This paper presents a methodology with which to construct an equivalent simulation model of closed-loop BCI testing for a vehicle component. The proposed model comprehensively takes the transfer impedance of the test configuration into account. The methodology used in this paper relies on circuit modeling and EM modeling as well. The BCI test probes are modeled as the equivalent circuits, and the frequency-dependent losses characteristics in the probe's ferrite are derived using a PSO algorithm. The measurement environments involving the harness cable, load simulator, DUT, and ground plane are designed through three-dimensional EM simulation. The developed circuit model and EM model are completely integrated in a commercial EM simulation tool, EMC Studio of EMCoS Ltd. The simulated results are validated through comparison with measurements. The simulated and measurement results are consistent in the range of 1MHz up to 400MHz.

Rehabilitation training with pedaling wheelchair in combination with functional electrical stimulation (FES) can be effective for decreasing the risk of falling significantly. Automatic adjustment of cycling speed and making a turn without standstill has been desired for practical applications of the training with mobile FES cycling. This study aimed at developing closed-loop control system of cycling speed with the pedaling wheelchair. Considering clinical practical use with no requirement of extensive modifications of the wheelchair, measurement method of cycling speed with inertial motion measurement units (IMUs) was introduced, and fuzzy controller for adjusting stimulation intensity to regulate cycling speed was designed. The developed prototype of closed-loop FES control system achieved appropriately cycling speed for the different target speeds in most of control trials with neurologically intact subjects. In addition, all the control trials of low speed cycling including U-turn achieved maintaining the target speed without standstill. Cycling distance and cycling time increased with the closed-loop control of low cycling speed compensating decreasing of cycling speed caused by muscle fatigue. From these results, the developed closed-loop fuzzy FES control system was suggested to work reliably in mobile FES cycling.

Fuzzy controller can be useful to realize a practical closed-loop FES controller, because it is possible to make it easy to design FES controller and to determine its parameter values, especially for controlling multi-joint movements by stimulating many muscles including antagonistic muscle pairs. This study focused on using fuzzy controller for the closed-loop control of cycling speed during FES cycling with pedaling wheelchair. However, a designed fuzzy controller has to be tested experimentally in control performance. In this paper, a closed-loop fuzzy FES controller was designed and tested in knee extension movements comparing to a PID controller with healthy subjects before applying to FES cycling. The developed fuzzy controller showed good control performance as a whole in comparing to PID controller and its parameter values were determined through simple control tests of the target movement.

Small loop gain and low crossover frequency result in poor dynamic performance of a single-loop output voltage controlled boost converter in continuous conduction mode. Multi-loop current control can improve the dynamic performance, however, the cost, size and weight of the circuit will also be increased. Sensorless multi-loop control solves the problems, however, the difficulty of the closed-loop characteristics evaluation will be severely aggravated, because there are more parameters in the loops, meanwhile, different from the single-loop, the relationships between the loop gains and closed-loop characteristics including audio susceptibility and output impedance are generally indirect for the multi-loop. Therefore, in this paper, a novel robust H∞ synthesis approach in the time-domain is proposed to design a sensorless controller for boost converters, which need not solve any algebraic Riccati equation or linear matrix inequalities, and most importantly, provides an approach to parameterizing the controller by an adjustable parameter. The adjustable parameter behaves like a ‘knob’ on the dynamic performance, consequently, which makes the closed-loop characteristics evaluation straightforward. A boost converter is used to verify the proposed synthesis approach. Simulations show the great convenience of the closed-loop characteristics evaluation. Practical experiments confirm the simulations.

This paper provides a prototype neural prosthesis system dedicated to restoring continence and micturition function for patients with lower urinary tract diseases, such as detrusor hyperreflexia and detrusor-sphincter dyssynergia. This system consists of an ultra low-noise electroneurogram (ENG) signal recording module, a bi-phasic electrical stimulator module and a control unit for closed-loop bladder monitoring and controlling. In order to record extremely weak ENG signal from extradural sacral nerve roots, the system provides a programmable gain from 80 dB to 117 dB. By combining of advantages of commercial-off-the-shelf (COTS) electronics and custom designed IC, the recording front-end acquires a fairly low input-referred noise (IRN) of 0.69 μVrms under 300 Hz to 3 kHz and high area-efficiency. An on-chip multi-steps single slope analog-to-digital converter (ADC) is used to digitize the ENG signals at sampling rate of 10 kSPS and achieves an effective number of bits (ENOB) of 12.5. A bi-phasic current stimulus generator with wide voltage supply range (±0.9 V to ±12.5 V) and variable output current amplitude (0-500 μA) is introduced to overcome patient-depended impedance between electrode and tissue electrolyte. The total power consumption of the entire system is 5.61 mW. Recording and stimulation function of this system is switched by control unit with time division multiplexing strategy. The functionality of this proposed prototype system has been successfully verified through in-vivo experiments from dogs extradural sacral nerve roots.

