JPH11217080A - Control device for electric power steering device - Google Patents

Abstract

(57) [Summary] (with correction) [PROBLEMS] To perform offset correction of a motor current detecting means and a measure at the time of failure in a control device of an electric power steering device. SOLUTION: The control means comprises a storage means and an offset value abnormality detection means, wherein the storage means stores a first offset value at an initial time and a second offset value at the time of operation of the motor current detection means, The abnormality detection means is
At start-up, the relay connected to the drive circuit power supply is turned off, and the second offset value output from the motor current detection unit is read while all the drive elements of the drive circuit are turned off, The first offset value and the second offset value are compared, and when the difference is equal to or less than a predetermined value, the second offset value is set as a correction value of the motor current value, and when the difference is equal to or more than the predetermined value, the correction is performed. It is determined that the motor current detecting means has failed, and the motor output and the off state of the relay are maintained until the ignition key is turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an electric power steering device which applies a steering assist force by a motor to a steering system of an automobile or a vehicle, and more particularly to a motor current detecting means for detecting the motor current value. The present invention relates to a control device for an electric power steering device provided with control means for performing offset correction and processing at the time of failure.

[0002]

2. Description of the Related Art An electric power steering apparatus for energizing a steering apparatus of an automobile or a vehicle with an auxiliary load by the rotational force of a motor uses a transmission mechanism such as a gear or a belt through a speed reducer to transmit the driving force of the motor to a steering shaft or the like. An auxiliary load is applied to the rack shaft. Such a conventional electric power steering apparatus performs feedback control of a motor current in order to accurately generate an assist torque (a steering assist torque). The feedback control adjusts the motor applied voltage so as to reduce the difference between the current control value and the motor current detection value. Generally, the adjustment of the motor applied voltage is performed by a PWM (pulse width modulation) control. This is done by adjusting the tee ratio.

Here, the general structure of an electric power steering apparatus will be described with reference to FIG.
Is connected to a tie rod 6 of a steered wheel via a reduction gear 3, universal joints 4a and 4b, and a pinion rack mechanism 5. The shaft 2 is provided with a torque sensor 10 for detecting a steering torque of the steering wheel 1. A motor 20 for assisting the steering force of the steering wheel 1 is coupled to the shaft 2 via a clutch 21 and a reduction gear 3. Have been. The control unit 30 for controlling the power steering device includes an ignition key 1 from the battery 14.
1 is supplied with power through the control unit 30
Calculates the steering assist command value I of the assist command based on the steering torque T detected by the torque sensor 10 and the vehicle speed V detected by the vehicle speed sensor 12, and calculates the steering assist command value I based on the calculated steering assist command value I. The current supplied to the motor 20 is controlled. The clutch 21 is turned on / off by the control unit 30.
It is OFF controlled and is ON (coupled) in a normal operation state. The clutch 21 is turned off (disengaged) when the control unit 30 determines that the power steering device has failed, and when the power of the battery 14 is turned off by the ignition key 11.

The control unit 30 is mainly composed of a CP
FIG. 5 shows general functions executed by a program inside the CPU.
For example, the phase compensator 31 does not indicate a phase compensator as independent hardware, but indicates a phase compensation function executed by the CPU. The function and operation of the control unit 30 will be described. The steering torque T detected and input by the torque sensor 10 is phase-compensated by a phase compensator 31 in order to enhance the stability of the steering system. TA is input to the steering assist command value calculator 32. The vehicle speed V detected by the vehicle speed sensor 12 is also input to the steering assist command value calculator 32. The steering assist command value calculator 32 determines a steering assist command value I which is a control target value of the current supplied to the motor 20 based on the input steering torque TA and the vehicle speed V. Is provided with a memory 33. The memory 33 stores a steering assist command value I corresponding to the steering torque using the vehicle speed V as a parameter, and is used for calculating the steering assist command value I by the steering assist command value calculator 32. The steering assist command value I is input to a subtractor 30A, and also to a feedforward differential compensator 34 for increasing the response speed.
The deviation (I-i) of the subtractor 30A is input to a proportional calculator 35, and the proportional output is input to an adder 30B and an integral calculator 3 for improving the characteristics of the feedback system.
6 is input. The outputs of the differential compensator 34 and the integration compensator 36 are also added to the adder 30B, and the current control value E, which is the result of the addition in the adder 30B, is input to the motor drive circuit 37 as a motor drive signal. The motor current value i of the motor 20 is detected by the motor current detection circuit 38, and the motor current value i is input to the subtractor 30A and fed back.

