JPH05161371A - Controller for motor and controlling method - Google Patents

Abstract

PURPOSE:To stop a motor at a given position in a minimum time with a controller automatically accommodated to the motor and load characteristics, by generating a deceleration commencement point and a speed instruction in a deceleration region on the basis of acceleration level detected at two or more spots in a maximum acceleration range. CONSTITUTION:A signal from an encoder 2 for detecting a rotational location of a motor 1 is provided to a location theta detecting means 4 and to a speed omegadetecting means 5 in a microcomputer 3. At a maximum acceleration time, the speed omega is stored as omega1, omega2, and omega3 in a memory means 7 every time a signal is generated from a constant-interval timing generator 6. A mechanical time constant taum and a steady speed omegaf are calculated and stored in a memory means 8, and a current speed omega is measured. Then, a stopping distance for a motor from the speed omega is calculated from the read-out data of the mechanical time constant taum and a steady speed omegaf. A deceleration commencement point is determined from the stopping distance and a detected location theta. A rotational direction changing signal and a PWM signal are provided to a predriver 9. Consequently, the motor is controlled and moved at a maximum deceleration speed in a reverse direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor control device or an electric motor control method, and more particularly to an electric motor control method and control device for stopping and controlling a commanded predetermined stop position in the shortest time.

[0002]

2. Description of the Related Art Various methods have been proposed for stopping an electric motor at a predetermined commanded position.

The time required to stop at a predetermined stop position varies depending on the determination of the deceleration start position and the control method within the deceleration region. For positioning control of the electric motor, for example,
As shown in FIG. 5, a method is known in which maximum acceleration is performed until the DC motor reaches a deceleration start position, and after reaching the deceleration start position, deceleration is started and the DC motor is stopped.

An example of the method of determining the deceleration start position and the control method at the time of deceleration related to this method is described in the literature of the Institute of Electrical Engineers of Japan, Information Processing Research Group, Material No. IP-82-34, "All-Digital Control of DC Servo Motor". ..

[0005]

In the above document, the speed ω and the position θ of the DC motor are measured, and the speed command ωc at the position θ is calculated from the measured value and the deceleration β of the DC motor, A method of performing deceleration based on that is described.

In this method, a speed command ωc represented by the following equation is calculated from the calculated position θ and a preset deceleration β of the DC motor, and linear deceleration control is performed based on the speed command ωc. ..

[0007]

[Equation 1]

Β: deceleration of the DC motor θ: position The above speed command ωc is a speed command for linear deceleration, and at the same time, the DC motor is allowed to stop at the position θ. Represents the maximum speed of.

Further, as is apparent from FIG. 6, the point at which the speed ω of the DC motor matches the speed command ωc of the above-mentioned equation 1 can be set as the deceleration start position, and therefore maximum acceleration is performed to that position. After that, deceleration is performed based on the speed command ωc until the DC motor stops.

According to this method, when the speed becomes zero, the position θ also becomes zero, and it can be stopped at a predetermined position without generating vibration. However, the number 1
The deceleration β of is a value that changes depending on the characteristics of the DC motor and the characteristics of the load. Therefore, the deceleration β should be set assuming the slowest deceleration conditions (conditions that make it difficult to stop the DC motor), taking into consideration variations in the manufacturing characteristics of the DC motor, load, etc., and changes over time. Must. Thus, in consideration of the variation of the deceleration β, a value smaller than the maximum capacity of the DC motor is set to perform deceleration, and as a matter of course, there is an inconvenience that the movement time to a predetermined position becomes longer accordingly. is there.

As one method for solving the above inconvenience, the acceleration α is measured when accelerating to the deceleration start position,
The method of calculating the speed command ωc with deceleration β = acceleration α is introduced in the above-mentioned information processing research institute materials of the Institute of Electrical Engineers of Japan. This is because the deceleration β is generated by the DC motor if the influence of the load torque is small. It is determined by the ratio between the torque and the inertia of the rotating shaft, and is based on the principle that it substantially matches the acceleration α.

