Magnetorheological machining regulation and control system based on instantaneous current sensing and machining method thereof

Abstract

The invention relates to the technical field of magneto-rheological, in particular to a magneto-rheological machining regulation and control system based on instantaneous current sensing and a machining method thereof.The system comprises a polishing platform, a polishing assembly, a detection circuit and a computer, and the polishing assembly comprises an industrial robot and a magneto-rheological polishing module; when the magneto-rheological polishing module is used for machining a polishing test piece, first instantaneous currents corresponding to the magneto-rheological polishing module at different working rotating speeds are collected, the corresponding relation between the working rotating speeds of the magneto-rheological polishing module and ideal instantaneous currents is obtained through calculation, and second instantaneous currents are judged according to the relation. And whether the working rotating speed of the magneto-rheological polishing module is adjusted or not is determined according to the judgment result. In the process, the step of calibrating parameters such as gravity compensation is not needed, the precision of measured data is only limited by the current measurement precision of the second instantaneous current between the magneto-rheological polishing module and the polishing to-be-measured piece, the measurement result is more accurate, a force sensor does not need to be added, and the equipment cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of magnetorheological technology, and particularly relates to a magnetorheological processing control system based on instantaneous current sensing and a processing method thereof. Background Art

[0002] Magnetorheological Finishing (MRF) is an advanced optical manufacturing technology developed in recent years. It has many advantages such as a stable removal function, controllable edge effect, small subsurface damage layer, no copying effect, strong shaping ability, and high processing accuracy. Therefore, the magnetorheological finishing technology has received extensive attention in high-precision optical processing. The existing magnetorheological finishing processing centers mainly integrate the magnetorheological finishing module on a numerically controlled machine tool. However, there are some deficiencies in the numerically controlled machine tool (such as low degrees of freedom, large floor area, high cost, etc.), which limit the deviation of the aspherical surface and make it difficult to perform precise pose control along the surface normal. In view of these deficiencies of the numerically controlled machine tool, researchers have introduced six-degree-of-freedom industrial robots into the field of optical processing in recent years. The six-degree-of-freedom industrial robot has the advantages of high degrees of freedom, small floor area, large processing range, low cost, etc., making up for the deficiencies of the numerically controlled machine tool. Therefore, when the magnetorheological finishing module is integrated into the industrial robot, it is theoretically possible to achieve high-precision processing of large-aperture complex-surface optical elements. However, due to the influence of factors such as processing, assembly, load, trajectory planning, and reduction ratio, the end-effector accuracy of the robot is relatively low, and the polishing gap changes greatly during the processing. At the same time, the magnetorheological finishing technology is an optical processing technology with a high degree of certainty of the removal function, and has high requirements for the change of the polishing gap during the polishing process. Generally, the change of the polishing gap in a magnetorheological numerically controlled processing center is in the order of dozens of micrometers (PV < 0.1 mm), while the trajectory accuracy of common commercial robots is generally in the sub-millimeter to millimeter range, and it cannot meet the requirements of the magnetorheological finishing technology for the change of the polishing gap during high-precision polishing.

[0003] At present, the force-position control method has gradually become a new type of constant force regulation and polishing control method for robots. A common application method is to place a force sensor between the processing tool and the robot. First, gravity calibration is performed on the force sensor to ensure the accuracy of measurement. The pose error is calculated by measuring the change in force, and then the robot pose error is compensated by means of the robot body or other motion compensation mechanisms to achieve constant force control. The high-efficiency processing of large-aperture optical elements relies on the magnetorheological processing equipment of large-size polishing wheels, and the weight of the magnetorheological processing module of large-size polishing wheels is generally over a hundred kilograms. However, for a magnetorheological processing module weighing over a hundred kilograms, the force change caused by the robot pose error is only a few dozen Newtons. When performing high-precision processing, the force needs to be constant at a few Newtons or even a fraction of a Newton, which requires the absolute measurement accuracy of measurement equipment such as force sensors to reach one ten-thousandth, and the force sensor also needs to be in a state of variable speed and variable pose motion. Force sensors that meet these requirements are often extremely expensive, greatly increasing the cost of the equipment. Summary of the Invention

[0004] To solve the above problems, the present invention provides a magnetorheological processing regulation system and a processing method based on instantaneous current sensing, which only need to adjust the rotation speed of the polishing wheel or the liquid pump to solve the problem that the regulation of the polishing wheel in the prior art requires data acquisition by means of a high-precision force sensor, and the high-precision force sensor has a high cost.

[0005] To achieve the above object, the technical solution of the present invention is realized as follows: A magnetorheological processing regulation system based on instantaneous current sensing, comprising: A polishing platform, on which a test polishing element and a to-be-polished element are arranged; A polishing assembly, including an industrial robot and a magnetorheological polishing module. The industrial robot is used to drive the magnetorheological polishing module to move to the position where the test polishing element is located or drive the magnetorheological polishing module to move to the position where the to-be-polished element is located; the magnetorheological polishing module includes a polishing wheel, a nozzle, and a liquid pump. The liquid pump is used to provide magnetorheological fluid to the nozzle, the nozzle is used to spray the magnetorheological fluid onto the polishing wheel, and the polishing wheel is used to process the test polishing element or the to-be-polished element; the working rotation speed of the magnetorheological polishing module is the rotation speed of the liquid pump or the rotation speed of the polishing wheel; A detection circuit, which is used to output a constant voltage, and when the magnetorheological polishing module contacts the surface of the test polishing element, form a first closed loop and detect the first instantaneous current in the first closed loop in real time, or when the magnetorheological polishing module contacts the surface of the to-be-polished element, form a second closed loop and detect the second instantaneous current in the second closed loop in real time; A computer is used to calculate the corresponding relationship between the working speed of a magnetorheological polishing module and the ideal instantaneous current according to polishing data, where the polishing data includes first instantaneous current data detected by a detection circuit at different working speeds of the magnetorheological polishing module; and the computer is used to adjust the working speed of the current magnetorheological polishing module when it is determined that the error between the second instantaneous current detected by the detection circuit and the ideal instantaneous current corresponding to the current working speed of the magnetorheological polishing module exceeds a preset error range, so that the error between the second instantaneous current detected by the detection circuit after the working speed of the magnetorheological polishing module is adjusted and the ideal instantaneous current corresponding to the current working speed is within the preset error range.

