Assist device

Abstract

To provide a technique capable of relaxing a load applied to a user in a standing posture, by tension on a belt body.SOLUTION: An assist device 10 comprises: a first mounting fixture 11 mounted on a shoulder part; a second mounting fixture 12 mounted on a leg part; a belt body 13 provided over the first and second mounting fixtures 11, 12; an actuator 14 for winding a part of the belt body 13 and feeding the part of the belt body; a control part 40; a sensor 38 for detecting an angle of an upper half body of the user; and a rotation detector 36 for detecting an operation speed of the actuator 14. The control part 40 executes: determination processing 40a1 for determining whether, an upper body angle θ and the rotation speed V satisfy a prescribed condition; and first switching processing 40a2 for, when it is determined that, the upper half body angle θ and the rotation speed V satisfy the prescribed condition, switching the mode from a normal mode for applying tension which is prescribed initial tension or greater than that, to the belt body 13, to a low tension mode for reducing the tension applied to the belt body 13 relative to the initial tension.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an assist device.

Background Art

[0002] For example, Patent Document 1 discloses an assist device including a first attachment device worn on the user's shoulder, a second attachment device worn on the user's left and right legs, a belt body provided along the back side of the user across the first attachment device and the second attachment device, and an actuator provided in the first attachment device. This assist device generates tension in the belt body by winding up a part of the belt body with the actuator. This tension acts on the user as an assist force that assists the rotation of the user's thigh.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above conventional assist device, when the assist force is not generated, the actuator is controlled to operate in the direction of winding up the belt body with a weaker force than when the assist force is generated. As a result, a weak tension (initial tension) is applied to the belt body. This initial tension suppresses the loosening of the belt body.

[0005] The above initial tension is applied to the belt body even when the user is maintaining an upright posture. Therefore, even when the user in an upright posture is not particularly performing work, a load due to the initial tension is applied to the user's shoulder.

Means for Solving the Problems

[0006] The assist device, according to this embodiment, comprises a first attachment worn on at least the shoulders of the user, second attachments worn on the left and right legs of the user, a belt body provided along the user's back, spanning the first and second attachments, an actuator provided on the first attachment that enables winding and unwinding of a portion of the belt body, a control unit that controls the actuator, a first sensor that detects the angle of the user's upper body, and a second sensor that detects the operating speed of the actuator. The control unit performs a determination process to determine whether the angle satisfies a predetermined first condition and whether the operating speed satisfies a predetermined second condition, and, if it is determined that the angle and the operating speed satisfy the first and second conditions, it performs a first switching process to switch the operating mode of the actuator from a normal mode that applies tension greater than or equal to a predetermined initial tension to the belt body to a low-tension mode that reduces the tension applied to the belt body to less than the initial tension. [Effects of the Invention]

[0007] According to this disclosure, the load applied to the user by the tension of the belt can be alleviated. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a rear view of the assist device according to an embodiment. [Figure 2] Figure 2 is a rear view of the assist device attached to the user's body. [Figure 3] Figure 3 is a side view of the assist device attached to the user's body. [Figure 4] Figure 4 shows the inside of the control box. [Figure 5] Figure 5 is a block diagram showing the control configuration of the assist device. [Figure 6] Figure 6 is an explanatory diagram illustrating how a user wearing the assist device changes their posture. [Figure 7] Figure 7 is a flowchart showing an example of the mode switching process performed by the control unit. [Figure 8A] Figure 8A is a graph showing an example of the change over time between the upper body angle and the current command value when the assist device of this embodiment is in operation. [Figure 8B] Figure 8B is a graph showing an example of the change over time between the upper body angle and the current command value when a conventional assist device is in operation. [Modes for carrying out the invention]

[0009] First, the details of the embodiment will be listed and explained. [Summary of the Embodiment] (1) The assist device according to the embodiment comprises a first attachment worn on at least the shoulders of the user, a second attachment worn on the left and right legs of the user, a belt body provided along the back of the user spanning the first and second attachments, an actuator provided on the first attachment that enables winding and unwinding of a portion of the belt body, a control unit that controls the actuator, a first sensor that detects the angle of the user's upper body, and a second sensor that detects the operating speed of the actuator. The control unit performs a determination process to determine whether the angle satisfies a predetermined first condition and whether the operating speed satisfies a predetermined second condition, and, if it is determined that the angle and the operating speed satisfy the first and second conditions, performs a first switching process to switch the operating mode of the actuator from a normal mode that applies tension to the belt body with a tension greater than or equal to a predetermined initial tension to a low-tension mode that reduces the tension applied to the belt body to less than the initial tension.

[0010] According to the above configuration, if the first and second conditions are set to conditions that can be determined to be an upright posture, then when it is determined that the user is in an upright posture, the system can be controlled to apply a tension to the belt that is smaller than the initial tension. As a result, the load on the user in an upright position due to the tension of the belt can be alleviated.

