JP3904426B2 - Electric power steering control device - Google Patents

Description

[0001]
BACKGROUND 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]
[Prior art]
2. Description of the Related Art Conventionally, an electric power steering control device mounted on a battery forklift or the like is capable of supplying steering torque to an EPS sensor including a potentiometer that detects a rotational operation angle from a neutral position of a steering wheel and a steering wheel. Some include a power steering motor arranged and a control unit that controls the power steering motor so as to obtain a motor output value corresponding to a detection value of the EPS sensor.
[0003]
In such an electric power steering control device, alignment is performed so that the detected value of the EPS sensor becomes zero when the steering handle is in the neutral position. Specifically, the potentiometer is fixed to the steering handle side with a screw or the like while the detected value of the EPS sensor is maintained at zero in a state where the steering handle is in a neutral position without being operated. Subtle alignment is performed by interposing.
[0004]
Then, as shown in FIG. 8, a dead band N having a predetermined width that is a predetermined numerical range centering on the detected value zero of the EPS sensor is provided, and if the detected value of the EPS sensor is within the predetermined numerical range, the motor output value Is zero. If the detected value of the EPS sensor is not within the dead zone N, the motor output value is derived by multiplying the detected value of the EPS sensor by a predetermined gain. Thus, the motor output value pattern MC is created and held in a memory or the like, and the motor output value corresponding to the detected value of the EPS sensor accompanying the rotation operation of the steering wheel is read out to control the output of the power steering motor. ing. Here, the dead zone N is a numerical range of the detected value of the EPS sensor in which the motor output value is zero with respect to the detected value of the EPS sensor. In FIG. 8, SH indicates a neutral position of the steering wheel, and ML and MR indicate mechanical ends.
[0005]
[Problems to be solved by the invention]
However, in the conventional case, as shown in FIG. 8, since the width of the dead zone N is fixed to a constant value, there are the following problems.
[0006]
That is, when the dead zone width is too large, even when the steering wheel is swung due to the unevenness of the road surface when traveling on an uneven road surface, the detected value of the EPS sensor does not have an effect. On the other hand, there is a disadvantage that the position of the steering wheel and the steering wheel becomes large and the operability is deteriorated, and that the steering wheel feels heavy when the steering wheel is operated due to the relationship between the detected value of the EPS sensor and the motor output value. In particular, for cargo handling vehicles such as forklifts, it is necessary to load and unload luggage with the vehicle facing properly.Therefore, when loading and unloading luggage, the steering handle is manipulated or switched. Sometimes. Therefore, the positional deviation between the steering wheel and the steering wheel and the weight when operating the steering wheel are extremely serious problems.
[0007]
On the other hand, when the dead zone width is too small, there is an advantage that the positional deviation between the steering wheel and the steering wheel is small and the operability is good. On the other hand, when driving on a rough road surface, the influence of the road surface unevenness When the steering wheel is swung due to this, the influence appears in the detected value of the EPS sensor, and the driver is steered even when the steering wheel is not operated. In particular, a cargo handling vehicle such as a forklift sometimes travels in a relatively narrow place such as a passage in a warehouse, so if the vehicle is steered without operating the steering handle, There is a risk of accidents coming into contact with the surrounding shelves.
[0008]
Therefore, the present invention can reduce the operability of the steering wheel during operation of the steering handle, and can realize a stable running without the steering handle being steered even when the vehicle is running when the steering handle is not operated. The purpose is to provide.
[0009]
[Means for Solving the Problems]
In order to achieve the above-described object, the present invention includes an angle detection sensor that detects a rotation operation angle from a neutral position of a steering wheel, and a power steering motor that is arranged so as to supply steering torque to a steered wheel. An electric power steering apparatus that controls the power steering motor so as to obtain a motor output value corresponding to a detection value of the angle detection sensor; and a determination unit that determines whether or not the steering handle is in a non-operating state; When the detection value of the angle detection sensor is within a predetermined numerical range, a dead zone is set in which the motor output value is zero, and when the determination unit determines that the steering handle is in a non-operating state, the numerical value If the range is increased to widen the dead zone and the steering wheel is in the operating state It is characterized in that a control unit for controlling so as to narrow the width of the dead zone by reducing the value range is when it is disconnected.
