JP2006137391A - Method of detecting malfunction of vehicle speed sensor on carrying device with power assist - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent trouble in traveling due to sensor failure by quickly and accurately detecting the malfunction of a vehicle speed sensor. <P>SOLUTION: Determination is made on the presence/absence of L-side (determination object side) drive output (S11), and if the drive output is not present, a counter 1 is cleared (S14), and, if present, determination is then made on the presence/absence of a vehicle speed sensor signal (S12). If a signal is present, the counter 1 is cleared (S13), and, if not, the counter 1 is made to count up (S15). Next, the speed of an R-side (non-determination object side) drive wheel is detected and compared with α (S21). If the speed is not greater than α, a counter 2 is cleared (S27), and if greater than α, the speed of a drive wheel on the determination object side is detected and compared with β (S22). If the speed is greater than β, the counter 2 is cleared (S23), and, if not, the counter 2 is made to count up (S28). After that, the counter values C1 and C2 of the counter 1 and 2 are compared with specified values CS1 and CS2 (S24), and, if C1 is larger than CS1 or C2 is larger than CS2, judgment is made that the sensor is malfunctioning (S25). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control method for a transport device used for moving a sick person, a luggage, and the like, and more particularly, to an abnormality detection technique for a vehicle speed sensor in a transport device that supplies an assist force during movement by an electric motor.

  In hospitals, nursing homes, factories, warehouses, etc., a large number of transfer devices powered by motors are used, such as electric beds and stretchers, food carts and cargo carts. In such a conveying apparatus, driving wheels driven by an electric motor are attached to a main body frame having casters arranged at four corners, and assist force during movement is supplied by the driving wheels. Further, an electric motor, a battery for power supply, a controller for motor control, and the like are attached to the main body frame. On the main body frame, a mat is placed if it is a bed, and a cargo bed is provided if it is a carriage.

  Moreover, a handle for power assist is generally provided with a handle for operation, and Japanese Patent Application Laid-Open No. 11-262111 discloses a configuration for detecting the force applied to the handle and controlling the assist force. Yes. There, a sensor for detecting an operating force is provided at the left and right bases of the handle, and the force applied to the handle when the transport device is moved is detected by both sensors. Then, based on the detected left and right handle operating forces, the rotations of the left and right drive wheels arranged on both sides of the apparatus are adjusted to appropriately control the assist force and the traveling direction of the transport device.

On the other hand, for assist force control, a power assisted transfer device has been developed that realizes a more sophisticated and user-friendly control mode by detecting the traveling speed of the drive wheels. In such a transport apparatus, a vehicle speed sensor that detects a traveling speed is provided on an axle, a motor shaft, or the like. For example, when the motor rotates, a rotation pulse signal is output according to the motor rotation speed. Yes. Since the rotational speed of the motor and the rotational speed of the driving wheel have a correlation, in this case, the rotational speed of the driving wheel, that is, the traveling speed (vehicle speed) of the bed is detected by detecting the motor rotational speed based on the rotational pulse signal. It can be detected. Then, based on the acquired vehicle speed and steering wheel operation force information, the assist force of the transfer device is controlled to perform control that matches the operator's request and sensitivity.
Japanese Utility Model Publication No. 48-44793 JP 60-122561 JP JP 7-257387 A JP-A-8-175381 Japanese Patent Laid-Open No. 10-35499 Japanese Patent Laid-Open No. 11-262111 Japanese Patent Application No. 2004-257494

  However, in the transfer device that controls the assist force based on the vehicle speed information as described above, when an abnormal situation such as a signal not being output or an abnormal signal being output due to a failure of the vehicle speed sensor, Control based on travel speed cannot be performed. For this reason, when the vehicle speed sensor breaks down, there is a possibility that normal conveyance operation cannot be executed. Even if such a situation occurs, if the sensor for detecting the steering wheel operation force is normal, it is possible to perform the assist force control based on the sensor, but it is easier for the operator to use than the control considering the vehicle speed information. It is undeniable that will decline.

  An object of the present invention is to quickly and accurately detect an abnormality of a vehicle speed sensor, and to prevent a traveling trouble due to a sensor failure.

  According to the present invention, there is provided a vehicle speed sensor abnormality detection method for a power assisted transfer device, wherein a plurality of drive wheels driven by an electric motor and a rotational speed of the drive wheels provided corresponding to each of the drive wheels are detected. Provided with a power assist that includes a plurality of vehicle speed sensors and a handle attached to the operation force sensor, and a driving assist force controlled based on detection values of the vehicle speed sensor and the operation force sensor is applied to the drive wheels. An abnormality detection method for the vehicle speed sensor in a transport device, wherein a vehicle speed signal cannot be acquired from the vehicle speed sensor that is a determination target when the steering wheel is operated and a driving assist force is applied to the drive wheels. In this case, it is determined that an abnormality has occurred in the vehicle speed sensor to be determined.

