阅读说明：本技术 一种用于机器人打磨铸件的刀具末端轨迹自适应方法 (Tool tail end track self-adaption method for robot casting polishing ) 是由 吴震宇 曹令亚 于 2021-01-22 设计创作，主要内容包括：本发明涉及机加工技术领域,尤其涉及一种用于机器人打磨铸件的刀具末端轨迹自适应方法,其包括：利用3D传感器对铸件进行扫描,计算铸件在机器人的基坐标系中的工件坐标系,补偿铸件误差；选择压力式柔性顺从打磨工具总成的工作模式,工作模式包括刚性模式和柔性模式；基于选择的工作模式,驱动安装于主轴上的刀具旋转并沿打磨轨迹移动,以对铸件进行刚性切割或柔性打磨；切换压力式柔性顺从打磨工具总成的工作模式,完成铸件打磨。采用上述技术方案能够满足切割和打磨刀具末端轨迹自适应的需要,简化机器人示教编程要求,降低工装和夹具要求,保证打磨效果和机器人打磨设备的安全性,提高了机器人打磨设备混线兼容能力。(The invention relates to the technical field of machining, in particular to a tool tail end track self-adaption method for polishing castings by a robot, which comprises the following steps: scanning the casting by using a 3D sensor, calculating a workpiece coordinate system of the casting in a base coordinate system of the robot, and compensating for casting errors; selecting a mode of operation for the pressure-type compliant sanding tool assembly, the mode of operation including a rigid mode and a compliant mode; based on the selected working mode, driving a cutter arranged on the main shaft to rotate and move along the grinding track so as to perform rigid cutting or flexible grinding on the casting; and switching the working mode of the pressure type flexible compliance grinding tool assembly to finish casting grinding. By adopting the technical scheme, the self-adaptive requirements of the tail end track of the cutting and polishing cutter can be met, the teaching programming requirements of the robot are simplified, the requirements of the tool and the fixture are reduced, the polishing effect and the safety of the robot polishing equipment are ensured, and the wire mixing compatibility of the robot polishing equipment is improved.)

1. A tool tip trajectory adaptive method for robotic polishing of castings, comprising:

scanning the reference casting to generate a first workpiece coordinate system of the reference casting, and storing the spatial position of the reference casting in the first workpiece coordinate system;

generating a polishing track of a reference casting according to the first workpiece coordinate system;

replacing the reference casting with a casting to be polished, and scanning the casting to be polished to generate a second workpiece coordinate system of the casting to be polished;

updating the spatial position of the reference casting according to the first workpiece coordinate system and the second workpiece coordinate system, and taking the updated spatial position as the spatial position of the casting to be polished to obtain a polishing track with updated coordinates;

selecting a working mode of a pressure type flexible compliant grinding tool assembly of the robot, wherein the working mode comprises a rigid mode and a flexible mode;

Based on the selected working mode, the cutter arranged on the main shaft is driven to rotate and move along the grinding track of the casting to be ground so as to carry out rigid cutting or flexible grinding on the casting to be ground and finish the grinding of the casting to be ground.

2. The tool tip trajectory adaptive method for robotic sanding of castings according to claim 1, wherein scanning the reference casting to generate a first workpiece coordinate system of the reference casting and saving a spatial location of the reference casting within the first workpiece coordinate system comprises:

calibrating by a robot hand and eye to obtain a coordinate transformation matrix;

acquiring point cloud data of a reference casting, and acquiring a first position coordinate of the robot;

and establishing a workpiece coordinate system of the reference casting according to the point cloud data of the reference casting, and converting the workpiece coordinate system of the reference casting to a base coordinate system of the robot according to the coordinate transformation matrix and the first pose coordinate of the robot to obtain a first workpiece coordinate system.

3. The tool tip trajectory adaptive method for robotic grinding of castings according to claim 2, wherein scanning the casting to be ground to generate a second workpiece coordinate system of the casting to be ground comprises:

Acquiring point cloud data of a casting to be polished, and acquiring second position and posture coordinates of the robot;

and establishing a workpiece coordinate system of the casting to be polished according to the point cloud data of the casting to be polished, and converting the workpiece coordinate system of the casting to be polished to a base coordinate system of the robot according to the coordinate transformation matrix and the second position and posture coordinate of the robot to obtain a second workpiece coordinate system.

4. The tool tip trajectory adaptive method for robotic grinding of castings according to claim 3, wherein the point cloud data of the reference casting and the point cloud data of the casting to be ground are acquired by a 3D sensor, respectively.

5. The tool tip trajectory adaptive method for robotic sanding of castings according to any of claims 1-4, characterized in that in rigid mode, the locking mechanism is controlled to lock the spindle and the floating mount; in the flexible mode, the locking mechanism is controlled to unlock the main shaft and the floating seat, and the floating holding force of the piston cylinder is adjusted to be a first preset pressure so that the main shaft can deflect relative to the floating seat.

6. The tool tip trajectory adaptive method for robotic sanding of castings according to claim 5, wherein in the rigid mode, the floating holding force of the piston cylinder is adjusted to a second predetermined pressure, the second predetermined pressure being greater than the first predetermined pressure.

7. The tool tip trajectory adaptive method for robotic sanding of castings according to claim 6, wherein the first predetermined pressure is 0.2MPA to 0.4MPA and the second predetermined pressure is 0.6MPA to 0.8 MPA.

8. The tool tip trajectory adaptive method for robotic sanding of castings according to claim 6, wherein the piston cylinder is a first cylinder connected to a compressed air source; the compressed air source is connected with the first air cylinder through an electric proportional valve;

the floating holding force of the piston cylinder can be adjusted from the first preset pressure to the second preset pressure or from the second preset pressure to the first preset pressure through the electric proportional valve.

9. The method of claim 8, wherein the drive unit of the locking mechanism is a second cylinder connected to a compressed air source, and wherein the compressed air source is connected to the second cylinder via a solenoid valve.

10. The tool tip trajectory adaptive method for robotic sanding of castings according to claim 5, wherein in rigid mode, said tool is a disc wheel; in the flexible mode, the tool is a cylindrical grinding wheel.

