Wheel-legged robot based on stability control technology and control method thereof

Abstract

The invention discloses a wheel-legged robot based on a stability control technology and a control method of the wheel-legged robot. The wheel-legged robot comprises a fixed frame; the control box is mounted on the fixed frame; the obstacle avoidance detection module, the signal receiving module, the IMU module and the controller are all mounted in the control box; the power supply is mounted on the fixed frame; the leg connecting rod mechanisms are symmetrically arranged below the fixed frame; the pair of driving wheels are respectively connected to the bottom ends of the first connecting rod mechanism and the second connecting rod mechanism; a hub motor is embedded in the axis of the driving wheel and used for driving the driving wheel to roll. The robot is simple in structure, and efficient and stable control over the robot is achieved by controlling the hub motor, the front servo motor and the rear servo motor; and the control method is simple and efficient, and has low requirements on computing power.

Description

Technical Field

[0001] The present application relates to the field of robotics technology, and in particular to a wheel-legged robot based on stable control technology and a control method thereof. Background Art

[0002] In recent years, robotics technology has been widely used and deeply developed in various fields. In particular, wheel-legged robots, as a mobile robot with superior dynamic performance and high maneuverability, have gradually attracted more and more attention. Compared with traditional wheeled or legged robots, wheel-legged robots can not only overcome terrain obstacles, but also complete more complex motion tasks. They have broad application prospects in military, exploration, rescue and other fields. The kinematics and dynamics of wheel-legged robots are relatively complex, and it is necessary to efficiently solve multivariable nonlinear control problems in real-time control. Therefore, the control of wheel-legged robots faces challenges, and a simple, efficient, and lightweight wheel-legged control system with low computing power requirements is needed. Summary of the invention

[0003] The purpose of this application is to provide a wheel-legged robot and a control method thereof based on stable control technology.

[0004] On the one hand, the present application provides a wheel-legged robot based on stable control technology, comprising:

[0005] Fixed frame;

[0006] A control box is mounted on the fixed frame;

[0007] The obstacle avoidance detection module, signal receiving module, IMU module and controller are all installed in the control box;

[0008] Power supply, mounted on the fixed frame;

[0009] A pair of leg link mechanisms are symmetrically arranged under the fixed frame; each leg link mechanism includes a front servo motor, a rear servo motor and a link mechanism; the front servo motor and the rear servo motor are installed on the fixed frame front and back, and the link mechanism includes a first link mechanism and a second link mechanism, the first link mechanism includes a front upper end connecting rod connected to the output of the front servo motor, and a front lower end connecting rod rotatably connected to the front upper end connecting rod; the second link mechanism includes a rear upper end connecting rod connected to the output of the rear servo motor, and a rear lower end connecting rod rotatably connected to the rear upper end connecting rod;

[0010] The front servo motor is used to control and adjust the angle formed by the front upper connecting rod and the front lower connecting rod, and the rear servo motor is used to control and adjust the angle formed by the rear upper connecting rod and the rear lower connecting rod, thereby controlling the contraction and extension of the first connecting rod mechanism and the second connecting rod mechanism;

[0011] A pair of driving wheels are respectively connected to the bottom ends of the first connecting rod mechanism and the second connecting rod mechanism; a hub motor is embedded in the axis of the driving wheel, and the hub motor is used to drive the driving wheel to roll.

[0012] On the other hand, the control method of the above-mentioned wheel-legged robot provided by the present application is:

[0013] When the terrain is detected to be flat, the robot's posture and speed are controlled to reach the expected values, including:

[0014] The robot is equivalent to an inverted pendulum structure with a gimbal, and the IMU module is used to collect actual posture information. Based on the actual posture information, a linear quadratic regulator is used to control the balance of the inverted pendulum structure. Specifically, the driving torque of the hub motor, the front servo motor, and the rear servo motor is controlled to control the inverted pendulum structure to achieve balance.

