CN102114917B - Processing method for enhancing control precision of magnetic torquer - Google Patents

Abstract

The present invention provides a kind of processing method that improves the control precision of magnetic torque device, adopts the mode of pulse width modulation to carry out magnetic control when its satellite is in orbit normal operation; Concrete steps are: (a) calculate and obtain magnetic torque device output magnetic moment M _i (i=x, y, z); (b) Then calculate the working pulse width W _mi of the magnetic torque device (i=x, y, z); (c) calculate and obtain the compensation and install them on the three axes of the satellite respectively The working pulse width of the magnetic torque device W _mi ′, i=x, y, z. The invention compensates the output of the magnetic torque device, can improve the actual output efficiency of the magnetic torque device, thereby improving the control precision of the system.

Description

A Processing Method for Improving the Control Accuracy of Magnetic Torque Device

technical field

The invention relates to aerospace automatic control technology, in particular to a processing method for improving the control precision of a magnetic torque device.

Background technique

The satellite's attitude and orbit control subsystem generally consists of sensors, actuators and controllers. The controller calculates the control amount through the space environment information collected by the sensor, and sends the control signal to the actuator to complete the closed-loop control of the satellite attitude and orbit.

The magnetic torque device is one of the main actuators of the satellite, which is composed of a magnetic bar wound with a coil and its drive circuit, as shown in Figure 1. The controller gives the control voltage, and the magnetic torque device circuit is converted into the coil current Im, and the direction of the current is different, and the magnetic moments in different directions are generated. The interaction between the magnetic moment and the geomagnetic field produces a moment, which unloads the momentum wheel and performs attitude control, that is,

$\stackrel{\&Right\; Arrow;}{T}=\stackrel{\&Right\; Arrow;}{m}\×\stackrel{\&Right\; Arrow;}{B}=\left[\begin{array}{ccc}0& -m_z& m_{\mathrm{the\; y}}\\ m_z& 0& -m_x\\ -m_{\mathrm{the\; y}}& m_x& 0\end{array}\right]\·\left[\begin{array}{c}{B}_x\\ B_{\mathrm{the\; y}}\\ B_z\end{array}\right]=\left[\begin{array}{c}-m_z{B}_{\mathrm{the\; y}}+m_{\mathrm{the\; y}}{B}_z\\ m_z{B}_x-m_x{B}_z\\ -m_{\mathrm{the\; y}}{B}_x+m_x{B}_{\mathrm{the\; y}}\end{array}\right]$ Formula 1)

In the above formula:

为力矩，单位为“牛顿·米·秒”，即Nms；

is the torque, and the unit is "Newton meter second", that is, Nms;

为磁力矩器产生的磁矩，单位为“安培·米²”，即A·m²；

is the magnetic moment generated by the magnetic torque device, and the unit is "ampere ^m2 ", that is, A ^m2 ;

为地磁场，单位为“特斯拉”，即T；

is the geomagnetic field, and the unit is "Tesla", that is, T;

B _i (i=x, y, z) is the component of the geomagnetic field on the satellite body coordinate system (x _b , y _b , z _b );

M _i (i=x, y, z) is the component of the output magnetic moment of the magnetic torque device in the coordinate system (x _b , y _b , z _b ) of the satellite body.

The control system generally uses three magnetic torque devices, and the installation method is shown in Figure 2. The directions of the positive magnetic moments generated by the magnetic torque devices are respectively parallel to the three inertial axes of the satellite.

When the satellite is in normal operation in orbit, it usually adopts pulse width modulation for magnetic control. The relationship between magnetic moment and working pulse width is shown in formula (2)

式(2)

Formula (2)

In the above formula:

M _max is the maximum magnetic moment that the magnetic torque device can output, unit A·m ² ;

Attitude control cycle: the discrete step length of the designed satellite for attitude calculation and control, unit: second;

W _mi , i=x, y, z: the working pulse width of the magnetic torquer installed on the three axes of the satellite, unit: second.

After the control system calculates the required control torque through the space environment information, it calculates the required pulse width of the magnetic torque device, and gives the control voltage of the corresponding width, and the magnetic torque device circuit gives the corresponding coil current according to this voltage. The relationship between the magnetic moment M output by an ideal magnetic torque device and the control voltage is shown in Figure 3. However, due to the existence of the coil inductance of the magnetic torque device, the actual output magnetic moment is shown in Figure 4. The actual working pulse width is narrowed due to the rising delay time and falling delay time, so that the torque generated by the interaction between the output magnetic moment and the earth's magnetic field has a large deviation from the torque required by the controller calculation, which affects the control efficiency of the satellite.