[0006] Further, the magnetorheological polishing module further includes a magnetorheological mounting frame, a magnet, a driving wheel, a driven wheel, a synchronous belt and a driving motor; wherein, the magnetorheological mounting frame is connected to an industrial robot, the magnet and the driving motor are respectively arranged on the magnetorheological mounting frame with the polishing wheel, a bearing seat is installed on the magnetorheological mounting frame, a bearing is installed in the bearing seat, the bearing is connected to the polishing wheel, the driven wheel is sleeved on the bearing, the driving wheel is sleeved on the output end of the driving motor, and the synchronous belt is tensioned between the driven wheel and the driving wheel.

[0007] A magnetorheological processing regulation method based on the regulation of the polishing wheel speed is realized by using the above-mentioned magnetorheological processing regulation system based on instantaneous current sensing. The magnetorheological processing regulation method includes the following steps: The industrial robot drives the magnetorheological polishing module to move until it contacts the surface of the test polishing element. The computer sets different polishing wheel speeds to process the test polishing element, and the detection circuit detects the first instantaneous current in the first closed loop in real time to obtain the corresponding relationship between the polishing wheel speed and the first instantaneous current , denotes the polishing wheel speed, denotes the first instantaneous current, denotes the conversion relationship between the polishing wheel speed and the first instantaneous current. Multiple groups of first instantaneous currents and the corresponding polishing wheel speeds are mapped and stored to obtain polishing data. The computer calculates the corresponding relationship between the polishing wheel speed and the ideal instantaneous current according to the polishing data; The industrial robot drives the magnetorheological polishing module to move until it contacts the surface of the element to be polished. The detection circuit detects the second instantaneous current in the second closed loop in real time. When the computer determines that the error between the second instantaneous current and the ideal instantaneous current corresponding to the current polishing wheel speed exceeds the preset error range, the polishing wheel speed is adjusted by controlling the driving motor so that the error between the second instantaneous current detected by the detection circuit after the polishing wheel speed is adjusted and the corresponding ideal instantaneous current is within the preset error range.

[0008] Further, the sampling period for the detection circuit to collect the second instantaneous current is denoted as , adjust the polishing wheel speed to the maximum adjustment value ∆v max The shortest time required is recorded as , , the shortest switching time between two adjacent processing trajectory points on the component to be polished is recorded as , ;in, The fastest adjustment speed for the polishing wheel speed change. is the maximum moving speed of the industrial robot. Indicates the distance between two adjacent machining track points on the component to be polished; The method for adjusting the sampling frequency of the detection circuit includes: judge 、 、 Does the relationship between satisfy the formula: ; If it is not satisfied, the sampling frequency of the detection circuit collecting the second instantaneous current is adjusted until the formula is satisfied. The sampling frequency is .

[0009] Furthermore, by controlling the driving motor to adjust the polishing wheel speed at the current processing trajectory point Make adjustments, including: If the second instantaneous current Does not exceed the allowable variation range When the drive motor is not controlled, the polishing wheel speed at the current processing trajectory point is maintained. constant; If the second instantaneous current Exceeding the allowable variation range and When the polishing wheel speed at the current processing trajectory point is controlled, the drive motor is controlled according to the following formula: To make adjustments: ; in, represents the ideal instantaneous current value, Indicates the adjustment amplitude of the second instantaneous current; If the second instantaneous current Exceeding the allowable variation range and When the polishing wheel speed at the current processing trajectory point is controlled, the drive motor is controlled according to the following formula: To make adjustments: ; in, Indicates the set initial speed of the polishing wheel.

[0010] A method for controlling magnetorheological machining based on the regulation of the rotational speed of a liquid pump, which is realized by using the above-mentioned magnetorheological machining control system based on instantaneous current sensing. The magnetorheological machining control method includes the following steps: The industrial robot drives the magnetorheological polishing module to move until it contacts the surface of the test polishing element. The computer sets different rotational speeds of the liquid pump to machine the test polishing element, and the detection circuit detects the first instantaneous current in the first closed loop in real time to obtain the corresponding relationship between the height of the liquid pump and the first instantaneous current , denotes the first instantaneous current, denotes the rotational speed of the liquid pump, denotes the conversion relationship between the rotational speed of the liquid pump and the first instantaneous current. Multiple groups of first instantaneous currents and the corresponding rotational speeds of the liquid pump are mapped and stored to obtain polishing data. The computer calculates the corresponding relationship between the rotational speed of the liquid pump and the ideal instantaneous current according to the polishing data; The industrial robot drives the magnetorheological polishing module to move until it contacts the surface of the element to be polished. The detection circuit detects the second instantaneous current in the second closed loop in real time. When the computer determines that the error between the second instantaneous current and the ideal instantaneous current corresponding to the current rotational speed of the liquid pump exceeds the preset error range, the rotational speed of the liquid pump is adjusted so that the error between the second instantaneous current detected by the detection circuit after the adjustment of the rotational speed of the liquid pump and the corresponding ideal instantaneous current is within the preset error range.

[0011] Further, the sampling period for the detection circuit to collect the second instantaneous current is denoted as , the shortest time required to adjust the rotational speed of the liquid pump to the maximum adjustment amount is denoted as , , the shortest time for switching between two adjacent machining trajectory points on the element to be polished is denoted as , ; where is the fastest adjustment speed of the rotational speed change of the liquid pump, is the highest moving speed of the industrial robot, denotes the distance between two adjacent machining trajectory points on the element to be polished; The adjustment method for the sampling frequency of the detection circuit includes: Judge whether the relationship between , , satisfies the formula: ; If not, adjust the sampling frequency of the detection circuit to collect the second instantaneous current until the formula is satisfied, and the sampling frequency is .

[0012] Further, adjust the rotational speed of the liquid pump at the current machining trajectory point which includes: If the second instantaneous current does not exceed the allowable change range then do not control the motor of the liquid pump and keep the rotational speed of the liquid pump at the current machining trajectory point unchanged; If the second instantaneous current exceeds the allowable change range and then adjust the rotational speed of the liquid pump at the current machining trajectory point according to the following formula: ; wherein, represents the ideal instantaneous current value, represents the adjustment amplitude of the second instantaneous current; If the second instantaneous current exceeds the allowable change range and then adjust the rotational speed of the liquid pump at the current machining trajectory point according to the following formula: ; wherein, represents the initially set rotational speed of the liquid pump.

