CN109202720B - Control method of grinding process and method for determining grinding lower limit position of machined workpiece - Google Patents

Control method of grinding process and method for determining grinding lower limit position of machined workpiece Download PDF

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Publication number
CN109202720B
CN109202720B CN201710533185.6A CN201710533185A CN109202720B CN 109202720 B CN109202720 B CN 109202720B CN 201710533185 A CN201710533185 A CN 201710533185A CN 109202720 B CN109202720 B CN 109202720B
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grinding
pressure
workpiece
grinding tool
preset
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CN109202720A (en
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三原秀一
凌夏冰
周雯瑾
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Yaskawa Electric China Co Ltd
Yaskawa Electric Corp
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Yaskawa Electric Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B49/00—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation
    • B24B49/02—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation according to the instantaneous size and required size of the workpiece acted upon, the measuring or gauging being continuous or intermittent
    • B24B49/04—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation according to the instantaneous size and required size of the workpiece acted upon, the measuring or gauging being continuous or intermittent involving measurement of the workpiece at the place of grinding during grinding operation
    • B24B49/05—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation according to the instantaneous size and required size of the workpiece acted upon, the measuring or gauging being continuous or intermittent involving measurement of the workpiece at the place of grinding during grinding operation including the measurement of a first workpiece already machined and of another workpiece being machined and to be matched with the first one
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B49/00—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation
    • B24B49/16—Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation taking regard of the load
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
    • G05B19/404—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Human Computer Interaction (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Constituent Portions Of Griding Lathes, Driving, Sensing And Control (AREA)
  • Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)

Abstract

The invention discloses a control method of a grinding process and a method for determining a grinding lower limit position of a processed workpiece in the grinding process, wherein the method comprises the following specific steps: before grinding work begins, the mechanical arm drives the grinding tool to move towards a standard position of a machined workpiece, the contact pressure between the grinding tool and the machined workpiece is detected in the moving process, and the contact position of the machined workpiece and the grinding tool in the current state is defined as a grinding lower limit position under the condition that the contact pressure reaches a preset pressure; wherein the reference position is the position of the surface to be polished of the workpiece to be polished, which is to be formed after the surface to be polished is polished. Compared with the prior art, the method provided by the invention has the advantages that before the grinding process is carried out, the grinding tool is driven by the mechanical arm to contact the standard position once, so that the grinding lower limit position can be determined, the grinding lower limit position can be accurately and quickly determined, the subsequent grinding process is favorable for grinding and forming the machined workpiece once, and the grinding efficiency is further improved.

Description

Control method of grinding process and method for determining grinding lower limit position of machined workpiece
Technical Field
The invention relates to the technical field of grinding, in particular to a control method of a grinding process and a method for determining a grinding lower limit position of a processed workpiece.
Background
The robot grinding system is an automatic production system for grinding products by using a robot. The system can quickly and effectively remove redundant materials on the surface of a processed part, so that the robot grinding system is widely applied to various industrial fields.
The grinding quality of the surface of the machined part is a constant focus of attention by those skilled in the art.
Disclosure of Invention
In order to solve the technical problem, the invention provides a method for determining a grinding lower limit position of a processed workpiece in a grinding process, which comprises the following specific steps: before grinding work begins, a mechanical arm drives the grinding tool to move towards a standard position of a processed workpiece, contact pressure between the grinding tool and the processed workpiece is detected in the moving process, and the contact position of the processed workpiece and the grinding tool in the current state is defined as a grinding lower limit position under the condition that the contact pressure reaches a preset pressure;
the standard position is the position of the surface to be ground of the workpiece to be ground after the surface to be ground is ground.
Compared with the prior art, the method provided by the invention has the advantages that before the grinding process is carried out, the grinding tool is driven by the mechanical arm to contact the standard position once, so that the grinding lower limit position can be determined, the grinding lower limit position can be accurately and quickly determined, the subsequent grinding process is favorable for grinding and forming the machined workpiece once, and the grinding efficiency is further improved.
Optionally, while determining the polishing lower limit position, the encoder of the driving part feeds back the position information to the controller to record the polishing lower limit position inside the controller of the driving part.
Thus, automatic control can be realized.
