JPH08107696A - Controller for power steering - Google Patents

Abstract

PURPOSE: To stabilize a control system without degrading responsibility even though a battery voltage has been fluctuated by setting a control gain for input and output systems based on a detected voltage value of voltage detecting means. CONSTITUTION: A battery voltage detected by a battery voltage detecting circuit 66 and a microcomputer 21 is read through an A/D converter 27, and a PWM gain corresponding to the battery voltage is set by, for example, multiplying a predetermined proportional coefficient by the battery voltage. Next, a proportional gain as a control gain is calculated based on a reference proportional gain during the design of a current feedback control system of controller 13 and the reference PWM gain in a motor drive circuit 30. In motor drive control processing, a motor current corresponding to a detected torque value from a torque sensor 3 and a count value of a counter 26, that is, a detected value of vehicle speed are retrieved and the result is set as a motor current command value and therefore the control characteristics during the design of the controller can be definitely maintained.

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 system which applies a steering assist force by an electric motor to a steering system of a vehicle.

[0002]

2. Description of the Related Art Conventionally, as a control device for an electric power steering apparatus, a steering torque detector such as a torque sensor for detecting steering torque is attached to an input shaft to which a steering wheel is fixed, and steering detected by the steering torque detector is used. It is known that an assist torque corresponding to the torque is generated by an electric motor to assist the steering torque.

This electric motor is controlled by a controller, which controls the assist current based on the steering torque detection signal detected by the torque sensor and the vehicle speed of the vehicle detected by the vehicle speed sensor. By supplying the electric motor, the steering force of the steering wheel is assisted. The assisting action of the electric motor facilitates the steering operation during low-speed cornering or garage entry. In addition, when the vehicle is traveling at high speed, it is possible to obtain a feeling of response of the steering wheel and ensure traveling stability.

In this conventional controller, a current feedback control system is constructed to perform proportional control, proportional integral control,
Alternatively, the assist current to the electric motor is controlled by proportional-plus-integral-derivative control. FIG. 11 shows the configuration of a controller that controls the assist current by proportional-plus-integral-derivative control. This controller 13 includes a phase compensator 25, a counter 26, a current command calculator 32, a current feedback control circuit 33, and a motor. It is composed of a drive circuit 93 and a current detection circuit 91.

A torque detection signal T _V from the torque sensor 3
Is phase-compensated by the phase compensator 25 and output as a torque compensation signal T _P to the current command calculator 32.
The vehicle speed detection signal V _P from the vehicle speed sensor 17 is a counter 26.
Is input to the current command calculator 32 as a vehicle speed detection value V via. The current command calculator 32 calculates a corresponding motor current based on the vehicle speed detection value V and the torque compensation signal T _P , and outputs this to the current feedback control circuit 33 as a motor current command value S _I.

Then, the current feedback control circuit 33
Then, the motor current command value S _I from the current command calculator 32
And a motor current detection value i _M from the current detection circuit 91, a motor drive signal S _M for driving the motor 12 is generated and output to the motor drive circuit 93. The motor drive circuit 93 is, for example, as shown in FIG. 12, an H bridge circuit 40, a PWM signal output circuit 46, a current direction signal output circuit 47, a boosting power source 48, and an FET gate drive circuit 4.
The PWM signal output circuit 46 and the current direction signal output circuit 47 include the current feedback control circuit 3
Based on the motor drive signal S _M supplied from No. 3, a duty signal D ′ composed of a pulse signal representing the duty ratio D
And a direction signal S _H, and the FET gate drive circuit 49
In the FET gate drive circuit 49, the duty signal D ′ is supplied to the FETs 41 and 42.
The motor 12 is driven and controlled by turning on and off 1 and 42 according to the direction signal S _H. That is, when the direction signal S _H is supplied to the FET 43, the duty signal D ′ is supplied only to the FET 42, and the motor drive current flows from the FET 42 to the FET 43 via the motor 12, while the direction signal S is supplied to the FET 44.
_{When H} is supplied, the duty signal D ′ is supplied only to the FET 41, the motor drive current flows from the FET 41 to the FET 44 via the motor 12, and the motor drive current corresponding to the duty signal D ′ is supplied to the H bridge circuit 40. Is supplied to.

In the current detection circuit 61, the H bridge circuit 4
0 connected to the FETs 43 and 44 in series,
The magnitude and direction of the motor current are detected based on the voltages generated in the left and right current direction detection resistors R _R and R _L , and the left and right motor current detection values i _R and i _L are obtained. The motor current detection value i _M is calculated from i _R and i _L as i _M = i _R −i _L , and the motor current detection value i _M is supplied to the adder 37a of the current feedback control circuit 33 shown in FIG. .

The current feedback control circuit 33 comprises a differential compensator 36, a proportional calculator 38, an integral calculator 39, and adders 37a and 37b, as shown in FIG. The current deviation e _M, which is the difference between the motor current detection value i _M and the motor current command value S _I , is multiplied by a predetermined value in the proportional calculator 38 and supplied to the adder 37b as the proportional processing value f _P , and this proportional The processed value f _P is integrated by the integration calculator 39 and supplied to the adder 37b as an integrated processed value f _I. Further, the motor current command value S _I is determined by the differential compensator 3
In step 6, a predetermined process such as a differential process is performed and the differential process value f _D
Is supplied to the adder 37b. And the adder 37
In b, the proportional processing value f _P , the integral processing value f _I, and the differential processing value f _D are added, and the addition result is the motor drive signal S _M.
Is output to the motor drive circuit 93. In this way, the PID control (proportional / integral / derivative) is performed on the motor current so that the motor current accurately and stably follows the motor current command value S _I.

[0009]

However, in the control device for the conventional electric power steering system, the on-vehicle battery 16 is directly used as the power source for the H bridge circuit 40 of the motor drive circuit 93, and this battery voltage is used. Varies over a wide range according to the change over time of the battery and the driving state of the vehicle. Therefore, it is possible to stabilize the battery voltage by using a regulator or the like, but this is not preferable because it leads to high cost. Therefore, generally, the battery 16 and the H bridge circuit 40 are directly connected.

