Position control device

Abstract

The present invention provides a position control device that can maintain high command tracking performance even when multiple backlash sections exist in the torque transmission path. [Solution] The position control device of the target plant 100 temporarily operates the target plant 100 in a manner that reverses the direction of travel with backlash compensation turned OFF, and the position detection value of the load end 104 X L Based on the position command value X at the time when the position deviation DIF between the position command value X and the position command value X increases sharply, multiple backlash sections BL k For each of these, the coefficient M for inversion detection. k A coefficient calculation unit 10 calculates the coefficient M, and operates the target plant 100 with the backlash compensation turned ON, and the coefficient M k The position command value X and the moment of inertia J of the entire load. L Based on this, the load-side transmission torque τ Lk The reversal detection unit 12 detects the timing when the reversal occurs, and at the detected timing, the backlash compensation value X BLc It includes a compensation value calculation unit 13 that increases or decreases the value.

Description

[Technical Field]

[0001] This specification discloses a position control device for a target plant in which a backlash section exists in the torque transmission path from the motor. [Background technology]

[0002] Position control devices have long been widely known that control motors so that the position of the target plant (hereinafter referred to as the "load position") follows a position command value. Such position control devices are applied, for example, to the axis control of numerically controlled machines.

[0003] In this case, a backlash may exist in the torque transmission path between the motor and the target plant. This backlash is the gap or deflection between the torque transmission members. This backlash creates a dead zone where torque is temporarily not transmitted when the direction of motion reverses. This backlash then causes command tracking errors.

[0004] Therefore, techniques have been proposed to eliminate command tracking errors caused by backlash. For example, Patent Document 1 discloses a correction device for correcting backlash that occurs between the driving gear and the driven gear. The correction device in Patent Document 1 calculates the transmission torque applied from the driving gear to the driven gear based on position command information. The correction device then determines that backlash has occurred when the sign of this transmission torque reverses, and corrects the command value to compensate for the backlash. According to this technique, command tracking errors caused by backlash can be reduced to some extent. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2002-366230 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, depending on the configuration of the torque transmission path, there may be not just one, but multiple backlash sections. Conventional technologies such as Patent Document 1 cannot handle cases where there are multiple backlash sections in the torque transmission path. As a result, conventional technologies suffered from reduced command tracking performance when multiple backlash sections were present in the torque transmission path.

[0007] Therefore, this specification discloses a position control device that can maintain high command tracking performance even when multiple backlash sections exist in the torque transmission path. [Means for solving the problem]

[0008] The position control device disclosed herein is a position control device for a target plant in which a motor and a load end are connected via a torque transmission path having a plurality of backlash sections, and comprises: a coefficient calculation unit that, with backlash compensation turned OFF, temporarily operates the target plant to reverse the direction of travel, and calculates a coefficient for reversal detection for each of the plurality of backlash sections based on the position command value at the timing when the position deviation between the position detection value and the position command value of the load end increases sharply, or the speed command value and acceleration command value at the timing when the deviation increases sharply; a reversal detection unit that operates the target plant with backlash compensation turned ON, and detects the timing when the load-side transmission torque at each of the plurality of backlash sections reverses based on the coefficient for reversal detection, the position command value, and the moment of inertia of the entire load; a compensation value calculation unit that increases or decreases the backlash compensation value at the timing when the load-side transmission torque reverses; and a position control loop unit that controls the position of the motor so that the position detection value of the load end becomes the position command value after correction by the backlash compensation value.

[0009] In this case, the compensation value calculation unit may add or subtract the backlash amount of the k-th backlash portion from the motor to the current backlash compensation value at the timing when the load-side transmission torque reverses in the k-th backlash portion.

[0010] Also, the position control loop unit controls the position of the motor so that the absolute value of the position error, which is the difference between the compensated position command value and the position feedback value, becomes small. The position feedback value may include the sum of the position detection value at the load end and the backlash compensation value.

[0011] Also, the position command value in the preliminary operation is sinusoidal represented by X = X0 + R0×sinθ. When the coefficient calculation unit sets θ to be the θ at which the position deviation suddenly increases due to the k-th backlash portion counted from the motor , L , L , and sets the inertia moment of the entire load to J L the coefficient M k corresponding to the k-th backlash portion may be calculated based on M k =(sinθ1 / sinθ k )×J L .

[0012] Also, when the compensation value calculation unit sets the load-side transmission torque in the k-th backlash portion to τ Lk , the sliding friction torque to τ F , and the acceleration command value to A, the load-side transmission torque τ Lk may be calculated by the formula τ k =M F ×A + τ Lk .

