A motor torque electromechanical servo control system based on frequency conversion regulation

Abstract

The application relates to the technical field of motor servo control and variable frequency driving, in particular to a motor torque electromechanical servo control system based on variable frequency regulation, which comprises a motor, an inverter, an encoder, a current sensor and a controller; the controller obtains mechanical angle data and converts the mechanical angle data into basic electric angle, at least twice continuous sampling is carried out in the space vector pulse width modulation zero vector action interval, stator current data are obtained and the current change rate is calculated, the back electromotive force is estimated in combination with the motor stator equivalent inductance and the motor stator resistance, the rotor instantaneous position is reconstructed and the instantaneous compensation angle is output, then the dynamic weight is generated according to the mechanical angular velocity change rate, the basic electric angle is superposed to form a combined electric angle, which is used for coordinate transformation and current closed-loop control; the application can correct the decoupling angle deviation caused by the encoder delay when the load suddenly changes without changing the original current closed-loop main link.

Description

Technical Field

[0001] This invention relates to the field of motor servo control and variable frequency drive technology, specifically to a motor torque electromechanical servo control system based on variable frequency regulation. Background Technology

[0002] With the widespread application of motor servo drive systems in industrial automation, CNC equipment, and high-dynamic actuators, motor torque control based on frequency conversion regulation has put forward higher technical requirements for response speed, decoupling accuracy, and resistance to load disturbances. Especially when the motor is in operation and there are conditions such as rapid loading, step impact, or short-term jamming, how to ensure the real-time and accuracy of rotor electrical angle acquisition within the control cycle has become a key issue affecting servo control performance. Traditional motor torque servo control currently mainly relies on the following methods: using encoder mechanical angle to convert electrical angle for coordinate transformation, implementing current closed-loop control based on conventional current sampling, and completing space vector pulse width modulation drive output under a fixed control structure; However, encoder angle conversion control, conventional current closed-loop sampling, and fixed decoupling angle control all have certain drawbacks. For example, encoder feedback is easily affected by transmission and processing delays under sudden load changes, resulting in a deviation between the actual decoupling angle and the true rotor position. Conventional single current sampling is mainly used for current loop feedback and is difficult to reflect instantaneous electromagnetic changes in the zero vector range. Fixed decoupling angle control is not adaptable to highly dynamic sudden operating conditions, affecting the speed and stability of motor torque output. Summary of the Invention

[0003] The purpose of this invention is to provide a motor torque electromechanical servo control system based on frequency conversion regulation, and to solve the following technical problems: Without altering the original current closed-loop main link, it can compensate for the delay of the encoder mechanical angle by utilizing the current change information within the pulse width modulation zero vector interval, thereby correcting the decoupling angle deviation caused by encoder delay under dynamic operating conditions that exceed the rated load change rate threshold.

[0004] The objective of this invention can be achieved through the following technical solutions: A motor torque electromechanical servo control system based on frequency conversion regulation includes: a motor, an inverter connected to the motor, an encoder, a current sensor, and a controller. The controller includes: The servo control module is used to acquire the mechanical angle data output by the encoder and convert it into a basic electrical angle, perform closed-loop control of the stator current of the motor, and output a space vector pulse width modulation drive signal to the inverter. The current sampling module is used to perform at least two consecutive samplings through the current sensor within the zero vector action interval corresponding to the space vector pulse width modulation drive signal, based on the space vector pulse width modulation drive signal, to obtain the three-phase stator current sampling values, perform coordinate transformation, and output the stator current data at two sampling times in the two-phase stationary coordinate system. The current change rate calculation module is used to acquire stator current data at two sampling times in a two-phase stationary coordinate system, perform differential calculation on the stator current change in the two-phase stationary coordinate system, and output the current change rate in the stationary coordinate system. The compensation angle calculation module is used to estimate the back electromotive force based on the current change rate and pre-stored motor body parameters to reconstruct the instantaneous rotor position and output the instantaneous compensation angle. The angle synthesis module is used to calculate the rate of change of angular velocity based on mechanical angle data, generate dynamic weights based on the rate of change of angular velocity, multiply the dynamic weights by the instantaneous compensation angle and superimpose them onto the basic electrical angle, and output the synthesized electrical angle to the servo control module.

[0005] In one possible implementation, the current sampling module includes: monitoring the space vector pulse width modulation drive signal, identifying the state intervals of all three-phase upper bridge arms being off or all being on according to the order of occurrence, and outputting zero vector interval data; within the zero vector interval data, determining the first sampling time and the second sampling time in chronological order. Analog-to-digital conversion is triggered at the first and second sampling times respectively to obtain the three-phase stator current sampling values. Clark coordinate transformation is then performed on the three-phase stator current sampling values ​​to output the first stator current data in the two-phase stationary coordinate system at the first sampling time and the second stator current data in the two-phase stationary coordinate system at the second sampling time.

[0006] In one possible implementation, the current change rate calculation module includes: acquiring a first sampling time, a second sampling time, first stator current data, and second stator current data; and calculating the time difference between the second sampling time and the first sampling time. Calculate the difference between the second stator current data and the first stator current data in the two-phase stationary coordinate system, divide the difference by the time difference, and output the rate of change of current in the stationary coordinate system.

[0007] In one possible implementation, the motor body parameters include the equivalent inductance data of the motor stator and the stator resistance data, and the compensation angle calculation module includes: Obtain the equivalent inductance data and stator resistance data of the motor stator; multiply the equivalent inductance data of the motor stator by the rate of change of current, and multiply the stator resistance data of the motor stator by the first stator current data, add the two together, and output the estimated value of back electromotive force. The arctangent of the back electromotive force estimate in the stationary coordinate system is calculated, and the estimated electrical angle is output. The difference between the estimated electrical angle and the base electrical angle is calculated, and the instantaneous compensation angle is output.