FIG. 13 is a characteristic diagram showing the correspondence between the duty ratio D for driving the H-bridge circuit 40 and the motor applied voltage Vm to the motor 12 as the voltage of the battery 16 changes. At 100%, a voltage equal to the battery voltage is applied to the motor 12. Therefore, as the battery voltage changes, the PWM gain K _PWM, which is the ratio of the duty ratio D to the motor applied voltage Vm, also changes. For example, when the battery voltage changes from B _MAX to B _MIN , the PWM gain K _PWM also changes from K _{PWM (MAX)} to K
Change to _{PWM (MIN)} .

In this state, for example, when the battery voltage B changes and becomes smaller than the reference voltage B ', even if the duty ratio D is set to 100% as shown in the characteristic b, the battery is Since the voltage B is B <B ', the motor applied voltage Vm becomes Vm <B', and conversely,
When the battery voltage B becomes higher than the reference voltage B ′, and when the duty ratio D is set to 100% as shown in the characteristic c, the battery voltage B is B> B ′. The motor applied voltage Vm becomes Vm> B '.

FIG. 14 is a block diagram showing the transfer function of the current feedback control system of the controller 13 shown in FIG. 11, where 81 is a differential compensator, 82 is a proportional element, 83 is an integral element, and 84 is a motor. The transfer function of the drive circuit 40 and 85 are transfer functions of the electric circuit of the motor 12.
In FIG. 14, when the value of K _PWM , which is the transfer function of the motor drive circuit 40, changes, the gain of the open-loop transfer function of the static characteristics of the current feedback control system becomes K _P × K
_PWM x (1 / R) also changes. Therefore, the control performance set by the reference battery voltage B'is not maintained due to the change in the battery voltage B. For example, if the battery voltage B is B
_{When MAX} , the gain of the open loop transfer function of the static characteristic of the current feedback control system becomes high and the current response becomes oscillatory, and when the battery voltage B is B _MIN , the open loop transfer function of the static characteristic of the current feedback control system. However, there is an unsolved problem that the gain becomes low and the current response characteristic deteriorates.

Therefore, the present invention has been made by paying attention to the unsolved problem of the above-mentioned conventional example, and it is a battery 16 and an H.
An object of the present invention is to provide a control device for an electric power steering device, which is capable of stabilizing a control system without impairing responsiveness even when the battery voltage fluctuates when directly connected to the bridge circuit 40. There is.

[0014]

In order to achieve the above object, a control device for an electric power steering apparatus according to the present invention includes a steering torque detecting means for detecting a steering torque of a steering system and a steering torque detecting means for the steering system. An electric motor that generates a steering assist force, a control unit that outputs a control signal that generates a steering assist force to the electric motor based on a torque detection value of at least the steering torque detection unit, and a control signal from the control unit. In a control device for an electric power steering apparatus including a motor drive circuit that controls the energization direction and the energization amount of the electric motor based on the voltage detection means for detecting a voltage supplied to the motor drive circuit, and the steering torque. Based on a preset control gain of the input / output system from the detection means to the electric motor and the voltage detection value of the voltage detection means, Characterized in that it comprises a gain setting means for setting a control gain of the output system.

[0015]

In the present invention, the control means generates a control signal based on the steering torque detection value of the steering system detected by the steering torque detection means, and the motor drive circuit drives and controls the electric motor based on the generated control signal. Then, a steering assist force corresponding to the steering torque is generated in the steering system. At this time, the voltage detection value of the voltage supplied to the motor drive circuit detected by the voltage detection means and the input / output system from the steering torque detection means to the electric motor Based on the preset control gain of
By setting the control gain of the input / output system, for example,
Even when the control characteristic at the time of designing the control device is deteriorated due to the change in the supply voltage to the motor drive circuit, the gain setting means adjusts the gain of the entire control device according to the fluctuation of the supply voltage to the motor drive circuit. By setting the control gain based on the control gain at the time of design so that does not change, the control characteristic at the time of design of the control device is maintained regardless of the voltage fluctuation.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention. In the figure, reference numeral 1 denotes a steering wheel, and a steering force applied to the steering wheel is transmitted to a steering shaft 2 composed of an input shaft 2a and an output shaft 2b. One end of the input shaft 2a is connected to the steering wheel 1, and the other end is connected to one end of the output shaft 2b via a torque sensor 3 as steering torque detecting means. Then, the steering force transmitted to the output shaft 2b is transmitted to the lower shaft 5 via the universal joint 4 and further transmitted to the pinion shaft 7 via the universal joint 6. The steering force is further transmitted to the tie rod 9 via the steering gear 8 to steer the steered wheels. The steering gear 8 is of a rack-and-pinion type having a pinion 8a and a rack 8b, and the rotary motion transmitted to the pinion 8a is converted into a linear motion by the rack 8b.

The output shaft 2b of the steering shaft 2 is connected to a reduction gear 10 for transmitting an auxiliary steering force (assist force) to the output shaft 2b. For example, an output shaft of a motor 12 as an electric motor configured of, for example, a DC servo motor that generates an auxiliary steering force is connected via an electromagnetic clutch device 11 (hereinafter, referred to as a clutch) configured of an electromagnetic type. Has been done. The clutch 11 has a solenoid, and an exciting current i _C is supplied to the solenoid by a controller 13 to be described later, so that the reduction gear 10 and the motor 12 are mechanically connected to each other, and the exciting current i _C is generated.
Will be discontinued due to suspension of supply.

The torque sensor 3 is arranged on the steering wheel 1 and detects the steering torque transmitted to the input shaft 2a. For example, the torsion torque is inserted between the input shaft 2a and the output shaft 2b. The torsion angle displacement of the bar is converted into a torsion angle displacement, and the torsion angle displacement is detected by a potentiometer.
By steering the steering shaft 2
The torque detection signal T _V, which is an analog voltage corresponding to the magnitude and direction of the twist that occurs in, is output. The torque sensor 3 outputs a predetermined neutral voltage V ₀ as the torque detection signal T _V when the steering wheel 1 is in the neutral state, as shown in FIG. Turning to the right turns the voltage that increases from the neutral voltage V ₀ according to the steering torque at that time, and turning to the left turns the neutral voltage V ₀ according to the steering torque at that time.
It is designed to output a voltage that decreases more.

