Time delay compensation method and system for permanent magnet synchronous motor speed control system

Abstract

The application discloses a time delay compensation method and system of a permanent magnet synchronous motor speed control system. The method comprises the following steps: obtaining a speed feedback signal of the permanent magnet synchronous motor speed control system; obtaining a system total delay time of the permanent magnet synchronous motor speed control system, wherein the system total delay time comprises a digital control delay, an inverter switching delay and an equivalent delay of a motor body of the permanent magnet synchronous motor speed control system; processing the speed feedback signal by using a tracking differentiator to obtain a smooth tracking value and a noiseless differential value; weighting the noiseless differential value based on the system total delay time, and superimposing the weighted differential value and the smooth tracking value to generate a predicted speed feedback signal; and inputting the predicted speed feedback signal into a speed loop controller of the permanent magnet synchronous motor speed control system to replace an original lag speed feedback signal to participate in closed-loop control. The application realizes delay compensation without relying on an accurate model.

Description

Technical Field

[0001] This invention belongs to the technical field of permanent magnet synchronous motor control, specifically relating to a time delay compensation method and system for a permanent magnet synchronous motor speed control system. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) possess advantages such as high power density, high efficiency, fast dynamic response, and reliable operation, and are widely used in industrial servo systems, robot joints, CNC equipment, and electric drive systems. In these applications, the speed loop control performance directly affects the dynamic response, disturbance rejection capability, and steady-state operating quality of the motor drive system. Sliding mode control, due to its strong robustness and low model dependence, is often used in the speed loop control of PMSMs to improve the system's adaptability to load disturbances and parameter changes.

[0003] However, in practical digital control systems, speed control commands cannot be applied to the controlled motor immediately. The control signal typically needs to pass through a series of stages, including sampling and calculation by the digital controller, PWM modulation and inverter switching output, electromagnetic energy conversion of the motor, and mechanical inertial response, before it is reflected in the sampled feedback signal. These stages introduce controller delay, inverter delay, and electromagnetic and electromechanical dynamic phase lag in the motor itself. When the controller performs closed-loop adjustment based on the lagging speed feedback, it can easily lead to a decrease in the speed loop phase margin, causing problems such as overshoot, speed chattering, increased current fluctuations, and reduced stability.

[0004] Existing delay compensation methods for permanent magnet synchronous motors (PMSMs) mostly focus on compensating for digital sampling delay, PWM update delay, or inverter switching delay, typically failing to adequately consider the equivalent delay introduced by the PMSM as an energy conversion device and inertial system. Traditional Smith predictor compensation can theoretically offset pure time delays in a closed-loop system, but it relies on a relatively accurate mathematical model of the controlled object. In practical engineering, motor parameter perturbations, load disturbances, friction changes, and unmodeled dynamics can reduce model matching accuracy, limiting the applicability of traditional Smith predictor compensation.

[0005] Therefore, there is an urgent need to provide a time delay compensation method and system for the speed control system of permanent magnet synchronous motor. Summary of the Invention

[0006] The main objective of this invention is to provide a time delay compensation method and system for a permanent magnet synchronous motor speed control system, which does not rely on an accurate motor model and can comprehensively compensate for the delays of the controller, inverter, and motor body, thereby overcoming the shortcomings of the prior art.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: An embodiment of the present invention provides a time delay compensation method for a speed control system of a permanent magnet synchronous motor, comprising: Obtain the speed feedback signal of the permanent magnet synchronous motor speed control system; The total system delay time of the permanent magnet synchronous motor speed control system is obtained. The total system delay time includes digital control delay, inverter switching delay, and the equivalent delay of the motor body of the permanent magnet synchronous motor speed control system. The velocity feedback signal is processed using a tracking differentiator to obtain a smooth tracking value and a noise-free differential value; The noise-free derivative value is weighted based on the total system delay time, and the weighted derivative value is superimposed with the smoothed tracking value to generate a predicted velocity feedback signal. The predicted speed feedback signal is input into the speed loop controller of the permanent magnet synchronous motor speed control system to replace the original lagging speed feedback signal in the closed-loop control.

[0008] In a preferred embodiment, the equivalent delay of the motor body is a pure delay obtained by equivalent conversion of the electromagnetic hysteresis and electromechanical hysteresis of the motor body in the low-frequency band. The equivalent delay of the motor body in the total system delay time is the sum of the pure delay corresponding to the electromagnetic hysteresis and the pure delay corresponding to the electromechanical hysteresis.

[0009] In a preferred embodiment, the electromagnetic hysteresis and the electromechanical hysteresis respectively correspond to a first-order inertial element. Under low-frequency conditions, the phase hysteresis of the first-order inertial element is equivalent to a pure-delay phase hysteresis.

[0010] In a preferred embodiment, the equivalent delay of the motor body is equal to the sum of the first-order time constants; The digital control delay is estimated based on the sampling period of the digital controller included in the permanent magnet synchronous motor speed control system, and is taken as N sampling periods, where N is a positive number; The inverter switching delay is estimated based on the switching frequency of the inverter included in the permanent magnet synchronous motor speed control system.

