JPH0813197B2 - DC motor load detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is a DC motor load that can be easily added to a DC motor system to measure the load of the DC motor easily. Regarding a detection device.

(Prior Art) Conventionally, various load detection devices have been proposed to detect a load (that is, output) P of a DC motor, but the load of the DC motor is derived from the following relational expression. The armature current Ia which is the current flowing into the terminal of the DC motor
Is usually measured directly.

P = Ec + Ia (1) However, Ec is a back electromotive force appearing in the armature winding.

Further, since the counter electromotive force Ec can be calculated by the following equation (2), the load of the DC motor is ultimately the voltage (terminal voltage) V applied between the terminals of the DC motor and the armature current.
It was calculated from the measured value of Ia.

Ec = V-Ia + R (2) However, R is the resistance of the armature circuit (problems to be solved by the invention). However, even in the load detection device of the DC motor as described above, it is still insufficient. However, there were the following problems.

In the conventional DC motor load detection device, it is essential to measure the armature current Ia flowing into the DC motor as described above.

As is well known, for current measurement, an electric wire through which a current is flowing is wound, a detection coil for a current pickup is newly provided, and a voltage induced in the detection coil is measured. Alternatively, it is necessary to select a configuration in which a minute resistor is connected to the electric wire and the voltage appearing across the minute resistor is measured.

However, the former configuration using the detection coil is
The detection coil increases the cost of the detection system, and the detection coil increases the size and weight of the detection system.

On the other hand, the latter one using a small resistance also consumes electric power due to the small resistance to reduce efficiency, lowers the voltage, and introduces new problems such as heat dissipation of Joule heat generated by the small resistance. It was something that was invited.

The present invention has been made to solve the above problems, and while maximizing the characteristics of the DC motor, it has a simple structure that does not require measurement of the armature current Ia of the DC motor. It is an object of the present invention to provide an excellent DC motor load detection device capable of detecting the load.

Configuration of the Invention (Means for Solving the Problems) The means configured according to the present invention for solving the above problems is, as shown in the basic configuration diagram of FIG. 1, a terminal for detecting a terminal voltage of a DC motor DM. Voltage detection means
C1 and rotation speed detection means for detecting the rotation speed of the DC motor DM
C2, load characteristic storage means C3 for storing the characteristics of the DC motor DM with respect to the load of the DC motor DM and the variable terminal voltage detection means C1 and the rotation speed detection means C2 The gist is a load detecting device for a DC motor, comprising: load estimating means C4 for estimating the load of the DC motor DM from the stored contents of the load characteristic storing means C3 based on the detection result.

(Operation) In the DC motor load detection device of the present invention, the terminal voltage detection means C1 functions as a so-called voltmeter that detects the terminal voltage V applied between the terminals of the DC motor DM.

The rotation speed detecting means C2 is for detecting the rotation speed N of the DC motor DM, and may have any configuration. For example, a conventional encoder or one that detects the pulsating frequency of the armature current Ia of the DC motor DM, etc.
It is realized in various configurations. Further, the detection is not limited to the one in which the rotation speed is directly aimed, and a cycle or the like closely related to the rotation speed may be a detection target.

The load characteristic storage means C3 is the terminal voltage V of the DC motor DM.
The characteristics of the DC motor DM with respect to the load P, which has the number of revolutions N as a variable, are stored. As is well known, the DC motor DM is roughly classified into a separately excited type and a self-excited type according to the difference in its excitation method. Further, the self-excited type motor is classified into a shunt winding type, a series winding type, and a multiple winding type. Common to all of these various excitation type DC motors DM, as described above, is the DC motor DM.
The load P of is expressed by equation (1). Therefore, in order to detect the load P, the armature current Ia and the back electromotive force Ec must be known.

Here, the counter electromotive force Ec is obtained by knowing the terminal voltage V and the armature current Ia under the condition that the resistance R of the armature circuit of the DC motor DM is stable, as is clear from the equation (2). It can be calculated. That is, the counter electromotive force Ec is
A function f1 of the terminal voltage V and the armature current Ia as shown in equation (3)
Can be represented by

Ec = f1 (V, Ia) (3) On the other hand, as is well known, the armature current Ia and the rotational speed N of the DC motor DM have a relationship as shown in equation (4).

