Department for Automation, Biocybernetics and Robotics





Control of kinematically redundant mechanisms

Research activity duration: 1995 -
Research area: Automation and Intelligent Control of Robots
Activity funding: Research Agency
Activity leader: Bojan Nemec
Coworkers:
Bojan Nemec
Damir Omrčen
Leon Žlajpah

Abstract

Control algorithms for kinematically redundant mechanisms, Null-space motion optimization, obstacle avoidance, stability of null-space control algorithms, experiments

Activity description

The research deals with the control of kinematically redundant manipulators. We compared and emphasized the conceptual difference between pseudo-inverse and minimal null-space based control algorithms. We demonstrated that minimal null-space based control algorithms might become computational unstable and proposed an efficient solution to this problem. Furthermore, we investigated the problem and benefits of vision, tactile, proximity and force sensors interaction in the control loop. Based on these sensors we proposed a method for on-line obstacle avoidance applying the force control of redundant robots. Furthermore, we proposed an obstacle avoidance algorithm by reducing inertia in the null-space and proposed alternative solutions for obstacle avoidance using vision system. It is widely known that the majority of modern control algorithms become inefficient or even unstable in the presence of limits imposed by the real mechanism. Therefore we developed and efficient algorithm for compensation of velocity and/or acceleration limits for redundant robots. The proposed algorithms improves the performance of robots in industrial applications as well as improves the performance of special research, service and humanoid robots when executing actions that require high dynamic response, such as jumping, running, throwing, etc .. Developed algorithms were tested on real robots and numerous experiments proved our theoretical achievements.

Multimedia

Mimimization of the null space compliant force (bump4.avi, 6628 kb)
Simulation of trajectory optimization using virtal mechanism (VirtMech0007.avi, 4529 kb)
Simulation of trajectory optimization using virual mechanism - fixed orientation (VirtMech0003.avi, 7515 kb)
Simulation of obstacle avoidance using virtal mechanism (VirtMech0001.avi, 1934 kb)
Basic principle of obstacle avoidance using virual mechanism (VirtualMechBasic.avi, 3324 kb)

Publications

Article

  • Nemec B., Žlajpah L., Omrčen D., Comparison of null-space and minimal null-space control algorithms, 2007. [More] [PDF]
  • Žlajpah L., Nemec B., Force strategies for on-line obstacle avoidance for redundant manipulators, 2003. [More]
  • Nemec B., Žlajpah L., Force control of redundant robots in unstructured environment, 2002. [More]
  • Nemec B., Žlajpah L., Experiments with force control of redundant robots in unstructured environment using minimal null-space formulation, 2002. [More] [PDF]
  • Nemec B., Žlajpah L., Null space velocity control with dynamically consistent pseudo-inverse, 2000. [More] [PDF]
  • Žlajpah L., Influence of external forces on the behaviour of redundant manipulators, 1999. [More]
  • Lenarčič J., Nemec B., Steepest descent optimisation in the secondary space of redundant manipulators, 1997. [More]

Inproceedings

  • Nemec B., Žlajpah L., Task redundancy resolution using virtual mechanism apporach, 2008. [More] [PDF]
  • Omrčen D., Nemec B., Kos A., Lahajnar L., Babič J., Gams A., Ude A., Žlajpah L., Integration of a redundant mobile manipulator system : a drink serving task, 2006. [More]
  • Nemec B., Žlajpah L., Omrčen D., Stability of null-space control algorithms, 2003. [More] [PDF]
  • Žlajpah L., Nemec B., Kinematic control algorithms for on-line obstacle avoidance for redundant manipulators, 2002. [More]
  • Nemec B., Žlajpah L., Force control of redundant robot using the extended space, 2001. [More]
  • Žlajpah L., Nemec B., Control algorithms for on-line obstacle avoidance for redundant robots, 2001. [More]
  • Nemec B., Žlajpah L., Experiments with force control of redundant robots in ustructured environment using minimal null space formulation, 2000. [More]
  • Žlajpah L., On-line obstacle avoidance control for redundant robots using tactile sensors, 1999. [More]
  • Žlajpah L., On obstacle avoidance for redundant robots using tactile sensors, 1999. [More]
  • Nemec B., Žlajpah L., Experiments on impedance control of redundant manipulators, 1999. [More]
  • Nemec B., Žlajpah L., Force controlled redundant robot - theory and application, 1998. [More]
  • Nemec B., Žlajpah L., Implementation of force control on redundant robot, 1998. [More]
  • Žlajpah L., Obstacle avoidance control for redundant manipulators utilizing the contact forces, 1998. [More]
  • Žlajpah L., Dynamics of internal motion of redundant manipulators, 1998. [More]
  • Žlajpah L., Control of redundant robots in presence eof external forces, 1997. [More]
  • Nemec B., Force control of redundant robots, 1997. [More]
  • Nemec B., Pseudoinverses and null space velocity controller, 1997. [More]
  • Žlajpah L., Dexterity measures for optimal path control of redundant manipulators, 1996. [More]
  • Nemec B., Regulacija sile pri redundantnih mehanizmih, 1996. [More]
  • Lenart L., Žlajpah L., Globalna optimizacija navorov v zglobih pri redundantnih robotih, 1995. [More]
  • Nemec B., Control of redundant manipulators with limited torque, 1994. [More]
  • Žlajpah L., Lenarčič J., On line minimum joint torque motion generation for redundant manipulators, 1994. [More]
  • Žlajpah L., Lenarčič J., Generacija gibanja z minimizacijo navorov v zglobih za redundantne manipulatorje, 1994. [More]

Misc

  • Žlajpah L., Godler I., Janežič R., Mrak S., Opeka J., Izdelava ravninskega redundantnega mehanizma, 1996. [More]