Reference numeral 13 is a controller for controlling the driving of the motor 12 and for controlling the steering assist force to the steering system, which is operated by being supplied with power from the battery 16 mounted on the vehicle. The negative electrode of the battery 16 is grounded, and the positive electrode of the battery 16 is connected to the controller 13 via the ignition switch 14 and the fuse 15a for starting the engine and directly connected to the controller 13 via the fuse 15b. The power supplied via 15b is used, for example, for memory backup. Then, the controller 13 controls the drive of the motor 12 based on the torque detection signal T _V from the torque sensor 3 and the vehicle speed detection signal V _P from the vehicle speed sensor 17 arranged on the output shaft of the transmission, for example, and the clutch. 11 is controlled to control the output shaft of the motor 12 and the reduction gear 10 in a coupled / disengaged state.

FIG. 3 is a block diagram showing the configuration of the controller 13. The controller 13 includes, for example, a control circuit 20 as a control means, a motor drive circuit 30, a current detection circuit 61, a clutch control circuit 62, a relay drive circuit. 6
3, a fail relay 64 and a battery voltage detection circuit 66 as voltage detection means. The control circuit 20 is composed of a microcomputer 21, A / D converters 22, 23, 24, 27, a phase compensator 25, and a counter 26.

The microcomputer 21 is formed to include at least an interface section for performing input / output processing with an externally connected device and a storage section such as ROM and RAM. The phase compensator 25 performs phase compensation processing such as advancing the phase with respect to the input torque detection signal T _V in order to stabilize the control system, and the torque detection signal T from the torque sensor 3 is used. Phase compensation is performed on _V and the torque compensation signal T _P is output to the A / D converter 22. The A / D converter 22 receives the torque compensation signal T _P from the phase compensator 25, converts it into a digital value, and outputs it as a torque detection value T to the microcomputer 21.

Further, the counter 26 inputs a vehicle speed detection signal V _P which is a pulse signal from a vehicle speed sensor 17 such as a rotation speed sensor which generates a pulse signal in response to the rotation of an output shaft of a transmission (not shown), and the unit thereof is a unit. When the number of pulses per time is integrated and the integrated value is read into the microcomputer 21, a reset signal R from the microcomputer 21
_The count value is reset by _C.

Then, the microcomputer 21
The torque detection value T from the D / D converter 22 and the vehicle speed detection value V from the counter 26 are input, and the current detection circuit 61
The rightward motor current detection signal I _R from the A / D converter 2
4 and the left motor current detection signal I _L
The voltage is input via the / D converter 23, and the battery voltage B detected by the battery voltage detection circuit 66 is input via the A / D converter 27. Then, the microcomputer 21 calculates a motor drive signal S _M to be supplied to the motor 12 by PID control (proportional / integral / derivative) based on these input signals, and performs PWM based on the motor drive signal S _M. (Pulse Width Modulation) signal is generated, and the left pulse width modulation signal PW is generated based on this PWM signal.
M _L , right pulse width modulation signal PWM _R , right direction signal D _R ,
The left direction signal D _L is generated and each of these command signals PW is generated.
The M _L , PWM _R , D _R , and D _L are output to the motor drive circuit 30.

Further, the microcomputer 21 executes a predetermined failure detection process at the time of start-up, and when it is normal, the relay control signal S _R to the relay drive circuit 63.
Is output as "HIGH", the clutch control circuit 6
The clutch control signal S _C that gradually increases to 2 is output.
Further, at the time of controlling the drive of the motor 12, the current detection circuit 61
Based on the lateral direction of the motor current detection value i _R and i _L from performs abnormality monitoring processing, each command signal PWM _L to the motor drive circuit 30 at the time of abnormality _{detection, PWM R, D R, D} L
Is output as "LOW" to form and output a clutch control signal S _C that puts the clutch 11 into a disengaged state, and then forms a relay control signal S _R that opens the fail relay 64 to the relay drive circuit 63. The output is performed and predetermined processing is performed when an abnormality occurs, such as turning on an abnormality lamp. Further, at the end, in order to absorb the elastic energy stored in the steering system, for example, a clutch control signal S _C proportional to the motor angular velocity is generated and output to the clutch control circuit 62, and is controlled so as to give a viscous load for a predetermined time. Have been like doing.

The motor drive circuit 30 includes at least an H bridge circuit 40 having four switching elements, and gate drive circuits 51 to 51 for driving these switching elements.
And 54. The H-bridge circuit 40 has, for example, four FETs 41 to 44 such as enhanced N-channel MOS type FETs (field effect transistors), the FETs 41 and 43 are connected in series, and the FETs 42 and 44 are also connected in series. Are connected in parallel, and the drain sides of the FETs 41 and 42 are connected to the battery 16 via the fail relay 64 and the ignition switch 14. And F
The motor 12 is connected between the connection point between the ETs 41 and 43 and the connection point between the FETs 42 and 44. In addition, FET
The source side of 43 is grounded through the right direction current detection resistor R _R , and similarly, the source side of FET 44 is grounded through the left direction current detection resistor R _L.

Of the gate terminals G _{1 to} G ₄ of these FETs 41 to 44, the gate terminal G ₁ is the gate drive circuit 51, the gate terminal G ₂ is the gate drive circuit 52, and the gate terminal G ₃ is the gate drive circuit. 53 and the gate terminal G ₄ are respectively connected to the gate drive circuit 54, and when a predetermined voltage is supplied from the gate drive circuits 51 to 54 to the gate terminals G _{1 to} G ₄ , the corresponding FETs 41 to 44 are turned on. It is designed to be in a state. Then, when only the FET 41 and 44 is turned on, FET 41, the motor 12, FET 44, the motor 12 is reversely rotated is energized in the direction of the left current detection resistor R _L, FET 42 and 43
When only one is turned on, FET 42, motor 1
2, the FET 43 is energized in the direction of the right direction current detection resistor R _R , and the motor 12 is rotated forward.

