JP2686516B2 - Electric vehicle speed control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device for an electric vehicle, and more particularly to a speed control device suitable for speed control of a wheelchair or the like having a maximum speed limit. [Prior Art] Among electric vehicles, for example, an electric wheelchair has a maximum speed set by law. Therefore, a certain torque value of the driving motor, for example, the maximum speed is determined by suppressing the number of rotations in the driving torque on a flat road within a certain range, or the number of rotations of the driving motor is detected by a sensor means, Means such as closed loop control by feeding back this is performed. [Problems to be Solved by the Invention] However, in the former method, it is practically difficult to suppress variations in the rotation of the motor, particularly when the load is light, and it is difficult to control within the legally regulated speed. Or, there is no choice but to take a method of shifting the target speed to the low speed side with a margin. This is not preferable in terms of cost and performance. Further, in the latter method, it is easy to control the rotation of the motor, but a unique problem occurs due to the closed loop control. That is, since speed control is required over almost the entire area, hunting and rattling occur particularly at low speeds, which is not desirable in terms of traveling feeling. In addition to these, there is also a method in which the motor rotation range is set to a high value in advance and speed control is performed by PWM (pulse width modulation), but since the duty ratio does not reach 100%, the capacity of the control device is increased. There are inconveniences such as the necessity and not being able to make full use of the motor performance. [Object of the invention] The object of the present invention is made in view of the above points,
An object of the present invention is to provide a speed control device for an electric vehicle that can improve the feeling during low-speed traveling and can effectively utilize the motor performance. [Means for Solving Problems] Therefore, in the present invention, a drive instruction amount adjusting means for adjusting and outputting the level so that the maximum operation amount of the accelerator operated by the user corresponds to a preset maximum speed. When,
Current detection means for detecting the drive current of the motor, detection value output means for outputting the value of the detected drive current in the case of a predetermined high load, and the value of the drive current based on the output of this means According to the above, the triangular wave output means for changing and outputting the level of the triangular wave so as to increase the drive current, and the modulating means for modulating the triangular wave output from this means by the output of the drive instruction amount adjusting means to obtain the pulse width modulation output. It is equipped with and. [Operation] In the present invention, first, the level of the triangular wave required for the PWM control is changed according to the load application state to the motor. At high load, the level of the triangular wave is changed to the lower one, so the duty ratio can be 100%. However, at the time of a predetermined low load, control is performed so that the above level change of the triangular wave is not performed. [Embodiment] An embodiment of the present invention will be described below with reference to the accompanying drawings. First, the basic configuration of the embodiment will be described with reference to FIG. In FIG. 1, an accelerator 100 operated by a user of an electric wheelchair (not shown) is a drive instruction amount adjusting means 1
It is connected to the input side of 02. The drive instruction amount adjusting means 102 adjusts the level so as to output the instruction amount so that the maximum operation amount of the accelerator 100 corresponds to a preset maximum speed. Connected to the side. A motor 108 is connected to the output side of the modulation means 104 via a driving means 106. The drive current or load current of the motor 108 is detected by the drive current detection means 110,
The detection result is input to the detection value output means 112. This detection value means 112, the value of the detected drive current,
This is output except for the case of a predetermined low load. Its output side is connected to the input side of the triangular wave output means 114. The triangular wave output means 114 changes and outputs the level of the triangular wave based on the S output of the detection value output means 112. Next, the output side of the triangular wave output means 114 is connected to the input side of the modulation means 104 described above. This modulation means 104
Has a function of modulating the triangular wave output from the triangular wave output means 114 by the output of the drive instruction amount adjusting means 102 and outputting a pulse width modulation signal. Next, the operation of the above-described basic configuration will be described. First, basically, the modulation means 104 according to the operation of the accelerator 100.
