CN114244196B - A fault-tolerant control method for Hall sensor of permanent magnet synchronous motor - Google Patents

Abstract

The invention belongs to the technical field of permanent magnet synchronous motor control, and specifically discloses a fault-tolerant control method for a Hall sensor of a permanent magnet synchronous motor. Under the assumption of constant speed operation, a position error calculation formula of a Hall sensor signal is obtained; when an upper diode of an inverter is used to perform a freewheeling operation, the relationship between parameters such as phase current and back electromotive force is used to deduce the commutation time of the motor; when a lower diode of the inverter is used to perform a freewheeling operation, the commutation time is derived according to an expression of a DC bus voltage; an optimal advance time and an optimal lead angle are derived according to the commutation times of two working states of the motor; and an active lead angle of a Hall sensor compensation method is summarized, which overcomes the shortcomings of the prior art, can accurately estimate the optimal angle for compensating the Hall sensor when the installation position of the Hall sensor is inaccurate, and improves the accuracy of the movement of the permanent magnet synchronous motor.

Description

A fault-tolerant control method for Hall sensor of permanent magnet synchronous motor

Technical Field

The invention belongs to the technical field of permanent magnet synchronous motor control, and in particular relates to a fault-tolerant control method of a Hall sensor of a permanent magnet synchronous motor.

Background Art

Permanent magnet synchronous motor has many advantages such as simple structure, high power density, simple control, etc. In recent years, permanent magnet synchronous motor has been increasingly widely used in industrial fields such as high-performance speed regulation system and servo control system.

The Hall sensors in brushless DC motors are ideally placed at 120 electrical degrees. However, the placement of the Hall sensors can be inaccurate, especially in high-precision and small-size motors. These misaligned Hall sensors can cause severe torque ripples and are difficult to apply.

Due to the absence of Hall sensors, the sensorless control scheme of BLDC motor is a good choice to avoid Hall sensor errors. The sensorless methods of BLDC motor can be divided into back-EMF voltage sensing, flux estimation and freewheeling diode conduction detection, however, none of them can work properly in all speed ranges, especially in the low speed range. Usually, the practical minimum speed of traditional sensorless drives is about 10% of the rated speed. Therefore, low-speed sensorless operation requires an additional control method.

Summary of the invention

The purpose of the present invention is to provide a fault-tolerant control method for a permanent magnet synchronous motor Hall sensor, which overcomes the shortcomings of the prior art and solves the problem in the prior art that it is difficult to accurately estimate the rotor position of a permanent magnet synchronous motor after the Hall sensor is incorrectly installed, resulting in the motor being unable to drive normally.

To solve the above problems, the technical solutions adopted by the present invention are as follows:

A permanent magnet synchronous motor Hall sensor fault-tolerant control method, when the permanent magnet synchronous motor Hall sensor is installed in an incorrect position, the relationship between the Hall sensor signal, input voltage and input current is obtained to obtain the optimal advance angle to adjust the motor, including:

Step 1: Under the assumption of constant speed operation, the relative error compensation angle of the Hall sensor is derived using the interval relationship of the Hall sensor signal compensation;

Step 2: When the upper diode of the inverter is used to perform freewheeling operation, the voltage equation of the motor is derived using the relationship between the phase current, back electromotive force and DC bus voltage;

Step 3: Integrate the voltage equation and use the integral equation of back electromotive force to obtain the commutation time of the motor;

Step 4: When the inverter's lower diode is used to perform freewheeling operation, a voltage equation is obtained through the DC bus voltage and the neutral line voltage, and the commutation time is obtained by integration;

Step 5: Derivation of the optimal advance time and optimal lead angle of the motor commutation by obtaining the commutation time of the motor in two working states;

Step 6: Combine the relative error compensation angle of the Hall sensor and the optimal advance angle to summarize the optimal advance angle for commutation. During the operation of the motor, correct the commutation time of the Hall sensor with the wrong installation position.

