High-speed sensorless control method in permanent magnet synchronous motor

Abstract

The invention discloses a high-speed sensorless control method in a permanent magnet synchronous motor, and relates to the field of motor control. The method comprises the following steps: replacing a traditional proportional-integral controller with a nonsingular terminal sliding mode controller in a speed outer ring design, using an integral sliding mode surface, omitting an integral link of a q-axis given current, and replacing a sign function with a Sigmoid function to improve the dynamic performance and robustness of a system; in the current inner loop design, in order to optimize the current following capability, dead-beat current control is adopted, and the system given is directly substituted into the current given at the next time point; a position-free sensor is carried, system buffeting caused by a traditional sliding mode observer is reduced through a super-spiral sliding mode observer, angle compensation is carried out for phase delay caused by a low-pass filter, and meanwhile when an arc tangent is used for calculating an angle, a quadrant where a rotor is located is estimated to carry out angle correction; an expansion observer is adopted to observe an external abrupt change load, feed-forward compensation is carried out, external interference is resisted, and the robustness of the system is improved; according to the invention, the nonsingular sliding mode speed controller, the dead-beat current controller and the disturbance observer are applied to the superhelix algorithm-based position-less sensor, so that the dynamic performance of the system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a speed control method of a non-singular terminal sliding mode speed controller and a medium-high speed and high performance position sensorless control strategy. Background Art

[0002] The most traditional control strategy in the speed outer loop of the permanent magnet synchronous motor (PMSM) in the vector control system (FOC) is proportional integral control (PI), which changes the torque current through the combined effect of proportion and integral. However, PI control cannot provide sufficient control force under complex working conditions, resulting in poor control effect and difficulty in achieving high-performance speed control. In the current inner loop, the most traditional control strategy is proportional integral control (PI). The PI controller needs to be parameterized, which usually involves trial and error or other optimization algorithms. The process is cumbersome and there are errors, and dynamic following will be delayed. In the medium and high-speed position sensorless control method, the sliding film observer will inevitably cause discontinuous vibration due to the existence of its switching function, affecting the observation of back electromotive force, and cannot meet the requirements of system stability and dynamic performance in high-performance control. Summary of the invention

[0003] The purpose of the present invention is to provide a permanent magnet synchronous motor system control method equipped with both a non-singular terminal sliding mode speed controller and a super-helical sliding film observer, which can enable the system to operate efficiently under complex working conditions, save costs and improve overall operating efficiency.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A control method for a permanent magnet synchronous motor system equipped with both a non-singular terminal sliding mode speed controller and a super-helical sliding film observer, characterized in that it includes:

[0006] The speed outer loop uses a non-singular terminal sliding mode controller and a sliding film surface with an integral link, so that when solving the output i q * The integral link is eliminated and the Sigmoid function is used as the sliding membrane switching function to reduce the output jitter.

[0007] The current inner loop establishes the dq axis current equation in the rotating coordinate system of the permanent magnet synchronous motor, and the first-order Euler forward discretization method is used to discretize the above equation. q(k+1) =i q * Substitute the above formula and solve the dq axis voltage equation to achieve zero-beat tracking of the current.

[0008] The disturbance observer is used to observe the external disturbance and bring it into the speed loop for feedforward compensation.

[0009] In the medium and high speed position sensorless control strategy, the estimation effect of the sliding mode controller is good, but there is a serious vibration in the output result. The super helical algorithm is now used for optimization to reduce the vibration.

[0010] Step 1: According to the kinematic equation, establish the mechanical speed ω m With torque current i q The relationship between i and the integral sliding surface and exponential approach rate is used to solve q * .

[0011] Step 2: Use the Sigmoid function instead of the sign function.

[0012] Step 3: Establish the current equation in the rotating coordinate system of the permanent magnet machine and perform discretization to obtain the torque current at the next moment i q(k+1) Expression, while letting i q(k+1) =i q * The response voltage expression is obtained.

[0013] Step 4: Establish a high-gain disturbance observer to observe the sudden load disturbance in real time, and bring the observed value into the speed loop for feedforward compensation.

