JP2003118619A - Electric power steering control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering control device capable of improving operation performance of a steering wheel. SOLUTION: A CPU squares a detection value of an EPS sensor (angle detection sensor) read in the step S2 (S10) and multiplies it by a specified gain determined in advance to form a motor output value pattern (S11) which is to be stored in a RAM. From the pattern, the motor output value corresponding to the detection value of the EPS sensor associated with the rotation operation (including a rotation direction) of the steering wheel is read out, then output control over a power steering motor is performed according to the value (S12).

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 mounted on a battery forklift, an electric vehicle or the like.

[0002]

2. Description of the Related Art Conventionally, an electric power steering control device mounted on a battery forklift or the like has an EPS sensor including a potentiometer for detecting a rotational operation angle from a neutral position of a steering wheel and a steering torque to a steered wheel. Some include a power steering motor arranged so as to be able to supply the power steering motor, and a control unit for controlling the power steering motor so that the motor output value corresponds to the detection value of the EPS sensor.

In such an electric power steering control device, positioning is performed so that the detection value of the EPS sensor becomes zero when the steering handle is in the neutral position. Specifically, with the steering handle in the neutral position without being operated, the potentiometer is fixed to the steering handle with screws while keeping the detected value of the EPS sensor at zero. Subtle alignment is performed by inserting.

Then, as shown in FIG. 5, a dead zone N having a predetermined width, which is a predetermined numerical value range centered on the zero detection value of the EPS sensor, is provided, and when the detection value of the EPS sensor is within the predetermined numerical value range. Set the motor output value to zero. Also,
If the detected value of the EPS sensor is not within the dead zone N, EPS
The detection value of the sensor is multiplied by a predetermined gain to derive the motor output value. In this way, the motor output value pattern MC is created and stored in a memory or the like, and the motor output value corresponding to the detection value of the EPS sensor associated with the rotation operation of the steering wheel is read to control the output of the power steering motor. ing. In FIG. 5, SH indicates the neutral position of the steering wheel, and ML and MR indicate the mechanical end.

[0005]

However, as shown in FIG. 5, the motor output value is set so as to change linearly with respect to the detection value of the EPS sensor, and if the inclination of this straight line is increased. While the steering wheel becomes lighter and the feeling becomes better, when the steering wheel is operated slowly, the hunting of the power steering motor occurs near the point where the motor output value rises from the dead zone and the operation feeling becomes worse. There was a problem.

On the other hand, if the inclination of the straight line of the motor output value with respect to the detection value of the EPS sensor is made small, the above-mentioned hunting of the power steering motor is suppressed, but
When the steering wheel is operated, the driver feels that the drive of the power steering motor starts slightly behind the steering wheel around the dead zone (see FIG. 5). Further, the steering wheel becomes heavier as the steering wheel is operated at high speed, so that the feeling is never good. In particular, for cargo handling vehicles such as forklifts, small turning ability is important,
Since a driving method is often used in which the steering wheel is rapidly rotated to greatly change the direction of the driving wheels during work, a heavy steering wheel causes fatigue of the driver and lowers work efficiency. There was a problem.

Therefore, it is an object of the present invention to provide an electric power steering control device capable of improving the steering wheel operating performance.

[0008]

In order to achieve the above object, the present invention provides an angle detection sensor for detecting a rotational operation angle from a neutral position of a steering wheel, and a steering torque can be supplied to steered wheels. In the electric power steering device for controlling the power steering motor so that the motor output value corresponds to the detection value of the angle detection sensor, the detection value of the angle detection sensor is A controller for deriving the motor output value having a non-linear relationship with the detection value of the angle detection sensor by performing a predetermined calculation using the motor output value and controlling the power steering motor based on the derived motor output value. Is characterized by.

According to this structure, since the relationship between the motor output value and the detection value of the angle detection sensor is made non-linear, the motor output value rises smoothly when the steering wheel is slowly operated. As described above, hunting does not occur, and the drive of the power steering motor does not give a feeling that the drive is started with a slight delay. on the other hand,
Compared to the conventional case where the motor output value changes linearly with respect to the detection value of the angle detection sensor, the motor output value reaches the maximum quickly, so when operating the steering handle at high speed, It can be operated lightly.

