JP3047050B2 - Electric power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus for assisting a steering operation.

[0002]

2. Description of the Related Art A vehicle speed detector detects a vehicle speed and a torque detector detects a steering torque applied to a steering wheel.
When the detected torque exceeds a predetermined dead zone, a driving current determined according to the detected torque and the detected vehicle speed is passed to a steering assist motor to drive the motor, and the force required for steering the vehicle is determined by the motor. 2. Description of the Related Art An electric power steering device has been developed which assists a driver with a rotational force to provide a comfortable steering feeling to a driver. The control of the steering assist force is performed by a CPU.
In the CPU, the detected torque signal and the detected vehicle speed signal, which are input as analog signals, are A / D-converted, and the CPU performs predetermined arithmetic processing based on the A / D-converted signals. The current was determined.

Some of the above-described electric power steering devices have a dual CPU system in order to guarantee the safety of the system against abnormal operation such as runaway of the CPU. In an electric power steering device having a dual CPU, a main CPU for controlling steering assist force and a main CPU
It has a sub CPU that detects an abnormality of the main CPU by monitoring the input / output of the main CPU.
When the abnormality of U is detected, the sub CPU performs a fail-safe control such as stopping of the motor for ensuring the safety of the system.

[0004] When the CPU has a dual system, the CP
In consideration of the occurrence of abnormal operation of the CPU due to the fluctuation of the power supply voltage of U, it is necessary to provide a power supply circuit for each CPU so that the power supply circuit has a dual system.

[0005]

However, when the power supply circuit is a dual system as described above, power is supplied to each CPU from a different power supply circuit, so that the CPU A / A
There is a risk that the reference voltage of the D converter may be different. If the reference voltage is different, the two CPUs will have different A / D conversion results for the same input signal. There is a risk that the executing sub CPU may erroneously detect an abnormality in the main CPU based on the difference between the A / D conversion results, thereby causing a problem that the fail-safe control may malfunction, and the reliability of monitoring the abnormality of the CPU may be reduced. Sex was low.

The present invention has been made in view of such circumstances, and an electric power steering apparatus that suppresses a malfunction of fail-safe control when a CPU is a dual system and improves the reliability of CPU abnormality monitoring. The purpose is to provide.

[0007]

An electric power steering apparatus according to the present invention converts an analog detection signal provided for steering assist based on a first reference voltage supplied from a first power supply circuit. Then, first steering assist related data is obtained based on the A / D conversion result, and the obtained first
Of steering assist control using steering assist related data
A / D-converting the analog detection signal based on a second reference voltage supplied from a second power supply circuit, and obtaining second steering assist-related data based on the A / D conversion result. The first steering assist-related data is compared with the first steering assist-related data.
An electric power steering apparatus comprising: a second CPU that performs control for monitoring an abnormal operation of the CPU;
Means for determining a relationship between the A / D conversion result of the monitoring voltage in the CPU and a predetermined standard value of the A / D conversion result of the monitoring voltage; and a method for determining the relationship based on the relationship determined by the means. Means for correcting the A / D conversion result for the analog detection signal in the second CPU, wherein the second steering assist related data is obtained based on the correction result of the means.

[0008]

The monitoring voltage may be a voltage at which the A / D conversion in the first CPU is known in advance. When such a monitoring voltage is A / D converted based on the second reference voltage,
The conversion result is the A / A of the monitoring voltage in the first CPU.
This indicates how much the A / D conversion result in the second CPU is the monitoring voltage that should result in the D conversion result being a known standard value. If the relationship between the standard value and the conversion result is obtained, the A / D conversion result of the first CPU and the second C
The relationship with the A / D conversion result of the PU becomes clear. Based on this relationship, the A / D conversion result of the first CPU and the A / D conversion
By obtaining a correction value that equalizes the D conversion result and correcting the A / D conversion result of the second CPU with the correction value, even if the first reference voltage and the second reference voltage are different,
The A / D conversion result of the first CPU and the A / D conversion result of the second CPU for the same level of the analog detection signal become equal.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a block diagram showing a configuration of an electric power steering device according to the present invention.

In FIG. 1, reference numeral 1 denotes a main CPU 1 for performing steering assist control.
The operation state of the main CPU 1 is monitored by the sub CPU 2 operating at the same rated power supply voltage.

The main CPU 1 is supplied with power supply voltages (power supply voltage V _DD for the CPU body and power supply voltage AV _DD for A / D conversion) from a battery power supply 3 via a power supply circuit 31. The main CPU 1 has a grounded reference potential (CPU
The operation is performed by the power supply voltage with respect to the main body reference potential V _SS A / D converter reference potential AV _SS ).

