A driving circuit for a Lorentz motor based on current closed-loop feedback control principle

Abstract

This invention discloses a Lorentz motor drive circuit based on the current closed-loop feedback control principle, belonging to the field of circuit control technology for Lorentz planar motors. It includes a control signal pre-amplification module, a differential amplifier module, a current sampling module, a signal conversion module, and a feedback loop. The control signal pre-amplification module outputs a voltage control signal V1 to the differential amplifier module under the combined action of the control signal Vc and the feedback signal Vi. The differential amplifier module outputs V1 as motor drive signals V+ and V-, which serve as the input voltages across the Lorentz motor coil. The current sampling module samples and amplifies the current Im generated inside the motor coil into feedback voltages Vi+ and Vi-. The signal conversion module converts Vi+ and Vi- into a single-ended feedback signal Vi, which, after passing through the feedback loop, acts together with the control signal Vc on the control signal pre-amplification module. The Lorentz motor drive circuit provided by this invention has the advantages of high output current control accuracy, small steady-state error, and large control bandwidth.

Description

Technical Field

[0001] This invention belongs to the field of circuit control technology for Lorentz planar motors, and more specifically, relates to a Lorentz motor drive circuit based on the current closed-loop feedback control principle. Background Technology

[0002] Lorentz planar motors are a new type of motor that has emerged with the rapid development of power electronics technology and high-performance permanent magnet materials. They possess advantages such as good linearity, high speed and precision, simple structure, and low inertia. They have enormous application potential in modern precision and ultra-precision manufacturing equipment such as lithography machines and chip manufacturing equipment. Related technologies are developing rapidly both domestically and internationally, and Lorentz motor drives are widely considered a key technology for advanced manufacturing. As the requirements for high speed and precision in motors become increasingly stringent, Lorentz motor drives should possess characteristics such as excellent linearity, high bandwidth, and minimal static error.

[0003] Over the years, Lorentz motor drive circuits have been developed into two types: PWM drive and DC drive. PWM drive offers advantages such as high efficiency, small size, and high power, but its disadvantages include large current ripple and narrow bandwidth. Furthermore, the input and output signals of PWM drive do not satisfy a linear relationship, making driver design more complex. DC drive, on the other hand, is simple and intuitive, with a linear relationship between input and output, and a simpler driver design. It also boasts high bandwidth and low current ripple. However, DC drive suffers from low driving efficiency and large size. In addition, due to temperature drift in the circuit, the steady-state error of the system is relatively large.

[0004] In order to achieve both high-precision Lorentz motor drive and resistance to high-frequency interference, it is necessary to design a Lorentz motor drive circuit that is simple in structure, highly efficient, and meets the above requirements. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a Lorentz motor drive circuit based on the current closed-loop feedback control principle, thereby solving the problems of large system steady-state error and low current control accuracy in existing DC-driven Lorentz motor drive circuits.

[0006] To achieve the above objectives, this invention provides a Lorentz motor drive circuit based on the current closed-loop feedback control principle, comprising a control signal pre-amplification module, a differential amplification module, a current sampling module, a signal conversion module, and a feedback loop. The control signal pre-amplification module outputs a voltage control signal V1 to the differential amplification module under the combined action of the control signal Vc and the feedback signal Vi. The differential amplification module outputs the input voltage control signal V1 as motor drive signals V+ and V-, which serve as the input voltages across the Lorentz motor coil. The current sampling module samples and amplifies the motor drive signals V+ and V- into feedback voltages Vi+ and Vi-. The signal conversion module converts the feedback voltages Vi+ and Vi- into a single-ended feedback signal Vi, which, after passing through the feedback circuit, acts together with the control signal Vc on the control signal pre-amplification module.

[0007] The control signal prevention module mainly consists of operational amplifier U1 and a PI control circuit. The PI control circuit can reduce high-frequency amplitude and bandwidth, improve low-frequency gain without increasing high-frequency noise, and improve steady-state accuracy. By configuring R5, R6, C9, and C10 in the peripheral PI control circuit of amplifier U1, the low-frequency amplification factor is adjusted to improve the signal-to-noise ratio. Under the combined action of control signal Vc and feedback signal Vi, the output voltage control signal V1 is generated. R5 and C9 are connected in series and then in parallel between the input and output pins of U1, and R6 and C10 are connected in series and then in parallel between the input and output pins of U1. The transfer function of the control signal prevention module is:

[0008]

[0009] Where s is the Laplace operator.

