinding.

[0058] This invention also discloses a method for automatically grinding and processing the tip radius of blades using a robot, comprising the following steps:

[0059] 1) Calibrate the tool coordinate system of the grinding tool in the robot module, the workpiece coordinate system in the worktable module, and the force sensor coordinate system. Transform the three coordinate systems relative to the base coordinates of the robot module to achieve coordinate unification of the equipment system.

[0060] In this embodiment, the calibration of the grinding tool and workpiece coordinate system includes:

[0061] 101) The tool coordinate system calibration is performed by determining the origin and direction of the coordinate system using the four-point method (existing technology) and the ABC two-point method respectively. When using the ABC two-point method for calibration, the calibration tool is used to determine the initial point, a point in the positive X-axis direction, and a point in the negative Y-axis direction, thereby completing the establishment of the tool coordinate system.

[0062] In the method of this invention, the workpiece coordinate system is calibrated indirectly by establishing the workpiece coordinate system on the blade tip. First, four positioning points on the worktable in the 3D model of the assembly are selected in the 3D modeling software, and the coordinate values ​​of these four positioning points in the workpiece coordinate system are recorded. Then, the tool tip of the calibrated reference tool coordinate system is used to sequentially approach the corresponding feature points on the workpiece, and the corresponding coordinate values ​​in the 3D model are input into the robot teach pendant. After completing the above operations, the robot controller establishes the transformation of the workpiece coordinate system relative to the robot base coordinate system, thus completing the calibration of the workpiece coordinate system.

[0063] In this embodiment, the tool coordinate system is calibrated using both the four-point method and the ABC two-point method. The four-point method is used to determine the origin of the tool coordinate system, while the ABC two-point method is used to determine the coordinate direction.

[0064] When calibrating the origin of the coordinate system using the four-point method, the grinding wheel axis is aligned with a fixed point on the worktable in four different orientations. The calibrated grinding wheel axis position is the origin of the tool coordinate system.

[0065] The ABC two-point method is used to determine the direction of the coordinate system. Figure 6 The calibration tool is calibrated as follows: First, the calibration tool is nested in the spindle fixture 22 and fixed. Through teaching, the tip of the first positioning rod 71 is aligned with the tip of the fixed clamp on the worktable, and the current position coordinates are recorded. The robot moves the tip of the second positioning rod 72 to the tip of the fixed clamp on the worktable, and the position coordinates are recorded. The direction of movement from the first positioning rod 71 to the second positioning rod 72 is the negative X direction of the tool coordinate system. Then, the tip of the third positioning rod 73 is aligned with the tip of the fixed clamp on the worktable, and the position coordinates are recorded. The direction of movement from the second positioning rod 72 to the third positioning rod 73 is the positive Y direction of the tool coordinate system. Using the right-hand rule, the Z direction of the tool coordinate system is perpendicular to the XY plane.

[0066] 102) The workpiece coordinate system is measured using an indirect method. Four positioning points on the worktable are selected, and the coordinate values ​​of these positioning points are input into the robot controller to calculate and form the workpiece coordinate system.

[0067] Workpiece coordinate system calibration process: First, calibrate the cusp of a reference tool coordinate system to obtain the coordinates of the cusp in the reference tool coordinate system; then, align this point with the four fixed points on the workpiece in sequence to determine the coordinates of the four points in the workpiece coordinate system; since the relative positional relationship of other points in the workpiece coordinate system is determined, the coordinates of all points in the entire workpiece coordinate system can be obtained.

[0068] 2) Import the 3D model of the blade into trajectory generation software (existing technology), select the top surface of the blade tip, extract the contour curve of the right-angle vertex of the blade tip, set the feed direction, and set the step size according to the curvature change of the curve to discretize along the feed direction to obtain multiple discrete points.

[0069] In this embodiment, the selected axis directions are the feed direction X+ and the normal direction Z+. The trajectory is discretized along the feed direction with a step size determined by the magnitude of the curve curvature change. The coordinates of each discrete point are read, and the direction forming a 45-degree angle between this discrete point and the top surface is set as the normal direction. Combined with the feed direction setting, and based on the right-hand rule, the position coordinates and attitude angles of all discrete points are generated and read, thus generating the trajectory coordinates of all discrete points.

[0070] 3) Read the coordinate position of each discrete point, set the direction of the angle between the discrete point and the top surface (45 degrees in this machining) as the normal direction, combine the feed setting direction, and generate and read the position coordinates and attitude angles of all discrete points according to the right-hand coordinate rule, and generate the trajectory coordinates of all discrete points (including position and attitude).

