Small celestial body weak gravity condition detection robot movement control method and device

Abstract

The application discloses a kind of small celestial body weak gravity condition under detection robot movement control method and device, the method of the present application includes first to detection robot is carried out steady gait planning, at the end time of the foot end trajectory obtained, add the active attachment bias Δr for ensuring that detection robot is attached to the clamping of small celestial body star table;Then the foot end trajectory is as leg desired position, inverse kinematics is solved to obtain the desired joint angle of each joint, obtains the current joint angle of each joint of detection robot, and calculates the deviation between the current joint angle and the desired joint angle of each joint, and the deviation is input into the movement controller to obtain the joint output control torque, the corresponding joint is controlled by joint output control torque, until the deviation is less than set value.The present application can realize the stable attachment and movement of detection robot on the surface of small celestial body under the condition of weak gravity of small celestial body, create prerequisite for the smooth development of detection task.

Description

Technical Field

[0001] This invention belongs to the field of space robot dynamics and control, specifically relating to a method and device for controlling the movement of a probe robot under weak gravitational conditions of a small celestial body. Background Technology

[0002] Currently, small body exploration has evolved from flyby and rendezvous probes to soft landing and sample return missions. Against this backdrop, compared to large probes, cost-effective and low-risk space robots, especially small mobile probe robots, have become a widely recognized and highly promising solution for celestial surface exploration.

[0003] Because the gravity of small celestial bodies is extremely weak, robots face risks such as adhesion rebound and attitude loss during exploration, posing a significant challenge to their movement and exploration on the surface of these bodies. Therefore, to achieve mobile exploration by a footed robot under weak gravity, it is necessary to compensate for the weak gravitational pull of small celestial bodies, enabling the robot to actively and stably attach to their surface. However, current weak-gravity surface attachment technologies, such as electrostatic adsorption, drilling fixation, and suction cup attachment, limit the robot's mobile exploration capabilities, hindering the expansion of the depth and breadth of small celestial body exploration missions.

[0004] Designing a motion control method for a probe robot to address the weak gravitational conditions on the surface of small celestial bodies is a novel problem. Using existing technologies, the following issues need to be addressed: designing a gait planning method for the probe robot to effectively suppress the normal impact on the robot's feet when lifting and landing, thus adapting to the weak gravitational environment of the small celestial body; researching an attachment method for the probe robot under weak gravity to ensure that the robot adheres to the surface without detaching and moves without slipping, ultimately achieving active attachment and movement of the robot on the surface of the small celestial body. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method and device for controlling the movement of a probe robot under the weak gravity conditions of a small celestial body. The present invention can achieve stable attachment and movement of the probe robot on the surface of the small celestial body under the weak gravity conditions, thus creating the preconditions for the smooth implementation of the probe mission.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for controlling the movement of a probe robot under weak gravitational conditions on a small celestial body includes:

[0008] S101, perform planar dynamic planning on the probe robot, and the calculation function expression for the vertical displacement component Z(t) of the foot trajectory obtained by the planning is as follows:

[0009]

[0010] In the above formula, h is the maximum height that the detection robot can reach when its legs swing, sgn is the sign function, and t swing To detect the time of a single leg swing of the robot, t is time, f E (t) is an intermediate variable function, and we have:

[0011] f E (t)=t / t swing -(1 / 4π)sin(4πt / t swing );

[0012] S102, At the end of the foot trajectory obtained by the steady-state planning, add an active attachment bias Δr to ensure the gripping and attachment of the probe robot to the small celestial body surface.

[0013] S103, the foot trajectory after adding active attachment bias Δr is taken as the desired position of the leg, and inverse kinematics calculation is performed to obtain the desired joint angle of each joint. The current joint angle of each joint of the probe robot is obtained, and the deviation between the current joint angle and the desired joint angle of each joint is calculated. The deviation is input into the motion controller to obtain the joint output control torque. The corresponding joint is controlled by the joint output control torque until the deviation is less than the set value.

[0014] Optionally, in step S101, when performing steady-state planning on the probe robot, the calculation function expression for the time-varying component X(t) of the foot trajectory in the forward direction is:

[0015]

[0016] In the above formula, s is the step size of the probe robot.

[0017] Optionally, the computation function expression of the symbolic function is:

[0018]

[0019] Optionally, the calculation function expression for the active attachment bias Δr is:

[0020]

[0021] In the above formula, x c y c and z c To determine the position coordinates of the robot's center of mass in the reference coordinate system; x s y s and z sTo detect the position coordinates of the robot's foot in the reference coordinate system, K is the active attachment bias ratio coefficient.