  In the present invention, when there is a driving output to the electric motor and a driving assist force is applied to the driving wheel, it is determined whether or not there is a signal from a vehicle speed sensor that should normally be present, and the signal cannot be acquired. In this case, it is determined that there is a sensor abnormality. For this reason, since the state of the vehicle speed sensor is determined only when there is a drive output, there is no need to constantly monitor the vehicle speed sensor, and the burden on the control device is reduced.

  According to another embodiment of the present invention, there is provided a vehicle speed sensor abnormality detection method in a power assisted transfer device, and a plurality of drive wheels driven by an electric motor, and a rotational speed of the drive wheels provided corresponding to each of the drive wheels. A power provided with a plurality of vehicle speed sensors to be detected and a handle attached to the operation force sensor, and a driving assist force controlled based on detection values of the vehicle speed sensor and the operation force sensor. A method of detecting an abnormality of the vehicle speed sensor in the assisted transfer device, wherein the first drive wheel indicates a speed of the drive wheel corresponding to the vehicle speed sensor based on a detection value from the vehicle speed sensor that is not a determination target. When the speed is detected and the first driving wheel speed is compared with a first threshold, and the first driving wheel speed exceeds the first threshold, the vehicle to be determined Based on a detection value of the sensor, a second driving wheel speed indicating a speed of the precursor driving wheel corresponding to the vehicle speed sensor is detected, and the second driving wheel speed is compared with a second threshold value, and the second driving is performed. When the wheel speed is equal to or lower than the second threshold, it is determined that an abnormality has occurred in the vehicle speed sensor to be determined.

  In the present invention, when the driving wheel corresponding to the vehicle speed sensor that is not the determination target is activated and exceeds the first threshold value, the speed of the driving wheel on the determination target side is detected, and when it is equal to or lower than the second threshold value. It is determined that the vehicle speed sensor is abnormal. Since this determination is made based only on the vehicle speed and is based on information not directly related to the steering operation, even if the steering wheel is operated back and forth due to load fluctuations during the transport operation, and the drive output is repeatedly turned ON / OFF. Thus, the abnormality of the vehicle speed sensor can be detected without being affected by this.

  In the vehicle speed sensor abnormality detection method in the power assisted transfer device, when the state in which the second drive wheel speed is equal to or lower than the second threshold continues for a predetermined time or more, an abnormality occurs in the vehicle speed sensor to be determined. You may make it judge. Further, as the first threshold value, a maximum value of a speed difference (for example, an inner / outer wheel speed difference) generated between the drive wheels when the transport device turns on the spot or turns at a small angle may be set. Further, a value smaller than the first threshold value may be set as the second threshold value.

  In the vehicle speed sensor abnormality detection method in the power assisted transfer device, when the steering wheel is operated and a driving assist force is applied to the drive wheel, when a vehicle speed signal cannot be obtained from the determination target vehicle speed sensor, It may be determined that an abnormality has occurred in the vehicle speed sensor to be determined. As a result, even when the vehicle speed sensors that are not subject to determination are both in an abnormal state, it is possible to detect abnormality of the vehicle speed sensor.

  In the vehicle speed sensor abnormality detection method in the power assisted transfer device, a state in which a vehicle speed signal cannot be acquired from the determination target vehicle speed sensor when the steering wheel is operated and a driving assist force is applied to the drive wheel. If it continues for a predetermined time or more, it may be determined that an abnormality has occurred in the vehicle speed sensor to be determined. Further, when a steering wheel arranged on the same side as the determination target vehicle speed sensor is operated and a driving assist force is applied to the driving wheel, when a vehicle speed signal cannot be obtained from the determination target vehicle speed sensor, It may be determined that an abnormality has occurred in the vehicle speed sensor to be determined.

  According to the abnormality detection method of the vehicle speed sensor in the power assisted transfer device of the present invention, the vehicle speed signal is output from the vehicle speed sensor to be determined when the steering wheel is operated and the driving assist force is applied to the drive wheel. When it cannot be obtained, it is determined that an abnormality has occurred in the vehicle speed sensor, so the state of the vehicle speed sensor is determined only when there is a drive output, and it is not necessary to constantly monitor the vehicle speed sensor, reducing the burden on the control device. It becomes possible to plan.

  According to the abnormality detection method for the vehicle speed sensor in the other power assisted transfer device of the present invention, the first drive wheel speed is detected based on the detection value from the vehicle speed sensor that is not the object of determination, and the first threshold value. If the first drive wheel speed exceeds the first threshold, the second drive wheel speed is detected based on the detection value of the vehicle speed sensor that is the determination target, and the second threshold is calculated. In comparison, when the second driving wheel speed is equal to or lower than the second threshold value, it is determined that an abnormality has occurred in the vehicle speed sensor to be determined, so that the abnormality determination of the vehicle speed sensor can be performed only by the vehicle speed. For this reason, the abnormality determination of the vehicle speed sensor can be executed based on the information not directly related to the steering operation, and the influence is caused even if the steering wheel is operated back and forth and the driving output is repeatedly turned ON / OFF due to the load fluctuation during the transportation operation. Abnormality of the vehicle speed sensor can be detected without being subjected to this. Therefore, the detection accuracy of the sensor abnormality is improved, the safety as the transport device is improved, and it is possible to take more appropriate measures such as repair according to the abnormal situation. Further, even when the conveyance device is moved by pushing a place other than the handle, it is possible to detect an abnormality in the vehicle speed sensor.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a front view showing an example of an electric bed (transport device) for a hospital to which an abnormality detection method for a vehicle speed sensor according to a first embodiment of the present invention is applied. FIG. 2 is a plan view showing an outline of the electric bed in FIG. It is. The hospital electric bed according to the present embodiment includes a drive unit 1 and a bed unit 2. A motor 1 and various actuators are accommodated in the drive unit 1, and a mat 3 is placed on the bed unit 2. The bed portion 2 is supported by an arm 4 attached to the drive unit 1. The arm 4 is driven by the drive unit 1, and the height and posture of the bed unit 2 can be changed by the vertical movement of the arm 4.

