JPH03255370A - Control device of vehicle body - Google Patents

Abstract

PURPOSE:To simplify a control device by using a servo capacitance type acceleration sensor as an acceleration sensor, and inputting a pulse width modulation signal of a capacitance servo circuit as a sensor detecting signal to a waveform shaping circuit. CONSTITUTION:An output signal of a pulse width modulator 8 of a capacitance- type acceleration sensor 10 is directly taken into a control circuit 20 since it is a digital signal, and digitally operated. A pulse edge of the voltage input to the circuit 20 is shaped by a waveform shaping circuit 22 and input to a digital input port 23. The circuit 20 knows when a vehicle wheel is locked at the breaking time from operations of detecting signals of a velocity sensor or the like and detecting signals of the acceleration sensor 10, with outputting a control signal to release the lock of the vehicle wheel to an object 21 to be controlled from an output port 24. Since the output of the acceleration sensor is directly taken into the control device, the control device is simplified, thereby lowering the manufacturing costs.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a vehicle body control device, and more particularly to a vehicle body control device that controls suspension, traction, anti-lock brakes, etc. using detection signals from a capacitive acceleration sensor. .

[Conventional technology]

It has become common for various types of control of automobiles to be performed by control devices equipped with a CPU that performs arithmetic processing using digital signals. Analog detection signals from various sensors are converted into digital signals using A/D converters. The information is then imported into the control device. For example, in the conventional technology described in JP-A-1-95923 and JP-A-1-95924, an analog output signal of an acceleration sensor is converted into a digital signal by an A/D converter, and the signal is input to a control device. ing.

Japanese Patent Laid-Open No. 56-51619 describes a control device used for engine control rather than vehicle body control, in which the detection output signal of an air flow sensor is converted directly into a digital signal instead of an analog signal. ing.

[Problem to be solved by the invention]

The control device using the above-mentioned acceleration sensor requires an A/D converter for converting an analog detection signal into a digital signal, and there is a problem that the configuration of the input section of the control device becomes complicated and costs increase. In recent years, it has become common for automobile control to have separate control devices equipped with CPUs, one for engine control and one for vehicle body control, each equipped with a CPU.
A single car is now equipped with as many as 2 to 30 types of control devices, ranging from several types to many types. Therefore, unless efforts are made to reduce the cost of each individual control device, the entire control device will become very expensive. Furthermore, when a sensor is installed around the engine, noise and temperature from the engine tend to affect the signal line, and if countermeasures are taken, this also causes an increase in costs. In particular, CP compensates for the effects of temperature.
If this is done using U's arithmetic processing, the load on the CPU will be heavy and other processing will be affected. Furthermore, individual acceleration sensors have variations in characteristics, and this conventional technology cannot adjust the detection output in response to the variations in characteristics.
There is also the problem that high-precision control is not possible.

The output of the air flow sensor is converted into a digital signal.

The conventional technology that allows this output signal to be input directly to the control device has the advantage that it does not require an A/D converter, but it has the advantage of not having to provide an A/D converter. Special circuit configuration required. This circuit configuration is unique to a hot wire type air flow sensor, and this prior art cannot be applied to the vehicle body control device that is the object of the present invention.

The first object of the present invention is to convert the output signal of the acceleration sensor into A/
It is an object of the present invention to provide a vehicle body control device that can input data to a digital control device without passing through a D converter and does not require special noise countermeasures.

A second object of the present invention is to provide a vehicle body control device that enables highly accurate control regardless of the characteristics of individual sensors.

A third object of the present invention is to provide a vehicle body control device that reduces the burden of arithmetic processing for temperature compensation executed by an arithmetic processing unit of a control device.

[Means to solve the problem]

The first purpose is to use a servo-type capacitive acceleration sensor as an acceleration sensor, and use the pulse width modulation signal of the electrostatic servo circuit as a sensor detection signal to a waveform shaping circuit normally provided at the input stage of a control device. This is achieved by configuring the input.

The second object is achieved by providing a zero-span adjustment circuit that adjusts the relationship between the pulse width modulation signal (duty voltage waveform) and acceleration.

The third objective is achieved by providing a temperature compensation circuit.

