Robot foot part structure and robot

Abstract

Provided are: a robot foot part structure that has few constraints, has a simple structure, and makes it possible to detect reaction force from a walking surface; and a robot. A foot part (100) of a robot (1) includes: a first sole member (110) arranged in the rear section of the foot part (100); a second sole member (120) arranged in front of the first sole member (110); a joint mechanism (150) that has the second sole member (120) attached thereto and includes a movable member (152) capable of moving relative to the first sole member (110); a first sensor (161) that is arranged on the first sole member (110) and detects reaction force from a walking surface (2); and a second sensor (162) that is arranged on the second sole member (120) and detects reaction force from the walking surface (2).

Description

Robot foot structure and robot

[0001] The present invention relates to a foot structure for a robot and a robot.

[0002] Robots have been developed that have legs and can walk by moving their legs. In such robots, sensors for detecting reaction forces from the walking surface, such as the floor or ground, are sometimes attached to the feet that come into contact with the walking surface. This makes it possible to calculate the position of the center of gravity of the robot and control the robot so that its posture relative to the walking surface is appropriate.

[0003] Patent Document 1 below discloses that a strain-generating body that undergoes bending deformation is placed between an instep member connected to the leg of a robot and a sole member that comes into contact with the walking surface, and multiple strain sensors are placed on the strain-generating body to detect the reaction force from the walking surface. Patent Document 2 below also discloses that a force sensor placed on the other side of an elastic body with a fulcrum on either the instep member or the sole member is pressed against the other to detect the reaction force from the walking surface.

[0004] JP 2019-194418 A JP 2019-194417 A

[0005] In the foot structures described in Patent Documents 1 and 2, the sole member is formed of a single plate, which places restrictions on the movement of the robot's sole.

[0006] An object of the present disclosure is to provide a robot foot structure and a robot that improve the degree of freedom of movement of the sole of the foot and can appropriately detect reaction forces from the walking surface.

[0007] A foot structure according to the present disclosure may be a foot structure provided at the lower end of a leg of a robot, and may include a first sole member disposed at the rear of the foot structure and in contact with a walking surface, a second sole member disposed in front of the first sole member and in contact with the walking surface, a joint mechanism to which the second sole member is attached and which includes a movable member that can move relative to the first sole member, a first sensor disposed on the first sole member and detecting a reaction force from the walking surface acting on the first sole member, and a second sensor disposed on the second sole member and detecting a reaction force from the walking surface acting on the second sole member. This improves the degree of freedom of movement of the sole and makes it possible to appropriately detect the reaction force from the walking surface.

[0008] Furthermore, the robot according to the present disclosure may be a robot having legs and foot structures provided at the lower ends of the legs, and may include a first sole member disposed at the rear of the foot structure and in contact with a walking surface, a second sole member disposed in front of the first sole member and in contact with the walking surface, a joint mechanism to which the second sole member is attached and which includes a movable member that can move relative to the first sole member, a first sensor disposed on the first sole member and detecting a reaction force from the walking surface on the first sole member, and a second sensor disposed on the second sole member and detecting a reaction force from the walking surface on the second sole member. This improves the degree of freedom of movement of the soles and makes it possible to appropriately detect the reaction force from the walking surface.

[0009] 2D. A diagram showing the layout of actuators possessed by a robot proposed in the present disclosure. A perspective view showing the upper side of a foot of a robot. A perspective view showing the underside of a foot of a robot. A plan view showing a foot of a robot. A side view showing a foot of a robot. A cross-sectional view showing a cross-section of the foot at III-III in FIG. 2D. A cross-sectional view showing a cross-section of the foot at IV-IV in FIG. 2D. A side view showing a state in which the second sole member has moved from the position shown in FIG. 2D. A cross-sectional view showing a cross-section of the foot at VI-VI in FIG. 4. A cross-sectional view showing a cross-section of the foot in a state in which the second sole member is in a second posture. A diagram showing an example of electronic components mounted on a circuit board of the foot.

[0010] An embodiment of the present disclosure will be described below with reference to the drawings. FIG. 1 is a diagram showing the layout of actuators included in a robot 1 proposed in the present disclosure. In the following description, the X1 and X2 directions of the X axis shown in FIG. 1 and other figures are defined as left and right, respectively. Furthermore, the Y1 and Y2 directions of the Y axis perpendicular to the X axis shown in FIG. 1 and other figures are defined as forward and backward, respectively. Furthermore, the Z1 and Z2 directions of the Z axis perpendicular to the X and Y axes shown in FIG. 1 and other figures are defined as upward and downward, respectively. However, these directions and positions are defined to explain the shapes and relative positional relationships of elements (components, members, and sections) of the robot 1, and do not limit the posture or orientation of the robot 1.

