JPH0365984B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for controlling an assistance patient transfer device used for assisting bedridden patients in medical facilities such as hospitals and rehabilitation centers. It is something.

<Conventional technology> In medical facilities such as hospitals and rehabilitation centers, patient transfer devices that automatically pick up bedridden patients and transport them to toilets, bathrooms, treatment rooms, etc. not only reduce the burden on caregivers, but also There are increasing social expectations for the realization of this technology, which aims to assist patients in acting according to their own will.

FIG. 3 shows an example of this, which consists of a seat portion 1 that slides horizontally and lifts up a patient on the bed, and an omnidirectional movable trolley 2.

In this device, the seat portion 1 consists of a substantially horizontal waist support portion 3, leg support portions 4 on the front and rear thereof, and a back support portion 5, and each of the support portions 3, 4, and 5 are approximately horizontal. The wheelchair can be changed from a stretcher shape to a wheelchair shape with the leg supports 4 turned downward and the back support 5 turned upwards. By inserting it, it is possible to lift the patient.

FIG. 4 shows the seat portion of the patient transfer device shown in FIG.

This part is an insertion plate 6 that can be slid horizontally.
The belt 7 is wrapped around the plate 6, and the upper and lower ends of the belt 7 are separately wound around rollers 8 and 9.

Figure 5 a, b, c, and d show how to lift a patient using the above-mentioned device, and the insertion plate 6
performs a sliding motion, and the patient 10 and the bed 11
At that time, only the lower roller 9 lets out the belt 7 so that the belt 7 is always connected to the patient 10.
By preventing the relative relationship between the insertion plate 6 and the bed from changing, friction between the insertion plate 6 and the bed is reduced, allowing smooth insertion.

In addition, in FIGS. 4 and 5, another plate 12 below the insertion plate 6 connects the lower front end 15 to the lower base 1.
A lower belt 14 fixed to the lower belt 14 is placed over the lower belt 14, and the lower belt 14 is inserted between the patient 10 and the bed 11 at the same time as the insertion plate 6. However, the relative relationship between the lower belt 14 and the lower belt 11 is kept constant, and the It has the function of reducing friction between 11 and 11.

Further, as for the drive motors, as shown in 15 and 16 in FIG. 4, one each is arranged on the upper and lower sides for rotating the belt rollers 8 and 9, and one motor (not shown) is arranged for driving the insertion plate 6. has been done.

In a patient transfer device having the above mechanism, when lifting and inserting a patient, the insertion plate 6 must be operated at a constant speed that does not cause discomfort to the human body.

If the speed is too high, it may cause discomfort such as pain to the patient, and if the speed is not constant, it will also be uncomfortable.

Further, during insertion, it is necessary to rotate the lower belt roller 9 in accordance with the advancement of the insertion plate 6.

At this time, the speed of the insertion plate 6 is V _bd (t), and the speed at the lower part of the belt 7 that is hung on the insertion plate 6 is V _b2
(t), then V _b2 (t) ...(1) If the control is performed so that the belt 7 on the upper part of the insertion plate 6 remains stopped and there is no relative change in the patient contact position, the process will be smooth. insertion is possible.

Therefore, when the drive motor of the plate 6 and the drive motor 16 of the lower belt roller 9 are rotated separately at a constant speed, a control method that adds an integral compensation operation to proportional control, that is, PI control, is often used.

Now, consider the motor drive current i as i=Kp(ω ₀ −ω)+Ki∫(ω ₀ −ω)dt (2). Here, ω ₀ is the target rotational angular velocity of the motor, and ω is the current value of the angular velocity. The target values of the rotational speeds of the insertion plate 6 and the rollers 9 may be selected so as to satisfy equation (1), taking into consideration the respective rotation transmission mechanisms.

<Problems to be Solved by the Invention> In the control device for the patient transfer device as described above, when inserting the insertion plate 6 between the patient 10 and the bed, the weight of the patient 10 causes a disturbance to the plate drive servo system. Acts as.

That is, at the point when the insertion of the insertion plate 6 between the patient 10 and the bed 11 is started, a frictional force that resists the rotation of the motor is generated between the patient 10, the belt 7, and the insertion plate 6 as a disturbance, and the rotation speed is constant until then. The speed of the insertion plate 6, which was being driven at , decreases.

