JP2663684B2 - Adjustment method of motor speed control system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a speed control system for adjusting and optimizing a speed controller of a motor control device having a current control system as a minor loop and a speed control system as a main loop. Regarding the adjustment method.

[Conventional technology]

FIG. 3 is a circuit diagram of the motor speed control device. In this figure, the AC of an AC power supply 100 is rectified by a rectifier 1 and converted to DC, which is supplied to a DC motor 3 and driven. The load 30 is connected to the DC motor 3, and the load 30 rotates as the DC motor 3 rotates. The rotation speed n of the DC motor 3 is measured by a speed detector 31.
The control system is composed of a double closed-loop control system consisting of a minor loop 200 of a current control system and a main loop of a speed control system. The main loop 300 uses the speed n of the DC motor 3 detected by the speed detector 31 as a feedback. And the subtractor 9
Is subtracted from the speed set value n ^* to obtain a deviation e. This deviation e is input to the speed controller 8. The speed adjuster 8 comprises a so-called PI adjuster composed of a proportional element and an integral element, and the coefficient of each element is set to an optimum value ^. Is output.

The minor loop 200 receives the current set value i ^* as an input signal, and subtracts the actual value i of the armature current of the DC motor 3 measured by the current transformer 2 from the subtractor 5 and inputs the subtracted value to the current controller 4. The output signal of the current regulator 4 becomes a control signal of the rectifier 1, and the output voltage of the rectifier 1 is changed by the control signal. Normally, the current controller 4 is also constituted by a PI controller like the speed controller 8. Although the actual current value i is illustrated as being measured by the current transformer 2 and input to the subtracter 5 as it is, the output of the current transformer 2 is actually an alternating current. By the conversion, a measured value proportional to the current supplied to the DC motor 3 is obtained, and the current measuring circuit shown in the drawing is a schematic diagram simply omitting the rectifier. Instead of measuring this current on the AC side of the rectifier 1 as shown in the figure, a method is adopted in which a shunt or a DC current transformer is inserted into a DC circuit between the rectifier 1 and the DC motor 3 to measure the current. Is also good.

The current set value i ^* is set as a value proportional to the torque τ generated by the DC motor 3, and the DC motor 3 generally generates a torque τ by maintaining a constant magnetic flux Φ generated by the field poles. Since it is proportional to the current I, there is a feature that instantaneous value control becomes possible. Therefore, this DC motor is often used in a device requiring high-precision speed control. In recent years, with the progress of inverters using semiconductor elements, AC motors such as induction motors and synchronous motors have been replaced with DC motors and their use has been expanded, but in this case, DC motors are also controlled by a method called vector control. In the same manner as described above, a method of controlling the generated torque so as to be proportional to the primary current is employed.

In the speed controller 8 and the current controller 4, coefficients such as a proportional coefficient of a proportional element and a time constant of an integral element are set so that respective control systems are optimized. In the case of the current regulator 4, the control target is a current, and the control characteristics of the minor loop 200 are determined by various constants of the electric circuit of the rectifier 1 and the DC motor 3, so that the time constant determined by the circuit constant included therein is Since it is a small value on the order of 10 milliseconds and is relatively easy to obtain from measurement by an electrical test, it is easy to optimally set the constant of the current regulator 4 and, furthermore, there is some error. However, the degree of influence on the entire control system is small. On the other hand, in the case of speed control, since a mechanical system such as the moment of inertia of a DC motor is included, the time constant is a relatively slow response on the order of seconds or more. It is necessary to accurately grasp the mechanical system constants.

[Problems to be solved by the invention]

As described above, the control characteristics of the motor speed control device are mainly determined by the characteristics of the speed control system, particularly the characteristics of the mechanical system of the motor and the load. Therefore, it is necessary to perform optimal adjustment of the control system after accurately grasping the constants that govern these mechanical systems. However, in general, it is often difficult to grasp the constants of the mechanical system. For this reason, the speed control system should be roughly adjusted using the constants obtained from the design values first, and the control device and motor In practice, a trial-and-error method is employed in which the control characteristics are actually measured by operating in combination with each other, and the optimum conditions are searched for based on the results. Therefore,
Not only does the cost of tuning increase due to the time required to search for the optimal conditions, but also many of these tests are performed on-site where the equipment is installed, but the local There is also a problem that the period of the installation work in the above becomes long.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for adjusting a motor speed control system that can easily and quickly adjust a speed regulator for optimizing a control characteristic of a main loop as a speed control system.

