JP3370040B2 - Speed control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device using a speed command having an acceleration / deceleration rate. 2. Description of the Related Art A conventional speed control apparatus includes an overshoot and / or overshoot of a control object (for example, the rotation speed of an electric motor) which occurs when shifting from a speed change range of an acceleration / deceleration rate as a speed command to a constant speed range. Alternatively, speed fluctuations due to load disturbances (fluctuations) occur, and the following performance of speed control or the like is reduced. For this reason, the accuracy of speed control or the accuracy of positioning cannot be increased, and therefore, the accuracy of feeding, cutting, and processing of materials and the like cannot be obtained. [0003] Such a conventional speed control device will be described. 6 shows a conventional speed control block diagram, FIG. 7 shows a control block diagram obtained by converting the conventional speed control block diagram into a transfer function, and FIG. 8 shows a conventional acceleration / deceleration rate diagram. [0004] As shown in FIG.
The speed command ω * is input to the speed controller 52 through the subtractor 51, and its output is input to the inertia load (control target) 20, and the inertia load 20 detects the speed detection value ω. By feeding back the detected speed detection value ω to the subtractor 51, a speed control loop is formed. The control method of the speed controller 52 is generally a proportional-integral speed control method (hereinafter referred to as PI speed control).
Has been adopted. For this reason, when the speed command ω * having acceleration / deceleration is input, as shown in FIG. 8, when shifting from the shift range to the constant speed range, an overshoot of the control target (for example, the rotation speed of the electric motor) occurs, In addition, the speed fluctuation due to the load disturbance causes the following performance of the speed control device or the like to deteriorate. For this reason, the accuracy of the speed control or the accuracy of the positioning cannot be increased, which causes a failure in obtaining the feed accuracy, the cutting accuracy, and the processing accuracy. In any case, the overshoot generated when shifting from the speed change range of the acceleration / deceleration rate, which is the speed command, to the constant speed range, and speed fluctuation due to load disturbance are caused by PI speed control. In the case of (1), when shifting from the shift range to the constant speed range, the overshoot disappears, but when a load disturbance occurs, the speed fluctuation becomes a steady-state deviation. In the case of PI speed control, the steady-state deviation of speed fluctuation due to load disturbance is small, but overshoot occurs. The PI speed control will be described using a transfer function. FIG. 7 illustrates the speed control loop of FIG. 6 using a transfer function, and includes a subtractor 51, a proportional speed controller 52A, an integral speed controller 52B, an adder 53, and an inertia load 20. Further, the inertia load 20 shown in FIG.
Is an inertia load having a small viscous resistance having a steady load fluctuation, and the speed control device adopts a PI speed control method and can perform speed control with a high torque response. From FIG. 7, a speed deviation e = ω * −ω between the speed command ω * and the speed feedback ω is calculated by the proportional controller 52.
A, the integrator 52 of the integration time T _i by the adder 53
The sum with B is given to the inertia load 20 as a torque command. In this case, the speed response to the load disturbance τ _L is given by: ## EQU1 ## Here, S indicates a differential operator. Further, for the speed command ω *, ## EQU1 ## The disturbance response in the case of the proportional control having no integral element is given by T _i = ∞, where And the desired value response is: ## EQU1 ## As described above, the disturbance response of PI speed control is required to make the speed fluctuation zero with respect to the steady load disturbance τ _L. Therefore, the target response to the speed command having acceleration / deceleration is Overshoot occurs as shown in FIG. In the case of proportional control, the target response to the speed command does not cause overshoot, but the disturbance response causes a steady speed deviation with respect to the load disturbance τ _L. In this PI speed control, the response speed of the speed control system is hindered depending on the compensation condition of the inertia load 20 having a small viscous resistance and having a steady load fluctuation, so that the target speed control characteristic cannot be satisfied. There is a problem. Also, as described above, the PI speed control
