A method for measuring the parking brake angular displacement of a three-phase motor

Abstract

The present invention relates to the field of angular displacement measurement technology, and in particular to a method for measuring the parking brake angular displacement of a three-phase motor. The method first collects the line voltages of the three-phase electricity; obtains the reversal moment when the line voltages of the three-phase electricity are reversely reversed at the same time and the line voltages of the three-phase electricity corresponding to the reversal moment; according to a fixed sampling rate, the line voltages of the three-phase electricity are continuously collected at different moments until a stop condition is triggered, and the line voltage measurement is stopped. Different methods are used to determine the angular displacement of the three-phase motor for different triggered stop conditions. The present invention improves the accuracy of capturing the event edge and measuring the corresponding physical quantity itself.

Description

Technical Field

[0001] The invention relates to the technical field of angular displacement measurement, and in particular to a method for measuring the parking brake angular displacement of a three-phase motor. Background Art

[0002] After the three-phase motor stops, due to load inertia, the motor will still rotate in the existing direction after the power is cut off. In many cases, this will cause some unexpected consequences. For example, extreme situations such as the vehicle braking distance is too long and the crane hook slips during braking will cause safety accidents. Therefore, a method is needed to detect or monitor the angular displacement from motor braking to parking in real time, and finally convert the linear displacement of the equipment from motor braking to final stop.

[0003] At present, the common method is to directly measure the linear displacement or angular displacement itself. The problem with direct sampling measurement is that the capture of the event edge and the measurement of the corresponding physical quantity itself cannot achieve high accuracy.

[0004] If you are concerned about the wear of brake pads or fatigue of other brake equipment, this measurement method can directly feedback the results to users and relevant regulatory agencies, reminding them to evaluate the fatigue of equipment and related components, so as to facilitate targeted treatment, such as taking medium and major repair procedures, or simply appointing technicians to adjust the brake system. Summary of the invention

[0005] In order to solve the technical problem that the accuracy of capturing the event edge and measuring the corresponding physical quantity itself is low when measuring the linear displacement or angular displacement itself, the purpose of the present invention is to provide a method for measuring the parking brake angular displacement of a three-phase motor. The technical solution adopted is as follows:

[0006] Collect the line voltage of each three-phase electricity;

[0007] Obtain the reversal time when the line voltages of the three-phase electricity are reversely reversed at the same time and the line voltages of the three-phase electricity corresponding to the reversal time;

[0008] According to the fixed sampling rate, the line voltages of the three-phase electricity are continuously collected at different times until the stop condition is triggered, and the line voltage measurement is stopped. Different methods are used to determine the angular displacement of the three-phase motor for different triggered stop conditions;

[0009] Among them, when the triggered stop condition is that all line voltages of the three-phase electricity are less than the preset voltage threshold, the angular displacement from braking to parking is determined according to the phase angle of the sum of the line voltage vectors of the three-phase electricity at adjacent moments when the collection starts and the collection ends.

[0010] Preferably, the trigger stop condition includes:

[0011] When the difference between the last acquisition time and the first acquisition time is greater than the preset time threshold, the line voltage measurement is stopped;

[0012] When the phase of the line voltage of each of the three-phase electricity is reversed here, the measurement of the line voltage is stopped;

[0013] When all line voltages of the three-phase power are less than the preset voltage threshold, the line voltage measurement is stopped.

[0014] Preferably, the method of using different methods to determine the angular displacement of the three-phase motor for different triggered stop conditions includes:

[0015] When the difference between the last acquisition time and the first acquisition time is greater than a preset time threshold, it is determined that the angular displacement of the three-phase motor is infinite;

[0016] When the phase of the line voltage of each of the three-phase electricity is reversed here, a fault prompt is output;

[0017] When all line voltages of the three-phase electricity are less than a preset voltage threshold, the angular displacement is determined according to the phase angle of the sum of the line voltage vectors of the three-phase electricity at adjacent moments when the acquisition starts and when the acquisition ends.