Furthermore, in step 1, the three-phase Hall sensor of the permanent magnet synchronous motor divides one electrical cycle of the permanent magnet synchronous motor into six regions, and the six regions are equally spaced by 60 electrical degrees. However, due to the misalignment of the Hall sensor, the combination of the actual sensor signal is irregularly repeated, as shown in Figure 1. Assuming that the motor runs at a constant speed, the relative error compensation angle of the Hall sensor can be derived as:

Furthermore, in step 2, when the upper diode of the inverter is used to perform the freewheeling operation, the back electromotive force is a sine wave, and the sum of the phase currents is zero. The equivalent circuit diagram is shown in FIG2 . Ignoring the resistance component, the relationship between the u-phase and v-phase voltages can be obtained through the expression of the DC bus voltage in the equivalent circuit. Combined with the above formula, the voltage equation can be written as:

Furthermore, in step 3, considering that the inverter is operated based on the pulse width modulation method, the voltage equation in step 2 is a voltage equation based on the instantaneous time model, so the voltage equation is integrated and combined with the equivalent circuit diagram to obtain:

Where L is the phase inductance, iu, iv and iw are the phase currents, Vdc is the input voltage, eu, ev and ew are the back EMFs, and D is the duty cycle.

Combined with the integral equation of back electromotive force, the commutation time t2-t1 can be obtained as:

In order to obtain the best lead angle, the relationship between I3 and I2 is derived by combining the relationship between steps 2 and 3. The commutation time is obtained by substituting it into:

Furthermore, in step 4, according to the relationship between the voltage equation in step 2 and the DC bus voltage, the DC bus voltage can be rewritten as:

From the above formula, we can conclude that the relationship between phase u and phase v is:

Using the relationship between the neutral voltage and the u-phase and v-phase voltages, the motor commutation time is integrated as follows:

Furthermore, in step 5, considering that the back EMF has different signs in step 3 and step 4, the commutation time can be summarized as:

The best advance time is half of the commutation time. Converting it into radians, the best lead angle is:

Where f is the electrical angular frequency, which is the inverse of the electrical angular period.

In step six, the optimal advance angle of commutation is obtained. The specific method is as follows:

Combining the relative error compensation angle of the Hall sensor in step one and the optimal advance angle in step five, the optimal advance angle for commutation is obtained. By referring to the obtained optimal advance angle, the problem of motor imbalance caused by incorrect installation of the Hall sensor position can be avoided, and commutation can be achieved more accurately.

Compared with the prior art, the present invention has the following beneficial effects:

1. By obtaining the relationship between the Hall sensor signal, input voltage and input current, the optimal advance angle is obtained to adjust the motor, solving the problem of motor imbalance caused by incorrect installation of the Hall sensor position of the permanent magnet synchronous motor in the prior art;

2. The relationship between the Hall sensor signal, input voltage and input current is obtained to obtain the optimal advance angle to adjust the motor, solving the problem of low accuracy of the commutation time estimation method during the operation of the permanent magnet synchronous motor;

3. By obtaining the relationship between the Hall sensor signal, input voltage and input current, the optimal advance angle is obtained to adjust the motor. When the installation position of the Hall sensor is inaccurate, the optimal angle to compensate the Hall sensor can be accurately estimated, thereby improving the accuracy of the permanent magnet synchronous motor movement.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 Hall sensor signal generated by incorrect installation of the Hall sensor;

FIG2 is an equivalent circuit diagram when the upper diode of the inverter is used to perform freewheeling operation;

FIG3 is an equivalent circuit diagram when the lower diode of the inverter is used to perform a freewheeling operation;

FIG4 is a flow chart of a fault-tolerant control method of a Hall sensor of a permanent magnet synchronous motor.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

As shown in the figure, the present invention provides a permanent magnet synchronous motor Hall sensor fault-tolerant control method, as shown in FIG4, comprising the following steps:

Step S1: The permanent magnet synchronous motor is generally equipped with three symmetrically installed Hall sensors. The coded signal generated by the three-phase Hall sensor can divide one electrical cycle of the permanent magnet synchronous motor (there is a linear relationship between the electrical cycle and the physical cycle, and its proportionality coefficient depends on the number of motor pole pairs) into six regions, because the Hall sensor is ideally placed between 120 electrical degrees. However, due to the misalignment of the Hall sensors, the combination of actual sensor signals is irregularly repeated, as shown in Figure 1.

