JPH06153559A - Method for detecting overload in servo-control equipment - Google Patents

Abstract

PURPOSE:To detect overloaded one of the phases of a motor or power elements, if any, and thereby to prevent a device from being burnt. CONSTITUTION:CPU 1 calculates the heat loss in circuits due to the passage of a current, excluding radiation energy, based on each of the current commands for the currents passing through transistors 41, 42,..., 46 and phases u, v, w of a motor, which are generated by multipliers 21, 22 and 23 based on torque commands. CPU 1 then compares each heat loss with preset allowable values, and detects as overloading if an allowable value is exceeded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overload detection method for a servo control device, which detects an overload of a motor of a servo control device and a power element of a power supply circuit for supplying electric power to the motor.

[0002]

2. Description of the Related Art Conventionally, this type of overload detection method has been described in connection with A.A.
C. In the servo control device, the multiplier 2 and the base drive circuit 3 are operated by a given torque command for the entire motor.
And the motor is driven by the power supplied by the control circuit by the power transistor 4, and the CPU 1 inputs this torque command to obtain the value a calculated from the torque command and the constant b as shown in FIG. 4 (step 41), a is integrated by the sampling time dt to obtain a heat loss amount value c excluding the heat radiation amount (step 42), and then c is compared with a predetermined allowable value d (step 43). Overload was detected. Further, as for the overload detection of the power transistor, one example is shown in FIG. C. In the servo control device, D. C. A thermostat 17 for detecting overheating of the power transistor is installed in the vicinity of the power transistors 14 ₁ , 14 ₂ , 14 ₃ , 14 ₄ for supplying electric power to the motor 16, and the operation of the thermostat 17 is controlled by C
PU11 detects and detects power transistors 14 ₁ , 14
The overload of ₂ , 14 ₃ and 14 ₄ was detected.

[0003]

The above-described conventional overload detection method detects the overload of the motor circuit by the torque command of the entire motor, or the operation of the thermostat installed close to the power transistor causes the overload of the power transistor. Since the load is detected, even if current is concentrated in one phase with the motor or the power transistor with the power supply circuit, such as when the motor is stopped or rotating at a low speed, the overall load is overloaded. However, there is a drawback in that electric power elements such as a motor and a power transistor may be burned out due to overheating. An object of the present invention is to provide a servo control device capable of detecting an overload in the case where a current is concentrated on one phase of a motor and one power transistor such as a power transistor of a power supply circuit that supplies power to the motor. Is to provide an overload detection method.

[0004]

According to the present invention, there is provided an overload detecting method for a servo control device, wherein a current of the current value is determined by a current value of each phase of the motor and a power element of a power supply circuit for supplying power to the motor. Among the energy heat loss due to the flow of the heat energy, the loss amount contributing to the temperature rise is calculated and compared with a predetermined allowable value, and when the loss amount exceeds the allowable value, it is detected as an overload.

[0005]

The energy heat loss amount is calculated from the current value of each phase of the motor and the power element of the power supply circuit and compared with the allowable value, so that the current concentrates on one phase of the motor or one power element. Even when it flows, it can be detected as an overload.

[0006]

Embodiments of the present invention will now be described with reference to the drawings.
Explain. FIG. 1 shows an embodiment of the overload detection method of the present invention.
Is applied. C. Block diagram of servo controller, diagram
2 is a flowchart of the process of the overload detection method of the servo control device of FIG.
It is a row chart. This servo controller and CPU1
Multiplier 2₁ , 2₂ , 2₃ And base drive circuit 3 and power
-Transistor 4₁ , 4₂ , 4₃ , 4_Four , 4_Five , 4₆ When
Torque finger provided with a motor (not shown)
Based on the law, multiplier 2₁ , 2₂ , 2 ₃ By the phase
i, which is a current command for each of u, v, and w_u , I_{u +}，
i_u-, I_v , I_{v +}, I_v-, I_w , I_{w +}, I_w-Produces
Power transistor 4 via base drive circuit 3
₁ , 4₂ , 4₃ , 4_Four , 4_Five , 4₆ More u phase, v phase, w
By supplying current for each phase, C. Drive the motor
It is like this.

Here, i _u , i _{u +} , i _u- are current commands for the currents flowing through the u-phase of the motor and the power transistors 4 ₁ , 4 ₄ , respectively, and i _v , i _{v +} , i _v- are The v phase of the motor flows through the power transistors 4 ₂ and 4 ₅ , and i _w and i
_{w +} , i _w- are the w-phase of the motor, power transistors 4 ₃ , 4
It is a current command for the current flowing through each of the _six . The overload detection method of this servo control device is, as shown in FIG.
U1 first calculates energy for each phase excluding the heat radiation energy by the following equation in order to judge the energy generated by the current flowing through the transistor and the motor as an overload (step 21). P = Ri ² -q [W] here, P: Energy [W] R: resistance of the circuit including the motor [Omega] i: Current [A] q: radiating energy [W] That is, the power transistors _41, 42 ₂ , ..., 4
Energy loss values a ₁ , a ₂ , a due to the current flowing through ₆
Loss energy values a ₇ , a ₈ and a ₉ due to currents flowing in ₃ , a ₄ , a ₅ and a ₆ and motor phases u, v and w are as follows.