[0011] (2) In the assist device described above, in the first switching process, if the state in which the angle and the operating speed satisfy the first condition and the second condition continues for a predetermined period of time, it is preferable to switch the operating mode of the actuator from the normal mode to the low tension mode. In this case, even if the user's posture is in a transient state after the first and second conditions are met, by waiting for a predetermined period of time to elapse before switching modes, it is possible to reliably switch to low-tension mode at the timing when the user reaches the posture targeted by the first and second conditions (upright posture). Furthermore, it is possible to suppress switching to low-tension mode when it is judged that the first and second conditions have been temporarily met, and to suppress hunting during mode switching.

[0012] (3) In addition, in the assist device described above, if the control unit determines in the determination process that at least one of the angle and the operating speed does not satisfy the first condition and the second condition, it is preferable to further execute a second switching process to switch the operating mode of the actuator from the low tension mode to the normal mode. In this case, if it is determined that at least one of the angle and operating speed does not meet the first and second conditions, the system switches to normal mode, so the conditions for switching are more relaxed than in the first switching process. As a result, it is possible to prevent the low-tension mode from being maintained for longer than necessary.

[0013] (4) The control unit is configured to control the actuator by setting a current command value to be supplied to the actuator, and in the low tension mode, the current command value may be set to 0.

[0014] (5) Also, in the assist device, the first condition may include that the angle is not more than a first threshold value set for the angle, and the second condition may include that the operating speed is not more than a second threshold value set for the operating speed.

[0015] (6) The operating speed includes the rotational speed of a motor for winding and feeding out a part of the belt body, or the winding speed and feeding speed of a part of the belt body. In this case, mode switching can be performed based on the rotational angle of the motor, or the winding speed and feeding speed of a part of the belt body.

[0016] [Details of the Embodiment] Hereinafter, preferred embodiments will be described with reference to the drawings. [Overall Configuration of Assist Device 10] FIG. 1 is a rear view of an assist device according to an embodiment. FIG. 2 is a rear view of the assist device attached to the user's body. FIG. 3 is a side view of the assist device attached to the user's body.

[0017] In the assist device 10 of the present disclosure, left and right refer to the left and right for the user in the upright posture wearing the assist device 10, front and back refer to the front and back for the user, and up and down refer to the up and down for the user. Up is the head side of the user, and down is the foot side of the user.

[0018] The assist device 10 shown in FIG. 1 includes one first wearing tool 11 and two second wearing tools 12. The first wearing tool 11 is worn on the left and right shoulder parts BS which are part of the user's (person's) body. The first wearing tool 11 may be worn on at least one of the user's shoulders and chest, and may be in a form other than the illustrated one. The second attachment device 12 is attached to the left and right leg portions BL, which are other parts of the user's body. In this disclosure, the second attachment device 12 is attached to the knee portion BN within the leg portion BL. The left and right second attachment devices 12 are symmetrical, but their configurations are the same. The second attachment device 12 may also take forms other than those shown in the illustration. The first attachment device 11 and the two second attachment devices 12 are attached to two locations separated from the waist BW and hip joint, namely the shoulder BS and leg BL.

[0019] The first attachment 11 includes a base 21, a pair of shoulder straps 22, and a pair of armpit straps 23. The base 21 includes a control box 30 that houses the control device 15 and other components, which will be described later. The base 21 is carried on the user's back by a pair of shoulder straps 22 and a pair of underarm straps 23. A pair of shoulder straps 22 are mounted on the top of the base 21 (control box 30). A pair of underarm straps 23 are connected to the end 22a of each of the shoulder straps 22. A pair of underarm belts 23 connect the base 21 (control box 30) to the ends 22a of a pair of shoulder belts 22. The length of the underarm belts 23 is adjustable. By adjusting the length of the underarm belts 23, the base 21 is in close contact with the user's back (rear) BB. As a result, the first attachment device 11 is attached to the shoulder BS in a way that prevents movement in the front-to-back, left-to-right, and up-and-down directions. The first attachment device 11 may include, for example, a rigid member as a part that rests on the shoulder BS. Although not shown, the first attachment device 11 may further have an attachment (waist belt) that is attached to the user's waist BW. The waist belt is connected to the base 21.

[0020] The second attachment 12 is made of a flexible fabric or the like. The second attachment device 12 has a knee body 24 that is attached to the user's knee BN, and a pair of knee belts 25 that extend from the knee body 24. The pair of knee belts 25 are wrapped around the upper and lower positions of the knee BN, respectively. The ends of the pair of knee belts 25 are fixed to the knee body 24. The length of the wrap around the knee BN can be adjusted by fastening members such as belts and buckles or hook-and-loop fasteners. This ensures that the knee body 24 is in close contact with the rear side of the knee BN. The second attachment device 12 is attached to the knee BN in a way that prevents movement in the front-to-back, left-to-right, and up-and-down directions.

[0021] In addition to the first attachment device 11 and the left and right second attachment devices 12, the assist device 10 includes a belt body 13, an actuator 14, a control device 15, a battery 37, and a sensor 38.