Therefore, the operation feeling of the steering wheel can be greatly improved as compared with the conventional one.

According to the present invention, the control unit sets the motor output value to zero when the detection value of the angle detection sensor is within a predetermined numerical range, and the detection value of the angle detection sensor is a predetermined numerical value. If it is not within the range, the detected value of the angle detection sensor is subjected to a predetermined exponentiation operation and is multiplied by a predetermined gain to derive the motor output value.

According to this structure, since the motor output value has a non-linear relationship with the detection value of the angle detection sensor, the motor output value is smoothed even if the width of the so-called dead zone where the motor output value is zero is reduced. The dead band width can be reduced and the operability of the steering wheel can be reduced. Furthermore, by making the motor output value a non-linear relationship with the detection value of the angle detection sensor, a smooth and gentle rise of the motor output value,
Also, it is possible to easily achieve the maximum value early.

Further, according to the present invention, when the derived motor output value is less than or equal to the maximum output value of the power steering motor, the control unit uses the derived motor output value as a command signal for the power steering. When it is transmitted to the motor and the derived motor output value exceeds the maximum output value of the power steering motor, it is transmitted to the power steering motor as a command signal for setting the maximum output value of the power steering motor as the motor output value. Is characterized by.

With such a configuration, if the relationship between the motor output value and the detection value of the angle detection sensor is made non-linear, the change in the detection value of the angle detection sensor has a large effect on the motor output value, and therefore the motor output value is If the maximum output value of the power steering motor is exceeded, use the maximum output value of the power steering motor as the command signal to set the motor output value.If the motor output value is less than or equal to the maximum output value of the power steering motor, set the motor output value. By transmitting the command signal to the power steering motor, the output of the power steering motor can be reliably limited to the maximum output value or less. The maximum value of the power steering motor is the maximum output value that the power steering motor can output by design, or the maximum output value of the power steering motor that is allowed in the operating state of the power steering motor.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment in which the present invention is applied to a counterbalance type forklift.
It will be described with reference to FIGS. However, FIG. 1 is a perspective view of a counterbalance type forklift, FIG. 2 is a block diagram of a control system, FIG. 3 is an operation explanatory diagram, and FIG. 4 is an operation explanatory flowchart.

The counterbalanced forklift according to this embodiment is constructed as shown in FIG. 1, for example. That is, a battery (not shown) is mounted and housed below the seat 3 provided in the driver's seat 2 of the vehicle body 1, and the traveling motor and the hydraulic motor (neither motor is shown) are powered by this battery. In response to the depression of the accelerator pedal 4, the traveling motor is driven based on an output command value from a control device (which will be described later) including a microcomputer and the vehicle body 1 travels in the forward direction or the backward direction set by operating the directional lever. To do.

Reference numeral 5 is a steering handle and 6 is a brake pedal. As shown in the block diagram of FIG. 2, an angle detection sensor (hereinafter referred to as an EP sensor) including a potentiometer or the like for detecting a rotation operation angle from the neutral position of the steering wheel 5 is provided on the rotation shaft of the steering wheel 5.
(Referred to as S sensor) 7 is attached. At this time, the EPS sensor 7 is fixed to the steering handle 5 side with a screw or the like while maintaining the output value of the EPS sensor 7 at zero while the steering handle 5 is in the neutral position without being operated. A power steering motor 25 is mounted on the vehicle body 1 and is connected to the steered wheels via a rotating mechanism for changing the direction of the steered wheels.

Further, as shown in FIG. 1, a mast 8 is telescopically attached to the front portion of the vehicle body 1, and a pair of L-shaped forks 10 are attached to the mast 8 via a lift bracket 9.
Is attached. Then, by operating the lift lever 12 provided in the driver's seat 2, the hydraulic motor is driven based on the output command value from the control device, the lift cylinder operates, and the mast 8 expands and contracts. 10 moves up and down. In addition to the lift lever 12, the driver's seat 2 is provided with a tilt lever 14,
The tilt cylinder is operated by the operation of the tilt lever 14, and the mast 8 is tilted to tilt the fork 1
0 tilts with mast 8.

