Motor start control method

Abstract

The application provides a motor starting control method. The method comprises the following steps: sequentially outputting a control instruction sequence. Whether the position of the rotor meets a preset condition is determined based on the induced voltage of a suspended phase. If the preset condition is not met, the control instruction sequence outputted is adjusted and the determination is continued; if the preset condition is met, an inner synchronization running state is switched to. In this way, qualitative determination is performed based on the induced voltage of the suspended phase, the control signal outputted has part of the closed-loop characteristics, can cope with various different working conditions and loads, and has high robustness. On the other hand, the difficulty of calibration of the control instruction sequence is reduced, the design cost of the controller is reduced, and a series of problems caused by starting of the brushless direct current motor without a position sensor through the open-loop control signal calibrated in advance in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a motor starting control method. Background Technology

[0002] Sensorless brushless DC motors are driven by the switching of current in each phase of the stator windings. The moment when the on / off state of any two phases in the stator windings switches is called the commutation moment. When the motor is running stably, the back electromotive force (EMF) can be sampled based on the three-phase terminal voltage to determine whether it has crossed zero, and the appropriate commutation moment can be determined based on the result. This method is called the back EMF zero-crossing method. The back EMF zero-crossing method requires the motor to have reached a certain speed. Therefore, it is not applicable during the process from zero speed to a certain speed. In this case, a motor starting control method is also needed.

[0003] like Figure 1 As shown, sensorless brushless DC motors typically employ a three-stage starting scheme: rotor positioning, external synchronous acceleration, and switching to self-synchronous operation. The speed variation trends at each stage can be referenced. Figure 2 .

[0004] Rotor positioning stage ( Figure 2 ①): Determine the initial position of the motor rotor so that the rotor can start from a fixed position each time when stationary.

[0005] Low-power brushless DC motors typically employ magnetic braking rotor positioning under light load conditions. By energizing any two phases of the motor, the magnetic flux generated within the motor can forcibly attract the rotor to the direction of the magnetic flux for a certain period of time. The energizing time on any two sets of windings and the PWM duty cycle can be calibrated.

[0006] External synchronous open-loop acceleration stage ( Figure 2 ②): By changing the external voltage and / or commutation signal of the motor through an open-loop control command sequence, the motor speed is gradually increased from a standstill.

[0007] After successful rotor positioning, the motor must be accelerated by altering the applied voltage and commutation signal to reach a speed sufficient for detecting zero-crossing. In practical applications, an acceleration curve is typically set based on the specific motor characteristics and load to control the commutation signal switching frequency and PWM duty cycle. The external synchronous acceleration phase is the first guarantee for successful startup; the control performance after the acceleration curve (corresponding to the open-loop control command sequence) calibration directly affects the success rate of operating state switching. This acceleration curve relies on manual experimental calibration based on specific operating conditions and the controlled object, and requires a certain level of system stability. This calibration step takes a considerable amount of time.

[0008] Running state switching stage Figure 2 Stage 3): Switching from the external synchronization acceleration stage to the self-synchronization motor closed-loop control running stage after reaching the required rotating speed. When the motor reaches a certain rotating speed through the external synchronization acceleration stage, the back electromotive force signal can be accurately detected, and the drive mode of motor commutation is triggered by judging the characteristic signal point (referred to as the zero-crossing point) to replace the artificially set commutation frequency, while the current, rotating speed, torque or position and other targets are adjusted through closed loop. This step is the key and also the most difficult to achieve. Too early or too late switching can easily lead to out-of-step control and startup failure, resulting in stalling or overcurrent events.

[0009] The prior art solution adopts the following external synchronization acceleration method. The appropriate acceleration curve is determined through online calibration. In this solution, only the calibration process is online, and the control still adopts the calibrated curve for open-loop control.

[0010] The prior art solution adopts the following two switching methods. One is to determine the switchable motor rotating speed through offline calibration, and switching can be performed when this rotating speed is reached. The other is to detect the time when the predetermined switching rotating speed is reached through testing, and switching can be performed when the software timer counts to the switching time.

[0011] It can be seen that the success rate of switching is seriously dependent on the accuracy of calibration and testing, and is only suitable for specific loads and specific conditions. However, the motor and load characteristics can be affected by the environment (supply voltage and temperature), and the motor itself also has its differences, so there are the following shortcomings.

[0012] 1. Dependence on accurate calibration: The accuracy of any calibration is affected by the performance of the test equipment, the test object and the actual operation of the test personnel. For example, in the application of the oil pump motor of the dual-clutch automatic transmission hydraulic control system, the motor has been integrated into the valve body of the transmission, and its rotating speed cannot be measured. The controller uses a direct connection to the valve body connector, and its three-phase current cannot be measured.

[0013] 2. Incomplete coverage of working conditions: Any calibration can only be completed under specific loads and test conditions. Considering the cost, time and technical limitations, it is difficult to completely realize the calibration of each working point under full application conditions and full environmental conditions. For example, in the application of the oil pump motor of the dual-clutch automatic transmission hydraulic control system, full application conditions need to consider oil pressure (0-83 bar), the combined action of 4 shift forks and 2 clutches. Full environmental conditions include oil temperature (-40 degrees to 125 degrees) and supply voltage (10.5V to 14.8V, including steady state and fluctuation). The combination of full application and environmental conditions is too complex.

[0014] 3. Robustness is poor: actual system operation will also be affected by other factors, such as motor body difference, aging, vibration, electromagnetic interference, unexpected load change, etc. For example, in the application of oil pump motor in gearbox hydraulic control system, the motor process cannot guarantee the performance consistency of all batches of products, there are various up and down deviations and aging, and the same calibration parameters will produce different control results. Impurities may also be mixed in the oil circuit to cause accidental changes in the load, and the original calibration parameters cannot adapt to such disturbances.

[0015] 4. Specific load: because the starting parameters are calibrated under specific load and working condition and remain unchanged during the life cycle, only limited load tolerance and load change can be supported.

