Patent Publication Number: US-2015066277-A1

Title: Manually propelled vehicle

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a manually propelled vehicle (e.g., ambulatory assist vehicles, baby carriages, dollies, wheelchairs, and the like). 
     RELATED ART 
     In recent years, manually propelled vehicles (e.g., ambulatory assist vehicles to support elderly people with a weak physique or people with trouble walking, to go out) with human-power assist functions (so-called assisted functions) have been studied. 
     A conventional manually propelled vehicle comprises a sensor for detecting a movement and position of its own vehicle body, a sensor for detecting an operating force applied from a user, and the assist function determines assistance (assisting force) according to the information from these sensors. Accordingly, when there is an error such as a failure in the sensor, the assist mechanism does not function properly and there is a risk that an assisting force that differs from the operation of the user is applied. 
     A sensor failure determination device for determining a failure of each sensor above has been proposed for secure assistance by the assist mechanism (e.g., refer to Patent Document 1). 
     The sensor failure determination device according to Patent Document 1 is used in a vehicle where an acceleration sensor is attached, and when the vehicle is traveling or moving at a speed faster than a predetermined speed, it uses the characteristics of the acceleration sensor in which variation in output values becomes larger than a constant value. That is, the vehicle may comprise an arithmetic circuit that generates a failure detection signal by determining that the acceleration sensor has failed when variation of the output from the acceleration sensor is equal to or less than the predetermined value while the vehicle is traveling at a speed of not less than the predetermined value. A malfunction of the assisting function due to the failure of the acceleration sensor can be prevented by providing the sensor failure determination device of the sensor. 
     DOCUMENTS OF THE RELATED ART 
     Patent Documents 
     
         
         [Patent Document 1] Japanese Unexamined Patent Application Publication 2002-22766. 
       
    
     However, in the sensor failure determination device according to a configuration in Patent Document 1, the vehicle must be traveling at a speed equal to or faster than a fixed speed, and therefore, the failure of the acceleration sensor cannot be determined until reaching that speed. In other words, while the vehicle speed has not reached the fixed speed, the acceleration sensor failure cannot be determined even if the acceleration sensor has failed, and the assist function may not be able to be operated safely. 
     Further, because the sensor failure determination device described above is to detect a sensor failure, it is difficult to detect an abnormal condition (e.g., falling, abandonment, or the like) of the user, and therefore, there is a risk of not being able to assist the user safely. 
     SUMMARY OF THE INVENTION 
     One or more embodiments of the present invention provide a manually propelled vehicle that can assist the operation of the user while ensuring safety. 
     According to one or more embodiments, a manually propelled vehicle having an assist function that assists walking of a user may comprise: a vehicle body; a wheel for moving the vehicle body; sensor that detects an operating force; power driver that supplies power (drive force or assisting force) to the wheel based on the operating force; a motion sensor that detects a movement of the vehicle body according to the operating force detected by the sensor; and controller that controls the power driver, wherein, when the user operates the manually propelled vehicle while the assist function is deactivated, the controller may activate the assist function based on the movement of the vehicle body detected by the motion sensor. 
     By having such a configuration, for example, a failure in the sensor, the motion sensor, and the operation state of the manually propelled vehicle can be detected. Thus, one or more embodiments of the invention can prevent use when the assist function is not normal. Accordingly, reliable assistance can be performed while ensuring the safety of a user. 
     According to one or more embodiments, the manually propelled vehicle may further comprise a rotation angle sensor that detects rotation of the wheel, wherein the controller may activate the assist function when the rotation angle sensor detects that the drive wheel has rotated a predetermined amount from a stationary state of the manually propelled vehicle. By configuring in this manner, for example, after the manually propelled vehicle has started traveling or moving from the stationary state, a failure can be accurately found before traveling a specific distance. Accordingly, even when a failure is found immediately after operation is started by the user, one or more embodiments of the invention can reduce a burden on the user because of the reduced speed and operating amount of the vehicle. 
     According to one or more embodiments, the manually propelled vehicle may further comprise a rotation angle sensor that detects rotation of the wheel, wherein the controller activates the assist function after a predetermined time has elapsed from a stationary state of the manually propelled vehicle. By configuring in this manner, for example, even when a failure is found immediately after operation is started by the user, one or more embodiments of the invention can reduce a burden on the user because of the reduced speed and operating amount of the vehicle. 
     According to one or more embodiments, the manually propelled vehicle may further comprise a switch that cuts off the power from the power driver so that the power is not transferred to the wheel when the assist function is deactivated. By having such configuration, for example, one or more embodiments of the invention can reduce a burden on the user when the assist function is activated. 
     According to one or more embodiments, the controller may detect the operating force detected by the sensor or the movement of the vehicle body detected by the motion sensor while the assist function is activated, and deactivate the assist function when a periodic fluctuation associated with walking by the user is not verified in at least one of either the detected operating force or the movement of the vehicle body. By having such configuration, for example, even when user is operating the manually propelled vehicle by using the assist function, one or more embodiments of the invention can accurately detect a failure in the sensor and (or) the motion sensor. 
     According to one or more embodiments, the manually propelled vehicle may further comprise a grip for the user to grip while operating the manually propelled vehicle; and a grip sensor that detects when the user grips the grip, wherein if the grip sensor does not detect gripping of the grip and the motion sensor does not detect movement of the vehicle body, the controller may activate the assist function when the operating force detected by the sensor is within a predetermined range. By having such configuration, for example, one or more embodiments of the invention can detect a failure in the sensor while the manually propelled vehicle is completely stationary, and also prevent the user from using the manually propelled vehicle with a failure. 
     According to one or more embodiments, the manually propelled vehicle may further comprise a grip for the user to grip while operating the manually propelled vehicle; and a grip sensor that detects when the user grips the grip, wherein if the grip sensor does not detect gripping of the grip, the controller may deactivate the assist function when the motion sensor repeatedly and continuously detects movement of the vehicle body for a predetermined number of times. By having such configuration, for example, one or more embodiments of the invention can detect a failure in the motion sensor while the manually propelled vehicle is completely stationary, and also prevent the user from using the manually propelled vehicle with a failure. 
     According to one or more embodiments, a manually propelled vehicle having an assist function that assists walking of a user may comprise: a vehicle body; a wheel to move the vehicle body; sensor that detects an operating force; a power driver that supplies power to the wheel based on the operating force; a motion sensor that detects a movement of the vehicle body; and a controller that controls the power driver, wherein the controller may detect the operating force detected by the sensor or the movement of the vehicle body detected by the motion sensor while the assist function is activated, and deactivate the assist function when a periodic fluctuation associated with walking by the user is not verified in at least one of either the detected operating force or the movement of the vehicle body. 
