JPH05254454A - Motor-operated power steering control device - Google Patents

Abstract

PURPOSE:To extract sufficient pertormance of an electric motor by providing a current detecting means to detect the energizing current of the electric motor, and an overload estimating means to estimate that the electric motor is in an overload state when the integrated value of the current detector of an energization detecting means exceeds a given threshold. CONSTITUTION:A computing processing device 9b calculates a motor current command value IM based on the steering torque detecting value T of a steering torque detector 13. A calculated value therefrom is outputted to a motor drive circuit 17 through a DA converter 16. The current detected value ID of a current detector 15 is read and integration of the current detected value ID is started when the current detected value ID is increased in a positive or a negative direction from zero. Motor overload estimating processing is put in practice, under such conditions that when a motor current command value is reduced to zero or polarity is inverted, an integrated value is reset, and it is estimated that the electric motor is in an overload state when the integrated value exceeds a preset threshold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering control device for generating a steering assist force for controlling an electric motor for generating a steering assist force for a steering system, and particularly for an industrial vehicle having a high stationary frequency. To an improvement of the electric power steering control device.

[0002]

2. Description of the Related Art An electric power steering control device of this type is applied to a vehicle such as an industrial vehicle having a high stationary frequency, and a large steering assist force generated by an electric motor causes a large load on the electric motor. Become. Therefore, if the overload state of the electric motor continues, there is a risk of burning due to heat generation.Therefore, conventionally, the energizing current that energizes the electric motor is detected, and the state in which this energizing current exceeds a preset threshold value continues for a predetermined time or longer. At that time, the supply of the energizing current to the electric motor is restricted.

[0003]

However, in the above-described conventional electric power steering control device, when the state in which the energizing current exceeds the threshold value continues for a predetermined time or more,
Since it is estimated that the electric motor is in an overload state leading to burnout, as shown in FIG. 6, after the threshold value is exceeded at time T ₁ , the threshold value is less than or equal to the threshold value at time T ₂ shorter than the set time t _2. when it becomes the temporarily resets the count of the duration at which point T _2, and starts counting the duration from time T ₃ when again exceeds the threshold, at time T ₄ beyond the duration set time t ₂ There is a problem in that the motor current is reduced by presuming an overload state, and the heating state of the electric motor may continue to cause burnout.

Further, if the threshold value to be set is high, and if the state of the current value slightly lower than that is continued for a long time, there is a risk of burning out without being presumed to be an overload state. If is set to a low value, it is necessary to set a long setting time, and even in a high load state where the current value is large, it may take time before it is estimated to be an overload state, resulting in burning.

As described above, in the conventional example, it is not possible to set the threshold value and the set time suitable for the characteristics of the electric motor, and it is not possible to adequately prevent the burning of the electric motor while the performance of the electric motor is sufficiently obtained. Therefore, in consideration of safety, the fact is that an electric motor with a large load capacity must be used. Therefore, the object of the present invention was made in view of the problems of the above-described conventional example, and an electric power steering control capable of accurately estimating an overload state leading to burnout and sufficiently bringing out the performance of an electric motor. To provide a device.

[0006]

In order to solve the above problems, an electric power steering control device according to the present invention comprises:
Steering torque detecting means for detecting the steering torque of the steering system,
An electric power steering control device including an electric motor that generates a steering assist force for the steering system, and a control unit that controls a drive current supplied to the electric motor based on a steering torque detection value of the steering torque detection unit. At
Current detecting means for detecting a current flowing through the electric motor,
And an overload estimating means for estimating that the electric motor is in an overload state when the integrated value of the detected current value of the energization detecting means exceeds a predetermined threshold value.

[0007]

According to the present invention, the current flowing to the electric motor is detected by the current detecting means, and when the integrated value of the detected current exceeds the predetermined threshold value, it can be estimated that the motor is overloaded, and a large current is generated. When it occurs, the threshold value will be exceeded in a short time, and if a small current continues, it will be estimated that the electric motor is overloaded after a relatively long time, and the electric motor heating Accurately estimate the overload state according to the state.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an electric power steering control device according to the present invention. In the figure, 1 is a steering wheel, the steering force of which is the steering shaft 2.
Is transmitted to the steering gear 3 via the steering wheel to steer the steered wheels.

