CN114273681A - Ring surface worm helicoid processing system and method based on serial mechanical arm - Google Patents
Ring surface worm helicoid processing system and method based on serial mechanical arm Download PDFInfo
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Abstract
The invention relates to a toroidal worm helicoid processing system and a toroidal worm helicoid processing method based on a serial mechanical arm. Compared with the prior art, the invention realizes the high-efficiency automatic processing of the enveloping worm, simultaneously ensures the processing precision, can effectively improve the consistency of the processing efficiency and the batch production, reduces the production cost, and is particularly suitable for processing the enveloping worm with large size.
Description
Technical Field
The invention relates to the technical field of processing of enveloping worms, in particular to a system and a method for processing a helicoid of an enveloping worm based on a serial mechanical arm.
Background
Compared with cylindrical worm transmission, the enveloping worm transmission has the advantages of strong bearing capacity, small volume, high transmission efficiency and long service life, is widely applied to transmission devices of mining and metallurgy, petrifaction, hoisting and transportation, ships, power and light industrial machinery, and particularly has more superior performance than the straight-profile enveloping worm transmission, such as plane, double conical surface and the like.
At present, the processing steps of the helicoid of the enveloping worm comprise two parts of rough processing and finish processing, wherein the rough processing is completed by turning or milling, and the finish processing is completed by grinding, the traditional grinding mode is carried out on a special machine tool with a rotary table, the centre distance is adjusted by moving the rotary table along the radial direction of the worm during processing, the transmission ratio is adjusted by matching a hanging wheel, even if the numerical control machine tool is adopted for processing, a special grinding head with a complex structure is required to be configured, and a special tool is required for the tool setting process.
For the processing of the spiral surface of the planar enveloping ring surface worm, a special grinding head needs to be arranged on a B-axis turntable of a machine tool, the B axis and the C axis are linked to realize the grinding of the spiral surface on one side, when the other side of the spiral surface is processed, the worm needs to be arranged in a turning way, or the grinding head rotates around the B axis for 360 degrees for reverse processing, and secondary clamping and reverse processing inevitably lead to the increase of repeated positioning error and lower efficiency;
for the processing of the helicoids of the conical surface enveloping ring worm, although the helicoids on the left side and the right side can be formed simultaneously, the special grinding head has a complex structure, the machine tool is complex to adjust, the processing period is long, the cost is high, the processing range is limited by the diameter of the rotary table, the special grinding head is not favorable for the efficient automatic processing of the enveloping worm, and the development and application requirements of the existing enveloping worm are difficult to meet.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a toroidal worm helicoid processing system and method based on a serial mechanical arm so as to realize efficient and automatic processing of a toroidal worm and ensure processing precision.
The purpose of the invention can be realized by the following technical scheme: the utility model provides a torus worm helicoid system of processing based on mechanical arm establishes ties, includes processing platform and arm, the centre gripping installation remains to process the torus worm on the processing platform, the end of arm is connected with the processing cutter through electric main shaft, the torus worm takes place to rotate according to setting for the rotational speed on the processing platform, the arm is according to the working position and the processing power of processing cutter of processing orbit and instruction control of setting for to accomplish the processing to the torus worm.
Further, an electric motor is arranged on the processing platform, and an output shaft of the electric motor is connected with the enveloping worm to be processed.
Further, the processing cutter is a grinding cutter or a turning cutter.
A toroidal worm helicoid processing method based on a serial mechanical arm comprises the following steps:
s1, establishing a kinematic model of the machining system, and calibrating a base coordinate system;
s2, generating a spiral surface processing path of the enveloping worm;
s3, planning the spiral surface track of the torus worm;
s4, preliminarily determining the machining track and the control instruction of the mechanical arm;
s5, aiming at the helicoid of the toroidal worm to be processed, establishing a mechanical arm processing simulation model, and adjusting the processing track and the control instruction of the mechanical arm according to the simulation result;
s6, generating a control program for the mechanical arm to process the helicoid of the toroidal worm in an off-line manner according to the adjusted processing track and the control instruction of the mechanical arm;
s7, mounting the enveloping worm to be machined to a machining platform, and mounting a machining tool at the tail end of the mechanical arm through an electric spindle;
the enveloping worm to be processed rotates according to the set rotating speed, and meanwhile, the mechanical arm correspondingly controls the processing cutter according to the control program to complete the processing of the helicoid of the enveloping worm to be processed.