     According to one or more embodiments, a manually propelled vehicle having an assist function that assists walking of a user may comprise a vehicle body, a wheel for moving the vehicle body, sensor that detects an operating force, power driver that supplies assisting force to the wheel based on the operating force, motion sensor that detects a movement of the vehicle body, controller that controls the power driver, grip where the user grips at the time of operation, and grip sensor for detecting when the user grips the grip; and while gripping of the grip is not detected by the grip sensor and movement of the vehicle body is not detected by the motion sensor, the controller activates the assist function when the operating force detected by the sensor is within a predetermined range. 
     According to one or more embodiments, a method for controlling a manually propelled vehicle comprising an assist function that assists walking of a user, a vehicle body and a wheel for moving the vehicle body may comprise: detecting an operating force; supplying power to the wheel based on the operating force; detecting a movement of the vehicle body according to the detected operating force; controlling the power driver; and when the user operates the manually propelled vehicle while the assist function is deactivated, activating the assist function based on the detected movement of the vehicle body. 
     One or more embodiments of the present invention can provide a manually propelled vehicle that can assist the operation of a user while ensuring safety. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a front view of one example of a manually propelled vehicle according to one or more embodiments of the invention. 
         FIG. 1B  is a back view of the manually propelled vehicle illustrated in  FIG. 1A . 
         FIG. 1C  is a side view of the manually propelled vehicle illustrated in  FIG. 1A . 
         FIG. 1D  is a bottom view of the manually propelled vehicle illustrated in  FIG. 1A . 
         FIG. 2A  is a schematic perspective view of a handle of the manually propelled vehicle illustrated in  FIG. 1A . 
         FIG. 2B  is a diagram illustrating a schematic disposition of the handle illustrated in  FIG. 2A . 
         FIG. 3  is a block diagram of one example of a manually propelled vehicle according to one or more embodiments of the invention. 
         FIG. 4  is a block diagram of one example of a power assist device provided in the manually propelled vehicle illustrated in  FIG. 3 . 
         FIG. 5  is a schematic diagram illustrating one example of a configuration of a wheel and a power driver of the manually propelled vehicle illustrated in  FIG. 1A . 
         FIG. 6  is a flowchart showing a normal assist state of a manually propelled vehicle according to one or more embodiments of the invention. 
         FIG. 7  is a flowchart of an operation verification of a manually propelled vehicle according to one or more embodiments of the invention. 
         FIG. 8  is a flowchart of another example of an operation verification of a manually propelled vehicle according to one or more embodiments of the invention. 
         FIG. 9  is a flowchart of yet another example of an operation verification of a manually propelled vehicle according to one or more embodiments of the invention. 
         FIG. 10  is a graph showing output of a sensor of a manually propelled vehicle according to one or more embodiments of the invention. 
         FIG. 11A  is a schematic diagram illustrating an example of inappropriate operation of a manually propelled vehicle by a user according to one or more embodiments of the invention. 
         FIG. 11B  is a schematic diagram illustrating an example of a non-steady operation of a manually propelled vehicle by a user according to one or more embodiments of the invention. 
         FIG. 12  is a flowchart of yet another example of an operation verification of a manually propelled vehicle according to one or more embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described below with reference to drawings. 
       FIG. 1A  is a front view of one example of a manually propelled vehicle according to one or more embodiments of the invention;  FIG. 1B  is a back view of the manually propelled vehicle illustrated in  FIG. 1A ;  FIG. 1C  is a side view of the manually propelled vehicle illustrated in  FIG. 1A ; and  FIG. 1D  is a bottom view of the manually propelled vehicle illustrated in  FIG. 1A . Further,  FIG. 2A  is a schematic perspective view of a handle of the manually propelled vehicle illustrated in  FIG. 1A ; and  FIG. 2B  is a diagram illustrating a schematic disposition of the handle illustrated in  FIG. 2A . Furthermore,  FIG. 3  is a block diagram of one example of a manually propelled vehicle according to one or more embodiments of the invention,  FIG. 4  is a block diagram of one example of an power assist device provided in the manually propelled vehicle illustrated in  FIG. 3 , and  FIG. 5  is a schematic diagram of one example of a configuration of a wheel and a power driver of the manually propelled vehicle illustrated in  FIG. 1A . The arrow shown with a double line in  FIG. 3  and  FIG. 4  illustrates transmission of power. 
       FIG. 1  is a manually propelled vehicle  1  (e.g., ambulatory assist vehicle) according to one or more embodiments. The manually propelled vehicle  1  may be a so-called walker to assist walking of a user (e.g., elderly with weak lower body) and may also be used as a basket for carrying baggage and a seat for resting. As illustrated in the drawing of  FIGS. 1A to 1D ,  FIG. 3 , and  FIG. 4 , the manually propelled vehicle  1  may comprise a vehicle body  10 , a handle  20 , a wheel  30 , a baggage compartment part  40 , a backrest  50 , and a power assist device  110 . Further, the power assist device  110  may comprise a motion sensor  60  (motion sensor or sensing circuit), sensor  70  (sensor or sensing circuit), a controller  80  (controller or control circuit), a power driver  90  (power driver or driving circuit), and a power source  100 . 
     The vehicle body  10  may be a frame (framework) of the manually propelled vehicle  1  on which the configuration elements  20  to  100  listed above may be mounted. A metal material such as stainless steel, aluminum alloy, or the like, and a resin material such as FRP or the like may be used for the frame material forming the vehicle body  10 . 
     As illustrated in  FIGS. 2A and 2B , the handle  20  may be a member for gripping when the user is moving or traveling and is connected to a strut member  11  of the vehicle body  10 . The handle  20  may comprise a rod-like handle bar  21 , a grip  22  attached to the handle bar  21 , and a handle holder  23  that supports the handle bar  21 , and may be attached to the vehicle body  10 . The user may hold the handle  20  to apply an operating force to the vehicle body  10 , and the manually propelled vehicle  1  can be advanced, reversed, braked, and turned right and left by applying the operating force. 
     The handle holder  23  may be a U-shaped member where the upper part is open and has a front wall  231  and a rear wall  232 . The center portion in the lengthwise direction of the handle bar  21  may be supported by a U-shaped recessed part of the handle holder  23 , and a gap may be formed between the handle bar  21  and the front wall  231  and the rear wall  232 . Further, a screw member  233  that passes through the rear wall  232  and is screwed into the front wall  231  may be attached to the handle holder  23 . This screw member  233  may pass through a through hole formed in the handle bar  21 , and the through hole may have an inner diameter larger than the outer form of the screw member  233 . Further, a force sensor  71  of the sensor  70  may be attached in the gap between the handle bar  21  and the front wall  231  and the rear wall  232 . The handle bar  21  may be disposed so as to rest by contacting the force sensor  71 . 