[0022] Optionally, step S103 performs inverse kinematics calculation to obtain the functional expression of the expected joint angle for each joint:

[0023] θ3:

[0024] θ2:

[0025] θ1:

[0026] In the above formula, θ1, θ2, and θ3 are the joint angles of the root joint, hip joint, and knee joint of the probe robot, respectively. 1，i (t) and θ 1,ii (t) represents the different expected joint angle components of θ1, θ 2，i (t), θ 2，ii (t), θ 2，iii (t) and θ 2，iv (t) represents the different expected joint angle components of θ2, θ 3,i (t) and θ 3，ii (t) represents the different expected joint angle components of θ3, atan is the arctangent function, and p x p y and p z These represent the positions of the foot trajectory in each direction; A and B are intermediate variables, a3 is the DH parameter of the third joint of the probe robot; s3 = sinθ3, s 3,i =sinθ 3,i s 3,ii =sinθ 3,ii c3 = cosθ3, c 3,i =cosθ 3,i c 3,ii =cosθ 3,ii A = a² + a³c³

[0027] Optionally, the motion controller in step S103 is a PID controller.

[0028] Optionally, in step S101, when performing steady-state planning for the probe robot, the step of determining the functional expression of the time-varying component Z(t) of the vertical displacement of the foot end includes:

[0029] S201, Determine the constraints on the foot trajectory in the vertical direction, including position constraints, velocity constraints, and acceleration constraints:

[0030]

[0031] In the above formula, Z| t＝0 , and These represent the position, velocity, and acceleration at time t=0, respectively. and They are respectively Position, velocity, and acceleration at any given moment and They are respectively Position, velocity, and acceleration at any given moment;

[0032] S202, based on the constraint of the foot trajectory in the vertical direction, the vertical acceleration function designed to suppress normal impact is shown in the following equation:

[0033]

[0034] In the above formula, Let be the acceleration at time t, A be the amplitude of the acceleration, and n be a parameter representing the period of acceleration change. swing To detect the time of a single leg swing of the robot, t is time;

[0035] S203, based on the vertical acceleration function used to suppress normal impact, the expression for calculating the time-varying component Z(t) of the vertical displacement is designed as follows:

[0036]

[0037] In the above formula, h is the maximum height that the detection robot can reach when its legs swing, sgn is the sign function, and t swing To detect the time of a single leg swing of the robot, t is time, f E (t) is an intermediate variable function, and we have:

[0038] f E (t)=t / t swing -(1 / 4π)sin(4πt / t swing ).

[0039] Optionally, in step S103, when controlling the corresponding joint by outputting control torque, the method further includes detecting the horizontal and vertical ground forces, tangential and normal static friction forces on the feet of each supporting leg using sensors, and verifying the effectiveness of the mobile control method for the probe robot under weak gravity conditions of a small celestial body by judging whether the dynamic constraint relationship for stable attachment shown in the following formula holds during attachment:

[0040]

[0041] The effectiveness of the probe robot's movement control method under weak gravity conditions on small celestial bodies is verified by judging whether the dynamic constraint relationship satisfying stable movement shown in the following formula holds during movement:

[0042]

[0043] If the dynamic constraint relationship holds, the mobile control method of the probe robot under the weak gravity condition of the small celestial body is deemed effective; where n is the number of supporting legs of the probe robot; μ1 and μ2 are the tangential and normal friction coefficients; and These are the horizontal and vertical forces exerted by the ground on the foot end of the i-th supporting leg, respectively. and These represent the tangential and normal static friction forces exerted on the foot end of the i-th supporting leg, respectively; m is the robot's mass; g s，N Let g be the vertical component of the gravitational acceleration of the small celestial body. s ，τ D represents the horizontal component of the gravitational acceleration of a small celestial body. N D is the vertical component of the disturbance force acting on the robot. τ This represents the horizontal component of the disturbance force experienced by the robot.

[0044] Furthermore, the present invention also provides a mobile control device for a probe robot under weak gravitational conditions of a small celestial body, comprising a microprocessor and a memory interconnected thereto, wherein the microprocessor is programmed or configured to execute the mobile control method for the probe robot under weak gravitational conditions of a small celestial body.

[0045] Furthermore, the present invention also provides a computer-readable storage medium storing a computer program for being programmed or configured by a microprocessor to execute the method for controlling the movement of a probe robot under weak gravitational conditions of a small celestial body.

[0046] Compared with the prior art, the present invention has the following main advantages:

[0047] 1. To address the issues of attachment bounce and attitude loss caused by the movement of a probe robot in a weak gravity environment, this invention performs steady-state planning on the probe robot. By utilizing the calculation function expression of the vertical displacement component Z(t) of the foot trajectory obtained from the planning, the impact effect on the foot during the movement process can be suppressed, effectively reducing the impact effect on the probe robot's legs when they lift and fall.

