JP2001079041A - Electric wheelchair abnormality detection method - Google Patents

Abstract

(57) [Problem] In an electric wheelchair drive system in which a two-phase encoder 4 is attached to a motor 3 to perform speed feedback control as a speed sensor, a speed deviation which is a difference between a speed command value and an actually measured speed is large. When it becomes, it cannot be distinguished whether it is over an obstacle or an encoder disconnection / failure is occurring. When an encoder disconnection / failure occurs, abnormal processing cannot be performed promptly. SOLUTION: An armature resistance and an induced voltage constant of a motor 3 are stored as data, and an equivalent motor application calculated based on these data, a measured armature current of the motor, and a measured voltage. Based on the voltage, the rotational speed or the vehicle speed is estimated and calculated. The estimated rotational speed or the estimated vehicle speed is compared with the measured rotational speed or the measured vehicle speed actually measured from the pulse of the encoder 4 to detect an abnormality of the encoder 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art An electric wheelchair has a motor as a drive source, and in many high-end models, the speed of the motor is controlled. When controlling the speed of the motor, measure the period of the pulse output from the encoder as the rotation speed detection means attached to the output shaft of the motor, or count the number of pulses per unit time to calculate the motor speed, It is common practice to compare this with a speed command value as a feedback signal and control the voltage or current of the motor so that the speed deviation becomes zero. In this case, the reliability of the speed feedback signal is important.For example, if the speed feedback signal becomes small or becomes zero due to some failure even if the motor is rotating, or becomes the opposite polarity, the speed command value is determined. And the speed deviation, which is the difference from the above, increases, and the motor attempts to rotate at a higher speed.

[0003] Considering the case where the motor is used in a wheelchair, it is easy to imagine that a runaway occurs when it occurs on both wheels, and a sharp turn occurs when it occurs on one wheel, which is very dangerous.

As a failure of the encoder, disconnection / contact failure / element failure can be considered. Considering the case where the encoder signal is a two-phase output having a 90 ° phase difference to detect the rotation direction, if the pulse of one phase changes but the pulse of the other phase does not change, the motor is moved to one position. It is considered that a simple vibration phenomenon in which the vibration is repeated in the above occurs or one phase is disconnected / the element is in failure.

The former can be excluded from the causes depending on the number of pulses of the encoder and the mechanism design, and can be used as a one-phase disconnection / element failure detection method. But,
When there is no pulse change in both phases, a large load is applied to the motor in an attempt to get over an obstacle such as a step, and the motor is unable to rotate despite the current flowing, or the encoder is in the 2nd state. Both phases are considered to be when disconnection / element failure or encoder power supply disconnection / element failure.

[0006] In the case of a brushless DC motor, a commutation sensor signal accompanying the rotation of the motor is provided separately from the encoder signal. Therefore, if the motor is rotating, the commutation sensor signal changes and the motor rotates. You can see that it is doing. At this time, if there is no change in the pulse of the encoder signal, it can be determined that the encoder power supply has a disconnection / element failure or that both encoders have a disconnection / element failure.

However, in the case of a brushed DC motor,
Since there is no signal corresponding to the commutation sensor signal, two-phase disconnection of the encoder / element failure and power supply disconnection /
Element failure cannot be determined. For this reason, a method of detecting the two-phase encoder disconnection / element failure or the power supply disconnection / element failure by means of detecting that the velocity deviation equal to or more than a predetermined value continues for a predetermined time or more (speed deviation integral value) is performed.

[0008]

However, in the above-mentioned conventional method, when the wheelchair goes over a step and the motor output does not have enough margin for the load over the step, the overload state continues for a long time. Unless the speed deviation integral value is set to a considerably large value, an error occurs in the middle of the step.

For this reason, the error detection value of the speed deviation integration must be determined with a margin so that even if the motor output decreases at the time of the voltage drop, the obstacle such as the assumed step can be sufficiently overcome.

