Fault Tolerant Control Method for Symmetrical Six-Phase Motors

Abstract

Fault-tolerant control method for a symmetrical six-phase motor. First, diagnose the number, location, and type of faults that occur. Second, diagnose the phase angle between the faulty phases. Third, according to the relationship between the maximum phase angle of the faulty phases and 120°, it can be divided into four cases of two or three faulty phases in the cases of less than, equal to, and greater than 120° for fault-tolerant control. When the maximum phase angle between the faulty phases is less than 120°, two phases that form 60° or 120° with the faulty phases are used for vector synthesis to be equivalent to a compensation phase for control. When the phase angles of the faulty phases are all 120°, six-phase to three-phase conversion is used for control. When the maximum phase angle between the faulty phases is greater than 120° and only two phases are faulty, four-phase synthesis to three-phase is used for control. When the maximum phase angle between the faulty phases is greater than 120° and three phases are faulty, the remaining three phases are used to synthesize two phases that are 90° apart from each other for control. The present invention performs fault-tolerant control according to different faults, ensures the normal operation of the system, and can greatly improve the reliability of the system.

Description

Technical Field

[0001] The present invention relates to the field of multiphase motor control, and more particularly, to a fault-tolerant control method for multiphase motors. Background Art

[0002] In high-reliability application scenarios, such as manned aerospace and other fields, in order to improve the reliability of the execution servo system, redundancy techniques are usually adopted. However, this brings about disadvantages such as increased volume / weight, high control complexity, and high cost. Therefore, it is crucial to enhance the fault-tolerant performance of the drive system. For multiphase motors, there is greater potential for exploration in this regard. However, for six-phase motors, there is relatively little research in this area. Summary of the Invention

[0003] The technical problem solved by the present invention is: Since there are few fault-tolerant methods for existing six-phase motors, a control method for six-phase motor fault tolerance is provided to improve the fault-tolerant performance of six-phase motors, thereby enhancing the reliability and robustness of the motor system.

[0004] The technical solution of the present invention is: A fault-tolerant control method for a symmetric six-phase motor, the steps are as follows:

[0005] 1) Diagnose the number, location, and type of faults that occur. When there are more than one fault, it is also necessary to diagnose the phase angle between the faulty phases.

[0006] 2) When there is only one fault, the principle of power conservation or torque conservation before and after the fault can be adopted for fault tolerance, that is, the power or torque output by the remaining five phases is made consistent with that before the fault does not occur, and then the amplitude and phase of the remaining phases are obtained; alternatively, the fault-tolerant control method of step 4) can be adopted.

[0007] 3) When the number of faults is more than one, according to the relationship between the maximum phase angle of the faulty phases and 120°, it can be divided into four cases of less than, equal to, and greater than, and two or three faulty phases are used for fault-tolerant control.

[0008] 4) When the maximum angle between the faulty phases of the six-phase motor is less than 120°, two normal phases with a 60° difference from the faulty phases can be used for vector synthesis to be equivalent to a compensation phase, or two phases with a 120° difference from the faulty phases can be used for vector synthesis to be equivalent to a compensation phase, to make up for the loss caused by the faulty phases in terms of output power and output torque, and ensure power or torque conservation before and after the fault, so as to achieve the purpose of fault-tolerant control.

[0009] 5) When the angles between the faulty phases of the six-phase motor are all equal to 120°, the six-phase motor can be converted into three phases for fault-tolerant control.

[0010] 6) When the maximum angle between the faulty phases of a six-phase motor is greater than 120°, and only these two phases are faulty, the normal four-phase drive system among the six phases can be used. That is, two normal-phase vectors adjacent to the faulty phase by 60° or two normal-phase vectors adjacent to the faulty phase by 120° are synthesized and equivalent to the compensation phase of this faulty phase. At the same time, another two normal phases with a phase difference of 120° from the faulty phase are selected to work, thus forming a three-phase drive system with a phase angle difference of 120° from each other to achieve fault-tolerant control and ensure the normal operation of the system.

