JP2000134971A - Control method of electric wheelchair - Google Patents

Abstract

(57) [Abstract] [Problem] In an electric wheelchair used when people who have difficulty walking due to injury, illness, aging, etc. move,
It is an object of the present invention to provide an energy-efficient electric wheelchair while ensuring smooth startability. SOLUTION: Smooth starting is performed by performing complementary PWM control (second control mode) at a low speed at the time of starting and switching to normal PWM control (first control mode) at a predetermined speed or more to operate. The result is an electric wheelchair that has both high efficiency and high energy efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for an electric wheelchair used when a person who has difficulty walking due to injury, illness, aging, etc. moves.

[0002]

2. Description of the Related Art Conventionally, an electric wheelchair used for people who have difficulty walking is supposed to be used indoors by a driver without physical strength or indoors. Required.

[0003] When ordinary PWM control is performed on a DC motor that rotates the driving wheels of such an electric wheelchair,
When a low speed command is issued from the stop state, the pulse signal becomes extremely narrow. On the other hand, in the amplifier for amplifying the pulse signal, a parasitic capacitance is generated in the switching element as shown in FIG. 8A, and a parasitic transmission as shown in FIG. 8B occurs as it is. . In order to prevent such parasitic oscillation, it is usual to provide a CR circuit as shown in FIG. 9A, and as a result, a narrow pulse signal as shown in FIG. It is greatly attenuated by the CR circuit,
In extreme cases, it will be absorbed and not appear as output. Therefore, as shown in FIG. 10, the output of the amplifier does not provide sufficient output until the speed command reaches a certain level, the motor does not rotate, and the speed command becomes a certain level. Only when the output reaches a sufficient level, the DC motor suddenly starts rotating. Therefore, it can be said that it is not appropriate to use ordinary PWM control as it is in an electric wheelchair.

Therefore, in an electric wheelchair, a DC motor for rotating drive wheels is energized alternately by forward and reverse currents under PWM control, and the direction and speed of rotation are controlled by changing the balance of the currents. Have been done. That is,
When it is desired to stop the motor, forward and reverse currents of the same magnitude alternately flow for the same time, thereby canceling the forward and reverse torques, and the motor maintains the stopped state. When it is desired to rotate the motor in the forward direction, the time in which the forward current flows is made longer than the time in which the reverse current flows, so that the torque in the forward direction becomes larger and the motor rotates in the forward direction. Then, as the difference between the times during which the current flows in the forward and reverse directions increases, the torque increases and the motor rotates at a high speed. When the electric motor is rotated in the reverse direction, the reverse control is performed.

The above control is generally performed by using a complementary PWM.
This control method is used in equipment such as an electric wheelchair because control can be performed smoothly even when the speed is gradually increased from the stop state.

[0006]

In the conventional electric wheelchair as described above, a current always flows to the DC motor, and a current in the reverse rotation direction is rotated when the motor is rotating forward. When rotating, the current in the forward rotation direction generates a braking torque, which has the disadvantage that it must be a very energy-efficient control method. There is a strong demand for an electric wheelchair that can handle the situation.

An object of the present invention is to provide an electric wheelchair which can be started smoothly and has high energy efficiency.

[0008]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention provides a structure in which starting is performed by complementary PWM control capable of performing a smooth start, and when a predetermined speed is reached, normal PWM control is switched. It was done.