     Supporting the handle bar  21  by the handle holder  23  in this manner allows the handle bar  21  to move within a predetermined range relative to the handle holder  23 . The handle bar  21  may move in a front-back direction so as to eliminate the gap with the front wall  231  or the gap with the rear wall  232 . At that time, the force sensor  71  attached on the handle holder  23  may be pressed to output an electric signal. 
     Further, because the inner diameter of the through hole provided in the handle bar  21  may be larger than the outer diameter of the screw member  233 , the handle bar  21  can also move in the rotational direction for only that portion of the gap between the screw member  233  and the through hole. Movement at this time may also allow the handle bar  21  to push the force sensor  71  to output an electric signal from the force sensor  71 . 
     As illustrated in  FIGS. 2A and 2B , one force sensor  71  may be provided on both end parts in the lengthwise direction of the front wall  231  and the rear wall  232  for a total of four force sensors. From a combination of the electric signals outputted from these four force sensors  71 , the operation of the handle bar  21  can be determined. 
     For example, when electric signals are outputted from two force sensors  71  of the front wall  231 , the handle bar  21  is applied operating force in the forward direction by the user. Further, when electric signals are outputted from the force sensor  71  on the left side of the front wall  231  and the force sensor  71  on the right side of the rear wall  232 , an operating force to turn the handle bar  21  in the right direction is applied by the user. The force sensor  71  is not limited to such a configuration, and various sensors can be disposed in various locations to determine the direction where the operating force of the handle bar  21  is applied. 
     The grip  22  may be attached on both end parts in the lengthwise direction of the handle bar  21 . The grip sensor  221  may be embedded into the grip  22 . The grip sensor  221  may detect if the user is gripping the grip  22  and may have a wide detection region in the lengthwise direction (axial direction of the handle bar  21 ) of the grip  22 . This grip sensor  221  may detect if the grip  22  is gripped by a hand of the user, and may even distinguish whether an object contacting the grip  22  is a hand of the user, or hooked with an umbrella, a baggage, or the like. The determination method may be performed, for example, in the following manner. 
     When a hand of the user grips the grip  22 , the contact area of the grip  22  with the hand of user may be wide. On the other hand, when hooking an umbrella, baggage or the like on the grip  22 , the contact area of the grip  22  with the umbrella, baggage, or the like may be narrow. The size of the contact area may help determine whether the hand of the user is touched, or other article is hooked on the grip  22 . Further, by increasing accuracy of the grip sensor  221 , a size of the hand of the user gripping the grip  22  can be distinguished. A gender of the user, body figure, and the like may even be distinguished. For such grip sensor  221 , for example, a well-known conventional sensor such as a pressure sensor applying a conductive rubber, a human sensory sensor of electrostatic capacitance type, or the like may be used. 
     The wheel  30  may be attached to the bottom surface of the vehicle body  10 , having a wheel to move the manually propelled vehicle  1  along the ground by rotating in accordance with walking of the user. As illustrated in  FIG. 5 , the wheel  30  may be a four-wheel structure comprising drive wheels  31  (left drive wheel  31 L and the right drive wheel  31 R), and idler wheels  32  (left idler wheel  32 L and the right idler wheel  32 R). The drive wheels  31  may rotate around the axle attaching to the vehicle body  10 , and may receive an operating force from the user and driving force (power or assisting force) from a power driver  90  to be rotated. The idler wheels  32  may be the wheels used for turning. As illustrated in  FIG. 5 , the left and right drive wheels  32 L and  32 R may be driven and controlled independently on the rotation speed and rotation direction respectively by wheel drivers  91 L and  91 R that correspond, respectively. 
     The baggage compartment  40  may be a box-shape member that can store personal belongings inside. A cushion member may be attached on the upper lid of the baggage compartment  40 , and may function as a seating surface for the user to sit down on when seating. The baggage compartment  40  may be a detachable configuration relative to the vehicle body  10 . 
     The backrest  50  may be a plate-like member for the user to lean back on when seating. In one or more embodiments of the manually propelled vehicle  1  illustrated in  FIGS. 1A to 1D , the vehicle body  10  may be formed to be wider or the strut member  11  may be diverted as the backrest  50 . 
     The motion sensor  60  may detect a state of the manually propelled vehicle  1 , including an acceleration sensor  61 , a gyro sensor  62 , and a distance measuring sensor  63 . The acceleration sensor  61  may detect the acceleration caused by the movement of the manually propelled vehicle  1 . The acceleration sensor  61  may be used to detect acceleration, for example, in a direction along the axes of three orthogonal axes of front-back, left-right, and top-bottom. 
     The gyro sensor  62  may detect an inclination (angular velocity) of the manually propelled vehicle  1 . The gyro sensor  62  may include a sensor that detects an angular velocity around three axes of the front-back, left-right, and top-bottom. The motion sensor  60  according to one or more embodiments of the present example may adopt a six-axis motion sensor that combines the acceleration sensor  61  and the gyro sensor  62  on a single chip. Further, the motion sensor  60  may be provided on the handle  20  near the user in the manually propelled vehicle  1 ; however, the motion sensor  60  may be provided elsewhere, such as on the vehicle body  10 . 
     The distance measuring sensor  63  may measure between the manually propelled vehicle  1  and the user, and detect a walking state of the user by measuring the distance between the manually propelled vehicle  1  and the user. By providing the distance measuring sensor  63  and measuring the distance between the manually propelled vehicle  1  and the user, a positional relationship of the manually propelled vehicle  1  and the user may be detected. A sensor (e.g. an infrared sensor) that only verifies the user may be used instead of the distance measuring sensor  63 . 
     The sensor  70  may detect an operating force applied to the manually propelled vehicle  1  from the user and may comprise a force sensor  71 . The force sensor  71  may detect the operating force from the user applied to the handlebar  21 , and a pressure sensor where a conductive rubber is applied may be used here. The force sensor  71  as illustrated in  FIG. 2B  is attached between the handlebar  21  and the handle holder  23 . The force sensor  71  may detect the operating force from the user applied to the handlebar  21 . 
     In the manually propelled vehicle  1 , the handlebar  21  may be supported so as to allow a displacement within a predetermined range with respect to the handle holder  23 . Further, the force sensor  71  may be disposed between the handlebar  21  and the handle holder  23 , and when the handlebar  21  is displaced with respect to the handle holder  23 , the handlebar  21  may press the force sensor  71  to detect the pressure. Based on this pressure, the operating force applied to the handle bar  21  may be detected. 
     The configuration in one or more embodiments of the present example may be arranged such that the force sensor  71  is disposed between the handlebar  21  and the handle holder  23 ; however, other configurations are possible. For example, the force sensor  71  may be embedded into the grip  22  same as the grip sensor  221 . In this case, the grip sensor  221  and the force sensor  71  may be used in common with one sensor. 