Further, the specific process of step S1 is as follows: establishing a closed-chain kinematic relationship among the mechanical arm, the processing tool and the processing platform, namely a mechanical arm base, a mechanical arm tail end, the processing tool, a processing position point and a processing platform base;
and then calibrating the processing system by using a laser tracker, wherein the coordinate system of the laser tracker is a fixed measurement coordinate system, respectively calibrating transformation matrixes of the base coordinate systems of the mechanical arm and the processing platform relative to the measurement coordinate system, and calculating to obtain a relative transformation matrix between the base coordinate systems of the mechanical arm and the processing platform based on a relative coordinate transformation principle.
Further, the specific process of step S2 is as follows: firstly, selecting a plurality of characteristic points on a spiral line, and fitting based on a trigonometric function method to obtain a processing track equation;
then discretizing a machining track equation to obtain a unit tangent vector and a unit internal normal vector of a corresponding discrete point, and determining the machining pose information of the tail end of the mechanical arm, wherein path points on the machining track comprise the unit tangent vector and the unit internal normal vector, and the posture of a machining tool at the tail end of the mechanical arm is determined according to the two vector directions;
according to the processing technological requirements of the helicoid of the enveloping worm, the attitude of the processing tool at the tail end of the mechanical arm is specified as follows: during the machining operation, the normal vector f of the path point on the machining path and the X of the grinding tool TCP coordinate systemtThe directions are overlapped and are the directions of constant force control of the machining tool at the tail end of the mechanical arm and the Y of a TCP coordinate systemtThe direction is the tangent vector tau of the path point and points to the next processing point, and is also the moving direction of the processing tool, Z of the processing tool TCP coordinate systemtThe direction w, which is a cross product of the normal vector f and the tangent vector τ, coincides with the right-hand rule.
Further, the specific process of step S3 is as follows: given the speed of rotation omega of the worm1And the transmission ratio i of the worm gear pair is as per i-omega1/ω2Calculating to obtain the rotation speed omega of the tail end of the grinding tool2；
When the machining tool rotates anticlockwise to the end position along with the mechanical arm from the initial position, the worm rotates around the axis of the worm in the positive direction, and the speed direction of the worm is outward along the paper surface; when the machining tool rotates clockwise from the initial position to the final position along with the mechanical arm, the worm rotates reversely around the axis of the worm, the speed direction of the worm is inward along the paper surface, and the machining surface of the machining tool is always tangent to the main base circle of the worm wheel in the rotation process of the mechanical arm.
Further, in step S3, for the planar double-enveloping worm, the machining tool rotates counterclockwise with the mechanical arm to machine the left-side spiral surface of the worm, and the machining tool rotates clockwise with the mechanical arm to machine the right-side spiral surface of the worm;
for the conical surface double-enveloping ring surface worm, the machining tool machines the helicoids on the left side and the right side of the worm simultaneously in the anticlockwise and clockwise rotation processes of the mechanical arm;
for a multi-head ring surface worm, after a machining tool rotates along with a mechanical arm to machine a spiral surface of a first head of the worm, the initial installation position of the worm needs to rotate 360/z around the rotation axis of the worm1Angle, wherein z1And (4) counting the number of the heads of the worm, continuously processing the helicoid of the second head, and continuously updating the processing track until the helicoid of the multi-head ring surface worm is processed.
Further, the specific process of step S4 is as follows: the mechanical arm is based on a position control mode, so that the machining track is accurately tracked, the machining contact force is collected in real time through a six-dimensional force sensor arranged at the tail end of the mechanical arm, and the tail end X of a machining tool is machined based on an impedance control algorithmtConstant machining force control of direction.
Further, the specific process of step S5 is as follows: the proportion of the built physical platform to the physical platform is 1: 1, adopting a Solidworks and Matlab/Simulink module to jointly build a spiral surface system simulation platform of the processing ring surface worm of the serial mechanical arm;
after the simulation is finished, a rotation angle sequence diagram, a joint angle track tracking error diagram and an expected track and actual track comparison diagram of each joint of the serial mechanical arm are generated;
and determining whether the series mechanical arm stably and continuously moves according to the joint angle sequence diagram, the joint angle track tracking error diagram and the expected track and actual track comparison diagram to determine the accuracy of the processing track and the control instruction, so as to adjust the processing track and the control instruction of the mechanical arm.
