The integration of manipulation and vision for assembly and quality control

The recent, development of industrial robots has produced quite powerful and cost-effective manipulators. Some crucial operations, as managing parts with random orientation or realigning pieces, can now be solved with the aid of vision systems connected with the manipulator. Quality control can be partially done during the assembly itself.

The solutions we may adopt to integrate manipulation and vision can be various. If we want to make it easy to program the system as a whole, with the same programming language, we should study solutions in which manipulation and vision use high-level languages To this end we will discuss how the choice of the programming language for the application programs is crucial.

The hardware and software structures of an operational example of such a system are presented. Examples of programs are given     

Structurally fixed modes or systems described by Rosenbrock's polynomial matrices

A full characterization of structurally fixed modes for systems described by Rosenbrock's polynomial matrices is given. The constraints imposed on the feedback structure are quite general, so that the decentralized-control problem can be viewed as a particular case. The results are obtained in the digraph-theory framework and provide computationally efficient tests.     

Proteolytic activity among psychrotrophic bacteria isolated from refrigerated raw milk

Psychrotrophic bacteria were isolated from refrigerated raw milk from a processing plant in Southern Brazil. Psychrotrophic counts were between 4.9 and 7.8 log cfu/mL, and 5.3 to 7.2 log cfu/mL, for samples collected at the truck and the milk storage silo, respectively. Among the bacterial isolates, 90% were Gram-negative. Most strains presented low proteolytic activity, but strains of Burkholderia cepacia, Klebsiella oxytoca and Aeromonas sp. showed higher than 20 U/mL on azocasein as substrate. Crude proteases from selected strains were resistant to conventional heat treatments and caused coagulation of UHT milk after 5 days storage at room temperature.     

SENSORY THRESHOLDS OF CONSISTENCY OF SEMILIQUID FOODS: EVALUATION BY SQUEEZING FLOW VISCOMETRY*

Identification of subtle textural differences or changes in foods in isolation has been a difficult task because they are usually accompanied by differences or changes in other sensory properties. Textural modification of semi liquid foods can easily be produced by mechanical means without affecting their taste and appearance. The changes can be then quantified using squeezing flow viscometry without introducing new uncontrolled modifications. Comparison of the measurements with sensory evaluations of the same samples can establish the threshold of sensory detection, at least in principle. To test this hypothesis, the consistency of practically intact mayonnaise, tomato paste, yogurt and strawberry jam of two commercial brands each were evaluated by squeezing flow viscometry using an Instron UTM. Other samples of the same brands were stirred mildly to modify their consistency and then compared with the undisturbed samples. The textural differences were expressed in terms of the apparent stress at three compressed specimen heights, and the residual stress after 60 and 120 s at the final height. Relatively large differences, as judged by these mechanical measures were also detected by an untrained sensory panel, but the ‘correct identifications’ never reached a 100%. In the case of the two different brands of yogurt, the panel failed to establish the existence of differences, which were clearly detected by the instrument. This suggests that not every difference, detectable instrumentally, has a corresponding sensory response. Although the number of results in this preliminary work was too small to establish the exact threshold for sensory detection, the methodology seems to be appropriate for such a purpose. This is because of the high reproducibility of the squeezing flow parameters and their sensitivity to even subtle difference in the tested specimens consistency.