[0071] 4) According to the feed setting direction, the discrete data of the discrete points in the feed direction are converted into continuous data using the spline interpolation method, and the feed direction of the machining trajectory is smoothed.

[0072] 5) The pose control method of adjusting the tool coordinate system deflection angle by adjusting the trajectory between rows is used to achieve rounded corner centering and reduce interference when grinding the leaf basin and leaf back;

[0073] In this embodiment, the grinding wheel axis is deflected by 15 degrees around the Y-axis of the tool coordinate system, and the Z-axis of the tool coordinate system forms a 45-degree angle with the top surface of the blade tip, thereby achieving rounded corner centering and reducing interference during grinding of the blade base and blade back.

[0074] 6) Automatically generate a robot-recognizable trajectory code program from the smoothed and offset machining trajectory and add pre-guided code, then import the generated trajectory code program into the robot controller;

[0075] In this embodiment, between steps 5 and 6), the method further includes: based on the diameter of the elastic grinding wheel and the fact that during the grinding process, while the elastic grinding wheel is feeding along the positive X direction of the tool coordinate system, it also offsets along the negative Z direction of the tool coordinate system, with the offset direction as follows: Figures 8A-8B As shown. The offset distance is 80% of the axial length of the grinding wheel, making the grinding line spiral, increasing the contact length between the grinding wheel and the workpiece, and improving the service life of the grinding wheel;

[0076] 7) Set the entry and exit methods. The entry and exit directions are based on the tangent direction of the right-angle vertex contour curve of the blade tip. The initial point is set at the negative X-axis of the tool coordinate system, and the end point is set at the positive X-axis of the tool coordinate system, and the exit point is set at the positive X-axis of the tool coordinate system.

[0077] In this embodiment, the trajectory planned in the trajectory generation software is converted into trajectory program code that the robot can recognize, and pre-guidance code is added. The program code is then imported into the robot controller. A feed method with a set distance for entry and exit is adopted. The entry and exit directions are based on the tangent direction of the blade tip right-angle vertex contour curve. The feed direction and normal direction for grinding are selected as follows: the feed direction is along the tangent direction of the blade tip right-angle vertex contour curve, and the normal direction is along the axis of the elastic grinding wheel.

[0078] 8) Set process parameters, grind the right angle of the blade, and adjust and optimize the process parameters and processing trajectory based on the test results such as the morphology and fillet size after grinding;

[0079] 801) Adjustments and optimizations include:

[0080] The process parameters are adjusted and optimized, including grinding force, grinding speed, feed rate, abrasive type, grit size, and tool coordinate deflection angle. After grinding, different combinations of process parameters are selected according to the radius of the fillet to perform grinding processing, and the optimal combination of process parameters is determined (adjustment and optimization mainly include the combination of the magnitudes of various process parameters, which belongs to the optimization of manufacturing process parameters).

[0081] 802) Adjustment and optimization of the processing trajectory: Adjusting the deflection angle of the grinding wheel and increasing the deflection angle of the grinding wheel axis along the Y-axis of the tool coordinate system can reduce interference to the blade basin and blade back during the grinding process. However, an excessively large deflection angle will affect the surface quality and morphology of the rounded corners after grinding.

[0082] 9) Select optimized grinding force, grinding speed, feed rate, grit size, tool coordinate deflection angle and other combined process parameters to grind the right angle of the blade tip, and process the right angle of the blade tip into a rounded corner with a small radius arc;

[0083] During the processing, the grinding tool is driven by a robot and begins grinding according to the generated processing trajectory at the set entry angle. The robot's movement is measured in real time by a force sensor and controlled and adjusted by a computer. The robot's processing trajectory error is compensated and adjusted in real time to ensure that the grinding wheel and the blade tip processing normal direction maintain a constant grinding force during the grinding process, so as to achieve the consistency of the blade tip radius after processing.

[0084] After completing one round of grinding, the robot moves the grinding tool to cut out a pre-set distance and returns to the initial point, ready for the next round of grinding. It's important to note that due to wear on the grinding wheel, after a certain interval of grinding, the grinding wheel should be fed a distance equal to the wear amount along the negative Y-axis of the tool coordinate system. In the robot trajectory control program, a loop statement is written using the robot controller to control the robot to shift the planned grinding trajectory by the amount of grinding wheel wear along the negative Y-axis of the tool coordinate system at regular intervals, thus ensuring consistent processing quality.

[0085] 10) Scan and measure the shape of the rounded corners of the processed blade tip to determine whether the radius of the rounded corners meets the processing quality requirements.

