JP2011193901A - Leg assisting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leg assisting device having processing for the time of abnormality occurrence suited to situations.SOLUTION: The leg assisting device 10 includes a leg device 12 and a controller 40. The leg device 12 includes an upper link 14 mounted on the thigh of a user, a lower link 16 mounted on the lower thigh of the user, a rotary joint 20b for swingably connecting the upper link 14 and the lower link 16, and a motor 32 for swinging the lower link relative to the upper link. The controller 40 outputs a command value to the motor 32 so that the swing angle of the lower link 16 follows a target truck. The controller 40 further executes according to the kind of detected abnormality, either one of joint fixing processing of inhibiting the backward swing of the lower link 16 and joint releasing processing of turning the lower link 16 to a state in which it can be swung passively in both forward and backward directions.

Description

  The present invention relates to a leg assist device that applies torque to a leg joint of a user to assist the operation of the leg. Research has been conducted on motion assist devices that reinforce the user's muscle strength by applying torque to the joints of the user's limbs (libms). Such devices typically include multi-link articulated robotic mechanisms that are worn along the user's limbs. A motion assisting device having such a mechanism is sometimes called a “robot suit”, an “exoskelton robot”, or a “powered orthosis”. It is a kind of such a device, and particularly relates to a device (leg support device) that is worn along a user's leg.

  There are two types of leg assist devices: devices for personnel who have been trained to handle devices, such as workers and military personnel, and devices to be used by those who are not trained to handle devices, such as non-healthy people. The technology disclosed in the present specification relates to the latter apparatus. Hereafter, some of the terms used in this specification are confirmed just in case. In this specification, a leg that a user can freely move is referred to as a “sound leg”, and a leg that cannot freely move at least one joint is referred to as an “affected leg”. Further, in this specification, a portion between the knee and the ankle is referred to as “lower leg”, and a portion between the hip joint and the knee joint is referred to as a thigh.

  As a typical mechanism, a leg assist device that assists leg movement has a leg brace that is attached to a user's leg. The leg orthosis includes an upper link to be attached to the user's thigh, a lower link to be attached to the user's lower leg, a rotary joint that pivotably connects the upper link and the lower link, and a lower link to the upper link. The actuator is made to swing. The leg assist device mainly applies torque to the knee joint of the user to assist the walking motion, the seating motion, or the standing motion. The leg assist device may include an actuator that applies torque to the ankle joint and the hip joint in addition to the knee joint. However, since a human operation has a heavy burden on the knee joint, the main purpose of such a leg assist device is to apply torque to the knee joint, that is, to reduce the burden on the knee joint.

  In the case of a leg assist device that assists in the operation of the leg, there is a risk of falling if a malfunction occurs. For this reason, it is preferable that the leg assisting device has a mechanism (measures) that avoids a fall as much as possible when some trouble occurs. In particular, it is important to provide such a mechanism in a leg assist device used for an unhealthy person who cannot freely move the leg.

  As an example of such a mechanism, Patent Document 1 discloses a device that interrupts power transmission to a user when an abnormality is detected. Further, Patent Document 2 discloses a leg assist device that employs a ball screw as a torque transmission mechanism to the knee joint so that the transmission mechanism can continue to support the knee joint even when power supply is stopped.

JP 2006-61460 A JP 2002-191654 A

  The technique of Patent Document 1 makes the knee joint passively swingable when an abnormality occurs. The technique of Patent Document 2 restrains (locks) the knee joint when an abnormality occurs. Here, “passive swinging freely” means that the lower leg is allowed to move by a force applied from the outside. Making the knee joint passively swingable can prevent excessive force from being applied to the knee joint, but cannot support weight. When the knee joint is locked, the weight can be supported, but an excessive force may be applied to the knee joint. How to deal with abnormalities depends on the situation. The present specification provides a leg assist device including a process in the event of an abnormality suitable for a situation.

  The leg assist device disclosed in this specification includes a leg brace and a controller. The leg orthosis includes an upper link to be attached to the user's thigh, a lower link to be attached to the user's lower leg, a rotary joint that pivotably connects the upper link and the lower link, and a lower link to the upper link. And an actuator for swinging. The controller outputs a command value to the actuator so that the swing angle of the lower link follows the target trajectory. The controller further includes a joint fixing process for prohibiting the lower link from swinging backward according to the type of abnormality detected, and a joint for allowing the lower link to be passively swingable in either the forward or backward direction. Execute one of the release processing. In the joint fixing process, it is only necessary to prohibit the lower link from swinging at least backward. For example, both backward swing and forward swing may be prohibited like a brake. Preferably, it is a one-way clutch that prohibits rearward swinging but allows forward swinging.

  The above-mentioned leg assist device uses a joint fixing process and a joint releasing process properly depending on the situation. Said leg assistance apparatus is provided with the process at the time of abnormality generation according to a condition.

  The processing when an abnormality occurs according to the situation is, for example, as follows. The controller determines whether the user is seated based on the swing angle of the lower link. When it is determined that the controller is seated, the controller performs joint release processing, and when it is determined that the controller is not seated, the controller performs joint fixing processing.