[0011] In a preferred embodiment, the step of weighting the noise-free differential value based on the total system delay time and superimposing the weighted differential value with the smoothed tracking value to generate a predicted velocity feedback signal includes: Multiplying the noise-free differential value by the total system delay time yields the phase lead compensation amount. The phase lead compensation amount is based on the Smith predictive control concept and the first-order Taylor expansion, and is equivalent to superimposing a differential term proportional to the total delay time onto the original feedback signal. The smoothed tracking value is added to the phase advance compensation amount to generate the predictive feedback signal, so as to achieve phase advance compensation without relying on the accurate controlled object model.

[0012] In a preferred embodiment, the tracking differentiator is positioned after the sensor output that acquires the velocity feedback signal and before the velocity loop controller; The tracking differentiator uses the actual acquired motor speed as the speed feedback signal, extracts the smoothed tracking value of the speed feedback signal, and outputs the noise-free differential value after suppressing measurement noise.

[0013] In a preferred embodiment, obtaining the total system delay time of the permanent magnet synchronous motor speed control system includes: Based on the sampling period of the digital controller, the switching frequency of the inverter, and the motor parameters of the motor body, an initial estimate of the total system delay time is calculated. Under the actual operating conditions of the permanent magnet synchronous motor speed control system, the initial estimated value is experimentally corrected to obtain the final total system delay time.

[0014] In a preferred embodiment, the step of experimentally correcting the initial estimated value under the actual operating conditions of the permanent magnet synchronous motor speed control system to obtain the final total system delay time includes: Under the same speed, load, and controller parameters, multiple sets of candidate compensation delay times are set. For each group of candidate compensation delay times, the corresponding speed response, current response, speed ripple, and current ripple are collected; Based on the principle of minimizing speed ripple and current ripple, the candidate value that minimizes speed ripple and current ripple and optimizes dynamic response is selected from the multiple sets of candidate compensation delay times, and is taken as the final total system delay time.

[0015] Another embodiment of the present invention provides a speed control system for a permanent magnet synchronous motor, including a digital controller, an inverter, a motor body, a sensor, and a delay compensation module; The sensor is used to collect the speed feedback signal of the motor body; The delay compensation module is configured to execute the time delay compensation method of the permanent magnet synchronous motor speed control system as described in any of the above items to generate a predicted speed feedback signal. The digital controller includes a speed loop controller, which is configured to receive the predicted speed feedback signal to replace the original hysteresis speed feedback signal, and generate speed control commands based on the predicted speed feedback signal. The inverter is configured to drive the motor body to operate according to the speed control command.

[0016] Another embodiment of the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the time delay compensation method for the permanent magnet synchronous motor speed control system as described in any of the preceding claims.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: First, comprehensive compensation: It incorporates digital control delay, inverter switching delay, and electromagnetic and electromechanical lag of the motor body into the total system delay, making up for the shortcomings of traditional methods that ignore the equivalent delay of the motor body, and making the compensation more complete and closer to the actual physical system.

[0018] Second, it does not rely on an accurate model: It is based on the Smith prediction idea but does not require the establishment of an accurate mathematical model of the permanent magnet synchronous motor. Only the estimated value of the total system delay time is needed to achieve phase advance compensation, which significantly reduces the dependence of traditional Smith prediction compensation on model accuracy and enhances engineering practicality.

[0019] Third, it has strong noise resistance: by using a tracking differentiator to extract the smooth tracking value and its derivative from the actual noisy velocity feedback, the measurement noise amplification problem is effectively suppressed while constructing the prediction signal, and the high-frequency interference caused by the pure differentiator is avoided.

[0020] Fourth, the controller has good compatibility: the delay compensation framework proposed in this embodiment is decoupled from the specific form of the speed loop controller, and can be used in combination with various robust control methods such as sliding mode control, active disturbance rejection control, and terminal sliding mode control, thus having good engineering compatibility.

[0021] Fifth, improve system performance: reduce speed chattering, overshoot and current ripple caused by feedback lag, and improve the dynamic response and steady-state operation quality of the permanent magnet synchronous motor speed control system. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of a traditional Smith predictive control structure.

[0024] Figure 2This is a schematic diagram of a Smith-TD time delay compensation structure based on a tracking differentiator according to one embodiment of this application.

[0025] Figure 3 This is a schematic diagram of the delay generation stage of a speed control system for a permanent magnet synchronous motor according to one embodiment of this application.

[0026] Figure 4a , 4b Figures 4c and 4d are comparison diagrams of speed and current response under different compensation delay times in one embodiment of this application.