When performing the existing position control, paying attention to accelerating once, the acceleration α is measured at the time of acceleration, and the value is used as the deceleration β to calculate the speed command ωc of equation (1).

[0013]

[Equation 2]

Α: Acceleration In this way, the acceleration α at the time of acceleration is measured, and the deceleration β is estimated and obtained from this acceleration α to perform the control automatically adapted to the load and stop the positioning in a short time. Is realized.

According to the above-mentioned conventional method, by obtaining the speed command ωc during deceleration from the acceleration α during acceleration, the torque of the DC motor and the inertia of the rotary shaft are adapted to suppress the vibration and to shorten the time. It can be moved to a predetermined position and stopped. However, this method obtains ωc during deceleration under the condition that the acceleration α and the deceleration β are substantially equal to each other, so that complete load adaptation is possible only when the influence of the load torque is small.

This relates to factors such as inertia of the rotating shaft, load torque, torque of the DC motor, etc. which determine the operating characteristics of the DC motor. For example, when the inertia of the rotating shaft is large, both the acceleration α and the deceleration β are small, but the load is large. When the torque is large, the acceleration α is small, but the deceleration β is large. On the contrary, it is because the motion during deceleration cannot be completely specified only from the acceleration α during acceleration.

Therefore, when selecting the deceleration β from the acceleration α measured during acceleration, it is necessary to consider a factor that cannot be specified only from the acceleration α, and as a result, the deceleration start position and the deceleration β in FIG. The maximum capacity of the DC motor must be set with some margin. Therefore, the time required to move to the predetermined position accordingly increases.

The method of moving to a predetermined position in the shortest time is to apply a maximum forward voltage to the DC motor to the deceleration start position to accelerate the DC motor, and after reaching the deceleration start position until the DC motor stops. This is a method of decelerating by applying a reverse direction maximum voltage. However, in the conventional method, deceleration is performed by speed control based on the speed command ωc represented by Formula 1. Therefore, from that point as well, the moving time There was a problem that the maximum capacity of the electric motor was increased.

The present invention automatically adapts to the DC motor and the load characteristics by considering all the influences of the inertia of the rotating shaft, the load torque, etc. when positioning and stopping at a predetermined position, and further, the DC motor. It is an object of the present invention to provide a control method and an apparatus capable of accelerating and decelerating with the maximum capacity of, and enabling positioning stop in the shortest time.

[0020]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an electric motor, a position detector attached to the electric motor, and a speed for detecting a speed based on a signal from the position detector. Detecting means, drive device for applying electric power for driving the electric motor, decelerating means for applying braking force to the electric motor, acceleration detecting means for detecting acceleration at startup, and deceleration start based on the acceleration detecting means In a motor control device having a calculation function for calculating a position and a storage unit for storing the calculation result, the acceleration detection unit is configured to perform two measurements specified by at least three predetermined points in a starting acceleration region. The calculation means includes a function of measuring acceleration in a region, and the computing means is configured to determine the two accelerations measured by the acceleration detecting means and the braking start position from a designated stop position. It is accomplished by determining.

Further, the object is to detect a speed, a position and an acceleration, generate a deceleration start position deceleration speed command from these detection results, and decelerate and stop the electric motor based on this command. When moving to
The maximum positive voltage is applied until the predetermined set speed is reached to perform maximum acceleration, the acceleration is detected in at least two regions within this maximum acceleration region, and the deceleration start position is based on the two detected accelerations. This is achieved by a method of controlling a motor that generates a speed command within a deceleration region and decelerates and stops at a predetermined stop position based on this command.

[0022]

The details of the method of calculating the mechanical time constant τm and the steady speed ωf and the method of calculating the deceleration start position will be described below, including the general operating characteristics of the DC motor.

The operating characteristics of the DC motor are expressed by the steady speed ωf and the mechanical time constant τm. For example, the speed ω of the DC motor when maximum acceleration is performed is expressed by the following equation.