[0013] Also, the position command value in the preliminary operation is sinusoidal represented by X = X0 + R0×sinθ. When the coefficient calculation unit sets the acceleration command value at the time when the position deviation suddenly increases due to the k-th backlash portion counted from the motor to A k the coefficient N k corresponding to the k-th backlash portion may be set to N k=sgn(V k ) / A k It may also be calculated based on the following formula.

[0014] Furthermore, the compensation value calculation unit determines the determination parameter r when the velocity command value is V, the acceleration command value is A, and the sign function is sgn. Lk to, r Lk =-A×N k The calculation is based on the formula +sgn(V), and the determination parameter r Lk The timing at which the sign of the value reverses may be detected as the timing at which the load-side transmission torque in the k-th backlash section reverses. [Effects of the Invention]

[0015] According to the technology disclosed herein, high command tracking performance can be maintained even when multiple backlash sections are present in the torque transmission path. [Brief explanation of the drawing]

[0016] [Figure 1] This is a block diagram showing the configuration of a position control device. [Figure 2] This is a schematic diagram of the target plant. [Figure 3] This figure shows an example of changes in position command value, acceleration command value, and sliding friction torque. [Figure 4] This figure shows the changes in position command value, torque, and position deviation within the range Sa shown in Figure 3. [Figure 5] This is a schematic diagram of a target plant that has only one backlash section. [Figure 6] This figure shows the changes in position command values ​​and torque in the target plant shown in Figure 5. [Figure 7] This is a block diagram showing other examples of position control devices. [Modes for carrying out the invention]

[0017] The configuration of the position control device will be described below with reference to the drawings. Figure 1 is a block diagram showing the configuration of the position control device. Figure 2 is a schematic diagram of the target plant 100. As shown in Figure 2, the target plant 100 has a motor 102, a torque transmission path 110, a load end 104, and a current control unit 120. The output torque of the motor 102 is transmitted to the load end 104 via the torque transmission path 110. The position control device controls the position X of the load end 104 according to the position command value X commanded from a higher-level device (not shown). L To control the torque command value τ of motor 102, m The current control unit 120 calculates the torque command value τ. m A current corresponding to the current is applied to the motor 102. The current control unit 120 includes, for example, an inverter. Such position control devices are applied, for example, to the axis control of numerically controlled machines (e.g., machine tools) or robots. Such position control devices require system stability and high command tracking performance.

[0018] Here, as shown in Figure 2, the torque transmission path 110 of the target plant 100 has multiple (two in the illustrated example) backlash sections BL1 and BL2. In the following, if it is not necessary to distinguish between multiple backlash sections BL1 and BL2, the subscript will be omitted and it will be written as "backlash section BL". Also, the k-th backlash section counting from the motor 102 will be referred to as "backlash section BL k This will be written as "[...]". The same applies to other elements.

[0019] The backlash section BL is the area where a gap or deflection occurs when the drive direction is reversed. Backlash amount X BLk Each backlash section BL k This is the amount of gap or deflection in the backlash section BL. Because of this backlash section BL, when the drive direction reverses, a dead zone occurs where movement is temporarily not transmitted to the load side, i.e., backlash. This backlash causes a command tracking error. To illustrate this, Figure 2 shows the moment of inertia J. Lk and backlash section BL kThe diagram illustrates a model composed solely of these elements.

[0020] As mentioned above, the position control device in this example is used for axis control of numerically controlled machines or robots. Typically, the axis to be controlled is connected to a first load end that drives in the first axis direction and a second load end that drives in the second axis direction. By driving these first and second load ends in a sinusoidal wave pattern with a phase difference of 90 degrees from each other, the axis to be controlled is driven in an arc shape. Below, we will explain using the case where the load end 104 is driven in a sinusoidal wave pattern as an example to drive the axis to be controlled in an arc shape. When the load end 104 is driven in a sinusoidal wave pattern, the position command value X is expressed by Equation 1 using the radius of the arc R0, the offset of the arc center X0, the angular velocity ω0, and the time t. X = X0 + R0 × sin(ω0t) =X0+R0×sinθ Equation 1

[0021] A position control device is, physically, a computer having a processor and memory. Such a position control device may be configured, for example, by combining multiple physically separated computers. Alternatively, the position control device may be configured, for example, as a numerical control device.

