Control of haptic interaction : an energy-based approach


Franken, Michaël Christianus Johannes (2011) Control of haptic interaction : an energy-based approach. thesis.

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Abstract:Haptic feedback systems are systems that exert a desired force, to be experienced by the
user, to recreate a physical interaction. This type of systems can increase the realism of the
interaction with objects that are not in the direct area of influence of the user. The same
applies to the interaction with virtual objects. The fundamental problem in the control
of these systems is how to maximize the transparency of the system, and related to that
the realism of the interaction as perceived by the user, while guaranteeing stability of the
interaction under all possible operating conditions.
The stability analysis is complicated due to the presence of a closed loop, which can
contain multiple unknown, non-linear, and time-varying elements, e.g. the user, a physical
environment, and time delays in a possible communication channel. Furthermore,
the control algorithm is executed on a discrete medium which, depending on the algorithm,
parameter settings, and remaining elements, can have a significant influence on the
stability of the interaction.
In this thesis a solution is sought to all these factors by means of energy- and portbased
reasoning. For both applications an algorithm is derived that is based on the energy
exchange between the physical world and the system. By enforcing energy neutrality, in
other words passivity, of this exchange a stable interaction is guaranteed.
The algorithm for the interaction with virtual environments provides a passive coupling
between the physical system and the discrete system. The dynamic behavior of the
virtual object is computed with an energy-based integration method. Each iteration the
algorithm evaluates the energy that is present in the system. A redistribution of that energy
over the energy storing elements is computed based on the model that describes the
dynamic behavior of the physical object. This algorithm ensures stability independent of
the sample frequency of the algorithm, but adapts the realism of the interaction in such a
way that passivity is maintained.
The second algorithm divides the control objectives for the passive interaction with
physical objects in remote environments by means of a telemanipulation system into two
layers that are placed in a hierarchical order. The top layer, the Transparency-layer, contains
an arbitrary control algorithm that provides the desired measure of transparency.
The Passivity-layer contains an algorithm that guarantees passivity of the interaction and
when necessary adapts the desired forces computed by the Transparency-layer to maintain
passivity. The implementation of this algorithm also works in the presence of communication
delays, by e.g. physical distance, between both locations that are connected by the
system, the user and remote environment, respectively.
Item Type:Thesis
Electrical Engineering, Mathematics and Computer Science (EEMCS)
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