580 research outputs found
High speed, precision motion strategies for lightweight structures
Research on space telerobotics is summarized. Adaptive control experiments on the Robotic Arm, Large and Flexible (RALF) were preformed and are documented, along with a joint controller design for the Small Articulated Manipulator (SAM), which is mounted on the RALF. A control algorithm is described as a robust decentralized adaptive control based on a bounded uncertainty approach. Dynamic interactions between SAM and RALF are examined. Unstability of the manipulator is studied from the perspective that the inertial forces generated could actually be used to more rapidly damp out the flexible manipulator's vibration. Currently being studied is the modeling of the constrained dynamics of flexible arms
Control of a Lightweight Flexible Robotic Arm Using Sliding Modes
This paper presents a robust control scheme for flexible link robotic
manipulators, which is based on considering the flexible mechanical structure
as a system with slow (rigid) and fast (flexible) modes that can be controlled
separately. The rigid dynamics is controlled by means of a robust sliding-mode
approach with wellestablished stability properties while an LQR optimal design
is adopted for the flexible dynamics. Experimental results show that this
composite approach achieves good closed loop tracking properties both for the
rigid and the flexible dynamics
Dynamic simulation of task constrained of a rigid-flexible manipulator
A rigid-flexible manipulator may be assigned tasks in a moving environment
where the winds or vibrations affect the position and/or orientation of surface
of operation. Consequently, losses of the contact and perhaps degradation of
the performance may occur as references are changed. When the environment is
moving, knowledge of the angle α between the contact surface and the
horizontal is required at every instant. In this paper, different profiles for
the time varying angle α are proposed to investigate the effect of this
change into the contact force and the joint torques of a rigid-flexible
manipulator. The coefficients of the equation of the proposed rotating surface
are changing with time to determine the new X and Y coordinates of the moving
surface as the surface rotates
Robotic manipulation with flexible link fingers
A robot manipulator is a spatial mechanism consisting essentially of a series of bodies, called "links", connected to each other at "joints". The joints can be of
various types: revolute, rotary, planar, prismatic, telescopic or combinations of these. A serial connection of the links results in an open-chain manipulator. Closed-chain
manipulators result from non-serial (or parallel) connections between links. Actuators at the joints of the manipulator provide power for motion.
A robot is usually not designed for a very specific or repetitive task which can be done equally well by task-specific machines. Its strength lies in its ability to handle a range of tasks by virtue of being "re-programmable". Therefore, in addition to the mechanical hardware two other elements are integral to the description of a robot: sensors and control. With the advent of micro-electronics and digital computers the availability of sensors is ever increasing and the control is usually done by software executed by computers which also collect the sensory data. It is possible to model quite accurately, the dynamics of robot manipulators for purposes of control. However, for most practical robots the models are complex and numerically intensive to calculate in real-time.
Traditional analyses of robot manipulators consider the whole mechanism to be rigid. Relaxation of the assumption of rigidity leads to further complication of the dynamics of the manipulator, leading to more difficulties in control. The overall motion of the manipulator is augmented by additional motion due to the dynamics of flexibility which must be considered. Sensing is also made more difficult. However, the ability to control robots with significant structural flexibilities, referred to as flexible robots in the rest of this thesis, influences robotics in many ways. It allows for consideration of new applications, observance of less conservative structural design and performance enhancements in certain classes of robotic tasks, which will
be addressed in greater detail in the sections which follow
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