Control of Voluntary Movement in Indefinite Environment - Real-time Optimization of Reaching Patterns by Constraints Emergence and Satisfaction

Humans achieve reaching movements even when environmental conditions change unexpectedly, and because the human arm is redundant, constraints should be needed in the controller. To adapt to environmental changes, we have previously proposed new constraints for reaching movement, based on realtime optimization of motion patterns. However, consistency of our model to conventional models, which were based on offline optimization, has not been investigated. In this paper, we have compared our model to the conventional minimum torque change model for a redundant three joints arm. In a slow reaching condition, our model produced similar motion to the one by minimum torque change, whereas in a fast condition, the minimum torque change was not satisfied by our model but it generated postures with comfortable joint angles. These results indicated that our model would include minimum torque change criterion along with another criterion which evaluates kinematic comfort determined by the arm posture.