392 research outputs found
Action module planning and Cartesian based control of an experimental climbing robot
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997.Includes bibliographical references (leaves 88-95).by David M. Bevly.M.S
Hybrid force and position control in robotic surface processing
PhD ThesisThis programme of research was supported by NEI Parsons Ltd. who sought
a robotic means of polishing mechanical components.
A study of the problems associated with robot controlled surface
processing is presented. From this evolved an approach consistent with
the formalisation of the demands of workpiece manipulation which
included the adoption of the Hybrid robot control scheme capable of
simultaneous force and position control.
A unique 3 axis planar experimental manipulator was designed which
utilized combined parallel and serial drives. A force sensing wrist was
used to measure contact force. A variant of the Hybrid control 'scheme
was successfully implemented on a twin computer control system. A
number of manipulator control programs are presented.
The force control aspect is shown both experimentally and analytically
to present control problems and the research has concentrated on this
aspect.
A general analysis of the dynamics of force control is given which shows
force response to be dependent on a number' of important parameters
including force sensor, environment and manipulator dynamics. The need
for a robust or adaptable force controller is discussed.
A series of force controlled manipulator experiments is described and
the results discussed in the context of general analyses and specific
single degree of freedom simulations. Improvements to manipulator force
control are suggested and some were implemented. These are discussed
together with their immediate application to the improvement of robot
controlled surface processing.
This work also lays important foundations for long term related
research. In particular the new techniques for actively controlled
assembly and force control under 'fast' operation.Science and Engineering Research Council
NEI Parsons Ltd
Biomimetic Manipulator Control Design for Bimanual Tasks in the Natural Environment
As robots become more prolific in the human environment, it is important that safe operational
procedures are introduced at the same time; typical robot control methods are
often very stiff to maintain good positional tracking, but this makes contact (purposeful
or accidental) with the robot dangerous. In addition, if robots are to work cooperatively
with humans, natural interaction between agents will make tasks easier to perform with
less effort and learning time. Stability of the robot is particularly important in this
situation, especially as outside forces are likely to affect the manipulator when in a close
working environment; for example, a user leaning on the arm, or task-related disturbance
at the end-effector.
Recent research has discovered the mechanisms of how humans adapt the applied force
and impedance during tasks. Studies have been performed to apply this adaptation to
robots, with promising results showing an improvement in tracking and effort reduction
over other adaptive methods. The basic algorithm is straightforward to implement,
and allows the robot to be compliant most of the time and only stiff when required by
the task. This allows the robot to work in an environment close to humans, but also
suggests that it could create a natural work interaction with a human. In addition, no
force sensor is needed, which means the algorithm can be implemented on almost any
robot.
This work develops a stable control method for bimanual robot tasks, which could also
be applied to robot-human interactive tasks. A dynamic model of the Baxter robot is
created and verified, which is then used for controller simulations. The biomimetic control
algorithm forms the basis of the controller, which is developed into a hybrid control
system to improve both task-space and joint-space control when the manipulator is disturbed
in the natural environment. Fuzzy systems are implemented to remove the need
for repetitive and time consuming parameter tuning, and also allows the controller to
actively improve performance during the task. Experimental simulations are performed,
and demonstrate how the hybrid task/joint-space controller performs better than either
of the component parts under the same conditions. The fuzzy tuning method is then applied
to the hybrid controller, which is shown to slightly improve performance as well as
automating the gain tuning process. In summary, a novel biomimetic hybrid controller
is presented, with a fuzzy mechanism to avoid the gain tuning process, finalised with a
demonstration of task-suitability in a bimanual-type situation.EPSR
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