CN108591139A - A kind of hydraulic power chuck clamping force control system and clamping force control method - Google Patents

Abstract

The invention discloses a hydraulic power chuck clamping force control system, which includes a controller, a servo motor and a pressure sensor are respectively connected to the controller, a gear pump is connected to the other end of the servo motor, and a gear pump is connected to the gear pump through a hydraulic pipeline. The rotary hydraulic cylinder, the gear pump and the rotary hydraulic cylinder are connected with a three-position four-way electromagnetic reversing valve, and the rotary hydraulic cylinder is also connected with a chuck. The invention also discloses a control method using the clamping force control system of the hydraulic power chuck. The servo motor drives the gear pump to rotate, and the programmable controller PLC is used to adjust the output signal of the servo driver in real time to adjust the speed of the servo motor to control the slave. Pressure delivered by the gear pump to the swing cylinder. The system has good response performance, flexible control, high precision and simple structure, and can effectively control the pressure of the servo system to achieve the purpose of controlling the clamping force of the chuck.

Description

A hydraulic power chuck clamping force control system and clamping force control method

technical field

The invention belongs to the technical field of fluid transmission and control methods, in particular to a hydraulic power chuck clamping force control system, and also to a hydraulic power chuck clamping force control method.

Background technique

Modern manufacturing is developing in the direction of high speed, high efficiency, high precision and flexibility. Therefore, corresponding requirements are put forward for CNC machine tools and their tooling. The hydraulic power chuck has large clamping force, high speed and compact structure, and has become an indispensable basic functional part of medium and high speed CNC lathes, grinding machines and turning and milling centers. The hydraulic power chuck of CNC machine tools is composed of a tie rod cylinder installed at both ends of the machine tool spindle and a linear drive power chuck. The tie rod passes through the through hole of the machine tool spindle to connect the piston rod in the cylinder and the chuck body piston sleeve, and the piston is driven by the tie rod and the piston sleeve. The transmission mechanism in the chuck body realizes force-increasing and radial synchronous movement of the claws to clamp the workpiece. 20%-60% of the machining deviation in machining is caused by clamping, especially for the machining of thin-walled parts. During the cutting process, the unstable cutting force caused by external disturbance and improper clamping will lead to chatter, which will reduce the cutting amount and the surface quality of the workpiece, generate noise, and even cause the tool to be scrapped in advance. Therefore, the control of the clamping force of the hydraulic power chuck is very important in the machining process, especially the machining of thin-walled parts.

The traditional valve control system uses an electro-hydraulic proportional relief valve to adjust the system pressure and then control the clamping force of the chuck. Although this system has excellent control characteristics such as high precision and high frequency response, the servo valve is extremely sensitive to oil pollution. And the system has throttling loss, which reduces the reliability of the system, increases the cost, energy consumption and heat generation, and the electro-hydraulic proportional overflow valve cannot meet the requirements of small and adjustable clamping process of thin-walled parts due to the dead zone. clamping force requirements.

Contents of the invention

The object of the present invention is to provide a hydraulic power chuck clamping force control system, which solves the problem of poor control precision of the hydraulic power chuck clamping force in the prior art.

The purpose of the present invention is also to provide a method for controlling the clamping force of the above-mentioned hydraulic power chuck.

The first technical solution adopted in the present invention is a hydraulic power chuck clamping force control system, including a controller, a servo motor is connected to the controller, and a gear pump is connected to the other end of the servo motor, and the gear pump passes through The hydraulic pipeline is connected with a rotary hydraulic cylinder,

A chuck is also connected to the rotary hydraulic cylinder,

The hydraulic pipeline between the gear pump and the rotary hydraulic cylinder is also equipped with a three-position four-way electromagnetic directional valve, and the hydraulic pipeline between the gear pump and the three-position four-way electromagnetic directional valve is also connected with a relief valve.

A pressure sensor is also connected to the controller through wires, and the signal acquisition end of the pressure sensor is connected to the hydraulic pipeline of the overflow valve and the three-position four-way electromagnetic reversing valve.

