Method and device for controlling the motion of one or more collaborative robots

1. A method for controlling one or more collaborative robots, each one of said one or more collaborative robots being mounted on a fixed or movable base and being equipped with:

one or more terminal members;

a motion controller configured to move, along predetermined directions, said one or more terminal members based on a position of at least a human operator;

wherein said method comprises the following iterative steps:

determining position coordinates of said human operator;

determining position coordinates of each one of said terminal members;

for each terminal member determining, as a function of both said position coordinates of said terminal member and said position coordinates of said human operator, a plurality of productivity indices;

each productivity index being associated with a respective one of said predetermined directions;

each productivity index being indicative of a maximum speed at which a respective terminal member can move, in a respective one of said predetermined directions, at least in case of a presence of said human operator;

supplying to said motion controller said productivity indices;

activating said motion controller to move, along said predetermined directions, said one or more terminal members based on said productivity indices.

2. The method according to claim 1 , wherein each collaborative robot comprises at least a robotic manipulator provided with a number n of joints; each terminal member being coupled to a respective robotic manipulator;

wherein:

said determining position coordinates of each one of said terminal members comprises:

cyclically reading a linear position or angular position of each joint of a respective robotic manipulator;

collecting said linear positions or said angular positions of each joint in a position vector q having n components; and

calculating a speed vector {dot over (q)} as a function of said position vector q;

said determining position coordinates of said human operator comprises:

cyclically determining a number η of points detected on said human operator; and

collecting said number η of points in an operator position vector p; said operator position vector p having 3*η components, corresponding to a three position coordinates of a respective point;

said determining a plurality of productivity indices comprises:

calculating a matrix E(p,q) and a vector f(p,q), wherein:

E(p,q)is a matrix of 2*n*η×n size, calculated as a function of both said operator position vector p and said position vector q;

f(p,q) is a vector of 2*n*η components; calculated as a function of both said operator position vector p and said position vector q; and

determining said productivity indices as a function of said matrix E(p,q) and said vector f(p,q), wherein the relation E(p,q){dot over (q)}≤f (p,q) holds.

3. The method according to claim 2 , wherein said determining a plurality of productivity indices further comprises:

calculating a singular value decomposition of said matrix E(p,q), obtaining matrices U, S and V; wherein:

said matrix U is an orthogonal square matrix of (2*n*η×2*n*η) size;

said matrix S is a matrix of (2*n*η, n) size containing singular values of said matrix E(p,q);

said matrix V is an orthogonal square matrix of (n×n) size; each column i of said matrix V corresponding to a respective movement direction v i , in a joint coordinate system, of a respective terminal member;

for each movement direction v i , calculating a respective value φ i max =max{φ}, in the joint coordinate system, corresponding to a maximum intensity of a movement speed along a respective direction v i , wherein the relations:

φ E ( p,q )ν i ≤f ( p,q )

|φν i |≤{dot over (q)} max

hold, {dot over (q)} max being a vector of maximum speeds that a single joint coordinate can assume;

for each movement direction v i , converting said value φ i max from the joint coordinate system into a coordinate system based on said position coordinates of said respective terminal member;

for each movement direction v i , calculating said productivity indices as a function of said value φ i max in said coordinate system based on said position coordinates of said respective terminal member.

4. The method according to claim 1 , wherein said activating said motion controller to move said one or more terminal members based on said productivity indices further comprises one or more of the following:

executing a direction of motion or path which is alternative to said predetermined direction;

executing a new path with an alternative final position, possibly not known a priori, which is different than said predetermined movement final position;

slowing down the motion of said robot;

stopping the motion of said robot.

5. The method according to claim 4 , wherein said controller for controlling the motion of one or more robots decides to take said actions on the basis of a priority mechanism that depends on the type of activity that the robot must carry out and/or the type of movement that said terminal member must make and/or a criterion of profitability of the task to be carried out.

6. A device for controlling the motion of one or more collaborative robots, wherein said device comprises means for implementing the method according to claim 1 , said means comprising:

at least one vision system adapted to cyclically determining said position coordinates of one or more human operators over time;

means for determining said position coordinates of each one of said terminal members; and

means for determining said set of productivity indices associated with respective directions of motion of the terminal member of the robot.