Suboptimal control of underactuacted manipulators via actuation redundancy

Author(s)

Benedito Carlos de Oliveira Maciel

• Document type: Master's Dissertation
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2001-06-21

Examining board members

Marco Henrique Terra; João Yoshiyuki Ishihara; Paulo Sérgio Pereira da Silva

• Advisor: Marco Henrique Terra

Abstract

This work presents a control methodologie for the position of the passive joints of an underactuated manipulator in a suboptimal way. The term underactuated refers to the fact that not all the joints or degrees of freedom of the system are equipped with actuators, which occurs in practice due to failures or as design result. The passive joints of manipulators like this are indirectly controlled by the motion of the active joints using the dynamic coupling characteristics. The utilization of actuation redundancy of the active joints allows the minimization of some criteria, like energy consumption, for example. Although the kinematic structure of an underactuated manipulator is identical to that of a similar fully actuated one, in general their dynamic characteristics are different due to the presence of passive joints. Thus, we present the dynamic modelling of an underactuated manipulator and the concept of coulpling index. This index is used in the sequence of the optimal conirol of the manipulator. The hipotheses that the number of active joints is greatter than the number of passives (na>np) allows the optimal control of the passive joints, since there are more inputs (torques at the actuators of the active joints), than elements to be controlled (position of the passive joints). At this point resides the contribution of this dissertation to the state of the art, once there is no publication that proposes the optimal control of the passive joints in this case. (AU)