JPH07159438A - Correcting device of acceleration sensor - Google Patents

Abstract

PURPOSE:To correctly distinguish a sloping road and also to suitably correct a zero drift of an acceleration sensor, by storing a value of the acceleration sensor in a stopping time, on detecting a change from one state to the other state between the traveling and stoppage of a car. CONSTITUTION:In an acceleration sensor 40, a weight 42 is provided in one end side of a rod-like sensor member 41, and a strain produced in the sensor member 41 by accelerating is detected as a change of voltage by a strain detecting part 43. In a car, an electronic control circuit 50 for controlling a running state, etc., of the car and for carrying out various operation processings of the zero point correction of the sensor 40, etc., is provided. The circuit 50 comprises a CPU 51, ROM 52, RAM 53, etc. On detecting a change from one state to the other state between the traveling and stoppage of the car, a value of the sensor 40 in a stopping time is stored in the RAM 53, therewith the CPU 51 integrates values of the sensor 40 stored by a drift amount computing means, averages them to find a drift amount from zero point, and carries out zero point correction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a correction device for an acceleration sensor of the type that detects absolute acceleration, and more particularly to a correction device for an acceleration sensor that corrects zero-point drift of the acceleration sensor.

[0002]

2. Description of the Related Art Conventionally, as an acceleration sensor, for example, an acceleration sensor which calculates a relative acceleration from a change in wheel speed has been known. Strain)
An acceleration sensor called a so-called G sensor (for example, a DC sensor) that detects absolute acceleration by grasping it as a change in current or voltage
Acceleration sensors) are known.

The acceleration sensor of the type that detects absolute acceleration has a problem that the zero point gradually drifts due to long-term use because of the structure of detecting acceleration from the strain of the sensor member. For example, if this acceleration sensor is used for a long period of time, the sensor member itself may be distorted due to aging, causing electrical changes,
Acceleration may be slightly output even when the vehicle is stopped.

[0004]

As a countermeasure to this problem, for example, a method may be considered in which the initial characteristics of the acceleration sensor are rigorously driven so that even if the zero point drifts due to a change over time, the design will be within the required accuracy. However, there is a problem that the work for improving the accuracy is difficult and the cost is increased.

In addition to the above, there is a technique of correcting the output of the G sensor by comparing the vehicle body acceleration estimated from the wheel speed with the output of the G sensor. However, with this method, since the G component due to the slope and the drift of the G sensor cannot be distinguished, both are corrected at the same time, resulting in another problem that the slope cannot be detected.

Further, in Japanese Patent Laid-Open No. 63-116917, when the absolute values of a plurality of upper and lower G sensors simultaneously exceed a set value and the state continues for a predetermined time or longer, it is determined to be a slope or a bank. The average value of the G sensor output
A technique of subtracting from the output of the sensor is disclosed. However, in this case as well, the G component and G
There is a similar problem because the sensor drift cannot be distinguished, and there is also a problem that the structure becomes complicated because a plurality of G sensors are required.

The present invention has been made in order to solve the occurrence of such a problem, and provides an acceleration sensor capable of accurately distinguishing a slope and correcting the zero-point drift due to a change with time of the acceleration sensor. An object is to provide a correction device.

[0008]

The invention according to claim 1 for achieving the above object is a correction device for an acceleration sensor for detecting an absolute acceleration of a vehicle as shown in FIG. A vehicle state detecting means for detecting a change from one state to the other of the two states of stop and
When the vehicle state detection means detects that the state of the vehicle has changed, a storage means for storing the value of the acceleration sensor when the vehicle is stopped, and a value of the acceleration sensor stored by the storage means Drift amount calculation means for obtaining the drift amount from the zero point by integrating and averaging, and zero point correction means for performing the zero point correction by subtracting the drift amount obtained by the drift amount calculation means from the value of the acceleration sensor. A gist is a correction device for an acceleration sensor, which is provided with.

[0009]

The present invention for achieving the above object is a correction device for an acceleration sensor for detecting the absolute acceleration of a vehicle, wherein one of the two states, running and stopping, of the vehicle is detected by the vehicle state detecting means. When it is detected that the state has changed, the storage means stores the value of the acceleration sensor when the vehicle is stopped, and the drift amount calculation means integrates and averages the stored values of the acceleration sensor. Then, the drift amount from 0 point is obtained. Then, the zero point correction means subtracts this drift amount from the value of the acceleration sensor to perform the zero point correction.