[0022] The belt body 13 is positioned along the user's back. The belt body 13 connects the first attachment device 11 and the second attachment device 12. The belt body 13 includes a first belt 16, a second belt 17, and a connecting member 18. The first belt 16 is provided on the upper body side of the user. The second belt 17 is provided on the lower body side of the user. The connecting member 18 connects the first belt 16 and the second belt 17. The first belt 16 and the second belt 17 are long and flexible. The connecting member 18, as will be explained later, consists of a rectangular ring-shaped body 27, which is called, for example, a "flat ring" or "square ring," and a fastener 28 such as a buckle.

[0023] The first belt 16 and the second belt 17 are strip-shaped members made of cloth or leather, and are bendable to conform to the shape of the body. The first belt 16 and the second belt 17 may also be string-shaped belts (wire-like members). The first belt 16 and the second belt 17 in this disclosure are non-stretchable members. That is, the first belt 16 and the second belt 17 have the characteristic of being difficult or impossible to stretch in the longitudinal direction.

[0024] The actuator 14, control device 15, battery 37, and sensor 38 are housed within a control box 30, which is a casing. Figure 4 shows the inside of the control box 30. The control box 30 has a back plate 31 and a cover 32 that covers the back plate 31. In Figure 4, the cover 32 is shown by a dashed line (two-dot dashed line). An opening (notch) 32a is provided at the lower end of the cover 32. The first belt 16 passes through the opening 32a.

[0025] The actuator 14 enables the winding and unwinding of a portion of the belt body 13. In other words, the actuator 14 expands and contracts the belt body 13 between the first mounting device 11 and the second mounting device 12. The actuator 14 includes a motor 33, a reduction gear 34, and a drive pulley 35. Motor 33 is a brushless DC motor. Motor 33 rotates at a predetermined torque and rotational speed based on control commands provided by the control device 15. Motor 33 can also rotate in both forward and reverse directions based on control commands.

[0026] The rotation parameters of the motor 33, such as the rotation angle, rotation speed, or rotational speed, are detected by the rotation detector 36. The rotation detector 36 is provided on the motor 33. The rotation detector 36 in this disclosure is a rotary encoder, but it may also be a Hall sensor or a resolver. The output of the rotation detector 36 is provided to the control device 15.

[0027] The reduction gear unit 34 is composed of multiple gears. The reduction gear unit 34 reduces the rotational speed of the motor 33 and rotates the output shaft 34a of the reduction gear unit 34. A drive pulley 35 is integrally connected to the output shaft 34a so as to be able to rotate together with it. One end 16a of the first belt 16 is fixed to the drive pulley 35. When the motor 33 rotates in the forward direction, the drive pulley 35 rotates in one direction, and the first belt 16 is wound onto the drive pulley 35. When the motor 33 rotates in the reverse direction, the drive pulley 35 rotates in the other direction, and the first belt 16 is fed out from the drive pulley 35. In this way, the actuator 14 can wind up and unwind the first belt 16, which is part of the belt body 13.

[0028] The control device 15 includes, for example, a computer and a drive circuit for the motor 33. The control device 15 has the function of controlling the actuator 14 based on the output of the rotation detector 36 and the output of the sensor 38. The processing performed by the control device 15 will be described later.

[0029] The sensor 38 includes, for example, a 3-axis accelerometer. The output of the sensor 38 is supplied to the control device 15. The sensor 38 may consist of one sensor unit or multiple sensor units. Furthermore, the sensor 38 may be a tilt sensor, a gyroscope, or a combination thereof, in addition to an acceleration sensor. Furthermore, the sensor 38 may be located outside the control box 30. The battery 37 supplies power to various parts of the assist device, such as the control device 15 and the motor 33.

[0030] [Regarding belt body 13] As described above, the belt body 13 has a first belt 16, a second belt 17, and a connecting member 18. One end 16a of the first belt 16 is wound around and fixed to the drive pulley 35. The other end 16b of the first belt 16 is fixed to the connecting member 18. When the first belt 16 is wound around the drive pulley 35, the connecting member 18 is pulled up. When the connecting member 18 is forcibly pulled down, the first belt 16 is unwound (pulled out) from the drive pulley 35. There is a correlation between the amount of winding or unwinding (pulling out) of the first belt 16 in the drive pulley 35 and the amount of rotation of the output shaft of the motor 33. Therefore, the amount of winding or unwinding of the first belt 16 can be obtained based on the parameters related to the rotation of the motor 33.

[0031] The connecting member 18 (see Figure 4) includes an annular body 27 and a fastener (buckle) 28. The fastener 28 has a first member 28a and a second member 28b. The first member 28a and the second member 28b are separable and connectable. The first member 28a is attached to the other end 16b of the first belt 16. The second member 28b and the annular body 27 are connected by a short belt 29. The second belt 17 is inserted through the annular body 27.

[0032] The second belt 17 is folded back at the annular body 27 and draped over the annular body 27. The annular body 27 supports the folded second belt 17. As a result, the second belt 17 is supported by the annular body 27 without being fixed to it. Therefore, the second belt 17 is freely movable in both directions along its longitudinal direction (arrow X direction in Figure 4).

