Patent Publication Number: US-2022211567-A1

Title: Electric power assist device and control device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-001727 filed on Jan. 7, 2021, incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to an electric power assist device and a control device. 
     2. Description of Related Art 
     Japanese Unexamined Patent Application Publication No. 2010-075658 (JP 2010-075658 A) discloses an electric power assist device that assists a user in walking with the electric power assist device worn on the body of the user. In a configuration described in JP 2010-075658 A, output of an actuator is changed according to a charging state of a battery. As a result, the output of the actuator decreases as a remaining battery level decreases, so that the user can recognize that the remaining battery level is low. 
     SUMMARY 
     In the configuration described in JP 2010-075658 A, an operation amount of the electric power assist device is controlled such that length of stride while walking is assisted becomes constant. Therefore, even when the user is in poor physical condition, the length of stride is controlled to be the same as that in a normal condition, which may cause fatigue or pain to the user. 
     The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide an electric power assist device and a control device capable of controlling an actuator according to a physical condition of the user. 
     An electric power assist device according to the present disclosure includes a processor that includes hardware, and the processor controls an operation amount and an operation speed of an actuator that assists a user in walking with the electric power assist device worn on the user, detects biometric information of the user, and controls the actuator such that the operation amount becomes larger than the operation amount in normal times but length of stride or the operation speed while walking is assisted becomes smaller than the length of stride or the operation speed in normal times, when determination is made that a physical condition of the user is poor based on the detected biometric information. 
     A control device according to the present disclosure includes a processor that includes hardware, and the processor controls an operation amount and an operation speed of an electric power assist device that assists a user in walking with the electric power assist device worn on the user, detects biometric information of the user who wears the electric power assist device, and controls an actuator of the electric power assist device such that the operation amount becomes larger than the operation amount in normal times but length of stride or the operation speed while walking is assisted becomes smaller than the length of stride or the operation speed in normal times, when determination is made that a physical condition of the user is poor based on the detected biometric information. 
     According to the present disclosure, the actuator can be controlled according to the physical condition of the user. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein: 
         FIG. 1  is a schematic view schematically showing an electric power assist device according to an embodiment; 
         FIG. 2  is a block diagram showing a functional block of the electric power assist device; 
         FIG. 3  is a flowchart showing a processing flow when an assist level is automatically set; 
         FIG. 4  is a flowchart showing a processing flow in a manual mode; 
         FIG. 5  is a flowchart showing a processing flow in a charge alarm; and 
         FIG. 6  is a diagram illustrating length of stride while walking is assisted. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an electric power assist device and a control device according to an embodiment of the present disclosure will be specifically described with reference to the drawings. Further, the present disclosure is not limited to the embodiment described below. 
       FIG. 1  is a schematic view schematically showing the electric power assist device according to the embodiment. An electric power assist device  1  is an electric power device that assists a user  2  in walking with the electric power assist device worn on the body of the user  2 . The electric power assist device  1  is worn on the leg of the user  2  and electrically assists bending and stretching of the ankle joint. For example, as shown in  FIG. 1 , the electric power assist device  1  is worn on the thigh of the user  2  and electrically assists lifting and swinging of the leg. Alternatively, the electric power assist device  1  is worn on the knee of the user  2  and electrically assists bending and stretching of the knee. Alternatively, the electric power assist device  1  is worn on the ankle of the user  2  and electrically assists plantar flexion and dorsal flexion of the ankle. Then, the user  2  is assisted by the electric power assist device  1  in a state where the user  2  wears the electric power assist device  1 , and length of stride is controlled. 
       FIG. 2  is a block diagram showing a functional block of the electric power assist device. As shown in  FIG. 2 , the electric power assist device  1  includes a biometric information detection unit  11 , a disability grade input unit  12 , a state of charge (SOC) detection unit  13 , a control unit  14 , a storage unit  15 , a battery  16 , a motor  17 , an assist unit  18 , a mode switching unit  19 , a level switching unit  20 , an adjustment unit  21 , and a notification unit  22 . 
     The biometric information detection unit  11  is a sensor that detects biometric information of the user  2 . The biometric information detection unit  11  detects the pulse, the body temperature, the muscle mass, and the like of the user  2  as biometric information. The biometric information detection unit  11  can detect the biometric information of the user  2  in real time with the electric power assist device  1  worn on the user  2 . The biometric information detected by the biometric information detection unit  11  is output to the control unit  14  and stored in the storage unit  15 . 
