A sliding mode control method for permanent magnet synchronous motor

Abstract

The invention discloses a sliding mode control method for a permanent magnet synchronous motor. The speed of the permanent magnet synchronous motor is controlled by a sliding mode speed controller, a load torque observer observes the load torque, and the output of the load torque observer is used to perform load torque compensation on the output of the sliding mode speed controller. The load torque observation adopts an algorithm for automatically adjusting the feedback gain according to the change of the load torque given value and the change of the load torque observation value. When the system parameters change or the load is disturbed, resulting in the change of the load torque given value or / and the load torque observation value, the observation error of the load torque can be quickly reduced and the load torque observation value can be feed-forward compensated to the current regulator, thereby effectively weakening the jitter of the system, and the dynamic response speed is fast, the robustness is high, and the control accuracy of the permanent magnet synchronous motor is improved.

Description

[0001] This invention patent application is a divisional application. The original application number is 202010918597.3. The application date is September 4, 2020. The name of the invention is permanent magnet synchronous motor control method for industrial robots. Technical Field

[0002] The present invention relates to the technical field of permanent magnet synchronous motors, and more specifically, to a sliding mode control method for a permanent magnet synchronous motor. Background Art

[0003] Permanent magnet synchronous motors have the advantages of high efficiency, high torque, and good speed performance, and are widely used in manufacturing, electric vehicles, industrial production and other fields. The working environment of industrial robots is complex and changeable, the load moment of inertia varies greatly, the speed regulation range is wide, and the time required for the motor to obtain the command signal and complete the working state required by the command is short. The vector control method based on the PI controller cannot meet the rapidity requirements of the motor drive for industrial robots. The sliding mode control method improves the rapidity of the system response, but when load disturbances or internal parameter perturbations occur, the motor speed will produce obvious jitter. Summary of the invention

[0004] The purpose of the present invention is to provide a permanent magnet synchronous motor control method for providing feed-forward compensation of observed load torque to a current regulator, thereby improving the load torque observation response speed and reducing the torque observation volatility, in view of the large load torque variation and wide speed regulation range, comprising:

[0005] A sliding mode control method for a permanent magnet synchronous motor, wherein the speed of the permanent magnet synchronous motor is controlled by a sliding mode speed controller, characterized in that the sliding mode speed controller adopts an integral sliding mode control method; a load torque observer adjusts the feedback gain according to the change of the load torque given value output by the sliding mode speed controller, and adjusts the feedback gain according to the rotor angular velocity ω and the current i q Observe the load torque and obtain the load torque observation value Load torque observation value output by the load torque observer is sent to the sliding mode speed controller.

[0006] Define the state variables of the sliding mode speed controller as

[0007]

[0008] Where ω is the rotor angular velocity, ω * is the given rotor angular velocity;

[0009] The sliding surface of the sliding mode speed controller is s y =c y y 1 +y 2 , cy is the sliding surface parameter, and c y >0; Load torque given value output by sliding mode speed controller and q-axis torque current given value for

[0010]

[0011] Where J is the moment of inertia, p is the number of motor pole pairs, ψ f is the permanent magnet flux, B is the friction coefficient; the coefficient μ 1 and coefficient μ 2 is the exponential approach rate coefficient of speed sliding mode control, and μ 1 >0,μ 2 >0.

[0012] The load torque observer is

[0013]

[0014] in, is the estimated value of the rotor angular velocity, g is the feedback gain of the load torque observer and g<0; U=k g · k g is the sliding mode gain of the load torque observer.

[0015] The method by which the load torque observer adjusts the feedback gain according to the change of the load torque given value output by the sliding mode speed controller is:

[0016] Step 1: Calculation

[0017] Step 2: Judgement Is it greater than the torque change comparison threshold ε? When it is greater than the torque change comparison threshold ε, the feedback gain g is equal to g min ;when When the torque change comparison threshold ε is less than or equal to, the feedback gain g is equal to g max ;

[0018] Step (iii): The load torque observer observes the load torque to obtain the load torque observation value; the sliding mode speed controller performs control calculation to obtain

[0019] Among them, ε>0; g max is the high value of feedback gain, g min is the low value of feedback gain, and g min <g max <0. Observe the load torque observation value Then, the observed value of the load torque Converted into torque current compensation component i″ q Feedforward compensation to the input of the q-axis current PI controller, the torque current given component i′ output by the sliding mode speed controller q To compensate. Select g min , g max , ε 1 , ε 2 The value method is:

[0020] Step 1), the load torque observer and the sliding mode speed controller are both in steady state and keep the given rotor angular velocity and load torque constant;

[0021] Step 2), let the feedback gain g gradually decrease from a larger value. When the steady-state error of the load torque observation reaches the steady-state error limit of the load torque observation, determine the feedback gain g value at this time as g max ;

[0022] Step 3), keep the given rotor angular velocity and load torque constant and set the feedback gain g equal to g max , and repeat this process n times The value is measured and n times Maximum m in the measurement The average value of the measured values ​​is used as the torque change comparison threshold ε; n≥20, 5≤m≤0.5n;

[0023] Step 4), fine-tuning the feedback gain g, when the load torque observer and the sliding mode speed controller are both in steady state, keeping the given rotor angular velocity unchanged and making the load torque suddenly change, under the premise of ensuring that the torque observation tracking overshoot of the load torque observer output observation value is within the torque observation tracking overshoot limit, measuring the tracking adjustment time of the load torque observer;

[0024] Step 5), repeat step 4), select the feedback gain g with the shortest tracking adjustment time as g min value.

[0025] Sliding mode gain k g according to

[0026]

[0027] Make a selection; among them, is the load torque observation error, α≥1; further, 1≤α≤5.

[0028] The permanent magnet synchronous motor sliding mode control method detects the rotor position θ of the permanent magnet synchronous motor and the three-phase current i a 、i b and i c ; According to the three-phase current ia 、i b and i c Clark transformation is performed on the permanent magnet synchronous motor to obtain the current i in the α-β axis coordinate system: α 、i β , according to the current i α 、i β Perform Park transformation on the rotor position θ to obtain the current i in the dq axis coordinate system d 、i q .

[0029] The permanent magnet synchronous motor speed control is implemented by a permanent magnet synchronous motor speed control system including a sliding mode speed controller, a load torque observer, a q-axis current controller, a d-axis current controller, a Clarke transformation module, a position and speed detection module, a Park transformation module, a Park inverse transformation module, an SVPWM module and a three-phase inverter.