[0016] 5. In order to ensure the effectiveness of the open-loop control algorithm, the initial position of the motor is positioned, so that the rotor positioning stage must be designed, and a long enough time is waited in the rotor positioning stage (assuming that theoretically 0.1s rotor can be positioned, but in order to ensure that various special cases are handled, it may need to wait for 0.3s before entering the outer synchronization open-loop acceleration stage to ensure that the rotor is in the correct position), thereby prolonging the starting time.

[0017] In summary, in the prior art, the brushless direct current motor without position sensor is started by the open-loop control signal calibrated in advance, which has large calibration cost, incomplete working condition coverage, poor robustness, limited load change support, long starting time, and cannot be accurately calibrated under specific working conditions. SUMMARY

[0018] The purpose of the present application is to provide a motor starting control method to solve the problem that the brushless direct current motor without position sensor in the prior art is started by the open-loop control signal calibrated in advance, which has large calibration cost, incomplete working condition coverage, poor robustness, limited load change support, long starting time, and cannot be accurately calibrated under specific working conditions.

[0019] In order to solve the above technical problems, the present application provides a motor starting control method applied to a motor, the motor being a brushless direct current motor without position sensor, the motor starting control method comprising the following steps: sequentially outputting a control instruction sequence; wherein the control target of the control instruction sequence includes commutation frequency and current value of the conducting phase, and the control instruction sequence is an open-loop control instruction. Determine whether the position of the rotor meets a preset condition based on the induced voltage of the suspended phase; wherein the suspended phase is a phase that is not conducting. If the preset condition is not met, adjust the output control instruction sequence and continue to determine whether the position of the rotor meets the preset condition based on the induced voltage of the suspended phase. And if the preset condition is met, switch to an internal synchronization running state.

[0020] Optionally, the motor starting control method further comprises the following steps: after outputting the nth control instruction of the control instruction sequence, outputting the nth control instruction cyclically; wherein n is the total number of control instructions in the control instruction sequence. Whether the position of the rotor satisfies a preset condition is determined based on the induced voltage of the open phase. If the preset condition is not satisfied, the control instruction sequence output is adjusted and whether the position of the rotor satisfies the preset condition is determined based on the induced voltage of the open phase. If the preset condition is satisfied, the internal synchronization running state is switched to.

[0021] Optionally, the motor starting control method further comprises the following steps: if the number of cycles of outputting the nth control instruction reaches a preset upper limit, a stop signal is output to drive the motor to stop.

[0022] Optionally, the preset condition is that the angle of the rotor lagging behind the stator magnetic potential is within a preset range.

[0023] Optionally, the step of determining whether the position of the rotor satisfies the preset condition based on the induced voltage of the open phase comprises: measuring the induced voltage e1 and the reference voltage U1 at a first preset time in each commutation period, and measuring the induced voltage e2 and the reference voltage U2 at a second preset time in each commutation period; wherein the reference voltage is calculated based on the measured values of the voltages of the two conducting phases. If (e1-0.5U1)(e2-0.5U2) is not less than 0, the result is that the preset condition is not satisfied.

[0024] Optionally, the step of determining whether the position of the rotor satisfies the preset condition based on the induced voltage of the open phase further comprises: if (e1-0.5U1)(e2-0.5U2) is less than 0, the result is that the preset condition is satisfied.

[0025] Alternatively, the step of determining whether the position of the rotor satisfies the preset condition based on the induced voltage of the open phase further comprises: measuring the induced voltage e 3,i and the reference voltage U 3,i at a third preset time in each commutation period; wherein the number of the third preset times is at least one, e 3,i represents the induced voltage of the open phase corresponding to the ith time in the third preset times, U 3,i represents the reference voltage corresponding to the ith time in the third preset times, i ranges from 1 to imax, and imax represents the total number of the third preset times. If (e1-0.5U1)(e2-0.5U2) is less than 0, the result is that the preset condition is satisfied. 3,i 3,i ​Further determine whether the determination result meets the preset condition.

[0026] Optionally, the step of adjusting the control instruction sequence comprises: if (e1≤0.5U1)&&(e2≤0.5U2), additionally increasing the current value of the conducting phase and / or additionally decreasing the commutation frequency based on the control target of the control instruction sequence; and if (e1≥0.5U1)&&(e2≥0.5U2), additionally decreasing the current value of the conducting phase and / or additionally increasing the commutation frequency based on the control target of the control instruction sequence.

[0027] Optionally, the step of adjusting the control instruction sequence further comprises: selecting a unit correction amount from a parameter matrix according to the current power supply voltage and motor temperature to obtain a cumulative adjustment amount; and superimposing the cumulative adjustment amount on the control instruction sequence to realize the adjustment process.

[0028] Optionally, the reference voltage is an absolute value of a difference between the measured values of the voltages of the two conducting phases, or the reference voltage is an absolute value of a sum of the measured values of the voltages of the two conducting phases.

[0029] Optionally, the first preset time and the second preset time are symmetrical about a midpoint time of the commutation period.

[0030] Compared with the prior art, the motor starting control method provided by the application comprises the following steps: sequentially outputting a control instruction sequence; determining whether the position of the rotor meets a preset condition based on the induced voltage of the suspended phase; if the preset condition is not met, adjusting the control instruction sequence output and continuing to determine whether the position of the rotor meets the preset condition based on the induced voltage of the suspended phase; and if the preset condition is met, switching to an internal synchronization running state. In this way, qualitative determination is performed based on the induced voltage of the suspended phase, so that the output control signal has a part of closed-loop characteristics, can cope with various different working conditions and loads, and has high robustness; on the other hand, the difficulty of calibration of the control instruction sequence is reduced, and the design cost of the controller is reduced; and the problems of the prior art, i.e., the brushless direct-current motor without a position sensor is started by using an open-loop control signal calibrated in advance, the calibration cost is high, the working conditions are not fully covered, the robustness is poor, limited load changes are supported, the starting time is long, and accurate calibration cannot be performed in a specific working condition, are solved. BRIEF DESCRIPTION OF DRAWINGS

[0031] Those skilled in the art will understand that the provided drawings are for better understanding of the application and do not constitute any limitation on the scope of the application. Among them:

[0032] Figure 1is a flow chart of a brushless DC motor control without position sensor;

[0033] Figure 2 is a trend chart of the rotation speed during three-stage starting;

[0034] Figure 3 is a flow chart of a motor starting control method according to an embodiment of the present application;

[0035] Figure 4 is a chart of the energization and magnetic field variation of a brushless DC motor under ideal working conditions;

[0036] Figure 5 is a chart of the phase voltage waveform of a three-phase brushless DC motor when any phase is suspended;

[0037] Figure 6 is another flow chart of a motor starting control method according to an embodiment of the present application;

[0038] Figure 7 is a chart of the first preset time and the second preset time according to an embodiment of the present application;

[0039] Figure 8 is a chart of the phase voltage sampling timing according to an embodiment of the present application.