[0027] Figure 5 This is a flowchart illustrating a time delay compensation method for a permanent magnet synchronous motor speed control system according to an embodiment of this application. Detailed Implementation

[0028] The invention will be more fully understood through the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of the invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as intended to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0029] This application provides a time delay compensation method and system for a permanent magnet synchronous motor (PMSM) speed control system. Addressing the problems of time delay introduced by the controller, inverter, and motor body in existing PMSM speed control systems, leading to speed feedback lag, reduced phase margin, chattering, and increased overshoot, the method estimates the total system delay time and uses a tracking differentiator to obtain the smoothed tracking value and its derivative of the speed feedback signal. Based on the first-order Taylor approximation, a phase-leading predicted speed feedback is constructed, thereby achieving speed loop delay compensation without relying on an accurate PMSM model. The method will be described first through specific embodiments, followed by a description of the system.

[0030] Example 1.

[0031] See Figure 5 This embodiment provides a time delay compensation method for a permanent magnet synchronous motor speed control system, including: S101, Obtain the speed feedback signal of the permanent magnet synchronous motor speed control system; Specifically, the speed feedback signal is acquired, for example, by a sensor mounted on the shaft of a permanent magnet synchronous motor.

[0032] S102, obtain the total system delay time of the permanent magnet synchronous motor speed control system; the total system delay time includes digital control delay, inverter switching delay and the equivalent delay of the motor body of the permanent magnet synchronous motor speed control system. In this application, the digital control delay, inverter switching delay, motor body equivalent delay, and total system delay all refer to time intervals, that is, the length of time from signal generation to its manifestation in the response of the controlled object.

[0033] Specifically, related delay compensation techniques often only focus on the sampling and calculation delay of the digital controller and the PWM switching delay of the inverter, while ignoring the dynamic lag introduced by the permanent magnet synchronous motor as an energy conversion device and a mechanical inertial system. In this embodiment, the total system delay time is redefined as a comprehensive delay parameter. Among them, the digital control delay mainly originates from algorithm calculation and the zero-order hold effect; the inverter switching delay originates from the operating cycle of the power devices; and the equivalent delay of the motor body is the pure delay time obtained by equivalently converting the current response lag caused by the inductance of the motor's electromagnetic windings and the speed response lag caused by the rotor's rotational inertia in the frequency domain.

[0034] By quantifying these three delays into the total system delay time, subsequent compensation actions can cover the entire process from command issuance to physical response, avoiding compensation residuals caused by model deficiencies.

[0035] S103, The speed feedback signal is processed using a tracking differentiator to obtain a smooth tracking value and a noise-free differential value; Specifically, the tracking differentiator (TD) is specifically positioned in the feedback channel, that is, after the sensor output and before the speed loop controller. The tracking differentiator takes the actual noisy speed feedback signal obtained in step S101 as input, and through its internal nonlinear filtering mechanism, on the one hand, it extracts the smooth tracking value after filtering out high-frequency interference, which truly reflects the current speed state of the motor; on the other hand, it analyzes the noiseless differential value of the speed change trend without amplifying the measurement noise.

[0036] S104, The noise-free derivative value is weighted based on the total system delay time, and the weighted derivative value is superimposed with the smooth tracking value to generate a predicted speed feedback signal; Specifically, the generation of the predicted velocity feedback signal can be achieved by using the first-order Taylor expansion approximation principle to reconstruct the future velocity state in the time domain; multiplying the noise-free differential value obtained in step S103 by the total system delay time determined in step S102 to obtain a compensation amount representing phase lead; and then adding this compensation amount to the smooth tracking value to obtain the predicted velocity feedback signal.

[0037] From a mechanistic perspective, this is equivalent to predicting the speed the motor should reach after the total system delay, without relying on a precise transfer function model of the controlled object. This prediction mechanism based on the characteristics of the signal itself eliminates the strong dependence of traditional Smith predictors on precise mathematical models of the motor, significantly enhancing the robustness of the algorithm when motor parameters are perturbed or when unmodeled dynamics exist.

[0038] S105, The predicted speed feedback signal is input to the speed loop controller of the permanent magnet synchronous motor speed control system to replace the original lagging speed feedback signal in the closed-loop control.

[0039] This can be understood as the speed loop controller no longer receiving the hysteresis signal directly output by the sensor, but rather a predicted speed feedback signal generated in step S104 that leads the original signal in phase. Because this predicted signal cancels out the hysteresis effect caused by the total system delay on the time axis, the controller can use higher bandwidth parameters while ensuring stability. This effectively suppresses speed chattering, overshoot, and current ripple caused by feedback hysteresis, improving the dynamic response quality and steady-state operation accuracy of the permanent magnet synchronous motor speed control system.

