Lilantha Samaranayake

Speed controller strategies for distributed motion control via Ethernet

Investigations on adapting Ethernet for distributed control systems is an interesting topic in the motion control industry, due to its commercially off the shelf hardware availability and compatibility at a comparatively lower price. Conversely, the communication through shared media in standard Ethernet is non-deterministic resulting in stochastic delays of data transfer. This paper experiments the solutions, through a control engineering perspective, for the time delay problem encountered in distributing the speed control loop of a Brushless DC motor via an Ethernet network. The mean of the control delay (T) is used in standard controller strategies modified for time delayed systems.

Incorporating semiconducting single-walled carbon nanotubes as efficient charge extractors in organic solar cells

We report on the improvement of power conversion efficiency (PCE) of PTB7/PC70BM solar cells by the addition of small quantities (0.02%–0.04%) of pristine single-walled carbon nanotubes (SWNTs) in the active-layer. SWNTs and purified semiconducting SWNTs (S-SWNTs) were added in quantities, which is 2 orders of magnitude lower than previously reported value and resulted in a reduction in the series resistance of the solar cell with minor changes on the shunt resistance. On addition of purified S-SWNT, the PCE of air measured devices enhanced by 29% from 4.9% to 6.3%, with short-circuit current density (Jsc) improving from 12.1 mA/cm2 to 14.4 mA/cm2 and a fill factor improvement from 54% to 61%. In addition, the role of processing additive N-Methyl-2-pyrrolidone, which acts as a SWNT dispersant, is also investigated. A single diode model of a solar cell is used to extract the cell parameters and understand the effect of SWNTs. Based on experimental data and its fitting to the single diode model, we propose...

Development of a Novel Drive Topology for a Five Phase Stepper Motor

In this paper, a novel drive topology for a five phase stepper motor is described in detail. Commercially off the shelf, low cost, standard stepper motor drive ICs are used to derive a novel drive topology for five phase stepper motors which enables closed loop speed and position control powered by inner current control loop. It is proved that the derived topology can be generalized to any stepper motor with higher odd number of phases. The designed driver consists of full step, half step, clockwise and counter clockwise drive modes with the speed control and current control.

Fuzzy Logic Control for energy saving in Autonomous Electric Vehicles

Limited battery capacity and excessive battery dimensions have been two major limiting factors in the rapid advancement of electric vehicles. An alternative to increasing battery capacities is to use better: intelligent control techniques which save energy on-board while preserving the performance that will extend the range with the same or even smaller battery capacity and dimensions. In this paper, we present a Type-2 Fuzzy Logic Controller (Type-2 FLC) as the speed controller, acting as the Driver Model Controller (DMC) in Autonomous Electric Vehicles (AEV). The DMC is implemented using realtime control hardware and tested on a scaled down version of a back to back connected brushless DC motor setup where the actual vehicle dynamics are modelled with a Hardware-In-the-Loop (HIL) system. Using the minimization of the Integral Absolute Error (IAE) has been the control design criteria and the performance is compared against Type-1 Fuzzy Logic and Proportional Integral Derivative DMCs. Particle swarm optimization is used in the control design. Comparisons on energy consumption and maximum power demand have been carried out using HIL system for NEDC and ARTEMIS drive cycles. Experimental results show that Type-2 FLC saves energy by a substantial amount while simultaneously achieving the best IAE of the control strategies tested.

Relating Sampling Period and Control Delay in Distributed Control Systems

The control delay in distributed control systems may be compensated on-line or off-line depending on the required quality of the output, available computational power of the controller node, time stamping and clock synchronizing facilities etc. Irrespective of the compensation technique, there is an upper bound to the constant or variable control delay, which is decided by the plant, controller and the selected sampling period of the distributed computer controlled system. It is shown that in general, if the control delay exceeds the sampling period, the system becomes multi-rate; deteriorate performance as the plant updates do not correspond to the output samples. This paper introduces an adaptive sampling scheme to ensure the control delay is less than the sampling period in steady state and uses the maximum tolerable delay of the system at a particular sampling interval to ensure stable transform from one sampling period to another

