Humanoid robot gait control method

Abstract

The invention discloses a humanoid robot gait control method, and relates to the technical field of robot adaptive control, and the method comprises the steps: collecting the lifting height of a front foot; all joints of the rear legs are controlled to rotate, so that the rear feet are located under the gravity center of the humanoid robot; after the forefoot makes contact with the object, the pressure distribution condition of the forefoot is collected; whether the forefoot state is stable or not is judged, and if not, the rotation angle of the forefoot is collected; if the rotating angle is smaller than the angle threshold value, the front leg and the rear leg are converted, otherwise, the front foot is lifted, the joint angle of the front leg is adjusted, so that the object making contact with the front foot is changed, and the pressure distribution condition of the front foot is collected again. The walking stability is improved through inward rotation of the rear legs and reverse bending of the knee joints, the front feet can feel the pressure distribution condition of the contact surface, and when environment information detected by the sensing unit is not very accurate, the adaptability of gaits to the environment is improved through pressure sensing of the front feet, and the walking stability is improved. And the walking stability of the humanoid robot is further improved.

Description

Technical Field

[0001] The present application relates to the technical field of robot adaptive control, and in particular to a gait control method for a humanoid robot. Background Art

[0002] A humanoid robot is a bionic robot. Since many environments and equipment in real life are designed for human body structures, humanoid robots are used to replace humans to perform some heavy or high-risk tasks, so that the robots can adapt to various related environments and equipment to the greatest extent possible during the operation process, without the need to adjust the environment or equipment, thereby reducing the cost of the operation.

[0003] As a type of robot, humanoid robots have common features with other robots, such as moving along a set path. However, there are differences between humanoid robots and other types of robots. For example, when a humanoid robot adopts a bipedal or multi-legged structure, it is necessary to consider the stability during the movement process, and ensure that the humanoid robot will not collide or fall while achieving the purpose of movement. For this type of bionic robot, the prior art has proposed a variety of gait control technologies. For example, CN118387212A proposed a bionic gait control method and walking robot for a multimodal robot. The patent achieves the stability control of the robot by adjusting the folding angle of the trunk. For example, CN118170033A proposed a flat ground gait optimization method and system for a bipedal robot. The patent improves the control algorithm for the gait of a bipedal robot on flat ground. However, when a humanoid robot is used in a complex and unpredictable scene, such as in a mine, additional requirements are put forward for the control of the humanoid robot. When working underground, the flatness of the ground cannot be accurately perceived in advance, and humanoid robots usually carry heavy objects such as tools during underground operations, and the state of the torso needs to be maintained. Therefore, existing gait control methods for robots cannot be directly applied to underground scenarios. Summary of the invention

[0004] The embodiment of the present application provides a gait control method for a humanoid robot, which is used to solve the problem that the gait control method of the robot in the prior art cannot be directly applied to underground scenarios.

[0005] The present application provides a method for controlling gait of a humanoid robot, including:

[0006] Collecting the lifting height of the forefoot during the walking of the humanoid robot;

[0007] According to the lifting height, the hip joint drive unit of the hind leg is controlled to rotate according to the hip joint internal rotation angle and the hip joint rearward rotation angle, the knee joint drive unit is controlled to rotate according to the knee joint external rotation angle and the knee joint forward rotation angle, and the ankle joint drive unit is controlled to rotate according to the ankle joint external rotation angle and the ankle joint rearward rotation angle. Under the joint action of the hip joint drive unit internal rotation and rearward rotation, the knee joint drive unit external rotation and forward rotation, and the ankle joint drive unit external rotation and rearward rotation, the contact position of the foot of the hind leg with the ground is located directly below the center of gravity of the humanoid robot;

[0008] After the forefoot contacts the object, the pressure distribution of the forefoot and the object is collected; a plurality of pressure detection units are arranged at the bottom of the forefoot, and the pressure detection units are used to detect the real-time pressure of each position when the forefoot contacts the object, and the real-time pressure detected by the plurality of pressure detection units constitutes the pressure distribution;

[0009] Determine whether the state of the forefoot is stable according to the pressure distribution. If it is unstable, collect the rotation angle of the ankle joint drive unit on the forefoot;

[0010] If the rotation angle of the forefoot is less than the angle threshold after it stops rotating, the front leg and the hind leg are switched; if the rotation angle is greater than or equal to the angle threshold, the forefoot is lifted, and the forward rotation angle of the hip joint drive unit on the front leg and the backward rotation angle of the knee joint drive unit on the front leg are adjusted to change the object contacted by the forefoot, and the pressure distribution when the forefoot contacts the object is re-collected until the front leg and the hind leg are switched.