However, in PI control, as the error between the current speed and the target speed increases, the output of the integral term gradually increases, and the output that is sufficient to resist the disturbance is obtained, and even if there is friction due to the human weight, the output of the integral term gradually increases. has the property of returning to its original speed.

On the other hand, the frictional force caused by the human weight acts as a disturbance on the plate drive motor, but does not cause a disturbance on the drive motor 16 of the belt 7.

The speed of the drive motor for the insertion plate 6 temporarily decreases when the insertion of the insertion plate 6 is started, but during this time the motor 16 that feeds out the belt does not decrease in speed and continues to rotate at a constant speed.

While the speed of the insertion plate 6 is decreasing, the relationship in equation (1) above is broken, so the excess belt 7 is unavoidably let out, resulting in slack as shown in Fig. 6. .

Next, patient 10 is placed on the patient transfer device.
When the lower belt roller 9 is rolled up and the upper belt roller 8 is rotated in the feeding direction and moved on the device as shown in Fig. 7 to correct the positional deviation, both rollers 8 and 9 are the same. Although it is sufficient to rotate at a high speed, it is the lower roller 9 that pulls the load of the patient 10.

Therefore, the speed of the roller 9 to which the load is applied decreases, but since no load is applied to the upper roller 8, it continues to rotate at a constant speed.

Therefore, the belt 7 becomes slack as in the case described above.

The slackness of the belt 7 as described above hinders the next operation.

That is, the belt 7 is tightened until there is no slack in the belt 7.
The tensile force of is not transmitted to the patient 10.

Furthermore, since the relationship between the amount of winding of the belt 7 becomes unstable, there is a problem that an initialization operation is required every time the child is picked up.

In order to solve the above problem, there is also a method as shown in FIG.

In this method, a target speed signal ω ₀ of the drive motor of the insertion plate 6 is inputted to the insertion plate drive motor speed control means 21, and the insertion plate drive motor is controlled by the output signal to operate the insertion plate.

However, the current operating speed ω of the insertion plate 6 is
0 and the bed 11, the speed of the insertion plate 6 is constantly monitored by detecting this current motor speed ω, and the signal is input to the speed conversion means 2, and the output signal ω is ' ₀ is input to the belt roller motor speed control means 23,
The belt roller drive motor is controlled by the output signal ω' to synchronize the current speed of the insertion plate 6 and the speed of the belt 7.

In this method, the speed of the belt roller is adjusted in real time, so the lifting, insertion of the insertion plate 6,
It works effectively for other operations.

However, this method is basically realized by speed control, and does not pay attention to the positional relationship between the insertion plate 6 and the belt 7 at each point in time, so minute errors caused by one insertion operation remain unchanged. remain.

Therefore, the method shown in FIG. 8 does not cause any problems when the insertion operation is repeated several times, but when the insertion operation is repeated several dozen times, errors accumulate and problems such as loosening of the belt 7 occur. There is a problem.

Further, as another conventional example, a patient transfer device disclosed in Japanese Patent Application Laid-Open No. 60-5151 is known. This invention is
As stated in the upper right column of Article 322 of the same bulletin,
Synchronization of the expansion and contraction of the upper and lower arms and the rotation of the upper and lower arm cover take-up rollers is achieved by combining the drive motors of the upper and lower arms and the motor of the take-up roller using a synchronization system.

Here, when the above two motors are coupled by a synchronous system, when the upper arm is moved to extend or contract, this serves as a trigger, and the above-mentioned winding roller rotates at a constant speed corresponding to the moving speed of the upper and lower arms. It does not mean that the speed of roller rotation is adjusted according to the speed of expansion and contraction.

Moreover, this prior art example does not include any prediction that the speed of the telescoping mechanism will be reduced due to the resistance of the patient's weight, nor does it describe any techniques for preventing such adverse effects.

In this conventional example, although it is possible to prevent the speed of the telescoping mechanism from slowing down by using a powerful motor, it increases the feeling of pressure on the patient.
In fact, it is not desirable to increase the output of the motor in the event that hair or the like gets caught, or in consideration of miniaturization and lower power consumption of the device.

