Motor control device and motor control method

Abstract

The objective is to improve control stability even when using feedback control of the speed or position of an electric motor, which is part of a control system that cannot be considered a rigid body but can be considered a two-inertia frame, and when using a high FB control gain that makes control stabilization difficult without dead time compensation or with conventional dead time compensation methods. [Solution] An electric motor control device that provides feedback control of the speed or position of an electric motor in a control object that can be considered as a two-inertia system in which an electric motor and a mechanical load are coupled, wherein the electric motor control device compensates for the phase delay caused by the dead time of the speed control loop that controls the speed of the electric motor by using a mechanical model in which the inertia, anti-resonant frequency and resonant frequency have values ​​corresponding to the actual values ​​of the control object, and the damping coefficient has a value of (1 / √2) or more and 1 or less.

Description

[Technical Field]

[0001] This disclosure relates to an electric motor control device and an electric motor control method. [Background technology]

[0002] When detecting the position and speed of an electric motor and performing position control or speed control using feedback (FB) control, it is desirable to increase the FB control gain to improve tracking performance. However, if the FB control gain is too high, the phase margin decreases, making the system prone to instability. This is more likely to occur when the dead time due to torque control delay or position / speed detection delay is large. As a solution to this problem, a control method for dead time systems called Smith compensation (dead time compensation method) is known (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Naoto Abe and Hidetaka Nobuyama, "Control of Delay Time Systems - From Introduction to the Latest Trends, Part 1: Introduction to Delay Time Systems 1 - An Approach from Transfer Functions," Measurement and Control, Vol. 44, No. 11, pp. 799-804. [Overview of the project] [Problems that the invention aims to solve]

[0004] In conventional position control and velocity control, the one-inertia model, which treats the mechanical system as a rigid body, is used as the controlled object model for the above-mentioned dead-time compensation, regardless of whether the actual controlled object can be considered as a one-inertia frame (rigid body) or not. When the actual controlled object is not a rigid body (for example, behaves as a two-inertia frame), even if dead-time compensation is performed using the conventional method with a one-inertia model, the control may not be stabilized unless the FB control gain is significantly reduced. Not only when the actual controlled object is a two-inertia frame, but even when it is a multi-inertia frame with three or more inertia, if there is only one vibration mode that affects the control, the controlled object can be considered as a two-inertia frame.

[0005] This disclosure aims to improve control stability in cases where the speed or position of an electric motor, which is part of a controlled object that cannot be considered a rigid body but can be considered a two-inertia frame, is subjected to feedback control, even when dead time compensation is not performed or when a high FB control gain is used that makes control stabilization difficult when conventional dead time compensation methods are used. [Means for solving the problem]

[0006] As one aspect of this disclosure, An electric motor control device that provides feedback control of the speed or position of an electric motor in a control object that can be considered as two inertial systems, in which an electric motor and a mechanical load are coupled, Using a mechanical model in which the inertia, anti-resonant frequency, and resonant frequency correspond to the actual values ​​of the controlled object, and the damping coefficient is between (1 / √2) and 1, the phase lag caused by the dead time in the speed control loop that controls the speed of the electric motor is compensated. An electric motor control device is provided.

[0007] Another aspect of this disclosure is, A motor control method for feedback-controlling the speed or position of a motor in a control system that can be considered as two inertial systems, in which the motor and a mechanical load are coupled, Using a mechanical model in which the inertia, anti-resonant frequency, and resonant frequency correspond to the actual values ​​of the controlled object, and the damping coefficient is between (1 / √2) and 1, the phase lag caused by the dead time in the speed control loop that controls the speed of the electric motor is compensated. A method for controlling an electric motor is provided. [Effects of the Invention]

[0008] According to this disclosure, even when feedback control is performed on the position or speed of an electric motor in a controlled object that can be considered as a two-inertia frame, using an FB control gain so high that control stabilization is difficult when no dead time compensation is performed or when conventional dead time compensation methods are used, control stability can be improved. [Brief explanation of the drawing]

[0009] [Figure 1] This is a diagram illustrating an example of an electric motor control system. [Figure 2] This is a diagram illustrating an example of an electric motor control system that performs speed control. [Figure 3] This is a block diagram of a first example of a control system that includes a controlled object that can be considered as two inertial frames and a control device that controls the velocity of that controlled object. [Figure 4] This diagram illustrates a controlled system model using two inertial systems. [Figure 5] This block diagram shows the relationship between torque and motor speed for a controlled system with two inertia frames. [Figure 6] This figure shows the first example of a controlled system with two inertial frames. [Figure 7] This figure shows a second example of a controlled system with two inertial frames. [Figure 8] This figure shows a third example of a controlled system with two inertia. [Figure 9] This figure shows an example of the frequency characteristics of (motor speed / torque). [Figure 10] This diagram illustrates the frequency characteristics of resonance. [Figure 11] This is a block diagram of a second example of a control system that includes a controlled object that can be considered as two inertial frames and a control device that controls the velocity of that controlled object. [Figure 12] This is a block diagram showing a control system that includes a controlled object that can be considered as two inertial frames and a control device (first control example) that controls the velocity of that controlled object. [Figure 13] This is a block diagram showing a control system that includes a controlled object that can be considered as two inertial frames and a control device (second control example) that controls the velocity of that controlled object. [Figure 14] This is a block diagram showing a control system that includes a controlled object that can be considered as two inertial frames and a control device (third control example) that controls the velocity of that controlled object. [Figure 15]This is a block diagram showing a control system that includes a controlled object that can be considered as two inertial frames and a control device (fourth control example) that controls the velocity of that controlled object. [Figure 16] This figure shows the simulation results for the first control example. [Figure 17] This figure shows the simulation results for the second control example. [Figure 18] This figure shows the simulation results for the third control example. [Figure 19] This figure shows the simulation results for the fourth control example. [Figure 20] This is the Bode plot of the loop transfer function Ga(s) for the first control example. [Figure 21] This is the Bode plot of the loop transfer function Gb(s) for the second control example. [Figure 22] This shows the transfer function of the controlled object and the gain diagram of the transfer function of the mechanical model in the dead time compensator in the second control example. [Figure 23] This is the Bode plot of the loop transfer function Gc(s) for the third control example. [Figure 24] This shows the transfer function of the controlled object and the gain diagram of the transfer function of the mechanical model in the dead time compensator in the third control example. [Figure 25] This is the Bode plot of the loop transfer function Gd(s) for the fourth control example. [Figure 26] This shows the transfer function of the controlled object and the gain diagram of the transfer function of the mechanical model in the dead time compensator in the fourth control example. [Figure 27] This is a block diagram of the first example of a control system that includes a controlled object that can be considered as two inertial frames, and a control device that performs position control while incorporating velocity control of the controlled object. [Figure 28] This is a block diagram of a second example of a control system that includes a controlled object that can be considered as two inertial frames, and a control device that performs position control while incorporating velocity control of the controlled object. [Modes for carrying out the invention]

