Method for sensorless detection of stepping motor load torque based on current chopping mode

Abstract

The invention relates to the technical field of motor load torque detection, and discloses a method for sensorless detection of a stepping motor load torque based on a current chopping mode, and the method comprises the steps: carrying out the statistics of the charging and discharging time of an inductor on a motor winding in the rotation process of a motor through current chopping; the change of the load torque is judged according to the energy change of the charging and discharging stages of the inductor, an open-loop control mode is adopted, a sensor is not adopted to measure the load torque, and the change of the load torque is estimated by calculating the time integral difference value of tON and tFD in a current chopping period instead of detecting the winding end voltage when the current crosses the zero point. The load torque is estimated by measuring the back electromotive force of the BEMF, open-loop control is achieved, a sensor is not used, the circuit is simple, cost is low, and the problem that in the prior art, load torque detection cost is high is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of motor load torque detection, and in particular to a method for detecting the load torque of a stepping motor by sensorless method based on a current chopping mode. Background Art

[0002] The output torque of a stepper motor is related to the current. In a traditional stepper motor open-loop drive system, in order to generate sufficient torque, the current is maintained at the maximum value. However, the actual torque required by the load is not that large in most cases (for example, ATM machines are mostly at rest or at a low speed). That is, if the torque output by the motor is too abundant, it will cause a lot of energy loss, and the temperature rise will affect the life of the motor.

[0003] Therefore, it is an important function of the stepper motor drive system to increase the detection of load torque and adjust the current accordingly. In order to detect the load torque, there are two existing technologies. One is called closed-loop control, which relies on position sensors to accurately detect the load torque changes, but the cost will increase. The other is open-loop control. Under the micro-stepping chopper control technology, when the current waveform on the stepper motor winding passes through the zero point, the voltage across the winding is detected. This voltage can show the size of the back electromotive force BEMF at the current speed, and the size of the load torque can be indirectly calculated.

[0004] In the existing technology, closed-loop control relies on sensors, which increases the complexity and cost of the system; open-loop control detects the voltage across the winding when the current passes through the zero point, that is, the back electromotive force BEMF. The disadvantages are: 1) the current zero point is difficult to control accurately. If the winding current is not zero, the collected voltage includes the voltage of the resistance and inductance on the winding; 2) the collection window will limit the motor from running at high speed, and when switching to zero point, there may be a period of voltage oscillation on the winding, and it is necessary to wait for it to stabilize, which will further extend the collection window time; 3) It must be detected under micro-stepping operation. Under full-step application, there is no zero crossing and it cannot be detected; 4) The back electromotive force BEMF is too small at low speed to be detected. Summary of the invention

[0005] The object of the present invention is to provide a method for sensorless detection of load torque of a stepper motor based on a current chopping mode, aiming to solve the problem of high cost of detecting load torque in the prior art.

[0006] The present invention is implemented in this way. In a first aspect, the present invention provides a method for detecting the load torque of a stepper motor based on a current chopping mode without a sensor, comprising: The stepper motor is controlled to rotate by a current chopping mode, wherein the current chopping mode includes a charging stage, a fast decay stage, and a slow decay stage; Performing a period analysis of a current waveform on a motor winding of a stepper motor in a current chopping mode to divide the current sinusoidal waveform period of the motor winding into four quadrants, namely, Q1, Q2, Q3 and Q4; Mark the motor winding in the stepper motor that needs to perform load torque estimation as the target estimation winding, and select the quadrant corresponding to the winding for four quadrants Q1, Q2, Q3 and Q4 according to the target estimation winding to obtain the target analysis quadrant; Performing time accumulation processing on the target analysis quadrant during the charging phase and the rapid decay phase to obtain the total charging time and the total rapid decay time in the target analysis quadrant; Performing a difference analysis on the total charging time and the total fast decay time to obtain a torque change feedback characteristic; The step-out deviation value of the stepping motor is obtained, and the torque change feedback characteristic is subjected to deviation correction processing according to the step-out deviation value to obtain a load torque estimation value of a target estimation winding of the stepping motor.