     The disability grade input unit  12  is an input unit for inputting a disability grade of the user  2 . The disability grade input unit  12  is operated by manual operation of the user  2 , and the disability grade is input. Information on the disability grade input by operating the disability grade input unit  12  is output to the control unit  14 . 
     The SOC detection unit  13  is a sensor that detects the state of charge (SOC) of the battery  16 . The SOC represents a charging state of the battery  16 . The SOC detection unit  13  can detect the current SOC. 
     The control unit  14  includes a processor and a memory. The processor is composed of a central processing unit (CPU), a digital signal processor (DSP), a field-programmable gate array (FPGA), and the like. The memory is a main storage device, and is composed of a random access memory (RAM), a read-only memory (ROM), and the like. The control unit  14  loads a program stored in the storage unit  15  into the work area of the memory (main storage device) and executes the program, and controls each component, etc. through the execution of the program such that the function that satisfies a predetermined purpose can be realized. 
     The storage unit  15  is composed of a recording medium such as erasable programmable ROM (EPROM). The storage unit  15  stores various programs executed by the control unit  14 . For example, the storage unit  15  stores a program for executing electric power assist control that assists the user  2  in walking by the output of the motor  17 . That is, the control unit  14  executes the electric power assist control that assists the user  2  in walking based on the program stored in the storage unit  15 . The control unit  14  executes the electric power assist control, and drives the motor  17  using the electric power of the battery  16 . When the motor  17  is driven, the assist unit  18  is operated by power output from the motor  17 . At that time, the control unit  14  controls the output (torque and rotation speed) of the motor  17  to control the operation amount of the assist unit  18 . The operation amount of the assist unit  18  is an assist amount for assisting the operation of the user  2 . 
     The battery  16  is a storage battery that stores electric power to be supplied to the motor  17 . The battery  16  is composed of a secondary battery such as a lithium ion battery. For example, the battery  16  is electrically connected to an external power source via a charging cable. Then, the electric power assist device  1  charges the battery  16  with the electric power supplied from the external power source under the control of the control unit  14 . Further, since the battery  16  is electrically connected to the motor  17 , the electric power charged in the battery  16  can be supplied to the motor  17 . 
     The motor  17  is an electric motor that is driven using the electric power stored in the battery  16 . The power output from the motor  17  is transmitted to the assist unit  18 . For example, a member (power transmission member) for transmitting the power is provided between the rotation shaft of the motor  17  and the assist unit  18 . The assist amount by the electric power assist device  1  changes depending on the output of the motor  17 , that is, the operation amount and operation speed of the motor  17 . 
     The assist unit  18  is a portion that applies the power of the motor  17  to the leg of the user  2 , and is a member that is worn on the leg of the user  2 . For example, the assist unit  18  is worn on the thigh of the user  2  and operates to assist lifting and swinging of the leg. In this case, the electric power assist device  1  shown in  FIG. 1  represents a portion corresponding to the assist unit  18 . Alternatively, the assist unit  18  is worn on the ankle of the user  2  and operates to assist plantar flexion and dorsal flexion of the ankle. Alternatively, the assist unit  18  is worn on the knee of the user  2  and operates to assist stretching and bending of the knee. 
     The mode switching unit  19  is a switch capable of switching between control modes by manual operation of the user  2 . The control modes include an automatic mode and a manual mode. The automatic mode is a control mode in which an assist level is automatically set by the control unit  14 . The manual mode is a control mode in which the assist level is set by the manual operation of the user  2 . The user  2  can select the manual mode by manually operating the mode switching unit  19 . 
     Further, the assist level is a level in which the assist amount by the electric power assist device  1  is set stepwise. The control unit  14  controls the operation amount and the operation speed of the motor  17  such that the assist amount corresponds to the assist level. The higher the assist level, the larger the assist amount by the electric power assist device  1 . The lower the assist level, the smaller the assist amount by the electric power assist device  1 . 
     The level switching unit  20  is an operation unit that can switch between assist levels by the manual operation of the user  2 . The level switching unit  20  is configured to be included in an operation panel or the like. For example, when the manual mode is selected by manually operating the mode switching unit  19 , the control unit  14  sets an assist level to the assist level selected by the level switching unit  20 . Further, the control unit  14  can display the current assist level selected by the level switching unit  20  on the operation panel. 