[0048] 2. The present invention includes adding an active attachment bias Δr at the end of the foot trajectory obtained by steady-state planning to ensure the gripping and attachment of the probe robot to the surface of a small celestial body, which can solve the attachment problem under weak gravity conditions.

[0049] Through the above-mentioned steady-state planning and active attachment bias, the present invention enables the probe robot to achieve stable attachment and movement on the surface of small celestial bodies under the weak gravity conditions, creating preconditions for the smooth implementation of the exploration mission. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0051] Figure 1 This is a schematic diagram illustrating the design of the method in an embodiment of the present invention.

[0052] Figure 2 This is a diagram illustrating the design effect of the foot trajectory in an embodiment of the present invention.

[0053] Figure 3 This is a schematic diagram of the active attachment deviation in an embodiment of the present invention.

[0054] Figure 4 This is a schematic diagram of the inverse kinematics solution process in an embodiment of the present invention.

[0055] Figure 5 This is a schematic diagram of the control flow of the mobile controller in an embodiment of the present invention.

[0056] Figure 6 This is a schematic diagram of the ground force and static friction force acting on the robot's foot in an embodiment of the present invention.

[0057] Figure 7 This is a diagram illustrating the effect of controlling torque output in an embodiment of the present invention.

[0058] Figure 8 This is a diagram showing the measurement results of foot adhesion force in an embodiment of the present invention. Detailed Implementation

[0059] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the invention.

[0060] like Figure 1 As shown, the mobile control method for the probe robot under the weak gravity conditions of a small celestial body in this embodiment includes:

[0061] S101, perform planar dynamic planning on the probe robot, and the calculation function expression for the vertical displacement component Z(t) of the foot trajectory obtained by the planning is as follows:

[0062]

[0063] In the above formula, h is the maximum height that the detection robot can reach when its legs swing, sgn is the sign function, and t swing To detect the time of a single leg swing of the robot, t is time, f E (t) is an intermediate variable function, and we have:

[0064] f E (t)=t / t swing -(1 / 4π)sin(4πt / t swing );

[0065] For robot movement under weak gravity conditions, planar dynamic planning establishes the spatiotemporal coordination relationship of each leg. By designing the foot trajectory, it can effectively suppress the normal impact on the feet during movement. In this embodiment, the single swing time t of the robot's legs is detected. swing The maximum height h that the detection robot can reach when its legs swing is 30mm, which is 1 second.

[0066] S102, at the end of the foot trajectory obtained by the steady-state planning, add an active attachment bias Δr to ensure the gripping and attachment of the probe robot to the small celestial body surface; based on the stable attachment of the end gait bias, by introducing an active attachment bias Δr to the foot trajectory, the probe robot can actively attach to the small celestial body surface under weak gravity conditions.

[0067] S103, the foot trajectory after adding active attachment bias Δr is taken as the desired position of the leg, and inverse kinematics calculation is performed to obtain the desired joint angle of each joint. The current joint angle of each joint of the probe robot is obtained, and the deviation between the current joint angle and the desired joint angle of each joint is calculated. The deviation is input into the motion controller to obtain the joint output control torque. The corresponding joint is controlled by the joint output control torque until the deviation is less than the set value.

[0068] The purpose of planar dynamic planning is to optimize the trajectory of the robot's swinging leg foot to reduce the normal impact on the foot when it lifts up and lands. In this embodiment, the step of determining the functional expression of the time-varying component Z(t) of the vertical displacement of the foot during planar dynamic planning of the probe robot in step S101 includes:

[0069] S201, Determine the constraints on the foot trajectory in the vertical direction, including position constraints, velocity constraints, and acceleration constraints:

[0070]

[0071] In the above formula, Z| t＝0 , and These represent the position, velocity, and acceleration at time t=0, respectively. and They are respectively Position, velocity, and acceleration at any given moment and They are respectively Position, velocity, and acceleration at any given moment;

[0072] S202, based on the constraint of the foot trajectory in the vertical direction, the vertical acceleration function designed to suppress normal impact is shown in the following equation:

[0073]

[0074] In the above formula, Let be the acceleration at time t, A be the amplitude of the acceleration, and n be a parameter representing the period of acceleration change. swing To detect the time of a single leg swing of the robot, t is time;

[0075] S203, based on the vertical acceleration function used to suppress normal impact, the calculation function expression for the time-varying component Z(t) of the vertical displacement can be determined through integration and constraint conditions as follows:

[0076]

[0077] The function expression for calculating the time-varying component X(t) of the foot trajectory in the forward direction is:

[0078]

[0079] In the above formula, h is the maximum height that the detection robot can reach when its legs swing, sgn is the sign function, and t swing To detect the time of a single leg swing of the robot, t is time, f E (t) is an intermediate variable function, s is the step size of the probe robot, and we have:

[0080] f E (t)=t / t swing -(1 / 4π)sin(4πt / t swing ).

