Analog-digital mixed galvanometer motor controller based on grating encoder

Abstract

The invention discloses an analog-to-digital mixed galvanometer motor controller based on a grating encoder, and the controller comprises a position decoding circuit which amplifies and converts a position feedback analog signal and a position input analog signal into digital signals; the control operation circuit adopts an FPGA (Field Programmable Gate Array) + ARM (Advanced RISC Machines) coprocessing architecture, performs data acquisition and control algorithm task division collaboratively by utilizing respective characteristics of double processors, outputs a driving control signal and realizes high-speed servo control on a galvanometer motor; and the driving execution circuit collects a motor current signal, realizes current loop negative feedback, serves as an execution mechanism of the controller to output a driving power signal, and drives the motor to rotate forwards and backwards. A mixed framework of an analog circuit and a digital circuit is adopted, the complex algorithm processing capability of the digital circuit and the signal processing rapidity of the analog circuit are both considered, the design is simplified, and the precision and the anti-interference capability of a galvanometer motor system are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of high-precision motor control, in particular to an analog-digital hybrid galvanometer motor controller based on a grating encoder. Background Art

[0002] The galvanometer motor is a limited-angle DC motor with mechanical limit, which includes a motor body, a swing mirror, and a grating encoder. During operation, the galvanometer motor is required to follow the position input signal quickly, accurately, and stably.

[0003] The motor body is generally an integrated structure, consisting of a stator assembly, a rotor assembly, a terminal plate, a pin, a damping ring and a bearing; the stator assembly includes a coil assembly, a bearing retaining ring, a protective sleeve and a stator housing; the rotor assembly includes a permanent magnet, a damping ring, a rotor front and rear shaft and a pin; the bearing is a deep groove ball bearing made of stainless steel, and is preloaded with a spring for constant pressure.

[0004] Galvanometer motor controllers are divided into analog and digital controllers. Analog controllers have fast response speeds and can meet the high-speed scanning requirements of galvanometer motors. However, they cannot apply intelligent control algorithms, consume high power, have poor portability, suffer from large temperature drift, and are susceptible to external interference. Digital control methods have strong anti-interference capabilities and high reliability, but they require digital-to-analog conversion, process large amounts of data, and have complex circuits. Summary of the Invention

[0005] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology and provide an analog-to-digital hybrid galvanometer motor controller based on a grating encoder, thereby improving the response speed and scanning accuracy of the galvanometer motor control system, reducing circuit complexity, and improving the system's anti-interference ability.

[0006] The technical solution of the present invention is to provide an analog-digital hybrid galvanometer motor controller based on a grating encoder, comprising:

[0007] The position decoding circuit collects the position input signal and converts it into a position input digital signal; it processes the position feedback signal output by the grating encoder of the controlled galvanometer motor to obtain a position feedback digital signal proportional to the actual angle of the galvanometer motor;

[0008] The control operation circuit adopts FPGA+ARM collaborative processing architecture. FPGA uses a parallel bus interface to collect position input digital signals and position feedback digital signals and transmits them to ARM. ARM adopts position loop + speed loop dual closed-loop PID control to calculate the drive control signal and send it to the drive execution circuit.

[0009] The drive execution circuit samples the winding current of the controlled galvanometer motor to obtain the motor current signal, forming a current loop negative feedback; the drive control signal output by the ARM is converted into a drive power signal to drive the controlled motor.

[0010] Furthermore, the position decoding circuit includes:

[0011] The operational amplifier circuit collects the position input signal and the position feedback signal, and performs amplification and filtering. The position feedback signal includes a sine position signal and a cosine position signal, which are respectively amplified and filtered to obtain a sine precision code signal and a cosine precision code signal.

[0012] A coarse code conversion circuit converts the sine fine code signal and the cosine fine code signal into a sine coarse code digital signal and a cosine coarse code digital signal;

[0013] The analog-to-digital conversion circuit converts the amplified and filtered position input signal, the sine precision code signal, and the cosine precision code signal into a digital signal;

[0014] The position feedback digital signal collected by FPGA includes coarse sine and cosine digital signals and fine sine and cosine digital signals.