[0013] Compared with the prior art, the present invention can achieve the following beneficial effects: When using the magnetorheological polishing module to process the polishing test piece, collect the different working rotational speeds of the magnetorheological polishing module and the corresponding first instantaneous current, then calculate the corresponding relationship between the working rotational speed of the magnetorheological polishing module and the ideal instantaneous current through the collected working rotational speed and the first instantaneous current of the magnetorheological polishing module. After that, judge the second instantaneous current through this relationship, and decide whether to adjust the working rotational speed of the magnetorheological polishing module according to the judgment result, so as to realize the real-time adjustment of the working rotational speed by the computer, make the flow rate fluctuation of the magnetorheological fluid at each machining trajectory point meet the high-precision polishing requirements, and ensure the constancy of the removal function. This process does not require calibration steps for parameters such as gravity compensation, and is not affected by factors such as the weight of the magnetorheological processing module of the robot magnetorheological processing equipment, the running accuracy of the equipment itself, the running speed, the posture, the inertia, and other factors. The accuracy of the measurement data is only limited by the current measurement accuracy of the second instantaneous current between the magnetorheological polishing module and the test piece to be polished. The measurement result is more accurate, and there is no need to add equipment such as high-precision force sensors, reducing the equipment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1Schematic structural diagram of the magnetorheological machining control system based on instantaneous current sensing according to the embodiments of the present invention.

[0015] Reference numerals: polishing platform 1, industrial robot 21, polishing wheel 221, nozzle 222, liquid pump 223, magnetorheological mounting bracket 224, mounting bracket 225, drive motor 226, driving pulley 227, driven pulley 228, synchronous belt 229, current intensity controller 230, computer 3, test polishing element 4, and element to be polished 5. Detailed implementation manners

[0016] In the following, embodiments of the present invention will be described with reference to the drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, their detailed descriptions will not be repeated.

[0017] In order to make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation to the present invention.

[0018] In a first aspect, the present embodiment provides a magnetorheological machining control system based on instantaneous current sensing. The structure of the system is as Figure 1As shown in the figure, it includes a polishing platform 1, a polishing component, a detection circuit, and a computer 3. A test polishing element 4 and a component to be polished 5 are arranged on the polishing platform 1. The polishing component includes an industrial robot 21 and a magnetorheological polishing module. The industrial robot 21 is used to drive the magnetorheological polishing module to move to the position where the test polishing element 4 is located or the position where the component to be polished 5 is located, and is used to adjust the polishing gap between the magnetorheological polishing module and the test polishing element 4 or adjust the polishing gap between the magnetorheological polishing module and the component to be polished 5. The magnetorheological polishing module includes a polishing wheel 221, a nozzle 222, and a liquid pump 223. The liquid pump 223 is used to supply magnetorheological fluid to the nozzle 222, and the nozzle 222 is used to spray the magnetorheological fluid onto the polishing wheel 221. The working speed of the magnetorheological polishing module is the speed of the liquid pump 223 or the speed of the polishing wheel 221. The detection circuit is used to output a constant voltage, and when the magnetorheological polishing module contacts the surface of the test polishing element 4, a first closed loop is formed, and the first instantaneous current in the first closed loop is detected in real time. Or when the magnetorheological polishing module contacts the surface of the component to be polished 5, a second closed loop is formed, and the second instantaneous current in the second closed loop is detected in real time. The computer 3 is used to calculate the corresponding relationship between the working speed of the magnetorheological polishing module and the ideal instantaneous current according to the polishing data. The polishing data includes the first instantaneous current data detected by the detection circuit at different working speeds of the magnetorheological polishing module. And the computer 3 is used to adjust the working speed of the current magnetorheological polishing module when it is determined that the error between the second instantaneous current detected by the detection circuit and the ideal instantaneous current corresponding to the current working speed of the magnetorheological polishing module exceeds the preset error range, so that the error between the second instantaneous current detected by the detection circuit after the working speed of the magnetorheological polishing module is adjusted and the ideal instantaneous current corresponding to the current working speed is within the preset error range.

[0019] In this embodiment, the polishing platform 1 refers to a working platform for experiments, on which a test polishing element 4, a component to be polished 5, and other polishing components are placed. For example, the magnetorheological fluid required for polishing, the supporting tooling for the component to be polished, etc. Among them, the test polishing element 4 is a reference part required for calculating the ideal instantaneous current corresponding to the working speed, and the component to be polished 5 is the part that needs to be processed by magnetorheological polishing.

[0020] In this embodiment, the industrial robot 21 can adopt a six-degree-of-freedom robotic arm or other robots with pose adjustment functions.

[0021] The magnetorheological polishing module includes a magnetorheological mounting bracket 224, a magnet (not shown in the figure), a driving motor 226, a driving pulley 227, a driven pulley 228, and a timing belt 229. Among them, the magnetorheological mounting bracket 224 is connected to the industrial robot 21. The magnet, the driving motor 226, and the polishing wheel 221 are respectively arranged on the magnetorheological mounting bracket 224. The magnet is mounted on the magnetorheological mounting bracket 224 and near the working point of the polishing wheel 221 (in the embodiment of the present invention, it is stipulated that the working point of the polishing wheel 221 is the point of maximum contact between the polishing wheel 221 and the surface of the element to be polished 5 along the normal direction of the surface of the element to be polished 5). The magnet is used to generate a magnetic field, so that the magnetorheological fluid is affected by the magnetic field intensity, thereby changing the stiffness of the magnetorheological fluid. A bearing seat is mounted on the magnetorheological mounting bracket 224, a bearing is mounted in the bearing seat, the bearing is connected to the polishing wheel 221, the driven pulley 228 is sleeved on the bearing, the driving pulley 227 is sleeved on the output end of the driving motor 226, and the timing belt 229 is tensioned between the driven pulley 228 and the driving pulley 227. The polishing wheel 221 is driven to rotate by the driving motor 226. Reference can be made to the Chinese patent with the publication date of July 12, 2024 and the publication number of CN118322074A. By driving the polishing wheel 221 to rotate at a high speed by the driving motor 226, the magnetorheological fluid is brought into the magnetic field action area. The magnetorheological fluid flow forms a magnetorheological ribbon under the action of the magnetic field. The size parameters of the magnetorheological ribbon change with the change of the rotation speed of the polishing wheel 221 or the change of the rotation speed of the liquid pump 223.

