A method for controlling the autonomous rotation of a control torque gyroscope on orbit

Abstract

A method for autonomous on-orbit spin-up control of control moment gyros (CMGs) enables autonomous spin-up of CMGs after orbital entry, independent of ground support. During this process, faulty CMGs can be diagnosed and repaired, without generating additional interfering torque on the satellite, enabling rapid reconnection for attitude control. During steady-state control, the theoretical frame position of the CMGs is planned based on the current state of the CMGs connected to the system. When the number of connected gyros exceeds three, zero-motion control is implemented, and command calculations are performed using the theoretical frame position as the target, preventing the CMGs from remaining near a fixed position in the on-orbit frame.

Description

Technical Field

[0001] The invention relates to an on-orbit autonomous rotation control method for a control moment gyroscope, belonging to the technical field of satellite attitude control. Background Art

[0002] With the continuous development of satellite attitude control technology and the continuous improvement of mission requirements, modern satellites have increasingly higher requirements for attitude control systems, such as high precision, high stability, large-angle rapid maneuvering, etc. In order to meet system requirements, such satellites mostly use control torque gyroscopes as actuators, which generate control force through angular momentum exchange. Compared with flywheels, they have the advantages of large output torque, strong torque amplification effect, and large angular momentum envelope.

[0003] Existing research on control moment gyros (CMGs) has focused on controllability and singularity avoidance. These efforts include dynamically escaping singularities through robust pseudo-inverse and zero motion methods, or avoiding singularities through advance planning and additional frame angular velocities. Some of this research has been verified on-orbit and demonstrates effective singularity avoidance, ensuring the effective completion of various control tasks. These studies assume that the CMGs have established a sound operating state on-orbit. In practical engineering, integrating CMGs into systems requires consideration of spin-up, fault diagnosis, and reconfiguration. While some researchers have proposed solutions to the latter two issues, ensuring that on-orbit switching does not affect attitude control, few have investigated CMG spin-up. Furthermore, in steady-state conditions without attitude maneuvers, the CMG frame angle typically remains near a certain position. This can easily lead to wear and tear, leading to malfunction and unavailability. Existing approaches typically involve periodically injecting a new set of target frame angles from the ground, but this requires frequent ground manipulation and can also create a risk of the frame angle remaining fixed for short periods of time. Summary of the Invention

[0004] The technical problem solved by the present invention is: in view of the problem that traditional control means in the current existing technology require ground control intervention and there are control risks, a method for controlling the autonomous rotation of a control torque gyroscope on orbit is proposed.

[0005] The present invention solves the above technical problems by the following technical solutions:

[0006] A method for controlling an autonomous on-orbit spin of a control moment gyroscope, comprising:

[0007] Determine the fault condition of each control moment gyro, set the initial access state according to the fault condition and send a power-on command to all control moment gyros;

[0008] Determine the target frame angular position according to the initial access state, and send a target frame angular position control instruction to each control moment gyro;

[0009] Determine whether the frame angle position of each control moment gyro is adjusted in place, and if the judgment result is that the adjustment is not in place, send a power-off command to each control moment gyro; if the judgment result is that the adjustment is in place, send a frame angle position holding command;

[0010] After the control moment gyro that is not adjusted in place is powered off and then powered on again, the target frame angle position control instruction is received again according to the initial access state, and a secondary frame angle position judgment is performed. If the secondary judgment result is still not in place, all control moment gyros are cut out. If the secondary judgment result is in place, the initial access state is updated to the successful state.

[0011] In the successful position state, according to the frame angle position holding instruction, the control torque gyro sends the inner rotor rotation instruction;

[0012] The inner rotor speed of the control moment gyroscope is judged, and if the inner rotor speed meets the standard, a spin-up success flag is set; if the inner rotor speed does not meet the standard, a spin-up failure flag is set;

[0013] After each control moment gyro sets the spin success flag, the access state is updated to the spin success state. If the number of control moment gyros in the spin success state meets the control requirements, the control moment gyros other than the spin success state are switched out; otherwise, all control moment gyros are switched out.

[0014] The frame angle of the control moment gyro in each successful spinning state is autonomously adjusted, and the control moment gyro that completes a round of autonomous adjustment is subjected to zero motion control.

