JPH0246084B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sensor processing device that calculates the absolute value of displacement from the output of a mechanical position sensor.

The sensor processing method that calculates the absolute value of displacement by subtracting the minimum value from the current value of the sensor output that detects mechanical position (distance, angle) can be divided into the following two methods depending on how the minimum value is handled. Broadly classified. The first method is to detect the mechanical limit point (lower limit) of the sensor using a limit switch or the like and set the sensor output at that time to the lowest value. The second method does not detect the lower limit using a limit switch or the like, but always updates and stores the lowest value of the sensor output.

FIG. 2 shows a mechanical throttle opening sensor as a typical example of a position sensor used in an automobile. 1 is a resistor (actually arc-shaped) constituting the potentiometer; 2 is a voltage detection contact that slides into contact with the resistor according to the throttle opening; 3
is a contact for a limit switch that moves integrally with contact 2 and contacts terminal 4 at the mechanical lower limit of this sensor. One end of resistor 1 is connected to the power supply Vcc (for example
5V) and the other end is connected to ground, so from contact 2 there is a voltage V which is the resistance-divided voltage of Vcc.
is obtained. On the other hand, since the terminal 4 is connected to the ground, when the contact 3 contacts the terminal 4, a limit point detection signal LL of 0V is output.

The first method is to set the output of contact 2 at the time when this signal LL is detected as the minimum value Vmin of the sensor. Thereafter, the minimum value (offset) Vmin is subtracted from the current pressure value V obtained from the contact point 2 to obtain the displacement amount (actual opening degree). The disadvantage of this method is that
Since a certain degree of width must be allowed for the mechanical limit point, the accuracy of the obtained absolute value is poor. For this reason, currently the second method is mainstream, in which the lowest value appearing in the output V of contact 2 is sequentially updated and stored without using a lower limit switch using contact 3 and terminal 4. However, this method produces abnormally low values that cannot occur under normal operation.
If it is stored as Vmin, the value will never be updated again, so there is a drawback that all subsequent absolute values will contain abnormal errors.

The present invention improves the second method to obtain a highly accurate absolute value output, and is characterized by successively updating the lowest value of the output obtained from the mechanical position sensor. A sensor processing device which calculates the absolute value of the displacement amount at each point in time by storing the sensor output in a memory circuit and detecting the difference between the current value of the sensor output and the minimum value using a difference detection means. The structure of the position sensor is such that a limit point detection signal is generated at a mechanical lower limit, and a comparison means for comparing the absolute value with a preset reference value at the time when the limit point detection signal is generated, and the absolute value and updating means for updating the contents of the memory circuit with the current value at that time or a constant value when the value exceeds the reference value.

The present invention will be described in detail below with reference to the embodiment shown in FIG. In the figure, 10 is a circuit that sequentially updates and stores the above-mentioned maximum resistance value Vmin, and 11
compares the current value V and the lowest value Vmin and finds that V<
If it is Vmin, a comparator turns on the switch 12 and updates the contents (Vmin) of the memory circuit 10 with the current value V. 13 is a difference detector that calculates V-Vmin at each time point and obtains the absolute value. . These circuits 1
0 to 13 are necessary elements when executing the conventional second method, and with only these elements, the lowest value in the memory circuit 10
Vmin is always updated only in the lower direction. Therefore, if an abnormally low value is stored, the output of the comparator 11 will always be V>Vmin from then on, and the contents of the storage circuit 10 will never return to within the normal value range.

In this example, to make this possible, switch 1
4, a difference detector 15 and a comparator 16 are provided. The switch 14 normally falls to the solid line side and the difference detector 15
Both inputs are set to the current value V (therefore, the difference output DIF is 0), but the limit point detection signal LL (=
0V), it switches to the dashed line side, and the difference detector 1
Let the two inputs of No. 5 be the current value V and the minimum value Vmin. As a result, the difference detector 15 outputs a difference DIF=V-
Calculate Vmin. The current value V at the time when the signal LL is generated is usually a value close to the minimum value Vmin. Therefore, if the memory circuit 10 is operating normally, the differential output DIF is a small value, but if the lowest value Vmin in the memory circuit 10 is an abnormally low value (the lowest value is 0), the differential output becomes large, and the comparator 16 When the output becomes DIF>REF, the switch 12, which is an updating means for updating the contents of the memory circuit 10, is turned on. As a result, the current value V at that point in the relationship of V>Vmin is the subsequent lowest value Vmin
It is stored in the memory circuit 10 as . Note that the value stored at this time may not be the current value V, but may be a predetermined initial value. Further, the reference value REF used by the comparator 16 is a constant value that is set assuming the minimum value that Vmin can take in normal operation from a mechanical standpoint. Furthermore, since FIG. 1 is a functional representation, its configuration can be modified in various ways. For example, the difference detector 15 can be omitted if the output (V-Vmin) of the difference detector 13 is guided to the DIF input of the comparator 16 only when the signal LL is generated by the switch 14.

As described above, according to the present invention, the absolute value of the displacement amount can be determined with high accuracy from the output of a mechanical position sensor such as a throttle sensor.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is an explanatory diagram of the throttle sensor. In the figure, 2 is a contact for detecting the current position, 3 is a contact for lower limit position detection, 10 is a minimum value storage circuit, 11, 16
is a comparator, 12 and 14 are switches, and 13 and 15 are difference detectors.

Claims (1)

[Claims] 1 The lowest value of the output obtained from the mechanical position sensor is stored in the memory circuit while being updated sequentially.
The sensor processing device determines the absolute value of the amount of displacement at each point in time by detecting the difference between the current value of the sensor output and the minimum value using a difference detection means, and the structure of the position sensor is set to a mechanical lower limit. a comparison means for comparing the absolute value with a preset reference value at the time when the limit point detection signal is generated; and updating means for updating the contents of the memory circuit with a current value or a constant value.