[0081] In this embodiment, when performing steady-state planning on the probe robot in step S101, the calculation function expression for the time-varying component X(t) of the foot trajectory in the forward direction is as follows:

[0082]

[0083] In the above formula, s is the step size of the probe robot. Figure 2The diagram shows a schematic representation of the foot trajectory within the XOZ phase plane planned in this embodiment. In this embodiment, the step length s of the detection robot is 100 mm.

[0084] In this embodiment, the expression for calculating the symbolic function is:

[0085]

[0086] Based on the structural characteristics and locomotion of legged robots, an approach is taken to enable their supporting legs to grasp the star surface, thereby achieving attachment. End-effector gait biasing is applied to the probe robot. This involves introducing an active attachment bias Δr onto the foot trajectory obtained through gait planning, ensuring the robot's gripping and attachment (active attachment) to the small celestial body surface. In this embodiment, the calculation function expression for the active attachment bias Δr is:

[0087]

[0088] In the above formula, x c y c and z c To determine the position coordinates of the robot's center of mass in the reference coordinate system; x s y s and z s To detect the position coordinates of the robot's foot in the reference coordinate system, K is the active attachment bias ratio coefficient. The active attachment bias ratio coefficient K is manually assigned, and in this embodiment, K = 0.001. Figure 3 This is a schematic diagram of the active attachment deviation in this embodiment, as shown below. Figure 3 As shown, (x c y c , z c Let (x) be the coordinates of the robot's center of mass in the reference coordinate system. c y c -z c Let (x) be the coordinates of the point symmetric to the centroid about the horizontal surface in the reference coordinate system. s y s , z s ) represents the coordinates of the point of contact between the foot and the ground in the reference coordinate system, and r represents the vector from the point of contact to the symmetrical point. The active attachment bias Δr is in the same direction as r.

[0089] Inverse kinematics calculation is part of the robot's motion model. In this embodiment, establishing the kinematic model of the probe robot to achieve forward / inverse kinematics calculation includes: constructing a robot coordinate system. First, for the description of the robot's specific position, a reference coordinate system ∑ is established. a : Origin O a Designated by a person, X a Ya Z a The orientation of the three axes depends on specific needs and must satisfy the right-hand rule (in this embodiment, in the reference coordinate system ∑). a In this context, let the robot's horizontal movement be the X-direction and its vertical direction be the Z-direction. The reference coordinate system is an inertial frame, and its spatial orientation remains constant. Next, establish the robot's body coordinate system ∑ b Its origin O b Typically chosen as a point on the robot's base, X b Y b Z b The orientation of the three axes depends on specific needs, but must satisfy the right-hand rule. Body coordinate system ∑ b The link is fixed to the probe robot, and its relative spatial relationship with the probe robot remains unchanged. The DH parameter method is used to describe the state of the probe robot's legs from the perspectives of link position and orientation, and joint variables, respectively, and the relationship between the two is established. The process of solving for link position and orientation from joint variables is called forward kinematics solution; the process of solving for joint variables from link position and orientation is called inverse kinematics solution.

[0090] The results of the robot's forward kinematics solution are as follows:

[0091]

[0092] In the above formula, T is the homogeneous coordinate transformation matrix between adjacent members, and θ i α i a i and d i Let θ be the joint variable corresponding to the i-th joint. i For the joint angle, a i α is the length of the rod; i It is the angle of the member, d i It is the link offset. For simplicity, let's remember it as:

[0093]

[0094] The inverse kinematics solution for the three-degree-of-freedom supporting leg probing robot can be obtained as follows:

[0095]

[0096] In this embodiment, step S103 involves performing inverse kinematics calculations sequentially to obtain the functional expression for the desired joint angle of each joint:

[0097] θ3:

[0098] θ2:

[0099] θ1:

[0100] In the above formula, θ1, θ2, and θ3 are the joint angles of the root joint, hip joint, and knee joint of the probe robot, respectively. The subscripts i, ii, iii, and iv in each joint angle are used to distinguish different expected joint angle components of the same joint angle. 1，i (t) and θ 1，ii (t) represents the different expected joint angle components of θ1, θ 2，i (t), θ 2，ii (t), θ 2，iii (t) and θ 2，iv (t) represents the different expected joint angle components of θ2, θ 3，i (t) and θ 3，ii (t) represents the different expected joint angle components of θ3, atan is the arctangent function, and p x p y and p z These represent the positions of the foot trajectory in each direction; sinθ j =s j cosθ j =c j j = "3,i", "3,ii" or "3", for example: s3 = sinθ3,s 3，i =sinθ 3,i s 3，ii =sinθ 3，ii c3 = cosθ3, c 3，i =cosθ 3，i c 3，ii =cosθ 3，ii A and B are intermediate variables, and A = a² + a³c³. a3 is the DH parameter of the third joint of the probe robot.