[0015] The number of the control moment gyroscopes is N, and the method for setting the initial access state is:

[0016] The fault conditions of each control moment gyro are collected. If any control moment gyro is in a faulty state, the faulty control moment gyro is not connected, and the control moment gyro without fault is set to be connected;

[0017] If the number of control moment gyros in the connected state without faults is less than 3, the spin control is terminated, otherwise the initial connected state is set to SW CMG and sends a power-on command to the control moment gyro in the connected state.

[0018] The method for determining whether the frame angular position of each control moment gyro is adjusted to the correct position is as follows:

[0019] After each control moment gyro receives the target frame angle position control instruction t1, the relationship between the frame angle difference between the actual frame angle position and the target frame angle position of the control moment gyro in each connected state and the frame angle threshold is judged. If the frame angle difference is less than the frame angle threshold △δ within the continuous time length △t, it is adjusted into place. If not, the power is cut off.

[0020] If the result of the first frame angle position adjustment is that the adjustment is in place, a frame angle position holding instruction is sent to the control moment gyro that is adjusted in place, and a power-off instruction is sent to the control moment gyro that is not adjusted in place.

[0021] The method of controlling based on the secondary judgment result is:

[0022] If the number of frame angle positions of the control moment gyros that are still not in place after power is re-applied is less than 3, all control moment gyros are cut out and a stop and hold command is sent; if the number of frame angle positions of the control moment gyros that are in place after power is re-applied is greater than or equal to 3, the initial access state is updated to the successful state.

[0023] The method for judging the speed of the inner rotor of the control moment gyroscope is:

[0024] After the control torque gyro for the counter-rotation sends the inner rotor rotation instruction, the inner rotor speed is monitored in real time. When the difference between the inner rotor speed and the target speed is continuously less than the preset value △n for a period of time △t, the current inner rotor rotation is successful, and the rotation success flag QX_Flag[i] is set to 1; otherwise, the rotation duration flag QX_Flag[i] is set to 0.

[0025] The method for judging whether the number of control moment gyros meets the control requirements in the successful spinning state is as follows:

[0026] If the number of control torque gyros in the spinning-up state is greater than or equal to 3, the control requirements are considered met;

[0027] If the number of control torque gyros in the spinning-up state is less than 3, it is considered that the control requirements are not met;

[0028] If the control requirements are met, each control moment gyro is controlled normally, the control moment gyro in the non-spinning state is cut off and a power-off command is sent; if the control requirements are not met, all control moment gyros are cut off and wait for processing by the ground control station.

[0029] The method for autonomously adjusting the frame angle of the control moment gyro in each successful spinning state is as follows:

[0030] If the number of control moment gyros in the successful spinning state is greater than 3, the target frame angle position of each control moment gyro is planned in ascending order according to the number of the control moment gyros.

[0031] The planning method for the target frame angular position of each control moment gyro is:

[0032] Set the planning period according to the number of control moment gyros;

[0033] In the first cycle, the target frame angle of the first control moment gyro is planned and set to a preset theoretical value;

[0034] In the subsequent N cycles, the target frame angle of the Nth control moment gyro is planned and set to a preset theoretical value;

[0035] When the last cycle is finished, wait for the ground control station to perform the next round of autonomous adjustments.

[0036] The zero motion control is:

[0037] The planned value of the autonomously adjusted frame angle of this wheel is used as the zero motion target, the zero motion control rate is set, and the frame angle position of each control moment gyro is adjusted to ensure that the frame angle position is within the adjustment range centered on the zero motion target and does not always stay at any fixed value.

[0038] The advantages of the present invention compared with the prior art are:

[0039] (1) The present invention provides a method for controlling the autonomous spin-up of a control moment gyro on orbit. The method can autonomously complete the spin-up of the control moment gyro after entering orbit without relying on the ground. During this process, the method can diagnose and recover a faulty control moment gyro, without generating additional interference torque on the satellite, enabling the gyro to quickly access the system for attitude control. During steady-state control, based on the current state of the control moment gyro access to the system, when the number of accesses is greater than three, the theoretical frame position of the control moment gyro is planned, zero motion control is added, and command resolution is performed with the theoretical frame position as the target, to prevent the control moment gyro from remaining near a fixed position in the on-orbit frame.