[0033] As shown in Figures 1 and 2, the second belt 17 is attached to the second mounting device 12. More specifically, the second belt 17 is made up of a single strip-shaped member. One end 17a of the second belt 17 is attached to the second mounting device 12 on the left. The other end 17d of the second belt 17 is attached to the second mounting device 12 on the right. The middle section 17c of the second belt 17 is looped over the connecting member 18.

[0034] The second belt 17 includes, in addition to the intermediate section 17c, a left leg belt section 19 from the connecting member 18 (intermediate section 17c) to the left second attachment 12, and a right leg belt section 20 from the connecting member 18 (intermediate section 17c) to the right second attachment 12. As described above, since the second belt 17 is not fixed to the annular body 27, the lengths of the left leg belt portion 19 and the right leg belt portion 20 can be freely changed. However, the sum of the lengths of the left leg belt portion 19 and the right leg belt portion 20 is constant. With this configuration, the user's walking, for example, is not restricted by the second belt 17, and the user can walk easily.

[0035] The second belt 17 further includes a connecting member 39. The connecting member 39 connects the left leg belt portion 19 and the right leg belt portion 20. By providing the connecting member 39, it becomes possible to prevent the gap between the left leg belt portion 19 and the right leg belt portion 20 from widening when, for example, the user changes their posture from an upright position to a bent-over position as shown in Figure 4. In other words, it becomes possible to prevent the left leg belt portion 19 and the right leg belt portion 20 from not conforming to the back side of the user's leg portion BL.

[0036] [Regarding the control of assist force by the control device 15] Figure 5 is a block diagram showing the control configuration of the assist device 10. As shown in Figure 5, the control device 15 is connected to a rotation detector 36 and a sensor 38. The control device 15 controls these devices and also acquires the outputs from the rotation detector 36 and the sensor 38. The control device 15 includes a control unit 40 consisting of a computer or the like, and a drive circuit (motor driver) 42. The drive circuit 42 controls the operation of the motor 33 based on control commands provided by the control unit 40.

[0037] The control unit 40 includes a CPU (Central Processing Unit) 40a and a storage device 40b such as memory or a hard disk. The CPU 40a executes various processes based on various programs and parameters stored in the storage device 40b. The CPU 40a has a function to control the assist force according to the user's posture. Based on the outputs of the rotation detector 36 and the sensor 38, the CPU 40a generates control commands to control the motor 33 (actuator 14) and provides them to the drive circuit 42. The CPU 40a sets the current command value to be supplied to the actuator 14 and provides the current command value as a control command to the drive circuit 42. This current command value causes the actuator 14 to generate an assist force according to the user's posture. In this way, the CPU 40a controls the assist force according to the user's posture.

[0038] Furthermore, the CPU 40a has the function of executing a determination process 40a1, a first switching process 40a2, and a second switching process 40a3. The determination process 40a1, the first switching process 40a2, and the second switching process 40a3 will be explained later.

[0039] The following describes the control of the assist force, which is normally performed by the CPU 40a (control unit 40). As described above, the control unit 40 controls the actuator 14 based on the output of the rotation detector 36 and the output of the sensor 38. The control unit 40 acquires the amount of movement and operating speed of the actuator 14 (motor 33) based on the output of the rotation detector 36. The amount of movement of the actuator 14 includes the rotation angle of the motor 33 and the amount of winding and unwinding of the belt body 13. The operating speed of the actuator 14 includes the rotation speed of the motor 33 and the winding speed and unwinding speed of the belt body 13. In this embodiment, the rotation detector 36 detects the rotation angle of the motor 33 as the amount of operation of the actuator 14. The rotation detector 36 also functions as a second sensor that detects the rotation speed of the motor 33 as the operating speed of the actuator 14.

[0040] When no assist force is generated, the control unit 40 controls the actuator 14 to operate in the winding direction of the belt body 13 with a weaker force than when an assist force is generated (to generate torque). As a result, a weak tension (initial tension) is applied to the belt body 13 by the actuator 14. Therefore, the belt body 13 does not loosen.

[0041] For example, when a user changes from an upright posture to a forward-leaning posture, tension is generated in the belt 13 due to this change in posture. In this case, the tension in the belt 13 caused by the change in posture forces the motor 33 to rotate (the motor 33 spins freely). Therefore, the belt 13 is moved forward without the power of the actuator 14. Alternatively, when a change in posture to a forward-leaning posture is initiated, the control unit 40 operates the actuator 14 and moves the belt 13 forward.

[0042] Conversely, when the user changes from a forward-leaning posture to an upright posture, the belt 13 tends to loosen due to this change in posture. In this case, when the change in posture to an upright posture begins, the control unit 40 operates the actuator 14 to retract the belt 13 in order to maintain the tension acting on the belt 13.

[0043] Thus, tension is always applied to the belt body 13. For this reason, there is a correlation between the amount of belt body 13 wound up and unwound by the drive pulley 35 and the user's posture. In addition, the rotation angle of the motor 33 increases in proportion to the amount the belt body 13 is unwound when it is fed out, and decreases in proportion to the amount the belt body 13 is wound up when it is rewound. Therefore, there is a correlation between the rotation angle of the motor 33 that winds up or unwinds the belt 13 and the user's posture.

