JP5157888B2 - Walking assist device - Google Patents

Description

  The present invention relates to a walking assist device that assists a user's walking motion. In this specification, a leg that a user can freely move is referred to as a healthy leg, and a leg that cannot be freely moved is referred to as an affected leg.

  A walking assist device that assists the user's walking by applying torque to the joint of the affected leg has been studied. For example, Patent Document 1 discloses a walking assist device that applies torque to a joint of an affected leg so as to be the same as the movement of a healthy leg.

JP 2003-116893 A

  One type of walking assistance device has walking pattern data describing the movement of the leg during walking, and applies torque to the joint of the leg so that the movement of the user's leg follows the walking pattern. A walking assistance device that employs a walking pattern has the following advantages. That is, the walking pattern describes a smooth movement of the leg, and if the user's leg moves so as to follow the walking pattern, a smooth walking is realized. When employing a walking pattern, the walking assistance device needs to change the walking pattern data in accordance with the slope angle of the walking surface. Alternatively, the walking assist device needs to switch the walking pattern data according to the slope angle of the walking surface. Therefore, such a type of walking assistance device needs to detect the slope angle of the walking surface while the user is walking. The present invention was created in view of the above problems. An object of the present invention is to realize a walking assist device that can detect a slope angle of a walking surface while a user is walking.

  The walking assist device of the present invention includes a multi-link mechanism, a plurality of ground sensors, an inclination angle sensor, and an angle sensor. The multi-link mechanism is attached along a user's leg and has a structure in which a plurality of links are connected by a joint. The lower end link of the multi-link mechanism is fixed to the user's sole. In this specification, the lower end link of the multi-link mechanism is referred to as a sole link. The plurality of ground sensors are attached to the sole link so as to be separated in the front-rear direction. The inclination angle sensor is attached to the upper end link of the multi-link mechanism, and measures the inclination angle of the upper end link with respect to the vertical. The angle sensor detects the angle of each joint of the multi-link mechanism. This walking assist device is characterized by measuring the angle of the bottom of the foot with respect to the vertical as the slope angle of the ground contact surface from the outputs of the inclination angle sensor and the angle sensor while all of the ground contact sensors detect the ground contact. To do. Hereinafter, the angle with respect to the vertical is referred to as an absolute inclination angle.

  This walking assist device uses the slope angle of the walking surface as the absolute inclination angle of the bottom surface of the sole link, provided that a plurality of grounding sensors spaced apart in the front-rear direction detect the grounding. Measure as By satisfying the above conditions, the walking surface and the sole link are guaranteed to be parallel. Therefore, this walking assistance device can accurately measure the slope angle of the walking surface.

  In addition, this walking assist device is also characterized in that an inclination sensor for measuring an absolute inclination angle is provided in the upper end link of the multi-link mechanism. The multi-link mechanism is attached along the leg of the user and swings as the leg moves. On the other hand, the tilt angle sensor that measures the absolute tilt angle is sensitive to shaking. If an inclination angle sensor is attached to a link or a sole link in the middle of the multi-link mechanism, the accuracy of the sensor data measurement value decreases. The walking assist device of the present invention prevents a decrease in measurement accuracy of the tilt angle sensor by mounting the tilt angle sensor on the upper end link with the least shaking. The upper end link is preferably fixed to the trunk of the user.

  The walking assistance device of the present invention preferably includes the following technical features. That is, the walking assist device has a pair of multi-link mechanisms that are worn along each leg of the user, and both the sole links are both horizontal and the vertical distance between both the sole links. It is determined that the step is walking when is non-zero. By providing such a technical feature, the walking assistance device can detect not only the slope angle but also the step. This walking assistance device can perform walking assistance suitable for step walking by correcting the walking pattern according to the step. Alternatively, this walking assistance device can perform walking assistance suitable for step walking by switching the walking pattern according to the step.

  The walking assist device of the present invention can detect the slope angle of the walking surface while the user is walking.

  A walking assistance device of an embodiment will be described with reference to the drawings. FIG. 1 shows a schematic diagram of a walking assistance device 10 worn by a user. 1A shows a front view, and FIG. 1B shows a side view. In the present embodiment, it is assumed that the user cannot freely move the knee joint of the left leg. The walking assist device 10 applies an appropriate torque to the user's left knee joint to assist the user's walking motion.