[0010] The embodiments of this disclosure will be described below with reference to the drawings.

[0011] Figure 1 is a configuration diagram showing an example of an electric motor control system. The electric motor control system 200 shown in Figure 1 is a drive control device that controls the drive of the electric motor 2 for moving a mechanical load 3. The electric motor control system 200 drives the mechanical load 3 using the electric motor 2 by outputting three-phase or single-phase AC power from the electric motor control device 100 to the electric motor 2. The electric motor control system 200 comprises the electric motor 2 and the electric motor control device 100.

[0012] The electric motor 2 is mechanically connected to the mechanical load 3 and drives the mechanical load 3. The electric motor 2 is an AC motor, such as a permanent magnet synchronous motor.

[0013] The mechanical load 3 is, for example, mechanical equipment such as production equipment installed in a factory. For example, if the mechanical load 3 is a conveying device that uses a ball screw, the electric motor 2 can drive the conveying device, which is the mechanical load 3, by driving the ball screw.

[0014] The system including the electric motor 2 and the mechanical load 3 driven by the electric motor 2 is represented as the mechanical system 4.

[0015] The motor control device 100 is a power conversion device that converts input power from power source 1 into power supplied to motor 2. For example, if motor 2 is a synchronous motor, the motor control device 100 converts the three-phase or single-phase AC power input from power source 1 into three-phase AC power having a predetermined voltage and phase corresponding to the rotational position, and drives motor 2 by supplying the three-phase AC power to motor 2.

[0016] The motor control device 100 includes a main circuit 10, a current sensor 18, a control device 30, and a drive circuit 20.

[0017] The main circuit 10 converts the input power from the power supply 1 into power to be supplied to the motor 2, and drives the motor 2 by outputting the converted power to the motor 2. The main circuit 10 includes, for example, a converter circuit 11, a DC link 12, and an inverter circuit 14.

[0018] The converter circuit 11 converts the AC or DC supplied from the power supply 1 into DC. The converter circuit 11 may also be a rectifier circuit that converts the AC supplied from the power supply 1 into DC. Specific examples of the converter circuit 11 include a diode bridge and a PWM converter.

[0019] The DC link 12 is a circuit that connects the converter circuit 11 and the inverter circuit 14. The DC link 12 includes, for example, a capacitor 13 that smooths the DC voltage input to the inverter circuit 14.

[0020] The inverter circuit 14 converts the DC input from the converter circuit 11 via the DC link 12 into AC, and supplies the converted AC to the motor 2. The inverter circuit 14 has a plurality of semiconductor devices 15. The semiconductor devices 15 have switching elements that turn on or off according to the corresponding drive signal SG among a plurality of drive signals SG supplied from the drive circuit 20.

[0021] The inverter circuit 14 is a power conversion circuit that converts the input DC into AC by switching the switching elements of each of the multiple semiconductor devices 15. The inverter circuit 14 supplies single-phase or three-phase AC current to the motor 2.

[0022] The semiconductor device 15 has semiconductor elements for power conversion. For example, multiple semiconductor devices 15 each have a transistor 16 and a diode 17 connected in antiparallel to the transistor 16. The transistor 16 is an example of a switching element. Specific examples of the transistor 16 include power semiconductors such as IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). If a MOSFET is used as the transistor 16, the diode 17 may be a parasitic diode. The transistor 16 and the diode 17 may be provided on separate semiconductor devices 15.

[0023] The current sensor 18 detects the output current I from the motor control device 100 to the motor 2. In this example, the current sensor 18 detects the current value of the AC current output from the inverter circuit 14 to the motor 2, and the detected current value I represents the detected current value. det The current sensor 18 outputs a current detection signal to the control device 30 accordingly. The current sensor 18 detects, for example, the current flowing through the output line connecting the inverter circuit 14 and the motor 2. The current detection signal output from the current sensor 18 is received by the control device 30 of the motor control device 100. As a result, the control device 30 determines the detected value of the output current I flowing through the motor 2 (current detection value I) based on the current detection signal from the current sensor 18. det ) can be obtained.

[0024] The position sensor 5 is installed on the motor 2 and detects the position of the motor 2 (movement position if the motor 2 is a linear motor, rotation position if the motor 2 is a rotary motor). The position sensor 5 is, for example, an optical or magnetic encoder. The position sensor 5 detects the position of the motor 2 (position detection value x det The position sensor 5 outputs a position detection signal corresponding to the position detection value x. The position detection signal output from the position sensor 5 is taken up by the control device 30 of the motor control device 100. Based on the position detection signal from the position sensor 5, the control device 30 determines the magnetic pole position of the rotor of the motor 2 (position detection value x). det) can be obtained, and the position detection value x det By differentiating, the detected value (speed detection value v) of the speed (moving speed or rotational speed) of the electric motor 2 can be obtained. det ) can be obtained.

[0025] The control device 30 operates the inverter circuit 14 by operating the drive circuit 20 so that the current detection signal follows the current command generated based on the torque command generated within the control device 30, based on the current detection signal from the current sensor 18 and the position detection signal from the position sensor 5.