[Means for solving the problem]

According to the present invention, there is provided a method for adjusting a speed control system of a motor control device having a current control system as a minor loop and a speed control system as a main loop. Of the integral terms, the integral term is fixed, and the motor is driven at a constant torque using the current control system to measure the acceleration at that time, and the moment of inertia of the motor is determined based on the measured acceleration. It is assumed that the proportional coefficient of the speed controller of the speed control system is set using this moment of inertia.

[Action]

In the configuration of the present invention, the motor is started with a constant torque in a no-load state using a current control system, the acceleration at that time is measured, and the moment of inertia of the motor is obtained from the measured acceleration and torque. By substituting the value of the moment of inertia into a predetermined formula, the proportional coefficient of the speed regulator can be easily determined.

〔Example〕

Hereinafter, the present invention will be described based on examples. FIG. 1 is a circuit diagram showing an embodiment of the present invention. The same reference numerals as in FIG. 3 denote the same constituent elements, and a detailed description thereof will be omitted. In this figure, the control of the current proportional to the torque of the minor loop 200 is used to determine the constants of the mechanical system necessary for adjusting the speed regulator 8 by a test. In this figure, the current set value i ^* is maintained at a constant value, so that the DC motor 3 is driven with a constant torque. The timer 7 measures the time from the start to the end when the start and the end signals are input from the outside. The signal 301 is a pulse signal for notifying the start time, and the timer is set at the time set by the pulse of the signal 301. The storage of the integration time of 7 is cleared and the integration is started again from 0. The comparator 6 compares the rotation speed n of the DC motor 3 detected by the speed detector 31 with the target speed _nm, and since the motor 3 is accelerated with a constant torque, the speed n rising in a ramp shape is larger. A pulse is output at the moment when the timer 7 is turned on, and the timer 7 is stopped by the pulse signal. At this time, the display time of the timer 7 is a measured time value T from the start time to the stop time.

Assuming that the inertia of the DC motor 3 is M, the generated torque is τ, and the rotation speed is n, the following relationship generally holds between them. Here, t is time.

Assuming that the torque is a constant value τ ^* , n = 0 at t = 0, t =
These relations at T can be obtained by integrating the equation (1) between t = 0 and T as a result.

_{^{τ * T = Mn m ...... (}} 2) the following equation is solved with respect to this formula M is obtained, the moment of inertia of the DC motor 3 time measurement value T and the torque setpoint tau ^*, from the target speed n _m from the equation M can be calculated.

M = τ ^* T / _nm (3) Next, a method of obtaining the coefficient of the speed controller 8 using the moment of inertia M will be described. There are various methods for optimizing the controllability, and the method can be used depending on the purpose. Here, as an example, a calculation method based on a method called a Symmetries method will be described.

FIG. 2 is a block diagram showing FIG. 3 in another form for control characteristic analysis. In this figure, the blocks in FIG. 3 corresponding to the components in FIG. 1 on a one-to-one basis are given the same reference numerals to clarify the correspondence. The speed controller 8 comprises a proportional element having a coefficient Kp and an integral element having a time constant T _I / K _P. The expression in the block representing the speed controller 8 is a slightly modified expression. The minor loop 200 is represented as one delay element. The time constant is T _CR and the proportional coefficient K _C. The current regulator 4 of FIG. 1 is optimally adjusted so that the minor loop 200 can approximate a first order delay element with a sufficiently small time constant.

The block representing the DC motor 3 is a multiplication element 32 and a subtractor 33
And consist integral element 3 _4, the product of the magnetic flux Φ that occur are field poles are inputted to the current i is the torque tau _M. The torque τ _L of the load shown in FIG. 2 is subtracted from the torque τ _M by a subtractor 33, and then input to an integration element 34 simulating the inertia of the DC motor 3 to output a rotation speed n.

Actual speed value n for speed set value n ^* in FIG.
Is as follows. However, it is assumed that the load torque τ = 0.

However, Substituting equation (4) into equation (3) and rearranging yields the following equation.

Two coefficients of speed regulator 8 by applying Jinmetorisshie method this equation, i.e. the proportional coefficient K _P and the integral term T _I is given by the following equation.