[0022] The liquid pump 223 is mounted on one side of the polishing platform 1 through the mounting bracket 225 and is used to supply the magnetorheological fluid to the nozzle 222. The nozzle 222 is mounted on the magnetorheological mounting bracket 224 along the rotation direction of the polishing wheel 221. The liquid pump 223 adopts the DFLD vertical multi-stage pump of Shanghai Orient Pump Industry Co., Ltd.

[0023] In this embodiment, taking the test polishing element 4 as an example to illustrate the polishing principle: when the polishing wheel is processing, the magnetorheological fluid is affected by the magnetic field change, changes from a liquid state to a quasi-solid state, forms a Bingham fluid, and the Bingham fluid applies a shear force to the outer surface of the test polishing element 4 through the rotation of the polishing wheel 221, so as to realize the polishing of the test polishing element 4. The shear forces corresponding to different rotation speeds of the polishing wheel 221 are different, and the achieved polishing effects are different. The shear forces applied to the outer surface of the test polishing element 4 by different rotation speeds of the liquid pump 223 are also different, realizing different polishing effects.

[0024] Through the magnetorheological polishing module, flexible polishing of various components can be realized, especially for optical elements with high-precision requirements on the outer surface.

[0025] It should be noted that there is a strong magnetic phenomenon in the working area where the magnetorheological polishing module is located. The connection of various circuits needs to avoid the working area to prevent the wires from being adsorbed to the magnetorheological polishing module and affecting the normal operation. Preferably, the fixed voltage should not exceed the human safety voltage, and the instantaneous current value measured by the contact resistance should not exceed the human safety current.

[0026] In this embodiment, the detection circuit is built based on the principle of resistance change. There are pressures between the magnetorheological polishing module and the test polishing element 4, and between the magnetorheological polishing module and the element to be polished 5. The pressures corresponding to different polishing gaps are different, and the change in pressure will cause a change in the contact resistance, so the current passing through the contact resistance will change. Taking the test polishing element 4 as an example, the same applies to the element to be polished 5, and the details are as follows: The detection circuit applies a fixed voltage between the magnetorheological polishing module and the test polishing element 4. Using the relationship between the contact resistance and the pressure, the resistance value caused by the pressure change is calculated, and then through the relationship between the fixed voltage, the contact resistance and the instantaneous current, the instantaneous current value is calculated by Ohm's law. The instantaneous current value in the first closed loop is the first instantaneous current. The relationship between the pressure and the contact resistance can be expressed by the following formula: ; Among them, is the resistance value of the contact resistance, is the material coefficient, is the pressure when the magnetorheological polishing module contacts the test polishing element 4, is the coefficient corresponding to the contact form (including point contact, surface contact, line contact, etc.). In this embodiment, is surface contact, so .

[0027] The detection circuit can be implemented by the current intensity controller 230. The current intensity controller 230 can use the DA conversion module of the Smart200 series of Siemens to sense the first instantaneous current between the test polishing element 4 and the polishing wheel 221.

[0028] In this embodiment, the computer 3 is used to calculate the corresponding relationship between the different working speeds of the magnetorheological polishing module and the ideal instantaneous current according to the polishing data collected by the detection circuit at different working speeds of the magnetorheological polishing module. The polishing data includes the first instantaneous current data in the first closed loop detected by the detection circuit at different working speeds.

[0029] The working speed of the magnetorheological polishing module can be preset. Different working speeds should cover the maximum and minimum polishing gaps that the industrial robot 21 can drive the magnetorheological polishing module to move to. The polishing data can be collected multiple times, and finally, the error between multiple groups of polishing data can be reduced by numerical calculation methods such as taking the mean or variance. Then, based on the polishing data, the relationship between the ideal instantaneous current and the working speed of the magnetorheological polishing module can be calculated.

[0030] In this embodiment, the computer 3 calculates the corresponding relationship between different working speeds of the magnetorheological polishing module and the ideal instantaneous current through the correlation between the first instantaneous current data in the first closed loop and the working speed of the magnetorheological polishing module corresponding thereto. With this as a reference, when processing the element to be polished 5, by comparing whether the difference between the second instantaneous current corresponding to the working speed of the magnetorheological polishing module in the second closed loop of the element to be polished 5 and the ideal instantaneous current at this working speed is within the preset error range. If not, the working speed of the magnetorheological polishing module is adjusted so that the second instantaneous current is the same as or within the same preset error range as the ideal instantaneous current corresponding to the current working speed of the magnetorheological polishing module. This method can achieve the effect of real-time adjustment of the working speed of the magnetorheological polishing module during the polishing process based on the corresponding relationship between the working speed and the instantaneous current of the magnetorheological polishing module, thereby realizing the automatic compensation function of the working speed of the magnetorheological polishing module.

[0031] When using the magnetorheological polishing module to process the test polishing element 4, the different working speeds of the magnetorheological polishing module and the corresponding first instantaneous current are collected. Then, the corresponding relationship between the working speed of the magnetorheological polishing module and the ideal instantaneous current is calculated through the working speed and the first instantaneous current of the magnetorheological polishing module. After that, the second instantaneous current is judged based on this relationship, and whether to adjust the working speed of the magnetorheological polishing module is determined according to the judgment result, so as to realize the real-time adjustment of the working speed of the magnetorheological polishing module, making the flow rate fluctuation of the magnetorheological fluid at each processing trajectory point meet the requirements of high-precision polishing and ensuring the constancy of the removal function. This process does not require calibration steps for parameters such as gravity compensation and is not affected by factors such as the weight of the magnetorheological processing module of the robot magnetorheological processing equipment, the running accuracy, running speed, posture, inertia, and other factors of the equipment itself. The accuracy of the measurement data is only limited by the current measurement accuracy of the second instantaneous current between the magnetorheological polishing module and the element to be polished, and the measurement result is more accurate. There is no need to add equipment such as high-precision force sensors, reducing the equipment cost.