An example of the configuration of the motor drive circuit 37 will be described with reference to FIG. 6. The motor drive circuit 37 uses a field effect transistor (FE) based on a current control value E from an adder 30B.
T) An FET gate drive circuit 371 for driving the gates of FET1 to FET4, an H bridge circuit composed of FET1 to FET4, a boost power supply 372 for driving the high side of FET1 and FET2, and the like. FET1 and FET2 are turned ON / OFF by a PWM (pulse width modulation) signal having a duty ratio D1 determined based on the current control value E.
It is turned off, and the magnitude of the current Ir actually flowing to the motor is controlled. FET3 and FET4 have a duty ratio D
In a small area of 1, the duty ratio D2 defined by a predetermined linear function expression (D2 = a.D1 + b where a and b are constants)
In the region where the duty ratio D1 is large, it is turned ON / OFF according to the rotation direction of the motor determined by the sign of the PWM signal. For example, when the FET 3 is in the conductive state, the current flows through the FET 1, the motor 20, the F
The current flows through the ET3 and the resistor R1, and a current flows in the motor 20 in the positive direction. When the FET 4 is in the conductive state, the current flows through the FET 2, the motor 20, the FET 4, and the resistor R2, and a negative current flows through the motor 20. Therefore, the current control value E from the adder 30B is also a PWM output. The motor current detection circuit 38 detects the magnitude of the positive current based on the voltage drop across the resistor R1, and detects the magnitude of the negative current based on the voltage drop across the resistor R2. The motor current value i detected by the motor current detection circuit 38 is input to the subtractor 30A and fed back.

Here, an operational amplifier is generally used as an element for a current detection circuit. However, since the operational amplifier outputs a signal slightly offset with respect to an input signal, the offset value is large when the amplification factor is large. Is also amplified, and an error that cannot be ignored with respect to the detected current value occurs. Also,
Although no motor current actually flows, F
In the ET drive circuit, the value of the duty ratio is calculated in accordance with the current value including the relative error of the detected offset value, and as a result, an undesired oscillating current is generated, which causes the steering feeling to deteriorate. Had become.

On the other hand, for detecting the motor current, a common resistor is inserted downstream of the two opposing arms of the H-bridge circuit, and a voltage drop across the resistor is detected to detect the current. In this case, since the detected current value includes the offset value of the operational amplifier, the control in the vicinity of the neutral position where delicate control is required also cannot provide smooth steering assistance, and the steering feeling is reduced. The result was worse.

[0008]

An apparatus which has solved the above-mentioned problems is disclosed in, for example, JP-A-9-24846. That is, FIG.
00, motor drive circuit 110 and motor current detection circuit 1
20 shows an example of the configuration of FIG. The motor control circuit 100 generates a PWM signal having a duty ratio D determined based on the current control value E input from the adder 30B,
It comprises a PWM circuit 101 that outputs a rotation direction signal that determines the rotation direction of the motor based on the sign of the current control value E, and a gate drive circuit 102 that drives the gates of the FETs 1 to 4 of the H-bridge circuit. The motor drive circuit 110 is the above-described H-bridge circuit. The input terminal of the motor drive circuit 110 is supplied with the power of the voltage Vb from the battery 14 via the ignition key 11 and the relay 40, and the motor 20 is connected between the output terminals. Have been. The motor current detection circuit 120 includes a current detection resistor R connected to the motor drive circuit 110, an operational amplifier OP connected to both ends of the resistor R, and an A / D connected to the output side of the operational amplifier OP.
It comprises a converter 121, a current correction calculator 122 for outputting a corrected motor current value i, and a memory 123 for storing an offset value and its relative error.

