A coaxial motor rotating speed estimation method and system based on power generation measurement

Abstract

The application relates to the technical field of motor rotating speed calculation, in particular to a coaxial motor rotating speed calculation method and system based on power generation measurement, which comprises the following steps: synchronously acquiring the driving current of a main motor, the direct current end voltage and load current of a permanent magnet direct current auxiliary motor, a reference temperature and a positive rotating speed instruction; determining an overload limiting amplitude attenuation coefficient; calculating a transient temperature rise; correcting a reference internal resistance and a preset reference back electromotive force constant to obtain a real internal resistance and a comprehensive back electromotive force constant; during a constant current limiting amplitude safety mode, adjusting a preset programmable gain amplifier setting equivalent quantization resolution to continuously acquire the absolute value of the direct current end voltage; and if the absolute value of the direct current end voltage is not smaller than a dead zone threshold value, the rotating speed is calculated based on the direct current end voltage, the load current, the real internal resistance and the comprehensive back electromotive force constant to adjust the main motor. The application can solve the problem of inaccurate rotating speed calculation caused by low speed dead zone and temperature drift.

Description

Technical Field

[0001] This application relates to the technical field of motor speed estimation, and in particular to a method and system for estimating the speed of a coaxial motor based on power generation measurement. Background Technology

[0002] Permanent magnet motors are widely used in automation equipment and industrial drives. In coaxial drive topologies containing a main motor and a permanent magnet DC auxiliary motor, the overall mechanical speed of the system is usually estimated by measuring the back electromotive force (EMF) of the permanent magnet DC auxiliary motor. When the system executes heavy-load drive or low-speed start commands, the back EMF amplitude of the permanent magnet DC auxiliary motor is weak and close to the sampling noise floor due to low-speed operation. At this time, the electromagnetic interference and power supply disturbance introduced by the surge in peak drive current of the main motor under heavy load will further reduce the reliability of back EMF observation, thus causing the system to fall into a low-speed measurement dead zone where back EMF cannot be reliably observed. If the drive current is blindly increased within the measurement dead zone, there is a risk of power device breakdown. At the same time, in the compact coaxial structure, the large amount of Joule heat generated during long-term operation may be conducted to the permanent magnet DC auxiliary motor along the rigid mechanical structure of the coaxial structure, which may cause the armature winding coil resistance of the permanent magnet DC auxiliary motor to increase and the equivalent back EMF constant to drift due to temperature. Temperature drift directly alters the parameter mapping relationship between the DC terminal voltage and load current of the permanent magnet DC auxiliary motor, causing the back electromotive force to deviate from the fixed linear ratio with the actual speed.

[0003] Chinese Patent Publication No. CN102074312B discloses a current control system for a permanent magnet motor based on predictive compensation. The system includes a thermal field identification module, a response offset identification module, a correction trajectory generation module, a limiting interval decision module, and a compensation command output module. The control logic involves acquiring the stator temperature rise curve, the permanent magnet temperature change rate, and torque fluctuation values; constructing a thermal load surface in three-dimensional space; and extracting magnetic performance reduction feature points. The system establishes a predictive drift window by comparing the phase difference between the target current vector and the actual sampled current before and after the feature point. After identifying the trend offset interval, the module performs differential processing on the two sets of current data to generate a predictive correction trajectory. After setting the amplitude clipping boundary by combining the inductance change rate, it outputs a current execution command superimposed with the response delay correction amount to compensate for the magnetic performance attenuation caused by thermal drift of a single permanent magnet motor.

[0004] The aforementioned existing technology uses a unified data flow model to correlate the temperature rise and magnetic performance decay within the motor, with data extraction and compensation operations completed within a single current closed loop. However, in specific speed measurement conditions where the main motor and permanent magnet DC auxiliary motor are coaxially connected, the weak observation dead zone of the back EMF caused by low speed and the slow impedance temperature drift caused by Joule heat conduction belong to completely different time scales. This system attributes parameter differences to response drift and performs single-dimensional differential superposition. Under conditions of sudden heavy load on the main motor causing current fluctuations or low-speed start-up, the three-dimensional thermal load surface constructed based on slow temperature changes cannot promptly address signal extraction interference in the unobservable low back EMF zone. Limited by the unified data flow model, this trajectory differential correction logic mixes sampling errors from the unobservable low-speed weak back EMF state with slow thermal impedance drift, causing the induced EMF at the permanent magnet DC auxiliary motor end to deviate from the true ratio, increasing estimation errors, and distorting the mechanical speed calculated from the back EMF reconstructed based on generator parameters. Summary of the Invention

[0005] To address the inaccurate speed calculations caused by low-speed dead zones and temperature drift, this application provides a method and system for calculating the speed of a coaxial motor based on power generation measurement.

