CN114684295B - Foot lifting step planning method for foot robot, controller and foot robot - Google Patents

Abstract

The invention belongs to the field of robots, and provides a leg-type robot lifting gait planning method, a controller and the leg-type robot. Among them, the foot-lifting gait planning method of the legged robot adopts the same-speed retreat method, so that the movement of the swing leg and the support leg in the front-back direction is associated, and the movement speed of the swing leg relative to the torso is the same as that of the support leg relative to the torso , so as to ensure that the legs of the legged robot are lifted vertically when moving forward, and avoid kicking the facade of the ground to affect the balance.

Description

A foot-lifting gait planning method for a legged robot, a controller, and the legged robot

technical field

The invention belongs to the field of robots, and in particular relates to a foot-lifting gait planning method for a legged robot, a controller and the legged robot.

Background technique

The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

Large terrestrial animals on the earth generally move on their feet. Goats, blue sheep, etc. can move freely on rocks and cliffs, which proves that the footed movement has strong terrain adaptability. Inspired by animals, footed robotics has also begun to flourish, where obstacle-surmounting capabilities are a top priority. At present, the common gait planning methods of legged robots include the planning method based on the central mode generator, the planning method based on the spring-loaded inverted pendulum model, the planning method based on the preset foot end motion trajectory, and the hybrid planning method based on these methods, etc. . The inventors have found that in the above method, when the legged robot lifts its feet, it may kick an obstacle, affect its balance, or even trip over an obstacle.

Contents of the invention

In order to solve at least one technical problem in the above-mentioned background technology, the present invention provides a foot-lifting gait planning method, a controller and a legged robot, which avoid The end of the foot collides with an obstacle.

In order to achieve the above object, the present invention adopts the following technical solutions:

The first aspect of the present invention provides a foot-lifting gait planning method for a legged robot.

A foot-lifting gait planning method for a legged robot, which uses the same-speed retreat method to correlate the movement of the swing leg and the support leg in the front and rear directions, so as to ensure the movement speed of the swing leg relative to the torso and the movement speed of the support leg relative to the torso The same, thereby ensuring that the legs of the legged robot are lifted vertically when moving forward, and avoid kicking the facade of the ground to affect the balance.

As an optional embodiment, the overspeed retreat method is adopted, so that the retreat speed of the swinging leg exceeds the kicking speed of the supporting leg, so as to avoid being pressed by the protruding part of the facade of the ground obstacle when lifting the foot and destroying the balance.

As an optional implementation, the overspeed retreat method is described by speed: the retreat speed of the swinging leg=k*the kicking speed of the supporting leg; wherein, k is greater than 1.

As an optional implementation, the overspeed retreat method is described by position: the retreat position of the swing leg = the position of the supporting leg - the ratio of the distance to retreat after the foot is lifted and the expected duration of the swing phase * entering the swing phase after the timing.

As an optional implementation, the trajectory of the swinging leg when lifting the foot is divided into an X-axis trajectory and a Z-axis trajectory. The X-axis trajectory is positive forward, and the Z-axis trajectory is the position of the swinging leg on the Z axis = stride and height Ratio to the expected duration of the swing phase * the timing time after entering the swing phase.

As an optional implementation manner, the timing time after entering the swing phase is greater than or equal to 0, and less than or equal to the retreat time of the swing leg.

As an optional implementation manner, from the perspective of the ground coordinate system, there is no horizontal initial velocity at the foot end of the swing leg.

As an optional implementation, when the legged robot is on a slope, the swinging leg also acts as a vertical foot lift.

A second aspect of the invention provides a controller.

A controller, which includes a computer-readable storage medium, and a computer program is stored on the computer-readable storage medium, and when the program is executed by a processor, the steps in the above-mentioned foot-lifting gait planning method for a legged robot are realized .

A third aspect of the present invention provides a legged robot.

A legged robot includes the above-mentioned controller.

Compared with prior art, the beneficial effect of the present invention is:

Innovatively proposed a foot-lifting gait planning method for a legged robot, and developed a foot-raising gait planning system for a footed robot, using the same-speed retreat method to make the moving speed of the swinging leg relative to the torso and the moving speed of the supporting leg relative to the torso The same, so as to ensure that the swing leg of the legged robot is lifted vertically when moving forward, and avoid kicking the facade of the ground to affect the balance; adopt the overspeed retreat method, so that the retreat speed of the swing leg exceeds the kicking speed of the supporting leg, thereby avoiding When the foot is lifted, it is pressed by the protruding part of the facade of the ground obstacle and destroys the balance. It solves the problem that the legged robot swings its legs and easily kicks the stair facade when climbing the stairs, and the legged robot may kick the obstacle when lifting the foot. The problem of affecting balance or even being tripped by obstacles improves the stability of legged robot movement, which is suitable for gravel terrain, grass and other situations where legged robots may trip when lifting their feet.

