A selectable-bandwidth 3.5 mW, 0.03 mm(2) self-oscillating Sigma Delta modulator with 71 dB dynamic range at 5 MHz and 65 dB at 10 MHz bandwidth

In this paper we present a dual-mode third order continuous time Sigma Delta modulator that combines noise shaping and pulse-width-modulation (PWM). In our 0.18 micro-m CMOS prototype chip the clock frequency equals 1 GHz, but the PWM carrier is only around 125 MHz. By adjusting the loop filter, the ADC bandwidth can be set to 5 or 10 MHz. In the 5 MHz mode the peak SNDR equals 64 dB and the dynamic range 71 dB. In the 10 MHz mode the peak SNDR equals 58 dB and the DR 65 dB. This performance is achieved at an attractively low silicon area of 0.03 mm^2 and a power consumption of 3.5 mW

Analysis and modeling of power supply induced jitter for high speed driver and low dropout voltage regulator

”With the scaling of power supply voltage levels and improving trans-conductance of drivers, the sensitivity of drivers to power supply induced delays has increased. The power supply induced jitter (PSIJ) has become one of the major concerns for high-speed system. In this work, the PSIJ analysis and modeling method are proposed for high speed drivers and the system with on-die low dropout (LDO) voltage regulator. In addition, a jitter-aware target impedance concept is proposed for power distribution network (PDN) design to correlate the PSIJ with PDN parasitic. The proposed PSIJ analysis model is based on the driver power supply rejection ratio (PSRR) response, transition edge slope and the propagation delay. It is demonstrated that the proposed model can be generalized for different type of drivers. Following the proposed PSIJ model, a method for improving the PSIJ simulation accuracy in the input/output buffer information (IBIS) model is also proposed. A PSIJ analysis method is also proposed for system with on-die LDO. The approach relies on separate analysis of the LDO block PSRR response and the buffer block PSIJ sensitivity. This procedure allows designer to evaluate the system PSIJ with fewer and faster simulations. For the jitter-aware target impedance, a systematic procedure to develop the target impedance curves is formulated and developed for common CMOS buffer circuits. Given the transient IC switching current and the jitter specification, multiple target impedance curves can be defined for a specific circuit. The proposed design procedure can largely relieve over-constrain in the PDN designed based on the original target impedance definition”--Abstract, page iv

Cost effective combined axial fan and throttling valve control of ventilation rate

This paper is concerned with Proportional-Integral-Plus (PIP) control of ventilation rate in mechanically ventilated agricultural buildings. In particular, it develops a unique fan and throttling valve control system for a 22m3 test chamber, representing a section of a livestock building or glasshouse, at the Katholieke Universiteit Leuven. Here, the throttling valve is employed to restrict airflow at the outlet, so generating a higher static pressure difference over the control fan. In contrast with previous approaches, however, the throttling valve is directly employed as a second control actuator, utilising airflow from either the axial fan or natural ventilation. The new combined fan/valve configuration is compared with a commercially available PID-based controller and a previously developed scheduled PIP design, yielding a reduction in power consumption in both cases of up to 45%

Controlling a contactless planar actuator with manipulator

An existing magnetically levitated planar actuator with manipulator has been studied and improved from a control point of view. This prototype consists of a magnetically levitated six-degree-of-freedom (6-DOF) planar actuator with moving magnets, with a 2-DOF manipulator on top of it. This system contains three different contactless technologies: contactless bearing and propulsion of the planar actuator, wireless powering of the manipulator, and wireless communication and control of the manipulator. The planar actuator (PA) consists of a Halbach magnet array, which is levitated and controlled in all six DOF’s above a stationary coil array. The PA is propelled in two horizontal translational DOF’s while the other four DOF’s are stabilized to accomplish a stiff bearing. Each active coil contributes to the production of forces and torques acting on the magnet array. Since the number of active coils is much larger than the number of DOF’s, the desired force production can be distributed over many coils. Therefore, a commutation algorithm has to be used to invert the mapping of the forces and torques exerted by the set of active coils as a function of the coil currents and the position and orientation of the translator. One method for linearization and decoupling of the forces and torques was developed in the past. The method is called direct wrench decoupling and guaranties minimal dissipation of energy. However, no constraints on the maximum current can be given. This study proposes two novel, norm-based commutation methods: l8-norm and clipped l2-norm based commutation. Both methods can put bounds on the maximum currents in the coils to prevent saturation of the current amplifiers. The first method focuses on minimization of the maximum current whereas the second method limits the peak current while it minimizes the power losses. Consequently, a higher acceleration of the translator can be achieved and/or less powerful (cheaper) current amplifiers can be utilized and/or fewer commutation errors arise. Only a long-stroke translational movement of the moving magnet planar actuators has been considered in the past. The possibility of a completely propelled and controlled rotation about the vertical axis instead of just stabilizing it for bearing has been analyzed in this thesis from a control point of view. Enhancing the planar actuator with a long-range rotation will increase its utility value and opens new application areas. Based on this investigation, a novel coil array with a triangular grid of rounded coils has been proposed for better controllability in any orientation of the PA. In addition, other coil and magnet topologies have been studied from a control point of view for their suitability for full rotation. The influence of different kinds of error-causes on the commutation precision has been studied. From this investigation, it has been found that the offsets of the measurement system have the highest influence on the precision of the commutation. Investigation of the convergence of the procedure for estimation and elimination of these offsets has been performed. Although it was not proven that the procedure could be applied on the whole workspace of the PA, the convergence has been shown at least for all the investigated points. From this investigation, convergence for any position in the workspace of the PA is expected. It was found that it is possible to use the procedure also with different topologies and with different commutations. A novel wireless link has been developed for the real-time control of a fast motion system. The wireless link communicates via infrared-light transceivers and the link has a delay and a packet-loss ratio almost indistinguishable from the wired connection for the bandwidth of the system up to several kilohertz. The clipped l2-norm based commutation method has been successfully tested on the experimental setup after improving the measurement system, the contactless energy transfer and the wireless communication. With a new, interferometer sensor system, a well-controlled PA with two long-stroke DOF’s has become available. Improved contactless energy transfer does not cause increased electromagnetic interference during switching between the primary coils any more and the wireless connection using the infrared link provides a reliable communication channel between the manipulator and the fixed world. Several control approaches have been tested on the experimental setup. Both, the classical PID control, Sliding-mode control and Iterative learning control have been implemented. Each controller brought better performance than the previous one. Also, a fourth-order trajectory and enhanced feedforward control helped to improve performance. Finally, the tracking errors, in comparison to the initial situation, were reduced by a factor 10 (and even more than by a factor 50 with deactivated contactless energy transfer) while the velocity and acceleration of the system were a factor 4 and 14, respectively, higher

