JP2010273748A - Landing timing specifying apparatus and walking assisting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a landing timing specifying apparatus which specifies the landing timing of the second leg by means of a sensor having a device fitted to the first leg. <P>SOLUTION: A walking assisting apparatus 10 comprises a reaction force sensor 22, an acceleration sensor 34 and a timing specifying section 42. The reaction force sensor 22 detects grounding reaction force applied on the sole of the first leg to which a leg device 12 is fitted. The acceleration sensor 34 detects vertical acceleration of the thigh of the first leg. The timing specifying section 44 specifies the reaction force timing when the detected grounding reaction force exceeds a predetermined reaction force threshold and the acceleration timing when the detected acceleration exceeds a predetermined acceleration threshold, and specifies the landing timing of the second leg on the basis of the timings. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is a landing timing specifying device that is mounted on one leg of a user, detects a physical state of the one leg, and specifies a landing timing of the other leg from the physical state during walking of the user, The present invention relates to a walking assist device that applies landing timing specifying technology. The walking assist device is worn along the thigh from the thigh of one leg of the user, and assists the walking motion by applying torque to the knee. In this specification, in order to distinguish each leg of the user, one leg may be referred to as a first leg and the other leg may be referred to as a second leg.

  So-called powered suits have been developed that are worn along the user's legs and arms to enhance the user's muscle strength. As an application of the powered suit, there is a walking assist device that is attached to a user's leg and assists walking motion. In one form of the walking assist device, a leg brace having a multi-link mechanism with an actuator is worn from the user's thigh to the lower leg to assist the walking motion. For example, Patent Document 1 discloses a walking assistance device that attaches a leg brace with an actuator to each leg of a user and assists the movement of both legs. Patent Document 2 discloses a walking assist device that attaches a leg brace with an actuator only to one leg of a user and assists the operation of the one leg.

JP 2003-135543 A JP 2006-314670 A

  Since the walking movement is a coordinated movement of both legs, it is necessary to assist the movement of the other leg according to the movement of one leg. Therefore, it is desirable to detect the physical state of the second leg to assist the movement of the first leg. Since the walking assist device of Patent Literature 1 attaches the brace to both legs of the user, a sensor for detecting the physical state of the leg may be attached to each brace. In the walking assistance device of Patent Document 2, it is necessary to wear a leg brace with an actuator on the first leg and to wear a leg motion detection brace on the second leg.

  A walking assistance device for a user who is disabled only on one leg only needs to be equipped with a device with an actuator only on the disabled leg. As in the walking assist device of Patent Document 2, it is troublesome for the user to attach a leg motion detection device to the other leg. A technique that can specify the state of the other leg from the sensor of the appliance attached to the first leg without attaching a sensor or the like to the second leg is desired. Furthermore, a walking assistance device that assists the walking action of the first leg based on the specified state of the second leg without attaching a sensor or the like to the second leg is desired.

  The landing timing of the other leg is an important factor in controlling the leg brace that assists the walking movement of one leg. This is because the state changes greatly from one leg stand to both leg stand legs at the landing timing of the legs. The present invention provides a technique for specifying the landing timing of the second leg using only the sensor provided in the brace attached to the first leg. The present invention further provides a walking assistance device to which a technique for specifying landing timing is applied. The walking assist device according to the present invention specifies the landing timing of the second leg only with a device with an actuator attached to the first leg without attaching a sensor or the like to the second leg, and cooperates with the operation of the second leg. A single leg walking operation can be assisted.

  One aspect of the present invention can be embodied in a landing timing specifying device that specifies the landing timing of the second leg from the physical state of the first leg while the user is walking. The timing specifying device includes a reaction force sensor, an acceleration sensor, and a timing specifying unit. This landing timing specifying device may be embodied as a leg brace typically attached to the first leg of the user. The reaction force sensor detects a ground reaction force applied to the sole of the first leg wearing the leg brace. The acceleration sensor detects the vertical acceleration of the thigh of the first leg. More precisely, the acceleration sensor detects a vertical acceleration component of a leg brace part fixed to the thigh. The acceleration sensor only needs to be able to detect the approximate magnitude of the vertical component of the acceleration generated in the thigh. The timing specifying unit specifies a reaction force timing at which the detected ground reaction force crosses a predetermined reaction force threshold and an acceleration timing at which the detected acceleration crosses a predetermined acceleration threshold, and based on these timings To determine the landing timing of the second leg.

