A Fault-Tolerant Control Method for the Rotational Speed of the Driving Motor of a Deep-Sea Robot

Abstract

The present invention discloses a fault-tolerant control method for the rotational speed of a driving motor of a deep-sea robot, which includes the following steps: Step S1, establish a discrete state-space model of the motor based on its electrical and mechanical equations; Step S2, determine the fault characteristic parameters to describe the loss probability of the control signal when it is under attack and interference; Step S3, calculate the feedback control matrix according to the fault characteristic parameters; Step S4, calculate the feedforward control matrix according to the fault characteristic parameters; Step S5, construct a controller based on the feedback control matrix and the feedforward control matrix, calculate the control signal online and transmit it to the actuator; Step S6, the actuator receives the control signal. If a signal loss occurs, the stored control signal is used instead and the control is executed in real time. The present invention can achieve fault-tolerant control of the motor speed under the condition of random loss of the control signal and ensure that the motor speed can stably track a predetermined trajectory.

Description

Technical Field

[0001] The present invention relates to the technical field of deep - sea motor control, and more specifically, to a method for fault - tolerant control of the rotational speed of a driving motor of a deep - sea robot. Background Technique

[0002] As an important driving and control component of underwater equipment, deep - sea DC motors usually have the characteristics of small volume and high power, and the motor housing is generally designed to be sealed to prevent seawater intrusion. Therefore, heat conduction and dissipation of the motor are key issues that must be taken seriously. For this purpose, the heat dissipation system can be optimized through the design of a multi - modular stator structure, that is, using multiple armatures to drive the same rotor and adding impellers between the armatures to improve the heat dissipation efficiency inside the motor. In addition, when the motor operates in the deep - sea environment, it faces various potential attacks and interferences such as cyber - attacks, seawater corrosion, and physical damage. Therefore, when applying deep - sea motors, these potential risks should be considered and corresponding countermeasures should be taken to ensure the stability and reliability of underwater equipment.

[0003] Currently, there are some methods for fault - tolerant control of motors. For example, the Chinese invention patent with publication number CN113844267A discloses a fault - tolerant control system for four - wheel hub motors based on the SQP algorithm, the Chinese invention patent with publication number CN115149883A discloses a fault - tolerant control method for an interior - type five - phase permanent - magnet fault - tolerant motor, and the Chinese invention patent with publication number CN113162517A discloses a fault - tolerant control system and method for a magnetic levitation motor based on self - sensing technology. However, fault - tolerant control methods specifically for deep - sea motors are scarce, especially a method for fault - tolerant control of the rotational speed of a driving motor of a deep - sea robot with a multi - module stator has not yet appeared.

[0004] Therefore, it is necessary to propose a new fault - tolerant control method for the driving motor of a deep - sea robot with a multi - module stator. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above - mentioned deficiencies of the prior art and provide a method for fault - tolerant control of the rotational speed of a driving motor of a deep - sea robot.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A method for fault - tolerant control of the rotational speed of a driving motor of a deep - sea robot includes the following steps:

[0008] Step S1, establishing a discrete state - space model of the motor based on its electrical and mechanical equations;

[0009] Step S2, determining fault characteristic parameters to describe the loss probability of control signals when suffering from attacks and interferences;

[0010] Step S3, calculate the feedback control matrix according to the fault characteristic parameters;

[0011] Step S4, calculate the feedforward control matrix according to the fault characteristic parameters;

[0012] Step S5, construct a controller based on the feedback control matrix and the feedforward control matrix, calculate the control signal online and transmit it to the actuator;

[0013] Step S6, the actuator receives the control signal. If the signal is lost, the stored control signal is used instead and the control is executed in real time.

[0014] Further, in step S1, the process of establishing the electrical and mechanical equations of each armature is as follows:

[0015] For a motor with n armatures driving the same rotor, for the jth (j = 1, 2,..., n) armature, write its electrical equation:

[0016] (1)

[0017] In formula (1), is the armature voltage, is the armature resistance, is the armature current, is the armature inductance, is the time variable, is the armature electromotive force and

[0018] (2)

[0019] In formula (2), is the electromotive force constant of the jth (j = 1, 2,..., n) armature, is the rotor speed;

[0020] The mechanical equation of the motor rotor includes the total torque generated by all armatures:

[0021] (3)

[0022] In formula (3), is the torque constant of the jth (j = 1, 2,..., n) armature;

[0023] The mechanical equation of the motor rotor can be written as:

[0024] (4)

[0025] In formula (4), is the moment of inertia, is the load torque, is the friction coefficient.