[0044] As described above, the amount of winding and unwinding of the belt body 13 by the drive pulley 35, and the rotation angle of the motor 33, are the amounts of operation of the actuator 14. In other words, there is a correlation between the amount of operation of the actuator 14 and the user's posture. Therefore, the control unit 40 can detect the user's posture and movements based on the output of the rotation detector 36.

[0045] Furthermore, the control unit 40 acquires the upper body angle based on the output of the sensor 38. The upper body angle is the angle of the user's upper body relative to the vertical. The sensor 38 is a 3-axis accelerometer. The sensor 38 is installed on the user's upper body. Therefore, the control unit 40 can acquire the upper body angle (angle of the upper body) based on the output of the sensor 38. In other words, the sensor 38 functions as a first sensor that detects the angle of the user's upper body. The control unit 40 can detect the posture and movement of the user's upper body based on the output of the sensor 38.

[0046] The control unit 40 sets a current command value based on at least one of the outputs of the rotation detector 36 and the sensor 38, and provides the current command value to the drive circuit 42. This allows the control unit 40 to control the actuator 14. The actuator 14 operates based on the operation control of the drive circuit 42 to which a current command value is given, and performs actions such as winding up and unwinding the belt body 13, and temporarily pausing its operation. As a result, the actuator 14 is controlled according to the user's posture.

[0047] Figure 6 is an explanatory diagram illustrating how a user wearing the assist device 10 changes their posture. Figure 6 shows a user in an upright posture and a user in a forward-leaning posture. An upright posture refers to a position in which the user's upper body and thighs are almost vertically aligned. A forward-leaning posture refers to a position in which the user's upper body is tilted forward with the user's knee joint (BN) being almost completely unflexed.

[0048] Here, we will explain the case where the user in Figure 6 changes posture between an upright posture and a forward-leaning posture. First, when a user in an upright position begins to change their posture towards a forward-leaning position, the belt 13 is propelled forward without the power of the actuator 14. This allows the user to adopt a forward-leaning posture without strain. As shown in Figure 6, when the upper body angle θ, which is the angle of the user's upper body UB with respect to the vertical line VL, reaches θ1, and the forward-leaning posture is maintained with the upper body angle θ at θ1, the belt body 13 stops being fed out. The start and end of the posture change can be detected by the output of the rotation detector 36 or the output of the sensor 38.

[0049] Next, when a user in a forward-leaning posture begins to change their posture toward an upright posture, the control unit 40 detects, based on the output of the rotation detector 36 or the output of the sensor 38, that the user has begun to change their posture toward an upright posture, and operates the actuator 14 to rewind the belt body 13. At this time, the control unit 40 controls the actuator 14 so that a larger torque is generated than when initial tension is applied.

[0050] When the actuator 14 (motor 33) winds the first belt 16 onto the drive pulley 35, the connecting member 18 pulls the second belt 17 towards the actuator 14, i.e., upward. The second belt 17 has both ends 17a and 17d attached to the left and right second attachments 12. The second attachments 12 are fixed to the knee portion BN. Therefore, when the first belt 16 is wound onto the drive pulley 35, tension acts on both the first belt 16 and the second belt 17. This tension acts as an assisting force (supporting force) for the user.

[0051] This tension generates a force F1 acting on the first attachment 11 in a backward direction. In other words, a force F1 is generated that causes the user's upper body, which is in a forward-leaning posture, to stand up. At the same time, the tension generates a force F2 acting on the second belt 17 that pushes the user's left and right buttocks forward. In other words, the actuator 14 generates an assisting force that helps rotate the thigh between the first attachment 11 and the second attachment 12. This allows users to easily return from a forward-leaning posture to an upright posture, reducing the strain on the back muscles and quadriceps muscles during forward bending, and assisting the user's movements.

[0052] Thus, when a user in a forward-leaning posture begins to change their posture toward an upright posture, the control unit 40 generates torque in the actuator 14 to provide assistance to the user.

[0053] [Regarding mode switching process] As described above, the control unit 40 of the assist device 10 in this embodiment controls the actuator 14 so that initial tension is applied to the belt body 13 when no assist force is generated. Furthermore, when a user in a forward-leaning posture begins to change their posture toward an upright position, the actuator 14 is controlled to generate a torque greater than the initial tension, thereby providing the user with the necessary assistive force.

[0054] For example, if the control unit 40 were to always perform the above-described control, the control unit 40 would apply initial tension to the belt body 13 even if the user was maintaining an upright posture without performing any work. As a result, the user would be subjected to a load due to the initial tension.

[0055] Therefore, the assist device 10 of this embodiment has a function to reduce the tension applied to the belt body 13 from the initial tension when the user is in an upright position. The control unit 40 performs either the normal mode or the low-tension mode as the operating mode of the actuator 14.