The invention also provides a control method of the grinding process, which comprises the following specific steps:
determining a grinding lower limit position in advance according to the method, and forming a grinding lower limit position range according to the grinding lower limit position;
detecting the pressure between a grinding tool and a processed workpiece in the process that the grinding tool of the grinding device is relatively close to the processed workpiece;
judging the initial contact pressure between the grinding tool and the machined workpiece and the preset contact pressure, when the initial contact pressure is smaller than the preset contact pressure, increasing the output torque of the driving part until the pressure between the grinding tool and the machined workpiece reaches the preset contact pressure, and then continuously increasing the output torque of the driving part to enable the pressure between the grinding tool and the machined workpiece to be gradually increased to a preset grinding pressure range from the preset contact pressure;
and maintaining the pressure between the grinding tool and the workpiece in the preset grinding pressure range to grind the workpiece, and controlling the grinding position to be in the grinding lower limit position range.
Two control parameters are set in the control method of the invention: the preset contact pressure F0 and the preset grinding pressure F1 are that in the grinding contact process of the grinding tool and the processed workpiece, the pressure between the grinding tool and the processed workpiece reaches a smaller preset contact pressure, then the output torque of the driving part is continuously increased, the preset contact pressure F0 is increased to a preset grinding pressure range, and the increase control of the pressure between the grinding tool and the processed workpiece is divided into two stages: the first stage is to increase the initial contact pressure F' to the preset contact pressure F0, the second stage is to increase the preset contact pressure F0 to the preset grinding pressure range, the increasing speed of the first stage is not easy to control, namely, the increasing speed is relatively fast, and the increasing speed of the second stage is relatively easy to control and can be slower than that of the first stage. Compared with the method that the pressure between the grinding tool and the workpiece is directly increased to the preset grinding pressure range from the initial contact pressure, the control method provided by the invention can play a good force buffering role, can well protect the grinding tool, can prolong the service life of the grinding tool and can increase the surface processing precision of the workpiece.
Alternatively, when the detected pressure is greater than or equal to the preset contact pressure, the output torque of the driving member is directly increased to gradually increase the pressure therebetween from the pressure in the current state to the predetermined grinding pressure range.
Therefore, the pressure between the grinding tool and the machined workpiece does not need to be adjusted back, the controller directly increases the output torque, and the pressure between the grinding tool and the machined workpiece is gradually increased to a preset grinding pressure range from the initial contact pressure F' at a proper speed, so that the processing efficiency is improved, and the control logic is simplified.
Optionally, a pressure sensor for detecting a pressure between the grinding tool and the workpiece is disposed between the driving component and a grinding tool assembly including the grinding tool; the control method further corrects the detected pressure before the determining step: correcting the detected pressure in consideration of the self-weight factor of the grinder assembly.
Thus, the accuracy of the output torque of the driving member can be improved to increase the accuracy of control, and the accuracy of the ground surface can be further improved.
Optionally, the correction method specifically includes:
acquiring attitude information of a mechanical arm clamping the grinding tool and a pressure signal of a pressure sensor;
and judging the attitude position of the grinding tool assembly according to the attitude information of the mechanical arm, calculating the pressure of the gravity of the grinding tool assembly on the machined workpiece or the pressure sensor according to the attitude position of the grinding tool assembly, further correcting the pressure signal, and calculating the pressure between the grinding tool and the machined workpiece according to the corrected pressure signal.
Therefore, the posture information of the mechanical arm can be directly obtained from the inside of the controller of the robot, and the calculation efficiency is improved.
Optionally, the step of grinding the workpiece within the predetermined grinding pressure range specifically includes: detecting a current grinding position, judging whether the current grinding position reaches a grinding lower limit position range, and if the current grinding position does not reach the grinding lower limit position range, controlling the grinding tool to continuously grind the processed workpiece within the preset grinding pressure range; and if the current grinding position reaches the grinding lower limit position range, controlling the mechanical arm to move to the next station position.
Therefore, excessive grinding of the workpiece is avoided by controlling the grinding position.