The present invention is also characterized in that,

The controller is sequentially composed of an analog input module, a host computer, a programmable logic controller PLC, an analog output module, and a servo driver. The analog input module is connected to a pressure sensor, and the servo driver is connected to a servo motor.

The working oil port B of the three-position four-way electromagnetic reversing valve is connected to the rod chamber of the rotary hydraulic cylinder, and the working oil port A of the three-position four-way electromagnetic reversing valve is connected to the rodless chamber of the rotary hydraulic cylinder, and the three-position four-way The oil return port T of the electromagnetic reversing valve is also connected to the oil return tank through the hydraulic pipeline.

The outlet of the overflow valve is connected to the return tank.

The second technical solution adopted by the present invention is a method for controlling the clamping force of a hydraulic power chuck, which is specifically implemented according to the following steps:

Step 1: Building the Adaptive Controller

Step 1.1, fuzzy input and output

When the system is working, the system pressure deviation e and deviation change rate ec collected by the pressure sensor are used as the input of the controller, and ΔK _p , ΔK _i , and ΔK _d are used as the changes in the output parameters of the controller. The domain of discussion for determining e and ec is : {-6, -4, -2, 0, 2, 4, 6}, the domain of ΔK _p is: {-0.015, -0.01, -0.005, 0, 0.005, 0.01, 0.015}, the theory of ΔK _i The domain is: {-0.03, -0.02, -0.01, 0, 0.01, 0.02, 0.03}, the domain of ΔK _d is: {-0.0006, -0.0004, -0.0002, 0, 0.0002, 0.0004, 0.0006}, select the system The fuzzy subsets of variables e, ec, ΔK _p , ΔK _i , ΔK _d are: {NB, NM, NS, ZO, PS, PM, PB},

Step 1.2, establishment of fuzzy control rules

According to different combinations of input quantities e and ec, the controller gives the fuzzy variables ΔK _p , ΔK _i , ΔK _d of the output parameters K _p /K _i /K _d according to the fuzzy control rules, and obtains the output parameter variables ΔK _p , ΔK _i and the fuzzy rule table of ΔK _d ,

Step 1.3, Defuzzification and Fuzzy Query

The fuzzy variables ΔK _p , ΔK _i , and ΔK _d are clarified by the area center of gravity method, and the query tables of ΔK _p , ΔK _i and ΔK _d are respectively obtained by using the fuzzy toolbox and the fuzzy rule tables of ΔK _p , ΔK _i and ΔK _d . That is, the adaptive controller is obtained;

Step 2: Write the designed adaptive controller into the PLC controller to realize the speed control of the servo motor, thereby realizing the clamping force control of the chuck.

In step 2, write the designed adaptive controller into the PLC controller to realize the speed control of the servo motor, so as to realize the clamping force control of the chuck. The specific steps are as follows:

Step 2.1: Put the adaptive controller obtained in step 1 into the PLC controller, and the upper computer (10) compares the pressure signal collected by the pressure sensor (3) with the system set pressure in real time to obtain the pressure deviation e and Deviation rate of change ec;

Step 2.2: Calculate the output of the programmable controller PLC according to the pressure deviation e and deviation change rate ec obtained in step 2.1;

Step 2.3: According to the output of the programmable controller PLC obtained in step 2.2, adjust the output signal of the servo controller to realize the speed control of the servo motor, thereby realizing the clamping force control of the chuck.

