Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the present patent;
The technical scheme of the invention is further described below with reference to the accompanying drawings and examples.
Example 1
Referring to fig. 1, the present embodiment provides a method for controlling repetitive motion of a mobile robot based on discrete time neural dynamics, which includes the following steps:
S1: and collecting motion data of the mobile robot.
S2: and constructing a position layer kinematics equation, a speed layer kinematics equation and a physical limit constraint of the mobile robot, and converting the physical limit constraint into a speed layer double-end inequality constraint.
S3: and constructing a repeated motion control scheme of the mobile robot based on the time-varying quadratic optimization problem by combining the position layer kinematics equation, the speed layer kinematics equation and the speed layer double-end inequality constraint.
In this embodiment, by uniformly converting the combination angle vector and the physical limit constraint of the combination speed vector of the mobile robot into an expression based on the combination speed vector, that is, the speed layer double-end inequality constraint, a repetitive motion control scheme of the mobile robot with a decision variable being the combination speed vector is constructed, so that the repetitive motion control scheme is re-expressed as a standard time-varying quadratic optimization problem resolved on the speed layer.
S4: and introducing an exponential penalty strategy into the repeated motion control scheme of the mobile robot based on the time-varying quadratic form optimization problem based on the zero-change neurodynamics design rule, and constructing a continuous time zero-change neurodynamics model.
S5: and constructing a discrete time zero nerve dynamics model according to a five-step explicit linear multi-step rule and the continuous time zero nerve dynamics model.
S6: and inputting the motion data of the mobile robot into the discrete time zero neural dynamics model, and calculating the control variable of the mobile robot.
S7: and carrying out repeated motion control on the mobile robot according to the control variable.
The method comprises the steps of constructing a position layer kinematics equation, a speed layer kinematics equation and a speed layer double-end inequality constraint of a mobile robot, designing a repeated motion control scheme of the mobile robot based on a time-varying quadratic form optimization problem, introducing an exponential penalty strategy and a five-step explicit linear multi-step rule on the basis of the repeated motion control scheme of the mobile robot, constructing a discrete time zero-change neural dynamics model, and accurately predicting a solving result of the next time point in each calculation time interval only by updating and calculating the current and previous known data information once, thereby realizing high-precision real-time repeated motion control of the mobile robot containing physical limit constraint, effectively eliminating non-repeated motion phenomenon, and effectively improving the motion instantaneity, path tracking precision and physical limit constraint processing capacity of the mobile robot.
Example 2
Referring to fig. 2-8, the present embodiment provides a method for controlling repetitive motion of a mobile robot based on discrete time neural dynamics, which includes the following steps:
s1: collecting motion data of a mobile robot;
In this embodiment, the motion data of the mobile robot includes a combined angle vector of the mobile robot, an actual position vector of the end effector, rotation angles of a left driving wheel and a right driving wheel of the mobile platform, a joint angle vector of a six-joint redundancy mechanical arm fixed on the mobile platform, a heading angle of the mobile platform, a combined speed vector of the mobile robot, and an expected path of the end effector.
S2: constructing a position layer kinematics equation, a speed layer kinematics equation and a physical limit constraint of the mobile robot, and converting the physical limit constraint into a speed layer double-end inequality constraint:
S2.1: determining a discrete time point of the motion of the mobile robot, and constructing a positional layer kinematics equation at the discrete time point.
In the present embodiment, at discrete points in timeIn the method, a position layer kinematic equation is constructed, and the expression is as follows:
Φ(Θk+1)=ractual,k+1
where k is the update index, For a time step, t final is the final point in time of the entire calculation time interval,As an array of non-linear mapping functions,For a real set, Θ k+1 is the combined angle vector of the mobile robot, r actual,k+1 is the actual position vector of the end effector,For the rotation angle set of the left driving wheel and the right driving wheel of the mobile platform, theta k+1 is the joint angle vector of the six-joint redundancy mechanical arm fixed on the mobile platform.
