Workpiece anti-slip motion control method for a video measuring machine stage

Abstract

The application discloses a workpiece anti-slipping motion control method for a worktable of a video measuring instrument, and steps include presetting a control speed curve equation, respectively determining a corresponding acceleration curve equation and a displacement curve equation; based on a workpiece target moving distance, a preset moving speed and a maximum acceleration, simultaneously solving the speed curve equation and the acceleration curve equation, and solving unknown constant terms in the equation; using a grating ruler to obtain a real-time position of the workpiece, based on the solved control speed curve equation and the displacement curve equation, solving a motion time through a Newton iteration method; and substituting the motion time into the solved control speed curve equation to obtain an expected motion speed. The application can completely eliminate workpiece slipping, avoid setting a tool clamp and manual clamping, and effectively improve continuous measurement efficiency.

Description

Technical Field

[0001] This invention relates to the field of anti-slip control technology, and more specifically to a method for controlling the anti-slip movement of a workpiece on a stage of an image measuring instrument. Background Technology

[0002] Automatic image measuring instrument is a high-precision measuring device based on optical imaging. The workpiece to be measured is placed on a moving platform, and the motor drives the X and Y axes to move, thereby acquiring a complete image of the workpiece, identifying the edge pixels of the workpiece contour, and obtaining accurate dimensional results through calculation.

[0003] However, the unstable movement of the stage can cause relative slippage of the workpiece on the stage, resulting in the stitched image not truly corresponding to the contour of the workpiece, thus introducing a large uncertainty in the system measurement error.

[0004] To prevent unexpected relative slippage of the workpiece under test, the traditional method is to use tooling fixtures to fix it to ensure the stability of the workpiece. However, this method requires the design of specific fixtures for each different workpiece under test, which has poor versatility. In addition, each workpiece needs to be manually installed and fixed, which is time-consuming and labor-intensive, resulting in low measurement efficiency. Summary of the Invention

[0005] In view of this, in order to solve the above-mentioned technical problems, the present invention provides a workpiece anti-slip motion control method for a stage of an image measuring instrument.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preventing workpiece slippage motion control on a stage of an image measuring instrument, comprising:

[0008] Pre-set the control velocity curve equation, and determine the corresponding acceleration curve equation and displacement curve equation respectively;

[0009] Based on the target moving distance of the workpiece, the preset moving speed and the maximum acceleration, the control speed curve equation and the acceleration curve equation are combined to solve for the unknown constant terms in the equations.

[0010] The real-time position of the workpiece is obtained using a grating ruler. Based on the solved control velocity curve equation and displacement curve equation, the motion time is solved using the Newton-Raphson iteration method.

[0011] Substituting the motion time into the solved control speed curve equation, the expected motion speed is obtained;

[0012] Update the current motor speed using the expected speed.

[0013] In one optional embodiment, the acceleration curve equation is determined by differentiation of the control velocity curve equation, and the displacement curve equation is determined by integration of the control velocity curve equation.

[0014] In an optional embodiment, the equation for the control speed curve is: ;

[0015] The equation for the acceleration curve is: ;

[0016] The equation of the displacement curve is: ;

[0017] and For the unknown constant term in the equation, Indicates speed control. Indicates acceleration. denoted by displacement, and t represents time t.

[0018] In one optional embodiment, solving for the unknown constant term in the equation includes:

[0019] When the workpiece can accelerate to a preset speed within the target moving distance, solve the problem by simultaneously solving the velocity curve equation and the acceleration curve equation: ;

[0020] In the formula, The equation for the velocity curve is... The equation for the acceleration curve is... To preset the movement speed, For maximum speed, This represents the maximum acceleration time.

[0021] In an optional embodiment, solving for the unknown constant term in the equation further includes:

[0022] When the workpiece cannot accelerate to the preset speed within the target moving distance, the maximum speed that the workpiece can accelerate to within the target moving distance is used to replace the preset moving speed in order to correct the unknown constant term.

