1. Universidade Federal de Vicosa
2. Institute of Robotics and Mechatronics, German Aerospace Center (DLR), Wessling, Germany
3. Universidade Federal do Espirito Santo, Vitoria, ES, BR
4. Universidade Federal do Espirito Santo: Vitoria, ES, BR
5. Department of Electrical Engineering, Universidade Federal de Vicosa, Vicosa - MG, Brazil