Technical Field

The invention relates to the technical field of machining, in particular to a tool tail end track self-adaption method for a robot to polish castings.

Background

The casting polishing process by a robot comprises cutting and polishing, wherein a disc-shaped grinding wheel is adopted to cut casting head residues, a vent needle, an exhaust sheet, fleshing and the like; and (3) polishing joint flash, burrs, orifice separation skin and the like by using a cylindrical grinding wheel. Wherein, the polishing track (cutting) of the disc-shaped grinding wheel is mostly a plurality of discrete straight line segments; most of the grinding tracks (grinding) of the cylindrical grinding wheels are curves, and profiling machining is required to be realized according to the specific shape of a parting surface. However, the clamping error of the casting, the size deformation and the copying precision of the tail end track of the cutter can influence the grinding quality of the robot. Meanwhile, the factors also seriously affect the reliability of the robot polishing equipment, the safety of the polishing process, the service life of a cutter, the wire mixing compatibility of the robot polishing equipment and the like.

The corresponding flexible mechanism is arranged in the market at present, the profiling precision of the tail end track of the robot polishing cutter is improved, and the shape following polishing effect is achieved. The technology provides adjustable radial pressure for the main shaft by using compressed air as a power source, so that the cutter can generate radial floating, and the problem of insufficient tail end track profiling precision of the robot in the process of processing a complex curved surface is solved. However, the cutting requirements of casting head residue, vent needles, exhaust fins, fleshing and the like cannot be met, and the casting polishing and cutting are usually completed by replacing corresponding cutters by adopting the same main shaft, so that the production efficiency of equipment is improved, and the cost of the equipment is reduced. However, the spindle equipped with the flexible mechanism for cutting has problems of unstable grinding quality, low grinding efficiency, knife clamping, knife collision, short tool life and the like. On the other hand, through the flexible mechanism technology, a high-precision tool and a high-precision clamp still need to be designed to ensure the safety and the polishing effect of the polishing process, and the problem of mixed line compatibility of the robot cannot be fundamentally solved.

Disclosure of Invention

Technical problem to be solved

The invention mainly aims to provide a tool tail end track self-adaption method for polishing castings by a robot, and aims to solve the problems that the conventional tool tail end profiling precision is insufficient and the existing tool tail end profiling method cannot adapt to the mixed line compatibility of robot polishing equipment.

(II) technical scheme

In order to achieve the above object, the present invention provides a tool tip trajectory adaptive method for robotic casting grinding, comprising:

scanning the reference casting to generate a first workpiece coordinate system of the reference casting, and storing the spatial position of the reference casting in the first workpiece coordinate system;

generating a polishing track of a reference casting according to the first workpiece coordinate system;

replacing the reference casting with a casting to be polished, and scanning the casting to be polished to generate a second workpiece coordinate system of the casting to be polished;

updating the spatial position of the reference casting according to the first workpiece coordinate system and the second workpiece coordinate system, and taking the updated spatial position as the spatial position of the casting to be polished to obtain a polishing track with updated coordinates;

selecting a working mode of a pressure type flexible compliant grinding tool assembly of the robot, wherein the working mode comprises a rigid mode and a flexible mode;

Based on the selected working mode, the cutter arranged on the main shaft is driven to rotate and move along the grinding track of the casting to be ground so as to carry out rigid cutting or flexible grinding on the casting to be ground and finish the grinding of the casting to be ground.

(III) advantageous effects

The invention has the beneficial effects that: firstly, based on the comparison between a standard casting and a casting to be polished, establishing a workpiece coordinate system and a polishing track which are matched with the position relation and the size relation of the casting to be polished, and relatively locking a main shaft and a floating seat in a rigid mode; in the flexible mode, the spindle is able to deflect relative to the floating mount. According to the flexible working mode that switches of actual conditions, the drive is installed and is rotated and remove along the orbit of polishing of treating the foundry goods of polishing in the cutter on the main shaft to carry out rigid cutting or the flexibility to the foundry goods and polish, can satisfy the needs of cutting and the terminal orbit self-adaptation of the cutter of polishing, simplify the teaching programming requirement of robot, reduce frock and anchor clamps requirement, guarantee the security of effect of polishing and the robot equipment of polishing, improved the robot and polished the equipment and mixed line compatible ability.

Drawings

FIG. 1 is a schematic diagram of an application of the pressure-type flexible compliant abrading tool assembly of the present invention;

FIG. 2 is a schematic diagram of a half-section of a pressure-type flexible compliant grinding tool assembly of the present invention;

FIG. 3 is a schematic view in half section of the compliance mode of the pressure-type compliant sanding tool assembly of the present invention;

FIG. 4 is a schematic view of a half-section of a rigid mode of the pressure-type compliant sanding tool assembly of the present invention;

FIG. 5 is a schematic diagram of the pneumatic control unit of the pressure-type flexible compliant sanding tool assembly of the present invention;

FIG. 6 is a flow chart of a tool tip trajectory adaptive method of the present invention for robotic polishing of castings;

FIG. 7 is a flow chart of a robot acquiring various parameters of a reference casting according to one embodiment of the present invention;

FIG. 8 is a flow chart of a robot acquiring parameters of a casting to be polished according to one embodiment of the present invention;

FIG. 9 is a schematic view of a robotic work system according to one embodiment of the present invention;

FIG. 10 is a schematic diagram of establishing a coordinate system of an object according to one embodiment of the invention;

FIG. 11 is a flowchart of a pose correction method when a robot processes a casting according to one embodiment of the present invention;

[ description of reference ]

100: a pressure-type flexible compliant sanding tool assembly;

1: a main shaft; 11: a sliding sleeve; 111: a slip ring;

2: a floating mechanism; 21: a floating seat; 22: a piston cylinder; 23: a fixing ring; 231: a sliding groove; 24: a gas interface; 25: a movable sealing ring; 26: a dust cover;

3: a locking mechanism; 31: a locking sleeve; 32: a second cylinder; 33: mounting a plate;

4: an air control unit; 41: a gas source; 42: a filtering pressure reducing valve; 43: an electromagnetic valve; 44: an electric proportional valve;

101: a cylindrical grinding wheel; 102: a disc-shaped grinding wheel; 103: a robot;

200: casting; 201: parting surface flash; 202: a gate residual block;

300: a tooling fixture; 400: a 3D sensor.