[0008] In one possible implementation, the angle synthesis module includes: dividing the mechanical angle data into mechanical angle data for the current control cycle and mechanical angle data for the previous control cycle according to the time series; The mechanical angle data of the current control cycle and the mechanical angle data of the previous control cycle are differentially processed to obtain the mechanical angular velocity data of the current control cycle and the mechanical angular velocity data of the previous control cycle. Calculate the difference between the mechanical angular velocity data of the current control cycle and the mechanical angular velocity data of the previous control cycle; divide the difference by the preset pulse width modulation cycle time, take the absolute value, and output the rate of change of angular velocity.

[0009] In one possible implementation, the angle synthesis module further includes: obtaining a preset first abrupt change threshold; and comparing the rate of change of angular velocity with the first abrupt change threshold. When the rate of change of angular velocity is less than or equal to the first mutation threshold, it is determined to be in steady state, and a weight value of zero is generated, and the first weight result is output.

[0010] In one possible implementation, the angle synthesis module further includes: obtaining a preset second mutation threshold; when the rate of change of angular velocity is greater than the first mutation threshold and less than the second mutation threshold, it is determined to be a dynamic mutation state; Calculate the difference between the rate of change of angular velocity and the first mutation threshold, divide the difference by the difference between the second mutation threshold and the first mutation threshold to generate the transition weight value, and output the second weight result.

[0011] In one possible implementation, the angle synthesis module further includes: comparing the rate of change of angular velocity with a second abrupt change threshold; when the rate of change of angular velocity is greater than or equal to the second abrupt change threshold, determining it as a step impact state, generating a weight value of one, and outputting a third weight result.

[0012] In one possible implementation, the angle synthesis module further includes: outputting the corresponding first weight result, second weight result, or third weight result as the target weight value according to the current determined state; Multiply the target weight value by the instantaneous compensation angle to output the weighted compensation angle; add the weighted compensation angle to the base electrical angle to output the composite electrical angle.

[0013] In one possible implementation, the servo control module includes: acquiring the composite electrical angle and stator current data in a two-phase stationary coordinate system; performing coordinate transformation on the stator current data in the two-phase stationary coordinate system based on the composite electrical angle, and outputting direct-axis current data and quadrature-axis current data in a synchronous rotating coordinate system; The direct-axis current data and quadrature-axis current data are input into the current loop regulator built into the servo control module, which outputs a space vector pulse width modulation drive signal.

[0014] The beneficial effects of this invention are: 1. This invention calculates the basic electrical angle from the mechanical angle data output by the encoder, and uses the stator current change information extracted in the zero vector interval as a bypass compensation input without changing the original current closed-loop main link. This enables the system to maintain the encoder angle-dominated control structure under steady-state conditions, thereby avoiding changes to the existing servo control architecture topology. By estimating the back electromotive force and reconstructing the instantaneous rotor position based on the current change rate and pre-stored motor stator equivalent inductance data and motor stator resistance data, the angle delay generated by the encoder under rapid loading, step impact, or short-term jamming conditions can be corrected, thereby improving the consistency between the decoupled angle and the actual rotor position and improving the torque control response speed. 2. This invention monitors the space vector pulse width modulation drive signal and identifies the zero vector interval where all three-phase upper bridge arms are either off or on. Within the same zero vector interval, the first and second sampling times are determined sequentially, and analog-to-digital conversion is triggered accordingly. This ensures that the dual sampling window remains consistent with the inverter's switching state, thereby reducing the impact of switching transients on the sampling results. By performing coordinate transformation on the three-phase stator current sampling values ​​obtained from the two samplings and outputting two sets of stator current data in a two-phase stationary coordinate system, it provides observations under the same voltage conditions for subsequent differential calculations, thus compensating for the inadequacy of conventional single current sampling in reflecting instantaneous electromagnetic changes in the zero vector interval. 3. This invention acquires two sampling times and the corresponding stator current data in the two-phase stationary coordinate system, calculates the time difference between the two sampling times, and divides the current difference on each coordinate axis by the time difference to output the current change rate in the stationary coordinate system. This can uniformly convert the double sampling results obtained under different zero vector lengths into change rate information with a consistent physical scale, thereby improving the comparability and effectiveness of subsequent compensation angle estimation. By stopping the compensation branch of the current cycle when the time difference is zero, below the resolvable accuracy, or when data on any coordinate axis is missing, it can avoid using incomplete data to form a distorted current change rate, thereby improving the stability of the compensation link operation. 4. This invention estimates the back electromotive force (EMF) based on the stator resistance voltage drop and inductor voltage drop during the zero-vector action period. After directional compensation, it calculates the arctangent of the estimated back EMF in the stationary coordinate system to obtain the estimated electrical angle. Then, it calculates the difference between the estimated back EMF and the base electrical angle to obtain the instantaneous compensation angle. This can directly convert the electromagnetic response during the zero-vector period into an angle correction that can be superimposed on the original decoupling link, thereby improving the real-time performance of electrical angle acquisition under high dynamic change conditions. By setting the instantaneous compensation angle to zero when motor parameters are missing or the estimated back EMF is close to zero, it can avoid introducing invalid angle offsets when parameters are not ready or the rate of change of current is lower than the set zero-point drift threshold, thereby ensuring the reliability of the control results. 5. This invention obtains mechanical angular velocity data by differentially processing the mechanical angle data of the current control cycle and the previous control cycle, and further calculates the rate of change of angular velocity as a criterion for load abrupt change state. It can identify the degree of load change using the existing mechanical angle channel without adding additional sensors, thereby improving the targeting of compensation logic triggering. By setting a first abrupt change threshold and a second abrupt change threshold, zero weight is output in steady state, transition weight is output between the two thresholds, and a weight with a value of one is output when the second abrupt change threshold is reached or exceeded. This enables the instantaneous compensation angle to be smoothly connected or fully connected according to the amplitude of the load angular velocity change rate, thereby avoiding the insufficient adaptability of the fixed decoupled angle control method to high dynamic abrupt change conditions and the angle jump caused by the abrupt change of compensation amount. 6. This invention selects a target weight value from zero-value weight, transition weight value, and full weight value based on the current judgment state, and multiplies the target weight value by the instantaneous compensation angle to obtain a weighted compensation angle, which is then superimposed on the base electrical angle to form a synthetic electrical angle. This enables the unified fusion between mechanical angle and electromagnetic observation angle, thereby improving the angle correction effect under sudden operating conditions while maintaining the steady-state control structure. By directly sending the synthetic electrical angle into the servo control module for coordinate transformation, and outputting the direct-axis current data and quadrature-axis current data in the synchronous rotating coordinate system, which are then processed by the current loop regulator to form a space vector pulse width modulation drive signal, the current change information extracted from the zero vector interval can be finally implemented in the current decoupling and inverter drive output, thereby improving the speed, stability, and anti-load disturbance capability of the motor torque output. Attached Figure Description

