213 research outputs found
Observer-based tuning of two-inertia servo-drive systems with integrated SAW torque transducers
This paper proposes controller design and tuning
methodologies that facilitate the rejection of periodic load-side disturbances applied to a torsional mechanical system while simultaneously compensating for the observerâs inherent phase delay. This facilitates the use of lower-bandwidth practically realizable disturbance observers. The merits of implementing full- and reduced-order observers are investigated, with the latter being implemented with a new low-cost servo-machine-integrated highband width
torque-sensing device based on surface acoustic wave
(SAW) technology. Specifically, the authorsâ previous work based on proportionalâintegralâderivative (PID) and resonance ratio control (RRC) controllers (IEEE Trans. Ind. Electron., vol. 53, no. 4, pp. 1226â1237, Aug. 2006) is augmented with observer disturbance feedback. It is shown that higher-bandwidth disturbance observers are required to maximize disturbance attenuation over the low-frequency band (as well as the desired rejection frequency), thereby attenuating a wide range of possible frequencies. In such cases, therefore, it is shown that the RRC controller is
the preferred solution since it can employ significantly higher observer bandwidth, when compared to PID counterparts, by virtue of reduced noise sensitivity. Furthermore, it is demonstrated that the prototype servo-machine-integrated 20-N · mSAWtorque transducer is not unduly affected by machine-generated electromagnetic
noise and exhibits similar dynamic behavior as a
conventional instrument inline torque transducer
SAW torque transducers for disturbance rejection and tracking control of multi-inertia servo-drive systems
The paper proposes a resonance ratio control (RRC) technique for the coordinated motion control of multi-inertia mechanical systems, based on the measurement of shaft torque via a SAW-based torque sensor. Furthermore, a new controller structure, RRC plus disturbance feedback is proposed, which enables the controller to be designed to independently satisfy tracking and regulation performance. A tuning method for the RRC structure is given based on the ITAE index, normalized as a function of the mechanical parameters enabling a direct performance comparison between a basic proportional and integral (PI) controller. The use of a reduced-order state observer is presented to provide a dynamic estimate of the load-side disturbance torque for a multi-inertia mechanical system, with an appraisal of the composite closed-loop dynamics. It is shown that the integrated formulation of the tuning criteria enables lower bandwidth observers to be implemented with a corresponding reduction in noise and computational load. The control structures are experimentally validated via a purpose designed test facility and demonstrate significant improvement in dynamic tracking performance, whilst additionally rejecting periodic load side disturbances, a feature previously unrealisable except by other, high-gain control schemes that impose small stability margins
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
Improved performance of motor-drive systems by SAW shaft torque feedback
The paper describes the application of a non-contact, high bandwidth, low cost, SAW-based torque
measuring system for improving the dynamic performance
of industrial process motor-drive systems. Background to
the SAW technology and its motor integration is discussed
and a resonance ratio control (RRC) technique for the
coordinated motion control of multi-inertia mechanical
systems, based on the measurement of shaft torque via a
SAW-based torque sensor is proposed. Furthermore, a
new controller structure, RRC plus disturbance feedback
is proposed, which enables the controller to be designed to
independently satisfy tracking and regulation
performance. A tuning method for the RRC structure is
given based on the ITAE index, normalized as a function of
the mechanical parameters enabling a direct performance
comparison between a basic proportional and integral (PI)
controller. The use of a reduced-order state observer is
presented to provide a dynamic estimate of the load-side
disturbance torque for a multi-inertia mechanical system,
with an appraisal of the composite closed-loop dynamics.
