JP2933085B2 - Control device for electric power steering - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control device for an electric power steering that controls an electric motor according to a forward / reverse rotation signal of a steering wheel and an output signal from a PWM circuit.

(Prior Art) In the conventional apparatus shown in FIGS. 3 to 7, a pinion 3 is connected to a tip of an input shaft 2 connected to a handle h, and the pinion 3 is engaged with a rack 6. Both sides of the rack 6 are connected to the knuckle arm 4 via side rods 5.

Further, a speed reducer 7 is connected to the electric motor m which can be rotated forward and backward, and a pinion 9 is provided on an output shaft 8 of the speed reducer 7, and the pinion 9 is engaged with the rack 6.

Further, a vehicle speed sensor 10 for detecting a vehicle speed of the vehicle, a torque sensor for detecting a steering torque acting on the input shaft 2.
11, both of which are connected to the signal processing device 12. This signal processing device 12 is connected to the motor control device a,
Is as shown in the block diagram of FIG.

The motor control device a, but the motor current control signal V _I according to the running condition of the vehicle is provided with a correction means b for entering, the motor current control signal V _I, as shown in FIG. 5 are those determined vehicle speed v as a parameter with respect to the steering torque T _in. The motor current is controlled according to the motor current control signal as shown in FIG.

The correction means b is a differential input type operational amplifier 13.
The a, the control signal V _I is input to one input terminal 13a, the other input terminal 13b is connected to the motor current detecting means 14. The motor current detecting means 14 detects a current flowing through the electric motor m and outputs it as a voltage signal Vi. The correcting means b has three resistors Ra, Rs, and Rf, and the resistor Rf is sufficiently larger than the resistor Rs.

The correction means b which as described above, when a said control signal V _I and the voltage signal Vi is inputted to the operational amplifier 13, the output voltage Vo at that time _{Vo = V I + (Rf /} Rs) (V I - Vi).

Therefore, when the control signal V _I and the voltage signal Vi is equal, the output signal Vo is equal to V _I. Also, if greater than the voltage signal Vi is the control signal V _I from the motor current detecting means 14, to reduce the output signal Vo, contrary to the signal Vi is the smaller, to increase the output signal Vo.

The positive / negative determining means 15 and the absolute value means 16 are connected to the correcting means b as described above.

The positive / negative determining means 15 includes first and second AND gates 17 and 18.
And through the knot gate 19, the third and fourth
And gates 20 and 21 are also connected.

An oscillation circuit 22 for outputting a predetermined pulse signal is connected to the first and third AND gates 17 and 20.
The AND gates 18 and 21 have a PW connected to the absolute means 16.
M circuit 23 is connected.

Now, for example, when the positive rotation signal A is output from the positive / negative determination means 15, this normal rotation signal A is output to the first and second AND gates 17,
Enter in 18. However, when a signal other than the forward rotation signal, that is, a reverse rotation signal is output from the positive / negative determination means 15, the NOT gate 19 functions to output a reverse rotation signal, and the reverse rotation signal is output to the third and fourth AND gates 20, 21. To enter.

Therefore, the positive rotation signal A from the positive / negative determination means 15
When input to the AND gate 17, the pulse signal C identical to the pulse signal I of the oscillation circuit 22 is output from the first AND gate 17 while the normal rotation signal A is input. When the inverted signal output from the NOT gate 19 is input to the third AND gate 20, a pulse signal D identical to the pulse signal I is output from the third AND gate 20 while the inverted signal is input. Is done.

Further, when the normal rotation signal A is being input to the second AND gate 18, while the normal rotation signal is being inputted,
The AND gate 18 outputs a PWM signal E. Further, when the reverse signal from the NOT gate 19 is input to the fourth AND gate 21, the PWM signal F is output from the fourth AND gate 21 while the reverse signal is input.