[0011] A humanoid robot gait control method in this application has the following advantages:

[0012] The stability of the humanoid robot during walking is improved by turning the hind legs inward and bending the knee joints of the hind legs in the opposite direction. Even when the front legs of the humanoid robot encounter obstacles and need to stop briefly or even retreat, the humanoid robot can maintain a stable posture. The front legs can sense the pressure distribution on the contact surface and make corresponding actions. When the environmental information detected by the perception unit is not very accurate, the pressure perception of the forefoot improves the adaptability of the gait to the environment, further improving the walking stability of the humanoid robot. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1A flowchart of a humanoid robot gait control method provided in an embodiment of the present application;

[0015] Figure 2 A schematic diagram of the front view of a humanoid robot in a walking process provided by an embodiment of the present application;

[0016] Figure 3 A schematic diagram of the side state of a humanoid robot provided in an embodiment of the present application during walking;

[0017] Figure 4 A schematic diagram of the state of the feet of a humanoid robot in a spatial coordinate system during walking provided in an embodiment of the present application.

[0018] Explanation of the accompanying drawings: 100, torso; 200, head; 300, upper limbs; 410, thigh; 411, hip joint drive unit; 420, calf; 421, knee joint drive unit; 430, foot; 431, ankle joint drive unit; 500, ground protrusion. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] Figure 1 A flowchart of a gait control method for a humanoid robot provided in an embodiment of the present application. An embodiment of the present application provides a gait control method for a humanoid robot, comprising:

[0021] S100, collects the lifting height of the forefoot during the walking of the humanoid robot.

[0022] For example, Figure 2 and 3 As shown, the humanoid robot comprises a trunk 100, a head 200, upper limbs 300 and lower limbs, wherein the number of upper limbs 300 and lower limbs are both two, the upper limbs 300 are used to grasp tools or objects, and the lower limbs are used to move. The lower limbs comprise a thigh 410, a calf 420 and a foot 430 from top to bottom, the upper end of the thigh 410 is rotatably connected to the lower end of the trunk 100 through a hip joint drive unit 411, the upper end of the calf 420 is rotatably connected to the lower end of the thigh 410 through a knee joint drive unit 421, and the foot 430 is rotatably connected to the lower end of the calf 420 through an ankle joint drive unit 431.

[0023] It should be understood that, similar to the human body, the thigh 410, calf 420 and foot 430 of the humanoid robot in the present application can all rotate in the front-to-back direction and the left-to-right direction. Therefore, the hip joint drive unit 411, knee joint drive unit 421 and ankle joint drive unit 431 in the embodiment of the present application have the ability to rotate in both the front-to-back direction and the left-to-right direction.

[0024] During the walking process of the humanoid robot, the two lower limbs need to repeat the actions of lifting, stepping forward, and landing, while the front legs and the hind legs are only related positional relationships, and any lower limb can become a front leg or a hind leg. After the walking action is split, it can be specifically described as a situation where one lower limb is used as a front leg and the other lower limb is used as a hind leg. In this action unit, the front leg is gradually lifted from the state of being at the same height and position as the hind leg. While lifting, the hip joint drive unit 411 of the front leg rotates forward, so that the thigh 410 rotates to the front of the trunk 100, and the knee joint drive unit 421 rotates backward by a certain angle, forming a state in which the calf 420 is bent backward relative to the thigh 410, which is the same as the state of the front legs when the human body walks. For the hind legs, while the hip joint drive unit 411 of the front leg rotates forward, the hip joint drive unit 411 of the hind leg will rotate backward, and the knee joint drive unit 421 of the hind leg will rotate forward, so that the calf 420 of the hind leg forms a state of bending forward relative to the thigh 410, which is opposite to the state of the hind legs when the human body walks.