In calculating K _P and T _I based on this equation, T _CR and K _C
Since is obtained as a result of adjustment of the minor loop 200, it is a known value at the present time when this adjustment has already been completed. Therefore, if the time constant T _M is known, the equation (6) can be calculated. Since the integral term T _I has a known K _CR, (7)
It becomes a fixed value as is clear from the equation.

By the way, the integral element 34 represents the relationship between the torque τ _M generated by the DC motor 3 and the rotation speed n of the DC motor as described above. From the comparison of the expression (1), T _M is proportional to the moment of inertia M. Value. That is, if the moment of inertia _M is known, T _M can be known. Therefore, two optimum coefficients of the speed regulator 8 are obtained based on the equation (7). As a result, optimization of the main loop as the speed control system is performed. It will be done easily. N in the block diagram of FIG.
And i are values proportional to the actual DC motor N and the armature current I, but are treated as voltage signals in the actual control circuit, and are represented by the ratio of the rated value of the DC motor 3 in order to match the dimensions. Is the fact. The relationship between the time constant T _M and the moment of inertia M must consider such a dimensionless coefficient.

Assuming that the rated current of the DC motor 3 is I ₀ , the rated output is P ₀ , the rated torque is τ ₀ , and the rated speed is N ₀ , the following expression results from the expression (1).

The method for obtaining the acceleration according to FIG.
Adopts a method to stop at the start and a predetermined speed n _m a, than the timer stop speed n _m instead of such a scheme by setting a small appropriate starting speed n _s, the speed of the DC motor 3 When n exceeds the starting speed n _s , the timer 7 may start accumulating time. To start the timer 7 at the starting speed n _s , another comparator similar to the comparator 6 is used, and when the speed n exceeds the starting speed n _s , the starting pulse 301
Should be generated. Alternatively, a method may be employed in which the speed n at the time of start and at the end is stored, and the speed n which is accelerated by a constant torque and is in the process of increasing is obtained from the values at the beginning and end of a predetermined period. .
In any case, any method may be used as long as the DC motor 3 can determine the acceleration in a state where the speed increases at a constant acceleration.

In FIGS. 1 and 2, the combination of the rectifier 1 and the DC motor 3 is shown as an embodiment. However, as described above, the method in which the motor can be driven by controlling the motor at a constant torque is used for controlling the speed of the AC motor. There is a vector control system adopted, and the present invention can be applied to a speed control device of a motor adopting this system to achieve an effect. In this case, it is a combination of inverter and AC motor,
Although the control device has a more complicated configuration as compared with the configuration in FIG. 1, for example, an arithmetic unit for determining the current set value i ^* in FIG. 2 is provided, the minor loop of the current control system and the speed control system are still used. The third embodiment is basically the same as the third embodiment in that a main loop is formed and an adjuster is provided for each. The accuracy and difficulty of calculating the moment of inertia of the rotating part at the time of manufacture and the ease of calculating the moment of inertia from the acceleration as in the above-described embodiment are not significantly different between an AC motor and a DC motor.

〔The invention's effect〕

According to the present invention, as described above, the motor is started with a constant torque using the current control system that is a minor loop, the acceleration at that time is measured, and the moment of inertia of the motor is obtained from the measured acceleration and torque. By substituting the value of the moment of inertia with a predetermined formula, the effect that the proportionality coefficient of the speed regulator can be easily determined is obtained. As a result, the time required for adjusting the speed control system, which required a lot of time due to trial and error on-site, has been improved, and no on-site adjustment is required or the required time has been significantly reduced. Is obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a motor speed control system, and FIG. 3 is a circuit diagram showing a conventional motor speed control device. DESCRIPTION OF SYMBOLS 1 ... Rectifier, 2 ... Current transformer, 3 ... DC motor (motor), 31 ... Speed detector, 4 ... Current regulator, 5,9 ... Subtractor, 6 ... Comparator, 7 … Timer, 8… Speed controller, 200… Minor loop, 300… Main loop, 30… Load, 100… AC power supply.

Claims (1)

(57) [Claims] In a method of adjusting a speed control system of a motor control device in which a current control system is a minor loop and a speed control system is a main loop, an integral term (integral term of a proportional coefficient and an integral term in a speed regulator of the speed control system). T _I ), and drive the motor with a constant torque using the current control system, measure the acceleration at that time, obtain the moment of inertia of the motor based on the measured acceleration, and use this moment of inertia. A method for adjusting a motor speed control system, comprising: setting a proportional coefficient (K _P ) of a speed controller by using a motor.