[0011] [1. Overview of the Robot] The robot 1 is, for example, a humanoid robot capable of walking on two legs. As shown in FIG. 1 , the robot 1 may have a chest 10U and a buttocks 10D, and actuators 11 to 13 corresponding to the hip joints for moving the chest relative to the buttocks 10D. The robot 1 may also have a right leg 20R and a left leg 20L, and multiple actuators for moving these legs 20R and 20L. Each of the legs 20R and 20L may have actuators 26 and 27 corresponding to the ankle joints, an actuator 25 corresponding to the knee joint, and actuators 22 to 24 corresponding to the hip joints. The robot 1 may also have a right arm 30R and a left arm 30L, and multiple actuators for moving these arms 30R and 30L. Each of the arms 30R, 30L may have an actuator 35 corresponding to an elbow joint, an actuator 34 disposed on the upper arm, and actuators 32, 33 corresponding to shoulder joints. The robot 1 may also have a head 40 and a plurality of actuators 42 to 44 corresponding to joints in the neck for moving the head 40.

[0012] The three actuators 11 to 13 corresponding to the hip joints of the robot 1 may be rotatable around the Z-axis, X-axis, and Y-axis directions, respectively. This allows the chest 10U of the robot 1 to change its angle relative to the buttocks 10D along three axes: roll, pitch, and yaw. The three actuators 42 to 44 corresponding to the neck joints of the robot 1 may also be rotatable around the Z-axis, X-axis, and Y-axis directions, respectively. This allows the head 40 of the robot 1 to change its angle relative to the chest 10U along three axes: roll, pitch, and yaw.

[0013] The layout of the actuators in the robot 1 is not limited to that shown in FIG. 1. For example, the number of actuators that the robot 1 has may be more or less than that shown in FIG. 1. Furthermore, the robot 1 may not have a head 40, a chest 10U, or arms 30R and 30L. Furthermore, the robot 1 is not limited to a humanoid robot as shown in FIG. 1, but may be a quadrupedal robot that imitates an animal such as a dog or a cat. In this case, the robot 1 may have four legs: a front right leg, a front left leg, a rear right leg, and a rear left leg.

[0014] [2. Robot Foot Structure] As shown in FIG. 1 , each leg 20R, 20L of the robot 1 may have a foot 100 (foot structure) at its bottom that contacts a walking surface 2, such as a desk, floor, or ground. The foot 100 may be connected to an actuator 27 corresponding to the ankle joint of the leg 20R, 20L. The actuators 26, 27 of each leg 20R, 20L may be rotatable about the X-axis and Y-axis, respectively. This allows the roll angle and pitch angle of the foot 100 of each leg 20R, 20L to be changed. Furthermore, the actuators 24 to 27 provided on each leg 20R, 20L move at appropriate angles, allowing the robot 1 to walk on the walking surface 2. The walking surface 2 is not limited to a flat surface, and may also be an uneven or stepped surface.

[0015] Fig. 2A is a perspective view showing the upper side of the foot 100 of the robot 1. Fig. 2B is a perspective view showing the underside of the foot 100 of the robot 1. Fig. 2C is a plan view showing the foot 100 of the robot 1. Fig. 2D is a side view showing the foot 100 of the robot 1. Fig. 3 is a cross-sectional view showing the cross section of the foot 100 taken along line III-III in Fig. 2D. Fig. 4 is a cross-sectional view showing the cross section of the foot 100 taken along line IV-IV in Fig. 2D.

[0016] 2A , the foot 100 may have a first sole member 110 disposed at the rear of the foot 100 and in contact with the walking surface 2 (see FIG. 1 ), and a second sole member 120 disposed in front of the first sole member 110 and in contact with the walking surface 2. In the foot 100, the first sole member 110 may be a portion corresponding to the heel, and the second sole member 120 may be a portion corresponding to the toe. The first sole member 110 and the second sole member 120 may be made of metal such as iron or aluminum, or may be made of resin, rubber, or elastomer.

[0017] When the first sole member 110 is made of metal or resin, an anti-slip member 110a may be disposed on the bottom of the first sole member 110, as shown in FIG. 2B . At least a portion of the anti-slip member 110a may be formed of rubber or elastomer. The anti-slip member 110a may be attached to the first sole member 110 by fasteners 201 such as screws. Similarly, an anti-slip member 120a formed of rubber or elastomer may be disposed on the bottom of the second sole member 120. As shown in FIG. 3 , the anti-slip member 120a may be attached to the second sole member 120 by fitting a flange-shaped protrusion into a hole formed in the second sole member 120. However, the anti-slip members 110a, 120a may also be attached with an adhesive or the like.

[0018] As shown in Fig. 2A, the foot 100 may have an instep member 130 disposed on the first sole member 110. The instep member 130 may be formed of metal, resin, or the like. The instep member 130 may be connected to the leg 20R or leg 20L (see Fig. 1). The instep member 130 may be disposed between the leg 20R or leg 20L and the first sole member 110 in the vertical direction.