     Further, in the manually propelled vehicle  1  of one or more embodiments of the present example, the pressure sensor that detects the operation input as pressure from a hand of the user may be used; however, other configurations are possible. For example, a sensor that detects the handlebar  21  when an operating force is inputted, or that detects an amount of deflection of the supporting member  11 , may be attached. For such sensor, for example, a strain gauge, a pressure sensor, or the like may be used. 
     The controller  80  may comprise a motion sensor  60 , a sensor  70 , and a power driver  90 , in other words, a logic circuit (circuit a MPU, CPU, or the like) that controls the power assist device  110  comprehensively. The controller  80  may comprise a processor  801  as a function block that sets various parameters (drive target values such as the rotation direction, rotation speed, rotation torque, and the like) to drive motors  911 L and  911 R of the power driver  90 , and a wheel drive controller  802  that outputs a control signal. The processor  801  and the wheel drive controller  802  are described as an independent block in the controller  80  in  FIG. 3  and  FIG. 4 ; however, they may be a part of the same circuit that configures the controller  80  or a program, and they are not limited to being completely independent. 
     The processor  801  may determine drive target values of the left and right drive wheels  31 L and  31 R based on an input signal from, for example, the motion sensor  60  and the sensor  70 . Further, the wheel drive controller  802  may send a control signal that controls respectively and independently the rotation direction and rotation speed of the left and right drive wheels  31 L and  31 R according to the drive target value from the processor  801  to the corresponding wheel drivers  91 L and  91 R. 
     Furthermore, the controller  80  may comprise a memory  81  to store various information and a timer  82  to acquire time. The memory  81  may comprise read only ROM, a readable and writable RAM, and the like. The timer  82  may be a commonly known timekeeping means to detect time. Details of operation of the controller  80  will be described later. 
     The power driver  90  may assist an operation of the user according to the control signal from the controller  80 , including a wheel driver  91  that outputs driving force to the manually propelled vehicle  1  (the left drive wheel  31 L and right drive wheel  31 R). As illustrated in  FIG. 4 , the wheel drivers  91 L and  91 R may be provided separately to drive and control the left and right drive wheels  31 L and  31 R respectively and independently. 
     A power source  100  may supply power to the motion sensor  60 , sensor  70 , controller  80 , and power driver  90 . A secondary battery (such as a nickel-hydrogen battery and lithium-ion battery) attaching to the vehicle body  10  in removable manner may be used for the power source  100 . 
     Next, the power driver  90  will be described in detail. As illustrated in  FIG. 4 , the power driver  90  may comprise the wheel drivers  91   l  and  91 R. The wheel drivers  91 R and  91 L may comprise motors  911 L and  911 R, motor drivers  912 L and  912 R, current sensors  913 L and  913 R, and rotation angle sensors  914 L and  914 R, respectively. 
     Each of the motors  911 L and  911 R may rotate and drive the left and right drive wheels  31 L and  31 R, independently. Each of the motor drives  912 L and  912 R may be an inverter circuit for generating a drive current of the motors  911 L and  911 R according to a control signal from the controller  80 , respectively. Each of the current sensors  913 L and  913 R may be a sensor that detects the driving current that flows the motors  911 L and  911 R, respectively. The current sensors  913 L and  913 R may include, for example, a shunt resistor or a magnetic sensor. Each of the rotation angle sensors  914 L and  914 R may detect respectively a rotation angle of the motors  911 L and  911 R. The rotation angle sensors  914 L and  914 R may include, for example, an optical rotary encoder or a hall element. 
     The wheel drive controller  802  may acquire each output value from the current sensors  913 L and  913 R and the rotation angle sensors  914 L and  914 R. The wheel drive controller  802  may generate a driving signal based on the drive target value from the processor  801  to the motor drivers  912 L and  912 R. Further, the wheel drive controller  82  may perform a feedback control of the motor drivers  912 L and  912 R to match the rotation direction and rotation speed of the motors  911 L and  911 R the target value according to each output value of the current sensors  913 L,  913 R and the rotation angle sensors  914 L,  914 R. 
     Furthermore, the driver  90  may comprise transmissions  92 L and  92 R to transfer the driving force of the motors  911 L and  911 R to the left and right drive wheels  31 L and  31 R, respectively. Each of the driving forces of the motors  911 L and  911 R may be transferred to the left and right drive wheels  31 L and  31 R via a power shaft, and the transmissions  92 L and  92 R may be attached to the power shaft. The transmissions  92 L and  92 R may connect or release the power shaft by following the instructions of the wheel drive controller  802 . When the transmissions  92 L and  92 R release the power shaft, the driving forces from the motors  911 L and  911 R are prevented from transferring to the left and right drive wheels  31 L and  31 R, respectively. 
     Such transmissions  92 L and  92 R may comprise a transmission mechanism provided with a friction clutch. By using the friction clutch, the power shaft can be connected with less impact even when the motors  911 L and  911 R are rotating. Alternatively, a mechanism that can switch between transmitting the power and cutting off the power may be used. Further, a speed reducer that can reduce speed of the rotation speed of the motors  911 L and  911 R, increase the torque, and also transfer to the left and right drive wheel wheels  31 L and  31 R may be attached integrally. 
     By using such transmissions  92 L and  92 R, the left and right drive wheels  31 L and  31 R can be rotated in a state where the load by the motors  911 L and  911 R is not employed when the motors  911 L and  911 R are not operated, for example, by releasing the transmissions  92 L and  92 R. 
     Next, a description of operation of the manually propelled vehicle  1  will be given with reference to drawings.  FIG. 6  is a flowchart showing a normal assisting state of a manually propelled vehicle according to one or more embodiments. For example, the manually propelled vehicle  1  can safely assist an operation of the manually propelled vehicle  1  by a user by giving an appropriate assisting force to an operating force by the user. Therefore, the processor  801  of the manually propelled vehicle  1  may detect the operating force based on output from the force sensor  71 . 
     The controller  80  of the manually propelled vehicle  1  may acquire output of the force sensor  71 , and detect whether or not there is an operating force input from the user to a handle  20  based on the output (step S 11 ). When there is no operating force input (NO in step S 11 ), the controller  80  may wait until it detects the operating force input. 
     When the operating force from the user is detected (YES in step S 11 ), the controller  80  may determine that the force is applied to the handle  20 , and may determine if the user is trying to operate the manually propelled vehicle  1 . In other words, the controller  80  may determine whether or not there is a user at a predetermined position behind the manually propelled vehicle  1  based on the output from a distance measuring sensor  63  (step S 12 ). For example, when the user is seated on the seating surface of the manually propelled vehicle  1  and operating the handle  20 , the controller  80  can determine that the user is not using the manually propelled vehicle  1  in a standard use method although an operating force is inputted. Further, there is a case that the force other than the operating force by the user is employed to the handle  20 , and assistance can be controlled when it is not used in the standard use method. 