[0056] The normal mode is a mode in which assisting force is applied to the user based on at least one of the output of the rotation detector 36 and the output of the sensor 38, as described above. In the normal mode, a tension greater than or equal to the initial tension is applied to the belt body 13. The low-tension mode is a mode in which the tension applied to the belt body 13 is reduced to the initial tension, regardless of the output of the rotation detector 36 and the sensor 38.

[0057] Figure 7 is a flowchart showing an example of the mode switching process performed by the control unit 40. The control unit 40 continuously performs mode switching processing. In the mode switching process, the control unit 40 first sets the counter value C of the counter functionally provided by the control unit 40 to 0 (step S1 in Figure 7). Next, the control unit 40 switches the operating mode of the actuator 14 to normal mode (step S2 in Figure 7). As a result, the control unit 40 controls the actuator 14 so that the tension applied to the belt body 13 is equal to or greater than the initial tension.

[0058] After switching the operating mode to normal mode, the control unit 40 determines whether the upper body angle θ is less than or equal to the threshold θth (step S3 in Figure 7). The upper body angle θ is obtained based on the output of sensor 38, as described above. The threshold θth is a threshold (first threshold) set for the upper body angle θ, and is used to determine whether or not the user's upper body is tilted. The threshold θth is set to a value that allows the user's upper body to be considered as being upright.

[0059] If the control unit 40 determines in step S3 that the upper body angle θ is less than or equal to the threshold θth, it proceeds to step S4 and determines whether the rotational speed V of the motor 33 is less than or equal to the threshold Vth (step S4 in Figure 7). The rotational speed V of the motor 33 is detected by the rotation detector 36, as described above. The control unit 40 obtains the rotational speed V based on the output of the rotation detector 36. The threshold Vth is a threshold (second threshold) set for the rotational speed V, and is used to determine whether or not the motor 33 needs to operate. The threshold Vth is set to a value smaller than the rotational speed of the motor 33 when the user's posture changes between a forward-leaning posture and an upright posture.

[0060] If the control unit 40 determines in step S4 that the rotational speed V of the motor 33 is less than or equal to the threshold Vth, it proceeds to step S5 and determines whether the counter value C is greater than the threshold Cth (step S5 in Figure 7). If the control unit 40 determines in step S5 that the counter value C is greater than the threshold Cth, it switches the operating mode of the actuator 14 to the low tension mode (step S6 in Figure 7) and returns to step S3.

[0061] Here, the counter value C is a value that is incremented when the judgment results for both step S3 and step S4 are positive. In other words, the counter value C is a value that indicates the elapsed time during which the judgment results for both step S3 and step S4 are positive. The threshold Cth is a value used to determine whether the positive result of steps S3 and S4 continues for a predetermined period of time.

[0062] If in step S5 the control unit 40 determines that the counter value C is not greater than the threshold Cth (i.e., less than or equal to the threshold Cth), the control unit 40 proceeds to step S8, adds 1 to the counter value C (step S8 in Figure 7), and returns to step S3. Therefore, if the determination results in steps S3 and S4 remain positive, the control unit 40 repeats steps S3, S4, S5, and S8. If the determination results of steps S3 and S4 remain positive for a predetermined period determined by the threshold Cth, the control unit 40 switches the operating mode of the actuator 14 to the low-tension mode.

[0063] If the control unit 40 determines in step S3 that the upper body angle θ is not less than or equal to the threshold θth (i.e., greater than the threshold θth), it proceeds to step S7, sets the counter value C to 0, and proceeds to step S9. In step S9, the control unit 40 switches the operating mode of the actuator 14 to normal mode (step S9 in Figure 7) and returns to step S3.

[0064] Furthermore, if in step S4 the control unit 40 determines that the rotation speed V is not less than or equal to the threshold Vth (i.e., greater than the threshold Vth), the control unit 40 proceeds to step S7, sets the counter value C to 0, and proceeds to step S9. In step S9, the control unit 40 switches the operating mode of the actuator 14 to normal mode (step S9 in Figure 7) and returns to step S3.

[0065] Therefore, even if the judgment results of steps S3 and S4 remain positive for a certain period of time, if at least one of the judgment results of steps S3 and S4 becomes negative, the control unit 40 sets the counter value C to 0 (step S7) and switches the operating mode of the actuator 14 to normal mode (step S9).

[0066] In the above mode switching process, the control unit 40 executes a determination process 40a1 (Figure 5) which determines whether the upper body angle θ satisfies the condition of step S3 (first condition) and whether the rotation speed V (operating speed of actuator 14) satisfies the condition of step S4 (second condition) (steps S3 and S4 in Figure 7).

[0067] Furthermore, if the control unit 40 determines that the upper body angle θ and rotation speed V satisfy the conditions of step S3 and step S4 for a predetermined period of time, it executes a first switching process 40a2 (Figure 5) to switch the operating mode of the actuator 14 from normal mode to low tension mode (steps S5, S6, S8 in Figure 7).