[For production]

When the movable electrode attempts to move due to acceleration, the electrostatic servo circuit attached to the capacitive acceleration sensor generates a pulse width modulation signal corresponding to the change in capacitance due to this movement, and transmits this signal to the sensor. It works by applying an attractive force between the electrodes in the direction opposite to the direction in which the movable electrode moves, so that the movable electrode does not move. This pulse width modulation signal, that is, the duty voltage waveform is a signal whose pulse width is proportional to the magnitude of acceleration received by the sensor. In other words, the electrostatic servo type capacitive acceleration sensor can directly input this pulse width modulation signal to the digital control device without designing any special circuit. Even if there is noise on the signal line or the pulse waveform is distorted due to the capacitance of the signal line, the noise components are removed by the waveform shaping circuit installed at the input stage of the digital control device, without adding any filters. Ru. Conventional capacitive acceleration sensors convert the pulse width modulation signal mentioned above into an analog signal,
The signal was converted back into a digital signal using an A/D converter, but the configuration of the present invention eliminates the need for an A/D converter.

Even if there are variations in the individual characteristics of the capacitive acceleration sensor, the output characteristics can be adjusted using the zero/span adjustment circuit, so the control characteristics will not change depending on the sensor characteristics.

Further, by providing a temperature compensation circuit and performing temperature compensation of the detection signal using hardware, the computational processing load on the arithmetic processing device can be reduced.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is an overall configuration diagram of a vehicle body control device according to an embodiment of the present invention. The acceleration detection section 9 of the capacitive acceleration sensor 10 includes a movable electrode 2 formed at the tip of a silicon cantilever 1, a fixed electrode 3 disposed opposite to the movable electrode 2,
Consists of 4. Depending on the magnitude and direction of acceleration G applied to the vehicle body (not shown), the movable electrode 2 moves up and down between the fixed electrodes 3 and 4 in the illustrated example, and this vertical movement causes a change in the distance between the movable electrode 2 and the fixed electrodes 3 and 4. From the change in capacitance ΔC, the movable electrode 2
It is possible to detect the vertical displacement, that is, the magnitude of acceleration.

The fixed electrodes 3 and 4 and the movable electrode 2 (via the cantilever 1) are electrically connected to an electrostatic servo circuit 5. Here, it is assumed that the voltage applied between the movable electrode 2 and the fixed electrode 3 is Vl, and the voltage applied between the movable electrode 2 and the fixed electrode 4 is v2. An electrostatic force acts between the movable electrode 2 and the fixed electrodes 3 and 4 according to the applied voltages Vl and V2, respectively. This electrostatic force is caused by the gap between the movable electrode 2 and the fixed electrodes 3 and 4. is constant, the voltage Vl
, V2. Therefore, the voltages Vl, V
By changing 2, an arbitrary electrostatic force can be applied to the movable electrode 2. That is, the displacement of the movable electrode 2 is detected from the change in capacitance, and electrostatic force is applied between the movable electrode 2 and the fixed electrodes 3 and 4 in a feedback control manner so that this displacement becomes a predetermined value do. As a result, the acceleration G
This allows the force acting on the movable electrode 2 and the electrostatic force to be balanced. By detecting this balanced electrostatic force from the voltages Vl and V2, the acceleration G can be detected.

Next, the electrostatic servo circuit 5 will be explained. This electrostatic servo circuit 5 includes a ΔC detection section 6, an amplifier 7, and a pulse width modulator 8.

In the case of this embodiment, the voltage V1. applied to the fixed electrodes 3, 4 with respect to the movable electrode 2 is applied so that the displacement ΔC of the capacitance becomes zero.
For example, the voltage Vl.

2 is a rectangular wave, and by changing the pulse width, the voltages Vl and V2 are changed, and the movable electrode 2 is replaced with the fixed electrodes 3 and 4.
hold it in the center position between the two. In the case of this embodiment, the voltage Vl is in opposite phase to the voltage v2 and has the same magnitude. Then, the acceleration G applied to the movable electrode 2 is detected based on the pulse width of the duty voltage waveform of the voltage v1.

2 and 3 show the relationship between the duty voltage waveform and the acceleration G. In both figures, the duty ratio of the duty voltage waveform 1 is expressed as T w /T, and in FIG. 3, the vertical axis represents the acceleration G, and the horizontal axis represents the duty ratio. As shown in this figure, a signal V1=duty voltage waveform proportional to acceleration G is output from the capacitive acceleration sensor 10.