[0010] The differential amplifier module mainly consists of LM4766 chips U2 and U3, which are two linear power amplifiers. They adopt a differential DC output method and a symmetrical circuit structure to output the output voltage control signal V1 as motor drive signals V+ and V-, and use the output as the input voltage across the Lorentz motor coil. The peripheral circuit includes R13, R14, R17, R18, R25, R33, R34, C17, C18, and C24. R14 is connected at one end to the output pin of U1 and at the other end to the input pin of U2. R25 and R34 are connected in series and then in parallel between the input and output pins of U2. R14, R25, and R34 form the feedback loop of U2. R13 is connected at one end to the output pin of U1 and at the other end to the input pin of U3. R17 is connected in series between the input pin of U3 and GND. R33 is connected in parallel between the input and output pins of U2. R13, R17, and R33 form the feedback loop of U3. R18, C17, C18, and C24 configure the external power supply circuit for U2. The transfer function of the differential amplifier module is:

[0011]

[0012] Where s is the Laplace operator.

[0013] Furthermore, one end of the Lorentz motor coil is connected to R45 and then to the U2 output pin, and the other end is connected to R46 and then to the U3 output pin. The transfer function is:

[0014]

[0015] Among them, R m L is the resistance of the motor coil. m It is the inductance of the motor coil.

[0016] The current sampling module is based on chips U4 and U5 and uses two small-value, high-precision sampling resistors for sampling. It uses a symmetrical circuit structure to treat the voltage across the sampling resistor as the voltage applied across the Lorentz motor coil and samples and amplifies the motor drive signals V+ and V- into feedback voltages Vi+ and Vi-. The amplification factor can be achieved by changing the resistance value of the external resistors. The peripheral circuit includes R45, R46, R53, R54, R57, R59, C45, and C46. R45 is connected in series between the non-inverting and inverting input pins of U4. One end of R53 is connected to the inverting input pin of U4, and the other end is connected to GND. R57 is connected in parallel between the inverting input pin and the output pin of U4. R46 is connected in series between the non-inverting and inverting input pins of U5. One end of R54 is connected to the inverting input pin of U5, and the other end is connected to GND. R59 is connected in parallel between the inverting input pin and the output pin of U5. C45 and C46 are configured for the external power supply circuits of U4 and U5, respectively. The transfer function is:

[0017]

[0018] Where s is the Laplace operator.

[0019] The signal conversion module mainly consists of operational amplifier U6 and its peripheral circuitry. Its primary function is to convert the feedback voltages Vi+ and Vi- into a single-ended feedback signal Vi, which, after passing through the feedback circuit, interacts with the control signal Vc to power the control signal pre-amplification module. The peripheral circuitry includes resistors R69, R70, R71, R81, C53, and C57. One end of R70 is connected to the output pin of U4, and the other end is connected to the inverting input pin of U6. R81 and C57 are connected in parallel, with one end connected to the inverting input pin of U6 and the other end to the output pin of U6. One end of R71 is connected to the output pin of U5, and the other end to the non-inverting input pin of U6. R69 and C53 are connected in parallel, with one end connected to the non-inverting input pin of U6 and the other end connected to GND. The transfer function is:

[0020]

[0021] Where s is the Laplace operator.

[0022] Furthermore, the feedback loop includes R1 and R38. One end of R38 is connected to the output of U6 and the other end is connected to the input of U1. One end of R1 is connected to the control signal Vc and the other end is connected to the input of U1. The feedback coefficient is:

[0023]

[0024] Open-loop transfer function:

[0025] G open =G1G2G3G4G5.