[0015] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of a motor torque electromechanical servo control system based on frequency conversion regulation provided in an embodiment of this application. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Please see Figure 1 A motor torque electromechanical servo control system based on frequency conversion regulation includes: a motor, an inverter connected to the motor, an encoder, a current sensor, and a controller. The controller includes: The servo control module is used to acquire the mechanical angle data output by the encoder and convert it into a basic electrical angle, perform closed-loop control of the stator current of the motor, and output a space vector pulse width modulation drive signal to the inverter. The current sampling module is used to perform at least two consecutive samplings through the current sensor within the zero vector action interval corresponding to the space vector pulse width modulation drive signal, based on the space vector pulse width modulation drive signal, to obtain the three-phase stator current sampling values, perform coordinate transformation, and output the stator current data at two sampling times in the two-phase stationary coordinate system. The current change rate calculation module is used to acquire stator current data at two sampling times in a two-phase stationary coordinate system, perform differential calculation on the stator current change in the two-phase stationary coordinate system, and output the current change rate in the stationary coordinate system. The compensation angle calculation module is used to estimate the back electromotive force based on the current change rate and pre-stored motor body parameters to reconstruct the instantaneous rotor position and output the instantaneous compensation angle. The angle synthesis module is used to calculate the rate of change of angular velocity based on mechanical angle data, generate dynamic weights based on the rate of change of angular velocity, multiply the dynamic weights by the instantaneous compensation angle and superimpose them onto the basic electrical angle, and output the synthesized electrical angle to the servo control module.

[0018] In this embodiment, during the vector frequency conversion adjustment of the permanent magnet synchronous motor, without changing the original current closed-loop main link, the current change information in the pulse width modulation zero vector interval is used to compensate for the delay of the encoder mechanical angle. By continuing to use the mechanical position information provided by the encoder as the source of steady-state angle, while extracting the instantaneous rate of change of stator current from the zero vector interval, and reconstructing the instantaneous rotor position in the current control cycle based on the motor body parameters, it is then determined whether to superimpose the reconstruction result into the basic electrical angle based on the degree of load change. This system is applied to a permanent magnet synchronous motor servo drive device that uses space vector pulse width modulation. During operation, the motor may experience rapid loading, step load impact, or jamming with a duration less than the control cycle within the rated torque range. The encoder is mounted on the motor shaft and outputs mechanical angle data; the inverter is connected to the three-phase windings of the motor; the current sensor collects the three-phase stator current; the software logic in the controller is executed cyclically according to the pulse width modulation cycle. At the start of a control cycle, the servo control module first reads the mechanical angle data uploaded by the encoder and calculates the basic electrical angle by combining it with the number of motor pole pairs. This basic electrical angle is first stored in the controller's internal storage area as the default decoupling angle in the main control link of this cycle, and is used for superposition and correction by the subsequent angle synthesis module. At the same time, the servo control module performs current closed-loop calculation based on the current feedback and setpoint obtained in the previous cycle, and forms a new space vector pulse width modulation drive signal, which is sent to the inverter to drive the motor. In parallel with the main control link, the current sampling module continuously monitors the space vector pulse width modulation drive signal within the current cycle; when it detects that the three-phase bridge arm has entered the zero vector action interval, the current sampling module calls the current sensor to perform at least two consecutive samplings within this interval to obtain the three-phase stator current sampling values ​​at two moments. After coordinate transformation, the sampled values ​​are used to form the stator current data at the first moment and the stator current data at the second moment in a two-phase stationary coordinate system. These two sets of data are written into the current observation cache for this cycle, so that the current change rate calculation module can read them directly without having to re-access the original three-phase sampling channels. After obtaining the two sets of current data in the stationary coordinate system, the current change rate calculation module performs a differential operation on the current difference on the same coordinate axis and combines the time interval between the two samplings to obtain the current change rate in the stationary coordinate system. This result reflects the rate of change of the stator current in the zero vector action interval, and its value is transmitted to the compensation angle calculation module. The compensation angle calculation module reads the equivalent inductance data and stator resistance data of the motor stator from the motor parameter area pre-stored in the controller, and estimates the back electromotive force by combining the current change rate. The back electromotive force corresponds to the electrical angle direction of the current cycle in the stationary coordinate system, from which the estimated electrical angle can be calculated; the difference between the estimated electrical angle and the current base electrical angle is output as the instantaneous compensation angle; this compensation angle retains the current encoder angle and is input to the angle synthesis module for weighted processing; The angle synthesis module performs differential analysis on the mechanical angle data of the current control cycle and the previous control cycle to obtain the mechanical angular velocity, and further obtains the rate of change of angular velocity. The rate of change of angular velocity is used to characterize whether the load change in the current cycle has reached the level that requires the introduction of electromagnetic compensation. If it is determined to be a steady state or a slowly changing state, the dynamic weight remains zero, and the composite electrical angle is equal to the base electrical angle. If it is determined to be a dynamic sudden change or a step impact state, a dynamic weight greater than zero is generated according to the set logic, and the dynamic weight is multiplied by the instantaneous compensation angle to obtain the weighted compensation amount, which is then superimposed on the base electrical angle to form the composite electrical angle. The composite electrical angle is written back to the decoupled angle register of the servo control module in the current cycle to complete coordinate transformation and current closed-loop control. To ensure the continuity of the control cycle, if no zero vector interval that meets the sampling conditions is detected within a certain pulse width modulation cycle, or if the length of the zero vector interval is insufficient to accommodate two valid samples, the compensation angle calculation for this cycle will not be triggered, and the angle synthesis module will directly use the basic electrical angle for coordinate transformation. If the encoder data is not updated in the current cycle, the angle synthesis module can continue to call the mechanical angle data from the previous valid cycle to participate in the differential calculation, and make the dynamic weight of the current cycle fall back to zero, thereby avoiding amplifying the compensation amount when the mechanical information is incomplete. In the above scenario, the main control link is still based on the encoder angle, while the bypass link only participates when the load changes abruptly. Therefore, it is possible to correct the decoupling angle deviation caused by encoder delay under dynamic conditions that exceed the rated load change rate threshold while keeping the steady-state control structure unchanged.