[0018] Preferably, the step of determining the angular displacement from braking to parking according to the phase angle of the sum of the line voltage vectors of the three-phase electricity at adjacent moments when the acquisition starts and when the acquisition ends comprises:

[0019] Obtaining a difference group of line voltages of three phases adjacent to each other in the three groups of line voltages acquired the last three times;

[0020] Obtaining a group of difference values ​​of line voltages of three phases adjacent to each other in three groups of line voltages obtained from the first three acquisitions at the beginning;

[0021] Calculate the voltage and vector of the line voltage in the difference group corresponding to the first three acquisitions at the beginning of the acquisition, and calculate the corresponding angle of the voltage and vector; calculate the voltage and vector of the line voltage in the difference group corresponding to the last three acquisitions, and calculate the corresponding angle of the voltage and vector;

[0022] The angular displacement of the three-phase motor is determined based on the voltage and the phase angle corresponding to the vector.

[0023] Preferably, determining the angular displacement of the three-phase motor according to the voltage and the phase angle corresponding to the vector comprises:

[0024] θ=[(360*Count cycle )+(θ end -θ start )] / N

[0025] Where, θ is the angular displacement of the three-phase motor; θ end is the voltage of the line voltage of the three-phase electricity for the last time and the corresponding phase angle of the vector; θ start is the voltage of the line voltage of the three-phase power at the beginning and the corresponding phase angle of the vector; N is the number of motor poles; Count cycle is the cycle count value.

[0026] Preferably, the method for obtaining the cycle count value is:

[0027] In the process of continuously measuring the tracking measurement of the line voltages of the three-phase electricity, the measured values ​​of the line voltages of the three-phase electricity at the starting moment are recorded as the respective phase zero points, and cycle counting is performed. When an event of passing the phase zero point occurs, the cycle count value is increased by 1, wherein the cycle count value is 0 at the starting moment.

[0028] The embodiments of the present invention have at least the following beneficial effects:

[0029] The present invention directly measures the power input line voltage or line current; the rotation speed itself must be lower than the power supply oscillation frequency due to the factor of the pole logarithm. The power failure event is also reflected in the phase voltage and phase current at the earliest, so the acquisition and measurement can be carried out through the source of the highest frequency and the parking event. This measurement does not require the installation of other additional sensing equipment. There is no additional cost for the installation, maintenance, and calibration of sensor equipment, and there is no hidden danger of cumulative errors and possible failure due to long-term operation, which improves the accuracy of capturing the event edge and measuring the corresponding physical quantity itself. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 A method flow chart of a method for measuring the parking brake angular displacement of a three-phase motor provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of the method for measuring the parking brake angular displacement of a three-phase motor proposed by the present invention, its specific implementation method, structure, features and effects, in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0033] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0034] The embodiment of the present invention provides a specific implementation method of a method for measuring the parking brake angular displacement of a three-phase motor, and the method is applicable to the parking brake angular displacement measurement scenario. In this scenario, in order to solve the problem of low accuracy in capturing the event edge and measuring the corresponding physical quantity itself when directly measuring the linear displacement or the angular displacement itself. The present invention directly measures the power input line voltage or line current; the rotation speed itself must be lower than the power supply oscillation frequency due to the factor of the pole pair number. The power failure event is also reflected in the phase voltage and phase current at the earliest, so the highest frequency and the source of the parking event can be used for collection and measurement, and this measurement does not require the installation of other additional sensing equipment. There is no additional cost for the installation, maintenance, and calibration of the sensor equipment, and there is no hidden danger of cumulative errors and possible failure due to long-term operation.

[0035] A specific scheme of a method for measuring the parking brake angular displacement of a three-phase motor provided by the present invention is described in detail below with reference to the accompanying drawings.

[0036] See also Figure 1 , which shows a flowchart of a method for measuring the parking brake angular displacement of a three-phase motor provided by an embodiment of the present invention, the method comprising the following steps:

[0037] Step S100, collecting the line voltages of the three-phase electricity.

[0038] Most common power-type three-phase motors are asynchronous motors, so we take the asynchronous motor as an example to illustrate the process from braking to parking.