N = (V−Ia + R) / K + φ (4) where φ is the number of effective magnetic flux [Wb] of each magnetic pole K is a proportional constant When this is solved for the armature current Ia, the equation (4) becomes (5), and the armature current Ia is expressed as a function f2 of the terminal voltage V, the rotation speed N, and the magnetic flux φ as shown in expression (6).

Ia = (V−N + L + φ) / R (5) Ia = f2 (V, N, φ) (6) Here, the effective magnetic flux φ is obtained from the hysteresis characteristic of the field by knowing the field current If. It is of a nature that is diagrammatically determined. However, if the DC motor DM is a separately excited motor, the field current If is a constant that always shows a constant value, and the equation (6) is simply a function of the terminal voltage V and the rotation speed N.

Even in a self-excited motor, since the terminal voltage V is directly connected to the excitation winding and the field current If flows in the shunt motor, the effective magnetic flux φ excited by the field current If is
The value of is a function f3 of the terminal voltage V as in the expression (7), and eventually the armature current Ia is a function of the terminal voltage V and the rotation speed N as in the case of the separately excited motor.

φ = f3 (V) (7) On the other hand, in the self-excited series-wound motor, the armature current Ia directly flows into the exciting circuit and the exciting current If (= I
a). That is, in the case of a series-wound motor, the effective magnetic flux φ is expressed by the equation (8) as a function f4 of the armature current Ia, and even in this case, the armature current Ia is the terminal voltage V and the rotation speed N. Will be expressed as a function of.

φ = f4 (Ia) (8) In addition, there is a compound winding motor as a self-excited motor, but this is a combination of the shunt winding motor and the series winding motor. The characteristics are obtained by adding the two or by taking the difference. Therefore, as is apparent from the above description, the effective magnetic flux φ is the terminal voltage V and the armature current Ia.
It is expressed as a function f5 of (9).

φ = f5 (V, Ia) (9) That is, the armature current Ia of the DC motor DM is effective regardless of its excitation method, depending on other factors from the function f2 of the equation (6). The characteristic is expressed as a function f6 of only the terminal voltage V and the rotation speed N as shown in the equation (10) excluding the magnetic flux φ, and the function f6 can be obtained by performing a characteristic test of the DC motor DM in advance. Or the terminal voltage V
Can be obtained as a two-dimensional table of the rotation speed N and the rotation speed N.

Ia = f6 (V, N) (10) In addition, the formula for expressing the counter electromotive force Ec in the above formula (3) is obtained by substituting the formula (10) into the armature current Ia. Similarly, it can be expressed as a function f7 of the terminal voltage V and the rotation speed N, and Ec = f7 (V, N) (11) Therefore, the target load P of the DC motor DM is
By substituting the equations (10) and (11) into the equation (1), respectively, it can be seen that it is expressed as a function f of the terminal voltage V and the rotation speed N.

P = f (V, N) (12) The load characteristic storage means C3 in the present invention stores the function f as a mathematical expression or as a two-dimensional table of the terminal voltage V and the rotation speed N. The load P can be easily calculated from the terminal voltage V and the rotation speed N.

The load estimation means C4 estimates the load of the DC motor DM from the stored contents of the load characteristic storage means C3 based on the detection results of the terminal voltage detection means C1 and the rotation speed detection means C2. That is, the load characteristic storage means C3, which stores the load P as a function f of the terminal voltage V and the rotation speed N as described above, is detected by the terminal voltage detection means C1 and the rotation speed detection means C2. For example, if the load characteristic storage means C4 stores the load characteristic as a mathematical expression, it is substituted into the mathematical expression, or if it is stored as a table, The load P is searched by searching the table while performing interpolation calculation.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(Embodiment) FIG. 2 is a block diagram showing a configuration in which the load detecting device for a DC motor of the embodiment is applied to control of a power window of a vehicle.

In order to operate the DC motor 10 that is a power source for raising and lowering the window provided in the vehicle, a 2-contact type UP-DOWN switch (hereinafter,
12) is provided. An on-vehicle battery 14 is used as the voltage source of the DC motor 10.