Optionally, the process step of moving the mechanical arm to the next station specifically includes: and judging whether the pressure between the grinding tool and the processed workpiece is larger than the upper limit value of the preset grinding pressure range, if so, reducing the output torque of the driving part until the pressure between the grinding tool and the processed workpiece approaches the preset contact pressure, and then increasing the output torque of the driving part to enable the pressure between the grinding tool and the processed workpiece to be gradually increased to the preset grinding pressure range from the preset contact pressure.
Therefore, the grinding tool can be prevented from being damaged by overlarge grinding force and reducing the precision of the grinding surface when the grinding tool moves to the next station along with the mechanical arm, and the service life of the grinding tool and the precision of the grinding surface can be prolonged.
Optionally, increasing the preset contact pressure to the preset grinding pressure range according to a prestored pressure increase curve; wherein, the pressure increase curve is a curve of the pressure value changing along with the time.
Therefore, the control logic can be simplified, and the processing efficiency can be improved.
Optionally, a pressure increase curve is determined according to the pressure in the current state and the predetermined grinding pressure range, so as to control the pressure increase acceleration to be within a preset range, wherein the pressure increase curve is a curve of a pressure value between the grinding tool and the machined workpiece changing along with time.
Optionally, the driving part is a servo motor.
Drawings
FIG. 1 is a schematic view of a polishing apparatus according to an embodiment of the present invention;
FIG. 2 is a flow chart illustrating a method for controlling the polishing process according to the first embodiment of the present invention;
FIG. 3 is a flow chart of a control method according to a second embodiment of the present invention;
FIG. 4 is a flowchart illustrating a control for determining a lower grinding limit position range according to an embodiment of the present invention;
FIG. 5 is a flow chart illustrating a process for correcting a pressure between a grinding tool and a workpiece during a grinding process according to an embodiment of the present invention;
FIG. 6 is a block diagram of a control system in accordance with an embodiment of the present invention;
fig. 7 is a graph of two different control methods for increasing the initial contact pressure to a predetermined grinding pressure range.
Wherein, the one-to-one correspondence between component names and reference numbers in fig. 1 is as follows:
the robot arm 100, the free end portion 100a, the table 200;
a servo motor 11, a screw rod 12, a nut 13 and a pressure sensor 14;
a mounting frame 20, a power component 21, a grinding tool 22, a driving pulley 23, a driven pulley 24 and a transmission belt 25;
a work piece 30.
Detailed Description
The robot grinding system utilizes a grinding tool arranged at the free end part of the robot to process and grind the surface of a product to be ground. In the product grinding process, factors influencing the quality of the formed surface of a ground product are many, such as the type of a grinding tool, the material quality of a workpiece, the grinding force and the like, wherein the grinding force is one of important factors influencing the quality of the finally ground formed surface.
Currently, the grinding force is mainly determined by the following means: an operator selects a proper grinding force value according to the grinding precision requirement of the surface to be ground, and adjusts the proper distance position of the grinding tool on the surface to be ground by combining the operation experience, so that the pressure applied to the surface to be ground by the grinding tool approximately meets the working requirement during grinding.
Practice proves that although the robot grinding system in the prior art can quickly finish grinding the surface of a product, the grinding surface precision is not uniform and sometimes has large difference, namely the precision of a part of the grinding surface meets the requirement, and the precision of a part of the grinding surface does not meet the requirement. Sometimes, the surface after grinding needs to be partially ground, which is labor-consuming and time-consuming.
Based on the above findings, the present invention has been made to further study and search, and has proposed a solution to the above-mentioned technical problem of large difference in the precision of the polished surface.
In order to make the technical solution of the present invention better understood by those skilled in the art, the present invention will be further described in detail with reference to a grinding apparatus, a control method, a control system, a drawing and specific examples.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a polishing apparatus according to an embodiment of the present invention.
The robot polishing system includes a robot having a free end portion generally formed by a multi-joint multi-degree-of-freedom robot arm 100, a polishing device attachable to the free end portion 100a, a work 30 fixed to a table 200 by a jig, and a polishing device for polishing the surface of the work 30 by moving the free end portion 100a of the robot along a predetermined path. Of course, the workpiece 30 may be disposed at the free end 100a of the robot, the polishing device is fixed to the table 200, and the robot drives the workpiece 30 to move along the predetermined path, thereby completing the polishing of the surface of the workpiece 30.