Detailed Description

For the purpose of better explaining the present invention and to facilitate understanding, the present invention will be described in detail by way of specific embodiments with reference to the accompanying drawings.

As shown in fig. 1-4, a pressure-type flexible compliant abrading tool assembly 100 for use with the present invention comprises: a main shaft 1, a floating mechanism 2 and a locking mechanism 3. The first end of the main shaft 1 is used for installing a tool, a sliding sleeve 11 is fixedly sleeved outside the main shaft 1, and a sliding ring 111 extending outwards along the radial direction is formed on the sliding sleeve 11. The floating mechanism 2 comprises a floating seat 21, a fixing ring 23 fixed on the floating seat 21 and sleeved outside the sliding sleeve 11, and a plurality of piston cylinders 22 arranged in the floating seat 21 and distributed at intervals along the circumferential direction of the main shaft 1; each piston cylinder 22 has a predetermined floating holding force and can extend and contract along the axial direction of the main shaft 1, and the sliding ring 111 is clamped between the free end of the piston cylinder 22 and the fixed ring 23; a gap exists between the floating seat 21 and the main shaft 1, and a gap exists between the sliding ring 111 and the floating seat 21, so that the main shaft 1 can deflect relative to the floating seat 21. In addition, the locking mechanism 3 includes a driving unit provided on the main shaft 1 and a locking sleeve 31 sleeved on the main shaft 1, and the driving unit can drive the locking sleeve 31 to reciprocate along the axial direction of the main shaft 1 to lock or release the floating seat 21.

Under the condition that the main shaft 1 and the floating seat 21 are mutually released, when the reaction force generated when the cutter is contacted with the casting 200 for grinding, gravity, friction force and the like are superposed in one direction and are larger than the floating holding force in the corresponding direction, the piston cylinder 22 corresponding to the direction is contracted; when the reaction force generated when the tool is in contact with the casting 200 for grinding is superposed with gravity, friction force and the like in one direction and is smaller than the floating holding force in the corresponding direction, the piston cylinder 22 corresponding to the direction is extended, and the piston cylinders 22 in all directions flexibly support the sliding ring 111 without being separated from the sliding ring 111, so that the main shaft 1 can maintain the flexible balance effect corresponding to the floating seat 21, and the working mode is a flexible mode. When the piston cylinder 22 on one side of the main shaft 1 contracts and the piston cylinder 22 on the other side extends, a deflection effect as shown in fig. 3 is generated, and a deflection included angle β is generated between the axial direction of the main shaft 1 and the axial direction of the floating seat 21, wherein the size of the included angle β can be limited according to the clearance between the floating seat 21 and the main shaft 1 and the clearance between the sliding ring 111 and the floating seat 21. For example, in fig. 3, specifically, the piston cylinder 22 on the upper side of the spindle 1 is extended and the piston cylinder 22 on the lower side is contracted, so that the upper half of the spindle 1 is inclined toward one end on which the tool is mounted, and the lower half of the spindle 1 is inclined toward the opposite other end.

Further stress analysis was as follows: in this flexible mode, the force acting between the piston cylinder 22 and the sliding sleeve 11 (floating holding force) can completely overcome the weight of the spindle 1, the locking mechanism 3 and the tool. During grinding, grinding force is applied to the spindle 1 along the radial direction, the grinding force and the gravity of each component are defined as working force, and when the working force in one direction exceeds the floating holding force in the direction, the sliding sleeve 11 deflects (swings) along with the spindle 1 around the sliding groove 231 on the fixed ring 23 until the working force and the floating holding force reach balance; when the working force in each direction is smaller than the corresponding floating holding force (grinding force is eliminated), the main shaft 1 is restored to the initial balance state along with the sliding sleeve 11, and the axial direction of the main shaft 1 is coincident with or parallel to the axial direction of the floating seat 21. In summary, in this working mode, the floating mechanism 2 can provide radial floating for the tool, i.e. the tool follows the spindle 1 to deflect relative to the axial direction of the floating seat 21 or to achieve initial balance, and the floating holding force can be adjusted according to actual requirements.

In contrast, in the case where the main shaft 1 and the floating seat 21 are locked to each other, for example, as shown in fig. 4, the locking sleeve 31 is driven to move in the axial direction of the main shaft 1 to be caught in the gap between the main shaft 1 and the floating seat 21, so that the main shaft 1 and the floating seat 21 are kept locked, and thus the main shaft 1 is prevented from deflecting relative to the floating seat 21, and the main shaft 1 and the floating seat 21 are rigidly connected to facilitate rigid cutting of an unnecessary cast structure on the casting 200, and this operation mode is a rigid mode.

The pressure type flexible compliant grinding tool assembly 100 in the above embodiment has two working modes of rigid cutting and flexible grinding, can meet the process requirements of cutting and grinding at the same time, and can realize flexible switching of the two working modes through the locking mechanism 3, thereby improving the grinding efficiency of the casting 200. When the flexible sanding is required, the drive unit on the spindle 1 drives the locking sleeve 31 away from the floating seat 21 to release the floating seat 21, so that the spindle 1 can be deflected relative to the floating seat 21. At this time, the plurality of piston cylinders 22 apply corresponding pressure to the sliding ring 111 under the action of a preset floating holding force, so that the main shaft 1 can keep flexible balance along with the sliding ring 111, and further, the grinding wheel working surface can follow the shape of the casting 200 to perform copying (compliant) grinding, so that the grinding effect is smooth and flat, and meanwhile, the copying precision requirement on the grinding track of the robot 103 is reduced. When rigid cutting is needed, the driving unit on the main shaft 1 can drive the locking sleeve 31 to be in close contact with the floating seat 21 so as to lock the floating seat 21, the main shaft 1 and the floating seat 21 are in rigid connection, and a cutter on the main shaft 1 can overcome cutting resistance and meet cutting requirements on a sprue residual block 202, a vent needle, an exhaust sheet, meat enrichment and the like on a casting 200. The mode that adopts the combination of hardness and softness can promote the quality of polishing and the efficiency of polishing to guarantee the life-span of cutter, can effectively promote the application and the popularization that the work piece was automatic to polish through this technique.