In other words, the present invention integrates and averages the values of the acceleration sensor every time the vehicle is stopped, based on the idea that, in normal driving, a slope goes down when it climbs up, and there is no slope that lasts forever. By doing so, the influence of the slope is eliminated to obtain the drift amount, and the zero amount of the actual acceleration sensor is corrected using this drift amount. Specifically, as shown in FIG. 2, for example, in the case of an acceleration sensor in which the 0 point drifts by +1 and the vehicle is stopped on each of the uphill +10 and down-10 slopes, the sensor outputs are +11. , -9, and when they are integrated and then averaged, (+ 111-9) / 2 = + 1 and the influence of the slope is ± 0. Therefore, the drift amount (+1) for the 0-point correction is accurate. You will be asked.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a schematic configuration diagram showing a system configuration of a vehicle provided with the acceleration sensor correction device of the present embodiment. It should be noted that this vehicle can perform traction control based on the value of the acceleration sensor.

As shown in FIG. 3, 1 is an engine, 2 is an intake pipe, 3 is an air flow meter, 4 is a fuel injection valve, 5 is an ignition plug, 6 is a distributor, 7 is an engine speed consisting of a gear and an electromagnetic pickup. A sensor, 8 is a first throttle valve that is driven according to the depression amount of an accelerator pedal 9 to adjust the intake air amount, 10 is a second throttle valve that adjusts the intake air amount during traction control (acceleration slip control), and 11 is a second throttle valve. D that drives the throttle valve 10
C motor, 12 is a first throttle sensor that detects the opening of the first throttle valve 8, and 13 is a second throttle sensor that detects the opening of the second throttle valve 10.

Further, 20 and 21 are drive wheels, 24 and 25 are drive wheel speed sensors for detecting the rotational speeds of the left and right drive wheels 20 and 21, 26 and 27 are guide wheels, and 28 and 29 are guide wheel speed sensors. Yes, each speed sensor 24, 25, 28, 29
Is composed of a gear and an electromagnetic pickup. The brakes 30 to 33 are provided on the wheels 20, 21, 26, and 27, and the brakes 30 to 33 are provided on the brakes 30 to 33.
Brake hydraulic circuits 35 to 38 for driving the are connected.

Further, in this embodiment, an acceleration sensor 40 is arranged as a G sensor for detecting absolute acceleration. The location of the acceleration sensor 40 may be, for example, the center of the vehicle, but is not particularly limited as long as the acceleration in the front-rear direction of the vehicle can be detected. As shown in FIG. 4, the acceleration sensor 40 is provided with a weight 42 on the tip side of a rod-shaped sensor member 41, and detects strain generated in the sensor member 41 due to acceleration as a change in voltage by a strain detection unit 43. The acceleration is detected by the output from the strain detector 43. Therefore, for example, when the vehicle is stopped on a level ground, an output indicating a predetermined 0 point is obtained, and when acceleration is performed, an output according to the acceleration is obtained, but when the vehicle is stopped on a slope, When the vehicle is present, a predetermined output (for example, + for uphill and − for downhill) is obtained by the component of gravity corresponding to the slope of the slope.

Further, the vehicle is provided with an electronic control circuit (E) as a device for controlling the traveling state of the vehicle and for performing various arithmetic processing such as zero point correction of the acceleration sensor 40 described later.
CU) 50 is provided. This ECU 50 is shown in FIG.
As shown in, the well-known CPU 51, ROM 52, RAM 5
3, an input unit 54, an output unit 55, a bus 56 connecting them, and the like, and configured as a microcomputer. Of these, the input section 54 includes an air flow meter 3, an engine speed sensor 7, a first throttle sensor 1
2, second throttle sensor 13, drive wheel speed sensor 2
4, 25, induced wheel speed sensors 28, 29, and acceleration sensor 40 are connected. On the other hand, the output unit 55 is provided with a fuel injection valve 4, a distributor 6, a DC motor 11, and brake hydraulic circuits 35 to 38 via a drive circuit (not shown).
Are connected.

Next, in the above-mentioned configuration, the zero point correction process of the acceleration sensor 40, which is the main part of this embodiment, will be described.
This will be described based on the flowchart of FIG. As shown in FIG. 6, in a state where the engine 1 is started and is rotating, in S100, it is determined whether the vehicle is stopped or not based on the outputs from the driven wheel speed sensors 28 and 29. It is determined by whether it is "0". If an affirmative determination is made here, the process proceeds to S110, and if a negative determination is made, S14.
Go to 0.