The control structures are experimentally validated and
demonstrate significant improvement in dynamic tracking
performance, whilst additionally rejecting periodic load
side disturbances, a feature previously unrealisable except
by other, high-gain control schemes that impose small
stability margins
Observer based tuning techniques and integrated SAW torque transducers for two-inertia servo-drive systems
A controller design and tuning methodology is proposed that facilitates the rejection of periodic load-side disturbances applied to a torsional mechanical system, whilst simultaneously compensating for the disturbance observer's inherent phase delay, thereby facilitating the used of lower bandwidth, practically realisable, disturbance observers. The merits of implementing both a full- and reduced order observer, is investigated, with the latter being implemented with a new low-cost, high-bandwidth torque sensing device based on surface acoustic wave technolog
Rotor Position Estimation of a Pseudo Direct Drive PM machine using Extended Kalman Filter
The paper describes an improved method to control
a Pseudo Direct Drive (PDD) permanent magnet machine with
only one sensor on the low-speed rotor (LSR). Due to the
magnetic coupling between the two rotors, the PDD machine
exhibits low stiffness and non-linear torque transmission
characteristics, and hence, the position of the high-speed rotor
(HSR) cannot be determined using a simple gear ratio
relationship. An extended kalman filter is proposed to
accurately estimate the position of the HSR which is used to
provide electronic commutation for the drive. The technique
has been implemented on a prototype PDD subjected to
various speed and load torque profiles
Influence of control structures and load parameters on performance of a pseudo direct drive
The paper describes an in-depth and systematic analysis of a pseudo direct drive permanent magnet machine in closed loop control. Due to the torque being transmitted from the high-speed rotor (HSR) to the low-speed rotor (LSR), through a relatively low stiffness magnetic gear with non-linear characteristics, speed oscillations appear in the drive output with a conventional proportional integral (PI) controller. Therefore two candidate controllers have been proposed as an alternative to the PI control and all controllers have been optimally tuned with a genetic algorithm against a defined criterion. Furthermore, closed loop models are established in the complex frequency domain to determine the system damping and the cause of the oscillations. Consequently, the best controller structure that improves the dynamic behaviour of the system in terms of speed tracking and disturbance rejection could be identified, based on the frequency domain analysis. Experimental results are presented to validate the analysis and the proposed control technique
Pneumatic motion control systems for modular robots
This thesis describes a research study in the design,
implementation, evaluation and commercialisation of
pneumatic motion control systems for modular robots. The
research programme was conducted as part of a collaborative
study, sponsored by the Science and Engineering Research
Council, between Loughborough University and Martonair (UK)
Limited.
Microprocessor based motion control strategies have been
used to produce low cost pneumatic servo-drives which can be
used for 'point-to-point' positioning of payloads. Software
based realtime control strategies have evolved which
accomplish servo-controlled positioning while compensating
for drive system non-linearities and time delays. The
application of novel compensation techniques has resulted in
a significant improvement in both the static and dynamic
performance of the drive.
A theoretical foundation is presented based on a
linearised model of a pneumatic actuator, servo-valve, and
load system. The thesis describes the design and evolution
of microprocessor based hardware and software for motion
control of pneumatic drives. A British Standards based
test-facility has allowed control strategies to be evaluated
with reference to standard performance criteria.
It is demonstrated in this research study that the dynamic
and static performance characteristics of a pneumatic motion
control system can be dramatically improved by applying
appropriate software based realtime control strategies. This
makes the application of computer controlled pneumatic
servos in manufacturing very attractive with cost
performance ratios which match or better alternative drive
technologies.
The research study has led to commercial products
(marketed by Martonair Ltd), in which realtime control
algorithms implementing these control strategy designs are
executed within a microprocessor based motion controller
Electronic Control of Torque Ripple in Brushless Motors
Merged with duplicate record 10026.1/727 on 27.02.2017 by CS (TIS)Brushless motors are increasingly popular because of their high power density, torque to
inertia ratio and high efficiency. However an operational characteristic is the occurrence of
torque ripple at low speeds. For demanding direct drive applications like machine tools,
robot arms or aerospace applications it is necessary to reduce the level of torque ripple.
This thesis presents an in depth investigation into the production and nature of torque
ripple in brushless machines. Different torque ripple reduction strategies are evaluated and
one reduction strategy using Park's transform as a tool is identified as the promising
strategy. The unified machine theory is checked to clarify the theory behind Park's
transform; in particular assumptions made and general validity of the theory. This torque
ripple reduction strategy based on Park's transform is extended to include the effect of
armature reaction. A novel adaptive torque ripple reduction algorithm is designed. The
ineffectiveness of the conventional approach is demonstrated. Further a novel torque ripple
reduction strategy using direct measurements of the torque ripple is suggested, reducing
implementation time and allowing higher accuracies for torque ripple reduction. Extensive
measurements from the experimental system show the validity of the novel torque ripple
reduction strategies. The experimental results allow derivation of a formula for all load
situations. This formula makes it possible to further increase the reduction accuracy and
enables improved real time implementation of the torque ripple reduction algorithm.
The work presented here makes a substantial contribution towards understanding the nature
of torque ripple in brushless motors and solving the associated problems. The novel
reduction strategies form the basis for the development of intelligent dynamometers for
motor test beds. Further the torque ripple reduction method presented here can be used to
overcome manufacturing imperfections in brushless machines thus removing the cost for
precise manufacturing tools. Future designs of controllers can "build" their own correction
formula during set-up runs, providing a motor specific torque ripple correction.Automotive Motion Technology Lt
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