Abstract: Since the actuator capacity is limited, in the real
application of active control systems under sever earthquakes it is
conceivable that the actuators saturate, hence the actuator saturation
should be considered as a constraint in design of optimal controllers.
In this paper optimal design of active controllers for nonlinear
structures by considering actuator saturation, has been studied. The
proposed method for designing optimal controllers is based on
defining an optimization problem which the objective has been to
minimize the maximum displacement of structure when a limited
capacity for actuator has been used. To this end a single degree of
freedom (SDF) structure with a bilinear hysteretic behavior has been
simulated under a white noise ground acceleration of different
amplitudes. Active tendon control mechanism, comprised of prestressed
tendons and an actuator, and extended nonlinear Newmark
method based instantaneous optimal control algorithm have been
used. To achieve the best results, the weights corresponding to
displacement, velocity, acceleration and control force in the
performance index have been optimized by the Distributed Genetic
Algorithm (DGA). Results show the effectiveness of the proposed
method in considering actuator saturation. Also based on the
numerical simulations it can be concluded that the actuator capacity
and the average value of required control force are two important
factors in designing nonlinear controllers which consider the actuator
saturation.
Abstract: This paper describes various stages of design and prototyping of a modular robot for use in various industrial applications. The major goal of current research has been to design and make different robotic joints at low cost capable of being assembled together in any given order for achieving various robot configurations. Five different types of joins were designed and manufactured where extensive research has been carried out on the design of each joint in order to achieve optimal strength, size, modularity, and price. This paper presents various stages of research and development undertaken to engineer these joints that include material selection, manufacturing, and strength analysis. The outcome of this research addresses the birth of a new generation of modular industrial robots with a wider range of applications and greater efficiency.
Abstract: Since straightness error of linear motor stage is hardly
dependent upon machining accuracy and assembling accuracy, there is
limit on maximum realizable accuracy. To cope with this limitation,
this paper proposed a servo system to compensate straightness error of
a linear motor stage. The servo system is mounted on the slider of the
linear motor stage and moves in the direction of the straightness error
so as to compensate the error. From position dependency and
repeatability of the straightness error of the slider, a feedforward
compensation control is applied to the platform servo control. In the
consideration of required fine positioning accuracy, a platform driven
by an electro-magnetic actuator is suggested and a sliding mode
control was applied. The effectiveness of the sliding mode control was
verified along with some experimental results.
Abstract: In this paper the reference current for Voltage Source
Converter (VSC) of the Shunt Active Power Filter (SAPF) is
generated using Synchronous Reference Frame method,
incorporating the PI controller with anti-windup scheme. The
proposed method improves the harmonic filtering by compensating
the winding up phenomenon caused by the integral term of the PI
controller.
Using Reference Frame Transformation, the current is transformed
from om a - b - c stationery frame to rotating 0 - d - q frame. Using
the PI controller, the current in the 0 - d - q frame is controlled to
get the desired reference signal. A controller with integral action
combined with an actuator that becomes saturated can give some
undesirable effects. If the control error is so large that the integrator
saturates the actuator, the feedback path becomes ineffective because
the actuator will remain saturated even if the process output changes.
The integrator being an unstable system may then integrate to a very
large value, the phenomenon known as integrator windup.
Implementing the integrator anti-windup circuit turns off the
integrator action when the actuator saturates, hence improving the
performance of the SAPF and dynamically compensating harmonics
in the power network. In this paper the system performance is
examined with Shunt Active Power Filter simulation model.
Abstract: The study of human hand morphology reveals that developing an artificial hand with the capabilities of human hand is an extremely challenging task. This paper presents the development of a robotic prosthetic hand focusing on the improvement of a tendon driven mechanism towards a biomimetic prosthetic hand. The design of this prosthesis hand is geared towards achieving high level of dexterity and anthropomorphism by means of a new hybrid mechanism that integrates a miniature motor driven actuation mechanism, a Shape Memory Alloy actuated mechanism and a passive mechanical linkage. The synergy of these actuators enables the flexion-extension movement at each of the finger joints within a limited size, shape and weight constraints. Tactile sensors are integrated on the finger tips and the finger phalanges area. This prosthesis hand is developed with an exact size ratio that mimics a biological hand. Its behavior resembles the human counterpart in terms of working envelope, speed and torque, and thus resembles both the key physical features and the grasping functionality of an adult hand.