  The operation of the landing timing specifying device will be described. The landing timing specifying device specifies the landing timing of the second leg from the physical state of the first leg. The physical state of the first leg here is a ground reaction force and a vertical acceleration component of the thigh. This landing timing specifying device specifies the landing timing of the second leg based on the reaction force timing and acceleration timing of the first leg.

  The landing timing specifying device according to the present invention applies the phenomenon that the vertical acceleration of the thigh of the first leg changes due to the impact when the second leg lands, and the sole of the first leg when the second leg lands. Use the phenomenon that the ground reaction force changes. Specifically, since the impact when the second leg lands is transmitted to the first leg, the vertical acceleration generated in the first leg also changes suddenly at the landing timing. In addition, since the one leg standing leg changes to the both leg standing leg at the landing timing of the second leg, the grounding reaction force of the first leg rapidly decreases at the landing timing of the second leg. Although it is possible to specify the landing timing of the second leg only by the acceleration of the thigh of the first leg or the ground reaction force, the acceleration and the ground reaction force always change during walking. There is a risk that the landing timing may be specified by mistake. Therefore, the landing timing specifying device of the present invention specifies acceleration timing and reaction force timing, and specifies landing timing by a combination of these two different physical quantities. By doing so, the landing timing specifying device of the present invention can reliably specify the landing timing.

  A detailed analysis of the occurrence of the acceleration timing and reaction force timing caused by the landing significantly changes the ground reaction force following a sudden change in acceleration. Therefore, it is preferable that the timing specifying unit specifies the reaction force timing following the acceleration timing as the landing timing. Strictly speaking, the second leg is landing at the acceleration timing, but by specifying the reaction force timing following the acceleration timing as the landing timing, it is possible to avoid erroneous specification of the landing timing due to only the acceleration. According to the study by the inventors, the timing difference between the acceleration timing and the reaction force timing is slight, so that the reaction of the reaction force timing generated following the acceleration timing may be handled as the landing timing without any trouble in controlling the leg brace. It turns out.

  Furthermore, it is preferable that the timing specifying unit specifies the reaction force timing detected within a predetermined limit time from the acceleration timing as the landing timing. Such a landing timing specifying device does not determine the reaction force timing detected after the elapse of the limit time as the landing timing. By setting the limit time, erroneous specification of the landing timing can be prevented more reliably. Note that the reaction force threshold value, the acceleration threshold value, and the limit time may be determined in advance by experiments or simulations.

  As described above, the landing timing of the second leg is used to assist the movement of the first leg. On the other hand, if it can be determined that the user is about to stop walking at the landing timing of the second leg, the movement assistance of the first leg is switched to the transitional movement assistance leading to the stop instead of the assistance of the periodic walking movement. To help. The landing timing specifying device according to the present invention can output a stop determination signal for determining the intention of the user to stop walking at the landing timing by providing the following technical features. That is, the landing timing specifying device includes a joint sensor that detects at least one of the joint angle and the joint angular velocity of the first leg. And a timing specific | specification part outputs the stop determination signal which determines a walk stop, when the value of the joint sensor in the specified landing timing is remove | deviating from the predetermined range. This technical feature is based on the knowledge that the posture determined by the joint angle of the first leg or the motion speed determined by the joint angular velocity differs greatly between the landing timing while continuing walking and the landing timing when trying to stop walking. Yes. The joint angle or joint angular velocity used for determining the intention to stop may be, for example, an angle or angular velocity around the pitch axis of the hip joint of the first leg.

  Another aspect of the present invention can be embodied in a walking assist device that applies a technique for specifying the landing timing of the second leg. The walking assist device of the present invention includes a leg brace with an actuator, a reaction force sensor, an acceleration sensor, and a controller that controls the leg brace. The leg orthosis has a multi-link mechanism in which a thigh link and a crus link are connected by a drive joint so as to be swingable. The drive joint corresponds to the actuator. The drive joint is configured to be positioned adjacent to the user's knee joint when the thigh link and the crus link are respectively fixed to the thigh and crus of the user's first leg. The reaction force sensor detects a ground reaction force applied to the sole of the first leg. The acceleration sensor detects the acceleration in the vertical direction of the thigh link of the leg brace. The controller controls the drive joint so as to follow a predetermined joint angular trajectory pattern. In the walking assistance device of the present invention, the controller is based on the reaction timing at which the detected ground reaction force crosses a predetermined reaction force threshold and the acceleration timing at which the detected acceleration crosses a predetermined acceleration threshold. The joint angular trajectory pattern is switched from the standing joint angular trajectory pattern to the free leg joint angular trajectory pattern. The timing for switching the joint angle trajectory pattern corresponds to the specified landing timing in the landing timing specifying device described above. That is, this walking assist device switches the target angular trajectory pattern of the drive joint from the standing joint angular trajectory pattern to the free leg joint angular trajectory pattern at the specified landing timing. The controller of the walking assist device preferably switches from the standing leg joint angular trajectory pattern to the free leg joint angular trajectory pattern at the reaction force timing detected subsequent to the acceleration timing.

