An Energy-Based Approach for the Multi-Rate Control of a Manipulator on an Actuated Base

Abstract

In this paper we address the problem of controlling a robotic system mounted on an actuated floating base for space applications. In particular, we investigate the stability issues due to the low rate of the base control unit. We propose a passivity-based stabilizing controller based on the time domain passivity approach. The controller uses a variable damper regulated by a designed energy observer. The effectiveness of the proposed strategy is validated on a basemanipulator multibody simulation.

Multi-Rate Tracking Control for a Space Robot on a Controlled Satellite: A Passivity-Based Strategy

“…To achieve this goal, the controller at the base will be function of the end-effector desired trajectory. This is in contrast with [16] where only regulation control was implemented for both the base and end-effector and therefore, the tracking terms did not appear. However, this is a natural consequence of the coupled dynamics between base and end-effector motions and must be taken into account in the design of the control laws.…”

“…is the error (in position and orientation) between the measured and desired base pose. Notice that the orientation error for the base and manipulator exploits the quaternion representation calculated from the relative orientation matrix error (see [16] for more details).…”

“…This is due to the inertial coupling between the base and endeffector tracking motions. Therefore, the regulation control law proposed in [16] for the base controller will not be suitable. Otherwise it might result in instability during the tracking.…”

“…During the inter-sampling period (k m and k b ), the discrete control law might not cancel the respective power terms, as can be seen by substituting F m (k m ) from (16) and F b (k b ) from (17) into (14). Therefore, the discrete nature of the controllers leads to creation of virtual energy which destroys the passivity of the system and it might lead to instability [23].…”

“…[14]) because they can jeopardize the stability of the system [15]. Within this context, a first approach was developed in our previous work [16] in which, however, only the regulation problem for the manipulator and its base was treated and this might not be suitable for a trajectory-tracking control needed in the approach phase.…”