Discrete time pointsFrom the sum of kThe value determination is generally referred to as the next discrete point in time, while t k is generally referred to as the current discrete point in time. The expression at the discrete time point t k+1 can better illustrate that the solution and problem to be solved is for the next discrete time point.
S2.2: and constructing a velocity layer kinematic equation according to the position layer kinematic equation.
In this embodiment, to monitor and control the process of the end effector tracking the desired path, the positioning error vector of the end effector is defined as e k+1=ractual,k+1-rdesired,k+1, where r desired,k+1 is the desired path of the end effector.
By introducing the end effector positioning error described above as error feedback, the expression of the velocity layer kinematic equation is as follows:
Wherein phi k+1 is the course angle of the mobile platform, For a combined velocity vector of the mobile robot,For a set of rotational speeds of the left and right drive wheels of the mobile platform,For the joint velocity vector of the six-joint redundancy mechanical arm fixed on the mobile platform, J (phi k+1,θk+1) is a matrix related to jacobian; ζ k+1 is a vector containing end effector position error feedback,R desired,k+1 is the desired path of the end effector, lambda 1 is a settable parameter, which is the time derivative of the desired path of the end effector.
S2.3: the physical limit constraint is constructed by a set of discrete time-varying double-ended inequalities.
In this embodiment, the expression of the physical limit constraint of the mobile robot is as follows:
Wherein Θ - represents the lower limit of the combined angle vector of the mobile robot, Θ + represents the upper limit of the combined angle vector of the mobile robot, Representing the lower limit of the combined velocity vector of the mobile robot,The upper limit of the combined velocity vector of the mobile robot is represented.
S2.4: based on an exponential limit conversion strategy, the physical limit constraint is converted into a speed layer double-end inequality constraint, and the expression is as follows:
Where α k+1 represents the lower limit of the double-ended inequality constraint, β k+1 represents the upper limit of the double-ended inequality constraint, the i-th element α i,k+1 of α k+1 (i=1, 2, …, n), and the i-th element β i,k+1 of β k+1 (i=1, 2, …, n), respectively, are defined as follows:
Wherein exp (·) represents an exponential function; σ 1 >0 is a settable parameter for adjusting the deceleration amplitude; the parameter sigma 2 epsilon (0, 1) is a settable parameter for adjusting the critical area range where deceleration is required, i.e And
S3: and constructing a repeated motion control scheme of the mobile robot based on a time-varying quadratic optimization problem by combining the position layer kinematics equation, the speed layer kinematics equation and the speed layer double-end inequality constraint:
S3.1: and designing a repeated motion control scheme of the mobile robot by combining a position layer kinematics equation, a speed layer kinematics equation and a speed layer double-end inequality constraint, wherein the expression is as follows:
Wherein D k+1 represents a coefficient matrix of the repetitive motion performance index, D k+1 represents a coefficient vector of the repetitive motion performance index, and expressions of D k+1 and D k+1 are respectively as follows:
Wherein, C k+1 represents an auxiliary matrix related to the course angle of the mobile platform, and lambda 2、λ3 and lambda 4 are positive design parameters; p connection,k+1=[xconnection,k+1;yconnectioh,k+1 is the connection point between the mobile platform and the mechanical arm, X connection,k+1 represents the coordinate of the connection point on the X axis, and Y connection,k+1 represents the coordinate of the connection point on the Y axis; p connection (0) represents the initial state of a connection point between the mobile platform and the mechanical arm, phi (0) is the initial state of a course angle of the mobile platform, theta (0) represents the initial state of a joint angle vector of the mechanical arm, and a is the distance from the left driving wheel and the right driving wheel to the midpoint of two wheel shafts; b is the distance from the midpoint of the two wheel shafts to the connecting point p connection,k+1, and gamma is the radius of the left driving wheel and the right driving wheel; 0 represents a zero matrix and I represents an identity matrix.