When the motor 20 rotates in the forward direction, a motor current flows through the resistor R. Therefore, a difference between voltages generated at both ends of the resistor R is detected by the operational amplifier OP, and the A / D converter 121 detects the A / D. After the conversion, the current correction calculator 122
And is stored in the memory 123. Also, when the motor 10 rotates in the negative direction, a motor current flows through the resistor R, so that a difference in voltage generated between both ends of the resistor R is detected by the operational amplifier OP, and the signal is processed by a peak hold circuit or the like to perform signal processing. After being A / D-converted by the / D converter 121, it is input to the current correction calculator 122 and stored in the memory 123. The current correction calculator 122 calculates the motor current value from the detected voltage difference between both ends of the resistor R in cooperation with the memory 123 and corrects the relative error of the offset value of the operational amplifier OP. And the corrected motor current value i is fed back to the subtractor 30A.

Here, the operation of the current correction calculator 122 will be described. First, the calculation of the motor current value is performed. When the difference between the voltages generated at both ends of the resistor R is detected by the operational amplifier OP, it is inputted. The motor current value is obtained by dividing the difference between the applied voltages by the value of the resistor R. The correction calculation of the relative error of the offset value of the operational amplifier OP is performed as follows.
First, when the ignition key 11 is turned from OFF to ON, all FETs constituting the H-bridge circuit are OFF.
, No motor current actually flows. Then, when the motor current is detected at this time, it can be recognized as an offset value from zero, which is the actual current value, and the detected motor current value is stored in the memory 123 as an offset value. Let it. At this time, the output of the operational amplifier OP is input, and the relative error is stored in the memory 123 as an offset value. Then, after the steering device enters the operating state, the offset value of the motor current value stored in the memory 123 is subtracted from the sampled and detected motor current value at predetermined time intervals to correct the motor current value i. Calculate.

FIG. 8 is a flowchart mainly showing an operation example of a portion related to the current correction calculation processing. First, the ignition key 11 is turned on (step P1), the detected value of the motor current is read as an offset value, and the relative error is stored in the memory 123 (step P2). Next, each unit of the control device is inspected (initial check) (step P3), and it is determined whether or not the control device is normal (step P4). If the control device is normal, the normal process is performed (step P5), and the ignition key 11 is determined to be OFF (step P6). If not, the process returns to step P4 to continue the control operation, and the ignition key 11 is turned off. If it is OFF, the control operation is stopped. If it is determined in step P4 that the control device is abnormal, a process at the time of abnormality is performed (step P7), and the control operation is stopped.

FIG. 9 is a flowchart showing details of the normal processing in step P5 in the flowchart shown in FIG. That is, the steering torque T and the vehicle speed V are read by sampling processing at predetermined time intervals (step P1).
1, P12), and calculates a current command value I which is a control target value of the current supplied to the motor 20 (step P13). The detected value of the motor current is read (step P14), and the relative error of the offset value stored in the memory 123 is subtracted from the detected motor current value to correct and calculate the motor current value i (step P15). Feedback control based on current command value I and motor current value i is performed, and current control value E to be supplied to motor 20 is calculated (step P16). Then, based on the current control value E, a PWM signal for driving the FET constituting the H-bridge circuit at a predetermined duty ratio and a rotation direction signal for determining the rotation direction of the motor are generated (Step P17), and the gate drive circuit is generated. It is output to 102 (step P18).