[0030] The beneficial effect of the present invention is that the output item of the sliding mode speed controller includes the compensation sub-item load torque observation value, which is equivalent to feeding the load torque observation value forward to the given value of the current regulator. Without the need for a large adjustment of the given current part of the sliding mode speed controller output, it can offset the relevant influence caused by the load disturbance or the change of system parameters, and effectively weaken the system jitter. The algorithm that automatically adjusts the feedback gain according to the change of the load torque given value avoids the problem that the load torque observer selects a fixed small feedback gain to cause large torque observation fluctuations and selects a fixed large feedback gain to cause a long convergence time. When the control parameters, model parameters, etc. of the system change or the load is disturbed, resulting in a change in the given sub-item part of the load torque given value or / and a change in the load torque observation value part, the observation error of the load torque can be quickly reduced, and the observation effect and the rapidity and accuracy of the motor speed control are improved. The feedback gain is automatically adjusted when the load torque given value changes. When the load torque observation value has not changed significantly, but the given sub-item part of the load torque given value changes due to the change of the rotor angular velocity given value and / or the change of the actual value of the rotor angular velocity, or the given sub-item part of the load torque given value changes due to the change of the system model parameters, which will cause the load torque observation value to fluctuate greatly, the feedback gain can be adjusted in advance. When the load torque observation value actually produces an observation error, the response speed of the observer is accelerated, the observation error of the load torque observation value is quickly reduced, and the speed and accuracy of the motor speed control are further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a block diagram of a permanent magnet synchronous motor speed control system embodiment 1;

[0032] Figure 2 This is a flow chart of Embodiment 1 of the feedback gain automatic adjustment method;

[0033] Figure 3 This is a flow chart of Embodiment 2 of the feedback gain automatic adjustment method;

[0034] Figure 4 This is a block diagram of a permanent magnet synchronous motor speed control system embodiment 2;

[0035] Figure 5 This is a flow chart of Example 3 of the feedback gain automatic adjustment method. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0037] The sliding mode control method of the permanent magnet synchronous motor is realized by the permanent magnet synchronous motor speed control system. Figure 1 It is a block diagram of Example 1 of a permanent magnet synchronous motor speed control system. Figure 1 In the Clarke transformation module, the three-phase current i of the permanent magnet synchronous motor (PMSM) is input a 、i b and i c , output the current i in the two-phase stationary α-β axis coordinate system α 、Current i β ; The position sensor in the position and speed detection module detects the rotor position θ of the permanent magnet synchronous motor and converts it into the rotor angular velocity ω output; the Park conversion module inputs the current i α 、Current i β and the rotor position θ, the output current i in the rotating dq axis coordinate system d 、Current i q ;Sliding mode speed controller SMC input rotor given angular velocity ω * and rotor angular velocity ω, output load torque given value T L * and torque current given component i′ q ; Load torque observer inputs load torque given value T L * , rotor angular velocity ω and current i q , output torque current compensation component i″ q ; Torque current given component i′ q and torque current compensation component i″ q After adding, it is used as the q-axis torque current given value i * q ; q-axis current PI controller input q-axis torque current given value i * q and current i d, output control voltage U in q-axis coordinate system q ; d-axis current PI controller input q-axis torque current given value i * d and current i d , output control voltage U in d-axis coordinate system d , d-axis torque current given value i * d =0; the control voltage U in the dq axis coordinate system is input to the Park inverse transformation module d , U q , output the control voltage U in the α-β axis coordinate system α , U β SVPWM module (i.e. space vector pulse width modulation module) input control voltage U α , U β , output pulse signal to the three-phase inverter, the three-phase inverter converts the DC voltage U dc Convert to three-phase AC power supply U a , U b , U c , thereby driving the permanent magnet synchronous motor to operate.

[0038] Ignoring the influence of core eddy current and hysteresis loss, the i d =0, the PMSM rotor magnetic field oriented control is established, and the mathematical model of PMSM in the dq axis rotating coordinate system is established. The voltage equation is:

[0039]

[0040] For the use of i d =0 control mode of salient pole PMSM vector control system, the electromagnetic torque equation is:

[0041] T e =1.5pψ f i q (2)

[0042] The PMSM motion equation is:

[0043]

[0044] In formula (1), (2), and (3), u d 、u q are the voltages of the dq axes respectively; i d 、i q are the currents of d and q axes respectively; L d , L q are the inductance of d and q axes respectively; T e is the electromagnetic torque; T Lis the load torque; R is the stator resistance; p is the number of motor poles; ω e is the rotor electrical angular velocity, i.e. angular frequency; ω is the rotor angular velocity, i.e. the motor rotor mechanical angular velocity; ψ f is the permanent magnet flux; J is the moment of inertia; B is the friction coefficient; t is time.

[0045] Let the motor's rotor angular velocity error e = ω * -ω,ω * is the given rotor angular velocity of the motor. The state variables of the permanent magnet synchronous motor speed control system embodiment 1 are defined as:

[0046]

[0047] From equations (2), (3) and (4), we can get:

[0048]

[0049] Simplify equation (5) and let D = 1.5pψ f / J, The system state space equation of the permanent magnet synchronous motor speed control system embodiment 1 is obtained as follows:

[0050]

[0051] Select the sliding surface function as:

[0052] s=cx 1 +x 2 (7)

[0053] In formula (7), s is the sliding surface, c is the sliding surface parameter, and c>0. In formula (7), c is the coefficient of the rotor angular velocity error term. Its influence on the control effect is similar to the proportional coefficient in PID control. The value of c also takes into account the balance of the rotor angular velocity error and the rotor angular velocity error change rate. Usually, it is selected within the range of greater than 0 and less than 1000. For example, c=60. Derivative of formula (7) yields:

[0054]

[0055] The expression of the traditional exponential reaching law is:

[0056]

[0057] In formula (9), sgn() is the sign function, -k 1 sgn(s) is the constant velocity approach term, -k 2 s is the exponential approach term, k 1 , k 2The two coefficients determine the chattering and approaching motion quality of the sliding surface, respectively, and k 1 , k 2 All are greater than 0. In order to improve the system response speed, the traditional exponential approach rate is improved, and the constant speed approach term is changed to a variable speed approach term. The improved approach law is:

[0058]

[0059] where k 1 >0,k 2 >0,0 <k 3 <1, k 4 >0. When |s| is large, The variable speed approaching term has a larger approaching speed, which can accelerate the sliding mode approaching motion speed; when |s| is smaller, The speed approaching item has a low approaching speed, which can reduce vibration. 4 The value can be selected by referring to the rotor angular velocity change rate of the permanent magnet synchronous motor when it is started at rated load, and selected near the inverse value of the rotor angular velocity change rate, and further, selected within the range of 50% to 120% of the inverse value; for example, assuming that the time taken for a permanent magnet synchronous motor to start at rated load to a rated speed of 1500r / min is 0.2s, then the average rotor angular velocity change rate is 785rad / s 2 , it is recommended that k 4 The value of k is in the range of 0.00064 to 0.016. 3 It is usually taken around 0.5. Furthermore, k 3 Generally, the value is in the range of 0.4 to 0.6. Generally, when controlling a small-power permanent magnet synchronous motor, the coefficient k 1 and coefficient k 2 The values ​​of are all less than 2000; the coefficient k 2 The larger the value is, the faster the system state can approach the sliding mode. 1 Determines the speed to reach the switching surface, k 1 The smaller the value, the smaller the distance and jitter across the switching surface. 1 and k 2 are the variable speed approach term coefficient and the exponential approach term coefficient respectively. The value of changes around 1, so the speed approaching term coefficient k in formula (10) 1 and the exponential approach coefficient k 2 It can be adjusted by adjusting the coefficient of the medium-speed approach term and the coefficient of the exponential approach term in the traditional exponential approach rate. 3 is the migration coefficient, whose magnitude changes the critical point of speed change; k 4 is the speed coefficient, and its size changes the speed of the speed change. The e in formula (10) is the natural exponent, that is, the base of the natural logarithm.

[0060] Combining equations (8) and (10), the calculated q-axis given current is used as the torque current given component i′ q , we can get the load torque given value T output by the sliding mode speed controller L * and torque current given component i′ q for:

[0061]

[0062] Permanent magnet synchronous motor speed control system embodiment 1 The output of the sliding mode speed controller contains an integral term. Filtering the control quantity can weaken the system chattering and reduce the steady-state error of the system. The Lyapunov function is defined as:

[0063]

[0064] From formula (10) and formula (12), we can get:

[0065]

[0066] In formula (13), k 1 >0,k 2 >0,s·sgn(s)≥0, Therefore It shows that the system tracking error can converge to zero in a finite time and the system can operate stably.