  The operational effects of the walking assist device will be described. When the human walking motion is analyzed in detail, the standing leg motion and the free leg motion are greatly different. Since the stance leg needs to support the weight, a great burden is applied to the knee joint. On the other hand, the free leg does not need to support the weight but is required to move smoothly. As described above, since the movement of the stance leg and the free leg is greatly different, the walking assist device has different joint angle trajectory patterns for the standing leg and the free leg, and switches those trajectory patterns at the landing timing of the second leg. Is preferred. Such a walking assist device gives the user a sense of incongruity when the timing of switching the track pattern is different from the actual landing timing. The walking assist device of the present invention specifies the landing timing of the second leg by the acceleration timing and the reaction force timing, and switches the trajectory pattern at the specified landing timing, so that the walking motion of the first leg can be performed without giving the user a sense of incongruity. Can assist.

  A typical limb joint angle trajectory pattern has a substantially constant joint angle during its terminal period, and a typical free leg joint angular trajectory pattern rotates the drive joint in the flexion direction of the knee joint during its initial period. Has an orbit. This is based on the following findings. During the end of the one-leg stance period in which the weight is supported only by the first leg, the knee joint of the first leg maintains a substantially constant angle until the second leg lands. When the second leg lands, the first leg shifts from the standing leg state to the free leg state. When shifting to the free leg state, the knee joint of the first leg starts to rotate in the bending direction, and the entire first leg is swung forward. That is, immediately before the second leg lands, the knee joint of the first leg is kept substantially constant, and when the second leg lands, the knee joint of the first leg starts to rotate in the bending direction. The above-mentioned joint angular track pattern for standing legs and the joint angular track pattern for free legs match such a user's walking pattern. Here, if the timing for switching to the free leg joint angular trajectory pattern deviates from the user's walking movement, the swing timing of the knee joint during the transition from the standing leg to the free leg and the leg brace in the bending direction The timing for starting the rotation is shifted, and the user feels uncomfortable. The walking assist device of the present invention starts to rotate the driving joint that applies torque to the knee joint in the bending direction of the knee by switching the trajectory pattern at the specified landing timing of the second leg. As described above, the walking assistance device of the present invention can smoothly assist the operation of the first leg in accordance with the walking motion of the user without arranging a sensor or the like on the second leg. In other words, the walking assistance device of the present invention can apply a torque in the bending direction to the knee joint of the first leg at the landing timing of the second leg, and assist the walking motion without giving the user a sense of incongruity. Can do.

  When the user intends to stop walking, it is preferable to control the drive joint so that the walking assist device also follows the transitional trajectory pattern leading to the stop instead of the periodic trajectory pattern for walking assist. In order to realize such a function, the walking assistance device of the present invention preferably has the following technical features. The leg brace includes a joint sensor that detects at least one of a joint angle and a joint angular velocity of the first leg. Then, when the output of the joint sensor at the reaction force timing detected subsequent to the acceleration timing is out of the predetermined range, the controller determines the joint angle track pattern for standing legs and the joint angle track pattern for free legs. Switch to a different third joint angular trajectory pattern to control the drive joint. The “third joint angular trajectory pattern” is not a periodic walking pattern, but a trajectory pattern indicating a target angular trajectory of the knee joint that is aperiodic and leads to a stop of walking.

  According to the present invention, it is possible to realize a landing timing specifying device that specifies the landing timing of the second leg without attaching a sensor or the like to the second leg. Furthermore, according to the present invention, the technique for specifying the landing timing is applied, and the first leg is coordinated with the operation of the second leg only by the appliance with the actuator attached to the first leg without attaching the sensor or the like to the second leg. A walking assist device that assists the movement of the leg can be realized.

FIG. 1 is a schematic diagram of a walking assist device. FIG. 2 is a schematic block diagram of a controller of the walking assist device. FIG. 3 is a diagram for explaining an algorithm for specifying the landing timing. FIG. 4 is a flowchart of processing for specifying the landing timing. FIG. 5 is a flowchart of the trajectory pattern switching process according to the landing timing.

