Constraint on the actuation and power resources is often the critical limiting factor for a robot to perform desired tasks. Increasing torque and energy capacity may be a solution, but is seldom viable for robots already built. An attractive alternative is to carefully generate motion trajectories that maximally leverages upon the limited torque and energy resources. In this endeavor, singularity, which is deemed undesirable due to lose of manipulability, could be utilized to an advantage. This paper presents analysis of force and momentum generated through contact in relation to the singularity. The analysis shows that a motion at or near singularity not only maximally leverages the torque limits to generate forces in quasi-static motions, but is also optimally energy efficient for dynamical motion when it comes to momentum generation. Based on a simplified model, we discuss mechanical advantage aspects of a robotic leg and describe range of feasible forces that can be generated together with directions in which singular position becomes minimum torque configuration. Then we define stroke motion and establish upper bounds on the momentum generated through contact. Collinear stroke, where motion is along a straight line, is examined with respect to singularity.

In-pipe robots are important for inspection of pipe network that form vital infrastructure of modern society. Nevertheless, most in-pipe robots developed so far are targeted at working inside gas pipes and not suitable for liquid pipes. This paper presents a new approach for designing in-pipe robot to work inside a liquid environment in the presence of high drag forces. Three major subsystems - propulsion, braking, and turning - are described in detail with new concepts and mechanisms that differ from conventional in-pipe robots. Prototypes of each subsystem are designed, built and tested for validation. Resulting is a robot design that navigates efficiently inside liquid pipe network and can be used for practical inspection purposes.

In-pipe wheeled robots require friction on the wheels to maintain traction. Ability to vary this friction is highly desirable but conventionally used linkage mechanism is not suitable for it. This paper presents a novel mechanism generating adjustable friction with minimal energy consumption for in-pipe robots. The mechanism uses permanent magnets to achieve the objective. An appropriate model for the system is also presented and discussed. The paper identifies the important design parameters, and more importantly establishes the relation between the design parameters and the system's performance. In addition, a prototype of the mechanism was designed, fabricated and tested for validation.