[0067] When designing a sliding mode speed controller, set the parameters c and k 1 , k 2 , k 3 , k 4 The method is to first determine k 3 , k 4 The value of q-axis torque current is given by i * q Only the input torque current given component i′q is included (i.e., no load torque compensation control is performed), and then the sliding surface parameter c and the speed approach term coefficient k are adjusted from small to large in the sliding mode of the system. 1 until the system shows obvious chattering. On this basis, the sliding surface parameter c and the speed-changing approach term coefficient k are appropriately reduced while taking into account both the suppression of chattering and the convergence speed of the system state. 1 Finally, while taking into account the suppression of sliding mode chattering, the exponential approach term coefficient k is adjusted mainly based on the rapidity of the system arrival segment (for example, the motor start-up phase of the step response). 2 and make appropriate fine-tuning on other parameter values ​​of the sliding mode speed controller.

[0068] According to the PMSM electromagnetic torque and motion equation, for a constant step load, it can be considered as a constant value within the change cycle, that is, The motor rotor angular velocity and load torque are used as state variables to form the PMSM state equation:

[0069]

[0070] Based on formula (14), taking load torque and motor rotor angular velocity as observation objects, load torque observer embodiment 1 is established as:

[0071]

[0072] In formula (15), is the observed value of the load torque, is the estimated value of the rotor angular velocity, g is the feedback gain of the load torque observer, k g is the sliding mode gain of the load torque observer embodiment 1, and the load torque observer embodiment 1 is a sliding mode observer. Compared with the load torque, the motor friction accounts for a small proportion, so let B = 0, ignoring the influence of friction, then the load torque observer embodiment 1 of formula (15) becomes:

[0073]

[0074] According to (14) and (16) when B=0, the error equation of the load torque observer embodiment 1 is obtained as follows:

[0075]

[0076] In formula (17), is the rotor angular velocity estimation error, is the load torque observation error, and the observer sliding surface is defined as According to the sliding mode reachability condition, the stability condition of the observer system in equation (16) is k g ≤-|e 2 / J|, and g<0.

[0077] Based on formula (14), with load torque and motor rotor angular velocity as observation objects, load torque observer embodiment 2 can also be established as:

[0078]

[0079] Compared with the load torque, the motor friction accounts for a small proportion. Let B = 0 and ignore the influence of friction. Then the load torque observer embodiment 2 of formula (18) becomes:

[0080]

[0081] In formula (18) and (19), is the observed value of the load torque, is the estimated value of the rotor angular velocity, g is the feedback gain of the load torque observer, k W is the proportional gain of the load torque observer embodiment 2, and the load torque observer embodiment 2 is a state observer. According to equation (14) and equation (19) when B=0, the error equation of the load torque observer embodiment 2 is obtained as follows:

[0082]

[0083] In formula (20), is the rotor angular velocity estimation error, is the load torque observation error. The state observer of equation (19) is an autonomous linear system. W <0, and g<0, the observer is asymptotically stable. Formula (15) of the load torque observer embodiment 1 and formula (18) of the load torque observer embodiment 2 both take into account the friction factor of the motor. The addition of small friction damping will have an adverse effect on the rapidity of the system response, but can increase the stability based on formulas (16) and (19), respectively.

[0084] When the observer embodiment 1 of equations (15) and (16) is selected, the sliding mode gain k g The setting method is to follow

[0085]

[0086] In formula (21), α≥1; generally, the value of α is selected in the range of 1 to 5, for example, α is selected to be equal to 1.5. Load torque observer embodiment 1 In the process of observing the load torque, k g The absolute value of |e is too small. 2 When | is large, the observer cannot enter the sliding mode state; g The absolute value of is large enough to ensure that the observer enters the sliding mode state, but the steady-state observation fluctuation of the load torque becomes larger; g The value of changes with the load torque observation error, which can simultaneously increase the stability of the observer and reduce the steady-state observation fluctuation of the load torque.

[0087] When the observer embodiment 2 of equations (18) and (19) is selected, the proportional gain k W The setting method is to follow

[0088]

[0089] In formula (22), TN is the rated torque of the motor, β>0; generally, the β value is selected in the range of 1 to 20, for example, β=10. When β is selected to increase, the steady-state fluctuation of the load torque observation becomes larger, but the torque observation tracking overshoot becomes smaller; when β is selected to decrease, the steady-state fluctuation of the load torque observation becomes smaller, but the torque observation tracking overshoot becomes larger.

[0090] In the observers represented by equations (15), (16) or equations (18), (19), the value of the feedback gain g has a great influence on the load torque observation result. The larger the feedback gain g, the smaller the observed torque fluctuation, but the slower the observed torque identification speed; the smaller the feedback gain g, the faster the observed torque speed, but the greater the observed torque fluctuation. In consideration of this problem, in the traditional load torque observer, the observation speed and fluctuation of the load torque are comprehensively considered, and the feedback gain g is taken as a compromise value, but this will abandon the advantages of small fluctuation when the feedback gain is large and fast observation speed when the feedback gain is small.

[0091] The motor sliding mode speed control mainly suppresses the influence of parameter changes and external load disturbances on the system by increasing the amplitude of the discontinuous term in the controller, but the increase in amplitude will cause the inherent chattering of the sliding mode. In order to solve the contradiction between the chattering and anti-disturbance of the sliding mode control system, the observer is used to observe the load disturbance changes in real time, and the load torque observation value is feed-forward compensated to the current regulator to reduce the amplitude of the discontinuous term in the sliding mode control, weaken the given torque change caused by parameter changes, or the system chattering caused by load disturbances. In order to make full use of the advantages of the feedback gain g at high and low values, according to the load torque observation value and the load torque given value change at two adjacent moments, when the load torque given value changes little and the load torque observation value changes little, a larger feedback gain g is given to make the observation result less volatile and more stable; when the load torque given value changes greatly or the load torque observation value changes greatly, a smaller feedback gain g is given to speed up the observation speed. Finally, by adjusting the feedback gain g, a comprehensive result of fast observation speed, small fluctuation and stronger stability is obtained.

[0092] Load torque observer embodiment 1, or load torque observer embodiment 2 is used for Figure 1 In the permanent magnet synchronous motor speed control system embodiment 1, the load torque observer is based on the load torque given value and load torque observation The feedback gain g is adjusted according to the change of the rotor angular velocity ω and the current i q Observe the load torque and obtain a new load torque observation value

[0093] Figure 2The flow chart of the feedback gain automatic adjustment method embodiment 1 is used in the load torque observer embodiment 1 or the load torque observer embodiment 2. Figure 1 In the permanent magnet synchronous motor speed control system embodiment 1, the feedback gain is automatically adjusted. Figure 2 In, ε 1 is the given torque change comparison threshold, ε 2 is the comparison threshold for observing torque changes, ΔT L * is the difference between the two most recent load torque given values, is the difference between the two most recent load torque observations. In a periodic control process of the motor speed, Figure 2 The feedback gain g shown in (a) is adjusted before the load torque observation and the output calculation of the sliding mode speed controller, which is:

[0094] Step 1. Calculation

[0095] Step 2: Judgement Is it greater than the given torque change comparison threshold ε? 1 ;when Greater than the given torque change comparison threshold ε 1 When the feedback gain g is equal to g min And go to step 4; when Less than or equal to the given torque change comparison threshold ε 1 When , go to step 3;