Further, a bridge circuit is configured by first to fourth field effect transistors 24 to 27 (hereinafter referred to as first to fourth FETs) via the electric motor m. Then, the gate sides of the first and third FETs 24 and 26 are connected to the first and third AND gates 17 and 20 via voltage conversion means 28 and 29, and the gate side of the second FET 25 is directly connected to the knot gate 19, The gate side of the fourth FET 27 is directly connected to the positive / negative determination means 15.

In the above-described bridge circuit, the first and third FETs 24 and 26 are connected to the positive side of the battery 30, and the voltages V ₁ and V ₄ between the second and fourth FETs 25 and 27 are set to the ground potential. Further, the voltages V ₁ and V ₃ of the electric motor m are guided to voltage conversion means 28 and 29.

The voltage conversion means 28 and 29 described above are composed of first and third FETs.
This is to secure the gate voltages G and H of 24 and 26. That is, the source voltages V ₂ and V _{2 of the second} and fourth FETs 25 and 27
_{Although 4} is always the ground potential, the source voltages V ₁ and V ₃ of the _first and _third FETs 24 and 26 vary up to the voltage of the battery 30 at the maximum. Then, the voltage conversion means 28 and 29 are made to function, and the gate voltages G and H of the _first and _third FETs 24 and 26 and the source voltages V ₁ and V ₃
And keep the relative difference.

The voltage conversion means 28 and the first FET 24 are connected to the second AND gate 18 via the fifth FET 31 and the knot gate 32, and the drain side of the fifth FET 31 is set to the ground potential.

The voltage conversion means 29 is connected between the third FET 26 and the fourth AND gate 21 via the sixth FET 33 and the knot gate 34. The drain side of the sixth FET 33 is also set to the ground potential.

Now, for example, if the forward rotation signal A is output from the positive / negative determination means 15, while the forward rotation signal is being output, the pulse signal C is output from the first AND gate 17, and
This pulse signal C is input to the voltage conversion means 28. When the pulse signal C is input to the voltage converter 28, the gate voltage G for the first FET 24 is output from the voltage converter 28.

Further, when the normal rotation signal A is output as described above, the normal rotation signal A is also input to the second AND gate 18, so that
The output signal B from the PWM circuit 23 is supplied to the second AND gate 18.
Is output as a PWM signal E. In this way the second
The PWM signal E output from the AND gate 18 is input to a knot gate 32, which outputs a knot signal that turns on when the PWM signal is off and turns off when the PWM signal is on, The knot signal is 5F
Input to the gate side of ET31. When the knot signal input to the gate side of the fifth FET 31 is on, in other words, the PWM
When the signal E is off, a voltage is applied to the gate side of the fifth FET 31, and the fifth FET 31 is naturally turned on.

When the fifth FET 31 is turned on in this way, the gate side of the first FET 24 is grounded, so that the gate voltage G output from the voltage converter 28 is not supplied to the gate side of the first FET 24.

Conversely, when the knot signal E is off, in other words, when the PWM signal E is on, no voltage is applied to the gate side of the fifth FET 31. Therefore, while the PWM signal E is on, the fifth FET 31 is not energized, and
From 28, the gate voltage G is continuously applied to the first FET 24. Therefore, as is clear from the time chart of FIG. 7, the first FET 24 is also turned on and off in accordance with the duty ratio of the PWM signal E.

When a signal that is not a forward rotation signal is input from the positive / negative determination means 15, a reverse rotation signal is output from the NOT gate 19, and the reverse rotation signal is input to the third AND gate 20. While the inverted signal is being input to the third AND gate 20, the pulse signal D is output from the third AND gate 20, and the pulse signal D is input to the voltage conversion means 29. When the pulse signal D is input to the voltage converter 29, the voltage converter 29 outputs a gate voltage H to the third FET 26.

At this time, since the reverse signal is also input to the fourth AND gate 21, the output signal B from the PWM circuit 23 is output as the PWM signal F from the fourth AND gate 21. And
When the PWM signal F is input to the knot gate 34 and the sixth FET 33 is controlled by the knot signal F output from the knot gate 34, it is the same as the case of the fifth FET 31.

