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Integral control is often added to control systems to ensure robustness against unmodelled dynamics and external disturbances. This paper considers the Control-by-Interconnection interpretation of integral control when applied to port-Hamiltonian systems. The interpretation allows the integral controller to be described as a port-Hamiltonian system independent of the plant dynamics. Using this interpretation, we present physical realizations of integral control for a mechanical and an electro-mechanical system.

In this note, we extend a recent hybrid passive momentum observer for mechanical system to nonholonomic systems. The momentum observer assumes that configuration measurements of the underlying system are available, but measurements of the momentum or velocity are not available. Utilising a hybrid observer definition, the resulting observer converges at an exponential rate and has a lower dimension when compared to similar results. The observer additionally has a passive input-output pair which is used to interconnect with a control-by-interconnection (CbI) scheme, guaranteeing stability of the joint observer and controller system.

In this paper the application of PID control to passive systems via passive interconnection is explored. The stability properties of PID control applied to linear systems is well understood, but the application to nonlinear system is more complex. In this work we exploit the passive structure of a PID controller by interconnecting with passive plants to ensure closed-loop stability. In many cases, however, the regulation output does not coincide with the passive output of the plant and the integral of the passive output is the regulation output of interest. Two methods for applying PID to the integral of the passive output via passive interconnection are introduced.

In this paper we consider the problem of path following control for fully-actuated mechanical systems using the technique of total energy shaping. To this end, a closed-loop potential function is designed which is minimised along the desired path. In addition, the kinetic energy is shaped to ensure that the trajectories of the system converge exponentially to the desired path. The design method is applied to a 2-DOF robotic manipulator and simulations are presented to demonstrate the closed-loop performance.

In this paper, we propose a hybrid momentum observer for mechanical systems that has the momentum estimate error as a passive output. It is shown that, in the absence of additional input terms, the proposed observer is exponentially stable with a tunable rate of convergence. Then, by interconnecting the observer with the plant, the momentum estimate is shown to be a passive output from the combined plant and observer systems. Using this property, asymptotic stability of the closed-loop system is possible via negative feedback using the momentum estimate. The approach is demonstrated on a planar 2 degree-of-freedom robotic manipulator.

Night Sky with Exit Wounds Ocean Vuong, 8g pgs, Copper Canyon Press, coppercanyonpress.org, $16 USD Ocean Vuong's most recent collection of poetry kicked my ass. His writing is beautiful and [...]

Calling Down the Sky Rosanna Deerchild, 80 pgs, BookLand Press, booklandpress.com, $16.95 Rosanna Deerchild's second book of poetry gives an account of survivors' experiences at residential schools and the marks [...]

In this paper, we present a method to robustify asymptotically stable nonlinear systems by adding an integral action that rejects unknown additive disturbances. The proposed approach uses a port-Hamiltonian (pH) representation of the open-loop dynamics, which, relying on the asymptotic stability property, is guaranteed to exist. The integral action controller preserves the pH structure, and, by adding a suitable cross term between the plant and the controller states to the closed-loop energy function, it avoids the unnatural coordinate transformation used in the past. The controller is shown to be robust against some common types of modeling uncertainty, including unknown friction dynamics in mechanical systems. [ABSTRACT FROM AUTHOR]

Poems by Gerard Legro [ILLUSTRATION OMITTED] Jerrold Levy and Richard Negro, edited by Alessandro Porco, 117 pgs, BookThug, bookthug.ca, $22 Gerard Legro was many things over the course of his [...]

Charleswood Road: Stories M C Joudrey, 104 pgs, At Bay Press, atbaypress.com, $22.99 I've periodically been trying finish my review of this short story collection for three months now. While [...]

In this paper we present an energy shaping control law for set-point regulation of the Chaplygin sleigh. It is well known that nonholonomic mechanical systems cannot be asymptotically stabilised using smooth control laws as they do no satisfy Brockett’s necessary condition for smooth stabilisation. Here, we propose a discontinuous control law that can be interpreted as a potential energy shaping and damping injection controller. The proposed controller is shown to be robust against the parameters of both the inertia matrix and the damping structure of the open-loop system.

Interconnection and damping assignment, passivity-based control (IDA-PBC) has proven to be a successful control technique for the stabilisation of many nonlinear systems. In this paper, we propose a method to robustify a system which has been stabilised using IDA-PBC with respect to constant, matched disturbances via the addition of integral action. The proposed controller extends previous work on the topic by being robust against uncertainty in the damping structure of the system, a quantity which may not be known in many applications.

In this paper we present a method for the addition of integral action to nonpassive outputs of a class of port-Hamiltonian (pH) systems. The proposed integral controller is a dynamic extension, constructed from the open-loop system, such that the closed loop preserves the pH form. It is shown that the controller is able to reject the effects of both matched and unmatched disturbances, preserving the regulation of the nonpassive outputs. Previous solutions to this problem have relied on a change of coordinates whereas the presented solution is developed using the original state vector and, therefore, retains its physical interpretation. In addition, the resulting closed-loop dynamics have a natural interpretation as a control by interconnection scheme. [ABSTRACT FROM AUTHOR]

In this paper we present a method of bidirectional control of a vehicle string that achieves l2weak string stability. Previous work required short-range communications between vehicles within the string. Here, we utilise some recent results on integral action to remove the requirement of communications altogether.

In this paper, a switched controller for the Chaplygin Sleigh system based on passivity and energy shaping is presented. The Chaplygin sleigh cannot be asymptotically stabilised with a smooth control law, since Brockett’s necessary conditions for smooth stabilisation is not satisfied. To asymptotically stabilise the origin, two potential energy shaping control laws are developed that render the system asymptotically stable to two equilibrium manifolds, which intersect at the origin. A switching strategy between the energy shaping controllers is derived that ensures the system converges to the intersection of the equilibrium manifolds.

The poem "Last Things Lasting" by Joel Robert Ferguson is presented. First Line: Enhazed magenta sun rises on the eastern prayer; he sets; Last Line: So much and not at all.

A poem 'A Second Bar Poem' by Joel Robert Ferguson is presented including first line: Though this one wasn't written at a bar; last line: It's probably best to end this now.

The poem "On-the-Job Braining" by Joel Robert Ferguson is presented. First Line: How to be a body for eight hours. Last Line: How to win and go on winning.