[0026] The control device 30 controls the operation of each of the multiple semiconductor devices 15 in the inverter circuit 14 based on current detection signals, etc. The control device 30 generates multiple control signals Sg to control the pulse voltage output by the inverter circuit 14 that generates AC power supplied to the motor 2, based on current detection signals, etc.

[0027] The control device 30 is an electronic circuit including, for example, a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), or an ASIC (Application Specific Integrated Circuit). The control device 30 may also be a computer having memory and a processor. The control device 30 may also be a programmable logic controller (PLC). The control device 30 performs the various control operations described in this specification by executing a program such as instruction code stored in memory, or by designing a circuit for a specific application.

[0028] The drive circuit 20 generates multiple drive signals SG to drive the gates of each switching element of the multiple semiconductor devices 15 in the inverter circuit 14, according to multiple control signals Sg generated by the control device 30.

[0029] Figure 2 is a configuration diagram showing an example of an electric motor control system that performs speed control. The electric motor control system 200A shown in Figure 2 is an example of the above-mentioned electric motor control system 200. Figure 2 illustrates a case where the converter circuit 11 is a diode bridge, the inverter circuit 14 is a three-phase inverter circuit, and the electric motor 2 is a permanent magnet synchronous motor (PMSM). The electric motor control system 200A includes a control device 30A.

[0030] Figure 2 shows each functional block of the control device 30A. The control device 30A shown in Figure 2 is an example of the above-mentioned control device 30. The control device 30A performs speed control of the mechanical system 4 by feedback controlling the speed of the electric motor 2, which is a part of the mechanical system 4, based on the speed command v r . The mechanical system 4 is an object (control object) controlled by the control device 30A.

[0031] The control device 30A includes a controller 31, a current command calculator 61, a current coordinate converter 62, a current controller 63, a coordinate converter 64, and a PWM generator 65. The controller 31 includes a speed controller 34, a dead time compensator 40, and an adder 32.

[0032] The controller 31 of the control device 30A is a speed controller that performs speed control of the electric motor 2. The controller 31 calculates the speed detection value v det by differentiating the position detection value x det . The controller 31 has a speed controller 34 that performs feedback control (FB control) to make the deviation between the speed command v r for the mechanical system 4 and the speed estimation value v est of the mechanical system 4 approach zero, thereby generating a torque command T0. Examples of control for generating the torque command T0 in the controller 31 include P control, PI control, or I-P control (P: proportional control, I: integral control).

[0033] The dead time compensator 40 is a compensator that compensates for the phase delay caused by the dead time of the speed control loop for controlling the speed of the electric motor 2. The adder 32 adds the output value v c of the dead time compensator 40 and the speed detection value v detBy adding these together, we obtain the estimated velocity v est Perform the calculation.

[0034] The current command calculator 61 calculates a command value to control the current flowing to the motor 2 via the inverter circuit 14. The current command calculator 61 calculates a command value to control the current flowing to the motor 2 via the torque command T0 and the speed detection value v det or velocity estimate v est Based on this, current command values ​​Idref and Iqref are generated. Current command value Idref represents the command value of the d-axis current, which is the current that generates magnetic flux in the d-axis direction (magnetic pole direction) of motor 2. Current command value Iqref represents the command value of the q-axis current, which is the current that generates magnetic flux in the q-axis direction (direction perpendicular to the magnetic poles when viewed in terms of electrical angle) of motor 2.

[0035] The current coordinate converter 62 receives the position detection value x det Using the value converted to electrical angle, the current detection value I det The three-phase phase current detection values ​​(iu, iv, iw) are converted to current detection values ​​on the dq coordinate system (d-axis current detection value Id and q-axis current detection value Iq).

[0036] The current controller 63 calculates the d-axis current difference ΔId between the current command value Idref and the d-axis current detection value Id, and the q-axis current difference ΔIq between the current command value Iqref and the q-axis current detection value Iq. The current controller 63 uses PI control or the like to adjust the d-axis voltage command value Vd so that the d-axis current difference ΔId converges to zero. * It generates the q-axis current difference ΔIq and the q-axis voltage command value Vq so that it converges to zero. * This generates the current. The current controller 63 also performs non-interference control, which includes induced voltage compensation and de-interference control to eliminate dq-axis interference.

[0037] The coordinate converter 64 uses the position detection value x det Using the value converted to an electrical angle, the voltage command value Vd on the dq coordinate system * ,Vq * The phase voltage command value of the three phases (U phase voltage command value Vu * V-phase voltage command value Vv * W-phase voltage command value Vw * Convert to ).

[0038] The PWM generator 65 outputs the three-phase phase voltage command value (U phase voltage command value Vu * V-phase voltage command value Vv * W-phase voltage command value Vw * Based on this, it generates PWM signals, which are multiple control signals Sg for switching the six upper and lower arms.

[0039] Figure 3 is a block diagram of a first example of a control system including a controlled object that can be considered as two inertial frames and a control device that controls the speed of the controlled object. The mechanical system 4 is a controlled object that can be considered as two inertial frames. The control device 30A provides feedback control to the speed of the electric motor 2, which is part of the mechanical system 4. The input-output relationship of the mechanical system 4, which takes torque as input and motor speed as output, is expressed by the transfer function G(s) shown in Equation 1.

[0040]

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[0041] J t The total inertia (total moment of inertia) of mechanical system 4, ω z The anti-resonance frequency [rad / s] of mechanical system 4, ω μ The resonant frequency [rad / s] of mechanical system 4, ζ z The damping coefficient of the anti-resonance point of mechanical system 4, ζ μ Let be the damping coefficient of the resonance point of mechanical system 4, and let s be the Laplace operator. Total inertia J t This corresponds to the sum of the motor-side inertia J1 and the load-side inertia J2 (details will be explained later).

[0042] In the case of a mechanical system 4 where vibrations tend to persist, the input-output relationship may be expressed by the transfer function G(s) shown in Equation 2.

[0043]

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[0044] This explains why the input / output relationship of mechanical system 4 is expressed as shown in equations 1 and 2.