Left pulse width modulation signal P from control circuit 20
WM _L is output to the gate drive circuit 51, and the right pulse width modulation signal PWM _R is output to the gate drive circuit 52 and the right direction signal D
_{The R} is output to the gate drive circuit 53, and the left direction signal D _L is output to the gate drive circuit 54. Then, in the gate drive circuits 51 to 54, the input command signals PWM _L and P are input.
Based on WM _R , D _R , D _L , a voltage is supplied to the gate terminals G ₁ and G ₂ of the FETs 41 and 42 by a boosting power source (not shown), and the battery voltage is supplied to the gate terminals G ₃ and G ₄ of the FETs 43 and 44. And the command signal is “HIG
A predetermined voltage is supplied to the corresponding gate terminal while it is "H", and the voltage supply to the corresponding gate terminal is stopped while the command signal is "LOW".

The current detection circuit 61, for example, amplifies the voltage generated at both ends of the right direction current detection resistor R _R and the left direction current detection resistor R _L and removes noise, and outputs the right direction motor current detection signal I _R and The leftward motor current detection signal I _L is output to the control circuit 20. The clutch control circuit 62 controls the clutch 11 in accordance with the clutch control signal S _C from the control circuit 20, supplies the exciting current i _C to the solenoid of the clutch 11, and connects the output shaft of the motor 12 and the reduction gear 10. It controls mechanical connection and disconnection.

The relay drive circuit 63 performs on / off control of the fail relay 64 based on the relay control signal S _R from the control circuit 20, and the fail relay 64 has a normally open contact switch. That is, the power supply of the battery 16 to the H bridge circuit 40 is ON / OFF controlled. Here, when the relay control signal S _R is "HIGH", the relay drive circuit 63 energizes the coil 64L of the fail relay 64 to close the relay contact 64a, and the battery 16 transfers to the H bridge circuit 40. Of the fail relay 64 when the relay control signal S _R is "LOW".
The power supply to the H-bridge circuit 40 from the battery 16 is cut off by cutting off the energization of the coil 64L to open the relay contact 64a.

The battery voltage detection circuit 66 is inserted between the fail relay 64 and the H bridge circuit 40, measures the power supply voltage value supplied to the H bridge circuit 40, and outputs the battery voltage B as the control circuit 20. Output to. The battery voltage detection circuit 66 is composed of, for example, two resistors connected in series, supplies a power supply voltage across both ends of the series resistor, and is attenuated corresponding to the resistance ratio of the two resistors from the connection point of the resistors. Detected voltage, and the detected voltage is detected by the control circuit 2
Supply 0.

Next, the processing procedure of the drive control processing of the motor 12 in the microcomputer 21 will be described based on the flowcharts shown in FIGS. 4 and 5. The microcomputer 21 executes a predetermined failure detection process when the ignition switch 14 is turned on, and when no abnormality is detected, the relay control signal S _{R is set} to “H”.
After being output to the relay drive circuit 63 as “IGH”, a clutch control signal S _C that gradually increases based on a clutch control process (not shown) is generated and output to the clutch control circuit 62. By energizing the coil 64L, the fail relay 64 is closed and energizing the H-bridge circuit 40. Further, the clutch control circuit 62 causes the solenoid of the clutch 11 to respond to the clutch control signal S _C. Exciting current i
By supplying _C , the rotation shaft of the motor 12 and the reduction gear 10 are gradually brought into a mechanically coupled state. Further, the microcomputer 21 outputs each command signal to the gate drive circuits 51 to 54 as "LOW" at the time of starting.

When these processes are completed, the microcomputer 21 first executes the gain setting process as the gain setting means shown in FIG.
The control gain in the motor drive control process shown in is set. In this gain setting process, first, the battery voltage B detected by the battery voltage detection circuit 66 is read through the A / D converter 27 in step S31, and then, in step S32, for example, a predetermined proportional coefficient is set to the battery voltage B. PWM corresponding to the battery voltage B by multiplying by
Set the gain K _PWM . Here, PWM gain K _PWM
Represents the ratio of the motor applied voltage Vm to the duty ratio D in FIG. 13 described above.

Then, the process proceeds to step S33, where K _P =
A proportional gain K _P as a control gain is calculated from α / K _PWM . Here, α is a reference proportional gain K _P ′ and a PWM gain in the motor drive circuit 30 when the battery voltage B when designing the current feedback control system of the controller 13 shown in FIG. 8 described later is the reference voltage B ′. It is a value determined by the product with a certain reference PWM gain K _PWM ′.

Then, the process proceeds to step S34, the proportional gain K _P calculated in step S33 is stored in a predetermined storage area, and the process ends. After this gain setting process is completed, the microcomputer 21 performs the motor drive control process shown in FIG. 5 by a timer interrupt at preset predetermined time intervals.

In this motor drive control processing, first, in step S1, the phase compensator 25 is passed through the A / D converter 22.
The torque detection value T from the torque sensor 3 for which the phase compensation has been performed is read. Then, the process proceeds to step S2, T = T
The calculation of −V ₀ is performed, and the offset process is performed so that the torque detection value T at neutral is zero.

Then, the process proceeds to step S2a, the count value of the counter 26, that is, the vehicle speed detection value V is read, the reset signal R _C is output to the counter 26 to reset the counter value, and then the process proceeds to step S3. hand,
Referring to the characteristic diagram showing the correspondence between the steering torque, the vehicle speed, and the motor current shown in FIG. 6, for example, the motor current corresponding to the torque detection value T and the vehicle speed detection value V is searched, and this is searched for as a motor current command. Set as the value S _I.

This characteristic diagram shows the steering shaft 2
The motor torque required to drive the motor 12 to generate an auxiliary steering force corresponding to the steering torque input to the motor 12, the steering torque, and the vehicle speed. Is smaller, the motor current command value is larger, and as the steering torque is larger, the motor current command value is larger.

Then, the process proceeds to step S4, where the motor current command value S _{I is} subjected to a predetermined differential processing or the like and is multiplied by a predetermined differential gain K _D to obtain a differential processed value f _D, and then step S5 Read the motor current detection value i _R in the right direction and the motor current detection value i _L in the left direction with and read the motor current detection value i _R in the right direction as a positive value and the motor current detection value i _L in the left direction as a negative value. And the motor current detection value i _M is calculated from the sum of these detection signals. That is, i _M =
calculated by i _R -i _L.

Here, it is assumed that the current detection circuit 61 performs sufficient filtering on the respective signals so that the effective values of the motor current detection signals I _R and I _{L in} the left and right directions can be obtained. Next, the process proceeds to step S5a, and, for example, an abnormality monitoring process as shown in the flowchart of FIG. 7 is performed.