  Safety fences 5 are attached to both sides of the bed portion 2. A bed moving handle 6 is attached to the front end side (the user's head side) of the bed portion 2. Here, the front and rear mean the longitudinal direction of the bed, and the side means both ends in the width direction (left and right direction) orthogonal to the longitudinal direction. As shown in FIG. 3, one handle 6 is provided on each of the left and right sides (6L, 6R). A handle operating force sensor 7 (7L, 7R, hereinafter referred to as sensor 7) provided at the front end of the bed 2 is provided. Abbreviated). A control panel 8 is disposed between the handles 6, and a power switch 8a, an emergency stop switch 8b, a bed lift switch 8c, an LED display panel 8d, and the like are provided.

  The sensor 7 detects an operation load applied to the handle 6 when the bed is moved. The handle 6 is connected to a torsion bar (not shown) in the sensor 7, and a torsional displacement occurs in the torsion bar in accordance with the operating force of the handle 6. The sensor 7 measures the direction and amount of the torsional displacement using a potentiometer, and calculates the direction and magnitude of the operating force applied to the handle 6 based on the measured value. The sensor 7 individually detects the handle operating force by the left and right sensors 7L and 7R, and the traveling direction of the bed is also controlled based on the detected value.

  For example, when the operator pushes the handle 6 to advance the bed, the torsion bar is twisted in one direction by the pressing force of the handle 6, and the traveling direction of the bed is detected from the twist direction at this time. In addition, if the handle 6 is pressed strongly, the torsion angle of the torsion bar increases, and the torsion angle changes due to the handle pressing force. Based on this, a change in the force of pressing the bed can be detected. Further, when the outputs of the sensors 7L and 7R are compared and it is detected that the force pushing the left handle 6L is large, it is determined that the operator is going to bend the bed to the right. Conversely, when the force pushing the right handle 6R is large, it is determined that the operator is trying to bend the bed to the left.

  FIG. 4 is a perspective view showing the configuration of the drive unit 1. The drive unit 1 has a configuration in which a drive unit 12, an elevating actuator 13, and the like are provided on a steel frame 11. The steel frame 11 includes a main frame 11a extending in the front-rear direction and a connecting bar 11b provided so as to connect the main frames 11a and extending in the width direction. Casters 14 are attached to the lower surfaces of both ends of the main frame 11a. As shown in FIG. 1, a synthetic resin cover 15 is attached to the frame 11, and FIG. 4 shows a state in which the cover 15 is removed.

  The drive unit 12 is placed on the motor base 16. In the drive unit 12, two sets of a DC motor 17 (17L, 17R) and a speed reduction mechanism 18 (18L, 18R) are provided. Two rotating shafts 19 project from the left and right sides of the drive unit 12, and the rotation of the motor 17 is decelerated by the speed reduction mechanism 18 and output to the rotating shaft 19. Drive wheels 21 (21L, 21R) are fixed to each rotary shaft 19. The drive wheel 21 includes a wheel 22 and a rubber tire 23 fixed to the rotary shaft 19.

  The drive unit 12 is further provided with a vehicle speed sensor 39 (39L, 39R, hereinafter abbreviated as a sensor 39 as appropriate) for detecting the traveling speed of the electric bed. The sensor 39 is composed of a multipolar magnetized magnet attached to the rotating shaft of the motor 17 and a magnetic detecting element that is disposed in the vicinity of the magnet and outputs a pulse signal when the magnetic pole changes. When the motor 17 rotates, a rotation pulse signal is output from the magnetic detection element according to the motor rotation speed. The rotational speed of the motor 17 and the rotational speed of the driving wheel 21 have a correlation, and the rotational speed of the driving wheel 21, that is, the traveling speed (vehicle speed) of the bed can be detected by detecting the motor rotational speed by the sensor 39.

  A tower 24 is erected on the motor base 16. The tower 24 is connected to the lifting / lowering actuator 13, and the drive unit 12 moves up and down by the operation of the lifting / lowering actuator 13, so that the driving wheel 21 contacts and separates from the floor surface (traveling surface) 25. FIG. 5 is an explanatory diagram showing a connection structure between the drive unit 12 and the lift actuator 13. As shown in FIG. 5, the base 24 a of the tower 24 is rotatably supported on the arm 27 by a pivot 26. The arm 27 is fixed to the connecting bar 11b, and the motor base 16 is supported by the frame 11 so as to be swingable in the vertical direction (X direction in FIG. 5) about the pivot 26.