[0045] Figure 4 illustrates a controlled system model of a two-inertia system. In the two-inertia mechanical system 4, the electric motor 2 and the mechanical load 3 are connected by a shaft or the like. The electric motor side inertia J1 represents the moment of inertia of the electric motor 2, and the load side inertia J2 represents the moment of inertia of the mechanical load 3. In the two-inertia system in which the electric motor side inertia J1 and the load side inertia J2 are coupled, when a torque T is applied to the electric motor 2, the equation of motion for the electric motor side inertia J1 is given by equation 3A, and the equation of motion for the load side inertia J2 is given by equation 3B.

[0046]

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[0047] T tor θ1 represents the torsional torque between motor 2 (motor-side inertia J1) and mechanical load 3 (load-side inertia J2). K represents the elastic modulus between motor 2 (motor-side inertia J1) and mechanical load 3 (load-side inertia J2). C represents the viscosity coefficient between motor 2 (motor-side inertia J1) and mechanical load 3 (load-side inertia J2). θ1 represents the rotation angle on the motor 2 side. θ2 represents the rotation angle on the mechanical load 3 side. v1 represents the rotational speed (motor speed) on the motor 2 side. v2 represents the rotational speed (load speed) on the mechanical load 3 side.

[0048] Figure 5 shows a block diagram illustrating the relationship between torque and motor speed for a controlled system in two inertial frames. The controlled system model defined by the equations of motion expressed by equations 3A and 3B is represented by the block diagram shown in Figure 5.

[0049] After applying the Laplace transforms to equations 3A and 3B, we get T tor Eliminating the term yields equations 4A and 4B. Combining equations 4A and 4B yields equation 4C, from which equation 4C can be derived equation 4D.

[0050]

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[0051] Focusing only on v1 in Equation 4D, we can derive Equation 5 from Equation 4D.

[0052]

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[0053] Equation 5 can be transformed into Equation 6.

[0054]

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[0055] ω z This represents the anti-resonant frequency [rad / s] of mechanical system 4. ω μ This represents the resonant frequency [rad / s] of mechanical system 4. ζ z and ζ μ This represents the damping coefficient ζ of mechanical system 4. ζ can be in the range of 0 to 1, but in inertial frame 2 where vibration is likely to persist (viscosity coefficient C is close to zero), ζ is close to zero. Conversely, if ζ is close to 1, it indicates a mechanical system that is less prone to vibration.

[0056]

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[0057] Since Equation 7 holds true, according to Equations 6 and 7, the input-output relationship of the controlled systems of the two inertial systems can be expressed by the transfer function G(s) shown above in Equation 1 or Equation 2.

[0058] Next, the total inertia J t Next, we will explain the relationship between the motor-side inertia J1 and the load-side inertia J2.

[0059] Figure 6 shows the first example of a controlled system with two inertia. The total inertia J of the mechanical system 4, which is the controlled system with two inertia. t This represents the inertia of the entire mechanical system 4 and corresponds to the sum of the motor-side inertia J1 and the load-side inertia J2 (J t=J1+J2). The motor-side inertia J1 includes the inertia of the motor itself. The boundary is the point in the entire mechanical system 4 where the coupling is weakest (the point where the coupling is weak and twisting occurs, and the frequency of the vibration associated with that twisting is the lowest). The total inertia on the motor 2 side of that boundary is defined as the motor-side inertia J1, and the total inertia on the mechanical load 3 side of that boundary is defined as the load-side inertia J2.

[0060] Figure 7 shows a second example of a controlled system with two inertia. Suppose we add another machine 3b to the end of machine 3a connected to electric motor 2, and that the stiffness of the additional connection point 3c is known to be the weakest in the entire machine system 4. In this case, the total inertia on the electric motor 2 side with respect to the additional connection point 3c can be defined as the electric motor side inertia J1, and the total inertia on the machine 3b side with respect to the additional connection point 3c can be defined as J2. By moving machine 3a with electric motor 2 in the state before the additional connection of the load side inertia J2, the electric motor side inertia J1 can be estimated from the ratio of acceleration torque to acceleration during acceleration and deceleration operation.

[0061] Figure 8 shows a third example of a controlled system with two inertia. Even if there is a weak point somewhere in the entire mechanical system 4, if it is not possible to isolate and drive at that weak point, the motor-side inertia J1 can be estimated based on the frequency characteristics of (motor speed / torque).

[0062] Figure 9 shows an example of the frequency characteristics of (motor speed / torque). Figure 9 is a log-log graph drawn by acquiring the frequency characteristics of (motor speed / torque). The frequency characteristics of (motor speed / torque) are the anti-resonance frequency ω z At lower frequencies, 1 / J t The frequency dependence of ω is represented by a straight line L1, and the resonant frequency ω μ At higher frequencies, it is represented by a straight line L2 due to the frequency dependence of 1 / J1ω. By extending the straight line L2 on the high-frequency side to the low-frequency side (or the high-frequency side), finding the difference between the values ​​of the straight line L1 and the straight line L2 at a certain frequency, and converting back to the value before logarithmic representation, (J t The total inertia J (J1) is obtained. tSince this can be estimated by performing acceleration and deceleration driving, J1 can also be estimated.

[0063] Next, returning to Figure 3, we will describe the control system including the control device 30A and the mechanical system 4.

[0064] As described above, the dead time compensator 40 is a compensator that compensates for the phase delay caused by the dead time in the speed control loop that controls the speed of the electric motor 2. Based on the torque command T0, it uses the mechanical model 41 described later to predict the difference between the speed when the speed control loop does not include dead time and the speed when it does include dead time. The dead time compensator 40 uses the prediction result to compensate for the phase delay caused by the dead time in the speed control loop that controls the speed of the electric motor 2.

[0065] Control system dead time τ d For example, the dead time τ due to torque control delay. d1 and dead time τ due to speed detection delay d2 This includes: Torque control delay is the delay until the torque based on the torque command T0 is actually applied to the motor 2. Speed ​​detection delay is the delay until the speed is actually detected and the speed detection value v det This is the delay until the signal is input to adder 32.

[0066] Transfer function F of the dead time element due to torque control delay d1 (s) is expressed by equation 8A. Transfer function F of the dead time element due to velocity detection delay. d2 (s) is expressed by equation 8B.

