MIT Space Engineering Research Center

The Space Engineering Research Center (SERC) at MIT, started in Jul. 1988, has completed two years of research. The Center is approaching the operational phase of its first testbed, is midway through the construction of a second testbed, and is in the design phase of a third. We presently have seven participating faculty, four participating staff members, ten graduate students, and numerous undergraduates. This report reviews the testbed programs, individual graduate research, other SERC activities not funded by the Center, interaction with non-MIT organizations, and SERC milestones. Published papers made possible by SERC funding are included at the end of the report

Dynamics and control of dual-hoist cranes moving distributed payloads

Crane motion induces payload oscillation that makes accurate positioning of the payload a challenging task. As the payload size increases, it may be necessary to utilize multiple cranes for better control of the payload position and orientation. However, simultaneously maneuvering multiple cranes to transport a single payload increases the complexity and danger of the operation. This thesis investigates the dynamics and control of dual-hoist bridge cranes transporting distributed payloads. Insights from this dynamic analysis were used to design input shapers that reduce payload oscillation originating from various crane motions. Also, studies were conducted to investigate the effect input shaping has on the performance of human operators using a dual-hoist bridge crane to transport distributed payloads through an obstacle course. In each study, input shaping significantly improved the task completion time. Furthermore, input-shaping control greatly decreased operator effort, as measured by the number of interface button pushes needed to complete a task. These results clearly demonstrate the benefit of input-shaping control on dual-hoist bridge cranes. In addition, a new system identification method that utilizes input shaping for determining the modal frequencies and relative amplitude contributions of individual modes was developed to aid in the dynamic analysis of dual-hoist bridge cranes, as well as other multi-mode systems. This method uses a new type of input shaper to suppress all but one mode to a low level. The shaper can also be used to bring a small-amplitude mode to light by modifying one of the vibration constraints.M.S

Modal regulator of drive moving electrode of the arc furnace

В роботі розглянуто питання керування дугової сталеплавильної печі. Розрахунки проводяться на основі лінеаризованої математичної моделі системи печі. Складено матричну форму представленої моделі в змінних стану. Порівняння результатів матричних обчислень з біноміальним розподілом Ньютона дозволило розробити структуру керуючого модального регулятора. Проведено порівняне моделювання дій систем дугової сталеплавильної печі, що керуються класичним та модальним регуляторами. Порівняння показало, що використання розробленого модального регулятора дозволяє мінімізувати величину перерегулювання та тривалість перехідного процесу при випадкових зрушеннях режиму плавки.In this article the questions of management of the arc-furnace (EAF) are considered. The aim is to construction of automatic furnace regulator. The basis for constructing such a regulator is the mathematical model of the control object – EAF. Experience shows that the use of classical automatic regulators does not provide sufficient quality control of the EAF modes. It is proposed to use a modal regulator. The procedure for calculating the parameters of a modal regulator for a particleboard system is given. The basis for the calculation is a linearized mathematical model of the EAF system. Basic calculations are performed using standard software. Based on the linearized model of the chipboard, a matrix form of the model is constructed in the state of the variables. Using the matrix calculations we obtain the characteristic equation of a closed system of EAF. Comparing the obtained expression with the standard binomial distribution of Newton we calculate the coefficients of the modal regulator for EAF. In steady state, the current of the arc should be equal to the given value, and all increments of variables should be equal to zero. From these conditions we calculate the last coefficient of the modal controller from the system of equations, which is represented in the matrix form. The proposed procedure for calculating the modal regulator for EAF system is relatively simple. It does not require significant computational resources, even in the case of such a complex control object as the EAF. A comparative modeling of the control system of the EAF with the synthesized modal and classical regulators was carried out. The simulation results indicate a shorter duration of transients and a low level of overregulation of the drive for moving the electrodes of the chipboard. The use of the developed modal regulator should provide an opportunity for better control of the main processes of chipboard. In addition, such a control system avoids the share of emergency situations that occur when the charge is melting

Dynamics and Control of Smart Structures for Space Applications

Smart materials are one of the key emerging technologies for a variety of space systems ranging in their applications from instrumentation to structural design. The underlying principle of smart materials is that they are materials that can change their properties based on an input, typically a voltage or current. When these materials are incorporated into structures, they create smart structures. This work is concerned with the dynamics and control of three smart structures: a membrane structure with shape memory alloys for control of the membrane surface flatness, a flexible manipulator with a collocated piezoelectric sensor/actuator pair for active vibration control, and a piezoelectric nanopositioner for control of instrumentation. Shape memory alloys are used to control the surface flatness of a prototype membrane structure. As these actuators exhibit a hysteretic nonlinearity, they need their own controller to operate as required. The membrane structures surface flatness is then controlled by the shape memory alloys, and two techniques are developed: genetic algorithm and proportional-integral controllers. This would represent the removal of one of the main obstacles preventing the use of membrane structures in space for high precision applications, such as a C-band synthetic aperture radar antenna. Next, an adaptive positive position feedback law is developed for control of a structure with a collocated piezoelectric sensor/actuator pair, with unknown natural frequencies. This control law is then combined with the input shaping technique for slew maneuvers of a single-link flexible manipulator. As an alternative to the adaptive positive position feedback law, genetic algorithms are investigated as both system identification techniques and as a tool for optimal controller design in vibration suppression. These controllers are all verified through both simulation and experiments. The third area of investigation is on the nonlinear dynamics and control of piezoelectric actuators for nanopositioning applications. A state feedback integral plus double integral synchronization controller is designed to allow the piezoelectrics to form the basis of an ultra-precise 2-D Fabry-Perot interferometer as the gap spacing of the device could be controlled at the nanometer level. Next, an output feedback linear integral control law is examined explicitly for the piezoelectric actuators with its nonlinear behaviour modeled as an input nonlinearity to a linear system. Conditions for asymptotic stability are established and then the analysis is extended to the derivation of an output feedback integral synchronization controller that guarantees global asymptotic stability under input nonlinearities. Experiments are then performed to validate the analysis. In this work, the dynamics and control of these smart structures are addressed in the context of their three applications. The main objective of this work is to develop effective and reliable control strategies for smart structures that broaden their applicability to space systems

Roadmap on structured light

Structured light refers to the generation and application of custom light fields. As the tools and technology to create and detect structured light have evolved, steadily the applications have begun to emerge. This roadmap touches on the key fields within structured light from the perspective of experts in those areas, providing insight into the current state and the challenges their respective fields face. Collectively the roadmap outlines the venerable nature of structured light research and the exciting prospects for the future that are yet to be realized.Peer ReviewedPostprint (published version