     The adjustment unit  21  is an operation unit that can adjust the operation amount and the operation speed of the motor  17  by the manual operation of the user  2 . The adjustment unit  21  is configured to be included in the operation panel or the like. Further, the adjustment unit  21  is a unit for adjusting the operation amount and the operation speed of the motor  17  without changing the assist level. That is, the adjustment unit  21  is used when the user  2  wishes to adjust the output of the motor  17  (the assist amount by the electric power assist device  1 ) although the user  2  does not wish to change the assist level. Therefore, when the operation of the adjustment unit  21  is received, the control unit  14  adjusts the output according to the operation of the adjustment unit  21  while maintaining the assist level. 
     Further, the control unit  14  includes a level setting unit  141 , a motor control unit  142 , and a charge alarm unit  143 . 
     The level setting unit  141  sets the assist level according to the set control mode (the manual mode, the automatic mode). When the control mode is set to the manual mode, the level setting unit  141  sets an assist level to the assist level selected by the level switching unit  20 . On the other hand, when the control mode is set to the automatic mode, the level setting unit  141  calculates an assist level based on the biometric information detected by the biometric information detection unit  11  and the information on the disability grade input by operating the disability grade input unit  12 , and sets an assist level to the calculated assist level. In this case, the level setting unit  141  sets an assist level according to the disability grade. That is, the level setting unit  141  sets a high assist level when information on the disability grade indicating that the disability is severe is received, and sets a low assist level when information on the disability grade indicating that the disability is not severe is received. Then, the level setting unit  141  sets an assist level to the assist level according to the detected biometric information. When the biometric information indicating that the physical condition of the user  2  is normal is detected, the level setting unit  141  sets an assist level to the assist level in normal times. The assist level in normal times is, for example, an assist level set according to the disability grade, an assist level registered in the storage unit  15  by initial setting, or the like. Then, when the biometric information indicating that the physical condition of the user  2  is poor is detected, the level setting unit  141  sets an assist level to the assist level higher than that in normal times. For example, the level setting unit  141  sets a higher assist level by one step than the assist level set according to the disability grade information. This is because when the physical condition of the user  2  is poor, it is considered that the length of stride of the user  2  may be smaller than that in normal times, and the user  2  may wish larger assist amount by the electric power assist device  1  than that in normal times. 
     The motor control unit  142  controls the output of the motor  17  according to the assist level. For example, when the assist level is set to be high, the motor control unit  142  controls the output (the operation amount and the operation speed) of the motor  17  such that the output of the motor  17  becomes large, which leads to a larger assist amount. For example, when the assist level is set to be low, the motor control unit  142  controls the output (the operation amount and the operation speed) of the motor  17  such that the output of the motor  17  becomes small, which leads to a smaller assist amount. 
     Further, the motor control unit  142  controls the output of the motor  17  according to the operation of the adjustment unit  21 . For example, when the adjustment unit  21  is operated such that assist amount becomes large, the motor control unit  142  controls the output (the operation amount and the operation speed) of the motor  17  such that the output of the motor  17  becomes large. For example, when the adjustment unit  21  is operated such that assist amount becomes small, the motor control unit  142  controls the output (the operation amount and the operation speed) of the motor  17  such that the output of the motor  17  becomes small. 
     The charge alarm unit  143  notifies that the SOC of the battery  16  has been reduced below a predetermined value. The charge alarm unit  143  sets a threshold value of the SOC according to the disability grade and the assist level. For example, when the disability grade input by operating the disability grade input unit  12  is high, the assist amount becomes large and the power consumption of the battery  16  becomes large, so that the charge alarm unit  143  sets the threshold value of the SOC to a high value. That is, the charge alarm unit  143  sets the threshold value of the SOC to a high value when an assist level in which the power consumption of the battery  16  increases is set. Then, when the SOC of the battery  16  is reduced below the threshold value, the charge alarm unit  143  uses the notification unit  22  to generate an alarm by sound, light, or vibration. The notification unit  22  is composed of a speaker, a lamp, a vibration unit, and the like. The notification unit  22  notifies the user  2  of the charging state of the battery  16 . Therefore, the user  2  can recognize that the battery  16  needs to be charged in the near future by receiving the notification generated by the notification unit  22 . 
       FIG. 3  is a flowchart showing a processing flow when the assist level is automatically set. The control shown in  FIG. 3  is executed when the control mode is set to the automatic mode. 
     The biometric information detection unit  11  detects biometric information of the user  2  (step S 101 ). In step S 101 , the biometric information detection unit  11  detects, as the current biometric information, the pulse, the body temperature, the muscle mass, and the like of the user  2  who wears the electric power assist device  1 . Step S 101  is performed in a case where the user  2  starts to use the electric power assist device  1  at the time when the user  2  wears the electric power assist device  1  and in a case where a predetermined time has elapsed since the user  2  wears the electric power assist device  1 . 