[0019] In a preferred embodiment of the present invention, the current sampling module includes: monitoring the space vector pulse width modulation drive signal, identifying the state intervals of all three-phase upper bridge arms being turned off or all being turned on according to the order of occurrence, and outputting zero vector interval data; within the zero vector interval data, determining the first sampling time and the second sampling time in chronological order; Analog-to-digital conversion is triggered at the first and second sampling times respectively to obtain the three-phase stator current sampling values. Clark coordinate transformation is then performed on the three-phase stator current sampling values ​​to output the first stator current data in the two-phase stationary coordinate system at the first sampling time and the second stator current data in the two-phase stationary coordinate system at the second sampling time.

[0020] This embodiment provides a sampling triggering method within the zero vector interval; if a single sampling is performed only at a normal position within the pulse width modulation period, the obtained current value is mainly used for current loop feedback and it is difficult to form a quantity reflecting the change in the electromagnetic response of the motor during the zero vector period. Therefore, this embodiment identifies the state where all three-phase upper arms are off and the state where all three-phase upper arms are on, and uses the corresponding zero vector interval as a dedicated sampling window. The current sampling module within the controller triggers sampling by decoding the space vector pulse width modulation drive signal within the current cycle; The decoding process marks the intervals belonging to the zero vector according to the sequence of changes in the conduction signals of the three-phase bridge arms; when all three upper bridge arms are turned off, it corresponds to one of the zero vector states. When all three phase upper arms are conducting, it corresponds to another zero vector state; the current sampling module writes the two states into zero vector interval data and records their start and end time positions. After obtaining the zero vector interval data, the sampling module sequentially selects two sampling times from within the interval; the first sampling time is located at the effective stable position after the start of the zero vector interval, and the second sampling time is located after the first sampling time, but is still within the same zero vector interval; The above process avoids sampling points being close to the switch flip edge, thereby reducing the impact of switch transients on the analog-to-digital conversion results; the module triggers analog-to-digital conversion at the first sampling time and the second sampling time respectively to obtain the three-phase stator current sampling values; After the three-phase stator current sampling values ​​are entered into the Clark coordinate transformation program, they are converted into stator current data in a two-phase stationary coordinate system. The transformation result corresponding to the first sampling time forms the first stator current data, and the transformation result corresponding to the second sampling time forms the second stator current data; both sets of data are saved in the sampling order and have their respective corresponding sampling time marks, so that they can be directly called in subsequent differential calculations; To avoid overlapping sampling due to the time span of the zero vector interval being less than the time threshold required for two analog-to-digital conversions, if the sampling module determines that the duration of the zero vector is less than the set sampling time threshold in the current cycle, it will abandon the second sampling trigger and only retain the original conventional current control sampling of this cycle, without providing the first stator current data and the second stator current data to the subsequent stage. If the first sampling time has been triggered but the second sampling time does not obtain a valid analog-to-digital conversion result due to interference, then the double sampling data of this cycle is considered invalid and stops participating in the compensation angle calculation, thereby avoiding the distortion of the current change rate calculation due to the use of incomplete data; In the above scenario, the identification of the zero vector interval and the double sampling action are directly constrained by the space vector pulse width modulation drive signal, so that the sampling window is consistent with the inverter switching state, thereby making the subsequent calculations based on the same voltage conditions.

[0021] In a preferred embodiment of the present invention, the current change rate calculation module includes: acquiring a first sampling time, a second sampling time, first stator current data, and second stator current data; and calculating the time difference between the second sampling time and the first sampling time. Calculate the difference between the second stator current data and the first stator current data in the two-phase stationary coordinate system, divide the difference by the time difference, and output the rate of change of current in the stationary coordinate system.

[0022] This embodiment presents the logical process of forming the rate of change of current in the stationary coordinate system from two sampling results within the zero vector interval; If only the difference between two sampled values ​​is used without introducing the corresponding time interval, the difference itself does not have a uniform physical scale under different pulse width modulation duty cycles or different zero vector lengths, and cannot be directly used as the basis for estimating the compensation angle; therefore, this implementation uses the time difference and current difference together. The current change rate calculation module reads the first sampling time, the second sampling time, the first stator current data, and the second stator current data from the current observation cache; The first stator current data includes the α-axis current and β-axis current in the stationary coordinate system at the first moment, and the second stator current data includes the corresponding current values ​​at the second moment. The module first calculates the time difference obtained by subtracting the first sampling time from the second sampling time, then calculates the current difference between the second time and the first time on the α axis and β axis respectively, and divides the difference of each axis by the time difference to obtain the rate of change of current in the stationary coordinate system. The obtained current change rate is based on the instantaneous change within the same pulse width modulation period, and therefore can directly reflect the direction and speed of change of the motor winding current under the current physical state during the zero vector period; The result is input into the compensation angle calculation module, which is used together with the stator resistance and stator equivalent inductance to estimate the back electromotive force; If the time difference calculation result is zero, or less than the controller's preset resolvable time accuracy, the current change rate for that cycle will not be output, and subsequent compensation angle calculations will stop in this cycle. If data for any coordinate axis in the first stator current data or the second stator current data is missing, the rate of change of that coordinate axis will not be included in the calculation, and the entire compensation branch will exit in this cycle. This is to avoid affecting the reconstruction of the back electromotive force direction and the estimation of the angle due to the absence of any stationary coordinate system component. In the above scenario, by normalizing the current difference with time difference, the double sampling results obtained in different pulse width modulation periods can be uniformly converted into comparable current change rates, providing direct input for subsequent compensation angle calculation.