It should be noted that the piston cylinder 22 of the present invention may be a cylinder, a hydraulic cylinder, or the like, and may be a structure in which the piston is driven by a compression spring as long as a predetermined floating holding force can be provided. The preset floating holding force can be a uniform value all the time, and can also be flexibly adjusted to be a variable value according to requirements. In a preferred embodiment, the piston cylinder 22 is a first cylinder, and the first cylinder is provided with a gas port 24, and compressed air with a proper pressure can be filled into the piston cylinder 22 through the gas port 24, so that the floating retention force of the piston cylinder 22 can be flexibly adjusted according to actual requirements. In addition, in order to facilitate the control of the position of the locking sleeve 31, the driving unit may include a second cylinder 32 and a mounting plate 33 fixed to the second end of the main shaft 1, one end of the second cylinder 32 is fixed to the mounting plate 33, and the other end of the second cylinder 32 is connected to the locking sleeve 31. When the main shaft 1 and the floating mechanism 2 are kept rigidly connected, the pressure of the compressed air entering the floating mechanism 2 is adjusted to the maximum pressure of the system. In this mode of operation, the radial cutting forces to which the tool is subjected during operation are transmitted via the spindle 1 to the locking sleeve 31, the locking sleeve 31 being further transmitted to the floating seat 21, the floating seat 21 and the robot 103 being fixed against the cutting resistance.

As shown in fig. 5, in order to flexibly adjust the pressure in the first cylinder and the second cylinder 32 according to different working conditions, the floating mechanism 2 further includes an air control unit 4, the air control unit 4 includes an air source 41 (which may be compressed air), an air supply header, a first branch pipe for supplying air to the air interface 24, an electric proportional valve 44 disposed on the first branch pipe, a second branch pipe for supplying air to the second cylinder 32, and an electromagnetic valve 43 disposed on the second branch pipe, and the air source 41 is connected to the first branch pipe and the second branch pipe through the air supply header, respectively.

Wherein the electromagnetic valve 43 controls the gas pressure in the second cylinder 32, indirectly controls the position of the locking sleeve 31, and thus realizes the locking and releasing between the main shaft 1 and the floating seat 21. The electric proportional valve 44 is a continuously controlled valve, and is characterized in that the output quantity changes with the change of the input quantity, and a certain proportional relation exists between the output quantity and the input quantity, so that the stepless regulation of pressure and speed can be realized. The air supply pressure to the piston cylinder 22 is adjusted through the electric proportional valve 44, so that the floating holding force of the main shaft 1 is adjusted, and the acting force between the cutter and the casting 200 can be indirectly adjusted through adjusting the compressed air pressure according to different grinding contents. In addition, increasing the floating holding force of the piston cylinder 22 can also assist the locking mechanism 3 to complete the locking work of the main shaft 1 and the floating seat 21, so that the main shaft 1 can be completely kept locked with the floating seat 21 in the original state.

Referring again to fig. 5, in order to ensure that the first and second cylinders 32 can fully exert various performances, a filtering and pressure reducing valve 42 may be further disposed on the air supply main, and the filtering and pressure reducing valve 42 may dry and lubricate the compressed air and may regulate and stabilize the outlet pressure. The filter pressure reducing valve 42 for compressed air adopts a rolling type diaphragm, and when the input end fluctuates, the diaphragm of the pressure reducing valve automatically adjusts, so that the pressure is stably output, and the pressure stability is ensured. In addition, the filtering pressure reducing valve 42 may also be a combined filtering pressure reducing valve, which can be a high-precision pressure reducing valve according to the requirement of the output pressure precision; in the using process, after the compressed air is subjected to two-stage three-section type filter to remove impurities such as oil, water, dust and the like in the compressed air, the service life of the pressure reducing valve membrane and the precision of pressure regulation are greatly improved; because the service life of the filter element is long, the filter element and the pressure reduction element can be repaired independently in maintenance, the integral replacement is not needed, and the cost is greatly saved.

In addition, referring again to fig. 2, a sliding groove 231 is formed on the fixed ring 23 on a side contacting the sliding ring 111, and one end of the sliding ring 111 is fitted into the sliding groove 231. The slide groove 231 is formed as an annular groove on the fixed ring 23, and the outer side of the slide ring 111 extends toward the fixed ring 23 and is inserted into the slide groove 231 so that the slide ring 111 can be deflected (swung) based on the slide groove 231. As shown in fig. 3, the cross section of the sliding groove 231 may be semicircular, and the cross section of the end of the sliding ring 111 that is adapted to the sliding groove 231 may also be semicircular, so that the sliding ring 111 can be more smoothly deflected with respect to the sliding groove 231. In other embodiments, the cross-section of the sliding groove 231 may have other shapes as long as the sliding ring 111 can be deflected.

Further, referring again to fig. 3 and 4, the pressure-type flexible compliant sanding tool assembly 100 further includes a dust cover 26 disposed on the floating seat 21, the dust cover 26 covering the second end of the spindle 1, so as to prevent dust from entering between the spindle 1 and the floating mechanism 2, and to ensure that the spindle 1, the floating mechanism 2, and the locking mechanism 3 can maintain good working conditions.

In a more preferred embodiment, as shown in fig. 2, a dynamic seal ring 25 may be provided between the sliding sleeve 11 and the fixed ring 23, so as to achieve a sealing effect without affecting the swing of the main shaft 1. The dynamic seal 25 may be an O-ring or a star-ring, for example, to seal between the relatively moving parts.

