[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Droplet based microfluidics is a rapidly growing interdisciplinary field of research combining soft matter physics, biochemistry and microsystems engineering. Its applications range from fast analytical systems or the synthesis of advanced materials to protein crystallization and biological assays for living cells. Precise control of droplet volumes and reliable manipulation of individual droplets such as coalescence, mixing of their contents, and sorting in combination with fast analysis tools allow us to perform chemical reactions inside the droplets under defined conditions. In this paper, we will review available drop generation and manipulation techniques. The main focus of this review is not to be comprehensive and explain all techniques in great detail but to identify and shed light on similarities and underlying physical principles. Since geometry and wetting properties of the microfluidic channels are crucial factors for droplet generation, we also briefly describe typical device fabrication methods in droplet based microfluidics. Examples of applications and reaction schemes which rely on the discussed manipulation techniques are also presented, such as the fabrication of special materials and biophysical experiments.

https://iopscience.iop.org/article/10.1088/0034-4885/75/1/016601/pdf

Droplet based microfluidics

IEEE transactions on computer-aided design of integrated circuits and systems : a publication of the IEEE Circuits and Systems Society

Feedback systems: Input-output properties

In this paper, a feedback linearization (FL)-based control law made implementable using an extended state observer (ESO) is proposed for the trajectory tracking control of a flexible-joint robotic system. The FL-based controller cannot be implemented unless the full transformed state vector is available. The design also requires exact knowledge of the system model making the controller performance sensitive to uncertainties. To address these issues, an ESO is designed, which estimates the state vector, as well as the uncertainties in an integrated manner. The FL controller uses the states estimated by ESO, and the effect of uncertainties is compensated by augmenting the FL controller with the ESO-estimated uncertainties. The closed-loop stability of the system under the proposed observer-controller structure is established. The effectiveness of the ESO in the estimation of the states and uncertainties and the effectiveness of the FL + ESO controller in tracking are demonstrated through simulations. Lastly, the efficacy of the proposed approach is validated through experimentation on Quanser's flexible-joint module.

Extended-State-Observer-Based Control of Flexible-Joint System With Experimental Validation

We consider a design of decentralized control for a class of interconnected non-linear dynamical systems having uncertainty. This uncertainty is (possibly fast) time-varying, and it may appear in each system as uncertain parameter and input disturbance. It also may appear in the interconnections. No statistical information about the uncertainty is imposed; only its possible bound is assumed to be known. The two control schemes proposed here, namely the linear and the non-linear, take the bounds of the interconnections into account. The use of the non-linear control requires more assumptions than the use of linear control. In applications where these assumptions are met, the designers have both controls at their disposal, and depending on the particular application, one may be preferable to the other.

Robust control design for interconnected systems with time-varying uncertainties

A mechanical system is required to obey a set of constraints. The tools to accomplish this performance requirement are a set of servo controls1 that is, the servo controls are to generate the appropriate constraint force. In this article, the servo control design problem for constraint-following is thoroughly discussed. The problem is formulated as an algebraic setting in which a second order constraint is adopted. The control is a solution to the problem, whose projection to a subspace is used to ensure conformation to the constraint. The complete solution to this problem is provided in analytical form. It is shown that the environmentally constrained system simply adopts the minimum form of the complete solution. The setting presented here helps to broaden the scope of traditional Lagrangian mechanics.

Constraint-following Servo Control Design for Mechanical Systems:

This paper proposes a novel ten-phase fault-tolerant permanent-magnet synchronous motor (FTPMSM) with two stators and two rotors on the same shaft. Furthermore, a concentrated, single-layer, and alternate-teeth-wound winding is adopted to enhance the fault isolation capacity of the motor. In addition, we propose a new approach to the speed control of the developed motor, which takes the electromagnetic torque ripple in the fault switch process into account. The control can guarantee the uniform boundedness and uniform ultimate boundedness of the system regardless of the load disturbance and the parameter variation, particularly for the fault switch process after a fault occurrence before the fault-tolerant control can take effect. Moreover, an optimal torque control is adopted to further improve the fault-tolerant performance, which enables a ripple-free torque operation under open-circuit and short-circuit fault conditions. Simulation and experimental results show that the FTPMSM system with the proposed control strategy has excellent fault-tolerant performance and good robustness. This paper provides an innovative approach by employing a robust control for a speed loop to guarantee the fault-tolerant performance of the proposed motor system under normal and fault conditions, even in the fault switch process.

Robust Control of Fault-Tolerant Permanent-Magnet Synchronous Motor for Aerospace Application With Guaranteed Fault Switch Process

A New Approach to the Control Design of Fuzzy Dynamical Systems

The acceleration form of constraint equations is utilized in this paper to solve for the inverse dynamics of servo-constraints. A condition for the existence of control forces that enforce servo-constraints is derived. For overactuated dynamical systems, the generalized Moore-Penrose inverse of the constraint matrix is used to parameterize the solutions for these control forces in terms of free parameters that can be chosen to satisfy certain requirements or optimize certain criterions. In particular, these free parameters can be chosen to minimize the Gibbsian (i.e., the acceleration energy of the dynamical system), resulting in “ideal” control forces (those satisfying the principle of virtual work when the virtual displacements satisfy the servo-constraint equations). To achieve this, the nonminimal nonholonomic form recently derived by the authors in the context of Kane’s method is used to determine the accelerations of the system, and hence to determine the forces to be generated by the redundant manipulators. Finally, an extension to inverse dynamics of servo-constraints involving control variables is made. The procedures are illustrated by two examples.

Ye-Hwa Chen

Papers

Robust control design for interconnected systems with time-varying uncertainties

Constraint-following Servo Control Design for Mechanical Systems:

Robust Control of Fault-Tolerant Permanent-Magnet Synchronous Motor for Aerospace Application With Guaranteed Fault Switch Process

A New Approach to the Control Design of Fuzzy Dynamical Systems

Inverse Dynamics of Servo-Constraints Based on the Generalized Inverse