[0026] Furthermore, a state - space model of the motor under no - load conditions is established based on the electrical and mechanical equations of the armature, including the following steps:

[0027] Based on Equation (1) and Equation (2), we can obtain:

[0028] (5)

[0029] Arrange Equation (5) into matrix form. Let the motor load torque , and we can obtain the state - space model of the motor under no - load conditions:

[0030] (6)

[0031] In Equation (6), , , ,

[0032] , ,

[0033] is the state vector, is the input vector, is the controlled output.

[0034] Furthermore, a discrete - state - space model of the motor is established based on the state - space model of the motor under no - load conditions, including the following steps:

[0035] Discretize Equation (6) to obtain the discrete - state - space model of the motor:

[0036] (7)

[0037] In Equation (7), is the discrete - time variable, , , is the sampling period, is the base of the natural logarithm.

[0038] Furthermore, in step S2, the process of determining the fault - characteristic parameters is as follows:

[0039] Based on the control signal in the discrete - state - space model of the motor and each component of it, assume The probability of loss is .

[0040] Furthermore, in step S3, the process of calculating the feedback - control matrix is as follows:

[0041] Step S301, initialization, given the matrix in Equation (7) an identity matrix of the same dimension and a zero matrix , given a termination iteration error constant ;

[0042] Step S302, based on the matrix in Equation (7) and , update the value of according to Equation (8);

[0043] (8)

[0044] where , is an all - ones square matrix of order n,

[0045] , the symmetric matrix Q is the weighting matrix for the state vector in Equation (7), representing the degree of emphasis on different state components, the symmetric matrix R is the weighting matrix for the control input in Equation (7), representing the degree of emphasis on the cost of the control input. By adjusting the values of Q and R, a trade - off between the state and the control input can be achieved. The symbol represents the Hadamard product operation of matrices, the superscript represents the transpose operation of matrices, and the superscript represents the inverse operation of matrices;

[0046] Step S303, update the value of such that ;

[0047] Step S304, if , then go to Step S305, otherwise go to Step S302;

[0048] Step S305, calculate and output the feedback control matrix:

[0049] (9).

[0050] Furthermore, in Step S4, the process of calculating the feed - forward control matrix is as follows:

[0051] Step S401, establish an autonomous system model in the form of Equation (10) to describe the preset rotational speed signal that the motor needs to track in real - time,

[0052] (10)

[0053] In Equation (10), is the discrete - time variable, is the state vector of the autonomous system, is the preset rotational speed signal that the motor needs to track in real time, and the matrix and are determined according to the specific form of the rotational speed signal;

[0054] Step S402, calculate the values of the matrix variables and based on Equation (11),

[0055] (11);

[0056] Step S403, calculate the feedforward control matrix based on the values of the matrix variables and obtained from Equation (11) and the feedback control matrix,

[0057] (12)

[0058] In Equation (12), is the feedback control matrix, is the feedforward control matrix.

[0059] Furthermore, in Step S5, the process of calculating the control signal online is as follows:

[0060] Based on the feedback control matrix and the feedforward control matrix construct a controller, and the controller calculates the real-time control signal online according to Equation (13), and sends the obtained control signal to the actuator of the motor in real time,

[0061] (13)

[0062] In Equation (13), and are the state vectors of Equation (7) and Equation (11) respectively.

[0063] Furthermore, in Step S6, the process of executing the control signal in real time is as follows:

[0064] Step S601, the driver in the motor actuator receives the control signal sent by the controller in real time and stores it ;

[0065] Step S602, if at moment, the motor driver does not receive the control signal due to an attack or interference, and the component in it is not received, then use the control signal stored at the previous moment to replace it, and use the following control signal:

[0066] (14)

[0067] and store ;

[0068] Step S603, the motor driver uses the control signal to drive the motor.