[0019] As shown in Fig. 2A, a circuit board 180 may be attached to the upper part of the instep member 130. The circuit board 180 may be fixed to the instep member 130 by a plurality of fasteners 208 (see Fig. 2C) such as screws. The instep member 130 may also have a connecting member 140 on its upper part. The connecting member 140 may be made of metal, resin, or the like. The connecting member 140 may be fixed to the instep member 130 by a plurality of fasteners 202 (see Fig. 2B) such as screws.

[0020] The instep member 130 may be connected to the actuator 27 of the leg 20R or the leg 20L via a connecting member 140. However, this is not limiting, and the instep member 130 may be connected directly to the actuator 27 of the leg 20R or the leg 20L without using a member such as the connecting member 140. The instep member 130 and the connecting member 140 may be made of metal such as iron or aluminum, or may be made of resin.

[0021] As shown in FIG. 2D , the foot 100 may have a joint mechanism 150 that functions as a joint of the foot 100. The joint mechanism 150 may include a frame 151 extending in the front-rear direction in front of the first sole member 110 and a movable member 152 provided at the front end of the frame 151. The frame 151 may be formed of metal, resin, or the like. The frame 151 may include a left frame 151L (see FIG. 2B ) extending in the front-rear direction at a position shifted to the left of a center line CX (see FIG. 2C ) in the left-right direction of the foot 100, and a right frame 151R (see FIG. 2B ) extending in the front-rear direction at a position shifted to the right of the center line CX. The frame 151 may be attached to the underside of the instep member 130 with fasteners 203 such as screws.

[0022] As shown in Figures 2A and 4, a space may be provided inside the frame 151 (for example, between the left frame 151L and the right frame 151R), and at least a portion of the movable member 152 may be disposed in this space. The movable member 152 may be made of metal, resin, or the like. A second sole member 120 may be attached to the movable member 152. As will be described later, the movable member 152 may be able to move relative to the first sole member 110 and the instep member 130. This allows the second sole member 120 attached to the movable member 152 to move relative to the first sole member 110 and the instep member 130.

[0023] 3, a first sensor 161 may be disposed on the first sole member 110 to detect a reaction force from the walking surface 2 acting on the first sole member 110. This allows the first sole member 110, which is disposed on the rear part of the foot 100 (e.g., the part corresponding to the heel), to detect the reaction force from the walking surface 2.

[0024] 4, a second sensor 162 for detecting a reaction force from the walking surface 2 acting on the second sole member 120 may also be disposed on the second sole member 120. This allows the reaction force from the walking surface 2 to be detected even on the second sole member 120 disposed on the front part of the foot 100 (for example, the part corresponding to the toes).

[0025] As described above, the second sole member 120 is attached to the movable member 152 and is therefore capable of moving relative to the first sole member 110. This allows for greater freedom of movement of the sole compared to when the sole member is formed from a single plate, for example. Furthermore, sensors 161, 162 that detect reaction forces from the walking surface 2 are provided on both the first sole member 110 and the second sole member 120. This makes it possible to properly detect reaction forces acting on the first sole member 110 and the second sole member 120, for example, when walking on a walking surface 2 that has unevenness or steps.

[0026] The first sole member 110 may be able to tilt left and right relative to the instep member 130, for example, by standing on a walking surface 2 having an uneven surface or a step. In the example shown in FIG. 3 , one of the left end 110L and the right end 110R of the first sole member 110 may move up and down relative to the other end. Here, the first sensor 161 disposed on the first sole member 110 may include a sensor 161L disposed to the left of a center line CX (see FIG. 2C ) in the left-right direction of the foot 100, and a sensor 161R disposed to the right of this center line CX. By detecting the reaction force from the walking surface 2 with both the sensor 161L and the sensor 161R, it is possible to determine whether the reaction force from the walking surface 2 is greater on the left or right side of the first sole member 110.

[0027] The second sole member 120 may also be able to tilt left and right relative to the movable member 152 when placed on a walking surface 2 having an uneven surface or a step. In the example shown in FIG. 4 , one of the left end 120L and the right end 120R of the second sole member 120 may move up and down relative to the other. Here, the second sensor 162 disposed on the second sole member 120 may also include a sensor 162L disposed to the left of the center line CX (see FIG. 2C ) in the left-right direction of the foot 100, and a sensor 162R disposed to the right of this center line CX. By detecting the reaction force from the walking surface 2 with both the sensor 162L and the sensor 162R, it is possible to determine whether the reaction force from the walking surface 2 is greater on the left or right side of the second sole member 120.

[0028] As described above, the foot 100 may have a sensor 161L positioned toward the rear left of the foot 100, a sensor 161R positioned toward the rear right of the foot 100, a sensor 162L positioned toward the front left of the foot 100, and a sensor 162R positioned toward the front right of the foot 100. This configuration makes it possible to determine, for example, which of the rear left, rear right, front left, and front right of the foot 100 is experiencing a larger reaction force. Furthermore, the four sensors 161L, 161R, 162L, and 162R may be positioned at each vertex of a rectangle (e.g., a rectangle with long sides extending in the front-to-rear direction). This facilitates calculation of the center of gravity of the foot 100 by the processor 191 (see FIG. 8 ), which will be described later.

