CN100392268C - An integrated magnetic levitation flywheel magnetic bearing digital control device - Google Patents

Abstract

An integrated magnetic levitation flywheel magnetic bearing digital control device is used to actively control the magnetic levitation flywheel magnetic bearing system, and mainly includes an interface circuit, an analog-to-digital conversion chip, and an FPGA module. The device obtains the magnetic bearing rotor displacement signal, coil current, and speed signal data through the interface circuit and the analog-to-digital conversion chip. The FPGA module generates the control amount according to the control algorithm based on hardware programming in the FPGA chip. The signal is PWM modulated and then output to the power amplifier link to generate the control current required by the magnetic bearing coil, thereby realizing the active control of the magnetic bearing system of the magnetic levitation flywheel.

Description

An integrated magnetic levitation flywheel magnetic bearing digital control device

technical field

The invention relates to an integrated magnetic bearing digital control device for a magnetic levitation flywheel, which is used for controlling magnetic bearing systems such as a magnetic levitation flywheel, and is suitable for applications such as high reliability, high integration, and low power consumption, and is especially suitable for aerospace and space applications .

Background technique

The flywheel is the basic attitude control actuator on small and medium-sized satellites. Compared with the traditional mechanical bearing flywheel, the magnetic levitation flywheel has the advantages of no contact, no friction, no lubrication, high precision, long life, etc., so it has broad application prospects in satellites.

The existing maglev flywheel controllers are divided into two categories: analog controllers and digital controllers. The analog controller has the disadvantages of large power consumption, poor anti-interference ability, difficult modification of control parameters, complicated debugging process, and difficulty in implementing more complex control algorithms. The advantages of the digital controller are: easy parameter modification, suitable for integration, and significantly reduced power consumption, which is very attractive for aerospace applications.

There are two types of existing digital controllers. At present, the magnetic bearing controller with Ti's C2000 series DSP as the core is relatively common. It has the advantages of convenient parameter debugging, high integration, and low power consumption. , temperature and other special conditions often have the problem of poor reliability, so they cannot be applied in aerospace and space environments. Another type of digital controller uses Ti's C3000 floating-point DSP as the control algorithm, uses an FPGA chip to control peripheral devices, and communicates with the DSP at the same time. This type of controller has the advantages of high performance, but because the control signals required by the control algorithm, such as the displacement of the magnetic bearing rotor and the current of the magnetic bearing coil, are obtained by the FPGA, and the control algorithm must be implemented by software inside the DSP, and the control algorithm is generated The control amount must be sent back to the FPGA for PWM modulation, so there must be frequent data communication between the DSP module and the FPGA module, which also has poor reliability for aerospace and space applications, and because the DSP chip and the FPGA chip are used at the same time , Compared with other digital controllers, its integration is poor and power consumption is high.

Contents of the invention

The technical problem of the present invention is to overcome the problems of poor reliability, poor integration, and high power consumption of the existing two types of digital controllers for aerospace and space applications, and provide a highly reliable, integrated, and low-power magnetic levitation flywheel Digital controls.

Technical solution of the present invention: an integrated magnetic levitation flywheel magnetic bearing digital control device, characterized in that it includes:

Interface circuit: connected with the current signal analog-to-digital conversion chip and the displacement signal analog-to-digital conversion chip, including the current sensor interface circuit and the displacement sensor interface circuit, which converts the current signal input by the current sensor and the displacement signal input by the displacement sensor into 0~5V The analog voltage signal;

Current signal analog-to-digital conversion chip and displacement signal analog-to-digital conversion chip: convert the 0-5V analog voltage signal output by the interface circuit into a 0-5V digital current signal and displacement signal and output it to the level conversion chip;

Level conversion chip: connected with current signal analog-to-digital conversion chip, displacement signal analog-to-digital conversion chip, Hall sensor and FPGA module, digital current signal and displacement signal of 0-5V and 0-5V outputted by Hall sensor The flywheel speed signal is converted to 0~3.3V and sent to the FPGA module;

FPGA module: control the current signal conversion module and the displacement signal conversion module to sample the current signal input by the current sensor and the displacement signal input by the displacement sensor; according to the speed measurement logic, the 0~3.3V flywheel speed signal converted by the level conversion chip Carry out calculation of rotational speed; carry out arithmetic processing on the digitized displacement signal and rotational speed signal after level conversion, and obtain the control amount required by the power amplifier.

