A method for controlling the compliance force of a sanding belt machine

Abstract

The present invention belongs to the field of intelligent manufacturing equipment, and more specifically, relates to a new type of sanding belt machine compliance force control equipment and method. In view of the fact that existing sanding belt machines are prone to vibration and cannot accurately control the contact force during the processing, resulting in the grinding process not meeting the requirements of high-precision processing, the present invention proposes a new type of sanding belt machine equipment and a new control method that can improve the flexibility of the sanding belt machine, accurately control the normal contact force during the sanding belt grinding process, and improve the grinding processing quality of the product. Compared with the existing technology, the traditional sanding belt machine structure is modified and a moving part is added to ensure the flexibility of the sanding belt machine. A one-dimensional force sensor is installed on the moving part of the sanding belt machine to measure the normal contact force of the contact wheel grinding part. A compliance force control strategy for the sanding belt machine is proposed to ensure constant contact force during the workpiece grinding process, reduce the vibration of the sanding belt machine, and improve the processing quality of the sanding belt machine grinding surface.

Description

Technical Field

[0001] The present invention belongs to the field of intelligent manufacturing equipment, and more specifically, relates to a sanding machine compliance force control device and method for improving the flexibility of the sanding machine and ensuring constant normal contact force of the sanding belt during grinding. Background Art

[0002] With the continuous development of advanced manufacturing technology, abrasive belt machines are increasingly used in modern industrial processing. Abrasive belt grinding is developing towards high precision, high surface quality and high processing efficiency. As a precision grinding method, the normal contact force in the traditional abrasive belt grinding process cannot be perceived and controlled, resulting in the inability to accurately control the grinding amount in the grinding process, and the vibration in the grinding process makes the surface roughness not high. In order to change the above problems in traditional abrasive belt grinding, it is necessary to develop abrasive belt machine equipment that can accurately control the grinding normal contact force, reduce the vibration in the abrasive belt grinding process, and improve the grinding quality. Summary of the Invention

[0003] In view of the fact that existing belt grinding machines are prone to vibration during grinding and the inability to accurately control the normal contact force during belt grinding, which leads to the inability to meet the quality requirements of high-precision grinding, the present invention proposes a belt grinding machine compliance control equipment and method that can improve the flexibility of the belt grinding machine, accurately control the normal contact force during the belt grinding process, reduce the belt grinding vibration, and improve the belt grinding quality.

[0004] (1) During the grinding process, the expected normal contact force is f d , the actual normal contact force measured by the one-dimensional force sensor is f e , the deviation between the expected normal contact force and the actual normal contact force is Δf, and the following impedance control model is used to transform the belt sander control system:

[0005]

[0006] where m d is the quality coefficient of the belt sander, b d is the damping coefficient of the belt sander, Δf is the deviation between the expected normal contact force and the actual normal contact force, e is the deviation between the expected position and the actual position of the belt sander, is the second-order derivative of the position error, is the first-order derivative of the position deviation;

[0007] (2) Actual normal contact force f during belt grinding e The actual normal contact force f is detected by a one-dimensional force sensor and fed back to the control system. e and the expected normal contact force f d Calculate the difference to obtain the deviation Δf between the expected normal contact force and the actual normal contact force;

[0008] (3) From the impedance control model in step (1), it can be concluded that the normal contact force deviation is converted into the position offset of the moving part. The running speed of the moving part before and after each sampling cycle is expressed as:

[0009]

[0010] Discretize the sampling period, the time t, x(t) is the speed of the moving part running forward and backward at time t, Δf is the deviation between the expected normal contact force and the actual normal contact force, where m d is the quality coefficient of the belt sander, b d Is the damping coefficient of the belt sander, which can be adjusted m d and b d The value of is used to change the flexibility of the sanding machine, x(0) is the initial position speed, is the integral symbol, dt represents the time differential, e is the deviation between the expected position and the actual position of the sanding machine, and τ is the time delay of the system.

[0011] (4) Discretize the expression obtained in (3) above to obtain the forward and backward motion speed v of the moving part in the belt sander n (k);

[0012] (5) According to the relationship between the speed and displacement of the moving part of the belt sander, the position offset Δx(k) of the moving part of the belt sander at time k is obtained;

[0013] (6) The position offset is sent to the servo driver, which drives the linear drive cylinder to move forward and backward, thereby causing the upper and lower rollers to move forward and backward on the upper and lower guide rails, controlling the normal contact force of the belt grinding process to be constant.