  Alternatively, the controller determines whether or not the detected abnormality is an abnormality in the actuator control system. If the controller determines that the control system is abnormal, the controller immediately determines whether the user is seated, cuts off torque transmission, and performs either joint release processing or joint fixing processing according to the determination result. Execute. In addition, when the controller determines that the detected abnormality is an abnormality other than the actuator control system, the controller determines whether or not the user is seated after continuing control of the actuator to a predetermined timing on the target trajectory. Determination is performed, torque transmission is interrupted, and either joint release processing or joint fixing processing is executed according to the determination result. In addition to the above, a novel abnormality occurrence process disclosed in the present specification will be clarified through examples.

  Note that “cutting off torque transmission” has two types: cutting off the supply of a power source (for example, electric power) to the actuator and cutting off the power transmission path from the actuator to the lower link. In the latter case, for example, a clutch is provided between the output shaft of the actuator and the lower link, and torque transmission can be interrupted by releasing the clutch. Further, “backward swing of the lower link” means swinging of the lower link in a direction in which the user's knee is bent. The “swing of the lower link forward” means swinging of the lower link in the direction in which the user's knee extends. Hereinafter, for the sake of simplicity, “backward swing of the lower link” is expressed as “backward swing” or “backward swing”, and “backward swing of the lower link” is referred to as “backward swing”. Expressed as “forward swing” or “forward swing”.

The front view of a leg assistance apparatus is shown. A side view of a leg auxiliary device is shown. An example of the target trajectory of the knee joint swing angle is shown. It is a figure explaining the parameter used in FIG. The control block diagram of a leg auxiliary device is shown. It is a flowchart which shows the flow of control of the whole leg assistance apparatus. It is a flowchart of a control system abnormality determination process. It is a flowchart of a 1st abnormality determination process. It is a flowchart of a 2nd abnormality determination process. It is a flowchart of a 3rd abnormality determination process. It is a flowchart of a 4th abnormality determination process. It is a flowchart of other mounting forms of an abnormality determination process. It is a flowchart of other implementation form of abnormality determination processing. It is a flowchart of a takeoff determination process. It is a flowchart of the process at the time of pressing down a stop button.

  Preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1: shows the front view of the leg assistance apparatus 10 of an Example. FIG. 2 shows a side view of the leg assist device 10. The leg assist device 10 includes a leg brace 12 attached along the user's right leg and a controller 40. A broken line drawn in the controller 40 represents the battery 50. The battery 50 supplies electric power (power) to the motor 32 while supplying electric power to the controller. The leg assist device 10 of the present embodiment is a device for a user who cannot freely move the knee joint of the right leg, and assists the user's walking motion, sitting motion, or standing motion. That is, the leg assist device 10 is a leg assist device for a non-healthy person having one affected leg.

  The mechanical structure of the leg orthosis 12 will be described. The leg orthosis 12 is attached to the outside of the right leg from the user's thigh to the lower leg. The leg orthosis 12 is composed of an articulated multi-link mechanism having an upper link 14, a lower link 16, and a foot link 18. An upper end of the upper link 14 is swingably connected to the waist link 30 through the first joint 20a. The upper end of the lower link 16 is slidably connected to the lower end of the upper link 14 by the second joint 20b. The foot link 18 is swingably connected to the lower end of the lower link 16 by a third joint 20c. The upper link 14 is fixed to the user's thigh with a belt. The lower link 16 is fixed to the user's lower limb with a belt. The foot link 18 is fixed to the sole of the user with a belt. The belt for fixing the foot link 18 is not shown. The waist link 30 is fixed to the trunk (waist) of the user. The joints 20a, 20b, and 20c are rotary joints that swing adjacent links.

  When the user wears the leg brace 12, the first joint 20a, the second joint 20b, and the third joint 20c are substantially coaxial with the pitch axis of the user's right hip joint, the knee pitch axis, and the ankle pitch axis, respectively. To position. Each link of the leg brace 12 can swing according to the movement of the user's right leg. Each joint has an encoder 21. The encoder 21 detects a swing angle between two adjacent links connected to the joint. That is, the encoder 21 detects the angle of each joint. The encoder 21 of the first joint 20a detects the joint angle around the pitch axis of the user's right hip joint. The encoder 21 of the second joint 20b detects the joint angle around the user's right knee pitch axis. The encoder 21 of the third joint 20c detects a joint angle around the user's right ankle pitch axis. Hereinafter, the encoder group 21 attached to each joint may be collectively referred to as an angle sensor 21. The angle between the two links corresponds to the swing angle. The swing angle of the link corresponds to the joint angle of the corresponding user. For example, the swing angle of the second joint 20b positioned coaxially with the knee joint corresponds to the angle of the user's knee joint.

  A ground sensor 19 is attached to the foot link 18. The grounding sensor 19 is attached at two locations in front of and behind the sole. The ground sensor 19 detects whether or not the right foot is grounded. The ground sensor 19 is typically an ON / OFF switch that outputs an “ON” signal when the sole of the foot link 18 is grounded and outputs an “OFF” signal when the sole is floating. It may be a pressure sensor that measures pressure. In the case of a pressure sensor, if the detected pressure is greater than a predetermined threshold, it is determined as “ground”, and if it is less than the threshold, it is determined as “non-ground”.