[0040] In the drawings:

[0041] 1 - rotor positioning stage; 2 - external synchronization open-loop acceleration stage; 3 - running state switching stage; 4 - north pole of stator magnetic field; 5 - optimal position of rotor. DETAILED DESCRIPTION

[0042] In order to make the objects, advantages and features of the present application clearer, the following will make further detailed description of the present application in combination with the drawings and specific embodiments. It should be noted that the drawings are all very simplified and not drawn in proportion, and are only used to facilitate and clarify the purpose of assisting the description of the embodiments of the present application. In addition, the structures shown in the drawings are often part of the actual structures. In particular, the emphasis of each drawing is different, and sometimes different proportions are used.

[0043] As used in the present application, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. The term "or" is generally employed in its sense of "and / or" unless the content clearly dictates otherwise. The term "plurality" is generally employed in its sense of "at least one" unless the content clearly dictates otherwise. The term "at least two" is generally employed in its sense of "two or more" unless the content clearly dictates otherwise. Furthermore, the terms "first", "second", "third", etc. are used only to describe a particular object and do not imply or suggest relative importance or imply a specific number of the technical features indicated. Thus, features defined with "first", "second", "third" can explicitly or implicitly include one or at least two of the features. The term "proximal" generally refers to the end closer to the operator, and the term "distal" generally refers to the end closer to the patient. The terms "one end" and "the other end" and "proximal" and "distal" generally refer to two parts corresponding to each other, which not only includes the end points. The terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrated; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through intermediate medium; it can be internal communication of two elements or interaction relationship between two elements. In addition, as used in the present application, a component disposed in another component generally only indicates that there is a connection, coupling, cooperation or transmission relationship between the two components, and the two components can be directly or indirectly connected, coupled, cooperated or transmitted through an intermediate component, and cannot be understood as indicating or suggesting the spatial positional relationship between the two components, i.e. one component can be in any orientation inside, outside, above, below or one side of another component, unless the content clearly indicates otherwise. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0044] The core idea of the present application is to provide a motor starting control method to solve the problems in the prior art that the brushless DC motor without position sensor is started by open-loop control signal through prior calibration, the cost of calibration is high, the working condition coverage is not complete, the robustness is poor, the supported load change is limited, the starting time is long, and accurate calibration cannot be performed under certain working conditions.

[0045] The following is described with reference to the accompanying drawings.

[0046] Please refer to Figures 3 to 8 , wherein, Figure 3 is a flowchart of the motor starting control method of an embodiment of the present application; Figure 4 is the energization and magnetic field change of the brushless DC motor under ideal working conditions; Figure 5 is a schematic diagram of the phase voltage waveform when any phase of the three-phase brushless DC motor is suspended; Figure 6 is another flowchart of the motor starting control method of an embodiment of the present application; Figure 7is a schematic diagram of the first preset time and the second preset time of an embodiment of the present application; Figure 8 is a phase voltage sampling timing diagram of an embodiment of the present application.

[0047] As Figure 3 shown, the embodiment provides a motor starting control method applied to a motor, the motor being a brushless direct current motor without position sensor, the motor starting control method comprising the following steps:

[0048] S20 sequentially outputs a control instruction sequence, wherein a control target of the control instruction sequence comprises a commutation frequency and a current value of a conducting phase, and the control instruction sequence is an open-loop control instruction.

[0049] S30 judges whether a position of the rotor satisfies a preset condition based on an induced voltage of a suspended phase, wherein the suspended phase is a phase that is not conducting.

[0050] S40 if the preset condition is not satisfied, adjusts the output control instruction sequence and continues to judge whether the position of the rotor satisfies the preset condition based on the induced voltage of the suspended phase.

[0051] and S50 if the preset condition is satisfied, switches to an inner synchronization running state.

[0052] In the background section of the present application, it has been introduced that the prior art uses a prior calibration open-loop control instruction sequence to control the starting of a brushless direct current motor without position sensor, and the present embodiment uses the induced voltage of a suspended phase for judgment and corrects the output control signal according to the judgment result, so that the control signal has a certain degree of closed-loop characteristics, improves the starting performance and increases the robustness of the system. It should be understood that during the motor starting stage, the induced voltage of the suspended phase cannot accurately and stably feedback the accurate position of the rotor, so the closed-loop control algorithm based on the induced voltage of the suspended phase cannot be directly realized. The inventors have reached the following conclusion based on creative thinking: although the induced voltage of the suspended phase is not accurate, it can still provide certain feedback information in a qualitative way, and the present embodiment is designed based on the above design idea. In step S30, only the induced voltage of the suspended phase is used for a T / F Boolean judgment, on the one hand, the information contained in the induced voltage of the suspended phase is reasonably utilized, and on the other hand, additional errors are not introduced due to the accuracy of the induced voltage of the suspended phase, and significant beneficial effects are obtained.

[0053] In some embodiments, the motor starting control method further comprises: S10 outputting a preparation positioning instruction to drive the rotor to move to and stop at a starting preparation position. However, step S10 is not a necessary step. Since the motor starting control method adopted in the embodiment has the characteristic of closed-loop control, the initial position of the motor rotor is not sensitive, and the setting of step S10 can also shorten the overall time of motor starting. Even if step S10 is set, the waiting time for the rotor to stop can be set to be relatively short, and the technical problems raised in the background art can also be solved.