Next, the control circuit 20 will be explained. The control circuit 20 includes an MPU, a RAM, a ROM, etc., and receives detection signals from various capacitive acceleration sensors and performs various calculations in order to control a controlled object (suspension, traction, brake system, etc.) 21. , the output signal of the pulse width modulator 8 of the capacitive acceleration sensor 10 described above is:
Since it is a digital signal, the control circuit 20 can directly take in this signal and perform digital calculations on it. The voltage Vl (duty voltage waveform) that is directly input from the pulse width modulator 8 of the capacitive acceleration sensor 10 to the control circuit 20 through the signal line 25 is first shaped into pulse edges by the waveform shaping circuit 22. The capacitive acceleration sensor 10 is installed in the engine room or undercarriage of a vehicle.

It is installed in a place with poor electrical noise and temperature environment, and is connected by a signal line 25 from here to the place where the control circuit 20 is installed. Otherwise, the pulse edge may become dull due to the capacitance of the signal line, and if arithmetic processing is performed based on the distorted signal, highly accurate control cannot be achieved. However, by using the signal shaped by the waveform shaping circuit 22, highly accurate control becomes possible.

The acceleration sensor detection signal whose waveform has been shaped by the waveform shaping circuit 22 is input to the digital input port 23 . The duty value is measured, for example, by counting the time widths of Tw and T using a clock in the MPU, based on the rise and fall of the pulse.

The control circuit 20 calculates whether the wheels are locked during braking based on a detection signal from a vehicle speed sensor (not shown) and a detection signal from the acceleration sensor 10 described above, and outputs a control signal to release the wheel locks. 24 to the controlled object 21.

According to this embodiment, the acceleration sensor outputs a duty voltage waveform proportional to acceleration that can be directly processed by the digital arithmetic processing unit, and the control unit directly takes in the duty voltage waveform. This eliminates the need for a D converter, simplifies the configuration of the control device, and has the effect of reducing manufacturing costs and downsizing. Further, since the waveform shaping circuit provided in the control device can be used as is to remove noise and correct waveform distortion, there is also the effect that a special noise removal filter or the like is not required.

FIG. 4 is a configuration diagram of a capacitance type acceleration sensor according to a second embodiment of the present invention. In the capacitance type acceleration sensor 10 of this embodiment, a zero/span adjustment circuit is provided on the sensor 10 side. The only difference from the first embodiment is that a temperature compensation circuit 11 and a temperature compensation circuit 12 are provided, and the other configurations are the same as the first embodiment. It is provided between the output side of the device 8 and the signal line 25, and adjusts the relationship between the duty voltage waveform and acceleration.
This makes it possible to adjust the zero point of each of the five sensors 10. Further, by providing the temperature compensation circuit 12, temperature correction calculation processing by software on the control circuit 20 side is not required, and the burden on the MPU is reduced. By providing these, the software is simplified and
Furthermore, even more precise control becomes possible.

〔Effect of the invention〕

According to the present invention, there are the following effects.

(a) Since the output signal of the pulse width modulator that is originally included in the servo-type capacitive acceleration sensor is directly input to the digital control device as a sensor output, A/ D-converters and hard filters are no longer required, simplifying the control device.
Space saving and cost reduction can be achieved.

(b) Since the servo-type capacitive acceleration sensor is provided with a zero/span adjustment circuit, it is possible to adjust the zero point for each sensor, and high-precision control is possible.

(c) Since a temperature compensation circuit is provided in the servo-type capacitive acceleration sensor, there is no need for the control device to perform arithmetic processing for temperature compensation, and the software is simplified.
The processing load on the arithmetic processing device is reduced.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a vehicle body control device according to a first embodiment of the present invention, FIG. 2 is a duty voltage waveform diagram, FIG. 3 is a graph showing the relationship between acceleration and duty ratio, and FIG. 4 is a diagram of the present invention. FIG. 2 is a configuration diagram of a vehicle body control device according to a second embodiment of the present invention. 2... Movable electrode, 3, 4... Fixed electrode, 5... Electrostatic servo circuit, 6... ΔC detection section, 8... Pulse width modulator. 9... Acceleration pressure detection unit, 10... Capacitive acceleration sensor. 11...Zero/span adjustment circuit, 12...Temperature compensation circuit. 20... Control circuit, 21... Controlled object, 22...
Waveform shaping circuit, 25... signal line.

