JP2001169581A - Motor control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase inertia identification accuracy when speed is close to zero if a speed command is small. SOLUTION: The motor control device is provided with a speed command generation part, a speed control for determining a torque command according to a speed command Vref and an actual motor speed Vfb, a model speed control for simulating the speed control according to a model, an identification part for identifying the inertia J according to the ratio of values STref, STref obtained by time-integrating a torque command Tref of the speed control and a torque command Tref' of the model speed control by each specific section [a, b], and an adjustment part for adjusting a speed loop gain Kv of the model speed control based on the inertia J. In the motor control device, the model from the torque command to speed in the model speed control is expressed by model inertia J', viscous friction disturbance Dc, and Coulomb friction disturbance Tc, and then negative inclination friction disturbance O where friction disturbance increases from a specific speed and characteristic disturbance P for assisting an acceleration torque when the speed decelerates to zero and speed accelerates from zero, respectively, thus reducing the inertia identification error.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a robot or a machine tool, and more particularly to a motor control device for identifying control constants such as inertia.

[0002]

2. Description of the Related Art As a conventional motor control device for identifying a control constant of a motor, for example, Japanese Unexamined Patent Publication No.
There is an apparatus disclosed in JP-A-1-46489. In this device,
The section for integrating the model and the actual torque command and the speed command are set so that they are not affected as much as possible by viscous friction disturbance, Coulomb friction disturbance, constant disturbance torque, and static friction disturbance, and the ratio of the integral value of each torque command is set. The inertia is identified by the above method, and the constant disturbance torque and the viscous friction disturbance can be identified very easily.

[0003]

However, in the above conventional example, an inertia identification error occurs depending on a speed command for performing inertia identification. FIG. 4 shows the relationship between the speed command and the inertia identification value. In FIG. 4, the horizontal axis is the speed command (rpm), and the vertical axis is the inertia identification value J /.
J '. It can be seen from the figure that when the speed command is small, the inertia identification value becomes small. Therefore, an object of the present invention is to provide a general-purpose motor control device capable of accurately identifying inertia even when a speed command is small or acceleration / deceleration is small.

[0004]

In order to achieve the above object, the invention according to claim 1 comprises a command generator for generating a speed command, a speed command Vref and an actual motor speed Vfb.
A speed control unit that determines a torque command and controls a motor speed, a model speed control unit that simulates the speed control unit using a model, and a torque command T of the speed control unit.
STr obtained by integrating ref with respect to time in a predetermined section [a, b]
an identification unit that identifies the inertia J by a ratio of a value STref ′ obtained by time-integrating the torque command Tref ′ of the model speed control unit in the same section, and an identification unit that identifies the inertia J based on the identified inertia J. An adjustment unit for adjusting the speed loop gain Kv, wherein a model from the torque command to the speed in the model speed control unit is referred to as a model inertia J ′, a viscous friction disturbance Dc, a Coulomb friction disturbance Tc, When the speed decreases to zero, the frictional disturbance increases from a predetermined speed, and when the speed increases from zero, it is represented by a spring characteristic disturbance that assists the acceleration torque. Further, the invention according to claim 2 is characterized in that the spring characteristic disturbance is a disturbance when acceleration torque starts continuously from a disturbance when the speed is reduced to zero. . According to the motor control device having the above configuration, the speed Vf is calculated from the torque command Tref ′ in the model speed control unit.
The models up to b ′ are model inertia J ′, viscous friction disturbance Dc, Coulomb friction disturbance Tc, a negative gradient friction disturbance in which the friction disturbance increases from a predetermined speed when the speed is reduced from zero, and a speed from zero. When accelerating, it is expressed as a spring characteristic disturbance that assists the acceleration torque due to the disturbance when the acceleration torque starts continuously from the disturbance when the speed becomes zero, so if the speed command is large, Coulomb friction disturbance and viscous friction Inertia is identified by the model represented by the disturbance,
When the speed command is small near zero, the deceleration starts when the speed decelerates to zero, and the friction disturbance torque increases when the speed reaches a predetermined speed.Negative gradient friction disturbance causes continuous friction when the speed accelerates from zero. Similarly, inertia is identified by the model in which the disturbance torque changes.
Regardless of the magnitude of the speed command, even in the case of low speed, inertia identification with a small identification error can be performed at the time of inertia identification.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a motor control device according to an embodiment of the present invention. FIG. 2 is a diagram showing a model represented by a negative gradient friction disturbance and a spring characteristic disturbance in the motor control device of FIG. FIG. 3 is a diagram showing an inertia identification result by the model shown in FIG. In FIG. 1, the speed control unit is indicated by a large block 1 at the top.
The lower large block 2 is a model speed controller,
Is an inertia J identification unit, and 4 is a speed loop gain Kv adjustment unit. In the speed control unit 1, proportional-integral control (PI control) is set, and only the inertia J is controlled, and similarly, the PI control is also set in the model control unit 2, and only the inertia J 'is controlled. In FIG. 1, the speed control unit 1
Is equal to the speed Vfb 'of the model speed control unit 2, and the torque command integral value S of the speed control unit 1 is set based on the condition that the speeds Vfb and Vfb' are not zero.
Equation (1) holds between Tref and inertia J, and the torque command integral value STref 'and inertia J' of the model speed control unit 2. Therefore, the identification unit 3 can obtain the inertia J from equation (2). it can. J / J ′ = STref / STref ′ (1) J = (STref / STref ′) × J ′ (2) However, generally, viscous friction disturbance Dc, constant disturbance torque Td, and Coulomb friction disturbance. Since Tc exists and it is necessary to remove the influence thereof, the method will be described below. For the viscous friction disturbance Dc, the integral value of the speed Vfb in the predetermined section “a, b” may be zero, and for the constant disturbance torque Td, a certain speed Vre
inertia J1 obtained by f1 and speed command Vref
Inertia J may be an average value of the inertia 2 and Vref2 obtained by inverting the sign of 1 with respect to the inertia 2. As for the Coulomb friction disturbance Tc, the section “a, b” and the speed command Vref may be set so that the forward rotation time and the reverse rotation time of the motor in the previous section “a, b” are equal. The above is the principle of obtaining inertia by a method that is not easily affected by the constant disturbance torque Td, Coulomb friction disturbance Tc, and viscous friction disturbance Dc. The adjusting unit 4 adjusts the speed loop gain Kv based on the inertia value thus obtained.

