JPS6157024B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speed control device for an electric wheelchair, and more particularly to a speed control device for an electric wheelchair that performs pulse control only in low rotational speed ranges such as starting and stopping.

The electric wheelchair has two small casters (swivel wheels) on the front wheels, and drive motors on the rear wheels, which are controlled by an open control device.

When such an electric wheelchair is driven at low speed on a pavement, when the road surface is inclined toward the roadway, the casters are guided toward the roadway, making it difficult to drive straight.
For this reason, a rotation speed control method has been adopted in which the rotation speed (speed) of the motor is always maintained by a control device so that the motor does not drift in one direction even when the road surface is sloped.

However, this rotational speed control method attempts to generate the full torque by faithfully following the commanded rotational speed, so when the rotational command suddenly changes from stop to full open, a considerable amount of shock is applied to the wheelchair itself. Added.

For this reason, it has been considered to provide a current limiting circuit and gradually increase the rotational speed, but this has the disadvantage that it is not smooth when driving on steep slopes.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a speed control device for an electric wheelchair that allows smooth running in a low rotation range and can eliminate insufficient torque for the load during running.

In order to achieve the above object, a speed control device for an electric wheelchair according to the present invention includes a drive motor, a motor drive circuit that rotates the drive motor in forward and reverse directions, a tachogenerator that detects the number of rotations of the drive motor, and a motor drive circuit that rotates the drive motor in forward and reverse directions. The speed of an electric wheelchair that has a command section that commands a rotation speed to a motor, and a first comparator that connects the command voltage to a motor drive circuit when the detected voltage of the tachogenerator is higher than the command voltage from the command section. In the control device, a delay circuit that delays a command voltage from the command section, an absolute value amplifier that amplifies the delayed signal of the delay circuit to an absolute value, a reference oscillator that outputs a sawtooth wave, and the reference oscillator and the absolute a second comparator that compares the outputs of the value amplifiers and generates a sustained pulse in proportion to the difference; and a second comparator that generates a pulse that lasts in proportion to the difference; It consists of a connected gate circuit.

According to the above structure, the object of the present invention can be completely achieved.

Hereinafter, the present invention will be explained in more detail with reference to the drawings and the like.

FIG. 1 is a block diagram showing an embodiment of the speed control device for an electric wheelchair according to the present invention, and FIG. 2 is a waveform diagram for explaining the operation.

When the operating lever of an electric wheelchair is pushed forward, the wheelchair moves forward, and the speed is determined by the inclination angle of the operating lever, and when the operating lever is pulled toward the user, the wheelchair moves backward. The operation of the operating lever is converted into a command voltage v ₁ by the rotation speed command unit 1, and the command voltage v ₁ is varied depending on the inclination angle of the operating lever. Command voltage v ₁ is v _cc at full speed forward,
It is set to m when in neutral and zero when in full speed reverse.

The command voltage v ₁ is delayed by the delay circuit 2, and one of the delayed signals is connected to the non-inverting input terminal of the first comparator 3. The first comparator 3 outputs "+1", "0", and "-" in response to forward, neutral, and backward command voltage _v1 .
Outputs a 1” signal.

The other delayed signal is connected to an absolute value amplifier 4. The absolute value amplifier 4 takes the absolute value of the delayed signal, regardless of whether it is positive or negative, and amplifies its amplitude. Absolute value amplifier 4
The output of is connected to the non-inverting input terminal of the second comparator 5. The inverting input terminal of the second comparator 5 is connected to the output v ₀ of a reference oscillator 6 that generates a triangular wave.

The output of the first comparator 3 is connected to one input terminal of the gate circuit 7, and the output of the second comparator 5 is connected to the other input terminal. The output of the gate circuit 7 also corresponds to the output of the first comparator 3.
The output of the gate circuit 7 is connected to the motor drive circuit 8.

The motor drive circuit 8 includes an inverter 9, four transistors T ₁ to T ₄ arranged in a bridge shape, a driving motor M capable of forward and reverse rotation, and a battery B.
It is composed of. One of the outputs of the gate circuit 7 is connected to the bases of the transistors T ₁ and T ₄ , and the other is connected to the transistors via the inverter 9.
Connected to the base of T ₂ and T ₃ .

Battery B is connected to the collectors of transistors T ₁ and T ₂ , and the emitters of transistors T ₁ and T ₂ are connected to the collectors of transistors T ₃ and T ₄ , respectively. The emitters of transistors T ₃ and T ₄ are grounded. A motor M is connected between transistors _T1 to _T4 .

The motor M is provided with a tachogenerator 10, which detects the rotation speed of the motor M and outputs a detected voltage.
v ₂ is connected to the inverting input terminal of the first comparator 3. The tachogenerator 10 outputs v ₂ =m when the motor M is stopped.

Next, the operation will be explained with reference to FIG.

When the electric wheelchair starts, the rotation command voltage _v1 is generated from the rotation speed command section 1 by tilting the operating lever forward (FIG. 2a). The command voltage v ₁ is delayed by the delay circuit 2 and becomes as shown in FIG. 2b. The rotational speed command signal v ₁ is input to the non-inverting input terminal of the first comparator 3, and since the motor M is not yet rotating, the output v ₂ of the tachogenerator 10 is v ₁ > v ₂ . The output of comparator 3 becomes “+1”,
A “+1” signal is input to the gate circuit 7.