[0029] Four cables 211L, 211R, 212L, and 212R (see FIG. 2C) such as flexible substrates may be attached to the four sensors 161L, 161R, 162L, and 162R, respectively. Four connectors 181a to 181d (see FIG. 2C) may be mounted on the circuit board 180. Terminals of the four cables 211L, 211R, 212L, and 212R may be connected to the four connectors 181a to 181d.

[0030] As shown in Figure 3, the foot 100 may have a first flexure body 171 attached to the first sole member 110 and the instep member 130. The first flexure body 171 may be a member that elastically bends and deforms in response to movement of the first sole member 110 relative to the instep member 130. The first flexure body 171 may be, for example, a leaf spring extending in the left-right direction. The first flexure body 171 may be disposed between the first sole member 110 and the instep member 130 in the up-down direction.

[0031] 3 , the first flexure body 171 may have a lower attachment portion 171a attached to the first sole member 110 by fasteners 203 such as screws, and an upper attachment portion 171b attached to the instep member 130 by fasteners 204 such as screws. The first sole member 110 is attached to the instep member 130 via the first flexure body 171, and can elastically tilt with respect to the instep member 130. For example, the first flexure body 171 may elastically deform, and the right portion of the first flexure body 171 and the right portion of the first sole member 110 may be positioned higher than the center of the first flexure body 171 in the left-right direction and the first sole member 110. Conversely, the left portion of the first flexure body 171 and the left portion of the first sole member 110 may be positioned higher than the center of the first flexure body 171 in the left-right direction and the first sole member 110.

[0032] As shown in FIG. 3 , the first flexure body 171 may have two lower mounting portions 171a attached to the first sole member 110 at different positions from each other and two upper mounting portions 171b attached to the instep member 130 at different positions from each other. The two lower mounting portions 171a and the two upper mounting portions 171b may be aligned in the left-right direction. The two upper mounting portions 171b may be disposed between the two lower mounting portions 171a in the left-right direction. The two lower mounting portions 171a may be located closer to the end of the first flexure body 171 than the two upper mounting portions 171b. In the first flexure body 171, the two upper mounting portions 171b may be integrally connected or separated from each other.

[0033] The two sensors 161L, 161R included in the first sensor 161 may be strain sensors attached to the first strain body 171. That is, the first sensor 161 may include a strain sensor 161L attached to the left of a center line CX (see FIG. 2C ) in the left-right direction of the foot 100, and a strain sensor 161R attached to the right of the center line CX. The processor 191 (see FIG. 8 ), which will be described later, may calculate the reaction force from the walking surface 2 at the positions of the strain sensors 161L, 161R based on the outputs (e.g., numerical values ​​representing the magnitude of the strain) from the strain sensors 161L, 161R. This allows the reaction force from the walking surface 2 to be detected at both the left and right positions of the first sole member 110.

[0034] As shown in FIG. 4 , the foot 100 may have a second flexure body 172 attached to the second sole member 120 and the movable member 152. The second flexure body 172 may be a member that elastically bends and deforms in response to movement of the second sole member 120 relative to the movable member 152. The second flexure body 172 may be, for example, a leaf spring extending in the left-right direction. The second flexure body 172 may be disposed on the second sole member 120 and the movable member 152. The second flexure body 172 may have a first attachment portion 172a attached to the second sole member 120 by a fastener 205 such as a screw, and a second attachment portion 172b attached to the movable member 152 by a fastener 206 such as a screw. The second sole member 120 is attached to the movable member 152 via the second flexure body 172, and thus can elastically tilt with respect to the movable member 152. For example, the second flexure body 172 may be elastically deformed, and the positions of the right part of the second flexure body 172 and the right part of the second sole member 120 may become higher relative to the center in the left-right direction of the second flexure body 172 and the second sole member 120. Conversely, the positions of the left part of the second flexure body 172 and the left part of the second sole member 120 may become higher relative to the center in the left-right direction of the second flexure body 172 and the second sole member 120.

[0035] As shown in Fig. 4, the second flexure body 172 may have two first mounting portions 172a attached to the second sole member 120 at different positions from each other and two second mounting portions 172b attached to the movable member 152 at different positions from each other. The two first mounting portions 172a and the two second mounting portions 172b may be aligned in the left-right direction. The two first mounting portions 172a may be disposed between the two second mounting portions 172b in the left-right direction. The two second mounting portions 172b may be provided at positions closer to the ends of the second flexure body 172 than the two first mounting portions 172a. In the second flexure body 172, the two first mounting portions 172a may be integrally connected to each other or may be separated from each other.