[0022] Functionally, the position control device controls the torque command value τ, as shown in Figure 1. m The system is broadly divided into a position control loop unit 20 that calculates the position command value X and a backlash compensation unit 21 that compensates for backlash. The position control loop unit 20 receives the position command value X from a higher-level device. The position control loop unit 20 also receives the load position detection value X L and motor position detection value X m Accepts. Load position detection value X L This is a position detection signal installed at the load end 104. Also, the motor position detection value X m This is a signal obtained by converting the signal from the rotation angle detector installed on the motor 102 into a linear distance signal.

[0023] The position command value X is the backlash compensation value X output from the backlash compensation unit 21. BLcThis is added and compensated. Compensated position command value X c However, it is differentiated with respect to time by the differentiator 51, and the velocity feedforward quantity V fc This is the result. Also, the subtractor 50 calculates the compensated position command value X. c Position feedback value X f Subtract the position error er. Note that the position feedback value X f The calculation of will be described later. The position error amplifier 52 amplifies the position error er by a position loop gain of Kp. The outputs of the differentiator 51 and the position error amplifier 52 are added together by the adder 54 to obtain a speed command. The converter 60 converts this speed command into angular velocity to obtain the angular velocity command value ω m * Outputs.

[0024] Motor position detection value X m This is differentiated with respect to time by the differentiator 56, and then the motor speed ω is obtained by the converter 19. m It is converted to the speed command value ω. Subtractor 55 converts the speed command value ω m * From motor speed ω m Subtracting this value outputs the speed error. The speed error is multiplied by Gv (generally proportional-integral amplification is used) by the speed error amplifier 57, and the torque command value τ m It will be output as follows.

[0025] Position feedback value X f This is the load position detection value X L Motor position detection value X m The detected value deviation ΔX obtained by subtracting the backlash compensation value X BLc This is the compensated value. More specifically, the load position detection value X L Motor position detection value X m This is subtracted, and the detected value deviation ΔX is calculated. Next, the backlash compensation value X is added to this detected value deviation ΔX. BLc This value is added. This added value is then subjected to low-pass filtering by the LPF processing unit 17. The output value of the LPF processing unit 17 and the motor position detection value X m And are added together, resulting in the position feedback value X f This is the result. Position feedback value Xf The reason for calculating it this way will be explained later.

[0026] Next, the backlash compensation unit 21 will be described. Before describing the detailed configuration of the backlash compensation unit 21, the behavior of the target plant 100 when the drive direction is reversed will be described. Figure 3 shows the position command value X, the acceleration command value A, and the sliding friction torque τ. F This figure shows an example of the changes.

[0027] As described above, in this example, a sinusoidal position command value X = X0 + R0 × sin(θ) is input. In this case, the drive direction reverses at the timings θ = 1 / 2π and θ = 3 / 2π. The acceleration command value A is obtained by differentiating the position command value X twice. This acceleration command value A has a waveform with a phase difference of π relative to the position command value X. Sliding friction torque τ F This is the sliding friction torque required to drive the load.

[0028] In this case, backlash occurs in the ranges Sa and Sb, which are around 1 / 2π and 3 / 2π, respectively. The load-side transmission torque τ in this range Sa. Lk The changes will be explained with reference to Figures 4 to 6.

[0029] First, let's consider the case where there is only one backlash section BL1 in the torque transmission path 110, as shown in Figure 5. In Figure 5, J m This indicates the moment of inertia of motor 102, and J L1 This shows the moment of inertia from the backlash section BL1 to the load end 104. Note that in the example in Figure 5, J L1 This is the total moment of inertia J, which is the moment of inertia of the entire load. L It is equal to . Also, the sliding friction torque τ when moving the load end 104 is at the load end 104. F This is at work. Below, the left direction of the page will be referred to as the "N direction," and the right direction of the page will be referred to as the "P direction."

[0030] The backlash portion BL1 has an output end OUT on the N-direction side N and an output end OUT on the P-direction side P In the example of FIG. 5, the input end IN is in contact with the output end OUT N while being separated from the output end OUT P Therefore, in the state of FIG. 5, when moving in the N direction, the load position detection value X L is consistent with the motor position detection value X m and X L = X m is established. On the other hand, when the moving direction is reversed and moving in the P direction, the motor 102 needs to operate additionally by the backlash amount X BL1 That is, it is necessary to make X L = X m + X BL1

[0031] Therefore, it is conceivable to compensate the speed feedforward amount V fc with the backlash speed V BL at the timing of the reversal of the traveling direction of the position command value X. The backlash speed V BL is, for example, a time function of the impulse response of the time constant T represented by V BL = V BL0 × e -t÷T and the area thereof corresponds to the backlash amount X BL1 It is conceivable to add or subtract this backlash speed V BL to the speed feedforward amount V fc according to the reversed direction at the timing of the reversal of the traveling direction.