[0011] 7) When the maximum angle between the faulty phases of a six-phase motor is greater than 120°, and it is a three-phase fault, the remaining normal phases are synthesized into two-phase vectors with a 120° angle and equivalent to a virtual phase that is 90° from the third normal phase. In this way, a two-phase drive system with a 90° phase difference is formed to achieve fault-tolerant control and ensure the normal operation of the system.

[0012] In step 4), two normal phases with a 60° phase difference from the faulty phase can be used for vector synthesis and equivalent to the compensation phase, or two phases with a 120° phase difference from the faulty phase can be used for vector synthesis and equivalent to the compensation phase, making up for the loss caused by the faulty phase in terms of output power and output torque, ensuring the conservation of power or torque before and after the fault, and achieving the purpose of fault-tolerant control.

[0013] Taking the case where phase A fails as an example, the two-phase vectors of phase C and phase E with a 120° phase angle difference from it are synthesized and equivalent to the compensation phase to replace the work of phase A. The vector synthesis formula is as follows:

[0014]

[0015] Let Then

[0016]

[0017]

[0018]

[0019] In this way, the two-phase vectors of C and E can be synthesized and equivalent to the fault-tolerant control compensation vector for the work of phase A.

[0020] The method of changing the six-phase drive system to a three-phase drive system in step 5). Since the six phases are symmetrically and evenly distributed, when the angle between the faulty phases is 120° each, the remaining phases will surely be able to form a three-phase drive system with a phase angle difference of 120° from each other.

[0021] If at least two of the three phases B, D, and F fail, the remaining normal phases can be used to form a three-phase drive system with a 120° phase difference, that is, the three-phase drive system of ACE.

[0022] Step 6) Method for changing a six-phase drive system to a four-phase drive system. Select two phases separated by 120° from the remaining phases and add two phases separated by 60° from the faulty phase to form a four-phase drive system.

[0023] Taking the failure of phases A and D as an example, select phases C and E as two of the three phases, and synthesize the third phase with phases B and F, thus forming a four-phase drive system. The formula for synthesizing the third phase with phases B and F is as follows:

[0024] U A' = U B cos(60°) + U F cos(60°)

[0025] Let U B = U F , then

[0026]

[0027] Thus, the six-phase drive system can be changed to a four-phase drive system.

[0028] Step 7) Method for changing a six-phase drive system to a two-phase drive system. Select two phases separated by 120° from the remaining normal phases and synthesize them vectorially to be equivalent to a virtual phase that is 90° to the third normal phase, forming a two-phase drive system with a 90° phase difference.

[0029] Taking the failure of phases A, D, and E as an example, select phases B and F and synthesize them vectorially to be equivalent to a virtual phase that is 90° to the third normal phase, thus forming a two-phase drive system with a 90° phase difference. The formula for synthesizing the virtual phase with phases B and F is as follows:

[0030] U N = U B cos(30°)

[0031] U F = -U B sin(30°)

[0032] The virtual phase U N obtained in this way forms a 90° angle with the original normal phase U C . Thus, the six-phase drive system can be changed to a two-phase drive system.

[0033] The advantages of the present invention compared with the prior art are as follows: The fault-tolerant control method of the symmetric six-phase motor of the present invention can greatly improve the fault-tolerant performance of the six-phase motor, providing a new control method for the fault-tolerant control of the six-phase motor. It can greatly improve the service life of the six-phase motor and the task completion ability under harsh environments, fully exploit the fault-tolerant potential of the six-phase motor, and add a more solid insurance measure for the use of the six-phase motor. Description of the Drawings

[0034] Figure 1 is a flowchart of the method of the present invention;

[0035] Figure 2 is a diagram of two-phase vector synthesis fault tolerance control;

[0036] Figure 3 is a diagram of three-phase drive system fault tolerance control;

[0037] Figure 4 is a diagram of four-phase vector synthesis fault tolerance control;