Contents of the invention

The purpose of the present invention is to provide a processing method for improving the control precision of the magnetic torque device, which compensates the output of the magnetic torque device, improves the actual output efficiency of the magnetic torque device, and thereby improves the system control precision.

The technical scheme that realizes the object of the present invention: a kind of processing method that improves the control precision of magnetic torque device, adopts the mode of pulse width modulation to carry out magnetic control when its satellite is in orbit normal operation; The method is carried out as follows:

(a) According to the formula (1), the output magnetic moment M _i (i=x, y, z) of the magnetic torque device is calculated

$\stackrel{\&Right\; Arrow;}{T}=\stackrel{\&Right\; Arrow;}{m}\×\stackrel{\&Right\; Arrow;}{B}=\left[\begin{array}{ccc}0& -m_z& m_{\mathrm{the\; y}}\\ m_z& 0& -m_x\\ -m_{\mathrm{the\; y}}& m_x& 0\end{array}\right]\·\left[\begin{array}{c}{B}_x\\ B_{\mathrm{the\; y}}\\ B_z\end{array}\right]=\left[\begin{array}{c}-m_z{B}_{\mathrm{the\; y}}+m_{\mathrm{the\; y}}{B}_z\\ m_z{B}_x-m_x{B}_z\\ -m_{\mathrm{the\; y}}{B}_x+m_x{B}_{\mathrm{the\; y}}\end{array}\right]$ Formula 1)

In the formula:

为力矩，单位为“牛顿·米·秒”，

通过敏感器采集数据及姿态动力学计算得出；

is the moment, and the unit is "Newton meter second",

It is obtained by collecting data from sensors and calculating attitude dynamics;

为磁力矩器产生的磁矩，单位为“安培·米²”；

is the magnetic moment generated by the magnetic torque device, and the unit is "ampere ^m2 ";

为地磁场，单位为“特斯拉”；

is the geomagnetic field, and the unit is "Tesla";

B _i (i=x, y, z) is the component of the geomagnetic field on the satellite body coordinate system (x _b , y _b , z _b );

B _i (i=x, y, z) is calculated from the satellite orbit;

M _i (i=x, y, z) is the component of the magnetic torque output magnetic moment in the satellite body coordinate system (x _b , y _b , z _b );

(b) Then calculate the working pulse width W _mi (i=x, y, z) of the magnetic torque device according to the formula (2)

式(2)

Formula (2)

In the formula:

M _max is the maximum magnetic moment that the magnetic torquer can output, and the unit is "ampere ^m2 ";

The attitude control period is the discrete step length of the designed satellite for attitude calculation and control, and the unit is "second";

W _mi , i=x, y, z is the working pulse width of the magnetic torque device installed on the three axes of the satellite respectively, and the unit is "second";

(c) Using formula (3) to calculate the working pulse width W _mi ′ of the magnetic torque device installed on the three axes of the satellite after compensation, i=x, y, z

$W_{\mathrm{mi}}^{\′}=W_{\mathrm{mi}}+\mathrm{sign}\left(W_{\mathrm{mi}}\right)\·[(1/\mathrm{\τ}-k/2)\&Center\; Dot;(1-e^{-\mathrm{\τ}\left|W_{\mathrm{mi}}\right|})],i=x,\mathrm{the\; y},z$ Formula (3)

In the formula:

τ: rising time constant, the unit is "second";

k: The maximum delay constant for falling, the unit is "second".

A processing method for improving the control accuracy of the magnetic torque device as described above, the constants τ and k are determined by the magnetic torque device coil and the characteristics of the drive line, and are obtained by fitting after actual measurement; that is, without the magnetic torque device compensation In the case of a given working pulse width, measure the rise time and fall maximum delay time with an oscilloscope.

The effect of the present invention is: a kind of processing method that improves the control precision of magnetic torque device described in the present invention, it obtains the working pulse width of magnetic torque device on the three axes of the satellite after compensation, and the magnetic torque device output is compensated, can Improve the actual output efficiency of the magnetic torque device, thereby improving the system control accuracy.