  The walking assist device 10 includes a right leg orthosis 12R and a left leg orthosis 12L. The right leg orthosis 12R is attached to the outside of the leg along the thigh from the user's thigh. The right leg orthosis 12R is a multi-link mechanism having an upper link 14R, a lower link 16R, and a sole link 26R. The left and right leg appliances 12R and 12L are connected by a support link 30. The support link 30 is disposed on the back side of the user and connects the upper end of the right leg orthosis 12R and the upper end of the left leg orthosis 12L. That is, the support link 30 corresponds to the upper end link of the multi-link mechanism.

  The upper end of the upper link 14R is connected to the support link 30 via a waist joint. A waist encoder 22R that detects the angle of the upper link 14R is attached to the waist joint. The lower link 16R is connected to the upper link 14R by a knee joint located outside the knee. A knee encoder 20R that detects the angle of the lower link 16R is attached to the knee joint. The sole link 26R is swingably connected to the lower link 16R by an ankle joint located outside the user's heel. An ankle encoder 24R that detects the angle of the sole link 26R is attached to the ankle joint.

  The upper link 14R is fixed to the user's thigh with a belt. The lower link 16R is fixed to the user's lower leg with a belt. The sole link 26 is fixed to the user's sole with a belt. The belt for fixing the sole link 26 is not shown. The support link 30 is fixed to the trunk (waist) of the user.

  A plurality of ground sensors 28R are attached to the bottom surface of the sole link 26R. The ground sensor attached to the bottom surface of the left leg sole link 26L is denoted by reference numeral 28L. As shown in FIG. 1 (B), the plurality of ground sensors are attached to the front link and the rear in a spaced manner. Reference numeral 28La in FIG. 1B indicates a front ground sensor, and reference numeral 28Lb indicates a rear ground sensor. The front ground sensor 28La is attached at a position corresponding to the user's thumb ball, and the rear ground sensor 28Lb is attached at a position corresponding to the user's thumb. Each grounding sensor detects the grounding between the sole link 26R and the walking surface.

  Since the structure of the left leg orthosis 12L is the same as that of the right leg orthosis 12R, description thereof is omitted. However, the left leg orthosis 12L includes a motor 32. The motor 32 is provided in the knee joint of the left leg orthosis 12L, and is located outside the user's knee joint. The motor 32 can rotate the lower link 16L with respect to the upper link 14L. That is, the motor 32 can apply torque to the user's left knee joint.

  A controller 40 is attached to the support link 30. A tilt sensor 27 is provided inside the controller 40. The inclination sensor 27 detects an absolute inclination angle of the support link 30. That is, the inclination sensor 27 detects an inclination angle (absolute inclination angle) of the support link 30 with respect to the vertical direction. The absolute inclination angle of the support link 30 corresponds to the absolute inclination angle of the user trunk.

  Hereinafter, the encoder group attached to the left and right leg orthoses will be collectively referred to as “angle sensor 20”, and the ground sensor group attached to the left and right sole links will be collectively referred to as “ground sensor 28”.

  The controller 40 controls the motor 32 based on the outputs of the tilt angle sensor 27, the angle sensor 20, and the ground sensor 28. Specifically, the controller 40 corrects the walking pattern stored in advance according to the user's stride, walking speed, and slope angle of the walking surface, and follows the walking pattern in which the user's left leg is corrected. Torque is applied to the user's knee joint. The walking pattern of the walking assistance device and the correction thereof are disclosed in detail in the patent applications already filed by the inventors (Japanese Patent Application No. 2008-235463, filed on September 12, 2008), and thus the description thereof is omitted here. .

  Processing performed by the walking assist device 10 will be described. In FIG. 2, the flowchart of the main process which the walking assistance apparatus 10 performs for every control period is shown. First, the walking assistance device 10 acquires data of various sensors (the inclination angle sensor 27, the angle sensor 20, and the ground sensor 28) (S10). Next, the walking assistance device 10 passes the acquired sensor data through a low-pass filter to remove noise (S12). The walking assistance device 10 obtains the position and speed of each foot from the angle of each joint by the angle sensor (S14). The conversion from the joint angle to the foot position is obtained using well-known robot forward kinematics calculations. Further, the conversion from the angular velocity of the joint to the velocity of the foot can be obtained using a well-known Jacobian matrix. The angular velocity of the joint is obtained from the change of the joint angle with time obtained from the angle sensor 20. Next, the walking assistance device 10 identifies each slope of the walking surface (S16). The slope angle identification process will be described later.