     When the user is not at the predetermined position behind the manually propelled vehicle  1  (NO in step S 12 ), the controller  80  may verify whether or not the assisting is being carried out (step S 13 ). When the assisting is not carried out (NO in step S 13 ), the controller  80  may return to the detection of the operating force (step S 11 ). When the assisting is carried out (YES in step S 13 ), the controller  80  may stop assisting (supplying the assisting force) (step S 14 ) and return to the detection of the operating force (step S 11 ). 
     Further, when the user is at the predetermined position behind the manually propelled vehicle  1  while detecting the operating force (YES in step S 12 ), the controller  80  may acquire an acceleration and angular velocity from the output from an acceleration sensor  61  and a gyro sensor  61  (step S 15 ). The controller  80  may acquire rotation angles of the left and right drive wheels  31 L and  31 R from rotation angle sensors  914 L and  914 R, and may determine whether or not the manually propelled vehicle  1  is traveling (step S 16 ). 
     When the manually propelled vehicle  1  is not traveling (NO in step S 16 ), the controller  80  may determine that the operating force is applied from the user to manually propelled vehicle  1  in a stationary state. Further, the processor  801  may determine a drive target value including the rotation direction, rotation speed, and rotation torque of the motors  911 L and  911 R and delivers to a wheel drive controller  802  (step S 17 ). The wheel drive controller  802  may generate a control signal based on the drive target value and send to the motor drivers  912 L and  912 R. The motor drivers  912 L and  912 R may supply driving currents to the left and right drive wheels  31 L and  31 R based on the control signal respectively to start assisting (step S 18 ). Even after starting the assist (after step S 18 ), there may be cases where the operating force fluctuates, and therefore, the process returns to the detection of the operating force (step S 11 ). 
     Meanwhile, when the manually propelled vehicle  1  is traveling (YES in step S 16 ), the controller  80  may verify whether the manually propelled vehicle is assisting the operation of the user (step S 19 ). When the manually propelled vehicle is not assisting (NO in step S 19 ), the process advances to step S 17  and step S 18 , to determine the drive target value and start assisting. The determination of the drive target value and initiation of the assist may be the same as described above. 
     When the manually propelled vehicle  1  is assisting the operation of the user (YES in step S 19 ), the processor  801  may adjust the drive target value so that the acceleration, angular velocity, speed, and traveling direction of the manually propelled vehicle  1  correspond to the operating force (step S 111 ). Further, the drive wheel controller  802  may generate a drive signal based on the adjusted drive target value, and performs adjustment of the assisting force of the motors  911 L and  911 R (step S 112 ). 
     By operating as described above, the manually propelled vehicle  1  according to one or more embodiments can provide safe assistance for the operation by the user. Further, the manually propelled vehicle  1  may monitor the rotation angle of the motors  911 L and  911 R and also monitor current supply. Therefore, the manually propelled vehicle  1  can verify if the proper current is supplied and the motor  911 L and  911 R are securely operated so that more safe and secure assistance can be provided. 
     First Example 
     One or more embodiments of the operation verification procedure of a manually propelled vehicle according to a first example of the present invention will be described with reference to drawings.  FIG. 7  is a flowchart of the operation verification of the manually propelled vehicle according to one or more embodiments of the present invention. In the manually propelled vehicle  1 , sensors including the motion sensor  60  and the sensor  70  operate accurately to assist the operation by the user safely and securely. Accordingly, in the manually propelled vehicle  1  according to one or more embodiments of the present example, when the user starts pushing the stationary manually propelled vehicle  1 , the operation verification of each sensor may be performed. A procedure for performing the operation verification of the sensor will be described below with reference to drawings. Each part of the manually propelled vehicle  1  may be as described above. 
     In the manually propelled vehicle  1 , when the transmissions  92 L and  92 R are released, the connection of the left and right drive wheels  31 L and  31 R with the motors  911 L and  911 R may be disconnected. When the left and right drive wheels  31 L and  31 R rotate in this state, the motors  922 L and  922 R may not load. That is, when the transmissions  92 L and  92 R are released, the left and right drive wheels  31 L and  31 R may be axially supported rotatably similar to the idler wheels  32 L and  32 R. At that time, when the operating force is applied from the user, the manually propelled vehicle  1  may move in the direction at the acceleration, angular velocity, and speed corresponding to the operating force. The manually propelled vehicle  1  according to one or more embodiments of the present example may use these types of characteristics to determine whether the sensors are running properly. 
     First, the controller  80  may determine whether or not the operating force is employed to a handle  20  based on the output of a sensor  70  (step S 21 ). When the operating force is not detected (step S 21 ), the process waits until the operating force is detected. When the operating force is detected (YES in step S 21 ), a wheel drive controller  802  may send an operation signal to release the transmissions  92 L and  92 R (step S 22 ). Then, the wheel drive controller  802  may acquire outputs of the rotation angle sensor  914 L and  914 R (step S 23 ). Further, the controller  80  may simultaneously acquire an output of the sensor  70  (step S 24 ). Furthermore, the controller  80  may simultaneously acquire an output of a motion sensor  60  and outputs of an acceleration sensor  61  and a gyro sensor  62  (step S 25 ). 
     The wheel drive controller  802  may verify whether the manually propelled vehicle  1  has traveled a specific distance after the connecting parts  92 L and  92 R are released (step S 26 ). The movement of the manually propelled vehicle  1  may be determined based on the output of rotation angle sensors  914 L and  914 R to detect the rotation angle of the left and right drive wheels  31 L and  31 R, and by the rotation angle and the outer periphery length of the left and right drive wheels  31 L and  31 R. The specific distance, for example, may be a distance where the left and right drive wheels  31 L and  31 R are rotated about ⅓ round. When the manually propelled vehicle  1  has not been moved the specific distance (NO in step S 26 ), the process returns to acquire the output of the rotation angle sensors  914 L and  914 R (step S 23 ). 
     When the manually propelled vehicle  1  has been moved by the specific distance (YES in step S 26 ), the process determines whether the output of the sensor  70  and the output of the motion sensor  60  correspond (step S 27 ). When the drive shaft is released by the transmissions  92 L and  92 R, the manually propelled vehicle  1  may be moved by the operating force from the user. A processor  802  may compare a theoretical value of a variety of parameters (acceleration, angle velocity, direction, speed, and the like) when the operating force is applied to the manually propelled vehicle  1 , to an actual measured value that has been actually measured by each sensor of the motion sensor  60  to determine that the difference is within an acceptable range. 