     The control unit  14  determines whether the user  2  is in poor physical condition based on the biometric information detected by the biometric information detection unit  11  (step S 102 ). In step S 102 , it is determined whether the physical condition of the user  2  is normal or poor by comparing the detected biometric information of the user  2  with information on the physical condition of the user  2  in normal times stored in the storage unit  15  in advance. The information on the physical condition in normal times may be information based on a preset value, or may be information obtained by accumulating the biometric information detected by the biometric information detection unit  11 . When the accumulated data is used, an average value or the like of the accumulated data as the biometric information is compared with an actual measurement value detected by the biometric information detection unit  11 . When there is a large difference between the average value and the actual measurement value, it is possible to determine that the physical condition of the user  2  is poor. Step S 102  is performed in a case where the user  2  starts to use the electric power assist device  1  at the time when the user  2  wears the electric power assist device  1  and in a case where a predetermined time has elapsed since the user  2  wears the electric power assist device  1 . The control unit  14  is configured to be able to determine whether the predetermined time has elapsed since the user  2  wears the electric power assist device  1 . 
     When it is determined that the physical condition of the user  2  is poor (step S 102 : Yes), the control unit  14  automatically sets an assist level to the assist level higher than that in normal times (step S 103 ). In step S 103 , the level setting unit  141  sets the assist level to a value higher than that in normal times. When the process of step S 103  is executed, this control routine ends. 
     When it is determined that the physical condition of the user  2  is as usual (step S 102 : No), the control unit  14  automatically sets an assist level to the assist level in normal times (step S 104 ). In step S 104 , the level setting unit  141  sets the assist level to a value in normal times. When the process of step S 104  is executed, this control routine ends. 
     For example, when the control shown in  FIG. 3  is executed at the time when the user  2  wears the electric power assist device  1 , the initial assist level is set by the processes of steps S 103  and S 104 . That is, when the user  2  will try to walk, the assist level is initially set before the user  2  starts to walk. Alternatively, when the control shown in  FIG. 3  is executed while the user  2  is using the electric power assist device  1 , the assist level is automatically changed by the processes of steps S 103  and S 104 . Specifically, when the physical condition of the user  2  becomes worse than in normal times during walking, the assist level is automatically changed according to the poor physical condition of the user  2 . As a result, the assist amount can be adjusted according to the physical condition of the user  2 . When the physical condition of the user  2  that has become worse returns to be normal, the control unit  14  may automatically change the assist level according to the normal physical condition of the user  2 . 
       FIG. 4  is a flowchart showing a processing flow in the manual mode. The control shown in  FIG. 4  is executed by the control unit  14 . 
     The control unit  14  determines whether to set the control mode to the manual mode (step S 201 ). In step S 201 , it is determined whether the manual mode is selected by the operation of the mode switching unit  19 . For example, it is determined whether a request for switching from the automatic mode to the manual mode has been received. 
     When the control mode is set to the manual mode (step S 201 : Yes), the control unit  14  sets an assist level to the assist level selected by the level switching unit  20  (step S 202 ). In step S 202 , the assist level selected by the level switching unit  20  is set such that the assist level selected by the user  2  is set. For example, when the control mode is switched from the automatic mode to the manual mode, the level setting unit  141  changes the assist level set in the automatic mode to the assist level selected by the level switching unit  20 . When the process of step S 202  is executed, this control routine ends. 
     On the other hand, when the control mode is not set to the manual mode (step S 201 : No), this control routine ends. 
       FIG. 5  is a flowchart showing a processing flow in the charge alarm. The control shown in  FIG. 5  is executed by the control unit  14 . 
     The control unit  14  sets the threshold value of the SOC of the charge alarm according to the assist level (step S 301 ). In step S 301 , when the control mode is set to the automatic mode, the threshold value of the SOC is set according to the assist level automatically set by the level setting unit  141 . When the control mode is set to the manual mode, the threshold value of the SOC is set according to the assist level selected by the manual operation of the level switching unit  20 . The set threshold value of the SOC is stored in the storage unit  15 . 
     Further, the control unit  14  sets a charge alarm based on the set threshold value of the SOC (step S 302 ). In step S 302 , the charge alarm is set. 
     Then, the control unit  14  determines whether the SOC of the battery  16  is reduced below the threshold value (step S 303 ). In step S 303 , it is determined whether the current SOC detected by the SOC detection unit  13  is reduced below the threshold value set in step S 301 . 