[0054] In step S10, the starting preparation position is determined by the structure of the motor and the working purpose, which is a position convenient for motor starting. The technical means for driving the rotor to move to and stop at the starting preparation position can be set according to actual needs, for example: turning on the preset two phases to generate a constant magnetic field, or other means. In step S20, the control instruction sequence can be understood as a prior calibrated open-loop control instruction sequence. In the prior art, whether the motor can start normally completely depends on the control effect of the control instruction sequence, so a lot of manpower and material resources are needed for calibration; in the embodiment, although the control instruction sequence also needs to be calibrated, since the control signal will be corrected according to the feedback information in the subsequent steps, the calibration process can be simplified, or the control instruction sequence can be calibrated offline, thereby reducing the design cost. The control target of the control instruction sequence includes the commutation frequency and the current value of the conducting phase, for example, one or more switching control signals can be used to control the commutation time of the driving current, and a PWM wave can be used to control the current value of the conducting phase. The specific scheme can be set according to the type of the motor driving circuit and the working condition of the motor, which will not be described here. In step S30, the preset condition refers to the condition for switching, which can be calculated first, and then expanded or contracted according to reliability, safety and other angles to obtain the preset condition. In step S40, the correction signal is set based on the judgment result of S30 and finally superimposed on the control instruction sequence for output. In step S50, the internal synchronization running state refers to the state in which the motor can work stably, at this time, the position of the rotor can be accurately back calculated according to the induced voltage of the suspended phase, so that closed-loop control can be performed. After the motor switches to the internal synchronization running state, the motor starting process has ended, and any suitable position / speed feedback closed-loop control algorithm can be used to control the motor.

[0055] Please continue to refer to Figure 3 , the motor starting control method further comprises the following steps:

[0056] S60 outputs the n th control instruction of the control instruction sequence, and then loops to output the n th control instruction; wherein n is the total number of control instructions in the control instruction sequence.

[0057] S31 determines whether the position of the rotor meets a preset condition based on the induced voltage of the open phase.

[0058] S41, if the preset condition is not met, adjusts the output control instruction sequence and continues to determine whether the position of the rotor meets a preset condition based on the induced voltage of the open phase.

[0059] S51, if the preset condition is met, switches to an internal synchronization running state.

[0060] S60 is to extend the motor starting time by looping the last control instruction when the control instruction sequence is output and the switching is not successful, thereby further increasing the robustness of the motor starting control method. Steps S31-S51 can be understood according to the content of S30-S50, and their specific details can be the same or different.

[0061] In addition, the motor starting control method further comprises the following steps: S70, if the number of loops of outputting the n th control instruction reaches a preset upper limit, output a shutdown signal to drive the motor to shut down. In this way, it is ensured that the motor will not be damaged or cause other unexpected safety accidents due to starting in extreme special working conditions.

[0062] Further, the preset condition is that the angle of the rotor lagging behind the stator magnetic potential is within a preset range. It should be understood that the angle of the rotor lagging behind the stator magnetic potential is a relative concept. For example, the angle between the north pole of the rotor magnetic field and the stator magnetic potential can be regarded as the lagging angle, or the angle between the south pole of the rotor magnetic field and the stator magnetic potential can be regarded as the lagging angle, or the angle between a special structure in the rotor and the stator magnetic potential can be regarded as the lagging angle. Therefore, the specific measurement method of the lagging angle is not limited here. It is only necessary that the preset range and the lagging angle can correspond to each other. It should be understood that the judgment logic in step S30 and the preset range are not necessarily the same. For example, the preset range can be 60°-120°, but considering the error in judgment, the angle is actually determined to be within 75°-105° according to the induced voltage of the open phase, that is, whether a measurement value is within interval A is used to determine whether the physical value corresponding to the measurement value is within interval B. In some embodiments, it is also possible to determine whether multiple measurement values meet or do not meet certain conditions, thereby comprehensively determining the relationship between the lagging angle and the preset range.

[0063] As to the preset range, please refer to Figure 4 for understanding. Figure 4 The energization and magnetic field variation of the brushless DC motor in ideal state are shown; in Figure 4 , x-A, y-B, z-C respectively represent three-phase windings of the motor, the arrow in the figure points to the north pole 4 of the stator magnetic field, and the shaded area represents the rotor optimal position 5, when the rotor is at the rotor optimal position 5, a larger driving force can be obtained. When the rotor moves away from one optimal position, the current conduction state of the stator needs to be switched synchronously, so that the north pole 4 of the stator magnetic field moves, and the rotor optimal position 5 also moves accordingly, so that the rotor is always subjected to a larger force. Figure 4 The rotor optimal position 5 in can also be understood as the preset range. If the north pole of the rotor magnetic field and the north pole 5 of the stator magnetic field are taken as the reference direction, the preset range is 60°-120°.

[0064] Please refer to Figure 5 , in ideal state, whether the north pole of the rotor magnetic field and the north pole 5 of the stator magnetic field are exactly 90° or 270° can be judged according to whether the phase voltage of the open phase passes through the "zero crossing point". Figure 5 In DC , U A represents the reference voltage, e DC represents the minimum value of the induced voltage of the open phase. Generally, whether the "zero crossing point" is passed through can be judged according to the size of the phase voltage of the open phase and 0.5U

[0065] That is, the step S30 of judging whether the position of the rotor meets the preset condition based on the induced voltage of the open phase comprises: measuring the induced voltage e1 of the open phase and the reference voltage U1 at the first preset time of each commutation period, and measuring the induced voltage e2 of the open phase and the reference voltage U2 at the second preset time of each commutation period; wherein the reference voltage is calculated based on the measured values of the voltages of the two conducting phases. If (e1-0.5U1)(e2-0.5U2)<0 is not established, the judgment result is that the preset condition is not met. When (e1-0.5U1)(e2-0.5U2)<0 is established, if in ideal state, e1 and e2 are exactly located at 0.5U DCIf the rotor is located within the preset range, then at a certain time between the first preset time and the second preset time, the rotor magnetic field north pole and the stator magnetic field north pole just pass through 90°, then the rotor is necessarily located within the preset range for a period of time. However, in actual situations, due to the influence of measurement accuracy and the physical state itself is not stable enough, the measurement value may not 100% reflect the true situation. At this time, the following two schemes can be selected. Selection one: when (e1-0.5U1)(e2-0.5U2)<0 is established, it is directly considered to meet the condition, which is a scheme more inclined to reduce the design cost. Selection two: further design other measurement values and judgment logic for judgment, which is a scheme more inclined to improve the accuracy. However, no matter which scheme is selected, it can be determined that if (e1-0.5U1)(e2-0.5U2)<0 is not established, the judgment result must be that the preset condition is not met.