Under the assumption of constant speed operation, the interval of compensating the Hall sensor signal can be expressed as:

Where Δφ'12, Δφ'23 and Δφ'31 are the intervals of compensated Hall sensor signals, Δφ12, Δφ23 and Δφ31 are the intervals of actual Hall sensors, and φ1, φ2 and φ3 are the position errors of Hall sensor signals. The distance between the compensated Hall sensor signals is 120 degrees, and the sum of the Hall sensor signal intervals is 2π. Therefore, Δφ and the Hall sensor signal intervals can be expressed as:

Through equations (1)-(3), the Hall sensor signal error can be derived as:

Assuming that the Hall sensor error φ1 is zero, (4) can be rewritten as:

Step S2: When the freewheeling operation is performed using the upper diode of the inverter, the equivalent circuit during the commutation transient is shown in Figure 2. Therefore, the phase current and back EMF can be written as

In the equivalent circuit, the DC-link voltage can be expressed as:

Assuming the resistance component is neglected, the voltage equation can be written as:

By using (7) and (8), the DC link voltage can be rewritten as:

From (9), the relationship between the u-phase and v-phase voltages can be derived as:

From these equations, the voltage equation can be derived as:

Step S3: Considering that the inverter is operated based on the pulse width modulation method, the voltage equation in formula (11) is a voltage equation based on the instantaneous time model, so the voltage equation is integrated and combined with the equivalent circuit diagram to obtain:

Where L is the phase inductance, iu, iv and iw are the phase currents, Vdc is the input voltage, eu, ev and ew are the back EMFs, and D is the duty cycle.

The integral equation of back EMF can be expressed as:

From (12) and (13), the commutation time t2-t1 can be obtained as:

Substituting formula (14) into formula (12), we get:

Where E is the RMS value of the back EMF. Before commutation, I2 is the same as Idc. From (14) and (15), the commutation time t2-t1 can be obtained as:

Step S4: When the bottom diode of the inverter is used to perform the freewheeling operation, the equivalent circuit during the commutation transient is shown in FIG3 , and the DC bus voltage can be expressed as:

Combining equations (8) and (17), the DC bus voltage can be rewritten as:

From equation (18), we can conclude that the relationship between phase u and phase v is:

By using (22), the neutral voltage vs can be expressed as:

From these equations, the voltage equation can be derived as follows:

From (13) and (21), the commutation time t2-t1 can be obtained as:

To obtain I3, using I2, (26) is substituted into (25):

For I3, formula (23) can be summarized as:

Before commutation, I2 is the same as Idc. From (22) and (24), the commutation time t2-t1 can be derived as:

Considering the different signs of the back EMF components in the commutation time expressions of step 3 and step 4, the commutation time can be summarized as:

Step S5: Since the optimal advance time is half of the commutation time, the optimal advance time ta can be derived as:

Equation (31) is a time equation. By converting it into radians, the optimal lead angle θ _a can be calculated:

From step 4, it can be seen that there is a linear relationship between the motor acceleration and Δi _q =i _q ^* -i _q . In the motor acceleration and deceleration operation stage, the difference Δi _q =i _q ^* -i _q between the set torque current i _q ^* and the actual torque current i _q is large, so Δi _q =i _q ^* -i _q is introduced into the angular acceleration estimation formula to improve the control performance in the acceleration and deceleration stage. When the motor runs at a low speed, that is, the estimated speed n is the rated speed. To reduce the error, The torque current difference is introduced into the estimated angular acceleration calculation. That is, the estimated angular acceleration for:

Step S6: As shown in Table 1, the corresponding optimal advance angle of commutation is obtained by combining the relative error compensation angle of the Hall sensor in step 1 and the optimal lead angle in step 5. The optimal lead angle of commutation is different according to the working range of the rotor. The optimal lead angle is applied according to the rotor position, thereby avoiding the imbalance problem caused by damage to the Hall sensor.

Table 1

In summary, the fault-tolerant control method of the Hall sensor of a permanent magnet synchronous motor described in the present invention analyzes a brushless DC motor with a sinusoidal back electromotive force and compensates for the Hall sensor signal error. Through the mathematical analysis of the sinusoidal brushless DC motor with Hall sensor misalignment, a method of using the Hall sensor signal, input voltage and input current to improve the performance and current ripple of the brushless DC motor system by adopting an online advance angle adjustment method without increasing the configuration of the brushless DC motor system is proposed. In particular, the optimal advance angle adjustment method can be applied to the sensor brushless DC motor system.