[0025] When the forefoot is lifted, its lifting height can be determined according to the angle of the hip joint drive unit 411, the angle of the knee joint drive unit 421 and the angle of the ankle joint drive unit 431, where the angle includes the rotation angle of each joint in the front-to-back direction and the rotation angle of the left-to-right direction. In the embodiment of the present application, in addition to the servo motor for changing the angle in each joint, an angle detection unit is also provided on the servo motor, which can collect the rotation angle of the servo motor relative to the standard position in real time, and then obtain the angle of each joint.

[0026] S110, according to the lifting height, the hip joint driving unit 411 of the hind leg is controlled to rotate according to the hip joint internal rotation angle and the hip joint posterior rotation angle, the knee joint driving unit 421 is controlled to rotate according to the knee joint external rotation angle and the knee joint forward rotation angle, and the ankle joint driving unit 431 is controlled to rotate according to the ankle joint external rotation angle and the ankle joint posterior rotation angle. Under the combined action of the internal rotation and posterior rotation of the hip joint driving unit 411, the external rotation and forward rotation of the knee joint driving unit 421, and the external rotation and posterior rotation of the ankle joint driving unit 431, the contact position of the foot 430 of the hind leg with the ground is located directly below the center of gravity of the humanoid robot.

[0027] Exemplarily, a laser radar is provided on the humanoid robot, and the laser radar is used to collect ground state data of the ground in front of the humanoid robot. The processing unit of the humanoid robot analyzes the ground state data and determines the height difference between the front foot and the hind foot at a predetermined contact position. If the lifting height is greater than the height difference, the hip joint drive unit 411, the knee joint drive unit 421 and the ankle joint drive unit 431 of the hind leg are controlled to rotate.

[0028] Specifically, after the laser radar generates a large number of lasers in different directions, the reflection of the laser by the object can obtain a point cloud corresponding to the distance and shape of the surrounding environment. By fitting the point cloud, the environment in front of the humanoid robot can be perceived, including the height and distance of obstacles, the flatness of the ground, etc. In the embodiment of the present application, during each walking process of the humanoid robot, the internal rotation angle of the hip joint, the posterior rotation angle of the hip joint, the external rotation angle of the knee joint, the forward rotation angle of the knee joint, the external rotation angle of the ankle joint and the posterior rotation angle of the ankle joint are all fixed to ensure the gait consistency of the humanoid robot each time it walks. When these angles are determined, the stride of each walk is also fixed. After the laser radar determines the information of the surrounding environment, the processing unit of the humanoid robot can estimate the position of the front foot on the ground after it falls, that is, the predetermined contact position. The predetermined contact position may be flush with the ground, or it may be higher or lower than the ground, that is, the height difference can be roughly estimated in advance, but the accuracy of the height difference will not be very high. Although the accuracy of the height difference is not very high, when the lifting height of the front foot is equal to the height difference, the front foot has a very high probability of contacting with an object, including the ground and an obstacle. Before contacting the object, the stability of the humanoid robot needs to be ensured, that is, when the lifting height is greater than the height difference, the hip joint drive unit 411, the knee joint drive unit 421 and the ankle joint drive unit 431 of the hind leg need to be kept in a rotating state so that the contact position between the hind foot and the object is always directly below the center of gravity of the humanoid robot. Once the lifting height of the front foot is reduced to be equal to the height difference, the hip joint drive unit 411, the knee joint drive unit 421 and the ankle joint drive unit 431 of the hind leg need to rotate the hip joint internal rotation angle, the knee joint external rotation angle and the ankle joint external rotation angle in opposite directions respectively, so that the hind leg rotates to a vertical plane. At this time, the front leg and the hind leg are respectively in the vertical planes on both sides of the trunk 100. When both the front leg and the hind leg are in contact with the object, the weight of the humanoid robot will be evenly distributed on the front foot and the hind foot.

