JPH01119472A - Electric power steering device - Google Patents

Abstract

PURPOSE:To quickly smooth the fluctuation of steering torque by adding correction torque obtained by subtracting steering speed correction torque from the differential value of the variation of normal steering auxiliary torque to the value of the normal steering auxiliary torque to correct the steering auxiliary torque. CONSTITUTION:A direct current servomotor 15 to supply steering auxiliary torque to a steering system 10 is connected to the steering system 10 through an electromagnetic clutch 15a and a worm gear 12b fixed to its output shaft. A steering torque sensor 17 functioning as a steering torque detecting means is composed of a strain gauge, and output analog voltage according to the magnitude and direction of torsion of a steering shaft. A steering angle sensor 18 outputs a steering angle detecting signal according to the direction and number of revolution of the steering shaft. A control device 19 outputs signals to control the servomotor 15 and the electromagnetic clutch 15a on a signal issued from each of the sensors 16-18 to control them.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an electric power steering device in which steering force is assisted by the output of an electric motor, and in particular, it is designed to provide a stable steering feeling. is.

[Conventional technology]

An example of a conventional electric power steering device is the one described in Japanese Unexamined Patent Publication No. 62-29466. This is an electric loss reduction gear mechanism that outputs the full amount of steering assist torque and is connected to the steering system, and controls the output torque of the electric motor according to the detected torque of the steering torque detection means. An electric power steering device that performs Lv correction on the differential value of torque during calculation, which calculates a reference steering assist torque based on the output of a steering torque detection means, and further calculates the total differential value of the reference steering assist torque value. and calculate the correction value t,
Both calculated values are added by a steering assist torque calculation means to obtain an actual steering assist torque, and the electric power applied to the electric motor is controlled.

[Problem that the invention seeks to solve]

However, in such a conventional electric power steering device, the detected steering torque value T is used to determine the value of the assist torque Tm to be supplied.
Differentiation of the standard steering assist torque as a time difference to the calculated value of the standard steering assist torque, which is calculated by multiplying s by a constant constant coefficient (determined based on vehicle running conditions such as vehicle speed). By adding and correcting the value, the steering assist torque can be increased or decreased in immediate response to actual torque fluctuations to return to a steady state. A problem has arisen in that it takes time to cool down, and in some cases it lasts forever, which is conveyed to the driver as a feeling of instability in the steering force.

This invention was made by focusing on the problems of the conventional example, and provides a steering speed correction torque that is calculated according to the steering speed from the differential value of the standard steering assist torque with the steering assist torque as a time difference. By subtracting the ratio value and using it as a correction torque, and correcting it in addition to the reference steering assist torque, the purpose is to quickly respond to actual torque fluctuations and quickly return the steering assist torque to a steady state, thereby solving the above problem. It is said that

[Elaborate means to solve all problems]

In order to achieve the above object, the present invention, as shown in the basic configuration of FIG. means, a reference steering assist torque calculating means for calculating the entire reference steering assist torque based on the steering torque detection value of the steering torque detecting means, and differentiation based on a differential value of the reference steering assist torque from the reference steering assist torque calculating means. A differential correction value calculation means for calculating a correction value, a steering angle detection means for detecting a steering angle of the steering system, and a steering speed calculation means for calculating a turning speed based on a steering angle detection value of the steering angle detection means. and a steering speed correction torque calculation means that calculates the total turning speed correction torque based on the turning speed calculated by the turning speed calculation means, and a turning speed correction torque calculation means that calculates the turning speed from the calculation result of the differential correction value calculation means. A correction torque calculation means that calculates the total correction torque by subtracting the calculation result of the correction torque calculation means, and a correction torque calculation means that calculates the total correction torque by subtracting the calculation result of the correction torque calculation means, and adds the calculation result of the reference steering assist torque calculation means and the calculation result of the correction torque calculation means to calculate the actual steering assistance. The present invention is characterized in that it is equipped with a steering assist torque calculating means for calculating torque, and a driving means for converting the calculation result of the steering assist torque calculating means into a drive current value for the electric motor and outputting it to the electric motor.