[0026] Closed-loop transfer function:

[0027]

[0028] The Lorentz motor drive circuit based on current closed-loop feedback control principle provided by this invention has the advantages of small size, good low-frequency characteristics, strong high-frequency anti-interference ability, high output current control accuracy, good linearity, small steady-state error, and large control bandwidth (approximately 3kHz). This invention uses low-voltage power supply, and under the action of the control signal Vc (-10V to 10V), it outputs current through a fixed amplification gain to meet the driving requirements of the Lorentz motor. Addressing the problem of poor thermal stability and temperature drift in linear power amplifiers, a hardware-based PID control method is adopted, effectively ensuring the accuracy of its output current. Furthermore, differential drive and a symmetrical circuit structure are used to eliminate system errors, improve steady-state accuracy, and enhance the anti-interference capability of the drive system. Attached Figure Description

[0029] Figure 1 This is a structural block diagram of the present invention;

[0030] Figure 2 This is the circuit schematic diagram of the present invention;

[0031] Figure 3 This is the open-loop Bode diagram of the present invention;

[0032] Figure 4 This is the closed-loop Bode plot of the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0034] This invention provides a Lorentz motor drive circuit based on the current closed-loop feedback control principle, such as... Figure 1 As shown, the system includes a control signal pre-amplification module, a differential amplification module, a current sampling module, a signal conversion module, and a feedback circuit. The control signal pre-amplification module outputs a voltage control signal V1 to the differential amplification module under the combined action of the control signal Vc and the feedback signal Vi. The differential amplification module outputs the input voltage control signal V1 as motor drive signals V+ and V-, which are used as the input voltages across the Lorentz motor coil. The current sampling module samples and amplifies the motor drive signals V+ and V- into feedback voltages Vi+ and Vi-. The signal conversion module converts the feedback voltages Vi+ and Vi- into a single-ended feedback signal Vi, which, after passing through the feedback circuit, acts together with the control signal Vc on the control signal pre-amplification module.

[0035] like Figure 2 As shown, the input voltage passes through a PI regulation circuit and then enters the differential amplifier module. The differential amplifier module uses two linear power amplifiers to form a differential DC output, improving the anti-interference capability of the output current. The linear power amplifiers use a symmetrical circuit structure to eliminate system errors and improve steady-state accuracy. The current is sampled and converted into voltage by a current sampling circuit and amplified, serving as a feedback signal. This invention allows adjustment of the overall amplification gain of the circuit by changing the resistance values ​​of R1 and R38, easily achieving motor drive. The entire system exhibits good low-frequency characteristics, strong high-frequency anti-interference capability, high output current control accuracy and linearity, small steady-state error, and a large control bandwidth. The hardware-based PID control implementation effectively ensures the accuracy of the output current. The use of differential drive and a symmetrical circuit structure eliminates system errors, improves steady-state accuracy, and enhances the anti-interference capability of the drive system. It is well-suited as a drive circuit for various Lorentz planar motors. The principles of each part will be described in detail below.

[0036] The main function of the control signal prevention module is to generate the required output gain by configuring R5, R6, C9, and C10 of the peripheral PI adjustment circuit of amplifier U1. The PI adjustment circuit can reduce high-frequency amplitude and bandwidth, improve low-frequency gain without increasing high-frequency noise, and improve steady-state accuracy. The prevention module amplifies the deviation between the control signal Uc within the control bandwidth and the feedback signal Ui from the current detection circuit, improving the signal-to-noise ratio. After passing through the pre-amplification module, the output voltage control signal V1 enters the differential amplifier module. The transfer function of the control signal prevention module is:

[0037]

[0038] The differential amplifier module is mainly based on LM4766 chips U2 and U3. The output voltage control signal V1 is amplified by two power amplifiers U2 and U3. By configuring resistors R14 = R34 = R17, R25 = R33, the circuit structure is made symmetrical, at which point V+ = -V-, and the output is used as the input voltage across the motor coil. The differential amplifier module uses differential drive and a symmetrical circuit structure to eliminate system errors and improve steady-state accuracy. The transfer function of the differential amplifier module is:

[0039]

[0040] When motor drive signals V+ and V- are applied to the two ends of the Lorentz motor coil, a current Im will be generated inside the coil. The transfer function is:

[0041]

[0042] R m L represents the resistance of the motor coil, measured in Ω. m It is the inductance of the motor coil, and the unit is (H).