The FPGA module includes a hardware circuit part and a control algorithm part realized based on hardware programming in the FPGA chip. The hardware circuit part includes a configuration chip and an FPGA chip. The FPGA chip uses a XinlinxXC3S×× chip; the control algorithm part is realized based on hardware programming, including analog-to-digital conversion control algorithm, speed calculation algorithm, decentralized PID+cross feedback control algorithm and PWM modulation algorithm. The FPGA chip controls the current signal analog-to-digital conversion chip and the displacement signal analog-to-digital conversion chip through the analog-to-digital conversion control algorithm to perform analog-to-digital conversion on the current signal and the displacement signal; Calculation; the distributed PID+cross feedback control algorithm calculates the displacement signal and the speed signal to obtain the control quantity required by the PWM modulation algorithm; the control quantity generated by the decentralized PID+cross feedback control algorithm and the analog-to-digital conversion control algorithm are obtained by the PWM modulation algorithm The current signal is PWM modulated, and the modulated result is output to the power amplifier to complete the control of the five degrees of freedom of the maglev flywheel rotor.

Principle of the present invention: the FPGA chip adopts the analog-to-digital conversion control algorithm realized based on hardware programming to control the current signal analog-to-digital conversion chip and the displacement signal analog-to-digital conversion chip, to sample the current signal and the displacement signal, and read the conversion result into the FPGA chip. in RAM. When there is a speed signal, the speed calculation algorithm designed on the FPGA chip will calculate the speed to obtain the speed value, and the hardware-based decentralized PID+cross feedback control algorithm implemented on the FPGA chip will execute the control algorithm to obtain the control amount according to the displacement and speed value. The PWM modulation algorithm designed by the FPGA chip is based on the control amount obtained by the control algorithm, combined with the current signal sampling value for modulation, and the PWM modulation is output to the power amplifier link, so as to obtain the required control current in the magnetic bearing coil and realize the magnetic levitation flywheel magnetic bearing system active control.

Compared with the analog controller and two types of digital controllers commonly used in the existing maglev flywheel magnetic bearings, it has the following characteristics: the present invention uses a high-performance FPGA chip XC3S×× to construct the execution core of the maglev flywheel control algorithm, based on hardware programming The control algorithm is implemented, and the peripheral devices are controlled at the same time to obtain the magnetic bearing rotor displacement signal and the magnetic bearing coil current signal required by the control algorithm, and modulate the PWM signal required by the power module according to the control amount obtained by the control algorithm. Because the present invention realizes the control algorithm by hardware, and the acquisition of the sensor signal, the calculation of the control amount and the modulation of the PWM signal are carried out in the same chip, which reduces the link of intermediate software and hardware communication, so it has high reliability, integration, low power advantage of consumption. The advantage of the present invention compared with prior art is:

(1) Compared with the traditional analog controller with an operational amplifier as the core, the present invention has the advantages of a digital controller: flexible debugging, convenience, small size, light weight, and easy implementation of more complex control algorithms. Compared with the existing digital controller with fixed-point DSP as the core and the digital controller with floating-point DSP combined with FPGA, the control algorithm adopted in the present invention is implemented by FPGA chip based on hardware programming, and the acquisition of sensor signals and the calculation of control amount Both modulation and PWM signal modulation are carried out in the same chip, which reduces the link of intermediate software and hardware communication, so its reliability is significantly improved, and it can meet the reliability requirements in aerospace and space applications.

(2) The invention realizes the digitalization and integration of the system, reduces the power consumption of the controller, and improves the reliability of the control system, and is especially suitable for aerospace and other fields that have strict requirements on power consumption and reliability.

