Sensor-free force/torque sensing in an articulated electromechanical actuator-driven robot

A non-transitory computer readable medium having stored thereon a computer program which, when executed by at least one processor, causes the at least one processor to perform force or torque sensing in an electromechanical actuator-driven robot comprising one or more links, one or more joints, an end effector and a controller, the computer program comprising processor-executable code to perform operation comprising:

• injecting a high-frequency low-amplitude (HFLA) signal to the joints to reduce the torque noise so as to improve repeatability of joint current measurements;
• estimating a first set of load torques in one or more joints in a given configuration of the robot without external force or load applied to the end effector;
• identifying gravitational and frictional components in the first set of load torques;
• estimating a second set of load torques in the one or more joints in the given configuration of the robot with an external force or load applied to the end effector;
• calculating a difference between the second set of load torques and the first set of load torques, taking into account the identified gravitational and frictional components;
• calculating an external force or torque acting on the end effector based on the difference between the second set of load torques and the first set of load torques using a Jacobian matrix for the given configuration of the robot;
• iteratively analyzing condition number values of the Jacobian matrix for the given configuration so as to detect singularities and identify operational regions in the robot workspace, where rate of preciseness of the calculations using the Jacobian matrix exceeds a threshold;
• calibrating the calculated external force or torque using scale factors computed for payloads of various control weights, known a priori;
• and
• presenting the external force or torque in a Cartesian space.