Energy-Shaping Controller for Time-Invariant Multiple Contacts
Ehtisham ul Hasan, Angelika Peer
AI summary
Problem
Current human-robot safety controllers are designed for single interaction points, leaving a critical gap in managing energy and power limits during tasks requiring multiple simultaneous human contacts.
Approach
The authors extend a Port-Hamiltonian framework with grasp matrices to model object dynamics and dynamically scale impedance parameters, ensuring total energy and dissipated power at each contact point stay within ISO safety thresholds.
Key results
- Controller successfully bounds system energy and contact power below safety limits
- Experimental validation on a Franka robot confirms stability with passive and active human collaborators
- Grasp matrix integration accurately maps multi-point human forces to object dynamics
- Energy tank mechanism guarantees passivity and prevents instability near kinematic singularities
Why it matters
Provides a practical, mathematically grounded safety framework for industrial robots engaged in complex co-manipulation tasks with multiple human contact points.
Abstract
While in the past industrial robots were strictly separated from humans, today robots serve humans in a variety of industrial applications that also involve close or even physical human-robot interaction. Hereby, safety is of utmost importance and thus, the design of the control system needs to ensure a stable and safe operation. In this context, safety has been mainly addressed for single interaction points. In this article, we present an energy shaping controller that is capable of ensuring safety even in the case of multiple human contact points that may occur when co-manipulating an object. The presented approach is tested and validated in experiments. Re- sults indicate that for the studied co-manipulation task involving time-invariant multiple human contacts, a safe interaction can be achieved.