183 research outputs found
Observer Sliding Mode Control Design for lower Exoskeleton system: Rehabilitation Case
Sliding mode (SM) has been selected as the controlling technique, and the state observer (SO) design is used as a component of active disturbance rejection control (ADRC) to reduce the knee position trajectory for therapeutic purposes. The suggested controller will improve the needed position performances for the Exoskeleton system when compared to the proportional-derivative controller (PD) and SMC as feed-forward in the ADRC approach, as shown theoretically and through computer simulations. Simulink tool is used in this comparison to analyze the nominal case and several disruption cases. The results of mathematical modeling and simulation studies demonstrated that SMC with a disturbance observer strategy performs better than the PD control system and SMC in feed-forward with a greater capacity to reject disturbances and significantly better than these controllers. Performance indices are used for numerical comparison to demonstrate the superiority of these controllers
Optimized active disturbance rejection control for DC-DC buck converters with uncertainties using a reduced-order GPI observer
The output voltage regulation problem of a PWM- based DC-DC buck converter under various sources of uncertainties and disturbances is investigated in this paper via an optimized active disturbance rejection control (ADRC) approach. Aiming to practical implementation, a new reduced-order generalized proportional integral (GPI) observer is first designed to estimate the lumped (possibly time-varying) disturbances within the DC- DC circuit. By integrating the disturbance estimation information raised by the reduced-order GPI observer (GPIO) into the output prediction, an optimized ADRC method is developed to achieve optimized tracking performance even in the presence of distur- bances and uncertainties. It is shown that the proposed controller will guarantee the rigorous stability of closed-loop system, for any bounded uncertainties of the circuit, by appropriately choosing the observer gains and the bandwidthfactor. Experimental results illustrate that the proposed control solution is characterised by improved robustness performance against various disturbances and uncertainties compared to traditional ADRC and integral MPC approaches
Design synthesis & prototype implementation of parallel orientation manipulators for optomechatronic applications
This thesis documents a research endeavor undertaken to develop high-performing
designs for parallel orientation manipulators (POM) capable of delivering the speed
and the accuracy requirements of a typical optomechatronic application. In the
course of the research, the state of the art was reviewed, and the areas in the
existing design methodologies that can be potentially improved were identified, which
included actuator design, dimensional synthesis of POMs, control system design, and
kinematic calibration. The gaps in the current art of designing each of these POM
system components were addressed individually. The outcomes of the corresponding
development activities include a novel design of a highly integrated voice coil actuator
(VCA) possessing the speed, the size, and the accuracy requirements of small-scale
parallel robotics. Furthermore, a method for synthesizing the geometric dimensions
of a POM was developed by adopting response surface methodology (RSM) as the
optimization tool. It was also experimentally shown how conveniently RSM can be
utilized to develop an empirical quantification of the actual kinematic structure of
a POM prototype. In addition, a motion controller was formulated by adopting the
active disturbance rejection control (ADRC) technology. The classic formulation of
the ADRC algorithm was modified to develop a resource-optimized implementation
on control hardware based on field programmable gate arrays (FPGA).
The practicality and the effectiveness of the synthesized designs were ultimately
demonstrated by performance benchmarking experiments conducted on POM prototypes constructed from these components. In specific terms, it was experimentally
shown that the moving platforms of the prototyped manipulators can achieve highspeed
motions that can exceed 2000 degrees/s in angular velocity, and 5Ć105 degrees/s2
in angular acceleration
Conceptual Design of a Flight Validation Mission for a Hypervelocity Asteroid Intercept Vehicle
Near-Earth Objects (NEOs) are asteroids and comets whose orbits approach or cross Earth s orbit. NEOs have collided with our planet in the past, sometimes to devastating effect, and continue to do so today. Collisions with NEOs large enough to do significant damage to the ground are fortunately infrequent, but such events can occur at any time and we therefore need to develop and validate the techniques and technologies necessary to prevent the Earth impact of an incoming NEO. In this paper we provide background on the hazard posed to Earth by NEOs and present the results of a recent study performed by the NASA/Goddard Space Flight Center s Mission Design Lab (MDL) in collaboration with Iowa State University s Asteroid Deflection Research Center (ADRC) to design a flight validation mission for a Hypervelocity Asteroid Intercept Vehicle (HAIV) as part of a Phase 2 NASA Innovative Advanced Concepts (NIAC) research project. The HAIV is a two-body vehicle consisting of a leading kinetic impactor and trailing follower carrying a Nuclear Explosive Device (NED) payload. The HAIV detonates the NED inside the crater in the NEO s surface created by the lead kinetic impactor portion of the vehicle, effecting a powerful subsurface detonation to disrupt the NEO. For the flight validation mission, only a simple mass proxy for the NED is carried in the HAIV. Ongoing and future research topics are discussed following the presentation of the detailed flight validation mission design results produced in the MDL
Focal Spot, Spring 2009
https://digitalcommons.wustl.edu/focal_spot_archives/1111/thumbnail.jp
An automated targeting mechanism with free space optical communication functionality for optomechatronic applications
This thesis outlines the development of an agile, reliable and precise targeting mechanism
complete with free space optical communication (FSOC) capabilities for employment
in optomechatronic applications. To construct the complex mechanism,
insight into existing technologies was required. These are inclusive to actuator design,
control methodology, programming architecture, object recognition and localization
and optical communication. Focusing on each component individually resulted in a
variety of novel systems, commencing with the creation of a fast (1.3 msā»Ā¹), accurate
(micron range) voice coil actuator (VCA). The design, employing a planar, compact
composition, with the inclusion of precision position feedback and smooth guidance
fulfills size, weight and power (SWaP) characteristics required by many optomechatronic
mechanisms. Arranging the VCAs in a parallel nature promoted the use of a
parallel orientation manipulator (POM) as the foundation of the targeting structure.