[0096] Step 3: Judgement Is it greater than the observed torque change comparison threshold ε 2 ;when Greater than the observed torque change comparison threshold ε 2 When the feedback gain g is equal to g min And go to step 4; when Less than or equal to the observed torque change comparison threshold ε 2 When the feedback gain g is equal to g max And go to step 4;

[0097] Step 4: Load torque observer calculates load torque T L Observe and obtain the load torque observation value The sliding mode speed controller performs control calculation to obtain the load torque given value At this time for for Until the next feedback gain g adjustment, the becomes becomes

[0098] In the process of periodic control of motor speed, Figure 2 The feedback gain g shown in (b) is adjusted later than the load torque observation and the output calculation of the sliding mode speed controller. The feedback gain g adjustment method changes the above step 4 to step 1, steps 1-3 to steps 2-4, and the entry to step 4 in each step is changed to exit, and

[0099] When |ΔT L * |Greater than ε 1 When the load torque is set to T L * Due to the changes in system model parameters, rotor angular velocity set values, and actual rotor angular velocity values, the load torque observation value is in a state of large change. The load torque observation value either has a large fluctuation or will have a large fluctuation. The feedback gain g is selected to be equal to g min Rapid identification and observation of load torque; when |ΔT L * |Less than or equal to ε 1 ,and Greater than ε 2 When the load torque observation value fluctuates greatly, the feedback gain g is selected to be equal to g min Rapid identification and observation of load torque; when |ΔT L * |Less than or equal to ε 1 ,and Less than or equal to ε 2 When the load torque given value changes little and the state load torque observed value fluctuates little, the feedback gain g is selected to be equal to g max Perform torque identification and observation. Figure 2 In the given torque change comparison threshold ε 1 >0, observation torque change comparison threshold ε 2 >0,ε 1 , ε 2 The specific value of is related to the sampling control period (cycle time) of the sliding mode speed controller, the permanent magnet synchronous motor and its load conditions. 1 , ε 2 The value is greater than 0 and generally less than 5% of the rated torque. 1 , ε 2 They can take the same value or different values. For example, if the rated torque is 22N·m, ε 1 =ε 2 =0.2N·m, or take ε 1 =0.2N·m,ε 2 =0.25N·m. The value of feedback gain g satisfies gmin <g max <0, in general, g min ≥-5000. g min The value should be selected so that when the load torque changes suddenly, the torque observation tracking overshoot of the load torque observer output observation value is within the torque observation tracking overshoot limit; g max The value should be the change of the last two load torque observation values ​​when the load torque is constant and the load torque observer and sliding mode speed controller are both in steady state. Less than ε 2 ; For example, select the feedback gain g max =-0.5, g min =-10. Select g min , g max , ε 1 , ε 2 The specific method of value is:

[0100] Step ①, the load torque observer and the sliding mode speed controller are both in steady state and keep the given rotor angular velocity and load torque unchanged; the sliding mode speed controller is in steady state means that the sliding mode speed controller is stably in sliding mode; the load torque observer is in steady state means that the observer is in the working state after the torque observation transition process;

[0101] Step ②, let the feedback gain g gradually decrease from a larger value, for example, let the feedback gain g gradually decrease from -0.01. When the steady-state error of the load torque observation reaches the steady-state error limit of the load torque observation, determine the feedback gain g value at this time to be g max ;

[0102] Step ③: Keep the given rotor angular velocity and load torque constant and set the feedback gain g equal to g max , and repeat this process n times The value is measured and n times Maximum m in the measurement The average value of the measured values ​​is used as the comparison threshold ε of the observed torque change 2 ; Given torque change comparison threshold ε 1 The observed torque change is compared with the threshold ε 2 The value is in the range of 0.5 to 1.5 times;

[0103] Step ④, fine-tune the feedback gain g. When the load torque observer and the sliding mode speed controller are both in steady state, keep the given rotor angular velocity unchanged and make the load torque change suddenly. Under the premise of ensuring that the torque observation tracking overshoot is within the torque observation tracking overshoot limit, measure the tracking adjustment time of the load torque observer.

[0104] Step ⑤, repeat step ④, select the feedback gain g value with the shortest tracking adjustment time g min Normally, when the torque observation tracking overshoot is close to the torque observation tracking overshoot limit, the tracking adjustment time of the load torque observer is shorter.

[0105] Figure 3 The flow chart of the feedback gain automatic adjustment method embodiment 2 is shown in the load torque observer embodiment 1 or the load torque observer embodiment 2. Figure 1 In the permanent magnet synchronous motor speed control system embodiment 1, the feedback gain is automatically adjusted. Figure 3 In the figure, ε is the torque change comparison threshold, ΔT L * is the difference between the two most recent load torque given values, is the difference between the two most recent load torque observations. In a periodic control process of the motor speed, Figure 3 The feedback gain g shown in (a) is adjusted before the load torque observation and the output calculation of the sliding mode speed controller, which is:

[0106] Step I: Calculation

[0107] Step II: Judgment Is it greater than the torque change comparison threshold ε? When it is greater than the torque change comparison threshold ε, the feedback gain g is equal to g min ;when When the torque change comparison threshold ε is less than or equal to, the feedback gain g is equal to g max ; where ε>0, g max is the high value of feedback gain, g min is the low value of feedback gain;

[0108] Step III: Load torque observer for load torque T L Observe and obtain the load torque observation value The sliding mode speed controller performs control calculation to obtain At this time for for Until the next feedback gain g adjustment, the becomes becomes

[0109] In the process of periodic control of motor speed, Figure 3The feedback gain g shown in (b) is adjusted later than the load torque observation and the output calculation of the sliding mode speed controller. The feedback gain g adjustment method changes the above step III into step I, and steps I-II into steps II-III, and

[0110] When the sum of the changes in the load torque given value and the load torque observed value for the last two times When it is greater than ε, it indicates that the load torque observation value fluctuates greatly, or the load torque given value changes greatly due to changes in system model parameters, rotor angular velocity given value, and rotor angular velocity actual value, which will cause the load torque observation value to fluctuate greatly. The feedback gain g is selected to be equal to g min Rapid identification and observation of load torque; when When it is less than or equal to ε, it indicates that the load torque given value changes little and the state load torque observation value fluctuates little, and the feedback gain g is selected to be equal to g max Perform load torque identification and observation. Figure 3 The specific value of ε is related to the sampling control period (cycle time) of the sliding mode speed controller, the permanent magnet synchronous motor and its load conditions. ε is greater than 0 and generally less than 5% of the rated torque. For example, if the rated torque is 22N·m, ε can be taken as 0.2N·m or ε can be taken as 0.3N·m. The value of the feedback gain g satisfies g min <g max <0, in general, g min ≥-5000. g min The value should be selected so that when the load torque changes suddenly, the torque observation tracking overshoot of the load torque observer output observation value is within the torque observation tracking overshoot limit; g max The value should be the sum of the changes in the load torque given value and the load torque observed value for the last two times when the load torque remains unchanged and the load torque observer and the sliding mode speed controller are both in a steady state. Less than ε; for example, select the feedback gain g max =-0.5, g min =-10. Select g min , g max , the specific method of ε value is:

[0111] Step (1), the load torque observer and the sliding mode speed controller are both in steady state and keep the given rotor angular velocity and load torque unchanged;

[0112] Step (2), let the feedback gain g gradually decrease from a larger value, for example, let the feedback gain g gradually decrease from -0.01. When the steady-state error of the load torque observation reaches the steady-state error limit of the load torque observation, determine the feedback gain g value at this time to be g max ;

[0113] Step (3): Keep the given rotor angular velocity and load torque constant and set the feedback gain g equal to g max , and repeat this process n times Value and The value is measured and the largest m values ​​among n measurements are The average value of the sum is used as the torque change comparison threshold ε;

[0114] Step (4), fine-tuning the feedback gain g, when the load torque observer and the sliding mode speed controller are both in a steady state, keeping the given rotor angular velocity unchanged and making the load torque suddenly change, and measuring the tracking adjustment time of the load torque observer on the premise that the torque observation tracking overshoot of the load torque observer is within the torque observation tracking overshoot limit;

[0115] Step ⑸, repeat step ⑷, select the feedback gain g value with the shortest tracking adjustment time g min Normally, when the torque observation tracking overshoot is close to the torque observation tracking overshoot limit, the tracking adjustment time of the load torque observer is shorter.