Compared with the prior art, the processing platform and the mechanical arm are arranged, and the processing platform is used for clamping and mounting the enveloping worm to be processed, so that the enveloping worm rotates on the processing platform according to the set rotating speed; the tail end of the mechanical arm is connected with a machining tool through an electric spindle, and the mechanical arm is used for controlling the working position and the machining force of the machining tool according to the set machining track and the set command, so that the machining of the enveloping worm is completed, the automatic machining of the enveloping worm is realized, repeated positioning operation is not needed, the machining efficiency is improved, and the machining precision is guaranteed.
According to the method, firstly, a closed-chain kinematic model of the mechanical arm, a machining tool and a machining platform is established, a machining path of the helicoid of the toroidal worm is generated, a machining track is planned, and the machining track and a control instruction of the mechanical arm are determined by combining with simulation model adjustment, so that the accuracy of the set machining track and the control instruction is ensured, and the precision of machining the toroidal worm can be effectively improved.
Drawings
FIG. 1 is a schematic diagram of the system of the present invention;
FIG. 2 is a schematic diagram of a coordinate system of the grinding system in the embodiment;
FIG. 3 is a schematic diagram of a grinding trace in the embodiment;
FIG. 4 is a diagram illustrating normal vectors and tangent vectors of path points in an embodiment;
FIG. 5 is a schematic view illustrating the grinding operation of the robot arm according to the embodiment;
FIG. 6 is a diagram illustrating pose constraint relationships in an embodiment;
FIG. 7 is a schematic diagram of a control architecture of the robot arm in an embodiment;
the notation in the figure is: 1. the machining device comprises a mechanical arm, 2, a machining platform, 3, a ring surface worm, 4, an electric spindle, 5 and a machining tool.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments.
Examples
As shown in fig. 1, a toroidal worm helicoid processing system based on serial mechanical arms comprises a processing platform 2 and a mechanical arm 1, wherein a toroidal worm 3 to be processed is clamped and mounted on the processing platform 2, the tail end of the mechanical arm 1 is connected with a processing tool 5 through an electric spindle 4, the toroidal worm 3 rotates on the processing platform 2 according to a set rotating speed, and the mechanical arm 1 controls the working position of the processing tool 5 according to a set processing track and a set command so as to complete the processing of the toroidal worm 3.
Wherein, the processing platform 2 is provided with an electric motor, and an output shaft of the electric motor is connected with the enveloping worm 3 to be processed so as to drive the enveloping worm 3 to rotate.
According to the processing requirement, the processing cutter 5 can be a grinding cutter or a turning cutter.
The system is applied to practice to realize a toroidal worm helicoid processing method based on a series mechanical arm, and the method comprises the following steps:
s1, establishing a kinematic model of the machining system, and calibrating a base coordinate system, specifically:
establishing a closed-chain kinematic relationship among the mechanical arm, the processing tool and the processing platform, namely a mechanical arm base, a mechanical arm tail end, the processing tool, a processing position point and a processing platform base;
then, calibrating the processing system by using a laser tracker, wherein the coordinate system of the laser tracker is a fixed measurement coordinate system, respectively calibrating transformation matrixes of the base coordinate systems of the mechanical arm and the processing platform relative to the measurement coordinate system, and calculating to obtain a relative transformation matrix between the base coordinate systems of the mechanical arm and the processing platform based on a relative coordinate transformation principle;
s2, generating a spiral surface processing path of the enveloping worm, specifically:
firstly, selecting a plurality of characteristic points on a spiral line, and fitting based on a trigonometric function method to obtain a processing track equation;
then discretizing a machining track equation to obtain a unit tangent vector and a unit internal normal vector of a corresponding discrete point, and determining the machining pose information of the tail end of the mechanical arm, wherein path points on the machining track comprise the unit tangent vector and the unit internal normal vector, and the posture of a machining tool at the tail end of the mechanical arm is determined according to the two vector directions;
according to the processing technological requirements of the helicoid of the enveloping worm, the attitude of the processing tool at the tail end of the mechanical arm is specified as follows: during the machining operation, the normal vector f of the path point on the machining path and the X of the grinding tool TCP coordinate systemtThe directions are overlapped and are the directions of constant force control of the machining tool at the tail end of the mechanical arm and the Y of a TCP coordinate systemtThe direction is the tangent vector tau of the path point and points to the next processing point, and is also the moving direction of the processing tool, Z of the processing tool TCP coordinate systemtThe cross direction w of the normal vector f of the direction and the path point and the tangent vector tau is coincident with f multiplied by tau and accords with the right-hand rule;