[0040] Because the control signal of the permanent magnet synchronous motor speed control system needs to go through multiple stages in actual operation, such as digital controller sampling and calculation, PWM modulation and update, inverter switching output, and electromagnetic energy conversion and mechanical inertial response of the motor body, each of these stages introduces independent digital control delay, inverter switching delay, and electromagnetic and electromechanical dynamic phase lag of the motor body. Moreover, the equivalent delay of the motor body varies with the operating conditions and is difficult to accurately model through simple linear superposition, resulting in a decrease in the speed loop phase margin when the controller performs closed-loop regulation based on lag feedback. Although traditional Smith predictor control can offset the closed-loop delay through parallel compensators, its compensator structure depends on an accurate mathematical model of the permanent magnet synchronous motor controlled object. However, in actual operation, motor parameter perturbations, load disturbances, frictional nonlinearity, and unmodeled dynamics cause model mismatch, which limits the applicability of traditional Smith predictor compensation.

[0041] Therefore, the predicted signal (predicted speed feedback signal) provided in this embodiment leads the original lag signal in phase, enabling the speed loop controller to adjust based on feedback quantities that are closer to the actual current operating state of the motor. Without relying on a precise permanent magnet synchronous motor model, it effectively compensates for the phase lag caused by the total system delay, increases the speed loop phase margin, and thus reduces speed overshoot, chattering, and current ripple caused by feedback lag, improving the system's dynamic response and steady-state operating quality. Furthermore, since this compensation acts on the speed feedback channel and is decoupled from the specific form of the speed loop controller, it is compatible with various robust control methods.

[0042] In an exemplary embodiment, the equivalent delay of the motor body is a pure delay obtained by equivalent conversion of the electromagnetic hysteresis and electromechanical hysteresis of the motor body in the low-frequency band. The equivalent delay of the motor body in the total system delay time is the sum of the pure delay corresponding to the electromagnetic hysteresis and the pure delay corresponding to the electromechanical hysteresis.

[0043] Therefore, through this embodiment, the inertial element of the motor body is transformed into a quantifiable pure delay, which makes up for the shortcomings of traditional methods that only compensate for hardware delay, and makes the compensation model closer to the actual physical system.

[0044] In an exemplary embodiment, the electromagnetic hysteresis and the electromechanical hysteresis respectively correspond to a first-order inertial element. Under low-frequency conditions, the phase hysteresis of the first-order inertial element is equivalent to a pure-delay phase hysteresis. The electromagnetic time constant corresponding to the electromagnetic hysteresis and the electromechanical time constant corresponding to the electromechanical lag They are represented as follows: In the formula, For stator inductance, For stator resistance, For rotational inertia, The back electromotive force constant is... is the torque constant.

[0045] For a surface-mounted permanent magnet synchronous motor, Kt can be represented as: In the formula, p n This represents the number of pole pairs of the motor. ψ The permanent magnet flux linkage. The initial estimate of the total system delay time τ can be obtained through equations (1) to (5) in this application.

[0046] Therefore, the technical solution provided in this embodiment simplifies the computational complexity by ignoring higher-order terms, enabling the embedded controller to execute in real time and cooperate with subsequent correction mechanisms.

[0047] In an exemplary embodiment, the total system delay τ is expressed as: In the formula, For the digital control delay, For the inverter switching delay, The equivalent delay of the motor body; The digital control delay The sampling period of the digital controller included in the speed control system of the permanent magnet synchronous motor is estimated and taken as N sampling periods, where N is a positive number; The inverter switching delay Based on the switching frequency of the inverter included in the permanent magnet synchronous motor speed control system The estimation is expressed as: ; The equivalent delay of the motor body It equals the sum of all first-order time constants, expressed as: (3).

[0048] In an exemplary embodiment, the step of weighting the noise-free derivative value based on the total system delay time and superimposing the weighted derivative value with the smoothed tracking value to generate a predicted velocity feedback signal includes: Multiplying the noise-free differential value by the total system delay time yields the phase lead compensation amount. The phase lead compensation amount is based on the Smith predictive control concept and the first-order Taylor expansion, and is equivalent to superimposing a differential term proportional to the total delay time onto the original feedback signal. The smoothed tracking value is added to the phase advance compensation amount to generate the predictive feedback signal, so as to achieve phase advance compensation without relying on the accurate controlled object model.

[0049] Specifically, traditional Smith predictive compensators require constructing a mathematical model that perfectly matches the controlled object to separate the delay element. Once motor parameters (such as inductance, resistance, and inertia) are perturbed or unmodeled dynamics exist, model mismatch will lead to compensation failure or even system instability. In contrast, the predictive feedback signal generated in this embodiment relies only on the measurable feedback signal itself and its differential information, as well as the total system delay time, effectively providing phase lead compensation.

[0050] In one exemplary embodiment, the tracking differentiator is positioned after the sensor output that acquires the velocity feedback signal and before the velocity loop controller; The tracking differentiator uses the actual acquired motor speed as the speed feedback signal, extracts the smoothed tracking value of the speed feedback signal, and outputs the noise-free differential value after suppressing measurement noise. The predicted velocity feedback signal Represented as: In the formula, For the smooth tracking value, This is the total system delay time. This is the noise-free differential value.