[0010]
According to such a configuration, the dead zone width of the motor output value is changed small by the control unit during operation of the steering handle, and the dead zone width of the motor output value is changed greatly by the control unit when the steering handle is not operated. The
[0011]
Therefore, by reducing the dead zone width, the positional deviation between the steering wheel and the steering wheel is reduced, and the operability of the steering wheel can be reduced during the steering wheel operation.
[0012]
On the other hand, by increasing the dead zone width, it is possible to prevent the detected value of the angle detection sensor from appearing even if the steering wheel swings due to the unevenness of the road surface when traveling on a rough road surface. When the steering wheel is not operated, even if the vehicle travels on a rough road surface, the steering handle is not arbitrarily steered and stable traveling can be realized.
[0013]
In the present invention, the determination unit includes a timer that counts a predetermined time, and a state in which the detection value of the angle detection sensor is within the numerical range continues for the predetermined time counted by the timer. Further, it is characterized in that it is determined that the steering handle is not operated.
[0014]
According to such a configuration, the operating state and non-operating state of the steering wheel can be reliably determined, the dead band width can be prevented from frequently switching between large and small, and the dead band width can be controlled by operating or not operating the steering wheel. It can be accurately changed according to.
[0015]
Further, the present invention is characterized in that the control unit controls the power steering motor to apply an electric brake to the power steering motor when the width of the dead zone is greatly changed.
[0016]
According to such a configuration, since the electric brake is applied to the power steering motor when the steering handle is not operated, it is possible to suppress the influence of the steering wheel from the road surface when driving on a rough road surface, and stable driving It can be performed.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment in which the present invention is applied to a counterbalance forklift will be described with reference to FIGS. However, FIG. 1 is a perspective view of a counterbalance forklift, FIG. 2 is a block diagram of a control system, FIG. 3 is a partial connection diagram, FIGS. 4 and 5 are operation explanatory diagrams, and FIG. .
[0018]
The counterbalance forklift in this embodiment is configured as shown in FIG. 1, for example. That is, a battery (not shown) is mounted and accommodated below the seat 3 provided in the driver's seat 2 of the vehicle body 1, and a power is supplied to a travel motor and a hydraulic motor (not shown) by this battery. In response to the depression of the accelerator pedal 4, the travel motor is driven based on an output command value from a control device, which will be described later, such as a microcomputer, and the vehicle body 1 travels in the forward or backward direction set by the operation of the directional lever. To do.
[0019]
Incidentally, 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 EPS sensor) comprising a potentiometer or the like for detecting the rotational operation angle from the neutral position of the steering handle 5 is provided on the rotating shaft of the steering handle 5. 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 the detected value of the EPS sensor 7 is maintained at zero while the steering handle 5 is in a neutral position without being operated. In addition, a power steering motor 25 is mounted on the vehicle body 1 and is connected to the steering wheel via a rotation mechanism for changing the direction of the steering wheel.
[0020]
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. 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 is actuated, the mast 8 is expanded and contracted, and the fork is expanded and contracted. 10 goes 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 14 is operated by the operation of the tilt lever 14, the mast 8 is tilted, and the fork 10 is moved together with the mast 8. Tilt.
[0021]
Next, the configuration of the control device will be described with reference to the block diagram of FIG. As shown in FIG. 2, the detection signal from the EPS 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 in detail later.
[0022]
Further, as shown in FIG. 2, a control signal from the CPU 22 is output to a power steering motor 25 including a permanent magnet motor and a drive circuit to be described later via a parallel output unit (hereinafter referred to as PO) 24. The power steering motor 25 is controlled to a motor output value corresponding to the detection value of the sensor 7, and the steering wheel is steered by the driving force of the power steering motor 25.
[0023]
At this time, the power steering motor 25 is provided with a drive circuit DR including four FETs T1, T2, T3, and T4 as shown in FIG. 3, and from the PO24 to the gates of the FETs T1, T2, T3, and T4. In response to the output control signal, the FETs T1 and T4 are turned on, and the current from the battery B is passed through the power steering motor 25, the power steering motor 25 is rotated forward, and the FETs T3 and T2 are turned on to turn on the power steering motor 25. The current from the battery B is passed, and the power steering motor 25 rotates in the reverse direction. When the turning mechanism is driven by the power steering motor 25 so as to swing or slide in a direction corresponding to the rotation direction of the power steering motor 25, the steering wheel is turned by the operation of the turning mechanism. Thus, so-called steering is performed in which the direction of the steering wheel is changed.