[0023] In a preferred embodiment of the present invention, the motor body parameters include motor stator equivalent inductance data and motor stator resistance data, and the compensation angle calculation module includes: acquiring motor stator equivalent inductance data and motor stator resistance data; Multiply the equivalent inductance data of the motor stator by the rate of change of current, and multiply the stator resistance data of the motor by the first stator current data. Add the two together to output the estimated value of back electromotive force. The arctangent of the back electromotive force estimate in the stationary coordinate system is calculated, and the estimated electrical angle is output. The difference between the estimated electrical angle and the base electrical angle is calculated, and the instantaneous compensation angle is output.

[0024] Since the change in current is affected by the combined effect of winding inductance and resistance, the compensation angle calculation module introduces the pre-stored equivalent inductance data and resistance data of the motor stator, converts the rate of change of current in the stationary coordinate system into an estimated value of back electromotive force, and then obtains the estimated electric angle from the direction of back electromotive force. After receiving the rate of change of current in the stationary coordinate system, the compensation angle calculation module reads the equivalent inductance data of the motor stator and the motor stator resistance data corresponding to the current motor from the controller parameter storage area. exist shaft and The following processing is performed on each axis: First, the equivalent inductance data of the motor stator is multiplied by the rate of change of the current on the corresponding axis. Then, the stator resistance data of the motor is multiplied by the stator current data at the first sampling time. The two results are added together to form the estimated value of the back electromotive force in the stationary coordinate system. The stator current data at the first sampling moment is used so that the stator current data corresponds to the starting point of the difference between the two sampling times, thereby completing the discretization of the voltage equation within the same observation interval; get shaft and After estimating the back electromotive force of the shaft, the module performs arctangent calculation to form the estimated electrical angle for the current cycle; when the permanent magnet synchronous motor is in the zero vector action period, the stator terminal voltage U output by the inverter is zero, and its stator voltage equation is expressed as: in, For stator resistance, For stator current, For stator equivalent inductance, The rate of change of stator current. It is the back electromotive force; Under the physical constraints of this equation, the estimated back electromotive force obtained by adding the stator resistance voltage drop and the inductor voltage drop is physically equal to the opposite vector of the real back electromotive force, that is, the directions are 180° apart. Therefore, when reconstructing the electrical angle by performing arctangent calculation, the module synchronously introduces a 180-degree phase compensation offset based on the calculation results, or inverts the estimated values ​​of each axis before performing arctangent calculation, so as to eliminate the electrical angle reversal error caused by the opposite direction and ensure that the output estimated electrical angle can accurately point to the current real rotor flux position. This estimated electrical angle represents the rotor electrical angle direction reconstructed from the electromagnetic response during the zero vector period; To integrate it into the existing control link, the module subtracts the base electrical angle obtained by converting the encoder mechanical angle in the current control cycle from the estimated electrical angle after directional compensation. The difference is the instantaneous compensation angle. This instantaneous compensation angle is cached in the angle synthesis area of ​​the current cycle, waiting for the angle synthesis module to decide whether to superimpose it and the corresponding weighting ratio based on the load change state. If the equivalent inductance data or the stator resistance data of the motor are missing in the parameter storage area, the compensation angle calculation module will not perform the back electromotive force estimation for this cycle, and the instantaneous compensation angle will be set to zero directly. If the estimated back electromotive force is close to zero on both axes of the stationary coordinate system at the same time, causing the estimated electrical angle to be unstable, the basic electrical angle will still be used in this cycle and the triggering of compensation superposition will be stopped. This is to prevent the introduction of invalid angle offset when the rate of change of current is lower than the preset zero drift threshold or the parameters are not ready. The compensation angle calculation module does not attempt to replace the encoder position. It only reconstructs an instantaneous electrical angle observation value using the electromagnetic quantities during the zero vector period within the current control cycle and converts it into an angle difference with the same dimension as the basic electrical angle, which facilitates subsequent fusion.

[0025] In a preferred embodiment of the present invention, the angle synthesis module includes: dividing the mechanical angle data into mechanical angle data of the current control cycle and mechanical angle data of the previous control cycle according to the time sequence; The mechanical angle data of the current control cycle and the mechanical angle data of the previous control cycle are differentially processed to obtain the mechanical angular velocity data of the current control cycle and the mechanical angular velocity data of the previous control cycle. Calculate the difference between the mechanical angular velocity data of the current control cycle and the mechanical angular velocity data of the previous control cycle; divide the difference by the preset pulse width modulation cycle time, take the absolute value, and output the rate of change of angular velocity.

