CN1057037C - High frequency response, large stroke and high precision microstep feeder - Google Patents

Abstract

A high-response, large-stroke, and high-precision micro-feeding device belongs to an accessory device of a machine tool. The micro-feeding device is composed of two parts: the actuator and the control system; the actuator is composed of a linear motion mechanism and a position feedback element. The linear motion mechanism has a linear motion shaft, and a frame with coils is installed on the shaft. In a magnetic field generated by a magnet, both ends of the motion shaft are supported on bearings, the position feedback element is a linear displacement sensor, and the control system includes a computer, decoding and driving circuit, A/D, D/A conversion circuit, parallel interface circuit, amplifier circuit. The micro-feeding device has a simple structure and less frictional resistance during movement, so it can meet the requirements of high frequency response and large stroke.

Description

High-frequency response, large stroke and high-precision micro-feeding device

The invention relates to a feeding device of a machine tool, which belongs to an accessory device of the machine tool.

The micro-feed device is the key technology of precision machining and dynamic error compensation control system. Among today's numerous micro-feeding devices, although the micro-feeding device using a mechanical transmission mechanism can have a certain stroke and accuracy, its frequency response is very low; piezoelectric crystals, electrostrictive, magnetostrictive, elastic deformation, etc. The frequency response and precision of the micro-feeding devices are high but the stroke is small, so they cannot have the characteristics of high frequency response and large stroke. In some applications, such as the CNC turning of convex and variable ellipse pistons, etc., the micro-feed device is required to have the characteristics of high frequency response, large stroke and high precision. European patent EP315469 discloses a processing equipment. The feeding device of the processing equipment is composed of an actuator and a control system. The actuator includes a linear motion mechanism and a position feedback element. The linear motion mechanism has a linear motion axis. It is in a magnetic field formed by a magnet, and its two ends are supported by bearings. The position feedback element includes a linear displacement sensor installed at one end of the motion shaft. The control system includes a computer, drive circuit, A/D, D/A conversion circuit, interface Circuits, amplifier circuits, etc., but the processing equipment is a rotating electric grinding head, which only rotates. As mentioned above, the existing micro-feeding devices are difficult to meet this requirement.

The purpose of the present invention is to provide a high-precision micro-feeding device with high-response and large-stroke characteristics.

The high-response, large-stroke, high-precision micro-feeding device of the present invention is composed of two parts: an actuator and a control system. The actuator is composed of a linear motion mechanism and a position feedback element; the linear motion mechanism has a linear motion axis (1) ( See Fig. 1) install the frame (3) that is wound with coil (2) on the motion shaft (1), this frame (3) is in the magnetic field that is produced by magnet (4), the two ends of motion shaft (1) Supported on the bearing (5), when the coil (2) passes through the current, the motion axis (1) will be linearly moved by the Lorentz force; the position feedback element is a linear displacement sensor (laser interferometer or eddy current The sensor) (7) is installed at one end of the motion shaft (1); it is used to detect the actual displacement of the motion shaft (1), and the displacement signal is sent to the control system through the interface circuit for position control.

When the position feedback element is a laser interferometer, the control system (Figure 2) consists of a parallel interface circuit (I), a computer (II), a decoding and driving circuit (III), a D/A conversion circuit (IV), and an amplifier circuit ( V) form, parallel interface circuit (I) adopts parallel interface chip 8255, is used for receiving the position signal that laser interferometer outputs and inputs computer, computer (II) can adopt general computer, is used for calculating the signal of laser interferometer And given the control signal, the decoding and driving circuit (III) is composed of a tri-state transceiver (74LS245), a decoder (74LS138), an inverter (74LS04), an AND gate (74LS21, 74LS08) and its peripheral resistors. The three-state transceiver is connected with the computer bus to improve the driving capability of the computer system bus, and the decoder and the gate circuit perform address decoding to provide the address of the parallel interface and the D/A converter, and the D/A conversion circuit (IV ) consists of a D/A conversion chip (DAC1210) and an operational amplifier (OP07), which is used to convert the digital control signal output by the computer into an analog voltage signal. The amplifying circuit (V) consists of an operational amplifier (L465), a transistor (MJ024 , MJ025) and peripheral resistors, the operational amplifier (L465) pre-amplifies the voltage signal from the D/A conversion circuit (IV), and the triode and its peripheral resistors form a power amplifier circuit to amplify the pre-amplified signal. And output to the actuator (linear motion mechanism). The working process of the whole control system is as follows: the laser interferometer detects the actual displacement of the moving shaft, and sends it to the computer through the parallel interface circuit, and the computer outputs the corresponding control signal (digital quantity), which is converted into the corresponding voltage by the D/A conversion circuit and sent to Into the amplifier circuit to drive the actuator.

