Multi center impedance control

A method for controlling a robot to install a vehicle door part on a vehicle body by inserting two hinge pins on the door part into two hinge openings on the vehicle body, said method comprising:

• defining a reference point at a tip of each of the hinge pins on the door part and a corresponding target point for each reference point in the two hinge openings on the vehicle body;
• calculating, by a robot controller, a spring-damping force at each of the reference points based on a velocity of the reference point and a displacement of the reference point with respect to the corresponding target point;
• measuring a contact force and torque by a sensor coupled between the robot and the door part and communicating the contact force and torque to the controller;
• calculating, by the controller, a resultant force and torque as a sum of the spring-damping forces and the contact force and torque about a center of gravity of the hinge pins on the door part;
• calculating, by the controller, a new pose of the door part using an impedance controller calculation based on the resultant force and torque;
• and
• moving the door part to the new pose by the robot in response to signals from the controller.

A system for performing an assembly operation of inserting a plurality of pins of a first workpiece into a plurality of cavities of a second workpiece, said system comprising:

• an industrial robot configured to move the first workpiece;
• a force and torque sensor coupled between the first workpiece and the robot;
• and
• a robot controller having a processor and memory, said controller being in communication with the robot and receiving signals from the sensor, said controller being configured to perform steps including;
• defining a reference point at a tip of each of the pins on the first workpiece and a corresponding target point for each reference point in a cavity of the second workpiece;
• calculating a spring-damping force at each of the reference points based on a velocity of the reference point and a displacement of the reference point with respect to the corresponding target point;
• calculating a resultant force and torque as a sum of the spring-damping forces and a contact force and torque measured by the sensor;
• calculating a new pose of the first workpiece based on the resultant force and torque;
• and
• sending signals to the robot causing the robot to move the first workpiece to the new pose.