Referring again to fig. 1, 3 and 4, in the above embodiment, the tool may be a disc-shaped grinding wheel 102 or a cylindrical grinding wheel 101, and the tool is provided with a tool shank, which can be mounted on the first end of the spindle 1, and the tool is replaced by replacing the tool shank. The cylindrical grinding wheel 101 is used for grinding parting surface flash 201 on the casting 200, and the disc-shaped grinding wheel 102 is used for cutting a vent pin or gate remnant block 202 on the casting 200.

In the above-described embodiments, the spindle 1 may be an electric spindle or a mechanical spindle. The electric spindle is a technology which integrates a machine tool spindle and a spindle motor into a whole and is found in the field of numerical control machines, and comprises the electric spindle and accessories thereof, and specifically comprises the electric spindle, a high-frequency conversion device, an oil mist lubricator, a cooling device, a built-in encoder, a tool changing device and the like. The rotor of the spindle motor is directly used as the spindle of the machine tool, the shell of the spindle unit is the base of the spindle motor, and the spindle motor and the machine tool spindle are integrated by matching with other parts. When the electric spindle is used as the spindle 1, the sliding sleeve 11 is fixedly arranged outside the shell of the electric spindle, and the free end of the rotor is used for installing a cutter. The mechanical spindle is a shaft on a machine tool for driving a workpiece or a tool to rotate, and motion and torque are transmitted in the machine mainly through transmission parts such as gears and belt wheels. When the mechanical spindle is adopted as the spindle 1, the belt wheel can be arranged on the mechanical spindle, and the transmission from the motor to the mechanical spindle is carried out through the cooperation of the belt wheel and the belt, so that the mechanical spindle can rotate and float relative to the floating seat 21.

Further, referring to fig. 6, the present invention provides a tool tip trajectory adaptive method for robotic grinding of castings, comprising:

s100, scanning the reference casting to generate a first workpiece coordinate system of the reference casting, and storing the spatial position of the reference casting in the first workpiece coordinate system. Where the first workpiece coordinate system is generated based on the reference casting, "first" is not a limitation on the number.

S200, generating a polishing track of a reference casting according to the first workpiece coordinate system; wherein the grinding track can be generated by a common manual teaching mode based on the generated coordinate system, the manual action is simulated by the robot, and then the teaching action is used for finishing the operation.

S300, replacing the reference casting with a casting to be polished, scanning the casting to be polished, and generating a second workpiece coordinate system of the casting to be polished. Wherein the second workpiece coordinate system is generated based on the casting to be ground, and the "second" is not limited in number, but is used as a distinction from the "first workpiece coordinate system".

S400, updating the spatial position of the reference casting according to the first workpiece coordinate system and the second workpiece coordinate system, and taking the updated spatial position as the spatial position of the casting to be polished to obtain a polishing track with updated coordinates. That is to say, deposit the second work piece coordinate system in robot control system, update the spatial position of all processing point positions through the update of coordinate system, realize regarding the spatial position after the update as the spatial position of the foundry goods of treating to polish to realize through coordinate update that the orbit of polishing follows the foundry goods position and gesture and carry out self-adaptation correction, not only correction precision is high, can also greatly reduced calculated amount.

S500, selecting a working mode of the robot pressure type flexible compliant sanding tool assembly 100, wherein the working mode comprises a rigid mode and a flexible mode. Wherein, in the rigid mode, the locking mechanism 3 is controlled to lock the main shaft 1 and the floating seat 21; in the flexible mode, the locking mechanism 3 is controlled to unlock between the main shaft 1 and the floating seat 21, and to adjust the floating holding force of the piston cylinder 22 to a first preset pressure so that the main shaft 1 can deflect relative to the floating seat 21. Before polishing, the robot 103 may optionally select a working mode, for example, first perform a cutting process in a rigid mode or first enter a flexible mode, and then switch to another working mode in a subsequent step to continue polishing along the polishing track.

S600, based on the selected working mode, driving a cutter arranged on the main shaft to rotate and move along the grinding track of the casting to be ground so as to rigidly cut or flexibly grind the casting to be ground. Specifically, the robot 103 provides electric energy for the spindle 1 to drive the spindle 1 to rotate, and meanwhile, the robot 103 drives the whole floating seat 21 and the spindle 1 to move along a grinding track of a casting to be ground in a three-dimensional space;

S700, switching the working mode of the pressure type flexible compliance grinding tool assembly 100 to finish grinding the casting to be ground. Or, for example, if only the defect of flexible grinding is existed on the casting to be ground, the grinding can be completed by directly adopting the same mode without switching the working mode.

In the above embodiment of the present invention, a workpiece coordinate system and a polishing track matching the positional relationship and the dimensional relationship of the casting to be polished are established based on the comparison between the standard casting and the casting to be polished. In the rigid mode, the main shaft and the floating seat are relatively locked; in the flexible mode, the spindle is able to deflect relative to the floating mount. According to the flexible switching operating mode of actual conditions (the type of the defect of waiting to polish on the foundry goods), the cutter that the drive was installed on the main shaft is rotatory and remove along the orbit of polishing of waiting to polish the foundry goods to carry out rigid cutting or the flexibility to the foundry goods, can satisfy the needs of cutting and the terminal orbit self-adaptation of the cutter of polishing, simplify robot teaching programming requirement, reduce frock and anchor clamps requirement, guarantee the security of effect of polishing and the robot equipment of polishing, improved the robot equipment of polishing and mixed line compatible ability. Wherein, in the rigid mode, the cutter can be a disc-shaped grinding wheel; in the flexible mode, the tool may be a cylindrical grinding wheel.

Specifically, in one embodiment of the present invention, as shown in fig. 9, a robotic machining system may include a robot 103 (which includes a pressure-type flexible compliant sanding tool assembly 100), a tool holder 300, and a 3D sensor 400, among other auxiliary equipment. The 3D sensor may be, but is not limited to, a binocular 3D camera, a 3D camera composed of monocular and structured light; the 3D sensor can be loaded at the tail end of the robot or can be independently installed by being separated from the robot; the tooling clamp can be loaded at the tail end of the robot and can also be independently installed by being separated from the robot.