[0038] Figure 5 is a diagram of three-phase vector synthesis fault tolerance control. Detailed Embodiment

[0039] The flowchart of the present invention is shown in the appendix Figure 1 , and the specific steps are as follows:

[0040] 1) Diagnose the number, location, and type of faults that occur. When there are more than one fault, it is also necessary to diagnose the phase angle between the faulty phases;

[0041] 2) When there is only one fault, the principle of power conservation or torque conservation before and after the fault can be used for fault tolerance, that is, the power or torque output by the remaining five phases is the same as that before the fault did not occur, and then the amplitude and phase of the remaining phases are calculated; the fault tolerance control method in step 4) can also be used;

[0042] 3) When there are more than one fault, according to the relationship between the maximum angle of the faulty phases and 120°, it can be divided into four cases of less than, equal to, and greater than, and two or three faulty phases are damaged, and fault tolerance control is carried out in four cases;

[0043] 4) When the maximum angle between the faulty phases of the six-phase motor is less than 120°, two normal phases with a difference of 60° from the faulty phases can be used for vector synthesis to be equivalent to the compensation phase, or two phases with a difference of 120° from the faulty phases can be used for vector synthesis to be equivalent to the compensation phase, and the loss caused by the faulty phases is compensated in terms of output power and output torque, ensuring power or torque conservation before and after the fault, and achieving the purpose of fault tolerance control;

[0044] 5) When the angles between the faulty phases of the six-phase motor are all equal to 120°, the six-phase motor can be converted into a three-phase motor for fault tolerance control;

[0045] 6) When the maximum angle between the faulty phases of a six-phase motor is greater than 120°, and only these two phases are faulty, the normal four-phase drive system in the six phases can be used. That is, two normal-phase vectors adjacent to the faulty phase by 60° or two normal-phase vectors adjacent to the faulty phase by 120° are synthesized and equivalent to the compensation phase of this faulty phase. At the same time, another two normal phases with a 120° difference from the faulty phase are selected to work, thus forming a three-phase drive system with a 120° phase difference from each other to achieve fault-tolerant control and ensure the normal operation of the system.

[0046] 7) When the maximum angle between the faulty phases of a six-phase motor is greater than 120°, and it is a three-phase fault, the remaining normal phases are synthesized into a two-phase vector with a 120° angle and equivalent to a virtual phase with a 90° angle from the third normal phase. In this way, a two-phase drive system with a 90° phase difference is formed to achieve fault-tolerant control and ensure the normal operation of the system.

[0047] In step 4), two normal phases with a 60° difference from the faulty phase can be used for vector synthesis and equivalent to the compensation phase, or two phases with a 120° difference from the faulty phase can be used for vector synthesis and equivalent to the compensation phase, making up for the loss caused by the faulty phase in terms of output power and output torque, ensuring the conservation of power or torque before and after the fault, and achieving the purpose of fault-tolerant control.

[0048] Taking the example of phase A failure, as Figure 2 shown, the two-phase vectors of phase C and phase E with a 120° phase difference from it are synthesized and equivalent to the compensation phase to replace the work of phase A. The vector synthesis formula is as follows:

[0049]

[0050] Let Then

[0051]

[0052]

[0053]

[0054] In this way, the two-phase vectors of C and E can be synthesized and equivalent to the fault-tolerant control compensation vector for the work of phase A.

[0055] The method of changing the six-phase drive system to a three-phase drive system in step 5). Since the six phases are symmetrically and evenly distributed, when the phase angles between the faulty phases are all 120°, the remaining normal phases will surely form a three-phase drive system with a 120° phase difference from each other.

[0056] If at least two of the three phases B, D, and F fail, as Figure 3 shown, the remaining normal phases can be used to form a three-phase drive system with a 120° phase difference, that is, the three-phase drive system of ACE.

[0057] Step 6) Method for changing a six-phase drive system to a four-phase drive system: Select two phases separated by 120° from the remaining normal phases and add two phases separated by 60° from the faulty phase to form a four-phase drive system.

