A detection system for traction motor shaft power and electrical energy efficiency

Abstract

The application relates to the field of automobile motor detection, and discloses a detection system for shaft power and electric energy efficiency of a traction motor, which comprises the following: an axial magnetostrictive sensing unit collects differential magnetic communication signals and temperature signals of an output shaft; an electric power synchronous collection unit collects phase voltage and phase current signals; a harmonic torque compensation module extracts high-order harmonic vectors and fundamental wave vectors of the phase current signals, uses a phase shift angle to perform phase alignment on the high-order harmonic vectors, and calculates a parasitic pulsating torque component; a shaft power and efficiency calculation unit corrects a sensitivity coefficient according to the temperature signals to calculate an initial stress torque, subtracts the parasitic pulsating torque component to obtain a mechanical torque, and calculates the shaft power and the electric energy efficiency, thereby eliminating parasitic electromagnetic torque interference induced by an inverter, reducing signal interference of harmonics on shaft stress sensing, combining a temperature drift correction mechanism, and realizing accurate measurement of transient shaft power.

Description

Technical Field

[0001] This invention relates to the field of automotive motor testing technology, and more specifically, to a testing system for the shaft power and energy efficiency of a traction motor. Background Technology

[0002] Traction motors are the core power components of electric vehicles. Their dynamic output shaft power and energy efficiency curves are important indicators for evaluating the overall vehicle power performance and driving range. In actual operation and bench testing, traction motors are often subjected to non-steady-state conditions such as rapid acceleration, rapid deceleration, and regenerative braking. At this time, the voltage and current output by the drive inverter contain a large number of high-frequency carrier pulse width modulation harmonics, and the output shaft is also subject to axial stress fluctuations and large temperature changes caused by high-speed rotation. Therefore, accurately detecting transient mechanical torque and electrical power and ensuring their synchronization is an important requirement in traction motor performance testing.

[0003] Existing methods for traction motor torque detection mainly include contact measurement and estimation based on electromagnetic models. Contact sensors are typically installed in series between the motor output shaft and the load, which increases the rotational inertia and overall size of the transmission shaft system. It also increases the risk of mechanical contact failures under high-speed rotation conditions. Limited by the response speed of the sensor and transmission components, this method is also difficult to reflect transient shaft power changes in a timely manner. Estimation methods based on electromagnetic models usually calculate torque using fixed electromagnetic parameters. However, under high-frequency power supply conditions of the inverter, deep magnetic saturation of the iron core and winding heating can cause nonlinear changes in relevant electromagnetic parameters, resulting in torque estimation errors and affecting energy efficiency calculations. For example, Chinese invention patent application CN118159815A discloses a magnetostrictive torque sensor. By setting a physical sealing structure of the housing with a closed component and molding resin, it can suppress the intrusion of molding resin or external foreign objects into the detection coil space. However, this solution is based on a static physical isolation structure and can only cope with static working conditions such as physical intrusion of external media. When applied to the non-steady-state operation scenario of high-power traction motor, the high-frequency switching action of the drive inverter will induce a high-frequency pulsating magnetic field that penetrates the surface of the shaft in the air gap, generating a parasitic pulsating torque component; at the same time, the dynamic temperature rise of the output shaft will cause the material's permeability to drift nonlinearly.

[0004] Therefore, how to reduce the interference of high-frequency harmonics and output shaft temperature changes of the drive inverter on dynamic torque detection without changing the rotational inertia and structural rigidity of the transmission shaft system, and to achieve accurate transient synchronous detection of mechanical shaft power and electrical power, is a problem that existing detection technologies still need to solve. Summary of the Invention

[0005] To address the problems in the background art, the present invention provides a detection system for the shaft power and energy efficiency of a traction motor, comprising:

[0006] An axial magnetostrictive sensing unit, with a non-contact ring disposed around the output shaft of the traction motor, collects differential magnetic flux signals and temperature signals generated by the output shaft of the traction motor under torsional stress.

[0007] The power acquisition unit is connected to the input bus between the drive inverter and the traction motor. It synchronously acquires the three-phase phase voltage signal and the three-phase phase current signal. The switching action of the drive inverter induces parasitic pulsating torque components on the output shaft of the traction motor, causing the differential magnetic flux signal to be superimposed with electromagnetic interference.

[0008] The harmonic torque compensation module connects the axial magnetostriction sensing unit and the power acquisition unit. It extracts the carrier higher harmonic vector and the fundamental vector from the three-phase phase current signal, calculates the phase shift angle between the differential flux signal and the fundamental vector, uses the phase shift angle to perform phase alignment of the carrier higher harmonic vector, and calculates the parasitic pulsating torque component based on the aligned carrier higher harmonic vector.

[0009] The shaft power and efficiency calculation unit connects the harmonic torque compensation module and the speed sensor. Based on the temperature signal, it corrects the preset magnetostriction sensitivity coefficient, calculates the initial stress torque based on the differential magnetic flux signal and the corrected magnetostriction sensitivity coefficient, subtracts the parasitic pulsating torque component from the initial stress torque to obtain the mechanical torque, and calculates the output shaft power and energy conversion efficiency by combining the angular velocity signal output by the speed sensor and the input electrical power calculated based on the three-phase phase voltage signal and the three-phase phase current signal.

[0010] Preferably, the harmonic torque compensation module includes a harmonic component extraction circuit and a phase delay compensator; the harmonic component extraction circuit inputs the three-phase phase current signal into a high-pass filter to separate the carrier high-order harmonic vector; the phase delay compensator converts the aligned carrier high-order harmonic vector into direct-axis harmonic components and quadrature-axis harmonic components, and calculates the parasitic pulsating torque component based on the preset harmonic torque coupling coefficient.