[0116] Observe the load torque observation value Then, the observed value of the load torque Converted into torque current compensation component i″ q Feedforward compensation to the input of the q-axis current PI controller, the torque current given component i′ output by the sliding mode speed controller q The q-axis torque current given value i of the q-axis current PI controller is * q for:

[0117]

[0118] In formula (23), k q =1 / (1.5pψ f ) is the torque observation compensation coefficient. Comparing equation (11) with equation (23), it can be obtained that when the load is disturbed or the system parameters change, the load torque compensation is not added in equation (11), and a larger k needs to be selected. 1 , k 2 The value is used to provide a sufficiently large given current change to offset the impact of load disturbance or system parameter changes, so as to ensure that the motor speed can be quickly constant; while formula (23) feeds forward the load torque observation value to the current regulator, without the need for a large k 1 , k 2When the load is disturbed or the system parameters change, a sufficiently large given current change can be provided to offset the related impact of the load disturbance or the change of system parameters, reduce the output pressure of the sliding mode speed controller and the amplitude of the discontinuity term, and effectively weaken the system's jitter.

[0119] When the feedback gain value is fixed, the smaller the feedback gain g, the larger the oscillation amplitude of the load torque observation and the stronger the volatility; the larger the feedback gain g, the smaller the oscillation amplitude of the load torque observation and the higher the observation accuracy. The automatic gain adjustment algorithm solves the problem of large torque observation fluctuation caused by small feedback gain in the load torque observer and the problem of long convergence time of large feedback gain. The convergence time and fluctuation amplitude indicators are better than the compromise gain algorithm. It can quickly track the change value of the load torque and quickly reduce the observation error caused by the given change or parameter change. It has a small oscillation amplitude and high observation accuracy, achieving a good observation effect.

[0120] When the given speed is changed under the rated load torque, although the actual load torque does not change, it can be seen from the load torque observer constructed by equations (15), (16) or (18), (19) that when the rotor angular velocity ω changes, even if the load torque does not change, the observed torque observation value will change, resulting in observation error. When the given speed is changed under the rated load torque, the control and adjustment process of the sliding mode control system of the permanent magnet synchronous motor is that the sliding mode speed controller first changes the output load torque given value T according to the given speed. L * Change the torque current given value i * q changes, thus making the electromagnetic torque T of the permanent magnet synchronous motor e The feedback gain g is only based on the change of the load torque observation value. Automatic adjustment is performed. At this time, only when the rotor angular velocity ω changes, the load torque observation value After the change occurs, the feedback gain g is adjusted; the feedback gain g is also adjusted according to the change ΔT of the load torque given value. L * and the change in the observed value of load torque Automatic adjustment is performed. When the given speed changes, the load torque given value T L * Change, load torque observation value If the load torque has not changed, adjust the feedback gain g in advance. When an observation error actually occurs, the observer's response speed can be accelerated to eliminate (reduce) the load torque observation value as quickly as possible. The observation error is reduced, thereby improving the rapidity and accuracy of motor speed control. Similarly, when the system model parameters change, the load torque given value T L * Prior to load torque observation When the load torque is changed, the feedback gain g is also based on the change in the load torque given value ΔT L * and the change in the observed value of load torque Automatic adjustment can be performed to adjust the feedback gain g in advance, speed up the observer response speed, and eliminate (reduce) the load torque observation value as soon as possible The observation error can be reduced and the speed control of the motor can be further improved. Of course, if the load is disturbed and the observation value is When changes occur, When a major change occurs, Figure 2 , Figure 3 It can be seen that the feedback gain g can also be automatically adjusted to eliminate (reduce) the load torque observation value as quickly as possible. The observation error makes the load torque observation value Keep up with the load torque T as soon as possible L changes.

[0121] In the periodic control process of the permanent magnet synchronous motor speed control system embodiment 1, the load torque given value T calculated at the kth time (or the kth step) is L * T L * (k), load torque observation value Recorded as The k-1 moment is the moment of the periodic control process before the k moment, and the load torque given value T L * T L * (k-1), load torque observation value Recorded as The k-2 moment is the moment of the periodic control process before the k-1 moment, and the load torque given value T L * T L * (k-2), load torque observation value Recorded as Figure 2 (b) and Figure 3 In (b), load torque observation and speed control are performed first, and then feedback gain is automatically adjusted. The periodic control process of the motor speed includes the following steps:

[0122] Step 1: Detect the rotor position θ, rotor angular velocity ω and three-phase current i of the permanent magnet synchronous motor a 、i b and i c ;

[0123] Step 2: Based on the three-phase current i a 、i b and i c Clark transformation is performed on the permanent magnet synchronous motor to obtain the current i in the α-β axis coordinate system: α 、i β , according to the current i α 、i β Perform Park transformation on the rotor position θ to obtain the current i in the dq axis coordinate system d 、i q ;

[0124] Step 3: Load torque observer is based on rotor angular velocity ω and current i q Observe the load torque and obtain the load torque observation value and torque current compensation component i″ q ;

[0125] Step 4: The sliding mode speed controller is based on the input rotor given angular velocity ω * And the rotor angular velocity ω is used for control calculation to obtain the load torque given value and torque current given component i′ q ;

[0126] Step 5: The feedback gain g of the load torque observer is based on the load torque given value T L * and load torque observation to adjust for changes in

[0127] Step 6: Given component i' based on torque current q and torque current compensation component i″ q Calculate the q-axis torque current given value i q * ; The d-axis current controller is based on the d-axis torque current given value i d * and the current i in the d-axis coordinate system d The difference between them is used for PI control operation to obtain the control voltage U in the d-axis coordinate system d ; The q-axis current controller is based on the q-axis torque current given value i q * and the current i in the q-axis coordinate system q The difference between them is used for PI control operation to obtain the control voltage U in the q-axis coordinate system q; Based on the control voltage U in the dq axis coordinate system d , U q Perform Park inverse transformation to obtain the control voltage U in the α-β axis coordinate system α , U β ; d-axis torque current given value i d * is equal to 0;

[0128] Step 7: Set the control voltage U in the α-β axis coordinate system α , U β As the input of the SVPWM module, the SVPWM module controls the three-phase inverter to generate a three-phase AC power supply U a , U b , U c , thereby driving the permanent magnet synchronous motor to operate.

[0129] Figure 2 (a) and Figure 3 In (a), the feedback gain is automatically adjusted first, and then the load torque observation and speed control are performed. In the above steps, the order of step five and steps three and four should be interchanged, that is, step five should be performed first, and then steps three and four.