[0068] In this embodiment, the threshold θth for the upper body angle θ is, as described above, a threshold for determining whether or not the user is tilting their upper body. If the upper body angle θ satisfies the conditions of step S3, the user's upper body can be considered to be almost upright. Furthermore, the threshold Vth for the rotational speed V is, as described above, a threshold for determining whether or not the motor 33 needs to operate. If the rotational speed V satisfies the conditions of step S4, it can be assumed that the motor 33 does not need to operate and that the user's posture has hardly changed. Therefore, when the conditions of steps S3 and S4 are met, it can be determined that the user's posture is upright. In other words, the conditions of steps S3 and S4 are set to be conditions that allow it to be determined that the user's posture is upright.

[0069] Therefore, according to this embodiment, when the conditions of steps S3 and S4 are met and it is determined that the user is in an upright position, it is possible to switch to low-tension mode and control the belt body 13 to apply a tension smaller than the initial tension. As a result, the load applied to the user in an upright position by the tension of the belt body 13 can be alleviated.

[0070] Furthermore, in low-tension mode, the tension applied to the belt body 13 is reduced compared to the initial tension, thus suppressing the power consumption of the motor 33 compared to normal mode. Therefore, in this embodiment, the load on the user is reduced while also suppressing the power consumption of the motor 33.

[0071] Furthermore, in this embodiment, as described above, the operating mode of the actuator 14 is switched from normal mode to low tension mode after waiting for a predetermined period of time for the condition that the upper body angle θ and rotation speed V satisfy the conditions of step S3 and step S4 to continue. As a result, even if the user's posture is in a transient state after the conditions of step S3 and step S4 are met, the system can switch to low-tension mode at the precise moment the user reaches an upright posture by waiting for a predetermined period of time to elapse before switching modes. Furthermore, it is possible to suppress the switching to low-tension mode when it is determined that the conditions of step S3 and step S4 have been temporarily met, and to suppress hunting during mode switching.

[0072] Furthermore, if it is determined that at least one of the upper body angle θ and the rotation speed V does not satisfy the conditions of step S3 and step S4 (steps S3 and S4 in Figure 7), the control unit 40 sets the counter value C to 0 (step S7 in Figure 7) and executes a second switching process 40a3 (Figure 5) to switch the operating mode of the actuator 14 to normal mode (step S9 in Figure 7). In the second switching process 40a3, which switches to normal mode, the system switches to normal mode if it is determined that at least one of the upper body angle θ and the rotation speed V does not satisfy the conditions of step S3 and step S4. Therefore, the conditions for switching are more relaxed than in the first switching process 40a2. As a result, it is possible to prevent the low-tension mode from being maintained for longer than necessary.

[0073] Figure 8A is a graph showing an example of the change over time between the upper body angle θ and the current command value when the assist device 10 of this embodiment is operated. In Figure 8A, diagram g1 shows the change in the upper body angle θ over time, and diagram g2 shows the current command value that the control unit 40 provides to the drive circuit 42. In Figure 8A, prior to time t1, the user's posture changes from a forward-leaning posture to an upright posture. Time t1 indicates the timing at which the control unit 40 determines that the upper body angle θ and rotation speed V satisfy the conditions of step S3 and step S4. Prior to time t1, the control unit 40 operates in normal mode. From time t1 onward, the control unit 40 continues to operate in normal mode for a predetermined period until the counter value C becomes greater than the threshold Cth (steps S5 and S8 in Figure 7). During the period from time t1 to time t2, the control unit 40 sets the current command value to value a1. Value a1 is the current command value for generating torque for initial tension in the actuator 14.

[0074] Subsequently, suppose that at time t2 the counter value C becomes greater than the threshold Cth. In this case, the control unit 40 switches from normal mode to low tension mode at time t2 (step S6 in Figure 7). In low-tension mode, the control unit 40 sets the current command value to 0 regardless of the output of the rotation detector 36 and the sensor 38. As a result, almost no tension is applied to the belt body 13, and the tension of the belt body 13 can be made lower than the initial tension.

[0075] During the period from time t1 to time t3, the upper body angle θ and rotational speed V satisfy the conditions of step S3 and step S4. Time t3 indicates the point at which the rotational speed V no longer satisfies the conditions of step S4. The control unit 40 maintains the low tension mode during the period from time t2 to time t3. At time t3, when the rotational speed V no longer satisfies the conditions of step S4 (step S4 in Figure 7), the control unit 40 sets the counter value C to 0 (step S7 in Figure 7) and switches from low tension mode to normal mode (step S9 in Figure 7). The control unit 40 sets the current command value to value a1 after time t3 and applies initial tension to the belt body 13.

[0076] Figure 8B is a graph showing an example of the time-dependent changes in the upper body angle θ and current command value when a conventional assist device is in operation. In Figure 8B, diagram g3 shows the change in the upper body angle θ over time, and diagram g4 shows the current command value that the control unit 40 provides to the drive circuit 42. In Figure 8B, the upper body angle θ and rotational velocity V satisfy the conditions of step S3 and step S4 throughout the entire period shown in Figure 8B. However, in conventional assist devices, a current command value (a value corresponding to the value a1 in this embodiment) for applying initial tension to the belt body 13 is set throughout the period shown in Figure 8B. Therefore, conventional assist devices apply initial tension to the belt even if the user maintains an upright posture without performing any particular task.