[0026] To avoid interference from the high-frequency changes of zero-vector double sampling during steady state to the decoupling angle and normal current loop, the angle synthesis module extracts the rate of change of angular velocity from the mechanical angle data and uses it as the criterion for starting compensation. The angle synthesis module continuously saves the mechanical angle data of the current control cycle and the previous control cycle. Before the end of the current cycle, the module first calculates the difference between the mechanical angle of the current cycle and the mechanical angle of the cycle before that to obtain the mechanical angular velocity data of the current control cycle. The mechanical angle of the previous control cycle is then subtracted from the mechanical angle of the previous cycle to obtain the mechanical angular velocity data of the previous control cycle. The mechanical angular velocity data of the previous control cycle is then subtracted from the mechanical angular velocity data of the current control cycle to obtain the velocity change. This velocity change is then divided by the preset pulse width modulation cycle time, and the absolute value is taken to form the angular velocity change rate. The rate of change of angular velocity is stored in the current cycle state area and is subsequently used for comparison with a preset threshold. Since the rate of change of mechanical angular velocity can directly reflect whether the load changes abruptly within the preset time period, and this information still comes from the original encoder channel, no additional sensor is required. If the mechanical angle data for the current cycle has not been updated, or the mechanical angle data for the previous control cycle is missing, the angle synthesis module stops calculating the new rate of change of angular velocity, maintains the calculation results from the previous effective cycle, and restricts the weight generation process for this cycle to the steady-state branch. If the pulse width modulation period time parameter is not configured, the angular velocity change rate will not be output to avoid distortion of state judgment due to inconsistent time base; In the above scenario, the calculation link of the rate of change of angular velocity relies entirely on the existing mechanical angle data, so it does not change the original controller hardware structure. It only adds a criterion link in the software to determine when to enable the compensation angle.

[0027] In a preferred embodiment of the present invention, the angle synthesis module further includes: obtaining a preset first mutation threshold; comparing the rate of change of angular velocity with the first mutation threshold; when the rate of change of angular velocity is less than or equal to the first mutation threshold, determining it to be in a steady state, generating a weight value with a value of zero, and outputting a first weight result.

[0028] To maintain position decoupling stability under normal operating conditions and prevent the compensation branch from being falsely triggered when the amplitude of angular velocity fluctuation is below the steady-state dead zone, the system sets a first mutation threshold as the activation lower limit of the compensation logic. After obtaining the rate of change of angular velocity in the current cycle, the angle synthesis module reads the preset first abrupt change threshold and performs a comparison; when the rate of change of angular velocity is less than or equal to the first abrupt change threshold, the module determines that the motor is in a steady state or a slowly changing state. In this state, although the instantaneous compensation angle has been calculated in the previous stage, it does not participate in the decoupling angle correction of the current cycle; the module directly generates a weight value with a value of zero, saves it as the first weight result, and makes the weighted compensation angle zero in the subsequent angle synthesis stage; Since the encoder angle has a fixed communication delay under steady-state conditions, the resulting electrical angle deviation within adjacent control cycles is within the decoupling error band allowed by the system. Maintaining the basic electrical angle unchanged is sufficient to meet the decoupling requirements, and there is no need to introduce additional high-frequency compensation. If the angular velocity change rate calculation link is interrupted in this cycle, or the first mutation threshold is not successfully read, the module will process it as a steady state and set the first weight result to zero. This default processing mechanism ensures that when the threshold information is incomplete, the system will still maintain the original encoder-dominated control mode and will not erroneously trigger compensation due to missing threshold information. In the above scenario, the first mutation threshold acts as a filter, ensuring that the current derivative compensation branch is activated only when preset dynamic conditions are met, and remains closed during normal operation.

[0029] In a preferred embodiment of the present invention, the angle synthesis module further includes: obtaining a preset second mutation threshold; when the rate of change of angular velocity is greater than the first mutation threshold and less than the second mutation threshold, it is determined to be a dynamic mutation state; Calculate the difference between the rate of change of angular velocity and the first mutation threshold, divide the difference by the difference between the second mutation threshold and the first mutation threshold to generate the transition weight value, and output the second weight result.

[0030] To avoid abrupt changes in the decoupling angle caused by the compensation angle suddenly switching when crossing a single threshold, the system sets a second threshold for sudden changes and distributes the compensation amount in a linear transition manner between the first and second thresholds. When the angle synthesis module finds that the current rate of change of angular velocity is greater than the first mutation threshold and less than the second mutation threshold after comparison, the module will determine the current period as a dynamic mutation state. At this point, first calculate the difference between the rate of change of angular velocity and the first mutation threshold, then calculate the threshold interval between the second mutation threshold and the first mutation threshold. Divide the former by the latter to form a transition weight value between 0 and 1. This transition weight value is written into the current cycle weight area as the second weight result. The purpose of the second weighting result is to gradually increase the angle compensation amount as the rate of change of angular velocity increases, rather than abruptly connecting it in a switching manner. This approach is suitable for situations where the load increases rapidly but has not yet reached a significant step impact. For example, when the resistance step amplitude of the motor output shaft exceeds the preset first dynamic load lower limit in a short period of time but has not completely stalled, the system can first introduce electromagnetic compensation proportionally. If the second mutation threshold is not greater than the first mutation threshold, then the transition interval does not exist, the module does not generate the second weight result, and falls back to the steady-state branch for processing; This avoids abnormal division caused by incorrect threshold configuration; if the rate of change of angular velocity is exactly equal to the first mutation threshold, it will still be classified into the steady-state branch; if it is close to the second mutation threshold but has not yet been reached, the transition weight value will still be output proportionally. The second weighting result provides a smooth transition for the access of the compensation angle, enabling the system to gradually increase compensation under moderate load changes without changing the original control cycle structure.

[0031] In a preferred embodiment of the present invention, the angle synthesis module further includes: comparing the rate of change of angular velocity with a second mutation threshold; when the rate of change of angular velocity is greater than or equal to the second mutation threshold, determining it as a step impact state, generating a weight value of one, and outputting a third weight result.