[0015] Furthermore, control the robot's posture, including controlling the robot's pitch angle:

[0016] According to the expected value of pitch angle and the expected value of the robot displacement The difference between the actual value and the linear quadratic regulator is substituted into the control law Calculate the wheel hub motor driving torque and the five-link end drive torque ;

[0017] The expected leg length The difference between the actual value and the control quantity F is calculated by the PID controller;

[0018] F and Substitute the virtual model control law , calculate the driving torque of the front servo motor and the rear servo motor , ;

[0019] According to the wheel hub motor driving torque , front servo motor driving torque , Driving torque of rear servo motor Adjust the pitch angle.

[0020] Furthermore, control the robot's posture, including controlling the robot's roll angle:

[0021] Expected roll angle , when it is detected that the roll angle is not 0, the leg lengths of the two leg linkages are adjusted according to the control strategy so that the roll angle is always kept at 0;

[0022] Specifically, according to the difference between the pitch angle, roll angle, expected leg length, expected displacement and actual value, the driving torque of the hub motor, the front servo motor and the rear servo motor is calculated through the control rate, and the roll angle is adjusted.

[0023] Furthermore, control the robot's posture, including controlling the robot's yaw angle:

[0024] Steering control using differential drive, moving according to the differential plane Calculate the moving speed of the two moving wheels and , the moving speed of the two moving wheels and Substitute the control rate to calculate the driving torque of the hub motor, front servo motor, and rear servo motor, and adjust the yaw angle according to the driving torque; where, is the expected value of the yaw angle, is the distance between two moving wheels.

[0025] Furthermore, when an obstacle is detected in front, the robot is controlled to jump to overcome the obstacle. The jumping control is:

[0026] In each leg linkage mechanism, the front servo motor controls the first linkage mechanism and the rear servo motor controls the second linkage mechanism to contract; then, within a preset time, the front servo motor and the rear servo motor control the first linkage mechanism and the second linkage mechanism to extend, and the robot achieves jumping.

[0027] Compared with the prior art, this application has the following advantages and beneficial effects:

[0028] In this application, the wheel-legged robot structure is equivalent to an inverted pendulum structure with a pan-tilt system for modeling; the linear quadratic regulator LQR is used as the main balance control algorithm, and a virtual model control VMC is adopted for the five-link leg structure; the control of the wheel-legged robot is achieved by integrating the above algorithms.

[0029] The robot of the present application has a simple structure, and efficient and stable control of the robot is achieved by controlling the hub motor, the front servo motor, and the rear servo motor; and the control method is simple and efficient, and the computing power requirement is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution of the present application, other features, purposes and advantages of the present invention will become more apparent by reading the detailed description of the non-limiting implementation with reference to the following drawings:

[0031] Figure 1 This is a schematic diagram of the three-dimensional structure of the wheel-legged robot according to an embodiment of the present application;

[0032] Figure 2This is a schematic diagram of the front plan structure of the wheel-legged robot according to an embodiment of the present application;

[0033] Figure 3 This is a schematic diagram of the left-side plan structure of the wheel-legged robot according to an embodiment of the present application;

[0034] Figure 4 This is a schematic diagram of the right side plan structure of the wheel-legged robot according to an embodiment of the present application;

[0035] Figure 5 This is a schematic diagram of the top plan structure of the wheel-legged robot according to an embodiment of the present application;

[0036] Figure 6 This is a bottom-up perspective structural diagram of the wheel-legged robot according to an embodiment of the present application;

[0037] Figure 7 This is a schematic diagram of the structure of the wheel-legged robot in an upward-looking plane according to an embodiment of the present application;

[0038] Figure 8 It is a schematic diagram of a simplified plane model of the leg linkage mechanism of an embodiment of the present application;

[0039] Fig. 9 This is a schematic diagram of the control flow in the embodiment of the present application;

[0040] Fig.10 It is a schematic diagram of the pitch angle control principle;

[0041] Fig.11 It is a schematic diagram of the roll angle control principle;

[0042] Fig.12 Schematic diagram of yaw angle control principle.