[0015] Furthermore, the data communication method between ARM and FPGA is: FPGA is used as the external SRAM of ARM, and the address space of FPGA is mapped to the address space of ARM through the FSMC interface of ARM.

[0016] Furthermore, the FPGA controls the acquisition of two data channels, the position input digital signal and the position feedback digital signal. After the acquisition is completed, the two sets of data and a pre-set set of flag data are stored in three different addresses mapped by the ARM external interface; the ARM continuously queries whether the data in the address where the flag data is stored is the set value. If so, the two sets of data are read, otherwise, they are not read.

[0017] Furthermore, the PID control parameters of the speed loop and position loop at different temperatures are pre-calibrated in the temperature chamber and fitted into linear equations related to temperature. The ARM collects the temperature data output by the internal temperature sensor of the controlled galvanometer motor in real time, and uses the corresponding control parameters at the current temperature to calculate and realize automatic compensation of the control parameters.

[0018] Furthermore, the zero point drift at different temperatures is pre-calibrated in the temperature chamber and fitted into a temperature function. The ARM collects the temperature data output by the internal temperature sensor of the controlled galvanometer motor in real time, and uses the corresponding control parameters at the current temperature to calculate and realize automatic zero point compensation.

[0019] Furthermore, the control operation circuit is implemented using FPGA minimum system and ARM minimum system.

[0020] Furthermore, the driving execution circuit includes:

[0021] Current negative feedback circuit, real-time acquisition of motor current signal, forming a current loop negative feedback;

[0022] The power amplifier circuit amplifies the drive control signal output by the ARM and converts it into a drive power signal to drive the controlled motor to achieve forward or reverse rotation of the motor.

[0023] Furthermore, it also includes a power conversion circuit. The power conversion circuit uses an integrated DC / DC converter with isolation function to divide the internal power supply of the controller into two parts: digital power supply and power power supply. The two are isolated from each other to prevent the driving execution circuit from interfering with and damaging other circuits.

[0024] The present invention also provides a galvanometer motor control system, including the analog-to-digital hybrid galvanometer motor controller and galvanometer motor based on the grating encoder as described above. The controller receives an external position input signal, collects the signal output by the grating encoder of the galvanometer motor, drives the galvanometer motor, and causes the swing mirror of the galvanometer motor to scan according to the position input signal.

[0025] The advantages of the present invention compared with the prior art are:

[0026] (1) The present invention adopts a hybrid design of analog circuits and digital circuits, which not only uses advanced control algorithms to achieve high-precision control of the galvanometer motor, but also takes advantage of the rapidity of analog circuit signal processing to improve the response speed of the galvanometer motor.

[0027] (2) The present invention fully utilizes the advantages of FPGA logic control and ARM data processing through the architecture of FPGA+ARM dual processor collaborative processing. Compared with the existing galvanometer motor controller, it significantly improves the response speed and scanning accuracy of the galvanometer motor control system.

[0028] (3) The present invention adopts a high-speed analog / digital conversion chip with a parallel communication interface in hardware and a parallel communication algorithm in software, which solves the problems of slow control speed and long data transmission time in the serial communication of the existing digital controller and significantly improves the control speed.

[0029] (4) The present invention has the function of automatic compensation of control parameters and zero point, has strong environmental adaptability, and can maintain high control accuracy under extreme ambient temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The analog-digital hybrid galvanometer motor controller according to an embodiment of the present invention;

[0031] Figure 2 Schematic diagram of a galvanometer motor control system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to better understand the technical solution of the present invention, the specific implementation methods of the present invention are described below.

[0033] Figure 1 The figure shows the composition diagram of the analog-to-digital hybrid mirror motor controller, which mainly includes a position decoding circuit, a control operation circuit, and a drive execution circuit. Preferably, the power conversion circuit can also be designed inside the controller.