[0043] The current sampling module is mainly based on the AD628ARZ chips U4 and U5. Its amplification factor is related to the external resistor. Taking U4 as an example, its amplification factor is... By setting R57 = R59, R53 = R54, and other related parameters equal, the circuit structure becomes symmetrical. At this point, the amplification factors from V+ to Vi+ and V- to Vi- are the same. Furthermore, by connecting capacitors C45 and C46 to pin 3 of the AD628AR chip, a first-order low-pass circuit is formed with the internal circuitry to filter high-frequency noise. The basic principle of the current sampling module is to use R45 and R46 as two small-value, high-precision resistors. Approximating the voltage across R45 and R46 as the voltage across a Lorentz motor, and setting R45 = R46, the transfer function from the current Im in the motor coil to the output voltages Vi+ and Vi- can be obtained as follows:

[0044]

[0045] The main function of the signal conversion module is to convert the output voltages Vi+ and Vi- into a single-ended feedback signal Vi using operational amplifier U6. Let R70 = R71, R69 = R81, and C53 = C57. At this point, the external structure of the input and output terminals of U6 is symmetrical, and the transfer function of the signal conversion module is:

[0046]

[0047] To achieve feedback control of the Lorentz motor drive, a current feedback loop was designed so that the single-ended feedback signal Vi and the control signal Vc act together on U1, with a feedback coefficient...

[0048] For this circuit, with the input being a control signal Vc and the output being a current Im, its open-loop transfer function is:

[0049] G open =G1G2G3G4G5 (6)

[0050] Besides the motor coil inductance and resistance, by selecting other suitable parameters such as capacitance, resistance, amplification factor, and cutoff frequency, the open-loop transfer curve of the system can be obtained. For example... Figure 3 As shown in the figures, the horizontal axis of the upper and lower graphs represents the frequency of the control signal Vc, in kHz. The vertical axis of the upper graph represents the logarithm of the system input-output ratio, i.e., 20log. 10 (Im / Vc), in dB. The vertical axis of the graph below represents the phase difference between the system output and input, in degrees. At a low frequency of 1Hz, its open-loop gain reaches as high as 70dB. The overall system has a large low-frequency gain, resulting in small steady-state error, high steady-state accuracy, and good static characteristics. In the mid-frequency range, its open-loop cutoff frequency ω... c =2.7kHz, rolls off at a rate of approximately -27dB / dec near the amplitude crossover point, with a phase margin of approximately 30°, indicating that the system has relatively small damping and is stable. The frequency corresponding to the -3dB point is 3.33kHz, indicating that the control bandwidth is greater than 3kHz, in the high-frequency range (ω>10ω). c =27KHz), the curve rolls off at a rate of approximately -60dB / dec, demonstrating strong suppression of high-frequency signals and strong anti-interference capability of the system.

[0051] The closed-loop transfer function of the drive circuit is:

[0052]

[0053] Its closed-loop transmission characteristics are as follows Figure 4 As shown in the figures, the horizontal axis of the upper and lower graphs represents the frequency of the control signal Vc, in kHz. The vertical axis of the upper graph represents the logarithm of the system input-output ratio, i.e., log... 10 (Im / Vc), in dB. The vertical axis in the graph below represents the phase difference between the system output and input, in degrees. When the frequency of the control signal Vc varies from 0Hz to 3kHz, 20log 10 (Im / Vc) = 13.9, meaning the system gain is always 0.2, which fully demonstrates the good linearity of this drive circuit.

[0054] Those skilled in the art will readily understand 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 within the scope of protection of the present invention.