[0032] However, in order to ensure high tracking performance even after reversing the moving direction, it is necessary to quickly execute the motor operation corresponding to the backlash amount X L1 at the reversal timing of the load-side transmission torque τ BL1 The load-side transmission torque τ L1 is the torque transmitted from the backlash portion B L1 to the load side. When the second derivative value of the position command value X is used as the acceleration command value A, the load-side transmission torque τ​L1 is represented by the following Equation 2. τ L1 = J L1 × A + τ F Equation 2

[0033] The sliding friction torque τ F is a value whose absolute value is constant regardless of the speed and whose sign is reversed when moving in the P direction and when moving in the N direction. That is, the sliding friction torque τ F is expressed by Equation 3. In Equation 3, τ FP is a predetermined fixed value, and sgn(i) is a sign function. The sign function is a function that outputs 1 when the argument i is positive, outputs -1 when the argument i is negative, and outputs 0 when the argument i is 0. τ F = sgn(V) × τ FP Equation 3

[0034] In order to maintain high tracking performance, it is necessary to compensate the command value according to the state of the load side transmission torque τ L1 represented by Equation 2. FIG. 6 is a schematic diagram showing the changes in the position command value X and the torque in the target plant 100 of FIG. 5. In the case of the example of FIG. 6, θ1 at which τ F = J L1 × A holds is the timing at which the load side transmission torque τ L1 is reversed.

[0035] Here, when there is only one backlash portion BL, J L = J L1 is true. Further, the total inertia moment J L can be easily online identified from the motor inertia moment J m (constant value) and the real-time acceleration / deceleration characteristics. Also, the sliding friction torque τ F has been measured or identified in advance. Therefore, when there is only one backlash portion BL, the state of the load side transmission torque τ L1 can be easily determined from the total inertia moment J L of the load, the acceleration command value A, and the sliding friction torque τ F .

[0036] On the other hand, as shown in Figure 2, when there are multiple backlash sections in the torque transmission path 110, the load-side transmission torque τ is determined for each of the multiple backlash sections BL1, BL2. L1 ,τ L2 The state is determined, and the backlash compensation value X is set according to each determination result. BLc This needs to be changed. In other words, if there are multiple backlash sections, the load-side transmission torque τ of one backlash section BL1 obtained by equation 2 above. L1 Simply monitoring the backlash compensation value X is not enough to determine the appropriate backlash compensation value. BLc It is not possible to calculate this. As a result, high command tracking performance cannot be maintained. Therefore, in this example, multiple backlash sections BL k Load-side transmission torque τ in each case Lk The state is identified. The principle of backlash compensation in this example will be explained below.

[0037] First, referring to Figure 2, we will explain the case where there are multiple backlash sections BL1 and BL2 in the torque transmission path 110. Although Figure 2 only shows two backlash sections BL, in the following explanation, we will assume that there are n backlash sections BL. Furthermore, in the following, we will refer to the k-th backlash section BL, which is the k-th backlash section from the motor. k and the next backlash section BL k+1 (Backlash section BL) k+1 If not present, the moment of inertia between the load end 104) is defined as the "kth partial moment of inertia J Lk It is called "the kth backlash section BL". k The torque transmitted to the load side is defined as "the kth load-side transmission torque τ Lk It is called "sliding friction torque τ during load transfer". F All of these are defined as the sliding friction torque at the load end 104.

[0038] kth load-side transmission torque τ Lk This can be expressed by the following equations 4 and 5. τ Lk =M k ×A+τ F formula 4 M k = J Lk + J Lk+1 + ··· + J Ln Equation 5

[0039] Therefore, in the case of the example in FIG. 2, the first load side transmission torque τ L1 and the second load side transmission torque τ L2 become Equation ⑥ and Equation ⑦, respectively. τ L1 = (J L1 + J L2 ) × A + τ F = J L × A + τ F Equation ⑥ τ L2 = J L2 × A + τ F Equation ⑦

[0040] Next, consider the case where a sinusoidal position command value X is input with the backlash compensation value X BLc set to 0 (i.e., the backlash compensation is turned off). In this case, the position command value X is expressed as X = X0 + R0 × sin θ. Here, when θ is less than θ1 in FIG. 4, the position command value X is advancing in the N direction, but the first load side transmission torque τ L1 is less than 0. Therefore, the input end IN of the first backlash portion BL1 is in contact with the output end OUT N on the N-direction side. That is, the gap X N between the input end IN and the output end OUT S1 is 0.