Description of drawings

Fig. 1 is a structural block diagram of the present invention;

Fig. 2 is a control principle block diagram of the present invention;

Fig. 3 is the control algorithm block diagram based on hardware realization in the FPGA chip of the present invention;

Fig. 4 is the circuit schematic diagram of the displacement sensor interface circuit of the present invention;

Fig. 5 is the circuit schematic diagram of the current sensor interface circuit of the present invention;

Fig. 6 is the circuit of displacement signal analog-to-digital conversion chip and current signal analog-to-digital conversion chip of the present invention;

Fig. 7 is the circuit diagram that FPGA chip of the present invention is connected with other device signals;

Fig. 8 is the flow chart of the analog-to-digital conversion control algorithm adopted by the present invention;

Fig. 9 is a block diagram of the principle of decentralized PID+cross feedback control adopted by the present invention;

Fig. 10 is the flow chart of the rotational speed calculation algorithm that the present invention adopts;

Fig. 11 is a functional block diagram of the PWM modulation algorithm adopted in the present invention.

Detailed ways

As shown in Figure 1, the magnetic levitation flywheel magnetic bearing digital control device of the present invention is mainly made up of interface circuit 8, displacement signal analog-to-digital conversion chip 6, current signal analog-to-digital conversion chip 13, level conversion chip 14 and FPGA module 3, wherein The interface circuit 8 includes a displacement sensor interface circuit 7 and a current sensor interface circuit 12 , and the FPGA module 3 includes a configuration chip 1 and an FPGA chip 2 . The displacement sensor interface circuit 7 converts the magnetic bearing rotor displacement signal detected by the displacement sensor 10 into a displacement signal in the range of 0V to 5V required by the analog-to-digital conversion chip 6, and the current sensor interface circuit 12 converts the magnetic bearing coil current detected by the current sensor 11 The signal is converted into the range of 0V to 5V required by the current signal analog-to-digital conversion chip 13, and the FPGA chip 2 controls the displacement signal analog-to-digital conversion chip 6 and the current signal analog-to-digital conversion chip 13 respectively performs the magnetic bearing rotor displacement signal and the magnetic bearing coil signal. Sampling, the sampling result is converted by the level conversion chip 14 into the range of 0V to 3.3V required by the FPGA chip 2, and the FPGA chip 2 implements a control algorithm based on hardware programming to perform calculations on the magnetic bearing rotor displacement signal and speed signal to generate a control value , and combined with the sampling value of the current signal for modulation, the PWM modulation is output to the power amplifier link, thereby generating the control current required by the magnetic bearing coil, and realizing the active control of the magnetic bearing system of the magnetic levitation flywheel.

As shown in Figure 2, the control principle of the present invention is provided, the FPGA module 3 controls the displacement signal analog-to-digital conversion chip 6 and the current signal analog-to-digital conversion chip 13 samples the magnetic bearing rotor displacement signal and the magnetic bearing coil current signal, and simultaneously The FPGA module 3 detects the flywheel speed signal. According to the measured magnetic bearing rotor displacement signal and speed signal, the control quantity is calculated and combined with the current signal for PWM modulation, and the power amplifier 4 converts the PWM signal output by the FPGA module 3 into a corresponding coil current to realize the active control of the magnetic levitation flywheel.

As shown in Figure 3, the hardware-based control algorithms in the FPGA chip include: analog-to-digital conversion control algorithm 18, speed calculation algorithm 17, decentralized PID+cross feedback control algorithm 16 and PWM modulation algorithm 19. Wherein the FPGA chip 2 controls the current signal analog-to-digital conversion chip 13 and the displacement signal analog-to-digital conversion chip 6 through the analog-to-digital conversion control algorithm 18 to perform analog-to-digital conversion on the current signal and the displacement signal; The speed signal is given to calculate the speed; the hardware-based decentralized PID+cross feedback control algorithm 16 in the FPGA chip 2 calculates the displacement signal and the speed signal, and obtains the control amount required by the PWM modulation algorithm 19; the PWM modulation algorithm 19 pairs The control quantity generated by the distributed PID+cross feedback control algorithm 16 and the current signal obtained by the analog-to-digital conversion control algorithm 18 are PWM modulated, and the modulation result is output to the power amplifier 4 to complete the control of the 5 degrees of freedom of the maglev flywheel rotor.