[0101] The above kinematic model establishes the motion laws of each link of the robot and the motion relationship between the link and the joint from a geometric perspective. Using the relevant content of the forward and inverse kinematics of the supporting leg, an analytical expression for the motion of the robot's leg is given. Figure 4 This is a schematic diagram of the inverse kinematics solution process in this embodiment. See [link / reference]. Figure 4 It can be seen that when performing inverse kinematics calculation: firstly, based on the foot trajectory (X(t) and Z(t)), the two expected joint angle components θ3 of the root joint can be determined. 3，i (t) and θ 3，ii (t); then based on the expected joint angle component θ of the root joint. 3，i (t) can determine the desired joint angle component θ of the hip joint. 2，i (t) and θ 2，ii (t), based on the expected joint angle component θ of the root joint. 3，ii(t) can determine the desired joint angle component θ of the hip joint. 2，iii (t) and θ 2，iv (t); Finally, based on the expected joint angle component θ of the hip joint. 2，i (t) can determine the desired joint angle component θ of the knee joint. 1，i (t), based on the expected joint angle component θ of the hip joint 2，ii (t) can determine the desired joint angle component θ of the knee joint. 2，iii (t); based on the expected joint angle component θ of the hip joint 2，i (t) can determine the desired joint angle component θ of the knee joint. 2，iv (t).

[0102] In this embodiment, the motion controller in step S103 is a PID controller. The PID controller controls the joints of the robot's legs to control the robot's movement. The function expression of the PID controller is:

[0103]

[0104] In the above formula, τ(t) is the joint output control torque, and K p K is the proportionality coefficient. i K is the integral coefficient. d Here are the differential coefficients, and e(t) is the deviation. Let t be the first derivative of the deviation, and t be time. In this embodiment, the same PID controller is added to the 6×3=18 joints of the hexapod robot, and its parameters are shown in Table 1.

[0105] Table 1: PID controller parameter table.

[0106] <![CDATA[K p ]]> <![CDATA[K i ]]> <![CDATA[K d ]]> 100 0.01 10

[0107] like Figure 5 As shown, the foot trajectory after adding the active attachment bias Δr is taken as the desired position of the supporting leg, and the desired joint angle θ of each joint is obtained by inverse kinematics calculation. i The robot obtains the current joint angle of each joint and calculates the deviation e(t) between the current joint angle and the desired joint angle. This deviation e(t) is then input into the motion controller to obtain the joint output control torque τ(t). The corresponding joint is controlled by the joint output control torque τ(t) until the deviation e(t) is less than the set value. This process is repeated to achieve motion control of the robot.

[0108] Based on mechanical constraints such as position, velocity, and acceleration, this embodiment minimizes the impact effects experienced by the robot during movement, avoiding sudden acceleration changes. A stable, dynamically planned foot trajectory is used as the desired leg position. The desired joint angle is calculated using the robot's inverse kinematics. The deviation between the current joint angle and the desired joint angle is calculated. The PID controller receives this deviation and outputs a control torque τ(t) to the joint, bringing the joint angle closer to the desired value. This process is repeated to achieve robot movement control.

[0109] As an optional implementation, in step S103 of this embodiment, when controlling the corresponding joint by outputting control torque, the method further includes detecting the horizontal and vertical ground forces, tangential and normal static friction forces on the feet of each supporting leg using sensors, and verifying the effectiveness of the mobile control method for the exploration robot under weak gravity conditions of a small celestial body by judging whether the dynamic constraint relationship for stable attachment shown in the following formula holds during attachment:

[0110]

[0111] The effectiveness of the probe robot's movement control method under weak gravity conditions on small celestial bodies is verified by judging whether the dynamic constraint relationship satisfying stable movement shown in the following formula holds during movement:

[0112]

[0113] If the dynamic constraint relationship holds, the mobile control method of the probe robot under the weak gravity condition of the small celestial body is deemed effective; where n is the number of supporting legs of the probe robot; μ1 and μ2 are the tangential and normal friction coefficients; and These are the horizontal and vertical forces exerted by the ground on the foot end of the i-th supporting leg, respectively. and These represent the tangential and normal static friction forces exerted on the foot end of the i-th supporting leg, respectively; m is the robot's mass; g s,N Let g be the vertical component of the gravitational acceleration of the small celestial body. s ,τ D represents the horizontal component of the gravitational acceleration of a small celestial body.N D is the vertical component of the disturbance force acting on the robot. τ This represents the horizontal component of the disturbance force experienced by the robot.

