Abstract

Sliding modes control (SMC) is a nonlinear control method with a systematic design procedure that allows to obtain a explicit solution for the control input. This method has some advantages, such as robustness against external disturbances and unpredictable parametric variations. On this work, two conventional SMC techniques, one using the error and other using the error integral, are designed and validated in a heat exchange system composed of a single pass circulation electric heater, whose control objective is to regulate the output temperature of the fluid, under the influence of external disturbances, such as variations in the flow and inflow temperature, manipulating the electric current passing through the heater resistance. The two SMC algorithms are analyzed using numerical simulations and their performance is compared through the integral absolute error and the integral absolute control input, selecting the best one to be tested experimentally. The experimental results indicate that the SMC is capable of fulfilling the control objective with satisfactory performance.  Keywords: Conventional sliding modes control; heat exchange system; nonlinear control.

Abstract

Parallel cable robots are a special class of parallel robots which are formed by replacing rigid links with cables. Due to the characteristics provided by the cables, like low inertia and greater range of motion, this type of robots can perform a wide range of applications such as: moving cameras from one place to another in sporting events, motoring industry and mainly in rehabilitation of limbs. However, due to the unilateral property of cables, keeping them tensioned becomes a great challenge. This article describes the construction of a parallel robot driven by four cables with the aim to draw three figures through the study of the kinematic and dynamic model considering the redundancy, i.e., more cables than degrees of freedom, in order to avoid those cables that require more tension during the motion of the end-effector.