[0041] After that, when θ > θ1, the first load side transmission torque τ L1 > 0. As a result, the motor 102 is driven additionally so that the input end IN moves toward the output end OUT P on the P-direction side. Here, when the gap X S1 is less than the backlash amount X BL1 , torque is not transmitted to the end side from the first backlash portion BL1. Therefore, since the deceleration torque is insufficient, the load position detection value X LThe position command value X overshoots in the N direction. As a result, as shown in the third row of Figure 4, immediately after angle θ1, the position deviation DIF = XX L The number is rapidly increasing.

[0042] Similarly, in the second backlash section BL2, the second load side transmission torque τ L2 Immediately after the angle θ2 where the polarity reverses from negative to positive, the positional deviation DIF increases sharply. Note that θ in Figure 4 O The sharp increase in position deviation DIF in this context is due to the sliding friction torque τ F This is a delay in responding to sudden changes, and not a delay caused by backlash.

[0043] To suppress the sharp increase in position deviation DIF caused by backlash, the timing at which the position deviation DIF sharply increases, i.e., the transmission torque τ on the kth load side, is important. Lk The backlash compensation value X is added to the position command value X at the moment the sign of the symbol changes. BLc The k-th backlash section BL k Backlash amount X BLk It only needs to be increased or decreased by that amount. To explain it more generally, the k-th backlash section BL k The corresponding compensation value X BLck This is given by equation 8.

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[0044] Also, the backlash compensation value X is added to the position command value X. BLc This is a multiple backlash section BL k Each compensation value X BLck This is the value obtained by adding the backlash compensation value X. BLc This is given by equation 9. X BLc =X BLc1 +X BLc2 +···+X BLcn formula 9

[0045] By the way, as is clear from the explanation so far, the backlash compensation value XBLc To calculate this, multiple backlash sections BL k Load-side transmission torque τ in each case Lk It is necessary to understand the sign (i.e., positive or negative) of the torque. However, the load-side transmitted torque τ Lk To determine the sign of the coefficient M in Equation 4, k The value of coefficient M needs to be determined. k As shown in Equation 5, the corresponding backlash section BL k This is the moment of inertia from the load end 104, and the load-side transmitted torque τ. Lk This is the coefficient used for detecting inversion.

[0046] The coefficient M k To understand this, in this example, before operating the target plant 100 under normal conditions, the backlash compensation value X BLc With the value set to 0, the target plant 100 is temporarily operated by the position command value X of Equation 1, which changes sinusoidally. In this case, as described above, the load-side transmission torque τ Lk The timing at which the sign changes, that is, angles θ1, θ2, ..., θ n This causes a sharp increase in the positional deviation (DIF).

[0047] Here, the load-side transmission torque τ at angle θ1 L1 is, angle θ k Load-side transmission torque τ Lk It is equal to θ1,θ k The acceleration command values ​​A for each are A1 and A k In that case, the following equation 10 holds true. M1×A1+τ F =M k ×A k +τ F M1 × A1 = M k ×A k Formula 10

[0048] Furthermore, the acceleration command value A is the second derivative of the position command value X = X0 + R0 × sin(θ), so A = -R0ω0 2 ·sin(ω0t)=-R0ω0 2·sin(θ). Furthermore, M1 is the total moment of inertia J L Therefore, equation 10 can be transformed into equation 11. J L ×(-R0ω0 2 ·sin(θ1))=M k ×(-R0ω0 2 ·sin(θ k )) M k =(sinθ1 / sinθ k )×J L Formula 11

[0049] As is clear from Equation 11, the coefficient M k This refers to the angle θ indicated by the position command value X when the position deviation DIF increases sharply during trial operation. k And, the total moment of inertia J L Therefore, it can be calculated from the above. In this example, a trial run is performed before the normal operation of the target plant 100, and the angle θ when the position deviation DIF increases sharply is calculated. k Identify this angle θ. k and total moment of inertia J L Applying this to Equation 11, multiple backlash sections BL k The coefficient M corresponding to each k The coefficient M is calculated. k This coefficient M is stored in the reversal detection unit 12 as a coefficient for reversal detection. When the target plant 100 is operated under normal conditions, this coefficient M k Based on this, the load-side transmission torque τ Lk The sign state, and consequently the backlash compensation value X BLc Calculate.

