Fault-tolerant control method for injection molding manipulator

Abstract

The invention relates to a fault-tolerant control method for an injection molding manipulator. Comprising the following steps of: 1, performing Fourier series analysis on three-phase current when the driver has an open circuit fault, and deriving a Fourier series expression of fault phase current and a lumped parameter Fourier series expression of two normal working phase current; 2, calculating an electromagnetic torque generated after the driver has an open circuit fault; 3, solving a current lumped parameter; 4, deducing a given value of the three-phase current; and 5, comparing the real current value of the injection molding manipulator with the three-phase current given value by using the PI controller, so as to carry out open-circuit fault tolerance control on the driver. According to the method, the three-phase current given value during the open circuit fault is determined on the basis of the Fourier series expression by taking the minimum torque loss before and after the fault as the basic principle, and by means of the method, fault-tolerant control over the open circuit fault of a single power device in the injection molding manipulator servo system can be achieved only by means of an algorithm without additionally adding an auxiliary circuit.

Description

Technical Field

[0001] The invention belongs to the technical field of injection molding manipulators, in particular to a fault-tolerant control method for an injection molding manipulator. Background Art

[0002] In the field of injection molding robots, permanent magnet synchronous motors are widely used because of their high torque output, high power density and efficiency. Permanent magnet synchronous motors can ensure high-speed and precise motion control, thereby improving the working efficiency of equipment during the injection molding process. However, in actual applications, permanent magnet synchronous motor drive systems are prone to failures, especially short faults and open circuit faults are more common.

[0003] Circuit breaker faults usually include circuit breaker of motor windings and circuit breaker of power devices in inverter circuits. These faults will affect the normal operation of the motor, causing obvious torque fluctuations in the three-phase system of the motor, and eventually causing large mechanical vibrations in the injection molding robot, reducing the working stability and accuracy of the equipment, and even causing equipment shutdown in severe cases, affecting production efficiency.

[0004] In order to improve the safety and stability of the injection molding robot system, it is very necessary to design an effective fault-tolerant control strategy for the open-circuit fault of the power device of the permanent magnet synchronous motor inverter circuit. At present, many open-circuit fault-tolerant control methods rely on additional auxiliary circuits. This scheme usually changes the traditional controller structure, such as changing the three-phase three-bridge structure to a three-phase four-bridge arm structure. Although it can achieve fault tolerance, it also increases the complexity of the system. The introduction of complex circuits not only increases the possibility of failure, but also may reduce the reliability of the system.

[0005] Therefore, in the application of injection molding robots, it is necessary to develop a fault-tolerant control strategy that does not require additional auxiliary circuits to improve the system's fault tolerance while maintaining the existing controller structure and ensure that the equipment can still operate stably under fault conditions. This will help reduce equipment downtime and improve the reliability and work efficiency of the production line. Summary of the invention

[0006] To solve the above problems, the present invention provides a fault-tolerant control method for an injection molding robot. The method takes minimizing the torque loss before and after a fault as the basic principle and determines the three-phase current set value during a circuit breaker fault based on a Fourier series expression. Through this method, there is no need to add an additional auxiliary circuit, and only the algorithm is used to realize fault-tolerant control of a circuit breaker fault of a single power device in the servo system of the injection molding robot. The present invention can effectively deal with a single-tube circuit breaker fault in the injection molding robot driver, suppress the pulsation of torque and speed, reduce the torque loss time, optimize the fault current action time, realize smooth switching of the fault-tolerant control current, and thus avoid the overcurrent problem.

[0007] The technical solution of the present invention is described as follows in conjunction with the accompanying drawings:

[0008] A fault-tolerant control method for an injection molding robot comprises the following steps:

[0009] Step 1: Perform Fourier series analysis on the three-phase current when the drive has a circuit breaker fault, and derive the Fourier series expression of the fault phase current and the lumped parameter Fourier series expression of the two normal working phase currents;

[0010] Step 2: Based on the Fourier series expressions of the currents of the faulty phase and the normal phase, the electromagnetic torque T generated after the driver has a short circuit fault is calculated;

[0011] Step 3: Based on the maximum torque principle, the electromagnetic torque T after the fault is set to be equal to the electromagnetic torque when the equipment is working normally, so as to solve the current lumped parameters;

[0012] Step 4: Substitute the solved current lumped parameters into the Fourier series expression of the normal phase current, and combine with the Fourier series expression of the fault phase current to derive the given values ​​of the three-phase current;

[0013] Step 5: Use the PI controller to compare the actual current value of the injection molding robot with the three-phase current given value, and input the given value into the given value in the motor PI to perform fault-tolerant control.