Advantages of additional aspects of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations to the present invention.

Fig. 1 is a schematic diagram of the method of withdrawing at the same speed according to an embodiment of the present invention;

Fig. 2 is a schematic diagram of the method of retreating at the same speed when the robot of the embodiment of the present invention is on a slope;

Fig. 3 is a schematic diagram of an overspeed retreat method according to an embodiment of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the present invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It should be noted that the terminology used here is only for describing specific embodiments, and is not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

Embodiment one

When the footed robot is walking, the legs are divided into supporting legs and swinging legs according to the supporting state. The supporting legs push the ground, and the feet move back to push the trunk forward; the swinging legs vacate and stretch forward to prepare for touching the ground. Wherein, the swinging stage of the swinging leg is divided into an ascending stage and a descending stage according to the movement direction of the foot end on the Z-axis (positive vertically upward), and the ascending stage is the foot-lifting stage.

The foot-lifting gait planning method of the legged robot in this embodiment adopts the method of retreating at the same speed to associate the swing leg with the movement of the support leg in the front-rear direction, so as to ensure that the movement speed of the swing leg relative to the trunk is the same as the movement speed of the support leg relative to the trunk. The moving speed is the same, so as to ensure that the legs of the legged robot are lifted vertically when moving forward, so as to avoid kicking the facade of the ground and affecting the balance.

As shown in Figure 1, the trajectory of the swinging leg when lifting the foot can be divided into X-axis (positive forward) trajectory and Z-axis trajectory. The core of the same-speed retreat method is to ensure the moving speed and support of the swinging leg relative to the trunk. The legs move at the same speed relative to the torso, ie:

Therefore, from the point of view of the ground coordinate system, there is no horizontal initial velocity at the foot end of the swinging leg. is the retreat velocity of the swing leg; is the kicking velocity of the supporting leg.

For the Z-axis trajectory, any one of the following equations can be used:

①

②

③

Wherein, Z _max is the step height, t _Swing is the expected duration of the swing phase, t is the timing time after entering the swing phase, 0≤t≤t _Swing . p _{Z_Swing} is the position of the swing leg on the Z axis.

After obtaining the trajectory of the foot end, use the inverse kinematics equation of the foot end to convert the coordinates of the X-axis and Z-axis into the joint rotation angle, and then realize the movement through the joint servo. The inverse kinematic equations are determined by the leg mechanics and vary from leg to leg. Specifically, the movement is planned in the XOZ plane by planning the X-axis and Z-axis foot trajectories, and then converted to joint angles through inverse kinematics equations, and then realized through servo joint angles.

In the torso coordinate system, the swinging leg and the supporting leg retreat at the same speed, the supporting leg moves forward to push the torso forward, and the swinging leg retreats to avoid collision with obstacles. Viewed from the ground coordinate system, the end of the swing leg is lifted vertically.

When the legged robot is on a slope, the X-axis and Z-axis trajectory planning methods are the same as above, but at this time, the X-axis is no longer in the same direction as the forward direction, but rotates to the horizontal, and the Z-axis is vertically upward. The rotation angle is the pitch angle of the robot, which can be measured by an inertial measurement unit or other sensors installed on the robot body. At this time, the swinging leg is manifested as lifting the foot vertically, as shown in Figure 2.

When there is a bulge on the facade of the ground obstacle, the speeding back method can be used. This method can be described by speed or position, as shown in Figure 3. In the torso coordinate system, the receding velocity of the swinging leg is greater than that of the supporting leg. From the point of view of the ground coordinate system, the end of the swing leg is raised while retreating.

In a specific implementation, the retreat value of the swing leg can be achieved by increasing the speed or increasing the displacement.

The velocity description equation is:

Among them, k>1, this parameter can be adjusted according to the actual situation. is the retreat velocity of the swing leg; /> is the kicking velocity of the supporting leg.