This paper presents a new common-mode stabilization method for a CMOS differential cascode Class-E power amplifier with LC-tank based driver stage. The stabilization method is based on the identification of the poles and zeros of the closed-loop transfer function at a critical node. By adding a series resistor at the common-gate node of the cascode transistor, the right-half-plane poles are moved to the left half plane, improving the common-mode stability. The simulation results show that the new method is an effective way to stabilize the PA.

In this paper, the joint optimization issue of the cooperative precoder design is investigated for the transmission from the cooperative multi-point system to one mobile terminal. Based on the mean squared error minimization criterion, the problem is established for the cooperative precoder design. Unfortunately, this problem cannot be solved due to the block diagonal structure of the whole precoding matrix resulting from the fact that there is no data exchange among multiple base stations. In order to tackle this difficulty, the original problem is converted into an equivalent problem by stacking all of the nonzero entries in the block diagonal matrix into a long column vector. With the equivalent problem, the optimum solution is obtained in a closed-form expression by using the Lagrangian multiplier method. Numerical simulations illustrate the effectiveness of the proposed scheme in terms of bit error rate and spectral efficiency.

In this brief paper, both static and dynamic behaviors of an electrostatic-actuated MEMS mirror are modeled and studied. To overcome the intrinsic pull-in problem and the dynamic disadvantages in the open-loop controlled actuation, a novel closed-loop feedback control method is proposed assuming the mirror tilt angle can be measured. First, a fixed voltage slightly higher than the pull-in voltage is applied when the mirror tilt angle is small. Then Proportional-Derivative (PD) control is used when the mirror is approaching the target position. Simulink simulation results show that this combined PD closed-loop control can overcome the pull-in problem and improve the dynamic behavior; furthermore, it can also enhance the robustness of the mirror actuation system to overcome environmental disturbances.

Recently, novel full-diversity full-rate quasi-orthogonal space-time block codes (QSTBCs) with power scaling and double-symbol maximum likelihood (ML) decoding was proposed. Specifically, the codes can achieve full-diversity through linearly combining two adequately power scaled orthogonal space-time block codes (OSTBCs). In this letter, we derive expressions for mutual information and post-processing signal-to-noise ratio (SNR) for a system with four transmit antennas. By exploiting these formulas, we propose three transmit antenna grouping (TAG) methods for a closed-loop system with low-rate feedback information. The TAG methods make it possible to provide an excellent error-rate performance even with a low-complexity zero-forcing (ZF) detection, especially in spatially correlated fading channels.

We propose the Combined Symbol-based Closed-Loop Orthogonal Space-Time Block Code (CS-CL-OSTBC) for four transmit antennas. In the multiple antenna systems, the CS-CL-OSTBC not only achieves full rate and full diversity with linear maximum-likelihood detection but also obtains higher feedback gain than existing CL-OSTBCs due to more efficient utilization of channel feedback information. In the proposed scheme, all the complex-valued channel coefficients are rotated to positive real values with exact channel phase feedback information. As a result, the channel gain can be expressed as the square of the sum of all positive real values and can obtain the maximum value without any loss. Simulation results on bit error rate performance show that the CS-CL-OSTBC outperforms existing CL-OSTBCs for various modulation schemes.

In a closed-loop scenario, the performance of transmit-diversity schemes for a multiple antenna system depends on the reliability of the channel state information (CSI). However, estimating the reliability of the instantaneous CSI at the transmitter is a challenging task. In this paper, we propose a robust transmit-diversity scheme for the case when the instantaneous CSI available at the transmitter is imperfect and its reliability is unknown to the transmitter. We show by simulation that our proposed scheme is efficient when the CSI reliability varies arbitrarily in every channel realization.