[0029] Furthermore, in addition to the laser radar, the humanoid robot of the present application also integrates an ultrasonic ranging unit, which can detect the inclination angle of the ground in front of the humanoid robot, and then the processing unit adjusts the hip internal rotation angle, hip posterior rotation angle, knee external rotation angle, knee forward rotation angle, ankle external rotation angle and ankle posterior rotation angle of the hind legs according to the inclination angle, so as to keep the torso 100 upright on the ground at any angle.

[0030] S120, after the forefoot contacts the object, the pressure distribution of the forefoot when in contact with the object is collected; a plurality of pressure detection units are provided at the bottom of the forefoot, and the pressure detection units are used to detect the real-time pressure of each position when the forefoot contacts the object, and the real-time pressures detected by the plurality of pressure detection units constitute the pressure distribution.

[0031] For example, the forefoot of the present application is paved with a rubber layer on the bottom surface, which has both anti-skid and wear-resistant functions. The pressure detection units are distributed at multiple positions on the bottom surface of the rubber layer to accurately and timely detect the pressure when the forefoot contacts an object.

[0032] In the embodiment of the present application, the pressure data collected by each pressure detection unit will be fed back to the processing unit, and the processing unit will determine whether the pressure detected by each pressure detection unit exceeds the set pressure threshold. If the pressure detected by the pressure detection unit exceeds the pressure threshold, the processing unit will consider that the pressure detection unit has detected the real-time pressure. Otherwise, the pressure detected by the pressure detection unit will be ignored.

[0033] S130, determining whether the state of the forefoot is stable according to the pressure distribution, and if it is unstable, collecting the rotation angle of the ankle joint driving unit 431 on the forefoot.

[0034] For example, if the state of the forefoot is determined to be stable according to the pressure distribution, the processing unit will switch the front leg and the hind leg, that is, the hip joint drive unit 411 of the front leg rotates backwards, and the knee joint drive unit 421 rotates forwards, so that the calf 420 of the front leg is bent forward relative to the thigh 410, and the front leg will be transformed into the hind leg. The hip joint drive unit 411 of the hind leg rotates forwards, and the knee joint drive unit 421 rotates backwards, so that the calf 420 of the hind leg is bent backward relative to the thigh 410, and the hind leg will be transformed into the front leg.

[0035] Furthermore, the multiple pressure detection units include a pressure detection unit located in the center of the forefoot and multiple pressure detection units located at the edges of the forefoot. If the geometric center of a geometric shape formed by the positions of the multiple pressure detection units that detect the real-time pressure coincides with the center of the forefoot, the state of the forefoot is stable. If the geometric center of a geometric shape formed by the positions of the multiple pressure detection units that detect the real-time pressure does not coincide with the center of the forefoot, the state of the forefoot is unstable.

[0036] Specifically, the central pressure detection unit is preferably located at the geometric center of the foot 430, which is also the geometric center of the geometric shape formed by all edge pressure detection units. If there is only one contact point between the ground protrusion 500 and the foot 430, and the contact point happens to be the position of the central pressure detection unit, the forefoot will be stable at this time. If there are two or more contact points between the ground protrusion 500 and the forefoot, it is necessary to establish a geometric shape based on the position of the pressure detection unit on the forefoot that detects the real-time pressure. The processing unit analyzes the geometric shape, determines the geometric center of the geometric shape, such as the center of gravity, and determines whether the geometric center coincides with the center of the forefoot. If so, the forefoot will also be in a stable state. If they do not coincide, the forefoot will inevitably rotate.

[0037] Furthermore, the pressure detection units located on the edge of the forefoot include multiple groups, and each group of pressure detection units is symmetrically distributed around the central pressure detection unit. If the pressure detection unit that detects the real-time pressure is a pressure detection unit located in the center or a pressure detection unit belonging to the same group, the state of the forefoot is stable; if the pressure detection unit that detects the real-time pressure is a pressure detection unit belonging to a different group, the state of the forefoot is unstable.

[0038] Specifically, if two pressure detection units in a symmetrical group detect real-time pressure, and all the pressure detection units that detect real-time pressure belong to the same group, then the geometric shape formed by these edge pressure detection units must be an even-sided shape, such as a quadrilateral, hexagon, etc., and the geometric center of the geometric shape must also be the center of the forefoot, and the forefoot will also be stable at this time.