The position description equation is:

Among them, d is the distance to retreat after lifting the foot, which can be estimated according to the terrain, or can be dynamically set after scanning the terrain with sensors such as lidar or stereo cameras. p _{X_Swing} is the retreat position of the swing leg; p _{X_Support} is the position of the support leg. t _Swing is the expected duration of the swing phase, t is the timing time after entering the swing phase, 0≤t≤t _Swing .

The foot-lifting gait planning method of the legged robot described in Embodiment 1 is also applicable to gravel terrain, grassland and other situations where the legged robot may be tripped when the leg is lifted.

Embodiment two

This embodiment provides a controller, which includes a computer-readable storage medium, and a computer program is stored on the computer-readable storage medium. When the program is executed by a processor, the legged robot lift described in the first embodiment above is realized. Steps in the footstep planning method.

What needs to be explained here is that other structures of the controller are all existing structures, which will not be repeated here.

Embodiment three

This embodiment provides a legged robot, which includes the controller as described in the second embodiment above.

It should be noted here that the legged robot can be a robot with two legs, three legs or four legs, and other structures of the robot are existing structures, which will not be described in detail here.

Those skilled in the art should understand that the embodiments of the present invention may be provided as methods, systems, or computer program products. Accordingly, the present invention can take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage and optical storage, etc.) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each procedure and/or block in the flowchart and/or block diagram, and a combination of procedures and/or blocks in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions may be provided to a general purpose computer, special purpose computer, embedded processor, or processor of other programmable data processing equipment to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing equipment produce a An apparatus for realizing the functions specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to operate in a specific manner, such that the instructions stored in the computer-readable memory produce an article of manufacture comprising instruction means, the instructions The device realizes the function specified in one or more procedures of the flowchart and/or one or more blocks of the block diagram.

These computer program instructions can also be loaded onto a computer or other programmable data processing device, causing a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process, thereby The instructions provide steps for implementing the functions specified in the flow chart or blocks of the flowchart and/or the block or blocks of the block diagrams.

Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be implemented through computer programs to instruct related hardware, and the programs can be stored in a computer-readable storage medium. During execution, it may include the processes of the embodiments of the above-mentioned methods. Wherein, the storage medium may be a magnetic disk, an optical disk, a read-only memory (Read-Only Memory, ROM) or a random access memory (Random Access Memory, RAM) and the like.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (7)

1. A leg-type robot lifts a step gait planning method, is characterized in that, adopts the method of retreating at the same speed, makes the swing leg and the motion of the support leg in the front-back direction associated, guarantees that the movement speed of the swing leg relative to the torso is the same as that of the support leg The movement speed relative to the torso is the same, so as to ensure that the legs of the legged robot are lifted vertically when moving forward, and avoid kicking the facade of the ground to affect the balance; When there is a bulge on the facade of the ground obstacle, the overspeed retreat method is adopted to make the retreat speed of the swinging leg exceed the kicking speed of the supporting leg, so as to avoid being pressed by the protruding part of the facade of the ground obstacle when lifting the foot and destroying the balance ; The overspeed retreat method is described by speed: the retreat speed of the swinging leg=k*the kicking speed of the supporting leg; among them, k is greater than 1; Alternatively, the overspeed retreat method is described by position: the retreat position of the swing leg = the position of the supporting leg - the ratio of the distance to retreat after the foot is lifted to the expected duration of the swing phase * the timing time after entering the swing phase. 2. The foot-lifting gait planning method of a legged robot as claimed in claim 1, wherein the motion track when the swinging leg lifts the foot is divided into an X-axis track and a Z-axis track, and the X-axis track is positive forward, and the Z-axis track is forward. The trajectory is the position of the swing leg on the Z axis = the ratio of the step to height to the expected duration of the swing phase * the timing time after entering the swing phase. 3. The foot-lifting gait planning method of a legged robot according to claim 2, wherein the timing time after entering the swing phase is greater than or equal to 0, and less than or equal to the retreat time of the swing leg. 4. The foot-lifting gait planning method of a legged robot according to claim 1, wherein, viewed from the ground coordinate system, there is no horizontal initial velocity at the foot end of the swinging leg. 5. The foot-lifting gait planning method of a legged robot as claimed in claim 1, wherein when the legged robot is on a slope, the swinging leg also behaves as a vertical leg lift. 6. A controller, comprising a computer-readable storage medium, a computer program is stored on the computer-readable storage medium, characterized in that, when the program is executed by a processor, any one of claims 1-5 is realized Steps in the foot-lifting gait planning method for the legged robot. 7. A legged robot, characterized in that it comprises the controller according to claim 6.