s3, planning the spiral surface track of the toroidal worm, specifically:
given the speed of rotation omega of the worm1And the transmission ratio i of the worm gear pair is as per i-omega1/ω2Calculating to obtain the rotation speed omega of the tail end of the grinding tool2；
When the machining tool rotates anticlockwise to the end position along with the mechanical arm from the initial position, the worm rotates around the axis of the worm in the positive direction, and the speed direction of the worm is outward along the paper surface; when the machining tool rotates clockwise from the initial position to the final position along with the mechanical arm, the worm rotates reversely around the axis of the worm, the speed direction of the worm is inward along the paper surface, and the machining surface of the machining tool is always tangent to the main base circle of the worm gear in the rotating process of the mechanical arm;
for the planar double-enveloping ring surface worm, a machining tool rotates anticlockwise with a mechanical arm to machine a left side spiral surface of the worm, and the machining tool rotates clockwise with the mechanical arm to machine a right side spiral surface of the worm;
for the conical surface double-enveloping ring surface worm, the machining tool machines the helicoids on the left side and the right side of the worm simultaneously in the anticlockwise and clockwise rotation processes of the mechanical arm;
for a multi-head ring surface worm, after a machining tool rotates along with a mechanical arm to machine a spiral surface of a first head of the worm, the initial installation position of the worm needs to rotate 360/z around the rotation axis of the worm1Angle, wherein z1Counting the heads of the worm, then continuously processing the helicoid of the second head, and continuously updating the processing track until the helicoid of the multi-head ring surface worm is processed;
s4, preliminarily determining a machining track and a control command of the mechanical arm, specifically:
the mechanical arm is based on a position control mode, so that the machining track is accurately tracked, the machining contact force is collected in real time through a six-dimensional force sensor arranged at the tail end of the mechanical arm, and the tail end X of a machining tool is machined based on an impedance control algorithmtConstant machining force control of direction;
s5, aiming at the helicoid of the toroidal worm to be machined, establishing a mechanical arm machining simulation model, and adjusting the machining track and the control instruction of the mechanical arm according to the simulation result, specifically:
the proportion of the built physical platform to the physical platform is 1: 1, adopting a Solidworks and Matlab/Simulink module to jointly build a spiral surface system simulation platform of the processing ring surface worm of the serial mechanical arm;
after the simulation is finished, a rotation angle sequence diagram, a joint angle track tracking error diagram and an expected track and actual track comparison diagram of each joint of the serial mechanical arm are generated;
determining whether the series mechanical arm stably and continuously moves or not according to each joint corner angle sequence diagram, and determining the accuracy of a processing track and a control instruction according to a joint angle track tracking diagram, a joint angle track tracking error diagram and an expected track and actual track comparison diagram, so as to adjust the processing track and the control instruction of the mechanical arm;
s6, generating a control program for the mechanical arm to process the helicoid of the toroidal worm in an off-line manner according to the adjusted processing track and the control instruction of the mechanical arm;
s7, mounting the enveloping worm to be machined to a machining platform, and mounting a machining tool at the tail end of the mechanical arm through an electric spindle;
the enveloping worm to be processed rotates according to the set rotating speed, and meanwhile, the mechanical arm correspondingly controls the processing cutter according to the control program to complete the processing of the helicoid of the enveloping worm to be processed.
In the embodiment, the spiral surface of the enveloping worm is subjected to finish machining, so that a grinding tool is selected and installed at the tail end of the mechanical arm. In this embodiment, taking a modified torus worm pair as an example, the relevant parameters are: number of enveloping worm heads z 14, number of teeth of worm gear z240, the meshing center distance a is 160mm, the transmission ratio i is 10, and the diameter d of the top circle of the worm geara267mm, diameter d of worm rootf250mm, worm gear end face modulus mt10.45mm, major base circle diameter db95mm, working length L of wormw90mm corner of mechanical arm
The range of values of (1) is 0-0.8 rad.
A mechanical arm with the model number of ER20-C10 is adopted, the load of the mechanical arm is 20Kg, the self weight of the mechanical arm is 220Kg, the arm span is 1722mm, and a machine tool based on a serial mechanical arm grinding system comprises the mechanical arm, a grinding platform, a ring surface worm, an electric spindle and a grinding tool. The grinding platform is mainly used for clamping the enveloping worm, and the rotating speed of the enveloping worm during grinding is set according to the technical requirements of the machined enveloping worm; the electric spindle and the grinding tool are arranged at the tail end of the mechanical arm, the mechanical arm clamps the grinding tool, and the enveloping worm is processed according to the grinding track and the control method.