Although it matches the speed command value in the steady state, there is a problem that a smooth target response characteristic cannot be obtained because an offset occurs at the rise of the speed, or a problem that overshoot occurs. As one of countermeasures against this problem, a feed-forward control method is used for position control which is higher than speed control. For example, Japanese Patent Application Laid-Open No. 5-19861 discloses a position control device having a position control loop and a speed control loop for a position control device for controlling the position and the like of a feed shaft motor of a machine tool to improve the following performance. In order to eliminate overshoot, a feedforward control method is used in a position control loop. This position control device includes a position detector for detecting the position of the motor and a speed detector for obtaining a speed detection value from the position detection value output from the position detector. Problems caused by the following performance are basically caused by speed control, and these problems cannot be solved only by position control. As described above, in the speed control, the PI speed control uses the response speed of the speed control system depending on the compensation condition of the inertia load having a small viscous resistance having a steady load fluctuation. Therefore, there is a problem that the target speed control characteristic cannot be satisfied. This means that the disturbance response of the PI speed control is required to make the speed fluctuation to be zero with respect to the steady load disturbance. Therefore, in the PI speed control, the target response of the speed command having acceleration / deceleration is The problem of overshoot occurs.In proportional control, the target response of the speed command does not cause overshoot.However, in the disturbance response, a speed deviation occurs with respect to the load disturbance.In the steady state, the speed command value matches the speed command value. Since an offset occurs at the rise of the speed, there is a problem that a smooth target response characteristic cannot be obtained or a problem that an overshoot occurs. As described above, Japanese Patent Application Laid-Open No. 5-198
No. 61 discloses a position control device for controlling the position of a feed shaft motor of a machine tool and the like, wherein the position control device includes a position control loop and a speed control loop. The feedforward control method is used in the position control loop to improve the tracking performance and eliminate the overshoot, and is trying to solve these problems. However, these problems are basically caused by speed control, and these problems cannot be solved only by position control. As described above, depending on PI speed control, in the case of a speed command having an acceleration / deceleration rate, when shifting from the shift range to the constant speed range, overshoot occurs in the inertia load (rotational speed of the electric motor). Problems such as speed fluctuations caused by load fluctuations greatly affect the accuracy of position control or speed control of a rotary traveling cutting machine, traveling cutting machine, sizing feeder, or the like, so that feeding accuracy and / or material cutting accuracy are poor. Become. Further, in a machine tool or the like, an overshoot of the rotation speed of the motor, which occurs when shifting from the speed change region to the constant speed region, appears as a trajectory error at the time of synchronous position control, and reduces the shape accuracy of the workpiece. There is a problem that the surface roughness is reduced. Therefore, an object of the present invention is to solve the problem of overshoot caused by PI speed control, the problem of speed deviation due to load disturbance in disturbance response in proportional control, and the occurrence of offset in speed rise. , A problem that a smooth target response cannot be obtained, or
It solves the problem that overshoot occurs, improves the accuracy of speed control of rotary traveling cutting machines, traveling cutting machines, fixed-size feeders, etc., feeds position control accuracy, cutting accuracy, and improves the accuracy of workpieces such as machine tools. It is to improve the shape accuracy. According to the speed control device of the present invention, the speed control means converts the speed command signal into a reference speed command having a first-order lag element, and the speed signal detected from the inertia load. A speed control loop for feeding back is formed, and acceleration feed forward compensating means, estimated load disturbance feed forward compensating means and inertia identifying means are added to this speed control loop, and inertia which is a control parameter characterizing the operation characteristic of the controlled object is added. By performing identification without providing a special mode for identification, for example, a simulation mode or an auto-tuning mode, the overshoot that occurs when shifting from the speed change region of the acceleration / deceleration rate to the constant speed region is eliminated, and Suppress speed fluctuations due to load fluctuations and achieve target response (speed response) Is matched to the reference model response. According to the present invention, there is provided a speed control apparatus using a speed command having an acceleration / deceleration rate, wherein a reference model setting means for converting the speed command into a reference speed command having a first-order lag element; A speed control means for controlling an inertia load having a small viscous resistance having a load variation, and a speed detection value obtained from the means for detecting the speed of the inertia load, and fed back, and a speed error is obtained from the speed detection value and the reference speed command. Speed control loop means for obtaining and controlling, and an inertia identification means for outputting an inertia model value identified by a torque command obtained from the speed control loop means and a detected speed value of the inertia load,
Means for multiplying the reference speed command and the identified inertia model value and differentiating to obtain an acceleration feedforward control amount, and compensating for the acceleration feedforward,
