阅读说明：本技术 一种位置模式下的伺服电机压力和间隙控制装置 (Servo motor pressure and clearance control device under position mode ) 是由 李小强 孟庆阔 李东升 王烁 于 2019-09-09 设计创作，主要内容包括：本发明公开了一种位置模式下的伺服电机压力和间隙控制装置,其特征在于,包括伺服电机、伺服驱动缸、力传感器、弹性件、上模具座、下模具座、位置传感器和控制模块,所述控制模块包括伺服驱动器、I/O系统和主控制器,所述主控制器包括PLC、位置控制器、速度控制器和电流控制器。其中,位置传感器与PLC连接,建立位置环D,伺服电机的内部编码器的位置环C与所建立的位置环D相结合组成位置控制双闭环,实现上模具和下模具的间隙控制；力传感器与PLC连接,建立压力环E,伺服电机的内部编码器的位置环C和所建立的压力环E相结合组成力控制双闭环,实现上模具对试件的压力控制。(The invention discloses a servo motor pressure and gap control device in a position mode, which is characterized by comprising a servo motor, a servo driving cylinder, a force sensor, an elastic piece, an upper die base, a lower die base, a position sensor and a control module, wherein the control module comprises a servo driver, an I/O system and a main controller, and the main controller comprises a PLC (programmable logic controller), a position controller, a speed controller and a current controller. The position sensor is connected with the PLC to establish a position ring D, and a position ring C of an internal encoder of the servo motor is combined with the established position ring D to form a position control double closed loop so as to realize the gap control of the upper die and the lower die; the force sensor is connected with the PLC, a pressure ring E is established, a position ring C of an inner encoder of the servo motor is combined with the established pressure ring E to form a force control double closed loop, and pressure control of the upper die on the test piece is achieved.)

1. The servo motor pressure and gap control device under the position mode is characterized by comprising a servo motor (1), a servo driving cylinder (2), a force sensor (3), an elastic piece (4), an upper die base (5), a lower die base (6), a position sensor (7) and a control module, wherein the control module comprises a servo driver (8), an I/O system (9) and a main controller (12), the main controller (12) comprises a PLC (13), a position controller (14), a speed controller (15) and a current controller (16), and the position controller (14), the speed controller (15) and the current controller (16) control a position ring C forming an internal encoder (17) of the servo motor (1);

the servo motor (1) is connected with the driving end of the servo driving cylinder (2), the lower end of a piston rod of the servo driving cylinder (2) is sequentially connected with the force sensor (3), the elastic piece (4) and the upper die base (5), the lower die base (6) is arranged right below the upper die base (5) and fixed on a workbench, and the position sensor (7) is rigidly connected to the upper die base (5);

the position sensor (7) is connected with the PLC (13) to establish a position ring D, and a position ring C of an internal encoder (17) of the servo motor (1) is combined with the established position ring D to form a position control double closed loop, so that the gap control of the upper die (10) and the lower die (11) is realized; the force sensor (3) is connected with the PLC (13) to establish a pressure ring E, and a position ring C of an internal encoder (17) of the servo motor (1) and the established pressure ring E are combined to form a force control double closed loop, so that the pressure control of the upper die (10) on the test piece is realized.

2. Control device according to claim 1, characterized in that the elastic element (4) is a disc spring.

3. Control arrangement according to claim 1 or 2, characterized in that the position sensor (7) is rigidly connected to the side of the upper mould base (5).

4. A method for controlling servo motor pressure and gap in position mode using the control device according to any of claims 1-3, comprising the steps of:

s1: when the upper die (10) is moved to a test piece, an absolute motion module is used, according to the zero clearing position of the position sensor (7), the position ring C of an internal encoder (17) of the servo motor (1) is adopted for control, and the servo motor (1) is controlled to move the upper die (10) to the surface of the test piece at a speed V1 to be in contact with the test piece;

s2: the pressure ring E established by connecting the force sensor (3) with the PLC (13) is adopted for controlling the pressure of the upper die (10) on the test piece, and the specific process is as follows:

in the stage of carrying out pressure loading on the test piece by the upper die (10), using a relative motion module, and under the condition that the feedback value of the force sensor (3) is used as a condition, when the real-time pressure is less than 90% of the set pressure, carrying out pressure loading by using a position ring C of an internal encoder (17) of the servo motor (1) at a speed V2, wherein the speed V2 is less than the speed V1;

