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Hanz Richter is giving a talk on powered prosthetics

A modeling and control framework for semi-active robots with energy regeneration
Monday, October 21, 10:00 AM
General-Purpose ME Lab, SH14


A general model is presented for a multilink robot where some joints are semi-active, in the sense that their
mechanisms exchange power only with other robotic links and with an internal energy storage device. Power
transfer to and from the storage device is controlled by modulating one or more adjustable parameters of the
joint mechanism. The active joints are controlled in the usual way and draw power from an external source.
A control approach is proposed that relies on the ability to modulate semiactive joint parameters to match
a pre-determined virtual control. Virtual controls are assumed to have been designed to meet some objective,
for instance robust motion tracking, impedance control, force control or hybrid force/position control.
There is no restriction on the type of control: inverse dynamics, robust, adaptive, independent-joint PD
and open-loop optimal approaches are allowed. For first-order joint mechanism models, virtual control
matching results in first-order internal dynamics (zero dynamics) with a clear physical interpretation
in terms of energy storage. Energy balance equations are presented and conditions for self-powered
operation are given for the semiactive joints, along with expressions for the work required from the
active joints. A basic example is presented, as well as simulation results corresponding to the CCF robot
operating with an electromechanical knee. A map of research topics and problems arising from this
framework and control paradigm is presented, with a focus on prosthetic control applications.