[0086] This invention employs a robotic method for automatically grinding the rounded corners of blade tips. Based on a three-dimensional model of the blade, the top surface 33 of the blade tip is marked. The right-angled vertex contour curves (two right-angled vertex contour curves 32 formed by the intersection of the top surface 33 of the blade tip with the leaf base and the back of the blade) are extracted. The extracted contour curves are discretized according to step size requirements, and then smoothed, deflected, offset, and cut-in / cut-out processes are performed to generate a grinding trajectory for the right-angled vertex contour curves of the blade tip. A trajectory code program recognizable by the robot is generated according to the robot operating system control program requirements. The generated trajectory code program is imported into the robot controller, which then controls the robot to drive the grinding tool to perform grinding according to the processing trajectory, completing the automatic grinding of the blade tip rounded corners.

[0087] In the processing method provided by this invention, the relative positions of the grinding wheel 25 and the blade are as follows: Figure 5 As shown. To ensure the blade tip has a rounded shape after grinding, a 45-degree angle must be maintained between the blade tip's top surface and the machining tool's axis during processing. To prevent the elastic grinding wheel from interfering with the blade base and back due to elastic deformation during processing, the axis of the elastic grinding wheel should be deflected by 15 degrees along the Y-axis of the tool coordinate system. Simultaneously, the deflection angle between the grinding wheel and the workpiece should be kept constant during processing. Since the right-angled vertex contour curve of the blade tip is a complex curve, pose control should be used in the trajectory generation software to ensure the grinding wheel adjusts accordingly to the contour curve during processing.

[0088] The method of this invention involves six coordinate systems: the robot base coordinate system is the coordinate system where the robot module is located, the robot flange coordinate system is the coordinate system of the robot end effector flange, the reference tool coordinate system is used to calibrate the workpiece coordinate system, the tool coordinate system is the coordinate system where the grinding wheel is located, the workpiece coordinate system is the coordinate system where the blade is located, and the sensor coordinate system is the coordinate system where the force / torque sensor is located.

[0089] In the processing method proposed in this invention, the normal grinding force is controlled by constant force. The force sensor 26 is installed between the grinding tool module 2 and the end effector of the robot through the first and second flanges 27 and 28. The coordinate direction of the force sensor is in the same direction as the coordinate direction of the robot flange. Before the force sensor 26 measures the grinding force, the grinding tool module 2 needs to be gravity compensated to eliminate the influence of the weight of the grinding tool module 2 itself, so as to ensure that its measured value is the grinding force between the grinding wheel 25 and the workpiece.

[0090] This invention uses a grinding wheel with a polyester fiber elastic material matrix for grinding. During processing, the elastic deformation of the grinding wheel creates varying contact stress in the right-angle region of the blade tip, resulting in different material removal amounts and transforming the right angle into a rounded corner. During grinding, the wheel undergoes adaptive envelope deformation of the right-angle surface at the blade tip, forming a tiny envelope between the right-angle surface and the grinding wheel, achieving "micro-surface contact cutting." The contact stress in the contact area of ​​the blade tip exhibits a Hertzian contact stress distribution. Simultaneously, due to the compression of the elastic matrix, the number of abrasive grains participating in the grinding per unit time increases. Therefore, the material removal is greatest at the center of the contact area, decreasing gradually along both sides, resulting in a rounded morphology after processing. Figures 7A-7B As shown.

[0091] This invention achieves automatic grinding of right-angled blade tips into rounded corners through equipment system coordinate system calibration and unification, blade tip top surface marking in a 3D model, extraction and discretization of the blade tip right-angle contour curve, trajectory coordinate frame generation, trajectory smoothing and offsetting, trajectory generation and adjustment, trajectory code generation, process parameter combination optimization, blade tip right-angle grinding, and rounded corner morphology detection. By utilizing the elastic envelope deformation of the elastic grinding wheel during processing to achieve "micro-surface contact cutting," a Hertzian contact stress distribution is formed, transforming the blade tip right angle into a rounded corner with a small radius arc. This method enables the rounded corner processing of small-radius arcs on complex curved surfaces like blades, with controllable arc radius and surface quality. It is highly efficient while ensuring the stability and consistency of the rounded corner morphology after processing, providing an excellent solution for the automated processing of small-radius arc rounded corners on blade tips.