An acceleration torque command unit that adds the acceleration torque correction value and the acceleration feedforward control amount, which are outputs of the speed controller, and outputs the acceleration torque control amount, and an inertia model value that identifies the acceleration torque control amount. Means for dividing and integrating to obtain an estimated speed, obtaining an estimated load disturbance feedforward control amount resulting from a speed difference between the estimated speed and a speed detection value detected from the inertia load, and performing estimated load disturbance feedforward compensation. By providing inertia, which is a control parameter characterizing the operation characteristic of the controlled object, to the means for compensating the acceleration feedforward and the means for feedforward compensation for the estimated load disturbance without providing a special mode for identification, Occurs when shifting from the speed change range to the constant speed range Eliminate Bashuto, and to suppress the speed fluctuation due to load fluctuation, it is characterized in that to match the target response to the reference model response. According to the present invention, the inertia identifying means converts the detected speed value into a detected speed value having a time delay, and obtains a speed difference from the detected speed value, that is, an acceleration, Acceleration torque estimating means for calculating an acceleration with inertia before correction to obtain an estimated acceleration torque; and estimating the load torque by calculating the estimated acceleration torque output from the acceleration torque estimating means with the torque command to obtain the estimated load torque. Means for obtaining an acceleration torque command by subtracting the estimated acceleration torque from the torque command, and obtaining an identification error by subtracting the estimated acceleration torque from the acceleration torque command.
A means for outputting a corrected inertia by correcting the identification error, converting the identified inertia into a pre-corrected inertia having a time delay, outputting a sum of the corrected inertia and an identified inertia model value, Means for providing the identified inertia model value to the acceleration feedforward compensating means and the estimated load disturbance feedforward compensating means without providing a special constant mode for identification as inertia, which is a control parameter characterizing the operation characteristic of the controlled object. And An embodiment of the speed control device of the present invention will be described. FIG. 1 is a block diagram illustrating a configuration of a speed control device according to an embodiment of the present invention. FIG. 2 is a block diagram showing the speed control device of FIG. 1 by a transfer function. FIG. 3 is a block diagram showing a configuration of the inertia identifying means used in the speed control device of FIG. FIG. 5 is an acceleration / deceleration rate diagram in which the speed control device of the present invention eliminates overshoot. Referring to FIG. 1, a speed control device according to an embodiment of the present invention will be described. The speed controller 10 includes a reference model setter 11, an acceleration feedforward compensator 12, a subtractor 13, a speed controller 14, an adder 15, an adder 16, an estimated load disturbance feedforward compensator 1
8. It is constituted by inertia identifying means 19. FIG. 2 is a block diagram showing the speed controller of FIG. 1 using a transfer function. The acceleration feedforward compensator 12 includes a differentiator 21 and the estimated load disturbance feedforward controller 18 includes , An inertia load model (integrator) 22, a subtractor 23, and a load disturbance feedforward controller (coefficient K) 24. [0038] If the reference model setter 11 the speed command omega * is input, the speed command omega * input is output as norm speed command omega _m having a primary delay element. This output norms velocity command omega _m, the speed controller 14, an adder 1
Input to the inertia load 20 via 5 and 16;
The inertia load is driven. By detecting the speed detection value ω from the driven inertia load 20 and feeding back the speed detection value ω to the subtractor 13 for subtraction,
A speed control loop for outputting a speed error e is configured. On the other hand, the reference speed command ω _m having the first-order lag element output from the reference model setting unit 11 is input to the speed controller 14 and the acceleration feedforward compensating means 12, respectively. A correction signal is output. [0040] Then, by differentiating the normative speed command omega _m by the differentiator 21 of the acceleration feedforward compensation means 12,
By calculating the acceleration torque correction signal by calculating the inertia model (J _h ) identified by the inertia identification means 19, the acceleration torque correction signal and the speed controller 1
4 and the torque correction signal, which is the output signal of No. 4, is added by the adder 15 and output as an acceleration torque signal τ _ACC . The accelerating torque signal τ _ACC is calculated by the adder 16
Are input to the estimated load disturbance feedforward compensator 18, respectively.
The acceleration torque signal τ _ACC input to 8 is input to the integrator 22, which integrates the acceleration torque signal τ _ACC and identifies the inertia model (J _h ) identified by the inertia identification means 19.