[0006] Firstly, this application provides a method for estimating the speed of a coaxial motor based on power generation measurement, employing the following technical solution: A method for estimating the speed of a coaxial motor based on power generation measurement, applied to a coaxial system including a main motor and a permanent magnet DC auxiliary motor, comprising: The drive current of the main motor, the DC terminal voltage and load current of the permanent magnet DC auxiliary motor, the reference temperature and the forward speed command are acquired simultaneously. The overload limiting attenuation coefficient is determined based on the comparison between the instantaneous absolute value of the driving current and the preset overload limiting threshold. The transient temperature rise is calculated based on the load current, the reference internal resistance of the permanent magnet DC auxiliary motor, the preset thermal capacity parameters, and the preset thermal resistance parameters. The transient temperature rise is superimposed with the reference temperature to obtain the equivalent back EMF calibration temperature. Based on the equivalent back EMF calibration temperature, the impedance ratio and the equivalent back EMF temperature coefficient are matched, and the reference internal resistance and the preset reference back EMF constant are corrected respectively to obtain the true internal resistance and the comprehensive back EMF constant. If the absolute value of the DC terminal voltage is less than the preset dead zone threshold and the positive speed command is greater than zero, the main motor is driven in constant current limiting safety mode based on the overload limiting attenuation coefficient. If the state of the absolute value of the DC terminal voltage being less than the dead zone threshold continues for more than a preset time, the current command of the main motor is increased by a preset step size under the condition of not exceeding the preset maximum allowable current of the system, until the absolute value of the DC terminal voltage is detected to be not less than the dead zone threshold or a fault shutdown is triggered. During the constant current limiting safety mode, the preset programmable gain amplifier is adjusted to set the equivalent quantization resolution to continuously acquire the absolute value of the DC terminal voltage; If the absolute value of the DC terminal voltage is not less than the dead zone threshold, the speed is calculated based on the DC terminal voltage, the load current, the actual internal resistance, and the comprehensive back EMF constant to adjust the main motor.

[0007] Optionally, the step of synchronously acquiring the drive current of the main motor, the DC terminal voltage of the permanent magnet DC auxiliary motor, the load current, the reference temperature, and the forward speed command includes: At the start of the preset control cycle, the drive current, the DC terminal voltage, and the load current are synchronously acquired through a unified hardware trigger signal. The temperature at the interface between the main motor and the permanent magnet DC auxiliary motor is extracted and used as the reference temperature.

[0008] Optionally, determining the overload limiting attenuation coefficient based on the comparison result between the instantaneous absolute value of the driving current and the preset overload limiting threshold includes: If the instantaneous absolute value of the driving current is greater than the overload limiting threshold, the difference between the instantaneous absolute value of the driving current and the overload limiting threshold is taken as the excess difference, and the overload limiting attenuation coefficient is obtained by interpolation based on the excess difference in a preset lookup table. If the instantaneous absolute value of the driving current is not greater than the overload limiting threshold, the overload limiting attenuation coefficient is set to a preset constant and the lookup table is bypassed.

[0009] Optionally, the calculation of the transient temperature rise based on the load current, the reference internal resistance of the permanent magnet DC auxiliary motor, the preset thermal capacity parameter, and the preset thermal resistance parameter includes: Obtain the square value of the load current corresponding to each control cycle within a preset time window, and multiply the square value by the reference internal resistance to form a heat generation power sequence; The transient temperature rise is calculated by substituting the heating power sequence into the thermal state equation constructed by discretizing the heat capacity parameter and the thermal resistance parameter.

[0010] Optionally, the execution of the thermal state equation can be decentralized to a slower task thread after frequency reduction; The product of the thermal capacity parameter and the thermal resistance parameter constitutes the thermal time constant, and the execution cycle of the slow task thread is less than a preset proportion of the thermal time constant.

[0011] Optionally, the preset heat capacity parameter characterizes the equivalent heat capacity between the armature winding and the housing cooling surface of the permanent magnet DC auxiliary motor; The preset thermal resistance parameter characterizes the equivalent conductive thermal resistance between the armature winding of the permanent magnet DC auxiliary motor and the cooling surface of the housing.

[0012] Optionally, the step of matching the impedance ratio and the equivalent back EMF temperature coefficient based on the equivalent back EMF calibration temperature includes: The impedance ratio and the equivalent back EMF temperature coefficient are output based on the equivalent back EMF calibration temperature matching in a pre-set temperature drift matrix calibrated by a constant temperature test.

[0013] Optionally, the step of calculating the rotational speed based on the DC terminal voltage, the load current, the actual internal resistance, and the combined back EMF constant includes: The reconfigured voltage drop is obtained by multiplying the load current, which is specified as the outflow direction, by the actual internal resistance. The sum of the reconstructed voltage drop and the DC terminal voltage is used as the induced electromotive force; The ratio of the induced electromotive force to the comprehensive back electromotive force constant is used as the angular velocity and as the calculated rotational speed.