[0014] Furthermore, the faulty phase refers to a phase winding of a motor connected to a power device having a short circuit fault; and the normal phase refers to a phase winding connected to a power device operating normally.

[0015] Furthermore, the specific method of step one is as follows:

[0016] 11) The three phase windings of the injection molding robot are respectively recorded as A phase winding, B phase winding and C phase winding; each phase winding is connected to a midpoint of a bridge arm of the inverter circuit, and each bridge arm includes an upper bridge arm power device and a lower bridge arm power device;

[0017] 12) The Fourier series expression for determining the fault phase current is:

[0018]

[0019] In the formula, i n is the higher harmonic component of the fault phase current; I m is the amplitude of the stator current; θ e is the angle of the rotor position; i is the number of the corresponding ABC three-phase winding; c is the number of the upper and lower bridge faults; I dc is the DC component of the fault phase current; Δi n is the error of the higher harmonic components of the barrier phase current;

[0020] Among them, the DC component of the fault phase current

[0021] The higher harmonic components of the fault phase current are:

[0022]

[0023] 13) When the A phase winding fails, set n = A and corresponding i = 1; when the B phase winding fails, set n = B and corresponding i = 2; when the C phase winding fails, set n = C and corresponding i = 3; if the fault occurs in the power device of the upper arm of the bridge connected to the faulty phase, set c = -1; and when the fault occurs in the power device of the lower arm, set c = 1;

[0024] 14) Determine the lumped parameter Fourier series expression of the normal phase current:

[0025]

[0026] In the formula, i p is the current phasor, specifically the current value of the permanent magnet synchronous motor in the fault phase; I m is the maximum amplitude of the current, i.e. the peak current; θ e is the electrical angle, i.e. the angular position of the motor rotor; j is the phase sequence number, which takes values ​​of 1, 2, and 3, corresponding to phase A, phase B, and phase C, respectively; D p For supplementary value.

[0027] Furthermore, the specific method of step 2 is as follows:

[0028] 21) According to the position of the bridge arm where the power device with the circuit breaker fault is located in the driver, determine the fault phase and the normal phase in the A phase winding, the B phase winding and the C phase winding;

[0029] 22) Through the Fourier series expressions of the fault phase current and the normal phase current, the A phase winding current I A , B phase winding current I B and C phase winding current I C The corresponding expression of the electromagnetic torque T after the driver circuit breaker failure occurs ef The expression is:

[0030]

[0031] In the formula, i Af is the phase current of phase A winding; e A is the back electromotive force of phase A winding; i Bf is the phase current of the B phase winding; e Bis the back electromotive force of the B-phase winding; i Cf is the phase current of the C phase winding; e C is the back electromotive force of the C-phase winding; ω r is the motor rotor angular velocity;

[0032] Among them, e A , e B , e C The expression is as follows:

[0033]

[0034] Where P r is the number of motor pole pairs; ω r is the motor rotor angular velocity; F f is the permanent magnet flux; θ e is the rotor position angle.

[0035] Furthermore, the specific method of step three is as follows:

[0036] When an open circuit fault occurs in one of the upper or lower bridge arm power devices connected to the A phase winding, the current lumped parameter D of the B phase winding is obtained by substituting it into the solution. B and the current lumped parameter D of the C phase winding C They are:

[0037]

[0038] In the formula, I dc is the bus current, Δi A is the phase A current error, θ e is the rotor angular position;

[0039] When an open circuit fault occurs in one of the upper or lower bridge arm power devices connected to the B phase winding, the current lumped parameter D of the A phase winding is obtained by substituting it into the solution. A and the current lumped parameter D of the C phase winding C ;

[0040] When an open circuit fault occurs in one of the upper or lower bridge arm power devices connected to the C phase winding, the current lumped parameter D of the A phase winding is obtained by substituting it into the solution. A and the current lumped parameter D of the B phase winding B ;

[0041] Furthermore, the specific method of step 4 is as follows:

[0042] Substitute the solved current lumped parameters into the Fourier series expression of the healthy phase current, and combine them with the Fourier series expression of the fault phase current to obtain the given values ​​of the three-phase current.