Based on the method process proposed by the technical scheme, the application process of the embodiment includes:
firstly, a coordinate system for grinding the helicoids of the enveloping worms by using a series of mechanical arms is established, as shown in fig. 2. Wherein T iswRepresenting the world coordinate system, Tb1Indicating the base coordinate system, T, of the tandem robot armf1Representing the coordinate system of the end of the arm, TtRepresenting the coordinate system of the end of the grinding tool, Tb2Grinding tableCenter coordinate system, TjRepresenting the coordinate system T of any discrete point on the grinding path of the helicoid of the enveloping wormwAnd Tb1And (4) overlapping. The series mechanical arm and the grinding platform form a closed-chain kinematic relationship, and the expression of the mechanical arm 1 base, the mechanical arm 1 tail end, the grinding tool, the grinding point and the grinding platform 2 base is as follows:b1Tf1 f1Tt tTj jTb2＝b1Tb2，jtb2determined according to the specific grinding track requirements, is a known matrix,b1Tb2is determined by calibrating the base coordinate system,f1Ttdetermined by calibration of a TCP tool according to the installation mode,ttTjis an identity matrix, so thatb1Tf1＝b1Tb2(jTb2)-1(tTj)-1(f1T)-1Can obtainb1Tf1And determining a coordinate system of the end of the mechanical arm grinding tool according to the coordinate system, and then solving the motion angle of each joint according to the inverse kinematics. Through a laser tracker calibration system, wherein a laser tracker coordinate system is a fixed measurement coordinate system, transformation matrixes T of base coordinate systems of the serial mechanical arm and the grinding platform relative to the measurement coordinate system are respectively calibrated1,T2. Based on the principle of relative coordinate transformation, by formulab1Tb2＝T2 -1T1Calculating to obtain a relative pose homogeneous matrix between the serial mechanical arm and a base coordinate system of the grinding platformb2Tb1。
Secondly, taking 20 characteristic points on the 4-head ring surface worm indexing ring surface spiral line, fitting the points based on a trigonometric function method to generate a spiral line, obtaining a grinding track equation, as shown in fig. 3, discretizing the track equation to obtain surface normal vectors of corresponding discrete points, and determining the grinding pose information of the tail end of the serial mechanical arm; the path point on the grinding trajectory includes two directions of a unit tangent vector τ and a unit internal normal vector f as shown in fig. 4, and then the attitude of the end grinding tool of the tandem robot is further determined based on the two vector directionsAccording to the processing technology requirement of the enveloping worm, the attitude of the tail end grinding tool of the serial mechanical arm is specified as follows: during the machining operation, the normal vector f of the path point on the grinding track and the X of the grinding tool TCP coordinate systemtThe directions are overlapped, and simultaneously, the direction is controlled by the constant force at the tail end of the grinding tool of the serial mechanical arm, and the Y of a TCP coordinate systemtThe direction is the tangent vector tau of the path point and points to the next grinding point, which is also the direction of the movement of the grinding tool. Z of TCP coordinate system of grinding tooltThe direction w, which is a cross product of the normal vector f and the tangent vector τ, coincides with the right-hand rule.
Thirdly, the rotation speed omega of the worm is given11400r/min and the transmission ratio i of the worm gear pair is 10 according to i omega1/ω2Calculating to obtain the rotation speed omega of the tail end of the grinding tool2140 r/min. As shown in fig. 5, when the grinding tool starts from the initial position a and rotates along with the arm counterclockwise to the end position B, the worm rotates around its axis in the forward direction (the speed direction is outward along the paper surface), when the grinding tool starts from the initial position B and rotates along with the arm clockwise to the end position a, the worm rotates around its axis in the reverse direction (the speed direction is inward along the paper surface), and during the rotation of the arm, the machining surface of the grinding tool always has the radius r and the machining surface of the grinding tool always has the radius rbThe main base circle of the worm wheel is tangent, and the rotation center of the mechanical arm is OdThe angle of rotation is
Center distance O of worm gear pairdO1160mm, radius of tip circle R of worma133.5 mm. For the planar worm with the secondary enveloping ring surface, a grinding tool rotates anticlockwise with a mechanical arm to machine a left spiral surface of the worm, and the grinding tool rotates clockwise with the mechanical arm to machine a right spiral surface of the worm; for the conical surface secondary enveloping ring surface worm, the grinding tool simultaneously processes the left and right spiral surfaces of the worm in the anticlockwise and clockwise rotation processes of the mechanical arm; for a multi-start toroidal worm, after the grinding tool rotates with the arm to machine the helical surface of the first start of the worm, it is necessary to rotate 360/4-9 the initial installation position of the worm around its axis of rotationAnd (3) 0 degrees, then processing the spiral surface of the second head according to the method, and continuously updating the grinding track until the processing of the spiral surface of the multi-head ring surface worm is completed.