[0024]

[Equation 3]

[0025]

[Equation 4]

[0026]

[Equation 5]

Vs: voltage applied to the motor [V] KE: induced voltage constant [V / rad / S] KT: torque constant [kg.f.cm/A] Tl: load torque [kg.f.cm] Jl: Load inertia [kg · cm · S ² ] R: Armature resistance [Ω] KE, KT, Vs, Tl, and R in the equations 4 and 5 are factors that determine the characteristics of the DC motor and load, and DC This value depends on variations in the characteristics of the motor and load during manufacturing, and changes in characteristics over time. It is difficult to detect each of these values individually, but as is clear from Equation 3, the effect on the operating characteristics of the DC motor is that the steady-state speed ωf and mechanical time constant, which are complex physical quantities of various elements, are different. By detecting τm, it becomes possible to grasp the operating characteristics of the DC motor, including changes in the load characteristics.

Next, the above-mentioned steady speed ωf and mechanical time constant τ
A method of detecting m will be described.

First, the velocities ω ₁ , ω ₂ and ω ₃ are measured at each constant time interval Δt at the time of maximum acceleration. This ω ₁ , ω ₂ , ω ₃
Are respectively expressed by the following equations from Equation 3.

[0030]

[Equation 6]

[0031]

[Equation 7]

[0032]

[Equation 8]

Where t ₁ is the ratio of arbitrary times ω ₁ , ω ₂ , ω ₃

[0034]

[Equation 9]

[0035]

[Equation 10]

From equations 9 and 10

[0037]

[Equation 11]

[0038]

[Equation 12]

Further dividing Equation 11 by Equation 12

[0040]

[Equation 13]

Here, if (a-1) / (b-1) = C is set and Equation 13 is rearranged,

[0042]

[Equation 14]

[0043]

[Equation 15]

Solving Equation 15 for the mechanical time constant τm,

[0045]

[Equation 16]

Since Δt and t ₁ are preset values, the mechanical time constant τm is calculated by the equation 16. If τm is obtained, from Equation 6,

[0047]

[Equation 17]

The steady speed ωf can be obtained as

As described above, the steady speed ωf that characterizes the operating characteristics of the DC motor is obtained by measuring the speed at three points at preset constant time intervals during acceleration and performing the calculation based on the ratio thereof. The mechanical time constant τm can be detected.

Position control using the steady speed ωf and the mechanical time constant τm obtained by the above method will be described below.

When moving to a predetermined position, the speed ω and the position θ of the DC motor are measured at any time, and when the maximum deceleration is performed from a certain speed ωa, the distance S required to stop
It is possible to move in the shortest time by obtaining (hereinafter referred to as the stop distance S) and performing the maximum acceleration / deceleration with the point where the distance S and the position θ coincide as the deceleration start position.

The speed ω of the DC motor when the speed is reduced from the certain speed ωa by the reverse braking applying the reverse maximum voltage −Vs is expressed by the following equation.

[0053]

[Equation 18]

The time ts required for starting and stopping the deceleration can be obtained by solving ω = 0 with the above equation.

[0055]

[Formula 19]

On the other hand, the stopping distance S that the DC motor moves until it stops can be obtained by integrating Equation 18 from t = 0 to ts with respect to time t.

[0057]

[Equation 20]

In Equations 19 and 20, the mechanical time constant τm and the steady speed ωf are calculated during acceleration by the above-described method and can be treated as known constants. Therefore, the stop distance S is obtained as a function of only the speed ωa of the DC motor. be able to. Therefore, the speed ω of the DC motor is measured at any time, and
To calculate the stop distance S, compare it with the position θ, and obtain a coincident point, so that the deceleration start position adapted to the load characteristic can be obtained.

Further, since the above method defines the deceleration start condition of the DC motor in a certain speed state, the maximum voltage in the forward direction is applied until a certain set speed is reached in order to move to a predetermined position. It is also effective for a system in which the maximum acceleration is performed and the motor is operated to a predetermined position at a set speed, and then the DC motor is stopped by reverse braking by applying a reverse maximum voltage.