[0023] In an optional embodiment, the motion time is solved using Newton's iteration method, and the solution formula is: ;

[0024] In the formula, express The theoretical displacement at time t, express The derivative, This indicates that the grating ruler acquires the real-time position of the workpiece;

[0025] The iteration stopping condition is: , Indicates the error threshold. This represents the (n-1)th time. This represents the nth time point.

[0026] In one alternative embodiment, during the acceleration phase, the initial value of the iteration time is the maximum acceleration time. During the deceleration phase, the initial value at each iteration time is t. , This represents the total motion time.

[0027] In one optional embodiment, the expected motion speeds of the X-axis and Y-axis are obtained based on the maximum accelerations of the X-axis and Y-axis, respectively. The maximum accelerations of each axis are determined based on the thrust of the stage on the workpiece and the maximum static friction of the workpiece.

[0028] As can be seen from the above technical solution, the present invention discloses a workpiece anti-slip motion control method for a stage of an image measuring instrument. When the workpiece to be measured does not need to be fixedly placed on the moving stage, it can prevent slippage on the stage plane under any set motion speed and moving distance. Compared with the prior art, it can completely eliminate workpiece slippage, avoid the need for tooling fixtures and manual clamping, effectively improve motion efficiency and testing efficiency, and ensure positioning accuracy. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] Figure 1 This is a flowchart of the workpiece anti-slip motion control method for the stage of an image measuring instrument according to the present invention;

[0031] Figure 2 This is a schematic diagram of the movement of the stage of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0034] This invention discloses a workpiece anti-slip motion control method for a stage of an image measuring instrument. The purpose is to enable measurement to begin immediately when the workpiece to be measured is placed on the stage without the need for manual installation and fixation with clamps, while ensuring that the workpiece does not slip relative to the stage, and while meeting the measurement efficiency requirements.

[0035] The solution adopted in this invention is as follows: Figure 1 The steps are as follows:

[0036] Pre-set the control velocity curve equation, and determine the corresponding acceleration curve equation and displacement curve equation respectively;

[0037] Based on the target moving distance of the workpiece, the preset moving speed and the maximum acceleration, the velocity curve equation and the acceleration curve equation are combined to solve for the unknown constant term in the equation;

[0038] The real-time position of the workpiece is obtained using a grating ruler. Based on the solved control velocity curve equation and displacement curve equation, the motion time is solved using the Newton-Raphson iteration method.

[0039] Substituting the motion time into the solved control speed curve equation, the expected motion speed is obtained;

[0040] Update the current motor speed using the expected speed.

[0041] In this embodiment, the above scheme mainly includes two parts: solving for the unknown constant terms of the control equations and iteratively solving for the motion time.

[0042] In one embodiment, the first part includes:

[0043] A preset control velocity curve equation is used to determine the corresponding acceleration curve equation and displacement curve equation. Based on the target moving distance of the workpiece, the preset moving speed, and the maximum acceleration, the velocity curve equation and acceleration equation are combined to solve for the unknown constant terms in the equations.

[0044] In this embodiment, the acceleration curve equation is determined by differentiating the control velocity curve equation, and the displacement curve equation is determined by integrating the control velocity curve equation.

[0045] Meanwhile, the maximum acceleration is determined based on the thrust of the stage on the workpiece and the maximum static friction of the workpiece. In other words, the fundamental reason for relative slippage of the workpiece on the stage is that the acceleration and deceleration thrust of the stage exceeds the maximum static friction between the workpiece and the stage. Therefore, by controlling the acceleration and deceleration thrust of the stage, relative slippage of the workpiece on the stage can be prevented.

[0046] The thrust F exerted by the stage on the workpiece being measured = mass of the workpiece being measured m × acceleration of the stage. The maximum static friction force of the workpiece being tested =Dynamic friction factor × the mass of the workpiece being measured (m) × the acceleration due to gravity (g); therefore, it is necessary to control the thrust of the stage during acceleration and deceleration to not exceed the static friction force of the workpiece being measured, that is, to satisfy... Therefore, the maximum acceleration is: , It can be obtained based on material properties and prior data.