[Effect]

In this invention, the electric motor that outputs the full amount of steering assist torque is connected to the steering system through a reduction gear mechanism, and the output torque of the electric motor is controlled in accordance with the detected torque of the steering torque detecting means. In calculating the torque value, all corrections are made using the differential value of the torque and the steering speed.The electric power steering device calculates the standard steering assist torque based on the output of the steering torque detection means, and also calculates the reference steering assist torque based on the output of the steering torque detection means. The steering speed correction torque calculated from the steering speed is calculated by subtracting the entire steering speed correction torque calculated from the steering speed from the differential correction value calculated by differentiating the reference steering assist torque value, and the next correction torque is added by the steering assist torque calculating means to calculate the actual steering assist. By determining the torque and controlling the electric power applied to the electric motor, the steering torque fluctuations are quickly returned to a steady state and the feeling of instability in steering is eliminated.

[Implementation row]

Hereinafter, the present invention will be explained based on the 11th FI drawing.

FIGS. 2 to 7 are diagrams showing one embodiment of the present invention.

In FIG. 2, 10 is a component of the steering system, and 11
12 is a reduction gear mechanism consisting of a worm wheel 12a attached to a stack gift IIK and a worm gear 12b meshing with the worm wheel 12a; 13 is a staff at the end of the shaft 11; The pinion gear 13 is connected to the wheels through the entire rank 14 that meshes therewith, and further through a steering link mechanism (not shown).

Reference numeral 15 denotes a DC servo relaxer that adds steering assist torque to the steering system 10, and is fixed to an electromagnetic clutch 15a and its output shaft, and a worm gear 12b? via the steering system 1
Connected to 0.

Reference numeral 16 denotes a vehicle speed sensor serving as a vehicle speed detecting means, which detects the rotational speed of the output shaft of the transmission and outputs a pulse signal for the next cycle in response to this.

Reference numeral 17 denotes a steering torque sensor as a means for detecting steering torque; 6 (for example, a steering shirt) is composed of a fixed strain gauge; Outputs analog voltage accordingly.

Reference numeral 18 denotes a steering angle sensor as a steering angle detection means for detecting a steering angle, which is a rotating sensor consisting of a disc with a slit attached to the steering shaft and a photocoupler having two sets of detectors facing the slit. It is composed of a detector and outputs a steering angle detection signal consisting of a pulse number 1g corresponding to the rotation direction and rotation speed of the steering shaft.

Based on these detection signals, the control circuit 20 outputs control signals S1 to S3 for controlling the electric motor 15vi and a control signal 54t for controlling the electromagnetic clutch 15a, and its control signals 81 to S3 are supplied. Based on this, the drive circuit 30 is configured to drive the electric motor 1st.

The control circuit 20 has an A/D conversion i2 as shown in FIG.
1. It includes a microcomputer 22 and a D/A converter 23.

The microcomputer 22 is supplied with an input circuit 22a as an interface circuit, an output circuit 22b, calculations, a detection signal of the sensor 17 via the A/D converter 21, and a steering assist torque from the output circuit 22b. The corresponding motor current control signal S1 is sent to the D/A converter 23t.
- and the control signals 82 to S4 are directly output.

The arithmetic processing bag [22C executes predetermined arithmetic processing to calculate the reference steering assist torque TMk based on the steering torque detection signal Ts supplied to the input circuit 22a when the detected signal Ts is equal to or greater than a predetermined set value α, and further calculates the reference steering assist torque TMk. The reference steering assist torque detection value Tmt is differentiated and a differential correction value ΔTmt is calculated. Just in case, the steering speed δt1 is calculated from the steering angle detection signal θ3 supplied to the input circuit 22a, and the calculated nine steering speed a is calculated.
A predetermined calculation process is executed based on , to calculate the steering speed correction torque-accuracy.

The actual steering assist torque TM is calculated by subtracting the steering speed correction torque from the differential correction value ΔTm and is calculated based on the correction torque Tml and the reference steering assist torque, thereby outputting a motor control signal Slk for controlling the electric motor 1st. On the other hand, when the steering torque detection signal is less than the predetermined set value α, the generation of steering assist torque by the electric V&15 is completely stopped.

The storage device 22d stores a processing program necessary for the arithmetic processing of the arithmetic processing device 22c, a storage table showing the entire relationship between the steering torque T as the heavy speed v2 parameter and the reference steering assist torque Tm, and the steering speed δS and the steering speed. Correction torque T
It stores a storage table showing the relationship between the motor output torque and the motor drive current, a storage table showing the relationship between the motor output torque and the motor drive current, etc., and also sequentially stores all the calculation results of the calculation processing unit 22c.