The electronic control unit 20 connected to the DC motor 10, the switch 12 and the battery 14, respectively, serves as the center of control, and is configured as a digital circuit centered on a known microcomputer. ROM22 that stores procedures and tables in advance, CPU24 that executes logical operations according to the processing procedures, RAM26 that stores temporary information and assists the logical operations of CPU24, and these logic elements and other constituent electric elements It is provided with an input / output port 28 that enables information to be exchanged with it.
Further, the following electric elements are used to connect the input / output port 28 with the DC motor 10, the switch 12 and the battery 14 while matching them. First,
The buffer 30 is provided to detect the UP-DOWN operation state of the switch 12 and to convert the detection result into a digital signal. The UP terminal 12a and the DOWN operation which close the ground terminal 12a by the UP operation of the switch 12 are performed. Are connected to the ground terminal 12a and the closed DOWN terminal 12c. The relays 32 and 34 are driven by drive circuits 36 and 38 which operate by the output signals from the input / output port 28,
When the drive circuit 36 operates, the contact of the relay 32 is switched to the side of 32a, and one terminal 10a of the DC motor 10 is connected to the battery 1
While being connected to the positive terminal of 4, the other terminal 10b of the DC motor 10 is connected to the negative terminal of the battery 14. As a result, the DC motor 10 is driven in the normal direction to raise the window. When the drive circuit 38 operates and the contact of the relay 34 is switched to the side of 34a, the DC motor 10 and the battery 14 are connected in the opposite direction to the above state, and the DC motor 10 is driven in reverse to lower the window. Further, the primary winding of the transformer 40 is inserted in the line connecting the battery 14 and the DC motor 10 in order to detect the current waveform flowing into the motor by driving the DC motor 10, and is supplied to the DC motor 10. The induced voltage corresponding to the pulsation of the generated current is mutually induced in the secondary winding. The rotation detection circuit 42 is connected to the secondary winding of the transformer 40, converts the pulsating voltage generated by the mutual induction into a rectangular wave, and outputs the rectangular wave to the input / output port 28. As is well known, in the DC motor, the armature current pulsates every time the brush and the commutator segment are separated from each other in principle. Therefore,
If the pulsation is detected by the transformer 40 and the number of segments of the commutator is known, it is possible to easily detect the rotation degree such as the rotation angle and the rotation speed of the DC motor. Also, the analog / digital converter (A / D converter) 44 connected to the positive terminal of the battery 14 is the battery 14
It is provided to detect the terminal voltage of, and outputs a digital signal corresponding to the terminal voltage to the input / output port 20.

In the load detection device of the embodiment configured as described above, the electronic control device 20 executes control according to the program stored in the ROM 22. FIG. 3 is a flowchart of the program. The CPU 24 is activated by a rotating operation of a key (not shown) for starting the supply of electric power from the battery 14 to the electric system of the vehicle including the electronic control unit 20,
The processing according to this program is executed.

First, immediately after the start-up, initial setting processing such as initializing the RAM 26 is performed as a preparation for enabling the processing described below (step 100). Next, in order to determine whether or not the occupant has commanded the window up / down control, the UP operation in which the UP terminal 12b is closed with the ground terminal 12a in the operation state of the switch 12 from the output of the buffer 30 is performed. It is judged whether or not it is done (step
102), only when the UP operation is performed, the window raising process from the following steps 103 to 113 is executed.

First, in step 103, a drive signal is output to the drive circuit 36 via the input / output port 28 to immediately raise the window, and the relay 32 is driven to rotate the DC motor 10 in the forward direction. In the following step 104, which is a process for detecting the rising position of the window, the number of rectangular wave pulses input from the rotation detection circuit 42 is counted, and the count value of the position counter XC provided in the RAM 26 is incremented.

Here, the position counter XC has a content of 0 when it is detected that the window is fully opened as described later.
The rotation detecting means 42 is reset from the time when the window rising process (step 103) is started.
Each time the pulse signal is input, it is incremented (step 104). Further, in the DC motor 10 used in this embodiment, the brush and the segment are separated from each other 200 times while the window is rotationally driven from the fully open state to the fully closed state, and therefore the position counter XC is It is configured to have a counting capability of at least 200.

Therefore, by knowing the value of the position counter XC, it is possible to linearly detect the ascending / descending position of the window, but the following step 105 is a step for executing the processing, and the window value is calculated from the count value of the counter XC. When the position X is calculated, its contents are stored in the RAM 26.