Step 2.2 calculates the output of the programmable controller PLC, and the specific steps are as follows:

Step 2.2.1: Put the pressure deviation e and the deviation change rate ec into the register of the programmable controller PLC,

According to the formula and Convert the precise amount of e and ec to the change amount E and EC in the [-6,6] interval,

Among them, e ₁ and e ₂ are the minimum and maximum values of the pressure deviation e respectively, ec ₁ and ec ₂ are the minimum and maximum values of the pressure deviation ec respectively;

Step 2.2.2: According to the E and EC calculated in step 2.2.1, use the ΔK _p , ΔK _i and ΔK _d query table obtained in step 1.3 to query and output ΔK _p , ΔK _i and ΔK _d ;

Step 2.2.3: Add ΔK _p , ΔK _i , ΔK _d obtained in step 2.2.2 to K _p0 , K _i0 , K _d0 initially set in the programmable controller PLC respectively to obtain the final PID control parameter K _p =K _p0 +ΔK _p , K _i =K _i0 +ΔK _i , K _d =K _d0 +ΔK _d ;

Step 2.2.4: Use the formula u=f(K _p , K _i , K _d ) to obtain the control output, the output voltage at time k

Where j=1,2,…..k, e(j) is the pressure deviation at time j, e(k) is the pressure deviation at time k, e(k-1) is the pressure deviation at time k-1,

The output voltage acts on the servo driver to complete the speed control of the servo motor.

The beneficial effect of the present invention is that a hydraulic power chuck clamping force control system of the present invention has good response performance, flexible control, high precision and simple structure. The method is to control the system pressure through the output flow of the hydraulic pump. Practice has proved that this method can effectively control the pressure of the direct-drive pump-controlled electro-hydraulic servo system to achieve the purpose of controlling the clamping force of the chuck.

Description of drawings

Fig. 1 is a structural schematic diagram of a hydraulic power chuck clamping force control system of the present invention;

Fig. 2 is a structural diagram of a controller in a hydraulic power chuck clamping force control system of the present invention.

In the figure, 1. Rotary hydraulic cylinder, 2. Three-position four-way electromagnetic directional valve, 3. Pressure sensor, 4. Servo motor, 5. Gear pump, 6. Chuck, 7. Relief valve, 8. Controller , 9. Analog input module, 10. Host computer, 11. Programmable controller PLC, 12. Analog output module, 13. Servo driver.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

A kind of hydraulic power chuck clamping force control system structure of the present invention is shown in Figure 1, comprises controller 8, is connected with servomotor 4 on controller 8, and the other end of servomotor 4 is also connected with gear pump 5, gear pump 5 is connected with a rotary hydraulic cylinder 1 through a hydraulic pipeline,

The rotary hydraulic cylinder 1 is also connected with a chuck 6,

The hydraulic pipeline between the gear pump 5 and the rotary hydraulic cylinder 1 is also provided with a three-position four-way electromagnetic reversing valve 2, and the hydraulic pipeline between the gear pump 5 and the three-position four-way electromagnetic reversing valve 2 is also connected with an overflow valve. valve 7,

The controller 8 is also connected to a pressure sensor 3 through wires, and the signal acquisition end of the pressure sensor 3 is connected to the hydraulic pipeline of the overflow valve 7 and the three-position four-way electromagnetic reversing valve 2 .

The controller 8 is sequentially composed of an analog input module 9, a host computer 10, a programmable controller PLC 11, an analog output module 12, and a servo driver 13. The analog input module 9 is connected to the pressure sensor 3, and the servo driver 13 is connected to the servo motor. 4 connections.

The working oil port B of the three-position four-way electromagnetic reversing valve 2 is connected to the rod chamber of the rotary hydraulic cylinder 1, and the working oil port A of the three-position four-way electromagnetic reversing valve 2 is connected to the rodless chamber of the rotary hydraulic cylinder 1. The oil return port T of the three-position four-way electromagnetic reversing valve 2 is also connected to an oil return tank through a hydraulic pipeline.

The outlet of overflow valve 7 is connected to the oil return tank.

As shown in Figure 2, the controller is sequentially composed of an analog input module 9, a host computer 10, a programmable controller PLC 11, an analog output module 12, and a servo driver 13. The analog input module 9 is connected to the pressure sensor 3, and the servo The driver 13 is connected to the servo motor 4 .