[0039] Further, when the pressure detection unit that detects the real-time pressure is a pressure detection unit belonging to a different group, if the number of pressure detection units that detect the real-time pressure is three or more, a geometric shape is established with the pressure detection units that detect the real-time pressure as vertices, and it is determined whether the geometric center of the geometric shape coincides with the center of the forefoot; if they coincide, the state of the forefoot is stable; if they do not coincide, the state of the forefoot is unstable.

[0040] Specifically, when the pressure detection units that detect the real-time pressure belong to pressure detection units of different groups, there are two situations. One is that the number of pressure detection units that detect the real-time pressure is an even number, that is, the geometric shape is still an even-sided shape. At this time, the geometric center of the geometric shape will definitely not coincide with the center of the forefoot, and the forefoot will be in an unstable state. The second is that the number of pressure detection units that detect the real-time pressure is an odd number. The odd number of pressure detection units will form a geometric shape with an odd number of sides, such as a triangle or a pentagon. The geometric center of the geometric shape may coincide with the center of the forefoot, or it may not coincide with the center of the forefoot. At this time, the processing unit needs to perform accurate analysis and judgment to determine whether the forefoot is stable.

[0041] S140, if the rotation angle of the front foot is less than the angle threshold after the front foot stops rotating, the front leg and the hind leg are switched; if the rotation angle is greater than or equal to the angle threshold, the front foot is lifted, and the forward rotation angle of the hip joint drive unit 411 on the front leg and the backward rotation angle of the knee joint drive unit 421 on the front leg are adjusted to change the object contacted by the front foot, and the pressure distribution when the forefoot contacts the object is re-collected until the front leg and the hind leg are switched.

[0042] Exemplarily, when the forefoot contacts an object, it is parallel to the ground. After the forefoot is determined to be unstable based on the pressure distribution and the ankle joint drive unit 431 on the forefoot rotates, the forefoot rotates to a state where it intersects with the ground. During the rotation, the pressure distribution of the forefoot is collected, and whether the state of the forefoot is stable is determined based on the pressure distribution. If it is stable, the rotation angle of the ankle joint drive unit 431 on the forefoot is collected.

[0043] Specifically, there are two reasons why the forefoot stops rotating. One is that the rotation angle of the forefoot reaches the maximum rotation angle of the ankle joint drive unit 431, and the rotation angle must be greater than the angle threshold, such as 15° or 20°. Therefore, the forefoot stopping rotation caused by this reason will also be unstable. The second is that the forefoot encounters other ground protrusions 500 during the rotation process, which provides more support for the forefoot. At this time, the processing unit can determine whether the forefoot is in a stable state according to the pressure distribution. If it is, the rotation angle is collected. If not, the forefoot is directly controlled to be lifted and the object in contact with the forefoot is adjusted.

[0044] After detecting the rotation angle of the forefoot in the front-to-back and left-to-right directions, the processing unit can establish the following Figure 4The spatial coordinate system shown in the figure calculates the rotation angles in other directions based on the rotation angles in the front-back and left-right directions, and then determines whether all the rotation angles are greater than or equal to the angle threshold. If so, it means that the forefoot is in a stable state, but due to the large rotation angle, it is also possible that the humanoid robot will fall when the weight is distributed on the forefoot, so the processing unit will also consider the forefoot to be unstable. If the rotation angle of the forefoot is less than the angle threshold and the forefoot is also in a stable state, the processing unit will switch the front legs and hind legs to complete the walking control of the humanoid robot.