[0043] Figure numerals: control box 1, fixed frame 2, front servo motor 3, rear upper connecting rod 4, rear lower connecting rod 5, hub motor 6, moving wheel 7, obstacle avoidance detection module 8, support frame 9, front upper connecting rod 10, front lower connecting rod 11, signal receiving module 12, power box 13, sliding shaft 14, rear servo motor 15. DETAILED DESCRIPTION

[0044] The following will be combined with the accompanying drawings 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.

[0045] Please see attached Figures 1 to 7 , shown is a wheel-legged robot according to an embodiment of the present application, and the following will be combined with the attached Figures 1 to 7The structure of the wheel-legged robot of the present application is described in detail.

[0046] The wheel-legged robot of the present application embodiment comprises:

[0047] Fixed frame 2;

[0048] The control box 1 is installed on the fixed frame 2, and in this embodiment is installed on the top of the fixed frame 2. The control box 1 is installed with an obstacle avoidance detection module 8, a signal receiving module 12, an IMU module and a controller;

[0049] A power supply box 13 is installed on the fixed frame 2, and in this embodiment is installed at the bottom of the fixed frame 2, and a power supply is installed in the power supply box 13;

[0050] A pair of leg link mechanisms are symmetrically arranged under the fixed frame 2; each leg link mechanism includes a front servo motor 3, a rear servo motor 15 and a link mechanism; the front servo motor 3 and the rear servo motor 15 are installed on the fixed frame 2 front and back, and the link mechanism includes a first link and a second link, the first link includes a front upper end connecting rod 10 connected to the output of the front servo motor 3, and a front lower end connecting rod 11 rotatably connected to the front upper end connecting rod 10; the second link includes a rear upper end connecting rod 4 connected to the output of the rear servo motor 15, and a rear lower end connecting rod 5 rotatably connected to the rear upper end connecting rod 4;

[0051] A pair of moving wheels 7, both ends of their axes are connected to the bottom ends of the first connecting rod and the second connecting rod respectively; a hub motor 6 is embedded in the axis of the moving wheel 7, and the hub motor 6 is used to drive the moving wheel 7 to roll, thereby moving forward or backward.

[0052] In the present application, the front servo motor 3 adjusts the angle formed by the front upper connecting rod 10 and the front lower connecting rod 11, and the rear servo motor 15 adjusts the angle formed by the rear upper connecting rod 4 and the rear lower connecting rod 5, thereby controlling the extension and retraction of the connecting rod mechanism to achieve the purpose of controlling the posture of the robot.

[0053] For example, the robot's jumping mode can be set based on a pair of leg linkage mechanisms. The front servo motor 3 and the rear servo motor 15 control the extension and retraction of the linkage mechanism, and the height of the robot rises and falls accordingly. When the linkage mechanism is controlled to contract and extend within a preset short time, the accumulation and release of energy required for jumping will be completed, and the robot will achieve jumping.

[0054] The robot structure provided in the present application can increase the stability of the robot and reduce the shaking of the robot when it moves.

[0055] To facilitate understanding of the control principle of the wheel-legged robot of the present application, the technical theories involved in the present application are first elaborated in detail below.

[0056] In this application, the wheel-legged robot is equivalent to an inverted pendulum structure with a pan-tilt platform, and the simplified plane model of its leg connecting rod mechanism is shown in Figure 8 , where L1 represents the length of the front upper connecting rod 10, L2 represents the length of the front lower connecting rod 11, L3 represents the length of the rear lower connecting rod 5, L4 represents the length of the rear upper connecting rod 4, and L5 represents the distance between the front servo motor 3 and the rear servo motor 15. The center position C of the hub motor 6 is represented by a rectangular coordinate system (C x , C y ), the distance from the midpoint of L5 to point C is defined as the leg length of the robot, denoted by L0.