  A long hole 28 is formed in the upper portion of the tower 24. A pin 31 attached to the plunger 29 is inserted into the long hole 28 so as to be movable in the front-rear direction (left-right direction in the figure). The plunger 29 is attached to the upper part of the tower 24 so as to be movable in the front-rear direction, and is connected to the plunger 33 of the elevating actuator 13 via a spring 32. The elevating actuator 13 is driven by a DC motor 34, and the plunger 33 operates in the Y direction in FIG. The left end of the lifting actuator 13 in the figure is supported by a bracket 35 fixed to the connecting bar 11b so as to be swingable.

  As described above, the motor base 16 is connected to the lift actuator 13 via the spring 32. When the elevating actuator 13 is actuated to extend the plunger 33, the tower 24 is pushed through the spring 32, the plunger 29, and the pin 31, and the motor base 16 is rotated clockwise in FIG. Thereby, the drive wheel 21 moves to the floor surface 25 side and is pressed against the floor surface 25 with a predetermined ground load. On the other hand, when the plunger 33 contracts, the motor base 16 rotates counterclockwise around the pivot 26. As a result, the drive wheel 21 is detached and raised from the floor surface 25 and stored in a position separated from the floor surface 25.

  The frame 11 is further provided with a battery 36 for power supply, a controller (control means) 37 for motor control, an actuator 38 for bed posture control, and the like. The battery 36 supplies power to the motors 17 and 34, the controller 37, the actuator 38, and the like. The controller 37 is connected to the control panel 8 and performs drive control of each motor, actuator, etc. in accordance with an input instruction from the operator.

  FIG. 6 is a block diagram showing the configuration of the control system of the controller 37. The controller 37 is provided with input circuits 42 and 43, a drive output circuit 44, a power supply circuit 45 and a power supply input circuit 46 with the CPU 41 as the core. The input circuits 42 (42L, 42R) are connected to the sensors 7L, 7R, respectively, and a torque signal indicating the operating force of the left and right handles 6 is input. The input circuit 43 (43L, 43R) is connected to the sensors 39L, 39R, respectively, and receives a vehicle speed signal indicating the rotational speed of the left and right drive wheels 21.

  The drive output circuit 44 (44L, 44R) is connected to the left and right motors 17L, 17R. The motors 17L and 17R are PWM-controlled by the CPU 41, and a PWM duty command value is output from the CPU 41 to the drive output circuit 44. In response to this, the drive output circuit 44 supplies the motor 17 with a pulse voltage corresponding to the command value. The power circuit 45 is connected to the battery 36, and power is supplied to the CPU 41 from the battery 36 via the power circuit 45 and the power input circuit 46.

  A counter 47 is provided in the CPU 41. The counter 47 accumulates the count value in a cycle of a predetermined time using the internal clock of the CPU 41. The accumulated count value can be appropriately reset (cleared) by the CPU 41. The counter 47 can be provided with a plurality of counters capable of individually accumulating or resetting count values (counter 1, counter 2, etc.).

  In such a hospital electric bed, the following control is performed to detect an abnormality of the vehicle speed sensor 39 during assist force control. FIG. 7 is a flowchart showing a processing procedure of the vehicle speed sensor abnormality detection method according to the first embodiment of the present invention. Although the abnormality detection process for the L-side vehicle speed sensor 39L will be described here, the same process as in FIG. 7 is performed for the R-side vehicle speed sensor 39R, and the L-side and R-side abnormality detection processes are performed simultaneously. Executed.

  The processing in FIG. 7 is performed by the CPU 41. Here, first, in step S1, it is determined whether or not the L-side drive output is being output. In this case, the drive output is a signal (motor drive signal) for driving the motor 17L, which is output from the CPU 41 to the drive output circuit 44L in accordance with the operating force of the handle 6. The drive output is “with output” when the handle 6L is operated at a predetermined angle or more. When the handle 6L is not operated or the operation angle is less than the predetermined angle, the CPU 41 outputs a drive output circuit 44L. The motor drive signal is not output, and “no output” is set.

  If there is no drive output, the process proceeds to step S7, and the count value in the counter 47 is cleared. If there is no drive output in step S1, the bed is in a stopped state, an extremely low speed state that can be regarded as such, or coasting, and in this case, it is not practically possible to determine whether or not the vehicle speed sensor is abnormal. Since it is possible, the count value is cleared and the process proceeds to step S4.

  On the other hand, if there is a drive output, the process proceeds to step S2 to determine the presence or absence of a signal from the vehicle speed sensor 39L. The presence / absence of a signal from the vehicle speed sensor 39L is determined based on whether or not a pulse signal from the sensor has changed (rising or falling of a pulse). When there is a pulse interruption, it is determined that there is a signal. If there is a signal from the vehicle speed sensor 39L, it is determined that the sensor is operating normally, the process proceeds to step S3, the count value in the counter 47 is cleared, and the process proceeds to step S4.