The working oil port B of the three-position four-way electromagnetic reversing valve 2 is connected to the rod chamber of the rotary hydraulic cylinder 1, and the working oil port A of the three-position four-way electromagnetic reversing valve 2 is connected to the rodless chamber of the rotary hydraulic cylinder 1. The oil return port T of the three-position four-way electromagnetic reversing valve 2 is also connected to an oil return tank through a hydraulic pipeline.

The role of the analog output module 12 is to output control signals.

When the system is working, the servo motor drives the gear pump to rotate, and the flow and pressure delivered from the gear pump to the system are controlled by changing the motor speed. The controller compares the pressure signal detected by the pressure sensor with the set pressure to obtain a deviation. The servo driver uses this deviation signal to adjust the speed of the servo motor to drive the gear pump to provide flow and pressure for the system to achieve the clamping force of the hydraulic power chuck during the processing process. For the purpose of maintaining stability, the overflow valve is used as the safety valve of the system. By changing the position of the three-position four-way electromagnetic reversing valve, the movement direction of the rotary hydraulic cylinder piston is changed to change the clamping or loosening of the chuck.

The method for controlling the pressure of the rotary hydraulic cylinder in the present invention is as follows: when the system is working, the servo motor 4 drives the gear pump 5 to rotate, and the output signal of the servo driver 13 is adjusted in real time through the programmable controller PLC11 to adjust the speed of the servo motor 4 to control the slave gear pump. 5 The pressure delivered to the rotary hydraulic cylinder 1, the specific implementation steps are as follows:

Step 1: Building the Adaptive Controller

Step 1.1, fuzzy input and output

When the system is working, the system pressure deviation e and deviation change rate ec collected by the pressure sensor are used as the input of the controller, and ΔK _p , ΔK _i , and ΔK _d are used as the changes in the output parameters of the controller. The domain of discussion for determining e and ec is : {-6, -4, -2, 0, 2, 4, 6}, the domain of ΔK _p is: {-0.015, -0.01, -0.005, 0, 0.005, 0.01, 0.015}, the theory of ΔK _i The domain is: {-0.03, -0.02, -0.01, 0, 0.01, 0.02, 0.03}, the domain of ΔK _d is: {-0.0006, -0.0004, -0.0002, 0, 0.0002, 0.0004, 0.0006}, select the system The fuzzy subsets of variables e, ec, ΔK _p , ΔK _i , ΔK _d are: {NB, NM, NS, ZO, PS, PM, PB},

Step 1.2, establishment of fuzzy control rules

According to different combinations of input quantities e and ec, the controller gives the fuzzy variables ΔK _p , ΔK _i , ΔK _d of the output parameters K _p /K _i /K _d according to the fuzzy control rules, and obtains the output parameter variables ΔK _p , ΔK _i and the fuzzy rule table of ΔK _d ,

Step 1.3, Defuzzification and Fuzzy Query

The fuzzy variables ΔK _p , ΔK _i , and ΔK _d are clarified by the area center of gravity method, and the query tables of ΔK _p , ΔK _i and ΔK _d are obtained respectively by using the fuzzy toolbox and the fuzzy rule tables of ΔK _p , ΔK _i and ΔK _d . That is, the adaptive controller is obtained;

Step 2: Write the designed adaptive controller into the PLC controller to realize the speed control of the servo motor, thereby realizing the clamping force control of the chuck.

Step 2.1: The upper computer (10) compares the pressure signal collected by the pressure sensor (3) with the system set pressure in real time to obtain the pressure deviation e and the deviation change rate ec respectively;

Step 2.2: Calculate the output of the programmable controller PLC according to the pressure deviation e and deviation change rate ec obtained in step 2.1;

Step 2.2.1: Put the pressure deviation e and the deviation change rate ec into the register of the programmable controller PLC,

According to the formula and Convert the precise amount of e and ec to the change amount E and EC in the [-6,6] interval,

Among them, e ₁ and e ₂ are the minimum and maximum values of the pressure deviation e respectively, ec ₁ and ec ₂ are the minimum and maximum values of the pressure deviation ec respectively;