then, in the stage of carrying out dynamic pressure control on the test piece by the upper die (10), when the real-time pressure measured by the force sensor (3) is greater than 90% of the set pressure, the relative motion module carries out pressure loading at a speed V3 until the set pressure is reached, and the force control process of the upper die (10) on the test piece is completed, wherein the speed V3 is less than the speed V2;

or the gap control of the upper die (10) and the lower die (11) is realized by adopting the position ring D control established by connecting the position sensor (7) with the PLC (13), and the specific process is as follows:

in the stage that the upper die (10) carries out pressure loading on a test piece, a relative motion module is used, the condition that an actual position value is fed back by a position sensor (7) is taken as a condition, when the actual position of the upper die (10) does not reach a set condition, the upper die (10) moves downwards at a speed V2 by using a position ring C of an internal encoder (17) of a servo motor (1), and after the upper die reaches the set position, the upper die stops moving, so that the gap control process of the upper die (10) and the lower die (11) is completed.

5. The method according to claim 4, characterized in that when the pressure control of the upper die (10) on the test piece is realized by using a pressure ring E control established by connecting the force sensor (3) with a PLC (13), and according to the characteristics of the elastic member (4), when the real-time pressure measured by the force sensor (3) is greater than the set pressure, the pressure unloading speed V4 is less than the speed V3.

Technical Field

The invention belongs to the field of friction testing machines, and particularly relates to a servo motor pressure and gap control device in a position mode, which can provide high-precision and high-stability control for the pressure and the die gap of a low-tonnage plate friction testing machine.

Background

Accurate pressure and die clearance control devices are not available for the research of accurate friction conditions such as friction coefficient measurement, friction lubrication analysis and the like in the stamping process. Most of the existing friction test control devices at home and abroad adopt hydraulic pressure to control pressure, the control pressure is unstable in a small load range required by an aluminum alloy friction test, and the friction behavior between an aluminum alloy plate and a mold cannot be evaluated qualitatively and quantitatively. Aiming at aluminum alloy stamping, a pressure control device of a low-tonnage high-precision high-stability friction tester is urgently needed.

The servo motor has the characteristics of high precision and quick response. The servo motor has a torque and position control mode, and experimental research shows that the position mode has better control effect along with the increase of a set force value in the range of 500 plus 2500N, but has larger fluctuation range compared with the torque mode, and can improve a mechanical transmission system or optimize the inside of the control mode; however, the friction test system also needs high-precision gap value control, if a torque control mode is used, the gap value control needs to write a control program according to the torque value to control the displacement of the shaft, and the problems of speed, acceleration, soft limit and the like need to be considered, and the control difficulty is large because the unit force corresponds to smaller displacement variation.

Chinese patent CN109623134A discloses an axial friction welding device and friction welding process with position control mode and force control mode interaction, which uses a hydraulic servo system as a power source to control force in the force control mode and control displacement in the displacement control mode, so as to realize accurate force control and accurate displacement data monitoring. However, the hydraulic system adopted by the patent has the problems of easy oil leakage, complex structure, high manufacturing cost and the like, and has the problem of unstable control pressure in a small load range required by an aluminum alloy friction test.

Chinese patent CN201931200U discloses a friction welding machine using a servo motor to realize pressure and displacement control, wherein the pressure is controlled by using a torque control mode of the servo motor, the displacement is controlled by using a position control mode of the servo motor, the control process omits the layer-by-layer conversion of hydraulic and mechanical systems, and the displacement control precision is higher than that of the traditional hydraulic displacement control. However, the patent adopts two different control modes to control pressure and displacement, and because the servo motor can not simultaneously carry out the two control modes, the two control modes need to be repeatedly switched in the using process. The method is not applicable to occasions needing to control displacement and monitor pressure.

Disclosure of Invention

To this end, the present invention provides a small pressure and gap control apparatus suitable for an aluminum alloy friction test, which controls pressure using displacement instead of position pattern of a servo motor, and changes a system characteristic curve from pure rigidity to elasticity by an elastic member such as a disc spring, so that pressure variation caused by a unit step pitch of a motor is reduced, and provides a stable and controllable positive pressure and a die gap for a system when a friction test is performed.