  A motor (actuator) 32 is attached to the second joint 20b. The motor 32 is located outside the user's knee joint. The motor 32 is positioned substantially coaxially with the user's knee joint. The motor 32 can swing the lower link 16 relative to the upper link 14. That is, the motor 32 can apply torque to the right knee joint of the user. The joint 20b is provided with a one-way clutch 60. When the one-way clutch 60 is engaged with the joint 20b, the lower link 16 is allowed to swing forward but is not allowed to swing backward. Since the one-way clutch 60 is generally used in, for example, an automatic transmission of an automobile, the description of the mechanical structure is omitted. It should be noted that one-way clutches constructed with a ratchet mechanism are also well known.

  The leg assist device 10 applies torque to the user's right knee joint by the motor 32 to assist the walking motion, the seating motion, or the standing motion. The controller 40 of the leg assist device 10 has a target trajectory for the swing angle of the lower link 16. “Target trajectory” is time-series data of the target swing angle of the lower link 16. The “target trajectory” represents the temporal change in the swing angle of the lower leg when an ideal leg motion is realized. The leg assist device 10 guides the user's lower leg so that an ideal walking motion is realized by swinging the lower link 16 along the target trajectory.

  As described above, the target swing angle corresponds to the angle of the lower link 16 with respect to the upper link 14, and also corresponds to the knee joint angle of the user. The target trajectory may be stored in the controller 40 in advance, or may be generated in real time by the controller 40. For example, when assisting the walking motion, the controller 40 determines a target trajectory (standing leg target trajectory) when the right leg is in the standing leg period and a target trajectory (free leg target trajectory) when the right leg is in the swinging leg period. Generate alternately. At this time, when the right leg is in the swing leg period, the controller 40 generates a stance target trajectory for the next stance period according to the current state. In addition, when the right leg is in the stance period, the controller 40 generates a free leg target trajectory for the next free leg period according to the current state. In the case of a standing leg, the tip of the foot is fixed to the floor, and the free leg moves. Since the constraint conditions are different as described above, the leg assist device 10 divides one walking cycle into a standing target trajectory and a free leg target trajectory.

  A time-dependent change in the knee joint angle in the normal walking motion, that is, the standing target trajectory and the free leg target trajectory will be described in detail. FIG. 3 is a diagram for explaining the movement of the right leg during walking. The graph indicated by the symbol Ak indicates the time change of the right knee joint angle (knee angle). The knee angle Ak also corresponds to time-series data of the target swing angle of the lower link 16, that is, the target trajectory. It should be noted that the graph of FIG. 3 represents the outline (trend) of the temporal change (target trajectory) of the knee angle Ak and does not accurately represent the knee angle.

  FIG. 4 is a diagram illustrating the definition of the knee angle Ak. The solid line represents the right leg and the broken line represents the left leg. The solid line above the hip joint represents the trunk. The same applies to FIG. A straight line L1 indicates a straight line connecting the hip joint and the knee joint. The straight line L1 corresponds to a straight line along the longitudinal direction of the thigh. The knee angle Ak is expressed as an angle from the straight line L1 toward the lower leg. When the knee is fully extended, the knee angle Ak = 0. When the knee bends at a right angle corresponds to a knee angle Ak = + 90 degrees.

  Returning to FIG. 3, the description of the target trajectory will be continued. Timing Ta indicates the timing at which the right leg lands. Timing Td indicates the timing at which the right leg takes off. The period from timing Ta to Td corresponds to the stance period. The timing Tb is a timing at which the knee angle Ak becomes the largest during the standing period of the right leg. Timing Tc corresponds to the timing at which the heel of the right leg starts to float and the lower leg starts to swing backward in the last part of the stance period. Timing Tf indicates the timing at which the right leg lands again. Timing Te indicates a timing at which the knee angle Ak becomes maximum during the swing leg period. The form of the leg at each timing is shown in FIGS. As shown in (a) and (f), at the landing timings Ta and Tb, the knee of the right leg is fully extended, and the knee angle Ak is zero. FIG. 3C shows the shape of the leg at the timing Tc. As shown by the solid line (right leg) in (c), at this timing Tc, the lower leg starts to swing backward while the foot tip is grounded. That is, at the timing Tc, the knee angle Ak changes from decreasing to increasing. Further, the timing Tc corresponds to the timing at which the right leg is located most rearward, and after this timing, the right leg is swung forward.

  Timing Td is a timing at which the right leg takes off. (D) shows the form of the leg at the timing Td. The period from timing Tc to Td is a period in which the entire right leg swings forward while the leg leg is grounded, and is called a pressing period. Timing Te indicates a timing at which the knee angle Ak becomes maximum during the swing leg period. At the timing Te, the knee joint during the stance period also becomes the maximum value. Tb indicates the timing at which the knee angle Ak becomes maximum during the stance period, and the aspect of the leg shown in (e) and the aspect of the leg shown in (b) are the same except that the left and right legs are interchanged. is there.