[0014] Step 5: Build a sliding film observer in the speed feedback loop and use the super-helical algorithm to integrate the discontinuous terms in the sliding mode switching terms to make the system continuous, effectively reduce the inherent jitter caused by the sliding mode and optimize the system performance.

[0015] Step 6: Use the inverse tangent method to solve the angle information, and compensate and correct the angle.

[0016] Step 7: Build a complete surface-mounted permanent magnet synchronous motor vector control system based on the above.

[0017] Optionally, the speed outer loop establishes the time domain electromagnetic torque equation and kinematic equation of the permanent magnet machine in the rotating coordinate system, and uses the integral sliding surface and exponential approach rate to derive the torque current given value

[0018] The sliding surface uses an integral sliding surface with a Sigmoid switching function, and selects an exponential approach rate to solve the torque current given value.

[0019] Optionally, the current inner loop establishes the current time domain equation in the rotating coordinate system, and sets i q(k+1) =i q * Substitute into the equation to solve the dq axis voltage equation.

[0020] Optionally, a high-gain disturbance observer is built and the superhelical algorithm is used to achieve medium- and high-speed position sensorless control.

[0021] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0022] The invention discloses a high-speed position sensorless control method for a permanent magnet synchronous motor, and relates to the field of motor control. The method comprises: replacing a traditional proportional integral controller with a non-singular terminal sliding film controller in the speed outer loop design, using an integral sliding film surface, eliminating the integral link of the q-axis given current, and using a Sigmoid function instead of a sign function to improve the system dynamic performance and robustness; in the current inner loop design, in order to optimize the current following ability, using a deadbeat current control, directly bringing the system given current into the next time point; carrying a position sensorless, using a super-spiral sliding film observer to reduce the system jitter caused by the traditional sliding film observer, and performing angle compensation for the phase delay caused by the low-pass filter, and when using the inverse tangent to calculate the angle, estimating the quadrant where the rotor is located to perform angle correction; using an extended observer to observe the external sudden load, perform feedforward compensation, resist external interference, and improve the system robustness; the invention applies a non-singular sliding film speed controller, a deadbeat current controller and a disturbance observer to a position sensorless based on a super-spiral algorithm to improve the dynamic performance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0024] Figure 1 It is a schematic diagram of the process of the permanent magnet synchronous motor system of the present invention;

[0025] Figure 2 is a control block diagram of the present invention;

[0026] Among them: (a) is the control block diagram of the permanent magnet synchronous motor system; (b) is the control block diagram of the non-singular terminal sliding mode speed controller.

[0027] Figure 3 is a plane diagram of the Sigmoid function under different parameters in this embodiment;

[0028] Figure 4 The speed waveform of the permanent magnet synchronous motor control system of the present invention;

[0029] Figure 5It is a current inner loop deadbeat current control link in the permanent magnet synchronous motor control system of the present invention; wherein (a) is a d-axis voltage control module; and (b) is a q-axis voltage control module.

[0030] Figure 6 It is a disturbance observer control link in the permanent magnet synchronous motor control system of the present invention;

[0031] Wherein: (a) disturbance observer control module; (b) observed disturbance waveform.

[0032] Figure 7 It is a super-helical synovial film observer link in the permanent magnet synchronous motor control system of the present invention.

[0033] Among them, (a) is the super-helical synovial film observer module; (b) is the actual angle information of the motor; and (c) is the angle information estimated by the observer. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The purpose of the present invention is to provide a permanent magnet synchronous motor system control method that is equipped with both a non-singular terminal sliding mode speed controller and a super-helical sliding film observer. The method can be equipped with a non-singular terminal sliding mode speed controller and a super-helical sliding film observer for control, thereby saving control system costs and improving overall operating efficiency.