By calculating the outputs the estimated speed omega _h. The subtracted by the subtractor 23 and the velocity detection value omega detected by the estimated speed omega _h and inertia loads 20,
The signal is input to an estimated load disturbance feedforward controller (coefficient K) 24, and is calculated by the set coefficient K. The output signal is used as a load disturbance torque correction signal, and the adder 16 calculates the acceleration torque signal τ _ACC The values are added and output as a torque command signal τ *. The torque command signal τ * is input to the inertia identifying means 19 and the inertia load 20. The torque command signal τ * to the inertia load is the load disturbance (fluctuation)
It is subtracted by τ _L to drive the inertia load 20. The detected speed value ω detected from the driven inertia load 20 is input to the inertia identifying means 19 and is calculated by the torque command signal τ * input to the inertia identifying means 19. As an inertia model (J _h ) of the load 20,
The acceleration feed forward compensation means 12 and the estimated load disturbance feed forward compensation means 18 are supplied. Next, the inertia identifying means 19 will be described with reference to FIG. The inertia identifying means 19 includes the delay circuit 3
1, subtractor 32, acceleration torque estimator 33, subtractor 34,
It comprises an identification error corrector 35, an adder 36, a delay circuit 37, a subtractor 38, and a load torque estimator 39. As described above, the inertia identifying means 19
Is input with the torque command signal τ * added by the adder 16 and the speed detection value ω detected by the inertia load 20. The input speed detection value ω is input to the delay circuit 31. The output of the delay circuit 31 and the speed detection value ω are subtracted by the subtractor 32. The value Δω obtained by the subtraction is input to the acceleration torque estimator 33 as acceleration, and the estimated acceleration torque τ
Output as _ha . The estimated acceleration torque τ _ha is input to the load torque estimator 39 together with the torque command signal τ *, and the load torque estimator 39 outputs the estimated load torque τ _hL . The output estimated load torque τ _hL is calculated by the subtractor 3
8 is subtracted from the torque command signal tau * in, and outputs the acceleration torque command signal tau _a. This acceleration torque command signal τ _a is
The estimated acceleration torque τ _ha is subtracted by the subtractor 34, and the subtracted value is input to the identification error corrector 35 as an identification error signal. The identification error signal input to the identification error corrector 35 is added to the inertia before correction by the adder 36 as correction inertia, and is output as the identification inertia (J _h ). On the other hand, the identification inertia (J _h ) is
7, and its output is fed back to the acceleration torque estimator 33 as inertia before correction. Next, the identification of the inertia identifying means 19 will be described. In this identification, the inertia model (J _h ) is obtained by the following equation by the successive least squares method. [Equation 5] Where Δω (n) = ω (n) −ω (n−
1): speed variation rate, T _S: sampling time, gamma: an identification gain. Also, the following equation: From the following equation: The estimated load torque τ _hL is estimated as the load torque at the constant speed. Next, the identified inertia model (J _h )
To the estimated load disturbance feedforward compensation means 1 of FIG.
By giving the estimated speed ω _h to the inertia load model (integrator) 22 shown in FIG. The deviation from the actual speed ω is a speed deviation generated by a load disturbance. Given the high gain through the estimated load disturbance feedforward 24, the speed fluctuation caused by load disturbance tau _L becomes possible to suppress the small inertia load 20 viscous resistance having a load fluctuation of the constant, the inertia model 1 / J _h s fixed can do. Further, the disturbance response is as follows when the identified inertia J _h is equal to the inertia J to be controlled (J _h = J). Is obtained. Next, since the inertia load 20 is fixed to the inertia model (J _h ), by giving J _hs to the differentiator 21 of the acceleration feedforward compensating means 12, the following equation is obtained. And the speed response ω to the speed command ω *
Is given by: Ω = G _m (S) ω *, and
G _m (S) of reference model setter (reference model response) 11