[0011] Preferably, the shaft power and efficiency calculation unit includes a temperature correction circuit; the temperature correction circuit receives a temperature signal, calculates a temperature compensation correction factor based on a preset reference temperature and a preset sensitivity temperature coefficient, and calculates the initial stress torque using the temperature compensation correction factor, the differential magnetic flux signal, and a preset stress torque proportionality coefficient.

[0012] Preferably, the axial magnetostrictive sensing unit includes an excitation drive circuit, a multi-channel excitation coil, and an arrayed differential magnetic sensing probe; the output terminal of the excitation drive circuit is connected to the multi-channel excitation coil to inject alternating excitation current, and the arrayed differential magnetic sensing probe is arranged in a centrally symmetrical and mutually orthogonal orientation along the axis of the traction motor output shaft to output differential magnetic flux signal in a differential form.

[0013] Preferably, the power acquisition unit includes a Hall voltage sensor and a Rogowski coil current sensor; the Hall voltage sensor acquires three-phase phase voltage signals, the Rogowski coil current sensor acquires three-phase phase current signals, and the Hall voltage sensor and the Rogowski coil current sensor are connected to the same hardware clock trigger source to maintain synchronous sampling.

[0014] Preferably, the temperature compensation correction factor is equal to the difference between the temperature signal value and the reference temperature value, multiplied by the sensitivity temperature coefficient and then one. The temperature correction circuit performs a multiplication operation on the differential magnetic flux signal, the temperature compensation correction factor and the stress torque proportional coefficient to generate the initial stress torque.

[0015] Preferably, the shaft power and efficiency calculation unit includes a mechanical shaft power calculation circuit and an electrical energy conversion efficiency calculation circuit; the mechanical shaft power calculation circuit multiplies the mechanical torque and angular velocity signal to output shaft power, and the electrical energy conversion efficiency calculation circuit calculates the average value of the input electrical power within a preset sliding time window and divides the output shaft power by the average value to output the electrical energy conversion efficiency.

[0016] Preferably, the cutoff frequency of the high-pass filter is set to be equal to the carrier switching frequency of the inverter, and the signal output by the harmonic component extraction circuit with a frequency greater than or equal to 6 times the carrier switching frequency is used as the carrier higher harmonic vector.

[0017] Preferably, the preset harmonic torque coupling coefficient characterizes the stress magnetic effect transmission gain between the electromagnetic field inside the traction motor and the space of the traction motor output shaft. The phase delay compensator calculates the sum of the squares of the direct-axis harmonic components and the squares of the quadrature-axis harmonic components, and multiplies the sum of the squares with the preset harmonic torque coupling coefficient to obtain the parasitic pulsating torque component.

[0018] The embodiments of the present invention have at least the following beneficial effects:

[0019] 1. In the detection of traction motor shaft power and energy efficiency, the non-contact ring of the axial magnetostrictive sensing unit is located around the output shaft of the traction motor. It is not necessary to install force measuring components in series between the output shaft and the load. Therefore, it will not increase the rotational inertia of the transmission shaft system, nor will it change the original structural rigidity. On this basis, by calculating and subtracting the parasitic pulsating torque component generated by the high-frequency switching action of the drive inverter, the interference of the parasitic pulsating torque component on the differential flux signal can be reduced, making the detection results closer to the actual mechanical torque borne by the output shaft, and improving the detection accuracy of transient mechanical torque and output shaft power.

[0020] 2. The arrayed differential magnetic sensing probes are arranged in a centrally symmetrical and mutually orthogonal manner along the output shaft of the traction motor. They can cancel the common-mode magnetic flux changes caused by axial tension and lateral vibration in a differential manner, reducing the influence of non-torsional stress on the differential magnetic flux signal. Therefore, the detection system can more accurately reflect the torsional stress changes of the output shaft, reduce the interference of high-speed rotation and complex vibration states on mechanical torque measurement, and improve the signal-to-noise ratio of the differential magnetic flux signal.

[0021] 3. By correcting the magnetostriction sensitivity coefficient based on the output shaft temperature signal, the change in material permeability caused by the output shaft temperature rise can be compensated, reducing the impact of temperature drift on the initial stress torque and mechanical torque calculation results. As a result, the detection system can still maintain good measurement stability and result consistency when the output shaft temperature changes, avoiding continuous deviation of torque detection results caused by long-term high-load operation of the traction motor. Attached Figure Description

[0022] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings, in which several embodiments of the invention are illustrated by way of example and not limitation, wherein:

[0023] Figure 1 This is the overall topology and signal diagram of the detection system of the present invention;

[0024] Figure 2 This is a diagram showing the cascaded internal circuit structure of the shaft power and efficiency calculation unit of this invention. Detailed Implementation

[0025] The principles and spirit of the present invention will now be described with reference to several exemplary embodiments in conjunction with the accompanying drawings. It should be understood that these embodiments are provided merely to enable those skilled in the art to better understand and implement the present invention, and are not intended to limit the scope of the present invention in any way. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0026] A system for detecting the shaft power and energy efficiency of a traction motor, comprising:

[0027] An axial magnetostrictive sensing unit, with a non-contact ring disposed around the output shaft of the traction motor, collects differential magnetic flux signals and temperature signals generated by the output shaft of the traction motor under torsional stress.

[0028] The power acquisition unit is connected to the input bus between the drive inverter and the traction motor. It synchronously acquires the three-phase phase voltage signal and the three-phase phase current signal. The switching action of the drive inverter induces parasitic pulsating torque components on the output shaft of the traction motor, causing the differential magnetic flux signal to be superimposed with electromagnetic interference.

[0029] The harmonic torque compensation module connects the axial magnetostriction sensing unit and the power acquisition unit. It extracts the carrier higher harmonic vector and the fundamental vector from the three-phase phase current signal, calculates the phase shift angle between the differential flux signal and the fundamental vector, uses the phase shift angle to perform phase alignment of the carrier higher harmonic vector, and calculates the parasitic pulsating torque component based on the aligned carrier higher harmonic vector.