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] like Figure 1 As shown, the present invention provides a high-performance control method for a permanent magnet synchronous motor, comprising:

[0038] Step 100: The velocity outer loop uses the integral sliding surface to derive the i without integral link q * Expression, using Sigmoid function to reduce output jitter; specifically including:

[0039]

[0040] In the formula, is the permanent magnet flux; L d , L q are the dq axis inductance components respectively; ω mis the mechanical angular velocity; J is the moment of inertia; P n is the number of magnetic pole pairs; T e is the electromagnetic torque; T L is the load torque; B is the viscous friction coefficient.

[0041] Surface Mount Permanent Magnet Synchronous Motor L d =L q , so let

[0042]

[0043] The sliding surface uses an integral sliding surface with a Sigmoid switching function, and selects an exponential approach rate to solve the torque current given value. The specific calculation is as follows:

[0044] x1=ω m * -ω m

[0045]

[0046] In the formula, x1 is the system state error, x2 is the system state error derivative, ω m * is the given mechanical angular velocity; ω m is the actual mechanical angular velocity.

[0047]

[0048] Where s is the non-singular fast terminal sliding surface, where p, q> 0; 0<λ<1. Substitute the exponential approach rate into the solution i q :

[0049]

[0050] Use the Sigmoid function instead of the symbol function to draw the effect diagram of the Sigmoid function under different parameters. The parameters are selected as follows:

[0051] Sigmoid(x1)=2(1+exp(-2s)) -1 -1

[0052]

[0053] Step 200: List the dq axis current equations in the rotating coordinate system of the surface mounted permanent magnet synchronous motor, and discretize the above equations using the first-order Euler forward discretization method. q(k+1) =i q * Substitute the above formula to solve the dq axis voltage equation, including:

[0054]

[0055] Forward Euler discretization:

[0056]

[0057] Let i q(k+1) =i q * Bring in:

[0058]

[0059] Where i d 、i q are the dq axis components of the stator current respectively; T s is the sampling time; u d 、u q are the dq axis components of the corresponding stator voltage respectively;

[0060] Step 300: using a disturbance observer to observe external disturbances and perform feedforward compensation; specifically including:

[0061] State variable z1 = ω m , z2 = -d, output y = z1

[0062]

[0063] z1 and z2 are used as observation objects to establish a high gain feedback of the speed estimation error e as shown in the following formula

[0064]

[0065] Where z1 is the actual input mechanical angular velocity; is the mechanical angular velocity estimated by the observer; is the estimated matching disturbance. And μ>0, α1, α2 are positive real numbers, and a very small μ value is used to ensure high gain.

[0066] Step 400: Based on the super-helical synovial film observer, the above control method is applied to achieve high-performance control of the permanent magnet synchronous motor under medium and high speed conditions, specifically including:

[0067] Superhelix algorithm form:

[0068]

[0069] Where x n is the nth state variable of the system, a n is the synovial gain of the nth state variable of the system, represents the estimated error value of the nth state variable, ε n (xn ,t) is the disturbance of the nth variable.

[0070] The super spiral synovial observer is as follows:

[0071]

[0072] Where i α 、i β is the estimated current value in the stationary coordinate system, is the error between the estimated current value and the actual current value, L s is the inductance value of the surface-mount permanent magnet synchronous motor, L s =L d =L q .

[0073] The present invention applies a non-singular sliding film speed controller, a deadbeat current controller and a disturbance observer to a position sensorless system based on a super-helical algorithm, thereby improving the dynamic performance of the system.

[0074] Based on the above technical solution, the following embodiments are provided.

[0075] In the following control link example, the motor parameters are shown in Table 1:

[0076] Table 1

[0077]

[0078] First, the speed outer loop is analyzed: the kinematic equation of the permanent magnet synchronous motor is used to solve the information about the given torque current, the mechanical speed is used as the control target, and the integral sliding surface and exponential approach rate are used to make the sliding surface approach zero, that is, the mechanical speed converges to the given value:

[0079] x1=ω m * -ω m

[0080]

[0081] After taking its derivative, we can combine it with the exponential approach rate to get:

[0082]

[0083] The specified current expression obtained will inevitably contain a sliding membrane switching function term, and the system jitter caused by the switching function is also inevitable. To reduce the system jitter, the Sigmoid function is selected to make the switching process smoother to reduce the jitter.

