Co-handling robot having a mixed-force control law providing high effector sensitivity and enabling interaction with the body of the robot

A co-handling robot comprising:

• a kinematic chain of mechanical elements comprising a proximal-end element forming a base of the robot and a distal-end element, the elements being mounted with the ability to move relative to one another so that the distal-end element is able to move with respect to the proximal-end element;
• a tool and/or a gripper, which is configured to be manipulated by a human operator, the tool and/or the gripper being connected to the distal-end element in such a way that the tool and/or the gripper has the same degrees of freedom as the distal-end element;
• means for controlling at least part of the first chain of elements, comprising:
• actuators arranged on the chain to perform all the movements of the various elements of the chain relative to one another and/or to apply a force between them,
• means for measuring the displacement of the elements with respect to one another,
• a single multiaxis force sensor, arranged between the distal-end element and the tool and/or the gripper, so as to measure forces applied to the distal-end element and the tool and/or the gripper, and
• a controller for controlling the actuators on the basis of the measurements taken by the means for measuring displacement and by the measurements from the multiaxis force sensor, according to a control law implemented in the controller, said control law comprising:
• a force-increasing loop configured to amplify, at the robot joints, forces applied to the tool or the gripper and measured by the multiaxis force sensor, this being in respect of at least some of the degrees of freedom of the distal end, the force-increasing loop comprising a comparator to subtract, from the product of the integral gain Ki of the loop, the product of the anti-windup gain Kaw, and an integrator which receives the result from the comparator to supply the setpoint speeds for the various elements of the chain,
• an internal speed loop with proportional gain Kv which receives the speed setpoint from the force-increasing loop to supply the non-saturation reference torques for the various actuators,
• an internal speed loop saturation function, the saturation term τsat being chosen to be greater than or equal to the vector τf0 of the dry friction coefficients of the actuators, and
• an anti-windup component fed back to the input of the integrator of the force-amplification loop, and obtained as the product of the force correction applied by the saturation and the gain Kaw so that as soon as saturation comes into effect, the integrator of the force-increasing loop interrupts its integration.