Passivity-based control of robotic manipulators for safe cooperation with humans

Abstract

This paper presents a novel approach to the control of articulated robots in unstructured environments. The proposed control ensures several properties. First, the controller guarantees the achievement of a goal position without getting stuck in local minima. Then, the controller makes the closed-loop system passive, which renders the approach attractive for applications where the robot needs to safely interact with humans. Finally, the control law is explicitly shaped by the safety measure – the danger field. The proposed control law has been implemented and validated in a realistic experimental scenario, demonstrating the effectiveness in driving the robot to a given configuration in a cluttered environment, without any offline planning phase. Furthermore, the passivity of the system enables the robot to easily accommodate external forces on the tool, when a physical contact between the robot and the environment is established.

Keywords:

• robot control
• industrial robots
• Lyapunov stability

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Corrigendum

Notes

1. Note that this is a slight generalisation of the danger field with respect to Lacevic and Rocco (2010).

2. The dependency on s of both the SDF_e and the DDF_e is in all the quantities in (1(1) ) and (2(2) ) having subscript , which are affine functions of s.

3. Notice that can be defined for continuity to be zero for .

4. Depending on the nature of the joint (prismatic or rotational) the related component of and is a torque or a force.

5. For example, one could select W₁ = (1 − a)V and W₂ = (1 + a)V where 0 < a < 1.

6. This is a consequence of the passivity of the closed-loop system and, from the definition of DFin (3(3) ), of the boundedness of the control signal.

7. Artificial Repulsion from the Surface of the obstacle (FIRAS, from French), (Khatib, 1985).

8. Such a function has been designed to avoid fast motions to due large errors, which can be introduced by using, e.g. .

9. See also http://www.youtube.com/watch?v=yXSdurZ82FM.

Additional information

Funding

The research leading to these results has received funding from the European Community's Seventh Framework Programme FP7/2007-2013 Challenge 2 – Cognitive Systems, Interaction, Robotics [grant number 230902; project ROSETTA].