JP2640132B2 - Load driving method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a load driving method, and particularly to a load driving method in a power steering device.

[Conventional technology]

As a conventional load driving method, for example, Japanese Unexamined Patent Publication No.
There is a method described in JP-A-8916, which will be described with reference to FIGS. FIG. 6 is a circuit diagram showing a load driving circuit to which the conventional method is applied, and FIGS.
3 is a time chart and a flowchart for explaining the operation of the circuit shown in FIG.

In FIG. 6, 1 is a processing circuit, 2 is an A / D converter, 3
Is a comparator, 4 is a drive circuit, 5 is a transistor, 6
Is a solenoid, 7 is a diode, 8 is a current detection resistor,
9 is a signal generation circuit for generating a power steering signal.

The processing circuit 1 generates a pulse having a duty ratio determined according to the signal supplied from the signal generation circuit 9, and when the signal supplied to the terminal 1b deviates from a predetermined value determined according to the duty ratio. The duty ratio of the pulse transmitted from the terminal 1a is controlled so that the value of the signal supplied to the terminal 1b becomes the expected value. In addition, when a signal is supplied to the terminal 1c, the terminal
The pulse sent from 1a is cut off.

The operation of the device configured as described above is as follows.
Normally, a power steering signal determined by the vehicle speed, the steering signal and the like is supplied to the processing circuit 1, and as shown in a period T1 in FIG. Sent from. Then, this signal is supplied to the transistor 5 via the drive circuit 4, so that
The transistor 5 is turned on and off at a period determined by the duty ratio of the pulse signal, and the solenoid 6 is turned on during the period shown in FIG.
A current flows as indicated by T1.

Next, for some reason, the current flowing through the solenoid 6 at time t1 becomes excessive, and when the current exceeds the predetermined value I, the comparator 3 generates an output signal. As shown in (1), the pulse signal sent from the terminal 1a is cut off. As a result, the current flowing through the solenoid 6 is reduced as shown in FIG. 7 (b). Since the interruption of the pulse signal continues for a predetermined time T, the power supply to the solenoid 6 is stopped during this time.

Next, when the pause period T has elapsed, as shown in FIG. 7A, a pulse signal is supplied again from time t2, and the current shown in FIG. 7B flows through the solenoid 6.

FIG. 8 is a flowchart when the above operation is controlled by the microcomputer. The transistor 5 is turned on / off by the PWM control in step 100, and
The voltage generated at both ends of the current detection resistor 8 is detected by 1 and whether or not this voltage is abnormal is determined by step 102.
Returning to step 100, if abnormal, the transistor 5 shown in step 103 is turned off. After a certain period of time shown in step 104, the flow returns to step 100.

The above operation has been described for the case of excessive current,
Even in the case of an undercurrent, the comparator detects the current and performs the same operation.

[Problems to be solved by the invention]

As described above, in the conventional load driving method, detection of an excessively large or small abnormal current is determined based on an instantaneous current. Problem.

[Means for solving the problem]

In order to solve such a problem, the present invention calculates an average value of the load current, and when the average value is an abnormal value,
A load is driven by alternately repeating a duty ratio command value and a duty ratio lower than the duty ratio command value,
When the load current becomes a normal value within a predetermined time, the load drive is performed by the duty ratio command value, and when the load current does not become normal within the predetermined time, the load drive is stopped.

[Action]

In the load driving method according to the present invention, the load driving pulse signal is not interrupted even if surge noise or momentary interruption of the signal occurs.

〔Example〕

FIG. 4 is a circuit diagram showing a load driving circuit to which the load driving method according to the present invention is applied. In the figure, 11 is a microcomputer to which a vehicle speed signal a is input, 12 is a PWM generator which inputs a duty ratio signal b and outputs a PWM end signal c and a drive signal h, and 13 is a load current signal i. A
An A / D converter that outputs a / D conversion result signal e and an A / D end signal f, and d and g are start signals. In addition,
4, the same or corresponding parts as those in FIG. 6 are denoted by the same reference numerals.

Next, an embodiment of a load driving method according to the present invention will be described with reference to FIGS. In FIG. 1, first, initial settings are made (step 14). In the initial setting, the initial value of the duty ratio is set to the PWM generator 12, the A / D counter for calculating the average current value by taking in the load current value at a certain time interval is cleared, and the PWM generators 12 and A Enable interrupt from / D converter 13, start signal PWM generator 12
Output to the A / D converter 13 and clearing of the clock counter (C
NT = 0), reset of the flag SKIP (SKIP = 0), and the like. Next, a traveling state is determined from the vehicle speed signal a (step 15), and an average reference current value IR corresponding to the traveling state is determined (step 16).

When the PWM interrupt signal d is generated during the processing of FIG.
The process proceeds to the interrupt processing routine shown in FIG. The PWM end signal c in FIG. 4 is a signal notifying that the drive signal h has been output. In FIG. 2, first, the microcomputer 11
The average current value X, which is the value of the A / D counter, is read (step 18). Next, clear the A / D counter (step 1
9) It is determined whether the flag SKIP is "1" or "0" (step 20). Since the flag SKIP is “0”, the process proceeds to step 20. In step 20, it is determined whether or not X read from the A / D counter is 0.2 or less. If X is greater than 0.2 A, that is, if the load current is normal, the content CNT of the time counter is cleared (step 21), and X and the first
The reference current value IR obtained by the flow shown in the figure is compared (step 22). If X> IR, reduce the duty ratio and
If <IR, increase the duty ratio (Step 2
3,24). When X = IR, the duty ratio does not change.
Proceeding to the next step 25, the duty ratio command value DR is set in the PWM generator 12.