[0130] Figure 4 It is a block diagram of Example 2 of a permanent magnet synchronous motor speed control system. Figure 4 Example 2 and Figure 1 The difference of the first embodiment is that the sliding mode speed controller adopts the integral sliding mode control method, and the load torque observation value of the load torque observer is Sent to the sliding mode speed controller, the q-axis given current (torque current given component) output by the sliding mode speed controller already includes the load torque observation value Therefore, the q-axis given current (torque current given component) output by the sliding mode speed controller in Example 2 is directly used as the q-axis torque current given value, which can also play the role of load torque compensation; the load torque given value T output by the sliding mode speed controller L Δ The load torque observation value is also included in The load torque observer directly calculates the load torque given value T output by the sliding mode speed controller. L Δ The feedback gain is automatically adjusted according to the change in the load torque given value and the change in the load torque observation value for the last two times. The same is done for automatic feedback gain adjustment.

[0131] The state variables of the permanent magnet synchronous motor speed control system embodiment 2 are defined as:

[0132]

[0133] Select the sliding surface function as:

[0134]

[0135] In formula (25), s y is the sliding surface, c y is the sliding surface parameter, and c y >0. In formula (25), c y is the coefficient of the integral term of the rotor angular velocity error. Its influence on the control effect is similar to the proportional coefficient in PID control. y The value of also takes into account the balance of the rotor angular velocity error integral term and the rotor angular velocity error term. Usually, c y Select in the range greater than 0 and less than 100. Derivative of formula (25) yields:

[0136]

[0137] On the basis of the traditional exponential reaching law, a new reaching law is adopted:

[0138]

[0139] μ 1 >0,μ 2 >0, yes Add the absolute value of the rotor angular velocity error |y to the constant velocity approach term of the approach law 2 |, so that the speed of the system control quantity in the process of approaching the sliding surface and the absolute value of the error of the system rotor angular velocity |y 2 | is associated, the constant speed approaching term becomes a variable speed approaching term. 2 When | is large (greater than 1), the speed of the variable speed approach term is large, which can speed up the sliding mode approach motion speed; when |y 2 | is small (less than 1), the speed approaching term approaches a small speed, which can reduce vibration. Generally, when controlling a small-power permanent magnet synchronous motor, the exponential approaching rate coefficient μ of the speed sliding mode control is 1 and μ 2 The values ​​of μ are all less than 5000. 1 and μ 2 are the variable speed approach term coefficient and the exponential approach term coefficient respectively. Since |y 2 The value of | varies between 1 and the upper and lower regions of 1. Therefore, the speed approaching term coefficient μ in formula (27) is 1 and the exponential approach coefficient μ 2It can be adjusted by adjusting the moderate approaching term coefficient and the exponential approaching term coefficient in the traditional exponential approaching rate.

[0140] Combining equations (2), (3) and (26), we get:

[0141]

[0142] Combining equations (27) and (28), the calculated q-axis given current is directly used as the q-axis torque current given value i Δ q , the q-axis torque current given value u output by the controller can be obtained Δ q and load torque given value T L Δ for:

[0143]

[0144] In formula (29), the load torque value T L Use the output value of the load torque observer Instead, define the Lyapunov function as:

[0145]

[0146] From equation (25) and equation (27), we can get:

[0147]

[0148] In formula (31), μ 1 >0,μ 2 >0,s y ·sgn(s y )≥0, so It shows that the tracking error of the observer can converge to zero in a finite time and the system can operate stably.

[0149] When designing a sliding mode speed controller, the tuning parameter c y , μ 1 , μ 2 The method is to let the output value of the load torque observer in equation (29) (i.e., no load torque compensation control is performed), and the sliding mode surface parameter c is adjusted from small to large in the sliding mode of the system. y and the speed approach coefficient μ 1 until the system shows obvious chattering. On this basis, the sliding surface parameter c is appropriately reduced while taking into account both the suppression of chattering and the convergence speed of the system state. y and the speed approach coefficient μ 1Finally, while taking into account the suppression of sliding mode chattering, the exponential approach term coefficient μ is adjusted mainly based on the rapidity of the system arrival segment (for example, the motor start-up phase of the step response). 2 and make appropriate fine-tuning on other parameter values ​​of the sliding mode speed controller.

[0150] Figure 4 The load torque observer in the permanent magnet synchronous motor speed control system embodiment 2 still adopts the aforementioned load torque observer embodiment 1, or adopts the aforementioned load torque observer embodiment 2; at this time, the load torque observer is based on the load torque given value output by the sliding mode speed controller The feedback gain g is adjusted according to the change of the rotor angular velocity ω and the current i q Load torque T L Observe and obtain the load torque observation value

[0151] Figure 5 The flow chart of the feedback gain automatic adjustment method embodiment 3 is used in the load torque observer embodiment 1 or the load torque observer embodiment 2. Figure 4 In the permanent magnet synchronous motor speed control system embodiment 2, the feedback gain is automatically adjusted. Figure 5 In the figure, ε is the torque change comparison threshold, ΔT L Δ It is the difference between the two most recent load torque given values. Figure 5 As shown in (a) in the periodic control process of the motor speed, the adjustment of the feedback gain g precedes the load torque observation and the output calculation of the sliding mode speed controller. The specific method is:

[0152] Step 1: Calculation

[0153] Step 2: Judgement Is it greater than the torque change comparison threshold ε? When it is greater than the torque change comparison threshold ε, the feedback gain g is equal to g min ;when When the torque change comparison threshold ε is less than or equal to, the feedback gain g is equal to g max .

[0154] Step 3: Load torque observer measures load torque T L Observe and obtain the load torque observation value The sliding mode speed controller performs control calculation to obtain At this time for During the next periodic control of the motor speed,

[0155] Figure 5 As shown in (b) in the periodic control process of the motor speed, the adjustment of the feedback gain g is later than the load torque observation and the output calculation of the sliding mode speed controller. The specific method is:

[0156] Step A: The load torque observer calculates the load torque T according to the existing feedback gain g value. L Observe and obtain the load torque observation value The sliding mode speed controller performs control calculation to obtain At this time for During the next periodic control of the motor speed,

[0157] Step B: Calculation

[0158] Step C: Judgment Is it greater than the torque change comparison threshold ε? When it is greater than the torque change comparison threshold ε, the feedback gain g is equal to g min ;when When the torque change comparison threshold ε is less than or equal to, the feedback gain g is equal to g max .

[0159] Figure 5 In, ε>0; g max is the high value of feedback gain, g min is the low value of feedback gain, and g min <g max <0.