[0114] The aforementioned dynamic constraints on stable attachment and movement can be determined through dynamic analysis of the probe robot under weak gravity conditions. Based on fundamental mechanics, when the foot of the legged robot interacts with the surface of a small celestial body and makes contact, the foot will experience a supporting force from the surface. The prerequisite for this supporting force is contact between the foot and the celestial body surface; therefore, the supporting force exists in the robot's supporting legs. Let F be the supporting force experienced by the i-th supporting leg of the robot. i Then it can be written in three-dimensional vector form:

[0115]

[0116] In the above formula, and To support force F i The amount.

[0117] Furthermore, the support force F can be... i Decomposed into tangential forces in the horizontal plane and the normal force in the vertical direction Right now:

[0118]

[0119]

[0120] in, and The effect is manifested as contact compression; when the foot of the supporting leg tends to move relative to the surface, static friction will be generated. Specifically, relative motion within a horizontal plane corresponds to static friction. With normal force Related; the static friction force corresponding to the relative motion in the vertical direction. With tangential force Relatedly, it can be determined that, under weak gravity conditions, the dynamic constraint equations that the probe robot must satisfy to adhere to the surface of a small celestial body without detaching and to move without slipping are:

[0121]

[0122] In the formula, n is the number of supporting legs of the probe robot; and These are the horizontal and vertical forces exerted by the ground on the foot end of the i-th supporting leg, respectively. and These represent the horizontal and vertical static friction forces exerted on the foot end of the i-th supporting leg, respectively; m is the robot's mass; gs Let be the gravitational acceleration from the small celestial body; D represents the perturbation force acting on the robot, such as the sun's gravity; the superscripts τ and N represent the horizontal and vertical vector directions, respectively. The force analysis of the horizontal and vertical forces acting on the foot of the i-th supporting leg, as well as the horizontal and vertical static friction forces acting on it, is as follows: Figure 6 As shown.

[0123] Let the tangential and normal friction coefficients be μ1 and μ2, respectively. To ensure stable adhesion and movement, the following constraint relationship exists:

[0124]

[0125] remember The threshold value for tangential static friction is... The threshold value for normal static friction force.

[0126] Taking the movement of a small celestial body on a horizontal surface as an example, to ensure adhesion without detachment, the following must be satisfied in the vertical direction:

[0127]

[0128] To ensure movement without slipping, the following must be satisfied in the horizontal plane:

[0129]

[0130] The above dynamic analysis of the probe robot comprehensively considers the forces and torques acting on the robot on the surface of the small celestial body, establishes a foot-ground contact model for the robot, and derives the dynamic constraints that the probe robot must satisfy for stable attachment and movement under weak gravitational conditions. Furthermore, according to the above analysis, the tangential static friction threshold and the normal static friction threshold characterize the probe robot's attachment and movement capabilities on the surface of the small celestial body.

[0131] As an optional implementation, this embodiment designs a movement control method for a hexapod robot, where each leg is a three-degree-of-freedom anthropomorphic elbow support leg with identical structure, as shown in Tables 2-4. In this embodiment, the probe robot will use the triangular gait, the most common movement pattern for hexapod robots.

[0132] Table 2: Physical parameters of the supporting legs.

[0133] rod Length / mm mass / g base 52.00 43.22 Stocks 66.06 87.18 Tibia 137.71 116.19

[0134] Table 3: Dynamic parameters of the supporting leg.

[0135]

[0136] Table 4: DH parameters of the supporting leg.

[0137] <![CDATA[θ i / °]]> <![CDATA[d i / mm]]> <![CDATA[a i / mm]]> <![CDATA[α i / °]]> <![CDATA[θ1]]> 0 52.00 90 <![CDATA[θ2]]> 0 66.06 0 <![CDATA[θ3]]> 0 137.71 0

[0138] In Table 4, θ i Represents the joint angle, d i Represents the offset of the link, which consists of the base segment, femur, and tibialis segment that make up the robot's leg. i Represents the length of the rod, α i The value represents the torsion angle of the member, and the subscript i indicates the number of the support leg.

[0139] This embodiment uses Phobos, a representative small celestial body, as the target for detection, and a simulation environment is built in Gazebo. Table 5 shows the environmental parameters of Phobos.

[0140] Table 5: Environmental parameters of Phobos.