The above-mentioned motor current detecting means detects a weak voltage generated from the current detecting resistor R, amplifies the detection signal with an operational amplifier OP, and performs signal processing using, for example, a peak hold circuit or the like. / D conversion. At this time, an offset voltage is generated in an amplifier, a peak hold circuit, or the like, and the offset voltage is considered to fluctuate due to a voltage variation and a temperature in the control unit. The offset voltage affects the current detection value and causes a phenomenon that the motor 20 is recognized as if it is flowing even though no current is flowing, or a phenomenon appears that the current is flowing but cannot be detected. Therefore, in the above-described apparatus, when the motor is not driven in an initial state such as at the time of startup, the current detection value output from the current detection unit is read and stored as an offset value, and thereafter, when the current control is performed, By subtracting the offset value from the current detection value, the accuracy of the current detection value is improved.

However, if the motor current detecting means fails and the offset value is generated as an abnormally large value, if the abnormal offset value is directly corrected to the current detected value, it deviates from its intended purpose, and A dangerous situation may occur for the elderly. For example, when an abnormal offset value is generated on the negative side, a current larger than that in a normal state flows due to current control, and there is a danger that assist beyond the driver's expectation occurs. Further, when an abnormal offset value occurs on the positive side, a smaller amount of current flows than in the normal case, and the steering becomes heavy, causing the driver to feel uneasy.

SUMMARY OF THE INVENTION The present invention has been made in view of the circumstances described above, and it is an object of the present invention to accurately perform offset correction of a motor current detecting means and a process at the time of failure, and to make a driver dangerous. Another object of the present invention is to provide a control device for an electric power steering device which does not give a feeling of anxiety.

[0016]

SUMMARY OF THE INVENTION The present invention provides a steering mechanism for steering a steering mechanism based on a steering assist command value calculated based on a steering torque generated in a steering shaft and a current control value calculated from a current value of a motor. The present invention relates to a control device for an electric power steering device which controls the motor for providing an assisting force by driving control of an H-bridge circuit. The object of the present invention is to provide a motor current detection for detecting the motor current value. In addition to providing control means for performing offset correction of the means and processing at the time of failure, the control means comprises storage means and offset value abnormality detection means, and the storage means comprises a first offset value and an initial value of the motor current detection means at an initial stage. The second offset value at the time of operation is stored, and the offset value abnormality detecting means is connected to the drive circuit power supply at the time of startup. The second offset value output from the motor current detecting means is read with the relays turned off and all the drive elements of the drive circuit are turned off, and the first offset value and the second offset value are compared. When the difference is equal to or less than a predetermined value, the second offset value is used as a correction value of the motor current value. When the difference is equal to or more than the predetermined value, it is determined that the motor current detecting means is out of order. This is achieved by maintaining the output and relay off states until the ignition key is turned off.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to solve the above-mentioned conventional problems, according to the present invention, as shown in FIG. 1 corresponding to FIG. , EEPROM (Electrical
y Erasable Programmable R
OM), and an offset value abnormality detection means 13 for outputting a current detection means abnormality detection signal AS based on the outputs of the storage means 124 and 125.
0 is provided.

The operation of storing the offset value at the time of shipment adjustment in such a configuration will be described with reference to the flowchart of FIG. Set the control unit to the adjustment mode for shipping adjustment, etc., turn off the relay 40, and
The offset value of the motor current detection means is stored in the storage means 125 with the T1 to FET4 kept OFF, but the control unit is switched to the adjustment mode after turning on the ignition key 11 (Step S1) (Step S2). Thereafter, the relay 40 is turned off, and all the FETs are turned off (step S3), so that no current flows through the motor 20. Then, the resistance R and the current detection value output from the motor current detection means of the operational amplifier OP are read through the A / D converter 121 a plurality of times to read the RAM
(Step S5), and the reading is repeated until the value becomes the same as the value read last time (step S5).
6) When it becomes the same, the value is stored in the storage means 125 of the EEPROM as an offset value (step S).
7), turning off the ignition key 11 (step S8)
And ship the control unit.