[0066] Based on the above design idea, the step S30 of judging whether the position of the rotor meets the preset condition based on the induced voltage of the floating phase further comprises: if (e1-0.5U1)(e2-0.5U2)<0 is established, the judgment result is that the preset condition is met.

[0067] Alternatively, the step S30 of judging whether the position of the rotor meets the preset condition based on the induced voltage of the floating phase further comprises: measuring the induced voltage e 3,i of the floating phase at a third preset time in each commutation period 3,i ; wherein the number of the third preset time is at least one, e 3,i represents the induced voltage of the floating phase corresponding to the i-th time in the third preset time, U 3,i represents the reference voltage corresponding to the i-th time in the third preset time, and i takes a value in the range of 1 to imax, and imax represents the total number of the third preset time. And if (e1-0.5U1)(e2-0.5U2)<0 is established, based on all e 3,i and U 3,i , it is further judged to determine whether the judgment result is that the preset condition is met.

[0068] For example, one of the third preset times can be set before the first preset time, and if (e1-0.5U1)(e2-0.5U2)<0 is established, on this basis, it is further judged that (e1-0.5U1)(e 3,1 -0.5U 3,1whether (e1-0.5U1)(e2-0.5U2)<0 is established, and on this basis, further judging (e1-0.5U1)(e2-0.5U2)>0. If (e1-0.5U1)(e2-0.5U2)>0 is established, the result of the judgment is that the preset condition is met; otherwise, the result of the judgment is that the preset condition is not met. Alternatively, a third preset time point can be set, which is located after the second preset time point. If (e1-0.5U1)(e2-0.5U2)<0 is established, on this basis, further judging (e1-0.5U1)(e2-0.5U2)>0. 3,1 -0.5U 3,1 whether (e1-0.5U1)(e2-0.5U2)<0 is established, and on this basis, further judging (e1-0.5U1)(e2-0.5U2)>0. If (e1-0.5U1)(e2-0.5U2)>0 is established, the result of the judgment is that the preset condition is met; otherwise, the result of the judgment is that the preset condition is not met. Alternatively, a third preset time point can be set, which is located after the second preset time point. If (e1-0.5U1)(e2-0.5U2)<0 is established, on this basis, further judging (e1-0.5U1)(e2-0.5U2)>0. 3,1 -0.5U 3,1 whether (e1-0.5U1)(e2-0.5U2)<0 is established, and on this basis, further judging (e1-0.5U1)(e2-0.5U2)>0. If (e1-0.5U1)(e2-0.5U2)>0 is established, the result of the judgment is that the preset condition is met; otherwise, the result of the judgment is that the preset condition is not met. Alternatively, a third preset time point can be set, which is located after the second preset time point. If (e1-0.5U1)(e2-0.5U2)<0 is established, on this basis, further judging (e1-0.5U1)(e2-0.5U2)>0. 3,2 -0.5U 3,2 whether (e1-0.5U1)(e2-0.5U2)<0 is established, and on this basis, further judging (e1-0.5U1)(e2-0.5U2)>0. If (e1-0.5U1)(e2-0.5U2)>0 is established, the result of the judgment is that the preset condition is met; otherwise, the result of the judgment is that the preset condition is not met.

[0069] The above specific solutions are only for illustration, and those skilled in the art can set other numbers and time points of the third preset time point and set other additional judgment logic according to actual needs to improve the judgment accuracy.

[0070] Further, the step of adjusting the control instruction sequence includes: if (e1≤0.5U1)&&(e2≤0.5U2), additionally increasing the current value of the conducting phase and / or additionally reducing the commutation frequency on the basis of the control target of the control instruction sequence. And if (e1≥0.5U1)&&(e2≥0.5U2), additionally reducing the current value of the conducting phase and / or additionally increasing the commutation frequency on the basis of the control target of the control instruction sequence.

[0071] The reference voltage is the absolute value of the difference between the voltages of the two conducting phases. Alternatively, the reference voltage is the absolute value of the sum of the voltages of the two conducting phases. In this embodiment, considering that there is noise and interference when sampling the three-phase phase voltage, the second solution is adopted. The beneficial effects are as follows: assuming that noise and interference exist on the three phases at the same time, i.e., the actual voltage collected each time is e u +Δδ、e v +Δδ、e w +Δδ. Suppose e v is the non-conducting phase, e u , e w are the two conducting phases, UDC = |e u + e w + 2Δδ|e v + Δδ and U DC Half of the comparison can eliminate the error of Δδ. Wherein, Δδ is an error term caused by noise and interference. In other cases, the first scheme introduced in this paragraph can also be used to calculate the reference voltage, and the technical problems mentioned in the background art can also be solved.

[0072] During each stator commutation period, the detection and adjustment are performed once, and when the preset condition is not met, the stator conduction mode conversion (or commutation) is triggered according to the updated stator commutation frequency each time, and the stator commutation frequency and the stator output duty cycle correction amount are accumulated, the stator commutation period and the output duty cycle initial value come from the calibrated acceleration curve, and the final output commutation period and duty cycle are integrated initial value and correction amount. If the switching condition is not met after the number of commutations in the acceleration stage, the running state switching stage is directly entered to continue adjustment, and if the number of adjustments reaches the upper limit and the switching condition is not met, the current motor start can be stopped and the motor can be restarted. When the preset condition is met, the zero-crossing point detected during the current commutation period is used to calculate the commutation time and trigger commutation, and then the zero-crossing point detection method can be used to drive the motor to run.