A reduction gear 5 is attached to the steering shaft 2.
The output shaft 7a of the electric motor 7 driven by direct current through the
And the electric motor 7 is controlled by the controller 8.
Controlled. The controller 8 is, for example, an interface circuit.
Storage of path 9a, arithmetic processing unit 9b, RAM, ROM, etc.
A microcomputer 9 having at least the device 9c,
A / D converters are provided on the input side of the interface circuit 9a.
Steering wheel via converters 10, 11 and 12
Steering torque detector for detecting the steering torque applied to No. 1
13, a vehicle speed detector 14 for detecting the vehicle speed of the vehicle and an electric motor
The current detector 15 for detecting the current flowing through the motor 7 is connected.
Output to the electric motor 7 via the D / A converter 16
The motor drive circuit 17 that outputs the drive current is connected
It Here, the steering torque detector 13 is
When Eel 1 is cut to the right, it is forward, when it is cut to the left
The steering torque detection value T having a negative voltage is output. Well
In addition, the motor drive circuit 17 controls the controller as described later.
Positive motor current command value I from LA _MWhen is input
To control the energizing direction to the field winding of the electric motor 7.
Data current command value I_MThe exciting current for forward rotation proportional to
Supplied to the motor 7, and on the contrary, a negative motor current command value I_MIs input
The electric current to the field winding of the electric motor 7
The motor current command value I_MInverse proportional to
The divert excitation current is supplied to the electric motor 7.

The arithmetic processing unit 9b includes a steering torque detector 1
Based on the steering torque detection value T of No. 3, the motor current command value I is referred to by referring to the storage table corresponding to the characteristic diagram showing the relationship between the steering torque of the steering torque and the motor current command value of FIG. Calculate _M and set this to D
/ A converter 16 and outputs to the motor drive circuit 17, current detector 15 reads the current detection value I _D of the current detection value when the current detection value I _D increases in the positive or negative direction from zero When the integration of I _D is started, the integrated value is reset when the motor current command value is zero or the polarity is reversed, and the integrated value I _I exceeds a preset threshold value I _S in a motor overload state. The motor overload estimation processing that estimates that there is is executed.

The storage device 9c stores a processing program necessary for executing the processing of the arithmetic processing device, and also stores a storage table corresponding to the characteristic curve L ₁ of FIG. 2 and a threshold value I _S. And the values required in the processing process of the arithmetic processing unit are sequentially stored. The above is the configuration of the embodiment of the present invention. Next, the operation of the above embodiment will be described with reference to FIG. 3 showing the steering control processing of the arithmetic processing unit 8b.

In the steering control process of FIG. 3 of the arithmetic processing unit 9b, first, in step, the steering torque detection value T of the steering torque detector 13 and the vehicle speed detection value V of the vehicle speed detector 14 are read, and then in step FIG. 2 stored in the storage device 9c based on the detected torque value T and the detected vehicle speed V.
It calculates a motor current command value I _M with respect to the electric motor 7 by looking up the corresponding storage table,
This is updated and stored in the current command value storage area of the storage device 9c.

Next, in step, the energized current detection value I _D of the current detector 15 is read, and in step, the energized current detection value I _D is integrated to calculate an integrated value I _I , which is stored in the integrated value storage area. After updating and storing, in step, the motor current command value I _M in the current command value storage area is read, and it is determined whether or not this is zero or the polarity-inverted integral reset condition is satisfied, and the integral reset condition is satisfied. If so, in step, the integrated value I _I in the integrated value storage area is reset to zero and then the process proceeds to step. If the integral reset condition is not satisfied, the process directly proceeds to step.

In this step, it is determined whether the integrated value I _I stored in the integrated value storage area exceeds a preset threshold value I _S. This determination is to estimate whether or not the electric motor 7 is in a heated state, and I _I ≦ I
When it is _S , it is judged to be a normal state, and in step, the motor current command value I _M calculated in step and stored in the current command value storage area is directly used to drive the motor through the D / A converter 16. Output to circuit 17, I _I > I
When it is _S , it is estimated that the vehicle is in an overload state and the process proceeds to step a.

In step a, the motor current command value I _M calculated in step and stored in the current command value storage area is read, and from this, a predetermined value Δ preset.
A value obtained by subtracting I _M is set as a new motor current command value I _M , and this is set via the D / A converter 16 to the motor drive circuit 1
7 and update stored in the command current storage area (however, when the motor current command value I _M becomes zero or near zero, it is maintained at zero), and then in step b,
It is determined whether or not the current limit is released. In this determination, the motor current command value I _M corresponding to the steering torque detection value T is calculated in the same manner as the above-mentioned steps and, and the motor current command value I _M becomes zero or the polarity is reversed as in the above step. If the reset condition is not satisfied, the process returns to step a and the motor current command value I _M stored in the current command value storage area is subtracted. It continues until the current command value I _M becomes zero, and when the reset condition is satisfied, in step c, the integral value I _I stored in the integral value storage area is reset in the same manner as the above step to cancel the current limitation. Return to the step.