Some of the technical features of the walking assist device of the embodiment will be listed.
(1) The controller of the walking assist device starts to rotate the drive joint in the bending direction of the knee joint at the reaction force timing following the acceleration timing. Note that the timing at which the drive joint starts to rotate does not have to exactly coincide with the reaction force timing, and it is only necessary to start the drive joint in the bending direction with the reaction force timing following the acceleration timing as a trigger.
(2) The controller of the walking assist device notifies the user of the switching of the track pattern prior to switching from the joint angle track pattern for standing legs to the joint angle track pattern for free legs. Alternatively, the walking assistance device notifies the user of the start of rotation prior to starting to rotate the drive joint in the knee bending direction after specifying the landing timing. The controller notifies the user by outputting sound or by vibrating the drive joint.

  A walking assistance device of an embodiment will be described with reference to the drawings. In FIG. 1, the schematic diagram of the walking assistance apparatus 10 is shown. FIG. 1 (A) shows a front view of the walking assistance device 10 in a state worn by the user, and FIG. 1 (B) shows a side view of the walking assistance device 10 in a state worn by the user. In this embodiment, a walking assist device for a user who cannot move the left leg freely is assumed. The walking assist device 10 assists the user's walking motion by applying an appropriate torque to the user's left knee joint. The left leg corresponds to the first leg and the right leg corresponds to the second leg.

  The walking assist device 10 includes a leg brace 12 to be worn on the user's left leg and a controller 40 to be worn on the user's waist. The controller 40 is fixed to the support link 30 fixed to the user's waist. The support link 30 is connected to the upper end of the leg orthosis 12.

  The structure of the leg orthosis 12 will be described in detail. The leg brace 12 is attached to the outside of the left leg from the user's thigh to the lower leg. The leg orthosis 12 is a multi-link mechanism having a thigh link 14, a crus link 16, and a sole link 18. The upper end of the thigh link 14 is connected to the support link 30 via the crotch joint 20a. The lower leg link 16 is connected to the thigh link 14 by a knee joint 20b located outside the knee. The sole link 18 is connected to the crus link 16 by an ankle joint 20c located outside the user's heel. The thigh link 14 is fixed to the user's thigh with a belt. The lower leg link 16 is fixed to the user's lower leg by a belt. The sole link 18 is fixed to the user's sole with a belt. The belt for fixing the sole link 18 is not shown.

  When the user wears the leg brace 12, the crotch joint 20a, the knee joint 20b, and the ankle joint 20c are positioned adjacent to the user's hip joint, knee joint, and ankle joint, respectively. More specifically, when the user wears the leg brace 12, the hip joint 20a, the knee joint 20b, and the ankle joint 20c are respectively the pitch axis of the user's hip joint, the pitch axis of the knee joint, and the pitch of the ankle joint. Located coaxially with the shaft. The leg brace 12 can swing according to the movement of the user's left leg. An encoder 21 for detecting the angle between the links is attached to each joint. In the following, the angle between the links is referred to as the joint angle. Also, the joint angular velocity can be obtained by differentiating the joint angle detected by the encoder. The encoder 21 corresponds to a joint sensor that detects the angle or angular velocity of the joint.

  A motor 32 (actuator) is attached to the knee joint 20b. That is, the knee joint 20b corresponds to a drive joint. Hereinafter, the “knee joint 20b” may be referred to as a “drive joint 20b”. The motor 32 is located outside the user's knee joint. The motor 32 can rotate the crus link 16 with respect to the thigh link 14. That is, the motor 32 can apply torque to the user's left knee joint. As will be described later, the walking assist device 10 stores several trajectory patterns describing changes with time of the target angle of the drive joint. The walking assist device 10 selects one track pattern from the track patterns, and controls the drive joint 20b so as to follow the selected track pattern.

  An acceleration sensor 34 is fixed to the thigh link 14. The acceleration sensor 34 detects the acceleration in the sagittal plane of the thigh link 14. The “sagittal plane” means a plane orthogonal to the pitch axis. Further, as will be described later, in the present embodiment, attention is focused on only the vertical component of the acceleration detected by the acceleration sensor 34. The vertical component can be obtained from the inclination of the thigh link 14 detected by the encoder 21.