[0141] Gravitational acceleration <![CDATA[-5.7×10 -3 m / s 2 ]]> Soft constraint force mixed parameters 1.00 temperature 233K Soft error reduction parameter 0.20 Tangential friction coefficient 1.00 Contact point dynamic stiffness coefficient <![CDATA[2.15×10 9 ]]> Normal friction coefficient 1.00 Contact point dynamic damping coefficient 1.00

[0142] In this embodiment, the deviation e(t) is input into the motion controller to obtain the joint output control torque τ(t). Figure 7 As shown, the horizontal axis "time" represents time in seconds (s); the vertical axis "Force" represents the output control torque. x Torque y and Torque z These represent the components of the output control torque τ(t) along the x, y, and z axes, respectively. By controlling the corresponding joint through the output control torque τ(t), until the deviation e(t) is less than the set value, the robot can actively attach and move onto the small celestial surface. The adhesion force between the robot's feet and the small celestial surface is as follows: Figure 8 As shown, the horizontal axis "time" represents time, in seconds (s); the vertical axis "Force" represents adhesion force, in Newtons (N); and "Torque" represents the force applied to the surface. x Torque y and Torque z These represent the components of the adhesion force between the robot's feet and the surface of the small celestial body in the x, y, and z axes, respectively.

[0143] In summary, to achieve motion control of the exploration robot under weak gravity conditions, this embodiment conducted a dynamic analysis of the hexapod robot, establishing the mechanical constraints that it must satisfy to adhere to the surface of a small celestial body without detaching and to move without slipping. Secondly, for the robot's three-degree-of-freedom anthropomorphic elbow supporting leg, its inverse kinematics solution was presented. To adapt to the weak gravity environment of the small celestial body, a steady-state planning was performed, and the robot's foot trajectory was designed and optimized to reduce the normal impact experienced by the robot during movement. Subsequently, to ensure stable adhesion of the hexapod robot to the surface of the small celestial body, the active attachment bias was incorporated into the foot trajectory through end-effector gait bias. Finally, a PID controller was selected to control the movement of the hexapod robot, realizing the attachment and movement of the exploration robot under the weak gravity conditions of the small celestial body. Moreover, the method in this embodiment includes five steps: dynamic analysis, kinematic calculation, translational gait planning, final state biasing, and motion controller design. Among them, by constructing a translational gait planning method adapted to weak gravity conditions, the foot impact effect during the movement process is suppressed. Finally, based on translational gait, a stable attachment method based on end-effector gait bias is established to solve the attachment problem under weak gravity conditions. By combining the translational gait design of the probe robot with the end-effector final state bias, the method in this embodiment enables the probe robot to achieve stable attachment and movement on the surface of small celestial bodies under weak gravity conditions, creating the preconditions for the successful implementation of the exploration mission.

[0144] Furthermore, this embodiment also provides a mobile control device for a probe robot under weak gravitational conditions caused by a small celestial body, including a microprocessor and a memory interconnected thereto. The microprocessor is programmed or configured to execute the mobile control method for the probe robot under weak gravitational conditions caused by a small celestial body. Additionally, this embodiment also provides a computer-readable storage medium storing a computer program for being programmed or configured by the microprocessor to execute the mobile control method for the probe robot under weak gravitational conditions caused by a small celestial body.

[0145] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-readable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a machine for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The functions specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable apparatus for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0146] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling the movement of a probe robot under weak gravitational conditions on a small celestial body, characterized in that, include: S101, perform planar dynamic planning on the probe robot. The calculation function expression for the vertical displacement component Z(t) of the foot trajectory as a function of time is: In the above formula, h is the maximum height that the detection robot can reach when its legs swing, sgn is the sign function, and t swing To detect the time of a single leg swing of the robot, t is time, f E (t) is an intermediate variable function, and we have: f E (t)=t / t swing -(1 / 4π)sin(4πt / t swing ); S102, At the end of the foot trajectory obtained by the steady-state planning, add an active attachment bias Δr to ensure the gripping and attachment of the probe robot to the small celestial body surface. S103, the foot trajectory after adding active attachment bias Δr is taken as the desired position of the leg, and inverse kinematics calculation is performed to obtain the desired joint angle of each joint. The current joint angle of each joint of the probe robot is obtained, and the deviation between the current joint angle and the desired joint angle of each joint is calculated. The deviation is input into the motion controller to obtain the joint output control torque. The corresponding joint is controlled by the joint output control torque until the deviation is less than the set value.

2. The method for controlling the movement of a probe robot under weak gravitational conditions of a small celestial body according to claim 1, characterized in that, In step S101, when performing steady-state planning for the probe robot, the calculation function expression for the time-varying component X(t) of the foot trajectory in the forward direction is: In the above formula, s is the step size of the probe robot.

3. The method for controlling the movement of a probe robot under weak gravitational conditions of a small celestial body according to claim 1, characterized in that, The expression for the computation function of the symbolic function is:

4. The method for controlling the movement of a probe robot under weak gravitational conditions of a small celestial body according to claim 1, characterized in that, The calculation function expression for the active attachment bias Δr is: In the above formula, x c y c and z c To determine the position coordinates of the robot's center of mass in the reference coordinate system; x s y s and z s To detect the position coordinates of the robot's foot in the reference coordinate system, K is the active attachment bias ratio coefficient.