[0014] Optional, also includes: During the execution of the slow task thread, the first time derivative of the reference temperature is calculated in real time. When the absolute value of the first time derivative is continuously less than the preset equilibrium threshold within the preset observation window, the calibrated thermal resistance is obtained by using the ratio of the equivalent measured temperature rise of the armature winding of the permanent magnet DC auxiliary motor relative to the reference temperature to the steady-state mean value of the heating power sequence, which is obtained by the preset winding equivalent temperature acquisition unit. The calibrated thermal resistance is used to replace the thermal resistance parameter for steady-state background self-calibration, and the cumulative update of the thermal state equation is maintained.

[0015] Secondly, this application provides a coaxial motor speed estimation system based on power generation measurement, employing the following technical solution: A coaxial motor speed estimation system based on power generation measurement, applied to a coaxial system including a main motor and a permanent magnet DC auxiliary motor, comprising: The parameter synchronization acquisition module is used to synchronously acquire the drive current of the main motor, the DC terminal voltage and load current of the permanent magnet DC auxiliary motor, the reference temperature and the forward speed command. The overload limiting module is used to determine the overload limiting attenuation coefficient based on the comparison result between the instantaneous absolute value of the drive current and the preset overload limiting threshold. The parameter matching module is used to calculate the transient temperature rise based on the load current, the reference internal resistance of the permanent magnet DC auxiliary motor, the preset thermal capacity parameters and the preset thermal resistance parameters, and to superimpose the transient temperature rise with the reference temperature as the equivalent back EMF calibration temperature. Based on the equivalent back EMF calibration temperature, the impedance ratio and the equivalent back EMF temperature coefficient are matched. The parameter correction module is used to correct the reference internal resistance and the preset reference back EMF constant by using the impedance ratio and the equivalent back EMF temperature coefficient, respectively, to obtain the actual internal resistance and the comprehensive back EMF constant. The drive calculation module is used to drive the main motor in a constant current limiting safety mode based on the overload limiting attenuation coefficient if the absolute value of the DC terminal voltage is less than a preset dead zone threshold and the positive speed command is greater than zero. If the absolute value of the DC terminal voltage is continuously less than the dead zone threshold for a preset duration, the current command of the main motor is increased by a preset step size under the condition that it does not exceed the preset maximum allowable current of the system, until the absolute value of the DC terminal voltage is detected to be not less than the dead zone threshold or a fault shutdown is triggered. During the constant current limiting safety mode, the preset programmable gain amplifier is adjusted to set the equivalent quantization resolution to continuously obtain the absolute value of the DC terminal voltage. If the absolute value of the DC terminal voltage is not less than the dead zone threshold, the speed is calculated based on the DC terminal voltage, the load current, the actual internal resistance, and the comprehensive back EMF constant to adjust the speed of the main motor.

[0016] In summary, this application includes the following beneficial technical effects: 1. By synchronously acquiring the drive current of the main motor and the DC terminal voltage and load current of the auxiliary motor, and introducing an overload limiting attenuation coefficient to switch the constant current limiting safety mode, and combining transient temperature rise to correct the reference internal resistance and reference back EMF constant in real time, when the absolute value of the DC terminal voltage is lower than the dead zone threshold, the current command is actively increased to overcome static friction and the quantization resolution is improved by using a programmable gain amplifier. This effectively eliminates the coupling interference of the unobservable state of low speed weak back EMF and temperature drift on speed estimation, and avoids the risk of power devices breaking down due to dead zone stall.

[0017] 2. The heat generation power sequence formed by multiplying the square of the load current by the reference internal resistance is substituted into the thermal state equation constructed by discretizing the thermal capacity and thermal resistance parameters to calculate the transient temperature rise. The execution of the thermal state equation is decentralized to a slow task thread after frequency reduction, which reduces the computing power consumption of the control cycle. At the same time, the time accumulation characteristics of the thermal state equation are used to improve the numerical stability and continuity of the transient temperature rise calculation.

[0018] 3. During the execution of slow task threads, the first-order time derivative of the reference temperature is calculated in real time. When the absolute value of the derivative is continuously less than the equilibrium threshold, the thermal resistance parameter is calibrated by the ratio of the equivalent measured temperature rise of the winding to the steady-state average value of the heating power. This achieves steady-state background self-calibration of the preset thermal resistance parameter and maintains the cumulative update accuracy of the thermal state equation during long-term operation. Attached Figure Description

[0019] Figure 1 A flowchart of mode switching and speed calculation provided in this application embodiment; Figure 2 The schematic diagram of the closed-loop control principle of the main motor provided in the embodiment of this application. Detailed Implementation

[0020] The following is in conjunction with the appendix Figure 1-2 This application will be described in further detail.