[0032] In a second aspect, this embodiment further provides a magnetorheological processing control method based on the adjustment of the polishing wheel speed, which is implemented by using the above-mentioned magnetorheological processing control system based on instantaneous current sensing. The magnetorheological processing control method includes the following steps: The industrial robot drives the magnetorheological polishing module to move until it contacts the surface of the test polishing element. The computer sets different polishing wheel rotation speeds to process the test polishing element, and the detection circuit detects the first instantaneous current in the first closed loop in real time to obtain the corresponding relationship between the polishing wheel rotation speed and the first instantaneous current. , represents the polishing wheel rotation speed, represents the first instantaneous current, represents the conversion relationship between the polishing wheel rotation speed and the first instantaneous current. Multiple groups of first instantaneous currents and the corresponding polishing wheel rotation speeds are mapped and stored to obtain polishing data. The computer calculates the corresponding relationship between the polishing wheel rotation speed and the ideal instantaneous current according to the polishing data; The industrial robot drives the magnetorheological polishing module to move until it contacts the surface of the element to be polished. The detection circuit detects the second instantaneous current in the second closed loop in real time. When the computer determines that the error between the second instantaneous current and the ideal instantaneous current corresponding to the current polishing wheel rotation speed exceeds the preset error range, the driving motor is controlled to adjust the polishing wheel rotation speed so that the error between the second instantaneous current detected by the detection circuit after the polishing wheel rotation speed is adjusted and the corresponding ideal instantaneous current is within the preset error range.

[0033] In this embodiment, it is necessary to first obtain the corresponding relationship between the ideal instantaneous current and the polishing wheel rotation speed. The industrial robot drives the magnetorheological polishing module to move until it contacts the surface of the test polishing element. The part of the polishing wheel in contact with the test polishing element is recorded as the first processing trajectory point. During the measurement of the same set of polishing data, the first processing trajectory point remains unchanged. Optionally, when measuring multiple sets of polishing data, different first processing trajectory points can be selected on the test polishing element to facilitate improving the accuracy of the corresponding relationship between the ideal instantaneous current and the polishing wheel rotation speed.

[0034] During the process of the polishing wheel processing the test polishing element, the computer controls the driving motor to set different polishing wheel rotation speeds, collects the first instantaneous currents in the first closed loop corresponding to different polishing wheel rotation speeds, maps and stores multiple groups of first instantaneous currents and the corresponding polishing wheel rotation speeds to obtain polishing data, and the computer calculates the corresponding relationship between the polishing wheel rotation speed and the ideal instantaneous current according to the polishing data.

[0035] After obtaining the corresponding relationship between the ideal instantaneous current and the polishing wheel rotation speed, when processing the element to be polished, the polishing wheel rotation speed can be adjusted according to this corresponding relationship so that the second instantaneous current corresponding to the current polishing wheel rotation speed and the ideal instantaneous current are within the same preset error range.

[0036] In some embodiments, the correspondence between the polishing wheel rotation speed and the ideal instantaneous current is a functional curve relationship, which is characterized by the correspondence between the polishing wheel rotation speed and the first instantaneous current. The correspondence between the polishing wheel rotation speed and the first instantaneous current is obtained by fitting based on a plurality of discrete values of the polishing wheel rotation speed and the first instantaneous current.

[0037] In this embodiment, a plurality of polishing wheel rotation speeds correspond to a plurality of first instantaneous currents, and both the polishing wheel rotation speed and the first instantaneous current are discrete values. Therefore, it is necessary to fit the discrete values.

[0038] Fitting process: Import the discrete data into Matlab software, and use the polyfit fitting instruction of Matlab software to complete data fitting and solve the correspondence between the polishing wheel rotation speed and the current parameters. ; The Polyfit fitting instruction is a basic general instruction of matlab software. Finally, the correspondence between the polishing wheel rotation speed and the first instantaneous current is: .

[0039] In this way, the correspondence between the ideal instantaneous current and the polishing wheel rotation speed can be seen more intuitively. Based on this, the element to be polished under the same polishing conditions can be processed, and the automatic compensation effect of the polishing wheel rotation speed can be achieved.

[0040] In some embodiments, the sampling period for the detection circuit to collect the second instantaneous current is denoted as , the shortest time required to adjust the polishing wheel rotation speed to the maximum adjustment amount ∆v max is denoted as , , the shortest time for switching between two adjacent processing trajectory points on the element to be polished is denoted as , ; where is the fastest adjustment speed of the polishing wheel rotation speed change, is the highest moving speed of the industrial robot, represents the distance between two adjacent processing trajectory points on the element to be polished; The method for adjusting the sampling frequency of the detection circuit includes: Judge , , whether the relationship between them satisfies the formula: ; If not, adjust the sampling frequency of the detection circuit to collect the second instantaneous current until the formula is satisfied, and the sampling frequency is .

[0041] In this embodiment, the above formula gives the correspondence relationship among three time elements, that is: within a single sampling period, the industrial robot can adjust the magnetorheological polishing module so that it moves to the polishing wheel speed corresponding to the ideal instantaneous current, and then conducts the next sampling, avoiding the sampling period being too long resulting in too slow sampling frequency, making the sampling frequency not match the adjustment speed of the polishing wheel speed, and the adjustment being untimely, resulting in the inability to know the current state of the second instantaneous current and affecting the automatic compensation function of the polishing wheel speed.

[0042] In some embodiments, if the current polishing wheel speed is adjusted to the second instantaneous current and the error between the ideal instantaneous current corresponding to the current polishing wheel speed is equal to or greater than the upper threshold of the preset error range, the adjustment amplitude corresponding to the current polishing wheel speed is , the value of the second instantaneous current corresponding to the current polishing wheel speed is , represents the ideal instantaneous current value, represents the adjustment amplitude of the second instantaneous current; If the current polishing wheel speed is adjusted to the second instantaneous current and the error between the ideal instantaneous current corresponding to the current polishing wheel speed is equal to or greater than the lower threshold of the preset error range, the adjustment amplitude corresponding to the current polishing wheel speed is , the value of the second instantaneous current corresponding to the current polishing wheel speed is ; By controlling the drive motor to adjust the polishing wheel speed at the current machining trajectory point, it includes: If the second instantaneous current does not exceed the allowable change range , the drive motor is not controlled, and the polishing wheel speed at the current machining trajectory point is kept unchanged; If the second instantaneous current exceeds the allowable change range and , then control the drive motor and adjust the polishing wheel speed at the current machining trajectory point according to the following formula: ; Among them, represents the ideal instantaneous current value, represents the adjustment amplitude of the second instantaneous current; If the second instantaneous current exceeds the allowable variation range and at this time, then control the drive motor, and adjust the polishing wheel speed of the current machining trajectory point according to the following formula as follows: ; wherein, represents the set initial speed of the polishing wheel.