Abstract: This paper presents a new stable robust adaptive controller and observer design for a class of nonlinear systems that contain i. Coupling of unmeasured states and unknown parameters ii. Unknown dead zone at the system actuator. The system is firstly cast into a modified form in which the observer and parameter estimation become feasible. Then a stable robust adaptive controller, state observer, parameter update laws are derived that would provide global adaptive system stability and desirable performance. To validate the approach, simulation was performed to a single-link mechanical system with a dynamic friction model and unknown dead zone exists at the system actuation. Then a comparison is presented with the results when there is no dead zone at the system actuation.
Abstract: Even it has been recognized that Shape Memory
Alloys (SMA) have a significant potential for deployment actuators,
the number of applications of SMA-based actuators to the present
day is still quite small, due to the need of deep understanding of the
thermo-mechanical behavior of SMA, causing an important need for
a mathematical model able to describe all thermo-mechanical
properties of SMA by relatively simple final set of constitutive
equations. SMAs offer attractive potentials such as: reversible strains
of several percent, generation of high recovery stresses and high
power / weight ratios. The paper tries to provide an overview of the
shape memory functions and a presentation of the designed and
developed temperature control system used for a gripper actuated by
two pairs of differential SMA active springs. An experimental setup
was established, using electrical energy for actuator-s springs heating
process. As for holding the temperature of the SMA springs at certain
level for a long time was developed a control system in order to
avoid the active elements overheating.
Abstract: State-dependent Riccati equation based controllers are
becoming increasingly popular because of having attractive
properties like optimality, stability and robustness. This paper focuses
on the design of a roll autopilot for a fin stabilized and canard
controlled 122mm artillery rocket using state-dependent Riccati
equation technique. Initial spin is imparted to rocket during launch
and it quickly decays due to straight tail fins. After the spin phase, the
roll orientation of rocket is brought to zero with the canard deflection
commands generated by the roll autopilot. Roll autopilot has been
developed by considering uncoupled roll, pitch and yaw channels.
The canard actuator is modeled as a second-order nonlinear system.
Elements of the state weighing matrix for Riccati equation have been
chosen to be state dependent to exploit the design flexibility offered
by the Riccati equation technique. Simulation results under varying
conditions of flight demonstrate the wide operating range of the
proposed autopilot.
Abstract: In this paper, the modified optimal sliding mode control with a proposed method to design a sliding surface is presented. Because of the inability of the previous approach of the sliding mode method to design a bounded and suitable input, the new variation is proposed in the sliding manifold to obviate problems in a structural system. Although the sliding mode control is a powerful method to reject disturbances and noises, the chattering problem is not good for actuators. To decrease the chattering phenomena, the optimal control is added to the sliding mode control. Not only the proposed method can decline the intense variations in the inputs of the system but also it can produce the efficient responses respect to the sliding mode control and optimal control that are shown by performing some numerical simulations.
Abstract: In this paper, we propose a hardware and software
design method for automotive Electronic Control Units (ECU)
considering the functional safety. The proposed ECU is considered for
the application to Electro-Mechanical Actuator systems and the
validity of the design method is shown by the application to the
Electro-Mechanical Brake (EMB) control system which is used as a
brake actuator in Brake-By-Wire (BBW) systems. The importance of a
functional safety-based design approach to EMB ECU design has been
emphasized because of its safety-critical functions, which are executed
with the aid of many electric actuators, sensors, and application
software. Based on hazard analysis and risk assessment according to
ISO26262, the EMB system should be ASIL-D-compliant, the highest
ASIL level. To this end, an external signature watchdog and an
Infineon 32-bit microcontroller TriCore are used to reduce risks
considering common-cause hardware failure. Moreover, a software
design method is introduced for implementing functional
safety-oriented monitoring functions based on an asymmetric dual
core architecture considering redundancy and diversity. The validity
of the proposed ECU design approach is verified by using the EMB
Hardware-In-the-Loop (HILS) system, which consists of the EMB
assembly, actuator ECU, a host PC, and a few debugging devices.