Next, the configuration of the control device will be described with reference to the block diagram of FIG. As shown in FIG.
A detection signal from the sensor 7 is converted into a digital signal by an analog / digital conversion means (hereinafter referred to as A / D) 21 and taken into a CPU 22 described later.

Further, as shown in FIG. 2, the control signal from the CPU 22 is a parallel output section (hereinafter referred to as PO) 2
Is output to the power steering motor 25 via 4,
The power steering motor 25 is controlled so that the motor output value corresponds to the detection value of the EPS sensor 7, and the steered wheels are steered by the driving force of the power steering motor 25. Such control processing by the CPU 22 corresponds to the control unit in the present invention.

Further, as shown in FIG. 2, a RAM 27 is provided, in which the detection value of the EPS sensor 7 when the output value of the power steering motor 25 is set to zero is held as a reference and by the CPU 22. The CPU 2 stores the calculation data and the like temporarily in accordance with a predetermined control program stored in advance in the ROM 28.
2 controls the power steering motor 25 and the like.

The control processing of the power steering motor 25 by the CPU 22 will be described in detail below. When the steering handle 5 is rotated from the neutral state in a predetermined direction, the detection value of the EPS sensor 7 becomes larger than the intermediate value, and when the steering handle 5 is rotated from the neutral state in the direction opposite to the predetermined direction, the EPS is rotated. The value detected by the sensor 7 is smaller than the intermediate value. The intermediate value of the detection values of the EPS sensor 7 is the detection value of the EPS sensor 7 when the steering handle 5 is in the neutral state (that is, the straight traveling state of the vehicle). At this time, if the intermediate value is replaced with zero (hereinafter, this is referred to as a zero point), a value larger than the intermediate value is a positive value detected by the EPS sensor 7, and a value smaller than the intermediate value is the EPS.
The detection value of the sensor 7 can be regarded as a negative value.

The detection value of the EPS sensor 7 viewed from the zero point when the intermediate value is the zero point is (the detection value of the EPS sensor 7 viewed from the zero point = the detection value of the EPS sensor 7-the intermediate value). The dead zone N is set around this zero point. The dead zone N is the EPS sensor 7 viewed from the zero point.
If the absolute value of the detected value of is less than the predetermined boundary value, it is the range in which the motor output value becomes zero.

Further, when the absolute value of the detection value of the EPS sensor 7 seen from the zero point becomes equal to or more than a predetermined boundary value, the motor output value proportional to the square of the difference between the detection value of the EPS sensor 7 and the boundary value becomes. It is derived by calculation. The relationship between the detection value of the EPS sensor 7 and the motor output value is illustrated in the form of a square curve shown in FIG. The square curve has a shape that curves downward in FIG. 3 in a range where the detection value of the EPS sensor 7 has a positive value, and a shape that curves upward in a range that has a negative value.

Further, the square curve has a shape in which it is in contact with a straight line showing a motor output value of zero at a point where it becomes equal to the boundary value of the detection values of the EPS sensor 7, that is, at the end of the dead zone N. still,
The absolute value of the motor output value is limited to the maximum output value or less, and thus the motor output value pattern M as shown in FIG.
C is created and stored in the RAM 27.

In FIG. 3, SH represents the neutral position of the steering wheel 5, ML and MR represent the mechanical end, and E
When the detection value of the PS sensor 7 exceeds the mechanical ends ML and MR, the CPU 22 performs error processing such as forcibly setting the motor output value to zero.

Then, from the motor output value pattern MC of the RAM 27, the motor output value corresponding to the detection value of the EPS sensor 7 associated with the rotating operation of the steering wheel 5 is read out to control the output of the power steering motor 25.

Further, the CPU 22 causes the detected value of the EPS sensor 7 by the operation of the steering wheel 5 to be larger than a predetermined maximum value (when the detected value of the EPS sensor 7 is treated as a positive value) or smaller than the minimum value. When it is small (when the detection value of the EPS sensor 7 is treated as a negative value),
As an error process, the motor output value of the power steering motor 25 is set to zero to forcibly stop, or the driver seat 2
(See FIG. 1) Controls a display unit including an LCD provided to display a warning, or drives an LED or a buzzer provided in the driver's seat 2 to issue an alarm.