[0032] When the rate of change of angular velocity is greater than or equal to the second abrupt threshold, in order to suppress the expansion of phase deviation caused by mechanical angle delay, the system will connect the compensation angle to the decoupling link in full mode. The angle synthesis module compares the rate of change of the current cycle angular velocity with the second abrupt change threshold. When the rate of change of angular velocity is greater than or equal to the second abrupt change threshold, the module determines that the system is in a step impact state, such as when the motor suddenly stalls during high-speed operation, or when the rate of change of output torque exceeds the preset step overload threshold. In this state, the module directly generates a weight value of one, which is output as the third weight result; The output of the third weight result ensures that the instantaneous compensation angle obtained by the preceding compensation angle calculation module participates in the angle correction within this cycle. This allows the electrical angle information obtained from the zero vector current derivative reconstruction to directly enter the decoupling link when the mechanical feedback delay cannot cover rapid position changes. If the second mutation threshold has been read but the current cycle angular velocity change rate value is invalid, the module maintains the state of the previous valid cycle or rolls back to zero weight to prevent accidental full compensation when the state quantity is uncertain. In the above scenario, the third weight result is used to deal with the load step impact condition, so that the synthesized electrical angle is close to the current real electrical angle under such conditions.

[0033] In a preferred embodiment of the present invention, the angle synthesis module further includes: outputting the corresponding first weight result, second weight result or third weight result as the target weight value according to the current determined state; Multiply the target weight value by the instantaneous compensation angle to output the weighted compensation angle; add the weighted compensation angle to the base electrical angle to output the composite electrical angle.

[0034] In order to combine the compensation link with the basic electrical angle to form a single decoupled angle that can be used for control, the angle synthesis module converges the above three types of weight results to the same target weight value and combines it with the instantaneous compensation angle. The angle synthesis module selects the corresponding item from the first weight result, the second weight result, and the third weight result as the target weight value based on the state determination result of the current cycle; if the determination is a steady state, then the weight value of 0 is selected. If the state is determined to be a dynamic change state, a transition weight value is selected; if the state is determined to be a step impact state, a weight of one is selected; the target weight value is multiplied by the instantaneous compensation angle of the current cycle to obtain the weighted compensation angle. The weighted compensation angle is then added to the basic electrical angle to form the composite electrical angle actually sent into the decoupling link in the current control cycle; After the synthesized electrical angle is formed, it is written into the current cycle angle register area of ​​the servo control module, replacing the basic electrical angle obtained by the encoder alone in the coordinate transformation; in this way, the encoder angle still constitutes the basic part, while the angle difference obtained by the high-frequency current derivative is only superimposed on it as a correction amount. If the instantaneous compensation angle is not successfully generated in this cycle, the angle synthesis module will set the weighted compensation angle to zero regardless of the target weight value, and the synthesized electrical angle will degenerate into the basic electrical angle. If the target weight value is generated normally but the basic electrical angle is missing, no new synthetic electrical angle will be output in this cycle, and the servo control module will continue to use the angle from the previous valid cycle; this process ensures that the control link still has a fallback path when any branch upstream is abnormal. In the above scenario, the angle synthesis module completes the final combination between the mechanical angle and the electromagnetic observation angle, enabling the controller to introduce instantaneous compensation to varying degrees under different operating conditions.

[0035] In a preferred embodiment of the present invention, the servo control module includes: acquiring the composite electrical angle and stator current data in a two-phase stationary coordinate system; performing coordinate transformation on the stator current data in the two-phase stationary coordinate system according to the composite electrical angle, and outputting direct-axis current data and quadrature-axis current data in a synchronous rotating coordinate system; The direct-axis current data and quadrature-axis current data are input into the current loop regulator built into the servo control module, which outputs a space vector pulse width modulation drive signal.

[0036] To achieve closed-loop control of the actual output torque of the motor, the synthesized electrical angle is directly input into the coordinate transformation process of the servo control module; The servo control module simultaneously acquires stator current data in two-phase stationary coordinate systems and the synthesized electrical angle output by the angle synthesis module within the current control cycle. The module performs coordinate transformation based on the synthesized electrical angle, decomposing the stator current in the stationary coordinate system into direct-axis current data and quadrature-axis current data in the synchronous rotating coordinate system; wherein, the direct-axis current data corresponds to the flux linkage direction component, and the quadrature-axis current data corresponds to the torque direction component; The two current data points are then fed into the current loop regulator, where they are adjusted to form a space vector pulse width modulation drive signal, which is then output to the inverter. Specifically, in order to achieve observability and closed-loop integrity of the underlying control, the current loop regulator performs a difference operation between the actual direct-axis and quadrature-axis current data and the corresponding current command, and inputs the difference into the proportional-integral control link, outputting a voltage reference quantity in a synchronous rotating coordinate system. Using the same composite electrical angle, an inverse Park transformation is performed on the voltage reference quantity to obtain the voltage command in the two-phase stationary coordinate system. Finally, it is sent to the space vector modulation generator to be mapped into the switching pulses of the six inverter bridge arms, thus completing the physical generation of the drive signal. In this process, if the angle synthesis module of this cycle has already provided the corrected synthesized electrical angle, the coordinate transformation directly uses this angle to complete the current decoupling; If no new synthetic electrical angle is generated in this cycle, the servo control module will roll back to use the basic electrical angle for coordinate transformation in order to maintain the continuity of the control process. If the stator current data in the two-phase stationary coordinate system is missing, the current loop regulator in this cycle will not update the new drive quantity, but will continue to maintain the previous effective drive result or process it according to the existing protection strategy; this part is only used to ensure that the control closed loop in the current cycle is not interrupted due to a single missing sample. In the above scenario, the synthesized electric angle is directly used as the angle reference for the Parker transformation and enters the current control main link; Therefore, the current change information extracted from the zero vector interval is ultimately implemented in the direct-axis and quadrature-axis current decoupling and space vector pulse width modulation drive output, thereby completing the control closed loop of the entire system.