[0077] In this regard, according to the assist device 10 of this embodiment, when the conditions of steps S3 and S4 are met and it is determined that the user is maintaining an upright posture, the device switches to low tension mode, thereby reducing the load applied to the user in an upright posture by the tension of the belt body 13.

[0078] 〔others〕 The embodiments disclosed herein are illustrative in all respects and not restrictive. For example, in the above embodiment, the upper body angle θ, which is the angle of the upper body UB relative to the vertical line VL, was used as an example of the angle of the user's upper body UB. However, the angle of the upper body UB may be an angle relative to a preset reference angle. Furthermore, in this embodiment, the rotational speed V of the motor 33, which is the operating speed of the actuator 14, is exemplified by the rotation detector 36. However, instead of the rotation detector 36, an encoder for measuring the winding speed and unwinding speed of the belt body 13 by the drive pulley 35 can also be used.

[0079] Furthermore, although this embodiment illustrates a case where the current command value is set to 0 in low tension mode, the current command value set in low tension mode can be any value between the value a1, which is the current command value for initial tension, and 0. In this case as well, the tension applied to the belt body 13 can be made smaller than the initial tension.

[0080] Furthermore, in this embodiment, the operating mode of the actuator 14 is switched from normal mode to low-tension mode after waiting for a predetermined period of time for the condition in which the upper body angle θ and rotation speed V satisfy the conditions of step S3 and step S4 to continue (steps S5, S6, S8 in Figure 7). However, the actuator 14 may be configured to switch from normal mode to low-tension mode without waiting for the condition in which the upper body angle θ and rotation speed V satisfy the conditions of step S3 and step S4 to continue.

[0081] The scope of the present invention is not limited to the embodiments described above, but includes all modifications within the scope equivalent to the configurations described in the claims. [Explanation of symbols]

[0082] 10 Assist device 11 First attachment 12 Second attachment 13 Belt body 14 Actuator 15 Control device 16 First belt 16a One end 16b Other end 17 Second belt 17a One end 17c Middle section 17d Other end 18 Connecting member 19 Left leg belt 20 Right leg belt section 21 Base 22 Shoulder belt 22a Tip section 23 Underarm belt 24 Knee section 25 Knee belt 27 Ring 28 Fastener 28a First component 28b Second component 29 Short belt 30 Control box 31 Rear plate 32 Cover 32a Opening 33 Motor 34 Reducer section 34a Output shaft 35 Drive pulley 36 Rotation detector 37 Battery 38 Sensor 39 Connecting member 40 Control unit 40a CPU 40a1 Judgment process 40a2 First switching process 40a3 Second switching process 40b Storage device 42 Drive circuit BB Back BL Legs BN Knees BS Shoulders BW Waist UB Upper body VL vertical line

Claims

1. A first attachment device that is worn on at least the shoulder of the user, A second attachment device is attached to the left and right legs of the user, A belt body is provided along the user's back, spanning the first and second attachments, An actuator provided on the first mounting device that enables winding and unwinding of a portion of the belt body, A control unit that controls the actuator, A first sensor that detects the angle of the user's upper body, The system includes a second sensor for detecting the operating speed of the actuator, The control unit, A determination process to determine whether the angle satisfies a predetermined first condition and whether the operating speed satisfies a predetermined second condition, When it is determined that the angle and the operating speed satisfy the first and second conditions, a first switching process is performed to switch the operating mode of the actuator from a normal mode in which tension equal to or greater than a predetermined initial tension is applied to the belt body to a low-tension mode in which the tension applied to the belt body is less than the initial tension, If, in the determination process, it is determined that at least one of the angle and the operating speed does not satisfy the first and second conditions, a second switching process is performed to switch the operating mode of the actuator from the low-tension mode to the normal mode. Assist device.

2. In the first switching process, if the state in which the angle and the operating speed satisfy the first and second conditions continues for a predetermined period of time, the operating mode of the actuator is switched from the normal mode to the low-tension mode. The assist device according to claim 1.

3. The control unit is configured to control the actuator by setting a current command value to be supplied to the actuator. In the low-tension mode, the current command value is set to 0. The assist device according to claim 1 or claim 2.

4. The first condition includes that the angle is less than or equal to a first threshold set for the angle, The first threshold is a value at which the user's upper body can be considered to be upright when the angle is less than or equal to the first threshold. The second condition includes that the operating speed is less than or equal to a second threshold set for the operating speed, The second threshold is a value smaller than the speed of movement when the user's posture changes between a forward-leaning posture and an upright posture. The assist device according to any one of claims 1 to 3.

5. The aforementioned operating speed includes the rotational speed of the motor used to wind up and unwind a portion of the belt, or the winding speed and unwinding speed of a portion of the belt. The assist device according to any one of claims 1 to 4.

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