[0030] The shaft power and efficiency calculation unit connects the harmonic torque compensation module and the speed sensor. Based on the temperature signal, it corrects the preset magnetostriction sensitivity coefficient, calculates the initial stress torque based on the differential magnetic flux signal and the corrected magnetostriction sensitivity coefficient, subtracts the parasitic pulsating torque component from the initial stress torque to obtain the mechanical torque, and calculates the output shaft power and energy conversion efficiency by combining the angular velocity signal output by the speed sensor and the input electrical power calculated based on the three-phase phase voltage signal and the three-phase phase current signal.

[0031] Preferably, the harmonic torque compensation module includes a harmonic component extraction circuit and a phase delay compensator; the harmonic component extraction circuit inputs the three-phase phase current signal into a high-pass filter to separate the carrier high-order harmonic vector; the phase delay compensator converts the aligned carrier high-order harmonic vector into direct-axis harmonic components and quadrature-axis harmonic components, and calculates the parasitic pulsating torque component based on the preset harmonic torque coupling coefficient.

[0032] Preferably, the shaft power and efficiency calculation unit includes a temperature correction circuit; the temperature correction circuit receives a temperature signal, calculates a temperature compensation correction factor based on a preset reference temperature and a preset sensitivity temperature coefficient, and calculates the initial stress torque using the temperature compensation correction factor, the differential magnetic flux signal, and a preset stress torque proportionality coefficient.

[0033] Preferably, the axial magnetostrictive sensing unit includes an excitation drive circuit, a multi-channel excitation coil, and an arrayed differential magnetic sensing probe; the output terminal of the excitation drive circuit is connected to the multi-channel excitation coil to inject alternating excitation current, and the arrayed differential magnetic sensing probe is arranged in a centrally symmetrical and mutually orthogonal orientation along the axis of the traction motor output shaft to output differential magnetic flux signal in a differential form.

[0034] Preferably, the power acquisition unit includes a Hall voltage sensor and a Rogowski coil current sensor; the Hall voltage sensor acquires three-phase phase voltage signals, the Rogowski coil current sensor acquires three-phase phase current signals, and the Hall voltage sensor and the Rogowski coil current sensor are connected to the same hardware clock trigger source to maintain synchronous sampling.

[0035] Preferably, the temperature compensation correction factor is equal to the difference between the temperature signal value and the reference temperature value, multiplied by the sensitivity temperature coefficient and then one. The temperature correction circuit performs a multiplication operation on the differential magnetic flux signal, the temperature compensation correction factor and the stress torque proportional coefficient to generate the initial stress torque.

[0036] Preferably, the shaft power and efficiency calculation unit includes a mechanical shaft power calculation circuit and an electrical energy conversion efficiency calculation circuit; the mechanical shaft power calculation circuit multiplies the mechanical torque and angular velocity signal to output shaft power, and the electrical energy conversion efficiency calculation circuit calculates the average value of the input electrical power within a preset sliding time window and divides the output shaft power by the average value to output the electrical energy conversion efficiency.

[0037] Preferably, the cutoff frequency of the high-pass filter is set to be equal to the carrier switching frequency of the inverter, and the signal output by the harmonic component extraction circuit with a frequency greater than or equal to 6 times the carrier switching frequency is used as the carrier higher harmonic vector.

[0038] Preferably, the preset harmonic torque coupling coefficient characterizes the stress magnetic effect transmission gain between the electromagnetic field inside the traction motor and the space of the traction motor output shaft. The phase delay compensator calculates the sum of the squares of the direct-axis harmonic components and the squares of the quadrature-axis harmonic components, and multiplies the sum of the squares with the preset harmonic torque coupling coefficient to obtain the parasitic pulsating torque component.

[0039] Example 1: In a simulated test of rapid acceleration and regenerative braking of an electric vehicle traction motor, the traction motor output shaft generates torsional vibration under high-speed rotation, accompanied by significant temperature changes. An axial magnetostrictive sensing unit with a non-contact ring is positioned around the traction motor output shaft. Its excitation drive circuit injects a 50kHz alternating excitation current into the multi-channel excitation coil, forming an alternating magnetic field on the output shaft surface. An arrayed differential magnetic sensing probe collects the anisotropic change in permeability of the output shaft under torsional stress and outputs a differential magnetic flux signal in differential form. Simultaneously, an optical shaft temperature infrared sensing probe is integrated on both sides of the arrayed differential magnetic sensing probe inside the housing of the axial magnetostrictive sensing unit. This probe is perpendicularly aligned with the surface of the traction motor output shaft, maintaining a 1.5mm physical measurement gap. By sensing the infrared radiation energy on the shaft surface, it collects and outputs a temperature signal in real time, driving the high-order harmonics of the carrier wave generated by the inverter's high-frequency switch in the air gap between the traction motor stator and rotor. A high-frequency pulsating magnetic field is formed, which penetrates through the skin layer on the shaft surface to a depth of approximately 0.3 mm, generating a high-frequency alternating parasitic magnetic flux in the pole space of the arrayed differential magnetic sensor probe. Simultaneously, the high-frequency electromagnetic force acts on the shaft surface material, causing micron-level magnetostriction alternation, and inducing a parasitic pulsating torque component on the traction motor output shaft. This parasitic pulsating torque component essentially refers to the equivalent electromagnetic interference noise component superimposed on the differential magnetic flux signal induced by the high-frequency electromagnetic field of the drive inverter through the air gap in the arrayed differential magnetic sensor probe. Its physical properties belong to the high-frequency equivalent torque superposition value at the induced magnetic flux signal level, rather than the actual mechanical force borne by the output shaft. The harmonic torque compensation module calculates the parasitic pulsating torque component based on the carrier higher harmonic vector in the phase current signal and subtracts it in subsequent torque calculations, separating the interference generated by the high-frequency switching action of the drive inverter from the differential magnetic flux signal, while retaining the anisotropic magnetic flux change caused by the torsional stress of the output shaft.