[0024]
Further, as shown in FIG. 2, a RAM 27 is provided. In this RAM 27, the position of the steering wheel 5 when the detected value of the EPS sensor 7 becomes zero is held as a reference point, and calculation data by the CPU 22 is also stored. The CPU 22 controls the power steering motor 25 and the like according to a predetermined control program that is temporarily stored and held and stored in the ROM 28 in advance.
[0025]
By the way, the control processing of the power steering motor 25 by the CPU 22 will be described in detail. The CPU 22 sets a dead band having a predetermined width around the position of the steering handle 5 when the detected value of the EPS sensor 7 becomes zero as the motor output value. Then, the detection value of the EPS sensor 7 is multiplied by a predetermined gain, and a predetermined maximum value is set, for example, to create a motor output value pattern MC as shown in FIG. At this time, the absolute value of the motor output value is limited to the maximum output value or less, and the motor output value pattern MC thus created is stored in the RAM 27. In FIG. 4, SH represents the neutral position of the steering wheel 5, and ML and MR represent the mechanical ends. When the detected value of the EPS sensor 7 exceeds the mechanical ends ML and MR, the CPU 22 forces the motor output value. Error handling such as zeroing automatically.
[0026]
Then, the motor output value corresponding to the detected value of the EPS sensor 7 accompanying the rotation operation of the steering handle 5 is read from the motor output value pattern MC of the RAM 27 and the output control of the power steering motor 25 is performed.
[0027]
Further, the CPU 22 determines whether or not the steering handle 5 is in a non-operating state, determines that the steering handle 5 is not in operation, and increases the dead zone width while the non-operation of the steering handle 5 continues, as shown in FIG. The dead zone N1 having a large width as shown (for example, ± 5 ° in terms of the rotation operation angle of the steering wheel 5) is changed. On the other hand, if the CPU 22 determines that there is an operation of the steering handle 5 after changing to the wide dead zone N1, the dead zone width is reduced as shown in FIG. 5 while the operation of the steering handle 5 continues. The dead zone N2 having a small width (for example, ± 1 ° in terms of the rotational operation angle of the steering handle 5) is changed. Such a process of determining whether or not the steering wheel 5 is operated by the CPU 22 corresponds to a determination unit, and a dead zone setting process and a width change process thereof correspond to a control unit.
[0028]
At this time, the CPU 22 counts a predetermined t time (for example, t = 100 ms) by a built-in timer, and when the detected value of the EPS sensor 7 remains within a specified range near t time (100 ms), It is determined that the steering handle 5 is not operated. As the specified range, as described later in detail, it is preferable that the specified range is within the range of the dead zone set last time.
[0029]
Further, the CPU 22 determines that the steering handle 5 is not operated and sets a large dead zone N1, for example, from the PO 24 to the FETs T2, T4 of the driver circuit DR so as to apply the electric brake to the power steering motor 25. A control signal is output to the gate (see FIG. 3) to turn on both FETs T2 and T4.
[0030]
Further, the CPU 22 detects that the detected value of the EPS sensor 7 by operating the steering handle 5 is 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 (EPS). When the detection value of the 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 an LCD provided in the driver's seat 2 (see FIG. 1). The display unit comprising the above is controlled to display a warning, or an LED or a buzzer provided in the driver's seat 2 is driven to issue a warning.
[0031]
Next, a series of operations will be described with reference to the flowchart of FIG. 6. As shown in FIG. 6, initial setting is first performed (S 1), and the detected value of the EPS sensor 7 is captured by the CPU 22 (S 2). A determination is made as to whether or not the detected value of the captured EPS sensor 7 is equal to or greater than “0”, which is an intermediate value (S3). If this determination is YES, the rotation direction of the steering wheel 5 is the forward rotation direction (S4). If the determination result is NO, the rotation direction of the steering handle 5 is set to the reverse direction (S5).