[0069] The beneficial effect of the present invention is that the present invention can achieve fault-tolerant control of the motor speed in the case of random loss of the control signal, and ensure that the motor speed can stably track the predetermined trajectory. Description of the Drawings

[0070] Figure 1 is a control structure block diagram of a method for fault-tolerant control of the rotational speed of a driving motor of a deep-sea robot in this embodiment;

[0071] Figure 2 is an effect diagram of a method for fault-tolerant control of the rotational speed of a driving motor of a deep-sea robot in this embodiment;

[0072] Figure 3 is an error diagram of the controlled rotational speed tracking of a driving motor of a deep-sea robot in this embodiment. Detailed Embodiments

[0073] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0074] Embodiment: To solve the problem of fault-tolerant control of a driving motor of a deep-sea robot and improve its operation safety and reliability, this embodiment proposes a method for fault-tolerant control of the rotational speed of a driving motor of a deep-sea robot, as Figure 1 shown, including the following steps:

[0075] Step S1, establish its discrete state space model based on the electrical and mechanical equations of the motor;

[0076] Step S2, determine the fault characteristic parameters to describe the loss probability of the control signal when being attacked and interfered;

[0077] Step S3, calculate the feedback control matrix according to the fault characteristic parameters;

[0078] Step S4, calculate the feedforward control matrix according to the fault characteristic parameters;

[0079] Step S5: Construct a controller based on the feedback control matrix and the feedforward control matrix, calculate the control signal online, and transmit it to the actuator;

[0080] Step S6: The actuator receives the control signal. If a signal loss occurs, the stored control signal is used instead and the control is executed in real time.

[0081] Further, in Step S1, the process of establishing the discrete model of the motor is as follows:

[0082] Without loss of generality, consider a motor with n armatures driving the same rotor. For the j-th (j = 1, 2,..., n) armature, write its electrical equation:

[0083] (1)

[0084] In Equation (1), is the armature voltage, is the armature resistance, is the armature current, is the armature inductance, is the time variable, is the armature electromotive force and

[0085] (2)

[0086] In Equation (2), is the electromotive force constant of the j-th (j = 1, 2,..., n) armature, is the rotor speed;

[0087] The mechanical equation of the motor rotor includes the total torque generated by all armatures:

[0088] (3)

[0089] In Equation (3), is the torque constant of the j-th (j = 1, 2,..., n) armature;

[0090] The mechanical equation of the motor rotor can be written as:

[0091] (4)

[0092] In Equation (4), is the moment of inertia, is the load torque, is the friction coefficient;

[0093] Based on Equations (1) and (2), we can obtain:

[0094] (5)

[0095] Rearrange Equation (5) into matrix form, and let the motor load torque , then the state - space model of the motor under no - load condition can be obtained:

[0096] (6)

[0097] In Equation (6), , , ,

[0098] , ,

[0099] is the state vector, is the input vector, is the controlled output;

[0100] Discretize Equation (6) to obtain the discrete - time state - space model of the motor:

[0101] (7)

[0102] In Equation (7), is the discrete - time variable, , , is the sampling period, is the base of the natural logarithm.

[0103] Furthermore, in step S2, the process of determining the fault - characteristic parameters is as follows:

[0104] Considering potential attacks and interferences such as cyber - attacks and corrosion damage, each component in the control signal in the discrete - state model of the motor Equation (7) may face the situation of random loss,

[0105] Let the probability of loss be .

[0106] Furthermore, in step S3, the process of calculating the feedback - control matrix is as follows:

[0107] Step S301, perform initialization. Given the identity matrix with the same dimension as the matrix in Equation (7) and the zero matrix , and given the termination - iteration error constant ;

[0108] Step S302, based on the matrices and , update according to Equation (8) the value of;

[0109] (8)

[0110] wherein, , is an n-order all-ones square matrix,

[0111] , the symmetric matrix Q is the weighting matrix for the state vector in Equation (7), representing the degree of emphasis on different state components, the symmetric matrix R is the weighting matrix for the control input in Equation (7), representing the degree of emphasis on the cost of the control input. By adjusting the values of Q and R, a trade-off between the state and the control input can be achieved. The symbol represents the Hadamard product operation of matrices, the superscript represents the transpose operation of matrices, and the superscript represents the inverse operation of matrices;

[0112] Step S303, update the value of such that ;

[0113] Step S304, if , then go to Step S305, otherwise go to Step S302;

[0114] Step S305, calculate and output the feedback control matrix:

[0115] (9).