[0040] The power acquisition unit is connected to the input bus between the drive inverter and the traction motor, and synchronously acquires the three-phase phase voltage signals at a sampling frequency of 500kHz. , , and three-phase current signals , , The three-phase current signals are transmitted to the harmonic torque compensation module. The harmonic component extraction circuit connects the three-phase current signals to a high-pass filter, sets the cutoff frequency of the high-pass filter to the carrier switching frequency of the inverter, and uses signals with frequencies greater than or equal to six times the carrier switching frequency as carrier higher-order harmonic vectors. Simultaneously, the fundamental vector is extracted, and the phase delay compensator calculates the differential flux signal. The phase shift angle between the carrier and the fundamental wave vector is used to align the phase of the carrier higher harmonic vectors, and then the direct-axis harmonic components are obtained through the Park transform. With cross-axis harmonic components The parasitic pulsating torque component is calculated according to the following formula. : ,in, For parasitic pulsating torque components, The preset harmonic torque coupling coefficient is used to characterize the stress magnetic effect transmission gain between the internal electromagnetic field of the traction motor and the output shaft space of the traction motor. For direct-axis harmonic components, The quadrature axis harmonic components are used to calculate the parasitic pulsating torque components induced on the traction motor output shaft by the switching action of the drive inverter. .

[0041] The shaft power and efficiency calculation unit receives differential magnetic flux signals. Temperature signal With parasitic pulsating torque component The temperature correction circuit is based on the temperature signal. Reference temperature and sensitivity temperature coefficient Calculate the temperature compensation correction factor, and combine the temperature compensation correction factor with the differential flux signal. proportionality coefficient with stress moment Multiply the results to obtain the initial stress torque, then subtract the parasitic pulsating torque component. To obtain mechanical torque The calculation formula is as follows: ,in, For mechanical torque, Reference temperature The stress-moment proportionality coefficient is set to 700 N·m / T. The sensitivity temperature coefficient is set to -0.0012 / ℃. The reference temperature is 25℃. The output shaft surface temperature is measured in real time and is set to 65℃. The differential magnetic flux signal is measured in real time and has a value of 0.45T. The calculated parasitic pulsating torque component is taken as 3.2 N·m, with a temperature compensation correction factor. The value is 0.952, calculated by subtracting the parasitic pulsating torque component from the initial stress torque. Then, the mechanical torque is obtained. It is 296.68 N·m.

[0042] The speed sensor uses a photoelectric speed encoder to output angular velocity signals. Its value is 314.16 rad / s. The mechanical shaft power calculation circuit calculates the mechanical torque. With angular velocity signal Multiply to obtain the output shaft power. The power conversion efficiency calculation circuit is 93205.01W, within a preset 10ms sliding time window. The internal calculation measures the average input electrical power and the output shaft power. Dividing by this mean yields the power conversion efficiency. Under the condition that the average three-phase input power is 100,000W, the power conversion efficiency is calculated according to the following formula: ,in, For electrical energy conversion efficiency; The output shaft power is 93205.01W. This is a sliding time window with a value of 10ms; For time The instantaneous three-phase input power at the point is used to calculate the power conversion efficiency. The efficiency is 93.205%, and the shaft power and efficiency calculation unit outputs the shaft power and energy conversion efficiency accordingly.

[0043] Example 2: The current traction motor test bench is used to simulate rapid acceleration, rapid deceleration, and regenerative braking processes, and to measure the output shaft power and energy conversion efficiency of the power system. The test bench uses a traction motor with a rated power of 300kW, and the carrier switching frequency of the drive inverter is 10kHz. The axial magnetostrictive sensing unit is arranged around the output shaft of the traction motor. The excitation drive circuit injects a 50kHz alternating excitation current into the multi-channel excitation coil, forming an alternating magnetic field on the surface of the output shaft. The arrayed differential magnetic sensing probe collects the differential magnetic flux signal. The shaft temperature infrared monitoring sensor synchronously collects temperature signals. The power acquisition unit synchronously acquires three-phase voltage and three-phase current signals at a sampling frequency of 500kHz. Gaussian white noise with a signal-to-noise ratio of 20dB is superimposed on the test signal. The test process covers a speed range of 1000r / min to 6000r / min and a torque range of 50N·m to 500N·m. The surface temperature of the output shaft increases from 25℃ to 110℃.

[0044] Four test configurations were set up under the same operating conditions. The test group used a harmonic torque compensation module and a temperature correction circuit to calculate the parasitic pulsating torque component based on the carrier high-order harmonic vector in the three-phase phase current signal. And based on the temperature signal To correct the magnetostriction sensitivity coefficient, the control group (without a harmonic torque compensation module) will eliminate the parasitic pulsating torque component. Set to 0 N·m; control group two does not use a temperature correction circuit, and the sensitivity temperature coefficient is set to 0 N·m. The temperature was set to 0℃. In control group three, the torque was estimated using a motor electromagnetic model with fixed direct-axis inductance, quadrature-axis inductance, and flux linkage parameters. Measurements were taken under different temperature and load conditions for each group, and the torque deviation rate was calculated. Simultaneously, the experimental group was assessed based on the mechanical torque... Angular velocity signal Calculate the output shaft power from the input electrical power. and power conversion efficiency .