The grinding apparatus generally includes a grinder assembly including a mounting bracket 20, a power member 21, a grinder 22, a drive pulley 23, a driven pulley 24, and a drive belt 25. The grinding tool 22 is mainly used for contacting with and finishing the surface to be ground of the workpiece 30, and the suitable grinding tool 22 is selected according to the workpiece 30, and the material of the grinding tool 22 is not described in detail herein, and reference can be made to the prior art. The power unit 21 mainly provides the rotational force required for grinding the grinding tool 22, i.e., drives the grinding tool 22 to rotate. The power unit 21 may be a motor, and the power unit 21 is taken as an example to describe the technical solution, however, it should be understood by those skilled in the art that the power unit of the grinding tool herein is not limited to a motor, and may be other units as long as the power unit can provide the rotational power of the grinding tool.
Generally, the grinder 22, the power member 21, the driving pulley 23, the driven pulley 24 and the transmission belt 25 are all mounted on the mounting frame 20, wherein the driving pulley 23, the driven pulley 24 and the transmission belt 25 form a transmission member, and the power member 21 drives the grinder 22 to rotate through the driving pulley 23, the driven pulley 24 and the transmission belt 25, i.e., the power of the power member 21 is transmitted to the grinder 22 through the driving pulley 23, the driven pulley 24 and the transmission belt 25. Among them, the mounting frame 20, the driving pulley 23, the driven pulley 24 and the driving belt 25 are unnecessary components constituting the grinding tool assembly.
Generally, the grinding apparatus further includes a driving unit for driving one of the grinding tool 22 and the work material 30 to move relative to the other so as to adjust the distance between the grinding tool 22 and the work material 30. That is, the driving unit may drive the grinding tool 22 to approach or separate from the workpiece 30, or may drive the workpiece 30 to approach or separate from the grinding tool 22, that is, change the distance between the grinding tool 22 and the surface to be ground of the workpiece 30, and accordingly change the grinding force between the grinding tool 22 and the surface to be ground.
The driving means may directly drive the grinder 22 or the workpiece 30, or may indirectly drive the grinder 22 or the workpiece 30, that is, an intermediate means is provided, and the driving means drives the intermediate means to drive the grinder 22 or the workpiece 30. The driving member may be a telescopic shaft or a servomotor 11, and in this case, it is preferable that the servomotor 11 is controlled by a servomotor drive system, and the controller controls the servomotor 11 to operate by controlling the servomotor drive system.
Referring to fig. 2 and 6, fig. 2 is a flow chart illustrating a method for controlling a polishing process according to a first embodiment of the present invention; FIG. 6 is a block diagram of a control system in an embodiment of the present invention.
The invention provides a control method of a grinding process, which comprises the following specific steps:
s0, determining a grinding lower limit position, and forming a grinding lower limit position range according to the grinding lower limit position;
s1, detecting the pressure between the grinding tool and the processed workpiece in the relative approach process of the grinding tool 22 of the grinding device and the processed workpiece 30;
as described above, the free end of the robot arm 100 connected to the robot may be the grinder 22 or the workpiece 30, that is, the robot may clamp the grinder 22 close to the workpiece 30 or may clamp the workpiece 30 close to the grinder 22. For simplicity of description of the technical solution, the technical solution and the technical effects will be further described by taking the example that the grinder 22 is mounted at the free end of the mechanical arm 100 of the robot.
Of course, the control methods provided herein are also applicable to free end grinding systems in which the work piece 30 is mounted to a robotic arm 100 of a robot.
The driving component for adjusting the distance between the grinding tool 22 and the workpiece 30 can be a motor and a nut screw assembly, the grinding tool assembly is mounted on the screw 12, the motor drives the nut 13 to rotate, the screw 12 is driven to move back and forth, and the grinding tool 22 assembly is close to or far away from the workpiece 30. Of course, the drive component is not limited to the motor and nut-and-screw assembly described herein above, so long as relative movement of the abrasive article with respect to the work piece is achieved.
The pressure between the grinding tool 22 and the workpiece 30 can be detected by the pressure sensor 14.
