Closed-form solution of the direct kinematics of the 6–3 type Stewart Platform using one extra sensor

A procedure for the determination of the actual configuration of the 6–3 type Stewart Platform is presented. The procedure makes use of one extra sensor in addition to the six that provide the mechanism leg lengths. The use of one extra sensor suitably located on the mechanism allows the direct position analysis to be solved in closed form and makes it possible to obtain a one-to-one correspondence between the sensor measurements and the configuration of the mechanism in almost the entire workspace. Particular configurations where the correspondence is not one-to-one are outlined and criteria to identify them given. Sensitivity to sensor measurement errors is investigated.Paper presented at the 12th Italian Congress on Theoretical and Applied Mechanics AIMETA 1995, Napoli, 3–6 October 1995     

Predictive information and explorative behavior of autonomous robots

Measures of complexity are of immediate interest for the field of autonomous robots both as a means to classify the behavior and as an objective function for the autonomous development of robot behavior. In the present paper we consider predictive information in sensor space as a measure for the behavioral complexity of a two-wheel embodied robot moving in a rectangular arena with several obstacles. The mutual information (MI) between past and future sensor values is found empirically to have a maximum for a behavior which is both explorative and sensitive to the environment. This makes predictive information a prospective candidate as an objective function for the autonomous development of such behaviors. We derive theoretical expressions for the MI in order to obtain an explicit update rule for the gradient ascent dynamics. Interestingly, in the case of a linear or linearized model of the sensorimotor dynamics the structure of the learning rule derived depends only on the dynamical properties while the value of the MI influences only the learning rate. In this way the problem of the prohibitively large sampling times for information theoretic measures can be circumvented. This result can be generalized and may help to derive explicit learning rules from complexity theoretic measures.     

Automating combinatorial chemistry: A primer on benchtop robotic systems

Summary Benchtop robotic systems are inexpensive, flexible automation tools with potential applications in a wide array of disciplines such as combinatorial chemistry, high-throughput screening, and genomics. We explain the basic components of a benchtop system and explore factors to consider when purchasing or customizing a robot, such as automation benefits, vendor selection, and current system limitations. Issues involving system specification, software design, and hardware customization are then discussed. Additionally, system optimization, validation, and support are detailed. Given a properly designed and implemented system, the combinatorial laboratory can markedly increase compound synthesis and purification.     

Workspace and Optimal Design of a Pure Translation Parallel Manipulator

This paper presents a study of a pure translation three degrees of freedom fully-parallel manipulator, known as the Tsai manipulator. Based on the static analysis and on the determination of the singularity loci of the manipulator, criteria for the optimal geometric design of the manipulator for a given workspace free from singularities are proposed.     

The Physical Preparation of Geologic Samples For Chemical Analysis Using Laboratory Robotics

Abstract

An automated system to grind geologic samples has been successfully tested. A Zymate II robotic system, along with specially designed or modified hardware, was used to process partially pulverized geologic samples. the system is capable of processing samples on a 24-hour basis with an average per-samples grinding time of 12.4 minutes. A sample grinding period is followed by a cleanout sequence of air purges, vacuuming and grinding for surface cleaning with quartz sand. Routine operator involvement is limited to adjusting the grinding plates on the Bico vertical grinder at the beginning of each preparation interval. Studies conducted using variable amounts of cleaning sand between grinding of samples indicate that the adjustment interval can be extended to 50 samples (25g cleaning sand) using an acceptance criteria of 80% of sample passing 80 mesh. the processed samples are suitable for direct geochemical analysis using a variety of standard chemical digestions. Cross contamination studies using soil, chromite, and galena/sphalerite samples have revealed that the grinding system is capable of clean-out efficiencies exceeding 99% using as little as 25g of cleaning sand.     

Representation of robotic fractional dynamics in the pseudo phase plane

This paper analyses robotic signals in the perspective of fractional dynamics and the pseudo phase plane (PPP).It is shown that the spectra of several experimental signals can be approximated by trend lines whose slope characterizes their fractional behavior.For the PPP reconstruction of each signal,the time lags are calculated through the fractal dimension.Moreover,to obtain a smooth PPP,the noisy signals are filtered through wavelets.The behavior of the spectra reveals a relationship with the fractal dimension of the PPP and the corresponding time delay.     

Characterization and modeling of air muscles

Two flexible pneumatic actuators, McKibben and straight fiber, were analyzed. The muscles were modeled by finite element method. The numerical models take into account the non-linearity of the expanding rubber inner tube, and of the mechanism for transferring load to the braided cords surrounding the tube. Because of its own fabrication, McKibben muscle model may capture the initial backslash between rubber tube and cords.Despite of the McKibben specimen, a straight fiber muscle prototype was fabricated on purpose in the laboratory. In order to validate the numerical models, numerous experimental tests were carried out. The numerical results showed a good agreement with the data measured experimentally in terms of muscle pull force and of its deformed shape. Finally, the models of two muscles similar in terms of input energy allow their performances to be compared.     

Solvability theory for a class of hemivariational inequalities involving copositive plus matrices applications in robotics

The study of the equilibrium of an object-robotic hand system including nonmonotone adhesive effects and nonclassical friction effects leads to new inequality methods in robotics. The aim of this paper is to describe these inequality methods and provide a corresponding suitable mathematical theory.     

Concurrent laser welding and annealing exploiting robotically manipulated optical fibers

Present investigation reports on the effects of incorporating pre- and post-heating on the mechanical properties of laser-welded joints, in normal air condition. Two common types of steels, i.e. mild steel, and stainless steel were welded with Lumonic's MS 830 Nd³⁺:YAG laser machine, with an output capacity of 400 W. Due to the low integrated energy input required for laser welded joints, the welded region are often cooled too rapidly via conduction to the surrounding material and atmosphere, which leads to hardness discontinuities in the fusion and heat affected zone. The effects of in-process laser annealing on the mechanical properties and microstructure of laser-welded joints are important in any manufacturing operation. To improve the poor weld characteristics, this work investigates the use of automated dual-beam delivery system to implement a pre- or post-heating technique, simultaneously with the welding process. The results show that proper selection of the control parameters for the pre- or post-heating can reduce the hardness of the weld significantly and improve the welded joints mechanical properties, such as higher tensile strength and better durability.