[0067]

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[0068] Torque control delays include, for example, processing delays of the current command calculator 61, current controller 63, coordinate converter 64, and PWM generator 65 in Figure 2, as well as the operation delay of the inverter circuit 14. Speed ​​detection delays include, for example, the transmission delay of the position detection signal output from the position sensor 5 in Figure 2, and the speed detection value v detThis includes calculation delays, etc.

[0069] In Figure 3, the machine model 41 has a total inertia J t , anti-resonant frequency ω z and resonant frequency ω μ This has a value that corresponds to the actual mechanical system 4 value, and the damping coefficient ζ(ζ z and ζ μ ) is a virtual two-inertia model with a value between (1 / √2) and 1. The dead-time compensator 40 uses the mechanical model 41 with these values ​​to compensate for the phase delay caused by the dead time in the speed control loop that controls the speed of the motor 2, which is part of the mechanical system 4 in which the motor 2 and mechanical load 3 are coupled. By equipping the control device 30A with such a dead-time compensator 40, control stability can be improved even when the speed of the motor 2 on the mechanical system 4, which can be considered a two-inertia system, is feedback controlled, as shown in the simulation results described later. In particular, control stability is improved even when the speed of the motor 2 in the mechanical system 4, which can be considered a two-inertia system, is feedback controlled using an FB control gain so high that control stabilization is difficult when dead-time compensation is not performed or when conventional dead-time compensation methods are used.

[0070] The machine model 41 has a transfer function G, for example, shown in Equation 9. m (s) is represented by

[0071]

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[0072] Transfer function G shown in Equation 9 m By using the mechanical model 41 represented by (s), the dead time compensator 40 compensates for the phase delay caused by the dead time in the speed control loop, thereby improving control stability even when the speed of the motor 2, which is part of the mechanical system 4 that can be considered as a two-inertia system, is feedback controlled.

[0073] Mechanical model 41 is ζ z =ζ μ The transfer function G shown in Equation 10 corresponds to Equation 9 when = 1. mIt may also be represented as (s).

[0074]

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[0075] Transfer function G shown in Equation 10 m By using the mechanical model 41 represented by (s), the dead time compensator 40 compensates for the phase delay caused by the dead time in the speed control loop, thereby improving control stability even when the speed of the motor 2, which is part of the mechanical system 4 that can be considered as a two-inertia system, is feedback controlled.

[0076] The machine model 41 is not a hypothetical two-inertia model as described above, but rather a one-inertia transfer function G shown in Equation 11. m It can also be represented as (s).

[0077]

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[0078] Transfer function G shown in Equation 11 m By using the mechanical model 41 represented by (s), the dead time compensator 40 compensates for the phase delay caused by the dead time in the speed control loop, thereby improving control stability even when the speed of the electric motor 2, which is part of the mechanical system 4 that can be considered as a two-inertia system, is subjected to feedback control.

[0079] The machine model 41 has a transfer function G shown in Equation 12, which is obtained by substituting Equation 7 into Equation 11. m It may also be represented as (s).

[0080]

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[0081] Transfer function G shown in Equation 12 mBy using the mechanical model 41 represented by (s), the dead time compensator 40 compensates for the phase delay caused by the dead time in the speed control loop, thereby improving control stability even when the speed of the electric motor 2, which is part of the mechanical system 4 that can be considered as a two-inertia system, is subjected to feedback control.

[0082] Transfer function G shown in Equation 12 m The mechanical model 41 represented by (s) has no load-side inertia J2 but has motor-side inertia J1. The transfer function G shown in Equation 12 m (s) can be used even if the load-side inertia J2 is unknown, as long as the motor-side inertia J1 is known by the estimation method (estimation method) shown in Figure 6-9. Therefore, the dead time compensator 40 can be simplified, which reduces memory and computation costs.

[0083] Transfer function G shown in Equation 12 m The machine model 41, represented by (s), is given by the value calculated by equation 13 as J1 in equation 12.

[0084]

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[0085] Even if the true value of the motor-side inertia J1 is unknown, the total inertia J t and ω z ,ω μ If is known, the value calculated by equation 12A outside the machine model 41 can be given to the machine model 41 as J1 in equation 12. In this way, the transfer function G shown in equation 12 m The mechanical model 41 represented by (s) has a motor-side inertia J1 that is calculated by equation 13, which does not have load-side inertia J2 as a variable.

[0086] For example, total inertia J t and resonant frequency ω μ and anti-resonance frequency ω z If is known, then the transfer function G shown in Equation 9 m(s) represented mechanical model 41 can be used for phase compensation. However, the damping coefficient ζ μ , ζ z in the mechanical model 41 shall be set to a value between 1 / √2 and 1, regardless of the damping coefficient of the actual mechanical system 4.

[0087] The control device 30A may adjust the set value defining the dead time compensator 40 according to an adjustment signal input from outside the motor control device 100 by a user operation or an instruction from an external computer. Thereby, it can be adjusted to a set value suitable for compensating the phase lag caused by the dead time when actually controlling the control target (mechanical system 4). For example, the control device 30A may adjust the set value of the mechanical model 41, the dead time model 42, or the HPF 43 described later according to an adjustment signal from outside the motor control device 100. The set value of the mechanical model 41 is, for example, the total inertia J t , the motor-side inertia J1, the anti-resonance frequency ω z , the resonance frequency ω μ etc. The set value of the dead time model 42 is, for example, the dead time τ d1 or the dead time τ d2 etc. The set value of the HPF 43 is, for example, the filter time constant etc. The dead time τ d1 , τ d2 and the set value of the HPF 43 may be set as fixed values in the dead time compensator 40.

[0088] The control device 30A may select whether to compensate for the phase lag due to the dead time using a first mechanical model having the total inertia J t , or to compensate for the phase lag due to the dead time using a second mechanical model having no load-side inertia J2 but only the motor-side inertia J1. Thereby, a mechanical model 41 suitable for compensating the phase lag caused by the dead time when actually controlling the control target (mechanical system 4) can be selected and set. As an example of the first mechanical model, there is a model represented by the transfer function G m (s) of Equation 9, Equation 10, or Equation 11. As an example of the second mechanical model, there is a model represented by the transfer function G m (s) of Equation 12.