[0034] The position decoding circuit collects the position input signal, amplifies and filters it, and converts it into a position input digital signal, which is then sent to the control operation circuit. It processes the output of the grating encoder in the controlled galvanometer motor to obtain a position feedback digital signal proportional to the actual angle of the motor.

[0035] The control operation circuit is implemented using the FPGA minimum system and the ARM minimum system. The FPGA minimum system uses a parallel bus interface to send the position input digital signal and the position feedback digital signal to the ARM minimum system. The ARM minimum system uses a speed loop and a position loop PID controller with feedforward control to calculate the drive control signal and send it to the drive execution circuit.

[0036] The drive execution circuit samples the current flowing through the motor winding to obtain the motor current signal, forming a current loop negative feedback, and amplifies the drive control signal output by the ARM, converting it into a drive power signal to drive the motor to achieve forward or reverse rotation of the motor.

[0037] The power conversion circuit converts the external power input into various DC power supplies required by the grating encoder inside the digital controller and the controlled galvanometer motor.

[0038] The control operation circuit realizes high-speed servo control of the galvanometer motor and is the core of the controller. The specific design is as follows:

[0039] The controller adopts three-loop PID control, in which the operation circuit adopts position loop + speed loop dual closed-loop control, and the drive execution circuit collects the motor current to form a current loop.

[0040] The minimum FPGA system includes the FPGA, clock management, power management, reset circuit, JTAG debugging circuit, and configuration storage circuit. The power management includes the HWD70302 power supply chip and its peripheral circuits. Its two outputs, 2.5V first and 3.3V second, ensure the FPGA's core is powered on first, followed by its I / O. After the system power is turned on, the power supply chip maintains an RC delay of 0.1 seconds, then switches to a low-level enable through an inverter, ensuring startup reliability and stability. The minimum ARM system includes the ARM, clock management, power management, reset circuit, and SWD debugging circuit.

[0041] The high-speed data communication solution between ARM and FPGA is to use FPGA as the external SRAM of ARM, map the address space of FPGA to the address space of ARM through the FSMC interface of ARM to realize data communication.

[0042] Specifically, the FPGA controls the acquisition of two data channels: the position input digital signal and the position feedback digital signal. After acquisition, the two sets of data, along with a pre-set flag data, are stored at three different addresses mapped to the ARM external interface. The ARM continuously checks whether the data stored at the flag data storage address matches the set value. If so, the two sets of data are read; otherwise, they are not read.

[0043] ARM and FPGA use different external clock sources. The two sets of data collected by FPGA are stored for two beats and then read by ARM to solve the cross-clock domain metastable problem.

[0044] The controller has a temperature compensation function. The speed loop and position loop PID control parameters at different temperatures are pre-calibrated in the temperature chamber and fitted into linear equations related to temperature. The ARM collects the temperature data output by the motor's internal temperature sensor in real time and uses the corresponding control parameters at the current temperature for calculation.

[0045] The controller has an automatic zero-point compensation function. The zero-point drift at different temperatures is pre-calibrated in the temperature chamber and fitted into a temperature function. The ARM collects the temperature data output by the motor's internal temperature sensor in real time and uses the corresponding control parameters at the current temperature for calculation.

[0046] Preferably, the position decoding circuit includes an operational amplifier circuit, a coarse code conversion circuit, and an analog-to-digital conversion circuit, and is specifically designed as follows:

[0047] Operational amplifier circuit, collects position input signal and position feedback signal, amplifies and filters them;

[0048] A coarse code conversion circuit converts the amplified and filtered position feedback signal into a coarse code signal;

[0049] The analog-to-digital conversion circuit converts the amplified and filtered position input signal and position feedback signal into digital signals.