  From timing Ta to Td corresponds to the stance period, and from timing Td to Tf corresponds to the swing leg period. During the stance period, the feet are grounded and the toes do not move. During the free leg period, the toes of the legs float and move. The controller 40 generates a target trajectory (a stance target trajectory) for the next stance period in the free leg period, and generates a target trajectory (a free leg target trajectory) for the next free leg period in the stance period. The controller 40 stores the basic pattern of the target trajectory in advance, corrects the basic pattern according to the current state (for example, walking speed, etc.), and determines the target trajectory for the next period. There is a difference between the stance period and the free leg period in which the toes are fixed or floating, and the basic pattern correction algorithm is different. Therefore, the controller 40 sets the target trajectory for one walking cycle as the stance target trajectory. It is divided into free leg target trajectories.

  The controller 40 controls the motor 32 according to each target trajectory so that the lower link 16 follows a change with time indicated in the target trajectory. More specifically, the target trajectory corresponds to time-series data of command values for the motor 32, and the controller 40 sequentially outputs the command values to the motor 32.

  Next, a functional configuration of the leg assist device 10 will be described. FIG. 5 shows a block diagram of the leg assist device 10. In the controller 40, a target trajectory generation module 42, a command value output module 44, and a safety module 46 are prepared. These modules are realized by software (program). Actually, the CPU that executes the software functions as each module.

  Reference numeral 52 in FIG. 5 indicates a console operated by the user. Reference numeral 54 in FIG. 5 generically refers to all sensors included in the leg assist device 10. Therefore, the sensor 54 includes an encoder 21 that measures the swing angle of each link and a ground sensor 19 that detects whether or not the foot is grounded. Further, the sensor 54 includes, for example, a temperature sensor for detecting whether or not the motor 32 has overheated, a disconnection of a communication cable between the sensor and the controller, and a disconnection of a power cable that supplies power from the battery to another unit. And an overcurrent sensor for detecting whether or not an overcurrent has flowed through the motor 32. The safety module 46 detects the occurrence of an abnormality based on the sensor data of the sensors 54.

  5 denotes a main switch of the leg assist device 10. When the main switch is turned on, electric power (power) is supplied to the controller 40 and the motor 32. Reference numeral 56 denotes a power cutoff switch inserted between the battery 50 and the motor 32. The power cut-off switch 56 is opened while power is not supplied (cuts off the power supply path between the battery 50 and the motor 32), and is closed when power is supplied (power supply between the battery 50 and the motor 32). It is a so-called normally OFF type that connects routes). The safety module 46 supplies power to the power cutoff switch 56. That is, when the power supply from the safety module 46 is interrupted, the power cut-off switch 56 is opened and the power supply to the motor 32 is cut off.

  The controller 40 executes various functions such as walking motion assistance, standing motion assistance, or seating motion assistance based on user instructions input via the console 52. For example, when the user instructs walking motion assistance, the controller 40 generates a target trajectory for walking motion assistance. As described above, the target trajectory for assisting the walking motion is divided into the standing target trajectory and the free leg target trajectory. Alternatively, when the user instructs sitting assistance, the controller 40 generates a target trajectory for sitting action assistance. Alternatively, when the user instructs to assist the rising motion, the controller 40 generates a target trajectory for assisting the rising motion. The target trajectory generation module 42 is in charge of generating the target trajectory. The target trajectory generation module 42 stores a basic pattern of the target trajectory for each operation. The target trajectory generation module 42 corrects the basic pattern based on the sensor data of the sensor 54. The corrected basic pattern corresponds to the final target trajectory for driving the motor 32.

  The generated target trajectory is sent to the command value output module 44. The command value output module 44 outputs command values to the motor 32 at sampling cycle intervals. Even if electric power is supplied from the battery 50, the motor 32 does not rotate unless a command value is supplied. Specifically, the power supplied from the battery 50 is first supplied to a control circuit associated with the motor 32. The control circuit does not supply power to the rotor of the motor 32 until the command value is received from the host unit (the controller 40 in this embodiment). When receiving a command from the upper unit, the control circuit starts supplying power to the rotor. That is, the motor 32 rotates only after receiving a command value from the controller 40.

  The safety module 46 determines the occurrence of abnormality from the sensor data of the sensor 54. The safety module 46 cuts off the power supply to the motor 32, switches between engagement and disengagement of the one-way clutch 60, and controls the command value output module 44 according to the type of abnormality. When the power supply to the motor 32 is cut off, the safety module 46 cuts off the power supply to the power cut-off switch 56. The interruption of power supply to the motor 32 corresponds to an example of interrupting torque transmission from the motor 32 (actuator) to the user.

  Before describing the processing executed by the safety module 46, the overall control flow of the leg assist device 10 will be described. FIG. 6 shows a flowchart of control of the leg assist device 10 as a whole. When the user turns on the main switch 58 (S2), the controller 40 first starts up (S4). In step S4, the target trajectory generation module 42, the command value output module 44, and the safety module 46 are initialized. In the course of initialization of the safety module 46, power is supplied to the power cutoff switch 56, and the power cutoff switch 56 becomes conductive. Then, power supply to the motor 32 (actuator) is started (S6). Note that when step S6 is completed, the leg assist device 10 waits for an instruction input from the user (S8). When an instruction from the user is input, the leg assist device 10 executes motor control corresponding to the instruction (S10). For example, when the instruction from the user is a walking motion assist, the controller 40 alternately generates a target trajectory for walking control (that is, a standing target trajectory and a free leg target trajectory), while the lower link 16 becomes the target trajectory. The motor 32 is controlled to follow. When the process moves to step S10, command value output to the motor 32 starts.