Motion control was achieved by adopting a cascade PID-PID control methodology in
hardware, resulting in average settling times of 23 ms. In the pursuit of quick and
dependable computation, a custom printed circuit board (PCB) containing a field
programmable gate array (FPGA), microcontroller and image sensing technology were
developed. Subsequently, hardware-based object isolation and parameter identification
algorithms were constructed. Furthermore, by integrating these techniques with the
dynamic performance of the POM, mathematical equations were generated to allow
the targeting of an object in real-time with update rates of 70 ms. Finally, a FSOC architecture utilizing beam splitter technology was constructed and integrated into the
targeting device. Thus, producing a system capable of automatically targeting an infrared
(IR) light source while simultaneously receiving wireless optical communication
achieving ranges beyond 30 feet, at rates of 1 Mbits per second
Multimodal series elastic actuator for human-machine interaction with applications in robot-aided rehabilitation
Series elastic actuators (SEAs) are becoming an elemental building block in collaborative robotic systems. They introduce an elastic element between the mechanical drive and the end-effector, making otherwise rigid structures compliant when in contact with humans. Topologically, SEAs are more amenable to accurate force control than classical actuation techniques, as the elastic element may be used to provide a direct force estimate. The compliant nature of SEAs provides the potential to be applied in robot-aided rehabilitation. This thesis proposes the design of a novel SEA to be used in robot-aided musculoskeletal rehabilitation. An active disturbance rejection controller is derived and experimentally validated and multiobjective optimization is executed to tune the controller for best performance in human-machine interaction. This thesis also evaluates the constrained workspaces for individuals experiencing upper-limb musculoskeletal disorders. This evaluation can be used as a tool to determine the kinematic structure of devices centred around the novel SEA
Single chip solution for stabilization control & monocular visual servoing of small-scale quadrotor helicopter
This thesis documents the research undertaken to develop a high-performing design
of a small-scale quadrotor (four-rotor) helicopter capable of delivering the speed and
robustness required for agile motion while also featuring an autonomous visual servoing
capability within the size, weight, and power (SWaP) constraint package. The
state of the art research was reviewed, and the areas in the existing design methodologies
that can potentially be improved were identified, which included development
of a comprehensive dynamics model of quadrotor, design and construction of a performance
optimized prototype vehicle, high-performance actuator design, design of a
robust attitude stabilization controller, and a single chip solution for autonomous vision
based position control. The gaps in the current art of designing each component
were addressed individually. The outcomes of the corresponding development activities
include a high-fidelity dynamics and control model of the vehicle. The model
was developed using multi-body bond graph modeling approach to incorporate the
dynamic interactions between the frame body and propulsion system. Using an algorithmic
size, payload capacity, and flight endurance optimization approach, a quadrotor
prototype was designed and constructed. In order to conform to the optimized
geometric and performance parameters, the frame of the prototype was constructed
using printed circuit board (PCB) technology and processing power was integrated
using a single chip field programmable gate array (FPGA) technology. Furthermore, to actuate the quadrotor at a high update rate while also improving the power efficiency
of the actuation system, a ground up FPGA based brushless direct current
(BLDC) motor driver was designed using a low-loss commutation scheme and hall
effect sensors. A proportional-integral-derivative (PID) technology based closed loop
motor speed controller was also implemented in the same FPGA hardware for precise
speed control of the motors. In addition, a novel control law was formulated for robust
attitude stabilization by adopting a cascaded architecture of active disturbance rejection
control (ADRC) technology and PID control technology. Using the same single
FPGA chip to drive an on-board downward looking camera, a monocular visual servoing
solution was developed to integrate an autonomous position control feature with
the quadrotor. Accordingly, a numerically simple relative position estimation technique
was implemented in FPGA hardware that relies on a passive landmark/target
for 3-D position estimation.
The functionality and effectiveness of the synthesized design were evaluated by
performance benchmarking experiments conducted on each individual component as
well as on the complete system constructed from these components. It was observed
that the proposed small-scale quadrotor, even though just 43 cm in diameter, can lift
434 gm of payload while operating for 18 min. Among the ground up designed components,
the FPGA based motor driver demonstrated a maximum of 4% improvement in
the power consumption and at the same time can handle a command update at a rate
of 16 kHz. The cascaded attitude stabilization controller can asymptotically stabilize
the vehicle within 426 ms of the command update. Robust control performance under
stochastic wind gusts is also observed from the stabilization controller. Finally, the
single chip FPGA based monocular visual servoing solution can estimate pose information
at the camera rate of 37 fps and accordingly the quadrotor can autonomously
climb/descend and/or hover over a passive target
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