JPH0790837B2 - Bias momentum type satellite angular momentum vector changing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for changing the direction of an angular momentum vector of a bias momentum type artificial satellite from an arbitrary direction to a maximum inertia principal axis direction or a minimum inertia principal axis direction. .

(Prior art and its problems) As a method for changing the direction of such an angular momentum vector, for example, a passive method using a disturbance attenuator and an active method called a dual spin turn method using a momentum wheel are used. There are various methods. In the former case, the changed angular momentum vector direction is limited to the maximum inertial principal axis direction of the satellite, and the change takes time. The latter is installed by aligning the rotation axis of the momentum wheel with the angular momentum vector direction of the satellite after changing, and by rotating this momentum wheel, the initial angular momentum of the satellite is absorbed by the momentum wheel and the angular momentum vector direction of the satellite is changed. Is a method to match the axial direction of the momentum wheel. According to this method, the angular momentum vector direction of the satellite after the change can be arbitrarily selected by selecting the mounting direction of the rotation axis of the momentum wheel. The three main axes of the satellite (X axis, Y axis, Z axis) The change is not successful depending on the balance of the magnitudes of the moments of inertia of. In particular, when changing from the axial direction with the minimum moment of inertia to the axial direction with the maximum moment of inertia, the satellite rotates around the momentum wheel axis with an angular momentum twice as large as the momentum wheel. The wheel and satellite fall into an upside-down state with opposite angular momentum.

It is an object of the present invention to provide a bias momentum type artificial satellite angular momentum vector changing method that solves the drawbacks of these conventional methods.

(Means for Solving the Problems) In the method of changing the angular momentum vector of a satellite of the bias momentum system according to the present invention, as shown in FIG. 1 to FIG. From the maximum or minimum inertial spindle direction,
A device for detecting the satellite angular velocity ω around the main axis, an electronic control unit for generating a command of a torque Tc whose polarity is opposite to the polarity of the ω and whose magnitude is constant, and a torque Tc is generated around the main shaft according to this command. And an internal force torque generating means.

(Example) The angular momentum vector change of a bias momentum type artificial satellite performed by the method of the present invention will be described with reference to the drawings. In this embodiment, the maximum moment of inertia axis is the Z axis, and the angular momentum vector is changed in the X axis direction. In this embodiment, the rate gyro 2 is used as a means for detecting the angular velocity of the satellite, and the reaction wheel 1 is used as the internal force torque generating means. As shown in FIG. It is installed in parallel. In FIG. 1, the Z axis represents the maximum moment of inertia of the satellite, the Y axis represents the intermediate moment of inertia of the satellite, and the X axis represents the minimum moment of inertia of the satellite. As shown in FIG. 2, the electronic control unit 3 includes a rate gyro 2
The product of the detected angular velocity ωz around the Z-axis of the satellite becomes negative, that is, when ωz is positive, a negative torque command Tc is given to the reaction wheel 1 when ωz is negative. Occur.

The moment of inertia about the satellite's X-axis, Y-axis, and Z-axis, respectively
Ix, Iy, Iz, and the angular velocities around these axes are ω
When x, ωy, ωz, the rotational kinetic energy E of the satellite is expressed by the sum of kinetic energies around each axis as shown in the following equation.

E = 1/2 ・ Ix ・ ωx ² ＋1/2 ・ Iy ・ ωy ² ＋1/2 ・ Iz ・ ωz
² (1) In addition, the equations of motion around each axis expressed by the moment of inertia × angular acceleration = couple moment are as follows.

Ix · dωx / dt = (Iy−Iz) ωyωz−ωyh (2) Iy · dωy / dt = (Iz−Ix) ωxωz + ωxh (3) Iz · dωz / dt = (Ix−Iy) ωxωy + dh / dt (4) where Here, h is the angular momentum of the reaction wheel. Further, if the torque given to the satellite by the reaction wheel is T, the satellite torque increases by the time decrease of the angular momentum of the reaction wheel. Therefore, T = -dh / dt (5) Equation (1) at time t Differentiating, dE / dt = Ix ・ dωx / dt ＋ Iy ・ dωy / dt ＋ Iz ・ dωz / dt
(1) ', so (1)', (2), (3), (4),
From equation (5), dE / dt = ωz · T (6). Further, the torque T includes an electric torque T _E generated by an electric force of a spin motor or the like by a torque command Tc from the electronic control unit 3 and a friction torque T _F determined by the inertia ratio and the rotation speed of the reaction wheel 1. Therefore, T = T _E + T _F. T _E can be electrically much larger than T _F. Therefore, T = T _E approximately.
Here, as described above, since T _E ∝Tc, T ∝Tc and T and Tc always have the same sign. As shown in the input / output characteristic graph of FIG. 3, the electronic control unit 3 outputs the torque command Tc having the opposite sign to the input ωz, and therefore the product of T and ωz having the same sign as Tc, that is, the formula (6) The right side is always negative. In this way, since the operation is performed according to the control law such that dE / dt is always negative, the rotational kinetic energy E of the satellite continues to decrease and finally becomes zero. At this time, the rotation of the satellite stopped,
All the kinetic energy that the satellite had in the initial state is absorbed by the reaction wheel 1. Then, as shown in FIG. 2, switch off the electronic control unit 3.
When Tc is set to zero and the rotation of the reaction wheel 1 is transmitted to the satellite by friction, the satellite rotates about the Z axis that is the maximum moment of inertia parallel to the rotation axis of the reaction wheel 1. In this way, the angular momentum vector of the bias momentum type artificial satellite can be changed.

(Effects of the Invention) As described above, according to the method of the present invention, the angular momentum vector of the artificial satellite of the bias momentum method can be changed from any direction to the maximum inertial principal axis or the minimum inertial principal axis direction. Changes are reliable and fast.

[Brief description of drawings]

FIG. 1 is a view conceptually showing a mounting direction of a rotation shaft of a reaction wheel and a rate gyro. FIG. 2 is a diagram conceptually showing the function of the system of the present invention. FIG. 3 is a diagram showing the input / output characteristics of the electronic control unit. 1 ... Reaction wheel, 2 ... Rate gyro,
3 ... Electronic control unit.

Claims (1)

[Claims] 1. A method of changing an angular momentum vector of a bias momentum type artificial satellite from an arbitrary direction to a maximum or minimum inertial principal axis direction, wherein a device for detecting a satellite angular velocity ω around the principal axis and a polarity of the device are provided. An electronic control unit that generates a command of torque Tc having a constant magnitude opposite to the polarity of ω, and the torque around the main shaft according to this command
A method for changing the angular momentum vector of an artificial satellite characterized by comprising an internal force torque generating means for generating Tc.