Next, a series of operations will be described with reference to the flow chart of FIG. 4. First, as shown in FIG. 4, initial setting is performed (S1), and the detection value of the EPS sensor 7 is fetched by the CPU 22 ( S2), the imported EP
It is determined whether or not the detection value of the S sensor 7 is equal to or greater than the intermediate value "0" (S3). If the determination is YES, the rotation direction of the steering wheel 5 is the forward rotation direction (S3).
4) If the determination result is NO, the steering wheel 5
The rotation direction of is the reverse direction (S5).

After the processing of steps S4 and S5, the process proceeds to step S6, and the absolute value of the detection value of the EPS sensor 7 is taken (S6). This is because the motor output value pattern shown in FIG. 3 is symmetric with respect to the point where the detection value of the EPS sensor 7 is zero, so that one side (forward rotation side) motor output value pattern can be created. This is necessary processing.

Then, it is judged whether or not the detection value of the EPS sensor 7 is within a preset dead zone range (here, a range corresponding to half of the dead zone N shown in FIG. 3) (S).
7) If the determination result is YES, the motor output value is set to "0" (S8), and if the determination result is NO,
A dead zone having a predetermined width is set (S9).

Subsequently, after the processing of steps S8 and S9, the process proceeds to step S10, and the CPU 22 executes the EPS.
The detection value of the sensor 7 is squared (S10) and further multiplied by a predetermined gain, and the pattern on the other side (reverse rotation side) is created symmetrically, and the left and right maximum values are set to provide power steering. A motor output value pattern MC of the motor 25 is created (S11), the motor output value pattern MC is stored in the RAM 27, and the EPS associated with the rotation operation (including the rotation direction) of the steering wheel 5 is stored from the motor output value pattern MC. The motor output value corresponding to the detection value of the sensor 7 is read, the output of the power steering motor 25 is controlled by the read motor output value (S12), and then the process returns to step S2.

As described above, since the CPU 22 makes the relationship between the motor output value and the detection value of the EPS sensor 7 non-linear, the motor output value rises smoothly and gently when the steering wheel 5 is operated slowly. As in the conventional case, hunting does not occur, and the drive of the power steering motor 25 does not start with a slight delay with respect to the steering wheel 5.

On the other hand, as in the conventional case, the motor output value is EP
The motor output value reaches its maximum faster than when it changes linearly with respect to the detection value of the S sensor 7, so that the steering handle 5 becomes lighter when the steering handle 5 is operated at high speed.

Therefore, according to the above-described embodiment, the operation feeling of the steering wheel 5 can be greatly improved as compared with the conventional one.

Since the relationship between the motor output value and the detection value of the EPS sensor 7 is made non-linear, the dead zone N (see FIG. 3).
(Refer to FIG. 4), the motor output value can be raised smoothly, and by reducing the dead zone width, the response of the steered wheels to the steering wheel 5 can be improved and the feeling is improved. You can

Furthermore, by making the relationship between the motor output value and the detection value of the EPS sensor 7 non-linear by a square curve, a smooth and gentle rise of the motor output value,
Also, it is possible to easily achieve the maximum value early.

In the above embodiment, the case where the detection value of the EPS sensor 7 is squared and the motor output value pattern MC is locked has been described.
It may be raised to a power, and in short, the rising portion of the motor output value may have a non-linear pattern that rises in a curved shape from the end of the dead zone N as shown in FIG. However, 4th power, 6th
When the exponent of power and exponentiation is set to a large value, the maximum value is reached more quickly, but the range in which the motor output value rises gradually becomes narrower, and hunting is more likely to occur as in the past. , If the exponent of power calculation such as 1/2 power or 1/3 power is set to a value less than 1, the range where the motor output value gradually rises is widened, but the reaching of the maximum value is delayed and the steering handle becomes heavy. Most preferred is the power of multiplication.