[0043] It should be noted that the polishing wheel speed of the current machining trajectory point has the same meaning as the current polishing wheel speed.

[0044] After adjusting the polishing wheel speed of the current machining trajectory point so that the polishing wheel speed of the next machining trajectory point corresponding to the second instantaneous current returns to the allowable variation range to meet the requirements of the polishing gap change for magnetorheological high-precision machining.

[0045] When the above technical solution uses the magnetorheological polishing module to process the test polishing element, different polishing wheel speeds and the corresponding first instantaneous currents are collected, and then the corresponding relationship between the polishing wheel speed and the ideal instantaneous current is calculated through the collected polishing wheel speed and the first instantaneous current. After that, the second instantaneous current is judged based on this relationship, and whether to adjust the polishing wheel speed is determined according to the judgment result, so as to realize the real-time adjustment and compensation of the polishing wheel speed, make the flow rate fluctuation of the magnetorheological fluid at each machining trajectory point meet the requirements of high-precision polishing, and ensure the constancy of the removal function. This process does not require calibration steps for parameters such as gravity compensation, and is not affected by the weight of the magnetorheological processing module of the robot magnetorheological processing equipment, the running accuracy, running speed, attitude, inertia and other factors of the equipment itself. The accuracy of the measurement data is only limited by the current measurement accuracy of the second instantaneous current between the magnetorheological polishing module and the element to be polished. The measurement result is more accurate, and there is no need to add equipment such as high-precision force sensors, reducing the equipment cost.

[0046] In the third aspect, this embodiment also provides a magnetorheological processing control method based on the adjustment of the liquid pump speed, which is realized by using the above magnetorheological processing control system based on instantaneous current perception. The magnetorheological processing control method includes the following steps: The industrial robot drives the magnetorheological polishing module to move until it contacts the surface of the test polishing element. The computer sets different rotational speeds of the liquid pump to process the test polishing element. The detection circuit detects the first instantaneous current in the first closed loop in real time, and obtains the corresponding relationship between the height of the liquid pump and the first instantaneous current. , represents the first instantaneous current, represents the rotational speed of the liquid pump, represents the conversion relationship between the rotational speed of the liquid pump and the first instantaneous current. Multiple groups of first instantaneous currents and the corresponding rotational speeds of the liquid pump are mapped and stored to obtain polishing data. The computer calculates the corresponding relationship between the rotational speed of the liquid pump and the ideal instantaneous current according to the polishing data; The industrial robot drives the magnetorheological polishing module to move until it contacts the surface of the element to be polished. The detection circuit detects the second instantaneous current in the second closed loop in real time. When the computer determines that the error between the second instantaneous current and the ideal instantaneous current corresponding to the current rotational speed of the liquid pump exceeds the preset error range, the rotational speed of the liquid pump is adjusted so that the error between the second instantaneous current detected by the detection circuit after the adjustment of the rotational speed of the liquid pump and the corresponding ideal instantaneous current is within the preset error range.

[0047] In this embodiment, it is necessary to first obtain the corresponding relationship between the ideal instantaneous current and the rotational speed of the liquid pump. The industrial robot drives the magnetorheological polishing module to move until it contacts the surface of the test polishing element. The part of the polishing wheel in contact with the test polishing element is recorded as the first machining trajectory point. During the process of measuring the same set of polishing data, the first machining trajectory point remains unchanged. Optionally, when measuring multiple sets of polishing data, different first machining trajectory points can be selected on the test polishing element to facilitate improving the accuracy of the corresponding relationship between the ideal instantaneous current and the rotational speed of the liquid pump.

[0048] During the process of the polishing wheel processing the test polishing element, the computer controls the drive motor to set different rotational speeds of the liquid pump, collects the first instantaneous currents in the first closed loop corresponding to different rotational speeds of the liquid pump, maps and stores multiple groups of first instantaneous currents and the corresponding rotational speeds of the liquid pump to obtain polishing data. The computer calculates the corresponding relationship between the rotational speed of the liquid pump and the ideal instantaneous current according to the polishing data.

[0049] After obtaining the corresponding relationship between the ideal instantaneous current and the rotational speed of the liquid pump, when processing the element to be polished, the rotational speed of the liquid pump can be adjusted according to this corresponding relationship so that the second instantaneous current corresponding to the current rotational speed of the liquid pump and the ideal instantaneous current are within the same preset error range.

[0050] In some embodiments, the correspondence between the liquid pump speed and the ideal instantaneous current is a functional curve relationship, which is characterized by the correspondence between the liquid pump speed and the first instantaneous current. The correspondence between the liquid pump speed and the first instantaneous current is obtained by fitting based on multiple discrete values of the liquid pump speed and the first instantaneous current.

[0051] In this embodiment, the liquid pump speed and the first instantaneous current have a one-to-one correspondence, and both the liquid pump speed and the first instantaneous current are discrete values. Therefore, it is necessary to fit the discrete values.

[0052] Fitting process: Import the discrete data into Matlab software, and complete the data fitting with the help of the polyfit fitting instruction in Matlab software to solve the correspondence between the liquid pump speed and the current parameters. ; The Polyfit fitting instruction is a basic general instruction in Matlab software. Finally, the correspondence between the liquid pump speed and the first instantaneous current is as follows: .

[0053] In this way, the correspondence between the ideal instantaneous current and the liquid pump speed can be more intuitively seen. Based on this, the element to be polished under the same polishing conditions can be processed, and the automatic compensation effect of the liquid pump speed can be achieved.