  When the motor control according to the user's instruction is finished, the leg assist device 10 returns to the input waiting state again from the user. During this time, if the main switch is turned off (S12: YES), the controller 40 cuts off the power supply to the motor 32 (S14), and then executes an end process (S16). The state before step S10 is executed corresponds to “before command value output to motor 32”.

  Next, processing executed by the safety module 46 will be described. The safety module 46 includes a control system abnormality determination process (FIG. 7), a first abnormality determination process (FIG. 8), a second abnormality determination process (FIG. 9), a third abnormality determination process (FIG. 10), and a fourth abnormality. A determination process (FIG. 11) is executed. The safety module 46 executes each abnormality determination process in the above order. The safety module 46 repeatedly executes the above processing every predetermined cycle.

  The control system abnormality determination process (FIG. 7) will be described. When the safety module 46 detects an abnormality (S52), the safety module 46 first determines whether the type of abnormality is a control system abnormality or any other abnormality (S54). The following are examples of control system abnormalities. The safety module 46 determines that an abnormality in the control system has occurred when sensor data indicating motor overheating is received. The safety module 46 determines that a control system abnormality has occurred when the difference between the target value of the swing angle of the lower link and the measured value exceeds a predetermined threshold. Examples of abnormalities other than those in the control system are as follows. When the communication between the console 52 and the controller 40 is interrupted, the safety module 46 determines that an abnormality other than the control system has occurred. In addition, the safety module 46 determines that an abnormality other than the control system has occurred when the remaining amount of the battery 50 falls below a predetermined value. For example, the safety module 46 determines that an abnormality other than the control system has occurred when communication with any one of the plurality of ground sensors 19 is interrupted.

  When the safety module 46 determines that an abnormality has occurred in the control system (S56: YES), the safety module 46 immediately stops the power supply to the power cutoff switch 56. That is, the safety module 46 immediately cuts off the torque transmission (S60). Next, the safety module 46 engages the one-way clutch 60 (S62). The symbol “OWC” in the figure means a one-way clutch. That is, the safety module 46 (controller 40) determines whether or not the detected abnormality is an abnormality of the actuator control system prior to a first abnormality determination process (FIG. 8) described later (S56). If it is determined that there is an abnormality, the torque transmission is immediately interrupted (S60). When an abnormality of the control system occurs, the controller 40 immediately cuts off the torque transmission. With such a process, the leg assist device 10 reliably stops the actuator. If torque transmission from the actuator to the user is interrupted, torque is not applied to the user from at least the actuator, so that an excessive force can be prevented from being applied to the user from the actuator.

  If the abnormality that has occurred is an abnormality other than that in the control system, the safety module 46 next executes a first abnormality determination process (FIG. 8). In the first abnormality determination process, the safety module 46 determines whether or not the controller 40 is before outputting a command value to the motor 32 (S102). If it is before the command value is output (S102: YES), the safety module 46 immediately stops the power supply to the power cutoff switch 56. That is, the safety module 46 immediately cuts off the torque transmission (S104). If the controller 40 detects an abnormality before outputting the command value to the actuator, the controller 40 cuts off torque transmission from the actuator to the user (S104).

  If the timing at which the abnormality is detected is after the start of the command value output (S102: NO), the safety module 46 next executes a second abnormality determination process (FIG. 9). In the second abnormality determination process, the safety module 46 determines whether or not the lower link 16 is swinging (S202). When it is determined that the lower link 16 is not swinging (S202: NO), the safety module 46 interrupts torque transmission (S204) and engages the one-way clutch (S206).

  If it is determined that the lower link 16 is swinging (S202: YES), the safety module 46 then executes a third abnormality determination process (FIG. 10). In the third abnormality determination process, the safety module 46 first determines whether or not the leg assist device 10 is assisting a user's action (for example, walking action, rising action, or sitting action). To do. Here, “operation assistance” means that the controller 40 controls the motor 32 so that the lower link 16 follows the target trajectory. Determine the operating mode. For example, when the leg assist device 10 is operating in the walking motion assist mode, the determination in step S302 is “YES.” When the leg assist device 10 is assisting the operation (S302: YES), the safety module 46 is The command value is output to the end of the target trajectory (standing target trajectory or swing target trajectory) used when the abnormality is detected (S304) After outputting the command value to the end, the safety module 46 outputs torque. The transmission is cut off (S306), and at the same time, the safety module 46 engages the one-way clutch (S308).