S3.2: and converting the repeated motion control scheme into a time-varying quadratic optimization problem to obtain the repeated motion control scheme based on the time-varying quadratic optimization problem, wherein the expression is as follows:
s.t.Gk+1xk+1=gk+1
Hk+1xk+1≤hk+1
where T represents the transpose operator of the vector or matrix, For the decision variable vector to be solved for,For a positive definite symmetric coefficient matrix in the objective function,For the coefficient vector in the objective function,For a row-full rank coefficient matrix in the constraint of equations,For the coefficient vector in the constraint of the equation,As a coefficient matrix in the inequality constraint, Is a coefficient vector in the inequality constraint.
S4: based on a zero-change neural dynamics design rule, introducing an exponential penalty strategy into a repetitive motion control scheme of the mobile robot based on a time-varying quadratic form optimization problem, and constructing a continuous time zero-change neural dynamics model:
S4.1: introducing an exponential penalty strategy into a repetitive motion control scheme based on a time-varying quadratic optimization problem, eliminating inequality constraint in the repetitive motion control scheme, and obtaining the repetitive motion control scheme with the equality constraint only, wherein the expression is as follows:
s.t.Gk+1xk+1=gk+1
Wherein, Is an exponential penalty function, the expression of which is as follows:
Where σ i(xk+1,tk+1)=-Hi,k+1xk+1+hi,k+1 represents the ith auxiliary variable in the penalty function, H i,k+1 represents the row vector made up of the ith row element of matrix H k+1, H i,k+1 represents the ith element of vector H k+1, μ and ν represent positive design parameters.
S4.2: according to the Lagrangian multiplier method, the repetitive motion control scheme with only equality constraint is converted into a time-varying equation set problem, and the expression is as follows:
Uk+1yk+1+ω(xk+1,tk+1)=0
wherein the expressions of U k+1、yk+1 and ω (x k+1,tk+1) are respectively as follows:
Wherein, Is a lagrange multiplier vector.
S4.3: carrying out continuous operation on the time-varying equation set problem to obtain a continuous time-varying equation set problem, wherein the expression is as follows:
U(t)y(t)+ω(x(t),t)=0
s4.4: defining an error function of the continuous time-varying equation set problem as epsilon (t) =U (t) y (t) +omega (x (t), t) and combining a zero-ized neurodynamics design rule A continuous time nulling neuromotor model was obtained, the expression of which is as follows:
wherein η is a positive design parameter for adjusting the convergence rate; An array of monotonically increasing odd stimulus functions; m (x (t), t) represents a coefficient matrix, P (x (t), t) represents a time derivative matrix, u (x (t), t) represents a time derivative vector, and the expressions of M (x (t), P (x (t), t) and u (x (t), t) are respectively as follows:
s5: and constructing a discrete time zero nerve dynamics model according to a five-step explicit linear multi-step rule and the continuous time zero nerve dynamics model, and calculating a control variable of the mobile robot according to the discrete time zero nerve dynamics model.
In this embodiment, the five-step explicit linear multi-step rule is derived from a linear multi-step method, and can be used for discrete time solution of a differential equation form dynamics system. The model based on the five-step explicit linear multi-step rule can predictively calculate the solution of the next discrete time point through an explicit linear combination form by only using the results and derivative values of the current and previous five discrete time points, without using information of the next discrete time point. The five-step explicit linear multi-step rule involves six adjacent discrete points in time, i.e., includes five progressive steps, and is therefore referred to as five steps. And is called explicit since the five-step explicit linear multi-step rule does not need to use information to the next discrete point in time.
In this embodiment, the expression of the five-step explicit linear multistep rule is as follows:
Combining a five-step explicit linear multi-step rule with the continuous time zero-change neural dynamics model to obtain a discrete time zero-change neural dynamics model, wherein the expression is as follows:
Wherein, Calculating a value operator; The truncated error of the discrete time zero neural dynamics model is expressed as that the discrete time zero neural dynamics model has six-order calculation accuracy.
S6: and inputting the motion data of the mobile robot into the discrete time zero neural dynamics model, and calculating the control variable of the mobile robot.
S7: and carrying out repeated motion control on the mobile robot according to the control variable.