[0054] In some embodiments, the sampling period for the detection circuit to collect the second instantaneous current is denoted as , the shortest time required to adjust the liquid pump speed to the maximum adjustment amount is denoted as , , the shortest time for switching between two adjacent processing trajectory points on the element to be polished is denoted as , ; where is the fastest adjustment speed of the liquid pump speed change, is the highest moving speed of the industrial robot, represents the distance between two adjacent processing trajectory points on the element to be polished; The adjustment method for the sampling frequency of the detection circuit includes: Judge , , whether the relationship between them satisfies the formula: ; If not, adjust the sampling frequency of the detection circuit to collect the second instantaneous current until the formula is satisfied, and the sampling frequency is .

[0055] In this embodiment, the above formula gives the correspondence relationship among three time elements, that is: within a single sampling period, the industrial robot can adjust the magnetorheological polishing module so that it moves to the liquid pump speed corresponding to the ideal instantaneous current, and then conducts the next sampling, avoiding that the sampling period is too long resulting in too slow sampling frequency, making the sampling frequency not match the adjustment speed of the liquid pump speed, causing untimely adjustment, resulting in the inability to know the current state of the second instantaneous current, and affecting the automatic compensation function of the liquid pump speed.

[0056] In some embodiments, if the current liquid pump speed is adjusted to the second instantaneous current and the error between the ideal instantaneous current corresponding to the current liquid pump speed is equal to or greater than the upper threshold value of the preset error range, the adjustment amplitude corresponding to the current liquid pump speed is , the value of the second instantaneous current corresponding to the current liquid pump speed is , represents the ideal instantaneous current value, represents the adjustment amplitude of the second instantaneous current; If the current liquid pump speed is adjusted to the second instantaneous current and the error between the ideal instantaneous current corresponding to the current liquid pump speed is equal to or greater than the lower threshold value of the preset error range, the adjustment amplitude corresponding to the current liquid pump speed is , the value of the second instantaneous current corresponding to the current liquid pump speed is ; Adjusting the liquid pump speed of the current machining trajectory point includes: If the second instantaneous current does not exceed the allowable change range , the motor of the liquid pump is not controlled, and the liquid pump speed of the current machining trajectory point is kept unchanged; If the second instantaneous current exceeds the allowable change range and , then the liquid pump speed of the current machining trajectory point is adjusted according to the following formula: ; Among them, represents the ideal instantaneous current value, Represents the adjustment amplitude of the second instantaneous current; If the second instantaneous current exceeds the allowable variation range and at this time, then the liquid pump speed of the current machining trajectory point is adjusted according to the following formula as follows: ; wherein, represents the initially set liquid pump speed.

[0057] It should be noted that the liquid pump speed of the current machining trajectory point has the same meaning as the current liquid pump speed.

[0058] After adjusting the liquid pump speed of the current machining trajectory point so that the liquid pump speed of the next machining trajectory point corresponding to the second instantaneous current A i returns to the allowable variation range to meet the requirements of the polishing gap change for magnetorheological high-precision machining.

[0059] When the above technical solution uses the magnetorheological polishing module to process the test polishing element, different liquid pump speeds and the corresponding first instantaneous currents are collected, and then the corresponding relationship between the liquid pump speed and the ideal instantaneous current is calculated through the collected liquid pump speed and the first instantaneous current. After that, the second instantaneous current is judged through this relationship, and whether to adjust the liquid pump speed is determined according to the judgment result, so as to realize the real-time adjustment compensation of the liquid pump speed, make the flow rate fluctuation of the magnetorheological fluid at each machining trajectory point meet the requirements of high-precision polishing, and ensure the constancy of the removal function. This process does not require calibration steps for parameters such as gravity compensation, and is not affected by the weight of the magnetorheological processing module of the robot magnetorheological processing equipment, the running accuracy, running speed, posture, inertia and other factors of the equipment itself. The accuracy of the measurement data is only limited by the current measurement accuracy of the second instantaneous current between the magnetorheological polishing module and the element to be polished. The measurement result is more accurate, and there is no need to add equipment such as high-precision force sensors, reducing the equipment cost.

[0060] It should be understood that the various forms of the flow shown above can be used, with steps reordered, added or deleted. For example, the steps recorded in the disclosure of the present invention can be executed in parallel, sequentially or in a different order, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and no limitation is made herein.

[0061] The above specific embodiments do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A magnetorheological machining control system based on instantaneous current sensing, characterized in that, Comprising: A polishing platform, on which a test polishing element and a to-be-polished element are arranged; A polishing assembly, including an industrial robot and a magnetorheological polishing module. The industrial robot is used to drive the magnetorheological polishing module to move to the position where the test polishing element is located or drive the magnetorheological polishing module to move to the position where the to-be-polished element is located. The magnetorheological polishing module includes a polishing wheel, a nozzle, and a liquid pump. The liquid pump is used to supply magnetorheological fluid to the nozzle, the nozzle is used to spray the magnetorheological fluid onto the polishing wheel, and the polishing wheel is used to process the test polishing element or the to-be-polished element. The working speed of the magnetorheological polishing module is the rotational speed of the liquid pump or the rotational speed of the polishing wheel; A detection circuit, used to output a constant voltage, and when the magnetorheological polishing module contacts the surface of the test polishing element, form a first closed loop and detect the first instantaneous current in the first closed loop in real time, or when the magnetorheological polishing module contacts the surface of the to-be-polished element, form a second closed loop and detect the second instantaneous current in the second closed loop in real time; A computer, used to calculate the corresponding relationship between the working speed of the magnetorheological polishing module and the ideal instantaneous current according to the polishing data. The polishing data includes the first instantaneous current data detected by the detection circuit at different working speeds of the magnetorheological polishing module. And the computer is used to adjust the working speed of the current magnetorheological polishing module when it is determined that the error between the second instantaneous current detected by the detection circuit and the ideal instantaneous current corresponding to the current working speed of the magnetorheological polishing module exceeds the preset error range, so that the error between the second instantaneous current detected by the detection circuit after the working speed of the magnetorheological polishing module is adjusted and the ideal instantaneous current corresponding to the current working speed is within the preset error range.

2. The magnetorheological machining control system based on instantaneous current sensing according to claim 1, wherein The magnetorheological polishing module further includes a magnetorheological mounting bracket, a magnet, a driving wheel, a driven wheel, a synchronous belt, and a driving motor. Among them, the magnetorheological mounting bracket is connected to the industrial robot, the magnet and the driving motor are respectively arranged on the magnetorheological mounting bracket with the polishing wheel. A bearing seat is installed on the magnetorheological mounting bracket, a bearing is installed in the bearing seat, the bearing is connected to the polishing wheel, the driven wheel is sleeved on the bearing, and the driving wheel is sleeved on the output end of the driving motor. The synchronous belt is tensioned between the driven wheel and the driving wheel.