[0007] The present invention provides a method for detecting the load torque of a stepping motor without a sensor based on a current chopping mode, which has the following beneficial effects: The present invention controls the rotation of the motor through current chopping, counts the time of charging and discharging of the inductance on the motor winding, judges the change of load torque according to the change of energy in the two stages of inductance charging and discharging, adopts an open-loop control method, does not use a sensor to measure the load torque, and estimates the change of load torque by calculating the time integral difference between tON and tFD in the current chopping period, rather than detecting the winding terminal voltage when the current passes through zero point and measuring the BEMF back electromotive force to estimate the load torque. The open-loop control does not use a sensor, the circuit is simple and the cost is low, and the problem of high cost of detecting load torque in the prior art is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a schematic diagram of the steps of a method for sensorless detection of load torque of a stepping motor based on a current chopping mode provided by an embodiment of the present invention; Figure 2 is a structural schematic diagram of a stepping motor provided by an embodiment of the present invention; Figure 3 is a schematic diagram of another structural form of a stepping motor provided by an embodiment of the present invention; Figure 4 is a schematic diagram of a cycle of a stepper motor in a current chopping mode provided by an embodiment of the present invention; Figure 5 is a waveform diagram of the winding of the stepping motor provided by an embodiment of the present invention in the current rising stage; Figure 6is a waveform diagram of the winding of the stepping motor provided by an embodiment of the present invention in the current decreasing stage; Figure 7 It is a schematic diagram of the correlation between the current chopping period and the current falling phase of the stepping motor provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0009] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0010] The implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0011] Reference Figure 1-Figure 7 As shown, a preferred embodiment of the present invention is provided.

[0012] In a first aspect, the present invention provides a method for sensorless detection of load torque of a stepper motor based on a current chopping mode, comprising: S1: controlling the stepper motor to rotate through a current chopping mode, wherein the current chopping mode includes a charging stage, a fast decay stage, and a slow decay stage; S2: performing a period analysis of a current waveform on a motor winding of a stepper motor in a current chopping mode, so as to divide a period of a current sinusoidal waveform of the motor winding into four quadrants, namely, Q1, Q2, Q3 and Q4; S3: marking the motor winding in the stepper motor for which load torque estimation is required as the target estimation winding, and selecting the winding corresponding quadrants for the four quadrants Q1, Q2, Q3 and Q4 according to the target estimation winding to obtain the target analysis quadrant; S4: performing a time accumulation process of a charging phase and a fast decay phase on the target analysis quadrant to obtain a total charging time and a total fast decay time in the target analysis quadrant; S5: performing a difference analysis on the total charging time and the total fast decay time to obtain a torque change feedback feature; S6: Acquire the step-out deviation value of the stepper motor, perform deviation correction processing on the torque change feedback characteristic according to the step-out deviation value, and obtain the load torque estimation value of the target estimation winding of the stepper motor.

[0013] Specifically, in step S1 of the embodiment provided by the present invention, the current chopping mode is a method for controlling the current of a motor (especially a stepper motor and a DC motor). The core idea is to adjust the current by quickly switching the on and off state of the power supply, thereby achieving precise control of the motor. The current chopping mode usually uses PWM (Pulse Width Modulation) technology. The PWM control adjusts the current of the motor by changing the duty cycle of the pulse signal (that is, the switching time ratio of the pulse signal). The current chopping mode requires real-time monitoring of the current in the motor winding. When the current reaches the set upper limit value, the control circuit will quickly cut off the power supply (enter the fast or slow attenuation stage). When the current drops to the set lower limit value, the power supply is turned on again (entering the charging stage).

[0014] More specifically, the current chopping mode includes three main stages: charging stage: the power switch is turned on, the current starts to increase, and the current in the motor winding rises; fast decay stage: the power switch is turned off, and the current drops rapidly. This stage is usually achieved by a freewheeling diode in the winding; slow decay stage: the power switch is turned off, but the current slowly drops through the inductance of the motor winding. This stage is usually achieved by a free-running diode.

[0015] More specifically, as technology develops, in order to make the motor rotate more smoothly, micro-stepping technology is usually used to control the current shape loaded into the two-phase winding (phase A and phase B) of the stepper motor to be a sine waveform, making the current change smoother, and the phase difference between the two phases is 90° (reference Figure 4 ), since microstepping is a common technology, it will not be described here.

[0016] Specifically, in step S2 of the embodiment provided by the present invention, a periodic analysis of the current waveform of the motor winding of the stepper motor in the current chopping mode is performed to divide the current sinusoidal waveform period of the motor winding into four quadrants: Q1, Q2, Q3 and Q4.

[0017] More specifically, since the current on the current chopping control winding is a sinusoidal waveform, one sinusoidal cycle can be divided into four quadrants: Q1 / Q2 / Q3 / Q4. Taking the A-phase winding as an example, the current on the Q1 and Q2 windings flows from AOUT1 to AOUT2, and the current on the Q3 and Q4 windings flows from AOUT2 to AOUT1.