[0021] This embodiment discloses a method for estimating the speed of a coaxial motor based on power generation measurement, which is applied to a coaxial system including a main motor and a permanent magnet DC auxiliary motor. The power generation measurement involved in this application is essentially a back EMF reconstruction estimation process based on the electrical parameters at the generator end.

[0022] A main motor power and current sampling unit is installed on the stator side of the main motor, and a permanent magnet DC auxiliary motor voltage and current sensing unit is installed at the output terminals of the permanent magnet DC auxiliary motor. An equivalent winding temperature acquisition unit is installed at the armature winding of the permanent magnet DC auxiliary motor (the equivalent temperature can be estimated by attaching it to the winding end, inverting the thermal model of the housing, or using the internal resistance method). A coaxial thermal conductivity node reference unit is attached to the heat-conducting surface of the front flange at the junction of the main motor and the permanent magnet DC auxiliary motor. The outputs of the main motor power and current sampling unit, the permanent magnet DC auxiliary motor voltage and current sensing unit, the equivalent winding temperature acquisition unit, and the coaxial thermal conductivity node reference unit are communicatively connected to the joint decoupled main control unit. Regarding the direction of the speed command, if the system supports bidirectional operation, it is determined according to sign symmetry. This embodiment uses a positive speed command unidirectional drive as an example for explanation.

[0023] At the beginning of each control cycle, the joint decoupled main control unit synchronously acquires the drive current output by the main motor power and current sampling unit through a unified hardware timed trigger event. DC terminal voltage output by the voltage and current sensing unit of the permanent magnet DC auxiliary motor With load current It also acquires the forward rotation speed command; simultaneously, it synchronously acquires the reference temperature output from the coaxial heat conduction node reference unit. The load current flowing out of the permanent magnet DC auxiliary motor is specified as positive.

[0024] A multi-channel analog-to-digital converter (ADC) is employed to respond to a unified hardware-timed trigger event, compressing the phase deviation of the four-channel sampling to within a single conversion clock cycle. The multi-channel ADC is driven by a hardware-timed trigger event for injection sampling, with a basic quantization bit depth of at least 12 bits. Internally, this same multi-channel ADC includes a synchronous injection channel with a programmable gain amplifier, which can be individually activated during subsequent constant-current limiting safety mode. This is achieved by increasing the amplification factor of the programmable gain amplifier to ensure that the voltage corresponding to the least significant bit of the quantization meets the specified requirements. The conditions (where) This refers to the minimum voltage corresponding to the basic quantization resolution of a multi-channel analog-to-digital converter. The gain of the programmable gain amplifier. The system uses a preset dead-zone threshold and employs preset bias error calibration and hysteresis filtering to eliminate analog front-end noise interference, thereby setting an equivalent quantization resolution that matches the measurement accuracy required to measure the dead-zone threshold. The drive current is obtained through the DC bus shunt resistor, which can be replaced by a Hall current sensor or by synthesizing the phase current using the three resistors of the lower bridge arm of the inverter.

[0025] The joint decoupling main control unit converts the drive current into an instantaneous absolute value. Based on the verification analysis, the influence of leakage flux is negligible, therefore no corresponding compensation calculation is performed. The instantaneous absolute value is then compared with the overload limiting threshold formed by 1.2 to 1.5 times the rated current of the main motor. In comparison, this threshold is explicitly defined as an instantaneous value threshold. When the instantaneous absolute value exceeds the overload limiting threshold, the excess difference is calculated. The excess value is used as an index input to a preset lookup table, and the overload limiting attenuation coefficient is output through linear interpolation. The value of this coefficient ranges from 0 to 1. Its physical meaning is that in the subsequent constant current limiting safety mode, it is used as a scaling factor to directly scale and limit the current closed-loop given command amplitude of the main motor; when the instantaneous absolute value is not greater than the overload limiting threshold, the overload limiting attenuation coefficient is forcibly set to a preset constant of 1 and the preset lookup table is bypassed.

[0026] The overload limiting threshold is set to 1.35 times the rated current of the main motor, balancing false triggering suppression and overload safety capture. The preset lookup table is obtained through offline calibration using a dynamometer bench and is specifically used to extract the mapping relationship between the main motor overload current and the corresponding safety limiting attenuation amount. This avoids system crashes caused by model failure under complex operating conditions, and the preset lookup table can be replaced by second- to third-order polynomial fitting curves.