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

A robust loop-shaping approach to fast and accurate nanopositioning

Peer reviewedPreprin

Effect of State Feedback Coupling on the Design of Voltage Source Inverters for Standalone Applications

This Ph.D. thesis aims at investigating the effect of state feedback cross‐coupling decoupling of the capacitor voltage on the dynamics performance of Voltage Source Inverters for standalone microgrids/Uninterruptible Power Supply systems. Computation and PWM delays are the main factors which limit the achievable bandwidth of current regulators in digital implementations. In particular, the performance of state feedback decoupling is degraded because of these delays. Two decoupling techniques aimed at improving the transient response of voltage and current regulators are investigated, named nonideal and ideal capacitor voltage decoupling respectively. In particular, the latter solution consists in leading the capacitor voltage on the state feedback decoupling path in order to compensate for system delays. Practical implementation issues are discussed with reference to both the decoupling techniques. Moreover, different resonant regulators structures for the inner current loop are analysed and compared to investigate which is the most suitable for standalone microgrid applications. A design methodology for the voltage loop, which considers the closed loop transfer functions developed for the inner current loop, is also provided. Proportional resonant voltage controllers tuned at specific harmonic frequencies are designed according to the Nyquist criterion taking into account application requirements. For this purpose, a mathematical expression based on root locus analysis is proposed to find the minimum value of the resonant gain at the fundamental frequency. The exact model of the output LC filter of a three‐phase inverter is derived in the z‐domain. The devised formulation allows the comparison of two techniques based on a lead compensator and Smith predictor structure. These solutions permit the bandwidth of the current regulator to be widened while still achieving good dynamic performance. As a consequence, the voltage regulator can be designed for a wide bandwidth and even mitigates odd harmonics arising with unbalance loads supply. Discrete‐time domain implementation issues of an anti‐wind up scheme are discussed as well, highlighting the limitations of some discretization methods. Experimental tests performed in accordance to Uninterruptible Power Supply standards verify the theoretical analysis

A novel target following solution for the electric powered hospital bed

© 2015 IEEE. The paper proposes a novel target following solution for an electric powered hospital bed. First, an improved real-time decoupling multivariable control strategy is introduced to stabilize the overall system during its operation. Environment laser-based data are then collected and pre-processed before engaging a neural network classifier for target detection. Finally, a high-level control algorithm is implemented to guarantee safety condition while the hospital bed tracks its target. The proposed solution is successfully validated through real-time experiments

Proton beam steering control system for high precision radiotherapy at iThemba LABS : an investigation on actuator saturation constraints

Includes abstract.Includes bibliographical references (leaves 101-106).This thesis aims at studying some of the techniques used to deal with constraints with special application to the Proton beam steering control at iThemba LABS. The steering of charged particles occurring in research plants is one of the interests of control systems. In this work an investigation of the algorithm for the control of the proton beam steering system in the radiotherapy treatment facility at iThemba LABS is conducted. This algorithm is intended to autonomously maintain the beam centered with reference to the axis of the beamline, and keep the beam front parallel to the central axis of the beamline as stated by van Tubbergh and De Kock, 2006. Furthermore, the algorithm is responsible for monitoring the distribution of the proton beam, in a plane normal to the beam travel direction