[0018] More specifically, refer to Figure 5 , I_REF is the target current for each microstep. In the charging phase (i.e. tON phase), the current on the winding inductance rises. When I_REF is reached, the charging phase ends and then enters the decay phase (the decay period tOFF is configurable). Q1 and Q3 are in the current rising quadrant, and there is only a slow decay phase (i.e. tSD phase) (see Figure 6, tOFF=tSD), Q2 and Q4 are the current falling quadrant, which consists of a fast decay phase (i.e., tFD phase) and a slow decay phase (i.e., tSD phase) (the tFD cycle can also be configured, but tOFF=tFD+tSD must be satisfied), refer to Figure 7 , where tBLANK is the blanking time of the current comparator, which is the minimum delay from tON startup to the comparator stabilizing the detection current, also referred to as tBL.

[0019] Specifically, in step S3 of the embodiment provided by the present invention, the motor winding in the stepper motor for which load torque estimation is required is determined. Typically, the stepper motor has multiple windings (such as A-phase and B-phase windings), and one or more windings need to be selected as target estimation windings.

[0020] More specifically, the current sinusoidal waveform cycle of the stepper motor is divided into four quadrants: Q1, Q2, Q3, and Q4. Each quadrant represents a specific stage of the current waveform, for example: Q1: current rising stage, Q2: current reaches a peak value and begins to decrease, Q3: current decreasing stage, Q4: current reaches a valley value and begins to increase.

[0021] More specifically, according to the target estimated winding, the four quadrants of the current waveform cycle are selected for the corresponding quadrant of the winding. The goal of this step is to determine the current behavior in each quadrant in order to estimate the load torque. Based on the current characteristics of the target estimated winding, one or more quadrants are selected as the target analysis quadrant. The target analysis quadrant is an important time period for load torque estimation.

[0022] Specifically, in step S4 of the embodiment provided by the present invention, the time accumulation processing of the charging stage and the rapid decay stage is performed on the target analysis quadrant to obtain the total charging time and the total rapid decay time in the target analysis quadrant.

[0023] Specifically, in step S5 of the embodiment provided by the present invention, a difference analysis is performed on the total charging time and the total fast decay time to obtain the torque change feedback characteristics.

[0024] It should be noted that, from the energy perspective, in the current decreasing quadrant (sinusoidal waveform Q2 / Q4), the load torque change is calculated based on the changes in tON and tFD during the chopping period. Taking the A-phase winding sinusoidal current Q2 quadrant as an example, it should be clear that at the beginning of the current Q2 quadrant, the winding inductance has stored enough energy EL, which is filled by tON in the Q1 quadrant, and the entire Q2 quadrant is a process of inductor energy release. The energy to overcome the torque in this process mainly comes from EL and a very short power supply (tON moment).

[0025] More specifically, after the start of the Q2 phase, the energy changes during tON and tFD phases within each chopping cycle are analyzed separately.

[0026] More specifically, during the tON phase, the energy output by the power supply VM is EON=ELstore+ETon, where ELstore is the energy stored in the winding inductance, and ETon is the energy used to overcome the load torque. More specifically, during the tFD stage, the energy released by the winding inductance is ELrelease=EFD+ETfd, where EFD is the energy fed back to the power supply (which can be called useless work or reactive power), and ETfd is the energy to overcome the load torque.

[0027] More specifically, when the motor carries a small load or is unloaded, ETon and ETfd are very small, and the EON energy is converted into ELstore. In order to keep the sinusoidal current falling (Q2 / Q4), ELrelease≈EFD must be greater than ELstore, so that the energy EL stored in Q1 can be released, that is, EL+ELstore-ELrelease=0. In other words, the TtFD discharge time must be much longer than the TtON charging time (here TtFD and TtON refer to the total time of tON and tFD in all chopping cycles in the entire quadrant), otherwise the current cannot be controlled according to the sinusoidal waveform. This is determined by the characteristics of the current chopping mode.

[0028] More specifically, when the load increases, both ETon and ETfd increase, and at this time, EON is almost entirely provided to ETon, while ELstore is almost 0. Note that if ELrelease is released too quickly, ELstore still needs to replenish some energy, and the tON time will increase, that is, TtON will increase relatively. And ELrelease is almost entirely provided to ETfd, so EFD will decrease (EFD will not be 0, because each chopping cycle tFD is at least the same as tON The minimum tBL time), that is, TtFD will decrease relatively.

[0029] In summary, the difference between TtFD and TtON (the total time integral difference between tFD and tON, the unit can be microseconds, us) can indirectly feedback the change of load torque.

[0030] Specifically, in step S6 of the embodiment provided by the present invention, the step-out deviation value of the stepper motor is obtained, and the torque change feedback characteristic is subjected to deviation correction processing according to the step-out deviation value to obtain the load torque estimation value of the target estimation winding of the stepper motor.