Thus, the PWM signal is input to the driving means 106, and the speed control of the motor 108 is performed. Here, when the load is high, the triangular wave output means 114 changes the triangular wave level according to the degree of the drive current, and speed control is performed so that the duty becomes 100%. However, in the case of a predetermined low load, the level of the triangular wave is not changed, and the original triangular wave of the highest level is output from the triangular wave output means 114 to the modulation means 104. Next, an embodiment of the present invention will be described with reference to the block diagram of FIG. 2 and the time chart of FIG. In FIG. An operating voltage Vcc is applied to one end of a variable resistor 10 that is joined to a joystick lever (not shown) operated by a user of an electric wheelchair for driving, and the resistance value changes according to the driving amount of the lever. Vcc / 2 is applied to the neutral point. The other end is grounded. That is, Vcc / 2 is output when the lever is in the neutral state, and a voltage higher than that is output when the lever is moving forward, and a lower voltage is output when the lever is moving backward as a drive command signal from the variable resistor 10. It is like this. To the output side of the variable resistor 10, capacitors 12 and 14 are connected to the operating voltage side and the ground side via a resistor 16, respectively, and further, the input side of an absolute value amplifier 18 is connected. Vcc / 2 is also applied to the absolute value amplifier 18, and the input signal is amplified with reference to this. More specifically, when the electric wheelchair is in a stopped state, the output of the variable resistor 10 is Vcc / 2, which is the absolute value amplifier 18
Will be entered. Therefore, its output is "0". Next, when the electric wheelchair moves forward, Vvo1> (Vcc /
Since the voltage of 2) is output from the variable resistor 10, the output of the absolute value amplifier 18 becomes a voltage of positive corresponding magnitude. In the case of reverse travel, the voltage of Vvo1 <(Vcc / 2) is output from the variable resistor 10, so the absolute value amplifier 18
The output of is a negative corresponding magnitude voltage. These voltages are input to the variable resistor 20 from the absolute value amplifier 18, whereby the level is adjusted. That is, the output of the variable resistor 20 is maximum, and
The level is set so that the rotation of the motor becomes the duty ratio of the PWM that is the maximum value of the legal regulation when the current is supplied to the motor at the time of traveling on a flat road. The output side of the variable resistor 20 is connected to the plus input side of the comparator 22. Next, the triangular wave for performing the above-mentioned PWM control is supplied by the triangular wave generation circuit 24. The triangular wave generating circuit 24 is mainly composed of operational amplifiers 26 and 28, and the output of the operational amplifier 26 is shown in FIG.
It is a square wave as shown in, which is a resistor 30 and a capacitor.
When it passes through the filter constituted by 32 and 32, it becomes a triangular wave as shown in FIG. This is output as shown in FIG. 7C via the operational amplifier 28 which functions as a buffer. The triangular wave obtained as described above is input to the plus side of the operational amplifier 38 via the series resistor 34 and the parallel resistor 36, respectively. The output side of the comparator 22 is the motor drive means 40.
Connected to the input side of this motor drive means 40
The means side is connected to a motor 42 for driving an electric vehicle. A part of the drive current supplied from the motor drive means 40 to the drive motor 42 flows in the shunt flow path 44, and a voltage proportional to the magnitude of the part of the current flows through the capacitor 46. It is input to the positive input side of the operational amplifier 50 by the resistor 48 connected to the ground. The negative input side of the operational amplifier 50 is connected to a resistor 52 and an adjustment variable resistor 54, respectively, and a voltage proportional to the drive current of the drive motor 42 is output from the operational amplifier 50. This output is then fed to Zener diode 56 and resistor 58.
After the low-level cut output is adjusted via the parallel circuit of, the signal is input to the negative input side of the operational amplifier 38 via the resistor 60. The operational amplifier 38 has a function of controlling the level of the triangular wave, which is the positive side input, in accordance with the negative side input, and the level-controlled output is output to the negative input side of the comparator 22 described above. It has become. Further, the output side of the operational amplifier 50 described above is an operational amplifier.
This operational amplifier is connected to the minus input side of 62.
The reference voltage adjusted by the variable resistor 64 is input to the positive input side of 62, and the output side of the operational amplifier 62 is
Comparator 22 with operating voltage Vcc applied via resistor 66
Is connected to the output side. Here, the output of the variable resistor 10 described above is output to a signal processing circuit (not shown) for the motor drive means 40, etc., and the output of the triangular wave generation circuit 24 is output to the signal processing device 68 on one side. It is like this. That is, the drive motors are provided corresponding to the left and right wheels, respectively, and the signal processing devices of FIG. 2 are also provided correspondingly. Next, the operation of the above embodiment will be described with reference to the time chart in FIG. In the following description, as shown in FIG.