In this abnormality monitoring process, first, step S
At 21, it is determined whether the absolute value | i _M | of the motor current detection value i _M is smaller than a preset maximum current value I _MAX that the motor drive circuit 30 is considered to be operating normally.
When the absolute value | i _M | is smaller than the maximum current value I _MAX , the motor current detection value i _M is determined to be within the normal range and the process returns to the motor drive control processing program.

On the other hand, as a result of the judgment in step S21, | i
_{When M} | ≧ I _MAX , an excessive current is flowing in the H bridge circuit 40, and it is determined that an abnormality has occurred, and the process proceeds to step S22. In step S22, the command signals PWM _L , PWM _R , D to the gate drive circuits 51 to 54 are outputted.
_R and D _L are output as “LOW”, whereby the current path of the H bridge circuit 40 is cut off. Then, the processing proceeds to step S23, by stopping the output of the clutch control signal S _C to the clutch control circuit 62, operates the clutch 11 to the output shaft and the reduction gear 10 of the motor 12 in disengaged status .

Then, the process proceeds to step S24, in which the relay control signal S _R to the relay drive circuit 63 is output as "LOW", thereby activating the fail relay 64 to transfer the battery 16 to the H bridge circuit 40. The power supply is cut off, and in step S25, for example, an upper-level program such as the main processing program is notified of an abnormality, and the abnormality monitoring processing is ended. Thereafter, the upper drive program does not execute the motor drive control process.

When no abnormality is detected in the motor drive current as a result of the abnormality monitoring processing in step S5a, the process proceeds to step S6. In step S6, the motor current command value S _I set in step S3 and step S6
The difference from the motor current detection value i _M calculated in 5, that is,
The current deviation e _M is calculated from e _M = S _I −i _M.

Next, in step S7, the current deviation e _M is multiplied by a predetermined proportional gain K _P , and this is multiplied by a proportional processing value f _P.
Further, in step S8, the proportional processing value f _P is integrated and multiplied by a predetermined integral gain K _I , and this is integrated processing value f _I
And Then, in step S9, the differential processed value f _D , the proportional processed value f _P , and the integrated processed value f _I are added, and this is used as the motor drive signal S _M , and the process proceeds to step S10.

[0045] In step S10, the motor drive signal S _M is equal to or a S _M ≧ 0, when a S _M ≧ 0 and proceeds to step S11, the normal rotation of the rotation direction of the motor 12 Set the right direction signal D _R set to the direction to “HIG
H ", a duty ratio D for supplying a drive current to the motor 12 according to the motor drive signal S _M is set, and this is set as a right pulse width modulation signal PWM _R to the corresponding gate drive circuits 52 and 53. Then, the left pulse width modulation signal PWM _L and the left direction signal D _L are output as “LOW” to the gate drive circuits 51 and 54, and the process ends and the process returns to the main program.

On the other hand, if S _M ≧ 0 is not satisfied in step S10, the process proceeds to step S12, and the left direction signal D _L for setting the rotation direction of the motor 12 to the reverse rotation direction is set to "HIG.
H ″, and a duty ratio D for supplying a drive current to the motor 12 according to the motor drive signal S _M is set as a left pulse width modulation signal PWM _L , and the corresponding gate drive circuits 51 and 54 are provided. Output to
The right direction signal D _R and the right pulse width modulation signal PWM _R are “L
OW "is output to the gate drive circuits 52 and 53, respectively, and the process is terminated and the process returns to the main program.

Next, the operation of the above embodiment will be described. now,
Assumed a state in which the vehicle is stopped, assuming that the ignition switch 14 to the ON state from this state, the microcomputer 21 performs a predetermined failure monitoring process, if there is no abnormality, the relay control signal S _R Is output as "HIGH" to the relay drive circuit 63, and the clutch control signal S _C to the clutch control circuit 62 is gradually increased and output. As a result, the relay drive circuit 63
However, by energizing the coil 64L, the fail relay 64 is closed, and the power supply of the battery 16 can be supplied to the H bridge circuit 40. Further, the clutch 11 gradually operates, the rotation shaft of the motor 12 and the reduction gear 10 are mechanically connected, and the rotational driving force of the motor 12 can be transmitted to the steering shaft 2.

Then, in the microcomputer 21,
First, the gain setting process of FIG. 4 is executed to read the battery voltage B from the battery voltage detection circuit 66 (step S
31), for example by multiplying a predetermined proportional coefficient to calculate a PWM gain K _PWM (step S32), on the basis of the PWM gain K _PWM, calculates a proportional gain K _P by K _P = α / K _PWM ( Step S33). Then, the calculated proportional gain K _P is stored in a predetermined storage area set in advance (step S34), the gain setting process is terminated, and thereafter,
The motor drive control process is executed at a predetermined interrupt cycle.

At this time, assuming that the occupant is not performing the steering operation, the torque detection signal T from the torque sensor 3 is given.
_{Since V} becomes the neutral voltage V ₀ and the vehicle is stopped at this time, the vehicle speed detection value V becomes zero. Therefore, in the motor drive control processing of FIG. Since the value S _I becomes substantially zero, the motor 12 is not driven.

When the vehicle is brought into the running state from the stopped state, the torque detection value T from the torque sensor 3 is in the vicinity of the neutral position V ₀ during the non-steering state. , The motor current command value S _I becomes substantially zero, so the motor 12 is not driven. During this traveling, for example, when the occupant makes a right steering, the torque detection signal T _V from the torque sensor 3 becomes a voltage value larger than the neutral voltage V ₀ because the right steering is performed, and the microcomputer 21 Then, offset processing is performed by T = T−V ₀ based on the torque detection value T input via the A / D converter 22,
The torque detection value T that makes the neutral point zero is calculated.

Then, based on the torque detection value T and the vehicle speed detection value V, the corresponding motor current command value S _I is set from the characteristic diagram of FIG. 6 (step S3). At this time, since the right steering is performed, the offset torque detection value T has a positive value, and thus the motor current command value S _I set from FIG. 6 also has a positive value. At this time, for example, when the steering torque is large while the vehicle is traveling at a low speed, a large auxiliary steering force is required, so the motor current command value S _I
Is set to a large value, and at this time, when the vehicle is traveling at high speed, the motor current command value S is generated in order to generate a small auxiliary steering force so that the steering wheel 1 feels responsive.
_I is set to a small value. Similarly, when the steering torque is small, sets the higher the vehicle speed is less large motor current command value S _I, to a small motor current instruction value S _I to be a responsive feeling of the steering wheel 1 as the vehicle speed increases Is set.