     When the SOC of the battery  16  is reduced below the threshold value (step S 303 : Yes), the control unit  14  activates the charge alarm to notify that the SOC of the battery  16  is reduced (step S 304 ). In step S 304 , the notification unit  23  performs notification by sound, light, vibration, or the like under the control of the control unit  14 . When the process of step S 304  is executed, this control routine ends. 
     On the other hand, when the SOC of the battery  16  is not reduced below the threshold value (step S 303 : No), this control routine ends. 
       FIG. 6  is a diagram illustrating length of stride while waking is assisted. In  FIG. 6 , a case where the physical condition of the user  2  is as usual is described as “normal”, and a case where the physical condition of the user  2  is poor is described as “poor physical condition”. Further,  FIG. 6  illustrates, as examples, Example, Comparative Example 1, Comparative Example 2, and Comparative Example 3. 
     As shown in  FIG. 6 , in Example, in a case where the physical condition of the user  2  is as usual (normal), the assist amount is controlled to “10” by the electric power assist device  1  when the movement amount of the user  2  becomes “10”. The length of stride in this case is a length of stride while waking is assisted in normal times for the user  2 . That is, length of stride A when the assist amount becomes “10” and the user  2  recognizes that the movement amount is “10” is recognized by the user  2  as the assist level in normal times, which does not cause discomfort for the user  2 . 
     Comparative Example 1, Comparative Example 2, and Comparative Example 3 each illustrates, as an example, a configuration in which the poor physical condition of the user  2  cannot be detected. In Comparative Example 1, although the movement amount of the user  2  is “6” that is smaller than that in normal times because the user  2  is in poor physical condition, the assist amount is “10” because the electric power assist device cannot determine the physical condition of the user  2 . Length of stride while waking is assisted according to Comparative Example 1 is length of stride B smaller than the length of stride A in normal times. In Comparative Example 1, there is a difference between the movement amount of the user  2  and the assist amount by the electric power assist device. Therefore, in Comparative Example 2, when the movement amount of the user  2  becomes “6”, the assist amount is also controlled to be “6”. However, since the physical condition of the user  2  cannot be also determined in Comparative Example 2, the length of stride becomes considerably smaller than the length of stride A in normal times for the user  2  whose physical condition is normal, which results in discomfort for the user  2 . The deviation of the length of stride in Comparative Example 2 from the length of stride A is the same as that in Comparative Example 1. Therefore, Comparative Example 3 is configured to assist the user  2  such that a length of stride is set to be the same as that in normal times according to the movement amount of the user  2 . In Comparative Example 3, when the movement amount of the user  2  is “6”, the assist amount is controlled to be “14” such that the length of stride is set to be the length of stride A in normal times. However, in this case, when the user  2  is in poor physical condition and the movement amount is “6” smaller than that in normal times, the assist amount is “14” and the length of stride is the same as the length of stride A in normal times, which may result in discomfort and fatigue for the user  2 . Then, if the user  2  is in poor physical condition, it is considered that the user  2  wishes a larger assist amount than in normal times but wishes smaller length of stride than in normal times. 
     In Example, the output of the motor  17  can be adjusted according to the physical condition of the user  2 . Therefore, in Example, when it is detected that the physical condition of the user  2  is poor, the assist amount is controlled to be “10 to 13” when the movement amount of the user  2  becomes “6”. That is, when the user  2  is in poor physical condition, the electric power assist device  1  controls the assist amount such that the assist amount becomes larger than that in normal times, and controls the length of stride such that the length of stride while waking is assisted becomes smaller than that in normal times. As shown in  FIG. 6 , length of stride C while walking is assisted according to Example when the user  2  is in poor physical condition is smaller than the length of stride A in normal times and larger than the length of stride B while walking is assisted according to Comparative Example 1. As described above, according to Example, when the user  2  is in poor physical condition, it is possible to realize, as the user  2  wishes, a larger assist amount and smaller length of stride than those in normal times. 
     As described above, according to the embodiment, the output of the motor  17  can be controlled according to the physical condition of the user  2 . 
     The electric power assist device  1  is not limited to include the motor  17 , and may include other actuators. That is, a type of actuators is not particularly limited as long as the actuator is an electric actuator that consumes electric power of the battery  16 . For example, the electric power assist device  1  provided with an electric air pump as an actuator may be used. In this case, the electric air pump and the assist unit  18  are connected via a tube. 
     Further effects and modifications can be easily derived by those skilled in the art. The broader aspects of the present disclosure are not limited to the particular details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.