[0045] The test began under conditions of low temperature, low speed, and low input power, with the output shaft surface temperature at 25°C and the angular velocity signal... When the input power is 30kW and the speed is 104.72 rad / s, the torque deviation rates of the experimental group, control group 1, control group 2, and control group 3 are 0.12%, 1.85%, 0.15%, and 1.21%, respectively. The power conversion efficiency of the experimental group is... The efficiency was 91.25%, raising the output shaft surface temperature to 45°C, and the angular velocity signal... After the input power was increased to 209.44 rad / s and 60 kW, the torque deviation rates of the four groups were 0.14%, 1.92%, 1.12%, and 2.10%, respectively. The energy conversion efficiency of the test group was... The angular velocity signal is 92.40% when the output shaft surface temperature is 65℃. When the input current is 314.16 rad / s and the input power is 100 kW, the torque deviation rates of the four groups are 0.15%, 2.15%, 2.38%, and 3.45%, respectively. The energy conversion efficiency of the test group is... It is 93.21%.

[0046] Continue to increase the rotational speed, temperature, and input electrical power, with the output shaft surface temperature at 85°C and the angular velocity signal... When the input power is 150kW and the torque deviation rate is 418.88 rad / s, the torque deviation rates of the experimental group, control group 1, control group 2, and control group 3 are 0.17%, 2.41%, 3.65%, and 4.82%, respectively. The power conversion efficiency of the experimental group is... The efficiency was 93.85% when the output shaft surface temperature reached 105℃ and the angular velocity signal... When the torque reaches 523.60 rad / s and the input power reaches 200 kW, the torque deviation rates of the four groups are 0.19%, 2.78%, 4.88%, and 6.15%, respectively. The energy conversion efficiency of the test group is... It is 94.10%.

[0047] In the regenerative braking test, the output shaft surface temperature was set to 65℃, and the angular velocity signal was... Set at 314.16 rad / s and an input power of -40 kW, after processing the signal and torque calculations using the same methods, the torque deviation rates for the experimental group, control group 1, control group 2, and control group 3 were -0.16%, -2.20%, 2.35%, and -3.80%, respectively. The energy conversion efficiency of the experimental group... It is 88.50%.

[0048] To further compare the measurement results under different combinations of temperature, rotational speed, and input electrical power, the output shaft surface temperature was set to 95°C, and the angular velocity signal was... When the input current is 314.16 rad / s and the input power is 180 kW, the torque deviation rates of the four groups are 0.18%, 2.65%, 4.22%, and 5.40%, respectively. The energy conversion efficiency of the test group is... The angular velocity signal was 93.60% at an output shaft surface temperature of 35°C. When the input current is 523.60 rad / s and the input power is 120 kW, the torque deviation rates of the four groups are 0.13%, 2.05%, 0.62%, and 2.85%, respectively. The energy conversion efficiency of the test group is... The angular velocity signal was 92.90% when the output shaft surface temperature rose to 110℃. When the input current is 209.44 rad / s and the input power is 220 kW, the torque deviation rates of the four groups are 0.20%, 2.90%, 5.15%, and 6.80%, respectively. The energy conversion efficiency of the test group is... It is 91.80%.

[0049] Near the reference temperature and under low load, the change in magnetostrictive sensitivity caused by output shaft temperature rise is small. The torque deviation rate of control group 2 is close to that of the test group. Control group 1 did not calculate and deduct the parasitic pulsating torque component from the carrier higher harmonic vector. Direct-axis harmonic components and cross-axis harmonic components The corresponding parasitic pulsating torque is superimposed on the differential flux signal The torque deviation rate increases with the change of operating conditions. As the surface temperature of the output shaft rises, the magnetic permeability of the magnetostrictive material undergoes nonlinear drift. Since no temperature correction was performed, the torque deviation rate of control group 2 increases with the increase of temperature. Control group 3 uses fixed electromagnetic parameters for torque estimation. The parameter changes caused by the magnetic saturation of the motor core and the heating of the winding further increase the estimation deviation.

[0050] The experimental group used a harmonic component extraction circuit to extract the carrier higher harmonic vector, and a phase delay compensator to complete phase alignment and calculate the parasitic pulsating torque component. The shaft power and efficiency calculation unit subtracts the parasitic pulsating torque component from the initial stress torque; the temperature correction circuit simultaneously adjusts the temperature signal. Corrected differential flux signal The corresponding magnetostrictive sensitivity, after the above processing, allows the system to output mechanical torque under different temperatures, speeds, loads, and regenerative braking conditions. Output shaft power and power conversion efficiency .

[0051] Example 3: The current drive inverter uses pulse width modulation for power supply. Its carrier switching frequency varies from 2kHz to 20kHz depending on the operating conditions of the traction motor. When the traction motor is in the process of rapid acceleration and regenerative braking, the output shaft is simultaneously subjected to torsional vibration and temperature changes caused by high-speed rotation. The power acquisition unit synchronously acquires the three-phase voltage signal and the three-phase current signal through a high-bandwidth Hall voltage sensor and a Rogowski coil current sensor, and transmits the three-phase current signal to the harmonic torque compensation module.

[0052] The harmonic component extraction circuit employs a fourth-order Butterworth digital high-pass filter, and adjusts the filter parameters according to the real-time carrier switching frequency of the drive inverter, so that the cutoff frequency of the high-pass filter is equal to the carrier switching frequency. The filter generates 3dB attenuation at the cutoff frequency and attenuates the low-frequency fundamental signal at a roll-off rate of 24dB per octave. When the signal frequency reaches 6 times or more of the carrier switching frequency, the amplitude-frequency response of the filter enters the passband flat region, and the attenuation is less than 0.01dB. The harmonic component extraction circuit only uses passband signals with frequencies greater than or equal to 6 times the carrier switching frequency as carrier higher-order harmonic vectors to suppress the influence of low-order harmonics and fundamental components on subsequent calculations.

