Extreme terrain mobile robot accurate dynamic modeling method based on tether traction

Abstract

The invention provides an extreme terrain mobile robot accurate dynamics modeling method based on tether traction, and belongs to the field of mobile robot automation control. According to the method, a kinetic equation is deduced through the Lagrange method, and the movement and posture change of the robot in the complex extreme terrain are accurately described by combining the coupling effect of the tether traction force, the double-wheel input torque of the robot and the caster arm torque. Particularly, the influence of the pitch attitude of the robot on the dynamic behavior is considered, the tether tension serves as control input, and the mutual relation between the tether tension and the motion state and the external torque of the robot is comprehensively analyzed. According to the method, the motion description precision of the robot in a complex environment is improved, and an application basis is provided for technical researches such as robot control, trajectory planning and autonomous positioning in related fields.

Description

Technical Field

[0001] The invention belongs to the field of mobile robot automation control, and in particular relates to a precise dynamics modeling method for an extreme terrain mobile robot based on tether traction. Background Art

[0002] In response to the needs of extreme terrain exploration, a tethered mobile robot has been developed. This type of robot uses a rope with one end fixed to the mother robot or anchor point to provide the necessary tension or support, allowing it to descend along a steep slope and enter areas that ordinary wheeled robots cannot reach. This robot can perform in-situ scientific exploration tasks in extreme terrain, such as steep slopes, deep gullies, and even caves.

[0003] Accurate modeling is the basis for designing effective control strategies and optimizing system performance. In complex and extreme terrains, tether-based extreme terrain mobile robots face even more severe challenges, especially when facing environments such as irregular slopes, loose sand or rocks. How the robot can maintain a stable posture and effectively complete the task is an urgent problem to be solved. The accuracy of the robot's kinematic and dynamic models directly determines its adaptability and motion control performance in these harsh environments.

[0004] Existing robot models usually reduce the difficulty of modeling by simplifying the robot's posture changes and the coupling relationship between them and motion, but this simplification often ignores the complex motion behavior of the robot in extreme terrain. In addition, most existing models fail to fully consider the impact of tether traction on the robot's dynamic characteristics. Tether traction not only changes the robot's center of gravity, but also generates additional torque and tension during the robot's motion, which has an important impact on the robot's stability and flexibility in extreme terrain.

[0005] In terms of robot posture control, many existing models fail to deeply integrate the intrinsic connection between posture control and motion control, resulting in the robot's loss of control or instability in extreme environments. Especially on slopes or uneven terrain, the robot's motion and posture control are interdependent, and existing methods often have difficulty handling this complex coupling problem.

[0006] In response to these challenges, accurate kinematic and dynamic models can reveal the robot's motion characteristics in extreme terrain and provide a theoretical basis for subsequent motion control and autonomous positioning. Therefore, establishing an accurate modeling method that considers the influence of tether traction and integrates posture and motion control can effectively improve the robot's motion ability and stability in harsh terrain.

[0007] To solve the above problems, the present invention will focus on the dynamic modeling of a two-wheel differential mobile robot based on tether traction under extreme slope terrain. According to its mechanism characteristics and motion principles, an accurate kinematic and dynamic model will be established, and the influence of the robot's posture and the coupling effect of the tether tension will be considered to provide theoretical support for related technologies such as robot motion control and navigation positioning. Summary of the invention

[0008] The present invention proposes a precise dynamic modeling method for an extreme terrain mobile robot based on tether traction. According to the structural characteristics and motion principle of the robot, this method establishes a kinematic model including the connecting shaft and caster arm posture; then, based on the Lagrangian method, a precise dynamic model is derived, taking into account the influence of pitch posture changes on the dynamic behavior of the robot, and introducing the tether tension as the control input, analyzing its coupling effect with the dual-wheel torque and caster arm torque. Through the above modeling work, a theoretical basis is provided for the trajectory tracking and posture control problems of the robot in complex terrain.

[0009] Specifically, the technical solution of the present invention is as follows:

[0010] Step 1: Analyze the robot's mechanism and motion principle;

[0011] Step 2, modeling the scenario according to the robot's movement scenario in the extreme slope terrain;

[0012] Step 3, derive the kinematic constraints of the differential mobile robot;

[0013] Step 4: Based on the above, the kinematic model is derived according to the relationship between the speed control input and the robot state;

[0014] Step 5, based on the above, derive the dynamic model of the differential mobile robot based on tether traction according to the Lagrangian method and the robot structure and motion parameters.