According to an aspect of the present invention, there is provided a servo motor pressure and gap control apparatus in a position mode, comprising a servo motor, a servo driving cylinder, a force sensor, an elastic member, an upper die base, a lower die base, a position sensor, and a control module, the control module comprising a servo driver, an I/O system, and a main controller, the main controller mainly comprising a PLC, a position controller, a speed controller, and a current controller, the position controller, the speed controller, and the current controller controlling a position loop C forming an internal encoder of the servo motor;

the servo motor is connected with the driving end of the servo driving cylinder, the lower end of a piston rod of the servo driving cylinder is sequentially connected with the force sensor, the elastic piece and the upper die base, the lower die base is arranged right below the upper die base and fixed on a workbench, and the position sensor is rigidly connected to the upper die base;

the position sensor is connected with the PLC to establish a position ring D, and a position ring C of an internal encoder of the servo motor is combined with the established position ring D to form a position control double closed loop so as to realize the gap control of the upper die and the lower die; the force sensor is connected with the PLC to establish a pressure ring E, and a position ring C of an inner encoder of the servo motor is combined with the established pressure ring E to form a force control double closed loop, so that the pressure control of the upper die on the test piece is realized.

In some embodiments, the resilient member may be a disc spring.

In some embodiments, the position sensor may be rigidly attached to a side of the upper mold base.

The invention also provides a method for controlling the pressure and the clearance of the servo motor under the position mode by using the control device, which comprises the following steps:

s1: when the upper die is moved to a test piece, an absolute motion module is used, according to the zero clearing position of a position sensor, a position ring C of an internal encoder of a servo motor is adopted for controlling the servo motor to move the upper die to the surface of the test piece at a speed V1 to be in contact with the test piece;

s2: the pressure ring E established by connecting the force sensor with the PLC is used for controlling the pressure of the upper die on the test piece, and the specific process is as follows:

in the pressure loading stage of the test piece by the upper die, a relative motion module is used, the feedback value of a force sensor is taken as a condition, when the real-time pressure is less than 90% of the set pressure, the pressure loading is carried out by utilizing a position ring C of an internal encoder of a servo motor at a speed V2, and the speed V2 is less than the speed V1;

then, in the stage of carrying out dynamic pressure control on the test piece by the upper die, when the real-time pressure measured by the force sensor is greater than 90% of the set pressure, the relative motion module carries out pressure loading at a speed V3 until the set pressure is reached, and the force control process of the upper die on the test piece is completed, wherein the speed V3 is less than the speed V2;

or, the position ring D established by connecting the position sensor with the PLC is used for controlling, so that the gap control of the upper die and the lower die is realized, and the specific process is as follows:

and in the stage of carrying out pressure loading on the test piece by the upper die, using a relative motion module and taking the feedback of an actual position value by a position sensor as a condition, when the actual position of the upper die does not reach a set condition, the upper die moves downwards at a speed V2 by using a position ring C of an internal encoder of a servo motor, and after the upper die reaches the set position, the upper die stops moving, so that the gap control process of the upper die and the lower die is completed.

Further, when the pressure of the upper die on the test piece is controlled by adopting a pressure ring E established by connecting the force sensor with the PLC, and according to the characteristics of the elastic piece, when the real-time pressure measured by the force sensor is greater than the set pressure, the pressure unloading speed V4 is less than the speed V3.

The invention has the beneficial effects that:

(1) the device combines a servo control position mode with an external force sensor and a position sensor, and uses a force control double closed loop formed by combining a position loop of an internal encoder of a servo motor and a pressure loop built by a PLC (programmable logic controller), so that 1% high-precision stable pressure control is realized; the position control double closed loop formed by combining the position loop of the internal encoder of the servo motor and the position loop built by the PLC is used, so that the clearance value control of the high-precision die is realized;

based on the high-precision and high-stability control of the pressure, the device can automatically apply a test set pressure value to the test piece; when the tensile test piece moves, the pressure value can be kept stable; pressure can be applied quickly and accurately; the pressure of an actual test piece can be accurately monitored;

based on the realized accurate control of the die gap, the invention can monitor the gap value between the upper die and the lower die in real time; during testing, the die clearance value can be kept according to a set value until the testing is finished; the gap value can be stabilized without being affected by the thickness of the test piece and the surface scratch variation.

2) A servo motor is selected to replace hydraulic control to serve as a friction test pressure control device, and the servo motor has the advantages of being high in precision and fast in response.

3) Can provide stable and controllable positive pressure and die clearance in a small load range required by an aluminum alloy friction test.