     When the output of the sensor  70  and the output of the motion sensor  60  correspond (YES in step S 27 ), the controller  80  may determine that each sensor of the motion sensor  60  and the sensor  70  are operating normally (step S 28 ). Then, the wheel drive controller  802  may connect the transmissions  92 L and  92 R to activate the assist function (step S 29 ). 
     Meanwhile, when the output of the sensor  70  and the output of the motion sensor  60  do not correspond (NO in step S 27 ), the controller  80  may determine that there is a failure (has an error) in the motion sensor  60  and (or) in the sensor  70  (step S 210 ). Indication of the failure here may be considered a failure of the motion sensor  60  or the sensor  70 , damage or failure of the wheel  30  of the manually propelled vehicle  1 , an inability of the manually propelled vehicle  1  itself to move (such as being caught on something or the like), and the like. That is, any case in which the manually propelled vehicle  1  is not moving correctly relative to the operating force applied may be included. 
     Further, the controller  80  may notify the failure (error) by using a notification device (e.g., a device that outputs an image, lighting of a lamp, sound, or the like) omitted in the illustration (step S 211 ). Further, the controller  80  may continue the released state of the transmissions  92 L and  92 R to deactivate the assist function (step S 212 ). Switching the assist function to be deactivated while the user is operating the manually propelled vehicle  1  using the assist function may not be safe because the user may become accustomed to an abnormal operation sensation, or it may make the user use unreasonable operating force, at the moment of switching when disabling. Therefore, when disabling the assist function from the state in which the assist function is used, the assisting force (assisting amount) may be reduced gradually. 
     When a braking device (brake) is provided to the left and right drive wheels  31 L and  31 R, the assist function may be deactivated by activating the braking device to fix the manually propelled vehicle  1  so as to not move. Rendering the manually propelled vehicle  1  to be immovable can prevent the user from using the manually propelled vehicle  1  that is not able to provide a normal assistance. 
     The operation verification may be performed by acquiring outputs of each sensor (the acceleration sensor  61 , gyro sensor  62 , and force sensor  71 ) when the manually propelled vehicle  1  travels for the specific distance; however, this operation may be verified based on the traveling time rather than the traveling distance. For example, from immediately after traveling begins, time may be measured by a timer  82 , the outputs from each sensor are acquired until a predetermined time has elapsed, and the operation verification may be performed based on the outputs. 
     Alternatively, both the traveling distance and traveling time may be used. For example, the output from each sensor may be acquired until either one or both can be achieved where the specific distance is traveled or/and the predetermined time has elapsed. By using traveling distance and traveling time together, a failure in the rotation angle sensors  914 L and  914 R can also be detected. That is, when the controller  80  cannot detect that the left and right drive wheels  31 L and  31 R have traveled for the specific distance after the predetermined time has elapsed, the controller  80  can determine that there is an abnormality in the rotation angle sensors  914 L and  914 R. For example, there may be a case where the manually propelled vehicle  1  is pushed uphill. In that case, it may be difficult to travel for the specific distance at the predetermined time. Therefore, the condition (inclination and the like) of the manually propelled vehicle  1  from the output of the motion sensor  60  may be detected to change the time until the distance is detected. 
     The manually propelled vehicle  1  of one or more embodiments of the present example may be configured to perform operation verification at the time of initiating travel. Therefore, even when a failure (error) is found, the burden on the user can be reduced because the traveling distance, speed, and the like of the manually propelled vehicle  1  are small. Also, the user can be prevented from operating the manually propelled vehicle  1  without knowing that there is a failure, so the safety of the user can be ensured. Furthermore, when the user uses the manually propelled vehicle  1  with the knowledge that the assist function is not operating, the user may load baggage to the extent that the user can operate without the assistance, may use the manually propelled vehicle  1  in order to move to a location. Therefore, the burden on the user may be reduced. 
     Second Example 
     Another example of the operation verification procedure of a manually propelled vehicle according to one or more embodiments of the present invention will be described with reference to drawings.  FIG. 8  is a flowchart of another example of an operation verification of a manually propelled vehicle according to one or more embodiments of the present invention. Each part of the manually propelled vehicle  1  may be as described above. As described above, the manually propelled vehicle  1  may perform operation verification on a motion sensor  60  and the sensor  70  at the time of initiating travel, and when the controller determines that there is no error, the manually propelled vehicle  1  may start assisting the operation by the user as needed (step S 31 ). 
     When the manually propelled vehicle  1  starts the assist by the power assist device  110 , a drive signal may be sent to wheel drivers  92 L and  91 R from a wheel drive controller  802 . Then, the drive signal may be inputted to motor drivers  912 L and  912 R, and the motor drivers  912 L and  912 R may supply a driving current to motors  911 L and  911 R according to the drive signal. At that time, current sensors  913 L and  913 R provided in the wheel drivers  91 L and  91 R may detect a current value and send to the wheel drive controller  802  (step S 32 ). 
     Further, the controller  80  (the wheel drive controller  802 ) may acquire an output of rotation angle sensors  914 L and  914 R (step S 33 ). The controller  80  may acquire an output of a sensor  70  (step S 34 ) and acquire an output of a motion sensor  60  (step S 35 ). 
     The controller  80  may calculate a travel amount of the left and right drive wheels  31 L and  31 R from an output of rotation angle sensors  914 L and  914 R, and may determine whether or not the travel amount corresponds to the drive current value (step S 36 ). For example, when the manually propelled vehicle  1  is on an uphill, or in some sort of failure, there may be a case that the travel amount is small even though the drive current value is large. Therefore, the controller  80  may estimate a condition (inclination, road surface condition, and the like) of the manually propelled vehicle  1  from the output of the motion sensor  60  and output of the sensor  70  and compare the travel amount and the drive current value by considering the results. 
     When the travel amount of the left and right drive wheels  31 L and  31 R and the drive current value of the motors  911 L and  911 R correspond (YES in step S 36 ), the controller  80  may determine that the wheel drivers  91 L and  91 R are running normally (step S 37 ). Further, the controller  80  may continue the assist provided by the power assist device  110 . 
     When the travel amount of the left and right drive wheels  31 L and  31 R and the drive current value of the motors  911 L and  911 R do not correspond (NO in step S 36 ), the controller  80  may determine that there is a failure in the wheel drivers  91 L and  91 R (step S 39 ). Further, the controller  80  may notify that there is a failure in the wheel drivers  91 L and  91 R (step S 310 ) and deactivate the assist function (step S 310 ). 