A ₁ = b × ( _{iu +} ) ²⁻ fa ₂ = b × ( _{iv +} ) ²⁻ fa ₃ = b × (i _{w +} ) ²⁻ fa ₄ = b × ( _iu− ) ² _{-f a 5 = b × (i} u-) 2 -f a 6 = b × (i u-) 2 -f a 7 = g × (i u) 2 -h a 8 = g × (i u) 2 _{-h a 9 = g × (i} u) 2 -h here, b, g is a constant corresponding to the R, f, h is also a constant.

Next, a₁ , A₂ , A₃ , A_Four , A_Five , A
₆ , A₇ , A₈ , A₉ And sample time dt (s
ec) is integrated and c₁ , C₂ , C₃ , C_Four , C
_Five , C ₆ , C₇ , C₈ , C₉ (Step 2
2). c₁ = ∫a₁ dt c₂ = ∫a₂ dt c₃ = ∫a₃ dt c_Four = ∫a_Four dt c_Five = ∫a_Five dt c₆ = ∫a₆ dt c₇ = ∫a₇ dt c₈ = ∫a₈ dt c₉ = ∫a₉ dt Furthermore, c₇ , C₈ , C₉ And add c_TenAsk (su
Step 22). c_Ten= C₇ + C₈ + C₉

Subsequently, c ₁₀ is compared with a value d defined as an allowable value for the entire motor (step 23). If c ≧ d in step 23, it is determined that the entire load is overload, and c
_{If 4} <d, proceed to step 24. C in step 24
Each of ₁ , c ₂ , c ₃ , c ₄ , c ₅ , c ₆ is compared with a value e defined as an allowable value in one power transistor, and c ₁ , c ₂ , c ₃ , c ₄ , c ₅ , c ₆
If any one of them is equal to or larger than e, it is judged to be overload, and c ₁ , c ₂ , c ₃ , c ₄ , c
_When both ₅ and c ₆ are smaller than e, step 25
The process proceeds, each and _{c 7, c 8, c 9} , 1 of the motor
Compared with the value i defined as the allowable value in the phase, c
_When any one of ₇ , c ₈ and c ₉ is equal to or larger than i, it is determined to be overload, and when it is smaller than i, the process returns to step 21 at regular intervals and is repeated. Where the value of e is generally

[0011]

[Equation 1]

And in step 24, c ₁ , c ₂ , ...
.., when the value of c ₆ is equal to or larger than e, the corresponding power transistors 4 ₁ , 4 ₂ , ..., 4
₆ is an overload, and in step 25, if the value equal to or larger than i is c ₇ , the u phase of the motor, c ₈ is the v phase of the motor, and c ₉ is the overload of the w phase of the motor. Is. The overload detection method of the servo control device according to the present embodiment detects an overload when the current of the entire motor circuit is excessive, and even if the current of the entire circuit is not excessive, the phase of the motor or the power transistor If the current in one is too large, it is detected as an overload. Therefore, when the current is concentrated in one phase of the motor or when the current is concentrated in one power transistor, the motor or transistor is overheated. It is possible to prevent burnout and the like.

In the embodiment described above, the overload is detected by the current command, but the overload may be detected by the current value of the current flowing through each phase of the motor and each power element detected by the current detector. Needless to say.

[0014]

As described above, the present invention detects overload by the current value of each phase of the motor and each power element of the power supply circuit, so that even if the entire circuit is not overloaded. Since it is possible to detect when one phase of the motor and one power element of the power supply circuit are overloaded, it is possible to detect the one phase of the motor and the power supply circuit such as when the motor is stopped or rotating at a low speed. It is possible to prevent burnout of power elements such as motors and power transistors due to overheating due to concentrated current flowing in certain power elements, and it is possible to identify the overloaded motor phases and power elements. This has the effect of making it easy to find the point of the load.

[Brief description of drawings]

FIG. 1 is a diagram showing a case in which an embodiment of an overload detection method according to the present invention is applied. C. It is a block diagram of a servo control device.

FIG. 2 is a flowchart of steps of an overload detection method for the servo control device of FIG.

3A to 3C to which the first conventional example of the overload detection method is applied.
C. It is a block diagram of a servo control device.

4 is a flowchart of steps of an overload detection method of the servo control device of FIG.

FIG. 5 is a diagram illustrating a D. to which a second conventional example of an overload detection method is applied.
C. It is a block diagram of a servo control device.

[Explanation of symbols]

1 CPU 2 ₁ , 2 ₂ , 2 ₃ Multiplier 3 Base drive circuit 4 ₁ , 4 ₂ , 4 ₃ , 4 ₄ , 4 ₅ , 4 ₆ Power transistor 21, 22, 23, 24, 25 steps

Claims (1)

[Claims] 1. A method of detecting an overload of a servo control device, comprising: detecting an overload of a power element of a motor of the servo control device and a power supply circuit for supplying power to the motor.
Of the energy heat loss due to the flow of the current having the current value depending on the current value of each phase of the motor and each power element of the power supply circuit, the loss amount contributing to the temperature rise is calculated, and the predetermined allowable value is calculated. An overload detection method for a servo control device, comprising: detecting as an overload when the loss amount exceeds the allowable value as compared with a value.