[0116] Furthermore, in Step S4, the process of calculating the feedforward control matrix is as follows:

[0117] Step S401, establish an autonomous system model in the form of Equation (10) to describe the preset speed signal that the motor needs to track in real time,

[0118] (10)

[0119] In Equation (10), is the discrete-time variable, is the state vector of the autonomous system, is the preset speed signal that the motor needs to track in real time. The matrices and are determined according to the specific form of the speed signal;

[0120] Step S402, calculate the values of the matrix variables and based on Equation (11),

[0121] (11);

[0122] Step S403, based on the matrix variables obtained from Equation (11) and the value of, and the feedback control matrix obtained from Equation (9) calculate the feedforward control matrix,

[0123] (12)

[0124] In Equation (12), is the feedback control matrix, is the feedforward control matrix.

[0125] Furthermore, in Step S5, the process of online calculating the control signal is as follows:

[0126] Based on the feedback control matrix obtained from Equation (11) and the feedforward control matrix obtained from Equation (12) construct a controller, and the controller calculates the real-time control signal online according to Equation (13) , and sends the obtained control signal to the actuator of the motor in real time,

[0127] (13)

[0128] In Equation (13), and are the state vectors of Equation (7) and Equation (11) respectively.

[0129] Furthermore, in Step S6, the process of real-time executing the control signal is as follows:

[0130] Step S601, the driver in the motor actuator receives the control signal sent by the controller in real time and stores it ;

[0131] Step S602, if at time, the motor driver does not receive the component in the control signal due to an attack or interference , then use the control signal stored at the previous moment to replace it, that is, use the following control signal:

[0132] (14)

[0133] and store it ;

[0134] Step S603, the motor driver uses the control signal Drive motor

[0135] In this embodiment, a motor that uses three armatures to drive the same rotor is considered, that is , and the characteristic parameters in its electrical equation (1) and mechanical equation (4) are set as: , , , , , , and the sampling period is set , then the specific matrix parameters in the discrete state space model formula (7) of the motor are as follows:

[0136] ,

[0137] In this embodiment, the three components in the control signal , , have random loss probabilities of , , ;

[0138] Let the symmetric weighting matrix in formula (8) be:

[0139] , ;

[0140] The value of the matrix is obtained as follows:

[0141] ,

[0142] And the feedback control matrix is constructed according to formula (9) as follows:

[0143] ;

[0144] The rotational speed that the motor needs to track is set as: , is a generated signal;

[0145] The matrices and in formula (10) are set with the following numerical values:

[0146] , ,

[0147] Solve formula (11) and construct the feedforward control matrix according to formula (12) as follows:

[0148] .

[0149] The control input is obtained according to Equation (13) , and its three components , , are randomly lost with probabilities , , respectively. If a loss occurs, it is processed according to Equation (14), and the control effect of the motor is obtained as shown in Figure 2 , and the tracking error of the motor speed is as shown in Figure 3 . As shown in Figure 1 and Figure 2 , the speed of the motor can better track the predetermined sine trajectory under the condition of controlling random loss, indicating that the fault-tolerant control method of this embodiment can achieve a better fault-tolerant control effect.

[0150] The above are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A fault-tolerant control method for the speed of a deep-sea robot driving motor, characterized in that: The steps include: Step S1, establishing a discrete state space model of the motor based on its electrical and mechanical equations; Step S2, determining fault characteristic parameters to describe the probability of loss of the control signal when it is attacked and interfered; Step S3, calculating a feedback control matrix according to the fault characteristic parameters; Step S4, calculating a feedforward control matrix according to the fault characteristic parameters; Step S5, constructing a controller based on the feedback control matrix and the feedforward control matrix, calculating the control signal online and transmitting it to the actuator; Step S6, the actuator receives the control signal. If the signal is lost, the stored control signal is used instead and the control is performed in real time.