  On the other hand, if it is determined in step S2 that there is no pulse interruption from the vehicle speed sensor 39L and “no signal” is determined, the process proceeds to step S8, and the count value in the counter 47 is counted up. In this case, although the drive output has been confirmed in step S1, there is no signal from the vehicle speed sensor 39L, and some abnormality may have occurred in the vehicle speed sensor 39L. Therefore, in such a case, the count value is counted up and sensor abnormality recognition is started.

  After the processes in steps S3 and S8, the process proceeds to step S4, where the count value is compared with a predetermined specified value CS. The specified value CS is a vehicle speed sensor abnormality determination value, and a numerical value such as CS = 100 is set, for example. When the count value does not reach the predetermined specified value CS, the process returns to step S1 and the above-described processing is repeated. On the other hand, when the count value exceeds the specified value CS, that is, in the example of CS = 100, when the processing is performed at intervals of 0.1 seconds, the signal from the vehicle speed sensor 39L is output although there is a drive output. If no state has occurred continuously for 10 seconds, the process proceeds to step S5, where it is determined that there is a sensor abnormality. In step S6, the motor drive is stopped and the routine is exited.

  As described above, in the control process of FIG. 7, when there is a drive output and a driving assist force is applied to the drive wheel 21, it is determined whether or not there is a signal from the vehicle speed sensor 39 that should normally be present, and there is no signal. If the state continues for a predetermined time or more, it is determined that there is a sensor abnormality and the motor drive is stopped. Therefore, according to the control process, since the state of the vehicle speed sensor 39 is determined only when there is a drive output, it is not necessary to constantly monitor the vehicle speed sensor 39, and the control burden on the CPU 41 is reduced. When the motor is stopped due to a sensor abnormality, an error is displayed on the LED display panel 8d, and the fact is transmitted to the operator. As a result, the operator can recognize the abnormality of the vehicle speed sensor and can take measures such as repair according to the abnormality.

  Although the operability is reduced by the error display, it is also possible to cancel the control by the vehicle speed sensor and execute only the control based on the steering wheel operating force. In this way, the operator considers the environment where the bed is currently placed, and when the bed does not disturb the surroundings, the operator appropriately stops on the spot to investigate the cause of the failure or repair the failure. On the other hand, when the bed is in a narrow passage, the bed can be moved to a wide place while recognizing the failure state in order to move the bed to a place where it does not get in the way.

  Next, an abnormality detection method for a vehicle speed sensor, which is Embodiment 2 of the present invention, will be described. FIG. 8 is a flowchart showing the processing procedure. In this embodiment, the abnormality detection process for the sensor 39L will be described, but the same process as in FIG. 8 is executed for the sensor 39R, and the abnormality detection process for the L side and the R side is executed simultaneously. In the present embodiment, the same members and portions as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The control of the second embodiment is also applied to the hospital electric bed similar to that of the first embodiment, and step A in which processing similar to steps S1 to S3, S7, and S8 in FIG. 7 is performed, and step B unique to the present embodiment. Is implemented. In step A, as described above, it is first determined in step S11 whether or not there is an L side drive output. If there is no drive output, the process proceeds to step S14, the count value in the counter 47 is cleared, and the process proceeds to step B. In this case, two different counters 1 and 2 are provided in the counter 47, and the counter value of the counter 1 is cleared here.

  If there is a drive output in step S11, the process proceeds to step S12, and the presence / absence of a signal from the vehicle speed sensor 39L is determined. If there is a signal from the vehicle speed sensor 39L, the process proceeds to step S13, the count value of the counter 1 is cleared, and the process proceeds to step B. On the other hand, if there is no pulse interrupt from the vehicle speed sensor 39L in step S12, the process proceeds to step S15, the count value of the counter 1 is incremented, and the process proceeds to step B.

  Here, when the abnormality detection of the vehicle speed sensor is performed only by the process of Step A, the sensor abnormality may not always be accurately detected depending on the operation mode of the transport device. That is, when the operator presses the handle 6 in a stopped state in order to move the bed, a large operating force is first applied to the handle 6. As a result, the motor 17 is activated and assist force is applied. However, as the assist force is applied, the force with which the operator pushes the bed is reduced, and the handle operation force is reduced. The handle 6 is provided with a region called a dead zone within a predetermined angle range before and after the center point, and no assist force is applied when the handle is within the dead zone. Accordingly, when the handle operating angle temporarily becomes smaller than the dead zone angle as the handle operating force decreases, the application of assist force is stopped at that time.

  When the assist force is lost, a large force is required to move the bed, the operator pushes the handle 6, and the handle operating angle becomes larger than the dead zone angle again. Then, the motor 17 is activated again, the assist force is restored, and the handle operating force is reduced. When the assist force is applied and the bed moves away from the operator, the handle operation force decreases and the drive output also decreases. When the handle 6 enters the dead zone, the assist force becomes zero. When the assist force decreases and the operator catches up with the bed and presses the handle 6, the handle operation force increases again, and a drive output is generated and increased. That is, during bed conveyance, this operation is repeated due to load fluctuation, and in some cases, ON / OFF of the drive output is repeated.