     In the flowchart of the operation verification described above, the wheel drivers  91 L and  91 R are not particularly differentiated; however, when there is a failure on either side, the controller  80  may notify that the wheel driver has a failure. At that time, a failure of the current sensor may be detected by presence or absence of the output from the current sensor, and a failure of the rotation angle sensor may be detected by presence or absence of the output from the rotation angle sensor. Furthermore, after checking a failure in each sensor, the controller  80  may detect a comprehensive failure of the wheel driver by comparing the output of the current sensor and the output of the rotation angle sensor. Also such operation verification of the wheel driver may be constantly performed while the manually propelled vehicle  1  is operated, or may be performed at a regular cycle. 
     Accordingly, the user can be prevented from using the manually propelled vehicle  1  that is unable to assist due to the failure of the wheel drivers  91 L and  91 R. Thereby, the user can be prevented from being pulled by the manually propelled vehicle  1  due to excessive assist, becoming difficult to operate due to insufficient assist, or the operability from worsening due to a failure in only one side of the wheel driver  91 L or  91 R. 
     Third Example 
     Yet another example of the operation verification procedure of a manually propelled vehicle according to one or more embodiments of the present invention will be described with reference to drawings.  FIG. 9  is a flowchart of yet another example of operation verification of a manually propelled vehicle according to one or more embodiments of the present invention.  FIG. 10  is a graph showing an output of a sensor of a manually propelled vehicle according to one or more embodiments. Each part of the manually propelled vehicle  1  may be as described above. In one or more embodiments of the first example and one or more embodiments of the second example, the operation verification may be performed at the time of start traveling of the manually propelled vehicle  1 . However, there may be a case in which a failure occurs while the manually propelled vehicle  1  is traveling. Therefore, in the manually propelled vehicle  1  according to one or more embodiments of the present example, the operation verifications of a motion sensor  60  and a sensor  70  may be performed while traveling. Further, the vertical axis of the graph in  FIG. 10  is a voltage of an output signal of a force sensor  71  of the sensor  70 , and the horizontal axis is a time from the start of detection. 
     Before illustrating the operation verification procedure of the motion sensor  60  and the sensor  70 , a periodic speed change in human (user) walk will be described. When a human (user) walks, even when recognizing that walking has been at a constant speed, a periodic fluctuation in walking speed occurs viewed in a short period of time. In other words, the walking speed of a human may fluctuate due to a certain walking rhythm (behavior of the user). Further, when the user operates the manually propelled vehicle  1  while walking, components that periodically fluctuate caused by the walking rhythm are included even in the operating force when the user operates (pushes) the manually propelled vehicle  1 . For example, in the graph of  FIG. 10 , the output of the sensor  70  is affected by the component that fluctuates periodically caused by the walking rhythm, and a certain periodic fluctuation is recognized. 
     The controller  80  may use this periodic fluctuation when the operating force is applied to the manually propelled vehicle  1  to perform the operation verification of each part. First, the controller  80  may acquire an output of a sensor  70  (step  41 ), and acquire an output of a motion sensor  60  (mainly an acceleration sensor  61 ) (step S 42 ). The controller  80  may store the acquired information into a memory  81  in association with the time. The controller  80  may determine whether a predetermined time has elapsed from the acquisition of the sensor  70  and the acquisition of the output of the acceleration sensor  61  (step S 43 ). 
     When the predetermined time has not elapsed (NO in step S 43 ), the controller  80  may return to acquiring the output of the sensor  70  (step S 41 ). When the predetermined time has elapsed (YES in step S 43 ), the controller  80  may refer to the data where the outputs of the sensor  70  and outputs of the acceleration sensor  61  to determine whether there is a periodic behavior associated with walking in the data (step S 44 ). As a verification method for periodic behavior associated with walking, for example, repetition of the maximum value and minimum value of the outputs within a predetermined range of the output value may be identified. In addition, a determination may be performed whether a periodic behavior associated with walking by storing a portion of the acquired data previously into the memory  81  as sample data to compare with the sample data. 
     When there is behavior associated with walking in the stored data (YES in step S 44 ), the controller  80  may determine that the power assist device  110  of the manually propelled vehicle  1  is running normally (step S 45 ). Then, the controller  80  may newly acquire an output of the sensor  70  (return to step S 41 ). 
     When there is no behavior associated with walking in the stored data (NO in step S 44 ), the controller  80  may determine that there is a failure in the power assist device  110  of the manually propelled vehicle  1 , the user is operating the manually propelled vehicle  1  inappropriately or is giving unsteady operation (step S 46 ). Then, the controller  80  may notify an error (step S 47 ) and deactivate the assist function (step S 48 ). 
     In addition, a description of an inappropriate operation and unsteady operation by a user is described with reference to drawings.  FIG. 11A  is a schematic diagram illustrating an example of inappropriate operation of a manually propelled vehicle by a user; and  FIG. 11B  is a schematic diagram illustrating an example of an unsteady operation of a manually propelled vehicle by a user.  FIG. 11  is one example of inappropriate operation illustrating when a user Dr is riding on the seating surface of the manually propelled vehicle  1  and operating a grip  22  of a handle  20 . Because the user Dr applies an operating force onto the handle  20 , the controller  80  may acquire an output of the operating force from the sensor  70 . 
     Therefore, the controller  80  may start assisting; however, because no periodic behavior has occurred associated with walking in the operating force from the user Dr who is riding on the seating surface in this manner, the controller  80  may determine an error and stop assisting. The manually propelled vehicle  1  may determine whether or not the user Dr is present by a distance measuring sensor  63 , and detect that the user Dr is not behind the manually propelled vehicle  1  in the normal state. Therefore, in the normal state, assisting may not be performed in this type of operation. However, when the distance measuring sensor  63  has a failure, or when a different person is walking behind the manually propelled vehicle  1 , or the like, even though the output of the distance measuring sensor  63  is an output of when assisting is possible, the controller  80  can determine an error because there is no periodic behavior associated with walking in the output of the sensor  70 . The safety can be verified by the distance measuring sensor  63  and the operation verification of one or more embodiments of the present example. 
     Further, as illustrated in  FIG. 11B , when the user Dr pushes the handle  20  from the rear side of the manually propelled vehicle  1 , there may be a case in which the front side is lifted. In such case, the output of the sensor  70  may become an output indicating that the operating force of the user Dr is applied to the handle  20 . At that time, the controller  80  may perforin assisting; however, when the front side travels so as to be raised as is, a periodic behavior associated with walking does not appear in the output of the motion sensor  60 . Therefore, the controller  80  may determine that it is an error and not assist. 
     As described above, a periodic behavior associated with walking by the user can be verified in the output of the sensor  70  and the output of the motion sensor  60 , and therefore, even during travel of the manually propelled vehicle  1 , the operation verification of the sensor  70  and the motion sensor  60  can be performed. Further, even though abnormality in various sensors is not determined, the user can be assisted safely because the operation by the user can be determined either as normal or as having an error. 