[0043] Furthermore, the specific method of step five is as follows:

[0044] Using the PI controller, the actual current value of the injection molding robot is compared with the three-phase current given value, and the given value is input into the given value in the motor PI, so as to perform fault-tolerant control, as follows:

[0045] 51) Correct the current given value of the normal phase; determine the phase current given value after smooth transition correction of the normal phase

[0046] Where, ki is a positive current coefficient; Im is the amplitude of the stator current, and the parameter k corresponding to the normal phase after the fault phase in the phase sequence is 1, and the parameter k corresponding to the other normal phase is -1;

[0047] 52) When no fault occurs, that is, when all power devices on all bridge arms of the driver are working normally, the speed loop is used to obtain the q-axis current set value, and the d-axis current set value is taken and combined with the d-axis real current value id and the q-axis real current value iq, so as to control the on and off of each power device in the driver based on the SVPWM modulation method.

[0048] The beneficial effects of the present invention are:

[0049] 1) The present invention takes minimizing the torque loss before and after the fault as the basic principle, and determines the three-phase current given value when the circuit is broken based on the Fourier series expression. In this way, it is possible to achieve fault-tolerant control of the circuit breakage of a single power device in the injection molding robot servo system by relying only on the algorithm without adding additional auxiliary circuits;

[0050] 2) The present invention can effectively deal with the single-tube circuit breaker fault in the injection molding robot driver, suppress the pulsation of torque and speed, and reduce the torque loss time; the method also optimizes the fault current action time, realizes the smooth switching of fault-tolerant control current, thereby avoiding the overcurrent problem. In addition, the method also has good dynamic response capability and robustness to speed and load changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0052] Figure 1 This is a schematic diagram of the circuit structure of the injection molding robot driver;

[0053] Figure 2This is a control block diagram of the fault-tolerant control method proposed in this application. DETAILED DESCRIPTION

[0054] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0055] Embodiment 1

[0056] This embodiment provides a fault-tolerant control method for an injection molding robot. Figure 1 This common injection molding robot drive structure is implemented without additional auxiliary circuits, and fault-tolerant control is achieved only through software control. Please combine Figure 2 The control block diagram shown specifically includes the following steps:

[0057] Step 1: Perform Fourier series analysis on the three-phase current when the drive has a circuit breaker fault, and derive the Fourier series expression of the fault phase current and the lumped parameter Fourier series expression of the two normal working phase currents, as follows:

[0058] 11) If Figure 1 As shown, the injection molding robot includes three phase windings, which are respectively recorded as A-phase winding, B-phase winding and C-phase winding. Each phase winding is connected to the midpoint of a bridge arm of the inverter circuit, and each bridge arm includes an upper bridge arm power device and a lower bridge arm power device.

[0059] The fault-tolerant control method of this embodiment is mainly aimed at the situation where a single power device in the inverter circuit has a short circuit fault. When a power device has a short circuit fault, one phase winding of the injection molding robot with the short circuit fault power device is the fault phase, and the other two phase windings are normal phases. Figure 1 In the driver circuit structure, when the power device T1 has a short circuit fault, the A-phase winding is the faulty phase, and the B-phase winding and the C-phase winding are both normal phases.

[0060] Fault current analysis is performed when a single power device in the inverter circuit of the injection molding robot driver fails:

[0061] When all power devices in the inverter circuit are working normally, the phase current i of the A-phase winding, B-phase winding and C-phase winding in the injection molding robot is A 、i B 、i C In the stationary coordinate system it is expressed as:

[0062]

[0063] Where Im is the amplitude of the stator current and θe is the rotor position angle;

[0064] 12) The Fourier series expression of the determined fault phase current is:

[0065]

[0066] Among them, the DC component of the fault phase current is:

[0067]

[0068] Higher harmonic components of fault phase current:

[0069]

[0070] Wherein, N is the harmonic order; i is the serial number of the fault phase arranged by the phase number; when the fault phase n is the A phase winding, n=A and the corresponding i=1, or, when the fault phase n is the B phase winding, n=B and the corresponding i=2, or, when the fault phase n is the C phase winding, n=C and the corresponding i=3;

[0071] When the upper bridge arm power device of the bridge arm connected to the fault phase has a circuit breakage fault, c=-1; when the lower bridge arm power device of the bridge arm connected to the fault phase has a circuit breakage fault, c=1; for example, based on Figure 1 In the circuit diagram, when the power device T1 has a short circuit fault, the A phase winding is the fault phase and c=-1.