Drawings

Fig. 1 is a schematic structural diagram of a servo motor pressure and gap control device in a position mode according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of the mechanical and sensing portions of a servo motor pressure and gap control apparatus in position mode in accordance with an embodiment of the present invention.

FIG. 3 is a schematic diagram of a servo motor dual closed loop control according to the present invention.

Detailed Description

The invention is further described below with reference to the accompanying drawings and examples, it being understood that the examples described below are intended to facilitate the understanding of the invention, and are not intended to limit it in any way.

As shown in fig. 1 and 2, the servo motor pressure and gap control device in the position mode according to the embodiment of the present invention includes a servo motor 1, a servo drive cylinder 2, a force sensor 3, a disc spring 4, an upper die base 5, a lower die base 6, a position sensor 7, a servo driver 8, an I/O system 9, an upper die 10, a lower die 11, and a main controller 12. The servo motor 1, the servo driving cylinder 2, the disc spring 4, the upper die base 5, the lower die base 6, the upper die 10 and the lower die 11 form a mechanical part, the force sensor 3 and the position sensor 7 form a sensing part, the servo driver 8, the I/O system 9 and the main controller 12 form a control module, wherein the main controller 12 mainly comprises a PLC13, a position controller 14, a speed controller 15 and a current controller 16, and the control of the system also needs to use an internal encoder 17 of the servo motor.

As shown, the servo driver 8 is connected to a main controller 12, and the servo driver 8 is a controller for controlling the servo motor 1. The servo motor 1 is directly connected with the driving end of the servo driving cylinder 2, a speed reducing mechanism is not arranged in the middle, and the dynamic output characteristic of the system is good. The servo motor 1 outputs torque, rotating speed, rotating direction and revolution according to a position command and a moment command sent by the servo driver 8, and the servo driving cylinder 2 changes the rotation into linear motion to output force, displacement and speed.

The lower end of a piston rod of the servo driving cylinder 2 is directly connected with the force sensor 3 and the disc spring 4 and is used for monitoring the pressure value of the transmission chain. The disc spring 4 is directly connected with the upper die base 5. Advantageously, the disc spring 4 is arranged between the force sensor 3 and the upper die base 5, so that when the servo motor 1 controls the pressure output by using a position control mode, the system characteristic curve is changed from pure rigidity to elasticity, the pressure change caused by the unit step pitch of the servo motor 1 is reduced, and the pressure control is facilitated.

The position sensor 7 is rigidly connected to the upper die holder 5 and directly measures the actual position of the upper die 10. It should be understood that the compression of the disc spring 5 when compressed will cause the output displacement of the servo motor 1 to be inconsistent with the displacement of the position sensor 7, so that it is not possible to add the position sensor 7 to the inner closed loop of the servo driver 8 instead of the inner encoder 17 of the servo motor 1, and the position sensor 7 is fixed to the upper die base 5, and an accurate position value of the upper die 10 can be obtained based on the monitored value.

Fig. 3 shows a schematic diagram of a servo motor dual closed-loop control of the present invention, and as shown in the figure, in order to perform high-precision gap value control on an upper die and a lower die, the present invention performs pressure control on a test piece by using a position mode, and a system performs operations of a position controller 14, a speed controller 15 and a current controller 16 in the position control mode.

Specifically, the control of the servo motor 1 is generally three-loop control, i.e., 3 closed-loop negative feedback PID regulation systems. As shown in fig. 3, the current loop a (innermost PID loop), the controller in this loop is the current controller 16. The speed loop B is controlled by the speed controller 15 and the current controller 16, and the speed loop B and the current loop a are applied to the control of the speed loop B because a sensor such as the encoder 17 performs speed negative feedback PID adjustment and its adjustment output corresponds to the setting of the current loop a. The position loop C is controlled by the position controller 14, the speed controller 15, and the current controller 16, and the force sensor 3 or the position sensor 7 may be used as a negative feedback source, and the internal output is set as the speed loop B. The present invention performs the above three loop operations in the position control mode.

When the position mode is used for pressure and clearance control, the three feedback quantities of the internal encoder 17, the position sensor 7 and the force sensor 3 are used for the control in the device, and a force control double closed loop formed by combining the position loop C of the internal encoder 17 of the servo motor 1 and the pressure loop E built by the PLC13 is used for realizing the high-precision control of the pressure of the upper die 10 on the test piece; an encoder 17 is used in a servo to serve as a position mode closed loop C, the detection value of the position sensor 7 serves as closed loop D control through a PLC13, a position control double closed loop is formed, and high-precision control of the gap between the upper die 10 and the lower die 11 is achieved.