Further, in the above-described embodiment, the case where the error processing such as forcibly setting the motor output value to zero when the detection value of the EPS sensor 7 exceeds the mechanical end is described. Such error processing does not necessarily have to be performed.

In the above embodiment, the EPS sensor 7 including a potentiometer or the like is used as the angle detection sensor.
Although the case of using the
It goes without saying that the invention is not particularly limited to the one using a potentiometer as long as the rotational operation angle of the steering wheel 5 can be detected.

Further, in the above-mentioned embodiment, the case where the present invention is provided to the counterbalance type forklift has been described. However, other than the counterbalance type for which the present invention is applicable, other types such as a reach type forklift are also provided. It is needless to say that the present invention can be applied to general electric vehicles such as model forklifts and other electric vehicles, and in this case, the same effect as that of the above-described embodiment can be obtained.

The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention.

[0043]

As described above, according to the first aspect of the present invention, since the relationship between the motor output value and the detection value of the angle detection sensor is made non-linear, the motor output can be reduced when the steering wheel is slowly operated. Since the value rises smoothly, hunting does not occur as in the conventional case, and the drive of the power steering motor does not start with a slight delay relative to the steering wheel. On the other hand, as compared with the conventional case where the motor output value changes linearly with respect to the detection value of the angle detection sensor, the motor output value reaches the maximum quickly, so when operating the steering handle at high speed, The handle can be operated lightly.

Furthermore, the gradual rise and relatively steep rise of the motor output value relative to the detection value of the angle detection sensor do not change stepwise but continuously change, so the driver feels uncomfortable during operation. Without feeling
You can operate the steering wheel smoothly.

Therefore, it is possible to provide an electric power steering apparatus capable of significantly improving the operation feeling of the steering handle as compared with the conventional one.

According to the second aspect of the invention, since the motor output value has a non-linear relationship with the detection value of the angle detection sensor, the so-called dead zone width for making the motor output value zero can be reduced. The motor output value can be smoothly raised, and the dead band width can be reduced to reduce the operability of the steering wheel. Furthermore, by making the motor output value non-linear with the detection value of the angle detection sensor, it is possible to easily achieve a smooth and gradual rise of the motor output value and to reach the maximum value early. Become.

According to the third aspect of the invention, the output of the power steering motor can be surely limited to the maximum output value or less, and the failure of the power steering motor can be prevented.

[Brief description of drawings]

FIG. 1 is a perspective view of a counterbalanced forklift according to an embodiment of the present invention.

FIG. 2 is a block diagram of a control system in an embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of the embodiment of the present invention.

FIG. 4 is a flowchart for explaining the operation of the embodiment of the present invention.

FIG. 5 is an operation explanatory diagram of a conventional example.

[Explanation of symbols]

5 steering wheel 7 EPS sensor (angle detection sensor) 22 CPU (control unit) 25 power steering motor MC motor output value pattern

Claims (3)

[Claims] 1. An angle detection sensor for detecting a rotational operation angle from a neutral position of a steering wheel, and a power steering motor arranged so as to supply a steering torque to steered wheels. In an electric power steering device that controls the power steering motor so that a motor output value corresponding to a value is obtained, a predetermined calculation is performed using a detection value of the angle detection sensor and a non-linear relationship with the detection value of the angle detection sensor. The electric power steering control device further comprises: a control unit that derives the motor output value that is defined as follows and controls the power steering motor based on the derived motor output value. 2. The control unit sets the motor output value to zero when the detection value of the angle detection sensor is within a predetermined numerical range, and the detection value of the angle detection sensor is not within the predetermined numerical range. In this case, the electric power steering control device according to claim 1, wherein the detected value of the angle detection sensor is subjected to a predetermined power calculation and is multiplied by a predetermined gain to derive the motor output value. 3. The control unit, when the derived motor output value is less than or equal to the maximum output value of the power steering motor, transmits the derived motor output value as a command signal to the power steering motor and derives it. When the motor output value exceeds the maximum output value of the power steering motor, it is transmitted to the power steering motor as a command signal for setting the maximum output value of the power steering motor as the motor output value. Alternatively, the control device for the electric power steering according to the item 2.