[0052] Then, a differential processing such predetermined processing to the motor current command value S _I set, calculates the differential processing value f _D is multiplied by a derivative gain K _D (step S4).
Further, based on the detected motor current values i _R and i _L in the left-right direction, i _M = i _R −i _{L is used} to calculate the detected motor current value i _M as the value of the current flowing through the motor 12. Then, when the abnormality monitoring process is executed and it is determined to be normal, the current deviation e _M is calculated from the motor current command value S _I and the motor current detection value i _M. Then, reading the proportional gain K _P for storing set by the gain setting process of FIG. 4, calculated by multiplying the proportional gain K _P with the read current deviation e _M calculates a proportional process values f _P, ( step S7), and also, the integral gain K _I to the value obtained by the integration processing with respect to the proportional processed value f _P
To calculate an integrated processing value f _I (step S8),
These differential processed value f _D , proportional processed value f _P, and integrated processed value f
_I is added to calculate the motor drive signal S _M (step S9).

[0053] Then, it is determined current direction on the basis of the sign of the motor drive signal S _M, in this case, the motor drive signal S _M ≧
Since it becomes 0, the command signals PWM _L and D _{L become} “LO
W ”, the command signal D _R is“ HIGH ”, and the command signal PWM _R is a pulse signal having a duty ratio D corresponding to the motor drive signal S _M (step S11).

Therefore, while the gate drive circuit 53 supplies a predetermined voltage to turn on the FET 43 and the command signal PWM _R is "HIGH", the gate drive circuit 5 is turned on.
The FET 42 is controlled to be turned on and off by supplying a predetermined voltage to the FET 42. At this time, command signals PWM _L and D
_{Since L} is “LOW”, the gate drive circuit 51,
Since the FET 54 does not supply a predetermined voltage to the FETs 41 and 44, the FETs 41 and 44 remain off.

Therefore, when the FET 42 is turned on, the FET 4 is turned on by the power supply from the battery 16.
2, motor 12, FET 43, right direction current detection resistor R _R
Is energized in the direction of the
Is controlled to be turned on and off so that the motor drive signal S _M
Is supplied to drive control of the motor 12.

As a result, the rotational driving force of the motor 12 is transmitted to the steering shaft 2 via the reduction gear 10, and thus a predetermined steering assist force corresponding to the steering torque is transmitted and the vehicle is traveling at a low speed. When the steering torque is large, the motor current command value S _I is set to a large value, and a large steering assist force is transmitted from the motor 12 to the steering shaft 2. Therefore, for example, steering operation during garage entry or low speed cornering is performed. Further, when the vehicle is traveling at a high speed, a small steering assist force is transmitted from the motor 12 even when the steering torque is large, so that the steering wheel 1 can provide a feeling of response. .

FIG. 8 shows a block diagram of the current feedback control system in the controller 13 shown in FIG. 3, in which 81 is a differential compensator, 82 is a proportional element, 83 is an integral element, Reference numeral 84 represents the transfer function of the motor drive circuit 30, and 85 represents the transfer function of the motor 12,
The proportional gain K _P of the proportional element 82 is variably set by K _P = α / K _PWM according to the PWM gain K _PWM .

At this time, the fluctuation of the battery voltage B is equal to the change of the PWM gain K _PWM as described above, and when the battery voltage B detected by the battery voltage detection circuit 66 is equal to the reference voltage B ', the battery voltage is changed. Since the PWM gain K _PWM set according to B is equal to the reference PWM gain K _PWM ′, the proportional gain K _P calculated from K _P = α / K _PWM is equal to the reference proportional gain K _P ′. This is equal to the set value for realizing the performance when setting the parameters of the current feedback control system, so that the current feedback control system can maintain the performance when setting the parameters.

Then, for example, the detected battery voltage B
Is lower than the reference voltage B ′, the PWM gain K
_PWM decreases in proportion to the battery voltage B, but α is
Reference proportional gain K _P ′ and reference PWM gain K during design
_Since it is a fixed value determined by _PWM ', K _P =
The proportional gain K _P calculated by α / K _PWM is set to be larger than the reference proportional gain K _P ′. At this time, the product of the proportional gain K _P and the PWM gain K _PWM is α, and is therefore equal to the product of the reference proportional gain K _P ′ and the reference PWM gain K _PWM ′, so that in FIG. PWM gain K _PWM
However, since the gain of the entire current feedback control system is equal to the gain at the time of design, the battery voltage B
Even when the voltage drops, the stability and responsiveness at the time of design at the reference voltage B'can be maintained.

On the contrary, for example, when the detected battery voltage B is higher than the reference voltage B ', the PWM gain K _PWM
Is proportional to the battery voltage B, the proportional gain K _P is set smaller than the reference proportional gain K _P ′, and the product of the proportional gain K _P and the PWM gain K _PWM is the same as above. , Is equal to α which is the product of the reference proportional gain K _P ′ at the time of design and the reference PWM gain K _PWM ′, the gain of the entire current feedback control system is
Since it is equal to the overall gain at the time of design, stability and responsiveness at the time of design at the reference voltage B ′ can be maintained even when the battery voltage B rises.

Therefore, for example, when the voltage of the battery 16 decreases, the motor drive circuit 30 causes the control circuit 2 to operate.
Even when the H bridge circuit 40 is operated according to the motor drive signal S _M calculated by 0, the voltage applied to the motor 12 becomes low because the battery voltage B is smaller than the reference voltage B ′. At this time, the proportional gain K _P is set to increase according to the PWM gain K _PWM that decreases in proportion to the decrease in the battery voltage B, and the product of the proportional gain K _P and the PWM gain K _PWM is a constant value, that is, Since the value is set to be α, the stability and response of the current feedback control system can be maintained at the characteristics when the parameters are set.

