Automated formal synthesis of provably safe digital controllers for continuous plants

We present a sound and automated approach to synthesizing safe, digital controllers for physical plants represented as time-invariant models. Models are linear differential equations with inputs, evolving over a continuous state space. The synthesis precisely accounts for the effects of finite-precision arithmetic introduced by the controller. The approach uses counterexample-guided inductive synthesis: an inductive generalization phase produces a controller that is known to stabilize the model but that may not be safe for all initial conditions of the model. Safety is then verified via bounded model checking: if the verification step fails, a counterexample is provided to the inductive generalization, and the process further iterates until a safe controller is obtained. We demonstrate the practical value of this approach by automatically synthesizing safe controllers for physical plant models from the digital control literature.

Sustainability without Subsidy: Public Case for Vertically Integrated Rail Oligopolies for Freight

Maintaining rail freight networks without subsidy is an important transportation policy concern. Today’s vertically integrated rail oligopolies (VIROs) in the United States, Canada, and Mexico have enabled rail freight to be commercially self-sustaining. A combination of favorable geography involving a choice of railroads for most longer hauls and commercial freedom for railroads to set prices without prior regulatory approval have helped create a situation in which North American freight railroads are self-sustaining without government subsidies. This research examines the development of VIROs in the United States, Canada, and Mexico today. A largely hands-off policy, combined with a willingness to allow railroads to accumulate enough money to maintain their physical plants to high standards, have led to today’s major freight railroad duopolies in the eastern and western United States, Canada, and Mexico. Despite some complaints from shipper interests, today’s VIROs are largely stable (with the possible exception of broader policy changes in Mexico). Lawmakers and regulators should ensure that any future mergers do not adversely affect the performance of what has thus far been a largely satisfactory model.

Stability and Convergence Analysis of Direct Adaptive Inverse Control

In adaptive inverse control (AIC), adaptive inverse of the plant is used as a feed-forward controller. Majority of AIC schemes estimate controller parameters using the indirect method. Direct adaptive inverse control (DAIC) alleviates the adhocism in adaptive loop. In this paper, we discuss the stability and convergence of DAIC algorithm. The computer simulation results are presented to demonstrate the performance of the DAIC. Laboratory scale experimental results are included in the paper to study the efficiency of DAIC for physical plants.

Predictive Inverse Neurocontrol with Recycled Reference Trajectory

In this paper, the method of recycled reference trajectory for the plant output is considered within the main framework of the Predictive Inverse Neurocontrol (PIN) technique. The method allows to simplify the PIN controller synthesis and to improve the control quality of a PIN controller when operating with short prediction horizon . Moreover them it offers greater flexibility when choosing the desired of the plant's output response. The advantage of the proposed approach is illustrated by several examples of physical plants control.

A Virtual Plant System for Control System and Automation

This paper presents a virtual plant system, which is employed in the teaching process of the BTEC course of Control System and Automation. This system simulates different physical plants and demonstrates that experiments based on the virtual plant system can give students a vivid experience in this course. The virtual plant system has been proposed to reduce cost and simplify maintenance of lab facilities. As we do both, the development and employment of virtual plants, the paper includes approach to virtual plants development, description of some of them as well as our experience of their usage. The virtual plant system improves previous educational experiences in the course of Control System and Automation