As shown in Figure 4, the magnetic bearing rotor displacement signal obtained by the displacement sensor 10 is transformed into the 0V-5V voltage signal required by the analog-to-digital conversion chip 6 for the displacement signal after being scaled, level shifted, and clipped, and then passed through the anti- The aliasing low-pass filter removes the high-frequency noise and then sends the displacement signal to the analog-to-digital conversion chip 6 .

As shown in Figure 5, the current signal of the magnetic bearing coil obtained by the current sensor 11 is changed into the 0V-5V voltage signal required by the current signal analog-to-digital conversion chip 13 after being scaled, level shifted, and clipped, and then passed through the anti- The aliasing low-pass filter removes the high-frequency noise and then sends the current signal to the analog-to-digital conversion chip 13 .

As shown in Fig. 6, what the analog-to-digital conversion chip that the present invention adopts adopts is the ADS7861 of BB Company, and this chip has 12-bit precision, 4 road differential inputs, 8 independent sample holders, two 500KHZ converters and serial Line interface, and its power consumption is only 25mW. The use of three chips (12 input channels in total) can meet the requirements of the number of current signals and displacement signals (10 channels in total, including 5 channels of current signals, including 4 channels of radial current signals, 1 channel of axial current signals; 5 channels of displacement signals road, including 4 roads of radial displacement signal and 1 road of axial displacement signal), the independent sample and hold device ensures the phase relationship of the signal, two 500KHz converters can fully meet the real-time requirements of the system, and the high-speed serial interface guarantees The high-speed output of the conversion result reduces the noise to the system, and the low power consumption of 25mW makes the chip very suitable for aerospace applications. The interface signals of these three chips are connected to the FPGA chip after being level converted by a level conversion chip (74LVC164245 is used in this embodiment).

As shown in Fig. 7, the FPGA chip that the present invention adopts is XC3S400 of Xilinx Company, and this chip adopts the crystal oscillator of 50M as the system clock, internally has 400,000 logic gate circuits, 288K on-chip RAM, and is integrated with 16 18× The 18-bit multiplier ensures the high-speed execution of the control algorithm and PWM modulation, and the 264 user-defined I/O resources make the interface with peripheral chips very convenient. The chip controls the sampling of the displacement signal and the current signal. When the rotational speed signal is input, the rotational speed signal is calculated, and the displacement signal and the rotational speed signal are calculated by the control algorithm to generate the control amount, and then the PWM modulation algorithm is combined with the current signal sampling according to the control amount. The value executes the control algorithm of the power module, and outputs it to the power amplifier after PWM modulation.

The flow chart of the analog-to-digital conversion control algorithm adopted by the FPGA chip 2 of the present invention is as shown in Figure 8: when the set timing time (such as 0.1ms) arrives, the analog-to-digital conversion chip (ADS7861) is triggered to perform modulus on the current and the displacement signal Conversion; when the delay time (such as 0.5ns) is up, read the serial output result of the analog-to-digital conversion; when the 12-bit data is read, end the analog-to-digital conversion and wait for the next timing to arrive .

The block diagram of the distributed PID+cross feedback control algorithm adopted by the present invention is shown in Figure 9: the displacement signals Xa, Xb at both ends of the radial direction X of the flywheel and Ya, Yb of the displacement signals at both ends of the radial direction Y are detected by the displacement sensor, and one of them is sent to the Four decentralized PID control modules are used to realize the static suspension of the flywheel and the stable control at low speed; the other way, Xa and Xb are sent to the input terminal of the X-direction cross feedback control module, and Ya and Yb are sent to the Y-direction cross feedback control module The input terminal of the X-direction cross feedback control module is connected in parallel with the outputs of the two decentralized PID control modules at both ends of the Y direction with opposite polarities, and the outputs are OUTYa and OUTYb, which are used for the input of the PWM modulation algorithm. The output of the cross feedback control module is connected in parallel with the outputs of the two decentralized PID control modules at both ends of the X direction with opposite polarities, and the outputs are OUTXa and OUTYb, which are used for the input of the PWM modulation algorithm; at the same time, the speed calculation algorithm uses Hall The Hall signal given by the sensor is calculated to obtain the flywheel speed signal, which is sent to the X-direction and Y-direction cross feedback control module, which is used for the cross feedback control module to track the speed of the flywheel rotor, so that its phase lead and crossover can be adjusted at any time. amount of feedback.