[0039] The entire braking and parking process can be divided into the following stages:

[0040] Stage 1: When the contactor switch is activated, the three-phase power is not cut off immediately because it takes time for the spring to disconnect the contact. It is still oscillating with a sine wave.

[0041] Stage 2: When the contactor reed finally disconnects, the input voltage is removed instantly. At this time, the magnetic field is still there and the rotor circuit is closed. Therefore, the current in the rotor circuit continues, and the induced electromotive force excited on the stator coil is an induced electromotive force in the opposite direction of the stator phase current when it is removed. At this time, even if there is a brake pad, the rotor still rotates according to inertia, so an induced current will be excited in each phase current loop, which still maintains a regular 120-degree phase difference, but the speed is getting slower and slower.

[0042] Stage 3: If it is not a free stop, when the rotor finally stops, the induced current in the rotor circuit has not disappeared. At this time, the three-phase circuit will still gradually decay due to the rotor current. Because of the changing current, the magnetic flux changes, and it will still stimulate a gradually decaying induced electromotive force.

[0043] It should be noted that no matter how fast the brake is, the induced electromotive force generated by Stage 2 and Stage 3 is different. In Stage 2, the rotating magnetic field cuts the stator coils that are placed inconsistently in space. The rate of change of the current or terminal voltage of any two stator coil loops is δ I / δ t or δU / δ t , that is, the derivatives of the voltage or current curves will change with a variable phase relationship. Once it stops, it enters Stage 3, at which time the direction of the rotor magnetic field, or the angle of the rotor itself, has pointed to a specific direction. Therefore, the induced voltage or current is still changing, but at this time, the coils associated with the three phase voltages have different real-time voltages or currents due to their different spatial positions, but their decay speeds are synchronized.

[0044] By using the phase voltage and phase current, this characteristic during power-off parking can be used to determine when the motor actually stops. In addition, because there is a regular correspondence between the magnetic flux of the rotating magnetic field and the line voltage and line current of the three-phase coil, when the external power supply of the three-phase electricity is cut off, the three-phase line voltage will have a transient reverse phase switch. This moment is easy to capture. In addition, after the phase switch occurs, the instantaneous sampling value of the phase current or phase voltage can characterize the direction of the rotating magnetic field at this time. At this time, because the external power supply of the stator has been disconnected, the contactor contact part will introduce equivalent capacitance. The equivalent circuit parameters of the stator-rotor circuit will change, but the basic characteristics of the equivalent circuit are still there, because the mutual inductance generated by the coupling of the stator-rotor magnetic field is still there, and the T-type equivalent circuit that originally describes the circuit parameters of the three-phase motor is still applicable. Therefore, the direction of the magnetic flux of the rotating magnetic field at this time can be deduced from the line current of the three-phase circuit.

[0045] The above comparison shows Stage 2 and Stage 3 during the parking process. In the presence of the brake, due to rapid braking, the second edge, that is, the derivative of the phase voltage and current, changes from being inconsistent with each other to a fixed phase relationship. We can also capture this edge of the actual parking process. Therefore, during the process from braking to parking, the motor:

[0046] Braking starting state: the direction of the magnetic flux is known.

[0047] Parking is complete: the direction of the magnetic flux is still known.

[0048] The angular displacement of the motor from the start of braking to the completion of parking can be measured. If the angular displacement is known, the final braking distance of the equipment when parking can be easily obtained - the real-time slip rate of the equipment during the operation of the motor can also be measured in real time by the motor current.

[0049] The above inference is still applicable to permanent magnet motors. The only difference is that permanent magnet motors do not have Stage 3. When the rotor stops, there is no gradual attenuation of the induced current. Therefore, when the stator induced current disappears, the direction of the magnetic flux finally measured may not be accurate enough. This method is most suitable for three-phase asynchronous motors.

