7,657 research outputs found
High-performance control of dual-inertia servo-drive systems using low-cost integrated SAW torque transducers
AbstractâThis paper provides a systematic comparative
study of compensation schemes for the coordinated motion
control of two-inertia mechanical systems. Specifically, classical proportionalâintegral (PI), proportionalâintegralâderivative (PID), and resonance ratio control (RRC) are considered, with an enhanced structure based on RRC, termed RRC+, being proposed. Motor-side and load-side dynamics for each control structure are identified, with the âintegral of time multiplied by absolute
errorâ performance index being employed as a benchmark metric. PID and RRC control schemes are shown to be identical from a closed-loop perspective, albeit employing different feedback sensing mechanisms. A qualitative study of the practical effects of employing each methodology shows that RRC-type structures
provide preferred solutions if low-cost high-performance torque transducers can be employed, for instance, those based on surface acoustic wave tecnologies. Moreover, the extra degree of freedom afforded by both PID and RRC, as compared with the basic PI, is shown to be sufficient to simultaneously induce optimal closed-loop performance and independent selection of virtual inertia ratio. Furthermore, the proposed RRC+ scheme is subsequently
shown to additionally facilitate independent assignment
of closed-loop bandwidth. Summary attributes of the investigation are validated by both simulation studies and by realization of the methodologies for control of a custom-designed two-inertia system
Design and Evaluation of the LOPES Exoskeleton Robot for Interactive Gait Rehabilitation
This paper introduces a newly developed gait rehabilitation device. The device, called LOPES, combines a freely translatable and 2-D-actuated pelvis segment with a leg exoskeleton containing three actuated rotational joints: two at the hip and one at the knee. The joints are impedance controlled to allow bidirectional mechanical interaction between the robot and the training subject. Evaluation measurements show that the device allows both a "pa- tient-in-charge" and "robot-in-charge" mode, in which the robot is controlled either to follow or to guide a patient, respectively. Electromyography (EMG) measurements (one subject) on eight important leg muscles, show that free walking in the device strongly resembles free treadmill walking; an indication that the device can offer task-specific gait training. The possibilities and limitations to using the device as gait measurement tool are also shown at the moment position measurements are not accurate enough for inverse-dynamical gait analysis
Dual-spin attitude control for outer planet missions
The applicability of dual-spin technology to a Jupiter orbiter with probe mission was investigated. Basic mission and system level attitude control requirements were established and preliminary mechanization and control concepts developed. A comprehensive 18-degree-of-freedom digital simulation was utilized extensively to establish control laws, study dynamic interactions, and determined key sensitivities. Fundamental system/subsystem constraints were identified, and the applicability of dual-spin technology to a Jupiter orbiter with probe mission was validated
A 6D interferometric inertial isolation system
We present a novel inertial-isolation scheme based on six degree-of-freedom
(6D) interferometric sensing of a single reference mass. It is capable of
reducing inertial motion by more than two orders of magnitude at 100\,mHz
compared with what is achievable with state-of-the-art seismometers. This will
enable substantial improvements in the low-frequency sensitivity of
gravitational-wave detectors. The scheme is inherently two-stage, the reference
mass is softly suspended within the platform to be isolated, which is itself
suspended from the ground. The platform is held constant relative to the
reference mass and this closed-loop control effectively transfers the low
acceleration-noise of the reference mass to the platform. A high loop gain also
reduces non-linear couplings and dynamic range requirements in the
soft-suspension mechanics and the interferometric sensing
Enhanced Torque Control of a PMSM Supplied by a Four-Leg Voltage Source Inverter Using the Third Harmonic
This paper investigates an electrical drive composed of a four-leg voltage source inverter and a three-phase starconnected surface permanent magnet synchronous machine with concentrated windings. The inverter fourth leg is clamped to the neutral point of the machine. We find the current references leading to smooth torque and maximal torque per ampere operation in the presence of a third harmonic electromotive force component. We further analyze the advantages of the proposed topology in terms of torque increase and dc-link voltage requirements
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