As a result, it is possible to obtain an electric wheelchair with high energy efficiency while enabling smooth starting.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a DC motor for rotating a driving wheel of a wheelchair, a DC power supply for supplying power to the DC motor, and a positive electrode of the DC power supply. A first switching means connected between a first input terminal of the DC motor and a second switching means connected between a positive electrode of the DC power supply and a second input terminal of the DC motor; Switching means, third switching means connected between a negative electrode of the DC power supply and a first input terminal of the DC motor, a negative electrode of the DC power supply and a second electrode of the DC motor. An electric motor comprising: fourth switching means connected between the input terminal; control means for ON-OFF controlling the first to fourth switching means; and speed detection means for detecting a vehicle speed of the wheelchair. A method of controlling a chair, wherein the control means sets the first and fourth switching means to a group A, the second and third switching means to a group B, and turns off the group B when the DC motor is rotated forward. The first control mode in which the group A is switched and the group A is kept in the OFF state and the group B is switched to perform PWM control when the motor is rotated in the reverse direction, and the group A and the group B are alternately switched. A PWM control to change the balance of the duty ratio between the groups A and B to control the forward rotation, reverse rotation, stop, and rotation speed of the DC motor.
When the wheelchair is started, the vehicle operates in the second control mode when the vehicle speed is equal to or lower than a predetermined first speed level, and when the vehicle speed exceeds the first speed level, The operation is switched to the first control mode to continue the operation, and has an effect that the operation can be performed by switching the control mode according to the situation of the start and the normal operation.

According to a second aspect of the present invention, there is provided the electric wheelchair control method according to the first aspect, wherein when the vehicle speed of the wheelchair exceeds the first speed level, the first control mode is switched from the second control mode to the first control mode.
After switching to the first control mode, the control mode is not switched even when the vehicle speed is lower than the first speed level, and when the vehicle speed is lower than the second predetermined speed level, the first The control mode is switched from the control mode to the second control mode, and has an effect of preventing switching back to the original control mode even when the vehicle speed stays near the first speed level when switching the control mode. .

According to a third aspect of the present invention, there is provided the electric wheelchair control method according to the first aspect, wherein the control mode is switched by a driver-operated switch instead of switching in accordance with the vehicle speed. This has the effect that the vehicle speed detecting means and the speed signal processing circuit can be dispensed with.

According to a fourth aspect of the present invention, there is provided the electric wheelchair control method according to the first aspect, wherein the electric vehicle is driven in the second control mode only for a predetermined time after the start of the wheelchair, and then switched to the first control mode. Vehicle speed detection means,
There is an effect that the speed signal processing means is not required, and further, it is possible to switch to the second control mode at the time of starting and to the first control mode at the time of traveling without any particular operation by the driver.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram showing a configuration according to a first embodiment of the present invention.
FIG. 2A is a diagram for explaining the second control mode, and FIG.
FIG. 3B is a current waveform diagram in the second control mode, and FIG.
FIG. 3A is a diagram for explaining the first control mode, and FIG.
FIG. 4 shows a current waveform diagram in the first control mode, and FIG. 4 shows a relationship diagram between the speed and the control mode.

In FIG. 1, a DC motor 1 is for driving a driving wheel (not shown) of an electric wheelchair, and is provided for each of left and right driving wheels. In addition, a flat type ironless motor is used as the DC motor 1 so that the DC motor 1 can be accommodated in a narrow layout space in order to reduce the dimension between the left and right drive wheels and to provide an electric wheelchair having a small minimum turning radius. Further, the DC motor 1 has a first input terminal 1a.
And a second input terminal 1b. When an electric current flows from the first input terminal 1a, the electric wheelchair rotates in the forward direction to drive the electric wheelchair forward, and the electric current flows from the second input terminal 1b. When it flows in, it rotates in the opposite direction and drives the electric wheelchair backward.

The switching means 3Aa and 3Ab are A
The switching elements constituting the group, 3Ba and 3Bb, are the switching elements constituting the B group, and usually use semiconductor switching elements such as power transistors or MOSFETs. The switching means A and B are configured such that the elements belonging to the same group conduct simultaneously, and when one of the groups conducts, the other group is non-conductive.

The speed command input means 6 is operated by the driver to generate a signal for controlling the speed, direction of travel, etc. of the electric wheelchair, and uses a joystick, a variable resistor or the like.

The control means 4 sets the switching means 3Aa to 3Bb to O based on a control signal from the speed command input means 4.
This is for driving the electric wheelchair as intended by the driver by turning N-OFF and controlling the direction and magnitude of the input current to the DC motor 1. The signal generated by the speed command input means 6 is transmitted to the motor drive signal generating means 4f to generate a motor drive signal. The motor drive signal drives the switching means via the driving means in the first or second control mode. On the other hand, the speed signal output from the speed detecting means 5 is input to the speed comparing means 4a, and the speed is compared with a preset speed level. Here, the second control mode is selected by the control mode switching means 4e when the speed signal output from the speed detecting means 5 is equal to or lower than the preset speed level, and otherwise, the first control mode is selected.
Control mode is selected.