[0057] The forward kinematics model is as follows:

[0058] (1)

[0059] (2)

[0060] (3)

[0061] (4)

[0062] (5)

[0063] (6)

[0064] (7)

[0065] (8)

[0066] The inverse kinematics model is as follows:

[0067] (9)

[0068] (10)

[0069] According to different ground environments, the wheel-legged robot has two control modes: attitude and speed control mode on flat terrain, and jumping mode when crossing obstacles. Attitude control includes the control of pitch angle, roll angle and yaw angle. Under the control of pitch angle, roll angle and yaw angle, the axis motion is decoupled into pitch angle. , Roll Angle and yaw angle The process of attitude and speed control in this application can be found in Fig. 9, including: treating the robot as an inverted pendulum structure with a gimbal, using an onboard IMU module to collect actual posture information, and using a linear quadratic regulator (LQR) to control the balance of the inverted pendulum structure based on the actual posture information. Specifically, the inverted pendulum structure is balanced by controlling the driving torque of the hub motor, the front servo motor, and the rear servo motor.

[0070] (1) Pitch angle control:

[0071] According to the expected value of pitch angle and the expected value of the robot displacement The difference between the actual value and the linear quadratic regulator is substituted into the control law Calculate the wheel hub motor driving torque and the five-link end drive torque . Set the expected leg length The difference between the actual value and the control value F is calculated by the PID controller. Substitute the virtual model control law , calculate the driving torque of the front servo motor and the rear servo motor , According to the wheel hub motor driving torque , front servo motor driving torque , Driving torque of rear servo motor They work together to adjust the robot's posture. See the pitch angle control principle diagram Fig.10 .

[0072] (2) Roll angle control:

[0073] Expected roll angle ,Under uneven terrain, the roll angle changes. The leg lengths of the two leg linkages are adjusted according to the control strategy to keep the roll angle at 0 at all times.

[0074] According to the relationship between leg length and roll angle:

[0075] ;

[0076] According to the expected value of pitch angle , Roll Angle , Leg length expectation , and expected displacement The difference between the actual value and the actual value is used to calculate the driving torque of the hub motor, front servo motor and rear servo motor in the two symmetrical walking components through the designed control rate, so as to adjust the robot posture. Fig.11 .

[0077] (3) Yaw angle control:

[0078] Steering control uses differential drive to define the desired yaw angle According to the differential plane motion formula:

[0079]

[0080] in, and are the moving speeds of the two moving wheels respectively, Indicates the distance between two moving wheels.

[0081] According to the above formula, the speed of the left and right moving wheels can be obtained. Substituting into the control rate, the required driving torque is calculated to adjust the robot posture. The robot steering control block diagram is shown in the figure.

[0082] The IMU attitude information is collected, and the LQR controller is balanced and controlled according to the IMU attitude information. The LQR controller drives the wheel hub motor. At the same time, the VMC solution is performed according to the torque at the end of the five-link to drive the leg link joint.

[0083] (4) Jump control

[0084] In each leg linkage mechanism, when the front servo motor controls to reduce the angle formed by the front upper connecting rod and the front lower connecting rod, the first linkage mechanism contracts; when the control increases the angle formed by the front upper connecting rod and the front lower connecting rod, the first linkage mechanism extends; when the rear servo motor controls to reduce the angle formed by the rear upper connecting rod and the rear lower connecting rod, the second linkage mechanism contracts; when the control increases the angle formed by the rear upper connecting rod and the rear lower connecting rod, the second linkage mechanism extends.

[0085] When an obstacle is detected in front, the robot is controlled to jump to overcome the obstacle. The jumping control is:

[0086] In each leg linkage mechanism, the front servo motor controls the contraction of the first linkage mechanism and the rear servo motor controls the contraction of the second linkage mechanism; then, within a preset time, the front servo motor and the rear servo motor control the extension of the first linkage mechanism and the second linkage mechanism. Within a relatively short time, the first linkage mechanism and the second linkage mechanism complete the contraction and extension, the energy required for jumping is accumulated and released, and the robot achieves jumping.

[0087] Specifically, the jump control is based on the pitch angle control, and the leg length expected value is Set it as a pulse signal to achieve jump control.

[0088] Note that the above are only preferred embodiments of the present application and the technical principles used. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the protection scope of the present application. Therefore, although the present application is described in more detail through the above embodiments, the present application is not limited to the above embodiments, and may also include more other equivalent embodiments without departing from the concept of the present application, all of which belong to the protection scope of the present application.