In order to generate grinding tracks correspondingly according to the grinding requirements of different castings 200, the castings 200 are scanned to generate a workpiece coordinate system of the castings 200; and generating a grinding track according to the workpiece coordinate system. The grinding track is designed according to the position needing to be ground, and the robot 103 works according to the grinding track, so that casting head residues or burrs and the like needing to be ground on the casting 200 can be ground. The method specifically comprises the following steps: 1) before the robot 103 works, scanning a workpiece (sample) to obtain sample characteristics; 2) establishing a sample coordinate system by using the sample characteristics; 3) converting the sample coordinate system into a world coordinate system of the robot 103 to obtain the position of the workpiece relative to the robot coordinate system and generate a workpiece coordinate system; 4) establishing a polishing track of the robot by using a workpiece coordinate system as a reference coordinate system; 5) in the automatic polishing process of the robot, scanning a casting to be polished to extract the characteristics of the casting to be polished; 6) calculating to obtain a new workpiece coordinate system by utilizing the characteristic information of the casting to be polished; 7) the original workpiece coordinate system is updated to generate a new grinding track, so that the problem of errors caused by clamping of the casting can be solved (by the method, the positioning requirements on the tool and the clamp can be effectively reduced, and the mixed line compatibility of the robot grinding equipment is improved).

In order to further improve the stability of the spindle 1 in the rigid mode, increasing the floating holding force of the piston cylinder 22 can also assist the locking mechanism 3 to complete the locking work of the spindle 1 and the floating seat 21, so that the spindle 1 can be completely kept locked with the floating seat 21 in the original state. That is, the floating holding force of the adjusting piston cylinder 22 is set to a second preset pressure, which is greater than the first preset pressure. The first preset pressure can be 0.2 MPA-0.4 MPA, and the second preset pressure can be 0.6 MPA-0.8 MPA. During actual production, the floating holding force of the piston cylinder can be adjusted from the first preset pressure to the second preset pressure or from the second preset pressure to the first preset pressure through the electric proportional valve 44 according to requirements.

In a more preferred embodiment, as shown in fig. 7, step S100 specifically includes:

s110, calibrating by a robot hand and an eye to obtain a coordinate transformation matrix; and calibrating by a robot hand to obtain the position relation of the 3D sensor relative to the flange center of the robot or the base coordinate system of the robot.

In the embodiment of the invention, the robot hand-eye calibration, that is, the calibration of the 3D sensor is performed, so as to obtain the position and posture conversion relationship of the 3D sensor relative to the center of the end flange of the robot (when the 3D sensor is installed on the robot), or the relationship of the 3D sensor relative to the base coordinate system of the robot (when the 3D sensor is installed outside the robot), which is expressed by the coordinate transformation matrix Xs.

And S120, acquiring point cloud data of the reference casting and acquiring first position coordinates of the robot.

Optionally, according to one embodiment of the invention, the point cloud data of the reference casting is acquired by a 3D sensor. Specifically, a 3D sensor is used to scan a reference casting or directly shoot and collect a 3D point cloud of the reference casting, and the position and posture of the robot, i.e. the first position and posture coordinate Xr of the robot when the 3D sensor collects the point cloud data are recorded.

The scanning or shooting of the 3D sensor on the reference casting can be single time, and multiple areas can be processed for multiple times; the obtained point cloud can be a single point cloud set or a plurality of point cloud sets in different areas. Whether a single point cloud set or multiple different area cloud sets, is used for subsequent establishment of the workpiece coordinate system.

S130, establishing a workpiece coordinate system of the reference casting according to the point cloud data of the reference casting, and converting the workpiece coordinate system of the reference casting into a base coordinate system of the robot according to the coordinate transformation matrix and the first pose coordinate of the robot to obtain a first workpiece coordinate system.

Wherein the workpiece coordinate system of the reference casting comprises 6 degree of freedom components, denoted Xi. Moreover, for a single point cloud set, the gravity center of the point cloud set can be directly extracted, or a method for extracting a plurality of point cloud characteristics from the single point cloud set is adopted to establish a workpiece coordinate system of the reference casting; for the point cloud sets in a plurality of different areas, a method for extracting cloud characteristics of all points can be adopted to establish a workpiece coordinate system of the reference casting.

Specifically, in an embodiment of the present invention, when extracting point cloud features based on a cloud set of workpiece points, n is greater than or equal to 3 original feature point positions can be obtained, each feature point includes three components of x, y, and z, which are respectively represented as Xi1, Xi2, …, and Xin. The selected characteristic point is ideally a datum point of the casting.

Further, the original feature points are processed through an algorithm to establish the workpiece coordinate system of the reference casting by constructing three new feature points.

When the number n of the original feature points is 3, three new feature points are constructed in the following manner.

The first mode is that one of 3 original characteristic points is directly selected as the establishment of a first point P1; selecting one of the remaining 2 original feature points as a second point P2; and establishing the remaining original characteristic point as a third point P3. Among them, P1, P2, and P3 cannot be collinear in space.

The second way is to calculate the barycenter of 3 original feature points as the establishment of a first point P1; selecting one of the 3 original characteristic points as a second point P2; one of the remaining 2 feature points is selected as the creation of the third point P3. Wherein the 3 original feature points cannot be collinear in space.

When the number n of the original feature points is greater than 3, the center of gravity of all the original feature points is generally obtained, or a certain original feature point can be directly selected to be used as the establishment of a first point P1, the center of gravity of part of the original feature points is obtained, or a certain original feature point is directly selected to be used as the establishment of a second point P2; and (4) calculating the gravity center of part of the original feature points or directly selecting a certain original feature point to be used as the establishment of a third point P3.

Then, establishing a workpiece coordinate system of the reference casting based on the three new feature points, wherein the steps are as follows:

after obtaining P1, P2 and P3, the coordinate system is initially established, and P1 is first selected as the origin of the coordinate system, and then the axes of the coordinate system X, Y, Z are calculated, as shown in fig. 10.