[0051] Thus, the specific location of the tracking differentiator in the feedback channel and its signal processing function were clarified. By utilizing its filtering characteristics, high-frequency noise amplification was suppressed while extracting differential information, thus avoiding the problem of traditional pure differentiators being susceptible to interference.

[0052] In an exemplary embodiment, obtaining the total system delay time of the permanent magnet synchronous motor speed control system includes: Based on the sampling period of the digital controller, the switching frequency of the inverter, and the motor parameters of the motor body, an initial estimate of the total system delay time is calculated. Under the actual operating conditions of the permanent magnet synchronous motor speed control system, the initial estimated value is experimentally corrected to obtain the final total system delay time.

[0053] Therefore, by combining theoretical calculations with engineering measurements, the efficiency of parameter acquisition is ensured, and the deviation caused by the simplification of the theoretical model is eliminated through actual working condition correction, thereby improving the accuracy of the compensation parameters.

[0054] In an exemplary embodiment, the step of experimentally correcting the initial estimate under the actual operating conditions of the permanent magnet synchronous motor speed control system to obtain the final total system delay time includes: Under the same speed, load, and controller parameters, multiple sets of candidate compensation delay times are set. For each group of candidate compensation delay times, the corresponding speed response, current response, speed ripple, and current ripple are collected; Based on the principle of minimizing speed ripple and current ripple, the candidate value that minimizes speed ripple and current ripple and optimizes dynamic response is selected from the multiple sets of candidate compensation delay times, and is taken as the final total system delay time.

[0055] Therefore, by setting multiple candidate compensation delay times under the same working conditions, the optimal delay value is selected based on the principle of minimizing speed ripple and current ripple, thus avoiding the deviation between the theoretical estimate and the actual optimal value.

[0056] As an example, see Figures 4a to 4d The figure shows a comparison of speed and current response under different compensation delay times. Figures 4a to 4d Four operating conditions—no compensation (0ms), 5ms compensation, 10ms compensation, and 15ms compensation—were tested to verify the impact of the total system delay time selection on the delay compensation effect. Without compensation, the system remained in a continuous oscillation state due to feedback lag; the 5ms compensation was insufficient, resulting in limited performance improvement; with 10ms compensation, both speed ripple and current ripple were minimized, leading to the most stable operation; and with 15ms compensation, performance regressed due to overcompensation.

[0057] Therefore, by selecting 10ms, which minimizes both velocity ripple and current ripple, as the final compensation value for the total system delay time through experimental calibration, the deviation between the theoretical estimate and the actual optimal value can be effectively eliminated.

[0058] Compared to Figure 1 The provided traditional Smith predictive control structure, for reference Figure 2 and Figure 3 As an example, a specific implementation of a time delay compensation method for a permanent magnet synchronous motor speed control system is provided.

[0059] Figure 1 In this system, the overall architecture consists of a forward controller, the actual controlled object, and a predictive compensator forming a closed loop. From a signal flow perspective, the reference input is compared with the system feedback signal at the left summing node, forming an error signal which is then input to the speed controller C(s). The speed controller outputs a control quantity U(s), which is simultaneously fed into two branches: one branch passes through the actual controlled object (permanent magnet synchronous motor system), generating the actual system output Y(s); the other branch passes through a conventional Smith control, generating a compensation signal. The actual output and the predictive compensator output are algebraically superimposed at the right summing node, and the synthesized signal is returned as feedback to the left summing node, subtracted from the reference input, thus forming a complete closed-loop control circuit.

[0060] Figure 2 This paper presents an improved Smith predictive control structure, the core innovation of which is to replace the compensator in the traditional Smith predictive control, which relies on an accurate model, with a predictive mechanism based on a tracking differentiator (TD) (improved Smith control strategy).

[0061] This improved structure abandons the reliance of traditional Smith prediction on a precise mathematical model of the controlled object, and introduces a tracking differentiator in the speed feedback channel. The TD module simultaneously extracts smooth tracking values ​​and noise-free differential values ​​from the noisy speed feedback signal, and generates a phase-leading predictive feedback signal through linear combination, thereby achieving delay compensation without relying on a precise motor model.

[0062] Figure 3 This diagram illustrates the signal chain of the speed control system and the physical mechanism of the time delay introduced at each stage. The figure shows the signal chain from the given speed ω. refThe control link from SMC (sliding mode controller), PI controller (proportional-integral controller), coordinate transformation of dq and αβ, SVPWM (space vector pulse width modulator), inverter to PMSM (permanent magnet synchronous motor), and current and speed closed-loop link detected by sensors and fed back through coordinate transformation of abc, αβ, and dq (rotating coordinate system, two-phase stationary coordinate system, and three-phase stationary coordinate system, respectively, corresponding to coordinate transformation modules used to convert voltage and current signals between different reference systems).

[0063] The diagram identifies three delay generation stages: τ1 corresponds to the DSP digital control delay, τ2 corresponds to the inverter switching delay, and τ3 corresponds to the PMSM motor's equivalent delay. The total system delay is calculated as follows: calculate.

