Data/hora: 19/06/2024 20:08:46

Biblioteca(s): | Embrapa Instrumentação.
Data corrente: | 01/02/2001
Data da última atualização: | 24/08/2010
Autoria: | BERTUCCI-NETO, V.; PESSOA, J. D. C.; CRUVINEL, P. E.; CALBO, A. G.
Afiliação: | Embrapa Instrumentacao Agropecuaria.
Título: | Control systems-based design of a plant intracellular pressure measurement instrument.
Ano de publicação: | 1999
Fonte/Imprenta: | In: MASTORAKIS, N. E. (Ed.). Computers and computational engineering in control. [Athens]: World Scientific and Engineering Society, 1999.
Páginas: | p. 199-203.
ISBN: | 960-8052-12-2
Idioma: | Inglês
Conteúdo: | Cell turgor (plant intracellular pressure) is a parameter very know by physiologists and its determination is fundamental for the evaluation of water relations of higher (multicellular) plants. It is largely used in studies of plant tolerance or resistance to various stresses caused by irregular supply of nutrients, water and some other factors required by plant organism. The determination of cell turgor is also important for the development of models for water transport in plant tissues. Although this matter is of great importance to the physiologists, there are a few papers discribing realistic techniques for this purpose. Basically, the most reliable developed devices consisted of capillary filled with oil. It was used to puncture a plant cell and the meniscus moved itself according to the intracellular pressure. A hydraulic apparatus driven by a DC motor was used for counteracting the cell fissure, impelling pressure in the sense of the plant cell. The effort dispensed by the motor was correlated with the cell pressure. In a previous paper we have applied by the first time a control system approach to this problem. It was possible to determine the feasible work ranges, stability conditions, performance. The hydraulic system plus the DC motor was changed by external controlled temperature acting over the capillary wall. However the meniscus position detection was exposed to ambient temperature causing noisy measurement. In order to overcome this problem we propose in this paper a new design based on Linear Quadratic methods, specifically Proportional plus Integral Estimators in conjunction with Proportional Plus Integral State Feedback Regulator Designs. Main idea is to profit by the robustness characteristics of a PI controller together with the setting of the filter bandwidths for good noise filtering and transient responses. Morover, PI estimator can be optimum for a plant process noise which is high in intensity at low frequencies. The system was modeled and simulations were performed using parameters in limit conditions either of stability, or performance. Even in these conditions the response showed high robustness due  to large plant parameters variations and a reasonable noise filtering. Responses fails when the dead time, due to sample-hold circuits,optical sensor, and computer tasks, is increased. Limiting value found for the parameter was 0.2 second. It is sufficient to degenerate the system performance. Implications in to lower the dead time are related to rising the costs of the instrument. More expressive results are outlined in graphics followed by discussions.
Palavras-Chave: | Agricultural instrumentation; Controlador PI; Instrumentacao agropecuaria; LQG; LQR; Medida; Pressao intracelular; Pressure probe.
Thesaurus Nal: | measurement; turgor.
Categoria do assunto: | --
Registro original: | Embrapa Instrumentação (CNPDIA)
Exemplares: | CNPDIA - (5828-1) - UPC - PL - -- - PROCI - MAS - 2001. - DIS