  However, when ON / OFF of the drive output is repeated in this way, in step S11 of step A, the counter value is cleared in step S14 when the drive output is OFF. For this reason, even if the vehicle speed sensor 39 fails due to ON / OFF of the drive output, the counter value is not accumulated, and even if the counter value is accumulated due to the failure, if the drive output is turned OFF even once, Will be cleared. Therefore, when the above-described ON / OFF occurs during bed conveyance, it may be assumed that a failure of the vehicle speed sensor 39 cannot be detected.

  Therefore, in the control process of the second embodiment, in addition to the above-described step A, step B for detecting abnormality of the vehicle speed sensor 39L based on the speed of the left and right drive wheels 21 is executed to improve the accuracy of sensor abnormality detection. ing. In this step B, when the driving wheel (in this case, the driving wheel 21R) corresponding to the vehicle speed sensor 39R that is not the determination target is operating, the speed of the determination target side driving wheel is detected, and is determined from the predetermined value. Is also small, it is determined that the vehicle speed sensor 39R is abnormal. In other words, if the driving wheel that is not subject to determination is rotating, it is considered that the conveying device normally moves along with it, and the driving wheel on the determination subject side is also operating. If the wheel speed is less than or equal to the predetermined value, it is determined that an abnormal situation has occurred.

  In step B, first, in step S21, the speed (first driving wheel speed) of the driving wheel that is not the object of determination (here, the driving wheel 21R on the R side) is detected, and the detected value α ( km / h) (first threshold). That is, in step S21, it is determined whether a driving wheel that is not a determination target is driving and whether the speed exceeds α. Here, in step S21, the operation of the non-determination drive wheel is viewed as described above, as long as the other-side drive wheel is rotating, the determination-side drive wheel is normally operating. Because it is considered. However, if the bed is turning on the spot or turning at a small angle, the inner ring side may stop and only the outer ring side may be driven. The drive wheel may have stopped. For this reason, in step S21, the driving wheel speed that is not subject to determination is compared with α in consideration of the case where the bed is turning on the spot. Therefore, as this α, the maximum value of the speed difference generated between the inner and outer wheels when the bed turns on the spot or turns at a small angle is set.

  If the driving wheel speed not subject to determination is α or less, it is determined that the driving wheel 21R is slow or the bed is turning on the spot or turning at a small angle, so that the driving wheel 21R is slow, and the process proceeds to step S27. The counter value of the counter 2 in the counter 47 is cleared. On the other hand, if the driving wheel speed not subject to determination exceeds α, the process proceeds to step S22, and this time, the speed of the driving wheel 21L on the determination target side (second driving wheel speed) is detected. The specified value β (km / h) (second threshold value) is compared. As β, a speed value (for example, 0.5 km / h) at which it can be determined that the determination target driving wheel is in a stopped state is set. In this control, β is set to a value smaller than α (β <α).

  In step S22, when the speed of the drive wheel 21L is higher than β, a signal indicating a speed equal to or higher than a predetermined value also from the vehicle speed sensor 39L on the determination target side when the drive wheel 21R that is not the determination target is operating. Is obtained. Accordingly, since the drive wheel 21L is also rotated together with the drive wheel 21R and the information is obtained from the vehicle speed sensor 39L, it is determined that there is no abnormality in the sensor, the process proceeds to step S23, and the counter 2 counter Clear the value.

  On the other hand, when the speed of the driving wheel 21L is equal to or lower than β in step S22, the driving wheel 21L on the determination target side 21L is operated even though the driving wheel 21R that is not the determination target operates at a speed exceeding α. The speed is not detected. Therefore, although it is highly likely that the drive wheel 21L is rotating together with the drive wheel 21R, the information is not obtained from the vehicle speed sensor 39L, and it is determined that an abnormality has occurred in the sensor. Then, the counter value of counter 2 is counted up. Note that the driving wheel on the judgment target side becomes the inner wheel side when turning on the spot, and the vehicle speed may be β or less, and it may be erroneously determined as “sensor abnormality”. This mis-judgment is avoided by setting.

  After performing the process of step S23 or S28, the process proceeds to step S24, where the count value C1 of the counter 1 is compared with the predetermined specified value CS1, and the count value C2 of the counter 2 is compared with the predetermined specified value CS2. The specified values CS1 and CS2 are vehicle speed sensor abnormality determination values, and CS1 is set to a numerical value such as CS1 = 100, for example, as in the case of CS of the first embodiment. CS2 is an abnormality determination value in Step B, and a numerical value such as CS2 = 50 is set, for example. If one of C1 and C2 exceeds CS1 and CS2 in step S24, it indicates that one of steps A and B has detected a sensor abnormality for a predetermined time or more.

  Therefore, in the above example, when the processing is performed at intervals of 0.1 second, the speed of the driving wheel 21R exceeds α and the speed of the driving wheel 21L is equal to or lower than β for 5 seconds continuously. Therefore, C2> CS2 = 50, and it is determined that the sensor is abnormal. In addition, when both the left and right vehicle speed sensors 39L and 39R fail, C2 ≦ CS2 with respect to step B, but there is a drive output but no signal from the vehicle speed sensor 39L for 10 seconds continuously. Therefore, C1> CS1 = 100, and it is determined that the sensor is abnormal. In this example, CS1> CS2, and the abnormality detection in step B is preferentially applied.