In this embodiment, the lower computer controller is used to drive the mobile robot to execute the repetitive motion control task according to the control variable.
In a specific implementation process, in order to ensure the convergence rate of the discrete-time thermodynamic model, a power-S-shaped function is selected as an excitation function.
In conducting numerical experiments, the end effector of a mobile robot is expected to track a complex lissajous pattern path, expressed as follows:
Where δ 1、δ2 and δ 3 are three constants that determine the desired path position.
Setting a time stepThe duration of the single repetition movement is t final =10s, the distance a between the left and right driving wheels and the middle point of the two wheel shafts is 0.32m, the distance b between the middle point of the two wheel shafts and the connecting point between the mobile platform and the mechanical arm is 0.1m, the radius gamma of the left and right driving wheels is 0.1025m, other parameters are set to be eta=25, mu=0.004, v=300 and sigma 1=9,σ2=0.1,λ1=10,λ2=λ3=λ4 =30.
Furthermore, an initial position p connection(0)=[xconnection(0);yconnection (0) = [ 0] of the connection point between the mobile platform and the robot arm; 0]m, initial heading angle phi (0) =0.1 rad of the mobile platform, combined angle vector Θ (0) = [0, pi/12, pi/3 ] T rad of the mobile robot. The physical limit constraints of the mobile robot are set as follows:
Θ+=[∞,∞,0.524,2.356,1.088,6.283,6.283,6.283]Trad
Θ-=-[∞,∞,0.524,0.175,6.283,6.283,6.283,6.283]Trad
Finally, the discrete time zero neural dynamics model is utilized to calculate and obtain a control variable, so that the high-precision real-time repetitive motion control of the mobile robot with physical limit constraint is realized.
As shown in fig. 4, the motion track of the mobile robot and the actual track and the expected path of the end effector of the present invention, it can be seen from fig. 4 that the actual track of the end effector coincides with the expected lissajous figure path, and the final state and the initial state of the mobile robot coincide after the path tracking task is completed. Fig. 5 is a diagram of a connection point between a mobile platform and a mechanical arm and a course angle of the mobile platform, fig. 6 is a diagram of element trajectories of combined angle vectors of the mobile robot, and fig. 5 and 6 show that three important variables for realizing repeated motion, namely, a connection point p connection,k+1 between the mobile platform and the mechanical arm, a course angle phi k+1 of the mobile platform and a combined angle vector Θ k+1 of the mobile robot, are returned to their initial states finally, so that the aim of coordinated repeated motion control of the mobile robot can be realized after the closed path tracking task of an end effector is completed. Fig. 7 is an element trajectory diagram of the combined velocity vector of the mobile robot according to the present invention, fig. 8 is an element trajectory diagram of the end effector tracking error vector of the mobile robot according to the present invention, and it can be seen from fig. 7 and 8 that the combined velocity vector of the mobile robotThe element tracks of the end effector converge to zero after the task execution is finished, and the X, Y, Z axis component of the end effector positioning error vector epsilon k+1=ractual,k+1-rdesired,k+1 is smaller than 7×10 -6 m, so that the tracking precision of the end effector is obviously high enough. In addition, as can be seen from fig. 6 and 7, all elements of the combined angle vector and the combined speed vector of the mobile robot are limited within the given physical constraint upper and lower limits. In particular, the time-varying trajectory of the third joint angle θ 3,k+1 of the robotic arm of the mobile robot reaches the upper bound of the physical limit multiple times, but never crosses the upper bound. Obviously, when the angle theta 3,k+1 of the third joint is about to reach the upper limit of the physical limit, the double-end inequality constraint of the speed layer obtained based on the exponential limit conversion strategy is successfully activated, so that the speed of the third joint is further enabledDeceleration is performed to achieve avoidance of physical limits. It is worth noting that the average calculation time per update of the discrete time nulled neuro-dynamics model is about 9.3X10 -4 s, which is much smaller than the time step employedThereby meeting the requirement of strict real-time motion control of the mobile robot. In summary, these results well demonstrate high precision real-time repetitive motion control for mobile robots containing physical limit constraints.