  A plurality of pressure sensors 22 a and 22 b are attached to the bottom surface of the sole link 18. As shown in FIG. 1B, the plurality of pressure sensors are attached to the front link 18 at a distance from the front and the rear. The pressure sensor 22 a is attached to the front of the sole link 18, and the pressure sensor 22 b is attached to the rear of the sole link 18. The front pressure sensor 22a is attached to a position corresponding to the user's thumb ball, and the rear pressure sensor 22b is attached to a position corresponding to the user's eyelid. Hereinafter, the two pressure sensors 22 a and 22 b are collectively referred to as the pressure sensor 22. The pressure sensor 22 detects a ground reaction force applied to the sole of the left leg. Therefore, hereinafter, the “pressure sensor 22” may be referred to as “reaction force sensor 22”. In FIG. 1, the pressure sensor 22 is drawn so as to protrude downward from the sole link 18, but this is for helping understanding of the drawing, and the pressure sensor 22 is embedded in the sole link 18. . In addition, the sole link 18 of the left leg has the same thickness as the sole of the shoe worn by the user on the right leg, and is considered so that the right and left legs can be balanced.

  FIG. 2 shows a block diagram of the controller 40. The controller 40 includes a timing specifying unit 42, a motor control unit 44, and a storage device 46. Hereinafter, for the sake of simplicity, the “timing specifying unit 42” is simply referred to as the “specifying unit 42”.

  The function of the controller 40 will be outlined. The specifying unit 42 specifies the landing timing of the right leg of the user from the ground reaction force data detected by the reaction force sensor 22 and the vertical acceleration generated in the thigh link 14 detected by the acceleration sensor 34. Further, the specifying unit 42 determines whether or not the user intends to stop walking based on the angle and angular velocity of the hip joint detected by the encoder 21. This stop determination is performed based on the hip joint angle and angular velocity at the specified landing timing. The specified landing timing and stop determination signal are sent to the motor control unit 44. The motor control unit 44 controls the drive joint 20b based on the landing timing and the stop determination signal. The motor control unit 44 selects and selects one of the “joint angular track pattern for standing legs”, “joint angular track pattern for free legs”, and “joint angular track pattern for stop” stored in the storage device 46. The drive joint 20b is controlled so as to follow the trajectory pattern. In the figure, for the sake of simplicity, “joint angular track pattern for standing leg”, “joint angular track pattern for free leg”, and “joint angular track pattern for stop” are respectively referred to as “pattern for standing leg” and “pattern for free leg”. And “stop pattern”. This abbreviation is also used in the following description. These patterns are collectively referred to as “orbital patterns”. A specific example of the trajectory pattern will be described later.

  With reference to FIG. 3, a description will be given of a right leg landing timing specifying algorithm and a trajectory pattern switching algorithm based on the specifying result. The upper graph in FIG. 3 is a graph showing the temporal change in the vertical acceleration of the thigh link 14 detected by the acceleration sensor 34. The vertical axis of the graph represents acceleration with the upper vertical direction being positive. The middle graph is a graph showing the change over time of the ground reaction force detected by the reaction force sensor 22. The vertical axis of the graph indicates the magnitude of the ground reaction force. Since the ground reaction force cannot be less than zero, the graph takes only positive values. Ground reaction force = zero indicates that the left leg is floating. The lower graph is a graph showing a change with time of the target angle of the drive joint 20b. The time series of the target angle of the drive joint 20b corresponds to the trajectory pattern. The vertical axis represents the target angle of the drive joint 20b. Here, the target angle is set to zero when the thigh link 14 and the crus link 16 are in a straight line, and the direction in which the knee is bent is defined as a positive value. That is, the larger the value of the graph, the more the drive joint 20b rotates in the knee bending direction. Note that these graphs are schematic representations for illustration purposes. However, the trend of change over time is shown in FIG.

  The acceleration changes gently according to the movement of the thigh link 14, but changes abruptly when the impact when the right leg lands is transmitted to the thigh link 14. The change in acceleration indicated by the arrow a in FIG. 3 indicates the influence of the landing impact of the right leg. Since the left leg obtains a vertically upward acceleration due to the landing impact of the right leg, the graph suddenly changes upward at the right leg contact timing. The identifying unit 42 identifies the timing Tg at which the detected acceleration crosses a predetermined acceleration threshold Gth. This Tg corresponds to the acceleration timing. The identifying unit 42 identifies the timing Tf at which the ground reaction force crosses the reaction force threshold Fth between the detection of the acceleration timing Tg and the limit time TL. This timing Tf corresponds to the reaction force timing. An arrow b in FIG. 2 indicates the reaction force timing Tf. The reaction force timing Tf detected following the acceleration timing Tg corresponds to the landing timing. The specifying unit 42 specifies the reaction force timing Tf detected following the acceleration timing Tg as the landing timing, and outputs the specified landing timing to the motor control unit 44. The specifying unit 42 ignores the reaction force timing detected after the limit time TL has elapsed from the acceleration timing Tg. That is, the specifying unit 42 specifies and outputs the reaction force timing Tf detected within the limit time TL from the acceleration timing Tg as the landing timing, and ignores the reaction force timing Tf detected after the limit time TL has elapsed.