When the vehicle is stopped, a key switch (not shown) is turned on to power on the controller 8 and the steering control process shown in FIG. 3 is started. At this time, the initialization resets the integrated value I _{I in} the integrated value storage area to zero. When the steering wheel 1 is in the non-steering state in this stopped state, the steering torque detection value T of the steering torque detector 13 is zero, and the vehicle speed detection value V of the vehicle speed detector 14 is also zero. Therefore, when the memory table of FIG. 3 is looked up in step, the calculated motor current command value I _M
Is also zero. Since the energizing current detection value I _{D of the} current detector 15 read in the step is also zero, the integrated value I _{I of} the energizing current detection value I _D calculated in the step is also zero, and this is stored in the integrated value storage. Update and store in the area. Next, since it is determined in step that the integral reset condition is satisfied, the procedure proceeds to step, the integral value I _I stored in the integral value storage area is reset to zero, and then the procedure proceeds to step to integrate the integral value I _I is zero and the set threshold I
Since it is smaller than _S, it is determined that the electric motor 7 is in a normal state, and the process proceeds to step, and the zero motor current command value I _M stored in the current command value storage area is directly used for D / A.
It outputs to the motor drive circuit 17 via the converter 16. Therefore, the energizing current supplied from the motor drive circuit 17 to the electric motor 7 becomes zero as shown in FIG. 4, and the electric motor 7 does not generate a steering assist force.

From the non-steering state in this stopped state, as shown in FIG.
When the steering wheel 1 is turned to the right at time T ₁ to start stationary operation, the steering torque detector 13 outputs a steering torque detection value T that gradually increases in the positive direction. Therefore, the steering torque detection value T read in step increases in the positive direction, and the vehicle speed detection value V of the vehicle speed detector 14 increases.
Is zero, the steepest curve L ₁ is selected when the storage table of FIG. 2 is looked up in step, and the motor current command value I _M calculated as a result of this is in the positive direction. It will be a large value. On the other hand, since the energization current detection value I _D read in the step is zero, the integrated value I _I calculated in the step also becomes zero, and the step _{,
Then, the process} proceeds to the step, and the positive motor current command value I _M stored in the current command value storage area is output to the motor drive circuit 17, whereby the forward drive energization current is supplied from the motor drive circuit 17 to the electric motor 7. The electric motor 7 is supplied and a steering assist force is generated, and this is transmitted to the steering shaft 2 via the reduction gear 5, so that light steering can be performed.

After that, when the electric current is supplied to the electric motor 7, the integral value I _I calculated in the step becomes a positive value, which is updated and stored in the integral value storage area to reset the integral in the step. It is judged that the condition is not satisfied and the process directly proceeds to the step. When the vehicle is started from this stationary state, the vehicle speed detector 14
Since the vehicle speed detection value V of increases the characteristic curve having a small inclination when the storage table is looked up in step, the calculated motor current command value I
_{Since M} also has a small value, the energizing current value output from the motor drive circuit 17 also has a small value as shown in FIG.

After that, when the steering wheel 1 is returned to the neutral position and the vehicle travels straight at time T ₂ , the steering torque detection value T of the steering torque detector 13 becomes a small value near zero and is calculated in step. energizing current motor current instruction value I _M is supplied becomes zero, the electric motor 7 becomes zero as shown in FIG. Therefore, when the process of the next step is performed, the detected current value I _D becomes zero. Therefore, it is determined that the integral reset condition is satisfied in the step, the process proceeds to the step, and the value is stored in the integral value storage area. The integrated value I _I being reset is reset to “0”.

After that, when the steering wheel 1 is turned left at the time T ₃ to turn to the left, the steering torque detection value T of the steering torque detector 13 increases in the negative direction in response to this, whereby the above-described right turning is performed. Contrary to the turn-off state, the motor drive circuit 17 supplies a reverse rotation energizing current to the electric motor 7 as shown in FIG. 4, so that the electric motor 7 generates a steering assist force for left turn, which is decelerated. It is transmitted to the steering shaft 2 via the gear 5.