S2, judging the initial contact pressure F 'between the grinding tool 22 and the machined workpiece 30 and the preset contact pressure F0, and executing the step S21 when the initial contact pressure F' is smaller than the preset contact pressure F0;
s21, increasing the output torque of the driving part until the pressure between the grinding tool 22 and the processed workpiece 30 reaches a preset contact pressure F0, and then continuing to increase the output torque of the driving part to enable the pressure between the grinding tool and the processed workpiece to be gradually increased from the preset contact pressure to a preset grinding pressure range;
the predetermined grinding pressure range may be a specific value in theory, but the predetermined grinding pressure range may be a range of values in general, in consideration of the machining accuracy, machining efficiency, and other factors of the workpiece. The predetermined grinding pressure range may be determined by the predetermined grinding pressure F1 input to the controller. The magnitude of the preset contact pressure may be appropriately selected depending on the material of the work 30 and the material of the grinding tool 22. The preset contact pressure F0 and the predetermined grinding pressure range are stored in the controller before the grinding process is performed. For convenience of operation, the preset contact pressure F0 and the predetermined grinding pressure F1 may be input to the controller by the touch panel. The signal input port of the controller is connected with the signal output port of the pressure sensor 14, and the controller can receive the detection signal from the pressure sensor 14, and determine the specific value of the pressure between the grinding tool 22 and the workpiece 30 at this time through the detection signal.
As can be seen from the above description, the preset contact pressure F0 is smaller than a specific value in the predetermined grinding pressure range. Two control parameters are set in the control method of the invention: the preset contact pressure F0 and the preset grinding pressure F1 are that during the grinding contact between the grinding tool 22 and the workpiece 30, the pressure between the grinding tool 22 and the workpiece 30 reaches the relatively small preset contact pressure F0, and then the output torque of the driving part is continuously increased to be within the preset grinding pressure range from the preset contact pressure F0, that is, the increase control of the pressure between the grinding tool 22 and the workpiece 30 is divided into two stages: the first stage is to increase the initial contact pressure F' to the preset contact pressure F0, the second stage is to increase the preset contact pressure F0 to the preset grinding pressure range, the increasing speed of the first stage is not easy to control, namely, the increasing speed is relatively fast, and the increasing speed of the second stage is relatively easy to control and can be slower than that of the first stage. Compared with the method that the pressure between the grinding tool 22 and the processed workpiece 30 is directly increased to the preset grinding pressure range from the initial contact pressure, the control method provided by the invention can play a good role in buffering force, can play a good role in protecting the grinding tool 22, can prolong the service life of the grinding tool 22 and can increase the surface processing precision of the processed workpiece 30.
The pressure between the grinding tool 22 and the workpiece 30 gradually increasing from the preset contact pressure F0 to the preset grinding pressure range may be increased according to the following manner: increasing the preset contact pressure F0 to a preset grinding pressure range according to a prestored pressure increase curve; wherein, pressure increase curve is pressure value along with time variation's curve, predetermines contact pressure like this and increases to the in-process of predetermined grinding pressure scope and can increase according to predetermined speed, avoids increasing the loss of accelerating the grinding apparatus too fast, and then can further improve the life of grinding apparatus, can further improve simultaneously and grind the surface precision.
And S3, maintaining the pressure between the grinding tool 22 and the workpiece 30 in a preset grinding pressure range, grinding the workpiece, and controlling the grinding position to be in a grinding lower limit position range. I.e. a is less than or equal to FWhen in useB is not more than b, a is the minimum value of the preset grinding pressure range, b is the maximum value of the preset grinding pressure range, FWhen in useThe pressure between the grinding tool 22 and the workpiece 30 is the current state. It should be noted that a and b herein may not be equal; a and b may also be equal, i.e. maintaining the pressure (grinding force) of the current state in a predetermined grinding pressure range.
Therefore, the grinding surface of the workpiece 30 to be processed is roughly under the same grinding force for grinding, the surface precision after grinding is basically the same, the overall quality of the grinding surface of the workpiece 30 to be processed is greatly improved, the qualified rate of grinding products is improved, and the production efficiency is further improved.
Referring to fig. 3, fig. 3 is a flowchart illustrating a control method according to a second embodiment of the invention.