  Next, the walking assistance device 10 obtains the time required for the user to take one step, the stride, and the walking speed from the position and speed of each foot (S18). In this specification, these variables and the slope angle of the walking surface are collectively referred to as “walking state variables”. The slope angle of the walking surface is obtained in step S16. The walking assist device 10 stores reference walking data (reference walking data), corrects the reference walking data with the obtained walking state variable, and obtains walking data suitable for the user's walking motion ( S20). The walking data is represented by a time-series data sequence of foot and waist positions. The walking data can also be described as “a foot trajectory based on the leg position”.

  Next, the walking assistance device 10 determines the target position of the foot from the corrected walking data (S22). The target foot position corresponds to the foot position at the current control timing in the foot trajectory described in the corrected walking data. Then, the walking assistance device 10 converts the target position of the foot into the target knee angle based on the inverse kinematics of the robot (S24). A command value is output to the motor so that the knee angle of the user matches the target knee angle thus obtained (S26). The above process is repeated for each control cycle.

  FIG. 3 shows a flowchart of the slope angle identification process. The walking assistance device 10 identifies the slope angle of the walking surface when the two grounding sensors provided before and after the sole link detect the grounding (S40: YES). If any one of the ground sensors does not detect the ground, the process is terminated without identifying the slope angle (S40: NO). When the two ground sensors detect ground contact, the walking assistance device 10 calculates the absolute tilt angle of the bottom surface of the sole link based on the values of the tilt angle sensor 27 and the angle sensor 20 (S42). . The absolute inclination angle of the sole link calculated here corresponds to the identification value of the slope angle.

  Here, how to measure the slope angle of the walking surface will be described with reference to FIG. Here, the case where the right sole link 26R is grounded will be described as an example. FIG. 4 is a diagram for explaining the geometric relationship between the slope angle of the walking surface and the right leg orthosis 12R. In FIG. 4, reference signs θslope, θbody, θhip, θknee, and θankle respectively indicate the slope angle of the walking surface, the absolute inclination angle of the support link 30 (the absolute inclination angle of the user's trunk), and between the support link 30 and the upper link 14R. , An angle between the upper link 14R and the lower link 16R, and an angle between the lower link 16R and the sole link 26R. Here, the angle θankle of the sole link 26R is measured with reference to a line that intersects at right angles to the direction in which the lower link 16R extends. Further, the absolute inclination angle of the sole link 26R is expressed as a slope angle θslope. Moreover, the code | symbol VL has shown the vertical line.

  The slope angle θslope of the walking surface is expressed by the following equation (1). In Expression (1), the sign of each angle is ignored, and Expression (1) means that the slope angle θslope is calculated from the sum of θbody, θhip, θknee, and θankle. .

  In addition, the subscript “i” in Expression (1) indicates the number of times of measurement. That is, the walking assistance device 10 acquires the outputs of the inclination sensor 27 and the angle sensor 20 k times while the front and rear grounding sensors 28 detect the grounding, and outputs the average of the measured values of the slope angle k times. .

  Returning to FIG. 3, the description of the slope angle identification process will be continued. As described above, the position of each sole link is obtained in step S14 of FIG. In the slope angle identification process, the type of the walking surface on which the user is walking is determined using the slope angle θslope obtained previously and the height fz of the front foot link when the rear foot link is used as a reference. Identify. “The height of the foot link on the front side” corresponds to the vertical distance between the two foot links. Here, the type of walking surface means either a flat ground, a slope, or a step. When the absolute value of the height fz is smaller than the height threshold, the walking assistance device 10 determines that the user is walking on a flat ground (S44: YES, S48). The height threshold is given in advance. When the absolute value of the height fz is equal to or greater than the height threshold value and the slope angle θslope obtained in S42 is equal to or greater than the slope angle threshold value, the walking assistance device 10 determines that the user is walking on the inclined surface (S44: NO, S46: YES, and S50). When the absolute value of the height fz is equal to or greater than the height threshold value and the slope angle θslope obtained in S42 is smaller than the slope angle threshold value, the walking assistance device 10 determines that the user is walking on the step (S44: NO). , S46: NO, and S52). The slope angle threshold is a value close to zero and is given in advance. A case where the slope angle is close to zero means that the walking surface is horizontal. Accordingly, the process of shifting from S46 to S52 means that the soles of both sole links are both horizontal, and the vertical distance between both foot links is other than zero. Thus, the walking assistance device 10 determines the state of the walking surface.

  Even if the absolute value of the slope angle θslope calculated in step S42 is larger than the slope angle threshold value, it is determined that the walking is flat ground if the height fz is smaller than the height threshold value (S44: YES, S48). Although explanation is omitted, in this case, the walking assistance device 10 determines that there is a high possibility that one of the sensors is out of order.