[0027] The joint decoupling main control unit extracts the preset thermal resistance parameters stored in the memory. With preset heat capacity parameters And construct the thermal time constant The thermal resistance parameter has the standard physical conductivity thermal resistance dimension. The heat capacity parameter has a standard heat capacity dimension. The aforementioned preset thermal resistance and preset thermal capacity parameters respectively characterize the equivalent conductive thermal resistance and equivalent thermal capacity between the armature winding and the housing cooling surface of the permanent magnet DC auxiliary motor. The factory-preset reference internal resistance of the permanent magnet DC auxiliary motor is used. With reference back electromotive force constant Collect the square value of the load current for each control cycle within a preset time window, and compare the square value of the load current with the fixed reference internal resistance. Multiplication yields an approximate heating power for thermal state estimation, forming a heating power sequence. This completely severs the self-excited error divergence algebraic loop caused by thermal feedback calculations using the dynamic internal resistance of the current cycle. The heating power sequence is then substituted, step by step, into the first-order thermodynamic equation of state constructed by discretizing preset heat capacity and preset thermal resistance parameters. Solving transient temperature rise Here, the heating power input term at the current moment in the first-order thermodynamic equation of state... (dimensions are) After multiplying with the preset thermal resistance parameter, the output directly has standard temperature dimensions. The result.

[0028] To avoid the severe waste of computing power caused by calculating large time constants of hundreds of seconds within a microsecond-level control cycle, the system decentralizes the discretization of the first-order thermodynamic state equation to a slower task thread after frequency reduction. Furthermore, the execution cycle of this slower task thread is less than a preset proportion of the thermal time constant (e.g., no greater than...). or This ensures numerical stability. The reference temperature characterizes the slowly varying external conductive heat background transmitted from the main motor and mechanical connections, while the transient temperature rise only characterizes the additional heat generation temperature rise generated by the permanent magnet DC auxiliary motor itself relative to the housing reference point.

[0029] The transient temperature rise is then summed with the reference temperature to obtain the equivalent back potential calibration temperature. The temperature rise in the calculation is based on This indicates that the numerical increment is the same as the Celsius temperature difference, and when superimposed, it is directly processed as the temperature difference. The equivalent back electromotive force calibration temperature is used as the index input, and a preset temperature drift matrix constructed using the constant temperature chamber calibration method is used to match the output dynamic impedance ratio. Temperature coefficient of steady-state equivalent back electromotive force The preset temperature drift matrix is ​​obtained offline by placing the tested unit in a constant temperature chamber at different set temperature gradients (e.g., using discrete constant temperature anchor points of -20℃, 0℃, 25℃, 60℃, and 100℃, and outputting the results through linear interpolation or piecewise interpolation) to perform static volt-ampere characteristics and reverse drag no-load power generation tests. The equivalent back EMF temperature coefficient is used to reflect the drift of the back EMF constant obtained from the constant temperature calibration of the entire unit. The dynamic impedance ratio increases monotonically with increasing equivalent back EMF calibration temperature, while the steady-state equivalent back EMF temperature coefficient decreases monotonically with increasing equivalent back EMF calibration temperature.

[0030] The joint decoupling main control unit calculates the first-order time derivative of the reference temperature in real time during the execution of slow task threads. When the absolute value of the first-order time derivative of the reference temperature is continuously less than the preset equilibrium threshold of 0.1℃ / min within the preset observation window, the equivalent measured temperature rise of the armature winding of the permanent magnet DC auxiliary motor relative to the reference temperature (obtained by the equivalent temperature acquisition unit of the winding) is used to obtain the calibrated thermal resistance by the ratio of the equivalent measured temperature rise of the armature winding of the permanent magnet DC auxiliary motor relative to the reference temperature (to accurately eliminate the interference of external heat dissipation environment changes and make the reference calibration point conform to the physical definition of the equivalent conduction path from the armature winding to the cooling surface of the housing in thermodynamics) to the steady-state mean value of the current heat generation power sequence. The calibrated thermal resistance is used to replace the preset thermal resistance parameter for steady-state background self-calibration and to maintain the cumulative update of the first-order thermodynamic equation of state.

[0031] The joint decoupling main control unit uses dynamic impedance multiplication to correct the reference internal resistance and obtain the true internal resistance. Without performing leakage flux compensation calculations, for brushed permanent magnet DC motors, the non-negligible brush voltage drop is already used as a preset brush voltage drop constant and is equivalently incorporated into the preset dead zone threshold for compensation during the aforementioned calibration stage. Therefore, here we only use the steady-state equivalent back EMF temperature coefficient to correct the reference back EMF constant to obtain the comprehensive back EMF constant. The combined back potential constant has The unit of measurement is denoted by . The reconstructed voltage drop is obtained by multiplying the load current in the specified outflow direction by the actual internal resistance. The induced electromotive force is obtained by summing the reconstructed voltage drop with the DC terminal voltage.