Further, in the above method, the steady speed ωf and the mechanical time constant τm that determine the operating characteristics of the DC motor during acceleration are calculated, so that the acceleration / deceleration of the DC motor due to the inertia of the rotating shaft, the load torque, the torque of the DC motor, etc. Since it can comprehensively detect and judge the influence on the operation at the time, after applying the maximum voltage in the forward direction to accelerate to the maximum in order to move to a predetermined position, deceleration is performed while adjusting the voltage applied to the DC motor. A method of stopping the DC motor, or applying a maximum voltage in the positive direction to achieve maximum acceleration until a certain set speed is reached, and after operating at a set speed to a certain predetermined position, decelerating while adjusting the voltage applied to the DC motor. Even when decelerating while adjusting the voltage as in the method of performing the above and stopping the DC motor, the deceleration start position can be automatically adjusted in accordance with the load.

[0061]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a schematic diagram of the configuration of a control device that realizes the present invention.

Reference numeral 1 is a DC motor, and an encoder for detecting the rotational position is attached to the DC motor. The signal of the encoder 2 is input to the microcomputer 3 to detect the speed ω and the position θ of the DC motor 1 and detecting means 4, 5
To measure.

At the time of acceleration, the speeds ω ₁ , ω ₂ , ω ₃ of the DC motor 1 are stored in the storage means 7 at every constant time interval Δt generated by the interval timer 6 in the microcomputer, and are calculated by the microcomputer 3. , The mechanical time constant τm and the steady speed ωf are calculated and stored in the storage means 8. The speed ω of the DC motor 1 is measured, the stored mechanical time constant τm and the steady speed ωf are read, and the distance S required to stop from the speed ω is calculated at any time.

The stop distance S is compared with the position θ of the DC motor 1, and the coincident point is set as the deceleration start position. The microcomputer 3 outputs a rotation direction switching signal to the pre-driver to apply a voltage to the DC motor 1. The polarity of Vs is reversed. The drive circuit 10 has an H-shaped bridge structure in order to apply a voltage in both forward and reverse directions to the DC motor 1. 2 and 3 show the calculation of the mechanical time constant τm and the steady speed ωf,
3 shows a schematic flowchart of a program for detecting a deceleration start position.

FIG. 2 is for calculating the mechanical time constant τm and the steady speed ωf, and this processing is executed when the measurement of ω ₃ is completed. As specific processing contents, first, ω ₁ ,
ω ₂ and ω ₃ are read, the ratio between them is calculated, the mechanical time constant τm is calculated based on the equation 16, and written in the storage means, and then the steady speed ωf is calculated based on the equation 17 and written in the storage means. is there.

FIG. 3 is for detecting the deceleration start position. This processing is repeatedly executed after the calculation processing of the mechanical time constant τm and the steady speed ωf is completed and until the deceleration start position is detected.

The contents of the processing are as follows: the current speed ω of the DC motor
And the position θ are measured, and the mechanical time constant τm and the steady speed ω are measured.
f is read, and the time ts and the distance S required to stop from the current speed ω are calculated based on the speed ω and the expressions 19 and 20.

If the stop distance S and the position θ are compared and coincident with each other, a process of reversing the polarity of the voltage applied to the DC motor is performed, and if not, the process is terminated as it is.

FIG. 6 shows the operation of moving the DC motor to a predetermined position by the control device having the above processing configuration.

Based on the speeds ω ₁ , ω ₂ , ω ₃ measured at constant time intervals during acceleration, the forward maximum voltage Vs is applied up to the maximum deceleration start position that is automatically obtained by calculation. Maximum voltage in the reverse direction after moving and reaching the deceleration start position −
The movement is performed at the maximum deceleration by applying Vs. At this time, the deceleration start position is determined based on the mechanical time constant τm and the steady speed ωf. Therefore, when τm and ωf change, that is, when the conditions such as the inertia of the rotating shaft and the load torque change, those changes. The deceleration start position is automatically corrected by adapting to.