[0050] Next, the configuration of the backlash compensation unit 21, which is built based on these principles, will be described. As shown in Figure 1, the backlash compensation unit 21 has a coefficient calculation unit 10, an inversion detection unit 12, and a compensation value calculation unit 13. When the calculation flag Ftun is ON, the coefficient calculation unit 10 calculates the coefficient M described above. k The calculation is performed. Note that the calculation flag Ftun is also input to the compensation value calculation unit 13, and when the calculation flag Ftun is ON, the compensation value calculation unit 13 calculates the backlash compensation value X.BLc It outputs 0. In other words, when the calculation flag Ftun is ON, backlash compensation is OFF.

[0051] The coefficient calculation unit 10 receives the position command value X and the load position detection value X when Ftun=ON. L , and the total moment of inertia J L Based on this, coefficient M k The coefficient calculation unit 10 calculates the position command value X and the load position detection value X. L Based on this, the position deviation DIF is calculated. Then, at the moment when the position deviation DIF increases sharply, the angle θ indicated by the position command value X is calculated. k This is temporarily stored. The timing of a sharp increase in the position deviation DIF may also be determined, for example, from the time derivative of the position deviation DIF. That is, the timing when the time derivative of the position deviation DIF exceeds a predetermined threshold may be identified as the timing of a sharp increase in the position deviation DIF.

[0052] Multiple backlash sections BL k The corresponding angle θ k If the angle θ can be identified, the coefficient calculation unit 10 will determine k And, the total moment of inertia J L Applying this to equation 11, we get the coefficient M k Calculate the multiple backlash sections BL. k The coefficient M corresponding to each k If obtained, the coefficient calculation unit 10 calculates these multiple coefficients M k This is output to the inversion detection unit 12. Also, multiple coefficients M k However, once the calculation is complete, the calculation flag Ftun switches from ON to OFF, and backlash compensation is turned ON. This switching of the calculation flag Ftun may be done automatically according to the calculation status in the coefficient calculation unit 10, or it may be switched manually by the operator.

[0053] The inversion detection unit 12 uses multiple coefficients M k Based on this, multiple backlash sections BL k Load-side transmission torque τ in each case LkThe sign state is calculated. Specifically, the reversal detection unit 12 receives the velocity command value V obtained by first differentiating the position command value X, the acceleration command value A obtained by second differentiating the position command value X, and the sliding friction torque τ. F The following is input. Note that in normal operation with backlash compensation turned ON, the position command value X is not limited to sinusoidal commands, but various motion position command values ​​X are input. The inversion detection unit 12 has multiple backlash units BL k Load-side transmission torque τ in each case Lk The load-side transmission torque τ is calculated based on Equation 4. Lk The discriminant signal SN obtained by applying a sign function to it. k =sgn(τ Lk The result is output to the compensation value calculation unit 13. As described above, the sign function sgn(i) outputs 1 when the argument i is positive, -1 when the argument i is negative, and 0 when the argument i is 0.

[0054] The compensation value calculation unit 13 calculates the backlash compensation value X BLc The compensation value calculation unit 13 outputs the following in advance: k Each backlash amount X BLk It stores the following. Here, as mentioned above, when the calculation flag Ftun is ON, the compensation value calculation unit 13 calculates X BLc Set = 0. On the other hand, when the calculation flag Ftun is OFF, the compensation value calculation unit 13 calculates the backlash compensation value X according to equations 8 and 9. BLc Calculate the following. Note that in Equation 8, SN k If >0, X BLck =X BLk And, SN k If ≤ 0, X BLck = 0

[0055] Backlash compensation value X output from compensation value calculation unit 13 BLc This is added to the position command value X, resulting in the compensated position command value X. c This is the result. And this compensated position command value X c Based on this, the velocity feedforward amount V fcBy calculating this, the velocity feedforward amount V fc The backlash speed compensation value V BLc This will include multiple backlash sections BL. k Even when such a feature exists, high position tracking performance can be maintained.

[0056] Furthermore, as shown in Figure 1, in this example, the load position detection value X L and motor position detection value X m The deviation from the detected value (detection deviation ΔX) is given by the backlash compensation value X. BLc Add the compensated detection deviation ΔX c Furthermore, this compensated detection deviation ΔX is calculated. c The value obtained by applying the LPF processing unit 17 and the motor position detection value X m Adding these together, we get the position feedback value X f Calculate.