Therefore, the third FET 26 is also turned on and off in accordance with the duty ratio of the PWM signal F.

As is clear from the above, the first, 3FETs 24, 26
Is turned on / off in response to the PWM signal.
5, 27 maintain the ON state while the handle h is switched to the left or right. For example, while the normal rotation signal A is being output, the fourth FET 27 maintains the ON state. Therefore, even when the PWM signal is off, a regenerative current in the direction of the arrow 35 flows through the electric motor m. This electric motor m
Is detected by the motor current detecting means 14. Then, a voltage signal Vi proportional to the current I is output from the motor current detection means 14, and the signal Vi is fed back to the correction means b.

In the correction unit b, compares the control signal V _I and the voltage signal Vi as described above, when the voltage signal Vi is too large for the control signals V _I, for example, to zero the value of the control signal V _I Regardless, when the voltage signal Vi is equal to or greater than zero, the output voltage Vo is controlled so that the current I supplied to the electric motor m becomes zero.

(Problems to be Solved by the Invention) In the conventional device as described above, when the steering wheel is turned off and then released, the motor current becomes almost zero, and the steering wheel returns to the neutral point. When the handle returns to the neutral point, the rotor inertia of the electric motor acts. At this time, the motor current becomes zero, so that the rotor inertia acts directly on the handle. However, when the rotor inertia of the electric motor strongly acts on the handle, the inertia force causes an overshoot state in which the handle passes through the neutral point, and the so-called hand-off astringency deteriorates. In particular, in the case of an electric motor, since a speed reducer is connected, the inertia force is further increased, and the inertia force is further increased as the size of the electric motor increases.

As a result, this conventional device has poor hand-holding astringency as compared to manual steering, and is a hindrance when using an electric power steering device in a vehicle with a large displacement that requires a large electric motor. Was.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a control device having good hand-convergence without overshoot when a handle reaches a neutral point.

(Means for Solving the Problems) According to the present invention, a bridge circuit is configured by four transistors and an electric motor, and the four transistors are used when a PWM signal from a PWM circuit and a normal rotation signal of a steering wheel are input. A first transistor which is turned on, a third transistor which is turned on when a PWM signal and a reverse signal of the handle are inputted, a second transistor which is turned on when the handle is rotated forward, and which is turned on when the handle is reversed. It is assumed that the control device for electric power steering includes the fourth transistor.

The present invention is based on the premise that the torque sensor detects an input torque and a direction thereof, a motor current detecting unit detects a current supplied to the electric motor, and a direction of a voltage of the electric motor. A voltage detection unit, a neutral point sensor that outputs a neutral signal when a neutral point of the steering wheel is detected, and a regenerative brake signal output unit that outputs a regenerative brake signal for flowing a regenerative current to the electric motor. The brake signal output means detects a return state of the steering wheel by a signal from the torque sensor, the motor current detection means, and the voltage detection means, and outputs a regenerative brake signal when a neutral signal is input from the neutral point sensor in the return state of the steering wheel. It is characterized by the following.

(Operation of the Present Invention) Since the present invention is configured as described above, the direction of the motor torque is detected based on the motor current, and the direction of the motor voltage is detected based on which of the transistors is on. I do. Depending on these signals,
Determines if the handle is in the return state. When the neutral point sensor detects the neutral point of the steering wheel when the steering wheel is in the return state, the regenerative brake signal output means outputs a regenerative brake signal.

(Effect of the Present Invention) According to the control device of the present invention, when the steering wheel reaches the neutral point, a regenerative current flows and the electric motor is braked, so that overshooting of the steering wheel can be prevented, and the hand-held astringency can be reduced accordingly. Get better.

Further, since the regenerative brake is applied to the electric motor after the handle reaches the neutral point, the time required for the handle to return to the neutral point is not different from the conventional case. Therefore, the return of the steering wheel does not deteriorate.