[0089] The control device 30A may select a mechanical model 41 to be applied to the dead time compensator 40 from among a plurality of options according to a selection signal input from outside the motor control device 100 in response to a user operation or a command from an external computer. Thereby, it is possible to select and set a mechanical model 41 suitable for compensating for the phase delay caused by the dead time when controlling the actual control target (mechanical system 4). For example, the control device 30A defines a transfer function G representing the mechanical model 41 from among a plurality of expressions including at least one of the expressions of Equations 9, 10, 11, and 12 according to a selection signal from outside the motor control device 100. m (s) may be selected.

[0090] Next, an explanation will be given regarding the case where the damping factors ζ (ζ z and ζ μ ) are set to values between (1 / √2) and 1.

[0091] ζ z = ζ μ = 1, in which case, since a first-order phase delay / advance filter may be calculated twice in the same form, considering implementation in control software, setting ζ z = ζ μ = 1 is advantageous in terms of calculation cost. If calculation cost is not a concern, ζ z or ζ μ need not be 1. In this case, the desirable range of ζ is (1 / √2) ≤ ζ z ≤ 1 or (1 / √2) ≤ ζ μ ≤ 1.

[0092]

Equation

[0093] If we ignore the anti-resonance characteristics in the numerator of equation 14A and focus only on the resonance characteristics in the denominator, as in equation 14B, then this frequency characteristic shows that a resonance peak exists if ζ < 1 / √2 (Figure 10(a)), but no resonance peak exists if ζ ≥ 1 / √2 (Figure 10(b)). Therefore, when using a dummy two-inertia model with the resonance peak suppressed as the mechanical model 41, the damping coefficient ζ(ζ z and ζ μ It is preferable that the value of ) be between (1 / √2) and 1.

[0094] In Figure 3, the dead time compensator 40 may process the value to compensate for the phase delay caused by the dead time in the speed control loop that controls the speed of the motor 2 through a high-pass filter (HPF43). If the HPF43 is not present, even if the speed controller 34 has an integral term, the steady-state error cannot be reduced to zero due to steady-state disturbances. By providing the HPF43, speed control can be performed without steady-state errors even when steady-state disturbances are applied.

[0095] HPF43 is connected in series with machine model 41. The dead time compensator 40 takes the output value v obtained by applying a high-pass filter by HPF43 to the output of machine model 41. c Outputs.

[0096] Figure 11 is a block diagram of a second example of a control system that includes a controlled object that can be considered as two inertial frames and a control device that controls the speed of that controlled object. The control device 30B shown in Figure 11 differs from the control device 30A shown in Figure 3 in that it uses feedforward control (FF control) in combination with feedback control (FB control) of the speed of the electric motor 2, which is part of the mechanical system 4 that is the controlled object. The explanation of the configuration, operation, and effects of the control device 30B is the same as that of the control device 30A described above, so it will be omitted by referring to the explanation above.

[0097] The control device 30B shown in Figure 11 can achieve a desired target value response regardless of the FB control gain by using feedforward control in combination with feedback control. The control device 30B includes an FF controller 35 and an adder 37.

[0098] The FF controller 35 receives the speed command v r The feedforward torque signal (FF Torque T) for adjusting the torque of the electric motor 2 is filtered and then filtered. FF Feedforward control (FF control) is performed to generate the speed command v. For example, the FF controller 35 performs vibration-damping FF control to generate the speed command v. r For changes in velocity command v r FF Torque T to achieve a target value response that changes the actual speed of motor 2 in the street FF Generates.

[0099] The speed controller 34 issues a speed command v to the mechanical system 4. r and the estimated velocity v of mechanical system 4 est A feedback torque signal (FB Torque T) that brings the deviation closer to zero. FB The speed controller 34 performs feedback control (FB control) to generate the FB torque T. FB Generates.

[0100] Adder 37 is FF Torque T FF and FB Torque T FB By adding these two values, a torque command T0 for the electric motor 2 is generated.

[0101] The dead time compensator 40 is FB Torque T FB Based on this, the machine model 41 is used to predict the difference between the speed when the speed control loop does not include dead time and the speed when it does include dead time. The control device 30B, which uses FF control in combination with FB control, outputs the FB control (FB torque T FB ) is applied to the input of the dead time compensator 40, but the output of the FF control (FF torque T FF The ) is not applied to the input of the dead time compensator 40. As a result, the target value response by FF control is not affected by dead time compensation, and the FF control without dead time compensation can be used as is.

[0102] Next, to confirm the effects of the motor control device and motor control method according to the embodiments of this disclosure, the results of simulations for four examples are shown. Figure 12-15 is a block diagram showing a control system including a control object that can be considered as two inertial frames and a control device that controls the speed of that control object.

[0103] The control device 131 shown in the first control example in Figure 12 controls the speed of the mechanical system 4 without dead time compensation.

[0104] The control device 132 shown in the second control example in Figure 13 controls the speed of the mechanical system 4 by compensating for the phase delay due to dead time using a mechanical model 41 represented by the transfer function shown in the following equation 15 of the one-inertia model.

[0105]

number

[0106] The control device 133 shown in the third control example in Figure 14 performs speed control of the mechanical system 4 by compensating for the phase delay due to dead time using the mechanical model 41 represented by the transfer function shown in the above equation 10 of the two-inertia model.

[0107] The control device 134 shown in the fourth control example in Figure 15 performs speed control of the mechanical system 4 by compensating for the phase delay due to dead time using the mechanical model 41 represented by the transfer function shown in the above equation 12 of the two-inertia model.

[0108] Figure 12-15 shows an example of a control system that combines FB control with vibration-damping FF control. The FB control is PI control. This FF control ensures that, as long as no disturbances are applied, the commanded speed can be achieved simply by changing the speed command.

[0109] The parameters and other conditions for the speed control simulation are the same in all cases from Figures 12 to 15, as follows: When no dead time compensation is performed or when conventional dead time compensation methods are used, the FB control gain is so high that control stabilization is difficult.

