Giorgio Figliolini

The Synthesis of Elliptical Gears Generated by Shaper-Cutters

The synthesis of elliptical gears is formulated using envelope theory by means of a suitable shaper-cutter with involute tooth profile. A general algorithm producing the pitch curves of elliptical gears and their rack with any number of lobes is proposed. Evolutes of pitch curves can be also obtained in order to choose a suitable shaper-cutter, even for pitch curves with concave-convex profiles. The complete synthesis of both meshing elliptical gears and their rack is reported, several graphical results being shown for design and analysis purposes. Computer animations are also available.

A novel articulated mechanism mimicking the motion of index fingers

In this paper we propose an analytical formulation for simulation and design of a one d.o.f. articulated finger mechanism with three phalanges. The formulation is based on a study of the design and operation of an index human finger. In particular, we have proposed a suitable mechanical design for an anthropomorphic finger as both an approximation of human architecture and an easy practical design. Kinematic characteristics are illustrated with numerical examples.

Synthesis of the Base Curves For N-Lobed Elliptical Gears

Motivated by the need to synthesize the tooth profiles of noncircular gears, we approach the synthesis of the tooth profile of circular spur gears using their pitch circle, rather than their base circle. We do this by means of envelope theory. The proposed formulation gives the involute tooth profile and its well-known base circle for any pitch radius and profile angle of the rack cutter, which coincides with the pressure angle for circular gears. Then, the foregoing approach applies to the synthesis of the base curves of noncircular gears with involute tooth profiles and of their rack. We do this by resorting to basic differential geometry using the Euler–Savary Theorem, rather than to envelope theory. In particular, the formulation of both base curves for the right and left involute tooth profiles is obtained, for the first time, for N-lobed elliptical gears and their rack through the formulation of the pitch curves and their evolutes. The proposed formulation is illustrated with numerical results.

Algorithms for involute and octoidal bevel-gear generation

A suitable formulation and the implementing algorithms for involute and octoidal bevel-gear generation are proposed in this paper. In particular, the exact spherical involute tooth profile of bevel gears and their crown rack is obtained through the pure-rolling motion of a great circle of the fundamental sphere on the base cone. Moreover, the tooth flank surface of octoidal bevel gears is obtained as the envelope of the tooth flat flank of the octoidal crown rack during the pure-rolling motion of its flat pitch (surface) on the pitch cone. The proposed algorithms have been implemented in MATLAB; several examples are included to illustrate their applicability.

Walking programming for an electropneumatic biped robot

An anthropomorphic ElectroPneumatic WAlking Robot named as EP-WAR has been designed and built at the Laboratory of Robotics and Mechatronics of Cassino University. Stability problems have been solved by a suitable use of suction-cups, which have been installed on the underside of each foot. Each leg mechanism has been designed and composed by a pantograph with a double articulated parallelogram. The EP-WAR mechatronic design has been conceived by using a pneumatic actuation and electronic control via PLC (Programmable Logic Controller). In addition a suitable programming technique has been developed in order to increase the flexibility of the EP-WAR prototype that can walk along any trajectory in the plane of the motion. Three walking modules and subroutine programs have been introduced and discussed for straight line path, right turn and left turn. Any walking path can be easily obtained by assembling the proposed subroutines in a suitable main program.

Mechanics and Simulation of Six-Legged Walking Robots

Legged locomotion is used by biological systems since millions of years, but wheeled locomotion vehicles are so familiar in our modern life, that people have developed a sort of dependence on this form of locomotion and transportation. However, wheeled vehicles require paved surfaces, which are obtained through a suitable modification of the natural environment. Thus, walking machines are more suitable to move on irregular terrains, than wheeled vehicles, but their development started in long delay because of the difficulties to perform an active leg coordination. In fact, as reported in (Song and Waldron, 1989), several research groups started to study and develop walking machines since 1950, but compactness and powerful of the existent computers were not yet suitable to run control algorithms for the leg coordination. Thus, ASV (Adaptive-Suspension-Vehicle) can be considered as the first comprehensive example of six-legged walking machine, which was built by taking into account main aspects, as control, gait analysis and mechanical design in terms of legs, actuation and vehicle structure. Moreover, ASV belongs to the class of “statically stable” walking machines because a static equilibrium is ensured at all times during the operation, while a second class is represented by the “dynamically stable” walking machines, as extensively presented in (Raibert, 1986). Later, several prototypes of six-legged walking robots have been designed and built in the world by using mainly a “technical design” in the development of the mechanical design and control. In fact, a rudimentary locomotion of a six-legged walking robot can be achieved by simply switching the support of the robot between a set of legs that form a tripod. Moreover, in order to ensure a static walking, the coordination of the six legs can be carried out by imposing a suitable stability margin between the ground projection of the center of gravity of the robot and the polygon among the supporting feet. A different approach in the design of six-legged walking robots can be obtained by referring to biological systems and, thus, developing a biologically inspired design of the robot. In fact, according to the “technical design”, the biological inspiration can be only the trivial observation that some insects use six legs, which are useful to obtain a stable support during the walking, while a “biological design” means to emulate, in every detail, the locomotion of a particular specie of insect. In general, insects walk at several speeds of locomotion with a

An analytical design for three circular-arc cams

In this paper we have presented an analytical description for three circular-arc cam profiles. An analytical formulation for cam profiles has been proposed and discussed as a function of size parameters for design purposes. Numerical examples have been reported to prove the soundness of the analytical design procedure and show the engineering feasibility of suitable three circular-arc cams.

Climbing stairs with EP-WAR2 biped robot

A second prototype of a biped walking robot, called EP-WAR2 (Electropneumatic WAlking Robot), has been designed and built at LARM (Laboratory of Robotics and Mechatronics) in Cassino. In addition to the performances of the previous prototype EP-WAR, EP-WAR2 is able to climb stairs because of a new actuation system. A suitable programming of the programmable logic controller has been based on several subroutines, which run different walking motions and specifically to climb stairs. Experimental tests prove the validity of the proposed low-cost design and programming technique.

Descending stairs with EP-WAR3 biped robot

A third version of the biped robot prototype, named as EP-WAR3 (Electro-Pneumatic WAlking Robot), has been designed, built and tested at LARM (Laboratory of Robotics and Mechatronics) in Cassino. Compared to the performances of the previous versions, EP-WAR3 is also able to descend stairs because of a new actuation system. Moreover, a suitable programming technique of the PLC (Programmable-Logic-Controller) is based on the use of specific subroutines that operate EP-WAR3 to run different walking modes and additionally to descend stairs.

Synthesis of conjugate Geneva mechanisms with curved slots

A suitable algorithm for the kinematic synthesis of conjugate Geneva mechanisms with curved slots and for that of their pure-rolling cam-equivalent is proposed. The kinematic-equivalent pure-rolling cam mechanisms are obtained by using the centrodes of the relative motion between crank and Geneva wheel. The proposed indexing mechanisms are compared by using the pressure angle as a figure of merit of force transmission. Numerical results are included for design purposes.