[0015] Preferably, in step 1, the robot's mechanism must be driven by dual-wheel differential movement, and can independently control the dual wheels, connecting shafts, and caster arms of the conveying tether.

[0016] Preferably, in step 2, the robot's motion scene must be downward relative to the horizontal plane, and the scene modeling must be established on a two-dimensional plane, but the robot's pitch posture is taken into account. Finally, the robot's state variable q is selected, that is, the robot's generalized coordinates.

[0017] Preferably, in step 3, the kinematic constraints of the robot under extreme terrain should be considered as much as possible to make it conform to the kinematic characteristics in real conditions. This step should obtain the robot kinematic constraint equation in the following form:

[0018]

[0019] Among them, q is the generalized coordinate of the robot selected in step 2, and Λ(q) is the constraint matrix of the robot.

[0020] Preferably, in step 4, the state change of the robot is predicted mainly through speed control input, and a kinematic model of the following form is established:

[0021]

[0022] in is the generalized velocity of the robot, S(q) is the kinematic Jacobian matrix of the robot, and u is the velocity control input.

[0023] Preferably, in step 5, for a typical nonholonomic constraint system such as a differential mobile robot, the following Lagrange equation is solved:

[0024]

[0025] Where L is the Lagrangian function, q is the generalized coordinate, and F is the generalized force vector. The final dynamic model is in the form of:

[0026]

[0027] Among them, M(q) is an n-dimensional symmetric positive definite inertia matrix, is the Coriolis force and centripetal force matrix, G(q) is the gravity vector acting on the system, is the surface friction matrix, τ d is the unknown disturbance, B(q) is the input matching matrix, τ controls the input torque vector, Λ(q) is the matrix associated with the kinematic constraints, and λ is the Lagrange multiplier vector associated with the constraints.

[0028] In step 5, the coupling effect of the robot's pitch posture on the dynamic system is considered in the dynamic equation, and the tether tension is introduced as the control input to analyze its coupling effect with the dual-wheel torque and caster arm torque.

[0029] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects:

[0030] The present invention establishes a kinematic and dynamic model that conforms to the actual kinematic characteristics. By accurately deriving a kinematic model that includes the connecting shaft and the caster arm posture, a more accurate motion description is provided, which is more in line with the actual extreme terrain motion characteristics. By modeling the motion scene in extreme slope terrain, the model is made to conform to the actual situation; the dynamic modeling based on the Lagrangian method, especially on the basis of considering the pitch posture change, can better simulate the robot's motion behavior in complex extreme terrain; the coupling effect of the tether tension and the robot's two-wheel input torque and caster arm torque is established, avoiding the neglect of the tether traction force in the existing methods, thereby better describing the robot's motion characteristics in extreme terrain. As the basis of many studies, the present invention provides a more reliable and efficient theoretical basis for related research in other fields that need to be based on robot models, thereby providing a basis for innovation. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a differential mobile robot configuration based on tether traction;

[0032] Figure 2 For robot motion scenes;

[0033] Figure 3 is the robot structure and motion parameters;

[0034] Figure 4 is the tether tension F at X r O r Z r Projection on the surface;

[0035] Figure 5 is the projection of the tether tension F on the XOY plane. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0037] like Figure 1 As shown, the tether-based traction robot targeted by the present invention is essentially a two-wheel differential mobile robot, and its key components mainly include two driving wheels, a connecting shaft, a caster arm, a winch, and a tether system. By changing the tether tension by the drive motors of the left and right driving wheels and the tether winch, the robot's position on a two-dimensional plane can be controlled; the robot's pitch attitude can be controlled by the drive motor on the caster arm and the tether tension. The synergistic effect of the functions of each component enables the robot to move in extreme terrain.

[0038] Figure 2The robot's motion scene in extreme slope terrain is shown. In order to facilitate kinematic analysis, the flat star map can usually be simplified to a two-dimensional Cartesian plane. In order to effectively describe the position of the mobile robot in its environment, the kinematics of the extreme terrain mobile robot based on tether traction is simplified to a two-wheel differential mobile robot moving on a 2D plane; the generalized coordinates of the robot are selected as: q = [x, y, α, β, θ c ] T , the speed control input is Where x and y are the horizontal and vertical coordinates of the robot in the inertial system, α is the yaw angle, β is the pitch angle of the connecting axis, and θ c is the pitch angle of the caster arm relative to the robot body.