[0031] It should be noted that, assuming the load torque estimation value TorqueLoad = TtFD - TtON, according to the previous article, when the load is very small or no-load, TorqueLoad is much greater than 0, which may be hundreds of microseconds. When the load becomes larger, TorqueLoad will gradually decrease. When it drops to near 0, the load torque will exceed the maximum torque output by the motor, resulting in loss of step or stall. The specific value of TorqueLoad when the step is lost depends on the type of stepper motor (different resistance and inductance), power supply voltage, and operating current, because these parameters will affect the winding charge and discharge current, thereby causing tON and tOFF to change, resulting in the loss of step threshold may be between -100 and 100; therefore, it is necessary to add a loss of step deviation value Soffset, and change the formula to TorqueLoad = TtFD - TtON + Soffset. For the same model of stepper motor, Soffset is basically fixed.

[0032] Note that the load torque estimate can be calculated in the Q4 quadrant as well, except that the current direction is from AOUT2 to AOUT1. When AOUT2=H, AOUT1=L, tON is used; when AOUT2=L, AOUT1=H, tFD is used; and when AOUT2=L, AOUT1=L, tSD is used.

[0033] Therefore, in the Q2 / Q4 quadrant, the load torque estimate of winding A can be calculated, and similarly, in the Q1 / Q3 quadrant, the load torque estimate of winding B can be calculated. In this way, a TorqueLoad can be obtained in each quadrant.

[0034] The present invention provides a method for detecting the load torque of a stepping motor without a sensor based on a current chopping mode, which has the following beneficial effects: The present invention controls the rotation of the motor through current chopping, counts the time of charging and discharging of the inductance on the motor winding, judges the change of load torque according to the change of energy in the two stages of inductance charging and discharging, adopts an open-loop control method, does not use a sensor to measure the load torque, and estimates the change of load torque by calculating the time integral difference between tON and tFD in the current chopping period, rather than detecting the winding terminal voltage when the current passes through zero point and measuring the BEMF back electromotive force to estimate the load torque. The open-loop control does not use a sensor, the circuit is simple and the cost is low, and the problem of high cost of detecting load torque in the prior art is solved.

[0035] Preferably, the stepper motor has an A-phase winding and a B-phase winding, and the stepper motor has output terminals AOUT1 and AOUT2; In the Q1 and Q2 quadrants, the current of the A-phase winding flows from the AOUT1 to the AOUT2, and the current of the B-phase winding flows from the AOUT2 to the AOUT1; In the Q3 and Q4 quadrants, the current of the A-phase winding flows from the AOUT2 to the AOUT1 , and the current of the B-phase winding flows from the AOUT1 to the AOUT2 .

[0036] Specifically, the stepper motor has two windings: an A-phase winding and a B-phase winding. The output terminals of the motor are AOUT1 and AOUT2. In the Q1 and Q2 quadrants: the current of the A-phase winding flows from AOUT1 to AOUT2, and the current of the B-phase winding flows from AOUT2 to AOUT1; in the Q3 and Q4 quadrants: the current of the A-phase winding flows from AOUT2 to AOUT1, and the current of the B-phase winding flows from AOUT1 to AOUT2.

[0037] More specifically, the current flow direction in each quadrant is recorded and analyzed in detail: Q1 quadrant: the A-phase winding current rises, and the B-phase winding current decreases, Q2 quadrant: the A-phase winding current reaches a peak value and begins to decrease, and the B-phase winding current reaches a valley value and begins to rise, Q3 quadrant: the A-phase winding current decreases, and the B-phase winding current rises, Q4 quadrant: the A-phase winding current reaches a valley value and begins to rise, and the B-phase winding current reaches a peak value and begins to decrease.

[0038] Preferably, the step of marking the motor winding in the stepper motor for which load torque estimation is required as the target estimation winding, and selecting the winding corresponding quadrants of the four quadrants Q1, Q2, Q3 and Q4 according to the target estimation winding to obtain the target analysis quadrant comprises: S31: When the motor winding for which load torque estimation is required in the stepping motor is the A-phase winding, the A-phase winding is marked as a target estimation winding, and Q2 or Q4 is selected as a target analysis quadrant of the target estimation winding, the Q2 and Q4 quadrants are the current drop phase of the A-phase winding, and in the current drop phase, the current chopping cycle of the A-phase winding includes a charging phase, a fast decay phase, and a slow decay phase; S32: When the motor winding in the stepper motor that needs to perform load torque estimation is the B-phase winding, the B-phase winding is marked as the target estimation winding, and Q1 or Q3 is selected as the target analysis quadrant of the target estimation winding. The Q1 and Q3 quadrants are the current rising stage of the A-phase winding. In the current rising stage, the current chopping cycle of the A-phase winding includes a charging stage and a slow decay stage.