Next, in step 106, which is executed, the terminal voltage of the battery 14, which is the voltage source of the DC motor 10, is changed to the A / D converter 4
The value is read from the digital signal from 4, and this value is stored in the RAM 26 as the terminal voltage V applied between the terminals 10a and 10b of the DC motor 10 as described above. In the following description, the terminal voltage V of the DC motor 10 will be referred to as the power supply voltage V of the DC motor 10 or simply the power supply voltage V. Further, in the following step 107, a process of measuring the pulse frequency of the rotation detection circuit 42 that outputs a pulse signal at a frequency proportional to the rotation speed of the DC motor 10 is executed, and the pulse period T obtained by this process is also It is stored in the RAM 26 in the same manner as above.

By the processing of each of the above steps, the power supply voltage V of the DC motor 10 and the pulse period T indicating the reciprocal value of the rotation speed are 2
One value is stored in a predetermined address of the RAM 26, and the load P of the DC motor 10 is calculated by the search process of the table Y (V, T) using these values (step 1
08).

4 and 5 are explanatory views for qualitatively facilitating the understanding of the load P search processing. First, FIG. 4 shows two specific examples of the pulse signal input from the rotation detection circuit 42. In the figure, a is a very regular pulse train, and its period T is constant. Therefore, it is determined that the DC motor 10 at this time is performing stable operation without variations in the load P and the power supply voltage V.
On the other hand, in b, the cycle T is gradually increasing. This is because the load P of the DC motor 10 is gradually increased and thus the rotation speed is decreased, or the load P is constant but the power supply voltage V is decreased for some reason and the rotation speed is decreased. There are two possible causes.
That is, it is not possible to judge the increase / decrease of the load P of the DC motor 10 simply from the phenomenon of the reduction of the rotation speed, but by introducing the relation of the power supply voltage V into this, it is possible to accurately judge the increase / decrease of the load P. The result of this more quantitative analysis is clear from the above-mentioned equation (12), and is valid for all excitation-type DC motors 10. Therefore, in this embodiment, the characteristic test of the DC motor 10 is performed in advance, the load P is measured by using the power supply voltage V and the cycle T as parameter meters, and the measurement result is stored in the RAM 26 as a two-dimensional table Y (V, T). I remember it.

Next, FIG. 5 shows a search result as an example of the table Y (V, T) representing the load P stored in the RAM 26 as described above for each window position X. The solid line in the figure is the search result. As is clear from the figure, the window position X is 0 to 20.
Even while the temperature rises to 0, the load P of the DC motor 10 greatly changes due to the efficiency of the window regulator, mechanical friction, and the like. Then, when the window position X is 200, when the window is fully closed, the window is prevented from further rising, so that the load on the DC motor 10 becomes maximum.

In this way, the load P of the DC motor 10 is set to the table Y (V,
T), but in the following step 109,
Comparison of the detection result of the table Y (V, T) thus obtained and the pinching load HY (X) [Y (V, T)> HY
(X)] is performed. Here, the pinching load HY (X) is defined as a function of the window position X,
The search value Y of the previous load at a certain window position X
The value is determined by the following equation as a value larger than (V, T) by a predetermined value ΔY.

HY (X) = Y (V, T) + ΔY (13) In FIG. 5 described above, the dotted line represents the pinching load HY (X).

Therefore, in the normal case, the pinching load HY (X) is always larger by ΔY than the current search value Y (V, T) of the load, but the load value Y (V, T) searched this time. When T) becomes a large value due to the inclusion of something in the window, the determination at step 109 becomes affirmative, and only at this time is step 110 executed. Step 110 is a process for avoiding the entrapment of the window, and immediately stops the driving of the drive circuit 36 to cause the DC motor 10 to perform the reverse rotation operation, and commands the operation of the drive circuit 38 for the reverse rotation operation. The position X is lowered by the width W, and one processing of this program ends.

On the other hand, when the determination in step 109 is negative,
It is determined that no abnormality such as pinching has occurred, and the pinching load HY (X) is updated in the following step 111. This is because the load P of the DC motor 10 has many factors such as mechanical friction as described above.
These factors may accumulate over time and cause a large change, and are not constant. Therefore, without any correspondence, the pinching load that is a function of only the window position X
The value of HY (X) cannot hold the difference of the predetermined value ΔY with respect to the search value of the table Y (V, T) representing the load P of the normal DC motor 10 in which no entrapment has occurred, and finally it cannot be held. It is expected that erroneous detection of entrapment (step 109) will occur. Therefore, a new value of the pinching load HY (X) is determined using the search value of the table Y ((V, T) this time, and these values are stored in the RAM 26. The so-called updating process is performed.