5. The method for controlling the movement of a probe robot under weak gravitational conditions of a small celestial body according to claim 1, characterized in that, Step S103 performs inverse kinematics calculations to obtain the functional expression for the expected joint angles of each joint: θ3: θ2: θ1: In the above formula, θ1, θ2, and θ3 are the joint angles of the root joint, hip joint, and knee joint of the probe robot, respectively. 1,i (t) and θ 1,ii (t) represents the different expected joint angle components of θ1, θ 2,i (t), θ 2,ii (t), θ 2,iii (t) and θ 2,iv (t) represents the different expected joint angle components of θ2, θ 3,i (t) and θ 3,ii (t) represents the different expected joint angle components of θ3, atan is the arctangent function, and p x p y and p z These represent the positions of the foot trajectory in each direction; A and B are intermediate variables, a3 is the DH parameter of the third joint of the probe robot; s3 = sinθ3, s 3,i =sinθ 3,i s 3,ii =sinθ 3,ii c3 = cosθ3, c 3,i =cosθ 3,i c 3,ii =cosθ 3,ii A = a² + a³c³ 6. The method for controlling the movement of a probe robot under weak gravitational conditions of a small celestial body according to claim 1, characterized in that, The motion controller in step S103 is a PID controller.

7. The method for controlling the movement of a probe robot under weak gravitational conditions on a small celestial body according to claim 1, characterized in that, In step S101, when performing steady-state planning for the probe robot, the step of determining the functional expression of the time-varying component Z(t) of the vertical displacement of the foot end includes: S201, Determine the constraints on the foot trajectory in the vertical direction, including position constraints, velocity constraints, and acceleration constraints: In the above formula, Z| t＝0 , and These represent the position, velocity, and acceleration at time t=0, respectively. and They are respectively Position, velocity, and acceleration at any given moment and They are respectively Position, velocity, and acceleration at any given moment; S202, based on the constraint of the foot trajectory in the vertical direction, the vertical acceleration function designed to suppress normal impact is shown in the following equation: In the above formula, Let be the acceleration at time t, A be the amplitude of the acceleration, and n be a parameter representing the period of acceleration change. swing To detect the time of a single leg swing of the robot, t is time; S203, based on the vertical acceleration function used to suppress normal impact, the expression for calculating the time-varying component Z(t) of the vertical displacement is designed as follows: In the above formula, h is the maximum height that the detection robot can reach when its legs swing, sgn is the sign function, and t swing To detect the time of a single leg swing of the robot, t is time, f E (t) is an intermediate variable function, and we have: f E (t)=t / t swing -(1 / 4π)sin(4πt / t swing )。 8. The method for controlling the movement of a probe robot under weak gravitational conditions of a small celestial body according to claim 1, characterized in that, In step S103, when controlling the corresponding joint by outputting control torque, the method also includes detecting the horizontal and vertical ground forces, tangential and normal static friction forces on the feet of each supporting leg using sensors. Furthermore, during attachment, the effectiveness of the mobile control method for the probe robot under weak gravity conditions of a small celestial body is verified by determining whether the dynamic constraint relationship for stable attachment shown in the following formula holds: The effectiveness of the probe robot's movement control method under weak gravity conditions on small celestial bodies is verified by judging whether the dynamic constraint relationship satisfying stable movement shown in the following formula holds during movement: If the dynamic constraint relationship holds, the mobile control method of the probe robot under the weak gravity condition of the small celestial body is deemed effective; where n is the number of supporting legs of the probe robot; μ1 and μ2 are the tangential and normal friction coefficients; and These are the horizontal and vertical forces exerted by the ground on the foot end of the i-th supporting leg, respectively. and These represent the tangential and normal static friction forces exerted on the foot end of the i-th supporting leg, respectively; m is the robot's mass; g s,N Let g be the vertical component of the gravitational acceleration of the small celestial body. s,τ D represents the horizontal component of the gravitational acceleration of a small celestial body. N D is the vertical component of the disturbance force acting on the robot. τ This represents the horizontal component of the disturbance force experienced by the robot.

9. A mobile control device for a probe robot operating under weak gravity conditions on a small celestial body, comprising a microprocessor and a memory interconnected, characterized in that, The microprocessor is programmed or configured to execute the mobile control method for a probe robot under weak gravity conditions of a small celestial body as described in any one of claims 1 to 8.

10. A computer-readable storage medium storing a computer program, characterized in that, The computer program is used to be programmed or configured by a microprocessor to execute the mobile control method for a probe robot under weak gravity conditions of a small celestial body as described in any one of claims 1 to 8.

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