[0072] The Fourier series expression of the determined normal phase current including the current lumped parameters is:

[0073]

[0074] Where D p is the current lumped parameter of the normal phase p; j is the serial number of the normal phase arranged by the phase number, when the normal phase p is the A phase winding, p=A and the corresponding j=1, or, when the normal phase p is the B phase winding, p=B and the corresponding j=2, or, when the normal phase p is the C phase winding, p=C and the corresponding j=3. Since n≠p, i≠j.

[0075] Based on this, under six different fault conditions, when a single power device in the inverter circuit fails, the phase current I of the A phase winding is Af , the phase current I of the B phase winding Bf , the phase current I of the C phase winding Cf The Fourier series expressions are:

[0076] The upper bridge arm power device T1 connected to the A phase winding has a circuit breaker fault, and the expression is as follows:

[0077]

[0078] The lower bridge arm power device T2 connected to the A phase winding has a circuit breaker fault, and the expression is as follows:

[0079]

[0080] The upper bridge arm power device T3 connected to the B phase winding has a circuit breaker fault, and the expression is as follows:

[0081]

[0082] The lower bridge arm power device T4 connected to the B phase winding has a circuit breaker fault, and the expression is as follows:

[0083]

[0084] The upper bridge arm power device T5 connected to the C phase winding has a circuit breaker fault, and the expression is as follows:

[0085]

[0086] The lower bridge arm power device T6 connected to the C phase winding has a circuit breaker fault, and the expression is as follows:

[0087]

[0088] Step 2: Based on the Fourier series expressions of the currents of the faulty phase and the normal phase, the electromagnetic torque T generated by the drive after the short circuit fault occurs is calculated. The electromagnetic torque Tef after the fault is based on the expression of the current lumped parameters.

[0089] Electromagnetic torque of the injection molding robot under normal working conditions:

[0090]

[0091] Where P r F is the number of motor pole pairs; f is the permanent magnet flux; when there is a short circuit fault in the power device in the inverter circuit, the electromagnetic torque under the short circuit fault condition can no longer be calculated according to the above formula, but the electromagnetic torque T after the driver short circuit fault occurs ef It can still be generated by the interaction of phase current and back electromotive force. Therefore, the fault phase and normal phase in the A-phase winding, B-phase winding and C-phase winding are determined according to the bridge arm position where the power device with short circuit fault occurs in the driver, and the expressions of the phase current iAf of the A-phase winding, the phase current iBf of the B-phase winding and the phase current iCf of the C-phase winding are obtained according to the Fourier series expressions of the fault phase current and the normal phase current when a single power device short circuit fault occurs in the inverter circuit. According to:

[0092]

[0093] The electromagnetic torque T after the driver circuit breaker fault occurs can be obtained ef Expression of

[0094] In the formula, ω r is the motor rotor angular velocity; e A 、e B 、e C They are the back electromotive force of phase A winding, phase B winding, and phase C winding respectively:

[0095]

[0096] Step 3: Based on the maximum torque principle, the electromagnetic torque T after the fault is set to be equal to the electromagnetic torque when the equipment is working normally, so as to solve the current lumped parameters, as follows:

[0097] For example, in an example, when an open circuit fault occurs in one of the upper bridge arm power devices connected to the A phase winding, the current lumped parameter D of the B phase winding can be obtained by substituting B and the current lumped parameter D of the C phase winding C They are:

[0098]

[0099] In the formula, I dc is the bus current, Δi A is the current error of phase A, θ e is the rotor angular position;

[0100] When an open circuit fault occurs in one of the upper or lower bridge arm power devices connected to the B phase winding, the current lumped parameter D of the A phase winding is obtained by substituting it into the solution. A and the current lumped parameter D of the C phase winding C ;

[0101] When an open circuit fault occurs in one of the upper or lower bridge arm power devices connected to the C phase winding, the current lumped parameter D of the A phase winding is obtained by substituting it into the solution. A and the current lumped parameter D of the B phase winding B ;

[0102] In the normal operation of the injection molding robot, the phase current of the three-phase winding is sinusoidal and the electromagnetic torque remains stable. When a power device of the driver fails, the current of the faulty phase will deviate from the sinusoidal waveform. Since the sum of the three-phase current of the stator should be zero, the current of the healthy phase will also be affected, resulting in fluctuations and losses in the electromagnetic torque.

[0103] For example, when the upper bridge arm power device T_1 connected to the A-phase winding fails, the A-phase winding current i_Af loses the positive half cycle, while the negative half cycle remains close to the sine waveform, but slightly distorted. At the same time, the B-phase and C-phase winding currents i_Bf and i_Cf are also affected, which in turn causes significant fluctuations and losses in torque.