Claims (1)

[Scope of Claims] 1. In a vehicle body control device in which an arithmetic processing unit of a digital control circuit receives an acceleration signal detected by a capacitive acceleration sensor and performs various calculations to control the vehicle body, The device includes an electrostatic servo circuit that converts the output signal of the sensor into a duty voltage waveform, and a waveform shaping circuit that shapes the duty voltage waveform, and the arithmetic processing unit takes in the output of the waveform shaping circuit. A vehicle body control device featuring: 2. In a vehicle body control device in which a digital control circuit takes in an acceleration signal detected by a capacitance type acceleration sensor and performs various calculations to control the vehicle body, the output signal of the capacitance type acceleration sensor is used to detect the capacitance type acceleration sensor. A ΔC detection section that detects the amount of capacitance change between the electrodes of the acceleration sensor, a pulse width modulator that pulse width modulates the output signal of the ΔC detection section, and an output signal of the pulse width modulator that is input to the digital control circuit. 1. A vehicle body control device comprising a signal wire directly input to a waveform shaping circuit provided in a stage. 3. In a vehicle body control device that detects acceleration applied to a vehicle body using a capacitance type acceleration sensor and controls the vehicle body according to the acceleration, a pulse width modulation signal corresponding to the output voltage of the capacitance type acceleration sensor is transmitted to the static capacity type acceleration sensor. The pulse width modulation signal of the electrostatic servo circuit, which feeds back between the electrodes of the capacitive acceleration sensor and controls the movable electrode of the capacitive acceleration sensor so that it does not move when receiving acceleration, is directly captured and processed. A vehicle body control device comprising a digital control circuit for controlling the vehicle body. 4. In a vehicle body control device that detects acceleration applied to the vehicle body using a capacitance type acceleration sensor and controls the vehicle body according to the acceleration, a pulse width modulation signal corresponding to the output voltage of the capacitance type acceleration sensor is transmitted to the static capacity type acceleration sensor. The pulse width modulation signal of an electrostatic servo circuit that feeds back between the electrodes of a capacitive acceleration sensor and controls the movable electrode of the capacitive acceleration sensor so that it does not move when receiving acceleration is passed through a waveform shaping circuit. A vehicle body control device characterized by comprising a digital control circuit that performs arithmetic processing on the data and controls the vehicle body; 5. A vehicle body that detects acceleration applied to the vehicle body using a capacitive acceleration sensor and controls the vehicle body in accordance with the acceleration; In the control device, a pulse width modulation signal corresponding to the output voltage of the capacitive acceleration sensor is fed back between the electrodes of the capacitive acceleration sensor, and when the movable electrode of the capacitive acceleration sensor receives acceleration. A vehicle body control device comprising a digital control circuit that takes in the pulse width modulation signal of the electrostatic servo circuit that controls the electrostatic servo circuit so as not to move through a zero/span adjustment circuit, performs arithmetic processing, and controls the vehicle body. 6. In a vehicle body control device that detects acceleration applied to a vehicle body using a capacitance type acceleration sensor and controls the vehicle body according to the acceleration, a pulse width modulation signal corresponding to the output voltage of the capacitance type acceleration sensor is transmitted to the static capacity type acceleration sensor. A zero/span adjustment circuit for controlling the pulse width modulation signal of an electrostatic servo circuit that feeds back between electrodes of a capacitive acceleration sensor so that the movable electrode of the capacitive acceleration sensor does not move when receiving acceleration. A vehicle body control device characterized by comprising a digital control circuit that performs arithmetic processing by inputting data through a waveform shaping circuit and a waveform shaping circuit to control the vehicle body. 7. In a vehicle body control device in which an arithmetic processing unit of a digital control circuit receives an acceleration signal detected by a capacitance acceleration sensor and performs various calculations to control the vehicle body, the acceleration signal detected by the capacitance acceleration sensor is The arithmetic processing is applied to an electrostatic servo circuit that feeds back a pulse width modulation signal between the electrodes of the capacitive acceleration sensor and controls the movable electrode of the capacitive acceleration sensor so that it does not move when receiving acceleration. A vehicle body control device characterized by being provided with a temperature compensation circuit that reduces the burden on the device of calculating the temperature characteristics of the capacitance type acceleration sensor. 8. The vehicle body control device according to claim 7, wherein the digital control circuit is connected to a wiring that directly takes in the pulse width modulation signal. 9. The vehicle body control device according to claim 8, wherein the digital control circuit includes a pulse waveform shaping circuit at an initial stage that takes in the pulse width modulation signal. 10. The vehicle body control device according to any one of claims 1 to 9, wherein the vehicle body control is one of suspension control, traction control, and anti-lock brake.