FIG. 4 shows the braking stopped state by the above method.

[0073]

As described above, according to the present invention, the acceleration detecting means has the function of measuring the acceleration in the two measurement areas specified by at least three predetermined points in the start-up acceleration area. Since the calculation means obtains the braking start position from the two accelerations measured by the acceleration detection means and the designated stop position, the deceleration start position is automatically selected according to the load characteristics. Therefore, it is possible to provide a controller for an electric motor that can move to a predetermined position in the shortest time.

Further, according to the present invention, when moving to a predetermined position, maximum positive voltage is applied until the predetermined set speed is reached to perform maximum acceleration, and the acceleration is detected in at least two regions within the maximum acceleration region. Then, based on the detected two accelerations, the deceleration start position and the speed command in the deceleration area are generated, and the method of decelerating and stopping to the predetermined stop position based on this command is adopted. It is possible to obtain an electric motor that can move to the position of in the shortest time.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a flowchart of a program for calculating a mechanical time constant τm and a steady speed ωf in one embodiment of the present invention.

FIG. 3 is a diagram showing a flowchart of a deceleration start position detection program according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of the operation of the DC motor in one embodiment of the present invention.

FIG. 5 is a general operation schematic diagram of the DC motor when moving to a predetermined position.

FIG. 6 is a schematic view of the operation of the DC motor when moving to a predetermined position in a conventional example of position control for load adaptation.

[Explanation of symbols]

1 ... DC motor, 2 ... Encoder, 3 ... Microcomputer, 4 ...
Position detecting means, 5 ... Speed detecting means, 6 ... Interval timer, 7, 8 ... Data storing means, 9 ... Pre-driver, 1
0 ... Drive circuit.

Claims (7)

[Claims] 1. An electric motor, a position detector attached to the electric motor, speed detecting means for detecting a speed based on a signal from the position detector, and a drive device for supplying electric power for driving the electric motor. A deceleration means for applying a braking force to the electric motor, an acceleration detection means for detecting acceleration at the time of starting, a calculation function for calculating a deceleration start position based on the acceleration detection means, and a storage means for storing the calculation result. In the control device for the electric motor, the acceleration detecting means includes a function of measuring acceleration in two measurement areas specified by at least three predetermined points in the start-up acceleration area, and the calculating means includes:
An electric motor control device for obtaining the braking start position from two accelerations measured by the acceleration detecting means and a designated stop position. 2. The motor control device according to claim 1, wherein the deceleration means is reverse braking by applying a reverse maximum voltage applied to the motor by the drive device. 3. The motor control device according to claim 1, wherein acceleration detection is performed within a maximum acceleration region to which a positive maximum voltage is applied. 4. A method of controlling an electric motor, which detects a speed, a position and an acceleration, generates a deceleration start position deceleration speed command from these detection results, and decelerates and stops the electric motor based on the command, moving to a predetermined position. At this time, the maximum voltage in the positive direction is applied until the predetermined set speed is reached to perform maximum acceleration, and the acceleration is detected in at least two regions within this maximum acceleration region,
A method for controlling an electric motor that generates a deceleration start position and a speed command within a deceleration region based on two detected accelerations, and decelerates to a predetermined stop position based on the commands. 5. The deceleration start position and the speed of the deceleration region according to a change in the load characteristic by detecting the operating characteristic of the electric motor including the load system from the innumerable number of accelerations detected at the time of maximum acceleration. A method for controlling an electric motor that adjusts a command. 6. The load characteristic according to claim 5, wherein accelerations in a plurality of regions are measured during acceleration of the electric motor, and a steady speed ωf and a mechanical time constant τm that determine the operating characteristics of the electric motor are calculated from the measured values. A control method for an electric motor that performs adaptive deceleration stop control. 7. The motor control device or the motor control method according to claim 1, wherein the motor is a DC motor driven by an inverter.