Therefore, the device of the invention can control the pressure and the clearance with high precision and high stability, and the pressure and the clearance with high precision and high stability of the invention are described in detail by taking a concrete test piece test as an example:

s1: in the stage of contact between the upper die 10 and the test piece, after setting a test gap or a force parameter, the main controller 12 sends a motion command to be converted by the servo driver 8, the signal reaches the servo motor 1 in the form of current magnitude, the servo motor 1 drives the upper die 10 to move through the servo driving cylinder 2 at a certain revolution according to the command, when the upper die 10 moves towards the test piece, an absolute motion module (which means that the upper die directly and quickly moves downwards to a certain specific point in a coordinate system) is used, and the servo motor 1 is controlled to quickly move the upper die 10 to the surface of the test piece at a speed of V1 to be contacted with the test piece by adopting the position ring C control of the internal encoder 17 of the servo motor 1 according to the position (cleared) of the.

S2: the pressure control of the upper die 10 on the test piece is realized by adopting the pressure ring E control established by connecting the force sensor 3 with the PLC13, and the specific process is as follows:

in the stage of pressure loading of the test piece by the upper die 10, a pressure ring E control is adopted, namely, a relative motion module (which refers to force control, downward motion of a point and a point until the force meets the requirement and is irrelevant to the absolute position in a coordinate system) is used, force signals are fed back to the I/O system 9 under the condition of a feedback value of the force sensor 3, the converted force signals reach the main controller 12 in a digital signal form, the main controller 12 adjusts an emitted command after logic operation and set parameter comparison, and when the real-time pressure is less than 90% of the set pressure, pressure loading is carried out by using a position ring C of an internal encoder 17 of the servo motor 1 at a speed V2(V2< V1). The external pressure E and the internal position loop C constitute a force controlled double closed loop.

Then, in the stage of dynamic pressure control of the test piece by the upper die 10, when the real-time pressure measured by the force sensor 3 is greater than 90% of the set pressure, the relative motion module is loaded at the speed of V3(V3< V2) until the set pressure value is reached, but when the real-time pressure exceeds the set pressure according to the characteristics of the disc spring 4, the pressure unloading speed is V4 which is less than V3, so that 1% stable pressure control can be obtained.

The gap control of the upper die 10 and the lower die 11 is realized by adopting the position ring D control established by connecting the position sensor 7 with the PLC13, and the specific process is as follows:

when the gap between the upper die 10 and the lower die 11 needs to be accurately controlled, the upper die 10 is used for carrying out pressure loading on a test piece, a relative motion module is used for feeding back a displacement signal to the I/O system 9 under the condition of an actual position value fed back by the position sensor 7 by adopting position ring D control, the displacement signal is converted and then reaches the main controller 12 in a digital signal form, and the main controller 12 adjusts a sent instruction after logical operation and set parameter comparison. When the actual position of the upper die 10 does not reach the set condition, the upper die 10 moves downwards at the speed V2 of the position ring C of the inner encoder 17 of the servo motor 1, the outer position ring D and the inner position ring C form a die gap control double closed loop, and after the actual position of the upper die 10 reaches the set position, the die stops moving, and the control process is completed.

The device realizes the simulation test of more accurate friction of the aluminum alloy by providing accurate pressure and die clearance values for the friction testing machine, and can accurately obtain the friction coefficient and evaluate the lubricating state. A large number of aluminum plate tests show that the pressure required by the aluminum plate friction test is within 2KN, and the existing testing machine basically controls the pressure by adopting hydraulic pressure, so that the precision requirement cannot be met. The device can automatically apply the pressure value set by the test to the test piece, the precision is +/-1%, the pressure is rapid in the implementation process, when the stretching operation is carried out, the pressure value is kept stable, the friction coefficient of the test piece can be obtained by combining the tensile force, the accurate die clearance and the force value control can also be used for the draw bead test, and effective guide data are provided for the plate forming process. In addition, the device has important significance and value for further popularizing the metal sheet forming process and improving the forming quality of the metal sheet.

It will be apparent to those skilled in the art that various modifications and improvements can be made to the embodiments of the present invention without departing from the inventive concept thereof, and these modifications and improvements are intended to be within the scope of the invention.