Furthermore, as another conventional example, JP-A-58-
A reloading and conveying device disclosed in Japanese Patent No. 41555 is known.

However, in this other conventional example, since the endless belt is wound around a pair of plates once, the endless belt does not become slack even if the speed of the plate decreases when the plate is inserted. On the other hand, there is a drawback in that the position of the patient on the device cannot be corrected by the operation of the endless belt alone without moving the plate.

This invention was made to solve the above-mentioned conventional problems, and is a control of a patient transfer device that can always perform patient transfer operations in good condition without causing speed reduction due to resistance due to the patient's weight. The purpose is to provide a method of movement.

<Means for Solving the Problems> This invention was made to solve the above problems, and consists of two flat plates that are stacked one above the other with a slight gap between them and are integrated. The insertion plate is attached to the board so that it can move forward and backward in the horizontal direction, and a pair of upper and lower rollers are placed behind the board. The lower belt is wound around a roller and its ends are fixed to each roller, and both ends of the lower belt, which is led downward from the upper surface of the lower flat plate around both ends, are fixed near the substrate, and each of the rollers is adjusted separately. A roller driving means for reversing the rotation is provided, and furthermore, an advancing/retracting driving means for advancing and retracting the insertion plate is provided on the base plate, and during insertion, the insertion plate is inserted under the patient by the advancing/retracting driving means. When the insertion plate is retracted, the upper and lower rollers are driven to cause the belt to retract together with the insertion plate.In the patient transfer device, the insertion plate is moved when the insertion plate drive motor is controlled so that the operation speed of the insertion plate is constant. Detect the position, calculate the amount of belt to be unwound by the upper roller or lower roller from the movement position of the insertion plate obtained by this, find the rotational position of the roller calculated backward from the roller diameter, This is to control the position of the roller drive motor so that it reaches the calculated rotational position.

<Function> According to the present invention, since the belt is given a different degree of freedom with respect to the insertion plate, the insertion plate and the belt roller can be controlled not by their speed relationship but by their absolute positional relationship. Thus, the insertion plate and the belt roller can always be maintained in an appropriate positional relationship. Therefore, it is possible to prevent position errors as much as possible, which was a problem when controlling only by conventional speed control.

<Embodiment> FIG. 1 shows an embodiment of an apparatus for carrying out the method of the present invention.

The operation of the insertion plate 6 is performed using the normal PI speed control means 25.
However, belt rollers can be used with PD or
A PID position control means 26 is used.

In the figure, 27 is a position conversion block, 28 is an insertion plate motor + insertion mechanism, and 29 is a belt roller motor +
It is a roller mechanism. For belt roller rotation angle θ and target angle θd, in the case of PD control, i = Kp (θd - θ) + Kd (θ〓d - θ〓) ... (3) In the case of PID control, i = Kp (θd - θ) + Kd (θ〓−θ〓) +Ki∫(θd−θ)dt ......(4) Determine the motor current value. The target value θd of the belt roller is used to calculate the operating position x of the insertion plate.

The calculation function is the position conversion block 27 in Figure 1.
It is.

The calculation algorithm in this block is shown below.

In FIG. 2, if the position of the tip of the insertion plate 6 is x, the rotation angle of the upper roller 8 is θ, and the rotation angle of the lower roller 9 is θ ₂ , then when the insertion plate 6 moves Δx in the insertion operation, the upper belt It is sufficient that the lower belt is unwound by 2Δx without being operated.

Also, if the rotation radius of belt rollers 8 and 9 is r ₂ , then from 2Δx=r ₂ Δθ ₂ ...(5), the increase in rotational position of the lower roller Δθ ₂ is Δθ ₂ = 2Δx/r ₂ ...(6) becomes. However, r ₂ gradually changes depending on the number of times the belt is wound around the roller.

Therefore, if t is the belt thickness, n ₂ is the number of turns of the belt, and r ₀ is the radius of the belt roller 9 itself, then r ₂ = r ₀ + n ₂ t ...(7), so in the end, Δθ ₂ = 2Δx /r ₀ n ₂ t (8) The increase in rotational position of the belt roller Δθ ₂ can be obtained.