Claims

1. A Lorentz motor drive circuit based on the current closed-loop feedback control principle, characterized in that, The system includes a control signal pre-amplification module, a differential amplification module, a current sampling module, a signal conversion module, and a feedback loop. The control signal pre-amplification module outputs a voltage control signal V1 to the differential amplification module under the combined action of the control signal Vc and the feedback signal Vi. The differential amplification module outputs the input voltage control signal V1 as motor drive signals V+ and V-, which are used as the input voltages across the Lorentz motor coil. The current sampling module samples and amplifies the current Im generated inside the motor coil into feedback voltages Vi+ and Vi-. The signal conversion module converts the feedback voltages Vi+ and Vi- into a single-ended feedback signal Vi, which, after passing through the feedback loop, works together with the control signal Vc to power the control signal pre-amplification module. The differential amplifier module includes power amplifiers U2 and U3 and their peripheral circuits; the current sampling module includes operational amplifiers U4 and U5 and their peripheral circuits. The peripheral circuits include resistors R45 and R46. R45 is connected in series between the non-inverting and inverting input pins of U4, and R46 is connected in series between the non-inverting and inverting input pins of U5. One end of the Lorentz motor coil is connected to R45 and then to the output pin of U2, and the other end is connected to R46 and then to the output pin of U3. The transfer function is: in, R m The resistance of the motor coil, L m It is the inductance of the motor coil. s For the Laplace operator.

2. The Lorentz motor drive circuit according to claim 1, characterized in that, The control signal pre-amplification module includes amplifier U1 and an external PI adjustment circuit. The external PI adjustment circuit includes resistors R5 and R6, and capacitors C9 and C10. R5 and C9 are connected in series and then in parallel between the input and output pins of U1. R6 and C10 are connected in series and then in parallel between the input and output pins of U1. The feedback loop includes R1, with one end connected to the control signal Vc and the other end connected to the input of U1. The transfer function of the control signal pre-amplification module is: in, s For the Laplace operator.

3. The Lorentz motor drive circuit according to claim 2, characterized in that, The differential amplifier module includes power amplifiers U2 and U3 and their peripheral circuits. The peripheral circuits include resistors R13, R14, R17, R18, R25, R33, and R34, and capacitors C17, C18, and C24. One end of R14 is connected to the output pin of U1, and the other end is connected to the input pin of U2. R25 and R34 are connected in series and then in parallel between the input and output pins of U2, forming the feedback loop of U2. One end of R13 is connected to the output pin of U1, and the other end is connected to the input pin of U3. R17 is connected in series between the input pin of U3 and GND, and R33 is connected in parallel between the input and output pins of U2, forming the feedback loop of U3. R18, C17, C18, and C24 configure the external power supply circuit for U2. The transfer function of the differential amplifier module is: in, s For the Laplace operator.

4. The Lorentz motor drive circuit according to claim 3, characterized in that, The current sampling module includes operational amplifiers U4 and U5 and their peripheral circuitry. The peripheral circuitry includes resistors R45, R46, R53, R54, R57, and R59, and capacitors C45 and C46. R45 is connected in series between the non-inverting and inverting input pins of U4. One end of R53 is connected to the inverting input pin of U4, and the other end is connected to GND. R57 is connected in parallel between the inverting input pin and the output pin of U4. R46 is connected in series between the non-inverting and inverting input pins of U5. One end of R54 is connected to the inverting input pin of U5, and the other end is connected to GND. R59 is connected in parallel between the inverting input pin and the output pin of U5. C45 and C46 are configured for the external power supply circuits of U4 and U5, respectively. The transfer function is: in, s For the Laplace operator.

5. The Lorentz motor drive circuit according to claim 4, characterized in that, The signal conversion module includes an operational amplifier U6 and its peripheral circuitry. The peripheral circuitry includes resistors R69, R70, R71, and R81, and capacitors C53 and C57. One end of R70 is connected to the output pin of U4, and the other end is connected to the inverting input pin of U6. R81 and C57 are connected in parallel, with one end connected to the inverting input pin of U6 and the other end connected to the output pin of U6. One end of R71 is connected to the output pin of U5, and the other end is connected to the non-inverting input pin of U6. R69 and C53 are connected in parallel, with one end connected to the non-inverting input pin of U6 and the other end connected to GND. The transfer function is: in, s For the Laplace operator.

6. The Lorentz motor drive circuit according to claim 5, characterized in that, The feedback circuit includes resistor R38, with one end of R38 connected to the output of U6 and the other end connected to the input of U1. The feedback coefficient is: 。 7. The Lorentz motor drive circuit according to claim 6, characterized in that, Open-loop transfer function: 。 8. The Lorentz motor drive circuit according to claim 7, characterized in that, Closed-loop transfer function: 。

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