[0036] The two sensors 162L, 162R included in the second sensor 162 may also be strain sensors attached to the second strain body 172. The second sensor 162 may include a strain sensor 162L attached to the left of a center line CX (see FIG. 2C ) in the left-right direction of the foot 100, and a strain sensor 162R attached to the right of this center line CX. The processor 191 (see FIG. 8 ), which will be described later, may calculate the reaction force from the walking surface 2 at the positions of the strain sensors 162L, 162R based on the outputs (e.g., numerical values ​​representing the magnitude of the strain) from the strain sensors 162L, 162R. This allows the reaction force from the walking surface 2 to be detected at both the left and right positions of the second sole member 120.

[0037] 5 is a side view showing the foot 100 of the robot 1, illustrating a state in which the second sole member 120 has moved from the position shown in FIG. 2D . The movable member 152 may be rotatable relative to the first sole member 110 and the instep member 130 about an axis Ax1 (see FIG. 4 ) along the left-right direction. This allows the second sole member 120 attached to the movable member 152 to rotate relative to the first sole member 110 and the instep member 130. For example, when the second sole member 120 is in contact with the walking surface 2, the first sole member 110 and the instep member 130 move forward and upward relative to the second sole member 120, allowing the movable member 152 to rotate relative to the first sole member 110 and the instep member 130.

[0038] As shown in Fig. 4, the movable member 152 may be formed with a shaft portion 152L that protrudes to the left and a shaft portion 152R that protrudes to the right. These shaft portions 152L and 152R may define an axis Ax1 that is the center line of rotation of the movable member 152. Furthermore, a bearing 153L may be provided between the frame 151 that houses the movable member 152 and the shaft portion 152L. Similarly, a bearing 153R may be provided between the frame 151 and the shaft portion 152R. This allows smooth movement of the movable member 152 relative to the frame 151.

[0039] A rotation sensor 154 for detecting the degree of rotation (e.g., rotation angle) of the movable member 152 may be provided at the tip of the shaft portion 152R protruding to the right or the shaft portion 152L protruding to the left of the movable member 152. In the example shown in FIG. 4 , the rotation sensor 154 is provided at the tip of the shaft portion 152R protruding to the right. The rotation sensor 154 may include a sensor rotation portion 154a attached to the tip of the shaft portion 152R and a sensor fixing portion 154b facing the sensor rotation portion 154a in the direction along the axis Ax1. The rotation sensor 154 may be a magnetic angle sensor that detects rotation using changes in magnetic flux. The sensor rotation portion 154a may be a magnet. The sensor fixing portion 154b may output a signal corresponding to the change in magnetic flux caused by the rotation of the sensor rotation portion 154a. The sensor fixing portion 154b may be a sensor substrate on which a Hall IC is mounted. However, the present invention is not limited to this, and the sensor rotating portion 154a may be a sensor substrate, and the sensor fixing portion 154b may be a magnet.

[0040] 2D and 5, the second sole member 120 may be movable about an axis Ax1 between a first position (see FIG. 2D) in which the bottom surface of the second sole member 120 (e.g., the non-slip member 120a) is aligned along the front-to-rear direction, and a second position (see FIG. 5) in which the bottom surface of the second sole member 120 is inclined relative to the front-to-rear direction. The first position is, for example, a position in which the bottom surface of the second sole member 120 faces downward. The second position is, for example, a position in which the bottom surface of the second sole member 120 faces diagonally forward and downward.

[0041] The joint mechanism 150 may have an elastic member 155 that biases the movable member 152 to which the second sole member 120 is attached so that the second sole member 120 changes from the second position shown in Fig. 5 to the first position shown in Fig. 2D. This allows the second sole member 120 to return to the first position, for example, when the foot 100 moves upward and the second sole member 120 separates from the walking surface 2 from a state in which only the second sole member 120 is in contact with the walking surface 2 and the second sole member 120 is in the second position.

[0042] As shown in Fig. 2B, the elastic member 155 may be a leaf spring having one end (e.g., the rear end) fixed to the rear portion of the foot 100 and the other end (e.g., the front end) biasing the movable member 152 (see Fig. 4). The rear end of the elastic member 155 may be fixed to the underside of the instep member 130 by one or more fasteners 207 (four in the example shown in Fig. 2B) such as screws. The elastic member 155 may be disposed between the left frame 151L and the right frame 151R.

[0043] By using a leaf spring as the elastic member 155 that biases the movable member 152 in this way, the size of the elastic member 155 can be made larger than when, for example, the movable member 152 is biased by a coil spring. This makes it easier for the elastic member 155 to bend elastically, and limits the magnitude of the force that moves the second sole member 120 from the second position (see FIG. 5) to the first position (see FIG. 2D). In other words, it is possible to prevent the second sole member 120, which has come into contact with the walking surface 2 and assumed the second position, from returning to the first position while still in contact with the walking surface 2.

[0044] Figure 6 is a cross-sectional view showing the cross section of the foot unit 100 taken along line VI-VI in Figure 4. Figure 7 is a cross-sectional view showing the cross section of the foot unit 100 when the second sole member 120 is in the second position (see Figure 5). The elastic member 155 may urge the second sole member 120 attached to the movable member 152 to the first position (see Figure 6) by pushing the movable member 152 upward at a position shifted rearward from the axis Ax1, which is the center line of rotation of the movable member 152.