On the other hand, the output v ₀ of the reference oscillator 6 oscillates a sawtooth wave as shown in FIG. Rotation speed command voltage
After v ₁ is delayed by the delay circuit 2, it is amplified by the absolute value amplifier 4, resulting in a waveform as shown in FIG. 2c. Since the second comparator 5 compares v ₀ and c, it generates an energization command signal e that generates a pulse only for a period corresponding to the voltage of c.

Therefore, the gate circuit 7 includes a second comparator 5.
The "+1" signal of the second comparator 3 is connected to the motor drive circuit 8 only when the output of the second comparator 3 is "+1".
When the output of the gate circuit 7 becomes "+1", the bases of the transistors T ₁ and T ₄ are at the "+1" level, and the transistors connected via the inverter 9
The bases of T ₂ and T ₃ are at the "-1" level.

Therefore, the current from battery B flows through transistor T ₁ , motor M, and transistor T ₄ to rotate the motor in the forward direction, and the wheelchair moves forward.

That is, in the low rotation range, the pulse width from the second comparator 5 gradually becomes longer, so that the motor M is driven smoothly.

When the rotation speed command voltage c passes the delay time and reaches the wave height of the sawtooth wave v ₀ , the output of the second comparator 5 always becomes a “+1” signal, and the gate circuit 7
always connects the output of the first comparator 3 to the motor drive circuit 8.

When the detection voltage v ₂ detected by the tachogenerator 10 of the rotation speed of the motor M reaches the command voltage v ₁ from the rotation speed command unit 1, the output of the first comparator 3 becomes “0” level, and the gate circuit 7 The output becomes "0" level. Therefore, the rotation speed of the motor M is controlled around this value.

When the rotational speed of the motor M decreases due to a steep slope, etc., the tachogenerator 10 detects the rotational speed, inputs it to the first comparator 3, and continues to output a "+1" signal until the command signal _v1 is reached. At this time, unless a command signal in the low rotation range is sent out by operating the control lever, forced pulse control by the reference oscillator 6 is not performed. Therefore, a lack of torque does not occur on steep slopes, etc.

Next, we will explain the operation when the vehicle changes from moving forward to a stopped state and immediately moves backward.

When the command voltage v ₁ from the rotation speed command unit 1 becomes low due to deceleration from the forward running state, and the amplified signal c from the absolute value amplifier 4 becomes lower than the wave height of the sawtooth wave v ₀ of the reference oscillator 6, the second The pulse wave e is sent out from the comparator 5 as described above. This time, the pulse width becomes gradually narrower, so the shock to the wheelchair body during deceleration is alleviated.

Furthermore, when reversing, it is assumed that the operating lever is pulled toward the user and the rotational speed command voltage _v1 falls below m as shown in FIG. 2h. After the command voltage v ₁ is delayed by the delay circuit 2 (FIG. 2i), it is input to the first comparator 3. When a negative signal enters the non-inverting input terminal of the first comparator 3 and its absolute value is larger than that of the inverting input terminal, "-1" is generated.

When the delayed signal h is amplified in absolute value by the absolute value amplifier 4, it becomes similar to the waveform of c as in the case of forward movement, and the second comparator 5 outputs a pulse signal e.

Since the first comparator 3 is sending a “-1” signal, the second comparator 5 is sending a “+” signal.
1", the gate circuit 7 connects a "-1" signal to the motor drive circuit 8. When the output of the gate circuit 7 becomes "-1", the transistors T ₁ and T ₄
The base of the transistor T ₂ and T ₃ connected through the inverter 9 is at the “+1” level.

Therefore, the current in battery B flows through transistor T ₂ , motor M, and transistor T ₃ , causing the motor to reverse, and the wheelchair to move backward.

When transitioning from forward movement to backward movement, etc., the pulse width of the pulse signal e sent from the second comparator 5 becomes gradually narrower during deceleration, and gradually becomes wider after the start of backward movement, so that switching is smooth.

As explained in detail above, according to the present invention,
Since pulse control is performed only when the rotational speed command voltage is in the low rotational range, operations such as starting and stopping become smoother, and the transition from forward movement to reverse movement becomes smoother.

Therefore, even if the rotational speed of the motor decreases due to a steep slope, etc., there will be no shortage of torque since pulse control is not performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the speed control device for an electric wheelchair according to the present invention, and FIG. 2 is a waveform diagram for explaining the operation. 1... Rotation speed command section, 2... Delay circuit, 3...
First comparator, 4... Absolute value amplifier, 5... Second comparator, 6... Reference oscillator, 7... Gate circuit, 8... Motor drive circuit, 9... Inverter,
10...Tachometer generator, M...Motor, B...
...Battery, _T1 to _T4 ...Transistor.

Claims (1)

[Claims] 1 a drive motor, a motor drive circuit that rotates the drive motor in forward and reverse directions, a tachometer generator that detects the rotation speed of the drive motor, a command section that commands the rotation speed of the drive motor, and a detection voltage of the tachometer generator that detects the rotation speed of the drive motor. A speed control device for an electric wheelchair having a first comparator that connects the command voltage to a motor drive circuit when the command voltage is higher than the command voltage from the command unit, a delay circuit that delays the command voltage from the command unit; an absolute value amplifier that amplifies the delayed signal of the delay circuit in absolute value; a reference oscillator that outputs a sawtooth wave; and comparing the outputs of the reference oscillator and the absolute value amplifier to generate a pulse that lasts in proportion to the difference. A speed control device for an electric wheelchair, comprising: a second comparator; and a gate circuit that connects the output of the first comparator to a motor drive circuit during a pulse generation period of the second comparator. .