3. A magnetorheological machining control method based on the regulation of the polishing wheel rotation speed, which is realized by using the magnetorheological machining control system based on instantaneous current sensing described in claim 2, and is characterized in that, The magnetorheological processing control method includes the following steps: The industrial robot drives the magnetorheological polishing module to move until it contacts the surface of the test polishing element. The computer sets different polishing wheel speeds to process the test polishing element, and the detection circuit detects the first instantaneous current in the first closed loop in real time to obtain the corresponding relationship between the polishing wheel speed and the first instantaneous current , represents the polishing wheel speed, represents the first instantaneous current, represents the conversion relationship between the polishing wheel speed and the first instantaneous current. Multiple groups of first instantaneous currents and the corresponding polishing wheel speeds are mapped and stored to obtain polishing data. The computer calculates the corresponding relationship between the polishing wheel speed and the ideal instantaneous current according to the polishing data; The industrial robot drives the magnetorheological polishing module to move until it contacts the surface of the to-be-polished element. The detection circuit detects the second instantaneous current in the second closed loop in real time. When the computer determines that the error between the second instantaneous current and the ideal instantaneous current corresponding to the current rotational speed of the polishing wheel exceeds the preset error range, the rotational speed of the polishing wheel is adjusted by controlling the driving motor so that the error between the second instantaneous current detected by the detection circuit after the rotational speed of the polishing wheel is adjusted and the corresponding ideal instantaneous current is within the preset error range.

4. The magnetorheological machining control method based on the polishing wheel speed adjustment according to claim 3, characterized in that Denote the sampling period for the detection circuit to collect the second instantaneous current as , and denote the shortest time required to adjust the polishing wheel speed to the maximum adjustment amount ∆v max as , , and denote the shortest switching time between two adjacent machining trajectory points on the component to be polished as , ; where is the fastest adjustment speed of the polishing wheel speed change, is the highest moving speed of the industrial robot, represents the distance between two adjacent machining trajectory points on the component to be polished; The adjustment method of the sampling frequency of the detection circuit includes: Determine and and whether the relationship between them satisfies the formula: ； If not satisfied, adjust the sampling frequency of the detection circuit for collecting the second instantaneous current until the formula is satisfied, and the sampling frequency is .

5. The magnetorheological machining control method based on the adjustment of the polishing wheel speed according to claim 4, characterized in that, Adjust the polishing wheel speed of the current machining trajectory point by controlling the driving motor The adjustment includes: If the second instantaneous current does not exceed the allowable change range the drive motor is not controlled, and the polishing wheel speed at the current machining trajectory point is maintained unchanged; If the second instantaneous current exceeds the allowable change range and at this time, then control the drive motor and adjust the polishing wheel speed of the current machining trajectory point according to the following formula as follows: ； Among them, represents the ideal instantaneous current value, represents the adjustment amplitude of the second instantaneous current; If the second instantaneous current exceeds the allowable change range and at this time, then control the drive motor and adjust the polishing wheel speed of the current machining trajectory point according to the following formula as follows: ； Among them, represents the set initial rotational speed of the polishing wheel.

6. A magnetorheological machining control method based on the rotational speed adjustment of a liquid pump, which is realized by using the magnetorheological machining control system based on instantaneous current sensing described in claim 1, characterized in that, The magnetorheological processing control method includes the following steps: The industrial robot drives the movement of the magnetorheological polishing module until it contacts the surface of the test polishing element. The computer sets different liquid pump speeds to process the test polishing element, and the detection circuit detects the first instantaneous current in the first closed loop in real time to obtain the corresponding relationship between the liquid pump height and the first instantaneous current. , represents the first instantaneous current, represents the liquid pump speed, represents the conversion relationship between the liquid pump speed and the first instantaneous current. Multiple groups of first instantaneous currents and the corresponding liquid pump speeds are mapped and stored to obtain polishing data. The computer calculates the corresponding relationship between the liquid pump speed and the ideal instantaneous current according to the polishing data; The industrial robot drives the magnetorheological polishing module to move until it contacts the surface of the element to be polished. The detection circuit detects the second instantaneous current in the second closed loop in real time. When the computer determines that the error between the second instantaneous current and the ideal instantaneous current corresponding to the current liquid pump speed exceeds the preset error range, the liquid pump speed is adjusted so that the error between the second instantaneous current detected by the detection circuit after the liquid pump speed is adjusted and the corresponding ideal instantaneous current is within the preset error range.

7. The magnetorheological machining control method based on the rotational speed regulation of a liquid pump according to claim 6, characterized in that, Denote the sampling period for the detection circuit to collect the second instantaneous current as , and denote the shortest time required to adjust the liquid pump speed to the maximum adjustment amount as . , , and denote the shortest switching time between two adjacent machining trajectory points on the component to be polished as . ; where is the fastest adjustment speed of the liquid pump speed change, is the highest moving speed of the industrial robot, represents the distance between two adjacent machining trajectory points on the component to be polished; The method for adjusting the sampling frequency of the detection circuit includes: Judge , , Whether the relationship between them satisfies the formula: ； If not satisfied, adjust the sampling frequency of the detection circuit for collecting the second instantaneous current until the formula is satisfied, and the sampling frequency is .

8. The magnetorheological machining control method based on the rotational speed regulation of a liquid pump according to claim 7, wherein Adjust the liquid pump speed of the current machining trajectory point including: If the second instantaneous current does not exceed the allowable change range the motor of the liquid pump is not controlled, and the rotational speed of the liquid pump at the current machining trajectory point is maintained unchanged; If the second instantaneous current exceeds the allowable change range and then, according to the following formula, the liquid pump speed of the current machining trajectory point is adjusted: ； Among them, represents the ideal instantaneous current value, represents the adjustment range of the second instantaneous current; If the second instantaneous current exceeds the allowable change range and at this time, then the liquid pump speed of the current machining trajectory point is adjusted according to the following formula: ； Among them, represents the initially set rotational speed of the liquid pump.

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