Talk on "Soft Robotics Design and Control" by Alin Albu-Schäffer Part2

In this talk

1. 0:01

   Decoupling Cartesian impedance

   Albu-Schäffer describes using simultaneous diagonalization of stiffness and inertia matrices to separate a robot’s behavior by direction. Demonstrations show low or zero stiffness in selected directions, stable quaternion-based orientation control, and a singularity-avoidance potential that prevents entry into singular configurations.

2. 9:05

   Passivity for flexible-joint robots

   For flexible joints, motor and link positions and velocities must be modeled separately, making torque part of the system state. Albu-Schäffer describes feedback that reduces effective motor inertia and friction, and a passivity-based framework intended to keep the robot stable despite modeling errors or unknown contact dynamics. He cites a comparison in which the lightweight robot outperformed a 250-kilogram KUKA carrying the same 14-kilogram load in three of five test categories.

3. 17:08

   Safety, assembly, and whole-body interaction

   The control approach extends to grasping, object-based impedance, and a 33-degree-of-freedom mobile system weighing 150 kilograms. For assembly, vision provides an approximate target and compliance limits contact forces; stability analysis can help choose stiffness and motions that work across a larger range of starting positions. Link-side torque sensing also supports collision detection within one millisecond and helps distinguish contact forces from gearbox friction.

4. 26:01

   Variable compliance and energy storage

   Albu-Schäffer presents mechanical compliance as useful for human interaction, impact tolerance, and storing energy for dynamic motion. A human-sized hand has 19 degrees of freedom and 38 actuators, with stiffness adjusted through tendon and spring mechanisms; the team is extending passivity-based control to these nonlinear, coupled systems. In a throwing example, storing spring energy lets a robot throw an object several meters, compared with about 0.8 meters without that stored energy.