When the position feedback element is an eddy current sensor, the control system (Fig. 3) consists of A/D conversion circuit (VI), computer (VII), decoding and driving circuit (VIII), D/A conversion circuit (IX), amplification Circuit (X), A/D conversion circuit (VI) is composed of A/D conversion chip AD574, latch 8212 and its peripheral resistors, the position signal output from the eddy current sensor enters the latch after A/D conversion , and then into the computer, the computer (VII) can be a general computer, and the decoding and driving circuit consists of a three-state transceiver (74LS245), a decoder (74LS138), an inverter (74LS04), an AND gate (74LS21, 74LS08) and Its peripheral resistance composition. The three-state transceiver is connected with the computer bus to improve the driving capability of the computer system bus, and the decoder and the gate circuit perform address decoding to provide the address of the parallel interface and the D/A converter, and the D/A special change circuit ( IX) It consists of a D/A conversion chip (DAC1210) and an operational amplifier (OP07), which is used to convert the digital control signal output by the computer into an analog voltage signal. The amplifying circuit (X) consists of an operational amplifier (L465), a transistor ( Composed of MJ024, MJ025) and peripheral resistors, the operational amplifier (L465) pre-amplifies the voltage signal from the D/A conversion circuit (IX), and the triode and its peripheral resistors form a power amplifier circuit to re-amplify the pre-amplified signal Amplified and output to the actuator (linear motion mechanism). The interaction process of the entire control system is as follows: A/D conversion circuit receives the analog voltage signal output by the eddy current sensor, converts it into a corresponding digital signal, and sends it to the computer, and the computer outputs the corresponding control signal (digital quantity). The /A conversion circuit converts the corresponding voltage into the amplifying circuit, and drives the actuator after the power is amplified.

The function of the control system is to receive the position feedback signal, and on this basis, generate a control signal to control the motion of the motion axis, so as to output the required motion quickly and accurately.

The position control of the present invention adopts the proportional-integral-derivative (PID) control of integral separation, and its equation is:

U(n)=K _p ×e(n)+ΔU ₁ (n)+K _d ×[e(n)-e(n-1)]+U ₁ (n-1)

=K _p ×e(n)+K ₁ ×K ₁ ×e(n)+K _d ×[e(n)-e(n-1)]+U ₁ (n-1) where:

K _p ---- proportional coefficient of PID controller

K ₁ ----Integral coefficient of PID controller

K _d ---- differential coefficient of PID controller

e(n)----the deviation signal obtained from the nth sampling

U(n)----the nth PID controller output

U ₁ (n-1)----Integral component of the n-1th control

U ₁ (n-1)=K ₁ ×K ₁ ×e(n-1)+U ₁ (n-2)

K ₁ ----integral logic switch

K ₁ =1, introduce integral action;

K ₁ ＝0, cancel integral function;

The position control is realized by the computer, and its interaction process is as follows (Figure 4): The computer obtains the displacement value required by the motion axis according to the displacement needs, receives the actual displacement signal of the motion axis from the position feedback element through the interface circuit, and then compares the required displacement with the Actual displacement, get the deviation signal, calculate according to the aforementioned PID control law, give the digital control voltage value, output to the D/A converter, change the corresponding analog voltage value through the D/A converter, and send it to the control system amplifying circuit.