[0032] Combination Figure 1The illustrated method logic flow begins with the top layer synchronously acquiring various parameters and commands as the starting trigger. Upon receiving the forward speed command, the system enters a conditional judgment branch based on whether the absolute value of the DC terminal voltage is less than a preset dead-zone threshold. If the absolute value of the DC terminal voltage is less than the preset dead-zone threshold and the forward speed command is greater than zero, the division calculation is disabled, the calculated speed is paused, and the system switches to a preset constant current limiting safety mode based on the overload limiting attenuation coefficient to drive the main motor. In this mode, the control structure is converted to a current closed loop, and the main motor's given current command is set to a constant limited current obtained by multiplying the system's maximum allowable current by the overload limiting attenuation coefficient. This prevents the risk of equipment damage caused by a large short-circuit current due to dead-zone stall, which could lead to power device breakdown. Simultaneously, to avoid the system falling into a permanent protection lockout state due to the limited current being unable to overcome static friction, resulting in the speed and back EMF remaining at zero for an extended period. If the absolute value of the DC terminal voltage remains below the dead zone threshold for more than a preset time, the main motor current command is increased by a preset step size within the preset maximum allowable current of the system to forcibly break the static friction balance. The current then continuously returns along the detection loop to the voltage absolute value judgment node at the front end until the absolute value of the DC terminal voltage is detected to be not less than the dead zone threshold or a fault shutdown alarm is triggered. During the constant current limiting safety mode, a synchronous injection channel with a programmable gain amplifier is configured. By adjusting the equivalent quantization resolution of the programmable gain amplifier, the absolute value of the DC terminal voltage is continuously acquired to determine whether the absolute value of the DC terminal voltage is not less than the dead zone threshold. Along another branch of the judgment node, if the absolute value of the DC terminal voltage exceeds the dead zone threshold, the constant current limiting safety mode is exited and calculation resumes. The ratio of the induced electromotive force to the comprehensive back electromotive force constant is used as the angular velocity to calculate the rotational speed. The calculated rotational speed is converted according to a preset conversion factor. Use the same units of measurement as conventional mechanical rotation speed to unify the dimensions.

[0033] The comprehensive back EMF constant is recalculated in each control cycle from the reference back EMF constant and the steady-state equivalent back EMF temperature coefficient, allowing the slow variable of temperature to evolve independently with respect to the power generation constant. Subsequently, the calculated rotational speed is limited, combined with... Figure 2 The main motor closed-loop control signal flow topology is shown. The main motor's operating status is fed back to the internal calculation stage, and the calculated speed feedback is generated by analyzing the actual internal resistance and the comprehensive back EMF constant. The positive speed command and the calculated speed are used as positive and negative reference terms at the front-end superposition node to obtain the control deviation. This deviation signal is proportionally scaled in the main forward channel through the overload limiting attenuation coefficient stage, and then fed into the outer loop PID controller to perform closed-loop speed regulation to drive the main motor. The upper and lower limits of the calculated speed limit are jointly constrained by the rated speed of the permanent magnet DC auxiliary motor and the dynamic range of the sampling chain.

[0034] This embodiment also discloses a coaxial motor speed estimation system based on power generation measurement, applied to a coaxial system including a main motor and a permanent magnet DC auxiliary motor, for executing the aforementioned coaxial motor speed estimation method based on power generation measurement. The system includes a parameter synchronization acquisition module, an overload limiting module, a parameter matching module, a parameter correction module, and a drive estimation module.

[0035] The parameter synchronization acquisition module is communicatively connected to the main motor power and current sampling unit, the permanent magnet DC auxiliary motor voltage and current sensing unit, the winding equivalent temperature acquisition unit, and the coaxial conduction heat node reference unit. It is configured to synchronously acquire the drive current of the main motor, the DC terminal voltage and load current of the permanent magnet DC auxiliary motor, and the reference temperature of the coaxial system within the same control cycle, and acquire the positive speed command.

[0036] The input terminal of the overload limiting module is electrically connected to the current output port of the parameter synchronization acquisition module. It is configured to acquire the instantaneous absolute value of the drive current and determine the overload limiting attenuation coefficient of the main motor based on the comparison result between the instantaneous absolute value and the preset overload limiting threshold.

[0037] The input terminals of the parameter matching module are electrically connected to the current output port and temperature output port of the parameter synchronization acquisition module, respectively. It is configured to acquire the reference internal resistance and preset thermal capacitance parameters and preset thermal resistance parameters of the permanent magnet DC auxiliary motor, calculate the transient temperature rise based on the load current, reference internal resistance, preset thermal capacitance parameters and preset thermal resistance parameters within a preset time window, superimpose the transient temperature rise with the reference temperature as the equivalent back EMF calibration temperature, and obtain the impedance ratio and equivalent back EMF temperature coefficient based on the equivalent back EMF calibration temperature.

[0038] The parameter correction module is connected to the parameter output port of the parameter matching module and is configured to use the impedance ratio and the equivalent back EMF temperature coefficient to correct the reference internal resistance and the preset reference back EMF constant, respectively, to obtain the actual internal resistance and the comprehensive back EMF constant.