Step 2.2.2: According to the E and EC calculated in step 2.2.1, use the ΔK _p , ΔK _i and ΔK _d query table obtained in step 1.3 to query and output ΔK _p , ΔK _i and ΔK _d ;

Step 2.2.3: Add ΔK _p , ΔK _i , ΔK _d obtained in step 2.2.2 to K _p0 , K _i0 , K _d0 initially set in the programmable controller PLC respectively to obtain the final PID control parameter K _p =K _p0 +ΔK _p , K _i =K _i0 +ΔK _i , K _d =K _d0 +ΔK _d ;

Step 2.2.4: Use the formula u=f(K _p , K _i , K _d ) to obtain the control output, the output voltage at time k

Where j=1,2,…..k, e(j) is the pressure deviation at time j, e(k) is the pressure deviation at time k, e(k-1) is the pressure deviation at time k-1,

The output voltage acts on the servo driver to complete the speed control of the servo motor.

Step 2.3: According to the output of the programmable controller PLC obtained in step 2.2, adjust the output signal of the servo controller to realize the speed control of the servo motor, thereby realizing the clamping force control of the chuck.

Table 1: Fuzzy rule table of ΔK _p , ΔK _i and ΔK _d

Table 2: ΔK _p lookup table

Table 3: ΔK _i lookup table

Table 4: ΔK _d lookup table

.

Claims (7)