The motor drive circuit 30, as shown in FIG.
a differential amplifier 31 whose input side is supplied with a current feedback signal from a current detector 40 for detecting current through a load of 5;
, a comparison circuit 33 as a pulse width modulation circuit to which the differential amplification output thereof and the sawtooth wave signal from the sawtooth wave generation circuit 32 are supplied to the input side, and a comparison circuit 33 which is a pulse width modulation circuit to which the differential amplification output thereof and the sawtooth wave signal from the sawtooth wave generation circuit 32 are supplied. Right rotation signal 82. The left rotation signal S3 is supplied with AND game) 34.35 and these AND game) 3
switching transistors 36.37 supplied with an output of 4.35 and these V! -Electric motor 15. Flywheel diode 3 protects from inductive energy stored in
8.39, and the switching transistor 3
6.37 collectors are connected to terminal B for right rotation and terminal LK for left rotation of tMJ machine 15C, respectively, and the motor drive is carried out.
Chopper control ◎ Next, the operation of the above-mentioned implementation train will be explained with reference to FIG. 5 showing the processing procedure in the arithmetic processing unit 22c.

5 is executed as a timer interrupt process for a predetermined main program K at predetermined time intervals (eg, 20-pssce).

First, in step (2), the vehicle speed detection signal from the vehicle speed sensor 16 is read, the number of pulses per unit time or the pulse interval is measured to calculate the vehicle speed, and this is set as the vehicle speed detection value V in the storage device 22d (D predetermined storage area temporarily memorized.

Next, the process moves to step (3), and the steering torque sensor 17
The steering torque detection signal is read in and temporarily stored in a predetermined storage area of the storage device 22d as the steering torque detection value T8.

Next, the process moves to step (3), where the steering angle detection signal from the steering angle sensor 18 is read, the steering direction and steering angle are determined, and all these steering direction detection values and steering angle detection value θ3 are stored in the storage device. Each time is stored in a predetermined storage area of 22d.

Next, the process moves to step (2), and the steering angle detection value θ8 stored in step (2) is completely differentiated to calculate the entire steering speed, and the steering angle detection value θ8 is stored in the storage device 22d.
is updated and stored in a predetermined storage area.

Next, the process moves to step (2), and it is determined whether or not the detected steering torque value T stored in step (2) is less than a predetermined set value α. The determination in this case is that the steering system 10 has an electric motor 1.
When determining whether or not to apply the steering assist torque according to step 5, if it is rarely found that Ts<α, it is determined that the steering assist torque is unnecessary and can be applied, and the process moves to step (3).

In this step (2), the clutch 1 from the output circuit 22b is
5a Control signal 8 with logic value "0" to set t-off state
4, the steering direction control signal S2.S3't is outputted to the clutch 15&, and the steering direction control signal S2.S3't of logical value '0' is outputted to the motor drive circuit 30, and then the interrupt processing is completely completed.

In this way, when the control signal S4 with the logical value "0" is supplied to the clutch 15a, the clutch 15m is turned off, and the connection state between the electric motor 15 and the reduction gear 12 of the steering system 10 is released. Steering system 10K.

On the other hand, the steering assist torque by the electric motor 15 is not transmitted, and the wheels are steered only by the steering force of the driver steering the steering wheel.

At this time, in the motor drive circuit 30, since the steering direction control signal 82.83 is set to the logical value "0", the output of the AND gate 34.35 maintains the logical value "0", and this t
Since the switching transistors 36 and 37 are maintained in the off state, the current supply circuit of the motor 15 is cut off, and the motor 15 is maintained in the stopped state.

On the other hand, the determination result of step ■ is Ts≧α (that is, Ts
-a≧0), it is determined that the steering assist torque by the electric motor 15 is necessary, and the process proceeds to step (2).

In this step (2), a control signal S4 with a logical value of "1" is supplied to the clutch 15a IC.
5a is turned on, the electric motor 15 and the steering system 10 are connected, and a steering assist torque by the electric motor 15 is applied to the steering system 10.