  If an abnormality occurs during the operation assistance, and if the abnormality is an abnormality other than that in the control system, it is highly possible that the operation assistance that has been performed for a while can be continued. In such a case, the leg assist device 10 continues the current stance control (or swinging leg control) until the end, and then interrupts the torque transmission. Both the standing leg control and the swing leg control are finished in a state where both feet are in contact with the ground (see the graph of FIG. 3). Therefore, by continuing to the last in any control, the controller 40 interrupts | blocks torque transmission, after both feet contact | ground. That is, the controller 40 cuts off the torque transmission while the user is in a stable state. Moreover, at this time, the controller 40 engages the one-way clutch 60. Therefore, since the lower link 16 is prohibited from swinging backward, the leg brace 12 can support the weight of the user.

  When the safety module 46 is not assisting the operation (S302, NO), the safety module 46 then executes a fourth abnormality determination process (FIG. 11). In the fourth abnormality determination process, the safety module 46 first interrupts torque transmission (S401). Next, the safety module 46 determines whether or not the user is seated based on the swing angle of the lower link 16 (S402). More specifically, the safety module 46 determines that the user is seated when the swing angle of the lower link is within a predetermined range. The predetermined range is, for example, 45 degrees or more. The swing angle of the lower link 16 being 45 degrees or more corresponds to the lower link 16 swinging backward by 45 degrees or more from the state where the knee is fully extended (see FIG. 4). When the lower link 16 swings backward by 45 degrees or more, there is a high possibility that the user is seated or the waist is lowered to just above the chair. That is, the fact that the lower link 16 swings backward by 45 degrees or more means that the possibility that the user is seated is extremely high. The safety module 46 may also determine whether the user is seated by using information on the inclination angle of the user's thigh (angle with respect to the vertical direction) and / or the load applied to the sole. Is preferred. By using such information, it can be determined with higher reliability whether the user is seated or not.

  When the safety module 46 determines that the user is seated (S402: YES), the safety module 46 executes joint release processing (S404). On the other hand, if it is determined that the safety module 46 is not seated (S402: NO), the joint fixing process is executed (S406). Here, the “joint release process” means that the lower link is in a freely swingable state in both the front and rear directions. The passive swingable state means that the lower link 16 is allowed to swing due to an external force. For example, the “passive swingable state” is achieved when the motor 32 is turned off when the starting torque from the lower link 16 toward the motor 32 is small. Further, when a clutch is provided between the motor 32 and the lower link 16, the “passive swingable state” is achieved by releasing the clutch. The “joint fixing process” means that at least the lower link 16 is prevented from swinging backward. For example, engaging the above-described one-way clutch corresponds to an example of “joint fixing process”. Also. When the motor 32 includes a brake, operating the brake corresponds to an example of “joint fixing process”. When the brake is operated, both the backward swing and the forward swing of the lower link 16 are prohibited.

  The processes of S402, S404, and S406 provide the following advantages. If the user is seated, the user is safe even if the joint is released. On the other hand, when the user is not seated, that is, when the possibility that the user is standing is high, the user may fall down when the joint is released. In such a case, by fixing the joint without releasing it, the leg brace 12 supports the weight of the user and prevents falling.

  Next, another implementation form of the abnormality determination process by the safety module 46 will be described. FIG. 12 shows a flowchart of another implementation of the abnormality determination process. The flowchart of FIG. 12 may be implemented in the safety module 46 instead of the abnormality determination process shown in FIGS.

  When detecting the abnormality (S502), the safety module 46 determines whether the detected abnormality is an abnormality of the actuator control system (S504). When it is determined that the detected abnormality is an abnormality in the control system (S504: YES), the safety module 46 immediately interrupts torque transmission (S507). On the other hand, when it is determined that the detected abnormality is an abnormality other than the actuator control system (S504: NO), the torque transmission is interrupted after continuing the control of the actuator to a predetermined timing predetermined on the target trajectory ( S506, S507). Here, the predetermined timing is typically a timing at which the right foot (affected leg) lands. That is, after detecting the abnormality, the safety module 46 continues the actuator control based on the target trajectory until the right foot (affected leg) has landed, and then interrupts the torque transmission. Whether or not the right foot (affected leg) is grounded is determined based on the sensor data of the ground sensor 19.

  The safety module 46 interrupts torque transmission and determines whether or not the user is seated (S508). The safety module 46 executes joint release processing when it is determined that the user is seated (S510), and performs joint fixing processing when it is determined that the user is not seated (S512).

  Still another embodiment of the abnormality determination process by the safety module 46 will be described. FIG. 13 shows a flowchart of another implementation form of the abnormality determination process. The flowchart of FIG. 13 may be implemented in the safety module 46 instead of the abnormality determination process shown in FIG. When the safety module 46 detects an abnormality (S602), it first determines the operation mode being executed by the controller 40 (S604). The operation mode is classified according to the type of target trajectory used for actuator control. The walking assist mode is a mode for assisting the user's walking motion, and is a case where either a free leg target trajectory or a stance target trajectory is employed. The seating operation assist mode is a mode for assisting the user's seating operation. The start-up operation assist mode is a mode that assists the user's start-up operation.

