Comparative experiments on task space control with redundancy resolution

Understanding the principles of motor coordination with redundant degrees of freedom still remains a challenging problem, particularly for new research in highly redundant robots like humanoids. Even after more than a decade of research, task space control with redundacy resolution still remains an incompletely understood theoretical topic, and also lacks a larger body of thorough experimental investigation on complex robotic systems. This paper presents our first steps towards the development of a working redundancy resolution algorithm which is robust against modeling errors and unforeseen disturbances arising from contact forces. To gain a better understanding of the pros and cons of different approaches to redundancy resolution, we focus on a comparative empirical evaluation. First, we review several redundancy resolution schemes at the velocity, acceleration and torque levels presented in the literature in a common notational framework and also introduce some new variants of these previous approaches. Second, we present experimental comparisons of these approaches on a seven-degree-of-freedom anthropomorphic robot arm. Surprisingly, one of our simplest algorithms empirically demonstrates the best performance, despite, from a theoretical point, the algorithm does not share the same beauty as some of the other methods. Finally, we discuss practical properties of these control algorithms, particularly in light of inevitable modeling errors of the robot dynamics.

Authors

• Jun Nakanishi
• Rick Cory
• Michael N. Mistry
• Jan Peters 0001
• Stefan Schaal

Keywords

• Redundancy
• Robot kinematics
• Orbital robotics
• Humanoid robots
• Control systems
• Robustness
• Acceleration
• Torque
• Anthropomorphism
• Lighting control
• Task Space
• Redundancy Resolution
• Task Space Control
• Decades Of Research
• Robotic Arm
• Contact Force
• Humanoid
• Properties Of Algorithm
• Acceleration Level
• Optimal Control
• Interference Effect
• Per Cycle
• Positive Definite Matrix
• Definite Matrix
• Joint Position
• Joint Space
• Pseudo-inverse
• Null Space
• Error Dynamics
• Null Vector
• Joint Torque
• Joint Acceleration
• Joint Velocity
• Inertia Matrix
• Inverse Kinematics
• Arbitrary Vector
• Numerical Differentiation
• Asymptotic Tracking
• Inverse Dynamics
• Coordination Task
• Null space optimization
• Dynamical decoupling