The interaction process of the entire micro-feeding device can be summarized as follows: the computer calculates the control signal (digital quantity) according to the given position and the actual position given by the position feedback element through the control software according to the aforementioned PID control law of integral separation, This signal is changed into corresponding analog voltage signal by D/A converter. The signal becomes a control current signal through the amplifying circuit of the control system. The motion axis directly outputs linear motion under the action of the control current. The position of the movement is detected by the position feedback element and sent to the computer to realize the closed-loop control of the position.

Because the motion axis directly moves in a straight line without a mechanical transmission mechanism, and the mass of the mover is small, it is beneficial for the micro-feeding device to obtain a higher response frequency and operating speed.

The accompanying drawings are as follows:

Fig. 1 is a structural schematic diagram of the actuator of the present invention.

Fig. 2 is a schematic circuit diagram of the control system when the position feedback element of the present invention adopts a laser interferometer.

Fig. 3 is a schematic circuit diagram of the control system when the position feedback element of the present invention adopts an eddy current sensor.

Fig. 4 is a flowchart of the control software of the control system of the present invention.

Fig. 5 is a schematic structural diagram of Embodiment 1 of the present invention.

Fig. 6 is a schematic structural diagram of Embodiment 2 of the present invention.

Fig. 7 is a schematic structural diagram of Embodiment 8 of the present invention.

Fig. 8 is a schematic structural diagram of Embodiment 4 of the present invention.

Embodiment is as follows in conjunction with accompanying drawing description:

Example 1

Fig. 5 is a schematic structural view of Embodiment 1 of the micro-feeding device of the present invention.

The magnetic field adopts a radial magnetization mode, the permanent magnet (8) is tile-shaped, and is circumferentially arranged along the inner side of the outer soft iron (9), and the direction of the magnetic force line of the permanent magnet (8) is radial. A magnetic closed circuit is formed by the inner soft iron (10), the outer soft iron (9) and the magnet (8) to generate a magnetic field. The coil (12) wound on the frame (11) is subjected to an axial electromagnetic force under the action of the gap magnetic field when the current from the control system is passed through the amplifying circuit. This force is transmitted to the motion shaft (13) by the frame, so that the motion shaft produces linear motion. Motion shaft (13) left end adopts spring (14) support, and the right end adopts dense bead rolling guide (15) support. The position feedback element adopts a single-frequency laser interferometer, and its moving mirror (16) is fixed on the left end of the moving shaft (13). The digital displacement signal output from the laser interferometer is transmitted to the computer through the I/O parallel interface board.

Example 2

Fig. 6 is a schematic structural diagram of Embodiment 2 of the micro-feeding device of the present invention.

The magnetic field adopts the radial magnetization method. The permanent magnets (18) become tile-shaped, and are arranged circumferentially along the inner side of the outer soft iron (19), and the direction of the magnetic lines of force of the permanent magnets is radial. A magnetic closed circuit is formed by the inner soft iron (20), the outer soft iron (19) and the magnet (18) to generate a magnetic field. The coil (22) wound on the frame (21) is subjected to an axial electromagnetic force under the action of the gap magnetic field when the current from the control system is passed through the amplifying circuit. This force is transmitted to the motion shaft (23) by the frame (21), so that the motion shaft (23) produces linear motion. Motion shaft (23) left end adopts spring (24) support, and the right end adopts dense bead rolling guide (25) support. The position feedback element adopts an eddy current displacement sensor (26), which is installed on the rear cover (17) at the left end of the motion shaft (23) to detect the motion displacement of the motion shaft (23), and the displacement signal is converted by the A/D converter. The digital signal is received by the computer.

Example 3

Fig. 7 is a schematic structural view of Embodiment 3 of the micro-feeding device of the present invention.