[0073] That is, the step of adjusting the control instruction sequence of the output further includes: selecting a unit correction amount from a parameter matrix according to the current power supply voltage and motor temperature to obtain a cumulative adjustment amount; and superimposing the cumulative adjustment amount and the control instruction sequence to realize the adjustment process.

[0074] The implementation principle of the embodiment is mainly to propose an adaptive control algorithm for external synchronization open-loop acceleration to switching self-synchronization link:

[0075] 1. Real-time estimation of the relative position between the stator and the rotor in the external synchronization open-loop acceleration stage, and the motor software control module adjusts the relative position and rotor speed of the stator and the rotor by adjusting the stator side commutation frequency and three-phase output driving voltage according to the adaptive algorithm. When the rotor stably follows the stator magnetic potential and lags behind by a fixed angular phase (60-120 electrical degrees), the switching condition is met, and the switching to the self-synchronization stage is triggered to detect the commutation of the reverse electromotive force zero-crossing point to drive the motor to work.

[0076] 2. If no switching is triggered in the completion of the outer synchronization open-loop acceleration phase, enter the running state switching phase, continue to rely on the detection of the relative position between the stator and the rotor, dynamically adjust the relative position between the stator and the rotor and the rotor speed by adjusting the commutation frequency of the stator side and the three-phase output driving voltage, so that the rotor speed exactly reaches the threshold requirement and stably follows the stator magnetic potential lagging a fixed angular phase (60-120 electrical degrees) rotation, thereby meeting the switching conditions from outer synchronization to self-synchronization, so that the motor can smoothly and stably transition to the reverse electromotive force zero-crossing detection commutation driving motor operation.

[0077] 3. If multiple adjustments do not meet the switching conditions in the running state switching phase, trigger a restart.

[0078] Compared with the prior art, the present application adopts an intelligent control algorithm. During the outer synchronization acceleration phase, the rotor position is judged whether it reaches the specified preset range in the current stator conduction mode by detecting the motor suspended phase back electromotive force signal, reference voltage and zero-crossing point. If the rotor position does not reach the preset range, it is considered that the rotor motion lags behind the stator commutation, and the stator magnetic field force needs to be increased or the stator commutation frequency needs to be slowed down. If the rotor position exceeds the preset range, it is considered that the stator commutation lags behind the rotor motion, and the stator magnetic field force needs to be reduced or the stator commutation frequency needs to be accelerated. After multiple adjustments, the rotor motion meets the expected rotor position specified in the current stator conduction mode, that is, the switching conditions are met.

[0079] Compared with the prior art, the present embodiment has the following invention points:

[0080] 1. Different design ideas: the prior art strictly calibrates the motor motion trajectory in the outer synchronization acceleration phase, and directly switches after completion, while the present application realizes closed-loop adjustment of the relative position between the stator and the rotor during the outer synchronization acceleration phase through an algorithm, and the goal is to correct the cumulative relative position error between the stator and the rotor in the starting process to meet the switching conditions.

[0081] 2. Different calibration strategies: the prior art needs to calibrate the most suitable acceleration curve parameters at as many as possible working condition points under various extreme samples in order to ensure that the starting performance meets the requirements in all application conditions and all environmental conditions; while the present application only needs to theoretically calculate the initial value of the acceleration curve parameters offline, and select a few key working conditions for parameter calibration for the lower limit sample, and other parameters can be obtained through linear interpolation algorithm, the goal is to determine the control amount of dynamic correction of the relative position between the stator and the rotor under different working conditions. The starting adaptive algorithm is used to compensate the calibration error of the acceleration curve.

[0082] 3. Application conditions are different: the prior art is suitable for application scenarios with constant load characteristics, good consistency and small external interference; for the position sensorless brushless DC motor control with the present technology, not only is it suitable for the above application scenarios, but also for variable load, external interference and various mechanical deviation aging effects, the goal is to enhance the control robustness and anti-interference performance.

[0083] 4. Zero-crossing determination method is different: the prior art detects the zero-crossing point by comparing the suspended phase voltage with the bus voltage, while the present application detects the zero-crossing point by comparing the suspended phase voltage with the voltage difference of the other two phases. Because there may be considerable interference and noise on the three phases of the motor, the reference voltage calculated by the voltage of the other two phases is more accurate.

[0084] Please refer to Figure 6 The flow of the present embodiment can also be understood according to Figure 6 Step S101 is used to trigger the motor start control method; S102 corresponds to step S10; steps S103 and S111 correspond to step S20, in step S111, x represents the serial number of the control instruction in the control instruction sequence; steps S104, S105, S106, S107, S108 correspond to step S30; step S109 corresponds to step S40; steps S110 and S112 correspond to step S60; steps S113, S114, S115, S116, S117, S118 correspond to step S31, step S120 corresponds to step S41, steps S118, S119, S100 correspond to step S70, and step S121 corresponds to steps S50 and S51. It should be understood that Figure 6 Step S102 in

[0085] In the present embodiment, the determination method of the key control parameters is as follows:

[0086] 1. Determination of the duty ratio and commutation frequency of each commutation point in the external synchronization acceleration stage:

[0087] The outer synchronization acceleration stage is a variable acceleration process of open-loop accelerating the motor from zero speed to a certain rotating speed. The motor is continuously accelerated by gradually adjusting the duty ratio and commutation frequency. The acceleration curve (the duty ratio and commutation frequency of each step) is fixed in the software in advance and obtained by manual calibration or theoretical calculation. The commutation frequency f determines the expected change rate ω of the angle θ between the stator and the rotor. The commutation frequency is gradually increased at each commutation to accelerate the rotor. The duty ratio r directly determines the size of the electromagnetic force generated on the stator winding. The appropriate electromagnetic force is output at each commutation in the outer synchronization acceleration stage. In the acceleration stage, the phase difference (60-120 degrees) between the stator and the rotor is controlled by adjusting the appropriate commutation frequency and duty ratio output to meet the requirements of not falling and continuously accelerating the rotating speed under the current load.

