In the period of reference (October 2011-November 2011) the following sub-tasks have been continued, according to the TESBE workplan:

T1.3: Numerical assessment of the selected control approaches

T2.2: Implementation and test of the collaborative control

T3.3: Detailed development of the gripper

In subtask 1.3, the activity has been focused on the design and implementation of a more sophisticated primary motion control and related stabilizing contributions, aiming at substantially increase the system performances achieved with the simple primary motion control analyzed in the previous reporting period, consisting of a high gain velocity control closed on the motor velocity.

An increase of the maximum achievable constant loop gain of the force control, of about 15 times with respect to that achieved with the previous motion control, has been achieved using the actuator as a force generator and controlling its force with suitable feed forward and full state feedback contributions.

An accelerometer has been used as addition sensor, due to the easiness of its integration into the existing BE mechanics and the quality of the state estimations that can be achieved.

The numerical evaluations and the experimental verifications have shown a good accordance with the theoretical predictions.

In subtask 2.2 the module of the collaborative control developed in the previous reporting period has been integrated into the existing control architecture of the Body Extender, in order to allow its experimental validation.

Before testing the system with a human operator, a specific test has been carried out, for evaluating the accuracy of the estimation of the projected position of the system center of gravity on the support plane.

The test has shown the existence of significant errors in the evaluation of the position of the system center of gravity, due to a series of causes that have been reduced or experimentally evaluated.

A compensated evaluation of the system center of gravity will be developed in the next reporting period, taking into account the experimentally quantified errors.

In subtask T3.3, the detailed design of the gripper has been updated in order to further reduce the weight and encumbrance of the device, host the control and drive electronics and increase the strength of the gripper body.

An evaluation prototype of the finger has been also constructed and tested, in order to verify the kinematics and the accuracy of the numerical estimations of the forces that can be exerted at the grasping surfaces.

In the next reporting period the detailed design of the device will be finalized and the construction of the mechanical parts will be initiated.