[0039] The input of the drive calculation module is connected to the parameter synchronization acquisition module, the overload limiting module, and the parameter correction module. It is configured to switch to constant current limiting safety mode to drive the main motor if the absolute value of the DC terminal voltage is less than the preset dead zone threshold and the positive speed command is greater than zero, based on the overload limiting attenuation coefficient. If the absolute value of the DC terminal voltage is less than the dead zone threshold for more than a preset time, the current command of the main motor is increased by a preset step size under the condition that it does not exceed the preset maximum allowable current of the system, until the absolute value of the DC terminal voltage is detected to be not less than the dead zone threshold or a fault shutdown is triggered. During the constant current limiting safety mode, the preset programmable gain amplifier is adjusted to set the equivalent quantization resolution to continuously acquire the absolute value of the DC terminal voltage. If the absolute value of the DC terminal voltage is not less than the dead zone threshold, the speed is calculated based on the DC terminal voltage, load current, actual internal resistance, and comprehensive back EMF constant to adjust the main motor.

[0040] The micro-algorithm details regarding the execution of the above logic by each module have been described in detail in the aforementioned method embodiments and will not be repeated here.

[0041] The system further includes a processor, memory, and a system bus. The processor and memory are connected via the system bus. The main motor power and current sampling unit, the permanent magnet DC auxiliary motor voltage and current sensing unit, the winding equivalent temperature acquisition unit, and the coaxial conduction heat node reference unit are connected to the processor via the system bus. The aforementioned functional modules are program instructions stored in the memory and executed by the processor, or hardware logic circuits instantiated by application-specific integrated circuits (ASICs) and field-programmable gate arrays (FPGAs).

[0042] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for estimating the rotational speed of a coaxial motor based on power generation measurement, applied to a coaxial system comprising a main motor and a permanent magnet DC auxiliary motor, characterized in that, include: The drive current of the main motor, the DC terminal voltage and load current of the permanent magnet DC auxiliary motor, the reference temperature and the forward speed command are acquired simultaneously. The overload limiting attenuation coefficient is determined based on the comparison between the instantaneous absolute value of the driving current and the preset overload limiting threshold. The transient temperature rise is calculated based on the load current, the reference internal resistance of the permanent magnet DC auxiliary motor, the preset thermal capacity parameters, and the preset thermal resistance parameters. The transient temperature rise is superimposed with the reference temperature to obtain the equivalent back EMF calibration temperature. Based on the equivalent back EMF calibration temperature, the impedance ratio and the equivalent back EMF temperature coefficient are matched, and the reference internal resistance and the preset reference back EMF constant are corrected respectively to obtain the true internal resistance and the comprehensive back EMF constant. If the absolute value of the DC terminal voltage is less than the preset dead zone threshold and the positive speed command is greater than zero, the main motor is driven in constant current limiting safety mode based on the overload limiting attenuation coefficient. If the state of the absolute value of the DC terminal voltage being less than the dead zone threshold continues for more than a preset time, the current command of the main motor is increased by a preset step size under the condition of not exceeding the preset maximum allowable current of the system, until the absolute value of the DC terminal voltage is detected to be not less than the dead zone threshold or a fault shutdown is triggered. During the constant current limiting safety mode, the preset programmable gain amplifier is adjusted to set the equivalent quantization resolution to continuously acquire the absolute value of the DC terminal voltage; If the absolute value of the DC terminal voltage is not less than the dead zone threshold, the speed is calculated based on the DC terminal voltage, the load current, the actual internal resistance, and the comprehensive back EMF constant to adjust the main motor.

2. The method according to claim 1, characterized in that, The synchronous acquisition of the drive current of the main motor, the DC terminal voltage of the permanent magnet DC auxiliary motor, the load current, the reference temperature, and the forward speed command includes: At the start of the preset control cycle, the drive current, the DC terminal voltage, and the load current are synchronously acquired through a unified hardware trigger signal. The temperature at the interface between the main motor and the permanent magnet DC auxiliary motor is extracted and used as the reference temperature.

3. The method according to claim 1, characterized in that, The step of determining the overload limiting attenuation coefficient based on the comparison result between the instantaneous absolute value of the driving current and the preset overload limiting threshold includes: If the instantaneous absolute value of the driving current is greater than the overload limiting threshold, the difference between the instantaneous absolute value of the driving current and the overload limiting threshold is taken as the excess difference, and the overload limiting attenuation coefficient is obtained by interpolation based on the excess difference in a preset lookup table. If the instantaneous absolute value of the driving current is not greater than the overload limiting threshold, the overload limiting attenuation coefficient is set to a preset constant and the lookup table is bypassed.