After such processing, in the subsequent step 112, it is determined whether or not the pulse signal from the rotation detection circuit 42 is obtained during the predetermined period, and it is determined whether or not the window has already reached the fully closed state. . That is, when the window is in the fully closed state, the DC motor 10 cannot rotate because the upward drive of the window is blocked no matter how the drive circuit 36 is operated, and the pulse signal from the rotation detection circuit 42 is not possible. Is not possible. Therefore, when this state is detected and the determination in step 112 is affirmative, it is determined that the window is in the fully closed state, and in the following step 113 the drive of the DC motor 10 is stopped and the position counter
Set XC to 200, which indicates the fully closed state, and
When the determination of step 112 is negative, the processing of step 113 is terminated without executing the processing of step 113.

On the other hand, when it is determined that the operation of the switch 12 is not the window raising operation by the processing of step 102, step 121 is executed instead of the above processing, and it is determined whether or not the window lowering operation is performed. . Next, the processing when the window lowering operation is performed in step 121 will be described.

At this time, a process (step 122) of immediately issuing a command to the drive circuit 38 to operate the relay 34 to lower the window is executed to lower the window. Then, in order to detect how much the window is lowered by this operation, the position counter XC is counted down every time a pulse signal is input from the rotation detection circuit 42 (step 123), and the window position X is calculated from this value. It is calculated and calculated (step 124). After these processes, as in the case described above, when the window is fully opened, the downward drive of the window is blocked, and the pulse signal from the rotation detection circuit 42 is not input and the non-input state is detected (step 125), and the pulse signal is detected. Step 126 is executed only when it is detected that is not input.
And the process of setting the count content of the position counter XC to 0 is executed (step 126).
The process for descending the window is completed.

Further, when it is determined by the processing of step 121 that the window lowering operation has not been performed, it is determined that no operation for the position of the window is necessary, and the processing proceeds to the above steps without performing the steps.
Moving to 130, the stop of the DC motor 10 is commanded and the processing of this program ends.

According to the load detecting device for the DC motor of the present embodiment configured as described above, the load P of the DC motor 10 has a simple and inexpensive hardware configuration that merely detects the pulsation of the power supply voltage V and the inflow current. It becomes possible to detect. That is, with a simple configuration that does not require measurement of the armature current Ia of the DC motor 10, without reducing the efficiency of the motor,
The load can be detected.

Further, it is a commonly used device configuration to detect the rotation speed of the motor for various controls. For example,
In this embodiment, the pulse signals are counted to detect the position of the window (step 104, step 123), or the state where the pulse signal is not input for a predetermined period is detected to detect the lock of the window. (Step 112, step 125). Therefore, according to the load detecting device of the present embodiment, the control device and the rotational speed detecting portion thereof are shared, so that further simplification of the device is achieved, which is a very advantageous configuration for use in combination with other devices. I can say.

Effects of the Invention As described above in detail with reference to the examples, the load detection device of the DC motor of the present invention is a simple configuration that does not require measurement of the armature current Ia of the DC motor, is inexpensive, and is simple. Can be realized.

Further, a resistor for blocking the armature current Ia is not required, and it is possible to drive the DC motor with high efficiency while maximizing the characteristics of the DC motor, which is an excellent load detection device for the DC motor.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram showing a basic configuration of a load detecting device for a DC motor of the present invention, FIG. 2 is an electric circuit diagram of a load detecting device for a DC motor of an embodiment, and FIG. 3 is used in the same embodiment. FIG. 4 and FIG. 5 are flowcharts of the program executed, and operation explanatory diagrams for explaining the operation of the embodiment. 10 ... DC motor, 12 ... Switch 14 ... Battery, 20 ... Electronic control circuit 24 ... CPU, 42 ... Rotation detection circuit

Claims (1)

[Claims] 1. A terminal voltage detecting means for detecting a terminal voltage of a DC motor, a rotation speed detecting means for detecting a rotation speed of the DC motor, and the DC motor having variables of the terminal voltage and the rotation speed of the DC motor. Load characteristic storage means for storing characteristics of the DC motor, and load estimation means for estimating the load of the DC motor from the stored contents of the load characteristic storage means based on the detection results of the terminal voltage detection means and the rotation speed detection means. A load detection device for a DC motor, comprising: