32,522 research outputs found
Computer simulation and design of a three degree-of-freedom shoulder module
An in-depth kinematic analysis of a three degree of freedom fully-parallel robotic shoulder module is presented. The major goal of the analysis is to determine appropriate link dimensions which will provide a maximized workspace along with desirable input to output velocity and torque amplification. First order kinematic influence coefficients which describe the output velocity properties in terms of actuator motions provide a means to determine suitable geometric dimensions for the device. Through the use of computer simulation, optimal or near optimal link dimensions based on predetermined design criteria are provided for two different structural designs of the mechanism. The first uses three rotational inputs to control the output motion. The second design involves the use of four inputs, actuating any three inputs for a given position of the output link. Alternative actuator placements are examined to determine the most effective approach to control the output motion
Robust Whole-Body Motion Control of Legged Robots
We introduce a robust control architecture for the whole-body motion control
of torque controlled robots with arms and legs. The method is based on the
robust control of contact forces in order to track a planned Center of Mass
trajectory. Its appeal lies in the ability to guarantee robust stability and
performance despite rigid body model mismatch, actuator dynamics, delays,
contact surface stiffness, and unobserved ground profiles. Furthermore, we
introduce a task space decomposition approach which removes the coupling
effects between contact force controller and the other non-contact controllers.
Finally, we verify our control performance on a quadruped robot and compare its
performance to a standard inverse dynamics approach on hardware.Comment: 8 Page
Linear actuators for locomotion of microrobots
University of Technology, Sydney. Faculty of Engineering.The successful development of the miniaturisation techniques for electronic components
and devices has paved the way for the miniaturisation in other technological fields. In
the past two decades, the research achievements in micromechatronics have spurred fast
development of micro machines and micro robotic systems. Miniature or micro
actuators are the critical components to make these machines more dexterous, compact
and cost effective.
The main purpose of this dissertation is to develop micro actuators suitable for the
locomotion of an in-pipe or endoscopic microrobot. The content of the thesis covers the
selection of the actuation principle, robotic system design, actuator design and prototype
construction, performance analysis, and design, analysis, and implementation of the
appropriate drive control system.
Among different types of actuation principles, piezoelectric and electromagnetic
actuators are the two major candidates for the micro robotic systems. In order to find a
suitable actuation principle for the desired robotic application, a comparative study was
conducted on the scaling effects, attainable energy density, and dynamic performances
of both types of actuators. Through the study, it was concluded that the electromagnetic
actuator is more suitable for the endoscopic microrobot.
Linear actuators are the common design used for the locomotion of microrobots due to
many advantages compared to their rotational counterparts. Through a thorough review
and comparison of the electromagnetic linear actuator topologies, a moving-coil tubular
linear actuator was chosen as the first design due to its simplest structure. Via the
magnetic circuit analysis and numerical magnetic field solutions, the actuator was
designed for optimum force capability, and the electromagnetic force and the machine
parameters of the actuator were predicted. According to the results obtained from the
magnetic field analysis, the dynamic model of the actuation system with a driving
control scheme was established and used in the actuation performance analysis of the
robotic system.
Based on the experience achieved through the first design, a new moving-magnet
tubular linear actuator was designed. The methodology developed in the design and
analysis of the moving-coil linear actuator was adopted for the moving-magnet actuator
design. However, the optimal design is more complicated due to the multi-pole and
multi-phase structure of the moving-magnet actuator. The electromagnetic force of the
actuator was analysed under the condition of different excitation methods. An enhanced
parameter computation method is proposed for predicting the actuator parameters.
Based on the results of magnetic field analysis, a comprehensive dynamic model of the
actuator was developed. Through the coupled field-circuit analysis, this model can
predict accurately the dynamic performance of the actuator. The characteristics analysis
shows that the performance of the moving-magnet actuator is much better than that of
the moving-coil actuator.
Two prototypes of the moving-magnet tubular linear actuator with different dimensions
were constructed to verify the performance and the scaling theory. Various precision
machining techniques were employed during the fabrication. The performances and
parameters of the two different prototypes were measured and the results agree
substantially with the theory.
The brushless DC drive method was chosen for the driving control of the proposed
linear actuator because of the compact circuit topology and simple implementation,
which are two essential factors for micro applications. A sensorless control scheme
based on the back EMF was developed as physical position sensors are not permitted in
such a micro system. The control scheme was then applied to the locomotion control of
the proposed microrobot. The system simulation shows that the control performances of
both the actuator and microrobot are satisfactory.
A dSPACE prototyping system based driving control hardware was designed and
implemented to experimentally verify the control design. The experimental results agree
substantially with the theoretical work
Analysis of Dynamic Performance Limitations of Fast Response /150 to 200 Hz/ Electrohydraulic Servos
Fast response electrohydraulic valve-controlled piston servo system
Continuous time controller based on SMC and disturbance observer for piezoelectric actuators
Abstract – In this work, analog application for the Sliding Mode Control (SMC) to piezoelectric actuators (PEA) is presented. DSP application of the algorithm suffers from ADC and DAC conversions and mainly faces limitations in sampling time interval. Moreover piezoelectric actuators are known to have very large bandwidth close to the DSP operation frequency. Therefore, with the direct analog application, improvement of the performance and high frequency operation are expected. Design of an appropriate SMC together with a disturbance observer is suggested to have continuous control output and related experimental results for position tracking are presented with comparison of DSP and analog control application
Eigenspace design techniques for active flutter suppression
The application of eigenspace design techniques to an active flutter suppression system for the DAST ARW-2 research drone is examined. Eigenspace design techniques allow the control system designer to determine feedback gains which place controllable eigenvalues in specified configurations and which shape eigenvectors to achieve desired dynamic response. Eigenspace techniques were applied to the control of lateral and longitudinal dynamic response of aircraft. However, little was published on the application of eigenspace techniques to aeroelastic control problems. This discussion will focus primarily on methodology for design of full-state and limited-state (output) feedback controllers. Most of the states in aeroelastic control problems are not directly measurable, and some type of dynamic compensator is necessary to convert sensor outputs to control inputs. Compensator design are accomplished by use of a Kalman filter modified if necessary by the Doyle-Stein procedure for full-state loop transfer function recovery, by some other type of observer, or by transfer function matching
Series active variable geometry suspension application to comfort enhancement
This paper explores the potential of the Series Active Variable Geometry Suspension (SAVGS) for comfort and road holding enhancement. The SAVGS concept introduces significant nonlinearities associated with the rotation of the mechanical link that connects the chassis to the spring-damper unit. Although conventional linearization procedures implemented in multi-body software packages can deal with this configuration, they produce linear models of reduced applicability. To overcome this limitation, an alternative linearization approach based on energy conservation principles is proposed and successfully applied to one corner of the car, thus enabling the use of linear robust control techniques. An H∞ controller is synthesized for this simplified quarter-car linear model and tuned based on the singular value decomposition of the system's transfer matrix. The proposed control is thoroughly tested with one-corner and full-vehicle nonlinear multi-body models. In the SAVGS setup, the actuator appears in series with the passive spring-damper and therefore it would typically be categorized as a low bandwidth or slow active suspension. However, results presented in this paper for an SAVGS-retrofitted Grand Tourer show that this technology has the potential to also improve the high frequency suspension functions such as comfort and road holding
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