Claims

1. A wheel-legged robot based on stable control technology, characterized in that: include: Fixed frame; A control box is mounted on the fixed frame; The obstacle avoidance detection module, signal receiving module, IMU module and controller are all installed in the control box; Power supply, mounted on the fixed frame; A pair of leg link mechanisms are symmetrically arranged under the fixed frame; each leg link mechanism includes a front servo motor, a rear servo motor and a link mechanism; the front servo motor and the rear servo motor are installed on the fixed frame front and back, and the link mechanism includes a first link mechanism and a second link mechanism, the first link mechanism includes a front upper end connecting rod connected to the output of the front servo motor, and a front lower end connecting rod rotatably connected to the front upper end connecting rod; the second link mechanism includes a rear upper end connecting rod connected to the output of the rear servo motor, and a rear lower end connecting rod rotatably connected to the rear upper end connecting rod; The front servo motor is used to control and adjust the angle formed by the front upper connecting rod and the front lower connecting rod, and the rear servo motor is used to control and adjust the angle formed by the rear upper connecting rod and the rear lower connecting rod, thereby controlling the contraction and extension of the first connecting rod mechanism and the second connecting rod mechanism; A pair of driving wheels are respectively connected to the bottom ends of the first connecting rod mechanism and the second connecting rod mechanism; a hub motor is embedded in the axis of the driving wheel, and the hub motor is used to drive the driving wheel to roll.

2. The control method of the wheel-legged robot according to claim 1, characterized in that: When the terrain is detected to be flat, the robot's posture and speed are controlled to reach the expected values, including: The robot is equivalent to an inverted pendulum structure with a gimbal, and the IMU module is used to collect actual posture information. Based on the actual posture information, a linear quadratic regulator is used to control the balance of the inverted pendulum structure. Specifically, the driving torque of the hub motor, the front servo motor, and the rear servo motor is controlled to control the inverted pendulum structure to achieve balance.

3. The control method according to claim 2, characterized in that: Control the robot's posture, including controlling the robot's pitch angle: According to the expected value of pitch angle and the expected value of the robot displacement The difference between the actual value and the linear quadratic regulator is substituted into the control law Calculate the wheel hub motor driving torque and the five-link end drive torque ; The expected leg length The difference between the actual value and the control quantity F is calculated by the PID controller; F and Substitute the virtual model control law , calculate the driving torque of the front servo motor and the rear servo motor , ; According to the wheel hub motor driving torque , front servo motor driving torque , Driving torque of rear servo motor Adjust the pitch angle.

4. The control method according to claim 2, characterized in that: Control the robot's posture, including controlling the robot's roll angle: Expected roll angle , when it is detected that the roll angle is not 0, the leg lengths of the two leg linkages are adjusted according to the control strategy so that the roll angle is always kept at 0; Specifically, according to the difference between the pitch angle, roll angle, expected leg length, expected displacement and actual value, the driving torque of the hub motor, the front servo motor and the rear servo motor is calculated through the control rate, and the roll angle is adjusted.

5. The control method according to claim 2, characterized in that: Control the robot's posture, including controlling the robot's yaw angle: Steering control using differential drive, moving according to the differential plane Calculate the moving speed of the two moving wheels and , the moving speed of the two moving wheels and Substitute the control rate to calculate the driving torque of the hub motor, front servo motor, and rear servo motor, and adjust the yaw angle according to the driving torque; where, is the expected value of the yaw angle, is the distance between two moving wheels.

6. The control method of the wheel-legged robot according to claim 1, characterized in that: When an obstacle is detected in front, the robot is controlled to jump to overcome the obstacle. The jumping control is: In each leg linkage mechanism, the front servo motor controls the first linkage mechanism and the rear servo motor controls the second linkage mechanism to contract; then, within a preset time, the front servo motor and the rear servo motor control the first linkage mechanism and the second linkage mechanism to extend, and the robot achieves jumping.

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