[0039] Specifically, the motor winding for which load torque estimation is required is determined according to actual needs. If the target estimation winding is the A-phase winding, it is marked as the target estimation winding; if the target estimation winding is the B-phase winding, it is marked as the B-phase winding accordingly.

[0040] More specifically, if the target estimated winding is the A-phase winding: select Q2 or Q4 as the target analysis quadrant. The Q2 and Q4 quadrants are the current drop phases of the A-phase winding, and in these quadrants, the current chopping cycle of the A-phase winding includes a charging phase, a fast decay phase, and a slow decay phase.

[0041] More specifically, if the target estimated winding is the B-phase winding, Q1 or Q3 is selected as the target analysis quadrant. The Q1 and Q3 quadrants are the current rising phase of the A-phase winding, and in these quadrants, the current chopping cycle of the A-phase winding includes a charging phase and a slow decay phase.

[0042] More specifically, in the target analysis quadrant, the current chopping cycle of the target estimated winding is carefully analyzed, including: charging phase: the current passes through the winding and increases, fast decay phase (only in the Q2 and Q4 quadrants): the current drops quickly, usually releasing energy through the reverse diode, slow decay phase: the current drops slowly, and the current is gradually reduced by controlling the switch (such as PWM).

[0043] Preferably, the step of performing time accumulation processing of the charging phase and the rapid decay phase on the target analysis quadrant to obtain the total charging time and the total rapid decay time in the target analysis quadrant comprises: S41: collecting the stage time of the charging stage in the target analysis quadrant to obtain the stage time of each charging stage in the target analysis quadrant, and accumulating the stage time of each charging stage in the target analysis quadrant to obtain the total charging time in the target analysis quadrant; wherein the total charging time is positively correlated with the load of the stepper motor, and the greater the load of the stepper motor, the longer the total charging time; S42: collecting the stage time of the fast decay stage in the target analysis quadrant to obtain the stage time of each fast decay stage in the target analysis quadrant, and accumulating the stage time of each fast decay stage in the target analysis quadrant to obtain the total fast decay time in the target analysis quadrant; wherein the total fast decay time is negatively correlated with the load of the stepper motor, and the smaller the load of the stepper motor, the longer the total fast decay time.

[0044] Specifically, if the target estimated winding is the A-phase winding, select the Q2 or Q4 quadrant, and if the target estimated winding is the B-phase winding, select the Q1 or Q3 quadrant.

[0045] More specifically, within the target analysis quadrant, each charging stage is identified, the time of each charging stage is collected using a timing analysis tool (such as an oscilloscope or a dedicated data acquisition system), and the time of all charging stages within the target analysis quadrant is accumulated to obtain the total charging time.

[0046] More specifically, in the target analysis quadrant, each fast decay stage is identified, the time of each fast decay stage is collected using the same timing analysis tool as the charging stage, and the time of all fast decay stages in the target analysis quadrant is accumulated to obtain the total fast decay time.

[0047] More specifically, the collected charging stage time and fast decay stage time are processed and analyzed. The total charging time is the accumulation of the time of all charging stages, and the total fast decay time is the accumulation of the time of all fast decay stages.

[0048] More specifically, the load torque is calculated based on the total charging time and the total rapid decay time. The total charging time is positively correlated with the load: the larger the load, the longer the total charging time. The total rapid decay time is negatively correlated with the load: the smaller the load, the longer the total rapid decay time. Therefore, the total charging time and the total rapid decay time can provide feedback on the load torque.

[0049] More specifically, based on the estimated load torque, the drive control parameters (such as current limit, PWM duty cycle, etc.) are adjusted to optimize the motor operation.

[0050] It can be understood that through precise time acquisition and cumulative processing, the load of the stepper motor can be estimated more accurately, avoiding the errors that may be caused by relying solely on the current amplitude. The total charging time and the total rapid decay time directly reflect the load condition of the motor. Through real-time monitoring and adjustment, the operating state of the motor can be optimized and performance can be improved.

[0051] Preferably, stepper motors of the same model have consistent step-out deviation values, and the step of obtaining the step-out deviation value of the stepper motor includes: S61: testing the step-out deviation values ​​of various types of stepper motors in advance to obtain the step-out deviation values ​​of the various types of stepper motors, and recording the step-out deviation values ​​of the various types of stepper motors in a preset database; S62: Obtain the model of the stepper motor to be estimated, and retrieve the corresponding step-out deviation value from the preset database, so as to obtain the step-out deviation value of the stepper motor.