However, when a two-phase disconnection / element failure of the encoder and a power supply disconnection / element failure of the encoder occur, the motor is full until the speed deviation integral value reaches the error value because the error detection value is large. Acceleration is considered dangerous.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention stores armature resistance and induced voltage constant of a motor used in a wheelchair as data in advance, and stores these data and The motor rotational speed or the wheelchair speed is estimated and calculated from the armature current of the motor measured by the current detecting means and the equivalent motor applied voltage calculated based on the voltage measured by the voltage detecting means. The abnormality of the encoder can be detected by comparing the number or the estimated speed with the actual rotation speed or the actually measured speed actually measured and calculated from the pulse of the encoder directly connected to the motor.

For example, when the actually measured rotation speed or the actually measured speed is
When it is smaller than the estimated rotation speed or the estimated speed, it can be determined that two-phase disconnection / element failure of the encoder or disconnection / element failure of the encoder power supply occurs.

According to this method, two-phase disconnection /
When an element failure or encoder power supply disconnection / element failure occurs, it is possible to promptly enter an abnormality process without a redundant margin, thereby providing a safe wheelchair drive system.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 of the present invention provides a motor drive control means for storing an armature resistance and an induced voltage constant of a motor in advance and operating using a storage battery as a power supply, A motor driven by the means, a motor speed detecting means for detecting a motor speed, a motor voltage detecting means for detecting a motor applied voltage, and a motor current detecting means for detecting a motor armature current. A motorized wheelchair abnormality detection method in which a propulsion force is given through a deceleration mechanism by the motor drive control means, wherein the motor application control means obtains an armature resistance and an induced voltage constant stored in advance and a motor applied voltage obtained by each detection means. An estimated rotation speed of the motor is calculated from the motor armature current, and thereafter, the estimated rotation speed and the motor actually measured and obtained by the rotation speed detection means are calculated. When the state in which the difference between the estimated rotation speed and the actually measured motor rotation speed is equal to or greater than a predetermined value continues for a predetermined time or more, it is determined that an abnormality has occurred in the rotation speed detection unit. This has the effect that the abnormality of the rotation speed detecting means can be detected promptly.

According to a second aspect of the present invention, there is provided a temperature detecting means for detecting the temperature of the motor, wherein the temperature of the armature resistance and the induced voltage constant of the motor, which are inputted in advance as data, are corrected by the detected temperature. Therefore, even when the motor temperature changes and the motor constant changes, an accurate determination can be made.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows the configuration of an electric wheelchair drive system according to an embodiment of the present invention. In FIG. 1, 1 is a drive control circuit, 2 is a storage battery, 3
Is a motor, 4 is an encoder (rotation speed detecting means), 5 is a motor current detecting means, 6 is an electromagnetic brake, 7 is a speed reducer, 8
Is a wheel. The drive control circuit 1 reads the motor current from the motor current detecting means 5 and reads the voltage from the storage battery 2. The control unit 1 stores an armature resistance Ra and an induced voltage constant Ke in advance. The PWM duty is recognized by the drive control circuit 1. FIG. 2 shows a flow of the error processing. In electric wheelchairs, electromagnetic brakes are provided as standard equipment except for simple models. Electromagnetic brakes are often of the non-excitation type for safety. this is,
When there is no excitation of the electromagnetic brake, the brake function operates to lock the motor shaft. At this time, since the abnormality detection processing relating to the rotation speed detecting means of the present invention is not necessary, the encoder abnormality is only observed when the excitation is being performed.
Due to the nature of the abnormality processing, it is necessary to detect the abnormality as soon as possible, and wasteful processing must be omitted. However,
This does not apply when there is a sufficient margin for the calculation time.

Next, it is checked whether the encoder has one-phase disconnection / element failure. If one phase has not changed and the other phase has changed by N pulses or more, it is not a simple vibration phenomenon in which the motor shaft vibrates alternately around one point. And a stop process is performed.

Next, it is checked whether or not the state where the difference between the estimated rotational speed and the measured rotational speed is equal to or greater than a predetermined value continues for a predetermined time or more. For the rotational speed estimation formula, for example, in the case of a brushed DC motor, the following formula is used.

[0020]

(Equation 1)

When the wheelchair is going over an obstacle, for example, the estimated rotation speed and the actually measured rotation speed are close to zero, so that this check does not deem it to be abnormal.

When the power supply line of the encoder has a disconnection / element failure or two-phase simultaneous disconnection / element failure, the estimated rotational speed shows a certain value, but the measured rotational speed shows around zero. Since the speed difference is generated and continues for a predetermined time or more, it can be determined that there is an abnormality.