In S110, a stop flag TF indicating that the vehicle is stopped is turned on (ON), and the process proceeds to S120. In S120, since the vehicle is stopped, the average value Gs (n) of the output when the acceleration sensor 40 is stopped is calculated. That is, sampling is performed n times (for example, 4 times) during the stop, and the more stable average value Gs (n) is obtained.
Is calculated, and this value is used as the acceleration sensor 40 at one stop.
Is stored as the output value of.

On the other hand, in S140, where the vehicle is judged to be running in S100, it is judged whether or not the vehicle speed exceeds a predetermined value V (for example, 10 km / h) indicating a low speed,
If an affirmative decision is made here, the operation proceeds to S150, whereas if a negative decision is made, the operation proceeds to S130. That is, this determination is to pass the process for calculating the drift amount when the vehicle speed is low.

In S150, it is determined whether or not the stop flag TF is on, that is, whether or not the vehicle was previously stopped. If an affirmative decision is made here, the operation proceeds to step S160, while if a negative decision is made, the operation proceeds to step S130. In S160, since the vehicle is currently traveling, the stop flag TF is turned off (OFF), and S
Proceed to 170.

In S170, it is determined whether or not the absolute value of the average value Gs (n) of the acceleration sensor 40 calculated in S120 is below a predetermined determination value kGs. If a positive determination is made here, S180 If the answer is negative, S
Proceed to 130. That is, this process is performed by the acceleration sensor 40.
It is for checking whether the average value Gs (n) of is an abnormal value.

At S180, since the vehicle has changed from the stopped state to the running state, the average value Gs of the acceleration sensor 40 obtained when the vehicle is stopped, obtained at S120.
(N) is integrated, and the integrated value is divided by the number of integrations n to obtain the drift amount G0 (n). It should be noted that, here, the integration and the division are represented by one formula, but more specifically, as shown in FIG. 7, the average value Gs (n) of the acceleration sensor 40 is sequentially calculated every time the vehicle travels (S181). Accumulate (S1
82), when the number of times of integration reaches a predetermined value n as judged by the counter C (S183, S184),
Drift amount G0
(N) is obtained (S185).

Returning to FIG. 6, in S190, it is determined whether or not the calculated drift amount G0 (n) is less than a predetermined −kG0. If an affirmative determination is made here, the process proceeds to S200 and the drift amount G0 (n). Set guard value -kG0 as
Proceed to. On the other hand, if a negative determination is made in S190, S210
Contrary to S190, the calculated drift amount G0
It is determined whether or not (n) exceeds a predetermined kG0. If an affirmative determination is made here, the routine proceeds to S220, where the drift amount G0
As (n), the guard value kG0 is set and the process proceeds to S130. On the other hand, if a negative determination is made, the process directly proceeds to S130.

Then, in S130, the drift amount G0 (n) calculated in S180 is subtracted from the output value G (n) of the acceleration sensor 40 detected this time to obtain 0.
Perform point correction to obtain the corrected acceleration GH (n),
This process ends once. That is, in this process, each time the vehicle stops, the average value Gs (n) of the acceleration sensor 40 is obtained, and the average value Gs (n) is accumulated for a predetermined number of times n at each stop and divided by n. Thus, the drift amount G0 (n) at the zero point can be accurately obtained by averaging. Therefore, the zero point of the acceleration sensor 40 can be easily corrected by using the drift amount G0 (n).

In particular, the drift amount G0 obtained in this embodiment
(N) is the acceleration sensor 4 on the uphill and downhill roads.
Since the influence of the slope is eliminated by accumulating the output of 0, it is possible to accurately subtract the drift amount G0 (n) from the actual output of the acceleration sensor 40 to accurately obtain the zero point drift caused by the change with time or the like. The remarkable effect that the correction can be performed. Therefore, the mechanical accuracy is not so severely required, so the device can be simplified,
There is an advantage that the cost can be reduced.

Next, the actual control using the above-mentioned zero point correction will be described with reference to the flowchart of FIG. This control is an example in which the corrected acceleration GH (n) is used for the traction control performed on an uphill road. As shown in FIG. 8, in S300, it is determined whether or not the vehicle is stopped depending on whether or not the vehicle speed is “0”. If an affirmative decision is made here, the operation proceeds to step S310, whereas if a negative decision is made, the operation proceeds to step S340.

In S310, the corrected acceleration GH (n) calculated in the process shown in FIG. 6 is fetched, and the corrected acceleration GH (n) is a predetermined value Ks (for example, −0. 1G) is determined. That is, this determination is to determine whether or not the vehicle is on an uphill.