4. The method according to claim 1, characterized in that, The calculation of the transient temperature rise based on the load current, the reference internal resistance of the permanent magnet DC auxiliary motor, the preset thermal capacity parameter, and the preset thermal resistance parameter includes: Obtain the square value of the load current corresponding to each control cycle within a preset time window, and multiply the square value by the reference internal resistance to form a heat generation power sequence; The transient temperature rise is calculated by substituting the heating power sequence into the thermal state equation constructed by discretizing the heat capacity parameter and the thermal resistance parameter.

5. The method according to claim 4, characterized in that, The execution of the thermal state equation is pushed down to a slower task thread after frequency reduction; The product of the thermal capacity parameter and the thermal resistance parameter constitutes the thermal time constant, and the execution cycle of the slow task thread is less than a preset proportion of the thermal time constant.

6. The method according to claim 1, characterized in that, The preset heat capacity parameter characterizes the equivalent heat capacity between the armature winding and the housing cooling surface of the permanent magnet DC auxiliary motor; The preset thermal resistance parameter characterizes the equivalent conductive thermal resistance between the armature winding of the permanent magnet DC auxiliary motor and the cooling surface of the housing.

7. The method according to claim 1, characterized in that, The matching of the impedance ratio and the equivalent back electromotive force temperature coefficient based on the equivalent back electromotive force calibration temperature includes: The impedance ratio and the equivalent back EMF temperature coefficient are output based on the equivalent back EMF calibration temperature matching in a pre-set temperature drift matrix calibrated by a constant temperature test.

8. The method according to claim 1, characterized in that, The calculation of the rotational speed based on the DC terminal voltage, the load current, the actual internal resistance, and the combined back EMF constant includes: The reconfigured voltage drop is obtained by multiplying the load current, which is specified as the outflow direction, by the actual internal resistance. The sum of the reconstructed voltage drop and the DC terminal voltage is used as the induced electromotive force; The ratio of the induced electromotive force to the comprehensive back electromotive force constant is used as the angular velocity and as the calculated rotational speed.

9. The method according to claim 5, characterized in that, Also includes: During the execution of the slow task thread, the first time derivative of the reference temperature is calculated in real time. When the absolute value of the first time derivative is continuously less than the preset equilibrium threshold within the preset observation window, the calibrated thermal resistance is obtained by using the ratio of the equivalent measured temperature rise of the armature winding of the permanent magnet DC auxiliary motor relative to the reference temperature to the steady-state mean value of the heating power sequence, which is obtained by the preset winding equivalent temperature acquisition unit. The calibrated thermal resistance is used to replace the thermal resistance parameter for steady-state background self-calibration, and the cumulative update of the thermal state equation is maintained.

10. A coaxial motor speed estimation system based on power generation measurement, applied to a coaxial system comprising a main motor and a permanent magnet DC auxiliary motor, characterized in that, For performing the method according to any one of claims 1 to 9, comprising: The parameter synchronization acquisition module is used to synchronously acquire the drive current of the main motor, the DC terminal voltage and load current of the permanent magnet DC auxiliary motor, the reference temperature and the forward speed command. The overload limiting module is used to determine the overload limiting attenuation coefficient based on the comparison result between the instantaneous absolute value of the drive current and the preset overload limiting threshold. The parameter matching module is used to calculate the transient temperature rise based on the load current, the reference internal resistance of the permanent magnet DC auxiliary motor, the preset thermal capacity parameters and the preset thermal resistance parameters, and to superimpose the transient temperature rise with the reference temperature as the equivalent back EMF calibration temperature. Based on the equivalent back EMF calibration temperature, the impedance ratio and the equivalent back EMF temperature coefficient are matched. The parameter correction module is used to correct the reference internal resistance and the preset reference back EMF constant by using the impedance ratio and the equivalent back EMF temperature coefficient, respectively, to obtain the actual internal resistance and the comprehensive back EMF constant. The drive calculation module is used to drive the main motor in a constant current limiting safety mode based on the overload limiting attenuation coefficient if the absolute value of the DC terminal voltage is less than a preset dead zone threshold and the positive speed command is greater than zero. If the absolute value of the DC terminal voltage is continuously less than the dead zone threshold for a preset duration, the current command of the main motor is increased by a preset step size under the condition that it does not exceed the preset maximum allowable current of the system, until the absolute value of the DC terminal voltage is detected to be not less than the dead zone threshold or a fault shutdown is triggered. During the constant current limiting safety mode, the preset programmable gain amplifier is adjusted to set the equivalent quantization resolution to continuously obtain the absolute value of the DC terminal voltage. If the absolute value of the DC terminal voltage is not less than the dead zone threshold, the speed is calculated based on the DC terminal voltage, the load current, the actual internal resistance, and the comprehensive back EMF constant to adjust the speed of the main motor.

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