[0050] In a specific embodiment of the present invention:

[0051] The operational amplifier circuit includes at least two operational amplifiers and their peripheral circuits, and is used to collect the position feedback signal (including the sine position signal and the cosine position signal) output by the grating encoder, and obtain the sine precision code signal and the cosine precision code signal after amplification and filtering respectively;

[0052] A coarse code conversion circuit converts the sine fine code signal and the cosine fine code signal into a square wave sine coarse code signal and a cosine coarse code signal, i.e., a sine coarse code digital signal and a cosine coarse code digital signal; preferably, an LM119W and its peripheral circuits are used;

[0053] The analog-to-digital conversion circuit converts the amplified and filtered position input signal, sine precision code signal, and cosine precision code signal into digital signals, namely, the position input digital signal, sine precision code signal, and cosine precision code signal. A high-speed 16-bit analog-to-digital conversion chip AD7606 and its peripheral circuits are preferably used. The AD7606 has a sampling frequency of 200kHz and a high-speed parallel data communication interface. The two analog voltage signals, position input and position feedback signal, processed by the operational amplifier circuit, are converted into 16-bit digital signals.

[0054] The position feedback digital signal collected by FPGA includes coarse sine and cosine digital signals and fine sine and cosine digital signals.

[0055] Preferably, the driving execution circuit includes a current negative feedback circuit and a power amplifier circuit, and is specifically designed as follows:

[0056] Current negative feedback circuit, real-time acquisition of motor current, and forming a current loop negative feedback;

[0057] The power amplifier circuit amplifies the drive control signal output by the ARM and converts it into a drive power signal for driving the motor to achieve forward or reverse rotation of the motor.

[0058] In a specific embodiment of the present invention, the power amplifier circuit adopts a high-performance audio power amplifier chip LM3886 with a mute function and its peripheral circuits. The chip has a MUTE (mute) terminal that can control whether the chip is working or not. Based on this feature, a protection amplifier circuit is designed at the MUTE terminal to control the operation of the chip.

[0059] In a specific embodiment of the present invention, the power conversion circuit uses an integrated DC / DC converter with isolation function to achieve isolated conversion of the external power supply input +28V into three outputs of +5V, +12V, and -12V to power the position decoding circuit and the control operation circuit; a common-mode inductor is placed at the input end of the DC / DC converter to suppress external electromagnetic interference; the internal power supply of the controller is divided into two parts, digital power supply and power power supply, which are isolated from each other, avoiding noise interference of the drive execution circuit on other circuits inside the controller, and at the same time avoiding large current damage to the internal chip of the controller when the drive execution circuit operates abnormally, thereby improving the reliability of the control system.

[0060] Figure 2The figure shows an analog-to-digital hybrid galvanometer motor controller based on a grating encoder provided by the present invention. The working process is that the controller receives an external position input signal, collects the grating encoder signal in the controlled galvanometer motor, executes the control algorithm and drives the galvanometer motor, so that the oscillating mirror scans according to the position input signal.

[0061] In one specific embodiment of the present invention, the motor body is an integrated moving-iron motor, characterized by low inertia, high electromagnetic torque, and a high torque-to-inertia ratio. A oscillating mirror is pinned to the front shaft of the motor rotor and located at the motor head. The grating encoder is an absolute photoelectric encoder that stores angle values as codes on a code disk. The processed output angular position code is a single-valued function of the rotation angle, has a fixed zero point, and exhibits strong anti-interference capabilities. It can be reactivated after a power outage without requiring recalibration.

[0062] The present invention provides a high-speed galvanometer motor control system based on FPGA+ARM, which gives full play to the advantages of FPGA logic control and ARM data processing. Compared with the existing digital control system, it significantly improves the response speed and scanning accuracy of the galvanometer motor control system.

[0063] It will be understood that the present invention is described by way of example, and it will be appreciated by those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and any embodiment that falls within the scope of the claims of this application is intended to be within the scope of protection of the present invention.

[0064] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. An analog-digital hybrid galvanometer motor controller based on a grating encoder, characterized in that: include: Position decoding circuit, collecting position input signals and converting them into position input digital signals; Processing the position feedback signal output by the grating encoder of the controlled galvanometer motor to obtain a position feedback digital signal proportional to the actual angle of the galvanometer motor; The control operation circuit adopts FPGA+ARM collaborative processing architecture. FPGA uses a parallel bus interface to collect position input digital signals and position feedback digital signals and transmits them to ARM. ARM adopts position loop + speed loop dual closed-loop PID control to calculate the drive control signal and send it to the drive execution circuit. The driving execution circuit samples the winding current of the controlled galvanometer motor to obtain the motor current signal and form a current loop negative feedback; The drive control signal output by ARM is converted into a drive power signal to drive the controlled motor.