[0104] In order to ensure that the injection molding robot can continue to work when a fault occurs, it is necessary to suppress the torque drop after the short circuit fault. The ideal fault-tolerant control should make the torque characteristics of the motor as similar as possible to those in normal operation. Therefore, in order to minimize the torque loss before and after the fault, the electromagnetic torque T_ef after the fault is set equal to the electromagnetic torque T_e during normal operation, and the current lumped parameter D_p of the two healthy phases is solved through this condition. For example, in an example, when the upper bridge arm power device T1 connected to the A-phase winding has a short circuit fault, the current lumped parameter DB of the B-phase winding and the current lumped parameter DC of the C-phase winding can be solved as follows:

[0105]

[0106] In other fault situations, the current lumped parameters of the two normal phases can be obtained by substituting the same logic, and the present invention will not elaborate on them one by one.

[0107] Step 4: Substitute the solved current lumped parameters into the Fourier series expression of the normal phase current, and combine them with the Fourier series expression of the fault phase current to derive the given values ​​of the three-phase current, as follows:

[0108] For example, in an example, when the upper bridge arm power device T1 connected to the A phase winding has a short circuit fault, the current lumped parameters DB and DC obtained above are substituted into the expression to obtain the current given values ​​of the A phase winding, the B phase winding and the C phase winding. The values ​​are:

[0109]

[0110] The three-phase current given values ​​can be obtained similarly for other fault conditions, which will not be described in detail in the present invention.

[0111] Step 5: Use the PI controller to compare the actual current value of the injection molding robot with the three-phase current given value, so as to perform circuit breaker fault tolerance control on the driver, as follows:

[0112] For example, when the upper bridge arm power device T1 connected to the A phase winding has a circuit breaker fault, θ e The phase current given value after smooth transition correction of the B-phase winding and the C-phase winding within the range of ∈[θ1, θ2] is:

[0113]

[0114] Then, the above given value is directly input into the given value input in the motor PI, thereby performing fault-tolerant control.

[0115] When no fault occurs, that is, when all power devices on each bridge arm of the driver are working normally, the speed loop is used to obtain the q-axis current set value, and the d-axis current set value is taken and combined with the d-axis real current value id and the q-axis real current value iq, so as to control the on and off of each power device in the driver based on the SVPWM modulation method.

[0116] In summary, the present invention takes minimizing the torque loss before and after the fault as the basic principle, and determines the three-phase current given value at the time of the circuit breaker fault based on the Fourier series expression. Through this method, there is no need to add additional auxiliary circuits, and only the algorithm can be used to realize the fault-tolerant control of the circuit breaker fault of a single power device in the injection molding robot servo system. This scheme can effectively deal with the single-tube circuit breaker fault in the injection molding robot driver, suppress the pulsation of torque and speed, and reduce the torque loss time; the method also optimizes the fault current action time, realizes the smooth switching of the fault-tolerant control current, thereby avoiding the overcurrent problem. In addition, the method has good dynamic response capability and robustness to speed and load changes.

[0117] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A fault-tolerant control method for an injection molding robot, characterized in that: The following steps are involved: Step 1: Perform Fourier series analysis on the three-phase current when the drive has a circuit breaker fault, and derive the Fourier series expression of the fault phase current and the lumped parameter Fourier series expression of the two normal working phase currents; Step 2: Based on the Fourier series expressions of the currents of the faulty phase and the normal phase, calculate the electromagnetic torque T generated by the drive after a circuit breaker fault occurs. ef ; Step 3: Based on the maximum torque principle, set the electromagnetic torque T after the fault ef It is equal to the electromagnetic torque when the equipment is working normally, so the current lumped parameters are solved; Step 4: Substitute the solved current lumped parameters into the Fourier series expression of the normal phase current, and combine with the Fourier series expression of the fault phase current to derive the given values ​​of the three-phase current; Step 5: Use the PI controller to compare the actual current value of the injection molding robot with the three-phase current given value, and input the given value into the given value in the motor PI to perform fault-tolerant control.

2. The fault-tolerant control method for an injection molding robot according to claim 1, characterized in that: The fault phase refers to the motor phase winding connected to the power device with the short circuit fault; the normal phase refers to the phase winding connected to the power device with the normal operation.