[0088] It is assumed that the acceleration stage can allow the upper limit of the number of accelerations to be n steps. The electromagnetic force required in the xth step (x∈[2,n]) mainly depends on the current commutation period 1 / f x The change of the angle θ between the direction of the electromagnetic force of the inner stator and the direction of the rotor magnetic field and the size of the load T L (change in the form of torque). The angular acceleration a of the rigid body (the motor body and the object being dragged) is directly proportional to the resultant external torque M and inversely proportional to the moment of inertia J of the rigid body. The resultant external torque is determined by the electromagnetic torque T θ , the load torque T L , the mass m of the rigid body, the vector length d, and the angle θ between the force and the direction of the rotor magnetic field. In a commutation period, the average angular velocity ω x of the rigid body is determined by the average angular acceleration a x and the commutation period 1 / f x . Since the motor supply voltage U DC directly affects the electromagnetic force on the stator side of the motor, the temperature t m of the motor directly affects the electromagnetic characteristics of the motor, and the duty ratio r x and the commutation frequency f x of the xth step are functions of the following parameters, i.e.:

[0089]

[0090] Generally, according to an acceleration curve, the commutation frequency gradually increases, and the duty ratio gradually increases.

[0091] 2. Determination of the initial stator commutation frequency in the outer synchronization acceleration stage:

[0092] The first commutation frequency in the acceleration stage should be at least equal to the lowest rotating speed n BEMF-MIN at which the motor back electromotive force can be collected (provided by the motor supplier), so the initial commutation frequency f1 needs to meet the following parameter function, i.e.:

[0093] p is the number of motor pole pairs.

[0094] 3. Determination of the primary duty cycle and the unit correction of stator commutation frequency in the outer synchronization acceleration phase:

[0095] The size of the primary correction determines how quickly the acceleration phase can be completed. In the adjustment process, the unit correction and the load change rate ΔT L related to the deviation of the stator and rotor position D e related to the deviation of the stator and rotor position (D e + is the deviation of the actual rotor position from the expected position, D e - is the deviation of the actual rotor position from the expected position, and since the motor supply voltage U DC directly affects the electromagnetic force on the stator side of the motor, the motor temperature t m also directly affects the electromagnetic properties of the motor, therefore Δr and Δf are functions of the following parameters, i.e.:

[0096]

[0097] Generally, the smaller U DC or the larger ΔT L or the larger t m or the larger D e , the larger |Δr| and |Δf| are. Through the correction of the acceleration phase duty cycle and commutation frequency, the motor's starting operating state ultimately meets the switching condition and directly switches to the self-synchronous closed-loop phase.

[0098] 4. Determination of the actual output duty cycle and stator commutation frequency in the outer synchronization acceleration phase:

[0099] The actual output duty cycle and commutation frequency in the xth step of the outer synchronization acceleration phase are the sum of the initial fixed value and the cumulative value of the unit correction, i.e.

[0100]

[0101] 5. Determination of the rotor expected position checkpoint in the outer synchronization acceleration phase and the operating state switching phase:

[0102] As shown in FIG. 1, a 60-degree commutation period is shown, wherein, Figure 7

[0103]

[0104] The ideal back-EMF zero-crossing point should occur at the center time t z ​The phase voltage before the center point should be lower than half of the reference voltage, and the phase voltage after the center point should be higher than half of the reference voltage; or the phase voltage before the center point should be higher than half of the reference voltage, and the phase voltage after the center point should be lower than half of the reference voltage. A pair of sampling times (t1, t2) can be set equidistant from the center point, where t1 is the first preset time and t2 is the second preset time. The error D of the actual zero-crossing point deviating from the expected zero-crossing point (30-degree center point) is determined by two or more sets of voltage differences. e The sampling time must satisfy the following function, namely:

[0105] |t1-t z |=|t2-t z |

[0106] The above logic can also be summarized as follows: the first preset time and the second preset time are symmetrical about the midpoint of the commutation period. Of course, as described above, an additional third preset time can be set to improve the judgment accuracy. The third preset time can be set symmetrically or asymmetrically about the center point, and the number can be chosen to be odd or even.

[0107] Typically, based on the system's allowable deviation tolerance, selectable checkpoints include, for example, (15°, 45°) and (20°, 40°). The closer the checkpoint is to the center point, the more stringent the switching conditions, and the higher the reliability. Conversely, the farther the checkpoint is from the center point, the more lenient the switching conditions, and the lower the reliability. Those skilled in the art can select appropriate first and second preset times based on the actual situation. It should be understood that the specific times of the first and second preset times are also related to the total duration of a single commutation cycle, and the specific measurement timing can be calculated in real-time based on the total duration of a single commutation cycle and the angle value corresponding to the checkpoint. Finally, this method completes the sampling and calculation of two checkpoints between two commutation times.

[0108] 6. Floating phase voltage e A and reference voltage U DC Determination:

[0109] like Figure 8 The diagram shows the phase voltage sampling timing. The sampling time is based on the rising edge of the motor control carrier frequency PWM out signal offset by a delay time D. This time is determined to avoid switching noise and hardware delay. The sampling trigger signal Trigger to ADC sample generated by the offset has the same frequency as the motor control carrier frequency. Its rising edge triggers the hardware analog signal sampling module to simultaneously sample the three-phase phase voltage e of the motor. u e v and e w .Figure 8 In the formula, Ts represents the width of a single pulse. According to the three-phase conduction mode at the sampling time, it is known which phase is the suspended phase. For example, if the non-conduction phase (also referred to as the suspended phase) at a certain sampling time is the V phase, the suspended phase voltage can be obtained as e A = e v , and the reference voltage is U DC = |e u + e w |. During a high duty cycle of a motor control carrier cycle, one or more voltage samples can be completed, and the sampling data can be averaged to obtain a higher precision sampling value.