[0040] (2) The present invention completes the autonomous on-orbit spin-up of the control torque gyro through autonomous diagnosis and autonomous processing, which can not only ensure that the available control torque gyro completes the spin-up quickly and effectively, but also isolate the faulty gyro and perform simple processing to restore it. After recovery, it can continue to be used normally, while the unusable one is isolated from the system, and no additional interference torque is generated to the system. During the entire spin-up process, the control torque gyro can be quickly connected to the system for use without ground intervention. In steady state, the satellite autonomously plans the frame angle position to ensure that the frame angle position does not stay near a certain value for a long time, reducing ground intervention and effectively controlling risks;

[0041] (3) The present invention uses the original measurement information and processing methods on the satellite to complete the autonomous rotation and troubleshooting of the control moment gyro through logical judgment. The frame angle position planning is simple and does not require the introduction of complex algorithms. The software is simple to implement and ground verification is convenient, making it suitable for engineering use. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A flow chart of the autonomous rotation of the controlled torque gyroscope provided by the present invention;

[0043] Figure 2 This is a flow chart of the autonomous frame angular position adjustment of the control force rejection gyro provided by the present invention. DETAILED DESCRIPTION

[0044] A method for autonomous on-orbit spin-up control of control moment gyros (CMGs) enables autonomous spin-up of CMGs after orbital entry, independent of ground support. During this process, faulty CMGs can be diagnosed and repaired, without generating additional interfering torque on the satellite, enabling rapid reconnection for attitude control. During steady-state control, the theoretical frame position of the CMGs is planned based on the current state of the CMGs connected to the system. When the number of connected gyros exceeds three, zero-motion control is implemented, and command calculations are performed using the theoretical frame position as the target, preventing the CMGs from remaining near a fixed position in the on-orbit frame.

[0045] The control method for autonomously spinning a control moment gyro on orbit includes the following steps:

[0046] Determine the fault condition of each control moment gyro, set the initial access state according to the fault condition and send a power-on command to all control moment gyros;

[0047] Determine the target frame angular position according to the initial access state, and send a target frame angular position control instruction to each control moment gyro;

[0048] Determine whether the frame angle position of each control moment gyro is adjusted in place, and if the judgment result is that the adjustment is not in place, send a power-off command to each control moment gyro; if the judgment result is that the adjustment is in place, send a frame angle position holding command;

[0049] After the control moment gyro that is not adjusted in place is powered off and then powered on again, the target frame angle position control instruction is received again according to the initial access state, and a secondary frame angle position judgment is performed. If the secondary judgment result is still not in place, all control moment gyros are cut out. If the secondary judgment result is in place, the initial access state is updated to the successful state.

[0050] In the successful position state, according to the frame angle position holding instruction, the control torque gyro sends the inner rotor rotation instruction;

[0051] The inner rotor speed of the control moment gyroscope is judged, and if the inner rotor speed meets the standard, a spin-up success flag is set; if the inner rotor speed does not meet the standard, a spin-up failure flag is set;

[0052] After each control moment gyro sets the spin success flag, the access state is updated to the spin success state. If the number of control moment gyros in the spin success state meets the control requirements, the control moment gyros other than the spin success state are switched out; otherwise, all control moment gyros are switched out.

[0053] The frame angle of the control moment gyro in each successful spinning state is adjusted autonomously;

[0054] Perform zero motion control on the control moment gyro that completes one round of autonomous adjustment.

[0055] The number of control moment gyros is N. The method to set the initial access state is:

[0056] The fault conditions of each control moment gyro are collected. If any control moment gyro is in a faulty state, the faulty control moment gyro is not connected, and the control moment gyro without fault is set to be connected;

[0057] If the number of control moment gyros in the connected state without faults is less than 3, the spin control is terminated, otherwise the initial connected state is set to SW CMG and sends a power-on command to the control moment gyro in the connected state.

[0058] The method for judging whether the frame angle position of each control moment gyro is adjusted in place is as follows:

[0059] After each control moment gyro receives the target frame angle position control instruction t1, the relationship between the frame angle difference between the actual frame angle position and the target frame angle position of the control moment gyro in each connected state and the frame angle threshold is judged. If the frame angle difference is less than the frame angle threshold △δ within the continuous time length △t, it is adjusted into place. If not, the power is cut off.