[0039] In step 3, the kinematic constraints of the differential mobile robot can be described by two sets of basic nonholonomic constraint equations, corresponding to the assumption of no lateral sliding and pure rolling motion of the robot, respectively. The derived results are as follows;

[0040]

[0041] where φ R and φ L They correspond to the angular positions of the two wheels of the robot, respectively, and will play a role in eliminating nonholonomic constraints in dynamic modeling.

[0042] In step 4, based on the robot's motion relationship in the two-dimensional plane and the pitch angle, the following kinematic equation can be derived:

[0043]

[0044] In step 5, according to Figure 3 The detailed structural parameters and motion parameters are shown. According to these parameters, and based on the kinematic constraints and kinematic models, we can derive the dynamic model of the robot's posture and pitch posture coupling on the two-dimensional plane by the Lagrangian method. And because the robot is subjected to tether tension as an additional control input of the robot in addition to the dual-wheel input torque and caster arm torque during movement in extreme terrain, it is necessary to derive the coupling effect of tether tension and the robot's dual-wheel input torque and caster arm torque. Here, two projection views of the robot are used to analyze the tether tension F, as shown in the figure. Figure 4 and Figure 5 As shown in the figure, θ t is the angle between F and the XOY plane, γ is the angle between F and X r O r Z r The angle between the planes. First, consider the components of F on the X, Y, and Z axes:

[0045] FX =F cos θ t cos(α+γ)

[0046] F Y =F cos θ t sin(α+γ)

[0047] F Z =F sin θ t

[0048] Since the robot does not move along the Z axis during its motion, the angle θ t During the robot control process, it tends to zero, so F Z The value of will also tend to zero, so the impact on the overall dynamics can be ignored. Therefore, the component force F in the Z-axis direction is ignored in the following analysis. Z Next, the torque generated by force F on the robot includes the torque around O r Z r The moment M a With around O r Y r The moment M θc , respectively for the robot's yaw angle α and the pitch angle θ of the caster arm relative to the robot body c The expression for the effect is:

[0049] M α =F sin(γ)(d+a)

[0050] M θc =F sin(θ t -β-θ c )(d+a)

[0051] In summary, taking force F as the control input of the robot, the control input term B(q)τ in the dynamic equation can be obtained as:

[0052]

[0053] where τ L , τ R are the driving torques of the left and right wheels respectively, τ c is the driving torque of the caster arm, F is the tether tension, and a is half the length of the caster arm.

[0054] Based on the above analysis, the precise dynamic model of the robot derived based on the Lagrangian method is:

[0055]

[0056] in:

[0057]

[0058] And c 1 =cos(β+θ c ), s 1 = sin(β+θ c ), c 2 = cosα,s 2 =sinα.

[0059] In an embodiment of the present invention, a precise dynamic modeling method is provided for an extreme terrain mobile robot based on tether traction. The method considers the influence of the robot body and the pitch posture of the caster arm on the robot dynamic system based on the Lagrangian method, and combines the coupling effect of the tether traction force with the robot's dual-wheel input torque and the caster arm torque, providing reliable theoretical support for the description of the robot's behavior in complex environments.

[0060] The specific application of the present invention is very extensive, and the above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, various improvements or modifications thereof, without departing from the core technical concept of the present invention, should be deemed to belong to the protection scope of the present invention.

Claims

1. A precise dynamic modeling method for an extreme terrain mobile robot based on tether traction, characterized in that: The method comprises: (1) Aiming at the special motion scenarios of tethered extreme terrain mobile robots, modeling is performed in complex terrains such as extreme slopes and rugged ground to enhance the motion accuracy and robustness of the system in complex environments; (2) When the Lagrangian method is used to derive the robot's dynamic equations, the influence of the robot's pitch posture on its dynamic behavior is derived based on the characteristics of the tether-driven extreme terrain mobile robot; (3) Taking the tether tension as the control input, the coupling relationship between it and the robot's dual-wheel input torque and caster arm torque motion state is analyzed.

2. The method for accurate dynamic modeling of an extreme terrain mobile robot based on tether traction according to claim 1 is characterized in that: The extreme terrain includes steep slopes and rugged terrain, and the model can predict the posture changes and motion states of the robot in such terrain in real time.

3. The method for accurate dynamic modeling of an extreme terrain mobile robot based on tether traction according to claim 1 is characterized in that: The pitch attitude affects the dynamic behavior of the robot in complex terrain.

4. The method for accurate dynamic modeling of an extreme terrain mobile robot based on tether traction according to claim 1 is characterized in that: The robot is a dual-wheel differential drive robot, and there is a coupling relationship between the dual-wheel input torque and the tether traction force, which affects the stability and accuracy of the robot's movement.

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