[0160] Because T L Δ The output items include the given sub-item J(c y y 2 +μ 1 |y 2 |sgn(s y )+μ 2 s y )+Bω, including the observed value of the compensation sub-item load torque When the change in the last two load torque reference values ​​|ΔT L Δ When | is greater than ε, it indicates that the load torque observation value fluctuates greatly, or the system model parameters change, the rotor angular velocity set value change, and the rotor angular velocity actual value change, which makes T L ΔThe given sub-item in the equation changes greatly and will cause the load torque observation value to fluctuate greatly. The feedback gain g is selected to be equal to g min Perform torque identification and observation; when |ΔT L Δ When | is less than or equal to ε, it indicates that the load torque observation value fluctuates little and the factors that will cause the load torque observation value to fluctuate greatly (i.e., T L Δ The given sub-item in the formula (g) changes little, and the feedback gain g is selected to be equal to g max Perform torque identification and observation. Figure 5 The specific value of ε is related to the sampling control period (cycle time) of the sliding mode speed controller, the permanent magnet synchronous motor and its load conditions. ε is greater than 0 and generally less than 5% of the rated torque. For example, if the rated torque is 22N·m, ε can be taken as 0.2N·m or 0.3N·m. In general, g min ≥-5000. g min The value should be selected so that when the load torque changes suddenly, the torque observation tracking overshoot of the load torque observer output observation value is within the torque observation tracking overshoot limit; g max The value should be the difference between the last two load torque given values ​​|ΔT when the load torque remains unchanged and the load torque observer and sliding mode speed controller are both in steady state. L Δ | is less than ε; for example, the feedback gain g is selected max =-0.5, g min =-10. Select g min and g max The specific method of value is:

[0161] Step 1), the load torque observer and the sliding mode speed controller are both in steady state and keep the given rotor angular velocity and load torque constant;

[0162] Step 2), let the feedback gain g gradually decrease from a larger value, for example, let the feedback gain g gradually decrease from -0.01. When the steady-state error of the load torque observation reaches the steady-state error limit of the load torque observation, determine the feedback gain g value at this time as g max ;

[0163] Step 3), keep the given rotor angular velocity and load torque constant and set the feedback gain g equal to g max , and repeat this process n times The value is measured and n times Maximum m in the measurement The average value of the measured values ​​is used as the torque change comparison threshold ε;

[0164] Step 4), fine-tuning the feedback gain g, when the load torque observer and the sliding mode speed controller are both in steady state, keeping the given rotor angular velocity unchanged and making the load torque suddenly change, under the premise of ensuring that the torque observation tracking overshoot of the load torque observer output observation value is within the torque observation tracking overshoot limit, measuring the tracking adjustment time of the load torque observer;

[0165] Step 5), repeat step 4), select the feedback gain g with the shortest tracking adjustment time as g min Normally, when the torque observation tracking overshoot is close to the torque observation tracking overshoot limit, the tracking adjustment time of the load torque observer is shorter.

[0166] In each of the above, select g min , g max In the specific methods of setting the value and comparison threshold, the parameters in the sliding mode speed controller have been adjusted and are implemented under the condition of load torque compensation control; it is recommended that n is an integer greater than or equal to 20, and m is an integer greater than or equal to 5 and less than or equal to 0.5n.

[0167] The output term of the sliding mode speed controller in formula (29) includes the compensation sub-item load torque observation value This is equivalent to feeding the load torque observation value forward to the given value of the current regulator in equation (23). Without the need for a large adjustment of the given current part of the sliding mode speed controller output, it can offset the related effects caused by load disturbances or changes in system parameters, effectively weakening the system jitter. The feedback gain g is based on the change in the load torque given value ΔT L Δ The automatic adjustment algorithm avoids the problem that the load torque observer selects a fixed small feedback gain, which causes a large torque observation fluctuation, and selects a fixed large feedback gain, which causes a long convergence time. It can quickly reduce the observation error of the load torque when the control parameters, model parameters, etc. of the system change or the load is disturbed, resulting in a change in the given sub-item part of the load torque given value or / and a change in the load torque observation value, thereby improving the observation effect and the rapidity and accuracy of the motor speed control. The feedback gain g is automatically adjusted when the load torque given value changes. When the load torque observation value has not changed significantly, but the given sub-item part of the load torque given value changes due to the change of the rotor angular velocity given value or / and the change of the actual value of the rotor angular velocity, or the given sub-item part of the load torque given value changes due to the change of the system model parameters, which will cause the load torque observation value to have a large fluctuation, the feedback gain g is adjusted in advance. When the load torque observation value actually generates an observation error, the response speed of the observer is accelerated, the observation error of the load torque observation value is quickly reduced, and the rapidity and accuracy of the motor speed control are further improved.

[0168] The sliding mode speed controller adopts the permanent magnet synchronous motor speed control system embodiment 2 of the integral sliding mode control method, and its feedback gain is based on the load torque given value T L Δ The algorithm for automatically adjusting the change in the amount of load torque is used in the permanent magnet synchronous motor speed control system embodiment 1. The feedback gain is based on the sum of the change in the load torque given value and the change in the load torque observation value for the last two times. The same algorithm is used for automatic adjustment, which avoids the problem that the load torque observer selects a fixed small feedback gain, which leads to large torque observation fluctuations, and selects a fixed large feedback gain, which leads to a long convergence time. It can be used when the control parameters, model parameters, etc. of the system change or the load is disturbed, resulting in the load torque given value T L Δ When the load torque changes (including the given item changes and / or the compensation item changes), the observation error of the load torque is quickly reduced, which improves the observation effect and the speed and accuracy of the motor speed control. The feedback gain g changes according to the load torque given value T L Δ Automatic adjustment can be performed at the load torque observation value If there is no significant change, but the given sub-item of the load torque given value changes due to the change of the rotor angular velocity given value or / and the actual value of the rotor angular velocity, or the given sub-item of the load torque given value changes due to the change of the system model parameters, which will cause the load torque observation value to fluctuate greatly, adjust the feedback gain g in advance. When the load torque observation value When an observation error actually occurs, speed up the observer's response speed and quickly reduce the load torque observation value. The observation error can be reduced and the speed and accuracy of motor speed control can be further improved.

[0169] In the periodic control process of the permanent magnet synchronous motor speed control system embodiment 2, the load torque given value calculated at the kth time (or the kth step) is Recorded as Load torque observation value Recorded as The k-1 moment is the moment of the periodic control process before the k moment, and the load torque is given by Recorded as Load torque observation value Recorded as The k-2 moment is the moment of the periodic control process before the k-1 moment, and the load torque given value Recorded as Load torque observation value Recorded as according to Figure 5When the feedback gain g is adjusted in (a), the periodic control process of the motor speed includes the following steps:

[0170] Step 1: Detect the rotor position θ, rotor angular velocity ω and three-phase current i of the permanent magnet synchronous motor a 、i b and i c ;

[0171] Step 2: Based on the three-phase current i a 、i b and i c Clark transformation is performed on the permanent magnet synchronous motor to obtain the current i in the α-β axis coordinate system: α 、i β , according to the current i α 、i β Perform Park transformation on the rotor position θ to obtain the current i in the dq axis coordinate system d 、i q ;

[0172] Step 3: The feedback gain g of the load torque observer is based on the load torque given value. to adjust for changes in

[0173] Step 4: Load torque observer is based on rotor angular velocity ω and current i q Observe the load torque and obtain the load torque observation value

[0174] Step 5: The sliding mode speed controller is based on the input rotor given angular velocity ω * , rotor angular velocity ω and load torque observations Perform control calculation to obtain the load torque given value and q-axis torque current given value

[0175] Step 6: The d-axis current controller is based on the d-axis torque current given value i d * and the current i in the d-axis coordinate system d The difference between them is used for PI control operation to obtain the control voltage U in the d-axis coordinate system d ; The q-axis current controller is based on the q-axis torque current given value and the current i in the q-axis coordinate system q The difference between them is used for PI control operation to obtain the control voltage U in the q-axis coordinate system q ; Based on the control voltage U in the dq axis coordinate system d , U q Perform Park inverse transformation to obtain the control voltage U in the α-β axis coordinate system α , Uβ ;

[0176] Step 7: Set the control voltage U in the α-β axis coordinate system α , U β As the input of the SVPWM module, the SVPWM module controls the three-phase inverter to generate a three-phase AC power supply U a , U b , U c , thereby driving the permanent magnet synchronous motor to operate.