[0060] If the result of the first frame angle position adjustment is that the adjustment is in place, a frame angle position holding instruction is sent to the control moment gyro that is adjusted in place, and a power-off instruction is sent to the control moment gyro that is not adjusted in place.

[0061] The method of controlling based on the secondary judgment result is:

[0062] If the number of frame angle positions of the control moment gyros that are still not in place after power is re-applied is less than 3, all control moment gyros are cut out and a stop and hold command is sent; if the number of frame angle positions of the control moment gyros that are in place after power is re-applied is greater than or equal to 3, the initial access state is updated to the successful state.

[0063] The method for judging the speed of the inner rotor of the control moment gyroscope is:

[0064] After the control torque gyro for the counter-rotation sends the inner rotor rotation instruction, the inner rotor speed is monitored in real time. When the difference between the inner rotor speed and the target speed is continuously less than the preset value △n for a period of time △t, the current inner rotor rotation is successful, and the rotation success flag QX_Flag[i] is set to 1; otherwise, the rotation duration flag QX_Flag[i] is set to 0.

[0065] The method for judging whether the number of control moment gyros meets the control requirements in the successful spinning state is as follows:

[0066] If the number of control torque gyros in the spinning-up state is greater than or equal to 3, the control requirements are considered met;

[0067] If the number of control torque gyros in the spinning-up state is less than 3, it is considered that the control requirements are not met;

[0068] If the control requirements are met, each control moment gyro is controlled normally, the control moment gyro in the non-spinning state is cut off and a power-off command is sent; if the control requirements are not met, all control moment gyros are cut off and wait for processing by the ground control station.

[0069] The method for autonomously adjusting the frame angle of the control moment gyro in each successful spinning state is as follows:

[0070] If the number of control moment gyros in the successful spinning state is greater than 3, the target frame angle position of each control moment gyro is planned in ascending order according to the number of the control moment gyros.

[0071] The planning method for the target frame angular position of each control moment gyro is:

[0072] Set the planning period according to the number of control moment gyros;

[0073] In the first cycle, the target frame angle of the first control moment gyro is planned and set to a preset theoretical value;

[0074] In the subsequent N cycles, the target frame angle of the Nth control moment gyro is planned and set to a preset theoretical value;

[0075] When the last cycle is finished, wait for the ground control station to perform the next round of autonomous adjustments.

[0076] Zero motion control is:

[0077] The planned value of the autonomously adjusted frame angle of this wheel is used as the zero motion target, the zero motion control rate is set, and the frame angle position of each control moment gyro is adjusted to ensure that the frame angle position is within the adjustment range centered on the zero motion target and does not always stay at any fixed value.

[0078] The following is further described in conjunction with the accompanying drawings and preferred embodiments:

[0079] In the current embodiment, the process of the on-orbit autonomous control method of the control moment gyro is as follows: Figure 1 As shown, after entering orbit, the control moment gyro can be independently completed to spin up without relying on the ground. During this process, the faulty control moment gyro can be diagnosed and restored, and no additional interference torque is generated on the satellite, so that it can be quickly connected to the system for attitude control. During steady-state control, according to the current state of the control moment gyro connected to the system, when the number of connected gyros is greater than 3, the theoretical frame position of the control moment gyro is planned, zero motion control rate control is added, and command solution is performed with the theoretical frame position as the target to prevent the control moment gyro from staying near a fixed position in the orbital frame. The present invention is further elaborated below in conjunction with the accompanying drawings.

[0080] Step 1: Set the initial CMG access status SW according to the CMG fault condition in the current system CMG By default, all N CMGs are connected. If a CMG is in faulty state, the CMG will not be connected. If the number of CMGs connected to the system is less than 3, the spin-up ends. Otherwise, a power-on command is sent to the unpowered CMGs connected to the system, and the following steps are performed;

[0081] Step 2: According to the CMG status SW of the current access system CMG , select the corresponding target frame angle position δc, and send the frame angle position control instruction to the CMG connected to the system;

[0082] Step 3: After a period of time t1 after the command is sent, determine whether the frame angles of all CMGs connected to the system are in place (judgment method: the difference between the frame angle position returned by the connected CMGs and the command angle position is continuously △t less than the threshold △δ). If they are in place, execute steps 6 to 7. If they are not in place, execute step 4.