Next, the process moves to step (2), where it is determined whether the steering can be turned to the right or to the left. At this time, when the right turn is completed, K moves to step 2, and the right rotation control signal 82 from the output circuit 22b is set to the logical value "engine", and when the left turn is completed, K moves to step 0. Then, the left rotation control signal 53
t-logical value “1”.

Then, the process moves from step ■ or step 0 to step ◎, and the vehicle speed V is determined based on the detected vehicle speed value V stored in step ■ and the detected steering torque value Ts stored in step ■.
The gain Ks t is determined by referring to a storage table showing the relationship between the nine required steering torques and the steering assist torque (stored in advance in the storage device 22d) for all parameters.

Next, proceeding to step O, the steering torque detection value Ts
, for the gain, %Based on the set value α of the steering assist start torque, a standard steering assist torque Tm=+(Ts−α) is calculated, and this is temporarily stored in a predetermined storage area of the storage device 22d.

Next, the process moves to step 0, and the change per unit time of the reference steering assist torque Tm calculated in step 0, that is, the differential value ΔTm, is calculated as a correction term. This is the differential coefficient of the difference between the current reference steering assist torque value Tm and the reference steering assist torque value Tmo a certain period of time ago.
By multiplying ΔTm=Kt (Tm Tm
o ).

Next, shift to slap 0, and based on the steering speed tag calculated in step (3) above, refer to a storage table showing the relationship between the steering speed δ and the steering speed correction torque (storage device 22d K The steering speed correction torque Tw (stored in advance) is calculated and temporarily stored in a predetermined storage area of the storage device 22d.

Next, the process moves to step @, and the correction torque Tmt-Δ'I' is calculated based on the differential correction value ΔTm calculated in step 0 and the steering speed correction torque Tw calculated in step 0.
This is calculated as m-'rw and stored in a predetermined storage area 9-o of the storage device 22d.

Next, the process moves to step 0, and based on the correction torque Tml calculated in step ◎ above and the reference steering assist torque Tm calculated in step ◎, the steering assist torque TM t'' to be actually applied to the steering system is calculated as TM=Tm + Tmx. This is calculated and temporarily stored in a predetermined storage area of the storage device 22d.

Next, the process moves to step ◎, and the motor drive current value is calculated by referring to a table stored in advance in the storage device 22d, which represents the relationship between the steering assist torque TM and the motor drive current value IM, as shown in FIG. Mt- is calculated and temporarily stored in a predetermined storage area of the storage device 22d.

Next, proceeding to step 0, the motor drive current value Ix
'r is outputted from the output circuit 22b to the D/A converter 23 as the motor drive control signal S1.

In this way, when the motor drive control signal S1 is output,
This is converted into an analog current by the D/A converter 23, and this is supplied to the motor drive circuit 30. Therefore, in the motor drive circuit 30, if the electric motor 15 is in a stopped state, the load current detector 40 detects the entire load current.
Since the detection signal is zero, the differential amplifier 31 outputs a relatively high level differential amplification output corresponding to the motor drive current value IM supplied from the control circuit 20. A pulse modulation signal with a large duty ratio (the width of the on state is larger than the width of the off state) is output from the comparator circuit 33, and this is output from the AND gate 34.
35. At this time, the pilot turned the steering wheel to the right! ll (also turning left), since the right rotation control signal S2 (or left rotation control signal 83) is output from the output circuit 22b, the AND gate 3
Nine outputs are obtained from 4 (or 35) according to the pulse modulation signal, and the switching transistor 34 (or 35) is controlled on/off by this. As a result, the electric motor 15
starts rotating to the right (or left), and the rotational torque is transmitted to the stub shaft 11 of the steering system 10 via the clutch 15a and the reduction gear mechanism 12.

When the motor 15 starts rotating, the load current detection value of the load current detector 40 increases, so the output of the differential amplifier 31 decreases, and the duty ratio of the pulse modulation signal from the comparison circuit 33 also decreases accordingly. As a result, the electric motor 15 is rotationally driven so as to apply a companion steering assist torque to the steering system 10 in response to the steering assist torque TM output from the control circuit 20.

Note that the processing in steps 0 and 0 corresponds to the reference steering assist torque calculation means, the processing in step ◎ corresponds to the differential correction value calculation means, the processing in step ◎ corresponds to the turning speed correction torque calculation means, The processing in step @ corresponds to the correction torque calculation means, the processing in step 0 corresponds to the steering assist torque calculation means, and the processing in steps ◎ and 0 and the motor drive circuit 30 correspond to the drive means busy.