[0053] The phase delay compensator receives the differential magnetic flux signal output by the axial magnetostrictive sensing unit. The three-phase current signal is projected onto a stationary orthogonal coordinate system via Clarke transform. Simultaneously, the phase delay compensator sends the three-phase current signal and the differential flux signal to the built-in hardware zero-crossing comparator. The internal timer counter with a sampling frequency of 100MHz captures the time difference between the rising edges of the two signals at the zero-crossing point, and directly calculates the physical channel transmission delay value. Based on this physical channel transmission delay value, the phase delay compensator performs address pointer offset correction on the carrier high-order harmonic current sampling sequence buffered in the ring FIFO register with a corresponding microsecond-level time step, thereby achieving time-domain phase alignment of the sampled signal to correct the phase lag caused by signal transmission and electromagnetic induction path.

[0054] After phase alignment is completed, the phase delay compensator converts the carrier higher harmonic vector into direct-axis harmonic components through the Park transform. and cross-axis harmonic components The rotational phase angle required for the Park transformation is determined by the angle information output by the speed sensor. The speed sensor uses a photoelectric encoder, which outputs 4096 quadrature counting pulses and 1 zero-position latch signal per revolution of the output shaft. The hardware timer / counter inside the phase delay compensator establishes a timing reference based on the zero-position latch signal, accumulates the quadrature counting pulses, and combines them with the preset 4 pairs of magnetic pole parameters of the traction motor. The accumulated pulse count is multiplied by 360°, divided by 4096, and then multiplied by the number of pole pairs 4 to obtain the rotor electrical angle phase angle at the current moment. The carrier higher harmonic vector in the three-phase current signal is synchronously input to the rotating coordinate transformation module along with the rotor electrical angle phase angle to obtain the direct-axis harmonic components. and cross-axis harmonic components .

[0055] Harmonic torque coupling coefficient Before the system was put into measurement, it was calibrated by bench injection test. During calibration, the output shaft of the traction motor was in an unloaded state, and high-order harmonic current was injected into the three-phase windings. The differential magnetic flux signal was recorded. The response amplitude is determined, and based on offline discrete calibration tests, the fundamental excitation current amplitude of the traction motor, sampled discretely in 50A steps within the range of 0A to 300A, is compared with the corresponding discrete harmonic torque transmission gain to form a two-dimensional numerical comparison table, which is directly stored in the non-volatile memory 0x01A0 register address segment of the harmonic torque compensation module. During online detection, the module directly reads the current fundamental excitation current amplitude and performs one-dimensional linear interpolation on the two-dimensional numerical comparison set, using the resulting discrete gain value as the deterministic harmonic torque coupling coefficient under the current operating condition. During the test, this preset value remains unchanged, and the phase delay compensator calculates the direct-axis harmonic components. The square of the cross-axis harmonic components The sum of the squares is then combined with the preset harmonic torque coupling coefficient. Multiplying them together yields the parasitic pulsating torque component. .

[0056] The shaft power and efficiency calculation unit receives differential magnetic flux signals. Temperature signals collected by shaft temperature infrared monitoring sensor and parasitic pulsating torque components The temperature correction circuit uses a temperature compensation correction factor to correct the magnetostriction sensitivity coefficient, and then uses the corrected magnetostriction sensitivity coefficient and differential magnetic flux signal as the basis for the correction. Calculate the initial stress torque, and then subtract the parasitic pulsating torque component from the initial stress torque. To obtain mechanical torque The mechanical shaft power calculation circuit calculates the mechanical torque. Angular velocity signal output by the speed sensor Multiply to obtain the output shaft power. .

[0057] Before each test condition begins, the power conversion efficiency calculation circuit sets a preset sliding time window based on the rotation period measured by the photoelectric encoder under that condition. The preset sliding time window The value should be an integer multiple of a single rotation period, and not less than 10 ms; within the same test condition, its value should remain unchanged, angular velocity signal. When the speed is low, a longer preset sliding time window that covers the entire electrical angle cycle of the motor is selected. The power conversion efficiency calculation circuit calculates the average input power within this window and outputs the power... Dividing by this mean yields the power conversion efficiency. Through the above processing, the system can synchronously calculate mechanical torque, output shaft power and power conversion efficiency under the conditions of carrier switching frequency change and core magnetic saturation.

[0058] Example 4: This example combines Figures 1 to 2 This paper describes a detection system for the shaft power and energy efficiency of a traction motor, such as... Figure 1As shown, during operation, the traction motor output shaft transmits torsional stress and temperature to the axial magnetostrictive sensing unit. The axial magnetostrictive sensing unit, with a non-contact ring positioned around the traction motor output shaft, collects the differential flux signal and temperature signal generated by the traction motor output shaft under torsional stress. The differential flux signal is then transmitted to the harmonic torque compensation module, and simultaneously, the differential flux signal and temperature signal are transmitted to the shaft power and efficiency calculation unit. The drive inverter input bus provides input power to the power acquisition unit, which is connected to the drive inverter input bus. The power acquisition unit synchronously collects three-phase voltage and current signals, transmitting the three-phase current signal to the harmonic torque compensation module, and simultaneously, the three-phase voltage and current signals to the shaft power and efficiency calculation unit. The harmonic torque compensation module internally includes a harmonic component extraction circuit and a phase delay compensator, receiving signals from the power acquisition unit. The three-phase current signal and the differential flux signal from the axial magnetostrictive sensing unit are aligned with the phase of the higher harmonics and the fundamental wave, and the parasitic pulsating torque component is calculated. The parasitic pulsating torque component is then output to the shaft power and efficiency calculation unit. The speed sensor collects the angular velocity signal of the traction motor output shaft and transmits the angular velocity signal to the shaft power and efficiency calculation unit. The shaft power and efficiency calculation unit integrates a temperature correction circuit, a mechanical shaft power calculation circuit, and an energy conversion efficiency calculation circuit. It comprehensively receives the differential flux signal and temperature signal from the axial magnetostrictive sensing unit, the three-phase voltage signal and three-phase current signal from the power acquisition unit, the parasitic pulsating torque component from the harmonic torque compensation module, and the angular velocity signal from the speed sensor. It corrects the sensitivity coefficient, calculates the initial stress torque, subtracts the parasitic pulsating torque component to obtain the mechanical torque, and then calculates and finally outputs the shaft power and energy conversion efficiency.