  If C1> CS1 or C2> CS2 in step S24, the process proceeds to step S25, where it is determined that there is a sensor abnormality, the process proceeds to step S26, the motor drive is stopped, and the routine is exited. When the motor is stopped due to a sensor abnormality, an error is displayed on the LED display panel 8d, and the fact is transmitted to the operator. On the other hand, when C1 ≦ CS1 and C2 ≦ CS2, the count values C1 and C2 do not reach the predetermined specified values CS1 and CS2, and it is not determined that there is a sensor abnormality, and the process returns to step S11 and described above. Repeat the process.

  Thus, in the control process of FIG. 8, in addition to the process of FIG. 7, the state of the vehicle speed sensor 39 that is the determination target is determined using the speed of the drive wheel that is not the determination target. That is, since the abnormality of the vehicle speed sensor 39 is determined based on information not directly related to the steering wheel operation, even if the driving output is repeatedly turned ON / OFF during the transport operation, the influence is affected as long as the bed is moving. It is possible to detect an abnormality of the sensor without receiving any. Therefore, the detection accuracy of the sensor abnormality is improved, the safety as the transport device is improved, and it is possible to take more corrective measures such as repairs according to the abnormal situation, so that troubles caused by sensor failure can be prevented. Can be prevented. Even when the bed is moved by pushing a place other than the handle 6, the abnormality of the vehicle speed sensor 39 can be detected according to Step B.

  In the control process of FIG. 8, it is set to perform step B after step A, but either step A or B may be performed first. Further, it is possible to detect an abnormality only in step B. However, if both the left and right vehicle speed sensors 39L, 39R fail, the process of step B cannot be performed. Therefore, it is desirable to use in combination with step A, which can cope with the failure of both sensors 39L, 39R.

  Further, the values of C1 and C2 may be stored in a non-illustrated non-volatile memory, and these values may be held even after the power switch 8a is turned off. Thus, even if the power switch 8a is turned off while C1 and C2 are accumulated, when the power switch 8a is turned on again, an abnormality of the vehicle speed sensor 39 is detected immediately. Further, even when the power switch 8a is turned off in the state where the abnormality of the vehicle speed sensor 39 is detected and then the operator is switched, the failure can be accurately displayed and the subsequent operator can be surely recognized of the failure. Can do. Of course, the values of C1 and C2 are held when the power switch 8a is not turned off.

  Further, in the control process of FIG. 8, the determination of step S24 is provided at the end of the process, but this determination may be provided immediately after the start of the abnormality detection process. As a result, even if the motor is stopped due to a sensor failure and then the operator is changed, if an attempt is made to move the bed again, a sensor abnormality is immediately determined and the failure state is accurately transmitted.

It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.
For example, in the above-described embodiment, an example in which the transfer device of the present invention is applied to a hospital bed is shown. The present invention can be widely applied to a carrier device that performs power assist, such as a carriage. In the above-described embodiment, the drive unit 12 is arranged on one motor base 16, and the drive wheel 21 is moved up and down by the single lift actuator 13. Separate drive units 12 may be used, which may be mounted on separate motor bases 16 and individually actuated by two lift actuators 13.

  In the above-described embodiment, the speed of the bed is detected using the motor rotation pulse. However, a rotation sensor is disposed on the drive wheel 21 or the caster 14 and the rotation speed of the drive wheel 21 is confirmed using the output signal. Thus, the bed speed may be detected. In the above-described embodiment, the magnet and the magnetic detection element are used as the vehicle speed sensor. However, the present invention is not limited to this combination as long as the rotation of the motor, the driving wheel, the caster, or the like can be detected.

  Furthermore, in the above-described embodiment, the configuration in which the sensors 7L and 7R are provided on the left and right separate handles 6, respectively, but a single handle formed in an inverted U shape as in the transport vehicle disclosed in Japanese Patent Laid-Open No. 11-262111. The sensor means may be provided on the left and right bases. In this case, the number of sensor means is not limited to one each on the left and right. In addition, the thing of various structures, such as a T-shaped thing, can be used for the form of a handle | steering-wheel.