In FIG. 2A, Ia is a current in a direction for rotating the motor in a forward direction, and Ib is a current in a direction for rotating the motor in a reverse direction. 3Aa constituting the switching means A group,
3Ab and 3Ba, 3Bb constituting the group B are alternately turned ON.
Since it is turned off, a current Ia for generating a forward rotation torque and a current Ib for generating a reverse rotation torque alternately flow through the motor 1 as shown in FIG. 2B. FIG.
In the case of (1), since Ia is larger than Ib, the electric motor 1 rotates in the forward direction.

In FIG. 3A, Ia is a current for rotating the motor forward. Since FIG. 3 shows the case of the forward rotation direction, the switching means B group is kept in a non-conductive state,
Only the switching means A group repeats ON-OFF.
As a result, a current as shown in FIG. 3B flows through the motor, and the motor rotates in the forward direction.

In FIG. 4, the horizontal axis represents the speed of the electric wheelchair,
The vertical axis represents the state of the control mode. The speed of the electric wheelchair is a predetermined first speed level of 0.75 km / h.
In the following cases, the vehicle is operated in the control mode 2 and the speed is 0.75.
When the speed exceeds km / h, the operation is switched to the control mode 1.

(Embodiment 2) FIG. 5 is a diagram showing a relationship between a speed and a control mode in a second embodiment of the present invention. In FIG. 5, the horizontal axis represents the speed of the electric wheelchair, and the vertical axis represents the state of the control mode. When the speed of the electric wheelchair is equal to or lower than the preset first speed level of 0.75 km / h, the vehicle is operated in the control mode 2 and the speed is 0.75 km / h.
Is the same as that of the first embodiment up to the point where the operation is switched to the control mode 1 when the vehicle speed exceeds the control mode. However, even if the speed of the electric wheelchair falls below the first speed level after the operation mode is switched to the control mode 1, The switching to the second control mode is performed when the speed of the electric wheelchair falls below 0.4 km / h, which is a second speed level separately determined, without switching to the second control mode.

(Embodiment 3) FIG. 6 is a block diagram showing the configuration of a third embodiment of the present invention.

In the case of this embodiment, the control mode is directly switched by a changeover switch operated by the driver. For example, the second control mode is used only when the low speed traveling is instructed in conjunction with the speed changeover switch. When the vehicle is instructed to run at a speed (medium speed to high speed), the vehicle is driven in the first control mode.

(Embodiment 4) FIG. 7 is a block diagram showing a configuration of a fourth embodiment of the present invention.

In the case of the present embodiment, the timer is started upon detecting a signal for guiding the electric wheelchair input by the driver, the vehicle is driven in the second control mode only for a predetermined time, and thereafter the first control mode is performed. It is to switch to the control mode.

As for the operation time in the second control mode, a constant value is set in the control means from the beginning, of course.
It is also possible to set individually according to the driver's weight in advance, or to detect in advance the driver's weight at the time of starting, the inclination of the floor surface, the unevenness of the floor surface, etc. Can also be set.

[0029]

As described above, according to the first aspect of the present invention, the complementary PWM control is performed in the extremely low speed range at the time of starting, and the normal PWM control is performed during the normal running, so that the energy can be secured while ensuring a smooth starting performance. An advantageous effect that an electric wheelchair with high efficiency can be realized is obtained.

According to the second aspect of the present invention, the first control mode at the time of stoppage is lower than the speed level at which the second control mode at the start is switched to the first control mode.
Since the speed level at which the control mode is switched to the control mode is set smaller, an advantageous effect is obtained in that the speed can be switched stably even when the speed of the electric wheelchair is gradually changing.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration according to a first embodiment of the present invention;

FIG. 2A is a diagram for explaining a second control mode. FIG. 2B is a current waveform diagram in the second control mode.