[0045] In Figure 7, the elastic member 155 when the second sole member 120 is in the first position (see Figure 6) is shown by a two-dot chain line. As shown in Figure 7, the amount of deformation of the elastic member 155 when the second sole member 120 is in the second position is greater than the amount of deformation of the elastic member 155 when the second sole member 120 is in the first position. As a result, when the second sole member 120 in the second position leaves the walking surface 2, the restoring force of the elastic member 155 pushes up the movable member 152, allowing the second sole member 120 attached to the movable member 152 to return to the first position.

[0046] As shown in Figures 6 and 7, the joint mechanism 150 may have a pressed member 156 that can move up and down at a position shifted rearward from the axis Ax1 and is pressed by an elastic member 155. The elastic member 155 may press the pressed member 156 upward (in the direction indicated by arrow L1 in Figures 6 and 7), thereby pressing the movable member 152 upward. The elastic member 155 may urge the second sole member 120 toward the first position (see Figure 6) by pressing the movable member 152 via the pressed member 156. However, the elastic member 155 may also urge the second sole member 120 toward the first position by directly pressing the movable member 152.

[0047] As shown in FIG. 4 , the pressed member 156 may be attached to a shaft member 157 extending in the left-right direction at a position shifted rearward from the axis Ax1. A space S may be formed inside the movable member 152, and at least a portion of the pressed member 156 and the shaft member 157 may be housed in this space S. Furthermore, a support member 158 that supports the shaft member 157 may be disposed below the shaft member 157 in the space S inside the movable member 152. As shown in FIG. 2B , the movable member 152 and the support member 158 may be exposed at the front surface of the second sole member 120. The pressed member 156, the shaft member 157, and the support member 158 may be made of metal, resin, rubber, or elastomer.

[0048] A pressed member 156 disposed to the left of a center line CX (see FIG. 2C ) in the left-right direction of the foot 100, and another pressed member 156 disposed to the right of the center line CX, may be disposed in the space S inside the movable member 152. The number of pressed members 156 provided in the space S is not limited to two, and may be one, or three or more.

[0049] As shown in FIG. 6 , the pressed member 156 may be annular. The pressed member 156 may be rotatable around an axis Ax2 defined by an axis member 157. This reduces friction between the pressed member 156 and the elastic member 155 and between the pressed member 156 and the movable member 152. This configuration reduces friction between the elastic member 155 and the movable member 152 compared to when the elastic member 155 directly presses the movable member 152, preventing the movement of the movable member 152 from being impeded by friction. In other words, the second sole member 120 attached to the movable member 152 can move smoothly, and the second sole member 120 can be returned to the first position (see FIG. 6 ) using an elastic member 155 with a small deformation amount and restoring force.

[0050] 6 and 7, the inner edge 152a of the space S provided inside the movable member 152 may be formed in an arc shape corresponding to the shape of the pressed member 156. In this way, the elastic member 155 can press the second sole member 120 upward via the pressed member 156, regardless of whether the second sole member 120 is in the first position (see FIG. 6) or the second position (see FIG. 7). The elastic member 155 may press the pressed member 156 and the second sole member 120 in a direction intersecting with the axis Ax2.

[0051] FIG. 8 is a diagram showing an example of electronic components mounted on the robot 1. As shown in FIG. 8, the foot 100 or the robot 1 may have a processor 191 and a storage device 192 in addition to the connectors 181a to 181d mounted on the circuit board 180. The processor 191 is an electronic component that executes data processing, such as a CPU (Central Processing Unit). The storage device 192 is a memory element, such as a ROM (Read Only Memory) or RAM (Random Access Memory). The storage device 192 may store data, such as programs and formulas, executed by the processor 191. The processor 191 and the storage device 192 may be mounted on the circuit board 180, or may be mounted on a circuit board different from the circuit board 180 (a circuit board attached to the robot 1).

[0052] The processor 191 may calculate the position of the center of gravity of the foot 100 based on the detection results of each of the four feet 161L, 161R, 162L, and 162R. In this way, the processor 191 or another processor (for example, a processor located at a position different from the foot 100 of the robot 1) can determine the state of the walking surface 2 and control the actuators 11 to 13, 26, 27, 32 to 35, and 42 to 44 of the robot 1 so that the posture of the robot 1 relative to the walking surface 2 is appropriate.

[0053] 3. Modifications The present invention is not limited to the above-described embodiments. For example, as shown in FIGS. 5 and 6 , the embodiment has been described in which the elastic member 155 pushes the movable member 152 upward at a position shifted rearward from the axis Ax1, which is the rotation center line of the movable member 152, thereby biasing the second sole member 120 attached to the movable member 152 toward the first position (see FIG. 5 ). However, this is not limiting, and the elastic member 155 may also push the movable member 152 downward at a position shifted forward from the axis Ax1. In this case, the foot 100 may have a member to which the elastic member 155 is attached, located in front of the movable member 152 (e.g., in front of the second sole member 120). This also allows the second sole member 120 attached to the movable member 152 to be biased toward the first position.