  The physical meaning of the acceleration timing Tg and the reaction force timing Tf will be described. In the period preceding the acceleration timing Tg, the right leg is in a free leg state and only the left leg is grounded. Therefore, before the acceleration timing Tg, the magnitude of the ground reaction force of the left leg is substantially equal to the user's own weight. When the right leg lands, the impact is transmitted to the thigh link 14 and the acceleration changes greatly. The location of the arrow a shows the state. After the landing of the right leg, the grounded right leg also begins to support its own weight, so the ground reaction force of the left leg decreases rapidly. As described above, the acceleration of the left leg suddenly changes simultaneously with the landing of the right leg, and immediately after that, the ground reaction force of the left leg rapidly decreases. The specifying unit 42 specifies the reaction force timing Tf following the detection of the acceleration timing Tg as the landing timing. The specifying unit 42 specifies the landing timing of the right leg by a combination of different physical quantities such as acceleration and ground reaction force. With such an algorithm, the landing timing of the right leg can be reliably specified without erroneous determination. In addition, since the period from the acceleration timing Tg to the reaction force timing Tf is very short, there is substantially no inconvenience in considering the reaction force timing Tf as the landing timing. In the middle reaction force graph of FIG. 3, the timing at which the ground reaction force of the left leg becomes zero indicates the timing at which the left leg leaves the floor.

  The function of the motor control unit 44 will be described. Until the landing timing (reaction force timing Tf) is specified, the motor control unit 44 controls the drive joint 20b so as to follow the standing pattern (standing joint angular path pattern). The symbol Pa in the lower part of FIG. The standing pattern Pa is a target angle pattern in the period described as “standing period” in FIG. 3. The change in the target angle of the drive joint 20b is small during the stance, and the target angle is constant during the terminal period. A period surrounded by a broken line indicated by reference sign Pae indicates a termination period. In response to specifying the landing timing, the motor control unit 44 switches the track pattern from the standing pattern to the free leg pattern (free leg joint angle track pattern). The code | symbol Pb of FIG. 3 has shown the pattern for free legs. The free leg pattern Pb corresponds to a target angle pattern in the period described as “free leg period” in FIG. In the free leg pattern, the target angle increases toward the flexion side of the knee in the initial period Pbs. In other words, the free leg pattern has a trajectory that rotates the drive joint 20b to the knee flexion side during the initial period Pbs. In other words, the motor control unit 44 starts rotating the drive joint 20b to the knee flexion side at the specified landing timing Tf.

  Switching from the standing leg pattern to the free leg pattern with the landing timing Tf as a trigger has the following advantages. The landing timing of the right leg changes depending on the walking speed of the user or the height of the planned landing surface. For example, when the planned landing surface is higher than the previous landing, the landing timing is advanced. On the other hand, if the planned landing surface is lower than the previous landing, the landing timing is delayed. In either case, the user starts bending the knee joint of the left leg to the bending side at the landing timing of the right leg. In the walking assist device 10 according to the embodiment, the target angle of the drive joint 20b is kept constant during the end period of the standing pattern, and the drive joint 20b starts to rotate to the bending side at the specified landing timing. Such a trajectory pattern switching algorithm matches well with the bending motion of the knee joint of the user's left leg in the walking motion. The walking assist device 10 can apply torque to the knee joint of the left leg without a sense of incongruity according to the user's walking motion without attaching a sensor or the like to the right leg.

  The operation of the controller 40 can also be expressed as follows. That is, the controller 40 starts rotating the drive joint 20b in the bending direction of the knee joint at the reaction force timing following the acceleration timing. Note that the timing at which the drive joint 20b starts to rotate does not have to exactly coincide with the reaction force timing, and the drive joint 20b may be started to rotate in the bending direction using detection of the reaction force timing following the acceleration timing as a trigger. .