  In the seating operation assist mode, the safety module 46 continues assisting until the user is seated (S610). Thereafter, the safety module 46 cuts off torque transmission and executes joint release processing (S611, S612). In the stand-up operation assist mode, the safety module 46 continues assist until the user stands up (S613). Thereafter, the safety module 46 interrupts torque transmission and executes joint fixing processing (S614, S615). On the other hand, in the walking motion mode, the safety module 46 continues the actuator control based on the target trajectory until both legs come in contact with the ground (S620). When the affected leg is in the swing leg period, the safety module 46 monitors the sensor data of the ground sensor 19 and determines whether or not the affected leg is grounded. After confirming the contact of the affected leg, the safety module 46 cuts off torque transmission and executes joint fixing processing (S622, S624). Whether or not the affected leg is grounded is determined based on the sensor data of the ground sensor 19.

  In addition to any one of the abnormality determination processes described above, the safety module 46 of the leg assist device 10 preferably performs the takeoff determination process shown in FIG. The safety module 46 determines whether or not the joint is fixed (S702). When the joint is fixed (S702: YES), the safety module 46 determines whether the affected leg is grounded based on the sensor data of the ground sensor 19 (S704). If the affected leg is not in contact with the ground (S704: NO), the safety module 46 releases the fixed joint (S706).

  In the takeoff determination process, when the affected leg is taken off after the second joint 20b of the leg appliance 12 is fixed, the second joint 20b is released. “Fixing the second joint 20b” means prohibiting the lower link 16 from swinging backward. Therefore, if the second joint 20b is fixed, the leg brace 12 supports the weight of the user. Thereafter, the fact that the affected leg leaves the ground indicates that the user is likely to have started to fall. In such a case, the second joint 20b is released, that is, the second joint 20b is set in a passive swingable state so that the user's knee can swing flexibly according to an external force. Such a treatment prevents an unexpected excessive load from being applied to the knee.

  The leg assist device 10 also includes a plurality of stop buttons. A stop button is provided on the console 52. One stop button is a “normal stop button” and the other one is an “emergency stop button”. The “emergency stop button” is a button that is pressed when the user feels an abnormality. That is, distinguishing the operation of the “normal stop button” and the operation of the “emergency stop button” is also a kind of abnormality type determination. FIG. 15 shows a flowchart of processing at the time of button operation. When the safety module 46 detects the operation of any one of the stop buttons (S802), the safety module 46 determines the type of the operated button (S804). When the emergency stop button is operated, the safety module 46 immediately stops the torque transmission (S808) and executes the joint fixing process (S810). On the other hand, when the normal stop button is operated, the safety module 46 continues the control based on the target trajectory until the foot comes in contact with the ground (S808). Thereafter, the safety module 46 stops torque transmission (S808) and executes joint fixing processing (S810).

  The features of the leg assist device 10 of the embodiment described above and the modifications thereof will be summarized. The second joint 20b is a rotary joint and includes a one-way clutch. The one-way clutch prohibits the lower link from swinging backward and allows forward swing. In the first abnormality determination process, the controller 40 determines whether or not the lower link is swinging when it is determined that the abnormality detection is after starting to output the command value to the actuator. The controller 40 engages the one-way clutch when it is determined that the lower link is not swinging. Those processes correspond to the second abnormality determination process described above.

  When assisting the user's walking motion, the controller 40 alternately generates a stance target trajectory for standing leg control and a free leg target trajectory for swing leg control. At the same time, the controller 40 outputs a command value based on the stance target trajectory when the leg wearing the leg brace 12 is a standing leg, and the command value based on the free leg target trajectory when the leg wearing the leg brace is a free leg. Is output. When the controller 40 determines that the lower link is swinging in the second abnormality determination process, the controller 40 outputs the command value to the end of the target trajectory used when the abnormality is detected. The controller 40 outputs the command value to the end of the target trajectory, and then interrupts torque transmission and engages the one-way clutch. Those processes correspond to the above-described third abnormality determination process.

  The leg assist device 10 includes a sensor 54 that detects an abnormality. The controller 40 controls the actuator so that the swing angle of the lower link follows the target trajectory. The controller further executes either a joint fixing process for prohibiting backward swinging of the lower link or a joint releasing process for making the lower link passively swingable in accordance with the detected abnormality type.

  The controller 40 determines whether or not the user is seated based on the swing angle of the lower link. When it is determined that the controller 40 is seated, the controller 40 performs joint release processing, and when it is determined that the controller 40 is not seated, the controller 40 performs joint fixing processing.

  The controller 40 determines whether or not the detected abnormality is an actuator control system abnormality. When it is determined that the control system is abnormal, the controller 40 immediately determines whether or not the user is seated and interrupts torque transmission. Thereafter, the controller 40 executes either a joint release process or a joint fixing process according to the determination result.

  If the controller 40 determines that the detected abnormality is an abnormality other than the actuator control system, whether or not the user is seated after continuing control of the actuator to a predetermined timing on the target trajectory. Determine. Next, the controller 40 cuts off the torque transmission and executes either the joint release process or the joint fixing process according to the determination result.

  When the controller 40 detects an abnormality while controlling the actuator based on the rising assist target trajectory for assisting the user's rising motion, the controller 40 controls the actuator to the end of the rising assist target trajectory, and then transmits the torque. And joint release processing is executed.