[0045] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0046] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A gait control method for a humanoid robot, characterized in that: include: Collecting the lifting height of the forefoot during the walking of the humanoid robot; According to the lifting height, the hip joint drive unit (411) of the hind leg is controlled to rotate according to the hip joint internal rotation angle and the hip joint rearward rotation angle, the knee joint drive unit (421) is controlled to rotate according to the knee joint external rotation angle and the knee joint forward rotation angle, and the ankle joint drive unit (431) is controlled to rotate according to the ankle joint external rotation angle and the ankle joint rearward rotation angle, and under the combined action of the internal rotation and rearward rotation of the hip joint drive unit (411), the external rotation and forward rotation of the knee joint drive unit (421), and the external rotation and rearward rotation of the ankle joint drive unit (431), the contact position of the foot (430) of the hind leg with the ground is located directly below the center of gravity of the humanoid robot; After the forefoot contacts the object, the pressure distribution of the forefoot when in contact with the object is collected; a plurality of pressure detection units are provided at the bottom of the forefoot, and the pressure detection units are used to detect the real-time pressure of each position when the forefoot contacts the object, and the real-time pressure detected by the plurality of pressure detection units constitutes the pressure distribution; Determining whether the state of the forefoot is stable according to the pressure distribution, and if it is unstable, collecting the rotation angle of the ankle joint drive unit (431) on the forefoot; If the rotation angle is less than the angle threshold after the front foot stops rotating, the front leg and the hind leg are switched; if the rotation angle is greater than or equal to the angle threshold, the front foot is lifted, and the forward rotation angle of the hip joint drive unit (411) on the front leg and the backward rotation angle of the knee joint drive unit (421) on the front leg are adjusted to change the object contacted by the front foot, and the pressure distribution when the front foot contacts the object is re-collected until the front leg and the hind leg are switched.

2. A humanoid robot gait control method according to claim 1, characterized in that: When it is determined according to the pressure distribution that the state of the front foot is stable, the front leg and the rear leg are switched.

3. A humanoid robot gait control method according to claim 2, characterized in that: The multiple pressure detection units include a pressure detection unit located at the center of the forefoot and multiple pressure detection units located at the edges of the forefoot. If the geometric center of a geometric shape formed by the positions of the multiple pressure detection units that detect the real-time pressure coincides with the center of the forefoot, the state of the forefoot is stable. If the geometric center of a geometric shape formed by the positions of the multiple pressure detection units that detect the real-time pressure does not coincide with the center of the forefoot, the state of the forefoot is unstable.

4. A humanoid robot gait control method according to claim 3, characterized in that: The pressure detection units located on the edge of the forefoot include multiple groups, and each group of pressure detection units is symmetrically distributed around the central pressure detection unit. If the pressure detection unit that detects the real-time pressure is the pressure detection unit located in the center or belongs to the same group, the state of the forefoot is stable; if the pressure detection unit that detects the real-time pressure is a pressure detection unit belonging to a different group, the state of the forefoot is unstable.

5. A humanoid robot gait control method according to claim 4, characterized in that: When the pressure detection unit that detects the real-time pressure belongs to a different group, if the number of the pressure detection units that detect the real-time pressure is three or more, the geometric shape is established with the pressure detection unit that detects the real-time pressure as the vertex, and it is determined whether the geometric center of the geometric shape coincides with the center of the forefoot; if so, the state of the forefoot is stable; if not, the state of the forefoot is unstable.

6. The method for controlling gait of a humanoid robot according to claim 3, characterized in that: When the pressure detected by the pressure detection unit exceeds a pressure threshold, it is considered that the pressure detection unit has detected the real-time pressure.

7. The method for controlling gait of a humanoid robot according to claim 1, characterized in that: When the forefoot contacts an object, it is in a state parallel to the ground. After it is determined that the forefoot is unstable based on the pressure distribution and the ankle joint drive unit (431) on the forefoot rotates, the forefoot rotates to a state where it intersects the ground. During the rotation, the pressure distribution of the forefoot is collected. Based on the pressure distribution, it is determined whether the state of the forefoot is stable. If it is stable, the rotation angle of the ankle joint drive unit (431) on the forefoot is collected.

8. The method for controlling gait of a humanoid robot according to claim 1, characterized in that: The humanoid robot is provided with a laser radar, which is used to collect ground state data of the ground in front of the humanoid robot. The processing unit of the humanoid robot analyzes the ground state data and determines the height difference between the front foot and the rear foot at a predetermined contact position. If the lifting height is greater than the height difference, the hip joint drive unit (411), the knee joint drive unit (421) and the ankle joint drive unit (431) of the rear leg are controlled to rotate.

Images