According to the processing technology requirement, the serial mechanical arm needs to carry out constant grinding force control while working along the grinding track, so that in the Cartesian operation space of the mechanical arm, the mechanical arm is subjected to force/position operation space decomposition, namely in XtDirection of constant force control, Yt、ZtThe direction is controlled, and the pose constraint relation is shown in fig. 6. During grinding, the serial arm holds the grinding tool while maintaining the constant force control direction coincident with the normal direction f of the path point, so that the X-ray in the coordinate system of the grinding tool of the serial armtThe direction is controlled by constant force and is always kept horizontal, namely the grinding attitude isb1RT＝[1 0 0]TIn Y att，ZtThe direction is controlled to follow the grinding track. Calculating the position of the end of the grinding tool from the kinematic modelb1PT＝[xt yt zt]T＝b1Tb2(jTb2)-1(tTj)-1[xj yj zj 1]T. Finally, the kinematic angle of each joint can be obtained by inverse solution of kinematics. The transformation matrix T comprises a position vector P and a rotation matrix R, wherein:
P＝[px py pz]T
fourthly, the serial mechanical arm accurately tracks the grinding track based on a position control mode, and the control framework is shown in fig. 7. Because the control period of the control system built by the invention is short, the characteristic of integral is not considered,the series mechanical arm adopts a single-joint PD control mode. Desired position θ of each jointtiCalculated by inverse kinematics, the joint position thetaiVelocity of joint
The driving quantity of each joint of the mechanical arm is acquired by a six-dimensional force sensor in real time
Wherein k ispiIs a proportionality coefficient, kviIs a differential coefficient.
Control parameter k in servo control system for each jointpi、kviThe adjustment of (3) continuously adjusting the proportional coefficient according to the amplitude of the deviation oscillation to quickly reduce the error, then adjusting the differential coefficient to reduce the oscillation frequency of the deviation, quickly and accurately tracking the change of the track, and ensuring that the motion controlled process of the whole serial mechanical arm is stable. And each joint in the joint servo control system is regarded as a single-input single-output system, each joint is independently controlled, and then synchronous linkage control of each joint is completed through a periodic synchronous interpolation mode of a driver, so that accurate motion control of the serial mechanical arm is realized.
The series mechanical arm acquires contact force information with the enveloping worm in real time through a six-dimensional force sensor arranged at the tail end, and X is obtained after filtering and gravity compensation of the force sensortDirectional actual grinding force F, which is in contact with the desired contact force FdDeviation f ofeAs an input to a second order low pass filter, output XtAnd feeding the corrected value delta X back to the reference motion track of the robot in the X direction in the Cartesian operation space through the selection matrix S, S', updating the motion track of the mechanical arm, obtaining each joint angle through kinematic calculation of the mechanical arm, continuously acquiring grinding force contact information by a six-dimensional force sensor at the tail end of the mechanical arm when the mechanical arm enters the next grinding period, and repeatedly executing the steps to continuously update the grinding track until the task of grinding the spiral surface of the toroidal worm is completed.
And fifthly, building a simulation environment, and firstly, developing kinematics, trajectory planning and control algorithm of the serial mechanical arm grinding system by using an M file and an S function in MATLAB/Simulink. A grinding system CAD model is established by utilizing SolidWorks three-dimensional software, then the system CAD model is exported into an XML format file and a STEP model which can be read by MATLAB through a Simscape Multibody Link plug-in, finally the STEP model of the system is loaded into MATLAB/Simulink through reading the XML format file, and a Simscape simulation model of the grinding system is generated by combining algorithms of kinematics, trajectory planning and the like. Generally, an original system simulation model imported into Simulink cannot be directly controlled, the model needs to be further optimized and relevant control parameter configuration, including STEP model path modification, Rotation input and output quantity configuration, mechanical arm initial posture joint angle configuration, joint Rotation positive direction setting and the like, and finally the model is packaged into an independent module. And then, performing kinematics, trajectory planning and control algorithm development of the grinding system by using an M file and an S function in MATLAB/Simulink, performing related algorithm simulation based on a simulation platform, dynamically verifying the feasibility of the algorithm through a built simulation environment, and further analyzing the algorithm performance by using a Scope component and a To Workspace component To store data.
