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Research
I. Integrated Planning and Control of Various Mobile Robots Using Differential Flatness
• Tractor with a steerable trailer
• NIST (National Institute of Standards and Technology) HLPR Chair
We implemented the differential flatness-based control algorithm into the HLPR Chair developed by NIST.
II. Differential Flat Designs of Under-actuated Mobile Manipulators
If a manipulator arm is mounted on mobile vehicles, the dynamics becomes highly nonlinear. A challenging question is how to perform point-to-point motions of such a system in the state space of the mobile manipulator. Moreover, if some of the actuators are absent in the mechanical arm, the mobile manipulator becomes under-actuated and consequently even harder to plan and control. We investigated a methodology for design of a mobile manipulator, mounted with under-actuated arms operating either in a horizontal plane or in a vertical plane such that the combined system is differentially flat. We showed that by appropriate inertia distribution of the links and addition of torsion springs at the joints, a wide range of under-actuated designs are possible where the under-actuated mobile manipulator system is differentially flat.
I have conducted team work research for experimental validation of the differential flatness approach to mobile manipulators. We provided the differential flatness-based control algorithm for a planar mobile manipulator developed at the University at Buffalo (SUNY). Even though the manipulator arm is not under-actuated as described above, the simulation and experiment results showed the effectiveness of the differential flatness approach to mobile manipulators.
- The two-link mobile manipulator and experimental results, developed and conducted by the SUNY Buffalo.
III. Differential
Flatness-based Robust Controller
For various reasons,
slip between the ground and the wheel often exists in most of the real
applications of mobile robots. To
achieve the desired performance when slip occurs, a controller that is
robust
to slip disturbances is required. In
the development of robust trajectory-tracking controllers, the
structure of the
differential flatness controller, which provides an integrated
framework for
planning and control, is extended to account for slip disturbances by
adding a
corrective control term. The simulation and experimental results showed
that
the proposed robust controllers are very effective in the presence of
slip.
IV. Various Control Problems
A control
methodology
for a two-wheeled differentially driven mobile robot was developed in
order to
make the robot, which can be used as a mobility assistive robot, have
passive
mobility characteristics for the user’s safety. The
control law creates damper-like resistive forces on
the wheels.
This work was another team work project for autonomous control of an agricultural farming tractor. We provided a Lyapunov-based control algorithm and our coworkers at the University of Valladolid (Spain) conducted experimental validation of the idea.
V. Baby Robot (Robot Enhanced Mobility)
:
The Capacity for Young Infants to Learn Real World Navigation, and Its
Effect
on Perception, Action and Cognition Development
- All necessary host, joystick, and control programs were coded with C/C++ under Linux.