The sub CPU 2 supplies a power supply voltage (CPU power supply voltage V _DD and CPU power supply voltage V _DD) from a battery power supply 3 through a power supply circuit 32.
A / D conversion power supply voltage AV _DD ) is supplied, and the sub CPU 2 is connected to the grounded reference potential (CPU main body reference potential V _SS A / D conversion reference potential AV _SS ). It operates by the power supply voltage.

The battery power supply 3 is connected to a main CPU 1 and a sub-CPU 1 through a series circuit of a key switch 5 which is turned on / off by operation of an engine key and an interface 50.
When the key switch 5 is turned on by operating an engine key, the interface 50 is connected to the CPU 2.
Supplies an engine start signal indicating that the engine has started to the main CPU 1 and the sub CPU 2.

The main CPU 1 also has an amplifier for detecting the result of the torque detector 41 for detecting the steering torque of the steered wheels.
The detection signal amplified by 410, the detection signal of the engine speed detector 42 for detecting the engine speed, and the analog detection signal of the vehicle speed detector 43 for detecting the vehicle speed are provided.

The sub CPU 2 has an analog detection signal obtained by amplifying the detection result of the torque detector 41 by an amplifier 410, a detection signal of the vehicle speed detector 43, and the power supply circuit.
Power supply voltage supplied to the main CPU 1 from the main CPU 1 (main CPU
Resistor 4a voltages) corresponding to one of the A / D conversion power supply voltage AV _DD, dividing the monitoring voltage AV _M is adapted to be given by 4b.

The main CPU 1 is provided as described above,
A / D conversion of the analog detection signal from the torque detector 41,
Based on the A / D conversion result and the vehicle speed detection signal, a drive current for driving the steering assist motor 8 and a rotation direction of the motor 8 are obtained by a predetermined calculation. Then, the main CPU 1 supplies a PWM drive signal corresponding to the obtained drive current to the motor drive circuit 7, and when the rotation direction of the obtained motor 8 is clockwise, the motor 8 is turned off. A first AND gate which is a gate for supplying a right rotation signal for right rotation to the motor drive circuit 7
When the logical signal applied to the motor 61 is at a high level, while the rotation direction of the motor 8 is counterclockwise, a second AND gate, which is a gate for applying a counterclockwise rotation signal for rotating the motor 8 to the motor drive circuit 7, is provided. The logic signal given to 62 is set to high level.

Similarly to the main CPU 1, the sub CPU 2 A / D converts the analog detection signal from the torque detector 41. In this A / D conversion, the A / D conversion provided to the sub CPU 2 is performed. after the D conversion power supply voltage AV _DD was the a / D converter with a reference voltage of the a / D conversion is corrected by the method described later in connection with the conversion result to the monitoring voltage AV _M. Then, based on the correction result, the drive current for driving the steering assist motor 8 and the rotation direction of the motor 8 are obtained by the same calculation as that of the main CPU 1, and a fail-safe process as described later is executed. It has become.

The first AND gate 61 sets the right rotation signal given to the motor drive circuit 7 to a high level when the logic signals from the main CPU 1 and the sub CPU 2 are both at a high level. The second AND gate 62 is connected to the main CPU
When both the logic signals from the sub CPU 1 and the sub CPU 2 go high, the left rotation signal given to the motor drive circuit 7 is high.

The motor drive circuit 7 determines the rotation direction of the motor 8 based on the right rotation signal and the left rotation signal, and drives the motor 8 based on a PWM drive signal provided from the main CPU 1. In the motor drive circuit 7,
When both the logic signals from the first AND gate 61 and the second AND gate 62 become low level, the driving of the motor 8 is prohibited. The drive current of the motor 8 is a current detection resistor.
The detection result is supplied to the main CPU 1 and the sub CPU 2 via the amplifier 9.

In the electric power steering apparatus configured as described above, the main CPU 1 includes the torque detector 41
Based on the analog detection signal from the vehicle and the detection signal from the vehicle speed detector 43, the control regarding the steering assist is performed, and the sub CPU 2
However, as described above, the control operation of the motor 8 by the main CPU 1 is monitored.

Next, the main CPU executed by the sub CPU 2
1 will be described. Figure 2 shows the sub CPU 2
6 is a flowchart showing a procedure of operation monitoring control of the main CPU 1 executed by the CPU.