However, the speed command Vre for identification is
When f is small or when the acceleration / deceleration is small, near the speed zero, the inertia identification value (J / J ') as shown in FIG.
And the identification error increases. When this state is viewed in FIG. 5 of the conventional device, for example, when the speed command is a continuous speed command in which forward / reverse switching is performed at a zero cross point by a trapezoidal speed pattern (acceleration-constant speed-deceleration)
The straight line at the lower right of the figure corresponds to the forward deceleration curve of the command,
It corresponds to the reverse acceleration curve followed by the negative straight line in the upper left. However, the friction characteristics at the time of deceleration and the friction characteristics at the time of acceleration are, for example, in the case of a rolling guide mechanism used in a one-axis slider, changes in the film thickness (oil film thickness) between the ball and the rail and elastic deformation due to driving conditions. Is not point-symmetric with respect to zero velocity.

Therefore, in the speed-friction disturbance model shown in FIG. 2, when the speed is reduced, stopped, and accelerated, the friction disturbance force becomes negative gradient friction disturbance characteristic (O) → intersection (Q) → It changes from the spring characteristic disturbance characteristic (P). That is, as the speed decreases, the linear curve of the deceleration curve on the normal rotation side changes to a quadratic curve of the upper convex portion, and reaches the point Q. Further, as the vehicle accelerates in the reverse direction from the point Q, the spring disturbance characteristic (P) increases steeply, and then shifts to linearity. As a result, the continuity is restored at the point Q even in the forward / reverse rotation curve at the time of low speed control, and a step between mn as shown in FIG. 5 is eliminated, and a smooth operation is guaranteed. The actual low-speed to high-speed motor control by the model in FIG. 2 is a model control in a linear region represented by Coulomb frictional disturbance and viscous disturbance similar to the conventional one in FIG. 5 when the speed is high, and when the speed is low near zero speed. The control is based on the negative gradient friction disturbance curve (O) and the spring characteristic disturbance curve (P). FIG. 3 shows an experimental result when the model of FIG. 2 is used. FIG. 3 shows the speed command (rpm) on the horizontal axis and the inertia identification value J / J 'on the vertical axis. When this is compared with the conventional example of FIG. 5, the error of the inertia identification value J / J ′ in the case of FIG. 3 is about 0.5, which can be reduced to ３ from 1.5 of the conventional example of FIG. It turns out that. In addition, when the acceleration / deceleration of the speed command is small, similarly to the case where the speed command is small, the inertia identification error can be improved by applying the negative gradient friction disturbance and the spring characteristic disturbance.

[0008]

As described above, according to the present invention,
Speed loop gain K based on the identified inertia J
In the motor control device for adjusting v, the model from the torque command to the speed in the model speed control unit is represented by model inertia J ′, viscous friction disturbance Dc, and Coulomb friction disturbance T
c, a negative gradient friction disturbance in which the friction disturbance increases from a predetermined speed when the speed is reduced to zero, and a spring characteristic disturbance that assists the acceleration torque when the speed is accelerated from zero. Even when the command is small or the acceleration / deceleration is small, the inertia identification can be performed with high accuracy, so that there is an effect that a very versatile motor control device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a motor control device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a model represented by negative gradient friction disturbance and spring characteristic disturbance in the motor control device of FIG. 1;

FIG. 3 is a diagram showing an inertia identification result by the model shown in FIG. 2;

FIG. 4 is a diagram showing an inertia identification result of a conventional motor control device.

FIG. 5 is a diagram showing a control model of the motor control device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Speed control part 2 Model speed control part 3 Identification part 4 Adjustment part O Negative gradient disturbance characteristic part P Spring characteristic disturbance characteristic part

Claims (2)

[Claims] 1. A speed controller for generating a speed command, a speed controller for determining a torque command based on a speed command Vref and an actual motor speed Vfb and controlling a motor speed, and simulating the speed controller by a model. A value STref 'obtained by time-integrating a torque command Tref of the model speed control unit and the torque command Tref of the speed control unit in a predetermined section [a, b] and a value STref' obtained by time-integrating the torque command Tref 'of the model speed control unit in the same section. A motor controller comprising: an identification unit that identifies the inertia J based on the ratio of the inertia J; and an adjustment unit that adjusts the speed loop gain Kv of the model speed control unit based on the identified inertia J. The model from the torque command to the speed is given by the model inertia J ′, viscous friction disturbance Dc, Coulomb friction disturbance Tc, and speed. Motor control apparatus characterized by represented by the negative slope of friction disturbance friction disturbance is increased from a predetermined speed, if the speed is accelerated from zero to the spring characteristic disturbance help acceleration torque when decelerating the filtration. 2. The system according to claim 1, wherein the spring characteristic disturbance is a disturbance in a case where the acceleration torque continuously starts from a disturbance in a case where the speed is reduced to zero.
The motor control device according to any one of the preceding claims.