3. The fault-tolerant control method for an injection molding robot according to claim 2, characterized in that: The specific method of step one is as follows: 11) The three phase windings of the injection molding robot are respectively recorded as A phase winding, B phase winding and C phase winding; each phase winding is connected to a midpoint of a bridge arm of the inverter circuit, and each bridge arm includes an upper bridge arm power device and a lower bridge arm power device; 12) The Fourier series expression for determining the fault phase current is: In the formula, i n is the higher harmonic component of the fault phase current; I m is the amplitude of the stator current; θ e is the angle of the rotor position; i is the number of the corresponding ABC three-phase winding; c is the number of the upper and lower bridge faults; I dc is the DC component of the fault phase current; Δi n It is the higher harmonic component of the barrier phase current; Among them, the DC component of the fault phase current The higher harmonic components of the fault phase current are: 13) When the A phase winding fails, set n = A and corresponding i = 1; when the B phase winding fails, set n = B and corresponding i = 2; when the C phase winding fails, set n = C and corresponding i = 3; if the fault occurs in the power device of the upper arm of the bridge connected to the faulty phase, set c = -1; and when the fault occurs in the power device of the lower arm, set c = 1; 14) Determine the lumped parameter Fourier series expression of the normal phase current: In the formula, i p is the current phasor, specifically the current value of the permanent magnet synchronous motor in the fault phase; I m is the maximum amplitude of the current, i.e. the peak current; θ e is the electrical angle, i.e. the angular position of the motor rotor; j is the phase sequence number, which takes values ​​of 1, 2, and 3, corresponding to phase A, phase B, and phase C, respectively; D p For supplementary value.

4. The fault-tolerant control method for an injection molding robot according to claim 1, characterized in that: The specific method of step 2 is as follows: 21) According to the position of the bridge arm where the power device with the circuit breaker fault is located in the driver, determine the fault phase and the normal phase in the A phase winding, the B phase winding and the C phase winding; 22) Through the Fourier series expressions of the fault phase current and the normal phase current, the A phase winding current I A , B phase winding current I B and C phase winding current I C The corresponding expression of the electromagnetic torque T after the driver circuit breaker failure occurs ef The expression is: In the formula, i Af is the phase current of phase A winding; e A is the back electromotive force of phase A winding; i Bf is the phase current of the B phase winding; e B is the back electromotive force of the B-phase winding; i Cf is the phase current of the C phase winding; e C is the back electromotive force of the C-phase winding; ω r is the motor rotor angular velocity; Among them, e A , e B , e C The expression is as follows: Where P r is the number of motor pole pairs; ω r is the motor rotor angular velocity; F f is the permanent magnet flux; θ e is the rotor position angle.

5. The fault-tolerant control method for an injection molding robot according to claim 1, characterized in that: The specific method of step three is as follows: When an open circuit fault occurs in one of the upper or lower bridge arm power devices connected to the A phase winding, the current lumped parameter D of the B phase winding is obtained by substituting it into the solution. B and the current lumped parameter D of the C phase winding C They are: In the formula, I dc is the bus current, Δi A is the phase A current error, θ e is the rotor angular position; When an open circuit fault occurs in one of the upper or lower bridge arm power devices connected to the B phase winding, the current lumped parameter D of the A phase winding is obtained by substituting it into the solution. A and the current lumped parameter D of the C phase winding C ; When an open circuit fault occurs in one of the upper or lower bridge arm power devices connected to the C phase winding, the current lumped parameter D of the A phase winding is obtained by substituting it into the solution. A and the current lumped parameter D of the B phase winding B。 6. The fault-tolerant control method for an injection molding robot according to claim 1, characterized in that: The specific method of step 4 is as follows: Substitute the solved current lumped parameters into the Fourier series expression of the healthy phase current, and combine them with the Fourier series expression of the fault phase current to obtain the given values ​​of the three-phase current.

7. The fault-tolerant control method for an injection molding robot according to claim 1, characterized in that: The specific method of step five is as follows: Using the PI controller, the actual current value of the injection molding robot is compared with the three-phase current given value, so as to perform circuit breaker fault tolerance control on the driver, as follows: 51) Correct the current given value of the normal phase; determine the phase current given value after smooth transition correction of the normal phase Where, ki is a positive current coefficient; Im is the amplitude of the stator current, and the parameter k corresponding to the normal phase after the fault phase in the phase sequence is 1, and the parameter k corresponding to the other normal phase is -1; 52) When all power devices on all bridge arms of the driver are operating normally, the speed loop is used to obtain the q-axis current given value and the d-axis current given value is taken and combined with the d-axis real current value id and the q-axis real current value iq to control the on and off of each power device in the driver based on the SVPWM modulation method.

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