In FIG. 2, when X ≦ 0.2 A, the flag SKIP is set to “1” (step 26), and the content CNT of the time counter is increased by 1 (step 27). Next, it is determined whether or not CNT is 10 or more (step 28). Since CNT <10, the duty ratio of the PWM generator 12 is set to 0% (step 29).

Next, when a PWM end interrupt occurs, the flag SKIP is “1”, so the process proceeds from step 19 to step 30 to set the flag SKIP = 0, and in step 25 the duty ratio command value DR is sent to the PWM generator 12. Is set.

When a PWM end interrupt occurs, the flag S
Since the KIP is "0", steps 19 and 20 to step 26
Then, the duty ratio of the PWM generator 12 is set to 0%.

As can be seen from the above description, the duty ratio repeats between 0% and the command value DR. After some repetitions, step 28
When CNT ≧ 10, the PWM interrupt is prohibited (step 31). That is, X ≦ 0.2A while CNT <10
Is released, that is, when the load current returns to the normal value within the predetermined time, the load drive circuit performs the normal operation shown in steps 18 to 25, but the load current returns to the normal value within the predetermined time. If not, the PWM interrupt is disabled and the PWM generator
12 keeps 0%.

FIG. 5 is a time chart for explaining the operation in this embodiment. 5A shows the duty ratio signal b, FIG. 5B shows the load current signal i, and FIG. 5C shows the average current calculated by the microcomputer 11. S is a detection level for detecting the presence or absence of an abnormality in the load current, and corresponds to 0.2A in FIG. When the load current signal i is normal, the average current value is equal to or higher than the detection level, and the load drive circuit performs a normal operation. When the load current signal i decreases and the average current value becomes lower than the detection level S, that is, X ≦ 0.2 A, the duty ratio signal b repeats the command value DR and 0% as shown in steps 26 to 30 in FIG. Signal. This state is continued for a predetermined time as shown in step 28 of FIG. 2, and within this predetermined time, as shown in FIG.
And the average current value is equal to or higher than the detection level S, that is, X>
At 0.2 A, the duty ratio signal b becomes a signal corresponding to the command value DR as shown in FIG. If the load current signal i remains reduced even after the predetermined time has elapsed, PW
The M interrupt is prohibited (see step 31 in FIG. 2), and the duty ratio = 0% is maintained.

FIG. 3 is a flowchart showing the interrupt processing of the A / D conversion result signal e by the A / D end signal f. In order to calculate the average load current value, the A / D conversion result is added to the A / D counter. I do.

In the above embodiment, the case where the load current is excessively small has been described. However, the same method can be adopted when the load current is excessively large. That is, X ≦ 0.2A in step 20 of FIG.
May be set to, for example, X ≦ 0.2A or X ≧ 10A. 10A
Is an example of an excessive current detection level.

Thus, in this embodiment, even if instantaneous excessive current or undercurrent such as surge noise or instantaneous interruption of signal occurs, the presence or absence of abnormality is detected by the average current. It is no longer determined to be abnormal, and it is possible to prevent interruption of the load drive pulse signal due to an instantaneous excessive current or excessive current.

〔The invention's effect〕

As described above, the present invention calculates the average value of the load current, and when the average value is an abnormal value, alternately repeats the duty ratio command value and the duty ratio having a value lower than the duty ratio command value. Drive the load, and if the load current becomes a normal value within the predetermined time, perform the load drive with the duty ratio command value.If the load current does not become normal within the predetermined time, stop the load drive. Accordingly, even if a surge noise or an instantaneous interruption of a signal occurs, it is not determined that the load current is abnormal, and an effect of preventing interruption of a load driving pulse signal due to the surge noise or an instantaneous interruption of a signal is obtained.

[Brief description of the drawings]

1 to 3 are flowcharts for explaining an embodiment of a load driving method according to the present invention, FIG. 4 is a circuit diagram showing a load driving circuit to which the embodiment of the present invention is applied, and FIG. FIG. 6 is a time chart for explaining the operation in the embodiment of the present invention, and FIGS. 6, 7 and 8 are a load driving circuit, a time chart and a flow chart for explaining a conventional load driving method. 5 ... transistor, 6 ... solenoid, 7 ... diode, 8 ... current detection resistor, 11 ... microcomputer, 12 ... PWM generator, 13 ... A / D converter.

Claims (1)

(57) [Claims] In a load driving method for controlling a load current value by driving a load with a pulse current and changing a duty ratio of the pulse, an average value of the load current is calculated, and the average value is an abnormal value. The load is driven by alternately repeating a duty ratio command value and a duty ratio having a value lower than the duty ratio command value. If the load current becomes a normal value within a predetermined time, the load based on the duty ratio command value is used. A load driving method comprising: driving the load; and stopping the load drive if the load current does not become normal within a predetermined time.