When the pressure detected in the above step S2 is greater than or equal to the preset contact pressure F0, step S22 is performed;
s22, directly increasing the output torque of the driving member to gradually increase the pressure therebetween from the pressure in the present state (initial contact pressure F') to a predetermined grinding pressure range.
That is, when the initial contact pressure F 'between the grinding tool 22 and the work material 30 is greater than the preset contact pressure F0 without adjusting the pressure between the grinding tool 22 and the work material 30, the controller directly increases the output torque to gradually increase the pressure between the grinding tool 22 and the work material 30 from the initial contact pressure F' to the predetermined grinding pressure range at an appropriate speed. The growth rate can be calculated from the initial contact pressure F' and the predetermined grinding pressure range.
Thus, the pressure increase curve between the grinding tool 22 and the work material 30 can be appropriately adjusted according to the initial contact pressure therebetween. The pressure increase curve in this state can be determined according to the pressure increase speed or acceleration and other parameters prestored in the controller and combined with the pressure in the current state and the preset grinding pressure range.
Two curves are given in fig. 7: a curve S1 and a curve S2, where the abscissa in fig. 7 represents time and the ordinate represents force, and it can be seen from the graphs that the contact time t1 of the grinding tool with the workpiece and the initial contact pressure F 'in the curve S1 are greater than the preset contact pressure F0, the pressure between the grinding tool 22 and the workpiece 30 is directly increased from the initial contact pressure F' to the preset grinding pressure F1 along the curve S1. At the contact time t1 when the grinding tool 22 contacts the workpiece 30, the initial contact pressure in the curve S2 is smaller than the preset contact pressure F0, and the pressure between the grinding tool and the workpiece is directly increased from F0 along the curve S2 to the preset grinding pressure F1.
Of course, the pressure increase curve between the grinding tool 22 and the workpiece 30 is not limited to the linear shape described herein, and may have other shapes.
In the process of grinding the workpiece, the grinding position of the grinding tool needs to be detected to avoid excessive grinding of the workpiece, so that S3 in the control method specifically includes the following steps:
s31, controlling the grinding tool 22 and the workpiece 30 to grind in a preset grinding pressure range and detecting the current grinding position;
s32, judging whether the current grinding position reaches the grinding lower limit position range, if the current grinding position does not reach the grinding lower limit position range, returning to the step S31; if the current grinding position reaches the grinding lower limit position range, executing step S33;
and S33, controlling the mechanical arm to move to the next station position.
The specific steps in the process that the mechanical arm moves to the next station are as follows:
s331, judging whether the pressure between the grinding tool 22 and the processed workpiece 30 is larger than the upper limit value of a preset grinding pressure range in the moving process of the mechanical arm, and if so, executing a step S332;
s332, reducing the output torque of the driving component until the pressure between the grinding tool 22 and the machined workpiece 30 approaches to a preset contact pressure F0, then increasing the output torque of the driving component to enable the pressure between the grinding tool 22 and the machined workpiece 30 to be gradually increased to a preset grinding pressure range from the preset contact pressure F0, and then entering the step S31;
if not, returning to the step S331; that is, the lower grinding limit of the previous station can be directly accessed to the next station.
Therefore, the grinding tool can be prevented from being damaged by overlarge grinding force and reducing the precision of the grinding surface when the grinding tool moves to the next station along with the mechanical arm, and the service life of the grinding tool and the precision of the grinding surface can be prolonged.
Referring to fig. 4, fig. 4 is a control flow chart illustrating the determination of the polishing lower limit position range according to an embodiment of the present invention.
The polishing lower limit position range in the above embodiment may be a specific position or may be a single position range. The determination can be specifically determined by the following method: the lower grinding limit position is determined by: before the grinding operation starts, the mechanical arm 100 drives the grinding tool 22 to move towards the standard position of the workpiece 30, and detects the contact pressure between the grinding tool 22 and the workpiece 30 during the movement, and defines the contact position between the workpiece 22 and the current state as the grinding lower limit position under the condition that the contact pressure reaches the predetermined pressure. Before the grinding operation is started, the following steps are performed (i.e., step S0 includes the following steps):
s01, the mechanical arm drives the grinding tool 22 to move towards the standard position of the processed workpiece 30, and the contact pressure between the grinding tool 22 and the processed workpiece 30 is detected in the moving process;
s02, judging the contact pressure between the grinding tool 22 and the machined workpiece 30 in the current state and the preset pressure; when the contact pressure is greater than or equal to the predetermined pressure, step S03 is executed; otherwise, continuing to execute step S01;
s03, defining the contact position of the processed workpiece 30 and the grinding tool 22 in the current state as a grinding lower limit position;
the polishing lower limit position is a specific position, and may be set to a range, i.e., a polishing lower limit position range, according to the polishing lower limit position, in consideration of control efficiency, machining efficiency, and the like. While determining the polishing lower limit position, the encoder of the driving part feeds back the position information to the controller to record the polishing lower limit position inside the controller of the driving part.