[0014] Furthermore, the forward and backward movement speed v of the moving part in the belt sander is calculated according to the following formula n (k),

[0015]

[0016] where f e (k) is the actual normal contact force measured by the one-dimensional force sensor at time k, v n (k-1) is the speed of the sanding machine at the previous moment, Δt is the controller sampling time, where f d is the desired normal contact force.

[0017] Furthermore, the displacement offset Δx(k) of the front-back motion of the belt sander moving part at time k is calculated according to the following formula:

[0018] Δx(k)=v n (k)Δt

[0019] Furthermore, vn (k) is the velocity of the moving part at time k, Δx(k) is the position offset of the moving part moving forward and backward at the current moment, and Δt is the controller sampling time.

[0020] A belt machine force control device, comprising a belt machine body, a belt machine grinding system, a motion part and a servo control system;

[0021] The moving part comprises: a mounting plate, an upper pulley assembly, a lower pulley assembly, an upper guide rail, a lower guide rail, a servo drive, a linear drive cylinder, and the upper and lower pulley assemblies and the upper and lower guide rails are arranged on the mounting plate;

[0022] The said belt machine compliance force control system comprises: a controller, a one-dimensional force sensor;

[0023] The end of the linear drive cylinder is connected to one end of a one-dimensional force sensor, and the other end of the one-dimensional force sensor is connected to the mounting plate through a connecting block, so as to measure the normal contact force during the grinding process of the contact wheel;

[0024] The abrasive belt is supported by the contact wheel to grind the workpiece to be ground, and the grinding contact force is fed back to the one-dimensional force sensor. The tension of the abrasive belt during the grinding process can be adjusted by the tensioning wheel. Through the control algorithm proposed by the present invention, the servo driver and the linear drive cylinder drive the upper roller assembly and the lower roller assembly to move forward and backward on the upper guide rail and the lower guide rail. The upper roller assembly and the lower roller assembly are rigidly connected to the mounting plate. The forward and backward movement of the linear drive cylinder will drive the mounting plate to move forward and backward. When the actual measured normal contact force is greater than the expected normal contact force, the upper and lower rollers move backward, driving the mounting plate to move backward, and correspondingly, the contact wheel and the abrasive belt move backward synchronously to reduce the actual normal contact force of the workpiece to be ground; if the actual measured normal contact force is less than the expected normal contact force, the upper and lower rollers move forward, driving the mounting plate to move forward, and correspondingly, the contact wheel and the abrasive belt move forward synchronously to increase the actual normal contact force of the workpiece to be ground.

[0025] As a preferred abrasive belt grinder system, it comprises: a tensioning wheel, a contact wheel, a synchronous belt motor, and an abrasive belt; the synchronous belt motor drives the abrasive belt through the contact wheel, and the tension of the abrasive belt is adjusted by the tensioning wheel.

[0026] Preferably, the belt grinder system further comprises a grinding receiving box for receiving dust and grinding chips during the grinding process.

[0027] Preferably, the belt grinder system further comprises a belt deviation correction wheel for correcting the position of the belt on the contact wheel to ensure the quality of the grinding process.

[0028] Preferably, the belt grinder system further comprises a floating device for adjusting the tension of the belt to ensure the tension of the belt on the contact wheel.

[0029] Compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages: (1) the structure of the traditional belt sander is modified and a moving part is added to ensure the flexibility of the belt sander; (2) a one-dimensional force sensor is installed on the moving part of the belt sander to measure the normal contact force of the contact wheel grinding part; (3) a compliance force control strategy of the belt sander is proposed to ensure constant contact force during the workpiece grinding process, reduce the vibration of the belt sander, and improve the processing quality of the grinding surface of the belt sander. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Attachment Figure 1 This is the overall structure diagram of the belt sander.

[0031] Attachment Figure 2 This is the structural diagram of the belt grinding system.

[0032] Attachment Figure 3 It is a structural diagram of the motion control components of the belt sander.

[0033] Attachment Figure 4 This is the structure diagram of the sanding machine control system. DETAILED DESCRIPTION

[0034] The technical solution adopted to realize the present invention includes: the improved belt sander system includes a belt sander body 1, a belt sander grinding system 2, a moving part 3, and a servo control system 4.