[0110] Controlled parameter: Total inertia J t = 0.0001 kgm 2 , anti-resonant frequency ω z =1000rad / s, resonant frequency ω μ = 2400 rad / s Control condition: PI control = J t k vp (1+k vi / s);k vp =1000 rad / s, k vi =k vp / 3,F d1 and F d2 Total wasted time τ d =τ d1 +τ d2 = 0.3ms Operating conditions: A speed command of 40 rad / s is given at time 0.01 s, and a disturbance of 1 Nm is applied at time 0.03 s.

[0111] Figures 16-19 show the simulation results for the first control example in Figure 12, the second control example in Figure 13, the third control example in Figure 14, and the fourth control example in Figure 15, respectively. In all cases shown in Figures 16-19, the speed corresponding to the speed command is achieved by vibration-damping FF control before the disturbance is applied. After the application of the disturbance, speed control becomes impossible in the first and second control examples. In contrast, speed control can be continued even after the application of the disturbance in the third and fourth control examples.

[0112] The following explains the reasons why the simulation results shown in Figures 16-19 were obtained.

[0113] Loop transfer function G in the first control example shown in Figure 12 a (s) is expressed in equation 16.

[0114]

number

[0115] Figure 20 shows the loop transfer function G in the first control example shown in Figure 12. a This is the Bode plot of (s). Figure 20(a) is the gain plot showing the frequency characteristics of the gain. Figure 20(b) is the phase plot showing the frequency characteristics of the phase. As shown in Figure 20, ω > ω μ At the frequency where the gain becomes 0 dB (gain crossover frequency), the phase lag is 180 degrees or more, which leads to instability.

[0116] The loop transfer function G in the second control example shown in Figure 13. b (s) is expressed by equation 17.

[0117]

number

[0118] ω≫ω μ So, the loop transfer function G b (s) is expressed as shown in Equation 18, and the dead time τ d This remains in the term.

[0119]

number

[0120] In other words, even if we try to compensate for dead time using this method, dead time τ d The term cannot be offset, k vp It cannot be stabilized unless it is lowered.

[0121] Figure 21 shows the loop transfer function G in the second control example shown in Figure 13. bThis is the Bode plot of (s). Figure 21(a) is the gain plot showing the frequency characteristics of the gain. Figure 21(b) is the phase plot showing the frequency characteristics of the phase. In the frequency response calculation, the phase lag at the gain crossover frequency is barely less than 180 degrees, but there is almost no phase margin. Therefore, the speed control diverges in the simulation.

[0122] Figure 22 shows the gain diagrams of the transfer function of the controlled object (Equation 2) and the transfer function of the mechanical model in the dead time compensator (Equation 15) in the second control example. ω<ω z On the low-frequency side, the mechanical model within the dead-time compensator exhibits frequency characteristics that are almost identical to those of the actual controlled system. However, ω > ω z On the high-frequency side, the mechanical model within the dead-time compensator exhibits different frequency characteristics from the actual controlled system, making it impossible to properly suppress phase lag on the high-frequency side.

[0123] The loop transfer function G in the third control example shown in Figure 14. c (s) is expressed in equation 19.

[0124]

number

[0125] ω≫ω μ So, the loop transfer function G c (s) is expressed as in equation 20, and the dead time τ d The entry disappears.

[0126]

number

[0127] via wasted time τ d This term can be canceled out, resulting in a delay of approximately 90 degrees, which can then be stabilized.

[0128] Figure 23 shows the loop transfer function G in the third control example of Figure 14. cThis is the Bode plot of (s). Figure 23(a) is a gain plot showing the frequency characteristics of the gain. Figure 23(b) is a phase plot showing the frequency characteristics of the phase. The frequency response calculation shows that the phase lag on the high-frequency side is suppressed and the speed control is stabilized.

[0129] Figure 24 shows the gain diagrams of the transfer function of the controlled object (Equation 2) and the transfer function of the mechanical model in the dead time compensator (Equation 10) in the third control example. ω<ω z The low-frequency side and ω>ω μ On both the high-frequency and high-frequency sides, the mechanical model within the dead-time compensator exhibits frequency characteristics that are nearly identical to those of the actual controlled system.

[0130] The loop transfer function G in the fourth control example shown in Figure 15. d (s) is expressed by equation 21.

[0131]

number

[0132] ω≫ω μ So, the loop transfer function G d (s) is expressed as shown in Equation 22, and the dead time τ d The entry disappears.

[0133]

number

[0134] via wasted time τ d This term can be canceled out, resulting in a delay of approximately 90 degrees, which can then be stabilized.

[0135] Figure 25 shows the loop transfer function G in the fourth control example of Figure 15. d This is the Bode plot of (s). Figure 25(a) is a gain plot showing the frequency characteristics of the gain. Figure 25(b) is a phase plot showing the frequency characteristics of the phase. The frequency response calculation shows that the phase lag on the high-frequency side is suppressed and the speed control is stabilized.

[0136] Figure 26 shows the gain diagrams of the transfer function of the controlled object (Equation 2) and the transfer function of the mechanical model in the lag compensator (Equation 12) in the fourth control example. ω<ω μ On the low-frequency side, the mechanical model within the dead-time compensator exhibits different frequency characteristics from the actual controlled system. However, ω > ω μ At high frequencies, the mechanical model within the dead time compensator exhibits frequency characteristics nearly identical to those of the actual controlled system. It is crucial that dead time compensation functions correctly at high frequencies where phase lag is significant, but it is less problematic at low frequencies where phase lag is small. Therefore, a method of dead time compensation using the mechanical model 41, represented by the transfer function shown in equation 12 of the two-inertia model, can also be used as a control stabilization technique.

[0137] Figure 27 is a block diagram of a first example of a control system that includes a control object that can be considered as two inertial frames and a control device that performs position control while incorporating velocity control of the control object. The control device 30C shown in Figure 27 receives a position command x r The control device 30C differs from the control device 30A shown in Figure 3 in that it controls the position of the mechanical system 4 by feedback control of the position of the electric motor 2 side of the mechanical system 4 based on the above. The explanation of the configuration, operation, and effects of the control device 30C is the same as that of the control devices 30A and 30B, so it will be omitted by referring to the explanation above.

