Virtual Constraints and Hybrid Zero Dynamics for Realizing Underactuated Bipedal Locomotion

Underactuation is ubiquitous in human locomotion and should be ubiquitous in bipedal robotic locomotion as well. This chapter presents a coherent theory for the design of feedback controllers that achieve stable walking gaits in underactuated bipedal robots. Two fundamental tools are introduced, virtual constraints and hybrid zero dynamics. Virtual constraints are relations on the state variables of a mechanical model that are imposed through a time-invariant feedback controller. One of their roles is to synchronize the robot's joints to an internal gait phasing variable. A second role is to induce a low dimensional system, the zero dynamics, that captures the underactuated aspects of a robot's model, without any approximations. To enhance intuition, the relation between physical constraints and virtual constraints is first established. From here, the hybrid zero dynamics of an underactuated bipedal model is developed, and its fundamental role in the design of asymptotically stable walking motions is established. The chapter includes numerous references to robots on which the highlighted techniques have been implemented.Comment: 17 pages, 4 figures, bookchapte

Sufficient Conditions for Dynamical Output Feedback Stabilization via the Circle Criterion

This paper suggests sufficient conditions for asymptotically stable dynamical output feedback controller design based on the circle criterion. It is shown that a dynamic output feedback stabilization problem with impending problems of finite escape time, previously attacked by observer-based design, can be successfully solved using circle criterion design. Stability of the closed-loop system is global and robust to parameter uncertainty

Development of an experimental model of a tourist thermoelectric generator and researching ways to increase its efficiency

The paper describes the development of an experimental model of a tourist thermoelectric generator (TTEG). TTEG is a compact portable thermoelectric device that provides direct conversion of thermal energy into electricity and is designed to boil water and charge mobile devices in camp conditions. This paper describes the model of the developed TTEG and provides an analysis of its design. The operational conditions of the TTEG are determined and the ways of optimizing its design are investigated. The main requirements for the developed TTEG model are identified in order to increase the efficiency of the device. The application of the electric load control unit with the function of the maximum power point tracking (MPPT) is described. © Published under licence by IOP Publishing Ltd