  If the controller 40 detects an abnormality while controlling the actuator based on the seating assist target track for assisting the user's seating operation, the controller 40 controls the actuator to the end of the seating assist target track, and then transmits the torque. And joint fixing processing is executed.

  When the controller 40 detects an abnormality while controlling the actuator based on the walking assist target trajectory for assisting the user's walking motion, the controller 40 detects the right foot (the affected leg and the leg wearing the leg brace 12). Continue to control the actuator according to the walking assist target trajectory until the foot) lands. When the controller 40 detects the ground contact of the right foot, it cuts off the torque transmission and executes the joint fixing process. When a one-way clutch is adopted, joint fixing processing is executed at the timing when an abnormality is detected to assist the knee joint in supporting weight. When the affected leg is a swing leg, the controller 40 continues assisting until the swing leg lands, and then interrupts torque transmission.

  The leg assist device 10 includes a console (including an emergency stop switch operated by a user and a normal stop switch). The controller 40 immediately cuts off the torque transmission when the emergency stop switch is operated. When the normal stop switch is operated, the controller 40 continues the actuator control until a predetermined timing on the target trajectory. The controller 40 cuts off the torque transmission when the predetermined timing is reached.

  Points to note about the embodiment and further preferred modifications will be described. After the torque transmission is interrupted, the controller 40 prohibits the lower link from swinging backward according to at least one of the swing angle of the lower link and the determination as to whether or not the user's right foot is in contact with the ground. It is preferable to execute either a fixing process or a joint releasing process for making the lower link passively swingable. Whether or not the user is landing can be determined based on the swing angle of the lower link. Furthermore, even when the right foot is not in contact with the ground, it can be estimated that there is a high possibility that the user has not landed.

The operation of the safety module 46 of the embodiment is generally expressed as follows. The safety module 46 executes one of the following four processes according to the detected abnormality type (and the state of the leg assist device 10).
(1) Immediate joint fixing process for immediately fixing the swing angle between links.
(2) Immediate joint release processing that immediately makes the link passively swingable.
(3) Post-operation joint fixing processing for fixing the swing angle between links after continuing control to follow the target track on the target track until a predetermined timing.
(4) Post-operation joint release processing for making the link passively swingable after continuing control to follow the target trajectory until a predetermined timing on the target trajectory.

  In the leg assist device 10 of the embodiment, the means for interrupting torque transmission is the power cutoff switch 56 that shuts off the power supply to the motor 32. In addition, the means for interrupting the torque transmission may be realized by a clutch disposed between the output shaft of the motor 32 and the lower link 16. When the clutch is released, the torque transmission path is interrupted.

  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: Leg assist device 12: Leg orthosis 14: Upper link 16: Lower link 18: Foot link 19: Ground sensors 20a, 20b, 20c: Joint 21: Encoder (angle sensor)
30: waist link 32: motor 40: controller 42: target trajectory generation module 44: command value output module 46: safety module 50: battery 52: console 54: sensor 56: power cut-off switch 58: main switch 60: one-way clutch

Claims (7)

An upper link to be mounted on the user's thigh, a lower link to be mounted on the user's lower leg, a rotary joint that connects the upper link and the lower link in a swingable manner, and an actuator that swings the lower link with respect to the upper link A leg brace having
A controller that outputs command values to the actuator;
With
The controller
Depending on the type of abnormality detected, either the joint fixing process that prohibits the lower link from swinging backward or the joint release process that makes the lower link passively swingable in either the forward or backward direction. A leg assisting device characterized by performing the above. The controller
Determine whether the user is seated based on the swing angle of the lower link,
2. The leg assist device according to claim 1, wherein joint release processing is executed when it is determined that the user is seated, and joint fixing processing is executed when it is determined that the user is not seated. The controller
Determine whether the detected abnormality is an actuator control system abnormality,
If it is determined that the control system is abnormal, it is immediately determined whether the user is seated, the torque transmission is cut off, and either the joint release process or the joint fixing process is executed according to the determination result The leg auxiliary device according to claim 2 characterized by things. The controller
When it is determined that the detected abnormality is other than the actuator control system, it is determined whether the user is seated after continuing control of the actuator to a predetermined timing on the target trajectory, and torque 4. The leg assist device according to claim 3, wherein the transmission is interrupted and either the joint release process or the joint fixing process is executed according to the determination result.   If the controller detects an abnormality while controlling the actuator based on the rising assist target trajectory for assisting the user's rising motion, the controller immediately cuts off torque transmission and executes joint release control. The leg auxiliary device according to claim 1.   When the controller detects an abnormality while controlling the actuator based on the seating assist target trajectory for assisting the user's seating operation, the controller immediately cuts off the torque transmission and executes the joint fixing process. The leg auxiliary device according to claim 1.   If the controller detects an abnormality while controlling the actuator based on the walking assist target trajectory for assisting the user's walking motion, the walking assist target trajectory until the leg wearing the leg brace lands. 2. The leg assisting device according to claim 1, wherein the control of the actuator according to claim 1 is continued, and when the leg wearing the leg brace lands, torque transmission is interrupted and joint fixing processing is executed.

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