  FIG. 5 shows the geometric relationship between the leg brace and the walking surface when the walking surface is a slope (FIG. 5A) and when the walking surface is a step (FIG. 5B). As shown in FIG. 5A, while the user is walking on the slope, the vertical distance fz of both sole links is larger than the height threshold, and the front sole link (in this case, the right sole link 26R). The absolute inclination angle (slope angle) θslope of is greater than the slope angle threshold. On the other hand, as shown in FIG. 5B, when the user is walking on the step, the vertical distance fz of both sole links is larger than the height threshold, and the absolute values of both sole links 26L and 26R are absolute. Both inclination angles (slope angles) θslope are substantially horizontal. In addition, the arrow which the code | symbol F shows in FIG. 5 (A), (B) has shown the vector from the rear side sole link to the front side sole link. As shown in FIGS. 5A and 5B, even if the vectors F are substantially the same, the slope walking depends on the absolute inclination angle of the front sole link (that is, the identified slope angle θslope). It is possible to classify whether it is a step or a step walk.

  The technical features of the walking assist device 10 of the embodiment will be summarized. The walking assist device 10 includes an inclination angle sensor 27 that measures the absolute inclination angle of the support link 30 on the support link 30 that is positioned at the upper end of a leg brace (multi-link mechanism) that is mounted along the leg of the user. The support link 30 is fixed to the user's trunk. The support link 30 fixed to the user's trunk is less swayed compared to other links, particularly the sole link fixed to the user's foot. Since the tilt angle sensor 27 is mounted on the support link 30 with less shaking, noise added to the output of the tilt angle sensor 27 can be suppressed.

  The walking assist device 10 has a sole link based on the outputs of the inclination angle sensor 27 and the angle sensor 20 while the ground sensors provided on one sole link so as to be separated from each other in the front-rear direction are detecting the ground contact. The absolute inclination angle of is calculated. The calculated absolute inclination angle of the sole link is adopted as the identification value of the slope angle of the walking surface. Since it is provided while being spaced apart from the front and back and the grounding sensors are both detecting the grounding, parallelism between the sole link and the grounding surface is ensured. Therefore, the absolute inclination angle of the sole link calculated by this walking assistance device accurately reflects the slope angle of the walking surface. The walking assist device corrects the walking pattern based on the accurate slope angle of the walking surface, and applies torque to the leg so as to follow the corrected walking pattern. The walking assistance device also corrects the walking pattern even when the walking surface is a step, and applies torque to the leg so as to follow the corrected walking pattern. Therefore, this walking assistance device can correct the walking pattern in accordance with the slope angle or level difference of the walking surface and appropriately assist the user's walking motion.

  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.

The schematic of the walking assistance apparatus of an Example is shown. The flowchart of the main process which a walking assistance apparatus performs is shown. The flowchart of the identification process of a slope angle is shown. It is a figure explaining the geometric relationship between a leg orthosis and a slope angle. It is a figure explaining the difference between slope walking and step walking.

Explanation of symbols

10: Walking assist device 12R, 12L: Orthosis 14R, 14L: Upper link 16R, 16L: Lower link 20R, 20L: Knee encoder 22R, 22L: Waist encoder 24R, 24L: Ankle encoder 26R, 26L: Sole link 27: Inclination Sensors 28R, 28L: Ground sensor 30: Support link 40: Controller

Claims (2)

It is a walking assistance device that assists the user's walking movement,
A multi-link mechanism attached along the user's leg and connected by a joint with multiple links;
A plurality of ground sensors attached to a sole link which is a lower end link of the multi-link mechanism and is fixed to a user's foot, and separated in the front-rear direction;
An inclination angle sensor that is attached to the upper end link of the multi-link mechanism and measures the inclination angle of the upper end link with respect to the vertical;
An angle sensor for detecting the angle of each joint of the multi-link mechanism,
A walking assist device that measures the angle of the bottom of the foot with respect to the vertical as the slope angle of the ground contact surface from the outputs of the inclination angle sensor and the angle sensor while all of the ground contact sensors detect the ground contact. Both have a pair of multi-link mechanisms mounted along each leg of the user, and a plurality of ground sensors provided on each of the pair of multi-link mechanisms both detect grounding. 2. The walking assist according to claim 1, wherein the step is determined to be walking when the soles of the sole links are both horizontal and the vertical distance between both the sole links is other than zero. apparatus.

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