Assuming that the target position of the belt roller for all rotations is θ _2c , the next target position θ′ _2c can be found as θ′ _2c =θ _2c +Δθ ₂ .

That is, since θ' _2c is the next rotational target position of the lower roller, the motor is controlled by the following equation in which θ _d in equation (4) is replaced by θ' _2c .

i ₂ = Kp ₂ (θ′ _2c −θ ₂ )+Kd ₂ (θ〓′ _2c −θ〓 ₂ )+K _i2 ∫(θ′ _2c −θ ₂ )dt……(9) Here, i ₂ is the lower roller drive Drive current of motor for
θ ₂ is the current angular position of the lower roller.

The positional relationship between the belt roller drive motor and the roller is given as a linear relationship by constants due to the unique transmission system such as the reduction ratio of gears, and therefore equation (9) can be expressed using the rotational position of the motor. Therefore, the control system may have a configuration related to motor rotation. There is no need to directly measure the rotation angle of the belt roller itself using a complicated method.

The gains Kp ₂ , Kd ₂ , and Ki ₂ in equation (9) above can be determined by determining the transfer function from the dynamic characteristics of the entire system and setting them so that the system exhibits stable behavior, but in the case of this configuration, The interrelationship between the insertion plate and the patient's weight is complex, and it is difficult to quantify the dynamic characteristics.
Therefore, it is usually determined through trial and error experiments.

During the retraction operation following the insertion operation, the upper roller,
Since the amount of belt unwound (unwound) from the lower roller is Δx, it can be calculated by setting 2Δx in equation (8) to Δx.

<Effects> As described above, this invention controls the insertion plate and belt roller of the patient transfer device not by their speed relationship but by their absolute positional relationship. The proper positional relationship is always maintained.

Therefore, phenomena such as accumulation of position errors, which was a problem when controlling only by speed control, do not occur.

Therefore, the patient transfer operation can always be performed in a good condition for continuous operation.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an apparatus for implementing the control method of the present invention, Fig. 2 is an enlarged side view showing the relationship between the belt and the upper and lower rollers, Fig. 3 is a perspective view of the patient transfer device, and Fig. 4 is an enlarged side view showing the relationship between the belt and upper and lower rollers. Perspective view of the seat portion same as above, No. 5
Figures a, b, c, and d are front views showing each step of lifting by the above device, Figure 6 is a front view showing slack in the belt, and Figure 7 is a front view showing how to correct misalignment due to rotation of the roller. 8 are block diagrams showing an example of a conventional control method. 6... Insertion plate, 7... Belt, 8... Upper roller, 9... Lower roller, 25... PI speed control means,
26...PD or PID position control means, 27...
...Position conversion block, 28...Insertion plate motor + insertion mechanism, 29...Belt roller motor + roller mechanism.

Claims (1)

[Claims] 1. An insertion board consisting of two flat plates stacked one above the other with a slight gap is attached to the board so that it can move forward and backward in the horizontal direction, and a pair of upper and lower rollers are placed behind the board to insert the board. Both ends of the upper belt, which is passed up and down from the front edge of the flat plate at the top of the board and guided backwards, are wound around the upper and lower rollers, and the ends are fixed to each roller, and the belt is passed around both ends from the top surface of the flat plate at the bottom. Both ends of the lower belt guided downward are fixed close to the substrate, roller driving means are provided for driving each of the rollers in forward and reverse directions separately, and furthermore, the substrate is provided with driving means for advancing and retracting the insertion plate, At the time of insertion, the insertion plate is advanced by a drive means for advancing and retracting, and the upper roller is stopped and a belt is let out from the lower roller to insert the insertion plate under the patient. When the insertion plate is retracted, the insertion plate is moved up and down In a patient transfer device in which the belt moves back together with the insertion plate by driving rollers, the moving position of the insertion plate is controlled when controlling the insertion plate drive motor so that the operating speed of the insertion plate is constant. Calculate the amount of belt to be unwound by the upper roller or lower roller from the position detecting means to be detected and the moving position of the insertion plate obtained by this position detecting means, and calculate the rotational position of the roller back calculated from the roller diameter. 1. A method of controlling a patient transfer device, comprising: position control means for controlling the position of a motor for driving an upper roller or a lower roller so that the motor is at a calculated rotational position.