A disposable injection molded bioreactor for growing tissue-engineered heart valves is controlled to mimic the physiological heart cycle. Tissue-engineered heart valves, cultured from human stem cells, are a possible alternative for replacing failing aortic heart valves, where nowadays biological and mechanical heart valves are used. Growing and conditioning is done by mechanically stimulating the tissue in a bioreactor.
A continuously variable hydraulic pressure converter utilizing high-speed on–off valves is studied in this paper. The hydraulic pressure converter is analogous to a switchmode buck converter in power electronics. Substituting the electronic components in the buck converter with their hydraulic counterparts, a hydraulic pressure converter is built. The steady state and fluctuation characteristics of the hydraulic pressure converter are studied in both the theoretical analysis and the simulation. The hydraulic pressure converter was built and tested. Experimental results show that the system output pressure can be continuously adjusted by changing the duty ratio of the PWM signal supplied to the high-speed on–off valve. Although there is fluctuation on the output pressure, the system output pressure has a quasi linear relationship with the PWM signal duty ratio. Results also show that the output pressure fluctuation is greatly influenced by the PWM signal frequency and the flywheel inertia. The hydraulic pressure converter based on high-speed on–off valves brings a new way to transform system pressure continuously.
Acquisition of the displacements and deformations of a loaded component is generally a not easy operation. This is especially the case as the component often presents a complex geometry and the deformations involve more degrees of freedom or a combination of them.
Hysteresis effect degrades the positioning accuracy of a piezostage, and hence the nonlinearity has to be suppressed for ultrahigh-precision positioning applications. This paper extends least squares support vector machines (LS-SVM) to the domain of hysteresis modeling and compensation for a piezostage driven by piezoelectric stack actuators.
This article presents the development of a linear micropositioner for a micro electrical discharge machine (lEDM). A linear open-loop micropositioner was developed using a solenoid-flexural element architecture. The power system varies the force delivered by the solenoid using the technique of pulse width modulation (PWM).
The platform of a hexapod is a part of the structure whose six degrees of freedom are constrained by six linearly independent line constraints. The six line constraints are utilized for developing simply supported, ’’joint less’’ connector configuration for the transmission of axial forces. Six beam transducers are utilized to serve as a base of a hexapod structure. The applied wrench information is obtained by measuring the six forces on the beam transducers at the fixed base. The idea of ‘‘joint less’’ structure and beam transducers resolve issues of precision and sensitivity in measuring a very small wrench. The validity of the design is proved by developing a prototype sensor as well as conducting various experiments. The results of the experiments are discussed in detail.
This paper describes the development of a new and unique 2-DOF tilting actuator that has a remote center of rotation. The tilting actuator is part of a non-contact handling tool that allows thin contat sensitive objects like silicon wafers or coated sheet metal to be manipulated without any contact between the tool and the object.
Based on Takagi–Sugeno (T–S) fuzzy approach we design a fuzzy speed control system for a permanent magnet synchronous motor (PMSM). We derive sufficient conditions for the existence of a T–S fuzzy speed regulator and acceleration observer in terms of linear matrix inequalities (LMIs). We parameterize the gain matrices using the LMI conditions. We implement the proposed T–S fuzzy speed control system by using a TMS320F28335 floating point DSP, and we give simulation and experimental results to verify that our method is practical and useful for controlling a PMSM under model parameter and load torque variations.
In order to improve the performance of a magnetically levitated (maglev) axial flow blood pump, threedimensional (3-D) finite element analysis (FEA) was used to optimize the design of a hybrid magnetic bearing (HMB). Radial, axial, and current stiffness of multiple design variations of the HMB were calculated using a 3-D FEA package and verified by experimental results.
This paper presents a new model predictive control method for time-optimal point-to-point motion control of mechatronic systems. The formulation of time-optimal behavior within the model predictive control framework and the structure of the underlying optimization problem are discussed and modifications are presented ...