In the period of reference (February 2012-March 2012) the following sub-tasks have been continued/completed, according to the TESBE workplan:

T1.4: Experimental assessment of the developed control approaches

T2.2: Implementation and test of the collaborative control

T2.4: Assessment of the combination of the haptic cues and the collaborative control

T3.3: Detailed development of the gripper

T3.4: Validation of the new gripper

In subtask 1.4, the extension to the multi-DOF case of the force control developed in the previous reporting period has been initiated.

In accordance with the structure of new force control developed for the 1 DoF case, the vector of the required motor torques (control law) have been expressed as the sum of a feed-forward contribution and a full state feedback contribution. These contributions have been defined taking into account the dynamics of the robots with flexible joints.

On the basis of the assumption that the full state feedback could produce enough damping action to reduce at minimum the difference between the joint and position accelerations, the feed forward contribution has been evaluated as in the case of rigid manipulators.

To complete the definition of the feed-forward contribution, an optimal load distribution between the two legs when both the feet are in contact with the ground has been defined, with the aim of reducing the internal forces and the amount of the torques transferred to the soil by each foot.

In subtasks T2.2 and T2.4 the validation of the Collaborative Control (CC) involving human subjects has been completed, after having achieved a satisfactory accuracy of the evaluation of the BE Center of Gravity (CG) performed by the CC.

With respect to the previous reporting period the inaccuracy of the evaluation has been significantly reduced (form 25mm to 8mm), through a better calibration procedure of the offset parameters, the development of a more realistic model of the leg compliance and the implementation of an evaluation method more robust to possible residual inaccuracies in the estimation of the joint angular positions.

Then, the validation of the CC involving human subjects has been carried on with two types of tests, the first providing the physical interaction with the BE from the external (i.e. without wearing the device) and the other providing the wearing of the device.

The tests demonstrated the good ability of the CC to keep the Zero Moment Point always inside the support polygon, for any random desired motion of the subject. Furthermore the intervention of the CC is felt by the subject as natural and smooth, making them highly confident of the capability of the device to keep the equilibrium of the system.

In subtasks T3.3 and T3.4, the revision 3 of the gripper has been finalized, taking into account all the feedbacks emerged in the technical meetings with SSSA.

The overall device dimensions and weight have been optimized according to structural analysis.  

The construction of the device in now in progress and it will be completed for the beginning of May.