[0058] Taking the failure of phases A and D as an example, as Figure 4 shown, select phases C and E as two of the three phases, and synthesize the third phase with phases B and F. Thus, a four-phase drive system is formed. The formula for synthesizing the third phase with phases B and F is as follows:

[0059] U A' = U B cos(60°) + U F cos(60°)

[0060] Let U B = U F , then

[0061]

[0062] Thus, the six-phase drive system can be changed to a four-phase drive system.

[0063] Step 7) Method for changing a six-phase drive system to a two-phase drive system: Select two phases separated by 120° from the remaining normal phases and synthesize them vectorially to be equivalent to a virtual phase that is 90° from the third normal phase, forming a two-phase drive system with a 90° phase difference.

[0064] Taking the failure of phases A, D, and E as an example, as Figure 5 shown, select phases B and F and synthesize them vectorially to be equivalent to a virtual phase that is 90° from the third normal phase. Thus, a two-phase drive system with a 90° phase difference is formed. The formula for synthesizing the virtual phase with phases B and F is as follows:

[0065] U N = U B cos(30°)

[0066] U F = -U B sin(30°)

[0067] The virtual phase U N obtained in this way forms a 90° angle with the original normal phase U C . Thus, the six-phase drive system can be changed to a two-phase drive system.

[0068] The specific embodiments described above further elaborate on the object, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Fault-tolerant control method for a symmetrical six-phase motor, characterized by the following steps: 1) Diagnose the number, location, and type of faults. When there are more than one fault, the phase angle between the faulty phases also needs to be diagnosed. 2) When there is only one fault, fault tolerance is performed using the principle of power conservation or torque conservation before and after the fault, that is, the power or torque output by the remaining five phases is the same as before the fault occurred, and then the amplitude and phase of the remaining phases are calculated; or the fault-tolerant control method of step 4) is used. 3) When there are more than one fault, according to the relationship between the maximum angle of the faulty phases and 120°, it is divided into four cases of less than, equal to, and greater than, and two or three faulty phases are handled for fault-tolerant control. 4) When the maximum angle between the faulty phases of the six-phase motor is less than 120°, two normal phases with a 60° difference from the faulty phases are used for vector synthesis to be equivalent to a compensation phase, or two phases with a 120° difference from the faulty phases are used for vector synthesis to be equivalent to a compensation phase, making up for the loss caused by the faulty phases in terms of output power and output torque, ensuring power or torque conservation before and after the fault, and achieving the purpose of fault-tolerant control. 5) When the angles between the faulty phases of the six-phase motor are all equal to 120°, the six-phase motor is converted to a three-phase motor for fault-tolerant control. 6) When the maximum angle between the faulty phases of the six-phase motor is greater than 120° and only these two phases are faulty, the normal four-phase drive system of the six phases is used, that is, two normal phases adjacent to the faulty phases by 60° or two normal phases adjacent to the faulty phases by 120° are vector-synthesized to be equivalent to the compensation phase of this faulty phase, and at the same time, another two normal phases with a 120° difference from the faulty phases are selected to work, thus forming a three-phase drive system with a phase angle difference of 120° from each other, achieving fault-tolerant control and ensuring the normal operation of the system. 7) When the maximum angle between the faulty phases of the six-phase motor is greater than 120° and there are three faulty phases, two normal phases with a 120° difference from each other among the remaining normal phases are vector-synthesized to be equivalent to a virtual phase that is 90° from the third normal phase, thus forming a two-phase drive system with a 90° difference, achieving fault-tolerant control and ensuring the normal operation of the system.

2. The fault-tolerant control method of the symmetric six-phase motor according to claim 1, characterized in that: The method of converting the six-phase drive system to a three-phase drive system in step 5). Since the six phases are symmetrically and evenly distributed, when the angles between the faulty phases are all 120°, the remaining normal phases will surely form a three-phase drive system with a phase angle difference of 120° from each other.

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