On the other hand, when the operation is to be performed after being incorporated in the vehicle, as shown in the flowchart of FIG. 3, the ignition key 11 is first turned on in an initial state at the time of starting (step S10), and then the relay 40 is turned off. All F
With the ET1 to FET4 turned OFF (step S11), the current is not passed through the motor 20, and the current detection value output from the motor resistance R and the current detection means of the operational amplifier OP is output to the A / D converter 121. Then, the data is read out and stored in the storage means 124 (step S12). Next, the offset value stored in the storage means 125 in advance is read (step S13), and the difference from the current detection value is compared (step S14). It is determined whether or not the difference is equal to or smaller than a specified value (step S15).
The offset value is stored in the storage means 124 of the AM (step S16). Then, in the normal operation state,
The stored offset value is subtracted from the current detection value detected by the motor current detection means, and a value obtained by correcting the offset of the current detection means is used as the current detection value i in the above-described normal control and the like. Next, in the initial state at the time of startup, the read current detection value is compared with the offset value, and if the difference is equal to or greater than a specified value (step S15), the current detection value is read and compared with the offset value a plurality of times. (Step S17). If the difference between the offset value and the current detection value is equal to or larger than the predetermined value even after the predetermined number of comparisons, it is determined that the motor current detection means has failed (step S18), and the subsequent sequence is stopped to stop the motor output and the relay 40. Is maintained until the ignition key 11 is turned off.

[0020]

As described above, according to the control apparatus of the electric power steering apparatus of the present invention, the control means for correcting the offset of the motor current detecting means for detecting the motor current value and performing a measure at the time of failure is provided. Is determined and the abnormal operation is determined a plurality of times, so that the offset correction of the motor current detecting means and the measures at the time of failure can be reliably performed without making the driver dangerous.

[Brief description of the drawings]

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

FIG. 2 is a flowchart illustrating an example of an operation of storing an offset value during shipping adjustment according to the present invention.

FIG. 3 is a flowchart illustrating an example of an operation of storing an offset value during normal control according to the present invention.

FIG. 4 is a block diagram showing an example of an electric power steering device.

FIG. 5 is a block diagram showing a general internal configuration of a control unit.

FIG. 6 is a connection diagram illustrating an example of a motor drive circuit.

FIG. 7 is a block diagram illustrating an example of a conventional device.

FIG. 8 is a flowchart showing an operation example of a conventional device.

FIG. 9 is a flowchart showing an operation example of a conventional device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 steering handle 5 pinion rack mechanism 10 torque sensor 12 vehicle speed sensor 20 motor 30 control unit 31 phase compensator 37 motor drive circuit 38 motor current detection circuit 100 motor control circuit 110 motor drive circuit 120 motor current detection circuit 124, 125 storage means 130 Offset value abnormality detection means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B62D 13:00

Claims (1)

[Claims] 1. A motor that applies a steering assist force to a steering mechanism based on a current control value calculated from a steering assist command value calculated based on a steering torque generated in a steering shaft and a motor current value of the motor. A control device for controlling an electric power steering device which is controlled by a drive circuit of an H-bridge circuit, wherein a control means for performing offset correction of a motor current detection means for detecting the motor current value and processing at the time of failure is provided; The control means comprises a storage means and an offset value abnormality detection means, wherein the storage means stores a first offset value of the motor current detection means at an initial time and a second offset value at the time of operation of the motor current detection means; Means for turning off a relay connected to the drive circuit power supply at start-up;
The second offset value output from the motor current detection unit is read while all the driving elements of the drive circuit are turned off, and the first offset value and the second offset value are compared, and the difference is equal to or less than a predetermined value. In this case, the second offset value is used as a correction value of the motor current value, and when the difference is equal to or more than the predetermined value, it is determined that the motor current detection means has failed, and the motor output and the off state of the relay are turned off. A control device for an electric power steering device, wherein a key is maintained until the key is turned off.