[0050] The number of pole pairs of three-phase asynchronous motors has a regular multiple relationship with the theoretical rotation speed of the magnetic field. The angle of the converted three-phase electric single-turn coil magnetic flux can be converted into the angle of the actual magnetic field flux by dividing it by the number of pole pairs. Therefore, the above method is also applicable to dual-speed motors. For motors with frequency converters, the above electrical characteristics analysis involved in parking does not involve frequency conversion characteristics, so it is still applicable.

[0051] The specific process is to first continuously collect the line voltages Va, Vb, and Vc of the three-phase power. The sampling rate is configured so that when the power frequency is 10 times higher than when the vehicle is parked, the maximum angular displacement measurement accuracy can reach 1 / 10; when the power frequency is 100 times higher than when the vehicle is parked, the maximum angular displacement measurement accuracy can reach 1 / 100. The sampling rate can be adjusted by the implementer according to the actual situation.

[0052] Step S200, obtaining the reversal time when the line voltages of the three-phase electricity are reversely reversed simultaneously and the line voltages of the three-phase electricity corresponding to the reversal time.

[0053] When the line voltages Va, Vb, and Vc of the three-phase power system reverse at the same time, record this moment as the starting moment T start , and record the measured values ​​of Va, Vb, and Vc at this time [Va start , Vb start , Vc start]. That is, the line voltages of the three-phase electricity corresponding to the mixed reversal moment when the line voltages of the three-phase electricity are reversely reversed at the same time are obtained.

[0054] Step S300, continuously collecting the line voltages of the three-phase electricity at different times according to a fixed sampling rate until a stop condition is triggered, then stopping measuring the line voltages, and using different methods to determine the angular displacement of the three-phase motor for different triggered stop conditions.

[0055] Then record the second set of measured values ​​[Va] collected at a fixed sampling rate after this moment occurs. start+1 ,Vb start+1 ,Vc start+1 ].

[0056] The line voltages Va, Vb, and Vc of the three-phase electricity are continuously measured until the stop condition is triggered, and the line voltage measurement is stopped. That is, the line voltages of the three-phase electricity are continuously collected at different times until the stop condition is triggered, and the line voltage measurement is stopped.

[0057] The trigger stop condition includes:

[0058] (1) When the difference between the last acquisition time and the first acquisition time is greater than the preset time threshold, the line voltage measurement is stopped.

[0059] (2) When the phase of each line voltage of the three-phase electricity is reversed here, the line voltage measurement is stopped.

[0060] (3) When all line voltages of the three-phase power are less than the preset voltage threshold, the line voltage measurement is stopped.

[0061] Whenever an event occurs, the last valid measurement value [Va end , Vb end , Vc end ], the second to last set of measurements [Va end-1 , Vb end-1 , Vc end-1 ], the third to last set of measurements [Va end-2 , Vb end-2 , Vc end-2 Then, exit the measurement process. In the process of continuously measuring the line voltages of the three-phase power, record the starting time T start When the three-phase power is running, the measured values ​​of the line voltages of the three-phase power are the respective phase zero points. The cycle count is performed. If an event of a phase zero point is found, the count is recorded. cycle =Count cycle +1; in step S200, T start At this moment, the cycle count value is initialized to 0. cycleRecorded as the cycle count value. That is, in the process of continuously measuring the tracking measurement of the line voltages of the three-phase electricity, the measured values ​​of the line voltages of the three-phase electricity at the start time are recorded as the respective phase zero points, and the cycle count is performed. When an event of passing the phase zero point occurs, the cycle count value is increased by 1, wherein the cycle count value is 0 at the start time.

[0062] After the stop condition is triggered, different methods are used to determine the angular displacement of the three-phase motor for different triggered stop conditions.

[0063] (1) When the difference between the last acquisition time and the first acquisition time is greater than a preset time threshold, it is determined that the angular displacement of the three-phase motor is infinite, that is, the output angular displacement is infinite.

[0064] (2) When the phase of the line voltage of each of the three-phase electricity is reversed, a fault prompt is output.