[0047] The motion stage of the imaging measuring instrument includes two axes, X and Y, such as... Figure 2 As shown, based on the movement trajectory of the workpiece being measured, the maximum thrust along both the X and Y axes is calculated, provided that the maximum net thrust does not exceed the critical value of static friction. Assuming the linear trajectory of the workpiece makes an angle θ with the X-axis, the maximum permissible thrust along the X-axis is... Maximum permissible thrust along the Y-axis Further calculate the maximum allowable acceleration along each of the X and Y axes. .

[0048] To control the moving platform to not exceed the maximum thrust calculated by the above theory during the movement, the traditional PID control algorithm is difficult to apply to the specific motion control scenario. At the same time, in order to improve the smoothness of the motion process, this embodiment proposes a full-stroke closed-loop maximum acceleration tracking control algorithm.

[0049] The algorithm includes two scenarios:

[0050] 1) When the workpiece can accelerate to a preset speed within the target moving distance, solve for the unknown constant terms in the equations by simultaneously solving the velocity curve equation and the acceleration curve equation: ;

[0051] In the formula, To preset the movement speed, For maximum speed, This represents the maximum acceleration time.

[0052] 2) If the workpiece cannot be accelerated to the preset speed within the target moving distance, the maximum speed that the workpiece can accelerate to within the target moving distance is replaced with the preset moving speed to correct the unknown constant term;

[0053] In some implementation schemes, the entire process of a single movement includes:

[0054] The equation for the control speed curve is: ;

[0055] The equation for the acceleration curve is: ;

[0056] The equation of the displacement curve is: .

[0057] In the above formula, t represents time, and the only unknown constant term is... and .

[0058] When the entire travel distance The internal acceleration can reach the speed set by the software. Solve the following equations simultaneously: ;

[0059] Solving for:

[0060] , , ;

[0061] At this point, the equations of the curves during the acceleration phase are:

[0062] ;

[0063] ;

[0064] ;

[0065] When distance If the speed is too small to accelerate to the set speed, the maximum acceleration is kept constant. The preset speed is replaced with the maximum speed that can be accelerated to correct the unknown coefficients, and the solution is obtained according to the corrected motion model.

[0066] At this point, the acceleration time is: ;

[0067] In one embodiment, the second part includes:

[0068] After solving the unknown constant terms of the equations, the definite control velocity curve equation and displacement curve equation can be obtained.

[0069] At this time, the real-time position of the workpiece is obtained by using a grating ruler. The position information is fed back in real time by the grating ruler, which directly reflects the spatial position state of the moving platform. Using position information as the input of the model has higher robustness than time information in the actual control process.

[0070] Then, based on the solved control speed curve equation and displacement curve equation, the motion time is solved using Newton's iteration method; the motion time is then substituted into the solved control speed curve equation to obtain the expected motion speed; and the current motor motion speed is updated using the expected motion speed.

[0071] In this embodiment, the solution for the motion time is obtained using Newton's iteration method, and the formula is as follows: ;

[0072] In the formula, express The theoretical displacement at time t, express The derivative, This indicates that the grating ruler acquires the real-time position of the workpiece; it continues to iterate until the following condition is met: , Indicates the error threshold. This represents the (n-1)th time. This represents the nth moment, at which the motion time is calculated. .

[0073] Furthermore, based on the current motion time obtained through iterative solution... Calculate the current expected speed of motion as And update the current motor speed to .

[0074] To further optimize the above technical solution and ensure the convergence of Newton's iterative solution within the interval, the initial value in the acceleration phase of this embodiment is the maximum acceleration time. The initial value during the deceleration phase is set to the minimum value, i.e., at time [time value missing]. , The total exercise time, The maximum deceleration time is preset to be equal to the maximum acceleration time in this scheme.