[0059] like Figure 2 As shown, the shaft power and efficiency calculation unit consists of a temperature correction circuit, a mechanical shaft power calculation circuit, and an electrical energy conversion efficiency calculation circuit. The output of the temperature correction circuit is connected to the mechanical shaft power calculation circuit, and the output of the mechanical shaft power calculation circuit is connected to the electrical energy conversion efficiency calculation circuit. The electrical energy conversion efficiency calculation circuit receives the outputs of the aforementioned circuits in sequence, performs calculations, and finally outputs the electrical energy conversion efficiency.

[0060] Example 5: With the current traction motor output shaft in a no-load, zero-torque installation state, the axial magnetostrictive sensing unit first performs zero-point reference calibration. The excitation drive circuit injects a 50kHz alternating excitation current into the multi-channel excitation coil. The arrayed differential magnetic sensing probe collects the initial differential magnetic flux signal of the output shaft under no external torque. The value is stored in the register as a zero-point bias, and the shaft temperature infrared monitoring sensor in the axial magnetostrictive sensing unit is at the reference temperature. The initial thermal radiation intensity of the output shaft surface was collected at 25℃, and the infrared emissivity parameters were corrected by combining them with standard contact temperature measurement points to prepare for subsequent acquisition of differential magnetic flux signals. and temperature signal Provides an initial physical reference.

[0061] After the output shaft switches from a stationary state to a rotating no-load condition, the test bench drives the traction motor output shaft to accelerate within the range of 1000 r / min to 6000 r / min. The arrayed differential magnetic sensing probes collect the common-mode magnetic flux offset caused by centrifugal tension and lateral vibration. The harmonic torque compensation module calculates the differential offset gain based on the symmetrical orthogonal arrangement of the probes, and the shaft power and efficiency calculation unit calculates the mechanical torque. At that time, first from the differential magnetic flux signal Subtract the initial differential magnetic flux signal The differential offset gain is used to cancel the common-mode flux offset; the temperature correction circuit is based on the temperature signal. The magnetostriction sensitivity coefficient is corrected, and the initial stress torque is calculated based on the corrected magnetostriction sensitivity coefficient and the corrected differential flux signal. Then, the parasitic pulsating torque component calculated by the harmonic torque compensation module is subtracted. To obtain mechanical torque After zero-point bias and common-mode flux offset correction, the calculated output torque under zero-torque conditions converges to 0 N·m, and the sensor installation stress and centrifugal common-mode interference are no longer superimposed on the measurement results.

[0062] Example 6: When the traction motor undergoes rapid regenerative braking, the output shaft is subjected to transient thermal shock. Surface heat is conducted radially into the shaft body, forming a temperature gradient. The shaft temperature infrared monitoring sensor in the axial magnetostrictive sensing unit collects the temperature signal. Simultaneously record the rate of temperature change. The arrayed differential magnetic sensor probe acquires the differential magnetic flux signal generated by the output shaft under the combined action of torsional stress and torsional vibration. The power acquisition unit synchronously acquires three-phase voltage and current signals, and transmits the three-phase current signals to the harmonic torque compensation module. The harmonic component extraction circuit extracts the carrier high-order harmonic vector from the three-phase current signals, and the phase delay compensator completes phase alignment to obtain the direct-axis harmonic components. and cross-axis harmonic components Based on this, the parasitic pulsating torque component is calculated. .

[0063] The shaft power and efficiency calculation unit receives temperature signals. Differential magnetic flux signal and parasitic pulsating torque component The temperature correction circuit is based on the temperature signal. Reference temperature and sensitivity temperature coefficient Calculate the temperature compensation correction factor, and then use this temperature compensation correction factor and differential flux signal. proportionality coefficient with stress moment Multiply to obtain the initial stress torque, then subtract the parasitic pulsating torque component. To obtain mechanical torque The speed sensor synchronously outputs angular velocity signals. The mechanical shaft power calculation circuit calculates the mechanical torque. With angular velocity signal Multiply to obtain the output shaft power. The power conversion efficiency calculation circuit calculates the average input power within a preset sliding time window and outputs the power... Divide by this mean to obtain the power conversion efficiency. .

[0064] To evaluate the conduction hysteresis between surface temperature and internal thermal stress caused by transient thermal shock, the rate of temperature change was also considered. Bench calibration was performed using a 40Cr alloy steel shaft. Transient thermal shock gradients ranging from 1.0℃ / s to 10.0℃ / s were applied to the shaft. Simultaneously, infrared surface temperature change rates and mechanical torque measured by high-precision strain gauges were acquired. The thermal stress deviation was fitted using the least squares method, and the second-order correction coefficients obtained during calibration were used. The value is -0.0002 s / ℃; when the temperature signal... 85℃, temperature change rate At a temperature of 5.0℃ / s, the corresponding synthetic correction factor is 0.927. This set of data is used to evaluate transient heat conduction hysteresis and is not used as a unit for online calculation of mechanical torque in shaft power and efficiency calculations. The input time, online calculation still uses temperature signals. Reference temperature and sensitivity temperature coefficient Determined temperature compensation correction factor.