2. According to claim 1, a deep-sea robot driving motor speed fault-tolerant control method is characterized in that: In step S1, the process of establishing the electrical and mechanical equations for each armature is as follows: For a motor with n armatures driving the same rotor, write the electrical equation for the jth (j=1,2,…,n) armature: (1) In formula (1), is the armature voltage, is the armature resistance, is the armature current, is the armature inductance, is the time variable, is the armature emf and (2) In formula (2), is the electromotive force constant of the jth (j=1,2,…,n) armature, is the rotor speed; The mechanical equation for the motor rotor includes the total torque produced by all armatures: (3) In formula (3), is the torque constant of the jth (j=1,2,…,n) armature; The mechanical equation of the motor rotor can be written as: (4) In formula (4), is the moment of inertia, is the load torque, is the friction coefficient.

3. According to claim 2, a deep-sea robot driving motor speed fault-tolerant control method is characterized in that: The state space model of the motor under no-load condition is established based on the armature electrical and mechanical equations, including the following steps: Based on formula (1) and formula (2), we can get: (5) Arrange equation (5) into a matrix form, and let the motor load torque , the state space model of the motor under no-load condition can be obtained: (6) In formula (6), , , , ， ， is the state vector, is the input vector, For the controlled output.

4. According to claim 3, a deep-sea robot driving motor speed fault-tolerant control method is characterized in that: The motor discrete state space model is established based on the state space model of the motor in the no-load state, including the following steps: Discretizing equation (6) yields the discrete state space model of the motor: (7) In formula (7), is a discrete time variable, , , is the sampling period, is the base of natural logarithms.

5. According to claim 1, a deep-sea robot driving motor speed fault-tolerant control method is characterized in that: In step S2, the process of determining the fault characteristic parameters is as follows: Control signals based on the discrete state space model of the motor Each component in , ,set up The probability of loss is .

6. A method for fault-tolerant control of the speed of a deep-sea robot driving motor according to claim 4, characterized in that: In step S3, the process of calculating the feedback control matrix is ​​as follows: Step S301, initialization, given by the matrix in formula (7) Identity matrix of the same dimensions and zero matrix , given the termination iteration error constant ; Step S302, based on the matrix in equation (7) and , update according to formula (8) The value of (8) in, , is an n-order square matrix with all ones. The symmetric matrix Q is the state vector in equation (7) The weighted matrix represents the importance of different state components, and the symmetric matrix R is the control input in equation (7) The weighted matrix represents the importance of the cost of the control input. By adjusting the values ​​of Q and R, the trade-off between the state and the control input can be achieved. The symbol represents the Hadamard product operation of the matrix, the superscript Indicates the transpose operation of the matrix, the superscript Represents the inverse operation of a matrix; Used to indicate control input The probability of loss of each component in is a scalar greater than 0 and less than or equal to 1; Step S303, update The value of ; Step S304, if , then go to step S305, otherwise go to step S302; Step S305, calculate and output the feedback control matrix: (9)。 7. A method for fault-tolerant control of the speed of a deep-sea robot driving motor according to claim 6, characterized in that: In step S4, the process of calculating the feedforward control matrix is ​​as follows: Step S401, establish an autonomous system model in the form of formula (10) to describe the preset speed signal that the motor needs to track in real time, (10) In formula (10), is a discrete time variable, is the state vector of the autonomous system, The matrix is ​​the preset speed signal that the motor needs to track in real time. and Determined according to the specific form of the speed signal; Step S402, calculate the matrix variable based on formula (11) and The value of (11)； Step S403, based on the matrix variable obtained by formula (11) and The value of the feedback control matrix is ​​used to calculate the feedforward control matrix, (12) In formula (12), is the feedback control matrix, is the feedforward control matrix.

8. A method for fault-tolerant control of the speed of a deep-sea robot driving motor according to claim 7, characterized in that: In step S5, the process of online calculation of the control signal is as follows: Based on the feedback control matrix and the feedforward control matrix Construct a controller that calculates the real-time control signal online according to formula (13) , and send the obtained control signal to the motor's actuator in real time. (13) In formula (13), and are the state vectors of equation (7) and equation (11) respectively.

9. A method for fault-tolerant control of the speed of a deep-sea robot driving motor according to claim 8, characterized in that: In step S6, the process of executing the control signal in real time is as follows: Step S601: The driver in the motor actuator receives the control signal sent by the controller in real time. and store ; Step S602, if At this moment, the motor driver does not receive the control signal due to attack or interference. The amount in , the control signal stored at the previous moment is used instead, and the following control signal is used: ， (14) and store ; Step S603: the motor driver uses a control signal Drive motor.

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