[0084] Sigmoid(x1)=2*(1+exp(-2*u(1))) (-a) -1

[0085] The selection of a is related to the system jitter amplitude, given by Figure 3 It can be seen that as the value of a decreases, the curve becomes steeper, the value becomes larger, and the response speed becomes slower; in summary, a=-1 is selected as a compromise to obtain:

[0086] Sigmoid(x1)=2(1+exp(-2s)) -1 -1

[0087]

[0088] The results show that after the Sigmoid function is introduced, the corresponding jitter of the system is reduced from 0.1 to around 0.02.

[0089] The second step is to analyze the current inner loop. The traditional proportional-integral controller has poor current tracking effect under complex working conditions, and its response speed is one cycle slower than the given current. Therefore, the deadbeat current control is used to directly bring the given current in the first step into the system to solve the problem of slow response speed, while also eliminating the tedious steps of adjusting the proportional-integral parameters.

[0090] First, the AC and DC axis current equations of the motor are listed and discretized to obtain the expression of the current difference at adjacent sampling moments:

[0091]

[0092] Forward Euler discretization:

[0093]

[0094] Let i q(k+1) =i q * Bring in:

[0095]

[0096] From the above formula, we can get the AC and DC axis voltage expressions, such as Figure 5 As shown in the control block diagram; perform an inverse Park transformation to obtain the voltage value in the stationary coordinate system, and send it to the Svpwm modulation module; after modulation, the drive signal g is obtained and sent to the inverter link to obtain the corresponding drive voltage under a given current, and then send it to the input motor module;

[0097] The third step is to estimate and compensate for the uncertainty and nonlinear factors in the system, such as external load disturbances, internal friction, system parameter changes, etc. Therefore, a new disturbance observation link is selected, and the speed is feedforward compensated; the use of disturbance observers can improve the robustness of the system, reduce the dependence on model accuracy, and improve performance without increasing system complexity. The disturbance observer can be described by the state space equation, where the selection of the observer gain is usually based on the stability and performance requirements of the system.

[0098] It should be noted that, considering the changes in system parameters and load torque, we can get:

[0099]

[0100] Where a = -B / J, u is the control law to be designed; Δa, Δb, Δc represent the parameter changes of the motor; d represents the total disturbance of the system including internal parameter disturbance and external load disturbance. Therefore, the designed control law is:

[0101]

[0102] Let the state variable z1 = ω m , z2 = -d, output y = z1

[0103]

[0104] z1 and z2 are used as observation objects to establish a high gain feedback of the speed estimation error e as shown in the following formula

[0105]

[0106] Where z1 is the actual input mechanical angular velocity; is the mechanical angular velocity estimated by the observer; is the estimated matching disturbance. And μ>0, α1, α2 are positive real numbers, and a very small μ value is used to ensure high gain.

[0107] After the above process, if Figure 6 Figure (a) shows the control block diagram of the disturbance observer. Figure (b) shows that the observer can accurately observe external disturbances and has strong tracking ability.

[0108] Fourth, the traditional feedback link usually uses an encoder to feedback the speed. The existence of this hardware will undoubtedly cause system vibration, and even lead to loss of control in severe cases. The super-helical synovial observer is an advanced observer design method used to estimate system states and unknown disturbances. Compared with traditional observers, the super-helical synovial observer has stronger robustness and can handle a wider range of uncertainties and nonlinear problems.

[0109] Superhelix algorithm form:

[0110]

[0111] Where x n is the nth state variable of the system, a n is the synovial gain of the nth state variable of the system, represents the estimated error value of the nth state variable, ε n (x n ,t) is the disturbance of the nth variable.

[0112] The super spiral synovial observer is as follows:

[0113]

[0114] Where i α 、i β is the estimated current value in the stationary coordinate system, is the error between the estimated current value and the actual current value, L s is the inductance value of the surface-mount permanent magnet synchronous motor, L s =L d =L q .