The magnetic field adopts the axial magnetization method. The permanent magnet (27) is a hollow conical shape in the middle, and its magnetic field line direction is axial. A magnetic closed circuit is formed by the inner soft iron (28), the outer soft iron (29) and the magnet (27) to generate a magnetic field. The coil (31) wound on the frame (30) is subjected to an axial electromagnetic force under the action of the gap magnetic field when the current from the control system is passed through the amplifying circuit. This force is transmitted to the motion shaft (32) through the frame (30), so that the motion shaft (32) produces linear motion. Motion shaft (32) left end adopts spring (33) support, and the right end adopts dense bead rolling guide (34) support. The position feedback element adopts a single-frequency laser interferometer, and its moving mirror (35) is fixed on the left end of the moving shaft (32). The digital displacement signal output from the laser interferometer is transmitted to the computer through the I/O parallel interface board. Example 4

Fig. 8 is a schematic structural view of Embodiment 4 of the micro-feeding device of the present invention.

The magnetic field adopts the axial magnetization method. The permanent magnet (36) is a hollow cone shape in the middle, and its magnetic field line direction is axial. A magnetic closed circuit is formed by the inner soft iron (37), the outer soft iron (38) and the magnet (36) to generate a magnetic field. The coil (40) wound on the frame (39) is subjected to an axial electromagnetic force under the action of the gap magnetic field when the current from the control system is passed through the amplifying circuit. This power is transmitted to the motion shaft (41) by the frame (39), so that the motion shaft (41) produces linear motion. Motion shaft (41) left end adopts spring (42) support, and the right end adopts dense bead rolling guide (43) support. The position feedback element adopts an eddy current displacement sensor (44), which is installed on the rear cover (45) at the left end of the motion shaft (41) to detect the motion displacement of the motion shaft (41), and the displacement signal is converted by the A/D converter. The digital signal is received by the computer.

The high-response, large-stroke, and high-precision micro-feeding device of the present invention has a simple structure of the actuator, and the motion axis directly moves in a straight line, without the need for mechanism transmission machinery, and the mass of the mover is small, so it is beneficial for the micro-feeding device to obtain higher Response frequency and motion speed; the motion axis adopts dense ball guide rail rolling bearing, so the frictional damping between the moving part and the fixed part is small, which is conducive to reducing frictional heat and improving the system response speed, and its friction characteristics are constant, which is beneficial to the system. Control: the combination of dense bead guide rail rolling support and spring support is used to ensure that the movement stroke of the movement shaft is not limited by the support form, so it has a larger stroke. On the basis of position feedback, by adopting appropriate control methods, the micro-feeding device can comprehensively have the characteristics of high frequency response, large stroke and high precision.

The micro-feeding device provided by the present invention can have the characteristics of high frequency response and large stroke under the condition of high precision. When using a laser interferometer as a position feedback element, the performance indicators are as follows:

Frequency Response: 200HZ

Travel distance: 2mm

Positioning accuracy: ±0.3μm

When using an eddy current displacement sensor as a position feedback element, the performance indicators are as follows:

Frequency Response: 200HZ

Travel distance: 2mm

Positioning accuracy: ±2μm

Claims (2)

1, a kind of high frequency response, big stroke, high precision microstep feeder, this device is made up of executing agency and control system two parts, executing agency is made up of straight-line motion mechanism, position feedback element, said straight-line motion mechanism has a linear motion axis, described position feedback element is a linear displacement transducer, is installed in an end of kinematic axis; Described control system comprises computer, decoding and drive circuit, A/D, D/A change-over circuit, parallel interface, amplifying circuit, it is characterized in that, the framework be wound with coil is installed on axle, and this framework is in the magnetic field that is produced by magnet, the two supports of kinematic axis is on bearing.

2, according to the said high frequency response of claim 1, big stroke, high precision microstep feeder, it is characterized in that block bearing is spring and close pearl rolling guide.

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