Therefore, the motor 12 does not vibrate or the responsiveness does not decrease due to the change in the characteristics of the current feedback control system due to the fluctuation of the battery voltage B, and the steering wheel 1 does not vibrate due to the vibration of the motor 12 or the like. It is possible to reliably prevent the vehicle from vibrating and giving an occupant an unpleasant feeling. Further, the setting of the proportional gain K _P by the gain setting process is executed only when the ignition key 14 is turned on, and thereafter, the proportional gain K _P is set.
_{Since P} is not changed, by changing the control gain of the current feedback control system during operation, the current of the motor 12 vibrates, and the occupant feels uncomfortable because the steering wheel 1 vibrates. There is no such thing.

In the above embodiment, the case where the right steering is performed has been described, but the same effect as above can be obtained even when the left steering is performed. Further, in the above embodiment, the case where the FET is used as the switching element of the H-bridge circuit has been described, but the present invention is not limited to this, and other switching elements such as a bipolar transistor may be applied.

In the above embodiment, the case where the proportional gain K _P is set according to the fluctuation of the battery voltage B has been described. However, the present invention is not limited to this, and the gain of the entire current feedback control system is equal to the gain at the time of design. If so, not only the proportional gain K _P but also other gains can be set, and not only one control gain but also a plurality of control gains are set according to the battery voltage B. It is also possible.

In the above embodiment, the case where the drive control of the motor 12 is performed by the PID control has been described, but the present invention is not limited to this, and the control may be performed by PI control, P control, or the like. Further, in the above embodiment,
Although the case where the motor current command value is set based on the steering torque and the vehicle speed has been described, the present invention is not limited to this. For example, the motor current command value can be set based only on the steering torque. .

Further, in the above embodiment, the controller 13
Was described using the micro computer 21, but not limited to this, it is also possible to combine electronic circuits such as an arithmetic circuit, an adder circuit, and a logic circuit, and FIG. 9 shows an example thereof. It is shown. The controller 13 will be briefly described with reference to FIG.
Is, for example, the phase compensator 25, the counter 26, the current command calculator 32, the current feedback control circuit 33, the H bridge circuit 40, the H bridge drive circuit 93a, the current detection circuit 91, and the battery voltage detection circuit 66 as the voltage detection means. It consists of Then, the H-bridge drive circuit 93a includes, for example, the PWM signal output circuit 46, the current direction signal output circuit 47, and the boost power source 48 shown in FIG.
And an FET gate drive circuit 49, and the H bridge drive circuit 93a and the H bridge circuit 40 correspond to the motor drive circuit 93 in FIG.

Here, the phase compensator 25, the counter 26,
Current command calculator 32 and current feedback control circuit 3
3 corresponds to the control means. Then, the phase compensator 25
The motor current command value S _I is set by the current command calculator 32 based on the torque compensation signal T _P from the counter and the vehicle speed detection value V from the counter 26.
For example, in the characteristic diagram of FIG. 6 described above, which is formed by a function generator, a function is selected based on the vehicle speed, the required motor current for the steering torque is calculated, and this is set as the motor current command value S _I. Output to the current feedback control circuit 33.

This current feedback control circuit 33
For example, it comprises a differential compensator 36, adders 37a and 37b, a proportional calculator 38, an integral calculator 39, and a gain setting circuit 101 as a gain setting means. The battery voltage B detected by the battery voltage detection circuit 66 is output to the gain setting circuit 101, and this gain setting circuit 101
Is composed of, for example, a voltage control type continuous variable gain circuit, and the proportional gain K corresponding to K _P = α / K _PWM based on the PWM gain K _PWM proportional to the input battery voltage B.
_P is output to the proportional calculator 38, and the proportional calculator 38 proportionally processes the input signal according to the proportional gain K _P.

On the other hand, the motor current command value S _I from the current command calculator 32 is input to the differential compensator 36 and the adder 37a, and the differential compensator 36 differentiates the input motor current command value S _I and differentiates it. The derivative processing value f _D proportional to the value is output to the adder 37b, and the adder 37a outputs the motor current command value S
_I and the motor current detection value i _M calculated by the current detection circuit 91
And the difference is calculated and output as the current deviation e _M to the proportional calculator 38.
According to the proportional gain K _P set by 1, the current deviation e
Proportional processing is performed on _M , and the proportional processed value f _P is output to the adder 37b and the integral calculator 39.

Then, the integration processing value f _I subjected to the integration processing by the integration calculator 39, the differentiation processing value f _D, and the proportional processing value f _p are added by the adder 37b to obtain H as the motor drive signal S _M.
The signal is output to the bridge drive circuit 93a, and in the H bridge drive circuit 93a, similarly to the above, based on the motor drive signal S _M , it is converted into a duty signal D ′ composed of a pulse signal representing a duty ratio D and a direction signal S _H. And corresponding F
The motor 12 is drive-controlled by turning on / off the ETs 41 to 44.

Furthermore, in the above embodiment, the motor drive control for detecting the steering state based only on the detected torque value and generating the auxiliary steering torque according to the detected torque value has been described. When changing the driving lane during high-speed running, in addition to the steering torque, the steering state is detected according to the steering angular velocity and the steering angular acceleration of the steering wheel, and auxiliary torque is generated according to these values. It is also possible to perform motor drive control.

FIG. 10 is a schematic block diagram showing an example of a control circuit for detecting the steering state based on the detected torque value, the steering angular velocity value and the steering angular acceleration value. This control circuit 20a
10, the current command calculator 32, the adder 37a, the proportional calculator 38, the integral calculator 39, the adder 37b, the steering angular velocity acceleration calculator 102, and the damper coefficient circuit 103, as shown in FIG. And an inertia compensation coefficient circuit 104.

The detected torque value T is determined by the control circuit 20.
It is input to the current command calculator 32 of a, converted into a predetermined motor current command value S _I , and then supplied to the adder 37a. In addition to the motor current command value S _I , the adder 37a further includes a motor current detection value i _M , which is the output signal of each of the current detection circuit 91, the damper coefficient circuit 103, and the inertia compensation coefficient circuit 104, and a damper signal D _I. Then, the inertia signal K _I ′ is supplied, and the motor current command value S _I is subjected to processing of subtracting the motor current detection value i _M , subtracting the damper signal D _I , and adding the inertia signal K _I ′. Adder 37
In the proportional calculator 38 to which the output signal of a is supplied, a predetermined proportional gain is multiplied, and the multiplication value is directly supplied to the adder 37b and added via the integral calculator 39 which performs a predetermined integration process. It is supplied to the container 37b. The output signal from the adder 37b, which is the addition processing of these input signals, is supplied to the motor drive circuit 93b, and the motor drive circuit 9b
In 3b, a pulse width modulation signal PWM having a predetermined pulse width is formed based on this output signal and is supplied to the steering angular velocity acceleration calculation circuit 102, and the motor 12 is driven according to the formed pulse width modulation signal PWM. To drive.