[0054] Furthermore, the number of sensors 161L, 161R, 162L, 162R provided on the foot 100 does not have to be four, and may be two, three, or five or more. For example, one strain sensor may be provided on the first flexure body 171 attached to the first sole member 110 and the instep member 130, and one strain sensor may be provided on the second flexure body 172 attached to the second sole member 120 and the movable member 152. Even in this case, it is possible to determine whether the reaction force is greater on the front side or the rear side of the foot 100.

[0055] Furthermore, the sensors 161L, 161R included in the first sensor 161 are not limited to strain sensors attached to the first strain body 171. These sensors may be pressure sensors attached to one of the first sole member 110 and the instep member 130 to measure pressure from the other member, or optical distance measuring sensors attached to one member to measure the distance to the other member. Similarly, the sensors 162L, 162R included in the second sensor 162 are not limited to strain sensors attached to the second strain body 172. These sensors may also be pressure sensors attached to one of the second sole member 120 and the movable member 152 to detect pressure from the other member, or optical distance measuring sensors attached to one member to measure the distance to the other member. This also enables the foot 100 of the robot 1 to appropriately detect the reaction force from the walking surface 2.

[0056] [4. Summary] (1) As described above, the foot structure described in this disclosure may be a foot structure provided at the lower end of a leg of a robot. The foot structure may include a first sole member disposed at the rear of the foot structure and in contact with a walking surface, a second sole member disposed in front of the first sole member and in contact with the walking surface, a joint mechanism to which the second sole member is attached and which includes a movable member that can move relative to the first sole member, a first sensor disposed on the first sole member and detecting a reaction force from the walking surface acting on the first sole member, and a second sensor disposed on the second sole member and detecting a reaction force from the walking surface acting on the second sole member. This improves the degree of freedom of movement of the sole and enables appropriate detection of the reaction force from the walking surface.

[0057] (2) In the foot structure of (1), the second sole member may be tiltable relative to the movable member. The second sensors may include a sensor disposed to the left of a center line of the foot structure in the left-right direction, and a sensor disposed to the right of the center line. This makes it possible to determine whether the reaction force from the walking surface is greater on the left or right side of the second sole member.

[0058] (3) The foot structure of (1) or (2) above may further include an instep member connected to the leg and positioned between the leg and the first sole member in the up-down direction. The first sole member may be tiltable relative to the instep member. The first sensor may include a sensor positioned to the left of a center line of the foot structure in the left-right direction, and a sensor positioned to the right of the center line. This makes it possible to determine whether the reaction force from the walking surface is greater on the left or right side of the first sole member.

[0059] (4) The foot structure of any one of (1) to (3) above may further include a strain body attached to the movable member and the second sole member, and causing bending deformation in response to movement of the second sole member relative to the movable member. The second sensor may include a strain sensor attached to the strain body at a position shifted to the left of the center line and a strain sensor attached to the strain body at a position shifted to the right of the center line.

[0060] (5) The foot structure according to any one of (1) to (4) above may further include a strain sensor attached to the instep member and the first sole member, the strain sensor causing bending deformation in response to movement of the first sole member relative to the instep member. The first sensor may include a strain sensor attached to the strain sensor at a position shifted to the left of the center line and a strain sensor attached to the strain sensor at a position shifted to the right of the center line.

[0061] (6) In any of the foot structures (1) to (5) above, the movable member may be rotatable relative to the first sole member about an axis extending in the left-right direction, thereby allowing the second sole member attached to the movable member to rotate relative to the first sole member.

[0062] (7) In the foot structure of (6) above, the second sole member may be movable about the axis between a first position in which the bottom surface of the second sole member is aligned with the front-to-rear direction and a second position in which the bottom surface of the second sole member is inclined with respect to the front-to-rear direction. The joint mechanism may further include an elastic member that biases the movable member to which the second sole member is attached so that the second sole member changes from the second position to the first position. In this way, when the second sole member separates from the walking surface from a state in which only the second sole member is in contact with the walking surface and the second sole member is in the second position, the second sole member can be returned to the first position.

[0063] (8) In the foot structure of (7) above, the elastic member may be a leaf spring having one end fixed to the rear of the foot structure and the other end biasing the movable member. This allows the elastic member to be easily elastically flexible, and limits the magnitude of the force that moves the second sole member from the second position to the first position. This prevents the second sole member, which has come into contact with the walking surface and assumed the second position, from returning to the first position while still in contact with the walking surface.

[0064] (9) In the foot structure of (7) or (8) above, the elastic member may urge the second sole member toward the first position by pushing the movable member upward or downward at a position shifted forward or backward from the axis.