[0065] In the above bench calibration, the second-order correction factor When the absolute value is below 0.0001 s / ℃, the compensation for surface thermal stress delay under transient thermal shock is insufficient; when the absolute value is above 0.0005 s / ℃, overcompensation will occur after the temperature rise tends to stabilize. This calibration data allows for an independent assessment of temperature measurement lag under transient thermal shock conditions, while maintaining mechanical torque. Output shaft power and power conversion efficiency The online calculation path is consistent with the established calculation relationship of the temperature compensation correction factor.

[0066] The above description is only a few preferred embodiments of the present invention and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present invention is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned inventive concept. For example, technical solutions formed by replacing the above-mentioned features with the technical features with similar functions disclosed in the embodiments of the present invention.

Claims

1. A detection system for the shaft power and energy efficiency of a traction motor, characterized in that, Include: An axial magnetostrictive sensing unit, with a non-contact ring disposed around the output shaft of the traction motor, collects differential magnetic flux signals and temperature signals generated by the output shaft of the traction motor under torsional stress. The power acquisition unit is connected to the input bus between the drive inverter and the traction motor. It synchronously acquires the three-phase phase voltage signal and the three-phase phase current signal. The switching action of the drive inverter induces parasitic pulsating torque components on the output shaft of the traction motor, causing the differential magnetic flux signal to be superimposed with electromagnetic interference. The harmonic torque compensation module connects the axial magnetostriction sensing unit and the power acquisition unit. It extracts the carrier higher harmonic vector and the fundamental vector from the three-phase phase current signal, calculates the phase shift angle between the differential flux signal and the fundamental vector, uses the phase shift angle to perform phase alignment of the carrier higher harmonic vector, and calculates the parasitic pulsating torque component based on the aligned carrier higher harmonic vector. The shaft power and efficiency calculation unit connects the harmonic torque compensation module and the speed sensor. Based on the temperature signal, it corrects the preset magnetostriction sensitivity coefficient, calculates the initial stress torque based on the differential magnetic flux signal and the corrected magnetostriction sensitivity coefficient, subtracts the parasitic pulsating torque component from the initial stress torque to obtain the mechanical torque, and calculates the output shaft power and energy conversion efficiency by combining the angular velocity signal output by the speed sensor and the input electrical power calculated based on the three-phase phase voltage signal and the three-phase phase current signal.

2. The detection system for traction motor shaft power and energy efficiency according to claim 1, characterized in that, The harmonic torque compensation module includes a harmonic component extraction circuit and a phase delay compensator. The harmonic component extraction circuit inputs the three-phase phase current signal into a high-pass filter to separate the carrier high-order harmonic vector. The phase delay compensator converts the aligned carrier high-order harmonic vector into direct-axis harmonic components and quadrature-axis harmonic components, and calculates the parasitic pulsating torque component based on the preset harmonic torque coupling coefficient.

3. The detection system for traction motor shaft power and energy efficiency according to claim 1, characterized in that, The shaft power and efficiency calculation unit includes a temperature correction circuit. The temperature correction circuit receives the temperature signal, calculates the temperature compensation correction factor based on the preset reference temperature and the preset sensitivity temperature coefficient, and calculates the initial stress torque using the temperature compensation correction factor, the differential magnetic flux signal, and the preset stress torque proportionality coefficient.

4. The detection system for traction motor shaft power and energy efficiency according to claim 1, characterized in that, The axial magnetostrictive sensing unit includes an excitation drive circuit, a multi-channel excitation coil, and an arrayed differential magnetic sensing probe. The output of the excitation drive circuit is connected to the multi-channel excitation coil to inject alternating excitation current. The arrayed differential magnetic sensing probe is arranged in a centrally symmetrical and mutually orthogonal orientation along the axis of the traction motor output shaft, and outputs differential magnetic flux signal in a differential form.

5. The detection system for traction motor shaft power and energy efficiency according to claim 1, characterized in that, The power acquisition unit includes a Hall voltage sensor and a Rogowski coil current sensor; the Hall voltage sensor acquires the three-phase phase voltage signal, and the Rogowski coil current sensor acquires the three-phase phase current signal. The Hall voltage sensor and the Rogowski coil current sensor are connected to the same hardware clock trigger source to maintain synchronous sampling.

6. The detection system for traction motor shaft power and energy efficiency according to claim 3, characterized in that, The temperature compensation correction factor is equal to the difference between the temperature signal value and the reference temperature value, multiplied by the sensitivity temperature coefficient and then added by one. The temperature correction circuit multiplies the differential magnetic flux signal, the temperature compensation correction factor and the stress torque proportional coefficient to generate the initial stress torque.

7. The detection system for traction motor shaft power and energy efficiency according to claim 1, characterized in that, The shaft power and efficiency calculation unit includes a mechanical shaft power calculation circuit and an electrical energy conversion efficiency calculation circuit. The mechanical shaft power calculation circuit multiplies the mechanical torque and angular velocity signal to output shaft power. The electrical energy conversion efficiency calculation circuit calculates the average value of the input electrical power within a preset sliding time window and divides the output shaft power by the average value to output the electrical energy conversion efficiency.

8. A detection system for traction motor shaft power and energy efficiency according to claim 2, characterized in that, The cutoff frequency of the high-pass filter is set to be equal to the carrier switching frequency of the inverter. The harmonic component extraction circuit outputs a signal with a frequency greater than or equal to 6 times the carrier switching frequency as the carrier higher harmonic vector.

9. A detection system for traction motor shaft power and energy efficiency according to claim 2, characterized in that, The preset harmonic torque coupling coefficient characterizes the stress magnetic effect transmission gain between the internal electromagnetic field of the traction motor and the output shaft space of the traction motor. The phase delay compensator calculates the sum of the squares of the direct-axis harmonic components and the squares of the quadrature-axis harmonic components, and multiplies the sum of the squares with the preset harmonic torque coupling coefficient to obtain the parasitic pulsating torque component.

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