Description of drawings

Figure 1 is the composition and schematic diagram of the magnetic torque device;

Figure 2 is a diagram of the installation method of the magnetic torque device;

Fig. 3 is the output magnetic moment diagram of the magnetic torque device under the ideal state;

Figure 4 is the actual magnetic moment output diagram;

Fig. 5 is a diagram of the relationship between the pulse width of the magnetic torque device and the control voltage before adding compensation;

Fig. 6 is a graph showing the relationship between the output pulse width of the magnetic torque device and the compensation time.

Detailed ways

A kind of processing method of improving the control precision of magnetic torque device described in the present invention, its satellite adopts the mode of pulse width modulation to carry out magnetic control when it is in orbit normal operation; Specifically carry out according to the following steps:

(a) According to the formula (1), the output magnetic moment M _i (i=x, y, z) of the magnetic torque device is calculated

$\stackrel{\&Right\; Arrow;}{T}=\stackrel{\&Right\; Arrow;}{m}\×\stackrel{\&Right\; Arrow;}{B}=\left[\begin{array}{ccc}0& -m_z& m_{\mathrm{the\; y}}\\ m_z& 0& -m_x\\ -m_{\mathrm{the\; y}}& m_x& 0\end{array}\right]\&Center\; Dot;\left[\begin{array}{c}{B}_x\\ B_{\mathrm{the\; y}}\\ B_z\end{array}\right]=\left[\begin{array}{c}-m_z{B}_{\mathrm{the\; y}}+m_{\mathrm{the\; y}}{B}_z\\ m_z{B}_x-m_x{B}_z\\ -m_{\mathrm{the\; y}}{B}_x+m_x{B}_{\mathrm{the\; y}}\end{array}\right]$ Formula 1)

In the formula:

为力矩，单位为“牛顿·米·秒”，

通过敏感器采集数据及姿态动力学计算得出；

is the moment, and the unit is "Newton meter second",

It is obtained by collecting data from sensors and calculating attitude dynamics;

为磁力矩器产生的磁矩，单位为“安培·米²”；

is the magnetic moment generated by the magnetic torque device, and the unit is "ampere ^m2 ";

为地磁场，单位为“特斯拉”；

is the geomagnetic field, and the unit is "Tesla";

B _i (i=x, y, z) is the component of the geomagnetic field on the satellite body coordinate system (x _b , y _b , z _b );

B _i (i=x, y, z) is calculated from the satellite orbit;

M _i (i=x, y, z) is the component of the magnetic torque output magnetic moment in the satellite body coordinate system (x _b , y _b , z _b );

(b) According to the formula (2), the working pulse width W _mi of the magnetic torque device is calculated (i=x, y, z)

Formula (2)

In the formula:

M _max is the maximum magnetic moment that the magnetic torquer can output, and the unit is "ampere ^m2 ";

The attitude control period is the discrete step length of the designed satellite for attitude calculation and control, and the unit is "second";

W _mi , i=x, y, z is the working pulse width of the magnetic torque device installed on the three axes of the satellite respectively, and the unit is "second";

(c) Use the formula (3) to calculate the magnetic distance of the compensation part, and obtain the working pulse width W _mi ′ of the magnetic torque device installed on the three axes of the satellite after compensation, i=x, y, z

$W_{\mathrm{mi}}^{\′}=W_{\mathrm{mi}}+\mathrm{sign}\left(W_{\mathrm{mi}}\right)\·[(1/\mathrm{\τ}-k/2)\·(1-e^{-\mathrm{\τ}\left|W_{\mathrm{mi}}\right|})],i=x,\mathrm{the\; y},z$ Formula (3)

In the formula:

τ: rising time constant, the unit is "second";

k: The maximum delay constant for falling, the unit is "second";

The above constants τ and k are determined by the characteristics of the magnetic torque device coil and the drive line, and are obtained by fitting after actual measurement; that is, in the absence of magnetic torque device compensation, given a certain working pulse width, use an oscilloscope to measure the rise time and the maximum delay of the fall time.

A processing method for improving the control precision of the magnetic torque device according to the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. This example is carried out under the technical solution of the present invention, but the scope of the present invention is not limited to this example.