The calculation process of the X, Y and Z axes of the coordinate system is as follows:

first, construct with P1, P2 pointsThe spatial vector is a vector of the spatial vector,

second, construct with P1, P3 pointsThe spatial vector is a vector of the spatial vector,

thirdly, carrying out normalization processing on the vector,

the fourth step, calculate the X axis as

The fifth step is toAndthe vector cross-multiplication obtains the Z axis of the coordinate systemWherein the content of the first and second substances,andthe cross-multiplication sequence of the vectors needs to satisfy a right-hand rule;

and sixthly, the Y axis of the coordinate system is Z multiplied by X.

Thus, the coordinate system is formed by the origin of the coordinate system and the three axes X, Y, Z, as shown in fig. 10.

In this embodiment, the gravity center calculation method is: taking the example of finding the center of gravity for M points, each point is C1, and C2 … Cm, the center of gravity M is (C1+ C2+ … Cm)/M.

Therefore, the workpiece coordinate system of the reference casting is established by the method, the coordinate system error caused by poor workpiece consistency can be reduced to a certain extent, and the precision of the robot for processing the casting is improved.

Optionally, in an embodiment of the present invention, when the workpiece coordinate system of the reference casting is converted to the first workpiece coordinate system of the robot, when the 3D sensor is mounted on the robot, the workpiece coordinate system of the reference casting is converted to the base coordinate system of the robot according to a formula Xb ═ Xr Xs Xi to obtain the first workpiece coordinate system, where Xb is the first workpiece coordinate system, Xr is the first pose coordinate of the robot, Xs is the coordinate conversion matrix, and Xi is the workpiece coordinate system of the reference casting.

For the equation Xb ═ Xr Xs × Xi, each variable in the equation may be a homogeneous transformation matrix of 4 × 4, which may be specifically expressed as:

the upper left 3 x 3 sub-matrix of each matrix in the above formula is the rotation component of the pose, and the last column of each matrix is the position component of the pose.

When the 3D sensor is installed outside the robot, converting the workpiece coordinate system of the reference casting to the base coordinate system of the robot according to the formula Xb-Xs-Xi to obtain a first workpiece coordinate system, wherein Xb is the first workpiece coordinate system, Xs is the coordinate conversion matrix, and Xi is the workpiece coordinate system of the reference casting.

For the equation Xb — Xs × Xi, each variable in the equation may be a homogeneous transformation matrix of 4 × 4, which may be specifically expressed as:

likewise, the top-left 3 × 3 sub-matrix of each matrix in the above formula is the rotational component of the pose, and the last column of each matrix is the positional component of the pose.

In the embodiment of the invention, after a first workpiece coordinate system Xb is established, the first workpiece coordinate system Xb is stored in a robot control system, manual teaching is started in the first workpiece coordinate system Xb, the spatial point coordinates of the grinding tracks of all the reference castings are stored in the Xb coordinate system, the spatial position of the reference casting can be obtained and stored in the Xb coordinate system, then the taught machining program is operated, and the casting can be replaced after the machining of the reference casting is finished.

Alternatively, according to an embodiment of the present invention, as shown in fig. 8, step S300 includes:

S310, point cloud data of the casting to be polished are obtained, and second position and posture coordinates of the robot are obtained.

Optionally, according to one embodiment of the invention, the point cloud data of the casting to be polished is acquired by a 3D sensor. In other words, the 3D sensor is used for scanning the casting to be polished or directly shooting and collecting the 3D point cloud of the casting to be polished, and the position and the posture of the robot, namely the second position and posture coordinate Xrnew of the robot when the 3D sensor collects the point cloud data are recorded.

It is understood that in embodiments of the present invention, the second pose coordinate Xrnew may be the same as the first pose coordinate Xr, i.e., the robot position and pose may remain unchanged while the point cloud data is collected by the 3D sensor.

Similarly, the 3D sensor can scan or shoot the casting to be polished for a single time or process a plurality of areas for a plurality of times; the obtained point cloud can be a single point cloud set or a plurality of point cloud sets in different areas. Whether a single point cloud set or multiple different area cloud sets, is used for subsequent establishment of the workpiece coordinate system.

S320, establishing a workpiece coordinate system of the casting to be polished according to the point cloud data of the casting to be polished, and converting the workpiece coordinate system of the casting to be polished into a base coordinate system of the robot according to the coordinate transformation matrix and the second position and posture coordinate of the robot to obtain a second workpiece coordinate system.

The workpiece coordinate system of the casting to be ground comprises 6 freedom degree components which are marked as Xinew.

It should be noted that the process of establishing the workpiece coordinate system of the casting to be polished may be the same as the process of establishing the workpiece coordinate system of the reference casting, and details thereof are not repeated here.

Optionally, as an embodiment, when the workpiece coordinate system of the casting to be ground is converted to the base coordinate system of the robot, when the 3D sensor is mounted on the robot, the workpiece coordinate system of the casting to be ground is converted to the base coordinate system of the robot according to a formula Xbnew ═ xrew x s xi ew to obtain a second workpiece coordinate system, where Xbnew is the second workpiece coordinate system, xrew is the second pose coordinate of the robot, Xs is the coordinate conversion matrix, and Xinew is the workpiece coordinate system of the casting to be ground; when the 3D sensor is installed outside the robot, converting the workpiece coordinate system of the casting to be ground to the base coordinate system of the robot according to a formula Xbnew (Xs) Xinew to obtain a second workpiece coordinate system, wherein Xbnew is the second workpiece coordinate system, Xs is the coordinate conversion matrix, and Xinew is the workpiece coordinate system of the casting to be ground.

Moreover, the process of converting the workpiece coordinate system of the casting to be polished into the base coordinate system of the robot is the same as the process of converting the workpiece coordinate system of the reference casting into the base coordinate system of the robot, and is not repeated here.

In the embodiment of the present invention, all the robot machining space position points are stored in the first object coordinate system described with respect to the base coordinate system of the robot when performing the reference casting commissioning. After the first workpiece coordinate system is updated according to the second workpiece coordinate system, it is necessary to ensure that the robot machining space position point remains unchanged in the workpiece coordinate system, that is, the position of the machining tool relative to the casting to be polished is unchanged, so that after the casting position is changed, the position of the robot machining space position relative to the base coordinate system of the robot must be changed to process along with the casting position. The kinematics conversion process can be automatically completed by the robot control system, so that not only can the position and the posture of the casting be accurately corrected, but also too many calculation processes are not needed, the calculation amount is reduced, and a foundation is provided for ensuring the machining consistency of the casting.