Matches. This reference model setting unit 11 is expressed by the following equation: If the first-order lag response is selected as follows, the velocity response ω becomes: As shown in FIG. 5, a response is obtained in which no overshoot occurs in the target value response to acceleration / deceleration and no speed deviation occurs with respect to the load disturbance τ _L. As described above, the inertia, which is a control parameter characterizing the operation characteristics of the inertia load 20, is identified and identified without providing a special mode for identification, that is, the simulation mode or the auto tuning mode. by estimated by estimating the load disturbance feedforward compensating for load disturbance tau _L from the difference of inertia (J _h) the estimated velocity omega _h and the actual speed omega obtained from and fixable to identify the inertia model (J _h) By providing the inertia load 20 with the acceleration feedforward compensation and the reference model of the target response, it becomes possible to make the speed response match the response of the reference model with respect to the variable speed command, and at the same time, to suppress the steady load fluctuation. , Rotary traveling cutting machine, traveling cutting machine, positioning feeder, The positioning accuracy of a variable speed control device such as a working machine is improved. FIG. 4 shows an example in which the speed control device 10 of the present invention is applied to a rotary cutter device. As shown in FIG. 4, there is a pair of rotary cutters 2 having blades around the axial direction. A reduction gear 3 is mounted on the main shaft of the rotary cutter 2, and an electric motor 4 for driving the rotary cutter 2 is provided. Are combined. This motor is provided with a pulse generator 5 for detecting the rotation speed and rotation angle of the motor, that is, the rotation angle of the main shaft of the rotary cutter 2. On the other hand, a length measuring wheel 7 for detecting the amount of movement of the running seat 1 is provided, and a pulse generator 8 for detecting the amount of movement is provided on the axis of the length measuring wheel 7. . The numerical control device of the rotary cutter 2 includes a position control device 40 and a speed control device 10 according to the present invention. The position control device 40 includes an integrator 41, a position command generator 42, a differentiator 43, and an adder / subtractor 4.
4, integrator 45, position controller ( _Kp ) 46, adder 4
7, a position command feedforward compensation (α) 48 and an adder 49. The pulse generated by the pulse generator 8 as the seat 1 travels is input to the integrator 41. The input pulse is time-integrated by the integrator 41 and output as the material movement distance X, and is input to the position command generator 42. The position command generator 42 provides a position command f (x) as a function of the material moving distance X in accordance with any speed instruction made in accordance cut length L _0. On the other hand, the moving speed V _B of the rotary cutter 2 is obtained from the pulse generated by the pulse generator 5 with the rotation of the rotary cutter 2. The output of the position command generator 42, that is, the cutter speed command df (x) / dt obtained by differentiating the position command f (x) with time by the differentiator 43 is calculated by the adder / subtractor 44 by the material speed. V _L and which is the cutter speed V _B and the subtraction input to the integrator 45, the positional deviation e is obtained.
The positional deviation e is entered to the position controller 46 is output as a compensation speed V _c. [0081] The compensation velocity V _c is the adder 49,47, cutter speed command and the material speed is added, the speed command omega * is formed. The speed command ω * is given to the speed control device 10. The torque command signal τ * is formed by the speed control device 10 as described above, and is supplied to the drive control circuit 6. According to the rotary cutter device, since the speed control device of the present invention is used, cutting accuracy is improved. According to the speed control apparatus of the present invention, the speed control means converts the speed command signal into a reference speed command having a primary delay element, and the speed control which feeds back the speed signal detected from the inertia load. A velocity control loop, and an acceleration feedforward compensating means, an estimated load disturbance feedforward compensating means and an inertia identifying means are added to the velocity control loop to identify inertia which is a control parameter characterizing the operation characteristic of the controlled object. By identifying without providing a special mode, for example, a simulation mode or an auto tuning mode, the overshoot that occurs when shifting from the speed change region of the acceleration / deceleration rate to the constant speed region is eliminated, and the speed due to the load fluctuation is reduced. Suppress fluctuations and target response (speed response) to reference model The problem is that overshooting caused by PI speed control is caused by matching the answer, the problem of speed deviation with respect to load disturbance is caused by the disturbance response in the proportional control, and the offset is generated at the speed rise, so that the smooth target The problem that response characteristics cannot be obtained, or the problem that overshoot occurs, etc. can be solved, and more accurate speed control can be performed.