[0065] (10) In the foot structure of (9) above, the joint mechanism may further include a pressable member that is movable up and down at a position shifted in the front-rear direction from the axis. The elastic member may urge the second sole member to the first position by pressing the movable member via the pressable member.

[0066] (11) In the foot structure of any one of (1) to (10) above, the first sensor may include a sensor disposed to the left of a center line in the left-right direction of the foot structure and a sensor disposed to the right of the center line. The second sensor may include a sensor disposed to the left of the center line and a sensor disposed to the right of the center line. The foot structure may further include a processor that calculates the position of the center of gravity of the foot structure based on the detection results of the first sensor and the second sensor. This makes it possible to calculate the position of the center of gravity of the foot structure.

[0067] (12) The robot described in the present disclosure may be a robot having legs and foot structures provided at the lower ends of the legs. The robot may include a first sole member disposed at the rear of the foot structure and in contact with a walking surface, a second sole member disposed in front of the first sole member and in contact with the walking surface, a joint mechanism to which the second sole member is attached and which includes a movable member that can move relative to the first sole member, a first sensor disposed on the first sole member and detecting a reaction force from the walking surface acting on the first sole member, and a second sensor disposed on the second sole member and detecting a reaction force from the walking surface acting on the second sole member. This improves the degree of freedom of movement of the soles and enables appropriate detection of the reaction force from the walking surface.

Claims

1. A foot structure provided at the lower end of a robot's leg, comprising: a first sole member located at the rear of the foot structure and in contact with a walking surface; a second sole member located in front of the first sole member and in contact with the walking surface; a joint mechanism to which the second sole member is attached and which includes a movable member that can move relatively to the first sole member; a first sensor located on the first sole member and detecting a reaction force from the walking surface to the first sole member; and a second sensor located on the second sole member and detecting a reaction force from the walking surface to the second sole member.

2. A foot structure as described in claim 1, wherein the second sole member is capable of tilting relative to the movable member, and the second sensor includes a sensor positioned to the left of a center line in the left-right direction of the foot structure, and a sensor positioned to the right of the center line.

3. A foot structure as described in claim 1, further comprising an instep member connected to said leg and positioned between said leg and said first sole member in the up-down direction, said first sole member being capable of tilting relative to said instep member, and said first sensors including a sensor positioned to the left of a center line of said foot structure in the left-right direction, and a sensor positioned to the right of said center line.

4. A foot structure as described in claim 2, further comprising a strain sensor attached to the movable member and the second sole member and causing bending deformation in response to the movement of the second sole member relative to the movable member, and the second sensor includes a strain sensor attached to the strain sensor at a position shifted to the left of the center line and a strain sensor attached to the strain sensor at a position shifted to the right of the center line.

5. A foot structure as described in claim 3, further comprising a strain sensor attached to the instep member and the first sole member and causing bending deformation in response to movement of the first sole member relative to the instep member, and the first sensor includes a strain sensor attached to the strain sensor in a position shifted to the left of the center line and a strain sensor attached to the right of the center line.

6. The foot structure according to claim 1, wherein the movable member is rotatable relative to the first sole member about an axis extending in the left-right direction.

7. The foot structure described in claim 6, wherein the second sole member is capable of moving about the axis between a first position in which the bottom surface of the second sole member is aligned along the fore-aft direction and a second position in which the bottom surface of the second sole member is inclined relative to the fore-aft direction, and the joint mechanism further includes an elastic member that biases the movable member to which the second sole member is attached so that the position of the second sole member changes from the second position to the first position.

8. The foot structure according to claim 7, wherein the elastic member is a leaf spring having one end fixed to the rear part of the foot structure and the other end for biasing the movable member.

9. A foot structure as described in claim 7, wherein the elastic member urges the second sole member to the first position by pushing the movable member upward or downward at a position offset forward or backward from the axis.

10. A foot structure as described in claim 9, wherein the joint mechanism further includes a pressable member that can move up and down at a position shifted in the front-rear direction from the axis, and the elastic member urges the second sole member to the first position by pressing the movable member through the pressable member.

11. A foot structure as described in claim 1, wherein the first sensors include a sensor arranged to the left of a center line in the left-right direction of the foot structure and a sensor arranged to the right of the center line, the second sensors include a sensor arranged to the left of the center line and a sensor arranged to the right of the center line, and further including a processor that calculates a center of gravity position of the foot structure based on the detection results of the first sensor and the second sensor.

12. A robot having legs and foot structures attached to the lower ends of the legs, comprising: a first sole member arranged at the rear of the foot structure and in contact with a walking surface; a second sole member arranged in front of the first sole member and in contact with the walking surface; a joint mechanism to which the second sole member is attached and which includes a movable member capable of moving relatively to the first sole member; a first sensor arranged on the first sole member for detecting a reaction force from the walking surface to the first sole member; and a second sensor arranged on the second sole member for detecting a reaction force from the walking surface to the second sole member.

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