2. The analog-to-digital hybrid galvanometer motor controller based on a grating encoder according to claim 1, characterized in that: The position decoding circuit comprises: The operational amplifier circuit collects the position input signal and the position feedback signal, and performs amplification and filtering. The position feedback signal includes a sine position signal and a cosine position signal, which are respectively amplified and filtered to obtain a sine precision code signal and a cosine precision code signal. A coarse code conversion circuit converts the sine fine code signal and the cosine fine code signal into a sine coarse code digital signal and a cosine coarse code digital signal; The analog-to-digital conversion circuit converts the amplified and filtered position input signal, the sine precision code signal, and the cosine precision code signal into a digital signal; The position feedback digital signal collected by FPGA includes coarse sine and cosine digital signals and fine sine and cosine digital signals.

3. The analog-digital hybrid galvanometer motor controller based on a grating encoder according to claim 1, characterized in that: The data communication method between ARM and FPGA is: FPGA is used as the external SRAM of ARM, and the address space of FPGA is mapped to the address space of ARM through the FSMC interface of ARM.

4. The analog-digital hybrid galvanometer motor controller based on a grating encoder according to claim 3, characterized in that: FPGA controls the acquisition of two data channels: position input digital signal and position feedback digital signal. After the acquisition is completed, the two sets of data and a pre-set set of flag data are stored in three different addresses mapped by the ARM external interface. The ARM continuously checks whether the data in the address where the flag data is stored is the set value. If so, the two sets of data are read; otherwise, they are not read.

5. The analog-to-digital hybrid galvanometer motor controller based on a grating encoder according to claim 1, characterized in that: The speed loop and position loop PID control parameters at different temperatures are pre-calibrated in the temperature chamber and fitted into linear equations related to temperature. The ARM collects the temperature data output by the internal temperature sensor of the controlled galvanometer motor in real time, and uses the corresponding control parameters at the current temperature to calculate and realize automatic compensation of the control parameters.

6. The analog-digital hybrid galvanometer motor controller based on a grating encoder according to claim 1, characterized in that: The zero point drift at different temperatures is pre-calibrated in the temperature chamber and fitted into a temperature function. The ARM collects the temperature data output by the internal temperature sensor of the controlled galvanometer motor in real time, and uses the corresponding control parameters at the current temperature to calculate and realize automatic zero point compensation.

7. The analog-digital hybrid galvanometer motor controller based on a grating encoder according to claim 1, characterized in that: The control operation circuit is implemented by using FPGA minimum system and ARM minimum system.

8. The analog-digital hybrid galvanometer motor controller based on a grating encoder according to claim 1, characterized in that: The driving execution circuit includes: Current negative feedback circuit, real-time acquisition of motor current signal, forming a current loop negative feedback; The power amplifier circuit amplifies the drive control signal output by the ARM and converts it into a drive power signal to drive the controlled motor to achieve forward or reverse rotation of the motor.

9. The analog-digital hybrid galvanometer motor controller based on a grating encoder according to claim 1, characterized in that: It also includes a power conversion circuit. The power conversion circuit uses an integrated DC / DC converter with isolation function to divide the internal power supply of the controller into two parts: digital power supply and power power supply. The two are isolated from each other to prevent the driving execution circuit from interfering with and damaging other circuits.

10. A galvanometer motor control system, characterized in that: It includes an analog-to-digital hybrid galvanometer motor controller and a galvanometer motor based on a grating encoder as described in any one of claims 1 to 9, the controller receives an external position input signal, collects the signal output by the grating encoder of the galvanometer motor, drives the galvanometer motor, and causes the swing mirror of the galvanometer motor to scan according to the position input signal.

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