The attitude control period of a satellite is 1s, and a 50Am ² magnetic torquer is used (ie M _max = 50Am ² ). Before the magnetic torquer pulse width compensation, the relationship between the working pulse width and the control voltage calculated by the existing method is shown in the figure 5. The horizontal axis is the calculated working pulse width W _mi of the magnetic torque device, and the vertical axis is the control voltage V. It can be seen from Figure 5 that the rise time is about 0.35 seconds when the pulse width is 0.4 seconds. From the formula (2), it can be seen that the magnetic moment required for control is calculated according to the required control torque:

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 50</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; 0.4</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 20</span>}\mathrm{<span\; class="notranslate">\; A</span>}{\mathrm{<span\; class="notranslate">\; m</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}$

In fact, the magnetic moment output does not output all the maximum magnetic moment within 0.4 seconds, and the actual output magnetic moment is only 76% of the required magnetic moment through fitting calculation.

When τ=10.25ms, k=40ms, the obtained pulse width before and after compensation is shown in Figure 6. The horizontal axis is the pulse width before compensation calculated by the existing method, and the vertical axis is the pulse width after compensation calculated by the formula (3). It can be seen from the figure that the pulse width of 0.4 seconds before compensation is about 0.477 seconds after compensation.

After the pulse width compensation of the magnetic torque device is carried out according to the above method, the actual output magnetic moment is equivalent to the magnetic moment required by the theoretical calculation.

Claims (1)

1. processing method that improves the magnetic torquer control accuracy, its satellite adopts the mode of pulse duration modulation to carry out magnetic control when rail normally moves; This method is carried out as follows:

(a) calculate magnetic torquer output magnetic moment M according to formula (1) _i(i=x, y, z)

$\stackrel{\&RightArrow;}{T}=\stackrel{\&RightArrow;}{M}\&times;\stackrel{\&RightArrow;}{B}=\left[\begin{array}{ccc}0& -M_z& M_y\\ M_z& 0& -M_x\\ -M_y& M_x& 0\end{array}\right]\&CenterDot;\left[\begin{array}{c}{B}_x\\ B_y\\ B_z\end{array}\right]=\left[\begin{array}{c}-M_z{B}_y+M_y{B}_z\\ M_z{B}_x-M_x{B}_z\\ -M_y{B}_x+M_x{B}_y\end{array}\right]$ Formula (1)

In the formula:

is moment; Unit is " newton meter second ", and calculates through sensor image data and attitude dynamics;

Be the magnetic moment that magnetic torquer produces, unit is " an ampere per meter ²";

is the geomagnetic field, and unit is " tesal ";

B _i(i=x, y are that the geomagnetic field is at (the x of satellite body coordinates system z) _b, y _b, z _b) on component; B _i(i=x, y z) are calculated by satellite orbit;

M _i(i=x, y are (x for magnetic torquer output magnetic moment in the satellite body coordinates z) _b, y _b, z _b) component;

(b) calculate magnetic torquer work pulsewidth W according to formula (2) then _Mi(i=x, y, z)

formula (2)

In the formula:

M _MaxBe the maximum magnetic moment that magnetic torquer can be exported, unit is " an ampere per meter ²";

The discrete steps that the attitude control cycle carries out Attitude Calculation and control for the design-calculated satellite, unit is " second ";

W _Mi, i=x, y, z is for being installed on the magnetic torquer work pulsewidth on three axles of satellite respectively, and unit is " second ";

It is characterized in that: adopt formula (3) to calculate to obtain to be installed on the magnetic torquer work pulsewidth W on three axles of satellite respectively after the compensation _Mi', i=x, y, z

$W_{\mathrm{Mi}}^{\&prime;}=W_{\mathrm{Mi}}+\mathrm{Sign}\left(W_{\mathrm{Mi}}\right)\&CenterDot;[(1/\mathrm{\&tau;}-k/2)\&CenterDot;(1-e^{-\mathrm{\&tau;}\left|W_{\mathrm{Mi}}\right|})],i=x,y,z$ Formula (3)

In the formula:

τ: rise-time constant, unit is " second ";

K: decline maximum delay constant, unit are " second ";

Described constant τ and k are obtained through match after the actual measurement by magnetic torquer coil and the decision of driver circuit characteristic; Promptly do not having under the magnetic torquer compensation situation, given certain work pulsewidth is with oscilloscope measurement build up time and decline maximum delay time.

Images