[0037] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A motor torque electromechanical servo control system based on frequency conversion regulation, characterized in that, include: A motor, an inverter connected to the motor, an encoder, a current sensor, and a controller, the controller comprising: The servo control module is used to acquire the mechanical angle data output by the encoder and convert it into a basic electrical angle, perform closed-loop control on the stator current of the motor, and output a space vector pulse width modulation drive signal to the inverter. The current sampling module is used to perform at least two consecutive samplings through the current sensor within the zero vector action interval corresponding to the space vector pulse width modulation drive signal, according to the space vector pulse width modulation drive signal, to obtain the three-phase stator current sampling values, perform coordinate transformation, and output the stator current data at two sampling times in the two-phase stationary coordinate system. The current change rate calculation module is used to acquire stator current data at two sampling times in the two-phase stationary coordinate system, perform differential calculation on the stator current change in the two-phase stationary coordinate system, and output the current change rate in the stationary coordinate system. The compensation angle calculation module is used to estimate the back electromotive force based on the current change rate and pre-stored motor body parameters to reconstruct the instantaneous rotor position and output the instantaneous compensation angle. An angle synthesis module is used to calculate the rate of change of angular velocity based on the mechanical angle data, generate dynamic weights based on the rate of change of angular velocity, multiply the dynamic weights by the instantaneous compensation angle and then add them to the base electrical angle, and output the synthesized electrical angle to the servo control module.

2. The motor torque electromechanical servo control system based on frequency conversion regulation according to claim 1, characterized in that, The current sampling module includes: The space vector pulse width modulation drive signal is monitored, and the state intervals of all three-phase upper bridge arms being turned off or all being turned on are identified according to the order of occurrence. Zero vector interval data is output. Within the zero vector interval data, the first sampling time and the second sampling time are determined in chronological order. Analog-to-digital conversion is triggered at the first sampling time and the second sampling time respectively to obtain the three-phase stator current sampling values. The three-phase stator current sampling values ​​are then subjected to Clark coordinate transformation to output the first stator current data in the two-phase stationary coordinate system at the first sampling time and the second stator current data in the two-phase stationary coordinate system at the second sampling time.

3. The motor torque electromechanical servo control system based on frequency conversion regulation according to claim 2, characterized in that, The current change rate calculation module includes: Acquire the first sampling time, the second sampling time, the first stator current data, and the second stator current data; calculate the time difference between the second sampling time and the first sampling time; Calculate the difference between the second stator current data and the first stator current data in the two-phase stationary coordinate system, and divide the difference by the time difference to output the current change rate in the stationary coordinate system.

4. The motor torque electromechanical servo control system based on frequency conversion regulation according to claim 3, characterized in that, The motor body parameters include the equivalent inductance data of the motor stator and the stator resistance data of the motor. The compensation angle calculation module includes: Obtain the equivalent inductance data of the motor stator and the stator resistance data of the motor; multiply the equivalent inductance data of the motor stator by the rate of change of current, and multiply the stator resistance data of the motor by the first stator current data, add the two together, and output the back electromotive force estimate; The arctangent of the estimated back electromotive force in the stationary coordinate system is calculated to output the estimated electrical angle; the difference between the estimated electrical angle and the basic electrical angle is calculated to output the instantaneous compensation angle.

5. The motor torque electromechanical servo control system based on frequency conversion regulation according to claim 1, characterized in that, The angle synthesis module includes: The mechanical angle data is divided into mechanical angle data for the current control cycle and mechanical angle data for the previous control cycle according to the time series. The mechanical angle data of the current control cycle and the mechanical angle data of the previous control cycle are differentially processed to obtain the mechanical angular velocity data of the current control cycle and the mechanical angular velocity data of the previous control cycle. Calculate the difference between the mechanical angular velocity data of the current control cycle and the mechanical angular velocity data of the previous control cycle; divide the difference by the preset pulse width modulation period time, take the absolute value, and output the rate of change of angular velocity.

6. The motor torque electromechanical servo control system based on frequency conversion regulation according to claim 5, characterized in that, The angle synthesis module also includes: Obtain a preset first mutation threshold; compare the rate of change of angular velocity with the first mutation threshold; When the rate of change of angular velocity is less than or equal to the first mutation threshold, it is determined to be in a steady state, and a weight value of zero is generated, and the first weight result is output.

7. The motor torque electromechanical servo control system based on frequency conversion regulation according to claim 6, characterized in that, The angle synthesis module also includes: Obtain a preset second mutation threshold; when the rate of change of angular velocity is greater than the first mutation threshold and less than the second mutation threshold, it is determined to be a dynamic mutation state; Calculate the difference between the rate of change of angular velocity and the first mutation threshold, divide the difference by the difference between the second mutation threshold and the first mutation threshold to generate a transition weight value, and output the second weight result.

8. The motor torque electromechanical servo control system based on frequency conversion regulation according to claim 7, characterized in that, The angle synthesis module also includes: The rate of change of angular velocity is compared with the second mutation threshold; when the rate of change of angular velocity is greater than or equal to the second mutation threshold, it is determined to be a step impact state, and a weight value of one is generated, and the third weight result is output.

9. The motor torque electromechanical servo control system based on frequency conversion regulation according to claim 8, characterized in that, The angle synthesis module also includes: Based on the current determination status, the corresponding first weight result, second weight result, or third weight result will be output as the target weight value; Multiply the target weight value by the instantaneous compensation angle to output the weighted compensation angle; add the weighted compensation angle to the base electrical angle to output the composite electrical angle.

10. The motor torque electromechanical servo control system based on frequency conversion regulation according to claim 9, characterized in that, The servo control module includes: Acquire the combined electrical angle and stator current data in the two-phase stationary coordinate system; perform coordinate transformation on the stator current data in the two-phase stationary coordinate system based on the combined electrical angle, and output the direct-axis current data and quadrature-axis current data in the synchronous rotating coordinate system; The direct-axis current data and the quadrature-axis current data are input into the current loop regulator built into the servo control module, and the space vector pulse width modulation drive signal is output.

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