[0177] according to Figure 5 When the feedback gain g is adjusted in (b), in the steps of the above control process, the contents of steps 4 and 5 are performed first, and the contents of step 3 are performed later.

[0178] In the above embodiments, the torque observation tracking overshoot limit is usually 1% to 10% of the rated torque of the motor. Specifically, the torque observation tracking overshoot limit is 2% of the rated torque, or 5% of the rated torque, or 10% of the rated torque, and so on. The load torque changes suddenly from one fixed value to another fixed value. The time from the start of the sudden change to the time when the load torque observer outputs the observed value and stably enters the load torque observation steady-state error limit range is the torque observation transition process. The tracking adjustment time refers to the transition process time. The load torque observation steady-state error refers to the error between the instantaneous value of the observed torque and the load torque when the load torque is constant and the load torque observer is in a steady state. This error includes the observation error caused by the sliding mode observer's own jitter and the observation error caused by interference reasons other than load fluctuations, or the observation error caused by the state observer due to the rotor angular velocity jitter and the observation error caused by interference reasons other than load fluctuations. The load torque observation steady-state error limit is the maximum absolute value of the load torque observation steady-state error allowed by the load torque observer. The load torque observation steady-state error limit is usually 1% to 5% of the rated torque of the motor. Specifically, the load torque observation steady-state error limit is 1% of the rated torque, or 2% of the rated torque, or 5% of the rated torque, etc. The torque observation tracking overshoot refers to the load torque suddenly changing from one fixed value to another fixed value, and the observed value output by the load torque observer exceeds the maximum deviation value of the load torque after the sudden change. When the steady-state error of the load torque observation is within the vicinity of the steady-state error limit of the load torque observation, for example, within the range of 95% to 105%, or within the range of 98% to 102%, it is considered that the steady-state error of the load torque observation increases to the steady-state error limit of the load torque observation. The sliding mode speed controller is in steady state, which means that the sliding mode speed controller is stably in sliding mode; the rotor angular velocity steady-state error refers to the difference between the instantaneous value and the steady-state value of the motor rotor angular velocity in steady state, and the rotor angular velocity steady-state error limit is the maximum absolute value of the rotor angular velocity steady-state error allowed by the system. In the load torque observer, the sliding mode observer of Example 1 is in steady state, which means that the sliding mode observer is stably in sliding mode; the state observer of Example 2 is in steady state, which means that the state observer is in the working state after the torque observation transition process. The rotor angular velocity steady-state error refers to the difference between the instantaneous value and the steady-state value of the motor rotor angular velocity in steady state, and the rotor angular velocity steady-state error limit is the maximum absolute value of the rotor angular velocity steady-state error allowed by the system.

[0179] The permanent magnet synchronous motor speed control system and the permanent magnet synchronous motor speed control method including the permanent magnet synchronous motor sliding mode control method of the present invention can be used in other permanent magnet synchronous motor application occasions in addition to industrial robots.

[0180] In addition to the technical features described in the specification, other technologies involved in the present invention are conventional technologies mastered by those skilled in the art. For example, the q-axis current controller and the d-axis current controller use PI controllers for control and controller parameter selection, the sliding mode speed controller control parameter selection, the position and speed detection module uses a rotary transformer or a photoelectric encoder to detect the rotation angle and rotation speed of the permanent magnet synchronous motor rotor, and the Clarke transformation module, Park transformation module, Park inverse transformation module and SVPWM module, three-phase inverter transformation method and application method, etc., are all conventional technologies mastered by those skilled in the art.

Claims

1. A sliding mode control method for a permanent magnet synchronous motor, wherein the speed of the permanent magnet synchronous motor is controlled by a sliding mode speed controller, characterized in that: The sliding mode speed controller adopts the integral sliding mode control method; The load torque observer adjusts the feedback gain according to the change of the load torque given value output by the sliding mode speed controller, and adjusts the feedback gain according to the rotor angular velocity ω and current i q Observe the load torque and obtain the load torque observation value Load torque observation value output by the load torque observer is sent to the sliding mode speed controller; Define the state variables of the sliding mode speed controller as Where ω is the rotor angular velocity, ω * is the given rotor angular velocity; the sliding surface of the sliding mode speed controller is s y =c y y1+y2,c y is the sliding surface parameter, and c y >0; Load torque given value output by sliding mode speed controller and q-axis torque current given value for Where J is the moment of inertia, p is the number of motor pole pairs, ψ f is the permanent magnet flux, B is the friction coefficient; coefficient μ1 and coefficient μ2 are the exponential approach rate coefficients of speed sliding mode control, and μ1>0, μ2>0; The load torque observer is in, is the estimated value of the rotor angular velocity, g is the feedback gain of the load torque observer and g<0; k g is the sliding mode gain of the load torque observer and follows Select where α≥1, is the load torque observation error; The method by which the load torque observer adjusts the feedback gain according to the change of the load torque given value output by the sliding mode speed controller is: Step 1: Calculation Step 2: Judgement Is it greater than the torque change comparison threshold ε? When it is greater than the torque change comparison threshold ε, the feedback gain g is equal to g min ;when When the torque change comparison threshold ε is less than or equal to, the feedback gain g is equal to g max ; Step (iii): The load torque observer observes the load torque to obtain the load torque observation value; the sliding mode speed controller performs control calculation to obtain Among them, ε>0; g max is the high value of feedback gain, g min is the low value of feedback gain, and g min <g max <0; Observe the load torque observation value Then, the observed value of the load torque Converted into torque current compensation component i″ q Feedforward compensation to the input of the q-axis current PI controller, the torque current given component i′ output by the sliding mode speed controller q Make compensation.

2. The sliding mode control method of a permanent magnet synchronous motor according to claim 1, characterized in that: Select g min , g max , ε1, ε2 values ​​are: Step 1), the load torque observer and the sliding mode speed controller are both in steady state and keep the given rotor angular velocity and load torque constant; Step 2), let the feedback gain g gradually decrease from a larger value. When the steady-state error of the load torque observation reaches the steady-state error limit of the load torque observation, determine the feedback gain g value at this time as g max ; Step 3), keep the given rotor angular velocity and load torque constant and set the feedback gain g equal to g max , and repeat this process n times The value is measured and n times Maximum m in the measurement The average value of the measured values ​​is used as the torque change comparison threshold ε; n≥20, 5≤m≤0.5n; Step 4), fine-tuning the feedback gain g, when the load torque observer and the sliding mode speed controller are both in steady state, keeping the given rotor angular velocity unchanged and making the load torque suddenly change, under the premise of ensuring that the torque observation tracking overshoot of the load torque observer output observation value is within the torque observation tracking overshoot limit, measuring the tracking adjustment time of the load torque observer; Step 5), repeat step 4), select the feedback gain g with the shortest tracking adjustment time as g min value.

3. The sliding mode control method of a permanent magnet synchronous motor according to claim 1, characterized in that: 1≤α≤5。 4. The sliding mode control method of a permanent magnet synchronous motor according to claim 1, characterized in that: Detect the rotor position θ and three-phase current i of the permanent magnet synchronous motor a 、i b and i c ; According to the three-phase current i a 、i b and i c Clark transformation is performed on the permanent magnet synchronous motor to obtain the current i in the α-β axis coordinate system: α 、i β , according to the current i α 、i β Perform Park transformation on the rotor position θ to obtain the current i in the dq axis coordinate system d 、i q .

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