Claims

1. A method for automatically grinding and machining the tip radius of a blade using a robot, comprising the following steps: 1) Calibrate the tool coordinate system of the grinding tool in the robot module, the workpiece coordinate system in the worktable module, and the force sensor coordinate system. Transform the three coordinate systems relative to the base coordinates of the robot module to achieve coordinate unification of the equipment system. 2) Import the 3D model of the blade into the trajectory generation software, select the top surface of the blade tip, extract the contour curve of the right-angle vertex of the blade tip, and set the feed direction; set the step size according to the curvature change of the curve, and discretize along the feed direction to obtain multiple discrete points; 3) Read the coordinates of each discrete point, set the direction of the angle between the discrete point and the top surface as the normal direction, combine the feed setting direction, and generate and read the position coordinates and attitude angles of all discrete points according to the right-hand coordinate rule, and generate the trajectory coordinates of all discrete points. 4) According to the feed setting direction, the discrete data of the discrete points in the feed direction are converted into continuous data using the spline interpolation method, and the feed direction of the machining trajectory is smoothed. 5) The pose control method of adjusting the tool coordinate system deflection angle by adjusting the trajectory between rows is used to achieve rounded corner centering and reduce interference when grinding the leaf basin and leaf back; 6) Automatically generate a robot-recognizable trajectory code program from the smoothed and offset machining trajectory and add pre-guided code, then import the generated trajectory code program into the robot controller; 7) Set the entry and exit methods. The entry and exit directions are based on the tangent direction of the right-angle vertex contour curve of the blade tip. The initial point is set at the negative X-axis of the tool coordinate system, and the end point is set at the positive X-axis of the tool coordinate system, and the exit point is set at the positive X-axis of the tool coordinate system. 8) Set process parameters, grind the right angle of the blade, and adjust and optimize the process parameters and processing trajectory based on the morphology and fillet size test results after grinding; 9) Select the optimized combination of grinding force, grinding speed, feed rate, grit size, and tool coordinate deflection angle to grind the right angle of the blade tip, and process the right angle of the blade tip into a rounded corner with a small radius arc; 10) Scan and measure the shape of the rounded corners of the processed blade tip to determine whether the radius of the rounded corners meets the processing quality requirements.

2. The method for automatically grinding and machining the blade tip radius using a robot according to claim 1, characterized in that... Step 1) includes the calibration of the grinding tool coordinate system and the workpiece coordinate system, which includes: 101) The coordinate system calibration of the grinding tool is performed by determining the origin and direction of the coordinate system using the four-point method and the ABC two-point method respectively. When using the ABC two-point method for calibration, the calibration tool is used to determine the initial point, a point in the positive X-axis direction, and a point in the negative Y-axis direction, thereby completing the establishment of the tool coordinate system. 102) The workpiece coordinate system is measured using an indirect method. Four positioning points on the worktable are selected, and the coordinate values ​​of these positioning points are input into the robot controller to calculate and form the workpiece coordinate system.

3. The method for automatically grinding and machining the blade tip radius using a robot according to claim 1, characterized in that... In step 5), the grinding wheel axis is deflected by 15 degrees around the Y-axis of the tool coordinate system, and the Z-axis of the tool coordinate system forms a 45-degree angle with the top surface of the blade tip, so as to achieve rounded corner centering and reduce interference during grinding of the blade basin and blade back.

4. The method for automatically grinding and machining the blade tip radius using a robot according to claim 1, characterized in that... Between steps 5 and 6, the process further includes: based on the diameter of the elastic grinding wheel and the fact that during the grinding process, while the elastic grinding wheel is feeding along the positive X direction of the tool coordinate system, it also shifts along the negative Z direction of the tool coordinate system. The shift distance is 80% of the axial length of the grinding wheel, so that the grinding line is spiral-shaped, increasing the contact length between the grinding wheel and the workpiece.

5. The method for automatically grinding and machining the blade tip radius using a robot according to claim 1, characterized in that... In step 7), a feed method with a set distance for cutting in and cutting out is adopted, and the feed direction and normal direction for grinding are selected, namely, the feed direction along the tangent direction of the right-angle contour line of the blade tip and the normal direction along the axis of the elastic grinding wheel.

6. The method for automatically grinding and machining the blade tip radius using a robot according to claim 1, characterized in that... Step 8) involves adjusting and optimizing the process parameters and machining trajectory, including: 801) Adjustment and optimization of process parameters, including grinding force, grinding speed, feed rate, abrasive type, grit size, and tool coordinate deflection angle. Based on feedback of the radius of the fillet, different combinations of process parameters are selected for grinding to determine the optimal combination of process parameters. 802) Adjustment and optimization of the processing trajectory: Adjust the deflection angle of the grinding wheel and increase the deflection angle of the grinding wheel axis along the Y-axis of the tool coordinate system to reduce interference to the blade basin and blade back during the grinding process.

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