And (3) generating angle, speed and acceleration change graphs of all joints of the mechanical arm, wherein if the curves in the change graphs are stable and continuous, the kinematic model of the grinding toroidal worm helicoid system of the serial mechanical arm built in the step one is correct. Secondly, generating a comparison graph of the actual track and the expected track and a tracking error graph of the joint angle track, wherein if the actual track can move according to the expected track and the error is small, the serial mechanical arm is correct based on a PD position control mode; to the tail end X of the mechanical armtAnd applying an external force in the direction, observing whether the track graph can adapt to the external force to adjust and then return to the grinding path again, if the mechanical arm can adapt to the change of the external force to adjust the motion track, and when the interference force is zero, the serial mechanical arm can quickly and stably continue to track the expected track, so that the grinding constant force control of the serial mechanical arm based on the position impedance control algorithm is feasible.
And sixthly, aiming at the simulation result, adjusting the process of grinding the helicoid of the enveloping worm of the serial mechanical arm, and generating a program of grinding the helicoid of the enveloping worm of the mechanical arm off line after comprehensive adjustment.
In the embodiment, finish machining is performed on the enveloping worm, and if only rough machining is needed in practical application, the grinding tool of the embodiment is replaced by a turning tool.
In conclusion, the technical scheme provided by the invention can realize the automatic processing of the enveloping worm, avoid repeated positioning, effectively ensure the consistency of the precision of the enveloping worm in batch production, improve the processing efficiency and reduce the production cost, and is particularly suitable for processing the enveloping worm with large size.
Claims (10)
1. The utility model provides an anchor ring worm (3) helicoid system of processing based on series connection arm (1), its characterized in that, includes processing platform (2) and arm (1), the centre gripping installation remains to process anchor ring worm (3) on processing platform (2), the end of arm (1) is connected with processing cutter (5) through electric spindle (4), anchor ring worm (3) take place to rotate according to setting for the rotational speed on processing platform (2), arm (1) is according to the operating position and the processing power of processing cutter (5) of processing orbit and command control of setting for to the completion is to the processing of anchor ring worm (3).
2. The helicoidal system of enveloping worm (3) based on tandem arm (1) according to claim 1, wherein the processing platform (2) is provided with an electric motor, the output shaft of which is connected to the enveloping worm (3) to be processed.
3. The helicoidal system of a toroidal worm (3) based on a tandem robot arm (1) according to claim 1, characterized in that the machining tool (5) is a grinding tool or a turning tool.
4. A toroidal worm helicoid processing method based on a serial mechanical arm is characterized by comprising the following steps:
s1, establishing a kinematic model of the machining system, and calibrating a base coordinate system;
s2, generating a spiral surface processing path of the enveloping worm;
s3, planning the spiral surface track of the torus worm;
s4, preliminarily determining the machining track and the control instruction of the mechanical arm;
s5, aiming at the helicoid of the toroidal worm to be processed, establishing a mechanical arm processing simulation model, and adjusting the processing track and the control instruction of the mechanical arm according to the simulation result;
s6, generating a control program for the mechanical arm to process the helicoid of the toroidal worm in an off-line manner according to the adjusted processing track and the control instruction of the mechanical arm;
s7, mounting the enveloping worm to be machined to a machining platform, and mounting a machining tool at the tail end of the mechanical arm through an electric spindle;
the enveloping worm to be processed rotates according to the set rotating speed, and meanwhile, the mechanical arm correspondingly controls the processing cutter according to the control program to complete the processing of the helicoid of the enveloping worm to be processed.
5. The method for processing the helicoid of the enveloping worm based on the serial mechanical arm as claimed in claim 4, wherein the specific process of step S1 is as follows: establishing a closed-chain kinematic relationship among the mechanical arm, the processing tool and the processing platform, namely a mechanical arm base, a mechanical arm tail end, the processing tool, a processing position point and a processing platform base;
and then calibrating the processing system by using a laser tracker, wherein the coordinate system of the laser tracker is a fixed measurement coordinate system, respectively calibrating transformation matrixes of the base coordinate systems of the mechanical arm and the processing platform relative to the measurement coordinate system, and calculating to obtain a relative transformation matrix between the base coordinate systems of the mechanical arm and the processing platform based on a relative coordinate transformation principle.