[0110] 7. Determination of the upper limit n of the external synchronization acceleration stage and the upper limit m (i.e., the preset upper limit) of the running state switching stage:

[0111] The calibration of the upper limit needs to be based on the system requirements of the specific motor application scenario. For example, the gearbox valve body oil pump system application needs to ensure that the oil pressure is established from 0 bar to the target oil pressure within T0 time, and the motor can meet the requirement of increasing the oil pressure from 0 bar to the target oil pressure within T1 time at the rated speed, so the time (T0-T1) is the time allowed for the motor to attempt to start. Given that the one-time running state switching position adjustment time is about f x -1 and the rotor pre-positioning time is T p , the allowed starting time should include the sum of the rotor pre-positioning stage, the external synchronization acceleration stage, and the running state switching stage time, i.e.,

[0112]

[0113] In summary, the embodiment provides a motor starting control method. The method includes the following steps: sequentially outputting a control instruction sequence. Determining whether the position of the rotor meets a preset condition based on the induced voltage of the suspended phase. If the preset condition is not met, adjusting the output control instruction sequence and continuing to determine whether the position of the rotor meets the preset condition based on the induced voltage of the suspended phase. And if the preset condition is met, switching to an internal synchronization running state. In this way, the induced voltage of the suspended phase is qualitatively judged, so that the output control signal has a part of the closed-loop characteristic, can cope with various working conditions and loads, and has high robustness. On the other hand, it also reduces the difficulty of calibrating the control instruction sequence and reduces the design cost of the controller. It solves the problems of the prior art that the brushless direct current motor without a position sensor starts through an open-loop control signal calibrated in advance, has high calibration cost, incomplete working condition coverage, poor robustness, supports limited load changes, long starting time, and cannot be accurately calibrated in a specific working condition.

[0114] The above description is only a description of the preferred embodiments of the present application, and is not any limitation on the scope of the present application. Any modification or change made by those skilled in the art according to the above disclosure is within the protection scope of the technical scheme of the present application.

Claims

1. A motor starting control method, characterized in that, Applied to an electric motor, wherein the electric motor is a sensorless brushless DC motor, the motor start-up control method includes the following steps: The control command sequence is output sequentially; wherein, the control target of the control command sequence includes the commutation frequency and the current value of the conducting phase, and the control command sequence is an open-loop control command; The rotor position is determined based on the induced voltage of the suspended phase to determine whether the preset conditions are met; wherein, the suspended phase is a phase that is not conducting. If the preset conditions are not met, the output control command sequence is adjusted and the rotor position is further determined based on the induced voltage of the suspended phase to determine whether the preset conditions are met; and, If the preset conditions are met, switch to internal synchronization operation mode; The motor start-up control method further includes the following steps: After outputting the nth control instruction in the control instruction sequence, the nth control instruction is output cyclically; where n is the total number of control instructions in the control instruction sequence. The position of the rotor is determined based on the induced voltage of the suspended phase to determine whether the preset conditions are met. If the preset conditions are not met, the output control command sequence is adjusted and the rotor position is further determined based on the induced voltage of the suspended phase to determine whether the preset conditions are met; and, If the preset conditions are met, the system will switch to internal synchronization mode.

2. The motor starting control method according to claim 1, characterized in that, The motor start-up control method further includes the following steps: If the number of cycles of the nth control command is reached to a preset upper limit, a stop signal is output to drive the motor to stop.

3. The motor starting control method according to claim 1, characterized in that, The preset condition is that the angle by which the rotor lags behind the stator magnetomotive force is within a preset range.

4. The motor starting control method according to claim 3, characterized in that, The step of determining whether the rotor position meets the preset conditions based on the induced voltage of the suspended phase includes: At the first preset moment of each commutation cycle, the induced voltage e1 and reference voltage U1 of the suspended phase are measured, and at the second preset moment of each commutation cycle, the induced voltage e2 of the suspended phase and the reference voltage U2 are measured; wherein, the reference voltage is calculated based on the measured values ​​of the voltages of the two conducting phases. If (e1-0.5U1)(e2-0.5U2)<0 is not true, then the judgment result is that the preset condition is not met.

5. The motor starting control method according to claim 4, characterized in that, The step of determining whether the rotor position meets the preset conditions based on the induced voltage of the floating phase further includes: If (e1-0.5U1)(e2-0.5U2)<0 is true, then the judgment result is that the preset condition is met; or, The step of determining whether the rotor position meets the preset conditions based on the induced voltage of the floating phase further includes: The induced voltage e of the suspended phase is measured at the third preset time of each commutation cycle. 3,i and the reference voltage U 3,i ;wherein, the number of the third preset time points is at least one, e 3,i U represents the induced voltage of the suspended phase corresponding to the i-th time in the third preset time. 3,i This represents the reference voltage corresponding to the i-th time point in the third preset time period, where i ranges from 1 to imax, and imax represents the total number of the third preset time points; and, If (e1-0.5U1)(e2-0.5U2)<0 holds true, then based on all e 3,i and U 3,i Further judgment is made to determine whether the judgment result satisfies the preset conditions.

6. The motor starting control method according to claim 4, characterized in that, The steps of adjusting the output control command sequence include: If (e1≤0.5U1)&&(e2≤0.5U2), the current value of the conducting phase is additionally increased and / or the commutation frequency is additionally decreased based on the control target of the control command sequence; and, If (e1≥0.5U1)&&(e2≥0.5U2), the current value of the conducting phase is further reduced and / or the commutation frequency is further increased based on the control target of the control command sequence.

7. The motor starting control method according to claim 6, characterized in that, The step of adjusting the control command sequence of the output further includes: Based on the current supply voltage and motor temperature, a unit correction value is selected from the parameter matrix and accumulated to obtain the cumulative adjustment amount; and, The cumulative adjustment amount is superimposed on the control command sequence to achieve the adjustment process.

8. The motor starting control method according to claim 4, characterized in that, The reference voltage is the absolute value of the difference between the measured values ​​of the voltages of the two conducting phases, or the reference voltage is the absolute value of the sum of the measured values ​​of the voltages of the two conducting phases.

9. The motor starting control method according to claim 4, characterized in that, The first preset time and the second preset time are symmetrical about the midpoint of the commutation period.

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