Output, that is, the drive current of the drive motor 42 has changed. That is, the electric wheelchair travels on a climbing road from a flat road and then travels on a flat road again. Assuming that the Zener voltage Vz of the Zener diode 56 is at the level shown in (H) in the figure, the negative input _VA of the operational amplifier 38 becomes as shown in (I) in the figure. Note that the scales of the vertical axes in FIGS. 11 (H) and 11 (I) are not the same. Further, in FIG. 1 (I), the shaded portion is a leakage of the resistor 58 connected in parallel with the Zener diode 56. When such an adjustment voltage V _A is input to the operational amplifier 38, the level of the input triangular wave V _B changes as described above. The changes in the output of the operational amplifier 38 are shown in (D) and (E) of the same figure. The case where the adjustment voltage V _{A is} almost “0” is shown in (D), and the adjustment voltage V _A is maximum. Are shown in (E). The reason for performing such output adjustment is to change the maximum applied voltage to the drive motor 42 when the drive current is small by not changing the duty ratio in PWM control at low drive current, that is, when traveling at light load. This is to reduce Therefore, during normal driving on a flat road, the output of the operational amplifier 50 is the Zener diode 56 because the driving voltage is small.
Becomes less than the Zener voltage V _{Z of,} and the level of the triangular wave V _B hardly changes. Since the triangular wave V _{B of} this figure (D) is input to the comparator 22, the output of the comparator 22 is the variable resistor 10 linked with the accelerator.
PWM control will be performed within the maximum fluctuation range of the output voltage. That is, during normal traveling such as on a flat road, drive control of the electric wheelchair is performed at an arbitrary speed possible. For example, if the maximum value V _VRmax of the output V _VR of the absolute value amplifier 18 is output to the comparator 22 (see (D) in the same figure), the output becomes as shown in (F) in the same figure. In addition, in order to make the rotation of the drive motor 42 corresponding to the PWM duty ratio in this case the maximum value of the legal regulation,
The level is being adjusted by. Next, when the vehicle is traveling on a climbing road, the load on the drive motor 42 is gradually amplified, and the output of the operational amplifier 50 is also gradually amplified as shown in FIG. Then, when this voltage approaches the Zener voltage V _Z , the adjustment voltage V _A begins to be output (see (I) in the same figure), and at the maximum value, the operational amplifier
The output of 38 is as shown in FIG. On the other hand, the output V _VR of the absolute value amplifier 18 changes from 0 to V _VRmax as in the case of the flat road described above. For this reason,
The output of the comparator 22 near V _VRmax is (see (E) in the figure),
It is in a state of full conduction (see (G) in the figure). That is, in the medium and high load range, the maximum duty ratio is 10
The control is performed so as to be 0%, and the utilization efficiency of the drive motor 42 is improved. Note that the adjustment voltage V _A takes the maximum value at the maximum current value initially set by the variable resistor 64. Further, in the case of PWM control in which the drive motor 42 cannot be fully opened, the motor drive means 40 needs a maximum current to compensate for the maximum duty difference in order to generate the same maximum torque. As described above, this embodiment has the following effects. . Since the method of controlling the rotation by detecting and feeding back the rotation speed of the motor is not used, the detecting means for the rotation speed is not required. Further, even when the stop timing or the like is detected by rotation detection, the accuracy of the detector is not required to be as high as the speed control. . By adjusting the voltage by the Zener diode 56, the duty control by positive feedback of the drive current is not performed in the low load range, so that the traveling is stable and the riding comfort is improved. . 100% switching duty if required
Therefore, the maximum drive power is output. The present invention is not limited to the above embodiment, and various design changes can be made so as to achieve the same operation. In addition, although the present invention is applied to the electric wheelchair in the above embodiment, the present invention is also applied to other electric vehicles. [Effects of the Invention] As described above, according to the present invention, there is an effect that the device performance can be effectively utilized and a good traveling feeling can be obtained with a simple circuit configuration.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the basic structure of an embodiment of the present invention, FIG. 2 is a circuit diagram showing the circuit structure of the embodiment, and FIG. 3 is a time chart showing the operation of the embodiment. It is a chart. 100 ... accelerator, 102 ... drive instruction amount adjusting means, 104 ...
… Modulation means, 106 …… Driving means, 108 …… Motor, 110…
... Drive current detection means 112 ... detection value output means 114 ...
Triangular wave output means.

Claims (1)

(57) [Claims] In a speed control device for an electric vehicle that controls a speed of a motor by a pulse width modulation method based on a drive instruction amount instructed by a user's accelerator operation, the maximum operation amount of the accelerator corresponds to a preset maximum speed. As described above, the drive instruction amount adjusting means for adjusting and outputting the level, the current detecting means for detecting the drive current of the motor, and the value of the detected drive current are output in the case of a predetermined high load. Detecting value output means, a triangular wave output means for changing and outputting the level of the triangular wave so as to increase the drive current according to the value of the drive current based on the output of this means, and the triangular wave output from this means. And a modulator that obtains a pulse width modulated output by modulating the output of the drive instruction amount adjuster.