[0138] The control device 30C shown in Figure 27 includes a position and speed controller that performs position control and speed control of the electric motor 2. The control device 30C receives the position detection value x det By differentiating this, the velocity detection value v det The control device 30C includes a position controller 33.

[0139] The position controller 33 issues a position command x to the mechanical system 4. r and the position detection value x of mechanical system 4 det A speed command v that brings the deviation from zero closer to zero. r This is a feedback control unit that generates [something].

[0140] Since the control device 30C is equipped with the above-mentioned dead time compensator 40, control stability can be improved even when feedback control is performed on the position and speed of the motor 2 side of the mechanical system 4, which is a controlled object that can be considered as two inertial systems. In particular, control stability is improved even when feedback control is performed on the position and speed of the motor 2 in the mechanical system 4, which can be considered as two inertial systems, using an FB control gain that is so high that control stabilization is difficult when dead time compensation is not performed or when conventional dead time compensation methods are used.

[0141] Figure 28 is a block diagram of a second example of a control system that includes a control object that can be considered as two inertial frames and a control device that performs position control while incorporating velocity control of the control object. The control device 30D shown in Figure 28 differs from the control device 30C shown in Figure 27 in that it uses feedforward control (FF control) in combination with feedback control (FB control) of the position of the mechanical system 4, which is the control object. The explanation of the configuration, operation, and effects of the control device 30D, which are the same as those of the control devices 30A, 30B, and 30C described above, will be omitted by referring to the explanation above.

[0142] The control device 30D shown in Figure 28 can achieve a desired target value response regardless of the FB control gain by using feedforward control in combination with feedback control. The control device 30D includes an FF controller 36.

[0143] The FF controller 36 receives the position command x r Based on this, FF speed command v FF Generates.

[0144] The FF controller 35 receives the FF speed command v FF Filtering is applied to FF Torque T FF Generates position command x r Directly from FF Torque T FF You may perform the calculation.

[0145] The speed controller 34 issues a speed command v to the mechanical system 4. r and the estimated speed v of the electric motor 2, which is part of the mechanical system 4. est A feedback torque signal (FB Torque T) that brings the deviation closer to zero.FB Feedback control (FB control) is performed to generate the speed command v. r This includes the speed command generated by the position controller 33 and the FF speed command v generated by the FF controller 36. FF It is equivalent to the sum of the two.

[0146] Since the control device 30D is equipped with the above-mentioned dead time compensator 40, control stability can be improved even when feedback control is performed on the position and speed of the electric motor 2, which is part of the mechanical system 4 that can be considered as two inertial systems. In particular, control stability is improved even when feedback control is performed on the position and speed of the electric motor 2 in the mechanical system 4 that can be considered as two inertial systems using an FB control gain that is so high that control stabilization is difficult when dead time compensation is not performed or when conventional dead time compensation methods are used.

[0147] The present invention is not limited by the embodiments described above. The embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, and modifications are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0148] 2 electric motor 3 Mechanical load 4. Mechanical Engineering 5. Position Sensor 10 Main circuit 20 Drive Circuit 30, 30A, 30B, 30C, 30D control devices 31 Controller 34 Speed ​​controller 40. Waste Time Compensator 41 Machine Models 42. Wasted Time Model 43. High-pass filter (HPF) 100 Electric motor control device 131, 132, 133, 134 Control device 200,200A Motor Control System

Claims

1. An electric motor control device that provides feedback control of the speed or position of an electric motor in a control object that can be considered as two inertial systems, in which an electric motor and a mechanical load are coupled, A speed controller that performs feedback control to generate a torque command that brings the deviation between the speed command and the estimated speed closer to zero, A compensator that incorporates a mechanical model in which the inertia, anti-resonant frequency, and resonant frequency have values ​​corresponding to the actual values ​​of the controlled object, and the damping coefficient has a value of (1 / √2) or more and 1 or less, and further comprises a compensator that compensates for the phase delay caused by the dead time of the speed control loop that controls the speed of the electric motor, The estimated speed value is calculated by adding the output value of the compensator and the detected speed value. Electric motor control device.

2. J ｔ Let inertia be ω ｚ The anti-resonance frequency is ω μ The resonant frequency is ζ ｚ and ζ μ When is the damping coefficient and s is the Laplace operator, The aforementioned mechanical model has a transfer function G shown in Equation 9. ｍ (s) represents, The electric motor control device according to claim 1. [Math 1]

3. The mechanical model is ζ ｚ = ζ μ When = 1, the transfer function G ｍ represented by (s), The electric motor control device according to claim 2. [Math 2]

4. The phase delay caused by the aforementioned dead time is compensated for via a high-pass filter. The electric motor control device according to any one of claims 1 to 3.

5. Feedforward control is used in combination with the feedback control of the speed or position of the aforementioned electric motor. The electric motor control device according to claim 4.

6. Feedforward control is used in combination with the feedback control of the speed or position of the aforementioned electric motor. The electric motor control device according to any one of claims 1 to 3.

7. The output of the feedforward control is not applied to the input of the compensator that compensates for the phase delay caused by the dead time. The motor control device according to claim 6.

8. A motor control method using a motor control device that provides feedback control of the speed or position of a motor in a control object that can be considered as two inertial frames, in which a motor and a mechanical load are coupled, The aforementioned electric motor control device is A speed controller that performs feedback control to generate a torque command that brings the deviation between the speed command and the estimated speed closer to zero, A compensator that incorporates a mechanical model in which the inertia, anti-resonant frequency, and resonant frequency have values ​​corresponding to the actual values ​​of the controlled object, and the damping coefficient has a value of (1 / √2) or more and 1 or less, and further comprises a compensator that compensates for the phase delay caused by the dead time of the speed control loop that controls the speed of the electric motor, The estimated speed value is calculated by adding the output value of the compensator and the detected speed value. Electric motor control method.

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