International Journal of Hydromechatronics (4 papers in press)

Regular Issues

• Robust active disturbance rejection control for modular fluidic soft actuators  
  by Yunce Zhang, Tao Wang, Xuqu Hu 
  Abstract: Delicate dynamic control of soft actuators is a challenging task due to their strongly nonlinearities. This article focuses on the dynamic control of the modular fluidic soft actuators governed by pneumatic proportional valves. Since it is difficult to accurately describe the complex coupling relationships among the chambers of the soft actuators, the dynamic control of the soft actuators cannot be implemented by using advanced control algorithms based on precise model in usual. To improve the manipulability and extend the application scenarios, we design a robust active disturbance rejection control method based on linear extended state observer, which only requires an approximate model of the soft actuators. Experimental results show that closed-loop stability and good tracking performance are achieved by the proposed method, meanwhile better disturbance rejection ability is guaranteed in comparison to the commonly used proportional-integral-differential control method.
  Keywords: controller design; state observation; dynamic performance; fluidic power; modular soft actuators.
  DOI: 10.1504/IJHM.2023.10059853
   
  
• Determination of the flow rate characteristics of porous media under the positive pressure and vacuum  
  by Wei Zhong, Yihao Wang, Kaiwen Fu, Chong Li, Jiang Shao, Pengfei Qian 
  Abstract: Porous media is widely used to replace the conventional orifices as restrictors in vacuum handling process. In this study, a theoretical model describing the flow rate characteristics, including effects from both viscosity and inertia, is established based on Darcy-Forchheimer’s law. The simulation work is firstly conducted, followed by establishing apparatuses to determine permeability and inertial coefficients. The permeability is determined within a small pressure difference (< 2 kPa) and the inertial coefficient is obtained with Re > 0.1 as the boundary. The average permeability is 1.21 × 10^-12 m² , 1.56 × 10^-12 m² , 3.41 × 10^-12 m² and 12.21 × 10^-12 m² , respectively. The inertial coefficient is determined under the positive pressure at the maximum pressure difference and vacuum with pressure difference from 50 kPa to 70 kPa. For different pressure conditions, it is confirmed that the theoretical flow rate can predict the experimental data within a 3% uncertainty which is sufficient for most applications. Finally, to obtain the inertial coefficient, two methods including the single-point method and the multi-point method are proposed. We found that the single-point method gives an error of 3.1% while the multi-point method gives an error of 1.9% for the determination of the entire flow rate characteristics.
  Keywords: flow rate characteristics; porous media; positive pressure; vacuum; permeability; inertial coefficient.
  DOI: 10.1504/IJHM.2024.10062649
   
  
• Metal additively manufactured air-cooled condenser for enhanced thermohydraulic performance  
  by Muhammad Noorazri Bin Samad, Leymus Yong Xiang Lum, Jin Yao Ho, Teck Neng Wong, Kai Choong Leong 
  Abstract: This study involves the development of an air-cooled condenser with porous lattice P-cell structures of 7 mm unit cell size on the air-side from an aluminium alloy (AlSi10Mg) powder by selective laser melting (SLM). The internal flow channels for enhanced condensation of R134a were designed with triangular cross-sections and a hydraulic diameter of 5 mm. Experiments were conducted to evaluate the condenser’s thermohydraulic performance. The results demonstrate that the P-cell design increased the heat transfer rate per unit volume and per air mass flow rate of the air-cooled condenser by a factor of 2.81 as compared to a conventional plate fin-and-tube heat exchanger. The fan power efficiency is comparable to a conventional plate-fin-and-tube heat exchanger. The feasibility of using SLM to fabricate a robust air-cooled condenser for high pressure operation is demonstrated.
  Keywords: additive manufacturing; selective laser melting; SLM; porous lattice; air-cooled condenser; heat exchanger.
  DOI: 10.1504/IJHM.2024.10064163
   
  
• Evolutionary design investigation applied to mixed convection heat transfer flows over semi-elliptical blocks inserted into a rectangular channel  
  by Andre Luis Razera, Roberta Juliana Collet Da Fonseca, Liércio André Isoldi, Elizaldo Domingues Dos Santos, Luiz Alberto Oliveira Rocha, Cesare Biserni 
  Abstract: This numerical manuscript focuses on the constructal design of a system characterised by mixed convection heat transfer flows over the heated semi-elliptical devices installed into a horizontally oriented channel. The primary aim of this study is to increase the heat transfer rate and decrease the pressure drop in the system by changing the two blocks’ geometry. The constraints, degrees of freedom, and performance metrics are chosen according to the constructal design method. The technique for order preference by similarity to the ideal solution method evaluates the multi-objective problem. By comparing the best and worst shapes, an increase of 40% for the thermal and 703% for fluid dynamic performances is noticed in the second optimisation level. Also noteworthy is the importance of evaluating different arrangements of the blocks within the channel, and the difference in performance obtained is up to 40% for the thermal and 12% for the fluid dynamic cases, respectively. In the multi-objective viewpoint, the above-cited method allowed the achievement of recommendations for designing the intruded fins, considering several scenarios where the fluid dynamic and thermal purposes are more or less dominant.
  Keywords: elliptical blocks; mixed convection; constructal design method; cooling; TOPSIS method.
  DOI: 10.1504/IJHM.2024.10064164