Then, the detected motor current detection value i (i _R , i _L ) is output from the motor 12 to the steering angular velocity acceleration calculation circuit 102 and the current detection circuit 91. In the steering angular velocity acceleration calculation circuit 102, The steering angular velocity ω ₀ calculated based on the input pulse width modulation signal PWM and the detected motor current value i is output to the damper coefficient circuit 103, and the calculated steering angular acceleration ω ₁ is output to the inertia compensation coefficient circuit 104. .

Calculation of the steering angular velocity ω ₀ and the steering angular acceleration ω ₁ in the steering angular velocity acceleration calculation circuit 102 is performed as follows. Assuming that the duty ratio of the pulse width modulation signal PWM is D and the power supply voltage V _BAT (= battery voltage B), the average voltage V supplied to the motor 12 is expressed as follows. V = D · V _BAT (1) Further, the counter electromotive force is generated by the rotation of the motor 12, and the counter electromotive force constant is k _T , the counter electromotive voltage generated in the motor 12 is k _T · ω ₀ Therefore, the average voltage V supplied to the motor 12 having the coil resistance R is also expressed as follows.

[0076] _{V = k T · ω 0 +} R · i ... (2) Thus, from the equation (1) and (2), the steering angular velocity ω ₀ is obtained as follows. ω ₀ = (D · V _BAT −R · i) / k _T (3) The steering angular acceleration ω ₁ is calculated by differentiating the formula (3) with respect to the time t. The calculated steering angular velocity ω ₀ is multiplied by a predetermined damper coefficient K _{V in the} damper coefficient circuit 103,
This multiplied value is subtracted from the motor current command value S _I to execute the damper control, whereby an electric viscous resistance is given to the steering system and the stability of the vehicle is improved. Further, the calculated steering angular acceleration ω ₁ is multiplied by a predetermined inertia compensation coefficient K _{G in} the inertia compensation coefficient circuit 104, and the multiplication value and the motor current command value S _I are added to execute inertia compensation control. Thus, the delay in the response of the motor due to the motor inertia is compensated. The steering angular acceleration ω ₁ may be directly detected by a sensor, or, for example, the angular value detected by the angle sensor attached to the motor shaft is differentiated with respect to the time t to first obtain the steering angular velocity ω ₀ , Further, the steering angular acceleration ω ₁ may be obtained by differentiating again.

[0077]

As described above, according to the control device for the electric power steering apparatus of the present invention, the control means generates the control signal based on the steering torque detection value of the steering system detected by the steering torque detection means. The electric motor is driven and controlled by the motor drive circuit based on the generated control signal, and a steering assist force corresponding to the steering torque is generated in the steering system. At this time, supply to the motor drive circuit detected by the voltage detection means. By setting the control gain of this input / output system based on the voltage detection value of the voltage and the preset control gain of the input / output system from the steering torque detection means to the electric motor, for example, Even if the control characteristics at the time of designing the control device are deteriorated due to fluctuations in the supply voltage, the gain setting means can adapt to the fluctuations in the supply voltage to the motor drive circuit. Te, by the gain of the entire control device sets the original to control the gain of the control gain at the time so as not preset design change, the control characteristics at the time of design of the control device can be reliably maintained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a steering torque and an output voltage of a torque sensor.

FIG. 3 is a block diagram of a controller.

FIG. 4 is a flowchart showing a processing procedure of a gain setting processing.

FIG. 5 is a flowchart showing a processing procedure of motor drive control processing.

FIG. 6 is a characteristic diagram showing correspondence between steering torque and motor current value with vehicle speed as a parameter.

FIG. 7 is a flowchart showing a processing procedure of abnormality monitoring processing.

FIG. 8 is a block diagram of a current feedback control system according to the present invention.

FIG. 9 is a block diagram when the controller according to the present invention is configured by an electronic circuit.

FIG. 10 is a schematic block diagram of a control circuit that detects a steering state based on a detected torque value, a steering angular velocity value, and a steering angular acceleration value.

FIG. 11 is a block diagram of a conventional controller.

FIG. 12 is a configuration diagram of a motor drive circuit 93.

FIG. 13 is a characteristic diagram showing a correspondence between a duty ratio and a motor applied voltage according to a change in battery voltage.

FIG. 14 is a block diagram of a current feedback control system in a conventional controller.

[Explanation of reference numerals] 1 steering wheel 3 torque sensor 11 electromagnetic clutch device (clutch) 12 motor 13 controller 16 battery 17 vehicle speed sensor 20 control circuit 21 microcomputer 26 counter 30 motor drive circuit 40 H bridge circuit 41 to 44 FET (electric field effect) Transistor) 51-54 Gate drive circuit 61 Current detection circuit 62 Clutch control circuit 63 Relay drive circuit 66 Battery voltage detection circuit

Front Page Continuation (72) Inventor Kuga Kogai 78 Toba-cho, Maebashi-shi, Gunma Nippon Seiko Co., Ltd.

Claims (1)

[Claims] 1. A steering torque detecting means for detecting a steering torque of a steering system, an electric motor for generating a steering assist force for the steering system, and the electric motor based on at least a torque detection value of the steering torque detecting means. An electric power steering apparatus including a control unit that outputs a control signal for generating a steering assist force to a motor, and a motor drive circuit that controls the energization direction and the energization amount of the electric motor based on the control signal from the control unit. In the control device, the voltage detection means for detecting the voltage supplied to the motor drive circuit, the preset control gain of the input / output system from the steering torque detection means to the electric motor, and the voltage of the voltage detection means. An electric power steering apparatus comprising: a gain setting unit that sets a control gain of the input / output system based on a detected value. Control device.