  A flowchart of the landing timing specifying process executed by the specifying unit 42 is shown in FIG. The “G flag” shown in FIG. 4 is a flag for specifying the timing at which the detected acceleration crosses the acceleration threshold Gth. The “G flag” is set to ON when the detected acceleration crosses the acceleration threshold Gth. As will be described later, the “G flag” is reset to OFF after the landing timing is detected. The “landing flag” is a flag that is set to ON when the identifying unit 42 identifies the landing timing of the right leg. The “landing flag” is set OFF while the ground reaction force of the left leg is zero. The “stop determination flag” is a flag indicating a determination result that the user intends to stop walking. The “stop determination flag” is set to OFF when the walking assist device is activated, and is set to ON when the intention to stop walking is determined.

  First, the controller 40 acquires values of the reaction force sensor 22, the acceleration sensor 34, and the encoder 21 (S2). A Kalman filter is employed to extract the acceleration component in the vertical direction from the acceleration in the sagittal plane acquired by the acceleration sensor 34. When the G flag is not ON, the controller 40 compares the detected acceleration with the acceleration threshold Gth (S4: NO, S6). As described above, the acceleration value is below the acceleration threshold Th before the landing timing. When the detected acceleration exceeds the acceleration threshold Gth, in other words, when the detected acceleration crosses the acceleration threshold Gth, the controller 40 sets the G flag to ON (S6: YES, S8). At this time, the controller 40 starts a timer (S8). The process of FIG. 4 is executed for each control cycle, and the controller 40 repeats the above process until the detected acceleration crosses the acceleration threshold Gth (S6: NO).

  When the G flag is set to ON, the controller 40 compares the detected ground reaction force with the reaction force threshold Fth until the time of the timer exceeds the limit time (S4: YES, S10: NO, S12). When the grounding reaction force detected within the limit time falls below the reaction force threshold Fth, in other words, when the detected grounding reaction force crosses the reaction force threshold Fth within the limit time, the controller 40 turns on the landing flag. Is set (S12: YES, S14). The timing when ON is set in the landing flag corresponds to the landing timing.

  After the landing flag is set to ON, the controller 40 determines whether or not the hip joint angle and the joint angular velocity around the pitch axis of the first leg are within a prescribed range (S16). Here, the “specified range” is obtained in advance by an experiment or the like, and is set to a range where the hip joint angle and the angular velocity can be taken at the right leg landing timing while walking is continued. That is, when the hip joint angle and the joint angular velocity around the pitch axis of the first leg are out of the prescribed ranges, the user is very likely to stop walking. The controller 40 determines that the user is about to stop walking when the hip joint angle and the angular velocity at the landing timing are out of the prescribed ranges. That is, when the hip joint angle and the joint angular velocity around the pitch axis of the first leg at the landing timing exceed the specified range, the controller 40 sets the stop determination flag to ON (S16: NO, S18).

  Note that after the landing flag is set to ON in step S14, or after the timer time exceeds the limit time in the branch of step S10, the controller 40 resets the G flag to OFF in preparation for the detection of the next landing timing. (S20). The controller 40 also stops the timer simultaneously with the resetting of the G flag (S20).

  The flowchart of FIG. 4 is executed for each control sampling. The specifying unit 42 outputs a landing flag and a stop determination flag to the motor control unit 44. Further, the process of FIG. 4 is executed in parallel with a process executed by a motor control unit 44 described later. That is, the landing timing specified by the specifying unit 42 is used by the motor control unit 44 in real time. In other words, as described later, the motor control unit 44 switches the track pattern at the specified landing timing.

  With reference to FIG. 5, the flowchart of the process which the motor control part 44 performs is shown. The motor control unit 44 receives the landing flag and the stop determination flag from the specifying unit 42. When the stop determination flag is set to ON, the motor control unit 44 selects a stop pattern from the storage device 46 and controls the motor 32 (S30: YES, S32). On the other hand, when the stop determination flag is not ON and the landing flag is set to ON, the motor control unit 44 selects the free leg pattern from the storage device 46 and follows the selected pattern. The motor 32 is controlled (S34: YES, S36). Finally, when the stop determination flag is not ON and the landing flag is not set to ON, the controller 40 selects the standing pattern from the storage device 46 and follows the selected trajectory pattern. 32 is controlled (S38). As described above, the controller switches the track pattern at the landing timing specified by the right leg. The stop pattern is a track pattern different from the standing leg pattern and the free leg pattern. Specifically, the stop pattern is a trajectory pattern in which the target angular velocity of the drive joint 20b gradually approaches zero and finally the drive joint 20b is stopped at an angle of zero.

