JPS6155387B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering device for an electric wheelchair, and more particularly, to a power steering device for an electric wheelchair that forcibly performs pulse control at the final stage of steering operation.

The steering device of an electric wheelchair has a method in which the front wheels are small casters, and the steering is performed by changing the rotation speed of drive motors that are installed independently on the left and right rear wheels. There is a method in which the left and right wheels are set at the same rotation speed and the front wheels are steered by a steering motor.

Here, the basic configuration of a power steering device for an electric wheelchair using the latter steering motor will be explained with reference to FIG. 1, and its problems will be discussed.

Electric wheelchairs are steered by tilting the steering lever left and right. Also, by tilting the steering lever forward, the vehicle moves forward, and the speed is determined by the angle of inclination, and similarly, by tilting the steering lever toward this side, the vehicle moves backward. In other words, the steering lever also functions as an accelerator lever.

The angle command unit 1 converts a mechanical steering angle given by a steering lever into an electrical signal, and outputs a steering angle command signal _v1 . command signal v ₁
distinguishes the direction of rotation by its positive or negative sign. A steering angle command signal v ₁ is connected to a non-inverting input terminal of a comparator 2, and an angle detection signal v ₂ from an angle detector 5, which will be described later, is connected to an inverting input terminal of the comparator 2. A high level signal from the comparator 2 causes a steering servo motor 4 to rotate in forward and reverse directions via a motor drive circuit 3, thereby steering the front wheels of the wheelchair left and right. An angle detector 5 is attached to the servo motor 4.
is provided to detect the current position of the steering motor, and the output voltage v ₂ of the detector 5 is connected to the inverting input terminal of the comparator 2.

When the operator sets the steering angle in the first direction with the steering lever, an angle designation signal v ₁ (v ₁ >0) proportional to the steering angle is generated, and the comparator 2
is input to the non-inverting input terminal of The angle detection signal v ₂ of the angle detector 5 is input to the inverting input terminal of the comparator 2, but since the motor 4 is not yet driven, v ₂ = 0, and the output of the comparator 2 is at a high level. be. When a high level signal is input to the drive circuit 3, a drive signal in the first direction is sent out, and the motor 4 is driven to tilt the wheelchair towards the front wheels (in the steering direction).
When the motor 4 is driven, the angle detector 5
Detects the rotation angle of and sends the angle detection signal v ₂ to comparator 2
is input to the inversion input terminal of , and the motor 4 rotates in the first direction until v ₁ <v ₂ .

Similarly, when the steering lever is tilted in the second direction, the angle command signal _v1 becomes negative, and the output of the comparator 2 becomes a low level. When a low level signal is input to the drive circuit 3, a drive signal in the second direction is sent out to drive the motor 4, and the front wheels of the wheelchair are tilted in the second direction. This state continues until v ₁ > v ₂ . In other words, the servo motor 4 always rotates in the first direction or the second direction, and to eliminate this,
When a zero level signal is input to the drive circuit 3 in the region of |v ₁ - v ₂ |≒0, the motor 4 will not move in any direction.
Measures are being taken to ensure that no electricity is applied to the

As described above, the power steering device for an electric wheelchair usually constitutes a closed loop, and adjustment is often difficult due to hunting at the time of convergence and mismatch in response speed.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a power steering device for an electric wheelchair that has improved followability when traveling straight.

In order to achieve the above object, a power steering device for an electric wheelchair according to the present invention includes a steering motor, a motor drive circuit that selectively drives the steering motor in a first direction and a second direction;
an angle detector that detects the current position of the steering motor; a command unit that commands the angle of the steering motor; and a first command unit that commands the direction of the motor by comparing outputs of the angle detector and the angle command unit. In the power steering device for an electric wheelchair having a comparator, a difference amplifier outputs a difference between an output of the angle detector and a set value of the command unit;
a sawtooth oscillator; a second comparator that compares the outputs of the sawtooth oscillator and the differential amplifier and generates a pulse for a period proportional to the difference; and a control circuit that connects the output of the first comparator to the motor drive 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. 2 is a block diagram showing an embodiment of the power steering device for an electric wheelchair according to the present invention, and FIG. 3 is a waveform diagram for explaining the operation.

The angle command unit 1 converts a mechanical steering angle given by a steering lever into an electrical signal, and outputs a steering angle command signal _v1 . command signal v ₁
distinguishes the direction of rotation by its positive or negative sign. The steering angle command signal v ₁ is connected to the non-inverting input terminal of the first comparator 2, and the angle detection signal _v 2 from the angle detector 5 is connected to the inverting input terminal of the first comparator 2.
is connected. The output signal of the first comparator 2 is connected to a control circuit 9.

The output of the control circuit 9 is transmitted through the motor drive circuit 3 to rotate the steering servo motor 4 in forward and reverse directions, thereby steering the front wheels of the wheelchair left and right. The servo motor 4 is provided with an angle detector 5 to detect the current position of the steering motor, and the output voltage v ₂ of the detector 5 is connected to the inverting input terminal of the first comparator 2.

The difference amplifier 6 takes the difference between the set value v ₁ from the angle command section 1 and the angle detection signal v ₂ that detects the current position of the steering motor 4, and generates a signal v ₃ by amplifying the difference.
Output. The sawtooth oscillator 7 outputs a sawtooth wave v ₀ as shown in FIG. 3a.

The output v ₃ of the differential amplifier 6 is connected to the non-inverting input terminal of the second comparator 8 , and the output v ₃ of the sawtooth oscillator 7 is connected to the inverting input terminal of the second comparator 8 . Therefore, the output v ₄ of the second comparator 8 is the fourth
As shown in Figure b, when v ₃ > v ₀ , the level is high; when v ₃ <
Sends low level output when v is ₀ . In other words, a pulse train is generated for a period proportional to _v3 . The output of the second comparator 8 is input to the control circuit 9, and when the pulses of the pulse train _v4 are generated,
The output of the first comparator 2 is connected to a motor drive circuit 3 to drive the steering motor 4.

As explained in detail above, according to the present invention,
When the steering motor approaches the steering angle, pulse width control is forcibly performed to reduce the rotational torque, which weakens the rotational force and suppresses hunting.

Furthermore, since there is no need to provide a dead zone or so-called play area in the steering wheel, fine adjustments can be made while driving.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the basic configuration of a power steering device for an electric wheelchair, Fig. 2 is a block diagram showing an embodiment of the power steering device for an electric wheelchair according to the present invention, and Fig. 3 is a waveform for explaining the operation. It is a diagram. DESCRIPTION OF SYMBOLS 1...Angle command part, 2...First comparator, 3...Drive circuit, 4...Motor, 5...Angle detector, 6...Difference amplifier, 7...Sawtooth oscillator, 8...Second comparator, 9...
control circuit.

Claims (1)

[Claims] 1. A steering motor, a motor drive circuit that selectively drives the steering motor in first and second directions, an angle detector that detects the current position of the steering motor, and a command unit that commands the angle of the steering motor. , a power steering device for an electric wheelchair having a first comparator that compares the output of the angle detector and the angle command unit to instruct the motor in a direction, the output of the angle detector and the setting of the command unit; a difference amplifier that outputs a difference in values; a sawtooth oscillator; a second comparator that compares the outputs of the sawtooth oscillator and the difference amplifier and generates a pulse for a period proportional to the difference; A power steering device for an electric wheelchair, comprising: a control circuit that connects the output of the first comparator to a motor drive circuit during a pulse generation period of the first comparator.