The flow chart of the rotational speed calculation algorithm adopted by the FPGA chip 2 of the present invention is shown in FIG. 10 : in this embodiment, any two of the three Halls of the flywheel motor are used to calculate the rotational speed. When the first Hall signal arrives, the timer is started to count; when the next Hall signal arrives, the count value is latched and the speed is calculated. The speed calculation formula is:

The principle block diagram of the PWM modulation algorithm adopted by the FPGA chip 2 of the present invention is as shown in Figure 11: the control quantity produced by the current signal and the decentralized PID+cross feedback control is obtained by weighted summation to obtain the modulation quantity to be PWM modulated; the modulation quantity and The current value of the carrier signal counter is compared by a comparator, and the output of the comparator is the modulated PWM signal.

Although the present invention is a control device for a magnetic suspension flywheel magnetic bearing system, it can also be used as a general-purpose magnetic bearing control platform as a controller for other magnetic bearing systems. The user can modify the FPGA design according to its special application field to be flexible and convenient. realize its function.

Claims (2)

1. An integrated magnetic levitation flywheel magnetic bearing digital control device, characterized in that: comprising: Interface circuit (8): connected with the current signal analog-to-digital conversion chip (13) and the displacement signal analog-to-digital conversion chip (6), including the current sensor interface circuit (12) and the displacement sensor interface circuit (7), which will be controlled by the current sensor ( 11) The input current signal and the displacement signal input by the displacement sensor (10) are converted into an analog voltage signal of 0-5V; Current signal analog-to-digital conversion chip (13) and displacement signal analog-to-digital conversion chip (6): convert the 0-5V analog voltage signal output by the interface circuit (8) into a 0-5V digital current signal and output the displacement signal to the electric circuit Flat conversion chip (14); Level conversion chip (14): connected with current signal analog-to-digital conversion chip (13), displacement signal analog-to-digital conversion chip (6), Hall sensor (9) and FPGA module (3), digitizes 0-5V The current signal, the displacement signal and the 0-5V flywheel speed signal output by the Hall sensor (9) are converted into 0-3.3V and sent to the FPGA module (3); FPGA module (3): control the current signal conversion module (13) and the displacement signal conversion module (6) to sample the current signal input by the current sensor (11) and the displacement signal input by the displacement sensor (10); The 0-3.3V flywheel speed signal converted by the level conversion chip (14) is used for calculation of the speed; the digital displacement signal and the speed signal after the level conversion are processed to obtain the control amount required by the power amplifier (4). 2. integrated maglev flywheel magnetic bearing digital control device according to claim 1, is characterized in that: described FPGA module (3) comprises hardware circuit part and the control algorithm part realized based on hardware programming in FPGA chip; The circuit part includes a configuration chip (1) and an FPGA chip (2), wherein the FPGA chip (2) adopts a Xinlinx XC3S×× chip; the control algorithm part is realized based on hardware programming, including an analog-to-digital conversion control algorithm (18), and a speed calculation algorithm (17), decentralized PID+cross feedback control algorithm (16) and PWM modulation algorithm (19), the FPGA chip (2) controls the current signal analog-to-digital conversion chip (13) and the displacement signal modulus through the analog-to-digital conversion control algorithm (18) The conversion chip (6) performs analog-to-digital conversion on the current signal and the displacement signal; at the same time, the speed calculation algorithm (17) is used to calculate the speed of the speed signal given by the Hall sensor (9); the decentralized PID+cross feedback control algorithm (16) Calculate the displacement signal and the rotational speed signal to obtain the control quantity required by the PWM modulation algorithm (19); the control quantity generated by the decentralized PID+cross feedback control algorithm (16) and the analog-to-digital conversion control algorithm ( 18) PWM modulation is performed on the obtained current signal, and the modulation result is output to the power amplifier (4), so as to complete the control of the 5 degrees of freedom of the rotor of the magnetic levitation flywheel.

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