In the stationary state, the detected steering torque value T becomes a large value and the electric motor 7 becomes overloaded. However, in the normal steering state, the overloaded state continues for a long time as described above. However, when the overload state continues for a relatively long time, such as after time T _{5 in} FIG. 4, the integral reset condition is not satisfied, so the integral value I _I of the energizing current calculated in step is If the integral value I _I exceeds the preset threshold I _S at time T ₆ as the increasing tendency continues, it is estimated that the motor is overloaded and the process proceeds from step to step a. with a value obtained by subtracting a predetermined value [Delta] I _M from the motor current command value I _M which is stored in the current command value storage area as a new motor current instruction value I _M, which is updated and stored in the current command value storage area, the motor Drive And outputs it to the road 17,
A current limiting process for reducing the energizing current supplied to the electric motor 7 is performed. After that, the process proceeds to step b, and it is determined whether or not the integral reset condition is satisfied. If the integral reset condition is not satisfied, the process returns to step a, the current limiting process is continued, and the motor current command value I _M When it becomes zero, the state of zero is maintained.

After that, when the steering wheel 1 is set to the non-steering state and the steering torque detection value T of the steering torque detector 13 becomes zero, or the steering wheel 1 is set to the reverse steering state and the steering torque detection value T becomes the opposite polarity. Since it is determined in step b that the integral value reset condition is satisfied, the process proceeds to step c, and the integral value I _I of the energizing current stored in the integral value storage area is reset to “0”. Returning to the step, the normal control state described above is restored.

As described above, according to the above embodiment, it is estimated that the motor is overloaded when the integrated value I _{I of the} energizing current supplied to the electric motor 7 exceeds the preset threshold I _S. Since it is designed to reduce the energizing current,
As shown in FIG. 5, when an overcurrent is supplied to the electric motor 7, it is a short time t ₁ , and when the current value is small, it continues for a relatively long time corresponding to the current value. The state can be estimated and the overload state of the electric motor can be accurately detected.

In the above embodiment, when the integrated value I _I of the energized current exceeds the threshold value I _S , the motor current command value I _M
The case has been described which performs reduction processing for gradually decreasing, immediately the motor current command value I _M may be "0" when a I _I> I _S is not limited thereto. In the above embodiment has described the case of performing the integration process of the energization current by applying the microcomputer 9, the integral of the current detection value I _D of the current detector 15 is not limited to this integrated to an integrator The output may be compared with the threshold value I _S by a comparison circuit.

Further, in the above embodiment, the case where the storage table having the vehicle speed as a parameter is used has been described, but the present invention is not limited to this, and the steering torque detection value and the motor current command value are set to one to one. You may make it correspond. Further, in the above-described embodiment, the case where the present invention is applied to the battery forklift has been described, but the present invention is not limited to this and can be applied to other industrial vehicles in which the electric motor is frequently overloaded.

[0026]

As described above, according to the electric power steering control device of the present invention, it is estimated that the electric motor is in the overload state when the integrated value of the energizing current to the electric motor exceeds the set threshold value. Therefore, it is possible to accurately predict the overload state of the electric motor that occurs when an excessive current is supplied in a short time or when the current value is small but the energization continues for a long time. Therefore, an excellent effect that a fail-safe function can be provided while maximizing the performance by applying an electric motor having a small rated capacity as an electric motor for an electric power steering device can be exerted.

[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 detection value and a motor current command value with vehicle speed as a parameter.

3 is a flowchart showing an example of processing of a controller applicable to the embodiment in FIG. 1. FIG.

FIG. 4 is a time chart for explaining the operation of the embodiment of FIG.

FIG. 5 is a characteristic diagram showing the relationship between the electric current supplied to the electric motor and the overload estimation determination time.

FIG. 6 is a time chart for explaining the operation of the conventional example.

[Explanation of symbols]

 1 Steering Wheel 2 Steering Shaft 3 Steering Gear 7 Electric Motor 8 Controller 9 Microcomputer 9a Interface Circuit 9b Arithmetic Processing Device 9c Storage Device 13 Steering Torque Detector 14 Vehicle Speed Detector 15 Current Detector

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area B62D 137: 00

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 a steering torque detection value of the steering torque detecting means. In an electric power steering control device having a control means for controlling a drive current supplied to the electric current steering means, a current detecting means for detecting a conducting current of the electric motor, and an integrated value of current detection values of the conducting current detecting means have a predetermined threshold value. An electric power steering control device, comprising: an overload estimating unit that estimates that the electric motor is in an overload state when the electric power exceeds the limit.