[0064] The rotational speed signal detected by the sensor is a delayed ω. m After being processed by the tracking differentiator, the signal, together with the observer, forms a speed feedback channel and participates in the speed closed-loop control.

[0065] The specific implementation of the time delay compensation method for the speed control system of permanent magnet synchronous motor is as follows: Step 1: Construct a speed control system for the permanent magnet synchronous motor and determine the delay generation mechanism. The speed control system includes a speed setpoint input, a speed loop controller, a current loop controller, a coordinate transformation module, an SVPWM module, a three-phase inverter, the permanent magnet synchronous motor, and a speed sensor. The speed setpoint is compared with the speed feedback value to form a speed error. The speed loop controller outputs a q-axis reference current, and the current loop controller generates a voltage control command based on the d-axis and q-axis current errors. This command is then transmitted via SVPWM and the inverter to drive the permanent magnet synchronous motor.

[0066] In the control chain described above, the delay mainly originates from three parts: the first part is the sampling, calculation, and PWM update delay of the digital controller, denoted as τ1; the second part is the inverter switching delay, denoted as τ2; and the third part is the electromagnetic and electromechanical hysteresis of the permanent magnet synchronous motor itself, denoted as τ3. The total system delay is denoted as τ, and its expression is: (1) In the formula, τ represents the combined term for small delays in signal transmission, interface circuitry, sensor conditioning, and data processing. When these small delays are negligible, the total system delay can be approximately expressed as τ≈τ1+τ2+τ3.

[0067] Step 2: Obtain an initial estimate of the total system delay. For a digital controller using a fixed sampling period Ts, the digital control delay τ1 can be determined based on the sampling, calculation, and PWM update methods, and is typically taken as several sampling periods. For example, in a typical digital servo control system, τ1 can be approximately 1.5Ts.

[0068] For a switching frequency of f sw For an inverter, the inverter switching delay τ2 can be approximately estimated based on the switching period: (2) To more clearly explain the theoretical basis of the equivalent transformation involved in this application, the phase characteristics of a first-order inertial element and a pure delay element are analyzed. Electromagnetic hysteresis and electromechanical hysteresis correspond to the first-order inertial element, respectively. Under low-frequency conditions, the phase hysteresis of the first-order inertial element is equivalent to the phase hysteresis of a pure delay element. The specific derivation process is as follows: 1. Phase lag of a first-order inertial element Motor electromagnetic hysteresis and electromechanical lag For each of the two first-order inertial elements, their transfer function forms are as follows: in The time constant ( or ).

[0069] Its frequency response (let) )for: Amplitude and phase frequency characteristics: That is, the phase lag is .

[0070] The transfer function for pure delay (transmission delay) is: Its frequency response: Phase lag is: 2. Approximation conditions and equivalence relations when (i.e., in the low-frequency range), the phase lag of a first-order inertial element can be approximated as: Compare the phase lag of first-order lag with that of pure delay: First-order lag: Pure delay: Make them equal: Therefore, in the low-frequency range, a time constant is... The first-order inertial hysteresis can be equivalent to a pure time delay. .

[0071] 3. Equivalent total delay when multiple first-order lags are connected in series The electromagnetic hysteresis and electromechanical hysteresis of the motor are in series (they work together). The total phase hysteresis of the system is the sum of the two: Under the low-frequency approximation: This is equivalent to the phase lag of a pure delay element. ,in: (3) Therefore, the equivalent pure delay time (equivalent delay of the motor body) is equal to the sum of the first-order time constants.

[0072] Where T3e is the electromagnetic time constant and T3m is the electromechanical time constant, they are expressed as follows: (4) In the formula, L is the stator inductance, R is the stator resistance, J is the moment of inertia, Ke is the back electromotive force constant, and Kt is the torque constant. For a surface-mounted permanent magnet synchronous motor, Kt can be expressed as: (5) In the formula, pn is the number of pole pairs of the motor, and ψ is the flux linkage of the permanent magnet. The initial estimate of the total system delay time τ can be obtained through equations (1) to (5).

[0073] Step 3: Establish a first-order delay compensation relationship based on the Smith predictor concept. Traditional Smith predictor control compensates for delays in the closed-loop system by connecting a parallel compensator to the controlled object. Let the equivalent control input of the speed loop be U(s), the equivalent model of the permanent magnet synchronous motor controlled object be G(s), and the total system delay be τ. Then, the relationship between the output Y(s) and the input U(s) in the traditional Smith predictor structure can be expressed as: (6) According to Taylor's expansion: (7) When τ is small and the system operates in the low-frequency speed regulation range, taking e^(τs)≈1+τs, then equation (6) can be rewritten as: (8) As shown in equation (8), the delay compensation can be equivalent to constructing a composite signal consisting of the original signal and its differential term in the control or feedback channel, i.e., U(s) + τsU(s) as the phase lead compensation amount. Since the accurate model G(s) of the actual permanent magnet synchronous motor is difficult to obtain, this application does not directly rely on G(s) to construct the traditional Smith compensator, but uses the tracking differentiator to construct the predictive feedback signal after the speed feedback sampling position to achieve equivalent phase lead compensation.