[0032]
Then, after the processes of steps S4 and S5, the process proceeds to step S6, and the absolute value of the output of the EPS sensor 7 is taken (S6). This is because the motor output value pattern MC shown in FIG. 4 or FIG. 5 is symmetric with respect to the point where the detected value of the EPS sensor 7 is zero, and therefore the motor output value pattern on one side (forward rotation side) is This process is necessary to create.
[0033]
Thereafter, it is determined whether or not the detected value of the EPS sensor 7 is within the previously set dead zone (here, a range corresponding to half of the dead zones N1 and N2 shown in FIG. 4 or FIG. 5) (S7). If this determination result is NO, it can be determined that the steering wheel 5 is being operated, so the count value of the built-in timer of the CPU 22 is cleared (S8), and a small dead zone N2 (see FIG. 5) is set (see FIG. 5). S9), the electric brake of the power steering motor 25 by the driver circuit DR (see FIG. 3) is turned off (S10).
[0034]
On the other hand, if the determination result in step S7 is YES, it is determined whether the elapsed time is within t time (100 ms) (S11). If the determination result is YES, the built-in timer of the CPU 22 counts up. (S12) If the determination result is NO, it can be determined that the steering wheel 5 is not being operated. Therefore, after the large dead zone N1 (see FIG. 4) is set (S13), the driver circuit DR ( The electric brake of the power steering motor 25 according to FIG. 3 is turned on (S14).
[0035]
Subsequently, after passing through the processing of steps S10, S12, and S14 described above, the process proceeds to step S15, where the detected value of the EPS sensor 7 is within the range of the dead zone N1 or N2 set previously (in this case, the dead zones N1 and N2). (S15). If the determination result is YES, the motor output value is set to “0” (S16). If the determination result is NO, the dead zone is detected. Settings are made (S17).
[0036]
Thereafter, after the processing of steps S16 and S17, the process proceeds to step S18, where the CPU 22 multiplies the detection value of the EPS sensor 7 by a predetermined gain, and the other side (reverse side) pattern is symmetrical. The motor output value pattern MC of the power steering motor 25 is generated (S18), and this motor output value pattern MC is stored in the RAM 27. From this motor output value pattern MC, the rotation operation (the rotation direction is also changed). After the motor output value corresponding to the detected value of the EPS sensor 7 is read and the power steering motor 25 is output-controlled with the read motor output value (S19), the process returns to step S2.
[0037]
As described above, the dead zone width of the motor output value is changed by the CPU 22 while the steering handle 5 is operated, and the dead zone width of the motor output value is changed by the CPU 22 when the steering handle 5 is not operated.
[0038]
Therefore, according to the above-described embodiment, the position gap between the steering handle 5 and the steering wheel is reduced by reducing the dead zone width, and the operability of the handle can be lightened during the operation of the steering handle 5.
[0039]
On the other hand, by increasing the dead zone width, it is possible to prevent the detected value of the EPS sensor 7 from appearing even if the steering wheel shakes due to the unevenness of the road surface when traveling on a road surface with many unevennesses. When the steering wheel 5 is not operated, even if the vehicle travels on a road surface with many irregularities, the steering handle 5 does not change and stable traveling can be realized.
[0040]
Further, when the detected value of the EPS sensor 7 remains within the predetermined dead time t (100 ms) dead zone, it is determined that the steering handle 5 is not operated. The operating state can be reliably determined, the dead band width can be prevented from frequently switching between large and small, and the dead band width can be accurately changed according to whether the steering handle 5 is operated or not.
[0041]
In addition, since the electric brake is applied to the power steering motor 25 when the steering handle 5 is not operated, the influence of the steered wheels from the road surface when driving on a rough road surface can be suppressed, and stable driving can be performed. it can.
[0042]
In the above-described embodiment, as illustrated in FIGS. 4 and 5, the case where the relationship between the motor output value and the detection value of the EPS sensor 7 is linearly changed has been described. However, as illustrated in FIG. 7. In addition, even if the detected value of the EPS sensor 7 is squared so that the relationship between the detected value of the EPS sensor 7 and the motor output value becomes non-linear, the present invention can be implemented in the same manner as described above. An effect equivalent to that of the embodiment can be obtained.
[0043]
Furthermore, in the above-described embodiment, the case where the electric brake is applied by switching the current flow state to the permanent magnet motor by the drive circuit DR has been described. However, the electric brake separately from the power steering motor 25 is described. A device may be provided, and the electric steering device 25 may be operated to brake the power steering motor 25 when the steering wheel has not been operated for a predetermined time.