[0083] Step 4: If the CMG connected to the system is not in place, first power off the CMG that is not in place, then power it back on, and resend the frame angle control command according to the original connection status. If it is in place, proceed to step 6; if not, proceed to step 5.

[0084] Step 5: If the frame corner still cannot be put into place after power is turned off again, the CMG that is not in place will be cut out of the system. If the number of CMGs in place is greater than or equal to 3, the CMG access status will be updated to CMG in place successfully, and the system will return to step 2 and start again. If the number of CMGs in place is less than 3, all CMGs will be cut off, and all CMGs will send a stop and hold command to wait for ground processing.

[0085] Step 6: If the frame angles of all CMGs connected to the system are in place, a frame angle position hold instruction is sent, and an inner rotor rotation instruction is sent to the CMGs connected to the system but not rotating;

[0086] Step 7: After the spin-up command is sent, the CMG inner rotor speed is determined in real time. If the difference between the inner rotor speed and the target speed is continuously less than Δn for Δt, the CMG is considered to have successfully spun up. The corresponding spin-up success flag QX_Flag[i] is set to 1 (i represents the i-th CMG in the system). Otherwise, QX_Flag[i] remains at 0. Execute step 8.

[0087] Step 8: After reaching the set autonomous spin-up time t_qx, update the CMG access system status SW according to the current access status and spin-up success status CMG If the number of available CMGs in the updated state is greater than or equal to 3, normal control will be started, the unconnected CMGs will be cut out of the system, and a power-off command will be sent. If the available number is less than 3, all CMGs will be cut off and wait for ground processing.

[0088] Step 9: After the CMG successfully starts to spin, if the number of CMGs connected to the system is greater than 3, the frame angle autonomous adjustment function is started. The target frame angle position of each CMG is planned in order from small to large according to the CMG number of the connected system. For example, the frame angle planning cycle of each control moment gyro is set to Tcmg. In the first cycle, the target frame angle of the first CMG can be set to δc1+f(t), where t>0 and <=Tcmg, and f(0)=f(Tcmg)=0. In the second cycle, the target frame angle of the second CMG is δc2+f(t), and so on. After the last cycle ends, it starts again from the first cycle. Figure 2 shown.

[0089] Step 10: Add zero motion control rate. The target value of zero motion is the planned frame angle position. The zero motion control rate ensures that the CMG frame angle position will not always stay near a fixed value.

[0090] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solutions of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the scope of protection of the technical solutions of the present invention.

[0091] 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. A method for controlling an autonomous on-orbit rotation of a control moment gyroscope, characterized in that include: Determine the fault condition of each control moment gyro, set the initial access state according to the fault condition and send a power-on command to all control moment gyros; Determine the target frame angular position according to the initial access state, and send a target frame angular position control instruction to each control moment gyro; Determine whether the frame angle position of each control moment gyro is adjusted in place, and if the judgment result is that the adjustment is not in place, send a power-off command to each control moment gyro; if the judgment result is that the adjustment is in place, send a frame angle position holding command; After the control moment gyro that is not adjusted in place is powered off and then powered on again, the target frame angle position control instruction is received again according to the initial access state, and a secondary frame angle position judgment is performed. If the secondary judgment result is still not in place, all control moment gyros are cut out. If the secondary judgment result is in place, the initial access state is updated to the successful state. In the successful position state, according to the frame angle position holding instruction, the control torque gyro sends the inner rotor rotation instruction; The inner rotor speed of the control moment gyroscope is judged, and if the inner rotor speed meets the standard, a spin-up success flag is set; if the inner rotor speed does not meet the standard, a spin-up failure flag is set; After each control moment gyro sets the spin success flag, the access state is updated to the spin success state. If the number of control moment gyros in the spin success state meets the control requirements, the control moment gyros other than the spin success state are switched out; otherwise, all control moment gyros are switched out. The frame angle of the control moment gyro in each successful spinning state is autonomously adjusted, and the control moment gyro that completes a round of autonomous adjustment is subjected to zero motion control.