[0074] Step 4: Determine the compensation delay time. After obtaining the initial estimate of the total delay time τ according to equations (1) to (5), τ can be corrected under experimental platform or actual operating conditions. The correction method includes: setting several candidate compensation delay times under the same speed, the same load, and the same controller parameters, and collecting the corresponding speed response, current response, speed ripple, and current ripple; selecting the candidate values ​​with smaller speed ripple and current ripple and better dynamic response as the final compensation delay time.

[0075] Through the above steps, the total delay of the permanent magnet synchronous motor speed control system is decomposed into three parts: digital control delay, inverter switching delay, and equivalent delay of the motor itself. A quantitative estimation method for the equivalent delay of the motor itself (combining electromagnetic and electromechanical time constants) is also provided. Based on the first-order Taylor expansion e^τs≈1+τs, the Smith prediction compensation is equivalent to superimposing a differential term proportional to the total delay time onto the original feedback signal, thus establishing a phase lead compensation relationship independent of the precise controlled object model. A tracking differentiator is introduced after the speed feedback sampling position, using the actual acquired motor speed as input, to simultaneously obtain the smoothed tracking value and the noise-suppressed differential value, which are used to construct the predicted speed feedback signal. Multiple candidate compensation delay times are set under the same operating conditions, and the optimal delay value is selected based on the principle of minimizing speed ripple and current ripple, avoiding the deviation between the theoretical estimate and the actual optimal value.

[0076] In another example, the permanent magnet synchronous motor drive system uses a DSP digital controller, with both the current control frequency and the inverter switching frequency at 10kHz. In this case, the inverter delay is approximately 0.1ms, and the DSP control delay is approximately 1.5 sampling cycles, or about 0.15ms. Considering the electromagnetic and electromechanical phase lag of the motor itself and small delays in signal transmission, the initial estimate of the total system delay is approximately 9.5ms. See Table 1 below for specific motor parameters.

[0077] Table 1 Specific Motor Parameters for Implementation In the above example, a sliding mode controller based on a novel obstacle function is used as the speed controller, and the tracking differentiator is placed at the speed sampling position for delay compensation. Comparisons were made with no compensation, 5ms compensation, 10ms compensation, and 15ms compensation. Experimental results show that the speed ripple is largest without compensation, the q-axis reference current fluctuates significantly, and this further causes q-axis current and speed chattering. 5ms compensation can reduce speed and current ripple, but the compensation amount is insufficient. Both 10ms and 15ms compensation can significantly improve the system's operating state, with 10ms compensation being slightly better. Therefore, in this embodiment, 10ms is selected as the final compensation delay time for the system.

[0078] Therefore, the technical solution provided in this embodiment has the following beneficial effects: First, comprehensive compensation: It incorporates digital control delay, inverter switching delay, and electromagnetic and electromechanical lag of the motor body into the total system delay, making up for the shortcomings of traditional methods that ignore the equivalent delay of the motor body, and making the compensation more complete and closer to the actual physical system.

[0079] Second, it does not rely on an accurate model: It is based on the Smith prediction idea but does not require the establishment of an accurate mathematical model of the permanent magnet synchronous motor. Only the estimated value of the total system delay time is needed to achieve phase advance compensation, which significantly reduces the dependence of traditional Smith prediction compensation on model accuracy and enhances engineering practicality.

[0080] Third, it has strong noise resistance: by using a tracking differentiator to extract the smooth tracking value and its derivative from the actual noisy velocity feedback, the measurement noise amplification problem is effectively suppressed while constructing the prediction signal, and the high-frequency interference caused by the pure differentiator is avoided.

[0081] Fourth, the controller has good compatibility: the delay compensation framework proposed in this embodiment is decoupled from the specific form of the speed loop controller, and can be used in combination with various robust control methods such as sliding mode control, active disturbance rejection control, and terminal sliding mode control, thus having good engineering compatibility.

[0082] Fifth, improve system performance: reduce speed chattering, overshoot and current ripple caused by feedback lag, and improve the dynamic response and steady-state operation quality of the permanent magnet synchronous motor speed control system.

[0083] Example 2.

[0084] This embodiment provides a speed control system for a permanent magnet synchronous motor, including a digital controller, an inverter, a motor body, sensors, and a delay compensation module; The sensor is used to collect the speed feedback signal of the motor body; The delay compensation module is configured to execute the time delay compensation method of the permanent magnet synchronous motor speed control system as described in any one of Embodiment 1, so as to generate a predicted speed feedback signal; The digital controller includes a speed loop controller, which is configured to receive the predicted speed feedback signal to replace the original hysteresis speed feedback signal, and generate speed control commands based on the predicted speed feedback signal. The inverter is configured to drive the motor body to operate according to the speed control command.