1. A hydraulic power chuck clamping force control system, characterized in that it comprises a controller (8), the controller (8) is connected with a servo motor (4), the other end of the servo motor (4) A gear pump (5) is also connected, and a rotary hydraulic cylinder (1) is connected to the gear pump (5) through a hydraulic pipeline, and a chuck (6) is also connected to the rotary hydraulic cylinder (1). A three-position four-way electromagnetic reversing valve (2) is also arranged on the hydraulic pipeline between the gear pump (5) and the rotary hydraulic cylinder (1), and the gear pump (5) and the three-position four-way electromagnetic reversing valve (2) is also communicated with a relief valve (7) on the hydraulic pipeline, The controller (8) is also connected to a pressure sensor (3) through a wire, and the signal acquisition end of the pressure sensor (3) is connected to the overflow valve (7) and the three-position four-way electromagnetic reversing valve (2) on the hydraulic pipeline. 2. A hydraulic power chuck clamping force control system according to claim 1, characterized in that the controller (8) consists of an analog input module (9), a host computer (10), a programmable A controller PLC (11), an analog output module (12), and a servo driver (13) are connected, the analog input module (9) is connected to a pressure sensor (3), and the servo driver (13) is connected to a servo motor (4) Connection. 3. A hydraulic power chuck clamping force control system according to claim 1, characterized in that, the working oil port B of the three-position four-way electromagnetic reversing valve (2) is connected to the rotary hydraulic cylinder (1 ), the working oil port A of the three-position four-way electromagnetic reversing valve (2) is connected to the rodless chamber of the rotary hydraulic cylinder (1), and the three-position four-way electromagnetic reversing valve (2) The oil return port T of the oil return tank is also connected to the oil return tank through the hydraulic pipeline. 4. A hydraulic power chuck clamping force control system according to claim 3, characterized in that the outlet of the overflow valve (7) is connected to the oil return tank. 5. A clamping force control method adopting the clamping force control system of the hydraulic power chuck as claimed in claim 2, characterized in that, when the system is working, the servo motor (4) drives the gear pump (5) to rotate, through The programmable controller PLC (11) adjusts the output signal of the servo driver (13) in real time to adjust the rotation speed of the servo motor (4) to control the pressure delivered from the gear pump (5) to the rotary hydraulic cylinder (1). The specific implementation steps are as follows : Step 1: Building the Adaptive Controller Step 1.1, fuzzy input and output When the system is working, the system pressure deviation e and deviation change rate ec collected by the pressure sensor are used as the input of the controller, and ΔK _p , ΔK _i , and ΔK _d are used as the changes in the output parameters of the controller. The domain of discussion for determining e and ec is : {-6, -4, -2, 0, 2, 4, 6}, the domain of ΔK _p is: {-0.015, -0.01, -0.005, 0, 0.005, 0.01, 0.015}, the theory of ΔK _i The domain is: {-0.03, -0.02, -0.01, 0, 0.01, 0.02, 0.03}, the domain of ΔK _d is: {-0.0006, -0.0004, -0.0002, 0, 0.0002, 0.0004, 0.0006}, select the system The fuzzy subsets of variables e, ec, ΔK _p , ΔK _i , ΔK _d are: {NB, NM, NS, ZO, PS, PM, PB}, Step 1.2, establishment of fuzzy control rules According to different combinations of input quantities e and ec, the controller gives the fuzzy variables ΔK _p , ΔK _i , ΔK _d of the output parameters K _p /K _i /K _d according to the fuzzy control rules, and obtains the output parameter variables ΔK _p , ΔK _i and the fuzzy rule table of ΔK _d , Step 1.3, Defuzzification and Fuzzy Query The fuzzy variables ΔK _p , ΔK _i , and ΔK _d are clarified by the area center of gravity method, and the query tables of ΔK _p , ΔK _i and ΔK _d are respectively obtained by using the fuzzy toolbox and the fuzzy rule tables of ΔK _p , ΔK _i and ΔK _d . That is, the adaptive controller is obtained; Step 2: Write the designed adaptive controller into the PLC controller to realize the speed control of the servo motor, thereby realizing the clamping force control of the chuck. 6. the clamping force control method of a kind of hydraulic power chuck according to claim 5, it is characterized in that, write the self-adaptive controller that designs in PLC controller described in step 2, realize the speed of servo motor The specific steps to realize the clamping force control of the chuck are as follows: Step 2.1: Put the adaptive controller obtained in step 1 into the PLC controller, and the upper computer (10) compares the pressure signal collected by the pressure sensor (3) with the system set pressure in real time to obtain the pressure deviation e and Deviation rate of change ec; Step 2.2: Calculate the output of the programmable controller PLC according to the pressure deviation e and deviation change rate ec obtained in step 2.1; Step 2.3: According to the output of the programmable controller PLC obtained in step 2.2, adjust the output signal of the servo controller to realize the speed control of the servo motor, thereby realizing the clamping force control of the chuck. 7. The clamping force control method of a kind of hydraulic power chuck according to claim 6, is characterized in that, the output volume of the calculation programmable logic controller PLC described in step 2.2, concrete steps are as follows: Step 2.2.1: Put the pressure deviation e and the deviation change rate ec into the register of the programmable controller PLC, According to the formula and Convert the precise amount of e and ec to the change amount E and EC in the [-6,6] interval, Among them, e ₁ and e ₂ are the minimum and maximum values of the pressure deviation e respectively, ec ₁ and ec ₂ are the minimum and maximum values of the pressure deviation ec respectively; Step 2.2.2: According to the E and EC calculated in step 2.2.1, use the ΔK _p , ΔK _i and ΔK _d query table obtained in step 1.3 to query and output ΔK _p , ΔK _i and ΔK _d ; Step 2.2.3: Add ΔK _p , ΔK _i , ΔK _d obtained in step 2.2.2 to K _p0 , K _i0 , K _d0 initially set in the programmable controller PLC respectively to obtain the final PID control parameter K _p =K _p0 +ΔK _p , K _i =K _i0 +ΔK _i , K _d =K _d0 +ΔK _d ; Step 2.2.4: Use the formula u=f(K _p , K _i , K _d ) to obtain the control output, the output voltage at time k Where j=1,2,…..k, e(j) is the pressure deviation at time j, e(k) is the pressure deviation at time k, e(k-1) is the pressure deviation at time k-1, The output voltage acts on the servo driver to complete the speed control of the servo motor.