[0044]
In the above-described embodiment, when the EPS sensor 7 exceeds the predetermined maximum value or falls below the minimum value, a case where error processing such as forcing the motor output value to zero is performed is described. However, such error processing is not necessarily performed.
[0045]
Furthermore, in the above-described embodiment, the case where the electric brake is turned on to the power steering motor 25 when the non-operating state of the steering handle 5 continues for t time and the wide dead zone N1 is set has been described. This electric brake does not necessarily have to be turned on.
[0046]
In the above-described embodiment, the case where the EPS sensor 7 including a potentiometer or the like is used as the angle detection sensor has been described. However, the angle detection sensor is particularly potentiometer as long as it can detect the rotation operation angle of the steering handle 5. It goes without saying that the present invention is not limited to those used.
[0047]
Furthermore, in the above-described embodiment, the case where the present invention is provided to the counterbalance type forklift has been described. However, in addition to the counterbalance type to which the present invention can be applied, other types of forklifts including a reach type forklift can be used. Needless to say, the present invention can also be applied to other electric vehicles such as electric vehicles, and in this case, the same effect as that of the above-described embodiment can be obtained.
[0048]
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.
[0049]
【The invention's effect】
As described above, according to the first aspect of the present invention, the position shift between the steering wheel and the steering wheel can be reduced by reducing the dead zone width, and the operability of the steering wheel can be reduced during operation of the steering wheel. It becomes possible. On the other hand, by increasing the dead zone width, it is possible to prevent the detected value of the angle detection sensor from appearing even if the steering wheel swings due to the unevenness of the road surface when traveling on a rough road surface. When the steering wheel is not operated, the steering handle does not change even when the vehicle travels on a rough road surface, and stable traveling can be realized.
[0050]
According to the first aspect of the present invention, the operating state and non-operating state of the steering handle can be reliably determined, the dead band width can be prevented from frequently switching between large and small, and the dead band width can be reduced to the steering handle. It becomes possible to change it appropriately according to the operation or non-operation.
[0051]
According to the first aspect of the present invention, since the electric brake is applied to the power steering motor when the steering handle is not operated, it is possible to suppress the influence of the steering wheel from the road surface when traveling on a rough road surface. Can be performed stably.
[Brief description of the drawings]
FIG. 1 is a perspective view of a counterbalance forklift according to an embodiment of the present invention.
FIG. 2 is a block diagram of a control system in one embodiment of the present invention.
FIG. 3 is a partial connection diagram of an embodiment of the present invention.
FIG. 4 is an operation explanatory diagram of one embodiment of the present invention.
FIG. 5 is an operation explanatory diagram of one embodiment of the present invention.
FIG. 6 is a flowchart for explaining the operation of the embodiment of the present invention.
FIG. 7 is an operation explanatory diagram of another embodiment of the present invention.
FIG. 8 is an operation explanatory diagram of a conventional example.
[Explanation of symbols]
5 Steering handle 7 EPS sensor (angle detection sensor)
22 CPU (determination unit, control unit)
25 Power steering motor N1, N2 Dead band MC Motor output value pattern

Claims (1)

A motor that includes an angle detection sensor that detects a rotation operation angle from a neutral position of a steering handle, and a power steering motor that is arranged so as to supply a steering torque to a steered wheel, according to a detection value of the angle detection sensor In the electric power steering apparatus that controls the power steering motor to be an output value, a determination unit that determines whether or not the steering handle is in a non-operation state, and a detection value of the angle detection sensor is within a predetermined numerical range In some cases, a dead zone in which the motor output value is zero is set, and when the steering unit determines that the steering handle is in a non-operating state, the numerical range is increased to set a wide dead zone N1. When it is determined that the steering wheel is in an operating state, the numerical range is Fence and a control unit for controlling so as to set a small dead zone N2 width than the dead zone N1, also the determination unit includes a timer for counting a predetermined time, the detection value of the angle detection sensor When the state within the numerical value range continues for the predetermined time counted by the timer, the steering handle is determined not to be operated, and the control unit further sets the wide dead band N1. An electric power steering control device for controlling the power steering motor to apply an electric brake to the power steering motor when set .

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