[0085] Example 3.

[0086] This embodiment provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the time delay compensation method of the permanent magnet synchronous motor speed control system as described in any one of Embodiment 1.

[0087] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the described embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this document is not intended to limit the invention to the specific embodiments disclosed for carrying out the invention, but rather to include all embodiments falling within the scope of the appended claims.

Claims

1. A time delay compensation method for a speed control system of a permanent magnet synchronous motor, characterized in that, include: Obtain the speed feedback signal of the permanent magnet synchronous motor speed control system; The total system delay time of the permanent magnet synchronous motor speed control system is obtained. The total system delay time includes digital control delay, inverter switching delay, and the equivalent delay of the motor body of the permanent magnet synchronous motor speed control system. The velocity feedback signal is processed using a tracking differentiator to obtain a smooth tracking value and a noise-free differential value; The noise-free derivative value is weighted based on the total system delay time, and the weighted derivative value is superimposed with the smoothed tracking value to generate a predicted velocity feedback signal. The predicted speed feedback signal is input into the speed loop controller of the permanent magnet synchronous motor speed control system to replace the original lagging speed feedback signal in the closed-loop control.

2. The method according to claim 1, characterized in that, The equivalent delay of the motor body is a pure delay obtained by equivalent conversion of the electromagnetic hysteresis and electromechanical hysteresis of the motor body in the low-frequency band. The equivalent delay of the motor body in the total system delay time is the sum of the pure delay corresponding to the electromagnetic hysteresis and the pure delay corresponding to the electromechanical hysteresis.

3. The method according to claim 2, characterized in that, The electromagnetic hysteresis and the electromechanical hysteresis respectively correspond to the first-order inertial element. Under low-frequency conditions, the phase hysteresis of the first-order inertial element is equivalent to the phase hysteresis of pure delay.

4. The method according to claim 3, characterized in that, The equivalent delay of the motor body is equal to the sum of the first-order time constants; The digital control delay is estimated based on the sampling period of the digital controller included in the permanent magnet synchronous motor speed control system, and is taken as N sampling periods, where N is a positive number; The inverter switching delay is estimated based on the switching frequency of the inverter included in the permanent magnet synchronous motor speed control system.

5. The method according to claim 1, characterized in that, The step of weighting the noise-free derivative value based on the total system delay time and then superimposing the weighted derivative value with the smoothed tracking value to generate a predicted velocity feedback signal includes: Multiplying the noise-free differential value by the total system delay time yields the phase lead compensation amount. The phase lead compensation amount is based on the Smith predictive control concept and the first-order Taylor expansion, and is equivalent to superimposing a differential term proportional to the total delay time onto the original feedback signal. The smoothed tracking value is added to the phase advance compensation amount to generate the predictive feedback signal, so as to achieve phase advance compensation without relying on the accurate controlled object model.

6. The method according to claim 5, characterized in that, The tracking differentiator is positioned after the output of the sensor that acquires the speed feedback signal and before the speed loop controller; The tracking differentiator uses the actual acquired motor speed as the speed feedback signal, extracts the smoothed tracking value of the speed feedback signal, and outputs the noise-free differential value after suppressing measurement noise.

7. The method according to claim 1, characterized in that, The total system delay time for obtaining the speed control system of the permanent magnet synchronous motor includes: Based on the sampling period of the digital controller, the switching frequency of the inverter, and the motor parameters of the motor body, an initial estimate of the total system delay time is calculated. Under the actual operating conditions of the permanent magnet synchronous motor speed control system, the initial estimated value is experimentally corrected to obtain the final total system delay time.

8. The method according to claim 7, characterized in that, Under the actual operating conditions of the permanent magnet synchronous motor speed control system, the initial estimated value is experimentally corrected to obtain the final total system delay time, including: Under the same speed, load, and controller parameters, multiple sets of candidate compensation delay times are set. For each group of candidate compensation delay times, the corresponding speed response, current response, speed ripple, and current ripple are collected; Based on the principle of minimizing speed ripple and current ripple, the candidate value that minimizes speed ripple and current ripple and optimizes dynamic response is selected from the multiple sets of candidate compensation delay times, and is taken as the final total system delay time.

9. A speed control system for a permanent magnet synchronous motor, characterized in that, It includes a digital controller, inverter, motor body, sensors, and delay compensation module; The sensor is used to collect the speed feedback signal of the motor body; The delay compensation module is configured to execute the time delay compensation method of the permanent magnet synchronous motor speed control system as described in any one of claims 1 to 8, so as to generate a predicted speed feedback signal; The digital controller includes a speed loop controller, which is configured to receive the predicted speed feedback signal to replace the original hysteresis speed feedback signal, and generate speed control commands based on the predicted speed feedback signal. The inverter is configured to drive the motor body to operate according to the speed control command.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the time delay compensation method for the speed control system of a permanent magnet synchronous motor as described in any one of claims 1 to 8.

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