18,270 research outputs found
Robots that can adapt like animals
As robots leave the controlled environments of factories to autonomously
function in more complex, natural environments, they will have to respond to
the inevitable fact that they will become damaged. However, while animals can
quickly adapt to a wide variety of injuries, current robots cannot "think
outside the box" to find a compensatory behavior when damaged: they are limited
to their pre-specified self-sensing abilities, can diagnose only anticipated
failure modes, and require a pre-programmed contingency plan for every type of
potential damage, an impracticality for complex robots. Here we introduce an
intelligent trial and error algorithm that allows robots to adapt to damage in
less than two minutes, without requiring self-diagnosis or pre-specified
contingency plans. Before deployment, a robot exploits a novel algorithm to
create a detailed map of the space of high-performing behaviors: This map
represents the robot's intuitions about what behaviors it can perform and their
value. If the robot is damaged, it uses these intuitions to guide a
trial-and-error learning algorithm that conducts intelligent experiments to
rapidly discover a compensatory behavior that works in spite of the damage.
Experiments reveal successful adaptations for a legged robot injured in five
different ways, including damaged, broken, and missing legs, and for a robotic
arm with joints broken in 14 different ways. This new technique will enable
more robust, effective, autonomous robots, and suggests principles that animals
may use to adapt to injury
Pushing towards the Limit of Sampling Rate: Adaptive Chasing Sampling
Measurement samples are often taken in various monitoring applications. To
reduce the sensing cost, it is desirable to achieve better sensing quality
while using fewer samples. Compressive Sensing (CS) technique finds its role
when the signal to be sampled meets certain sparsity requirements. In this
paper we investigate the possibility and basic techniques that could further
reduce the number of samples involved in conventional CS theory by exploiting
learning-based non-uniform adaptive sampling.
Based on a typical signal sensing application, we illustrate and evaluate the
performance of two of our algorithms, Individual Chasing and Centroid Chasing,
for signals of different distribution features. Our proposed learning-based
adaptive sampling schemes complement existing efforts in CS fields and do not
depend on any specific signal reconstruction technique. Compared to
conventional sparse sampling methods, the simulation results demonstrate that
our algorithms allow less number of samples for accurate signal
reconstruction and achieve up to smaller signal reconstruction error
under the same noise condition.Comment: 9 pages, IEEE MASS 201
System identification and adaptive current balancing ON/OFF control of DC-DC switch mode power converter
PhD ThesisReliability becomes more and more important in industrial application of Switch Mode Power
Converters (SMPCs). A poorly performing power supply in a power system can influence its operation
and potentially compromise the entire system performance in terms of efficiency. To maintain a high
reliability, high performance SMPC effective control is necessary for regulating the output of the SMPC
system. However, an uncertainty is a key factor in SMPC operation. For example, parameter variations
can be caused by environmental effects such as temperature, pressure and humidity. Usually, fixed
controllers cannot respond optimally and generate an effective signal to compensate the output error
caused by time varying parameter changes. Therefore, the stability is potentially compromised in this
case. To resolve this problem, increasing interest has been shown in employing online system
identification techniques to estimate the parameter values in real time. Moreover, the control scheme
applied after system identification is often called “adaptive control” due to the control signal selfadapting to the parameter variation by receiving the information from the system identification process.
In system identification, the Recursive Least Square (RLS) algorithm has been widely used because it
is well understood and easy to implement. However, despite the popularity of RLS, the high
computational cost and slow convergence speed are the main restrictions for use in SMPC applications.
For this reason, this research presents an alternative algorithm to RLS; Fast Affline Projection (FAP).
Detailed mathematical analysis proves the superior computational efficiency of this algorithm.
Moreover, simulation and experiment result verify this unique adaptive algorithm has improved
performance in terms of computational cost and convergence speed compared with the conventional
RLS methods. Finally, a novel adaptive control scheme is designed for optimal control of a DC-DC
buck converter during transient periods. By applying the proposed adaptive algorithm, the control signal
can be successfully employed to change the ON/OFF state of the power transistor in the DC-DC buck
converter to improve the dynamic behaviour. Simulation and experiment result show the proposed
adaptive control scheme significantly improves the transient response of the buck converter, particularly
during an abrupt load change conditio
Development of Hybrid PS-FW GMPPT Algorithm for improving PV System Performance Under Partial Shading Conditions
A global maximum power point tracking (MPPT) algorithm hybrid based on Particle Swarm Fireworks (PS-FW) algorithm is proposed which is formed with Particle Swarm Optimization and Fireworks Algorithm. The algorithm tracks the global maximum power point (MPP) when conventional MPPT methods fail due to occurrence of partial shading conditions. With the applied strategies and operators, PS-FW algorithm obtains superior performances verified under simulation and experimental setup with multiple cases of shading patterns
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