[0035] The belt grinder system 2 includes: a tensioning wheel 21, a contact wheel 22, a belt deflection correction wheel 23, a floating device 24, a synchronous belt motor 25, a grinding receiving box 26, and a sanding belt 27; the synchronous belt motor 25 drives the sanding belt 27 through the contact wheel 22, and the tension of the sanding belt 27 is adjusted by the tensioning wheel 21. The belt deflection correction wheel 23 is used to adjust the left and right offset of the sanding belt. The floating device 24 uses a cylinder to move back and forth to adjust the tensioning wheel pressure. The grinding receiving box 26 is used to collect grinding waste. (See attached Figure 2 )

[0036] The moving part 3 includes: a mounting plate 31, an upper pulley assembly 32, a lower pulley assembly 33, an upper guide rail 34, a lower guide rail 35, a servo driver 36, and a linear drive cylinder 37; the upper and lower pulley assemblies and the upper and lower guide rails are arranged on the mounting plate 31. (See attached Figure 3 )

[0037] The belt sander compliance control system 4 mainly includes a controller 41 and a one-dimensional force sensor 42 .

[0038] The end of the linear drive cylinder 37 on one side of the servo driver is connected to one end of a one-dimensional force sensor 42 , and the other end of the one-dimensional force sensor 42 is connected to the mounting plate 31 through a connecting block 38 .

[0039] When the belt sander is working, the workpiece to be ground is placed on the outside of the contact wheel 22, and the contact wheel 22 supports the abrasive belt 27 to grind the workpiece to be ground. At the same time, the grinding contact force is fed back to the one-dimensional force sensor 42. The tension of the abrasive belt 27 during the grinding process can be adjusted by the tensioning wheel 21. Through the control algorithm proposed by the present invention, the servo driver 36 and the linear drive cylinder 37 drive the upper roller assembly 32 and the lower roller assembly 33 to move back and forth on the upper guide rail 34 and the lower guide rail 35. The upper roller assembly 32 and the lower roller assembly 33 are rigidly connected to the mounting plate 31. Then, the forward and backward movement of the linear drive cylinder 37 will drive the mounting plate 31 to move forward and backward. When the actual measured normal contact force is greater than the expected normal contact force, the upper and lower rollers move backward, driving the mounting plate 31 to move backward, and correspondingly, the contact wheel 22 and the abrasive belt 27 move backward synchronously, reducing the actual normal contact force on the workpiece to be ground; if the actual measured normal contact force is less than the expected normal contact force, the upper and lower rollers move forward, driving the mounting plate 31 to move forward, and correspondingly, the contact wheel 22 and the abrasive belt 27 move forward synchronously, increasing the actual normal contact force on the workpiece to be ground.

[0040] The sanding belt machine control system method of the present invention:

[0041] S1: The impedance control strategy adopted by the belt machine compliance control system is: during the grinding process, the expected normal contact force is f d , the actual normal contact force measured by the one-dimensional force sensor is f e , the deviation between the expected normal contact force and the actual normal contact force is calculated as Δf, and the belt sander system is modified using the following impedance control model:

[0042]

[0043] where m d is the quality coefficient of the belt sander, b d is the damping coefficient of the belt sander, Δf is the deviation between the expected normal contact force and the actual normal contact force, e is the deviation between the expected position and the actual position of the belt sander, is the second-order derivative of the position error, is the first-order derivative of the position deviation.

[0044] S2: Actual normal contact force f during belt grinding e The actual normal contact force f is detected by a one-dimensional force sensor and fed back to the control system. e and the expected normal contact force f d The difference is calculated to obtain the deviation Δf between the expected normal contact force and the actual normal contact force.

[0045] S3: From the impedance control model in step (1), it can be concluded that the normal contact force deviation is converted into the position offset of the moving part. The running speed expression of the moving part before and after each sampling cycle is:

[0046]

[0047] Discretize the sampling period, the time t, x(t) is the speed of the moving part running forward and backward at time t, Δf is the deviation between the expected normal contact force and the actual normal contact force, where m d is the quality coefficient of the belt sander, b d Is the damping coefficient of the belt sander, which can be adjusted m d and b d The value of is used to change the flexibility of the sanding machine, x(0) is the initial position speed, is the integral symbol, dt represents the differential with respect to time, e is the deviation between the expected position and the actual position of the belt sander, and τ is the time delay of the system;

[0048] S4: Discretize the expression obtained in S3 to obtain the forward and backward movement speed v of the moving part in the belt sander n (k),

[0049]

[0050] where f e (k) is the actual normal contact force measured by the one-dimensional force sensor at time k, v n (k-1) is the speed of the sanding machine at the previous moment, Δt is the controller sampling time, where f d is the desired normal contact force.