Furthermore, it is shown that the existing sensor fault tolerant control
system can be used more effectively for mitigating the effects of
hardware and software faults by applying the proposed ECU design
method.
Abstract: Reno-pin contact test is a method that is controlled by
DC motor used to characterize electronic chips. This method is used in
electronic and telecommunication devices. A new electric
performance testing system is developed in which the testing method
is controlled by using Piezoelectric Transducer (PZT) instead of DC
motor which reduces vibration and noise. The vertical displacement of
the Reno-pin is very short in the Reno-pin contact testing system. Now
using a flexible guide in the new Reno-pin contact system, the vertical
movement of the Reno-pin is increased many times of the existing
Reno-pin contact testing method using DC motor. Using the present
electric performance testing system with a flexible hinge and PZT
instead of DC motor, manufacturing of electronic chips are able to
characterize chips with low cost and high speed.
Abstract: This paper details few mechanical modeling and
design issues of RF MEMS switches. We concentrate on an
electrostatically actuated broad side series switch; surface
micromachined with a crab leg membrane. The same results are
extended to any complex structure. With available experimental data
and fabrication results, we present the variation in dynamic
performance and compliance of the switch with reference to few
design issues, which we find are critical in deciding the dynamic
behavior of the switch, without compromise on the RF
characteristics. The optimization of pull in voltage, transient time and
resonant frequency with regard to these critical design parameters are
also presented.
Abstract: In this paper, Fabless Prototyping Methodology is
introduced for the design and analysis of MEMS devices.
Conventionally Finite Element Analysis (FEA) is performed before
system level simulation. In our proposed methodology, system level
simulation is performed earlier than FEA as it is computationally less
extensive and low cost. System level simulations are based on
equivalent behavioral models of MEMS device. Electrostatic
actuation based MEMS Microgripper is chosen as case study to
implement this methodology. This paper addresses the behavioral
model development and simulation of actuator part of an
electrostatically actuated Microgripper. Simulation results show that
the actuator part of Microgripper works efficiently for a voltage range
of 0-45V with the corresponding jaw displacement of 0-4.5425μm.
With some minor changes in design, this range can be enhanced to
15μm at 85V.
Abstract: This paper presents a new type of mechanism and trajectory planning strategy for bipedal walking robot. The newly designed mechanism is able to improve the performance of bipedal walking robot in terms of energy efficiency and weight reduction by utilizing minimum number of actuators. The usage of parallelogram mechanism eliminates the needs of having an extra actuator at the knee joint. This mechanism works together with the joint space trajectory planning in order to realize straight legged walking which cannot be achieved by conventional inverse kinematics trajectory planning due to the singularity. The effectiveness of the proposed strategy is confirmed by computer simulation results.
Abstract: Due to their high power-to-weight ratio and low cost, pneumatic actuators are attractive for robotics and automation applications; however, achieving fast and accurate control of their position have been known as a complex control problem. The paper presents a methodology for obtaining controllers that achieve high position accuracy and preserve the closed-loop characteristics over a broad operating range. Experimentation with a number of conventional (or "classical") three-term controllers shows that, as repeated operations accumulate, the characteristics of the pneumatic actuator change requiring frequent re-tuning of the controller parameters (PID gains). Furthermore, three-term controllers are found to perform poorly in recovering the closed-loop system after the application of load or other external disturbances. The key reason for these problems lies in the non-linear exchange of energy inside the cylinder relating, in particular, to the complex friction forces that develop on the piston-wall interface. In order to overcome this problem but still remain within the boundaries of classical control methods, we designed an auto selective classicaql controller so that the system performance would benefit from all three control gains (KP, Kd, Ki) according to system requirements and the characteristics of each type of controller. This challenging experimentation took place for consistent performance in the face of modelling imprecision and disturbances. In the work presented, a selective PID controller is presented for an experimental rig comprising an air cylinder driven by a variable-opening pneumatic valve and equipped with position and pressure sensors. The paper reports on tests carried out to investigate the capability of this specific controller to achieve consistent control performance under, repeated operations and other changes in operating conditions.