     Behavior of both outputs of the sensor  70  and output of the motion sensor  60  may be verified as a method to verify periodic behavior associated with walking in one or more embodiments of the present example; however, the invention is not limited to such a configuration. A periodic behavior associated with walking may also appear in outputs of the rotation angle sensors  914 L and  914 R, and therefore, the outputs of the rotation angle sensors  914 L and  914 R may be used. Furthermore, outputs of all of these may be used, or output of at least one of them may be used. 
     Characteristics other than these are the same as the characteristics of one or more embodiments of the first example and one or more embodiments of the second example. 
     Fourth Embodiment 
     A manually propelled vehicle (manually propelled vehicle  1 ) according to one or more embodiments of the present invention may determine an assisting force to assist operation by the user based on output of a motion sensor  60  and output of a sensor  70 . The outputs thereof correspond to each sensor. Therefore, the manually propelled vehicle  1  in one or more embodiments of the present example may perform operation verification in a stationary state.  FIG. 12  is a flowchart of yet another example of operation verification of a manually propelled vehicle according to one or more embodiments of the present invention. 
     As illustrated in  FIG. 12 , a controller  80  may acquire output of a grip sensor  221  (step S 51 ). The controller  80  may determine whether a user is gripping a grip  22  from the output of the grip sensor  221  (step S 52 ). There may be cases where a personal belonging or umbrella may be hooked on the handle  20  other than a hand of the user. The grip sensor  221 , as described above, can detect a width of the contact portion, and the controller  80  may determine whether or not an object in contact with the grip  22  is a hand of the user based on the information of the width. 
     When the controller  80  determines that a hand of the user is contacting the grip  22  (YES in step S 52 ), the controller  80  may resume acquiring the output of the grip sensor  221  (return to step S 51 ). When the controller  80  determines that a hand of the user is not contacting the grip  22  (NO in step S 52 ), the controller  80  may acquire the output of the motion sensor  60  (step S 53 ). The controller  80  may determine whether the manually propelled vehicle  1  is stationary from the output of the motion sensor  60  (step S 54 ). 
     When the controller  80  determines that the manually propelled vehicle  1  is not stationary (NO in step S 54 ), the controller may resume acquiring the output of the grip sensor  221  (return to step S 51 ). When the controller  80  determines that the manually propelled vehicle  1  is stationary (YES in step S 54 ), the controller  80  may acquire the output of the sensor  70  (step S 55 ). 
     When an operating force is applied from the user, the assisting force may be applied to the manually propelled vehicle  1  from the power assist device  110 . Consequently, when the manually propelled vehicle  1  is stationary, the operating force may not be applied to the handle  20  from the user. The controller  80  may use this fact and determine whether the operating force is input. When the operating force is not applied to the handle, the theoretical value of output of the sensor  70  may be “0”; however, in one or more embodiments, the output rarely becomes absolute “0” in an actual sensor, and a small output value within a predetermined range is constantly outputted. Accordingly, the controller  80  of the manually propelled vehicle  1  according to one or more embodiments of the present example may be designed so that the operating force is not applied to the handle  20  as long as an absolute value of the output value of the sensor  70  does not exceed the threshold. 
     That is, the controller  80  may determine whether the absolute value of the output value of the sensor  70  is not more than the threshold (step S 56 ). When the absolute value of the output value of the sensor  70  is below the threshold (YES in step S 56 ), the controller  80  determines that the sensor  70  is running normally (step S 57 ). After determining that the sensor  70  is normal, the controller  80  performs again from the acquisition of output of the grip sensor  221  (return to step S 51 ). It may be performed continuously; however, it may also be performed in a regular cycle. 
     When the acquired absolute value of the output value of the sensor  70  exceeds the threshold (NO in step S 56 ), the controller  80  may determine there is a failure (error) in the sensor  70  (step S 58 ). Then, the controller  80  may notify an error (step S 59 ) of the sensor  70  and deactivate the assist function (step S 510 ). 
     As described above, when the manually propelled vehicle  1  is stationary, the operation verification of the sensor  70  can be performed. Therefore, the user can be prevented from using the manually propelled vehicle  1  with the problem. Accordingly, one or more embodiments of the present invention can assist the operation by the user more safely and more accurately. 
     When determining whether the manually propelled vehicle  1  is stationary from the output of the motion sensor  60  (step S 54 ), the controller  80  may determine whether the absolute value of the output value exceeds the threshold. Further, at that time, the controller  80  may count a number of repeated times to determine whether the manually propelled vehicle  1  is stationary, and when the determination of stationary is repeated a predetermined number of times or more, it may be determined that there is a failure (error) in the motion sensor  60 . Accordingly, detection of a failure in the motion sensor  60  and the sensor  70  becomes possible. 
     The characteristics other than this may be the same as the characteristics of one or more embodiments of the first example to one or more embodiments of the third example. 
     One or more embodiments of the manually propelled vehicle  1  may be used in those for assisting a wheelchair or the like, or carrying a heavy load such as a dolly. It can widely include a configuration that can transfer assisting force to a wheel and assisting an operating force of a user. 
     Various embodiments of the present invention have been described; however, the present invention is not limited to these contents. Also, the features of these embodiments can be used in various combinations with each other, and are not intended to be limited to the specific combinations disclosed herein. Further, the embodiments of the present invention can add various modifications without departing from the spirit of the invention. 
     Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present invention. Furthermore, those of ordinary skill in the art would appreciate that certain “units,” “parts,” “elements,” or “portions” of one or more embodiments of the present invention may be implemented by a circuit, processor, etc. using known methods. Accordingly, the scope of the invention should be limited only by the attached claims. 
     DESCRIPTION OF THE REFERENCE NUMERALS 
     
         
           1  manually propelled vehicle 
           10  vehicle body 
           11  supporting member 
           20  handle 
           21  handlebar 
           22  grip 
           221  grip sensor 
           23  handle holder 
           231  front wall 
           232  rear wall 
           233  screw member 
           30  wheel 
           31  ( 31 L,  31 R) drive wheel 
           32  ( 32 L,  32 R) idler wheel 
           40  baggage compartment 
           50  backrest 
           60  motion sensor 
           61  acceleration sensor 
           62  gyro sensor 
           63  distance measuring sensor 
           70  sensor 
           71  force sensor 
           80  controller 
           801  processor 
           802  wheel drive controller 
           81  memory 
           82  timer 
           90  power driver 
           91 L,  91 R wheel driver 
           911 L,  911 R motor 
           612 L,  912 R motor driver 
           913 L,  913 R current sensor 
           914 L,  914 R rotation angle sensor 
           100  power source 
           10  power assist device