[0052] Specifically, prepare the out-of-step test equipment, including high-precision encoders, controllers and measurement software, select the stepper motor model to be tested, ensure that the sample is representative, set standard test conditions (such as voltage, current, load and frequency, etc.), install the encoder on the output shaft of the stepper motor to accurately measure the actual displacement of the motor, run the stepper motor, apply a certain load and stepping instructions, and repeat the test multiple times to ensure the reliability and consistency of the data.

[0053] More specifically, a statistical analysis is performed on the test data to calculate the average and standard deviation of the out-of-step deviation value, and the out-of-step deviation value of each model of stepper motor is recorded, including the average and standard deviation. A preset database is designed to store the out-of-step deviation values ​​of various models of stepper motors, and the out-of-step deviation value data is entered into the database and associated with the corresponding motor model.

[0054] More specifically, in practical applications, the model of the stepper motor to be estimated is identified, the out-of-step deviation value of the corresponding model is retrieved from a preset database, and the obtained out-of-step deviation value is used to calibrate and adjust the stepper motor control system. During operation, real-time monitoring and adjustment are performed based on the out-of-step deviation value to improve the accuracy and stability of the system.

[0055] Preferably, the step of testing the step-out deviation values ​​of various types of stepper motors in advance to obtain the step-out deviation values ​​of various types of stepper motors includes: S611: preparing a plurality of stepper motors of the same model, performing a running test on each stepper motor of the same model, and collecting torque change feedback characteristics of the stepper motors undergoing the running test to obtain torque change feedback characteristics of each stepper motor; S612: collecting the load torque of the stepper motors under test by using a sensor or a voltage measurement method to obtain the load torque value of each stepper motor; S613: performing difference calculation and mean analysis according to the load torque value and torque change feedback characteristics of each stepper motor to obtain the step-out deviation value of the stepper motor of this model; S614: Repeat the above steps for various types of stepper motors to obtain the step-out deviation values ​​of the various types of stepper motors.

[0056] Specifically, several stepper motors of the same model are selected to ensure the representativeness and reliability of the test results, and necessary test equipment is prepared, including high-precision torque sensors, voltage measuring instruments, controllers, and data acquisition systems.

[0057] More specifically, a torque sensor is installed on the output shaft of the stepper motor to monitor the torque change in real time. The stepper motor is operated according to the set control parameters to simulate the actual working conditions. During the operation, the torque change feedback characteristics of the stepper motor are collected in real time. Depending on the specific situation, the sensor method or voltage measurement method is selected to measure the load torque, and the load torque value of each stepper motor under different operating conditions is recorded.

[0058] More specifically, the difference between the load torque value of each stepper motor and its corresponding torque change feedback characteristic is calculated, and the difference data is statistically analyzed to calculate the mean and standard deviation to obtain the out-of-step deviation value of this model of stepper motor, ensuring that the sample size is large enough to improve the reliability and representativeness of the statistical results.

[0059] More specifically, the above steps are repeated for other models of stepper motors to obtain the out-of-step deviation values ​​of various models, and the test results are recorded in a preset database for subsequent query and application.

[0060] Preferably, after the load torque estimation value of the stepping motor is obtained, a step-out analysis is performed on the load torque estimation value according to a preset threshold value, and when the load torque estimation value decreases below the threshold value, a step-out report is generated.

[0061] Specifically, the detection of step loss and stalling is done by setting a threshold value, such as 50us. When the load torque increases, TorqueLoad drops below 50, and a step loss is reported. In the application of slide control of stepper motors, the step loss report can let the system know that the slide has moved to the edge of the guide rail, which is conducive to its positioning without the need for additional limiters. At the same time, once a step loss is detected, the motor can be controlled to stop rotating to prevent stalling, because stalling will increase the current of the motor and may burn the motor.

[0062] Preferably, after the load torque estimation value of the stepper motor is obtained, a current adjustment analysis is performed on the stepper motor according to the load torque estimation value to obtain a current adjustment scheme for the stepper motor, and current adjustment processing is performed on the stepper motor according to the current adjustment scheme; The step of performing current adjustment analysis on the stepper motor according to the load torque estimation value to obtain the current adjustment scheme of the stepper motor comprises: Analyzing and processing the load torque estimation value according to a preset adjustment execution threshold value, and when the load torque estimation value reaches the adjustment execution threshold value for the first time, retrieving a corresponding preliminary adjustment amplitude preset in advance as a current adjustment scheme; The load torque estimation value of the stepper motor after executing the current adjustment scheme is collected, and the load torque estimation value is analyzed and processed according to the preset adjustment execution threshold. If the load torque estimation value still reaches the adjustment execution threshold, the preset corresponding setting re-adjustment amplitude is called as the current adjustment scheme.