Abstract: The blood ducts must be occluded to avoid loss of
blood from vessels in laparoscopic surgeries. This paper presents a
locking mechanism to be used in a ligation laparoscopic procedure
(LigLAP I), as an alternative solution for a stapling procedure.
Currently, stapling devices are being used to occlude vessels. Using
these devices may result in some problems, including injury of bile
duct, taking up a great deal of space behind the vessel, and bile leak.
In this new procedure, a two-layer suture occludes a vessel. A
locking mechanism is also required to hold the suture. Since there is
a limited space at the device tip, a Shape Memory Alloy (SMA)
actuator is used in this mechanism. Suitability for cleanroom
applications, small size, and silent performance are among the
advantages of SMA actuators in biomedical applications. An
experimental study is conducted to examine the function of the
locking mechanism. To set up the experiment, a prototype of a
locking mechanism is built using nitinol, which is a nickel-titanium
shape memory alloy. The locking mechanism successfully locks a
polymer suture for all runs of the experiment. In addition, the effects
of various surface materials on the applied pulling forces are studied.
Various materials are mounted at the mechanism tip to compare the
maximum pulling forces applied to the suture for each material. The
results show that the various surface materials on the device tip
provide large differences in the applied pulling forces.
Abstract: A multivariable discontinuous feedback linearization approach is proposed to position control of an electrically driven fast robot manipulator. A desired performance is achieved by selecting a useful controller and suitable sampling rate and considering saturation for actuators. There is a high flexibility to apply the proposed control approach on different electrically driven manipulators. The control approach can guarantee the stability and satisfactory tracking performance. A PUMA 560 robot driven by geared permanent magnet dc motors is simulated. The simulation results show a desired performance for control system under technical specifications.
Abstract: In this paper, different approaches to solve the
forward kinematics of a three DOF actuator redundant hydraulic
parallel manipulator are presented. On the contrary to series
manipulators, the forward kinematic map of parallel manipulators
involves highly coupled nonlinear equations, which are almost
impossible to solve analytically. The proposed methods are using
neural networks identification with different structures to solve the
problem. The accuracy of the results of each method is analyzed in
detail and the advantages and the disadvantages of them in
computing the forward kinematic map of the given mechanism is
discussed in detail. It is concluded that ANFIS presents the best
performance compared to MLP, RBF and PNN networks in this
particular application.
Abstract: Active Vibration Control (AVC) is an important
problem in structures. One of the ways to tackle this problem is to
make the structure smart, adaptive and self-controlling. The objective
of active vibration control is to reduce the vibration of a system by
automatic modification of the system-s structural response. This
paper features the modeling and design of a Periodic Output
Feedback (POF) control technique for the active vibration control of
a flexible Timoshenko cantilever beam for a multivariable case with
2 inputs and 2 outputs by retaining the first 2 dominant vibratory
modes using the smart structure concept. The entire structure is
modeled in state space form using the concept of piezoelectric
theory, Timoshenko beam theory, Finite Element Method (FEM) and
the state space techniques. Simulations are performed in MATLAB.
The effect of placing the sensor / actuator at 2 finite element
locations along the length of the beam is observed. The open loop
responses, closed loop responses and the tip displacements with and
without the controller are obtained and the performance of the smart
system is evaluated for active vibration control.
Abstract: This paper has been investigated a technique that predicts the performance of a bar-type unimorph piezoelectric vibration actuator depending on the frequency. This paper has been proposed an equivalent circuit that can be easily analyzed for the bar-type unimorph piezoelectric vibration actuator. In the dynamic analysis, rigidity and resonance frequency, which are important mechanical elements, were derived using the basic beam theory. In the equivalent circuit analysis, the displacement and bandwidth of the piezoelectric vibration actuator depending on the frequency were predicted. Also, for the reliability of the derived equations, the predicted performance depending on the shape change was compared with the result of a finite element analysis program.