FIG. 7 shows another embodiment of the steering speed correction torque calculation. This is a sophisticated method in which the steering speed correction torque t- is calculated by multiplying the steering speed from the steering speed calculating means by a coefficient which is a function according to the vehicle speed.

When the vehicle speed is zero, the coefficient is set to -0, and up to a predetermined vehicle speed V1, the coefficient is gradually increased by δ, and K is set to a constant value of the predetermined I&j speed v haste 1 or more coefficient =.

This is done to reduce the need for heavy steering force when the vehicle is stationary or at extremely low speeds.

As explained in the embodiments above, since the steering assist torque is corrected according to the steering speed, a damping effect is added to the steering torque fluctuation, and the torque fluctuation is quickly stabilized, resulting in smooth steering. becomes possible.

Therefore, when driving, it is easy to turn the steering wheel and drive comfortably, and the steering wheel is stable when you let go.

In the above embodiment, the following case was explained in which the worm gear and the worm wheel were all applied as the reduction gear mechanism, but the invention is not limited to this, and it is of course possible to apply all the reduction gears such as other bevel gears. Ru.

In the above embodiment, the case where the entire microcomputer 22 is actually applied as the control circuit 20 has been described, but the invention is not limited to this, and all combinations of electronic circuits such as logic circuits, comparison circuits, function generators, etc. It can also be a constructor.

〔Effect of the invention〕

As explained above, with this invention, the detected steering torque value is multiplied by a constant determined depending on the driving conditions such as vehicle speed, and the calculated standard steering assist torque value is calculated based on the basic M steering assist torque change. The steering assist torque is corrected by adding the correction torque obtained by subtracting the steering speed correction torque from the differential value as the time difference of It is possible to immediately respond to sudden changes in steering torque due to disturbances at the time of starting or during steering, and to quickly settle fluctuations in steering torque to a steady state, resulting in the effect that a stable steering feeling can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram showing an overview of the invention, Fig. 2 is a block diagram showing an embodiment of the invention, Fig. 3 is a block diagram showing one row of control circuits, and Fig. 4 is a block diagram showing a motor drive circuit. FIG. 5 is a flowchart showing -gAUTh of the processing procedure of the arithmetic processing unit, and FIG. 6 is the relationship between motor output torque and motor current? 7 is a graph showing another implementation pt+ for determining the steering speed correction torque. In FIG. 0, 10 is the steering system, 11 is the stub shaft, 13 is the pinion gear, 14 is the rack, and 15 is the graph shown in FIG. t motive,
15a is an electromagnetic clutch, 16ii desk speed sensor, 17
18 is a steering torque sensor, 18 is a steering angle sensor, 19 is a control device (control means), 20 is a control circuit, 22 is a microcomputer, and 3 (it motor drive circuit). Patent Applicant: Nissan Motor Co., Ltd. FIG. Figure 4 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1) An electric motor connected to a steering system that generates a steering assist torque, a steering torque detection means for detecting the steering torque of the steering system, and a steering torque detection means based on a steering torque detection value of the steering torque detection means. , a reference steering assist torque calculating means for calculating a reference steering assist torque; a differential correction value calculating means for calculating a differential correction value based on a differential value of the reference steering assist torque from the reference steering assist torque calculating means; a steering angle detection means for detecting a steering angle of the system; a turning speed calculation means for calculating a steering speed based on a steering angle detection value of the steering angle detection means; A steering speed correction torque calculation means that calculates a steering speed correction torque based on the rudder speed, and a correction torque is calculated by subtracting the calculation result of the steering speed correction torque calculation means from the calculation result of the differential correction value calculation means. a correction torque calculation means for calculating an actual steering assist torque by adding the calculation result of the reference steering assist torque calculation means and the calculation result of the correction torque calculation means, and the steering assist torque calculation means for calculating an actual steering assist torque; An electric power steering device characterized by comprising: drive means for converting the calculation result of the calculation means into a drive current value for the electric motor and outputting the same to the electric motor. 2) The steering speed correction torque calculation means is configured to calculate the steering speed correction torque by multiplying the turning speed from the steering speed calculation means by a coefficient that is a function according to the vehicle speed. An electric power steering device according to claim 1.