[0057] Here, if we express the output of the LPF processing unit 17 as α times the input (where 0 ≤ α ≤ 1), then the position feedback value X f This can be expressed by equation 12. X f =α{(X L -X m )+X BLc}+X m =X L +(1-α)(X m -X L ) + α × X BLc Formula 12

[0058] Here, (X m -X L ) and X BLc If they are equal, X c =X m And, X c =X L +X BLc , in other words, X = X L A position control system can be constructed in which both conditions are met. This ensures high position tracking performance. Thus, according to the position control device in this example, the position command value X is set to a backlash compensation value X. BLc Compensated position command value X (with added compensation)c Even when a fully closed position control system is configured with X as the input, the load position detection value X depends on the direction of movement. L Backlash compensation value X BLc Therefore, no physical displacement will occur.

[0059] Furthermore, in this example, the backlash compensation value X BLc This is applied to the position command value X, not the speed command value. Therefore, the response operation of the position control system can compensate for the response error of the speed control system. As a result, at each part where backlash operation occurs, the load position detection value X of the target plant 100 is applied. L This reduces the tracking error with respect to the position command value X.

[0060] Next, other forms will be described. In the above description, the load-side transmission torque τ shown in Equation 4 is Lk Based on the calculation results, multiple backlash sections BL k The corresponding compensation value X BLck The timing of the switchover is being determined. However, the compensation value X BLck When determining the switching timing, the load-side transmitted torque τ is not necessarily the determining factor. Lk There is no need to perform the calculation.

[0061] In other words, substituting equations 3 and 11 into equation 4, the load-side transmission torque τ Lk This can be converted to equation 13. τ LK =J L (sinθ1 / sinθ k ) × A + τ FP ×sgn(V) Equation 13

[0062] Here, the backlash compensation value X BLc When the target plant 100 is put into temporary operation with =0, the first load side transmission torque τ is at angle θ1 corresponding to the transmission torque sign reversal timing. L1 = 0. The velocity command value V1 at this angle θ1 is V1 = R0 × ω0 × cosθ1, and the acceleration command value A1 is A1 = -R0 × ω0 2This becomes ×sinθ1. Substituting these equations into equation 13 yields equation 14.

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[0063] Furthermore, rearranging equation 14 yields equation 15.

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[0064] Substituting equation 15 into equation 13 and rearranging, we obtain equation 16.

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[0065] Here, τ FP This is a predetermined fixed value, and its sign is always positive. Therefore, the load-side transmitted torque τ Lk Determining the sign of is done using the determination parameter r shown in Equation 17. Lk This is equivalent to determining whether something is positive or negative.

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[0066] Here, A k =-R0×ω0 2 ×sinθ k Therefore, from Figure 4, sgn(ω0cosθ1)=sgn(V1)=sgn(V k ) Substituting these into equation 17 and rearranging, we obtain equation 18.

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[0067] And the determination parameter r shown in equation 18. Lk The timing at which the positive and negative signs reverse is determined by multiple backlash sections BL k Each load-side transmitted torque τ LkThis can be considered the moment when the sign of the function reverses.

[0068] In this case, the coefficient calculation unit 10 calculates the coefficient N shown in Equation 19. k The coefficient for inversion detection is calculated and output to the inversion detection unit 12. N k =sgn(V k ) / A k formula 19

[0069] Furthermore, the inversion detection unit 12 determines the determination parameter r according to equation 18. Lk The inversion detection unit 12 calculates the determination parameter r. Lk Apply the sign function to the discriminant signal SN k =sgn(r Lk The output is as follows: The compensation value calculation unit 13 calculates the discrimination signal SN k Depending on the situation, the backlash compensation value X BLc Change it.

[0070] Even in this case, the load-side transmission torque τ Lk The timing of the reversal can be accurately determined, and consequently, the backlash compensation value X BLc The amount is increased or decreased at the appropriate time. As a result, multiple backlash sections BL k Even when such a feature exists, high position tracking performance can be maintained.

