Dynamic capture of free-moving objects

Abstract

A new stiffness control method is proposed for robotic systems to capture free-moving objects with minimum jerk. A bell-shaped stiffness curve is shown to minimize the jerk that occurs during capture tasks. The results verify that the method can be used to successfully decelerate objects over a predefined distance, while keeping the jerk experienced during the capture within limits. Shortcomings with the method are identified from the results, and an adaptive control scheme is proposed. An adaptive controller is designed to actively interact with the object to estimate the kinetic energy during the capture and scale the amount of force being applied accordingly. Simulation results confirm that the adaptive control scheme overcomes the shortcomings in previous methods.

Robotic Pre-manipulation - Real-Time Polynomial Trajectory Control for Dynamic Object Interception with Minimum Jerk

“…When the cart approaches the end effector, the linear actu- ator would execute a smooth trajectory to match the cart's position, velocity, and acceleration at the capture point. Once contact is established, the object can be decelerated in a predefined workspace such as that described in (Nagendran et al, 2011).…”

“…The end effector cannot move beyond its inner workspace limit D lim (m). The mass is therefore required to be decelerated over a distance D stop (m), a method for which was first described in (Nagendran et al, 2007) and improved upon in (Nagendran et al, 2011). From the known velocity of the incoming mass, an intercept point for the end effector and the object is computed (object travels a distance D intercept (m) before impact).…”