6. The method for processing the helicoid of the enveloping worm based on the serial mechanical arm as claimed in claim 4, wherein the specific process of step S2 is as follows: firstly, selecting a plurality of characteristic points on a spiral line, and fitting based on a trigonometric function method to obtain a processing track equation;
then discretizing a machining track equation to obtain a unit tangent vector and a unit internal normal vector of a corresponding discrete point, and determining the machining pose information of the tail end of the mechanical arm, wherein path points on the machining track comprise the unit tangent vector and the unit internal normal vector, and the posture of a machining tool at the tail end of the mechanical arm is determined according to the two vector directions;
according to the processing technological requirements of the helicoid of the enveloping worm, the attitude of the processing tool at the tail end of the mechanical arm is specified as follows: during the machining operation, the normal vector f of the path point on the machining path and the X of the grinding tool TCP coordinate systemtThe directions are overlapped and are the directions of constant force control of the machining tool at the tail end of the mechanical arm and the Y of a TCP coordinate systemtThe direction is the tangent vector tau of the path point and points to the next processing point, and is also the moving direction of the processing tool, Z of the processing tool TCP coordinate systemtThe direction w, which is a cross product of the normal vector f and the tangent vector τ, coincides with the right-hand rule.
7. The method for processing the helicoid of the enveloping worm based on the serial mechanical arm as claimed in claim 4, wherein the specific process of step S3 is as follows: given the speed of rotation omega of the worm1And the transmission ratio i of the worm gear pair is as per i-omega1/ω2Calculating to obtain the rotation speed omega of the tail end of the grinding tool2；
When the machining tool rotates anticlockwise to the end position along with the mechanical arm from the initial position, the worm rotates around the axis of the worm in the positive direction, and the speed direction of the worm is outward along the paper surface; when the machining tool rotates clockwise from the initial position to the final position along with the mechanical arm, the worm rotates reversely around the axis of the worm, the speed direction of the worm is inward along the paper surface, and the machining surface of the machining tool is always tangent to the main base circle of the worm wheel in the rotation process of the mechanical arm.
8. The method according to claim 7, wherein in step S3, for a planar double-enveloping toroidal worm, the machining tool rotates clockwise with the mechanical arm to machine a left helical surface of the worm, and the machining tool rotates clockwise with the mechanical arm to machine a right helical surface of the worm;
for the conical surface double-enveloping ring surface worm, the machining tool machines the helicoids on the left side and the right side of the worm simultaneously in the anticlockwise and clockwise rotation processes of the mechanical arm;
for a multi-head ring surface worm, after a machining tool rotates along with a mechanical arm to machine a spiral surface of a first head of the worm, the initial installation position of the worm needs to rotate 360/z around the rotation axis of the worm1Angle, wherein z1And (4) counting the number of the heads of the worm, continuously processing the helicoid of the second head, and continuously updating the processing track until the helicoid of the multi-head ring surface worm is processed.
9. The method for processing the helicoid of the enveloping worm based on the serial mechanical arm as claimed in claim 4, wherein the specific process of step S4 is as follows: the mechanical arm is based on a position control mode, so that the machining track is accurately tracked, the machining contact force is collected in real time through a six-dimensional force sensor arranged at the tail end of the mechanical arm, and the tail end X of a machining tool is machined based on an impedance control algorithmtConstant machining force control of direction.
10. The method for processing the helicoid of the enveloping worm based on the serial mechanical arm as claimed in claim 4, wherein the specific process of step S5 is as follows: building a simulation platform with the ratio of 1: 1 to the physical platform, and building a series mechanical arm processing ring surface worm helicoid system simulation platform by combining a Solidworks module and a Matlab/Simulink module;
after the simulation is finished, a rotation angle sequence diagram, a joint angle track tracking error diagram and an expected track and actual track comparison diagram of each joint of the serial mechanical arm are generated;
and determining whether the series mechanical arm stably and continuously moves according to the joint angle sequence diagram, the joint angle track tracking error diagram and the expected track and actual track comparison diagram to determine the accuracy of the processing track and the control instruction, so as to adjust the processing track and the control instruction of the mechanical arm.
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