The standard position is the position of the surface to be ground of the workpiece to be ground, which is to be formed after the surface to be ground is ground.
The pressure sensor is not directly mounted on the contact surface of the grinding tool 22 and the work material 30 in consideration of the quality of grinding of the work material 30 and the life of the pressure sensor. As can be seen from fig. 1, a pressure sensor for detecting a pressure between the grinding tool 22 and the workpiece 30 in the grinding apparatus is generally provided between the driving member and the grinding tool 22 assembly. When the grinding tool 22 is in a different attitude, the pressure value actually detected by the pressure sensor 14 may not be the same as the actual contact pressure between the grinding tool 22 and the work material 30. That is, the feedback value of the pressure sensor 14 is not the actual pressure value between the grinding tool 22 and the workpiece 30. In order to compensate for the accuracy of the pressure value detected by the pressure sensor 14, the control method of the present invention further corrects the detected pressure before the determining step: the detected pressure is corrected in consideration of the self-weight factor of the grinder assembly. The posture of the grinding tool assembly can be judged in various modes, and a position sensor can be arranged on the grinding tool assembly to judge the posture of the grinding tool assembly at the moment. For a robot system, a sensor for detecting motion displacement of the robot arm 100 is usually disposed on the robot arm 100 of the robot, so that the correction of the pressure signal in the method of the present invention is specifically performed according to the following method, please refer to fig. 6, which includes the following specific steps:
s001, acquiring attitude information of a mechanical arm clamping the grinding tool and a pressure signal of a pressure sensor;
s002, judging the attitude position of the grinding tool assembly according to the attitude information of the mechanical arm, calculating the pressure of the gravity of the grinding tool assembly on the machined workpiece or the pressure sensor according to the attitude position of the grinding tool assembly, further correcting the pressure signal, and calculating the pressure between the grinding tool and the machined workpiece according to the corrected pressure signal;
and S003, calculating the actual pressure between the grinding tool and the machined workpiece under the current working condition according to the corrected pressure signal, and controlling the grinding tool to grind the surface of the machined workpiece by taking the actual pressure as a parameter.
The method for correcting the pressure between the grinding tool and the machined workpiece fully considers the influence of the gravity of the grinding tool assembly at different positions on the pressure signal detected by the pressure sensor, further corrects the pressure signal detected by the pressure sensor 14 to obtain the actual pressure between the grinding tool 22 and the machined workpiece 30, and controls the grinding tool to grind the surface of the machined workpiece 30 by taking the actual pressure as a parameter. This is advantageous for achieving the purpose that the surface of the workpiece 30 is ground by the grinding tool 22 with equal grinding force, improving the consistency of the ground surface precision of the workpiece, and improving the grinding efficiency.
The pressure detected in the control method in each embodiment is further corrected by taking the gravity factor of the grinding tool assembly into consideration so as to calculate the output torque of the driving part.
And the acquisition of the attitude information of the robot arm 100 can be directly read from the inside of a controller for controlling the motion of the robot, thereby improving the calculation efficiency.
In the method, the gravity of the grinding tool assembly is considered, and the output torque of the driving part is adjusted so as to realize equal pressure grinding between the grinding tool 22 and the workpiece 30, and improve the precision of the ground surface.