Cost functions for degradation control of electric motors in electric vehicles

This paper introduces a novel set of electric motor degradation cost functions based on energy usage, energy loss and work output, against their continuous operation rated values recommended by the manufacturer. Unlike conventional electric motor degradation indicators such as the bearing life and insulation life based service factors, these cost functions account for the quantified time in the degradation process. The cost functions are evaluated throughout the operational life of the motor using real-time measurements. Hence, they give a very accurate indication, which may be adapted for online controller tuning. This solid establishment of a degradation cost function also enables the system designer to give the user a choice between performance and degradation minimization. The proposed cost function scheme has experimentally been verified using a hardware-in-the-loop electric powertrain test-rig where standard drive cycles are used to conduct the experiments. The experimental results reveal that the degradation cost functions Cumulative Input Energy Ratio (CIER), Cumulative Loss Ratio (CLR) and Cumulative Work Ratio (CWR) accurately represent the electric motor degradation both qualitatively and quantitatively.

IPv6 multi-homing with structured CIDR

IPv6 is the next generation Internet Protocol. After a decade of deployment and platform integration, it stands ready to revolutionize the internet, networking, and the telecommunications industry. With the increasing number of networks, router performance needs to be upgrade with time. However with the present global routing table about 3k many routers face difficulties of handling the routing table. Ipv6 networks also blooming the internet gradually, which is a must to cater the IPv4 depreciating issue? Routing table handling issue may be huge with the IPv6 because the huge address space will cause for many routes. Multi-homing becomes the key issue with such implementation in future. Proper mechanism need to be followed to safeguard routing tables as well as networks.

Delay Compensation, Design and Simulation of Controllers for Distributed Control Systems

This paper is focused on controller design for distributed control systems. The performance degradation due to time varying control delays in the loop closed through a network has been addressed by a novel predictor based delay compensation method supported by an adaptive sampling scheme when the control delay exceeds the sampling period. Both continuous and discrete time domains have been considered in the design and a methodology has been derived to transform a continuous time design to discrete time implementation without loosing performance. Since the existing simulation tools support only constant sampling frequencies, a different approach based on a set of differential equations representing the system has also been presented

Distributed control of permanent magnet synchronous motor drive systems

A vast amount of attentions has been given to permanent magnet synchronous motors (PMSM) in a variety of industrial applications due to recent developments in rare-earth permanent magnet (PM) materials and power electronics. These PM motors present numerous advantageous, such as a higher torque-to-inertia ratio and power density, over the other conventional machines used for ac servo drives. Applying the concepts of distributed control systems (DCS), wherein the control loops are closed through a network enables closing the slower speed control loop through a network. It consequently offers the capability of controlling many such systems from a single location at a lower installation and maintenance cost. This paper presents a study on the distributed control of the PMSM drive systems, using Ethernet as a remedy for common commercial fieldbus systems. However, the insertion of the non-deterministic communication network complicates the analysis and design as conventional control theories with many ideal assumptions, such as synchronized control, non-delayed sensing and actuation, must be re-evaluated. If these issues are addressed effectively, this state of the art concept may have promising applications in aero dynamic, naval, material processing etc., industries.

Nonlinear Model Predictive Control for traction motor degradation minimization

Nonlinear Model Predictive Control is used to solve a multi-objective optimal control problem that minimizes degradation while ensuring desired closed loop performance of Permanent Magnet Synchronous Motors used for traction in Electric and Hybrid Electric Vehicles. Unlike industrial motors subjected to constant load demands, motors in electric vehicles have to cater dynamic torque and speed demands depending on the drive cycle. Therefore, it is important to have a control technique which will assure minimum degradation of the motor, while delivering the output similar to or better than conventional controllers. The control scheme is tested for extreme transient conditions that would occur in the practical scenario as well as for standard drive cycles. Performance comparison with the state of the art control scheme reveals that the nonlinear model predictive control scheme results in substantially lower degradation. It effectives saves the motor lifetime by 7.6% for NEDC and 15.7% for ARTEMIS drive cycles.