It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and range of equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims (7)

1. A fault-tolerant control method for a permanent magnet synchronous motor Hall sensor, characterized in that it comprises the following steps: Step 1: Under the assumption of constant speed operation, the relative error compensation angle of the Hall sensor is derived using the interval relationship of the Hall sensor signal compensation; Step 2: When the upper diode of the inverter is used to perform freewheeling operation, the voltage equation of the motor is derived using the relationship between the phase current, back electromotive force and DC bus voltage; Step 3: Integrate the voltage equation and use the integral equation of back electromotive force to obtain the commutation time of the motor; Step 4: When the inverter's lower diode is used to perform freewheeling operation, a voltage equation is obtained through the DC bus voltage and the neutral line voltage, and the commutation time is obtained by integration; Step 5: Derivation of the optimal advance time and optimal lead angle of the motor commutation by obtaining the commutation time of the motor in two working states; Step 6: Combine the relative error compensation angle of the Hall sensor and the optimal advance angle to summarize the optimal advance angle for commutation. During the operation of the motor, correct the commutation time of the Hall sensor with the wrong installation position. Under the assumption of constant speed operation, the interval of the compensated Hall sensor signal is expressed as: Where Δφ'12, Δφ'23 and Δφ'31 are the intervals of compensated Hall sensor signals, Δφ12, Δφ23 and Δφ31 are the intervals of actual Hall sensors, and φ1, φ2 and φ3 are the position errors of Hall sensor signals. 2. According to claim 1, a fault-tolerant control method for a permanent magnet synchronous motor Hall sensor is characterized in that: in the step 1, the three-phase Hall sensor of the permanent magnet synchronous motor divides one electrical cycle of the permanent magnet synchronous motor into six regions, and the six regions are equally spaced by 60 electrical degrees. However, due to the misalignment of the Hall sensor, the combination of actual sensor signals is repeated irregularly; assuming that the motor runs at a constant speed, the relative error compensation angle of the Hall sensor can be derived as: 3. A fault-tolerant control method for a permanent magnet synchronous motor Hall sensor according to claim 2, characterized in that: in the step 2, when the upper diode of the inverter is used to perform the freewheeling operation, the back electromotive force is a sine wave, the sum of the phase currents is zero, and the resistance component is ignored. The relationship between the u-phase and v-phase voltages can be obtained through the expression of the DC bus voltage in the equivalent circuit. Combined with the above formula, the voltage equation can be written as: 4. According to claim 3, a fault-tolerant control method for a permanent magnet synchronous motor Hall sensor is characterized in that: in the step 3, considering that the inverter is operated based on a pulse width modulation method, the voltage equation in the step 2 is a voltage equation based on an instantaneous time model, so the voltage equation is integrally transformed and combined with the equivalent circuit diagram to obtain: Where L is the phase inductance, i _u , _iv and i _w are the phase currents, V _dc is the input voltage, _eu , _ev and _ew are the back electromotive force, and D is the duty cycle. Combining the integral equation of the back electromotive force, the commutation time t ₂ -t ₁ can be obtained as: In order to obtain the best lead angle, the relationship between I ₃ and I ₂ is derived by combining the relationship between steps 2 and 3. The commutation time is obtained by substituting it into: . 5. The fault-tolerant control method of a permanent magnet synchronous motor Hall sensor according to claim 4 is characterized in that: in the step 4, according to the relationship between the voltage equation in step 2 and the DC bus voltage, the DC bus voltage can be rewritten as: From the above formula, we can conclude that the relationship between phase u and phase v is: Using the relationship between the neutral voltage and the u-phase and v-phase voltages, the motor commutation time is integrated as follows: 6. A fault-tolerant control method for a permanent magnet synchronous motor Hall sensor according to claim 5, characterized in that: in the step 5, considering that the signs of the back electromotive force in step 3 and step 4 are different, the commutation time can be summarized as: The best advance time is half of the commutation time. Converting it into radians, the best lead angle is: Where f is the electrical angular frequency, which is the inverse of the electrical angular period. 7. A fault-tolerant control method for a permanent magnet synchronous motor Hall sensor according to claim 6, characterized in that: the optimal advance angle of commutation is obtained in step six, and the specific method is as follows: combining the relative error compensation angle of the Hall sensor in step one and the optimal advance angle in step five, the optimal advance angle of commutation is obtained by reference.