Further, since the electric motor is braked by the regenerative current, no electric power is required.

(Embodiment of the present invention) In the embodiment shown in FIG.
In response to an instruction V _I, but controls the motor current I, with respect to its current control, the same as the conventional one described above, together with the detailed description will be omitted, the same components as those of the prior art, with the same reference numerals I will explain.

The greatest feature of this embodiment is that when the handle is released from the handle and returned, the regenerative brake current is supplied to the electric motor when the handle reaches the neutral point. Therefore, the following mainly describes this point.

First, what is important in this embodiment is that the handle h
Is to determine whether is in a return state,
The criteria are as follows.

That is, when the steering wheel h is returning to the left, the output direction of the motor torque T is to the right and the motor speed is to the left in the region II 'in FIG. That is, the motor torque T
Is output to the right, but the action of the self-aligning torque overcomes and the motor m rotates to the left, and the steering wheel h returns to the left.

Further, when the steering wheel is in a right-turn state, the second direction in which the output direction of the motor torque T is left and the motor rotation speed is right.
This is the area II in the figure. That is, although the motor torque T is output in the left direction, the effect of the self-aligning torque overcomes and the motor m rotates to the right, and the steering wheel h returns to the right.

And the above situation is based on the motor current V _I ′ and the motor voltage
It can be grasped by detecting V ₁ , which is as follows.

Left return Right return Motor current V _I ′ Right Left Motor voltage V ₁ reverse positive Input torque T _in right Left In the above, the motor current V _I ′ corresponds to the left and right of the motor torque T. Further, when the motor voltage V ₁ is the inverse while the second 2FET25 and the 3FET26 is turned on, when positive are those with first 1FET24 and the 4FET27 is turned on.

Further, the input torque signal T _in is configured to detect by the conventional torque sensor 11, the torque signal is a contained in the motor current signal V _I and inputs to the operational amplifier 13.

Further, a regenerative brake signal output means 37 is connected to a neutral point sensor 36 for detecting that the handle h has reached the neutral point, and the output terminal 1 of the regenerative brake signal output means 37 has a first or second OR gate 38, 39 is connected to one input terminal of the knot gate 40.

The other input terminal of the first OR gate 38 is connected to the output terminal of the NOT gate 19, and the output terminal of the first OR gate 38 is connected to the gate side of the second FET 25. The other input terminal of the second OR gate 39 is connected to the positive / negative determining means 15, and the output terminal of the second OR gate 39 is connected to the gate side of the fourth FET 27.

Further, the output terminal of the knot gate 40 is connected to the input terminals of the first AND gate 17 and the third AND gate 20.

A motor current detecting means 41 for detecting an actual current supplied to the electric motor m is provided, and the motor current detecting means 41 is connected to a current processing means 42. Is outputted motor current V _I 'is the current processing means 42 in this manner, the output signal is to be input to the output unit 43 for outputting a signal of the motor current. The output terminal of the output means 43 is connected to the operational amplifier 13.

The direction of the voltage with respect to the electric motor m is the first to fourth FETs.
The determination is made based on which of the FETs 24 to 27 is in the ON state. That is, when the second FET 25 and the third FET 26 are in an ON state, a current flows in the direction of arrow 44,
This shows the opposite situation. Further, when the first FET 24 and the fourth FET 27 are in the ON state, a current flows in the direction of the arrow 45 to indicate a positive state.

Hereinafter, it is assumed that the motor m rotates right when the current flows in the positive direction, and the motor m rotates left when the current flows in the opposite direction.

Thus, the return state of the steering wheel is detected according to the following situation.