According to the error compensation method for the robot to process the casting, firstly, a coordinate transformation matrix is obtained through calibration of a hand eye of the robot, then point cloud data of the reference casting is obtained when the reference casting is placed into a tool clamp, a first position coordinate of the robot at the moment is obtained, a workpiece coordinate system of the reference casting is established according to the point cloud data of the reference casting, the workpiece coordinate system of the reference casting is converted into a base coordinate system of the robot according to the coordinate transformation matrix and the first position coordinate of the robot to obtain a first workpiece coordinate system, then the point cloud data of the casting to be polished is obtained after the casting is replaced, a second position coordinate of the robot at the moment is obtained, a workpiece coordinate system of the casting to be polished is established according to the point cloud data of the casting to be polished, and the workpiece coordinate system of the casting to be polished is converted into the base coordinate system of the robot according to the coordinate transformation matrix and the second position coordinate of the robot to obtain a second workpiece coordinate system And finally, updating the spatial position of the reference casting according to the first workpiece coordinate system and the second workpiece coordinate system, and taking the updated spatial position as the spatial position of the casting to be polished to realize the pose correction of the casting. Therefore, the self-adaptive correction of the polishing track along with the position and the posture of the casting is realized through coordinate updating, so that the design of a tool clamp is not required to be optimized, the universality of the tool clamp is improved, the design of a workpiece tool clamp is simplified, the clamp only needs to ensure that the workpiece is not loosened during processing, the position and the posture of the clamped workpiece are allowed to change, the design difficulty and the workload of the clamp are reduced, the processing consistency of the casting is ensured, the problem of processing errors of the workpiece is effectively solved, and the processing quality is ensured.

In one embodiment of the present invention, as shown in fig. 11, a posture correcting method in machining a casting by a robot includes the steps of:

and S11, calibrating the 3D sensor to obtain the position and posture conversion relation of the 3D sensor relative to the flange plate at the tail end of the robot (the 3D sensor is installed on the robot), or the relation of the 3D sensor relative to the base coordinate system of the robot (the 3D sensor is installed outside the robot), and recording as Xs.

And S12, scanning the reference casting by using the 3D sensor or directly shooting and acquiring the 3D point cloud of the reference casting, and recording the position and the posture of the robot when the 3D sensor acquires data as Xr. The scanning or shooting of the 3D sensor on the reference casting can be single time, and multiple areas can be processed for multiple times; the obtained point cloud can be a single point cloud set or a plurality of point cloud sets in different areas.

And S13, establishing a workpiece coordinate system of the reference casting by using the point cloud collected in the step S12. Wherein the object coordinate system comprises 6 components of freedom, denoted Xi. Moreover, for a single point cloud set, the gravity center of the point cloud set can be directly extracted, or a method for extracting a plurality of point cloud characteristics from the single point cloud set is adopted to establish a workpiece coordinate system of the reference casting; for the point cloud sets in a plurality of different areas, a method for extracting cloud characteristics of all points can be adopted to establish a workpiece coordinate system of the reference casting.

The specific process of establishing the workpiece coordinate system is as described above, and will not be described herein again.

And S14, converting the workpiece coordinate system established in the step S13 into a base coordinate system of the robot to obtain a first workpiece coordinate system, which is marked as Xb. Wherein Xb ═ Xr × Xs × Xi (3D sensor mounted on robot); xb ═ Xs × Xi (3D sensors mounted outside the robot).

For the equation Xb ═ Xr Xs × Xi, each variable in the equation is a homogeneous transformation matrix of 4 × 4, which may be specifically expressed as:

the upper left 3 x 3 sub-matrix of each matrix in the above formula is the rotation component of the pose, and the last column of each matrix is the position component of the pose.

For the equation Xb — Xs × Xi, each variable in the equation is a homogeneous transformation matrix of 4 × 4, which can be specifically expressed as:

similarly, the upper left 3 × 3 sub-matrix of each matrix in the above formula is the rotation component of the pose, and the last column of each matrix is the position component of the pose.

And S15, storing the Xb coordinate system into the robot control system, starting manual teaching, and storing the space point coordinates of all the grinding tracks in the Xb coordinate system.

And S16, operating the program of manual teaching to finish the processing of the reference casting (debugging sample piece) and replacing the casting.

And S17, scanning or shooting the replaced casting again by using the 3D sensor to obtain a new 3D point cloud of the current casting, wherein the acquisition mode is the same as the step S12. And the position and the posture of the robot are still Xr when the 3D sensor collects data.

And S18, establishing a workpiece coordinate system for the current casting by using the point cloud acquired in the step S17, wherein the coordinate system also comprises 6 freedom degree components and is recorded as Xinew.

Wherein the method of establishing the object coordinate system is as described above.

S19, converting the workpiece coordinate system of the current casting to the base coordinate system of the robot, and obtaining a second workpiece coordinate system, which is denoted as Xbnew, Xbnew ═ Xr × Xs × Xinew (the 3D sensor is mounted on the robot); xbnew (3D sensor mounted outside the robot). Here, the coordinate conversion process is the same as step S14, and is not described here again.

And S20, transmitting the Xbnew coordinate system to a robot control system, and automatically updating all processing positions by the control system to realize pose correction when the robot processes the casting.

According to the method for correcting the pose of the robot during casting machining, the spatial positions of all machining point positions are updated through updating of the coordinate system, the updated spatial positions are used as the spatial positions of the current casting, therefore, the grinding track is corrected in a self-adaptive mode along with the position and the posture of the casting through coordinate updating, the correction precision is high, and the calculation amount can be greatly reduced.

It should be understood that the above description of specific embodiments of the present invention is only for the purpose of illustrating the technical lines and features of the present invention, and is intended to enable those skilled in the art to understand the contents of the present invention and to implement the present invention, but the present invention is not limited to the above specific embodiments.