Dramatic gains in channel capacity can be achieved in the closed-loop MIMO system under the assumption that the base station (BS) can acquire the downlink channel state information (CSI) accurately. However, transmitting CSI with high precision is a heavy burden that wastes a lot of uplink bandwidth, while transmitting CSI within a limited bandwidth leads to the degradation of system performance. To address this problem, we propose a zero-overhead downlink CSI feedback scheme based on the hybrid pilot structure. The downlink CSI is contained in the hybrid pilots at mobile terminal (MT) side, fed back to BS via the uplink pilot channel, and recovered from hybrid pilot at BS side. Meanwhile the uplink channel is estimated based on the hybrid pilot at BS side. Since transmitting the hybrid pilots occupies the same bandwidth as transmitting traditional code division multiplexing based uplink pilots, no extra uplink channel bandwidth is occupied. Therefore, the overhead for downlink CSI feedback is zero. Moreover, the hybrid pilots are formed at MT side by superposing the received analog downlink pilots directly on the uplink pilots. Thus the downlink CSI estimation process is unnecessary at MT side, and MT's complexity can be reduced. Numerical Simulations prove that, the proposed downlink CSI feedback has the higher precision than the traditional feedback schemes while the overhead for downlink CSI feedback is zero.

In this paper, we present and analyze a predictive closed-loop power control (CLPC) scheme which employs a comb-type sample arrangement to effectively compensate multiple power control group (PCG) delays over mobile fading channels. We consider both least squares and recursive least squares filters in our CLPC scheme. The effects of channel estimation error, prediction filter error, and power control bit transmission error on the performance of the proposed CLPC method along with competing non-predictive and predictive CLPC schemes are thoroughly investigated. Our results clearly indicate the superiority of the proposed scheme with its improved robustness under non-ideal conditions. Furthermore, we carry out a Monte-Carlo simulation study of a 55 square grid cellular network and evaluate the user capacity. Capacity improvements up to 90% are observed for a typical cellular network scenario.

This letter proposes an efficient transmit power allocation using partial channel information feedback for the closed-loop sorted QR decomposition (SQRD) based V-BLAST systems. For the feedback information, the positive real-valued diagonal elements of R are forwarded to the transmitter. With the proposed transmit power allocation that is numerically derived by the Lagrange optimization method, the bit error rate performance of the system can be remarkably improved compare to the conventional open-loop SQRD based V-BLAST systems without increasing the receiver complexity.

In this paper, we propose an enhanced signal to interference ratio (SIR) measurement algorithm and evaluate the performance of the proposed algorithm in a WCDMA forward link receiver with closed-loop fast transmit power control. The proposed algorithm reduces measured SIR offset by using a pilot channel (CPICH) to compensate for the attenuated signal power in fading channel environment. The proposed SIR measurement algorithm outperforms conventional SIR measurement algorithm with regard to mean SIR values and jitter, especially in high speed mobile channel environment. Also, performance results with closed loop power control show that the proposed algorithm has better performance than the conventional algorithm.

Packet-based and stream-based traffic will be widely accommodated in third generation mobile systems. In direct sequence code division multiple access (DS-CDMA) systems, the impact of packet-based traffic is different from stream-based traffic because of different power control schemes adopted in a multipath fading environment. In this paper, a closed-loop like power control scheme is considered for packet-based traffic on the reverse link. The concept of packet cost is introduced that represents how packet traffic consumes the link capacity of stream-based traffic. The effects of the response delay, the fading maximum Doppler frequency, and the number of resolvable paths on the packet cost for a single cell system are investigated by using Markov modeling for a multipath fading channel with a uniform power delay profile.

A model of the prefrontal cortical circuit has been constructed to investigate the dynamics for working memory processing. The model circuit is multi-layered and consists of a number of circuit modules or columns, each of which has local, excitatory and inhibitory connections as well as feedback connections. The columns interact with each other via the long-range horizontal connections. Besides these intrinsic connections, the pyramidal and spiny cells in the superficial layers receive the specific cue-related input and all the cortical neurons receive a hypothetical bias input. The model cortical circuit amplifies the response to the transient, cue-related input. The dynamics of the circuit evolves autonomously after the termination of the input. As a result, the circuit reaches in several hundred milliseconds an equilibrium state, in which the neurons exhibit graded-level, sustained activity. The sustained activity varies gradually with the cue direction, thus forming memory fields. In the formation of the memory fields, the feedback connections, the horizontal connections, and the bias input all play important roles. Varying the level of the bias input dramatically changes the dynamics of the model cortical neurons. The computer simulations show that there is an optimum level of the input for the formation of well-defined memory fields during the delay period.