[0063] Specifically, after obtaining the load torque estimate, the working current is changed according to the value to achieve energy saving and cooling. When the TorqueLoad value is large, it means that the torque output by the current motor is much greater than the load demand. At this time, the working current can be reduced. For example, when TorqueLoad is greater than 400us, the working current can be reduced (the reduction amplitude can be set). If it is still greater than 400us, it will continue to be reduced to a minimum of 50% of the original current. In this way, the ohmic loss (I / 2)2R can be reduced by 75% compared with the I2R before the reduction, and the energy saving effect is significant. At the same time, the motor temperature will be greatly reduced, extending the life of the motor. When the load torque suddenly increases, TorqueLoad will decrease. A threshold can be set. For example, when it is less than 100us, the working current is increased (the increase amplitude can be set) to ensure that the torque output by the motor is sufficient to meet the load demand. This function can be called torque adaptive function.

[0064] Preferably, the method for detecting the load torque of a stepper motor based on the current chopping mode sensorless method has an effective range of motor speed. When the speed of the stepper motor is within the effective range of motor speed, the load torque estimation value obtained by the method for detecting the load torque of a stepper motor based on the current chopping mode sensorless method is a valid value.

[0065] Specifically, the load torque estimation method of the present invention has certain limitations when used. First, at low speeds, the value of TorqueLoad may be negative. The reason is that the stepping speed of the motor is slow, and the duration of each quadrant of the sinusoidal current is long. In the current falling quadrant, in order to keep the waveform a sinusoidal curve, there must be a sufficiently long tON to charge the winding inductance, which will cause TtON to be greater than TtFD and make TorqueLoad a negative value. Therefore, TorqueLoad can only be effective if it is set above a certain speed. Secondly, at high speeds, the micro-stepping control method can no longer control the current to maintain a sinusoidal waveform, and the waveform will be distorted and may become a triangular wave. At this time, TorqueLoad is no longer accurate. Therefore, when using it, the minimum speed and maximum speed must be set. For example, the load torque estimation value is valid when the speed is above 60RPM and below 240RPM.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for detecting stepper motor load torque without sensor based on current chopping mode, characterized in that: include: The stepper motor is controlled to rotate by a current chopping mode, wherein the current chopping mode includes a charging stage, a fast decay stage, and a slow decay stage; Performing a period analysis of a current waveform on a motor winding of a stepper motor in a current chopping mode to divide the current sinusoidal waveform period of the motor winding into four quadrants, namely, Q1, Q2, Q3 and Q4; Mark the motor winding in the stepper motor that needs to perform load torque estimation as the target estimation winding, and select the quadrant corresponding to the winding for four quadrants Q1, Q2, Q3 and Q4 according to the target estimation winding to obtain the target analysis quadrant; Performing time accumulation processing on the target analysis quadrant during the charging phase and the rapid decay phase to obtain the total charging time and the total rapid decay time in the target analysis quadrant; Performing a difference analysis on the total charging time and the total fast decay time to obtain a torque change feedback characteristic; The step-out deviation value of the stepping motor is obtained, and the torque change feedback characteristic is subjected to deviation correction processing according to the step-out deviation value to obtain a load torque estimation value of a target estimation winding of the stepping motor.

2. The method for detecting the load torque of a stepper motor based on a current chopping mode sensorless as claimed in claim 1, characterized in that: The stepper motor has an A-phase winding and a B-phase winding, and the stepper motor has output terminals AOUT1 and AOUT2; In the Q1 and Q2 quadrants, the current of the A-phase winding flows from the AOUT1 to the AOUT2, and the current of the B-phase winding flows from the AOUT2 to the AOUT1; In the Q3 and Q4 quadrants, the current of the A-phase winding flows from the AOUT2 to the AOUT1 , and the current of the B-phase winding flows from the AOUT1 to the AOUT2 .

3. The method for detecting the load torque of a stepper motor based on a current chopping mode sensorless as claimed in claim 2, characterized in that: The steps of marking the motor windings in the stepper motor for which load torque estimation is required as target estimation windings, and selecting the winding corresponding quadrants for four quadrants Q1, Q2, Q3 and Q4 according to the target estimation windings to obtain the target analysis quadrants include: When the motor winding for which load torque estimation is required in the stepping motor is the A-phase winding, the A-phase winding is marked as a target estimation winding, and Q2 or Q4 is selected as a target analysis quadrant of the target estimation winding, the Q2 and Q4 quadrants are the current drop phase of the A-phase winding, and in the current drop phase, the current chopping cycle of the A-phase winding includes a charging phase, a fast decay phase, and a slow decay phase; When the motor winding in the stepper motor that needs to perform load torque estimation is the B-phase winding, the B-phase winding is marked as the target estimation winding, and Q1 or Q3 is selected as the target analysis quadrant of the target estimation winding. The Q1 and Q3 quadrants are the current rising stage of the A-phase winding. In the current rising stage, the current chopping cycle of the A-phase winding includes a charging stage and a slow decay stage.