  Other features of the walking assist device 10 will be described. The walking assist device 10 vibrates the drive joint 20b prior to switching the track pattern from the standing leg pattern to the free leg pattern. This vibration notifies the user of switching of the trajectory pattern. As described above, the drive joint 20b starts to rotate in the knee bending direction by switching to the free leg pattern. Since the user can know the start of rotation of the drive joint 20b by the vibration, the user can know the movement of the walking assist device 10 in advance. Note that the walking assist device 10 may employ sound output instead of vibration.

  In the above embodiment, the walking assist device 10 that switches the trajectory pattern at the reaction force timing following the acceleration timing has been described. Of the walking assistance devices 10, the device that executes the landing timing specifying process shown in FIG. 4 corresponds to the landing timing specifying device.

  In the embodiment, an example of the standing leg pattern and the free leg pattern has been described. The trajectory pattern switched at the specified landing timing is not limited to the embodiment. Further, the acceleration sensor 34 may be attached to the support link 30 positioned above the thigh link 14. Further, in addition to the knee joint 20b, a motor may be attached to the crotch joint 20a or the ankle joint 20c of the leg brace 12, and these joints may be employed as the drive joint.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

10: Walking assist device 12: Leg orthosis 14: Thigh link 16: Lower thigh link 18: Sole link 20a: Crotch joint 20b: Knee joint (drive joint)
20c: Ankle joint 21: Encoder 22: Pressure sensor (reaction force sensor)
30: Support link 32: Motor 34: Acceleration sensor 40: Controller 42: Timing specifying unit 44: Motor control unit 46: Storage device

Claims (8)

A landing timing specifying device that specifies the landing timing of the second leg from the physical state of the first leg during walking of the user,
A reaction force sensor for detecting a ground reaction force applied to the sole of the first leg;
An acceleration sensor for detecting the vertical acceleration of the thigh of the first leg;
The reaction force timing at which the detected ground reaction force crosses a predetermined reaction force threshold and the acceleration timing at which the detected acceleration crosses a predetermined acceleration threshold are specified, and the specified reaction force timing and acceleration timing are specified. A timing specifying unit for specifying the landing timing of the second leg based on the second leg;
A landing timing specifying device comprising:   The landing timing specifying device according to claim 1, wherein the timing specifying unit specifies a reaction force timing following the acceleration timing as a landing timing.   The landing timing specifying device according to claim 2, wherein the timing specifying unit specifies a reaction force timing detected within a predetermined limit time from the acceleration timing as a landing timing. A joint sensor for detecting at least one of a joint angle and a joint angular velocity of the first leg;
The timing specifying unit outputs a stop determination signal for determining stop of walking when the output value of the joint sensor at the specified landing timing is out of a predetermined range. The landing timing specifying device according to any one of the above. A walking assist device that is attached to the user's first leg and assists the user's walking motion,
The thigh link and the crus link are swingably connected by the drive joint, and when the thigh link and the crus link are respectively fixed to the thigh and the crus of the user's first leg, the drive joint is connected to the user's knee joint. A leg brace located adjacent to,
A reaction force sensor for detecting a ground reaction force applied to the sole of the first leg;
An acceleration sensor for detecting the vertical acceleration of the leg brace;
A controller that controls the drive joint so as to follow a predetermined joint angular orbit pattern,
The controller determines the joint angle trajectory pattern based on the reaction timing at which the detected ground reaction force crosses a predetermined reaction force threshold and the acceleration timing at which the detected acceleration crosses a predetermined acceleration threshold. A walking assist device that switches from a track pattern to a joint angle track pattern for free legs.   The walking assist device according to claim 5, wherein the controller switches from the standing-leg joint angular trajectory pattern to the free-leg joint angular trajectory pattern at a reaction force timing detected subsequent to the acceleration timing.   A joint angle is constant during the end period of the joint angle trajectory pattern for standing legs, and the joint angle trajectory pattern for the free leg has a trajectory that rotates the drive joint in the bending direction of the knee joint in the initial period. The walking assist device according to claim 6. The leg brace includes a joint sensor that detects at least one of a joint angle and a joint angular velocity of the first leg,
When the output of the joint sensor at the reaction force timing detected subsequent to the acceleration timing is out of the predetermined range, the controller determines that the joint angle track pattern for standing leg and the joint angle track pattern for free leg are different. The walking assist device according to claim 6, wherein the driving joint is controlled by switching to three joint angle trajectory patterns.

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