[0051] S5: The relationship between the speed and displacement of the moving part of the belt sander can be used to obtain the displacement offset Δx(k) of the moving part of the belt sander at time k.

[0052] Δx(k)=v n (k)Δt (Formula 4)

[0053] where v n (k) is the velocity of the moving part at time k, Δx(k) is the offset that needs to be compensated for the forward and backward movement of the moving part at the current moment, and Δt is the controller sampling time.

[0054] S6: The position offset is sent to the servo driver, which drives the linear drive cylinder to move back and forth, thereby causing the upper and lower rollers to move back and forth on the upper and lower guide rails, controlling the normal contact force of the belt grinding process to be constant.

[0055] The contact wheel of this embodiment can float back and forth to adaptively fit the surface of the workpiece to be ground; the grinding contact force can be sensed, adjusted and monitored in real time; the contact force can be controlled with high precision based on the real-time position compensation function of the moving part during the grinding process; the sanding belt speed can be automatically adjusted; it has the sanding belt tensioning and deviation correction functions; the flexible sanding belt machine can be used in conjunction with other equipment such as robots, and has a wide range of applications and strong applicability.

[0056] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for controlling the compliance of a belt sander, characterized in that: (1) During the grinding process, the expected normal contact force is f d , the actual normal contact force measured by the one-dimensional force sensor is f e , the deviation between the expected normal contact force and the actual normal contact force is Δf, and the following impedance control model is used to transform the belt sander control system: where m d is the quality coefficient of the belt sander, b d is the damping coefficient of the belt sander, Δf is the deviation between the expected normal contact force and the actual normal contact force, e is the deviation between the expected position and the actual position of the belt sander, is the second-order derivative of the position error, is the first-order derivative of the position deviation; (2) Actual normal contact force f during belt grinding e The actual normal contact force f is detected by a one-dimensional force sensor and fed back to the control system. e and the expected normal contact force f d Calculate the difference to obtain the deviation Δf between the expected normal contact force and the actual normal contact force; (3) From the impedance control model in step (1), it can be concluded that the normal contact force deviation is converted into the position offset of the moving part. The running speed of the moving part before and after each sampling cycle is expressed as: Discretize the sampling period, the time t, x(t) is the speed of the moving part running forward and backward at time t, Δf is the deviation between the expected normal contact force and the actual normal contact force, where m d is the quality coefficient of the belt sander, b d Is the damping coefficient of the belt sander, which can be adjusted m d and b d The value of is used to change the flexibility of the sanding machine, x(0) is the initial position speed, is the integral symbol, dt represents the time differential, e is the deviation between the expected position and the actual position of the belt sander, and τ is the time delay of the system; (4) Discretize the expression obtained in (3) above to obtain the forward and backward motion speed v of the moving part in the belt sander n (k); (5) According to the relationship between the speed and displacement of the moving part of the belt sander, the position offset Δx(k) of the moving part of the belt sander at time k is obtained; (6) The position offset is sent to the servo driver, which drives the linear drive cylinder to move forward and backward, thereby causing the upper and lower rollers to move forward and backward on the upper and lower guide rails, controlling the normal contact force of the belt grinding process to be constant.

2. A method for controlling the compliance force of a sanding belt machine according to claim 1, characterized in that: Calculate the forward and backward movement speed v of the moving part in the belt sander according to the following formula n (k), where f e (k) is the actual normal contact force measured by the one-dimensional force sensor at time k, v n (k-1) is the speed of the sanding machine at the previous moment, Δt is the controller sampling time, where f d is the desired normal contact force.

3. The method for controlling the compliance force of a sanding belt machine according to claim 1, wherein: The displacement offset Δx(k) of the front and back motion of the belt sander moving part at time k is calculated according to the following formula: Δx(k)=v n (k)Δt where v n (k) is the velocity of the moving part at time k, Δx(k) is the position offset of the moving part moving forward and backward at the current moment, and Δt is the controller sampling time.

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