Example 3
Referring to fig. 9, the present embodiment provides a mobile robot repetitive motion control system based on discrete time neural dynamics, including:
and the acquisition module is used for acquiring the motion data of the mobile robot.
The first construction module is used for constructing a position layer kinematics equation, a speed layer kinematics equation and a physical limit constraint of the mobile robot and converting the physical limit constraint into a speed layer double-end inequality constraint.
In this embodiment, a discrete time point is determined according to the update index and the time step, and a positional layer kinematic equation is constructed at the discrete time point.
In this embodiment, a velocity layer kinematic equation is constructed according to the position layer kinematic equation.
In this embodiment, the physical limit constraint is constructed by a set of discrete time-varying double-ended inequalities.
In this embodiment, the physical limit constraint is converted into a speed layer double-ended inequality constraint based on an exponential limit conversion strategy.
And the second construction module is used for constructing a repeated motion control scheme of the mobile robot based on the time-varying quadratic optimization problem by combining the position layer kinematics equation, the speed layer kinematics equation and the speed layer double-end inequality constraint.
In this embodiment, a repetitive motion control scheme of the mobile robot is designed in combination with a positional layer kinematic equation, a velocity layer kinematic equation, and a velocity layer double-end inequality constraint.
In this embodiment, the repetitive motion control scheme is converted into a time-varying quadratic optimization problem, and a repetitive motion control scheme based on the time-varying quadratic optimization problem is obtained.
And the third construction module is used for introducing an exponential penalty strategy into the repeated motion control scheme of the mobile robot based on the time-varying quadratic optimization problem based on the zero-change neural dynamics design rule, and constructing a continuous time zero-change neural dynamics model.
In this embodiment, an exponential penalty strategy is introduced into a repetitive motion control scheme based on a time-varying quadratic optimization problem, and inequality constraint in the repetitive motion control scheme is eliminated, so as to obtain a repetitive motion control scheme with only equality constraint.
The repetitive motion control scheme with only equality constraints is converted to a time-varying system of equations problem according to the Lagrangian multiplier method. And carrying out continuous operation on the time-varying equation set problem to obtain a continuous time-varying equation set problem, providing an error function of the continuous time-varying equation set problem, and combining a zero-change neural dynamics design rule to obtain a continuous time zero-change neural dynamics model.
And the fourth construction module is used for constructing a discrete time zero-change nerve dynamics model according to a five-step explicit linear multi-step rule and the continuous time zero-change nerve dynamics model, and calculating a control variable of the mobile robot according to the discrete time zero-change nerve dynamics model.
And the calculation module is used for calculating the control variable of the mobile robot according to the motion data of the mobile robot and the discrete time zero neural dynamics model.
And the control module is used for carrying out repeated motion control on the mobile robot according to the control variable.
In this embodiment, the lower computer controller is used to drive the mobile robot to execute the repetitive motion control task according to the control variable.
The method comprises the steps of constructing a position layer kinematics equation, a speed layer kinematics equation and a speed layer double-end inequality constraint of a mobile robot, designing a repeated motion control scheme of the mobile robot based on a time-varying quadratic form optimization problem, introducing an exponential penalty strategy and a five-step explicit linear multi-step rule on the basis of the repeated motion control scheme of the mobile robot, constructing a discrete time zero-change neural dynamics model, and accurately predicting a solving result of the next time point in each calculation time interval only by updating and calculating the current and previous known data information once, thereby realizing high-precision real-time repeated motion control of the mobile robot containing physical limit constraint, effectively eliminating non-repeated motion phenomenon, and effectively improving the motion instantaneity, path tracking precision and physical limit constraint processing capacity of the mobile robot.
The terms describing the positional relationship in the drawings are merely illustrative, and are not to be construed as limiting the present patent;
it is to be understood that the above examples of the present invention are provided by way of illustration only and are not intended to limit the scope of the invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the invention are desired to be protected by the following claims.