[0075] This application determines the motor speeds of the X and Y axes using the above-mentioned scheme, thereby ensuring that the workpiece being measured does not slip on the platform plane under any set speed and distance, without the need for clamping and fixing.

[0076] In one or more embodiments, a workpiece anti-slip motion control system for the stage of the image measuring instrument is provided, including an industrial computer, and a motion controller, a motor driver and a linear motor connected thereto in sequence, as well as a feedback grating ruler;

[0077] First, determine the maximum acceleration in the X and Y axes, then determine the target movement distance and preset the movement speed; and solve the control velocity curve equation and displacement curve equation.

[0078] Furthermore, by using a grating ruler for sampling, the actual position information of the workpiece is obtained. Based on the control speed curve equation and the displacement curve equation, the motion time is solved using the Newton-Raphson iteration method, thereby calculating the unexpected motion speed so as to update the current motor speed and thus achieve precise control of the workpiece.

[0079] This case applies to fields such as semiconductor manufacturing, precision medicine, and aerospace, and represents a technological leap in precision motion control that eliminates the need for manual clamping intervention.

[0080] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0081] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preventing workpiece slippage motion control on a stage of an image measuring instrument, characterized in that, A preset control velocity curve equation is used; the acceleration curve equation is determined by differentiating the control velocity curve equation; and the displacement curve equation is determined by integrating the control velocity curve equation. The equation for the control speed curve is: ; The equation for the acceleration curve is: ; The equation of the displacement curve is: ; and For the unknown constant term in the equation, Indicates speed control. Indicates acceleration. The displacement is represented by t, and t represents time t. Based on the target moving distance of the workpiece, the preset moving speed and the maximum acceleration, the control speed curve equation and the acceleration curve equation are combined to solve for the unknown constant term in the equation; the maximum acceleration is determined based on the thrust of the stage on the workpiece and the maximum static friction force of the workpiece. The real-time position of the workpiece is obtained using a grating ruler. Based on the solved control velocity curve equation and displacement curve equation, the motion time is solved using the Newton-Raphson iteration method. Substituting the motion time into the solved control speed curve equation, the expected motion speed is obtained; Update the current motor speed using the expected speed.

2. The workpiece anti-slip motion control method according to claim 1, characterized in that, Solving for the unknown constant term in the equation includes: When the workpiece can accelerate to a preset speed within the target moving distance, solve the problem by simultaneously solving the velocity curve equation and the acceleration curve equation: ; In the formula, The equation for the velocity curve is... The equation for the acceleration curve is... To preset the movement speed, For maximum speed, This represents the maximum acceleration time.

3. The workpiece anti-slip motion control method according to claim 2, characterized in that, Solving for the unknown constant term in the equation includes: When the workpiece cannot accelerate to the preset speed within the target moving distance, the maximum speed that the workpiece can accelerate to within the target moving distance is used to replace the preset moving speed in order to correct the unknown constant term.

4. The workpiece anti-slip motion control method according to claim 1, characterized in that, The solution for the motion time using Newton's iteration method is as follows: ; In the formula, express The theoretical displacement at time t, express The derivative, This indicates that the grating ruler acquires the real-time position of the workpiece; The iteration stopping condition is: , Indicates the error threshold. This represents the (n-1)th time. This represents the nth time point.

5. The workpiece anti-slip motion control method according to claim 4, characterized in that, During the acceleration phase, the initial value at each iteration time is the maximum acceleration time. During the deceleration phase, the initial value at each iteration time is t. , This represents the total motion time.

6. The workpiece anti-slip motion control method according to claim 1, characterized in that, The motion stage of the image measuring instrument includes two axes, X and Y. The expected motion speed of the X and Y axes is obtained based on the maximum acceleration of the X and Y axes, respectively. The maximum acceleration of each axis is determined based on the thrust of the stage on the workpiece being measured and the maximum static friction force of the workpiece being measured.

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