[0065] (3) When all the line voltages of the three-phase power are less than the preset voltage threshold, the angular displacement from braking to parking is determined based on the phase angle of the sum of the line voltage vectors of the three-phase power at the adjacent moments when the acquisition starts and when the acquisition ends. Then, the subsequent step of calculating the angular displacement is entered.

[0066] The two groups of changes [ΔVa1, ΔVb1, ΔVc1] and [ΔVa2, ΔVb2, ΔVc2] of the three groups of line voltages finally measured are obtained, and the changes are also the difference groups. That is, the difference groups [ΔVa1, ΔVb1, ΔVc1] and [ΔVa2, ΔVb2, ΔVc2] of the line voltages of the three adjacent phases in the three groups of line voltages collected for the last three times are obtained. These two groups of difference groups are respectively taken as the penultimate difference group and the penultimate difference group.

[0067] Where, ΔVa1=Va end -Va end-1 , where Va end is the value of Va in the three-phase neutral voltage measured last time; Va end-1 is the value of Va in the three-phase neutral voltage measured at the second last time; ΔVa2=Va end-1 -Va end-2 , where Va end-1 is the value of Va in the three-phase neutral voltage measured at the second last time; Va end-2 is the value of Va in the third-to-last measured three-phase neutral line voltage, and so on, we can get ΔVb1, ΔVc1, ΔVb2, and ΔVc2.

[0068] Obtain the difference groups of the line voltages of the three phases adjacent to each other in the three groups of line voltages obtained by the first three acquisitions at the beginning of the acquisition. The two groups of difference groups are respectively used as the first group of difference groups and the second group of difference groups.

[0069] According to the phase relationship of the three channels, each of which differs by 120 degrees, the first difference group, the second difference group, the penultimate difference group, and the penultimate difference group are calculated. The three-phase voltage sum of the four measured values ​​is recorded as [SumV start , SumV start+1 , SumV end-1 , SumV end ].

[0070] The four measured values ​​are recorded as [θ start ,θ start+1 ,θ end-1 ,θ end ], that is, to obtain the phase angle of the voltage vector and.

[0071] Finally, the difference [Δ start , Δ end ], that is, to find the difference between the first difference group and the second difference group, and to find the difference between the third difference group and the fourth difference group.

[0072] Among them, Δ start =θ start+1 –θ start ; Δ end =θ end –θ end-1 .

[0073] At this time, (ΔVa2 / ΔVa1)=(ΔVb2 / ΔVb1), indicating that the motor has finally stopped. The measurement of angular displacement follows the following formula:

[0074] From power failure to motor stop, the relative angular displacement of the motor rotor is:

[0075] θ=[(360*Count cycle )+(θ end -θ start )] / N

[0076] Where, θ is the angular displacement of the three-phase motor; θ end is the voltage of the line voltage of the three-phase electricity for the last time and the corresponding phase angle of the vector; θ start is the voltage of the line voltage of the three-phase power at the beginning and the corresponding phase angle of the vector; N is the number of motor poles; Count cycle is the cycle count value.

[0077] The core of the present invention is to use the moment of phase reversal to identify the moment of braking starting point; track the difference of line voltage to identify the stop moment, and in the embodiment, a voltage attenuation threshold can be used as a replacement; finally, the phase angle of the line voltage vector sum is used to calculate the angular position of braking to parking. In summary, the present invention first collects the line voltage of each of the three-phase electricity; obtains the reversal moment when the line voltage of each of the three-phase electricity simultaneously reverses and the line voltage of each of the three-phase electricity corresponding to the reversal moment; according to a fixed sampling rate, continuously collects the line voltage of each of the three-phase electricity at different moments until the stop condition is triggered, stops measuring the line voltage, and uses different methods to judge the angular displacement of the three-phase motor for different triggered stop conditions; wherein, when the triggered stop condition is that all the line voltages of the three-phase electricity are less than the preset voltage threshold, the angular displacement is determined according to the difference in the line voltages of each of the three-phase electricity at adjacent moments when the collection starts and when the collection ends. This measurement also does not require the installation of other additional sensing devices. There is no additional cost of installation, maintenance, and calibration of sensing equipment, and there is no hidden danger of cumulative errors and possible failure due to long-term operation.