The method for controlling the grinding process and the method for determining the grinding lower limit position of the workpiece provided by the invention are described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

Claims (10)

1. A method for determining a grinding lower limit position of a processed workpiece in a grinding process is characterized by comprising the following specific steps:
before grinding work begins, a mechanical arm drives a grinding tool of a grinding device to move towards a standard position of a machined workpiece, contact pressure between the grinding tool and the machined workpiece is detected in the moving process, and the contact position of the machined workpiece and the grinding tool in the current state is defined as a grinding lower limit position under the condition that the contact pressure reaches preset pressure;
the standard position is the position of a surface to be formed after the surface to be ground of the workpiece is ground;
and simultaneously determining the grinding lower limit position, feeding back the position information to the controller by the encoder of the driving part so as to record the grinding lower limit position inside the controller of the driving part to form a grinding lower limit position range of a subsequent grinding process.
2. A control method of a grinding process is characterized by comprising the following steps:
determining a lower grinding limit position in advance according to the method in claim 1, and forming a lower grinding limit position range according to the lower grinding limit position;
detecting the pressure between a grinding tool and a processed workpiece in the process that the grinding tool of the grinding device is relatively close to the processed workpiece;
judging the initial contact pressure between the grinding tool and the machined workpiece and the preset contact pressure, when the initial contact pressure is smaller than the preset contact pressure, increasing the output torque of the driving part until the pressure between the grinding tool and the machined workpiece reaches the preset contact pressure, and then continuously increasing the output torque of the driving part to enable the pressure between the grinding tool and the machined workpiece to be gradually increased to a preset grinding pressure range from the preset contact pressure;
and maintaining the pressure between the grinding tool and the workpiece in the preset grinding pressure range to grind the workpiece, and controlling the grinding position to be in the grinding lower limit position range.
3. The control method of a grinding process according to claim 2, wherein when the detected pressure is greater than or equal to the preset contact pressure, the output torque of the driving part is directly increased to gradually increase the pressure therebetween from the pressure in the present state to the predetermined grinding pressure range.
4. The method of controlling a grinding process according to claim 3, wherein a pressure sensor for detecting a pressure between the grinding tool and the work piece is provided between the driving part and a grinding tool assembly including the grinding tool; the control method further corrects the detected pressure before the determining step: correcting the detected pressure in consideration of the self-weight factor of the grinder assembly.
5. The method of claim 4, wherein the modifying method specifically comprises:
acquiring attitude information of a mechanical arm clamping the grinding tool and a pressure signal of a pressure sensor;
and judging the attitude position of the grinding tool assembly according to the attitude information of the mechanical arm, calculating the pressure of the gravity of the grinding tool assembly on the machined workpiece or the pressure sensor according to the attitude position of the grinding tool assembly, further correcting the pressure signal, and calculating the pressure between the grinding tool and the machined workpiece according to the corrected pressure signal.
6. A method for controlling a grinding process according to claim 3, wherein when grinding a work at a pressure within the predetermined grinding pressure range, the specific steps are: detecting a current grinding position, judging whether the current grinding position reaches a grinding lower limit position range, and if the current grinding position does not reach the grinding lower limit position range, controlling the grinding tool to continuously grind the processed workpiece within the preset grinding pressure range; and if the current grinding position reaches the grinding lower limit position range, controlling the mechanical arm to move to the next station position.
7. The method of claim 6, wherein the step of moving the robot arm to the next station comprises: and judging whether the pressure between the grinding tool and the processed workpiece is larger than the upper limit value of the preset grinding pressure range, if so, reducing the output torque of the driving part until the pressure between the grinding tool and the processed workpiece approaches the preset contact pressure, and then increasing the output torque of the driving part to enable the pressure between the grinding tool and the processed workpiece to be gradually increased to the preset grinding pressure range from the preset contact pressure.
8. The control method of the grinding process according to any one of claims 2 to 7, wherein the pressure between the grinding tool and the work piece is increased from the preset contact pressure to the predetermined grinding pressure range according to a prestored pressure increase curve; wherein, the pressure increase curve is a curve of the pressure value changing along with the time.
9. The method of controlling an abrasive process according to any one of claims 4 to 7, wherein a pressure increase curve is determined based on the pressure in the current state and the predetermined grinding pressure range to control the pressure increase acceleration within a preset range, wherein the pressure increase curve is a curve of a pressure value between the abrasive tool and the work material with time.
10. The method of controlling a polishing process according to any one of claims 2 to 7, wherein the driving means is a servo motor.
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