[0115] like Figure 7 As shown in FIG. 1 , (a) is an implementation block diagram of the super-helical synovial observer. It should be noted that due to the existence of the sign function, the discontinuity of the system leads to failure in extracting the angle, so a low-pass filter is added to extract accurate angle information, but it will undoubtedly bring about a phase delay in the system, so an angle compensation link is added; the present invention adopts the inverse tangent method to solve the angle value, but the range of the inverse tangent solution is only between -pi / 2 and pi / 2, so the angle needs to be corrected. According to the inverse tangent value and E β The positive or negative value can correct the angle; Figure 7 (b) and (c) are the actual angle and estimated angle information respectively. It can be seen from the figure that the angle estimation is more accurate.

[0116] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0117] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for controlling a permanent magnet synchronous motor at a medium and high speed without a position sensor, characterized in that: include: The speed outer loop uses a non-singular terminal sliding mode controller and a sliding film surface with an integral link, so that when solving the output i q * The integral link is eliminated and the Sigmoid function is used as the sliding membrane switching function to reduce the output jitter. The current inner loop establishes the dq axis current equation in the rotating coordinate system of the permanent magnet synchronous motor, and the first-order Euler forward discretization method is used to discretize the above equation. q(k+1) =i q * Substitute the above formula and solve the dq axis voltage equation to achieve zero-beat tracking of the current. The disturbance observer is used to observe the external disturbance and bring it into the speed loop for feedforward compensation. In the medium and high speed position sensorless control strategy, the estimation effect of the sliding mode controller is good, but there is a serious vibration in the output result. The super helical algorithm is now used for optimization to reduce the vibration. Step 1: According to the kinematic equation, establish the mechanical speed ω m With torque current i q The relationship between i and the integral sliding surface and exponential approach rate is used to solve q * . Step 2: Use the Sigmoid function instead of the sign function. Step 3: Establish the current equation in the rotating coordinate system of the permanent magnet machine and perform discretization to obtain the torque current at the next moment i q(k+1) Expression, while letting i q(k+1)＝ i q * The response voltage expression is obtained. Step 4: Establish a high-gain disturbance observer to observe the sudden load disturbance in real time, and bring the observed value into the speed loop for feedforward compensation. Step 5: Build a sliding film observer in the speed feedback loop and use the super-helical algorithm to integrate the discontinuous terms in the sliding mode switching terms to make the system continuous, effectively reduce the inherent jitter caused by the sliding mode and optimize the system performance. Step 6: Use the inverse tangent method to solve the angle information, and compensate and correct the angle. Step 7: Build a complete surface-mounted permanent magnet synchronous motor vector control system based on the above.

2. A method for controlling a permanent magnet synchronous motor at a medium and high speed without a position sensor according to claim 1, characterized in that: The speed outer loop establishes the time domain electromagnetic torque equation and kinematic equation of the permanent magnet machine in the rotating coordinate system, and uses the integral sliding surface and exponential approach rate to derive the torque current given value.

3. A method for controlling a permanent magnet synchronous motor at a medium and high speed without a position sensor according to claim 1, characterized in that: The sliding surface uses an integral sliding surface with a Sigmoid switching function, and selects an exponential approach rate to solve a given value of torque current.

4. A method for controlling a permanent magnet synchronous motor at medium and high speed without position sensor according to claim 1, characterized in that: The current inner loop establishes the current time domain equation in the rotating coordinate system, let i q(k+1) =i q * Substitute into the equation to solve the dq axis voltage equation.

5. The method for controlling a permanent magnet synchronous motor at a medium and high speed without position sensor according to claim 1, characterized in that: Build a high-gain disturbance observer.

6. A method for controlling a permanent magnet synchronous motor at medium and high speed without position sensor according to claim 1, characterized in that: Medium and high speed sensorless control is achieved using the superhelical algorithm.

7. A control system, characterized in that: Vector oriented control is used as a framework to execute the control method according to claims 1-6.

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