[0071] It should be noted that the configurations described so far are all examples, and other configurations may be changed as long as the configuration of claim 1 is met. For example, the backlash section BL k The number of such values ​​is not particularly limited, as long as it is 2 or more. Also, the position feedback value X f The method of calculation may also be changed. For example, in the example in Figure 1, the position feedback value X f The motor position detection value X m However, addition and subtraction are performed. However, as shown in Figure 7, the motor position detection value X m This is the position feedback value X f It is also acceptable to configure it so that it is not entered into the input field. [Explanation of symbols]

[0072] 10 Coefficient calculation unit, 12 Inversion detection unit, 13 Compensation value calculation unit, 17 LPF processing unit, 19, 60 Converter, 20 Position control loop unit, 21 Backlash compensation unit, 50, 55 Subtractor, 51, 56 Differentiator, 52 Position error amplifier, 54 Adder, 57 Speed ​​error amplifier, 100 Target plant, 102 Motor, 104 Load terminal, 110 Torque transmission path, 120 Current control unit, A Acceleration command value, BL Backlash unit, DIF Position deviation, Ftun Calculation flag, IN Input terminal, J L Total moment of inertia, J Lk k-th partial moment of inertia, J m Motor moment of inertia, M k ,N k Coefficient, OUT N Output terminal, OUT P Output terminal, SN k Discrimination signal, X position command value, X BLc Backlash compensation value, X BLk Backlash amount, X L Load position detection value, X c Compensated position command value, X f Position feedback value, X m Motor position detection value, τ F Sliding friction torque, τ Lk k-th load side transmission torque, τ m Torque command value.

Claims

1. A position control device for a target plant, in which a motor and a load end are connected via a torque transmission path having multiple backlash sections, With backlash compensation turned OFF, the target plant is temporarily operated to reverse the direction of travel, and a coefficient calculation unit calculates a coefficient for reversal detection for each of the multiple backlash sections based on the position command value at the moment when the position deviation between the position detection value and the position command value of the load end increases sharply, or the speed command value and acceleration command value at the moment of the sharp increase. The target plant is operated with the backlash compensation turned ON, and a reversal detection unit detects the timing at which the load-side transmission torque reverses at each of the multiple backlash sections based on the reversal detection coefficient, the position command value, and the moment of inertia of the entire load. A compensation value calculation unit that increases or decreases the backlash compensation value at the timing when the load-side transmission torque reverses, A position control loop unit controls the position of the motor such that the position detection value at the load end becomes the position command value after correction by the backlash compensation value, A position control device characterized by comprising:

2. A position control device according to claim 1, The position control device is characterized in that the compensation value calculation unit adds or subtracts the amount of backlash in the k-th backlash section from the current backlash compensation value at the timing when the load-side transmission torque reverses in the k-th backlash section counting from the motor.

3. A position control device according to claim 2, The position control loop controls the motor's position such that the absolute value of the position error, which is the difference between the compensated position command value and the position feedback value, becomes smaller. The position feedback value includes the sum of the position detection value of the load end and the backlash compensation value. A position control device characterized by the following:

4. A position control device according to claim 1, The position command value in the aforementioned trial run is X = X ０ +R ０ It is a sinusoidal wave represented by ×sinθ, When the position deviation rapidly increases due to the k-th backlash portion counted from the motor, the coefficient calculation unit sets θ as θ ｋ ; when the moment of inertia of the entire load is J Ｌ , the coefficient M ｋ corresponding to the k-th backlash portion is calculated based on M ｋ = (sinθ １ / sinθ ｋ ) × J Ｌ . A position control device characterized by the following:

5. A position control device according to claim 4, The compensation value calculation unit calculates the load-side transmission torque in the k-th backlash section as τ Ｌｋ , sliding friction torque τ Ｆ If the acceleration command value is A, then τ Ｌｋ = M ｋ ×A + τ Ｆ In the equation, the load-side transmission torque τ Ｌｋ A position control device characterized by calculating a value.

6. A position control device according to claim 1, The position command value in the aforementioned trial run is X = X ０ +R ０ It is a sinusoidal wave represented by ×sinθ, The coefficient calculation unit calculates the acceleration command value A when the position deviation increases sharply due to the k-th backlash section counting from the motor. ｋ In this case, the coefficient N corresponding to the k-th backlash portion ｋ N ｋ = sgn(V ｋ ) / A ｋ It is calculated based on the formula, A position control device characterized by the following:

7. A position control device according to claim 6, The compensation value calculation unit determines the determination parameter r when the velocity command value is V, the acceleration command value is A, and the sign function is sgn. Ｌｋ to, r Ｌｋ = -A × N ｋ The determination parameter r is calculated based on the formula +sgn(V). Ｌｋ A position control device characterized by detecting the timing when the sign of the value is reversed as the timing when the load-side transmission torque in the k-th backlash section is reversed.

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