A hydraulic flexible joint inspired by the actuation system of spiders is investigated in this paper. Its design and characteristics are discussed and a mathematical model is developed to describe its static behaviour. Results of experimental tests are presented to validate its performance. A comparison to other hydraulic actuation systems is performed. The use of the proposed hydraulic flexible joint in adaptive robotic structures is addressed and discussed.
Most animals and insects use opposing muscles, called flexors and extensors, to
articulate the joints of their limbs. However, some spiders do not have extensors in some of their
joints and use, instead, a simple and efficient miniaturized hydraulic system to extend their limbs.
An actuator inspired by the hydraulic system of spiders, which can be embedded on adaptive
structures, is investigated in robot-like configurations in this paper. Its design and characteristics are
discussed and the effects of the geometrical parameters on its performance are investigated.
This paper presents design and implementation of a super twisting sliding mode control for superheat temperature and evaporating temperature of refrigerant fluid in an evaporator of HVAC (Heating-Ventilation and Air Conditioning)-Refrigeration system. Based on a nonlinear model of the evaporator two control approaches are presented. The first approach is based on a Multi-Input Multi Output (MIMO) system in which there are two control inputs; inlet mass flow and outlet mass flow rate, and the outputs are the length of two phase flow and evaporating temperature of refrigerant. The second approach considers the system as a Single input single output (SISO) one, and by using inlet mass flow, superheat temperature is controlled. In the first approach, by implementing a feedback linearization method the two control inputs are decoupled. By decoupling the effects of both inputs, the two state variables of system are controlled separately and effectively. By applying sliding mode control robustness against the disturbances and uncertainties is guaranteed. Super-twisting algorithm is applied as a remedy for chattering problem in classical sliding mode control and achieving finite time convergence. Controller and model of systems are simulated using MATLAB and Simulink. The results of simulations show the effectiveness of designed controller in presence of uncertainties.
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