Therefore, if an affirmative determination is made here, the road is a slope, so the process proceeds to S320, and the slope flag HF is turned on. On the other hand, if a negative determination is made, the process proceeds to S330, the slope flag HF.
Is turned off and the process proceeds to S340. In S340, it is determined whether or not the slope flag HF is on. If an affirmative determination is made here, the process proceeds to S350, and if a negative determination is made, S380 is performed.
Proceed to.

In S350, it is determined whether or not the vehicle is in a starting state, based on whether or not the vehicle speed is in a low speed range (for example, 10 km / h) or less. If an affirmative decision is made here, S36
On the other hand, if the determination is negative, the process proceeds to S380. S3
At 60, it is determined whether or not the road surface is a low μ road (for example, a frozen road surface) by, for example, whether or not the wheel acceleration of the driven wheel is equal to or less than a predetermined value (for example, 0.2 G). If an affirmative judgment is made here, the routine proceeds to S370, while if a negative judgment is made, the routine proceeds to S380.

At S370, since it is determined at S340 to S360 that the vehicle is starting on an uphill road on a low μ road, special traction control for that purpose is performed. That is, on an uphill road on a low μ road, it is difficult to climb unless the acceleration slip amount of the wheel is made as small as possible, so the following control is performed, for example. The traction control determination and the target slip ratio during control are corrected to be small (for example, the normal + 10% is corrected to + 3%).
The feedback gain for the deviation between the target slip ratio and the actual wheel slip is largely corrected.

On the other hand, in S380, the above S340 to S3 are performed.
At 60, it is determined that it is not time to start on an uphill road on a low μ road, so normal traction control is performed, and this processing is once terminated. In other words, in this process, the slope can be detected with certainty by using the accurate acceleration GH (n) obtained by performing the above-described zero point correction, so that appropriate traction control according to the slope can be performed. There is an effect that can be.

Although the embodiment of the present invention has been described above, the present invention is not limited to the embodiment, and it goes without saying that the present invention can be implemented in various modes. For example, in the above-described embodiment, each time the vehicle changes from the stopped state to the running state, the acceleration at the time of stop is integrated, but conversely, each time the vehicle changes from the running state to the stopped state, Acceleration may be integrated. Further, the acceleration immediately after the start (output from the acceleration sensor) may be integrated.

[0032]

As described above in detail, in the present invention, the value of the acceleration sensor when the vehicle is stopped is integrated and averaged to obtain the drift amount from the zero point, and this drift amount is subtracted from the value of the acceleration sensor. By doing so, the zero point correction can be performed easily and accurately.

That is, according to the present invention, by using the drift amount obtained by averaging the values of the acceleration sensor every time the vehicle is stopped, the influence of the slope can be reliably and easily eliminated, and the acceleration sensor can be changed with time. There is a remarkable effect that only the drift amount from the 0 point can be suitably corrected. Also,
In that case, there is an advantage that the cost can be reduced because the device is not complicated and it is not necessary to improve the accuracy of the device.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram illustrating a configuration of the present invention.

FIG. 2 is an explanatory diagram showing the principle of the present invention.

FIG. 3 is a block diagram showing the system configuration of the present embodiment.

FIG. 4 is an explanatory diagram showing a structure of an acceleration sensor.

FIG. 5 is a block diagram showing an electrical configuration of the present embodiment.

FIG. 6 is a flowchart showing a process for correcting a 0 point.

FIG. 7 is a flowchart showing a process of calculating a drift amount.

FIG. 8 is a flowchart showing a traction control process.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine (engine) 7 ... Engine speed sensor 24, 25 ... Drive wheel speed sensor 28, 29 ... Guide wheel speed sensor 40 ... Acceleration sensor 50 ... Electronic control circuit (ECU) 35, 36, 37, 38 ... Brake Hydraulic circuit

Claims (1)

[Claims] 1. A correction device for an acceleration sensor for detecting an absolute acceleration of a vehicle, the vehicle state detecting means detecting a change from one state to another state of both running and stopped states of the vehicle. And a storage unit that stores the value of the acceleration sensor when the vehicle is stopped when the vehicle state detection unit detects that the state of the vehicle has changed, and a value of the acceleration sensor stored by the storage unit. Is added and averaged to obtain the drift amount from the zero point, and the drift amount obtained by the drift amount calculating means is subtracted from the value of the acceleration sensor to perform zero point correction.
A correction device for an acceleration sensor, comprising: a point correction means.