FIG. 3A illustrates a first control mode. FIG. 3B illustrates a current waveform in the first control mode.

FIG. 4 is a diagram showing a relationship between a speed and a control mode according to the first embodiment of the present invention;

FIG. 5 is a diagram showing a relationship between a speed and a control mode according to a second embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration according to a third embodiment of the present invention;

FIG. 7 is a block diagram showing a configuration according to a fourth embodiment of the present invention;

FIG. 8A is an explanatory diagram when a CR circuit is not added. FIG. 8B is a voltage waveform diagram when a CR circuit is not added.

9A is an explanatory diagram when a CR circuit is added, and FIG. 9B is a voltage waveform diagram when a CR circuit is added.

FIG. 10 is a characteristic diagram showing a relationship between a speed command (duty ratio) and an amplifier output.

[Explanation of symbols]

 Reference Signs List 1 DC motor 1a First input terminal of DC motor 1b Second input terminal of DC motor 2 DC power supply 2a Positive electrode of DC power supply 2b Negative electrode of DC power supply 3Aa First switching means 3Ab Fourth switching means 3Ba Second switching means 3Bb Third switching means 4 Control means 4a Speed comparing means 4b Control mode switching judgment 4c First control mode means 4d Second control mode means 4e Control mode switching means 4f Motor drive signal generating means 4g Timer 5 Speed detection means 6 Speed command input means 7 Control mode switch 8 Start detection

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yukihiro Ashizaki 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Koji Kamada 1006 Kadoma Kadoma, Kadoma City Osaka Pref. Term (reference) 3D035 BA00 5H115 PA11 PG06 PI16 PU02 PV03 PV23 PV24 QE01 QE02 QE03 QE12 QH02 QN06 QN12 RB17 SE03 TB01 5H571 AA02 BB02 EE02 EE09 FF01 FF06 FF07 FF08 FF09 GG02 HA08 HA09 HD02 JJ02

Claims (4)

[Claims] 1. A DC motor for rotating a driving wheel of a wheelchair, a DC power supply for supplying power to the DC motor, and a connection between a positive electrode of the DC power supply and a first input terminal of the DC motor. First switching means, a second switching means connected between a positive electrode of the DC power supply and a second input terminal of the DC motor,
A negative electrode of the DC power supply and a first electrode of the DC motor;
A third switching means connected between the input terminal of the DC motor, a fourth switching means connected between a negative electrode of the DC power supply and a second input terminal of the DC motor, Turn on the first to fourth switching means.
A method for controlling an electric wheelchair, comprising: control means for performing OFF control; and speed detection means for detecting a vehicle speed of the wheelchair, wherein the control means sets first and fourth switching means to A
Group, the second and third switching means as group B,
When the DC motor is rotated forward, the group B is kept OFF and the group A is switched, and when the DC motor is rotated backward, the group A is kept OFF and the group B is switched to perform PWM control. Mode, group A and B
The groups are alternately switched to perform PWM control, and A,
A second control mode for controlling the forward rotation, reverse rotation, stop, and rotation speed of the DC motor by changing the balance of the duty ratio between the groups B, wherein the first speed is a predetermined speed. A method for controlling an electric wheelchair, comprising: driving in the second control mode when the vehicle speed is equal to or lower than the level, and switching to the first control mode to continue driving when the speed exceeds the first speed level. 2. The method for controlling an electric wheelchair according to claim 1, wherein after switching from the second control mode to the first control mode due to the vehicle speed of the wheelchair exceeding the first speed level, Even if the vehicle speed falls below the first speed level, the control mode is not switched, and when the vehicle speed falls below a second predetermined speed level, the control mode is switched from the first control mode to the second control mode. A method for controlling an electric wheelchair, characterized by switching to (1). 3. The control method for an electric wheelchair according to claim 1, wherein the control mode is switched by a switch operated by a driver instead of switching according to the vehicle speed. Method. 4. The method for controlling an electric wheelchair according to claim 1, wherein the operation is performed in the second control mode only for a predetermined time after the start of the wheelchair, and then the operation is switched to the first control mode. Characteristic control method of electric wheelchair.