[0078] It should be noted that the sequence of the above embodiments of the present invention is only for description and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0079] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

Claims

1. A method for measuring the parking brake angular displacement of a three-phase motor, characterized in that: The method comprises the following steps: Collect the line voltage of each three-phase electricity; Obtain the reversal time when the line voltages of the three-phase electricity are reversely reversed at the same time and the line voltages of the three-phase electricity corresponding to the reversal time; According to the fixed sampling rate, the line voltages of the three-phase electricity are continuously collected at different times until the stop condition is triggered, and the line voltage measurement is stopped. Different methods are used to determine the angular displacement of the three-phase motor for different triggered stop conditions; Among them, when the triggering stop condition is that all line voltages of the three-phase electricity are less than the preset voltage threshold, the angular displacement from braking to parking is determined according to the phase angle of the sum of the line voltage vectors of the three-phase electricity at adjacent moments when the collection starts and when the collection ends; Among them, according to the phase angle of the line voltage vector sum of the three-phase electricity at adjacent moments when the collection starts and the collection ends, the angular displacement from braking to parking is determined, including: Obtain the difference group of line voltages of each of the three adjacent phases in the three groups of line voltages obtained by the last three acquisitions; obtain the difference group of line voltages of each of the three adjacent phases in the three groups of line voltages obtained by the first three acquisitions at the beginning of the acquisition; calculate the voltage and vector of the line voltage in the difference group corresponding to the first three acquisitions at the beginning of the acquisition, and calculate the phase angle corresponding to the voltage and vector; calculate the voltage and vector of the line voltage in the difference group corresponding to the last three acquisitions, and calculate the phase angle corresponding to the voltage and vector; determine the angular displacement of the three-phase motor according to the phase angle corresponding to the voltage and vector.

2. A method for measuring the parking brake angular displacement of a three-phase motor according to claim 1, characterized in that: The trigger stop condition includes: When the difference between the last acquisition time and the first acquisition time is greater than the preset time threshold, the line voltage measurement is stopped; When the phase of the line voltage of each of the three-phase electricity is reversed here, the measurement of the line voltage is stopped; When all line voltages of the three-phase power are less than the preset voltage threshold, the line voltage measurement is stopped.

3. A method for measuring the parking brake angular displacement of a three-phase motor according to claim 2, characterized in that: The method of using different methods to determine the angular displacement of the three-phase motor for different triggered stop conditions includes: When the difference between the last acquisition time and the first acquisition time is greater than a preset time threshold, it is determined that the angular displacement of the three-phase motor is infinite; When the phase of the line voltage of each of the three-phase electricity is reversed here, a fault prompt is output; When all line voltages of the three-phase electricity are less than a preset voltage threshold, the angular displacement is determined according to the phase angle of the sum of the line voltage vectors of the three-phase electricity at adjacent moments when the acquisition starts and when the acquisition ends.

4. The method for measuring the parking brake angular displacement of a three-phase motor according to claim 1, characterized in that: The method of determining the angular displacement of the three-phase motor according to the voltage and the phase angle corresponding to the vector comprises: θ=[(360*Count cycle )+(θ end -θ start )] / N Where, θ is the angular displacement of the three-phase motor; θ end is the voltage of the line voltage of the three-phase electricity for the last time and the corresponding phase angle of the vector; θ start is the voltage of the line voltage of the three-phase power at the beginning and the corresponding phase angle of the vector; N is the number of motor poles; Count cycle is the cycle count value.

5. A method for measuring the parking brake angular displacement of a three-phase motor according to claim 4, characterized in that: The method for obtaining the cycle count value is: In the process of continuously measuring the tracking measurement of the line voltages of the three-phase electricity, the measured values ​​of the line voltages of the three-phase electricity at the starting moment are recorded as the respective phase zero points, and cycle counting is performed. When an event of passing the phase zero point occurs, the cycle count value is increased by 1, wherein the cycle count value is 0 at the starting moment.

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