Left return Right return Motor current V _I ′ Right Left Motor voltage V ₁ reverse positive Input torque T _in right left In the above, the forward and reverse of the motor voltage V ₁ is determined by using voltage detection means (not shown) as follows. Is determined. For example, if the motor m rotates in the reverse direction due to the self-aligning torque of the vehicle, an electromotive force is generated in the motor m. The voltage due to the electromotive force is opposite to the direction of the voltage when the power assist force is exerted. And
The direction of the voltage when the power assisting force is exerted can be grasped by which FET is turned on. However, in the released state, the current is very small, so that the voltage direction is totally reversed by the electromotive force of the motor m. Therefore, if the current direction of the motor voltage is determined based on the direction of the voltage when the power assisting force is exerted, it is possible to determine whether or not the return to the neutral state without the hand is performed.

Then, when the steering wheel is in the return state and the neutral point sensor 36 detects the neutral point of the steering wheel, the regenerative brake signal output means 37 outputs a high brake signal J. When the high signal J is output in this manner, the signal is input to the first and second OR gates 38 and 39, so that the first and second OR gates output the high signals K and L regardless of other signals. Is done. When the high signals are output from the first and second OR gates 38 and 39, the second FET 25 and the fourth
ET27 is turned on.

On the other hand, the signal on the output terminal side of the knot gate 40 becomes a low signal, so that the low signal is input to the input terminals of the first and third AND gates 17 and 20. Therefore, the output signals from the first and third AND gates become low signals irrespective of other signals, so that the first FET 24 and the second FET 26 are turned off.

Therefore, a regenerative current flows between the second and fourth FETs 25 and 27 in the direction of the arrow. The electric motor m
The regenerative current at this time flows in a direction to stop the rotation of the motor.

On the other hand, when the brake signal is not output from the regenerative brake signal output means 37, the signal J becomes low and the signal on the output terminal side of the NOT gate 40 becomes high, so that the first and second OR gates 38, 39 and The first and third AND gates 17 and 20 are operated by signals other than the brake signal. In other words, the control device performs normal control.

As described above, according to the control device of this embodiment, in the return state of the handle h, when the handle reaches the neutral point, the regenerative brake current is caused to flow to the electric motor. Overshoot can be prevented. Therefore, the hand-held convergence of the steering mechanism is very good.

[Brief description of the drawings]

1 and 2 show an embodiment of the present invention.
FIG. 2 is a block diagram showing a control circuit, FIG. 2 is a graph showing the relationship between motor torque and motor speed, FIGS. 3 to 7 show a conventional device, FIG. FIG. 5 is a block diagram of a control circuit, FIG. 5 is a graph showing a relationship between a steering torque and a motor current control signal using the vehicle speed as a parameter, FIG. 6 is a graph showing a relationship between the motor current control signal and the motor current, FIG. 7 is a timing chart. h: Handle, m: Electric motor, 23: PWM circuit, 2
4 to 27: first to fourth field effect transistors, 36: neutral point sensor, 37: regenerative brake signal output means, 41:
Motor current detection means.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B62D 5/04 B62D 6/00

Claims (1)

(57) [Claims] 1. A bridge circuit comprising four transistors and an electric motor, wherein the four transistors are a first transistor that is turned on when a PWM signal from a PWM circuit and a normal rotation signal of a steering wheel are input; A third transistor is turned on when the PWM signal and the reverse signal of the steering wheel are input, a second transistor is turned on when the steering wheel is rotated forward, and a fourth transistor is turned on when the steering wheel is reversed. In a control device for an electric power steering, a torque sensor for detecting an input torque and its direction, a motor current detecting means for detecting a current supplied to the electric motor, and a voltage detecting means for detecting a direction of a voltage of the electric motor, , A neutral point sensor that outputs a neutral signal when the neutral point of the steering wheel is detected, and an electric motor Regenerative brake signal output means for outputting a regenerative brake signal for flowing to the motor, wherein the regenerative brake signal output means detects a return state of the steering wheel by a signal from a torque sensor, a motor current detecting means, and a voltage detecting means. And a regenerative braking signal is output when a neutral signal is input from a neutral point sensor in a return state of the steering wheel.