It is a front view which shows an example of the electric bed (conveyance apparatus) for hospitals to which the control method of this invention is applied. It is a top view which shows the outline | summary of the electric bed of FIG. It is explanatory drawing which shows the structure of the handle | steering-wheel attached to the electric bed of FIG. It is a perspective view which shows the structure of the drive part of the electric bed of FIG. It is explanatory drawing which shows the connection structure of the drive unit and raising / lowering actuator in a drive part. It is a block diagram which shows the structure of the control system of a controller. It is a flowchart which shows the process sequence of the abnormality detection method of the vehicle speed sensor which is Example 1 of this invention. It is a flowchart which shows the process sequence of the abnormality detection method of the vehicle speed sensor which is Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive part 2 Bed part 3 Mat 4 Arm 5 Safety fence 6, 6L, 6R Handle 7, 7L, 7R Handle operation force sensor 8 Control panel 8a Power switch 8b Emergency stop switch 8c Bed lift switch 8d LED display panel 11 Frame 11a Main Frame 11b Connecting bar 12 Drive unit 13 Lifting actuator 14 Caster 15 Cover 16 Motor base 17, 17L, 17R DC motor 18 Reduction mechanism 19 Rotating shaft 21, 21L, 21R Drive wheel 22 Wheel 23 Rubber tire 24 Tower 24a Base 25 Floor 26 Pivot 27 Arm 28 Long hole 29 Plunger 31 Pin 32 Spring 33 Plunger 34 DC motor 35 Bracket 36 Battery 37 Controller 38 Actuator 39, 39L, 39R Vehicle speed sensor 41 CPU
42 Input Circuit 43 Input Circuit 44, 44L, 44R Drive Output Circuit 45 Power Supply Circuit 46 Power Supply Input Circuit 47 Counter
C1 count value
C2 count value
CS regulation value
CS1 default value
CS2 Specified value α Specified value β Specified value

Claims (8)

A plurality of driving wheels driven by an electric motor, a plurality of vehicle speed sensors provided corresponding to each of the driving wheels and detecting the rotational speed of the driving wheels, and a handle attached to the operation force sensor An abnormality detection method for the vehicle speed sensor in a power assisted transfer device in which a travel assist force controlled based on detection values of the vehicle speed sensor and the operation force sensor is applied to the drive wheel,
When the steering wheel is operated and a driving assist force is applied to the drive wheel, when a vehicle speed signal cannot be obtained from the vehicle speed sensor that is the determination target, an abnormality has occurred in the vehicle speed sensor that is the determination target. An abnormality detection method for a vehicle speed sensor in a power-assisted transfer device, characterized in that: A plurality of driving wheels driven by an electric motor, a plurality of vehicle speed sensors provided corresponding to each of the driving wheels and detecting the rotational speed of the driving wheels, and a handle attached to the operation force sensor An abnormality detection method for the vehicle speed sensor in a power assisted transfer device in which a travel assist force controlled based on detection values of the vehicle speed sensor and the operation force sensor is applied to the drive wheel,
Based on a detection value from the vehicle speed sensor that is not a determination target, a first drive wheel speed indicating a speed of the drive wheel corresponding to the vehicle speed sensor is detected, and the first drive wheel speed and a first threshold value are detected. And compare
When the first driving wheel speed exceeds the first threshold value, the second driving wheel indicating the speed of the precursor driving wheel corresponding to the vehicle speed sensor based on the detection value of the vehicle speed sensor that is the determination target Detecting the speed and comparing the second drive wheel speed with a second threshold;
An abnormality detection method for a vehicle speed sensor in a power-assisted transfer device, wherein when the second drive wheel speed is equal to or less than a second threshold, it is determined that an abnormality has occurred in the vehicle speed sensor to be determined.   3. The vehicle speed sensor abnormality detection method for a power assisted transfer apparatus according to claim 2, wherein the determination target vehicle speed sensor is abnormal when the second drive wheel speed is below a second threshold value for a predetermined time or more. A method for detecting an abnormality of a vehicle speed sensor in a power assisted transfer device, characterized by:   4. The vehicle speed sensor abnormality detection method for a power-assisted transfer apparatus according to claim 2 or 3, wherein the first threshold value is a difference in speed generated between the drive wheels when the transfer apparatus turns on the spot or turns at a small angle. An abnormality detection method for a vehicle speed sensor in a power-assisted transfer apparatus, characterized in that a maximum value is set.   5. The vehicle speed sensor abnormality detection method for a power assisted conveyance apparatus according to claim 2, wherein the second threshold value is smaller than the first threshold value. An abnormality detection method for a vehicle speed sensor in a transport apparatus.   6. The vehicle speed sensor abnormality detection method for a power-assisted transfer device according to claim 2, wherein the determination is performed when the steering wheel is operated and a driving assist force is applied to the drive wheel. An abnormality detection method for a vehicle speed sensor in a power-assisted transfer device, wherein when a vehicle speed signal cannot be acquired from a target vehicle speed sensor, it is determined that an abnormality has occurred in the determination target vehicle speed sensor.   7. The vehicle speed sensor abnormality detection method for a power assisted transfer apparatus according to claim 6, wherein when the steering wheel is operated and a driving assist force is applied to the drive wheel, a vehicle speed signal is output from the vehicle speed sensor to be determined. An abnormality detection method for a vehicle speed sensor in a power assisted transfer device, wherein an abnormality has occurred in the determination target vehicle speed sensor when a state in which acquisition is impossible continues for a predetermined time or more.   8. The abnormality detection method for a vehicle speed sensor in a power-assisted transfer device according to claim 6 or 7, wherein a steering wheel arranged on the same side as the vehicle speed sensor to be determined is operated to apply a driving assist force to the drive wheels. When the vehicle speed signal cannot be obtained from the determination target vehicle speed sensor, it is determined that an abnormality has occurred in the determination target vehicle speed sensor.

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