First, it is determined whether or not an engine start signal is provided from the interface 50 by turning on the key switch 5 (step S1). If it is determined that the engine start signal is provided, the monitoring voltage AV _M is set. The data is read and A / D converted (step S2). And the resistors 4a,
4b and a standard value of the A / D conversion result of the monitoring voltage AV _M which is predetermined based on the resistance value of the A / D conversion power supply voltage AV _{DD supplied} from the power supply circuit 31 to the main CPU 1. And the voltage ratio between the A / D conversion result in step S2 and the voltage ratio is determined, and this voltage ratio is determined as a correction value of the A / D conversion result in the sub CPU 2 (step S3).

Next, the analog detection signal from the torque detector 41 is converted into an A / D conversion power supply voltage A supplied to the sub CPU 2.
A / D conversion is performed using V _DD as a reference voltage (step S4).
The A / D conversion result is corrected by multiplying the result by the correction value (step S5).

Then, fail-safe processing is performed based on the correction result in step S5 (step S6). In the fail-safe processing, the drive current and the rotation direction of the motor 8 are determined by the same calculation as that of the main CPU 1 based on the correction result, and the determined drive current and the drive of the motor 8 given as described above are determined. Compare with current. If the difference between these drive currents is smaller than a predetermined value, it is determined that the main CPU 1 is operating normally and the first CPU
The logic signals applied to the AND gate 61 and the second AND gate 62 are all set to the high level. On the other hand, if the difference between the drive currents is larger than a predetermined value, it is determined that an abnormality has occurred in the operation of the main CPU 1, and the first AND gate 61 and the second AND gate 61 are determined.
The driving of the motor 8 is prohibited by setting all the logic signals given to 62 to low level.

After the execution of the fail-safe processing, the flow returns to step S4. And Step S4 ~ Step
The processing of S6 is repeated.

When the above control is performed, the main CPU 1
Even if the value of the A / D conversion power supply voltage AV _DD differs between the sub CPU 2 and the sub CPU 2, the sub CPU 2 outputs the A / D conversion result of the main CPU 1 for the same analog detection signal and the sub CPU 2
The A / D conversion result is corrected so that the A / D conversion result is equal to the A / D conversion result.
If the value of the conversion power supply voltage AV _DD is different, the sub CPU 2
However, it does not mistakenly determine that the main CPU 1 operating normally is abnormal.

In this embodiment, the A / A signal supplied to the main CPU 1 as the monitoring voltage in the sub CPU 2
A voltage obtained by dividing the D conversion power supply voltage AV _DD was used.
Without applying divided voltages signals other than D conversion power supply voltage AV _DD it may be used as a monitoring voltage.

[0028]

As described above in detail, in the electric power steering apparatus according to the present invention, the A / D conversion result of the first CPU and the A / D conversion result of the second CPU for the analog detection signal of the same level are equal. Is corrected and the A / D conversion result of the second CPU is corrected with the correction value. Therefore, the reference voltage for A / D conversion of the first CPU, the reference voltage for A / D conversion of the second CPU, Are different, the first CP for the analog detection signal of the same level
Since the A / D conversion result of U and the A / D conversion result of the second CPU are equal, the malfunction of the fail-safe control when the CPU is a dual system is suppressed, and the reliability of monitoring the abnormality of the CPU is improved. For example, the present invention has excellent effects.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an electric power steering device according to the present invention.

FIG. 2 is a flowchart illustrating a procedure of operation monitoring control of a main CPU executed by a sub CPU.

[Explanation of symbols]

 1 Main CPU 2 Sub CPU 4a, 4b Resistor 31,32 Power supply circuit

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification code FI B62D 127: 00 (58) Investigated field (Int.Cl. ⁷ , DB name) B62D 6/00 B62D 5/04 G05B 9/03

Claims (1)

(57) [Claims] An A / D conversion is performed on an analog detection signal provided for assisting steering based on a first reference voltage provided from a first power supply circuit, and a first signal is converted based on a result of the A / D conversion. A first CPU for obtaining steering assist related data and performing steering assist control using the obtained first steering assist related data
And A / D conversion of the analog detection signal based on a second reference voltage provided from a second power supply circuit.
The first CP is obtained by obtaining second steering assist related data based on the D conversion result and comparing the obtained second steering assist related data with the first steering assist related data.
An electric power steering apparatus comprising: a second CPU that performs control for monitoring an abnormal operation of a U; and an A / D conversion result of a monitoring voltage in the second CPU and an A / D conversion of a predetermined monitoring voltage. Means for obtaining a relationship between the result and a standard value; and means for correcting an A / D conversion result for an analog detection signal in the second CPU based on the relationship obtained by the means. An electric power steering device, wherein the second steering assist-related data is obtained based on the second steering assist-related data.