It is possible to improve the accuracy of speed control of a traveling cutting machine, a fixed-size feeding device, and the like, and to improve the feeding accuracy of position control, the cutting accuracy, and the shape accuracy of a workpiece such as a machine tool.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a speed control device embodying the present invention. FIG. 2 is a control block diagram showing a speed control device according to an embodiment of the present invention by a transfer function. FIG. 3 is a block diagram of inertia identifying means used in the speed control device of the present invention. FIG. 4 is a block diagram of a rotary cutter control device embodying the present invention. FIG. 5 is an acceleration / deceleration rate diagram in which overshoot is eliminated by a speed control device embodying the present invention. FIG. 6 is a conventional speed control block diagram. FIG. 7 is a control block diagram of a conventional speed control device represented by a transfer function. FIG. 8 is a conventional acceleration / deceleration rate diagram. [Description of Signs] 1 Running material 2 Rotary shear 3 Gear 4 Electric motor 5 Pulse generator 6 Drive control circuit 7 Length measuring roll 8 Pulse generator 10 Speed controller 11 Reference model setter (G _m (S)) 12 Acceleration feed forward Compensation unit 13 Subtractor 14 Speed controller ( _Kv ) 15 Adder 16 Adder 17 Subtractor 18 Estimated load disturbance feedforward compensation unit 19 Inertia identification unit (unit) 20 Object of inertia load control (1 / Js) 21 Acceleration feed forward compensator (J _h s) 22 inertia load model (1 / J _h s) 23 subtractor 24 load disturbance feedforward controller (K) 31 delay circuit (Z ^-1) 32 subtractor 33 acceleration torque estimator 34 subtracts vessel 35 identification error corrector 36 the adder 37 delay circuits (Z ^-1) 38 subtractor 39 Load torque estimator 40 position controller 41 integrator 42 position command generator 43 differentiator 44 subtracter 45 the integrator 46 the position controller (K _p) 47 adder 48 the position command feedforward compensation (alpha) 49 adder

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI H02P 5/00 H02P 5/00 X (56) References JP-A-8-331879 (JP, A) JP-A-63-24301 ( JP, A) JP-A-61-248104 (JP, A) JP-A-4-302309 (JP, A) JP-A-62-126881 (JP, A) JP-A-5-284774 (JP, A) JP 62-128684 (JP, A) JP-A-6-78579 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G05B 13/02-13/04 B23Q 5/22 G05B 11 / 32 G05D 13/62 H02P 5/00

Claims (1)

(57) [Claim 1] In a speed control device using a speed command having an acceleration / deceleration rate, reference model setting means for converting the speed command into a reference speed command having a primary delay element; By the reference speed command, a speed control means for controlling an inertia load having a small viscous resistance having a steady load fluctuation, a means for detecting a speed of the inertia load, and a speed detection value from a means for detecting a speed of the inertia load. Speed control loop means for obtaining and controlling a speed error from the detected speed value and the reference speed command, and calculating a torque command obtained from the speed control loop means and a detected speed value of the inertia load. Inertia identifying means for outputting an inertia model value identified by the following: the reference speed command and the identified inertia model value Multiplying and differentiating to obtain an acceleration feed forward control amount, and a means for compensating the acceleration feed forward; and adding an acceleration torque correction value output from the speed control means and the acceleration feed forward control amount to obtain an acceleration torque. Acceleration torque commanding means for outputting as a control amount, calculating the estimated speed by dividing the acceleration torque control amount by the identified inertia model value and integrating to obtain an estimated speed, the estimated speed and a speed detection value detected from the inertia load, Means for obtaining an estimated load disturbance feedforward control amount resulting from the speed difference of the above, and for estimating the load disturbance feedforward compensation, wherein the inertia identifying means converts the detected speed value into a detected speed value having a time delay.
Then, a speed difference from the detected speed value, that is, an acceleration is obtained.
Means for calculating the acceleration and the inertia before correction to estimate the acceleration torque
And an estimated acceleration torque output from the acceleration torque estimating means.
Is calculated with the torque command to obtain an estimated load torque.
And the estimated load torque is reduced from the torque command.
To obtain the acceleration torque command, and from this acceleration torque command
The identification error is obtained by subtracting the estimated acceleration torque.
Means to correct the identification error and output the corrected inertia.
Before the correction with a time delay.
To the inertia, find the sum with the corrected inertia, and
Means for outputting a set inertia model value, eliminates overshoot that occurs when shifting from the speed change region of the acceleration / deceleration rate to the constant speed region, suppresses speed change due to load change, and sets a target speed response. A speed control device characterized by matching a response to a reference model response.