In the above description, the case where the abnormality of the motor rotational speed detecting means is determined has been described. However, the vehicle speed of the electric wheelchair is detected and compared with the estimated vehicle speed of the electric wheelchair converted from the motor rotational speed and the reduction ratio, or The same applies to the case where the detected wheelchair speed is converted into a motor rotation speed using a reduction ratio and compared with the estimated motor rotation speed to determine an abnormality in the motorized wheelchair speed detection means.

(Embodiment 2) FIG. 3 is a block diagram relating to temperature-corrected error detection of an electric wheelchair, and FIG. 4 shows a temperature-corrected error processing flow.

The second embodiment differs from the first embodiment in that a temperature sensor 9 is mounted on the motor 3 as shown in FIG. 3, and the armature resistance read in advance as shown in FIG. And that the induced voltage constant is a function of the temperature θ.

[0026]

(Equation 2)

In order to obtain the wheelchair speed from the estimated rotation speed, for example, the following equation is used.

[0028]

(Equation 3)

In the above description, the motor system is assumed to be an inexpensive brush DC motor.
Brushless DC for longer life and various control possibilities
A motor may be used, and even in this case, the abnormality detection method of the present invention can be implemented.

Further, if the motor of another principle is also a motor equipped with a speed sensor, and if a speed estimation formula can be described, the abnormality detection method of the present invention can be similarly implemented.

[0031]

As described above, according to the first aspect of the present invention, when the speed deviation, which is the difference between the speed command value and the actually measured speed, increases, the wheelchair can be referred to by referring to the estimated speed value. Is over obstacles such as steps,
Since it is possible to distinguish whether a disconnection / failure has occurred in the encoder, abnormal processing can be performed promptly without waiting for redundant time. Thereby, a safe electric wheelchair drive system can be provided.

According to the second aspect of the present invention, even if the temperature changes, there is an advantage that the armature resistance and the induced voltage constant are corrected in accordance therewith, so that stable operation is ensured.

[Brief description of the drawings]

FIG. 1 is a block diagram for performing error processing according to an embodiment of the present invention;

FIG. 2 is a diagram showing error processing according to an embodiment of the present invention;

FIG. 3 is a block diagram for performing temperature-corrected error processing according to an embodiment of the present invention;

FIG. 4 is a diagram showing temperature-corrected error processing according to an embodiment of the present invention;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drive control circuit 2 Storage battery 3 Motor 4 Encoder (rotation speed detecting means) 5 Motor current detecting means 6 Electromagnetic brake 7 Reduction mechanism 8 Wheel 9 Temperature sensor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Joji Nakamura 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Terms (reference) 5H115 PA08 PC06 PG06 PI13 PI29 PU02 PV03 QE10 QI07 QN03 QN06 RB08 RB19 SE03 TB01 TI05 TO05 TO12 TO13 TO30 TR07 TW10 TZ05

Claims (2)

[Claims] 1. A motor drive control means for storing an armature resistance and an induced voltage constant of a motor in advance and operating using a storage battery as a power supply, a motor driven by the motor drive control means, and detecting a motor speed. Rotation speed detecting means, motor voltage detecting means for detecting a motor applied voltage,
A motor current detecting means for detecting a motor armature current, wherein the motor is provided with a propulsive force via a deceleration mechanism by the motor. The estimated rotational speed of the motor was calculated from the resistance and the induced voltage constant and the motor applied voltage and the motor armature current obtained by the respective detecting means, and thereafter, the estimated rotational speed and the rotational speed were actually measured and obtained by the rotational speed detecting means. Compare with motor speed,
When the state in which the difference between the estimated rotation speed and the actually measured motor rotation speed is equal to or more than a predetermined value continues for a predetermined time or more, it is determined that an abnormality has occurred in the rotation speed detecting means. Anomaly detection method. 2. A method for detecting an abnormality of an electric wheelchair according to claim 1, further comprising a temperature detecting means for detecting a temperature of the motor, and detecting an armature resistance and an induced voltage constant of the motor which are input in advance as data. A method for detecting an abnormality of an electric wheelchair, wherein the temperature is corrected by a temperature.