2. The method for controlling an autonomous on-orbit spin of a control moment gyroscope according to claim 1, characterized in that: The number of the control moment gyroscopes is N, and the method for setting the initial access state is: The fault conditions of each control moment gyro are collected. If any control moment gyro is in a faulty state, the faulty control moment gyro is not connected, and the control moment gyro without fault is set to be connected; If the number of control moment gyros in the connected state without faults is less than 3, the spin control is terminated, otherwise the initial connected state is set to SW CMG and sends a power-on command to the control moment gyro in the connected state.

3. The method for controlling an autonomous on-orbit spin of a control moment gyroscope according to claim 2, characterized in that: The method for determining whether the frame angular position of each control moment gyro is adjusted to the correct position is as follows: After each control moment gyro receives the target frame angle position control instruction t1, the relationship between the frame angle difference between the actual frame angle position and the target frame angle position of the control moment gyro in each connected state and the frame angle threshold is judged. If the frame angle difference is less than the frame angle threshold △δ within the continuous time length △t, it is adjusted into place. If not, the power is cut off.

4. The method for controlling an autonomous on-orbit spin of a control moment gyroscope according to claim 3, characterized in that: If the result of the first frame angle position adjustment is that the adjustment is in place, a frame angle position holding instruction is sent to the control moment gyro that is adjusted in place, and a power-off instruction is sent to the control moment gyro that is not adjusted in place.

5. The method for controlling an autonomous on-orbit spin of a control moment gyroscope according to claim 2, characterized in that: The method of controlling based on the secondary judgment result is: If the number of frame angle positions of the control moment gyros that are still not in place after power is re-applied is less than 3, all control moment gyros are cut out and a stop and hold command is sent; if the number of frame angle positions of the control moment gyros that are in place after power is re-applied is greater than or equal to 3, the initial access state is updated to the successful state.

6. The method for controlling an autonomous on-orbit spin of a control moment gyroscope according to claim 2, characterized in that: The method for judging the speed of the inner rotor of the control moment gyroscope is: After the control torque gyro for the counter-rotation sends the inner rotor rotation instruction, the inner rotor speed is monitored in real time. When the difference between the inner rotor speed and the target speed is continuously less than the preset value △n for a period of time △t, the current inner rotor rotation is successful, and the rotation success flag QX_Flag[i] is set to 1; otherwise, the rotation duration flag QX_Flag[i] is set to 0.

7. The method for controlling an autonomous on-orbit spin of a control moment gyroscope according to claim 2, characterized in that: The method for judging whether the number of control moment gyros meets the control requirements in the successful spinning state is as follows: If the number of control torque gyros in the spinning-up state is greater than or equal to 3, the control requirements are considered met; If the number of control torque gyros in the spinning-up state is less than 3, it is considered that the control requirements are not met; If the control requirements are met, each control moment gyro is controlled normally, the control moment gyro in the non-spinning state is cut off and a power-off command is sent; if the control requirements are not met, all control moment gyros are cut off and wait for processing by the ground control station.

8. The method for controlling an autonomous on-orbit spin of a control moment gyroscope according to claim 2, characterized in that: The method for autonomously adjusting the frame angle of the control moment gyro in each successful spinning state is as follows: If the number of control moment gyros in the successful spinning state is greater than 3, the target frame angle position of each control moment gyro is planned in ascending order according to the number of the control moment gyros.

9. The method for controlling an autonomous on-orbit spin-up of a control moment gyroscope according to claim 8, characterized in that: The planning method for the target frame angular position of each control moment gyro is: Set the planning period according to the number of control moment gyros; In the first cycle, the target frame angle of the first control moment gyro is planned and set to a preset theoretical value; In the subsequent N cycles, the target frame angle of the Nth control moment gyro is planned and set to a preset theoretical value; When the last cycle is finished, wait for the ground control station to perform the next round of autonomous adjustments.

10. The method for controlling an autonomous on-orbit spin-up of a control moment gyroscope according to claim 9, characterized in that: The zero motion control is: The planned value of the autonomously adjusted frame angle of this wheel is used as the zero motion target, the zero motion control rate is set, and the frame angle position of each control moment gyro is adjusted to ensure that the frame angle position is within the adjustment range centered on the zero motion target and does not always stay at any fixed value.

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