4. The method for detecting stepper motor load torque based on current chopping mode sensorless according to claim 1, characterized in that: The step of performing time accumulation processing on the target analysis quadrant in the charging phase and the rapid decay phase to obtain the total charging time and the total rapid decay time in the target analysis quadrant comprises: The stage time of the charging stage is collected for the target analysis quadrant to obtain the stage time of each charging stage in the target analysis quadrant, and the stage time of each charging stage in the target analysis quadrant is accumulated to obtain the total charging time in the target analysis quadrant; wherein the total charging time is positively correlated with the load of the stepper motor, and the greater the load of the stepper motor, the longer the total charging time; The stage time of the fast decay stage of the target analysis quadrant is collected to obtain the stage time of each fast decay stage in the target analysis quadrant, and the stage time of each fast decay stage in the target analysis quadrant is accumulated to obtain the total fast decay time in the target analysis quadrant; wherein the total fast decay time is negatively correlated with the load of the stepper motor, and the smaller the load of the stepper motor, the longer the total fast decay time.

5. The method for detecting stepper motor load torque based on current chopping mode sensorless according to claim 1, characterized in that: The same model of stepper motors have consistent step-out deviation values. The steps for obtaining the step-out deviation value of the stepper motor include: Performing out-of-step deviation value tests on various types of stepper motors in advance to obtain out-of-step deviation values ​​of various types of stepper motors, and recording the out-of-step deviation values ​​of various types of stepper motors in a preset database; The model of the stepper motor to be estimated is obtained, and the corresponding out-of-step deviation value is retrieved from the preset database, so as to obtain the out-of-step deviation value of the stepper motor.

6. The method for detecting stepper motor load torque based on current chopping mode sensorless as claimed in claim 5, characterized in that: The steps of testing the step-out deviation values ​​of various types of stepper motors in advance to obtain the step-out deviation values ​​of various types of stepper motors include: Prepare a plurality of stepper motors of the same model, perform operation tests on each stepper motor of the same model, and collect torque change feedback characteristics of the stepper motors in the operation tests to obtain torque change feedback characteristics of each stepper motor; The load torque of the stepper motor under test is collected by a sensor or voltage measurement method to obtain the load torque value of each stepper motor; According to the load torque value and torque change feedback characteristics of each stepper motor, difference calculation and mean analysis are performed to obtain the step-out deviation value of the stepper motor of this model; Repeat the above steps for various types of stepper motors to obtain the step-out deviation values ​​of the various types of stepper motors.

7. The method for detecting stepper motor load torque based on current chopping mode sensorless according to claim 1, characterized in that: After the load torque estimation value of the stepper motor is obtained, a step-out analysis is performed on the load torque estimation value according to a preset threshold value, and when the load torque estimation value decreases below the threshold value, a step-out report is generated.

8. The method for detecting stepper motor load torque based on current chopping mode sensorless according to claim 1, characterized in that: After the load torque estimation value of the stepper motor is obtained, a current adjustment analysis is performed on the stepper motor according to the load torque estimation value to obtain a current adjustment scheme for the stepper motor, and a current adjustment process is performed on the stepper motor according to the current adjustment scheme; The step of performing current adjustment analysis on the stepper motor according to the load torque estimation value to obtain the current adjustment scheme of the stepper motor comprises: Analyzing and processing the load torque estimation value according to a preset adjustment execution threshold value, and when the load torque estimation value reaches the adjustment execution threshold value for the first time, retrieving a corresponding preliminary adjustment amplitude preset in advance as a current adjustment scheme; The load torque estimation value of the stepper motor after executing the current adjustment scheme is collected, and the load torque estimation value is analyzed and processed according to the preset adjustment execution threshold. If the load torque estimation value still reaches the adjustment execution threshold, the preset corresponding setting re-adjustment amplitude is called as the current adjustment scheme.

9. The method for detecting stepper motor load torque based on current chopping mode sensorless according to claim 1, characterized in that: The method for detecting the load torque of a stepper motor by sensorless based on the current chopping mode has an effective range of motor speed. When the speed of the stepper motor is within the effective range of motor speed, the load torque estimation value obtained by the method for detecting the load torque of a stepper motor by sensorless based on the current chopping mode is a valid value.

Images